CN112333449A - Method and apparatus for video decoding, computer device and storage medium - Google Patents

Abstract

The embodiment of the application provides a video decoding method and device, computer equipment and a storage medium. The method comprises the following steps: decoding prediction information for a block of a coded region in video from a coded video bitstream, the prediction information comprising advanced signaling information; determining whether a prediction mode of the block is an intra block copy, IBC, mode based on a value of the high level signaling information and constraint information, the value of the high level signaling information indicating a maximum number of motion vector prediction candidates in a motion vector prediction candidate list of the IBC mode; and decoding the block based on whether the prediction mode of the block is determined to be the IBC mode.

Description

Method and apparatus for video decoding, computer device and storage medium

Incorporated herein by reference

The present application claims priority from U.S. provisional application No. 62/883,081 entitled "SIGNALING of prediction candidate list SIZE FOR INTRA PICTURE BLOCK COMPENSATION" (preliminary CANDIDATE LIST SIZE SIGNALING FOR INTRA PICTURE BLOCK COMPENSATION) "filed on 5.8.2019, and U.S. application No. 16/932,146 entitled" method and apparatus FOR INTRA PICTURE BLOCK COMPENSATION "filed on 17.7.2020, the entire contents of which are incorporated herein by reference.

Technical Field

The present application relates to video encoding and decoding techniques. In particular, the present application relates to a method and apparatus for video decoding, a computer device and a storage medium.

Background

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

One purpose of video encoding and decoding is to reduce redundant information of an input video signal by compression. Video compression may help reduce the bandwidth and/or storage requirements described above, by two or more orders of magnitude in some cases. Lossless compression and lossy compression, as well as combinations of both, may be employed. Lossless compression refers to a technique for reconstructing an exact copy of an original signal from a compressed original signal. When lossy compression is used, the reconstructed signal may not be identical to the original signal, but the distortion between the original signal and the reconstructed signal is small enough that the reconstructed signal is useful for the intended application. Lossy compression is widely used for video. The amount of distortion tolerated depends on the application. For example, some users consuming streaming media applications may tolerate higher distortion than users of television applications. The achievable compression ratio reflects: higher allowable/tolerable distortion may result in higher compression ratios.

Video encoders and decoders may utilize several broad classes of techniques, including, for example: motion compensation, transformation, quantization and entropy coding.

Video codec techniques may include known intra-coding techniques. In intra coding, sample values are represented without reference to samples or other data of a previously reconstructed reference picture. In some video codecs, a picture is spatially subdivided into blocks of samples. When all sample blocks are encoded in intra mode, the picture may be an intra picture. Intra pictures and their derivatives (e.g., independent decoder refresh pictures) can be used to reset the decoder state and thus can be used as the first picture in an encoded video bitstream and video session, or as still images. Samples of the intra block may be used for the transform, and the transform coefficients may be quantized prior to entropy encoding. Intra prediction may be a technique that minimizes sample values in the pre-transform domain. In some cases, the smaller the transformed DC value and the smaller the AC coefficient, the fewer bits are needed to represent the block after entropy coding at a given quantization step size.

As is known from techniques such as MPEG-2 coding, conventional intra-coding does not use intra-prediction. However, some newer video compression techniques include: techniques are attempted to derive data chunks from, for example, surrounding sample data and/or metadata obtained during spatially adjacent encoding/decoding and prior to the decoding order. This technique was later referred to as an "intra-prediction" technique. It is noted that, at least in some cases, intra prediction uses only the reference data of the current picture being reconstructed, and not the reference data of the reference picture.

There may be many different forms of intra prediction. When more than one such technique may be used in a given video coding technique, the technique used may be coded in an intra-prediction mode. In some cases, a mode may have sub-modes and/or parameters, and these modes may be encoded separately or included in a mode codeword. Which codeword is used for a given mode/sub-mode/parameter combination affects the coding efficiency gain through intra prediction, and so does the entropy coding technique used to convert the codeword into a bitstream.

Disclosure of Invention

Embodiments of the present application provide a method and apparatus, a computer device, and a storage medium for video decoding, which aim to solve the problem of how to determine whether to enable or disable IBC mode for a block based on an encoded region of video in an encoded video bitstream.

According to an embodiment of the present application, there is provided a method of video decoding. The method comprises the following steps: decoding prediction information for a block of a coded region in video from a coded video bitstream, the prediction information comprising advanced signaling information; determining whether a prediction mode of the block is an intra block copy, IBC, mode based on a value of the high level signaling information and constraint information, the value of the high level signaling information indicating a maximum number of motion vector prediction candidates in a motion vector prediction candidate list of the IBC mode; and decoding the block based on whether the prediction mode of the block is determined to be the IBC mode.

The embodiment of the application also provides a video decoding device. The device includes: a first decoding module for decoding prediction information for a block of an encoded region in video from an encoded video bitstream, the prediction information comprising advanced signaling information; a determination module to determine whether a prediction mode of the block is an intra block copy, IBC, mode based on a value of the high level signaling information and constraint information, the value of the high level signaling information indicating a maximum number of motion vector prediction candidates in a motion vector prediction candidate list of the IBC mode; and a second decoding module for decoding the block based on whether the prediction mode of the block is determined to be the IBC mode.

Embodiments of the present application also provide a non-transitory computer-readable storage medium storing program instructions that, when executed by a computer for video encoding/decoding, cause the computer to perform the method of video decoding described in the above embodiments.

Embodiments of the present application also provide a computer device including one or more processors and one or more memories, in which at least one program instruction is stored, and the at least one program instruction is loaded and executed by the one or more processors to implement the video decoding method according to the above embodiments.

In an embodiment of the present application, whether the IBC mode is enabled or disabled for a block can be determined by prediction information of the block decoded from an encoded region in a video and some constraints, so that the block can be decoded quickly and accurately in a suitable mode.

Drawings

Other features, properties, and various advantages of the disclosed subject matter will be further apparent from the following detailed description and the accompanying drawings, in which:

FIG. 1 shows a schematic diagram of an exemplary subset of intra prediction modes;

FIG. 2 shows a diagram of exemplary intra prediction directions;

FIG. 3 shows a schematic diagram of a simplified block diagram of a communication system according to an embodiment;

FIG. 4 shows a schematic diagram of a simplified block diagram of a communication system according to another embodiment;

FIG. 5 shows a schematic diagram of a simplified block diagram of a decoder according to an embodiment;

FIG. 6 shows a schematic diagram of a simplified block diagram of an encoder according to an embodiment;

FIG. 7 shows a block diagram of an encoder according to another embodiment;

FIG. 8 shows a block diagram of a decoder according to another embodiment;

fig. 9 illustrates an exemplary embodiment of intra picture block compensation according to an embodiment;

10A-10D illustrate various exemplary embodiments of intra picture block compensation according to an embodiment;

fig. 11 shows exemplary locations of spatial merge candidates according to an embodiment;

fig. 12 shows a flow chart of a video decoding method according to an embodiment;

FIG. 13 shows a schematic diagram of a computer system, according to an embodiment.

Detailed Description

H.264 introduces an intra prediction mode that is improved in h.265 and further improved in newer coding techniques such as joint development model (JEM)/universal video coding (VVC)/reference set (BMS). A prediction block may be formed by using neighboring sample values belonging to already available samples. In some examples, sample values of neighboring samples are copied into a prediction block in a certain direction. The reference to the direction used may be encoded in the bitstream or may itself be predicted.

Referring to fig. 1, the bottom right depicts a subset of nine prediction directions known from the 33 possible prediction directions of h.265 (33 angular modes corresponding to 35 intra modes). The point (101) where the arrows converge represents the sample being predicted. The arrows indicate the direction in which the samples are being predicted. For example, arrow (102) represents the prediction of a sample (101) from one or more samples at an angle of 45 degrees to the horizontal from the upper right. Similarly, arrow (103) represents the prediction of a sample (101) from one or more samples at an angle of 22.5 degrees to the horizontal at the bottom left.

Still referring to fig. 1, a square block (104) comprising 4 x 4 samples is shown at the top left (indicated by the thick dashed line). The square block (104) includes 16 samples, each labeled with "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 in the Y dimension (starting from the top) and the first sample in the X dimension (starting from the left). Similarly, sample S44 is the fourth sample in the block (104) in both the Y dimension and the X dimension. Since the block is a 4 × 4 sample size, S44 is located at the lower right corner. Reference samples following a similar numbering scheme are also shown. The reference sample is labeled with R, and its Y position (e.g., row index) and X position (e.g., column index) relative to the block (104). In h.264 and h.265, the prediction samples are adjacent to the block being reconstructed, so negative values need not be used.

Intra picture prediction can be performed by copying the reference sample values from the neighbouring samples occupied by the signaled prediction direction. For example, assume that the encoded video bitstream includes signaling indicating, for the block, a prediction direction that coincides with the arrow (102), i.e. samples are predicted from one or more predicted samples whose upper right is at a 45 degree angle to the horizontal direction. In this case, samples S41, S32, S23, and S14 are predicted from the same reference sample R05. Then, a sample S44 is predicted from the reference sample R08.

