Video coding and decoding method and device

文档序号：174668 发布日期：2021-10-29 浏览：30次中文

阅读说明：本技术 视频编解码方法和装置 (Video coding and decoding method and device ) 是由李贵春李翔许晓中刘杉于 2020-06-04 设计创作，主要内容包括：本申请的各方面提供了视频编解码方法和装置。该装置包括处理电路,处理电路从已编码视频码流中解码出当前块(CB)的编码信息。编码信息指示CB是使用基于子块的仿射运动模型进行编码的,该基于子块的仿射运动模型包括仿射参数,仿射参数是基于CB的多个控制点运动矢量(MV)。处理电路基于编码信息,确定是否选择一用于基于对应的子块MV生成CB的仿射子块中的样本的预测值的子块特性。响应于选择了该子块特性,处理电路基于仿射参数中的至少一个仿射参数,确定子块特性。子块特性指示以下之一：(i)生成样本的预测值时使用的子块大小；和(ii)仿射子块的插值滤波器类型。(Aspects of the present application provide a video encoding and decoding method and apparatus. The apparatus comprises a processing circuit which decodes the coding information of the Current Block (CB) from the coded video stream. The encoding information indicates that the CB is encoded using a sub-block based affine motion model that includes affine parameters, the affine parameters being a plurality of control point Motion Vectors (MVs) based on the CB. The processing circuit determines whether to select a sub-block characteristic for generating a prediction value for samples in an affine sub-block of the CB based on the corresponding sub-block MV based on the encoding information. In response to selecting the sub-block characteristic, the processing circuit determines the sub-block characteristic based on at least one of the affine parameters. The sub-block characteristic indicates one of: (i) a sub-block size used in generating a prediction value for a sample; and (ii) interpolation filter type for affine sub-blocks.)

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

decoding encoding information for a current block, CB, from an encoded video stream, wherein the encoding information indicates that the CB is encoded using a sub-block-based affine motion model comprising affine parameters based on a plurality of control point, CP, motion vectors, CPMVs, of the CB, the CB comprising an affine sub-block with sub-block MVs;

determining, based on the encoding information, whether to select a sub-block characteristic for generating a prediction value of samples in the affine sub-block based on the sub-block MV;

in response to selecting the sub-block characteristic, determining the sub-block characteristic based on at least one of the affine parameters, the sub-block characteristic indicating one of: (i) a sub-block size used in generating a prediction value for the sample; and (ii) interpolation filter type for the affine sub-block; and

reconstructing samples in the affine sub-block based on the determined sub-block characteristics.

2. The method of claim 1,

when the sub-block based affine motion model is a 4-parameter based affine motion model,

the CB comprises a top-left CP with a first CPMV and a top-right CP with a second CPMV;

the affine parameters comprise a first affine parameter and a second affine parameter, the first affine parameter indicating a ratio of an x-component of a first MV difference between the second CPMV and the first CPMV to a width of the CB, the second affine parameter indicating a ratio of a y-component of the first MV difference to a width of the CB;

when the sub-block based affine motion model is a 6 parameter based affine motion model,

the CBs include the upper left corner CP with the first CPMV, the upper right corner CP with the second CPMV, and the lower left corner CP with a third CPMV;

the affine parameters comprise a first affine parameter, a second affine parameter, a third affine parameter, and a fourth affine parameter, wherein the third affine parameter indicates a ratio of an x-component of a second MV difference between the third CPMV and the first CPMV to a height of the CB, and the fourth affine parameter indicates a ratio of a y-component of the second MV difference to a height of the CB.

3. The method of claim 2, wherein determining the sub-block characteristics further comprises:

determining the sub-block characteristics based on at least one of the affine parameters and one of: (i) a threshold value; and (ii) a predefined range, wherein the sub-block size is an affine sub-block size of the affine sub-block, the interpolation filter type comprising a first interpolation filter having a first length or a second interpolation filter having a second length, the first length being smaller than the second length.

4. The method of claim 3, wherein:

at least one of the affine parameters comprises a plurality of affine parameters; and is

Determining the sub-block characteristics comprises:

determining whether absolute values of the plurality of affine parameters satisfy a predefined condition that is one of: (i) the maximum value of the absolute value is greater than the threshold; (ii) the maximum value of the absolute value is greater than or equal to the threshold; (iii) the minimum value of the absolute values is greater than the threshold; (iv) the minimum value of the absolute values is greater than or equal to the threshold; and (v) the absolute value is outside the predefined range;

in response to the absolute value satisfying the predefined condition, determining that the sub-block characteristic is indicative of one of: the affine sub-block size is a first size and the interpolation filter type is the first interpolation filter; and is

In response to the absolute value not satisfying the predefined condition, determining that the sub-block characteristic is indicative of one of: the affine sub-block size is a second size and the interpolation filter type is the second interpolation filter, wherein the second size is larger than the first size.

5. The method of claim 2,

the CB comprises a gradient subblock used in gradient calculation in correcting an optical flow prediction value of the CB by a PROF;

the subblock size is a size of a gradient subblock; and is

The gradient calculation is (i) a block-based gradient calculation if the sub-block size is equal to a block size of the CB; or (ii) based on gradient calculations of sub-blocks if the sub-block size is smaller than the block size.

6. The method of claim 5,

at least one of the affine parameters comprises a plurality of affine parameters; and is

The method also includes determining whether the gradient computation is block-based or sub-block-based on one of: (i) a maximum or minimum of absolute values of the plurality of affine parameters and a threshold; and (ii) the absolute value and a predefined range.

7. The method of claim 5, further comprising:

for the block-based gradient computation, filling neighboring samples of the CB by one of: (i) interpolating using a corresponding subblock MV comprising a subblock of the neighboring sample; (ii) copying from an integer sample position in a reference picture of the CB that is nearest to the neighboring sample; and (iii) copying from the predicted values of the samples in the CB that are closest to the neighboring samples, wherein the neighboring samples of the CB are used for the block-based gradient computation.

8. The method of claim 2,

the sub-block size is one of: a width of the affine sub-block, a height of the affine sub-block, a width of an affine PROF sub-block used in PROF for the CB, a height of the affine PROF sub-block, a width of a gradient sub-block used in gradient calculation in the PROF, and a height of the gradient sub-block; and is

The interpolation filter type is one of: (i) a first interpolation filter having a first length for horizontal interpolation; (ii) a second interpolation filter having a second length for horizontal interpolation; (iii) a first interpolation filter having the first length for vertical interpolation; and (iv) a second interpolation filter having the second length for vertical interpolation, wherein the second length is greater than the first length.

9. The method of claim 1, further comprising:

determining another sub-block characteristic based on at least another one of the affine parameters, the at least another one of the affine parameters being different from or the same as at least one of the affine parameters, the another sub-block characteristic being different from the sub-block characteristic.

10. The method of claim 1,

at least one of the affine parameters comprises a plurality of affine parameters;

determining the sub-block characteristic comprises determining the sub-block characteristic based on one of: (i) a threshold and a minimum value, a maximum value, a minimum absolute value, a maximum absolute value, or an average value of the plurality of affine parameters; and (ii) a predefined range and a range of values for the plurality of affine parameters.

11. The method of claim 8,

at least one of the affine parameters comprises a plurality of affine parameters;

the sub-block characteristics are determined based on maximum absolute values of the plurality of affine parameters and a threshold;

in response to the maximum absolute value being one of greater than the threshold and greater than or equal to the threshold, determining that the sub-block characteristic is indicative of one of: (i) the sub-block size is a first size; (ii) the interpolation filter type is the first interpolation filter for horizontal interpolation; and (iii) the interpolation filter type is the first interpolation filter for vertical interpolation; and is

In response to the maximum absolute value not being one of greater than the threshold and greater than or equal to the threshold, determining that the sub-block characteristic is indicative of one of: (i) the sub-block size is a second size; (ii) the interpolation filter type is a second interpolation filter for horizontal interpolation; and (iii) the interpolation filter type is a second interpolation filter for vertical interpolation, wherein the second size is larger than the first size.

12. A video decoding apparatus comprising processing circuitry, wherein the processing circuitry is configured to:

determining, based on the encoding information, whether to select a sub-block characteristic for generating a prediction value of samples in the affine sub-block based on the sub-block MV;

reconstructing samples in the affine sub-block based on the determined sub-block characteristics.

13. The apparatus of claim 12,

when the sub-block based affine motion model is a 4-parameter based affine motion model,

the CB comprises a top-left CP with a first CPMV and a top-right CP with a second CPMV; and is

The affine parameters comprise a first affine parameter and a second affine parameter, the first affine parameter indicating a ratio of an x-component of a first MV difference between the second CPMV and the first CPMV to a width of the CB, the second affine parameter indicating a ratio of a y-component of the first MV difference to a width of the CB; and is

When the sub-block based affine motion model is a 6 parameter based affine motion model,

the CBs include the upper left corner CP with the first CPMV, the upper right corner CP with the second CPMV, and the lower left corner CP with a third CPMV; and is

The affine parameters include a first affine parameter, a second affine parameter, a third affine parameter, and a fourth affine parameter, the third affine parameter indicating a ratio of an x-component of a second MV difference between the third CPMV and the first CPMV to a height of the CB, the fourth affine parameter indicating a ratio of a y-component of the second MV difference to a height of the CB.

14. The apparatus of claim 13, wherein the processing circuit is configured to:

15. The apparatus of claim 14, wherein:

at least one of the affine parameters comprises a plurality of affine parameters; and is

The processing circuitry is configured to:

16. The apparatus of claim 13,

the CB comprises a gradient subblock used in gradient calculation in correcting an optical flow prediction value of the CB by a PROF;

the subblock size is a size of a gradient subblock; and is

17. The apparatus of claim 16, wherein the processing circuit is further configured to:

18. The apparatus of claim 13,

19. The apparatus of claim 12,

at least one of the affine parameters comprises a plurality of affine parameters; and is

The processing circuit is configured to determine the sub-block characteristics based on one of: (i) a threshold and a minimum value, a maximum value, a minimum absolute value, a maximum absolute value, or an average value of the plurality of affine parameters; and (ii) a predefined range and a value range.

20. The apparatus of claim 18,

at least one of the affine parameters comprises a plurality of affine parameters;

the sub-block characteristics are determined based on maximum absolute values of the plurality of affine parameters and a threshold; and is

The processing circuitry is configured to:

in response to the maximum absolute value not being one of greater than the threshold and greater than or equal to the threshold, determining that the sub-block characteristic is indicative of one of: (i) the sub-block size is a second size; (ii) the interpolation filter type is the second interpolation filter for horizontal interpolation; and (iii) the interpolation filter type is the second interpolation filter for vertical interpolation, the second size being larger than the first size.

Technical Field

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

Background

The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present application.

Encoding and decoding of video may be performed using inter-picture prediction with motion compensation. Uncompressed digital video may include a series of pictures, each picture having a spatial dimension, e.g., 1920 x 1080 luma samples and associated chroma samples. The series of pictures may have a fixed or variable picture rate (informally, also referred to as frame rate), for example, 60 pictures per second or 60 hertz (Hz). Uncompressed video has significant bit rate requirements. For example, 1080p 604: 2:0 video (1920 × 1080 luminance sample resolution at 60Hz frame rate) with 8 bits per sample requires a bandwidth of approximately 1.5 Gbit/s. Such video requires more than 600GB of storage space for one hour.

One purpose of video encoding and decoding may be to reduce redundancy in the input video signal by compression. Compression may help reduce the bandwidth or storage requirements described above, by two or more orders of magnitude in some cases. Both lossless and lossy compression, as well as combinations thereof, may be used for video encoding and decoding. Lossless compression refers to a technique by which an exact copy of an original signal can be reconstructed from a compressed original signal. When lossy compression is used, the reconstructed signal may not be exactly identical to the original signal, but the distortion between the original signal and the reconstructed signal is small enough that the reconstructed signal can be used for the intended application. Lossy compression is widely used in video. The amount of distortion allowed for lossy compression depends on the application; for example, users of certain consumer streaming applications may tolerate higher distortion than users of television distribution applications. The achievable compression ratio may reflect: the higher the allowable/tolerable distortion, the higher the compression ratio that can be produced.

Motion compensation may be a lossy compression technique and may involve the following techniques: specimen data blocks derived from previously reconstructed pictures or parts thereof (reference pictures) are used to predict newly reconstructed pictures or picture parts after spatial shifting in the direction indicated by the motion vector (hereafter referred to as MV). 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 dimensions, or three dimensions, the third for indicating the reference picture in use (the latter indirectly can be the temporal dimension).

In some video compression techniques, an MV applicable to a certain sample data region may be predicted from other MVs, e.g., from an MV preceding the MV in decoding order with respect to another sample data region spatially adjacent to the region being reconstructed. This can substantially reduce the amount of data required to codec the MVs, thereby eliminating redundancy and enhancing compression. MV prediction can be efficiently performed, for example, because when an input video signal derived from a camera (referred to as natural video) is encoded, there is a statistical likelihood that a plurality of regions larger than a region to which a single MV is applicable move in similar directions, and thus, MV prediction can be performed using similar motion vectors derived from a plurality of MVs of a neighboring region 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 coding, can in turn be represented by a smaller number of bits than used for directly coding 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., sample stream). In other cases, MV prediction itself may be lossy, for example, because there may be rounding errors when the predictor is calculated from several surrounding MVs.

Various MV prediction mechanisms are described in H.265/HEVC (ITU-T H.265 recommendation, "High Efficiency Video Coding", 2016 (12 months) to Hi-Fi). Among the various MV prediction mechanisms provided by h.265, described herein is a technique referred to hereinafter as "spatial merging.

Referring to fig. 1, a current block (101) includes samples that have been found by an encoder during a motion search process, which samples can be predicted from previous blocks of the same size that have generated spatial offsets. In addition, the MVs may be indicated from metadata associated with one or more reference pictures, rather than directly encoding the MVs. For example, MVs associated with any of the five surrounding samples a0, a1 and B0, B1, B2 (102-106, respectively) are derived (in decoding order) from the metadata of the most recent reference picture. In h.265, MV prediction can use the prediction value of the same reference picture that the neighboring block is also using.

