WO2025118292A1 - Encoding and decoding method, code stream, decoder, encoder, and storage medium - Google Patents

Abstract

Embodiments of the present application provide an encoding and decoding method, a code stream, a decoder, an encoder, and a storage medium. The method at a decoding end comprises: parsing a code stream, and determining first syntax identification information; when the first syntax identification information indicates that a current chroma block uses a cross-component prediction mode based on a chroma intra block copy technology, on the basis of a current co-located luma block corresponding to the current chroma block, determining a reference motion vector; when the reference motion vector is valid, on the basis of a reference luma block and a reference chroma block corresponding to the reference motion vector, determining a cross-component prediction model; on the basis of the cross-component prediction model, determining a predicted chroma value of a predicted chroma block; and on the basis of the predicted chroma value of the predicted chroma block, determining a reconstructed chroma value of the current chroma block. Thus, the present application improves the flexibility and diversity of determining the cross-component prediction model such that the cross-component prediction model can flexibly cope with more complex encoding and decoding scenarios, thereby improving the encoding and decoding efficiency of the current chroma block.

Description

Coding and decoding method, code stream, decoder, encoder and storage medium Technical Field

The embodiments of the present application relate to the field of video coding and decoding technology, and in particular, to a coding and decoding method, a bit stream, a decoder, an encoder, and a storage medium.

Background Art

Based on the reference software test platform of the latest video coding standard AVS3, a two-step cross-component prediction mode (TSCPM) is proposed. TSCPM is an inter-component prediction technology that removes inter-component redundancy by exploring the linear relationship between different components.

On the exploration software platform of the new generation video coding standard AVS4, a chroma block copy intra-frame prediction mode is proposed. Under this scheme, the chroma block can directly use the block vector or string vector of the luminance co-located block for motion compensation without the need for additional motion estimation. The final chroma prediction value is obtained by copying the chroma reconstruction value pointed to by the block motion vector.

At present, in the process of TSCPM performing cross-component linear model derivation, the reconstructed pixels in one row and one column adjacent to the current chrominance block are usually used as the model derivation information source, which results in the current TSCPM being unable to flexibly cope with more complex encoding and decoding scenarios, thereby reducing the encoding and decoding efficiency of the chrominance block.

Summary of the invention

The embodiments of the present application provide a coding and decoding method, a bit stream, a decoder, an encoder and a storage medium, which can improve the coding and decoding efficiency of chroma blocks.

The technical solution of the embodiment of the present application can be implemented as follows:

In a first aspect, an embodiment of the present application provides a decoding method, which is applied to a decoder, and the method includes:

Parsing the code stream to determine first syntax identification information;

When the first syntax identification information indicates that the current chroma block adopts a cross-component prediction mode based on a chroma intra block copying technique, determining a reference motion vector according to a current co-located luminance block corresponding to the current chroma block;

When the reference motion vector is valid, determining a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector;

Determining a predicted chroma value of a predicted chroma block based on the cross-component prediction model;

Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block.

In a second aspect, an embodiment of the present application provides an encoding method, which is applied to an encoder, and the method includes:

Determine a reference motion vector according to a current co-located luminance block corresponding to the current chrominance block;

When the reference motion vector is valid, determining the cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector;

Based on the cross-component prediction model, determine a predicted chroma value of the predicted chroma block, and determine first syntax identification information according to the predicted chroma value; wherein the first syntax identification information is used to indicate whether the current chroma block adopts a cross-component prediction mode based on a chroma intra block copy technology;

Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block.

In a third aspect, an embodiment of the present application provides a code stream, which is generated by bit encoding according to information to be encoded; wherein the information to be encoded includes at least one of the following:

The value of the first syntax identification information, the value of the second syntax identification information, the value of the third syntax identification information, and the quantized chroma residual value of the current chroma block; wherein the first syntax identification information is used to indicate whether the current chroma block adopts a cross-component prediction mode based on the chroma intra-frame block copy technology; the second syntax identification information is used to indicate whether the current chroma block adopts a chroma intra-frame block copy prediction mode; the third syntax identification information is used to indicate whether the current chroma block adopts a chroma intra-frame block copy prediction mode or a cross-component prediction mode based on the chroma intra-frame block copy technology.

In a fourth aspect, an embodiment of the present application provides a decoder, the decoder comprising a decoding part and a first determining part, wherein:

The decoding part is configured to parse the code stream and determine the first syntax identification information;

The first determining part is configured to indicate that the current chroma block adopts the chroma intra-frame block copying technology based on the first syntax identification information. In the case of a cross-component prediction mode of the current chrominance block, determining a reference motion vector according to a current co-located luminance block corresponding to the current chrominance block;

When the reference motion vector is valid, determining a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector;

Determining a predicted chroma value of a predicted chroma block based on the cross-component prediction model;

Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block.

In a fifth aspect, an embodiment of the present application provides an encoder, the encoder comprising a second determining part, wherein:

The second determining part is configured to determine a reference motion vector according to a current co-located luminance block corresponding to the current chrominance block;

When the reference motion vector is valid, determining the cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector;

Based on the cross-component prediction model, determine a predicted chroma value of the predicted chroma block, and determine first syntax identification information according to the predicted chroma value; wherein the first syntax identification information is used to indicate whether the current chroma block adopts a cross-component prediction mode based on a chroma intra block copy technology;

Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block.

In a sixth aspect, an embodiment of the present application provides a decoder, the decoder comprising a first memory and a first processor, wherein:

The first memory is configured to store a computer program that can be executed on the first processor;

The first processor is configured to execute the method according to the first aspect when running the computer program.

In a seventh aspect, an embodiment of the present application provides an encoder, the encoder comprising a second memory and a second processor, wherein:

The second memory is configured to store a computer program that can be executed on the second processor;

The second processor is configured to execute the method according to the second aspect when running the computer program.

In an eighth aspect, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program is executed, it implements the method described in the first aspect or the second aspect.

The embodiments of the present application provide a coding and decoding method, a bit stream, a decoder, an encoder and a storage medium. At the decoding end, the bit stream is parsed to determine the first syntax identification information; when the first syntax identification information indicates that the current chroma block adopts the cross-component prediction mode based on the chroma intra-frame block copy technology, a reference motion vector is determined according to the current co-located luminance block corresponding to the current chroma block; when the reference motion vector is valid, a cross-component prediction model is determined based on the reference luminance block and the reference chroma block corresponding to the reference motion vector; based on the cross-component prediction model, a predicted chroma value of the predicted chroma block is determined; and according to the predicted chroma value of the predicted chroma block, a reconstructed chroma value of the current chroma block is determined. At the encoding end, a reference motion vector is determined based on the current co-located luminance block corresponding to the current chrominance block; when the reference motion vector is valid, a cross-component prediction model is determined based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector; based on the cross-component prediction model, a predicted chrominance value of the predicted chrominance block is determined, and first syntax identification information is determined based on the predicted chrominance value; wherein the first syntax identification information is used to indicate whether the current chrominance block adopts a cross-component prediction mode based on the chrominance intra-frame block copy technology; based on the predicted chrominance value of the predicted chrominance block, a reconstructed chrominance value of the current chrominance block is determined. Since the cross-component prediction model is determined by the reference luminance block and the reference chrominance block corresponding to the reference motion vector, compared with the cross-component prediction model derived from the reconstructed pixels of the adjacent row and column of the current chrominance block, the flexibility and diversity of determining the cross-component prediction model can be improved, so that the cross-component prediction model can flexibly cope with more complex encoding and decoding scenarios, thereby improving the encoding and decoding efficiency of the current chrominance block.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a schematic diagram 1 of an optional method of adopting a YCbCr color space provided in an embodiment of the present application;

FIG1b is a second schematic diagram of an optional YCbCr color space adoption method provided in an embodiment of the present application;

FIG1c is a third schematic diagram of an optional YCbCr color space adoption method provided in an embodiment of the present application;

FIG1d is a fourth schematic diagram of an optional YCbCr color space adoption method provided in an embodiment of the present application;

FIG2 is a schematic block diagram of an optional encoder provided in an embodiment of the present application;

FIG3 is a schematic block diagram of an optional decoder provided in an embodiment of the present application;

FIG4 is a schematic diagram of a network architecture of an optional encoding and decoding system provided in an embodiment of the present application;

FIG5 is a schematic diagram of a flow chart of an optional two-step cross-component prediction mode provided in an embodiment of the present application;

FIG6a is a schematic diagram 1 of an optional method for selecting adjacent reference sample points provided in an embodiment of the present application;

FIG6b is a second schematic diagram of an optional method for selecting adjacent reference sample points provided in an embodiment of the present application;

FIG6c is a third schematic diagram of an optional method for selecting adjacent reference sample points provided in an embodiment of the present application;

FIG6d is a fourth schematic diagram of an optional method for selecting adjacent reference sample points provided in an embodiment of the present application;

FIG6e is a fifth schematic diagram of an optional method for selecting adjacent reference sample points provided in an embodiment of the present application;

FIG7 is a schematic diagram of an optional template selection method for adjacent blocks provided in an embodiment of the present application;

FIG8 is a schematic diagram of an optional method for selecting brightness samples of a cross-component nonlinear prediction model provided in an embodiment of the present application;

FIG9 is a schematic diagram of a reference motion vector of an optional intra-block copy prediction technology provided in an embodiment of the present application;

FIG10 is a schematic diagram of a luma co-located block in an optional chroma block copy intra prediction mode provided in an embodiment of the present application;

FIG11 is a schematic flow chart of an optional decoding method provided in an embodiment of the present application;

FIG12a is a schematic diagram of an optional reference brightness block provided in an embodiment of the present application;

FIG12b is a schematic diagram of an optional reference chromaticity block provided in an embodiment of the present application;

FIG13a is a schematic diagram 1 of an optional preset sample point selection method provided in an embodiment of the present application;

FIG13b is a second schematic diagram of an optional preset sample point selection method provided in an embodiment of the present application;

FIG13c is a third schematic diagram of an optional preset sample point selection method provided in an embodiment of the present application;

FIG13d is a fourth schematic diagram of an optional preset sample point selection method provided in an embodiment of the present application;

FIG13e is a fifth schematic diagram of an optional preset sample point selection method provided in an embodiment of the present application;

FIG14 is a schematic diagram of an optional multiple cross-component prediction sub-model provided in an embodiment of the present application;

FIG15 is a schematic diagram of an optional six-tap filter provided in an embodiment of the present application;

FIG16 is a schematic diagram of a flow chart of an optional encoding method provided in an embodiment of the present application;

FIG17 is a schematic diagram of the composition structure of an optional decoder provided in an embodiment of the present application;

FIG18 is a schematic diagram of a specific hardware structure of an optional decoder provided in an embodiment of the present application;

FIG19 is a schematic diagram of the composition structure of an optional encoder provided in an embodiment of the present application;

FIG20 is a schematic diagram of a specific hardware structure of an optional encoder provided in an embodiment of the present application;

FIG. 21 is a schematic diagram of the composition structure of an optional encoding and decoding system provided in an embodiment of the present application.

DETAILED DESCRIPTION

In order to enable a more detailed understanding of the features and technical contents of the embodiments of the present application, the implementation of the embodiments of the present application is described in detail below in conjunction with the accompanying drawings. The attached drawings are for reference only and are not used to limit the embodiments of the present application.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

In the following description, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

It should also be pointed out that the terms "first\second\third" involved in the embodiments of the present application are only used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second\third" can be interchanged in a specific order or sequence where permitted, so that the embodiments of the present application described here can be implemented in an order other than that illustrated or described here.

Digital video compression technology is mainly used to compress huge digital video data for transmission and storage. In other words, digital video compression technology is a technology that saves storage space and transmission bandwidth by reducing the amount of video data. Video data usually takes up a lot of space, and compression technology can effectively reduce the file size while maintaining quality loss that is imperceptible to the human eye. With the surge in Internet videos and people's increasing requirements for video clarity, although the existing digital video compression standards can save a lot of video data, there is still a need to pursue better digital video compression technology to reduce the bandwidth and traffic pressure of digital video transmission.

Video compression usually relies on specific coding standards. Common video coding standards include H.264/AVC, H.265/HEVC, VP9, AV1, etc. These standards define the algorithms and specifications for video compression to ensure the compatibility of videos on different devices. Video compression technology is mainly divided into intra-frame compression and inter-frame compression. Intra-frame compression relies on the encoding of a single video frame, while inter-frame compression exploits the similarity between frames. In inter-frame compression, motion compensation is a key technology. By detecting motion in adjacent frames and predicting the position of pixels based on motion information, the amount of data can be reduced while maintaining video quality. Quantization is the process of mapping pixel values in an image or video to a smaller set, thereby reducing the representation range of the data. Entropy coding optimizes the encoding process by utilizing statistical information in the data to further reduce the amount of data. There are usually spatial and temporal correlations between adjacent pixels in a video. Compression algorithms use these correlations to reduce data redundancy through prediction and difference coding. Compression technology usually allows users to choose different resolutions and bit rates while maintaining acceptable quality. This allows for better adaptation to different needs during storage and transmission. Some applications have high real-time requirements for video transmission, such as video conferencing, real-time monitoring, etc. Therefore, some compression standards and technologies focus on providing low-latency solutions. In general, digital video compression technology has been widely used in the multimedia field, which not only affects the efficiency of video storage and transmission, but also has a positive impact on the user experience of video applications.

Video compression includes multiple modules such as intra-frame prediction (spatial domain) and/or inter-frame prediction (temporal domain) for reducing or removing inherent redundancy in the video, quantization and inverse quantization of residual information, loop filtering and entropy coding for improving subjective and objective reconstruction quality. Most mainstream video compression standards describe block-based compression technology. A video clip, a frame of a picture or a series of pictures will be divided into basic units called CTUs, which are further divided into blocks called CUs. Intra-frame blocks are predicted using the pixels surrounding the block as a reference, while inter-frame blocks refer to the spatial neighboring block information and reference information in other frames. Compared with the prediction signal, the residual information is transmitted in blocks. Transform, quantize and entropy encode into bitstream. These technologies are described in standards and implemented in various fields related to video compression. Internationally, the current mainstream standards include H.264/Advanced Video Coding (AVC), H.265/High Efficiency Video Coding (HEVC) standard, H.266/Versatile Video Coding (VVC) and the extensions of these standards. Video devices can achieve more efficient video encoding and decoding and transmission and storage by implementing these technologies.

In some embodiments, digital video is a video recorded in digital form, which is composed of a series of digital images, each image is composed of a number of rows and columns of pixels, and each pixel is represented by a digital value. In order to express the colors observed by the human eye, people have defined a series of different color models from a mathematical model, including RGB, YUV, etc. In order to project these color models to the corresponding mathematical expressions, different color spaces are generated according to different processing methods and storage formats for different color data. Color space is a specific form of color organization, and color space defines a way to represent and organize color information. Different color spaces use different coordinate systems or parameters to describe colors, which makes it easy to represent, edit, analyze and process colors.

In some embodiments, the color space includes RGB format (Red Green Blue), YUV format (Luminance-Chrominance-Saturation), HSV format (Hue-Saturation-Value), Lab format and CMYK format (Cyan-Magenta-Yellow-Key). It should be noted that the color spaces listed above each have their specific application fields and advantages, and the selection of an appropriate color space depends on specific needs and application scenarios. In practical applications, in the fields of image processing, computer vision and multimedia, it is often necessary to convert and process between different color spaces to meet the requirements of different devices and tasks.

In some embodiments, the RGB color space uses three components, red, green, and blue, to represent colors, and the value range of each component is usually 0 to 255. The RGB color space is widely used in computer graphics and display technology, and is used for displays, cameras, digital images, etc. RGB is characterized by being intuitive, easy to process and display, but the RGB color space in different devices and standards may be slightly different.

In some embodiments, the YUV color space includes three components: brightness (Y) and chrominance (U, V), which represent brightness information and chrominance information respectively. The YUV color space is mainly used in video coding, such as H.264, H.265, etc. The separation of chrominance information makes it easier to remove some color details that are not easily perceived by the human eye when compressing the video. The YUV color space is suitable for video coding, which separates brightness and chrominance and improves compression efficiency.

In some embodiments, the HSV color space uses three parameters: hue, saturation, and value to describe color. The HSV color space is mainly used in image editing and graphic design because it is more in line with human perception of color. The characteristics of the HSV color space are intuitive and easy to understand and adjust colors. Hue indicates the type of color, saturation indicates the purity of the color, and value indicates the brightness of the color.

In some embodiments, the Lab color space includes brightness (L) and two chromaticity components (a, b). The Lab color space is used to describe the color differences perceived by human vision and is a device-independent color space. The Lab color space can more accurately describe the differences between colors and is widely used in applications such as color matching and color correction.

In some embodiments, the CMYK color space uses four color components, cyan, magenta, yellow, and black, which respectively represent the ink content of the ink cartridge. The CMYK color space is mainly used in the printing field to define printing colors. The CMYK color space is suitable for the printing process. Various colors can be obtained by adjusting the content of different color components.

In some embodiments, the color object is an objective object, and different color spaces only measure the same object from different angles, and do not change the nature of the color object. The color organization methods of color space are diverse and varied. According to incomplete statistics, there are 40 different models, the common ones are RGB, CMY (K), HSI, YUV, YIQ, YCbCr, etc. Among them, the models based on the three primary colors are mainly RGB and CMY (K), and the models based on brightness and chromaticity are mainly HIS, YUV, YIQ, and YCbCr. The main uses of different color space models are also different. RGB is mainly used in display systems, CMY (K) is mainly used in printers, YUV is used for PAL color TVs, YIQ is used for NTSC color TVs, and YCbCr is used for digital color TVs. At present, YCbCr color space is the main form of expression of digital video encoding source, where Y represents brightness, that is, grayscale value, Cb represents the difference between the blue signal part and the brightness value, and Cr represents the difference between the red signal part and the brightness value. This format separates brightness information from color information, and uses the characteristics of human eyes that are sensitive to brightness but not to chrominance to compress some color information, thereby achieving the purpose of reducing bandwidth. YCbCr has many sampling formats, such as 4:4:4, 4:2:2, 4:1:1 and 4:2:0.

FIG. 1a shows a schematic diagram of a sampling point of 4:4:4, FIG. 1b shows a schematic diagram of a sampling point of 4:2:2, FIG. 1c shows a schematic diagram of a sampling point of 4:1:1, and FIG. 1d shows a schematic diagram of a sampling point of 4:2:0. Wherein, the sampling point of 4:4:4 means that the brightness (Y) component and the chrominance (Cb and Cr) components are sampled in units of each pixel in the horizontal and vertical directions, that is, each pixel has independent chrominance information and brightness information. The sampling method of 4:4:4 retains the highest color information and is suitable for scenes with high color accuracy requirements, but it also requires more storage and transmission bandwidth. The sampling point of 4:2:2 means that the sampling rate of the brightness (Y) component is 4 pixels per row, and the sampling rate of the chrominance (Cb and Cr) is 2 pixels per row. Specifically, when the sampling point is 4:4:4, the Y component is sampled only once for every 4 pixels in the horizontal direction, that is, the brightness information is shared for each group of 4 pixels. The Cb and Cr components are sampled only once for every two pixel values in the horizontal direction, that is, the chrominance information is shared for every two pixels. Compared with the sampling method with a sampling point of 4:4:4, this method can reduce the sampling rate of the chrominance component, thereby reducing the amount of data and saving storage and transmission bandwidth. The sampling point of 4:1:1 means that the luminance (Y) component is sampled in units of each pixel in the horizontal direction, while the chrominance (Cb and Cr) components are sampled once every 4 pixels in the horizontal direction, that is, each pixel has independent luminance information, and every 4 pixels share a set of chrominance information. The sampling method of 4:1:1 has a lower sampling rate for the chrominance component than the sampling method of 4:2:2, which can reduce the amount of data and save storage and transmission bandwidth. The sampling point of 4:2:0 means that the luminance (Y) component is sampled in units of each pixel in the horizontal and vertical directions, while the chrominance (Cb and Cr) components are sampled once every 2 pixels in the horizontal direction and once every 2 lines in the vertical direction, that is, each pixel has independent luminance information, and every 4 pixels share a set of chrominance information. The sampling method of 4:2:0 has a lower sampling rate for the chrominance component than the sampling method of 4:4:4, which can significantly reduce the amount of data and is suitable for video compression and transmission.

With the purpose of exploring the next generation of digital video compression technology, a two-step cross-component prediction mode (TSCPM) is proposed based on the reference software test platform (VVC Test Model, VTM) of the latest video coding standard H.266/VVC. TSCPM is an inter-component prediction technology that removes inter-component redundancy by exploring the linear relationship between different components. The workflow of TSCPM mainly includes the following two steps:

1) Luma Prediction

First, use the luma block corresponding to the current chroma block to be encoded. The linear model parameters α and β, as well as the reference samples of the luma block, are used to calculate a temporary luma prediction block of the same size. The goal of this step is to establish a linear relationship between the luma and chroma components. The linear model parameters α and β are calculated by analyzing the reference samples of the luma block and the corresponding chroma reference samples.

2) Chroma Prediction

After the luma prediction is completed, the temporary luma prediction block is downsampled to obtain the corresponding chroma prediction value. The downsampling operation usually involves operating the luma block in the horizontal and vertical directions to match the resolution of the chroma component. The result of downsampling is used to generate the prediction block of the chroma component, which will be used for intra prediction.

In general, TSCPM establishes a linear relationship between luminance and chrominance components, first predicts luminance, and then obtains chrominance prediction through downsampling, thereby achieving efficient prediction of chrominance components. This method helps to improve the efficiency of video coding, reduce data redundancy, and improve compression performance. TSCPM is mainly used in modern video coding standards such as H.264, H.265, etc.

At present, video compression technology is also a traditional codec based on blocks, which can include multiple modules, such as block division, intra-frame prediction, inter-frame prediction, transformation, quantization, entropy coding, loop and post-processing filtering, etc. The embodiment of the present application mainly improves the prediction part to improve the coding performance of TSCPM.

Here, the prediction part may include multiple techniques, including luma prediction mode and chroma prediction mode.

Referring to Fig. 2, it shows a schematic block diagram of a composition of an encoder provided by an embodiment of the present application. As shown in Fig. 2, the encoder 100 may include a transform and quantization unit 101, an intra-frame estimation unit 102, an intra-frame prediction unit 103, a motion compensation unit 104, a motion estimation unit 105, an inverse transform and inverse quantization unit 106, a filter control analysis unit 107, a filtering unit 108, an encoding unit 109 and a decoded image cache unit 110, etc., wherein the filtering unit 108 may implement deblocking filtering and sample adaptive offset (Sample Adaptive Offset, SAO) filtering, and the encoding unit 109 may implement header information encoding and context-based adaptive binary arithmetic coding (Context-based Adaptive Binary Arithmetic Coding, CABAC). For the input original video signal, a video coding block can be obtained by dividing the coding tree unit (CTU), and then the residual pixel information obtained after intra-frame or inter-frame prediction is transformed by the transformation and quantization unit 101 to transform the video coding block, including transforming the residual information from the pixel domain to the transform domain, and quantizing the obtained transform coefficients to further reduce the bit rate; the intra-frame estimation unit 102 and the intra-frame prediction unit 103 are used to perform intra-frame prediction on the video coding block; specifically, the intra-frame estimation unit 102 and the intra-frame prediction unit 103 are used to determine the intra-frame prediction mode to be used to encode the video coding block; the motion compensation unit 104 and the motion estimation unit 105 are used to perform inter-frame prediction coding of the received video coding block relative to one or more blocks in one or more reference frames to provide temporal prediction information; the motion estimation performed by the motion estimation unit 105 is a process of generating a motion vector, and the motion vector can estimate the motion of the video coding block, and then the motion compensation unit 104 is based on the motion vector obtained by the motion estimation unit 105. The motion vector determined by the motion estimation unit 105 performs motion compensation; after determining the intra-frame prediction mode, the intra-frame prediction unit 103 is also used to provide the selected intra-frame prediction data to the encoding unit 109, and the motion estimation unit 105 also sends the calculated and determined motion vector data to the encoding unit 109; in addition, the inverse transform and inverse quantization unit 106 is used to reconstruct the video coding block, reconstruct the residual block in the pixel domain, and the reconstructed residual block is removed by the filter control analysis unit 107 and the filtering unit 108. The block effect artifacts are then removed, and the reconstructed residual block is then added to a predictive block in the frame of the decoded image buffer unit 110 to generate a reconstructed video coding block; the encoding unit 109 is used to encode various coding parameters and quantized transform coefficients. In the CABAC-based coding algorithm, the context content can be based on adjacent coding blocks and can be used to encode information indicating the determined intra-frame prediction mode and output the code stream of the video signal; and the decoded image buffer unit 110 is used to store the reconstructed video coding block for prediction reference. As the video image encoding proceeds, new reconstructed video encoding blocks are continuously generated, and these reconstructed video encoding blocks are stored in the decoded image buffer unit 110 .

Refer to FIG3 , which shows a schematic block diagram of a decoder provided by an embodiment of the present application. As shown in FIG3 , the decoder 200 includes a decoding unit 201, an inverse transform and inverse quantization unit 202, an intra-frame prediction unit 203, a motion compensation unit 204, a filtering unit 205, and a decoded image cache unit 206, etc., wherein the decoding unit 201 can implement header information decoding and CABAC decoding, and the filtering unit 205 can implement deblocking filtering and SAO filtering. After the input video signal is encoded in FIG2 , the code of the video signal is output. The code stream is input into the decoder 200, and first passes through the decoding unit 201 to obtain the decoded transform coefficients; the transform coefficients are processed by the inverse transform and inverse quantization unit 202 to generate residual blocks in the pixel domain; the intra-frame prediction unit 203 can be used to generate prediction data for the current video decoding block based on the determined intra-frame prediction mode and the data from the previously decoded blocks of the current frame or picture; the motion compensation unit 204 determines the prediction information for the video decoding block by analyzing the motion vector and other associated syntax elements, and uses the prediction information to generate the video being decoded. The decoded video block is formed by summing the residual block from the inverse transform and inverse quantization unit 202 and the corresponding predictive block generated by the intra-frame prediction unit 203 or the motion compensation unit 204; the decoded video signal passes through the filtering unit 205 to remove the block effect artifacts, which can improve the video quality; and then the decoded video block is stored in the decoded image buffer unit 206, which stores the reference image for subsequent intra-frame prediction or motion compensation, and is also used for the output of the video signal, that is, the restored original video signal is obtained.

