Video coding method, video codec and computer readable medium

Abstract

An embodiment of the present application provides a video encoding and decoding method, a video codec and a computer-readable medium. The decoding method includes: receiving a coded video bit stream, determining whether the size of a first coding tree unit CTU corresponding to a current block in the coded video bit stream is smaller than the size of a reference sample memory, and determining a second CTU corresponding to a reference block of the current block; in response to determining that the size of the first CTU is smaller than the size of the reference sample memory, determining whether a distance between the second CTU and the first CTU is smaller than a threshold, wherein the threshold is calculated based on a ratio of the size of the reference sample memory to the size of the first CTU; in response to determining that the distance is smaller than the threshold, retrieving one or more samples from the memory location corresponding to the reference block to decode the current block.

Description

[0001] This application is a divisional application of an actively modified version of a patent application with a filing date of January 13, 2020, Chinese patent application number 202080007690.7, and invention name “Method and device for reuse of reference sample memory for intra-frame picture block compensation”. Technical Field

[0002] This application describes embodiments generally related to video encoding and decoding. Background Art

[0003] The background description provided herein is for the purpose of generally describing the context of the present disclosure. To the extent described in this background section, the work of the currently designated inventors and aspects of the description that may not be in the prior art at the time of filing the application are neither explicitly nor implicitly admitted as prior art to the present disclosure.

[0004] Video encoding and decoding may be performed using inter-picture prediction with motion compensation. An uncompressed digital video may include a series of pictures, each picture having spatial dimensions of, for example, 1920×1080 luma samples and associated chroma samples. The series of pictures may have a fixed or variable picture rate (also informally referred to as a frame rate), for example, 60 pictures per second or 60 Hz. Uncompressed video has very high bitrate requirements. For example, at 8 bits per sample, 1080p60 4:2:0 video (with a resolution of 1920×1080 luma samples at a 60 Hz frame rate) requires a bandwidth of nearly 1.5 Gbit / s. One hour of such video requires more than 600 GB of storage space.

[0005] One purpose of video encoding and decoding can be to reduce redundancy in the input video signal through compression. Compression can help reduce the above-mentioned bandwidth or storage space requirements, in some cases by two orders of magnitude or more. Lossless compression, lossy compression, and combinations thereof can be used. Lossless compression refers to a technique that can reconstruct an exact copy of the original signal from the compressed original signal. When lossy compression is used, the reconstructed signal may be different from the original signal, but the distortion between the original signal and the reconstructed signal is small enough to make the reconstructed signal usable for the intended application. In the case of video, lossy compression is widely used. The amount of distortion that can be tolerated depends on the application; for example, some users of consumer streaming applications can tolerate higher distortion than users of television distribution applications. The achievable compression rate can reflect that the higher the allowable / tolerable distortion, the higher the compression rate that can be produced.

[0006] Motion compensation may be a lossy compression technique and may involve the following technique: a block of sample data from a previously reconstructed picture or portion thereof (reference picture) is used to predict a newly reconstructed picture or picture portion after being spatially shifted in a direction indicated by a motion vector (hereinafter MV). In some cases, the reference picture may be the same as the picture currently being reconstructed. The MV may have two dimensions, X and Y, or three dimensions, with the third dimension indicating the reference picture being used (the latter may indirectly be a temporal dimension).

[0007] In some video compression techniques, the MV applicable to a region of sample data can be predicted based on other MVs, for example, based on an MV related to another region of sample data that is spatially adjacent to the region being reconstructed and that precedes the MV in decoding order. Doing so can greatly reduce the amount of data required to encode the MV, thereby eliminating redundancy and increasing the compression rate. MV prediction can work effectively, for example, because when encoding an input video signal derived from a camera (called natural video), there is a statistical possibility that a larger region than the region for which a single MV is applicable moves in a similar direction, so in some cases, similar motion vectors derived from MVs of adjacent regions can be used to predict the larger region. This makes the MV found for a given region similar or identical to the MV predicted from the surrounding MVs, and then after entropy coding, the MV found for the given region can be represented with fewer bits than the number of bits used when the MV is directly encoded. In some cases, MV prediction can be an example of lossless compression of a signal (i.e., MV) derived from an original signal (i.e., a sample stream). In other cases, MV prediction itself can be lossy, for example, due to rounding errors when calculating predicted values ​​based on multiple surrounding MVs.

[0008] Various MV prediction mechanisms are described in H.265 / HEVC (ITU-T Recommendation H.265, "High Efficiency Video Coding", December 2016). Among the various MV prediction mechanisms provided by H.265, this article describes a technique referred to below as "spatial merging".

[0009] When decoding a current block using intra block copy, the memory is referenced to retrieve samples used to decode the current block. Since the size of the memory is limited, when the memory is updated with samples from the most recently decoded block, multiple portions of the memory are overwritten. Therefore, new methods are needed to efficiently utilize the memory to perform intra block copy. Summary of the invention

[0010] According to an exemplary embodiment of the present application, a video decoding method for a decoder includes receiving a coded video bitstream. The method further includes determining whether the size of a first coding tree unit CTU corresponding to a current block in the coded video bitstream is smaller than the size of a reference sample memory, and determining a second CTU corresponding to a reference block of the current block; in response to determining that the size of the first CTU is smaller than the size of the reference sample memory, determining whether the distance between the second CTU and the first CTU is smaller than a threshold, wherein the threshold is calculated based on the ratio of the size of the reference sample memory to the size of the first CTU; in response to determining that the distance is smaller than the threshold, retrieving one or more samples from the memory location corresponding to the reference block to decode the current block.

[0011] According to an exemplary embodiment of the present application, a video decoder for video decoding includes a processing circuit. The processing circuit is configured to receive a coded video bitstream. The processing circuit is further configured to determine whether the size of a first coding tree unit CTU corresponding to a current block in the coded video bitstream is smaller than the size of a reference sample memory, and to determine a second CTU corresponding to a reference block of the current block; in response to determining that the size of the first CTU is smaller than the size of the reference sample memory, determine whether the distance between the second CTU and the first CTU is smaller than a threshold, wherein the threshold is calculated based on the ratio of the size of the reference sample memory to the size of the first CTU; in response to determining that the distance is smaller than the threshold, retrieve one or more samples from the memory location corresponding to the reference block to decode the current block.

