Video decoding method, apparatus and computer program

Abstract

Aspects of the present disclosure include a method and apparatus for video coding. The apparatus includes a processing circuit that receives coding information for a current block in a current picture. The current block is predicted based on a reference block in the current picture indicated by a block vector (BV), and is determined based on a BV predictor (BVP) and a BV difference (BVD). The processing circuit determines a BVD list including BVD candidates based at least on a BVD offset from the BVP, determines a BVD from the BVD candidates in the BVD list, and reconstructs the current block using the BVD. For each adjacent pair of BVD offsets, an initial interval size indicates the difference between the adjacent pair of BVD offsets. Each initial interval size is different from other initial interval sizes corresponding to other adjacent pairs of BVD offsets.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Application No. 63 / 438,490, entitled "IBC Merge Mode with BV Difference," filed January 11, 2023, which claims the benefit of priority to U.S. Patent Application No. 18 / 409,445, entitled "IBC MERGE MODE WITH A BLOCK VECTOR DIFFERENCE," filed January 10, 2024. The disclosures of the prior applications are incorporated herein by reference in their entireties.

[0002] This disclosure describes embodiments that relate generally to video coding. [Background technology]

[0003] The discussion of the background art provided herein is intended to generally present the context for the present disclosure. The work of the presently named inventors, to the extent that that work is described in this background art section, as well as aspects of the description that may not qualify as prior art at the time of filing, are not admitted expressly or impliedly as prior art to the present disclosure.

[0004] Image / video compression can help transmit image / video data across different devices, storage, and networks with minimal quality degradation. In some examples, video codec techniques can compress video based on spatial and temporal redundancy. In one example, a video codec can use a technique called intra-prediction, which can compress images based on spatial redundancy. For example, intra-prediction can use reference data from a current picture being reconstructed for sample prediction. In another example, a video codec can use a technique called inter-prediction, which can compress images based on temporal redundancy. For example, inter-prediction can predict samples in a current picture from a previously reconstructed picture using motion compensation. Motion compensation can be indicated by a motion vector (MV). Summary of the Invention [Means for solving the problem]

[0005] Aspects of the present disclosure include methods and apparatuses for video encoding / decoding. In some examples, the apparatus for video decoding includes a processing circuit. The processing circuit receives a coded video bitstream including coding information for a current block in a current picture. The current block may be predicted based on a reference block in the current picture indicated by a block vector (BV) to be determined based on a BV predictor (BVP) and a BV difference (BVD), which is a difference between the BV and the BVP. The processing circuit determines a BVD list including BVD candidates based at least on a BVD offset from the BVP. The processing circuit determines a BVD from the BVD candidates in the BVD list and reconstructs the current block using the determined BVD. For each adjacent pair of BVD offsets, an initial interval size indicates a difference between the adjacent pair of BVD offsets, and each initial interval size is different from other initial interval sizes corresponding to other adjacent pairs of BVD offsets.

[0006] In one example, the initial interval sizes are arranged in ascending order.

[0007] The initial interval size may be a power of two.

[0008] In one example, the initial interval size includes K sizes, each of which is 2 i-1 where i is an integer ranging from 1 to K, and K is greater than 1.

[0009] In one example, the initial interval size is stored in a lookup table.

[0010] In one example, one of the initial interval sizes is not a power of two.

[0011] In one aspect, the processing circuit determines initial BVD candidates based on (i) a BVD offset and (ii) a BVD direction. Each of the initial BVD candidates has one of the BVD offsets and a corresponding one of the BVD directions. The processing circuit determines a template matching (TM) cost associated with each initial BVD candidate among the initial BVD candidates between a current template of the current block and each reference template of the candidate reference blocks. The candidate reference blocks are indicated by the initial BV candidates, which are the sum of the BVD candidate and each initial BVD candidate. The processing circuit determines the BVD list based on the TM cost.

[0012] In one example, the processing circuitry selects K initial BVD candidates from the initial BVD candidates as BVD candidates in the BVD list, where the K initial BVD candidates correspond to the lowest TM costs among the TM costs.

[0013] In one example, the processing circuit selects K initial BVD candidates from the initial BVD candidates. The K initial BVD candidates correspond to the lowest TM costs among the TM costs. For each of the K initial BVD candidates having a respective BVD offset and BVD direction, a first candidate and a second candidate associated with each initial BVD candidate among the K initial BVD candidates may be determined when the BVD offset is the only BVD offset in the BVD offsets that is greater than the first BVD offset and less than the second BVD offset. The first candidate and the second candidate have the same BVD direction as the initial BVD candidate. The BVD offset of the first candidate is the average of the BVD offset and the first BVD offset, and the BVD offset of the second candidate is the average of the BVD offset and the second BVD offset. The processing circuit determines new TM costs associated with the first candidate and the second candidate, respectively. The processing circuitry determines the BVD list based on the updated TM costs, including (i) the lowest TM cost among the TM costs corresponding to the K initial BVD candidates, and (ii) the new TM cost.

[0014] In one example, the processing circuit determines a BVP, determines a BV as the sum of the BVP and the determined BVD, and reconstructs the current block using the determined BV.

[0015] Aspects of the present disclosure also provide a non-transitory computer-readable medium storing instructions that, when executed by a computer, cause the computer to perform any of the described methods for video decoding / encoding.

[0016] Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and accompanying drawings. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of an exemplary block diagram of a communication system (100). [Figure 2] FIG. 2 is a schematic diagram of an exemplary block diagram of a decoder. [Figure 3] FIG. 2 is a schematic diagram of an exemplary block diagram of an encoder. [Figure 4A] 1 illustrates an example of an intra-block copy (IBC) mode according to an example of the present disclosure. [Figure 4B] 1 illustrates an example of an intra-template matching prediction (IntraTMP) mode according to an aspect of the present disclosure. [Figure 5A] 1 illustrates an example of a template matching procedure according to one aspect of the present disclosure. [Figure 5B] 1 illustrates a template and reference samples of the template in a reference picture according to one aspect of the present disclosure. [Figure 6] 1 illustrates a current template for a current block in a current picture and a reference template in a reference picture that corresponds to the current template, according to one embodiment of the present disclosure. [Figure 7] 10 illustrates an example of refinement positions along k×π / 8 diagonal angles, according to one embodiment of the present disclosure. [Figure 8] 1 illustrates an example process for deriving an IBC merge mode (MBVD) list using block vector differences, according to one aspect of the present disclosure. [Figure 9] 10 illustrates an example of a constant offset every Mth position in MBVD list construction by using a TM, according to one embodiment of the present disclosure. [Figure 10] FIG. 10 illustrates an example of a set of offsets, according to one aspect of the present disclosure. [Figure 11] 1 illustrates an example of a set of offsets according to an aspect of the present disclosure. [Figure 12] 1 illustrates an example of a set of offsets according to an aspect of the present disclosure. [Figure 13] 1 illustrates an example of a BVD offset according to an embodiment of the present disclosure. [Figure 14] 1 shows a flowchart outlining a decoding process according to some embodiments of the present disclosure. [Figure 15] 1 shows a flowchart outlining an encoding process according to some embodiments of the present disclosure. [Figure 16] FIG. 1 is a schematic diagram of a computer system according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] 1 shows a block diagram of a video processing system (100) in some examples. The video processing system (100) is exemplary of an application of the disclosed subject matter, a video encoder and a video decoder, in a streaming environment. The disclosed subject matter may be equally applicable to other video-enabled applications, including, for example, video conferencing, digital TV, streaming services, storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0019] The video processing system (100) includes a video source (101) and a capture subsystem (113) that may include, for example, a digital camera, creating a stream of uncompressed video pictures (102). In one example, the stream of video pictures (102) includes samples captured by the digital camera. The stream of video pictures (102), shown in bold to emphasize its high data volume compared to the encoded video data (104) (or coded video bitstream), may be processed by an electronic device (120) that includes a video encoder (103) coupled to the video source (101). The video encoder (103) may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter, as described in more detail below. The encoded video data (104) (or coded video bitstream), shown in thin to emphasize its low data volume compared to the stream of video pictures (102), may be stored on a streaming server (105) for future use. One or more streaming client subsystems, such as the client subsystems (106) and (108) of FIG. 1, can access the streaming server (105) to retrieve copies (107) and (109) of the encoded video data (104). The client subsystem (106) can include, for example, a video decoder (110) within an electronic device (130). The video decoder (110) decodes an input copy (107) of the encoded video data and creates an output stream of video pictures (111) that can be rendered on a display (112) (e.g., a display screen) or other rendering device (not shown). In some streaming systems, the encoded video data (104), (107), and (109) (e.g., a video bitstream) can be encoded according to a particular video coding / compression standard. Examples of these standards include ITU-T Recommendation H.265.In one example, a video coding standard under development is informally known as Versatile Video Coding (VVC), and the disclosed subject matter may be used in the context of VVC.

[0020] It should be noted that the electronic devices (120) and (130) may include other components (not shown). For example, the electronic device (120) may include a video decoder (not shown), and the electronic device (130) may also include a video encoder (not shown).

[0021] 2 shows an exemplary block diagram of a video decoder (210). The video decoder (210) can be included in an electronic device (230). The electronic device (230) can include a receiver (231) (e.g., a receiving circuit). The video decoder (210) can be used in place of the video decoder (110) in the example of FIG. 1.

[0022] The receiver (231) may receive one or more coded video sequences, e.g., contained in a bitstream, to be decoded by the video decoder (210). In one embodiment, one coded video sequence is received at a time, and the decoding of each coded video sequence is independent of the decoding of other coded video sequences. The coded video sequences may be received from a channel (201), which may be a hardware / software link to a storage device that stores the coded video data. The receiver (231) may receive the coded video data along with other data, e.g., coded audio data and / or auxiliary data streams, that may be forwarded to respective using entities (not shown). The receiver (231) may separate the coded video sequences from other data. To combat network jitter, a buffer memory (215) may be coupled between the receiver (231) and the entropy decoder / parser (220) (hereinafter, "parser (220)"). In certain applications, the buffer memory (215) is part of the video decoder (210). In other cases, it may be external to the video decoder (210) (not shown). In yet other embodiments, there may be a buffer memory (not shown) external to the video decoder (210), e.g., to combat network jitter, and in addition, there may be another buffer memory (215) internal to the video decoder (210), e.g., to handle playback timing. When the receiver (231) is receiving data from a storage / forwarding device with sufficient bandwidth and controllability or from an isosynchronous network, the buffer memory (215) may not be required or may be small. For use over best-effort packet networks such as the Internet, the buffer memory (215) may be required, may be relatively large, may advantageously be adaptively sized, and may be implemented at least in part in an operating system or similar element (not shown) external to the video decoder (210).

[0023] The video decoder (210) may include a parser (220) for reconstructing symbols (221) from the coded video sequence. These symbol categories include information used to manage the operation of the video decoder (210) and, potentially, information for controlling a rendering device, such as a rendering device (212) (e.g., a display screen) that is not an integral part of the electronic device (230) but may be coupled to the electronic device (230), as shown in FIG. 2. The control information for the rendering device(s) may be in the form of a supplemental enhancement information (SEI) message or a video usability information (VUI) parameter set fragment (not shown). The parser (220) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may follow a video coding technique or standard and may follow various principles, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, etc. The parser (220) can extract, from the coded video sequence, a set of subgroup parameters for at least one of a subgroup of pixels in a video decoder based on at least one parameter corresponding to the group. The subgroup can 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 (220) can also extract information from the coded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, etc.

