Video coding and decoding method and device

文档序号：144879 发布日期：2021-10-22 浏览：32次中文

阅读说明：本技术 视频编解码的方法和装置 (Video coding and decoding method and device ) 是由李贵春李翔许晓中刘杉于 2020-03-19 设计创作，主要内容包括：本公开的方面提供了视频编解码的方法和装置。在一些示例中,该装置包括处理电路,所述处理电路确定当前块的多个子块的多个第一子块运动矢量,并且根据所述多个第一子块运动矢量和第一目标范围,确定多个第二子块运动矢量。所述处理电路还确定与当前子块中的当前样本位置相关联的一组梯度值,确定与所述当前样本位置相关联的调整矢量,并且根据所述一组梯度值和所述调整矢量,确定与所述当前样本位置相关联的一组调整值。所述处理电路根据参考子块中的对应样本和所述一组调整值的组合,生成与所述当前样本位置相关联的预测样本。(Aspects of the present disclosure provide methods and apparatus for video encoding and decoding. In some examples, the apparatus includes a processing circuit that determines a plurality of first sub-block motion vectors for a plurality of sub-blocks of a current block, and determines a plurality of second sub-block motion vectors based on the plurality of first sub-block motion vectors and a first target range. The processing circuit also determines a set of gradient values associated with a current sample position in a current sub-block, determines an adjustment vector associated with the current sample position, and determines a set of adjustment values associated with the current sample position based on the set of gradient values and the adjustment vector. The processing circuit generates a predicted sample associated with the current sample position from a combination of a corresponding sample in a reference sub-block and the set of adjustment values.)

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

determining a plurality of first sub-block motion vectors of a plurality of sub-blocks of a current block according to a plurality of control point motion vectors of the current block;

determining a first target range of the current block along a first coordinate direction;

determining a plurality of second sub-block motion vectors according to the plurality of first sub-block motion vectors and the first target range, wherein the first target range defines a first coordinate direction component of the plurality of second sub-block motion vectors;

determining a set of gradient values associated with a current sample position in a current sub-block of the plurality of sub-blocks according to a reference sub-block identified by a current second sub-block motion vector of the plurality of second sub-block motion vectors, the current second sub-block motion vector corresponding to the current sub-block;

determining an adjustment vector associated with the current sample position based on a plurality of control point motion vectors for the current block;

determining a set of adjustment values associated with the current sample position based on the set of gradient values and the adjustment vector; and

generating a prediction sample associated with the current sample position from a combination of a corresponding sample in the reference sub-block and the set of adjustment values.

2. The method of claim 1,

the first target range defines a maximum difference of integer pixel parts of first coordinate direction components of the plurality of second sub-block motion vectors to be not greater than a first target difference.

3. The method of claim 2, wherein the first target difference is in a range of 0 to 3 integer pixels.

4. The method of claim 2, further comprising:

determining the first target difference according to one or more of a size and a shape of the current block.

5. The method of claim 2, further comprising:

the first target difference is determined from a predetermined value set by a video codec standard or signaled by an encoded video bitstream.

6. The method of claim 1,

the determining a first target range of the current block along a first coordinate direction comprises:

determining one of an upper limit value and a lower limit value of the first target range in the first coordinate direction according to a maximum value or a minimum value of a first coordinate direction component of the plurality of first sub-block motion vectors; and

determining one of the upper and lower values of the first target range in the first coordinate direction and a first target difference according to the determined one of the upper and lower values and the first target difference, and

the determining a plurality of second sub-block motion vectors according to the plurality of first sub-block motion vectors and the first target range comprises:

determining whether a first coordinate direction component of one of the plurality of first sub-block motion vectors is greater than the upper limit value or less than the lower limit value, the one of the plurality of first sub-block motion vectors being for the one of the plurality of sub-blocks;

setting a first coordinate direction component of one of the plurality of second sub-block motion vectors to the upper limit value when it is determined that the first coordinate direction component of one of the plurality of first sub-block motion vectors is greater than the upper limit value, the one of the plurality of second sub-block motion vectors being for one of the plurality of sub-blocks; and

setting the first coordinate direction component of one of the plurality of second sub-block motion vectors as the lower limit value when it is determined that the first coordinate direction component of one of the plurality of first sub-block motion vectors is smaller than the lower limit value.

7. The method of claim 6, wherein determining a plurality of second sub-block motion vectors according to the plurality of first sub-block motion vectors and a first target range further comprises:

setting the first coordinate direction component of one of the plurality of second sub-block motion vectors to be the same as the first coordinate direction component of one of the plurality of first sub-block motion vectors when it is determined that the first coordinate direction component of one of the plurality of first sub-block motion vectors is not greater than the upper limit value and not less than the lower limit value.

8. The method of claim 1, further comprising:

determining a second target range of the current block along a second coordinate direction, the second target range defining a second coordinate direction component of the plurality of second sub-block motion vectors,

wherein the determining the plurality of second sub-block motion vectors is performed according to the plurality of first sub-block motion vectors, the first target range, and the second target range.

9. The method of claim 8,

the first target range defines a first maximum difference of integer pixel parts of first coordinate direction components of the plurality of second sub-block motion vectors to be not more than a first target difference, and

the second target range defines a second maximum difference of integer pixel parts of second coordinate direction components of the plurality of second sub-block motion vectors to be not greater than a second target difference.

10. The method of claim 9,

each of the plurality of sub-blocks has a size of 4 x 4 pixels,

the first target difference is 1 pixel, and

the second target difference is 1 pixel.

11. The method of claim 1, further comprising:

determining a set of adjustment vectors associated with a sample position in the current sub-block according to a plurality of control point motion vectors for the current block, the sample position being a relative position with respect to the current sub-block,

wherein the set of adjustment vectors applies to all other sub-blocks of the current block.

12. The method of claim 1, wherein said determining a set of gradient values is performed based on said reference sub-blocks and a 3-tap filter.

13. An apparatus, comprising:

a processing circuit configured to:

determining a plurality of first sub-block motion vectors of a plurality of sub-blocks of a current block according to a plurality of control point motion vectors of the current block;

determining a first target range of the current block along a first coordinate direction;

determining an adjustment vector associated with the current sample position based on a plurality of control point motion vectors for the current block;

determining a set of adjustment values associated with the current sample position based on the set of gradient values and the adjustment vector; and

generating a prediction sample associated with the current sample position from a combination of a corresponding sample in the reference sub-block and the set of adjustment values.

14. The apparatus of claim 13,

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

determining one of the upper and lower values of the first target range in the first coordinate direction and a first target difference based on the determined other of the upper and lower values,

16. The apparatus of claim 15, wherein the processing circuit is further configured to:

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

Determining the plurality of second sub-block motion vectors further according to the second target range.

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

the set of adjustment vectors applies to all other sub-blocks of the current block.

19. A non-transitory computer-readable medium storing instructions that, when executed by a computer for video decoding, cause the computer to perform:

determining a first target range of the current block along a first coordinate direction;

determining an adjustment vector associated with the current sample position based on a plurality of control point motion vectors for the current block;

determining a set of adjustment values associated with the current sample position based on the set of gradient values and the adjustment vector; and

generating a prediction sample associated with the current sample position from a combination of a corresponding sample in the reference sub-block and the set of adjustment values.

