RU2850055C1 - Method for encoding coefficients, encoder and decoder - Google Patents

Abstract

FIELD: video encoding.

SUBSTANCE: perform bitstream analysis with sequence level flag acquisition. Analyse the bitstream with acquisition of the last significant coefficient reverse position flag and information about the coordinates of the last significant coefficient when the sequence level flag indicates that the video satisfies the specified condition. When the last significant coefficient reverse position flag indicates that the position of the last significant coefficient has been reversed for the current block, determine the position of the last significant coefficient by calculating using the information about the coordinates of the last significant coefficient, wherein the coordinate information of the last significant coefficient is the horizontal distance and the vertical distance from the position of the last significant coefficient to the lower right corner of the current block. Decoding is performed according to a predetermined scanning order of all coefficients before the position of the last significant coefficient to determine the coefficients of the current block.

EFFECT: improved video encoding efficiency.

10 cl, 17 dwg, 10 tbl

Description

Region techniques, To which refers to invention

[1] Embodiments of the present invention relate to the field of video coding technology, and in particular to a coefficient coding method, an encoder and a decoder.

Prerequisites creation inventions

[2] Computer vision-related fields are attracting increasing attention as people demand higher video display quality. In recent years, image processing technologies have been successfully applied in all areas of life. In the video image coding process, the image data to be coded is transformed and quantized on the coding side, and then subjected to compression coding using an entropy coding element. The bitstream generated from the entropy coding is transmitted to the decoding side. On the decoding side, the bitstream is analyzed, and then inverse quantized and inversely transformed, so that the original input image data can be reconstructed.

[3] Currently, compared with low-bit-depth, low-quality, and low-bit-rate video encoding (referred to as "normal video"), high-bit-depth, high-quality, and high-bit-rate video encoding (referred to as "triple-HD video") typically requires encoding a larger number of large coefficients. In this case, using existing corresponding solutions for triple-HD video may result in high resource consumption and wasteful resource utilization, and even affect the encoding speed and bandwidth.

Essence inventions

[4] The present invention provides a coefficient encoding method, an encoder, and a decoder that can improve the throughput and encoding speed of coefficient encoding while improving the compression efficiency in high-bit-depth, high-bit-rate, high-quality, or lossless compression video encoding scenarios.

[5] In a first aspect of the present invention, there is provided a coefficient decoding method applied to a decoder and comprising:

bit stream analysis to obtain sequence level flag;

analyzing the bit stream to obtain a last significant coefficient reverse position flag when the sequence level flag indicates that the video satisfies a given condition;

analyzing the bit stream to obtain information about the prefix of the horizontal coordinate of the last significant coefficient, information about the prefix of the vertical coordinate of the last significant coefficient, information about the suffix of the horizontal coordinate of the last significant coefficient, and information about the suffix of the vertical coordinate of the last significant coefficient;

determining the horizontal coordinate of the last significant coefficient according to the information about the prefix of the horizontal coordinate of the last significant coefficient and the information about the suffix of the horizontal coordinate of the last significant coefficient;

determining the vertical coordinate of the last significant coefficient according to the information about the prefix of the vertical coordinate of the last significant coefficient and the information about the suffix of the vertical coordinate of the last significant coefficient; and

determining information about the coordinates of the last significant coefficient according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient;

determining the position of the last significant coefficient by calculating using the coordinate information of the last significant coefficient when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is reversed for the current block; and

decoding, according to a given scanning order, all coefficients before the position of the last significant coefficient to determine the coefficients of the current block,

in this case, the value of the horizontal coordinate of the last significant coefficient in a given scanning order within the current block is found as follows

if last_sig_coeff_x_suffix is not present, then:

LastSignificantCoeffX = last_sig_coeff_x_prefix;

if last_sig_coeff_x_suffix is present, then:

LastSignificantCoeffX = (1<<((last_sig_coeff_x_prefix>>1) -1)) * (2+(last_ sig_coeff_x_prefix&1)) + last_sig_coeff_x_suffix; And

if reverse_last_sig_coeff_flag is 1, then:

LastSignificantCoeffX = (1<<log2ZoTbWidth) -1-LastSignificantCoeffX; And

the value of the vertical coordinate of the last significant coefficient in a given scanning order within the current block is found as follows:

if last_sig_coeff_y_suffix is not present, then:

LastSignificantCoeffY = last_sig_coeff_y_prefix;

if last_sig_coeff_y_suffix is present, then:

LastSignificantCoeffY= (1<<((last_sig_coeff_y_prefix>>1) -1)) * (2+(last_sig_coeff_y_prefix&1)) + last_sig_coeff_y_suffix; And

if reverse_last_sig_coeff_flag is 1, then:

LastSignificantCoeffY= (1<<log2ZoTbHeight) -1-LastSignificantCoeffY;

wherein (1<<log2ZoTbWidth) represents the width of the transformation block after zero output, (1<<log2ZoTbHeight) represents the height of the transformation block after zero output, LastSignificantCoeffX represents the value of the horizontal coordinate of the last significant coefficient in the given scan order within the current block, LastSignificantCoeffY represents the value of the vertical coordinate of the last significant coefficient in the given scan order within the current block, last_sig_coeff_x_prefix represents the information of the prefix of the horizontal coordinate of the last significant coefficient, last_sig_coeff_y_prefix represents the information of the prefix of the vertical coordinate of the last significant coefficient, last_sig_coeff_x_suffix represents the information of the suffix of the horizontal coordinate of the last significant coefficient, the last_sig_coeff_y_suffix represents the information of the suffix of the vertical coordinate of the last significant coefficient, and reverse_last_sig_coeff_flag represents the flag of the reverse position of the last significant coefficient.

[6] In one embodiment, the method further comprises:

determining the position of the last significant coefficient directly according to the coordinate information of the last significant coefficient, when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is not reversed for the current block; and

decoding, according to a given scanning order, all coefficients before the position of the last significant coefficient to determine the coefficients of the current block.

[7] In another embodiment, the method further comprises:

when the sequence level flag has the first value, determining that the sequence level flag indicates that the video satisfies a specified condition; or

when the sequence level flag has a second value, determining that the sequence level flag indicates that the video does not satisfy the specified condition.

[8] In another embodiment, the specified condition includes at least one of: high bit depth, high quality, high bit rate, high frame rate, or lossless compression.

[9] In another embodiment, the method further comprises:

when the last significant coefficient position reverse flag has the first value, determining that the last significant coefficient position reverse flag indicates that the position of the last significant coefficient has been reversed for the current block; or

when the last significant coefficient position reverse flag has the second value, determining that the last significant coefficient position reverse flag indicates that the position of the last significant coefficient is not reversed for the current block.

[10] In another embodiment, the method further comprises:

determining the coordinate information of the last significant coefficient as a horizontal distance and a vertical distance from the position of the last significant coefficient to the lower right corner of the current block, when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is reversed for the current block; and

accordingly, determining the position of the last significant coefficient by calculating using information about the coordinates of the last significant coefficient includes:

defining the width and height of the current block;

obtaining the horizontal coordinate of the last significant coefficient by subtracting from the width of the current block the horizontal distance from the position of the last significant coefficient to the lower right corner of the current block;

obtaining the vertical coordinate of the last significant coefficient by subtracting from the height of the current block the vertical distance from the position of the last significant coefficient to the lower right corner of the current block; and

determining the position of the last significant coefficient according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient.

[11] In another embodiment, the method further comprises:

determining the coordinate information of the last significant coefficient as a horizontal distance and a vertical distance from the position of the last significant coefficient to the upper left corner of the current block, when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is not reversed for the current block; and

determining the position of the last significant coefficient according to the horizontal distance and vertical distance from the position of the last significant coefficient to the upper left corner of the current block.

[12] In another embodiment, the last significant coefficient reverse position flag is at least one of a sequence level, a picture level, a slice level, or a block level flag.

[13] In a second aspect of the present invention, there is provided a coefficient encoding method applied to an encoder and comprising:

determination of the sequence level flag and the position of the last significant coefficient;

determining a flag of the reverse position of the last significant coefficient when the sequence level flag indicates that the video satisfies a given condition;

determining information about the coordinates of the last significant coefficient according to the position of the last significant coefficient and the flag of the reverse position of the last significant coefficient;

determining the information about the prefix of the horizontal coordinate of the last significant coefficient, the information about the prefix of the vertical coordinate of the last significant coefficient, the information about the suffix of the horizontal coordinate of the last significant coefficient and the information about the suffix of the vertical coordinate of the last significant coefficient according to the information about the coordinates of the last significant coefficient; and

encoding all coefficients before the position of the last significant coefficient according to a given scanning order and providing bit information obtained by encoding a sequence level flag, information about a prefix of a horizontal coordinate of the last significant coefficient, information about a prefix of a vertical coordinate of the last significant coefficient, information about a suffix of a horizontal coordinate of the last significant coefficient and information about a suffix of a vertical coordinate of the last significant coefficient to a bit stream,

in this case, the value of the horizontal coordinate of the last significant coefficient in a given scanning order within the current block is found as follows:

if last_sig_coeff_x_suffix is not present, then:

LastSignificantCoeffX = last_sig_coeff_x_prefix;

if last_sig_coeff_x_suffix is present, then:

LastSignificantCoeffX = (1<<((last_sig_coeff_x_prefix>>1) -1)) * (2+(last_ sig_coeff_x_prefix&1)) + last_sig_coeff_x_suffix; And

if reverse_last_sig_coeff_flag is 1, then:

LastSignificantCoeffX = (1<<log2ZoTbWidth) -1-LastSignificantCoeffX; And

the value of the vertical coordinate of the last significant coefficient in a given scanning order within the current block is found as follows:

if last_sig_coeff_y_suffix is not present, then:

LastSignificantCoeffY = last_sig_coeff_y_prefix;

if last_sig_coeff_y_suffix is present, then:

LastSignificantCoeffY= (1<<((last_sig_coeff_y_prefix>>1) -1)) * (2+(last_sig_coeff_y_prefix&1)) + last_sig_coeff_y_suffix; And

if reverse_last_sig_coeff_flag is 1, then:

LastSignificantCoeffY= (1<<log2ZoTbHeight) -1-LastSignificantCoeffY;

wherein (1<<log2ZoTbWidth) represents the width of the transformation block after zero output, (1<<log2ZoTbHeight) represents the height of the transformation block after zero output, LastSignificantCoeffX represents the value of the horizontal coordinate of the last significant coefficient in the given scan order within the current block, LastSignificantCoeffY represents the value of the vertical coordinate of the last significant coefficient in the given scan order within the current block, last_sig_coeff_x_prefix represents the information of the prefix of the horizontal coordinate of the last significant coefficient, last_sig_coeff_y_prefix represents the information of the prefix of the vertical coordinate of the last significant coefficient, last_sig_coeff_x_suffix represents the information of the suffix of the horizontal coordinate of the last significant coefficient, the last_sig_coeff_y_suffix represents the information of the suffix of the vertical coordinate of the last significant coefficient, and reverse_last_sig_coeff_flag represents the flag of the reverse position of the last significant coefficient.

[14] In one embodiment, defining a sequence level flag includes:

defining a sequence level flag as the first value when the video satisfies a given condition; or

defining a sequence level flag as a second value when the video does not satisfy a given condition.

[15] In another embodiment, the specified condition includes at least one of: high bit depth, high quality, high bit rate, high frame rate, or lossless compression.

[16] In another embodiment, determining the last significant coefficient reverse position flag includes:

defining the last significant coefficient position reversal flag as the first value when the last significant coefficient position is reversed for the current block; or

defining the last significant coefficient position reversal flag as the second value when the last significant coefficient position is not reversed for the current block.

[17] In another embodiment, the position of the last significant coefficient comprises an initial horizontal coordinate and an initial vertical coordinate of the last significant coefficient, wherein the initial horizontal coordinate is a horizontal distance from the position of the last significant coefficient to the upper left corner of the current block, and the initial vertical coordinate is a vertical distance from the position of the last significant coefficient to the upper left corner of the current block; and

accordingly, determining the information about the coordinates of the last significant coefficient according to the position of the last significant coefficient and the flag of the reverse position of the last significant coefficient includes:

when the last significant coefficient reverse position flag has the first value, determining the coordinate information of the last significant coefficient by calculating according to the initial horizontal coordinate and the initial vertical coordinate of the last significant coefficient; or

when the last significant coefficient reverse position flag has the second value, determining the coordinate information of the last significant coefficient directly according to the initial horizontal coordinate and the initial vertical coordinate of the last significant coefficient.

[18] In another embodiment, determining the coordinate information of the last significant coefficient by calculating according to the initial horizontal coordinate and the initial vertical coordinate of the last significant coefficient includes:

defining the width and height of the current block;

obtaining the horizontal coordinate of the last significant coefficient by subtracting the initial horizontal coordinate of the last significant coefficient from the width of the current block;

obtaining the vertical coordinate of the last significant coefficient by subtracting the initial vertical coordinate of the last significant coefficient from the height of the current block; and

determining information about the coordinates of the last significant coefficient according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient.

[19] In another embodiment, the method further comprises:

when the last significant coefficient reverse position flag has the first value, defining the coordinate information of the last significant coefficient as the horizontal distance and the vertical distance from the position of the last significant coefficient to the lower right corner of the current block; or

when the last significant coefficient reverse position flag has the second value, defining the coordinate information of the last significant coefficient as the horizontal distance and the vertical distance from the position of the last significant coefficient to the upper left corner of the current block.

[20] In a third aspect of the present invention, there is provided an encoder comprising a processor and a memory device storing a computer program that, when executed by the processor, causes the processor to perform the following:

definitions of the sequence level flag and the position of the last significant coefficient;

determining the flag of the reverse position of the last significant coefficient when the sequence level flag indicates that the video satisfies a given condition;

determining information about the coordinates of the last significant coefficient according to the position of the last significant coefficient and the flag of the reverse position of the last significant coefficient;

determining the information about the prefix of the horizontal coordinate of the last significant coefficient, the information about the prefix of the vertical coordinate of the last significant coefficient, the information about the suffix of the horizontal coordinate of the last significant coefficient and the information about the suffix of the vertical coordinate of the last significant coefficient according to the information about the coordinates of the last significant coefficient; and

encoding all coefficients before the position of the last significant coefficient according to a given scanning order and providing bit information obtained by encoding, a sequence level flag, information about the prefix of the horizontal coordinate of the last significant coefficient, information about the prefix of the vertical coordinate of the last significant coefficient, information about the suffix of the horizontal coordinate of the last significant coefficient and information about the suffix of the vertical coordinate of the last significant coefficient into a bit stream,

in this case, the value of the horizontal coordinate of the last significant coefficient in a given scanning order within the current block is found as follows:

if last_sig_coeff_x_suffix is not present, then:

LastSignificantCoeffX = last_sig_coeff_x_prefix;

if last_sig_coeff_x_suffix is present, then:

LastSignificantCoeffX = (1<<((last_sig_coeff_x_prefix>>1) -1)) * (2+(last_ sig_coeff_x_prefix&1)) + last_sig_coeff_x_suffix; And

if reverse_last_sig_coeff_flag is 1, then:

LastSignificantCoeffX = (1<<log2ZoTbWidth) -1-LastSignificantCoeffX; And

the value of the vertical coordinate of the last significant coefficient in a given scanning order within the current block is found as follows:

if last_sig_coeff_y_suffix is not present, then:

LastSignificantCoeffY = last_sig_coeff_y_prefix;

if last_sig_coeff_y_suffix is present, then:

LastSignificantCoeffY= (1<<((last_sig_coeff_y_prefix>>1) -1)) * (2+(last_sig_coeff_y_prefix&1)) + last_sig_coeff_y_suffix; And

if reverse_last_sig_coeff_flag is 1, then:

LastSignificantCoeffY= (1<<log2ZoTbHeight) -1-LastSignificantCoeffY;

wherein (1<<log2ZoTbWidth) represents the width of the transformation block after zero output, (1<<log2ZoTbHeight) represents the height of the transformation block after zero output, LastSignificantCoeffX represents the value of the horizontal coordinate of the last significant coefficient in the given scan order within the current block, LastSignificantCoeffY represents the value of the vertical coordinate of the last significant coefficient in the given scan order within the current block, last_sig_coeff_x_prefix represents the information of the prefix of the horizontal coordinate of the last significant coefficient, last_sig_coeff_y_prefix represents the information of the prefix of the vertical coordinate of the last significant coefficient, last_sig_coeff_x_suffix represents the information of the suffix of the horizontal coordinate of the last significant coefficient, the last_sig_coeff_y_suffix represents the information of the suffix of the vertical coordinate of the last significant coefficient, and reverse_last_sig_coeff_flag represents the flag of the reverse position of the last significant coefficient.

[21] In a fourth aspect of the present invention, a decoder is provided, comprising a processor and a memory device storing a computer program that, when executed by the processor, causes the processor to perform the following:

bit stream analysis to obtain a sequence level flag;

analyzing the bit stream to obtain a flag of the reverse position of the last significant coefficient when the sequence level flag indicates that the video satisfies a given condition;

analyzing the bit stream to obtain information about the prefix of the horizontal coordinate of the last significant coefficient, information about the prefix of the vertical coordinate of the last significant coefficient, information about the suffix of the horizontal coordinate of the last significant coefficient, and information about the suffix of the vertical coordinate of the last significant coefficient;

determining the horizontal coordinate of the last significant coefficient according to the information about the prefix of the horizontal coordinate of the last significant coefficient and the information about the suffix of the horizontal coordinate of the last significant coefficient;

determining the vertical coordinate of the last significant coefficient according to the information on the prefix of the vertical coordinate of the last significant coefficient and the information on the suffix of the vertical coordinate of the last significant coefficient; and

determining information about the coordinates of the last significant coefficient according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient;

determining the position of the last significant coefficient by calculating using the coordinate information of the last significant coefficient when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is reversed for the current block; and

decoding, according to a given scanning order, all coefficients before the position of the last significant coefficient to determine the coefficients of the current block,

in this case, the value of the horizontal coordinate of the last significant coefficient in a given scanning order within the current block is found as follows

if last_sig_coeff_x_suffix is not present, then:

LastSignificantCoeffX = last_sig_coeff_x_prefix;

if last_sig_coeff_x_suffix is present, then:

LastSignificantCoeffX = (1<<((last_sig_coeff_x_prefix>>1) -1)) * (2+(last_ sig_coeff_x_prefix&1)) + last_sig_coeff_x_suffix; And

if reverse_last_sig_coeff_flag is 1, then:

LastSignificantCoeffX = (1<<log2ZoTbWidth) -1-LastSignificantCoeffX; And

the value of the vertical coordinate of the last significant coefficient in a given scanning order within the current block is found as follows:

if last_sig_coeff_y_suffix is not present, then:

LastSignificantCoeffY = last_sig_coeff_y_prefix;

if last_sig_coeff_y_suffix is present, then:

LastSignificantCoeffY= (1<<((last_sig_coeff_y_prefix>>1) -1)) * (2+(last_sig_coeff_y_prefix&1)) + last_sig_coeff_y_suffix; And

if reverse_last_sig_coeff_flag is 1, then:

LastSignificantCoeffY= (1<<log2ZoTbHeight) -1-LastSignificantCoeffY;

wherein (1<<log2ZoTbWidth) represents the width of the transformation block after zero output, (1<<log2ZoTbHeight) represents the height of the transformation block after zero output, LastSignificantCoeffX represents the value of the horizontal coordinate of the last significant coefficient in the given scan order within the current block, LastSignificantCoeffY represents the value of the vertical coordinate of the last significant coefficient in the given scan order within the current block, last_sig_coeff_x_prefix represents the information of the prefix of the horizontal coordinate of the last significant coefficient, last_sig_coeff_y_prefix represents the information of the prefix of the vertical coordinate of the last significant coefficient, last_sig_coeff_x_suffix represents the information of the suffix of the horizontal coordinate of the last significant coefficient, the last_sig_coeff_y_suffix represents the information of the suffix of the vertical coordinate of the last significant coefficient, and reverse_last_sig_coeff_flag represents the flag of the reverse position of the last significant coefficient.

Brief description graphic materials

[22] Fig. 1 shows a schematic representation of the application of the coding structure presented in the prior art.

[23] Fig. 2 is a schematic diagram illustrating the position relationship between the current coefficient and the neighboring coefficients presented in the prior art.

[24] Fig. 3 is a schematic block diagram of the arithmetic decoding process for a binary number as presented in the prior art.

[25] Fig. 4 is a schematic block diagram of the arithmetic decoding process for a binary solution presented in the prior art.

[26] Fig. 5 shows a schematic block diagram of the renormalization of the arithmetic decoding engine presented in the prior art.

[27] Fig. 6 is a schematic block diagram of the bypass decoding process presented in the prior art.

[28] Fig. 7 is a schematic diagram illustrating the position relationship between the region that may have significant coefficients and the zero output region presented in the prior art.

[29] Fig. 8A is a schematic diagram of the composition of the encoder system provided in embodiments of the present invention.

[30] Fig. 8B is a schematic diagram of the composition of a decoder system as provided in embodiments of the present invention.

[31] Fig. 9 is a schematic flow chart of a coefficient decoding method provided in embodiments of the present invention.

