Scaling process for joint chroma coded blocks

Abstract

The present invention relates to demultiplexing the Cb channel and the Cr channel in a video bitstream before dequantization rather than after inverse transform. In this way, conventional Cb and Cr quantization control parameters can be used, optionally with minor adjustments when the video block is jointly chroma encoded. In one embodiment, some specific quantization control parameters can be specified. In another embodiment, separate Cb offsets and Cr offsets can be specified for the joint chroma encoding block. In another embodiment, quantization control parameters specific to the joint chroma editing block can be used for both the Cb channel and the Cr channel, rather than the nominal chroma quantization parameters.

Description

Technical Field

[0001] At least one of the embodiments herein generally relates to a method or an apparatus for video encoding or decoding, compression or decompression. Background Art

[0002] To achieve high compression efficiency, image and video coding schemes typically use prediction, including motion vector prediction, and transforms to exploit spatial and temporal redundancy in video content. In general, intra-frame or inter-frame prediction is used to exploit intra-frame or inter-frame correlations, and then the difference between the original image and the predicted image (usually expressed as a prediction error or prediction residual) is transformed, quantized, and entropy encoded. To reconstruct the video, the compressed data is decoded by the inverse process corresponding to entropy coding, quantization, transform, and prediction. Summary of the invention

[0003] At least one of the embodiments of the present invention generally relates to a method or apparatus for video encoding or decoding, and more particularly to a method or apparatus for simplifying a coding mode based on neighboring sample dependent parameters.

[0004] According to a first aspect, a method is provided. The method comprises the following steps: when encoding joint Cb / Cr for a video block, demultiplexing Cb and Cr from the video block; dequantizing the demultiplexed Cb and Cr data; inverse transforming the dequantized Cb and Cr data; and decoding the video block using the inverse transformed Cb and Cr data.

[0005] According to a first aspect, a method is provided. The method comprises the following steps: parsing a video bitstream and scaling Cb and Cr for a video block; dequantizing the demultiplexed Cb and Cr data; inverse transforming the dequantized Cb and Cr data; and decoding the video block using the inverse transformed Cb and Cr data.

[0006] According to another aspect, a device is provided. The device includes a processor. The processor can be configured to encode a video block or decode a bitstream by executing any one of the aforementioned methods.

[0007] According to another general aspect of at least one embodiment, there is provided an apparatus comprising: an apparatus according to any of the embodiments in the decoding implementation; and at least one of the following items: (i) an antenna configured to receive a signal, the signal including a video block; (ii) a band limiter configured to limit the received signal to a frequency band including the video block; and (iii) a display configured to display an output representing the video block.

[0008] According to another general aspect of at least one embodiment, there is provided a non-transitory computer-readable medium containing data content generated according to any of the described encoding embodiments or variations.

[0009] According to another general aspect of at least one embodiment, there is provided a signal comprising video data generated according to any of the described encoding embodiments or variants.

[0010] According to another general aspect of at least one embodiment, a bitstream is formatted to include data content generated according to any of the described encoding embodiments or variations.

[0011] According to another general aspect of at least one embodiment, there is provided a computer program product comprising instructions which, when executed by a computer, cause the computer to perform any of the described coding embodiments or variations.

[0012] These and other aspects, features and advantages of the general aspects will become apparent from the following detailed description of exemplary embodiments, which is to be read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The scaling and transform function diagrams are shown.

[0014] Figure 2 A diagram of the dequantization function is shown.

[0015] Figure 3 A functional diagram of quantization parameter derivation is shown.

[0016] Figure 4 A diagram showing the scaling and transform functions for joint chroma coding.

[0017] Figure 5 The residual block decoding process of the current coding scheme is shown.

[0018] Figure 6 A standard general purpose video compression scheme is shown.

[0019] Figure 7 A standard general purpose video decompression scheme is shown.

[0020] Figure 8 A diagram showing the scaling and transform functions used for joint chroma coding in the described aspect is shown.

[0021] Fig. 9 The proposed residual block decoding process is shown.

[0022] Fig.10 A processor-based system for encoding / decoding is shown in a generally described context.

[0023] Fig.11 One embodiment of the method is shown in the context of the generally described aspects.

[0024] Fig.12 A further embodiment of the method within the generally described context is shown.

[0025] Fig.13 An exemplary apparatus is shown in the context of the described aspects.

[0026] Fig.14 Coding tree units and coding tree concepts for representing compressed HEVC pictures are shown.

[0027] Fig.15 An exemplary partitioning of coding tree units into coding units, prediction units and transform units is shown.

[0028] Fig.16 An exemplary quadtree plus binary tree (QTBT) CTU representation is shown. DETAILED DESCRIPTION

[0029] The embodiments described herein belong to the field of video compression and generally relate to video compression and video encoding and decoding, and more specifically to the quantization step of video compression schemes. The general aspects described are intended to provide a mechanism for manipulating restrictions in high-level video coding syntax or video coding semantics to constrain the set of possible tool combinations.

[0030] To achieve high compression efficiency, image and video coding schemes typically use prediction, including motion vector prediction, and transforms to exploit spatial and temporal redundancy in video content. In general, intra-frame or inter-frame prediction is used to exploit intra-frame or inter-frame correlations, and then the difference between the original image and the predicted image (usually expressed as a prediction error or prediction residual) is transformed, quantized, and entropy encoded. To reconstruct the video, the compressed data is decoded by the inverse process corresponding to entropy coding, quantization, transform, and prediction.

[0031] In the HEVC (High Efficiency Video Coding, ISO / IEC 23008-2, ITU-T H.265) video compression standard, motion compensated temporal prediction is used to exploit the redundancy existing between consecutive pictures of a video.

[0032] To this end a motion vector is associated with each prediction unit (PU). Each coding tree unit (CTU) is represented by a coding tree in the compressed domain. This is a quadtree partitioning of the CTU, where each leaf is called a coding unit (CU).

[0033] Then, each CU is given some intra or inter prediction parameters (prediction information). To do this, it is spatially partitioned into one or more prediction units (PUs), each of which is assigned some prediction information. Intra or inter coding modes are assigned at the CU level.

[0034] In JVET (Joint Video Exploration Team) which is proposing a new video compression standard called Joint Exploration Model (JEM), it has been proposed to accept a Quadtree Binary Tree (QTBT) block partition structure due to high compression performance. A block in a binary tree (BT) can be divided into two equal-sized sub-blocks by splitting horizontally or vertically in the middle. Therefore, a BT block can have a rectangular shape with unequal width and height, which is different from a block in QT, where a block has a shape that is always square with equal height and width. In HEVC, the angular intra prediction direction is defined as spanning 180 angles from 45 degrees to -135 degrees, and the angular intra prediction direction is maintained in the JEM, which defines the angular direction independently of the target block shape.