Further, the embodiment of the present application also provides a network architecture of a codec system including an encoder and a decoder, wherein FIG4 shows a schematic diagram of a network architecture of a codec system provided by an embodiment of the present application. As shown in FIG4, the network architecture includes one or more electronic devices 13 to 1N and a communication network 01, wherein the electronic devices 13 to 1N can perform video interaction through the communication network 01. The electronic device can be various types of devices with video codec functions during implementation, for example, the electronic device can include a smart phone, a tablet computer, a personal computer, a personal digital assistant, a navigator, a digital phone, a video phone, a television, a sensor device, a server, etc., and the embodiment of the present application is not specifically limited. Here, the decoder or encoder described in the embodiment of the present application can be the above-mentioned electronic device.

It should be noted that the method of the embodiment of the present application is mainly applied to the prediction part shown in Figure 4 and the prediction part shown in Figure 3. That is to say, the embodiment of the present application can be applied to both the encoder and the decoder, and can even be applied to both the encoder and the decoder at the same time, but the embodiment of the present application is not specifically limited. In addition, the prediction part here can include an intra-frame prediction part and an inter-frame prediction part.

It should also be noted that, at the encoding end, the "current block" specifically refers to the encoding block currently to be subjected to chroma prediction; at the decoding end, the "current block" specifically refers to the decoding block currently to be subjected to chroma prediction. Here, the current block can be a coding unit (Coding Unit, CU), a coding tree unit (Coding Tree Unit, CTU), or even a prediction unit (Prediction Unit, PU) or a transform unit (Transform Unit, TU), which is not specifically limited here.

To facilitate understanding of the technical solutions of the embodiments of the present application, the relevant technologies of the embodiments of the present application are described below. The following related technologies can be arbitrarily combined with the technical solutions of the embodiments of the present application as optional solutions, and they all belong to the protection scope of the embodiments of the present application.

1. Two-step cross-component prediction mode

Two-step cross-component prediction mode (TSCPM) is an inter-component prediction technology that removes inter-component redundancy by exploring the linear relationship between different components. TSCPM is performed in two steps, as shown in Figure 5. First, the luma block corresponding to the current chroma block to be encoded (i.e., the co-located luma reconstruction block) is used to generate a temporary prediction block of the same size (i.e., the intermediate predicted chroma block) through parameters α and β, and then down-sampled to obtain the predicted value of the chroma component (i.e., the final predicted chroma block) (Final Chroma Prediction Block). Among them, the co-located luma reconstruction block can be expressed as _RL (x, y), the intermediate predicted chroma block can be expressed as _P'c (x, y) = α* _RL (x, y) + β, and the final predicted chroma block can be expressed as _Pc (x, y).

1) Linear Model

In some embodiments, the values of the linear model parameters α and β are calculated by reconstructing the luminance reference sample and the corresponding chrominance reference sample of the previous reference row and the left reference column of the current coding block. The specific derivation process is as follows:

First, according to the availability of adjacent block pixels, we divide them into three cases to get four available pixel pairs. We calculate alpha and beta through the four available pixel pairs. After getting alpha and beta, we reconstruct the pixels with brightness to get the chromaticity prediction value according to the linear relationship between brightness and chromaticity.

In some embodiments, when selecting four pairs of available pixels, the availability of upper pixels and left pixels needs to be considered, which is divided into the following three cases:

Case 1: If both the upper and left pixels of the current block are "available", 2 pixel pairs are selected from the upper side and 2 pixel pairs are selected from the left side.

Case 2: If only the upper side of the current block is available, the four pixel pairs are all selected from the upper side, and the selected position widths are: 0/4, 1/4, 2/4, 3/4.

Case 3: If only left pixels are available in the current block, the four pixel pairs are all selected from the left side, and the selected positions are: 0/4, 1/4, 2/4, 3/4 of the height.

In some embodiments, it is assumed that the size of the chrominance block to be encoded is WxH, its width is W, and its height is H. The upper reference row and the left reference column are defined as row[i] (0<=i<=M-1) and col[j] (0<=j<=N-1), respectively. Then, the selection methods of the adjacent reference sample point x[k] (0<=k<=4) are as follows:

Case 1: When both row[i] and col[j] are "available":

● As shown in Figure 6a, when W = H: x[0] = row[0], x[1] = row[W-1], x[3] = col[0], x[4] = col[H-1];

● As shown in Figure 6b, when W>H: x[0]=row[0], x[1]=row[W-W/H], x[3]=col[0], x[4]=col[H-1];

●As shown in Figure 6c, when W<H: x[0]＝row[0], x[1]＝row[W-1], x[3]＝col[0], x[4]＝col[H-H/W].

Case 2: As shown in Figure 6d, when row[i] is "available" and col[j] is "unavailable":
x[0]=row[0], x[1]=row[W/4], x[3]=row[2×W/4], x[4]=row[3×W/4].

Case 3: As shown in Figure 6e, when row[i] is "unavailable" and col[j] is "available":
x[0]=col[0], x[1]=col[H/4], x[3]=col[2×H/4], x[4]=col[3×H/4].

In some embodiments, after acquiring four adjacent reference sample points, four quick comparisons are performed to obtain two points with larger brightness values and two points with smaller brightness values, and the mean points of these two groups are used to derive the linear model parameters. Assuming that the mean point value of the two points with larger brightness values is xMax, and the mean point value of the two points with smaller brightness values is xMin, similarly, the corresponding larger and smaller mean points of the corresponding chromaticity points can be obtained, represented by yMax and yMin respectively, then the value of α is (yMax-yMin)/(xMax-xMin), and the value of M is yMin-α*xMin. In the actual implementation process, the division method for calculating the value of α can be replaced by a lookup table method to reduce the implementation complexity, and a shift precision value shift is added to ensure the calculation accuracy.

In some embodiments, when both row[i] and col[j] are "unavailable", the default values are used, where the default value of α is 0 and the default value of β is 1<<(BitDepth-1), where BitDepth represents the bit depth value of the sample.

In some embodiments, according to the linear model parameters α and β, and the brightness reconstruction pixel value at the corresponding position, an intermediate prediction pixel block of the same size as the corresponding brightness block can be calculated. The calculation process can be shown by formula (1):
P _c ′(x,y)=α×R _L (x,y)+β (1)

In formula (1), (x, y) represents the coordinate position of the pixel point of the chrominance block to be encoded, _RL (x, y) represents the luminance reconstructed pixel value with the coordinate position (x, y) in the co-located luminance block corresponding to the chrominance block to be encoded, and _Pc ′(x, y) represents the pixel value of the intermediate prediction block.

In some embodiments, the intermediate predicted pixel value is downsampled, and a six-tap filter [1 2 1; 1 2 1] is used by default to downsample to obtain the predicted pixel value of the final chrominance block to be encoded. The calculation process can be shown by formula (2):
P _c (x,y)＝(2×P′ _c (2x,2y)+2×P′ _c (2x,2y+1)+P′ _c (2x-1,2y)+P′ _c (2x+1,2y)+
P′ _c (2x-1,2y+1)+P′ _c (2x+1,2y-1)+4)>>3 (2)

In formula (2), P _c (x, y) is the predicted pixel value of the chrominance block to be encoded.

2) Nonlinear Model

In some embodiments, the nonlinear cross-component model building process may include the following steps:

Step 1: downsample the brightness of the current block (co-located brightness block) and the adjacent template area to obtain downsampled brightness samples.

In some embodiments, the present application takes the sampling format of 4:2:0 as an example for explanation, and downsampling in the following generally refers to dividing the width and height by 2 to obtain downsampled brightness samples.

Step 2: Based on the neighboring templates, a cross-component prediction model of luminance (Y) and chrominance (U/V) is constructed.

In some embodiments, the template selection method of the neighboring block is shown in FIG7 , and the current chrominance block (shown as a white area in FIG7 ) is used as a reference: the upper left (i.e., area A), upper (i.e., area B), upper right (i.e., area C), left (i.e., area D), and lower left (i.e., area E) of the current block are selected to construct a template. Among them, the width of area C is equal to the width of the current block (i.e., W), and the height of area E is equal to the height of the current block (i.e., H); the template width θ is fixedly set to 6 here, and will be adaptively adjusted according to the availability of neighboring samples; when the lower right corner of area C (area E) is not reconstructed or exceeds the image boundary, area C (area E) is unavailable.

In some embodiments, as shown in Figure 8, the model of the cross-component nonlinear prediction model selects the target chrominance sample (i.e., C) of the current chrominance block, the associated position C in the downsampled luminance image, and the downsampled luminance samples around it, and the surrounding downsampled luminance samples include: the sample above the associated position C (i.e., N), the sample below the associated position C (i.e., S), the sample to the left of the associated position C (i.e., W), and the sample to the right of the associated position C (i.e., E).

In some embodiments, in order to reduce the complexity of template calculation, only some sample points in the template area are selected for calculation of the cross-component nonlinear prediction model. Specifically, only sample points whose horizontal coordinates and vertical coordinates in the template area meet the following constraints are selected, that is, sample points whose horizontal coordinates and vertical coordinates are not odd numbers. The above process can be expressed as:! (x%2==1&&y%2==1).

In some embodiments, multiple equations are constructed to solve the linear equations to obtain the model parameters of the cross-component nonlinear prediction model. The model is solved using the LDL solution method, and the entire process uses an integer calculation process.

Step 3: Based on the cross-component model, the downsampled luminance samples corresponding to the current block in step 1 are input to obtain the predicted value of chrominance (U/V).

2. Intra Block Copy (IBC)

In some embodiments, for screen content sequences such as text and graphics, there are many repeated textures in the same frame, that is, there is a strong spatial correlation. If the encoded block of the current frame can be referenced when encoding the current block, the encoding efficiency can be greatly improved in view of the strong spatial correlation of the screen image. This technology of referring to the encoded block of the current frame and using it for the prediction value of the current block is called IBC technology. IBC is similar to inter-frame image prediction, except that the prediction block of IBC is generated by the reconstructed block of the current encoded image frame. As shown in Figure 9, In the Coding Tree Unit (CTU), the white block on the lower right is the current Coding Unit (CU), and the coded white block on the upper left is the Predictor Block (PB). The current CU is similar to the prediction block. If the position of the upper left white block is found by searching at the encoder, only the position vectors (Block Vector, BV) of the two blocks (i.e., reference motion vectors) need to be transmitted. The decoder can obtain a more accurate prediction value through this information. Compared with the ordinary intra-frame prediction method, IBC can make better use of the redundant information within the frame, thereby improving the coding performance.

In some embodiments, a reference (Candidate) matching the current block is found through a hash search or a full search within a maximum range of 64*64.

In some embodiments, the hash search range is limited to the current CTU and the n CTUs to the left of the current CTU, where n varies according to the CTU size. If the CTU size is 128*128, then n is 1.

In some embodiments, the maximum allowed IBC size in the bitstream is 64*64, but the encoder currently only searches for blocks of 16*16 or less for acceleration.

In some embodiments, bv is transmitted with integer pixel precision, without prediction of bvp.

In some embodiments, the IBC mode only supports PB of 2N*2N, but the TB size can be N*N or 2N*2N.

In some embodiments, because 2*N blocks are not allowed in AVS3, the Luma block and Chroma block are divided differently in some small blocks. If such division inconsistency occurs, the Chroma block is consistently restricted to intra mode.

In some embodiments, if bv is an odd number, then for 420yuv, chroma pixels need to be interpolated, using 1:1 2tap interpolation.

3. Chroma block copy intra prediction mode

In some embodiments, the chroma block copy intra prediction mode is a chroma intra prediction mode. AVS allows the use of a block partitioning structure of a local dual tree, which allows the luminance block and the chroma block to have different partitioning structures. Currently, the minimum length or width of the luminance block and the chroma block is at least 4 pixels. When the coding unit performs block partitioning, if the block size after the partition is less than the minimum value, the partitioning will not be performed. Therefore, it may occur that the chroma block has stopped partitioning while the luminance block continues to be partitioned. Under this block partitioning structure, the luminance block and the chroma block will be encoded separately. In this case, the chroma block is restricted to using only the intra prediction mode. In order to solve the problem that the IBC technology cannot be used for specific chroma blocks, an IBC prediction scheme specifically for chroma is proposed. Under this scheme, the chroma block can directly use the block vector or string vector of the luminance co-located block for motion compensation, without the need for additional motion estimation, and the final chroma prediction value is obtained by copying the chroma reconstruction value pointed to by the block motion vector.

In some embodiments, the process of chroma block copy intra prediction mode includes the following steps:

Step 1, as shown in Figure 10, if the luminance sample located at the position {C, TL, TR, BL, BR} on the luminance co-located block corresponding to the CU of the chrominance block is a block copy intra-frame prediction mode or a normal string sub-mode of string copy intra-frame prediction, then the current block can use the chrominance block copy mode, where C represents the middle position, TL represents the upper left position, TR represents the upper right position, BL represents the lower position, and BR represents the lower right position.

Step 2: If the luma sample has an available displacement vector, the chroma block uses the displacement vector for motion compensation.

Step 3: Otherwise, if there is at least one available displacement vector among the default displacement vectors {(-w, 0), (0, -h)}, use the first available displacement vector for motion compensation.

Step 4: Otherwise, if there is no available displacement vector, the prediction values of all samples of the current chroma block are set to 2 ^BitDepth-1 , where BitDepth is the coding sample precision.

Step 5: The chroma block encodes a flag cibc_flag in the bitstream to indicate whether to use the chroma block copy intra prediction mode.

In the prior art, when the TSCPM technology is performing cross-component linear model derivation, only the reconstructed pixels in one row and one column adjacent to the current block are used as the model derivation information source, which cannot flexibly cope with various complex encoding scenarios. As a result, the current TSCPM cannot flexibly cope with more complex encoding and decoding scenarios, thereby reducing the encoding and decoding efficiency of the chrominance block.

Based on this, an embodiment of the present application provides a coding and decoding method, a bit stream, an encoder, a decoder and a storage medium. At the decoding end, the bit stream is parsed to determine the first syntax identification information; when the first syntax identification information indicates that the current chroma block adopts a cross-component prediction mode based on the chroma intra-frame block copy technology, a reference motion vector is determined according to the current co-located luminance block corresponding to the current chroma block; when the reference motion vector is valid, a cross-component prediction model is determined based on the reference luminance block and the reference chroma block corresponding to the reference motion vector; based on the cross-component prediction model, a predicted chroma value of the predicted chroma block is determined; according to the predicted chroma value of the predicted chroma block, a reconstructed chroma value of the current chroma block is determined. At the encoding end, a reference motion vector is determined based on the current co-located luminance block corresponding to the current chrominance block; when the reference motion vector is valid, a cross-component prediction model is determined based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector; based on the cross-component prediction model, a predicted chrominance value of the predicted chrominance block is determined, and first syntax identification information is determined based on the predicted chrominance value; wherein the first syntax identification information is used to indicate whether the current chrominance block adopts a cross-component prediction mode based on the chrominance intra-frame block copy technology; based on the predicted chrominance value of the predicted chrominance block, a reconstructed chrominance value of the current chrominance block is determined. Since the cross-component prediction model is determined by the reference luminance block and the reference chrominance block corresponding to the reference motion vector, compared with the cross-component prediction model derived from the reconstructed pixels of the adjacent row and column of the current chrominance block, the flexibility and diversity of determining the cross-component prediction model can be improved, so that the cross-component prediction model can flexibly cope with more complex encoding and decoding scenarios, thereby improving the encoding and decoding efficiency of the current chrominance block.

The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

FIG. 11 is a schematic flow chart of an optional decoding method provided in an embodiment of the present application. As shown in FIG. 11 , the method may include S301 to S305:

S301: parse a bitstream to determine first syntax identification information.

It should be noted that the decoding method of the embodiment of the present application is applied to a decoder. In addition, the decoding method may specifically refer to a chrominance prediction method. Among them, in the chrominance prediction mode, this is mainly a technical improvement for a chrominance prediction mode, more specifically, it may be a cross-component prediction mode based on chrominance intra-frame block copy technology in the prediction mode, so as to avoid the problem that TSCPM in the related art cannot flexibly cope with more complex encoding and decoding scenarios, thereby reducing the encoding and decoding efficiency of the chrominance block.

In the embodiment of the present application, the decoder determines the first syntax identification information by parsing the bitstream, wherein the first syntax identification information is used to indicate whether the current chroma block adopts the cross-component prediction mode based on the chroma intra-frame block copy technology.

In the embodiment of the present application, the implementation of parsing the bitstream in S301 and determining the first syntax identification information may include the following two situations:

Case 1: In some embodiments of the present application, the implementation before S301 may include: parsing the code stream to determine the second syntax identification information;

When the second syntax identification information indicates that the current chroma block does not adopt the chroma intra block copy prediction mode, the step of parsing the code stream to obtain the first syntax identification information is performed.

In some embodiments of the present application, parsing the code stream and determining the implementation of the second syntax identification information may include:

If the value of the second syntax identification information is the first value, it is determined that the current chroma block adopts the chroma intra block copy prediction mode; or,

If the value of the second syntax identification information is the second value, it is determined that the current chroma block does not adopt the chroma intra block copy prediction mode.

Exemplarily, the second syntax identification information may be represented as cibc_flag.

It should be noted that, in the embodiment of the present application, the first value is different from the second value, and the first value and the second value can be in parameter form or in digital form. Specifically, the second syntax identification information can be a parameter written in the profile or a flag value, which is not specifically limited here.

Exemplarily, for the first value and the second value, the first value can be set to 1 and the second value can be set to 0; or, the first value can be set to 0 and the second value can be set to 1; or, the first value can be set to true and the second value can be set to false; or, the first value can be set to false and the second value can be set to true; but this is not specifically limited here.

In the embodiment of the present application, taking the flag written into the bitstream as an example, assuming that the first value is set to 1 (true) and the second value is set to 0 (false), if the value of the second syntax identification information is 0 (false), then it can be determined that the current chroma block adopts the chroma intra-frame block copy prediction mode, that is, there is no need to execute the decoding method described in the embodiment of the present application; if the value of the second syntax identification information is 1 (true), then it can be determined that the current chroma block does not adopt the chroma intra-frame block copy prediction mode, that is, it may be necessary to execute the decoding method described in the embodiment of the present application.

It can be understood that, when the value of the second syntax identification information is the first value, it is determined that the current chroma block adopts the chroma intra-frame block copy prediction mode, and redundant information is reduced by intra-frame block copying, thereby achieving a compression effect. When the value of the second syntax identification information is the second value, it is determined that the current chroma block does not adopt the chroma intra-frame block copy prediction mode, which can avoid or limit the use of chroma intra-frame block copying, improve decoding stability, or avoid performance problems in some specific situations.

In some embodiments of the present application, for situation 1, the implementation of parsing the code stream in S301 and determining the first syntax identification information may include:

If the value of the first syntax identification information is the third value, it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology; or,

If the value of the first syntax identification information is the fourth value, it is determined that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra block copy technology.

Exemplarily, the first syntax identification information may be represented as tcibc_flag.

It should be noted that, in the embodiment of the present application, the third value is different from the fourth value, and the third value and the fourth value can be in parameter form or in digital form. Specifically, the first syntax identification information can be a parameter written in the profile or a flag value, which is not specifically limited here.

Exemplarily, for the third value and the fourth value, the third value can be set to 1 and the fourth value can be set to 0; or, the third value can be set to 0 and the fourth value can be set to 1; or, the third value can be set to true and the fourth value can be set to false; or, the third value can be set to false and the fourth value can be set to true; but this is not specifically limited here.

In an embodiment of the present application, taking the flag written into the bitstream as an example, assuming that the third value is set to 1 (true) and the fourth value is set to 0 (false), if the value of the second syntax identification information is 0 (false), then it can be determined that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra-frame block copy technology, that is, there is no need to execute the decoding method described in the embodiment of the present application; if the value of the first syntax identification information is 1 (true), then it can be determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra-frame block copy technology, that is, it is necessary to execute the decoding method described in the embodiment of the present application.

In the embodiment of the present application, the first syntax identification information plays the role of a switch, that is, when the first syntax identification information is the first value (for example, 1 or true), it indicates that the decoding algorithm described in the embodiment of the present application is not started, that is, the decoding algorithm described in the embodiment of the present application is not executed; when the first syntax identification information is a second value (such as 0 or false), it indicates that the decoding algorithm described in the embodiment of the present application is started, that is, the decoding algorithm described in the embodiment of the present application is executed.

Case 2: The implementation before S301 may include: parsing the code stream to determine the third syntax identification information;

When the third syntax identification information indicates that the current chroma block adopts the chroma intra block copy prediction mode or the cross-component prediction mode based on the chroma intra block copy technology, the step of parsing the code stream to obtain the first syntax identification information is performed.

In some embodiments of the present application, parsing the code stream and determining the third syntax identification information may include:

If the value of the third syntax identification information is the fifth value, it is determined that the current chroma block adopts the chroma intra block copy prediction mode or the cross-component prediction mode based on the chroma intra block copy technology; or,

If the value of the third syntax identification information is the sixth value, it is determined that the current chroma block does not adopt the chroma intra block copy prediction mode or the cross-component prediction mode based on the chroma intra block copy technology.

Exemplarily, the third syntax identification information may be represented as cibc_flag.

It should be noted that, in the embodiment of the present application, the fifth value is different from the sixth value, and the fifth value and the sixth value can be in parameter form or in digital form. Specifically, the second syntax identification information can be a parameter written in the profile or a flag value, which is not specifically limited here.

Exemplarily, for the fifth value and the sixth value, the fifth value can be set to 1 and the sixth value can be set to 0; or, the fifth value can be set to 0 and the sixth value can be set to 1; or, the fifth value can be set to true and the sixth value can be set to false; or, the fifth value can be set to false and the sixth value can be set to true; but no specific limitation is made here.

In the embodiment of the present application, taking the flag written into the bitstream as an example, assuming that the fifth value is set to 1 (true) and the sixth value is set to 0 (false), if the value of the third syntax identification information is 0 (false), then it can be determined that the current chroma block does not adopt the chroma intra-frame block copy prediction mode or the cross-component prediction mode based on the chroma intra-frame block copy technology, that is, there is no need to execute the decoding method described in the embodiment of the present application; if the value of the second syntax identification information is 1 (true), then it can be determined that the current chroma block adopts the chroma intra-frame block copy prediction mode or the cross-component prediction mode based on the chroma intra-frame block copy technology, that is, it may be necessary to execute the decoding method described in the embodiment of the present application.

In some embodiments of the present application, for situation 2, the implementation of parsing the code stream in S301 and determining the first syntax identification information may include:

If the value of the first syntax identification information is the seventh value, it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology; or

If the value of the first syntax identification information is the eighth value, it is determined that the current chroma block adopts the chroma intra block copy prediction mode.

Exemplarily, the first syntax identification information may be represented as tcibc_flag.

It should be noted that, in the embodiment of the present application, the seventh value is different from the eighth value, and the seventh value and the eighth value can be in parameter form or in digital form. Specifically, the first syntax identification information can be a parameter written in the profile or a flag value, which is not specifically limited here.

Exemplarily, for the seventh value and the eighth value, the seventh value can be set to 1 and the eighth value can be set to 0; or, the seventh value can be set to 0 and the eighth value can be set to 1; or, the seventh value can be set to true and the eighth value can be set to false; or, the seventh value can be set to false and the eighth value can be set to true; but no specific limitation is made here.

In an embodiment of the present application, taking the flag written into the bitstream as an example, assuming that the seventh value is set to 1 (true) and the eighth value is set to 0 (false), if the value of the second syntax identification information is 0 (false), then it can be determined that the current chroma block adopts the chroma intra-frame block copy prediction mode, that is, there is no need to execute the decoding method described in the embodiment of the present application; if the value of the first syntax identification information is 1 (true), then it can be determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra-frame block copy technology, that is, it is necessary to execute the decoding method described in the embodiment of the present application.

In the embodiment of the present application, the first grammar identification information acts as a switch, that is, when the first grammar identification information is a first value (such as 1 or true), it indicates that the decoding algorithm described in the embodiment of the present application is not started, that is, the decoding algorithm described in the embodiment of the present application is not executed; when the first grammar identification information is a second value (such as 0 or false), it indicates that the decoding algorithm described in the embodiment of the present application is started, that is, the decoding algorithm described in the embodiment of the present application is executed.

It should be noted that the first value, the second value, the third value, the fourth value, the fifth value, the sixth value, the seventh value and the eighth value may be expressed in the same form (i.e., parameter form or digital form). For example, the first value, the third value, the fifth value and the seventh value may be 1 or True, and the second value, the fourth value, the sixth value and the eighth value may be 0 or False.

S302: When the first syntax identification information indicates that the current chroma block adopts a cross-component prediction mode based on the chroma intra block copy technology, determine a reference motion vector according to a current co-located luminance block corresponding to the current chroma block.

In the embodiment of the present application, the current chroma block is also called the current block, the current block to be decoded, the current chroma block to be decoded, the block to be decoded, the chroma block to be decoded, etc., and the embodiment of the present application does not impose any limitation on this.

In the embodiment of the present application, when the value of the first syntax identification information is 1 or True, it is determined that the current chrominance block adopts the Cross-component prediction mode for chroma intra block copy technique.

In the embodiment of the present application, the co-located luminance block refers to a luminance block corresponding to the current chrominance block. For example, in the YCbCr color space, for each chrominance block (Cb or Cr block), there is a luminance block in the same position or relative position, and this luminance block is called the co-located luminance block.

In an embodiment of the present application, there is a co-location relationship between the chrominance block and the brightness block. Exemplarily, in the YCbCr color space, the image is divided into a brightness component (Y) and two chrominance components (Cb, Cr). The brightness component (Y) contains the black and white information of the image, while the chrominance components (Cb, Cr) contain color information. The sampling rate of the chrominance component is usually lower than that of the brightness component, which means that for each brightness block, there may be multiple chrominance blocks. For each chrominance block, there is a co-location brightness block, which means that they have the same position or a certain relative position relationship in the image. Usually, the size of the brightness block is larger than the size of the chrominance block. For example, a brightness block may correspond to a 4x4 or 8x8 pixel block, while the chrominance block may correspond to a smaller 2x2 or 4x4 pixel block.

In the embodiment of the present application, the reference motion vector is used to predict the motion information of the current image block. Generally, the current co-located luminance block corresponding to the current chrominance block has the same motion vector. The obtained motion vector is applied to the current chrominance block to predict the position of the current chrominance block. This prediction process helps to reduce the residual caused by motion and improve decoding efficiency.

S303: When the reference motion vector is valid, determine a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector.

In the embodiment of the present application, as shown in FIG12a, it shows the reference luminance block (Ref Luma) corresponding to the reference motion vector for the collocated luminance block (Col-Luma) corresponding to the current chrominance block (Current Block) under the luminance channel (Luma Channel). As shown in FIG12b, it shows the reference chrominance block (Ref Chroma) corresponding to the reference motion vector for the current chrominance block under the chrominance channel (Chroma Channel).

