阅读说明：本技术 用于视频编解码的方法和装置 (Method and apparatus for video encoding and decoding ) 是由 李贵春 李翔 刘杉 许晓中 于 2020-10-01 设计创作，主要内容包括：本公开的各方面提供用于视频解码的方法和装置,该装置包括处理电路。处理电路从已编码视频码流中解码分区信息。分区信息指示将双树中的色度编码树结构应用于色度块,并指示以亮度样本为单位的色度块的块大小和以亮度样本为单位的最小允许色度四叉树(QT)叶节点大小。处理电路确定以亮度样本为单位的色度块的块大小是否小于或等于以亮度样本为单位的最小允许色度QT叶节点大小。响应于以亮度样本为单位的色度块的块大小小于或等于以亮度样本为单位的最小允许色度QT叶节点大小,处理电路确定不允许对色度块进行QT分割。(Aspects of the present disclosure provide methods and apparatus for video decoding, the apparatus including a processing circuit. The processing circuitry decodes the partition information from the encoded video stream. The partition information indicates that a chroma coding tree structure in a dual tree is applied to a chroma block, and indicates a block size of the chroma block in units of luma samples and a minimum allowed chroma Quadtree (QT) leaf node size in units of luma samples. The processing circuit determines whether a block size of a chroma block in units of luma samples is less than or equal to a minimum allowed chroma QT leaf node size in units of luma samples. In response to the block size of the chroma block in units of luma samples being less than or equal to the minimum allowed chroma QT leaf node size in units of luma samples, the processing circuitry determines that QT partitioning of the chroma block is not allowed.)

1. A method for video decoding in a decoder, comprising:

decoding partition information from an encoded video bitstream, the partition information indicating that a chroma coding tree structure in a dual tree is applied to chroma blocks, the partition information further indicating a block size of the chroma blocks in units of luma samples and a minimum allowed chroma quadtree QT leaf node size in units of luma samples;

determining whether the block size of the chroma block in units of luma samples is less than or equal to the minimum allowed chroma Quadtree (QT) leaf node size in units of luma samples; and

determining that QT partitioning of the chroma block is not allowed in response to the block size of the chroma block in units of luma samples being less than or equal to the minimum allowed chroma quadtree QT leaf node size in units of luma samples.

2. The method of claim 1,

the partition information further indicates a multi-type tree MTT depth indicating whether the chroma block is an MTT node from an MTT partition, a chroma level sub-sampling factor, and a prediction mode type of the chroma block; and

in response to the block size of the chroma block in luma samples being greater than the minimum allowed chroma Quadtree (QT) leaf node size in luma samples, determining that QT partitioning of the chroma block is not allowed based on at least one of: (i) the multi-type tree MTT depth to indicate that the chroma block is the MTT node, (ii) the block size of the chroma block in luma samples divided by the chroma horizontal sub-sampling factor is less than or equal to 4, and (iii) the prediction mode type to indicate that intra prediction mode and intra block copy, IBC, mode are allowed.

3. The method of claim 1,

the partition information further indicates a minimum allowed chroma coding block size in units of luma samples and a minimum allowed luma coding block size in units of luma samples; and

the minimum allowed chroma coding block size in luma samples is smaller than the minimum allowed luma coding block size in luma samples.

4. The method of claim 3,

the encoded video stream includes a chroma syntax element for indicating the minimum allowed chroma coding block size in units of luma samples and a luma syntax element for indicating the minimum allowed luma coding block size in units of luma samples.

5. The method of claim 3,

deriving the minimum allowed chroma coding block size in luma samples based on the minimum allowed luma coding block size in luma samples.

6. The method of claim 1,

the partition information further indicates a minimum allowed luma QT leaf node size in units of luma samples; and

the minimum allowed chroma quadtree QT leaf node size in units of luma samples is smaller than the minimum allowed luma QT leaf node size in units of luma samples.

7. A method for video decoding in a decoder, comprising:

decoding partition information from an encoded video bitstream, the partition information indicating that a chroma coding tree structure in a dual tree is applied to chroma blocks, the partition information further indicating a block size of the chroma blocks in units of luma samples, a chroma vertical sub-sampling factor, and a minimum allowed chroma Quadtree (QT) leaf node size;

determining whether QT partitioning of the chroma block is not allowed based on at least the block size of the chroma block in units of luma samples, the chroma vertical sub-sampling factor, and the minimum allowed chroma Quadtree (QT) leaf node size; and

in response to disallowing the QT partitioning of the chroma block, determining whether at least one of binary tree partitioning and ternary tree partitioning of the chroma block is disallowed.

8. The method of claim 7,

the minimum allowed chroma quadtree QT leaf node size is in units of luma samples,

the partition information further indicates a chroma level sub-sampling factor, an

The determining whether to disallow the QT partitioning comprises determining whether to disallow the QT partitioning of the chroma block based on at least the block size of the chroma block in units of luma samples, the chroma vertical sub-sampling factor, the chroma horizontal sub-sampling factor, and the minimum allowed chroma quadtree QT leaf node size in units of luma samples.

9. The method of claim 8, wherein the determining whether the QT split is not allowed further comprises:

determining a parameter equal to the minimum allowed chroma Quadtree (QT) leaf node size in units of luma samples multiplied by the chroma vertical subsampling factor and divided by the chroma horizontal subsampling factor; and

determining that the QT partition is not allowed for the chroma block in response to the block size of the chroma block in luma samples being less than or equal to the parameter.

10. The method of claim 8,

the partition information further indicates a multi-type tree MTT depth and a prediction mode type of the chroma block, the multi-type tree MTT depth indicating whether the chroma block is an MTT node from an MTT split; and

the determining whether the QT split is not allowed comprises: determining whether the QT partitioning of the chroma block is not allowed based further on the multi-type tree MTT depth and the prediction mode type.

11. The method of claim 7,

the partition information further indicates a minimum allowed chroma coding block size in units of luma samples and a minimum allowed luma coding block size in units of luma samples; and

the minimum allowed chroma coding block size in luma samples is smaller than the minimum allowed luma coding block size in luma samples.

12. The method of claim 11,

the encoded video stream includes a chroma syntax element for indicating the minimum allowed chroma coding block size in luma samples and a luma syntax element for indicating the minimum allowed luma coding block size in luma samples.

13. The method of claim 11,

deriving the minimum allowed chroma coding block size in luma samples based on the minimum allowed luma coding block size in luma samples.

14. The method of claim 7,

the partition information further includes a minimum allowed luminance QT leaf node size in units of luminance samples; and

the minimum allowed chroma quadtree QT leaf node size in units of luma samples is smaller than the minimum allowed luma QT leaf node size in units of luma samples.

15. The method of claim 7,

the minimum allowed chroma quadtree QT leaf node size is in units of chroma samples; and

the determining whether the QT split is not allowed comprises: determining that the QT partition is not allowed for the chroma block based on the block size of the chroma block in units of luma samples divided by the chroma vertical sub-sampling factor being less than or equal to the minimum allowed chroma quadtree QT leaf node size in units of chroma samples.

16. The method of claim 15,

the partition information further indicates a chroma level sub-sampling factor, a multi-type tree MTT depth indicating whether the chroma block is an MTT node from an MTT partition, and a prediction mode type of the chroma block; and

in response to the block size of the chroma block in units of luma samples divided by the chroma vertical subsampling factor being greater than the minimum allowed chroma Quadtree (QT) leaf node size in units of chroma samples, the method further comprises:

determining whether the QT partition is not allowed for the chroma block based on the block size of the chroma block in units of luma samples, the chroma level sub-sampling factor, the multi-type tree MTT depth, and the prediction mode type.

17. An apparatus for video decoding, comprising processing circuitry configured to:

decoding partition information from an encoded video bitstream, the partition information indicating that a chroma coding tree structure in a dual tree is applied to chroma blocks, the partition information further indicating a block size of the chroma blocks in units of luma samples and a minimum allowed chroma quadtree QT leaf node size in units of luma samples;

determining whether the block size of the chroma block in units of luma samples is less than or equal to the minimum allowed chroma Quadtree (QT) leaf node size in units of luma samples; and

determining that QT partitioning of the chroma block is not allowed in response to the block size of the chroma block in units of luma samples being less than or equal to the minimum allowed chroma quadtree QT leaf node size in units of luma samples.

18. The apparatus of claim 17,

the partition information further indicates a multi-type tree MTT depth indicating whether the chroma block is an MTT node from an MTT partition, a chroma level sub-sampling factor, and a prediction mode type of the chroma block; and

in response to the block size of the chroma block in luma samples being greater than the minimum allowed chroma Quadtree (QT) leaf node size in luma samples, the processing circuitry is configured to determine that QT partitioning of the chroma block is not allowed based on at least one of: (i) the multi-type tree MTT depth to indicate that the chroma block is the MTT node, (ii) the block size of the chroma block in luma samples divided by the chroma horizontal sub-sampling factor is less than or equal to 4, and (iii) the prediction mode type to indicate that intra prediction mode and intra block copy, IBC, mode are allowed.

19. The apparatus of claim 17,

the partition information further indicates a minimum allowed chroma coding block size in units of luma samples and a minimum allowed luma coding block size in units of luma samples; and

the minimum allowed chroma coding block size in luma samples is smaller than the minimum allowed luma coding block size in luma samples.

20. The apparatus of claim 19,

the encoded video stream includes a chroma syntax element for indicating the minimum allowed chroma coding block size in units of luma samples and a luma syntax element for indicating the minimum allowed luma coding block size in units of luma samples.

Technical Field

Embodiments are described that relate generally to video coding and decoding.

Background

The background description provided herein is intended to be a general presentation of the background of the application. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description, is not admitted to be prior art by inclusion in this application, nor is it expressly or implied that it is prior art to the present application.

Video encoding and decoding may be performed by an inter-picture prediction technique with motion compensation. Uncompressed digital video may comprise a series of pictures, each picture having spatial dimensions of, for example, 1920x1080 luma samples and related chroma samples. The series of pictures has a fixed or variable picture rate (also informally referred to as frame rate), e.g. 60 pictures per second or 60 Hz. Uncompressed video has certain bit rate requirements. For example, 1080p 604: 2:0 video (1920x1080 luminance sample resolution, 60Hz frame rate) with 8 bits per sample requires close to 1.5Gbit/s bandwidth. One hour of such video requires more than 600GB of storage space.

One purpose of video encoding and decoding is to reduce redundant information of an input video signal by compression. Video compression may help reduce the bandwidth and/or storage requirements described above, by two or more orders of magnitude in some cases. Lossless and lossy compression, as well as combinations of both, may be employed. Lossless compression refers to a technique for reconstructing an exact copy of an original signal from a compressed original signal. When lossy compression is used, the reconstructed signal may not be identical to the original signal, but the distortion between the original signal and the reconstructed signal is small enough that the reconstructed signal is useful for the intended application. Lossy compression is widely used for video. The amount of distortion tolerated depends on the application. For example, some users consuming streaming media applications may tolerate higher distortion than users of television applications. The achievable compression ratio reflects: higher allowable/tolerable distortion may result in higher compression ratios.

Video encoders and decoders may utilize techniques from several broad categories, including, for example, motion compensation, transform, quantization, and entropy coding.

Video codec techniques may include a technique referred to as intra-coding. In intra coding, sample values are represented without reference to samples or other data from previously reconstructed reference pictures. In some video codecs, a picture is spatially subdivided into blocks of samples. When all sample blocks are encoded in intra mode, the picture may be an intra picture. Intra pictures and their derivatives (such as independent decoder refresh pictures) can be used to reset decoder states and thus can be used as the first picture in an encoded video bitstream and video session, or as still images. Samples of an intra block may be exposed to a transform and transform coefficients may be quantized prior to entropy coding. Intra prediction may be a technique that minimizes sample values in the pre-transform domain. In some cases, the smaller the transformed DC value, and the smaller the AC coefficient, the fewer bits are needed to represent the entropy coded block at a given quantization step size.

Conventional intra-coding, such as known from, for example, MPEG-2 generation coding techniques, does not use intra-prediction. However, some newer video compression techniques include techniques that attempt from, for example, surrounding sample data and/or metadata that is obtained during encoding/decoding of spatially neighboring data blocks and precedes the data blocks in decoding order. This technique is hereinafter referred to as an "intra prediction" technique. Note that in at least some cases, intra prediction only uses reference data from the current picture in reconstruction, and does not use reference data from the reference picture.

There may be many different forms of intra prediction. When more than one such technique may be used in a given video codec technique, the technique used may be encoded in intra-prediction mode. In some cases, a mode may have sub-modes and/or parameters, and these sub-modes and/or parameters may be encoded separately or included in a mode codeword. The codewords to be used for a given mode/sub-mode/parameter combination may have an effect on coding efficiency gain through intra prediction, and so does the entropy coding and decoding technique that converts the codewords into a code stream.

Some mode of intra prediction is introduced along with h.264, improved in h.265, and further improved in newer coding techniques such as Joint Exploration Mode (JEM), universal video coding (VVC), and reference set (BMS). The predictor block may be formed using neighboring sample values belonging to already available samples. The sample values of adjacent samples are copied into the predictor block according to the direction. The reference to the in-use direction may be encoded in the codestream or may predict itself.

Referring to fig. 1A, the bottom right depicts a subset of nine prediction directions known from the 33 possible prediction directions of h.265 (33 angular modes corresponding to 35 intra modes). The point (101) where the arrows converge represents the sample being predicted. The arrows indicate the direction in which the samples are being predicted. For example, arrow (102) represents the prediction of a sample (101) from one or more samples at an angle of 45 degrees to the horizontal from the upper right. Similarly, arrow (103) represents the prediction of a sample (101) from one or more samples at an angle of 22.5 degrees to the horizontal at the bottom left.

Still referring to fig. 1A, a square block (104) comprising 4x4 samples is shown at the top left (indicated by the thick dashed line). The square block (104) includes 16 samples, each labeled with "S", and its position in the Y dimension (e.g., row index) and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample in the Y dimension (starting from the top) and the first sample in the X dimension (starting from the left). Similarly, sample S44 is the fourth sample in the block (104) in both the X and Y dimensions. Since the block is a 4 × 4 sample size, S44 is located at the lower right corner. Reference samples following a similar numbering scheme are also shown. The reference sample is labeled with "R" and its Y position (e.g., row index) and X position (e.g., column index) relative to the block (104). In h.264 and h.265, the prediction samples are adjacent to the block being reconstructed, so negative values need not be used.

Intra picture prediction can be performed by copying the reference sample values from the neighbouring samples occupied by the signaled prediction direction. For example, assume that the encoded video bitstream includes signaling indicating, for the block, a prediction direction that coincides with the arrow (102), i.e. samples are predicted from one or more predicted samples whose upper right is at a 45 degree angle to the horizontal direction. In this case, samples S41, S32, S23, and S14 are predicted from the same reference sample R05. From the reference sample R08, a sample S44 is predicted.

In some cases, the values of multiple reference samples may be combined, for example by interpolation, to compute the reference sample, especially when the direction cannot be divided exactly by 45 degrees.

As video coding techniques have evolved, the number of possible directions has increased. In h.264 (2003), nine different directions can be represented. There are 33 increases in H.265 (2013) and JEM/VVC/BMS, and up to 65 orientations can be supported at the time of this application. Experiments have been performed to identify the most likely directions and some techniques in entropy coding are used to represent those possible directions using a small number of bits, accepting some cost for less likely directions. Furthermore, sometimes the direction itself can be predicted from the neighboring directions used in neighboring, already decoded blocks.

Fig. 1B shows a schematic diagram (105) for depicting 65 intra prediction directions according to JEM to show the increasing number of prediction directions over time.

The mapping of the intra prediction direction bits representing the direction in the coded video stream may differ from one video coding technique to another and may for example be a simple direct mapping from the prediction direction to the intra prediction mode to a codeword, to a complex adaptation scheme involving the most probable mode and similar techniques. In all cases, however, there may be certain directions in the video content that are statistically less likely to occur than certain other directions. Since the goal of video compression is to reduce redundancy, those unlikely directions will be represented by a greater number of bits than more likely directions in a well-working video codec technique.

Motion compensation may be a lossy compression technique and may involve the following: a specimen data block from a previously reconstructed picture or a portion of a reconstructed picture (reference picture) is spatially shifted in the direction indicated by a motion vector (hereinafter referred to as MV) for prediction of the newly reconstructed picture or portion of the picture. In some cases, the reference picture may be the same as the picture currently being reconstructed. The MV may have two dimensions X and Y, or three dimensions, where the third dimension represents the reference picture in use (the latter may be indirectly the temporal dimension).

In some video compression techniques, an MV applied to a certain sample data region may be predicted from other MVs, e.g., from those MVs that are related to another sample data region spatially adjacent to the region being reconstructed and that precede the MV in decoding order. This can greatly reduce the amount of data required to encode the MV, thereby eliminating redundant information and increasing the amount of compression. MV prediction can be performed efficiently, for example, when encoding an input video signal derived from a camera (referred to as natural video), there is a statistical possibility that regions having areas larger than the applicable region of a single MV will move in similar directions, and thus prediction can be performed using similar motion vectors derived from MVs of neighboring regions in some cases. This results in the MVs found for a given region being similar or identical to the MVs predicted from the surrounding MVs and, after entropy encoding, can in turn be represented by a smaller number of bits than the number of bits used when directly encoding the MVs. In some cases, MV prediction may be an example of lossless compression of a signal (i.e., MV) derived from an original signal (i.e., a sample stream). In other cases, MV prediction itself may be lossy, for example due to rounding errors that occur when calculating the predicted values from several surrounding MVs.

h.265/HEVC (ITU-T rec.h.265, "high efficiency video coding", month 2016) describes various MV prediction mechanisms. Among the various MV prediction mechanisms provided by h.265, described herein is a technique referred to hereinafter as "spatial merging".

Referring to fig. 2, a current block (201) includes samples found by an encoder during a motion search, which can be predicted from a previous block spatially shifted by the same size. The MV is not directly encoded but is derived from metadata associated with one or more reference pictures, e.g. from the nearest (in decoding order) reference picture, by using the MV associated with any of the five surrounding samples. Of these, five surrounding samples are represented by a0, a1 and B0, B1, B2 (from 202 to 206), respectively. In h.265, MV prediction can use the prediction value of the same reference picture that neighboring blocks are using.

Disclosure of Invention

The present disclosure provides methods and apparatus for video encoding and/or decoding. In some examples, a video decoding apparatus includes a processing circuit. The processing circuitry may decode partition information from the encoded video bitstream, the partition information indicating that a chroma coding tree structure in a dual tree is applied to chroma blocks, the partition information further indicating a block size of the chroma blocks in units of luma samples and a minimum allowed chroma quadtree QT leaf node size in units of luma samples; the processing circuitry may determine whether the block size of the chroma block in units of luma samples is less than or equal to the minimum allowed chroma Quadtree (QT) leaf node size in units of luma samples; and in response to the block size of the chroma block in luma samples being less than or equal to the minimum allowed chroma QT quadtree leaf node size in luma samples, the processing circuit determines that QT partitioning of the chroma block is not allowed.

