Intra-block copy within adaptive local reference range

Abstract

To provide a method for a video decoding, a device, and a non-temporary computer readable storage medium.SOLUTION: A video decoding apparatus includes processing circuitry configured to reconstruct an area in a block in a current picture from a coded video bitstream. The block includes one or more coding blocks (CBs) in the current picture. After the reconstructing, the processing circuitry determines whether to update a previous local reference range for an intra block copy (IBC) mode based on (i) a content of the reconstructed area and / or (ii) prediction information of the reconstructed area. In response to a determination not to update the previous local reference range for the IBC mode, the previous local reference range for the IBC mode is not updated. The processing circuitry decodes a coding block in the current picture using the IBC mode that is based on the previous local reference range, which does not include the reconstructed area.SELECTED DRAWING: Figure 19

Description

[Technical field]

[0001] [Incorporated by reference] This application claims the benefit of priority to U.S. Patent Application No. 17 / 893,877 entitled "INTRA BLOCK COPY WITH AN ADAPTIVE LOCAL REFERENCE RANGE," filed August 23, 2022, which claims the benefit of priority to U.S. Provisional Application No. 63 / 237,098 entitled "IntraBC with Adaptive Local Reference Range," filed August 25, 2021. The entire disclosure of the prior application is incorporated by reference.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0022] Aspects of the present disclosure provide methods and apparatus for video encoding and decoding. In some examples, the apparatus for video decoding includes a processing circuit. The processing circuit is configured to reconstruct a region in a block in a current picture from an encoded video bitstream. The block includes one or more coding blocks (CB) in the current picture. After reconstruction, the processing circuit can determine whether to update a previous local reference range of an intra block copy (IBC) mode based on (i) the content of the reconstructed region and / or (ii) prediction information of the reconstructed region. In response to a decision not to update the previous local reference range of the IBC mode, the previous local reference range of the IBC mode is not updated, and the processing circuit decodes the coding block (CB) in the current picture using the IBC mode based on the previous local reference range that does not include the reconstructed region.

[0023] In one embodiment, the processing circuit determines a content of the reconstructed region based on the reconstructed samples in the reconstructed region, the content of the reconstructed region indicating a proportion of texture content and / or a proportion of screen content in the reconstructed region. The processing circuit can determine whether to update the previous local reference range of the IBC mode based on the proportion of texture content and / or the proportion of screen content in the reconstructed region. In one example, the content of the reconstructed region does not include screen content, and the processing circuit determines that the previous local reference range of the IBC mode is not updated.

[0024] In one embodiment, the processing circuit decodes prediction information for a region indicating a prediction mode for the region, and determines whether to update the previous local reference range for the IBC mode based on whether the prediction mode is in a set of predetermined prediction modes.

[0025] In one embodiment, the processing circuit decodes prediction information of the region indicating whether to update the previous local reference range with the reconstructed samples in the reconstructed region, and the processing circuit determines whether to update the previous local reference range of the IBC mode based on the indication in the prediction information of whether to update the previous local reference range with the reconstructed samples in the reconstructed region.

[0026] In one example, whether to update the previous local reference range with the reconstructed samples in the reconstruction region is indicated by a flag included in the prediction information of the region, and the processing circuit determines whether to update the previous local reference range in the IBC mode based on the flag. In one example, the flag indicates whether any reconstructed samples in the block are used when updating the local reference range in the IBC mode.

[0027] In one embodiment, a previous local reference range for the IBC mode is determined to be updated, and the previous local reference range includes a plurality of regions stored in a reference sample memory (RSM). The plurality of regions may include reference samples. The processing circuitry may rank the plurality of regions based on contents of the plurality of regions, each of the contents corresponding to a respective one of the plurality of regions. The processing circuitry may select a region in the plurality of regions to be replaced by a reconstructed sample in the reconstruction region based on the ranking of the plurality of regions, and generate a current local reference range by replacing the selected region in the previous local reference range with the reconstructed sample in the reconstruction region.

[0028] In one example, each of the content corresponding to a respective one of the plurality of regions is indicated by a percentage of screen content or a percentage of texture content within the corresponding region, and the processing circuitry ranks the plurality of regions based on the respective percentage of screen content or the respective percentage of texture content of the plurality of regions.

[0029] In one embodiment, a previous local reference range for the IBC mode is determined to be updated, and the previous local reference range includes a plurality of regions stored in the RSM. Each region of the plurality of regions includes a plurality of specially coded reference samples in the respective region, coded in one or more prediction modes in a set of predetermined prediction modes. The processing circuitry can rank the plurality of regions based on each of the plurality of specially coded reference samples in the plurality of regions. The processing circuitry can select a region in the plurality of regions to be replaced by a reconstructed sample in the reconstructed region based on the ranking of the plurality of regions, and generate a current local reference range by replacing the selected region in the previous local reference range with the reconstructed sample in the reconstructed region.

[0030] In one embodiment, a previous local reference range for the IBC mode is determined to be updated, and the previous local reference range includes a plurality of regions stored in the RSM. A reference frequency associated with each region of the plurality of regions indicates the number of times the respective region is referenced by a block vector used to predict the CB in the current picture. The processing circuitry can rank the plurality of regions based on the reference frequency of each of the plurality of regions. The processing circuitry can select a region in the plurality of regions to be replaced by a reconstructed sample in the reconstructed domain based on the ranking of the plurality of regions, and generate a current local reference range by replacing the selected region in the previous local reference range with the reconstructed sample in the reconstructed domain.

[0031] In one embodiment, the previous local reference range includes a plurality of regions. Reconstructed samples of the plurality of regions are stored in the RSM, except for reconstructed samples of a sub-region in one of the plurality of regions. The reconstructed samples of the sub-region in one of the plurality of regions are replaced by a padding process that stores padded samples corresponding to the sub-region in one of the plurality of regions in the RSM.

[0032] In one embodiment, the reconstruction region is a reconstructed coding block, or the size of the reconstruction region is the size of a memory update region unit.

[0033] Aspects of the present disclosure also provide a non-transitory computer-readable storage medium storing a program executable by at least one processor to perform a method for video decoding. [Brief description of the drawings]

[0034] Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and the accompanying drawings. [Figure 1A] FIG. 2 is a schematic diagram of an example subset of intra-prediction modes. [Figure 1B] FIG. 2 is an illustration of an exemplary intra-prediction direction. [Diagram 2] An example of a current block (201) and its surrounding samples in one example is shown. [Diagram 3] FIG. 3 is a schematic diagram of an example block diagram of a communication system (300). [Figure 4] FIG. 4 is a schematic diagram of a simplified block diagram of a communication system (400) according to an embodiment. [Diagram 5] FIG. 2 is a schematic diagram of an example block diagram of a decoder. [Figure 6] FIG. 2 is a schematic diagram of an example block diagram of an encoder; [Figure 7] 1 shows a block diagram of an exemplary encoder. [Figure 8] 1 shows a block diagram of an exemplary decoder. [Figure 9] 4 illustrates a block vector associated with a current coding unit according to an embodiment of the present disclosure. [Figure 10A] 1 illustrates a reference area for intra block copy (IBC) mode according to an embodiment of the present disclosure. [Figure 10B] 1 illustrates a reference area for intra block copy (IBC) mode according to an embodiment of the present disclosure. [Figure 10C] 1 illustrates a reference area for intra block copy (IBC) mode according to an embodiment of the present disclosure. [Figure 10D] 1 illustrates a reference area for intra block copy (IBC) mode according to an embodiment of the present disclosure. [Figure 11] 1 illustrates an exemplary continuous updating process of a spatial reference sample memory (RSM). [Figure 12] 1 shows an example of a restricted immediate reconstruction region. [Figure 13] 1 illustrates an exemplary memory reclamation mechanism. [Figure 14A] 13 illustrates an exemplary memory update process in the RSM during the current encoding of SB. [Figure 14B] 13 illustrates an exemplary memory update process in the RSM during the current encoding of SB. [Figure 15]13 illustrates an exemplary adaptive memory update process in the RSM when the current SB is being decoded. [Figure 16] 1 illustrates an exemplary padding process used in an adaptive memory updating process. [Figure 17] 1 illustrates an exemplary adaptive memory update process in an RSM. [Figure 18] 1 shows a flowchart outlining an encoding process according to one embodiment of the present disclosure. [Figure 19] 1 shows a flow chart outlining a decoding process according to one embodiment of the present disclosure. [Figure 20] FIG. 1 is a schematic diagram of a computer system according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] I. Overview of Video / Image Coding Technology

[0036] FIG. 3 illustrates an example block diagram of a communication system (300). The communication system (300) includes a plurality of terminal devices that can communicate with each other, for example, via a network (350). For example, the communication system (300) includes a first pair of terminal devices (310) and (320) interconnected via the network (350). In the example of FIG. 3, the first pair of terminal devices (310) and (320) perform a unidirectional transmission of data. For example, the terminal device (310) may encode video data (e.g., a stream of video pictures captured by the terminal device (310)) for transmission to the other terminal device (320) via the network (350). The encoded video data may be transmitted in the form of one or more encoded video bitstreams. The terminal device (320) may receive the encoded video data from the network (350), decode the encoded video data to reconstruct the video pictures, and display the video pictures according to the reconstructed video data. One-way data transmission may be common, such as in media service applications.

[0037] In another example, the communication system (300) includes a second pair of terminal devices (330) and (340) performing bidirectional transmission of encoded video data, for example during a video conference. For the bidirectional transmission of data, in one example, each of the terminal devices (330) and (340) may encode video data (e.g., a stream of video pictures captured by the terminal device) for transmission to the other of the terminal devices (330) and (340) over the network (350). Each of the terminal devices (330) and (340) may receive the encoded video data transmitted by the other of the terminal devices (330) and (340), decode the encoded video data to reconstruct the video pictures, and display the video pictures on an accessible display device in accordance with the reconstructed video data.

[0038] In the example of FIG. 3, terminal devices (310), (320), (330), and (340) are shown as a server, a personal computer, and a smartphone, respectively, although the principles of the present disclosure may not be so limited. Embodiments of the present disclosure find application in laptop computers, tablet computers, media players, and / or dedicated video conferencing equipment. Network (350) represents any number of networks that convey encoded video data between terminal devices (310), (320), (330), and (340), including, for example, wired (wired) and / or wireless communication networks. Communications network (350) may exchange data in circuit-switched and / or packet-switched channels. Exemplary networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of discussion herein, the architecture and topology of network (350) may not be important to the operation of the present disclosure, unless otherwise described below.

[0039] 4 shows a video encoder and a video decoder in a streaming environment as an example of an application for the disclosed subject matter. The disclosed subject matter may be equally applicable to other video-enabled applications including, for example, video conferencing, digital TV, streaming services, storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0040] The streaming system may include a video source (401), e.g., a digital camera, and may include a capture subsystem (413) that generates, e.g., a stream of uncompressed video pictures (402). In one example, the stream of video pictures (402) includes samples captured by a digital camera. The stream of video pictures (402), depicted as a thick line to emphasize its high data volume compared to the encoded video data (404) (or encoded video bitstream), may be processed by an electronic device (420) that includes a video encoder (403) coupled to the video source (401). The video encoder (403) may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter, as described in more detail below. The encoded video data (404) (or encoded video bitstream), depicted as a thin line to emphasize its lower data volume compared to the stream of video pictures (402), may be stored in a streaming server (405) for future use. One or more streaming client subsystems, such as the client subsystems (406) and (408) of FIG. 4, can access the streaming server (405) to retrieve copies (407) and (409) of the encoded video data (404). The client subsystem (406) can include a video decoder (410), for example within an electronic device (430). The video decoder (410) decodes an input copy (407) of the encoded video data and generates an output stream (411) of video pictures that can be rendered on a display (412) (e.g., a display screen) or other rendering device (not shown). In some streaming systems, the encoded video data (404), (407), and (409) (e.g., a video bitstream) can be encoded according to a particular video encoding / compression standard. Examples of these standards include ITU-T Recommendation H.265.In one example, the developing video coding standard is informally known as Versatile Video Coding (VVC), and the disclosed subject matter may be used in the context of VVC.

[0041] It is noted that electronic devices 420 and 430 may include other components (not shown). For example, electronic device 420 may include a video decoder (not shown), and electronic device 430 may also include a video encoder (not shown).

[0042] 5 shows an example block diagram of a video decoder (510). The video decoder (510) can be included in an electronic device (530). The electronic device (530) can include a receiver (531) (e.g., a receiving circuit). The video decoder (510) can be used in place of the video decoder (310) in the example of FIG. 4.

[0043] The receiver (531) may receive one or more coded video sequences to be decoded by the video decoder (510). In some embodiments, one coded video sequence is received at a time, and the decoding of each coded video sequence is independent of the decoding of the other coded video sequences. The coded video sequences may be received from a channel (501), which may be a hardware / software link to a storage device that stores the coded video data. The receiver (531) may receive the coded video data together with other data, such as coded audio data and / or auxiliary data streams, which may be forwarded to respective usage entities (not shown). The receiver (531) may separate the coded video sequences from the other data. To combat network jitter, a buffer memory (515) may be coupled between the receiver (531) and the entropy decoder / parser (520) (hereinafter the "parser"). In certain applications, the buffer memory (515) is part of the video decoder (510). In other applications, it may be external to the video decoder (510) (not shown). In still other applications, there may be a buffer memory (not shown) external to the video decoder (510), e.g., to combat network jitter, and yet another buffer memory (515) internal to the video decoder (510), e.g., to handle playback timing. If the receiver (531) is receiving data from a store / forward device of sufficient bandwidth and controllability, or from an isochronous network, the buffer memory (515) may not be needed or may be small. For use with best-effort packet networks such as the Internet, the buffer memory (515) may be required and may be relatively large, advantageously of adaptive size, and may be implemented at least in part in an operating system or similar element (not shown) external to the video decoder (510).