In the embodiment of the present application, whether the reference motion vector is valid can be determined from the following aspects:

1) Range of reference motion vector:

In the embodiment of the present application, the reference motion vector is an integer value in pixels. For example, the range of motion vectors specified by the H.264 standard is a specific number of pixels, usually with upper and lower limits in the horizontal and vertical directions. At the decoding end, it is necessary to check whether the decoded motion vector is within the specified range. If the value of the motion vector exceeds the specified range, it may indicate that the reference motion vector is invalid.

2) Reference motion vector flag:

In the embodiment of the present application, there may be a flag or a special mark in the bitstream to indicate whether the motion vector of the current block is valid. This flag is usually included in the header information of the block. At the decoding end, the decoder will check this flag. If the flag indicates that the motion vector is invalid, the decoder will not use the vector for motion compensation.

3) Availability of the reference frame corresponding to the reference motion vector:

Motion vectors are usually relative to a reference frame. At the decoding end, it is necessary to ensure that the reference frame corresponding to the reference motion vector is available, that is, it has been decoded or is already in the cache. If the reference frame is not available, the motion vector cannot be correctly applied to the current frame. If the reference frame is not available, the decoder may need to adopt some error handling strategies, such as skipping motion compensation for the current block or using other strategies for intra-frame prediction.

In some embodiments of the present application, the invalidity (unavailable) here may specifically refer to:

1) Not reconstructed, that is, the reference luminance block and the reference chrominance block (also referred to as the template area of the current chrominance block mentioned above) are not reconstructed, but usually, the area above and to the left of the current chrominance block (i.e., the template area), or the reference luminance block and the reference chrominance block have been reconstructed;

2) Out of bounds, that is, the original image does not exist or the hardware device exceeds the range of pixels that can be obtained;

3) The condition setting is not met. Generally, some specially designed modes only allow the current block to use the pixels in the left template or only allow the current block to use the pixels in the upper template.

It can be understood that the above-mentioned influencing factors for determining whether the reference motion vector is valid are only examples, and other influencing factors may also be included in actual application scenarios, and the embodiments of the present application do not impose any limitation on this.

In some embodiments of the present application, when the reference motion vector satisfies at least one of the following conditions: the reference luminance block or the reference chrominance block corresponding to the reference motion vector has not been reconstructed, the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector does not match, and the reference motion vector is out of bounds, the reference motion vector is determined to be invalid; or,

The reference motion vector is determined to be valid when the reference motion vector satisfies that the reference luminance block or reference chrominance block corresponding to the reference motion vector has been reconstructed, the prediction mode of the reference luminance block or reference chrominance block corresponding to the reference motion vector matches, and the reference motion vector does not cross the boundary.

In the embodiment of the present application, the implementation of determining whether the reference motion vector is valid may include the following steps:

Step 1: Check whether the reference luminance block or reference chrominance block corresponding to the reference motion vector has been reconstructed.

In the embodiment of the present application, at the decoding end, the reference block may not be reconstructed because the corresponding block in the reference frame has not been completely decoded, or the decoder has not completed decoding of the reference frame. In this case, the decoder may need to wait for the reference block to be completely reconstructed, or use some Error handling mechanism. For example, you can choose to skip motion compensation for the current block and temporarily use other methods to fill or interpolate to prevent errors caused by incomplete decoding.

Step 2: Check whether the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector matches.

In the embodiments of the present application, the reference block may use a prediction mode that does not match the current block. This may occur in intra-frame prediction, where the reference block may use a different prediction mode. At this time, the decoder may need to detect and correct the prediction mode mismatch, which may involve trying to adjust the prediction mode of the reference block according to the prediction mode of the current block, or performing other error recovery strategies.

Step 3: Check whether the reference motion vector is out of bounds.

In the embodiment of the present application, the value of the reference motion vector may exceed the specified range, which may be caused by a coding error, a transmission error or other abnormal situation. At the decoding end, it is necessary to detect and handle the out-of-bounds situation. Possible processing methods include clipping the value of the motion vector to keep it within the valid range, or using other error handling methods.

It is understandable that the above steps are to ensure the legitimacy of the reference motion vector and prevent erroneous or invalid reference motion vectors from affecting the decoding quality. The decoder ensures the accuracy and robustness of decoding by detecting and processing these situations, thereby improving the reliability of video decoding.

S304: Determine a predicted chrominance value of the predicted chrominance block based on the cross-component prediction model.

In the embodiment of the present application, the cross-component prediction model characterizes that the reconstructed luminance value of the current co-located luminance block corresponding to the current chrominance block has a relationship with the predicted chrominance value of the predicted chrominance block.

In some embodiments of the present application, the cross-component prediction model characterizes that the reconstructed luminance value of the current co-located luminance block corresponding to the current chrominance block has a linear or nonlinear relationship with the predicted chrominance value of the predicted chrominance block.

It should be noted that the linear cross-component prediction model can improve decoding efficiency and remove the redundancy of the chrominance component, so that the model can better fit the relationship between brightness and chrominance in actual scenes. By using a linear cross-component prediction model, the decoder can more accurately estimate the value of the chrominance component, thereby achieving better compression effect during the decoding process, which is beneficial to improving the performance and quality of video decoding.

In the embodiments of the present application, although the linear relationship can effectively capture the relationship between the same-position luminance block and the predicted chrominance block in many cases, there may sometimes be some nonlinear relationships. In order to more accurately model the nonlinear relationship, a more complex nonlinear model may also be used. In general, whether to use a linear or nonlinear relationship model depends on the actual coding standard, application scenario, and optimization requirements. Linear models are usually simpler, but in some cases may not be sufficient to accurately express complex relationships. Nonlinear models are more flexible, but usually require more computing resources.

In some embodiments of the present application, the decoding method further includes S306:

S306: When the reference motion vector is invalid, determine the predicted chroma value of the predicted chroma block according to the sample accuracy of the current chroma block.

In an embodiment of the present application, the sample accuracy of the current chrominance block refers to the representation accuracy of the chrominance component (Chroma), which is usually expressed in bits (Bit-Depth), and a higher sample accuracy is usually used to retain the details and color information in the image. For example, 8-bit sample accuracy means that each chrominance component is represented by 8 binary bits (or bits). In this way, each chrominance component can have 2^8=256 different discrete levels. These levels correspond to color changes, so higher sample accuracy means that more color details can be represented. Higher sample accuracy can provide more color levels, thereby improving color resolution. This is very important for retaining subtle color differences in images. High sample accuracy helps to more accurately represent colors in the real world and improve color fidelity. Selecting an appropriate sample accuracy also involves a balance in coding efficiency. Higher sample accuracy may require more bits to represent each pixel, thereby increasing the amount of encoded data.

In the embodiment of the present application, the sample accuracy of the current chroma block can be expressed as BitDepth.

In the embodiment of the present application, the sample accuracy of the current chroma block may include the following:

1) 8-bit sample accuracy: Each component is represented by 8 bits. This is the most common sample accuracy, widely used in many real-time video transmission and storage applications, providing 256 different brightness or chrominance levels.

2) 10-bit sample precision: Each component is represented using 10 bits, which provides higher precision than 8-bit sample precision and allows the representation of 1024 different brightness or chrominance levels, which is often used in some professional video and film production.

3) 12-bit sample accuracy: Each component is represented by 12 bits, which can provide higher accuracy and allow 4096 different brightness or chromaticity levels to be represented. This is usually used in professional fields and for special needs.

4) 16-bit sample accuracy: Each component is represented by 16 bits, which can provide very high accuracy and allow the representation of 65536 different brightness or chromaticity levels. This is usually used in special application areas such as medical imaging, which require extremely high image accuracy.

It should be noted that the sample accuracy listed above is only an example, and different sample accuracy is suitable for different application scenarios. Higher sample accuracy can usually provide richer color details and image quality, but also requires more storage space and transmission bandwidth. When selecting sample accuracy, it is necessary to balance image quality and data transmission efficiency according to the needs of specific applications. The embodiment of the present application does not impose any restrictions on sample accuracy, and it can be selected according to the actual scenario.

In some embodiments of the present application, in S306, the predicted chroma value of the predicted chroma block is determined according to the sample accuracy of the current chroma block. Implementation may include S3061 to S3062:

S3061. Perform a subtraction operation on the sample accuracy and the first preset value to obtain a fourth intermediate parameter.

S3062. Perform an exponential operation on the second preset value and the fourth intermediate parameter to obtain a predicted chromaticity value of each pixel in the predicted chromaticity block.

In the embodiment of the present application, the first preset value and the second preset value are pre-set values. For example, the first preset value is 1 and the second preset value is 2.

In the embodiment of the present application, the fourth intermediate parameter can be expressed as BitDepth-1.

In the embodiment of the present application, the predicted chrominance value of each pixel in the predicted chrominance block can be expressed as 2 ^BitDepth-1 .

It can be understood that the predicted chrominance value of each pixel in the predicted chrominance block is generated through sample precision, preset value and exponential operation. By adjusting the sample precision and different preset values, different predicted chrominance values can be explored, thereby providing more flexible adjustment and optimization options in video encoding, which helps to better adapt to different application scenarios and requirements in video decoding.

S305 . Determine a reconstructed chrominance value of a current chrominance block according to the predicted chrominance value of the predicted chrominance block.

In some embodiments of the present application, the implementation of determining the reconstructed chroma value of the current chroma block according to the predicted chroma value of the predicted chroma block in S305 may include S3051 to S3053:

S3051, parsing the bit stream to obtain the chroma residual value of the current chroma block;

S3052, performing inverse transformation and inverse quantization on the chroma residual value to obtain an inverse quantized chroma residual value of the current chroma block;

S3053. Determine the reconstructed chroma value of the current chroma block according to the inverse quantized chroma residual value and the predicted chroma value.

In the embodiment of the present application, the chrominance residual value represents the difference between the current chrominance block and the predicted value. These residual values are usually encoded and stored in the bit stream, and parsing the bit stream is to extract these residual values from the bit stream.

In the embodiment of the present application, the chrominance residual value may have been transformed and quantized, and in order to obtain the actual residual value, it is necessary to perform inverse transformation and inverse quantization. The purpose of this step is to restore the encoded residual value to the original difference value.

In the embodiment of the present application, the reconstructed chrominance value of the current chrominance block is obtained by adding the inverse quantized residual value to the predicted chrominance value. This is the last step of chrominance block reconstruction, and the obtained reconstructed chrominance value will be used to construct the final image frame.

It can be understood that, on the one hand, the inverse quantization and inverse transformation process helps to accurately restore the original chrominance residual information at the decoding end. This helps to improve the compression ratio of the video, that is, to reduce the file size while maintaining the image quality. The inverse quantization and inverse transformation process helps to minimize the distortion introduced by the encoding. On the one hand, by correctly restoring the residual information at the decoding end, the original image can be restored more accurately and the image quality can be improved. On the one hand, the above process is intended to minimize the computational complexity in the encoding and decoding process while maintaining the image quality, which helps to improve the efficiency of encoding and decoding.

In an embodiment of the present application, a decoding method is provided, the method comprising: at a decoding end, parsing a bitstream to determine first syntax identification information; when the first syntax identification information indicates that the current chroma block adopts a cross-component prediction mode based on a chroma intra-frame block copying technology, determining a reference motion vector according to a current co-located luminance block corresponding to the current chroma block; when the reference motion vector is valid, determining a cross-component prediction model based on a reference luminance block and a reference chroma block corresponding to the reference motion vector; determining a predicted chroma value of the predicted chroma block based on the cross-component prediction model; and determining a reconstructed chroma value of the current chroma block according to the predicted chroma value of the predicted chroma block. . Since the cross-component prediction model is determined by the reference luminance block and the reference chroma block corresponding to the reference motion vector, compared with the cross-component prediction model derived from the reconstructed pixels of an adjacent row and column of the current chroma block, the flexibility and diversity of determining the cross-component prediction model can be improved, so that the cross-component prediction model can flexibly cope with more complex encoding and decoding scenarios, thereby improving the encoding and decoding efficiency of the current chroma block.

It can be understood that, on the one hand, the reference motion vector is determined according to the current co-located luminance block corresponding to the current chrominance block. This step helps to introduce the information of the luminance block into the decoding process of the chrominance block to improve the accurate processing of motion correlation. On the one hand, based on the cross-component prediction model, the predicted chrominance value of the predicted chrominance block is determined, which makes full use of the information of the luminance block, helps to improve the prediction accuracy of the chrominance block, and helps to more accurately restore the chrominance information in the original image at the decoding end, thereby improving the image quality. In general, the above process can improve the decoding accuracy of the chrominance block, enhance the image quality, and utilize cross-component correlation. By introducing the information of the luminance block, the decoding process more comprehensively utilizes the association between different components in the video image, thereby improving the decoding effect.

In some embodiments of the present application, the implementation of determining the reference motion vector according to the current co-located luminance block corresponding to the current chrominance block in S302 may include S401:

S401: Determine candidate reference samples that meet a preset prediction mode in a current co-located luminance block, and use motion vectors corresponding to the candidate reference samples as reference motion vectors.

In some embodiments of the present application, the preset prediction mode is: the candidate reference samples adopt the block copy intra prediction mode (Intra Block Copy, IBC) or the ordinary string mode of string copy intra prediction.

In an embodiment of the present application, the decoder determines candidate reference samples that satisfy the block copy intra prediction mode or the common string sub-mode of string copy intra prediction in the current co-located luminance block, and uses the motion vector corresponding to the candidate reference sample as the reference motion vector.

In the embodiment of the present application, by parsing the corresponding syntax elements or identification information in the video bitstream, the decoder determines whether the current block adopts the block copy intra prediction mode or the common string sub-mode of the string copy intra prediction. If the current block adopts the block copy intra prediction mode or the common string sub-mode of the string copy intra prediction, the decoder will obtain the corresponding prediction mode parameters, which may include the direction of the block copy (horizontal or vertical) or the direction of the string mode. According to the prediction mode parameters, candidate reference samples satisfying the block copy intra prediction mode or the common string mode of the string copy intra prediction are determined in the current co-located luminance block. For the determined candidate reference samples, their corresponding motion vectors are used as reference motion vectors.

It is understandable that the purpose of the above process is to accurately describe the relationship between the current block and the blocks in the reference frame during the decoding process to improve the accuracy of the prediction. By determining the candidate reference samples and the corresponding motion vectors, the decoder can better restore the content of the current block and achieve better image quality.

In the embodiment of the present application, in the block copy intra prediction mode (IBC), the prediction value of the current block is directly copied from the coded block in the adjacent area. This means that the content of the current block is similar to the coded block adjacent to it, so the prediction can be performed by directly copying the pixel values of the adjacent block. This method can effectively improve the accuracy of the prediction in some cases.

In the embodiment of the present application, the ordinary string sub-mode of the string copy intra prediction is an intra prediction mode, which involves the copy relationship between the pixel values in the current block and the pixel values in the adjacent blocks. In this mode, the generation of the prediction value involves the copying of the pixel values of the adjacent blocks, usually from left to right or from top to bottom, to form a "string". This method can be used for some linear or regular patterns.

It should be noted that both the block copy intra prediction mode and the common string sub-mode of string copy intra prediction are designed for prediction within a frame. By copying the pixel values in the encoded block, a simple and effective prediction method based on adjacent blocks is provided. The block copy intra prediction mode mainly emphasizes the copying of the entire block, while the common string sub-mode of string copy intra prediction emphasizes the orderly concatenation of pixel values. The choice of which mode to use usually depends on the decoding standard and the specific image content. These intra prediction modes help improve the efficiency of video decoding and reduce the amount of data, thereby achieving better compression performance.

In some embodiments of the present application, the cross-component prediction model is a linear model; determining the implementation of the cross-component prediction model based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector in S303 may include S3031 to S3032:

S3031. Determine at least two reference luminance samples in a reference luminance block according to a preset sample selection method, and determine reference chrominance samples corresponding to the at least two reference luminance samples in a reference chrominance block according to a preset sample selection method.

In the embodiments of the present application, the preset sample point selection method is usually based on certain rules or algorithms, such as uniform distribution within a block, selection in a specific direction, and the like.

In the embodiment of the present application, for each reference luminance sample determined in the reference luminance block, a reference chrominance sample corresponding thereto is found according to the chrominance sampling structure (such as 4:2:0 or 4:4:4). If the sampling structure of the chrominance block is 4:2:0, the corresponding reference chrominance samples may be at adjacent positions in the horizontal and vertical directions.

It can be understood that selecting at least two reference luminance sampling points and at least two reference luminance samples according to a preset sampling point selection method helps to establish a relationship between luminance and chrominance, thereby improving the accuracy of intra-frame prediction.

In some embodiments of the present application, the preset sample point selection method includes any one of the following: a center selection method, a vertical selection method, a horizontal selection method, a diagonal selection method, and a vertex selection method.

In the embodiment of the present application, as shown in FIG13a, in the center selection method, the center position of the reference chromaticity block is first determined, and the center position may be calculated by the midpoint of the width and height of the block, and then the center position is selected as the reference chromaticity sample point. Further, according to the reference chromaticity sample point in the reference chromaticity block, the corresponding reference luminance sample point is determined in the reference luminance block.

In the embodiment of the present application, as shown in FIG. 13b , in the vertical selection mode, the reference chromaticity sample is determined by the vertical center line (e.g., the leftmost line) of the reference chromaticity block. The position of the vertical center line is usually obtained by combining half of the height of the block and the left edge of the block. Then, according to the reference chromaticity sample in the reference chromaticity block, the corresponding reference luminance sample is determined in the reference luminance block.

In the embodiment of the present application, as shown in FIG13c, in the horizontal selection mode, the reference chromaticity sample is determined by the horizontal center line of the reference chromaticity block. The position of the horizontal center line is usually obtained by combining half of the width of the reference chromaticity block and the top boundary of the block. Then, according to the reference chromaticity sample in the reference chromaticity block, the corresponding reference luminance sample is determined in the reference luminance block.

In the embodiment of the present application, as shown in FIG. 13d , in the diagonal selection method, the reference chromaticity sample is determined by the diagonal of the upper left corner and the lower right corner of the reference chromaticity block. It is usually calculated by the diagonal midpoint of the width and height of the reference chromaticity sample. Then, according to the reference chromaticity sample in the reference chromaticity block, the corresponding reference luminance sample is determined in the reference luminance block.

In an embodiment of the present application, as shown in FIG. 13e , in the vertex selection method, the positions of the four vertices of the reference chromaticity block are determined. These vertices are usually the four corners of the reference chromaticity block. Then, according to the reference chromaticity sample points in the reference chromaticity block, the corresponding reference luminance sample points are determined in the reference luminance block.

It is understandable that after determining these reference luminance samples, the chrominance samples corresponding to these luminance samples can be determined through the corresponding chrominance sampling structure to establish a relationship between luminance and chrominance. Such a relationship helps to improve the accuracy of intra-frame prediction, thereby better restoring the original video frame at the decoding end.

It is understandable that, on the one hand, different selection methods can better adapt to different image contents and motion patterns. In some scenes, a certain selection method may be more able to capture important information in the image, thereby improving coding efficiency. On the other hand, different selection methods may help provide more accurate motion vector information. By selecting appropriate samples, motion can be estimated more accurately, thereby improving the accuracy of prediction. On the one hand, the clever selection of preset sample selection methods can improve the effect of intra-frame prediction. By selecting appropriate samples, the relationship between brightness and chrominance can be better modeled, thereby improving the quality of intra-frame prediction. On the other hand, some selection methods may have lower complexity during decoding, allowing the decoder to perform prediction and motion estimation more efficiently, thereby reducing the overall decoding complexity. In general, by selecting appropriate preset sample selection methods, video decoders can better adapt to the needs of different scenarios, improve image quality, and reduce complexity while maintaining decoding efficiency.

In some embodiments of the present application, the preset sample point selection method is a center selection method; the width of the reference chroma block is W, and the height of the reference chroma block is H; the width of the reference luminance block is 2W, and the height of the reference luminance block is 2H.

In some embodiments of the present application, at least two reference luma samples include: a first reference luma sample, a second reference luma sample, a third reference luma sample, and a fourth reference luma sample; and the reference chroma samples corresponding to the at least two reference luma samples include: a first reference chroma sample, a second reference chroma sample, a third reference chroma sample, and a fourth reference chroma sample.

The position coordinates of the first reference chromaticity sample point in the reference chromaticity block are (1, 0); the first reference chromaticity sample point is the chromaticity sample point at the upper left corner of the reference chromaticity block;

The position coordinates of the second reference chromaticity sample point in the reference chromaticity block are (W-2, 0);

The position coordinates of the third reference chromaticity sample point in the reference chromaticity block are (1, H-1);

The position coordinates of the fourth reference chromaticity sample point in the reference chromaticity block are (W-2, H-1);

The position coordinates of the first reference brightness sample point in the reference brightness block are (2, 0); the first reference brightness sample point is the brightness sample point at the upper left corner of the reference brightness block;

The position coordinates of the second reference brightness sample point in the reference brightness block are (2×(W-2), 0);

The position coordinates of the third reference brightness sample point in the reference brightness block are (2,2×(H-1));

The position coordinates of the fourth reference luminance sample point in the reference luminance block are (2×(W-2), 2×(H-1)).

In some embodiments of the present application, the preset sample point selection method is a vertex selection method; the width of the reference chroma block is W, and the height of the reference chroma block is H; the width of the reference luminance block is 2W, and the height of the reference luminance block is 2H;

In some embodiments of the present application, at least two reference luma samples include: a first reference luma sample, a second reference luma sample, a third reference luma sample, and a fourth reference luma sample; and the reference chroma samples corresponding to the at least two reference luma samples include: a first reference chroma sample, a second reference chroma sample, a third reference chroma sample, and a fourth reference chroma sample.

The position coordinates of the first reference chromaticity sample point in the reference chromaticity block are (0, 0); the first reference chromaticity sample point is the chromaticity sample point at the upper left corner of the reference chromaticity block;

The position coordinates of the second reference chromaticity sample point in the reference chromaticity block are (W-1, 0);

The position coordinates of the third reference chromaticity sample point in the reference chromaticity block are (0, H-1);

The position coordinates of the fourth reference chromaticity sample point in the reference chromaticity block are (W-1, H-1);

The position coordinates of the first reference brightness sample point in the reference brightness block are (0, 0); the first reference brightness sample point is the brightness sample point at the upper left corner of the reference brightness block;

The position coordinates of the second reference brightness sample point in the reference brightness block are (2×(W-1), 0);

The position coordinates of the third reference brightness sample point in the reference brightness block are (0, 2×(H-1));

The position coordinates of the fourth reference luminance sample point in the reference luminance block are (2×(W-1), 2×(H-1)).

It should be noted that the above-listed center selection method and vertex selection method are only examples. In actual applications, other numbers of reference luminance samples and reference chrominance samples may be selected. In addition, other methods are also included for the coordinate positions of the selected reference luminance samples and reference chrominance samples. In other words, any one of the reference luminance samples and reference chrominance samples may be selected, and the specific selection method may be selected according to the actual application scenario, and the embodiments of the present application do not impose any limitation on this.

In the embodiment of the present application, the first reference chromaticity sample corresponds to the first reference luminance sample, the second reference chromaticity sample corresponds to the second reference luminance sample, the third reference chromaticity sample corresponds to the third reference luminance sample, and the fourth reference chromaticity sample corresponds to the fourth reference luminance sample.

It is understandable that the setting method of vertex selection helps to establish a more accurate cross-component prediction model through the relationship between luma samples and chroma samples. During the decoding process, referring to these samples can improve the prediction accuracy of chroma information, thereby improving video quality.

S3032. Determine a cross-component prediction model according to at least two reference luma samples and at least two reference chroma samples; wherein the at least two reference luma samples correspond to the at least two reference chroma samples.

In an embodiment of the present application, when the current chroma block corresponds to a cross-component prediction model, the cross-component prediction model is determined according to at least two reference luma samples and at least two reference chroma samples.

In some embodiments of the present application, the cross-component prediction model includes one or more cross-component prediction sub-models; determining the implementation of the cross-component prediction model according to at least two reference luma samples and at least two reference chroma samples in S3032 may include S30321 to S30322:

S30321, according to the brightness values of at least two reference brightness samples, at least two reference brightness samples and at least two reference chrominance samples The points are grouped to obtain at least one reference sample point group; wherein each reference sample point group includes at least two luminance sample points and at least two chrominance sample points; the at least two luminance sample points correspond to the at least two chrominance sample points; the at least two reference luminance sample points include at least two luminance sample points; the at least two reference chrominance sample points include at least two chrominance sample points; and at least one reference sample point group corresponds to a different preset luminance range.

In the embodiment of the present application, for different reference sample groups, the luma samples and chroma samples contained therein have different preset luma ranges. This distinction may help to better adapt to the brightness changes in different areas of the video. By specifying a different preset luma range for each reference sample group, the brightness differences that may exist in the video can be handled more flexibly, thereby improving the adaptability and performance of decoding.

Exemplarily, at least one reference sample point group includes: a first sample point group, a second sample point group, a third sample point group and a fourth sample point group. The first sample point group corresponds to a brightness range of 0 to 50, the second sample point group corresponds to a brightness range of 51 to 100, the third sample point group corresponds to a brightness range of 101 to 150, and the fourth sample point group corresponds to a brightness range of 151 to 255.

In an embodiment of the present application, as shown in FIG. 14 , a schematic diagram of multiple cross-component prediction sub-models is shown, where the horizontal axis is the reconstructed luminance value of the co-located luminance block, and the vertical axis is the predicted chrominance value of the predicted chrominance block corresponding to the current chrominance block. It can be seen that the cross-component prediction model includes two cross-component prediction sub-models, namely a first cross-component prediction sub-model and a second cross-component prediction sub-model. Among them, the scaling factor corresponding to the first cross-component prediction sub-model is 1 (α ₁ =1), and the offset factor is 1 (β ₁ =1), and the scaling factor corresponding to the second cross-component prediction sub-model is 1/2 (α ₂ =1/2), and the offset factor is 1 (β ₂ =1). Therefore, through multiple cross-component prediction sub-models, the reconstructed luminance values of different co-located luminance blocks can be matched to different cross-component prediction sub-models, so that the adaptability and performance of decoding can be improved.

S30322. For each reference sample point group in at least one reference sample point group, determine a cross-component prediction sub-model corresponding to each reference sample point group according to at least two luma samples and at least two chroma samples in each reference sample point group.