In some embodiments, the partition information further indicates a multi-type tree MTT depth, a chroma level sub-sampling factor, and a prediction mode type of the chroma block, the MTT depth indicating whether the chroma block is an MTT node from an MTT partition; and in response to the block size of the chroma block in luma samples being greater than the minimum allowed chroma QT leaf node size in luma samples, determining that QT segmentation is not allowed for the chroma block based on at least one of: (i) the MTT depth to indicate that the chroma block is the MTT node, (ii) the block size of the chroma block in luma samples divided by the chroma horizontal sub-sampling factor is less than or equal to 4, and (iii) the prediction mode type to indicate that intra prediction mode and intra block copy, IBC, mode are allowed.

In some embodiments, the partition information further indicates a minimum allowed chroma coding block size in units of luma samples and a minimum allowed luma coding block size in units of luma samples. The minimum allowed chroma coding block size in luma samples is smaller than the minimum allowed luma coding block size in luma samples. In one example, the encoded video bitstream includes a chroma syntax element indicating the minimum allowed chroma coding block size in luma samples and a luma syntax element indicating the minimum allowed luma coding block size in luma samples. In one example, the minimum allowed chroma coding block size in luma samples is derived based on the minimum allowed luma coding block size in luma samples.

In some embodiments, the partition information further indicates a minimum allowed luminance QT leaf node size in units of luminance samples; and the minimum allowed chroma QT leaf node size in units of luma samples is smaller than the minimum allowed luma QT leaf node size in units of luma samples.

In some examples, an apparatus for video decoding includes a processing circuit. The processing circuitry may decode partition information from an encoded video bitstream, the partition information indicating that a chroma coding tree structure in a dual tree is applied to chroma blocks, the partition information further indicating a block size, a chroma vertical sub-sampling factor, and a minimum allowed chroma quadtree, QT, leaf node size of the chroma blocks in units of luma samples; the processing circuitry determines whether QT partitioning of the chroma block is not allowed based on at least the block size of the chroma block in units of luma samples, the chroma vertical sub-sampling factor, and the minimum allowed chroma QT leaf node size; and in response to disallowing the QT splitting of the chroma block, the processing circuitry may determine whether at least one of binary tree splitting and ternary tree splitting of the chroma block is disallowed.

In an embodiment, the minimum allowed chroma QT leaf node size is in units of luma samples, the partition information further indicates a chroma horizontal sub-sampling factor, and the determining whether to disallow the QT segmentation comprises determining whether to disallow the QT segmentation for the chroma blocks based on at least the block size of the chroma blocks in units of luma samples, the chroma vertical sub-sampling factor, the chroma horizontal sub-sampling factor, and the minimum allowed chroma QT leaf node size in units of luma samples.

In one example, the processing circuitry determines a parameter equal to the minimum allowed chroma QT leaf node size in units of luma samples multiplied by the chroma vertical subsampling factor and divided by the chroma horizontal subsampling factor; and determining that the QT partitioning is not allowed for the chroma block in response to the block size of the chroma block in units of luma samples being less than or equal to the parameter.

In one example, the partition information further indicates a multi-type tree MTT depth and a prediction mode type of the chroma block, the MTT depth indicating whether the chroma block is an MTT node from an MTT split; the processing circuit further determines whether the QT partition is not allowed for the chroma block based on the MTT depth and the prediction mode type.

In one example, the partition information further indicates a minimum allowed chroma coding block size in units of luma samples and a minimum allowed luma coding block size in units of luma samples; and the minimum allowed chroma coding block size in luma samples is smaller than the minimum allowed luma coding block size in luma samples.

In one example, the encoded video bitstream includes a chroma syntax element indicating the minimum allowed chroma coding block size in units of luma samples and a luma syntax element indicating the minimum allowed luma coding block size in units of luma samples.

In one example, the minimum allowed chroma coding block size in luma samples is derived based on the minimum allowed luma coding block size in luma samples.

In one example, the partition information further includes a minimum allowed luminance QT leaf node size in units of luminance samples; and the minimum allowed chroma QT leaf node size in units of luma samples is smaller than the minimum allowed luma QT leaf node size in units of luma samples.

In one example, the minimum allowed chroma QT leaf node size is in units of chroma samples; and the processing circuitry determines that the chroma block is not allowed to be subjected to the QT partitioning based on the block size of the chroma block in units of luma samples divided by the minimum allowed chroma QT leaf node size in units of chroma samples being less than or equal to the minimum allowed chroma QT leaf node size in units of chroma samples.

In one example, the partition information further indicates a chroma level sub-sampling factor, a MTT depth indicating whether the chroma block is from a MTT node of a MTT partition, and a prediction mode type of the chroma block. In response to the block size of the chroma block in luma samples divided by the chroma vertical sub-sampling factor being greater than the minimum allowed chroma QT leaf node size in chroma samples, the processing circuit determines whether the QT partitioning is not allowed for the chroma block based on the block size of the chroma block in luma samples, the chroma horizontal sub-sampling factor, the MTT depth, and the prediction mode type.

Aspects of the present disclosure also provide a non-transitory computer-readable medium storing instructions that, when executed by a computer for video decoding, cause the computer to perform a method for video decoding.

Drawings

Other features, properties, and various advantages of the disclosed subject matter will be more apparent from the following detailed description and the accompanying drawings, in which:

fig. 1A is a schematic diagram of an exemplary subset of intra prediction modes.

Fig. 1B is a diagram illustrating exemplary intra prediction directions.

Fig. 2 is a schematic diagram illustrating an exemplary current block and its surrounding spatial merge candidates.

Fig. 3 is a schematic diagram of a simplified block diagram of a communication system (300) according to an embodiment.

Fig. 4 is a schematic diagram of a simplified block diagram of a communication system (400) according to an embodiment.

Fig. 5 is a schematic diagram of a simplified block diagram of a decoder according to an embodiment.

Fig. 6 is a schematic diagram of a simplified block diagram of an encoder according to an embodiment.

Fig. 7 shows a block diagram of an encoder according to another embodiment.

Fig. 8 shows a block diagram of a decoder according to another embodiment.

Fig. 9 is an example of a chroma sub-sampling format according to an embodiment of the present disclosure.

Fig. 10A-10C illustrate nominal vertical and horizontal relative positions of corresponding luma and chroma samples in respective pictures according to embodiments of the disclosure.

Fig. 11 shows an example of a picture (1100) divided into CTUs (1101) according to an embodiment of the present disclosure.

Fig. 12 shows an example of raster scan stripe partitioning of a picture (1200) according to an embodiment of the present disclosure.

Fig. 13 illustrates an example of rectangular strip partitioning of a picture (1300) according to an embodiment of the present disclosure.

Fig. 14 shows an example of a picture (1400) divided into tiles, bricks (1401) - (1411), and rectangular strips (1421) - (1424) according to an embodiment of the disclosure.

Fig. 15 illustrates exemplary segmentation types (1521) - (1524) in an MTT structure according to an embodiment of the disclosure.

Fig. 16 illustrates an example of split flag signaling for a Quadtree (QT) with a nested MTT coding tree structure according to an embodiment of the present disclosure.

Fig. 17 illustrates an example of an MTT split pattern according to an embodiment of the present disclosure.

FIG. 18 shows an example of a QT with nested MTT coding block structure according to an embodiment of the present disclosure.

Fig. 19 illustrates an example of a restriction on a Ternary Tree (TT) partition according to an embodiment of the present disclosure.

Fig. 20 illustrates an example of a redundant partition mode of a Binary Tree (BT) BT partition and a TT partition according to an embodiment of the present disclosure.

Fig. 21 shows an example of disallowed TT and BT partitions according to an embodiment of the disclosure.

Fig. 22 shows an example syntax related to partition and block sizes in an SPS (2200) in accordance with an embodiment of the disclosure.

Fig. 23 shows an example of a stripe type according to an embodiment of the present disclosure.

Fig. 24 illustrates an exemplary derivation of variables for parallel TT partitioning and coding block size in accordance with an embodiment of the disclosure.

Fig. 25 illustrates an exemplary derivation of variables for coding block size according to an embodiment of the disclosure.

Fig. 26 illustrates an exemplary syntax table according to an embodiment of the present disclosure.

Fig. 27 shows a flowchart outlining a process (2700) according to an embodiment of the present disclosure.

Fig. 28 shows a flowchart outlining a process (2800) according to an embodiment of the present disclosure.

FIG. 29 shows a schematic diagram of a computer system according to an embodiment of the application.

Detailed Description

Fig. 3 is a simplified block diagram of a communication system (300) according to an embodiment disclosed herein. The communication system (300) includes a plurality of terminal devices that can communicate with each other through, for example, a network (350). For example, a communication system (300) includes a first pair of terminal devices (310) and a terminal device (320) interconnected by a network (350). In the embodiment of fig. 3, terminal device (310) and terminal device (320) perform unidirectional data transmission. For example, a terminal device (310) may encode video data, such as a video picture stream captured by the terminal device (310), for transmission over a network (350) to another terminal device (320). The encoded video data is transmitted in the form of one or more encoded video streams. The terminal device (320) may receive encoded video data from the network (350), decode the encoded video data to recover the video data, and display a video picture according to the recovered video data. Unidirectional data transmission is common in applications such as media services.

In another embodiment, the communication system (300) includes a second pair of terminal devices (330) and (340) that perform bi-directional transmission of encoded video data, which may occur, for example, during a video conference. For bi-directional data transmission, each of the terminal device (330) and the terminal device (340) may encode video data (e.g., a stream of video pictures captured by the terminal device) for transmission over the network (350) to the other of the terminal device (330) and the terminal device (340). Each of terminal device (330) and terminal device (340) may also receive encoded video data transmitted by the other of terminal device (330) and terminal device (340), and may decode the encoded video data to recover the video data, and may display video pictures on an accessible display device according to the recovered video data.

In the embodiment of fig. 3, the terminal device (310), the terminal device (320), the terminal device (330), and the terminal device (340) may be a server, a personal computer, and a smart phone, but the principles disclosed herein may not be limited thereto. Embodiments disclosed herein are applicable to laptop computers, tablet computers, media players, and/or dedicated video conferencing equipment. Network (350) represents any number of networks that communicate encoded video data between terminal device (310), terminal device (320), terminal device (330), and terminal device (340), including, for example, wired (wired) and/or wireless communication networks. The communication network (350) may exchange data in circuit-switched and/or packet-switched channels. The network may include a telecommunications network, a local area network, a wide area network, and/or the internet. For purposes of this discussion, the architecture and topology of the network (350) may be immaterial to the operation of the present disclosure, unless explained below.

By way of example, fig. 4 illustrates the placement of a video encoder and a video decoder in a streaming environment. The subject matter disclosed herein is equally applicable to other video-enabled applications including, for example, video conferencing, digital TV, storing compressed video on digital media including CDs, DVDs, memory sticks, and the like.

The streaming system may include an acquisition subsystem (413), which may include a video source (401), such as a digital camera, that creates an uncompressed video picture stream (402). In an embodiment, the video picture stream (402) includes samples taken by a digital camera. The video picture stream (402) is depicted as a thick line to emphasize a high data amount video picture stream compared to the encoded video data (404) (or the encoded video bitstream), the video picture stream (402) being processable by an electronic device (420), the electronic device (420) comprising a video encoder (403) coupled to a video source (401). The video encoder (403) may comprise hardware, software, or a combination of hardware and software to implement or embody aspects of the disclosed subject matter as described in more detail below. The encoded video data (404) (or encoded video codestream (404)) is depicted as a thin line to emphasize the lower data amount of the encoded video data (404) (or encoded video codestream (404)) as compared to the video picture stream (402), which may be stored on a streaming server (405) for future use. One or more streaming client subsystems, such as client subsystem (406) and client subsystem (408) in fig. 4, may access a streaming server (405) to retrieve copies (407) and copies (409) of encoded video data (404). The client subsystem (406) may include, for example, a video decoder (410) in an electronic device (430). The video decoder (410) decodes incoming copies (407) of the encoded video data and generates an output video picture stream (411) that may be presented on a display (412), such as a display screen, or another presentation device (not depicted). In some streaming systems, encoded video data (404), video data (407), and video data (409) (e.g., video streams) may be encoded according to certain video encoding/compression standards. Examples of such standards include ITU-T H.265. In an embodiment, the Video Coding standard under development is informally referred to as next generation Video Coding (VVC), and the present application may be used in the context of the VVC standard.

It should be noted that electronic device (420) and electronic device (430) may include other components (not shown). For example, electronic device (420) may include a video decoder (not shown), and electronic device (430) may also include a video encoder (not shown).

Fig. 5 is a block diagram of a video decoder (510) according to an embodiment of the present disclosure. The video decoder (510) may be disposed in an electronic device (530). The electronic device (530) may include a receiver (531) (e.g., a receive circuit). The video decoder (510) may be used in place of the video decoder (410) in the fig. 4 embodiment.

The receiver (531) may receive one or more encoded video sequences to be decoded by the video decoder (510); in the same or another embodiment, the encoded video sequences are received one at a time, wherein each encoded video sequence is decoded independently of the other encoded video sequences. The encoded video sequence may be received from a channel (501), which may be a hardware/software link to a storage device that stores encoded video data. The receiver (531) may receive encoded video data as well as other data, e.g. encoded audio data and/or auxiliary data streams, which may be forwarded to their respective usage entities (not indicated). The receiver (531) may separate the encoded video sequence from other data. To prevent network jitter, a buffer memory (515) may be coupled between the receiver (531) and the entropy decoder/parser (520) (hereinafter "parser (520)"). In some applications, the buffer memory (515) is part of the video decoder (510). In other cases, the buffer memory (515) may be disposed external (not labeled) to the video decoder (510). While in other cases a buffer memory (not labeled) is provided external to the video decoder (510), e.g., to prevent network jitter, and another buffer memory (515) may be configured internal to the video decoder (510), e.g., to handle playout timing. The buffer memory (515) may not be required to be configured or may be made smaller when the receiver (531) receives data from a store/forward device with sufficient bandwidth and controllability or from an isochronous network. Of course, for use over traffic packet networks such as the internet, a buffer memory (515) may also be required, which may be relatively large and may be of adaptive size, and may be implemented at least partially in an operating system or similar element (not labeled) external to the video decoder (510).

The video decoder (510) may include a parser (520) to reconstruct symbols (521) from the encoded video sequence. The categories of these symbols include information for managing the operation of the video decoder (510), as well as potential information to control a display device, such as a display screen (512), that is not an integral part of the electronic device (530), but may be coupled to the electronic device (530), as shown in fig. 5. The control Information for the display device may be a parameter set fragment (not shown) of Supplemental Enhancement Information (SEI message) or Video Usability Information (VUI). The parser (520) may parse/entropy decode the received encoded video sequence. Encoding of the encoded video sequence may be performed in accordance with video coding techniques or standards and may follow various principles, including variable length coding, Huffman coding, arithmetic coding with or without contextual sensitivity, and so forth. A parser (520) may extract a subgroup parameter set for at least one of the subgroups of pixels in the video decoder from the encoded video sequence based on at least one parameter corresponding to the group. A subgroup may include a Group of Pictures (GOP), a picture, a tile, a slice, a macroblock, a Coding Unit (CU), a block, a Transform Unit (TU), a Prediction Unit (PU), and so on. The parser (520) may also extract information from the encoded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, and so on.

The parser (520) may perform entropy decoding/parsing operations on the video sequence received from the buffer memory (515) to create symbols (521).

The reconstruction of the symbol (521) may involve a number of different units depending on the type of the encoded video picture or portion of the encoded video picture (e.g., inter and intra pictures, inter and intra blocks), among other factors. Which units are involved and the way they are involved can be controlled by subgroup control information parsed from the coded video sequence by a parser (520). For the sake of brevity, such a subgroup control information flow between parser (520) and the following units is not described.

In addition to the functional blocks already mentioned, the video decoder (510) may be conceptually subdivided into several functional units as described below. In a practical embodiment operating under business constraints, many of these units interact closely with each other and may be integrated with each other. However, for the purposes of describing the disclosed subject matter, a conceptual subdivision into the following functional units is appropriate.

The first unit is a scaler/inverse transform unit (551). The scaler/inverse transform unit (551) receives the quantized transform coefficients as symbols (521) from the parser (520) along with control information including which transform scheme to use, block size, quantization factor, quantization scaling matrix, etc. The sealer/inverse transform unit (551) may output a block comprising sample values, which may be input into an aggregator (555).

In some cases, the output samples of sealer/inverse transform unit (551) may belong to an intra-coded block; namely: predictive information from previously reconstructed pictures is not used, but blocks of predictive information from previously reconstructed portions of the current picture may be used. Such predictive information may be provided by an intra picture prediction unit (552). In some cases, the intra picture prediction unit (552) generates surrounding blocks of the same size and shape as the block being reconstructed using the reconstructed information extracted from the current picture buffer (558). For example, the current picture buffer (558) buffers a partially reconstructed current picture and/or a fully reconstructed current picture. In some cases, the aggregator (555) adds the prediction information generated by the intra prediction unit (552) to the output sample information provided by the scaler/inverse transform unit (551) on a per sample basis.

In other cases, the output samples of sealer/inverse transform unit (551) may belong to inter-coded and potential motion compensated blocks. In this case, the motion compensated prediction unit (553) may access a reference picture memory (557) to fetch samples for prediction. After motion compensating the extracted samples according to the sign (521), the samples may be added to the output of the scaler/inverse transform unit (551), in this case referred to as residual samples or residual signals, by an aggregator (555), thereby generating output sample information. The motion compensated prediction unit (553) fetching prediction samples from an address within the reference picture memory (557) may be motion vector controlled and used by the motion compensated prediction unit (553) in the form of the symbol (521), the symbol (521) comprising, for example, X, Y and a reference picture component. Motion compensation may also include interpolation of sample values fetched from a reference picture memory (557), motion vector prediction mechanisms, etc., when using sub-sample exact motion vectors.

The output samples of the aggregator (555) may be employed by various loop filtering techniques in the loop filter unit (556). The video compression techniques may include in-loop filter techniques that are controlled by parameters included in the encoded video sequence (also referred to as an encoded video bitstream) and that are available to the loop filter unit (556) as symbols (521) from the parser (520). However, in other embodiments, the video compression techniques may also be responsive to meta-information obtained during decoding of previous (in decoding order) portions of the encoded picture or encoded video sequence, as well as to sample values previously reconstructed and loop filtered.

The output of the loop filter unit (556) may be a sample stream that may be output to a display device (512) and stored in a reference picture memory (557) for subsequent inter picture prediction.

Once fully reconstructed, some of the coded pictures may be used as reference pictures for future prediction. For example, once the encoded picture corresponding to the current picture is fully reconstructed and the encoded picture is identified (by, e.g., parser (520)) as a reference picture, current picture buffer (558) may become part of reference picture memory (557) and a new current picture buffer may be reallocated before starting reconstruction of a subsequent encoded picture.