[0024] The parser (220) can perform entropy decoding / parsing operations on the video sequence received from the buffer memory (215) to create symbols (221).

[0025] The reconstruction of the symbols (221) can involve several different units, depending on the type of coded video picture or portion thereof (e.g., inter-picture and intra-picture, inter-block and intra-block, etc.), as well as other factors. Which units participate and how may be controlled by subgroup control information parsed from the coded video sequence by the parser (220). The flow of such subgroup control information between the parser (220) and the following units is not shown for clarity.

[0026] Beyond the functional blocks already mentioned, the video decoder (210) may be conceptually subdivided into several functional units, as described below. In an actual implementation operating under commercial constraints, many of these units will interact closely with each other and may be at least partially integrated with each other. However, for purposes of describing the disclosed subject matter, the following conceptual subdivision into functional units is appropriate.

[0027] The first unit is a scalar / inverse transform unit (251), which receives quantized transform coefficients and control information from the parser (220) as symbol(s) (221), including which transform to use, block size, quantization coefficients, quantization scaling matrices, etc. The scalar / inverse transform unit (251) can output blocks containing sample values ​​that can be input to an aggregator (255).

[0028] In some cases, the output samples of the scaler / inverse transform unit (251) may relate to intra-coded blocks. An intra-coded block is a block that does not use prediction information from a previously reconstructed picture but can use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by the intra-picture prediction unit (252). In some cases, the intra-picture prediction unit (252) generates a block of the same size and shape as the block being reconstructed using surrounding, already reconstructed information fetched from the current picture buffer (258). The current picture buffer (258), for example, buffers partially reconstructed and / or fully reconstructed current pictures. The aggregator (255) may add, on a sample-by-sample basis, the prediction information generated by the intra-prediction unit (252) to the output sample information provided by the scaler / inverse transform unit (251).

[0029] In other cases, the output samples of the scalar / inverse transform unit (251) may relate to an inter-coded, potentially motion-compensated, block. In such cases, the motion-compensated prediction unit (253) may access a reference picture memory (257) to fetch samples used for prediction. After motion-compensating the fetched samples according to the symbols (221) associated with the block, these samples may be added by the aggregator (255) to the output of the scalar / inverse transform unit (251) (referred to as residual samples or residual signals in this case) to generate output sample information. The addresses in the reference picture memory (257) from which the motion-compensated prediction unit (253) fetches prediction samples may be controlled by motion vectors available to the motion-compensated prediction unit (253), for example, in the form of symbols (221) that may have X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​fetched from the reference picture memory (257) when sub-sample accurate motion vectors are used, motion vector prediction mechanisms, and the like.

[0030] The output samples of the aggregator (255) may be subjected to various loop filtering techniques in a loop filter unit (256). Video compression techniques may include in-loop filtering techniques controlled by parameters contained in the coded video sequence (also referred to as the coded video bitstream) and made available to the loop filter unit (256) as symbols (221) from the parser (220). Video compression may also be responsive to meta-information obtained during decoding of previous portions (in decoding order) of the coded picture or coded video sequence, as well as to previously reconstructed loop-filtered sample values.

[0031] The output of the loop filter unit (256) may be a sample stream that may be output to a rendering device (212) and stored in a reference picture memory (257) for use in future inter-picture prediction.

[0032] Once a particular coded picture is fully reconstructed, it can be used as a reference picture for future prediction. For example, once a coded picture corresponding to a current picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by the parser (220)), the current picture buffer (258) can become part of the reference picture memory (257), and a new current picture buffer can be reallocated before beginning reconstruction of the next coded picture.

[0033] The video decoder (210) may perform decoding operations in accordance with a given video compression technology or standard, such as ITU-T Recommendation H.265. A coded video sequence may comply with the syntax specified by the video compression technology or standard being used, in the sense that the coded video sequence conforms to both the syntax of the video compression technology or standard and a profile documented in the video compression technology or standard. Specifically, a profile may select specific tools from all tools available in the video compression technology or standard as the only tools available for use under that profile. Compliance may also require that the complexity of the coded video sequence be within a range defined by the level of the video compression technology or standard. In some cases, the level limits the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limits set by the level may, in some cases, be further restricted through a hypothetical reference decoder (HRD) specification and metadata for HRD buffer management signaled in the coded video sequence.

[0034] In one embodiment, the receiver (231) can receive additional (redundant) data along with the encoded video. The additional data may be included as part of the coded video sequence(s). The additional data may be used by the video decoder (210) to properly decode the data and / or to more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0035] 3 shows an example block diagram of a video encoder (303). The video encoder (303) is included in an electronic device (320). The electronic device (320) includes a transmitter (340) (e.g., a transmission circuit). The video encoder (303) can be used in place of the video encoder (103) in the example of FIG. 1.

[0036] The video encoder (303) may receive video samples from a video source (301) (not part of the electronic device (320) in the example of FIG. 3) that may capture the video image(s) to be coded by the video encoder (303). In another example, the video source (301) is part of the electronic device (320).

[0037] The video source (301) can provide a source video sequence to be coded by the video encoder (303) in the form of a digital video sample stream, which can be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...), and any suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media serving system, the video source (301) can be a storage device that stores previously prepared video. In a video conferencing system, the video source (301) can be a camera that captures local image information as a video sequence. The video data can be provided as multiple individual pictures that, when viewed in sequence, impart motion. The pictures themselves can be organized as a spatial array of pixels, where each pixel can comprise one or more samples depending on the sampling structure, color space, etc., in use. The following discussion focuses on samples.

[0038] According to one embodiment, the video encoder (303) can code and compress pictures of a source video sequence into a coded video sequence (343) in real time, or under any other time constraints as needed. Enforcing the appropriate coding rate is one function of the controller (350). In some embodiments, the controller (350) controls and is operatively coupled to other functional units as described below. Coupling is not shown for clarity. Parameters set by the controller (350) can include rate control-related parameters (e.g., picture skip, quantizer, lambda value for rate-distortion optimization techniques), picture size, group-of-picture (GOP) layout, maximum motion vector search range, etc. The controller (350) can be configured with other appropriate functions associated with the video encoder (303) optimized for a particular system design.

[0039] In some embodiments, the video encoder (303) is configured to operate in a coding loop. As an overly simplified explanation, in one example, the coding loop can include a source coder (330) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be coded and reference picture(s)) and a (local) decoder (333) embedded in the video encoder (303). The decoder (333) reconstructs the symbols to create sample data in a manner similar to that of the (remote) decoder. The reconstructed sample stream (sample data) is input to a reference picture memory (334). Because decoding of the symbol stream yields bit-exact results regardless of the location of the decoder (local or remote), the contents of the reference picture memory (334) are also bit-exact between the local and remote encoders. In other words, the predictive portion of the encoder "sees" the exact same sample values ​​as the decoder "sees" when using prediction during decoding. This basic principle of reference picture synchronism (and the drift that occurs when synchronism cannot be maintained, for example due to channel errors) is also used in several related technologies.

[0040] The operation of the "local" decoder (333) may be the same as a "remote" decoder, such as the video decoder (210) already described in detail above in connection with Figure 2. However, with brief reference also to Figure 2, because symbols are available and the encoding / decoding of symbols into a coded video sequence by the entropy coder (345) and parser (220) may be lossless, the entropy decoding portion of the video decoder (210), including the buffer memory (215) and parser (220), may not be fully implemented in the local decoder (333).

[0041] In one embodiment, decoder technology, excluding analysis / entropy decoding, present in the decoder is present in the corresponding encoder in the same or substantially the same functional form. Therefore, the disclosed subject matter focuses on the operation of the decoder. A description of the encoder technology can be omitted, as it is the reverse of the decoder technology described comprehensively. In certain areas, more detailed descriptions are provided below.

[0042] In operation, in some examples, the source coder (330) may perform motion-compensated predictive coding, which predictively codes an input picture with reference to one or more previously coded pictures from a video sequence designated as “reference pictures.” In this manner, the coding engine (332) codes differences between pixel blocks of the input picture and pixel blocks of reference picture(s) that may be selected as predictive references for the input picture.

[0043] The local video decoder (333) may decode coded video data of pictures that may be designated as reference pictures based on symbols created by the source coder (330). The operation of the coding engine (332) may advantageously be a lossy process. When the coded video data is decoded in a video decoder (not shown in FIG. 3), the reconstructed video sequence may generally be a replica of the source video sequence with some errors. The local video decoder (333) may replicate the decoding process that may be performed by the video decoder on the reference pictures and store the reconstructed reference pictures in a reference picture memory (334). In this way, the video encoder (303) may locally store copies of reconstructed reference pictures that have content in common with the reconstructed reference pictures that will be obtained by the far-end video decoder (without transmission errors).

[0044] The predictor (335) can perform a predictive search for the coding engine (332). That is, for a new picture to be coded, the predictor (335) can search the reference picture memory (334) for sample data (as candidate reference pixel blocks) or specific metadata, such as reference picture motion vectors, block shapes, etc., that can serve as suitable prediction references for the new picture. The predictor (335) can operate on a pixel block-by-pixel block basis to find suitable prediction references. In some cases, as determined by search results obtained by the predictor (335), the input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (334).

[0045] The controller (350) can manage the coding operations of the source coder (330), including, for example, setting the parameters and subgroup parameters used to encode the video data.

[0046] The output of all the above functional units can undergo entropy coding in an entropy coder (345), which converts the symbols produced by the various functional units into a coded video sequence by applying lossless compression to the symbols according to techniques such as Huffman coding, variable length coding, or arithmetic coding.

[0047] The transmitter (340) can buffer the coded video sequence(s) created by the entropy coder (345) and prepare them for transmission over a communication channel (360), which can be a hardware / software link to a storage device that stores the encoded video data. The transmitter (340) can merge the coded video data from the video encoder (303) with other data to be transmitted, such as coded audio data and / or auxiliary data streams (sources not shown).

[0048] The controller (350) can manage the operation of the video encoder (303). During coding, the controller (350) can assign a particular coded picture type to each coded picture, which can affect the coding technique that can be applied to the respective picture. For example, pictures can often be assigned as one of the following picture types:

[0049] An intra-picture (I-picture) can be coded and decoded without using any other picture in the sequence as a source of prediction. Some video codecs allow different types of intra-pictures, including, for example, independent decoder refresh ("IDR") pictures.

[0050] Predictive pictures (P pictures) may be coded and decoded using intra- or inter-prediction, which uses motion vectors and reference indices to predict the sample values ​​of each block.

[0051] Bidirectionally predicted pictures (B pictures) can be coded and decoded using intra- or inter-prediction, which uses two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple predicted pictures can use more than two reference pictures and associated metadata for the reconstruction of a single block.

[0052] A source picture is generally spatially subdivided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and may be coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks, as determined by the coding assignment applied to the block's respective picture. For example, blocks of an I-picture may be non-predictively coded, or they may be predictively coded with reference to already coded blocks of the same picture (spatial prediction or intra-prediction). Pixel blocks of a P-picture may be predictively coded via spatial prediction or via temporal prediction with reference to one previously coded reference picture. Blocks of a B-picture may be predictively coded via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

[0053] The video encoder (303) may perform coding operations in accordance with a predetermined video coding technique or standard, such as ITU-T Recommendation H.265. In doing so, the video encoder (303) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancy in the input video sequence. Thus, the coded video data may conform to a syntax specified by the video coding technique or standard being used.

