Method, apparatus and medium for decoding current video block of video bitstream

Abstract

The present disclosure relates generally to video coding, and more particularly to methods and systems for providing a signaling scheme for limiting motion vector differences (MVDs). An exemplary method includes receiving an encoded video bitstream; obtaining a motion vector difference (MVD) of a current video block from the encoded video bitstream; determining whether the MVD is signaled for only one prediction direction; in response to determining that the MVD is signaled for only one prediction direction, limiting the MVD to a predefined direction; and decoding the current video block based on the MVD.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on and claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 257,856, filed on October 20, 2021, which is incorporated herein by reference in its entirety. This application is also based on and claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 289,118, filed on December 13, 2021, which is incorporated herein by reference in its entirety. This application is also based on and claims the benefit of priority of U.S. Non-Provisional Patent Application No. 17 / 960,206, filed on October 5, 2022, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to video coding, and more particularly to methods and systems for providing a signaling scheme for limiting motion vector difference (MVD). Background Art

[0004] The background description provided herein is for the purpose of presenting the content of the present disclosure in general. The extent to which the work of the presently named inventors described in the background section and various aspects of this specification is performed does not indicate that it is prior art at the time of filing this application, and it is never explicitly or implicitly admitted that it is prior art to the present disclosure.

[0005] Video encoding and decoding may be performed using inter-picture prediction with motion compensation. An uncompressed digital video may include a series of pictures, each picture having a spatial size of, for example, 1920×1080 luminance samples and associated full chrominance samples or subsampled chrominance samples. The series of pictures may have a fixed or variable picture rate (or frame rate) of, for example, 60 pictures per second or 60 frames per second. Uncompressed video has specific bit rate requirements for streaming or data processing. For example, a video with a pixel resolution of 1920×1080, a frame rate of 60 frames per second, and a chrominance subsampling of 4:2:0 at 8 bits per pixel for each color channel requires a bandwidth of nearly 1.5 Gbit / s. One hour of such video requires more than 600 GB of storage space.

[0006] One purpose of video encoding and decoding can be to reduce redundancy in an input uncompressed video signal by compression. Compression can help reduce the bandwidth and / or storage space requirements mentioned above, in some cases by two orders of magnitude or more. Lossless compression and lossy compression and their combinations can be used. Lossless compression refers to a technique that can reconstruct an exact copy of the original signal from the compressed original signal through a decoding process. Lossy compression refers to an encoding / decoding process in which the original video information cannot be completely retained during the encoding process and cannot be completely restored during the decoding process. When lossy compression is used, the reconstructed signal may be different from the original signal, but the distortion between the original signal and the reconstructed signal is small enough so that the reconstructed signal can be used for the intended application although some information is lost. In the case of video, lossy compression is widely used in many applications. The amount of distortion that can be tolerated depends on the application. For example, users of certain consumer video streaming applications can tolerate higher distortion than users of movie or television broadcast applications. The compression ratio achievable by a particular encoding algorithm can be selected or adjusted to reflect various distortion tolerances: higher tolerable distortion generally allows encoding algorithms that produce higher losses and higher compression ratios.

[0007] Video encoders and decoders may utilize techniques from several broad categories and steps including, for example, motion compensation, Fourier transforms, quantization, and entropy coding.

[0008] Video codec techniques may 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, pictures are spatially subdivided into blocks of samples. When all sample blocks are encoded in intra-mode, the picture may be referred to as an intra-picture. Intra-pictures and their derivatives (e.g., independent decoder refresh pictures) can be used to reset the decoder state and can therefore be used as the first picture in an encoded video stream and video session, or as a still image. The samples of the block after intra-prediction can then be subjected to a transform in the frequency domain, and the transform coefficients thus generated can be quantized before entropy coding. Intra-prediction represents a technique for minimizing sample values ​​in the pre-transform domain. In some cases, the smaller the DC value after the transform and the smaller the AC coefficient, the fewer bits are required to represent the block after entropy coding at a given quantization step size.

[0009] Traditional intra-frame coding, such as known from coding techniques such as MPEG-2, does not use intra-frame prediction. However, some newer video compression techniques include techniques for encoding / decoding a block based on surrounding sample data and / or metadata obtained, for example, during spatially adjacent encoding and / or decoding, preceding the data block encoded or decoded within the frame in decoding order. Such techniques are hereinafter referred to as "intra-frame prediction" techniques. It should be noted that, at least in some cases, intra-frame prediction uses only reference data from the current picture being reconstructed, and does not use reference data from other reference pictures.

[0010] Intra-frame prediction can take many different forms. When more than one such technique can be used in a given video coding technique, the technique in use can be referred to as an intra-frame prediction mode. One or more intra-frame prediction modes can be provided in a particular codec. In some cases, a mode may have sub-modes and / or may be associated with various parameters, and the mode / sub-mode information and intra-frame coding parameters for a video block may be encoded separately or collectively included in a mode codeword. Which codeword is used for a given mode, sub-mode and / or parameter combination may affect the coding efficiency gain through intra-frame prediction, and therefore may affect the entropy coding technique used to convert the codeword into a bitstream.

[0011] H.264 introduced a certain intra prediction mode, which was improved in H.265 and further improved in newer coding technologies such as the Joint Exploration Model (JEM), Next Generation Video Coding (VVC), and Benchmark Set (BMS). In general, for intra prediction, the prediction block can be formed using values ​​belonging to neighboring samples that have become available. For example, the available values ​​of a particular group of neighboring samples along a particular direction and / or line can be copied to the predictor block. A reference to the direction in use can be encoded in the bitstream, or it can be predicted itself.

[0012] refer to Figure 1A , a subset of 9 prediction directions specified in the 33 possible intra-frame prediction directions of H.265 (corresponding to the 33 angular modes of the 35 intra-frame modes specified in H.265) is depicted at the bottom right. The point (101) where the arrows converge represents the sample being predicted. The arrows represent the directions of the neighboring samples from which the sample at 101 is predicted. For example, arrow (102) indicates that sample (101) is predicted from one or more neighboring samples at the upper right and at an angle of 45 degrees to the horizontal. Similarly, arrow (103) indicates that sample (101) is predicted from one or more neighboring samples at an angle of 22.5 degrees to the horizontal and at the lower left of sample (101).

[0013] Still reference Figure 1A, a square block (104) of 4×4 samples is depicted in the upper left (indicated by the bold dashed line). The square block (104) includes 16 samples, each of which is labeled with "S", its position in the Y dimension (e.g., row index), and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample in the Y dimension (starting from the top) and the first sample in the X dimension (starting from the left). Similarly, sample S44 is the fourth sample in the block (104) in both the Y and X dimensions. Since the size of the block is 4×4 samples, S44 is located in the lower right corner. An exemplary reference sample following a similar numbering scheme is also shown. The reference sample is labeled with R, its Y position (e.g., row index) and X position (column index) relative to the block (104). In H.264 and H.265, prediction samples that are immediately adjacent to the block being reconstructed are used.

[0014] The intra picture prediction of block 104 may start by copying reference sample values ​​from neighboring samples according to a signaled prediction direction. For example, assuming that the encoded video code stream includes signaling indicating the prediction direction of arrow (102) for this block 104, i.e., predicting samples from one or more prediction samples at the top right and at a 45 degree angle to the horizontal direction. In this case, samples S41, S32, S23, and S14 are predicted from the same reference sample R05. Sample S44 is then predicted from reference sample R08.

[0015] In some cases, the values ​​of multiple reference samples may be combined, such as by interpolation, to compute the reference sample; particularly when the directions are not evenly separated by 45 degrees.

[0016] As video coding technology continues to develop, the number of possible directions increases. In H.264 (2003), for example, nine different directions can be used for intra-frame prediction. In H.265 (2013), this increased to 33 directions, and at the time of this disclosure, JEM / VVC / BMS can support up to 65 directions. Experimental studies have been conducted to help identify the most appropriate intra-frame prediction directions, and some techniques in entropy coding can be used to encode those most appropriate directions with a small number of bits, accepting a positioning cost for the direction. In addition, the direction itself can sometimes be predicted based on the neighboring directions used in the intra-frame prediction of the already decoded neighboring blocks.

[0017] Figure 1B A schematic diagram (180) is shown depicting 65 intra prediction directions according to JEM to illustrate the increase in the number of prediction directions in various coding techniques developed over time.

[0018] The manner in which the bits representing the intra prediction direction are mapped to the prediction direction in the coded video bitstream may vary from one video coding technique to another; for example, it may range from a simple direct mapping of the prediction direction to the intra prediction mode, to a codeword, to a complex adaptive scheme involving the most probable mode, and the like. However, in all cases, there may be certain directions for intra prediction that are statistically less likely to occur in the video content than certain other directions. Since the goal of video compression is to reduce redundancy, in a well-designed video coding technique, those less likely directions will be represented by more bits than more likely directions.

[0019] Inter-picture prediction or inter-frame prediction may be based on motion compensation. In motion compensation, a block of sample data from a previously reconstructed picture or part thereof (reference picture) may be used to predict a newly reconstructed picture or picture part (e.g., block) after being spatially shifted in a direction indicated by a motion vector (hereinafter MV). In some cases, the reference picture may be the same as the picture currently being reconstructed. The MV may have two dimensions, X and Y, or three dimensions, with the third dimension indicating the reference picture being used (similar to the temporal dimension).

[0020] In some video compression techniques, the current MV applicable to a region of sample data may be predicted based on other MVs, for example, based on other MVs related to other regions of sample data that are spatially adjacent to the region being reconstructed and precede the current MV in decoding order. Doing so can greatly reduce the amount of data required to encode the MV by relying on removing redundancy in the related MVs, thereby improving compression efficiency. MV prediction can work effectively, for example, because when encoding an input video signal obtained from a camera (called natural video), there is a statistical probability that a larger area than the area to which a single MV applies moves in a similar direction in the video sequence, so in some cases, similar motion vectors derived from MVs of neighboring areas can be used to predict the larger area. This makes it believed that the actual MV for a given area is similar or identical to the MV predicted from the surrounding MVs. After entropy coding, such an MV can be represented with fewer bits than the number of bits used when the MV is directly encoded rather than predicted from neighboring MVs. In other cases, MV prediction can be an example of lossless compression of a signal (i.e., MV) derived from the original signal (i.e., sample stream). In other cases, the MV prediction itself may be lossy, for example due to round-off errors when computing the prediction value from multiple surrounding MVs.

[0021] Various MV prediction mechanisms are described in H.265 / HEVC (ITU-T Recommendation H.265, "High Efficiency Video Coding", December 2016). Among the multiple MV prediction mechanisms specified by H.265, this article describes a technique referred to below as "spatial merging".

[0022] Specifically, refer to Figure 2 , the current block (201) includes samples that have been found by the encoder during the motion search process, which can be predicted from a previous block of the same size that has been spatially offset. Instead of encoding the MV directly, the MV can be derived from metadata associated with one or more reference pictures, for example using the MV associated with any of the five surrounding samples labeled A0, A1 and B0, B1, B2 (corresponding to 202 to 206), and the MV is derived from the nearest reference picture (in decoding order). In H.265, MV prediction can use prediction values ​​from the same reference picture used by neighboring blocks. Summary of the invention

[0023] The present disclosure describes various embodiments of methods, apparatus, and computer-readable storage media for limiting motion vector differences (MVD).

[0024] According to one aspect, an embodiment of the present disclosure provides a method for decoding a current video block of a video bitstream. The method includes receiving an encoded video bitstream by a device. The device includes a memory storing instructions and a processor communicating with the memory. The method also includes obtaining a motion vector difference (MVD) for a current video block from the encoded video bitstream by the device, wherein the current video block is an inter-frame coded block in a composite reference mode; the device determines whether the MVD is signaled for only one prediction direction; in response to determining that the MVD is signaled for only one prediction direction, the device limits the MVD to a predefined direction; and the device decodes the current video block based on the MVD.

[0025] According to another aspect, an embodiment of the present disclosure provides a device for decoding a current video block of a video bitstream. The device includes a memory storing instructions and a processor communicating with the memory. When the processor executes the instructions, the processor is configured to cause the device to perform the above-mentioned method for video decoding and / or encoding.

[0026] In another aspect, an embodiment of the present disclosure provides a non-transitory computer-readable medium storing instructions, which, when executed by a computer for video decoding and / or encoding, causes the computer to perform the above-mentioned method for video decoding and / or encoding.

[0027] The above-mentioned aspects and other aspects and their implementations are described in more detail in the drawings, the description and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, properties and various advantages of the disclosed subject matter will become more apparent from the following detailed description and the accompanying drawings, in which:

[0029] Figure 1A A schematic diagram showing an exemplary subset of intra prediction direction modes;

[0030] Figure 1B A diagram showing exemplary intra prediction directions;

[0031] Figure 2 A schematic diagram showing a current block and its surrounding spatial merging candidates for motion vector prediction in an example;

[0032] Figure 3 A schematic diagram showing a simplified block diagram of a communication system (300) according to an example embodiment;

[0033] Figure 4 A schematic diagram showing a simplified block diagram of a communication system (400) according to an example embodiment;

[0034] Figure 5 A schematic diagram showing a simplified block diagram of a video decoder according to an example embodiment;

[0035] Figure 6 A schematic diagram showing a simplified block diagram of a video encoder according to an example embodiment;

[0036] Figure 7 shows a block diagram of a video encoder according to another example embodiment;

[0037] Figure 8 shows a block diagram of a video decoder according to another example embodiment;

[0038] Fig. 9 A scheme for encoding block partitioning according to an exemplary embodiment of the present disclosure is shown;

[0039] Fig.10 Another scheme of coding block partitioning according to an exemplary embodiment of the present disclosure is shown;

[0040] Fig.11 Another scheme of coding block partitioning according to an exemplary embodiment of the present disclosure is shown;

[0041] Fig.12 An example of partitioning a basic block into coding blocks according to an example partitioning scheme is shown;

[0042] Fig.13 An example ternary partitioning scheme is shown;

[0043] Fig.14 An example quadtree binary tree coding block partitioning scheme is shown;

[0044] Fig.15 A scheme for partitioning a coding block into a plurality of transform blocks and a coding order of the transform blocks according to an exemplary embodiment of the present disclosure are shown;

[0045] Fig.16 Another scheme for partitioning a coding block into a plurality of transform blocks and a coding order of the transform blocks according to an exemplary embodiment of the present disclosure are shown;

[0046] Fig.17 Another scheme for partitioning a coding block into multiple transform blocks according to an example embodiment of the present disclosure is shown;

[0047] Fig.18 A flowchart showing a method according to an example embodiment of the present disclosure is shown;

[0048] Fig.19 A schematic diagram of a computer system according to an example embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0049] Throughout the specification and claims, terms may have nuanced meanings that are suggested or implied by the context beyond their explicitly stated meanings. The phrases "in one embodiment" or "in some embodiments" as used herein do not necessarily refer to the same embodiment, and the phrases "in another embodiment" or "in other embodiments" as used herein do not necessarily refer to different embodiments. Similarly, the phrases "in one implementation" or "in some implementations" as used herein do not necessarily refer to the same implementation, and the phrases "in another implementation" or "in other implementations" as used herein do not necessarily refer to different implementations. For example, the claimed subject matter is intended to include a combination of all or part of the exemplary embodiments / implementations.