The video decoder (510) may perform decoding operations according to predetermined video compression techniques, such as in the ITU-T h.265 standard. The encoded video sequence may conform to the syntax specified by the video compression technique or standard used, in the sense that the encoded video sequence conforms to the syntax of the video compression technique or standard and the configuration files recorded in the video compression technique or standard. In particular, the configuration file may select certain tools from all tools available in the video compression technology or standard as the only tools available under the configuration file. For compliance, the complexity of the encoded video sequence is also required to be within the limits defined by the level of the video compression technique or standard. In some cases, the hierarchy limits the maximum picture size, the maximum frame rate, the maximum reconstruction sampling rate (measured in units of, e.g., mega samples per second), the maximum reference picture size, and so on. In some cases, the limits set by the hierarchy may be further defined by a Hypothetical Reference Decoder (HRD) specification and metadata signaled HRD buffer management in the encoded video sequence.

In an embodiment, the receiver (531) may receive additional (redundant) data along with the encoded video. The additional data may be part of an encoded video sequence. The additional data may be used by the video decoder (510) to properly decode the data and/or more accurately reconstruct the original video data. The additional data may be in the form of, for example, a temporal, spatial, or signal-to-noise ratio (SNR) enhancement layer, a redundant slice, a redundant picture, a forward error correction code, and so forth.

Fig. 6 is a block diagram of a video encoder (603) according to an embodiment of the disclosure. The video encoder (603) is disposed in an electronic device (620). The electronic device (620) includes a transmitter (640) (e.g., a transmission circuit). The video encoder (603) may be used in place of the video encoder (403) in the fig. 4 embodiment.

Video encoder (603) may receive video samples from a video source (601) (not part of electronics (620) in the fig. 6 embodiment) that may capture video images to be encoded by video encoder (603). In another embodiment, the video source (601) is part of the electronic device (620).

The video source (601) may provide a source video sequence in the form of a stream of digital video samples to be encoded by the video encoder (603), which may have any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit … …), any color space (e.g., bt.601y CrCB, RGB … …), and any suitable sampling structure (e.g., Y CrCB 4:2:0, Y CrCB 4:4: 4). In the media service system, the video source (601) may be a storage device that stores previously prepared video. In a video conferencing system, the video source (601) may be a camera that captures local image information as a video sequence. Video data may be provided as a plurality of individual pictures that are given motion when viewed in sequence. The picture itself may be constructed as an array of spatial pixels, where each pixel may comprise one or more samples, depending on the sampling structure, color space, etc. used. The relationship between pixels and samples can be readily understood by those skilled in the art. The following text focuses on describing the samples.

According to an embodiment, the video encoder (603) may encode and compress pictures of a source video sequence into an encoded video sequence (643) in real-time or under any other temporal constraint required by an application. It is a function of the controller (650) to implement the appropriate encoding speed. In some embodiments, the controller (650) controls and is functionally coupled to other functional units as described below. For simplicity, the couplings are not labeled in the figures. The parameters set by the controller (650) may include rate control related parameters (picture skip, quantizer, lambda value of rate distortion optimization technique, etc.), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. The controller (650) may be used to have other suitable functions relating to the video encoder (603) optimized for a certain system design.

In some embodiments, the video encoder (603) operates in an encoding loop. As a brief description, in an embodiment, an encoding loop may include a source encoder (630) (e.g., responsible for creating symbols, e.g., a stream of symbols, based on input pictures and reference pictures to be encoded) and a (local) decoder (633) embedded in a video encoder (603). The decoder (633) reconstructs the symbols to create sample data in a similar manner as a (remote) decoder creates sample data (since in the video compression techniques considered herein any compression between the symbols and the encoded video bitstream is lossless). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since the decoding of the symbol stream produces bit accurate results independent of decoder location (local or remote), the content in the reference picture store (634) also corresponds bit accurately between the local encoder and the remote encoder. In other words, the reference picture samples that the prediction portion of the encoder "sees" are identical to the sample values that the decoder would "see" when using prediction during decoding. This reference picture synchronization philosophy (and the drift that occurs if synchronization cannot be maintained due to, for example, channel errors) is also used in some related techniques.

The operation of the "local" decoder (633) may be the same as a "remote" decoder, such as the video decoder (510) described in detail above in connection with fig. 4. However, referring briefly to fig. 5 additionally, when symbols are available and the entropy encoder (645) and parser (520) are able to losslessly encode/decode the symbols into an encoded video sequence, the entropy decoding portion of the video decoder (510), including the buffer memory (515) and parser (520), may not be fully implemented in the local decoder (633).

At this point it can be observed that any decoder technique other than the parsing/entropy decoding present in the decoder must also be present in the corresponding encoder in substantially the same functional form. For this reason, the present application focuses on decoder operation. The description of the encoder techniques may be simplified because the encoder techniques are reciprocal to the fully described decoder techniques. A more detailed description is only needed in certain areas and is provided below.

During operation, in some embodiments, the source encoder (630) may perform motion compensated predictive coding. The motion compensated predictive coding predictively codes an input picture with reference to one or more previously coded pictures from the video sequence that are designated as "reference pictures". In this way, an encoding engine (632) encodes differences between pixel blocks of an input picture and pixel blocks of a reference picture, which may be selected as a prediction reference for the input picture.

The local video decoder (633) may decode encoded video data for a picture that may be designated as a reference picture based on the symbols created by the source encoder (630). The operation of the encoding engine (632) may be a lossy process. When the encoded video data can be decoded at a video decoder (not shown in fig. 6), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (633) replicates a decoding process that may be performed on reference pictures by the video decoder, and may cause reconstructed reference pictures to be stored in a reference picture cache (634). In this way, the video encoder (603) may locally store a copy of the reconstructed reference picture that has common content (no transmission errors) with the reconstructed reference picture to be obtained by the remote video decoder.

Predictor (635) may perform a prediction search for coding engine (632). That is, for a new picture to be encoded, predictor (635) may search reference picture memory (634) for sample data (as candidate reference pixel blocks) or some metadata, such as reference picture motion vectors, block shapes, etc., that may be referenced as appropriate predictions for the new picture. The predictor (635) may operate on a block-by-block basis of samples to find a suitable prediction reference. In some cases, from search results obtained by predictor (635), it may be determined that the input picture may have prediction references derived from multiple reference pictures stored in reference picture memory (634).

The controller (650) may manage the encoding operations of the source encoder (630), including, for example, setting parameters and subgroup parameters for encoding the video data.

The outputs of all of the above functional units may be entropy encoded in an entropy encoder (645). The entropy encoder (645) losslessly compresses the symbols generated by the various functional units according to techniques such as huffman coding, variable length coding, arithmetic coding, etc., to convert the symbols into an encoded video sequence.

The transmitter (640) may buffer the encoded video sequence created by the entropy encoder (645) in preparation for transmission over a communication channel (660), which may be a hardware/software link to a storage device that will store the encoded video data. The transmitter (640) may combine the encoded video data from the video encoder (603) with other data to be transmitted, such as encoded audio data and/or an auxiliary data stream (sources not shown).

The controller (650) may manage the operation of the video encoder (603). During encoding, the controller (650) may assign a certain encoded picture type to each encoded picture, but this may affect the encoding techniques applicable to the respective picture. For example, pictures may be generally assigned to any of the following picture types:

intra pictures (I pictures), which may be pictures that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs tolerate different types of intra pictures, including, for example, Independent Decoder Refresh ("IDR") pictures. Those skilled in the art are aware of variants of picture I and their corresponding applications and features.

Predictive pictures (P pictures), which may be pictures that may be encoded and decoded using intra prediction or inter prediction that uses at most one motion vector and reference index to predict sample values of each block.

Bi-predictive pictures (B-pictures), which may be pictures that can be encoded and decoded using intra-prediction or inter-prediction that uses at most two motion vectors and reference indices to predict sample values of each block. Similarly, multiple predictive pictures may use more than two reference pictures and associated metadata for reconstructing a single block.

A source picture may typically be spatially subdivided into blocks of samples (e.g., blocks of 4x4, 8x8, 4x 8, or 16 x 16 samples) and encoded block-wise. These blocks may be predictively encoded with reference to other (encoded) blocks that are determined according to the encoding allocation applied to their respective pictures. For example, a block of an I picture may be non-predictive encoded, or the block may be predictive encoded (spatial prediction or intra prediction) with reference to an already encoded block of the same picture. The pixel block of the P picture can be prediction-coded by spatial prediction or by temporal prediction with reference to one previously coded reference picture. A block of a B picture may be prediction coded by spatial prediction or by temporal prediction with reference to one or two previously coded reference pictures.

The video encoder (603) may perform encoding operations according to a predetermined video encoding technique or standard, such as the ITU-T h.265 recommendation. In operation, the video encoder (603) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancies in the input video sequence. Thus, the encoded video data may conform to syntax specified by the video coding technique or standard used.

In an embodiment, the transmitter (640) may transmit the additional data while transmitting the encoded video. The source encoder (630) may take such data as part of an encoded video sequence. The additional data may include temporal/spatial/SNR enhancement layers, redundant pictures and slices, among other forms of redundant data, SEI messages, VUI parameter set segments, and the like.

The captured video may be provided as a plurality of source pictures (video pictures) in a time sequence. Intra-picture prediction, often abbreviated as intra-prediction, exploits spatial correlation in a given picture, while inter-picture prediction exploits (temporal or other) correlation between pictures. In an embodiment, the particular picture being encoded/decoded, referred to as the current picture, is partitioned into blocks. When a block in a current picture is similar to a reference block in a reference picture that has been previously encoded in video and is still buffered, the block in the current picture may be encoded by a vector called a motion vector. The motion vector points to a reference block in a reference picture, and in the case where multiple reference pictures are used, the motion vector may have a third dimension that identifies the reference picture.

In some embodiments, bi-directional prediction techniques may be used in inter-picture prediction. According to bi-prediction techniques, two reference pictures are used, e.g., a first reference picture and a second reference picture that are both prior to the current picture in video in decoding order (but may be past and future, respectively, in display order). A block in a current picture may be encoded by a first motion vector pointing to a first reference block in a first reference picture and a second motion vector pointing to a second reference block in a second reference picture. In particular, the block may be predicted by a combination of a first reference block and a second reference block.

Furthermore, merge mode techniques may be used in inter picture prediction to improve coding efficiency.

According to some embodiments disclosed herein, prediction such as inter-picture prediction and intra-picture prediction is performed in units of blocks. For example, according to the HEVC standard, pictures in a sequence of video pictures are partitioned into Coding Tree Units (CTUs) for compression, the CTUs in the pictures having the same size, e.g., 64 × 64 pixels, 32 × 32 pixels, or 16 × 16 pixels. In general, a CTU includes three Coding Tree Blocks (CTBs), which are one luminance CTB and two chrominance CTBs. Further, each CTU may be further split into one or more Coding Units (CUs) in a quadtree. For example, a 64 × 64-pixel CTU may be split into one 64 × 64-pixel CU, or 4 32 × 32-pixel CUs, or 16 × 16-pixel CUs. In an embodiment, each CU is analyzed to determine a prediction type for the CU, such as an inter prediction type or an intra prediction type. Furthermore, depending on temporal and/or spatial predictability, a CU is split into one or more Prediction Units (PUs). In general, each PU includes a luma Prediction Block (PB) and two chroma blocks PB. In an embodiment, a prediction operation in encoding (encoding/decoding) is performed in units of prediction blocks. Taking a luma prediction block as an example of a prediction block, the prediction block includes a matrix of pixel values (e.g., luma values), such as 8 × 8 pixels, 16 × 16 pixels, 8 × 16 pixels, 16 × 8 pixels, and so on.

Fig. 7 is a diagram of a video encoder (703) according to another embodiment of the present disclosure. A video encoder (703) is used to receive a processing block (e.g., a prediction block) of sample values within a current video picture in a sequence of video pictures and encode the processing block into an encoded picture that is part of an encoded video sequence. In this embodiment, a video encoder (703) is used in place of the video encoder (403) in the embodiment of fig. 4.

In an HEVC embodiment, a video encoder (703) receives a matrix of sample values for a processing block, e.g., a prediction block of 8 × 8 samples, etc. A video encoder (703) determines whether to encode the processing block using intra mode, inter mode, or bi-directional prediction mode using, for example, rate-distortion (RD) optimization. When encoding a processing block in intra mode, the video encoder (703) may use intra prediction techniques to encode the processing block into an encoded picture; and when the processing block is encoded in inter mode or bi-prediction mode, the video encoder (703) may encode the processing block into the encoded picture using inter-prediction or bi-prediction techniques, respectively. In some video coding techniques, the merge mode may be an inter-picture prediction sub-mode, in which motion vectors are derived from one or more motion vector predictors without resorting to coded motion vector components outside of the predictors. In some other video coding techniques, there may be motion vector components that are applicable to the subject block. In an embodiment, the video encoder (703) includes other components, such as a mode decision module (not shown) for determining a processing block mode.

In the embodiment of fig. 7, the video encoder (703) includes an inter encoder (730), an intra encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general purpose controller (721), and an entropy encoder (725) coupled together as shown in fig. 7.

The inter encoder (730) is configured to receive samples of a current block (e.g., a processed block), compare the block to one or more reference blocks in a reference picture (e.g., blocks in previous and subsequent pictures), generate inter prediction information (e.g., redundant information descriptions, motion vectors, merge mode information according to inter coding techniques), and calculate an inter prediction result (e.g., a predicted block) using any suitable technique based on the inter prediction information. In some embodiments, the reference picture is a decoded reference picture that is decoded based on encoded video information.

The intra encoder (722) is used to receive samples of a current block (e.g., a processing block), in some cases compare the block to a block already encoded in the same picture, generate quantized coefficients after transformation, and in some cases also generate intra prediction information (e.g., intra prediction direction information according to one or more intra coding techniques). In an embodiment, the intra encoder (722) also calculates an intra prediction result (e.g., a predicted block) based on the intra prediction information and a reference block in the same picture.

The general purpose controller (721) is used to determine general purpose control data and control other components of the video encoder (703) based on the general purpose control data. In an embodiment, a general purpose controller (721) determines a mode of a block and provides a control signal to a switch (726) based on the mode. For example, when the mode is intra mode, the general purpose controller (721) controls the switch (726) to select an intra mode result for use by the residual calculator (723), and controls the entropy encoder (725) to select and add intra prediction information in the code stream; and when the mode is an inter mode, the general purpose controller (721) controls the switch (726) to select an inter prediction result for use by the residual calculator (723), and controls the entropy encoder (725) to select and add inter prediction information in the code stream.

A residual calculator (723) is used to calculate the difference (residual data) between the received block and the prediction result selected from the intra encoder (722) or the inter encoder (730). A residual encoder (724) is operative to operate on the residual data to encode the residual data to generate transform coefficients. In an embodiment, a residual encoder (724) is used to convert residual data from the time domain to the frequency domain and generate transform coefficients. The transform coefficients are then subjected to a quantization process to obtain quantized transform coefficients. In various embodiments, the video encoder (703) also includes a residual decoder (728). A residual decoder (728) is used to perform the inverse transform and generate decoded residual data. The decoded residual data may be suitably used by an intra encoder (722) and an inter encoder (730). For example, inter encoder (730) may generate a decoded block based on decoded residual data and inter prediction information, and intra encoder (722) may generate a decoded block based on decoded residual data and intra prediction information. The decoded blocks are processed appropriately to generate a decoded picture, and in some embodiments, the decoded picture may be buffered in a memory circuit (not shown) and used as a reference picture.

The entropy coder (725) is for formatting the codestream to produce coded blocks. The entropy encoder (725) generates various information according to a suitable standard such as the HEVC standard. In an embodiment, the entropy encoder (725) is used to obtain general control data, selected prediction information (e.g., intra prediction information or inter prediction information), residual information, and other suitable information in the code stream. It should be noted that, according to the disclosed subject matter, there is no residual information when a block is encoded in the merge sub-mode of the inter mode or bi-prediction mode.

Fig. 8 is a diagram of a video decoder (810) according to another embodiment of the present disclosure. A video decoder (810) is for receiving an encoded image that is part of an encoded video sequence and decoding the encoded image to generate a reconstructed picture. In an embodiment, a video decoder (810) is used in place of the video decoder (410) in the fig. 4 embodiment.

In the fig. 8 embodiment, video decoder (810) includes an entropy decoder (871), an inter-frame decoder (880), a residual decoder (873), a reconstruction module (874), and an intra-frame decoder (872) coupled together as shown in fig. 8.

An entropy decoder (871) is operable to reconstruct from an encoded picture certain symbols representing syntax elements constituting the encoded picture. Such symbols may include, for example, a mode used to encode the block (e.g., intra mode, inter mode, bi-prediction mode, a merge sub-mode of the latter two, or another sub-mode), prediction information (e.g., intra prediction information or inter prediction information) that may identify certain samples or metadata for use by an intra decoder (872) or an inter decoder (880), respectively, residual information in the form of, for example, quantized transform coefficients, and so forth. In an embodiment, when the prediction mode is inter or bi-directional prediction mode, inter prediction information is provided to an inter decoder (880); and providing the intra prediction information to an intra decoder (872) when the prediction type is an intra prediction type. The residual information may be inverse quantized and provided to a residual decoder (873).

An inter decoder (880) is configured to receive inter prediction information and generate an inter prediction result based on the inter prediction information.

An intra-decoder (872) is configured to receive intra-prediction information and generate a prediction result based on the intra-prediction information.

A residual decoder (873) is used to perform inverse quantization to extract dequantized transform coefficients and process the dequantized transform coefficients to convert the residual from the frequency domain to the spatial domain. The residual decoder (873) may also need some control information (to obtain the quantizer parameters QP) and that information may be provided by the entropy decoder (871) (data path not labeled as this is only low-level control information).

The reconstruction module (874) is configured to combine the residuals output by the residual decoder (873) and the prediction results (which may be output by the inter prediction module or the intra prediction module) in the spatial domain to form a reconstructed block, which may be part of a reconstructed picture, which in turn may be part of a reconstructed video. It should be noted that other suitable operations, such as deblocking operations, may be performed to improve visual quality.

It should be noted that video encoder (403), video encoder (603), and video encoder (703), as well as video decoder (410), video decoder (510), and video decoder (810), may be implemented using any suitable techniques. In an embodiment, video encoder (403), video encoder (603), and video encoder (703), and video decoder (410), video decoder (510), and video decoder (810) may be implemented using one or more integrated circuits. In another embodiment, the video encoder (403), the video encoder (603), and the video encoder (703), and the video decoder (410), the video decoder (510), and the video decoder (810) may be implemented using one or more processors executing software instructions.

Aspects of the present disclosure relate to codec tools for partitioning in video codecs, such as methods in which Coding Block (CB) size is constrained for Quadtree (QT) partitioning, etc. Further, aspects of the present disclosure include methods of deriving a minimum size of a chroma coding block, a minimum size of a chroma QT node, and so on.