In some cases, the values of multiple reference samples may be combined, for example by interpolation, to compute the reference sample, especially when the direction cannot be divided exactly by 45 degrees.

As video coding techniques have evolved, the number of possible directions has increased. In h.264 (2003), nine different directions can be represented. There are 33 increases in H.265 (2013) and JEM/VVC/BMS, and up to 65 orientations can be supported at the time of this application. Experiments have been performed to identify the most likely directions and some techniques in entropy coding are used to represent those possible directions using a small number of bits, accepting some cost for less likely directions. Furthermore, sometimes the direction itself can be predicted from the neighboring directions used in neighboring, already decoded blocks.

Fig. 2 shows a schematic diagram (201) depicting 65 intra prediction directions according to JEM to illustrate the increase in the number of prediction directions over time.

The mapping of intra prediction direction bits in the coded video bitstream representing directions may differ from one video coding technique to another and may for example range from a simple direct mapping of intra prediction modes to prediction directions of codewords to a complex adaptation scheme including most probable modes and similar techniques. In all cases, however, there may be certain directions in the video content that are statistically less likely to occur than other directions. Since the goal of video compression is to reduce redundancy, in well-functioning video coding techniques, those unlikely directions will be represented using a greater number of bits than the more likely directions.

Fig. 3 is a simplified block diagram of a communication system (300) according to an embodiment of the present disclosure. The communication system (300) includes a plurality of terminal devices that can communicate with each other through, for example, a network (350). For example, a communication system (300) includes a first end device (310) and a second end device (320) interconnected by a network (350). In the embodiment of fig. 3, the first terminal device (310) and the second terminal device (320) perform unidirectional data transmission. For example, a first end device (310) may encode video data, such as a stream of video pictures captured by the end device (310), for transmission over a network (350) to a second end device (320). The encoded video data is transmitted in the form of one or more encoded video streams. The second terminal device (320) may receive the encoded video data from the network (350), decode the encoded video data to recover the video data, and display a video picture according to the recovered video data. Unidirectional data transmission is common in applications such as media services.

In another embodiment, a communication system (300) includes a third terminal device (330) and a fourth terminal device (340) that perform bidirectional transmission of encoded video data, which may occur, for example, during a video conference. For bi-directional data transmission, each of the third terminal device (330) and the fourth terminal device (340) may encode video data (e.g., a stream of video pictures captured by the terminal device) for transmission over the network (350) to the other of the third terminal device (330) and the fourth terminal device (340). Each of the third terminal device (330) and the fourth terminal device (340) may also receive encoded video data transmitted by the other of the third terminal device (330) and the fourth terminal device (340), and may decode the encoded video data to recover the video data, and may display video pictures on an accessible display device according to the recovered video data.

In the embodiment of fig. 3, the first terminal device (310), the second terminal device (320), the third terminal device (330), and the fourth terminal device (340) may be a server, a personal computer, and a smart phone, but the principles of the present disclosure may not be limited thereto. Embodiments of the present disclosure are applicable to laptop computers, tablet computers, media players, and/or dedicated video conferencing equipment. Network (350) represents any number of networks that communicate encoded video data between first terminal device (310), second terminal device (320), third terminal device (330), and fourth terminal device (340), including, for example, wired (wired) and/or wireless communication networks. The communication network (350) may exchange data in circuit-switched and/or packet-switched channels. The network may include a telecommunications network, a local area network, a wide area network, and/or the internet. For purposes of this disclosure, the architecture and topology of the network (350) may be immaterial to the operation of this disclosure, unless explained below.

By way of example, fig. 4 illustrates the placement of a video encoder and a video decoder in a streaming environment. The disclosed subject matter is equally applicable to other video-enabled applications including, for example, video conferencing, digital TV, storing compressed video on digital media including CDs, DVDs, memory sticks, and the like.

The streaming system may include an acquisition subsystem (413), which may include a video source (401), such as a digital camera, that creates an uncompressed video picture stream (402). In an embodiment, the video picture stream (402) includes samples taken by a digital camera. The video picture stream (402) is depicted as a thick line to emphasize a high data amount video picture stream compared to the encoded video data (404) (or the encoded video bitstream), the video picture stream (402) being processable by an electronic device (420), the electronic device (420) comprising a video encoder (403) coupled to a video source (401). The video encoder (403) may comprise hardware, software, or a combination of hardware and software to implement or embody aspects of the disclosed subject matter as described in more detail below. The encoded video data (404) (or encoded video codestream (404)) is depicted as a thin line to emphasize the lower data amount of the encoded video data (404) (or encoded video codestream (404)) as compared to the video picture stream (402), which may be stored on a streaming server (405) for future use. One or more streaming client subsystems, such as client subsystem (406) and client subsystem (408) in fig. 4, may access a streaming server (405) to retrieve copies (407) and copies (409) of encoded video data (404). The client subsystem (406) may include, for example, a video decoder (410) in an electronic device (430). The video decoder (410) decodes incoming copies (407) of the encoded video data and generates an output video picture stream (411) that may be presented on a display (412), such as a display screen, or another presentation device (not depicted). In some streaming systems, encoded video data (404), video data (407), and video data (409) (e.g., video streams) may be encoded according to certain video encoding/compression standards. Examples of such standards include ITU-T H.265. In an embodiment, the Video Coding standard being developed is informally referred to as next generation Video Coding (VVC), and the present disclosure may be used in the context of the VVC standard.

It should be noted that electronic device (420) and electronic device (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).

Fig. 5 is a block diagram of a video decoder (510) according to an embodiment of the present disclosure. The video decoder (510) may be disposed in an electronic device (530). The electronic device (530) may include a receiver (531) (e.g., a receive circuit). The video decoder (510) may be used in place of the video decoder (410) in the fig. 4 embodiment.

The receiver (531) may receive one or more encoded video sequences to be decoded by the video decoder (510); in the same or another embodiment, the encoded video sequences are received one at a time, wherein each encoded video sequence is decoded independently of the other encoded video sequences. The encoded video sequence may be received from a channel (501), which may be a hardware/software link to a storage device that stores encoded video data. The receiver (531) may receive encoded video data as well as other data, e.g. encoded audio data and/or auxiliary data streams, which may be forwarded to their respective usage entities (not indicated). The receiver (531) may separate the encoded video sequence from other data. To prevent network jitter, a buffer memory (515) may be coupled between the receiver (531) and the entropy decoder/parser (520) (hereinafter "parser (520)"). In some applications, the buffer memory (515) is part of the video decoder (510). In other cases, the buffer memory (515) may be disposed external (not labeled) to the video decoder (510). While in other cases a buffer memory (not labeled) is provided external to the video decoder (510), e.g., to prevent network jitter, and another buffer memory (515) may be configured internal to the video decoder (510), e.g., to handle playout timing. The buffer memory (515) may not be required to be configured or may be made smaller when the receiver (531) receives data from a store/forward device with sufficient bandwidth and controllability or from an isochronous network. Of course, for use over traffic packet networks such as the internet, a buffer memory (515) may also be required, which may be relatively large and may be of adaptive size, and may be implemented at least partially in an operating system or similar element (not labeled) external to the video decoder (510).

The video decoder (510) may include a parser (520) to reconstruct symbols (521) from the encoded video sequence. The categories of these symbols include information for managing the operation of the video decoder (510), as well as potential information to control a display device, such as a display screen (512), that is not an integral part of the electronic device (530), but may be coupled to the electronic device (530), as shown in fig. 5. The control Information for the display device may be a parameter set fragment (not shown) of Supplemental Enhancement Information (SEI message) or Video Usability Information (VUI). The parser (520) may parse/entropy decode the received encoded video sequence. Encoding of the encoded video sequence may be performed in accordance with video coding techniques or standards and may follow various principles, including variable length coding, Huffman coding, arithmetic coding with or without contextual sensitivity, and so forth. A parser (520) may extract a subgroup parameter set for at least one of the subgroups of pixels in the video decoder from the encoded video sequence based on at least one parameter corresponding to the group. A subgroup may include a Group of Pictures (GOP), a picture, a tile, a slice, a macroblock, a Coding Unit (CU), a block, a Transform Unit (TU), a Prediction Unit (PU), and so on. The parser (520) may also extract information from the encoded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, and so on.

The parser (520) may perform entropy decoding/parsing operations on the video sequence received from the buffer memory (515) to create symbols (521).

The reconstruction of the symbol (521) may involve a number of different units depending on the type of the encoded video picture or portion of the encoded video picture (e.g., inter and intra pictures, inter and intra blocks), among other factors. Which units are involved and the way they are involved can be controlled by subgroup control information parsed from the coded video sequence by a parser (520). For the sake of brevity, such a subgroup control information flow between parser (520) and the following units is not described.

In addition to the functional blocks already mentioned, the video decoder (510) may be conceptually subdivided into several functional units as described below. In a practical embodiment operating under business constraints, many of these units interact closely with each other and may be integrated with each other. However, for the purposes of describing the disclosed subject matter, a conceptual subdivision into the following functional units is appropriate.