[0044] The video decoder (510) may include a parser (520) for reconstructing symbols (521) from the coded video sequence. These categories of symbols include information used to manage the operation of the video decoder (510) and potentially information for controlling a rendering device such as a render device (512) (e.g., a display screen). The rendering device may not be an integral part of the electronic device (530) as shown in FIG. 5, but may be coupled to the electronic device (530). The control information for the rendering device(s) may be in the form of Supplementary Enhancement Information (SEI messages) or Video Usability Information (VUI) parameter set fragments (not shown). The parser (520) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may follow a video coding technique or standard and may follow various principles including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, etc. The parser (520) can extract from the coded video sequence a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder based on at least one parameter corresponding to the group. The subgroups can include Groups of Pictures (GOPs), pictures, tiles, slices, macroblocks, Coding Units (CUs), blocks, Transform Units (TUs), Prediction Units (PUs), etc. The parser (520) can also extract information from the coded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, etc.

[0045] The parser (520) can perform an entropy decoding / parsing operation on the video sequence received from the buffer memory (515) to generate symbols (521).

[0046] The reconstruction of symbols (521) can involve several different units, depending on the type of coded video picture or portions thereof (e.g., inter and intra pictures, inter and intra blocks) and other factors. Which units are involved and how can be controlled by subgroup control information parsed by the parser (520) from the coded video sequence. The flow of such subgroup control information between the parser (520) and the following units is not depicted for clarity.

[0047] In addition to the functional blocks already mentioned, the video decoder (510) can be conceptually divided into a number of functional units, as described below. In a practical implementation operating under commercial constraints, many of these units will interact closely with each other and may be at least partially integrated with each other. However, for purposes of describing the disclosed subject matter, the following conceptual subdivision into functional units is adequate.

[0048] The first unit is a scalar / inverse transform unit (551). The scalar / inverse transform unit (551) receives quantized transform coefficients and control information as symbol(s) (521) from the parser (520). The control information includes which transform to use, block size, quantization factor, quantization scaling matrix, etc. The scalar / inverse transform unit (551) can output blocks containing sample values ​​that can be input to an aggregator (555).

[0049] In some cases, the output samples of the scaler / inverse transform (551) may relate to intra-coded blocks, which are blocks that do not use prediction information from a previously reconstructed picture, but can use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by an intra-picture prediction unit (552). In some cases, the intra-picture prediction unit (552) generates a block of the same size and shape as the block being reconstructed using surrounding already reconstructed information taken from a current picture buffer (558). The current picture buffer (558) buffers, for example, a partially reconstructed current picture and / or a fully reconstructed current picture. The aggregator (555) optionally adds, on a sample-by-sample basis, the prediction information generated by the intra-prediction unit (552) to the output sample information provided by the scaler / inverse transform unit (551).

[0050] In other cases, the output samples of the scalar / inverse transform unit (551) may relate to an inter-coded, potentially motion-compensated block. In such cases, the motion compensation prediction unit (553) may access a reference picture memory (557) to fetch samples used for prediction. After motion compensating the fetched samples according to the symbols (521) for the block, these samples may be added by an aggregator (555) to the output of the scalar / inverse transform unit (in this case referred to as residual samples or residual signals) to generate output sample information. The addresses in the reference picture memory (557) from which the motion compensation unit (553) fetches prediction samples may be controlled by motion vectors available to the motion compensation unit (553) in the form of symbols (521). The symbols may have, for example, X, Y, and reference picture components. Motion compensation may include interpolation of sample values ​​fetched from the reference picture memory (557) when subsample accurate motion vectors are used, motion vector prediction mechanisms, and the like.

[0051] The output samples of the aggregator (555) may be subjected to various loop filtering techniques in a loop filter unit (556). Video compression techniques may include in-loop filter techniques controlled by parameters contained in the coded video sequence (also called the coded video bitstream) and made available to the loop filter unit (556) as symbols (521) from the parser (520). Video compression may also be responsive to meta-information obtained during decoding of previous portions (in decoding order) of the coded picture or coded video sequence, as well as to previously reconstructed loop filtered sample values.

[0052] The output of the loop filter unit (556) can be a sample stream, which can be output to a render device (512) or stored in a reference picture memory (557) for use in future inter-picture prediction.

[0053] Once a coded picture is fully reconstructed, it can be used as a reference picture for future prediction. For example, once a coded picture corresponding to a current picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by the parser (520)), the current picture buffer (558) can become part of the reference picture memory (557), and a fresh current picture buffer can be reallocated before starting the reconstruction of a subsequent coded picture.

[0054] The video decoder (510) may perform decoding operations according to a given video compression technique or standard, such as ITU-T Recommendation H.265. The encoded video sequence may be compliant with the syntax prescribed by the video compression technique or standard being used, in the sense that the encoded video sequence follows the syntax of the video compression technique or standard and a profile documented in the video compression technique or standard. In particular, a profile may select a particular tool from all tools available in the video compression technique or standard as the only tool available for use under that profile. Compliance may also require that the complexity of the encoded video sequence be within a range defined by a level of the video compression technique or standard. In some cases, the level constrains the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in units of megasamples per second), maximum reference picture size, etc. The limits set by the level may be further constrained through a Hypothetical Reference Decoder (HRD) specification and metadata for HRD buffer management, possibly signaled in the encoded video sequence.

[0055] In some embodiments, the receiver (531) may receive additional (redundant) data along with the encoded video. The additional data may be included as part of the encoded video sequence(s). The additional data may be used by the video decoder (510) to properly decode the data and / or to more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0056] 6 shows an example block diagram of a video encoder (603). The video encoder (603) is included in an electronic device (620). The electronic device (620) includes a transmitter (640) (e.g., a transmission circuit). The video encoder (603) can be used in place of the video encoder (403) in the example of FIG. 4.

[0057] The video encoder (603) can receive video samples from a video source (601) (which is not part of the electronic device (620) in the example of FIG. 6) that can capture video images to be encoded by the video encoder (603). In another example, the video source (601) is part of the electronic device (620).

[0058] The video source (601) may provide a source video sequence to be encoded by the video encoder (603) in the form of a digital video sample stream that may be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 YCrCB, RGB, ...) and any suitable sampling structure (e.g., YCrCb 4:2:0, YCrCb 4:4:4). In a media service system, the video source (601) may be a storage device that stores pre-prepared video. In a video conferencing system, the video source (601) may be a camera that captures image information locally as a video sequence. The video data may be provided as a number of individual pictures that impart motion when viewed in sequence. The pictures themselves may be organized as a spatial array of pixels, each of which may contain one or more samples, depending on the sampling structure, color space, etc., in use. Those skilled in the art can easily understand the relationship between pixels and samples. The following description focuses on samples.

[0059] According to an embodiment, the video encoder (603) can encode and compress pictures of a source video sequence into an encoded video sequence (643) in real time or under any other required time constraint. Enforcing an appropriate encoding rate is one function of the controller (650). In some embodiments, the controller (650) controls and is operatively coupled to other functional units, such as those described below. Such couplings are not depicted for clarity. Parameters set by the controller (650) can include parameters related to rate control (picture skip, quantizer, lambda value for rate-distortion optimization techniques, ...), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. The controller (650) can be configured to have other suitable functions for the video encoder (603) optimized for a particular system design.

[0060] In some embodiments, the video encoder (603) is configured to operate in an encoding loop. As a simplistic description, in one example, the encoding loop can include a source encoder (630) (e.g., responsible for generating symbols, such as a symbol stream, based on an input picture to be encoded and a reference picture(s)) and a (local) decoder (633) embedded in the video encoder (603). The decoder (633) reconstructs the symbols to generate sample data in a similar manner that a (remote) decoder would also generate. The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since the decoding of the symbol stream results in bit-exact results regardless of the decoder location (local or remote), the contents of the reference picture memory (634) are also bit-exact between the local and remote encoders. In other words, the prediction part of the encoder "sees" exactly the same sample values ​​as the decoder "sees" when using the prediction during decoding as reference picture samples. This basic principle of reference picture synchrony (and the resulting drift when synchrony cannot be maintained, for example due to channel errors) is also used in several related techniques.

[0061] The operation of the "local" decoder (633) may be the same as the operation of a "remote" decoder, e.g., the video decoder (410), already described in detail above in connection with Figure 5. However, referring also briefly to Figure 5, because symbols are available and the encoding / decoding of the symbols into a coded video sequence by the entropy coder (645) and parser (420) may be lossless, the entropy decoding portion of the video decoder (410), including the buffer memory (415) and the parser (420), may not be fully implemented in the local decoder (633).

[0062] In some embodiments, the decoder techniques, except for parsing / entropy decoding, present in the decoder are present in the same or substantially the same functional form in the corresponding encoder. Thus, the disclosed subject matter focuses on the decoder operation. A description of the encoder techniques can be omitted, since they are the inverse of the decoder techniques described generically. In certain areas, more detailed descriptions are provided below.

[0063] During operation, in some examples, the source encoder (630) may perform motion-compensated predictive encoding, which predictively encodes an input picture with reference to one or more previously encoded pictures from a video sequence, designated as “reference pictures.” In this manner, the encoding engine (632) encodes differences between pixel blocks of the input picture and pixel blocks of a reference picture(s) that may be selected as predictive references for the input picture.

[0064] The local video decoder (633) can decode the encoded video data of the pictures that may be designated as reference pictures based on the symbols generated by the source encoder (630). The operation of the encoding engine (632) can advantageously be a lossy process. When the encoded video data can be decoded in a video decoder (not shown in FIG. 6), the reconstructed video sequence can be a copy of the source video sequence, typically with some errors. The local video decoder (633) can replicate the decoding process that may be performed on the reference pictures by the video decoder and store the reconstructed reference pictures in the reference picture memory (634). In this way, the video encoder (603) can locally store copies of reconstructed reference pictures that have common content (in the absence of transmission errors) as the reconstructed reference pictures that would be obtained by the far-end video decoder.

[0065] The predictor (635) may perform a prediction search for the coding engine (632). That is, for a new picture to be coded, the predictor (635) may search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or specific metadata, such as reference picture motion vectors, block shapes, etc., that may serve as suitable prediction references for the new picture. The predictor (635) may operate on a sample block-by-pixel block basis to find suitable prediction references. In some cases, as determined by the search results obtained by the predictor (635), the input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (634).

[0066] The controller (650) may manage the encoding operations of the source encoder (630), including, for example, setting the parameters and subgroup parameters used to encode the video data.

[0067] The output of all of the above functional units may undergo entropy coding in an entropy coder (645), which converts the symbols produced by the various functional units into a coded video sequence by applying lossless compression to the symbols according to techniques such as Huffman coding, variable length coding, arithmetic coding, etc.

[0068] The transmitter (640) can buffer the encoded video sequence generated by the entropy encoder (645) and prepare it for transmission over a communication channel (660), which may be a hardware / software link to a storage device that stores the encoded video data. The transmitter (640) can merge the encoded video data from the video encoder (630) with other data to be transmitted, such as encoded audio data and / or auxiliary data streams (sources not shown).

[0069] The controller (650) may manage the operation of the video encoder (603). During encoding, the controller (650) may assign a certain coding picture type to each coded picture. The coding picture type may affect the coding technique that may be applied to each picture. For example, pictures may often be assigned as one of the following picture types:

[0070] An intra picture (I-picture) may be one that can be coded and decoded without using other pictures in a sequence as a source of prediction. Some video codecs allow different types of intra pictures, including, for example, Independent Decoder Refresh ("IDR") pictures. Those skilled in the art will recognize these variations of I-pictures and their respective uses and characteristics.

[0071] A predictive picture (P-picture) may be one that can be encoded and decoded using intra- or inter-prediction, which uses at most one motion vector and reference index to predict the sample values ​​of each block.

[0072] Bidirectionally predicted pictures (B-pictures) may be those that can be coded and decoded using intra- or inter-prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multi-predictive pictures can use more than two reference pictures and associated metadata for the reconstruction of a single block.

[0073] A source picture is usually spatially divided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and may be coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks, as determined by the coding assignment applied to the respective picture of the block. For example, blocks of an I-picture may be non-predictively coded or may be predictively coded with reference to already coded blocks of the same picture (spatial or intra prediction). Pixel blocks of a P-picture may be predictively coded via spatial prediction or via temporal prediction with reference to one previously coded reference picture. Blocks of a B-picture may be predictively coded via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

[0074] The video encoder (603) may perform encoding operations according to a given video encoding technique or standard, such as ITU-T Recommendation H.265. In its operations, the video encoder (603) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancy in the input video sequence. Thus, the encoded video data may conform to a syntax specified by the video encoding technique or standard used.

