RU2816202C2 - Method and apparatus for affine external prediction of chroma subunits - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to image encoding means. Chromaticity scaling factors are determined in the horizontal and vertical directions based on the chromaticity format information. Chromaticity format information indicates the chromaticity format of the current picture to which the block of the current picture belongs. Set (S) of luma subunits of the luma block is determined based on the chroma scaling coefficients. Chroma motion vector is determined for a chroma subunit of a chroma block based on motion vectors of one or more luma subunits in a set (S) of luma subunits. When SubW WidthC and SubHeightC are equal to 1, set of subunits (S) of brightness contains subunit of brightness, indexed as S₀ = (xSbIdx, ySbIdx). When at least one of SubWIDTHC and SubHeightC is not equal to 1, the set of luma subunits (S) comprises: a first luma subunit, indexed as S₀ = ((xSbIdx >> (SubWidthC – 1) << (SubWidthC – 1)), (ySbIdx >> (SubHeightC − 1) << (SubHeightC − 1))), and a second brightness subunit, indexed as S₁ = ((xSbIdx >> (SubWidthC − 1) << (SubWidthC − 1)) + (SubWidthC − 1), (ySbIdx >> (SubHeightC − 1) << (SubHeightC − 1)) + (SubHeightC − 1)).

EFFECT: high efficiency of encoding images.

33 cl, 33 dwg

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to U.S. Provisional Patent Application No. 62/809,551, filed February 22, 2019, priority to U.S. Provisional Patent Application No. 62/823,653, filed March 25, 2019, and priority to U.S. Provisional Patent Application No. 62/824,302, filed 26 March 2019 The disclosure of the above patent applications is incorporated herein by reference in its entirety.

Field of technology

Embodiments of the present disclosure generally relate to the field of image processing and, more particularly, to affine inter-prediction (affine motion compensation), in particular, to a method and apparatus for inferring a motion vector for affine inter-prediction of chroma sub-blocks based on a chroma format, and a method and hardware for affine external prediction of chrominance subblocks.

State of the art

Video encoding (video encoding and/or decoding) is used in a wide range of digital video applications, such as digital broadcast television, video transmission over the Internet and mobile networks, and real-time conversational applications such as video chat, video conferencing, DVDs, and Blu Discs. -ray, systems for collecting and editing video content and video cameras for security applications.

The amount of video data required to present even a relatively short video can be significant, which can lead to difficulties when the data must be streamed or otherwise transmitted over a communications network with limited bandwidth. Thus, video data is typically compressed before being transmitted over modern telecommunications networks. Video size can also be an issue when the video is stored on a storage device, as memory resources may be limited. Video compression devices often use software and/or hardware at the source to encode video data before transmission or storage, thereby reducing the amount of data required to represent digital video images. The compressed data is then received at its destination by a video decompression device, which decodes the video data. With limited network resources and ever-increasing demands for higher video quality, improved compression and decompression techniques with higher compression ratios and virtually no loss of picture quality are desired.

In particular, the current Universal Video Test Model (VTM) encoder mainly supports 4:2:0 chroma format as an input picture format. A VTM encoder crash may occur when the input chroma format becomes 4:4:4. To avoid this problem, an encoder that supports other color formats (such as 4:4:4 or 4:2:2) for a wide variety of applications is highly desirable and even required.

The essence of the invention

In view of the above problems, the present disclosure proposes a modification of the video encoding process to support multiple color formats. In particular, embodiments of the present application are aimed at providing an apparatus, encoder, decoder, and corresponding methods for inferring a motion vector for affine inter-prediction of chroma subblocks based on a chroma format, which may be one of a variety of supported chroma formats, to improve encoding performance.

The embodiments of the invention are determined by the features of the independent claims, and additional advantageous implementations of the embodiments are determined by the features of the dependent claims.

Specific embodiments are set forth in the accompanying independent claims, and other embodiments are set forth in the dependent claims.

The above and other goals are achieved by the invention according to independent claims. Additional forms of implementation are obvious from the dependent claims, description and figures.

According to a first aspect of the present disclosure, there is provided a chroma motion vector inference method used in affine inter prediction of a block of a current picture containing a luminance block and a co-located chrominance block, the method comprising

determining chroma scaling factors (that is, chroma scaling factor values) in the horizontal and vertical directions based on the chromaticity format information, wherein the chrominance format information indicates the chrominance format of the current picture to which the current image block belongs;

determining a set (S) of luminance subblocks of the luminance block based on the values of the chroma scaling factors; and determining a motion vector for the chrominance subblock for the chrominance block based on the motion vectors of one or more luma subblocks (eg, one or two luma subblocks) in the set (S) of luma subblocks.

In the present disclosure, since a block or subblock (luminance or chroma) can be represented by its location, position or index, selecting/determining the block or subblock implies that the position, location or index of the block or subblock is selected or determined.

It should be noted that the term "block", "coding block" or "image block" as used in the present disclosure may represent a transformation unit (TU), a prediction unit (PU), a coding unit (CU), etc. In Universal Video Coding (VVC), transform units and encoding units are usually aligned with each other, except when TU tiling or subblock transform (SBT) is used. As such, the terms "block", "image block", "encoding block" and "transform block" may be used interchangeably in the present disclosure; and the terms "block size" and "transform block size" may be used interchangeably in the present disclosure. The terms "sample" and "pixel" may also be used interchangeably in the present disclosure.

The present disclosure is directed to a method for taking into account the chrominance format of a picture when deriving chroma motion vectors from luminance motion vectors. By averaging the luminance motion vectors, a linear subsampling of the luminance motion field is performed. When chroma color planes have the same height as the lumina plane, it makes more sense to select motion vectors from lumina blocks that are horizontally adjacent so that they have the same vertical position. Selecting luminance motion vectors depending on the chroma format of the picture results in a more accurate chroma motion field due to more accurate subsampling of the luminance motion vector field. This dependence on the chroma format allows the selection of the most appropriate luminance blocks when averaging the luminance motion vectors to generate a chroma motion vector. As a consequence of more accurate interpolation of the motion field, the prediction error is reduced, which has the technical effect of increasing compression performance, thus improving encoding performance.

In a possible implementation of the method according to the first aspect, a set (S) of luma subblocks is determined based on the values of the chroma scaling factors in the horizontal and vertical directions. That is, one or more luma subblocks (eg, one or two luma subblocks) are determined based on the values of the chroma scaling factors in the horizontal and vertical directions.

In a possible implementation of the method according to the first aspect, the chromaticity scaling factors in the horizontal and vertical directions are represented by the variables SubWidthC and SubHeightC.

In a possible embodiment of the method according to the first aspect, the position of each of the luma subblocks is represented by a subblock index in the horizontal direction and a subblock index in the vertical direction, and the position of each of the chroma subblocks is represented by a subblock index in the horizontal direction and a subblock index in the vertical direction.

In an exemplary embodiment of the method according to the first aspect, the positions of each of one or more luminance subblocks (eg, one or two luminance subblocks) in the set (S) are represented by a subblock index in the horizontal direction and a subblock index in the vertical direction.

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect itself, if the variables SubWidthC and SubHeightC are both equal to 1, the set of luminance subblocks (S) contains:

luma subblock indexed S0 = (xSbIdx, ySbIdx);

if at least one of SubWidthC and SubHeightC is not equal to 1, the luma subblock set (S) contains:

the first luma subblock indexed as S0 = ((xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1)), (ySbIdx >> (SubHeightC - ) << (SubHeightC - 1))), and

second luma subblock indexed as S1 = ((xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1))+(SubWidthC - 1), (ySbIdx >> (SubHeightC - 1) << (SubHeightC - 1)) +(SubHeightC - 1)),

where SubWidthC and SubHeightC represent the chromaticity scaling factors in the horizontal and vertical directions, respectively;

xSbIdx and ySbIdx represent the sub-block index in the horizontal direction and the sub-block index in the vertical direction for the luma sub-block in the set (S), respectively; “<<” represents an arithmetic left shift, and “>>” represents an arithmetic right shift; and xSbIdx=0..numSbX - 1 and ySbIdx=0..numSbY - 1, and numSbX indicates the number of luminance sub-blocks in a luminance block along the horizontal direction, and numSbY indicates the number of luminance sub-blocks in a luminance block along the vertical direction.

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect itself, the numbers of chroma subblocks in the horizontal and vertical directions are the same as the numbers of luminance subblocks in the horizontal and vertical directions, respectively.

In an exemplary form of implementation of the method according to any previous implementation of the first aspect or the first aspect itself, in which, if both SubWidthC and SubHeightC are 1, the set of luminance subblocks (S) comprises:

luminance subblock indexed S ₀ = (xCSbIdx, yCSbIdx);

if at least one of SubWidthC and SubHeightC is not equal to 1, the luma subblock set (S) contains:

the first luma subblock indexed as S0 = ((xCSbIdx >> (SubWidthC - 1) << (SubWidthC - 1)), (yCSbIdx >> (SubHeightC - 1) << (SubHeightC - 1))), and

second luma subblock indexed as S1 = (xCSbIdx >> (SubWidthC - 1) << (SubWidthC - 1))+(SubWidthC - 1), (yCSbIdx >> (SubHeightC - 1) << (SubHeightC - 1))+ (SubHeightC - 1)),

wherein the variables SubWidthC and SubHeightC represent, respectively, chromaticity scaling factors in the horizontal and vertical directions; xCSbIdx and yCSbIdx represent the sub-block index in the horizontal direction and the sub-block index in the vertical direction, respectively, for the luma sub-block in the set (S); and xCSbIdx=0..numCSbX - 1 and yCSbIdx=0..numCSbY - 1, and numCSbX indicates the number of chroma subblocks in a chroma block along the horizontal direction, and numCSbY indicates the number of chroma subblocks in a chroma block along the vertical direction.

In a possible embodiment of the method according to any previous implementation of the first aspect or the first aspect itself, wherein the size of each of the chrominance subblocks is the same as the size of each of the luminance subblocks. It is conceivable that when the number of chrominance subblocks is defined to be equal to the number of luminance subblocks, and when the size of the chrominance color plane is equal to the size of the luminance plane (for example, the chrominance format of the input picture is 4:4:4), the motion vectors of adjacent chrominance subblocks can take on the same value. When implementing this processing step, you can perform optimization by skipping the step of calculating duplicate values.

The present invention discloses a method for determining the size of a chrominance subblock equal to the size of a luminance subblock. In this case, the implementation can be simplified by unifying the processing of luma and chrominance, and, of course, redundant calculations of motion vectors can be avoided.

In a possible embodiment of the method according to any previous implementation of the first aspect or the first aspect itself, in the case where the size of each of the chrominance subblocks is the same as the size of each of the luminance subblocks, the number of chroma subblocks in the horizontal direction depends on the number of luminance subblocks in the horizontal direction and the values of the chroma scaling factor in the horizontal direction;

the number of chrominance subblocks in the vertical direction depends on the number of luminance subblocks in the vertical direction and the value of the chrominance scaling factor in the vertical direction.

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect itself, xCSbIdx is obtained based on xSbIdx and the SubWidth step value; and yCSbIdx is obtained based on ySbIdx and the step value of SubHeightC.

In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such,

numCSbX = numSbX>>(SubWidthC-1)

numCSbY = numSbY>>(SubHeightC - 1);

numCSbX and numCSbY represent the number of chrominance subblocks in the horizontal and vertical directions, respectively; And

numSbX and numSbY represent the number of luminance subblocks in a luminance block in the horizontal and vertical directions, respectively.

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect as such for a chroma block, the set of luminance subblocks (S) comprises one or more subblocks indexed by:

S ₀ = (xSbIdxL, ySbIdxL)

S ₁ = (xSbIdxL, ySbIdxL + (SubHeightC-1))

S ₂ = (xSbIdxL+ (SubWidthC-1), ySbIdxL)

S ₃ = (xSbIdxL+ (SubWidthC-1), ySbIdxL + (SubHeightC-1))

in this case the position or index S0 of the block brightness is represented by the subblock index xSbIdxL in the horizontal direction and the subblock index ySbIdxL in the vertical direction;

for the chrominance block position (for example, [xSbIdxL] [ySbIdxL] in mvCLX [xSbIdxL] [ySbIdxL],

The luminance block position or index S1 is represented by a subblock index in the horizontal direction, xSbIdxL, and a subblock index in the vertical direction, ySbIdxL + (SubHeightC-1);

The luminance block position or index S2 is represented by a subblock index in the horizontal direction, xSbIdxL + (SubWidthC-1), and a subblock index in the vertical direction, ySbIdxL;

The luminance block position or index S3 is represented by a subblock index in the horizontal direction, xSbIdxL + (SubWidthC-1), and a subblock index in the vertical direction, ySbIdxL + (SubHeightC-1).

In an exemplary form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, wherein the set of luminance subblocks (S) comprises two luminance subblocks indexed by:

S0 = (xSbIdxL, ySbIdxL)
S1 = (xSbIdxL+ (SubWidthC-1), ySbIdxL + (SubHeightC-1)),

wherein the position or index S0 of the luminance block is represented by a subblock index xSbIdxL in the horizontal direction and a subblock index ySbIdxL in the vertical direction;

The luminance block position or index S1 is represented by a subblock index in the horizontal direction, xSbIdxL + (SubWidthC-1), and a subblock index in the vertical direction, ySbIdxL + (SubHeightC-1).

In a possible form of implementation of the method according to any prior implementation of the first aspect or the first aspect as such,

in the case where the chrominance format is 4:4:4, the set (S) contains (consists of) one luma subblock, which is combined with a chrominance subblock;

in this case, if the chroma format is 4: 2: 2, the set (S) contains two luminance subblocks that are horizontally adjacent;

Moreover, in case the chroma format is 4: 2: 0, the set (S) contains two luminance subblocks that are diagonal.

In an exemplary form of implementation of the method according to any previous implementation of the first aspect or the first aspect itself, wherein, if there is more than one luma subblock in the set (S), determining a motion vector for the chrominance subblock based on the motion vector of at least one luma subblock in the set (S) brightness subblocks, contains:

averaging the motion vectors of brightness subblocks in the set S; And

inferring a motion vector for the chrominance subblock based on the average luminance motion vector.

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect itself, the averaging of the motion vectors of the luminance subblocks in the set S comprises:

averaging the horizontal components of the motion vectors of brightness subblocks in the set S; and/or

averaging of the vertical components of the motion vectors of brightness subblocks in the set S.

In an exemplary form of implementation of the method according to any previous implementation of the first aspect or the first aspect itself, wherein averaging the motion vectors of the luminance subblocks in the set S comprises checking whether the sum of the motion vectors of the luminance subblocks in the set S is greater than or equal to 0.

In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect itself, wherein the averaging of the motion vectors of the luminance subblocks in the set S comprises:

mvAvgLX = if mvAvgLX[ 0 ] is greater than or equal to 0, then mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + (N>>1) - 1) >> log2(N), otherwise, mvAvgLX[ 0 ] = - ( (- mvAvgLX[ 0 ] + (N>>1) - 1) >> log2(N) ) if mvAvgLX[ 1 ] is greater than or equal to 0, then mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + (N>>1) - 1) >> log2(N), otherwise, mvAvgLX[ 1 ] = - ( (- mvAvgLX[ 1 ] + (N>>1) - 1) >> log2(N)), where mvAvgLX is the result of averaging, mvAvgLX [0] - horizontal component of the motion vector mvAvgLX, mvAvgLX [1] - vertical component of the motion vector mvAvgLX, And - horizontal and vertical indices of the subblock Si in the set of subblocks (S) of brightness in the array of motion vectors, , brightness subblock motion vector with indices And , N is the number of elements (such as luminance subblocks) in the luminance subblock set (S), log2(N) is the logarithm of N to base 2 and the power to which the number 2 is raised to give the value of N, and “>>” is arithmetic shift to the right.

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect as such, N is equal to 2.

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect itself, the averaging of the motion vectors of the luminance subblocks in the set S comprises:

mvAvgLX = mvLX[(xSbIdx>>(SubWidthC - 1)<<(SubWidthC - 1))]

[(ySbIdx>>(SubHeightC - 1)<<(SubHeightC - 1))]+

mvLX[(xSbIdx>>(SubWidthC - 1)<<(SubWidthC - 1))+(SubWidthC - 1)]

[(ySbIdx>>(SubHeightC - 1)<<(SubHeightC - 1))+(SubHeightC - 1)]

if mvAvgLX[0] >= 0 then mvAvgLX[ 0 ] =( mvAvgLX[ 0 ] + 1 - (mvAvgLX[0] >= 0)) >> 1

if mvAvgLX[1] >= 0 then mvAvgLX[ 1 ] =( mvAvgLX[ 1 ] + 1 - (mvAvgLX[1] >= 0)) >> 1

where mvAvgLX [0] is the horizontal component of the averaged motion vector mvAvgLX, mvAvgLX [1] is the vertical component of the averaged motion vector mvAvgLX; where SubWidthC and SubHeightC represent chroma scaling factors in the horizontal and vertical directions, respectively; xSbIdx and ySbIdx represent the subblock index in the horizontal direction and vertical direction, respectively, for the luma subblock in the set (S), “<<” is the arithmetic left shift, and “>>” is the arithmetic right shift.

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect itself, if Case 1: mvAvgLX[ 0 ] >= 0, then the value for “(mvAvgLX[0] >= 0)” =1; if case 2：mvAvgLX[ 0 ] < 0, then the value for “(mvAvgLX[0] >= 0)” =0;

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect itself, the averaging of the motion vectors of the luminance subblocks in the set S comprises:

when the sum of motion vectors of luminance subblocks in a set S is greater than or equal to 0, the sum of motion vectors of luminance subblocks in set S is divided by a right shift operation depending on the number of elements (eg, luminance subblocks) in the luminance subblock set (S).

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect as such, determining the chroma scaling factors in the horizontal and vertical directions based on the chroma format information comprises:

determining chrominance scaling factors in the horizontal and vertical directions based on a mapping between the chroma format information and the chrominance scaling factors in the horizontal and vertical directions.

In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, further comprising

generating a chrominance subblock prediction based on the determined motion vector.

In a possible implementation of the method according to any previous implementation of the first aspect or the first aspect itself, the chroma format comprises one of a YUV 4:2:2 format, a YUV 4:2:0 format, or a YUV 4:4:4 format.

The method according to any previous implementation of the first aspect or the first aspect as such is implemented by an encoding device.

The method according to any previous implementation of the first aspect or the first aspect as such is implemented by a decoding device.

According to a second aspect of the invention, apparatus is provided for affine inter-prediction of a block of a current picture containing combined luma and chrominance blocks, wherein the apparatus comprises

a determination module configured to determine chrominance scaling factors in the horizontal and vertical directions based on chrominance format information, wherein the chrominance format information indicates the chrominance format of a current picture to which the current image block belongs; and determining a set (S) of luminance subblocks of the luminance block based on the values of the chroma scaling factors; And

a motion vector output module configured to determine a motion vector for a chrominance subblock of the chrominance block based on the motion vectors of one or more luminance subblocks in the luminance subblock set (S).

The method according to the first aspect of the invention can be carried out by apparatus according to the second aspect of the invention. Additional features and forms of implementation of the equipment according to the second aspect of the invention correspond to the characteristics and forms of implementation of the method according to the first aspect of the invention.

According to a third aspect, the invention relates to apparatus for de-video encoding a stream, including a processor and a memory. The memory stores instructions that cause the processor to execute the method according to the first aspect.

According to a fourth aspect, the invention relates to video stream encoding apparatus including a processor and a memory. The memory stores instructions that cause the processor to execute the method according to the first aspect.

According to a fifth aspect, there is provided a computer-readable storage medium that stores instructions that, when executed, call one or more processors configured to encode video data. The instructions cause one or more processors to perform a method according to the first aspect or any possible embodiment of the first aspect.

According to a sixth aspect, the invention relates to a computer program containing program code for performing a method according to the first or second aspect or any possible embodiment of the first when executed on a computer.

Details of one or more embodiments are set forth in the accompanying drawings and in the following description. Other features, objects and advantages will be apparent from the description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following embodiments, the inventions are described in more detail with reference to the accompanying figures and drawings, in which:

Fig. 1A is a block diagram showing an example of a video coding system configured to implement the embodiments presented herein;

Fig. 1B is a block diagram showing another example of a video coding system configured to implement the embodiments presented herein;

Fig. 2 is a block diagram showing an example of a video encoder configured to implement the embodiments presented herein;

Fig. 3 is a block diagram showing an exemplary structure of a video decoder configured to implement the embodiments presented herein;

Fig. 4 is a block diagram illustrating an example of encoding equipment or decoding equipment;

Fig. 5 is a block diagram illustrating another example of encoding equipment or decoding equipment;

Fig. 6a shows an example of control point motion vector positions for a 4-parameter affine motion model;

Fig. 6b shows an example of control point motion vector positions for a 6-parameter affine motion model;

Fig. 7 shows an example of a subblock motion vector field for an affine motion model;

Fig. 8 is a block diagram illustrating motion compensation using an affine motion model;

Fig. 9A shows an example of the nominal vertical and horizontal locations of 4:2:0 luma and chrominance samples in a picture;

Fig. 9B shows an example of the nominal vertical and horizontal positions of 4:2:2 luma and chrominance samples in a picture;

Fig. Fig. 9C shows an example of the nominal vertical and horizontal positions of 4:4:4 luma and chrominance samples in a picture;

Fig. 9D illustrates various sampling patterns;

Fig. 10A shows an example illustrating combined luma and chrominance blocks that are included in the current image block of the current picture, where the chrominance aspect ratio of the current picture is 4:2:0.

