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WO2020071617A1 - Procédé d'intra-prédiction basée sur un cclm et appareil associé - Google Patents

Procédé d'intra-prédiction basée sur un cclm et appareil associé

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Publication number
WO2020071617A1
WO2020071617A1 PCT/KR2019/007586 KR2019007586W WO2020071617A1 WO 2020071617 A1 WO2020071617 A1 WO 2020071617A1 KR 2019007586 W KR2019007586 W KR 2019007586W WO 2020071617 A1 WO2020071617 A1 WO 2020071617A1
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WIPO (PCT)
Prior art keywords
luma
block
samples
sampled
reference samples
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Ceased
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PCT/KR2019/007586
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English (en)
Korean (ko)
Inventor
최장원
허진
유선미
이령
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LG Electronics Inc
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LG Electronics Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/103—Selection of coding mode or of prediction mode
    • H04N19/105—Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/103—Selection of coding mode or of prediction mode
    • H04N19/11—Selection of coding mode or of prediction mode among a plurality of spatial predictive coding modes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/132—Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/186—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a colour or a chrominance component
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/593—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving spatial prediction techniques

Definitions

  • the present invention relates to an image coding technology, and more particularly, to an intra prediction method and apparatus based on a cross-component linear model (CCLM) in an image coding system.
  • CCLM cross-component linear model
  • HD images high definition (HD) images and ultra high definition (UHD) images
  • UHD images ultra high definition
  • the image data becomes higher resolution and higher quality, the amount of transmitted information or bit amount increases compared to the existing image data, so the image data is transmitted using a medium such as a conventional wired / wireless broadband line or the image data is stored using an existing storage medium.
  • the transmission cost and storage cost are increased.
  • a high-efficiency image compression technology is required to effectively transmit, store, and reproduce high-resolution, high-quality image information.
  • An object of the present invention is to provide a method and apparatus for improving image coding efficiency.
  • Another technical problem of the present invention is to provide a method and apparatus for improving the efficiency of video coding based on intra prediction.
  • Another technical problem of the present invention is to provide a method and apparatus for improving the efficiency of intra prediction based on CCLM.
  • Another technical problem of the present invention is to provide a method and apparatus for improving pipeline delay when implementing intra prediction based on CCLM in hardware.
  • Another technical problem of the present invention is to perform image coding efficiency by down-sampling neighboring luma reference samples of a 1-sample line (hereinafter, “1-sample line” refers to 1 line of samples) when performing intra prediction based on CCLM. It is to provide a method and apparatus for raising the.
  • Another technical problem of the present invention is that when the upper boundary of the luma block overlaps a boundary of a coding tree unit (CTU), the memory of the decoding apparatus to derive the down-sampled upper peripheral luma reference sample.
  • the memory efficiency is increased by down-sampling the upper peripheral luma reference samples stored in a single line buffer.
  • a picture decoding method performed by a decoding apparatus includes, when the intra prediction mode of the chroma block is a cross-component linear model (CCLM) mode, deriving neighboring chroma reference samples for the chroma block, neighboring luma reference samples of the luma block corresponding to the chroma block Deriving luma samples in the and luma block, downsampling the surrounding luma reference samples and the luma samples to derive down sampled peripheral luma reference samples and down sampled luma samples, the down sampled Deriving a linear model parameter based on the peripheral luma reference samples and the peripheral chroma reference samples, and generating predictive samples for the chroma block based on the linear model parameter and down-sampled luma samples of the luma block.
  • CCLM cross-component linear model
  • the peripheral luma reference samples refer to upper peripheral luma reference samples located above the upper boundary of the luma block and left peripheral luma reference located to the left of the left boundary of the luma block.
  • Samples, and the down-sampled peripheral luma reference samples include a down-sampled left peripheral luma reference sample and a down-sampled upper peripheral luma reference sample, and the upper boundary of the luma block is a coding tree unit (CTU).
  • CTU coding tree unit
  • the upper peripheral luma reference samples stored in a single line buffer of the memory of the decoding apparatus are downsampled to derive the down sampled upper peripheral luma reference sample, and the down sampled left peripheral Multiple line buffers in the memory to derive luma reference samples Said left around the luma samples stored in the reference is characterized by down-sampling.
  • a decoding apparatus for performing picture decoding.
  • the decoding device derives neighboring chroma reference samples for the chroma block, and the neighboring luma of the luma block corresponding to the chroma block
  • the addition unit is the chroma The chroma block is reconstructed
  • the upper peripheral luma reference samples stored in a single line buffer of the memory are downsampled to derive the down sampled upper peripheral luma reference sample, and the down sampled left peripheral Multiple line buffers in the memory to derive luma reference samples Said left around the luma samples stored in the reference is characterized by down-sampling.
  • a picture encoding method performed by an encoding device includes, when the intra prediction mode of the chroma block is a cross-component linear model (CCLM) mode, deriving neighboring chroma reference samples for the chroma block, neighboring luma reference samples of the luma block corresponding to the chroma block Deriving luma samples in the and luma block, downsampling the surrounding luma reference samples and the luma samples to derive down sampled peripheral luma reference samples and down sampled luma samples, the down sampled Deriving a linear model parameter based on the peripheral luma reference samples and the peripheral chroma reference samples, and generating predictive samples for the chroma block based on the linear model parameter and down-sampled luma samples of the luma block.
  • CCLM cross-component linear model
  • the prediction samples for the chroma block In contrast, deriving a residual sample for the chroma block and encoding picture information including information about the residual sample, wherein the surrounding luma reference samples are located above the upper boundary of the luma block.
  • the upper peripheral luma reference samples located and the left peripheral luma reference samples located to the left of the left boundary of the luma block, and the down-sampled peripheral luma reference samples include a down-sampled left peripheral luma reference sample and a down-sampled upper side.
  • a peripheral luma reference sample, and the upper boundary stored in a single line buffer of the memory of the decoding apparatus to derive the down sampled upper peripheral luma reference sample when the upper boundary of the luma block overlaps a boundary of a CTU Downsampling luma reference samples, and downsampling the To derive a luma left peripheral reference sample is characterized in that the down-sampled luma near the left reference samples stored in a plurality of line buffers in the memory.
  • an encoding apparatus for performing picture encoding.
  • the intra prediction mode of the memory and the chroma block is a cross-component linear model (CCLM) mode
  • the encoding device derives neighboring chroma reference samples for the chroma block, and the neighboring luma of the luma block corresponding to the chroma block
  • Prediction unit the prediction samples for the chroma block
  • a residual processing unit for deriving
  • the upper peripheral luma reference samples located above the boundary and the left peripheral luma reference samples located to the left of the left boundary of the luma block wherein the down sampled peripheral luma reference samples include a down sampled left peripheral luma reference sample and A down line sampled upper peripheral luma reference sample, and when the upper boundary of the luma block overlaps a CTU boundary, to a single line buffer in the memory of the decoding device to derive the down sampled upper peripheral luma reference sample.
  • Download the stored upper peripheral luma reference samples Coupling, and to derive the reference down-sampled left around the luma samples wherein the downsampling of the left peripheral reference luma samples stored in a plurality of line buffers in the memory.
  • a pipeline delay when implementing intra prediction based on CCLM in hardware, a pipeline delay can be improved.
  • image coding efficiency when performing intra prediction based on CCLM, image coding efficiency can be improved by down-sampling neighboring luma reference samples of the 1-sample line.
  • the upper peripheral luma stored in a single line buffer of the memory of the decoding apparatus to derive a down sampled upper peripheral luma reference sample Memory efficiency can be increased by downsampling the reference samples.
  • FIG. 1 is a diagram schematically illustrating a configuration of an encoding apparatus according to an embodiment.
  • FIG. 2 is a diagram schematically illustrating a configuration of a decoding apparatus according to an embodiment.
  • FIG. 3 is a diagram for explaining intra prediction based on CCLM according to an embodiment.