The first unit is a scaler/inverse transform unit (551). The scaler/inverse transform unit (551) receives the quantized transform coefficients as symbols (521) from the parser (520) along with control information including which transform scheme to use, block size, quantization factor, quantization scaling matrix, etc. The sealer/inverse transform unit (551) may output a block comprising sample values, which may be input into an aggregator (555).

In some cases, the output samples of sealer/inverse transform unit (551) may belong to an intra-coded block; namely: predictive information from previously reconstructed pictures is not used, but blocks of predictive information from previously reconstructed portions of the current picture may be used. Such predictive information may be provided by an intra picture prediction unit (552). In some cases, the intra picture prediction unit (552) generates surrounding blocks of the same size and shape as the block being reconstructed using the reconstructed information extracted from the current picture buffer (558). For example, the current picture buffer (558) buffers a partially reconstructed current picture and/or a fully reconstructed current picture. In some cases, the aggregator (555) adds the prediction information generated by the intra prediction unit (552) to the output sample information provided by the scaler/inverse transform unit (551) on a per sample basis.

In other cases, the output samples of sealer/inverse transform unit (551) may belong to inter-coded and potential motion compensated blocks. In this case, the motion compensated prediction unit (553) may access a reference picture memory (557) to fetch samples for prediction. After motion compensating the extracted samples according to the sign (521), the samples may be added to the output of the scaler/inverse transform unit (551), in this case referred to as residual samples or residual signals, by an aggregator (555), thereby generating output sample information. The motion compensated prediction unit (553) fetching prediction samples from an address within the reference picture memory (557) may be motion vector controlled and used by the motion compensated prediction unit (553) in the form of the symbol (521), the symbol (521) comprising, for example, X, Y and a reference picture component. Motion compensation may also include interpolation of sample values fetched from a reference picture memory (557), motion vector prediction mechanisms, etc., when using sub-sample exact motion vectors.

The output samples of the aggregator (555) may be employed by various loop filtering techniques in the loop filter unit (556). The video compression techniques may include in-loop filter techniques that are controlled by parameters included in the encoded video sequence (also referred to as an encoded video bitstream) and that are available to the loop filter unit (556) as symbols (521) from the parser (520). However, in other embodiments, the video compression techniques may also be responsive to meta-information obtained during decoding of previous (in decoding order) portions of an encoded picture or encoded video sequence, as well as to sample values previously reconstructed and loop filtered.

The output of the loop filter unit (556) may be a sample stream that may be output to a display device (512) and stored in a reference picture memory (557) for subsequent inter picture prediction.

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

The video decoder (510) may perform decoding operations according to predetermined video compression techniques, such as in the ITU-T h.265 standard. The encoded video sequence may conform to the syntax specified by the video compression technique or standard used, in the sense that the encoded video sequence conforms to the syntax of the video compression technique or standard and the configuration files recorded in the video compression technique or standard. In particular, the configuration file may select certain tools from all tools available in the video compression technology or standard as the only tools available under the configuration file. For compliance, the complexity of the encoded video sequence is also required to be within the limits defined by the level of the video compression technique or standard. In some cases, the hierarchy limits the maximum picture size, the maximum frame rate, the maximum reconstruction sampling rate (measured in units of, e.g., mega samples per second), the maximum reference picture size, and so on. In some cases, the limits set by the hierarchy may be further defined by a Hypothetical Reference Decoder (HRD) specification and metadata signaled HRD buffer management in the encoded video sequence.

In an embodiment, the receiver (531) may receive additional (redundant) data along with the encoded video. The additional data may be part of an encoded video sequence. The additional data may be used by the video decoder (510) to properly decode the data and/or more accurately reconstruct the original video data. The additional data may be in the form of, for example, a temporal, spatial, or signal-to-noise ratio (SNR) enhancement layer, a redundant slice, a redundant picture, a forward error correction code, and so forth.

Fig. 6 is a block diagram of a video encoder (603) according to an embodiment of the disclosure. The video encoder (603) is disposed in an electronic device (620). The electronic device (620) includes a transmitter (640) (e.g., a transmission circuit). The video encoder (603) may be used in place of the video encoder (403) in the fig. 4 embodiment.

Video encoder (603) may receive video samples from a video source (601) (not part of electronics (620) in the fig. 6 embodiment) that may capture video images to be encoded by video encoder (603). In another embodiment, the video source (601) is part of the electronic device (620).

The video source (601) may provide a source video sequence in the form of a stream of digital video samples to be encoded by the video encoder (603), which may have any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit … …), any color space (e.g., bt.601y CrCB, RGB … …), and any suitable sampling structure (e.g., Y CrCB4:2:0, Y CrCB4: 4: 4). In the media service system, the video source (601) may be a storage device that stores previously prepared video. In a video conferencing system, the video source (601) may be a camera that captures local image information as a video sequence. Video data may be provided as a plurality of individual pictures that are given motion when viewed in sequence. The picture itself may be constructed as an array of spatial pixels, where each pixel may comprise one or more samples, depending on the sampling structure, color space, etc. used. The relationship between pixels and samples can be readily understood by those skilled in the art. The following text focuses on describing the samples.

According to an embodiment, the video encoder (603) may encode and compress pictures of a source video sequence into an encoded video sequence (643) in real-time or under any other temporal constraint required by an application. It is a function of the controller (650) to implement the appropriate encoding speed. In some embodiments, the controller (650) controls and is functionally coupled to other functional units as described below. For simplicity, the couplings are not labeled in the figures. The parameters set by the controller (650) may include rate control related parameters (picture skip, quantizer, lambda value of rate distortion optimization technique, etc.), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. The controller (650) may be used to have other suitable functions relating to the video encoder (603) optimized for a certain system design.

In some embodiments, the video encoder (603) operates in an encoding loop. As a brief description, in an embodiment, an encoding loop may include a source encoder (630) (e.g., responsible for creating symbols, e.g., a stream of symbols, based on input pictures and reference pictures to be encoded) and a (local) decoder (633) embedded in a video encoder (603). The decoder (633) reconstructs the symbols to create sample data in a manner similar to the way a (remote) decoder creates the sample data (since any compression between the symbols and the encoded video bitstream is lossless in the video compression techniques contemplated by this disclosure). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since the decoding of the symbol stream produces bit accurate results independent of decoder location (local or remote), the content in the reference picture store (634) also corresponds bit accurately between the local encoder and the remote encoder. In other words, the reference picture samples that the prediction portion of the encoder "sees" are identical to the sample values that the decoder would "see" when using prediction during decoding. This reference picture synchronization philosophy (and the drift that occurs if synchronization cannot be maintained due to, for example, channel errors) is also used in some related techniques.

The operation of the "local" decoder (633) may be the same as a "remote" decoder, such as the video decoder (510) described in detail above in connection with fig. 5. However, referring briefly to fig. 5 additionally, when symbols are available and the entropy encoder (645) and parser (520) are able to losslessly encode/decode the symbols into an encoded video sequence, the entropy decoding portion of the video decoder (510), including the buffer memory (515) and parser (520), may not be fully implemented in the local decoder (633).

At this point it can be observed that any decoder technique other than the parsing/entropy decoding present in the decoder must also be present in the corresponding encoder in substantially the same functional form. For this reason, the present disclosure focuses on decoder operation. The description of the encoder techniques may be simplified because the encoder techniques are reciprocal to the fully described decoder techniques. A more detailed description is only needed in certain areas and is provided below.

During operation, in some embodiments, the source encoder (630) may perform motion compensated predictive coding. The motion compensated predictive coding predictively codes an input picture with reference to one or more previously coded pictures from the video sequence that are designated as "reference pictures". In this way, an encoding engine (632) encodes differences between pixel blocks of an input picture and pixel blocks of a reference picture, which may be selected as a prediction reference for the input picture.

The local video decoder (633) may decode encoded video data, which may be designated as reference pictures, based on the symbols created by the source encoder (630). The operation of the encoding engine (632) may be a lossy process. When the encoded video data can be decoded at a video decoder (not shown in fig. 6), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (633) replicates a decoding process that may be performed on reference pictures by the video decoder, and may cause reconstructed reference pictures to be stored in a reference picture cache (634). In this way, the video encoder (603) may locally store a copy of the reconstructed reference picture that has common content (no transmission errors) with the reconstructed reference picture to be obtained by the remote video decoder.

Predictor (635) may perform a prediction search for coding engine (632). That is, for a new picture to be encoded, predictor (635) may search reference picture memory (634) for sample data (as candidate reference pixel blocks) or some metadata, such as reference picture motion vectors, block shapes, etc., that may be referenced as appropriate predictions for the new picture. The predictor (635) may operate on a block-by-block basis of samples to find a suitable prediction reference. In some cases, from search results obtained by predictor (635), it may be determined that the input picture may have prediction references derived from multiple reference pictures stored in reference picture memory (634).

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

The outputs of all of the above functional units may be entropy encoded in an entropy encoder (645). The entropy encoder (645) losslessly compresses the symbols generated by the various functional units according to techniques such as huffman coding, variable length coding, arithmetic coding, etc., to convert the symbols into an encoded video sequence.