[0054] In one embodiment, the transmitter (340) can transmit additional data along with the encoded video. The source coder (330) may include such data as part of the coded video sequence. The additional data may comprise temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0055] Video may be captured as multiple source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often abbreviated as intra-prediction) exploits spatial correlation within a given picture, while inter-picture prediction exploits correlation (temporal or otherwise) between pictures. In one example, a particular picture being encoded / decoded, referred to as the current picture, is divided into blocks. When a block in the current picture is similar to a reference block in a previously coded and still buffered reference picture in the video, the block in the current picture may be coded by a vector referred to as a motion vector. A motion vector points to a reference block within a reference picture and may have a third dimension that identifies the reference picture if multiple reference pictures are used.

[0056] In some embodiments, bi-prediction techniques can be used in inter-picture prediction. According to bi-prediction techniques, two reference pictures, such as a first reference picture and a second reference picture, are used, both of which are earlier in decoding order than the current picture in the video (but may be in the past and future, respectively, in display order). A block in the current picture may be coded 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. A block may be predicted by a combination of the first reference block and the second reference block.

[0057] Furthermore, merge mode techniques may be used in inter-picture prediction to improve coding efficiency.

[0058] According to some embodiments of the present disclosure, predictions such as inter-picture prediction and intra-picture prediction are performed in units of blocks. For example, according to the HEVC standard, pictures in a sequence of video pictures are partitioned into coding tree units (CTUs) for compression, and the CTUs in a picture have the same size, such as 64x64 pixels, 32x32 pixels, or 16x16 pixels. Generally, a CTU includes three coding tree blocks (CTBs), one luma CTB and two chroma CTBs. Each CTU may be recursively quadtree partitioned into one or more coding units (CUs). For example, a 64x64 pixel CTU may be partitioned into one CU of 64x64 pixels, four CUs of 32x32 pixels, or 16 CUs of 16x16 pixels. In one example, each CU is analyzed to determine the prediction type of the CU, such as an inter-prediction type or an intra-prediction type. A CU is divided into one or more prediction units (PUs) according to temporal and / or spatial predictability. Generally, each PU includes a luma prediction block (PB) and two chroma PBs. In one embodiment, prediction operations in coding (encoding / decoding) are performed in units of prediction blocks. Using a luma prediction block as an example of a prediction block, the prediction block includes a matrix of values ​​(e.g., luma values) for pixels, such as 8x8 pixels, 16x16 pixels, 8x16 pixels, 16x8 pixels, etc.

[0059] It should be noted that the video encoders (103) and (303) and the video decoders (110) and (210) may be implemented using any suitable technology. In one embodiment, the video encoders (103) and (303) and the video decoders (110) and (210) may be implemented using one or more integrated circuits. In another embodiment, the video encoders (103) and (303) and the video decoders (110) and (210) may be implemented using one or more processors executing software instructions.

[0060] END Boilerplate An example of intra block copy mode (also referred to as IBC mode or intra BC mode), as used in HEVC and VVC, is described below.

[0061] FIG. 4A illustrates an example of an IBC mode according to an example of the present disclosure. The reference block used to predict the current CU (401) may be indicated by a block vector (BV) associated with the current CU (401). Each square (400) may represent a CTU. The gray shaded areas represent regions or areas that have already been coded, and the white unshaded areas represent regions or areas to be coded. The current CTU (400(4)) being reconstructed includes the current CU (401), a coded region (402), and a to-be-coded region (403). In one example, the region (403) is coded after coding the current CU (401).

[0062] For example, in HEVC, the gray shaded area excluding the two CTUs (400(1) to 400(2)) to the upper right of the current CTU (400(4)) can be used as a reference area in IBC mode to enable wavefront parallel processing (WPP). A BV permitted in HEVC can point to a block within the reference area (e.g., the gray shaded area excluding the two CTUs (400(1) to 400(2))). For example, a BV (405) permitted in HEVC points to the reference block (411).

[0063] In one example, in VVC, in addition to the current CTU (400(4)), only the left neighboring CTU (400(3)) to the left of the current CTU (400(4)) is allowed as a reference region in IBC mode. In one example, the reference region used in IBC mode in VVC is within the dotted line region (415) and contains the sample to be coded. For example, the BV (406) allowed in VVC refers to the reference block (412).

[0064] In one aspect, IBC is a tool adopted in the HEVC extension for screen content coding (SCC). IBC can significantly improve the coding efficiency of screen content material. Since IBC mode is implemented as a block-level coding mode, block matching (BM) may be performed in the encoder to find the optimal block vector (or motion vector) for each CU. Here, the block vector (BV) may be used to indicate the displacement from the current block to a reference block already reconstructed in the current picture. The luma block vectors of IBC-coded CUs may be integer precision. The chroma block vectors may also be rounded to integer precision. When combined with AMVR, IBC mode can switch between 1-pixel motion vector precision and 4-pixel motion vector precision. IBC-coded CUs can be treated as a third prediction mode other than intra- or inter-prediction modes. IBC mode can be treated as a third prediction mode different from intra-prediction and inter-prediction. IBC mode may be applicable to CUs whose width and height are both 64 luma samples or less.

[0065] On the encoder side, hash-based motion estimation can be performed for IBC mode. The encoder performs an RD check for blocks with either width or height not greater than 16 luma samples. For non-merge modes, a block vector search can be performed first using a hash-based search. If the hash search does not return a valid candidate, a block-matching-based local search is performed.

[0066] In a hash-based search, hash key matching (32-bit CRC) between the current block and the reference block can be extended to the allowed block size (e.g., all allowed block sizes). The hash key calculation for all locations in the current picture can be based on sub-blocks (e.g., 4x4 sub-blocks). For larger-sized current blocks, a hash key can be determined to match the hash key of a reference block when the hash keys of the sub-blocks (e.g., all hash keys of all 4x4 sub-blocks) match the hash keys in the corresponding reference locations. If the hash keys of multiple reference blocks are found to match the hash key of the current block, a block vector cost for each matched reference can be calculated, and the one with the smallest cost is selected.

[0067] In a block matching search, in one example, the search range is set to cover both the previous CTU and the current CTU.

[0068] At the CU level, the IBC mode is signaled using a flag, and the IBC mode can be signaled as IBC AMVP mode or IBC skip / merge mode as follows: IBC Skip / Merge Mode: The merge candidate index is used to indicate which block vector in a list (e.g., merge list) from neighboring candidate IBC-coded blocks is used to predict the current block. The merge list can include spatial candidates, HMVP candidates, and pairwise candidates. IBC AMVP mode: Block vector differentials are coded in the same way as motion vector differentials. The block vector prediction method uses two candidates as predictors, one from the left neighbor and one from the above neighbor (when IBC coded, e.g., when the left and above neighbors are IBC coded). If either neighbor is not available, a default block vector is used as the predictor. A flag is signaled to indicate the block vector predictor index.

[0069] 4B illustrates an example of an intra-template matching prediction (IntraTMP) mode according to one embodiment of the present disclosure. In one embodiment, such as in Extended Compression Model (ECM) software, IntraTMP is a special intra-prediction mode that can copy the best predicted block (e.g., matching block (421)) from the reconstructed portion of the current frame (or current picture), where the template (e.g., L-shaped template) (420) of the best predicted block can match the current template (430) of the current block (431) (e.g., current PU or current CU). For a predefined search range, the encoder can search for the template most similar to the current template in the reconstructed portion of the current frame and use the corresponding block as the predicted block. The encoder can signal the use of IntraTMP mode, and the same prediction operation can be performed at the decoder side.

[0070] The prediction signal can be generated by matching a current template (430), such as an L-shaped causal neighborhood of the current block (431), with a template of another block within a predefined search area. The exemplary search area shown in FIG. 4B can include multiple CTUs (or superblocks). Referring to FIG. 4B, the search area can include the current CTU R1 (e.g., a portion of the current CTU R1), the upper-left CTU R2, the upper CTU R3, and the left CTU R4. The cost function can include any suitable cost function, such as sum of absolute differences (SAD).

[0071] Within each region, the decoder can search for the template with the smallest cost (e.g., smallest SAD) relative to the current template, and can use the block associated with the template with the smallest cost as the predicted block.

[0072] The dimensions of the region denoted by (SearchRange_w, SearchRange_h) can be set to be proportional to the block dimensions (BlkW, BlkH) to have a fixed number of SAD comparisons per pixel. SearchRange_w=a×BlkW Equation (1) SearchRange_h=a×BlkH Equation (2)

[0073] The parameter "a" may be a constant that controls the tradeoff between gain and complexity. In one example, "a" is 5.

[0074] In one example, to speed up the template matching process, the search range (e.g., the search range of the entire search region) is subsampled by a factor of two, which results in a reduction in the template matching search by a factor of four. After the best match (or initial best match) is found, a refinement process can be performed. The refinement is performed via a second template matching search around the best match (or initial best match) with a reduced range. The reduced range is defined as min(BlkW,BlkH) / 2.

[0075] The intra template matching tool may be enabled for CUs with width and height sizes less than or equal to 64. The maximum CU size (e.g., 64) for intra template matching may be configurable.

[0076] In this disclosure, the term "IBC" can refer to the IBC mode or variant described in FIG. 4A, and the IntraTMP mode or variant described in FIG. 4B.

[0077] In one example, to further improve the compression efficiency of certain video coding techniques used in the VVC standard, tools beyond VVC capabilities may be used. Template matching (TM) can refine motion at the decoder side. In TM mode, motion can be refined by building a template from reconstructed samples of the left and top neighbors and finding the closest match between the template and a reference frame in the current picture.

[0078] FIG. 5A illustrates an example of a template matching procedure according to one aspect of the present disclosure. In FIG. 5A, the current template (521) of the current block (501) in the current picture (510) can have any suitable shape and any suitable size. In one embodiment, the current template (521) of the current block (501) includes a top template (522) and a left template (523). Each of the top template (522) and the left template (523) can have any suitable shape and any suitable size. The top template (522) can include samples in one or more top neighboring blocks of the current block (501). In one example, the top template (522) includes N1 (e.g., 1 or 4) rows of samples in one or more top neighboring blocks of the current block (501). The left template (523) can include samples in one or more left neighboring blocks of the current block (501). In one example, the left template (523) includes N2 (eg, 1 or 4) columns of samples in one or more left neighboring blocks of the current block (501).

[0079] In one embodiment, an initial MV, such as the MV (502), points from the current block (501) to the reference block (503) in the reference picture (511). The shape and size of the reference template may match the shape and size of the current template (521), respectively. In FIG. 5A, the reference template (525) of the reference block (503) in the reference picture (511) may have the same shape and size as the current template (521) in the current picture (510). For example, the reference template (525) of the reference block (503) includes a top template (526) in the reference picture (511) and a left template (527) in the reference picture (511). The top template (526) may include samples in one or more top neighboring blocks of the reference block (503). The left template (527) may include samples in one or more left neighboring blocks of the reference block (503).