[0050] In general, terms can be understood at least in part from the usage in the context. For example, terms such as "and", "or" or "and / or" used herein may include various meanings, which may depend at least in part on the context in which the terms are used. Typically, "or" if used in an association list, such as A, B or C, is intended to represent A, B and C (the meaning used herein for inclusion) as well as A, B or C (the meaning used herein for exclusion). In addition, the terms "one or more" or "at least one" used herein, at least in part depending on the context, may be used to describe any feature, structure or characteristic in a singular sense, or may be used to describe a combination of features, structures or characteristics in a plural sense. Similarly, terms such as "a", "an" or "the" may also be understood to express singular usage or to express plural usage, at least in part depending on the context. In addition, terms such as "based on" or "determined by..." may be understood to not necessarily be intended to express a set of exclusive factors, but may allow the presence of other factors that are not necessarily explicitly described, which also depends at least in part on the context. Figure 3 A simplified block diagram of a communication system (300) according to one embodiment of the present disclosure is shown. The communication system (300) includes a plurality of terminal devices that can communicate with each other via, for example, a network (350). For example, the communication system (300) includes a first pair of terminal devices (310) and (320) interconnected via the network (350). Figure 3 In the example of , the first terminal device pair (310) and (320) can perform unidirectional data transmission. For example, the terminal device (310) can encode video data (e.g., time-frequency data of a video picture stream collected by the terminal device (310)) for transmission to another terminal device (320) via a network (350). The encoded video data can be transmitted in the form of one or more encoded video code streams. The terminal device (320) can receive the encoded video data from the network (350), decode the encoded video data to restore the video picture, and display the video picture based on the restored video data. The unidirectional data transmission can be implemented in applications such as media services.

[0051] In another example, the communication system (300) includes a second terminal device pair (330) and (340) that performs bidirectional transmission of encoded video data, which can be implemented, for example, during a video conferencing application. For bidirectional data transmission, in one example, each of the terminal devices (330) and (340) can encode video data (e.g., video data of a video picture stream collected by the terminal device) for transmission to the other terminal device (330) and (340) via a network (350). Each of the terminal devices (330) and (340) can also receive the encoded video data transmitted by the other terminal device (330) and (340), and can decode the encoded video data to restore the video picture, and can display the video picture on an accessible display device based on the restored video data.

[0052] exist Figure 3 In the example of, terminal device (310), terminal device (320), terminal device (330) and terminal device (340) can be implemented as a server, a personal computer and a smart phone, but the applicability of the basic principles of the present disclosure may not be limited to this. Embodiments of the present disclosure may be implemented on a desktop computer, a laptop computer, a tablet computer, a media player, a wearable computer, a dedicated video conferencing device and / or the like. Network (350) represents any number or type of network that transmits encoded video data between terminal devices (310), terminal devices (320), terminal devices (330) and terminal devices (340), including, for example, wired (wired) and / or wireless communication networks. Communication network (350) can exchange data in circuit switching channels, packet switching channels and / or other types of channels. Representative networks include telecommunication networks, local area networks, wide area networks and / or the Internet. For the purpose of this discussion, unless explicitly stated herein, the architecture and topology of network (350) may be irrelevant to the operation of the present disclosure.

[0053] As examples of applications for the disclosed subject matter, Figure 4 The placement of the video encoder and the video decoder in a video streaming environment is shown. The disclosed subject matter is equally applicable to other video applications, including, for example, video conferencing, digital TV broadcasting, gaming, virtual reality, storing compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0054] The video streaming system may include a video acquisition subsystem (413), which may include a video source (401), such as a digital camera, for creating an uncompressed video picture or image stream (402). In one example, the video picture stream (402) includes samples recorded by the digital camera of the video source (401). The video picture stream (402), which is depicted as a thick line to emphasize the high amount of data compared to the encoded video data (404) (or the encoded video bitstream), can be processed by an electronic device (420), which includes a video encoder (403) coupled to the video source (401). The video encoder (403) may include hardware, software, or a combination of hardware and software to implement or implement various aspects of the disclosed subject matter as described in more detail below. The encoded video data (404) (or encoded video bitstream), depicted as thin lines to emphasize the lower data volume compared to the uncompressed video picture stream (402), can be stored on the streaming server (405) for future use or directly stored to a downstream video device (not shown). One or more streaming client subsystems, such as Figure 4 The client subsystem (406) and the client subsystem (408) in the streaming server (405) can access the copy (407) and the copy (409) of the encoded video data (404). The client subsystem (406) may include, for example, a video decoder (410) in the electronic device (430). The video decoder (410) decodes the incoming copy (407) of the encoded video data and generates an uncompressed output video picture stream (411) that can be presented on a display (412) (e.g., a display screen) or other presentation device (not depicted). The video decoder 410 can be configured to perform some or all of the various functions described in the present disclosure. In some streaming systems, the encoded video data (404), (407) and (409) (e.g., video bitstreams) can be encoded according to certain video encoding / compression standards. Examples of these standards include ITU-T Recommendation H.265. In one example, the video coding standard under development is informally referred to as Next Generation Video Coding (VVC). The disclosed subject matter may be used in the context of VVC as well as other video coding standards.

[0055] It should be noted that the electronic device (420) and the electronic device (430) may include other components (not shown). For example, the electronic device (420) may include a video decoder (not shown), and the electronic device (430) may also include a video encoder (not shown).

[0056] Figure 5A block diagram of a video decoder (510) according to any of the embodiments disclosed below is shown. The video decoder (510) may be included in an electronic device (530). The electronic device (530) may include a receiver (531) (e.g., a receiving circuit). The video decoder (510) may be used to replace Figure 4 A video decoder (410) in an example of FIG.

[0057] The receiver (531) may receive one or more encoded video sequences to be decoded by the video decoder (510). In the same or another embodiment, one encoded video sequence may be decoded at a time, wherein the decoding of each encoded video sequence is independent of the other encoded video sequences. Each video sequence may be associated with multiple video frames or images. The encoded video sequence may be received from a channel (501), which may be a hardware / software link leading to a storage device storing the encoded video data or to a streaming source that sends the encoded video data. The receiver (531) may receive the encoded video data and other data, such as encoded audio data and / or ancillary data streams, which may be forwarded to their respective processing circuit systems (not depicted). The receiver (531) may separate the encoded video sequence from the other data. To prevent network jitter, a buffer memory (515) may be provided between the receiver (531) and the entropy decoder / parser (520) (hereinafter referred to as "parser (520)"). In some applications, the buffer memory (515) may be implemented as part of the video decoder (510). In other applications, the buffer memory (515) may be located outside the video decoder (510) or separate from the video decoder (510) (not depicted). In still other applications, a buffer memory (not depicted) may be provided outside the video decoder (510) for purposes such as preventing network jitter, and another additional buffer memory (515) may be provided inside the video decoder (510) for purposes such as handling playback timing. When the receiver (531) receives data from a storage / forward device with sufficient bandwidth and controllability or from an isochronous network, the buffer memory (515) may not be required or may be made smaller. For use on a traffic packet network such as the Internet, a buffer memory (515) of sufficient size may be required, which may be relatively large. Such a buffer memory may be implemented to have an adaptive size and may be implemented at least in part in an operating system or similar element (not depicted) external to the video decoder (510).

[0058] The video decoder (510) may include a parser (520) to reconstruct symbols (521) from the encoded video sequence. The categories of symbols include information for managing the operation of the video decoder (510) and potential information for controlling a presentation device such as a display (512) (e.g., a display screen), which may or may not be an integral part of the electronic device (530), but may be coupled to the electronic device (530), such as Figure 5 As shown. The control information for the rendering device may be in the form of a Supplemental Enhancement Information (SEI) message or a video usability information (VUI) parameter set fragment (not depicted). The parser (520) may parse / entropy decode the encoded video sequence received by the parser (520). The entropy encoding of the encoded video sequence may be performed according to 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) may extract a subgroup parameter set for at least one subgroup of the subgroups of pixels in the video decoder from the encoded video sequence based on at least one parameter corresponding to the subgroup. The subgroup may include a group of pictures (GOP), a picture, a tile, a slice, a macroblock, a coding unit (CU), a block, a transform unit (TU), a prediction unit (PU), etc. The parser (520) may also extract information such as transform coefficients (e.g., Fourier transform coefficients), quantizer parameter values, motion vectors, etc. from the encoded video sequence.

[0059] The parser (520) may perform entropy decoding / parsing operations on the video sequence received from the buffer memory (515), thereby creating symbols (521).

[0060] Depending on the type of coded video picture or portion of coded video picture (e.g., inter-picture and intra-picture, inter-block and intra-block) and other factors, the reconstruction of the symbol (521) may involve multiple different processing or functional units. The units involved and how they are involved may be controlled by the parser (520) through subgroup control information parsed from the coded video sequence. For the sake of brevity, such subgroup control information flow between the parser (520) and the multiple processing or functional units described below is not depicted.

[0061] In addition to the functional blocks already mentioned, the video decoder (510) can be conceptually subdivided into a number of functional units as described below. In actual implementations operating under commercial constraints, many of these functional units interact closely with each other and may be at least partially integrated with each other. However, for the purpose of clearly describing the various functions of the disclosed subject matter, the conceptual subdivision into multiple functional units is applicable in the following disclosure.

[0062] The first unit may include a sealer / inverse transform unit (551). The sealer / inverse transform unit (551) may receive quantized transform coefficients as symbols (521) and control information from the parser (520), including information indicating which type of inverse transform to use, block size, quantization factors / parameters, quantization scaling matrix, etc. The sealer / inverse transform unit (551) may output a block including sample values, which may be input into an aggregator (555).

[0063] In some cases, the output samples of the scaler / inverse transform unit (551) may belong to an intra-coded block; that is, a block that does not use prediction information from a previously reconstructed picture, but may 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) may use surrounding block information that has already been reconstructed and stored in a current picture buffer (558) to generate a block of the same size and shape as the block being reconstructed. For example, the current picture buffer (558) buffers a partially reconstructed current picture and / or a fully reconstructed current picture. In some implementations, the aggregator (555) may add the prediction information generated by the intra-prediction unit (552) to the output sample information provided by the scaler / inverse transform unit (551) on a per-sample basis.

[0064] In other cases, the output samples of the scaler / inverse transform unit (551) may belong to a block that is inter-coded and potentially motion compensated. In this case, the motion compensated prediction unit (553) may access the reference picture memory (557) to extract samples for inter-picture prediction. After the extracted samples are motion compensated according to the symbols (521) belonging to the block, these samples may be added to the output of the scaler / inverse transform unit (551) by the aggregator (555) (the output of unit 551 may be referred to as residual samples or residual signals), thereby generating output sample information. The extraction of prediction samples by the motion compensated prediction unit (553) from the address in the reference picture memory (557) may be controlled by a motion vector, which may be provided to the motion compensated prediction unit (553) in the form of symbols (521), which may have, for example, an X component, a Y component (shift) and a reference picture component (time). Motion compensation may also include interpolation of sample values ​​extracted from the reference picture memory (557) when using sub-sample accurate motion vectors, and may also be associated with a motion vector prediction mechanism, etc.

[0065] The output samples of the aggregator (555) may be subjected to various loop filtering techniques in a loop filter unit (556). The video compression techniques may include in-loop filter techniques controlled by parameters included in the coded video sequence (also referred to as a coded video bitstream) and available to the loop filter unit (556) as symbols (521) from the parser (520), however, the video compression techniques may also be responsive to meta information obtained during decoding of a previous (in decoding order) portion of the coded picture or coded video sequence, as well as to previously reconstructed and loop filtered sample values. Several types of loop filters may be included as part of the loop filter unit 556 in various orders, as described in further detail below.

[0066] The output of the loop filter unit (556) may be a sample stream that may be output to a rendering device (512) and stored in a reference picture memory (557) for future inter-picture prediction.

[0067] Once fully reconstructed, certain coded pictures may be used as reference pictures for future inter-picture prediction. For example, once the coded picture corresponding to the 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) may become part of the reference picture memory (557), and a new current picture buffer may be reallocated before starting to reconstruct a subsequent coded picture.

[0068] The video decoder (510) may perform decoding operations according to a predetermined video compression technique employed in a standard such as ITU-T Recommendation H.265. The encoded video sequence may conform to the syntax specified by the video compression technique or standard used in the sense that the encoded video sequence follows the syntax of the video compression technique or standard and the profile recorded in the video compression technique or standard. Specifically, the profile may select certain tools from all the tools available in the video compression technique or standard as the only tools available for use under the profile. For compliance, the complexity of the encoded video sequence may be within a range defined by the hierarchy of the video compression technique or standard. In some cases, the hierarchy limits the maximum picture size, maximum frame rate, maximum reconstruction sampling rate (measured in, for example, mega samples per second), maximum reference picture size, etc. In some cases, the limits set by the hierarchy may be further defined by the hypothetical reference decoder (HRD) specification and metadata of the HRD buffer management signaled in the encoded video sequence.

[0069] In some exemplary embodiments, the receiver (531) may receive additional (redundant) data when receiving the encoded video. The additional data may be included as part of the encoded video sequence. The additional data may be used by the video decoder (510) to properly decode the data and / or more accurately reconstruct the original video data. The additional data may take the form of, for example, temporal, spatial or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0070] Figure 6 A block diagram of a video encoder (603) according to an exemplary embodiment of the present disclosure is shown. The video encoder (603) may be included in an electronic device (620). The electronic device (620) may also include a transmitter (640) (e.g., a transmission circuit). The video encoder (603) may be used to replace Figure 4 A video encoder (403) in an example.

[0071] The video encoder (603) can be used to obtain the video source (601) (not Figure 6 In an example of an electronic device (620) of FIG. 6 , a video source (601) may receive video samples and may capture video images to be encoded by a video encoder (603). In another example, the video source (601) may be implemented as a part of the electronic device (620).

[0072] The video source (601) may provide a source video sequence in the form of a digital video sample stream to be encoded by a video encoder (603), the digital video sample stream may have any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 YCrCB, RGB, XYZ, ...), 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 capable of storing previously prepared videos. In a video conferencing system, the video source (601) may be a camera that captures local image information as a video sequence. The video data may be provided as a plurality of separate pictures or images that are given motion when viewed sequentially. The picture itself may be constructed as a spatial pixel array, wherein each pixel may include one or more samples depending on the sampling structure, color space, etc. used. The relationship between pixels and samples may be easily understood by those skilled in the art. The following description focuses on the samples.

[0073] According to some exemplary embodiments, the video encoder (603) may encode and compress pictures of a source video sequence into an encoded video sequence (643) in real time or under any other time constraints required by the application. Implementing an appropriate encoding speed constitutes a function of the controller (650). In some embodiments, the controller (650) may be functionally coupled to and control other functional units as described below. For the sake of brevity, the coupling is not depicted in the figure. The parameters set by the controller (650) may include rate control related parameters (picture skipping, quantizer, lambda value of rate distortion optimization techniques, etc.), picture size, picture group (GOP) layout, maximum motion vector search range, etc. The controller (650) may be configured to have other suitable functions that are related to the video encoder (603) optimized for a certain system design.

[0074] In some exemplary embodiments, the video encoder (603) may be configured to operate in an encoding loop. As an oversimplified description, in one example, the encoding loop may include a source encoder (630) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be encoded and a reference picture) and a (local) decoder (633) embedded in the video encoder (603). The decoder (633) reconstructs the symbols to create sample data in a manner similar to the (remote) decoder, even if the embedded decoder 633 processes the encoded video stream encoded by the source encoder (630) without entropy coding (because in the video compression techniques considered in the disclosed subject matter, any compression between the symbols and the encoded video code stream in entropy coding can be lossless). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since the decoding of the symbol stream produces a bit-accurate result that is independent of the decoder location (local or remote), the contents of the reference picture memory (634) are also bit-accurately corresponding between the local encoder and the remote encoder. In other words, the reference picture samples "seen" by the prediction part of the encoder are exactly the same sample values ​​that the decoder will "see" when using the prediction during decoding. This basic principle of reference picture synchronization (and the drift that occurs when synchronization cannot be maintained, e.g. due to channel errors) is also used to improve encoding quality.

[0075] The operation of the "local" decoder (633) may be similar to that described above in conjunction with Figure 5 The "remote" decoder of the video decoder (510) described in detail is identical. However, additional brief reference is made to Figure 5, since the symbols are available and the entropy encoder (645) and the parser (520) are capable of losslessly encoding / decoding the symbols into the encoded video sequence, the entropy decoding portion of the video decoder (510) including the buffer memory (515) and the parser (520) may not be fully implemented in the encoder's local decoder (633).