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

The controller (650) may manage the operation of the video encoder (603). During encoding, the controller (650) may assign a certain encoded picture type to each encoded picture, but this may affect the encoding techniques applicable to the respective picture. For example, pictures may be generally assigned to any of the following picture types:

intra pictures (I pictures), which may be pictures that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs tolerate different types of intra pictures, including, for example, Independent Decoder Refresh ("IDR") pictures. Those skilled in the art are aware of variants of picture I and their corresponding applications and features.

Predictive pictures (P pictures), which may be pictures that may be encoded and decoded using intra prediction or inter prediction that uses at most one motion vector and reference index to predict sample values of each block.

Bi-predictive pictures (B-pictures), which may be pictures that can be encoded and decoded using intra-prediction or inter-prediction that uses at most two motion vectors and reference indices to predict sample values of each block. Similarly, multiple predictive pictures may use more than two reference pictures and associated metadata for reconstructing a single block.

A source picture may typically be spatially subdivided into blocks of samples (e.g., blocks of 4 x 4, 8 x 8, 4 x 8, or 16 x 16 samples) and encoded block-wise. These blocks may be predictively encoded with reference to other (encoded) blocks that are determined according to the encoding allocation applied to their respective pictures. For example, a block of an I picture may be non-predictive encoded, or the block may be predictive encoded (spatial prediction or intra prediction) with reference to an already encoded block of the same picture. The pixel block of the P picture can be prediction-coded by spatial prediction or by temporal prediction with reference to one previously coded reference picture. A block of a B picture may be prediction coded by spatial prediction or by temporal prediction with reference to one or two previously coded reference pictures.

The video encoder (603) may perform encoding operations according to a predetermined video encoding technique or standard, such as the ITU-T h.265 recommendation. In operation, the video encoder (603) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancies in the input video sequence. Thus, the encoded video data may conform to syntax specified by the video coding technique or standard used.

In an embodiment, the transmitter (640) may transmit the additional data while transmitting the encoded video. The source encoder (630) may take such data as part of an encoded video sequence. The additional data may include temporal/spatial/SNR enhancement layers, redundant pictures and slices, among other forms of redundant data, SEI messages, VUI parameter set segments, and the like.

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

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

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

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

Fig. 7 is a diagram of a video encoder (703) according to another embodiment of the present disclosure. A video encoder (703) is used to receive a processing block (e.g., a prediction block) of sample values within a current video picture in a sequence of video pictures and encode the processing block into an encoded picture that is part of an encoded video sequence. In this embodiment, a video encoder (703) is used in place of the video encoder (403) in the embodiment of fig. 4.

In an HEVC embodiment, a video encoder (703) receives a matrix of sample values for a processing block, e.g., a prediction block of 8 × 8 samples, etc. A video encoder (703) determines whether to encode the processing block using intra mode, inter mode, or bi-directional prediction mode using, for example, rate-distortion (RD) optimization. When encoding a processing block in intra mode, the video encoder (703) may use intra prediction techniques to encode the processing block into an encoded picture; and when the processing block is encoded in inter mode or bi-prediction mode, the video encoder (703) may encode the processing block into the encoded picture using inter-prediction or bi-prediction techniques, respectively. In some video coding techniques, the merge mode may be an inter-picture prediction sub-mode, in which motion vectors are derived from one or more motion vector predictors without resorting to coded motion vector components outside of the predictors. In some other video coding techniques, there may be motion vector components that are applicable to the subject block. In an embodiment, the video encoder (703) includes other components, such as a mode decision module (not shown) for determining a processing block mode.

In the embodiment 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 purpose controller (721), and an entropy encoder (725) coupled together as shown in fig. 7.

The inter encoder (730) is configured to receive samples of a current block (e.g., a processed block), compare the block to one or more reference blocks in a reference picture (e.g., blocks in previous and subsequent pictures), generate inter prediction information (e.g., redundant information descriptions, motion vectors, merge mode information according to inter coding techniques), and calculate an inter prediction result (e.g., a predicted block) using any suitable technique based on the inter prediction information. In some embodiments, the reference picture is a decoded reference picture that is decoded based on encoded video information.

The intra encoder (722) is used to receive samples of a current block (e.g., a processing block), in some cases compare the block to a block already encoded in the same picture, generate quantized coefficients after transformation, and in some cases also generate intra prediction information (e.g., intra prediction direction information according to one or more intra coding techniques). In an embodiment, the intra encoder (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.

The general purpose controller (721) is used to determine general purpose control data and control other components of the video encoder (703) based on the general purpose control data. In an embodiment, a general purpose controller (721) determines a mode of a block and provides a control signal to a switch (726) based on the mode. For example, when the mode is intra mode, the general purpose controller (721) controls the switch (726) to select an intra mode result for use by the residual calculator (723), and controls the entropy encoder (725) to select and add intra prediction information in the code stream; and when the mode is an inter mode, the general purpose controller (721) controls the switch (726) to select an inter prediction result for use by the residual calculator (723), and controls the entropy encoder (725) to select and add inter prediction information in the code stream.

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

The entropy coder (725) is for formatting the codestream to produce coded blocks. The entropy encoder (725) generates various information according to a suitable standard such as the HEVC standard. In an embodiment, the entropy encoder (725) is used to obtain general control data, selected prediction information (e.g., intra prediction information or inter prediction information), residual information, and other suitable information in the code stream. It should be noted that, according to the disclosed subject matter, there is no residual information when a block is encoded in the merge sub-mode of the inter mode or bi-prediction mode.

Fig. 8 is a diagram of a video decoder (810) according to another embodiment of the present disclosure. A video decoder (810) is for receiving an encoded image that is part of an encoded video sequence and decoding the encoded image to generate a reconstructed picture. In an embodiment, a video decoder (810) is used in place of the video decoder (410) in the fig. 4 embodiment.

In the fig. 8 embodiment, video decoder (810) includes an entropy decoder (871), an inter-frame decoder (880), a residual decoder (873), a reconstruction module (874), and an intra-frame decoder (872) coupled together as shown in fig. 8.

An entropy decoder (871) is operable to reconstruct from an encoded picture certain symbols representing syntax elements constituting the encoded picture. Such symbols may include, for example, a mode used to encode the block (e.g., intra mode, inter mode, bi-prediction mode, a merge sub-mode of the latter two, or another sub-mode), prediction information (e.g., intra prediction information or inter prediction information) that may identify certain samples or metadata for use by an intra decoder (872) or an inter decoder (880), respectively, residual information in the form of, for example, quantized transform coefficients, and so forth. In an embodiment, when the prediction mode is inter or bi-directional prediction mode, inter prediction information is provided to an inter decoder (880); and providing the intra prediction information to an intra decoder (872) when the prediction type is an intra prediction type. The residual information may be inverse quantized and provided to a residual decoder (873).

An inter decoder (880) is configured to receive inter prediction information and generate an inter prediction result based on the inter prediction information.

An intra-decoder (872) is configured to receive intra-prediction information and generate a prediction result based on the intra-prediction information.

A residual decoder (873) is used to perform inverse quantization to extract dequantized transform coefficients and process the dequantized transform coefficients to convert the residual from the frequency domain to the spatial domain. The residual decoder (873) may also need some control information (to obtain the quantizer parameters QP) and that information may be provided by the entropy decoder (871) (data path not labeled as this is only low-level control information).

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

It should be noted that video encoder (403), video encoder (603), and video encoder (703), as well as video decoder (410), video decoder (510), and video decoder (810), may be implemented using any suitable techniques. In an embodiment, video encoder (403), video encoder (603), and video encoder (703), and video decoder (410), video decoder (510), and video decoder (810) may be implemented using one or more integrated circuits. In another embodiment, the video encoder (403), the video encoder (603), and the video encoder (703), and the video decoder (410), the video decoder (510), and the video decoder (810) may be implemented using one or more processors executing software instructions.

Block-based compensation from different pictures may be referred to as motion compensation. Similarly, block-based compensation may also be performed from a previously reconstructed region within the same picture, which may be referred to as intra picture block compensation, Current Picture Reference (CPR), or Intra Block Copy (IBC). A displacement vector indicating an offset between the current block and the reference block may be referred to as a Block Vector (BV). Unlike motion vectors in motion compensation, which can be arbitrary values (positive or negative in the x-or y-direction), block vectors can have some constraints. For example, the reference block to which the current block refers (points to) must be available and already reconstructed. Furthermore, some reference regions, i.e. tile boundaries or wavefront trapezoidal boundaries, are excluded in view of parallel processing.

The block vector may be encoded in an explicit mode or an implicit mode. In the explicit mode (also called AMVP mode in inter coding), the difference between a block vector and its prediction value can be signaled. In the implicit mode (merge mode), the block vector can be recovered only from the prediction value of the block vector in a similar manner to the motion vector in the merge/skip mode. In some embodiments, the resolution of the block vector may be limited to integer positions. In other systems or embodiments, resolution may be allowed to point to fractional locations.