In some embodiments of the present application, S30322 determines the implementation of the cross-component prediction sub-model corresponding to each reference sample group according to at least two luma samples and at least two chroma samples in each reference sample group, which may include:

According to the brightness values of the at least two brightness samples, at least two brightness samples and at least two chrominance samples in each reference sample group are grouped to obtain a first sample group and a second sample group; wherein the first sample group and the second sample group each include at least one brightness sample and at least one chrominance sample; the at least one brightness sample corresponds to the at least one chrominance sample; and a reconstructed brightness value of at least one brightness sample in the first sample group is greater than or equal to a reconstructed brightness value of at least one brightness sample in the second sample group;

Determine a maximum reference luminance value and a first reference chrominance value according to a reconstructed luminance value of at least one luminance sample point and a reconstructed chrominance value of at least one chrominance sample point in the first sample point group, respectively;

Determine a minimum reference luminance value and a second reference chrominance value according to a reconstructed luminance value of at least one luminance sample point and a reconstructed chrominance value of at least one chrominance sample point in the second sample point group;

Determining a scaling factor and an offset factor based on a maximum reference luminance value, a first reference chrominance value, a minimum reference luminance value, and a second reference chrominance value;

According to the scaling factor and the offset factor, the cross-component prediction sub-model corresponding to each reference sample point group is determined.

In the embodiment of the present application, the maximum reference brightness value can be expressed as xMax, the first reference chromaticity value can be expressed as yMax, the minimum reference brightness value can be expressed as xMin, and the second reference chromaticity value can be expressed as yMin. The scaling factor can be expressed as a, and the offset factor can be expressed as b.

It should be noted that the process of grouping and sorting the at least two luma samples and the at least two chroma samples in each reference sample group is performed based on the luma values of the at least two luma samples, and the chroma values are operated according to the corresponding luma values. Therefore, the first reference chroma value corresponding to the maximum reference luma value is not necessarily the largest. Similarly, the second reference chroma value corresponding to the minimum reference luma value is not necessarily the smallest.

Exemplarily, when the reconstructed luminance value of the first reference luminance sample is greater than or equal to the reconstructed luminance value of the second reference luminance sample, the reconstructed luminance value of the second reference luminance sample is greater than or equal to the reconstructed luminance value of the third reference luminance sample, and the reconstructed luminance value of the third reference luminance sample is greater than or equal to the reconstructed luminance value of the fourth reference luminance sample, the first reference luminance sample, the second reference luminance sample, the first reference chroma sample corresponding to the first reference luminance sample, and the second reference chroma sample corresponding to the second reference luminance sample are divided into a first sample group, and the third reference luminance sample, the fourth reference luminance sample, the third reference chroma sample corresponding to the third reference luminance sample, and the fourth reference chroma sample corresponding to the fourth reference luminance sample are divided into a second sample group. Further, the average of the reconstructed luminance values of the first reference luminance sample and the second reference luminance sample is used as the maximum reference luminance value (xMax), the average of the reconstructed chroma values of the first reference chroma sample and the second reference chroma sample is used as the first reference chroma value (yMax), the average of the reconstructed luminance values of the third reference luminance sample and the fourth reference luminance sample is used as the minimum reference luminance value (xMin), and the average of the reconstructed chroma values of the third reference chroma sample and the fourth reference chroma sample is used as the second reference chroma value (yMin).

In some embodiments of the present application, determining the scaling factor and the offset factor based on the maximum reference luminance value, the first reference chrominance value, the minimum reference luminance value, and the second reference chrominance value may include:

Subtracting the first reference chromaticity value (yMax) from the second reference chromaticity value (yMin) to obtain a first intermediate parameter;

Subtracting the maximum reference brightness value (xMax) from the minimum reference brightness value (xMin) to obtain a second intermediate parameter;

Dividing the first intermediate parameter by the second intermediate parameter to obtain a scaling factor (a);

The scaling factor (a) and the minimum reference brightness value (xMin) are multiplied to obtain a third intermediate parameter;

The second reference chromaticity value (yMin) and the third intermediate parameter are subtracted to obtain an offset factor (b).

In the embodiment of the present application, the first intermediate parameter can be expressed as yMax-yMin. The second intermediate parameter can be expressed as xMax-xMin. The scaling factor can be expressed as a=(yMax-yMin)/(xMax-xMin). The third intermediate parameter can be expressed as a×xMin. The offset factor can be expressed as yMin-a×xMin.

It is understandable that determining the scaling factor and the offset factor can map the reference luminance and chrominance values to a standard range, thereby achieving normalization, which helps to process luminance and chrominance information more consistently in different scenarios. By determining the scaling factor and the offset factor, the prediction model can be made more robust and adaptable to different luminance and chrominance conditions. By performing appropriate luminance and chrominance mapping, data redundancy can be reduced, decoding efficiency can be improved, and image information can be represented more compactly. In general, by determining the scaling factor and the offset factor, the relationship between luminance and chrominance can be better handled, and the decoding performance and image quality can be improved.

In some embodiments of the present application, the cross-component prediction model is a nonlinear model; determining the implementation of the cross-component prediction model based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector in S304 may include:

Selecting all or part of the reference chromaticity samples in the reference chromaticity block;

A cross-component prediction model is determined based on all or part of the reference chroma samples, reference luma samples in a reference luma block that respectively correspond to all or part of the reference chroma samples, and neighborhood reference luma samples of the reference luma samples.

In the embodiment of the present application, when the sizes of the reference luminance block and the reference chrominance block are inconsistent, the reference luminance block is downsampled to obtain downsampled luminance samples. The downsampling process can be expressed as:
L′(x,y)＝(L(x-1,y)+2L(x,y)+L(x+1,y)+L(x-1,y+1)+2L(x,y+1)+
L(x+1,y+1))/8 (3)

In formula (3), L(x, y) represents a pixel point in the reference luminance block, and L′(x, y) represents the downsampled luminance sample point corresponding to the pixel point L(x, y).

In an embodiment of the present application, the sampled reference luminance block and the reference chrominance block are used as templates for parameter derivation.

In the embodiment of the present application, when the cross-component prediction model is a nonlinear model, the cross-component prediction model can be expressed by formula (4):

In formula (4), p ₀ , p ₁ , p ₂ , p ₃ , p ₄ , p ₅ , B are model parameters of the cross-component prediction model, C is the reconstructed luminance value of the target luminance sample corresponding to the target chrominance sample of the current chrominance block in the same luminance block, N is the reconstructed luminance value of the luminance sample located above the target luminance sample, S is the reconstructed luminance value of the luminance sample located below the target luminance sample, W is the reconstructed luminance value of the luminance sample located to the left of the target luminance sample, and E is the reconstructed luminance value of the luminance sample located to the right of the target luminance sample. C′ is the predicted chrominance value corresponding to the target chrominance sample of the current chrominance block.

In an embodiment of the present application, all or part of the reference chroma samples are selected in the reference chroma block, and based on all or part of the reference chroma samples, the reference luminance samples corresponding to all or part of the reference chroma samples in the reference luminance block, and the neighborhood reference luminance samples of the reference luminance samples, multiple equations are constructed to solve the linear equation system, and the LDL solution method is used to obtain model parameters _p0 , _p1 , _p2 , _p3 , _p4 , _p5 , B of the cross-component prediction model, thereby obtaining a nonlinear cross-component prediction model.

In the embodiment of the present application, samples whose horizontal coordinates and vertical coordinates satisfy preset constraints can be selected in the reference luminance block and the reference chrominance block, that is, samples whose horizontal coordinates and vertical coordinates are not odd numbers. It can be expressed as: (x%2==1&&y%2==1).

It can be understood that by establishing a cross-component prediction model based on reference chrominance samples and corresponding reference luma samples, the adaptability of the prediction model can be enhanced to better adapt to video content of different types and scenes. Considering the neighborhood reference luma samples of the reference luma samples can more comprehensively capture the luma information, which helps to improve the accuracy of the prediction model, which may be important for processing information such as local features and textures in the image. By more accurately modeling cross-component relationships, it can be expected to reduce the distortion introduced by the prediction, thereby improving the overall video quality, including higher compression efficiency and better visual quality.

In some embodiments of the present application, the neighborhood reference brightness samples include one or more of the following: a reference brightness sample (N) located above the reference brightness sample, a reference brightness sample (S) located below the reference brightness sample, a reference brightness sample (W) located to the left of the reference brightness sample, and a reference brightness sample (E) located to the right of the reference brightness sample.

In an embodiment of the present application, by considering the above-mentioned neighborhood reference brightness samples, the context and local features of the brightness information can be more comprehensively captured, which helps to improve the accuracy and adaptability of the cross-component prediction model. Such information consideration can usually better simulate the changes and textures of the brightness components in the image.

In some embodiments of the present application, the implementation of determining candidate reference samples satisfying a preset prediction mode in the current co-located luminance block in S401 may include:

According to the preset M position information, the candidate reference sample points corresponding to the preset M position information are traversed in the current co-located luminance block to obtain the candidate reference sample points that meet the preset prediction mode; wherein M is a positive integer greater than or equal to 1, and i is an integer less than M. Positive integer.

In an embodiment of the present application, M pieces of preset position information are provided, each of which may include information such as coordinates or indices, for specifying a certain position in the current co-located luminance block. For each preset position information, a traversal operation is performed, and in each traversal, the candidate reference sample points corresponding to the position information are considered. For each position information, the candidate reference sample points corresponding thereto are found, and these candidate reference sample points may be determined in the current co-located luminance block according to the coordinates or indices of the position information. For each candidate reference sample point, it is checked whether it satisfies the preset prediction mode. The candidate reference sample points that satisfy the preset prediction mode are collected for subsequent use.

In some embodiments of the present application, the M pieces of location information include one or more of the following:

The position of the middle of the current co-located luminance block;

The upper left position of the current co-located luminance block;

The upper right position of the current co-located luminance block;

The lower left position of the current co-located luminance block;

The lower right position of the current co-located luma block.

In the embodiment of the present application, the preset M position information can be expressed as {C, TL, TR, BL, BR}, where C represents the middle position of the current co-located luminance block, TL represents the upper left position of the current co-located luminance block, TR represents the upper right position of the current co-located luminance block, BL represents the lower left position of the current co-located luminance block, and BR represents the lower right position of the current co-located luminance block.

In some embodiments of the present application, according to the preset M pieces of position information, candidate reference sample points corresponding to the preset M pieces of position information are traversed in the current co-located luminance block to obtain candidate reference sample points that meet the preset prediction mode, including:

For the i-th position information among the preset M position information, if the i-th candidate reference sample corresponding to the i-th position information in the current co-located luminance block does not satisfy the preset prediction mode, continue to traverse the i+1-th candidate reference sample corresponding to the i+1-th position information in the current co-located luminance block until the i+1-th candidate reference sample satisfies the preset prediction mode, and determine the i+1-th candidate reference sample as a candidate reference sample that satisfies the preset prediction mode; or,

In the case that the i-th candidate reference sample point satisfies the preset prediction mode, the i-th candidate reference sample point is determined as a candidate reference sample point that satisfies the preset prediction mode.

In the embodiment of the present application, for the i-th position information among the preset M position information, the i-th candidate reference sample corresponding thereto is considered. It is determined whether the i-th candidate reference sample in the current co-located luminance block satisfies the preset prediction mode. If the i-th candidate reference sample does not satisfy the preset prediction mode, then the i+1-th candidate reference sample corresponding to the i+1-th position information in the current co-located luminance block is traversed. If the i-th candidate reference sample satisfies the preset prediction mode, then the i-th candidate reference sample is determined as a candidate reference sample that satisfies the preset prediction mode.

It can be understood that, on the one hand, by checking each position information one by one, it can be ensured that the selected candidate reference samples better match the preset conditions in the prediction mode, thereby improving the accuracy of the prediction. On the one hand, selecting candidate reference samples that meet the preset conditions helps to improve the prediction quality of the image block, thereby improving the visual quality of the overall image. On the one hand, through the preset position information and conditions, appropriate candidate reference samples can be selected according to different scenarios and requirements, making the prediction mode more flexible and adaptable. On the one hand, the effective selection of candidate reference samples can reduce redundant information, thereby improving the efficiency and performance of decoding in video compression. In general, the above steps help to improve the performance of the cross-component prediction model in video coding, so that it can better adapt to different prediction scenarios and requirements.

In some embodiments of the present application, the implementation of determining the predicted chroma value of the predicted chroma block based on the cross-component prediction model in S304 may include S3041 to S3042:

S3041. Determine the candidate predicted chrominance value of the candidate chrominance prediction block according to the reconstructed luminance value of each pixel in the current co-located luminance block through a cross-component prediction model; wherein the size of the candidate chrominance prediction block is different from that of the current chrominance block.

In an embodiment of the present application, the reconstructed luminance value of each pixel in the current co-located luminance block is input into a cross-component prediction model to obtain a candidate predicted chrominance value of the candidate chrominance prediction block.

In some embodiments of the present application, the cross-component prediction model includes at least one cross-component prediction sub-model; the implementation of determining the candidate predicted chrominance value of the candidate chrominance prediction block according to the reconstructed luminance value of each pixel in the current co-located luminance block through the cross-component prediction model in S3041 may include:

For each pixel in the current co-located luminance block, the reconstructed luminance value of each pixel is input into the corresponding cross-component prediction sub-model to obtain a candidate predicted chrominance value corresponding to each pixel; wherein the preset luminance range corresponding to the reconstructed luminance value of each pixel matches the cross-component prediction sub-model;

Determine the candidate predicted chrominance value of the candidate chrominance prediction block according to the candidate predicted chrominance value corresponding to each pixel in the current co-located luminance block.

Exemplarily, at least one cross-component prediction submodel includes: a first cross-component prediction submodel, a second cross-component prediction submodel, a third cross-component prediction submodel and a fourth cross-component prediction submodel. The first cross-component prediction submodel corresponds to a brightness range of 0 to 50, the second cross-component prediction submodel corresponds to a brightness range of 51 to 100, the third cross-component prediction submodel corresponds to a brightness range of 101 to 200, and the fourth cross-component prediction submodel corresponds to a brightness range of 201 to 255. Then, if the pixel of a brightness sample in the current co-located brightness block If the pixel point of a luma sample in the current co-located luma block is 40, the luma sample uses the first cross-component prediction sub-model to obtain the candidate predicted chroma value of the chroma sample corresponding to the luma sample. If the pixel point of a luma sample in the current co-located luma block is 60, the luma sample uses the second cross-component prediction sub-model to obtain the candidate predicted chroma value of the chroma sample corresponding to the luma sample. If the pixel point of a luma sample in the current co-located luma block is 155, the luma sample uses the third cross-component prediction sub-model to obtain the candidate predicted chroma value of the chroma sample corresponding to the luma sample. If the pixel point of a luma sample in the current co-located luma block is 220, the luma sample uses the fourth cross-component prediction sub-model to obtain the candidate predicted chroma value of the chroma sample corresponding to the luma sample.

It can be understood that, on the one hand, the use of different cross-component prediction sub-models for each pixel can better adapt to the brightness and chrominance characteristics of different areas in the image. This adaptability helps to improve the performance of the decoder in various image scenarios. On the one hand, the use of the preset brightness range corresponding to each pixel and the cross-component prediction sub-model provides fine-grained control of different pixels, which enables the decoder to better cope with subtle differences that may exist in the image and improves the flexibility of decoding. In general, the above steps help to better capture the relationship between brightness and chrominance through a more refined cross-component prediction sub-model, thereby improving the quality of chrominance prediction and decoding efficiency.

S3042. Downsample the candidate predicted chroma values of the candidate chroma prediction block to obtain predicted chroma values of the predicted chroma block.

In the embodiment of the present application, the candidate predicted chrominance values of the candidate chrominance prediction block are downsampled by a six-tap filter [1 2 1; 1 2 1]. This process can be expressed by formula (5):
P _chroma (x,y)＝(P _t (2x-1,2y)+2×P _t (2x,2y)+P _t (2x+1,2y)+P _t (2x-1,2y+1)+
2×P _t (2x,2y+1)+P _t (2x+1,2y-1)+4)>>3 (5)

In formula (5), P _chroma represents the predicted chroma value of the final predicted chroma block. Assuming that the size of the predicted chroma block is W×H, the value range of x is [0, W-1], and the value range of y is [0, H-1]. As shown in Figure 15, the relationship between the shape of the six-tap filter and the corresponding positions of the chroma block prediction pixels and the intermediate prediction block pixels (candidate prediction chroma values of the candidate chroma prediction block).

It can be understood that, on the one hand, the cross-component prediction model allows for better capture of the complex relationship between luminance and chrominance, and by using the reconstructed luminance value of the co-located luminance block, the predicted chrominance value can more accurately reflect the details and features in the image. On the other hand, since the size of the candidate chrominance prediction block is different from the current chrominance block, this method can adapt in size, making the prediction more adaptable to the details and structures of different regions in the image. In general, the above steps combine the advantages of information capture, size adaptability, and decoding efficiency, which helps to improve the quality of chrominance prediction and reduce the amount of data while maintaining efficient decoding.

In another embodiment of the present application, referring to FIG16 , a schematic flow chart of an encoding method provided in an embodiment of the present application is shown. As shown in FIG16 , the method may include S501 to S504:

S501. Determine a reference motion vector according to a current co-located luminance block corresponding to a current chrominance block.

In the embodiment of the present application, the co-located luminance block refers to a luminance block corresponding to the current chrominance block. For example, in the YCbCr color space, for each chrominance block (Cb or Cr block), there is a luminance block in the same position or relative position, and this luminance block is called the co-located luminance block.

In an embodiment of the present application, there is a co-location relationship between the chrominance block and the brightness block. Exemplarily, in the YCbCr color space, the image is divided into a brightness component (Y) and two chrominance components (Cb, Cr). The brightness component (Y) contains the black and white information of the image, while the chrominance components (Cb, Cr) contain color information. The sampling rate of the chrominance component is usually lower than that of the brightness component, which means that for each brightness block, there may be multiple chrominance blocks. For each chrominance block, there is a co-location brightness block, which means that they have the same position or a certain relative position relationship in the image. Usually, the size of the brightness block is larger than the size of the chrominance block. For example, a brightness block may correspond to a 4x4 or 8x8 pixel block, while the chrominance block may correspond to a smaller 2x2 or 4x4 pixel block.

In the embodiment of the present application, the reference motion vector is used to predict the motion information of the current image block. Usually, the current co-located luminance block corresponding to the current chrominance block has the same motion vector. The obtained motion vector is applied to the current chrominance block to predict the position of the current chrominance block. This prediction process helps to reduce the residual caused by motion and improve coding efficiency.

S502: When the reference motion vector is valid, determine a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector.

In some embodiments of the present application, when the reference motion vector satisfies at least one of the following conditions: the reference luminance block or the reference chrominance block corresponding to the reference motion vector has not been reconstructed, the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector does not match, and the reference motion vector is out of bounds, the reference motion vector is determined to be invalid; or,

The reference motion vector is determined to be valid when the reference motion vector satisfies that the reference luminance block or reference chrominance block corresponding to the reference motion vector has been reconstructed, the prediction mode of the reference luminance block or reference chrominance block corresponding to the reference motion vector matches, and the reference motion vector does not cross the boundary.

In the embodiment of the present application, the implementation of determining whether the reference motion vector is valid may include the following steps:

Step 1: Check whether the reference luminance block or reference chrominance block corresponding to the reference motion vector has been reconstructed.

In the embodiment of the present application, at the encoding end, the corresponding block in the reference frame may not be fully encoded, or the encoder may not have completed The encoding of the reference frame results in the reference block not being reconstructed. At this point, the encoder may need to wait for the reference block to be fully reconstructed, or use some error handling mechanism. For example, it may choose to skip motion compensation for the current block and temporarily use other methods for filling or interpolation to prevent errors caused by incomplete encoding.

Step 2: Check whether the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector matches.

In an embodiment of the present application, the reference block may use a prediction mode that does not match the current block. This may occur in intra-frame prediction, where the reference block may use a different prediction mode. At this time, the encoder may need to detect and correct the prediction mode mismatch, which may involve trying to adjust the prediction mode of the reference block according to the prediction mode of the current block, or performing other error recovery strategies.

Step 3: Check whether the reference motion vector is out of bounds.

In an embodiment of the present application, the value of the reference motion vector may exceed the specified range, which may be caused by a coding error, a transmission error, or other abnormal conditions. At the encoding end, it is necessary to detect and handle the out-of-bounds situation. Possible processing methods include clipping the value of the motion vector to keep it within the valid range, or using other error handling methods.

It is understandable that the above steps are to ensure the legitimacy of the reference motion vector and prevent erroneous or invalid reference motion vectors from affecting the encoding quality. The encoder ensures the accuracy and robustness of the encoding by detecting and processing these situations, thereby improving the reliability of video encoding.

S503. Determine a predicted chroma value of a predicted chroma block based on a cross-component prediction model, and determine first syntax identification information according to the predicted chroma value; wherein the first syntax identification information is used to indicate whether the current chroma block adopts a cross-component prediction mode based on a chroma intra-frame block copy technology.

In the embodiment of the present application, the cross-component prediction model characterizes that the reconstructed luminance value of the current co-located luminance block corresponding to the current chrominance block has a relationship with the predicted chrominance value of the predicted chrominance block.

In some embodiments of the present application, the cross-component prediction model characterizes that the reconstructed luminance value of the current co-located luminance block corresponding to the current chrominance block has a linear or nonlinear relationship with the predicted chrominance value of the predicted chrominance block.

It should be noted that the linear cross-component prediction model can improve coding efficiency and remove the redundancy of chrominance components, so that the model can better fit the relationship between brightness and chrominance in actual scenes. By using a linear cross-component prediction model, the encoder can more accurately estimate the value of the chrominance component, thereby achieving better compression effect during the encoding process, which is beneficial to improving the performance and quality of video encoding.

In some embodiments of the present application, the implementation of determining the first syntax identification information according to the predicted chrominance value in S503 may include:

Determine a chroma residual value of the current chroma block according to an original chroma value and a predicted chroma value of the current chroma block;

Performing rate-distortion cost calculation on the chroma residual value of the current chroma block to obtain a first rate-distortion cost value corresponding to the cross-component prediction mode based on the chroma intra-frame block copy technology adopted by the current chroma block;

Determining a prediction mode adopted by a current chroma block according to a first rate-distortion cost value;

The first syntax identification information is determined according to the prediction mode adopted by the current chroma block.

In the embodiment of the present application, the original chromaticity value at the corresponding position is subtracted from the predicted chromaticity value to obtain the chromaticity residual (i.e., chromaticity residual value) of each pixel. This is to quantify the prediction error by comparing the difference between the actually observed chromaticity value and the value predicted by the model.

In an embodiment of the present application, the distortion between the original chrominance value and the reconstructed chrominance value of the current chrominance block is calculated. Various measurement methods can be used for distortion, common ones include mean square error (MSE) or other structural similarity index (SSI). This step represents the image quality loss introduced in compression and decompression. Calculate the number of bits used to represent the chrominance residual value. This number of bits is usually measured by the length of the output data of the encoder, which represents the number of bits required in transmission or storage to represent the chrominance residual of the current chrominance block. Combine the distortion and compression rate to form a comprehensive evaluation index. A common calculation method is to linearly combine the distortion and compression rate, or to perform a more sophisticated evaluation through some complex mathematical models.

In the embodiments of the present application, some common rate-distortion optimization algorithms, such as variable bit rate (VBR) and constant bit rate (CBR), are usually used to minimize distortion while meeting a given bit rate or quality requirement. This helps to achieve more efficient video compression and transmission.

In some embodiments of the present application, the first syntax identification information is encoded, and the obtained encoded bits are written into a bitstream.

In some embodiments of the present application, the implementation of determining the prediction mode adopted by the current chroma block according to the first rate-distortion cost value may include:

When the first rate-distortion cost value is less than or equal to the second rate-distortion cost value corresponding to each of the one or more preset candidate prediction modes, determining that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology;

When the first rate-distortion cost value is greater than the second rate-distortion cost value corresponding to each of the one or more preset candidate prediction modes, it is determined that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra block copy technology.

It can be understood that, on the one hand, by selecting an appropriate prediction mode, the distortion of the image or video can be reduced and the visual quality can be improved. On the one hand, by selecting an appropriate prediction mode, the distortion of the image or video can be reduced and the visual quality can be improved. On the one hand, the dynamic decision mechanism allows the system to adjust the prediction mode according to the actual situation, so as to better adapt to different types of content and scenes. Video coding efficiency can provide a better user experience under limited bandwidth and storage conditions.

In some embodiments of the present application, the one or more candidate prediction modes include: a chroma intra block copy prediction mode; when the first rate-distortion cost value is greater than the second rate-distortion cost value corresponding to each of the one or more preset candidate prediction modes, determining that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra block copy technology includes:

When the first rate-distortion cost value is greater than the second rate-distortion cost value corresponding to the chroma intra block copy prediction mode, it is determined that the current chroma block adopts the chroma intra block copy prediction mode.

In some embodiments of the present application, the implementation of determining the first syntax identification information according to the prediction mode adopted by the current chroma block may include:

In the case where it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology, determining that the value of the first syntax identification information is a third value; or,

When it is determined that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra block copy technology, it is determined that the value of the first syntax identification information is a fourth value.

Exemplarily, the first syntax identification information may be represented as tcibc_flag.

It should be noted that, in the embodiment of the present application, the third value is different from the fourth value, and the third value and the fourth value can be in parameter form or in digital form. Specifically, the first syntax identification information can be a parameter written in the profile or a flag value, which is not specifically limited here.

Exemplarily, for the third value and the fourth value, the third value can be set to 1 and the fourth value can be set to 0; or, the third value can be set to 0 and the fourth value can be set to 1; or, the third value can be set to true and the fourth value can be set to false; or, the third value can be set to false and the fourth value can be set to true; but this is not specifically limited here.

In an embodiment of the present application, taking the flag written into the bitstream as an example, assuming that the third value is set to 1 (true) and the fourth value is set to 0 (false), at this time if the value of the second syntax identification information is 0 (false), then it can be determined that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra-frame block copy technology; if the value of the first syntax identification information is 1 (true), then it can be determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra-frame block copy technology.

In some embodiments of the present application, the method further comprises:

Determining second grammar identification information;

Encoding the second syntax identification information, and writing the obtained coded bits into the bitstream;

Determining the second grammar identification information includes:

When it is determined that the current chroma block adopts the chroma intra block copy prediction mode, the value of the second syntax identification information is set to the first value; or,

When it is determined that the current chroma block does not adopt the chroma intra block copy prediction mode, the value of the second syntax identification information is set to the second value.

It should be noted that, in the embodiment of the present application, the first value is different from the second value, and the first value and the second value can be in parameter form or in digital form. Specifically, the second syntax identification information can be a parameter written in the profile or a flag value, which is not specifically limited here.