[0012] According to an exemplary embodiment of the present application, a non-transitory computer-readable medium stores instructions that, when executed by a processor in a video decoder, cause the video decoder to perform a method. The method includes receiving a coded video bitstream. The method further includes determining whether the size of a first coding tree unit CTU corresponding to a current block in the coded video bitstream is smaller than the size of a reference sample memory, and determining a second CTU corresponding to a reference block of the current block; in response to determining that the size of the first CTU is smaller than the size of the reference sample memory, determining whether the distance between the second CTU and the first CTU is smaller than a threshold, wherein the threshold is calculated based on the ratio of the size of the reference sample memory to the size of the first CTU; in response to determining that the distance is smaller than the threshold, retrieving one or more samples from the memory location corresponding to the reference block to decode the current block.

[0013] The embodiments of the present application have the following technical effects: by determining that a reference block is located in a different CTU, and determining a first area in the CTU of a current block (which is juxtaposed with a second area in a different CTU), and determining whether a memory location for the reference block in a reference sample memory is available based on a decoding state of the first area, one or more samples are retrieved from the memory location corresponding to the reference block to decode the current block, thereby overcoming the problem that, due to the limited size of the memory, multiple parts of the memory are overwritten when the memory is updated using samples from a recently decoded block, making it impossible to effectively utilize the memory to perform intra-frame block copying. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Other features, properties and various advantages of the subject matter of the present application will be more apparent from the following detailed description and accompanying drawings.

[0015] In the attached picture:

[0016] Figure 1 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment;

[0017] Figure 2 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment;

[0018] Figure 3 is a schematic diagram of a simplified block diagram of a decoder according to one embodiment;

[0019] Figure 4 is a schematic diagram of a simplified block diagram of an encoder according to one embodiment;

[0020] Figure 5 shows a block diagram of an encoder according to another embodiment;

[0021] Figure 6 shows a block diagram of a decoder according to another embodiment;

[0022] Figure 7 is a schematic diagram of a current block and its surrounding spatial merging candidates in an example;

[0023] Figure 8 It is a schematic diagram of intra-frame picture block compensation;

[0024] 9A to 9D is a schematic diagram of intra picture block compensation with a coding tree unit (CTU) size search range;

[0025] FIG. 10A to FIG. 10D is a schematic diagram of a reference sample memory;

[0026] Fig.11 is a schematic diagram of a reference block in a first CTU and a corresponding concatenated block in a second CTU;

[0027] Fig.12 is a schematic diagram of a reference block in a first CTU and a corresponding concatenated block in a second CTU, wherein a third CTU is located between the first CTU and the second CTU;

[0028] Fig.13 and Fig.14 An embodiment of a process performed by an encoder is shown;

[0029] Fig.15 is a schematic diagram of a computer system according to one embodiment. DETAILED DESCRIPTION

[0030] Figure 1 A simplified block diagram of a communication system (100) according to one embodiment of the present disclosure is shown. The communication system (100) includes a plurality of terminal devices that can communicate with each other via, for example, a network (150). For example, the communication system (100) includes a first pair of terminal devices (110 and 120) interconnected via the network (150). Figure 1 In the example of , the first terminal device pair (110 and 120) performs unidirectional data transmission. For example, the terminal device (110) may encode video data (e.g., a video picture stream collected by the terminal device (110)) for transmission to another terminal device (120) via the network (150). The encoded video data may be transmitted in the form of one or more encoded video bitstreams. The terminal device (120) may receive the encoded video data from the network (150), decode the encoded video data to restore the video picture, and display the video picture based on the restored video data. Unidirectional data transmission is more common in applications such as media services.

[0031] In another example, the communication system (100) includes a second terminal device pair (130 and 140) that performs bidirectional transmission of encoded video data, which bidirectional transmission may occur, for example, during a video conference. For bidirectional data transmission, in one example, each of the terminal devices 130 and 140 may encode video data (e.g., a video picture stream collected by the terminal device) for transmission to the other terminal device (130 and 140) through the network (150). Each of the terminal devices (130 and 140) may also receive the encoded video data transmitted by the other terminal device (130 and 140), and may decode the encoded video data to restore the video picture, and may display the video picture on an accessible display device based on the restored video data.

[0032] exist Figure 1In the example of , the terminal devices (110, 120, 130 and 140) may be shown as servers, personal computers and smart phones, but the principles of the present disclosure may not be limited to this. Embodiments of the present disclosure are applicable to laptop computers, tablet computers, media players and / or dedicated video conferencing equipment. The network (150) represents any number of networks that transmit encoded video data between terminal devices (110, 120, 130 and 140), including, for example, wired (wired) and / or wireless communication networks. The communication network (150) can exchange data in circuit switching and / or packet switching channels. Representative networks include telecommunication networks, local area networks, wide area networks and / or the Internet. For the purposes of the present disclosure, the architecture and topology of the network (150) may be irrelevant to the operation of the present disclosure, unless explained below.

[0033] As examples of applications of the disclosed subject matter, Figure 2 The placement of the video encoder and video decoder in a streaming environment is shown. The disclosed subject matter is equally applicable to other video-enabled applications, including, for example, video conferencing, digital TV, and storing compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0034] The streaming system may include an acquisition subsystem (213), which may include a video source (201), such as a digital camera, which creates, for example, an uncompressed video picture stream (202). In one example, the video picture stream (202) includes samples captured by a digital camera. The video picture stream (202), depicted as thick lines to emphasize the high amount of data compared to the encoded video data (204) (or the encoded video bitstream), may be processed by an electronic device (220), which includes a video encoder (203) coupled to the video source (201). The video encoder (203) may include hardware, software, or a combination of hardware and software to implement or implement various aspects of the disclosed subject matter as described in more detail below. The encoded video data (204) (or the encoded video bitstream (204)), depicted as thin lines to emphasize the lower amount of data compared to the video picture stream (202), may be stored on a streaming server (205) for future use. One or more streaming client subsystems, such as Figure 2A client subsystem (206 and 208) in a streaming server (205) may access a copy (207 and 209) of the encoded video data (204). The client subsystem (206) may include, for example, a video decoder (210) in an electronic device (230). The video decoder (210) decodes the incoming copy (207) of the encoded video data and produces an outgoing video picture stream (211) that can be rendered on a display (212) (e.g., a display screen) or another rendering device (not depicted). In some streaming systems, the encoded video data (204, 207, and 209) (e.g., a video bitstream) may be encoded according to certain video encoding / compression standards. Examples of such standards include ITU-T Recommendation H.265. In one example, the video coding standard under development is informally referred to as Versatile Video Coding (VVC). The disclosed subject matter may be used in the context of VVC.