An exemplary relationship between a source picture given via a codestream and a decoded picture is described below. The video source represented by the codestream may be a sequence of pictures in decoding order. The source picture and the decoded picture may each include one or more sample arrays, such as (1) luma (Y) only (monochrome); (2) luminance and two chromaticities (e.g., YCbCr or YCgCo); (3) green, blue and red (GBR, also known as RGB); and (4) arrays (e.g., YZX, also known as XYZ) representing other unspecified monochromatic or tristimulus color sampling.

For convenience of notation and nomenclature in this disclosure, the variables and nomenclature associated with the above arrays may be referred to as luma (or L or Y) and chroma, where the two chroma arrays may be referred to as Cb and Cr, regardless of the color representation method actually used. The actually used color representation method may be further indicated by syntax.

When the source picture and the decoded picture include multiple sample arrays such as one or more luma and chroma arrays (or blocks), variables such as a chroma horizontal sub-sampling factor (e.g., SubWidthC) and a chroma vertical sub-sampling factor (e.g., subwehightc) between one or more chroma blocks and corresponding luma blocks may be specified. The variables SubWidthC and subwightc (also referred to as chroma subsampling rates) may be specified in table 1 (as shown in fig. 9) according to a chroma format sampling structure, which may be specified, for example, by a chroma subsampling format (also referred to as chroma format idc), and a flag (e.g., partial _ colour _ plane _ flag) (optional). Other values for chroma _ format _ idc, subwidtc, and subwight c may also be specified.

Referring to fig. 9, when the chroma format index (e.g., chroma format idc) is 0, the chroma sub-sampling format may be "monochrome" corresponding to monochrome sampling of only one sample array, which is nominally considered to be a luma array.

When the chroma format index is 1, the chroma sub-sampling format may be 4:2:0 or 4:2:0 samples, each of the two chroma arrays having half the height and half the width of the corresponding luma array.

When the chroma format index is 2, the chroma sub-sampling format may be 4:2:2 or 4:2:2 sampling, each of the two chroma arrays having the same height and half width as the luma array.

When the chroma format index is 3, the chroma sub-sampling format may be 4:4:4 or 4:4:4 samples, and the following applies according to the value of an individual color plane flag (e.g., separate _ color _ plane _ flag): (i) if the individual color plane index is equal to 0, then each of the two chroma arrays has the same height and width as the luma array; (ii) otherwise, the individual color plane flag is equal to 1, then the three color planes can be processed individually as monochrome sampled pictures.

The number of bits used to represent each sample in the luma array and the chroma array in the video sequence may range from 8 bits to 16 bits (inclusive), and the number of bits used in the luma array may be different from the number of bits used in the chroma array.

Fig. 10A-10C illustrate nominal vertical and horizontal relative positions of corresponding luma and chroma samples in respective pictures according to embodiments of the present disclosure. The optional chroma sample relative positions may be indicated in the video usability information.

Referring to fig. 10A, a value of a chroma format index (e.g., chroma format idc) equal to 1 may indicate 4:2: 0. Fig. 10A shows an example of nominal vertical and horizontal positions of corresponding luma and chroma samples in a picture.

Referring to fig. 10B, a value of the chroma format index equal to 2 may indicate 4:2:2, and thus the chroma samples are co-located (or co-located) with corresponding luma samples in the picture. Fig. 10B shows an example of nominal vertical and horizontal positions of corresponding luma and chroma samples in a picture.

Referring to fig. 10C, when the value of the chroma format index is equal to 3, all array samples (e.g., the luma array sample and the two chroma array samples) may be co-located (or co-located). Fig. 10C shows an example of nominal vertical and horizontal positions of corresponding luma and chroma samples in a picture.

Examples of partitions such as in VVCs are described below. In an embodiment, a picture may be partitioned into CTUs. A picture may be divided into a sequence of CTUs. For a picture with three arrays of samples, a CTU includes an nxn block of luma samples (e.g., a luma block) and two corresponding blocks of chroma samples (e.g., two chroma blocks). Fig. 11 shows an example of a picture (1100) divided into CTUs (1101) according to an embodiment of the present disclosure. In an example, the maximum allowed size of a luminance block in a CTU is specified as 128 × 128. In an example, the maximum size (maximum size) of the luminance transform block is 64 × 64.

A picture may be partitioned into slices, tiles, and/or bricks. A picture may be divided into one or more tile rows and one or more tile columns. A tile may be a sequence of CTUs covering a rectangular region of a picture. A tile may be divided into one or more bricks, each of which may include a number of rows of CTUs within the tile. Tiles that are not partitioned into multiple bricks may also be referred to as bricks. However, bricks that are a true subset of tiles may not be referred to as tiles.

A strip may comprise several tiles of a picture or several bricks of a tile. Two stripe modes may be supported, for example, a raster scan stripe mode and a rectangular stripe mode. In raster scan stripe mode, a stripe may comprise a sequence of tiles in a tile raster scan of a picture. In the rectangular strip mode, a strip may comprise several bricks of a picture, which together may form a rectangular area of the picture. The bricks in the rectangular strip are arranged according to the brick raster scanning sequence of the strip.

A picture may be partitioned into tiles and raster scan stripes. Fig. 12 shows an example of raster scan stripe partitioning of a picture (1200) according to an embodiment of the present disclosure. The picture (1200) may be divided into 12 tiles (1201) - (1212) (e.g., 12 tiles in 3 columns (or tile columns) and 4 rows (or tile rows)) and 3 raster scan stripes (1221) - (1223). For example, raster scan stripe (1221) includes tiles (1201) - (1202), raster scan stripe (1222) includes tiles (1203) - (1207), and raster scan stripe (1223) includes tiles (1208) - (1212).

A picture may be partitioned into tiles and rectangular stripes. Fig. 13 illustrates an example of rectangular strip partitioning of a picture (1300) according to an embodiment of the present disclosure. The picture (1300) may be divided into 24 tiles (1301) - (1324) (e.g., 24 tiles in 6 columns (or tile columns) and 4 rows (or tile rows)) and 9 rectangular stripes (1331) - (1339). For example, a rectangular strip (1331) includes tiles (1301) - (1302); the rectangular strip (1332) includes tiles (1303) - (1304); the rectangular strip (1333) includes tiles (1305) - (1306); the rectangular strip (1334) includes tiles (1307), (1308), (1313), and (1314); the rectangular strip (1335) includes tiles (1309), (1310), (1315), and (1316); the rectangular strip (1336) includes tiles (1311), (1312), (1317), and (1318); the rectangular strip (1337) includes tiles (1319) - (1320); rectangular strip (1338) includes tiles (1321) - (1322); and the rectangular strip (1339) includes tiles (1323) - (1324).

The picture may be partitioned into tiles, bricks, and rectangular strips. Fig. 14 shows an example of a picture (1400) divided into tiles, bricks (1401) - (1411), and rectangular strips (1421) - (1424) according to an embodiment of the disclosure. The picture (1400) may be divided into four tiles (e.g., two tile columns and two tile rows), eleven tiles (1401) - (1411), and four rectangular strips (1421) - (1424). The upper left block includes one brick (1401), the upper right block includes five bricks (1402) - (1406), the lower left block includes two bricks (1407) - (1408), and the lower right block includes three bricks (1409) - (1411). The rectangular strip (1421) comprises bricks (1401), (1407) and (1408); rectangular strip (1422) comprises bricks (1402) and (1403); the rectangular strip (1423) comprises bricks (1404) - (1406); and the rectangular strip (1424) includes bricks (1409) - (1411).

The CTUs may be partitioned using a tree structure. In one embodiment, for example in HEVC, a CTU may be partitioned into one or more CUs by using a quadtree or QT structure represented as a coding tree to accommodate various local features. The decision whether to use inter-picture (temporal) or intra-picture (spatial) prediction to encode a picture region may be made at the leaf CU level. Each leaf-CU may be further partitioned into one, two, or four PUs, depending on the PU partition type. Within a PU, the same prediction process may be applied and the relevant information may be transmitted to the decoder on a PU basis. After a residual block is obtained by applying a prediction process based on the PU partition type, a leaf CU may be partitioned into Transform Units (TUs) according to a QT structure similar to the coding tree of the CU. In an example, such as in an HEVC structure, multiple partition units (e.g., CU, PU, and TU) may be different.

In embodiments, such as in VVCs, a quadtree with nested multi-type trees that use binary and ternary partition segmentation structures may replace the concept of multiple partition unit types, and thus may eliminate the separation of CU, PU, and TU concepts and may support more flexibility in CU partition shapes. In some examples, when the size of a CU is too large for the maximum transform length, different sizes may be used for the CU, PU, and/or TU. In the coding tree structure, a CU may have a square or rectangular shape. The CTU may be partitioned first by the QT structure. The QT leaf nodes are then further partitioned by a Multi-type Tree (MTT) structure. Fig. 15 illustrates exemplary segmentation types (1521) - (1524) in an MTT structure according to an embodiment of the disclosure. The partition types (1521) - (1524) may include vertical binary partition (SPLIT _ BT _ VER) (1521), horizontal binary partition (SPLIT _ BT _ HOR) (1522), vertical ternary partition (SPLIT _ TT _ VER) (1523), and horizontal ternary partition (SPLIT _ TT _ HOR) (1524). MTT leaf nodes may be referred to as CUs and unless a CU is too large for the maximum transform length, the segments (or CUs) may be used for prediction and transform processing without any further partitioning. Thus, in most cases, a CU, PU, and TU may have the same block size in a QT with a nested MTT coding block structure. An exception may occur when the maximum supported transform length is less than the width or height of the color component of the CU.

Fig. 16 shows an example of split flag signaling for QT with nested MTT coding tree structure according to an embodiment of the present disclosure. Fig. 16 illustrates an exemplary signaling mechanism for partition partitioning information in QTs with a nested MTT coding tree structure. One node (1611), e.g., one CTU, may be considered the root of the QT, and when the QT split flag (e.g., QT _ split _ flag) is true (e.g., value '1'), it may first be partitioned into QT nodes by the QT structure to generate QT nodes (1621). When the QT split flag (e.g., QT _ split _ flag) is false (e.g., value '0'), the nodes are not split using QT split (1611), and thus may be referred to as QT leaf nodes (1611). Each QT leaf node (when large enough to allow partitioning) may be further partitioned by the MTT fabric and may be referred to as an MTT node. Referring to FIG. 16, MTT partitioning can be used to further partition QT leaf nodes or MTT nodes (1611).

In the MTT structure, a first flag (e.g., MTT _ split _ cu _ flag) may be signaled to indicate whether to partition the node (1611) further. When the node (1611) is not partitioned (e.g., MTT _ split _ cu _ flag is '0'), the node (1611) is referred to as a MTT leaf node (1611). When the node (1611) is further partitioned (e.g., mtt _ split _ cu _ flag is '1'), a second flag (e.g., mtt _ split _ cu _ vertical _ flag) may be signaled to indicate the split direction (horizontal split or vertical split), and then a third flag (e.g., mtt _ split _ cu _ binary _ flag) may be signaled to indicate whether the split is a binary split or a ternary split. Thus, the MTT node (1651) is generated based on a vertical binary partition (e.g., BT _ VER _ split) of the node (1611), the MTT node (1652) is generated based on a vertical ternary partition (e.g., TT _ VER _ split) of the node (1611), the MTT node (1653) is generated based on a horizontal binary partition (e.g., BT _ HOR _ split) of the node (1611), and the MTT node (1654) is generated based on a horizontal ternary partition (e.g., TT _ HOR _ split) of the node (1611).

Referring to fig. 17, based on values of the second flag (e.g., MTT _ split _ CU _ vertical _ flag) and the third flag (e.g., MTT _ split _ CU _ binary _ flag), a MTT split mode (e.g., mttssplit mode) of a CU may be derived, as shown in table 2. The MTT SPLIT modes may include vertical binary SPLIT (e.g., BT _ VER _ SPLIT or SPLIT _ BT _ VER), vertical ternary SPLIT (e.g., TT _ VER _ SPLIT or SPLIT _ TT _ VER), horizontal binary SPLIT (e.g., BT _ HOR _ SPLIT or SPLIT _ BT _ HOR), and horizontal ternary SPLIT (e.g., TT _ HOR _ SPLIT or SPLIT _ TT _ HOR).

FIG. 18 shows an example of a QT with nested MTT coding block structure according to an embodiment of the present disclosure. The CTU (1800) may be partitioned into CUs having a QT and nested MTT coding block structure, where bold block edges represent QT partitions and remaining edges represent MTT partitions. A QT with nested MTT partitions may provide a content adaptive coding tree structure that includes CUs. The size of a CU may be any suitable size. The size of a CU may be as large as the CTU (1800), or as small as 4 × 4 (in luma samples). In an example, for a 4:2:0 chroma format, the maximum chroma CB size may be 64 × 64 and the minimum chroma CB size may be 2 × 2.

In examples such as VVC, the maximum supported luma transform size is 64 × 64, and the maximum supported chroma transform size is 32 × 32. When the width or height of the CB is greater than the maximum transform width or height, the CB may be automatically divided in the horizontal and/or vertical direction to meet the transform size limit in the corresponding direction.

The following parameters may be defined and specified by a Sequence Parameter Set (SPS) syntax element for QT with nested MTT coding tree scheme. The following parameters may include: (1) CTU size, which is the root node size of the QT tree; (2) MinQTSize, which is the minimum allowed QT leaf node size, (3) MaxBTSize, which is the maximum allowed BT root node size, (4) MaxTtSize, which is the maximum allowed TT root node size, (5) MaxMttDepth, which is the maximum allowed hierarchical depth of MTTs split from the QT leaf, (6) MinBTSize, which is the minimum allowed BT leaf node size, (7) MinTtSize, which is the minimum allowed TT leaf node size, and so on.

In the example of QT with nested MTT coding tree structure, the CTU size is set to 128 × 128 luma samples with two corresponding 64 × 64 blocks of 4:2:0 chroma samples, MinQTSize is set to 16 × 16, MaxBTSize is set to 128 × 128, MaxTtSize is set to 64 × 64, MinBtSize and MinTtSize (for both width and height) are set to 4 × 4, and MaxMttDepth is set to 4. The QT partition may first be applied to the CTU to generate QT leaf nodes. QT leaf nodes may have sizes from 16 × 16 (e.g., MinQTSize) to 128 × 128 (e.g., CTU size). In an example, if the QT leaf node is 128 × 128, the QT leaf node is not further split by BT because the size exceeds MaxBtSize and MaxTtSize (e.g., 64 × 64). Otherwise, the QT leaf node may be further partitioned by MTT. Thus, the QT leaf node may also be the root node of the MTT and may have an MTT depth of 0 (e.g., MttDepth). When the MTT depth reaches MaxMttDepth (e.g., 4), no further segmentation is considered. When the width of the MTT node is equal to MinBtSize and less than or equal to 2 × MinTtSize, further horizontal partitioning is not considered. Similarly, when the height of the MTT node is equal to MinBTSize and less than or equal to 2 × MinTtSize, no further vertical partitioning is considered.

In an embodiment, to allow for 64x64 luma block and 32 x 32 chroma pipeline designs such as in a VVC hardware decoder, TT partitioning may be disabled when the width or height of a luma coded block is greater than a first threshold (e.g., 64), as shown in fig. 19. Therefore, TT partitioning is not applied to luma coding blocks larger than 64, such as 128 × 128 luma coding blocks. TT partitioning may also be disabled when the width or height of the chroma coding block is greater than a second threshold (e.g., 32). Referring to fig. 19, the first threshold is 64, and since the sizes of the luma coding blocks (1911) - (1915) are 128 × 128, TT division is prohibited in the luma coding blocks (1911) - (1915). For example, the luma coding blocks (1911) are not partitioned, and the luma coding blocks (1912) - (1913) are partitioned using BT. Luma coding blocks (1914) - (1915) are first split by QT into 64x64 blocks. TT partitioning may then be applied to luma coding blocks (1921) - (1922) of size 64x 64.

In an embodiment, the coding tree scheme supports the ability for the luma component and the corresponding one or more chroma components to have separate block tree structures. In an example, luma and chroma CTBs in a CTU share the same coding tree structure (e.g., a single tree) for P and B slices. For I slices, luma and chroma CTBs in a CTU may have separate block tree structures (e.g., dual trees). When a separate block TREE mode (e.g., DUAL TREE) is applied, the LUMA CTB may be partitioned into LUMA CUs by a LUMA coding TREE structure (e.g., DUAL _ TREE _ LUMA), and the CHROMA CTB may be partitioned into CHROMA CUs by a CHROMA coding TREE structure (e.g., DUAL _ TREE _ CHROMA). Thus, a CU in an I slice may comprise a coded block of a luma component or a coded block of two chroma components, and a CU in a P or B slice may comprise coded blocks of all three color components, unless the video is monochrome.

A CU may be partitioned at picture boundaries (also referred to as boundaries) as described below. In an example, such as in HEVC, when a portion of a tree node block exceeds a bottom picture boundary or a right picture boundary, the tree node block is forced to be partitioned until all samples of each encoded CU are within the picture boundary. In some examples, the following segmentation rules may be applied:

if a part of a tree node block exceeds both the bottom picture boundary and the right picture boundary,

if the tree node block is a QT node and the size of the tree node block is greater than the minimum QT size, the tree node block is forcibly split in the QT split mode.

Otherwise, the tree node block is forced to be partitioned in SPLIT _ BT _ HOR mode.

Else, if a part of the tree node block exceeds the bottom picture boundary,

if the tree node block is a QT node, and the size of the tree node block is greater than the minimum QT size, and the size of the tree node block is greater than the maximum BT size, then the tree node block is forcibly split in QT split mode.

Else, if the tree node block is a QT node, and the size of the tree node block is greater than the minimum QT size, and the size of the tree node block is less than or equal to the maximum BT size, then the tree node block is forcibly SPLIT in the QT SPLIT mode or the SPLIT _ BT _ HOR mode.

Else (if the tree node block is a BTT node or the size of the tree node block is less than or equal to the minimum QT size), the tree node block is forced to be partitioned in SPLIT _ BT _ HOR mode.

Else, if a part of the tree node block exceeds the right picture boundary,

if the tree node block is a QT node, and the size of the tree node block is greater than the minimum QT size, and the size of the tree node block is greater than the maximum BT size, then the tree node block is forcibly split in QT split mode.

Else, if the tree node block is a QT node, and the size of the tree node block is greater than the minimum QT size, and the size of the tree node block is less than or equal to the maximum BT size, then the tree node block is forcibly SPLIT in a QT SPLIT mode or a SPLIT _ BT _ VER mode.

Else (if the tree node block is a BTT node or the size of the tree node block is less than or equal to the minimum QT size, then the tree node block is forced to be partitioned in SPLIT _ BT _ VER mode.

Restrictions on redundant CU partitioning may be used. QTs with nested MTT coding block structures may provide a flexible block partitioning structure. Different fragmentation patterns may result in the same coded block structure due to the type of fragmentation supported in the MTT. In an example, such as in VVC, certain redundant split modes are not allowed.