Fig. 10B shows an example illustrating combined luminance and chrominance blocks that are included in the current image block of the current picture, where the chrominance aspect ratio of the current picture is 4:2:2;

Fig. 10C shows an example illustrating combined luma and chrominance blocks that are included in the current image block of the current picture, where the chrominance aspect ratio of the current picture is 4:4:4;

Fig. 11A is an example illustrating the positions of two luminance subblocks for a given chroma subblock position at the time of outputting chroma motion vectors from luminance motion vectors when the chroma format of the current picture is 4:2:0, as shown in FIG. 10A;

Fig. 11B is an example illustrating the positions of two luminance subblocks for a given chrominance subblock position at the time of outputting chroma motion vectors from luminance motion vectors when the chroma format of the current picture is 4:2:2, as shown in FIG. 10B;

Fig. 11C is an example illustrating a luminance subblock position for a given chroma subblock position at the time of outputting chroma motion vectors from luminance motion vectors when the chroma format of the current picture is 4:4:4, as shown in FIG. 10C;

Fig. 12A shows various examples of a subset S that contains luma subblock positions for a given chrominance subblock position when the chrominance format is set to 4:4:4;

Fig. 12B shows various examples of a subset S in which chrominance subblocks located on a chrominance block boundary have corresponding positions in a luma block, as in the fourth case "D" shown in FIG. 12A;

Fig. 13A shows an example illustrating the selection of two luminance sub-blocks to output a motion vector for a given chroma sub-block at the time of deriving chroma motion vectors from luminance motion vectors when the chrominance aspect of the current picture is 4:2:0;

Fig. 13B shows an example illustrating the selection of two luminance sub-blocks for a given chroma sub-block at the time of outputting chroma motion vectors from luminance motion vectors when the chrominance aspect ratio of the current picture is 4:2:2;

Fig. 13C shows an example illustrating the selection of a luminance sub-block for a given chroma sub-block at the time of outputting chroma motion vectors from luminance motion vectors when the chrominance aspect ratio of the current picture is 4:4:4;

Fig. 14A shows an example of dividing a 16×16 luma block into subblocks and dividing a chrominance block combined with a luma block when the chrominance format is YUV 4:2:0;

Fig. 14B shows an example of dividing a 16×16 luma block into subblocks and dividing a chrominance block combined with a luma block when the chrominance format is YUV 4:2:2;

Fig. 14C shows an example of dividing a 16×16 luma block into subblocks and dividing a chrominance block combined with a luma block when the chrominance format is YUV 4:4:4;

Fig. 15 is a flow chart depicting an exemplary motion vector inference process for affine inter prediction of chroma subblocks based on a chroma format in accordance with some aspects of the present disclosure;

Fig. 16 is a flow diagram depicting another example motion vector inference process for affine inter prediction of chroma subblocks based on a chroma format in accordance with some aspects of the present disclosure;

Fig. 17 shows a schematic diagram of an apparatus for affine inter prediction in accordance with certain aspects of the present disclosure;

Fig. 18 is a block diagram showing an exemplary structure of a content delivery system that implements a content delivery service; And

Fig. 19 is a block diagram showing the structure of an exemplary terminal device.

The following identical reference numerals refer to the same or at least functionally equivalent features, unless expressly indicated otherwise.

DETAILED DESCRIPTION OF IMPLEMENTATION OPTIONS

In the following description, reference is made to the accompanying drawings, which form a part of this disclosure and which show, by way of illustration, specific aspects of embodiments of the invention or specific aspects in which embodiments of the present invention may be used. It is understood that embodiments of the present invention may be used in other aspects and contain structural or logical changes not shown in the figures. Therefore, the following detailed description should not be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

For example, it will be understood that the disclosure associated with the described method may also apply to a corresponding device or system configured to perform the method, and vice versa. For example, if one or a plurality of specific method steps are described, the corresponding apparatus may include one or a plurality of blocks, such as functional blocks, to perform the one or multiple method steps described (e.g., one block performing one or a plurality of steps, or a plurality of blocks, each of which performs one or more of a plurality of steps), even if such one or more blocks are not explicitly described or illustrated in the figures. On the other hand, for example, if a particular device is described in terms of one or a plurality of blocks, such as functional blocks, the corresponding method may include one step for performing the functionality of the one or multiple blocks (e.g., one step performing the functionality of the one or multiple blocks , or a plurality of steps, each of which performs the functionality of one or more of a plurality of blocks), even if such one or multiple steps are not explicitly described or illustrated in the figures. It is further understood that features of various exemplary embodiments and/or aspects described herein may be combined with each other unless specifically stated otherwise.

Video encoding generally refers to the processing of the sequence of pictures that form a video or video sequence. Instead of the term "picture", the terms "frame" or "image" can be used interchangeably in the field of video coding. Video encoding (or encoding in general) contains two parts: video encoding and video decoding. Video encoding is performed at the source side and typically involves processing (eg, through compression) of the source video images to reduce the amount of data required to represent the video images (for more efficient storage and/or transmission). Video decoding is performed on the receiver (destination) side and usually contains reverse processing compared to the encoder for reconstructing video images. Embodiments relating to "encoding" of video pictures (or pictures in general) are to be understood as referring to "encoding" or "decoding" video pictures or corresponding video sequences. The combination of an encoding part and a decoding part is also called CODEC (encoding and decoding).

In the case of lossless video encoding, the original video images can be restored, i.e. The restored video images are of the same quality as the original video images (provided there are no transmission losses or other data loss during storage or transmission). In the case of lossy video encoding, additional compression is performed, for example through quantization, to reduce the amount of data representing video images that cannot be fully reconstructed at the decoder, i.e. the quality of the restored video images is lower or worse compared to the quality of the original video images.

Several video coding standards belong to the group of "hybrid lossy video codecs" (that is, they combine spatial and temporal prediction in the sample domain and 2D transform coding to apply quantization in the transform domain). Each picture of a video sequence is usually divided into a set of non-overlapping blocks, and encoding is usually performed at the block level. In other words, in an encoder, video is typically processed, that is, encoded, at the block (video block) level, for example, using spatial (intra-picture) prediction and/or temporal (external) prediction to generate a prediction block, the prediction block being subtracted from the current block ( block which is currently being processed/to be processed) to obtain a residual block, the residual block is transformed and this residual block is quantized in the transformation domain to reduce the amount of data (compression) to be transmitted, whereas in the decoder, reverse processing compared to the encoder is applied to an encoded or compressed block to reconstruct the current block for presentation. In addition, the encoder duplicates the decoder's processing loop so that they will both generate identical predictions (eg, intra and inter predictions) and/or reconstructions for processing, ie encoding, subsequent blocks.

The present disclosure relates to improvements in the external prediction process. In particular, the present disclosure relates to improvements in the process of inferring chroma motion vectors. In particular, the present disclosure relates to improvements in the motion vector inference process of affine chroma blocks (eg, chroma subblocks). More specifically, the present disclosure relates to improvements in the motion vector inference process for affine inter-prediction of chroma subblocks based on chroma format.

This document discloses improved mechanisms to support multiple chroma formats for the chroma motion vector inference process.

In the following embodiments, video encoding systems 10, video encoder 20, and video decoder 30 are described based on FIGS. from 1 to 3.

Fig. 1A is a schematic block diagram illustrating an example encoding system 10, such as video encoding system 10 (or encoding system 10 for short), which may use the techniques of the present application. Video encoder 20 (or encoder 20 for short) and video decoder 30 (or decoder 30 for short) of video encoding system 10 are examples of devices that may be configured to perform techniques in accordance with the various examples described herein.

As shown in FIG. 1A, encoding system 10 includes a source device 12 configured to provide encoded picture data 21, for example, to a destination device 14 for decoding the encoded picture data 21.

The source device 12 contains an encoder 20 and can additionally, i.e. optionally comprising a picture source 16, a preprocessor (or preprocessing unit) 18, such as a picture preprocessor 18, and a communications interface or communications unit 22.

The picture source 16 may contain or be any type of picture capturing device, such as a camera for capturing a real world picture, and/or any type of picture generating device, such as a computer graphics processor for generating a computer animated picture, or any type of other device for obtaining and /or providing a real-world image, a computer-generated image (e.g., screen content, virtual reality (VR) image), and/or any combination thereof (e.g., augmented reality (AR) image). The source of the picture can be any type of memory or storage that stores any of the above pictures.

In contrast to the preprocessor 18 and the processing performed by the preprocessing unit 18, the picture or picture data 17 may also be referred to as a raw picture or raw picture data 17.

The preprocessor 18 is configured to receive (raw) picture data 17 and perform preprocessing on the picture data 17 to produce a preprocessed picture 19 or preprocessed picture data 19. Preprocessing performed by preprocessor 18 may, for example, comprise cropping, color format conversion (eg, RGB to YCbCr), color correction, or noise reduction. It can be understood that the preprocessing unit 18 may be an optional component.

Video encoder 20 is configured to receive pre-processed picture data 19 and provide encoded picture data 21 (further details will be described below, eg based on FIG. 2).

The communication interface 22 of the source device 12 may be configured to receive encoded picture data 21 and transmit this encoded picture data 21 (or any further processed version thereof) over the communication channel 13 to another device, such as the destination device 14 or any other device, for saving or immediate restoration.

The recipient device 14 includes a decoder 30 (eg, video decoder 30) and may additionally, i.e. optionally comprising a communication interface or communication unit 28, a post processor 32 (or post processing unit 32) and a display device 34.

The communication interface 28 of the destination device 14 is configured to receive encoded picture data 21 (or any further processed version thereof), for example, directly from the source device 12 or from any other source, for example, a storage device, for example, an encoded picture data storage device, and providing the encoded picture data 21 to the decoder 30.

The communication interface 22 and the communication interface 28 may be configured to transmit or receive encoded picture data 21 or encoded data 21 through a direct communication link between the source device 12 and the destination device 14, such as a direct wired or wireless connection, or through any type of network , such as a wired or wireless network or any combination thereof, or any private and public network, or any combination thereof.

The communications interface 22 may, for example, be configured to package the encoded picture data 21 into an appropriate format, such as packets, and/or process the encoded picture data using any type of transmission encoding or processing for transmission over a communications link or network.

The communication interface 28, which is analogous to the communication interface 22, may, for example, be configured to receive transmitted data and process the transmission data using any type of appropriate transmission decoding or processing and/or decompression to obtain encoded picture data 21.

Both communication interface 22 and communication interface 28 may be configured as unidirectional communication interfaces, as shown by the arrow for communication channel 13 in FIG. 1A pointing from a source device 12 to a destination device 14, or as bidirectional communication interfaces, and may be configured to, for example, send and receive messages, for example to establish a connection, to confirm and exchange any other line-related information communication and/or data transmission, such as transmission of encoded image data.

The decoder 30 is configured to receive encoded picture data 21 and provide decoded picture data 31 or decoded picture 31 (further details will be described below, for example, based on FIG. 3 or FIG. 5.

The post-processor 32 of the recipient device 14 is configured to post-process the decoded picture data 31 (also called reconstructed picture data), such as the decoded picture 31, to obtain post-processed picture data 33, such as the post-processed picture 33. Post-processing performed by block 32 post-processing may include, for example, color format conversion (eg, from YCbCr to RGB), color correction, cropping or resampling, or any other processing, for example, to prepare the decoded picture data 31 for display, for example, by display device 34.

The display device 34 of the recipient device 14 is configured to receive post-processed picture data 33 for displaying the picture, for example, to a user or viewer. The display device 34 may be or include any type of display for presenting the reconstructed picture, such as an integrated or external display or monitor. The displays may, for example, comprise liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), plasma displays, projectors, micro-LED displays, liquid crystal on silicon (LCoS), digital light processor (DLP), or any other display type.

Although Fig. 1A illustrates source device 12 and destination device 14 as separate devices, embodiments of the devices may also include both or both functionality, source device 12 or corresponding functionality and destination device 14 or corresponding functionality. In such embodiments, source device 12 or related functionality and destination device 14 or related functionality may be implemented using the same hardware and/or software, or using separate hardware and/or software, or any combination thereof. .

As will be apparent to one skilled in the art from the description, the existence and (precise) separation of functionality of various blocks or functionality in source device 12 and/or destination device 14, as shown in FIG. 1A, may vary depending on the actual device and applications.

Encoder 20 (eg, video encoder 20) or decoder 30 (eg, video decoder 30) or both encoder 20 and decoder 30 may be implemented through a processing circuit as shown in FIG. 1B, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, hardware, dedicated video encoding, or any combination thereof. Encoder 20 may be implemented through processing circuit 46 to implement various modules, as discussed with respect to encoder 20 of FIG. 2 and/or any other encoder system or subsystem described in this document. Decoder 30 may be implemented through processing circuit 46 to implement various modules, as discussed with respect to decoder 30 of FIG. 3 and/or any other decoder system or subsystem described herein. The processing circuit may be configured to perform various operations, which will be described below. As shown in FIG. 5, if the techniques are partially implemented in software, the apparatus may store instructions for the software on a suitable non-transitory computer readable storage medium and may execute the instructions in hardware using one or more processors to execute the techniques of this disclosure. Either of video encoder 20 and video decoder 30 may be integrated as part of a combined encoder/decoder (CODEC) in a single device, for example, as shown in FIG. 1B.

Source device 12 and destination device 14 may comprise any of a wide range of devices, including any type of portable or desktop devices, such as laptops or notebook computers, mobile phones, smartphones, tablets or tablet computers, cameras, desktop computers, television set-top boxes, televisions, display devices, digital media players, game consoles, video streaming devices (such as content service servers or content delivery servers), broadcast receiver, broadcast sender, or the like, and may use or dispense with any type of operating system . In some cases, source device 12 and destination device 14 may be equipped for wireless communication. Thus, source device 12 and destination device 14 may be wireless communication devices.

In some cases, the video encoding system 10 illustrated in FIG. 1A is an example only, and the techniques of the present application may be applied to video encoding settings (such as video encoding or video decoding) that do not necessarily involve transmitting any data between encoding and decoding devices. In other examples, data is retrieved from local memory, streamed over a network, or the like. A video encoding device may encode and store data into memory, and/or a video decoding device may retrieve and decode data from memory. In some examples, encoding and decoding are performed by devices that do not communicate with each other, but simply encode data into memory and/or retrieve and decode data from memory.

For ease of description, embodiments of the present invention are described herein, for example, with reference to High Efficiency Video Coding (HEVC) or Versatile Video Coding (VVC) reference software, a next generation video coding standard being developed by the Joint Collaboration on Video Coding (JCT-VC) Expert Group. ITU-T Video Coding (VCEG) and ISO/IEC Moving Picture Expert Group (MPEG). One of ordinary skill in the art will understand that embodiments of the present invention are not limited to HEVC or VVC.

Encoder and encoding method

Fig. 2 shows a schematic block diagram of an exemplary video encoder 20 that is configured to implement the techniques of the present application. In the example in FIG. 2, video encoder 20 includes an input 201 (or input interface 201), a remainder calculation block 204, a transform processing block 206, a quantization block 208, an inverse quantization block 210 and an inverse transform processing block 212, a restoration block 214, a loop filter block 220, a buffer 230 ( DPB) of decoded pictures, a mode selection unit 260, an entropy encoding unit 270, and an output 272 (or output interface 272). The mode selection block 260 may include an inter prediction block 244, an intra prediction block 254, and a partitioning block 262. The inter prediction module 244 may include a motion estimation module and a motion compensation module (not shown). The video encoder 20 shown in FIG. 2 may also be called a hybrid video encoder or a video encoder according to a hybrid video codec.

The remainder calculation block 204, transform processing block 206, quantization block 208, mode selection block 260 may relate to the formation of the forward signal path of the encoder 20, while the inverse quantization block 210, inverse transform processing block 212, restoration block 214, buffer 216, contour filter 220, decoded picture buffer (DPB) 230, inter prediction block 244, and intra prediction block 254 may relate to generating a reverse signal path of video encoder 20, wherein the reverse signal path of video encoder 20 corresponds to the signal path of the decoder (see video decoder 30 on Fig. 3). The inverse quantization unit 210, the inverse transform processing unit 212, the restoration unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 are also relevant to forming the “on-chip decoder” of the video encoder 20.

Pictures and picture breakdown (pictures and blocks)

Encoder 20 may be configured to receive, for example, through input 201, a picture 17 (or picture data 17), for example a picture from a sequence of pictures forming a video or video sequence. The received picture or picture data may also be a preprocessed picture 19 (or preprocessed picture data 19). For simplicity, the following description refers to picture 17. Picture 17 may also be referred to as the current picture or the picture that is to be encoded (particularly in video encoding, to distinguish the current picture from other pictures, for example, previously encoded and/or decoded pictures of the same video sequence, i.e. a video sequence that also contains the current picture).

A (digital) picture is, or can be viewed as, a two-dimensional array or matrix of samples with intensity values. A selection in an array may also be referred to as a pixel (short form of picture element) or pel. The number of samples in the horizontal and vertical direction (or axis) of an array or picture determines the size and/or resolution of the picture. Three color components are usually used to represent color, i.e. the picture can be presented or include three arrays of samples. In RGB, or color space, a picture contains a corresponding array of red, green, or blue samples. However, in video encoding, each pixel is typically represented in a luminance-chrominance format or color space, such as YCbCr, which contains a luminance component, denoted Y (sometimes L is also used instead), and two chrominance components (chrominance components), denoted Cb and Cr. The luminance component Y (or luma for short) represents the brightness or intensity of the gray level (for example, as in a grayscale picture), while the two chrominance components Cb and Cr (or chroma for short) represent the chrominance information components or color. Accordingly, a picture in YCbCr format contains an array of brightness samples with values (Y) of brightness samples and two arrays of chrominance samples with values (Cb and Cr) of chromaticity. Pictures in RGB format can be converted or converted to YCbCr format and vice versa, the process is also known as color conversion or conversion. If the picture is monochrome, it can only contain an array of brightness samples. Accordingly, a picture can be, for example, an array of luminance samples in a monochrome format or an array of luminance samples and two corresponding arrays of chrominance samples in 4:2:0, 4:2:2 and 4:4:4 color formats.

Embodiments of video encoder 20 may include a picture splitter (not shown in FIG. 2) configured to split picture 17 into multiple (usually non-overlapping) picture blocks 203. These blocks may also be called root blocks, macroblocks (H.264/AVC) or coding tree blocks (CTB) or coding tree units (CTU) (H.265/HEVC and VVC). The picture splitter may be configured to use the same block size for all pictures in a video sequence and a corresponding grid defining the block size, or to vary the block size between pictures or subsets or groups of pictures and split each picture into appropriate blocks.

In additional embodiments, the video encoder may be configured to receive directly a block 203 of a picture 17, such as one, more, or all of the blocks forming a picture 17. The picture block 203 may also be referred to as a current picture block or a picture block to be encoded.

Like picture 17, picture block 203 is again, or can be thought of as, a two-dimensional array or matrix of samples with intensity values (sample values), albeit smaller in size than picture 17. In other words, block 203 may contain, for example, a single array of samples (e.g. , a brightness array in the case of a monochrome picture 17 or a brightness or chrominance array in the case of a color picture) or three arrays of samples (for example, brightness and two chrominance arrays in the case of color picture 17) or any other number and/or type of arrays depending on the color used format. The number of samples in the horizontal and vertical direction (or axis) of block 203 determines the size of block 203. Accordingly, the block may, for example, be an MxN array of samples (M-column by N-row) or an MxN array of transform coefficients.

Embodiments of video encoder 20 shown in FIG. 2 may be configured to encode picture 17 block by block, for example, encoding and prediction is performed for each block 203.

Embodiments of video encoder 20, as shown in FIG. 2 may be further configured to partition and/or encode a picture using slices (also referred to as video slices), wherein the picture may be partitioned into or encoded using one or more slices (usually non-overlapping), and each slice may contain one or more units (for example, CTU).

Embodiments of video encoder 20 shown in FIG. 2 may be further configured to partition and/or encode a picture using groups of tiles (also called video tile groups) and/or tiles (also called video tiles), wherein the picture may be partitioned into or encoded using one or more tile groups (usually not overlapping), and each group of tiles may contain, for example, one or more blocks (for example, CTU) or one or more tiles, each tile, by way of example, may be rectangular in shape and may contain one or more blocks ( e.g. CTU) such as full or fractional blocks.

Calculating the remainder

Residual calculation block 204 may be configured to calculate residual block 205 (also referred to as residual 205) based on picture block 203 and prediction block 265 (additional details about prediction block 265 are provided below), for example, by subtracting the sample values of prediction block 265 from the values samples the picture block 203, sample by sample (pixel by pixel), to obtain a residual block 205 in the sample region.

Conversion

Transform processing unit 206 may be configured to apply a transform, such as a discrete cosine transform (DCT) or a discrete sine transform (DST), to the sample values of the residual block 205 to obtain transform coefficients 207 in the transform domain. The transform coefficients 207 may also be referred to as residual transform coefficients and represent the residual block 205 in the transform domain.

Transform processing block 206 may be configured to apply DCT/DST integer approximations, such as the transforms defined for H.265/HEVC. Compared to the orthogonal DCT transform, such integer approximations are usually scaled by some factor. To preserve the norm of the residual block that is processed by the forward and inverse transforms, additional scaling factors are applied as part of the transform process. Scaling factors are typically chosen based on some constraints, e.g., scaling factors are powers of two for shift operations, bit depth of transform factors, tradeoff between accuracy and implementation cost, etc. Specific scaling factors, for example, are specified for inverse transform, such as by block 212 of the inverse transform processing (and the corresponding inverse transform, for example, by the inverse transform processing block 312 in the video decoder 30), and the corresponding scaling factors for the forward transform, for example, by the transform processing block 206, can be set appropriately in the encoder 20.

Embodiments of video encoder 20 (respectively transform processing unit 206) may be configured to output transform parameters, such as the type of transform or transforms, for example, directly or encoded or compressed via entropy encoding module 270, so that, for example, video decoder 30 may receive and use conversion parameters for decoding.

Quantization

The quantization unit 208 may be configured to quantize the transform coefficients 207 to obtain quantized coefficients 209, for example, by applying scalar quantization or vector quantization. Quantized coefficients 209 may also be referred to as quantized transform coefficients 209 or quantized residual coefficients 209.

The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, an n-bit transform factor may be rounded to an m-bit transform factor during quantization, where n is greater than m. The degree of quantization can be modified by adjusting the quantization parameter (QP). For example, for scalar quantization, different scaling may be applied to achieve finer or coarser quantization. Smaller quantization step sizes correspond to finer quantization, while larger quantization step sizes correspond to coarser quantization. The applicable quantization step size may be specified by the quantization parameter (QP). The quantization parameter may, for example, be an index to a predefined set of applicable quantization step sizes. For example, small quantization parameters may correspond to fine quantization (small quantization step sizes), and large quantization parameters may correspond to coarse quantization (large quantization step sizes), or vice versa. Quantization may include dividing by a quantization step size, and corresponding dequantization and/or inverse quantization, such as by inverse quantization unit 210, may include multiplying by a quantization step size. Embodiments in accordance with some standards, such as HEVC, may be configured to use a quantization parameter to determine the quantization step size. Typically, the quantization step size can be calculated based on the quantization parameter using a fixed point approximation of the equation involving division. Additional scaling factors can be introduced for quantization and dequantization to recover the residual block norm that may have been modified due to the scaling used in the fixed point approximation of said equation for the quantization step size and the quantization parameter. In one exemplary implementation, inverse transform scaling and dequantization may be combined. Alternatively, customized quantization tables can be used and signaled from encoder to decoder, for example in a bitstream. Quantization is a lossy operation in which the loss increases with the size of the quantization steps.