[0080] Referring to FIG. 5A , a better MV is searched for around the initial motion vector (e.g., MV (502)) of the current CU (e.g., current block (501)) within a search range (e.g., a [−8, +8] pixel search range) (540). For example, a TM cost corresponding to the MV candidate (e.g., the difference between the MV candidate and the MV (502) is within the search range (540)) is determined based on each pair of templates. For example, the template pair includes a current template (521) and a reference template associated with the MV candidate. If the MV candidate is the MV (502), the reference template is the reference template (525). In one example, the TM cost corresponding to the MV candidate is determined based on the sum of absolute differences (SAD) between the current template (521) and the reference template. Other functions, such as the sum of squared errors (SSE), variance, and partial SAD, can also be used to determine the TM cost. The TM cost can indicate a match between the current template (521) and the reference template. In one example, a final MV is determined based on the TM cost. For example, the final MV is determined as the MV candidate that corresponds to the lowest TM cost.

[0081] In one example, the template matching is modified as follows: The search step size is determined by the AMVR mode, and the TM can be cascaded with the bilateral matching process.

[0082] An example of adaptive reordering of merge candidates using template matching (ARMC-TM) is described below. Merge candidates can be adaptively reordered using template matching (TM). The reordering method can be applied to normal merge mode, TM merge mode, and affine merge mode (except for SbTMVP candidates). In one example, for TM merge mode, merge candidates are reordered before the refinement process.

[0083] In one example, an initial merge candidate list is first constructed according to a given check order, such as spatial merge candidate(s), TMVP, non-adjacent merge candidate(s), HMVP, pairwise merge candidate(s), and virtual merge candidate(s). Then, the candidates in the initial list (e.g., the initial merge candidate list) are divided into subgroups (e.g., multiple subgroups). In one example, in the case of a TM merge mode or an adaptive DMVR mode, each merge candidate in the initial list is first refined by using a TM / multi-pass DMVR, such as TM and / or multi-pass DMVR. The merge candidates in each subgroup can be sorted to generate a sorted merge candidate list, and the sorting can be according to a cost value based on template matching (e.g., TM cost). The index of the selected merge candidate in the sorted merge candidate list is signaled to the decoder. In one example, for simplicity, merge candidates in the last subgroup but not the first subgroup are not sorted. In one example, all zero candidates from the ARMC sorting process are excluded during construction of the merge motion vector candidate list. The subgroup size may be set to 5 for normal merge mode and TM merge mode. The subgroup size may be set to 3 for affine merge mode.

[0084] The template matching cost (TM cost) of a merge candidate during the reordering process may be measured by the SAD between the samples of the template (e.g., current template) of the current block and the corresponding reference samples. The template (e.g., current template) may include a set of reconstructed samples near the current block. The template's reference samples are identified by the motion information of the merge candidate.

[0085] FIG. 5B illustrates a template and a reference sample of the template in a reference picture according to one embodiment of the present disclosure. When a merge candidate utilizes bidirectional prediction, the reference sample of the template of the merge candidate may be generated by bidirectional prediction as shown in FIG. 5B. For example, if a merge candidate includes two MVs pointing to reference templates in two reference pictures, the TM cost can be determined as shown in FIG. 5B. Referring to FIG. 5B, a merge candidate in the merge candidate list includes two MVs, such as MV (504) pointing to a reference block (507) in the reference picture (512) and MV (506) pointing to a reference block (508) in the reference picture (513). The reference template (531) is associated with the reference block (507) in the reference picture (512). The reference template (532) is associated with the reference block (508) in the reference picture (513). The reference templates (531)-(532) may have the same shape and size as the current template (521). The TM cost can be determined based on the current template (521) and the reference templates (531)-(532). In one example, the predictor template of the merge candidate is determined based on the reference templates (531)-(532), e.g., the predictor template is an average (e.g., a weighted average) of the reference templates (531)-(532). The TM cost can be determined based on the current template (521) and the predictor template.

[0086] For a subblock-based merging candidate with a subblock size equal to W×H, the top template includes multiple subtemplates with a size of W×M (e.g., W×1), and the left template includes multiple subtemplates with a size of M×H (e.g., 1×H), where M and M are positive integers. As shown in FIG. 6, motion information of subblocks in the first row (e.g., A-D) and first column (e.g., A, E, F, and G) of the current block (601) is used to derive reference samples for each subtemplate.

[0087] If the merge candidate is a sub-block-based merge candidate, a reference template can be determined as shown in FIG. 6. FIG. 6 illustrates a current template (602) for a current block (601) in a current picture (611) and a reference template (603) in a reference picture (612) corresponding to the current template (602) according to one embodiment of the present disclosure. The current block (601) has sub-block-based motion information, and the reference template (603) can be determined based on the motion information indicated by the arrows associated with each of the sub-blocks A to G of the current block (601). Each of the sub-blocks A to G has a size of W×H. In one example, the current template (602) includes a top template (605) and a left template (606). The top template (605) can include sub-templates (e.g., the four sub-templates in FIG. 6) having a size of W×M1 (e.g., W×1). The left template (606) can include sub-templates (e.g., the four sub-templates in FIG. 6) with a size of M2×Hsub (e.g., 1×Hsub). Motion information, indicated by arrows, associated with sub-blocks A-G in the first row and first column of the current block (601) can be used to derive sub-templates (or reference sub-block templates) (631-638) in the reference template (603).

[0088] The motion information of each sub-block A-G in the current block (601) (indicated by the arrows associated with A-G) can point to reference sub-blocks AA-GG in the reference picture (612). The reference template (603) can include multiple reference sub-block templates (631)-(638) associated with the reference sub-blocks AA-GG. For example, the reference sub-block templates (631)-(634) are located above the reference sub-blocks AA-DD, and the reference sub-block templates (635)-(638) are located to the left of the reference sub-blocks AA and EE-GG. The reference template (603) can include an above reference template (622) and a left reference template (623). The above reference template (622) can include the reference sub-block templates (631)-(634). The left reference template (623) can include the reference sub-block templates (635)-(638). For subblock-based merging candidates with a subblock size equal to W×H, the top template (e.g., top reference template (622)) can include multiple subtemplates with a size of W×M, and the left template (e.g., left reference template (623)) can include multiple subtemplates with a size of M×H. In one example, M is 1. In one example, M is 1.

[0089] The samples in the reference template (603) may also be referred to as reference samples for the current template (602). In one example, the samples in the reference template (603) have already been reconstructed.

[0090] In one example, the reference sub-blocks AA-GG may be determined as follows: A co-located block (613) in the reference picture (612) may be determined based on the current block (601). The collocated sub-blocks A'-G' in the collocated block (613) may correspond to sub-blocks A-G, respectively, as shown in Figure 6. The reference sub-blocks AA-GG may be determined based on the co-located sub-blocks A'-G' and motion information (indicated by the arrows associated with A'-G') of each sub-block A-G in the current block (601).

[0091] In the reordering process, if the cost difference between a candidate and its predecessor is less than a lambda value (e.g., λ), for example, D1-D2<λ, the candidate may be considered redundant, where D1 and D2 are the costs obtained during the first ARMC reordering, and λ is the Lagrangian parameter used in the RD criterion at the encoder side. In one example, the algorithm is defined as follows: · Determine the minimum cost difference between a candidate and its predecessor among all candidates in the list. If the minimum cost difference is greater than or equal to λ (e.g., minimum cost difference ≥ λ), the list is considered diverse (e.g., sufficiently diverse) and sorting stops. If this minimum cost difference is less than λ (e.g., minimum cost difference < λ), the candidate is deemed redundant and is moved to a further position in the list. This further position is the first position where the candidate is sufficiently diverse compared to its predecessors. The algorithm stops after a finite number of iterations (if the minimum cost difference is not smaller than λ, e.g., minimum cost difference ≥ λ).

[0092] This algorithm can be applied to normal, TM, BM, and affine merge modes. Similar algorithms can be applied to merge MMVD and code MVD prediction methods, which also use ARMC for reordering.

[0093] The value of λ in the above algorithm can be set to the λ of the rate-distortion criterion used to select the best merging candidate at the encoder side in the case of a low-delay configuration, or to a value λ corresponding to another QP in the case of a random access configuration. A set of λ values ​​corresponding to each signaled QP offset can be given in the sequence parameter set (SPS) or in the slice header for QP offsets not present in the SPS.

[0094] The ARMC design is also applicable to AMVP modes in which AMVP candidates are sorted according to TM cost, such as the TM cost associated with each AMVP candidate. For template matching for advanced motion vector prediction (TM-AMVP) modes, an initial AMVP candidate list is constructed, followed by refinement from the TM to construct a refined AMVP candidate list. Additionally, MVP candidates with TM costs greater than a threshold equal to five times the cost of the first MVP candidate may be skipped.

[0095] In one example, if wrap-around motion compensation is enabled, the MV candidates are clipped to take into account the wrap-around offset.

[0096] The TM-based reordering for MMVD and affine MMVD modes is described as follows. The MMVD offset can be extended for MMVD and affine MMVD modes. FIG. 7 illustrates an example of additional refinement positions along the k×π / 8 diagonal angle according to one embodiment of the present disclosure. In the example illustrated in FIG. 7, directions can point from position (701) to another position indicated by a circle, e.g., directions (721) through (724) point from position (701) to positions (711) through (714), respectively. In one example, the number of directions is increased from four directions (721) through (724) to 16 directions indicated by circles. In one example, directions (721) through (724) correspond to angles of 0, π / 2, π, and 3π / 2, and the 16 directions correspond to angles from 0 through 15π / 8 with an increment of π / 8 between adjacent directions.

[0097] Furthermore, possible MMVD refinement positions (e.g., 16x6 MMVD refinement positions) for each base candidate (e.g., all possible MMVD refinement positions (16x6) for each base candidate) can be sorted based on the SAD cost between the template (e.g., a current template including one row above and one column to the left of the current block) and the reference template for each refinement position. The reference template may be referred to as a reference template. In one example, the 16x6 MMVD refinement positions include a combination of 16 MMVD directions and six MMVD magnitudes (also referred to as MMVD offsets) shown in FIG. 7. Each of the MMVD refinement positions indicates a respective MMVD candidate.

[0098] Furthermore, the top 1 / 8 refinement positions (e.g., 16 × 6 / 8 = 12 refinement positions) with the smallest template SAD cost may be retained as available positions and thus may be used for MMVD index coding. The MMVD index may be binarized by a Rice code with a parameter equal to 2. The MMVD index may indicate which MMVD or MMVD refinement position within the top 1 / 8 refinement positions is selected.

[0099] The affine MMVD sorting can be extended to add additional refinement positions along the k × π / 4 diagonal. After sorting, the top ½ refinement positions with the smallest template SAD costs can be retained. Referring to Figure 7, the four directions (721) to (724) can be extended to eight directions represented by circles (711) to (718) in the affine MMVD sorting. In one example, the eight directions represented by circles (711) to (718) correspond to angles from 0 to 7π / 4, with an increment of π / 4 between adjacent directions. For example, the angle between direction (721) and direction (725) is 2π / 8.

[0100] The first L motion candidates in the candidate list before reordering are used as base candidates for the MMVD mode and the affine MMVD mode. In one example, L is equal to 3 for the MMVD mode, and L is one of [1, 3] for the affine MMVD mode depending on the neighboring block affine flag. Depending on whether the offsets of other reference picture lists are mirrored or directly set to zero, two methods of adding MMVD offsets may be allowed, including "double-sided" and "single-sided." Which method is applied to a block depends on the TM cost.