Disclosure of Invention

Aspects of the present application provide a video encoding/decoding method and apparatus. In some examples, a video decoding apparatus includes a processing circuit. The processing circuitry may be configured to: and decoding the coding information of the current block CB from the coded video code stream. The encoding information may indicate that the CB is encoded using a sub-block based affine motion model. The sub-block based affine motion model may comprise affine parameters, which are affine parameters based on a plurality of control point CP motion vectors MV CPMV of the CB. The CB may include an affine sub-block having sub-blocks MV. The processing circuit may determine, based on the encoding information, whether to select a sub-block characteristic for generating a prediction value for samples in the affine sub-block based on the sub-block MV. In response to selecting the sub-block characteristic, the processing circuit may determine the sub-block characteristic based on at least one of the affine parameters. The sub-block characteristic may indicate one of: (i) a sub-block size used in generating a prediction value for the sample; and (ii) an interpolation filter type for the affine sub-block. The processing circuit may reconstruct samples in the affine sub-block based on the determined sub-block characteristics.

In an embodiment, when the sub-block based affine motion model is a 4-parameter based affine motion model, the CB includes an upper left CP having the first CPMV and an upper right CP having the second CPMV. The affine parameters include a first affine parameter and a second affine parameter. The first affine parameter may indicate a ratio of an x-component of a first MV difference between the second CPMV and the first CPMV to a width of the CB. The second affine parameter may indicate a ratio of a y-component of the first MV difference to a width of the CB. When the sub-block-based affine motion model is a 6-parameter-based affine motion model, the CBs include the upper-left CP having the first CPMV, the upper-right CP having the second CPMV, and the lower-left CP having a third CPMV. The affine parameters may include a first affine parameter, a second affine parameter, a third affine parameter, and a fourth affine parameter. The third affine parameter may indicate a ratio of an x-component of a second MV difference between the third CPMV and the first CPMV to a height of the CB. The fourth affine parameter may indicate a ratio of a y-component of the second MV difference to a height of the CB.

In an embodiment, the processing circuitry may determine the sub-block characteristics based on at least one of the affine parameters and one of: (i) a threshold value; and (ii) a predefined range. The sub-block size may be an affine sub-block size of the affine sub-block. The interpolation filter type may include a first interpolation filter having a first length or a second interpolation filter having a second length, wherein the first length is smaller than the second length.

In an embodiment, at least one of the affine parameters comprises a plurality of affine parameters. The processing circuit may determine whether absolute values of the plurality of affine parameters satisfy a predefined condition that is one of: (i) the maximum value of the absolute value is greater than the threshold; (ii) the maximum value of the absolute value is greater than or equal to the threshold; (iii) the minimum value of the absolute values is greater than the threshold; (iv) the minimum value of the absolute values is greater than or equal to the threshold; and (v) the absolute value is outside the predefined range. In response to the absolute value satisfying the predefined condition, the processing circuitry may determine that the sub-block characteristic is indicative of one of: the affine sub-block size is a first size and the interpolation filter type is the first interpolation filter. In response to the absolute value not satisfying the predefined condition, the processing circuitry may determine that the sub-block characteristic is indicative of one of: the affine sub-block size is a second size and the interpolation filter type is the second interpolation filter, wherein the second size is larger than the first size.

In an embodiment, the CB includes a gradient subblock for use in gradient calculations in optical flow prediction value modification (PROF) of the CB. The sub-block size is the size of a gradient sub-block. The gradient calculation is (i) a block-based gradient calculation if the sub-block size is equal to a block size of the CB; or (ii) based on gradient calculations of sub-blocks if the sub-block size is smaller than the block size.

In an embodiment, at least one of the affine parameters comprises a plurality of affine parameters. The processing circuit may determine whether the gradient calculation is block-based or sub-block-based on one of: (i) a maximum or minimum of absolute values of the plurality of affine parameters and a threshold; and (ii) the absolute value and a predefined range.

In an embodiment, the processing circuit may further pad neighboring samples of the CB for the block-based gradient computation by one of: (i) interpolating using a corresponding subblock MV comprising a subblock of the neighboring sample; (ii) copying from an integer sample position in a reference picture of the CB that is nearest to the neighboring sample; and (iii) copying from the predicted values of the samples in the CB that are closest to the neighboring samples, wherein the neighboring samples of the CB are used for the block-based gradient computation.

In an embodiment, the sub-block size is one of: a width of the affine sub-block, a height of the affine sub-block, a width of an affine PROF sub-block used in PROF for the CB, a height of the affine PROF sub-block, a width of a gradient sub-block used in gradient calculation in the PROF, and a height of the gradient sub-block. The interpolation filter type is one of: (i) a first interpolation filter having a first length for horizontal interpolation; (ii) a second interpolation filter having a second length for horizontal interpolation; (iii) a first interpolation filter having the first length for vertical interpolation; and (iv) a second interpolation filter for vertical interpolation having the second length, the length being greater than the first length.

In an embodiment, the processing circuit may determine another sub-block characteristic based on at least another one of the affine parameters. The at least one further one of the affine parameters may be different from or the same as the at least one of the affine parameters, and the further sub-block characteristic may be different from the sub-block characteristic.

In an embodiment, at least one of the affine parameters comprises a plurality of affine parameters. The processing circuit may determine the sub-block characteristics based on one of: (i) a threshold and a minimum value, a maximum value, a minimum absolute value, a maximum absolute value, or an average value of the plurality of affine parameters; and (ii) a predefined range and a range of values for the plurality of affine parameters.

In an embodiment, at least one of the affine parameters comprises a plurality of affine parameters. The sub-block characteristics are determined based on maximum absolute values of the plurality of affine parameters and a threshold. In response to the maximum absolute value being one of greater than the threshold and greater than or equal to the threshold, the processing circuitry may determine that the sub-block characteristic is indicative of one of: (i) the sub-block size is a first size; (ii) the interpolation filter type is the first interpolation filter for horizontal interpolation; and (iii) the interpolation filter type is the first interpolation filter for vertical interpolation. In response to the maximum absolute value not being one of greater than the threshold and greater than or equal to the threshold, the processing circuitry may determine that the sub-block characteristic is indicative of one of: (i) the sub-block size is a second size; (ii) the interpolation filter type is the second interpolation filter for horizontal interpolation; and (iii) the interpolation filter type is the second interpolation filter for vertical interpolation, wherein the second size is larger than the first size.

Aspects of the present application also provide a non-transitory computer-readable medium storing instructions that, when executed by a video encoding and decoding computer, cause the computer to perform any of the video decoding methods.

Drawings

Other features, nature, and various advantages of the subject matter of the present application will become more apparent from the following detailed description and the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a current block and its surrounding spatial merge candidates in one example;

fig. 2 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment.

Fig. 3 is a schematic diagram of a simplified block diagram of a communication system according to another embodiment.

Fig. 4 is a schematic diagram of a simplified block diagram of a decoder according to an embodiment.

FIG. 5 is a schematic diagram of a simplified block diagram of an encoder according to one embodiment.

Fig. 6 shows a block diagram of an encoder according to another embodiment.

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

FIG. 8A shows an affine motion model of a block (810A) according to an embodiment of the present application.

FIG. 8B shows an affine motion model of a block (810B) according to an embodiment of the present application.

Fig. 9 illustrates an example of sub-block based affine motion compensation according to an embodiment of the present application.

Fig. 10A shows an example of a candidate CU of the CU (1001) according to an embodiment of the present application.

Fig. 10B illustrates an example of control point motion vector inheritance according to an embodiment of the present application.

Fig. 11 shows an example of candidate positions for constructing affine merge candidates according to an embodiment of the present application.

Fig. 12 illustrates an optical flow prediction value modification (PROF) method according to an embodiment of the present application.

Fig. 13 illustrates an example of padding CBs in block-based gradient computation according to an embodiment of the present application.

Fig. 14 shows a flowchart outlining a method (1400) according to an embodiment of the present application.

FIG. 15 is a schematic diagram of a computer system according to an embodiment of the present application.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

Fig. 2 illustrates a simplified block diagram of a communication system (200) according to an embodiment of the present disclosure. The communication system (200) includes a plurality of terminal devices that can communicate with each other through, for example, a network (250). For example, a communication system (200) includes a first pair of terminal devices (210) and (220) interconnected by a network (250). In the example of fig. 2, the first pair of terminal devices (210) and (220) performs unidirectional data transmission. For example, a terminal device (210) may encode video data (e.g., a stream of video pictures captured by the terminal device (210)) for transmission over a network (250) to another terminal device (220). The encoded video data may be transmitted in the form of one or more encoded video streams. The terminal device (220) may receive encoded video data from the network (250), decode the encoded video data to recover the video data, and display a video picture according to the recovered video data. Unidirectional data transmission may be common in applications such as media services.

In another example, the communication system (200) includes a second pair of terminal devices (230) and (240) 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 (230) and the terminal device (240) may encode video data (e.g., a stream of video pictures captured by the terminal device) for transmission over the network (250) to the other of the terminal device (230) and the terminal device (240). Each of terminal device (230) and terminal device (240) may also receive encoded video data transmitted by the other of terminal device (230) and terminal device (240), 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 example of fig. 2, the terminal device (210), the terminal device (220), the terminal device (230), and the terminal device (240) may be illustrated as 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 (250) represents any number of networks that convey encoded video data between terminal device (210), terminal device (220), terminal device (230), and terminal device (240), including, for example, wired (wired) and/or wireless communication networks. The communication network (250) may exchange data in circuit-switched and/or packet-switched channels. Representative networks include telecommunications networks, local area networks, wide area networks, and/or the internet. For purposes of this discussion, the architecture and topology of the network (250) may be immaterial to the operation of the present disclosure, unless explained below.

As an example of the application of the subject matter disclosed in this application, fig. 3 shows 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 (313), which may include a video source (301), such as a digital camera, that creates an uncompressed video picture stream (302), for example. In one example, the video picture stream (302) includes samples taken by a digital camera. The video picture stream (302) is depicted as a bold line to emphasize that it has a higher data volume than the encoded video data (304) (or encoded video code stream), the video picture stream (302) being processable by an electronic device (320), the electronic device (320) comprising a video encoder (303) coupled to a video source (301). The video encoder (303) 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 (304) (or encoded video codestream (304)) is depicted as a thin line to emphasize that it has a lower amount of data than the video picture stream (302), which may be stored on the streaming server (305) for future use. One or more streaming client subsystems, e.g., client subsystem (306) and client subsystem (308) in fig. 3, may access the streaming server (305) to retrieve a copy (307) and a copy (309) of the encoded video data (304). The client subsystem (306) may include, for example, a video decoder (310) in an electronic device (330). A video decoder (310) decodes incoming copies (307) of the encoded video data and generates an output video picture stream (311) that may be presented on a display (312), such as a display screen, or another presentation device (not depicted). In some streaming systems, encoded video data (304), video data (307), and video data (309) (e.g., video streams) may be encoded according to certain video encoding/compression standards. Examples of such standards include the ITU-T H.265 recommendation. In one example, the Video Coding standard being developed is informally referred to as multi-function Video Coding (VVC), which may be used in the context of the VVC standard.

It should be noted that electronic device (320) and electronic device (330) may include other components (not shown). For example, the electronic device (320) may include a video decoder (not shown), and the electronic device (330) may also include a video encoder (not shown).

Fig. 4 is a block diagram of a video decoder (410) according to an embodiment of the present disclosure. The video decoder (410) may be disposed in an electronic device (430). The electronic device (430) may include a receiver (431) (e.g., a receive circuit). The video decoder (410) may be used in place of the video decoder (310) in the example of fig. 3.

The receiver (431) may receive one or more encoded video sequences to be decoded by the video decoder (410); 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 (401), which may be a hardware/software link to a storage device that stores encoded video data. The receiver (431) 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 depicted). The receiver (431) may separate the encoded video sequence from other data. To prevent network jitter, a buffer memory (415) may be coupled between the receiver (431) and the entropy decoder/parser (420) (hereinafter "parser (420)"). In some applications, the buffer memory (415) is part of the video decoder (410). In other cases, the buffer memory (415) may be disposed external (not depicted) to the video decoder (410). While in other cases a buffer memory (not depicted) is provided external to the video decoder (410), e.g. to prevent network jitter, and another buffer memory (415) may be configured internal to the video decoder (410), e.g. to handle playout timing. The buffer memory (415) may not be required or may be made smaller when the receiver (431) receives data from a store/forward device with sufficient bandwidth and controllability, or from an isochronous network. For use over best effort traffic packet networks such as the internet, a buffer memory (415) may also be needed, 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 depicted) external to the video decoder (410).

The video decoder (410) may include a parser (420) to reconstruct symbols (421) from the encoded video sequence. The categories of these symbols include information for managing the operation of the video decoder (410), as well as potential information to control a display device, such as a display screen (412), that is not an integral part of the electronic device (430), but may be coupled to the electronic device (430), as shown in fig. 4. The control Information for the display device may be a Supplemental Enhancement Information (SEI) message or a parameter set fragment (not depicted) of Video Usability Information (VUI). The parser (420) 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 (420) 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 sub-Group may include a Group of Pictures (GOP), a picture, a tile (tile), a slice (slice), a macroblock, a Coding Unit (CU), a block, a Transform Unit (TU), a Prediction Unit (PU), and so on. The parser (420) may also extract information from the encoded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, and so on.

The parser (420) may perform entropy decoding/parsing operations on the video sequence received from the buffer memory (415), thereby creating symbols (421).

The reconstruction of the symbol (421) 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 in which they are involved can be controlled by subgroup control information parsed from the coded video sequence by a parser (420). For the sake of brevity, such a subgroup control information flow between parser (420) and a plurality of units below is not described.