Embodiments of video encoder 20 (respectively quantization unit 208) may be configured to output quantization parameters (QPs), for example, directly or encoded through entropy encoding unit 270, so that, for example, video decoder 30 can receive and apply quantization parameters for decoding.

Inverse quantization

The inverse quantization block 210 is configured to apply the inverse quantization of the quantization block 208 to the quantized coefficients to obtain the dequantized coefficients 211, for example, by applying an inverse quantization scheme to the one applied by the quantization block 208, based on or using the same quantization step size as quantization unit 208. The dequantized coefficients 211 may also be referred to as the dequantized residual coefficients 211 and correspond, although they are typically not identical to the transform coefficients due to quantization loss, to the transform coefficients 207 .

Reverse conversion

The inverse transform processing unit 212 is configured to apply an inverse transform relative to the transform applied by the transform processing unit 206, such as an inverse discrete cosine transform (DCT) or an inverse discrete sine transform (DST) or other inverse transforms to obtain the reconstructed residual block 213 (or corresponding dequantized coefficients 213) in the sample area. The reconstructed residual block 213 may also be referred to as a transform block 213.

Recovery

A reconstruction block 214 (e.g., an add block or an adder 214) is configured to add a transform block 213 (i.e., a reconstructed residual block 213) with a prediction block 265 to obtain a reconstructed block 215 in the sample domain, for example, through addition, sample per sample, the sample values of the reconstructed residual block 213, and the sample values of the prediction block 265.

Filtration

Loop filter block 220 (or “loop filter” 220 for short) is configured to filter the reconstructed block 215 to obtain a filtered block 221, or more generally to filter the reconstructed samples to obtain filtered samples. The edge filter unit, for example, is configured to smooth pixel transitions or otherwise improve video quality. Loop filter block 220 may include one or more loop filters, such as a deblocking filter, a sample adaptive offset (SAO) filter, or one or more other filters, such as a two-way filter, an adaptive loop filter (ALF), anti-aliasing filters, boost filters, etc. sharpening or joint filters, or any combination of them. Although the loop filter block 220 is shown in FIG. 2 as a loop filter, in other configurations the loop filter block 220 may be implemented as a post-loop filter. Filtered block 221 may also be referred to as filtered reconstructed block 221.

Embodiments of video encoder 20 (respectively, loop filter block 220) may be configured to output loop filter parameters (such as sample-adaptive offset information), such as directly or encoded through entropy encoding block 270, so that, for example, decoder 30 can receive and apply similar loop filter parameters or corresponding loop filters for decoding.

Buffer of decoded pictures

Decoded picture buffer (DPB) 230 may be a memory that stores reference pictures or, generally, reference picture data for video encoding of data by video encoder 20. DPB 230 may be formed by any of a variety of storage devices, such as dynamic random access memory (DRAM). DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The decoded picture buffer (DPB) 230 may be configured to store one or more filtered blocks 221. The decoded picture buffer 230 may be further configured to store other previously filtered blocks, such as previously reconstructed and filtered blocks 221, the same current picture, or different pictures, for example, previously restored pictures, and can provide complete previously restored ones, i.e. decoded, pictures (and corresponding reference blocks and samples) and/or partially reconstructed current picture (and corresponding reference blocks and samples), for example, for inter-prediction. Decoded picture buffer (DPB) 230 may also be configured to store one or more unfiltered reconstructed blocks 215, or generally unfiltered reconstructed samples, for example, if reconstructed block 215 is not filtered by loop filter block 220, or any other further processed version of the reconstructed blocks or selections.

Mode selection (partitioning and prediction)

The mode selection unit 260 includes a partitioning unit 262, an inter-prediction unit 244, and an intra-prediction unit 254, and is configured to receive or obtain original picture data, such as the original block 203 (the current block 203 of the current picture 17), and reconstructed picture data, such as filtered and /or unfiltered reconstructed samples or blocks of the same (current) picture and/or from one or multiple previously decoded pictures, for example, from decoded picture buffer 230 or other buffers (eg, a line buffer, not shown). The reconstructed picture data is used as reference picture data for prediction, such as inter prediction or intra prediction, to obtain prediction block 265 or predictor 265. As will be described in detail below, embodiments presented herein provide improvements to inter prediction block 244. providing a more accurate motion vector prediction used by the inter prediction block when performing inter prediction, such as affine inter prediction or sub-block based inter prediction.

The mode selection module 260 may be configured to determine or select a split for the current block prediction mode (including no split) and prediction mode (eg, intra or inter prediction mode) and generate a corresponding prediction block 265 that is used to calculate the residual block 205 and to restore the recovered block 215.

Embodiments of the mode selector 260 may be configured to select a partition and prediction mode (eg, from those supported by or available to the mode selector 260) that provides the best match, or in other words, the minimum remainder (the minimum remainder means the best compression for transmission or storage), or minimal signaling overhead (minimum signaling overhead means better compression for transmission or storage), or which takes into account or balances both factors. The mode selector 260 may be configured to determine a partitioning and prediction mode based on rate distortion optimization (RDO), that is, selecting a prediction mode that provides minimal rate distortion. Terms such as "best", "minimum", "optimal", etc. in this context do not necessarily refer to the all-encompassing "best", "minimum", "optimal", etc., but may also refer to meeting a selection or termination criterion, such as when a value exceeds or falls below a threshold, or other constraints, potentially leading to "suboptimal selection" but reducing complexity and processing time.

In other words, splitter 262 may be configured to split block 203 into smaller block splits or subblocks (which form blocks again), for example, iteratively using a quadtree split (QT), a binary split (BT), or a ternary tree split (TT). ) or any combination thereof, and performing, for example, prediction for each of the block splits or subblocks, wherein the mode selection comprises selecting a tree structure of the split block 203 and the prediction modes are applied to each of the block splits or subblocks.

Next, the partitioning (e.g., through partitioner 260) and prediction processing (via inter prediction unit 244 and intra prediction unit 254) performed by the exemplary video encoder 20 are explained in more detail.

Splitting

The splitter 262 may split (or divide) the current block 203 into smaller splits, such as smaller blocks of square or rectangular size. These smaller blocks (which may also be called subblocks) can be further broken down into even smaller blocks. This is also called tree splitting or hierarchical tree splitting, in which a root block, for example at root level 0 of the tree (hierarchy level 0, depth 0), can be recursively split, for example split into two or more blocks of the next lower tree level, e.g. nodes at tree level 1 (hierarchy level 1, depth 1), and these blocks can be again split into two or more blocks of the next lower level, such as tree level 2 (hierarchy level 2, depth 2), etc. until the splitting is completed, for example due to a termination criterion being met, such as reaching the maximum tree depth or minimum block size. Blocks that are not further split are also called leaf blocks or leaf nodes of a tree. A tree that uses a two-partition is called a binary tree (BT), a tree that uses a three-partition is called a ternary tree (TT), and a tree that uses a four-partition is called a quadtree (QT).

As mentioned earlier, the term "block" as used herein can be a part, particularly a square or rectangular part of a picture. With respect to, for example, HEVC and VVC, a block may be or correspond to a coding tree unit (CTU), a coding unit (CU), a prediction unit (PU) and a transform unit (TU) and/or corresponding blocks, such as a coding tree block (CTB ), a coding block (CB), a transform block (TB), or a prediction block (PB).

For example, a coding tree unit (CTU) may be or contain a CTB of luma samples, two corresponding CTBs of chroma samples of a picture that has three arrays of samples, or a CTB of samples of a monochrome picture or a picture that is encoded using three separate color planes and the syntax structures used for encoding samples. Accordingly, a coding tree block (CTB) may be an N×N block of samples for some value of N, such that dividing a component by the CTB is a partition. A coding unit (CU) may be or comprise a luma sample encoding unit, two corresponding chroma sample encoding units for a picture that has three sample arrays, or a monochrome sample encoding unit or a picture that is encoded using three separate color planes and syntactic structures used for encoding samples. Accordingly, a coding block (CB) may be an M×N block of samples for some values of M and N, so that dividing the CTB into coding blocks is a partition.

In embodiments, for example, according to HEVC, a coding tree unit (CTU) can be partitioned into CUs using a quadtree structure designated as a coding tree. The decision of whether to encode a picture region using inter-prediction (temporal) or intra-prediction (spatial) is made at the CU level. Each CU can be further partitioned into one, two or four PUs according to the PU partition type. Within a single PU, the same prediction process is applied, and the relevant information is passed to the PU-based decoder. After obtaining the residual block by applying a prediction process based on the partition type on the PU, the CU can be divided into transform units (TUs) according to another quadtree structure similar to the encoding tree for the CU.

In embodiments, for example, in accordance with the newest video coding standard currently under development, called Versatile Video Coding (VVC), for example, a combined quadtree and binary tree (QTBT) partitioning is used to partition the encoding block. In a block structure, a QTBT CU can be either square or rectangular in shape. For example, a coding tree unit (CTU) is first split into a quadtree structure. The leaf nodes of a quadtree are further partitioned into a binary tree or a ternary (or ternary) tree structure. The leaf nodes of the partitioning tree are called coding units (CUs), and this partitioning is used to process prediction and transformation without any additional partitioning. This means that CU, PU and TU have the same block size in the QTBT coding block structure. In parallel, multiple partitioning, such as ternary tree partitioning, can be used in conjunction with the QTBT block structure.

In one example, the mode selector 260 of the video encoder 20 may be configured to perform any combination of partitioning methods described herein.

As described above, video encoder 20 is configured to determine or select the best or optimal prediction mode from a set of (eg, predefined) prediction modes. The set of prediction modes may comprise, for example, intra prediction modes and/or inter prediction modes.

Internal prediction

The set of intra prediction modes may contain 35 different intra prediction modes, for example, non-directional modes, such as DC (or average) mode and planar mode, or directional modes, for example, as defined in HEVC, or may contain 67 different intra prediction modes, for example , non-directional modes such as DC (or average) mode and planar mode, or directional modes such as those defined in VVC.

The intra prediction block 254 is configured to use reconstructed samples of adjacent blocks of the same current picture to generate an intra prediction block 265 according to an intra prediction mode of a set of intra prediction modes.

The intra prediction block 254 (or more generally the mode selector 260) is further configured to output intra prediction parameters (or more generally information indicating the selected intra prediction mode for the block) to the entropy encoding block 270 in the form of syntax elements 266 for including a coded picture in the data 21 so that, for example, the video decoder 30 can receive and use the prediction parameters for decoding.

External prediction

The set of (possible) inter prediction modes depends on the available reference pictures (i.e., previous, at least partially decoded pictures, e.g., stored in DPB 230) and other inter prediction parameters, such as whether the entire reference picture is used or only a portion, such as a region search windows around the area of the current block, a reference picture to search for the most matching reference block, and/or, for example, whether pixel interpolation, such as half-pixel and/or quarter-pixel interpolation, is applied or not.

In addition to the above prediction modes, a skip mode and/or a direct mode may be used.

The inter-prediction block 244 may include a motion estimation (ME) block and a motion compensation (MC) block (both not shown in FIG. 2). The motion estimator may be configured to receive or obtain a picture block 203 (current picture block 203 for the current picture 17) and a decoded picture 231, or at least one or a plurality of previously reconstructed blocks, e.g., reconstructed blocks of one or a plurality of other/different 231 previously decoded pictures for motion estimation. For example, the video sequence may contain the current picture and previously decoded pictures 231 or, in other words, the current picture and previously decoded pictures 231 may be part of or form a sequence of pictures making up the video sequence.

The encoder 20 may, for example, be configured to select a reference block from a plurality of reference blocks of the same or different pictures from a plurality of other pictures and provide a reference picture (or reference picture index) and/or an offset (spatial offset) between the position (x, y coordinates ) of the reference block and the position of the current block as inter-prediction parameters to the motion estimation block. This displacement is also called motion vector (MV).

The motion compensation unit is configured to obtain, for example, receiving an inter prediction parameter and performing inter prediction based on or using the inter prediction parameter to obtain an inter prediction unit 265. The motion compensation performed by the motion compensation block may include obtaining or generating a prediction block based on a motion vector/block determined by motion estimation, possibly performing interpolations with sub-pixel precision. Interpolation filtering can generate additional pixel samples from known pixel samples, thereby potentially increasing the number of candidate prediction blocks that can be used to encode an image block. After receiving the motion vector for the PU block of the current picture, the motion compensation unit can determine the location of the prediction block pointed to by the motion vector in one of the reference picture lists. In the present disclosure, improvements to inter-prediction (specifically, affine inter-prediction or sub-block-based inter-prediction) are accomplished by supporting multiple chrominance formats and refining the affine sub-block motion vector inference process. In particular, an improved method and apparatus for inferring a motion vector for affine inter-prediction of chrominance subblocks based on a chrominance format will be presented below.

The motion compensation block may also generate syntax elements associated with video blocks and slices for use by video decoder 30 when decoding the picture blocks of the video slice. In addition to or as an alternative to slices and corresponding syntax elements, groups of tiles and/or tiles and corresponding syntax elements may be generated or used.

Entropy coding

The entropy encoding block 270 is configured to employ, for example, an entropy encoding algorithm or scheme (e.g., a variable length coding (VLC) scheme, a context adaptive VLC (CAVLC) scheme, an arithmetic encoding scheme, binarization, a context adaptive binary arithmetic encoding ( CABAC) based on context adaptive binary arithmetic coding (SBAC), probability interval entropy entropy (PIPE) or other entropy coding method or methodology) or bypass (uncompressed) syntax with respect to quantized coefficients 209, inter prediction parameters, parameters intra prediction, loop filter parameters, and/or other syntax elements to obtain encoded picture data 21, which may be output via output 272, for example in the form of an encoded bitstream 21, so that, for example, video decoder 30 can receive and use these parameters for decoding. The encoded bitstream 21 may be transmitted to video decoder 30 or stored in memory for later transmission or retrieval by video decoder 30.

Other changes to the structure of video encoder 20 may be used to encode the video stream. For example, non-transform encoder 20 may quantize the residual signal directly without transform processing block 206 for some blocks or frames. In another implementation, encoder 20 may have a quantization unit 208 and an inverse quantization unit 210 combined into a single unit.

Decoder and decoding method

Fig. 3 shows an example of a video decoder 30 that is configured to implement the techniques of the present application. Video decoder 30 is configured to receive encoded picture data 21 (e.g., encoded bitstream 21), such as encoded by encoder 20, to obtain a decoded picture 331. The encoded picture data or bitstream contains information for decoding the encoded picture data, e.g., data that represents picture blocks of an encoded video slice (and/or tiles or groups of tiles) and associated syntax elements.

In the example in FIG. 3, decoder 30 includes an entropy decoding block 304, an inverse quantization block 310, an inverse transform processing block 312, a recovery block 314 (e.g., adder 314), a loop filter 320, a decoded picture buffer (DPB) 330, a mode applying block 360, a block 344 inter prediction and intra prediction block 354. The inter prediction unit 344 may be or include a motion compensation unit. Video decoder 30 may, in some examples, perform a decoding step that is generally the opposite of the encoding step described with respect to video encoder 100 in FIG. 2.

As described with respect to the encoder 20, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter-prediction unit 344, and the intra-prediction unit 354 also relate to forming the “on-chip decoder”. » video encoder 20. Accordingly, the inverse quantization block 310 may be identical in function to the inverse quantization block 110, the inverse transform processing block 312 may be identical in function to the inverse transform processing block 212, the restoration block 314 may be identical in function to the reconstruction block 214, loop filter 320 may be identical in function to loop filter 220, and decoded picture buffer 330 may be identical in function to decoded picture buffer 230. Therefore, the explanations provided for the corresponding blocks and functions of the video encoder 20 apply correspondingly to the corresponding blocks and functions of the video decoder 30.

Entropy Decoding

Entropy decoding unit 304 is configured to parse bit stream 21 (or generally encoded picture data 21) and perform, for example, entropy decoding on encoded picture data 21 to obtain, for example, quantized coefficients 309 and/or decoded encoding parameters (not shown in FIG. 3), for example, any or all of the inter prediction parameters (eg, reference picture index and motion vector), intra prediction parameter (eg, index or intra prediction mode), transform parameters, quantization parameters, contour parameters filter and/or other syntax elements. The entropy decoding block 304 may be configured to apply decoding algorithms or schemes corresponding to the encoding schemes as described with respect to the entropy encoding block 270 of the encoder 20. The entropy decoding block 304 may be further configured to provide inter prediction parameters, an intra prediction parameter, and/or or other syntax elements to block 360 for applying the mode and other parameters to other blocks of decoder 30. Video decoder 30 may receive syntax elements at the video slice level and/or video block level. In addition to or as an alternative to slices and corresponding syntax elements, groups of tiles and/or tiles and corresponding syntax elements may be accepted and/or used.

Inverse quantization

The inverse quantization unit 310 may be configured to receive quantization parameters (QPs) (or, more generally, information related to inverse quantization) and quantized coefficients from the encoded picture data 21 (e.g., by parsing and/or decoding, e.g., by entropy decoding block 304) and applying, based on the quantization parameters, inverse quantization on the decoded quantized coefficients 309 to obtain dequantized coefficients 311, which may also be referred to as transform coefficients 311. The inverse quantization process may include using a quantization parameter determined by video encoder 20 for each video block in a video slice (or tile or group of tiles) to determine the degree of quantization and, likewise, the degree of inverse quantization to be applied.

Reverse conversion

The inverse transform processing unit 312 may be configured to receive the dequantized coefficients 311, also referred to as transform coefficients 311, and apply a transform to the dequantized coefficients 311 to obtain reconstructed residual blocks 213 in the sample region. The reconstructed residual blocks 213 may also be referred to as transform blocks 313. The conversion may be an inverse transform, such as an inverse DCT, an inverse DST, an integer integer transform, or a conceptually similar inverse transform process. The inverse transform processing unit 312 may be further configured to receive transform parameters or corresponding information from the encoded picture data 21 (e.g., by parsing and/or decoding, e.g., by entropy decoding unit 304) to determine a transform to be applied to dequantized coefficients 311.

Recovery

The reconstruction block 314 (e.g., add block or adder 314) may be configured to add the reconstructed residual block 313 with the prediction block 365 to obtain a reconstructed block 315 in the sample domain, for example by adding the sample values of the reconstructed residual block 313 and the sample values of the block 365 predictions.

Filtration

A loop filter block 320 (either in the encoding loop or after the encoding loop) is configured to filter the reconstructed block 315 to produce a filtered block 321, for example, to smooth pixel transitions or otherwise improve video quality. Loop filter block 320 may include one or more loop filters, such as a deblocking filter, a sample-adaptive offset (SAO) filter, or one or more other filters, such as a two-way filter, an adaptive loop filter (ALF), anti-aliasing filters, boost filters, etc. sharpening or joint filters, or any combination of them. Although the loop filter block 320 is shown in FIG. 3 as a loop filter, in other configurations the loop filter block 320 may be implemented as a post-loop filter.

Buffer of decoded pictures

The decoded video picture blocks 321 are then stored in a decoded picture buffer 330, which stores the decoded pictures 331 as reference pictures for subsequent motion compensation for other pictures and/or for output or display.

The decoder 30 is configured to output the decoded picture 311, for example, through an output 312 for presentation or viewing to the user.

Prediction

The inter-prediction block 344 may be identical to the inter-prediction block 244 (in particular, the motion compensation block), and the intra-prediction block 354 may be identical to the inter-prediction block 254 in function, and makes partitioning or partitioning decisions and performs prediction based on the partitioning parameters and /or prediction or corresponding information received from the encoded picture data 21 (eg, by parsing and/or decoding, eg, by entropy decoding unit 304). The mode application block 360 may be configured to perform prediction (intra or inter prediction) for each block based on the reconstructed pictures, blocks, or corresponding samples (filtered or unfiltered) to obtain a prediction block 365.

When a video slice is encoded as an intra-encoded (I) slice, an intra prediction block 354 of a mode applying block 360 is configured to generate a prediction block 365 for a picture block of the current video slice based on the signaled intra prediction mode and data from previously decoded current picture blocks. When a video picture is encoded as an outer-encoded (i.e., B or P) slice, an inter-prediction block 344 (e.g., a motion compensation block) of the mode applying block 360 is configured to create prediction blocks 365 for the video block of the current video slice based on motion vectors and other syntax elements received from entropy decoding unit 304. For inter-prediction, prediction blocks may be created from one of the reference pictures within one of the reference picture lists. Video decoder 30 may construct reference picture lists, List 0 and List 1, using default construction techniques based on reference pictures stored in DPB 330. The same or similar may be used for or through embodiments using tile groups (e.g., video tile groups ) and/or tiles (eg, video tiles) in addition to or alternatively to slices (eg, video slices), for example, video may be encoded using groups of I, P or B tiles and/or tiles.

The mode applying unit 360 is configured to determine prediction information for a video block of the current video slice by parsing motion vectors or related information and other syntax elements, and uses the prediction information to create prediction blocks for the current video block to be decoded. For example, mode apply block 360 uses some of the received syntax elements to determine the prediction mode (intra or inter prediction) used to encode video blocks of a video slice, the type of inter prediction slice (e.g., B-slice, P-slice, or GPB slice), construction information for one or more reference picture lists for the slice, motion vectors for each outer-coded video block of the slice, inter-prediction status for each outer-coded video block of the slice, and other information for decoding the video blocks in the current video slice. The same or similar may apply to or through embodiments using tile groups (eg, video tile groups) and/or tiles (eg, video tiles) in addition to or alternatively to slices (eg, video slices), for example, video may be encoded with using groups of I, P or B tiles and/or tiles.

Embodiments of video decoder 30, as shown in FIG. 3 may be configured to split and/or decode a picture using slices (also referred to as video slices), wherein a picture may be split into or encoded using one or more slices (usually non-overlapping), and each slice may contain one or more blocks (for example, CTU).

Embodiments of video decoder 30 shown in FIG. 3 may be configured to partition and/or decode a picture using groups of tiles (also called video tile groups) and/or tiles (also called video tiles), wherein the picture can be partitioned into or decoded using one or more tile groups (usually not overlapping), and each group of tiles may contain, for example, one or more blocks (for example, CTU) or one or more tiles, each tile, by way of example, may be rectangular in shape and may contain one or more blocks ( e.g. CTU) such as full or fractional blocks.