  • FIG. 4 is a diagram for explaining intra prediction based on CCLM according to another embodiment.
  • FIG. 5 is a flowchart illustrating an intra prediction process based on CCLM according to an embodiment.
  • FIG. 6 is a diagram illustrating an example of a hardware pipeline of intra prediction based on CCLM according to an embodiment.
  • FIG. 7 is a diagram illustrating an example of a hardware pipeline of intra prediction based on CCLM according to another embodiment.
  • FIG. 8 is a flowchart illustrating an intra prediction process based on CCLM according to another embodiment.
  • FIG. 9 is a diagram illustrating an example of a hardware pipeline of intra prediction based on CCLM according to another embodiment.
  • FIG. 10 is a flowchart illustrating an intra prediction process based on CCLM according to another embodiment.
  • FIG. 11 is a diagram illustrating an intra prediction process based on CCLM according to another embodiment.
  • FIG. 12 is a flowchart illustrating an intra prediction process based on CCLM according to another embodiment.
  • FIG. 13 is a flowchart illustrating an operation of an encoding apparatus according to an embodiment.
  • FIG. 14 is a block diagram showing the configuration of an encoding apparatus according to an embodiment.
  • 15 is a flowchart illustrating an operation of a decoding apparatus according to an embodiment.
  • 16 is a block diagram showing the configuration of a decoding apparatus according to an embodiment.
  • a picture decoding method performed by a decoding apparatus includes, when the intra prediction mode of the chroma block is a cross-component linear model (CCLM) mode, deriving neighboring chroma reference samples for the chroma block, neighboring luma reference samples of the luma block corresponding to the chroma block Deriving luma samples in the and luma block, downsampling the surrounding luma reference samples and the luma samples to derive down sampled peripheral luma reference samples and down sampled luma samples, the down sampled Deriving a linear model parameter based on the peripheral luma reference samples and the peripheral chroma reference samples, and generating predictive samples for the chroma block based on the linear model parameter and down-sampled luma samples of the luma block.
  • CCLM cross-component linear model
  • the peripheral luma reference samples refer to upper peripheral luma reference samples located above the upper boundary of the luma block and left peripheral luma reference located to the left of the left boundary of the luma block.
  • the samples are used, and when the upper boundary of the luma block overlaps a boundary of a coding tree unit (CTU), the used to derive the down-sampled neighboring luma reference samples among the neighboring luma reference samples.
  • the number of upper peripheral luma reference samples is less than the number of left peripheral luma reference samples used to derive the down sampled peripheral luma reference samples.
  • each configuration in the drawings described in the present invention is shown independently for convenience of description of the different characteristic functions, it does not mean that each configuration is implemented in separate hardware or separate software from each other.
  • two or more components of each component may be combined to form one component, or one component may be divided into a plurality of components.
  • Embodiments in which each component is integrated and / or separated are also included in the scope of the present invention without departing from the essence of the present invention.
  • the methods / embodiments disclosed in this document may include a versatile video coding (VVC) standard, an essential video coding (EVC) standard, an AOMedia Video 1 (AV1) standard, a 2nd generation of audio video coding standard (AVS2), or next-generation video / It can be applied to the method disclosed in the image coding standard (ex. H.267, H.268, etc.).
  • VVC versatile video coding
  • EVC essential video coding
  • AV1 AOMedia Video 1
  • AVS2 2nd generation of audio video coding standard
  • next-generation video / It can be applied to the method disclosed in the image coding standard (ex. H.267, H.268, etc.).
  • video may refer to a set of images over time.
  • a picture generally refers to a unit representing one image in a specific time period, and a slice is a unit constituting a part of a picture in coding.
  • One picture may be composed of a plurality of slices, and if necessary, a picture and a slice may be used interchangeably.
  • a pixel or pel may mean a minimum unit constituting one picture (or image).
  • 'sample' may be used as a term corresponding to a pixel.
  • the sample may generally represent a pixel or a pixel value, and may indicate only a pixel / pixel value of a luma component or only a pixel / pixel value of a saturation component.
  • the unit represents a basic unit of image processing.
  • the unit may include at least one of a specific region of a picture and information related to the region.
  • the unit may be used interchangeably with terms such as a block or area depending on the case.
  • the MxN block may represent samples of M columns and N rows or a set of transform coefficients.
  • the encoding / decoding device may include a video encoding / decoding device and / or a video encoding / decoding device, and the video encoding / decoding device is used as a concept including the video encoding / decoding device, or the video encoding / decoding device is It may also be used as a concept including a video encoding / decoding device.
  • the (video) encoding apparatus 100 includes a picture partitioning module (105), a prediction module (110), a residual processing module (120), and an entropy encoding unit ( It may include an entropy encoding module (130), an adder (140), a filter (filtering module, 150) and a memory (memory, 160).
  • the residual processing unit 120 includes a subtractor (121), a transform module (122), a quantization module (123), a rearrangement module (124), an inverse quantization module (125) ) And an inverse transform module 126.
  • the picture division unit 105 may divide the input picture into at least one processing unit.
  • the processing unit may be called a coding unit (CU).
  • the coding unit may be recursively divided according to a quad-tree binary-tree (QTBT) structure from a largest coding unit (LCU).
  • QTBT quad-tree binary-tree
  • LCU largest coding unit
  • one coding unit may be divided into a plurality of coding units of a deeper depth based on a quad tree structure, a binary tree structure, and / or a ternary tree structure.
  • a quad tree structure may be applied first, and a binary tree structure and a ternary tree structure may be applied later.
  • a binary tree structure / ternary tree structure may be applied first.
  • the coding procedure according to the present invention can be performed based on the final coding unit that is no longer split.
  • the maximum coding unit may be directly used as a final coding unit based on coding efficiency according to image characteristics, or the coding unit may be recursively divided into coding units having a lower depth than optimal if necessary.
  • the coding unit of the size of can be used as the final coding unit.
  • the coding procedure may include procedures such as prediction, transformation, and reconstruction, which will be described later.
  • the processing unit may include a coding unit (CU) prediction unit (PU) or a transformation unit (TU).
  • the coding unit may be split from a largest coding unit (LCU) into coding units of a deeper depth along a quad tree structure.
  • LCU largest coding unit
  • the maximum coding unit may be directly used as a final coding unit based on coding efficiency according to image characteristics, or the coding unit may be recursively divided into coding units having a lower depth than optimal if necessary.
  • the coding unit of the size of can be used as the final coding unit. If a smallest coding unit (SCU) is set, the coding unit cannot be divided into smaller coding units than the smallest coding unit.
  • the final coding unit means a coding unit that is the basis of partitioning or partitioning into a prediction unit or a transformation unit.
  • the prediction unit is a unit partitioned from a coding unit, and may be a unit of sample prediction. At this time, the prediction unit may be divided into sub blocks.
  • the transform unit may be split along the quad tree structure from the coding unit, and may be a unit that derives transform coefficients and / or a unit that derives a residual signal from transform coefficients.
  • the coding unit may be referred to as a coding block (CB), the prediction unit as a prediction block (PB), and the transform unit as a transform block (TB).
  • CB coding block
  • PB prediction block
  • TB transform block
  • the prediction block or prediction unit may mean a specific area in the form of a block in a picture, and may include an array of prediction samples.
  • the transform block or transform unit may mean a specific area in the form of a block in a picture, and may include transform coefficients or an array of residual samples.
  • the prediction unit 110 performs prediction on a block to be processed (hereinafter, it may also mean a current block or a residual block), and generates a predicted block including prediction samples for the current block can do.
  • the unit of prediction performed by the prediction unit 110 may be a coding block, a transform block, or a prediction block.
  • the prediction unit 110 may determine whether intra prediction or inter prediction is applied to the current block. For example, the prediction unit 110 may determine whether intra prediction or inter prediction is applied in units of CUs.