[0035] To encode these blocks, intra prediction is used to provide an estimated version of the block using previously reconstructed neighboring samples. The difference between the source block and the prediction is then encoded. In the classical codecs described above, a single line of reference samples is used at the left and top of the current block.

[0036] In HEVC (High Efficiency Video Coding, H.265), frames of a video sequence are encoded based on a quadtree (QT) block partition structure. Based on the rate-distortion (RD) criterion, the frame is divided into square coding tree units (CTUs), which are all subjected to quadtree-based partitioning into multiple coding units (CUs). Each CU is intra-predicted, that is, each CU is spatially predicted from a causally adjacent CU, or inter-predicted, that is, each CU is temporally predicted from an already decoded reference frame. In I slices, all CUs are intra-predicted, while in P slices and B slices, CUs can be both intra-predicted or inter-predicted. For intra prediction, HEVC defines 35 prediction modes, which include one plane mode (indexed as mode 0), one DC mode (indexed as mode 1), and 33 angular modes (indexed as mode 2 to mode 34). The angular mode is associated with a prediction direction ranging from 45 degrees to -135 degrees in the clockwise direction. Since HEVC supports a quadtree (QT) block partition structure, all prediction units (PUs) have a square shape. Therefore, the definition of the prediction angle from 45 degrees to -135 degrees is confirmed from the perspective of the PU (prediction unit) shape. For a target prediction unit of NxN pixel size, the top reference array and the left reference array are each 2N+1 samples, which need to cover the aforementioned angle range of all target pixels. Considering that the height and width of the PU are equal in length, it also makes sense that the lengths of the two reference arrays are equal.

[0037] The present invention belongs to the field of video compression. Compared with existing video compression systems, the present invention aims to improve the bi-prediction in inter-frame coding blocks. The present invention also proposes separate luminance and chrominance coding trees for inter-frame slices.

[0038] In the HEVC video compression standard, pictures are divided into so-called coding tree units (CTUs), which are usually 64×64, 128×128 or 256×256 pixels in size. Each CTU is represented by a coding tree in the compressed domain. This is a quadtree partitioning of the CTU, where each leaf is called a coding unit (CU), see Fig.14 .

[0039] Then, each CU is given some intra-frame or inter-frame prediction parameters (prediction information). To this end, it is spatially partitioned into one or more prediction units (PUs), each of which is assigned some prediction information. Intra-frame or inter-frame coding modes are assigned at the CU level, see Fig.15 .

[0040] New emerging video compression tools are proposed including a coding tree unit representation in the compressed domain to represent picture data in a more flexible way in the compressed domain. The advantage of this more flexible representation of the coding tree is that it provides increased compression efficiency compared to the CU / PU / TU arrangement of the HEVC standard.

[0041] The Quadtree plus Binary Tree (QTBT) coding tool provides this increased flexibility. It contains a coding tree where the coding unit can be partitioned in a quadtree and binary tree manner. Fig.16 Such a coding tree representation of a coding tree unit is shown.

[0042] The decision to partition the coding units on the encoder side is made through a rate-distortion optimization procedure that involves determining the QTBT representation of the CTU at a minimum rate-distortion cost.

[0043] In QTBT technology, the CU has a square or rectangular shape. The size of the coding unit is always a power of 2 and is usually from 4 to 128.

[0044] In addition to the various rectangular shapes of the coding units, the new CTU representation has the following different characteristics compared to HEVC.

[0045] The QTBT decomposition of a CTU consists of two stages: first, the CTU is split in a quadtree fashion, and then each quadtree leaf can be further divided in a binary fashion. Fig.16 , where the solid line represents the quadtree decomposition stage and the dashed line represents the binary decomposition spatially embedded in the leaves of the quadtree.

[0046] The general aspects described herein belong to the field of video compression. A video codec consists of a combination of multiple encoding tools. It is common practice to standardize the decoder side (syntax and decoding process).

[0047] exist Figure 1 A general functional diagram of the scaling (or dequantization) and transform process in current coding schemes (e.g., such as VVC Proposal 6) is shown in FIG, where the coding coefficients of a given transform block (TransCoeffLevel) are dequantized (Dequant) to give scaled transform coefficients (d) and then inverse transformed (T -1 ), generate the residual samples (res) of the block.

[0048] Figure 2 The dequantization part is shown in FIG.

[0049] As in HEVC, the scaling (or dequantization) process of VVC consists of scaling the transformed coefficients by the quantization step qStep and the quantization matrix m[][], thereby producing dequantized coefficients d[][]. This is detailed in the following equation (for simplicity, ignoring quantization-dependent features and other minor variations):

[0050] d[x][y]=Clip3(coeffMin,coeffMax,

[0051] ((TransCoeffLevel[xTbY][yTbY][cIdx][x][y]*m[x][y]*

[0052] levelScale[qP%6]<<(qP / 6))+(1<<(bdShift-1)))>>bdShift)

[0053] in:

[0054] • TransCoeffLevel[...] is the absolute value of the transformed coefficient of the current block identified by its spatial coordinates xTbY, yTbY and its component index cIdx.

[0055] x and y are the horizontal / vertical frequency indices.

[0056] qP is the current quantization parameter.

[0057] Multiplying by levelScale[qP%6] and left offset (qP / 6) is equivalent to multiplying by the quantization step qStep =

[0058] (levelScale[qP%6]<<(qP / 6))

[0059] m[…][…] is a two-dimensional quantization matrix

[0060] bdShift is an additional scaling factor used to take into account the image sample bit depth.

[0061] (bdShift-1)) is used to round to the nearest integer.

[0062] d[…] is the absolute value of the resulting dequantized transformed coefficient

[0063] Quantization control is a combination of syntax used to control the QP and quantization matrix for a specific coding block.

[0064] • The quantization parameter (QP) depends on various offsets that can be specified at PPS, picture, slice or CU level, depending on the color component.

[0065] Figure 3The functional diagram in Figure 1 shows the QP derivation, where equation (1) is used for luminance and equation (2) is used for

[0066] For chroma, where 'x' in Cx means the current chroma channel.