Other embodiments of the video decoder 30 may be used to decode the encoded picture data 21. For example, decoder 30 may produce an output video stream without loop filtering block 320. For example, the non-transform decoder 30 may perform inverse quantization of the residual signal directly without detransforming processing unit 312 for some blocks or frames. In another implementation, video decoder 30 may have an inverse quantization block 310 and an inverse transform processing block 312 combined into one block.

It should be understood that in the encoder 20 and decoder 30, the result of processing of some current stage may be further processed and then output to the next stage. For example, after interpolation filtering, motion vector inference, or contour filtering, an additional operation, such as trimming or shifting, may be performed on the result of the interpolation filtering, motion vector inference, or contour filtering processing.

It should be noted that additional operations may be applied to the derived motion vectors of the current block (including, but not limited to, affine mode checkpoint motion vectors, affine mode, planar, ATMVP mode subblock motion vectors, temporary motion vectors, and the like). For example, the value of a motion vector is limited to a predefined range according to its representing bit. If the representing bit of the motion vector is bitDepth, then the range is -2^(bitDepth-1) ~ 2^(bitDepth-1)-1, where "^" means exponentiation. For example, if bitDepth is 16, the range is -32768~32767; if bitDepth is 18, the range is -131072~131071. For example, the value of the derived motion vector (eg, the MV of four 4x4 sub-blocks in one 8x8 block) is limited such that the maximum difference between the whole portions of the MV of the four 4x4 sub-blocks is no more than N pixels, eg, no more than 1 pixel. Here are two ways to constrain the motion vector according to bitDepth.

Method 1: Removing MSB (Most Significant Bit) Overflow via Streaming Operations

ux=(mvx+2 ^bitDepth ) % 2 ^bitDepth (1)

mvx=( ux >= 2 ^bitDepth-1 ) ? (ux - 2 ^bitDepth ): ux (2)

uy=(mvy+2 ^bitDepth ) % 2 ^bitDepth (3)

mvy=( uy >= 2 ^bitDepth-1 ) ? (uy - 2 ^bitDepth ): uy (4)

where mvx represents the horizontal component of the motion vector of a picture block or sub-block, mvy represents the vertical component of the motion vector of a picture block or sub-block, and ux and uy indicate an intermediate value;

For example, if the value of mvx is -32769, after applying formulas (1) and (2), the resulting value is 32767. In a computer system, decimal numbers are stored as two's complement. The two's complement for -32769 is 1,0111,1111,1111,1111 (17 bits), then the MSB is discarded, so the resulting two's complement is 0111,1111,1111,1111 (decimal is 32767), which is the same as the output from the application of formulas (1) and (2).

ux=(mvpx + mvdx +2 ^bitDepth ) % 2 ^bitDepth (5)

mvx=( ux >= 2 ^bitDepth-1 ) ? (ux - 2 ^bitDepth ): ux (6)

uy=(mvpy + mvdy +2 ^bitDepth ) % 2 ^bitDepth (7)

mvy=( uy >= 2 ^bitDepth-1 ) ? (uy - 2 ^bitDepth ): uy (8)

Operations can be applied during the summation of mvp and mvd, as shown in formulas (5) to (8).

Method 2: Remove MSB overflow by truncating the value

vx=Clip3(-2 ^bitDepth-1 , 2 ^bitDepth-1 -1, vx)

vy=Clip3(-2 ^bitDepth-1 , 2 ^bitDepth-1 -1, vy)

where vx represents the horizontal component of the motion vector of the picture block or sub-block, vy represents the vertical component of the motion vector of the picture block or sub-block; x, y and z respectively correspond to the three input values of the MV clipping process, and the definition of the Clip3 function is as follows:

Clip3( x, y, z ) =

Fig. 4 is a schematic diagram of a video encoding apparatus 400 according to an embodiment of the present disclosure. Video encoding apparatus 400 is suitable for implementing the disclosed embodiments that are described herein. In an embodiment, video encoding device 400 may be a decoder, such as video decoder 30 of FIG. 1A, or an encoder such as video encoder 20 of FIG. 1A.

The video encoding device 400 includes input ports 410 (or input ports 410) and receiver (Rx) blocks 420 for receiving data; a processor, logical unit, or central processing unit (CPU) 430 for processing data; transmitter (Tx) blocks 440 and output ports 450 (or output ports 450) for data transmission; and a memory 460 for storing data. Video encoding device 400 may also include optical-to-electrical (OE) components and electrical-to-optical (EO) components connected to input ports 410, receiver blocks 420, transmitter blocks 440, and output ports 450 to provide optical or optical input or output. electrical signals.

The processor 430 is implemented in hardware and software. Processor 430 may be implemented as one or more CPU chips, cores (eg, a multi-core processor), FPGA, ASIC, and DSP. Processor 430 communicates with input ports 410, receiver units 420, transmitter units 440, output ports 450, and memory 460. Processor 430 includes an encoding module 470. Encoding module 470 implements the disclosed embodiments described above. For example, encoding module 470 implements, processes, prepares, or provides various encoding operations. Therefore, turning on the encoding module 470 provides a significant improvement in the functionality of the video encoding device 400 and allows the video encoding device 400 to be transformed into a different state. Alternatively, encoding module 470 is implemented as instructions stored in memory 460 and executed by processor 430.

Memory 460 may include one or more disks, tape drives, and solid-state drives and may be used as an overflow storage device for storing programs when such programs are selected for execution and for storing instructions and data that are read during execution of the programs. Memory 460 may be, for example, volatile and/or non-volatile and may be read only memory (ROM), random access memory (RAM), ternary memory associative memory (TCAM), and/or static random access memory (SRAM).

Fig. 5 is a simplified block diagram of apparatus 500 that may be used as one or both of source device 12 and destination device 14 of FIG. 1 according to an exemplary embodiment.

The processor 502 in the hardware 500 may be a central processing unit. Alternatively, processor 502 may be any other type of device or plurality of devices capable of manipulating or processing information that currently exists or will be developed in the future. Although the disclosed implementations may be practiced with a single processor, as shown, for example, with processor 502, speed and efficiency benefits may be achieved by using more than one processor.

Memory 504 in hardware 500 may be read-only memory (ROM) or random access memory (RAM) in an implementation. Memory 504 may be any other suitable type of storage device. Memory 504 may include code and data 506 accessed by processor 502 using bus 512. Memory 504 may further include an operating system 508 and application programs 510, wherein application programs 510 include at least one program which allows the processor 502 to perform the methods described herein. For example, application programs 510 may include applications 1 through N, which further include a video encoding application that performs the methods described herein.

Device 500 may also include one or more output devices, such as a display 518. Display 518 may be, in one example, a touch-sensitive display that combines a display with a touch-sensitive element capable of sensing touch inputs. Display 518 may be coupled to processor 502 via bus 512.

Although depicted here as a single bus, bus 512 of apparatus 500 may be composed of multiple buses. In addition, secondary storage 514 may be directly coupled to other components of hardware 500 or may be accessible over a network and may comprise a single plug-in unit, such as a memory card, or multiple units, such as multiple memory cards. Thus, the apparatus 500 can be implemented in a wide variety of configurations.

The embodiments presented herein will be described in more detail as follows. The video source, represented by a bitstream, may include a sequence of pictures in decoding order. Each of the pictures (which may be the original picture or the decoded picture) includes one or more of the following sample arrays:

-- Brightness (Y) only (monochrome).

- - Brightness and two chromaticities (YCbCr or YCgCo).

- - Green, Blue and Red (GBR, also known as RGB).

-- Arrays representing other undefined monochrome or tricolor color samples (for example, YZX, also known as XYZ).

For convenience of notation and terminology in the present disclosure, the variables and terms associated with these arrays are referred to as luma (or L or Y) and chroma, where the two chroma arrays are referred to as Cb and Cr.

Fig. 9A illustrates the location of the chrominance component in the case of a 4:2:0 sampling scheme. Examples of other sampling schemes are shown in Fig. 9B and 9C.

As shown in FIG. 9A, in a 4:2:0 sampling scheme there may be a shift between the luma and chrominance component grids. In a 2×2 pixel block, the chrominance components are actually shifted vertically by half a pixel compared to the luminance component (see FIG. 9A). This shift can affect interpolation filters when downsampling an image or upsampling an image. In fig. 9D shows various sampling patterns in the case of an interlaced picture. This means that parity is also taken into account, that is, whether the pixels are in the top or bottom margins of the interlaced picture.

According to the draft Versatile Video Coding (VVC) specification, a special flag "sps_cclm_colocated_chroma_flag" is signaled at the sequence parameter level. A flag "sps_cclm_colocated_chroma_flag" equal to 1 indicates that the top left subsampled luminance sample in the intra-prediction intercomponent linear modeling is colocated with the top left luminance sample. sps_cclm_colocated_chroma_flag equal to 0 indicates that the top left subsampled luminance sample in the intercomponent linear intra prediction model is horizontally colocated with the top left luminance sample, but shifted vertically by 0.5 luminance sample units relative to the top left luminance sample.

Affine prediction with motion compensation

In the real world, there are many types of motion, such as zoom in/out, rotation, perspective motion, translational motion, and other irregular motions. In HEVC (ITU-T H.265), only the displacement motion model is used for motion compensation prediction (MCP). VVC uses motion compensation prediction with affine transformation. The affine motion field of a block is described by two or three control point motion vectors (CPMVs), which correspond to a four-parameter affine motion model and a six-parameter affine motion model, respectively. The CPMV positions for the 4-parameter affine motion model are depicted in Fig. 6a, and the CPMV positions for the affine motion model with 6 parameters are depicted in Fig. 6b.

In the case of a 4-parameter motion model, the motion vector field (MVF) of a block is described by the following equation:

(1)

Where (v _0x , v _0y ) is the movement vector of the control point of the upper left corner, and (v _1x , v _1y ) is the movement vector of the control point of the upper right corner. (v _x , v _y ) is the motion vector at a given location (x, y) in the block. The Rate Distortion Overhead (RDC) check is used to determine which pair of motion vectors is selected as the reference point motion vectors of the current CU.

CPMVs can be inferred based on the movement information of neighboring blocks (for example, during the subblock merging mode). Alternatively or additionally, CPMVs can be obtained by deriving CPMV predictors (CPMVPs) and obtaining the difference between CPMVs and CPMVPs from the bitstream.

To simplify motion compensation prediction, block-based affine transformation prediction is applied. For example, to output the motion vector of each 4 × 4 sub-block, the motion vector of the center sample of each sub-block as shown in FIG. 7 is calculated according to the above equation (1) and rounded to the nearest 1/16th. Motion compensation interpolation filters are applied to generate a prediction of each sub-block with the derived motion vector.

After motion compensation prediction (MCP), the higher precision motion vector for each sub-block is rounded and stored with the same precision as the normal motion vector, with ¼ precision.

Fig. 8 shows an example flowchart depicting a process 800 for affine inter-prediction (ie, motion compensation using an affine motion model). Process 800 may include the following steps:

At step 810, a reference point motion vector is output to generate reference point motion vectors cpMvLX [cpIdx];

At step 830, an array of motion vectors is output to create an array mvLX[xSbIdx][ySbIdx] of luma subblock motion vectors and an array mvCLX[xSbIdx][ySbIdx] of chroma subblock motion vectors. Step 830 may include:

Step 831, where luminance motion vector array is output to generate luminance subblock motion vector array mvLX[xSbIdx][ySbIdx];

Step 833, where an array of chroma motion vectors is output to generate an array mvCLX [xSbIdx] [ySbIdx] of chroma subblock motion vectors;

At step 850, an interpolation process is performed to generate a prediction of each subblock with the derived motion vector, that is, an array of predSamples of prediction samples.

The embodiments presented here primarily focus on step 833 for outputting an array of chroma motion vectors (this block is highlighted in bold in FIG. 8).

The details of the chroma motion vector derivation process in the previous design (traditional way) are described as follows:

The inputs to this process (output of an array of chroma motion vectors) include:

array mvLX [xSbIdx] [ySbIdx] with xSbIdx=0..numSbX - 1, ySbIdx=0 .. numSbY - 1 of luminance subblock motion vectors and X equal to 0 or 1

Horizontal chroma sampling factor, SubWidthC

Vertical chroma sampling factor, SubHeightC

Output:

array mvCLX [xSbIdx] [ySbIdx] with xSbIdx=0..numSbX - 1, ySbIdx=0 .. numSbY - 1 chroma subblock motion vectors and X equal to 0 or 1.

This process is implemented as follows:

The average luminance motion vector mvAvgLX is derived as follows:

mvAvgLX = mvLX[ ( xSbIdx >> 1 << 1) ][ (ySbIdx>>1<<1) ] +

mvLX[ ( xSbIdx >> 1 << 1 ) + 1 ][ (ySbIdx>>1<<1) + 1 ] (2)

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] >= 0 ? ( mvAvgLX[ 0 ] + 1) >> 1 :

- ( (- mvAvgLX[ 0 ] + 1 ) >>1 ) ) (3)

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] >= 0 ? ( mvAvgLX[ 1 ] + 1) >> 1 :

- ( (- mvAvgLX[ 1 ] + 1 ) >> 1 ) ) (4)

- - Scaling mvAvgLX according to the refIdxLX value of the reference index. Specifically,

If the reference picture corresponding to refIdxLX for the current encoding unit is not the current picture, the following applies:

mvCLX[0] = mvLX[0] * 2/SubWidthC

mvCLX[1] = mvLX[1] * 2/SubHeightC

Otherwise (the reference picture corresponding to refIdxLX for the current encoding unit is the current picture), the following applies:

mvCLX [0] = ((mvLX [0] &gt;&gt; (3+SubWidthC)) * 32

mvCLX [1] = ((mvLX [1] &gt;&gt; (3+SubHeightC)) * 32

In the above scheme, the chroma subsampling is not taken into account when calculating mvAvgLX. This leads to an inaccurate estimate of the motion field for cases where one of the variables SubWidthC and SubHeightC is equal to 1.

Embodiments of the present invention solve this problem by subsampling the luminance motion field based on the chroma format of the picture, thereby improving the accuracy of the chroma motion field. More specifically, embodiments of the present invention disclose a method for taking into account the chrominance format of a picture when deriving chroma motion vectors from luminance motion vectors. By averaging the luminance motion vectors, a linear subsampling of the luminance motion field is performed. Selecting luminance motion vectors based on the picture's chroma format results in a more accurate chroma motion field due to more accurate subsampling of the luminance motion vector field. This dependence on the chroma format allows the selection of the most appropriate luminance blocks when averaging the luminance motion vectors. As a consequence of more accurate interpolation of the motion field, the prediction error is reduced, which gives the technical result of increasing compression efficiency.

In one exemplary implementation, Table 1-1 shows the chrominance formats that may be supported in the present disclosure. Chroma format information, such as chroma_format_idc and/or own_colour_plane_flag, can be used to determine the values of the SubWidthC and SubHeightC variables.

chroma_format_idc separate_colour_plane_flag Color Format SubWidthC SubHeightC 0 0 Monochrome 1 1 1 0 4:2:0 2 2 2 0 4:2:2 2 1 3 0 4:4:4 1 1 3 1 4:4:4 1 1

Table 1-1.

chroma_format_idc specifies the chroma sample relative to the luma sample. The chroma_format_idc value must be in the range 0 to 3 inclusive.

separate_colour_plane_flag equal to 1 indicates that the three color components of the 4:4:4 chroma format are encoded separately. separate_colour_plane_flag equal to 0 indicates that color components are not encoded separately. When separate_colour_plane_flag is absent, it is assumed to be 0. When separate_colour_plane_flag is 1, the encoded picture consists of three separate components, each consisting of encoded samples of a single color plane (Y, Cb, or Cr) and using monochrome encoding syntax.

Chroma format determines the priority and subsampling of chroma arrays;

In a monochrome sample there is only one sample array, which is nominally considered the luma array.

With 4:2:0 sampling, each of the two chroma arrays has half the height and half the width of the lumina array, as shown in Figure 1. 9A.

With 4:2:2 sampling, each of the two chroma arrays has the same height and half the width of the lumina array, as shown in Fig. 9B.

When sampling 4:4:4, depending on the value of own_colour_plane_flag, the following applies:

-- If separate_colour_plane_flag is 0, each of the two chroma arrays has the same height and width as the luma array, as shown in Fig. 9C.

-- Otherwise (separate_colour_plane_flag is 1), the three color planes are treated separately as monochrome sampled pictures.

In other example implementations, Table 1-2 also shows the chroma formats that may be supported in the present disclosure. Chroma format information, such as chroma_format_idc and/or own_colour_plane_flag, can be used to determine the values of the SubWidthC and SubHeightC variables.

chroma_format_idc separate_colour_plane_flag Color Format SubWidthC SubHeightC 2(0) 0 4:2:2 2 1 3(1) 0 4:4:4 1 1 3(1) 1 4:4:4 1 1

Table 1-2.

The number of bits required to represent each of the samples in the luma and chrominance arrays in a video sequence ranges from 8 to 16, inclusive, and the number of bits used in the luma array may differ from the number of bits used in the chrominance arrays.

When the value of chroma_format_idc is 1, the nominal vertical and horizontal relative locations of luma and chrominance samples in pictures are shown in FIG. 9A. Alternative relative locations of the chroma samples may be specified in the video availability information.

When the value of chroma_format_idc is 2, the chroma samples are combined with the corresponding luma samples, and the nominal locations in the picture are as shown in FIG. 9B.

When the value of chroma_format_idc is 3, all array samples are combined for all picture cases, and the nominal locations in the picture are as shown in FIG. 9C.

In one example implementation, the SubWidthC and SubHeightC variables are listed in Table 1-1 or 1-2, depending on the chroma format sampling structure, which is specified via chroma_format_idc and own_colour_plane_flag. It can be understood that chroma format information such as a chroma format sampling structure is indicated through chroma_format_idc and own_colour_plane_flag.

Unlike the previous embodiment, in the present disclosure, the determination of positions in the motion vector array of the luminance subblock can be applied to different chroma formats and depends on the value of the chroma scaling factor (eg, SubWidthC and SubHeightC). It should be understood that the “horizontal and vertical direction chroma scaling factor” may also be referred to as the “horizontal and vertical direction chroma sampling factor”.

Alternatively, in another example implementation, SubWidthC and SubHeightC could be defined as SubWidthC = (1 + log2(w_luma)-log2(w_chroma)) and SubHeightC = (1 + log2(h_luma)-log2(h_chroma)), where w_luma And h_luma are the width and height of the brightness array, respectively, and w_chroma And h_chroma- width and the height of the chroma array, respectively.

In possible implementations of some embodiments of the present disclosure, for a given chroma format, the process of determining positions or indices in the luminance motion vector array for a given index of a co-located chroma subblock may be performed as follows:

First, the values of SubWidthC and SubHeightC are determined based on the chromaticity format of the currently encoded or decoded picture (or frame).

Then, for each of the spatial chroma positions indicated by the indices xSbIdx=0..numSbX - 1, ySbIdx=0 .. numSbY - 1 and X equal to 0 or 1, the chroma motion vector value is stored as a corresponding mvCLX element. The steps to determine the chroma motion vector are as follows:

The first step is to perform a rounding to determine the x and y indices of the co-located luminance subblock:

xSbIdx _L = (xSbIdx >> (SubWidthC - 1)) << (SubWidthC - 1);

ySbIdx _L = (ySbIdx >> (SubHeightC - 1)) << (SubHeightC - 1).

The second step is to define a set of luma subblock positions that further define the chrominance motion vector. A possible example of defining such a set S can be described below:

S0 = _(xSbIdxL, ySbIdxL)

S1 = _{(xSbIdxL +} (SubWidthC- _1), ySbIdxL + (SubHeightC-1))

The third step is to calculate the average vector mvAvgLX:

When a set S contains N elements, N is a power of two, in one example implementation the motion vector mvAvgLX is defined as follows:

- mvAvgLX =

- mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + N>>1) >> log2(N)

- mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + N>>1) >> log2(N)

Where And x and y coordinates of position S _i .

To summarize, in one example implementation, the definition of the mean vector mvAvgLX for averaging can be formulated as follows:

mvAvgLX = mvLX[(xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1))]

[(ySbIdx >> (SubHeightC - 1) << (SubHeightC - 1))]+

mvLX[(xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1))+(SubWidthC - 1)]

[(ySbIdx >> (SubHeightC - 1) << (SubHeightC - 1))+(SubHeightC - 1)] (Equation 1)

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + N>>1) >> log2(N) (Equation 2)

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + N>>1) >> log2(N) (Equation 3)

It should be noted that the method presented here for averaging luminance motion vectors is not limited as stated above, and that the averaging function in the present disclosure may be implemented in various implementations.

It should be understood that although the above process is described as a three-step process, the determination of the average vector mvAvgLX as stated above in Equation 1-3 can be performed in any order.

In another exemplary implementation, the third step could also be implemented as follows:

mvAvgLX =

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] >= 0 ? ( mvAvgLX[ 0 ] + N>>1) >> log2(N) :

- ( (- mvAvgLX[ 0 ] + N>>1 ) >> log2(N) ) (5)

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] >= 0 ? ( mvAvgLX[ 1 ] + N>>1) >> log2(N) :

- ( (- mvAvgLX[ 1 ] + N>>1 ) >> log2(N) ) ) (6)

Where And x and y coordinates of position S _i .

It should be noted that the method presented here for averaging luminance motion vectors is not limited as stated above, and that the averaging function in the present disclosure may be implemented in various implementations.

The next step is to scale mvAvgLX according to the reference index value refIdxLX. In some examples, the scaling process is performed as follows by replacing mvLX with mvAvgLX (i.e. mvLX[0] will be replaced with mvAvgLX[0], and mvLX[1] will be replaced with mvAvgLX[1]):

If the reference picture corresponding to refIdxLX for the current encoding unit is not the current picture, the following applies:

mvCLX[0] = mvLX[0] * 2/SubWidthC

mvCLX[1] = mvLX[1] * 2/SubHeightC

Otherwise (the reference picture corresponding to refIdxLX for the current encoding unit is the current picture), the following applies:

mvCLX[0]=((mvLX[0]>>(3 + SubWidthC ) ) * 32

mvCLX[1]=((mvLX[1]>>(3 + SubHeightC ) ) * 32

Similarly, the chroma motion vector inference process in clause 8.5.2.13 described below can be called with mvAvgLX and refIdxLX as input and with the chroma motion vector array mvCLXSub[xCSbIdx][yCSbIdx] as output. In the process described in clause 8.5.2.13, mvLX will be replaced by mvAvgLX, and in particular, mvLX[0] will be replaced by mvAvgLX[0], and mvLX[1] will be replaced by mvAvgLX[1].