Fig. 20 illustrates an example of redundant split modes of BT splitting and TT splitting according to an embodiment of the present disclosure. Two-level consecutive BT partitions in one direction may have the same coding block structure as the TT partition after the BT partition of the center partition. In the above case, BT partitioning (in a given direction) of the center partition of TT partitioning may be blocked (e.g., not allowed), e.g., by syntax. In an example, the above-described restrictions apply to CUs in each picture.

In an example, the coding block structure (2001) is generated by two levels of consecutive BT partitions in the vertical direction (e.g., a first level BT partition (2011) followed by second level BT partitions (2021) - (2022)). The coding block structure (2002) may be generated by a vertical TT partition (2012) followed by a vertical BT partition (2023) of a center partition of the vertical TT partition (2012). The coding block structure (2001) may be the same as the coding block structure (2002) and thus BT partitioning (2023) (in the vertical direction) of the center partition of the TT partitioning (2012) is prevented, e.g. by syntax.

In an example, the code block structure (2003) is generated from two levels of consecutive BT partitions in the horizontal direction (e.g., a first level BT partition (2013) followed by second level BT partitions (2024) - (2025)). The coding block structure (2004) may be generated by a horizontal TT partition (2014) followed by a horizontal BT partition (2026) of the center partition of the horizontal TT partition (2014). The coding block structure (2003) may be the same as the coding block structure (2004) and thus BT partitioning (2026) (in the horizontal direction) of the center partition of TT partitioning (2014) is prevented, e.g., by syntax.

When segmentation is prohibited as described above, the signaling of the corresponding syntax element may be modified to address the prohibited case. For example, referring to fig. 20, when a case where BT partition (2023) or (2026) is prohibited for a CU of a central partition is identified, for example, the decoder does not signal a syntax element (e.g., mtt _ split _ CU _ binary _ flag) indicating whether the partition is BT partition or TT partition and infers it as being equal to 0. Therefore, BT division of the CU is prohibited.

Virtual Pipeline Data Units (VPDUs) can be defined as non-overlapping units in a picture. In a hardware decoder, successive VPDUs can be processed simultaneously by multiple pipeline stages. In most pipeline stages, the VPDU size is roughly proportional to the buffer size, so it is important to keep the VPDU size relatively small. In various examples, for example in most hardware decoders, the VPDU size may be set to the maximum Transform Block (TB) size. In some examples, such as in VVC, TT and BT partitions may result in an increase in VPDU size. To keep the VPDU size to a particular size, such as 64x64 luma samples, the following canonical partition restriction (with exemplary syntax signaling modifications) may be applied, as shown in fig. 21. Fig. 21 shows an example of disallowed TT and BT partitions according to an embodiment of the disclosure.

TT partitioning is not allowed for CUs with width, height, or both width and height equal to 128. For example, TT segmentation (2001), (2002), and (2005) - (2008) are not allowed.

For 128xN CU (i.e. width equal to 128 and height less than 128) with N ≦ 64, horizontal BT partitioning is not allowed. For example, for 128x64CU, horizontal BT segmentation is not allowed (2004).

For Nx128CU where N ≦ 64 (i.e., height equal to 128 and width less than 128), vertical BT splitting is not allowed. For example, for 64x128CU, vertical BT splitting is not allowed (2003).

Intra chroma partitioning and prediction limits are described below. Since the dual-tree in intra pictures can apply different partitions in the chroma coding tree compared to the luma coding tree, the dual-tree can introduce a longer coding pipeline. The QTBT MinQTSizeC value range, MinBtSizeY and MinTTSizeY in the chroma coding tree may allow for small chroma blocks such as 2x2, 4x2 and 2x 4. In the example, MinQTSizeC refers to the minimum allowed chroma QT leaf node size. Thus, practical decoder design can be challenging. In addition, some prediction modes, such as cross-component linear model (CCLM), planar mode, and angular mode, may use multiplication. To mitigate the above challenges, small chroma block sizes (e.g., 2x2, 2x4, and/or 4x2) may be limited to partition limits in a dual tree.

In various hardware video encoders and decoders, for example, processing throughput may be reduced when a picture has more small intra blocks due to sample processing data correlation between adjacent intra blocks. Predictor generation for intra blocks may reconstruct samples using the upper and left boundaries from neighboring blocks. Thus, in the example, intra prediction is processed sequentially block by block.

In some examples, such as in HEVC, the smallest intra CU is an 8x8 luma sample. The luma component of the smallest intra CU may be further partitioned into four 4x4 luma intra PUs, and the chroma component of the smallest intra CU cannot be further partitioned. Thus, in an example, hardware processing throughput may be reduced when processing a 4x4 chroma intra block or a 4x4 luma intra block. In some examples, chroma intra CB smaller than 16 chroma samples may be prohibited by constraining the partitioning of chroma intra CB in order to improve throughput. In a single coding tree, a minimum chroma intra prediction unit (SCIPU) may be defined as a coding tree node having a chroma block size greater than or equal to 16 chroma samples and having at least one sub-luma block of less than 64 luma samples. In each SCIPU, all CBs are inter-predicted or non-inter-predicted (e.g., intra-prediction or intra-block copy (IBC)). For non-inter SCIPU, in an example, one or more chroma CBs of the non-inter SCIPU are not further partitioned, and luma CBs of the SCIPU are further partitioned. Accordingly, the minimum chroma intra CB size may be 16 chroma samples, and thus 2x2, 2x4, and 4x2 chroma CBs may be removed. Additionally, in the example, chroma scaling does not apply to non-inter SCIPU. Here, no additional syntax is signaled, and whether SCIPU is non-inter predicted can be derived by the prediction mode of the first luma CB in SCIPU. If the current slice is an I slice or a SCIPU has a 4x4 luma partition therein after being further partitioned once, it can be inferred that the type of SCIPU (inter SCIPU or non-inter SCIPU) is non-inter SCIPU (because inter 4x4 is not allowed in VVC, for example); otherwise, the type of SCIPU may be indicated by a flag before parsing the CU in the SCIPU. In addition, restrictions on picture size may be considered to avoid 2x2, 2x4, or 4x2 intra chroma blocks at picture corners by considering picture width and height as multiples of max (8, MinCbSizeY).

Fig. 22 shows an example syntax related to partition and block sizes in an SPS (2200) in accordance with an embodiment of the disclosure. The syntax (2200) may include Raw Byte Sequence Payload (RBSP) syntax. An RBSP may refer to a syntax structure comprising an integer number of bytes, which is encapsulated in a Network Abstraction Layer (NAL) unit and is empty or in the form of a data bit string comprising a syntax element followed by an RBSP stop bit and zero or more subsequent bits equal to 0. In an example, the RBSP stop bit is the last non-zero bit in the RBSP.

The following describes semantics related to the partition and block sizes associated with the grammar (2200) in FIG. 22.

Qtbtt _ dual _ tree _ intra _ flag equal to 1 is used to indicate that for I slices, each CTU is partitioned into CUs with 64x64 luma samples using implicit QT partitioning, and to indicate that the CU can be the root of two separate coding _ tree syntax structures for luma and chroma. The qtbttt _ dual _ tree _ intra _ flag equal to 0 may indicate that a separate coding _ tree syntax structure is not used for the I slice. When qtbtt _ dual _ tree _ intra _ flag is not present, it can be inferred to be equal to 0.

The variable log2_ min _ luma _ coding _ block _ size _ minus2 plus 2 (i.e., log2_ min _ luma _ coding _ block _ size _ minus2+2) may indicate the minimum luma coding block size. The value range of log2_ min _ luma _ coding _ block _ size _ minus2 may be in the range of 0 to log2_ ctu _ size _ minus5+3 (inclusive).

The variables MinCbLog2SizeY, MinCbSizeY, IbcBufWidthY, IbcBufWidthC, and Vsize may be derived as follows:

MinCbLog2SizeY＝log2_min_luma_coding_block_size_minus2+2 (1)

MinCbSizeY＝1<<MinCbLog2SizeY (2)

IbcBufWidthY＝256*128/CtbSizeY (3)

IbcBufWidthC＝IbcBufWidthY/SubWidthC (4)

VSize＝Min(64，CtbSizeY) (5)

the MinCbSizeY value can be less than or equal to VSize.

The variables CtbWidthC and ctbhightc specify the width and height, respectively, of the array for each chroma CTB and can be derived as follows:

if chroma _ format _ idc is equal to 0 (monochrome) or separate _ colour _ plane _ flag is equal to 1, then both CtbWidthC and ctbhight c are equal to 0.

Otherwise, CtbWidthCc and CtbHeightC are derived as follows:

CtbWidthC＝CtbSizeY/SubWidthC (6)

CtbHeightC＝CtbSizeY/SubHeightC (7)

for log2BlockWidth ranging from 0 to 4 (inclusive) and log2BlockHeight ranging from 0 to 4 (inclusive), the upper right diagonal and Raster scan order array initialization process can be invoked using 1< < log2BlockWidth and 1< < log2BlockHeight as inputs, and the outputs can be assigned to DiagScanOrder [ log2BlockWidth ] [ log2BlockHeight ] and Raster2DiagScanPos [ log2BlockWidth ] [ log2BlockHeight ].

For log2BlockWidth ranging from 0 to 6 (inclusive) and log2BlockHeight ranging from 0 to 6 (inclusive), the horizontal and vertical traversal scan order array initialization process can be invoked using 1< < log2BlockWidth and 1< < log2BlockHeight as inputs, and the outputs can be assigned to HorTravScanOrder [ log2BlockWidth ] [ log2BlockHeight ] and VerTravScanOrder [ log2BlockWidth ] [ log2BlockHeight ].

The partition _ constraints _ override _ enabled _ flag equal to 1 may indicate the presence of the partition _ constraints _ override _ flag in the Picture Header (PH) of the reference SPS. The partition _ constraints _ override _ enabled _ flag equal to 0 may specify that the partition _ constraints _ override _ flag does not exist in the PH of the reference SPS.

SPS _ log2_ diff _ min _ QT _ min _ cb _ intra _ slice _ luma may indicate a default difference between the base-2 logarithm of the minimum size in luma samples of the luma leaf blocks resulting from the QT partitioning of the CTU and the base-2 logarithm of the minimum coding block size in luma samples of the luma CU in the slice where slice _ type of the reference SPS is equal to 2 (indicating I slices). When partition _ constraints _ override _ enabled _ flag is equal to 1, the default difference may be overridden by pic _ log2_ diff _ min _ qt _ min _ cb _ luma in the PH of the reference SPS. The value of sps _ log2_ diff _ min _ qt _ min _ cb _ intra _ slice _ luma may range from 0 to CtbLog2SizeY-MinCbLog2SizeY, inclusive. The base 2 logarithm of the minimum size in luminance samples of a luminance leaf block resulting from the QT segmentation of the CTU can be derived as follows:

MinQtLog2SizeIntraY＝

sps_log2_diff_min_qt_min_cb_intra_slice_luma+MinCbLog2SizeY (8)

SPS _ log2_ diff _ min _ QT _ min _ cb _ inter _ slice may indicate a default difference between the base-2 logarithm of the minimum size in luma samples of the luma leaf block resulting from the QT splitting of the CTU and the base-2 logarithm of the minimum luma coding block size in luma samples of the luma CU in a slice with slice _ type equal to 0 (indicating a B slice) or 1 (indicating a P slice) that considers SPS. When partition _ constraints _ override _ enabled _ flag is equal to 1, the default difference may be covered by pic _ log2_ diff _ min _ qt _ min _ cb _ luma present in the PH of the reference SPS. The value of sps _ log2_ diff _ min _ qt _ min _ cb _ inter _ slice may range from 0 to CtbLog2SizeY-MinCbLog2SizeY, inclusive. The base 2 logarithm of the minimum size in luminance samples of a luminance leaf block resulting from the QT segmentation of the CTU can be derived as follows:

MinQtLog2SizeInterY＝

sps_log2_diff_min_qt_min_cb_inter_slice+MinCbLog2SizeY (9)

SPS _ max _ MTT _ hierarchy _ depth _ inter _ slice may indicate a default maximum hierarchical depth of a coding unit resulting from MTT splitting of QT leaves in a slice of which slice _ type of the reference SPS is equal to 0 (indicating a B slice) or 1 (indicating a P slice). When partition _ constraints _ override _ enabled _ flag is equal to 1, the default maximum hierarchical depth may be covered by pic _ max _ mtt _ hierarchy _ depth _ inter _ slice present in the PH of the reference SPS. The value of sps _ max _ mtt _ hierarchy _ depth _ inter _ slice may be in the range of 0 to 2x (CtbLog2SizeY-MinCbLog2SizeY), inclusive.

SPS _ max _ MTT _ hierarchy _ depth _ intra _ slice _ luma may indicate a default maximum hierarchical depth of a coding unit resulting from MTT splitting of QT leaves in a slice of reference SPS whose slice _ type is equal to 2 (indicating an I-slice). When partition _ constraints _ override _ enabled _ flag is equal to 1, the default maximum hierarchical depth may be covered by pic _ max _ mtt _ hierarchy _ depth _ intra _ slice _ luma present in the PH of the reference SPS. The value of sps _ max _ mtt _ hierarchy _ depth _ intra _ slice _ luma may be in the range of 0 to 2x (CtbLog2SizeY-MinCbLog2SizeY), inclusive.

SPS _ log2_ diff _ max _ bt _ min _ QT _ intra _ slice _ luma may indicate a default difference between the base-2 logarithm of the maximum size (width or height) in luma samples of a luma coded block that may be partitioned using binary partitioning and the minimum size (width or height) in luma samples of a luma leaf block produced by QT partitioning of a CTU in a slice of reference SPS where slice _ type is equal to 2 (indicating I slices). When partition _ constraints _ override _ enabled _ flag is equal to 1, the default difference may be covered by pic _ log2_ diff _ max _ bt _ min _ qt _ luma present in the PH of the reference SPS. The value of sps _ log2_ diff _ max _ bt _ min _ qt _ intra _ slice _ luma may range from 0 to CtbLog2SizeY-MinQtLog2 sizeinray, inclusive. When sps _ log2_ diff _ max _ bt _ min _ qt _ intra _ slice _ luma is not present, it may be inferred that the value of sps _ log2_ diff _ max _ bt _ min _ qt _ intra _ slice _ luma is equal to 0.

SPS _ log2_ diff _ max _ tt _ min _ QT _ intra _ slice _ luma may specify a default difference between the base-2 logarithm of the maximum size (width or height) in luma samples of a luma coded block that may be partitioned using ternary partitioning and the minimum size (width or height) in luma samples of a luma leaf block produced by QT partitioning of a CTU in a slice of the reference SPS where slice _ type is equal to 2 (indicating an I slice). When partition _ constraints _ override _ enabled _ flag is equal to 1, the default difference may be covered by pic _ log2_ diff _ max _ tt _ min _ qt _ luma present in the PH of the reference SPS. The value of sps _ log2_ diff _ max _ tt _ min _ qt _ intra _ slice _ luma may range from 0 to CtbLog2SizeY-MinQtLog2SizeIntraY, inclusive. When sps _ log2_ diff _ max _ tt _ min _ qt _ intra _ slice _ luma is not present, it may be inferred that the value of sps _ log2_ diff _ max _ tt _ min _ qt _ intra _ slice _ luma is equal to 0.

SPS _ log2_ diff _ max _ bt _ min _ QT _ inter _ slice may specify a default difference between the base-2 logarithm of the maximum size (width or height) in luma samples of a luma coded block that may be partitioned using binary partitioning and the minimum size (width or height) in luma samples of the luma leaf blocks produced by QT partitioning of the CTU in slices where slice _ type of the reference SPS is equal to 0 (indicating a B slice) or 1 (indicating a P slice). When partition _ constraints _ override _ enabled _ flag is equal to 1, the default difference may be covered by pic _ log2_ diff _ max _ bt _ min _ qt _ luma present in the PH of the reference SPS. The value of sps _ log2_ diff _ max _ bt _ min _ qt _ inter _ slice may range from 0 to CtbLog2SizeY-MinQtLog2 sizeiny, inclusive. When sps _ log2_ diff _ max _ bt _ min _ qt _ inter _ slice is not present, it can be inferred that the value of sps _ log2_ diff _ max _ bt _ min _ qt _ inter _ slice is equal to 0.

SPS _ log2_ diff _ max _ tt _ min _ QT _ inter _ slice may indicate a default difference between the base-2 logarithm of the maximum size (width or height) in luma samples of a luma coded block that may be partitioned using ternary partitioning and the minimum size (width or height) in luma samples of the luma leaf blocks produced by QT partitioning of the CTU in slices where slice _ type of the reference SPS is equal to 0 (indicating a B slice) or 1 (indicating a P slice). When partition _ constraints _ override _ enabled _ flag is equal to 1, the default difference may be covered by pic _ log2_ diff _ max _ tt _ min _ qt _ luma present in the PH of the reference SPS. The value of sps _ log2_ diff _ max _ tt _ min _ qt _ inter _ slice may range from 0 to CtbLog2SizeY-MinQtLog2 sizeiny, inclusive. When sps _ log2_ diff _ max _ tt _ min _ qt _ inter _ slice is not present, it can be inferred that the value of sps _ log2_ diff _ max _ tt _ min _ qt _ inter _ slice is equal to 0.

SPS _ log2_ diff _ min _ qt _ min _ cb _ intra _ slice _ CHROMA may indicate a default difference between the base-2 logarithm of the minimum size in units of luma samples of a CHROMA leaf block resulting from a quadtree partitioning of a CHROMA CTU with a TREE type (treeType) equal to DUAL _ TREE _ CHROMA and the base-2 logarithm of the minimum coded block size in units of luma samples of a CHROMA CU with a TREE type (treeType) equal to 2 (indicating an I slice) in a slice of the reference SPS. When partition _ constraints _ override _ enabled _ flag is equal to 1, the default difference may be covered by pic _ log2_ diff _ min _ qt _ min _ cb _ chroma present in the PH of the reference SPS. The value of sps _ log2_ diff _ min _ qt _ min _ cb _ intra _ slice _ chroma may range from 0 to CtbLog2SizeY-MinCbLog2SizeY, inclusive. When not present, the value of sps _ log2_ diff _ min _ qt _ min _ cb _ intra _ slice _ chroma may be inferred to be equal to 0. The base-2 logarithm of the minimum size in units of luma samples for chroma leaf blocks resulting from a QT split of CTU with treeType equal to DUAL _ TREE _ chroma mactu can be derived as follows:

MinQtLog2SizeIntraC＝

sps_log2_diff_min_qt_min_cb_intra_slice_chroma+MinCbLog2SizeY (10)

SPS _ max _ mtt _ hierarchy _ depth _ intra _ slice _ CHROMA may indicate a default maximum hierarchical depth of CHROMA coding units in a slice of the reference SPS that has a slice _ type equal to 2 (indicating an I slice) resulting from multi-type TREE splitting of CHROMA quad-TREE leaves with treeType equal to DUAL _ TREE _ CHROMA. When partition _ constraints _ override _ enabled _ flag is equal to 1, the default maximum hierarchical depth may be covered by pic _ max _ mtt _ hierarchy _ depth _ chroma present in the PH of the reference SPS. The value of sps _ max _ mtt _ hierarchy _ depth _ intra _ slice _ chroma may range from 0 to 2x (CtbLog2SizeY-MinCbLog2SizeY), inclusive. When not present, the value of sps _ max _ mtt _ hierarchy _ depth _ intra _ slice _ chroma may be inferred to be equal to 0.