[0075] In some embodiments, the transmitter (640) may transmit additional data along with the encoded video. The source encoder (630) may include such data as part of the encoded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0076] A video may be captured as multiple source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often abbreviated as intra-prediction) exploits spatial correlation in a given picture, while inter-picture prediction exploits correlation (temporal or other) between pictures. In one example, a particular picture to be coded / decoded, called a current picture, is divided into blocks. If a block in the current picture is similar to a reference block in a previously coded and still buffered reference picture in the video, that block in the current picture can be coded by a vector called a motion vector. A motion vector points to a reference block in a reference picture, and may have a third dimension that identifies the reference picture if multiple reference pictures are used.

[0077] In some embodiments, bi-prediction techniques can be used in inter-picture prediction. According to bi-prediction techniques, two reference pictures are used, such as a first reference picture and a second reference picture, both of which precede the current picture in decoding order (but may also be past and future, respectively, in display order) in the video. A block in the current picture can be coded by a first motion vector that points to a first reference block in the first reference picture and a second motion vector that points to a second reference block in the second reference picture. A block can be predicted by a combination of the first and second reference blocks.

[0078] Furthermore, to improve coding efficiency, merge mode techniques can be used in inter-picture prediction.

[0079] According to some embodiments of the present disclosure, predictions such as inter-picture prediction and intra-picture prediction are performed on a block-by-block basis. For example, according to the HEVC standard, pictures in a sequence of video pictures are divided into coding tree units (CTUs) for compression, and the CTUs in a picture have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTU includes three coding tree blocks (CTBs), one luma CTB and two chroma CTBs. Each CTU can be recursively quadtree partitioned into one or more coding units (CUs). For example, a CTU of 64×64 pixels can be partitioned into one CU of 64×64 pixels, or four CUs of 32×32 pixels, or 16 CUs of 16×16 pixels. In one example, each CU is analyzed to determine a prediction type for that CU, such as an inter prediction type or an intra prediction type. A CU is divided into one or more prediction units (PUs) depending on temporal and / or spatial predictability. In general, each PU includes a luma prediction block (PB) and two chroma PBs. In an embodiment, prediction operations in coding (encoding / decoding) are performed in units of prediction blocks. Taking a luma prediction block as an example of a prediction block, the prediction block includes a matrix of values ​​(e.g., luma values) for pixels, such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, etc.

[0080] 7 shows an example diagram of a video encoder (703). The video encoder (703) is configured to receive a processed block of sample values ​​(e.g., a predictive block) in a current video picture in a sequence of video pictures and to encode the processed block into a coded picture that is part of a coded video sequence. In one example, the video encoder (703) is used in place of the video encoder (403) in the example of FIG. 4.

[0081] In an HEVC example, the video encoder (703) receives a matrix of sample values ​​for a processing block, such as a predictive block, such as 8×8 samples. The video encoder (703) determines whether the processing block is best coded using intra mode, inter mode, or bi-predictive mode, e.g., using rate-distortion optimization. If the processing block is coded in intra mode, the video encoder (703) may use intra prediction techniques to code the processing block into a coded picture. If the processing block is coded in inter mode or bi-predictive mode, the video encoder (703) may use inter prediction techniques or bi-predictive techniques, respectively, to code the processing block into a coded picture. In certain video coding techniques, a merge mode may be an inter-picture prediction sub-mode in which motion vectors are derived from one or more motion vector predictors, but without the benefit of coded motion vector components outside the predictors. In certain other video coding techniques, there may be motion vector components applicable to the current block. In one example, the video encoder (703) includes other components, such as a mode decision module (not shown) for determining the mode of the processing blocks.

[0082] In the example of FIG. 7, the video encoder (703) includes an inter-encoder (730), an intra-encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721), and an entropy coder (725), coupled together as shown in FIG.

[0083] The inter-encoder (730) is configured to receive samples of a current block (e.g., a processing block), compare the block with one or more reference blocks in a reference picture (e.g., blocks in previous and subsequent pictures), generate inter-prediction information (e.g., a description of redundant information due to inter-coding techniques, motion vectors, merge mode information), and calculate an inter-prediction result (e.g., a predicted block) based on the inter-prediction information using any suitable technique. In some examples, the reference picture is a decoded reference picture that is decoded based on the coded video information.

[0084] The intra encoder (722) is configured to receive samples of a current block (e.g., a processing block), possibly compare the block with blocks already encoded in the same picture, generate transformed and quantized coefficients, and possibly also generate intra prediction information (e.g., intra prediction direction information according to one or more intra encoding techniques). In one example, the intra encoder (722) also calculates an intra prediction result (e.g., a predicted block) based on the intra prediction information and a reference block in the same picture.

[0085] The general controller (721) is configured to determine general control data and control other components of the video encoder (703) based on the general control data. In one example, the general controller (721) determines the mode of the block and provides a control signal to the switch (726) based on the mode. For example, if the mode is an intra mode, the general controller (721) controls the switch (726) to select the result of the intra mode for use by the residual calculator (723), and controls the entropy encoder (725) to select intra prediction information and include the intra prediction information in the bitstream. If the mode is an inter mode, the general controller (721) controls the switch (726) to select the result of inter prediction for use by the residual calculator (723), and controls the entropy encoder (725) to select inter prediction information and include the inter prediction information in the bitstream.

[0086] The residual calculator (723) is configured to calculate a difference (residual data) between the received block and a prediction result selected from the intra-encoder (722) or the inter-encoder (730). The residual encoder (724) is configured to encode the residual data to generate transform coefficients based on the residual data. In one example, the residual encoder (724) is configured to transform the residual data from the spatial domain to the frequency domain to generate transform coefficients. The transform coefficients are then subjected to a quantization process to obtain quantized transform coefficients. In various embodiments, the video encoder (703) also includes a residual decoder (728). The residual decoder (728) is configured to perform an inverse transform to generate decoded residual data. The decoded residual data can be suitably used by the intra-encoder (722) and the inter-encoder (730). For example, the inter-encoder (730) can generate decoded blocks based on the decoded residual data and the inter-prediction information, and the intra-encoder (722) can generate decoded blocks based on the decoded residual data and the intra-prediction information. The decoded blocks are suitably processed to generate decoded pictures, which can be buffered in a memory circuit (not shown) and used as reference pictures in some examples.

[0087] The entropy encoder (725) is configured to format a bitstream to include the encoded block. The entropy encoder (725) is configured to include various information in the bitstream according to a suitable standard, such as the HEVC standard. In one example, the entropy encoder (725) is configured to include general control data, selected prediction information (e.g., intra-prediction information or inter-prediction information), residual information, and other suitable information in the bitstream. Note that in accordance with the disclosed subject matter, when encoding a block in a merged sub-mode of either the inter mode or the bi-prediction mode, the residual information is not present.

[0088] 8 shows an example diagram of a video decoder (810). The video decoder (810) is configured to receive encoded pictures that are part of an encoded video sequence and decode the encoded pictures to generate reconstructed pictures. In one example, the video decoder (810) is used in place of the video decoder (410) in the example of FIG. 4.

[0089] In the example of FIG. 8, the video decoder (810) includes an entropy decoder (871), an inter decoder (880), a residual decoder (873), a reconstruction module (874), and an intra decoder (872) coupled together as shown in FIG. 8.

[0090] The entropy decoder (871) may be configured to reconstruct from the coded picture certain symbols representing the syntax elements of which the coded picture is composed. Such symbols may include, for example, prediction information (e.g., intra- or inter-prediction information, etc.) that may identify the mode in which the block is coded (e.g., intra- or inter-prediction mode, merged submode, or the latter two in another submode), and the specific samples or metadata used for prediction by the intra-decoder (872) or the inter-decoder (880), respectively. The symbols may also include residual information, for example in the form of quantized transform coefficients, etc. In one example, if the prediction mode is an inter- or bi-prediction mode, the inter-prediction information is provided to the inter-decoder (880). If the prediction type is an intra-prediction type, the intra-prediction information is provided to the intra-decoder (872). The residual information may undergo inverse quantization and is provided to the residual decoder (873).

[0091] The inter decoder (880) is configured to receive inter prediction information and to generate inter prediction results based on the inter prediction information.

[0092] The intra decoder (872) is configured to receive intra prediction information and generate a prediction result based on the intra prediction information.

[0093] The residual decoder (873) is configured to perform inverse quantization to extract dequantized transform coefficients, and to process the dequantized transform coefficients to transform the residual information from the frequency domain to the spatial domain. The residual decoder (873) may also require certain control information (including quantizer parameters (QP)), which may be provided by the entropy decoder (871) (data path not depicted since this is only low volume control information).

[0094] The reconstruction module (874) is configured to combine, in the spatial domain, the residual information output by the residual decoder (873) and the prediction result (output by the intra- or inter-prediction module, as the case may be) to form a reconstructed block, which may be part of a reconstructed picture, which may be part of a reconstructed video. It is noted that other suitable operations, such as a deblocking operation, may be performed to improve visual quality.

[0095] It should be noted that the video encoders (403), (603), (703) and the video decoders (410), (510), (810) may be implemented using any suitable technology. In some embodiments, the video encoders (403), (603), (703) and the video decoders (410), (510), (810) may be implemented using one or more integrated circuits. In other embodiments, the video encoders (403), (603), (703) and the video decoders (410), (510), (810) may be implemented using one or more processors executing software instructions.

[0096] II. Intra Block Copy (IBC or IntraBC) Mode

[0097] This disclosure describes advanced video / image coding techniques related to intra block copy modes with local reference scope.

[0098] II.1 IBC Mode in HEVC and VVC

[0099] II.1.1 Current Picture Referencing (CPR) in HEVC

[0100] The IBC coding tool can be used as CPR in the HEVC Screen Content Coding (SCC) extension. The IBC mode can use the coding technique used for inter prediction where the current picture is used as a reference picture in the IBC mode. The advantage of using the IBC mode is that the reference structure of the IBC mode can use a two-dimensional (2D) spatial vector as a representation of the addressing mechanism for referencing samples. The advantage of the IBC mode architecture is that the integration of IBC requires relatively small changes to the specification, which can reduce the implementation burden if the manufacturer has already implemented a specific inter prediction technique such as HEVC version 1. The CPR in the HEVC SCC extension can be a special inter prediction mode, resulting in the same syntax structure as the syntax structure of the inter prediction mode and a decoding process similar to the decoding process of the inter prediction mode.

[0101] IBC mode can be integrated into the inter prediction process. In some examples, IBC mode (or CPR) is an inter prediction mode, and intra-only predicted slices become predicted slices that enable the use of IBC mode. When IBC mode is applicable, the coder can extend the reference picture list by one entry for the pointer to the current picture. For example, the current picture uses a one-picture-sized buffer of a shared decoded picture buffer (DPB). Signaling of IBC mode can be done implicitly. For example, the CU can use IBC mode if the selected reference picture points to the current picture. In various embodiments, the reference samples used in the IBC process are not filtered, which is different from normal inter prediction. The corresponding reference picture used in the IBC process is a long-term reference. To minimize memory requirements, the coder can release the buffer after reconstructing the current picture, for example, the coder releases the buffer immediately after reconstructing the current picture. The filtered version of the reconstructed picture can be put back into the DPB by the coder as a short-term reference if the reconstructed picture is a reference picture.

[0102] In block vector (BV) coding, the reference to the reconstructed domain can be performed via 2D BVs similar to inter prediction. The prediction and coding of the BVs can reuse the MV prediction and coding in the inter prediction process. In one example, the luma BVs are at integer resolution instead of the 1 / 4 precision of the MVs used for regular inter coded CTUs.

[0103] FIG. 9 illustrates a BV associated with a current CU (901) according to an embodiment of the present disclosure. Each square (900) may represent a CTU. The gray shaded areas represent areas that have already been coded (e.g., areas that have already been encoded), and the white unshaded areas represent areas to be coded (e.g., areas to be coded). The current CTU (900(4)) being reconstructed includes the current CU (901), a coded area (902), and an area to be coded (903). In one example, after coding the current CU (901), the area (903) is coded.

[0104] In an example such as HEVC, the gray shaded area excluding the two CTUs (900(1)-900(2)) in the upper right corner of the current CTU (900(4)) can be used as a reference area in IBC mode to enable Wavefront Parallel Processing (WPP). BVs allowed in HEVC can point to blocks that are within the reference area (e.g., the gray shaded area (900(1)-900(2)) excluding the two CTUs). For example, BVs allowed in HEVC (905) point to the reference block (911).

[0105] In an example such as VVC, only the current CTU (900(4)) and the left adjacent CTU (900(3)) to the left of the current CTU (900(4)) are allowed as reference regions in IBC mode. In one example, the reference region used in IBC mode in VVC is within the dotted region (915) and contains the coded samples. For example, the BV (906) allowed in VVC refers to the reference block (912).

[0106] In some examples, the decoded motion vector difference (MVD) (also called BV difference (BVD)) of a BV can be left shifted by 2 before being added to the corresponding BV predictor to reconstruct the final BV.

