Motion vector constraints for out-of-frame conditions

Abstract

Aspects of the present disclosure provide a method and apparatus for video decoding. The apparatus includes a processing circuit that determines motion information of a current block. The motion information indicates one or more reference blocks of the current block. If the motion information constraint indicates that the one or more reference blocks are within a picture boundary of one or more reference pictures, respectively, the processing circuit reconstructs the current block based on the one or more reference blocks. If a first motion vector (MV) points from a region within the current block to a first reference region of the first reference block that is outside the picture boundary of the first reference picture, the processing circuit determines a first clipping MV that points from the region to an updated first reference region by clipping the first MV, where the updated first reference region is within the picture boundary.

Description

[Technical field]

[0001] [Incorporated by reference] This application claims the benefit of priority to U.S. Patent Application No. 17 / 965,737 entitled "MOTION VECTOR RESTRICTION FOR OUT-OF-FRAME BOUNDARY CONDITIONS," filed October 13, 2022, which claims the benefit of priority to U.S. Provisional Application No. 63 / 298,774 entitled "MV RESTRICTION OF BI-PREDICTION FOR OUT-OF-FRAME BOUNDARY CONDITIONS," filed January 12, 2022. The entire disclosure of the prior application is incorporated by reference.

[0002] [Technical field] This disclosure describes embodiments generally related to video coding. [Background technology]

[0003] The background discussion provided herein is intended to generally present the context of the present disclosure. Work of the inventors named in this application, to the extent that their work is described in this background section, and aspects of this description that may not otherwise qualify as prior art at the time of filing, are not admitted, either explicitly or implicitly, as prior art to the present disclosure.

[0004] An uncompressed digital image and / or video may include a sequence of pictures, each having spatial dimensions of, for example, 1920x1080 luminance samples and associated chrominance samples. The sequence of pictures may have a fixed or variable picture rate (also informally known as frame rate), for example, 60 pictures per second or a picture rate of 60 Hz. Uncompressed images and / or videos have specific bitrate requirements. For example, 1080p60 4:2:0 video (1920x1080 luminance sample resolution at a frame rate of 60 Hz) with 8 bits per sample requires a bandwidth approaching 1.5 Gbit / s. One hour of such video requires more than 600 Gbytes of storage space.

[0005] One objective of image and / or video encoding and decoding may be the reduction of redundancy in the input image and / or video signal through compression. Compression may help to reduce the aforementioned bandwidth and / or storage space requirements, in some cases by more than one order of magnitude. Although the description herein uses video encoding / decoding as an illustrative example, the same techniques may be equally applicable to image encoding / decoding without departing from the spirit of this disclosure. Both lossless and lossy compression, as well as combinations thereof, may be used. Lossless compression refers to techniques whereby an exact copy of the original signal can be reconstructed from the compressed original signal. When using lossy compression, the reconstructed signal may not be identical to the original signal, but the distortion between the original and reconstructed signals is small enough to make the reconstructed signal useful for the intended application. For video, lossy compression is widely used. The amount of acceptable distortion depends on the application, e.g., users of a particular consumer streaming application may tolerate higher distortion than users of a television distribution application. The achievable compression ratio may reflect that a higher tolerable / acceptable distortion can result in a higher compression ratio.

[0006] Video encoders and decoders can utilize techniques from a number of broad categories, including, for example, motion compensation, transform processing, quantization, and entropy coding.

[0007] Video codec techniques can include a technique known as intra-coding. In intra-coding, sample values ​​are represented without reference to samples or other data from previously reconstructed reference pictures. In some video codecs, a picture is spatially divided into blocks of samples. If all blocks of samples are coded in intra mode, the picture may be an intra picture. Intra pictures and their derivatives, such as independent decoder refresh pictures, can be used to reset the decoder state and thus can be used as the first picture in a coded video bitstream and video session or as a still image. Samples of an intra block can be subjected to a transform, and the transform coefficients can be quantized before entropy coding. Intra prediction can be a technique that minimizes sample values ​​in the pre-transform domain. In some cases, the smaller the DC value and the smaller the AC coefficients after the transform, the fewer bits are needed for a given quantization step size to represent the block after entropy coding.

[0008] Traditional intra-coding, e.g., as used in MPEG-2 generation coding techniques, does not use intra-prediction. However, some newer video compression techniques include techniques that attempt to perform prediction based on, e.g., surrounding sample data and / or metadata obtained during the encoding / decoding of a block of data. Such techniques are referred to below as "intra-prediction" techniques. Note that, at least in some cases, intra-prediction uses only reference data from the current picture being reconstructed, and not from reference pictures.

[0009] There may be various forms of intra prediction. If more than one such technique is available for a given video coding technique, the particular technique used may be coded as a particular intra prediction mode using the particular technique. In certain cases, an intra prediction mode may have sub-modes and / or parameters that may be coded separately or may be included in a mode codeword that defines the prediction mode. Which codeword is used for a given mode, sub-mode and / or parameter combination may affect the coding efficiency gain through intra prediction, as well as the entropy coding technique used to convert the codeword into a bitstream.

[0010] Certain modes of intra prediction were introduced in H.264, refined in H.265, and further refined in newer coding techniques such as the Joint Exploration Model (JEM), Versatile Video Coding (VVC), and Benchmark Set (BMS). A predictor block can be formed using neighboring sample values ​​of already available samples. The sample values ​​of the neighboring samples are copied to the predictor block according to a certain direction. The reference to the direction used can be coded in the bitstream or it may be predicted itself.

[0011] Referring to FIG. 1A, at the bottom right, a subset of 9 known predictor directions is depicted from the 33 possible predictor directions defined in H.265 (corresponding to the 33 angle modes out of the 35 intra modes). The point (101) where the arrows converge represents the sample to be predicted. The arrows represent the direction in which the sample is predicted. For example, arrow (102) indicates that sample (101) is predicted from the sample(s) to the top right and at an angle of 45 degrees from the horizontal. Similarly, arrow (103) indicates that sample (101) is predicted from the sample(s) to the bottom left of sample (101), at an angle of 22.5 degrees from the horizontal.

[0012] 1A, at the top left, a square block (104) of 4×4 samples is depicted (indicated by a thick dashed line). The square block (104) contains 16 samples, each labeled with an “S” and its position in the Y dimension (e.g., row index) and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample (from the top) in the Y dimension and the first sample (from the left) in the X dimension. Similarly, sample S44 is the fourth sample in the block (104) in both the Y and X dimensions. Since the block is 4×4 samples in size, S44 is at the bottom right. Additionally, a reference sample is shown that follows a similar numbering scheme. The reference sample is labeled R and its Y position (e.g., row index) and X position (column index) relative to the block (104). In both H.264 and H.265, the predicted samples are neighbors of the block being reconstructed, so there is no need to use negative values.

[0013] Intra-picture prediction can work by copying reference sample values ​​from neighboring samples indicated by a signaled prediction direction. For example, assume that the coded video bitstream includes signaling for this block indicating a prediction direction that is consistent with the arrow (102). That is, the sample is predicted from the top right sample at an angle of 45 degrees from the horizontal. Then samples S41, S32, S23, and S14 are predicted from the same reference sample R05. Then sample S44 is predicted from reference sample R08.

[0014] In certain cases, especially when the direction is not divisible by 45 degrees, the values ​​of multiple reference samples may be combined, for example by interpolation, to calculate the reference sample.

[0015] As video coding techniques have developed, the number of possible directions has increased. In H.264 (2003), nine different directions could be represented. This increased to 33 in H.265 (2013). Currently, JEM / VVC / BMS can support up to 65 directions. Experiments are performed to identify the most likely directions, and specific techniques in entropy coding are used to represent those more likely directions with a small number of bits, while accepting some penalty for the less likely directions. Furthermore, the direction itself can sometimes be predicted from nearby directions used in nearby already decoded blocks.

[0016] FIG. 1B shows a schematic diagram (110) depicting 65 intra prediction directions with JEM to illustrate the increasing number of prediction directions over time.

[0017] The mapping of intra-prediction direction bits in the coded video bitstream to represent directions can vary from one video coding technique to another. Such mappings can range, for example, from simple direct mappings to complex adaptation schemes involving codewords, most probable modes, and similar techniques. However, in most cases, there may be certain directions that are statistically less likely to occur in the video content than other certain directions. Since the goal of video compression is to reduce redundancy, in a well-performing video coding technique, such less likely ways are represented by a larger number of bits than more probable directions.

[0018] Image and / or video encoding and decoding can be performed using inter-picture prediction with motion compensation. Motion compensation can be a lossy compression technique and can refer to a technique in which blocks of sample data from a previously reconstructed picture or part thereof (reference picture) are used for prediction of a newly reconstructed picture or part thereof after being spatially shifted in a direction indicated by a motion vector (hereinafter MV). In some cases, the reference picture can be the same as the picture currently being reconstructed. The MV can have two dimensions, X and Y, or three dimensions, with the third dimension being an indication of the reference picture used (which can indirectly be the temporal dimension).

[0019] In some video compression techniques, the MV applicable to a region of sample data can be predicted from other MVs, e.g., from an MV associated with another region of sample data that is spatially adjacent to the region being reconstructed and precedes it in decoding order. Doing so can significantly reduce the amount of data required to encode the MV, thereby removing redundancy and increasing compression. MV prediction can work effectively because, for example, when encoding an input video signal derived from a camera (known as natural video), there is a statistical probability that regions larger than the region to which a single MV is applicable move in a similar direction and can therefore be predicted, in certain cases, using similar motion vectors derived from the MVs of nearby regions. As a result, the MV found for a given region will be similar or identical to the MV predicted from the surrounding MVs, which, after entropy encoding, can be represented with fewer bits than would be used if encoding the MVs directly. In some cases, MV prediction can be an example of lossless compression of a signal (i.e., an MV) derived from the original signal (i.e., a sample stream). In other cases, the MV prediction itself may be lossy, for example due to rounding errors in computing the predictor from several surrounding MVs.

[0020] Various MV prediction mechanisms are described in H.265 / HEVC (ITU-T Rec. H.265, "High Efficiency Video Coding", December 2016). Among the many MV prediction mechanisms provided by H.265, one that will be described with reference to FIG. 2 is a technique hereafter referred to as "spatial merge".

[0021] Referring to Figure 2, a current block (201) contains samples that the encoder found during the motion search process to be predictable from a previous block of the same size but spatially shifted. Instead of directly encoding its MV, the MV can be derived from metadata associated with one or more reference pictures, for example from the most recent reference picture (in decoding order) using MVs associated with any of the five surrounding samples, denoted A0, A1, and B0, B1, B2 (202-206, respectively). In H.265, MV prediction can use predictors from the same reference picture that neighboring blocks use. Summary of the Invention

[0022] Aspects of the present disclosure provide methods and apparatus for video encoding and decoding. In some examples, the apparatus for video decoding includes a processing circuit. The processing circuit is configured to determine motion information of a current block predicted with inter prediction. The motion information indicates one or more reference blocks of the current block associated with one or more reference pictures, respectively. If the motion information constraint indicates that the one or more reference blocks are within a picture boundary of the one or more reference pictures, respectively, the processing circuit can reconstruct the current block based on the one or more reference blocks. A first motion vector (MV) indicated by the motion information can point from an area in the current block to a first reference area that is an area of ​​the first reference block in the one or more reference blocks. If the first reference region is outside a picture boundary of a first reference picture of the one or more reference pictures and the picture boundary includes the picture boundary of the first reference picture, the processing circuit can determine a first clipping MV that points from an area in the current block to the updated first reference region by clipping the first MV such that the updated first reference region is within an updated first reference block that is within the picture boundary of the first reference picture. The processing circuit can reconstruct an area in the current block based on the updated first reference region.

[0023] In one embodiment, the current block is bidirectionally predicted in an adaptive motion vector prediction (AMVP) mode. The motion information indicates a first MV that points from the current block to a first reference block and a second MV that points from the current block to a second reference block associated with a second reference picture. The one or more reference blocks are composed of a first reference block and a second reference block. The motion information constraint indicates that the first reference block is within a picture boundary of the first reference picture, and the second reference block is within a picture boundary of the second reference picture, and the picture boundary includes the picture boundary of the second reference picture.

[0024] In one embodiment, the motion information indicates MV predictor (MVP) candidates in a candidate list, and the MVP candidates indicate a first MVP and a second MVP. The first MVP points to a first intermediate reference block corresponding to the current block within a picture boundary of a first reference picture. The second MVP points to a second intermediate reference block corresponding to the current block within a picture boundary of a second reference picture. The processing circuit can determine a first MV based on the first MVP and a first MV difference (MVD), and determine a second MV based on the second MVP and a second MVD. The second MV points to a second reference block.

[0025] In one embodiment, the current block is bidirectionally predicted in affine mode and includes a plurality of sub-blocks. The motion information indicates MV pairs, each associated with one of the plurality of sub-blocks. Each MV pair associated with a respective sub-block in the plurality of sub-blocks includes a first MV pointing from the respective sub-block to a first reference sub-block in the first reference block and a second MV pointing from the respective sub-block to a second reference sub-block in the second reference block associated with the second reference picture. The one or more reference blocks are composed of a first reference block and a second reference block. The motion information constraint indicates that each of the first reference sub-blocks is within a picture boundary of the first reference picture and each of the second reference sub-blocks is within a picture boundary of the second reference picture, the picture boundary including the picture boundary of the second reference picture.