SPS _ log2_ diff _ max _ bt _ min _ QT _ intra _ slice _ CHROMA may specify a default difference between the base-2 logarithm of the maximum size (width or height) in units of luma samples of a CHROMA coded block that may be partitioned using ternary partitioning and the minimum size (width or height) in units of luma samples of a CHROMA leaf block resulting from QT partitioning of a CHROMA CTU with treeType equal to DUAL _ TREE _ CHROMA in a slice of reference SPS where slice _ type is equal to 2 (indicating an I slice). When partition _ constraints _ override _ enabled _ flag is equal to 1, the default difference may be covered by pic _ log2_ diff _ max _ bt _ min _ qt _ chroma present in the PH of the reference SPS. The value of sps _ log2_ diff _ max _ bt _ min _ qt _ intra _ slice _ chroma may range from 0 to CtbLog2SizeY-MinQtLog2 sizeintranrac, inclusive. When sps _ log2_ diff _ max _ bt _ min _ qt _ intra _ slice _ chroma is not present, it may be inferred that the value of sps _ log2_ diff _ max _ bt _ min _ qt _ intra _ slice _ chroma is equal to 0.

SPS _ log2_ diff _ max _ tt _ min _ qt _ intra _ slice _ CHROMA may indicate a default difference between the base-2 logarithm of the maximum size (width or height) in units of luma samples of a CHROMA coded block that may be partitioned using ternary partitioning and the minimum size (width or height) in units of luma samples of a CHROMA leaf block resulting from quadtree partitioning of CHROMA CTUs with treeType equal to DUAL _ TREE _ CHROMA in a slice of the reference SPS that is equal to 2 (indicating an I slice). When partition _ constraints _ override _ enabled _ flag is equal to 1, the default difference may be covered by pic _ log2_ diff _ max _ tt _ min _ qt _ chroma present in the PH of the reference SPS. The value of sps _ log2_ diff _ max _ tt _ min _ qt _ intra _ slice _ chroma may range from 0 to CtbLog2SizeY-MinQtLog2SizeIntrac, inclusive. When sps _ log2_ diff _ max _ tt _ min _ qt _ intra _ slice _ chroma is not present, it may be inferred that the value of sps _ log2_ diff _ max _ tt _ min _ qt _ intra _ slice _ chroma is equal to 0.

A sps _ max _ luma _ transform _ size _64_ flag equal to 1 may indicate that the maximum transform size in units of luma samples is equal to 64. Sps _ max _ luma _ transform _ size _64_ flag equal to 0 may specify a maximum transform size in units of luma samples equal to 32. When CtbSizeY is less than 64, the value of sps _ max _ luma _ transform _ size _64_ flag may be equal to 0.

The variables MinTbLog2SizeY, MaxTbLog2SizeY, MinTbSizeY and MaxTbSizeY can be derived as follows:

MinTbLog2SizeY＝2 (11)

MaxTbLog2SizeY＝sps_max_luma_transform_size_64_flag6：5 (12)

MinTbSizeY＝1<<MinTbLog2SizeY (13)

MaxTbSizeY＝1<<MaxTbLog2SizeY (14)

…

pic _ log2_ diff _ min _ QT _ min _ cb _ intra _ slice _ CHROMA may specify the difference between the base-2 logarithm of the minimum size in units of luma samples of a CHROMA leaf block resulting from QT splitting of a CHROMA CTU with treeType equal to DUAL _ TREE _ CHROMA and the base-2 logarithm of the minimum coding block size in units of luma samples of a CHROMA CU with treeType equal to DUAL _ TREE _ CHROMA in a slice with slice _ type equal to 2 (indicating I slices) associated with PH. The value of pic _ log2_ diff _ min _ qt _ min _ cb _ intra _ slice _ chroma may range from 0 to CtbLog2SizeY-MinCbLog2SizeY, inclusive. When not present, the value of pic _ log2_ diff _ min _ qt _ min _ cb _ intra _ slice _ chroma can be inferred to be equal to sps _ log2_ diff _ min _ qt _ min _ cb _ intra _ slice _ chroma.

slice _ type can specify the encoding and decoding type of the slice according to table 3 in fig. 23. For example, slice _ types of 0 to 2 correspond to B, P, and I slices, respectively.

When nal _ unit _ type is a value of nal _ unit _ type within a range of IDR _ W _ RADL to CRA _ NUT (inclusive), and the current picture is the first picture in an access unit, slice _ type may be equal to 2.

The variables MinQtLog2SizeY, MinQtLog2SizeC, MinQtSizeY, MinQtSizeC, MaxBtSizeY, MaxBtSizeC, MinBtSizeY, MaxTtSizeY, MaxTtSizeC, MinTtSizeY, MaxMttDepthY and MaxMttDepthC can be derived as follows:

MinQtSizeY＝1<<MinQtLog2SizeY (15)

MinQtSizeC＝1<<MinQtLog2SizeC (16)

MinBtSizeY＝1<<MinCbLog2SizeY (17)

MinTtSizeY＝1<<MinCbLog2SizeY (18)

if slice _ type is equal to 2(I stripe),

MinQtLog2SizeY＝MinCbLog2SizeY+pic_log2_diff_min_qt_min_cb_intra_slice_luma (19)

MinQtLog2SizeC＝MinCbLog2SizeC+pic_log2_diff_min_qt_min_cb_intra_slice_chroma (20)

MaxBtSizeY＝1<<(MinQtLog2SizeY+pic_log2_diff_max_bt_min_qt_intra_slice_luma) (21)

MaxBtSizeC＝1<<(MinQtLog2SizeC+pic_log2_diff_max_bt_min_qt_intra_slice_chroma) (22)

MaxTtSizeY＝1<<(MinQtLog2SizeY+pic_log2_diff_max_tt_min_qt_intra_slice_luma) (23)

MaxTtSizeC＝1<<(MinQtLog2SizeC+pic_log2_diff_max_tt_min_qt_intra_slice_chroma) (24)

MaxMttDepthY＝pic_max_mtt_hierarchy_depth_intra_slice_luma (25)

MaxMttDepthC＝pic_max_mtt_hierarchy_depth_intra_slice_chroma (26)

CuQpDeltaSubdiv＝pic_cu_qp_delta_subdiv_intra_slice (27)

CuChromaQpOffsetSubdiv＝pic_cu_chroma_qp_offset_subdiv_intra_slice (28)

otherwise (slice _ type equals 0(B slice) or 1(P slice)),

MinQtLog2SizeY＝MinCbLog2SizeY+pic_log2_diff_min_qt_min_cb_inter_slice (29)

MinQtLog2SizeC＝MinCbLog2SizeC+pic_log2_diff_min_qt_min_cb_inter_slice (30)

MaxBtSizeY＝1<<(MinQtLog2SizeY+pic_log2_diff_max_bt_min_qt_inter_slice) (31)

MaxBtSizeC＝1<<(MinQtLog2SizeC+pic_log2_diff_max_bt_min_qt_inter_slice) (32)

MaxTtSizeY＝1<<(MinQtLog2SizeY+pic_log2_diff_max_tt_min_qt_inter_slice) (33)

MaxTtSizeC＝1<<(MinQtLog2SizeC+pic_log2_diff_max_tt_min_qt_inter_slice) (34)

MaxMttDepthY＝pic_max_mtt_hierarchy_depth_inter_slice (35)

MaxMttDepthC＝pic_max_mtt_hierarchy_depth_inter_slice (36)

CuQpDeltaSubdiv＝pic_cu_qp_delta_subdiv_inter_slice (37)

CuChromaQpOffsetSubdiv＝pic_cu_chroma_qp_offset_subdiv_inter_slice (38)

for certain chroma block sizes (such as 2xN sizes), chroma intra prediction may be disabled.

In an embodiment, 2xN chroma intra blocks in both the dual tree and the single tree may be removed, as described below. In a dual tree, the 2xN intra chroma may be limited by disabling certain partitions. For example, binary and ternary tree partitioning is prohibited for blocks of widths 4 and 8, respectively.

To remove 2xN in a single tree, two constraints can be used, including the extension of the local dual tree and the constraint of combined inter-frame/intra-prediction (CIIP) of chroma 2 xN.

In a first constraint, when a partition is 4 wide and the partition is a binary vertical partition, or 8 wide and the partition is a ternary vertical partition, the chroma component may be considered as SCIPU. Following the principle limitations of SCIPU, chroma components are not partitioned within intra SCIPU (all luma blocks are encoded using non-inter mode and non-partitioned chroma blocks are encoded using intra mode). For inter SCIPU (all luma and chroma blocks are coded using inter mode), the partition of the chroma component can be inherited from the luma component.

In a second limitation, in the example, for a 4xN CIIP block, CIIP is used only for the luma component, and only inter prediction is used for the chroma component.

The above-described limitation may ensure that the width of the intra chroma block is greater than or equal to 4, and thus intra processing of 2xN pixels may be removed. These limitations may make the implementation of video codecs a hardware implementation friendly example of the partition availability related process described below in terms of pipeline management, such as in VVC.

In an embodiment, the following describes an allowed quaternion segmentation process. The inputs to the allowed quaternion segmentation process may include:

a) the coded block size in units of luma samples (or cbSize),

b) MTT depth (or mttDepth),

c) a variable TREE type (or treeType) for indicating whether a SINGLE TREE (or SINGLE _ TREE) or a DUAL TREE is used to partition the coding TREE node, and whether a LUMA (DUAL _ TREE _ LUMA) component or a CHROMA component (DUAL _ TREE _ CHROMA) is currently processed when a DUAL TREE is used.

d) The variable MODE TYPE (also referred to as a prediction MODE TYPE, e.g., modeType) indicates whether an INTRA MODE (or an INTRA prediction MODE, MODE _ INTRA), an IBC MODE (or MODE _ IBC), and an INTER codec MODE (MODE _ TYPE _ ALL) may be used for a coding unit within a coding tree node, or whether only an INTRA codec MODE and an IBC codec MODE (MODE _ TYPE _ INTRA) may be used, or whether only an INTER codec MODE (MODE _ TYPE _ INTER) may be used. In an example, MODE _ TYPE _ ALL indicates that intra, IBC, and inter codec MODEs may be used.

The coding block size (or cbSize) in units of luma samples may represent the block size of a chroma coding block (or chroma block) having luma samples. Thus, the block size of a chroma coding block in chroma samples may be determined based on the coding block size in luma samples (or cbSize) and the corresponding chroma sub-sampling rate, e.g., as a chroma horizontal sub-sampling rate or a chroma sub-sampling rate in the horizontal direction (e.g., SubWidthC). For example, for chroma format 4:2:0, the coding block size in units of luma samples (or cbSize) is 16, so the block size of chroma coding blocks is 16 when represented using luma samples as units, or 8 when represented using chroma samples as units.

In an example, the encoding block size cbSize is set equal to the width (cbWidth) of the encoding block size in units of luma samples. For example, for chroma format 4:2:2, the width of the coding block size in units of luma samples is 16 luma samples and the chroma horizontal sub-sampling rate (SubWidthC) is 2, so the block size of a chroma coding block may be 16 luma samples or 16/2 (or 8) chroma samples. In addition, for chroma format 4:2:2, the height of the coding block size in units of luma samples is 16 luma samples and the chroma vertical sub-sampling rate (sub-height c) is 1, and thus, the height of a chroma coding block may be 16 luma samples or 16 chroma samples.

The output of the allowed quaternion split process may include a variable allowslitqt that indicates whether QT split is allowed (e.g., allowslitqt is true) or not allowed (e.g., allowslitqt is false). The variable allowSplitQt may be derived as follows:

the variable allowslitqt may be set equal to FALSE and QT split (or QT split) is not allowed if one or more of the following conditions (also referred to as conditions for QT split) are true:

omicron (a) treeType equal to SINGLE _ TREE or DUAL _ TREE _ LUMA and cbSize less than or equal to MinQtSizeY

Omicron (b) treeType equal to DUAL _ TREE _ CHROMA and cbSize/SubWidthC less than or equal to MinQtSizeC

O (c) mttDepth not equal to 0

Omicron (d) treeType equal to DUAL _ TREE _ CHROMA and (cbSize/SubWidthC) less than or equal to 4

Omicron (e) treeType equals to DUAL _ TREE _ CHROMA and modeType equals to MODE _ TYPE _ INTRA

Otherwise, allowslitqt may be set equal to TRUE. Thus, QT partitioning (or QT partitioning) may be allowed.

In various examples, certain conditions, such as conditions (b), (d), and (e) described above, include treeType equal to DUAL _ TREE _ CHROMA, so when QT segmentation is applied to CHROMA blocks, conditions (b), (d), and (e) may be true, while when QT segmentation is applied to luma blocks, conditions (b), (d), and (e) may not be true. Therefore, the conditions (b), (d), and (e) for the QT partition may be referred to as conditions for the chroma QT partition (or the chroma QT partition).

One or more of conditions (a) - (e) may be modified and/or omitted. One or more additional condition conditions(s) may be added to conditions (a) - (e).

In an example, the coding tree semantics including the variable allowslitqt may be derived as follows: the allowed quaternion segmentation process may be invoked with the coding block size cbSize (e.g., in luma samples) set equal to cbWidth, the current multi-type tree depth mttDepth, treeTypeCurr, and modeTypeCurr as inputs, and the output may be assigned to allowslitqt.

In an embodiment, the following describes an allowed binary segmentation process. The inputs to the allowed binary segmentation process may include:

a) binary split mode (or btSplit),

b) the coded block width (or cbWidth) in units of luma samples,

c) the coded block height (or cbHeight) in units of luma samples,

d) the position of the top left luminance sample of the considered coding block relative to the top left luminance sample of the picture (x0, y0),

e) a multi-type tree depth (or mttDepth),

f) the maximum multi-type tree depth with offset (or maxMttDepth),

g) the maximum binary tree size (or maxBtSize),

h) the minimum QT size (or minQtSize),

i) the partition index (or partIdx),

j) a variable TREE type (or treeType) indicating whether a SINGLE TREE (SINGLE _ TREE) or a DUAL TREE is used to partition the coding TREE node and whether a LUMA (DUAL _ TREE _ LUMA) component or a CHROMA component (DUAL _ TREE _ CHROMA) is currently processed when a DUAL TREE is used,

k) a variable MODE TYPE (or modeType) for indicating whether an INTRA codec MODE (MODE _ INTRA), an IBC codec MODE (MODE _ IBC), and an INTER codec MODE (MODE _ TYPE _ ALL) can be used for a coding unit within the coding tree node, or whether only the INTRA codec MODE and the IBC codec MODE (MODE _ TYPE _ INTRA) can be used, or whether only the INTER codec MODE (MODE _ TYPE _ INTER) can be used.

The output of the allowed binary split process may include the variable allowbtssplit.

In an example, the variables parallelTtSplit and cbSize are derived based on the variable btSplit, as shown in table 4 (fig. 24).

The variable allowstbsplit can be derived as follows:

-the variable allowBtSplit can be set equal to FALSE if one or more of the following conditions are true:

omicron cbSize is less than or equal to MinBtSizeY

Omicron cbWidth is greater than maxBtSize

Omicron cbHeight greater than maxBtSize

Omicron mttDepth is greater than or equal to maxMttDepth

Omicron type is equal to DUAL _ TREE _ CHROMA and (cbWidth/SubWidth C) x is less than or equal to 16

Omicron type is equal to DUAL _ TREE _ CHROMA and (cbWidth/SubWidthC) is equal to 4 and btSplit is equal to SPLIT _ BT _ VER

Omicron TYPE is equal to DUAL _ TREE _ CHROMA, and modeType is equal to MODE _ TYPE _ INTRA

Omicron cbWidth × cbHeight is equal to 32, and modeType is equal to MODE _ TYPE _ INTER

Else, if all of the following conditions are true, the variable eadlowbtsplit can be set equal to FALSE

Omicron btSplit equals SPLIT _ BT _ VER

Y0+ cbHeight is greater than pic _ height _ in _ luma _ samples

Else, the variable allowBtSplit may be set equal to FALSE if all of the following conditions are true

Omicron btSplit equals SPLIT _ BT _ VER

Omicron cbHeight is greater than 64

X0+ cbWidth is greater than pic _ width _ in _ luma _ samples

Else, the variable allowBtSplit may be set equal to FALSE if all of the following conditions are true

Omicron btSplit is equal to SPLIT _ BT _ HOR

Omicron cbWidth is greater than 64

Y0+ cbHeight is greater than pic _ height _ in _ luma _ samples

Else, the variable allowBtSplit may be set equal to FALSE if all of the following conditions are true

X0+ cbWidth is greater than pic _ width _ in _ luma _ samples

Y0+ cbHeight is greater than pic _ height _ in _ luma _ samples

Omicron cbWidth is greater than minQtSize

Else, the variable allowBtSplit may be set equal to FALSE if all of the following conditions are true

Omicron btSplit is equal to SPLIT _ BT _ HOR

X0+ cbWidth is greater than pic _ width _ in _ luma _ samples

Y0+ cbHeight is less than or equal to pic _ height _ in _ luma _ samples

Otherwise, the variable allowstbsplit may be set equal to FALSE if all of the following conditions are true:

omicron mttDepth greater than 0

Omicron paratidx equals 1

Omicron MttSplitMode [ x0] [ y0] [ mtDepth-1 ] is equal to paralleltTsSplit

Else, the variable allowBtSplit may be set equal to FALSE if all of the following conditions are true

Omicron btSplit equals SPLIT _ BT _ VER

Omicron cbWidth is less than or equal to 64

Omicron cbHeight is greater than 64

Else, the variable allowBtSplit may be set equal to FALSE if all of the following conditions are true

Omicron btSplit is equal to SPLIT _ BT _ HOR

Omicron cbWidth is greater than 64

Omicron cbHeight is less than or equal to 64

Otherwise, the variable allowBtSplit may be set equal to TRUE.