Details of possible implementations of calculating the average vector mvAvgLX in the process of deriving the chroma motion vector of the proposed method are described below in the format of a modification of the VVC project specification. There are several variations of this process.

1. One of the options for calculating the average vector mvAvgLX in the process of outputting the chroma motion vector of the proposed method can be described as follows in the format of a modification of the VVC project specification:

...

The average brightness motion vector mvAvgLX is derived as follows:

mvAvgLX =

mvLX[ ( xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1))]

[(ySbIdx >> (SubHeightC - 1) << (SubHeightC - 1))] +

mvLX[ ( xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1)) + ( 1 >> ( 2 - SubWidthC))]

[ ( ySbIdx >> (SubHeightC - 1) << (SubHeightC - 1) ) + (1 >> (2 - SubHeightC))]

Explanatory Notes: The above equation shows an example of selecting luma motion vectors to calculate the average motion vector (eg, selecting luma subblock positions for a given chrominance subblock position). The selected luma subblocks (and hence their corresponding positions) are represented by their corresponding subblock indices in the horizontal and vertical directions. For example, as shown above, for a given chrominance subblock (xSbIdx, ySbIdx), where xSbIdx and ySbIdx are the subblock indices for the chrominance subblock in the horizontal and vertical directions, respectively, the two luma subblocks (and hence their respective positions, e.g. their respective subblock indices) can be selected. One of the two selected luma subblocks can be represented by a subblock index in the horizontal direction as [(xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1))] and a subblock index in the vertical direction as [(ySbIdx >> (SubHeightC - 1) ) << (SubHeightC - 1))]. Another selected luma subblock can be represented by a subblock index in the horizontal direction as [(xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1)) + (1 >> (2 - SubWidthC))] and a subblock index in the vertical direction as [(ySbIdx >> (SubHeightC - 1) << (SubHeightC - 1)) + (1 >> (2 - SubHeightC))]). Accordingly, the choice of brightness blocks for averaging brightness motion vectors depends on the color format of the picture. In particular, the choice of luminance blocks for averaging luminance motion vectors depends on the chrominance scaling coefficients SubWidthC and SubHeightC, which are determined based on the chrominance format of the picture //

The mvAvgLX obtained above can be further processed:

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] >= 0 ? ( mvAvgLX[ 0 ] + 1) >> 1 :

- ( (- mvAvgLX[ 0 ] + 1 ) >>1 ) )

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] >= 0 ? ( mvAvgLX[ 1 ] + 1) >> 1 :

- ( (- mvAvgLX[ 1 ] + 1 ) >> 1 ) )

It should be noted that the method presented here for averaging luminance motion vectors is not limited as stated above, and that the averaging function in the present disclosure may be implemented in different ways.

-- The chroma motion vector inference process in clause 8.5.2.13, presented later in this disclosure, is called with mvAvgLX and refIdxLX as input and the chroma motion vector mvCLX [xSbIdx] [ySbIdx] as output.

...

2. Another option for calculating the average vector mvAvgLX in the process of chroma motion vector output of the proposed method can be described as follows in the format of a modification of the VVC project specification:

...

The average brightness motion vector mvAvgLX is derived as follows:

mvAvgLX =

mvLX [(xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1))]

[(ySbIdx >> (SubHeightC - 1) << (SubHeightC - 1))] +

mvLX [(xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1)) + (1 >> (4 - SubWidthC - SubHeightC))]

[(ySbIdx >> (SubHeightC - 1) << (SubHeightC - 1)) + ( 1 >> (4 - SubWidthC - SubHeightC))]

// Explanatory Notes: The above equation shows an example of selecting luma motion vectors to calculate the average motion vector (eg, selecting luma subblock positions for a given chrominance subblock position). The selected luma subblocks (and hence their corresponding positions) are represented by their corresponding subblock indices in the horizontal and vertical directions. For example, as shown above, for a given chrominance subblock (xSbIdx, ySbIdx), where xSbIdx and ySbIdx are the subblock indices for the chrominance subblock in the horizontal and vertical directions, respectively, the two luma subblocks (and hence their respective positions, e.g. their respective subblock indices) can be selected. One of the two selected luma subblocks can be represented by a subblock index in the horizontal direction as [( xSbIdx >> (SubWidthC 1) << (SubWidthC 1) ) ] and a subblock index in the vertical direction as [( ySbIdx >> (SubHeightC 1) << (SubHeightC 1) )]. Another selected luma subblock can be represented by the subblock index in the horizontal direction as [( xSbIdx >> (SubWidthC 1) << (SubWidthC 1) ) + ( 1 >> ( 4 SubWidthC SubHeightC) )] and the subblock index in the vertical direction as [( ySbIdx >> (SubHeightC 1) << (SubHeightC - 1) ) + ( 1 >> ( 4 SubWidthC SubHeightC ) )]) . Accordingly, the choice of brightness blocks for averaging brightness motion vectors depends on the color format of the picture. In particular, the choice of luminance blocks for averaging luminance motion vectors depends on the chromaticity scaling factors SubWidthC and SubHeightC, which are determined based on the chromaticity format of the picture //

Compared to the first embodiment, this embodiment uses different methods to determine the set of luminance subblocks. Specifically, 1 >> ( 4 - SubWidthC - SubHeightC ) is used to determine the index of the second luminance subblock (the adjacent luminance subblock to the first luminance subblock) in this embodiment, whereas 1 >> ( 2 - SubWidthC ) and 1 >> ( 2 - SubHeightC ) are used in the first option. In a first embodiment, the first luminance subblock itself, its diagonal neighbor, or its horizontal neighbor may be used as the second subblock. In the second embodiment, either the first luma subblock itself or its diagonal neighbor can be used as the second luma subblock depending on the chroma scaling factor values.

The mvAvgLX obtained above can be further processed:

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] >= 0 ? ( mvAvgLX[ 0 ] + 1) >> 1 :

- ( (- mvAvgLX[ 0 ] + 1 ) >>1 ) )

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] >= 0 ? ( mvAvgLX[ 1 ] + 1) >> 1 :

- ( (- mvAvgLX[ 1 ] + 1 ) >> 1 ) )

- The chroma motion vector inference process in clause 8.5.2.13 is called with mvAvgLX and refIdxLX as inputs and the chroma motion vector mvCLX [xSbIdx] [ySbIdx] as output.

...

It should be noted that the method presented here for averaging luminance motion vectors is not limited as stated above, and that the averaging function in the present disclosure may be implemented in different ways.

3. Another version of the chroma motion vector output process of the proposed method can be described as follows in the format of a modification of the VVC project specification:

...

The average brightness motion vector mvAvgLX is derived as follows:

mvAvgLX = mvLX[ ( xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1))]

[(ySbIdx >> (SubHeightC - 1) << (SubHeightC - 1))]

-- The chroma motion vector inference process in clause 8.5.2.13 is called with mvAvgLX and refIdxLX as input and the chroma motion vector mvCLX [xSbIdx] [ySbIdx] as output.

...

4. Another variant of the chroma motion vector inference process of the proposed method can be described as follows in the format of a modification of the VVC design specification:

...

The average brightness motion vector mvAvgLX is derived as follows:

If SubWidthC == 1 and SubHeightC == 1:

mvAvgLX=mvLX [xSbIdx] [ySbIdx]

otherwise

xSbIdxL = (xSbIdx >> (SubWidthC - 1)) << (SubWidthC - 1);

ySbIdxL = (ySbIdx >> (SubHeightC - 1)) << (SubHeightC - 1).

mvAvgLX = mvLX[xSbIdxL ][ySbIdxL ]+ mvLX[xSbIdxL + (SubWidthC-1)][ySbIdxL+(SubHeightC-1)]

// Explanatory Notes: The above equation shows an example of selecting luma motion vectors to calculate the average motion vector (eg, selecting luma subblock positions for a given chrominance subblock position). The selected luma subblocks (and hence their corresponding positions) are represented by their corresponding subblock indices in the horizontal and vertical directions. For example, as shown above, for a given chrominance subblock (xSbIdx, ySbIdx), where xSbIdx and ySbIdx are the subblock indices for the chrominance subblock in the horizontal and vertical directions, respectively, the two luma subblocks (and hence their respective positions, e.g. their respective subblock indices) can be selected. One of the two selected luma subblocks can be represented by a subblock index in the horizontal direction as [(xSbIdx >> (SubWidthC - 1) << (SubWidthC - 1))] and a subblock index in the vertical direction as [(ySbIdx >> (SubHeightC - 1) ) << (SubHeightC - 1))]; Another selected luminance subblock can be represented by a subblock index in the horizontal direction as [( xSbIdx >> (SubWidthC - 1 ) << ( SubWidthC - 1 ) ) + ( SubWidthC - 1 )] and a subblock index in the vertical direction as [( ySbIdx >> ( SubHeightC - 1 ) << ( SubHeightC - 1 ) ) + ( SubHeightC - 1 )]). Accordingly, the choice of brightness blocks for averaging brightness motion vectors depends on the color format of the picture. In particular, the choice of luminance blocks for averaging luminance motion vectors depends on the chrominance scaling coefficients SubWidthC and SubHeightC, which are determined based on the chrominance format of the picture //

The mvAvgLX obtained above can be further processed:

mvAvgLX[0] = mvAvgLX[0]>=0 ? mvAvgLX[0] >> 1 : -(( -mvAvgLX[0]) >> 1)

mvAvgLX[1] = mvAvgLX[1]>= 0 ? mvAvgLX[1] >> 1 : -(( -mvAvgLX[1]) >> 1)

It should be noted that the method presented here for averaging luminance motion vectors is not limited as stated above, and that the averaging function in the present disclosure may be implemented in different ways.

Details of determining luma subblock positions, which are further used in determining the chroma motion vector for various chroma formats, will be explained in combination with FIGS. 10A-10C and FIGS. 11A-11C as shown below.

Fig. 10A shows an example illustrating combined luma and chrominance blocks that are included in a current picture block (eg, an encoding block) of the current picture, where the chrominance format of the current picture is 4:2:0. As shown in FIG. 10A and Table 1-1 when the chroma format of the current picture is 4:2:0, SubWidthC=2 and SubHeightC=2. If the width of a luma block is W and the height of a luma block is H, the width of the corresponding chroma block is W/SubWidthC and the height of the corresponding chroma block is H/SubHeightC. In particular, for a block of the current picture containing combined luma and chrominance blocks, the luma block typically contains four times as many samples of the corresponding chrominance block.

Fig. 10B is an example illustrating combined luma and chrominance blocks that are included in a current picture block for a current picture where the chroma format of the current picture is 4:2:2. As shown in FIG. 10B and in Table 1-1 or 1-2 when the chroma format of the current picture is 4:2:2, SubWidthC=2 and SubHeightC=1. If the width of a luma block is W and the height of a luma block is H, the width of the corresponding chroma block is W/SubWidthC and the height of the corresponding chroma block is H/SubHeightC. In particular, for a block of the current picture containing combined luma and chrominance blocks, the luma block typically contains twice as many samples of the corresponding chrominance block.

Fig. 10C is an example illustrating combined luma and chrominance blocks that are included in a current picture block for a current picture where the chrominance format of the current picture is 4:4:4. As shown in FIG. 10C and in Table 1-1 or 1-2, when the chromaticity format of the current picture is 4: 2: 2, SubWidthC=1 and SubHeightC=1. If the width of a luma block is W and the height of a luma block is H, the width of the corresponding chroma block is W/SubWidthC and the height of the corresponding chroma block is H/SubHeightC. In particular, for a block of the current picture containing combined luma and chrominance blocks, the luma block typically contains the same number of samples of the corresponding chrominance block.

Fig. 11A is an example illustrating the positions of two luminance subblocks for a given chroma subblock position at the time of outputting chroma motion vectors from luminance motion vectors when the chroma format of the current picture is 4:2:0, as shown in FIG. 10A.

The x and y indices of a co-located luma subblock are determined using the corresponding x and y indices of the chrominance subblock (denoted xSbIdx, ySbIdx):

xSbIdx _L = (xSbIdx >> (SubWidthC - 1)) << (SubWidthC - 1);

ySbIdx _L = (ySbIdx >> (SubHeightC - 1)) << (SubHeightC - 1).

Two luminance affine subblocks are selected to further average their motion vectors. The positions of these two subblocks are defined as:

(xSbIdxL, ySbIdxL) and

(xSbIdxL + (SubWidthC-1), ySbIdxL + (SubHeightC-1)).

As shown in FIG. 11A, in the case of YUV 4:2:0 format, the motion vectors of the two luminance subblocks of the luminance block 1010 (luminance size 8x8) diagonally are used for averaging, and the averaged MV is used for the affine process of deriving the subblock motion vector for the chrominance subblock. In particular,

Index of luma subblock or chrominance subblock 0: xSbIdx=0, ySbIdx=0

Index of luma subblock or chrominance subblock 1: xSbIdx=1, ySbIdx=0

Index of luma subblock or chrominance subblock 2: xSbIdx=0, ySbIdx=1

Index of luma subblock or chrominance subblock 3: xSbIdx=1, ySbIdx=1;

Following embodiment 4, the motion vector of each chroma sub-block is output based on the average value, and the average value is obtained based on the motion vector of luminance sub-block 0 (mvLX[0][0]) and luminance sub-block 3 (mvLX[1][1]), which are diagonal.

Fig. 11B is an example illustrating the positions of two luminance subblocks for a given chrominance subblock position at the time of outputting chroma motion vectors from luminance motion vectors when the chroma format of the current picture is 4:2:2, as shown in FIG. 10B; As shown in FIG. 11B, in the case of YUV 4:2:2 format, the motion vectors of two horizontally adjacent luminance subblocks of the luminance block 1010 (luminance size 8x8) are used for averaging, and the averaged MV is used for the affine process of deriving subblock motion vectors for the chrominance subblock. In particular,

Index of luma subblock or chrominance subblock 0: xSbIdx=0, ySbIdx=0

Index of luma subblock or chrominance subblock 1: xSbIdx=1, ySbIdx=0

Index of luma subblock or chrominance subblock 2: xSbIdx=0, ySbIdx=1

Index of luma subblock or chrominance subblock 3: xSbIdx=1, ySbIdx=1;

Following the above embodiment 4, the motion vector of each chrominance subblock in the first row of chrominance block 920 is output based on the average value, and the average value is obtained based on the motion vectors of luminance subblock 0 (mvLX[0][0]) and luminance subblock 1 (mvLX [1] [0]), which are horizontally adjacent. The motion vector of each chrominance subblock in the second row of chroma block 920 is output based on the average value, and the average value is obtained based on the motion vectors of luminance subblock 2 (mvLX[0][1]) and luminance subblock 3 (mvLX[1][1]) , which are horizontally adjacent.

Fig. 11C is an example illustrating a luminance subblock position for a given chroma subblock position at the time of outputting chroma motion vectors from luminance motion vectors when the chroma format of the current picture is 4:4:4, as shown in FIG. 10C.

As shown in FIG. 11C, in the case of YUV 4:4:4 format, the co-located luminance subblock motion vector(s) of the luminance block 1010 (luminance size 8x8) are used for each chrominance subblock to perform affine prediction, i.e., an affine subblock motion vector inference process for chrominance is the same as for brightness.

It should be understood that averaging is not required, that is, the motion vector can be determined using the motion vector of a co-located luminance subblock, or this averaging operation will take as input the same MV twice and generate the same motion vector as output data. The luma or chrominance subblock size may be 4x4.

Fig. 12A shows several examples of a subset S that contains luma subblock positions for a given chrominance subblock position when the chroma format is set to 4:4:4. This example examines four cases of outputting a subset of S.

In the first case, the chroma position "A" (1201) has corresponding adjacent luminance blocks located at the positions "A" (1202).

In the second case, the chrominance position "B" (1203) is selected at the lower boundary of the chrominance block. In this case (except for the right-bottom position), the corresponding positions 1204 of luminance subblocks belonging to S are selected to be horizontally adjacent.

In the third case, the chrominance position “C” (1205) is selected at the right edge of the chrominance block. In this case (except for the lower right position), the corresponding positions 1206 of luminance subblocks belonging to S are selected to be vertically adjacent.

In the fourth case, the chrominance position "D" (1207) is selected at the lower right corner of the chrominance block. In this case, the set S contains a single luma subblock, which is located in the lower right corner of the luma block.

Fig. 12B shows another embodiment of obtaining a subset S. In this embodiment, chrominance blocks located on a chroma block boundary have corresponding positions in a luma block, as in the fourth case "D" shown in FIG. 12A.

In the embodiments of the present disclosure described above, the number of chrominance subblocks is the same as the number of co-located luminance subblocks in the case where chroma subsampling is used. Specifically, the number of luminance subblocks in the horizontal direction numSbX is the same as the number of chroma subblocks in the horizontal direction numSbX, and the number of luminance subblocks in the vertical direction numSbY is the same as the number of chroma subblocks in the vertical direction numSbY. Accordingly, the sizes of chrominance subblocks are different from the sizes of co-located luminance subblocks in the case where chroma subsampling is used.

In other scenarios, the sizes of the chrominance subblocks and luma subblocks are kept the same regardless of the chrominance format. In these scenarios, the number of chroma subblocks in a chroma block and the number of lumina subblocks in a combined lumina block may be different. The next embodiment aims to derive a chroma motion vector for subblocks of the same size for the chrominance and luma components. That is, for a current picture containing a block of the current picture containing co-located luminance and chrominance blocks, the luminance block of the current picture includes a set of luminance subblocks of the same size, and the chrominance block of the current picture includes a set of equal sized chrominance subblocks, and the size of the chrominance subblock is set equal to the size of the luma subblock. It can be understood that the number of chrominance subblocks is different from the number of co-located luminance subblocks in the case where chrominance subsampling is used. Specifically, the number of luminance subblocks in the horizontal direction, numSbX, is different from the number of chroma subblocks in the horizontal direction, numSbX, and the number of luminance subblocks in the vertical direction, numSbY, is different from the number of chroma subblocks in the vertical direction, numSbY.

As shown in FIG. 13A, in the case of YUV 4:2:0 format, for example, the luma block of the current picture has a size of 8×8, four luma subblocks of the same size are included in the luma block, and a set of chroma subblocks of the same size are included in the chroma block of the current picture (chroma subblock= chrominance block), with the size of the chrominance subblock being set equal to the size of the luminance subblock. The diagonal motion vectors of the two luma subblocks are averaged, and the averaged MV is used for the affine process of inferring the subblock motion vector for the chrominance subblock. In particular, since the number of subblocks is different, xSbIdx (subblock index of the luma subblock in the horizontal direction) will change with the step size SubWidth, and ySbIdx (subblock index of the luma subblock in the vertical direction) will change with the step size SubHeightC. For example, for 4:2:0 format xSbIdx=0, 2, 4, 6... and ySbIdx=0, 2, 4, 6...

As shown in FIG. 13B, in the case of YUV 4:2:2 format, the motion vectors of two horizontally adjacent luminance subblocks are used for averaging according to the equation of embodiment 4 above to generate a motion vector for the chrominance subblock. The averaged MV is used for the affine process of inferring the subblock motion vector for the chrominance subblock. In particular, since the number of subblocks is different, xSbIdx will change with the step size SubWidth, and ySbIdx will change with the step size SubHeightC. For example, for 4: 2: 2 xSbIdx=0, 2, 4, 8... and ySbIdx=0, 1, 2, 3...

As shown in FIG. 13C, in the case of YUV 4:4:4 format, both the number and size are equal for luma subblocks and chrominance subblocks. In this case, for each chroma subblock, the motion vector(s) of the co-located luminance subblock are used to perform affine prediction. In other words, the affine process of deriving the subblock motion vector for a chrominance block is the same as for a luminance block. For example, for 4:4:4 format xSbIdx=0, 1, 2, 3... and ySbIdx=0, 1, 2, 3... It should be noted that in this case the averaging operation specified in the equation of option 4 above , does not need to be performed because the two subblocks used for averaging are the same, and the averaging operation will output the same value as the input data. Essentially, in this case, the motion vector of the luma subblock can be selected for the chrominance subblock without going through the averaging operation formulated in the equation of any previous embodiment.

From the above, it can be seen that a block will have a number of chroma subblocks that is different from the number of luminance subblocks when SubWidthC is greater than 1 or SubHeightC is greater than 1. FIG. 14A shows an example of a 16x16 luma block subdivision and a co-located chrominance block subdivision for the YUV 4:2:0 chrominance format. In this example, the luma block is divided into 16 subblocks, each 4x4 in size. The chrominance block has a size of 8x8 samples and is divided into 4 subblocks, each of which has a size of 4x4 samples. These 4 chroma subblocks are grouped into 2 rows, each of which has 2 subblocks. The letters "A", "B", "C" and "D" indicate which luma subblocks are used to derive the motion vector for the corresponding chrominance subblock denoted by the same letter.

Fig. 14B illustrates the subdivision of a 16x16 luma block and its combined chrominance block in a picture having a YUV 4:2:2 chroma format. In this case, the chroma block has a size of 8x16 samples and is subdivided into 8 subblocks grouped into 4 rows, each the line has 2 subblocks. Each luma subblock and chrominance subblock has a sample size of 4x4. The letters "A", "B", "C", "D", "E", "F", "G" and "H" indicate which luma subblocks are used to derive the motion vector for the corresponding chroma subblock denoted by the same letter.

Assuming that the luma block is divided into numSbY rows of subblocks, each row has numSbX subblocks, and that a motion vector is specified or obtained for each of the luma subblocks, the embodiment presented here can be defined as follows:

1. The first step is to determine the values of SubWidthC and SubHeightC based on chrominance format information indicating the chrominance format of the current encoding or decoding picture (or frame). For example, the chroma format information may include the information presented in Table 1-1 or 1-2 above.

2. The second step may include: obtaining the number of chroma subblocks along the horizontal direction, numCSbX, and the number of chroma subblocks along the vertical direction, numCSbY, as follows:

numCSbX = numSbX >>( SubWidthC - 1), where numSbX is the number of luminance subblocks in the luminance block in the horizontal direction;

numCSbY = numSbY >>( SubHeightC - 1), where numSbY is the number of luminance subblocks in a luminance block in the vertical direction.

The luma block may be a block of a picture currently being encoded or decoded.

3. Designation of the chrominance subblock located in row yCSbIdx and column xCSbIdx, using spatial indices (xCSbIdx, yCSbIdx), where xCSbIdx=0, ..., numCSbX - 1 and yCSbIdx=0 .. numCSbY - 1, the value of the chroma motion vector for a chrominance subblock can be defined as follows:

Spatial indexes (xSbIdx_L, ySbIdx_L) together located subblock brightness are determined as follows:

xSbIdx _L = xCSbIdx << (SubWidthC - 1);

ySbIdx _L = yCSbIdx << (SubHeightC - 1).