[0067] Q Y = qP Y_PRED +CuQpDeltaVal, (1)

[0068] where qP Y_PRED Initially set to SliceQpY, and

[0069] SliceQpY=26+init_qp_minus26+slice_qp_delta. Then, qP Y_PRED

[0070] Shared by a group of CUs called a quantization group (QG). Y_PRED Exported as the left and top neighboring blocks of the top left corner of the current quantization group (qP Y_A and qP Y_B )’s average QP: qP Y_PRED =(qP Y_A +qP Y_B +1)>>1, CuQpDeltaVal can be specified once per QG once the transform block has non-zero coefficients.

[0071] Q Cx =ChromaQpTable[x][Qp Y ]+qP Cx +pps_cx_qp_offset+slice_cx_qp_offset

[0072] +CuQpOffset Cx (2)

[0073] A set of quantization matrices may be transmitted in an "adaptive parameter set" referred to in a given slice. Based on the block prediction mode (intra, inter, IBC), color component (Y, Cb, Cr) and block size, an identifier is used to select a quantization matrix from the set, as shown in Table 1, which specifies the identifier of the selected matrix based on the block characteristics. The selected quantization matrix is ​​then rescaled to match the block size.

[0074] Table 1: Quantization matrix identifiers according to block characteristics

[0075]

[0076] The current coding scheme (VVC Proposal 6) describes a joint chroma coded residual feature, where a single chroma channel is coded and the Cb / Cr chroma channels are reconstructed by a sign change (based on a slice level flag) and / or 1 / 2 scaling, depending on the joint chroma mode (TuCResMode), which is derived from the chroma transform block coded block flags tu_cbf_cb and tu_cbf_cr, as shown in Table 2:

[0077] Table 2: Joint chroma coding mode in VVC Proposal 6

[0078]

[0079] The CSign variable of Table 2 is derived as (1-2*pic_joint_cbcr_sign_flag), where pic_joint_cbcr_sign_flag is a syntax element decoded at the picture level.

[0080] Scaling and transformation process Figure 4 The scaling is performed as shown (and as specified in excerpt 8.7.2 pp.282-283 of VVC proposal 6), where a single coded chroma block is dequantized, then inverse transformed, and then separated into a Cb channel and a Cr channel (referred to as demultiplexing in the rest of this document). The "scaling" factor is -1, -1 / 2, +1 / 2, or +1, depending on CSign and TuCResMode, as detailed in Table 2. In this case, the gray portion of the secondary chroma channel, which is typically the secondary chroma channel, is not used. The coded channels and the Cb residual and Cr residual can be swapped according to the joint chroma mode, for simplicity, Figure 4 Not shown in the figure, but described in detail in Table 2.

[0081] Figure 5 The residual block decoding process specified in the current coding scheme is shown. The process is fed with the transform unit (TU) to be decoded and the input bitstream to be parsed.

[0082] • The first step consists in parsing the coded data associated with the considered CU. Specifically, this provides the parsed quantized transform coefficients contained in the residual block of the considered CU, and the joint_cb_cr_flag syntax element, which indicates the use of the joint Cb / Cr residual of the considered TU.

[0083] • Next, if joint_cb_cr_flag is false, the usual inverse quantization and inverse transform steps are performed in sequence, successively and separately for the Cb and Cr transform frames.

[0084] In the opposite case:

[0085] o A single inverse quantization step is applied on the joint Cb / Cr residual signal.

[0086] o Furthermore, a single inverse transform is applied on the inverse quantized joint Cb / Cr residual data. This results in a joint Cb / Cr residual signal decoded in the spatial domain.

[0087] ○ The decoded Cb and Cr are then calculated from the spatial domain decoded joint Cb / Cr residual block. This process depends on the TuCResMode variable associated with the TU and the CSign variable derived at the picture level. The demultiplexing of Cb and Cr follows the specification of Table 2.

[0088] In addition to Cb and Cr, the VVC proposal specifies additional quantization control parameters (chroma QP offset, QP mapping table, etc.) for joint chroma mode. An example of a slice header syntax structure is shown below:

[0089]

[0090] The embodiments presented here propose to move the demultiplexing of Cb residual and Cr residual after transform and before dequantization so that conventional separate Cb and Cr chrominance quantization control parameters (QP offset, quantization matrix) can be used without special joint CbCr quantization control parameters.

[0091] As mentioned above, the current coding scheme (VVC Proposal 6) includes specific quantization control parameters for the joint chroma mode, but not for all parameters: there is no specific quantization matrix (Cb or Cr quantization matrix selected as shown in Table 2). The problem to be solved is to make the quantization control consistent for all chroma coding modes (whether joint or not), while possibly removing the joint chroma coding mode-specific quantization control parameters. This is expected to result in a simpler coding scheme and fewer coded bits.

[0092] When the joint chroma mode is equal to 2 (see TuCResMode in Table 2), a previous proposal ([JVET-P0608]) proposed adding a joint chroma coding specific quantization matrix, where the table is modified as follows:

[0093] Table 7-6 - Specification of matrixId according to sizeId, prediction mode and color component

[0094]

[0095]

[0096] This has the disadvantage of adding more bits to the scaling_list_data syntax for transmitting custom quantization matrices.A second option proposed in JVET-P0608 to avoid transmitting an extra quantization matrix but still use a specific quantization matrix for a jointly chroma coded block is to use the average of the Cb and Cr quantization matrices.

[0097] In the current aspect described herein, the Cb channel and the Cr channel are demultiplexed before dequantization rather than after inverse transform. In this way, conventional Cb and Cr quantization control parameters can be used, optionally with minor adjustments when the current block is jointly chroma coded (e.g., universal QP offset).

[0098] In the current disclosure, the Cb channel and the Cr channel are reconstructed before dequantization rather than after inverse transformation, as shown in FIG. Figure 8 shown.

[0099] Fig. 9 The algorithm depicts the residual block decoding process according to the proposed implementation scheme. According to the main implementation scheme of the present invention, Fig. 9 The process is Figure 5 A modified version of the decoding process of the residual block of . It can be seen that Figure 5 Compared to , the order of operations is changed. Now, separate Cb residual and Cr residual are obtained in the quantized transform domain instead of in the spatial domain, as is the case in VVC proposal 6.

[0100] Therefore, in case joint_cb_cr_residual_flag is true at TU level, demultiplexing of joint Cb / Cr quantized residuals is first performed. Next, usual inverse quantization and inverse transform are applied separately on the obtained Cb and Cr residual blocks, in exactly the same way as for uncoded transform units in joint Cb / Cr mode.

[0101] In this way, exactly the same dequantization is used for blocks coded in joint Cb / Cr mode and other blocks. Specifically, due to the proposed modified decoding process, the same quantization matrix can be used for blocks coded in joint Cb / Cr mode and other blocks, making overall quantization control easier and clearer.