In an embodiment, an allowed ternary partitioning process is described below. The inputs to the allowed ternary partitioning process may include:

a) a ternary partitioning pattern (or ttSplit),

b) the coded block width (or cbWidth) in units of luma samples,

c) the coded block height (or cbHeight) in units of luma samples,

d) the position of the top left luminance sample of the considered coding block relative to the top left luminance sample of the picture (x0, y0),

e) multiclass tree depth (or mttDepth)

f) The maximum multi-type tree depth with offset (or maxMttDepth),

g) the maximum ternary tree size (or maxTtSize),

h) a variable TREE type (or treeType) indicating whether a SINGLE TREE (SINGLE _ TREE) or a DUAL TREE is used to partition the coding TREE node and, when a DUAL TREE is used, whether the currently processed LUMA (DUAL _ TREE _ LUMA) component or CHROMA (DUAL _ TREE _ CHROMA) component,

i) a variable MODE TYPE (or modeType) for indicating whether an INTRA codec MODE (MODE _ INTRA), an IBC codec MODE (MODE _ IBC), and an INTER codec MODE (MODE _ TYPE _ ALL) can be used for a coding unit within the coding tree node, or whether only the INTRA codec MODE and the IBC codec MODE (MODE _ TYPE _ INTRA) can be used, or whether only the INTER codec MODE (MODE _ TYPE _ INTER) can be used.

The output of the allowed ternary partitioning process may include the variable allowtsplit.

In an example, the variable cbSize can be derived based on the variable ttSplit, as shown in table 5 (fig. 25).

The variable allowtsplitt may be derived as follows:

-the variable allowtsplit may be set equal to FALSE if one or more of the following conditions are true:

omicron cbSize is less than or equal to 2 MinTtSizeY

Omicron cbWidth is greater than Min (64, maxTtSize)

Omicron cbHeight is greater than Min (64, maxTtSize)

Omicron mttDepth is greater than or equal to maxMttDepth

X0+ cbWidth is greater than pic _ width _ in _ luma _ samples

Y0+ cbHeight is greater than pic _ height _ in _ luma _ samples

Omicron type is equal to DUAL _ TREE _ CHROMA and (cbWidth/SubWidth C) x is less than or equal to 32

Omicron type is equal to DUAL _ TREE _ CHROMA and (cbWidth/SubWidthC) is equal to 8 and ttSplit is equal to SPLIT _ TT _ VER

Omicron TYPE is equal to DUAL _ TREE _ CHROMA, and modeType is equal to MODE _ TYPE _ INTRA

Omicron cbWidth × cbHeight is equal to 64, and modeType is equal to MODE _ TYPE _ INTER

Otherwise, the variable allowttssplit may be set equal to TRUE.

The derivation process for the availability of neighboring blocks may be described as follows.

The input to the derivation process of the availability of neighboring blocks may include:

a) the luminance position (xCurr, yCurr) of the upper left sample of the current block relative to the upper left luminance sample of the current picture,

b) luminance positions (xNbY, yNbY) of the top-left luminance samples relative to the current picture covered by the neighboring blocks,

c) a variable checkpredmode to indicate whether availability depends on the prediction mode,

d) a variable cIdx for indicating the color component of the current block.

The output of the derivation process may include the availability of neighboring blocks covering the location (xNbY, yNbY), denoted availableN. The neighboring block availability (or availableN) may be derived as follows:

availableN can be set equal to FALSE if one or more of the following conditions are true:

omicron xNbY is less than 0.

Omicron yNbY is less than 0.

Omicron xNbY is greater than or equal to pic _ width _ in _ luma _ samples.

Omicron y is greater than or equal to pic _ height _ in _ luma _ samples.

Omicron IsAvailable [ cIdx ] [ xNbY ] [ yNbY ] equals FALSE.

O neighboring blocks are included in a different strip than the current block.

The neighboring block is included in a different tile than the current block.

Omicron _ coding _ sync _ enabled _ flag is equal to 1 and (xNbY > > CtbLog2SizeY) is greater than or equal to (xCurr > > CtbLog2SizeY) + 1.

Otherwise, the variable availableN may be set equal to TRUE.

The variable availableN may be set equal to FALSE if all of the following conditions are true:

-checkPredModey equals TRUE.

CuPredMode [0] [ xNbY ] [ yNbY ] is not equal to CuPredMode [0] [ xCyrr ] [ yCurr ].

As described above, one of the conditions of the QT split (i.e., condition (b)) includes checking whether cbSize/SubWidthC is less than or equal to the minimum allowed chroma QT leaf node size (e.g., MinQtSizeC). cbSize may be an encoding block size of a chroma block in units of luma samples, and subwidth hc may be a chroma horizontal sub-sampling factor (or a chroma sub-sampling factor for the horizontal direction). In some examples, cbSize/SubWidthC corresponds to the width of a chroma block in chroma samples. When the chroma format is 4:2:2, the sub-sampling in the horizontal direction and the vertical direction may be different, and thus the width of a chroma block in units of chroma samples may be smaller than the height of the chroma block in units of chroma samples. Thus, for example, when cbSize is equal to MinQtSizeC, using cbSize/SubWidthC that is less than or equal to MinQtSizeC as a condition to disable (or disallow) the QT segmentation may have a higher chance of disabling chroma QT segmentation, and may reduce the codec performance of the chroma components in some examples.

The above condition (b) for chroma QT partitioning can be modified to allow more QT partitioning. According to aspects of the present disclosure, the modified condition (b) may compare the chroma block height (or height of the chroma block) with a minimum allowed chroma QT leaf node size (also referred to as a minimum allowed chroma block size for QT splitting) (MinQtSizeC).

According to aspects of the present disclosure, the allowed quaternion segmentation process described above may be modified by modifying condition (b), while other conditions (e.g., conditions (a) and (c) - (e) remain unchanged.

(b') treeType equal to DUAL _ TREE _ CHROMA and cbSize/SubHeightC less than or equal to MinQtSizeC.

The inputs to the allowed quaternion segmentation process may remain the same as described above, while the derivation of the output of the allowed quaternion segmentation process (e.g., the variable allowslitqt) may be updated as follows.

-the variable allowslitqt may be set equal to FALSE and QT split is not allowed if one or more of the following conditions are true:

omicron (a) treeType equal to SINGLE _ TREE or DUAL _ TREE _ LUMA and cbSize less than or equal to MinQtSizeY

(b') treeType equal to DUAL _ TREE _ CHROMA and cbSize/SubHeightC less than or equal to MinQtSizeC

O (c) mttDepth not equal to 0

Omicron (d) treeType equal to DUAL _ TREE _ CHROMA and (cbSize/SubWidthC) less than or equal to 4

Omicron (e) treeType equals to DUAL _ TREE _ CHROMA and modeType equals to MODE _ TYPE _ INTRA

Otherwise, allowslitqt may be set equal to TRUE. Therefore, QT splitting may be allowed.

In an embodiment, the minimum allowed chroma QT leaf node size (e.g., MinQtSizeC) is in units of chroma samples.

According to aspects of the present disclosure, partition information from an encoded video bitstream may be decoded. The partition information may indicate that, for example, one or more chroma components (e.g., one or more chroma CTBs) and corresponding luma components (e.g., luma CTBs) may be partitioned in a CTU using a separate coding tree structure. The partition information may indicate that a DUAL TREE is used and that a CHROMA coding TREE structure (e.g., indicated by DUAL _ TREE _ CHROMA) in the DUAL TREE may be applied to, for example, CHROMA blocks in the CTU. Thus, in an example, treeType is equal to DUAL _ TREE _ CHROMA. The partition information may further indicate a block size of a chroma block in units of luma samples (e.g., cbSize), a chroma vertical sub-sampling factor (e.g., SubHeightC), and a minimum allowed chroma Quadtree (QT) leaf node size (e.g., MinQtSizeC). Whether QT partitioning is not allowed for a chroma block may be determined based on at least a block size of the chroma block in units of luma samples, a chroma vertical sub-sampling factor, and a minimum allowed chroma QT leaf node size. In response to disallowing QT partitioning of the chroma block, it may be determined whether at least one of binary tree partitioning and ternary tree partitioning of the chroma block is disallowed.

In an embodiment, the partition information may further indicate a minimum allowed chroma QT leaf node size (e.g., MinQtSizeC) in units of chroma samples. When the block size of a chroma block in units of luma samples divided by the value of the chroma vertical sub-sampling factor is less than or equal to the minimum allowed chroma QT leaf node size in units of chroma samples (e.g., cbSize/subheight c is less than or equal to MinQtSizeC in units of chroma samples), it may be determined that QT partitioning is not allowed for the chroma blocks.

In an example, the block size of the chroma block in units of luma samples divided by the chroma vertical subsampling factor is the height of the chroma block in units of chroma samples. QT partitioning or QT partitioning of a chroma block may not be allowed in response to the height of the chroma block in chroma samples being less than or equal to a minimum allowed chroma QT leaf node size in chroma samples (e.g., cbSize/subheight c is less than or equal to MinQtSizeC in chroma samples). Thus, in an example, the modified condition (b') is used in allowing the quaternion segmentation.

Other conditions (e.g., one or more of conditions (a) and (c) - (e)) may be further examined to determine whether QT splitting is not allowed or allowed. In embodiments, the partition information may further indicate one or more of a chroma level sub-sampling factor (e.g., subwidtc), an MTT depth (e.g., mttDepth) for indicating whether the chroma block is an MTT node from MTT partitioning, and a prediction mode type (e.g., modeType) of the chroma block. Whether QT partitioning is not allowed for a chroma block may be determined based on a block size of the chroma block in units of luma samples, a chroma vertical sub-sampling factor, a minimum allowed chroma QT leaf node size in units of chroma samples, and one or more of a chroma horizontal sub-sampling factor, an MTT depth, and a prediction mode type.

In an example, in response to a height of a chroma block in chroma samples, e.g., a block size of the chroma block in luma samples divided by a chroma vertical sub-sampling factor, being greater than a minimum allowed chroma QT leaf node size in chroma samples, one or more of other conditions are further examined in an allowed quadpartition process. Whether QT partitioning is not allowed for chroma blocks is determined based on one or more of a block size of the chroma blocks in units of luma samples, a chroma level sub-sampling factor, an MTT depth, and a prediction mode type.

In an example, a CHROMA coding TREE structure in a DUAL TREE (e.g., indicated by DUAL _ TREE _ CHROMA or treeType equal to DUAL _ TREE _ CHROMA) is applied to a CHROMA block, and a height of the CHROMA block in CHROMA samples is determined to be greater than a minimum allowed CHROMA QT leaf node size in CHROMA samples. Therefore, it is possible to further determine whether QT partitioning is not allowed for a chroma block based on the block size of the chroma block in units of luma samples, the chroma level sub-sampling factor, the MTT depth, and the prediction mode type. For example, QT partitioning of chroma blocks is not allowed (e.g., allowslitqt is set equal to FALSE) if at least one of the following conditions is true: (c) the MTT depth is not equal to 0 (e.g., indicating that the chroma block is an MTT node), (d ') the width of the chroma block in units of chroma samples (e.g., cbSize/sub width hc) is less than or equal to 4, and (e') the prediction MODE TYPE (e.g., modeType) is MODE _ TYPE _ INTRA, which indicates that the INTRA prediction MODE (or INTRA MODE) and the IBC MODE are allowed. When the conditions (c) and (d ') - (e') are false and the height of the chroma block in chroma samples is greater than the minimum allowed chroma QT leaf node size in chroma samples, it may be determined that QT partitioning is allowed. The conditions (d ') - (e') and treeType equal to DUAL _ TREE _ CHROMA correspond to the conditions (d) - (e), respectively.

In general, the LUMA samples or the CHROMA samples may be used to specify a variable related to the partition size, such as a variable for a SINGLE TREE (e.g., SINGLE _ TREE for the LUMA component and one or more (optional) CHROMA components), a LUMA coding TREE structure (e.g., a DUAL TREE or DUAL _ TREE _ LUMA for the LUMA component), and/or a CHROMA coding TREE structure (e.g., a DUAL TREE or DUAL _ TREE _ CHROMA for one or more CHROMA components), and it may not be clear which of the LUMA samples and the CHROMA samples is used to indicate the variable related to the partition size. This is advantageous for indicating whether the variable related to the chroma partition size has a unit of luma samples or a unit of chroma samples.

In an embodiment, the unit of luma samples may be used to describe a CHROMA block size or CHROMA partition size related variable, e.g., in a CHROMA coding TREE structure (e.g., DUAL _ TREE _ CHROMA). For example, the minimum allowed chroma QT leaf node size (e.g., MinQtSizeC) may be described in units of luma samples. The corresponding block size in chroma samples may be derived from the chroma sub-sampling rates in table 1 (e.g., SubWidthC and subwight).

For example, when the chroma format is 4:2:2, the variable MinQtSizeC (or minimum allowed chroma QT leaf node size) in units of luma samples corresponds to MinQtSizeC/SubWidthC (or MinQtSizeC/2) in units of chroma samples because SubWidthC is 2. Therefore, when the variable MinQtSizeC in units of luma samples is 16 (luma samples), the minimum allowed chroma QT leaf node size is 16 (luma samples) or 8 (chroma samples).

When the chroma format is 4:4:4, the variable MinQtSizeC in units of luma samples corresponds to MinQtSizeC/SubWidthC in units of chroma samples, and the variable MinQtSizeC is equal to MinQtSizeC in units of chroma samples because SubWidthC is 1.

In an embodiment, when INTRA dual trees are used, the variable MODE TYPE (e.g., modeType) may be one or more of MODE _ INTRA (indicating that INTRA MODE may be used), MODE _ IBC (indicating that IBC MODE may be used), or MODE _ TYPE _ INTRA (indicating that INTRA and IBC MODEs may be used). In an example, when an intra dual tree is used, the variable mode type (e.g., modeType) can be any suitable non-inter prediction mode.

The minimum allowed chroma coding block size may be smaller than the minimum allowed luma coding block size. The partition information may indicate a minimum allowed chroma coding block size in units of luma samples and a minimum allowed luma coding block size in units of luma samples. The minimum allowed chroma coding block size in luma samples may be smaller than the minimum allowed luma coding block size in luma samples.

The minimum allowed chroma QT leaf node size may be smaller than the minimum allowed luma QT leaf node size. The partition information may indicate a minimum allowed luminance QT leaf node size in units of luminance samples. The minimum allowed chroma QT leaf node size in units of luma samples that allows QT segmentation of a CTU may be smaller than the minimum allowed luma QT leaf node size in units of luma samples (or the minimum luma leaf block size resulting from QT segmentation of a CTU).

According to aspects of the present disclosure, a chroma partition unit size, such as a minimum allowed chroma QT leaf node size (e.g., MinQtSizeC), may be described in units of luma samples. The allowed quaternion segmentation process for the chroma blocks described above may be modified by modifying condition (b) while the other conditions (e.g., conditions (a) and (c) - (e)) remain unchanged. The modified condition (denoted as condition (b ")) can be described as:

omicron (b ") treeType is equal to DUAL _ TREE _ CHROMA, and cbSize is less than or equal to MinQtSizeC.

Where cbSize is the block size of the chroma block in units of luma samples, and MinQtSizeC is in units of luma samples.

The inputs to the allowed quaternion segmentation process may remain the same as described above, while the derivation of the output of the allowed quaternion segmentation process (e.g., the variable allowslitqt) may be updated as follows.

-the variable allowslitqt may be set equal to FALSE and QT splitting is not allowed if one or more of the following conditions are true:

omicron (a) treeType equal to SINGLE _ TREE or DUAL _ TREE _ LUMA and cbSize less than or equal to MinQtSizeY

Omicron (b ") treeType is equal to DUAL _ TREE _ CHROMA, and cbSize is less than or equal to MinQtSizeC.

O (c) mttDepth not equal to 0

Omicron (d) treeType equal to DUAL _ TREE _ CHROMA and (cbSize/SubWidthC) less than or equal to 4

Omicron (e) treeType equals to DUAL _ TREE _ CHROMA and modeType equals to MODE _ TYPE _ INTRA

Otherwise, allowslitqt may be set equal to TRUE. Therefore, QT segmentation can be allowed.

According to aspects of the present disclosure, partition information may be decoded from an encoded video stream. The partition information may indicate that a CHROMA coding TREE structure (e.g., DUAL _ TREE _ CHROMA or treeType equal to DUAL _ TREE _ CHROMA) in the DUAL TREE is applied to the CHROMA block. The partition information may further indicate a block size of a chroma block in units of luma samples (e.g., cbSize) and a minimum allowed chroma QT leaf node size in units of luma samples (e.g., MinQtSizeC). It may be determined whether the block size of the chroma block in units of luma samples is less than or equal to the minimum allowed chroma QT leaf node size in units of luma samples. In response to the block size of the chroma block in units of luma samples being less than or equal to the minimum allowed chroma QT leaf node size in units of luma samples, it may be determined that QT partitioning is not allowed for the chroma blocks.

In an example, the partition information may further indicate an MTT depth (e.g., mttDepth) indicating whether the chroma block is an MTT node from MTT partitioning, a chroma level sub-sampling factor (e.g., SubWidthC), and a prediction mode type (e.g., modeType) of the chroma block. When the block size of a chroma block in units of luma samples is larger than the minimum allowed chroma QT leaf node size in units of luma samples, it may be determined that QT partitioning is not allowed for the chroma block based on at least one of the following conditions being true: (c) the MTT depth is not equal to 0, which indicates that the chroma block is a MTT node, (d ') the block size of the chroma block in units of luma samples divided by the chroma level sub-sampling factor is less than or equal to 4 (or cbSize/SubWidthC ≦ 4), and (e') the prediction MODE TYPE (or modeType) is MODE _ TYPE _ INTRA, which indicates that the INTRA MODE and IBC MODE are allowed. In an example, based on the conditions (c), (d ') and (e') being false, it may be determined that QT segmentation is allowed.

According to aspects of the present disclosure, a chroma partition unit size, such as a minimum allowed chroma QT leaf node size (e.g., MinQtSizeC), may be described in units of luma samples. The allowed quaternion segmentation process for the chroma blocks described above may be modified by modifying condition (b) while the other conditions (e.g., conditions (a) and (c) - (e)) remain unchanged. The modified condition (denoted as condition (b' ")) may be described as:

omicron (b' ") treeType is equal to DUAL _ TREE _ CHROMA and cbSize is less than or equal to (MinQtSizeC × SubHeightC/SubWidthC).

The inputs to the allowed quaternion segmentation process may remain the same as described above, while the derivation of the output of the allowed quaternion segmentation process (e.g., the variable allowslitqt) may be updated as follows.

-the variable allowslitqt may be set equal to FALSE and QT splitting is not allowed if one or more of the following conditions are true:

omicron (a) treeType equal to SINGLE _ TREE or DUAL _ TREE _ LUMA and cbSize less than or equal to MinQtSizeY

Omicron (b' ") treeType is equal to DUAL _ TREE _ CHROMA and cbSize is less than or equal to (MinQtSizeC × SubHeightC/SubWidthC).

O (c) mttDepth not equal to 0

Omicron (d) treeType equal to DUAL _ TREE _ CHROMA and (cbSize/SubWidthC) less than or equal to 4

Omicron (e) treeType equals to DUAL _ TREE _ CHROMA and modeType equals to MODE _ TYPE _ INTRA

Otherwise, allowslitqt may be set equal to TRUE. Therefore, QT segmentation can be allowed.