[0107] In some embodiments, special handling of IBC mode may be required for implementation and performance reasons, and IBC mode and inter prediction modes (e.g., normal inter prediction mode) may differ as described below. In one example, the reference samples used in IBC mode are not filtered (e.g., reconstructed samples before in-loop filtering processes such as DBF and sample adaptive offset (SAO) filters are applied). Other inter prediction modes of HEVC (e.g., normal inter prediction mode) can use filtered samples, e.g., reference samples filtered by an in-loop filtering process.

[0108] In some examples, luma sample interpolation is not performed in IBC mode. Chroma sample interpolation can be performed in IBC mode. In some examples, chroma sample interpolation is only required when a chroma BV is non-integer when the chroma BV is derived from the corresponding luma BV. In some examples, luma sample interpolation and chroma sample interpolation can be performed in normal inter prediction mode.

[0109] In IBC mode, a special case may occur when the chroma BV is a non-integer BV and the reference block is near the border of the available region (e.g., the reference region). For example, to perform chroma interpolation, the surrounding reconstructed samples may be outside the border. In one example, a BV pointing to a line next-to-border of a single border may cause the surrounding reconstructed samples to be outside the border.

[0110] II.1.2 IBC Architecture in VVC

[0111] The valid reference region for IBC mode in the HEVC SCC extension can include the entire already reconstructed region of the current picture, with some exceptions for parallel processing purposes, as described in FIG. 9. The drawbacks of the reference region used in HEVC can include the requirement of additional memory in the DPB, which may use external memory in hardware implementation. Additional access to external memory may increase memory bandwidth, making the use of the DPB unattractive. In some embodiments, a fixed memory (e.g., a fixed size memory) that can be realized on-chip for IBC mode can be used in VVC. On-chip fixed memory in IBC mode can significantly reduce the complexity of the implementation of IBC mode in hardware architectures. In one example, on-chip fixed memory in IBC mode can reduce latency. In some examples, as in the HEVC SCC extension, the changes address the concept of signaling away from integration within the inter prediction process.

[0112] In the example shown in Figures 10A-10D, a fixed memory can be allocated to store the reference region used in IBC mode. The fixed memory can be called a reference sample memory (RSM). Part of the RSM can be updated at different intermediate points during the coding process (e.g., encoding process or reconstruction process). Figures 10A-10D show the RSM update process at various intermediate points during the coding process (e.g., encoding process or reconstruction process) according to an embodiment of the present disclosure. Figures 10A-10D show the reference region of IBC mode in VVC and the configuration in VVC.

[0113] 10A to 10D, a current CTU (1020) is adjacent to a CTU (e.g., a left adjacent CTU) (1010) that is to the left of the current CTU (1020). In some examples, the current CTU (1020) includes four regions (1021) to (1024). The left adjacent CTU (1010) may include four regions (1011) to (1014) that correspond to the regions (1021) to (1024), respectively. The positions of the regions (1011) to (1014) are shifted left by the width of the CTU (1020) from the positions of the regions (1021) to (1024), respectively. The RSM may include a part of the current CTU (1020) and / or a part of the left adjacent CTU (1010). In the examples shown in FIG. 10A to 10D, the size of the RSM is equal to the size of the CTU. The light gray shaded area may include reference samples of the left adjacent CTU (1010), the dark gray shaded area may include reference samples of the current CTU (1020), and the white unshaded area may represent the area to be coded (e.g., the upcoming coding area).

[0114] 10A, at a first intermediate point in the coding process, which is the start of the coding process for the current CTU (1020), the RSM includes the entire left-neighboring CTU (1010), and at the start of the coding process for the current CTU (1020), the entire left-neighboring CTU (1010) can function as a reference region in IBC mode. The RSM at the start of the coding process for the current CTU (1020) does not include any of regions (1021)-(1024).

[0115] Referring to FIG. 10B, region (1021) includes sub-regions (1031) to (1033). Sub-region (1031) has already been coded (e.g., encoded or reconstructed), sub-region (1032) is the current CU being coded (e.g., being coded or reconstructed), and sub-region (1033) will be coded later. At a second intermediate point in the coding process of the current CTU (1020) where sub-region (1032) of the current CTU (1020) is coded, the RSM is updated to include a portion of the left adjacent CTU (1010) and a portion of the current CTU (1020). For example, the RSM includes regions (1012) to (1014) of the left adjacent CTU (1010) and sub-region (1031) of the current CTU (1020). The reference region at the second intermediate point in time may include the regions (1012) to (1014) of the left adjacent CTU (1010) and the sub-region (1031) of the current CTU (1020).

[0116] Referring to FIG. 10C, region (1022) includes subregions (1041) to (1043). Subregion (1041) (shaded in dark gray) has already been coded (e.g., encoded or reconstructed), subregion (1042) is the current CU being coded (e.g., being coded or reconstructed), and subregion (1043) (white) will be coded later. At a third intermediate point in the coding process of the current CTU (1020), in which subregion (1042) of the current CTU (1020) is coded, the RSM is updated to include (i) regions (1013) to (1014) of the left adjacent CTU (1010) and (ii) region (1021) and subregion (1041) of the current CTU (1020). In the RSM, region (1012) is replaced with subregion (1041). The reference region at the third intermediate point in time may include (i) the regions (1013) to (1014) of the left adjacent CTU (1010) and (ii) the region (1021) and subregion (1041) of the current CTU (1020).

[0117] 10D, region (1024) includes sub-regions (1051) to (1053). Sub-region (1051) (shaded in dark gray) has already been coded (e.g., encoded or reconstructed), sub-region (1052) is the current CU being coded (e.g., being coded or reconstructed), and sub-region (1053) (white) will be coded later. At a fourth intermediate point in the coding process of the current CTU (1020) where sub-region (1052) of the current CTU (1020) is coded, the RSM is updated to include regions (1021) to (1023) of the current CTU (1020) and sub-region (1051). The RSM at the fourth intermediate point does not include the region in the left adjacent CTU (1010). The reference region at the fourth intermediate point in time may include regions (1021) to (1023) and subregion (1051) of the current CTU (1020).

[0118] II.1.3 Syntax and semantics of IBC mode in VVC

[0119] The IBC architecture in VVC can form a dedicated coding mode in which the IBC mode is the third prediction mode in addition to the intra prediction mode and the inter prediction mode (e.g., the normal inter prediction mode). The bitstream can include an IBC syntax element indicating the IBC mode of the CU, for example, if the size of the CU is 64×64 or less. In some examples, the maximum CU size that can utilize the IBC mode is 64×64 to realize the continuous memory update mechanism of the RSM as described with reference to FIG. 10A-FIG. 10D. In one example, the reference sample addressing mechanism remains the same as that used in the HEVC SCC extension by indicating a 2D offset and reusing the vector (e.g., MV) coding process of the inter prediction mode. In one example, when the CST is active, the coder cannot derive the chroma BV from the corresponding luma BV, resulting in the use of the IBC mode only for the luma CB.

[0120] II.1.4 Reference area and sample memory in IBC mode in VVC

[0121] The IBC design in VVC may use a fixed memory size (e.g., 128×128) per color component to store reference samples. As mentioned above, the fixed memory size may allow for on-chip placement of memory (e.g., RSM) in hardware implementation. In an example such as VVC, the maximum CTU size and the fixed memory size of the IBC mode is 128×128. In one example, when the maximum CTU size configuration is equal to the fixed memory size (e.g., 128×128) of the IBC mode, the RSM contains samples of a single CTU.

[0122] The RSM is characterized by a continuous update mechanism that replaces the reconstructed samples of the left neighboring CTU with the reconstructed samples of the current CTU, as illustrated in Figures 10A-10D. Figures 10A-10D show examples of simplified RSMs of the update mechanism at four intermediate points during a coding process (e.g., a reconstruction process). The light gray shaded areas in Figures 10A-10C may include reference samples of the left neighboring CTU (1010), and the dark gray shaded areas in Figures 10B-10D may include reference samples of the current CTU (1020). Referring to Figure 10A, at the first intermediate point representing the start of coding (e.g., encoding or reconstruction) of the current CTU (1020), the RSM is composed of only the reference samples of the left neighboring CTU (1010). At the other three intermediate points shown in FIGS. 10B-10D, the coding process (eg, the encoding process or the reconstruction process) replaces samples of the left-neighboring CTU (1010) with samples of the current CTU (1020).

[0123] In some examples, the RSM is implicitly divided into four regions, e.g., four disjoint regions of 64x64. The reset of the regions in the RSM may occur when the coder processes the first CU in the corresponding region in the current CTU, facilitating the hardware implementation task. For example, the RSM is mapped to regions in a CTU (e.g., a left adjacent CTU and a current CTU). FIG. 11 illustrates a continuous update process (1100) of the RSM spatially. A left adjacent CTU (1010) and a current CTU (1020) are shown in FIG. 10A-FIG. 10D. The left adjacent CTU (1010) can include regions (1011)-(1014). The current CTU (1020) can include regions (1021)-(1024). The regions (1023) in the current CTU (1020) may include the current CU (1152) being coded, sub-regions (1151) that have already been coded, and sub-regions to be coded (1153). The grey shaded regions may include samples stored in the RSM, and the white unshaded regions may include replaced samples or samples that have not been coded (e.g., samples that have not been reconstructed).

[0124] At coding time (e.g., reconstruction time) shown in FIG. 11, the RSM update process replaces samples covered by white unshaded regions (e.g., regions (1011)-(1013)) in the left-neighboring CTU (1010) with gray shaded regions (e.g., regions (1021)-(1022) and sub-region (1151)) of the current CTU (1020). In FIG. 11, the RSM may include (i) region (1014) in the left-neighboring CTU (1010) and (ii) regions (1021)-(1022) and sub-region (1051) of the current CTU (1020).

[0125] In some examples, if the maximum CTU size is less than the RSM size (e.g., 128x128), the RSM may contain more than a single left adjacent CTU, and multiple adjacent CTUs may be used as reference regions in IBC mode. For example, if the maximum CTU size is 32x32, an RSM with a size of 128x128 may contain samples of 15 adjacent CTUs.

[0126] II.1.5 BV coding in IBC mode in VVC

[0127] BV coding can use the process specified for inter prediction (e.g., normal inter prediction). BV coding can use simpler rules for constructing candidate lists than those used in inter prediction (e.g., normal inter prediction).

[0128] For example, the inter prediction candidate list includes five spatial candidates, one temporal candidate, and six history-based candidates. To avoid duplicate entries in the final inter prediction candidate list, a comparison of multiple candidates can be used for the history-based candidates. The inter prediction candidate list may include pair-wise averaged candidates.

[0129] The candidate list for IBC mode can include two BVs from each spatial neighborhood and five history-based BVs (HBVPs). In one example, the candidate list for IBC mode is limited to two BVs from each spatial neighborhood and five history-based BVs (HBVPs). In one embodiment, in IBC mode, only the first HBVP is compared to the spatial candidates when the first HBVP is added to the candidate list.

[0130] The normal inter prediction mode can use two different candidate lists. For example, one candidate list is for the merge mode and the other candidate list is for the normal mode (e.g., the inter prediction mode that is not a merge mode). The candidate list in the IBC mode can be the same for both IBC modes (e.g., the merge IBC mode and the normal IBC mode). In the IBC mode, the merge mode may use up to six candidates in the candidate list, and the normal mode uses only the first two candidates in the candidate list.

[0131] Block vector difference (BVD) coding can use the MVD process used in normal inter prediction modes, and the final BV can have any size. The determined BV (e.g., the reconstructed BV) may point to an area outside the reference sample area. In one example, a correction to the absolute offset in each direction can be applied using modulo arithmetic based on the width and / or height of the RSM.

[0132] II.2 IBC mode in AV1

[0133] In some examples, such as AV1, IBC mode (or IntraBC mode) uses BV to find a predictive block in the same picture of the current block. BV can be signaled in the bitstream, and the precision of the signaled BV can be integer points. The prediction process in IBC mode can be similar to the prediction process in inter-prediction mode (e.g., inter-picture prediction). The differences between IBC mode and inter-picture prediction are described below. In IBC mode, the predictive block can be formed from reconstructed samples of the current picture (e.g., before applying loop filtering). IBC mode can be considered as "motion compensation" within the current picture, using BV as MV.

[0134] A flag indicating whether IBC mode is enabled for the current block can be transmitted in the bitstream. If IBC mode is enabled for the current block, a BV difference can be derived by subtracting the predicted BV from the current BV, and the BV difference can be classified into four types according to the horizontal and vertical components of the BV difference value. The type information can be signaled into the bitstream, and the BV difference values ​​of the two components (e.g., the horizontal and vertical components) can be signaled following the type information.

[0135] The IBC mode can be effective for coding screen content. The IBC mode can pose challenges to hardware design. To ease the hardware design, the following changes can be adopted in the IBC mode:

[0136] (i) When IBC mode is enabled, the loop filter can be disabled. The loop filter can include a deblocking filter, a Constrained Directional Enhancement Filter (CDEF), and a loop restoration (LR) filter. By disabling the loop filter, the second picture buffer dedicated to enabling IBC mode can be avoided.