Intra block copy may be applied at the block level by signaling a block level flag, e.g., IBC flag. In one embodiment, the IBC flag may be signaled when the current block is not encoded in merge mode. In another embodiment, the IBC flag may be signaled by way of a reference index, where the current picture being decoded may be considered a reference picture. In HEVC Screen Content Coding (SCC), such a reference picture (e.g., the current picture being decoded) may be placed at the last position of the reference picture list. In some embodiments, such special reference pictures (e.g., the current picture being decoded) may also be managed along with other temporal reference pictures in the Decoded Picture Buffer (DPB).

In some embodiments, intra block copy may be considered a third mode, which is different from either the intra prediction mode or the inter prediction mode. Therefore, block vector prediction in the merge mode and the AMVP mode can be separated from the conventional inter prediction mode. For example, a separate merge candidate list may be defined for the merge mode of the intra block copy mode, where the entries in the merge candidate list are all block vectors. Similarly, the block vector prediction list of AMVP mode for intra block copy mode may include only block vectors. According to the general rules applied to the two lists described above, both lists may follow the same logic as the inter-frame merging candidate list or AMVP prediction list in terms of the candidate derivation process. For example, for intra block copy, 5 spatially neighboring positions in HEVC or VVC inter merge mode may be accessed to derive a merge candidate list for intra block copy.

Fig. 9 illustrates an exemplary embodiment of intra block copy. As shown in fig. 9, a picture 900 may include a plurality of Coding Tree Units (CTUs), such as a first CTU 902 and a second CTU 904. The current block 906 may be located in a first CTU 902, while a reference block 908 of the current block 906 may be located in a second CTU 904. A block vector 910 may be applied to indicate the offset between the current block 906 and the reference block 908.

The search range for the Current Picture Reference (CPR) mode (or IBC mode) may be limited to the current CTU, e.g., as used in VVC. The effective memory requirement to store the reference samples for the CPR mode may be 1 CTU-sized sample. Considering that the existing reference sample memory stores reconstructed samples in the current 64 × 64 area, 3 reference sample memories of 64 × 64 size are also required. Based on the above facts, the effective search range of the CPR mode can be extended to some portion of the left CTU of the current CTU, while the total memory requirement for storing reference pixels can remain unchanged (e.g., 1 CTU size, 4 total 64 × 64 reference sample memories).

Fig. 10A-10D illustrate an exemplary search range for a Current Picture Reference (CPR) mode (or IBC mode) that is extended to some portion of the left CTU of the current CTU, while the total memory requirement for storing reference pixels may remain unchanged. As shown in fig. 10A-10D, the current CTU 1000A may include 4 coding regions 1002, 1004, 1006, and 1008, and the left CTU 1000B of the current CTU 1000A may include 4 coding regions 1010, 1012, 1014, and 1016. In fig. 10A, the coding region 1002 may be a current coding region decoded by the IBC mode. The search range may include coding regions 1012, 1014, and 1016 of left CTU 1000B. The coding region 1010 may be excluded so that the total memory requirement for storing reference pixels may be kept to 1 CTU size and 4 64 × 64 reference sample memories. In fig. 10B, the encoding region 1004 may be a current encoding region decoded by the IBC mode. The search range may include coding regions 1002, 1014, and 1016, and may exclude coding regions 1010 and 1012. In fig. 10C, the coding region 1006 may be a current coding region decoded by the IBC mode. The search range may include coding regions 1002, 1004, and 1016, and may exclude coding regions 1010, 1012, and 1014 in left CTU 1000B. Similarly, in fig. 10D, the coding region 1008 may be the current coding region decoded by the IBC mode. The search range may include coding regions 1002, 1004, and 1006, and the coding regions in left CTU 1000B are all excluded in order to keep the total memory requirement constant.

In some embodiments, the bitstream conformance condition for a valid block vector (mvL, using 1/16 pixel resolution) may be that a luma motion vector (or motion vector luma, or mvL) obeys the following constraint:

(a) a1: with the current luma position (xCurr, yCurr) and neighboring luma positions (xCb + (mvL [0] > >4), yCb + (mvL [1] > >4) set to (xCb, yCb) as inputs, the block availability derivation process specified in the neighboring block availability check process is invoked, and the output should be TRUE (TRUE).

(b) A2: the block availability derivation process specified in the neighboring block availability check process is invoked with the current luminance position (xCurr, yCurr) and the neighboring luminance position (xCb + (mvL [0] > >4) + cbWidth-1, yCb + (mvL [1] > >4) + cbHeight-1) set to (xCb, yCb) as inputs, and the output should be TRUE (TRUE).

(c) B1: one or both of the following conditions is true: (i) (mvL [0] > >4) + cbWidth is less than or equal to 0; (ii) the value of (mvL [1] > >4) + cbHeight is less than or equal to 0.

(d) C1: the conditions shown in equations (1) - (4) should be true:

(yCb+(mvL[1]>>4))>>CtbLog2SizeY＝yCb>>CtbLog2SizeY (1)

(yCb+(mvL[1]>>4)+cbHeight-1)>>CtbLog2SizeY＝yCb>>CtbLog2SizeY (2)

(xCb+(mvL[0]>>4))>>CtbLog2SizeY>＝(xCb>>CtbLog2SizeY)–1 (3)

(xCb+(mvL[0]>>4)+cbWidth-1)>>CtbLog2SizeY<＝(xCb>>CtbLog2SizeY) (4)

(e) c2: (xCb + (mvL [0] > >4)) > > CtbLog2SizeY is equal to (xCb > > CtbLog2SizeY) -1, with the current luminance position (xCurr, yCurr) and the neighboring luminance position (((xCb + (mvL [0] > >4) + CtbSizeY) > (CtbLog2SizeY-1)) < (CtbLog2SizeY-1) >) (yCb + (mvL [1] > >4)) > (CtbLog2SizeY-1)) < (CtbLog2SizeY-1)) set to (xCb, yCb) as inputs, a block availability derivation process specified in the neighboring block availability check process is invoked, and the output should be FALSE (FALSE).

In fig. 11, five spatial merging candidates such as in HEVC and VVC may be shown. The order in which the candidate list is formed from the positions shown in fig. 11 may be: a0- > B0- > B1- > A1- > B2.

The history-based MVP (hmvp) merge candidates may be added to the merge list after spatial Motion Vector Prediction (MVP) and Temporal Motion Vector Prediction (TMVP). The motion information of previously encoded blocks may be stored in a table and used as the MVP for the current CU, e.g., as used in HMVP. A table with multiple HMVP candidates may be maintained during the encoding/decoding process. The table may be reset (cleared) when a new CTU row is encountered. When a non-sub-block inter-coded CU is encountered, the associated motion information may be added as a new HMVP candidate to the last entry of the table.

The size S of the HMVP table may be set to 6, which means that up to 6 HMVP candidates may be added to the table, e.g., as used in VTM 3. When inserting new motion candidates in the table, a constrained first-in-first-out (FIFO) rule may be used, where a redundancy check is first applied to look up whether the same HMVP is present in the table. If the same HMVP is found, the same HMVP may be removed from the table and all HMVP candidates thereafter may be moved forward.

The HMVP candidates may be used to construct a merge candidate list. Several HMVP candidates that are up-to-date in the table may be checked in turn and inserted or added to the merge candidate list following the TMVP candidate. In addition, a redundancy check may be applied to the HMVP candidate relative to the spatial or temporal merge candidates.

To reduce the number of redundancy check operations, the following simplified procedure may be introduced: (a) the number of HMVP candidates for merge list generation can be set to (N ≦ 4)? M (8-N), wherein if N is less than or equal to 4, the number of HMVP candidates is set to M, and if N is greater than 4, the number of HMVP candidates is set to 8-N. N denotes the number of existing candidates in the merge candidate list and M denotes the number of available HMVP candidates in the table. (b) Once the total number of available merge candidates reaches the maximum number of allowed merge candidates minus 1, the build process of the merge candidate list of HMVPs may be terminated.

When intra block copy operates as a separate mode from inter mode, a separate history buffer, also known as history-based vector prediction (HBVP), may be used to store previously encoded intra block copy block vectors. As a mode separate from inter prediction, a simplified block vector derivation process may be applied to the intra block copy mode. For example, the candidate list for IBC BV prediction in AMVP mode may share a candidate list for IBC BV prediction in merge mode (merge candidate list) that includes 2 spatial candidates and 5 HBVP candidates.

The size of the merge candidate list for the IBC mode may be designated as MaxNumMergeCand, which may be determined by the size MaxNumMergeCand of the inter mode merge candidate list, and further designated as six _ minus _ max _ num _ merge _ cand. six minus max num merge cand specifies the maximum number of merge Motion Vector Prediction (MVP) candidates supported in the slice (e.g., I slice) subtracted from 6. The maximum number of merged MVP candidates MaxNumMergeCand can be derived from equation (5):

MaxNumMergeCand＝6-six_minus_max_num_merge_cand (5)

the value of MaxNumMergeCand may be in the range of 1 to 6 (including 1 and 6).