[0102] Note that a reordering of the proposed decoding steps is theoretically possible, since Cb / Cr demultiplexing consists of linear operations in the pixel direction, which can be easily sequenced with dequantization and inverse transformation.

[0103] The following is an example of a proposal text to implement the proposed solution:

[0104] […]

[0105] The variable codedCIdx is derived as follows:

[0106] – If cIdx is equal to 0 or TuCResMode[xTbY][yTbY] is equal to 0, codedCIdx is set equal to cIdx.

[0107] – Otherwise, if TuCResMode[xTbY][yTbY] is equal to 1 or 2, codedCIdx is set equal to 1.

[0108] – Otherwise, set codedCIdx equal to 2.

[0109] The variable cSign is set equal to (1-2*slice_joint_cbcr_sign_flag).

[0110] The (nTbW)x(nTbH) array of residual samples resSample is derived as follows:

[0111] 1. When cIdx is different from codedCIdx, the transform coefficient level TransCoeffLevel[xTbY][yTbY][cIdx][x][y] (where x=0..nTbW-1, y=0..nTbH-1) is derived as follows:

[0112] - If TuCResMode[xTbY][yTbY] is equal to 2, the following applies:

[0113] TransCoeffLevel[xTbY][yTbY][cIdx][x][y]=cSign

[0114] *TransCoeffLevel[xTbY][yTbY][codedCIdx][x][y] (1125)

[0115] - Otherwise, the following applies:

[0116] TransCoeffLevel[xTbY][yTbY][cIdx][x][y]=(cSign*TransCoeffLevel

[0117] [xTbY][yTbY][codedCIdx][x][y])>>1 (1126)

[0118] 2. The scaling process for the transform coefficients as specified in clause 8.7.3 is called with the transform block position (xTbY, yTbY), transform block width nTbW and transform block height nTbH, prediction mode predMode, and the color component variable cIdx is set equal to codedCIdx as input, and the output is a (nTbW)x(nTbH) array of scaled transform coefficients d.

[0119] 3. The (nTbW)x(nTbH) array of residual samples res is derived as follows:

[0120] If transform_skip_flag[xTbY][yTbY][codedCIdx] is equal to 1, the residual sample array value res[x][y] (where x=0..nTbW-1, y=0..nTbH-1) is derived as follows:

[0121] res[x][y]=d[x][y] (1127)

[0122] Otherwise (transform_skip_flag[xTbY][yTbY][codedCIdx] is equal to 0 or and cIdx is not equal to 0), the transform process for the scaled transform coefficient as specified in clause 8.7.4.1 is invoked with the transform block position (xTbY, yTbY), the transform block width nTbW and the transform block height nTbH, with the color component variable cIdx set equal to codedCIdx and the (nTbW)×(nTbH) array of scaled transform coefficients as input, and the output is the (nTbW)×(nTbH) array of residual samples.

[0123] See also Chroma QP Control Syntax and Semantics, and Chroma QP Derivation in §8.7.1 of the VVC proposal.

[0124] A variation consists of moving the right offset of (1126) to:

[0125] Dequantize the domain, subtract 6 to QP, or add one to bdShift (Equation 1135) in §8.7.3

[0126] or inverse transform domain by adding 1 to bdShift (Eq. 1166) in §8.7.4.1 (preferred option)

[0127] In one variant, for joint chroma coded blocks, some specific quantization control parameters (e.g. QP offsets currently defined in the VVC proposal, such as pps_joint_cbcr_qp_offset and / or slice_joint_cbcr_qp_offset) may be specified, possibly still used (directly for Cb and Cr, or preferably on top of regular Cb and Cr QP offsets). This may be justified by the specific nature of the joint chroma coded blocks (e.g. different scaling standards or different visual quality).

[0128] In a further variant, separate Cb / Cr offsets may be specified for jointly chroma coded blocks.

[0129] In another variant, quantization control parameters specific to joint chroma coding blocks (PPS and slice level offsets, chroma QP mapping table, etc.) as defined in VVC Proposal 6 can still be used for Cb and Cr channels instead of the regular chroma QP.

[0130] Fig.11 One embodiment of a method 1100 according to the general aspects described herein is shown in FIG. 1101. The method begins at start block 1101S, and control proceeds to block 1110S to demultiplex Cb and Cr from a video block when encoding joint Cb / Cr for the video block. Control proceeds from block 1110S to block 1120S for dequantizing the demultiplexed Cb and Cr data. Control proceeds from block 1120S to block 1130S for inverse transforming the dequantized Cb and Cr data. Control proceeds from block 1130S to block 1140S for decoding the video block using the inverse transformed Cb and Cr data.

[0131] Fig.12 1200 according to the general aspects described herein. The method begins at start block 1201S, and control proceeds to block 1210S for parsing the video bitstream and scaling Cb and Cr from the video block. Control proceeds from block 1210S to block 1220S for dequantizing the demultiplexed Cb and Cr data. Control proceeds from block 1220S to block 1230S for inverse transforming the dequantized Cb and Cr data. Control proceeds from block 1230S to block 1240S for decoding the video block using the inverse transformed Cb and Cr data.

[0132] Fig.13 An embodiment of an apparatus 1300 for encoding, decoding, compressing or decompressing video data using a simplification of a coding mode based on a neighboring sample dependent parameter model is shown. The apparatus includes a processor 1310 and may be interconnected to a memory 1320 via at least one port. Both the processor 1310 and the memory 1320 may also have one or more additional interconnects to connect to the outside.

[0133] The processor 1310 is also configured to insert or receive information in a bitstream and use any of the aspects described for compression, encoding or decoding.

[0134] This application describes various aspects, including tools, features, embodiments, models, methods, etc. Many of these aspects are specifically described, and at least individual characteristics are shown, usually in a manner that may sound limited. However, this is for the purpose of describing clearly and does not limit the application or scope of these aspects. In fact, all different aspects can be combined and interchanged to provide further aspects. In addition, these aspects can also be combined and interchanged with the aspects described in the previous submission.

[0135] The aspects described and contemplated in this patent application can be implemented in many different forms. Figure 1 , Figure 2 and Fig.10 Some embodiments are provided, but other embodiments are contemplated, and Figure 1 , Figure 2 and Fig.10 The discussion of does not limit the breadth of specific implementations. At least one of these aspects generally relates to video encoding and decoding, and at least one other aspect generally relates to transmitting a generated or encoded bitstream. These and other aspects can be implemented as methods, apparatus, a computer-readable storage medium having stored thereon instructions for encoding or decoding video data according to any of the methods, and / or a computer-readable storage medium having stored thereon a bitstream generated according to any of the methods.