20. The non-transitory computer-readable medium of claim 19,

the determining a first target range of the current block along a first coordinate direction comprises:

the determining a plurality of second sub-block motion vectors according to the plurality of first sub-block motion vectors and the first target range comprises:

Technical Field

The present disclosure describes embodiments that generally relate to video coding.

Background

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

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

One purpose of video encoding and decoding is to reduce redundancy of an 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. Lossless compression and lossy compression, and combinations of both, may be employed. Lossless compression refers to a technique for reconstructing an exact copy of an original signal from a compressed original signal. When lossy compression is used, the reconstructed signal may not be identical to the original signal, but the distortion between the original signal and the reconstructed signal is small enough that the reconstructed signal is useful for the intended application. Lossy compression is widely used for video. The amount of distortion tolerated depends on the application. For example, some users consuming streaming media applications may tolerate higher distortion than users of television applications. The achievable compression ratio reflects: higher allowable/tolerable distortion may result in higher compression ratios.

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

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

h.265/HEVC (ITU-T h.265 recommendation, "high efficiency video codec", 2016 month 12) describes various MV prediction mechanisms. Among the various MV prediction mechanisms provided by h.265, the present disclosure describes techniques referred to hereinafter as "spatial merging.

Referring to fig. 1, a current block (101) includes samples found by an encoder during a motion search, which can be predicted from previous blocks of the same size that have been spatially shifted. Instead of directly coding the MV, the MV is derived from metadata associated with one or more reference pictures, e.g., from the nearest (in decoding order) reference picture, using the MV associated with any of the five neighboring blocks. Of these, five surrounding samples are represented by a0, a1 and B0, B1, B2 (102 to 106, respectively). In h.265, MV prediction can use the prediction value of the same reference picture that neighboring blocks are using.

Disclosure of Invention

Aspects of the present disclosure provide methods and apparatuses for video encoding/decoding. In some examples, the apparatus includes processing circuitry to determine a plurality of first sub-block motion vectors for a plurality of sub-blocks of a current block based on a plurality of control point motion vectors for the current block, determine a first target range for the current block in a first coordinate direction, and determine a plurality of second sub-block motion vectors based on the plurality of first sub-block motion vectors and the first target range, the first target range defining a first coordinate direction component of the plurality of second sub-block motion vectors. The processing circuit also determines a set of gradient values associated with a current sample position in a current sub-block of the plurality of sub-blocks from a reference sub-block identified by a current second sub-block motion vector of the plurality of second sub-block motion vectors, the current second sub-block motion vector corresponding to the current sub-block, determines an adjustment vector associated with the current sample position from a plurality of control point motion vectors for the current block, and determines a set of adjustment values associated with the current sample position from the set of gradient values and the adjustment vector. The processing circuit generates a prediction sample associated with the current sample position from a combination of a corresponding sample in the reference sub-block and the set of adjustment values.

In some embodiments, the first target range defines a maximum difference of integer pixel portions of the first coordinate direction components of the plurality of second sub-block motion vectors to be not greater than a first target difference. In some embodiments, the first target difference is in the range of 0 to 3 integer pixels.

In some embodiments, the processing circuit further determines the first target difference based on one or more of a size and a shape of the current block. In some embodiments, the processing circuit further determines the first target difference based on a predetermined value set by a video codec standard or signaled by an encoded video bitstream.

In some embodiments, the processing circuit may determine the first target range of the current block in the first coordinate direction by determining one of an upper value and a lower value of the first target range in the first coordinate direction according to a maximum value or a minimum value of a first coordinate direction component of the plurality of first sub-block motion vectors, and determining the first target range of the current block in the first coordinate direction by determining the other of the upper value and the lower value of the first target range in the first coordinate direction according to the determined one of the upper value and the lower value and a first target difference.

In some examples, the determining a plurality of second sub-block motion vectors according to the plurality of first sub-block motion vectors and the first target range may include: determining whether a first coordinate direction component of one of the plurality of first sub-block motion vectors is greater than the upper limit value or less than the lower limit value, the one of the plurality of first sub-block motion vectors being for the one of the plurality of sub-blocks; setting a first coordinate direction component of one of the plurality of second sub-block motion vectors to the upper limit value when it is determined that the first coordinate direction component of one of the plurality of first sub-block motion vectors is greater than the upper limit value, the one of the plurality of second sub-block motion vectors being for one of the plurality of sub-blocks; and setting the first coordinate direction component of one of the plurality of second sub-block motion vectors as the lower limit value when it is determined that the first coordinate direction component of one of the plurality of first sub-block motion vectors is smaller than the lower limit value.

In some embodiments, said determining a plurality of second sub-block motion vectors based on said plurality of first sub-block motion vectors and a first target range further comprises: setting the first coordinate direction component of one of the plurality of second sub-block motion vectors to be the same as the first coordinate direction component of one of the plurality of first sub-block motion vectors when it is determined that the first coordinate direction component of one of the plurality of first sub-block motion vectors is not greater than the upper limit value and not less than the lower limit value.

In some embodiments, the processing circuit further determines a second target range for the current block along a second coordinate direction, the second target range defining a second coordinate direction component of the plurality of second sub-block motion vectors. Performing the determining a plurality of second sub-block motion vectors according to the plurality of first sub-block motion vectors, the first target range, and the second target range.

In some embodiments, the first target range defines a first maximum difference of integer pixel portions of the first coordinate direction components of the plurality of second sub-block motion vectors to be not greater than a first target difference. In some embodiments, the second target range defines a second maximum difference of integer pixel portions of second coordinate direction components of the plurality of second sub-block motion vectors to be not greater than a second target difference. In some examples, each of the plurality of sub-blocks has a size of 4 × 4 pixels, the first target difference is 1 pixel, and the second target difference is 1 pixel.

In some embodiments, the processing circuit further determines a set of adjustment vectors associated with sample positions in the current sub-block, the sample positions being relative positions with respect to the current sub-block, according to a plurality of control point motion vectors for the current block. The set of adjustment vectors may be applicable to all other sub-blocks of the current block.

In some embodiments, the determining a set of gradient values is performed according to the reference sub-blocks and a 3-tap filter.

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

Brief description of the drawings

Other features, properties, and various advantages of the disclosed subject matter will be further 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 (200) according to an embodiment.

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

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

Fig. 5 is a schematic diagram of a simplified block diagram of an encoder according to an 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 is a schematic diagram of a 6-parameter (from three control points) affine model according to an embodiment.

Fig. 8B is a schematic diagram of a 4-parameter (from two control points) affine model according to an embodiment.

Fig. 8C is a schematic diagram of a motion vector derived for a sub-block of a current block encoded according to an affine prediction method according to an embodiment.

Fig. 9 is a schematic diagram of spatial and temporal neighboring blocks of a current block encoded according to an affine prediction method according to an embodiment.

Fig. 10 is a schematic diagram of adjusting a motion vector according to an optical flow Prediction Refinement (PROF) method according to an embodiment.

Fig. 11 shows a flowchart of an overview process according to some embodiments of the present disclosure.

Fig. 12 is a schematic diagram of a computer system, according to an embodiment.

Detailed Description

I. Encoder and decoder for video encoding and decoding

Fig. 2 shows 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 embodiment 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, such as a video picture stream captured by the terminal device (210), for transmission over a network (250) to another terminal device (220). The encoded video data is 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 is common in applications such as media services.