[0076] It can be observed at this point that any decoder technology, except for the parsing / entropy decoding that may only exist in the decoder, can be present in the corresponding encoder in the same or substantially the same functional form. Therefore, the disclosed subject matter sometimes focuses on the decoder operation, which is associated with the decoding part of the encoder. Because the encoder technology is mutually inverse to the decoder technology described comprehensively, the description of the encoder technology can be simplified thereby. In some areas or aspects, a more detailed description of the encoder is provided below.

[0077] During operation, in some example implementations, the source encoder (630) may perform motion compensated predictive coding that predictively encodes an input picture by referencing one or more previously encoded pictures from a video sequence designated as "reference pictures." In this manner, the encoding engine (632) encodes the differences (or residuals) in color channels between pixel blocks of the input picture and pixel blocks of a reference picture that may be selected as a prediction reference for the input picture. The term "residual" and its adjective form "residual" may be used interchangeably.

[0078] The local video decoder (633) may decode the encoded video data of the picture that may be designated as the reference picture based on the symbol created by the source encoder (630). The operation of the encoding engine (632) may advantageously be a lossy process. When the encoded video data may be decoded at the video decoder ( Figure 6 When the video encoder (603) is decoded in a local video decoder (not shown), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (633) replicates the decoding process that may be performed by the video decoder on the reference picture and may cause the reconstructed reference picture to be stored in the reference picture memory (634). In this way, the video encoder (603) may store a copy of the reconstructed reference picture locally that has common content (absent transmission errors) with the reconstructed reference picture to be obtained by the far-end (remote) video decoder.

[0079] The predictor (635) may perform a prediction search for the encoding engine (632). That is, for a new picture to be encoded, the predictor (635) may search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or certain metadata, such as reference picture motion vectors, block shapes, etc., that may be used as appropriate prediction references for the new picture. The predictor (635) may operate on a pixel block by pixel block basis to find a suitable prediction reference. In some cases, as determined by the search results obtained by the predictor (635), the input picture may have prediction references taken from multiple reference pictures stored in the reference picture memory (634).

[0080] The controller (650) may manage encoding operations of the source encoder (630), including, for example, setting parameters and subgroup parameters for encoding video data.

[0081] The outputs of all the above functional units may be entropy encoded in an entropy encoder (645). The entropy encoder (645) performs lossless compression on the symbols generated by the various functional units according to techniques such as Huffman coding, variable length coding, arithmetic coding, etc., thereby converting the symbols into a coded video sequence.

[0082] The transmitter (640) can buffer the encoded video sequence created by the entropy encoder (645) in preparation for transmission over a communication channel (660), which can be a hardware / software link to a storage device that can store the encoded video data. The transmitter (640) can combine the encoded video data from the video encoder (603) with other data to be transmitted, such as encoded audio data and / or auxiliary data streams (source not shown).

[0083] The controller (650) may manage the operation of the video encoder (603). During encoding, the controller (650) may assign a certain coded picture type to each coded picture, but this may affect the coding techniques that can be applied to the corresponding picture. For example, a picture may generally be assigned to any of the following picture types:

[0084] An intra picture (I picture) may be a picture that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs allow for different types of intra pictures, including, for example, independent decoder refresh ("IDR") pictures. Those of ordinary skill in the art are aware of these variations of I pictures and their corresponding applications and features.

[0085] A predictive picture (P picture) may be a picture that can be encoded and decoded using intra prediction or inter prediction, which uses at most one motion vector and a reference index to predict sample values ​​for each block.

[0086] Bidirectional predictive pictures (B pictures), which can be pictures that can be encoded and decoded using intra-frame prediction or inter-frame prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple predictive pictures can use more than two reference pictures and associated metadata to reconstruct a single block.

[0087] The source picture can typically be spatially subdivided into multiple sample coding blocks (for example, blocks of 4×4, 8×8, 4×8 or 16×16 samples) and encoded block by block. These blocks can be predictively encoded with reference to other (encoded) blocks, which are determined by the coding allocation applied to the corresponding picture of the block. For example, blocks of I pictures can be non-predictively encoded, or blocks of I pictures can be predictively encoded (spatial prediction or intra-frame prediction) with reference to encoded blocks of the same picture. Pixel blocks of P pictures can be predictively encoded by spatial prediction or by temporal prediction with reference to a previously encoded reference picture. Blocks of B pictures can be predictively encoded by spatial prediction or by temporal prediction with reference to one or two previously encoded reference pictures. For other purposes, source pictures or intermediate processing pictures can be subdivided into other types of blocks. The division of coding blocks and other types of blocks may or may not follow the same approach, which will be described in further detail below.

[0088] The video encoder (603) may perform encoding operations according to a predetermined video encoding technique or standard, such as ITU-T H.265 Recommendation. In operation, the video encoder (603) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancy in an input video sequence. The encoded video data may accordingly conform to the syntax specified by the video encoding technique or standard used.

[0089] In some exemplary embodiments, the transmitter (640) may transmit additional data when transmitting 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.

[0090] The acquired video may be taken as a number of source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often simplified to intra-frame prediction) exploits spatial correlations in a given picture, while inter-picture prediction exploits (temporal or other) correlations between pictures. For example, a particular picture being encoded / decoded may be divided into blocks, and the particular picture being encoded / decoded is referred to as the current picture. Blocks in the current picture may be encoded by vectors called motion vectors when the blocks in the current picture are similar to reference blocks in reference pictures that were previously encoded in the video and are still buffered. The motion vector points to a reference block in a reference picture, and in the case where multiple reference pictures are used, the motion vector may have a third dimension that identifies the reference picture.

[0091] In some exemplary embodiments, a bidirectional prediction technique may be used for inter-picture prediction. According to the bidirectional prediction technique, two reference pictures are used, such as a first reference picture and a second reference picture that precede the current picture in the video in decoding order (but may be in the past or future in display order, respectively). A block in the current picture may be encoded by a first motion vector pointing to a first reference block in the first reference picture and a second motion vector pointing to a second reference block in the second reference picture. The block may be jointly predicted by a combination of the first reference block and the second reference block.

[0092] In addition, merge mode technology can be used for inter-picture prediction to improve coding efficiency.

[0093] According to some exemplary embodiments of the present disclosure, predictions such as inter-picture prediction and intra-picture prediction are performed in units of blocks. For example, a picture in a video picture sequence is divided into coding tree units (CTUs) for compression, and the CTUs in the picture may have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. Typically, a CTU may include three parallel coding tree blocks (CTBs), which are a luminance CTB and two chrominance CTBs. Each CTU may be recursively divided into one or more coding units (CUs) in a quadtree. For example, a 64×64 pixel CTU may be divided into a 64×64 pixel CU, or four 32×32 pixel CUs. Each of the one or more 32×32 blocks may be further divided into four 16×16 pixel CUs. In some exemplary embodiments, each CU may be analyzed during encoding to determine the prediction type of the CU among various prediction types such as an inter-frame prediction type or an intra-frame prediction type. Depending on temporal and / or spatial predictability, a CU may be divided into one or more prediction units (PUs). Typically, each PU includes one luma prediction block (PB) and two chroma PBs. In one embodiment, the prediction operation in encoding (encoding / decoding) is performed in units of prediction blocks. The CU can be divided into PUs (or PBs of different color channels) in various spatial modes. For example, one luma or chroma PB can include a matrix of values ​​(e.g., luma values) of samples such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, etc.

[0094] Figure 7 A diagram of a video encoder (703) according to another exemplary embodiment of the present disclosure is shown. The video encoder (703) is configured to receive a processed block (e.g., a predicted block) of sample values ​​within a current video picture in a sequence of video pictures, and encode the processed block into an encoded picture that is part of an encoded video sequence. In one example, the video encoder (703) may be used instead of Figure 4 A video encoder (403) in an example.

[0095] For example, the video encoder (703) receives a matrix of sample values ​​for a processing block, such as a prediction block of 8×8 samples, etc. The video encoder (703) then uses, for example, rate-distortion optimization (RDO) to determine whether to use intra mode, inter mode, or bidirectional prediction mode to best encode the processing block. When it is determined that the processing block is to be encoded in intra mode, the video encoder (703) may use intra prediction techniques to encode the processing block into an encoded picture; and when it is determined that the processing block is to be encoded in inter mode or bidirectional prediction mode, the video encoder (703) may use inter prediction or bidirectional prediction techniques to encode the processing block into an encoded picture, respectively. In some exemplary embodiments, the merge mode may be a sub-mode of inter-picture prediction, in which motion vectors are derived from one or more motion vector predictors without the aid of encoded motion vector components external to the predictor. In some other exemplary embodiments, there may be motion vector components applicable to the subject block. Accordingly, the video encoder (703) may include other modes not in the merge mode. Figure 7 Components explicitly shown in, such as a mode decision module for determining a prediction mode for a processing block.

[0096] exist Figure 7 In the example of FIG. 7 , the video encoder ( 703 ) includes Figure 7 The exemplary arrangement shown is an inter-frame encoder (730), an intra-frame encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721) and an entropy encoder (725) coupled together.

[0097] The inter-frame 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 a previous picture and a subsequent picture in display order), generate inter-frame prediction information (e.g., redundant information description according to an inter-frame coding technique, motion vectors, merge mode information), and calculate an inter-frame prediction result (e.g., a predicted block) based on the inter-frame prediction information using any suitable technique. In some examples, the reference picture is encoded using a decoded image embedded in a decoded image. Figure 6 The decoding unit 633 (shown as Figure 7 The residual decoder 728 (described in further detail below) decodes the decoded reference pictures based on the encoded video information.

[0098] The intra encoder (722) is configured to receive samples of a current block (e.g., a processing block), compare the block with an encoded block in the same picture, and generate quantization coefficients after transformation, and in some cases also generate intra prediction information (e.g., intra prediction direction information according to one or more intra coding techniques). The intra encoder (722) can calculate an intra prediction result (e.g., a predicted block) based on the intra prediction information and a reference block in the same picture.

[0099] The general controller (721) can be 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 a prediction mode for a block and provides a control signal to a switch (726) based on the prediction mode. For example, when the prediction mode is an intra-frame mode, the general controller (721) controls the switch (726) to select an intra-frame mode result for use by the residual calculator (723), and controls the entropy encoder (725) to select intra-frame prediction information and include the intra-frame prediction information in the bitstream; and when the prediction mode for the block is an inter-frame mode, the general controller (721) controls the switch (726) to select an inter-frame prediction result for use by the residual calculator (723), and controls the entropy encoder (725) to select inter-frame prediction information and include the inter-frame prediction information in the bitstream.

[0100] The residual calculator (723) may be configured to calculate the difference (residual data) between the received block and the prediction result for the block selected from the intra encoder (722) or the inter encoder (730). The residual encoder (724) may be configured to encode the residual data to generate a transform coefficient. For example, the residual encoder (724) may be configured to convert the residual data from the spatial domain to the frequency domain to generate the transform coefficient. The transform coefficient is then subjected to quantization to obtain a quantized transform coefficient. In various exemplary embodiments, the video encoder (703) further includes a residual decoder (728). The residual decoder (728) is configured to perform an inverse transform and generate decoded residual data. The decoded residual data may be appropriately used by the intra encoder (722) and the inter encoder (730). For example, the inter encoder (730) may generate a decoded block based on the decoded residual data and the inter prediction information, and the intra encoder (722) may generate a decoded block based on the decoded residual data and the intra prediction information. The decoded blocks are appropriately processed to generate decoded pictures, and the decoded pictures may be buffered in a memory circuit (not shown) and used as reference pictures.

[0101] The entropy encoder (725) may be configured to format the code stream to include the encoded blocks and perform entropy encoding. The entropy encoder (725) is configured to include various information in the bit stream. For example, the entropy encoder (725) may be configured to include general control data, selected prediction information (e.g., intra-frame prediction information or inter-frame prediction information), residual information, and other suitable information in the code stream. When the block is encoded in the merge sub-mode of the inter-frame mode or the bidirectional prediction mode, there may be no residual information.

[0102] Figure 8 A diagram of an example video decoder (810) according to another embodiment of the present disclosure is shown. The video decoder (810) is configured to receive an encoded picture as part of an encoded video sequence and decode the encoded picture to generate a reconstructed picture. In one example, the video decoder (810) may be used instead of Figure 4 A video decoder (410) in an example of FIG.

[0103] exist Figure 8 In the example of FIG. 8 , the video decoder ( 810 ) includes Figure 8 The example arrangement shown in FIG. 8 includes an entropy decoder (871), an inter-frame decoder (880), a residual decoder (873), a reconstruction module (874), and an intra-frame decoder (872) coupled together.

[0104] The entropy decoder (871) may be configured to reconstruct certain symbols from the encoded picture, the symbols representing syntax elements constituting the encoded picture. Such symbols may include, for example, a mode for encoding a block (e.g., intra mode, inter mode, bidirectional prediction mode, merge submode, or another submode), prediction information (e.g., intra prediction information or inter prediction information) that may identify certain samples or metadata used by an intra decoder (872) or an inter decoder (880) for prediction, residual information in the form of, for example, quantized transform coefficients, and the like. In one example, when the prediction mode is an inter or bidirectional prediction mode, the inter prediction information is provided to an inter decoder (880); and when the prediction type is an intra prediction type, the intra prediction information is provided to an intra decoder (872). The residual information may be subjected to inverse quantization and provided to a residual decoder (873).

[0105] The inter-frame decoder (880) may be configured to receive the inter-frame prediction information and generate an inter-frame prediction result based on the inter-frame prediction information.

[0106] The intra decoder (872) can be configured to receive intra prediction information and generate a prediction result based on the intra prediction information.

[0107] The residual decoder (873) may be configured to perform inverse quantization to extract dequantized transform coefficients, and process the dequantized transform coefficients to convert the residual from the frequency domain to the spatial domain. The residual decoder (873) may also require certain control information (to include quantizer parameters (QP)), which may be provided by the entropy decoder (871) (data path not depicted because this is only low data volume control information).

[0108] The reconstruction module (874) may be configured to combine the residual output by the residual decoder (873) with the prediction result (which may be output by the inter-frame prediction module or the intra-frame prediction module, as appropriate) in the spatial domain to form a reconstructed block, which forms part of a reconstructed picture, which is part of the reconstructed video. It should be noted that other suitable operations such as deblocking operations may be performed to improve visual quality.

[0109] It should be noted that the video encoder (403), video encoder (603) and video encoder (703) and video decoder (410), video decoder (510) and video decoder (810) may be implemented using any suitable technology. In some exemplary embodiments, the video encoder (403), video encoder (603) and video encoder (703) and video decoder (410), video decoder (510) and video decoder (810) may be implemented using one or more integrated circuits. In another embodiment, the video encoder (403), video encoder (603) and video encoder (603) and video decoder (410), video decoder (510) and video decoder (810) may be implemented using one or more processors that execute software instructions.

[0110] Turning to the block partitioning for encoding and decoding, general partitioning can start from the basic block and can follow a predefined set of rules, a specific pattern, a partition tree, or any partition structure or scheme. Partitioning can be hierarchical and recursive. After separating or partitioning the basic block according to any of the example partitioning processes described below or other processes or combinations thereof, a final set of partitions or coding blocks can be obtained. Each of these partitions can be at one of the various partition levels in the partition hierarchy and can have various shapes. Each partition can be referred to as a coding block (CB). For the various example partitioning implementations further described below, each resulting CB can be any of the allowed sizes and partition levels. Such partitions are called coding blocks because they can form units for which some basic encoding / decoding decisions can be made, and encoding / decoding parameters can be optimized, determined, and signaled in the encoded video bitstream to notify encoding / decoding parameters. The highest or deepest level in the final partition represents the depth of the coding block partition structure of the tree. The coding block can be a luminance coding block or a chrominance coding block. The CB tree structure for each color can be referred to as a coding block tree (CBT).

[0111] The coding blocks of all color channels may be collectively referred to as coding units (CUs). The hierarchical structure of all color channels may be collectively referred to as coding tree units (CTUs). The partition patterns or structures of various color channels in a CTU may be the same or different.