In addition to the functional blocks already mentioned, the video decoder (410) 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 at least partially 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 sealer/inverse transform unit (451). The sealer/inverse transform unit (451) receives the quantized transform coefficients as symbols (421) from the parser (420) along with control information including which transform scheme to use, block size, quantization factor, quantization scaling matrix, etc. The sealer/inverse transform unit (451) may output a block comprising sample values, which may be input into the aggregator (455).

In some cases, the output samples of sealer/inverse transform unit (451) 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 intra-prediction unit (452). In some cases, the intra prediction unit (452) generates a block of the same size and shape as the block being reconstructed using the surrounding reconstructed information extracted from the current picture buffer (458). For example, the current picture buffer (458) buffers a partially reconstructed current picture and/or a fully reconstructed current picture. In some cases, the aggregator (455) adds, on a per-sample basis, the prediction information generated by the intra prediction unit (452) to the output sample information provided by the scaler/inverse transform unit (451).

In other cases, the output samples of sealer/inverse transform unit (451) may belong to inter-coded and potential motion compensated blocks. In this case, motion compensated prediction unit (453) may access reference picture memory (457) to extract samples for prediction. After motion compensation of the extracted samples according to the symbols (421) belonging to the block, these samples may be added by an aggregator (455) to the output of the scaler/inverse transform unit (451), in this case referred to as residual samples or residual signals, thereby generating output sample information. The fetching of prediction samples by motion compensated prediction unit (453) from addresses within reference picture memory (457) may be controlled by motion vectors, and the motion vectors are used by motion compensated prediction unit (453) in the form of the symbol (421), e.g., comprising X, Y and a reference picture component. Motion compensation may also include interpolation of sample values fetched from the reference picture memory (457), motion vector prediction mechanisms, etc., when using sub-sample exact motion vectors.

The output samples of the aggregator (455) may be employed in a loop filter unit (456) by various loop filtering techniques. 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 which are available to the loop filter unit (456) as symbols (421) from the parser (420), but may also be responsive to meta-information obtained during decoding of previous (in decoding order) portions of the encoded picture or encoded video sequence, and to sample values previously reconstructed and loop filtered.

The output of the loop filter unit (456) may be a stream of samples that may be output to a display device (412) and stored in a reference picture memory (457) 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 (420)) as a reference picture, current picture buffer (458) may become part of reference picture memory (457) and a new current picture buffer may be reallocated before reconstruction of a subsequent encoded picture begins.

The video decoder (410) may perform decoding operations according to predetermined video compression techniques in standards such as the ITU-T h.265 recommendation. 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, receiver (431) 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 (410) 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. 5 is a block diagram of a video encoder (503) according to an embodiment of the present disclosure. The video encoder (503) is disposed in the electronic device (520). The electronic device (520) includes a transmitter (540) (e.g., a transmission circuit). The video encoder (503) may be used in place of the video encoder (303) in the fig. 2 embodiment.

The video encoder (503) may receive video samples from a video source (501) (not part of the electronic device (520) in the example of fig. 5) that may capture video images to be encoded by the video encoder (503). In another embodiment, the video source (501) is part of the electronic device (520).

The video source (501) may provide a source video sequence in the form of a stream of digital video samples to be encoded by the video encoder (503), 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 (501) may be a storage device that stores previously prepared video. In a video conferencing system, the video source (501) 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 (503) may encode and compress pictures of a source video sequence into an encoded video sequence (543) in real-time or under any other temporal constraints required by the application. It is a function of the controller (550) to perform the appropriate encoding speed. In some embodiments, the controller (550) 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 (550) 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 (550) may be used to have other suitable functions relating to the video encoder (503) optimized for a certain system design.

In some embodiments, the video encoder (503) operates in an encoding loop. As a brief description, in one example, an encoding loop may include a source encoder (530) (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 (533) embedded in a video encoder (503). The decoder (533) reconstructs the symbols to create sample data in a manner similar to the way a (remote) decoder creates the sample data (since any compression between the symbols and the encoded video stream is lossless in the video compression techniques contemplated by the subject matter disclosed herein). The reconstructed sample stream (sample data) is input to a reference picture memory (534). 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 (534) 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 "local" decoder (533) may be the same as a "remote" decoder, such as video decoder (410) that has been described in detail above in connection with fig. 3. However, referring briefly also to fig. 3, when symbols are available and the entropy encoder (545) and parser (420) are able to losslessly encode/decode the symbols into a codec video sequence, the entropy decoding portion of the video decoder (410), including the buffer memory (415) and parser (420), may not be fully implemented in the local decoder (533).

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 examples, the source encoder (530) may perform motion compensated predictive encoding, predictively encoding an input picture with reference to one or more previously encoded pictures from the video sequence that are designated as "reference pictures". In this way, an encoding engine (532) encodes difference values 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 (533) 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 (530). The operation of the encoding engine (532) may be a lossy process. When the encoded video data is decodable at a video decoder (not shown in fig. 5), the reconstructed video sequence may typically be a copy of the source video sequence with some error. The local video decoder (533) replicates a decoding process, which may be performed on reference pictures by the video decoder, and may cause reconstructed reference pictures to be stored in the reference picture cache (534). In this way, the video encoder (503) 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.

The predictor (535) may perform a prediction search against the coding engine (532). That is, for a new picture to be encoded, predictor (535) may search reference picture memory (534) for sample data (as candidate reference pixel blocks) or some metadata, e.g., reference picture motion vectors, block shapes, etc., that may be referenced as appropriate predictions for the new picture. The predictor (535) 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 (535), it may be determined that the input picture may have prediction references taken from multiple reference pictures stored in reference picture memory (534).

The controller (550) may manage encoding operations of the source encoder (530), including, for example, setting parameters and subgroup parameters for encoding video data.

The outputs of all of the above functional units may be entropy encoded in an entropy encoder (545). The entropy encoder (545) 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 (540) may buffer the encoded video sequence created by the entropy encoder (545) in preparation for transmission over a communication channel (560), which may be a hardware/software link to a storage device that will store the encoded video data. The transmitter (540) may combine the encoded video data from the video encoder (503) with other data to be transmitted, such as encoded audio data and/or an auxiliary data stream (sources not shown).

The controller (550) may manage the operation of the video encoder (503). During encoding, the controller (550) 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 multiple blocks of samples (e.g., blocks each having 4 × 4, 8 × 8,4 × 8, or 16 × 16 samples) and encoded block-by-block. 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 (503) 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 (503) 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 (540) may transmit the additional data and the encoded video. The source encoder (530) may include 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. The block may be predicted by a combination of the first reference block and the 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, e.g., 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), e.g., 8 × 8 pixels, 16 × 16 pixels, 8 × 16 pixels, 16 × 8 pixels, and so on.

Fig. 6 shows a diagram of a video encoder (603) according to another embodiment of the present disclosure. A video encoder (603) 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 (603) is used in place of the video encoder (303) in the example of fig. 3.

In the HEVC example, a video encoder (603) receives a matrix of sample values for a processing block, e.g., a prediction block of 8 × 8 samples, etc. The video encoder (603) uses, for example, rate-distortion (RD) optimization to determine whether to encode the processing block using intra mode, inter mode, or bi-directional prediction mode. When encoding a processing block in intra mode, the video encoder (603) 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 (603) 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 (603) comprises other components, e.g. a mode decision module (not shown) for determining the processing block mode.

In the example of fig. 6, the video encoder (603) includes an inter encoder (630), an intra encoder (622), a residual calculator (623), a switch (626), a residual encoder (624), a general controller (621), and an entropy encoder (625) coupled together as shown in fig. 6.

The inter encoder (630) is used 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 value (e.g., a predicted block) using any suitable technique based on the inter prediction information. In some examples, the reference picture is a decoded reference picture that is decoded based on encoded video information.

An intra encoder (622) is used to receive samples of a current block (e.g., process the 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 one example, the intra encoder (622) also computes an intra prediction result (e.g., a predicted block) based on the intra prediction information and a reference block in the same picture.

The universal controller (621) is used to determine universal control data and control other components of the video encoder (603) based on the universal control data. In an embodiment, a general purpose controller (621) determines a mode of a block and provides a control signal to a switch (626) based on the mode. For example, when the mode is intra, the general purpose controller (621) controls the switch (626) to select an intra mode result for use by the residual calculator (623), and controls the entropy encoder (625) to select and add intra prediction information in the code stream; and when the mode is an inter mode, the general purpose controller (621) controls the switch (626) to select an inter prediction result for use by the residual calculator (623), and controls the entropy encoder (625) to select and add inter prediction information in the code stream.

A residual calculator (623) is used to calculate the difference (residual data) between the received block and the prediction result selected from the intra encoder (622) or the inter encoder (630). A residual encoder (624) is operative based on the residual data to encode the residual data to generate transform coefficients. In an embodiment, a residual encoder (624) 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 (603) also includes a residual decoder (628). A residual decoder (628) is used to perform the inverse transform and generate decoded residual data. The decoded residual data may be suitably used by an intra encoder (622) and an inter encoder (630). For example, inter encoder (630) may generate a decoded block based on decoded residual data and inter prediction information, and intra encoder (622) 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.

An entropy coder (625) is used to format the code stream to produce coded blocks. The entropy encoder (625) generates various information according to a suitable standard such as the HEVC standard. In an embodiment, the entropy encoder (625) 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. 7 shows a diagram of a video decoder (710) according to another embodiment of the present disclosure. A video decoder (710) 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 one example, the video decoder (710) is used in place of the video decoder (310) in the example of fig. 3.

In the example of fig. 7, the video decoder (710) includes an entropy decoder (771), an inter-frame decoder (780), a residual decoder (773), a reconstruction module (774), and an intra-frame decoder (772) coupled together as shown in fig. 7.

An entropy decoder (771) may be used to reconstruct certain symbols from an encoded picture, which represent syntax elements that constitute the encoded picture. Such symbols may include, for example, the mode of the block encoding (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 772 or an inter decoder 780, respectively, residual information in the form of, for example, quantized transform coefficients, and so forth. In one example, when the prediction mode is an inter prediction mode or a bi-prediction mode, inter prediction information is provided to an inter decoder (780); and providing the intra prediction information to an intra decoder (772) when the prediction type is an intra prediction type. The residual information may be inverse quantized and provided to a residual decoder (773).

An inter-frame decoder (780) is configured to receive inter-frame prediction information and generate an inter-frame prediction result based on the inter-frame prediction information.

An intra decoder (772) is used for receiving intra prediction information and generating a prediction result based on the intra prediction information.

A residual decoder (773) 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 (773) may also need some control information (to obtain the quantizer parameter QP) and that information may be provided by the entropy decoder (771) (data path not labeled as this may only be low-level control information).

A reconstruction module (774) is used to combine the residuals output by the residual decoder (773) 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 (303), video encoder (503), and video encoder (603) as well as video decoder (310), video decoder (410), and video decoder (710) may be implemented using any suitable techniques. In an embodiment, video encoder (303), video encoder (503), and video encoder (603), and video decoder (310), video decoder (410), and video decoder (710) may be implemented using one or more integrated circuits. In another embodiment, the video encoder (303), the video encoder (503), and the video decoder (310), the video decoder (410), and the video decoder (510) may be implemented using one or more processors executing software instructions.

Aspects of the present application relate to inter prediction, e.g., affine motion compensation and correction.

In various embodiments, for inter-predicted CUs, the inter-prediction samples may be generated using motion parameters that include motion vectors, reference picture indices, reference picture list usage indices, and/or other additional information. Inter prediction may include unidirectional prediction, bidirectional prediction, and/or the like. In uni-directional prediction, reference picture lists (e.g., a first reference picture list or list 0(L0), a second reference picture list or list 1(L1)) may be used. In bi-directional prediction, both L0 and L1 may be used. The reference picture list use index may indicate that the reference picture list includes L0, L1, or L0 and L1.

The motion parameters may be signaled explicitly or implicitly. When a CU is coded in skip mode, the CU may be associated with a PU and may have no significant residual coefficients (e.g., residual coefficients of zero), no coded Motion Vector Differences (MVDs), or no reference picture indices.

A merge mode may be used in which the motion parameters of the current CU may be obtained from neighboring CUs, the neighboring CUs comprising spatial and temporal merge candidates, optionally other merge candidates. The merge mode may be applied to inter-predicted CUs and may be used for the skip mode. Alternatively, the motion parameters may be explicitly sent or signaled. For example, the motion vector, the corresponding reference picture index for each reference picture list, the reference picture list usage flag, and other information may be explicitly signaled for each CU.

In some embodiments, one or more of the following inter-prediction coding tools are used: (1) extended merge prediction, (2) merge mode with motion vector differences (MMVD), (3) advanced motion vector prediction with symmetric MVD signaling (AMVP) mode, (4) affine motion compensated prediction, (5) subblock-based temporal motion vector prediction (SbTMVP), (6) Adaptive Motion Vector Resolution (AMVR), (7) bi-directional prediction with weighted averaging (BWA), (8) bi-directional optical flow (BDOF), (9) decoder-side motion vector modification (DMVR), (10) triangle partition prediction, and (11) inter-frame and intra-frame joint prediction (CIIP).

In some examples, the translational motion model is applied to Motion Compensated Prediction (MCP). Block-based affine motion compensation (also referred to as affine motion compensation prediction, affine motion compensation method, affine motion prediction, affine motion model, affine transform motion compensation prediction) can be applied, for example, to model various types of motion, such as zoom-in/out, rotation, perspective motion, and other irregular motion (e.g., motion other than translational motion).

In fig. 8A, when a 4-parameter affine model (or a 4-parameter affine motion model) is used, the affine motion field of the block (810A) is described by the motion information of the two control points CP0 and CP 1. The motion information may include two MVs or two Control Points MV (CPMV) of CP0 and CP1, i.e., CPMV0 and CPMV 1. In fig. 8B, when a 6-parameter affine model (or a 6-parameter affine motion model) is used, the affine motion field of the block (810B) is described by the motion information of three CPs (i.e., CP0 to CP 2). The motion information may include three MVs of CP0-CP2 or three CPMVs, i.e., CPMV0-CPMV2, respectively.