  • the prediction unit 110 may derive a prediction sample for the current block based on a reference sample outside the current block in a picture (hereinafter, a current picture) to which the current block belongs. At this time, the prediction unit 110 may (i) derive a prediction sample based on an average or interpolation of neighboring reference samples of the current block, and (ii) reference of the surroundings of the current block
  • the prediction sample may be derived based on a reference sample existing in a specific (prediction) direction with respect to a prediction sample among the samples. In the case of (i), it may be called a non-directional mode or a non-angle mode, and in the case of (ii), a directional mode or an angular mode.
  • the prediction mode may have, for example, 33 directional prediction modes and at least two or more non-directional modes.
  • the non-directional mode may include a DC prediction mode and a planar mode (Planar mode).
  • the prediction unit 110 may determine a prediction mode applied to the current block by using a prediction mode applied to neighboring blocks.
  • the prediction unit 110 may derive a prediction sample for the current block based on the sample specified by the motion vector on the reference picture.
  • the prediction unit 110 may derive a prediction sample for the current block by applying any one of a skip mode, a merge mode, and a motion vector prediction (MVP) mode.
  • the prediction unit 110 may use motion information of neighboring blocks as motion information of the current block.
  • the skip mode a difference (residual) between the predicted sample and the original sample is not transmitted unlike the merge mode.
  • a motion vector of a current block may be derived using a motion vector of a neighboring block as a motion vector predictor by using a motion vector of a neighboring block as a motion vector predictor.
  • the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block present in the reference picture.
  • the reference picture including the temporal neighboring block may be referred to as a collocated picture (colPic).
  • the motion information may include a motion vector and a reference picture index.
  • Information such as prediction mode information and motion information (entropy) may be encoded and output in the form of a bitstream.
  • the highest picture on the reference picture list may be used as a reference picture.
  • the reference pictures included in the reference picture list may be sorted based on a difference of a picture order count (POC) between the current picture and the corresponding reference picture.
  • POC corresponds to a display order of pictures, and can be distinguished from a coding order.
  • the subtraction unit 121 generates a residual sample, which is a difference between the original sample and the predicted sample.
  • the residual sample may not be generated as described above.
  • the transform unit 122 converts a residual sample in units of transform blocks to generate transform coefficients.
  • the transform unit 122 may perform transform according to a size of the transform block and a prediction mode applied to a coding block or a prediction block spatially overlapping the transform block. For example, if intra prediction is applied to the coding block or the prediction block overlapping the transform block, and the transform block is a 4 ⁇ 4 residual array, the residual sample uses a DST (Discrete Sine Transform) transform kernel. It is transformed by using, and in other cases, the residual sample can be transformed by using a DCT (Discrete Cosine Transform) transform kernel.
  • DST Discrete Sine Transform
  • the quantization unit 123 quantizes the transform coefficients to generate a quantized transform coefficient.
  • the rearrangement unit 124 rearranges the quantized transform coefficients.
  • the reordering unit 124 may rearrange the quantized transform coefficients in a block form into a one-dimensional vector form through a coefficient scanning method.
  • the rearrangement unit 124 is described as a separate configuration, but the rearrangement unit 124 may be part of the quantization unit 123.
  • the entropy encoding unit 130 may perform entropy encoding on quantized transform coefficients.
  • Entropy encoding may include, for example, encoding methods such as exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC).
  • the entropy encoding unit 130 may encode information necessary for video reconstruction other than the quantized transform coefficient (eg, a value of a syntax element) together or separately according to entropy encoding or a preset method.
  • the encoded information may be transmitted or stored in units of network abstraction layer (NAL) units in the form of a bitstream.
  • the bitstream can be transmitted over a network or stored on a digital storage medium.
  • the network may include a broadcasting network and / or a communication network
  • the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD.
  • the inverse quantization unit 125 inversely quantizes the quantized values (quantized transform coefficients) in the quantization unit 123, and the inverse transform unit 126 inversely transforms the inverse quantized values in the inverse quantization unit 125 to measure the residual sample.
  • the adder 140 restores a picture by combining the residual sample and the predicted sample.
  • the residual sample and the prediction sample may be added in units of blocks to generate a reconstructed block.
  • the adding unit 140 has been described as a separate configuration, but the adding unit 140 may be a part of the prediction unit 110. Meanwhile, the adder 140 may be called a reconstruction module or a reconstruction block generator.
  • the filter unit 150 may apply a deblocking filter and / or a sample adaptive offset. Through deblocking filtering and / or sample adaptive offset, artifacts of a block boundary in a reconstructed picture or distortion in a quantization process can be corrected.
  • the sample adaptive offset may be applied on a sample basis, and may be applied after the deblocking filtering process is completed.
  • the filter unit 150 may also apply an adaptive loop filter (ALF) to the reconstructed picture. ALF may be applied to the reconstructed picture after the deblocking filter and / or sample adaptive offset is applied.
  • ALF adaptive loop filter
  • the memory 160 may store reconstructed pictures (decoded pictures) or information necessary for encoding / decoding.
  • the reconstructed picture may be a reconstructed picture in which a filtering procedure is completed by the filter unit 150.
  • the stored reconstructed picture may be used as a reference picture for (inter) prediction of another picture.
  • the memory 160 may store (reference) pictures used for inter prediction. At this time, pictures used for inter prediction may be designated by a reference picture set or a reference picture list.
  • the video decoding device may include an image decoding device.
  • the video decoding apparatus 200 includes an entropy decoding module (210), a residual processing module (220), a prediction module (230), and an adder (240). ), A filter module (250) and a memory (memory, 260).
  • the residual processing unit 220 may include a rearrangement module (221), an inverse quantization module (222), and an inverse transform module (223).
  • the video decoding apparatus 200 may include a receiver that receives a bitstream including video information. The receiving unit may be configured as a separate module or may be included in the entropy decoding unit 210.
  • the video decoding apparatus 200 may restore the video / image / picture corresponding to the process in which the video / image information is processed by the video encoding apparatus.
  • the video decoding apparatus 200 may perform video decoding using a processing unit applied in the video encoding apparatus.
  • the processing unit block of video decoding may be, for example, a coding unit, and another example may be a coding unit, a prediction unit, or a transformation unit.
  • the coding unit may be split along the quad tree structure, binary tree structure and / or ternary tree structure from the largest coding unit.
  • a prediction unit and a transformation unit may be further used in some cases, and in this case, the prediction block is a block derived or partitioned from a coding unit, and may be a unit of sample prediction. At this time, the prediction unit may be divided into sub-blocks.
  • the transform unit may be split along a quad tree structure from the coding unit, and may be a unit that derives transform coefficients or a unit that derives a residual signal from transform coefficients.
  • the entropy decoding unit 210 may parse the bitstream and output information necessary for video reconstruction or picture reconstruction. For example, the entropy decoding unit 210 decodes information in a bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and quantizes a value of a syntax element necessary for video reconstruction and a transform coefficient for residual. Can output
  • a coding method such as exponential Golomb coding, CAVLC, or CABAC
  • the CABAC entropy decoding method receives bins corresponding to each syntax element in the bitstream, and decodes the syntax element information to be decoded and decoding information of neighboring and decoding target blocks or information of symbols / bins decoded in the previous step.
  • the context model is determined by using, and the probability of occurrence of the bin is predicted according to the determined context model, and arithmetic decoding of the bin is performed to generate a symbol corresponding to the value of each syntax element. can do.
  • the CABAC entropy decoding method may update the context model using the decoded symbol / bin information for the next symbol / bin context model after determining the context model.
  • the entropy decoding unit 210 Among the information decoded by the entropy decoding unit 210, information about prediction is provided to the prediction unit 230, and the residual value, that is, the quantized transform coefficient, in which entropy decoding is performed by the entropy decoding unit 210 is rearranged ( 221).
  • the reordering unit 221 may rearrange the quantized transform coefficients in a two-dimensional block form.