Exemplarily, for the first value and the second value, the first value can be set to 1 and the second value can be set to 0; or, the first value can be set to 0 and the second value can be set to 1; or, the first value can be set to true and the second value can be set to false; or, the first value can be set to false and the second value can be set to true; but this is not specifically limited here.

In an embodiment of the present application, taking the flag written into the bitstream as an example, assuming that the first value is set to 1 (true) and the second value is set to 0 (false), if the value of the second syntax identification information is 0 (false), then it can be determined that the current chroma block adopts the chroma intra-frame block copy prediction mode; if the value of the second syntax identification information is 1 (true), then it can be determined that the current chroma block does not adopt the chroma intra-frame block copy prediction mode.

In the embodiment of the present application, in the AVS4 exploration phase reference software EVM-0.2, the prediction mode part of the current chroma block first encodes the CIBC related flag, then adds the related flag of the TSCPM_CIBC technology of this scheme, and then encodes other chroma intra-frame prediction mode flags. The structure of the first syntax identification information is shown in Table 1:

Table 1

In Table 1, it can be seen that when it is determined that the current chroma block adopts the chroma intra block copy prediction mode, the binary The binary string is 1. When it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra-frame block copy technology, the binary string written to the bitstream is 01. When it is determined that the current chroma block adopts other chroma intra-frame prediction modes, the binary string written to the bitstream is 00*.

In an embodiment of the present application, with respect to the structure of the first syntax identification information shown in Table 1, the mode indicates whether to use the cross-component prediction mode based on the chroma intra-frame block copying technology by encoding a flag bit tcibc_flag in the current chroma block related code stream.

Specifically, if the current chroma block does not use the CIBC mode, that is, cibc_flag is 0, and the conditions for starting the TSCPM_CIBC technology are met, a flag bit tcibc_flag needs to be encoded in the bitstream to indicate whether the mode is used. If tcibc_flag is 1, it means that the current chroma block uses the TSCPM_CIBC mode, and there is no need to continue encoding flag bits for other modes. If tcibc_flag is 0, it means that the current chroma block does not use the TSCPM_CIBC mode, and it is necessary to continue encoding other flag bits related to determining the prediction mode.

In some embodiments of the present application, the implementation of determining the first syntax identification information according to the prediction mode adopted by the current chroma block may include:

When it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology, the value of the first syntax identification information is set to the seventh value; or,

When it is determined that the current chroma block adopts the chroma intra block copy prediction mode, the value of the first syntax identification information is set to the eighth value.

Exemplarily, the first syntax identification information may be represented as tcibc_flag.

It should be noted that, in the embodiment of the present application, the seventh value is different from the eighth value, and the seventh value and the eighth value can be in parameter form or in digital form. Specifically, the first syntax identification information can be a parameter written in the profile or a flag value, which is not specifically limited here.

Exemplarily, for the seventh value and the eighth value, the seventh value can be set to 1 and the eighth value can be set to 0; or, the seventh value can be set to 0 and the eighth value can be set to 1; or, the seventh value can be set to true and the eighth value can be set to false; or, the seventh value can be set to false and the eighth value can be set to true; but no specific limitation is made here.

In an embodiment of the present application, taking the flag written into the bitstream as an example, assuming that the seventh value is set to 1 (true) and the eighth value is set to 0 (false), at this time if the value of the second syntax identification information is 0 (false), then it can be determined that the current chroma block adopts the chroma intra-frame block copy prediction mode; if the value of the first syntax identification information is 1 (true), then it can be determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra-frame block copy technology.

In some embodiments of the present application, the method further comprises:

Determining third grammar identification information;

Encoding the third syntax identification information, and writing the obtained coded bits into a bit stream;

Determining third grammar identification information includes:

When it is determined that the current chroma block adopts the chroma intra block copy prediction mode or the cross-component prediction mode based on the chroma intra block copy technology, the value of the third syntax identification information is set to the fifth value; or,

When it is determined that the current chroma block does not adopt the chroma intra block copy prediction mode or the cross-component prediction mode based on the chroma intra block copy technology, the value of the third syntax identification information is set to the sixth value.

Exemplarily, the third syntax identification information may be represented as cibc_flag.

It should be noted that, in the embodiment of the present application, the fifth value is different from the sixth value, and the fifth value and the sixth value can be in parameter form or in digital form. Specifically, the second syntax identification information can be a parameter written in the profile or a flag value, which is not specifically limited here.

Exemplarily, for the fifth value and the sixth value, the fifth value can be set to 1 and the sixth value can be set to 0; or, the fifth value can be set to 0 and the sixth value can be set to 1; or, the fifth value can be set to true and the sixth value can be set to false; or, the fifth value can be set to false and the sixth value can be set to true; but no specific limitation is made here.

In an embodiment of the present application, taking the flag written into the bitstream as an example, assuming that the fifth value is set to 1 (true) and the sixth value is set to 0 (false), at this time if the value of the third syntax identification information is 0 (false), then it can be determined that the current chroma block does not adopt the chroma intra-frame block copy prediction mode or the cross-component prediction mode based on the chroma intra-frame block copy technology; if the value of the second syntax identification information is 1 (true), then it can be determined that the current chroma block adopts the chroma intra-frame block copy prediction mode or the cross-component prediction mode based on the chroma intra-frame block copy technology.

It should be noted that the first value, the second value, the third value, the fourth value, the fifth value, the sixth value, the seventh value and the eighth value may be expressed in the same form (i.e., parameter form or digital form). For example, the first value, the third value, the fifth value and the seventh value may be 1 or True, and the second value, the fourth value, the sixth value and the eighth value may be 0 or False.

In the embodiment of the present application, in the AVS4 exploration phase reference software EVM-0.2, for the prediction mode part of the current chroma block, the structure of the first syntax identification information is shown in Table 2:

Table 2

In Table 2, it can be seen that when it is determined that the current chroma block adopts the chroma intra-frame block copy prediction mode, the binary string written to the code stream is 10, when it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra-frame block copy technology, the binary string written to the code stream is 11, and when it is determined that the current chroma block adopts other chroma intra-frame prediction modes, the binary string written to the code stream is 0*.

In an embodiment of the present application, with respect to the structure of the first syntax identification information shown in Table 2, the mode indicates whether to use the cross-component prediction mode based on the chroma intra-frame block copying technology by encoding a flag bit tcibc_flag in the current chroma block related code stream. If the value of the flag bit cibc_flag of the current chroma block is 0, the encoding of the CIBC mode and the TSCPM_CIBC mode is skipped. Other related flag bits for determining the prediction mode are continued to be encoded. If the value of the flag bit cibc_flag of the current chroma block is 1, the value of tcibc_flag is continued to be encoded to indicate whether the CIBC or TSCPM_CIBC mode is specifically used. If the value of tcibc_flag is 0, the prediction mode of the current block is CIBC; if the value of tcibc_flag is 1, the prediction mode of the current block is TSCPM_CIBC.

In some embodiments of the present application, the encoding method further includes S506:

S506: When the reference motion vector is invalid, determine the predicted chroma value of the predicted chroma block according to the sample accuracy of the current chroma block.

In an embodiment of the present application, the sample accuracy of the current chrominance block refers to the representation accuracy of the chrominance component (Chroma), which is usually expressed in bits (Bit-Depth), and a higher sample accuracy is usually used to retain the details and color information in the image. For example, 8-bit sample accuracy means that each chrominance component is represented by 8 binary bits (or bits). In this way, each chrominance component can have 2^8=256 different discrete levels. These levels correspond to color changes, so higher sample accuracy means that more color details can be represented. Higher sample accuracy can provide more color levels, thereby improving color resolution. This is very important for retaining subtle color differences in images. High sample accuracy helps to more accurately represent colors in the real world and improve color fidelity. Selecting an appropriate sample accuracy also involves a balance in coding efficiency. Higher sample accuracy may require more bits to represent each pixel, thereby increasing the amount of encoded data.

In some embodiments of the present application, the implementation of determining the predicted chroma value of the predicted chroma block according to the sample accuracy of the current chroma block in S506 may include S5061 to S5062:

S5061. Perform a subtraction operation on the sample accuracy and the first preset value to obtain a fourth intermediate parameter.

S5062. Perform an exponential operation on the second preset value and the fourth intermediate parameter to obtain a predicted chromaticity value of each pixel in the predicted chromaticity block.

In the embodiment of the present application, the first preset value and the second preset value are pre-set values. For example, the first preset value is 1 and the second preset value is 2.

In the embodiment of the present application, the fourth intermediate parameter can be expressed as BitDepth-1.

In the embodiment of the present application, the predicted chrominance value of each pixel in the predicted chrominance block can be expressed as 2 ^BitDepth-1 .

It can be understood that the predicted chrominance value of each pixel in the predicted chrominance block is generated through sample precision, preset value and exponential operation. By adjusting the sample precision and different preset values, different predicted chrominance values can be explored, thereby providing more flexible adjustment and optimization options in video encoding, which helps to better adapt to different application scenarios and requirements in video encoding.

S504: Determine a reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block.

In some embodiments of the present application, when it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology, the chroma residual value is transformed and quantized to obtain a quantized chroma residual value of the current chroma block;

The quantized chroma residual value of the current chroma block is encoded, and the obtained encoding bits are written into the bit stream.

In an embodiment of the present application, the chrominance residual value represents the difference between the original chrominance value and the predicted chrominance value of the current chrominance block, and these residual values need to be processed during encoding, including transformation and quantization. The chrominance residual value may change its representation through some transformations (such as discrete cosine transform, DCT). This transformation helps to represent the data as frequency domain coefficients, and usually improves the compression performance of the data by removing redundant information. The transformed frequency domain coefficients need to be quantized to reduce the amount of data. Quantization is achieved by mapping the coefficients to a discrete value domain, which introduces information loss. During the quantization process, different step sizes (quantization step sizes) can be used to control the compression level. Larger quantization step sizes will result in more information loss, but will also produce higher compression ratios.

It can be understood that through the above steps, the quantized chrominance residual values obtained can be encoded and transmitted more efficiently because their data volume is small. Accordingly, at the decoding end, the received quantized chrominance residual values are inversely quantized and inversely transformed to restore the final reconstructed chrominance values. This process is a key step in compression coding, which is used to maintain image quality as much as possible while reducing the amount of data.

In an embodiment of the present application, a coding method is provided, the method comprising: at the coding end, determining a reference motion vector according to a current co-located luminance block corresponding to a current chrominance block; when the reference motion vector is valid, determining a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector; determining a predicted chrominance value of the predicted chrominance block based on the cross-component prediction model, and determining first syntax identification information according to the predicted chrominance value; wherein the first syntax identification information is used to indicate whether the current chrominance block adopts a chrominance frame-based The cross-component prediction mode of the intra-block copy technology; according to the predicted chrominance value of the predicted chrominance block, the reconstructed chrominance value of the current chrominance block is determined. Since the cross-component prediction model is determined by the reference luminance block and the reference chrominance block corresponding to the reference motion vector, compared with the cross-component prediction model derived from the reconstructed pixels of the adjacent row and column of the current chrominance block, the flexibility and diversity of determining the cross-component prediction model can be improved, so that the cross-component prediction model can flexibly cope with more complex encoding scenarios, thereby improving the encoding efficiency of the current chrominance block.

It can be understood that, on the one hand, the reference motion vector is determined according to the current co-located luminance block corresponding to the current chrominance block. This step helps to introduce the information of the luminance block into the encoding process of the chrominance block to improve the accurate processing of motion correlation. On the one hand, based on the cross-component prediction model, the predicted chrominance value of the predicted chrominance block is determined, which makes full use of the information of the luminance block, helps to improve the prediction accuracy of the chrominance block, and helps to more accurately restore the chrominance information in the original image at the encoding end, thereby improving the image quality. In general, the above process can improve the encoding accuracy of the chrominance block, enhance the image quality, and utilize cross-component correlation. By introducing the information of the luminance block, the encoding process more comprehensively utilizes the correlation between different components in the video image, thereby improving the encoding effect.

In some embodiments of the present application, the implementation of determining the reference motion vector according to the current co-located luminance block corresponding to the current chrominance block in S502 may include S601:

S601: Determine candidate reference samples that meet a preset prediction mode in a current co-located luminance block, and use motion vectors corresponding to the candidate reference samples as reference motion vectors.

In some embodiments of the present application, the preset prediction mode is: the candidate reference samples adopt the block copy intra prediction mode (Intra Block Copy, IBC) or the ordinary string sub-mode of string copy intra prediction.

In an embodiment of the present application, the encoder determines candidate reference samples that satisfy the block copy intra prediction mode or the common string sub-mode of string copy intra prediction in the current co-located luminance block, and uses the motion vector corresponding to the candidate reference sample as the reference motion vector.

It is understandable that the purpose of the above process is to accurately describe the relationship between the current block and the blocks in the reference frame during the encoding process to improve the accuracy of the prediction. By determining the candidate reference samples and the corresponding motion vectors, the encoder can better restore the content of the current block and achieve better image quality.

It should be noted that both the block copy intra prediction mode and the common string sub-mode of string copy intra prediction are designed for prediction within a frame. By copying the pixel values in the coded block, a simple and effective prediction method based on adjacent blocks is provided. The block copy intra prediction mode mainly emphasizes the copying of the entire block, while the common string sub-mode of string copy intra prediction emphasizes the orderly concatenation of pixel values. The choice of which mode to use usually depends on the coding standard and the specific image content. These intra prediction modes help improve the efficiency of video coding and reduce the amount of data, thereby achieving better compression performance.

In some embodiments of the present application, the cross-component prediction model is a linear model; determining the implementation of the cross-component prediction model based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector in S503 may include S5031 to S5032:

S5031. Determine at least two reference luminance samples in a reference luminance block according to a preset sample selection method, and determine reference chrominance samples corresponding to the at least two reference luminance samples in a reference chrominance block according to a preset sample selection method.

In the embodiments of the present application, the preset sample point selection method is usually based on certain rules or algorithms, such as uniform distribution within a block, selection in a specific direction, and the like.

In the embodiment of the present application, for each reference luminance sample determined in the reference luminance block, a reference chrominance sample corresponding thereto is found according to the chrominance sampling structure (such as 4:2:0 or 4:4:4). If the sampling structure of the chrominance block is 4:2:0, the corresponding reference chrominance samples may be at adjacent positions in the horizontal and vertical directions.

It can be understood that selecting at least two reference luminance sampling points and at least two reference luminance samples according to a preset sampling point selection method helps to establish a relationship between luminance and chrominance, thereby improving the accuracy of intra-frame prediction.

In some embodiments of the present application, the preset sample point selection method includes any one of the following: a center selection method, a vertical selection method, a horizontal selection method, a diagonal selection method, and a vertex selection method.

It is understandable that, on the one hand, different selection methods can better adapt to different image contents and motion modes. In some scenes, a certain selection method may be more able to capture important information in the image, thereby improving coding efficiency. On the one hand, different selection methods may help provide more accurate motion vector information. By selecting appropriate samples, motion can be estimated more accurately, thereby improving the accuracy of prediction. On the one hand, the clever selection of preset sample selection methods can improve the effect of intra-frame prediction. By selecting appropriate samples, the relationship between brightness and chrominance can be better modeled, thereby improving the quality of intra-frame prediction. On the one hand, some selection methods may have lower complexity during encoding, allowing the encoder to perform prediction and motion estimation more efficiently, thereby reducing the overall encoding complexity. In general, by selecting an appropriate preset sample selection method, the video encoder can better adapt to the needs of different scenes, improve image quality, and reduce complexity while maintaining coding efficiency.

In some embodiments of the present application, the preset sampling point selection method is a center selection method; the width of the reference chroma block is W, and the height of the reference chroma block is H; the width of the reference luminance block is 2W, and the height of the reference luminance block is 2H;

The at least two reference luminance samples include: a first reference luminance sample, a second reference luminance sample, a third reference luminance sample, and a fourth reference luminance sample; and the reference chrominance samples corresponding to the at least two reference luminance samples include: a first reference chrominance sample, a second reference chrominance sample, a third reference chrominance sample, and a fourth reference luminance sample. A reference chrominance sample point, a third reference chrominance sample point and a fourth reference chrominance sample point; wherein,

The position coordinates of the first reference chromaticity sample point in the reference chromaticity block are (1, 0); the first reference chromaticity sample point is the chromaticity sample point at the upper left corner of the reference chromaticity block;

The position coordinates of the second reference chromaticity sample point in the reference chromaticity block are (W-2, 0);

The position coordinates of the third reference chromaticity sample point in the reference chromaticity block are (1, H-1);

The position coordinates of the fourth reference chromaticity sample point in the reference chromaticity block are (W-2, H-1);

The position coordinates of the first reference brightness sample point in the reference brightness block are (2, 0); the first reference brightness sample point is the brightness sample point at the upper left corner of the reference brightness block;

The position coordinates of the second reference brightness sample point in the reference brightness block are (2×(W-2), 0);

The position coordinates of the third reference brightness sample point in the reference brightness block are (2,2×(H-1));

The position coordinates of the fourth reference luminance sample point in the reference luminance block are (2×(W-2), 2×(H-1)).

In some embodiments of the present application, the preset sample point selection method is a vertex selection method; the width of the reference chroma block is W, and the height of the reference chroma block is H; the width of the reference luminance block is 2W, and the height of the reference luminance block is 2H;

In some embodiments of the present application, at least two reference luma samples include: a first reference luma sample, a second reference luma sample, a third reference luma sample, and a fourth reference luma sample; and the reference chroma samples corresponding to the at least two reference luma samples include: a first reference chroma sample, a second reference chroma sample, a third reference chroma sample, and a fourth reference chroma sample.

The position coordinates of the first reference chromaticity sample point in the reference chromaticity block are (0, 0); the first reference chromaticity sample point is the chromaticity sample point at the upper left corner of the reference chromaticity block;

The position coordinates of the second reference chromaticity sample point in the reference chromaticity block are (W-1, 0);

The position coordinates of the third reference chromaticity sample point in the reference chromaticity block are (0, H-1);

The position coordinates of the fourth reference chromaticity sample point in the reference chromaticity block are (W-1, H-1);

The position coordinates of the first reference brightness sample point in the reference brightness block are (0, 0); the first reference brightness sample point is the brightness sample point at the upper left corner of the reference brightness block;

The position coordinates of the second reference brightness sample point in the reference brightness block are (2×(W-1), 0);

The position coordinates of the third reference brightness sample point in the reference brightness block are (0, 2×(H-1));

The position coordinates of the fourth reference luminance sample point in the reference luminance block are (2×(W-1), 2×(H-1)).

It should be noted that the above-listed center selection method and vertex selection method are only examples. In actual applications, other numbers of reference luminance samples and reference chrominance samples may be selected. In addition, other methods are also included for the coordinate positions of the selected reference luminance samples and reference chrominance samples. In other words, any one of the reference luminance samples and reference chrominance samples may be selected, and the specific selection method may be selected according to the actual application scenario, and the embodiments of the present application do not impose any limitation on this.

In the embodiment of the present application, the first reference chromaticity sample corresponds to the first reference luminance sample, the second reference chromaticity sample corresponds to the second reference luminance sample, the third reference chromaticity sample corresponds to the third reference luminance sample, and the fourth reference chromaticity sample corresponds to the fourth reference luminance sample.

It is understandable that the setting method of vertex selection helps to establish a more accurate cross-component prediction model through the relationship between luma samples and chroma samples. During the encoding process, referring to these samples can improve the prediction accuracy of chroma information, thereby improving video quality.

S5032. Determine a cross-component prediction model according to at least two reference luma samples and at least two reference chroma samples; wherein the at least two reference luma samples correspond to the at least two reference chroma samples.

In some embodiments of the present application, the cross-component prediction model includes one or more cross-component prediction sub-models; determining the implementation of the cross-component prediction model according to at least two reference luma samples and at least two reference chroma samples in S5032 may include S50321 to S50322:

S50321. According to the brightness values of the at least two reference brightness samples, group the at least two reference brightness samples and the at least two reference chrominance samples to obtain at least one reference sample group; wherein each reference sample group includes at least two brightness samples and at least two chrominance samples; the at least two brightness samples correspond to the at least two chrominance samples; the at least two reference brightness samples include at least two brightness samples; the at least two reference chrominance samples include at least two chrominance samples; and at least one reference sample group corresponds to a different preset brightness range.

In the embodiment of the present application, for different reference sample groups, the luma samples and chroma samples contained therein have different preset luma ranges. This distinction may help to better adapt to the brightness changes in different areas of the video. By specifying a different preset luma range for each reference sample group, the brightness differences that may exist in the video can be handled more flexibly, thereby improving the adaptability and performance of the encoding.

Exemplarily, at least one reference sample point group includes: a first sample point group, a second sample point group, a third sample point group and a fourth sample point group. The first sample point group corresponds to a brightness range of 0 to 50, the second sample point group corresponds to a brightness range of 51 to 100, the third sample point group corresponds to a brightness range of 101 to 150, and the fourth sample point group corresponds to a brightness range of 151 to 255.

S50322. For each reference sample point group in at least one reference sample point group, determine a cross-component prediction sub-model corresponding to each reference sample point group according to at least two luma samples and at least two chroma samples in each reference sample point group.

In some embodiments of the present application, S50322 determines the implementation of the cross-component prediction sub-model corresponding to each reference sample group according to at least two luma samples and at least two chroma samples in each reference sample group, which may include:

According to the brightness values of the at least two brightness samples, at least two brightness samples and at least two chrominance samples in each reference sample group are grouped to obtain a first sample group and a second sample group; wherein the first sample group and the second sample group each include at least one brightness sample and at least one chrominance sample; the at least one brightness sample corresponds to the at least one chrominance sample; and a reconstructed brightness value of at least one brightness sample in the first sample group is greater than or equal to a reconstructed brightness value of at least one brightness sample in the second sample group;

Determine a maximum reference luminance value and a first reference chrominance value according to a reconstructed luminance value of at least one luminance sample point and a reconstructed chrominance value of at least one chrominance sample point in the first sample point group, respectively;

Determine a minimum reference luminance value and a second reference chrominance value according to a reconstructed luminance value of at least one luminance sample point and a reconstructed chrominance value of at least one chrominance sample point in the second sample point group;

Determining a scaling factor and an offset factor based on a maximum reference luminance value, a first reference chrominance value, a minimum reference luminance value, and a second reference chrominance value;

According to the scaling factor and the offset factor, the cross-component prediction sub-model corresponding to each reference sample point group is determined.

In the embodiment of the present application, the maximum reference brightness value can be expressed as xMax, the first reference chromaticity value can be expressed as yMax, the minimum reference brightness value can be expressed as xMin, and the second reference chromaticity value can be expressed as yMin. The scaling factor can be expressed as a, and the offset factor can be expressed as b.

In some embodiments of the present application, determining the scaling factor and the offset factor based on the maximum reference luminance value, the first reference chrominance value, the minimum reference luminance value, and the second reference chrominance value may include:

Subtracting the first reference chromaticity value (yMax) from the second reference chromaticity value (yMin) to obtain a first intermediate parameter;

Subtracting the maximum reference brightness value (xMax) from the minimum reference brightness value (xMin) to obtain a second intermediate parameter;

Dividing the first intermediate parameter by the second intermediate parameter to obtain a scaling factor (a);

The scaling factor (a) and the minimum reference brightness value (xMin) are multiplied to obtain a third intermediate parameter;

The second reference chromaticity value (yMin) and the third intermediate parameter are subtracted to obtain an offset factor (b).

In the embodiment of the present application, the first intermediate parameter can be expressed as yMax-yMin. The second intermediate parameter can be expressed as xMax-xMin. The scaling factor can be expressed as a=(yMax-yMin)/(xMax-xMin). The third intermediate parameter can be expressed as a×xMin. The offset factor can be expressed as yMin-a×xMin.

It is understandable that determining the scaling factor and the offset factor can map the reference luminance and chrominance values to a standard range, thereby achieving normalization, which helps to process luminance and chrominance information more consistently in different scenarios. By determining the scaling factor and the offset factor, the prediction model can be made more robust and adaptable to different luminance and chrominance conditions. By performing appropriate luminance and chrominance mapping, data redundancy can be reduced, encoding efficiency can be improved, and image information can be represented more compactly. In general, by determining the scaling factor and the offset factor, the relationship between luminance and chrominance can be better handled, and the encoding performance and image quality can be improved.

In some embodiments of the present application, the cross-component prediction model is a nonlinear model; determining the implementation of the cross-component prediction model based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector in S304 may include:

Selecting all or part of the reference chromaticity samples in the reference chromaticity block;

A cross-component prediction model is determined based on all or part of the reference chroma samples, reference luma samples in a reference luma block that respectively correspond to all or part of the reference chroma samples, and neighborhood reference luma samples of the reference luma samples.

In the embodiment of the present application, when the cross-component prediction model is a nonlinear model, the cross-component prediction model can be expressed by formula (3).

It can be understood that by establishing a cross-component prediction model based on reference chrominance samples and corresponding reference luma samples, the adaptability of the prediction model can be enhanced to better adapt to video content of different types and scenes. Considering the neighborhood reference luma samples of the reference luma samples can more comprehensively capture the luma information, which helps to improve the accuracy of the prediction model, which may be important for processing information such as local features and textures in the image. By more accurately modeling cross-component relationships, it can be expected to reduce the distortion introduced by the prediction, thereby improving the overall video quality, including higher compression efficiency and better visual quality.

In some embodiments of the present application, the neighborhood reference brightness samples include one or more of the following: a reference brightness sample (N) located above the reference brightness sample, a reference brightness sample (S) located below the reference brightness sample, a reference brightness sample (W) located to the left of the reference brightness sample, and a reference brightness sample (E) located to the right of the reference brightness sample.

In an embodiment of the present application, by considering the above-mentioned neighborhood reference brightness samples, the context and local features of the brightness information can be more comprehensively captured, which helps to improve the accuracy and adaptability of the cross-component prediction model. Such information consideration can usually better simulate the changes and textures of the brightness components in the image.

In some embodiments of the present application, the implementation of determining candidate reference samples satisfying a preset prediction mode in the current co-located luminance block in S601 may include:

According to the preset M position information, the candidate reference sample points corresponding to the preset M position information are respectively selected in the current co-located brightness block. Traverse to obtain candidate reference sample points that meet the preset prediction mode; wherein M is a positive integer greater than or equal to 1, and i is a positive integer less than M.

In some embodiments of the present application, the M pieces of location information include one or more of the following:

The position of the middle of the current co-located luminance block;

The upper left position of the current co-located luminance block;

The upper right position of the current co-located luminance block;

The lower left position of the current co-located luminance block;

The lower right position of the current co-located luma block.