[0112] In some implementations, the partition tree schemes or structures for the luma channel and the chroma channel may not need to be the same. In other words, the luma channel and the chroma channel may have separate coding tree structures or patterns. In addition, whether the luma channel and the chroma channel use the same or different coding partition tree structures and the actual coding partition tree structure to be used may depend on whether the slice being encoded is a P slice, a B slice, or an I slice. For example, for an I slice, the chroma channel and the luma channel may have separate coding partition tree structures or coding partition tree structure patterns, while for a P slice or a B slice, the luma channel and the chroma channel may share the same coding partition tree scheme. When a separate coding partition tree structure or pattern is used, the luma channel may be partitioned into CBs by one coding partition tree structure, and the chroma channel may be partitioned into chroma CBs by another coding partition tree structure.

[0113] In some example implementations, a predefined partitioning pattern may be applied to a basic block. Fig. 9As shown, the example 4-way partition tree may start from a first predefined level (e.g., 64×64 block level or other size as a basic block size), and the basic blocks may be hierarchically partitioned down to a predefined lowest level (e.g., 4×4 level). For example, the basic blocks may be subjected to four predefined partitioning options or patterns indicated by 902, 904, 906, and 908, and the partition designated as R is allowed for recursive partitioning because, as Fig. 9 The same partitioning pattern shown may be repeated at lower scales until partitioning reaches the lowest level (e.g., 4×4 level). In some implementations, additional restrictions may be applied to Fig. 9 The partition scheme of Fig. 9 In an implementation of , rectangular partitions (e.g., 1:2 / 2:1 rectangular partitions) may be allowed, but they are not allowed to be recursive, while square partitions are allowed to be recursive. Fig. 9 The partitioning in has recursion, if necessary, to generate a final set of coding blocks. The coding tree depth can be further defined to indicate the depth of the partition starting from the root node or root block. For example, the coding tree depth of the root node or root block (e.g., 64×64 block) can be set to 0, and the root block is in accordance with Fig. 9 After being further partitioned once, the coding tree depth increases by 1. For the above scheme, the maximum or deepest level from the 64×64 basic block to the 4×4 minimum partition will be 4 (starting from level 0). This partitioning scheme can be applied to one or more color channels. Each color channel can be divided according to Fig. 9 The partitioning scheme is performed independently (e.g., for each color channel at each hierarchical level, a partitioning pattern or option in a predefined pattern can be determined independently). Optionally, two or more color channels can share Fig. 9 The same hierarchical pattern tree in the (e.g., the same partition pattern or option in the predefined patterns can be selected for two or more color channels at each hierarchical level).

[0114] Fig.10 Another example of a predefined partitioning pattern that allows recursive partitioning to form a partition tree is shown. Fig.10 As shown, an exemplary 10-way partition structure or pattern may be predefined. A root block may start at a predefined level (eg, starting from a 128×128 level or a 64×64 level of basic blocks). Fig.10 Example partition structures include various 2:1 / 1:2 and 4:1 / 1:4 rectangular partitions. Fig.10 The partition type with 3 sub-partitions indicated by 1002, 1004, 1006 and 1008 in the second row of can be referred to as a "T-type" partition. The "T-type" partitions 1002, 1004, 1006 and 1008 can be referred to as a left T-type, an upper T-type, a right T-type and a lower T-type. In some exemplary implementations, Fig.10 None of the rectangular partitions are allowed to be further subdivided. The coding tree depth can be further defined to indicate the partition depth starting from the root node or root block. For example, the coding tree depth of the root node or root block (e.g., 128×128 block) can be set to 0, and the coding tree depth of the root block can be set to 0. Fig.10 After being further divided once, the coding tree depth increases by 1. In some implementations, only full square partitions in 1010 may be allowed to be divided according to Fig.10 In other words, for the square partitions within the T-patterns 1002, 1004, 1006, and 1008, recursive partitioning may not be allowed. Fig.10 The partitioning process of is recursive to generate a final set of coding blocks. This scheme can be applied to one or more color channels. In some implementations, more flexibility can be added to the use of partitions below the 8×8 level. For example, 2×2 chroma inter-frame prediction can be used in some cases.

[0115] In some other example implementations for coding block partitioning, a quadtree structure can be used to partition a basic block or an intermediate block into quadtree partitions. This quadtree partitioning can be applied hierarchically and recursively to any square partition. Whether to further quadtree partition a basic block or an intermediate block or a partition can be adjusted for various local features of the basic block or intermediate block / partition. The quadtree partitions at the picture boundaries can be further adjusted. For example, implicit quadtree partitioning can be performed at the picture boundaries so that the block will continue to be quadtree partitioned until the size of the block fits the picture boundary.

[0116] In some other example implementations, a hierarchical binary tree partitioning starting from a basic block can be used. For such a scheme, a basic block or an intermediate horizontal block can be partitioned into two partitions. The binary tree partitioning can be horizontal or vertical. For example, a horizontal binary tree partitioning can divide a basic block or an intermediate block into equal right and left partitions. Similarly, a vertical binary tree partitioning can divide a basic block or an intermediate block into equal upper and lower partitions. This binary tree partitioning can be hierarchical and recursive. A decision can be made at each of the basic blocks or intermediate blocks whether the binary tree partitioning scheme should be continued, and if the scheme does continue further, it is decided whether horizontal binary tree partitioning or vertical binary tree partitioning should be used. In some implementations, further partitioning can stop at a predefined minimum partition size (in one dimension or two dimensions). Optionally, further partitioning can be stopped once a predefined partition level or depth from a basic block is reached. In some implementations, the aspect ratio of the partition can be constrained. For example, the aspect ratio of the partition can be not less than 1:4 (or not greater than 4:1). Thus, a vertical strip partition having a vertical to horizontal aspect ratio of 4:1 may only be further vertically binary-tree partitioned into upper and lower partitions each having a vertical to horizontal aspect ratio of 2:1.

[0117] In some other examples, such as Fig.13 As shown, the ternary tree partitioning scheme can be used to partition the basic block or any intermediate block. The ternary tree pattern can be implemented vertically, such as Fig.13 1302, or horizontally implemented, such as Fig.13 1304. Fig.13 The example partition ratios in , whether horizontal or vertical, are shown as 1:2:1, and other ratios can be predefined. In some implementations, two or more different ratios can be predefined. This ternary tree partitioning scheme can be used to supplement the quadtree or binary tree partitioning structure, because this ternary tree partitioning can capture objects located at the center of the block in one continuous partition, while the quadtree and binary tree are always divided along the center of the block, thereby dividing the objects into different partitions. In some implementations, the width and height of the partitions of the example ternary tree are always powers of 2 to avoid additional transformations.

[0118] The above partitioning schemes can be combined in any way at different partitioning levels. As an example, the above quadtree and binary tree partitioning schemes can be combined to partition a basic block into a quadtree-binary-tree (QTBT) structure. In such a scheme, a basic block or intermediate block / partition can be a quadtree partition or a binary tree partition, if specified, subject to a set of predefined conditions. A specific example is Fig.14 As shown. Fig.14In the example of , a basic block is first quadtree-partitioned into four partitions, as shown in 1402, 1404, 1406, and 1408. Thereafter, each of the resulting partitions is either quadtree-partitioned into four further partitions (e.g., 1408), or binary-partitioned into two further partitions (e.g., horizontally or vertically partitioned, such as 1402 or 1406, both of which are symmetrical), or non-partitioned (e.g., 1404) at the next level. For square partitions, binary or quadtree partitions may be recursively allowed, as shown in the overall exemplary partition pattern of 1410 and the corresponding tree structure / representation in 1420, where solid lines represent quadtree partitions and dashed lines represent binary tree partitions. A flag may be used for each binary tree partition node (non-leaf binary tree partition) to indicate whether the binary tree partition is horizontally or vertically partitioned. For example, as shown in 1420, consistent with the partition structure of 1410, the flag "0" may indicate horizontal binary tree partitioning, and the flag "1" may indicate vertical binary tree partitioning. For quadtree partitioning, there is no need to indicate the partition type, because quadtree partitioning always divides a block or partition horizontally and vertically to produce 4 sub-blocks / sub-partitions of equal size. In some implementations, the flag "1" may indicate horizontal binary tree partitioning, and the flag "0" may indicate vertical binary tree partitioning.

[0119] In some example implementations of QTBT, the quadtree and binary tree partitioning rule sets may be represented by the following predefined parameters and corresponding functions associated therewith:

[0120] -CTU size: the root node size of the quadtree (the size of the basic block)

[0121] -MinQTSize: The minimum allowed quad leaf node size

[0122] -MaxBTSize: Maximum allowed binary tree root node size

[0123] -MaxBTDepth: Maximum allowed binary tree depth

[0124] -MinBTSize: The minimum allowed binary tree leaf node size

[0125] In some example implementations of the QTBT partition structure, the CTU size can be set to 128×128 luma samples with two corresponding 64×64 chroma sample blocks (when example chroma subsampling is considered and used), MinQTSize can be set to 16×16, MaxBTSize can be set to 64×64, MinBTSize (for both width and height) can be set to 4×4, and MaxBTDepth can be set to 4. Quadtree partitioning can be first applied to the CTU to generate quadtree leaf nodes. Quadtree leaf nodes can have sizes from their minimum allowed size of 16×16 (i.e., MinQTSize) to 128×128 (i.e., CTU size). If a node is 128×128, it will not be partitioned by the binary tree first because its size exceeds the MaxBTSize (i.e., 64×64). In addition, nodes that do not exceed MaxBTSize can be partitioned with a binary tree. Fig.14 In the example, the basic block is 128×128. According to the predefined set of rules, the basic block can only be partitioned by quadtree. The partition depth of the basic block is 0. Each of the four partitions obtained is 64x64, not exceeding MaxBTSize, and can be further partitioned by quadtree or binary tree at level 1. This process will continue. When the binary tree depth reaches MaxBTDepth (i.e. 4), further partitioning can be ignored. When the width of the binary tree node is equal to MinBTSize (i.e. 4), further horizontal partitioning can be ignored. Similarly, when the height of the binary tree node is equal to MinBTSize, further vertical partitioning is not considered.

[0126] In some example implementations, the above-mentioned QTBT scheme can be configured to support the flexibility of having the same QTBT structure or different QTBT structures for luma and chroma. For example, for P slices and B slices, the luma and chroma CTBs in a CTU can share the same QTBT structure. However, for I slices, the luma CTB can be partitioned into luma CBs by one QTBT structure, and the chroma CTB can be partitioned into chroma CBs by another QTBT structure. This means that a CU can be used to refer to different color channels in an I slice, for example, a CU in an I slice can consist of coding blocks of a luma component or coding blocks of two chroma components, while a CU in a P slice or a B slice can consist of coding blocks of all three color components.

[0127] In some other implementations, the QTBT solution can be supplemented by the above-mentioned ternary tree solution. This implementation can be called a multi-type-tree (MTT) structure. For example, in addition to the binary tree partitioning of the nodes, you can also choose Fig.13In some implementations, only square nodes can be subjected to ternary tree partitioning. An additional flag can be used to indicate whether the ternary tree partition is horizontal or vertical.

[0128] The design of two-level or multi-level trees, such as QTBT implementations and QTBT implementations supplemented by ternary tree partitioning, may be driven primarily by complexity reduction. In theory, the complexity of traversing the tree is T D , where T is the number of partition types and D is the depth of the tree. You can use multiple types (T) to make a trade-off while reducing the depth (D).

[0129] In some implementations, the CB may be further partitioned. For example, in order to perform intra-frame or inter-frame prediction during the encoding and decoding process, the CB may be further partitioned into a plurality of prediction blocks (PBs). In other words, the CB may be further divided into different sub-partitions, in which separate prediction decisions / configurations may be made. In parallel, in order to depict the level of performing the transformation or inverse transformation of the video data, the CB may be further partitioned into a plurality of transform blocks (TBs). The schemes for partitioning the CB into PBs and TBs may be the same or different. For example, each partitioning scheme may be performed using its own program based on various features of the video data, for example. In some example implementations, the PB and TB partitioning schemes may be independent. In some other example implementations, the PB and TB partitioning schemes and boundaries may be related. In some implementations, for example, the TB may be partitioned after the PB partitioning, and specifically, after determining the subsequent partitioning of the coding block, each PB may then be further partitioned into one or more TBs. For example, in some implementations, the PB may be divided into one, two, four, or other number of TBs.

[0130] In some implementations, in order to partition a basic block into a coding block and further partition it into a prediction block and / or a transform block, the luma channel and the chroma channel may be treated differently. For example, in some implementations, for the luma channel, it may be allowed to partition the coding block into a prediction block and / or a transform block, while for the chroma channel, it may not be allowed to partition the coding block into a prediction block and / or a transform block. In such an implementation, the transform and / or prediction of the luma block may be performed only at the coding block level. For another example, the minimum transform block size of the luma channel and the chroma channel may be different, for example, the size of the transform block and / or prediction block into which the coding block of the luma channel is partitioned may be smaller than the size of the transform block and / or prediction block into which the coding block of the chroma channel is partitioned. For yet another example, the maximum depth of dividing the coding block into transform blocks and / or prediction blocks may be different between the luma channel and the chroma channel, for example, the depth of the transform block and / or prediction block into which the coding block of the luma channel is partitioned may be allowed to be deeper than the depth of the transform block and / or prediction block into which the coding block of the chroma channel is partitioned. For a specific example, a luma coding block may be partitioned into transform blocks of multiple sizes, which may be represented by recursive partitioning down to at most 2 levels, and may allow transform block shapes such as square, 2:1 / 1:2, and 4:1 / 1:4, and transform block sizes from 4×4 to 64×64. However, for chroma blocks, only the largest possible transform block specified for the luma block may be allowed.

[0131] In some example implementations for partitioning a coding block into PBs, the depth, shape, and / or other characteristics of the PB partitions may depend on whether the PB is intra-coded or inter-coded.

[0132] Partitioning a coding block (or prediction block) into transform blocks can be implemented in various example schemes, including but not limited to recursively or non-recursively quadtree partitioning and partitioning with a predefined pattern, and additionally considering transform blocks at the boundaries of the coding block or prediction block. In general, the resulting transform blocks may be at different partition levels, may not have the same size, and may not need to be square in shape (e.g., may be rectangular with some allowed size and aspect ratio). Fig.15 , Fig.16 and Fig.17 Further examples are described in more detail.

[0133] However, in some other implementations, the CB obtained via any of the above-mentioned partitioning schemes may be used as a basic coding block or a minimum coding block for prediction and / or transformation. In other words, no further partitioning is performed for the purpose of performing inter-frame prediction / intra-frame prediction and / or transformation. For example, the CB obtained from the above-mentioned QTBT scheme can be directly used as a unit for performing prediction. Specifically, such a QTBT structure eliminates the concept of multiple partition types, that is, eliminates the separation of CU, PU and TU, and supports greater flexibility in the CU / CB partition shape as described above. In this QTBT block structure, the CU / CB can have a square or rectangular shape. The leaf nodes of this QTBT are used as units of prediction and transformation processing without any further partitioning. This means that in this example QTBT coding block structure, the CU, PU and TU have the same block size.

[0134] The various CB partitioning schemes described above and further partitioning from CB to PB and / or TB (excluding PB / TB partitioning) may be combined in any manner. The specific implementations provided below are non-limiting examples.