[0137] (ii) To facilitate parallel decoding, the prediction cannot exceed a limited area. The coordinates of the top-left position of a superblock are (x0,y0). In a superblock, a prediction at position (x,y) can be accessed in IBC mode if its vertical coordinate is less than y0 and its horizontal coordinate is less than (x0+2(y0-y)). In one example, a prediction at position (x,y) can be accessed in IBC mode only if its vertical coordinate is less than y0 and its horizontal coordinate is less than (x0+2(y0-y)). In one example, a prediction at position (x,y) can be accessed in IBC mode only if its vertical coordinate is less than or equal to y0 and its horizontal coordinate is less than (x0+2(y0-y)).

[0138] (iii) To allow for hardware writeback delay, the immediate reconstruction region is not accessible in IBC mode. The restricted immediate reconstruction region may include 1 to N superblocks, where N is a positive integer. In addition to modification (ii) above, if the coordinates of the top-left position of the superblock (1210) being reconstructed are (x0, y0), then a prediction at position (x, y) is accessible in IBC mode if its vertical coordinate is less than or equal to y0 and its horizontal coordinate is less than (x0+2(y0-y)-D). D may indicate the size of the immediate reconstruction region that is restricted for IBC mode. FIG. 12 shows an example of a restricted immediate reconstruction region. The gray shaded regions include permitted search regions accessible in IBC mode for each current superblock (1210) being reconstructed. The black shaded regions include prohibited search regions that are not accessible in IBC mode for each current superblock (1210). The white unshaded regions include superblocks to be coded (e.g., reconstructed). For the current superblock (1210(1)), the immediate reconstruction region includes the two superblocks (1221)-(1222) to the left of the current superblock (1210(1)) (e.g., N is 2). D denotes the size of 2W, where W is the width of each superblock. Superblocks (1221)-(1222) are not accessible to the current superblock (1210(1)). Region (1230) is accessible to the current superblock (1210(1)).

[0139] II.3 IBC mode with local reference scope in AV1

[0140] An on-chip memory (called RSM) with size M×M (e.g., 128×128) can be allocated to store reference samples used in IBC mode. In one embodiment, the size of the RSM is equal to the size of a superblock, and the size of the superblock is allocated to the RSM. A memory reuse mechanism can be applied to the RSM on an L×L (e.g., 64×64) basis. The RSM can be divided into I RSM units, where I is equal to the ratio of M×M to L×L. For example, if M×M is 128×128 and L×L is 64×64, then I is 4 (128×128 / (64×64)). In the IBC mode described in II.2, a local reference range can be used. The following modifications can be made to the IBC mode described in II.2.

[0141] (i) The maximum block size in IBC mode can be limited to L×L (e.g., 64×64).

[0142] (ii) A reference block in a current superblock (SB) and a corresponding current block may be in the same SB row. In one example, a reference block may only be located in the current SB or the left adjacent SB to the left of the current SB.

[0143] (iii) When an RSM unit with size L×L (e.g., 64×64) starts updating with the reconstructed samples of the current SB, previously stored reference samples within the entire L×L unit (e.g., reference samples of the left adjacent SB) can be marked as unavailable for generating predicted samples to be used in IBC mode.

[0144] FIG. 13 illustrates an exemplary memory reuse mechanism (1300) in which a memory (e.g., RSM (1310)) is updated during coding (e.g., encoding or decoding) of a current SB (1301) in a current picture according to one embodiment of the present disclosure. The top block illustrates the RSM (1310) in state (0). The top row illustrates the RSM (1310) in states (1)-(4). The bottom row illustrates the current SB (1301) being coded and the left neighboring SB (1302) in the current picture in states (0)-(4). The left neighboring SB (1302) can be to the left of the current SB (1301). In the example of FIG. 13, a quadtree partition is used at the SB root, and the SB can include four regions. In one example, the size of each of the four regions is 64×64. In one example, the current SB (1301) includes four regions 4-7, and the left adjacent SB (1302) includes four regions 0-3.

[0145] At the start state (0) of coding each SB, such as the current SB (1301), the RSM (1310) can store samples of the previously coded SB (e.g., the left adjacent SB (1302)). If the current block is located in one of the four regions (e.g., the four 64x64 regions) in the current SB (1301), the corresponding region in the RSM (1310) is emptied and can be used to store samples of the current coding region (e.g., the current 64x64 coding region). The samples in the RSM (1310) can be gradually updated by the samples in the current SB (1301).

[0146] Referring to state (1), the current block (1311) is currently located in region 4 in the SB (1301), and the corresponding region (e.g., the top left region) in the RSM (1310) is emptied and can be used to store samples of region 4, the current region being coded. Referring to the bottom row, a BV (e.g., encoded BV or decoded BV) (1321) can point from the current block (1311) to a reference block (1331) that is within a search range (1341) of the current block (1311) (the boundaries of the search range (1341) are marked with dashed lines). Referring to the top row, a corresponding offset (1351) in the RSM (1310) can point from the current block (1311) to a reference block (1331) in the RSM (1310). Referring to state (1), the search range (1341) includes areas 1 to 3 in the left adjacent SB (1302) and the coded sub-area (1361) in area 4. The search range (1341) does not include area 0 in the left adjacent SB (1302).

[0147] Referring to state (2), the current block (1312) is currently located in region 5 in the SB (1301), and the corresponding region in the RSM (1310) (e.g., the top right region) is emptied and can be used to store samples of region 5, the current region being coded. A BV (e.g., encoded BV or decoded BV) (1322) can point from the current block (1312) to a reference block (1332) that is within a search range (1342) of the current block (1312) (the boundaries of the search range (1342) are marked with dashed lines). A corresponding offset (1352) in the RSM (1310) can point from the current block (1312) to the reference block (1332) in the RSM (1310). Referring to state (2), the search range (1342) includes (i) areas 2-3 in the left adjacent SB (1302) and (ii) the coded sub-area (1362) in areas 4 and 5 in the current SB (1301). The search range (1342) does not include areas 0-1 in the left adjacent SB (1302).

[0148] Referring to state (3), the current block (1313) is currently located in region 6 in the SB (1301), and the corresponding region in the RSM (1310) (e.g., the bottom left region) is emptied and can be used to store samples of region 6, the current region being coded. The BV (e.g., the coded BV or the decoded BV) (1323) can point from the current block (1313) to a reference block (1333) that is within a search range (1343) of the current block (1313) (the boundaries of the search range (1343) are marked with dashed lines). The corresponding offset (1353) in the RSM (1310) can point from the current block (1313) to the reference block (1333) in the RSM (1310). Referring to state (3), the search range (1343) includes (i) region 3 in the left adjacent SB (1302) and (ii) the coded sub-region (1363) in regions 4-5 and region 6 in the current SB (1301). The search range (1343) does not include regions 0-2 in the left adjacent SB (1302).

[0149] Referring to state (4), the current block (1314) is currently located in region 7 in the SB (1301), and the corresponding region (e.g., the bottom right region) in the RSM (1310) is emptied and can be used to store samples of region 7, the current region being coded. A BV (e.g., an encoded BV or a decoded BV) (1324) can point from the current block (1314) to a reference block (1334) that is within a search range (1344) of the current block (1314) (the boundaries of the search range (1344) are marked with dashed lines). A corresponding offset (1354) in the RSM (1310) can point from the current block (1314) to a reference block (1334) in the RSM (1310). Referring to state (4), the search range (1344) includes regions 4-6 currently in the SB (1301) and the coded sub-region (1364) in region 7. The search range (1344) does not include areas 0 to 3 in the left adjacent SB (1302).

[0150] If the current SB (1301) is completely coded, the entire RSM (1310) can be filled with all samples of the current SB (1301).

[0151] In the example shown in Figure 13, the current SB (1301) is partitioned using quadtree partitioning. The coding order of the four regions in the current SB (1301) may be the top left region (e.g., region 4), the top right region (e.g., region 5), the bottom left region (e.g., region 6), and the bottom right region (e.g., region 7). In determining other block partitions as shown in Figures 14A-14B, the RSM update process may be similar to that shown in Figure 13, for example, by replacing each region in the RSM with a reconstructed sample in the current SB.

[0152] 14A-14B show an exemplary memory update process in the RSM during coding (e.g., encoding or decoding) of a current SB (1401). In FIG. 14A-14B, a left adjacent SB (1402) is to the left of the current SB (1401) being coded (e.g., encoded or decoded). In one example, the size of each of the current SB (1401) and the left adjacent SB (1402) is 128×128. Each of the current SB (1401) and the left adjacent SB (1402) can include four regions (e.g., four blocks) having a size of 64×64. The current SB (1401) can include blocks 4-7, and the left adjacent SB (1402) can include blocks 0-3.

[0153] In FIG. 14A, horizontal division is performed in the SB route, followed by vertical division. An SB (e.g., a current SB (1401)) may include four blocks: an upper left block (e.g., block 4), a lower left block (e.g., block 6), an upper right block (e.g., block 5), and a lower right block (e.g., block 7). The coding order of the current SB (1401) may be the upper left block (state 1), the upper right block (state 2), the lower left block (state 3), and the lower right block (state 4).

[0154] In Figure 14B, vertical division is performed in the SB route, followed by horizontal division. The coding order of the current SB (1401) can be the upper left block (state 1), the lower left block (state 2), the upper right block (state 3), and the lower right block (state 4).

[0155] Depending on the location of the current block (eg (1431)) relative to the current SB (1401), the following may apply:

[0156] (i) Referring to state (1) in Figures 14A and 14B, the current block (1431) is currently in the top left block (e.g., block 4) of the SB (1401), and the RSM may include reference samples in the bottom right block (e.g., block 3), bottom left block (e.g., block 2), and top right block (e.g., block 1) of the left-neighboring SB (1402) in addition to already reconstructed samples in block (1461) in block 4.

[0157] (ii) Referring to state (2) in FIG. 14A or state (3) in FIG. 14B, the current block (1432) is currently in the upper right block (e.g., block 5) of SB (1401).

[0158] As shown in state (2) in FIG. 14A , if the luma sample located at the top left corner of block 6 (e.g., (0,64) relative to current SB (1401)) has not yet been reconstructed, the current block (1432) can reference reference samples in the bottom left block (e.g., block 2) and bottom right block (e.g., block 3) of the left-neighboring SB (1402), in addition to the already reconstructed samples in block 4 and block (1462) in block 5. The corresponding RSM can include reference samples in the bottom left block (e.g., block 2) and bottom right block (e.g., block 3) of the left-neighboring SB (1402), in addition to block 4 and block 5 block (1462).

[0159] Otherwise, as shown in state (3) in Figure 14B, if the luma sample located in the upper left corner of block 6 (e.g., (0,64) relative to the current SB (1401)) is being reconstructed, then the current block (1432) can reference a reference sample in the lower right block (e.g., block 3) of the left-neighboring SB (1402). The corresponding RSM can include a reference sample in the lower right block (e.g., block 3) of the left-neighboring SB (1402) in addition to the already reconstructed samples in blocks 4 and 6 and block (1462) in block 5.

[0160] (iii) Referring to state (3) in FIG. 14A or state (2) in FIG. 14B, the current block (1433) is currently the bottom left block (eg, block 6) of SB (1401).

[0161] As shown in state (2) in Figure 14B, if the luma sample located at the top left corner of block 5 (e.g., (64,0) relative to current SB (1401)) has not yet been reconstructed, the current block (1433) can refer to reference samples in the top right block (e.g., block 1) and bottom right block (e.g., block 3) of the left neighboring SB (1402), in addition to the already reconstructed samples in block 4 and block (1463) currently in SB (1401). The corresponding RSM can include reference samples in the top right block (e.g., block 1) and bottom right block (e.g., block 3) of the left neighboring SB (1402), in addition to block 4 and block (1463) currently in SB (1401).

[0162] Otherwise, as shown in state (3) in Figure 14A, if the luma sample located in the upper left corner of block 5 (e.g., (64,0) relative to current SB (1401)) is being reconstructed, then the current block (1433) can reference a reference sample in the lower right block (e.g., block 3) of the left-neighboring SB (1402). The corresponding RSM can include a reference sample in the lower right block (e.g., block 3) of the left-neighboring SB (1402) in addition to the already reconstructed samples in blocks 4-5 and block (1463) in the current SB (1401).

[0163] (iv) Referring to state (4) in Figures 14A-14B, the current block (1434) is in the bottom right block (e.g., block 7) of the current SB (1401). The current block (1434) can reference already reconstructed samples in the current SB (1401), such as already reconstructed samples in blocks 4-6 and block (1464). The corresponding RSM can include reference samples in blocks 4-6 and block (1464). In one example, if the current block (1434) is the bottom right block of the current SB (1401), then the current block can only reference already reconstructed samples in the current SB (1401).

[0164] III. IBC mode with adaptive local reference scope

[0165] The performance of the IBC mode may be highly dependent on the reference range used in the IBC mode. In related techniques such as the IBC mode in VVC and the IBC mode with local reference range, a certain memory update mechanism can be used in the RSM. In one example, as described in FIG. 13, FIG. 14A, and FIG. 14B, the memory update in the RSM depends only on the block position of the current block and the partition of the current CTU or the current SB. The memory update does not depend on, for example, the content or prediction information of the current block during the memory update process. Thus, in some embodiments, for a region in a picture with little or no texture content, including the region in a reference range (e.g., a local reference range) and storing the region in the picture in the RSM may have limited benefits for prediction efficiency of the IBC mode. According to one embodiment of the present disclosure, an adaptive reference range, such as an adaptive local reference range, can be used in the IBC mode.