  • the reordering unit 221 may perform reordering in response to coefficient scanning performed by the encoding device.
  • the rearrangement unit 221 is described as a separate configuration, but the rearrangement unit 221 may be part of the inverse quantization unit 222.
  • the inverse quantization unit 222 may inverse quantize the quantized transform coefficients based on the (inverse) quantization parameter to output the transform coefficients. At this time, information for deriving a quantization parameter may be signaled from an encoding device.
  • the inverse transform unit 223 may inversely transform transform coefficients to derive residual samples.
  • the prediction unit 230 may perform prediction on the current block and generate a predicted block including prediction samples for the current block.
  • the unit of prediction performed by the prediction unit 230 may be a coding block, a transform block, or a prediction block.
  • the prediction unit 230 may determine whether to apply intra prediction or inter prediction based on the information about the prediction. At this time, a unit for determining whether to apply intra prediction or inter prediction and a unit for generating a prediction sample may be different. In addition, in inter prediction and intra prediction, a unit for generating a prediction sample may also be different. For example, whether to apply inter prediction or intra prediction may be determined in units of CUs. For example, in inter prediction, a prediction mode may be determined in PU units and a prediction sample may be generated, and a prediction mode may be determined in PU units in intra prediction and a prediction sample may be generated in TU units.
  • the prediction unit 230 may derive a prediction sample for the current block based on neighbor reference samples in the current picture.
  • the prediction unit 230 may derive a prediction sample for the current block by applying a directional mode or a non-directional mode based on the neighboring reference samples of the current block.
  • a prediction mode to be applied to the current block may be determined using the intra prediction mode of the neighboring block.
  • the prediction unit 230 may derive a prediction sample for the current block based on a sample specified on the reference picture by a motion vector on the reference picture.
  • the prediction unit 230 may derive a prediction sample for the current block by applying any one of a skip mode, a merge mode, and an MVP mode.
  • motion information required for inter prediction of a current block provided by the video encoding apparatus for example, motion vector, reference picture index, and the like, may be obtained or derived based on the prediction information.
  • the peripheral block may include a spatial peripheral block and a temporal peripheral block.
  • the prediction unit 230 may construct a merge candidate list with motion information of available neighboring blocks, and use information indicated by the merge index on the merge candidate list as a motion vector of the current block.
  • the merge index can be signaled from the encoding device.
  • the motion information may include a motion vector and a reference picture. When motion information of temporal neighboring blocks is used in the skip mode and the merge mode, the highest picture on the reference picture list can be used as a reference picture.
  • a motion vector of a current block may be derived using a motion vector of a neighboring block as a motion vector predictor.
  • the peripheral block may include a spatial peripheral block and a temporal peripheral block.
  • a merge candidate list may be generated using a motion vector of a reconstructed spatial neighboring block and / or a motion vector corresponding to a Col block that is a temporal neighboring block.
  • the motion vector of the candidate block selected from the merge candidate list is used as the motion vector of the current block.
  • the prediction information may include a merge index indicating a candidate block having an optimal motion vector selected from candidate blocks included in the merge candidate list.
  • the prediction unit 230 may derive a motion vector of the current block using the merge index.
  • a motion vector predictor candidate list is generated using a motion vector of a reconstructed spatial neighboring block and / or a Col block that is a temporal neighboring block.
  • the prediction information may include a prediction motion vector index indicating an optimal motion vector selected from among motion vector candidates included in the list.
  • the prediction unit 230 may select a prediction motion vector of the current block from among motion vector candidates included in the motion vector candidate list, using the motion vector index.
  • the prediction unit of the encoding device may obtain a motion vector difference (MVD) between a motion vector and a motion vector predictor of the current block, and may encode and output the motion vector difference. That is, the MVD may be obtained by subtracting the motion vector predictor from the motion vector of the current block.
  • the prediction unit 230 may obtain a motion vector difference included in the information about the prediction, and derive the motion vector of the current block by adding the motion vector difference and the motion vector predictor.
  • the prediction unit may also obtain or derive a reference picture index indicating the reference picture from the information on the prediction.
  • the adder 240 may reconstruct the current block or the current picture by adding the residual sample and the prediction sample.
  • the adder 240 may reconstruct the current picture by adding the residual sample and the prediction sample in block units. Since the residual is not transmitted when the skip mode is applied, the predicted sample may be a reconstructed sample.
  • the addition unit 240 is described as a separate configuration, but the addition unit 240 may be a part of the prediction unit 230. Meanwhile, the adder 240 may be referred to as a reconstruction module or a reconstruction block generator.
  • the filter unit 250 may apply a deblocking filtering sample adaptive offset, and / or ALF to the reconstructed picture.
  • the sample adaptive offset may be applied on a sample basis, or may be applied after deblocking filtering.
  • ALF may be applied after deblocking filtering and / or sample adaptive offset.
  • the memory 260 may store reconstruction pictures (decoded pictures) or information necessary for decoding.
  • the reconstructed picture may be a reconstructed picture in which a filtering procedure is completed by the filter unit 250.
  • the memory 260 may store pictures used for inter prediction. At this time, pictures used for inter prediction may be specified by a reference picture set or a reference picture list. The reconstructed picture can be used as a reference picture for other pictures. Also, the memory 260 may output the restored pictures according to an output order.
  • a predicted block including prediction samples for a current block as a block to be coded can be generated.
  • the predicted block includes prediction samples in a spatial domain (or pixel domain).
  • the predicted block is derived equally from an encoding device and a decoding device, and the encoding device decodes information (residual information) about the residual between the original block and the predicted block, not the original sample value itself of the original block. Signaling to the device can improve video coding efficiency.
  • the decoding apparatus may derive a residual block including residual samples based on the residual information, and combine the residual block and the predicted block to generate a reconstructed block including reconstructed samples, and reconstruct the reconstructed blocks.
  • a reconstructed picture can be generated.
  • the residual information may be generated through a transform and quantization procedure.
  • the encoding device derives a residual block between the original block and the predicted block, and performs transformation procedures on residual samples (residual sample array) included in the residual block to derive transformation coefficients. And, by performing a quantization procedure on the transform coefficients, the quantized transform coefficients are derived to signal related residual information (via a bitstream) to a decoding apparatus.
  • the residual information may include value information of the quantized transform coefficients, location information, a transform technique, a transform kernel, quantization parameters, and the like.
  • the decoding apparatus may perform an inverse quantization / inverse transformation procedure based on the residual information and derive residual samples (or residual blocks).
  • the decoding apparatus may generate a reconstructed picture based on the predicted block and the residual block.
  • the encoding apparatus may also inverse quantize / inverse transform quantized transform coefficients for reference for inter prediction of a picture to derive a residual block, and generate a reconstructed picture based thereon.
  • FIG. 3 is a diagram for explaining intra prediction based on CCLM according to an embodiment.
  • a cross-component linear model (CCLM) mode may be used as one of the prediction modes.
  • CCLM is a method of predicting a sample value (or pixel value) of a chroma image (or chroma block) based on a sample value of a reconstructed luma image (or luma block), and the correlation between the luma image and the chroma image is It is a method using the high characteristic.
  • intra prediction based on CCLM mode of Cb and Cr chroma images may be performed based on Equation 1 below.
  • Pred c (x, y) means the sample value of the Cb or Cr chroma image to be predicted
  • Rec ' L (x, y) means the sample value of the reconstructed luma block adjusted to the chroma block size
  • (x , y) means the coordinates of the sample.
  • the size of the luma image is twice that of the chroma image, and therefore, a Rec ' L of the chroma block size must be generated through downsampling, thus predating the sample value of the chroma image.
  • Samples of the luma image to be used for c (x, y) may be considered as well as Rec ' L (2x, 2y) and surrounding samples.
  • Rec ' L (x, y) may be derived based on sample values of six neighboring samples as in Equation 2.