[0135] The following describes a specific exemplary implementation of coding block and transform block partitioning. In such an exemplary implementation, recursive quadtree partitioning or the above-mentioned predefined partitioning pattern (e.g. Fig. 9 and Fig.10 The basic block is divided into coding blocks (those in ). At each level, it can be determined by the local video data characteristics whether further quadtree partitioning should be continued for a specific partition. The resulting CB can be at different quadtree partitioning levels and have different sizes. A decision on whether to use inter-picture (time) or intra-picture (space) prediction to encode the picture area can be made at the CB level (or CU level, for all three color channels). Each CB can be further divided into one, two, four or other number of PBs according to a predefined PB partition type. Within a PB, the same prediction process can be applied, and relevant information can be sent to the decoder based on the PB. After applying the prediction process based on the PB partition type to obtain the residual block, the CB can be divided into TBs according to another quadtree structure similar to the coding tree of the CB. In this specific implementation, the CB or TB can be, but not necessarily limited to, a square. In addition, in this specific example, for inter-frame prediction, the PB can be a square or rectangular, and for intra-frame prediction, the PB can be only a square. The coding block can be divided into, for example, four square TBs. Each TB can be further recursively partitioned (using quadtree partitioning) into smaller TBs, called residual quadtrees (RQTs).

[0136] Another exemplary implementation for partitioning a basic block into CB, PB and / or TB is further described below. Fig. 9 and Fig.10 Instead of the multiple partition unit types shown, a quadtree with a nested multi-type tree can be used, which uses a binary tree and a ternary tree to divide the partition structure (e.g., a QTBT as described above or a QTBT containing a ternary tree partition). Unless a CB whose size is too large for the maximum transform length is needed, such a CB may need to be further divided, otherwise the separation of CB, PB, and TB can be abandoned (i.e., the partitioning of CB into PB and / or TB, and the partitioning of PB into TB) can be abandoned. This exemplary partitioning scheme can be designed to support greater flexibility for the CB partition shape, so that both prediction and transformation can be performed at the CB level without further partitioning. In this coding tree structure, the CB can have a square or rectangular shape. Specifically, the coding tree block (CTB) can first be partitioned by a quadtree structure. Then, the quadtree leaf nodes can be further partitioned by a nested multi-type tree structure. Fig.11 An example of a nested multi-type tree structure using binary or ternary tree partitioning is shown. Specifically, Fig.11 The exemplary multi-type tree structure includes four types of partitions, namely vertical binary tree partition (SPLIT_BT_VER) (1102), horizontal binary tree partition (SPLIT_BT_HOR) (1104), vertical ternary tree partition (SPLIT_TT_VER) (1106) and horizontal ternary tree partition (SPLIT_TT_HOR) (1108). The CB then corresponds to the leaves of the multi-type tree. In this exemplary implementation, unless the CB is too large for the maximum transform length, the segment is used for prediction and transform processing without any further partitioning. This means that in most cases, in a quadtree with a nested multi-type tree coding block structure, the CB, PB and TB have the same block size. An exception occurs when the maximum supported transform length is smaller than the width or height of the color component of the CB. In some implementations, in addition to the binary tree or ternary tree partition, Fig.11 The nested pattern may also include quadtree partitioning.

[0137] Fig.12 A specific example of a quadtree with a nested multi-type tree coding block structure for block partitioning (including quadtree, binary tree and ternary tree partitioning options) for a basic block is shown. In more detail, Fig.12 The basic block 1200 is shown to be divided into four square partitions 1202, 1204, 1206 and 1208 by a quadtree. Fig.11 The multi-type tree structure and quadtree are used for further partitioning decisions. Fig.12In the example of FIG. 1204, partition 1204 is not further divided. Partitions 1202 and 1208 each use another quadtree division. For partition 1202, the upper left, upper right, lower left and lower right partitions of the second level quadtree division use the third level quadtree division, Fig.11 Horizontal binary tree partition 1104, no partition and Fig.11 The horizontal ternary tree partition 1108. The partition 1208 adopts another quadtree partition, and the upper left, upper right, lower left and lower right partitions of the second level quadtree partition are respectively Fig.11 The third level of vertical ternary tree partitioning 1106, no partitioning, no partitioning and Fig.11 The horizontal binary tree is divided into 1104. According to Fig.11 The horizontal binary tree partition 1104 and the horizontal ternary tree partition 1108 further divide the sub-partitions of the third horizontal upper left partition of the partition 1208 into two sub-partitions. The partition 1206 is divided into two sub-partitions according to Fig.11 The second horizontal partitioning pattern of the vertical binary tree partitioning 1102 is divided into two partitions, and the two partitions are divided into two partitions according to Fig.11 The horizontal ternary tree partition 1108 and the vertical binary tree partition 1102 are further divided at a third level, according to Fig.11 's horizontal binary tree partitioning 1104, further applying a fourth horizontal partitioning to one of them.

[0138] For the specific example above, the maximum luma transform size may be 64x64, and the maximum supported chroma transform size may be different from luma, at, for example, 32x32. Fig.12 The exemplary CB in the example is usually not further divided into smaller PBs and / or TBs, but when the width or height of the luminance coding block or the chrominance coding block is larger than the maximum transform width or height, the luminance coding block or the chrominance coding block can be automatically divided in the horizontal and / or vertical directions to meet the transform size limit in that direction.

[0139] In the above specific example for dividing the basic block into CBs, and as described above, the coding tree scheme can support luma and chroma having separate block tree structures. For example, for P slices and B slices, the luma and chroma CTBs in one CTU can share the same coding tree structure. For I slices, for example, luma and chroma can have separate coding block tree structures. When a separate block tree structure is applied, the luma CTB can be divided into luma CBs by one coding tree structure, and the chroma CTB can be divided into chroma CBs by another coding tree structure. This means that a CU in an I slice can consist of coding blocks of a luma component or coding blocks of two chroma components, while a CU in a P slice or a B slice always consists of coding blocks of all three color components unless the video is monochrome.

[0140] When the coding block is further partitioned into multiple transform blocks, the transform blocks therein can be sorted in the bitstream in various orders or in a scanning manner. Exemplary implementations for partitioning a coding block or prediction block into transform blocks and the encoding order of the transform blocks will be described in further detail below. In some exemplary implementations, as described above, transform partitioning can support transform blocks of multiple shapes, such as 1:1 (square), 1:2 / 2:1, and 1:4 / 4:1, where the transform block size ranges from, for example, 4×4 to 64×64. In some implementations, if the coding block is less than or equal to 64×64, the transform block partitioning can be applied only to the luminance component, so that for the chrominance block, the transform block size is the same as the coding block size. Otherwise, if the coding block width or height is greater than 64, both the luminance and chrominance coding blocks can be implicitly divided into multiples of min(W, 64)×min(H, 64) and min(W, 32)×min(H, 32) transform blocks, respectively.

[0141] In some exemplary implementations of transform block partitioning, for intra-coded blocks and inter-coded blocks, the coding blocks may be further partitioned into multiple transform blocks with a partition depth up to a predefined number of levels (e.g., 2 levels). The transform block partition depth and size may be associated. For some exemplary implementations, the mapping from the transform size of the current depth to the transform size of the next depth is shown in Table 1 below.

[0142] Table 1: Change partition size settings

[0143]

[0144] Based on the exemplary mapping of Table 1, for a 1:1 square block, the next level of transform partitioning can create four 1:1 square sub-transform blocks. For example, the transform partitioning can stop at 4×4. Therefore, the current depth of 4×4 is the same 4×4 size for the transform size corresponding to the next depth. In the example of Table 1, for a 1:2 / 2:1 non-square block, the next level of transform partitioning can create two 1:1 square sub-transform blocks, and for a 1:4 / 4:1 non-square block, the next level of transform partitioning can create two 1:2 / 2:1 sub-transform blocks.

[0145] In some example implementations, for the luma component of an intra-coded block, additional restrictions may be applied with respect to the transform block partitioning. For example, for each level of transform partitioning, all sub-transform blocks may be constrained to have equal size. For example, for a 32×16 coding block, a transform partition of level 1 creates two 16×16 sub-transform blocks, and a transform partition of level 2 creates eight 8×8 sub-transform blocks. In other words, a level 2 partition must be applied to all level 1 sub-blocks to keep the transform unit sizes equal. Fig.15An example of transform block partitioning following Table 1 for intra-coded square blocks and the coding order indicated by arrows is shown. Specifically, 1502 shows a square coding block. A first horizontal partitioning into 4 equal-sized transform blocks according to Table 1 is shown in 1504, where the coding order is indicated by arrows. A second horizontal partitioning into 16 equal-sized transform blocks according to Table 1 is shown in 1506, where the coding order is indicated by arrows.

[0146] In some example implementations, the above restrictions on intra coding may not apply to the luminance component of an inter-coded block. For example, after the first horizontal transform split, any of the sub-transform blocks may be further independently split into more than one level. Thus, the resulting transform blocks may or may not have the same size. Fig.16 An example partitioning of an inter-coded block into transform blocks is shown together with the coding order of the transform blocks. Fig.16 In the example of FIG. 1602, the inter-coded block 1602 is divided into two levels of transform blocks according to Table 1. At the first level, the inter-coded block is divided into four transform blocks of equal size. Then, only one of the four transform blocks (not all) is further divided into four sub-transform blocks, resulting in a total of 7 transform blocks with two different levels, as shown in 1604. The example coding order of these 7 transform blocks is as follows: Fig.16 As shown by the arrow in 1604.

[0147] In some example implementations, for chroma components, some additional restrictions on transform blocks may be applied. For example, for chroma components, the transform block size may be as large as the coding block size, but not smaller than a predefined size, such as 8×8.

[0148] In some other example implementations, for coding blocks with width (W) or height (H) greater than 64, both luma and chroma coding blocks may be implicitly split into min(W, 64)×min(H, 64) and min(W, 32)×min(H, 32) transform units, respectively. Here, in the present disclosure, "min(a, b)" may return the smaller value between a and b.

[0149] Fig.17 Another optional example scheme for partitioning a coding block or prediction block into transform blocks is further shown. Fig.17 As shown, instead of using recursive transform partitioning, a predefined set of partition types can be applied to the coding block according to the transform type of the coding block. Fig.17 In the specific example shown, one of six example partition types may be applied to divide a coding block into a different number of transform blocks. This scheme for generating transform block partitions may be applied to either a coding block or a prediction block.

[0150] In more detail, Fig.17 The partition scheme of provides up to 6 example partition types for any given transform type (transform type refers to, for example, the type of primary transform, such as ADST, etc.). In this scheme, a transform partition type can be assigned to each coding block or prediction block based on, for example, rate-distortion cost. In one example, the transform partition type assigned to a coding block or prediction block can be determined based on the transform type of the coding block or prediction block. A specific transform partition type can correspond to a transform block partition size and pattern, such as Fig.17 As shown in the 6 transform partition types shown. The correspondence between various transform types and various transform partition types can be predefined. An example is shown below, where the uppercase label indicates the transform partition type that can be assigned to the coding block or prediction block based on the rate-distortion cost:

[0151] PARTITION_NONE: Allocate a transform size equal to the block size.

[0152] PARTITION_SPLIT: Allocate a transform size whose width is 1 / 2 of the width of the block size and whose height is 1 / 2 of the height of the block size.

[0153] PARTITION_HORZ: Allocate a transform size with the same width as the block size and a height that is 1 / 2 the height of the block size.

[0154] PARTITION_VERT: Allocate a transform size with a width that is 1 / 2 the width of the block size and a height that is the same as the block size.

[0155] PARTITION_HORZ 4: Allocate a transform size with the same width as the block size and a height that is 1 / 4 of the block size's height.

[0156] PARTITION_VERT 4: Allocate a transform size with a width that is 1 / 4 of the width of the block size and a height that is the same as the block size.

[0157] In the above example, changing the partition type such as Fig.17 As shown, all contain a uniform transform size for the transform blocks of the partitions. This is only an example and not a limitation. In some other implementations, mixed transform block sizes can be used for the transform blocks of the partitions of a specific partition type (or pattern).

[0158] The PB (or CB, also referred to as PB when not further partitioned into prediction blocks) obtained from any of the above partitioning schemes can then become a separate block for encoding via intra-frame prediction or inter-frame prediction. For inter-frame prediction of the current PB, the residual between the current block and the prediction block can be generated, encoded, and included in the encoded bitstream.

[0159] Inter prediction may be implemented, for example, in a single reference mode or a composite reference mode. In some implementations, a skip flag may be first included in the bitstream of the current block (or included in a higher level) to indicate whether the current block is inter-coded and whether the current block is not skipped. If the current block is inter-coded, another flag may be further included in the bitstream as signaling to indicate whether the prediction for the current block uses a single reference mode or a composite reference mode. For a single reference mode, one reference block may be used to generate a prediction block for the current block. For a composite reference mode, two or more reference blocks may be used to generate a prediction block by, for example, weighted averaging. A composite reference mode may be referred to as more than one reference mode, two reference modes, or multiple reference modes. One or more reference blocks may be identified using one or more reference frame indexes and additionally using one or more corresponding motion vectors indicating an offset in position (e.g., in horizontal pixels and in vertical pixels) between the reference block and the current block. For example, an inter-frame prediction block of a current block may be generated from a single reference block identified as a prediction block in a single reference mode by a motion vector in a reference frame, while for a composite reference mode, a prediction block may be generated from a weighted average of two reference blocks in two reference frames indicated by two reference frame indices and two corresponding motion vectors. The motion vector may be encoded and included in the bitstream in various ways.

[0160] In some implementations, the encoding or decoding system may maintain a decoded picture buffer (DPB). Some images / pictures may be stored in the DPB waiting to be displayed (in the decoding system), and some images / pictures in the DPB may be used as reference frames to enable inter-frame prediction (in the decoding system or encoding system). In some implementations, the reference frames in the DPB may be marked as short-term references or long-term references for the current picture being encoded or decoded. For example, a short-term reference frame may include a frame for inter-frame prediction of a block in the current frame, or a frame for inter-frame prediction of a block in a predefined number (e.g., 2) of subsequent video frames closest to the current frame in the decoding order. Long-term reference frames may include frames in the DPB that can be used to predict image blocks in frames that are more than a predefined number away from the current frame in the decoding order. Information about such labels for short-term and long-term reference frames may be referred to as a reference picture set (RPS), and may be added to the header of each frame in the encoded bitstream. Each frame in the coded video stream can be identified by a Picture Order Counter (POC), which is numbered in an absolute manner according to the playback sequence or relative to a group of pictures, for example starting from an I frame.

[0161] In some example implementations, one or more reference picture lists containing identification of short-term and long-term reference frames for inter-frame prediction may be formed based on information in the RPS. For example, a single picture reference list may be formed for unidirectional inter-frame prediction, denoted as L0 reference (or reference list 0), while two picture reference lists may be formed for bidirectional inter-frame prediction, denoted as L0 (or reference list 0) and L1 (or reference list 1) for each of the two prediction directions. The reference frames included in the L0 and L1 lists may be ordered in various predefined ways. The lengths of the L0 and L1 lists may be signaled in the video bitstream. When multiple references used to generate a prediction block by weighted averaging in a composite prediction mode are on the same side of the block to be predicted, the unidirectional inter-frame prediction may be a single reference mode, or a composite reference mode. Bidirectional inter-frame prediction may be only a composite reference mode because bidirectional inter-frame prediction involves at least two reference blocks.

[0162] In some implementations, a merge mode (MM) for inter-frame prediction may be implemented. Typically, for merge mode, a motion vector in a single reference prediction of the current PB or one or more motion vectors in a composite reference prediction may be derived from other motion vectors, rather than being calculated and signaled separately. For example, in a coding system, the current motion vector of the current PB may be represented by the difference between the vector of the current motion and one or more other already encoded motion vectors (referred to as reference motion vectors). Instead of all of the current motion vector, this difference in motion vectors may be encoded and included in the bitstream and may be linked to the reference motion vector. Accordingly, in a decoding system, the motion vector corresponding to the current PB may be derived based on the decoded motion vector difference and the decoded reference motion vector linked thereto. As a specific form of general merge mode (MM) inter-frame prediction, this inter-frame prediction based on motion vector difference may be referred to as a merge mode with motion vector difference (MMVD). Therefore, a general MM or a specific MMVD may be implemented to improve coding efficiency by utilizing the correlation between motion vectors associated with different PBs. For example, adjacent PBs may have similar motion vectors, so the MVD may be small and may be efficiently encoded.For another example, for blocks that are similarly positioned / oriented in space, the motion vectors may be correlated in time (between frames).