[0136] In this application, the terms "reconstruction" and "decoding" can be used interchangeably, the terms "pixel" and "sample" can be used interchangeably, and the terms "image", "picture" and "frame" can be used interchangeably. Usually, but not necessarily, the term "reconstruction" is used at the encoding end, while "decoding" is used at the decoding end.

[0137] Various methods are described herein, and each method includes one or more steps or actions for implementing the method. Unless a specific order of steps or actions is required for proper operation of the method, the order and / or use of specific steps and / or actions may be modified or combined.

[0138] Various methods and other aspects described in this patent application may be used to modify modules (e.g., intra-frame prediction, entropy encoding and / or decoding modules (160, 145, 230)) of the video encoder 100 and decoder 200, such as Figure 1 and Figure 2 In addition, aspects of the present invention are not limited to VVC or HEVC, and may be applied, for example, to other standards and recommendations (whether pre-existing or developed in the future) and extensions of any such standards and recommendations (including VVC and HEVC). Unless otherwise specified or technically excluded, the aspects described in this application may be used alone or in combination.

[0139] Various numerical values ​​are used in this application. The specific values ​​are for illustrative purposes, and the aspects are not limited to these specific values.

[0140] Figure 1 An encoder 100 is illustrated. Variations of this encoder 100 are contemplated, but for clarity, the following describes the encoder 100 without describing all contemplated variations.

[0141] Prior to encoding, the video sequence may undergo pre-encoding processing (101), for example, applying a color transform to an input color picture (e.g., conversion from RGB 4:4:4 to YCbCr 4:2:0), or performing a remapping of input picture components in order to obtain a signal distribution that is more resilient to compression (e.g., using histogram equalization of one of the color components). Metadata may be associated with the pre-processing and attached to the bitstream.

[0142] In encoder 100, a picture is encoded by encoder elements as described below. The picture to be encoded is partitioned (102) and processed in units such as CUs. Each unit is encoded, for example, using intra mode or inter mode. When a unit is encoded in intra mode, it performs intra prediction (160). In inter mode, motion estimation (175) and compensation (170) are performed. The encoder decides (105) which of intra mode or inter mode is used to encode the unit, and indicates the intra / inter decision by, for example, a prediction mode flag. The prediction residual is calculated, for example, by subtracting (110) the predicted block from the original image block.

[0143] The prediction residual is then transformed (125) and quantized (130). The quantized transform coefficients, along with motion vectors and other syntax elements, are entropy encoded (145) to output a bitstream. The encoder may skip the transform and apply quantization directly to the untransformed residual signal. The encoder may bypass both the transform and quantization, i.e., encode the residual directly without applying the transform or quantization process.

[0144] The encoder decodes the coded block to provide a reference for further prediction. The quantized transform coefficients are dequantized (140) and inverse transformed (150) to decode the prediction residual. The decoded prediction residual and the prediction block are combined (155) to reconstruct the image block. A loop filter (165) is applied to the reconstructed image to perform, for example, deblocking / SAO (sample adaptive offset) filtering to reduce coding artifacts. The filtered image is stored in a reference picture buffer (180).

[0145] Figure 22 illustrates a block diagram of a video decoder 200. In the decoder 200, the bitstream is decoded by the decoder elements as described below. The video decoder 200 generally performs the same operations as described above. Figure 1 The encoding process is the reverse of the decoding process. Encoder 100 also typically performs video decoding as part of encoding the video data.

[0146] Specifically, the input to the decoder includes a video bitstream, which may be generated by the video encoder 100. The bitstream is first entropy decoded (230) to obtain transform coefficients, motion vectors and other encoded information. Picture partition information indicates how the picture is partitioned. Therefore, the decoder can divide (235) the picture according to the decoded picture partition information. The transform coefficients are dequantized (240) and inverse transformed (250) to decode the prediction residual. The decoded prediction residual and the prediction block are combined (255) to reconstruct the image block. The prediction block can be obtained (270) from intra-frame prediction (260) or motion compensated prediction (i.e., inter-frame prediction) (275). A loop filter (265) is applied to the reconstructed image. The filtered image is stored in a reference picture buffer (280).

[0147] The decoded picture may also undergo post-decoding processing (285), such as an inverse color transform (e.g., a transform from YCbCr 4:2:0 to RGB 4:4:4) or performing an inverse remapping of a remapping process performed in the pre-encoding process (101). The post-decoding processing may use metadata derived in the pre-encoding process and signaled in the bitstream.

[0148] Fig.10 Illustrated is a block diagram of an example of a system in which various aspects and embodiments are implemented.System 1000 can be embodied as a device including various components described below, and is configured to perform one or more aspects described in this document.Examples of such devices include, but are not limited to, various electronic devices, such as personal computers, laptop computers, smart phones, tablet computers, digital multimedia set-top boxes, digital television receivers, personal video recording systems, connected home appliances and servers.The elements of system 1000 can be embodied in a single integrated circuit (IC), multiple ICs and / or discrete components individually or in combination.For example, in at least one embodiment, the processing element and encoder / decoder element of system 1000 are distributed on multiple ICs and / or discrete components.In various embodiments, system 1000 is coupled to one or more other systems or other electronic devices via, for example, a communication bus or by a dedicated input and / or output port communication.In various embodiments, system 1000 is configured to realize one or more aspects described in this document.

[0149] The system 1000 includes at least one processor 1010 configured to execute instructions loaded therein for implementing, for example, various aspects described in this document. The processor 1010 may include embedded memory, input-output interfaces, and various other circuits known in the art. The system 1000 includes at least one memory 1020 (e.g., a volatile memory device and / or a non-volatile memory device). The system 1000 includes a storage device 1040, which may include a non-volatile memory and / or a volatile memory, including but not limited to an electrically erasable programmable read-only memory (EEPROM), a read-only memory (ROM), a programmable read-only memory (PROM), a random access memory (RAM), a dynamic random access memory (DRAM), a static random access memory (SRAM), a flash memory, a magnetic disk drive, and / or an optical disk drive. As a non-limiting example, the storage device 1040 may include an internal storage device, an attached storage device (including removable and non-removable storage devices), and / or a network-accessible storage device.