In another embodiment, 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, in one example, each of the terminal devices (230) and (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 devices (230) and (240). Each of terminal devices (230) and (240) may also receive encoded video data transmitted by the other of terminal devices (230) and (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 embodiment of fig. 2, the terminal devices (210), (220), (230), and (240) may be a server, a personal computer, and a smartphone, but the principles of the present disclosure may not be limited thereto. Embodiments of the present disclosure are applicable to laptop computers, tablet computers, media players, and/or dedicated video conferencing equipment. Network (250) represents any number of networks that transport encoded video data between terminal devices (210), (220), (230), and (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. The network may include a telecommunications network, a local area network, a wide area network, and/or the internet. For purposes of this disclosure, the architecture and topology of the network (250) may be immaterial to the operation of this disclosure, unless explained below.

As an embodiment of the disclosed subject matter, fig. 3 illustrates the placement of a video encoder and a video decoder in a streaming environment. The disclosed subject matter 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). In an embodiment, the video picture stream (302) includes samples taken by a digital camera. The video picture stream (302) is depicted as a thick line to emphasize a high data amount video picture stream compared to 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 the lower data amount of the encoded video data (304) (or encoded video codestream (304)) as compared to the video picture stream (302), which may be stored on a streaming server (305) for future use. One or more streaming client subsystems, such as client subsystem (306) and client subsystem (308) in fig. 3, may access streaming server (305) to retrieve copies (307) and copies (309) of encoded video data (304). The client subsystem (306) may include, for example, a video decoder (310) in an electronic device (330). The 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 ITU-T H.265. In an embodiment, the Video codec standard being developed is informally referred to as universal Video Coding (VVC), and the disclosed subject matter 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 shows 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 fig. 3 embodiment.

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 labeled). 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 labeled) to the video decoder (410). While in other cases a buffer memory (not labeled) 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 to be configured 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. Of course, for use over traffic packet networks such as the internet, a buffer memory (415) may also be required, which may be relatively large and may be of an adaptive size, and may be implemented at least partially in an operating system or similar element (not labeled) 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 parameter set fragment (not shown) of Supplemental Enhancement Information (SEI message) or 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 subgroup may include a Group of Pictures (GOP), a picture, a tile, a slice, a macroblock, a Coding Unit (CU), a block, a Transform Unit (TU), a Prediction Unit (PU), and so on. The parser (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 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 picture prediction unit (452). In some cases, the intra picture 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 compensating the extracted samples according to the sign (421), the samples may be added to the output of the scaler/inverse transform unit (451), in this case referred to as residual samples or residual signals, by an aggregator (455), 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 that are available to the loop filter unit (456) as symbols (421) from the parser (420). However, in other embodiments, the video compression techniques may also be responsive to meta-information obtained during decoding of previous (in decoding order) portions of the encoded picture or encoded video sequence, as well as to sample values previously reconstructed and loop filtered.

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

In an embodiment, 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 shows 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. 3 embodiment.

Video encoder (503) may receive video samples from a video source (501) (not part of electronics (520) in the fig. 5 embodiment) that may capture video images to be encoded by 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 an embodiment, an encoding loop may include a source encoder (530) (e.g., responsible for creating symbols, such as a symbol stream, based on input pictures and reference pictures to be encoded) and a (local) decoder (533) embedded in the video encoder (503). The decoder (533) reconstructs the symbols to create sample data in a manner similar to the way the (remote) decoder creates the sample data (since any compression between the symbols and the encoded video bitstream is lossless in the video compression techniques considered in the disclosed subject matter). 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. 4. However, referring briefly also to fig. 4, when symbols are available and the entropy encoder (545) and parser (420) are able to losslessly encode/decode the symbols into an encoded 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 disclosed subject matter focuses on decoder operation. The description of the encoder techniques may be simplified because the encoder techniques are reciprocal to the fully described decoder techniques. A more detailed description is only needed in certain areas and is provided below.

During operation, in some embodiments, the source encoder (530) may perform motion compensated predictive coding. The motion compensated predictive coding predictively codes an input picture with reference to one or more previously coded pictures from the video sequence that are designated as "reference pictures". In this way, an encoding engine (532) encodes differences between pixel blocks of an input picture and pixel blocks of a reference picture, which may be selected as a prediction reference for the input picture.

The local video decoder (533) may decode encoded video data, which 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 can be decoded 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 errors. 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, such as 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 blocks of samples (e.g., blocks of 4 x 4, 8 x 8, 4 x 8, or 16 x 16 samples) and encoded block-wise. These blocks may be predictively encoded with reference to other (encoded) blocks that are determined according to the encoding allocation applied to their respective pictures. For example, a block of an I picture may be non-predictive encoded, or the block may be predictive encoded (spatial prediction or intra prediction) with reference to an already encoded block of the same picture. The pixel block of the P picture can be prediction-coded by spatial prediction or by temporal prediction with reference to one previously coded reference picture. A block of a B picture may be prediction coded by spatial prediction or by temporal prediction with reference to one or two previously coded reference pictures.

The video encoder (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 while transmitting the encoded video. The source encoder (530) may treat 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, Supplemental Enhancement Information (SEI) messages, Visual Usability Information (VUI) parameter set segments, and the like.

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

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

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

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

Fig. 6 shows a schematic 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 embodiment of fig. 3.

In an HEVC embodiment, a video encoder (603) receives a matrix of sample values for a processing block, e.g., a prediction block of 8 × 8 samples, etc. A video encoder (603) uses, for example, rate-distortion (rate-distortion) optimization to determine whether to encode the processing block using intra mode, inter mode, or bi-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, such as a mode decision module (not shown) for determining a processing block mode.

In the embodiment of fig. 6, the video encoder (603) comprises 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 processing 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 inter prediction results (e.g., predicted blocks) using any suitable technique based on the inter prediction information. In some embodiments, the reference picture is a decoded reference picture that is decoded based on encoded video information.

An intra encoder (622) is used to receive samples of a current block (e.g., a processing block), in some cases compare the block to a block already encoded in the same picture, generate quantized coefficients after transformation, and in some cases also generate intra prediction information (e.g., intra prediction direction information according to one or more intra coding techniques). In an embodiment, the intra encoder (622) also computes intra prediction results (e.g., predicted blocks) based on the intra prediction information and reference blocks 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 spatial 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 schematic 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 an embodiment, the video decoder (710) is used in place of the video decoder (310) in the fig. 3 embodiment.

In the fig. 7 embodiment, 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, a mode used to encode the block (e.g., intra mode, inter mode, bi-prediction mode, a merge sub-mode of the latter two, or another sub-mode), prediction information (e.g., intra prediction information or inter prediction information) that may identify certain samples or metadata for use by an intra decoder 772 or an inter decoder 780, respectively, residual information in the form of, for example, quantized transform coefficients, and so forth. In an embodiment, when the prediction mode is inter or bi-directional prediction mode, inter prediction information is provided to an inter decoder (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 is only 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 encoder (603), and the video decoder (310), the video decoder (410), and the video decoder (710) may be implemented using one or more processors executing software instructions.

Inter picture prediction mode

In various embodiments, a picture may be divided into a plurality of blocks using a tree structure based partitioning scheme, for example. The resulting block may then be processed according to different processing modes, such as intra-prediction mode, inter-prediction mode (e.g., merge mode, skip mode, advanced motion vector prediction (AVMP) mode), etc. An intra-coded block may be a block coded with intra-prediction mode. Instead, an inter-coded block may be a block that is processed with inter-prediction mode.