[0035] It should be noted that the electronic devices (220 and 230) may include other components (not shown). For example, the electronic device (220) may include a video decoder (not shown), and the electronic device (230) may also include a video encoder (not shown).

[0036] Figure 3 A block diagram of a video decoder (310) according to an embodiment of the present disclosure is shown. The video decoder (310) may be included in an electronic device (330). The electronic device (330) may include a receiver (331) (e.g., a receiving circuit). The video decoder (310) may be used to replace Figure 2 A video decoder (210) in an example of FIG.

[0037] The receiver (331) may receive one or more encoded video sequences to be decoded by the video decoder (310); in the same or another embodiment, one encoded video sequence is received at a time, wherein the decoding of each encoded video sequence is independent of the decoding of the other encoded video sequences. The encoded video sequence may be received from a channel (301), which may be a hardware / software link to a storage device storing the encoded video data. The receiver (331) may receive the encoded video data and other data, such as encoded audio data and / or auxiliary data streams, which may be forwarded to their respective use entities (not depicted). The receiver (331) may separate the encoded video sequence from the other data. To prevent network jitter, a buffer memory (315) may be coupled between the receiver (331) and the entropy decoder / parser (320) (hereinafter referred to as "parser (320)"). In some applications, the buffer memory (315) is part of the video decoder (310). In other cases, the buffer memory (315) may be provided external to the video decoder (310) (not depicted). In other cases, a buffer memory (not depicted) may be provided outside the video decoder (310) to, for example, prevent network jitter, and another buffer memory (315) may be configured inside the video decoder (310) to, for example, handle playout timing. When the receiver (331) receives data from a storage / forward device with sufficient bandwidth and controllability or from an isochronous network, the buffer memory (315) may not be required, or may be made smaller. In order to maximize use on a traffic packet network such as the Internet, a buffer memory (315) may be required, which may be relatively large and may advantageously have an adaptive size, and may be at least partially implemented in an operating system or a similar element (not depicted) external to the video decoder (310).

[0038] The video decoder (310) may include a parser (320) to reconstruct symbols (321) from the encoded video sequence. The categories of these symbols include information for managing the operation of the video decoder (310) and potential information for controlling a rendering device such as a rendering device (312) (e.g., a display screen) that is not an integral part of the electronic device (330) but can be coupled to the electronic device (330), such as Figure 3. The control information for the rendering device may be in the form of a parameter set fragment (not depicted) of Supplemental Enhancement Information (SEI message) or Video Usability Information (VUI). The parser (320) may parse / entropy decode the received coded video sequence. The decoding of the coded video sequence may be performed according to a video coding technique or standard, and may follow various principles, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, and the like. The parser (320) may extract a subgroup parameter set for at least one subgroup of the subgroups of pixels in the video decoder from the coded video sequence based on at least one parameter corresponding to the group. The subgroup may include a Group of Pictures (GOP), a picture, a tile, a slice, a macroblock, a Coding Unit (CU), a block, a Transform Unit (TU), a Prediction Unit (PU), and the like. The parser (320) may also extract information such as transform coefficients, quantizer parameter values, motion vectors, and the like from the coded video sequence.

[0039] The parser (320) may perform entropy decoding / parsing operations on the video sequence received from the buffer memory (315), thereby creating symbols (321).

[0040] Depending on the type of coded video picture or portion of a coded video picture (e.g., inter- and intra-pictures, inter- and intra-blocks), and other factors, the reconstruction of the symbol (321) may involve multiple different units. Which units are involved and how they are involved may be controlled by subgroup control information parsed by the parser (320) from the coded video sequence. For the sake of brevity, such subgroup control information flow between the parser (320) and the multiple units below is not depicted.

[0041] In addition to the functional blocks already mentioned, the video decoder (310) can be conceptually subdivided into several functional units as described below. In a practical implementation operating under commercial constraints, many of these units interact closely with each other and may be at least partially integrated with each other. However, for the purpose of describing the disclosed subject matter, the conceptual subdivision into the following functional units is appropriate.

[0042] The first unit is a sealer / inverse transform unit (351). The sealer / inverse transform unit (351) receives quantized transform coefficients and control information as symbols (321) from the parser (320), including which transform method to use, block size, quantization factor, quantization scaling matrix, etc. The sealer / inverse transform unit (351) can output a block including sample values, which can be input into an aggregator (355).

[0043] In some cases, the output samples of the scaler / inverse transform unit (351) may belong to an intra-coded block; that is, a block that does not use predictive information from a previously reconstructed picture, but may use predictive information from a previously reconstructed portion of the current picture. Such predictive information may be provided by an intra-picture prediction unit (352). In some cases, the intra-picture prediction unit (352) generates a block of the same size and shape as the block being reconstructed using surrounding reconstructed information extracted from a current picture buffer (358). For example, the current picture buffer (358) buffers a partially reconstructed current picture and / or a fully reconstructed current picture. In some cases, the aggregator (355) adds the prediction information generated by the intra-prediction unit (352) to the output sample information provided by the scaler / inverse transform unit (351) on a per-sample basis.

[0044] In other cases, the output samples of the scaler / inverse transform unit (351) may belong to an inter-frame coded and potentially motion compensated block. In this case, the motion compensated prediction unit (353) may access the reference picture memory (357) to extract samples for prediction. After the extracted samples are motion compensated according to the symbols (321) belonging to the block, these samples may be added to the output of the scaler / inverse transform unit (351) (in this case referred to as residual samples or residual signals) by the aggregator (355) to generate output sample information. The motion compensated prediction unit (353) obtains the predicted samples from an address in the reference picture memory (357), which may be controlled by a motion vector, and the motion vector is provided to the motion compensated prediction unit (353) in the form of a symbol (321), which may have, for example, X, Y and reference picture components. Motion compensation may also include interpolation of sample values ​​extracted from the reference picture memory (357) when using sub-sample accurate motion vectors, as well as motion vector prediction mechanisms, etc.