[0150] The system 1000 includes an encoder / decoder module 1030, which is configured to process data, for example, to provide encoded video or decoded video, and the encoder / decoder module 1030 may include its own processor and memory. The encoder / decoder module 1030 represents a module that can be included in a device to perform encoding and / or decoding functions. As is well known, a device may include one or both of an encoding module and a decoding module. In addition, the encoder / decoder module 1030 can be implemented as an independent element of the system 1000, or can be combined in the processor 1010 as a combination of hardware and software known to those skilled in the art.

[0151] Program code to be loaded onto the processor 1010 or the encoder / decoder 1030 to perform various aspects described in this document may be stored in the storage device 1040 and subsequently loaded onto the memory 1020 for execution by the processor 1010. According to various embodiments, one or more of the processor 1010, the memory 1020, the storage device 1040, and the encoder / decoder module 1030 may store one or more of the various items during the execution of the processes described in this document. Such stored items may include, but are not limited to, input video, decoded video or partially decoded video, bitstreams, matrices, variables, and intermediate or final results of processing equations, formulas, operations, and operation logic.

[0152] In some embodiments, memory internal to the processor 1010 and / or encoder / decoder module 1030 is used to store instructions and provide working memory for processing required during encoding or decoding. However, in other embodiments, memory external to the processing device (e.g., the processing device may be the processor 1010 or the encoder / decoder module 1030) is used for one or more of these functions. The external memory may be memory 1020 and / or storage device 1040, such as dynamic volatile memory and / or non-volatile flash memory. In several embodiments, the external non-volatile flash memory is used to store, for example, the operating system of the television. In at least one embodiment, a fast external dynamic volatile memory such as RAM is used as working memory for video encoding and decoding operations, such as MPEG-2 (MPEG refers to Moving Picture Experts Group, MPEG-2 is also known as ISO / IEC 13818, and 13818-1 is also known as H.222, 13818-2 is also known as H.262), HEVC (HEVC refers to High Efficiency Video Coding, also known as H.265 and MPEG-H Part 2), or VVC (Versatile Video Coding, a new standard developed by the Joint Video Experts Team (JVET)).

[0153] Inputs to the elements of system 1000 may be provided through various input devices as shown in block 1130. Such input devices include, but are not limited to: (i) a radio frequency (RF) section that receives an RF signal transmitted over the air, for example, by a broadcaster; (ii) a component (COMP) input terminal (or a set of COMP input terminals); (iii) a universal serial bus (USB) input terminal; and / or (iv) a high-definition multimedia interface (HDMI) input terminal. Fig.10 Other examples not shown include composite video.

[0154] In various embodiments, the input device of block 1130 has associated corresponding input processing elements as known in the art. For example, the RF section may be associated with elements suitable for: (i) selecting a desired frequency (also referred to as selecting a signal, or band limiting a signal to a frequency band), (ii) down-converting the selected signal, (iii) again band-limiting to a narrower frequency band to select a signal frequency band that may be referred to as a channel in certain embodiments, (iv) demodulating the down-converted and band-limited signal, (v) performing error correction, and (vi) demultiplexing to select a desired packet stream. The RF section of various embodiments includes one or more elements for performing these functions, such as a frequency selector, a signal selector, a band limiter, a channel selector, a filter, a down-converter, a demodulator, an error corrector, and a demultiplexer. The RF section may include a tuner that performs various of these functions, including, for example, down-converting a received signal to a lower frequency (e.g., an intermediate frequency or near baseband frequency) or to baseband. In a set-top box embodiment, the RF part and its associated input processing element receive the RF signal transmitted by wired (for example, cable) medium, and perform frequency selection by filtering, down-conversion and filtering to required frequency band again.Various embodiments rearrange the order of above-mentioned (and other) elements, remove some elements in these elements, and / or add other elements of similar or different functions.Adding element can include inserting element between existing element, for example, inserting amplifier and analog-to-digital converter.In various embodiments, the RF part comprises antenna.

[0155] In addition, the USB and / or HDMI terminals may include corresponding interface processors for connecting the system 1000 to other electronic devices across the USB and / or HDMI connections. It should be understood that various aspects of input processing (e.g., Reed-Solomon error correction) may be implemented, for example, in a separate input processing IC or in the processor 1010 as needed. Similarly, aspects of USB or HDMI interface processing may be implemented, for example, in a separate interface IC or in the processor 1010 as needed. The demodulated stream, error correction stream, and demultiplexed stream are provided to various processing elements, including, for example, the processor 1010 and the encoder / decoder 1030, which operate in conjunction with the memory and storage elements to process the data stream as needed for presentation on the output device.

[0156] The various elements of system 1000 may be disposed within an integrated housing within which the various elements may be interconnected and data transmitted therebetween using a suitable connection arrangement (e.g., an internal bus as known in the art, including an Inter-IC (I2C) bus, wiring, and printed circuit boards).

[0157] The system 1000 includes a communication interface 1050 capable of communicating with other devices via a communication channel 1060. The communication interface 1050 may include, but is not limited to, a transceiver configured to transmit and receive data through the communication channel 1060. The communication interface 1050 may include, but is not limited to, a modem or a network card, and the communication channel 1060 may be implemented, for example, within a wired and / or wireless medium.

[0158] In various embodiments, a wireless network such as a Wi-Fi network, such as IEEE 802.11 (IEEE refers to the Institute of Electrical and Electronics Engineers), is used to transmit data streams or otherwise provide it to the system 1000. The Wi-Fi signals of these embodiments are received by a communication channel 1060 and a communication interface 1050 suitable for Wi-Fi communication. The communication channel 1060 of these embodiments is usually connected to an access point or a router, which provides access to an external network including the Internet, for allowing streaming applications and other cloud communications. Other embodiments use a set-top box to provide streaming data to the system 1000, which delivers data through the HDMI connection of the input block 1130. There are also other embodiments that use the RF connection of the input block 1130 to provide streaming data to the system 1000. As described above, various embodiments provide data in a non-streaming manner. In addition, various embodiments use wireless networks other than Wi-Fi, such as cellular networks or Bluetooth networks.

[0159] System 1000 can provide output signals to various output devices, including display 1100, speaker 1110 and other peripheral devices 1120. Display 1100 of various embodiments includes one or more of, for example, a touch screen display, an organic light emitting diode (OLED) display, a curved display and / or a foldable display. Display 1100 can be used for a television, a tablet, a notebook, a cellular phone (mobile phone) or other devices. Display 1100 can also be integrated with other components (for example, as in a smart phone), or it can be separate (for example, an external monitor of a laptop). In various examples of embodiments, other peripheral devices 1120 include one or more of an independent digital video disc (or digital versatile disc, both terms are DVR), a disc player, a stereo system and / or a lighting system. Various embodiments use one or more peripheral devices 1120 that provide functions based on the output of system 1000. For example, a disc player performs the function of playing the output of system 1000.