For a 4-parameter affine motion model, the motion vector at sample position (x, y) in block (810A) can be derived as:

wherein (mv)_0x,mv_0y) MV (CPMV0) which is the upper left corner CP (CP0), (MV)_1x,mv_1y) Is the MV (CPMV1) of the upper right corner CP (CP 1). Coordinates (x, y) are coordinates relative to the top left sample of the block (810A), and W represents the width of the block (810A).

For a 6 parameter affine motion model, the motion vector at sample position (x, y) in block (810B) can be derived as:

wherein (mv)_0x,mv_0y) MV (CPMV0) which is the upper left corner CP (CP0), (MV)_1x,mv_1y) MV (CPMV1) which is the upper right corner CP (CP1), (MV)_2x,mv_2y) Is the MV (CPMV2) of the lower left corner CP (CP 2). Coordinates (x, y) are coordinates relative to the top left sample of the block (810B), W represents the width of the block (810B), and H represents the height of the block (810B).

To simplify motion compensated prediction, in some embodiments sub-block based affine motion compensation (also referred to as sub-block based affine motion model) is applied, as shown in fig. 9. In sub-block based affine motion compensation, a current block (e.g., luma block) (900) may be divided into a plurality of sub-blocks (also referred to as affine sub-blocks) (902). The MVs of the respective samples in each of the plurality of sub-blocks (902) may be represented using MVs (also referred to as sub-block MVs) (901). In an example, the sub-block MV (901) of the sub-block (902) is the MV of the center sample of the sub-block (902). Therefore, the sub-block MV (901) may be calculated using an affine motion model of 4 parameters (e.g., equation (1)), an affine motion model of 6 parameters (e.g., equation (2)), or the like. Referring to fig. 9, a current block (900) is divided into 16 sub-blocks (902) having 16 sub-blocks MV (e.g., MVa-MVp).

Referring to fig. 9, an affine motion model of 4 parameters is used as an example.Andrespectively the CPMV of the top left CP (CP0) and the CPMV of the top right CP (CP 1). To derive the sub-block MV (901) of the sub-block (902), the MV of the center sample of the sub-block (902) may be calculated according to equation (1) and rounded to a fractional precision of 1/16 (e.g., the precision of the sub-block MV is 1/16 of samples or 1/16 of pixels). A motion compensated interpolation filter may be applied to generate a prediction value for each sub-block (902) using the derived MV (901).

The subblock size of the chrominance component may be set to 4 × 4. The sub-block MV of the 4 × 4 chroma sub-block may be calculated as an average of the sub-blocks MV of the four corresponding 4 × 4 luma sub-blocks.

Similar to translational motion inter-prediction, in some embodiments, two affine motion inter-prediction modes are employed: affine MERGE mode (or affine MERGE prediction, AF _ MERGE mode) and affine AMVP mode (or affine AMVP prediction).

In some embodiments, an affine MERGE mode (e.g., AF _ MERGE mode) may be applied to CUs having both width and height greater than or equal to 8. In the affine merging mode, the CPMV of the current CU may be generated based on motion information of spatially neighboring CUs of the current CU. Up to five CPMV predictor (CPMVP) candidates may be included in a candidate list (e.g., an affine merge candidate list), and an index may be signaled to indicate the CPMV predictor candidates to be used for the current CU. The following three types of CPMVP candidates may be used to form the affine merge candidate list: (a) inherited affine merge candidates extrapolated from CPMV of neighboring CUs (e.g., spatially neighboring CUs); (b) a constructed affine merge candidate derived using the panning MVs of neighboring CUs (e.g., spatially neighboring CUs and/or temporally neighboring CUs); and/or (c) zero MV.

In an embodiment, such as in VTM3, the candidate list (e.g., affine merge candidate list) includes up to two inherited affine merge candidates that can be derived from affine motion models of neighboring CUs (or neighboring blocks). For example, a first inherited affine merging candidate may be derived from the left neighboring CU, and a second inherited affine merging candidate may be derived from the upper neighboring CU. An exemplary candidate CU (or candidate block) for CU (1001) is shown in fig. 10A. To obtain the first inherited affine merge candidate (or left predictor), the scan order a0- > a1 may be applied. To obtain the second inherited affine merge candidate (or upper predictor), the scan order may be B0- > B1- > B2. In an example, only the first inherited candidate for each side (e.g., left and/or top) is selected. In addition, pruning check (pruning check) is not performed between the two inherited candidates. When a neighboring affine CU is identified, the CPMV of the neighboring affine CU can be used to derive the CPMVP candidate in the affine merging candidate list of the current CU. As shown in fig. 10B, if the adjacent lower left block a is coded in an affine motion mode, the upper left MV, the upper right MV, and the lower left MV of the CU (1002) including the block a can be obtained: v2, v3 and v 4. When the block a is encoded using the 4-parameter affine motion model, two CPMVs of the current CU (1000) can be calculated from v2 and v 3. When the block a is encoded using a 6-parameter affine motion model, three CPMVs of the current CU (1000) can be calculated from v2, v3, and v 4.

The constructed affine merging candidate of the CU may refer to a candidate constructed by combining adjacent translational motion information of each CP of the CU. The motion information of the CP may be derived from the spatial neighbor candidate and the temporal neighbor candidate of the current block (1100) shown in fig. 11. CPMV (compact peripheral component management video) system_K(k-1, 2, 3, 4) may represent the kth CP of the current block (1100). For CPMV₁Block B2, block B3, and block A2 may be checked. For example, the scanning order is B2->B3->A2, MV of the first available block can be used as CPMV₁. For CPMV₂For example, scan order B1 may be used>B0 checkblock B1And block B0. For CPMV₃For example, scan order A1->A0 checks Block A1 and Block A0. When a Temporal Motion Vector Predictor (TMVP) (denoted by T in fig. 11) is available, the TMVP can be applied as the CPMV₄。

After obtaining the MVs of the four CPs, affine merging candidates can be constructed from the motion information of the four control points. The following CPMV combinations may be used to sequentially construct affine merge candidates:

{CPMV₁,CPMV₂,CPMV₃}、{CPMV₁,CPMV₂,CPMV₄}、{CPMV₁,CPMV₃,CPMV₄}、{CPMV₂,CPMV₃,CPMV₄}、{CPMV₁,CPMV₂and { CPMV }and₁,CPMV₃}。

The combination of 3 CPMVs can construct an affine merging candidate with 6 parameters, and the combination of 2 CPMVs can construct an affine merging candidate with 4 parameters. To avoid using the motion scaling process, if the reference indices of the control points are different, the corresponding CPMV combination may be discarded.

After the inherited affine merge candidate and the constructed affine merge candidate are checked, if the affine merge candidate list is not full, a zero MV may be inserted at the end of the affine merge candidate list.

In some embodiments, the affine AMVP mode may be applied to CUs having both width and height greater than or equal to 16. An affine flag at the CU level may be signaled in the codestream to indicate whether affine AMVP mode is used, and then another flag may be signaled to indicate whether an affine motion model of 4 parameters is used or an affine motion model of 6 parameters is used. In affine AMVP mode, the difference between the CPMV of the current CU and the corresponding CPMV predictor (CPMVP) may be signaled in the codestream. The affine AMVP candidate list may be 2 in size and may be generated by using four types of CPMV candidates, e.g., in the order of (a) - > (b) - > (c) - > (d) (a) inherited affine AMVP candidates extrapolated from the CPMVs of neighboring CUs; (b) a constructed affine AMVP candidate derived using the translation MVs of neighboring CUs; (c) a translation MV from a neighboring CU; and (d) zero MV.

In an example, the checking order (or scanning order) of the inherited affine AMVP candidate is similar or identical to the checking order of the inherited affine merge candidate. In an example, the difference between the inherited affine AMVP candidate and the inherited affine merge candidate is that for the inherited affine AMVP candidate, only affine CUs having the same reference picture as in the current block are considered. When the inherited affine MV predictor (or the inherited affine AMVP candidate) is inserted into the affine AMVP candidate list, the pruning process is not applied.

The constructed AMVP candidate may be derived from the specified spatial neighborhood candidate shown in fig. 11. The same checking order as used when constructing the affine merge candidate(s) may be used. In addition, reference picture indexes of the neighboring blocks may also be checked. The first block in check order of the inter-coded, reference picture that is the same as the current CU may be used. When the current CU is encoded using a 4-parameter affine motion model and both CPMV1 and CPMV2 are available, the available CPMV (e.g., CPMV1 and CPMV2) may be added as a candidate to the affine AMVP candidate list. When the current CU is encoded using an affine motion mode of 6 parameters and all three CPMVs (e.g., CPMV1, CPMV2, and CPMV3) are available, the available CPMV can be added as a candidate to the affine AMVP candidate list. Otherwise, the constructed AMVP candidate may be set as unavailable.

If the affine AMVP candidate list has a size smaller than 2 after checking the inherited AMVP candidate(s) and the constructed AMVP candidate(s), the translation MVs of the neighboring CUs of the current block (1100), when available, may be added in the affine AMVP candidate list to predict all control points MVs of the current block (1100). Finally, if the affine AMVP candidate list is still not full, the affine AMVP candidate list may be populated with zero MVs.

The embodiments of the present application can be applied to affine sub-block motion compensation using an interpolation filter (e.g., a 6-tap interpolation filter or an 8-tap interpolation filter). In an example, inter prediction of a 4 × 4 luma block is disabled in addition to affine sub-block prediction. In one example, only inter uni-directional prediction is allowed for luma blocks of size 4 × 8 or 8 × 4.

In one example, for affine sub-block motion compensation with a luma sample size of 4 × 4, a 6-tap interpolation filter is used, as shown in table 1. For luminance motion compensation that is not based on an affine motion model, an 8-tap interpolation filter may be used, as shown in table 2.

Table 16 tap interpolation filter

Interpolation filter with 28 taps

The MV of each pixel (or sample) in a CU (e.g., block, luma block) may be derived, for example, based on equation (1) or equation (2), using affine motion model parameters or affine parameters (e.g., parameters in 4-parameter affine motion model as shown in equation 1, parameters in 6-parameter affine motion model as shown in equation 2). However, since performing pixel-based affine motion compensation has high complexity and memory access bandwidth requirements, in some embodiments sub-block-based affine motion compensation is implemented. In sub-block-based affine motion compensation, a current block (e.g., CU) may be divided into sub-blocks, and each of the sub-blocks may be assigned a sub-block MV derived from the CPMV of the current block. In one example, the size of a sub-block is 4 × 4 samples. Sub-block based affine motion compensation can improve codec efficiency and reduce codec complexity and memory access bandwidth.

In some embodiments, optical flow predictor modification (PROF), also referred to as the PROF method, may be implemented to improve sub-block based affine motion compensation to have finer granularity of motion compensation. In an embodiment, after performing sub-block based affine motion compensation, the difference (or correction value, correction amount, predicted value correction amount) derived based on the optical flow equations may be added to the prediction samples (e.g., luminance predicted samples or luminance prediction samples) to obtain corrected prediction samples.

Fig. 12 shows a schematic diagram of an example of a PROF method according to an embodiment of the application. The current block (1210) may be partitioned into four sub-blocks (1212, 1214, 1216, and 1218). Each sub-block (1212, 1214, 1216, and 1218) may be 4 × 4 pixels or 4 × 4 samples in size. The sub-block MV (1220) of the sub-block (1212) may be derived from the CPMV of the current block 1210, for example, using the center position of the sub-block (1212) and an affine motion model (e.g., 4-parameter affine motion model, 6-parameter affine motion model). Sub-block MV (1220) may point to reference sub-block (1232) in the reference picture. Initial sub-block prediction samples may be determined from the reference sub-block (1232).

In some examples, the translational motion from the reference sub-block (1232) to the sub-block (1212), described by the sub-block MV (1220), may not predict the sub-block (1212) with high accuracy. In addition to the translational motion described by sub-block MV (1220), sub-block (1212) may also undergo non-translational motion (e.g., rotation as seen in fig. 12). Referring to fig. 12, sub-block (1250), which has shaded samples (e.g., sample (1232a)) in the reference picture, corresponds to and may be used to reconstruct the samples in sub-block (1212). The shaded samples (1232a) may be shifted by pixel MV (1240) to reconstruct the samples (1212a) in sub-block (1212) with high accuracy. Thus, in some examples, when non-translational motion occurs, to improve prediction accuracy, an appropriate prediction value correction method may be applied in the affine motion model, as described below.

In one example, the PROF method is implemented using the following four steps. In step (1), sub-block-based affine motion compensation may be performed for a current sub-block (e.g., sub-block (1212)) to generate a predictor such as an initial sub-block predictor I (I, j), where I and j are coordinates corresponding to samples at position (I, j) (also referred to as sample position, sample orientation) in the current block (1212).

In step (2), the following gradient calculation may be performed: spatial gradient g of initial sub-block predictor I (I, j) at each sample position (I, j)_x(i, j) and spatial gradient g_y(i, j), a filter [ -1, 0, 1) using, for example, 3 taps can be made according to equation (3) and equation (4) as follows]And (3) calculating:

g_x(I, j) ═ I (I +1, j) -I (I-1, j) (equation 3)

g_y(I, j) ═ I (I, j +1) -I (I, j-1) (equation 4).

For the gradient calculation, one pixel may be extended on each side of the sub-block prediction block. In some embodiments, to reduce memory bandwidth and complexity, pixels on the extended boundary may be copied from their nearest integer pixel positions in a reference picture (e.g., a reference picture comprising sub-block (1232)). In this way, additional interpolation operations for the fill area can be avoided.

In step (3), the predicted value correction amount Δ I (I, j) may be calculated by the following equation (5):

ΔI(i，j)＝g_x(i，j)*Δmv_x(i，j)+g_y(i，j)*Δmv_y(i, j) (equation 5).