The spatial position of a chrominance subblock (sbX, sbY) within a chroma block can be inferred using spatial indices (xCSbIdx, yCSbIdx) as follows:

sbX=xCSbIdx * sbX;

sbY=yCSbIdx * sbY.

The same applies to determining the spatial position for the luma subblock within the spatial indices (xSbIdx, ySbIdx) of the luma block for the luma subblock:

sbX=xSbIdx * sbX;

sbY=ySbIdx * sbY.

Specific spatial indices of the co-located luminance subblock (xSbIdx_L,ySbIdx_L) can be extra used in determining the chromaticity motion vector. For example, a set of luminance subblocks may be defined as follows:

S ₀ = (xSbIdx _L , ySbIdx _L )

S ₁ = (xSbIdx _L + (SubWidthC-1), ySbIdx _L + (SubHeightC-1))

In this example, the luma subblock set includes two subblocks indexed S₀ and S₁, calculated above. Each of the S₀ and S₁includes a pair of spatial indices defining the position of the subblock.

A set of luminance subblocks is used to calculate the average motion vector mvAvgLX. Here and in the motion vector notation used below, X can be either 0 or 1, respectively indicating the reference list index for the motion vector being either L0 or L1. L0 indicates reference list 0, and L1 indicates reference list 1. It is assumed that motion vector calculations are performed by applying the appropriate formulas independently to the horizontal component mvAvgLX[0] and the vertical component mvAvgLX[1] of the motion vector.

If the brightness motion vector of a subblock with spatial indices (xSbIdx_L, ySbIdx_L) is designated like mvLX[ xSbIdx_L][ ySbIdx_L], average motion vector mvAvgLX_Maybebe obtained as follows:

mvAvgLX = mvAvgLX 0>= 0 ? mvAvgLX >> 1 : -(( -mvAvgLX) >> 1)

Where And horizontal and vertical spatial indices of the element _Si , as discussed above, where i=0, 1.

The motion vector of the chrominance subblock mvCLX with spatial indices (xCSbIdx, yCSbIdx) is obtained from the average motion vector mvAvgLX as follows:

mvCLX[0] = mvAvgLX[0] * 2/SubWidthC

mvCLX[1] = mvAvgLX[1] * 2/SubHeightC

The details of the luma and chrominance motion vector derivation process according to the embodiments presented here are described as follows in the format of part of the VVC design specification:

8.5.5.9 Process of deriving arrays of motion vectors from affine motion vectors of control points

The inputs for this process are as follows:

luminance location (xCb, yCb) of the top left sample of the current luminance encoding block relative to the top left luminance sample of the current picture,

two variables cbWidth and cbHeight, defining the width and height of the luminance encoding block, respectively,

number of control point motion vectors numCpMv,

control point motion vectors cpMvLX [cpIdx], with cpIdx=0..numCpMv - 1 and X equal to 0 or 1,

reference index refIdxLX and X are 0 or 1,

number of luminance coding subblocks in the horizontal direction (numSbX) and in the vertical direction (numSbY).

The output of this process is:

an array of motion vectors of the brightness subblock mvLX [xSbIdx] [ySbIdx] with xSbIdx=0..numSbX - 1, ySbIdx=0 .. numSbY - 1 and X equal to 0 or 1,

an array of motion vectors of the chromaticity subblock mvCLX [xSbIdx] [ySbIdx] with xSbIdx=0..numSbX - 1, ySbIdx=0 .. numSbY - 1 and X equal to 0 or 1.

The following assignments are made for x=xCb..xCb+cbWidth - 1 and y=yCb..yCb+cbHeight - 1:

CpMvLX [x] [y] [0] = cpMvLX [0]

CpMvLX [x] [y] [1] = cpMvLX [1]

CpMvLX [x] [y] [2] = cpMvLX [2]

The log2CbW and log2CbH variables are output as follows:

log2CbW=Log2 (cbWidth)

log2CbH=Log2 (cbHeight)

The variables mvScaleHor, mvScaleVer, dHorX and dVerX are output as follows:

mvScaleHor = cpMvLX[0][0] << 7

mvScaleVer = cpMvLX[0][1] << 7

dHorX = (cpMvLX[1][0] - cpMvLX[0][0]) << (7 - log2CbW)

dVerX = (cpMvLX[1][1] - cpMvLX[0][1]) << (7 - log2CbW)

The variables dHorY and dVerY are output as follows:

If numCpMv is 3, the following applies:

dHorY =(cpMvLX[2][0] - cpMvLX[0][0]) << (7 - log2CbH)

dVerY = (cpMvLX[2][1] - cpMvLX[0][1]) << (7 - log2CbH

Otherwise (numCpMv is 2) the following applies:

dHorY = - dVerX

dVerY=dHorX

For xSbIdx=0..numSbX - 1 and ySbIdx=0..numSbY - 1 the following applies:

The brightness motion vector mvLX [xSbIdx] [ySbIdx] is output as follows:

xPosCb=2+(xSbIdx << 2)

yPosCb = 2+(ySbIdx << 2)

mvLX[xSbIdx][ySbIdx][0]=(mvScaleHor+dHorX*xPosCb+dHorY*yPosCb)

mvLX[xSbIdx][ySbIdx][1] = (mvScaleVer + dVerX * xPosCb + dVerY * yPosCb)

The rounding process for motion vectors as specified in clause 8.5.2.14 is called with mvX set to mvLX [xSbIdx] [ySbIdx], rightShift set to 7 and leftShift set to 0 as input and rounded mvLX [xSbIdx] [ySbIdx ] as output.

Motion vectors mvLX [xSbIdx] [ySbIdx] are clipped as follows:

mvLX[xSbIdx][ySbIdx][0] = Clip3( -2 ¹⁷ , 2 ¹⁷ - 1, mvLX[xSbIdx][ySbIdx][0])

mvLX[xSbIdx][ySbIdx][1] = Clip3( -2 ¹⁷ , 2 ¹⁷ - 1, mvLX[xSbIdx][ySbIdx][1])

The variables numCSbX and numCSbY are defined as follows:

numCSbX = numCSbX >> (SubWidthC - 1)

numCSbY = numCSbY >> (SubHeightC - 1)

It should be noted that this embodiment is different from the previous embodiments. In previous embodiments, the number of luma subblocks in a luma block and the number of chrominance subblocks in a combined chrominance block are the same. In this embodiment, however, for 4:2:0 and 4:2:2 chrominance formats, the number of luminance subblocks in a luminance block and the number of chroma subblocks in a combined chroma block are different. Since the number of subblocks in a chroma block and a luma block are different, xSbIdx will change with the SubWidth step size, and ySbIdx will change with the SubHeightC step size, as can be seen below.

For xCSbIdx=0..numCSbX - 1 and yCSbIdx=0..numCSbY - 1 the following applies:

The average brightness motion vector mvAvgLX is derived as follows:

If SubWidthC == 1 and SubHeightC == 1:

mvAvgLX=mvLX [xCSbIdx] [yCSbIdx]

Otherwise

– xSbIdx _L = xCSbIdx << (SubWidthC - 1)

– ySbIdx _L = yCSbIdx << (SubHeightC - 1)

– mvAvgLX = mvLX[xSbIdx _L ][ySbIdx _L ]+ mvLX[ xSbIdx _L + (SubWidthC-1)][ySbIdx _L + (SubHeightC-1)]

mvAvgLX[0] = mvAvgLX[0] >= 0 ? (mvAvgLX[0]) >> 1 : -(( -mvAvgLX[0]) >> 1)

mvAvgLX[1] = mvAvgLX[1] >= 0 ? (mvAvgLX[1]) >> 1 : -(( -mvAvgLX[1]) >> 1)

The chroma motion vector inference process in clause 8.5.2.13 presented below is called with mvAvgLX and refIdxLX as input and with the chroma motion vector array mvCLXSub[xCSbIdx][yCSbIdx] as output.

An array of chroma subblock motion vectors mvCLX [xSbIdx] [ySbIdx] with xSbIdx=0..numSbX - 1, ySbIdx=0 .. numSbY - 1 is derived from mvCLXSub as follows:

mvCLX[xSbIdx][ySbIdx] = mvCLXSub[xSbIdx>>(SubWidthC-1) ][ySbIdx >> (SubHeightC - 1)]

It should be noted that the averaging operation presented above is for illustrative purposes and should not be construed as limiting. Various other methods of performing the averaging operation can be used in determining chroma motion vectors from luminance motion vectors.

8.5.2.13 Chroma motion vector output process

The input data for this process is the following:

brightness motion vector with an accuracy of 1/16 fractional sampling mvLX,

reference index refIdxLX.

The output of this process is a chroma motion vector accurate to 1/32 of the mvCLX fractional sample.

The chroma motion vector is derived from the corresponding luminance motion vector.

The mvCLX chroma motion vector is output as follows:

mvCLX[0] = mvLX[0] * 2/SubWidthC

mvCLX[1] = mvLX[1] * 2/SubHeightC

The operations of this derivation process depend on how the process is invoked. For example, it was previously described that "the chroma motion vector inference process in clause 8.5.2.13 is called with mvAvgLX and refIdxLX as input, and with the chroma motion vector array mvCLXSub[xCSbIdx][yCSbIdx] as output." In this example, mvLX in clause 8.5.2.13 described here will be replaced by mvAvgLX to perform operations as it is called.

There are additional aspects related to embodiments that take into account the offset between subsample positions for chroma samples relative to the position of luma samples.

An exemplary embodiment would define or define a set of S luminance subblocks according to the value of sps_cclm_colocated_chroma_flag. Specifically,

When SubHeightC=1 and SubWidthC=2 and sps_cclm_colocated_chroma_flag is set to 1, the set S consists of a single element S ₀ = ₍ xSbIdxL _, ySbIdxL )

Otherwise the set S includes

S ₀ = (xSbIdx _L , ySbIdx _L )

S ₁ = (xSbIdx _L + (SubWidthC-1), ySbIdx _L + (SubHeightC-1))

Another exemplary embodiment introduces a relationship between the determination of the average motion vector and the "sps_cclm_colocated_chroma_flag" value. In particular, weights are introduced in averaging operations and can be specified differently for different luminance subblocks. An example process for obtaining the average motion vector is as follows:

xSbIdx _L = xCSbIdx << (SubWidthC - 1)

ySbIdx _L = yCSbIdx << (SubHeightC - 1).

sps_cclm_colocated_chroma_flag is set to 1, the weights w0 and w1 are set as follows: w0=5, w1=3;

mvAvgLX = w0 * mvLX[ xSbIdx _L ][ySbIdx _L ] +

+ w1 * mvLX[xSbIdx _L + (SubWidthC-1)][ySbIdx _L + (SubHeightC-1)]

mvAvgLX[0] = mvAvgLX[0] >= 0 ? (mvAvgLX[0] + 3) >>3 : -(( -mvAvgLX[0] +3) >> 3)

mvAvgLX[1] = mvAvgLX[1] >= 0 ? (mvAvgLX[1] + 3) >> 3 : -( -AvgLX[1]+3) >> 3)

It should be noted that the averaging operation presented in this example is for illustration purposes and should not be construed as a limitation. Various other methods of performing the averaging operation can be used in determining chroma motion vectors from luminance motion vectors.

Fig. 15 is a flow diagram of an example method 1300 for affine inter-prediction of chroma subblocks, the method including:

At step 1501, determining chrominance scaling factors in the horizontal and vertical directions based on the chrominance format information, wherein the chrominance format information indicates the chrominance format of the current picture to which the block of the current picture belongs;

At step 1503, determining a set (S) of luminance subblocks of the luminance block based on the values of the chroma scaling factors; And

At step 1505, determining a motion vector for a chrominance subblock of said chrominance block based on the motion vectors of one or more luma subblocks in the set (S) of luma subblocks.

Fig. 16 is a flow diagram of another exemplary method 1300 for affine inter-prediction of chroma subblocks, the method comprising:

At step 1601, determining chrominance scaling factors in the horizontal and vertical directions based on the chrominance format information, wherein the chrominance format information indicates the chrominance format of the current picture to which the block of the current picture belongs;

At step 1603, determining a motion vector value for each luminance sub-block in a plurality of luminance sub-blocks, wherein N luminance sub-blocks are included in the luminance block;

At step 1605, averaging of motion vectors of luminance subblocks in a set S of luminance subblocks is performed, wherein the set (S) is determined based on chroma scaling factors; And

At step 1607, for a chrominance subblock in a plurality of chroma subblocks, a motion vector for the chroma subblock is output based on the average luminance motion vector, with the chrominance subblocks included in the chrominance block.

The present invention discloses a method for taking into account the chrominance format of a picture when deriving chroma motion vectors from luminance motion vectors. By averaging the brightness vectors, a linear subsampling of the brightness motion field is performed. When chroma color planes have the same height as the lumina plane, it makes more sense to select motion vectors from lumina blocks that are horizontally adjacent so that they have the same vertical position. The selection of luminance motion vectors, which depends on the chroma format of the picture, results in a more accurate chroma motion field due to more accurate subsampling of the luminance motion vector field. This dependence on the chromaticity format allows you to select the most appropriate positions of luminance blocks when averaging the luminance motion vectors. As a consequence of more accurate interpolation of the motion field, the prediction error is reduced, which has the technical result of improving compression characteristics.

In addition, when the number of chrominance subblocks is set equal to the number of lumina subblocks, and when the size of the chroma color plane is not equal to the size of the lumina plane, the motion vectors of adjacent chrominance subblocks may take on the same value. When implementing these processing steps, you can perform optimization by skipping the step of calculating duplicate values. The present invention discloses a method for determining the size of a chrominance subblock equal to the size of a luminance subblock. In this case, the implementation can be simplified by unifying the luminance and chrominance processing, and, naturally, redundant motion vector calculations can be avoided.

Fig. 17 illustrates an apparatus for affine inter prediction according to another aspect of the invention. The 1700 device contains:

a determination module 1701 configured to determine chrominance scaling factors in the horizontal and vertical directions based on chrominance format information, wherein the chrominance format information indicates the chrominance format of the current picture to which the block of the current picture belongs; and determine a set (S) of luminance subblocks of the luminance block based on the values of the chroma scaling factors; And

a motion vector derivation module 1703, configured to determine a motion vector for a chrominance subblock of a chroma block based on the motion vectors of one or more luminance subblocks in the luminance subblock set (S).

In an example, motion vector output module 1703 may include:

a luminance motion vector output unit 1703a, configured to determine a motion vector value for each luminance sub-block in a plurality of luminance sub-blocks, wherein the plurality of luminance sub-blocks are included in the luminance block;

a chroma motion vector output module 1703b, configured for a chroma subblock in a plurality of chrominance subblocks, determining a motion vector for the chroma subblock based on a motion vector of at least one luminance subblock in a set (S) of luminance subblocks, wherein the set (S) is determined based on the coefficients color scaling; wherein the chrominance subblocks are included in the chrominance block. In an equal-sized circuit, multiple chrominance subblocks may constitute only one chrominance subblock.

The device 1700 further includes: a motion compensation module 1705 configured to generate a chroma subblock prediction based on the determined motion vector.

Accordingly, in some example, an exemplary structure of device 1700 may correspond to encoder 200 in FIG. 2. In another example, an exemplary structure of device 1700 may correspond to decoder 300 in FIG. 3.

In another example, an exemplary structure of device 1700 may correspond to inter prediction block 244 in FIG. 2. In another example, an exemplary structure of device 1700 may correspond to inter prediction block 344 in FIG. 3.

The present disclosure provides the following additional aspects.

According to a first aspect of the invention, there is provided a method for deriving a chroma motion vector used in affine motion compensation of an inter prediction unit, PU, wherein the PU comprises combined luma and chrominance units, wherein the method comprises

determining the chromaticity scaling factors in the horizontal and vertical directions (SubWidthC and SubHeightC) based on the chromaticity format of the current picture (for example, the current encoding or decoding of the picture);

dividing the brightness block of the current picture into a first set of brightness subblocks;

obtaining a motion vector value for each luminance sub-block in the first set of luminance sub-blocks;

dividing the chrominance block of the current picture (in the example, the chrominance block and the luma block are contained in the same PU) into a set of chrominance subblocks;

for a chrominance subblock in a set of chrominance subblocks, a second set of luminance subblocks (S) is determined, wherein the positions of the luminance subblocks in the second set are determined by the chrominance format of the current picture; And

obtaining a motion vector for the chrominance subblock based on the motion vectors of the luminance subblocks in the second set S.

In a possible form of implementation of the method according to the first aspect as such, the second set of luminance subblocks (S) comprises any combination of the following subblocks:

S ₀ = (xSbIdxL, ySbIdxL)

S ₁ = (xSbIdxL, ySbIdxL + (SubHeightC-1))

S ₂ = (xSbIdxL+ (SubWidthC-1), ySbIdxL)

S ₃ = (xSbIdxL+ (SubWidthC-1), ySbIdxL + (SubHeightC-1))

In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, wherein the second set of luminance subblocks (S) comprises two subblocks:

S0 = (xSbIdxL, ySbIdxL)

S1 = (xSbIdxL + (SubWidthC-1), ySbIdxL + (SubHeightC-1)).

In an exemplary form of implementation of the method according to any previous implementation of the first aspect or the first aspect itself, wherein deriving a motion vector for a chroma subblock based on the motion vectors of the luma subblocks in the second set S comprises averaging the motion vectors of the luma subblocks in the second set S.

In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, wherein averaging the motion vectors of the luminance subblocks in the second set S comprises the following steps:

mvAvgLX =
mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + N>>1) >> log2(N)
mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + N>>1) >> log2(N),

where mvAvgLX is the result of averaging, mvAvgLX [0] is the horizontal component of the motion vector mvAvgLX, mvAvgLX [1] is the vertical component of the motion vector mvAvgLX, And - horizontal and vertical indices of the subblock S _i in the array of motion vectors, - motion vector of the brightness subblock with indices And , N is the number of elements in the second set of luma sub-blocks (S), log2(N) is the degree to which the number 2 must be increased to obtain the value N, and “>>” is the arithmetic shift to the right.

In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect itself, wherein averaging the motion vectors of the luminance subblocks in the second set S includes the following steps:

mvAvgLX =

if mvAvgLX[ 0 ] is greater than or equal to 0, then

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + N>>1) >> log2(N), otherwise,

mvAvgLX[ 0 ] = - ( - mvAvgLX[ 0 ] + N>>1 ) >> log2(N) )

if mvAvgLX[ 1 ] is greater than or equal to 0, then

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + N>>1) >> log2(N), otherwise,

mvAvgLX[ 1 ] = - ( - mvAvgLX[ 1 ] + N>>1 ) >> log2(N)), where mvAvgLX is the result of averaging, mvAvgLX [0] is the horizontal component of the motion vector mvAvgLX, mvAvgLX [1] is the vertical component motion vector mvAvgLX, And - horizontal and vertical indices of the subblock S _i in the array of motion vectors, - motion vector of the Luma subblock with indices And , N is the number of elements in the second set of luma subblocks (S), log2(N) is the degree to which the number 2 must be increased to obtain the value N, and “>>” is the arithmetic shift to the right.

According to a second aspect of the invention, there is provided a chroma motion vector output method used in affine motion compensation of an inter-prediction unit, PU, containing co-located luma and chrominance blocks, the method comprising:

obtaining a first set of luminance subblocks, wherein the first set of luminance subblocks is included in a luminance block of the current picture (eg, the current encoding or decoding of the picture);

obtaining a motion vector value for each luminance sub-block in the first set of luminance sub-blocks;

obtaining a set of chrominance subblocks, wherein the set of chrominance subblocks is included in the chrominance block of the current picture (in the example, the chroma block and the luma block are contained in the same PU); And

obtaining a motion vector for a chrominance subblock based on the motion vectors of luminance subblocks in the second set (S) of luminance subblocks, wherein for a chrominance subblock in a set of chrominance subblocks, the second set (S) of luminance subblocks (S) is determined from the first set of luminance subblocks according to the chrominance format of the current Pictures.

In a possible form of implementing the method according to the second aspect as such, wherein the second set of luminance subblocks (S) comprises any combination of the following subblocks:

S ₀ = (xSbIdxL, ySbIdxL)

S ₁ = (xSbIdxL, ySbIdxL + (SubHeightC-1))

S ₂ = (xSbIdxL+ (SubWidthC-1), ySbIdxL)

S ₃ = (xSbIdxL+ (SubWidthC-1), ySbIdxL + (SubHeightC-1))

In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the second set of luminance subblocks (S) comprises two subblocks:

S0 = (xSbIdxL, ySbIdxL)

S1 = (xSbIdxL + (SubWidthC-1), ySbIdxL + (SubHeightC-1)).

In an exemplary form of implementation of the method according to any previous implementation of the second aspect or the second aspect itself, wherein the output of a motion vector for a chroma subblock based on the motion vectors of luminance subblocks in the second set S comprises:

averaging the motion vectors of brightness subblocks in the second set S.

In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect itself, wherein the averaging of the motion vectors of the luminance subblocks in the second set S comprises:

averaging the horizontal component of the motion vectors of the brightness subblocks in the second set S; and/or

averaging of the vertical component of the motion vectors of brightness subblocks in the second set S.

In a possible implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein averaging the elements comprises checking whether the sum of the elements (e.g. greater than or equal to 0,

if the sum of the elements is greater than or equal to 0, the sum of the elements is divided by a shift operation depending on the number of elements;

otherwise, the absolute value of the sum of the elements is divided by a shift operation depending on the number of elements, and a negative value is obtained from the shifted result.

In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the step of dividing by a shift operation comprises:

round to zero;

rounding from zero;

rounding from infinity; or

rounding to infinity.

In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the averaging step comprises: averaging or rounding away from zero.

In a possible implementation of the method according to any previous implementation of the second aspect or the second aspect itself, wherein the averaging step comprises averaging or rounding to zero.

In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the averaging step comprises averaging or rounding away from infinity.

In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect itself, wherein the averaging step comprises averaging or rounding to infinity.