In some embodiments, for example in the context of the VVC standard, the motion information may include, for each CU encoded according to an inter prediction mode, a motion vector, a reference picture index, a reference picture list usage index, and other information to be used for inter prediction sample generation. All or part of the motion information may be signaled explicitly or implicitly. When a CU is encoded according to a merge mode, motion information of the current CU may be obtained from neighboring CUs (including candidates derived from spatial and temporal neighboring CUs). When a CU is encoded according to skip mode, the CU may be associated with one PU and have no significant residual coefficients, no motion vector delta to encode, or no reference picture index. In some embodiments, when a CU is not encoded according to the merge mode, the motion information of the current CU may be explicitly transmitted.

In some embodiments, the additional inter coding feature and refinement tool (refinement tool) may include at least (1) extended merge prediction, (2) merge mode with MVD (MMVD), (3) affine motion compensated prediction, (4) sub-block based temporal motion vector prediction (SbTMVP), (5) triangle partition prediction, (6) Combined Inter and Intra Prediction (CIIP), and (7) prediction refinement using optical flow (PROF).

1. Affine prediction mode

In some examples, the motion vector of the current block and/or the motion vector of the sub-block of the current block may be derived using an affine model (e.g., a 6-parameter affine model or a 4-parameter affine model). Fig. 8A is a schematic diagram of a 6-parameter (from three control points) affine model according to an embodiment.

In an example, 6 parameters of an affine encoded block (e.g., current block 802) can be determined by three different locations of the current block (e.g., control points CP0, CP1, and CP2 at the top left, top right, and bottom left corners in FIG. 8A)Also referred to as three Control Point Motion Vectors (CPMV), e.g. CPMV₀、CPMV₁And CPMV₂) To indicate. In some embodiments, for a 6-parameter affine model, the motion vector at sample position (x, y) in the current block (1202) may be derived as:

wherein (mv)_0x，mv_0y) Indicating the upper left corner Control Point (CPMV)₀) Motion vector of (mv)_1x，mv_1y) Indicating the upper right corner Control Point (CPMV)₁) Motion vector of (mv)_2x，mv_2y) Indicating the lower left corner Control Point (CPMV)₂) The motion vector of (2). Further, W represents the width of the current block (802), and H represents the height of the current block (802).

Fig. 8B is a schematic diagram of a 4-parameter (from two control points) affine model according to an embodiment. The simplified affine model may use four parameters to describe motion information of an affine coding block (e.g., current block 802), which may be represented by two motion vectors (also referred to as two CPMVs, e.g., CPMVs) at two different locations of the current block (e.g., control points CP0 and CP1 at the top left and right corners in fig. 8B)₀And CPMV₁) To indicate. In some embodiments, for a 4-parameter affine model, the motion vector at sample position (x, y) in the current block (1202) may be derived as:

wherein (mv)_0x，mv_0y) Indicating the upper left corner Control Point (CPMV)₀) Motion vector of (mv)_1x，mv_1y) Indicating the upper right corner Control Point (CPMV)₁) The motion vector of (2). Further, W represents the width of the current block (802).

In some embodiments, to simplify motion compensated prediction, a sub-block based affine prediction method is applied. Fig. 8C is a schematic diagram of a motion vector derived for a sub-block of a current block encoded according to an affine prediction method according to an embodiment. In fig. 8C, the current block (802) may be divided into a plurality of sub-blocks. In this example, each sub-block may be a 4 × 4 luma sub-block. The sub-block motion vector (MVa-MVp) corresponds to the center of each sub-block, and may be calculated according to the 4-parameter affine prediction method as described above. The sub-block motion vectors may be rounded to, for example, 1/16 fractional precision. A motion-compensated prediction image of the subblock may be generated according to the calculated subblock motion vector.

In some embodiments, the sub-block size of the chroma component may also be set to 4 × 4. The MV of the 4 × 4 chroma sub-block may be calculated as the average of the MVs of the four corresponding 4 × 4 luma sub-blocks.

In some embodiments, the CPMV may be explicitly signaled. In some embodiments, the CPMV may be determined according to various CPMV prediction methods, such as affine merge mode or affine AMVP mode.

1.1 affine merge mode

Fig. 9 is a schematic diagram of spatial neighboring blocks and temporal neighboring blocks of a current block (901) encoded according to an affine prediction method according to an embodiment. As shown, the spatial neighboring blocks are represented as a0, a1, a2, B0, B1, B2, and B3 (902, 903, 907, 904, 905, 906, and 908, respectively), and the temporal neighboring blocks are represented as C0 (912). In some examples, the spatially neighboring blocks a0, a1, a2, B0, B1, B2, and B3 are in the same picture as the current block (901). In some examples, the temporal neighboring block C0 is in a reference picture and corresponds to a location outside the current block (901) and adjacent to the lower right corner of the current block (901).

The motion information candidate list (also referred to as an affine merge candidate list) may be constructed based on motion information of one or more of the spatial neighboring blocks and/or the temporal neighboring blocks using an affine merge mode. In some examples, affine merge mode may be applied when the current block (901) has a width and height equal to or greater than 8 samples. According to the affine merge mode, the CPMV of the current block (901) can be determined based on the motion information candidates on the list. In some examples, the motion information candidate list may include up to five CPMV candidates, and the index may be signaled to indicate which CPMV candidate is to be used for the current block. In some embodiments, the CPMV candidates include all CPMVs of the affine model.

In some embodiments, the affine merge candidate list may have three types of CPVM candidates, including one or more inherited affine candidates, one or more constructed affine candidates, and a zero MV. Inherited affine candidates can be derived by inference from the CPMV of neighboring blocks. The constructed affine candidates can be derived using the translated MVs of the neighboring blocks.

In an example, there may be at most two inherited affine candidates derived from the corresponding affine motion models of the neighboring blocks, including one block from the left neighboring blocks (a0 and a1) and one block from the upper neighboring blocks (B0, B1, and B2). For candidates from the left, the neighboring blocks a0 and a1 may be checked sequentially, and the first available inherited affine candidate from the neighboring blocks a0 and a1 may be taken as the inherited affine candidate from the left. For candidates from above, neighboring blocks B0, B1, and B2 may be sequentially checked, and the first available inherited affine candidate from neighboring blocks B0, B1, and B2 may be taken as the inherited affine candidate from above. In some examples, no pruning check (pruning check) is performed between the two inherited affine candidates.

When a neighboring affine block is identified, corresponding inherited affine candidates to be added to the affine merge list of the current block (901) can be derived from the control point motion vectors of the neighboring affine block. In the example of fig. 9, if the neighboring block a1 is encoded in affine mode, the upper left corner of the block a1 (control point CP 0) may be obtained_A1) The upper right corner (control point CP1)_A1) And the lower left corner (control point CP2)_A1) The motion vector of (2). When the block A1 is encoded using a 4-parameter affine model, it can be determined from the control point CP0_A1And a control point CP1_A1Calculates two CPMVs as inherited affine candidates for the current block (901). When the block A1 is encoded using a 6-parameter affine model, it can be determined from the control point CP0_A1Control point CP1_A1And a control point CP2_A1Calculates three CPMVs as inherited affine candidates for the current block (901).

Furthermore, the constructed affine candidates can be derived by combining the neighboring translational motion information of each control point. The motion information of the control points CP0, CP1, and CP2 is derived from the specified spatially neighboring blocks a0, a1, a2, B0, B1, B2, and B3.