Where Δ MV (i, j) (e.g., Δ MV (1242)) is the pixel MV at sample position (i, j) or sample MV (i, j) (e.g., pixel MV (1240)) and sub-block MVMv (MV) of the sub-block (e.g., sub-block (1212))_SB(e.g., sub-block MV (1220)) where the sample position (i, j) is located in the sub-block. Δ mv (i, j) may be determined using equation (6) as follows.

Δmv(i，j)＝mv(i，j)-mv_SB(equation 6).

Δmv_x(i, j) and Δ mv_y(i, j) are the x-component (e.g., horizontal component) and y-component (e.g., vertical component) of the difference value MV Δ MV (i, j), respectively.

Due to affine model parameters and relative to the center of the sub-blockThe pixel position of the position does not change from sub-block to sub-block, so Δ mv (i, j) may be calculated for a first sub-block (e.g., sub-block (1212)) and reused for other sub-blocks (e.g., sub-block (1214), sub-block (1216), and sub-block (1218)) in the same current block (1210). In some examples, x and y represent horizontal and vertical offsets of sample position (i, j) relative to a center position of sub-block (1212), Δ mv (i, j) (e.g., including Δ mv_x(i, j) and Δ mv_y(i, j)) can be derived by the following equation (7),

wherein, Δ mv_x(x, y) is the x component Δ mv_x(i，j)，Δmv_y(x, y) is the y component Δ mv_y(i，j)。

In one example, for an affine motion model of 4 parameters,

for an affine motion model of 6 parameters,

wherein (mv)_0x，mv_0y)、(mv_1x，mv_1y) And (mv)_2x，mv_2y) Which may be an upper left corner CPMV, an upper right corner CPMV, and a lower left corner CPMV, w and h, respectively, are the width and height of the current block (1210) including the current sub-block (1212).

In step (4), a predicted value correction amount Δ I (I, j) (e.g., a luminance predicted value correction amount) may be added to the initial sub-block predicted value I (I, j) to generate another predicted value such as a corrected predicted value I' (I, j). The corrected predicted value I' (I, j) may be generated using equation (10) for sample (I, y) as follows:

i' (I, j) ═ I (I, j) + Δ I (I, j). (equation 10)

In an embodiment, a 6-tap interpolation filter is used in sub-block based affine motion compensation (or sub-block based affine motion model), where the affine sub-block has a size of 4 × 4 samples (e.g., 4 × 4 luma samples) (also referred to as affine sub-block size). Motion compensation using a 6-tap interpolation filter may have lower complexity and memory bandwidth requirements than an 8-tap interpolation filter. In some examples, the prediction accuracy may be increased when an 8-tap interpolation filter is used.

In an embodiment, in the PROF of a block (e.g., a luminance block) encoded with an affine motion model (e.g., a sub-block-based affine motion model), gradient calculations may be performed on each of 4 × 4 sub-blocks (e.g., luminance blocks), and each of the 4 × 4 luminance sub-blocks may be padded to a size of 6 × 6 in order to perform gradient calculations (e.g., gradient calculations described by equations (3) - (4)). However, multiple fill operations and gradient calculations can affect the complexity of the PROF.

According to aspects of the present disclosure, encoding information for a Current Block (CB) (e.g., CB (900)) may be decoded from an encoded video stream. The encoding information may indicate that the CB is encoded using a sub-block based affine motion model. The sub-block based affine motion model may include affine parameters, which may be CB-based CPMVs (e.g., as in fig. 9)And). In addition, the CB may include an affine sub-block (e.g., sub-block (902)) having a sub-block MV (e.g., sub-block MV (901)). The CB may include additional affine sub-block(s) with additional sub-block(s) MV.

It may be determined, based on the encoding information, whether to select a sub-block characteristic for generating a prediction value of samples in the affine sub-block based on the sub-block MV. In response to selecting the sub-block characteristic, the sub-block characteristic may be determined based on at least one of the affine parameters. The sub-block characteristic may indicate one of: (i) a sub-block size used in generating a prediction value for the sample; and (ii) interpolation filter type for affine sub-blocks. Additionally, samples in the affine sub-block may be reconstructed based on the determined sub-block characteristics.

The affine parameters may be determined based on the CPMV of the CB. In an embodiment, the sub-block based affine motion model is a 4-parameter based affine motion model, as shown in fig. 8A and described by equation (1) or equations (7) and (8). Referring to fig. 8A, a CB (e.g., (810A)) includes a first CPMV (e.g., CPMV)₀) And has a second CPMV (e.g., CPMV0)₁) The upper right corner CP (e.g., CP 1). The affine parameters may include first affine parameters (e.g.,) And a second affine parameter (e.g.,). The first affine parameter (e.g., "a") may indicate a ratio of an x-component of the first MV difference between the second CPMV and the first CPMV to a width (e.g., w) of the CB. The second affine parameter (e.g., "c") may indicate a ratio of the y component of the first MV difference to the width of the CB.

In an embodiment, the sub-block based affine motion model is a 6 parameter based affine motion model, as shown in fig. 8B and described by equation (2) or equations (7) and (9). Referring to fig. 8B, the CB (e.g., (810B)) includes a first CPMV (e.g., CPMV)₀) Has a second CPMV (e.g., CPMV) with an upper left corner CP (e.g., CP0)₁) And has a third CPMV (e.g., CPMV1)₂) The lower left corner CP (e.g., CP 2). The affine parameters include a first affine parameter (e.g.,) A second affine parameter (e.g.,) A third affine parameter (e.g.,) And a fourth affine parameter (e.g.,). The first affine parameter and the second affine parameter may be the same as those in the 4-parameter affine motion model, and thus a detailed description thereof is omitted for the sake of brevity. The third affine parameter (e.g., "b") may indicate a ratio of an x-component of the second MV difference between the third CPMV and the first CPMV to a height (e.g., h) of the CB. The fourth affine parameter (e.g., "d") may indicate a ratio of the y-component of the second MV difference to the height of the CB.

In an embodiment, one or more of the affine parameters represent an average MV difference of two neighboring pixels (or samples) along one direction (e.g., horizontal direction (width), vertical direction (height)) in the CB. For example, the first affine parameter "a" and the second parameter "c" represent the average MV difference (MVD) of two adjacent pixels along the horizontal direction (width). In addition, the first affine parameter "a" represents the x component, and the second affine parameter "c" represents the y component. For example, the third affine parameter "b" and the fourth parameter "d" represent the average MVDs of two adjacent pixels along the vertical direction (height). Further, the third affine parameter "b" represents the x component, and the fourth affine parameter "d" represents the y component.

In addition to or in lieu of including "a", "b", "c", and/or "d" as described above in the affine parameters, the affine parameters may include other parameters to describe various motions of the CB, such as zoom in/out (also referred to as zoom), rotation, and/or the like.

In addition to the above-described affine parameters, the parameters "e" and "f" (or translational motion parameters, translational parameters) related to translational motion may be derived using the following equation (11).

In one example, a 4 parameter affine motion model may be generated using a model such as the first affine parameter (e.g.,) A second affine parameter (e.g.,) 4 parameters like e, f. In one example, a 6 parameter affine motion model may be generated using a model such as the first affine parameter (e.g.,) A second affine parameter (e.g.,) A third affine parameter (e.g.,) A fourth affine parameter (e.g.,) E, f, etc. are described.

In an embodiment, the sub-block size is an affine sub-block size of the affine sub-block in the CB. The interpolation filter type may be an interpolation filter having any suitable length. In an example, the interpolation filter type is a first cross-correlation filter having a first length (e.g., 6 taps) or a second interpolation filter having a second length (e.g., 8 taps) filter, the first length being less than the second length. The sub-block characteristic may indicate an affine sub-block size or an interpolation filter type. The sub-block characteristics may be determined based on at least one of the affine parameters and one of: (i) a threshold value; and (ii) a predefined range.

In an example, one or more processes for affine motion compensation and/or affine correction (e.g., PROF) may be conditionally selected based on at least one of the affine parameters and a threshold (or predefined range).

In an embodiment, the threshold may be a predefined value known to the encoder and decoder. The threshold is not signaled. In an embodiment, the threshold may be signaled at a higher level (e.g., a level higher than the CU level), such as a sequence level, a picture block level, a tile group level, a slice level, etc.

According to aspects of the present application, the affine sub-block size and/or the interpolation filter type (e.g., affine sub-block interpolation filter with 6 taps, or affine sub-block interpolation filter with 8 taps) may be conditionally selected based on a comparison of the at least one affine parameter (or affine-related parameter) to the threshold. In an embodiment, when the affine parameters cause relatively large MV differences between neighboring sub-blocks (e.g., based on a comparison between the at least one affine parameter and the threshold), a small size (e.g., 4 x 4 samples) may be used for the affine sub-blocks. Otherwise, a large size (e.g., 8 × 8 samples) may be used. In addition, the number of taps of the interpolation filter for a small affine sub-block size may be smaller than the number of taps of the interpolation filter for a large affine sub-block size. For example, a 6-tap interpolation filter may be used to reduce complexity and memory bandwidth when using a small affine sub-block size. An 8-tap interpolation filter can be used for large affine sub-block sizes. In an example, the affine sub-block size (e.g., affine luma sub-block size) is 4 × 4 samples and uses a 6-tap interpolation filter.

As described above, the affine parameters can be calculated using the CPMV of the CB. In an example, the affine parameters include a, b, c, and d corresponding to the first affine parameter, the second affine parameter, the third affine parameter, and the fourth affine parameter. For the 4-parameter affine motion model, the affine parameters including a, b, c, and d can be described by equation (8). For affine motion model of 6 parameters, one canTo describe affine parameters including a, b, c and d by equation (9). (mv)_0x，mv_0y)、(mv_1x，mv_1y)、(mv_2x，mv_2y) Are the top left corner CPMV, top right corner CPMV and bottom left corner CPMV, w is the width of the CB, and h is the height of the CB.

The affine sub-block size (e.g., 4 x 4, 8 x 8) may be conditionally determined based on at least one of the affine parameters.

In an embodiment, at least one of the affine parameters comprises a plurality of affine parameters. It may be determined whether absolute values of the plurality of affine parameters satisfy a predefined condition. The predefined condition may be one of the following: (i) the maximum value of the absolute value is greater than the threshold; (ii) the maximum value of the absolute value is greater than or equal to the threshold; (iii) the minimum value of the absolute values is greater than the threshold value; (iv) the minimum value of the absolute values is greater than or equal to the threshold value; and (v) the absolute value is outside the predefined range.

In response to the absolute value satisfying the predefined condition, it may be determined that the sub-block characteristic indicates that the affine sub-block size is a first size (e.g., 4 × 4 samples) and/or indicates that the interpolation filter type is a first interpolation filter (e.g., a 6-tap interpolation filter). For example, the absolute value satisfying the predefined condition indicates that the affine parameters cause relatively large MV differences between adjacent sub-blocks, and thus using the first size and the second size (e.g., 8 × 8) of a smaller size (e.g., 4 × 4) as the affine sub-block sizes can improve, for example, prediction accuracy. The second size is larger than the first size.

In response to the absolute value not satisfying the predefined condition, it may be determined that the sub-block characteristic indicates the affine sub-block size is a second size (e.g., 8 × 8 samples) and/or that the interpolation filter type is a second interpolation filter (e.g., an 8-tap interpolation filter). For example, the absolute value not satisfying the predefined condition means that the affine parameters cause relatively small MV differences between adjacent sub-blocks, and therefore using the first size and the second size of the larger size (e.g., 8 × 8) as the affine sub-block sizes enables a prediction accuracy close to that using the smaller size (e.g., the first size of 4 × 4). In one example, using a larger size (e.g., a second size of 8 x 8) improves prediction efficiency.

The threshold may be set to any suitable value, such as a value equivalent to 1/4 samples (e.g., 1/4 luma samples), a value equivalent to 1/8 samples (e.g., 1/8 luma samples), and so on. In an example, 1/4 samples indicate that the MV difference between two adjacent samples (e.g., x-component of MV difference, y-component of MV difference) is 1/4 samples or 1/4 pixels.

The threshold is not limited to the value equivalent to 1/8 samples (e.g., 1/8 luma samples) of the above example (e.g., 1/4 luma samples). As mentioned above, the threshold may be a predefined value known to the decoder and therefore not signaled. Alternatively, the threshold may be explicitly signaled.

In an embodiment, the plurality of affine parameters comprises a, b, c and d for a 4 parameter affine motion model or a 6 parameter affine motion model. The maximum value among the absolute values of the plurality of affine parameters is represented as max _ parameter (e.g., max _ parameter { | a |, | b |, | c |, | d | }). When the maximum value of the absolute values is greater than or equal to the threshold value, the affine sub-block size may be smaller. In a first example, for CB, the affine sub-block size may be set to 4 × 4 samples (e.g., 4 × 4 luma samples) when the maximum value of the absolute values (e.g., max _ parameter) is above the threshold. Otherwise, when the maximum value of the absolute values is equal to or smaller than the threshold, the affine sub-block size may be set to 8 × 8 samples (e.g., 8 × 8 luma samples). In a second example, the affine sub-block size may be set to 4 × 4 samples (e.g., 4 × 4 luma samples) when the maximum value of the absolute values (e.g., max _ parameter) is higher than or equal to the threshold. Otherwise, when the maximum value of the absolute values is smaller than the threshold, the affine sub-block size may be set to 8 × 8 samples (e.g., 8 × 8 luma samples).