[0160] In various embodiments, control signals are transmitted between the system 1000 and the display 1100, speaker 1110, or other peripheral device 1120 using signaling such as AV.Link, consumer electronics control (CEC), or other communication protocols that enable device-to-device control with or without user intervention. Output devices can be communicatively coupled to the system 1000 via dedicated connections through respective interfaces 1070, 1080, and 1090. Alternatively, the output devices can be connected to the system 1000 via the communication interface 1050 using the communication channel 1060. The display 1100 and the speaker 1110 can be integrated into a single unit with other components of the system 1000 in an electronic device such as a television. In various embodiments, the display interface 1070 includes a display driver, such as, for example, a timing controller (T Con) chip.

[0161] Alternatively, if the RF portion of input 1130 is part of a separate set-top box, the display 1100 and speaker 1110 are optionally separate from one or more of the other components. In various embodiments where the display 1100 and speaker 1110 are external components, the output signal may be provided via a dedicated output connection (including, for example, an HDMI port, a USB port, or a COMP output).

[0162] These embodiments may be performed by the processor 1010 or by computer software implemented by hardware or by a combination of hardware and software. As a non-limiting example, these embodiments may be implemented by one or more integrated circuits. As a non-limiting example, the memory 1020 may be of any type suitable for the technical environment and may be implemented using any appropriate data storage technology, such as an optical memory device, a magnetic memory device, a semiconductor-based memory device, a fixed memory, and a removable memory. As a non-limiting example, the processor 1010 may be of any type suitable for the technical environment and may include one or more of a microprocessor, a general-purpose computer, a special-purpose computer, and a processor based on a multi-core architecture.

[0163] Various implementations participate in decoding. As used in this application, "decoding" may include, for example, all or part of a process performed on a received coded sequence to produce a final output suitable for display. In various embodiments, such processes include one or more processes typically performed by a decoder, such as entropy decoding, inverse quantization, inverse transform, and differential decoding. In various embodiments, such processes also include or alternatively include processes performed by a decoder of the various implementations described in this application.

[0164] As a further example, in one embodiment, "decoding" refers only to entropy decoding, in another embodiment, "decoding" refers only to differential decoding, and in yet another embodiment, "decoding" refers to a combination of entropy decoding and differential decoding. Whether the phrase "decoding process" refers specifically to a subset of operations or broadly to a broader decoding process will be clear based on the context of the specific description, and is believed to be well understood by those skilled in the art.

[0165] Various implementations involve encoding. In a manner similar to the discussion above about "decoding", "encoding" as used in this application may encompass, for example, all or part of a process performed on an input video sequence to produce an encoded bitstream. In various embodiments, such processes include one or more processes typically performed by an encoder, such as partitioning, differential encoding, transforms, quantization, and entropy encoding. In various embodiments, such processes also include or alternatively include processes performed by encoders of the various implementations described in this application.

[0166] As a further example, in one embodiment, "encoding" refers only to entropy encoding, in another embodiment, "encoding" refers only to differential encoding, and in yet another embodiment, "encoding" refers to a combination of differential encoding and entropy encoding. Whether the phrase "encoding process" refers specifically to a subset of operations or broadly to a broader encoding process will be clear based on the context of the specific description, and is believed to be well understood by those skilled in the art.

[0167] Note that the grammatical elements used herein are descriptive terms. Therefore, they do not exclude the use of other grammatical element names.

[0168] When the figures are presented as flow charts, it should be understood that they also provide block diagrams of corresponding devices. Similarly, when the figures are presented as block diagrams, it should be understood that they also provide flow charts of corresponding methods / processes.

[0169] Various embodiments may refer to parameter models or rate-distortion optimization. Specifically, during the encoding process, a balance or trade-off between rate and distortion is generally considered, which often takes into account constraints of computational complexity. It can be measured by rate-distortion optimization (RDO) metric or by least mean square (LMS), mean absolute error (MAE) or other such measurements. Rate-distortion optimization is generally described as minimizing a rate-distortion function, which is a weighted sum of rate and distortion. There are different methods to solve the rate-distortion optimization problem. For example, these methods can be based on extensive testing of all coding options (including all considered modes or coding parameter values) and fully evaluate their coding costs and the associated distortion of the reconstructed signal after encoding and decoding. Faster methods can also be used to reduce coding complexity, particularly for the calculation of approximate distortion based on prediction or prediction residual signals rather than reconstructed residual signals. A mixture of these two methods can also be used, such as by using approximate distortion for only some of the possible coding options and using full distortion for other coding options. Other methods only evaluate a subset of possible coding options. More generally, many approaches employ any of a variety of techniques to perform optimization, but optimization is not necessarily a complete assessment of both coding cost and associated distortion.

[0170] Implementations and aspects described herein may be implemented, for example, in a method or process, an apparatus, a software program, a data stream, or a signal. Even if discussed only in the context of a single form of implementation (e.g., discussed only as a method), the implementation of the features discussed may also be implemented in other forms (e.g., an apparatus or program). An apparatus may be implemented, for example, in appropriate hardware, software, and firmware. A method may be implemented, for example, in a processor, which generally refers to a processing device,

[0171] The processing device includes, for example, a computer, a microprocessor, an integrated circuit or a programmable logic device. The processor also includes a communication device, such as, for example, a computer, a cell phone, a portable / personal digital assistant ("PDA"), and other devices that facilitate information communication between end users.

[0172] Reference to "one embodiment" or "an embodiment" or "an implementation" or "an implementation" and other variations thereof means that a particular feature, structure, characteristic, etc. described in connection with the embodiment is included in at least one embodiment. Thus, the appearance of the phrase "in one embodiment" or "in an embodiment" or "in one implementation" or "in an implementation" and any other variations thereof in various places throughout this application are not necessarily all referring to the same embodiment.

[0173] Furthermore, the present application may refer to “determining” various information. Determining information may include, for example, one or more of estimating information, calculating information, predicting information, or retrieving information from a memory.

[0174] Furthermore, the present application may refer to "accessing" various information. Accessing information may include, for example, one or more of receiving information, retrieving information (e.g., from a memory), storing information, moving information, copying information, calculating information, determining information, predicting information, or estimating information.

[0175] Furthermore, the present application may refer to "receiving" various information. Like "accessing," receiving is intended to be a broad term. Receiving information may include, for example, one or more of accessing information or retrieving information (e.g., from a memory). Furthermore, "receiving" generally involves, in one way or another, during operations such as, for example, storing information, processing information, transmitting information, moving information, copying information, erasing information, calculating information, determining information, predicting information, or estimating information.