[0166] In the following description, the term block may be interpreted as a transform block (TB), PB, coding block (CB), coding unit (CU), superblock in a picture, CTU or CTB, etc. The block size may indicate a block width, a block height, a maximum value of the block width and the block height, a minimum value of the block width and the block height, a region size (e.g., block width x block height), an aspect ratio of a block (e.g., block width / block height, or block height / block width), etc.

[0167] In some examples, a size of 64×64 is used as an example of a memory update area unit. The memory update area unit can be any block size and is not limited to a size of 64×64. Examples of memory update area units include areas 0 to 7 in FIG. 13 and areas 0 to 7 in FIG. 14A to FIG. 14B.

[0168] According to an embodiment of the present disclosure, whether to update the local reference range used in IBC mode is determined based on a reconstructed region in the superblock being reconstructed in the current picture. The superblock may contain one or more CBs. The local reference range may be limited. In one example, the maximum size of the local reference range is limited to be the size of a plurality of superblocks, for example, the size of two superblocks shown in Figures 13, 14A, and 14B. In one example, the spatial extent of the local reference range is limited to be within a plurality of superblocks, for example, a superblock and its left neighboring superblock as shown in Figures 13, 14A, and 14B. In some embodiments, whether to update the previous local reference range is determined based on (i) the content of the reconstructed region and / or (ii) prediction information of the reconstructed region.

[0169] The size of the reconfiguration area may be equal to the size of a memory update area unit (e.g., 64×64) if the size of the memory update area unit is less than the size of the reconfigured CB. The reconfiguration area may be the reconfigured CB if the size of the reconfigured CB is less than or equal to the size of the memory update area unit.

[0170] The content of the reconstructed region may include texture content and / or screen content of the reconstructed region. The content of the reconstructed region may be determined based on reconstructed samples (or reconstructed pixels) of the reconstructed region.

[0171] The prediction information of the reconstructed region may indicate a prediction mode used to reconstruct the region. In one embodiment, whether to update the previous local reference range is determined based on whether the prediction mode is in a set of predefined prediction modes. If the prediction mode is in the set of predefined prediction modes, the previous local reference range may be updated. If the prediction mode is not in the set of predefined prediction modes, the previous local reference range is not updated. In one embodiment, the set of predefined prediction modes includes screen content coding modes such as IBC mode, palette mode, transform skip mode, block based delta pulse code modulation (BDPCM) mode, etc.

[0172] In one embodiment, the prediction information indicates whether to update the previous local reference range with the reconstructed samples in the reconstructed region, e.g., via a flag included in the prediction information for the region. Thus, whether to update the previous local reference range may be based on an indication (e.g., a flag) in the prediction information of whether to update the previous local reference range with the reconstructed samples in the reconstructed region.

[0173] In one embodiment, the memory update process in an IBC mode RSM depends on the contents (e.g., values ​​of the reconstructed samples) of the current block or region (e.g., a 64x64 region) and / or prediction information (or coded information) of the current block or region.

[0174] In one example, after a current block (e.g., a current CB) or region (e.g., a 64×64 region) is reconstructed, an evaluation of the contents (e.g., values ​​of reconstructed samples) of the current block or region is performed. Whether to perform a memory update can be determined based on the evaluation. FIG. 15 illustrates an exemplary adaptive memory update process in an RSM when a current SB (1501) is being decoded. Each of the current SB (1501) and the left neighboring SB (1502) of the current SB (1501) includes four regions. The current SB (1501) includes regions 4-7, and the left neighboring SB (1502) includes regions 0-3. In one example, each of the regions 0-7 has a size of 64×64. The left SB (1502), which includes regions 0-3, is being reconstructed. A previous local reference range used in the IBC mode is stored in the RSM. In one example, the previous local reference range includes regions 1-3. In the example shown in FIG. 15, the local reference range of region 5 does not include region 0.

[0175] Region 4 in the current SB (1501) is reconstructed, for example, after the reconstruction of the left SB (1502). The contents of region 4 (e.g., reconstruction samples) can be evaluated to determine whether to perform a memory update to update the RSM that stores the previous local reference range. If the decision is to not update the RSM, the RSM is not updated and the previous local reference range is not updated either. The previous local reference range can be used to reconstruct region 5 (e.g., the current region being reconstructed). In one example, the previous local reference range includes regions 1-3 and does not include region 4, which has already been reconstructed before the reconstruction of region 5. Thus, the search region for region 5 includes regions 1-3 and does not include region 4. In one example, the search region for region 5 includes the already reconstructed part of region 5 being reconstructed.

[0176] In one embodiment, the evaluation process determines whether the texture content of a reconstructed block or reconstructed region (e.g., a 64x64 region) satisfies a condition. With reference to Fig. 15, the texture content of the reconstructed region 4 can be evaluated. For example, the percentage of texture content of the reconstructed block or reconstructed region is determined. If the percentage of texture content of the reconstructed block or reconstructed region is equal to or greater than a threshold, it is determined that the condition is met. Otherwise, it is determined that the condition is not met.

[0177] The content of the reconstructed block or region can be determined by any suitable method, such as based on a histogram of intensity values ​​of one or more color components. In one example, if the histogram contains more than N0 and less than N1 distinct intensity values ​​in one or more color components, the reconstructed block or region is determined as a screen content region. Otherwise, the reconstructed block or region is determined as a texture region. A texture region can be captured by a camera and can be referred to as a natural region or a camera capture region. In one example, a screen content region is not captured by a camera. Referring to FIG. 15, a histogram of intensity values ​​in one or more color components associated with region 4 can be used to determine whether region 4 is a texture region or a screen content region.

[0178] In one embodiment, the evaluation process determines whether a reconstructed block or region (e.g., a 64×64 region) is coded by a prediction mode(s) from a set of predefined prediction modes. In one example, the set of predefined prediction modes includes screen content coding mode(s), such as IBC mode, palette mode, transform skip mode, BDPCM mode, etc.

[0179] In one embodiment, if the evaluation process determines that the screen content of a reconstructed block or reconstructed region (e.g., a 64x64 region) satisfies a condition, e.g., if the amount or percentage of the screen content is below a threshold, the memory update process is skipped for the reconstructed block or reconstructed region and therefore is not performed after coding (e.g., encoding or decoding) the block or region. If the memory update process is skipped, the previous local reference range stored in the RSM is used to decode another coded block or another region that is reconstructed. In one example, the reconstructed block or reconstructed region does not contain screen content, and the memory update process is skipped for the reconstructed block or reconstructed region and therefore is not performed after coding the block or region.

[0180] In the example shown in Figure 15, the size of each of areas 0 to 7 is equal to the size of a memory update area unit. The size of the RSM is equal to the size of a superblock. The embodiments described with reference to Figure 15 may be suitably applied to other situations where a superblock may include any suitable number of areas having any suitable size. The size of the RSM may be equal to the size of the superblock, or may be greater than the size of the superblock, or may be less than the size of the superblock.

[0181] In the example shown in Figure 15, the evaluation process is based on a region (e.g., region 4) that has the same size as the memory update region unit. Therefore, if the evaluation process indicates that the previous local reference range is updated after reconstructing the region, the reconstruction samples in the entire region are used to update the previous local reference range.

[0182] In some examples, the evaluation process is based on a portion of the region having the same size as the memory update region unit. For example, the size of the CB is smaller than the size of the memory update region unit, and the portion of the region is the CB. If the evaluation process indicates that the previous local reference range is updated after reconstructing the portion of the region (e.g., the CB), the reconstructed sample of the portion of the region (e.g., the CB) is used to update the previous local reference range. In one example, for a region having a size of the memory update region unit, the first portion of the region can be used to update the previous reference range, and the second portion of the region is not used to update the previous reference range. Thus, the local reference range can include the first reconstructed sample of the first portion of the region and does not include the second reconstructed sample of the second portion of the region. When the location(s) of the second reconstructed sample of the second portion of the region are referenced by the BV, a padding process can be used to generate samples used in the IBC mode, as shown in FIG. 16.

[0183] 16 illustrates an exemplary padding process used in the adaptive memory update process. Each of the current SB (1601) and the left adjacent SB (1602) of the current SB (1601) includes four regions. The current SB (1601) includes regions 4-7, and the left adjacent SB (1602) includes regions 0-3. In one example, each of regions 0-7 has a size of 64x64. The left SB (1602) includes regions 0-3, and regions 4-5 of the current SB (1601) have already been reconstructed.

[0184] Region 4 includes a first portion (1611) and a second portion (1612). In one example, the first portion (1611) is the first CB, and the second portion (1612) is the second CB. In one example, a memory update is performed, and the local reference range used in the IBC mode is updated to include the first CB (1611). A memory update is not performed after reconfiguring the second CB (1612), and the local reference range used in the IBC mode is not updated to include the second CB (1612). In one example, after reconfiguring region 5, the local reference range includes region 3, the first portion (1611) in region 4, and region 5. In the example shown in FIG. 16, the local reference range does not include regions 0 to 2 in the left adjacent SB (1602). The local reference range does not include the second portion (1612) in region 4. The second portion (1612) in region 4 is not stored in the RSM.

[0185] In one embodiment, when performing IBC prediction using a local reference range stored in the RSM, if not all of the reconstructed samples in a region (e.g., region 4 in FIG. 16) are stored in the RSM, a padding process can be applied to fill the region (e.g., region 4 in FIG. 16) in the RSM. Referring to FIG. 16, CB (1632) in region 6 is reconstructed in IBC mode. Samples of a second portion (1612) in region 4 can be generated by a padding process before being used as reference samples in IBC mode for CB (1632).

[0186] In one example, a single value is assigned to the second portion (1612) in region 4 of the local reference range stored in the RSM. For example, each sample in the second portion (1612) has the same value equal to the single value. In one example, the single value is based on a sample or samples that are available and adjacent to the second portion (1612). The samples that are available and adjacent to the second portion (1612) can be located within region 4 or outside region 4. In one example, the single value is equal to the value of one of the sample or samples that are adjacent to the second portion (1612).

[0187] In one example, the padding process is performed by performing a particular intra prediction, such as DC prediction, planar prediction, etc., on the second portion (1612) in region 4 in the RSM using available and neighboring samples of the second portion (1612) in region 4.

[0188] In one example, the padding process is performed by copying adjacent samples of the second portion (1612) that are available and within region 4.

[0189] In some examples, the padding process is performed on the outer border area of ​​region 4.

[0190] In one embodiment, when performing a memory update process in the RSM, the stored blocks (or stored regions) in the RSM can be ranked. Which of the stored blocks in the RSM is replaced during the memory update process can be determined based on the ranking. In one example, each of the stored blocks has a size of a memory update region unit (e.g., 64×64).

[0191] 17, the current SB (1701) and the left adjacent SB (1702) of the current SB (1701) each include four regions. The current SB (1701) includes regions 4 to 7, and the left adjacent SB (1702) includes regions 0 to 3. In one example, each of the regions 0 to 7 has a size of 64x64. The left SB (1702) including regions 0 to 3 is being reconstructed.

[0192] Referring to the left side of Figure 17, region 4 is being reconstructed, and regions 5-7 have not yet been reconstructed. The local reference range used in IBC mode is stored in the RSM. In one example, the local reference range includes regions 1-3 and does not include region 0.

[0193] 17, after reconstructing region 4, the local reference range is updated based on the reconstructed region 4. In one example, regions 1-3 stored in the RSM are ranked. Which of regions 1-3 is replaced by the reconstructed region 4 during the memory update process can be determined based on the ranking. For example, if the ranking indicates that region 2 is to be replaced, the local reference range is updated by replacing region 2 with the reconstructed region 4. The updated local reference range on the right side of FIG. 17 includes regions 1, 3, and 4.

[0194] In one example, a percentage of the reconstruction samples that correspond to the screen content is determined for each of the stored blocks in the RSM (e.g., areas 1-3 in FIG. 17). Based on the ranking of the percentage of the screen content for each stored block, it is determined which of the stored blocks stored in the RSM are replaced during the memory update process.

[0195] In one example, a proportion of the reconstruction samples corresponding to the texture region is determined for each of the stored blocks in the RSM (e.g., regions 1-3 in FIG. 17). Based on the ranking of the proportion of the texture region of each stored block, it is determined which of the stored blocks stored in the RSM are replaced during the memory update process.

[0196] In one example, a frequency (e.g., a reference frequency) associated with each of the blocks (e.g., areas 1-3 in FIG. 17) stored in the RSM is determined. In one example, the reference frequency indicates the number of times each stored block is referenced by a BV in IBC mode to predict a CB in a current picture or a part of a current picture. Based on the ranking of the reference frequency of each stored block, it is determined which of the blocks stored in the RSM are replaced during the memory update process.

[0197] In one example, the number of specially coded samples (e.g., region size) of each of the stored blocks (e.g., regions 1-3 in FIG. 17) is determined, and the specially coded samples are coded in one or more prediction modes within a set of predefined prediction modes. In one example, the set of predefined prediction modes includes screen content coding modes such as IBC mode, palette mode, transform skip mode, BDPCM mode, etc., as described above. Based on the ranking of the number of specially coded samples of each of the stored blocks, it is determined which of the stored blocks stored in the RSM are to be replaced during the memory update process.