[0045] The output samples of the aggregator (355) may be subjected to various loop filtering techniques in a loop filter unit (356). The video compression techniques may include in-loop filter techniques controlled by parameters included in the coded video sequence (also referred to as the coded video bitstream) and made available to the loop filter unit (356) as symbols (321) from the parser (320), and may also be responsive to meta-information obtained during decoding of a previous (in decoding order) portion of the coded picture or coded video sequence, and to previously reconstructed and loop filtered sample values.

[0046] The output of the loop filter unit (356) may be a sample stream that may be output to a rendering device (312) and stored in a reference picture memory (357) for use in future inter-picture prediction.

[0047] Once fully reconstructed, certain coded pictures may be used as reference pictures for future prediction. For example, once the coded picture corresponding to the current picture is fully reconstructed, and the coded picture is identified as a reference picture (e.g., by the parser (320)), the current picture buffer (358) may become part of the reference picture memory (357), and a new current picture buffer may be reallocated before starting reconstruction of a subsequent coded picture.

[0048] The video decoder (310) may perform decoding operations according to a predetermined video compression technique, such as in the ITU-T Recommendation 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 complies with the syntax of the video compression technique or standard and the profile recorded in the video compression technique or standard. Specifically, the profile may select certain tools from all the tools available in the video compression technique or standard as the only tools available for use under the profile. For compliance, the complexity of the encoded video sequence may also be required to be within the range defined by the hierarchy 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, for example, mega samples per second), the maximum reference picture size, etc. In some cases, the limits set by the hierarchy may be further limited by the Hypothetical Reference Decoder (HRD) specification and metadata of the HRD buffer management signaled in the encoded video sequence.

[0049] In one embodiment, the receiver (331) may receive additional (redundant) data along with the reception of the encoded video. The additional data may be included as part of the encoded video sequence. The additional data may be used by the video decoder (310) 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, temporal, spatial or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0050] Figure 4 A block diagram of a video encoder (403) according to an embodiment of the present disclosure is shown. The video encoder (403) is included in an electronic device (420). The electronic device (420) includes a transmitter (440) (e.g., a transmitting circuit). The video encoder (403) can be used to replace Figure 2 A video encoder (203) in an example.

[0051] The video encoder (403) can be used to obtain the video source (401) (not Figure 4 In another example, the video source (401) is a part of the electronic device (420) to receive video samples, the video source can capture video images to be encoded by the video encoder (403). In another example, the video source (401) is a part of the electronic device (420).

[0052] The video source (401) may provide a source video sequence in the form of a digital video sample stream to be encoded by the video encoder (403), the digital video sample stream may have any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...), and any suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media service system, the video source (401) may be a storage device storing previously prepared videos. In a video conferencing system, the video source (401) may be a camera that captures local image information as a video sequence. The video data may be provided as a plurality of separate pictures that are given motion when viewed sequentially. The picture itself may be constructed as a spatial pixel array, where each pixel may include one or more samples depending on the sampling structure, color space, etc. used. The relationship between pixels and samples may be easily understood by those skilled in the art. The following description focuses on the samples.

[0053] According to one embodiment, the video encoder (403) can encode and compress pictures of a source video sequence into an encoded video sequence (443) in real time or under any other time constraints required by the application. Enforcing an appropriate encoding speed is a function of the controller (450). In some embodiments, the controller (450) controls other functional units as described below and is functionally coupled to the other functional units. For the sake of brevity, the coupling is not depicted in the figure. The parameters set by the controller (450) may include rate control related parameters (picture skipping, quantizer, lambda value of rate distortion optimization techniques, etc.), picture size, picture group (GOP) layout, maximum motion vector search range, etc. The controller (450) can be configured to have other suitable functions that are related to the video encoder (403) optimized for a certain system design.

[0054] In some embodiments, the video encoder (403) is configured to operate in an encoding loop. As a simple description, in one example, the encoding loop may include a source encoder (430) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be encoded and a reference picture) and a (local) decoder (433) embedded in the video encoder (403). The decoder (433) reconstructs the symbols to create sample data in a manner similar to that in which the (remote) decoder creates sample data (because in the video compression techniques considered by the disclosed subject matter, any compression between the symbols and the encoded video bitstream is lossless). The reconstructed sample stream (sample data) is input to a reference picture memory (434). Since the decoding of the symbol stream results in a bit-accurate result that is independent of the decoder location (local or remote), the contents of the reference picture memory (434) also correspond bit-accurately between the local encoder and the remote encoder. In other words, the reference picture samples "seen" by the prediction portion of the encoder are exactly the same as the sample values ​​"seen" by the decoder when using prediction during decoding. This basic principle of reference picture synchronization (and drift caused by failure to maintain synchronization due to, for example, channel errors) is also used in some related techniques.

[0055] The operation of the "local" decoder (433) may be combined with, for example, Figure 3 The operation of the "remote" decoder is identical to that of the video decoder (310) described in detail. However, additional brief reference is made to Figure 3 , when symbols are available and the entropy encoder (445) and parser (320) can losslessly encode / decode the symbols into an encoded video sequence, the entropy decoding portion of the video decoder (310), including the buffer memory (315) and the parser (320), may not be fully implemented in the local decoder (433).

[0056] At this point it can be observed that any decoder techniques other than 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 disclosed subject matter focuses on the decoder operation. The description of encoder techniques can be simplified because encoder techniques are reciprocal to the fully described decoder techniques. A more detailed description is only required in certain areas and is provided below.

[0057] During operation, in some examples, the source encoder (430) may perform motion compensated predictive coding. The motion compensated predictive coding predictively encodes an input picture with reference to one or more previously encoded pictures from a video sequence designated as "reference pictures." In this manner, the encoding engine (432) encodes the difference between a pixel block of the input picture and a pixel block of a reference picture that may be selected as a prediction reference for the input picture.