In some video codec systems, such as in the VVC specification, the merge list size for IBC mode may be signaled separately from the merge list size for inter merge mode for all I/P/B slices. The merge list size for the IBC mode may range from 1 to 6 (including 1 and 6) as in the inter-frame merge mode. In one example, six minus max num ibc merge cand may be used to specify the maximum number of ibc merge Motion Vector Prediction (MVP) candidates supported in a slice (e.g., I slice) subtracted from 6. ibc the maximum number of merged MVP candidates MaxNumumBcMergeCand can be derived from equation (6):

MaxNumIbcMergeCand＝6-six_minus_max_num_ib_merge_cand (6)

the value of maxnumibcmrgecand may be in the range of 1 to 6 (including 1 and 6). Maxnumibccargecand is a high level signaling that is included in the prediction information of blocks of a coded region in video, which are decoded from the coded video bitstream. The value of the high level signaling information indicates the maximum number of motion vector prediction candidates in the motion vector prediction candidate list of IBC mode. Based on the value of the high level signaling information and some constraint information, it may be determined whether the prediction mode of the block is IBC mode. High level signaling typically refers to syntax elements above the block level, e.g., in the frame level, e.g., six minus max num ibc merge cand is a syntax element in the Sequence Parameter Set (SPS).

In some embodiments, it may be desirable to turn off IBC mode on a picture-basis or similar granularity (e.g., sequence-basis, group-of-pictures-basis, slice-basis, or tile-basis). Thus, the above-mentioned coded region may include at least one of a video sequence, a group of pictures GOP, a picture, a slice, and a tile.

In some embodiments, the block vector prediction candidate list of IBC mode may be shared by the merge mode and AMVP mode. For example, the merge mode and AMVP mode of the IBC mode may use the same prediction list, and the size of the prediction list may be controlled by a variable, i.e., the maximum number of IBC merge candidates (e.g., maxnumibcmrgecand). In some embodiments, the merge mode of the IBC mode and the AMVP mode of the IBC mode may have different block vector prediction candidate lists.

In some embodiments, maxnumibcmrgecand may range from 0 to N, where N is the target maximum number. In one embodiment, N ═ 6. In another embodiment, N is set equal to MaxUMMergeCand.

In some embodiments, maxnumibcmrgecand ═ 0 may be used to indicate that IBC mode is turned off for a slice (e.g., an I slice). Therefore, if maxnumibcmrgecand is 0, the IBC merge mode or the IBC AMVP mode cannot be applied to the slice. It should be noted that maxnumibcmrgecand ═ 0 may be used to indicate that IBC mode is turned off for a picture, sequence, group of pictures (GOP), tile, slice, or other level of granularity.

Table 1 shows an embodiment part of a syntax table for slice level merge candidate size signaling.

Table 1: syntax and semantics for slice level merge candidate size signaling

if(sps_ibc_enabled_flag)
		six_minus_max_num_ibc_merge_cand	ue(v)

As shown in table 1, six _ minus _ max _ num _ IBC _ merge _ cand specifies the maximum number of IBC merge Motion Vector Prediction (MVP) candidates supported in the slice subtracted from 6. The maximum number of IBC merging MVP candidates (e.g., maxnumib cmergecand) may be derived from equation (7):

MaxNumIbcMergeCand＝6-six_minus_max_num_ib_merge_cand (7)

the maxnumib cmergecand may have a value in the range of 0 to 6 (including 0 and 6). When maxnumib cmergecand is not present, six _ minus _ max _ num _ ib _ merge _ cand may be inferred to some value (e.g., value 6). When maxnumib cmergecand is equal to 0, IBC mode is disabled for the current slice.

Table 2 is a syntax table of the coding unit of the method provided in the present application.

Table 2: syntax table for coding unit

As shown in table 1, in one embodiment, when the value of maxnumib cmergecand is zero, the prediction mode of the block is not the IBC mode. In another embodiment, cu skip flag may be signaled when the value of maxnumib cmergecand is not zero and is responsive to constraint information, as shown in table 2, where cu skip flag may be referred to as first signaling information. The constraint information may include a combination of: (i) the coded region is an I slice, (ii) the CHROMA channel TYPE of the block is not a DUAL TREE MODE (e.g., treeType ═ DUAL _ TREE _ CHROMA), and (iii) the width of the block (e.g., cbWidth) is not equal to 4 pixels or the height of the block (e.g., cbHeight) is not equal to 4 pixels, and the first prediction MODE TYPE information of the constraint information indicates that the prediction MODE of the block is not an INTRA prediction MODE (e.g., modeType _ INTRA). Therefore, when cu _ skip _ flag is true, the prediction mode of the block is the skip mode of the IBC mode.

Still referring to table 2, a pred _ mode _ ibc _ flag may be signaled according to maxnumib cmerceland being greater than zero and constraint information, where pred _ mode _ ibc _ flag may be referred to as second signaling information. The constraint information may include a combination of: the CHROMA channel TYPE of the block is not a DUAL TREE MODE (e.g., treeType | ═ DUAL _ TREE _ CHROMA), the first prediction MODE TYPE information of the constraint information indicates that the prediction MODE of the block is not an INTER prediction MODE (e.g., modeType ═ MODE _ TYPE _ INTER), the width of the block (e.g., cbWidth) is equal to or less than 64 pixels, the height of the block (e.g., cbHeight) is equal to or less than 64 pixels, and one of: (i) the coded region is an I slice (e.g., slice _ type ═ I) and cu _ skip _ flag is false, (ii) the coded region is not an I slice (slice _ type ═ I), and the second prediction MODE type information indicates that the prediction MODE of the block is not an INTRA prediction MODE (e.g., CuPredMode [ chType ] [ x0] [ y0] | -MODE _ INTRA), and (iii) the coded region is not an I slice, the width of the block is equal to 4 pixels, the height of the block is equal to 4 pixels, and cu _ skip _ flag is false. Thus, pred _ mode _ IBC _ flag equal to 1 (i.e., the second signaling information is true) may specify that the current Coding Unit (CU) is coded in the IBC prediction mode. pred _ mode _ IBC _ flag equal to 0 (i.e., the second signaling information is false) may specify that the current coding unit is not coded in IBC prediction mode.

When pred _ mode _ ibc _ flag is not present (or not signaled), the following inference can be made for pred _ mode _ ibc _ flag:

(a) if cu _ skip _ flag [ x0] [ y0] is equal to 1, cbWidth is equal to 4 pixels, and cbHeight is equal to 4 pixels, then pred _ mode _ ibc _ flag is inferred to be equal to 1.

(b) Otherwise (e.g., cu _ skip _ flag [ x0] [ y0] is not equal to 1, cbWidth is not equal to 4 pixels, and cbHeight is not equal to 4 pixels), if cbWidth and cbHeight are both equal to 128 pixels, then pred _ mode _ ibc _ flag is inferred to be equal to 0.

(c) Otherwise (e.g., neither cbWidth nor cbHeight equals 128 pixels), if modeType equals MODE _ TYPE _ INTER, then pred _ MODE _ ibc _ flag is inferred to be equal to 0.

(d) Otherwise (e.g., modeType is not equal to MODE _ TYPE _ INTER), if treeType is equal to DUAL _ TREE _ CHROMA, then pred _ MODE _ ibc _ flag is inferred to be equal to 0.

(e) Otherwise (e.g., treeType is not equal to DUAL _ TREE _ CHROMA), pred _ mode _ ibc _ flag is inferred to be equal to the value of maxnumibmergecand when encoding I slices, and pred _ mode _ ibc _ flag is inferred to be equal to 0 when encoding P slices or B slices. For an I slice, pred _ mode _ ibc _ flag is inferred to be 1 when MaxNumbib Cmegerand is greater than zero, and pred _ mode _ ibc _ flag is inferred to be 0 when MaxNumbib Cmegerand is 0. In addition, when pred _ MODE _ IBC _ flag is equal to 1, the variable CuPredMode [ chType ] [ x ] [ y ] may be set equal to MODE _ IBC, where x is x0.. x0+ cbWidth-1, y is y0.. y0+ cbHeight-1.

Based on the above inference, when the coded region is one of a P-slice and a B-slice, it may be determined that the prediction mode of the block is not the IBC mode. When it is determined that the value of the high level signaling information (i.e., maxnumibmemegand) is greater than zero, the encoded region is an I-slice, and the constraint information includes a combination of the following, it may be determined that the prediction mode of the block is the IBC mode. The constraint information includes a combination of: (i) the first signaling information (i.e., cu _ skip _ flag) is false, the width of the block is not equal to 4 pixels, and the height of the block is not equal to 4 pixels, (ii) the width of the block is not equal to 128 pixels, and the height of the block is not equal to 128 pixels, (iii) the first prediction mode type information indicates that the prediction mode of the block is not an inter prediction mode, and (iv) the chroma channel type of the block is not a dual tree mode.

In some embodiments, the IBC mode includes at least one of a merge mode and an AMVP mode. The block vector prediction candidate list for IBC merge mode may be the same as or different from the block vector prediction candidate list for IBC AMVP mode (e.g., based on differentially encoded block vector prediction).