In the embodiment of the present application, the preset M position information can be expressed as {C, TL, TR, BL, BR}, where C represents the middle position of the current co-located luminance block, TL represents the upper left position of the current co-located luminance block, TR represents the upper right position of the current co-located luminance block, BL represents the lower left position of the current co-located luminance block, and BR represents the lower right position of the current co-located luminance block.

In some embodiments of the present application, according to the preset M pieces of position information, candidate reference sample points corresponding to the preset M pieces of position information are traversed in the current co-located luminance block to obtain candidate reference sample points that meet the preset prediction mode, including:

For the i-th position information among the preset M position information, if the i-th candidate reference sample corresponding to the i-th position information in the current co-located luminance block does not satisfy the preset prediction mode, continue to traverse the i+1-th candidate reference sample corresponding to the i+1-th position information in the current co-located luminance block until the i+1-th candidate reference sample satisfies the preset prediction mode, and determine the i+1-th candidate reference sample as a candidate reference sample that satisfies the preset prediction mode; or,

In the case that the i-th candidate reference sample point satisfies the preset prediction mode, the i-th candidate reference sample point is determined as a candidate reference sample point that satisfies the preset prediction mode.

In the embodiment of the present application, for the i-th position information among the preset M position information, the i-th candidate reference sample corresponding thereto is considered. It is determined whether the i-th candidate reference sample in the current co-located luminance block satisfies the preset prediction mode. If the i-th candidate reference sample does not satisfy the preset prediction mode, then the i+1-th candidate reference sample corresponding to the i+1-th position information in the current co-located luminance block is traversed. If the i-th candidate reference sample satisfies the preset prediction mode, then the i-th candidate reference sample is determined as a candidate reference sample that satisfies the preset prediction mode.

It can be understood that, on the one hand, by checking each position information one by one, it can be ensured that the selected candidate reference samples better match the preset conditions in the prediction mode, thereby improving the accuracy of the prediction. On the one hand, selecting candidate reference samples that meet the preset conditions helps to improve the prediction quality of the image block, thereby improving the visual quality of the overall image. On the one hand, through the preset position information and conditions, appropriate candidate reference samples can be selected according to different scenarios and requirements, making the prediction mode more flexible and adaptable. On the one hand, the effective selection of candidate reference samples can reduce redundant information, thereby improving the efficiency and performance of encoding in video compression. In general, the above steps help to improve the performance of the cross-component prediction model in video coding, so that it can better adapt to different prediction scenarios and requirements.

In some embodiments of the present application, the implementation of determining the predicted chroma value of the predicted chroma block based on the cross-component prediction model in S503 may include S5031 to S5032:

S5031. Determine the candidate predicted chrominance value of the candidate chrominance prediction block according to the reconstructed luminance value of each pixel in the current co-located luminance block through a cross-component prediction model; wherein the candidate chrominance prediction block is different in size from the current chrominance block.

In an embodiment of the present application, the reconstructed luminance value of each pixel in the current co-located luminance block is input into a cross-component prediction model to obtain a candidate predicted chrominance value of the candidate chrominance prediction block.

In some embodiments of the present application, the cross-component prediction model includes at least one cross-component prediction sub-model; the implementation of determining the candidate predicted chrominance value of the candidate chrominance prediction block according to the reconstructed luminance value of each pixel in the current co-located luminance block through the cross-component prediction model in S3041 may include:

For each pixel in the current co-located luminance block, the reconstructed luminance value of each pixel is input into the corresponding cross-component prediction sub-model to obtain a candidate predicted chrominance value corresponding to each pixel; wherein the preset luminance range corresponding to the reconstructed luminance value of each pixel matches the cross-component prediction sub-model;

Determine the candidate predicted chrominance value of the candidate chrominance prediction block according to the candidate predicted chrominance value corresponding to each pixel in the current co-located luminance block.

It can be understood that, on the one hand, the use of different cross-component prediction sub-models for each pixel can better adapt to the brightness and chrominance characteristics of different areas in the image. This adaptability helps to improve the performance of the encoder in various image scenarios. On the one hand, the use of the preset brightness range corresponding to each pixel and the cross-component prediction sub-model provides fine-grained control of different pixels, which enables the encoder to better cope with subtle differences that may exist in the image and improves the flexibility of encoding. In general, the above steps help to better capture the relationship between brightness and chrominance through a more refined cross-component prediction sub-model, thereby improving the quality of chrominance prediction and coding efficiency.

S5032. Downsample the candidate predicted chrominance values of the candidate chrominance prediction block to obtain predicted chrominance values of the predicted chrominance block.

In the embodiment of the present application, the candidate predicted chrominance values of the candidate chrominance prediction block are filtered by a six-tap filter [1 2 1; 1 2 1]. Sampling, the process can be expressed by formula (4).

It can be understood that, on the one hand, the cross-component prediction model allows for better capture of the complex relationship between luminance and chrominance, and by using the reconstructed luminance value of the co-located luminance block, the predicted chrominance value can more accurately reflect the details and features in the image. On the other hand, since the size of the candidate chrominance prediction block is different from the current chrominance block, this method can adapt in size, making the prediction more adaptable to the details and structures of different regions in the image. In general, the above steps combine the advantages of information capture, size adaptability, and coding efficiency, which helps to improve the quality of chrominance prediction and reduce the amount of data while maintaining efficient coding.

In another embodiment of the present application, a coding method is provided. The core idea of the method is to combine TSCPM with CIBC technology, which is hereinafter represented by TSCPM_CIBC. The main process includes four parts:

1) Obtain the luminance reference block (i.e., reference luminance block) and chrominance reference block (i.e., reference chrominance block) corresponding to the block motion vector (i.e., reference motion vector);

2) Derivation of a cross-component model (i.e., a cross-component prediction model) based on the acquired luminance reference block and chrominance reference block;

3) The pixel value of the intermediate prediction block (i.e., the candidate prediction chrominance value of the candidate prediction block) is calculated based on the derived cross-component model and the reconstructed pixel value of the co-located luminance block (i.e., the current co-located luminance block) corresponding to the current chrominance block to be encoded (i.e., the current chrominance block);

4) Downsample the intermediate prediction block to obtain the final chrominance prediction block (i.e., the predicted chrominance value of the predicted chrominance block).

In an embodiment of the present application, the encoding and decoding method may include the following steps:

Step 1. First, the activation condition of this mode is similar to the CIBC technology, that is, if the luminance sample located at the position {C, TL, TR, BL, BR} on the luminance co-located block of the current chrominance block to be encoded is a block copy intra-frame prediction mode or a normal string sub-mode of string copy intra-frame prediction, then the current block can use the cross-component prediction mode based on the chrominance intra-frame block copy technology.

In the embodiment of the present application, if the conditions for using the TSCPM_CIBC technology are met, first, according to the five preset positions {C, TL, TR, BL, BR} in the co-located luminance block corresponding to the current chrominance block to be encoded, they are traversed in a fixed order, and the BV at the luminance sample point that first meets the conditions is obtained as the reference BV of the current block, and the reference blocks corresponding to the luminance and chrominance are obtained respectively through the BV. If the BV is an invalid BV, that is, the valid reconstructed pixel value cannot be obtained through the BV, the prediction value of all samples of the current chrominance block is set to 2 ^BitDepth-1 .

Step 2: Select sample points from the obtained luminance reference block and chrominance reference block for deriving a cross-component model, where the sample points can be all or part of the sample points of the reference block, and the derived cross-component model can be a linear model or a nonlinear model.

In an embodiment of the present application, referring to the implementation scheme of the original AVS3 technology TSCPM, the selection of sample points is changed from obtaining 4 pixel points from the reconstructed pixels in an adjacent row and column of the original current block to selecting 4 pixel points from the reference block pointed to by BV. The current pixel point selection scheme is specifically: pixel points in the four area positions of the upper left, upper right, lower left, and lower right of the current block.

In the embodiment of the present application, assume that the chrominance block to be encoded is of size W×H, with a width of W and a height of H, x represents the horizontal coordinate, y represents the vertical coordinate, and the coordinate of the upper left corner of the current block is (0,0), then the positions of the four chrominance reconstruction pixels are (1,0), (w-2,0), (1,h-1), (w-2,h-1). The size of the corresponding luminance block to be encoded is 2W×2H, and the positions of the corresponding four luminance reconstruction pixels are (2,0), (2×(w-2),0), (2,2×(h-1)), (2×(w-2),2×(h-1)). The luminance reconstruction pixels and chrominance reconstruction pixels at the four corresponding positions are bound to each other one by one, and the four selected luminance reconstruction pixels are sorted and grouped, with the two points with larger pixel values forming a group and the two points with smaller pixel values forming a group. The average value of the group with larger luminance reconstruction pixel values is recorded as xMax, and the average value of the group with smaller pixel values is recorded as xMin. Similarly, the values corresponding to the chromaticity reconstruction pixel values are calculated and recorded as yMax and yMin respectively. The cross-component model of this scheme is a linear model, the scaling factor is recorded as a, and the offset factor is recorded as b. Then we can get a = (yMax-yMin)/(xMax-xMin), b = yMin-a×xMin.

Step 3: Based on the derived linear model parameters a and b, and the reconstructed pixel values in the co-located luminance block corresponding to the current chrominance block to be encoded, an intermediate prediction block can be generated. The size of this block is the same as that of the co-located luminance block, i.e., 2W×2H. The pixel values of the intermediate prediction block are calculated by the formula P _t (x, y) = a×R _Luma (x, y) + b, where (x, y) represents the horizontal and vertical coordinates of the corresponding pixel points, and both are integers. The value range of x is [0, 2W-1], and the value range of y is [0, 2H-1]. R _Luma represents the reconstructed pixel value of the co-located luminance block, and P _t represents the calculated intermediate prediction value of the intermediate prediction block.

Step 4: Downsample the intermediate prediction block to obtain the final chrominance prediction block. In this scheme, a six-tap filter [1 2 1; 1 2 1] is used for downsampling, and the final chrominance prediction block is used as the prediction output under TSCPM_CIBC mode.

In an embodiment of the present application, an implementation of a decoding end is provided, including:

The decoder obtains the bitstream information and parses the bitstream. When parsing the intra-frame prediction mode of the current chroma block to be encoded, the value of tcibc_flag is parsed. If the value of tcibc_flag is 0, other modes are used for prediction, and the prediction mode is set to the corresponding prediction mode; if tcibc_flag is 1, the prediction mode of the current chroma block is set to TSCPM_CIBC. Then continue to parse other related bitstream information.

During the prediction decoding process of the current coded chroma block, if the prediction mode is TSCPM_CIBC, the following prediction process is performed. According to the five preset positions {C, TL, TR, BL, BR} in the same luminance block corresponding to the current chroma block to be encoded, they are traversed in a fixed order, and the BV at the luminance sample that first meets the conditions is obtained as the reference BV of the current block. If the BV is an invalid BV, the prediction values of all samples of the current chroma block are set to 2BitDepth-1. If the BV is a valid BV, the corresponding reference blocks of luminance and chroma are obtained through the BV.

Note that the size of the current chrominance block is WxH, and the positions of the four images (1,0), (w-2,0), (1,h-1), and (w-2,h-1) are obtained from the chrominance reference block. The chromaticity reconstructed pixel value of the pixel point, the brightness reconstructed pixel values of the four pixels at positions (2,0), (2×(w-2),0), (2,2×(h-1)), (2×(w-2),2×(h-1)) are obtained from the brightness reference block. The brightness reconstructed pixel points and the chromaticity reconstructed pixel points at the four corresponding positions are bound to each other one by one, and the four selected brightness reconstructed pixel points are sorted and grouped, with the two points with larger pixel values as one group and the two points with smaller pixel values as one group. The average value of the group with larger brightness reconstructed pixel values is recorded as xMax, and the average value of the group with smaller pixel values is recorded as xMin. Similarly, the values corresponding to the chromaticity reconstructed pixel values are calculated and recorded as yMax and yMin respectively. The cross-component model of this scheme is a linear model, the scaling factor is recorded as a, and the offset factor is recorded as b. Then we can get a＝(yMax-yMin)/(xMax-xMin), b＝yMin-a×xMin. According to the derived linear model parameters a and b, the intermediate prediction block is calculated by the formula P _t (x, y) = a × R _Luma (x, y) + b, and finally a six-tap filter [1 2 1; 1 2 1] is used to downsample the intermediate prediction block to obtain the final chrominance prediction block. Then, the inverse transformation and inverse quantization operations are continued.

In an embodiment of the present application, an implementation of an encoding end is provided, including:

First, according to the preset five positions {C, TL, TR, BL, BR} in the same position luma block corresponding to the current chroma block to be encoded, traverse in a fixed order, and obtain the BV at the luma sample that first meets the conditions as the reference BV of the current block. If the BV is an invalid BV, that is, it is impossible to obtain a valid reconstructed pixel value through the BV, then the prediction value of all samples of the current chroma block is set to 2BitDepth-1. If the BV is a valid BV, the corresponding reference blocks of luma and chroma are obtained through the BV. Let the size of the current chroma block be WxH, and the chroma reconstructed pixel values of the four pixels at positions (1,0), (w-2,0), (1,h-1), and (w-2,h-1) are obtained from the chroma reference block, and the luma reconstructed pixel values of the four pixels at positions (2,0), (2×(w-2),0), (2,2×(h-1)), (2×(w-2),2×(h-1)) are obtained from the luma reference block. The brightness reconstruction pixels and chrominance reconstruction pixels at four corresponding positions are bound to each other one by one, and the four selected brightness reconstruction pixels are sorted and grouped, with the two pixels with larger pixel values forming one group and the two pixels with smaller pixel values forming one group. The average value of the group with larger brightness reconstruction pixel values is recorded as xMax, and the average value of the group with smaller pixel values is recorded as xMin. Similarly, the values corresponding to the chrominance reconstruction pixel values are calculated and recorded as yMax and yMin respectively. The cross-component model of this scheme is a linear model, with the scaling factor recorded as a and the offset factor recorded as b. Then a＝(yMax-yMin)/(xMax-xMin), b＝yMin-a×xMin. Based on the derived linear model parameters a and b, the intermediate prediction block is calculated by the formula P _t (x,y)＝a×R _Luma (x,y)+b, and finally a six-tap filter [1 2 1; 1 2 1] is used to downsample the intermediate prediction block to obtain the final chrominance prediction block.

Compare the current chroma prediction block with the original chroma block, calculate the pixel distortion value SAD, estimate the bit overhead bits of the coded bitstream, calculate the RDCost of this mode based on the above information, and compare it with the rate distortion cost of other prediction modes. If the rate distortion cost of the TSCPM_CIBC mode is the smallest, set the value of tcibc_flag to 1, otherwise, set the value of tcibc_flag to 0. Finally, in the coded bitstream stage, write the value of the flag bit tcibc_flag into the bitstream.

The performance test results of the encoding and decoding method provided in the embodiment of the present application on the AVS4 exploration phase reference software EVM-0.2, according to the general test conditions for screen content encoding, are shown in Table 3 below:

Table 3

It can be seen that the encoding and decoding method provided in the embodiment of the present application can effectively utilize the information of the chroma intra-frame block copy technology to obtain relatively matching luminance reference blocks and chroma reference blocks, and combine the spirit of the two-step cross-component prediction technology to derive a set of cross-component model parameters based on the obtained reference blocks, and apply them to the current block to be encoded to improve the accuracy of the prediction, thereby effectively improving the encoding performance without introducing additional complexity.

In an embodiment of the present application, a new cross-component prediction mode is proposed. This mode obtains a set of corresponding luminance reference blocks and chrominance reference blocks through the method of chrominance intra-frame block copy technology, and selects sample points from them to derive a set of cross-component models. Then, according to the methods of the two cross-component prediction modes, the cross-component model is applied to the co-located luminance block corresponding to the current chrominance block to be encoded to obtain an intermediate prediction block, and finally the final prediction block is generated by downsampling.

In the embodiment of the present application, the derivation process of the cross-component model is mainly carried out with reference to the original technology TSCPM of the AVS3 standard. Due to the different sources of the reference sample points, the methods for selecting the reference sample points are different. The sample point selection scheme in this scheme can be improved, including selecting 4 pixel points at different positions, or increasing the number of selected sample points, and changing the calculation scheme of the linear model.

In an embodiment of the present application, in TSCPM, there is only one linear model between the brightness and chrominance of the same coding block. If it is expanded to a multi-model cross-component linear model, multiple models can be provided for the same coding block. Adjacent brightness and chrominance pixels are divided into different categories according to the classification threshold, and the pixels in each category are used to calculate different model parameters.

In one embodiment of the present application, based on the same inventive concept as the above embodiment, a code stream is provided, wherein the code stream is based on the code to be encoded. The information to be encoded is generated by bit encoding; wherein the information to be encoded includes at least one of the following:

The value of the first syntax identification information, the value of the second syntax identification information, the value of the third syntax identification information, and the quantized chroma residual value of the current chroma block; wherein the first syntax identification information is used to indicate whether the current chroma block adopts a cross-component prediction mode based on the chroma intra-frame block copy technology; the second syntax identification information is used to indicate whether the current chroma block adopts a chroma intra-frame block copy prediction mode; the third syntax identification information is used to indicate whether the current chroma block adopts a chroma intra-frame block copy prediction mode or a cross-component prediction mode based on the chroma intra-frame block copy technology.

In another embodiment of the present application, based on the same inventive concept as the above-mentioned embodiment, refer to Figure 17, which shows a schematic diagram of the composition structure of a decoder provided in an embodiment of the present application. As shown in Figure 17, the decoder 1000 includes a decoding part 1001 and a first determining part 1002, wherein:

The decoding part 1001 is configured to parse the code stream and determine the first syntax identification information;

The first determining part 1002 is configured to determine a reference motion vector according to a current co-located luminance block corresponding to the current chrominance block when the first syntax identification information indicates that the current chrominance block adopts a cross-component prediction mode based on a chrominance intra block copy technique;

When the reference motion vector is valid, determining a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector;

Determining a predicted chroma value of a predicted chroma block based on the cross-component prediction model;

Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block.

In some embodiments, the cross-component prediction model characterizes that a reconstructed luminance value of a current co-located luminance block corresponding to the current chrominance block has a linear or nonlinear relationship with a predicted chrominance value of the predicted chrominance block.

In some embodiments, the first determining part 1002 is further configured to determine candidate reference samples that meet a preset prediction mode in the current co-located luminance block, and use the motion vector corresponding to the candidate reference sample as a reference motion vector.

In some embodiments, the first determination part 1002 is further configured to determine at least two reference luma samples in the reference luma block according to a preset sample selection method, and to determine reference chroma samples corresponding to the at least two reference luma samples in the reference chroma block according to the preset sample selection method; determine the cross-component prediction model according to the at least two reference luma samples and the at least two reference chroma samples; wherein the at least two reference luma samples correspond to the at least two reference chroma samples.

In some embodiments, the cross-component prediction model includes one or more cross-component prediction sub-models; the first determination part 1002 is also configured to group the at least two reference luma samples and the at least two reference chroma samples according to the luma values of the at least two reference luma samples to obtain at least one reference sample group; wherein each reference sample group includes at least two luma samples and at least two chroma samples; the at least two luma samples correspond to the at least two chroma samples; the at least two reference luma samples include the at least two luma samples; the at least two reference chroma samples include the at least two chroma samples; the at least one reference sample group corresponds to a different preset luma range; for each reference sample group in the at least one reference sample group, the cross-component prediction sub-model corresponding to each reference sample group is determined according to the at least two luma samples and the at least two chroma samples in each reference sample group.

In some embodiments, the first determining part 1002 is further configured to group the at least two luma samples and the at least two chroma samples in each reference sample group according to the luma values of the at least two luma samples to obtain a first sample group and a second sample group; wherein the first sample group and the second sample group each include at least one luma sample and at least one chroma sample; the at least one luma sample corresponds to the at least one chroma sample; the reconstructed luma value of at least one luma sample in the first sample group is greater than or equal to the reconstructed luma value of at least one luma sample in the second sample group; according to the The maximum reference luminance value and the first reference chrominance value are determined respectively based on the reconstructed luminance value of at least one luminance sample and the reconstructed chrominance value of at least one chrominance sample in the first sample point group; the minimum reference luminance value and the second reference chrominance value are determined respectively based on the reconstructed luminance value of at least one luminance sample and the reconstructed chrominance value of at least one chrominance sample in the second sample point group; a scaling factor and an offset factor are determined based on the maximum reference luminance value, the first reference chrominance value, the minimum reference luminance value and the second reference chrominance value; and the cross-component prediction sub-model corresponding to each reference sample point group is determined based on the scaling factor and the offset factor.

In some embodiments, the first determination part 1002 is further configured to perform a subtraction operation on the first reference chromaticity value and the second reference chromaticity value to obtain a first intermediate parameter; perform a subtraction operation on the maximum reference luminance value and the minimum reference luminance value to obtain a second intermediate parameter; perform a division operation on the first intermediate parameter and the second intermediate parameter to obtain the scaling factor; perform a multiplication operation on the scaling factor and the minimum reference luminance value to obtain a third intermediate parameter; and perform a subtraction operation on the second reference chromaticity value and the third intermediate parameter to obtain the offset factor.

In some embodiments, the cross-component prediction model is a nonlinear model; the first determination part 1002 is also configured to select all or part of the reference chroma samples in the reference chroma block; and determine the cross-component prediction model based on the all or part of the reference chroma samples, the reference luminance samples in the reference luminance block corresponding to the all or part of the reference chroma samples, and the neighborhood reference luminance samples of the reference luminance samples.

In some embodiments, the neighborhood reference luma samples include one or more of the following: a reference luma sample located above the reference luma sample, a reference luma sample located below the reference luma sample, a reference luma sample located to the left of the reference luma sample, and a reference luma sample located to the right of the reference luma sample.

In some embodiments, the first determination part 1002 is further configured to traverse the candidate reference sample points corresponding to each of the preset M position information in the current co-located luminance block according to the preset M position information, to obtain the candidate reference sample points that satisfy the preset prediction mode; wherein M is a positive integer greater than or equal to 1, and i is a positive integer less than M.

In some embodiments, the first determining part 1002 is further configured to, for the i-th position information among the preset M position information, if the i-th candidate reference sample corresponding to the i-th position information in the current co-located luminance block does not satisfy the preset prediction mode, continue to traverse the i+1-th candidate reference sample corresponding to the i+1-th position information in the current co-located luminance block until the i+1-th candidate reference sample satisfies the preset prediction mode, and determine the i+1-th candidate reference sample as a candidate reference sample that satisfies the preset prediction mode; or, if the i-th candidate reference sample satisfies the preset prediction mode, determine the i-th candidate reference sample as a candidate reference sample that satisfies the preset prediction mode.

In some embodiments, the M positions information include one or more of the following: the middle position of the current co-located brightness block; the upper left position of the current co-located brightness block; the upper right position of the current co-located brightness block; the lower left position of the current co-located brightness block; and the lower right position of the current co-located brightness block.

In some embodiments, the preset prediction mode is: the candidate reference samples adopt a block copy intra prediction mode or a common string sub-mode of a string copy intra prediction.

In some embodiments, the preset sample point selection method includes any one of the following: a center selection method, a vertical selection method, a horizontal selection method, a diagonal selection method, and a vertex selection method.

In some embodiments, the preset sample selection method is a center selection method; the width of the reference chroma block is W, and the height of the reference chroma block is H; the width of the reference luminance block is 2W, and the height of the reference luminance block is 2H; the at least two reference luminance samples include: a first reference luminance sample, a second reference luminance sample, a third reference luminance sample, and a fourth reference luminance sample; the reference chroma samples corresponding to the at least two reference luminance samples include: a first reference chroma sample, a second reference chroma sample, a third reference chroma sample, and a fourth reference chroma sample; wherein the position coordinates of the first reference chroma sample in the reference chroma block are (1,0); the first reference chroma sample is the chroma sample at the upper left corner of the reference chroma block; the second reference chroma sample is The position coordinates of the chromaticity sample in the reference chromaticity block are (W-2, 0); the position coordinates of the third reference chromaticity sample in the reference chromaticity block are (1, H-1); the position coordinates of the fourth reference chromaticity sample in the reference chromaticity block are (W-2, H-1); the position coordinates of the first reference luminance sample in the reference luminance block are (2, 0); the first reference luminance sample is the luminance sample at the upper left corner of the reference luminance block; the position coordinates of the second reference luminance sample in the reference luminance block are (2×(W-2), 0); the position coordinates of the third reference luminance sample in the reference luminance block are (2, 2×(H-1)); the position coordinates of the fourth reference luminance sample in the reference luminance block are (2×(W-2), 2×(H-1)).

In some embodiments, the first determining part 1002 is further configured to determine the predicted chroma value of the predicted chroma block according to the sample accuracy of the current chroma block when the reference motion vector is invalid.

In some embodiments, the first determination part 1002 is further configured to perform a subtraction operation on the sample accuracy and a first preset value to obtain a fourth intermediate parameter; and perform an exponential operation on the second preset value and the fourth intermediate parameter to obtain a predicted chromaticity value of each pixel in the predicted chromaticity block.

In some embodiments, the first determination part 1002 is further configured to determine that the reference motion vector is invalid when the reference motion vector satisfies at least one of the following conditions: the reference luminance block or the reference chrominance block corresponding to the reference motion vector has not been reconstructed, the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector does not match, and the reference motion vector is out of bounds; or, determine that the reference motion vector is valid when the reference motion vector satisfies the following conditions: the reference luminance block or the reference chrominance block corresponding to the reference motion vector has been reconstructed, the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector matches, and the reference motion vector is not out of bounds.

In some embodiments, the first determination part 1002 is further configured to determine the candidate predicted chrominance value of the candidate chrominance prediction block according to the reconstructed luminance value of each pixel in the current co-located luminance block through the cross-component prediction model; wherein the candidate chrominance prediction block is different in size from the current chrominance block; and downsample the candidate predicted chrominance value of the candidate chrominance prediction block to obtain the predicted chrominance value of the predicted chrominance block.

In some embodiments, the cross-component prediction model includes at least one cross-component prediction sub-model; the first determination part 1002 is also configured to input the reconstructed luminance value of each pixel in the current co-located luminance block into the corresponding cross-component prediction sub-model to obtain the candidate predicted chromaticity value corresponding to each pixel; wherein the preset luminance range corresponding to the reconstructed luminance value of each pixel matches the cross-component prediction sub-model; and determine the candidate predicted chromaticity value of the candidate chromaticity prediction block according to the candidate predicted chromaticity value corresponding to each pixel in the current co-located luminance block.

In some embodiments, the decoding part 1001 is further configured to parse the code stream to determine the second syntax identification information; when the second syntax identification information indicates that the current chroma block does not adopt the chroma intra block copy prediction mode, perform the parsing of the code stream to obtain the first The steps of the syntax identification information.