[32] Fig. 10A is a schematic diagram of the position of the last significant coefficient relative to the upper left corner of the current block, as shown in embodiments of the present invention.

[33] Fig. 10B is a schematic diagram of the position of the last significant coefficient relative to the lower right corner of the current block, as shown in embodiments of the present invention.

[34] Fig. 11 is a schematic flow chart of a coefficient encoding method provided in embodiments of the present invention.

[37] Fig. 12 is a schematic structural illustration of an encoder provided in embodiments of the present invention.

[36] Fig. 13 is a schematic diagram of a specific hardware structure of an encoder provided in embodiments of the present invention.

[37] Fig. 14 is a schematic structural diagram of a decoder provided in embodiments of the present invention.

[38] Fig. 15 is a schematic diagram of a specific hardware structure of a decoder provided in embodiments of the present invention.

Detailed description

[39] In order to be able to more fully understand the features and technical content of the embodiments of the present invention, the following is a detailed description of the embodiments of the present invention in conjunction with the accompanying drawings. The accompanying drawings are included for illustrative purposes only and are not intended to limit the embodiments of the present invention.

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

[41] In the following description, "some embodiments" mentioned herein describe a subset of all possible embodiments. It should be understood that "some embodiments" may be the same subset or a different subset of all possible embodiments and may be combined with each other if there is no contradiction. It should also be noted that the terms "first/second/third" in the embodiments of the present invention are used only to distinguish similar objects and do not represent a specific order for the objects. It should be understood that "first/second/third" may be interchangeable in a certain order when permitted, and therefore, the embodiments of the present invention described herein may be implemented in an order different from that illustrated or described herein.

[42] In a video image, the first color component, the second color component, and the third color component are usually used to characterize the coding block (CB). The three color components are the luminance component, the blue chrominance component, and the red chrominance component, respectively. Specifically, the luminance component is usually represented by the symbol Y, the blue chrominance component is usually represented by the symbol Cb or U, and the red chrominance component is usually represented by the symbol Cr or V. In this case, the video image can be represented in the YCbCr format or in the YUV format.

[43] Before the embodiments of the present invention are described in more detail, the terms and terminology used in the embodiments of the present invention are explained, and the terms and terminology used in the embodiments of the present invention are applicable to the following explanations:

Moving Picture Experts Group (MPEG)

International Organization for Standardization (ISO)

International Electrotechnical Commission (IEC)

Joint Video Engineering Team (JVET)

Alliance for Open Media (AOM)

next-generation video coding standard H.266/Versatile Video Coding (VVC)

Versatile Video Coding Test Model (VVC Test Model, VTM) benchmark software test platform

Audio and Video Standard (AVS)

High Performance Model (HPM) for AVS

context-based adjustable binary arithmetic coding (CABAC)

regular residual coding (RRC)

skip residual coding transform (TSRC)

[44] It should be understood that currently universal video coding standards (such as VVC) typically use block-based hybrid coding structures. Each video image is divided into largest coding units (LCUs), which are equal-sized squares (e.g., 128×128, 64×64, etc.). Each LCU can also be divided into rectangular coding units (CUs) according to a certain rule. Moreover, a CU can be divided into smaller prediction units (PUs) or transform units (TUs), etc. In particular, as illustrated in Fig. 1, the hybrid coding structure may include modules for tasks such as prediction, transform, quantization, entropy coding, and in-loop filter. The prediction module may include intra-prediction and intermediate prediction, and the intermediate prediction may include motion estimation and motion compensation. Since there is a strong correlation between adjacent samples in a video image, using intra-prediction in video coding can eliminate spatial redundancy between adjacent samples. Furthermore, since there is also a strong similarity between adjacent images in a video, using intermediate prediction in video coding can eliminate temporal redundancy between adjacent images. Thus, coding efficiency can be improved.

[45] The basic process of a video encoder is as follows. In the encoder, an image is divided into blocks. Intra-prediction or intermediate-prediction is applied to the current block to generate a prediction block of the current block. The prediction block is subtracted from the original block of the current block to obtain a residual block. Then, the residual block is transformed and quantized to generate a matrix of quantization coefficients. The matrix of quantization coefficients is entropy encoded and output to a bitstream. In the decoder, intra-prediction or intermediate-prediction is applied to the current block to generate a prediction block of the current block. In addition, the bitstream is decoded to obtain a matrix of quantization coefficients. The matrix of quantization coefficients is inversely quantized and inversely transformed to obtain a residual block, which is added to the prediction block to obtain a reconstructed block. The reconstructed blocks form a reconstructed image. The reconstructed image is filtered in an image-based or block-based loop to obtain a decoded image. The encoder also requires similar operations as the decoder to obtain a decoded image. The decoded image can be used as a reference image in intermediate prediction for subsequent images. The block partitioning information, as well as mode information or parameter information (e.g., for prediction, transform, quantization, entropy coding, and in-loop filter) determined by the encoder, are output to the bitstream if necessary. By analyzing and examining the available information, the decoder determines the same block partitioning information and mode information or parameter information (e.g., for prediction, transform, quantization, entropy coding, and in-loop filter) as the encoder, thereby ensuring that the decoded image obtained by the encoder is the same as the decoded image obtained by the decoder. The decoded image obtained by the encoder is also commonly referred to as the reconstructed image. The current block can be partitioned into PUs during prediction. The current block can be partitioned into TUs during transform. The PU partitioning and TU partitioning may be different. The above describes the core process of a video encoder with a block-based hybrid coding structure. As technology advances, some modules or operations of the structure or process may be optimized. Embodiments of the present invention are applicable to the core process of a video encoder with a block-based hybrid coding structure, but are not limited to the structure and process.

[46] The current block can be the current CU, the current PU, the current TU, etc.

[47] Block partition information, mode information, or parameter information for prediction, transformation, and quantization, coefficients, etc. are transmitted into the bitstream by entropy coding. Assuming that the probabilities of different elements are different, a shorter codeword is assigned to an element with a higher probability of occurrence, and a longer codeword is assigned to an element with a lower probability of occurrence, so that higher coding efficiency can be obtained than fixed-length coding. However, if the probabilities of different elements are close or essentially the same, entropy coding results in limited compression. CABAC is a common entropy coding method that is used in both HEVC and VVC for entropy coding. CABAC can improve the compression efficiency by using a context model. However, using and updating the context model results in more complex operations. CABAC has a bypass mode in which there is no need to use or update the context model, and thus higher throughput can be achieved. In embodiments of the present invention, the mode requiring the use and updating of a context model in CABAC may be referred to as the context mode.

[48] Generally, a context model needs to be determined according to the specified method. When calling the specified arithmetic decoding process for a binary decision, the parameters of the context model can be used as input. When selecting a context model, there is also a dependency relationship between neighboring coefficients. For example, Fig. 2 is a schematic diagram illustrating the position relationship between the current coefficient and neighboring coefficients presented in the prior art. In Fig. 2, the block in black indicates the current coefficient, and the blocks with grid lines indicate the neighboring coefficients. As shown in Fig. 2, which context model is selected for sig_coeff_flag of the current coefficient needs to be determined according to the information of five neighboring coefficients to the right, below, and below the right of the current coefficient. As can be seen from Fig. 2, the operations for the context mode are more complex than those for the bypass mode, and there is a dependency between the neighboring coefficients.

[49] For the CABAC arithmetic coding engine, if the context mode is used, it is necessary to call the specified arithmetic decoding process for the binary decision, which includes the state transition process, namely, updating the context model. During the arithmetic decoding process for the binary decision, the renormalization process of the arithmetic decoding engine is called. If the bypass mode is used, it is necessary to call the bypass decoding process.

[50] CABAC used in VVC is presented as an example as follows.

[51] For the CABAC arithmetic coding engine, the inputs to the arithmetic decoding process are ctxTable, ctxIdx, bypassFlag, and the arithmetic decoding engine state variables ivlCurrRange and ivlOffset, and the output of the arithmetic decoding process is the value bin.

[52] ctxTable is the table used when selecting the context mode. ctxIdx is the index of the context model.

[53] Fig. 3 is a schematic flow chart of the arithmetic decoding process for a binary number presented in the prior art. As shown in Fig. 3, to decode the value bin, the context index table ctxTable, ctxIdx, bypassFlag is passed as input to the arithmetic decoding process DecodeBin(ctxTable, ctxIdx, bypassFlag), which is defined as follows:

If bypassFlag is 1, the bypass decoding process DecodeBypass() is called.

Otherwise, if bypassFlag is 0, ctxTable is 0, and ctxIdx is 0, then DecodeTerminate() is called.

Otherwise (bypassFlag is 0 and ctxIdx is not 0), the specified arithmetic decoding process is called for the binary solution DecodeDecision(ctxTable, ctxIdx).

[54] Additionally, the inputs to the arithmetic decoding process for the binary solution are the variables ctxTable, ctxIdx, ivlCurrRange, and ivlOffset, and the outputs of the arithmetic decoding process are the decoded value binVal and the updated variables ivlCurrRange and ivlOffset.

[55] Fig. 4 is a schematic flow chart of the arithmetic decoding process for a binary solution presented in the prior art. As shown in Fig. 4, pStateIdx0 and pStateIdx1 represent two states of the current context model.

[56] (1) The value of the variable ivlLpsRange is displayed as follows:

Given the current value of ivlCurrRange, the variable qRangeIdx is output as follows:

qRangeIdx=ivlCurrRange >>5.

Given qRangeIdx, pStateIdx0 and pStateIdx1, the associated ctxTable and ctxIdx, valMPS and ivlLpsRange are output as follows:

pState=pStateIdx1+16×pStateIdx0;

valMps=pState >>14;

ivlLpsRange=(qRangeIdx×((valMps ? 32767-pState : pState)>>9)>>1)+4.

[57] (2) The ivlCurrRange variable is set equal to ivlCurrRange - ivlLpsRange and the following is applied:

If ivlOffset is greater than or equal to ivlCurrRange, then binVal is set to 1 - valMPS, ivlOffset is decremented by ivlCurrRange, and ivlCurrRange is set to ivlLpsRange.

Otherwise, (ivlOffset is less than ivlCurrRange) the value of the binVal variable is set equal to valMPS.

[58] For a given binVal value, the specified state transition is performed. Depending on the current value of ivlCurrRange, the specified renormalization may be performed.

[59] Furthermore, the inputs to the state transition process are the current pStateIdx0 and pStateIdx1, and the decoded value of binVal. The outputs of the process are the updated pStateIdx0 and pStateIdx1 context variables associated with ctxTable and ctxIdx. The variables shift0 and shift1 are derived from shiftIdx. The correspondence between shiftIdx and ctxTable, and ctxIdx is specified as follows:

shift0=(shiftIdx >>2)+2;

shift1=(shiftIdx & 3)+3+shift0.

[60] Depending on the decoded value of binVal, the two variables pStateIdx0 and pStateIdx1 associated with ctxTable and ctxIdx are updated as follows:

pStateIdx0=pStateIdx0-(pStateIdx0 >>shift0)+(1023×binVal >>shift0);

pStateIdx1=pStateIdx1-(pStateIdx1>>shift1)+(16383×binVal >>shift1).

[61] Additionally, the inputs to the arithmetic decoding engine's renormalization process are the bits from the fragment data and the ivlCurrRange and ivlOffset variables. The outputs of the process are the updated ivlCurrRange and ivlOffset variables.

[62] Fig. 5 shows a schematic block diagram of the renormalization of the arithmetic decoding engine presented in the prior art. As shown in Fig. 5, the current value of ivlCurrRange is first compared with 256, and the subsequent operations are performed as follows:

If ivlCurrRange is greater than or equal to 256, renormalization is not required and the RenormD process terminates.

Otherwise (ivlCurrRange is less than 256), a renormalization loop is introduced. Within this loop, the value of ivlCurrRange is doubled, i.e., shifted left by 1. The value of ivlOffset is doubled, i.e., shifted left by 1. The 1-bit is shifted into ivlOffset using read_bits(1).

[63] The bitstream must not contain data that would cause ivlOffset to be greater than or equal to ivlCurrRange when this process completes.

[64] Additionally, the inputs to the bypass decoding process for binary solutions are the bits from the chunk data and the ivlCurrRange and ivlOffset variables. The outputs of this process are the updated ivlOffset variable and the decoded binVal value.

[65] The bypass decoding process is called when bypassFlag is equal to 1. Fig. 6 shows a schematic flow chart of the bypass decoding process presented in the prior art. As shown in Fig. 6, first, the ivlOffset value is doubled, i.e., shifted left by 1, and a one bit is shifted into ivlOffset using read_bits(1). Then, the ivlOffset value is compared with the ivlCurrRange value, and the subsequent steps are performed as follows:

If ivlOffset is greater than or equal to ivlCurrRange, binVal is set to 1 and ivlOffset is decreased by ivlCurrRange.

Otherwise, (ivlOffset is less than ivlCurrRange) binVal is set to 0.

[66] The bitstream must not contain data that would cause ivlOffset to be greater than or equal to ivlCurrRange when this process completes.

[67] It should also be understood that in current video coding standards, one or more transforms and skip transforms are usually supported for residuals. The transforms include discrete cosine transform (DCT), etc. The transformed residual block usually exhibits certain characteristics after the transform (and quantization). For example, after some transforms (and quantization), since the energy is mainly concentrated in the low-frequency region, the coefficients in the upper-left region are relatively large, and the coefficients in the lower-right region are relatively small or even equal to 0. For skip transform, no transform is performed. The distribution pattern of the coefficients after skip transform is different from that of the coefficients after the transform, so different coefficient coding methods may be used. For example, in VVC, RRC is used for the coefficients after skip transform, and TSRC is used for the coefficients after skip transform.

[68] For common transforms such as the DCT, the transformed block has increasing frequencies from left to right and top to bottom. The upper left corner represents a lower frequency, and the lower right corner represents a higher frequency. Human eyes are more sensitive to low-frequency information and less sensitive to high-frequency information. With this property, intensive processing or removal of some high-frequency information has less visual impact. Some techniques, such as zero-output, may force some high-frequency information to be 0. For example, for a 64×64 block, the coefficients at positions with horizontal coordinates greater than or equal to 32 or with vertical coordinates greater than or equal to 32 are forced to be 0. The above is only a simple example, and there may be more complex ways to obtain the zero-output range that are not described here. As shown in Fig. 7, non-zero (or so-called significant) coefficients can exist in the upper left corner (namely, the region that possibly contains significant coefficients), and all coefficients in the lower right corner are set to zero (namely, the zero-output region). Therefore, subsequent encoding of the coefficients does not require encoding the coefficients in the zero-output region, since the coefficients must be equal to 0.

[69] In addition, since the distribution of coefficients shows the characteristic that the coefficients in the upper left corner are larger and many coefficients in the lower right corner are 0 after residual transformation (and quantization) in normal video, during coefficient coding, some methods are usually used to coding the coefficients within a certain range of the upper left corner, rather than coding the coefficients within a certain range of the lower right corner (by default, these coefficients are 0). One method is to first determine the position of the last significant coefficient of the block in the scan order when coding the coefficients of a block. Once this position is determined, all coefficients following the position of the last significant coefficient in the scan order are considered to be 0, that is, no coding is required. Only the last significant coefficient and its previous coefficients need to be coding. For example, in VVC, the position of the last significant coefficient (LastSignificantCoeffX, LastSignificantCoeffY) is determined using last_sig_coeff_x_prefix, last_sig_coeff_y_prefix, last_sig_coeff_x_suffix and last_sig_coeff_y_suffix.

[70] (a) last_sig_coeff_x_prefix specifies the prefix of the horizontal coordinate (or column) of the last significant coefficient in scan order within the current block. The value of last_sig_coeff_x_prefix must be in the range from 0 to ( log2ZoTbWidth << 1 ) - 1 , inclusive.

[71] If last_sig_coeff_x_prefix is not present, then last_sig_coeff_x_prefix is 0.

[72] (b) last_sig_coeff_y_prefix specifies the prefix of the vertical coordinate (or row) of the last significant coefficient in scan order within the current block. The value of last_sig_coeff_y_prefix must be in the range from 0 to ( log2ZoTbHeight << 1 ) - 1 , inclusive.

[73] If last_sig_coeff_y_prefix is not present, then last_sig_coeff_y_prefix is 0.

[74] (c) last_sig_coeff_x_suffix specifies the suffix of the horizontal coordinate (or column) of the last significant coefficient in scan order within the current block. The value of last_sig_coeff_x_suffix must be in the range from 0 to (1<< ( ( last_sig_coeff_x_prefix>>1)-1))-1, inclusive.

[75] LastSignificantCoeffX, i.e. the value of the horizontal coordinate (or column) of the last significant coefficient in the scan order within the current transformation block, is output as follows:

if last_sig_coeff_x_suffix is not present, then

LastSignificantCoeffX = last_sig_coeff_x_prefix;

Otherwise (last_sig_coeff_x_suffix is present),

LastSignificantCoeffX=(1<< ((last_sig_coeff_x_prefix>>1)-1))*(2+(last_ sig_coeff_x_prefix&1)) + last_sig_coeff_x_suffix.

[76] (d) last_sig_coeff_y_suffix specifies the suffix of the vertical coordinate (or row) of the last significant coefficient of the current transform block in scan order. The value of last_sig_coeff_x_suffix must be in the range from 0 to (1<< ((last_sig_coeff_y_prefix>>1)-1))-1, inclusive.

[77] LastSignificantCoeffY, i.e. the value of the vertical coordinate (or row) of the last significant coefficient of the current transform block in the scanning order, is output as follows:

if last_sig_coeff_y_suffix is not present, then

LastSignificantCoeffY = last_sig_coeff_y_prefix;

Otherwise (last_sig_coeff_y_suffix is present),

LastSignificantCoeffY = (1<< ((last_sig_coeff_y_prefix>>1)-1))*(2+(last_sig_coeff_y_prefix&1)) + last_sig_coeff_y_suffix.

[78] In addition, the last significant coefficient and its previous coefficients must be encoded. However, in normal video, a certain percentage of these coefficients are still 0. In VVC, the sb_coded_flag flag, which indicates whether the current sub-block is encoded, is used to determine whether the coefficients of the current sub-block need to be encoded. If encoding is not required, then all coefficients of the current sub-block are considered to be 0. In this case, the sub-block is typically an n×n sub-block, such as a 4×4 sub-block.

[79] sb_coded_flag[xS][yS] specifies the following for the subblock at location ( xS, yS ) within the current transform block, where subblock is an array of transform coefficient levels:

When sb_coded_flag[ xS ][ yS ] is 0, all sub-block transform coefficient levels at location ( xS, yS ) are considered to be 0.

When sb_coded_flag[ xS ][ yS ] is not present, it is assumed to be 1.

[80] Furthermore, when dealing with coefficient coding, the compression efficiency can be improved by exploiting the properties of the coefficients. For example, for normal video, a certain percentage of the coefficients to be coding are 0. Thus, a syntax element can be used to indicate whether the current coefficient is 0. This syntax element is typically a binary symbol (bin). If the current coefficient is 0, then it means that the coding of the current coefficient is complete. Otherwise, it is necessary to continue coding the current coefficient. As another example, for normal video, a certain percentage of significant coefficients have an absolute value of 1. Thus, a syntax element can be used to indicate whether the absolute value of the current coefficient is greater than 1. This syntax element is typically a bin. If the absolute value of the current coefficient does not exceed 1, then it means that the coding of the current coefficient is complete. Otherwise, it is necessary to continue coding the current coefficient. For example, the syntax element(s) involved in VVC are as follows.

[81] sig_coeff_flag[xC][yC] indicates for a transform coefficient location ( xC, yC ) within the current transform block whether the corresponding transform coefficient level at location ( xC, yC ) is non-zero as follows.

if sig_coeff_flag[ xC ][ yC ] is 0, the transformation coefficient level at location ( xC, yC ) is set to 0;

Otherwise (sig_coeff_flag[ xC ][ yC ] is 1) the transformation coefficient level at location ( xC, yC ) has a non-zero value.

[82] When sig_coeff_flag[ xC ][ yC ] is not present, it is calculated as follows:

If transform_skip_flag[ x0 ][ y0 ][ cIdx ] is 0 or sh_ts_residual_coding_disabled_flag is 1, the following applies:

if ( xC, yC ) is the last significant location (LastSignificantCoeffX, LastSignificantCoeffY) in scan order or all of the following conditions are true, sig_coeff_flag[ xC ][ yC ] is considered to be 1:

( xC & ( (1 << log2SbW ) - 1 ), yC & ( (1 << log2SbH ) - 1 ) ) is equal to ( 0, 0 );

inferSbDcSigCoeffFlag is equal to 1; and

sb_coded_flag[ xS ][ yS ] is equal to 1;

Otherwise, sig_coeff_flag[ xC ][ yC ] is considered equal to 0;

Otherwise ([ x0 ][ y0 ][ cIdx ] is 1 and sh_ts_residual_coding_disabled_flag is 0), the following applies:

If all the following conditions are true, sig_coeff_flag[ xC ][ yC ] is considered to be equal to 1:

( xC & ( (1 << log2SbW ) - 1 ), yC & ( (1 << log2SbH ) - 1 ) ) equals ( (1 << log2SbW ) - 1, (1 << log2SbH ) - 1 );

inferSbSigCoeffFlag is equal to 1; and

sb_coded_flag[ xS ][ yS ] is equal to 1;

Otherwise, sig_coeff_flag[ xC ][ yC ] is considered equal to 0.