[0163] In some example implementations, during the encoding process, an MM flag may be included in the bitstream to indicate whether the current PB is in merge mode. Additionally or optionally, during the encoding process, an MMVD flag may be included in the bitstream and signaled in the bitstream to indicate whether the current PB is in MMVD mode. The MM and / or MMVD flags or indicators may be provided at the PB level, CB level, CU level, CTB level, CTU level, slice level, picture level, etc. For a specific example, an MM flag and an MMVD flag may be included for the current CU, and the MMVD flag may be signaled immediately after the skip flag and the MM flag to clearly indicate whether the current CU uses the MMVD mode.

[0164] In some example implementations of MMVD, a list of reference motion vectors (RMV) or MV predictor candidates for motion vector prediction may be formed for a block being predicted. The RMV candidate list may contain a predefined number (e.g., 2) of MV predictor candidate blocks whose motion vectors may be used to predict the current motion vector. The RMV candidate blocks may include blocks selected from adjacent blocks and / or temporal blocks in the same frame (e.g., blocks at the same position in the previous or next frame of the current frame). This selection method represents blocks at these spatial or temporal positions relative to the current block that may have motion vectors similar to or the same as the current block. The size of the MV predictor candidate list may be predetermined. For example, the list may contain two or more candidates. In order to appear on the RMV candidate list, the candidate block, for example, may need to have the same one or more reference frames as the current block, must exist (e.g., when the current block is close to the edge of the frame, a boundary check needs to be performed), and must have been encoded during the encoding process, and / or decoded during the decoding process. In some implementations, the list of merge candidates may be first populated with spatially adjacent blocks (scanned in a specific predefined order) if available and satisfying the above conditions, and then the temporal blocks may be populated if space is still available in the merged candidate list. For example, adjacent RMV candidate blocks may be selected from the left block and the top block of the current block. The list of RMV predictor candidates may be dynamically formed at different levels (sequence, picture, frame, slice, super block, etc.) as a Dynamic Reference List (DRL). The DRL may be signaled in the bitstream.

[0165] In some implementations, the actual MV predictor candidate used as a reference motion vector for predicting the motion vector of the current block can be signaled. In the case where the RMV candidate list contains two candidates, a one-bit flag called a merge candidate flag can be used to indicate the selection of the reference merge candidate. For the current block predicted in composite mode, each of the multiple motion vectors predicted using the MV predictor can be associated with a reference motion vector from the merged candidate list. The encoder can determine which of the RMV candidates is closer to predicting the current coding block and send the selection as an index to the DRL.

[0166] In some example implementations of MMVD, after an RMV candidate is selected and used as a base motion vector predictor for a motion vector to be predicted, a motion vector difference (MVD or delta MV, representing the difference between the motion vector to be predicted and a reference candidate motion vector) may be calculated in the encoding system. Such an MVD may include information representing the magnitude of the MV difference and the direction of the MV difference, both of which may be signaled in the bitstream. The magnitude of the motion vector difference and the direction of the motion vector difference may be signaled in various ways.

[0167] In some example implementations of the MMVD, a distance index may be used to specify the magnitude information of a motion vector difference and indicate one of a set of predefined offsets representing a predefined motion vector difference relative to a starting point (reference motion vector). The MV offset according to the signaled index may then be added to the horizontal component or the vertical component of the starting (reference) motion vector. Whether the horizontal component or the vertical component of the reference motion vector should be offset may be determined by the direction information of the MVD. An exemplary predefined relationship between a distance index and a predefined offset is specified in Table 2.

[0168] Table 2: Exemplary relationship between distance index and predefined MV offsets

[0169]

[0170] In some example implementations of MMVD, a direction index may be further signaled and used to indicate the direction of the MVD relative to a reference motion vector. In some implementations, the direction may be limited to either the horizontal direction or the vertical direction. An example 2-bit direction index is shown in Table 3. In the example of Table 3, the understanding of the MVD may vary depending on the information of the start / reference MV. For example, when the start / reference MV corresponds to a single prediction block or to a double prediction block in which both reference frame lists point to the same side of the current picture (i.e., the POCs of both reference pictures are greater than the POC of the current picture, or are less than the POC of the current picture), the symbol in Table 3 may specify the symbol (direction) of the MV offset added to the start / reference MV. When the start / reference MV corresponds to a bi-predicted block in which two reference pictures are located on different sides of the current picture (i.e., the POC of one reference picture is greater than the POC of the current picture, and the POC of the other reference picture is less than the POC of the current picture), and the difference between the reference POC in picture reference list 0 and the current frame is greater than the difference between the reference POC in picture reference list 1 and the current frame, the symbols in Table 3 may specify the sign of the MV offset added to the reference MV corresponding to the reference picture in picture reference list 0, and the sign of the offset of the MV corresponding to the reference picture in picture reference list 1 may have an opposite value (opposite sign of the offset). Otherwise, if the difference between the reference POC in picture reference list 1 and the current frame is greater than the difference between the reference POC in picture reference list 0 and the current frame, the symbols in Table 3 may specify the sign of the MV offset added to the reference MV associated with picture reference list 1, and the sign of the offset of the reference MV associated with picture reference list 0 has an opposite value.

[0171] Table 3: Example implementation of the sign of the MV offset specified by the direction index

[0172] Directions to IDX 00 01 10 11 X-axis (horizontal) + – N / A N / A Y axis (vertical) N / A N / A + –

[0173] In some example implementations, the MVD may be scaled according to the difference in POC in each direction. If the difference in POC is the same in both lists, no scaling is required. Otherwise, if the difference in POC in reference list 0 is greater than the difference in POC in reference list 1, the MVD of reference list 1 is scaled. If the difference in POC in reference list 1 is greater than list 0, the MVD of list 0 may be scaled in the same manner. If the starting MV is unidirectionally predicted, the MVD is added to the available MV or reference MV.

[0174] In some example implementations of MVD encoding and signaling for bidirectional composite prediction, in addition to or instead of separately encoding and signaling two MVDs, symmetric MVD encoding can be implemented so that only one MVD needs to be signaled, and the other MVD can be derived from the signaled MVD. In such an implementation, motion information including reference picture indices for both list 0 and list 1 is signaled. However, only the MVD associated with, for example, reference list 0 is signaled, while the MVD associated with reference list 1 is not signaled but derived. Specifically, at the slice level, a flag can be included in the bitstream, called "mvd_11_zero_flag", to indicate whether reference list 1 is signaled in the bitstream. If the flag is 1, indicating that reference list 1 is equal to zero (and therefore not signaled), a bidirectional prediction flag called "BiDirPredFlag" can be set to 0, which means that there is no bidirectional prediction. In addition, if mvd_11_zero_flag is 0, BiDirPredFlag can be set to 1 if the nearest reference picture in list 0 and the nearest reference picture in list 1 form a forward and backward reference picture pair or a backward and forward reference picture pair, and both list 0 and list 1 reference pictures are short-term reference pictures. Otherwise, BiDirPredFlag is set to 0. BiDirPredFlag of 1 can indicate that the symmetry mode flag is additionally signaled in the bitstream. When BiDirPredFlag is 1, the decoder can extract the symmetry mode flag from the bitstream. For example, the symmetry mode flag can be signaled at the CU level (if necessary), and the symmetry mode flag can indicate whether the symmetric MVD coding mode is being used for the corresponding CU. When the symmetric mode flag is 1, it indicates that the symmetric MVD coding mode is used, and the reference picture indices of only list 0 and list 1 (called "mvp_10_flag" and "mvp_11_flag") and the MVD associated with list 0 (called "MVD0") are signaled, while another motion vector difference "MVD1" will be derived instead of signaled. For example, MVD1 can be derived as -MVD0. Therefore, only one MVD is signaled in the example symmetric MVD mode. In some other example implementations for MV prediction, the coordination scheme can be used to implement general merge mode, MMVD and some other types of MV prediction for single reference mode and composite reference mode MV prediction. Various syntax elements can be used to signal the way to predict the MV of the current block.

[0175] For example, for the single reference mode, the following MV prediction modes may be signaled:

[0176] NEARMV - directly uses one of the motion vector predictors (MVP) in the list indicated by the DRL index without any MVD.

[0177] NEWMV - uses one of the MVPs in the list signaled by the DRL index as a reference and applies a delta to that MVP (eg, using MVD).

[0178] GLOBALMV - Use motion vectors based on frame-level global motion parameters.

[0179] Likewise, for a composite reference inter prediction mode using two reference frames corresponding to two MVs to be predicted, the following MV prediction modes may be signaled:

[0180] NEAR_NEARMV—For each of the two MVs to be predicted, one of the MVPs in the list signaled by the DRL index is used without MVD.

[0181] NEAR_NEWMV - To predict the first of the two motion vectors, one of the MVPs in the list signaled by the DRL index is used as the reference MV without MVD; to predict the second of the two motion vectors, one of the MVPs in the list signaled by the DRL index is used as the reference MV, combined with an additionally signaled delta MV (MVD).

[0182] NEW_NEARMV - To predict the second of the two motion vectors, one of the MVPs in the list signaled by the DRL index is used as the reference MV without MVD; to predict the first of the two motion vectors, one of the MVPs in the list signaled by the DRL index is used as the reference MV in combination with an additionally signaled incremental MV (MVD).

[0183] NEW_NEWMV—Uses one of the MVPs in the list signaled by the DRL index as a reference MV, and combines it with the additionally signaled delta MV to predict each of the two MVs.

[0184] GLOBAL_GLOBALMV - Uses the MV from each reference based on its frame level global motion parameters.

[0185] Thus, the term "NEAR" above refers to MV prediction using a reference MV and not using an MVD as in the general merge mode, while the term "NEW" refers to MV prediction involving the use of a reference MV and offsetting the reference MV using a signaled MVD as in the MMVD mode. For composite inter prediction, both the reference base motion vector and the motion vector increment described above may be generally different or independent between the two references, even though they may be correlated, and this correlation may be exploited to reduce the amount of information required to signal the two motion vector increments. In this case, joint signaling of the two MVDs may be implemented and indicated in the bitstream.

[0186] The above dynamic reference list (DRL) can be used to store a set of indexed motion vectors that are dynamically maintained and considered as candidate motion vector predictors.

[0187] In some example implementations, a predefined resolution for the MVD may be allowed. For example, a motion vector precision (or accuracy) of 1 / 8 pixel may be allowed. The MVD in the various MV prediction modes described above may be constructed and signaled in various ways. In some implementations, various syntax elements may be used to signal the motion vector differences described above in reference frame list 0 or list 1.

[0188] For example, a syntax element called "mv_joint" may specify which components of the motion vector difference associated with it are non-zero. For MVD, this is signaled jointly for all non-zero components. For example, the value of mv_joint is

[0189] 0 may indicate that there is no non-zero MVD along the horizontal or vertical direction;

[0190] 1 may indicate that there is non-zero MVD only along the horizontal direction;

[0191] 2 may indicate that there is non-zero MVD only along the vertical direction;

[0192] 3 may indicate that there is non-zero MVD in both the horizontal and vertical directions.

[0193] When the "mv_joint" syntax element for MVD signals the absence of non-zero MVD components, no further MVD information may be signaled. However, if the "mv_joint" syntax signals the presence of one or two non-zero components, additional syntax elements may be further signaled for each non-zero MVD component, as described below.

[0194] For example, a syntax element called "mv_sign" may be used to additionally specify whether the corresponding motion vector difference amount is positive or negative.

[0195] For another example, a syntax element called "mv_class" may be used to specify a class of motion vector differences in a predefined set of classes corresponding to non-zero MVD components. For example, the predefined classes of motion vector differences may be used to divide the continuous amplitude space of motion vector differences into non-overlapping ranges, each range corresponding to an MVD class. Thus, the signaled MVD class indicates the amplitude range of the corresponding MVD component. In the exemplary implementation shown in Table 4 below, a higher class corresponds to a motion vector difference with a larger amplitude range. In Table 4, the symbol (n, m] is used to represent a range of motion vector differences greater than n pixels and less than or equal to m pixels.

[0196] Table 4: Magnitude classes for motion vector differences

[0197] Music Videos MVD Amplitude MV_CLASS_0 (0,2] MV_CLASS_1 (2,4] MV_CLASS_2 (4,8] MV_CLASS_3 (8,16] MV_CLASS_4 (16,32] MV_CLASS_5 (32,64] MV_CLASS_6 (64,128] MV_CLASS_7 (128,256] MV_CLASS_8 (256,512] MV_CLASS_9 (512,1024] MV_CLASS_10 (1024,2048]

[0198] In some other examples, a syntax element called "mv_bit" may be further used to specify the integer portion of the offset between a non-zero motion vector difference component and the starting amplitude of the correspondingly signaled MV class amplitude range. Thus, mv_bit may indicate the magnitude or amplitude of the MVD. The number of bits required in "my_bit" to signal the full range of each MVD class may vary as a function of the MV class. For example, MV_CLASS 0 and MV_CLASS 1 in the implementation of Table 4 may require only a single bit to indicate an integer pixel offset of 1 or 2 from a starting MVD of 0; each higher MV_CLASS in the exemplary implementation of Table 4 may require one more "mv_bit" bit than the previous MV_CLASS.

[0199] In some other examples, a syntax element called "mv_fr" may be further used to specify the first 2 decimal places of the motion vector difference corresponding to the non-zero MVD component, and a syntax element called "mv_hp" may be used to specify the 3rd decimal place (high resolution place) of the motion vector difference corresponding to the non-zero MVD component. The two "mv_fr" bits essentially provide a 1 / 4 pixel MVD resolution, while the "mv_hp" bits may further provide a 1 / 8 pixel resolution. In some other implementations, more than one "mv_hp" bit may be used to provide an MVD pixel resolution finer than 1 / 8 pixel. In some example implementations, an additional flag may be signaled at one or more of the various levels to indicate whether a 1 / 8 pixel or higher MVD resolution is supported. If the MVD resolution is not applied to a particular coding unit, then the syntax element above for the corresponding unsupported MVD resolution may not be signaled.

[0200] In some of the example implementations above, the resolution of the fractional digits may be independent of the different MVD classes. In other words, similar options for motion vector resolution may be provided using a predefined number of "mv_fr" and "mv_hp" bits for signaling the fractional digit MVD for non-zero MVD components, regardless of the magnitude of the motion vector difference.

[0201] However, in some other example implementations, the resolution of motion vector differences in various MVD amplitude classes may be distinguished. Specifically, a high-resolution MVD for a large MVD amplitude of a higher MVD class may not provide a statistically significant improvement in compression efficiency. Therefore, for a larger MVD amplitude range, the MVD can be encoded with a decreasing resolution (integer pixel resolution or fractional pixel resolution), and the larger MVD amplitude range corresponds to a higher MVD amplitude class. Similarly, typically for larger MVD values, the MVD can be encoded with a decreasing resolution (integer pixel resolution or fractional pixel resolution). This MVD resolution that depends on the MVD class or depends on the MVD amplitude may generally be referred to as an adaptive MVD resolution, an amplitude-dependent adaptive MVD resolution, or an amplitude-dependent MVD resolution. The term "resolution" may be further referred to as "pixel resolution", and the adaptive MVD resolution may be implemented in various ways as described in the following example implementations to achieve overall better compression efficiency. In particular, due to the statistical observation that processing MVD resolutions of large-amplitude or high-class MVDs at similar levels as low-amplitude or low-class MVDs in a non-adaptive manner may not significantly increase the inter-frame prediction residual coding efficiency of blocks with large-amplitude or high-class MVDs, the reduced number of signaling bits intended for lower-precision MVDs may be greater than the additional number of bits required to encode the inter-frame prediction residuals as a result of such lower-precision MVDs. In other words, using a higher MVD resolution for large-amplitude or high-class MVDs may not yield much coding gain over using a lower MVD resolution.