In some embodiments, the decoding part 1001 is further configured to determine that the current chroma block adopts the chroma intra-frame block copy prediction mode if the value of the second syntax identification information is a first value; or, if the value of the second syntax identification information is a second value, determine that the current chroma block does not adopt the chroma intra-frame block copy prediction mode.

In some embodiments, the decoding part 1001 is further configured to determine that the current chroma block adopts a cross-component prediction mode based on the chroma intra-frame block copy technology if the value of the first syntax identification information is a third value; or, if the value of the first syntax identification information is a fourth value, determine that the current chroma block does not adopt a cross-component prediction mode based on the chroma intra-frame block copy technology.

In some embodiments, the decoding part 1001 is also configured to parse the code stream to determine the third syntax identification information; when the third syntax identification information indicates that the current chroma block adopts the chroma intra-frame block copy prediction mode or the cross-component prediction mode based on the chroma intra-frame block copy technology, perform the step of parsing the code stream to obtain the first syntax identification information.

In some embodiments, the decoding part 1001 is further configured to determine that the current chroma block adopts the chroma intra-frame block copy prediction mode or the cross-component prediction mode based on the chroma intra-frame block copy technology if the value of the third syntax identification information is the fifth value; or, if the value of the third syntax identification information is the sixth value, determine that the current chroma block does not adopt the chroma intra-frame block copy prediction mode or the cross-component prediction mode based on the chroma intra-frame block copy technology.

In some embodiments, the decoding part 1001 is also configured to determine that the current chroma block adopts a cross-component prediction mode based on the chroma intra-frame block copy technology if the value of the first syntax identification information is the seventh value; or, if the value of the first syntax identification information is the eighth value, determine that the current chroma block adopts the chroma intra-frame block copy prediction mode.

In some embodiments, the decoding part 1001 is further configured to parse the bit stream to obtain the chroma residual value of the current chroma block.

In some embodiments, the first determination part 1002 is further configured to perform inverse transformation and inverse quantization on the chroma residual value to obtain an inverse quantized chroma residual value of the current chroma block; and determine the reconstructed chroma value of the current chroma block based on the inverse quantized chroma residual value and the predicted chroma value.

It is understandable that in the embodiments of the present application, "part" can be a part of a circuit, a part of a processor, a part of a program or software, etc., and of course it can also be a module, or it can be non-modular. Moreover, the components in the present embodiment can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of a software functional module.

If the integrated unit is implemented in the form of a software function module and is not sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this embodiment is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) or a processor to perform all or part of the steps of the method described in this embodiment. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc., various media that can store program codes.

Therefore, an embodiment of the present application provides a computer-readable storage medium, which is applied to the decoder 1000. The computer-readable storage medium stores a computer program, and when the computer program is executed by the first processor, the method described in any one of the aforementioned embodiments is implemented.

Based on the composition of the above-mentioned decoder 1000 and the computer-readable storage medium, refer to Figure 18, which shows a specific hardware structure diagram of the decoder 1000 provided in an embodiment of the present application. As shown in Figure 18, the decoder 1000 may include: a first communication interface 1101, a first memory 1102 and a first processor 1103; each component is coupled together through a first bus system 1104. It can be understood that the first bus system 1104 is used to achieve connection and communication between these components. In addition to the data bus, the first bus system 1104 also includes a power bus, a control bus and a status signal bus. However, for the sake of clarity, various buses are marked as the first bus system 1104 in Figure 18. Among them,

The first communication interface 1101 is used for receiving and sending signals during the process of sending and receiving information with other external network elements;

A first memory 1102, used to store a computer program that can be run on the first processor 1103;

The first processor 1103 is configured to, when running the computer program, execute:

Parsing the code stream to determine first syntax identification information;

When the first syntax identification information indicates that the current chroma block adopts a cross-component prediction mode based on a chroma intra block copying technique, determining a reference motion vector according to a current co-located luminance block corresponding to the current chroma block;

When the reference motion vector is valid, determining a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector;

Determining a predicted chroma value of a predicted chroma block based on the cross-component prediction model;

Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block.

It can be understood that the first memory 1102 in the embodiment of the present application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), Programmable ROM (PROM), Erasable PROM (EPROM), Electrically Erasable Programmable ROM (EEPROM) or Flash memory. Volatile memory can be Random Access Memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate Synchronous Dynamic Random Access Memory (DDRSDRAM), Enhanced Synchronous Dynamic Random Access Memory (ESDRAM), Synchronous Link Dynamic Random Access Memory (SLDRAM) and Direct Rambus RAM (DRRAM). The first memory 1102 of the system and method described in the present application is intended to include but is not limited to these and any other suitable types of memory.

The first processor 1103 may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by the hardware integrated logic circuit or software instructions in the first processor 1103. The above-mentioned first processor 1103 can be a general-purpose processor, a digital signal processor (Digital Signal Processor, DSP), an application-specific integrated circuit (Application Specific Integrated Circuit, ASIC), a field programmable gate array (Field Programmable Gate Array, FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The methods, steps and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in the embodiments of the present application can be directly embodied as a hardware decoding processor to execute, or the hardware and software modules in the decoding processor can be executed. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in the first memory 1102, and the first processor 1103 reads the information in the first memory 1102 and completes the steps of the above method in combination with its hardware.

It is understood that the embodiments described in this application can be implemented in hardware, software, firmware, middleware, microcode or a combination thereof. For hardware implementation, the processing unit can be implemented in one or more application specific integrated circuits (Application Specific Integrated Circuits, ASIC), digital signal processors (Digital Signal Processing, DSP), digital signal processing devices (DSP Device, DSPD), programmable logic devices (Programmable Logic Device, PLD), field programmable gate arrays (Field-Programmable Gate Array, FPGA), general processors, controllers, microcontrollers, microprocessors, other electronic units for performing the functions described in this application or a combination thereof. For software implementation, the technology described in this application can be implemented by a module (such as a process, function, etc.) that performs the functions described in this application. The software code can be stored in a memory and executed by a processor. The memory can be implemented in the processor or outside the processor.

Optionally, as another embodiment, the first processor 1103 is further configured to execute any one of the methods described in the foregoing embodiments when running the computer program.

The present embodiment provides a decoder, in which, since the cross-component prediction model is determined by a reference luminance block and a reference chrominance block corresponding to a reference motion vector, compared to a cross-component prediction model derived based on reconstructed pixels in an adjacent row and column of a current chrominance block, the flexibility and diversity of determining the cross-component prediction model can be improved, so that the cross-component prediction model can flexibly cope with more complex decoding scenarios, thereby improving the decoding efficiency of the current chrominance block.

In another embodiment of the present application, based on the same inventive concept as the above-mentioned embodiment, see FIG19 , which shows a schematic diagram of the composition structure of an encoder provided by an embodiment of the present application. As shown in FIG19 , the encoder 2000 may include a second determination part 2001 and an encoding part 2002; wherein,

The second determining part 2001 is configured to determine a reference motion vector according to a current co-located luminance block corresponding to a current chrominance block;

When the reference motion vector is valid, determining the cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector;

Based on the cross-component prediction model, determine a predicted chroma value of the predicted chroma block, and determine first syntax identification information according to the predicted chroma value; wherein the first syntax identification information is used to indicate whether the current chroma block adopts a cross-component prediction mode based on a chroma intra block copy technology;

Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block.

In some embodiments, the cross-component prediction model characterizes that a reconstructed luminance value of a current co-located luminance block corresponding to the current chrominance block has a linear or nonlinear relationship with a predicted chrominance value of the predicted chrominance block.

In some embodiments, the second determining part 2001 is further configured to determine candidate reference samples that satisfy a preset prediction mode in the current co-located luminance block, and use the motion vector corresponding to the candidate reference sample as a reference motion vector.

In some embodiments, the second determination part 2001 is further configured to determine at least two reference luma samples in the reference luma block according to a preset sample selection method, and to determine reference chroma samples corresponding to the at least two reference luma samples in the reference chroma block according to the preset sample selection method; determine the cross-component prediction model according to the at least two reference luma samples and the at least two reference chroma samples; wherein the at least two reference luma samples correspond to the at least two reference chroma samples.

In some embodiments, the cross-component prediction model includes one or more cross-component prediction sub-models; the second determining part 2001, It is also configured to group the at least two reference luminance samples and the at least two reference chrominance samples according to the luminance values of the at least two reference luminance samples to obtain at least one reference sample group; wherein each reference sample group includes at least two luminance samples and at least two chrominance samples; the at least two luminance samples correspond to the at least two chrominance samples; the at least two reference luminance samples include the at least two luminance samples; the at least two reference chrominance samples include the at least two chrominance samples; the at least one reference sample group corresponds to a different preset luminance range; for each reference sample group in the at least one reference sample group, the cross-component prediction sub-model corresponding to each reference sample group is determined according to the at least two luminance samples and the at least two chrominance samples in the each reference sample group.

In some embodiments, the second determining part 2001 is further configured to group the at least two luma samples and the at least two chroma samples in each reference sample group according to the luma values of the at least two luma samples to obtain a first sample group and a second sample group; wherein the first sample group and the second sample group each include at least one luma sample and at least one chroma sample; the at least one luma sample corresponds to the at least one chroma sample; the reconstructed luma value of at least one luma sample in the first sample group is greater than or equal to the reconstructed luma value of at least one luma sample in the second sample group; and according to the The maximum reference luminance value and the first reference chrominance value are determined respectively based on the reconstructed luminance value of at least one luminance sample and the reconstructed chrominance value of at least one chrominance sample in the first sample point group; the minimum reference luminance value and the second reference chrominance value are determined respectively based on the reconstructed luminance value of at least one luminance sample and the reconstructed chrominance value of at least one chrominance sample in the second sample point group; a scaling factor and an offset factor are determined based on the maximum reference luminance value, the first reference chrominance value, the minimum reference luminance value and the second reference chrominance value; and the cross-component prediction sub-model corresponding to each reference sample point group is determined based on the scaling factor and the offset factor.

In some embodiments, the second determination part 2001 is further configured to subtract the first reference chromaticity value from the second reference chromaticity value to obtain a first intermediate parameter; subtract the maximum reference luminance value from the minimum reference luminance value to obtain a second intermediate parameter; divide the first intermediate parameter and the second intermediate parameter to obtain the scaling factor; multiply the scaling factor and the minimum reference luminance value to obtain a third intermediate parameter; and subtract the second reference chromaticity value from the third intermediate parameter to obtain the offset factor.

In some embodiments, the cross-component prediction model is a nonlinear model; the second determination part 2001 is also configured to select all or part of the reference chroma samples in the reference chroma block; and determine the cross-component prediction model based on the all or part of the reference chroma samples, the reference luminance samples in the reference luminance block corresponding to the all or part of the reference chroma samples, and the neighborhood reference luminance samples of the reference luminance samples.

In some embodiments, the neighborhood reference luma samples include one or more of the following: a reference luma sample located above the reference luma sample, a reference luma sample located below the reference luma sample, a reference luma sample located to the left of the reference luma sample, and a reference luma sample located to the right of the reference luma sample.

In some embodiments, the second determination part 2001 is further configured to traverse the candidate reference sample points corresponding to each of the preset M position information in the current co-located luminance block according to the preset M position information, to obtain the candidate reference sample points that satisfy the preset prediction mode; wherein M is a positive integer greater than or equal to 1, and i is a positive integer less than M.

In some embodiments, the second determination part 2001 is further configured to, for the i-th position information among the preset M position information, if the i-th candidate reference sample corresponding to the i-th position information in the current co-located luminance block does not satisfy the preset prediction mode, continue to traverse the i+1-th candidate reference sample corresponding to the i+1-th position information in the current co-located luminance block until the i+1-th candidate reference sample satisfies the preset prediction mode, and determine the i+1-th candidate reference sample as a candidate reference sample that satisfies the preset prediction mode; or, if the i-th candidate reference sample satisfies the preset prediction mode, determine the i-th candidate reference sample as a candidate reference sample that satisfies the preset prediction mode.

In some embodiments, the M positions information include one or more of the following: the middle position of the current co-located brightness block; the upper left position of the current co-located brightness block; the upper right position of the current co-located brightness block; the lower left position of the current co-located brightness block; and the lower right position of the current co-located brightness block.

In some embodiments, the preset prediction mode is: the candidate reference samples adopt a block copy intra prediction mode or a common string sub-mode of a string copy intra prediction.

In some embodiments, the preset sample point selection method includes any one of the following: a center selection method, a vertical selection method, a horizontal selection method, a diagonal selection method, and a vertex selection method.

In some embodiments, the preset sample selection method is a center selection method; the width of the reference chroma block is W, and the height of the reference chroma block is H; the width of the reference luminance block is 2W, and the height of the reference luminance block is 2H; the at least two reference luminance samples include: a first reference luminance sample, a second reference luminance sample, a third reference luminance sample, and a fourth reference luminance sample; the reference chroma samples corresponding to the at least two reference luminance samples include: a first reference chroma sample, a second reference chroma sample, a third reference chroma sample, and a fourth reference chroma sample; wherein the position coordinates of the first reference chroma sample in the reference chroma block are (1,0); the first reference chroma sample is the chroma sample at the upper left corner of the reference chroma block; the position coordinates of the second reference chroma sample in the reference chroma block are (W-2,0); the position coordinates of the third reference chroma sample in the reference chroma block are (1,H-1); The position coordinates of the fourth reference chromaticity sample in the reference chromaticity block are (W-2, H-1); the position coordinates of the first reference luminance sample in the reference luminance block are (2, 0); the first reference luminance sample is the luminance sample at the upper left corner of the reference luminance block; the position coordinates of the second reference luminance sample in the reference luminance block are (2×(W-2), 0); the position coordinates of the third reference luminance sample in the reference luminance block are (2, 2×(H-1)); the position coordinates of the fourth reference luminance sample in the reference luminance block are (2×(W-2), 2×(H-1)).

In some embodiments, the second determining part 2001 is further configured to determine the predicted chroma value of the predicted chroma block according to the sample accuracy of the current chroma block when the reference motion vector is invalid.

In some embodiments, the second determination part 2001 is further configured to perform a subtraction operation on the sample accuracy and a first preset value to obtain a fourth intermediate parameter; and perform an exponential operation on the second preset value and the fourth intermediate parameter to obtain a predicted chromaticity value of each pixel in the predicted chromaticity block.

In some embodiments, the second determination part 2001 is further configured to determine that the reference motion vector is invalid when the reference motion vector satisfies at least one of the following conditions: the reference luminance block or the reference chrominance block corresponding to the reference motion vector has not been reconstructed, the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector does not match, and the reference motion vector is out of bounds; or, determine that the reference motion vector is valid when the reference motion vector satisfies the following conditions: the reference luminance block or the reference chrominance block corresponding to the reference motion vector has been reconstructed, the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector matches, and the reference motion vector is not out of bounds.

In some embodiments, the second determination part 2001 is further configured to determine the candidate predicted chromaticity value of the candidate chromaticity prediction block according to the reconstructed luminance value of each pixel in the current co-located luminance block through the cross-component prediction model; wherein the candidate chromaticity prediction block is different in size from the current chromaticity block; and downsample the candidate predicted chromaticity value of the candidate chromaticity prediction block to obtain the predicted chromaticity value of the predicted chromaticity block.

In some embodiments, the cross-component prediction model includes at least one cross-component prediction sub-model; the second determination part 2001 is also configured to input the reconstructed luminance value of each pixel in the current co-located luminance block into the corresponding cross-component prediction sub-model to obtain the candidate predicted chromaticity value corresponding to each pixel; wherein the preset luminance range corresponding to the reconstructed luminance value of each pixel matches the cross-component prediction sub-model; and determine the candidate predicted chromaticity value of the candidate chromaticity prediction block according to the candidate predicted chromaticity value corresponding to each pixel in the current co-located luminance block.

In some embodiments, the second determination part 2001 is further configured to determine the chroma residual value of the current chroma block based on the original chroma value and the predicted chroma value of the current chroma block; perform rate-distortion cost calculation on the chroma residual value of the current chroma block to obtain a first rate-distortion cost value corresponding to the cross-component prediction mode based on the chroma intra-frame block copy technology adopted by the current chroma block; determine the prediction mode adopted by the current chroma block based on the first rate-distortion cost value; and determine the first syntax identification information based on the prediction mode adopted by the current chroma block.

In some embodiments, the encoding part 2002 is configured to encode the first syntax identification information and write the obtained encoded bits into a bit stream.

In some embodiments, the second determination part 2001 is further configured to determine that the current chroma block adopts the cross-component prediction mode based on the chroma intra-frame block copy technology when the first rate-distortion cost value is less than or equal to the second rate-distortion cost value corresponding to each of the one or more preset candidate prediction modes; or determine that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra-frame block copy technology when the first rate-distortion cost value is greater than the second rate-distortion cost value corresponding to each of the one or more preset candidate prediction modes.

In some embodiments, the one or more candidate prediction modes include: a chroma intra block copy prediction mode; the second determination part 2001 is also configured to determine that the current chroma block adopts the chroma intra block copy prediction mode when the first rate-distortion cost value is greater than the second rate-distortion cost value corresponding to the chroma intra block copy prediction mode.

In some embodiments, the second determination part 2001 is further configured to determine that the value of the first syntax identification information is a third value when it is determined that the current chroma block adopts a cross-component prediction mode based on the chroma intra-frame block copy technology; or to determine that the value of the first syntax identification information is a fourth value when it is determined that the current chroma block does not adopt a cross-component prediction mode based on the chroma intra-frame block copy technology.

In some embodiments, the second determining part 2001 is further configured to determine second grammar identification information.

In some embodiments, the second determination part 2001 is further configured to set the value of the second syntax identification information to the first value when it is determined that the current chroma block adopts the chroma intra-frame block copy prediction mode; or to set the value of the second syntax identification information to the second value when it is determined that the current chroma block does not adopt the chroma intra-frame block copy prediction mode.

In some embodiments, the encoding part 2002 is further configured to encode the second syntax identification information and write the obtained encoded bits into a bit stream.

In some embodiments, the second determining part 2001 is further configured to, when it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra-frame block copy technology, set the value of the first syntax identification information to the seventh value; or, when it is determined that the current chroma block adopts the chroma intra-frame block copy prediction mode, set the value of the first syntax identification information to The eighth value.

In some embodiments, the second determining part 2001 is further configured to determine third grammar identification information.

In some embodiments, the second determination part 2001 is further configured to set the value of the third syntax identification information to a fifth value when it is determined that the current chroma block adopts the chroma intra-frame block copy prediction mode or the cross-component prediction mode based on the chroma intra-frame block copy technology; or, when it is determined that the current chroma block does not adopt the chroma intra-frame block copy prediction mode or the cross-component prediction mode based on the chroma intra-frame block copy technology, set the value of the third syntax identification information to a sixth value.

In some embodiments, the encoding part 2002 is further configured to encode the third syntax identification information and write the obtained encoded bits into a bit stream.

In some embodiments, the second determination part 2001 is further configured to, when it is determined that the current chroma block adopts a cross-component prediction mode based on the chroma intra-frame block copy technology, transform and quantize the chroma residual value to obtain a quantized chroma residual value of the current chroma block.

In some embodiments, the encoding part 2002 is further configured to encode the quantized chroma residual value of the current chroma block and write the obtained coded bits into the bitstream.

It can be understood that in this embodiment, "part" can be a part of the circuit, a part of the processor, a part of the program or software, etc., and of course it can also be a module, or it can be non-modular. Moreover, the components in this embodiment can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional modules.

If the integrated unit is implemented in the form of a software function module and is not sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, this embodiment provides a computer-readable storage medium, which is applied to the encoder 2000, and the computer-readable storage medium stores a computer program. When the computer program is executed by the second processor, the method described in any one of the above embodiments is implemented.

Based on the composition of the above-mentioned encoder 2000 and the computer-readable storage medium, refer to Figure 20, which shows a specific hardware structure diagram of the encoder 2000 provided in an embodiment of the present application. As shown in Figure 20, the encoder 2000 may include: a second communication interface 2101, a second memory 2102 and a second processor 2103; each component is coupled together through a second bus system 2104. It can be understood that the second bus system 2104 is used to realize the connection and communication between these components. In addition to the data bus, the second bus system 2104 also includes a power bus, a control bus and a status signal bus. However, for the sake of clarity, various buses are marked as the second bus system 2104 in Figure 20. Among them,

The second communication interface 2101 is used for receiving and sending signals during the process of sending and receiving information with other external network elements;

The second memory 2102 is used to store a computer program that can be run on the second processor 2103;

The second processor 2103 is configured to, when running the computer program, execute:

Determine a reference motion vector according to a current co-located luminance block corresponding to the current chrominance block;

When the reference motion vector is valid, determining the cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector;

Based on the cross-component prediction model, determine a predicted chroma value of the predicted chroma block, and determine first syntax identification information according to the predicted chroma value; wherein the first syntax identification information is used to indicate whether the current chroma block adopts a cross-component prediction mode based on a chroma intra block copy technology;

Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block.

Optionally, as another embodiment, the second processor 2103 is further configured to execute any one of the methods described in the foregoing embodiments when running the computer program.

It can be understood that the hardware functions of the second memory 2102 and the first memory 1102 are similar, and the hardware functions of the second processor 2103 and the first processor 1103 are similar; they will not be described in detail here.

The present embodiment provides an encoder, in which, since the cross-component prediction model is determined by a reference luminance block and a reference chrominance block corresponding to a reference motion vector, compared to a cross-component prediction model derived based on reconstructed pixels in an adjacent row and column of a current chrominance block, the flexibility and diversity of determining the cross-component prediction model can be improved, so that the cross-component prediction model can flexibly cope with more complex coding scenarios, thereby improving the coding efficiency of the current chrominance block.

In yet another embodiment of the present application, referring to FIG21 , a schematic diagram of the composition structure of a coding and decoding system provided in an embodiment of the present application is shown. As shown in FIG21 , the coding and decoding system 3000 may include a decoder 3001 and an encoder 3002 .

In the embodiment of the present application, the decoder 3001 may be the decoder described in any one of the aforementioned embodiments, and the encoder 3002 may be the encoder described in any one of the aforementioned embodiments.

It should be noted that, in this application, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. Without further restrictions, An element defined by the phrase "comprising a ..." does not exclude the existence of other identical elements in the process, method, article or apparatus comprising the element.

The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

The methods disclosed in several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments.

The features disclosed in several product embodiments provided in this application can be arbitrarily combined without conflict to obtain new product embodiments.

The features disclosed in several method or device embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments or device embodiments.

The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the embodiments of the present application.

Industrial Applicability

In an embodiment of the present application, at the decoding end, the bitstream is parsed to determine the first syntax identification information; when the first syntax identification information indicates that the current chroma block adopts a cross-component prediction mode based on the chroma intra-frame block copy technology, a reference motion vector is determined according to the current co-located luminance block corresponding to the current chroma block; when the reference motion vector is valid, a cross-component prediction model is determined based on the reference luminance block and the reference chroma block corresponding to the reference motion vector; based on the cross-component prediction model, a predicted chroma value of the predicted chroma block is determined; and based on the predicted chroma value of the predicted chroma block, a reconstructed chroma value of the current chroma block is determined. At the encoding end, a reference motion vector is determined based on the current co-located luminance block corresponding to the current chrominance block; when the reference motion vector is valid, a cross-component prediction model is determined based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector; based on the cross-component prediction model, a predicted chrominance value of the predicted chrominance block is determined, and first syntax identification information is determined based on the predicted chrominance value; wherein the first syntax identification information is used to indicate whether the current chrominance block adopts a cross-component prediction mode based on the chrominance intra-frame block copy technology; based on the predicted chrominance value of the predicted chrominance block, a reconstructed chrominance value of the current chrominance block is determined. Since the cross-component prediction model is determined by the reference luminance block and the reference chrominance block corresponding to the reference motion vector, compared with the cross-component prediction model derived from the reconstructed pixels of the adjacent row and column of the current chrominance block, the flexibility and diversity of determining the cross-component prediction model can be improved, so that the cross-component prediction model can flexibly cope with more complex encoding and decoding scenarios, thereby improving the encoding and decoding efficiency of the current chrominance block.