[83] abs_level_gtx_flag[ n ][ j ] indicates whether the absolute value of the transform gain level (at scan position n) is greater than ( j << 1 ) + 1. When abs_level_gtx_flag[ n ][ j ] is not present, abs_level_gtx_flag[ n ][ j ] is 0.

[84] Thus, if the encoding of the current coefficient is not complete after processing the above flags (or so-called syntax elements), then it is necessary to encode the remaining absolute value of the coefficient, such as abs_remainder in VVC.

[85] abs_remainder[ n ] represents the remaining absolute value of the transform coefficient level that is encoded by the Golomb-Rice code at scan position n. When abs_remainder[ n ] is not present, abs_remainder[ n ] is equal to 0.

[86] Furthermore, in VVC, syntax elements such as sig_coeff_flag and abs_level_gtx_flag are encoded using the context mode, while abs_remainder is encoded using the bypass mode. As mentioned above, context mode encoding is more complex than bypass mode encoding, which intuitively means lower processing speed. If more coefficients need to be encoded, heavy use of context mode encoding will impact the decoding speed. Therefore, the number of syntax elements encoded using the context mode may be limited. For example, if the number of binary numbers encoded using the context mode exceeds a threshold, subsequent coefficients are forced to encode using the bypass mode. For example, dec_abs_level in VVC.

[87] dec_abs_level[ n ] is the intermediate value which is encoded by Golomb-Rice code at scan position n. ZeroPos[ n ] can be derived during analysis of dec_abs_level[ n ], the absolute value of the transformation coefficient level at location ( xC, yC ) AbsLevel[ xC ][ yC ] is derived as follows:

If dec_abs_level[ n ] is not present or equal to ZeroPos[ n ], AbsLevel[ xC ][ yC ] is set to 0.

Otherwise, if dec_abs_level[ n ] is less than ZeroPos[ n ], AbsLevel[ xC ][ yC ] is set to dec_abs_level[ n ] + 1;

Otherwise (dec_abs_level[ n ] is greater than ZeroPos[ n ]), AbsLevel[ xC ][ yC ] is set equal to dec_abs_level[ n ].

[88] The above values are the absolute values of the coefficients. The sign of the significant coefficient can be determined using the coefficient sign flag coeff_sign_flag or some sign-detection methods. coeff_sign_flag[n] can be used to determine the sign of the transform coefficient at scan position n as follows:

if coeff_sign_flag[n] is 0, then the corresponding conversion coefficient is positive;

otherwise (coeff_sign_flag[n] is 1) the corresponding transformation coefficient is negative.

[89] If coeff_sign_flag[n] is not present, then coeff_sign_flag[n] is equal to 0. In this case, the sign of the transformation coefficient on the coordinates (xC, yC) is determined by CoeffSignLevel[xC][yC]:

if CoeffSignLevel[xC][yC] is 0, then the corresponding transformation coefficient is 0;

otherwise, if CoeffSignLevel[xC][yC] is 1, then the corresponding transformation coefficient is positive; otherwise (CoeffSignLevel[xC][yC] is -1), the corresponding transformation coefficient is negative.

[90] It should also be noted that CoeffSignLevel[xC][yC] can be obtained using other methods that will not be repeated in this paper.

[91] Additionally, VVC uses a parity flag, par_level_flag, for the coefficient value. The flag indicates the parity of the current coefficient and is used when determining the current coefficient value and for dependent quantization.

[92] par_level_flag [ n ] specifies the parity of the transform coefficient level at scan position n. When par_level_flag[ n ] is not present, par_level_flag[ n ] is 0.

[93] In addition to determining the parity of the conversion factor, par_level_flag can be further used to determine the value of the factor in combination with abs_level_gtx_flag, abs_remainder, etc.

[94] In this case, since context mode encoding requires selecting, using, and updating context modes, while bypass mode encoding does not, it is common practice to place context mode-encoded syntax elements together and bypass mode-encoded syntax elements together in a certain range, which is more convenient for hardware design. For example, all context mode-encoded syntax elements in a block are processed first, and then the bypass mode-encoded syntax elements are processed. All context mode-encoded syntax elements in the current block may be further divided into multiple groups, and all bypass mode-encoded syntax elements in a block may be further divided into multiple groups.

[95] In one specific example, the specific RRC syntax is illustrated in Table 1.

[96] The AbsLevel[xC][yC] array is an array of absolute values of the transformation coefficients of the current transformation block. The AbsLevelPass1[xC][yC] array is an array of absolute values of the partial reconstruction of the transformation coefficients of the current transformation block. The xC and yC indices of the array represent the position (xC, yC) in the current transformation block.

[97] After entering the residual_coding(x0, y0, log2TbWidth, log2TbHeight, cIdx) function, some information about the block size needs to be defined, such as defining the logarithms log2ZoTbWidth and log2ZoTbHeight of the block size after zero-output, where the coefficients with horizontal coordinate in the range [0, (1<<log2ZoTbWidth) - 1] and vertical coordinate in the range [0, (1<<log2ZoTbHeight) - 1] can be significant coefficients. In this case, (1<<log2ZoTbWidth) represents the width of the transform block after zero-output, and (1<< log2ZoTbHeight) represents the height of the transform block after zero-output. Then, the position of the last significant coefficient is determined based on last_sig_coeff_x_prefix, last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, last_sig_coeff_y_suffix, etc. The coefficients before (preceding) the last significant coefficient in the scan order may be significant coefficients. Then, the value of remBinsPass1 is determined, i.e., determined using remBinsPass1=((1<<(log2TbWidth+log2TbHeight)) x 7)>>2. remBinsPass1 indicates the number of syntax elements that are encoded using the context mode in the current block. In embodiments of the present invention, it should be understood that remBinsPass1 means the remaining binaries of inpass1, that is, the number of binaries remaining in the first cycle. The coefficients before the last significant coefficient in the scan order must be encoded. For subblocks containing these coefficients, a determination is made whether each current subblock should be encoded. If so, the method sets the context-mode-encoded syntax elements in the subblock in the first round, and the bypass-mode-encoded syntax elements later. For each coefficient, a maximum of four context-mode-encoded syntax elements may need to be processed, i.e., one sig_coeff_flag, two abs_level_gtx_flags, and one par_level_flag. In the first round, remBinsPass1 is decremented by 1 each time a context-mode-encoded syntax element is processed. If the coefficient is large enough, the remaining value, i.e., abs_remainder, should be processed after the context-mode-encoded syntax elements in the first round. If remBinsPass1 is already small enough (does not satisfy remBinsPass1>=4), the first loop ends and the remaining coefficients are processed directly in bypass mode, i.e. dec_abs_ level.

[98] In another concrete example, the specific syntax of TSRC is illustrated in Table 2.

[99] After entering the function residual_ts_coding(x0, y0, log2TbWidth, log2TbHeight, cIdx), it is necessary to determine some information about the block size. Then, the value of RemCcbs is determined using the equation RemCcbs=((1<<(log2TbWidth+log2TbHeight))x7)>>2. RemCcbs indicates the number of syntax elements in the current block that are encoded using the context mode. In embodiments of the present invention, it should be understood that RemCcbs means the remaining context-encoded binaries, that is, the number of remaining binaries encoded in the context mode. For each sub-block, it is determined whether encoding of the current sub-block is required. If a coding other than the above-described RRC is required, the TSRC method sets the context-mode-coded syntax elements in a sub-block in two rounds, with up to four context-mode-coded syntax elements being processed for each coefficient in the first and second rounds, respectively. Syntax elements encoded in the bypass mode are set later. In the first and second rounds, remBinsPass1 is decremented by 1 each time a context-mode-coded syntax element is processed. If the coefficient is large enough, the remaining value, i.e., abs_remainder, must be processed after the context-mode-coded syntax elements have been processed in the first and second rounds. If remBinsPass1 is small enough (does not satisfy remBinsPass1>=4), the first two rounds will be terminated, and the remaining coefficients will be processed directly in the bypass mode, in which case abs_remainder will still be used.

[100] In short, the current coefficient coding method available in the prior art has good compression efficiency for videos that are commonly used today, such as consumer video. Consumer video typically has a bit depth of 8 or 10 bits per pixel, and the bit rate is usually not too high, typically a few megabits per second (MB/s) or less. However, there are some applications in which video requires a higher bit depth, such as 12, 14, or 16 bits per pixel or higher. A higher bit depth usually results in larger coefficients, more significant coefficients, and therefore a higher bit rate. There are also applications in which higher quality video is required, which usually results in larger coefficients, more significant coefficients, and therefore a higher bit rate. A higher bit rate requires more processing power for the decoder, such as bandwidth.

[101] Video with high bit depth, high quality, and high bit rate (called "triple HD video") typically requires encoding more coefficients than video with low bit depth, low quality, and low bit rate (called "normal video"). For example, for a block of the same size, the number of coefficients that need to be encoded in triple HD video is much larger than in normal video. This is because for normal video, many coefficients in the block become 0 after prediction, transform, and quantization, while for triple HD video, many coefficients in the block are still significant coefficients after prediction, transform, and quantization. For normal video, since a large percentage of the coefficients to be encoded in a block after prediction, transformation, and quantization are 0, it is very effective to use the position of the last significant coefficient (LastSignificantCoeffX, LastSignificantCoeffY) to distinguish between regions with coefficients to be encoded and those not to be encoded. Furthermore, a large percentage of the coefficients before the position of the last significant coefficient are also 0, and thus it is very effective to further distinguish whether the current subblock needs encoding or not by using sb_coded_flag to indicate whether the subblock is encoded. However, when there are a large number of significant coefficients in the current block, or even most or all of the coefficients are significant coefficients, using the position of the last significant coefficient and the flag indicating whether the subblock is encoded, as mentioned above, cannot filter out too many significant coefficients. In addition, encoding the positions of the last significant coefficient and the flag indicating whether the sub-block is encoded in the bitstream will cause some overhead, resulting in resource wastage.

[102] On the other hand, the position of the last significant coefficient and the flag indicating whether the sub-block is encoded are encoded in the context mode, which is more complex than the bypass mode. Processing such information also affects the speed and throughput of software and hardware encoding.

[103] In another aspect, the current method for encoding the position of the last significant coefficient (LastSignificantCoeffX, LastSignificantCoeffY) is to encode the coordinates of the position of the last significant coefficient. In normal video, the values of LastSignificantCoeffX and LastSignificantCoeffY are usually small, since most of the significant coefficients are concentrated in the upper left corner, while a large area in the lower right corner has zero coefficients. However, in triple high definition video, a large number of significant coefficients are also present in the lower right corner, which usually leads to large values of LastSignificantCoeffX and LastSignificantCoeffY and, therefore, to greater resource consumption when encoding large values in the bitstream. Furthermore, the present method can be used in lossless compression, where quantization cannot be used, in which case the coefficients are usually more numerous and larger. In this case, using existing related schemes may lead to increased resource consumption and inefficient use of resources, and even affect the encoding speed and throughput.

[104] Embodiments of the present invention provide a coefficient decoding method that is applied to a decoder. A bitstream is analyzed to obtain a flag related to the video. When the video-related flag indicates that the video satisfies a predetermined condition, the bitstream is analyzed to obtain a last significant coefficient position inversion flag and information on the coordinate of the last significant coefficient. When the last significant coefficient position inversion flag indicates that the position of the last significant coefficient is reversed for the current block, the position of the last significant coefficient is determined by calculation using the information on the coordinate of the last significant coefficient. According to a predetermined scanning order, all coefficients before the position of the last significant coefficient are decoded to determine the coefficients of the current block.

[105] Embodiments of the present invention further provide a method for encoding coefficients that is applied to an encoder. A flag related to the video and the position of the last significant coefficient are determined. When the flag related to the video indicates that the video satisfies a predetermined condition, a flag of the inverse position of the last significant coefficient is determined. Information on the coordinate of the last significant coefficient is determined according to the position of the last significant coefficient and the flag of the inverse position of the last significant coefficient. All coefficients before the position of the last significant coefficient are encoded according to a predetermined scanning order, and the bit information obtained by encoding, the flag related to the video, and the information on the coordinate of the last significant coefficient are transmitted to a bitstream.

[106] Therefore, in high-bit-depth, high-bit-rate, high-quality, or lossless compression video coding scenarios, since the coefficient distribution pattern is different from that in conventional video scenarios, during coefficient coding, by reducing or even eliminating the number of syntax elements encoded in the context mode, such as syntax elements about the position of the last significant coefficient, coded sub-block flags, etc., or by additionally performing coordinate transformation in the case where the coordinate values of the last significant coefficient are too large, the resource consumption caused by coding in the bitstream can be reduced, and thus the throughput and coding speed of the coefficients can be improved. In addition, the compression efficiency can also be improved since the reduced or eliminated syntax elements have less impact on video coding in high-bit-depth, high-bit-rate, high-quality, or lossless compression scenarios.

[107] Embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

[108] As shown in Fig. 8A, Fig. 8A illustrates an exemplary block diagram of the composition of an encoder system presented in embodiments of the present invention. As shown in Fig. 8A, the encoder 100 may comprise a partitioning unit 101, a prediction unit 102, a first adder 107, a transform unit 108, a quantization unit 109, an inverse quantization unit 110, an inverse transform unit 111, a second adder 112, a filtering unit 113, a decoded picture buffer (DPB) unit 114, and an entropy encoding unit 115. In this case, the input data of the encoder 100 may be a video including a series of images or a still image, and the output data of the encoder 100 may be a bitstream representing a compressed version of the input video.

[109] The partitioning node 101 partitions an image in the input video into one or more coding tree units (CTUs). The partitioning node 101 partitions the image into a plurality of tiles and may further partition one tile into one or more packages, where a tile or package may include one or more full and/or partial CTUs. In addition, the partitioning node 101 may generate one or more slices, where one slice may include one or more tiles in raster order in the image, or one or more tiles covering a rectangular region in the image. The partitioning node 101 may also generate one or more image fragments, where one image fragment may include one or more slices, tiles, or packages.

[110] During the encoding process of the encoder 100, the partitioning node 101 transmits the CTU to the prediction node 102. Typically, the prediction node 102 may include a block partitioning node 103, a motion estimation (ME) node 104, a motion compensation (MC) node 105, and an intra-prediction node 106. In particular, the block partitioning node 103 further partitions the input CTU into smaller coding units (CUs) by iteratively using a quaternary tree-based partition, a binary tree-based partition, and a ternary tree-based partition. The prediction node 102 may use the ME node 104 and the MC node 105 to obtain an intermediate prediction block of the CU. The intra-prediction node 106 may obtain the intra-prediction block of the CU using various intra-prediction modes, including the MIP mode. In examples, a motion estimation method based on distortion level optimization (RDO) may be called by the ME node 104 and the MC node 105 to obtain an intermediate prediction block, and a mode determination method based on RDO may be called by the intra prediction node 106 to obtain an intra prediction block.

[111] The prediction unit 102 outputs a CU prediction block, and the first adder 107 calculates the difference, i.e., the residual CU, between the CU output by the partition unit 101 and the CU prediction block. The transform unit 108 reads the residual CU and performs one or more transforms on the residual CU to obtain coefficients. The quantization unit 109 quantizes the coefficients and outputs the quantized coefficients (i.e., levels). The inverse quantization unit 110 performs scaling operations on the quantized coefficients to output the reconstructed coefficients. The inverse transform unit 111 performs one or more inverse transforms corresponding to the transforms in the transform unit 108 and outputs the reconstructed residuals. The second adder 112 calculates the reconstructed CU by summing the reconstructed residuals and the CU prediction block from the prediction unit 102. The second adder 112 also transmits its output to the prediction unit 102 for use as a reference for intra prediction. After all CUs in the image or image sub-section have been reconstructed, the filtering unit 113 performs loop filtering on the reconstructed image or image sub-section. In this case, the filtering unit 113 comprises one or more filters, such as a deblocking filter, an adaptive discrete offset (SAO) filter, an adaptive loop filter (ALF), a luminance mapping filter with chroma scaling (LMCS), a neural network-based filter, etc. Alternatively, if the filtering unit 113 determines that the CU should not be used as a reference for coding other CUs, the filtering unit 113 performs loop filtering on one or more target pixels in the CU.

[112] The output of the filtering unit 113 is decoded images or sub-images, which are buffered in the DPB unit 114. The DPB unit 114 outputs the decoded images or sub-images based on the synchronization and control information. In this case, the images stored in the DPB unit 114 can also be used as a reference for the prediction unit 102 to perform intermediate prediction or intra prediction. Finally, the entropy encoding unit 115 converts the parameters necessary for decoding the images (for example, control parameters and additional information, etc.) from the encoder 100 into binary form, and transmits signals of such binary form into a bit stream according to the syntax structure of each data node, i.e., the encoder 100 finally outputs the bit stream.

[113] Furthermore, the encoder 100 may comprise a first processor and a first memory device that stores a computer program. When the first processor reads and runs the computer program, the encoder 100 reads the input video and generates a corresponding bitstream. Alternatively, the encoder 100 may be a computing device having one or more chips. These nodes, implemented as integrated circuits on a chip, have connection and data exchange functions similar to the corresponding nodes in Fig. 8A.

[114] As shown in Fig. 8B, Fig. 8B illustrates an exemplary block diagram of the composition of a decoder system presented in embodiments of the present invention. As shown in Fig. 8B, a decoder 200 may comprise an analysis unit 201, a prediction unit 202, an inverse quantization unit 205, an inverse transform unit 206, an adder 207, a filtering unit 208, and a DPB unit 209. In this case, the input of the decoder 200 is a bitstream representing a compressed version of a video or a still image, and the output of the decoder 200 may be a bitstream including decoded video including a series of images or a decoded still image.

[115] The input bitstream of the decoder 200 may be a bitstream generated by the encoder 100. The analysis unit 201 analyzes the input bitstream and obtains the values of the syntax elements from the input bitstream. The analysis unit 201 converts the binary representation of the syntax element into a numerical value and sends the numerical value to a node in the decoder 200 to obtain one or more decoded images. The analysis unit 201 may also analyze one or more syntax elements from the input bitstream to display the decoded image.

[116] During the decoding process of the decoder 200, the analysis node 201 sends to the node in the decoder 200 the values of the syntax elements and one or more variables set or determined according to the values of the syntax elements to obtain one or more decoded images.

[117] The prediction unit 202 determines a prediction block for the current decoding block (e.g., CU). In this case, the prediction unit 202 may include a motion compensation unit 203 and an intra prediction unit 204. In particular, when an intermediate decoding mode is indicated for decoding the current decoding block, the prediction unit 202 transmits the corresponding parameters from the analysis unit 201 to the motion compensation unit 203 to obtain the intermediate prediction block. When an intra prediction mode (including the MIP mode indicated by the MIP index value) is indicated for decoding the current decoding block, the prediction unit 202 transmits the corresponding parameters from the analysis unit 201 to the intra prediction unit 204 to obtain the intra prediction block.

[118] The inverse quantization unit 205 has the same function as the inverse quantization unit 110 in the encoder 100. The inverse quantization unit 205 performs scaling operations on the quantization coefficients (i.e., levels) from the analysis unit 201 to obtain reconstructed coefficients.

[119] The inverse transform unit 206 has the same function as the inverse transform unit 111 in the encoder 100. The inverse transform unit 206 performs one or more transforms (i.e., the inverse operations of one or more transforms performed by the inverse transform unit 111 in the encoder 100) to obtain reconstructed residuals.

[120] The adder 207 performs a summation operation on its input data (the prediction block from the prediction node 202 and the reconstructed residuals from the inverse transform node 206) to obtain a reconstructed block of the current decoding block. The reconstructed block is also sent to the prediction node 202 to be used as a reference for other blocks encoded in the intra-prediction mode.

[121] After all CUs in the image or sub-image are reconstructed, the filtering unit 208 performs loop filtering on the reconstructed image or sub-image. The filtering unit 208 comprises one or more filters, such as a deblocking filter, an adaptive sample compensation filter, an adaptive loop filter, brightness mapping and color scaling filters, and neural network-based filters. Alternatively, when the filtering unit 208 determines that the reconstructed block should not be used as a reference for decoding other blocks, the filtering unit 208 performs loop filtering on one or more target pixels in the reconstructed block. In this case, the output of the filtering unit 208 is a decoded image or sub-image, and the decoded image or sub-image is buffered in the DPB unit 209. The DPB unit 209 outputs the decoded image or sub-image based on the synchronization and control information. The image stored in the DPB node 209 may also be used as a reference for performing intermediate prediction or intra prediction by the prediction node 202.

[122] In addition, the decoder 200 may comprise a second processor and a second memory device that stores a computer program. When the first processor reads and runs the computer program, the decoder 200 reads the input bit stream and generates a corresponding decoded image. Alternatively, the decoder 200 may be a computing device having one or more chips. These nodes, implemented as integrated circuits on a chip, have connection and data exchange functions similar to the corresponding nodes in Fig. 8B.