  • linear model parameters used when applying CCLM mode Based on the difference between the cross-correlation (cross-correlation) and the average value between the reference sample area or template around the Cb or Cr and the surrounding luma reference area, such as the light shaded area in FIG. Equation 3 of can be derived.
  • Equation 3 t L denotes a neighboring luma reference sample of the luma block corresponding to the current chroma block, t CL denotes a neighboring reference chroma sample of the chroma block to which the current encoding is applied, and (x, y) denotes the sample position. it means.
  • M (A) means the average of A samples in the reference sample area.
  • the reference sample of the luma block may also be derived based on down sampling as shown in Equation 3 above.
  • a basic intra prediction mode for example, the basic intra prediction mode may include a DC mode, a PLANAR mode, and other directional intra prediction modes. Intra) can be performed based on intra prediction. Thereafter, CCLM is applied between the Cb chroma image and the Cr chroma image, and the CCLM applied result can be reflected in the existing prediction block as shown in Equation (3). At this time, it is possible to predict the other using either one of the Cb and Cr chroma images. In one example, when predicting the Cr chroma image using the Cb chroma image, Equation 4 below may be used.
  • pred Cr means the sample value of the final predicted Cr chroma block
  • pre_pred Cr means the sample value of the Cr chroma block predicted through Cr chroma intra prediction mode other than CCLM
  • residual Cb is already coded. It may mean a residual sample value (or residual pixel) of the Cb chroma image.
  • Cb and Cr chroma blocks may be calculated through cross-corelation between neighboring reference sample regions.
  • FIG. 4 is a diagram for explaining intra prediction based on CCLM according to another embodiment.
  • the upper reference sample line of the current (coding) block is located at the boundary of another Coding Tree Unit (CTU), instead of downsampling according to Equation 2, immediately above the current block as in Equation 5 below.
  • Reference sample down-sampling may be performed using only one reference sample line.
  • down-sampling of the samples of the luma block for CCLM uses 6 samples (or pixels), but in one embodiment according to Equation 5, the upper reference sample line of the current block is a different CTU. When located at the boundary of (or overlapping with the boundary of another CTU), downsampling may be performed using three samples of one reference sample line.
  • CCLM prediction can be performed using only one line buffer at the upper CTU boundary, and accordingly (half) the line buffer used at the upper CTU boundary.
  • the anchor of the experiment may be software in which CCLM technology is added to VTM1.0, and represents a result of encoding an image with an All Intra setting.
  • a CCLM mode may be applied based on a down sampling method such as Equation 6 or Equation 7 below.
  • the downsampling methods according to Equations 2 and 5 to 7 can be applied to the CCLM mode, which is a chroma intra prediction mode, and the chroma blocks predicted through the CCLM mode are different from the original image in the encoding device (or encoder). It may be used when acquiring a residual image (or residual image) through or may be used when acquiring a reconstructed image based on the sum of the residual signal (or residual signal) in the decoding device (or decoder).
  • FIG. 5 is a flowchart illustrating an intra prediction process based on CCLM according to an embodiment.
  • the decoding apparatus 200 may generate a down-sampled luma template. At this time, the decoding apparatus 200 determines whether the upper boundary of the current block overlaps the boundary of the CTU, and when the upper boundary of the current block overlaps the boundary of the CTU, generates an upper luma template based on 1-line down sampling. And, if the upper boundary of the current block does not overlap with the boundary of the CTU, an upper luma template may be generated based on 2-line down sampling. The decoding apparatus 200 may generate a left luma template based on 2-line down sampling.
  • Decoding apparatus 200 is a linear parameter model coefficient And Can be derived, a down-sampled luma block can be generated, and CCLM prediction can be performed based on Equation 1 above.
  • FIG. 6 is a diagram illustrating an example of a hardware pipeline of intra prediction based on CCLM according to an embodiment.
  • a method of removing correlation between sample lines of a block when downsampling a reconstructed luma image is proposed.
  • CCLM is a method of predicting a sample value of a chroma block using a sample value of a restored luma block
  • CCLM prediction of a chroma block may not be possible before the encoding of the luma block at the same location is completed.
  • FIG. 6 shows an example of a hardware pipeline with or without CCLM prediction in an 8x4 intra prediction block.
  • prediction and restoration of luma samples are performed in units of 4x1, and since 2 clocks are required to decode a 4x1 block, a total of 16 clocks may be required to decode all 8x4 block of luma samples. If there is no correlation between the luma and chroma images, the luma and chroma images are simultaneously decoded, so the decoding of the chroma images can be completed when the clock corresponding to half of the luma images (8 clocks in the example of FIG. 6) elapses. have.
  • CCLM when the CCLM algorithm is applied, after the encoding of the 2-sample lines of the luma block is completed by the correlation between the sample lines (line 4x1 in FIG. 6), CCLM can be applied to the 1-sample line of the chroma block. Therefore, even when the encoding of the luma block is finished, a 4 clock delay may occur for encoding of the chroma block.
  • FIG. 7 is a diagram illustrating an example of a hardware pipeline of intra prediction based on CCLM according to another embodiment.
  • a method of reducing clock delay of a hardware pipeline by removing correlation between sample lines may be provided.
  • down-sampling of the reconstructed luma block may be performed based on the following Equation 8, Equation 9, Equation 10, or Equation 11.
  • the downsampling proposed by Equations 8 to 11 above may be applied to an area except for the current peripheral reference sample area (or peripheral template area).
  • optimization of a hardware pipeline may be performed as shown in FIG. 7.
  • one sample line of the luma block can immediately decode the chroma block after the decoding is completed (No. 2 4x1 line in FIG. 7), and finally the third sample line of the luma block is After the decoding is completed (line 6 4x1 in FIG. 7), decoding of the second sample line of the chroma block may be performed.
  • the clock delay problem between the luma block and the chroma block can be solved through the method proposed in this embodiment, and through this, the disadvantages of the CCLM hardware implementation can be compensated.
  • the method proposed in this patent can be used in the CCLM mode, which is a chroma intra prediction mode, and the chroma block predicted through the CCLM mode is used when acquiring a residual image through a difference from the original image in the encoder, or a residual signal in the decoder It can be used when acquiring the reconstructed image through the sum of.
  • the CCLM mode which is a chroma intra prediction mode
  • the chroma block predicted through the CCLM mode is used when acquiring a residual image through a difference from the original image in the encoder, or a residual signal in the decoder It can be used when acquiring the reconstructed image through the sum of.
  • FIG. 8 is a flowchart illustrating an intra prediction process based on CCLM according to another embodiment.
  • the decoding apparatus 200 may generate a down-sampled luma template, which is a linear parameter model coefficient And Can be derived.
  • the decoding apparatus 200 may generate a down-sampled luma block. At this time, the decoding apparatus 200 may generate a luma sample based on 1-line down sampling.
  • the decoding apparatus 200 may perform CCLM prediction based on Equation 1 above.
  • FIG. 9 is a diagram illustrating an example of a hardware pipeline of intra prediction based on CCLM according to another embodiment.
  • hardware pipeline optimization may be performed when the CCLM mode is applied in intra prediction, but clock delay may occur when the horizontal length of the luma block is 4.
  • FIG. 9 an example of a hardware pipeline with or without CCLM prediction in a luma 4x4 intra prediction block is shown.
  • the correlation between the sample lines is also removed when down-sampling the reconstructed luma block is applied by applying the method according to the embodiment of FIG. 7, but it can be confirmed that a delay of 2 clocks still occurs.
  • the CCLM Suggests a method that does not apply. That is, it is possible to solve the hardware incompatibility problem of CCLM by removing the clock delay, which is a problem in hardware implementation.
  • the anchor of the experiment may be software with CCLM technology added to VTM1.0, and represents a result of encoding an image with an all-intra setting.