In an exemplary form of implementation of the method according to any previous implementation of the second aspect or the second aspect itself, wherein averaging the motion vectors of the luminance subblocks in the second set S comprises the following steps:

mvAvgLX =

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + N>>1) >> log2(N)

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + N>>1) >> log2(N),

where mvAvgLX is the result of averaging, mvAvgLX [0] is the horizontal component of the motion vector mvAvgLX, mvAvgLX [1] is the vertical component of the motion vector mvAvgLX, And - horizontal and vertical indices of the Si subblock in the array of motion vectors, - motion vector of the brightness subblock with indices And , N is the number of elements in the second set of luminance sub-blocks (S), log2(N) is the power to which the number 2 is raised to produce the value N, and “>>” is the arithmetic shift to the right

In an exemplary form of implementation of the method according to any previous implementation of the second aspect or the second aspect itself, wherein averaging the motion vectors of the luminance subblocks in the second set S comprises the following steps:

mvAvgLX =

if mvAvgLX[ 0 ] is greater than or equal to 0, then

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + N>>1) >> log2(N), otherwise,

mvAvgLX[ 0 ] = - ( - mvAvgLX[ 0 ] + N>>1 ) >> log2(N) )

if mvAvgLX[ 1 ] is greater than or equal to 0, then

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + N>>1) >> log2(N), otherwise,

mvAvgLX[ 1 ] = - ( - mvAvgLX[ 1 ] + N>>1 ) >> log2(N) ),

where mvAvgLX is the result of averaging, mvAvgLX [0] is the horizontal component of the motion vector mvAvgLX, mvAvgLX [1] is the vertical component of the motion vector mvAvgLX, And - horizontal and vertical indices of the Si subblock in the array of motion vectors, - motion vector of the brightness subblock with indices And , N is the number of elements in the second set of luminance sub-blocks (S), log2(N) is the power to which the number 2 is raised to obtain the value N, and “>>” is the arithmetic shift to the right.

In an exemplary form of implementation of the method according to any previous implementation of the second aspect or the second aspect itself, wherein averaging the motion vectors of the luminance subblocks in the second set S comprises the following steps:

mvAvgLX = if mvAvgLX[ 0 ] is greater than or equal to 0, then mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + (N>>1) - 1) >> log2(N), otherwise, mvAvgLX[ 0 ] = - ( (- mvAvgLX [ 0 ] + (N>>1) - 1) >> log2(N) ) if mvAvgLX[ 1 ] is greater than or equal to 0, then mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + (N>>1) - 1 ) >> log2(N), otherwise, mvAvgLX[ 1 ] = - ( (- mvAvgLX[ 1 ] + (N>>1) - 1) >> log2(N) ),

where mvAvgLX is the result of averaging, mvAvgLX [0] is the horizontal component of the motion vector mvAvgLX, mvAvgLX [1] is the vertical component of the motion vector mvAvgLX, And - horizontal and vertical indices of the Si subblock in the array of motion vectors, - motion vector of the brightness subblock with indices And , N is the number of elements in the second set of luminance sub-blocks (S), log2(N) is the power to which the number 2 is raised to obtain the value N, and “>>” is the arithmetic shift to the right.

According to a third aspect of the invention, there is provided a method for affine motion compensation of a current picture, which comprises:

dividing the brightness block of the current picture into a set of brightness subblocks of the same size, and

dividing the chrominance block of the current picture into a set of chrominance subblocks of the same size, with the size of the chrominance subblock set equal to the size of the luminance subblock.

In a possible form of implementing the method according to the third aspect as such, the method further includes:

determining the number of chroma subblocks in the horizontal and vertical directions based on the values of the chroma scaling factors.

In a possible implementation of the method according to any previous implementation of the third aspect or the third aspect itself, wherein the horizontal and vertical chroma scaling factors (SubWidthC and SubHeightC) are determined based on the chrominance format of the current picture (eg, the current encoding or decoding of the picture).

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, in which

numCSbX = numSbX >>(SubWidthC-1) and

numCSbY = numSbY >>( SubHeightC -1);

numCSbX and numCSbY represent the number of chrominance subblocks in the horizontal and vertical directions, respectively.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, wherein the chrominance block division of the current picture comprises:

dividing the chroma block of the current picture (in the example, the chroma block and the luma block are contained in the same PU) into numCSbY lines, each line having numCSbX chroma subblocks.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, where the method further includes:

for each of the chromaticity subblocks, a set of luminance subblocks (S) is determined, and the positions of the luminance subblocks in the set are determined by the chromaticity format of the current picture; And

outputs a motion vector for the chrominance subblock based on the motion vectors of the luminance subblocks in the set S.

In a possible implementation form of the method according to any previous implementation of the third aspect or the third aspect itself, wherein a motion vector is determined for each of the luminance subblocks belonging to the set S.

In an exemplary form of implementation of the method according to any previous implementation of the third aspect or the third aspect itself, wherein the set of luminance subblocks (S) comprises any combination of the following subblocks:

S ₀ = (xSbIdxL, ySbIdxL)

S ₁ = (xSbIdxL, ySbIdxL + (SubHeightC-1))

S ₂ = (xSbIdxL+ (SubWidthC-1), ySbIdxL)

S ₃ = (xSbIdxL+ (SubWidthC-1), ySbIdxL + (SubHeightC-1))

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, in which the set of luminance subblocks (S) contains two subblocks:

S0 = (xSbIdxL, ySbIdxL)

S1 = (xSbIdxL + (SubWidthC-1), ySbIdxL + (SubHeightC-1)).

In an exemplary form of implementation of the method according to any previous implementation of the third aspect or the third aspect itself, wherein deriving a motion vector for a chroma subblock based on the motion vectors of the lumina subblocks in the set S involves averaging the motion vectors of the luminance subblocks in the set S.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, wherein the averaging of the motion vectors of the luminance subblocks in the set S comprises:

averaging of the horizontal component of the motion vectors of brightness subblocks in the set S,

averaging of the vertical component of the motion vectors of brightness subblocks in the set S.

In a possible implementation of the method according to any previous implementation of the third aspect or the third aspect itself, wherein averaging the elements includes checking whether the sum of the elements is greater than or equal to 0.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, where averaging means averaging other than zero.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, where averaging means averaging towards zero.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, where averaging means averaging from infinity.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, where averaging means averaging to infinity.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect itself, wherein averaging the motion vectors of the luminance subblocks in the set S comprises the following steps:

mvAvgLX =

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + N>>1) >> log2(N)

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + N>>1) >> log2(N),

where mvAvgLX is the result of averaging, mvAvgLX [0] is the horizontal component of the motion vector mvAvgLX, mvAvgLX [1] is the vertical component of the motion vector mvAvgLX, And - horizontal and vertical indices of the Si subblock in the array of motion vectors, - motion vector of the brightness subblock with indices And , N is the number of elements in the second set of luminance sub-blocks (S), log2(N) is the power to which the number 2 is raised to obtain the value N, and “>>” is the arithmetic shift to the right.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, wherein averaging the motion vectors of the luminance subblocks in the set S comprises the following steps:

mvAvgLX =

if mvAvgLX[ 0 ] is greater than or equal to 0, then

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + N>>1) >> log2(N), otherwise,

mvAvgLX[ 0 ] = - ( - mvAvgLX[ 0 ] + N>>1 ) >> log2(N) )

if mvAvgLX[ 1 ] is greater than or equal to 0, then

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + N>>1) >> log2(N), otherwise,

mvAvgLX[ 1 ] = - ( - mvAvgLX[ 1 ] + N>>1 ) >> log2(N) ),

where mvAvgLX is the result of averaging, mvAvgLX [0] is the horizontal component of the motion vector mvAvgLX, mvAvgLX [1] is the vertical component of the motion vector mvAvgLX, And - horizontal and vertical indices of the Si subblock in the array of motion vectors, - motion vector of the brightness subblock with indices And , N is the number of elements in the second set of luminance sub-blocks (S), log2(N) is the power to which the number 2 is raised to obtain the value N, and “>>” is the arithmetic shift to the right.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, wherein averaging the motion vectors of the luminance subblocks in the set S comprises the following steps:

mvAvgLX =

if mvAvgLX[ 0 ] is greater than or equal to 0, then

mvAvgLX[ 0 ] = ( mvAvgLX[ 0 ] + (N>>1) - 1) >> log2(N), otherwise,

mvAvgLX[ 0 ] = - ( (- mvAvgLX[ 0 ] + (N>>1) - 1) >> log2(N) )

if mvAvgLX[ 1 ] is greater than or equal to 0, then

mvAvgLX[ 1 ] = ( mvAvgLX[ 1 ] + (N>>1) - 1) >> log2(N), otherwise,

mvAvgLX[ 1 ] = - ( (- mvAvgLX[ 1 ] + (N>>1) - 1) >> log2(N)),

where mvAvgLX is the result of averaging, mvAvgLX [0] is the horizontal component of the motion vector mvAvgLX, mvAvgLX [1] is the vertical component of the motion vector mvAvgLX, And - horizontal and vertical indices of the Si subblock in the array of motion vectors, - motion vector of the brightness subblock with indices And , N is the number of elements in the second set of luminance sub-blocks (S), log2(N) is the power to which the number 2 is raised to obtain the value N, and “>>” is the arithmetic shift to the right.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, where N is 1.

In a possible implementation of the method according to any previous implementation of the third aspect or the third aspect itself, wherein the set S is determined based on the value of sps_cclm_colocated_chroma_flag.

In an exemplary form of implementation of the method according to any previous implementation of the third aspect or the third aspect itself, wherein the average motion vector is inferred based on the value of sps_cclm_colocated_chroma_flag.

In a possible implementation of the method according to any previous implementation of the third aspect or the third aspect itself, in which the chroma format is specified as YUV 4:2:2.

In a possible form of implementation of the method according to any previous implementation of the third aspect or the third aspect as such, in which the chrominance block and the luminance block are contained in the same PU, and the luminance and chrominance blocks are combined.

A fourth aspect of the encoder (20) comprising processing circuitry for performing a method according to any of the first to third aspects.

A fifth aspect of the decoder (30) comprising processing circuitry for performing a method according to any of the first to third aspects.

A sixth aspect of a computer program product comprising program code for performing a method according to any of the first to third aspects.

The seventh aspect of the decoder, containing:

one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing a program for execution by the processors, wherein the program, when executed by the processors, configures a decoder to perform a method in accordance with any of the first to third aspects.

The eighth aspect of the encoder, containing:

one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing a program for execution by the processors, wherein the program, when executed by the processors, configures an encoder to perform a method in accordance with any of the first to third aspects.

Based on the foregoing, the present disclosure is aimed at disclosing a method for taking into account the chrominance format of a picture when deriving chroma motion vectors from luminance motion vectors. By averaging the luminance motion vectors, a linear subsampling of the luminance motion field is performed. When chroma color planes have the same height as the lumina plane, it makes more sense to select motion vectors from lumina blocks that are horizontally adjacent so that they have the same vertical position. Selecting luminance motion vectors depending on the chroma format of the picture results in a more accurate chroma motion field due to more accurate subsampling of the luminance motion vector field. This dependence on the chroma format allows the selection of the most appropriate luminance blocks when averaging the luminance motion vectors to generate a chroma motion vector. As a consequence of more accurate interpolation of the motion field, the prediction error is reduced, which leads to the technical result of improved compression characteristics.

The following will be an explanation of the applications of the encoding method as well as the decoding method as shown in the above-mentioned embodiments and the system using them.

Fig. 18 is a block diagram showing a content delivery system 3100 for implementing a content distribution service. This content delivery system 3100 includes a capture device 3102, a terminal device 3106, and optionally includes a display 3126. The capture device 3102 communicates with the terminal device 3106 via a communication line 3104. The communication link may include a communication channel 13 described above. Communication link 3104 includes, but is not limited to, WIFI, Ethernet, cable, wireless (3G/4G/5G), USB, or any combination thereof, or the like.

The capture device 3102 generates data and can encode the data using the encoding method shown in the above embodiments. Alternatively, capture device 3102 may distribute the data to a streaming server (not shown in the Figures), and the server encodes the data and transmits the encoded data to terminal device 3106. Capture device 3102 includes, but is not limited to, a camera, smartphone, or tablet. , a computer or laptop, a video conferencing system, a PDA, a vehicle-mounted device, or a combination of any of these, or the like. For example, capture device 3102 may include source device 12 described above. When the data includes video, the video encoder 20 included in the capture device 3102 may actually perform video encoding processing. When the data includes audio (ie, voice), an audio encoder included in the capture device 3102 may actually perform audio encoding processing. For some practical scenarios, capture device 3102 distributes encoded video and audio data by multiplexing them together. For other practical scenarios, such as in a video conferencing system, encoded audio data and encoded video data are not multiplexed. The capture device 3102 distributes the encoded audio data and the encoded video data to the terminal device 3106 separately.

In the content delivery system 3100, a terminal device 3106 receives and reproduces encoded data. Terminal device 3106 may be a device capable of receiving and retrieving data, such as a smartphone or tablet 3108, computer or laptop 3110, network video recorder (NVR)/digital video recorder (DVR) 3112, television 3114, set-top box (STB) 3116, video conferencing system 3118 , a video surveillance system 3120, a personal digital assistant (PDA) 3122, a vehicle-mounted device 3124, or a combination thereof, or the like, capable of decoding the above encoded data. For example, terminal device 3106 may include receiver device 14 described above. When the encoded data includes video, the video decoder 30 included in the terminal device is given priority to perform video decoding. When the encoded data includes audio, an audio decoder included in the terminal device is given priority to perform audio decoding processing.

For a terminal device with its own display, such as a smartphone or tablet 3108, a computer or laptop 3110, a network video recorder (NVR)/digital video recorder (DVR) 3112, a television 3114, a personal digital assistant (PDA) 3122, or a vehicle-mounted device 3124, terminal the device can transmit decoded data to its display. For a non-display terminal device, such as the STB 3116, video conferencing system 3118, or video surveillance system 3120, it communicates with an external display 3126 to receive and display the decoded data.

When each device in this system performs encoding or decoding, a picture encoding device or a picture decoding device may be used, as shown in the above embodiments.

Fig. 19 is a diagram showing the structure of an exemplary terminal device 3106. After the terminal device 3106 receives a stream from the capture device 3102, a protocol processing unit 3202 analyzes the transmission protocol of the stream. The protocol includes, but is not limited to, Real Time Streaming Protocol (RTSP), Hypertext Transfer Protocol (HTTP), HTTP Live Streaming Protocol (HLS), MPEG-DASH, Real Time Transport Protocol (RTP), Exchange Protocol real-time messaging (RTMP) or any combination thereof, or the like.

After the protocol processing unit 3202 processes the stream, a stream file is generated. The file is output to a demultiplexing block 3204. A demultiplexer 3204 may separate the multiplexed data into encoded audio data and encoded video data. As described above, in other practical scenarios, such as in a video conferencing system, encoded audio data and encoded video data are not multiplexed. In this situation, the encoded data is transmitted to the video decoder 3206 and audio decoder 3208 without using the demultiplexing module 3204.

Through demultiplexing processing, an elementary video stream (ES), audio ES, and optionally subtitles are generated. The video decoder 3206, which includes the video decoder 30 described in the above embodiments, decodes the ES video using the decoding method as shown in the above embodiments to generate a video frame and supplies this data to the synchronous block 3212. The audio decoder 3212 decodes the ES audio to generate audio frame and supplies this data to synchronous block 3212. Alternatively, a video frame may be stored in a buffer (not shown in FIG. Y) before it is supplied to synchronous block 3212. Similarly, an audio frame may be stored in a buffer (not shown in FIG. Y) before it is feeding into synchronous block 3212.

A synchronization block 3212 synchronizes a video frame and an audio frame and supplies video/audio to a video/audio display 3214. For example, a synchronization block 3212 synchronizes the presentation of video and audio information. Information may be encoded in syntax using timestamps relating to the presentation of the encoded audio and video data, as well as timestamps relating to the delivery of the data stream itself.

If subtitles are included in the stream, subtitle decoder 3210 decodes the subtitles and synchronizes them with the video frame and audio frame and transmits the video/audio/subtitles to the video/audio/subtitle display 3216.

The present invention is not limited to the above system, and either the picture encoding device or the picture decoding device in the above embodiments may be included in another system, such as an automobile system.

Mathematical operators

The mathematical operators used in this application are similar to those used in the C programming language. However, the results of the integer division and arithmetic shift operations are defined more precisely, and additional operations such as exponentiation and real-valued division are defined. Numbering and counting conventions specify starting at 0, for example, "first" is equivalent to 0, "second" is equivalent to 1, etc.

Arithmetic operators

The following arithmetic operators are defined as follows:

+ Addition - Subtraction (as a two-argument operator) or negation (as a unary prefix operator) * Multiplication, including matrix multiplication x ^y Exponentiation. Defines x to the power of y. In other contexts, this notation is used as a superscript that should not be interpreted as exponentiation. / Integer division with the result truncated towards zero. For example, 7/4 and -7/-4 are truncated to 1, and -7/4 and 7/-4 are truncated to -1. ÷ Used to indicate division in mathematical equations where truncation or rounding is not intended. Used to indicate division in mathematical equations where truncation or rounding is not intended. Summation f(i), where i takes all integer values from x to y inclusive. x % y Modulo operation. The remainder of x divided by y is defined only for integers x and y, where x>=0 and y>0.

Logical operators

The following logical operators are defined as follows:

x && y

x || y Boolean logical "or" for x and y

! Boolean logical "not"

x?y:z If x is TRUE or not 0, the value of y is calculated; otherwise, the z value is calculated.

Relational operators

The following relational operators are defined as follows:

> More

>= Greater than or equal to

< Less

<= Less than or equal to

= == Equal

!=Not equal

When a comparison operator is applied to a syntax element or variable that is assigned the value "na" (not applicable), the value "na" is treated as a separate value for the syntax element or variable. The value "na" is not considered equal to any other value.

Bit operators

The following bitwise operators are defined as follows:

& Bitwise "and". When operating on integer arguments, operates on the two's complement representation of an integer value. When working on a binary argument that contains fewer bits than another argument, the shorter argument is expanded by adding more significant bits that are 0.

| When operating on integer arguments, operates on the two's complement representation of an integer value. When working on a binary argument that contains fewer bits than another argument, the shorter argument is expanded by adding more significant bits that are 0.

^ When operating on integer arguments, operates on the two's complement representation of an integer value. When working on a binary argument that contains fewer bits than another argument, the shorter argument is expanded by adding more significant bits that are 0.

x >> y Arithmetic right shift of the two's complement integer representation of x by y binary digits. This function is defined only for non-negative integer values of y. The bits shifted to the most significant bits (MSB) by a right shift have a value equal to the MSB of x before the shift operation.

x << y Arithmetic left shift of the two's complement integer representation of x by y binary digits. This function is defined only for non-negative integer values of y. Bits shifted to the least significant bits (LSB) by left shifting have a value of 0.

Assignment Operators

The following arithmetic operators are defined as follows:

= assignment operator

+ +Increment, i.e. x+ + is equivalent to x=x+1; when used in an array index, evaluates to the value of the variable before the increment operation.

- - Decrease, i.e. x- - equivalent to x=x - 1; when used in an array index, evaluates the value of the variable before the decrement operation.

+= Increment by the specified amount, i.e. x += 3 is equivalent to x=x+3, and x += (-3) is equivalent to x=x + (-3).

-= Decrease by the specified amount, i.e. x -= 3 is equivalent to x=x - 3, and x -= (-3) is equivalent to x=x - (-3).

Range designation

The following notation is used to indicate a range of values:

x = y..z x takes integer values from y to z, inclusive, where x, y and z are integers and z is greater than y.

Mathematical functions

The following mathematical functions are defined:

Abs( x ) =

Asin( x ) is a trigonometric arcsine function operating on an argument x that ranges from 1.0 to 1.0 inclusive, with an output value ranging from -π÷2 to π÷2 inclusive, in units of radians.

Atan(x) is a trigonometric arctangent function operating on an argument x, with an output value ranging from -π÷2 to π÷2 inclusive, in units of radians.

Atan2( y, x ) =

Ceil( x ) is the smallest integer greater than or equal to x.

Clip1Y( x ) = Clip3( 0, ( 1 << BitDepthY ) - 1, x )

Clip1C( x ) = Clip3( 0, ( 1 << BitDepthC ) - 1, x )

Clip3( x, y, z ) =

Cos( x ) is a trigonometric cosine function that operates on x in units of radians.

Floor( x ) is the largest integer less than or equal to x.

GetCurrMsb( a, b, c, d ) =

Ln( x ) natural logarithm of x (logarithm to base e, where e is the base constant of the natural logarithm 2.718 281 828...).

Log2( x ) logarithm of x to base 2

Log10( x ) is the logarithm of x to base 10.

Min( x, y ) =

Max( x, y ) =

Round( x ) = Sign( x ) * Floor( Abs( x ) + )

Sign( x ) =

Sin( x ) is a trigonometric sine function that operates on x in units of radians.

Sqrt( x ) =

Swap( x, y ) = ( y, x )

Tan( x ) is a trigonometric tangent function that operates on x in units of radians.

Order of priority of operations

When the order of precedence in an expression is not explicitly specified using parentheses, the following rules apply:

-- Higher priority operations are evaluated before any lower priority operation.

-- Operations with the same priority are evaluated sequentially from left to right.

The table below lists the priority of operations from highest to lowest; a higher position in the table indicates higher priority.

For those operators that are also used in the C programming language, the order of precedence used in this description is the same as in the C programming language.

Table: Operation priority from highest (at the top of the table) to lowest (at the bottom of the table)

operations (with operands x, y and z) "x++", "x- -" "!x", "-x" (as unary prefix operator) xy "x * y", "x/y", "x ÷ y", " x % y" "x+y", "x - y" (as an operator with two arguments), " " "x << y", "x >> y" "x < y", "x <= y", "x > y", "x >= y" "x == y", "x != y" "x&y" "x | y" "x && y" "x | | y" "x ? y : z" "x..y" "x=y", "x += y", "x -= y"

Text description of logical operations

The text contains a definition of logical operations, which would be described mathematically in the following form:

if (condition 0 )

definition 0

else if (condition 1)

definition 1...

else /* informative comment on the remaining condition */ definition n

can be described as follows:

... as below / ... the following applies:

- if condition 0, definition 0

- Otherwise, if condition 1, definition 1

-...

-- Otherwise (informative comment on the remaining condition), definition n.

Each "if...otherwise, if...else,..." definition in the text is introduced by the words "...as follows" or "...the following applies" followed immediately by "if...". The final condition of “if...otherwise, if...otherwise,...” is always “otherwise,...”. Alternating definitions "if...otherwise, if...otherwise,..." can be identified by matching "...as follows" or "...the following applies" with the final "otherwise,...".