[123] It should also be noted that when embodiments of the present invention are applied to the encoder 100, the “current block” specifically refers to the current block to be encoded in the video image (which may also be referred to as a “coding block”). When embodiments of the present invention are applied to the decoder 200, the “current block” specifically refers to the current block to be decoded in the video image (which may also be referred to as a “decoding block”).

[124] In one embodiment of the present invention, referring to Fig. 9, Fig. 9 illustrates a schematic flow chart of a coefficient decoding method provided in embodiments of the present invention. As shown in Fig. 9, the method may include the following.

[125] In step S901, the bit stream is analyzed to obtain a flag related to the video.

[126] It should be noted that the coefficient decoding method in the embodiments of the present invention is applied to a decoder. In particular, based on the composition structure of the decoder 200 illustrated in Fig. 8B, the coefficient decoding method in the embodiments of the present invention is mainly applied to the “analysis unit 201” of the decoder 200. The analysis unit 201 may use an adaptive binary arithmetic coding mode based on a context model or a bypass mode to decode the values of associated flags (or syntax elements) and thus determine the coefficients of the current block.

[127] It should also be noted that coefficient coding, as commonly referred to in video standards, may include both encoding and decoding. Thus, coefficient coding includes a method for encoding coefficients on the encoder side and a method for decoding coefficients on the decoder side. An embodiment of the present invention is described with respect to a method for decoding coefficients on the decoder side.

[128] Typically, for example, for normal video, the method for decoding the coefficients is the same as the methods available in the prior art. However, for a specific case, such as a high bit depth, high quality, high bit rate, or lossless compression video coding scenario, embodiments of the present invention may modify the method for obtaining the position of the last significant coefficient.

[129] In embodiments of the present invention, it is first necessary to determine whether the current video satisfies a given condition, which may be represented by a flag related to the video. In some embodiments, the bitstream may be analyzed to obtain the flag related to the video as follows.

[130] If the video-related flag has the first value, it is determined that the video-related flag indicates that the video satisfies the specified condition.

[131] Alternatively, if the video-related flag has a second value, it is determined that the video-related flag indicates that the video does not satisfy the specified condition

[132] In this case, the first value is 1 and the second value is 0.

[133] It should be noted that in another specific example, the first value may also be set to the value "true" and the second value may also be set to the value "false." In yet another specific example, the first value may also be set to the value 0 and the second value may also be set to the value 1. Optionally, the first value may also be set to the value "false" and the second value may also be set to the value "true." The present invention is not limited thereto.

[134] It should also be noted that the specified condition includes at least one of: high bit depth, high quality, high bit rate, high frame rate, or lossless compression.

[135] That is, compared with conventional videos, the videos described in the embodiments of the present invention have the characteristic of high bit depth, high quality, high bit rate, high frame rate, or lossless compression.

[136] Furthermore, the flag related to the video may be a sequence-level flag or even a higher-level flag such as video usability information (VUI), supplemental optimization information (SEI), etc. Whether a video satisfies a given condition can be determined by determining whether the video satisfies high bit depth, or whether the video satisfies high bit rate, or whether the video satisfies high quality, or whether the video satisfies lossless compression, etc. Each of these four cases is described below as examples.

[137] In some embodiments, when the video-related flag is a high bit depth flag, the method may further include the following.

[138] If the high bit depth flag indicates that the video satisfies the high bit depth, it is determined that the video satisfies the specified condition.

[139] In some embodiments, when the video-related flag is a high bit rate flag, the method may further include the following.

[140] If the high bit rate flag indicates that the video satisfies the high bit rate, it is determined that the video satisfies the specified condition.

[141] In some embodiments, when the flag related to the video is a high quality flag, the method may further include the following.

[142] If the high quality flag indicates that the video meets the high quality, the video is determined to meet the specified condition.

[143] In some embodiments, when the video-related flag is a lossless compression flag, the method may further include the following.

[144] If the lossless compression flag indicates that the video satisfies lossless compression, the video is determined to satisfy the specified condition.

[145] Taking the sequence level as an example, the video-related flag may be a high bit depth flag (represented by sps_high_bit_depth_flag) to indicate whether the current video sequence is a high bit depth sequence. The video-related flag may also be a high bit rate flag (represented by sps_high_bit_rate_flag) to indicate whether the current video sequence is a high bit rate sequence. The video-related flag may also be another flag indicating high bit depth, high bit rate, high quality, or lossless compression, which is not particularly limited in the embodiments of the present invention.

[146] In step S902, when the flag related to the video indicates that the video satisfies a predetermined condition, the bit stream is analyzed to obtain a flag of the reverse position of the last significant coefficient and information about the coordinate of the last significant coefficient.

[147] It should be noted that when a flag related to a video indicates that the video satisfies a given condition, the bitstream may be further analyzed to obtain a flag of the reverse position of the last significant coefficient and information about the coordinate of the last significant coefficient.

[148] The coordinate information of the last significant coefficient may be determined from last_sig_coeff_x_prefix, last_sig_coeff_x_suffix, last_sig_coeff_y_prefix, and last_sig_coeff_y_suffix. Thus, in some embodiments, the bitstream may be parsed to obtain the coordinate information of the last significant coefficient as follows.

[149] The bit stream is analyzed to obtain information about the prefix of the horizontal coordinate of the last significant coefficient, information about the prefix of the vertical coordinate of the last significant coefficient, information about the suffix of the horizontal coordinate of the last significant coefficient, and information about the suffix of the vertical coordinate of the last significant coefficient. The horizontal coordinate of the last significant coefficient is determined according to the information about the prefix of the horizontal coordinate of the last significant coefficient and the information about the suffix of the horizontal coordinate of the last significant coefficient. The vertical coordinate of the last significant coefficient is determined according to the prefix of the vertical coordinate of the last significant coefficient and the suffix of the vertical coordinate of the last significant coefficient. The information about the coordinate of the last significant coefficient is determined according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient.

[150] It should be noted that the information about the prefix of the horizontal coordinate of the last significant coefficient is represented by last_sig_coeff_x_prefix, which indicates the prefix of the horizontal coordinate (or column) of the last significant coefficient in the given scan order in the current block. The information about the prefix of the vertical coordinate of the last significant coefficient is represented by last_sig_coeff_y_prefix, which indicates the prefix of the vertical coordinate (or row) of the last significant coefficient in the given scan order in the current block. The information about the suffix of the horizontal coordinate of the last significant coefficient is represented by last_sig_coeff_x_suffix, which indicates the suffix of the horizontal coordinate (or column) of the last significant coefficient in the given scan order in the current block. The information about the suffix of the vertical coordinate of the last significant coefficient is represented by last_sig_coeff_y_suffix, which indicates the suffix of the vertical coordinate (or row) of the last significant coefficient in the given scan order in the current block.

[151] It should also be noted that last_sig_coeff_x_prefix and last_sig_coeff_x_suffix indicate the abscissa (i.e., horizontal coordinate) of the last significant coefficient, and last_sig_coeff_y_prefix and last_sig_coeff_y_suffix indicate the ordinate (i.e., vertical coordinate) of the last significant coefficient. Thus, information about the coordinate of the last significant coefficient is obtained.

[152] The flag of the reverse position of the last significant coefficient may be represented as reverse_last_sig_coeff_flag. In embodiments of the present invention, the flag of the reverse position of the last significant coefficient may be at least a flag of the sequence level, the picture level, the slice level, or the block level; or even a flag of a higher level (e.g., VUI, SEI, etc.), which will not be limited in the present description.

[153] That is, reverse_last_sig_coeff_flag may be a sequence level or higher level flag, or may also be a picture level flag, a slice level flag, a block level flag, etc. Additionally, the block level flag may include a largest coding unit (LCU) level flag or a coding unit (CU) level flag, or another block level flag, which is not limited in the embodiments of the present invention.

[154] In some embodiments, the method may further include the following.

[155] If the last significant coefficient position reverse flag has the first value, it is determined that the last significant coefficient position reverse flag indicates that the position of the last significant coefficient has been reversed for the current block. If the last significant coefficient position reverse flag has the second value, it is determined that the last significant coefficient position reverse flag indicates that the position of the last significant coefficient has not been reversed for the current block.

[156] That is, in the example where the first value is 1 and the second value is 0, if reverse_last_sig_coeff_flag has the value 1, then it can be determined that reverse_last_sig_coeff_flag indicates that the position of the last significant coefficient is reversed for the current block. Alternatively, if reverse_last_sig_coeff_flag has the value 0, then it can be determined that reverse_last_sig_coeff_flag indicates that the position of the last significant coefficient is not reversed for the current block.

[157] In step S903, when the last significant coefficient reverse position flag indicates that the position of the last significant coefficient is reversed for the current block, the position of the last significant coefficient is determined by calculation using the coordinate information of the last significant coefficient.

[158] In step S904, according to a predetermined scanning order, all coefficients before the position of the last significant coefficient are decoded to determine the coefficients of the current block.

[159] It should be noted that in embodiments of the present invention, when the last significant coefficient position reverse flag indicates that the position of the last significant coefficient is reversed for the current block, the coordinate information of the last significant coefficient can be determined as a horizontal distance and a vertical distance from the position of the last significant coefficient to the lower right corner of the current block.

[160] In this case, in some embodiments, the position of the last significant coefficient may be determined by calculating using the coordinate information of the last significant coefficient as follows:

[161] The width and height of the current block are determined. The horizontal coordinate of the last significant coefficient is obtained by subtracting the horizontal distance from the position of the last significant coefficient to the lower right corner of the current block from the width of the current block. The vertical coordinate of the last significant coefficient is obtained by subtracting the vertical distance from the position of the last significant coefficient to the lower right corner of the current block from the height of the current block. The position of the last significant coefficient is determined according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient.

[162] It should be noted that the coordinate information of the last significant coefficient is usually the horizontal distance and the vertical distance between the position of the last significant coefficient and the upper left corner of the current block. For normal video, most of the significant coefficients are concentrated in the upper left corner, and a large area in the lower right corner has coefficients equal to 0. However, for coding video with high bit depth, high quality, or high bit rate, a large number of significant coefficients also appear in the lower right corner, so the coordinate information of the last significant coefficient usually has large values. In this case, in order to save resources, coordinate transformation (which can be a coordinate reversal calculation, that is, after coordinate reversal, the coordinate information of the last significant coefficient is the horizontal distance and the vertical distance between the position of the last significant coefficient and the lower right corner of the current block) is necessary during coefficient encoding. In this case, coordinate reversal calculation is also necessary during coefficient decoding. After reversing, the coordinate information of the last significant coefficient can be reconstructed as the horizontal and vertical distances between the position of the last significant coefficient and the upper-left corner of the current block. Thus, the position of the last significant coefficient can be determined, and then the coefficients before the position of the last significant coefficient in the current block can be decoded according to the specified scan order.

[163] It should also be noted that the current block here can be a block without zero-output transformation or a block after zero-output transformation. Taking a block after zero-output transformation as an example, the width of the current block is 1<<log2ZoTbWidth, and the height of the current block is 1<<log2ZoTbHeight. Then, in the case where reverse_last_sig_coeff_flag indicates that the position of the last significant coefficient is reversed for the current block (i.e., the value of reverse_last_sig_coeff_flag is 1):

LastSignificantCoeffX= (1<<log2ZoTbWidth) -1-LastSignificantCoeffX;

LastSignificantCoeffY= (1<<log2ZoTbHeight) -1-LastSignificantCoeffY.

[164] In the above example, (LastSignificantCoeffX, LastSignificantCoeffY) on the right side of the equation represents the coordinate information of the last significant coefficient obtained by decoding, and (LastSignificantCoeffX, LastSignificantCoeffY) on the left side of the equation represents the position of the last significant coefficient (which can also be regarded as the target coordinate information of the last significant coefficient).

[165] In some embodiments of the present invention, in the case where the value of reverse_last_sig_coeff_flag is 0, the method may further include the following.

[166] When the last significant coefficient position reverse flag indicates that the position of the last significant coefficient is not reversed for the current block, the coordinate information of the last significant coefficient is determined as the horizontal distance and the vertical distance from the position of the last significant coefficient to the upper left corner of the current block. The position of the last significant coefficient is determined according to the horizontal distance and the vertical distance from the position of the last significant coefficient to the upper left corner of the current block.

[167] It should be noted that if reverse_last_sig_coeff_flag indicates that the position of the last significant coefficient is not reversed for the current block, then the coordinate information of the last significant coefficient obtained through decoding can be regarded as the target coordinate information of the last significant coefficient. In embodiments of the present invention, the target coordinate information of the last significant coefficient is the horizontal distance and the vertical distance between the position of the last significant coefficient and the upper left corner of the current block.

[168] Furthermore, in some embodiments, the method may further include the following.

[169] When the last significant coefficient position reverse flag indicates that the position of the last significant coefficient is not reversed for the current block, the position of the last significant coefficient is determined directly according to the coordinate information of the last significant coefficient. All coefficients before the position of the last significant coefficient in the specified scan order are decoded to determine the coefficients of the current block.

[170] It should be noted that the given scanning order can be a diagonal order, a zigzag order, a horizontal order, a vertical order, a sub-block scanning order 4 4 or any other scanning order, which is not limited to the embodiments of the present invention.

[171] It should also be noted that after receiving reverse_last_sig_coeff_flag, if the value of reverse_last_sig_coeff_flag is 1, i.e., the position of the last significant coefficient needs to be reversed, then after receiving the coordinate information of the last significant coefficient through decoding, it is necessary to perform an additional calculation using the coordinate information of the last significant coefficient to determine the position of the last significant coefficient. Then, all the coefficients before the position of the last significant coefficient are decoded according to the specified scan order. If the value of reverse_last_sig_coeff_flag is 0, i.e., there is no need to reverse the position of the last significant coefficient, then after receiving the coordinate information of the last significant coefficient through decoding, the position of the last significant coefficient can be determined directly according to the coordinate information of the last significant coefficient. Then, all the coefficients before the position of the last significant coefficient are decoded according to the specified scan order.

[172] Thus, for certain cases, embodiments of the present invention provide a modified method for determining the position of the last significant coefficient during coefficient encoding. That is, in normal cases, the method for encoding the coefficients remains the same as the method available in the prior art. For example, certain cases may relate to high bit depth, high quality, or high bit rate video, or to lossless compression in video encoding. Typically, as shown in FIG. 10A, the horizontal coordinate of the position of the last significant coefficient, that is, the horizontal distance relative to the upper left corner of the current block, is encoded in last_sig_coeff_x_prefix and last_sig_coeff_x_suffix, and the vertical coordinate of the position of the last significant coefficient, that is, the vertical distance relative to the upper left corner of the current block, is encoded in last_sig_coeff_y_prefix and last_sig_coeff_y_suffix. For comparison, in the case of high bit depth, high quality, high bit rate, or lossless compression in video coding, the position of the last significant coefficient is usually close to the lower right corner of the region of all possible significant coefficients of the current block. In this case, as illustrated in Fig. 10B, the horizontal distance of the position of the last significant coefficient relative to the lower right corner of the region of all possible significant coefficients of the current block is encoded in last_sig_coeff_x_prefix and last_sig_coeff_x_suffix, and the vertical distance of the position of the last significant coefficient relative to the lower right corner of the region of all possible significant coefficients of the current block is encoded in last_sig_coeff_y_prefix and last_sig_coeff_y_suffix. For example, if the region of all possible significant coefficients of the current block is a rectangular region from (0, 0) to ((1<<log2ZoTbWidth) - 1, (1<<log2ZoTbHeight) - 1), then last_sig_coeff_x_prefix and last_sig_coeff_x_suffix are encoded to represent the horizontal distance of the position of the last significant coefficient relative to the current block ((1<<log2ZoTbWidth) - 1, (1<<log2ZoTbHeight) - 1). last_sig_coeff_y_prefix and last_sig_coeff_y_suffix are encoded to represent the vertical distance of the position of the last significant coefficient relative to the current block ((1<<log2ZoTbWidth) - 1, (1<<log2ZoTbHeight) - 1).

[173] The semantic changes are as follows.

[174] The LastSignificantCoeffX value of the horizontal coordinate (or column) of the last significant coefficient in a given scan order within the current block is output as follows:

If last_sig_coeff_x_suffix is not present, then:

LastSignificantCoeffX = last_sig_coeff_x_prefix;

Otherwise (last_sig_coeff_x_suffix is present):

LastSignificantCoeffX = (1<<((last_sig_coeff_x_prefix>>1) -1)) * (2+(last_ sig_coeff_x_prefix&1)) + last_sig_coeff_x_suffix.

If reverse_last_sig_coeff_flag is 1, then:

LastSignificantCoeffX = (1<<log2ZoTbWidth) -1-LastSignificantCoeffX.

[175] The LastSignificantCoeffY value of the vertical coordinate (or row) of the last significant coefficient in a given scan order within the current block is output as follows:

If last_sig_coeff_y_suffix is not present, then:

LastSignificantCoeffY = last_sig_coeff_y_prefix;

Otherwise (last_sig_coeff_y_suffix is present) the following applies:

LastSignificantCoeffY= (1<<((last_sig_coeff_y_prefix>>1) -1)) * (2+(last_sig_coeff_y_prefix&1)) + last_sig_coeff_y_suffix.

If reverse_last_sig_coeff_flag is 1, then:

LastSignificantCoeffY= (1<<log2ZoTbHeight) -1-LastSignificantCoeffY.

[176] In the above example, reverse_last_sig_coeff_flag is the flag of the reverse position of the last significant coefficient, which indicates whether the position of the last significant coefficient should be reversed or not. If the value of reverse_last_sig_coeff_flag is 1, it indicates that the position of the last significant coefficient should be reversed; otherwise, it indicates that the position of the last significant coefficient should not be reversed.

[177] It should also be noted that reverse_last_sig_coeff_flag may be a sequence-level or higher-level flag, or may also be an image-level flag, a slice-level flag, a block-level flag, etc. The block-level flag may include an LCU-level flag, a CU-level flag, or another block-level flag.

[178] In addition, reverse_last_sig_coeff_flag may depend on some other flags, such as the high bit depth flag or the high bit rate flag. That is, when the value of the high bit depth flag or the high bit rate flag is 1, it is necessary to decode reverse_last_sig_coeff_flag; otherwise, there is no need to decode reverse_last_sig_coeff_flag.

[179] In a specific example, taking the sequence level as an example, assume that there is a sequence-level flag sps_high_bit_length_flag that indicates whether the current video sequence is a high-bit-depth sequence. If the value of sps_high_bit_length_flag is 1, it means that the current video sequence is a high-bit-depth sequence; otherwise, it indicates that the current video sequence is not a high-bit-depth sequence. At the sequence level, if the value of sps_high_bit_length_flag is 1, then sps_reverse_last_sig_coeff_flag needs to be decoded. In this case, sps_reverse_last_sig_coeff_flag is the flag of the reverse position of the last significant coefficient of the current sequence. If the value of sps_reverse_last_sig_coeff_flag is 1, it indicates that the position of the last significant coefficient is reversed for the blocks in the current sequence; otherwise (i.e., the value of sps_reverse_last_sig_coeff_flag is 0), it indicates that the position of the last significant coefficient is not reversed for the blocks in the current sequence. reverse_last_sig_coeff_flag in the syntax table above will change to sps_reverse_last_sig_coeff_flag.

[180] The syntax elements are as follows (the RBSP syntax of the sequence parameter set), see Table 3.

[181] In another specific example, taking the slice level as an example, assume that there is a sequence-level flag sps_high_bit_length_flag that indicates whether the current video sequence is a high-bit-depth sequence or not. If the value of sps_high_bit_length_flag is 1, it means that the current video sequence is a high-bit-depth sequence; otherwise, it indicates that the current video sequence is not a high-bit-depth sequence. At the slice level, if the value of sps_high_bit_length_flag is 1, then sh_reverse_last_sig_coeff_flag needs to be decoded. In this case, sh_reverse_last_sig_coeff_flag is the flag of the reverse position of the last significant coefficient of the current slice. If sh_reverse_last_sig_coeff_flag is 1, it means that the position of the last significant coefficient is reversed for blocks in the current slice; otherwise (i.e., sh_reverse_last_sig_coeff_flag is 0), it means that the position of the last significant coefficient is not reversed for blocks in the current slice. reverse_last_sig_coeff_flag in the syntax table above is changed to sh_reverse_last_sig_coeff_flag.

[182] The syntax elements are as follows (Slice Header Syntax), see Table 4.

[183] It should also be understood that when a flag associated with a video indicates that the video satisfies a given condition, all coefficients that may need to be encoded are required to be encoded by default. In other words, the position of the last significant coefficient is no longer used, and instead, all possible significant coefficients of the current block are scanned in a given scanning order. Thus, embodiments of the present invention may also introduce a flag conditioned on the last coefficient to determine whether the position of the last coefficient is used for the current block.

[184] In some embodiments, when a flag related to a video indicates that the video satisfies a given condition, the method may further include the following.

[185] The bit stream is analyzed to obtain a flag determined by the last coefficient. When the flag determined by the last coefficient indicates that the position of the last coefficient is used for the current block, all coefficients before the position of the last coefficient are decoded according to a specified scan order to determine the coefficients of the current block.