[0026] In one embodiment, the current block is bidirectionally predicted in merge mode, and the candidate list of the current block includes one or more MV predictor (MVP) candidates. The processing circuit can determine an MVP candidate for the current block from one or more MVP candidates based on the MVP index. The MVP candidate indicates a first MVP associated with the first reference picture and a second MVP associated with the second reference picture. The processing circuit can determine that the first MV of the current block is the first MVP and the second MV of the current block is the second MVP. The motion information constraint indicates that (i) the first reference block pointed to by the first MV is within a picture boundary of the first reference picture, and (ii) the second reference block pointed to by the second MV is within a picture boundary of the second reference picture. The picture boundary includes the picture boundary of the second reference picture.

[0027] In one embodiment, for each MVP candidate in the one or more MVP candidates indicating a respective first MVP and a respective second MVP, the motion information constraint indicates that (i) a first intermediate reference block pointed to by the respective first MVP is within the picture boundary of the respective first reference picture, and (ii) a second intermediate reference block pointed to by the respective second MVP is within the picture boundary of the respective second reference picture.

[0028] In one embodiment, the current block is bidirectionally predicted in affine merge mode and includes a plurality of sub-blocks, and the candidate list of the current block includes one or more affine merge candidates. For each sub-block in the plurality of sub-blocks, the processing circuitry can determine, for each region in the respective sub-block, an MV pair for the respective region based on the affine merge candidates in the one or more affine merge candidates. The MV pair includes a respective first MV that points from the region to a first region in a first reference sub-block in a first reference block, and a respective second MV that points from the region to a second region in a second reference sub-block in a second reference block associated with a second reference picture. The first and second reference blocks correspond to the current block, and the first and second reference sub-blocks correspond to the respective sub-blocks. For each sub-block in the plurality of sub-blocks, the motion information constraint indicates that a respective first region is within a picture boundary of a first reference picture and a respective second region is within a picture boundary of a second reference picture, where the picture boundary includes the picture boundary of the second reference picture.

[0029] In one embodiment, the current block is bidirectionally predicted. The motion information indicates a first MV that points from the current block to a first reference block and a second MV that points from the current block to a second reference block associated with a second reference picture. The one or more reference blocks are composed of a first reference block and a second reference block. A first reference region of the first reference block is outside a picture boundary of the first reference picture. The processing circuit can determine a first clipping MV by clipping the first MV such that the updated first reference block is within a picture boundary of the first reference picture. If the second reference block is outside a picture boundary of the second reference picture, the processing circuit can determine a second clipping MV by clipping the second MV such that the updated second reference block is within a picture boundary of the second reference picture. The second clipping MV points from the current block to the updated second reference block, and the picture boundary includes the picture boundary of the second reference picture.

[0030] In one embodiment, the current block is bidirectionally predicted in affine mode and includes a plurality of subblocks. For each subblock in the plurality of subblocks, the processing circuitry can determine, for each region in the respective subblock, an MV pair for the respective region using the affine mode. The MV pair includes a respective first MV pointing from the region to a first reference region in a first reference subblock in a first reference block, and a second MV pointing from the region to a second reference region in a second reference subblock in a second reference block associated with a second reference picture. The first reference block and the second reference block correspond to the current block, and the first reference subblock and the second reference subblock correspond to the respective subblocks. The first reference region is in a first reference subblock in the first reference block, and the region in the current block is in a subblock of the plurality of subblocks corresponding to the first reference subblock. The first reference region is outside the picture boundary of the first reference picture. The processing circuit can determine a first clipping MV by clipping the first MV, where the first clipping MV points to a first reference region updated from a region within the sub-block.

[0031] Aspects of the present disclosure also provide a non-transitory computer-readable storage medium storing a program executable by at least one processor to perform a method for video decoding. [Brief description of the drawings]

[0032] Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and the accompanying drawings. [Figure 1A] FIG. 2 is a schematic diagram of an example subset of intra-prediction modes. [Figure 1B] FIG. 2 is an illustration of an exemplary intra-prediction direction. [Diagram 2] An example of a current block (201) and its surrounding samples in one example is shown. [Diagram 3] FIG. 3 is a schematic diagram of an example block diagram of a communication system (300). [Figure 4] FIG. 4 is a schematic diagram of a simplified block diagram of a communication system (400) according to an embodiment. [Diagram 5] FIG. 2 is a schematic diagram of an example block diagram of a decoder. [Figure 6] FIG. 2 is a schematic diagram of an example block diagram of an encoder; [Figure 7] 1 shows a block diagram of an exemplary encoder. [Figure 8] 1 shows a block diagram of an exemplary decoder. [Figure 9] 1 illustrates locations of spatial merge candidates according to one embodiment of the present disclosure. [Figure 10] 1 illustrates candidate pairs considered for redundancy checking of spatial merge candidates according to one embodiment of the present disclosure. [Figure 11] 13 illustrates an example motion vector scaling for temporal merge candidates. [Figure 12] 13 illustrates example candidate positions for temporal merge candidates for the current coding unit. [Figure 13] 1 shows examples of adaptive motion vector resolution (AMVR) shift values ​​corresponding to motion vector resolution (MVR). [Figure 14A] 1 illustrates an exemplary correction of motion vector differences in affine adaptive motion vector prediction (AMVP) mode and when AMVR mode is enabled. [Figure 14B] 1 illustrates an exemplary correction of motion vector differences in affine adaptive motion vector prediction (AMVP) mode and when AMVR mode is enabled. [Figure 15A] 4 shows the affine motion field for a block when a four-parameter affine model is used. [Figure 15B] 4 shows the affine motion field for a block when a six-parameter affine model is used. [Figure 16] 1 illustrates an example of sub-block based affine transform prediction. [Figure 17] An example of determining control point motion vector (CPMV) candidates in the affine merge list of a current CU will be described. [Figure 18] 1 shows examples of spatial and temporal neighbors of the current block. [Figure 19] 1 shows an example of a reference picture for a current block and a reference block for the current block. [Figure 20] 1 shows a flowchart outlining an encoding process according to one embodiment of the present disclosure. [Figure 21] 1 shows a flowchart outlining a decoding process according to one embodiment of the present disclosure. [Figure 22] FIG. 1 is a schematic diagram of a computer system according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] FIG. 3 illustrates an example block diagram of a communication system (300). The communication system (300) includes a plurality of terminal devices that can communicate with each other, for example, via a network (350). For example, the communication system (300) includes a first pair of terminal devices (310) and (320) interconnected via the network (350). In the example of FIG. 3, the first pair of terminal devices (310) and (320) perform a unidirectional transmission of data. For example, the terminal device (310) may encode video data (e.g., a stream of video pictures captured by the terminal device (310)) for transmission to the other terminal device (320) via the network (350). The encoded video data may be transmitted in the form of one or more encoded video bitstreams. The terminal device (320) may receive the encoded video data from the network (350), decode the encoded video data to reconstruct the video pictures, and display the video pictures according to the reconstructed video data. One-way data transmission may be common, such as in media service applications.

[0034] In another example, the communication system (300) includes a second pair of terminal devices (330) and (340) performing bidirectional transmission of encoded video data, for example during a video conference. For the bidirectional transmission of data, in one example, each of the terminal devices (330) and (340) may encode video data (e.g., a stream of video pictures captured by the terminal device) for transmission to the other of the terminal devices (330) and (340) over the network (350). Each of the terminal devices (330) and (340) may receive the encoded video data transmitted by the other of the terminal devices (330) and (340), decode the encoded video data to reconstruct the video pictures, and display the video pictures on an accessible display device in accordance with the reconstructed video data.

[0035] In the example of FIG. 3, terminal devices (310), (320), (330), and (340) are shown as a server, a personal computer, and a smartphone, respectively, although the principles of the present disclosure may not be so limited. Embodiments of the present disclosure find application in laptop computers, tablet computers, media players, and / or dedicated video conferencing equipment. Network (350) represents any number of networks that convey encoded video data between terminal devices (310), (320), (330), and (340), including, for example, wired (wired) and / or wireless communication networks. Communications network (350) may exchange data in circuit-switched and / or packet-switched channels. Exemplary networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of discussion herein, the architecture and topology of network (350) may not be important to the operation of the present disclosure, unless otherwise described below.

[0036] 4 shows a video encoder and a video decoder in a streaming environment as an example of an application for the disclosed subject matter. The disclosed subject matter may be equally applicable to other video-enabled applications including, for example, video conferencing, digital TV, streaming services, storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0037] The streaming system may include a video source (401), e.g., a digital camera, and may include a capture subsystem (413) that generates, e.g., a stream of uncompressed video pictures (402). In one example, the stream of video pictures (402) includes samples captured by a digital camera. The stream of video pictures (402), depicted as a thick line to emphasize its high data volume compared to the encoded video data (404) (or encoded video bitstream), may be processed by an electronic device (420) that includes a video encoder (403) coupled to the video source (401). The video encoder (403) may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter, as described in more detail below. The encoded video data (404) (or encoded video bitstream), depicted as a thin line to emphasize its lower data volume compared to the stream of video pictures (402), may be stored in a streaming server (405) for future use. One or more streaming client subsystems, such as the client subsystems (406) and (408) of FIG. 4, can access the streaming server (405) to retrieve copies (407) and (409) of the encoded video data (404). The client subsystem (406) can include a video decoder (410), for example within an electronic device (430). The video decoder (410) decodes an input copy (407) of the encoded video data and generates an output stream (411) of video pictures that can be rendered on a display (412) (e.g., a display screen) or other rendering device (not shown). In some streaming systems, the encoded video data (404), (407), and (409) (e.g., a video bitstream) can be encoded according to a particular video encoding / compression standard. Examples of these standards include ITU-T Recommendation H.265.In one example, the developing video coding standard is informally known as Versatile Video Coding (VVC), and the disclosed subject matter may be used in the context of VVC.

[0038] It is noted that electronic devices 420 and 430 may include other components (not shown). For example, electronic device 420 may include a video decoder (not shown), and electronic device 430 may also include a video encoder (not shown).

[0039] 5 shows an example block diagram of a video decoder (510). The video decoder (510) can be included in an electronic device (530). The electronic device (530) can include a receiver (531) (e.g., a receiving circuit). The video decoder (510) can be used in place of the video decoder (310) in the example of FIG. 4.

[0040] The receiver (531) may receive one or more coded video sequences to be decoded by the video decoder (510). In some embodiments, one coded video sequence is received at a time, and the decoding of each coded video sequence is independent of the decoding of the other coded video sequences. The coded video sequences may be received from a channel (501), which may be a hardware / software link to a storage device that stores the coded video data. The receiver (531) may receive the coded video data together with other data, such as coded audio data and / or auxiliary data streams, which may be forwarded to respective usage entities (not shown). The receiver (531) may separate the coded video sequences from the other data. To combat network jitter, a buffer memory (515) may be coupled between the receiver (531) and the entropy decoder / parser (520) (hereinafter the "parser"). In certain applications, the buffer memory (515) is part of the video decoder (510). In other applications, it may be external to the video decoder (510) (not shown). In still other applications, there may be a buffer memory (not shown) external to the video decoder (510), e.g., to combat network jitter, and yet another buffer memory (515) internal to the video decoder (510), e.g., to handle playback timing. If the receiver (531) is receiving data from a store / forward device of sufficient bandwidth and controllability, or from an isochronous network, the buffer memory (515) may not be needed or may be small. For use with best-effort packet networks such as the Internet, the buffer memory (515) may be required and may be relatively large, advantageously of adaptive size, and may be implemented at least in part in an operating system or similar element (not shown) external to the video decoder (510).

[0041] The video decoder (510) may include a parser (520) for reconstructing symbols (521) from the coded video sequence. These categories of symbols include information used to manage the operation of the video decoder (510) and potentially information for controlling a rendering device such as a render device (512) (e.g., a display screen). The rendering device may not be an integral part of the electronic device (530) as shown in FIG. 5, but may be coupled to the electronic device (530). The control information for the rendering device(s) may be in the form of Supplementary Enhancement Information (SEI messages) or Video Usability Information (VUI) parameter set fragments (not shown). The parser (520) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may follow a video coding technique or standard and may follow various principles including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, etc. The parser (520) can extract from the coded video sequence a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder based on at least one parameter corresponding to the group. The subgroups can include Groups of Pictures (GOPs), pictures, tiles, slices, macroblocks, Coding Units (CUs), blocks, Transform Units (TUs), Prediction Units (PUs), etc. The parser (520) can also extract information from the coded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, etc.

[0042] The parser (520) can perform an entropy decoding / parsing operation on the video sequence received from the buffer memory (515) to generate symbols (521).

[0043] The reconstruction of symbols (521) can involve several different units, depending on the type of coded video picture or portions thereof (e.g., inter and intra pictures, inter and intra blocks) and other factors. Which units are involved and how can be controlled by subgroup control information parsed by the parser (520) from the coded video sequence. The flow of such subgroup control information between the parser (520) and the following units is not depicted for clarity.