When the two candidate lists are not the same or the AMVP candidate list of the IBC is controlled independently of the merge list of the IBC, the slice level IBC mode can still be controlled to be turned on or off through the variable MaxUMIbcMergeCand. IBC mode may be disabled for slices when maxnumibcmrgecand is 0.

Fig. 12 shows a flow chart of a video decoding method (1200) according to an embodiment of the application. The method (1200) may be used for block reconstruction to generate a prediction block for a block being reconstructed. In various embodiments, the method (1200) is performed by processing circuitry, e.g., processing circuitry in terminal devices (310), (320), (330), and (340), processing circuitry that performs the functions of the video encoder (403), processing circuitry that performs the functions of the video decoder (410), processing circuitry that performs the functions of the video decoder (510), processing circuitry that performs the functions of the video encoder (603), and so forth. In some embodiments, the method (1200) is implemented in software instructions, such that when executed by processing circuitry, the processing circuitry performs the method (1200). The method starts at step (S1201), and execution proceeds to step (S1299) and ends.

As shown in fig. 12, the method (1200) starts at step (S1201), and performs step (S1210). In step (S1210), prediction information of a block of a coded region in video is decoded from a coded video bitstream, the prediction information including high level signaling information (e.g., maxnumibcmrgecand). Then, the method (1200) performs step (S1220). In step (S1220), it is determined whether the prediction mode of the block is an Intra Block Copy (IBC) mode based on the value of the high level signaling information indicating the maximum number of motion vector prediction candidates in the motion vector prediction candidate list of the IBC mode and constraint information.

In some embodiments, the encoded region may include at least one of a video sequence, a group of pictures (GOP), a picture, a slice, and a tile.

In some embodiments, when the value of the high level signaling information is zero, it is determined that the prediction mode of the block is not the IBC mode.

In some embodiments, the first signaling information is received when the value of the high level signaling information is not zero and is responsive to the constraint information. The constraint information may include a combination of: (i) the coded region is an I slice, (ii) the chroma channel type of the block is not dual-tree mode, and (iii) one of a width of the block is not equal to 4 pixels and a height of the block is not equal to 4 pixels, and the first prediction mode type information of the constraint information indicates that the prediction mode of the block is not an intra prediction mode. Therefore, when the first signaling information is true, the prediction mode of the block is a skip mode of the IBC mode.

In some embodiments, the second signaling information is received when the value of the high level signaling information is greater than zero and is responsive to the constraint information. The constraint information includes a combination of: the chroma channel type of the block is not a dual tree mode, the first prediction mode type information of the constraint information indicates that the prediction mode of the block is not an inter prediction mode, the width of the block is equal to or less than 64 pixels, and the height of the block is equal to or less than 64 pixels. The constraint information may further include one of: (i) the coded region is an I-slice and the first signaling information is false, (ii) the coded region is not an I-slice and the second prediction mode type information indicates that the prediction mode of the block is not an intra prediction mode, and (iii) the coded region is not an I-slice, the width of the block is equal to 4 pixels and the height of the block is equal to 4 pixels, and the first signaling information is false. Thus, when the second signaling information is true, the prediction mode of the block is IBC mode.

In some embodiments, when the coded region is one of a P-slice and a B-slice, it is determined that the prediction mode of the block is not the IBC mode. In some embodiments, when the value of the high level signaling information is greater than zero, the coded region is an I-slice, and the prediction mode of the block is determined to be IBC mode in response to the constraint information. The constraint information may include a combination of: (i) the first signaling information is false, the width of the block is not equal to 4 pixels, and the height of the block is not equal to 4 pixels, (ii) the width of the block is not equal to 128 pixels, and the height of the block is not equal to 128 pixels, (iii) the first prediction mode type information indicates that the prediction mode of the block is not an inter prediction mode, and (iv) the chroma channel type of the block is not a dual-tree mode. Accordingly, when the value of the high level signaling information is greater than zero, the prediction mode of the block may be the IBC mode, and when the value of the high level signaling information is equal to zero, the prediction mode of the block may not be the IBC mode.

In step (S1230), the block is decoded based on whether the prediction mode of the block is determined to be the IBC mode.

It should be noted that the methods provided by the embodiments of the present application may be used alone or in any combination thereof. Furthermore, each of the method (or embodiment), encoder and decoder may be implemented by processing circuitry (e.g., one or more processors, or one or more integrated circuits). In one embodiment, the one or more processors execute programs stored in a non-transitory computer readable storage medium. Furthermore, the term "block" may be interpreted as a prediction block, a coding block or a coding unit, i.e. a CU.

An embodiment of the present application further provides a video decoding apparatus, including:

a first decoding module for decoding prediction information for a block of an encoded region in video from an encoded video bitstream, the prediction information comprising advanced signaling information;

a determination module to determine whether a prediction mode of the block is an intra block copy, IBC, mode based on a value of the high level signaling information and constraint information, the value of the high level signaling information indicating a maximum number of motion vector prediction candidates in a motion vector prediction candidate list of the IBC mode; and

a second decoding module to decode the block based on whether the prediction mode of the block is determined to be the IBC mode.

The embodiment of the present application further provides a computer device, which includes one or more processors and one or more memories, where at least one program instruction is stored in the one or more memories, and the at least one program instruction is loaded and executed by the one or more processors to implement the above-mentioned video decoding method.

The techniques described above may be implemented as computer software via computer readable instructions and physically stored in one or more computer readable media. The computer readable medium may be a non-volatile computer readable storage medium storing program instructions that, when executed by a computer for video encoding/decoding, cause the computer to perform the method for video decoding described in the above embodiments. For example, fig. 13 illustrates a computer system (1300) suitable for implementing certain embodiments of the disclosed subject matter.

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

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

The components illustrated in FIG. 13 for computer system (1300) are exemplary in nature and are not intended to limit the scope of use or functionality of computer software implementing embodiments of the present application in any way. Neither should the configuration of components be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary embodiments of the computer system (1300).

The computer system (1300) may include some human interface input devices. Such human interface input devices may respond to input from one or more human users through tactile input (e.g., keyboard input, swipe, data glove movement), audio input (e.g., sound, applause), visual input (e.g., gestures), olfactory input (not shown). The human-machine interface device may also be used to capture media that does not necessarily directly relate to human conscious input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, photographic images obtained from still-image cameras), video (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

The human interface input device may include one or more of the following (only one of which is depicted): keyboard (1301), mouse (1302), touch pad (1303), touch screen (1310), data glove (not shown), joystick (1305), microphone (1306), scanner (1307), camera (1308).

The computer system (1300) may also include some human interface output devices. Such human interface output devices may stimulate the senses of one or more human users through, for example, tactile outputs, sounds, light, and olfactory/gustatory sensations. Such human interface output devices may include tactile output devices (e.g., tactile feedback through a touch screen (1310), data glove (not shown), or joystick (1305), but there may also be tactile feedback devices that do not act as input devices), audio output devices (e.g., speakers (1309), headphones (not shown)), visual output devices (e.g., screens (1310) including cathode ray tube screens, liquid crystal screens, plasma screens, organic light emitting diode screens, each with or without touch screen input functionality, each with or without haptic feedback functionality-some of which may output two-dimensional visual output or more-than-three-dimensional output by means such as stereoscopic picture output; virtual reality glasses (not shown), holographic displays and smoke boxes (not shown)), and printers (not shown).

The computer system (1300) may also include human-accessible storage devices and their associated media such as optical media including compact disc read-only/rewritable (CD/DVD ROM/RW) (1320) or similar media (1321) with CD/DVD, thumb drive (1322), removable hard drive or solid state drive (1323), conventional magnetic media such as tape and floppy disk (not shown), ROM/ASIC/PLD based application specific devices such as a security dongle (not shown), and the like.

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

The computer system (1300) may also include a network interface (1354) to one or more communication networks (1355). For example, the one or more communication networks (1355) may be wireless, wired, optical. The one or more communication networks (1355) may also be local area networks, wide area networks, metropolitan area networks, vehicular and industrial networks, real-time networks, delay tolerant networks, and the like. The one or more communication networks (1355) also include ethernet, wireless local area networks, local area networks such as cellular networks (GSM, 3G, 4G, 5G, LTE, etc.), television wired or wireless wide area digital networks (including cable, satellite, and terrestrial broadcast television), automotive and industrial networks (including CANBus), and so forth. Some networks typically require external network interface adapters for connecting to some general purpose data ports or peripheral buses (1349) (e.g., USB ports of computer system (1300)); other systems are typically integrated into the core of computer system 1300 (e.g., ethernet interface integrated into a PC computer system or cellular network interface integrated into a smart phone computer system) by connecting to a system bus as described below. Using any of these networks, the computer system (1300) may communicate with other entities. The communication may be unidirectional, for reception only (e.g., wireless television), unidirectional for transmission only (e.g., CAN bus to certain CAN bus devices), or bidirectional, for example, to other computer systems over a local or wide area digital network. Each of the networks and network interfaces described above may use certain protocols and protocol stacks.

The human interface device, human accessible storage device, and network interface described above may be connected to the core (1340) of the computer system (1300).