[186] It should be noted that the flag determined by the last coefficient may be represented as default_last_coeff_enabled_flag. In embodiments of the present invention, the flag determined by the last coefficient may be at least one of a sequence level, a picture level, a slice level, and a block level flag; or even a higher level flag (e.g., VUI, SEI, etc.), which is not limited here.

[187] That is, default_last_coeff_enabled_flag may be a sequence-level or higher-level flag, or may also be a picture-level flag, a slice-level flag, a block-level flag, etc. Additionally, the block-level flag may include an LCU-level flag, or a CU-level flag, or another block-level flag, which is not limited here.

[188] In some embodiments, the method may further include the following.

[189] When the flag determined by the last coefficient has the first value, it is determined that the flag determined by the last coefficient indicates that the position of the last coefficient is used for the current block. When the flag determined by the last coefficient has the second value, it is determined that the flag determined by the last coefficient indicates that the position of the last coefficient is not used for the current block.

[190] In this case, the first value is 1 and the second value is 0.

[191] It should be noted that in another specific example, the first value may also be set to the value "true" and the second value may also be set to the value "false." In yet another specific example, the first value may also be set to the value 0 and the second value may also be set to the value 1. Optionally, the first value may also be set to the value "false" and the second value may also be set to the value "true." The present invention is not limited thereto.

[192] Thus, in the example where the first value is 1 and the second value is 0, if default_last_coeff_enabled_flag has the value 1, then it can be determined that default_last_coeff_enabled_flag indicates that the last coefficient position is used for the current block. Alternatively, if default_last_coeff_enabled_flag has the value 0, then it can be determined that default_last_coeff_enabled_flag indicates that the last coefficient position is not used for the current block.

[193] In the case where the position of the last coefficient is used for the current block, all coefficients before the position of the last coefficient may be decoded according to the specified scan order, thus determining the coefficients of the current block.

[194] Additionally, in the case where the position of the last coefficient is not used for the current block, i.e., the flag determined by the last coefficient has a value of 0, in some embodiments, the method may further include the following.

[195] The bit stream is analyzed to obtain information about the prefix of the horizontal coordinate of the last significant coefficient, information about the prefix of the vertical coordinate of the last significant coefficient, information about the suffix of the horizontal coordinate of the last significant coefficient, and information about the suffix of the vertical coordinate of the last significant coefficient. The position of the last significant coefficient is determined according to the information about the prefix of the horizontal coordinate of the last significant coefficient, the information about the prefix of the vertical coordinate of the last significant coefficient, the information about the suffix of the horizontal coordinate of the last significant coefficient, and the information about the suffix of the vertical coordinate of the last significant coefficient. All coefficients before the position of the last significant coefficient are decoded in accordance with a given scanning order, thereby determining the coefficients of the current block.

[196] It should be noted that if the position of the last coefficient is not used for the current block, then it is necessary to decode the position of the last significant coefficient. Specifically, last_sig_coeff_x_prefix, last_sig_coeff_x_suffix, last_sig_coeff_y_prefix, and last_sig_coeff_y_suffix are obtained by analyzing the bitstream, and then the location of the last significant coefficient is determined based on last_sig_coeff_x_prefix, last_sig_coeff_x_suffix, last_sig_coeff_y_prefix, and last_sig_coeff_y_suffix. Otherwise, if the position of the last coefficient is used for the current block, there is no need to determine the position of the last significant coefficient, and then there is no longer any need to obtain last_sig_coeff_x_prefix, last_sig_coeff_x_suffix, last_sig_coeff_y_prefix, and last_sig_coeff_y_suffix.

[197] It should also be noted that if the position of the last coefficient is not used for the current block, then all coefficients before the position of the last coefficient can be decoded according to the specified scan order. If the position of the last coefficient is not used for the current block, then all coefficients before the position of the last significant coefficient can be decoded in the specified scan order. In this case, the specified scan order can be a diagonal order, a zigzag order, a horizontal order, a vertical order, or a sub-block scan order. 4 or any other scanning order, which is not limited in the embodiments of the present invention.

[198] Also, for the position of the last coefficient, in some embodiments, the position of the last coefficient is the position in the lower right corner of the matrix formed by all possible significant coefficients in the current block. Alternatively, the position of the last coefficient is the last position when scanning all possible significant coefficients in the current block according to a given scanning order.

[199] It should be noted that in embodiments of the invention, the position of the last coefficient does not represent the position of the last significant coefficient. This is because the coefficient at the position of the last significant coefficient may be equal to 0, while the coefficient at the position of the last significant coefficient does not have to be equal to 0.

[200] In a particular example, the method may further include setting the position of the last significant coefficient as the position of the last coefficient.

[201] That is, in embodiments of the present invention, the position of the last significant coefficient may still be used, in which case the position of the last significant coefficient should be set as the last position of all coefficients that may not be zero in the current block in the given scanning order.

[202] Additionally, the position of the last coefficient may be represented by (LastCoeffX, LastCoeffY), i.e., the last position of all possible significant coefficients in the current block in a given scan order. In some embodiments, the method may further include the following.

[203] The width and height of the transformation block obtained in a given operation on the current block are determined. Information on the coordinate of the lower right corner of the transformation block is obtained by calculating the coordinate according to the width and height of the transformation block. The position of the last coefficient is determined according to the information on the coordinate of the lower right corner of the transformation block.

[204] In this case, the specified operation includes at least the zero output operation.

[205] It should be noted that (LastCoeffX, LastCoeffY) is the coordinate information of the lower right corner of the transformation block after zero output, where (LastCoeffX, LastCoeffY) is obtained as follows:

LastCoeffX= (1<<log2ZoTbWidth) -1;

LastCoeffY= (1<<log2ZoTbHeight) -1.

[206] Thus, if default_last_coeff_enabled_flag is set to 1, then the position of the last coefficient can be determined based on (LastCoeffX, LastCoeffY).

[207] In a specific example, the position of the last significant coefficient is still used, and in this case, the position of the last significant coefficient may be set as the last position of all possible zero coefficients in the current block in a given scan order. In some embodiments, the method may further include the following.

[208] When the position of the last significant coefficient is set as the position of the last coefficient, the position of the last significant coefficient is determined according to the coordinate information of the lower right corner of the transformation block.

[209] That is, the position of the last significant coefficient can be represented as (LastSignificantCoeffX, LastSignificantCoeffY), where (LastSignificantCoeffX, LastSignificantCoeffY) is obtained as follows:

LastSignificantCoeffX= (1 << log2ZoTbWidth) -1;

LastSignificantCoeffY= (1 << log2ZoTbHeight) -1.

[210] As stated above, (LastSignificantCoeffX, LastSignificantCoeffY) represents the coordinate information of the lower right corner of the transform block after zero output. If the value of default_last_coeff_enabled_flag is 1, then the position of the last significant coefficient can be determined based on (LastSignificantCoeffX, LastSignificantCoeffY).

[211] Thus, in some cases, encoding is required by default for all coefficients that may need to be encoded. That is, in normal cases, the encoding method for the coefficients remains the same as the method available in the prior art. For example, certain cases may relate to high bit depth, high quality, or high bit rate video, or to lossless compression in video encoding. Encoding is required by default for all coefficients that may need to be encoded, i.e., the position of the last significant coefficient is no longer used, and instead, all possible significant coefficients of the current block are scanned in a given scan order. In other words, the last position of the coefficients that need to be encoded is set as the position of all possible significant coefficients of the current block in a given scan order. This position is typically the position in the lower right corner of the matrix formed by all possible significant coefficients of the current block. In this case, the position of the last coefficient to be encoded is used instead of the position of the last significant coefficient. This is because the coefficient in the position of the last significant coefficient to be encoded may be 0, while the coefficient in the position of the last significant coefficient must not be 0.

[212] In a particular case, the position of the last significant coefficient continues to be used, in which case the position of the last significant coefficient is set to the last position of all possible significant coefficients of the current block in the given scan order.

[213] Furthermore, all possible significant coefficients of the current block in the given scan order are mentioned here, since, besides the last significant coefficient, some coefficients are set to 0 by default using some other methods, such as zero-output, as mentioned above.

[214] The semantic changes are illustrated in Table 5.

[215] In embodiments of the present invention, a condition may be added before decoding the information needed for the last significant coefficient. That is, only when default_last_coeff_enabled_flag is false (i.e., default_last_coeff_enabled_flag is 0), is it necessary to decode syntax elements such as last_sig_coeff_x_prefix, last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, and last_sig_coeff_y_suffix. If default_last_coeff_enabled_flag is true (i.e., default_last_coeff_enabled_flag is 1), then there is no need to decode syntax elements such as last_sig_coeff_x_prefix, last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, and last_sig_coeff_y_suffix.

[216] In this case, default_last_coeff_enabled_flag is a flag associated with the default last coefficient, which is used to indicate whether the default last coefficient position should be used. If default_last_coeff_enabled_flag is 1, it indicates that the default last coefficient position is used, i.e., the position of the last coefficient to be encoded is set to the last position of all possible significant coefficients in the current block in the given scan order. Otherwise, it means that the default last coefficient position is not used.

[217] If the value of default_last_coeff_enabled_flag is 1, then the position of the last coefficient (LastCoeffX, LastCoeffY) is by default set to the last position of all possible significant coefficients in the current block in the given scan order. All coefficients before (LastCoeffX, LastCoeffY) in the given scan order must be scanned. In embodiments of the present invention, (LastCoeffX, LastCoeffY) is obtained as follows:

LastCoeffX= (1<<log2ZoTbWidth) -1;

LastCoeffY= (1<<log2ZoTbHeight) -1.

[218] (LastCoeffX, LastCoeffY) represents the coordinate information of the lower right corner of the transform block after zero output.

[219] A special case is to continue using the position of the last significant coefficient, which is set as the last position of all possible significant coefficients in the current block in a given scan order. In embodiments of the present invention, the position of the last significant coefficient (LastSignificantCoeffX, LastSignificantCoeffY) is obtained as follows:

LastSignificantCoeffX= (1<<log2ZoTbWidth) -1;

LastSignificantCoeffY= (1<<log2ZoTbHeight) -1.

[220] (LastSignificantCoeffX, LastSignificantCoeffY) represents the coordinate information of the lower right corner of the transform block after zero output.

[221] It should also be noted that default_last_coeff_enabled_flag may be a sequence-level or higher-level flag, or may also be an image-level flag, a slice-level flag, a block-level flag, etc. Additionally, a block-level flag may include an LCU-level flag, a CU-level flag, or another block-level flag.

[222] In addition, default_last_coeff_enabled_flag may depend on some other flags, such as the high bit depth flag or the high bit rate flag. That is, when the value of the high bit depth flag or the high bit rate flag is 1, it is necessary to decode default_last_coeff_enabled_flag; otherwise, there is no need to decode default_last_coeff_enabled_flag.

[223] In a specific example, taking the sequence level as an example, assume that there is a sequence-level flag sps_high_bit_length_flag that indicates whether the current video sequence is a high-bit-depth sequence. If the value of sps_high_bit_length_flag is 1, it means that the current video sequence is a high-bit-depth sequence; otherwise, it indicates that the current video sequence is not a high-bit-depth sequence. At the sequence level, if the value of sps_high_bit_depth_flag is 1, then sps_default_last_coeff_enabled_flag needs to be decoded. In this case, sps_default_last_coeff_enabled_flag is a flag determined by the default last coefficient of the current sequence. If sps_default_last_coeff_enabled_flag is 1, it indicates that the default last coefficient is used for blocks in the current sequence; otherwise (i.e., sps_default_last_coeff_enabled_flag is 0), it indicates that the default last coefficient is not used for blocks in the current sequence. default_last_coeff_enabled_flag in the syntax table above changes to sps_default_last_coeff_enabled_flag.

[224] The syntax elements are as follows (the RBSP syntax of the sequence parameter set), see Table 6.

[225] In another specific example, taking the slice level as an example, assume that there is a sequence-level flag sps_high_bit_length_flag that indicates whether the current video sequence is a high-bit-depth sequence or not. If the value of sps_high_bit_length_flag is 1, it means that the current video sequence is a high-bit-depth sequence; otherwise, it indicates that the current video sequence is not a high-bit-depth sequence. At the slice level, if the value of sps_high_bit_depth_flag is 1, then sh_default_last_coeff_enabled_flag needs to be decoded. In this case, sh_default_last_coeff_enabled_flag is a flag determined by the last coefficient, by default the last coefficient of the current slice. If sh_default_last_coeff_enabled_flag is 1, it means the default last coefficient is used for blocks in the current slice; otherwise (i.e., sh_default_last_coeff_enabled_flag is 0), it means the default last coefficient is not used for blocks in the current slice. default_last_coeff_enabled_flag in the syntax table above changes to sh_default_last_coeff_enabled_flag.

[226] The syntax elements are as follows (Slice Header Syntax), see Table 7.

[227] It is also understood that when a flag related to a video indicates that the video satisfies a given condition, encoding may be required by default for all scanned sub-blocks. In this case, there is no need to transmit sb_coded_flag in the bitstream, i.e., neither the encoder nor the decoder need to process this flag, which can speed up encoding. Therefore, in embodiments of the present invention, a default-coded sub-block flag is introduced to determine whether the sub-block to be decoded in the current block uses default encoding.

[228] In some embodiments, when a flag related to a video indicates that the video satisfies a given condition, the method may further include the following.

[229] The bitstream is analyzed to obtain a flag of the default coded sub-block. When the flag of the default coded sub-block indicates that the sub-block to be coded is used for encoding by default, it is determined that the flag of the coded sub-block has the first value, and all coefficients in the sub-block to be decoded in the current block are decoded.

[230] It should be noted that the default sub-block flag may be represented as default_sb_coded_flag. In embodiments of the present invention, the default sub-block coded flag is at least one of a sequence level, a picture level, a slice level, and a block level flag, or may even be a higher level flag (e.g., VUI, SEI, etc.), which is not limited in the present description.

[231] That is, default_sb_coded_flag may be a sequence-level or higher-level flag, or may also be a picture-level flag, a slice-level flag, a block-level flag, etc. Additionally, the block-level flag may include an LCU-level flag, or a CU-level flag, or another block-level flag, which is not limited here.

[232] In some embodiments, the method may further include the following.

[233] If the default coded sub-unit flag has the first value, it is determined that the default coded sub-unit flag indicates that the sub-unit to be coded is used for encoding by default. If the default coded sub-unit flag has the second value, it is determined that the default coded sub-unit flag indicates that the sub-unit to be coded is not used for encoding by default.

[234] In this case, the first value is 1 and the second value is 0.

[235] It should be noted that in another specific example, the first value may also be set to the value "true" and the second value may also be set to the value "false." In yet another specific example, the first value may also be set to the value 0 and the second value may also be set to the value 1. Optionally, the first value may also be set to the value "false" and the second value may also be set to the value "true." The present invention is not limited thereto.

[236] Thus, in the example where the first value is 1 and the second value is 0, if default_sb_coded_flag has the value 1, then it can be defined that default_sb_coded_flag indicates that the sub-block to be decoded requires encoding by default. Alternatively, if default_sb_coded_flag has the value 0, then it can be defined that default_sb_coded_flag indicates that the sub-block to be decoded does not require encoding by default.

[237] In the case where the sub-block to be decoded requires encoding by default, the value of default_sb_coded_flag is 1, which means that there is no need to decode sb_coded_flag. In this case, the default is to require decoding of all coefficients within the sub-block to be decoded.

[238] Additionally, in the case where the sub-block to be decoded does not require encoding by default, i.e. where the value of default_sb_coded_flag is 0, in some embodiments, the method may further include the following.

[239] The bitstream is analyzed to obtain the coded sub-block flag. All coefficients in the sub-block to be decoded are decoded when the coded sub-block flag has the first value.

[240] It should be noted that if the sub-block to be decoded does not require encoding by default, then it is necessary to decode the encoded sub-block flag, which determines whether to decode all coefficients within the sub-block to be decoded.

[241] Also, for the encoded sub-block flag, the method may further include the following.

[242] If the coded sub-block flag has the first value, it is determined that all coefficients within the sub-block are to be coded. Alternatively, if the coded sub-block flag has the second value, it is determined that all coefficients within the sub-block to be decoded are equal to zero.

[243] In embodiments of the present invention, the coded sub-block flag may be represented as sb_coded_flag. Taking the first value of 1 and the second value of 0 as an example, if the value of sb_coded_flag is 1, then it can be determined that all coefficients within the sub-block to be decoded need to be decoded. Alternatively, if the value of sb_coded_flag is 0, then it can be determined that it is not necessary to decode all coefficients within the sub-block to be decoded, and in this case, all coefficients within the sub-block to be decoded are zero.

[244] Thus, in certain cases, during coefficient coding, all scanned sub-blocks by default require coding, or all scanned sub-blocks by default contain significant coefficients. That is, in normal cases, the coefficient coding method remains the same as the method available in the prior art. For example, certain cases may relate to high-bit-depth, high-quality, or high-bit-rate videos, or to lossless compression in video coding. In this case, there are many significant coefficients, and almost all scanned sub-blocks require coding, or, in other words, almost all scanned sub-blocks contain significant coefficients. As such, there is no need to transmit sb_coded_flag in the bitstream, and the encoder/decoder does not need to process this flag, which provides a higher coding rate. In this case, there is also a small gain in compression efficiency due to the removal of the practically non-existent flag.

[245] The semantic changes are shown in Table 8.

[246] default_sb_coded_flag is a flag indicating whether the subblock is used for encoding by default. If default_sb_coded_flag is 1, then sb_coded_flag[xS][yS] can be determined to be 1, in which case there is no need to decode sb_coded_flag[xS][yS] from the bitstream. Otherwise (default_sb_coded_flag is 0), sb_coded_flag[xS][yS] still needs to be decoded from the bitstream.

[247] It should also be noted that default_sb_coded_flag may be a sequence-level or higher-level flag, or may also be a picture-level flag, a slice-level flag, a block-level flag, etc. Additionally, a block-level flag may include an LCU-level flag, a CU-level flag, or another block-level flag.

[248] In addition, default_sb_coded_flag may depend on some other flags, such as the high bit depth flag or the high bit rate flag. That is, when the value of the high bit depth flag or the high bit rate flag is 1, default_sb_coded_flag needs to be decoded; otherwise, there is no need to decode default_sb_coded_flag.

[249] In one specific example, taking the sequence level as an example, assume that there is a sequence-level flag sps_high_bit_length_flag that indicates whether the current video sequence is a high-bit-depth sequence. If the value of sps_high_bit_length_flag is 1, it means that the current video sequence is a high-bit-depth sequence; otherwise, it indicates that the current video sequence is not a high-bit-depth sequence. At the sequence level, if the value of sps_high_bit_length_flag is 1, then sps_default_sb_coded_flag needs to be decoded. In this case, sps_default_sb_coded_flag is a flag that indicates whether default encoding is required for the sub-blocks of the current sequence. If the value of sps_default_sb_coded_flag is 1, it means that subblocks of blocks in the current sequence require encoding by default; otherwise (i.e., the value of sps_default_sb_coded_flag is 0), it means that subblocks of blocks in the current sequence do not require encoding by default. default_sb_coded_flag in the syntax table above will change to sps_default_sb_coded_flag.

[250] The syntax elements are as follows (the RBSP syntax of the sequence parameter set), see Table 9.

[251] In another specific example, taking the slice level as an example, assume that there is a sequence-level flag sps_high_bit_length_flag that indicates whether the current video sequence is a high-bit-depth sequence or not. If the value of sps_high_bit_length_flag is 1, it means that the current video sequence is a high-bit-depth sequence; otherwise, it indicates that the current video sequence is not a high-bit-depth sequence. At the slice level, if the value of sps_high_bit_depth_flag is 1, then sh_default_sb_coded_flag needs to be decoded. In this case, sh_default_sb_coded_flag is a flag that indicates whether default encoding is required for sub-blocks for the current slice. If the value of sh_default_sb_coded_flag is 1, it means that sub-blocks of blocks in the current slice require encoding by default; otherwise (i.e., the value of sh_default_sb_coded_flag is 0), it means that sub-blocks of blocks within the current slice do not require encoding by default. default_sb_coded_flag in the syntax table above changes to sh_default_sb_coded_flag.

[252] The syntax elements are as follows (Slice Header Syntax), see Table 10.

[253] It is understood that embodiments of the present invention relate to three optimization methods, namely the following.

[254] Method 1: For some cases, when encoding a coefficient, encoding is required by default for all coefficients. That is, in normal cases, the encoding method for the coefficients remains the same as the method available in the prior art. For example, certain cases may relate to high bit depth, high quality, or high bit rate video, or to lossless compression in video encoding. Encoding is required by default for all coefficients that may need to be encoded, i.e., the position of the last significant coefficient is no longer used, and instead, all possible significant coefficients of the current block are scanned in a given scan order. In other words, the last position of the coefficients to be encoded is set as the position of all possible significant coefficients of the current block in a given scan order. In this case, the position of the last coefficient to be encoded is used instead of the position of the last significant coefficient. This is because the coefficient at the position of the last significant coefficient to be encoded may be equal to 0, while the coefficient at the position of the last significant coefficient does not have to be equal to 0.