For example, CPMV_k(k ═ 1, 2, 3, 4) represents the motion vector of the kth control point, where CPMV₁Corresponding to the control point CP0, CPMV₂Corresponding to the control point CP1, CPMV₃Corresponding to the control point CP2, CPMV₄Corresponding to a temporal control point based on the temporal neighboring block C0. For CPMV₁The neighboring blocks B2, B3, and a2 may be sequentially checked, and the first available motion vector from the neighboring blocks B2, B3, and a2 may be used as the CPMV₁. For CPMV₂The neighboring blocks B1 and B0 may be sequentially checked, and the first available motion vector from the neighboring blocks B1 and B0 may be used as the CPMV₂. For CPMV₃The neighboring blocks a1 and a0 may be sequentially checked, and the first available motion vector from the neighboring blocks a1 and a0 may be used as the CPMV₃. In addition, if a motion vector of the temporal neighboring block C0 is available, it can be used as the CPMV₄。

CPMV at the acquisition of four control points CP0, CP1, CP2 and the time control points₁、CPMV₂、CPMV₃And CPMV₄Thereafter, an affine merge candidate list may be constructed to include affine merge candidates constructed in the following order: { CPMV₁,CPMV₂,CPMV₃}、{CPMV₁,CPMV₂,CPMV₄}、{CPMV₁,CPMV₃,CPMV₄}、{CPMV₂,CPMV₃,CPMV₄}、{CPMV₁,CPMV₂And { CPMV }, and₁,CPMV₃}. Any combination of three CPMVs may form a 6-parameter affine merge candidate, and any combination of two CPMVs may form a 4-parameter affine merge candidate. In some examples, to avoid the motion scaling process, if the reference index of a set of control pointsOtherwise, the corresponding CPMV combination may be discarded.

In some embodiments, after checking the inherited affine merge candidate and the constructed affine merge candidate, if the list is still not full, a zero MV is inserted at the end of the list.

1.2 affine AMVP mode

In some embodiments, when the current block (901) has a width and height equal to or greater than 16 samples, an affine AMVP mode may be used to construct the motion information candidate list. According to the affine AMVP mode, an affine flag at CU level may be signaled in the bitstream to indicate whether the affine AMVP mode is used, and then another flag may be signaled to indicate whether the 4-parameter affine or 6-parameter affine is used. In affine AMVP mode, the difference of the CPMV of the current block and the corresponding CPMV predictor (CPMVP) can be signaled in the bitstream. In some embodiments, the affine AVMP candidate list may have a size of two candidates, and may be generated by sequentially using four types of CPMV candidates including (1) one or more inherited affine AMVP candidates inferred from CPMVs of one or more neighboring CUs; (2) one or more constructed affine AMVP candidates derived using the shifted MVs of the one or more neighboring CUs; (3) one or more panning MVs from one or more neighboring CUs; and (4) zero MV.

To derive the inherited affine AMVP candidate, in some examples, the order of checking of the inherited affine AMVP candidate is the same as the order of checking of the inherited affine merge candidate. The AVMP candidates may be determined only from affine CUs that have the same reference picture as the current block. In some embodiments, when the inherited affine motion predictor is inserted into the candidate list, no pruning process is applied.

To derive constructed affine AMVP candidates, in some examples, constructed AMVP candidates may be derived from one or more neighboring blocks shown in fig. 9 in the same checking order used in the construction of affine merge candidates. In addition, reference picture indexes of the neighboring blocks are also checked. For example, the first block in check order, which is inter-coded and has the same reference picture as the current block, may be used. In some embodiments, there may be only one constructed affine AMVP candidate. In some embodiments, when the current block is encoded according to a 4-parameter affine model, and the control point motion vectors of the checked neighbor blocks corresponding to its CP0 and CP1 are all available, the set of these control point motion vectors of the checked neighbor blocks may be added as candidates to the affine AMVP list. When the current block is encoded according to the 6-parameter affine model and the control point motion vectors of the checked neighbor blocks corresponding to its CP0, CP1, and CP2 are all available, the set of these control point motion vectors of the checked neighbor blocks may be added as candidates to the affine AMVP list. Otherwise, it may be determined that constructed AMVP candidates from the checked neighboring blocks are not available.

In some embodiments, if the affine AVMP candidate list has less than two candidates after checking the inherited affine AMVP candidate and the constructed AMVP candidate, candidates derived from one or more neighboring blocks according to the translation MV may be added to the affine AVMP candidate list. Finally, if the affine AVMP candidate list is still not full, the list may be populated with zero MVs.

2. Prediction refinement using optical flow (PROF)

In some embodiments, the motion vector for each pixel in the CU may be derived using affine motion model parameters. However, due to the high complexity of performing pixel-based affine prediction and the memory access bandwidth requirements, in some embodiments, a sub-block-based affine motion compensation approach is implemented. In some embodiments, a current block (e.g., a CU) may be divided into a plurality of sub-blocks, each having a size of 4 × 4 and allocated with a sub-block MV derived from a control point MV of the current block. Sub-block based affine motion compensation is a trade-off between improving coding efficiency, complexity and memory access bandwidth, at the cost of reduced prediction accuracy.

In some embodiments, a Predictive Refinement (PROF) approach using optical flow may be implemented to improve sub-block based affine motion compensation to have a more refined granularity of motion compensation. According to the PROF method, after performing sub-block based affine motion compensation, the luma prediction samples may be refined by adding a set of adjustment values derived from optical flow equations.

Fig. 10 is a schematic diagram of adjusting a motion vector according to the PROF method according to an embodiment. In the example shown in FIG. 10, the current block (1010) is divided into four sub-blocks (1012, 1014, 1016, and 1018). Each of the sub-blocks (1012, 1014, 1016, and 1018) has a size of 4 × 4 pixels. The sub-block MV (1020) of sub-block (1012) may be derived from affine prediction and point to the reference sub-block (1032). Initial sub-block prediction samples may be determined from the reference sub-block (1032). The refinement values to be applied to the initial sub-block prediction samples may be calculated as if each prediction sample is located at the position (e.g., position 1032a of sample 1012 a) indicated by the refined MV determined from the sub-block MV (e.g., sub-block MV 1020 of sub-block 1012) adjusted by the adjustment vector av (e.g., adjustment vector av 1042).

In some embodiments, the PROF method may begin by performing sub-block based affine motion compensation to generate initial sub-block prediction samples I (I, j), where I and j correspond to particular samples in the current sub-block. Next, a 3-tap filter [ -1, 0, 1 ] can be used]The spatial gradient g of the initial subblock predicted sample I (I, j) is calculated according to the following equation_x(i, j) and g_y(i,j)。

g_x(I, j) ═ I (I +1, j) -I (I-1, j), and

g_y(i,j)＝I(i,j+1)-I(i,j-1)

the sub-block prediction expands one pixel on each side for gradient computation. In some embodiments, to reduce memory bandwidth and complexity, pixels on the extended boundary may be copied from the nearest integer pixel position in the reference picture. Thus, additional interpolation for the fill area is avoided.