[0101] In an IBC mode such as shown in FIG. 4A or 4B, a BV may indicate a reference block of a current block to be coded. The reference block and the current block may be in the current picture. The BV may be coded using any appropriate method. In one aspect, the BV may be coded using a BV predictor (BVP) and a BV differential (BVD). In one example, the BV is a sum (vector sum) of the BVP and the BVD. The BVD may be coded using any appropriate method. In one example, the BVD is determined (e.g., selected) from a list of BVD candidates. In one example, the BVD candidates in the list of BVD candidates are predefined. In one example, the BVD candidates are determined based on an initial BVD candidate, such as in an IBC merge mode with block vector differential (MBVD) described below (referred to as IBC-MBVD mode).

[0102] In an example of the IBC-MBVD mode, the BVD may be referred to as an MBVD, and the BVD candidate may be referred to as an MBVD candidate. An MBVD or MBVD candidate may be a vector indicated by an MBVD amplitude or MBVD magnitude (also referred to as an offset or MBVD offset) and a direction (also referred to as an MBVD direction). A BV candidate may be a sum (e.g., a vector sum) of a BVP candidate and an MBVD candidate.

[0103] The BV may be coded using a BVP and an MBVD. The MBVD may be determined (e.g., selected) from MBVD candidates in an MBVD list or an MBVD candidate list (e.g., an IBC-MBVD list or an IBC-MBVD candidate list). The IBC-MBVD list may be determined using any suitable method. In one example, the IBC-MBVD list is determined based on a set of offsets (also referred to as a distance set) and a set of directions (e.g., the multiple directions shown in FIG. 7).

[0104] The term "template matching" or "TM" may refer to TM or variations thereof as described above, such as in Figures 5A, 5B, 6, and 7.

[0105] The IBC-MBVD list can be derived from sample positions along the MBVD direction. Referring to FIG. 8, the MBVD direction includes the directions (721) through (724) described in FIG. 7. The sample positions include positions indicated by an "x." Each position indicated by an "x" can indicate a BVD candidate (e.g., an MBVD candidate). Referring to FIG. 8, the MBVD candidate (812) associated with position 40 (40 pixels or 40 samples) along the direction (721) has an amplitude of 40 pixels and a direction along the direction (721). The MBVD candidate (812) can indicate that the BV candidate (813) is shifted from the BVP (811) by a 40-pixel offset along the direction (721). For example, the BV candidate (813) is the vector sum of the BVP (811) and the MBVD candidate (812). In FIG. 8, BVP (811) is indicated by position (801), for example, BVP (811) points to position (801).

[0106] The MBVD candidate search can begin by checking the template cost (also referred to as TM cost, such as template SAD cost) of offsets (e.g., including an offset of 40 pixels) added to the BVP (811) along each direction at intervals of M pixels. M can be a positive integer, such as 8. The search process iterates around the K candidates with the lowest TM cost in half intervals (e.g., M / 2). K is a positive integer, e.g., 8. The MBVD list (or IBC-MBVD list) can be derived when the interval reaches 1 pixel, and the K candidates with the lowest TM cost are included in a final list (e.g., a final IBC-MBVD list).

[0107] An adaptive BVD offset along the MBVD direction may be allowed. In one example, an MBVD list (or an IBC-MBVD list) of K candidates (e.g., K MBVD candidates) with the lowest TM cost (e.g., template SAD cost) is derived in the following steps as shown in FIG. Step 1. Let the maximum offset be N pixels, e.g., N=128, and the number of directions is N D , e.g., N D = 4 (e.g., left, right, top, and bottom indicated by (721), (723), (722), and (724) in Figures 7-8), the starting search interval is M pixels, e.g., M=8, and the number of candidates in the MBVD list is K, e.g., K=8. Step 2. Along each direction, check the TM cost (e.g., TM SAD cost calculated using SAD) for every Mth position offset not exceeding N, as shown in FIG. 8. The K lowest TM cost (TM SAD cost) candidates are kept in a list. Referring to FIG. 8, the eight candidates (e.g., the eight MBVD candidates marked with circles) associated with positions (or offsets) 32, 40, and 48 along direction (721), positions −8 and −48 along direction (722), position −56 along direction (723), and positions 8 and 16 along direction (724) have the lowest TM cost among the MBVD candidates. Step 3. For each candidate in the list, check the TM costs (e.g., TM SAD costs) of two candidates with an offset equal to + / -M / 2 (+M / 2 and -M / 2) along the direction. For example, M / 2 is 4, and the offsets are +4 and -4. The two candidates include a first candidate corresponding to +4 and a second candidate corresponding to -4. For the candidate corresponding to position 32 along the direction (721), the first candidate corresponds to an offset of +4, and therefore corresponds to position (32+4) or 36 along the direction (721), and the second candidate corresponds to an offset of -4, and therefore corresponds to position (32-4) or 28 along the direction (721) (FIG. 8). The K lowest TM SAD cost candidates are retained in the list. In step 3 of FIG. 8, the eight candidates indicated by circles (the updated eight candidates) are retained in the list. The eight candidates include MBVD candidates corresponding to positions 28, 32, and 36 along direction (721), positions −4, −8, and −12 along direction (722), and positions 4 and 8 along direction (724). Step 4. Repeat step 3, halving the previous spacing until the spacing reaches 1 pixel.

[0108] In one example, M is 8 and K is 8. Referring to step 1 of FIG. 8 , MBVD candidates (also referred to as initial MBVD candidates because the MBVD candidates in step 1 are obtained before updating the MBVD candidates) associated with positions indicated by "x" along each of the MBVD directions (721)-(724) have amplitudes of 8 pixels, 16 pixels, 24 pixels, 32 pixels, 40 pixels, 48 ​​pixels, 56 pixels, 64 pixels, ..., N pixels along each of the directions (721)-(724). N can be a positive integer, such as 128 or 256. N can be predefined. In some examples, N is less than 128, such as 16, 32, or 64. A first set of offsets (also referred to as a first distance set) can include {8 pixels, 16 pixels, 24 pixels, 32 pixels, 40 pixels, 48 ​​pixels, 56 pixels, 64 pixels, ..., N pixels}. Each offset in the first distance set may be an MBVD amplitude of the initial MBVD candidate. The initial MBVD candidate may have any suitable direction. In one example, the initial MBVD candidate has a direction that is one of directions 721 through 724 as shown in FIG. 8.

[0109] In one aspect, the initial MBVD candidates are a set of offsets {O1, O2, O3, ..., O J1} (e.g., a first distance set) and a set of directions {D1, D2, D3, ..., D J2} (e.g., directions (721) to (724), multiple directions in the directions shown in FIG. 7). Each of the initial MBVD candidates can be obtained based on a set of offsets {O1, O2, O3, ..., O J1} and the amplitudes from directions {D1,D2,D3,…,D J2} and the number of initial MBVD candidates is J1 × J2 in one example.

[0110] In step 2, the TM cost of each initial MBVD candidate is determined. The TM cost of the initial MBVD candidate can be determined based on the current template and the reference template of the current block. In one example, the candidate reference block is indicated by a BV candidate (e.g., the sum of the BVP (811) and the initial MBVD candidate). The reference template can include neighboring samples of the candidate reference block, such as one row above the candidate reference block and one row to the left of the candidate reference block. K (e.g., eight) MBVD candidates associated with the lowest TM cost are kept in a list. Referring to Figure 8, eight MBVD candidates are indicated by circles (e.g., positions 32, 40, and 48 along direction (721), positions -8 and -48 along direction (722), position -56 along direction (723), and positions 8 and 16 along direction (724)).

[0111] In step 3, an updated MBVD candidate search (e.g., a refined search of updated MBVD candidates) is performed around the MBVD candidates in the list (e.g., obtained in step 2). In one example, the interval (or search interval) is reduced by half, thus becoming 4. For each MBVD candidate in the list (e.g., obtained in step 2), the TM costs of two candidates with an offset equal to + / -M / 2 (+4 and -4) along the direction of the respective MBVD candidate are obtained as described above. Referring to step 3 of FIG. 8 , the TM costs obtained from steps 2 and 3 correspond to positions marked with "x"s and circles, including positions 28, 32, 36, 40, 44, 48, and 52 along direction (721), positions −4, −8, −12, −44, −48, and −52 along direction (722), positions −52, −56, and −60 along direction (723), and positions 4, 8, 12, 16, and 20 along direction (724). In one example, updated MBVD candidates (e.g., eight updated MBVD candidates) are determined based on the TM costs obtained from steps 2 and 3. Referring to FIG. 8 , the eight updated MBVD candidates correspond to positions 28, 32, and 36 along direction (721), positions −4, −8, and −12 along direction (722), and positions 4 and 8 along direction (724).

[0112] In one example, step 3 is repeated at intervals of 2, then at intervals of 1, respectively. In one example, eight final MBVD candidates are selected based on TM cost. In one example, an index (e.g., MBVD index) is signaled to indicate which of the eight final MBVD candidates is selected as the MBVD to be used with the BVP to determine the BV.

[0113] In one example, the number of MBVD candidates and MBVD index signaling is the same as in ECM-7.0.

[0114] In some examples, such as the example described above in step 1 of FIG. 8, the MBVD offsets of each initial MBVD candidate are equally spaced every Mth position (e.g., every 8th position) along each MBVD direction. The spacing may indicate the difference between pairs of adjacent offsets in the set of offsets. For example, the spacing refers to the number of samples or pixels between two adjacent offsets, such as an 8-sample spacing between offsets 40 and 48 samples along direction (721). In this disclosure, the terms "spacing" and "spacing size" may be used interchangeably. Equal spacing between pairs of adjacent offsets is used in the first distance set of FIG. 8.

[0115] In one example, the interval is M pixels (e.g., 8 pixels), as shown in FIG. 9. FIG. 9 shows an example of a constant offset every Mth position in MBVD list construction using a TM. In FIG. 9, the set of offsets for position (901) includes {M, 2M, 3M, 4M, 5M, ...}, corresponding to offsets (902) to (906), etc. The interval size between two adjacent offsets is M. The parameter M can be predefined and is therefore a constant. Therefore, offsets (902) to (906) can be considered to be constant. The offsets (902) to (906) for position (901) are equally spaced every Mth position along the MBVD direction (911). In FIG. 9, BVP (921) is indicated by position (901), for example, BVP (921) points to position (901). A BV candidate (913) can be the vector sum of a BVP (921) and an MBVD candidate (e.g., (912)). The MBVD candidate (912) has an amplitude offset (902) (e.g., M) along a direction (911). The MBVD direction (911) can represent any of the directions shown in Figure 7.

[0116] The term "MBVD" may refer to MBVD or variations thereof as described above, such as in Figures 8-9. In one example, the term "MBVD" is referred to as IBC-MBVD.