[0044] In addition to the functional blocks already mentioned, the video decoder (510) can be conceptually divided into a number of functional units, as described below. In a practical implementation operating under commercial constraints, many of these units will interact closely with each other and may be at least partially integrated with each other. However, for purposes of describing the disclosed subject matter, the following conceptual subdivision into functional units is adequate.

[0045] The first unit is a scalar / inverse transform unit (551). The scalar / inverse transform unit (551) receives quantized transform coefficients and control information as symbol(s) (521) from the parser (520). The control information includes which transform to use, block size, quantization factor, quantization scaling matrix, etc. The scalar / inverse transform unit (551) can output blocks containing sample values ​​that can be input to an aggregator (555).

[0046] In some cases, the output samples of the scaler / inverse transform (551) may relate to intra-coded blocks, which are blocks that do not use prediction information from a previously reconstructed picture, but can use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by an intra-picture prediction unit (552). In some cases, the intra-picture prediction unit (552) generates a block of the same size and shape as the block being reconstructed using surrounding already reconstructed information taken from a current picture buffer (558). The current picture buffer (558) buffers, for example, a partially reconstructed current picture and / or a fully reconstructed current picture. The aggregator (555) optionally adds, on a sample-by-sample basis, the prediction information generated by the intra-prediction unit (552) to the output sample information provided by the scaler / inverse transform unit (551).

[0047] In other cases, the output samples of the scalar / inverse transform unit (551) may relate to an inter-coded, potentially motion-compensated block. In such cases, the motion compensation prediction unit (553) may access a reference picture memory (557) to fetch samples used for prediction. After motion compensating the fetched samples according to the symbols (521) for the block, these samples may be added by an aggregator (555) to the output of the scalar / inverse transform unit (in this case referred to as residual samples or residual signals) to generate output sample information. The addresses in the reference picture memory (557) from which the motion compensation unit (553) fetches prediction samples may be controlled by motion vectors available to the motion compensation unit (553) in the form of symbols (521). The symbols may have, for example, X, Y, and reference picture components. Motion compensation may include interpolation of sample values ​​fetched from the reference picture memory (557) when subsample accurate motion vectors are used, motion vector prediction mechanisms, and the like.

[0048] The output samples of the aggregator (555) may be subjected to various loop filtering techniques in a loop filter unit (556). Video compression techniques may include in-loop filter techniques controlled by parameters contained in the coded video sequence (also called the coded video bitstream) and made available to the loop filter unit (556) as symbols (521) from the parser (520). Video compression may also be responsive to meta-information obtained during decoding of previous portions (in decoding order) of the coded picture or coded video sequence, as well as to previously reconstructed loop filtered sample values.

[0049] The output of the loop filter unit (556) can be a sample stream, which can be output to a render device (512) or stored in a reference picture memory (557) for use in future inter-picture prediction.

[0050] Once a coded picture is fully reconstructed, it can be used as a reference picture for future prediction. For example, once a coded picture corresponding to a current picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by the parser (520)), the current picture buffer (558) can become part of the reference picture memory (557), and a fresh current picture buffer can be reallocated before starting the reconstruction of a subsequent coded picture.

[0051] The video decoder (510) may perform decoding operations according to a given video compression technique or standard, such as ITU-T Recommendation H.265. The encoded video sequence may be compliant with the syntax prescribed by the video compression technique or standard being used, in the sense that the encoded video sequence follows the syntax of the video compression technique or standard and a profile documented in the video compression technique or standard. In particular, a profile may select a particular tool from all tools available in the video compression technique or standard as the only tool available for use under that profile. Compliance may also require that the complexity of the encoded video sequence be within a range defined by a level of the video compression technique or standard. In some cases, the level constrains the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in units of megasamples per second), maximum reference picture size, etc. The limits set by the level may be further constrained through a Hypothetical Reference Decoder (HRD) specification and metadata for HRD buffer management, possibly signaled in the encoded video sequence.

[0052] In some embodiments, the receiver (531) may receive additional (redundant) data along with the encoded video. The additional data may be included as part of the encoded video sequence(s). The additional data may be used by the video decoder (510) to properly decode the data and / or to more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0053] 6 shows an example block diagram of a video encoder (603). The video encoder (603) is included in an electronic device (620). The electronic device (620) includes a transmitter (640) (e.g., a transmission circuit). The video encoder (603) can be used in place of the video encoder (403) in the example of FIG. 4.

[0054] The video encoder (603) can receive video samples from a video source (601) (which is not part of the electronic device (620) in the example of FIG. 6) that can capture video images to be encoded by the video encoder (603). In another example, the video source (601) is part of the electronic device (620).

[0055] The video source (601) may provide a source video sequence to be encoded by the video encoder (603) in the form of a digital video sample stream that may be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 YCrCB, RGB, ...) and any suitable sampling structure (e.g., YCrCb 4:2:0, YCrCb 4:4:4). In a media service system, the video source (601) may be a storage device that stores pre-prepared video. In a video conferencing system, the video source (601) may be a camera that captures image information locally as a video sequence. The video data may be provided as a number of individual pictures that impart motion when viewed in sequence. The pictures themselves may be organized as a spatial array of pixels, each of which may contain one or more samples, depending on the sampling structure, color space, etc., in use. Those skilled in the art can easily understand the relationship between pixels and samples. The following description focuses on samples.

[0056] According to an embodiment, the video encoder (603) can encode and compress pictures of a source video sequence into an encoded video sequence (643) in real time or under any other required time constraint. Enforcing an appropriate encoding rate is one function of the controller (650). In some embodiments, the controller (650) controls and is operatively coupled to other functional units, such as those described below. Such couplings are not depicted for clarity. Parameters set by the controller (650) can include parameters related to rate control (picture skip, quantizer, lambda value for rate-distortion optimization techniques, ...), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. The controller (650) can be configured to have other suitable functions for the video encoder (603) optimized for a particular system design.

[0057] In some embodiments, the video encoder (603) is configured to operate in an encoding loop. As a simplistic description, in one example, the encoding loop can include a source encoder (630) (e.g., responsible for generating symbols, such as a symbol stream, based on an input picture to be encoded and a reference picture(s)) and a (local) decoder (633) embedded in the video encoder (603). The decoder (633) reconstructs the symbols to generate sample data in a similar manner that a (remote) decoder would also generate. The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since the decoding of the symbol stream results in bit-exact results regardless of the decoder location (local or remote), the contents of the reference picture memory (634) are also bit-exact between the local and remote encoders. In other words, the prediction part of the encoder "sees" exactly the same sample values ​​as the decoder "sees" when using the prediction during decoding as reference picture samples. This basic principle of reference picture synchrony (and the resulting drift when synchrony cannot be maintained, for example due to channel errors) is also used in several related techniques.

[0058] The operation of the "local" decoder (633) may be the same as the operation of a "remote" decoder, e.g., the video decoder (410), already described in detail above in connection with Figure 5. However, referring also briefly to Figure 5, because symbols are available and the encoding / decoding of the symbols into a coded video sequence by the entropy coder (645) and parser (420) may be lossless, the entropy decoding portion of the video decoder (410), including the buffer memory (415) and the parser (420), may not be fully implemented in the local decoder (633).

[0059] In some embodiments, the decoder techniques, except for parsing / entropy decoding, present in the decoder are present in the same or substantially the same functional form in the corresponding encoder. Thus, the disclosed subject matter focuses on the decoder operation. A description of the encoder techniques can be omitted, since they are the inverse of the decoder techniques described generically. In certain areas, more detailed descriptions are provided below.

[0060] During operation, in some examples, the source encoder (630) may perform motion-compensated predictive encoding, which predictively encodes an input picture with reference to one or more previously encoded pictures from a video sequence, designated as “reference pictures.” In this manner, the encoding engine (632) encodes differences between pixel blocks of the input picture and pixel blocks of a reference picture(s) that may be selected as predictive references for the input picture.

[0061] The local video decoder (633) can decode the encoded video data of the pictures that may be designated as reference pictures based on the symbols generated by the source encoder (630). The operation of the encoding engine (632) can advantageously be a lossy process. When the encoded video data can be decoded in a video decoder (not shown in FIG. 6), the reconstructed video sequence can be a copy of the source video sequence, typically with some errors. The local video decoder (633) can replicate the decoding process that may be performed on the reference pictures by the video decoder and store the reconstructed reference pictures in the reference picture memory (634). In this way, the video encoder (603) can locally store copies of reconstructed reference pictures that have common content (in the absence of transmission errors) as the reconstructed reference pictures that would be obtained by the far-end video decoder.

[0062] The predictor (635) may perform a prediction search for the coding engine (632). That is, for a new picture to be coded, the predictor (635) may search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or specific metadata, such as reference picture motion vectors, block shapes, etc., that may serve as suitable prediction references for the new picture. The predictor (635) may operate on a sample block-by-pixel block basis to find suitable prediction references. In some cases, as determined by the search results obtained by the predictor (635), the input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (634).

[0063] The controller (650) may manage the encoding operations of the source encoder (630), including, for example, setting the parameters and subgroup parameters used to encode the video data.

[0064] The output of all of the above functional units may undergo entropy coding in an entropy coder (645), which converts the symbols produced by the various functional units into a coded video sequence by applying lossless compression to the symbols according to techniques such as Huffman coding, variable length coding, arithmetic coding, etc.

[0065] The transmitter (640) can buffer the encoded video sequence generated by the entropy encoder (645) and prepare it for transmission over a communication channel (660), which may be a hardware / software link to a storage device that stores the encoded video data. The transmitter (640) can merge the encoded video data from the video encoder (630) with other data to be transmitted, such as encoded audio data and / or auxiliary data streams (sources not shown).

[0066] The controller (650) may manage the operation of the video encoder (603). During encoding, the controller (650) may assign a certain coding picture type to each coded picture. The coding picture type may affect the coding technique that may be applied to each picture. For example, pictures may often be assigned as one of the following picture types:

[0067] An intra picture (I-picture) may be one that can be coded and decoded without using other pictures in a sequence as a source of prediction. Some video codecs allow different types of intra pictures, including, for example, Independent Decoder Refresh ("IDR") pictures. Those skilled in the art will recognize these variations of I-pictures and their respective uses and characteristics.

[0068] A predictive picture (P-picture) may be one that can be encoded and decoded using intra- or inter-prediction, which uses at most one motion vector and reference index to predict the sample values ​​of each block.

[0069] Bidirectionally predicted pictures (B-pictures) may be those that can be coded and decoded using intra- or inter-prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multi-predictive pictures can use more than two reference pictures and associated metadata for the reconstruction of a single block.

[0070] A source picture is usually spatially divided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and may be coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks, as determined by the coding assignment applied to the respective picture of the block. For example, blocks of an I-picture may be non-predictively coded or may be predictively coded with reference to already coded blocks of the same picture (spatial or intra prediction). Pixel blocks of a P-picture may be predictively coded via spatial prediction or via temporal prediction with reference to one previously coded reference picture. Blocks of a B-picture may be predictively coded via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

[0071] The video encoder (603) may perform encoding operations according to a given video encoding technique or standard, such as ITU-T Recommendation H.265. In its operations, the video encoder (603) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancy in the input video sequence. Thus, the encoded video data may conform to a syntax specified by the video encoding technique or standard used.

[0072] In some embodiments, the transmitter (640) may transmit additional data along with the encoded video. The source encoder (630) may include such data as part of the encoded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0073] A video may be captured as multiple source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often abbreviated as intra-prediction) exploits spatial correlation in a given picture, while inter-picture prediction exploits correlation (temporal or other) between pictures. In one example, a particular picture to be coded / decoded, called a current picture, is divided into blocks. If a block in the current picture is similar to a reference block in a previously coded and still buffered reference picture in the video, that block in the current picture can be coded by a vector called a motion vector. A motion vector points to a reference block in a reference picture, and may have a third dimension that identifies the reference picture if multiple reference pictures are used.

[0074] In some embodiments, bi-prediction techniques can be used in inter-picture prediction. According to bi-prediction techniques, two reference pictures are used, such as a first reference picture and a second reference picture, both of which precede the current picture in decoding order (but may also be past and future, respectively, in display order) in the video. A block in the current picture can be coded by a first motion vector that points to a first reference block in the first reference picture and a second motion vector that points to a second reference block in the second reference picture. A block can be predicted by a combination of the first and second reference blocks.

[0075] Furthermore, to improve coding efficiency, merge mode techniques can be used in inter-picture prediction.

[0076] According to some embodiments of the present disclosure, predictions such as inter-picture prediction and intra-picture prediction are performed on a block-by-block basis. For example, according to the HEVC standard, pictures in a sequence of video pictures are divided into coding tree units (CTUs) for compression, and the CTUs in a picture have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTU includes three coding tree blocks (CTBs), one luma CTB and two chroma CTBs. Each CTU can be recursively quadtree partitioned into one or more coding units (CUs). For example, a CTU of 64×64 pixels can be partitioned into one CU of 64×64 pixels, or four CUs of 32×32 pixels, or 16 CUs of 16×16 pixels. In one example, each CU is analyzed to determine a prediction type for that CU, such as an inter prediction type or an intra prediction type. A CU is divided into one or more prediction units (PUs) depending on temporal and / or spatial predictability. In general, each PU includes a luma prediction block (PB) and two chroma PBs. In an embodiment, prediction operations in coding (encoding / decoding) are 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 values ​​(e.g., luma values) for pixels, such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, etc.