In an embodiment, the plurality of affine parameters comprises a, b, c and d for a 4 parameter affine motion model or a 6 parameter affine motion model. The maximum value among the absolute values of the plurality of affine parameters is represented as max _ parameter (e.g., max _ parameter { | a |, | b |, | c |, | d | }). The affine sub-block size may be larger when the maximum value in the absolute values is greater than or equal to the threshold value. In a first example, for CB, the affine sub-block size may be set to 8 × 8 samples (e.g., 8 × 8 luma samples) when the maximum value of the absolute values (e.g., max _ parameter) is above the threshold. Otherwise, when the maximum value of the absolute values is equal to or smaller than the threshold, the affine sub-block size may be set to 4 × 4 samples (e.g., 4 × 4 luma samples). In a second example, the affine sub-block size may be set to 8 × 8 samples (e.g., 8 × 8 luma samples) when the maximum value of the absolute values (e.g., max _ parameter) is higher than or equal to the threshold. Otherwise, when the maximum value of the absolute values is smaller than the threshold, the affine sub-block size may be set to 4 × 4 samples (e.g., 4 × 4 luma samples).

In an embodiment, the plurality of affine parameters comprises a, b, c and d for a 4 parameter affine motion model or a 6 parameter affine motion model. The smallest value among the absolute values of the plurality of affine parameters is represented as min _ parameter (e.g., min _ parameter { | a |, | b |, | c |, | d | }). The affine sub-block size may be smaller when the minimum value in the absolute values is greater than or equal to the threshold value. In a first example, for CB, the affine sub-block size may be set to 4 × 4 samples (e.g., 4 × 4 luma samples) when the minimum value in absolute values (e.g., min _ parameter) is above the threshold. Otherwise, when the minimum value of the absolute values is equal to or smaller than the threshold, the affine sub-block size may be set to 8 × 8 samples (e.g., 8 × 8 luma samples). In a second example, the affine sub-block size may be set to 4 × 4 samples (e.g., 4 × 4 luma samples) when the minimum value of the absolute values (e.g., min _ parameter) is higher than or equal to the threshold. Otherwise, when the minimum value of the absolute values is smaller than the threshold, the affine sub-block size may be set to 8 × 8 samples (e.g., 8 × 8 luma samples).

In an embodiment, the plurality of affine parameters comprises a, b, c and d for a 4 parameter affine motion model or a 6 parameter affine motion model. The smallest value among the absolute values of the plurality of affine parameters is represented as min _ parameter (e.g., min _ parameter { | a |, | b |, | c |, | d | }). The affine sub-block size may be larger when the minimum value of the absolute values is greater than or equal to the threshold value. In a first example, for CB, the affine sub-block size may be set to 8 × 8 samples (e.g., 8 × 8 luma samples) when the minimum value of the absolute values (e.g., min _ parameter) is above the threshold. Otherwise, when the minimum value of the absolute values is equal to or smaller than the threshold, the affine sub-block size may be set to 4 × 4 samples (e.g., 4 × 4 luma samples). In a second example, the affine sub-block size may be set to 8 × 8 samples (e.g., 8 × 8 luma samples) when the minimum value of the absolute values (e.g., min _ parameter) is higher than or equal to the threshold. Otherwise, when the minimum value of the absolute values is smaller than the threshold, the affine sub-block size may be set to 4 × 4 samples (e.g., 4 × 4 luma samples).

In an embodiment, the plurality of affine parameters comprises a, b, c and d for a 4 parameter affine motion model or a 6 parameter affine motion model. The affine sub-block size may be set based on whether one or more affine parameters of the plurality of affine parameters fall within the predefined range. In the example of CB, the affine sub-block size may be set to 8 × 8 samples (e.g., 8 × 8 luma samples) when the absolute values of the plurality of affine parameters are within the predefined range (or predefined range of values). Otherwise, when any of the absolute values is outside the predefined range, the affine sub-block size may be set to 4 × 4 samples (e.g., 4 × 4 luma samples). The predefined range may be represented as [ M, N ], where M and N are positive numbers. M and N may be predefined or signaled in the encoded codestream, such as in a Sequence Parameter Set (SPS), Picture Parameter Set (PPS), tile group header, picture header, slice header, and the like.

Use of an interpolation filter, such as whether an affine motion model (e.g., sub-block based affine motion model) uses a 6-tap interpolation filter or an 8-tap interpolation filter, may be conditionally determined based on affine parameters

In an embodiment, the plurality of affine parameters comprises a, b, c and d for a 4 parameter affine motion model or a 6 parameter affine motion model. The maximum value among the absolute values of the plurality of affine parameters is represented as max _ parameter (e.g., max _ parameter { | a |, | b |, | c |, | d | }). When the maximum value in the absolute values is greater than or equal to the threshold value, the number of taps of the interpolation filter may be small. In a first example, for CB, when the maximum value of the absolute values (e.g., max _ parameter) is above the threshold, a 6-tap interpolation filter may be used in the sub-block based affine motion model (or affine sub-block based motion compensation). Otherwise, when the maximum value in the absolute values is equal to or smaller than the threshold value, an 8-tap interpolation filter may be used in the sub-block-based affine motion model. In a second example, when the maximum value of the absolute values (e.g., max _ parameter) is higher than or equal to the threshold value, a 6-tap interpolation filter may be used in the sub-block based affine motion model. Otherwise, when the maximum value in the absolute values is smaller than the threshold, an 8-tap interpolation filter may be used in the sub-block-based affine motion model.

In an embodiment, the plurality of affine parameters comprises a, b, c and d for a 4 parameter affine motion model or a 6 parameter affine motion model. The maximum value among the absolute values of the plurality of affine parameters is represented as max _ parameter (e.g., max _ parameter { | a |, | b |, | c |, | d | }). When the maximum value in the absolute values is greater than or equal to the threshold value, the number of taps of the interpolation filter may be large. In a first example, for CB, when the maximum value of the absolute values (e.g., max _ parameter) is above the threshold, an 8-tap interpolation filter may be used in the sub-block based affine motion model (or affine sub-block based motion compensation). Otherwise, when the maximum value in the absolute values is equal to or smaller than the threshold value, a 6-tap interpolation filter may be used in the sub-block-based affine motion model. In a second example, when the maximum value (e.g., max _ parameter) of the absolute values is higher than or equal to the threshold, an 8-tap interpolation filter may be used in the sub-block-based affine motion model. Otherwise, when the maximum value in the absolute values is smaller than the threshold, a 6-tap interpolation filter may be used in the sub-block-based affine motion model.

In an embodiment, the plurality of affine parameters comprises a, b, c and d for a 4 parameter affine motion model or a 6 parameter affine motion model. The smallest value among the absolute values of the plurality of affine parameters is represented as min _ parameter (e.g., min _ parameter { | a |, | b |, | c |, | d | }). When the minimum value of the absolute values is greater than or equal to the threshold value, the number of taps of the interpolation filter may be small. In a first example, for CB, when the minimum of the absolute values (e.g., min _ parameter) is above the threshold, a 6-tap interpolation filter may be used in the sub-block based affine motion model (or affine sub-block based motion compensation). Otherwise, when the minimum value in the absolute values is equal to or smaller than the threshold value, an 8-tap interpolation filter may be used in the sub-block-based affine motion model. In a second example, when the minimum value (e.g., min _ parameter) in the absolute values is higher than or equal to the threshold, a 6-tap interpolation filter may be used in the sub-block based affine motion model. Otherwise, when the minimum value in the absolute values is smaller than the threshold, an 8-tap interpolation filter may be used in the sub-block-based affine motion model.

In an embodiment, the plurality of affine parameters comprises a, b, c and d for a 4 parameter affine motion model or a 6 parameter affine motion model. The smallest value among the absolute values of the plurality of affine parameters is represented as min _ parameter (e.g., min _ parameter { | a |, | b |, | c |, | d | }). When the maximum value in the absolute values is greater than or equal to the threshold value, the number of taps of the interpolation filter may be large. In a first example, for CB, when the minimum of the absolute values (e.g., min _ parameter) is above the threshold, an 8-tap interpolation filter may be used in the sub-block based affine motion model (or affine sub-block based motion compensation). Otherwise, when the minimum value in the absolute values is equal to or smaller than the threshold value, a 6-tap interpolation filter may be used in the sub-block-based affine motion model. In a second example, when the minimum value (e.g., min _ parameter) in the absolute values is higher than or equal to the threshold, an 8-tap interpolation filter may be used in the sub-block based affine motion model. Otherwise, when the minimum value in the absolute values is smaller than the threshold, a 6-tap interpolation filter may be used in the sub-block-based affine motion model.

In an embodiment, the plurality of affine parameters comprises a, b, c and d for a 4 parameter affine motion model or a 6 parameter affine motion model. Interpolation filters (e.g., a first interpolation filter and a second interpolation filter including different numbers of taps) may be set based on whether one or more affine parameters of the plurality of affine parameters fall within the predefined range. In the example of CB, when the absolute values of the plurality of affine parameters are within the predefined range (or predefined range of values), an 8-tap interpolation filter may be used in the sub-block based affine motion model. Otherwise, if any of the absolute values is outside the predefined range, a 6-tap interpolation filter may be used in the sub-block based affine motion model. The predefined range may be represented as [ M, N ], where M and N are positive numbers. M and N may be predefined or signaled in the encoded codestream, such as in a Sequence Parameter Set (SPS), Picture Parameter Set (PPS), tile group header, picture header, slice header, and the like.

Conditional selection of affine sub-block sizes and/or affine sub-block interpolation filters (e.g., 6-tap interpolation filter, 8-tap interpolation filter) such as described in the present application may be enabled or disabled by a syntax (e.g., high level syntax) such as sequence level, picture level, slice level, tile group level, and the like. In an example, the syntax is explicitly signaled.

In an example, CB is a luma block, the affine sub-block size is set to 8 × 8 luma samples, and the chroma sub-block size is 4 × 4. Instead of using the average luminance MV value, the MV of the chrominance block can be directly calculated.

In an embodiment, the CB includes a gradient sub-block for performing gradient calculations in the PROF of the CB. The sub-block size is the size of the gradient sub-block. The gradient calculation may be a block-based gradient calculation (also referred to as a whole-block-based gradient calculation), where the gradient subblock is a CB and the subblock size is equal to the block size of the CB. Alternatively, the gradient calculation may be a subblock-based gradient calculation. The CB includes gradient sub-blocks and additional gradient sub-blocks, so the sub-block size is smaller than the block size.

In an embodiment, at least one of the affine parameters may comprise a plurality of affine parameters. Whether the gradient calculation is based on the block or the sub-block may be determined based on a maximum value or a minimum value of absolute values of the plurality of affine parameters and a gradient threshold. The gradient threshold may be the same as or different from the threshold. Alternatively, whether the gradient calculation is block-based or sub-block-based may be determined based on the absolute values and the gradient predefined range. The predefined range of gradients may be the same or different than the predefined range.

In the example of PROF based on an affine motion model of sub-blocks, inter prediction (interpolation) may be performed on each affine sub-block in the CB (e.g., each 4 × 4 affine sub-block). The gradient calculation may be calculated based on the predicted output of the affine sub-block, using a 3-tap filter [ 10-1 ], and then the correction may be applied to the affine sub-block. To calculate the gradient of the affine sub-block, the affine sub-block may be padded to a larger size, e.g., 1 pixel extended on each side of the affine sub-block.

When inter prediction (interpolation) of all affine subblocks is completed, gradient calculation, which refers to block-based gradient calculation, may be performed for the entire CB (e.g., CB1310 in fig. 13). In block-based gradient computation, it may not be necessary to extend each affine sub-block in order to perform the gradient computation. Alternatively, to perform the gradient calculation, the entire CB may be extended by extending (or padding) 1 pixel over each boundary of the CB, which may not be as complex as extending the boundaries of the affine sub-blocks. Referring to fig. 13, CB (1310) may fill 1 pixel on the boundaries (1321) - (1324). Prediction value correction may be performed for each affine sub-block based on the gradient of the affine sub-block obtained from the block-based gradient calculation. For example, when the MV difference between neighboring affine sub-blocks is small, the block-based gradient calculation, which is a prediction of neighboring blocks, may be similar to or even more accurate than the sub-block-based gradient calculation. When the MV difference is large, a subblock-based gradient calculation may be used.

Block-based gradient computation or sub-block-based gradient computation may be switchable based on a condition. When the condition is satisfied, a block-based gradient calculation may be used, and thus the gradient calculation is performed for the entire CB. Otherwise, if the condition is not satisfied, sub-block based gradient calculations may be used, so the gradient calculation and padding process may be done for each affine sub-block. In some embodiments, a plurality of conditions for selecting between block-based gradient calculations or sub-block-based gradient calculations may be utilized. Additionally, the condition may be based on one or more affine parameters and a threshold or range.

In an embodiment, a condition is that the maximum of the absolute values of affine parameters a, b, c, and d (e.g., max _ parameter { | a |, | b |, | c |, | d | }) is below or not greater than a threshold. In an example, the threshold may correspond to 1 pixel per sample (or pixel/sample), 0.5 pixel per sample, and so on. For example, the threshold is 1 pixel/sample, and the component representing the MV difference over one sample (e.g., x-component, y-component) (or the component of the MVD between two adjacent samples) is 1 pixel. When max _ parameter | a |, the width w of the CB is 4 samples, v1x-v0x is 1 pixel, and max _ parameter 1 pixel/4 samples 0.25 pixel/sample. Thus, max _ parameter is less than the threshold, and thus, any component (e.g., x-component or y-component) of the average MV difference of two neighboring samples in CB is less than the gradient threshold.

In an embodiment, the threshold corresponds to 1 pixel per sample, half a pixel per sample, and so on. In an example, the internal affine motion uses (7+4) ═ 11 bits (e.g., value 2)¹¹2048 corresponds to a displacement of 1 pixel), the sub-block size is 4 × 4 samples. A threshold of 1 pixel per sample corresponds to a value of 512 (e.g., 2)¹¹/4). The threshold value of half a pixel per sample corresponds to the value 256.

In an embodiment, the condition for using the sub-block based gradient calculation may be that the minimum value of the absolute values of affine parameters a, b, c, and d (e.g., min _ parameter { | a |, | b |, | c |, | d |) is higher than or not less than a threshold.