[0058] The local video decoder (433) may decode the encoded video data of the picture that may be designated as the reference picture based on the symbol created by the source encoder (430). The operation of the encoding engine (432) may advantageously be a lossy process. When the encoded video data is available at the video decoder ( Figure 4 When the video encoder (403) is decoded at a remote location (not shown), the reconstructed video sequence may typically be a copy of the source video sequence, but with some errors. The local video decoder (433) replicates the decoding process that may be performed by the video decoder on the reference picture and may cause the reconstructed reference picture to be stored in the reference picture cache (434). In this way, the video encoder (403) may locally store a copy of the reconstructed reference picture that has common content (absent transmission errors) with the reconstructed reference picture to be obtained by the remote video decoder.

[0059] The predictor (435) may perform a prediction search for the encoding engine (432). That is, for a new picture to be encoded, the predictor (435) may search the reference picture memory (434) for sample data (as candidate reference pixel blocks) or certain metadata, such as reference picture motion vectors, block shapes, etc., that may serve as appropriate prediction references for the new picture. The predictor (435) may operate on a pixel block by pixel block basis to find a suitable prediction reference. In some cases, as determined by the search results obtained by the predictor (435), the input picture may have prediction references extracted from multiple reference pictures stored in the reference picture memory (434).

[0060] The controller (450) may manage encoding operations of the source encoder (430), including, for example, setting parameters and subgroup parameters for encoding video data.

[0061] The outputs of all the above functional units may be entropy encoded in an entropy encoder (445). The entropy encoder (445) performs lossless compression on the symbols generated by the various functional units according to techniques such as Huffman coding, variable length coding, arithmetic coding, etc., thereby transforming the symbols into a coded video sequence.

[0062] The transmitter (440) may buffer the encoded video sequence created by the entropy encoder (445) in preparation for transmission over a communication channel (460), which may be a hardware / software link to a storage device where the encoded video data will be stored. The transmitter (440) may combine the encoded video data from the video encoder (403) with other data to be transmitted, such as encoded audio data and / or ancillary data streams (source not shown).

[0063] The controller (450) may manage the operation of the video encoder (403). During encoding, the controller (450) may assign a certain encoding picture type to each encoded picture, but this may affect the encoding techniques that can be applied to the corresponding picture. For example, a picture may generally be assigned to any of the following picture types:

[0064] An intra picture (I picture) may be a picture that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs allow different types of intra pictures, including, for example, Independent Decoder Refresh ("IDR") pictures. Those skilled in the art are aware of the variations of I pictures and their corresponding applications and features.

[0065] A predictive picture (P picture) may be a picture that can be encoded and decoded using intra prediction or inter prediction, which uses at most one motion vector and a reference index to predict sample values ​​for each block.

[0066] Bidirectional predictive pictures (B pictures), which can be pictures that can be encoded and decoded using intra-frame prediction or inter-frame prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multi-directional predictive pictures can use more than two reference pictures and associated metadata for reconstructing a single block.

[0067] The source picture may typically be spatially subdivided into blocks of samples (e.g., blocks of 4×4, 8×8, 4×8, or 16×16 samples), and encoded block by block. These blocks may be predictively encoded with reference to other (coded) blocks, which are determined by the coding allocation applied to the block's corresponding picture. For example, a block of an I picture may be non-predictively encoded, or the block may be predictively encoded (spatial prediction or intra prediction) with reference to a coded block of the same picture. A block of a P picture may be predictively encoded by spatial prediction with reference to one previously coded reference picture or by temporal prediction. A block of a B picture may be predictively encoded by spatial prediction with reference to one or two previously coded reference pictures or by temporal prediction.

[0068] The video encoder (403) may perform encoding operations according to a predetermined video encoding technique or standard, such as ITU-T Recommendation H.265. In operation, the video encoder (403) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancy in an input video sequence. Thus, the encoded video data may conform to the syntax specified by the video encoding technique or standard used.

[0069] In one embodiment, the transmitter (440) may transmit additional data when transmitting the encoded video. The source encoder (430) may include such data as part of the encoded video sequence. The additional data may include other forms of redundant data such as temporal / spatial / SNR enhancement layers, redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0070] Video may be captured as multiple source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often shortened to intra-prediction) exploits spatial correlations in a given picture, while inter-picture prediction exploits (temporal or other) correlations between pictures. In one example, a particular picture being encoded / decoded is partitioned into blocks, and the particular picture being encoded / decoded is referred to as the current picture. When a block in the current picture is similar to a reference block in a reference picture that was previously encoded in the 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.

[0071] In some embodiments, bidirectional prediction techniques may be used in inter-picture prediction. According to the bidirectional prediction technique, two reference pictures are used, for example, a first reference picture and a second reference picture that are both before the current picture in the video in decoding order (but may be in the past and future in display order, respectively). A block in the current picture may be encoded by a first motion vector pointing to a first reference block in the first reference picture and a second motion vector pointing to a second reference block in the second reference picture. The block may be predicted by a combination of the first reference block and the second reference block.

[0072] In addition, merge mode technology can be used in inter-picture prediction to improve coding efficiency.

[0073] According to some embodiments of the present disclosure, predictions such as inter-picture prediction and intra-picture prediction are performed in units of blocks. For example, according to the HEVC standard, a picture in a video picture sequence is divided into coding tree units (CTUs) for compression, and the CTUs in the picture have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTU includes three coding tree blocks (CTBs), which are a luminance CTB and two chrominance CTBs. Each CTU can be recursively split into one or more coding units (CUs) using a quadtree. For example, a 64×64 pixel CTU can be split into a 64×64 pixel CU, or 4 32×32 pixel CUs, or 16 16×16 pixel CUs. In one example, each CU is analyzed to determine a prediction type for the CU, such as an inter-prediction type or an intra-prediction type. Depending on temporal and / or spatial predictability, the CU is split into one or more prediction units (PUs). Typically, each PU includes a luma prediction block (PB) and two chroma PBs. In one embodiment, the prediction operation in decoding (encoding / decoding) is performed in units of prediction blocks. Taking the luma prediction block as an example of a prediction block, the prediction block includes a matrix of values ​​(e.g., luma values) for pixels, such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

[0074] Figure 5 A block diagram of a video encoder (503) according to another embodiment of the present disclosure is shown. The video encoder (503) is configured to receive a processed block (e.g., a prediction block) of sample values ​​within a current video picture in a video picture sequence and encode the processed block into an encoded picture that is part of an encoded video sequence. In one example, the video encoder (503) is used to replace Figure 2 A video encoder (203) in an example.