[0077] 7 shows an example diagram of a video encoder (703). The video encoder (703) is configured to receive a processed block of sample values ​​(e.g., a predictive block) in a current video picture in a sequence of video pictures and to encode the processed block into a coded picture that is part of a coded video sequence. In one example, the video encoder (703) is used in place of the video encoder (403) in the example of FIG. 4.

[0078] In an HEVC example, the video encoder (703) receives a matrix of sample values ​​for a processing block, such as a predictive block, such as 8×8 samples. The video encoder (703) determines whether the processing block is best coded using intra mode, inter mode, or bi-predictive mode, e.g., using rate-distortion optimization. If the processing block is coded in intra mode, the video encoder (703) may use intra prediction techniques to code the processing block into a coded picture. If the processing block is coded in inter mode or bi-predictive mode, the video encoder (703) may use inter prediction techniques or bi-predictive techniques, respectively, to code the processing block into a coded picture. In certain video coding techniques, a merge mode may be an inter-picture prediction sub-mode in which motion vectors are derived from one or more motion vector predictors, but without the benefit of coded motion vector components outside the predictors. In certain other video coding techniques, there may be motion vector components applicable to the current block. In one example, the video encoder (703) includes other components, such as a mode decision module (not shown) for determining the mode of the processing blocks.

[0079] In the example of FIG. 7, the video encoder (703) includes an inter-encoder (730), an intra-encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721), and an entropy coder (725), coupled together as shown in FIG.

[0080] The inter-encoder (730) is configured to receive samples of a current block (e.g., a processing block), compare the block with one or more reference blocks in a reference picture (e.g., blocks in previous and subsequent pictures), generate inter-prediction information (e.g., a description of redundant information due to inter-coding techniques, motion vectors, merge mode information), and calculate an inter-prediction result (e.g., a predicted block) based on the inter-prediction information using any suitable technique. In some examples, the reference picture is a decoded reference picture that is decoded based on the coded video information.

[0081] The intra encoder (722) is configured to receive samples of a current block (e.g., a processing block), possibly compare the block with blocks already encoded in the same picture, generate transformed and quantized coefficients, and possibly also generate intra prediction information (e.g., intra prediction direction information according to one or more intra encoding techniques). In one example, the intra encoder (722) also calculates an intra prediction result (e.g., a predicted block) based on the intra prediction information and a reference block in the same picture.

[0082] The general controller (721) is configured to determine general control data and control other components of the video encoder (703) based on the general control data. In one example, the general controller (721) determines the mode of the block and provides a control signal to the switch (726) based on the mode. For example, if the mode is an intra mode, the general controller (721) controls the switch (726) to select the result of the intra mode for use by the residual calculator (723), and controls the entropy encoder (725) to select intra prediction information and include the intra prediction information in the bitstream. If the mode is an inter mode, the general controller (721) controls the switch (726) to select the result of inter prediction for use by the residual calculator (723), and controls the entropy encoder (725) to select inter prediction information and include the inter prediction information in the bitstream.

[0083] The residual calculator (723) is configured to calculate a difference (residual data) between the received block and a prediction result selected from the intra-encoder (722) or the inter-encoder (730). The residual encoder (724) is configured to encode the residual data to generate transform coefficients based on the residual data. In one example, the residual encoder (724) is configured to transform the residual data from the spatial domain to the frequency domain to generate transform coefficients. The transform coefficients are then subjected to a quantization process to obtain quantized transform coefficients. In various embodiments, the video encoder (703) also includes a residual decoder (728). The residual decoder (728) is configured to perform an inverse transform to generate decoded residual data. The decoded residual data can be suitably used by the intra-encoder (722) and the inter-encoder (730). For example, the inter-encoder (730) can generate decoded blocks based on the decoded residual data and the inter-prediction information, and the intra-encoder (722) can generate decoded blocks based on the decoded residual data and the intra-prediction information. The decoded blocks are suitably processed to generate decoded pictures, which can be buffered in a memory circuit (not shown) and used as reference pictures in some examples.

[0084] The entropy encoder (725) is configured to format a bitstream to include the encoded block. The entropy encoder (725) is configured to include various information in the bitstream according to a suitable standard, such as the HEVC standard. In one example, the entropy encoder (725) is configured to include general control data, selected prediction information (e.g., intra-prediction information or inter-prediction information), residual information, and other suitable information in the bitstream. Note that in accordance with the disclosed subject matter, when encoding a block in a merged sub-mode of either the inter mode or the bi-prediction mode, the residual information is not present.

[0085] 8 shows an example diagram of a video decoder (810). The video decoder (810) is configured to receive encoded pictures that are part of an encoded video sequence and decode the encoded pictures to generate reconstructed pictures. In one example, the video decoder (810) is used in place of the video decoder (410) in the example of FIG. 4.

[0086] In the example of FIG. 8, the video decoder (810) includes an entropy decoder (871), an inter decoder (880), a residual decoder (873), a reconstruction module (874), and an intra decoder (872) coupled together as shown in FIG. 8.

[0087] The entropy decoder (871) may be configured to reconstruct from the coded picture certain symbols representing the syntax elements of which the coded picture is composed. Such symbols may include, for example, prediction information (e.g., intra- or inter-prediction information, etc.) that may identify the mode in which the block is coded (e.g., intra- or inter-prediction mode, merged submode, or the latter two in another submode), and the specific samples or metadata used for prediction by the intra-decoder (872) or the inter-decoder (880), respectively. The symbols may also include residual information, for example in the form of quantized transform coefficients, etc. In one example, if the prediction mode is an inter- or bi-prediction mode, the inter-prediction information is provided to the inter-decoder (880). If the prediction type is an intra-prediction type, the intra-prediction information is provided to the intra-decoder (872). The residual information may undergo inverse quantization and is provided to the residual decoder (873).

[0088] The inter decoder (880) is configured to receive inter prediction information and to generate inter prediction results based on the inter prediction information.

[0089] The intra decoder (872) is configured to receive intra prediction information and generate a prediction result based on the intra prediction information.

[0090] The residual decoder (873) is configured to perform inverse quantization to extract dequantized transform coefficients, and to process the dequantized transform coefficients to transform the residual information from the frequency domain to the spatial domain. The residual decoder (873) may also require certain control information (including quantizer parameters (QP)), which may be provided by the entropy decoder (871) (data path not depicted since this is only low volume control information).

[0091] The reconstruction module (874) is configured to combine, in the spatial domain, the residual information output by the residual decoder (873) and the prediction result (output by the intra- or inter-prediction module, as the case may be) to form a reconstructed block, which may be part of a reconstructed picture, which may be part of a reconstructed video. It is noted that other suitable operations, such as a deblocking operation, may be performed to improve visual quality.

[0092] It should be noted that the video encoders (403), (603), (703) and the video decoders (410), (510), (810) may be implemented using any suitable technology. In some embodiments, the video encoders (403), (603), (703) and the video decoders (410), (510), (810) may be implemented using one or more integrated circuits. In other embodiments, the video encoders (403), (603), (703) and the video decoders (410), (510), (810) may be implemented using one or more processors executing software instructions.

[0093] Various inter prediction modes can be used in VVC. For an inter predicted CU, the motion parameters can include MV, one or more reference picture indexes, reference picture list usage index, and additional information for the specific coding features used for inter prediction sample generation. The motion parameters can be signaled explicitly or implicitly. If the CU is coded in skip mode, it can be associated with a PU and may not have significant residual coefficients, coded motion vector delta or MV difference (e.g., MVD) or reference picture index. A merge mode can be specified in which the motion parameters of the current CU are obtained from neighboring CUs, including spatial and / or temporal candidates, and optionally additional information as introduced in VVC. The merge mode can be applied not only to skip mode but also to inter predicted CUs. In one example, the selection for the merge mode is an explicit signaling of the motion parameters, and the MV, the corresponding reference picture index and reference picture list usage flag of each reference picture list, as well as other information, are explicitly signaled for each CU.

[0094] In a VVC-like embodiment, the VVC Test model (VTM) reference software supports a number of motion vector prediction modes, including enhanced merge prediction, merge motion vector difference (MMVD) mode, adaptive motion vector prediction (AMVP) mode with symmetric MVD signaling, affine motion compensation prediction, subblock-based temporal motion vector prediction (SbTMVP), adaptive motion vector resolution (AMVR), motion field storage (1 / 16 luma sample MV storage and 8x8 motion field compression), bi-prediction with CU-level weights (BCW), bi-directional optical flow (BDOF), prediction refinement using optical flow (PROF), decoder side motion vector refinement (DMVR), combined inter and intra prediction (CIIP), geometric partitioning mode (GPM), and motion vector compression (CMC). The present invention includes one or more sophisticated inter-prediction coding tools, including a multi-level coding (M-C) coding mode, etc. Inter-prediction and related methods are described in detail below.

[0095] In some cases, enhanced merge prediction can be used. In cases such as VTM4, the merge candidate list is constructed by including, in order, five types of candidates: spatial motion vector predictor (MVP) from spatially neighboring CUs, temporal MVP from co-located CUs, history-based MVP from a first-in-first-out (FIFO) table, pair-wise average MVP, and zero MV.

[0096] The size of the merge candidate list can be signaled in the slice header. In one example, the maximum allowed size of the merge candidate list is 6 in VTM4. For each CU coded in merge mode, the index of the best merge candidate (e.g., merge index) can be coded using truncated unary binarization (TU). The first bin of the merge index can be coded with context (e.g., context-adaptive binary arithmetic coding (CABAC)) and bypass coding can be used for the other bins.

[0097] Some examples of the generation process of each category of merge candidates are provided below. In one embodiment, spatial candidates are derived as follows: The derivation of spatial merge candidates in VVC can be the same as that in HEVC. In one example, up to four merge candidates are selected from the candidates at the positions shown in FIG. 9. FIG. 9 illustrates the positions of spatial merge candidates according to one embodiment of the present disclosure. With reference to FIG. 9, the derivation order is B1, A1, B0, A0, and B2. Position B2 is considered only if any CU at positions A0, B0, B1, and A1 is unavailable (e.g., because the CU belongs to another slice or another tile) or is intra-coded. After the candidate at position A1 is added, the addition of the remaining candidates is subject to a redundancy check, which ensures that candidates with the same motion information are removed from the candidate list, thereby improving the coding efficiency.

[0098] In order to reduce computational complexity, not all possible candidate pairs are considered in the above redundancy check. Instead, only pairs linked by arrows in FIG. 10 are considered, and a candidate is added to the candidate list only if the corresponding candidates used in the redundancy check do not have the same motion information. FIG. 10 illustrates candidate pairs considered for spatial merge candidate redundancy check according to one embodiment of the present disclosure. Referring to FIG. 10, each arrow-linked pair includes A1 and B1, A1 and A0, A1 and B2, B1 and B0, and B1 and B2. Thus, candidates at positions B1, A0, and / or B2 can be compared with candidates at positions A1, and candidates at positions B0 and / or B2 can be compared with candidates at positions B1.

[0099] In one embodiment, the temporal candidates are derived as follows: In one example, only one temporal merge candidate is added to the candidate list. FIG. 11 shows an example of motion vector scaling for a temporal merge candidate. To derive a temporal merge candidate for a current CU (1111) in a current picture (1101), a scaled MV (1121) (e.g., shown by dotted lines in FIG. 11) can be derived based on a co-located CU (1112) belonging to a co-located reference picture (1104). The reference picture list used to derive the co-located CU (1112) can be explicitly signaled in the slice header. The scaled MV (1121) for the temporal merge candidate can be obtained as shown by dotted lines in FIG. 11. The scaled MV (1121) can be scaled from the MV of the co-located CU (1112) using picture order count (POC) distances tb and td. The POC distance tb may be defined as the POC difference between the current reference picture (1102) of the current picture (1101) and the current picture (1101). The POC distance td may be defined as the POC difference between the co-located reference picture (1104) of the co-located picture (1103) and the co-located picture (1103). The reference picture index of the temporal merge candidate may be set to 0.

[0100] FIG. 12 shows exemplary candidate positions (e.g., C0 and C1) of temporal merge candidates for the current CU. The position of the temporal merge candidate can be selected between candidate position C0 and candidate position C1. Candidate position C0 is located at the bottom right corner of the current CU's co-located CU (1210). Candidate position C1 is located at the center of the current CU's co-located CU (1210). If the CU at candidate position C0 is not available, is intra-coded, or is outside the current row of the CTU, candidate position C1 is used to derive the temporal merge candidate. Otherwise, for example, if the CU at candidate position C0 is available, is intra-coded, and is in the current row of the CTU, candidate position C0 is used to derive the temporal merge candidate.

[0101] Adaptive motion vector resolution (AMVR) modes can be used in video / image coding such as VVC. In some technologies such as video coding standards HEVC and AVC / H.264, a fixed motion vector resolution (MVR) of 1 / 4 luma sample (or 1 / 4 pel) is used. Typically, an optimal trade-off between displacement vector rate and prediction error rate is selected to optimize rate-distortion. In related technologies such as VVC, AMVR mode is enabled when the MVR can be selected from multiple MVRs, e.g., at the coding block level, thus trading off bit rate against fidelity in signaling motion parameters. AMVR mode can be signaled, e.g., at the coding block level, when at least one component of the MVD is not equal to 0. The motion vector predictor (MVP) can be rounded to a given MVR such that the resulting MV (e.g., the sum of the MVP and MVD) can fit into the grid of the given MVR.