[255] Also, in a special case, the position of the last significant coefficient is still used, and in this case the position of the last significant coefficient is set to the last position of all possible significant coefficients of the current block in the given scan order.

[256] Method 2: In certain cases, when encoding the coefficients, the method for determining the position of the last significant coefficient is changed. That is, in normal cases, the method for encoding the coefficients remains the same as the method available in the prior art. For example, certain cases may relate to high bit depth, high quality, or high bit rate video, or to lossless compression in video encoding. Typically, the horizontal coordinate of the position of the last significant coefficient, that is, the horizontal distance relative to the upper left corner of the current block, is encoded in last_sig_coeff_x_prefix and Last_sig_coeff_x_suffix, and the vertical coordinate of the position of the last significant coefficient, that is, the vertical distance relative to the upper left corner of the current block, is encoded in last_sig_coeff_y_prefix and last_sig_coeff_y_suffix. For comparison, in the case of high bit depth, high quality, high bit rate, or lossless compression in video coding, the position of the last significant coefficient is usually close to the lower right corner of the region of all possible significant coefficients of the current block. In this case, the horizontal distance of the position of the last significant coefficient relative to the lower right corner of the region of all possible significant coefficients of the current block is encoded as last_sig_coeff_x_prefix and last_sig_coeff_x_suffix, and the vertical distance of the position of the last significant coefficient relative to the lower right corner of the region of all possible significant coefficients of the current block is encoded as last_sig_coeff_y_prefix and last_sig_coeff_y_suffix. For example, if the region of all possible significant coefficients of the current block is a rectangular region from (0, 0) to ((1<<log2ZoTbWidth) - 1, (1<<log2ZoTbHeight) - 1), then last_sig_coeff_x_prefix and last_sig_coeff_x_suffix are encoded to represent the horizontal distance of the position of the last significant coefficient relative to the current block ((1<<log2ZoTbWidth) - 1, (1<<log2ZoTbHeight) - 1). last_sig_coeff_y_prefix and last_sig_coeff_y_suffix are encoded to represent the vertical distance of the position of the last significant coefficient relative to the current block ((1<<log2ZoTbWidth) - 1, (1<<log2ZoTbHeight) - 1).

[257] Method 3: In certain cases, during coefficient encoding, all scanned sub-blocks by default require encoding, or in other words, all scanned sub-blocks by default contain significant coefficients. That is, in normal cases, the coefficient encoding method remains the same as the method available in the prior art. For example, certain cases may relate to high-bit-depth, high-quality, or high-bit-rate video, or to lossless compression in video encoding. In this case, there are many significant coefficients, and almost all scanned sub-blocks require encoding, or in other words, almost all scanned sub-blocks contain significant coefficients. As such, there is no need to transmit sb_coded_flag in the bitstream, and the encoder/decoder does not need to process this flag.

[258] For the above three methods, in high-bit-depth, high-bit-rate, high-quality, or lossless video coding scenarios, since the coefficient distribution pattern is different from that in normal video scenarios, during coefficient coding, by reducing or even eliminating the number of syntax elements encoded in the context mode, such as syntax elements about the position of the last significant coefficient, coded sub-block flags, etc., the overall coding speed and speed can be improved for coefficient coding. Furthermore, since these flags are used less in high-bit-depth, high-bit-rate, high-quality, or lossless video coding, removing these flags will not reduce the compression efficiency, but will instead improve the compression efficiency to some extent.

[259] Furthermore, in embodiments of the present invention, taking the sequence level as an example, the sequence level flag sps_high_bit_depth_flag, which indicates whether the current video sequence is a high bit depth sequence, may also be replaced by the flag sps_high_bit_rate_flag, which indicates whether the current video sequence is a high bit rate sequence, or may also be replaced by another flag indicating high bit width, high bit rate, high quality, or lossless coding, etc.

[260] It should also be noted that the coefficient decoding methods of the embodiments of the present invention are described based on an example in which the technical solution is used for all components in a video, where all components refer to, for example, R, G and B in RGB video or Y, U and V (Y, Cb and Cr) in YUV video, etc. Optionally, the coefficient decoding method of the embodiments of the present invention may be used only for a specific component, for example, only for the Y component of the YUV format. Optionally, the coefficient decoding method of the embodiments of the present invention may be used for each component separately, i.e., the possibility of use for each component may be controlled separately.

[261] The present embodiments provide a coefficient decoding method applied to a decoder. A bitstream is analyzed to obtain a flag related to a video. When the video-related flag indicates that the video satisfies a predetermined condition, the bitstream is analyzed to obtain a last significant coefficient position inversion flag and information on the coordinate of the last significant coefficient. When the last significant coefficient position inversion flag indicates that the position of the last significant coefficient is reversed for the current block, the position of the last significant coefficient is determined by calculation using the information on the coordinate of the last significant coefficient. According to a predetermined scanning order, all coefficients before the position of the last significant coefficient are decoded to determine the coefficients of the current block. Therefore, in high-bit-depth, high-bit-rate, high-quality, or lossless video coding scenarios, since the coefficient distribution pattern differs from that in conventional video scenarios, during coefficient coding, by reducing or even eliminating the number of syntax elements encoded in the context mode, such as syntax elements about the position of the last significant coefficient, coded sub-block flags, etc., or by additionally performing coordinate transformation when the coordinate values of the last significant coefficient are too large, the resource consumption caused by coding in the bitstream can be reduced, thereby improving the throughput and speed of coefficient coding. Furthermore, compression efficiency can also be improved, since the reduced or eliminated syntax elements have less impact on video coding in high-bit-depth, high-bit-rate, high-quality, or lossless compression scenarios.

[262] In another embodiment of the present invention, Fig. 11 illustrates a schematic flow chart of a coefficient encoding method provided in embodiments of the present invention. As shown in Fig. 11, the method may include the following.

[263] In step S1101, a flag related to the video and the position of the last significant coefficient are determined.

[264] In step S1102, when the flag related to the video indicates that the video satisfies a predetermined condition, a flag of the reverse position of the last significant coefficient is determined.

[265] In step S1103, the coordinate information of the last significant coefficient is determined according to the position of the last significant coefficient and the reverse position flag of the last significant coefficient.

[266] In step S1104, all coefficients before the position of the last significant coefficient are encoded according to a predetermined scanning order, and bit information obtained by encoding, a flag related to the video, and information about the coordinate of the last significant coefficient are transmitted to a bit stream.

[267] It should be noted that the coefficient encoding method in the embodiments of the present invention is applied to an encoder. In particular, based on the composition structure of the encoder 100 illustrated in Fig. 8A, the coefficient encoding method in the embodiments of the present invention is mainly applied to the “entropy encoding unit 115” of the encoder 100. The entropy encoding unit 115 may use an adaptive binary arithmetic encoding mode based on a context model or a bypass mode to perform entropy encoding of associated flags (or syntax elements) and then transmit a signal into a bitstream.

[268] It should also be noted that coefficient coding, as commonly referred to in video standards, may include both encoding and decoding. Thus, coefficient coding includes a method for encoding coefficients on the encoder side and a method for decoding coefficients on the decoder side. An embodiment of the present invention is described with respect to a method for encoding coefficients on the encoder side.

[269] Typically, for example, for a normal video, the method for encoding coefficients is the same as the methods available in the prior art. However, for a specific case, such as a scenario of encoding video with a high bit depth, high quality, high bit rate, or lossless compression, embodiments of the present invention may modify the method for obtaining the position of the last significant coefficient. In this case, in the embodiments of the present disclosure, a video-related flag and a last significant coefficient reverse position flag should be introduced to determine the position of the last significant coefficient, and then all coefficients before the position of the last significant coefficient within the current block are encoded according to a given scanning order.

[270] In embodiments of the present invention, it is first necessary to determine whether the current video satisfies a given condition, which may be represented by a flag related to the video. In some embodiments, the flag related to the video may be determined as follows.

[271] When a video satisfies a given condition, a flag related to the video is defined as the first value. Alternatively, when a video does not satisfy a given condition, a flag related to the video is defined as the second value.

[272] In this case, the first value is 1 and the second value is 0.

[273] It should be noted that in another specific example, the first value may also be set to the value "true" and the second value may also be set to the value "false." In yet another specific example, the first value may also be set to the value 0 and the second value may also be set to the value 1. Optionally, the first value may also be set to the value "false" and the second value may also be set to the value "true." The present invention is not limited thereto.

[274] It should also be noted that the specified condition includes at least one of: high bit depth, high quality, high bit rate, high frame rate, or lossless compression.

[275] In addition, the video-related flag may be a sequence-level flag or even a higher-level flag such as VUI, SEI, etc. Whether a video satisfies a given condition can be determined by determining whether the video satisfies high bit depth, or whether the video satisfies high bit rate, or whether the video satisfies high quality, or whether the video satisfies lossless compression, etc. Each of these four cases is described below as examples.

[276] In some embodiments, when the video-related flag is a high bit depth flag, the method may further include the following.

[277] If the video satisfies the high bit depth, it is determined that the high bit depth flag indicates that the video satisfies the specified condition.

[278] In some embodiments, when the video-related flag is a high bit rate flag, the method may further include the following.

[279] If the video satisfies the high bit rate, it is determined that the high bit rate flag indicates that the video satisfies the specified condition.

[280] In some embodiments, when the flag related to the video is a high quality flag, the method may further include the following.

[281] If the video satisfies the high quality, it is determined that the high quality flag indicates that the video satisfies the given condition.

[282] In some embodiments, when the video-related flag is a lossless compression flag, the method may further include the following.

[283] If the video satisfies lossless compression, the lossless compression flag is determined to indicate that the video satisfies the specified condition.

[284] As an example, taking the sequence level as an example, the video-related flag may be a high bit depth flag (represented by sps_high_bit_depth_flag) to indicate whether the current video sequence is a high bit depth sequence. The video-related flag may also be a high bit rate flag (represented by sps_high_bit_rate_flag) to indicate whether the current video sequence is a high bit rate sequence. The video-related flag may also be another flag indicating high bit depth, high bit rate, high quality, or lossless compression, which is not particularly limited in the embodiments of the present invention.

[285] Furthermore, with regard to the last significant coefficient reverse position flag, the last significant coefficient reverse position flag can be defined as follows.

[286] If the position of the last significant coefficient is reversed for the current block, the last significant coefficient position reverse flag is defined as the first value. If the position of the last significant coefficient is not reversed for the current block, the last significant coefficient position reverse flag is defined as the second value.

[287] In embodiments of the present invention, the reverse last significant coefficient position flag may be represented as reverse_last_sig_coeff_flag. In this case, the reverse last significant coefficient position flag may be at least a sequence-level flag, a picture-level flag, a slice-level flag, or a block-level flag; or even a higher-level flag (e.g., VUI, SEI, etc.), which will not be limited here.

[288] That is, reverse_last_sig_coeff_flag may be a sequence level or higher level flag, or may also be a picture level flag, a slice level flag, a block level flag, etc. Additionally, the block level flag may include an LCU level flag, a CU level flag, or another block level flag, which is not limited in the embodiments of the present invention.

[289] Thus, in the example where the first value is 1 and the second value is 0, if the position of the last significant coefficient is determined to be reversed for the current block, then reverse_last_sig_coeff_flag has the value 1. Alternatively, if the position of the last significant coefficient is determined to be not reversed for the current block, then reverse_last_sig_coeff_flag has the value 0.

[290] Additionally, the position of the last significant coefficient may include a starting horizontal coordinate and a starting vertical coordinate of the last significant coefficient. In the case where the starting horizontal coordinate is the horizontal distance from the position of the last significant coefficient to the upper left corner of the current block, and the starting vertical coordinate is the vertical distance from the position of the last significant coefficient to the upper left corner of the current block, the coordinate information of the last significant coefficient may be determined in accordance with the position of the last significant coefficient and the reverse position flag of the last significant coefficient as follows.

[291] If the last significant coefficient reverse position flag has the first value, the coordinate information of the last significant coefficient is determined by calculating according to the initial horizontal coordinate and the initial vertical coordinate of the last significant coefficient. Alternatively, if the last significant coefficient reverse position flag has the second value, the coordinate information of the last significant coefficient is determined directly according to the initial horizontal coordinate and the initial vertical coordinate of the last significant coefficient.

[292] In other words, in some embodiments, the method may further include the following.

[293] If the last significant coefficient inverse position flag has the first value, the coordinate information of the last significant coefficient is determined as the horizontal distance and the vertical distance from the position of the last significant coefficient to the lower right corner of the current block. Alternatively, if the last significant coefficient inverse position flag has the second value, the coordinate information of the last significant coefficient is determined as the horizontal distance and the vertical distance from the position of the last significant coefficient to the upper left corner of the current block.

[294] In other words, the coordinate information of the last significant coefficient is usually the horizontal distance and the vertical distance between the position of the last significant coefficient and the upper left corner of the current block. For normal video, most of the significant coefficients are concentrated in the upper left corner, and a large area in the lower right corner has coefficients equal to 0. However, for coding video with high bit depth, high quality, or high bit rate, a large number of significant coefficients also appear in the lower right corner, so the coordinate information of the last significant coefficient usually has large values. In this case, in order to save resources, coordinate transformation (which can be a coordinate reversal calculation, that is, after coordinate reversal, the coordinate information of the last significant coefficient is the horizontal distance and the vertical distance between the position of the last significant coefficient and the lower right corner of the current block) is necessary during coefficient encoding. In this case, coordinate reversal calculation is also necessary during coefficient decoding in the decoder. After reversing, the coordinate information of the last significant coefficient can be reconstructed as the horizontal and vertical distances between the position of the last significant coefficient and the upper left corner of the current block. This allows the position of the last significant coefficient to be determined.

[295] Additionally, in some embodiments, the coordinate information of the last significant coefficient may be determined according to the initial horizontal coordinate and the initial vertical coordinate of the last significant coefficient as follows.

[296] The width and height of the current block are determined. The horizontal coordinate of the last significant coefficient is obtained by subtracting the initial horizontal coordinate of the last significant coefficient from the width of the current block. The vertical coordinate of the last significant coefficient is obtained by subtracting the initial vertical coordinate of the last significant coefficient from the height of the current block. Information about the coordinate of the last significant coefficient is determined according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient.

[297] It should also be noted that the current block here can be a block without zero-output transformation or a block after zero-output transformation. Taking the block after zero-output transformation as an example, the width of the current block is 1<<log2ZoTbWidth, and the height of the current block is 1<<log2ZoTbHeight. Then, in the case where reverse_last_sig_coeff_flag indicates that the position of the last significant coefficient is reversed (i.e., the value of reverse_last_sig_coeff_flag is 1):

LastSignificantCoeffX= (1<<log2ZoTbWidth) -1-LastSignificantCoeffX;

LastSignificantCoeffY= (1<<log2ZoTbHeight) -1-LastSignificantCoeffY.

[298] In the above example, (LastSignificantCoeffX, LastSignificantCoeffY) on the right-hand side of the equation represents the coordinate information of the last significant coefficient obtained directly (i.e., the starting horizontal coordinate and the starting vertical coordinate of the last significant coefficient), and (LastSignificantCoeffX, LastSignificantCoeffY) on the left-hand side of the equation represents the coordinate information of the last significant coefficient after being reversed (i.e., the coordinate information of the last significant coefficient that is transmitted to the bitstream in case the position of the last significant coefficient is reversed for the current block).

[299] In some embodiments, information about the coordinate of the last significant coefficient may be transmitted in the bitstream as follows.

[300] Information about the prefix of the horizontal coordinate of the last significant coefficient, information about the prefix of the vertical coordinate of the last significant coefficient, information about the suffix of the horizontal coordinate of the last significant coefficient, and information about the suffix of the vertical coordinate of the last significant coefficient are determined according to the information about the coordinate of the last significant coefficient. Information about the prefix of the horizontal coordinate of the last significant coefficient, information about the prefix of the vertical coordinate of the last significant coefficient, information about the suffix of the horizontal coordinate of the last significant coefficient, and information about the suffix of the vertical coordinate of the last significant coefficient are transmitted in the bitstream.

[301] It should be noted that the information about the prefix of the horizontal coordinate of the last significant coefficient is represented as last_sig_coeff_x_prefix. The information about the prefix of the vertical coordinate of the last significant coefficient is represented as last_sig_coeff_y_prefix. The information about the suffix of the horizontal coordinate of the last significant coefficient is represented as last_sig_coeff_x_suffix. The information about the suffix of the vertical coordinate of the last significant coefficient is represented as last_sig_coeff_y_suffix. Then last_sig_coeff_x_prefix, last_sig_coeff_x_suffix, last_sig_coeff_y_prefix, and last_sig_coeff_y_suffix are transmitted in the bitstream, so that the decoder can determine the coordinate information of the last significant coefficient by analyzing the bitstream.

[302] Thus, embodiments of the present invention provide a modified method for determining the position of the last significant coefficient. That is, in general cases, the method for encoding the coefficients remains the same as the method available in the prior art. For example, certain cases may relate to high bit depth, high quality, or high bit rate video, or to lossless compression in video encoding. Generally, as shown in Fig. 10A, the horizontal coordinate of the position of the last significant coefficient, that is, the horizontal distance relative to the upper left corner of the current block, is encoded in last_sig_coeff_x_prefix and last_sig_coeff_x_suffix, and the vertical coordinate of the position of the last significant coefficient, that is, the vertical distance relative to the upper left corner of the current block, is encoded in last_sig_coeff_y_prefix and last_sig_coeff_y_suffix. For comparison, in the case of high bit depth, high quality, high bit rate, or lossless compression in video coding, the position of the last significant coefficient is usually close to the lower right corner of the region of all possible significant coefficients of the current block. In this case, as illustrated in Fig. 10B, the horizontal distance of the position of the last significant coefficient relative to the lower right corner of the region of all possible significant coefficients of the current block is encoded in last_sig_coeff_x_prefix and last_sig_coeff_x_suffix, and the vertical distance of the position of the last significant coefficient relative to the lower right corner of the region of all possible significant coefficients of the current block is encoded in last_sig_coeff_y_prefix, last_sig_coeff_y_suffix. Therefore, in the embodiments of the present invention, reverse_last_sig_coeff_flag is introduced so that the problem of large resource consumption caused by encoding large values in the bitstream can be solved.

[303] Also, when a flag associated with a video indicates that the video satisfies a given condition, all coefficients that may need to be encoded may require default encoding. In other words, the position of the last significant coefficient is no longer used, and instead, all possible significant coefficients of the current block are scanned in a given scanning order. Thus, embodiments of the present invention may also introduce a flag conditioned on the last coefficient to determine whether the position of the last coefficient is used for the current block.

[304] In some embodiments, when a flag related to a video indicates that the video satisfies a given condition, the method may further include the following.

[305] A flag determined by the last coefficient is used. When the flag determined by the last coefficient indicates that the position of the last coefficient is used for the current block, all coefficients before the position of the last coefficient are encoded according to a specified scanning order, and the bit information obtained by encoding, the flag related to the video, and the flag determined by the last coefficient are provided in the bitstream.

[306] It should be noted that the flag determined by the last coefficient may be represented as default_last_coeff_enabled_flag. In embodiments of the present invention, the flag determined by the last coefficient may be at least one of a sequence level, a picture level, a slice level, and a block level flag; or even a higher level flag (e.g., VUI, SEI, etc.), which is not limited here.

[307] It should be noted that, with respect to the flag determined by the last coefficient, in some embodiments, the flag determined by the last coefficient may be determined as follows.

[308] When the position of the last coefficient is used for the current block, the flag determined by the last coefficient is defined as the first value. Alternatively, when the position of the last coefficient is not used for the current block, the flag determined by the last coefficient is defined as the second value.

[309] Thus, in the example where the first value is 1 and the second value is 0, if it is determined that the last coefficient position is used for the current block, then default_last_coeff_enabled_flag has a value of 1. Alternatively, if it is determined that the last coefficient position is not used for the current block, then default_last_coeff_enabled_flag has a value of 0.

[310] Also, for the position of the last coefficient, in some embodiments, the position of the last coefficient is the position in the lower right corner of the matrix formed by all possible significant coefficients in the current block. Alternatively, the position of the last coefficient is the last position when scanning all possible significant coefficients in the current block according to a given scanning order.

[311] It should be noted that in embodiments of the invention, the position of the last coefficient does not represent the position of the last significant coefficient. This is because the coefficient at the position of the last significant coefficient may be equal to 0, whereas the coefficient at the position of the last significant coefficient does not have to be equal to 0.

[312] In a particular example, the method may further include setting the position of the last significant coefficient as the position of the last coefficient.

[313] That is, in embodiments of the present invention, the position of the last significant coefficient may still be used, in which case the position of the last significant coefficient should be set as the last position of all coefficients that may not be zero in the current block in the given scan order.

[314] Additionally, the position of the last coefficient may be represented by (LastCoeffX, LastCoeffY), i.e., the last position of all possible significant coefficients in the current block in a given scan order. In some embodiments, the method may further include the following.