The above modification including the condition (b' ") can be described as follows. As described above, in embodiments, the partition information may be decoded from the encoded video stream. The partition information may indicate that a CHROMA coding TREE structure (e.g., indicated by DUAL _ TREE _ CHROMA) in the DUAL TREE may be applied to the CHROMA blocks. The partition information may further indicate a block size of a chroma block in units of luma samples (e.g., cbSize), a chroma vertical sub-sampling factor (e.g., SubHeightC), and a minimum allowed chroma Quadtree (QT) leaf node size (e.g., MinQtSizeC). Whether QT partitioning is not allowed for a chroma block may be determined based on at least a block size of the chroma block in units of luma samples, a chroma vertical sub-sampling factor, and a minimum allowed chroma QT leaf node size. In response to not allowing QT partitioning for chroma blocks, it may be determined whether at least one of binary tree partitioning and ternary tree partitioning is not allowed for chroma blocks. In an example, the partition information further indicates a chroma level sub-sampling factor (e.g., SubWidthC) and indicates a minimum allowed chroma QT leaf node size (e.g., MinQtSizeC) in units of luma samples. Thus, whether or not QT partitioning of a chroma block is not allowed can be determined based on at least the block size of the chroma block in units of luma samples, the chroma vertical sub-sampling factor, the chroma horizontal sub-sampling factor, and the minimum allowed chroma QT leaf node size in units of luma samples.

In an embodiment, a parameter may be determined that is equal to the minimum allowed chroma QT leaf node size in units of luma samples (e.g., MinQtSizeC) multiplied by a chroma vertical sub-sampling factor (e.g., subheaightc) and divided by a chroma horizontal sub-sampling factor (e.g., SubWidthC). Therefore, this parameter is equal to MinQtSizeC × SubHeightC/SubWidthC. Further, as described above, when the block size (e.g., cbSize) of the chroma block in units of luma samples is less than or equal to the parameter, it may be determined that QT segmentation is not allowed for the chroma blocks.

In an example, the partition information may further indicate an MTT depth (e.g., mttDepth) indicating whether the chroma block is an MTT node from an MTT split and a prediction mode type (e.g., modeType) of the chroma block. Therefore, it is possible to further determine whether QT partitioning of a chroma block is not allowed based on the MTT depth and the prediction mode type. For example, it may be determined that QT partitioning is not allowed for chroma blocks if one of the following conditions is true: (b "") the block size of the chroma block in units of luma samples (e.g., cbSize) is less than or equal to the minimum allowed chroma QT leaf node size in units of luma samples multiplied by the chroma vertical sub-sampling factor and divided by the chroma level sub-sampling factor (or if cbSize ≦ minqtzizec × sub-height c/sub-width hc) (c) the MTT depth (e.g., mttDepth) is not equal to 0, indicating that the chroma block is an MTT node, (d ') the block size of the chroma block in units of luma samples divided by the chroma level sub-sampling factor is less than or equal to 4 (or cbSize/sub-width hc ≦ 4), and (e') the prediction MODE TYPE (or modeType) is MODE _ TYPE _ INTRA, indicating that the INTRA prediction MODE and IBC MODE can be used. When the conditions (b ""), (c), (d '), and (e') are false, it can be determined that QT segmentation is allowed. The condition (b ') and treeType equal to DUAL _ TREE _ CHROMA correspond to the condition (b'). As described above, the conditions (d ') - (e') and treeType equal to DUAL _ TREE _ CHROMA correspond to the conditions (d) - (e), respectively. Therefore, when the conditions (b' "), (c), (d), and (e) are false, it can be determined that QT segmentation is allowed.

The minimum chroma coding block size and the minimum allowed luma coding block size may be signaled separately. The minimum chroma coding block size in units of luma samples and the minimum allowed luma coding block size in units of luma samples may be signaled separately.

In some examples, a minimum chroma coding block size related variable (e.g., MinCbLog2SizeC) is used, such as in VVC. However, a method of deriving the minimum chroma coding block size may not be defined.

In an embodiment, an encoded video bitstream comprises a chroma syntax element for indicating a minimum allowed chroma coding block size in units of luma samples and a luma syntax element for indicating a minimum allowed luma coding block size in units of luma samples.

When intra dual trees are used, for example, a syntax element (e.g., a chroma syntax element, log2_ min _ chroma _ coding _ block _ size _ minus2) may be signaled in the encoded video stream to indicate a minimum chroma coding block size in units of luma samples. A different syntax element (e.g., luma syntax element) may be signaled to indicate a minimum allowed luma coding block size in luma samples. The minimum chroma coding block size in luma samples may be different from the minimum allowed luma coding block size in luma samples. For example, the minimum chroma coding block size in luma samples (e.g., MinCbSizeC) may be calculated as follows:

MinCbLog2SizeC＝log2_min_chroma_coding_block_size_minus2+2 (39)

MinCbSizeC＝1<<MinCbLog2SizeC (40)

in an example, the syntax table may be modified as shown in table 6 (fig. 26) to show the syntax elements indicated by block (2601) (e.g., log2_ min _ chroma _ coding _ block _ size _ minus 2).

The corresponding semantics can be described as follows: log2_ min _ chroma _ coding _ block _ size _ minus2 plus 2 may indicate the minimum chroma coding block size in units of luma samples. The value range of log2_ min _ chroma _ coding _ block _ size _ minus2 may be in the range of 0 to log2_ ctu _ size _ minus5+3 (inclusive). The variables MinCbLog2SizeC and MinCbSizeC can be derived using equations 39-40.

The minimum chroma coding block size in luma samples (or the minimum allowed chroma coding block size in luma samples) may be derived from the minimum luma coding block size in luma samples (or the minimum allowed luma coding block size in luma samples). In an example, MinCbLog2SizeC may be derived using the following equation:

MinCbLog2SizeC＝MinCbLog2SizeY (41)

in some embodiments, there is a compliance constraint, i.e., MinQtLog2SizeIntrac is not less than max (2, MinCbLog2SizeY) or max (2, MinCbLog2 SizeC).

Fig. 27 shows a flowchart outlining a process (2700) according to an embodiment of the present disclosure. The process (2700) may be used to reconstruct blocks (e.g., CBs) in pictures of a coded video sequence. The process (2700) may be used for reconstruction of a block to generate a prediction block for the block in reconstruction. The term block may be interpreted as a prediction block, CB, CU, etc. In various embodiments, process (2700) is performed by processing circuitry, e.g., processing circuitry in terminal devices (310), (320), (330), and (340), processing circuitry that performs the functions of video encoder (403), processing circuitry that performs the functions of video decoder (410), processing circuitry that performs the functions of video decoder (510), processing circuitry that performs the functions of video encoder (603), and so on. In some embodiments, process (2700) is implemented in software instructions such that when processing circuit executes these software instructions, processing circuit executes process (2700). The process starts at (S2701) and proceeds to (S2710). In an example, the block is a chroma block, such as chroma CB.

At (S2710), partition information may be decoded from the encoded video bitstream. The partition information may indicate that a CHROMA coding TREE structure (e.g., treeType is DUAL _ TREE _ CHROMA) in the DUAL TREE is applied to the CHROMA block. The partition information may further indicate a block size of a chroma block in units of luma samples (e.g., cbSize) and a minimum allowed chroma QT leaf node size in units of luma samples (e.g., MinQtSizeC).

At (S2720), it may be determined whether a block size of a chroma block in units of luma samples is less than or equal to a minimum allowed chroma QT leaf node size in units of luma samples. When it is determined that the block size of the chroma block in units of luma samples is less than or equal to the minimum allowed chroma QT leaf node size in units of luma samples, the process (2700) proceeds to (S2730). Otherwise, the process (2700) proceeds to (S2740).

At (S2730), it may be determined that QT segmentation is not allowed for the chroma blocks. The process (2700) proceeds to (S2799), and terminates.

At (S2740), one or more other conditions may be checked to determine whether QT splitting is not allowed. The other conditions may include: the MTT depth indicates that the chroma block is a MTT node, the block size of the chroma block in units of luma samples divided by the chroma level sub-sampling factor is less than or equal to 4 (or cbSize/SubWiddthC ≦ 4), and/or the prediction MODE TYPE (or modeType) is MODE _ TYPE _ INTRA, which indicates that the INTRA prediction MODE and IBC MODE are allowed. If at least one of the one or more other conditions is true, it may be determined that QT partitioning of the chroma block is not allowed (e.g., allowslitqt is set equal to FALSE). When the other condition is false and the height of the chroma block in chroma samples is greater than the minimum allowable chroma QT leaf node size in chroma samples, it may be determined that QT partitioning is allowed. The process (2700) proceeds to (S2799), and terminates.

The process may be modified as appropriate (2700). One or more steps in process (2700) may be modified and/or omitted. One or more additional steps may be added. Any suitable order of implementation may be used.

Fig. 28 shows a flowchart outlining a process (2800) according to an embodiment of the present disclosure. The process (2800) may be used to reconstruct a block (e.g., CB) in a picture of an encoded video sequence. The process (2800) may be used for reconstruction of a block to generate a prediction block for the block in reconstruction. The term block may be interpreted as a prediction block, CB, CU, etc. In various embodiments, process (2800) is performed by processing circuitry, e.g., processing circuitry in terminal devices (310), (320), (330), and (340), processing circuitry that performs the functions of video encoder (403), processing circuitry that performs the functions of video decoder (410), processing circuitry that performs the functions of video decoder (510), processing circuitry that performs the functions of video encoder (603), etc. In some embodiments, process (2800) is implemented in software instructions, such that when processing circuitry executes the software instructions, the processing circuitry performs process (2800). The process starts at (S2801) and proceeds to (S2810). In an example, the block is a chroma block, such as chroma CB.

At (S2810), partition information may be decoded from the encoded video bitstream. The partition information may indicate that a CHROMA coding TREE structure (e.g., treeType is DUAL _ TREE _ CHROMA) in the DUAL TREE is applied to the CHROMA block. The partition information may further indicate a block size of a chroma block in units of luma samples (e.g., cbSize), a chroma vertical sub-sampling factor (e.g., SubHeightC), and a minimum allowed chroma QT leaf node size (e.g., MinQtSizeC).

At (S2820), whether or not QT segmentation is not allowed for the chroma block may be determined based on at least a block size of the chroma block in units of luma samples, a chroma vertical sub-sampling factor, and a minimum allowed chroma QT leaf node size, as described above.

At (S2830), when it is determined that the QT partition is not allowed, it may be determined whether at least one of binary tree partition and ternary tree partition is not allowed for the chroma block. The process (2800) proceeds to (S2899), and terminates.

The process may be modified as appropriate (2800). One or more steps in the process (2800) may be modified and/or omitted. One or more additional steps may be added. Any suitable order of implementation may be used.

The embodiments in the present disclosure may be used alone or combined in any order. Further, each of the method (or embodiment), encoder and decoder may be implemented by a processing circuit (e.g., one or more processors or one or more integrated circuits). In one example, one or more processors execute a program stored in a non-transitory computer readable medium.

The techniques described above may be implemented as computer software via computer readable instructions and physically stored in one or more computer readable media. For example, fig. 30 illustrates a computer system (2900) suitable for implementing certain embodiments of the disclosed subject matter.

The computer software may be encoded in any suitable machine code or computer language, and by assembly, compilation, linking, etc., mechanisms create code that includes instructions that are directly executable by one or more computer Central Processing Units (CPUs), Graphics Processing Units (GPUs), etc., or by way of transcoding, microcode, etc.

The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablets, servers, smartphones, gaming devices, internet of things devices, and so forth.

The components illustrated in FIG. 29 for computer system (2900) are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing embodiments of the application. Neither should the configuration of components be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary embodiments of computer system (2900).

The computer system (2900) may include some human interface input devices. Such human interface input devices may respond to input from one or more human users through tactile input (e.g., keyboard input, swipe, data glove movement), audio input (e.g., sound, applause), visual input (e.g., gestures), olfactory input (not shown). The human-machine interface device may also be used to capture media that does not necessarily directly relate to human conscious input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, photographic images obtained from still-image cameras), video (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

The human interface input device may include one or more of the following (only one of which is depicted): keyboard (2901), mouse (2902), touch pad (2903), touch screen (2910), data glove (not shown), joystick (2905), microphone (2906), scanner (2907), camera (2908).

The computer system (2900) may also include certain human interface output devices. Such human interface output devices may stimulate the senses of one or more human users through, for example, tactile outputs, sounds, light, and olfactory/gustatory sensations. Such human interface output devices may include tactile output devices (e.g., tactile feedback through a touch screen (2910), data glove (not shown), or joystick (2905), but there may also be tactile feedback devices that do not act as input devices), audio output devices (e.g., speakers (2909), headphones (not shown)), visual output devices (e.g., screens (2910) including cathode ray tube screens, liquid crystal screens, plasma screens, organic light emitting diode screens, each with or without touch screen input functionality, each with or without haptic feedback functionality — some of which may output two-dimensional visual output or more than three-dimensional output by means such as stereoscopic picture output; virtual reality glasses (not shown), holographic displays, and smoke boxes (not shown)), and printers (not shown).

The computer system (2900) may also include human-accessible storage devices and their associated media, such as optical media including compact disk read-only/rewritable (CD/DVD ROM/RW) (2920) with CD/DVD or similar media (2921), thumb drive (2922), removable hard drive or solid state drive (2923), conventional magnetic media such as magnetic tape and floppy disk (not shown), ROM/ASIC/PLD based application specific devices such as security dongle (not shown), and so forth.

Those skilled in the art will also appreciate that the term "computer-readable medium" used in connection with the disclosed subject matter does not include transmission media, carrier waves, or other transitory signals.

The computer system (2900) may also include an interface to one or more communication networks. The network may be wireless, wired, optical. The network may also be a local area network, a wide area network, a metropolitan area network, a vehicular network, an industrial network, a real-time network, a delay tolerant network, and so forth. Examples of networks may include ethernet, wireless local area networks, local area networks such as cellular networks (GSM, 3G, 4G, 5G, LTE, etc.), television wired or wireless wide area digital networks (including cable, satellite, and terrestrial broadcast television), automotive and industrial networks (including CANBus), and so forth. Some networks typically require external network interface adapters for connecting to some general purpose data ports or peripheral buses (2949) (e.g., a USB port of computer system (2900)); other systems are typically integrated into the core of computer system (2900) (e.g., ethernet interface integrated into a PC computer system or cellular network interface integrated into a smart phone computer system) by connecting to a system bus as described below. Using any of these networks, computer system (2900) may communicate with other entities. The communication may be unidirectional, for reception only (e.g., wireless television), unidirectional for transmission only (e.g., CAN bus to certain CAN bus devices), or bidirectional, for example, to other computer systems over a local or wide area digital network. Each of the networks and network interfaces described above may use certain protocols and protocol stacks.

The human interface device, human accessible storage device, and network interface described above may be connected to the core (2940) of the computer system (2900).

The core (2940) may include one or more Central Processing Units (CPUs) (2941), Graphics Processing Units (GPUs) (2942), special purpose programmable processing units in the form of Field Programmable Gate Arrays (FPGAs) (2943), hardware accelerators (2944) for specific tasks, and so forth. These devices, as well as Read Only Memory (ROM) (2945), random access memory (2946), internal mass storage (e.g., internal non-user accessible hard drives, solid state drives, etc.) (2947), etc. may be connected via the system bus (2948). In some computer systems, the system bus (2948) may be accessed in the form of one or more physical plugs, so as to be extensible through additional central processing units, graphics processing units, and the like. The peripheral devices may be attached directly to the system bus (2948) of the core or connected through a peripheral bus (2949). The architecture of the peripheral bus includes peripheral controller interface PCI, universal serial bus USB, etc. In one example, the screen (2910) may be connected with a graphics adapter (2950). The architecture of the peripheral bus includes PCI, USB, etc.

The CPU (2941), GPU (2942), FPGA (2943), and accelerator (2944) may execute certain instructions, which in combination may constitute the computer code. The computer code may be stored in ROM (2945) or RAM (2946). The transitional data may also be stored in RAM (2946), while the persistent data may be stored in, for example, internal mass storage (2947). Fast storage and retrieval of any memory device can be achieved through the use of cache memory, which can be closely associated with one or more CPUs (2941), GPUs (2942), mass storage (2947), ROMs (2945), RAMs (2946), and the like.

The computer-readable medium may have computer code thereon for performing various computer-implemented operations. The media and computer code may be those specially designed and constructed for the purposes of the present application, or they may be of the kind well known and available to those having skill in the computer software arts.

By way of example, and not limitation, a computer system having architecture (2900), and in particular cores (2940), may provide functionality as a processor (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media may be media associated with the user-accessible mass storage described above, as well as certain storage with a non-volatile core (2940), such as core internal mass storage (2947) or ROM (2945). Software implementing various embodiments of the present application may be stored in such a device and executed by the core (2940). The computer-readable medium may include one or more memory devices or chips, according to particular needs. The software may cause the core (2940), and in particular the processors therein (including CPUs, GPUs, FPGAs, etc.), to perform certain processes or certain portions of certain processes described herein, including defining data structures stored in RAM (2946) and modifying such data structures in accordance with the software-defined processes. Additionally or alternatively, the computer system may provide functionality that is logically hardwired or otherwise embodied in circuitry (e.g., accelerator (2944)) that may operate in place of or in conjunction with software to perform certain processes or certain portions of certain processes described herein. Where appropriate, reference to software may include logic and vice versa. Where appropriate, reference to a computer-readable medium may include circuitry (e.g., an Integrated Circuit (IC)) storing executable software, circuitry comprising executable logic, or both. The present application includes any suitable combination of hardware and software.

Appendix: acronyms

Joint development model

VVC next generation video coding

BMS reference set

MV motion vector

HEVC (high efficiency video coding)

MPM most probable mode

WAIP wide-angle intra prediction

SEI supplemental enhancement information

VUI video usability information

GOPs group of pictures

TUs transformation unit

PUs prediction unit

Coding tree units for CTUs

Coding tree blocks of CTBs

PBs prediction block

HRD hypothetical reference decoder

SDR standard dynamic range

SNR to SNR ratio

CPU Central Processing Unit (CPU)

GPUs graphics processing units

CRT cathode ray tube

LCD (liquid crystal display)

OLED organic light emitting diode

CD, optical disk, DVD and digital video disk

ROM-ROM

RAM random access memory

ASIC application specific integrated circuit

PLD programmable logic device

LAN (local area network)

GSM global system for mobile communications

LTE Long term evolution

CANBus controller area network bus

USB (Universal Serial bus)

PCI peripheral interconnect

FPGA field programmable gate array

SSD field programmable gate array

IC integrated circuit

CU coding unit

PDPC location dependent predictive combining

Intra-frame sub-partitioning of ISP

SPS sequence parameter set

While the application has described several exemplary embodiments, various modifications, arrangements, and equivalents of the embodiments are within the scope of the application. It will thus be appreciated that those skilled in the art will be able to devise various systems and methods which, although not explicitly shown or described herein, embody the principles of the application and are thus within its spirit and scope.