  • the method proposed in the embodiment according to FIG. 7 and the embodiment according to FIG. 9 can be applied to the CCLM mode, which is a chroma intra prediction mode, and the chroma block predicted through the CCLM mode is an original image in an encoding device (or encoder). It can be used when acquiring a residual image (or residual image) through a difference from or, or when a reconstructed image is obtained based on a sum of a residual signal (or residual signal) in a decoding device (or a decoder). have.
  • FIG. 10 is a flowchart illustrating an intra prediction process based on CCLM according to another embodiment.
  • the decoding apparatus 200 generates a down-sampled luma template when the horizontal length (or width, width, etc.) of the luma block is not 4, and is a linear parameter model coefficient And Can be derived, a down-sampled luma block can be generated, and CCLM prediction can be performed based on Equation 1 above.
  • the horizontal length (or width, width, etc.) of the luma block is 4, the above-described procedure (down-sampled luma template is generated, and the linear parameter model coefficient is And And a procedure for generating a down-sampled luma block and performing CCLM prediction based on Equation 1) may be omitted.
  • FIG. 11 is a diagram illustrating an intra prediction process based on CCLM according to another embodiment.
  • One embodiment proposes a method for limiting the reference sample line when the upper reference sample line of the current (coding) block is located at the boundary of another luma / chroma block separation unit block.
  • the luma block and the chroma block may be separated to perform encoding and decoding.
  • the size of the luma / chroma block separation unit block may be 64 ⁇ 64, but the example is not limited thereto.
  • the luma / chroma block separation unit block may also be referred to as Virtual Pipeline Data Units (VPDU).
  • VPDU Virtual Pipeline Data Units
  • the reconstructed luma reference sample for CCLM may not be used at the upper boundary of the luma / chroma block separation unit block. That is, as illustrated in FIG. 11, by using only the left reference sample line for CCLM at the upper boundary of the luma / chroma block separation unit block, it is possible to prevent a duplicate issue in hardware pipeline implementation.
  • FIG. 12 is a flowchart illustrating an intra prediction process based on CCLM according to another embodiment.
  • the decoding apparatus 200 may generate a down-sampled luma template. At this time, the decoding apparatus 200 determines whether the upper boundary of the current block overlaps the boundary of the luma / chroma block separation unit block, and the upper boundary of the current block overlaps the boundary of the luma / chroma block separation unit block. If the upper luma template is not generated, and the upper boundary of the current block does not overlap with the boundary of the luma / chroma block separation unit block, the upper luma template may be generated based on 2-line down sampling. The decoding apparatus 200 may generate a left luma template based on 2-line down sampling.
  • Decoding apparatus 200 is a linear parameter model coefficient And Can be derived, a down-sampled luma block can be generated, and CCLM prediction can be performed based on Equation 1 above.
  • FIG. 13 is a flowchart illustrating an operation of an encoding device according to an embodiment
  • FIG. 14 is a block diagram showing a configuration of an encoding device according to an embodiment.
  • the encoding device according to FIGS. 13 and 14 may perform operations corresponding to the decoding device according to FIGS. 15 and 16 to be described later. Therefore, the contents described later in FIGS. 15 and 16 can be applied to the encoding apparatus according to FIGS. 13 and 14 as well.
  • Each step disclosed in FIG. 13 may be performed by the encoding apparatus 100 disclosed in FIG. 1. More specifically, S1300 and S1310 may be performed by the adder 140 disclosed in FIG. 1, S1320 to S1340 may be performed by the predictor 110 disclosed in FIG. 1, and S1350 disclosed in FIG. 1 It may be performed by the residual processing unit 120, and S1360 may be performed by the entropy encoding unit 130 disclosed in FIG. In addition, the operations according to S1300 to S1360 are based on some of the contents described in FIGS. 3 to 12. Accordingly, detailed descriptions that overlap with those described above in FIGS. 1 and 3 to 12 will be omitted or simplified.
  • the encoding apparatus may include a prediction unit 110, a residual processing unit 120, an entropy encoding unit 130, an addition unit 140, and a memory 160. have. However, in some cases, all of the components shown in FIG. 14 may not be essential components of the encoding device, and the encoding device may be implemented by more or less components than those shown in FIG. 14.
  • the prediction unit 110, the residual processing unit 120, the entropy encoding unit 130, the addition unit 140, and the memory 160 are implemented as separate chips, respectively. At least two or more components may be implemented through one chip.
  • the encoding apparatus may derive neighboring chroma reference samples for the chroma block (S1300). More specifically, when the intra prediction mode of the chroma block is the CCLM mode, the adder 140 of the encoding device may derive neighboring chroma reference samples for the chroma block.
  • the encoding apparatus may derive neighboring luma reference samples of the luma block corresponding to the chroma block and luma samples in the luma block (S1310). More specifically, the prediction unit 110 of the encoding apparatus may derive neighboring luma reference samples of the luma block corresponding to the chroma block and luma samples in the luma block.
  • the encoding apparatus may down-sample the peripheral luma reference samples and the luma samples to derive down-sampled peripheral luma reference samples and down-sampled luma samples (S1320). More specifically, the prediction unit 110 of the encoding apparatus may down-sample the peripheral luma reference samples and the luma samples to derive down-sampled peripheral luma reference samples and down-sampled luma samples.
  • the peripheral luma reference samples may include upper peripheral luma reference samples located above the upper boundary of the luma block and left peripheral luma reference samples located to the left of the left boundary of the luma block.
  • the down-sampled peripheral luma reference samples may include a down-sampled left peripheral luma reference sample and a down-sampled upper peripheral luma reference sample.
  • a single line buffer in the memory of the decoding apparatus to derive the down sampled upper peripheral luma reference sample
  • a single line buffer in the memory of the decoding apparatus to derive the down sampled upper peripheral luma reference sample
  • the number of the upper peripheral luma reference samples stored in the single line buffer is three, and the number of the left peripheral luma reference samples stored in the plurality of line buffers may be six.
  • luma samples stored in the single line buffer of the memory may be down sampled to derive the down sampled luma samples.
  • the CCLM mode may not be applied when intra prediction of the chroma block is performed.
  • the CCLM mode may not be applied when intra prediction of the chroma block is performed.
  • the down-sampled upper peripheral luma reference samples may not be derived.
  • the down-sampled upper peripheral luma reference sample is derived based on Equation 12 below,
  • Equation 12 pTopDsY [x] represents the down-sampled upper peripheral luma reference sample, x represents the down-sampled upper peripheral luma reference sample in the x-axis direction position, and pY [2 * x-1] [ -1], pY [2 * x] [-1] and pY [2 * x + 1] [-1] represent sample values of the upper peripheral luma reference samples, respectively, and the y-axis of the upper peripheral luma reference samples The direction position may be -1.
  • the encoding apparatus may derive a linear model parameter based on the down-sampled peripheral luma reference samples and the peripheral chroma reference samples (S1330). More specifically, the prediction unit 110 of the encoding apparatus may derive a linear model parameter based on the down-sampled peripheral luma reference samples and the peripheral chroma reference samples.
  • the encoding apparatus may generate prediction samples for the chroma block based on the linear model parameter and the down-sampled luma samples of the luma block (S1340). More specifically, the prediction unit 110 of the encoding apparatus may generate prediction samples for the chroma block based on the linear model parameter and the down-sampled luma samples of the luma block.
  • the encoding apparatus may derive residual samples for the chroma block based on the prediction samples for the chroma block (S1350). More specifically, the residual processing unit 120 of the encoding device may derive residual samples for the chroma block based on the prediction samples for the chroma block.
  • the encoding apparatus may encode picture information including information on the residual samples (S1360). More specifically, the entropy encoding unit 130 of the encoding device may encode picture information including information about the residual samples.