[0117] As described above in FIGS. 8-9 , the spacing size or interval between two adjacent offsets is a constant denoted by M (e.g., 8). When M is 8, the set of offsets may be a first distance set. In one example, first spacings between a first pair of adjacent offsets in the set of offsets are not identical, and second spacings between a second pair of adjacent offsets in the set of offsets are identical. In one example, the second distance set includes {1 pixel, 2 pixels, 4 pixels, 8 pixels, 12 pixels, 16 pixels, 24 pixels, 32 pixels, 40 pixels, 48 ​​pixels, 56 pixels, 64 pixels, 72 pixels, 80 pixels, 88 pixels, 96 pixels, 104 pixels, 112 pixels, 120 pixels, 128 pixels}. The first spacings between pairs of adjacent offsets in {1 pixel, 2 pixels, 4 pixels} include 1 pixel and 2 pixels and are therefore not identical. The second spacing between pairs of adjacent offsets in {16 pixels, 24 pixels, 32 pixels} contains 8 pixels and 8 pixels and is therefore identical.

[0118] In various examples, the difference between the BVP and the BV is relatively small, and therefore the BVD is relatively small (e.g., close to 0). Therefore, the probability of having a BVD with a larger offset may be smaller than the probability of having a BVD with a smaller offset. Therefore, in some examples, such as ECM, the MBVD list reconstruction described above using initial MBVD candidates as shown in FIGS. 8-9 may not be optimal for obtaining applicable candidates in the MBVD list. For example, in both the first distance set and the second distance set, the spacing between pairs of adjacent offsets may be the same (e.g., multiple spacings of 8 pixels), and therefore may not be optimal for obtaining applicable candidates in the MBVD list.

[0119] According to one aspect of the present disclosure, a set of offsets {O1, O2, O3, ..., O J1} the spacing (or spacing size) between pairs of adjacent offsets in {I1,I2,…,I J1} can be different. Interval I i O i -Oi-1 For example, I2 = O2 - O1. In one example, the set of offsets {O1, O2, O3, ..., O J1} is relative to a position (or reference position) with offset 0. Interval I1 can be the interval between offset O1 and 0, such as I1=O1. J1 is a positive integer. In one example, J1 is predefined. The offsets (e.g., BVD offsets or MBVD offsets) in the set of offsets can be arranged in a certain order (e.g., ascending or descending order). Each interval size is different from other interval sizes corresponding to other adjacent pairs in the set of offsets. An initial MBVD candidate is a set of offsets {O1, O2, O3, ..., O J1} and a set of MBVD directions. In one example, a BVD (e.g., MBVD) is determined from initial MBVD candidates. In one aspect, a TM process may be used to update the initial MBVD candidates and determine final MBVD candidates in an MBVD list (e.g., IBC-MBVD list). A BVD or MBVD may be selected from the final MBVD candidates. In one example, the TM process may be performed iteratively as shown in FIG. 8.

[0120] FIG. 10 illustrates a set of offsets (e.g., BVD offsets or MBVD offsets) {O1, O2, O3, ..., O J1 10 shows an example of offsets O1, O2, O3, ..., O J1 The set of MBVD candidates (1012) is relative to a position (1001) along a direction (1011) (e.g., the offset of position (1001) is 0). An MBVD candidate (1012) is determined based on the offset O4 and the direction (1011), and the MBVD candidate (1012) has a magnitude of the offset O4 and a direction of the direction (1011). A BVP (1021) can be indicated by the position (1001), e.g., BVP (1021) points to the position (1001). A BV candidate (1013) can be the vector sum of the BVP (1021) and the MBVD candidate (1012). The MBVD direction (1011) can represent any appropriate direction, such as one of the directions shown in FIG. 7.

[0121] Interval Size or Interval I i is the BVD offset {O1,O2,O3,…,O J1} adjacent pairs (e.g., O i-1 and O i ) can represent the difference between the intervals I and J. The parameter i can be 1, 2, ..., or J1. i O i -O i-1 For example, I2 = O2 - O1. I1 is the difference between O1 and the reference position (e.g., offset 0), which is position (1001). I1 can be the interval between offset O1 and 0, such as I1 = O1. Figure 10 shows the interval size or interval {I1, I2, ..., I J1 Each of the interval sizes may be different from other interval sizes corresponding to other adjacent pairs of offsets in the set, e.g., I i is I1,I2,…,I i-1 ,I i+1 ,…,I J1 For example, I1 is different from I2~I J1 is different.

[0122] Interval size or interval {I1,I2,…,I J1} may also be referred to as an initial interval size or initial interval, for example, because the initial interval size indicates the BVD offset used to determine the initial BVD candidate (e.g., the MBVD candidate obtained in step 1 in FIG. 8) that is used to determine the BVD candidate (e.g., the MBVD candidate) in the BVD list. In one aspect, the intervals or initial intervals {I1, I2, ..., I J1} is the starting point for building a BVD list using, for example, template matching.

[0123] A BVD list (e.g., an MBVD list or an IBC-MBVD list) including BVD candidates (e.g., MBVD candidates) may be determined (e.g., constructed) based at least on the BVD offsets from the BVP. A BVD may be determined from the BVD candidates in the BVD list, and the current block may be reconstructed using the determined BVD. According to one aspect of the present disclosure, for each adjacent pair of BVD offsets, an initial interval size indicates the difference between the adjacent pair of BVD offsets, and each initial interval size is different from other initial interval sizes corresponding to other adjacent pairs of BVD offsets. Different initial interval sizes may be used to construct the MBVD list with or without template matching.

[0124] A non-constant initial interval size (also referred to as non-constant interval size) can be used for each interval as a starting point for MBVD list construction by using template matching. The search step described in FIG. 8 and elsewhere can be applied to non-constant size intervals (or non-constant interval sizes). A non-constant interval size is defined as the interval size {I1, I2, ..., I} between each pair of adjacent offsets (or BVD offsets, MBVD offsets) as shown in FIG. 10. J1 It can be shown that} can be different.

[0125] In one example, the interval sizes (or initial interval sizes) are arranged in ascending order. The initial interval sizes may be powers of 2. In one example, the initial interval sizes include J interval sizes. Each of the initial interval sizes (e.g., I i ) is 2 i-1 where i is an integer ranging from 1 to J1, where J1 is greater than 1.

[0126] In one embodiment, the initial interval size is a power of 2 function. For example, initial interval sizes of 1, 2, 4, 8, 16, 32, and 64 are used in each direction. For example, interval sizes I1, I2, I3, I4, I5, I6, and I7 are 1, 2, 4, 8, 16, 32, and 64, respectively. With reference to FIGS. 10-11, interval sizes I1, I2, I3, I4, and I5 are 1, 2, 4, 8, and 16, respectively. The positions (1001) and directions (1011) in FIG. 11 are described in FIG. 10.

[0127] In this disclosure, high-level syntax may refer to syntax in any of a video parameter set (VPS), SPS, picture parameter set (PPS), adaptive parameter set (APS), slice header, picture header, tile header, CTU header, etc. In one example, high-level syntax refers to syntax at a higher level than a block or CU.

[0128] In one aspect, the initial interval sizes are stored in a lookup table. In one example, one of the initial interval sizes is not a power of two.

[0129] In one aspect, the initial interval size of each interval is derived by using a lookup table. Each initial interval size is stored in an associated element of the lookup table and can be looked up in the lookup table by using an interval index. In one example, the interval index is the MBVD index described above. This table (e.g., lookup table) can be a predefined table or can be signaled in a high-level syntax, such as the syntax in the VPS, SPS, PPS, APS, etc. described in this disclosure.

[0130] FIG. 12 shows an example of initial interval sizes stored in a lookup table (1201) according to one embodiment of the present disclosure. Initial intervals I2, I3, I4, I5, I6, etc. are intervals with offsets O1 to O6, etc. Initial interval I1 is O1. The positions (1001) and directions (1011) in FIG. 12 are shown in FIG. 10. Referring to FIG. 12, initial intervals I1, I2, I3, I4, I5, and I6 are 1, 2, 4, 8, 16, and 17, respectively. One of the initial interval sizes, I6, is not a power of two; for example, I6=17. Initial intervals I1, I2, I3, I4, I5, I6, etc. can be stored in the lookup table (1201). The initial interval sizes can be searched for in the lookup table (1201) using an interval index (1202).

[0131] In one aspect, the BVD list may be determined as follows: Initial BVD candidates may be determined based on (i) the BVD offset and (ii) the BVD direction. The BVD offset may be determined based on a set of offsets {O1, O2, O3, ..., O4} as illustrated in Figures 10-12. J1}. The BVD directions may include any suitable directions, such as the directions in FIG. 7. In one example, the BVD directions include directions (721) through (724). The BVD directions may include any suitable number of directions, such as four directions, eight directions, etc. Each of the initial BVD candidates may have one of the BVD offsets and a corresponding one of the BVD directions, as described in step 1 of FIG. 8 and in FIG. 13.

[0132] FIG. 13 illustrates the BVD offsets {O1, O2, O3, ..., O J113 shows an example of a BVD direction. The BVD offsets can include O1, O2, O3, O4, etc. The BVD offsets O1, O2, O3, O4, etc. can be relative to position (1001) as described in FIG. 10. Position (1001) can indicate BVP (1021) as described in FIG. 10. Initial intervals I2, I3, I4, etc. can be between adjacent offsets (e.g., O1, O2, O3, O4, etc.) in the BVD offsets. The initial interval I1 can be O1. The initial intervals I1, I2, I3, I4, etc. can be different. In one example, each of the initial intervals I1, I2, I3, I4, etc. is different from the other initial intervals. In the example of FIG. 13, the BVD directions include directions (721) to (724). Initial BVD candidates (indicated by "x") are obtained based on the BVD offsets and the BVD directions. For example, the initial BVD candidate (1301) has a magnitude of offset O4 and a direction of direction (721).

[0133] A TM cost associated with each initial BVD candidate among the initial BVD candidates may be determined. The TM cost may be between the current template of the current block and each reference template of the candidate reference block. In one example, the initial BVD candidates are determined based on the BVP(1021) and each initial BVD candidate (e.g., the initial BV candidate (e.g., (1313)) is the sum of the BVP(1021) and each initial BVD candidate (e.g., (1301))), and the candidate reference block is indicated by the initial BV candidate (e.g., the initial BV candidate point from the current block to the candidate reference block). The BVD list may be determined based on the TM cost. In one example, the BVD list is iteratively determined based on the TM cost as described in steps 2 to 4 of FIG. 8.

[0134] In one example, K (e.g., 8 or any suitable positive number) initial BVD candidates (e.g., indicated by circles) are selected from the initial BVD candidates as BVD candidates in the BVD list. The K initial BVD candidates correspond to the lowest TM costs among the TM costs, as described in step 2 in FIG. 8.

[0135] In one example, K initial BVD candidates (e.g., indicated by circles) are selected from the initial BVD candidates, where the K initial BVD candidates correspond to the lowest TM costs among the TM costs. For each of the K initial BVD candidates (e.g., initial BVD candidate (1302)) having a respective BVD offset and BVD direction, if the BVD offset (e.g., offset O3) is the only BVD offset that is greater than the first BVD offset (e.g., offset O2) and less than the second BVD offset (e.g., offset O4) among the K initial BVD candidates, a first candidate (e.g., (1303)) and a second candidate (e.g., (1304)) associated with each initial BVD candidate (e.g., initial BVD candidate (1302) having offset O3) among the K initial BVD candidates are determined. The first candidate and the second candidate may have the same BVD direction (e.g., direction (721)) as the initial BVD candidate (e.g., initial BVD candidate (1302)), the BVD offset of the first candidate may be the average of the BVD offset (e.g., offset O3) and the first BVD offset (e.g., offset O2), and the BVD offset of the second candidate may be the average of the BVD offset (e.g., offset O3) and the second BVD offset (e.g., offset O4). New TM costs associated with the first candidate and the second candidate corresponding to each initial BVD candidate among the K initial BVD candidates may be determined, respectively. The BVD list may be determined based on updated TM costs including (i) the lowest TM cost among the TM costs corresponding to the K initial BVD candidates and (ii) the new TM cost. The updated BVD candidates in the BVD list may include K candidate(s) (corresponding to the lowest new TM cost) among the K initial BVD candidates and / or candidate(s) among the first and second candidates.