The core (1340) may include one or more Central Processing Units (CPUs) (1341), Graphics Processing Units (GPUs) (1342), special purpose programmable processing units in the form of Field Programmable Gate Arrays (FPGAs) (1343), hardware accelerators (1344) for specific tasks, graphics adapters (1350), and so forth. These devices, as well as Read Only Memory (ROM) (1345), random access memory (1346), internal mass storage (e.g., internal non-user accessible hard drives, solid state drives, etc.) (1347), etc., may be connected via a system bus (1348). In some computer systems, the system bus (1348) may be accessed in the form of one or more physical plugs, so as to be expandable by additional central processing units, graphics processing units, and the like. The peripheral devices may be attached directly to the system bus (1348) of the core or connected through a peripheral bus (1349). In an embodiment, the display (i.e., touch screen 1310) is connected to a graphics adapter (1350). The architecture of the peripheral bus includes peripheral controller interface PCI, universal serial bus USB, etc.

The CPU (1341), GPU (1342), FPGA (1343) and accelerator (1344) may execute certain instructions, which in combination may constitute the computer code described above. The computer code may be stored in ROM (1345) or RAM (1346). The transitional data may also be stored in RAM (1346), while the permanent data may be stored in, for example, internal mass storage (1347). Fast storage and retrieval for any memory device can be achieved through the use of cache memories, which may be closely associated with one or more CPUs (1341), GPUs (1342), mass storage (1347), ROMs (1345), RAMs (1346), and the like.

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

By way of example, and not limitation, a computer system having an architecture (1300), and in particular a core (1340), may provide functionality as a processor (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software contained in one or more tangible computer-readable media. Such computer-readable media may be media associated with the user-accessible mass storage described above, as well as specific storage having a non-volatile core (1340), such as core internal mass storage (1347) or ROM (1345). Software implementing various embodiments of the present application may be stored in such devices and executed by the core (1340). The computer-readable medium may include one or more memory devices or chips, according to particular needs. The software may cause the core (1340), and in particular the processors therein (including CPUs, GPUs, FPGAs, etc.), to perform certain processes or certain portions of certain processes described herein, including defining data structures stored in RAM (1346) and modifying such data structures according to software-defined processes. Additionally or alternatively, the computer system may provide functionality that is logically hardwired or otherwise embodied in circuitry (e.g., accelerator (1344)) that may operate in place of or in conjunction with software to perform certain processes or certain portions of certain processes described herein. Where appropriate, reference to software may include logic and vice versa. Where appropriate, reference to a computer-readable medium may include circuitry (e.g., an Integrated Circuit (IC)) storing executable software, circuitry comprising executable logic, or both. The present application includes any suitable combination of hardware and software.

Appendix A: acronyms

JEM: joint development Model (Joint Exploration Model)

VVC: general purpose Video Coding (Versatile Video Coding)

BMS: reference Set (Benchmark Set)

MV: motion Vector (Motion Vector)

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

SEI: auxiliary Enhancement Information (supplement Enhancement Information)

VUI: video Usability Information (Video Usability Information)

GOPs: picture group (Groups of Pictures)

TUs: transformation unit (Transform Units)

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

CTUs: coding Tree unit (Coding Tree Units)

CTBs: coding Tree (Coding Tree Blocks)

PBs: prediction block (Prediction Blocks)

HRD: hypothetical Reference Decoder (Hypothetical Reference Decoder)

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

CPUs: central Processing unit (Central Processing Units)

GPUs: graphic Processing unit (Graphics Processing Units)

CRT: cathode Ray Tube (Cathode Ray Tube)

LCD: LCD Display (Liquid-Crystal Display)

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

CD: compact Disc (Compact Disc)

DVD: digital Video Disc (Digital Video Disc)

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

RAM: random Access Memory (Random Access Memory)

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

PLD: programmable Logic Device (Programmable Logic Device)

LAN: local Area Network (Local Area Network)

GSM: global System for Mobile communications

LTE: long Term Evolution (Long-Term Evolution)

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

USB: universal Serial Bus (Universal Serial Bus)

PCI: peripheral device Interconnect (Peripheral Component Interconnect)

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

SSD: solid state Drive (Solid-state Drive)

IC: integrated Circuit (Integrated Circuit)

CU: coding Unit (Coding Unit)

While the application has described several exemplary embodiments, various modifications, arrangements, and equivalents of the embodiments are within the scope of the application. It will thus be appreciated that those skilled in the art will be able to devise various systems and methods which, although not explicitly shown or described herein, embody the principles of the application and are thus within its spirit and scope.

Claims (14)

1. A method of video decoding, the method comprising:

decoding prediction information for a block of a coded region in video from a coded video bitstream, the prediction information comprising advanced signaling information;

determining whether a prediction mode of the block is an intra block copy, IBC, mode based on a value of the high level signaling information and constraint information, the value of the high level signaling information indicating a maximum number of motion vector prediction candidates in a motion vector prediction candidate list of the IBC mode; and

decoding the block based on whether a prediction mode of the block is determined to be the IBC mode.

2. The method of claim 1, wherein the coded region comprises at least one of a video sequence, a group of pictures (GOP), a picture, a slice, and a tile.

3. The method of claim 2, wherein the determining whether the prediction mode of the block is an Intra Block Copy (IBC) mode comprises:

determining that the prediction mode of the block is not the IBC mode when the value of the high level signaling information is zero.

4. The method of claim 2, further comprising:

receiving first signaling information when it is determined that the value of the advanced signaling information is not zero and the constraint information comprises a combination of:

(i) the coded region is an I-slice,

(ii) the chroma channel type of the block is not dual-tree mode, an

(iii) The width of the block is not equal to 4 pixels or the height of the block is not equal to 4 pixels, and the first prediction mode type information of the constraint information indicates that the prediction mode of the block is not an intra prediction mode.

5. The method of claim 4, wherein the determining whether the prediction mode of the block is an Intra Block Copy (IBC) mode comprises:

determining that the prediction mode of the block is a skip mode of the IBC mode when the first signaling information is true.

6. The method of claim 4, further comprising:

receiving second signaling information when it is determined that the value of the advanced signaling information is greater than zero and the constraint information comprises a combination of:

(a) the chroma channel type of the block is not dual-tree mode,

(b) the first prediction mode type information of the constraint information indicates that the prediction mode of the block is not an inter prediction mode,

(c) the width of the block is equal to or less than 64 pixels, the height of the block is equal to or less than 64 pixels, an

(d) One of the following: (i) the encoded region is the I-slice and the first signaling information is false, (ii) the encoded region is not the I-slice and second prediction mode type information indicates that the prediction mode of the block is not an intra prediction mode, and (iii) the encoded region is not the I-slice, a width of the block is equal to 4 pixels and a height of the block is equal to 4 pixels, and the first signaling information is false.

7. The method of claim 6, wherein the determining whether the prediction mode of the block is an Intra Block Copy (IBC) mode comprises:

determining that the prediction mode of the block is the IBC mode when the second signaling information is true.

8. The method of claim 4, wherein the determining whether the prediction mode of the block is an Intra Block Copy (IBC) mode comprises:

determining that a prediction mode of the block is not the IBC mode when the coded region is one of a P-slice and a B-slice; and

determining that a prediction mode of the block is the IBC mode when it is determined that the value of the high level signaling information is greater than zero, the coded region is the I-slice, and the constraint information comprises a combination of:

(i) the first signaling information is false, the width of the block is not equal to 4 pixels, and the height of the block is not equal to 4 pixels,

(ii) the width of the block is not equal to 128 pixels, and the height of the block is not equal to 128 pixels,

(iii) the first prediction mode type information indicates that the prediction mode of the block is not an inter prediction mode, and

(iv) the chroma channel type of the block is not dual-tree mode.

9. The method according to any of claims 1-8, wherein the IBC mode comprises at least one of a Merge mode and an Advanced Motion Vector Prediction (AMVP) mode.

10. The method of claim 9, wherein the merge mode of the IBC mode and the AMVP mode of the IBC mode share the motion vector prediction candidate list.

11. The method of claim 9, wherein a motion vector prediction candidate list for a merge mode of the IBC mode is different from a motion vector prediction candidate list for an AMVP mode of the IBC mode.

12. An apparatus for video decoding, comprising:

a first decoding module for decoding prediction information for a block of an encoded region in video from an encoded video bitstream, the prediction information comprising advanced signaling information;

a determination module to determine whether a prediction mode of the block is an intra block copy, IBC, mode based on a value of the high level signaling information and constraint information, the value of the high level signaling information indicating a maximum number of motion vector prediction candidates in a motion vector prediction candidate list of the IBC mode; and

a second decoding module to decode the block based on whether the prediction mode of the block is determined to be the IBC mode.

13. A non-transitory computer-readable storage medium storing program instructions for causing a computer for video encoding/decoding to perform the method for video decoding according to any one of claims 1 to 11 when the program instructions are executed by the computer.

14. A computer device comprising one or more processors and one or more memories having stored therein at least one program instruction, the at least one program instruction being loaded and executed by the one or more processors to implement the method of video decoding of any of claims 1-11.

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