[0075] In the HEVC example, the video encoder (503) receives a matrix of sample values ​​for a processing block, such as a prediction block of 8×8 samples. The video encoder (503) uses, for example, rate-distortion (RD) optimization to determine whether to best decode the processing block using intra mode, inter mode, or bidirectional prediction mode. When decoding the processing block in intra mode, the video encoder (503) may use intra prediction techniques to encode the processing block into a coded picture; and when decoding the processing block in inter mode or bidirectional prediction mode, the video encoder (503) may encode the processing block into a coded picture using inter prediction or bidirectional prediction techniques, respectively. In some video coding techniques, the merge mode may be an inter-picture prediction submode, in which the motion vector is derived from one or more motion vector predictors without the aid of an encoded motion vector component external to the predictor. In some other video coding techniques, there may be a motion vector component applicable to the current block. In one example, the video encoder (503) includes other components, such as a mode decision module (not shown) for determining the mode of the processing block.

[0076] exist Figure 5 In the example of FIG. 5 , the video encoder ( 503 ) includes: Figure 5 Shown are an inter-frame encoder (530), an intra-frame encoder (522), a residual calculator (523), a switch (526), ​​a residual encoder (524), a general controller (521), and an entropy encoder (525) coupled together.

[0077] The inter-frame encoder (530) is configured to receive samples of a current block (e.g., a processing block), compare the block with one or more reference blocks in a reference picture (e.g., blocks in a previous picture and a subsequent picture), generate inter-frame prediction information (e.g., redundant information description according to an inter-frame coding technique, motion vectors, merge mode information), and calculate an inter-frame prediction result (e.g., a predicted block) based on the inter-frame prediction information using any suitable technique. In some examples, the reference picture is a decoded reference picture decoded based on the encoded video information.

[0078] The intra encoder (522) is configured to receive samples of a current block (e.g., a processing block), compare the block with a coding block in the same picture in some cases, generate quantization coefficients after transformation, and in some cases also generate intra prediction information (e.g., generate intra prediction direction information according to one or more intra coding techniques). In one example, the intra encoder (522) 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.

[0079] The general controller (521) is configured to determine general control data and control other components of the video encoder (503) based on the general control data. In one example, the general controller (521) determines a mode of the block and provides a control signal to the switch (526) based on the mode. For example, when the mode is intra mode, the general controller (521) controls the switch (526) to select the intra mode result for use by the residual calculator (523), controls the entropy encoder (525) to select intra prediction information and includes the intra prediction information in the bitstream; and when the mode is inter mode, the general controller (521) controls the switch (526) to select the inter prediction result for use by the residual calculator (523), controls the entropy encoder (525) to select the inter prediction information and includes the inter prediction information in the bitstream.

[0080] The residual calculator (523) is configured to calculate the difference (residual data) between the received block and the prediction result selected from the intra-frame encoder (522) or the inter-frame encoder (530). The residual encoder (524) is configured to operate based on the residual data to encode the residual data and generate transform coefficients. In one example, the residual encoder (524) is configured to convert the residual data from the spatial domain to the frequency domain and generate transform coefficients. The transform coefficients are then subjected to quantization to obtain quantized transform coefficients. In various embodiments, the video encoder (503) also includes a residual decoder (528). The residual decoder (528) is configured to perform an inverse transform and generate decoded residual data. The decoded residual data can be used appropriately by the intra-frame encoder (522) and the inter-frame encoder (530). For example, the inter encoder (530) can generate a decoded block based on the decoded residual data and the inter prediction information, and the intra encoder (522) can generate a decoded block based on the decoded residual data and the intra prediction information. The decoded blocks are appropriately processed to generate a decoded picture, and in some examples, the decoded picture can be buffered in a memory circuit (not shown) and used as a reference picture.

[0081] The entropy encoder (525) is configured to format a bitstream to include coded blocks. The entropy encoder (525) is configured to include various information according to a suitable standard, such as the HEVC standard. In one example, the entropy encoder (525) is configured to include general control data, selected prediction information (such as intra-frame prediction information or inter-frame prediction information), residual information, and other suitable information in the bitstream. It should be noted that according to the disclosed subject matter, when a block is encoded in inter-frame mode or the merge sub-mode of the bi-directional prediction mode, there is no residual information.

[0082] Figure 6A block diagram of a video decoder (610) according to another embodiment of the present disclosure is shown. The video decoder (610) is configured to receive an encoded picture as part of an encoded video sequence and decode the encoded picture to generate a reconstructed picture. In one example, the video decoder (610) is used instead of Figure 2 A video decoder (210) in an example of FIG.

[0083] exist Figure 6 In the example of FIG. 6 , the video decoder ( 610 ) includes Figure 6 Shown are an entropy decoder (671), an inter-frame decoder (680), a residual decoder (673), a reconstruction module (674), and an intra-frame decoder (672) coupled together.

[0084] The entropy decoder (671) may be configured to reconstruct certain symbols from the coded picture, which symbols represent syntax elements constituting the coded picture. Such symbols may include, for example, a mode for encoding the block (e.g., intra mode, inter mode, bidirectional prediction mode, a merged submode of the latter two, or another submode), prediction information (e.g., intra prediction information or inter prediction information) that can identify certain samples or metadata used by the intra decoder (672) or the inter decoder (680) for prediction, respectively, residual information in the form of, for example, quantized transform coefficients, and the like. In one example, when the prediction mode is inter or bidirectional prediction mode, the inter prediction information is provided to the inter decoder (680); and when the prediction type is an intra prediction type, the intra prediction information is provided to the intra decoder (672). The residual information may be subjected to inverse quantization and provided to the residual decoder (673).