  • the encoding apparatus derives peripheral chroma reference samples for the chroma block when the intra prediction mode of the chroma block is the CCLM mode (S1300), Peripheral luma reference samples of the luma block corresponding to the chroma block and luma samples in the luma block are derived (S1310), and the down-sampled peripheral luma reference samples are downsampled by down-sampling the luma reference samples and the luma samples, and Deriving down-sampled luma samples (S1320), deriving a linear model parameter based on the down-sampled peripheral luma reference samples and the peripheral chroma reference samples (S1330), and down-loading the linear model parameters and the luma block Create predictive samples for the chroma block based on the sampled luma samples, (S1340), deriving residual samples for the chrom
  • the samples include a down sampled left peripheral luma reference sample and a down sampled upper peripheral luma reference sample, and when the upper boundary of the luma block overlaps a boundary of a coding tree unit (CTU), the down sampling An image stored in a single line buffer in the memory of the decoding device to derive an upper peripheral luma reference sample
  • Upper peripheral luma reference samples and the down-sampling, to derive the down-sampled left around the luma reference sample may be characterized in that the downsampling of the left around the luma reference samples stored in a plurality of line buffers in the memory.
  • image coding efficiency can be increased by down-sampling the peripheral luma reference samples of the 1-sample line, and when implementing intra prediction based on CCLM in hardware, a pipeline delay is implemented. Can improve. More specifically, when the upper boundary of the luma block overlaps the boundary of a coding tree unit (CTU), the upper peripheral luma stored in a single line buffer of the decoding apparatus memory to derive a down-sampled upper peripheral luma reference sample. Memory efficiency can be increased by downsampling the reference samples.
  • CTU coding tree unit
  • FIG. 15 is a flowchart illustrating an operation of a decoding apparatus according to an embodiment
  • FIG. 16 is a block diagram showing a configuration of a decoding apparatus according to an embodiment.
  • Each step disclosed in FIG. 15 may be performed by the decoding apparatus 200 disclosed in FIG. 2. More specifically, S1500, S1510 and S1550 may be performed by the adder 240 disclosed in FIG. 2, and S1510 to S1540 may be performed by the predictor 230 disclosed in FIG. 2. In addition, the operations according to S1500 to S1550 are based on some of the contents described in FIGS. 3 to 12. Therefore, detailed descriptions that overlap with those described above in FIGS. 2 to 12 will be omitted or simplified.
  • the decoding apparatus may include a prediction unit 230, an adder 240, and a memory 260. However, in some cases, all of the components shown in FIG. 16 may not be essential components of the decoding apparatus, and the decoding apparatus may be implemented by more or fewer components than those shown in FIG. 16.
  • the prediction unit 230, the adding unit 240, and the memory 260 may be implemented as separate chips, or at least two or more components may be implemented through one chip. have.
  • the decoding apparatus may derive neighboring chroma reference samples for the chroma block when the intra prediction mode of the chroma block is the CCLM mode (S1600). More specifically, when the intra prediction mode of the chroma block is the CCLM mode, the adder 140 of the decoding apparatus may derive (or reconstruct) neighboring chroma reference samples for the chroma block.
  • the decoding apparatus may derive neighboring luma reference samples of the luma block corresponding to the chroma block and luma samples in the luma block (S1610). More specifically, the prediction unit 230 and / or the adder 240 of the decoding apparatus may derive neighboring luma reference samples of the luma block corresponding to the chroma block and luma samples in the luma block.
  • the decoding apparatus may down-sample the peripheral luma reference samples and the luma samples to derive down-sampled peripheral luma reference samples and down-sampled luma samples (S1620). More specifically, the prediction unit 230 of the decoding apparatus may down-sample the peripheral luma reference samples and the luma samples to derive down-sampled peripheral luma reference samples and down-sampled luma samples.
  • the peripheral luma reference samples may include upper peripheral luma reference samples located above the upper boundary of the luma block and left peripheral luma reference samples located to the left of the left boundary of the luma block.
  • the down-sampled peripheral luma reference samples may include a down-sampled left peripheral luma reference sample and a down-sampled upper peripheral luma reference sample.
  • a single line buffer in the memory of the decoding apparatus to derive the down sampled upper peripheral luma reference sample
  • a single line buffer in the memory of the decoding apparatus to derive the down sampled upper peripheral luma reference sample
  • the number of the upper peripheral luma reference samples stored in the single line buffer is three, and the number of the left peripheral luma reference samples stored in the plurality of line buffers may be six.
  • luma samples stored in the single line buffer of the memory may be down sampled to derive the down sampled luma samples.
  • the CCLM mode may not be applied when intra prediction of the chroma block is performed.
  • the CCLM mode may not be applied in intra prediction of the chroma block.
  • the down-sampled upper peripheral luma reference samples may not be derived.
  • the used to derive the down-sampled peripheral luma reference samples among the peripheral luma reference samples may be less than the number of left peripheral luma reference samples used to derive the down sampled peripheral luma reference samples.
  • the upper peripheral luma reference samples may be included in a horizontal 1-sample line above the luma block.
  • the left peripheral luma reference samples may be included in a plurality of horizontal or vertical sample lines to the left of the luma block.
  • the left peripheral luma reference samples may be included in horizontal 2-sample lines to the left of the luma block, or may be included in vertical 3-sample lines to the left of the luma block, and examples are not limited thereto.
  • the down-sampled peripheral luma reference samples include down-sampled left peripheral luma reference samples and down-sampled upper peripheral luma reference samples, wherein the upper boundary of the luma block is the boundary of the CTU.
  • the number of the upper peripheral luma reference samples used to derive one down-sampled upper peripheral luma reference sample is three, and the left peripheral used to derive one down-sampled left peripheral luma reference sample.
  • the number of luma reference samples can be characterized as six.
  • the three upper peripheral luma reference samples are coordinates (2 * x-1, -1), (2), respectively.
  • the three upper peripheral luma reference samples are coordinates (-1, -1), (0, -1), respectively. ) And (1, -1).
  • the down-sampled upper peripheral luma reference sample is derived based on Equation 13 below,
  • Equation 13 pTopDsY [x] represents the down-sampled upper peripheral luma reference sample, x represents the down-sampled upper peripheral luma reference sample in the x-axis direction position, and pY [2 * x-1] [ -1], pY [2 * x] [-1] and pY [2 * x + 1] [-1] represent sample values of the upper peripheral luma reference samples, respectively, and the y-axis of the upper peripheral luma reference samples The direction position may be -1.
  • whether the upper boundary of the luma block overlaps the boundary of the CTU is determined based on whether Equation 14 below is TRUE or FALSE,
  • Equation 14 yCbC represents a y-axis position of the upper left sample of the current block with respect to the upper left sample of the current picture, and CtbLog2SizeY can represent a logarithmic value of luma CTB size.
  • a sample of the down-sampled upper peripheral luma reference sample when the x-axis position of the down-sampled upper peripheral luma reference sample is 0
  • pTopDsY [0] represents the sample value of the down-sampled upper peripheral luma reference sample when the x-axis direction position of the down-sampled upper peripheral luma reference sample is 0, and pY [-1] [ -1], pY [0] [-1] and pY [1] [-1] respectively represent sample values of the upper peripheral luma reference samples, and the y-axis position of the upper peripheral luma reference samples is -1 day You can.
  • the down-sampled upper peripheral luma reference sample may be derived based on Equation 13.
  • Equation 14 when the x-axis direction position of the down-sampled upper peripheral luma reference sample is 0, the sample value of the down-sampled upper peripheral luma reference sample is Equation 15 It can be derived based on.
  • the linear model parameter may include a first linear model parameter indicating a scaling factor and a second linear model parameter indicating an offset.
  • the decoding apparatus may derive a linear model parameter based on the down-sampled neighboring luma reference samples and the neighboring chroma reference samples (S1630). More specifically, the prediction unit 230 of the decoding apparatus may derive a linear model parameter based on the down-sampled peripheral luma reference samples and the peripheral chroma reference samples.