[315] The width and height of the transformation block obtained in a given operation on the current block are determined. Information on the coordinate of the lower right corner of the transformation block is obtained by calculating the coordinate according to the width and height of the transformation block. The position of the last coefficient is determined according to the information on the coordinate of the lower right corner of the transformation block.

[316] In this case, the specified operation includes at least the zero output operation.

[317] It should be noted that (LastCoeffX, LastCoeffY) is the coordinate information of the lower right corner of the transformation block after zero output, where (LastCoeffX, LastCoeffY) is obtained as follows:

LastCoeffX= (1<<log2ZoTbWidth) -1;

LastCoeffY= (1<<log2ZoTbHeight) -1.

[318] Thus, if default_last_coeff_enabled_flag is set to 1, then the position of the last coefficient can be determined based on (LastCoeffX, LastCoeffY).

[319] In a specific example, the position of the last significant coefficient is still used, and in this case, the position of the last significant coefficient may be set as the last position of all possible zero coefficients in the current block in a given scan order. In some embodiments, the method may further include the following.

[320] When the position of the last significant coefficient is set as the position of the last coefficient, the position of the last significant coefficient is determined according to the coordinate information of the lower right corner of the transformation block.

[321] That is, the position of the last significant coefficient can be represented as (LastSignificantCoeffX, LastSignificantCoeffY), where (LastSignificantCoeffX, LastSignificantCoeffY) is obtained as follows:

LastSignificantCoeffX= (1 << log2ZoTbWidth) -1;

LastSignificantCoeffY= (1 << log2ZoTbHeight) -1.

[322] As stated above, (LastSignificantCoeffX, LastSignificantCoeffY) represents the coordinate information of the lower right corner of the transform block after zero output. If the value of default_last_coeff_enabled_flag is 1, then the position of the last significant coefficient can be determined based on (LastSignificantCoeffX, LastSignificantCoeffY).

[323] Additionally, in the case where the position of the last coefficient is not used for the current block, the method may further include the following.

[324] Information about the prefix of the horizontal coordinate of the last significant coefficient, information about the prefix of the vertical coordinate of the last significant coefficient and information about the suffix of the vertical coordinate of the last significant coefficient are determined. The position of the last significant coefficient is determined according to the information about the prefix of the horizontal coordinate of the last significant coefficient, the information about the prefix of the vertical coordinate of the last significant coefficient, the information about the suffix of the horizontal coordinate of the last significant coefficient and the information about the suffix of the vertical coordinate of the last significant coefficient. All coefficients before the position of the last significant coefficient are encoded according to a given scanning order and signal information about the prefix of the horizontal coordinate of the last significant coefficient, the prefix of the vertical coordinate of the last significant coefficient, the information about the suffix of the horizontal coordinate of the last significant coefficient and the suffix of the vertical coordinate of the last significant coefficient are transmitted into a bit stream.

[325] It should be noted that if the position of the last coefficient is not used for the current block, the position of the last significant coefficient must be determined. In particular, last_sig_coeff_x_prefix, last_sig_coeff_x_suffix, last_sig_coeff_y_prefix, and last_sig_coeff_y_suffix do not need to be determined. Then last_sig_coeff_x_prefix, last_sig_coeff_x_suffix, last_sig_coeff_y_prefix, and last_sig_coeff_y_suffix are transmitted in the bitstream.

[326] Thus, when encoding a coefficient, encoding is required by default for all coefficients that may need to be encoded. That is, in normal cases, the method for encoding the coefficients remains the same as the method available in the prior art. For example, certain cases may relate to high-bit-depth, high-quality, or high-bit-rate video, or to lossless compression in video encoding. Encoding is required by default for all coefficients that may need to be encoded, i.e., the position of the last significant coefficient is no longer used, and instead, all possible significant coefficients of the current block are scanned in a given scan order. In other words, the last position of the coefficients that need to be encoded is set as the position of all possible significant coefficients of the current block in a given scan order. This position is typically the position in the lower right corner of the matrix formed by all possible significant coefficients of the current block. Therefore, in embodiments of the present disclosure, a default_last_coeff_enabled_flag may be introduced so that syntax elements related to the position of the last significant coefficient may be reduced or even eliminated, which may reduce resource consumption and avoid wasteful use of resources.

[327] Also, when a flag related to a video indicates that the video satisfies a given condition, encoding may be required by default for all scanned sub-blocks. In this case, there is no need to transmit sb_coded_flag in the bitstream, i.e., neither the encoder nor the decoder need to process this flag, which can speed up encoding. Therefore, in embodiments of the present invention, a default-coded sub-block flag is introduced to determine whether the sub-block to be decoded in the current block uses default encoding.

[328] In some embodiments, when a flag related to a video indicates that the video satisfies a given condition, the method may further include the following.

[329] A default sub-block flag is determined for a sub-block to be encoded in the current block. When the default sub-block flag indicates that the sub-block to be encoded is used for encoding by default, all coefficients in the sub-block to be encoded are encoded and the bit information obtained by encoding and the default sub-block flag are provided in the bitstream.

[330] It should be noted that the default sub-block flag may be represented as default_sb_coded_flag. In embodiments of the present invention, the default sub-block coded flag is at least one of a sequence level, a picture level, a slice level, and a block level flag, or may even be a higher level flag (e.g., VUI, SEI, etc.), which is not limited in the present description.

[331] It is also noted that for a default sub-block flag, in some embodiments, a default coded sub-block flag for a sub-block to be coded may be determined as follows.

[332] If the sub-unit to be encoded uses encoding by default, the default sub-unit flag is defined as the first value. Alternatively, if the sub-unit to be encoded does not use encoding by default, the default sub-unit flag is defined as the second value.

[333] Thus, in the example where the first value is 1 and the second value is 0, if it is determined that the sub-block to be encoded by default requires encoding, then default_sb_coded_flag has the value 1. Alternatively, if it is determined that the sub-block to be encoded by default does not require encoding, then default_sb_coded_flag has the value 0.

[334] In the case where the sub-block to be coded requires encoding by default, the value of default_sb_coded_flag is 1, which means that the value of sb_coded_flag is 1, i.e., there is no need to encode sb_coded_flag. However, in the case where the sub-block to be coded does not require encoding by default, i.e., the default coded sub-block flag indicates that the sub-block to be coded does not require encoding by default, in some embodiments, the method may further include determining a coded sub-block flag for the sub-block to be coded, and transmitting the coded sub-block flag to the bitstream.

[335] Also, in some embodiments, a default coded sub-block flag for a sub-block to be coded may be determined as follows.

[336] If encoding is required for the sub-block to be encoded, the default-coded sub-block flag is defined as the first value. Alternatively, if all coefficients in the sub-block are 0, the default-coded sub-block flag is defined as the second value.

[337] In embodiments of the present invention, the coded sub-block flag may be represented as sb_coded_flag. Taking the first value of 1 and the second value of 0 as an example, if it is determined that the sub-block to be coded should be coded, this means that the sub-block to be coded contains non-zero coefficients to be coded, then sb_coded_flag has a value of 1. Alternatively, if it is determined that the sub-block to be coded should not be coded, which means that all coefficients within the sub-block to be coded are 0, then sb_coded_flag has a value of 0.

[338] Thus, in certain cases, during coefficient coding, all scanned sub-blocks by default require coding, or all scanned sub-blocks by default contain significant coefficients. That is, in normal cases, the coefficient coding method remains the same as the method available in the prior art. For example, certain cases may relate to high bit depth, high quality, or high bit rate video, or to lossless compression in video coding. In this case, there are many significant coefficients, and almost all scanned sub-blocks require coding, or, in other words, almost all scanned sub-blocks contain significant coefficients. As such, there is no need to transmit sb_coded_flag in the bitstream, and the encoder/decoder does not need to process this flag, which provides a higher coding rate. In this case, there is also a small gain in compression efficiency due to the removal of the practically non-existent flag.

[339] The present embodiments further provide a coefficient encoding method applied to an encoder. A flag related to the video and the position of the last significant coefficient are determined. When the flag related to the video indicates that the video satisfies a predetermined condition, a flag of the inverse position of the last significant coefficient is determined. Information on the coordinate of the last significant coefficient is determined according to the position of the last significant coefficient and the flag of the inverse position of the last significant coefficient. All coefficients before the position of the last significant coefficient are encoded according to a predetermined scanning order, and the bit information obtained by encoding, the flag related to the video, and the information on the coordinate of the last significant coefficient are transmitted to a bitstream. Therefore, in high-bit-depth, high-bit-rate, high-quality, or lossless video coding scenarios, since the coefficient distribution pattern differs from that in conventional video scenarios, during coefficient coding, by reducing or even eliminating the number of syntax elements encoded in the context mode, such as syntax elements about the position of the last significant coefficient, coded sub-block flags, etc., or by additionally performing coordinate transformation when the coordinate values of the last significant coefficient are too large, the resource consumption caused by coding in the bitstream can be reduced, thereby improving the throughput and speed of coefficient coding. Furthermore, compression efficiency can also be improved, since the reduced or eliminated syntax elements have less impact on video coding in high-bit-depth, high-bit-rate, high-quality, or lossless compression scenarios.

[340] In another embodiment of the present invention, based on the same idea as in the previous embodiments, Fig. 12 illustrates a block diagram of an encoder 120 provided in the embodiments of the present invention. As shown in Fig. 12, the encoder 120 may include a first determining unit 1201 and an encoding unit 1202.

[341] The first determining unit 1201 is configured to determine a flag related to the video and a position of the last significant coefficient and determine a flag of the reverse position of the last significant coefficient when the flag related to the video indicates that the video satisfies a predetermined condition.

[342] The first determining unit 1201 is further configured to determine information about the coordinate of the last significant coefficient according to the position of the last significant coefficient and the reverse position flag of the last significant coefficient.

[343] The encoding unit 1202 is configured to encode all coefficients before the position of the last significant coefficient according to a given scanning order and transmit bit information obtained by encoding, a flag related to the video, and information about the coordinate of the last significant coefficient into a bit stream.

[344] In some embodiments, the first determining unit 1201 is further configured to determine a flag related to the video as a first value when the video satisfies a predetermined condition, or to determine a flag related to the video as a second value when the video does not satisfy the predetermined condition.

[345] In some embodiments, the specified condition includes at least one of: high bit depth, high quality, high bit rate, high frame rate, or lossless compression.

[346] In some embodiments, the first determining unit 1201 is further configured to determine the last significant coefficient position reversal flag as a first value when the position of the last significant coefficient is reversed for the current block, or to determine the last significant coefficient position reversal flag as a second value when the position of the last significant coefficient is not reversed for the current block.

[347] In some embodiments, the position of the last significant coefficient includes an initial horizontal coordinate and an initial vertical coordinate of the last significant coefficient, where the initial horizontal coordinate is the horizontal distance from the position of the last significant coefficient to the upper left corner of the current block, and the initial vertical coordinate is the vertical distance from the position of the last significant coefficient to the upper left corner of the current block.

[348] Accordingly, the first determining unit 1201 is further configured to: when the last significant coefficient reverse position flag has a first value, determine the coordinate information of the last significant coefficient by calculating in accordance with the initial horizontal coordinate and the initial vertical coordinate of the last significant coefficient, or when the last significant coefficient reverse position flag has a second value, determine the coordinate information of the last significant coefficient directly in accordance with the initial horizontal coordinate and the initial vertical coordinate of the last significant coefficient.

[349] In some embodiments, the first determining unit 1201 is further configured to: determine a width and a height of a current block; obtain a horizontal coordinate of the last significant coefficient by subtracting an initial horizontal coordinate of the last significant coefficient from the width of the current block; obtain a vertical coordinate of the last significant coefficient by subtracting an initial vertical coordinate of the last significant coefficient from the height of the current block; and determine information about the coordinate of the last significant coefficient according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient.

[350] In some embodiments, the first determining unit 1201 is further configured to: when the last significant coefficient inverse position flag has a first value, determine the coordinate information of the last significant coefficient as a horizontal distance and a vertical distance from the position of the last significant coefficient to the lower right corner of the current block; or when the last significant coefficient inverse position flag has a second value, determine the coordinate information of the last significant coefficient as a horizontal distance and a vertical distance from the position of the last significant coefficient to the upper left corner of the current block.

[351] In some embodiments, the encoding unit 1202 is further configured to determine information about a prefix of a horizontal coordinate of the last significant coefficient, information about a prefix of a vertical coordinate of the last significant coefficient, information about a suffix of a horizontal coordinate of the last significant coefficient, and information about a suffix of a vertical coordinate of the last significant coefficient in accordance with the information about the coordinate of the last significant coefficient, and transmit the information about the prefix of a horizontal coordinate of the last significant coefficient, the prefix of a vertical coordinate of the last significant coefficient, the suffix of a horizontal coordinate of the last significant coefficient, and the suffix of a vertical coordinate of the last significant coefficient to a bitstream.

[352] In some embodiments, the last significant coefficient reverse position flag is at least one of a sequence level, a picture level, a slice level, or a block level flag.

[353] In some embodiments, the first determining unit 1201 is further configured to determine a flag determined by the last coefficient when the flag related to the video indicates that the video satisfies a predetermined condition.

[354] The encoding unit 1202 is further configured to: when the flag associated with the last coefficient indicates that the position of the last coefficient is used for the current block, encode all coefficients before the position of the last coefficient according to a given scanning order, and provide bit information obtained by encoding the flag related to the video and the flag associated with the last coefficient into a bit stream.

[355] In some embodiments, the first determining unit 1201 is further configured to: when the position of the last coefficient is used for the current block, determine the flag determined by the last coefficient as a first value; or when the position of the last coefficient is not used for the current block, determine the flag determined by the last coefficient as a second value.

[356] In some embodiments, the position of the last coefficient is a position in the lower right corner of a matrix formed by all possible significant coefficients in the current block; or the position of the last coefficient is the last position when scanning all possible significant coefficients in the current block according to a given scanning order.

[357] In some embodiments, the first determining unit 1201 is further configured to set the position of the last significant coefficient as the position of the last coefficient.

[358] In some embodiments, the first determining unit 1201 is further configured to determine the width and height of the transformation block obtained in a given operation on the current block, obtain information about the coordinate of the lower right corner of the transformation block by calculating the coordinate according to the width and height of the transformation block; and determine the position of the last coefficient according to the information about the coordinate of the lower right corner of the transformation block.

[359] In some embodiments, the specified operation at least includes a zero output operation.

[360] In some embodiments, the first determining unit 1201 is further configured to determine the position of the last significant coefficient according to the coordinate information of the lower right corner of the transform block when the position of the last significant coefficient is set as the position of the last coefficient.

[361] In some embodiments, the first determining unit 1201 is further configured to: when the position of the last coefficient is not used for the current block, determine information about the prefix of the horizontal coordinate of the last significant coefficient, information about the prefix of the vertical coordinate of the last significant coefficient, information about the suffix of the horizontal coordinate of the last significant coefficient, and information about the suffix of the vertical coordinate of the last significant coefficient, and determine the position of the last significant coefficient in accordance with the information about the prefix of the horizontal coordinate of the last significant coefficient, the prefix of the vertical coordinate of the last significant coefficient, the suffix of the horizontal coordinate of the last significant coefficient, and the suffix of the vertical coordinate of the last significant coefficient.

[362] In some embodiments, the encoding unit 1202 is further configured to encode all coefficients before the position of the last significant coefficient according to a given scanning order and provide information about a prefix of a horizontal coordinate of the last significant coefficient, information about a prefix of a vertical coordinate of the last significant coefficient, information about a suffix of a horizontal coordinate of the last significant coefficient, and information about a suffix of a vertical coordinate of the last significant coefficient into the bitstream.

[363] In some embodiments, the flag determined by the last coefficient is at least one of a sequence level, a picture level, a slice level, or a block level flag.

[364] In some embodiments, the first determining unit 1201 is further configured to: when the flag related to the video indicates that the video satisfies a given condition, determine a flag of a default coded sub-block for a sub-block to be coded in the current block.

[365] The encoding unit 1202 is further configured to: when the default-coded flag of the sub-block indicates that the sub-block to be encoded is by default used for encoding, encode all coefficients in the sub-block to be decoded, and provide bit information obtained by encoding and the default-coded flag of the sub-block to the bitstream.

[366] In some embodiments, the first determining unit 1201 is further configured to: when the default coded sub-block flag indicates that the sub-block to be coded is not used for encoding by default, determine a coded sub-block flag for the sub-block to be coded, and provide the coded sub-block flag to the bitstream.

[367] In some embodiments, the first determining unit 1201 is further configured to determine the default-coded sub-block flag as a first value when the sub-block to be encoded uses the default encoding, or to determine the default-coded sub-block flag as a second value when the sub-block to be encoded does not use the default encoding.

[368] In some embodiments, the first determining unit 1201 is further configured to determine the coded sub-block flag as a first value when the sub-block requires encoding, or to determine the coded sub-block flag as a second value when all coefficients in the sub-block are equal to 0.

[369] In some embodiments, the default coded sub-block flag is at least one of a sequence level, a picture level, a slice level, or a block level flag.

[370] In some embodiments, the first value is 1 and the second value is 0.

[371] In some embodiments, the first determining unit 1201 is further configured to: when the flag related to the video is a high bit depth flag, determine that the high bit depth flag indicates that the video satisfies a predetermined condition if the video satisfies a high bit depth.

[372] In some embodiments, the first determining unit 1201 is further configured to: when the flag related to the video is a high bit rate flag, determine that the high bit rate flag indicates that the video satisfies a predetermined condition if the video satisfies a high bit rate.

[373] In some embodiments, the first determining unit 1201 is further configured to: when the flag related to the video is a high quality flag, determine that the high quality flag indicates that the video satisfies a predetermined condition if the video satisfies the high quality.

[374] In some embodiments, the first determining unit 1201 is further configured to: when the flag related to the video is a lossless compression flag, determine that the lossless compression flag indicates that the video satisfies a predetermined condition if the video satisfies lossless compression.

[375] It should be understood that in the embodiments of the present invention, a "node" may be a part of a circuit, a part of a processor, a part of a program or software, etc., and it may also be a module or may be non-modular. In addition, various components in the embodiments may be integrated into a single processing node, or each node may exist physically separately, or two or more nodes may be combined into a single node. The aforementioned integrated nodes may be implemented in the form of hardware or software functional modules.

[376] When implemented as a software functional module and not supplied or used as a stand-alone product, the integrated unit may be stored on a machine-readable storage medium. Based on this understanding, the technical solution of the present invention in whole or in part, or in a part that makes a significant contribution to the state of the art, may be implemented in the form of a software product. The computer program product is stored on a storage medium and includes a number of instructions to enable a computing device (which may be a personal computer, a server or a network device, etc.) or a processor to perform all or some of the operations of the method according to the present invention. The aforementioned storage medium comprises: USB flash drives, removable hard drives, read-only memory (ROM), random access memory (RAM), disks or CD-ROMs and other media on which program codes can be stored.

[377] Thus, embodiments of the present invention provide a computer storage medium in conjunction with the encoder 120. The computer storage medium stores a computer program that, when executed by a first processor, implements the method described in any of the above-described embodiments.

[378] Based on the composition of the above-mentioned encoder 120 and the computer storage medium, referring to Fig. 13, Fig. 13 is a schematic diagram of a specific hardware structure of the encoder 120 provided in an embodiment of the present invention. As shown in Fig. 13, the encoder 120 may include a first communication interface 1301, a first memory 1302, and a first processor 1303. The components are interconnected via a first bus system 1304. It can be understood that the first bus system 1304 is configured to implement a communication connection between these components. In addition to the data bus, the first bus system 1304 also includes a control power bus and a status signal bus. However, for clarity of explanation, various buses are designated as the first bus system 1304 in Fig. 13.

[379] The first communication interface 1301 is configured to receive and send signals during the process of sending and receiving information using other external network elements.

[380] The first memory device 1302 is configured to store a computer program that can be executed on the first processor 1303.

[381] The first processor 1303 is configured to perform the following operations when executing the computer program.

[382] A flag related to the video and the position of the last significant coefficient are determined. When the flag related to the video indicates that the video satisfies a predetermined condition, a flag of the inverse position of the last significant coefficient is determined. Information on the coordinate of the last significant coefficient is determined according to the position of the last significant coefficient and the flag of the inverse position of the last significant coefficient. All coefficients before the position of the last significant coefficient are encoded according to a predetermined scanning order, and the bit information obtained by encoding, the flag related to the video, and the information on the coordinate of the last significant coefficient are transmitted in a bitstream.

[383] It should be understood that the first memory device 1302 in embodiments of the present invention may be a volatile memory device or a non-volatile memory device, or may include both volatile and non-volatile memory devices. The non-volatile memory device may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or an electrical EPROM, EEPROM), or flash memory. The volatile memory device may be a random access memory (RAM), which is used as an external cache memory. By way of illustration, many types of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (ESDRAM), and flash memory. DRAM, synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced synchronous SDRAM (ESDRAM), Synchlink type DRAM (SLDRAM), and direct resident access bus RAM (DRRAM). The first memory device 1302 of the systems and methods described in this invention is intended to include, but is not limited to, these and any other suitable types of memory devices.