Then, the prediction refinement can be calculated by the optical flow equation:

ΔI(i,j)＝g_x(i,j)*Δv_x(i,j)+g_y(i,j)*Δv_y(i,j)

where Δ V (i, j) (e.g., Δ V1042) is the difference between the pixel MV (denoted by V (i, j)) at sample position (i, j) and the sub-block MV of the sub-block (e.g., sub-block MV 1020) to which pixel position (i, j) belongs. Since the affine model parameters and pixel position relative to the center of the sub-blocks do not vary between sub-blocks, Δ v (i, j) can be calculated for the first sub-block and reused for other sub-blocks in the same CU. In some examples, assuming x and y are the horizontal and vertical positions of Δ v (i, j) relative to the center of the sub-block, Δ v (i, j) may be derived from the following equation:

wherein, Δ v_x(x, y) is the x component of Δ v (i, j), Δ v_y(x, y) is the y component of Δ v (i, j).

For a 4-parameter affine model,

for a 6-parameter affine model,

wherein (V)_0x,V_0y)、(V_1x,V_1y) And (V)_2x,V_2y) Are the top left, top right and bottom left control point motion vectors, and w and h are the width and height of the CU.

Finally, a prediction refinement may be added to the initial sub-block prediction samples I (I, j). The final predicted sample I' according to the PROF method can be generated using the following equation:

I′(i,j)＝I(i,j)+ΔI(i,j)

3. affine sub-block motion vector constraint

In some embodiments, a sub-block motion vector constraint may be introduced to reduce the memory bandwidth of the sub-block based inter prediction mode. In some examples, when an inter block (having a width W and a height H) is encoded according to a sub-block based affine mode (e.g., affine, ATMVP, or flat MV prediction), sub-blocks MV of sub-blocks within an M × N region (M < ═ W, N < ═ H) may be restricted such that the maximum absolute difference between the integer parts of each component of the sub-blocks MV of each prediction list is not greater than some threshold (also referred to as a target difference), e.g., 0, 1, 2, or 3 integer pixels.

In some embodiments, the target difference may be determined according to one or more of a size and a shape of the current block. In some embodiments, the target difference may be a predetermined value set by a video codec standard or a predetermined value signaled by an encoded video bitstream.

Different sub-block motion vector clipping methods may be used to adaptively adjust (or also referred to as "clip" in this disclosure) the sub-block motion vectors of the sub-blocks within the M × N region to within the target range. In some embodiments, the target range may be determined based on the maximum and minimum values of the subblocks MV of the subblock within the M × N region.

In the present disclosure, "xy" denotes "x" of an x component in the x coordinate direction or "y" of a y component in the y coordinate direction, and the described calculation or equation is similarly applied to the x component and the y component. In some embodiments, MV _ i [ xy ] represents the i-th subblock MV (of the target reference list) within the M × N region, fracMvShift [ xy ] represents the number of bits representing the precision of the MV component, maxOffset [ xy ] (((1+ T [ xy ]) < < fracMvShift [ xy ]) -1) represents the maximum allowed difference. In one example, fracMvShift [ xy ] can be set to 4, which represents 1/16 pixel MV precision. Further, T [ xy ] is the maximum integer difference between the subblocks MV of the target reference list. When T xy is set to 0, the sub-blocks MV share the same integer part (for a given component of the target list).

In some embodiments, the target range may be determined from minMv [ xy ] or maxMv [ xy ] (e.g., including a minimum value "minMv [ x ] in the x-coordinate direction, a minimum value" minMv [ y ] in the y-coordinate direction, a maximum value "maxMv [ x ] in the x-coordinate direction, and a maximum value" maxMv [ y ] in the y-coordinate direction). In some embodiments, the range constraint in the x-coordinate direction and the range constraint in the y-coordinate direction may be the same or different. An example is shown in the following pseudo-code:

minMv [ xy ] ═ min (MV _ i [ xy ])); obtaining minimum MV component of subblock MVs of a target reference list

maxMv [ xy ] ═ max (MV _ i [ xy ]); obtaining the maximum MV component of the subblock MV of the target reference list

roundMin [ xy ] ═ minMv [ xy ] > > frammvshift [ xy ] < < frammvshift [ xy ]; // obtaining the integer part of minMv [ xy ]

roundMax [ xy ] (maxMv [ xy ] > > fracMvShift [ xy ] < < fracMvShift [ xy ]) + maxOffset [ xy ]; // obtaining the maximum possible value of the same integer part as maxMv [ xy ]

if((minMv[xy]-roundMin[xy])<(roundMax[xy]-maxMv[xy]))

{// when minMv [ xy ] is closer to an integer, derive based on minMv [ xy ]

minMv[xy]＝roundMin[xy]；

maxMv[xy]＝minMv[xy]+maxOffset[xy]；

}

else

{// when maxMv [ xy ] is closer to integer, derive based on maxMv [ xy ]

maxMv[xy]＝roundMax[xy]；

minMv[xy]＝maxMv[xy]-maxOffset[xy]；

}

Thus, in an example, the target range of the current block in the specific coordinate direction (e.g., x or y coordinate direction) may be determined by determining one of an upper limit value (e.g., maxMv [ xy ]) and a lower limit value (e.g., minMv [ xy ]) of the target range in the specific coordinate direction according to a maximum value (e.g., max (MV _ i [ xy ])) or a minimum value (e.g., min (MV _ i [ xy ])) of the plurality of first sub-block motion vectors in the specific coordinate direction. From one of the determined upper and lower limit values and the target difference (e.g., maxOffset [ xy ]), the other of the upper and lower limit values of the target range in the specific coordinate direction can be determined.

The target range may be defined according to the maximum and minimum values along the x-coordinate or y-coordinate (e.g., maxMv [ xy ] and minMv [ xy ]), to limit the subblock MVs of the target reference list.

In one example, the sub-block MV may be adjusted by first determining whether the sub-block MV in a particular coordinate direction is greater than an upper limit value or less than a lower limit value in the particular coordinate direction. When it is determined that the sub-block MV in the specific coordinate direction is greater than the upper limit value, the sub-block MV in the specific coordinate direction may be set as the upper limit value. When it is determined that the sub-block MV in the specific coordinate direction is less than the lower limit value, the sub-block MV in the specific coordinate direction may be set to the lower limit value. In some examples, when the sub-block MV in the specific coordinate direction is not greater than the upper limit value and not less than the lower limit value, the adjusted sub-block MV may be set to be the same as the initial sub-block MV in the specific coordinate direction. The same procedure may be applied to adjust the x-component of the sub-block MV in the x-coordinate direction and to adjust the y-component of the sub-block MV in the y-coordinate direction.

In some embodiments, each of the plurality of sub-blocks has a size of 4 × 4 pixels, the target difference in the x-coordinate direction is 1 pixel, and the target difference in the y-coordinate direction is 1 pixel.

PROF computation Using clipped subblocks MV

In some embodiments, when both a PROF (e.g., the method described in section ii.2) and an affine sub-block MV constraint (e.g., the method described in section ii.3) are applied to the current block, the sub-block motion vector for each sub-block may first be generated by an affine model and then adjusted according to the sub-block MV constraint. The prediction samples may be determined from the adjusted sub-block MV using a PROF method.

For example, as described in section ii.2, a PROF for affine includes the calculation of a trim vector Δ v (i, j), which is the motion vector difference between a pixel MV determined for a sample position (i, j), denoted as v (i, j), and the corresponding sub-block MV of the sub-block to which the sample position (i, j) belongs. The subblock MV of the PROF may be the subblock MV (denoted as SBMV) which has been adapted according to the affine subblock MV constraint described in section II.3_clip). Thus, the relationship between the pixel MV and the adjustment vector can be expressed as:

Δv(i,j)＝v(i,j)-SBMV_clip。

in some embodiments, each of the plurality of sub-blocks may have a size of 4 × 4 pixels, and the target difference in the x-coordinate direction may be set to 1 pixel and the target difference in the y-coordinate direction may be set to 1 pixel.