  • the decoding apparatus may generate prediction samples for the chroma block based on the linear model parameter and the down-sampled luma samples of the luma block (S1640). More specifically, the prediction unit 230 of the decoding apparatus may generate prediction samples for the chroma block based on the linear model parameter and the down-sampled luma samples of the luma block.
  • the decoding apparatus may reconstruct the chroma block based on the prediction samples for the chroma block (S1650). More specifically, the adder 240 of the decoding apparatus may reconstruct the chroma block based on the prediction samples for the chroma block.
  • intra prediction based on the CCLM described above in this specification may be implemented according to, for example, the following English specification.
  • This embodiments provides the experimental results of CCLM line buffer restriction Experimental results from All Intra configuration show 0.01%, 0.01%, and 0.04% bit-rate increase compared to VTM2.0.1 on Y, Cb, and Cr components, respectively.
  • the CCLM (cross-component linear model) method in the current VVC specification always uses 2 lines of reconstructed luma reference samples to get the down-sampled collocated luma.
  • this proposal to avoid the line buffer increase in the intra prediction, only one luma line (general line buffer in intra prediction) is used to make the downsampled luma samples when the upper reference line is at the CTU boundary.
  • the proposed method has been implemented using BMS-2.0.1 as software base and experimentally evaluated for VTM test according to the common test conditions defined in JVET-K1010 and Core Experiment description in JVET-K1023.
  • VTM the VTM configuration was enabled.
  • Table 3 and Table 4 show the test results in AI and RA configuration.
  • the current luma location (xTbY, yTbY) is derived as follows:
  • variable bCTUboudary is derived as follows:
  • pLeftDsY [y] (pY [-1] [2 * y] + pY [-1] [2 * y + 1] + 2 * pY [-2] [2 * y] + 2 * pY [-2] [2 * y + 1] + pY [-3] [2 * y] + pY [-3] [2 * y + 1] + 4) >> 3
  • nS, xS, yS, k0, k1 are derived as follows:
  • nS ((availL && availT)? Min (nTbW, nTbH): (availL? nTbH: nTbW))
  • variable l, c, ll, lc and k1 are modified as follows
  • a1 lc-((avgY * avgC) ⁇ k1 + avgY * errC + avgC * errY)
  • a2 ll-((avgY2) ⁇ k1 + 2 * avgY * errY)
  • a2t (a2s ⁇ 32)? 0: ((1 ⁇ (BitDepthY + 4)) + a2s / 2) / a2s
  • a4 Clip3 (-28, 28 -1, a3)
  • Equation 16 whether the upper boundary of the luma block overlaps the boundary of the CTU may be determined based on whether Equation 16 is TRUE or FALSE, and in Equation 16, yCbC is the upper left of the current chroma picture.
  • the y-axis position of the upper left sample of the current chroma block with respect to the sample may be indicated, and CtbLog2SizeY may indicate a log value of the luma CTB size.
  • Equation 17 is as follows.
  • Equation 17 pTopDsY [x] represents the sample value of the luma reference sample to which the downsampling is applied, located above the upper boundary of the luma block, and x represents the x-axis position of the luma reference sample to which the downsampling is applied.
  • pY [2 * x-1] [-1] pY [2 * x] [-1]
  • pY [2 * x + 1] [-1] respectively indicate the sample values of the luma reference samples located at the upper side.
  • the y-axis position of the luma reference samples located on the upper side is -1.
  • Equation 17 when the value of x is 0 and the sample value pY [-1] [-1] is present, Equation 17 may be expressed as Equation 18 below.
  • pTopDsY [0] refers to the luma to which the down-sampling is located above the upper boundary when the x-axis direction position of the down-sampled luma reference sample located above the upper boundary is 0.
  • the sample value of the sample, pY [-1] [-1], pY [0] [-1] and pY [1] [-1] respectively indicate the sample values of the luma reference samples located above,
  • the y-axis position of the upper luma reference samples is -1.
  • Equation 17 when the value of x is 0 and the sample value of pY [-1] [-1] does not exist, Equation 17 may be expressed as Equation 19 below.
  • Equation 19 pTopDsY [0] is applied to the downsampling located above the upper boundary when the x-axis direction position of the luma reference sample to which the downsampling located above the upper boundary of the luma block is 0 is applied.
  • the sample value of the luma reference sample is represented, and
  • pY [0] [-1] represents the sample value of the luma reference sample located above the luma block.
  • the decoding apparatus when the intra prediction mode of the chroma block is a cross-component linear model (CCLM) mode, the decoding apparatus derives neighboring chroma reference samples for the chroma block And (S1600), deriving the luma samples in the luma block and the luma samples in the luma block corresponding to the chroma block (S1610), and down-sampling the neighboring luma reference samples and the luma samples.
  • CCLM cross-component linear model
  • the left peripheral luma reference samples located on the left side of the left boundary of the luma block, and the down sampled peripheral luma reference samples include a down sampled left peripheral luma reference sample and a down sampled upper peripheral luma reference sample.
  • the upper boundary of the luma block overlaps a boundary of a coding tree unit (CTU)
  • CTU coding tree unit
  • image coding efficiency can be increased by down-sampling the peripheral luma reference samples of the 1-sample line, and when implementing intra prediction based on CCLM in hardware, a pipeline delay is implemented. Can improve. More specifically, when the upper boundary of the luma block overlaps the boundary of a coding tree unit (CTU), the upper peripheral luma stored in a single line buffer of the decoding apparatus memory to derive a down-sampled upper peripheral luma reference sample. Memory efficiency can be increased by downsampling the reference samples.
  • CTU coding tree unit
  • the above-described method according to the present invention can be implemented in software form, and the encoding device and / or decoding device according to the present invention performs image processing such as TV, computer, smartphone, set-top box, display device, etc. Device.
  • Each of the above-described parts, modules, or units may be a processor or a hardware part that executes continuous execution processes stored in a memory (or storage unit). Each of the steps described in the above-described embodiment may be performed by a processor or hardware parts. Each module / block / unit described in the above-described embodiment can operate as a hardware / processor. Also, the methods proposed by the present invention can be executed as code. This code can be written to a storage medium that can be read by a processor, and thus can be read by a processor provided by an apparatus.
  • the above-described method may be implemented as a module (process, function, etc.) that performs the above-described functions.
  • Modules are stored in memory and can be executed by a processor.
  • the memory may be internal or external to the processor, and may be connected to the processor by various well-known means.
  • the processor may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and / or data processing devices.
  • the memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media and / or other storage devices.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)

Abstract

La présente invention concerne un procédé de décodage d'image, exécuté par un appareil de décodage. Le procédé comprend les étapes consistant à : lorsqu'un mode de prédiction intra d'un bloc de chrominance est un modèle linéaire à composante transversale (CCLM), dériver des échantillons de référence de chrominance voisins par rapport au bloc de chrominance ; dériver des échantillons de référence de luminance voisins d'un bloc de luminance correspondant au bloc de chrominance et à des échantillons de luminance dans le bloc de luminance ; dériver des échantillons de référence de luminance voisins sous-échantillonnés et des échantillons de luminance sous-échantillonnés par sous-échantillonnage des échantillons de référence de luminance voisins et des échantillons de luminance, respectivement ; dériver un paramètre de modèle linéaire sur la base des échantillons de référence de luminance voisins sous-échantillonnés et des échantillons de référence de chrominance voisins ; générer des échantillons de prédiction par rapport au bloc de chrominance sur la base du paramètre de modèle linéaire et des échantillons de luminance sous-échantillonnés du bloc de luminance ; et reconstruire le bloc de chrominance sur la base des échantillons de prédiction par rapport au bloc de chrominance.
PCT/KR2019/007586 2018-10-04 2019-06-24 Procédé d'intra-prédiction basée sur un cclm et appareil associé Ceased WO2020071617A1 (fr)

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US20150085931A1 (en) * 2013-09-25 2015-03-26 Apple Inc. Delayed chroma processing in block processing pipelines
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