[384] Furthermore, the first processor 1303 may be a chip with integrated circuits with signal processing functionality. During implementation, the operations of the above-described methods may be performed by an integrated logic circuit in the form of hardware in the first processor 1003 or an instruction in the form of software. The first processor 1303 may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete logic element, or a transistor logic device, or a discrete hardware component, or the like. The methods, operations, and logical flow charts disclosed in the embodiments of the present invention may be implemented or executed by the first processor. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor or the like. The operations of the methods disclosed in conjunction with the embodiments of the present application may be directly implemented for execution and performed by a hardware decoding processor or executed and performed by a combination of hardware in the decoding processor and software modules. The software module may be located on a storage medium well known in the art, such as RAM, flash memory, ROM, PROM, EEPROM, a register, and the like. The storage medium is located in the first memory device 1302, and the first processor 1303 reads information in the first memory device 1302 and performs the operations of the above methods in conjunction with its hardware.

[385] It should be understood that the embodiments described in the present invention may be implemented using hardware, software, firmware, middleware, microcode, or a combination thereof. For a hardware-based implementation, the processing unit may be implemented in one or more ASICs, DSPs, DSP devices (DSPDs), programmable logic devices (PLDs), FPGAs, general-purpose processors, controllers, microcontrollers, microprocessors, other electronic units configured to perform the functions described in the present invention, or a combination thereof. For a software-based implementation, the technologies described in the present invention may be implemented by modules (e.g., processes, functions, etc.) that perform the functions described in the present invention. The software codes may be stored in a memory device and executed by a processor. The memory device may be implemented within the processor or outside the processor.

[386] Optionally, in another embodiment, the first processor 1303 is further configured to perform the method according to any of the above embodiments when executing the computer program.

[387] Embodiments provide an encoder that comprises a first determining unit and an encoding unit. Thus, in high-bit-depth, high-bit-rate, high-quality, or lossless-compression video encoding scenarios, since the coefficient distribution pattern differs from that in conventional video scenarios, during coefficient encoding, by reducing or even eliminating the number of syntax elements encoded in the context mode, the resource consumption caused by encoding in the bitstream can be reduced, and thus the throughput and encoding speed of the coefficients can be improved. In addition, compression efficiency can also be improved since the reduced or eliminated syntax elements have less impact on video encoding at high bit-depth, high bit-rate, high-quality, or lossless compression.

[388] In another embodiment of the present invention, based on the same idea as in the previous embodiments, a block diagram of a decoder 140 provided in the embodiments of the present invention is illustrated in Fig. 14. As shown in Fig. 14, the decoder 140 may comprise an analysis unit 1401 and a second determination unit 1402.

[389] The analysis unit 1401 is configured to analyze the bit stream to obtain a flag related to the video and to analyze the bit stream to obtain a flag of the inverse position of the last significant coefficient and information about the coordinate of the last significant coefficient when the flag related to the video indicates that the video satisfies a predetermined condition.

[390] The second determining unit 1402 is configured to determine the position of the last significant coefficient by calculating using the coordinate information of the last significant coefficient when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is reversed for the current block.

[391] The analysis unit 1401 is further configured to decode, according to a given scanning order, all coefficients before the position of the last significant coefficient to determine the coefficients of the current block.

[392] In some embodiments, the second determining unit 1402 is further configured to determine the position of the last significant coefficient directly according to the coordinate information of the last significant coefficient when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is not reversed for the current block.

[393] The analysis unit 1402 is further configured to decode, according to a given scanning order, all coefficients before the position of the last significant coefficient to determine the coefficients of the current block.

[394] In some embodiments, the second determining unit 1402 is further configured to: when the flag related to the video has a first value, determine that the flag related to the video indicates that the video satisfies a predetermined condition, or when the flag related to the video has a second value, determine that the flag related to the video indicates that the video does not satisfy a predetermined condition.

[395] In some embodiments, the specified condition includes at least one of: high bit depth, high quality, high bit rate, high frame rate, or lossless compression.

[396] In some embodiments, the second determining unit 1402 is further configured to: when the last significant coefficient position reverse flag has a first value, determine that the last significant coefficient position reverse flag indicates that the last significant coefficient position has been reversed for the current block, or when the last significant coefficient position reverse flag has a second value, determine that the last significant coefficient position reverse flag indicates that the last significant coefficient position has not been reversed for the current block.

[397] In some embodiments, the analysis unit 1401 is further configured to analyze the bitstream to obtain information about a prefix of a horizontal coordinate of the last significant coefficient, information about a prefix of a vertical coordinate of the last significant coefficient, information about a suffix of a horizontal coordinate of the last significant coefficient, and information about a suffix of a vertical coordinate of the last significant coefficient.

[398] The second determining unit 1402 is further configured to determine the horizontal coordinate of the last significant coefficient according to the information about the prefix of the horizontal coordinate of the last significant coefficient and the information about the suffix of the horizontal coordinate of the last significant coefficient, determine the vertical coordinate of the last significant coefficient according to the information about the prefix of the vertical coordinate of the last significant coefficient and the information about the suffix of the vertical coordinate of the last significant coefficient, and determine the information about the coordinate of the last significant coefficient according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient.

[399] In some embodiments, the second determining unit 1402 is further configured to determine the coordinate information of the last significant coefficient as a horizontal distance and a vertical distance from the position of the last significant coefficient to the lower right corner of the current block, when the last significant coefficient position reverse flag indicates that the position of the last significant coefficient is reversed for the current block.

[400] Also, the second determining unit 1402 is further configured to determine the width and the height of the current block; obtain a horizontal coordinate of the last significant coefficient by subtracting from the width of the current block a horizontal distance from the position of the last significant coefficient to the lower right corner of the current block; obtain a vertical coordinate of the last significant coefficient by subtracting from the height of the current block a vertical distance from the position of the last significant coefficient to the lower right corner of the current block; and determine the position of the last significant coefficient according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient.

[401] In some embodiments, the second determining unit 1402 is further configured to determine the coordinate information of the last significant coefficient as a horizontal distance and a vertical distance from the position of the last significant coefficient to the upper left corner of the current block, when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is not reversed for the current block, and to determine the position of the last significant coefficient according to the horizontal distance and the vertical distance from the position of the last significant coefficient to the upper left corner of the current block.

[402] In some embodiments, the last significant coefficient reverse position flag is at least one of a sequence level, a picture level, a slice level, or a block level flag.

[403] In some embodiments, the first analysis unit 1401 is further configured to analyze the bit stream to obtain a flag determined by the last coefficient and to decode, according to a given scanning order, all coefficients before the position of the last significant coefficient to determine the coefficients of the current block when the flag determined by the last coefficient indicates that the position of the last coefficient is used for the current block.

[404] In some embodiments, the second determining unit 1402 is further configured to: when the flag determined by the last coefficient has a first value, determine that the flag determined by the last coefficient indicates that the position of the last coefficient is used for the current block, or when the flag determined by the last coefficient has a second value, determine that the flag determined by the last coefficient indicates that the position of the last coefficient is not used for the current block.

[405] In some embodiments, the analysis unit 1401 is further configured to analyze the bitstream to obtain information about a prefix of a horizontal coordinate of the last significant coefficient, information about a prefix of a vertical coordinate of the last significant coefficient, information about a suffix of a horizontal coordinate of the last significant coefficient, and information about a suffix of a vertical coordinate of the last significant coefficient.

[406] The second determining unit 1402 is further configured to determine the position of the last significant coefficient according to the information about the prefix of the horizontal coordinate of the last significant coefficient, the information about the prefix of the vertical coordinate of the last significant coefficient, the information about the suffix of the horizontal coordinate of the last significant coefficient, and the information about the suffix of the vertical coordinate of the last significant coefficient; and to decode according to a predetermined scanning order all the coefficients before the position of the last significant coefficient to determine the coefficients of the current block.

[407] In some embodiments, the second determining unit 1402 is further configured to determine that the position of the last coefficient is a position in the lower right corner of a matrix formed by all possible significant coefficients in the current block; or the position of the last coefficient is the last position when scanning all possible significant coefficients in the current block according to a given scanning order.

[408] In some embodiments, the second determining unit 1402 is further configured to set the position of the last significant coefficient as the position of the last coefficient.

[409] In some embodiments, the second determining unit 1402 is further configured to determine the width and height of the transformation block obtained in a given operation on the current block, obtain information about the coordinate of the lower right corner of the transformation block by calculating the coordinate according to the width and height of the transformation block; and determine the position of the last coefficient according to the information about the coordinate of the lower right corner of the transformation block.

[410] In some embodiments, the specified operation at least includes a zero output operation.

[411] In some embodiments, the second determining unit 1402 is further configured to determine the position of the last significant coefficient according to the information about the coordinate of the lower right corner of the transform block, when the position of the last significant coefficient is set as the position of the last coefficient.

[412] In some embodiments, the flag determined by the last coefficient is at least a flag of one of: a sequence level, a picture level, a slice level, or a block level.

[413] In some embodiments, the first analyzing unit 1401 is further configured to: when a flag related to the video indicates that the video satisfies a given condition, analyze the bitstream to obtain a flag of a default coded sub-block; and determine that the flag of the coded sub-block has a first value, and decode all coefficients in the sub-block to be decoded in the current block, when the flag of the default coded sub-block indicates that the sub-block to be decoded is used for encoding by default.

[414] In some embodiments, the analysis unit 1401 is further configured to: when the default coded sub-block flag indicates that the sub-block to be decoded is not used for encoding by default, analyze the bitstream to obtain the coded sub-block flag, and decode all coefficients in the sub-block when the coded sub-block flag has a first value.

[415] In some embodiments, the second determining unit 1402 is further configured to: when the default-coded sub-block flag has a first value, determine that the default-coded sub-block flag indicates that the sub-block to be decoded uses encoding by default; or when the default-coded sub-block flag has a second value, determine that the default-coded sub-block flag indicates that the sub-block to be decoded does not use encoding by default.

[416] In some embodiments, the second determining unit 1402 is further configured to: determine whether to decode all coefficients in the sub-block to be decoded when the coded sub-block flag has a first value; or determine all coefficients in the sub-block to be decoded as equal to 0 when the coded sub-block flag has a second value.

[417] In some embodiments, the default coded sub-block flag is at least one of a sequence level, a picture level, a slice level, or a block level flag.

[418] In some embodiments, the first value is 1 and the second value is 0.

[419] In some embodiments, the second determining unit 1402 is further configured to: when the flag related to the video is a high bit depth flag, determine that the video satisfies a predetermined condition, when the high bit depth flag indicates that the video satisfies a high bit depth.

[420] In some embodiments, the second determining unit 1402 is further configured to: when the flag related to the video is a high bit rate flag, determine that the video satisfies a predetermined condition, when the high bit rate flag indicates that the video satisfies a high bit rate.

[421] In some embodiments, the second determining unit 1402 is further configured to: when the flag related to the video is a high quality flag, determine that the video satisfies a predetermined condition, when the high quality flag indicates that the video satisfies high quality.

[422] In some embodiments, the second determining unit 1402 is further configured to: when the flag related to the video is a lossless compression flag, determine that the video satisfies a predetermined condition, when the lossless compression flag indicates that the video satisfies lossless compression.

[423] It should be understood that in the embodiments of the present invention, a "node" may be a part of a circuit, a part of a processor, a part of a program or software, etc., and it may also be a module or may be non-modular. In addition, various components in the embodiments may be integrated into a single processing node, or each node may exist physically separately, or two or more nodes may be combined into a single node. The aforementioned integrated nodes may be implemented in the form of hardware or software functional modules.

[424] When implemented as a software functional module, rather than supplied or used as a stand-alone product, the integrated unit may be stored on a machine-readable storage medium. Based on this understanding, the technical solution of the present invention, in whole or in part, or in a part that makes a significant contribution to the state of the art, may be implemented in the form of a software product. The computer program product is stored on a storage medium and includes a number of instructions to enable a computing device (which may be a personal computer, a server, or a network device, etc.) or a processor to perform all or some of the operations of the method according to the present invention. The aforementioned storage medium comprises: USB flash drives, removable hard drives, ROM, RAM, disks or CD-ROMs and other media on which program codes can be stored.

[425] Thus, embodiments of the present invention provide a computer storage medium in connection with a decoder 140. The computer storage medium stores a computer program that, when executed by a second processor, implements the method described in any of the above-described embodiments.

[426] Based on the composition of the above-mentioned decoder 140 and the computer storage medium, referring to Fig. 15, Fig. 15 is a schematic diagram of a specific hardware structure of the decoder 140 provided in an embodiment of the present invention. As shown in Fig. 15, the decoder 140 may include a second communication interface 1501, a second memory 1502, and a second processor 1503. The components are interconnected via a second bus system 1504. It can be understood that the second bus system 1504 is configured to implement a communication connection between these components. In addition to the data bus, the second bus system 1504 also includes a control power bus and a status signal bus. However, for clarity of explanation, various buses are designated as the second bus system 1504 in Fig. 15.

[427] The second communication interface 1501 is configured to receive and send signals during the process of sending and receiving information using other external network elements.

[428] The second memory device 1502 is configured to store a computer program that can be executed on the second processor 1503.

[429] The second processor 1503 is configured to perform the following operations when executing the computer program.

[430] The bitstream is analyzed to obtain a flag related to the video. When the flag related to the video indicates that the video satisfies a predetermined condition, the bitstream is analyzed to obtain a last significant coefficient position inversion flag and information on the coordinate of the last significant coefficient. When the last significant coefficient position inversion flag indicates that the position of the last significant coefficient is reversed for the current block, the position of the last significant coefficient is determined by calculation using the information on the coordinate of the last significant coefficient. According to a predetermined scanning order, all coefficients before the position of the last significant coefficient are decoded to determine the coefficients of the current block.

[431] Optionally, in another embodiment, the second processor 1503 is further configured to perform the method according to any of the above embodiments when executing the computer program.

[432] It should be understood that the hardware functions of the second memory device 1502 and the first memory device 1302 are similar, and the hardware functions of the second processor 1503 and the first processor 1303 are similar, which will not be described in detail in this document.

[433] Embodiments provide a decoder comprising an analysis unit and a second determination unit. Thus, in high-bit-depth, high-bit-rate, high-quality, or lossless-compression video coding scenarios, since the coefficient distribution pattern differs from that in conventional video scenarios, during coefficient coding, by reducing or even eliminating the number of syntax elements encoded in the context mode, the resource consumption caused by coding in the bitstream can be reduced, and thus the throughput and coding speed of the coefficients can be improved. In addition, compression efficiency can also be improved since the reduced or eliminated syntax elements have less impact on video coding in high-bit-depth, high-bit-rate, high-quality, or lossless-compression scenarios.

[434] It should be understood that in this invention, the terms "including," "comprising," or any other variation thereof are intended to encompass a non-exclusive inclusion, such that a process, method, article, or device comprising a number of elements not only includes those elements but also includes other elements not expressly listed or inherent in such process, method, article, or device. Unless further limited, an element identified by the statement "comprising" does not exclude the presence of additional similar elements in a process, method, article, or device comprising that element.

[435] The above serial numbers of the embodiments of the present invention are for description only and do not represent the advantages and disadvantages of the embodiments.

[436] The methods disclosed in several embodiments of the method provided in this invention can be arbitrarily combined without contradiction to obtain new embodiments of the method.

[437] The characteristics disclosed in several embodiments of the product provided in this invention may be arbitrarily combined without contradiction to obtain new embodiments of the product.

[438] The characteristics disclosed in several embodiments of the method or device provided in the present invention can be arbitrarily combined without contradiction to obtain new embodiments of the method or embodiments of the device.

[439] The above descriptions are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that a person skilled in the art can easily imagine within the technical scope disclosed in this invention should be included in the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of protection of the claims.

Industrial applicability

[440] In some embodiments of the present invention, for both the encoder and the decoder, in high-bit-depth, high-bit-rate, high-quality, or lossless-compression video coding scenarios, since the coefficient distribution pattern differs from that in conventional video scenarios, during the coding of the coefficients, by reducing or even eliminating the number of syntax elements encoded in the context mode, such as syntax elements about the position of the last significant coefficient, coded sub-block flags, etc., or by additionally performing a coordinate transformation in the case where the coordinate values of the last significant coefficient are too large, the resource consumption caused by coding in the bitstream can be reduced, and thus the throughput and coding speed of the coefficients can be improved. In addition, the compression efficiency can also be improved since the reduced or eliminated syntax elements have less impact on the coding of video in high-bit-depth, high-bit-rate, high-quality, or lossless compression.

Claims (34)

1. A coefficient decoding method applied to a decoder and comprising: bit stream analysis to obtain sequence level flag; analyzing the bit stream to obtain a flag of the reverse position of the last significant coefficient and information about the coordinates of the last significant coefficient when the sequence level flag indicates that the video satisfies a given condition; when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is reversed for the current block, determining the position of the last significant coefficient by calculating using the coordinate information of the last significant coefficient, wherein the coordinate information of the last significant coefficient is a horizontal distance and a vertical distance from the position of the last significant coefficient to the lower right corner of the current block; and decoding according to a given scanning order of all coefficients before the position of the last significant coefficient to determine the coefficients of the current block. 2. The method according to paragraph 1, characterized in that it additionally includes: determining the position of the last significant coefficient directly according to the coordinate information of the last significant coefficient, when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is not reversed for the current block; and decoding, according to a given scanning order, all coefficients before the position of the last significant coefficient to determine the coefficients of the current block. 3. The method according to paragraph 1, characterized in that it additionally includes: when the sequence level flag has the first value, determining that the sequence level flag indicates that the video satisfies the specified condition; or, when the sequence level flag has a second value, determining that the sequence level flag indicates that the video does not satisfy the specified condition. 4. The method of claim 3, wherein the specified condition includes at least one of: high bit depth, high quality, high bit rate, high frame rate, or lossless compression. 5. The method according to paragraph 1, characterized in that it additionally includes: when the last significant coefficient position reverse flag has the first value, determining that the last significant coefficient position reverse flag indicates that the position of the last significant coefficient has been reversed for the current block; or, when the last significant coefficient position reverse flag has the second value, determining that the last significant coefficient position reverse flag indicates that the position of the last significant coefficient is not reversed for the current block. 6. The method according to paragraph 1, characterized in that determining the position of the last significant coefficient by calculation using information about the coordinates of the last significant coefficient includes: defining the width and height of the current block; obtaining the horizontal coordinate of the last significant coefficient by subtracting from the width of the current block the horizontal distance from the position of the last significant coefficient to the lower right corner of the current block; obtaining the vertical coordinate of the last significant coefficient by subtracting from the height of the current block the vertical distance from the position of the last significant coefficient to the lower right corner of the current block; and determining the position of the last significant coefficient according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient. 7. A method of encoding a coefficient applied to the encoder and comprising: determination of the sequence level flag and the position of the last significant coefficient; determining the flag of the reverse position of the last significant coefficient when the sequence level flag indicates that the video satisfies the specified condition; determining the coordinate information of the last significant coefficient according to the position of the last significant coefficient and the last significant coefficient reverse position flag, wherein the coordinate information of the last significant coefficient is determined as a horizontal distance and a vertical distance from the position of the last significant coefficient to the lower right corner of the current block, when the last significant coefficient reverse position flag indicates that the position of the last significant coefficient is reversed for the current block; and encoding all coefficients before the position of the last significant coefficient according to a given scanning order, and providing bit information obtained by encoding, a sequence level flag and information about the coordinate of the last significant coefficient, to a bit stream. 8. An encoder comprising a first detection node and an encoding node, wherein the first determining unit is configured to determine a sequence level flag and a position of the last significant coefficient and to determine a flag of the reverse position of the last significant coefficient when the sequence level flag indicates that the video satisfies a given condition; the first determining unit is further configured to determine information about the coordinates of the last significant coefficient according to the position of the last significant coefficient and the flag of the reverse position of the last significant coefficient, wherein the information about the coordinates of the last significant coefficient is determined as a horizontal distance and a vertical distance from the position of the last significant coefficient to the lower right corner of the current block, when the flag of the reverse position of the last significant coefficient indicates that the position of the last significant coefficient is reversed for the current block; and the coding unit is configured to encode all coefficients before the position of the last significant coefficient according to a given scanning order and transmitting the bit information obtained by coding, the sequence level flag and the information about the coordinate of the last significant coefficient into the bit stream. 9. A decoder comprising an analysis node and a second determination node, wherein the analysis unit is configured to analyze the bit stream to obtain a sequence level flag and analyze the bit stream to obtain a flag of the reverse position of the last significant coefficient and information about the coordinate of the last significant coefficient when the sequence level flag indicates that the video satisfies a given condition; the second determining unit is configured to determine, when the last significant coefficient position reversal flag indicates that the position of the last significant coefficient is reversed for the current block, the position of the last significant coefficient by calculating using the information about the coordinate of the last significant coefficient, wherein the information about the coordinate of the last significant coefficient represents a horizontal distance and a vertical distance from the position of the last significant coefficient to the lower right corner of the current block; and the analysis unit is additionally configured to decode, according to a given scanning order, all coefficients before the position of the last significant coefficient to determine the coefficients of the current block. 10. A computer storage medium on which is stored a computer program that, when executed on a processor, implements the method according to any of paragraphs 1–6 or the method according to paragraph 7.