[0198] In addition to or instead of determining whether to update the local reference range based on the content or prediction mode(s) of the reconstructed region or reconstructed block, whether to update the local reference range can be determined based on prediction information of the reconstructed region or reconstructed block indicating whether to update the local reference range. For example, the prediction information includes a flag (e.g., an indication flag) of the reconstructed region or reconstructed block that explicitly indicates whether to update the local reference range, and whether to update the local reference range is determined based on the flag. In some examples, whether to update the local reference range is determined based on the flag, content and / or prediction mode of the reconstructed region or reconstructed block.

[0199] In one embodiment, the adaptive memory update process is similar to the embodiment described in Figures 15-17, except that whether the memory update process is performed in an RSM in IBC mode depends on an indication (e.g., a flag) sent in the bitstream for each memory update area unit.

[0200] In one embodiment, for each coded region (e.g., the size of the coded region is the same as the size of the memory update region unit), a flag is signaled to indicate whether the reconstructed samples in the coded region are stored in the RSM. If the flag indicates that the reconstructed samples in the coded region are stored in the RSM, the memory update process is performed as described in this disclosure. Otherwise, if the flag indicates that the reconstructed samples in the coded region are not stored in the RSM, the reconstructed samples in the coded region do not need to be stored in the RSM. For example, the memory update process is skipped.

[0201] In one embodiment, when the current block size (e.g., the size of the CB) is larger than the size of the memory update region unit, the current block (e.g., the CB) can include multiple regions, each of the multiple regions having a size of the memory update region unit. A first flag of a first region in the current block can be signaled, and subsequent flags of other regions in the current block can be inferred or signaled. In one example, the subsequent flag can be inferred from the first flag of the first region in the current block. For example, the subsequent flag uses the same value as the first flag of the first region. In one example, the subsequent flag is signaled, and each flag is signaled separately for each of the multiple regions. Whether or not a sample in each region is stored in the RSM can be determined based on the respective flag signaled in the bitstream. Thus, multiple flags are signaled for the current block.

[0202] In one embodiment, a flag of the fixed-size region is signaled to indicate whether samples in the fixed-size region are stored in the RSM. The fixed-size region can be larger than the memory update region unit. For example, the fixed-size region is a superblock, CTU, or CTB, e.g., having a size of 128×128, and the size of the memory update region unit is 64×64. This flag can be used to indicate whether any samples in the fixed-size region (e.g., superblock, CTU, or CTB) are stored in the RSM.

[0203] In some embodiments of the present disclosure, a superblock is used as an example, as described with reference to Figures 15 to 17. The description is also applicable to a CTU or a CTB and can be adapted by replacing the superblock with a CTU or a CTB.

[0204] FIG. 18 shows a flow chart outlining an encoding process (1800) according to an embodiment of the present disclosure. In various embodiments, the process (1800) is performed by processing circuitry, such as processing circuitry within terminal devices (310), (320), (330), and (340), processing circuitry performing the functions of a video encoder (e.g., (403), (603), (703)), etc. In some embodiments, the process (1800) is implemented with software instructions, and thus the processing circuitry performs the process (1800) as the processing circuitry executes the software instructions. The process begins at (S1801) and proceeds to (S1810).

[0205] At (S1810), a region in a superblock or coding tree block (CTB) in a current picture may be coded based on prediction information of the region. The prediction information of the region may indicate one or more prediction modes of the region. The region may be coded based on one or more prediction modes of the region. In one example, the region is a CB in a superblock or CTB. In one example, the region is a part of a CB. In one example, the size of the superblock or CTB is 128×128. In one example, the size of the region is a size of a memory update region unit, such as 64×64.

[0206] In (S1820), it can be determined whether to update a previous local reference range for intra block copy (IBC) mode based on (i) the content of the region and / or (ii) the prediction information of the region. In one example, the content of the region is indicated by samples in a corresponding reconstructed region, where the samples are reconstructed samples in the spatial domain.

[0207] In one example, the content of the region indicates a percentage of texture content and / or a percentage of screen content in the region. Whether to update the previous local reference range of the IBC mode is determined based on the percentage of texture content and / or the percentage of screen content in the region. For example, the content of the region does not include screen content, and it is determined that the previous local reference range of the IBC mode is not updated.

[0208] In one example, whether to update the previous local reference range of an IBC mode is determined based on whether one or more prediction modes are in a set of predefined prediction modes.

[0209] In response to a decision not to update the previous local reference range in the IBC mode, the process (1800) proceeds to (S1830). Otherwise, in response to a decision to update the previous local reference range in the IBC mode, the process (1800) proceeds to a branch including (S1840) and (S1850).

[0210] In (S1830), the coding block (CB) in the current picture can be coded using an IBC mode based on the previous local reference range that does not include samples in the region. After (S1830), the process (1800) proceeds to (S1899) and ends.

[0211] In the branch including (S1840) and (S1850), it is determined that the previous local reference range in the IBC mode is updated.

[0212] At (S1840), a current local reference range can be generated based on the previous local reference range and the samples (eg, reconstructed samples) in the corresponding reconstruction domain.

[0213] The previous local reference range can include multiple regions stored in a reference sample memory (RSM). The current local reference range can be generated by replacing a reference sample in one of the multiple regions in the previous local reference range with a sample in the region.

[0214] In some embodiments, which of the multiple regions in the previous local reference range is replaced is determined based on a ranking of the multiple regions. Thus, the region in the multiple regions to be replaced by the sample in the region can be selected based on the ranking of the multiple regions. The current local reference range can be generated by replacing the selected region in the previous local reference range with the sample in the region.

[0215] In some examples, the multiple regions are ranked based on the content of the multiple regions, each of which can correspond to a respective one of the multiple regions. In one example, each of the content corresponding to a respective one of the multiple regions is indicated by a percentage of screen content or a percentage of texture content in the corresponding region, and the multiple regions are ranked based on the respective percentage of screen content or the respective percentage of texture content of the multiple regions.

[0216] In some examples, each region of the plurality of regions includes a plurality of specially coded reference samples in the respective region that are coded in one or more prediction modes in a set of predetermined prediction modes. The plurality of regions can be ranked based on each of the plurality of specially coded samples in the plurality of regions.

[0217] In some examples, the reference frequency associated with each region of the plurality of regions indicates the number of times the respective region is referenced by block vectors used to predict the CB in the current picture or a portion of the current picture. The plurality of regions can be ranked based on their respective reference frequencies.

[0218] After (S1840), the process (1800) proceeds to (S1850). In (S1850), the CB can be encoded using an IBC mode based on the current local reference range. After (S1850), the process (1800) proceeds to (S1899) and ends.

[0219] The process (1800) may be adapted to various scenarios as appropriate, and the steps within the process (1800) may be adjusted accordingly. One or more of the steps within the process (1800) may be adapted, omitted, repeated, and / or combined. Any suitable order may be used to perform the process (1800). Additional steps may be added.

[0220] In some examples, the prediction information includes a flag indicating whether to update a previous local reference range with samples in the region. The flag can be encoded and included in the video bitstream. In one example, a single flag is signaled for the CB. In one example, multiple flags are signaled for the CB. For example, the CB includes multiple regions, each of the multiple regions having a size of a memory update region unit, and a separate flag is signaled for each region.

[0221] FIG. 19 shows a flow chart outlining a decoding process (1900) according to an embodiment of the present disclosure. In various embodiments, the process (1900) is performed by processing circuitry such as processing circuitry in the terminal devices (310), (320), (330), and (340), processing circuitry performing the functions of a video encoder (403), processing circuitry performing the functions of a video decoder (410), processing circuitry performing the functions of a video decoder (510), processing circuitry performing the functions of a video encoder (603), etc. In some embodiments, the process (1900) is implemented with software instructions, and thus the processing circuitry performs the process (1900) as the processing circuitry executes the software instructions. The process begins at (S1901) and proceeds to (S1910).

[0222] At (S1910), a region within a block in a current picture can be reconstructed from the coded video bitstream. The block can include one or more coded blocks (CBs) in the current picture. The block can be a superblock or CTB in the current picture. In one example, a block such as a superblock or CTB is the largest CB in the current picture. In one example, the region is a CB within the superblock or CTB. In one example, the region is a portion of a CB within the superblock or CTB. In one example, the size of the block is 128×128. In one example, the size of the region is a size of a memory update region unit, such as 64×64.

[0223] In (S1920), as described in the present disclosure, such as in FIG. 15, after reconstruction, whether to update the previous local reference range in intra block copy (IBC) mode can be determined based on (i) the content of the reconstruction area and / or (ii) prediction information of the reconstruction area.

[0224] In one embodiment, whether to update the previous local reference range of the IBC mode is determined based on the content of the reconstructed region. For example, the content of the reconstructed region is determined based on the reconstructed samples in the reconstructed region, and the content of the reconstructed region indicates a proportion of texture content and / or a proportion of screen content in the reconstructed region. Therefore, whether to update the previous local reference range of the IBC mode is determined based on a proportion of texture content and / or a proportion of screen content in the reconstructed region. In one example, the content of the region does not include screen content, and it is determined that the previous local reference range of the IBC mode is not updated.

[0225] In one embodiment, whether to update the previous local reference range in the IBC mode is determined based on prediction information of the reconstructed region. The prediction information is decoded.

[0226] In one example, the prediction information of the region indicates one or more prediction modes of the region. Whether to update the previous local reference range of the IBC mode is determined based on whether the one or more prediction modes are in a set of predefined prediction modes. In one example, the set of predefined prediction modes includes screen content coding mode(s), such as IBC mode, palette mode, transform skip mode, BDPCM mode, etc.

[0227] In one example, the prediction information of the region indicates whether to update the previous local reference range with the reconstructed samples in the reconstructed region. Whether to update the previous local reference range of the IBC mode can be determined based on an indication of whether to update the previous local reference range with the reconstructed samples in the reconstructed region in the prediction information. For example, whether to update the previous local reference range with the reconstructed samples in the reconstructed region is indicated by a flag included in the prediction information of the region. Whether to update the previous local reference range of the IBC mode can be determined based on the flag. In one example, the flag is signaled in the coded video bitstream.

[0228] In one example, a separate flag is signaled for each region having a size in memory update region units, such as 64 x 64. In one example, a separate flag is signaled for each CB.

[0229] A separate flag is signaled for each superblock or CTB. In one example, the flag indicates whether any reconstructed samples in a block (e.g., superblock or CTB) are used when updating the local reference range in IBC mode. Thus, a single flag (e.g., flag) can be used to indicate whether reconstructed samples in multiple regions in a block (e.g., superblock or CTB) are used when updating the local reference range in IBC mode. In one example, each of the multiple regions is a CB or a portion of a CB. In one example, the size of each of the multiple regions is a size in memory update region units, such as 64×64.

[0230] In response to a decision not to update the previous local reference range in the IBC mode, the process (1900) proceeds to (S1930). Otherwise, in response to a decision to update the previous local reference range in the IBC mode, the process (1900) proceeds to a branch including (S1940) and (S1950).

[0231] In (S1930), it is determined that the previous local reference range of the IBC mode is not updated. Therefore, the previous local reference range of the IBC mode is not updated. A coding block (CB) in the current picture can be decoded using the IBC mode based on the previous local reference range that does not include the reconstruction region. In one example, the CB is in a superblock or a CTB.

[0232] After (S1930), the process (1900) proceeds to (S1999) and ends.

[0233] In the branch including (S1940) and (S1950), it is determined that the previous local reference range in the IBC mode is updated.

[0234] In (S1940), a current local reference range can be generated based on the previous local reference range and the reconstruction samples in the reconstruction domain.

[0235] The previous local reference range can include multiple regions stored in a reference sample memory (RSM), and the current local reference range can be generated by replacing a reference sample in one of the multiple regions in the previous local reference range with a reconstructed sample in the reconstructed region.

[0236] In some embodiments, which of the multiple regions in the previous local reference range is replaced is determined based on a ranking of the multiple regions. Thus, the region in the multiple regions to be replaced by the reconstructed sample in the reconstruction range can be selected based on the ranking of the multiple regions. The current local reference range can be generated by replacing the selected region in the previous local reference range with the reconstructed sample in the reconstruction range.

[0237] In some examples, the multiple regions are ranked based on the content of the multiple regions, each of which can correspond to a respective one of the multiple regions. In one example, each of the content corresponding to a respective one of the multiple regions is indicated by a percentage of screen content or a percentage of texture content in the corresponding region, and the multiple regions are ranked based on the respective percentage of screen content or the respective percentage of texture content of the multiple regions.

[0238] In some examples, each region of the plurality of regions includes a plurality of specially coded reference samples within the respective region that are coded in one or more prediction modes within a set of predetermined prediction modes. The plurality of regions can be ranked based on each of the plurality of specially coded reference samples within the plurality of regions.

[0239] In some examples, the reference frequency associated with each region of the plurality of regions indicates the number of times the respective region is referenced by block vectors used to predict the CB in the current picture or a portion of the current picture. The plurality of regions can be ranked based on their respective reference frequencies.

[0240] At (S1950), the CB in the current picture can be decoded using the IBC mode based on the current local reference range that includes the reconstructed region.

[0241] After (S1950), the process (1900) proceeds to (S1999) and ends.