[0085] The inter-frame decoder (680) is configured to receive the inter-frame prediction information and generate an inter-frame prediction result based on the inter-frame prediction information.

[0086] The intra decoder (672) is configured to receive intra prediction information and generate a prediction result based on the intra prediction information.

[0087] The residual decoder (673) is configured to perform inverse quantization to extract dequantized transform coefficients, and process the dequantized transform coefficients to transform the residual from the frequency domain to the spatial domain. The residual decoder (673) may also require certain control information (to include quantizer parameters (QP)), and this information may be provided by the entropy decoder (671) (data path not depicted as this may only be low-capacity control information).

[0088] The reconstruction module (674) is configured to combine the residual output by the residual decoder (673) with the prediction result (which may be output by the inter-frame prediction module or the intra-frame prediction module as the case may be) 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.

[0089] It should be noted that the video encoders (203, 403, and 503) and the video decoders (210, 310, and 610) may be implemented using any suitable technology. In one embodiment, the video encoders (203, 403, and 503) and the video decoders (210, 310, and 610) may be implemented using one or more integrated circuits. In another embodiment, the video encoders (203, 403, and 503) and the video decoders (210, 310, and 610) may be implemented using one or more processors that execute software instructions.

[0090] Merge candidates can be formed by examining motion information from spatial or temporal neighboring blocks of the current block. Figure 7 , the current block (701) includes samples that have been discovered by the encoder / decoder during the motion search process, which can be predicted based on a previous block of the same size that has generated a spatial offset. In some embodiments, motion vectors can be derived from metadata associated with one or more reference pictures instead of encoding the motion vectors directly, for example, using motion vectors associated with any of the five surrounding samples labeled D, A, C, B, and E (corresponding to 702 to 706, respectively), and deriving motion vectors from metadata of the nearest (in decoding order) reference picture. Blocks A, B, C, D, and E may be referred to as spatial merge candidates. These candidates may be checked sequentially in a merge candidate list. A pruning operation may be performed to ensure that duplicate candidates are removed from the list.

[0091] Block-based compensation from different pictures may be referred to as motion compensation. Block compensation may also be performed from previously reconstructed areas within the same picture, which may be referred to as intra-picture block compensation, intra-block copy (IBC), or current picture reference (CPR). For example, a displacement vector indicating the offset between a current block and a reference block is referred to as a block vector. According to some embodiments, a block vector points to a reference block that has been reconstructed and can be used for reference. In addition, for parallel processing considerations, reference areas that exceed tile / slice boundaries or wavefront trapezoid boundaries may also be excluded from being referenced by block vectors. Due to these constraints, block vectors may be different from motion vectors in motion compensation, where motion vectors may be any value (positive or negative in the x or y direction).

[0092] The encoding of the block vector can be explicit or implicit. In explicit mode (sometimes referred to as Advanced Motion Vector Prediction (AMVP) mode in inter-frame coding), the difference between the block vector and its predictor can be represented by a signal. In implicit mode, the block vector is recovered from the predictor of the block vector in a similar manner to the motion vector in merge mode. In some embodiments, the resolution of the block vector is limited to integer bits. In other embodiments, the resolution of the block vector may be allowed to point to fractional bits.

[0093] A block level flag (referred to as an IBC flag) may be used to signal that intra block copying is used at the block level. In one embodiment, the IBC flag is signaled when the current block is not coded in merge mode. The IBC flag may also be signaled by a reference indexing method, such as by treating the current decoded picture as a reference picture. In HEVC Screen Content Coding (HEVC SCC), this reference picture may be placed at the last position of the list. This special reference picture may also be managed with other temporal reference pictures in the Decoded Picture Buffer (DPB). IBC may also include variants such as flipped IBC (e.g., the reference block is flipped horizontally or vertically before being used to predict the current block), or row-based IBC (e.g., each compensation unit within an M×N coding block is an M×1 or 1×N row).

[0094] Figure 8 An embodiment of intra picture block compensation (eg, intra block copy mode) is shown. Figure 8 , the current picture 800 includes a set of block regions that are encoded / decoded (i.e., gray squares) and a set of block regions that have not yet been encoded / decoded (i.e., white squares). A block 802 of one of the block regions that have yet to be encoded / decoded may be associated with a block vector 804 that points to another block 806 that has been previously encoded / decoded. Therefore, any motion information associated with the block 806 may be used for the encoding / decoding of the block 802.

[0095] In some embodiments, the search range of the CPR mode is limited to the current CTU. The effective memory requirement for storing reference samples for the CPR mode is 1 CTU size of samples. Considering the existing reference sample memory storing reconstructed samples in the current 64×64 area, more than 3 64×64 sized reference sample memories are required. Embodiments of the present disclosure extend the effective search range of the CPR mode to a portion of the left CTU, while the total memory requirement for storing reference pixels remains unchanged (1 CTU size, a total of 4 64×64 reference sample memories).

[0096] 9A to 9D Example CTUs 900 and 902 are shown, each having four regions. CTU 902 is located to the left of CTU 900, and each of the four regions of CTU 902 has been previously decoded. FIG. 10A to FIG. 10D An embodiment of a reference sample memory having entries [1]-[4] corresponding to the size of one CTU is shown. The reference sample memory may store reference samples of previously decoded CTUs for future IBC reference. For example, when CTU 902 is decoded, reference sample memory entries [1]-[4] are populated with samples from four regions of CTU 902, where entry [1] corresponds to the upper left region, entry [2] corresponds to the upper right region, entry [3] corresponds to the lower left region, and entry [4] corresponds to the upper right region. When an entry of the reference sample memory is filled, the entry contains samples that can be used for future IBC reference.

[0097] exist Fig.9A In , the upper left region of CTU 900 is the current region being decoded. When the upper left region of CTU 900 is decoded, entry [1] of the reference sample memory is overwritten by the sample from that region, as Fig. 10A As shown (e.g., overwritten memory locations have cross-diagonal hatching). Fig. 9B In the example, the upper right region of CTU 900 is the next current region being decoded. When the upper right region of CTU 900 is decoded, entry [2] of the reference sample memory is overwritten by the sample from that region, as Fig. 10B As shown. Fig. 9C In the example, the lower left region of CTU 900 is the next current region being decoded. When the lower left region of CTU 900 is decoded, the entry [3] of the reference sample memory is overwritten by the sample from that region, such as Fig. 10C As shown. Fig.9D In the example, the lower right region of CTU 900 is the next current region being decoded. When the lower right region of CTU 900 is decoded, the entry [3] of the reference sample memory is overwritten by the sample from that region, as shown in FIG. Fig. 10D shown.