[0176] It should be understood that, for example, in the case of "A / B," "A and / or B," and "at least one of A and B," the use of any of the following " / ," "and / or," and "at least one of" is intended to encompass selecting only the first listed option (A), or only the second listed option (B), or both options (A and B). As a further example, in the case of "A, B, and / or C" and "at least one of A, B, and C," such phrases are intended to encompass selecting only the first listed option (A), or only the second listed option (B), or only the third listed option (C), or only the first listed option and the second listed option (A and B), or only the first listed option and the third listed option (A and C), or only the second listed option and the third listed option (B and C), or all three options (A and B and C). This can be extended to as many items as listed, as will be apparent to one of ordinary skill in this and related arts.

[0177] Moreover, as used herein, the word "signaling" refers to (among other things) indicating something to a corresponding decoder. For example, in certain embodiments, the encoder signals a specific one of a plurality of transforms, coding modes or marks. Thus, in one embodiment, the same transform, parameter or mode is used on both the encoder side and the decoder side. Therefore, for example, the encoder can transmit (explicit signaling) specific parameters to the decoder so that the decoder can use the same specific parameters. On the contrary, if the decoder already has specific parameters and others, signaling can be used without transmitting (implicit signaling) to simply allow the decoder to know and select specific parameters. By avoiding transmitting any actual function, bit saving is achieved in various embodiments. It should be understood that signaling can be implemented in various ways. For example, in various embodiments, one or more grammatical elements, marks, etc. are used to signal information to the corresponding decoder. Although the verb form of the word "signal" is previously related to, the word "signal" can also be used as a noun herein.

[0178] It will be apparent to one of ordinary skill in the art that a specific implementation may generate various signals formatted to carry, for example, storable or transmittable information. The information may include, for example, instructions for performing a method or data generated by one of the specific implementations. For example, a signal may be formatted to carry a bit stream of the embodiment. Such signals may be formatted, for example, as electromagnetic waves (e.g., using a radio frequency portion of a spectrum) or as baseband signals. Formatting may include, for example, encoding a data stream and modulating a carrier with the encoded data stream. The information carried by the signal may be, for example, analog or digital information. It is known that the signal may be transmitted over a variety of different wired or wireless links. The signal may be stored on a processor readable medium.

[0179] We have described multiple embodiments, across various claim categories and types. Features of these embodiments may be provided individually or in any combination. In addition, embodiments may include one or more of the following features, devices, or aspects, individually or in any combination, across various claim categories and types:

[0180] A process or apparatus for processing jointly coded Cb and Cr signals.

[0181] A process or apparatus for encoding a jointly coded Cb signal and a Cr signal.

[0182] • A process or apparatus including syntax or semantics for operating with jointly coded Cb and Cr signals.

[0183] • Use or insert syntax in the bitstream to control the jointly coded Cb and Cr signals in the encoder or decoder.

[0184] • A bitstream or signal comprising one or more of the described syntax elements or variants thereof.

[0185] - A bitstream or signal comprising syntax conveying information generated according to any of the described embodiments.

[0186] · Creation and / or transmission and / or reception and / or decoding according to any one of the described embodiments.

[0187] A method, process, apparatus, medium storing instructions, medium storing data or signal according to any one of the embodiments.

[0188] • Inserting syntax elements in the signaling, which enables the decoder to determine the tools in a way that corresponds to the encoding method used by the encoder.

[0189] • Creating and / or transmitting and / or receiving and / or decoding a bitstream or signal comprising one or more of the described syntax elements or variations thereof.

[0190] • A television, set-top box, cell phone, tablet or other electronic device performing a conversion method according to any of the described embodiments.

[0191] A television, set-top box, cell phone, tablet computer or other electronic device that performs the transformation method according to any of the described embodiments and displays the resulting image (e.g., using a monitor, screen or other type of display).

[0192] A television, set-top box, cellular phone, tablet or other electronic device that selects, band limits or tunes (e.g., using a tuner) a channel to receive a signal including an encoded image and performs the transformation method according to any of the described embodiments.

[0193] • A television, set-top box, cellular phone, tablet computer, or other electronic device that receives over the air (eg, using an antenna) a signal including the encoded image and performs the transformation method.

Claims

1. A method, comprising: When a joint Cb / Cr is encoded for a video block, demultiplexing Cb and Cr from the video block; Dequantizing the demultiplexed Cb and Cr data; specifying an identifier of a quantization matrix applied to chroma components during dequantization based on characteristics of the video block, and wherein the applied quantization matrix is ​​rescaled to match a size of the video block; Inversely transforming the dequantized Cb and Cr data; as well as The video block is decoded using the inverse transformed Cb data and the inverse transformed Cr data. The method according to claim 1 , wherein specific quantization control parameters are specified.

3. The method of claim 1, wherein separate Cb offsets and Cr offsets are specified for a joint chroma coded block.

4. The method of claim 1, wherein quantization control parameters specific to a joint chroma coding block are used for both the Cb channel and the Cr channel instead of nominal chroma quantization parameters.

5. A device, comprising: A processor, the processor being configured to: When a joint Cb / Cr is encoded for a video block, demultiplexing Cb and Cr from the video block; Dequantizing the demultiplexed Cb and Cr data; specifying an identifier of a quantization matrix applied to chroma components during dequantization based on characteristics of the video block, and wherein the applied quantization matrix is ​​rescaled to match a size of the video block; Inversely transforming the dequantized Cb and Cr data; as well as The video block is decoded using the inverse transformed Cb data and the inverse transformed Cr data. The apparatus of claim 5 , wherein a specific quantization control parameter is specified.

7. The apparatus of claim 5, wherein separate Cb offsets and Cr offsets are specified for a joint chroma coding block.

8. The apparatus of claim 5, wherein quantization control parameters specific to a joint chroma coding block are used for both the Cb channel and the Cr channel instead of nominal chroma quantization parameters.

9. A device, comprising: The device according to claim 5; as well as At least one of: (i) an antenna configured to receive a signal, the signal comprising a video block; (ii) a band limiter configured to limit the received signal to a frequency band comprising the video block; and (iii) a display configured to display an output representing the video block. 10 . A non-transitory computer readable medium having program instructions stored thereon, wherein when the program instructions are executed by a computer, the computer is caused to perform the method according to claim 1 .

11. A computer program product comprising instructions which, when executed by a computer, cause the computer to perform the method according to claim 1.

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