[0136] 14 shows a flowchart outlining a process (1400) according to one embodiment of the present disclosure. The process (1400) may be used in a video decoder. In various embodiments, the process (1400) is performed by a processing circuit, such as a processing circuit that performs the functions of the video decoder (110), a processing circuit that performs the functions of the video decoder (210), or the like. In some embodiments, the process (1400) is implemented with software instructions, and thus, the processing circuit performs the process (1400) when it executes the software instructions. The process starts at (S1401) and proceeds to (S1410).

[0137] At (S1410), a coded video bitstream including coded information of a current block in a current picture is received. The current block can be predicted based on a reference block in the current picture indicated by a block vector (BV). The BV should be determined based on a BV predictor (BVP) and a BV difference (BVD), which is the difference between the BV and the BVP. In one example, the current block is predicted using an IBC mode. In one example, the current block is predicted using an IntraTMP mode.

[0138] At (S1420), a BVD list including BVD candidates may be determined based at least on the BVD offset from the BVP, as described in FIG.

[0139] In one embodiment, for each adjacent pair of BVD offsets, an initial interval size indicates the difference between the adjacent pair of BVD offsets, and each initial interval size is different from other initial interval sizes corresponding to other adjacent pairs of BVD offsets. Figures 10-12 illustrate examples of BVD offsets.

[0140] In one example, the initial interval sizes are arranged in ascending order.

[0141] In one example, the initial interval size is a power of 2, as shown in Figure 11. In one example, the initial interval size includes J sizes, each of which is a power of 2. i-1 where i is an integer ranging from 1 to J1, and J1 is greater than 1.

[0142] In one example, the initial interval sizes are stored in a lookup table such as that shown in FIG.

[0143] In one example, one of the initial interval sizes is not a power of two, as shown in FIG.

[0144] In one example, the initial BVD candidates are determined based on (i) a BVD offset and (ii) a BVD direction. Each of the initial BVD candidates may have one of the BVD offsets and a corresponding one of the BVD directions, as shown in FIG. 13. A TM cost associated with each initial BVD candidate among the initial BVD candidates between the current template of the current block and each reference template of the candidate reference block may be determined. The candidate reference block may be indicated by an initial BV candidate, which is the sum of the BVD candidate and each initial BVD candidate. The BVD list may be determined based on the TM cost.

[0145] In one example, K initial BVD candidates from the initial BVD candidates are selected as BVD candidates in the BVD list, where the K initial BVD candidates correspond to the lowest TM costs among the TM costs.

[0146] In one example, K initial BVD candidates are selected from the initial BVD candidates. The K initial BVD candidates correspond to the lowest TM cost among the TM costs. For each of the K initial BVD candidates having a respective BVD offset and BVD direction, when the BVD offset is the only BVD offset that is greater than the first BVD offset and less than the second BVD offset among the BVD offsets, a first candidate and a second candidate associated with each initial BVD candidate among the K initial BVD candidates can be determined, as illustrated in FIG. 13. The first candidate and the second candidate have the same BVD direction as the initial BVD candidate. The BVD offset of the first candidate is the average of the BVD offset and the first BVD offset, and the BVD offset of the second candidate is the average of the BVD offset and the second BVD offset. New TM costs associated with the first candidate and the second candidate, respectively, can be determined. The BVD list may be determined based on updated TM costs, including (i) the lowest TM cost among the TM costs corresponding to the K initial BVD candidates, and (ii) the new TM cost.

[0147] At (S1430), the BVD can be determined from the BVD candidates in the BVD list.

[0148] At (S1440), the current block can be reconstructed using the determined BVD.

[0149] In one example, a BVP is determined. The BV is determined as the sum of the BVP and the determined BVD. The determined BV can be used to reconstruct the current block.

[0150] The process then proceeds to (S1499) and ends.

[0151] The process 1400 may be adapted as appropriate. Steps of the process(es) 1400 may be modified and / or omitted. Additional step(s) may be added. Any suitable order of implementation may be used.

[0152] 15 shows a flowchart outlining a process (1500) according to one embodiment of the present disclosure. The process (1500) can be used in a video encoder. In various embodiments, the process (1500) is performed by a processing circuit, such as a processing circuit that performs the functions of the video encoder (103), a processing circuit that performs the functions of the video encoder (303), or the like. In some embodiments, the process (1500) is implemented with software instructions, and thus, the processing circuit performs the process (1500) when it executes the software instructions. The process starts at (S1501) and proceeds to (S1510).

[0153] At (S1510), a block vector (BV) difference (BVD) list including BVD candidates may be determined based at least on a BVD offset from a BV predictor (BVP) of a current block in a current picture, as described at (S1420) of FIG. 14. The current block may be coded based on a reference block in the current picture indicated by the BV to be determined based on the BVP and the BVD. The current block may be coded using IBC mode or IntraTMP mode.

[0154] For each adjacent pair of BVD offsets, an initial interval size indicates the difference between the adjacent pair of BVD offsets. Each initial interval size may be different from other initial interval sizes corresponding to other adjacent pairs of BVD offsets, as described in Figures 10-12.

[0155] At (S1520), the BVD can be determined from the BVD candidates in the BVD list.

[0156] In (S1530), the current block can be coded using the determined BVD.

[0157] The process then proceeds to (S1599) and ends.

[0158] The process 1500 may be adapted as appropriate. Steps of the process(es) 1500 may be modified and / or omitted. Additional step(s) may be added. Any suitable order of implementation may be used.

[0159] The techniques described above may be implemented as computer software using computer-readable instructions and physically stored on one or more computer-readable media. For example, Figure 16 illustrates a computer system (1600) suitable for implementing certain embodiments of the disclosed subject matter.

[0160] Computer software can be coded using any suitable machine code or computer language that can be subject to mechanisms such as assembly, compilation, linking, etc. to create code containing instructions that can be executed by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc. directly, or via interpretation, microcode execution, etc.

[0161] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smartphones, gaming devices, Internet of Things devices, and the like.

[0162] 16 for computer system (1600) are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing embodiments of the present disclosure, nor should the arrangement of components be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary embodiment of computer system (1600).

[0163] The computer system (1600) may include certain human interface input devices that can respond to input by one or more human users, for example, via tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), and olfactory input (not shown). The human interface devices may also be used to capture certain media that are not necessarily directly associated with conscious human input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, photographic images obtained from a still image camera), and video (e.g., two-dimensional video, three-dimensional video, including stereoscopic video).

[0164] The input human interface devices may include one or more (only one of each is shown) of a keyboard (1601), a mouse (1602), a trackpad (1603), a touchscreen (1610), a data glove (not shown), a joystick (1605), a microphone (1606), a scanner (1607), and a camera (1608).

[0165] The computer system (1600) may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the human user's senses, for example, through tactile output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touchscreen (1610), data gloves (not shown), or joystick (1605), although some haptic feedback devices may not function as input devices), audio output devices (such as speakers (1609), headphones (not shown)), visual output devices (such as screens (1610), including CRT screens, LCD screens, plasma screens, and OLED screens, each with or without touchscreen input capability and each with or without haptic feedback capability, some of which may be capable of outputting two-dimensional visual output or three-dimensional or higher-dimensional output via means such as stereographic output, virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0166] The computer system (1600) may also include human-accessible storage devices and their associated media, such as optical media including CD / DVD ROM / RW (1620) with media (1621) such as CDs / DVDs, thumb drives (1622), removable hard drives or solid state drives (1623), legacy magnetic media such as tape and floppy disks (not shown), and dedicated ROM / ASIC / PLD-based devices such as security dongles (not shown).

[0167] Those skilled in the art should also understand that the term "computer-readable medium" as used in connection with the subject matter of this disclosure does not encompass transmission media, carrier waves, or other transitory signals.

[0168] The computer system (1600) may also include an interface (1654) to one or more communication networks (1655). The network may be, for example, wireless, wireline, or optical. The network may further be local, wide-area, metropolitan, vehicular, industrial, real-time, delay-tolerant, or the like. Examples of networks include local area networks such as Ethernet; wireless LANs; cellular networks including GSM, 3G, 4G, 5G, LTE, and the like; TV wireline or wireless wide-area digital networks including cable TV, satellite TV, and terrestrial broadcast TV; and vehicular and industrial networks including CAN Bus. Certain networks generally require an external network interface adapter attached to a particular general-purpose data port or peripheral bus (1649) (e.g., a USB port on the computer system (1600)), while other networks are generally integrated into the core of the computer system (1600) by attaching to a system bus, as described below (e.g., an Ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks, the computer system (1600) can communicate with other entities. Such communication may be unidirectional, receive only (e.g., broadcast TV), unidirectional transmit only (e.g., CANbus to a particular CANbus device), or bidirectional, for example, to other computer systems using local or wide area digital networks. Specific protocols and protocol stacks may be used with each of these networks and network interfaces, as described above.

[0169] The above-mentioned human interface devices, human-accessible storage devices, and network interfaces may be attached to the core (1640) of the computer system (1600).

[0170] The core (1640) may include one or more central processing units (CPUs) (1641), graphics processing units (GPUs) (1642), dedicated programmable processing units in the form of field programmable gate arrays (FPGAs) (1643), hardware accelerators for specific tasks (1644), graphics adapters (1650), etc. These devices, along with read-only memory (ROM) (1645), random access memory (1646), and internal mass storage (1647) such as a non-user-accessible internal hard drive or SSD, may be connected via a system bus (1648). In some computer systems, the system bus (1648) may be accessible in the form of one or more physical plugs to allow expansion with additional CPUs, GPUs, etc. Peripheral devices may be attached directly to the core's system bus (1648) or via a peripheral bus (1649). In one example, a screen (1610) may be connected to the graphics adapter (1650). Peripheral bus architectures include PCI, USB, etc.

[0171] The CPU (1641), GPU (1642), FPGA (1643), and accelerator (1644) can execute specific instructions that, in combination, can constitute the above-mentioned computer code. The computer code can be stored in ROM (1645) or RAM (1646). Temporary data can also be stored in RAM (1646), and persistent data can be stored, for example, in internal mass storage (1647). Cache memory, which can be closely associated with one or more CPUs (1641), GPUs (1642), mass storage (1647), ROM (1645), RAM (1646), etc., can be used to enable fast storage and retrieval to any of the memory devices.

[0172] The computer-readable medium may bear computer code for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of the present disclosure, or they may be of the kind well known and available to those skilled in the computer software arts.