[0202] In some general example implementations, the pixel resolution or precision of the MVD may decrease or may not increase as the MVD class increases. Decreasing the pixel resolution of the MVD corresponds to a coarser MVD (or a larger step size from one MVD level to the next MVD level). In some implementations, the correspondence between MVD pixel resolution and MVD class may be specified, predefined, or preconfigured, so that the correspondence may not need to be signaled in the encoded bitstream.

[0203] In some example implementations, the MV classes of Table 3 may each be associated with a different MVD pixel resolution.

[0204] In some example implementations, each MVD class may be associated with a single allowed resolution. In some other implementations, one or more MVD classes may be associated with two or more selectable MVD pixel resolutions. Thus, the signal in the bitstream for the current MVD component having such an MVD class may be followed by additional signaling indicating the selectable pixel resolutions selected for the current MVD component.

[0205] In some example implementations, the adaptively allowed MVD pixel resolutions may include, but are not limited to, 1 / 64 pixel, 1 / 32 pixel, 1 / 16 pixel, 1 / 8 pixel, 1 / 4 pixel, 1 / 2 pixel, 1 pixel, 2 pixels, 4 pixels ... (in descending order of resolution). Therefore, each class in the ascending MVD class may be associated with one of these MVD pixel resolutions in a non-ascending manner. In some implementations, the MVD class may be associated with two or more of the above resolutions, and the higher resolution may be lower than or equal to the lower resolution of the previous MVD class. For example, if the MV_CLASS_3 of Table 4 is associated with optional 1 pixel and 2 pixel resolutions, the highest resolution that the MV_CLASS_4 of Table 4 may be associated with will be 2 pixels. In some other implementations, the highest allowed resolution of the MV class may be higher than the lowest allowed resolution of the previous (lower) MV class. However, the average of the allowed resolutions for the ascending MV classes may only be non-ascending.

[0206] In some embodiments, when fractional pixel resolutions higher than 1 / 8 pixel are allowed, the "mv_fr" and "mv_hp" signaling may be correspondingly extended to a total of more than 3 fractional digits.

[0207] In some example implementations, fractional pixel resolutions may be allowed only for MVD classes that are lower than or equal to a threshold MVD class. For example, in Table 4, fractional pixel resolutions may be allowed only for MVD-CLASS 0 and not for all other MV classes. Similarly, fractional pixel resolutions may be allowed only for MVD classes that are lower than or equal to any one of the other MV classes in Table 4. For other MVD classes that are higher than the threshold MVD class, only integer pixel resolutions are allowed for the MVD. In this way, for MVDs signaled with MVD classes that are higher than or equal to the threshold MVD class, signaling of fractional resolutions such as one or more of the "mv-fr" and / or "mv-hp" bits may not be required. For MVD classes with resolutions lower than 1 pixel, the number of bits in the "mv-bit" signaling may be further reduced. For example, for MV_CLASS_5 in Table 4, the range of MVD pixel offsets is (32, 64], so 5 bits are required to signal the entire range with 1 pixel resolution. However, if MV_CLASS_5 is associated with 2-pixel MVD resolution (a resolution lower than 1 pixel resolution), then "mv-bit" may require 4 bits instead of 5 bits, and after signaling "mv_class" as MV-CLASS_5, neither "mv-fr" nor "mv-hp" needs to be signaled.

[0208] In some example implementations, fractional pixel resolutions may be allowed only for MVDs with integer values ​​below a threshold integer pixel value. For example, fractional pixel resolutions may be allowed only for MVDs less than 5 pixels. For this example, fractional resolutions may be allowed for MV_CLASS_0 and MV_CLASS_1 of Table 4, but not for all other MV classes. For another example, fractional pixel resolutions may be allowed only for MVDs less than 7 pixels. For this example, fractional resolutions may be allowed for MV_CLASS_0 and MV_CLASS_1 of Table 4 (with ranges below 5 pixels), but not for MV_CLASS_3 and higher MV classes (with ranges above 5 pixels). For an MVD belonging to MV_CLASS_2 with a pixel range containing 5 pixels, fractional pixel resolutions may or may be allowed for the MVD, depending on the "mv-bit" value. If the signaled "m-bit" value is 1 or 2 (such that the integer part of the signaled MVD is 5 or 6, calculated as the start of the pixel range of MV_CLASS_2 with an offset of 1 or 2 indicated by "m-bit"), then fractional pixel resolution may be allowed. Otherwise, if the signaled "mv-bit" value is 3 or 4 (such that the integer part of the signaled MVD is 7 or 8), then fractional pixel resolution may not be allowed.

[0209] In some other implementations, for MV classes equal to or higher than a threshold MV class, only a single MVD value may be allowed. For example, such a threshold MV class may be MV_CLASS 2. Therefore, only MV classes MV_CLASS_2 and higher than MV_CLASS_2 may be allowed to have a single MVD value without using fractional pixel resolution. The single allowed MVD values ​​for these MV classes may be predefined. In some examples, the allowed single value may be a higher end value of the corresponding ranges for these MV classes in Table 4. For example, MV_CLASS_2 to MV_CLASS_10 may be higher than or equal to the threshold class MV_CLASS 2, and the single allowed MVD values ​​for these classes may be predefined as 8, 16, 32, 64, 128, 256, 512, 1024, and 2048, respectively. In some other examples, the allowed single value may be an intermediate value for the corresponding ranges for these MV classes in Table 4. For example, MV_CLASS_2 to MV_CLASS_10 may be above the class threshold, and the single allowed MVD values ​​for these classes may be predefined as 3, 6, 12, 24, 48, 96, 192, 384, 768, and 1536, respectively. Any other value within the range may also be defined as the single allowed resolution for each MVD class.

[0210] In the above implementation, "mv_class" signaling is sufficient to determine the MVD value only when the signaled "mv_class" is equal to or above the predefined MVD class threshold. "mv_class" and "mv_sign" are then used to determine the magnitude and direction of the MVD.

[0211] Therefore, when the MVD is signaled for only one reference frame (from reference frame list 0 or list 1, but not from both), or when the MVD is signaled jointly for two reference frames, the accuracy (or resolution) of the MVD may depend on the associated class of the motion vector difference in Table 3 and / or the magnitude of the MVD.

[0212] In some other implementations, the pixel resolution or accuracy of the MVD may decrease or not increase with the increase of the MVD amplitude. For example, the pixel resolution may depend on the integer part of the MVD amplitude. In some implementations, fractional pixel resolution may be allowed only for MVD amplitudes less than or equal to an amplitude threshold. For a decoder, the integer part of the MVD amplitude may be first extracted from the bitstream. The pixel resolution may then be determined, and a judgment may then be made as to whether any fractional MVD exists in the bitstream and whether it needs to be parsed (e.g., if fractional pixel resolution is not allowed for a specific extracted MVD integer amplitude, then the fractional MVD bit may not be included in the bitstream that needs to be extracted). The example implementations of the adaptive MVD pixel resolution associated with the MVD class above are applied to the adaptive MVD pixel resolution associated with the MVD amplitude. For a specific example, an MVD class that is higher than or includes an amplitude threshold may be allowed to have only one predefined value.

[0213] In some implementations, the MVD may be distributed primarily along one or more specific directions, i.e., the MVD has a high probability of being along one or more specific directions, such as the horizontal direction and / or the vertical direction. For example, this statistical property may be exploited by imposing restrictions on the MVD in order to improve encoding / decoding efficiency and enhance the inter-frame coding mode structure. For a non-limiting example, when the one or more specific directions include the horizontal direction and / or the vertical direction, the MVD may be restricted along the horizontal direction and / or the vertical direction.

[0214] Fig.18 A flowchart 1800 of an example method following the basic principles of the above implementation for limiting motion vector differences (MVDs) is shown. The example decoding method flow starts at 1801 and may include some or all of the following steps: at step 1810, receiving an encoded video bitstream; at step 1820, obtaining a motion vector difference MVD of a current video block from the encoded video bitstream, wherein the current video block is an inter-coded block in a composite reference mode; at step 1830, determining whether the MVD is signaled for only one prediction direction; at step 1840, in response to determining that the MVD is signaled for only one prediction direction, limiting the MVD to a predefined direction; and / or at step 1850, decoding the current video block based on the MVD. The example method may stop at step 1899. In some implementations, when the current video block is an inter-coded block in a composite reference mode, the current video block is bidirectionally inter-predicted.

[0215] In some implementations, the direction of the reference frame relative to the current frame can be determined by whether the reference frame precedes the current frame in the display order, or whether the reference frame follows the current frame in the display order.

[0216] In some implementations, two reference frames may be used in a composite reference mode. When the POCs of both reference frames of a motion vector pair are greater than or less than the POC of the current frame, the directions of the two reference frames may be considered the same. Otherwise, when the POC of one reference frame is greater than the POC of the current frame and the POC of the other reference frame is less than the POC of the current frame, the directions of the two reference frames may be considered different.

[0217] In some implementations, only one MVD may be signaled for the current video block (or current frame), which may include at least one of the following cases: signaling the MVD in the coded video bitstream for only one reference frame in a composite reference mode; and / or jointly signaling the MVD for two reference frames in a composite reference mode. In some of the above cases, the MVD signaled for the first reference frame list (i.e., reference frame list 0) or the second reference frame list (i.e., reference frame list 1) may be restricted to one or more predefined directions (e.g., horizontal direction and / or vertical direction).

[0218] For a non-limiting example, when the MVD is signaled for only one prediction direction (e.g., the MVD is signaled for only reference frame list 0 or list 1, but not both, or the MVD is signaled for both reference frame lists jointly), the MVD of reference frame list 0 (or reference frame list 1) can be restricted to certain predefined directions.

[0219] In some implementations, the current video block is in a composite reference mode that includes at least one of a NEW_NEARMV mode or a NEAR_NEWMV mode. In some implementations, the MVD is restricted to one or more determined predefined directions only when the current video block is in a composite reference mode that includes at least one of a NEW_NEARMV mode or a NEAR_NEWMV mode. In some implementations, the MVD is not restricted to one or more determined predefined directions when the current video block is not in a NEW_NEARMV mode or a NEAR_NEWMV mode.

[0220] By way of non-limiting example, restricting the MVD to certain predefined directions only applies to NEW_NEARMV and / or NEAR_NEWMV modes.

[0221] In some implementations, in response to the current video block being in NEW_NEARMV mode or in NEAR_NEWMV mode, the predefined direction includes at least one of a horizontal direction or a vertical direction.

[0222] For a non-limiting example, for NEW_NEARMV (or NEAR_NEWMV) mode, the MVD of reference frame list 0 (or reference frame list 1) may be restricted to the horizontal and / or vertical directions.

[0223] In some implementations, Fig.18 The method in may further include obtaining, from the encoded video bitstream, a flag indicating whether there is a non-zero MVD in the horizontal direction and the vertical direction. In some implementations, the flag may refer to a syntax or a syntax element. For a non-limiting example, in order to signal the MVD for the NEW_NEARMV (or NEAR_NEWMV) mode in the reference frame list 0 (or the reference frame list 1), a flag (e.g., mvd_direction_flag) is signaled to indicate whether there is a non-zero MVD in the horizontal or vertical direction.

[0224] In some implementations, the value of the flag includes only one of the following: a first flag value indicating that neither the horizontal direction nor the vertical direction has a non-zero MVD; a second flag value indicating that only one of the horizontal direction and the vertical direction has a non-zero MVD; and a third flag value indicating that only the other of the horizontal direction and the vertical direction has a non-zero MVD.

[0225] In some implementations, in response to the current video block being in NEW_NEARMV mode: in response to the value of the flag being equal to the second flag value, the MVD corresponds to a vertical direction for a reference frame in the first reference frame list, and in response to the value of the flag being equal to the third flag value, the MVD corresponds to a horizontal direction for a reference frame in the first reference frame list; and in response to the current video block being in NEAR_NEWMV mode: in response to the flag being equal to the second flag value, the MVD corresponds to a horizontal direction for a reference frame in the second reference frame list, and in response to the flag being equal to the third flag value, the MVD corresponds to a vertical direction for a reference frame in the second reference frame list.

[0226] For non-limiting examples, the value of a flag (e.g., mvd_direction_flag) can only be 0, 1, or 2, where 0 indicates that there is no non-zero MVD along the vertical or horizontal direction, 1 indicates that there is a non-zero MVD only along the vertical (or horizontal) direction, and 2 indicates that there is a non-zero MVD only along the horizontal (or vertical) direction.

[0227] In some implementations, the value of the flag includes only one of: a first flag value indicating that only one of the horizontal and vertical directions has a non-zero MVD; or a second flag value indicating that only the other of the horizontal and vertical directions has a non-zero MVD.

[0228] In some implementations, in response to the current video block being in NEW_NEARMV mode: in response to the flag being equal to a first flag value, the MVD corresponds to a vertical direction for reference frames in a first reference frame list, and in response to the flag being equal to a second flag value, the MVD corresponds to a horizontal direction for reference frames in the first reference frame list; and in response to the current video block being in NEAR_NEWMV mode: in response to the flag being equal to the first flag value, the MVD corresponds to a horizontal direction for reference frames in a second reference frame list, and in response to the value of the flag being equal to the second flag value, the MVD corresponds to a vertical direction for reference frames in the second reference frame list.

[0229] For non-limiting examples, the value of a flag (eg, mvd_direction_flag) may be only 0 or 1, where 0 indicates that non-zero MVD exists only along the vertical (or horizontal) direction and 1 indicates that non-zero MVD exists only along the horizontal (or vertical) direction.

[0230] In some implementations, the flag is signaled in a high-level syntax, the high-level syntax comprising at least one of: a video parameter set VPS, a picture parameter set PPS, a sequence parameter set SPS, an adaptation parameter set APS, a picture header, a frame header, a slice header, a tile header, or a coding tree unit CTU header. For non-limiting examples, a flag indicating whether the non-zero MVD is along the horizontal direction or along the vertical direction is signaled in a high-level syntax including but not limited to a VPS, a PPS, a SPS, an APS, a frame header, or a slice header.

[0231] In some implementations, in response to the current video block being in NEW_NEARMV mode or NEAR_NEWMV mode, the predefined direction includes only one direction. For non-limiting examples, for NEW_NEARMV (or NEAR_NEWMV) mode, the MVD of reference frame list 0 (or reference frame list 1) may be restricted to only one direction of the horizontal direction or the vertical direction.

[0232] In some implementations, the method 1800 further includes determining whether the horizontal direction and the vertical direction have non-zero MVD based on the mode for the current video block.

[0233] In some implementations, in response to the current video block being in NEW_NEARMV mode, the MVD corresponds to a horizontal direction for reference frames in the first reference frame list, and / or in response to the current video block being in NEAR_NEWMV mode, the MVD corresponds to a vertical direction for reference frames in the second reference frame list.

[0234] In some implementations, in response to the current video block being in NEW_NEARMV mode, the MVD corresponds to a vertical direction for a reference frame in the first reference frame list, and / or in response to the current video block being in NEAR_NEWMV mode, the MVD corresponds to a horizontal direction for a reference frame in the second reference frame list.

[0235] For non-limiting examples, a flag indicating whether there is a non-zero MVD in the horizontal or vertical direction is inferred based on the inter-frame prediction mode, for example, the MVD direction in the horizontal direction (or vertical direction) can be configured as a predefined (or default) configuration based on the inter-frame prediction mode. For non-limiting examples, for NEW_NEARMV mode, the direction of the MVD can be inferred (or defaulted) to be the horizontal (or vertical) direction; and / or for NEAR_NEWMV mode, the direction of the MVD can be inferred (or defaulted) to be the vertical (or horizontal) direction.

[0236] In the embodiments and implementations of the present disclosure, any steps and / or operations may be combined or arranged in any number or order as needed. Two or more of the steps and / or operations may be performed in parallel. The embodiments and implementations in the present disclosure may be used alone or in combination in any order. In addition, each of the method (or embodiment), encoder, and decoder may be implemented by a processing circuit (e.g., one or more processors or one or more integrated circuits). In one example, one or more processors execute a program stored in a non-transitory computer-readable medium. The embodiments in the present disclosure may be applied to luminance blocks or chrominance blocks. The term "block" may be interpreted as a prediction block, a coding block, or a coding unit (CU). The term "block" here may also be used to refer to a transform block. In the following items, when referring to a block size, it may refer to the width or height of the block, or the maximum value of the width and height, or the minimum value of the width and height, or the area size of the block (width * height), or the aspect ratio (width: height, or height: width).