Fig. 11 shows a flowchart outlining a process (1100) according to some embodiments of the present disclosure. The process (1100) may be used to encode or decode a current block of a current picture, including obtaining a predicted image of the current block according to a stacked affine prediction method. In some embodiments, one or more operations are performed before or after process (1100), and some of the operations shown in FIG. 11 may be reordered or omitted.

In various embodiments, process (1100) is performed by processing circuitry, e.g., processing circuitry in terminal devices (210), (220), (230), and (240), processing circuitry that performs the functions of video decoder (310), processing circuitry that performs the functions of video decoder (410), etc. In some embodiments, process (1100) is implemented in software instructions, such that when processing circuitry executes the software instructions, the processing circuitry performs process (1100). The process starts from (S1101) and proceeds to (S1110).

At (S1110), a plurality of first sub-block motion vectors of a plurality of sub-blocks of the current block are determined according to a plurality of control point motion vectors of the current block. In some embodiments, the plurality of control point motion vectors and the first sub-block motion vector of the current block may be determined according to the examples described with reference to section ii.1 and fig. 8A-8C and 9.

At (S1120), one or more target ranges for defining sub-block motion vectors of the current block are determined. At (S1130), a plurality of second sub-block motion vectors may be determined according to the plurality of first sub-block motion vectors and one or more target ranges in (S1120).

In some embodiments, the first target range of the current block in the first coordinate direction (e.g., x-coordinate direction) may be determined according to the examples described with reference to section ii.3. In some embodiments, the second target range of the current block in the second coordinate direction (e.g., the y-coordinate direction) may be determined according to the examples described with reference to section ii.3.

In some embodiments, the first target range defines a maximum difference of integer pixel parts of the first coordinate direction components of the plurality of second sub-block motion vectors to be not greater than the first target difference. In some embodiments, the second target range defines a maximum difference of integer pixel parts of the second coordinate direction components of the plurality of second sub-block motion vectors to be not greater than the second target difference.

In some embodiments, the first target difference and the second target difference may be the same or different. In some embodiments, the first target difference or the second target difference is in the range of 0 to 3 integer pixels. In some embodiments, the first target difference or the second target difference may be determined according to one or more of a size and a shape of the current block. In some embodiments, the first target difference or the second target difference may be determined according to a predetermined value set by a video codec standard, or a predetermined value signaled by an encoded video bitstream.

In some embodiments, the first target range of the current block in the first coordinate direction may be determined by determining one of an upper limit value and a lower limit value of the first target range in the first coordinate direction according to a maximum value or a minimum value of the first coordinate direction components of the plurality of first sub-block motion vectors, and determining the other of the upper limit value and the lower limit value of the first target range in the first coordinate direction according to the determined one of the upper limit value and the lower limit value and the first target difference. The second target range may be determined in a similar manner according to the second target difference and the second coordinate direction components of the plurality of first sub-block motion vectors.

In some embodiments, the plurality of second sub-block motion vectors may be determined according to the plurality of first sub-block motion vectors and the first target range and/or the second target range. For example, the second sub-block motion vector may be determined from the first sub-block motion vector, where both sub-block motion vectors correspond to the same sub-block. For a component in the first coordinate direction, it is determined whether a first coordinate direction component of the first sub-block motion vector is greater than an upper limit value or less than a lower limit value of the first coordinate direction. When it is determined that the first coordinate direction component of the first sub-block motion vector is greater than the upper limit value, the first coordinate direction component of the second sub-block motion vector may be set as the upper limit value. In addition, when it is determined that the first coordinate direction component of the first sub-block motion vector is less than the lower limit value, the first coordinate direction component of the second sub-block motion vector may be set as the lower limit value. In some embodiments, when it is determined that the first coordinate direction component of the first sub-block motion vector is not greater than the upper limit value and not less than the lower limit value, the first coordinate direction component of the second sub-block motion vector is set to be the same as the first coordinate direction component of the first sub-block motion vector. The second coordinate direction component may be determined in a similar manner from the upper and lower limit values of the second coordinate direction.

In some embodiments, each of the plurality of sub-blocks may have a size of 4 × 4 pixels, the first target difference may be set to 1 pixel, and the second target difference may be set to 1 pixel.

At (S1140), a set of gradient values associated with a current sample position in a current sub-block of the plurality of sub-blocks is determined based on a reference sub-block identified by a current second sub-block motion vector of the plurality of second sub-block motion vectors, the current second sub-block motion vector corresponding to the current sub-block. In some embodiments, the set of gradient values may be determined according to the examples described with reference to section ii.2 and fig. 10.

At (S1150), an adjustment vector associated with the current sample position may be determined based on the plurality of control point motion vectors for the current block. In some embodiments, the adjustment vector may be determined according to the example described with reference to section ii.2 and fig. 10.

At (S1160), a set of adjustment values associated with the current sample position may be determined based on the set of gradient values and the adjustment vector. In some embodiments, the set of adjustment values may be determined according to the examples described with reference to section ii.2 and fig. 10.

At (S1170), a prediction sample associated with the current sample position is generated from a combination of the corresponding sample in the reference sub-block and the set of adjustment values. In some embodiments, the prediction samples may be determined according to the examples described with reference to section ii.2 and fig. 10.

After (S1170), the process (1100) may proceed to (S1199) and end.

The embodiments described herein may be used alone or in any order in combination. Furthermore, each of the embodiments, 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, the one or more processors execute a program stored in a non-transitory computer readable medium.

IV. computer system

The techniques described above may be implemented as computer software via computer readable instructions and physically stored in one or more computer readable media. For example, fig. 12 illustrates a computer system (1200) suitable for implementing certain embodiments of the disclosed subject matter.

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

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

The components illustrated in FIG. 12 for the computer system (1200) are exemplary in nature and are not intended to limit the scope of use or functionality of the computer software implementing embodiments of the present disclosure in any way. 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 (1200).

The computer system (1200) may include some human interface input devices. Such human interface input devices may respond to input from one or more human users through tactile input (e.g., keyboard input, swipe, data glove movement), audio input (e.g., sound, applause), visual input (e.g., gestures), olfactory input (not shown). The human-machine interface device may also be used to capture media that does not necessarily directly relate to human conscious input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, photographic images obtained from still-image cameras), video (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

The human interface input device may include one or more of the following (only one of which is depicted): keyboard (1201), mouse (1202), touch pad (1203), touch screen (1210), data glove (not shown), joystick (1205), microphone (1206), scanner (1207), camera (1208).

The computer system (1200) may also include certain human interface output devices. Such human interface output devices may stimulate the senses of one or more human users through, for example, tactile outputs, sounds, light, and olfactory/gustatory sensations. Such human interface output devices may include haptic output devices (e.g., haptic feedback through a touch screen (1210), data glove (not shown), or joystick (1205), but there may also be haptic feedback devices that do not act as input devices), audio output devices (e.g., speakers (1209), headphones (not shown)), visual output devices (e.g., screens (1210) including cathode ray tube screens, liquid crystal screens, plasma screens, organic light emitting diode screens, each with or without touch screen input functionality, each with or without haptic feedback functionality-some of which may output two-dimensional visual output or more than three-dimensional output by means such as stereoscopic picture output; virtual reality glasses (not shown), holographic displays and smoke boxes (not shown)), and printers (not shown).