[0173] By way of example and not limitation, a computer system having the architecture (1600), and in particular the core (1640), can provide functionality as a result of processor(s) (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media can be user-accessible mass storage as introduced above, as well as media associated with specific storage of the core (1640) that is non-transitory in nature, such as core internal mass storage (1647) or ROM (1645). Software implementing various embodiments of the present disclosure can be stored on such devices and executed by the core (1640). The computer-readable media can include one or more memory devices or chips according to particular needs. The software can cause the core (1640), and in particular the processor (including CPU, GPU, FPGA, etc.) therein, to perform particular processes or particular portions of particular processes described herein, including defining data structures stored in RAM (1646) and modifying such data structures in accordance with the software-defined processes. Additionally, or alternatively, a computer system may provide functionality as a result of logic hardwired or otherwise embodied in circuitry (e.g., accelerator (1644)) that can operate in place of or in conjunction with software to perform particular processes or portions of particular processes described herein. References to software can encompass logic, and vice versa, where appropriate. References to computer-readable media can encompass, where appropriate, circuitry (such as an integrated circuit (IC)) that stores software for execution, circuitry that embodies logic for execution, or both. The present disclosure encompasses any appropriate combination of hardware and software.

[0174] The use of "at least one of" or "one of" in this disclosure is intended to include any one or combination of the listed elements. For example, reference to at least one of A, B, or C; at least one of A, B, and C; at least one of A, B, and / or C; and at least one of A through C is intended to include A only, B only, C only, or any combination thereof. Reference to one of A or B, and one of A and B is intended to include A or B or (A and B). The use of "one of" does not exclude any combination of the listed elements, when applicable, such as when the elements are not mutually exclusive.

[0175] While this disclosure has described several exemplary embodiments, there are alterations, permutations, and various substitute equivalents that fall within the scope of this disclosure. It should thus be understood that those skilled in the art will be able to devise numerous systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and are therefore within its spirit and scope. [Explanation of symbols]

[0176] 100 video processing system, 101 video source, 102 stream, 103 video encoder, 104 encoded video data, 105 streaming server, 106 client subsystem, 107 copy, 108 client subsystem, 109 copy, 110 video decoder, 111 video picture, 112 display, 113 capture subsystem, 120 electronic device, 130 electronic device, 201 channel, 210 video decoder, 212 rendering device, 215 buffer memory, 220 parser, 221 symbol, 230 electronic device, 231 receiver, 251 scaler / inverse transform unit, 252 intra-picture prediction unit, 253 motion compensation prediction unit, 255 aggregator, 256 loop filter unit, 257 reference picture memory, 258 current picture buffer, 301 video source, 303 video encoder, 320 electronic device, 330 Source coder, 332, coding engine, 333, decoder, 334, reference picture memory, 335, predictor, 340, transmitter, 343, video sequence, 345, entropy coder, 350, controller, 360, communication channel, 400, CTU, square, 401, current CU, 402, region, 403, region, 405, BV, 406, BV, 411, reference block, 412, reference block, 415, dotted region, 420, L-shaped template, 421, matching block, 430, current template, 431, current block, 501, current block, 502, MV, 503, reference block, 507, reference block, 508, reference block, 510, current picture, 511, reference picture, 512, reference picture, 513, reference picture, 521, current template, 522, top template, 523, left template, 525 Reference template, 526 Top template, 527 Left template, 531 Reference template, 532 Reference template, 540 Search range, 601 Current block, 602 Current template, 603 Reference template, 605 Top template, 606 Left template, 611 Current picture, 612 Reference picture, 613 Block, 622 Top reference template, 623Left reference template, 631-638 Reference subblock template, 701 Position, 711-718 Circle, 711-714 Position, 721-724 Direction, 725 Direction, 801 Position, 811 BVP, 812 MBVD candidate, 813 BV candidate, 901 Position, 902-906 Offset, 911 MBVD direction, 912 MBVD candidate, 913 BV candidate, 1001 Position, 1011 Direction, 1012 MBVD candidate, 1013 BV candidate, 1021 BVP, 1201 Lookup table, 1202 Interval index, 1301 Initial BVD candidate, 1302 Initial BVD candidate, 1303 First candidate, 1304 Second candidate, 1313 Initial BV candidate, 1400 Process, 1500 Process, 1600 computer system, 1601 keyboard, 1602 mouse, 1603 trackpad, 1605 joystick, 1606 microphone, 1607 scanner, 1608 camera, 1609 speaker, 1610 touchscreen, 1621 media, 1622 thumb drive, 1623 solid state drive, 1640 core, 1641 CPU, 1642 GPU, 1643 FPGA, 1644 accelerator, 1645 ROM, 1646 random access memory, 1647 internal mass storage, 1648 system bus, 1649 peripheral bus, 1650 graphics adapter, 1654 interface, 1655 communication network

Claims

1. 1. A method of video decoding, comprising: receiving a coded video bitstream comprising coded information of a current block in a current picture, the current block being predicted based on a reference block in the current picture indicated by a block vector (BV) as determined based on a BV predictor (BVP) and a BV difference (BVD), the difference between the BV and the BVP; determining a BVD list containing BVD candidates based at least on a BVD offset from the BVP; determining the BVD from the BVD candidates in the BVD list; and reconstructing the current block using the determined BVD; For each adjacent pair of the BVD offsets, an initial interval size indicating the difference between the adjacent pairs of the BVD offsets; A method wherein each of the initial interval sizes is different from other initial interval sizes corresponding to other adjacent pairs of the BVD offsets.

2. The method of claim 1 , wherein the initial interval sizes are arranged in ascending order.

3. The method of claim 1 , wherein the initial interval size is a power of two.

4. The initial interval sizes include J1 sizes, and each of the initial interval sizes is 2 ｉ－１ 4. The method of claim 3, wherein i is an integer ranging from 1 to J1, and J1 is greater than 1.

5. The method of claim 1 , wherein the initial interval size is stored in a lookup table.

6. The method of claim 5 , wherein one of the initial interval sizes is not a power of two.

7. The step of determining the BVD list comprises: determining initial BVD candidates based on (i) the BVD offsets and (ii) BVD directions, each of the initial BVD candidates having one of the BVD offsets and a corresponding one of the BVD directions; determining a template matching (TM) cost associated with each initial BVD candidate among the initial BVD candidates between a current template of the current block and a reference template of each of candidate reference blocks, the candidate reference blocks being indicated by an initial BVD candidate that is a sum of the BVD candidate and the respective initial BVD candidate; and determining the BVD list based on the TM cost.

8. The step of determining the BVD list based on the TM cost comprises:

8. The method of claim 7, comprising selecting K initial BVD candidates from the initial BVD candidates as the BVD candidates in the BVD list, wherein the K initial BVD candidates correspond to the lowest TM costs among the TM costs.

9. The step of determining the BVD list based on the TM cost comprises: selecting K initial BVD candidates from the initial BVD candidates, wherein the K initial BVD candidates correspond to the lowest TM costs among the TM costs; For each of the K initial BVD candidates with a respective BVD offset and BVD direction, if the BVD offset is the only BVD offset in the BVD offsets that is greater than a first BVD offset and less than a second BVD offset, determining a first candidate and a second candidate associated with each initial BVD candidate among the K initial BVD candidates, wherein the first candidate and the second candidate have the same BVD direction as the initial BVD candidate, the BVD offset of the first candidate is an average of the BVD offset and the first BVD offset, and the BVD offset of the second candidate is an average of the BVD offset and the second BVD offset; determining new TM costs associated with the first candidate and the second candidate, respectively; and determining the BVD list based on updated TM costs, the updated TM costs including: (i) the lowest TM cost among the TM costs corresponding to the K initial BVD candidates; and (ii) the new TM cost.

10. The method further includes determining the BVP; The step of reconstructing comprises: determining the BV as the sum of the BVP and the determined BVD; and reconstructing the current block using the determined BV.

11. 1. An apparatus for video decoding, comprising: A processing circuit, receiving a coded video bitstream comprising coded information of a current block in a current picture, the current block being predicted based on a reference block in the current picture indicated by a block vector (BV) as determined based on a BV predictor (BVP) and a BV difference (BVD), the difference between the BV and the BVP; determining a BVD list containing BVD candidates based at least on a BVD offset from the BVP; determining the BVD from the BVD candidates in the BVD list; and reconstructing the current block using the determined BVD; For each adjacent pair of the BVD offsets, an initial interval size indicating the difference between the adjacent pairs of the BVD offsets; Each of the initial interval sizes is different from other initial interval sizes corresponding to other adjacent pairs of the BVD offsets.

12. The apparatus of claim 11 , wherein the initial interval sizes are arranged in ascending order.

13. The apparatus of claim 11 , wherein the initial interval size is a power of two.

14. The initial interval sizes include J1 sizes, and each of the initial interval sizes is 2 ｉ－１ 14. The apparatus of claim 13, wherein i is an integer in the range of 1 to J1, and J1 is greater than 1.

15. The apparatus of claim 11 , wherein the initial interval size is stored in a lookup table.

16. The apparatus of claim 15 , wherein one of the initial interval sizes is not a power of two.

17. The processing circuitry determining initial BVD candidates based on (i) the BVD offsets and (ii) BVD directions, each of the initial BVD candidates having one of the BVD offsets and a corresponding one of the BVD directions; determining a template matching (TM) cost associated with each initial BVD candidate among the initial BVD candidates between a current template of the current block and a reference template of each of candidate reference blocks, the candidate reference blocks being indicated by an initial BVD candidate that is a sum of the BVD candidate and the respective initial BVD candidate; and determining the BVD list based on the TM cost.

18. The processing circuitry 18. The apparatus of claim 17, configured to select K initial BVD candidates from the initial BVD candidates as the BVD candidates in the BVD list, the K initial BVD candidates corresponding to the lowest TM costs among the TM costs.

19. The processing circuitry selecting K initial BVD candidates from the initial BVD candidates, wherein the K initial BVD candidates correspond to the lowest TM costs among the TM costs; For each of the K initial BVD candidates with a respective BVD offset and BVD direction, if the BVD offset is the only BVD offset in the BVD offsets that is greater than a first BVD offset and less than a second BVD offset, determining a first candidate and a second candidate associated with each initial BVD candidate among the K initial BVD candidates, wherein the first candidate and the second candidate have the same BVD direction as the initial BVD candidate, the BVD offset of the first candidate is an average of the BVD offset and the first BVD offset, and the BVD offset of the second candidate is an average of the BVD offset and the second BVD offset; determining new TM costs associated with the first candidate and the second candidate, respectively; and determining the BVD list based on updated TM costs, the updated TM costs including: (i) the lowest TM cost among the TM costs corresponding to the K initial BVD candidates; and (ii) the new TM cost.

20. A non-transitory computer-readable storage medium storing instructions that, when executed by at least one processor, cause the at least one processor to: receiving a coded video bitstream comprising coded information of a current block in a current picture, the current block being predicted based on a reference block in the current picture indicated by a block vector (BV) as determined based on a BV predictor (BVP) and a BV difference (BVD), the difference between the BV and the BVP; determining a BVD list containing BVD candidates based at least on a BVD offset from the BVP; determining the BVD from the BVD candidates in the BVD list; reconstructing the current block using the determined BVD; For each adjacent pair of the BVD offsets, an initial interval size indicating the difference between the adjacent pairs of the BVD offsets; Each of the initial interval sizes is different from other initial interval sizes corresponding to other adjacent pairs of the BVD offsets.

Images