[0102] FIG. 13 shows examples of Amvr shift values ​​(e.g., AmvrShift) corresponding to resolutions (e.g., MVR). For each given resolution (e.g., MVR), the corresponding Amvr shift value (e.g., AmvrShift) indicates a shift operation (e.g., a left shift operation). For example, AmvrShift is defined to specify the MVR of an MVD with a left shift operation, and the number of bits to be shifted is indicated by AmvrShift.

[0103] In some examples, a flag such as an AMVR flag (e.g., amvr_flag) specifies the resolution (e.g., MVR) of the MVD. In one example, an AMVR flag (e.g., amvr_flag) equal to 0 specifies that the MVR of the MVD is 1 / 4 luma sample (1 / 4 pel). With reference to FIG. 13, an MVR of 1 / 4 pel corresponds to a 2-bit left shift operation (e.g., AmvrShift is 2 bits).

[0104] An AMVR flag (e.g., amvr_flag) equal to 1 specifies that the MVR of the MVD is further specified by additional information such as an index (e.g., an AMVR precision index or shown as amvr_precision_idx in FIG. 13) and / or a prediction mode. With reference to FIG. 13, the prediction mode can be an affine prediction mode or an affine mode indicated by the inter-affine flag, an IBC mode indicated by the parameter mode_IBC, or an inter prediction mode that is neither an affine prediction mode nor an IBC mode. For example, the inter prediction mode is a whole block-based inter prediction.

[0105] For example, if a coding block is predicted in AMVP mode and the AMVR flag (e.g., amvr_flag) is 1, and therefore the inter prediction mode (e.g., full block-based inter prediction) is neither an affine prediction mode nor an IBC mode, the MVR will be 1 / 2 luma sample (1 / 2 pel), 1 luma sample (1 pel), or 4 luma samples (4 pels) when the AMVR precision index is 0, 1, or 2, respectively. In one example, 1 / 2 pel, 1 pel, or 4 pels corresponds to an AmvrShift of 3, 4, or 6 bits.

[0106] A given MVD, denoted as MvdL0 and MvdL1 in AMVP mode or MvdCpL0 and MvdCpL1 in affine AMVP mode, can be modified as shown in FIG. 14A or FIG. 14B when AMVR mode is enabled.

[0107] In some examples, a translational motion model is applied for motion compensation prediction (MCP). However, the translational motion model may not be suitable for modeling other types of motion, such as zoom in / out, rotation, perspective motion, and other irregular motion. In some embodiments, a block-based affine transform motion compensation prediction is applied. In FIG. 15A, when a four-parameter affine model is used, the affine motion field of the block is described by two control point motion vectors (CPMVs), CPMV0 and CPMV1, of two control points (CPs), CP0 and CP1. In FIG. 15B, when a six-parameter affine model is used, the affine motion field of the block is described by three CPMVs, CPMV0, CPMV1, and CPMV3, of CPs, CP0, CP1, and CP2.

[0108] For a four-parameter affine motion model, the motion vector at a sample position (x,y) within a block is derived as follows:

number

[0109] For a six-parameter affine motion model, the motion vector at a sample position (x,y) within a block is derived as follows:

number

[0110] In formulas 1 and 2, (mv 0x ,mv 0y ) is the motion vector of the upper left corner control point, and (mv 1x ,mv 1y ) is the motion vector of the control point in the upper right corner, and (mv 2x ,mv 2y ) is the motion vector of the control point in the lower left corner. Furthermore, the coordinates (x, y) are relative to the upper left corner of each block, and W and H denote the width and height of each block.

[0111] In some embodiments, sub-block-based affine transformation prediction is applied to simplify motion compensation prediction. For example, in FIG. 16, a four-parameter affine motion model is used, and two CPMVs are used.

number

[0112] In some embodiments, two affine motion inter prediction modes are used, affine merge mode and affine AMVP mode, as well as translational motion inter prediction.

[0113] In some embodiments, the affine merge mode can be applied to CUs whose width and height are both equal to or greater than 8. Affine merge candidates for the current CU can be generated based on the motion information of spatially neighboring CUs. There can be up to five affine merge candidates, and an index is signaled to indicate the one to be used for the current CU. For example, the following three types of affine merge candidates are used to form the affine merge candidate list: (i) Inherited affine merge candidates extrapolated from the CPMVs of neighboring CUs; (ii) Construct affine merge candidates derived using the translation MVs of neighboring CUs; ​​and (iii) Zero MV

[0114] In some embodiments, there are at most two inherited affine candidates derived from the affine motion models of the neighboring blocks, one from the left neighboring CU and one from the top neighboring CU. For example, the candidate blocks can be located at the positions shown in Fig. 9. For the left predictor, the scan order is A0>A1, and for the top predictor, the scan order is B0>B1>B2. Only the first inherited candidate from each side is selected. No pruning check is performed between the two inherited candidates.

[0115] Once the neighboring affine CUs are identified, the CPMVs of the identified neighboring affine CUs are used to derive the CPMV candidates in the affine merge list of the current CU. As shown in Figure 17, the neighboring bottom-left block A of the current CU (1710) is coded in affine mode. The motion vectors for the top-left, top-right, and bottom-left corners of the CU (1720) containing block A are

number

number

number

number

[0116] Constructing affine candidates is constructed by combining the neighboring translational motion information of each control point. The motion information of a control point is derived from the specified spatial and temporal neighbors shown in Figure 18. CPMV k (k=1,2,3,4) represents the kth control point. For CPMV1, blocks with B2>B3>A2 are examined in order, and the MV of the first available block is used. For CPMV2, blocks with B1>B0 are examined, and for CPMV3, blocks with A1>A0 are examined. The TMVP in block T is used as CPMV4 if available.

[0117] After the MVs of the four control points are obtained, an affine merge candidate is constructed based on the motion information. The following combinations of control point MVs are used to construct the candidate affine merge candidate in order: {CPMV1,CPMV2,CPMV3}, {CPMV1,CPMV2,CPMV4}, {CPMV1,CPMV3,CPMV4}, {CPMV2,CPMV3,CPMV4}, {CPMV1,CPMV2}, {CPMV1,CPMV3}.

[0118] A combination of three CPMVs constructs a six-parameter affine merge candidate, and a combination of two CPMVs constructs a four-parameter affine merge candidate. To avoid the motion scaling process, if the reference indices of the control points are different, the associated control point MV combination is discarded.

[0119] After the inheritance and construction affine merge candidates have been examined, if the list is still not full, a zero MV is inserted at the end of the merge candidate list.

[0120] In some embodiments, the affine AMVP mode is applicable to CUs whose width and height are both 16 or greater. An affine flag at the CU level is signaled in the bitstream to indicate whether the affine AMVP mode is used, and then another flag is signaled to indicate whether a 4-parameter affine or a 6-parameter affine is used. The difference in CPMV of the current CU and its predictor is signaled in the bitstream. The affine AVMP candidate list size is 2 and can be generated by using the following four types of CPVM candidates in order: (i) Inherited affine AMVP candidates extrapolated from the CPMVs of neighboring CUs; (ii) Constructed affine AMVP candidates derived using the translational MVs of neighboring CUs; (iii) translational MVs from adjacent CUs, and (iv) Zero MV

[0121] In one example, the inspection order of the inherited affine AMVP candidate is similar to that of the inherited affine merge candidate. The difference is that for the AVMP candidate, the affine CU with the same reference picture as the current block is considered. When inserting the inherited affine motion predictor into the candidate list, the pruning process is not applied.

[0122] The constructed AMVP candidate is derived from the specified spatial neighborhood shown in Figure 18. The same check order is used as done in affine merge candidate construction. In addition, the reference picture indexes of the neighboring blocks are also checked. The first block in the check order that has the same reference picture as the current CU and is inter-coded is used. If the current CU is coded with a four-parameter affine model and both CPMV0 and CPMV1 are available, the available CPMV is added as one candidate in the affine AMVP list. If the current CU is coded with a six-parameter affine mode and all three CPMVs (CPMV0, CPMV1, and CPMV2) are available, the available CPMV is added as one candidate in the affine AMVP list. Otherwise, the constructed AMVP candidate is set to unavailable.

[0123] After the inherited affine AMVP candidates and the constructed AMVP candidates have been examined, if the affine AMVP list candidates are still less than two, translational motion vectors adjacent to the control points are added to predict all control point MVs of the current CU, if available. Finally, if the affine AMVP list is still not full, zero MVs are used to fill the affine AMVP list.

[0124] In related technologies such as VVC and ECM, an MV can point to a reference block outside a picture boundary or frame boundary in an inter-prediction mode (e.g., a unidirectional prediction mode or a bidirectional prediction mode). For example, one or more reference samples of a reference block pointed to by an MV are located outside the picture boundary of a reference picture. In some embodiments, if at least one MV crosses a frame boundary, an inter-predictor (e.g., a reference block in a unidirectional prediction mode, or a bidirectional predictor based on a first reference block and a second reference block for a bidirectional prediction mode) may not predict a current block accurately or efficiently.

[0125] 19 shows an example of a reference picture (1901) (shaded in gray) for a current block (not shown) and reference blocks (1911)-(1914) for the current block. The picture boundary or frame boundary of the reference picture (1901) can be determined by four corners C1-C4 of the reference picture (1901). The four corners C1-C4 are the upper left corner C1, the upper right corner C2, the lower left corner C3, and the lower right corner C4.

[0126] 19, the reference block (1911) is within the shaded region. If each reference sample in the reference block (1911) is within the reference picture (1901), then the reference block (1911) is within the reference picture (1901) or within the picture boundary of the reference picture (1901). The reference block (1911) has a rectangular shape, and the four corners D1 to D4 of the reference block (1911) are within the reference picture (1901).

[0127] If at least one reference sample in a reference block is outside the reference picture (1901), the reference block is outside the reference picture (1901) or outside the picture boundary of the reference picture (1901). For example, the reference block (1911) is outside the shaded area. The reference block (1912) is outside the reference picture (1901) or outside the picture boundary of the reference picture (1901). The four corners E1 to E4 of the reference block (1912) are outside the reference picture (1901).

[0128] The reference block (1913) is partially outside the shaded region. Corner F1 of the reference block (1913) is inside the reference picture (1901), and corners F2-F4 are outside the reference picture (1901). The reference block (1913) is outside the reference picture (1901) or outside the picture boundary of the reference picture (1901).

[0129] A current block in a current picture can be coded in an inter prediction mode. The current block can be coded based on one or more reference blocks of the current block associated with one or more reference pictures, respectively (e.g., (i) a first reference picture or (ii) a first reference picture and a second reference picture). According to an embodiment of the present disclosure, motion information of the current block can be constrained. The motion information constraint of the current block can indicate that one or more reference blocks are respectively within one or more reference pictures, i.e., that one or more reference blocks are respectively within a picture boundary of one or more reference pictures. The motion information constraint can be pre-determined and agreed upon between an encoder and a decoder. The motion information constraint can be transmitted (e.g., signaled) to the decoder.

[0130] In one example, the current block is coded based on a first reference block associated with a first reference picture in a unidirectional prediction mode. The motion information constraint of the current block may indicate that the first reference block is within the first reference picture. In one embodiment, the first reference block is within the first reference picture if each first reference sample in the first reference block is within the first reference picture (e.g., within the picture boundary of the first reference picture).

[0131] In one example, the current block is coded based on a first reference block associated with a first reference picture and a second reference block associated with a second reference picture in a bi-predictive mode. The motion information constraint of the current block may indicate that the first reference block is in the first reference picture and the second reference block is in the second reference picture.

[0132] In one embodiment, the current block is coded in a non-merge mode such as the AMVP mode. The MV (e.g., the final MV) of the current block can be determined (e.g., derived) from the MVP and MVD at a given AMVR resolution. For example, the MV is the sum of the MVP and the MVD. The MVP can be determined based on an index (e.g., the MVP index) and an MVP candidate list of the current block. The motion information constraint (e.g., the MV constraint) of the non-merge mode can indicate that the MV (e.g., the final MV) cannot point outside the picture boundary of the reference picture. For example, the reference block pointed to by the MV cannot be outside the picture boundary of the reference picture. In one example, each reference sample in the reference block is within the reference picture.

[0133] In one embodiment, the current block is bi-predicted (e.g., encoded or reconstructed in bi-predictive mode) in non-merge mode (e.g., AMVP mode). The above MV, MVP, MVD, reference picture, and reference block are referred to as the first MV, the first MVP, the first MVD, the first reference picture, and the first reference block, respectively. The second MV of the current block can be determined from the second MVP and the second MVD in the second AMVR resolution. In one example, the first MVP and the second MVP are determined based on the MVP candidates in the MVP candidate list. Motion information constraints can be applied to bi-prediction in non-merge mode. The motion information constraints in non-merge mode can indicate that the second MV cannot point outside the picture boundary of the second reference picture. For example, the second reference block pointed to by the second MV cannot be outside the picture boundary of the second reference picture. In one example, each second reference sample in the second reference block is within the second reference picture.