The text contains a definition of logical operations, which would be described mathematically in the following form:

if ( condition 0a && condition 0b )

definition 0

else if( condition 1a | | condition 1b )

definition 1...

Otherwise, the definition of n

can be described as follows:

... as below / ... the following applies:

-- If all of the following conditions are true, definition 0:

- condition 0a

- condition 0b

-- Else, if one or more of the following conditions are true, definition 1:

- condition 1a

- condition 1b

-...

- Otherwise, the definition of n

The text contains a definition of logical operations, which would be described mathematically in the following form:

if (condition 0 )

definition 0

if (condition 1)

definition 1

can be described as follows:

When condition is 0, definition is 0

When condition 1, definition 1

The invention has been described in connection with various embodiments herein. However, other variations of the disclosed embodiments may be understood and implemented by those skilled in the art in the practice of the claimed invention based on a study of the drawings, this disclosure, and the accompanying claims. In a claim, the word “comprising” does not exclude other elements or steps, and mentioning something in the singular does not exclude the plurality. One processor or other unit can perform the functions of several elements specified in the claims. The mere fact that certain measures are set forth in typically different dependent claims does not mean that a combination of these measures cannot be used to advantage. The computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium provided with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless communications systems.

One skilled in the art will understand that the "blocks" ("modules") in the various figures (method and apparatus) represent or describe the functionality of embodiments of the invention (and not necessarily individual "blocks" in hardware or software) and thus they equally describe the functions or features of embodiments of the device as well as embodiments of the method (block=step).

The term “block” is used for purposes of illustrating the functionality of encoder/decoder embodiments only and is not intended to limit this disclosure.

In several embodiments presented herein, it should be understood that the disclosed system, apparatus, and method may be implemented in other ways. For example, the hardware embodiment described is merely exemplary. For example, the division into blocks is only a logical division by function, and in the actual implementation there may be a different division. For example, multiple blocks or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the mutual connections or direct connections or communication connections shown or described may be implemented using certain interfaces. Indirect connections or communication connections between equipment or units can be electrical, mechanical, or other forms.

Blocks described as individual pieces may or may not be physically separate, and pieces shown as blocks may or may not be physical blocks, may be located in one location, or may be distributed across multiple network blocks. Some or all of the blocks may be selected according to actual requirements to achieve the objectives of the solutions in the embodiments.

Moreover, the functional blocks in embodiments of the present invention may be integrated into a single processing block, or each of the blocks may exist physically separately, or two or more blocks are integrated into a single block.

Embodiments of the invention may further include hardware, such as an encoder and/or decoder, that includes processing circuitry configured to perform any of the methods and/or processes described herein.

Although embodiments of the present invention have been primarily described in terms of video encoding, it should be noted that embodiments of encoding system 10, encoder 20, and decoder 30 (and thus system 10), as well as other embodiments described herein, may also be configured to process or encode a still picture, i.e. processing or encoding a single picture independently of any preceding or subsequent picture, as in video encoding. In general, only the inter prediction (encoder) and 344 (decoder) blocks 244 may not be available if the encoding for picture processing is limited to a single picture 17. All other functionality (also referred to as tools or technologies) of video encoder 20 and video decoder 30 may equally useful for still picture processing, such as residual computation 204/304, transform 206, quantization 208, inverse quantization 210/310, (inverse) transform 212/312, division 262/362, intra prediction 254/354, and/or contouring filtering 220, 320 and entropy encoding 270 and entropy decoding 304.

Embodiments of, for example, encoder 20 and decoder 30, as well as the functions described herein, for example, with respect to encoder 20 and decoder 30 may be implemented by hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on a computer-readable medium or transmitted through a communication medium in the form of one or more instructions or code and executed by a hardware processing unit. Computer-readable media may include computer-readable media that corresponds to a tangible medium, such as a storage medium, or a communication medium, including any medium that enables transmission of a computer program from one location to another, such as according to a communications protocol. Thus, computer readable media may typically correspond to (1) tangible computer readable media that is durable, or (2) a communication medium such as a signal or carrier wave. Storage media can be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementing the techniques described in this disclosure. The computer program product may include computer-readable media.

By way of example, and not limitation, such computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other media that can used to store desired program code in the form of instructions or data structures and can be accessed by a computer. Additionally, any connection is properly referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave communications, then coaxial cable, fiber optic cable, twisted pair, DSL or wireless technologies such as infrared, radio and microwave communications are included in the definition of media. However, it should be understood that computer readable and storage media do not include connections, carrier waves, signals, or other short-lived media, but are instead directed to long-term, tangible storage media. The disk and disc used in this document include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where discs ) typically reproduce data magnetically, while discs (discs) reproduce data optically using lasers. Combinations of the above should also be included in the scope of computer readable media.

The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Accordingly, the term “processor” as used herein can refer to any of the above structure or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided within specialized hardware and/or software modules configured for encoding and decoding or included in a bundled codec. In addition, the techniques may be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide variety of devices or hardware components, including a wireless telephone, an integrated circuit (IC), or a set of ICs (eg, a chipset). This disclosure describes various components, modules, or blocks to highlight functional aspects of devices configured to implement the disclosed technologies, but not necessarily required to be implemented by different hardware units. Rather, as described above, the various blocks may be combined into a codec hardware block or provided by a collection of interacting hardware blocks, including one or more processors as described above, together with suitable software and/or firmware.

Claims (135)

1. A method for obtaining a chrominance motion vector used in affine external prediction of a block of a current picture containing a luminance block and a co-located chrominance block, the method comprising determining chrominance scaling factors in the horizontal and vertical directions based on the chrominance format information, wherein the chrominance format information indicates the chrominance format of the current picture to which the block of the current picture belongs; determining a set (S) of luminance subblocks of the luminance block based on the values of the chroma scaling factors; And determining a chroma motion vector for a chroma subblock of the chrominance block based on the motion vectors of one or more luminance subblocks in the set (S) of luminance subblocks; when SubWidthC and SubHeightC are 1, the luminance subblock set (S) contains a luminance subblock indexed as S ₀ = (xSbIdx, ySbIdx); when at least one of SubWidthC and SubHeightC is not equal to 1, the luma subblock set (S) contains: the first luma subblock, indexed as S ₀ =((xSbIdx >> (SubWidthC − 1) << (SubWidthC − 1)), (ySbIdx >> (SubHeightC − 1) << (SubHeightC − 1))), and the second brightness subblock indexed as S ₁ =((xSbIdx >> (SubWidthC − 1) << (SubWidthC − 1)) + (SubWidthC − 1), (ySbIdx >> (SubHeightC − 1) << (SubHeightC − 1)) + (SubHeightC − 1 )), where SubWidthC and SubHeightC represent chroma scaling factors in the horizontal and vertical directions, respectively; xSbIdx and ySbIdx represent the sub-block index in the horizontal direction and the sub-block index in the vertical direction, respectively, for the luma sub-block in the set (S); "<<" represents an arithmetic left shift; ">>" represents an arithmetic right shift; xSbIdx = 0...numSbX - 1 and ySbIdx = 0...numSbY - 1; numSbX indicates the number of luma subblocks in the luma block in the horizontal direction; And numSbY indicates the number of luminance subblocks in a luminance block in the vertical direction. 2. The method of claim 1, wherein each of the one or more luminance subblocks in the set (S) is represented by a subblock index in the horizontal direction and a subblock index in the vertical direction. 3. The method according to claim 1 or 2, wherein the number of chrominance subblocks in the chrominance block in the horizontal direction and the vertical direction is the same as the number of luminance subblocks in the luminance block in the horizontal and vertical directions, respectively. 4. Method according to any one of paragraphs. 1-3, wherein for a chrominance subblock indexed by subblock index xSbIdxL in the horizontal direction and subblock index ySbIdxL in the vertical direction, the luminance subblock set (S) contains one or more subblocks indexed as: S ₀ = (xSbIdxL, ySbIdxL), S ₁ = (xSbIdxL, ySbIdxL + (SubHeightC-1)), S ₂ = (xSbIdxL + (SubWidthC-1), ySbIdxL), or S ₃ = (xSbIdxL + (SubWidthC-1), ySbIdxL + (SubHeightC-1)); in this case the index S₀ The luminance subblock is represented by the index xSbIdxL of the subblock in the horizontal direction and index ySbIdxL of the subblock in the vertical direction; index S₁ brightness block is presented subblock index in the horizontal direction xSbIdxL and subblock index in the vertical direction ySbIdxL + (SubHeightC-1); index S₂ brightness block presented subblock index in the horizontal direction xSbIdxL + (SubWidthC-1) and subblock index in the vertical direction ySbIdxL; And index S₃ brightness block is presented subblock index in the horizontal direction xSbIdxL + (SubWidthC-1) and subblock index in the vertical direction ySbIdxL + (SubHeightC-1). 5. Method according to any one of paragraphs. 1-4, in which the set of luminance subblocks (S) contains: the first luminance subblock indexed as S ₀ = (xSbIdxL, ySbIdxL), and the second luminance subblock indexed as S ₁ = (xSbIdxL + (SubWidthC-1), ySbIdxL + (SubHeightC-1)); in this case the position S₀ brightness block represented by the subblock index xSbIdxL in the horizontal direction and the subblock index ySbIdxL in the vertical direction; position S₁ brightness block is presented subblock index in the horizontal direction xSbIdxL + (SubWidthC-1) and subblock index in the vertical direction ySbIdxL + (SubHeightC-1). 6. Method according to any one of paragraphs. 1-5, in which: when the chroma format is 4:4:4, set (S) contains one luma subblock combined with a chroma subblock; when the chroma format is 4:2:2, set (S) contains two luminance subblocks horizontally adjacent to each other; when the chroma format is 4:2:0, set (S) contains two luminance subblocks that are diagonal. 7. Method according to any one of paragraphs. 1-6, wherein when there is more than one luminance sub-block in the set (S), said determination of a motion vector for a chroma sub-block based on the motion vector of one or more luminance sub-blocks in the set (S) of luminance sub-blocks comprises: averaging the motion vectors of the luminance subblocks in the set (S) to generate an average luminance motion vector; And obtaining a motion vector for the chrominance subblock based on the average luminance motion vector. 8. The method of claim 7, wherein the averaging of the motion vectors of the luminance subblocks in the set (S) comprises one or more of: averaging the horizontal component of the motion vectors of brightness subblocks in the set (S); And averaging the vertical component of the motion vectors of brightness subblocks in the set (S). 9. The method of claim 7 or 8, wherein averaging the motion vectors of the luminance subblocks in the set (S) to generate an average luminance motion vector comprises: mvAvgLX = , when mvAvgLX[0] is greater than or equal to 0, mvAvgLX[0] = (mvAvgLX[0] + (N>>1) - 1) >> log2(N), otherwise mvAvgLX[0] = −((−mvAvgLX[0] + (N>>1) - 1) >> log2(N)); when mvAvgLX[1] is greater than or equal to 0, mvAvgLX[1] = (mvAvgLX[1] + (N>>1) - 1) >> log2(N), otherwise mvAvgLX[1] = −((−mvAvgLX[1] + (N>>1) - 1) >> log2(N)), and mvAvgLX - the resulting averaging motion vector; mvAvgLX[0] - horizontal component of the resulting motion vector mvAvgLX and mvAvgLX[1] - vertical component of the resulting motion vector mvAvgLX; And - horizontal and vertical indices of the subblock S _i in the set of brightness subblocks (S) in the array of motion vectors, - motion vector of the brightness subblock with indices And , N is the number of elements in the set (S) of the luma subblock, log2(N) is the base-2 logarithm of N and is the power to which the number 2 is raised to obtain the value of N, and ">>" is the arithmetic shift to the right. 10. Method according to any one of paragraphs. 7-9, in which the averaging of the motion vectors of luminance subblocks in the set (S) contains: mvAvgLX = mvLX[(xSbIdx >> (SubWidthC − 1) << (SubWidthC − 1))] [(ySbIdx >> (SubHeightC − 1) << (SubHeightC − 1))] + mvLX[(xSbIdx >> (SubWidthC − 1) << (SubWidthC − 1)) + (SubWidthC − 1)] [(ySbIdx >> (SubHeightC − 1) << (SubHeightC − 1)) + (SubHeightC − 1)], if mvAvgLX[0] ≥0, then mvAvgLX[0] = (mvAvgLX[0] + 1 –(mvAvgLX[0] >= 0)) >> 1, if mvAvgLX[1] ≥ 0, then mvAvgLX[1] = (mvAvgLX[1] + 1 –(mvAvgLX[1] >= 0)) >> 1, wherein mvAvgLX[0] is the horizontal component of the averaged motion vector mvAvgLX, mvAvgLX[1] is the vertical component of the averaged motion vector mvAvgLX; where SubWidthC and SubHeightC represent chroma scaling factors in the horizontal and vertical directions, respectively; xSbIdx and ySbIdx represent the subblock index in the horizontal direction and the subblock index in the vertical direction, respectively, for the luminance subblock in the set (S), "<<" is the arithmetic left shift, and ">>" is the arithmetic right shift. 11. Method according to any one of paragraphs. 1-10, wherein said determination of chroma scaling factors in the horizontal and vertical directions based on chroma format information comprises: determining horizontal and vertical chroma scaling factors based on a mapping between the chroma format information and a pair of horizontal and vertical chroma scaling factors. 12. Method according to any one of paragraphs. 1-11, further comprising generating a chroma subblock prediction based on said determined motion vector. 13. Method according to any one of paragraphs. 1-12, wherein the chroma format comprises one of a YUV 4:2:2 format, a YUV 4:2:0 format, or a YUV 4:4:4 format. 14. Method according to any one of paragraphs. 1-13, implemented by the encoding device. 15. Method according to any one of paragraphs. 1-13, implemented by a decoding device. 16. An encoder (20) containing a processing circuit for performing the method according to any one of claims. 1-14. 17. A decoder (30) comprising a processing circuit for performing the method according to any one of claims. 1-13 and 15. 18. Decoder containing: one or more processors; And a non-volatile computer-readable storage medium coupled to the processors and storing a program for execution by the processors, wherein the program, when executed by the processors, configures a decoder to perform the method of any one of claims. 1-13 and 15. 19. Encoder containing: one or more processors; And a non-volatile computer-readable storage medium coupled to the processors and storing a program for execution by the processors, wherein the program, when executed by the processors, configures a decoder to perform the method of any one of claims. 1-14. 20. A non-transitory computer-readable storage medium carrying program code that, when executed by a computer device, causes the computer device to perform the method of any one of claims. 1-15. 21. A device for affine external prediction of a block of a current picture containing co-located brightness and chrominance blocks, wherein the device contains: a determination module configured to determine chromaticity scaling factors in the horizontal and vertical directions based on chrominance format information, wherein the chrominance format information indicates the chrominance format of the current picture to which the current picture block belongs, and determine a set (S) of luminance sub-blocks of said luminance block on based on chroma scaling factor values; And a motion vector output module configured to determine a motion vector for a chrominance subblock of a chrominance block based on motion vectors of one or more luminance subblocks in the luminance subblock set (S); and: when SubWidthC and SubHeightC are 1, the luminance subblock set (S) contains a luminance subblock indexed as S ₀ = (xSbIdx _, ySbIdx); when at least one of SubWidthC and SubHeightC is not equal to 1, the luma subblock set (S) contains: the first luma subblock, indexed as S ₀ = ((xSbIdx >> (SubWidthC − 1) << (SubWidthC − 1)), (ySbIdx >> (SubHeightC − 1) << (SubHeightC − 1))), and the second brightness subblock indexed as S ₁ =((xSbIdx >> (SubWidthC − 1) << (SubWidthC − 1)) + (SubWidthC − 1), (ySbIdx >> (SubHeightC − 1) << (SubHeightC − 1)) + (SubHeightC − 1 )), where SubWidthC and SubHeightC represent chroma scaling factors in the horizontal and vertical directions, respectively; xSbIdx and ySbIdx represent the sub-block index in the horizontal direction and the sub-block index in the vertical direction, respectively, for the luma sub-block in the set (S); "<<" represents an arithmetic left shift; ">>" represents an arithmetic right shift; xSbIdx = 0...numSbX - 1 and ySbIdx = 0...numSbY - 1; numSbX indicates the number of luma subblocks in the luma block in the horizontal direction; And numSbY indicates the number of luminance subblocks in a luminance block in the vertical direction. 22. The apparatus of claim 21, wherein each of the one or more luminance subblocks in the set (S) is represented by a subblock index in the horizontal direction and a subblock index in the vertical direction. 23. The device according to claim 22, wherein the number of chrominance subblocks in the chrominance block in the horizontal direction and vertical direction coincides with the number of luminance subblocks in the luminance block in the horizontal and vertical directions, respectively. 24. The device according to any one of paragraphs. 21-23, wherein for a chrominance subblock indexed by subblock index xSbIdxL in the horizontal direction and subblock index ySbIdxL in the vertical direction, the luminance subblock set (S) contains one or more indexed subblocks: S ₀ = (xSbIdxL, ySbIdxL), S ₁ = (xSbIdxL, ySbIdxL + (SubHeightC-1)), S ₂ = (xSbIdxL+ (SubWidthC-1), ySbIdxL) or S ₃ = (xSbIdxL+ (SubWidthC-1), ySbIdxL + (SubHeightC-1)); wherein the luminance subblock index S ₀ is represented by the subblock index xSbIdxL in the horizontal direction and the subblock index ySbIdxL in the vertical direction; index S₁ brightness block represented by a subblock index in the horizontal direction xSbIdxL and a subblock index in the vertical direction ySbIdxL + (SubHeightC-1); index S₂ brightness block is presented subblock index in the horizontal direction xSbIdxL + (SubWidthC-1) and subblock index in the vertical direction ySbIdxL; And index S₃ brightness block presented subblock index in the horizontal direction xSbIdxL + (SubWidthC-1) and subblock index in the vertical direction ySbIdxL + (SubHeightC-1). 25. The device according to any one of paragraphs. 21-24, wherein the set of brightness subblocks (S) contains: the first luminance subblock indexed as S ₀ = (xSbIdxL, ySbIdxL), and the second luminance subblock indexed as S ₁ = (xSbIdxL + (SubWidthC-1), ySbIdxL + (SubHeightC-1)); in this case the position S₀ block brightness is represented by the subblock index xSbIdxL in the horizontal direction and the subblock index ySbIdxL in the vertical direction; position S₁ brightness block is presented subblock index in the horizontal direction xSbIdxL + (SubWidthC-1) and subblock index in the vertical direction ySbIdxL + (SubHeightC-1). 26. The device according to any one of paragraphs. 21-25, with: when the chroma format is 4:4:4, set (S) contains one luma subblock combined with a chroma subblock; when the chroma format is 4:2:2, set (S) contains two luminance subblocks horizontally adjacent to each other; when the chroma format is 4:2:0, the (S) set contains two luminance subblocks that are diagonal. 27. The device according to any one of paragraphs. 21-26, wherein when there is more than one luminance sub-block in the set (S), the motion vector output module is configured to: averaging the motion vectors of the luminance subblocks in the set (S) to generate an average luminance motion vector; And obtaining a motion vector for the chrominance subblock based on the average luminance motion vector. 28. The apparatus of claim 27, wherein the motion vector output module is configured to: averaging the horizontal component of the motion vectors of brightness subblocks in the set (S); or averaging the vertical component of the motion vectors of brightness subblocks in the set (S). 29. The apparatus of claim 27 or 28, wherein the motion vector output module is configured to average the motion vectors of the luminance subblocks in the set (S) to generate an average luminance motion vector as follows: mvAvgLX = , when mvAvgLX[0] is greater than or equal to 0, mvAvgLX[0] = (mvAvgLX[0] + (N>>1) - 1) >> log2(N), otherwise mvAvgLX[0] = − ((−mvAvgLX[0] + (N>>1) - 1) >> log2(N) ); when mvAvgLX[1] is greater than or equal to 0, mvAvgLX[1] = (mvAvgLX[1] + (N>>1) - 1) >> log2(N), otherwise mvAvgLX[1] = −((−mvAvgLX[1] + (N>>1) - 1) >> log2(N) ), where mvAvgLX is the resulting averaging motion vector; mvAvgLX[0] is the horizontal component of the resulting mvAvgLX motion vector, and mvAvgLX[1] is the vertical component of the resulting mvAvgLX motion vector; And - horizontal and vertical indices of the subblock S _i in the set of brightness subblocks (S) in the array of motion vectors, - motion vector of the brightness subblock with indices And , N is the number of elements in the set (S) of luma subblocks, log2(N) is the logarithm of N to base 2 and represents the power to which the number 2 must be raised to obtain the value of N, and ">>" represents the arithmetic shift to the right. 30. The device according to any one of paragraphs. 27-29, wherein the motion vector output module is configured to average the motion vectors of the luminance subblocks in the set (S) to generate an average luminance motion vector as follows: mvAvgLX = mvLX[(xSbIdx >> (SubWidthC − 1) << (SubWidthC − 1))] [(ySbIdx >> (SubHeightC − 1) << (SubHeightC − 1))] + mvLX[(xSbIdx >> (SubWidthC − 1) << (SubWidthC − 1)) + (SubWidthC − 1)] [(ySbIdx >> (SubHeightC − 1) << (SubHeightC − 1)) + (SubHeightC − 1)], if mvAvgLX[0] ≥0, then mvAvgLX[0] = (mvAvgLX[0] + 1 –(mvAvgLX[0] >= 0)) >> 1, if mvAvgLX[1] ≥0, then mvAvgLX[1] = (mvAvgLX[1] + 1 –(mvAvgLX[1] >= 0)) >> 1, where mvAvgLX[0] is the horizontal component of the averaged motion vector mvAvgLX, mvAvgLX[1] is the vertical component of the averaged motion vector mvAvgLX; where SubWidthC and SubHeightC represent chroma scaling factors in the horizontal and vertical directions, respectively; xSbIdx and ySbIdx represent the subblock index in the horizontal direction and the subblock index in the vertical direction, respectively, for the luminance subblock in the set (S), "<<" is the arithmetic left shift, and ">>" is the arithmetic right shift. 31. The device according to any one of paragraphs. 21-30, wherein the determination module is configured to determine chroma scaling factors in the horizontal and vertical directions based on a mapping between the chrominance format information and a pair of chroma scaling factors in the horizontal and vertical directions. 32. The device according to any one of paragraphs. 21-31, further comprising a motion compensation module configured to generate a chrominance subblock prediction based on the determined motion vector. 33. The device according to any one of paragraphs. 21-32, wherein the chroma format comprises one of YUV 4:2:2 format, YUV 4:2:0 format and YUV 4:4:4 format.

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