In an embodiment, the condition for using the block-based gradient calculation may be that the absolute values of the affine parameters a, b, c, and d are within a predefined range. The predefined range may be represented as [ M, N ], where M and N are positive numbers. M and N may be predefined or signaled in the encoded codestream, such as signaled in SPS, PPS, tile group header, tile header, slice header, etc.

In an embodiment, such as in block-based gradient computation, padding for the entire CB is used. The neighboring samples of the CB may be filled (or generated) by interpolation using the corresponding sub-block MV of the sub-block including the neighboring samples. The neighboring samples may be generated by copying from the nearest integer sample position in the reference picture of the CB. The neighboring samples may be generated by a predictor from the nearest sample in the CB.

Referring to fig. 13, the neighboring sample (1330) may be generated by copying a prediction value of a sample (1301) closest thereto among CBs (1310). Similarly, the neighboring samples (1331) and neighboring samples (1332) may be generated by copying the predicted values of the samples (1301) that are closest to them.

In an embodiment, the sub-block size is one of: the width of the affine sub-block, the height of the affine sub-block, the width of the affine PROF sub-block used in the PROF for CB, the height of the affine PROF sub-block, the width of the gradient sub-block used in the gradient calculation in the PROF, and the height of the gradient sub-block. The interpolation filter type is one of the following: (i) a first interpolation filter having a first length (e.g., 6 taps) for horizontal interpolation; (ii) a second interpolation filter having a second length (e.g., 8 taps) for horizontal interpolation; (iii) a first interpolation filter having a first length for vertical interpolation; and (iv) a second interpolation filter having a second length for vertical interpolation. As described above, the second length is greater than the first length.

When CB is encoded using a sub-block based affine motion model, each of the following may be conditionally switchable based on at least one of the affine parameters: affine sub-block size, affine sub-block width, affine sub-block height, interpolation filter type, affine PROF sub-block size, affine PROF sub-block width, affine PROF sub-block height, gradient sub-block size, gradient sub-block width, and gradient sub-block height.

In an embodiment, the interpolation filter tap lengths (e.g., 6 taps, 8 taps) and/or parameters for sub-block based affine motion compensation may be selected for horizontal and vertical interpolation, respectively.

In an embodiment, the width and height of the sub-blocks (e.g., affine sub-block, affine PROF sub-block, gradient sub-block) may be individually selected according to at least one of the affine parameters.

In embodiments, the affine parameters used in the condition checking may be a subset of affine parameters or a combination of one or more of the affine parameters.

In an embodiment, different affine parameters or different affine parameter subsets may be used separately for conditional checking of the plurality of switchable sub-block characteristics. As described above, the sub-block characteristics (e.g., affine sub-block size) may be determined based on at least one of the affine parameters (e.g., the maximum of { | a |, | c | }). In one example, another sub-block characteristic (e.g., interpolation filter type) is determined based on at least another one of the affine parameters (e.g., a minimum value of { | a |, | c | }, { | a |, | b |, | c |, | d | }). At least one further parameter of the affine parameters may be different or the same as at least one of the affine parameters, and the further sub-block characteristic may be different from the sub-block characteristic.

In an embodiment, the one or more conditions applied to the selected affine parameters may be one or any combination of the following: minimum, maximum, minimum absolute, maximum absolute, range of values, and/or average. In an example, at least one of the affine parameters comprises a plurality of affine parameters. The sub-block characteristics may be determined based on one of: (i) a threshold and a minimum value, a maximum value, a minimum absolute value, a maximum absolute value, or an average value of the plurality of affine parameters; and (ii) a predefined range (e.g., [ M, N ]) and a range of values for the plurality of affine parameters.

In some examples, an affine motion model of 6 parameters is used as an example. The affine parameters a, b, c, and d described above using equations (7) and (9) may be used to determine affine sub-block size, interpolation filter type (or interpolation filter tap length), applicability of PROF processing to affine, and/or the like. These descriptions may be applicable to other affine motion models (e.g., 4-parameter affine motion models).

In an embodiment, at least one of the affine parameters comprises a plurality of affine parameters. The sub-block size is one of: the width of the affine sub-block, the height of the affine sub-block, the width of the affine PROF sub-block, the height of the affine PROF sub-block, the width of the gradient sub-block, and the height of the gradient sub-block. The interpolation filter type is one of the following: (i) a first interpolation filter (e.g., a 6-tap interpolation filter) for horizontal interpolation; (ii) a second interpolation filter for horizontal interpolation (e.g., an 8-tap interpolation filter); (iii) a first interpolation filter for vertical interpolation (e.g., a 6-tap interpolation filter); and (iv) a second interpolation filter for vertical interpolation (e.g., an 8-tap interpolation filter).

The sub-block characteristics may be determined based on a maximum absolute value of the plurality of affine parameters and a threshold. In an embodiment, in response to the maximum absolute value being greater than the threshold, it may be determined that the sub-block characteristic is indicative of one of: (i) the sub-block size is a first size (e.g., 4 samples), (ii) the interpolation filter type is a first interpolation filter for horizontal interpolation (e.g., a 6-tap interpolation filter), and (iii) the interpolation filter type is a first interpolation filter for vertical interpolation (e.g., a 6-tap interpolation filter). In response to the maximum absolute value being less than or equal to the threshold, it may be determined that the sub-block characteristic is indicative of one of: (i) the sub-block size is a second size (e.g., 8 samples); (ii) the interpolation filter type is a second interpolation filter for horizontal interpolation (e.g., 8-tap interpolation filter); and (iii) the interpolation filter type is a second interpolation filter for vertical interpolation (e.g., an 8-tap interpolation filter).

In an embodiment, in response to the maximum absolute value being greater than or equal to the threshold, it may be determined that the sub-block characteristic is indicative of one of: (i) sub-block size is 4 samples; (ii) the interpolation filter type is a 6-tap interpolation filter for horizontal interpolation; and (iii) the interpolation filter type is a 6-tap interpolation filter for vertical interpolation. In response to the maximum absolute value being less than the threshold, it may be determined that the sub-block characteristic is indicative of one of: (i) sub-block size exceeds 4 samples; (ii) the interpolation filter type is an 8-tap interpolation filter for horizontal interpolation; and (iii) the interpolation filter type is an 8-tap interpolation filter for vertical interpolation.

The width of the affine sub-block may be set based on one or more affine parameters. In an embodiment, for CB, when the maximum value of the absolute values of the affine parameters a and b (e.g., expressed as max _ param _ hor { | a |, | b | }) is greater than the threshold, the width of the affine sub-block may be set to 4 samples (e.g., 4 luma samples). Otherwise, when max _ param _ hor is equal to or less than the threshold, the width of the affine sub-block may be set to K samples (e.g., luma samples). In one example, K is greater than 4, such as 8. In an embodiment, for CB, when the maximum value of the absolute values of the affine parameters a and b is greater than or equal to the threshold, the width of the affine sub-block may be set to 4 samples (e.g., 4 luma samples). Otherwise, when max _ param _ hor is less than the threshold, the width of the affine sub-block may be set to K samples (e.g., luma samples). In one example, K is greater than 4, such as 8.

The height of the affine sub-block may be set based on one or more affine parameters. In an embodiment, for CB, when the maximum value of the absolute values of the affine parameters c and d (e.g., expressed as max _ param _ ver { | max { | c |, | d | }) is higher than the threshold, the height of the affine sub-block may be set to 4 samples. Otherwise, when max _ param _ hor is equal to or lower than the threshold, the height of the affine sub-block may be set to K samples. In one example, K is greater than 4, such as 8. In an embodiment, for CB, when the maximum of the absolute values of affine parameters c and d is higher than or equal to the threshold, the height of the affine sub-block may be set to 4 samples. Otherwise, when max _ param _ hor is below the threshold, the height of the affine sub-block may be set to K samples. In one example, K is greater than 4, such as 8.

The width and height of the affine sub-block may be set based on the first subset and the second subset of affine parameters, respectively. Alternatively, a region including the width and height of the affine sub-block may be set based on one or more of the affine parameters.

The interpolation filters (e.g., the first and second interpolation filters including different numbers of taps) may be set based on one or more affine parameters. In one embodiment, for CB, when the maximum of the absolute values of the affine parameters a and b is above a threshold, the sub-block based affine motion compensation (e.g., sub-block based affine motion compensation for a luma block) may use a 6-tap interpolation filter for horizontal interpolation (e.g., a 6-tap interpolation filter for luma samples). Otherwise, when max _ param _ hor is equal to or lower than the threshold, the sub-block based affine motion compensation may use an 8-tap interpolation filter for horizontal interpolation. In one embodiment, for CB, when the maximum of the absolute values of the affine parameters a and b is higher than or equal to the threshold, the sub-block based affine motion compensation may use a 6-tap interpolation filter for horizontal interpolation. Otherwise, when max _ param _ hor is below the threshold, the sub-block based affine motion compensation may use an 8-tap interpolation filter for horizontal interpolation.

In one embodiment, for CB, when the maximum of the absolute values of affine parameters c and d is above the threshold, sub-block based affine motion compensation (e.g., sub-block based affine motion compensation for luma blocks) may use a 6-tap interpolation filter (e.g., a 6-tap interpolation filter for luma samples) for vertical interpolation. Otherwise, when max _ param _ ver is equal to or lower than the threshold, the sub-block based affine motion compensation may perform vertical interpolation using an 8-tap interpolation filter. In one embodiment, for CB, when the maximum of the absolute values of affine parameters c and d is higher than or equal to the threshold, the sub-block based affine motion compensation may perform vertical interpolation using a 6-tap interpolation filter. Otherwise, when max _ param _ ver is below the threshold, the sub-block based affine motion compensation may use an 8-tap interpolation filter for vertical interpolation.

The width of the affine PROF sub-block may be set based on one or more affine parameters. In one embodiment, for CB, affine PROF may be performed based on the affine PROF sub-block having a width of 4 samples (e.g., luma samples) when the maximum of the absolute values of the affine parameters a and b is above the threshold. Otherwise, affine PROF may be performed based on the affine PROF sub-block having a width of K samples (e.g., luma samples) when max _ param _ hor is equal to or below the threshold. In an example, K is greater than 4, such as 8. In one embodiment, for CB, affine PROF may be performed based on the affine PROF sub-block having a width of 4 samples (e.g., luma samples) when the maximum of the absolute values of the affine parameters a and b is higher than or equal to the threshold. Otherwise, affine PROF may be performed based on the affine PROF sub-block having a width of K samples (e.g., luma samples) when max _ param _ hor is below the threshold. In an example, K is greater than 4, such as 8.

The height of the affine PROF sub-block may be set based on one or more affine parameters. In an embodiment, for CB, affine PROF may be performed based on the height of the affine PROF sub-block being 4 samples (e.g., luma samples) when the maximum of the absolute values of affine parameters c and d is above the threshold. Otherwise, affine PROF may be performed based on the height of the affine PROF sub-block being K samples when max _ param _ hor is equal to or below the threshold. In an example, K is greater than 4, such as 8. In an embodiment, for CB, affine PROF may be performed based on the height of the affine PROF sub-block being 4 samples (e.g., luma samples) when the maximum of the absolute values of affine parameters c and d is higher than or equal to the threshold. Otherwise, affine PROF may be performed based on the height of the affine PROF sub-block being K samples when max _ param _ hor is below the threshold. In an example, K is greater than 4, such as 8.

The width and height of the affine PROF sub-block may be set based on the first and second subsets of affine parameters, respectively. Alternatively, the region including the width and height of the affine PROF sub-block may be set based on one or more of the affine parameters.

Fig. 14 shows a flowchart outlining a method (1400) according to an embodiment of the present application. The method (1400) may be used for reconstruction of a block (e.g., CB) to generate a prediction block for the block in reconstruction. The term "block" may be interpreted as a prediction block, CB, luma CB, CU, PU, etc. In various embodiments, method (1400) is performed by processing circuitry such as processing circuitry in terminal device (210), terminal device (220), terminal device (230), and terminal device (240), processing circuitry performing the function of video encoder (303), processing circuitry performing the function of video decoder (310), processing circuitry performing the function of video decoder (410), processing circuitry performing the function of video encoder (503), and so forth. In some embodiments, the method (1400) is implemented in software instructions, such that when the software instructions are executed by the processing circuitry, the processing circuitry performs the method (1400). The method starts at (S1401) and proceeds to (S1410).

In (S1410), encoding information of a block may be decoded from an encoded video stream. The encoding information may indicate that the block is encoded using a sub-block based affine motion model. The sub-block based affine motion model may comprise affine parameters based on a plurality of CPMVs of the block. The block may comprise an affine sub-block with a corresponding sub-block MV.

The affine parameters may be similar to or the same as the affine parameters described above (e.g., 'a', 'b', 'c','d' in equation (7) -equation (9)). One or more of the affine parameters may indicate a ratio of MV difference (or MVD) to block size (e.g., width of block). Referring to fig. 8A, the first and second affine parameters may indicate a ratio of MVD to width of CB (810A) between CPMV1 and CPMV 0. More specifically, the first affine parameter may indicate a ratio of an x-component of the MVD between CPMV1 and CPMV0 to a width of the block (810A). The second affine parameter may indicate a ratio of a y component of the MVD to a width of the block between CPMV1 and CPMV 0.

Typically, one of the following: (i) a ratio of MVDs to block sizes; (ii) MVDs of two adjacent affine sub-blocks; and (iii) the MVDs of two adjacent samples, may be determined using the other of (i) - (iii). For example, the block includes 16 × 16 samples and is divided into 16 affine sub-blocks having an affine sub-block size of 4 × 4 samples. MVD between CPMV1 and CPMV0 (e.g., mv_1x-mv_0x) Is 4 pixels, so the ratio of MVD to block size is equal to 4 pixels/16 samples-0.25 pixels/sample. Thus, the MVDs of two adjacent samples are 0.25 pixels, and the MVDs of two adjacent affine sub-blocks are 1 pixel.

As described above, in addition to or instead of including "a", "b", "c", and/or "d", the affine parameters may include parameters for describing various motions of the block such as zoom-in/out, rotation, and/or the like.