[0134] The motion information constraints described above in non-merge mode can be applied to a current block that is unidirectionally or bidirectionally predicted using merge mode, e.g., the first MV and / or the second MV are determined from their respective MVPs without an MVD.

[0135] In one embodiment, the current block is coded in an affine mode (e.g., affine AMVP mode or affine merge mode) and includes multiple sub-blocks. In one example, each sub-block in the multiple sub-blocks has its own MV information (e.g., the first MV in uni-prediction mode or an MV pair in bi-prediction mode) as described in FIG.

[0136] In one example, the current block is coded in a unidirectional prediction mode. The MV information of each subblock indicates the first MV of the subblock that points from the subblock to the first reference subblock in the first reference block associated with the first reference picture. The motion information constraint can indicate that the first MV of each subblock in the current block coded in affine mode cannot point outside the picture boundary of the first reference picture. For example, the motion information constraint indicates that each first reference subblock in the first reference block is within the first reference picture.

[0137] The above description can be applied when the current block is coded in bidirectional prediction mode. For example, in addition to the first MV of the subblock, the MV information of each subblock further indicates a second MV that points from the subblock to a second reference subblock in a second reference block associated with a second reference picture. The motion information constraint can indicate that the first MV of each subblock in the current block coded in affine mode cannot point outside the picture boundary of the first reference picture, and the second MV of each subblock in the current block cannot point outside the picture boundary of the second reference picture. For example, the motion information constraint further indicates that each second reference subblock in the second reference block is in the second reference picture.

[0138] The motion information constraints in the above affine mode can be applied when a sub-block within the current block further includes one or more regions, each region having its own MV or MV pair, e.g., the respective MV or respective MV pair of each region is constrained such that the respective MV or respective MV pair of each region cannot point outside the respective picture boundaries of the respective reference pictures.

[0139] In one embodiment, when a MV points outside a picture boundary (e.g., a frame boundary), a clip or clipping operation is used to ensure that the reference block or part of the reference block pointed to by the MV is within (e.g., completely inside) the picture boundary of the reference picture.

[0140] In one example, the current block is bidirectionally predicted using a first MV and a second MV. The first MV can point from the current block to a first reference block associated with a first reference picture, and the second MV can point from the current block to a second reference block associated with a second reference picture. If the first MV points outside the picture boundary of the first reference picture (e.g., if a part of the first reference block is outside the first reference picture), a clip operation can be used to determine the first clipping MV. The first clipping MV can point from the current block to an updated first reference block, and the updated first reference block is within the first reference picture. The clipping operation can be applied to the second MV when a part of the second reference block is outside the second reference picture, as described above.

[0141] The above clipping operation for a bi-directionally predicted current block can be applied when the current block is uni-directionally predicted using the first MV, and the first MV can be clipped as above.

[0142] The above clip operation can be applied when the current block is coded in AMVP mode, and the first MV (or the second MV) is determined based on the MVP and MVD. The above clip operation can be applied when the current block is coded in merge mode, and the first MV (or the second MV) is determined based on the MVP without the MVD. For example, the MVP is determined by an MVP index that points to an MVP candidate in the candidate list of the current block.

[0143] The above clip operation can be applied when the current block is coded in an affine mode, such as affine AMVP mode, affine merge mode, etc. For example, the current block is bidirectionally predicted in affine mode and includes multiple sub-blocks. In one example, a sub-block in the multiple sub-blocks includes one or more regions, and each region in the one or more regions has respective MV information, such as an MV pair for each region. Thus, the sub-blocks can be coded with one or more MV pairs associated with the respective one or more regions. In one example, the one or more regions are a region, and the sub-block is a region, for example, an MV pair of a sub-block is applicable to the entire sub-block, as described in FIG. 16.

[0144] For each region in a subblock in the plurality of subblocks, the MV pair may include (i) a respective first MV pointing from the region to a first reference region in a first reference subblock in a first reference block associated with a first reference picture, and (ii) a respective second MV pointing from the region to a second reference region in a second reference subblock in a second reference block associated with a second reference picture. The first reference block and the second reference block correspond to a current block, and the first reference subblock and the second reference subblock correspond to a subblock. If the first reference region is outside the first reference picture, a clipping operation may be applied to the first MV. For example, a first clipping MV may be determined by clipping the first MV such that the first clipping MV points from the region in the subblock to an updated first reference region in the first reference picture. If the second reference region is outside the second reference picture, a clipping operation may be applied to the second MV.

[0145] The clipping operation described above for the bidirectionally predicted current block in affine mode can be applied when the current block is unidirectionally predicted in affine mode. For example, each region in the subblock of the current block is predicted based on a first reference region in a first reference subblock in a first reference block. The first reference region is pointed to by a first MV. When the current block is unidirectionally predicted, the second MV is not used. As described above, if the first region is outside the first reference picture, the clipping operation is applied.

[0146] The MVP candidate list of the current block may include one or more MVP candidates, which may include an MVP candidate for a uni-directional prediction mode and / or an MVP candidate for a bi-directional prediction mode.

[0147] According to an embodiment of the present disclosure, the construction of the MVP candidate list can be constrained, for example, the MVP candidate list can be constrained. In one example, the construction of the MVP candidate list is constrained if the current block is coded in a merge mode. In one example, the construction of the MVP candidate list is constrained if the current block is coded in a non-merge mode such as an AMVP mode. The construction of the MVP candidate list can be constrained for bi-prediction mode or uni-prediction mode.

[0148] In one example, the MVP candidate list is constrained such that one or more of the MVP candidates of the bidirectional prediction mode are constrained. The MVP candidates of the bidirectional prediction mode can include a first MVP and a second MVP. The first MVP can refer to a first intermediate reference block associated with a first reference picture from a current block. The second MVP can refer to a second intermediate reference block associated with a second reference picture from a current block. The MVP candidates of the bidirectional prediction mode are constrained such that the first intermediate reference block is in the first reference picture and the second intermediate reference block is in the second reference picture. In one example, each of the MVP candidates of the bidirectional prediction mode in the MVP candidate list is constrained.

[0149] In one example, the MVP candidate list is constrained such that one or more of the MVP candidates of the unidirectional prediction mode are constrained. The MVP candidates of the unidirectional prediction mode can include one MVP, such as the first MVP without the second MVP. The MVP candidates of the unidirectional prediction mode are constrained such that the first intermediate reference block is in the first reference picture. In one example, each of the MVP candidates of the unidirectional prediction mode in the MVP candidate list is constrained.

[0150] In one example, the MVP candidate list is constrained such that (i) one or more of the MVP candidates for bidirectional prediction modes are constrained as described above, and (ii) one or more of the MVP candidates for unidirectional prediction modes are constrained as described above.

[0151] In one embodiment, the construction of the MVP candidate list may be constrained or unconstrained. According to one embodiment of the present disclosure, the use of MVP candidates in the MVP candidate list is constrained. The MVP candidate list may include MVP candidates of bi-prediction mode and MVP candidates of uni-prediction mode. An index (e.g., MVP index) indicating an MVP candidate (e.g., (i) the first MVP of uni-prediction mode or (ii) the first MVP and the second MVP of bi-prediction mode) in the MVP candidate list points to the MVP candidate. In merge mode, an MV (e.g., in the case of uni-prediction mode) or an MV pair (e.g., in the case of bi-prediction mode) is determined based on the MVP candidate. For example, the MV is the first MVP in uni-prediction mode. In an example such as bi-prediction mode, the MV pair includes a first MV that is the first MVP and a second MV that is the second MVP. If the MV, the first MV, or the second MV points outside the picture boundary (e.g., frame boundary) of the respective reference picture, the index cannot be selected. In one example, the index is not selected and therefore not signaled. In one example, the MVP candidate corresponding to the index is constrained such that the MVP candidate cannot be used to code the current block.

[0152] The use of affine candidates in a candidate list (e.g., an affine candidate list) can be constrained if the current block is coded in affine mode. As mentioned above, the current block can include multiple sub-blocks. In one example, each sub-block in the multiple sub-blocks includes one or more regions, and each region in the one or more regions has a respective MV or a respective MV pair. The motion information of each sub-block can include (i) one or more MVs (in the case of unidirectional prediction mode) or (ii) one or more MV pairs (in the case of bidirectional prediction) associated with the respective one or more regions.

[0153] In one embodiment, the MV information of each subblock can be determined based on the affine candidates (e.g., affine merge candidates) in the affine candidate list of the current block. According to one embodiment of the present disclosure, the MV information of each subblock in the current block can be constrained, for example, one or more MVs (in the case of unidirectional prediction mode) or (ii) one or more MV pairs (in the case of bidirectional prediction mode) are constrained such that (i) one or more MVs or (ii) one or more MV pairs cannot point outside the picture boundary of the respective reference picture. Otherwise, if one of (i) one or more MVs or (ii) one or more MV pairs in the one or more MVs points outside the picture boundary of the respective reference picture, the affine candidates (e.g., affine merge candidates) of the current block cannot be selected, for example, for coding the current block.

[0154] In one embodiment, an affine candidate list (e.g., an affine merge candidate list) is constrained when the current block is coded in affine mode. The affine candidate list may include affine candidates. The affine candidate list may be constrained such that each of the affine candidates is constrained. In one example, the affine candidates are constrained such that the MV information of each sub-block in the current block determined based on the affine candidates (e.g., (i) one or more MVs of one or more respective regions in the sub-block or (ii) one or more MV pairs of one or more respective regions in the sub-block) is within a respective picture boundary in a respective reference picture as described above.

[0155] The embodiments described in this application can be combined in any suitable combination or in any suitable order. For example, if the current block is coded in a non-merge mode (e.g., AMVP mode), each MV associated with each reference picture is determined based on the MVP and MVD. The motion information constraint of the current block can indicate that (i) each MV is constrained as above (e.g., the reference block pointed to by the MV is in the respective reference picture) and (ii) the corresponding MVP is constrained as above (e.g., the intermediate reference block pointed to by the MVP is in the respective reference picture).

[0156] FIG. 20 shows a flow chart outlining an encoding process (2000) according to one embodiment of the present disclosure. In various embodiments, the process (2000) is performed by processing circuitry, such as processing circuitry in terminal devices (310), (320), (330), and (340), processing circuitry performing the functions of a video encoder (e.g., (403), (603), (703)), etc. In some embodiments, the process (2000) is implemented with software instructions, and thus the processing circuitry performs the process (2000) when it executes the software instructions. The process begins at (S2001) and proceeds to (S2010).

[0157] At (S2010), motion information of a current block to be coded with inter prediction may be determined. The motion information may indicate one or more reference blocks of the current block associated with one or more reference pictures, respectively.

[0158] In (S2020), if the one or more reference blocks are within the picture boundaries of the one or more reference pictures, respectively, the current block may be encoded based on the one or more reference blocks.

[0159] In (S2030), if the first reference region of the first reference block in the one or more reference blocks is outside the picture boundary of the first reference picture in the one or more reference pictures, a first clipping MV can be determined by clipping a first motion vector (MV) such that the updated first reference region in the updated first reference block is within the picture boundary of the first reference picture. The first MV indicated by the motion information can point to the first reference region from a region in the current block, and the first clipping MV can point to the updated first reference region from a region in the current block. The region in the current block can be coded based on the updated first reference region.

[0160] The process (2000) then proceeds to (S2099) and ends.

[0161] The process (2000) may be adapted to various scenarios and the steps in the process (2000) may be adjusted accordingly. One or more steps in the process (2000) may be adapted, omitted, repeated, and / or combined. Any suitable order may be used to implement the process (2000). Additional steps may be added.

[0162] In one example, in (S2020), if the reference block in the one or more reference blocks is outside the picture boundary of the respective reference picture in the one or more reference pictures, updated motion information for the current block can be determined such that the updated reference block indicated by the updated motion information is within the picture boundary of the respective reference picture in the one or more reference pictures. The updated motion information may be signaled for the current block, and the current block can be coded based on the updated reference block. In this example, step (S2030) is omitted.

[0163] FIG. 21 is a flow chart outlining a decoding process (2100) according to one embodiment of the present disclosure. In various embodiments, the process (2100) is performed by processing circuitry such as processing circuitry in the terminal devices (310), (320), (330), and (340), processing circuitry performing the functions of a video encoder (403), processing circuitry performing the functions of a video decoder (410), processing circuitry performing the functions of a video decoder (510), processing circuitry performing the functions of a video encoder (603), etc. In some embodiments, the process (2100) is implemented with software instructions, and thus the processing circuitry performs the process (2100) as the processing circuitry executes the software instructions. The process begins at (S2101) and proceeds to (S2110).

[0164] At (S2110), motion information of the current block predicted by inter prediction may be determined, the motion information indicating one or more reference blocks of the current block associated with one or more reference pictures, respectively.

[0165] In (S2120), if the motion information constraint indicates that one or more reference blocks are within the picture boundaries of one or more reference pictures, respectively, the current block can be reconstructed based on the one or more reference blocks.

[0166] In one embodiment, the current block is bidirectionally predicted in an adaptive motion vector prediction (AMVP) mode. The motion information indicates a first MV that points from the current block to a first reference block and a second MV that points from the current block to a second reference block associated with a second reference picture. The one or more reference blocks are composed of a first reference block and a second reference block. The motion information constraint indicates that the first reference block is within a picture boundary of the first reference picture, and the second reference block is within a picture boundary of the second reference picture, and the picture boundary includes the picture boundary of the second reference picture.