[0237] The above techniques may be implemented as computer software using computer-readable instructions and physically stored in one or more computer-readable media. Fig.19 A computer system (1900) suitable for implementing certain embodiments of the disclosed subject matter is shown.

[0238] Computer software may be encoded using any suitable machine code or computer language that may be subjected to assembly, compilation, linking or similar mechanisms to create code comprising instructions that may be executed directly by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., or through interpretation, microcode execution, etc.

[0239] 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, and the like.

[0240] Fig.19 The components of the computer system (1900) shown are exemplary in nature and are not intended to suggest any limitation on the scope of use or functionality of computer software implementing embodiments of the present disclosure. Neither should the configuration of components be interpreted as having any dependency or requirement relating to any one or combination of components shown in the exemplary embodiment of the computer system (1900).

[0241] The computer system (1900) may include certain human-machine interface input devices. Such human-machine interface input devices may be responsive to input from 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), olfactory input (not depicted). Human-machine interface devices may also be used to capture certain media that are not necessarily directly related to human conscious input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, captured images obtained from a still image camera), and videos (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

[0242] The human-machine interface input device may include one or more of the following (only one of each is shown): keyboard (1901), mouse (1902), touchpad (1903), touch screen (1910), data gloves (not shown), joystick (1905), microphone (1906), scanner (1907), camera (1908).

[0243] The computer system (1900) may also include certain human-computer interface output devices. Such human-computer interface output devices may stimulate one or more human user senses through, for example, tactile output, sound, light, and smell / taste. Such human-computer interface output devices may include tactile output devices (e.g., tactile feedback of a touch screen (1910), a data glove (not shown), or a joystick (1905), but may also be a tactile feedback device that is not an input device), audio output devices (e.g., speakers (1909), headphones (not depicted)), visual output devices (e.g., screens (1910) including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capabilities, each with or without tactile feedback capabilities, some of which are capable of outputting two-dimensional visual outputs or outputs in more than three dimensions through devices such as stereoscopic image output, virtual reality glasses (not depicted), holographic displays and smoke boxes (not depicted), and printers (not depicted).

[0244] The computer system (1900) may also include human-accessible storage devices and their associated media, such as optical media including CD / DVD ROM / RW (1920) with CD / DVD etc. media (1921), thumb drives (1922), removable hard drives or solid-state drives (1923), traditional magnetic media such as tapes and floppy disks (not depicted), dedicated ROM / ASIC / PLD based devices such as security dongles (not depicted), and the like.

[0245] Those skilled in the art should also understand that the term "computer-readable media" used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

[0246] The computer system (1900) may also include an interface (1954) to one or more communication networks (1955). The network may be, for example, a wireless network, a wired network, an optical network. The network may further be a local network, a wide area network, a metropolitan area network, a vehicle and industrial network, a real-time network, a delay-tolerant network, etc. Examples of networks include local area networks such as Ethernet, wireless LANs, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., television wired or wireless wide area digital networks including cable television, satellite television, and terrestrial broadcast television, vehicle and industrial networks including CANBus, etc. Some networks typically require an external network interface adapter attached to some general data port or peripheral bus (1949) (e.g., a USB port of the computer system (1900)); as described below, other network interfaces are typically integrated into the kernel of the computer system (1900) by attaching to the system bus (e.g., connected to an Ethernet interface in a PC computer system or connected to a cellular network interface in a smartphone computer system). The computer system (1900) can use any of these networks to communicate with other entities. Such communications may be one-way receive only (e.g., broadcast television), one-way send only (e.g., CANBus connected to certain CANBus devices), or bidirectional, for example, using a LAN or WAN digital network to connect to other computer systems. As described above, certain protocols and protocol stacks may be used on each of those networks and network interfaces.

[0247] The above-mentioned human-machine interface device, human-machine accessible storage device and network interface may be attached to the kernel (1940) of the computer system (1900).

[0248] The kernel (1940) may include one or more central processing units (CPUs) (1941), graphics processing units (GPUs) (1942), dedicated programmable processing units in the form of field programmable gate arrays (FPGAs) (1943), hardware accelerators (1944) for certain tasks, graphics adapters (1950), and the like. These devices, as well as read-only memory (ROM) (1945), random access memory (1946), internal mass storage (1947) such as internal non-user accessible hard drives, SSDs, and the like, may be connected via a system bus (1948). In some computer systems, the system bus (1948) may be accessed in the form of one or more physical plugs to enable expansion by additional CPUs, GPUs, and the like. Peripheral devices may be attached directly to the kernel's system bus (1948) or to the kernel's system bus (1948) via a peripheral bus (1949). In one example, a screen (1910) may be connected to a graphics adapter (1950). The architecture of the peripheral bus includes PCI, USB, and the like.

[0249] The CPU (1941), GPU (1942), FPGA (1943) and accelerator (1944) can execute certain instructions, which can be combined to form the above-mentioned computer code. The computer code can be stored in ROM (1945) or RAM (1946). Transitional data can be stored in RAM (1946), while permanent data can be stored, for example, in internal mass storage (1947). Fast storage and retrieval to any storage device can be performed by using a cache, which can be closely associated with the following: one or more CPUs (1941), GPUs (1942), mass storage (1947), ROM (1945), RAM (1946), etc.

[0250] The computer readable medium may have thereon computer codes for performing various computer-implemented operations. The medium and computer codes may be those specially designed and constructed for the purposes of the present disclosure, or the medium and computer codes may be of a type well known and available to those skilled in the art of computer software.

[0251] As a non-limiting example, a computer system having an architecture (1900), in particular a kernel (1940), may provide functionality due to one or more processors (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software contained in one or more tangible computer-readable media. Such computer-readable media may be media associated with user-accessible mass storage as described above, as well as memories of certain non-temporary kernels (1940), such as kernel internal mass storage (1947) or ROM (1945). Software implementing various embodiments of the present disclosure may be stored in such devices and executed by the kernel (1940). Depending on specific needs, the computer-readable medium may include one or more storage devices or chips. The software may enable the kernel (1940), in particular the processors therein (including CPUs, GPUs, FPGAs, etc.), to perform specific processes or specific parts of specific processes described herein, including defining data structures stored in RAM (1946) and modifying such data structures according to processes defined by the software. Additionally or alternatively, a computer system may provide functionality due to logic hardwired or otherwise embodied in circuitry (e.g., accelerator (1944)) that may replace software or operate in conjunction with software to perform specific processes or specific portions of specific processes described herein. Where appropriate, references to portions of software may include logic and vice versa. Where appropriate, references to portions of computer-readable media may include circuitry (e.g., integrated circuits (ICs)) storing software for execution, circuitry embodying logic for execution, or both. The present disclosure includes any suitable combination of hardware and software.

[0252] Although the present disclosure has described multiple exemplary embodiments, there are modifications, permutations, and various replacement equivalents that fall within the scope of the present disclosure. Therefore, it should be understood that those skilled in the art will be able to design many systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and therefore fall within the spirit and scope of the present disclosure.

[0253] Appendix A: Acronyms

[0254] JEM: Joint Exploration Model

[0255] VVC: Next Generation Video Coding

[0256] BMS: Benchmark Set

[0257] MV: Motion Vector

[0258] HEVC: High Efficiency Video Coding

[0259] SEI: Supplementary Enhancement Information

[0260] VUI: Video Availability Information

[0261] GOP: Group of Pictures

[0262] TU: Transform Unit

[0263] PU: prediction unit

[0264] CTU: Coding Tree Unit

[0265] CTB: Coding Tree Block

[0266] PB: prediction block

[0267] HRD: Hypothetical Reference Decoder

[0268] SNR: Signal to Noise Ratio

[0269] CPU: Central Processing Unit

[0270] GPU: Graphics Processing Unit

[0271] CRT: cathode ray tube

[0272] LCD: Liquid Crystal Display

[0273] OLED: Organic Light Emitting Diode

[0274] CD: compact disc

[0275] DVD: Digital Video Disc

[0276] ROM: Read Only Memory

[0277] RAM: Random Access Memory

[0278] ASIC: Application-Specific Integrated Circuit

[0279] PLD: Programmable Logic Device

[0280] LAN: Local Area Network

[0281] GSM: Global System for Mobile Communications

[0282] LTE: Long Term Evolution

[0283] CANBus: Controller Area Network Bus

[0284] USB: Universal Serial Bus

[0285] PCI: Peripheral Component Interconnect

[0286] FPGA: Field Programmable Gate Array

[0287] SSD: Solid State Drive

[0288] IC: Integrated Circuit

[0289] HDR: High Dynamic Range

[0290] SDR: Standard Dynamic Range

[0291] JVET: Joint Video Exploration Team

[0292] MPM: Most Probable Mode

[0293] WAIP: Wide Angle Intra Prediction

[0294] CU: Coding Unit

[0295] PU: prediction unit

[0296] TU: Transform Unit

[0297] CTU: Coding Tree Unit

[0298] PDPC: Location-Dependent Prediction Combination

[0299] ISP: Intra-frame sub-partitioning

[0300] SPS: Sequence Parameter Set

[0301] PPS: Picture Parameter Set

[0302] APS: Adaptive Parameter Set

[0303] VPS: Video Parameter Set

[0304] DPS: Decoding Parameter Set

[0305] ALF: Adaptive Loop Filter

[0306] SAO: Sample Adaptive Offset

[0307] CC-ALF: Cross-component adaptive loop filter

[0308] CDEF: Constrained Directional Enhancement Filter

[0309] CCSO: Sampling offset across components

[0310] LSO: Local Sampling Offset

[0311] LR: Loop Reconstruction Filter

[0312] AV1: AO Media Video 1

[0313] AV2: AO Media Video 2

[0314] MVD: Motion Vector Difference

[0315] CfL: Predicting chrominance components from luminance components

[0316] SDT: Semi-Decoupled Tree

[0317] SDP: Semi-Decoupled Partitioning

[0318] SST: Semi-Separating Tree

[0319] SB: Super Block

[0320] IBC (or IntroBC): Intra-Block Copy

[0321] CDF: Cumulative density function

[0322] SCC: Screen Content Coding

[0323] GBI: Comprehensive Bidirectional Forecast

[0324] BCW: CU-level weighted bidirectional prediction

[0325] CIIP: Combined Intra-Frame and Inter-Frame Prediction

[0326] POC: Image Sequential Counting

[0327] RPS: Reference Picture Set

[0328] DPB: Decoded Picture Buffer

[0329] MMVD: Merge mode with motion vector difference

[0330] MV: Motion Vector

[0331] MVP: Motion Vector Predictor

Claims

1. A method for decoding a current video block of a video bitstream, characterized in that The method comprises: receiving, by a device, an encoded video bitstream; The device obtains a motion vector difference MVD of a current video block from the encoded video bitstream, wherein the current video block is an inter-frame coded block in a composite reference mode; in the composite reference mode, two or more reference blocks are used to generate a prediction block by weighted averaging; determining, by the device, whether the MVD is signaled for only one prediction direction; In response to determining that the MVD is signaled for only one prediction direction, the device limits the MVD to a predefined direction, the predefined direction comprising a horizontal direction or a vertical direction; in response to determining that the MVD is signaled for only one prediction direction, the device limits the MVD to a predefined direction, comprising: limiting the MVD to one or more determined predefined directions when the current video block is in NEW_NEARMV mode or NEAR_NEWMV mode; The device obtains, from the encoded video bitstream, a flag indicating whether the horizontal direction and the vertical direction have non-zero MVD; wherein, when the flag indicating whether the horizontal direction and the vertical direction have non-zero MVD is a first flag, the value of the first flag is one of the following: a first flag value indicating that neither the horizontal direction nor the vertical direction has non-zero MVD; a second flag value indicating that only one of the horizontal direction and the vertical direction has non-zero MVD; or a third flag value indicating that only the other of the horizontal direction and the vertical direction has non-zero MVD; In response to the current video block being in the NEW_NEARMV mode: in response to the flag being equal to the second flag value, the MVD corresponds to a vertical direction for a reference frame in a first reference frame list, or, in response to the flag being equal to the third flag value, the MVD corresponds to a horizontal direction for the reference frame in the first reference frame list; In response to the current video block being in the NEAR_NEWMV mode: in response to the flag being equal to the second flag value, the MVD corresponds to a horizontal direction for a reference frame in a second reference frame list, or, in response to the flag being equal to the third flag value, the MVD corresponds to a vertical direction for the reference frame in the second reference frame list; The current video block is decoded by the apparatus based on the MVD.

2. The method according to claim 1, characterized in that The determining that the MVD is signaled for only one prediction direction includes: The MVD is signaled in the coded video bitstream for only one reference frame in the composite reference mode; or The MVD is jointly signaled for two reference frames in the composite reference mode.

3. The method according to claim 1, characterized in that When the flag indicating whether the horizontal direction and the vertical direction have non-zero MVD is a second flag, the value of the second flag is one of the following: a fourth flag value indicating that only one of the horizontal direction and the vertical direction has a non-zero MVD; or A fifth flag value indicating that only the other one of the horizontal direction and the vertical direction has a non-zero MVD.

4. The method according to claim 3, characterized in that The method further comprises: In response to the current video block being in the NEW_NEARMV mode: In response to the flag being equal to the fourth flag value, the MVD corresponds to a vertical direction for a reference frame in the first reference frame list, or In response to the flag being equal to the fifth flag value, the MVD corresponds to a horizontal direction for the reference frame in the first reference frame list; and In response to the current video block being in the NEAR_NEWMV mode: In response to the flag being equal to the fourth flag value, the MVD corresponds to a horizontal direction for a reference frame in the second reference frame list, or In response to the flag being equal to the fifth flag value, the MVD corresponds to a vertical direction for the reference frame in the second reference frame list.

5. The method according to claim 1, characterized in that The flag is signaled in a high-level syntax, and the high-level syntax includes at least one of the following: a video parameter set VPS, a picture parameter set PPS, a sequence parameter set SPS, an adaptive parameter set APS, a picture header, a frame header, a slice header, a tile header or a coding tree unit CTU header.

6. The method according to claim 1, characterized in that In response to determining that the MVD is signaled for only one prediction direction, limiting, by the device, the MVD to a predefined direction, comprises: In response to the current video block being in NEW_NEARMV mode or in NEAR_NEWMV mode, the predefined direction includes only one direction.

7. The method according to claim 1, characterized in that The method further comprises: Determining, by the apparatus based on a mode for the current video block, whether a horizontal direction and a vertical direction have a non-zero MVD.

8. The method according to claim 7, characterized in that The method further comprises: In response to the current video block being in NEW_NEARMV mode, the MVD corresponds to a horizontal direction for a reference frame in a first reference frame list, and In response to the current video block being in NEAR_NEWMV mode, the MVD corresponds to a vertical direction for a reference frame in a second reference frame list.

9. The method according to claim 7, characterized in that: The method further comprises: In response to the current video block being in NEW_NEARMV mode, the MVD corresponds to a vertical direction for a reference frame in a first reference frame list, and In response to the current video block being in NEAR_NEWMV mode, the MVD corresponds to a horizontal direction for a reference frame in a second reference frame list.

10. An apparatus for decoding a current video block of a video bitstream, characterized in that The device comprises: a memory for storing instructions; and A processor in communication with the memory, wherein when the processor executes the instructions, the processor is configured to cause the apparatus to perform the method of any one of claims 1 to 9.

11. A non-transitory computer-readable storage medium storing instructions, characterized in that: When the instructions are executed by a processor, the instructions are configured to cause the processor to perform the method according to any one of claims 1 to 9.

12. A method for processing a video code stream, characterized in that: The video code stream is decoded based on the decoding method described in any one of claims 1 to 9.

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