Claims (62)

A decoding method, applied to a decoder, comprising: Parsing the code stream to determine first syntax identification information; When the first syntax identification information indicates that the current chroma block adopts a cross-component prediction mode based on a chroma intra block copying technique, determining a reference motion vector according to a current co-located luminance block corresponding to the current chroma block; When the reference motion vector is valid, determining a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector; Determining a predicted chroma value of a predicted chroma block based on the cross-component prediction model; Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block. The method according to claim 1, wherein the cross-component prediction model characterizes that the reconstructed luminance value of the current co-located luminance block corresponding to the current chrominance block has a linear or nonlinear relationship with the predicted chrominance value of the predicted chrominance block. The method according to claim 1 or 2, wherein determining the reference motion vector according to the current co-located luminance block corresponding to the current chrominance block comprises: A candidate reference sample point satisfying a preset prediction mode is determined in the current co-located luminance block, and a motion vector corresponding to the candidate reference sample point is used as a reference motion vector. The method according to any one of claims 1 to 3, wherein the cross-component prediction model is a linear model; and determining the cross-component prediction model based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector comprises: Determine at least two reference luminance samples in the reference luminance block according to a preset sample selection method, and determine reference chrominance samples corresponding to each of the at least two reference luminance samples in the reference chrominance block according to the preset sample selection method; The cross-component prediction model is determined according to the at least two reference luma samples and the at least two reference chroma samples; wherein the at least two reference luma samples correspond to the at least two reference chroma samples. The method according to claim 4, wherein the cross-component prediction model includes one or more cross-component prediction sub-models; and determining the cross-component prediction model according to the at least two reference luma samples and the at least two reference chroma samples comprises: According to the brightness values of the at least two reference brightness samples, the at least two reference brightness samples and the at least two reference chrominance samples are grouped to obtain at least one reference sample group; wherein each reference sample group includes at least two brightness samples and at least two chrominance samples; the at least two brightness samples correspond to the at least two chrominance samples; the at least two reference brightness samples include the at least two brightness samples; the at least two reference chrominance samples include the at least two chrominance samples; and the at least one reference sample group corresponds to a different preset brightness range; For each reference sample point group in the at least one reference sample point group, the cross-component prediction sub-model corresponding to each reference sample point group is determined according to the at least two luma samples and the at least two chroma samples in the each reference sample point group. The method according to claim 5, wherein the determining, according to the at least two luma samples and the at least two chroma samples in each reference sample group, the cross-component prediction sub-model corresponding to each reference sample group comprises: According to the luminance values of the at least two luminance samples, the at least two luminance samples in each reference sample group and the at least two chrominance samples are grouped to obtain a first sample group and a second sample group; wherein the first sample group and the second sample group each include at least one luminance sample and at least one chrominance sample; the at least one luminance sample corresponds to the at least one chrominance sample; and a reconstructed luminance value of at least one luminance sample in the first sample group is greater than or equal to a reconstructed luminance value of at least one luminance sample in the second sample group; Determine a maximum reference luminance value and a first reference chrominance value according to a reconstructed luminance value of at least one luminance sample point and a reconstructed chrominance value of at least one chrominance sample point in the first sample point group, respectively; Determine a minimum reference luminance value and a second reference chrominance value according to a reconstructed luminance value of at least one luminance sample point and a reconstructed chrominance value of at least one chrominance sample point in the second sample point group; determining a scaling factor and an offset factor based on the maximum reference luminance value, the first reference chrominance value, the minimum reference luminance value, and the second reference chrominance value; The cross-component prediction sub-model corresponding to each reference sample point group is determined according to the scaling factor and the offset factor. The method according to claim 6, wherein the determining the scaling factor and the offset factor based on the maximum reference luminance value, the first reference chrominance value, the minimum reference luminance value, and the second reference chrominance value comprises: Subtracting the first reference chromaticity value from the second reference chromaticity value to obtain a first intermediate parameter; Subtracting the maximum reference brightness value from the minimum reference brightness value to obtain a second intermediate parameter; Performing a division operation on the first intermediate parameter and the second intermediate parameter to obtain the scaling factor; Multiplying the scaling factor by the minimum reference brightness value to obtain a third intermediate parameter; The second reference chromaticity value and the third intermediate parameter are subtracted to obtain the offset factor. The method according to any one of claims 1 to 3, wherein the cross-component prediction model is a nonlinear model; and determining the cross-component prediction model based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector comprises: Selecting all or part of the reference chromaticity samples in the reference chromaticity block; The cross-component prediction model is determined according to the all or part of the reference chroma samples, the reference luma samples in the reference luma block corresponding to the all or part of the reference chroma samples, and the neighborhood reference luma samples of the reference luma samples. The method according to claim 8, wherein the neighborhood reference luma samples include one or more of the following: a reference luma sample located above the reference luma sample, a reference luma sample located below the reference luma sample, a reference luma sample located to the left of the reference luma sample, and a reference luma sample located to the right of the reference luma sample. The method according to any one of claims 3 to 9, characterized in that determining the candidate reference sample points satisfying a preset prediction mode in the current co-located luminance block comprises: According to the preset M position information, the candidate reference sample points corresponding to each of the preset M position information are traversed in the current co-located luminance block to obtain the candidate reference sample points that meet the preset prediction mode; wherein M is a positive integer greater than or equal to 1, and i is a positive integer less than M. The method according to claim 10, characterized in that, according to the preset M pieces of position information, traversing the candidate reference sample points corresponding to the preset M pieces of position information in the current co-located luminance block to obtain the candidate reference sample points satisfying the preset prediction mode comprises: For the i-th position information among the preset M position information, when the i-th candidate reference sample corresponding to the i-th position information in the current co-located luminance block does not satisfy the preset prediction mode, continue to traverse the i+1-th candidate reference sample corresponding to the i+1-th position information in the current co-located luminance block until the i+1-th candidate reference sample satisfies the preset prediction mode, and determine the i+1-th candidate reference sample as a candidate reference sample that satisfies the preset prediction mode; or, In a case where the i-th candidate reference sample point satisfies the preset prediction mode, the i-th candidate reference sample point is determined as a candidate reference sample point that satisfies the preset prediction mode. The method according to claim 10 or 11, characterized in that the M pieces of location information include one or more of the following: The middle position of the current co-located luminance block; The upper left position of the current co-located luminance block; The upper right position of the current co-located luminance block; The lower left position of the current co-located luminance block; The lower right position of the current co-located luminance block. The method according to any one of claims 3 to 12 is characterized in that the preset prediction mode is: the candidate reference samples adopt a block copy intra-frame prediction mode or a normal string sub-mode of string copy intra-frame prediction. The method according to any one of claims 4 to 12, wherein the preset sample point selection method includes any one of the following: Center selection method, vertical selection method, horizontal selection method, diagonal selection method and vertex selection method. The method according to any one of claims 4 to 12, wherein the preset sample point selection method is a center selection method; the width of the reference chrominance block is W, and the height of the reference chrominance block is H; the width of the reference luminance block is 2W, and the height of the reference luminance block is 2H; The at least two reference luminance samples include: a first reference luminance sample, a second reference luminance sample, a third reference luminance sample, and a fourth reference luminance sample; the reference chrominance samples corresponding to the at least two reference luminance samples include: a first reference chrominance sample, a second reference chrominance sample, a third reference chrominance sample, and a fourth reference chrominance sample; wherein, The position coordinates of the first reference chromaticity sample point in the reference chromaticity block are (1 0); the first reference chromaticity sample point is the chromaticity sample point at the upper left corner of the reference chromaticity block; The position coordinates of the second reference chromaticity sample point in the reference chromaticity block are (W-2, 0); The position coordinates of the third reference chromaticity sample point in the reference chromaticity block are (1, H-1); The position coordinates of the fourth reference chromaticity sample point in the reference chromaticity block are (W-2, H-1); The position coordinates of the first reference brightness sample point in the reference brightness block are (2, 0); the first reference brightness sample point is the brightness sample point at the upper left corner of the reference brightness block; The position coordinates of the second reference brightness sample point in the reference brightness block are (2×(W-2), 0); The position coordinates of the third reference brightness sample point in the reference brightness block are (2,2×(H-1)); The position coordinates of the fourth reference luminance sample point in the reference luminance block are (2×(W-2), 2×(H-1)). The method according to any one of claims 1 to 15, wherein the method further comprises: When the reference motion vector is invalid, a predicted chroma value of the predicted chroma block is determined according to the sample precision of the current chroma block. The method according to claim 16, wherein the determining the predicted chroma value of the predicted chroma block according to the sample accuracy of the current chroma block comprises: Subtracting the sample accuracy from the first preset value to obtain a fourth intermediate parameter; An exponential operation is performed on the second preset value and the fourth intermediate parameter to obtain a predicted chromaticity value of each pixel in the predicted chromaticity block. The method according to claim 16 or 17, wherein the method further comprises: In the case where the reference motion vector satisfies at least one of the following conditions: the reference luminance block or the reference chrominance block corresponding to the reference motion vector has not been reconstructed, the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector does not match, and the reference motion vector is out of bounds, the reference motion vector is determined to be invalid; or, The reference motion vector is determined to be valid when the reference motion vector satisfies that the reference luminance block or the reference chrominance block corresponding to the reference motion vector has been reconstructed, the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector matches, and the reference motion vector does not cross the boundary. The method according to any one of claims 1 to 18, wherein determining the predicted chrominance value of the predicted chrominance block based on the cross-component prediction model comprises: Determining, by the cross-component prediction model, candidate predicted chrominance values of a candidate chrominance prediction block according to reconstructed luminance values of each pixel in the current co-located luminance block; wherein the candidate chrominance prediction block has a different size from the current chrominance block; Down-sampling the candidate predicted chroma values of the candidate chroma prediction block to obtain predicted chroma values of the predicted chroma block. The method of claim 19, wherein the cross-component prediction model comprises at least one cross-component prediction sub-model; The step of determining the candidate predicted chrominance value of the candidate chrominance prediction block according to the reconstructed luminance value of each pixel in the current co-located luminance block by using the cross-component prediction model includes: For the reconstructed luminance value of each pixel in the current co-located luminance block, input the reconstructed luminance value of each pixel into the corresponding cross-component prediction sub-model to obtain a candidate predicted chrominance value corresponding to each pixel; wherein the preset luminance range corresponding to the reconstructed luminance value of each pixel matches the cross-component prediction sub-model; Determine the candidate predicted chromaticity values of the candidate chromaticity prediction block according to the candidate predicted chromaticity values corresponding to each pixel in the current co-located luminance block. The method according to claim 1, wherein the method further comprises: Parsing the code stream to determine the second syntax identification information; When the second syntax identification information indicates that the current chroma block does not adopt the chroma intra block copy prediction mode, the step of parsing the code stream to obtain the first syntax identification information is performed. The method according to claim 21, wherein the parsing the code stream to determine the second syntax identification information comprises: If the value of the second syntax identification information is the first value, it is determined that the current chroma block adopts the chroma intra block copy prediction mode; or, If the value of the second syntax identification information is the second value, it is determined that the current chroma block does not adopt the chroma intra block copy prediction mode. The method according to any one of claims 1, 21 or 22, wherein the parsing the code stream to determine the first syntax identification information comprises: If the value of the first syntax identification information is the third value, it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology; or If the value of the first syntax identification information is the fourth value, it is determined that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra block copy technology. The method according to claim 1, wherein the method further comprises: Parsing the code stream to determine the third syntax identification information; When the third syntax identification information indicates that the current chroma block adopts the chroma intra block copy prediction mode or the cross-component prediction mode based on the chroma intra block copy technology, the step of parsing the code stream to obtain the first syntax identification information is performed. The method according to claim 24, wherein the parsing the code stream to determine the third syntax identification information comprises: If the value of the third syntax identification information is the fifth value, it is determined that the current chroma block adopts the chroma intra block copy prediction mode or the cross-component prediction mode based on the chroma intra block copy technology; or, If the value of the third syntax identification information is the sixth value, it is determined that the current chroma block does not adopt the chroma intra block copy prediction mode or the cross-component prediction mode based on the chroma intra block copy technology. The method according to any one of claims 1, 24 or 25, wherein the parsing the code stream to determine the first syntax identification information comprises: If the value of the first syntax identification information is the seventh value, it is determined that the current chroma block adopts the chroma intra-frame block copy technology or, If the value of the first syntax identification information is the eighth value, it is determined that the current chroma block adopts the chroma intra block copy prediction mode. The method according to any one of claims 1 to 26, wherein determining the reconstructed chroma value of the current chroma block according to the predicted chroma value of the predicted chroma block comprises: Parsing the bitstream to obtain the chroma residual value of the current chroma block; Performing inverse transformation and inverse quantization on the chroma residual value to obtain an inverse quantized chroma residual value of the current chroma block; The reconstructed chroma value of the current chroma block is determined according to the inverse quantized chroma residual value and the predicted chroma value. A coding method, applied to an encoder, comprising: Determine a reference motion vector according to a current co-located luminance block corresponding to the current chrominance block; When the reference motion vector is valid, determining a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector; Based on the cross-component prediction model, determine a predicted chroma value of the predicted chroma block, and determine first syntax identification information according to the predicted chroma value; wherein the first syntax identification information is used to indicate whether the current chroma block adopts a cross-component prediction mode based on a chroma intra block copy technology; Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block. The method according to claim 28, wherein the cross-component prediction model characterizes that the reconstructed luminance value of the current co-located luminance block corresponding to the current chrominance block has a linear or nonlinear relationship with the predicted chrominance value of the predicted chrominance block. The method according to claim 28 or 29, wherein determining the reference motion vector according to the current co-located luminance block corresponding to the current chrominance block comprises: A candidate reference sample point satisfying a preset prediction mode is determined in the current co-located luminance block, and a motion vector corresponding to the candidate reference sample point is used as a reference motion vector. The method according to any one of claims 28 to 30, wherein the cross-component prediction model is a linear model; and determining the cross-component prediction model based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector comprises: Determine at least two reference luminance samples in the reference luminance block according to a preset sample selection method, and determine reference chrominance samples corresponding to each of the at least two reference luminance samples in the reference chrominance block according to the preset sample selection method; The cross-component prediction model is determined according to the at least two reference luma samples and the at least two reference chroma samples; wherein the at least two reference luma samples correspond to the at least two reference chroma samples. The method of claim 31, wherein the cross-component prediction model comprises one or more cross-component prediction sub-models; The determining the cross-component prediction model according to the at least two reference luma samples and the at least two reference chroma samples comprises: According to the brightness values of the at least two reference brightness samples, the at least two reference brightness samples and the at least two reference chrominance samples are grouped to obtain at least one reference sample group; wherein each reference sample group includes at least two brightness samples and at least two chrominance samples; the at least two brightness samples correspond to the at least two chrominance samples; the at least two reference brightness samples include the at least two brightness samples; the at least two reference chrominance samples include the at least two chrominance samples; and the at least one reference sample group corresponds to a different preset brightness range; For each reference sample point group in the at least one reference sample point group, the cross-component prediction sub-model corresponding to each reference sample point group is determined according to the at least two luma samples and the at least two chroma samples in the each reference sample point group. The method according to claim 32, wherein the determining, according to the at least two luma samples and the at least two chroma samples in each reference sample group, the cross-component prediction sub-model corresponding to each reference sample group comprises: According to the luminance values of the at least two luminance samples, the at least two luminance samples in each reference sample group and the at least two chrominance samples are grouped to obtain a first sample group and a second sample group; wherein the first sample group and the second sample group each include at least one luminance sample and at least one chrominance sample; the at least one luminance sample corresponds to the at least one chrominance sample; and a reconstructed luminance value of at least one luminance sample in the first sample group is greater than or equal to a reconstructed luminance value of at least one luminance sample in the second sample group; Determine a maximum reference luminance value and a first reference chrominance value according to a reconstructed luminance value of at least one luminance sample point and a reconstructed chrominance value of at least one chrominance sample point in the first sample point group; Determine a minimum reference luminance value and a second reference chrominance value according to a reconstructed luminance value of at least one luminance sample and a reconstructed chrominance value of at least one chrominance sample in the second sample point group; determining a scaling factor and an offset factor based on the maximum reference luminance value, the first reference chrominance value, the minimum reference luminance value, and the second reference chrominance value; The cross-component prediction sub-model corresponding to each reference sample point group is determined according to the scaling factor and the offset factor. The method according to claim 33, wherein the determining a scaling factor and an offset factor based on the maximum reference luminance value, the first reference chrominance value, the minimum reference luminance value, and the second reference chrominance value comprises: Subtracting the first reference chromaticity value from the second reference chromaticity value to obtain a first intermediate parameter; Subtracting the maximum reference brightness value from the minimum reference brightness value to obtain a second intermediate parameter; Performing a division operation on the first intermediate parameter and the second intermediate parameter to obtain the scaling factor; Performing a multiplication operation on the scaling factor and the minimum reference brightness value to obtain a third intermediate parameter; The second reference chromaticity value and the third intermediate parameter are subtracted to obtain the offset factor. The method according to any one of claims 28 to 30, wherein the cross-component prediction model is a nonlinear model; and determining the cross-component prediction model based on the reference luminance block and the reference chrominance block corresponding to the reference motion vector comprises: Selecting all or part of the reference chromaticity samples in the reference chromaticity block; The cross-component prediction model is determined according to the all or part of the reference chroma samples, the reference luma samples in the reference luma block corresponding to the all or part of the reference chroma samples, and the neighborhood reference luma samples of the reference luma samples. The method according to claim 35, wherein the neighborhood reference luma samples include one or more of the following: a reference luma sample located above the reference luma sample, a reference luma sample located below the reference luma sample, a reference luma sample located to the left of the reference luma sample, and a reference luma sample located to the right of the reference luma sample. The method according to any one of claims 30 to 36, characterized in that the step of determining candidate reference samples satisfying a preset prediction mode in the current co-located luminance block comprises: According to the preset M position information, the candidate reference sample points corresponding to each of the preset M position information are traversed in the current co-located luminance block to obtain the candidate reference sample points that meet the preset prediction mode; wherein M is a positive integer greater than or equal to 1, and i is a positive integer less than M. The method according to claim 37, characterized in that, according to the preset M pieces of position information, traversing the candidate reference sample points corresponding to the preset M pieces of position information in the current co-located luminance block to obtain the candidate reference sample points satisfying the preset prediction mode comprises: For the i-th position information among the preset M position information, when the i-th candidate reference sample corresponding to the i-th position information in the current co-located luminance block does not satisfy the preset prediction mode, continue to traverse the i+1-th candidate reference sample corresponding to the i+1-th position information in the current co-located luminance block until the i+1-th candidate reference sample satisfies the preset prediction mode, and determine the i+1-th candidate reference sample as a candidate reference sample that satisfies the preset prediction mode; or, In a case where the i-th candidate reference sample point satisfies the preset prediction mode, the i-th candidate reference sample point is determined as a candidate reference sample point that satisfies the preset prediction mode. The method according to claim 37 or 38, characterized in that the M pieces of location information include one or more of the following: The middle position of the current co-located luminance block; The upper left position of the current co-located luminance block; The upper right position of the current co-located luminance block; The lower left position of the current co-located luminance block; The lower right position of the current co-located luminance block. The method according to any one of claims 30 to 39 is characterized in that the preset prediction mode is: the candidate reference samples adopt a block copy intra-frame prediction mode or a normal string sub-mode of string copy intra-frame prediction. The method according to any one of claims 31 to 39, wherein the preset sample point selection method includes any one of the following: Center selection method, vertical selection method, horizontal selection method, diagonal selection method and vertex selection method. The method according to any one of claims 31 to 39, wherein the preset sample point selection method is a center selection method; the width of the reference chrominance block is W, and the height of the reference chrominance block is H; the width of the reference luminance block is 2W, and the height of the reference luminance block is 2H; The at least two reference luminance samples include: a first reference luminance sample, a second reference luminance sample, a third reference luminance sample, and a fourth reference luminance sample; the reference chrominance samples corresponding to the at least two reference luminance samples include: a first reference chrominance sample, a second reference chrominance sample, a third reference chrominance sample, and a fourth reference chrominance sample; wherein, The position coordinates of the first reference chromaticity sample point in the reference chromaticity block are (1, 0); the first reference chromaticity sample point is the chromaticity sample point at the upper left corner of the reference chromaticity block; The position coordinates of the second reference chromaticity sample point in the reference chromaticity block are (W-2, 0); The position coordinates of the third reference chromaticity sample point in the reference chromaticity block are (1, H-1); The position coordinates of the fourth reference chromaticity sample point in the reference chromaticity block are (W-2, H-1); The position coordinates of the first reference brightness sample point in the reference brightness block are (2, 0); the first reference brightness sample point is the brightness sample point at the upper left corner of the reference brightness block; The position coordinates of the second reference brightness sample point in the reference brightness block are (2×(W-2), 0); The position coordinates of the third reference brightness sample point in the reference brightness block are (2,2×(H-1)); The position coordinates of the fourth reference luminance sample point in the reference luminance block are (2×(W-2), 2×(H-1)). The method according to any one of claims 28 to 39, wherein the method further comprises: When the reference motion vector is invalid, a predicted chroma value of the predicted chroma block is determined according to the sample precision of the current chroma block. The method according to claim 43, wherein the determining the predicted chroma value of the predicted chroma block according to the sample accuracy of the current chroma block comprises: Subtracting the sample accuracy from the first preset value to obtain a fourth intermediate parameter; An exponential operation is performed on the second preset value and the fourth intermediate parameter to obtain a predicted chromaticity value of each pixel in the predicted chromaticity block. The method according to claim 43 or 44, wherein the method further comprises: In the case where the reference motion vector satisfies at least one of the following conditions: the reference luminance block or the reference chrominance block corresponding to the reference motion vector has not been reconstructed, the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector does not match, and the reference motion vector is out of bounds, the reference motion vector is determined to be invalid; or, The reference motion vector is determined to be valid when the reference motion vector satisfies that the reference luminance block or the reference chrominance block corresponding to the reference motion vector has been reconstructed, the prediction mode of the reference luminance block or the reference chrominance block corresponding to the reference motion vector matches, and the reference motion vector does not cross the boundary. The method according to any one of claims 28 to 45, wherein determining the predicted chrominance value of the predicted chrominance block based on the cross-component prediction model comprises: Determining, by the cross-component prediction model, candidate predicted chrominance values of a candidate chrominance prediction block according to reconstructed luminance values of each pixel in the current co-located luminance block; wherein the candidate chrominance prediction block has a different size from the current chrominance block; Down-sampling the candidate predicted chroma values of the candidate chroma prediction block to obtain predicted chroma values of the predicted chroma block. The method of claim 46, wherein the cross-component prediction model comprises at least one cross-component prediction sub-model; The step of determining the candidate predicted chrominance value of the candidate chrominance prediction block according to the reconstructed luminance value of each pixel in the current co-located luminance block by using the cross-component prediction model includes: For the reconstructed luminance value of each pixel in the current co-located luminance block, input the reconstructed luminance value of each pixel into the corresponding cross-component prediction sub-model to obtain a candidate predicted chrominance value corresponding to each pixel; wherein the preset luminance range corresponding to the reconstructed luminance value of each pixel matches the cross-component prediction sub-model; Determine the candidate predicted chromaticity values of the candidate chromaticity prediction block according to the candidate predicted chromaticity values corresponding to each pixel in the current co-located luminance block. The method according to any one of claims 28 to 47, wherein determining the first syntax identification information according to the predicted chrominance value comprises: Determine a chroma residual value of the current chroma block according to an original chroma value of the current chroma block and the predicted chroma value; Performing rate-distortion cost calculation on the chroma residual value of the current chroma block to obtain a first rate-distortion cost value corresponding to the cross-component prediction mode based on the chroma intra block copy technology adopted by the current chroma block; Determining a prediction mode adopted by the current chroma block according to the first rate-distortion cost value; The first syntax identification information is determined according to a prediction mode adopted by the current chroma block. The method according to claim 48, wherein the method further comprises: The first syntax identification information is encoded, and the obtained encoded bits are written into a bit stream. The method according to claim 48, wherein determining the prediction mode adopted by the current chroma block according to the first rate-distortion cost value comprises: When the first rate-distortion cost value is less than or equal to the second rate-distortion cost value corresponding to each of the one or more preset candidate prediction modes, determining that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology; When the first rate-distortion cost value is greater than the second rate-distortion cost value corresponding to each of the one or more preset candidate prediction modes, it is determined that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra block copy technology. The method according to claim 50, wherein the one or more candidate prediction modes include: a chroma intra block copy prediction mode; when the first rate-distortion cost value is greater than the second rate-distortion cost value corresponding to each of the one or more preset candidate prediction modes, determining that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra block copy technology comprises: When the first rate-distortion cost value is greater than a second rate-distortion cost value corresponding to the chroma intra block copy prediction mode, it is determined that the current chroma block adopts the chroma intra block copy prediction mode. The method according to any one of claims 48 to 51, wherein the determining the first syntax identification information according to the prediction mode adopted by the current chroma block comprises: In the case where it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology, the first The value of the syntax identification information is a third value; or, When it is determined that the current chroma block does not adopt the cross-component prediction mode based on the chroma intra block copy technology, the value of the first syntax identification information is determined to be a fourth value. The method according to claim 52, wherein the method further comprises: Determining second grammar identification information; Encoding the second syntax identification information, and writing the obtained coded bits into a bit stream; The determining the second grammar identification information includes: When it is determined that the current chroma block adopts the chroma intra block copy prediction mode, the value of the second syntax identification information is set to the first value; or, When it is determined that the current chroma block does not adopt the chroma intra block copy prediction mode, the value of the second syntax identification information is set to a second value. The method according to any one of claims 48 to 51, wherein the determining the first syntax identification information according to the prediction mode adopted by the current chroma block comprises: In the case where it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology, the value of the first syntax identification information is set to the seventh value; or, When it is determined that the current chroma block adopts the chroma intra block copy prediction mode, the value of the first syntax identification information is set to the eighth value. The method according to claim 54, wherein the method further comprises: Determining third grammar identification information; Encoding the third syntax identification information, and writing the obtained coded bits into a bit stream; The determining of the third grammar identification information includes: In the case where it is determined that the current chroma block adopts the chroma intra block copy prediction mode or the cross-component prediction mode based on the chroma intra block copy technology, the value of the third syntax identification information is set to a fifth value; or When it is determined that the current chroma block does not adopt the chroma intra block copy prediction mode or the cross-component prediction mode based on the chroma intra block copy technology, the value of the third syntax identification information is set to the sixth value. The method according to any one of claims 28 to 55, wherein the method further comprises: When it is determined that the current chroma block adopts the cross-component prediction mode based on the chroma intra block copy technology, transform and quantize the chroma residual value to obtain a quantized chroma residual value of the current chroma block; The quantized chroma residual value of the current chroma block is encoded, and the obtained encoding bits are written into the bit stream. A code stream, wherein the code stream is generated by bit encoding according to information to be encoded; wherein the information to be encoded includes at least one of the following: The value of the first syntax identification information, the value of the second syntax identification information, the value of the third syntax identification information, and the quantized chroma residual value of the current chroma block; wherein the first syntax identification information is used to indicate whether the current chroma block adopts a cross-component prediction mode based on the chroma intra-frame block copy technology; the second syntax identification information is used to indicate whether the current chroma block adopts a chroma intra-frame block copy prediction mode; the third syntax identification information is used to indicate whether the current chroma block adopts a chroma intra-frame block copy prediction mode or a cross-component prediction mode based on the chroma intra-frame block copy technology. A decoder, comprising a decoding part and a first determining part, wherein: The decoding part is configured to parse the code stream and determine the first syntax identification information; The first determining part is configured to determine the reference motion vector according to the current co-located luminance block corresponding to the current chrominance block when the first syntax identification information indicates that the current chrominance block adopts the cross-component prediction mode based on the chrominance intra block copy technology; When the reference motion vector is valid, determining a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector; Determining a predicted chroma value of a predicted chroma block based on the cross-component prediction model; Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block. An encoder comprising a second determining part, wherein: The second determining part is configured to determine a reference motion vector according to a current co-located luminance block corresponding to the current chrominance block; When the reference motion vector is valid, determining a cross-component prediction model based on a reference luminance block and a reference chrominance block corresponding to the reference motion vector; Determine a predicted chroma value of a predicted chroma block based on the cross-component prediction model, and determine first syntax identification information according to the predicted chroma value; wherein the first syntax identification information is used to indicate whether the current chroma block adopts a cross-component prediction mode based on a chroma intra block copy technology; Determine the reconstructed chrominance value of the current chrominance block according to the predicted chrominance value of the predicted chrominance block. A decoder, comprising a first memory and a first processor, wherein: The first memory is configured to store a computer program that can be executed on the first processor; The first processor is configured to perform the method according to any one of claims 1 to 27 when running the computer program. An encoder, comprising a second memory and a second processor, wherein: The second memory is configured to store a computer program that can be executed on the second processor; The second processor is configured to perform the method according to any one of claims 28 to 56 when running the computer program. A computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed, the method according to any one of claims 1 to 27 is implemented, or the method according to any one of claims 28 to 56 is implemented.