[0167] In one embodiment, the motion information indicates MV predictor (MVP) candidates in a candidate list. The MVP candidates indicate a first MVP and a second MVP. The first MVP points to a first intermediate reference block corresponding to the current block within a picture boundary of a first reference picture. The second MVP points to a second intermediate reference block corresponding to the current block within a picture boundary of a second reference picture. The first MV is determined based on the first MVP and a first MV difference (MVD), and the second MV is determined based on the second MVP and a second MVD, and the second MV points to a second reference block.

[0168] In one embodiment, the current block is bidirectionally predicted in affine mode and includes a plurality of sub-blocks. The motion information indicates MV pairs, each associated with one of the plurality of sub-blocks. Each MV pair associated with a respective sub-block in the plurality of sub-blocks includes a first MV pointing from the respective sub-block to a first reference sub-block in the first reference block and a second MV pointing from the respective sub-block to a second reference sub-block in the second reference block associated with the second reference picture. The one or more reference blocks are composed of a first reference block and a second reference block. The motion information constraint indicates that each of the first reference sub-blocks is within a picture boundary of the first reference picture and each of the second reference sub-blocks is within a picture boundary of the second reference picture. The picture boundary includes a picture boundary of the second reference picture.

[0169] In one embodiment, the current block is bidirectionally predicted in merge mode. The candidate list of the current block includes one or more MV predictor (MVP) candidates. The MVP candidate of the current block can be determined from one or more MVP candidates based on the MVP index. The MVP candidate indicates a first MVP associated with a first reference picture and a second MVP associated with a second reference picture. The first MV of the current block is determined to be the first MVP, and the second MV of the current block is determined to be the second MVP. The motion information constraint indicates that (i) the first reference block pointed to by the first MV is within the picture boundary of the first reference picture, and the second reference block pointed to by the second MV is within the picture boundary of the second reference picture. The picture boundary includes the picture boundary of the second reference picture.

[0170] In one example, for each MVP candidate in one or more MVP candidates indicating a respective first MVP and a respective second MVP, the motion information constraint indicates that (i) a first intermediate reference block pointed to by the respective first MVP is within the picture boundary of the respective first reference picture, and (ii) a second intermediate reference block pointed to by the respective second MVP is within the picture boundary of the respective second reference picture.

[0171] In one embodiment, the current block is bi-directionally predicted in affine merge mode and includes a plurality of sub-blocks. The candidate list of the current block includes one or more affine merge candidates. For each sub-block in the plurality of sub-blocks, for each region in the respective sub-block, a MV pair for the respective region can be determined based on the affine merge candidates in the one or more affine merge candidates. The MV pair includes a respective first MV pointing from the region to a first region in a first reference sub-block in a first reference block, and a respective second MV pointing from the region to a second region in a second reference sub-block in a second reference block associated with a second reference picture. The first reference block and the second reference block correspond to the current block, and the first reference sub-block and the second reference sub-block correspond to the respective sub-blocks. The motion information constraint indicates that the respective first region is within a picture boundary of the first reference picture, and the respective second region is within a picture boundary of the second reference picture. The picture boundary includes a picture boundary of the second reference picture.

[0172] In (S2130), a first motion vector (MV) indicated by the motion information points from an area in the current block to a first reference area, the first reference area being an area of ​​a first reference block in one or more reference blocks. If the first reference area is outside a picture boundary of a first reference picture of one or more reference pictures, a first clipping MV can be determined that points from an area in the current block to the updated first reference area by clipping the first MV such that the updated first reference area is within the updated first reference block that is within the picture boundary of the first reference picture. The picture boundary includes the picture boundary of the first reference picture. The area in the current block can be reconstructed based on the updated first reference area.

[0173] In one embodiment, the current block is bidirectionally predicted. The motion information indicates a first MV that points from the current block to a first reference block and a second MV that points from the current block to a second reference block associated with a second reference picture. The one or more reference blocks are composed of a first reference block and a second reference block. A first reference region of the first reference block is outside the picture boundary of the first reference picture. A first clipping MV can be determined by clipping the first MV so that the updated first reference block is within the picture boundary of the first reference picture. If the second reference block is outside the picture boundary of the second reference picture, a second clipping MV can be determined by clipping the second MV so that the updated second reference block is within the picture boundary of the second reference picture. The second clipping MV points from the current block to the updated second reference block. The picture boundary includes the picture boundary of the second reference picture.

[0174] In one embodiment, the current block is bidirectionally predicted in affine mode and includes a plurality of subblocks. For each subblock in the plurality of subblocks, a MV pair for a respective region can be determined using the affine mode for each region in the respective subblock. The MV pair includes a respective first MV pointing from the region to a first reference region in a first reference subblock in a first reference block, and a second MV pointing from the region to a second reference region in a second reference subblock in a second reference block associated with a second reference picture. The first and second reference blocks correspond to the current block, and the first and second reference subblocks correspond to respective subblocks. The first reference region is in a first reference subblock in the first reference block, and the region in the current block is in a subblock of the plurality of subblocks corresponding to the first reference subblock. The first reference region is outside the picture boundary of the first reference picture. The first clipping MV can be determined by clipping the first MV, where the first clipping MV points to the updated first reference region from the region within the sub-block.

[0175] The process (2100) proceeds to (S2199) and ends.

[0176] The process (2100) may be adapted to various scenarios and the steps in the process (2100) may be adjusted accordingly. One or more steps in the process (2100) may be adapted, omitted, repeated, and / or combined. Any suitable order may be used to implement the process (2100). Additional steps may be added.

[0177] The embodiments in this disclosure may be used individually or combined in any order. Furthermore, each of the methods (or embodiments), the encoder, and the decoder may be implemented by a processing circuit (e.g., one or more processors or one or more integrated circuits). In one example, the one or more processors execute a program stored on a non-transitory computer-readable medium.

[0178] The techniques described above can be implemented as computer software using computer-readable instructions and can be physically stored on one or more computer-readable media. For example, Figure 22 illustrates a computer system (2200) suitable for implementing certain embodiments of the disclosed subject matter.

[0179] Computer software can be coded using any suitable machine code or computer language and can be subject to assembly, compilation, linking, or similar mechanisms to produce code containing instructions that can be executed by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., either directly, or through interpretation, microcode execution, etc.

[0180] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, Internet of Things devices, etc.

[0181] 22 for computer system (2200) are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing the embodiments of the present disclosure, nor should the arrangement of components be interpreted as having any dependency or requirement regarding any one or combination of components illustrated in the exemplary embodiment of computer system (2200).

[0182] The computer system (2200) may include certain human interface input devices that may be responsive to input by one or more human users through, for example, tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), and olfactory input (not shown). Human interface devices may also be used to capture certain media that are not necessarily directly related to conscious human input, such as audio (e.g., speech, music, ambient sounds), images (e.g., scanned images, photographic images obtained from still image cameras), and video (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

[0183] The input human interface devices may include one or more (only one of each is shown) of a keyboard (2201), a mouse (2202), a trackpad (2203), a touch screen (2210), a data glove (not shown), a joystick (2205), a microphone (2206), a scanner (2207), and a camera (2208).

[0184] The computer system (2200) may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the human user's senses, for example, through haptic output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touch screen (2210), data gloves (not shown), or joystick (2205); although there may be haptic feedback devices that do not act as input devices), audio output devices (e.g., speakers (2209), headphones (not shown)), visual output devices (e.g., screens (2210) including CRT screens, LCD screens, plasma screens, OLED screens; each may or may not have touch screen input capability, each may or may not have haptic feedback capability, some of which may output two-dimensional visual output or higher than three-dimensional output through such means as stereoscopic output; virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0185] The computer system (2200) may also include human accessible storage devices and associated media, such as optical media including CD / DVD ROM / RW (2220) along with CD / DVD or similar media (2221), thumb drives (2222), removable hard drives or solid state drives (2223), legacy magnetic media such as tapes and floppy disks (not shown), specialized ROM / ASIC / PLD based devices (not shown) such as security dongles, etc.

[0186] Those skilled in the art should also understand that the term "computer-readable medium" as used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

[0187] The computer system 2200 may also include an interface 2254 to one or more communication networks 2255. The networks may be, for example, wireless, wired, or optical. The networks may further be local, wide area, metropolitan, in-vehicle and industrial, real-time, delay tolerant, etc. Examples of networks include Ethernet, WLAN, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., TV wired or wireless wide area digital networks including cable television, satellite television, terrestrial broadcast television, in-vehicle and industrial including CANBus, etc. Certain networks usually require an external network interface adapter that is attached to a particular general-purpose data port or peripheral bus 2249 (e.g., a USB port of the computer system 2200, etc.). Others are usually integrated into the core of the computer system 2200 by attachment 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 (2200) can communicate with other entities. Such communications may be unidirectional, receive only (e.g., broadcast television), unidirectional transmit only (e.g., CANbus to a specific CANbus device), or bidirectional, for example, to other computer systems using local or wide area digital networks. Specific protocols and protocol stacks may be used with each of these networks and network interfaces as described above.

[0188] The aforementioned human interface devices, human accessible storage devices, and network interfaces may be attached to a core (2240) of the computer system (2200).

[0189] The cores (2240) may include one or more central processing units (CPUs) (2241), graphics processing units (GPUs) (2242), specialized programmable processing units in the form of field programmable gate arrays (FPGAs) (2243), hardware accelerators for specific tasks (2244), graphics adapters (2250), etc. These devices may be connected through a system bus (2248), along with read only memory (ROM) (2245), random access memory (2246), internal mass storage devices (2247), such as internal non-user accessible hard drives, solid state drives (SSDs), etc. In some computer systems, the system bus (2248) may be accessible in the form of one or more physical plugs to allow expansion with additional CPUs, GPUs, etc. Peripheral devices may be attached directly to the core's system bus (2248) or through a peripheral bus (2249). In one example, a screen (2210) may be connected to the graphics adapter (2250). Architectures for peripheral buses include PCI, USB, and the like.

[0190] The CPU (2241), GPU (2242), FPGA (2243), and accelerator (2244) may execute certain instructions that may combine to constitute the above-mentioned computer code. The computer code may be stored in a ROM (2245) or a RAM (2246). Temporary data may be stored in the RAM (2246), while persistent data may be stored, for example, in an internal mass storage device (2247). Rapid storage and retrieval from any of the memory devices may be enabled through the use of a cache memory that may be closely associated with one or more of the CPU (2241), GPU (2242), mass storage device (2247), ROM (2245), RAM (2246), etc.

[0191] The computer-readable medium can have computer code thereon for performing various computer-implemented operations. The medium 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.

[0192] By way of example and not limitation, the architecture (2200), and in particular a computer system having a core (2240), can provide functionality as a result of a processor (including a CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media can be user-accessible mass storage as introduced above as well as media associated with a particular storage of the core (2240) of a non-transitory nature, such as a mass storage device (2247) internal to the core or a ROM (2245). Software implementing various embodiments of the present disclosure can be stored in such devices and executed by the core (2240). The computer-readable media can include one or more memory devices or chips, depending on the particular needs. The software can cause the core (2240) and in particular the processors therein (including a CPU, GPU, FPGA, etc.) to execute certain processes or certain particular portions described herein, including defining data structures stored in RAM (2246) and modifying such data structures according to processes defined by the software. Additionally or alternatively, the computer system may provide functionality as a result of logic hardwired or otherwise embodied in circuitry (e.g., accelerator (2244)), which may operate in place of or in conjunction with software to perform particular processes or portions of particular processes described herein. Reference to software includes logic, and vice versa, as appropriate. Reference to a computer-readable medium may include circuitry (e.g., an integrated circuit (IC)) that stores software for execution, circuitry that embodies logic for execution, or both, as appropriate. The present disclosure encompasses any suitable combination of hardware and software.

[0193] Appendix A: Acronyms JEM: joint exploration model VVC: versatile video coding BMS: benchmark set MV: Motion Vector HEVC: High Efficiency Video Coding SEI: Supplementary Enhancement Information VUI: Video Usability Information GOP: Group of Pictures TU: Transform Unit PU: Prediction Unit CTU: Coding Tree Unit CTB: Coding Tree Block PB: Prediction Block HRD: Hypothetical Reference Decoder SNR: Signal Noise Ratio CPU: Central Processing Unit GPU: Graphics Processing Unit CRT: Cathode Ray Tube LCD: Liquid-Crystal Display OLED: Organic Light-Emitting Diode CD: Compact Disc DVD: Digital Video Disc ROM: Read-Only Memory RAM: Random Access Memory ASIC: Application-Specific Integrated Circuit PLD: Programmable Logic Device LAN: Local Area Network GSM: Global System for Mobile communications LTE: Long-Term Evolution CANBus: Controller Area Network Bus USB: Universal Serial Bus PCI: Peripheral Component Interconnect FPGA: Field Programmable Gate Areas SSD: solid-state drive IC: Integrated Circuit CU: Coding Unit RD: Rate-Distortion

[0194] While this disclosure has described several exemplary embodiments, there are alterations, substitutions, and various substitute equivalents, which fall within the scope of this disclosure. Thus, it will be appreciated that those skilled in the art will be able to devise many systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and are thus within the spirit and scope of the present disclosure.