The computer system (1200) may also include human-accessible storage devices and their associated media, such as optical media including compact disc read-only/rewritable (CD/DVD ROM/RW) (1220) or similar media (1221) with CD/DVD, thumb drives (1222), removable hard drives or solid state drives (1223), conventional magnetic media such as magnetic tapes and floppy disks (not shown), ROM/ASIC/PLD based proprietary devices such as security dongle (not shown), and the like.

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

The computer system (1200) may also include an interface to one or more communication networks. For example, the network may be wireless, wired, optical. The network may also be a local area network, a wide area network, a metropolitan area network, a vehicular network, an industrial network, a real-time network, a delay tolerant network, and so forth. The network also includes ethernet, wireless local area networks, local area networks such as cellular networks (GSM, 3G, 4G, 5G, LTE, etc.), television wired or wireless wide area digital networks (including cable, satellite, and terrestrial broadcast television), automotive and industrial networks (including CANBus), and so forth. Some networks typically require external network interface adapters for connecting to some general purpose data ports or peripheral buses (1249) (e.g., USB ports of computer system (1200)); other systems are typically integrated into the core of the computer system (1200) by connecting to a system bus as described below (e.g., an ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks, the computer system (1200) may communicate with other entities. The communication may be unidirectional, for reception only (e.g., wireless television), unidirectional for transmission only (e.g., CAN bus to certain CAN bus devices), or bidirectional, for example, to other computer systems over a local or wide area digital network. Each of the networks and network interfaces described above may use certain protocols and protocol stacks.

The human interface device, human accessible storage device, and network interface described above may be connected to the core (1240) of the computer system (1200).

The core (1240) may include one or more Central Processing Units (CPUs) (1241), Graphics Processing Units (GPUs) (1242), special purpose programmable processing units in the form of Field Programmable Gate Arrays (FPGAs) (1243), hardware accelerators (1244) for specific tasks, and so forth. These devices, as well as Read Only Memory (ROM) (1245), random access memory (1246), internal mass storage (e.g., internal non-user accessible hard drives, solid state drives, etc.) (1247), and so forth, may be connected by a system bus (1248). In some computer systems, the system bus (1248) may be accessed in the form of one or more physical plugs, so as to be expandable by additional central processing units, graphics processing units, and the like. The peripheral devices may be attached directly to the system bus (1248) of the core or connected through a peripheral bus (1249). The architecture of the peripheral bus includes peripheral component interconnect PCI, universal serial bus USB, etc.

The CPU (1241), GPU (1242), FPGA (1243) and accelerator (1244) may execute certain instructions, which in combination may constitute the computer code. The computer code may be stored in ROM (1245) or RAM (1246). Transitional data may also be stored in RAM (1246), while persistent data may be stored in, for example, internal mass storage (1247). Fast storage and retrieval of any memory device can be achieved through the use of cache memory, which can be closely associated with one or more CPUs (1241), GPUs (1242), mass storage (1247), ROM (1245), RAM (1246), and the like.

The computer-readable medium may have computer code thereon for performing various computer-implemented operations. The media and computer code may be those specially designed and constructed for the purposes of the present disclosure, 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 an architecture (1200), and in particular a core (1240), may provide functionality as a processor (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media may be media associated with the user-accessible mass storage described above, as well as certain memory having a non-volatile core (1240), such as core internal mass storage (1247) or ROM (1245). Software implementing various embodiments of the present disclosure may be stored in such devices and executed by the core (1240). The computer-readable medium may include one or more memory devices or chips, according to particular needs. The software may cause the core (1240), 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 (1246) and modifying such data structures according to software-defined processes. Additionally or alternatively, the computer system may provide functionality that is logically hardwired or otherwise embodied in circuitry (e.g., an accelerator (1244)) that may operate in place of or in conjunction with software to perform certain processes or certain portions of certain processes described herein. Where appropriate, reference to software may include logic and vice versa. Where appropriate, reference to a computer-readable medium may include circuitry (e.g., an Integrated Circuit (IC)) storing executable software, circuitry comprising executable logic, or both. The present disclosure includes any suitable combination of hardware and software.

Appendix A: acronyms

AMVP: advanced Motion Vector Prediction (Advanced Motion Vector Prediction)

ASIC: Application-Specific Integrated Circuit (Application-Specific Integrated Circuit)

BMS: reference Set (Benchmark Set)

CANBus: controller Area Network Bus (Controller Area Network Bus)

CD: compact Disc (Compact Disc)

CPMV: control Point Motion Vector (Control Point Motion Vector)

CPUs: central Processing unit (Central Processing Units)

CRT: cathode Ray Tube (Cathode Ray Tube)

CTUs: coding Tree unit (Coding Tree Units)

CU: coding Unit (Coding Unit)

DVD: digital Video Disc (Digital Video Disc)

FPGA: field Programmable Gate array (Field Programmable Gate Areas)

GBi: generalized Bi-prediction (Generalized Bi-prediction)

GOPs: picture group (Groups of Pictures)

GPUs: graphic Processing unit (Graphics Processing Units)

GSM: global System for Mobile communications

HEVC: high Efficiency Video Coding and decoding (High Efficiency Video Coding)

HMVP: history-based Motion Vector Prediction

HRD: hypothetical Reference Decoder (Hypothetical Reference Decoder)

IC: integrated Circuit (Integrated Circuit)

JEM: joint development Model (Joint Exploration Model)

LAN: local Area Network (Local Area Network)

LCD: LCD Display (Liquid-Crystal Display)

LTE: long Term Evolution (Long-Term Evolution)

MMVD: merging with motion vector differences (Merge with MVD)

MV: motion Vector (Motion Vector)

MVD: motion Vector Difference (Motion Vector Difference)

MVP: motion Vector prediction (Motion Vector Predictor)

An OLED: organic Light Emitting Diode (Organic Light-Emitting Diode)

PBs: prediction block (Prediction Blocks)

PCI: peripheral Component Interconnect (Peripheral Component Interconnect)

PLD: programmable Logic Device (Programmable Logic Device)

And (4) PUs: prediction Units (Prediction Units)

RAM: random Access Memory (Random Access Memory)

ROM: Read-Only Memory (Read-Only Memory)

SEI: auxiliary Enhancement Information (supplement Enhancement Information)

SNR: Signal-to-Noise Ratio (Signal Noise Ratio)

SSD: solid state Drive (Solid-state Drive)

SPS: sequence Parameter Set (Sequence Parameter Set)

SbTMVP: sub-block based Temporal Motion Vector Prediction (Subblock-based Temporal Motion Vector Prediction)

TMVP: temporal Motion Vector Prediction (Temporal Motion Vector Prediction)

TUs: transformation unit (Transform Units)

USB: universal Serial Bus (Universal Serial Bus)

VTM: general test model (Versatile test model)

VUI: video Usability Information (Video Usability Information)

VVC: general purpose video encoding and decoding (versatile video coding)

While this disclosure has described several exemplary embodiments, various modifications, permutations and various equivalents thereof are within the scope of this disclosure. 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 disclosure and are thus within its spirit and scope.

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Video coding and decoding method and device

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