In (S1420), it may be determined whether to select a sub-block characteristic for generating a prediction value of a sample in one of the affine sub-blocks based on the corresponding sub-block MV, based on the encoding information.

In an example, prediction of a sample refers to prediction using sub-block based affine motion compensation such as described in step (1) with reference to fig. 12 (e.g., initial sub-block prediction value I (I, j)).

The predicted value of the sample may refer to a corrected predicted value. Any suitable predictor modification method (e.g., PROF) may be used to generate a modified predictor. Referring back to fig. 12, in the example, the predicted value refers to a corrected predicted value I' (I, j) that can be obtained based on the initial predicted value I (I, j) and the predicted value correction amount Δ I (I, j).

The sub-block characteristics may indicate a sub-block size used to generate a prediction value for the sample, an interpolation filter type for the affine sub-block, and so on.

The sub-block size may include or indicate a size (e.g., width and/or height) of an affine sub-block, a size (e.g., width and/or height) of an affine PROF sub-block used in a PROF for the block, a size (e.g., width and/or height) of a gradient sub-block used in gradient calculations of the PROF. In an example, the affine sub-block size, affine PROF sub-block size, and gradient sub-block size are the same. In an example, the gradient sub-block size is larger than the affine sub-block size and the affine PROF sub-block size.

The sub-block size may comprise any suitable size (e.g., any suitable width and/or any suitable height). In an example, the sub-block size is conditionally selectable or conditionally switchable between a first size (e.g., a first width and/or a first height) and a second size (e.g., a second width and/or a second height). The second size (e.g., 8 samples or 8 x 8 samples) is larger than the first size (e.g., 4 samples or 4 x 4 samples).

The interpolation filter type may be an interpolation filter having any suitable length (e.g., 6 taps, 8 taps). The interpolation filter type may be one of: (i) a first interpolation filter having a first length (e.g., 6 taps) for horizontal interpolation; (ii) a second interpolation filter having a second length (e.g., 8 taps) for horizontal interpolation; (iii) a first interpolation filter having a first length for vertical interpolation; (iv) a second interpolation filter having a second length for vertical interpolation; (v) a first interpolation filter having a first length for interpolation; and (vi) a second interpolation filter having a second length for interpolation. The second length is greater than the first length. The interpolation filter type may be conditionally selectable or conditionally switchable among a plurality of (i) - (vi).

In response to selecting the sub-block characteristic for generating the predicted value of the sample, the process (1400) proceeds to (S1430). Otherwise, the process (1400) proceeds to (S1499), terminating.

In (S1430), the sub-block characteristics may be determined based on at least one of the affine parameters, as described above. The sub-block characteristic may indicate one of: (i) a sub-block size used in generating a prediction value for a sample; and (ii) interpolation filter type for affine sub-blocks.

In an embodiment, the sub-block characteristics may be determined based on at least one of the affine parameters and one of: (i) a threshold value; and (ii) a predefined range (e.g., [ M, N ]), as described above. The sub-block size may be an affine sub-block size, and the interpolation filter type may include the first interpolation filter or the second interpolation filter.

In an embodiment, the block comprises a gradient sub-block for gradient computation in the PROF, the sub-block size being the size of the gradient sub-block. The gradient calculation is (i) a block-based gradient calculation if the sub-block size is equal to the block size; or (ii) based on gradient calculations of the sub-blocks if the sub-block size is smaller than the block size. In an example, at least one of the affine parameters comprises a plurality of affine parameters. Whether the gradient calculation is based on blocks or sub-blocks may be determined based on one of: (i) a maximum value or a minimum value of absolute values of the plurality of affine parameters and a threshold value; and (ii) absolute values and predefined ranges.

In an embodiment, at least one of the affine parameters comprises a plurality of affine parameters. The sub-block characteristics may be determined based on one of: (i) a threshold and a minimum value, a maximum value, a minimum absolute value, a maximum absolute value, or an average value of the plurality of affine parameters; and (ii) a predefined range (e.g., [ M, N ]) and a value range.

The (S1420) and/or (S1430) may be repeated. For example, both (S1420) and (S1430) may be implemented to determine, for example, an affine sub-block size with sub-block characteristics of 4 × 4 luma samples based on the first subset of affine parameters. The (S1420) and (S1430) may be repeated to determine the sub-block characteristic as a gradient sub-block size, for example, based on the second subset of affine parameters, wherein the gradient sub-block size is a size of the block. Accordingly, the affine sub-block size is 4 × 4 luma samples, and the gradient sub-block size is the size of the block.

In (S1440), samples in the affine sub-block may be reconstructed based on the determined sub-block characteristics. For example, in case the affine sub-block size is 4 × 4 luma samples and the gradient sub-block size is the size of a block, a sub-block based affine motion model with PROF is implemented, wherein the affine PROF sub-block size is equal to the affine sub-block size. Accordingly, a corrected predicted value I' (I, j) may be obtained based on the affine sub-block size and the gradient sub-block size. In an example, the reconstructed sample value may be determined based on the modified predictor I' (I, j) and a residual of the sample (e.g., when the residual is non-zero).

For example, for block-based gradient computation, neighboring samples of the block may be filled by one of: (i) interpolating using a corresponding subblock MV comprising a subblock of the neighboring sample; (ii) copying from an integer sample position in a reference picture of the block that is nearest to the neighboring sample; and (iii) copying from the prediction value of the sample in the block closest to the neighboring sample, wherein the neighboring sample of the block can be used for block-based gradient computation.

The method (1400) may be suitably adapted for various scenarios, and the steps in the method (1400) may be adapted accordingly. One or more of the steps in the method (1400) may be adjusted, omitted, repeated, and/or combined. The method (1400) may be implemented using any suitable order. One (more) additional step(s) may be added.

The embodiments in this application may be used alone or in any order in combination. Further, each of the method (or embodiment), the encoder and the decoder may be implemented by processing circuitry (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 using computer readable instructions and physically stored in one or more computer readable storage media. For example, fig. 15 illustrates a computer system (1500) suitable for implementing certain embodiments of the disclosed subject matter.

The computer software may be encoded using any suitable machine code or computer language that may be subject to assembly, compilation, linking, or similar mechanisms to create code that includes instructions that are executable, either directly or through interpretation, microcode execution, etc., by one or more computer Central Processing Units (CPUs), Graphics Processing Units (GPUs), etc.

The instructions may be executed on various types of computers or computer components, including, for example, personal computers, tablets, servers, smart phones, gaming devices, internet of things devices, and the like.

The components shown in FIG. 15 for computer system (1500) 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 the computer system (1500).

The computer system (1500) may include some human interface input devices. Such human interface input devices may be responsive to input by one or more human users through, for example, tactile input (e.g., keys, swipes, data glove movements), audio input (e.g., speech, taps), visual input (e.g., gestures), olfactory input (not depicted). The human interface device may also be used to capture certain media that are not necessarily directly related to human conscious input, such as audio (e.g., speech, 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 input human interface device may include one or more of the following (only one depicted each): keyboard (1501), mouse (1502), trackpad (1503), touch screen (1510), data glove (not shown), joystick (1505), microphone (1506), scanner (1507), camera (1508).

The computer system (1500) may also include certain human interface output devices. Such human interface output devices may stimulate the perception of one or more human users through, for example, tactile output, sound, light, and smell/taste. Such human interface output devices may include tactile output devices (e.g., touch screen (1510), data gloves (not shown), or tactile feedback of a joystick (1505), although tactile feedback devices that do not serve as input devices may also be present), audio output devices (e.g., speakers (1509), headphones (not depicted)), visual output devices (e.g., screens (1510), including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capability, each with or without tactile feedback capability — some of which are capable of outputting two-dimensional visual output or output greater than three-dimensional by way of, for example, stereoscopic panned output; virtual reality glasses (not depicted), holographic displays, and smoke boxes (not depicted)), and printers (not depicted).

The computer system (1500) may also include human-accessible storage devices and associated media for storage devices, e.g., optical media, including CD/DVD ROM/RW (1520) with media (1521) such as CD/DVD, thumb drive (1522), removable hard or solid state drive (1523), older versions of magnetic media such as tape and floppy disks (not depicted), ROM/ASIC/PLD based application specific devices such as security devices (not depicted), and so forth.

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

The computer system (1500) may also include an interface to one or more communication networks. The network may be, for example, wireless, wired, optical. The network may also be local, wide area, metropolitan area, vehicle and industrial, real time, delay tolerant, etc. Examples of the network include a local area network such as ethernet, wireless LAN, a cellular network including GSM, 3G, 4G, 5G, LTE, etc., a TV cable or wireless wide area digital network including cable TV, satellite TV, and terrestrial broadcast TV, an in-vehicle network including CAN bus, an industrial network, and the like. Certain networks typically require external network interface adapters attached to certain general purpose data ports or peripheral buses (1549), such as USB ports of computer system (1500); other networks are typically integrated into the core of the computer system (1500) by attaching to a system bus as described below (e.g., into a PC computer system through an ethernet interface, or into a smartphone computer system through a cellular network interface). Using any of these networks, the computer system (1500) may communicate with other entities. Such communications may be unidirectional reception only (e.g., broadcast TV), unidirectional transmission only (e.g., CAN bus connected to some CAN bus devices), or bidirectional, e.g., connected to other computer systems using a local area digital network or a wide area digital network. Certain protocols and protocol stacks may be used on each of the networks and network interfaces as those described above.

The human interface device, human accessible storage device, and network interface described above may be attached to the core (1540) of the computer system (1500).

The core (1540) may include one or more Central Processing Units (CPUs) (1541), Graphics Processing Units (GPUs) (1542), dedicated Programmable processing units (1543) in the form of Field Programmable Gate Areas (FPGAs), hardware accelerators (1544) for certain tasks, and so forth. These devices, along with read-only memory (ROM) (1545), random access memory (1546), internal mass storage devices (1547), such as internal non-user accessible hard drives, SSDs, etc., may be connected by a system bus (1548). In some computer systems, the system bus (1548) may be accessible through one or more physical plug forms to enable expansion by additional CPUs, GPUs, and the like. The peripheral devices may be attached to the system bus (1548) of the core either directly or through a peripheral bus (1549). Architectures for peripheral buses include PCI, USB, and the like.

The CPU (1541), GPU (1542), FPGA (1543) and accelerator (1544) may execute certain instructions, which in combination may constitute the above-described computer code. The computer code may be stored in ROM (1545) or RAM (1546). Transitional data may also be stored in RAM (1546), while persistent data may be stored in an internal mass storage device (1547), for example. Fast storage and retrieval of any memory device may be achieved through the use of cache memory, which may be closely associated with one or more CPUs (1541), GPUs (1542), mass storage (1547), ROMs (1545), RAMs (1546), and so on.

Computer readable media 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 (1500), and in particular core (1540), may provide functionality resulting from 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 devices introduced above as well as certain storage of a non-transitory nature of the core (1540), such as core internal mass storage (1547) or ROM (1545). Software implementing various embodiments of the present application may be stored in such devices and executed by the core 1540. The computer readable medium may include one or more memory devices or chips, according to particular needs. The software may cause the core (1540), 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 (1546) and modifying such data structures according to processes defined by the software. Additionally or alternatively, the computer system may provide functionality that results from logic that is hardwired or otherwise embodied in circuitry, such as an accelerator (1544), which may operate in place of or in conjunction with software to perform a particular process or a particular portion of a particular process described herein. References to software may encompass logic, and vice versa, as appropriate. Where appropriate, reference to a computer-readable medium may encompass circuitry (e.g., an Integrated Circuit (IC)) that stores software for execution, circuitry that embodies logic for execution, or both. This application contemplates any suitable combination of hardware and software.

Appendix A: acronyms

JEM: joint development Model, Joint development Model

VVC: versatile Video Coding, multifunctional Video Coding

BMS: benchmark Set, reference Set

MV: motion Vector, Motion Vector

HEVC: high Efficiency Video Coding

SEI: supplementary Enhancement Information

VUI: video Usability Information, Video Usability Information

GOP: groups of Pictures, Groups of Pictures

TU: transform Unit, Transform Unit

PU (polyurethane): prediction Unit, Prediction Unit

And (3) CTU: coding Tree Unit

CTB: coding Tree Block

PB: prediction Block, Prediction Block

HRD: hypothetical Reference Decoder

SNR: signal Noise Ratio, Signal to Noise Ratio

A CPU: central Processing Unit

GPU: graphics Processing Unit

CRT: cathode Ray Tube (Cathode Ray Tube)

LCD: Liquid-Crystal Display (LCD)

An OLED: organic Light-Emitting Diode (OLED)

CD: compact Disc, optical Disc

DVD: digital Video Disc, Digital Video Disc

ROM: Read-Only Memory (ROM)

RAM: random Access Memory (RAM)

ASIC: Application-Specific Integrated Circuit, ASIC

PLD: programmable Logic Device

LAN: local Area Network (LAN)

GSM: global System for Mobile communications, Global System for Mobile communications

LTE: Long-Term Evolution, Long-Term Evolution

CANBus: controller Area Network Bus, Controller Area Network Bus

USB: universal Serial Bus

PCI: peripheral Component Interconnect, Peripheral device Interconnect

FPGA: field Programmable Gate Array

SSD: solid-state drive

IC: integrated Circuit

CU: coding Unit, Coding Unit

AMVP: advanced MVP, Advanced motion vector prediction

HMVP: history-based MVP, History-based motion vector prediction

MMVD: merge with MVD, Merge mode with motion vector difference

MVD: motion vector difference, Motion vector difference

MVP: motion vector predictor

SbTMVP: sub-block-based TMVP based on temporal motion vector prediction of sub-blocks

TMVP: temporal MVP, Temporal motion vector prediction

VTM: versatile test model, multifunctional test model

While this application describes several exemplary embodiments, there are alterations, permutations, and various substitute equivalents, which fall within the scope of this 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 the spirit and scope of the application.

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