Claims

1. 1. A method for video decoding in a video decoder, comprising: receiving a motion information constraint; determining motion information of a current block predicted with inter prediction, the motion information indicating one or more reference blocks of the current block associated with one or more reference pictures, respectively; if the motion information constraint indicates that the one or more reference blocks are within a picture boundary of one or more reference pictures, respectively, reconstructing the current block based on the one or more reference blocks; determining a first clipping MV that points from an area in the current block to a first reference area that is an area of ​​a first reference block in the one or more reference blocks and is outside a picture boundary of a first reference picture of the one or more reference pictures, the picture boundary including the picture boundary of the first reference picture, by clipping the first MV such that the updated first reference area is within an updated first reference block that is within the picture boundary of the first reference picture; reconstructing the area in the current block based on the updated first reference area; Including, The current block is bidirectionally predicted in an adaptive motion vector prediction (AMVP) mode; the motion information indicates a first MV that points from the current block to the first reference block and a second MV that points from the current block to a second reference block associated with a second reference picture; the one or more reference blocks are composed of the first reference block and the second reference block; A method according to claim 1, wherein the motion information constraint indicates that the first reference block is within the picture boundary of the first reference picture and the second reference block is within the picture boundary of the second reference picture, and the picture boundary includes the picture boundary of the second reference picture.

2. the motion information indicates a MV predictor (MVP) candidate in a candidate list, the MVP candidates indicating a first MVP and a second MVP; The first MVP refers to a first intermediate reference block that is within the picture boundary of the first reference picture and corresponds to the current block; The second MVP refers to a second intermediate reference block that is within the picture boundary of the second reference picture and corresponds to the current block; and The step of determining the motion information further comprises: determining the first MV based on the first MVP and a first MV difference (MVD); determining a second MV based on the second MVP and a second MVD, the second MV pointing to the second reference block; The method of claim 1 , comprising:

3. A method for video decoding in a video decoder, comprising: receiving a motion information constraint; determining motion information of a current block predicted with inter prediction, the motion information indicating one or more reference blocks of the current block associated with one or more reference pictures, respectively; if the motion information constraint indicates that the one or more reference blocks are within a picture boundary of one or more reference pictures, respectively, reconstructing the current block based on the one or more reference blocks; determining a first clipping MV that points from an area in the current block to a first reference area that is an area of ​​a first reference block in the one or more reference blocks and is outside a picture boundary of a first reference picture of the one or more reference pictures, the picture boundary including the picture boundary of the first reference picture, by clipping the first MV such that the updated first reference area is within an updated first reference block that is within the picture boundary of the first reference picture; reconstructing the area in the current block based on the updated first reference area; Including, the current block is bi-directionally predicted in affine mode and includes a plurality of sub-blocks; the motion information indicates MV pairs each associated with one of the plurality of sub-blocks; Each MV pair associated with a respective sub-block in the plurality of sub-blocks includes a first MV pointing from the respective sub-block to a first reference sub-block in the first reference block, and a second MV pointing from the respective sub-block to a second reference sub-block in a second reference block associated with a second reference picture; the one or more reference blocks are composed of the first reference block and the second reference block; A method according to claim 1, wherein the motion information constraint indicates that each of the first reference sub-blocks is within the picture boundary of the first reference picture and each of the second reference sub-blocks is within the picture boundary of the second reference picture, and the picture boundaries include the picture boundary of the second reference picture.

4. A method for video decoding in a video decoder, comprising: receiving a motion information constraint; determining motion information of a current block predicted with inter prediction, the motion information indicating one or more reference blocks of the current block associated with one or more reference pictures, respectively; if the motion information constraint indicates that the one or more reference blocks are within a picture boundary of one or more reference pictures, respectively, reconstructing the current block based on the one or more reference blocks; determining a first clipping MV that points from an area in the current block to a first reference area that is an area of ​​a first reference block in the one or more reference blocks and is outside a picture boundary of a first reference picture of the one or more reference pictures, the picture boundary including the picture boundary of the first reference picture, by clipping the first MV such that the updated first reference area is within an updated first reference block that is within the picture boundary of the first reference picture; reconstructing the area in the current block based on the updated first reference area; Including, The current block is bi-directionally predicted in merge mode; the candidate list for the current block includes one or more MV Predictor (MVP) candidates; The step of determining the motion information further comprises: determining an MVP candidate for the current block from the one or more MVP candidates based on an MVP index, the MVP candidate indicating a first MVP associated with the first reference picture and a second MVP associated with a second reference picture; determining that the first MV of the current block is to be the first MVP and that the second MV of the current block is to be the second MVP; Including, The motion information constraint is: the first reference block pointed to by the first MV is within the picture boundary of the first reference picture; The second reference block pointed to by the second MV is within the picture boundary of the second reference picture. and the picture boundary includes the picture boundary of the second reference picture.

5. For each MVP candidate in the one or more MVP candidates, each MVP candidate representing a respective first MVP and a respective second MVP, the motion information constraint a first intermediate reference block pointed to by each first MVP is within a picture boundary of each first reference picture; The second intermediate reference block pointed to by each second MVP is within the picture boundary of each second reference picture. The method according to claim 4 , wherein 6. A method for video decoding in a video decoder, comprising: receiving a motion information constraint; determining motion information of a current block predicted with inter prediction, the motion information indicating one or more reference blocks of the current block associated with one or more reference pictures, respectively; if the motion information constraint indicates that the one or more reference blocks are within a picture boundary of one or more reference pictures, respectively, reconstructing the current block based on the one or more reference blocks; determining a first clipping MV that points from an area in the current block to a first reference area that is an area of ​​a first reference block in the one or more reference blocks and is outside a picture boundary of a first reference picture of the one or more reference pictures, the picture boundary including the picture boundary of the first reference picture, by clipping the first MV such that the updated first reference area is within an updated first reference block that is within the picture boundary of the first reference picture; reconstructing the area in the current block based on the updated first reference area; Including, the current block is bi-directionally predicted in affine merge mode and includes a plurality of sub-blocks; the candidate list for the current block includes one or more affine merge candidates; For each sub-block in the plurality of sub-blocks, determining the motion information includes, for each region in the respective sub-block, determining an MV pair for the respective region based on an affine merge candidate in the one or more affine merge candidates, the MV pair including a respective first MV pointing from the region to a first region in a first reference sub-block in the first reference block and a respective second MV pointing from the region to a second region in a second reference sub-block in a second reference block associated with a second reference picture, the first reference block and the second reference block corresponding to the current block, and the first reference sub-block and the second reference sub-block corresponding to respective sub-blocks; The method of claim 1, wherein the motion information constraints indicate that each first region is within the picture boundary of the first reference picture and each second region is within the picture boundary of the second reference picture, and the picture boundaries include the picture boundary of the second reference picture.

7. The step of determining the first clipping MV comprises: determining the first clipping MV by clipping the first MV such that the updated first reference block is within the picture boundary of the first reference picture; if the second reference block is outside a picture boundary of the second reference picture, determining a second clipping MV by clipping the second MV such that an updated second reference block is within the picture boundary of the second reference picture, the second clipping MV points from the current block to the updated second reference block, and the picture boundary includes the picture boundary of the second reference picture; The method of claim 1 , comprising:

8. 1. An apparatus for video decoding including a processing circuit, comprising: Apparatus, wherein the processing circuitry is configured to perform a method according to any one of claims 1 to 7.

9. A computer program product causing at least one processor to carry out the method according to any one of claims 1 to 7.

10. 1. A method for video encoding in a video encoder, comprising: determining motion information of a current block predicted with inter prediction, the motion information indicating one or more reference blocks of the current block associated with one or more reference pictures, respectively; if a motion information constraint indicates that the one or more reference blocks are within a picture boundary of one or more reference pictures, respectively, encoding the current block based on the one or more reference blocks; determining a first clipping MV that points from an area in the current block to a first reference area that is an area of ​​a first reference block in the one or more reference blocks and is outside a picture boundary of a first reference picture of the one or more reference pictures, the picture boundary including the picture boundary of the first reference picture, by clipping the first MV such that the updated first reference area is within an updated first reference block that is within the picture boundary of the first reference picture; encoding the region in the current block based on the updated first reference region; transmitting said motion information constraints; Including, The current block is bidirectionally predicted in an adaptive motion vector prediction (AMVP) mode; the motion information indicates a first MV that points from the current block to the first reference block and a second MV that points from the current block to a second reference block associated with a second reference picture; the one or more reference blocks are composed of the first reference block and the second reference block; A method according to claim 1, wherein the motion information constraint indicates that the first reference block is within the picture boundary of the first reference picture and the second reference block is within the picture boundary of the second reference picture, and the picture boundary includes the picture boundary of the second reference picture.

11. A method for video encoding in a video encoder, comprising: determining motion information of a current block predicted with inter prediction, the motion information indicating one or more reference blocks of the current block associated with one or more reference pictures, respectively; if a motion information constraint indicates that the one or more reference blocks are within a picture boundary of one or more reference pictures, respectively, encoding the current block based on the one or more reference blocks; determining a first clipping MV that points from an area in the current block to a first reference area that is an area of ​​a first reference block in the one or more reference blocks and is outside a picture boundary of a first reference picture of the one or more reference pictures, the picture boundary including the picture boundary of the first reference picture, by clipping the first MV such that the updated first reference area is within an updated first reference block that is within the picture boundary of the first reference picture; encoding the region in the current block based on the updated first reference region; transmitting said motion information constraints; Including, the current block is bi-directionally predicted in affine mode and includes a plurality of sub-blocks; the motion information indicates MV pairs each associated with one of the plurality of sub-blocks; Each MV pair associated with a respective sub-block in the plurality of sub-blocks includes a first MV pointing from the respective sub-block to a first reference sub-block in the first reference block, and a second MV pointing from the respective sub-block to a second reference sub-block in a second reference block associated with a second reference picture; the one or more reference blocks are composed of the first reference block and the second reference block; A method according to claim 1, wherein the motion information constraint indicates that each of the first reference sub-blocks is within the picture boundary of the first reference picture and each of the second reference sub-blocks is within the picture boundary of the second reference picture, and the picture boundaries include the picture boundary of the second reference picture.

12. A method for video encoding in a video encoder, comprising: determining motion information of a current block predicted with inter prediction, the motion information indicating one or more reference blocks of the current block associated with one or more reference pictures, respectively; if a motion information constraint indicates that the one or more reference blocks are within a picture boundary of one or more reference pictures, respectively, encoding the current block based on the one or more reference blocks; determining a first clipping MV that points from an area in the current block to a first reference area that is an area of ​​a first reference block in the one or more reference blocks and is outside a picture boundary of a first reference picture of the one or more reference pictures, the picture boundary including the picture boundary of the first reference picture, by clipping the first MV such that the updated first reference area is within an updated first reference block that is within the picture boundary of the first reference picture; encoding the region in the current block based on the updated first reference region; transmitting said motion information constraints; Including, The current block is bi-directionally predicted in merge mode; the candidate list for the current block includes one or more MV Predictor (MVP) candidates; The step of determining the motion information further comprises: determining an MVP candidate for the current block from the one or more MVP candidates based on an MVP index, the MVP candidate indicating a first MVP associated with the first reference picture and a second MVP associated with a second reference picture; determining that the first MV of the current block is to be the first MVP and that the second MV of the current block is to be the second MVP; Including, The motion information constraint is: the first reference block pointed to by the first MV is within the picture boundary of the first reference picture; The second reference block pointed to by the second MV is within the picture boundary of the second reference picture. and the picture boundary includes the picture boundary of the second reference picture.

13. A method for video encoding in a video encoder, comprising: determining motion information of a current block predicted with inter prediction, the motion information indicating one or more reference blocks of the current block associated with one or more reference pictures, respectively; if a motion information constraint indicates that the one or more reference blocks are within a picture boundary of one or more reference pictures, respectively, encoding the current block based on the one or more reference blocks; determining a first clipping MV that points from an area in the current block to a first reference area that is an area of ​​a first reference block in the one or more reference blocks and is outside a picture boundary of a first reference picture of the one or more reference pictures, the picture boundary including the picture boundary of the first reference picture, by clipping the first MV such that the updated first reference area is within an updated first reference block that is within the picture boundary of the first reference picture; encoding the region in the current block based on the updated first reference region; transmitting said motion information constraints; Including, the current block is bi-directionally predicted in affine merge mode and includes a plurality of sub-blocks; the candidate list for the current block includes one or more affine merge candidates; For each sub-block in the plurality of sub-blocks, determining the motion information includes, for each region in the respective sub-block, determining an MV pair for the respective region based on an affine merge candidate in the one or more affine merge candidates, the MV pair including a respective first MV pointing from the region to a first region in a first reference sub-block in the first reference block and a respective second MV pointing from the region to a second region in a second reference sub-block in a second reference block associated with a second reference picture, the first reference block and the second reference block corresponding to the current block, and the first reference sub-block and the second reference sub-block corresponding to respective sub-blocks; The method of claim 1, wherein the motion information constraints indicate that each first region is within the picture boundary of the first reference picture and each second region is within the picture boundary of the second reference picture, and the picture boundaries include the picture boundary of the second reference picture.

Images