[0242] The process (1900) may be adapted to various scenarios as appropriate, and the steps within the process (1900) may be adjusted accordingly. One or more of the steps within the process (1900) may be adapted, omitted, repeated, and / or combined. Any suitable order may be used to perform the process (1900). Additional steps may be added.

[0243] In one example, the previous local reference range includes a plurality of regions. The reconstructed samples of the plurality of regions are stored in the RSM, except for the reconstructed samples of the subregions in one of the plurality of regions. The reconstructed samples of the subregions in one of the plurality of regions are replaced by a padding process that stores padded samples corresponding to the subregions in one of the plurality of regions in the RSM.

[0244] The embodiments in this disclosure may be used individually or combined in any order. Furthermore, each of the methods (or embodiments), the encoder, and the decoder may be implemented by a processing circuit (e.g., one or more processors or one or more integrated circuits). In one example, the one or more processors execute a program stored on a non-transitory computer-readable medium.

[0245] The techniques described above can be implemented as computer software using computer readable instructions and can be physically stored on one or more computer readable media. For example, Figure 20 illustrates a computer system (2000) suitable for implementing certain embodiments of the disclosed subject matter.

[0246] Computer software can be coded using any suitable machine code or computer language and can be subject to assembly, compilation, linking, or similar mechanisms to produce code containing instructions that can be executed by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., either directly, or through interpretation, microcode execution, etc.

[0247] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, Internet of Things devices, etc.

[0248] The components illustrated in Figure 20 for the computer system (2000) are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing the embodiments of the present disclosure, nor should the arrangement of components be interpreted as having any dependency or requirement regarding any one or combination of components illustrated in the exemplary embodiment of the computer system (2000).

[0249] The computer system (2000) may include certain human interface input devices that may be responsive to input by one or more human users through, for example, tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), and olfactory input (not shown). Human interface devices may also be used to capture certain media that are not necessarily directly related to conscious human input, such as audio (e.g., speech, music, ambient sounds), images (e.g., scanned images, photographic images obtained from still image cameras), and video (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

[0250] The input human interface devices may include one or more (only one of each is shown) of a keyboard (2001), a mouse (2002), a trackpad (2003), a touch screen (2010), a data glove (not shown), a joystick (2005), a microphone (2006), a scanner (2007), and a camera (2008).

[0251] The computer system (2000) may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the human user's senses, for example, through haptic output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touch screen (2010), data gloves (not shown), or joystick (2005); although there may be haptic feedback devices that do not act as input devices), audio output devices (e.g., speakers (2009), headphones (not shown)), visual output devices (e.g., screens (2010) including CRT screens, LCD screens, plasma screens, OLED screens; each may or may not have touch screen input capability, each may or may not have haptic feedback capability, some of which may output two-dimensional visual output or higher than three-dimensional output through means such as stereoscopic output; virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0252] The computer system (2000) may also include human accessible storage devices and associated media, such as optical media including CD / DVD ROM / RW (2020) along with CD / DVD or similar media (2021), thumb drives (2022), removable hard drives or solid state drives (2023), legacy magnetic media such as tapes and floppy disks (not shown), specialized ROM / ASIC / PLD based devices (not shown) such as security dongles, etc.

[0253] Those skilled in the art should also understand that the term "computer-readable medium" as used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

[0254] The computer system (2000) may also include an interface (2054) to one or more communication networks (2055). The networks may be, for example, wireless, wired, optical. The networks may further be local, wide area, metropolitan, in-vehicle and industrial, real-time, delay tolerant, etc. Examples of networks include Ethernet, WLAN, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., TV wired or wireless wide area digital networks including cable television, satellite television, terrestrial broadcast television, in-vehicle and industrial including CANBus, etc. Certain networks usually require an external network interface adapter that is attached to a particular general purpose data port or peripheral bus (2049) (e.g., a USB port of the computer system (2000)). Others are usually integrated into the core of the computer system (2000) by attachment to a system bus as described below (e.g., an Ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks, the computer system (2000) can communicate with other entities. Such communications may be unidirectional, receive only (e.g., broadcast television), unidirectional transmit only (e.g., CANbus to a specific CANbus device), or bidirectional, for example, to other computer systems using local or wide area digital networks. Specific protocols and protocol stacks may be used with each of these networks and network interfaces as described above.

[0255] The aforementioned human interface devices, human accessible storage devices, and network interfaces may be attached to a core (2040) of the computer system (2000).

[0256] The cores (2040) may include one or more central processing units (CPUs) (2041), graphics processing units (GPUs) (2042), specialized programmable processing units in the form of field programmable gate arrays (FPGAs) (2043), hardware accelerators for specific tasks (2044), graphics adapters (2050), etc. These devices may be connected through a system bus (2048), along with read only memory (ROM) (2045), random access memory (2046), internal mass storage devices (2047), such as internal non-user accessible hard drives, solid state drives (SSDs), etc. In some computer systems, the system bus (2048) 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 (2048) or through a peripheral bus (2049). In one example, a screen (2010) may be connected to the graphics adapter (2050). Architectures for peripheral buses include PCI, USB, and the like.

[0257] The CPU (2041), GPU (2042), FPGA (2043), and accelerator (2044) can execute certain instructions that, in combination, may constitute the above-mentioned computer code. The computer code may be stored in a ROM (2045) or a RAM (2046). Temporary data may be stored in the RAM (2046), while persistent data may be stored, for example, in an internal mass storage device (2047). Rapid storage and retrieval from any of the memory devices may be enabled through the use of a cache memory that may be closely associated with one or more of the CPU (2041), GPU (2042), mass storage device (2047), ROM (2045), RAM (2046), etc.

[0258] The computer-readable medium can have computer code thereon for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of the present disclosure, or they may be of the kind well known and available to those having skill in the computer software arts.

[0259] By way of example and not limitation, the architecture (2000), and in particular a computer system having a core (2040), can provide functionality as a result of a processor (including a CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media can be user-accessible mass storage as introduced above as well as media associated with a particular storage of the core (2040) of a non-transitory nature, such as a mass storage device (2047) internal to the core or a ROM (2045). Software implementing various embodiments of the present disclosure can be stored in such devices and executed by the core (2040). The computer-readable media can include one or more memory devices or chips, depending on the particular needs. The software can cause the core (2040) and in particular the processors therein (including a CPU, GPU, FPGA, etc.) to execute certain processes or certain particular portions described herein, including defining data structures stored in RAM (2046) and modifying such data structures according to processes defined by the software. Additionally or alternatively, the computer system may provide functionality as a result of logic hardwired or otherwise embodied in circuitry (e.g., accelerator (2044)), which may operate in place of or together with software to perform particular processes or portions of particular processes described herein. Reference to software includes logic, and vice versa, as appropriate. Reference to a computer-readable medium may include circuitry (e.g., an integrated circuit (IC)) that stores software for execution, circuitry that embodies logic for execution, or both, as appropriate. The present disclosure encompasses any suitable combination of hardware and software.

[0260] Appendix A: Acronyms JEM: joint exploration model VVC: versatile video coding BMS: benchmark set MV: Motion Vector HEVC: High Efficiency Video Coding SEI: Supplementary Enhancement Information VUI: Video Usability Information GOP: Group of Pictures TU: Transform Unit PU: Prediction Unit CTU: Coding Tree Unit CTB: Coding Tree Block PB: Prediction Block HRD: Hypothetical Reference Decoder SNR: Signal Noise Ratio CPU: Central Processing Unit GPU: Graphics Processing Unit CRT: Cathode Ray Tube LCD: Liquid-Crystal Display OLED: Organic Light-Emitting Diode CD: Compact Disc DVD: Digital Video Disc ROM: Read-Only Memory RAM: Random Access Memory ASIC: Application-Specific Integrated Circuit PLD: Programmable Logic Device LAN: Local Area Network GSM: Global System for Mobile communications LTE: Long-Term Evolution CANBus: Controller Area Network Bus USB: Universal Serial Bus PCI: Peripheral Component Interconnect FPGA: Field Programmable Gate Areas SSD: solid-state drive IC: Integrated Circuit CU: Coding Unit RD: Rate-Distortion

[0261] While this disclosure has described several exemplary embodiments, there are alterations, substitutions, and various substitute equivalents, which fall within the scope of this disclosure. Thus, it will be appreciated that those skilled in the art will be able to devise many systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and are thus within the spirit and scope of the present disclosure.

Claims

1. A method for video decoding performed by a video decoder, comprising: reconstructing an area within a current picture from an encoded video bitstream, the area including one or more encoded blocks (CBs) within the current picture; determining whether to update a previous local reference range in an intra block copy (IBC) mode with reconstructed samples within the reconstructed area; when it is determined that the previous local reference range in the IBC mode is not updated with the reconstructed samples within the reconstructed area, decoding an encoded block (CB) within the current picture using the IBC mode based on the previous local reference range not including the reconstructed area; A method comprising the above steps.

2. The step of determining whether to update the previous local reference range comprises: determining the content of the reconstructed area based on the reconstructed samples within the reconstructed area, the content of the reconstructed area indicating a ratio of a predetermined type of content within the reconstructed area; determining whether to update the previous local reference range in the IBC mode based on the ratio of the predetermined type of content within the reconstructed area; The method according to claim 1, comprising the above steps.

3. The content of the reconstructed area does not include screen content, The step of determining whether to update the previous local reference range comprises determining that the previous local reference range in the IBC mode is not updated. The method according to claim 2, comprising the above steps.

4. The step of determining whether to update the previous local reference range comprises: decoding prediction information of the area indicating a prediction mode of the area; determining whether to update the previous local reference range in the IBC mode based on the prediction mode; The method according to claim 1, comprising the above steps.

5. The step of determining whether to update the previous local reference range comprises: decoding prediction information of the area indicating whether to update the previous local reference range with the reconstructed samples within the reconstructed area; Among the prediction information, determining whether to update the previous local reference range in the IBC mode based on an instruction on whether to update the previous local reference range with the reconstruction samples within the reconstruction area The method according to claim 1, comprising: **Claim 6** Whether to update the previous local reference range with the reconstruction samples within the reconstruction area is indicated by a flag included in the prediction information of the area, The step of determining whether to update the previous local reference range includes the step of determining whether to update the previous local reference range in the IBC mode based on the flag. The method according to claim 5 **Claim 7** The flag indicates whether any reconstruction sample within the area is used when updating the local reference range in the IBC mode. The method according to claim 6 **Claim 8** It is determined that the previous local reference range in the IBC mode is to be updated, The previous local reference range includes a plurality of areas stored in a reference sample memory (RSM), and the plurality of areas include reference samples, The method includes: Ranking the plurality of areas based on the content of the plurality of areas, each of the content corresponding to one of the plurality of areas, Selecting an area within the plurality of areas to be replaced by the reconstruction samples within the reconstruction area based on the ranking of the plurality of areas, Generating a current local reference range by replacing the selected area within the previous local reference range with the reconstruction samples within the reconstruction area The method according to claim 1, further comprising: **Claim 9** Each of the content corresponding to each of the plurality of areas is indicated by a ratio of a predetermined type of content within the corresponding area, The step of ranking the plurality of areas includes ranking the plurality of areas based on each ratio of the predetermined type of content of the plurality of areas. The method according to claim 8 **Claim 10** It is determined that the previous local reference range in the IBC mode is to be updated, The previous local reference range includes a plurality of areas stored in a reference sample memory (RSM), Each of the plurality of regions includes a plurality of reference samples within each respective region that are coded in one or more prediction modes within a set of predetermined prediction modes. The method comprises: ranking the plurality of regions based on each of the plurality of reference samples within the plurality of regions; selecting, based on the ranking of the plurality of regions, a region within the plurality of regions to be replaced by a reconstruction sample within the reconstruction region; generating a current local reference range by replacing the selected region within the previous local reference range with the reconstruction sample within the reconstruction region. The method according to claim 1, further comprising.

11. When it is determined that the previous local reference range of the IBC mode is updated, the previous local reference range includes a plurality of regions stored in a reference sample memory (RSM), the reference frequency associated with each of the plurality of regions indicates the number of times each region is referenced by a block vector used to predict a CB within the current picture, The method comprises: ranking the plurality of regions based on the respective reference frequencies of the plurality of regions; selecting, based on the ranking of the plurality of regions, a region within the plurality of regions to be replaced by a reconstruction sample within the reconstruction region; generating a current local reference range by replacing the selected region within the previous local reference range with the reconstruction sample within the reconstruction region. The method according to claim 1, further comprising.

12. The previous local reference range includes a plurality of regions, the reconstruction samples of the plurality of regions are stored in a reference sample memory (RSM) except for the reconstruction samples of the sub-regions in one of the plurality of regions, The method according to claim 1, wherein the reconstruction sample of the sub-region in one of the plurality of regions is replaced by a padding process that stores padded samples corresponding to the sub-region in one of the plurality of regions in the RSM.

13. The method according to claim 1, wherein the reconstruction region is a reconstructed coded block or the size of the reconstruction region is the size of a memory update region unit.

14. An apparatus for video decoding including a processing circuit, The processing circuit is an apparatus configured to execute the method according to any one of claims 1 to 13. **Claim 15** A program causing at least one processor to execute the method according to any one of claims 1 to 13.

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