[0098] Embodiments of the present disclosure improve IBC performance under certain reference region constraints (e.g., when the size of the reference sample memory is constrained). In some embodiments, the size of the reference sample memory is limited to 128×128 luma samples (plus corresponding chroma samples). In one example, one CTU size of the reference samples is considered to be the specified memory size. Additional examples include different combinations of memory size / CTU size, such as 64×64 luma samples (plus corresponding chroma samples) applicable to the CTU size and 128×128 luma samples (plus corresponding chroma samples) applicable to the memory size, etc.

[0099] Fig.11 Example CTUs 1100 and 1102 are shown. Fig.11 As shown, CTU 1102 is located to the left of CTU 1100 and includes four previously decoded regions. CTU 1100 is the current CTU being decoded, and its upper left region has been decoded. The upper right region of CTU 1100 is the current region being decoded, and block 1104 is the current block of the upper right region being decoded. Block 1104 may have three reference blocks 1106A to 1106C. Fig.11 As shown, each of the reference blocks 1106A-1106C is located in CTU 902, which is located to the left of CTU 1100. In CTU 900, each of the blocks 1106A-1106C has a collocated block 1108A-1108C, respectively.

[0100] According to some embodiments, a collocated block refers to a pair of blocks having the same size as a block in a previously encoded CTU and another block in a current CTU. For example, if the storage buffer size is one CTU, the previous CTU means a CTU that is offset to the left of the current CTU by one CTU width luminance sample. In addition, the two blocks have the same position offset value relative to the upper left corner of their own CTUs, respectively. At this point, a pair of collocated blocks are two blocks that have the same y coordinate relative to the upper left corner of the picture, but differ from each other by one CTU width in the x coordinate (i.e., the two collocated blocks have the same position coordinates in each corresponding CTU). For example, in Fig.11 , reference block 1106A and its collocated block 1108A have the same x, y coordinates in CTU 1102 and 1100, respectively. Similarly, reference block 1106B and its collocated block 1108B have the same x, y coordinates in CTU 1102 and 1100, respectively. In addition, reference block 1106C and its collocated block 1108C have the same x, y coordinates in CTU 1102 and 1100, respectively.

[0101] exist Fig.11In FIG. 1 , it is assumed that the size of the reference sample memory is one CTU. Therefore, the reference block 1106C can be found in the reference sample memory because the corresponding collocated block 1108C in the current CTU has not yet been decoded, as evidenced by the collocated block 1108C being located in the white area. Therefore, the position in the reference sample memory corresponding to the reference block 1106 still stores the reference sample from the left CTU.

[0102] In contrast to reference block 1106C, reference block 1106A cannot be used because the corresponding collocated block 1108A in CTU 1100 has already been reconstructed (i.e., decoded), as evidenced by the collocated block 1108A being located in the gray area. Therefore, the location in the reference sample memory for reference block 1106A has been updated with reference samples from CTU 900 and is therefore no longer available. Similarly, reference block 1106B is not a valid reference block for decoding because a portion of the corresponding collocated block 1108B in CTU 900 has already been reconstructed and therefore the location in the reference sample memory corresponding to reference block 1106B has been updated with data from CTU 900.

[0103] According to some embodiments, if the corresponding collocated block of the reference block in the current CTU has not been reconstructed, the reference block in the previously decoded CTU can be used for IBC reference. In some embodiments, the collocated sample of the upper left corner sample of the reference block in the current CTU is checked. If the collocated sample in the current CTU has not been reconstructed, the rest of the reference block can be used for IBC reference. In some embodiments, if the memory size is 1 CTU, referencing the previously decoded CTU means referencing the CTU immediately to the left of the current CTU.

[0104] If the memory size is larger than CTU (e.g., allowing a reference sample memory of 2 CTUs), the previously coded CTU references the left CTU of the left CTU of the current CTU, such as Fig.12 For example, in Fig.12 1, CTU 1200 is a current CTU being decoded, and CTUs 1202 and 1204 are two previously decoded CTUs to the left of CTU 1200. Block 1204 is a current block being decoded, and reference block 1206 is a reference block for current block 1204. In addition, block 1208 is collocated with block 1206. However, in this example, the x-coordinate offset between blocks 1206 and 1208 is twice the CTU width.

[0105] According to some embodiments, the following conditions are true:

[0106] Equation 1:

[0107] (yCb+(mvL0[1]>>4))>>CtbLog2SizeY=yCb>>CtbLog2SizeY

[0108] Equation 2:

[0109] (yCb+(mvL0[1]>>4)+cbHeight-1)>>CtbLog2SizeY=yCb>>CtbLog2SizeY Equation 3:

[0110] (xCb+(mvL0[0]>>4))>>CtbLog2SizeY>=(xCb>>CtbLog2SizeY)-1

[0111] Equation 4:

[0112] (xCb+(mvL0[0]>>4)+cbWidth-1)>>CtbLog2SizeY>=(xCb>>CtbLog2SizeY)-1

[0113] Equations 1-4 can be used to locate the reference block. Equations 1 and 2 mean that the top and bottom of the reference block should be located in the same CTU row. Equations 3 and 4 mean that the left and right sides of the reference block should be located in the current CTU or the left CTU. In the above equations, xCb and yCb are the x and y coordinates of the current block, respectively. The variables cbHeight and cbWidth are the height and width of the current block, respectively. The variable CtbLog2SizeY refers to the CTU size in the log2 domain. For example, CtbLog2SizeY=7 means that the CTU size is 128×128. The variables mvL0[0] and mvL0[1] refer to the x and y components of the block vector mvL0, respectively.

[0114] According to some embodiments, when it is determined that a reference block of a current block is located in a CTU different from a current CTU of the current block, a reference sample memory is checked to determine whether samples corresponding to the reference block are available. In some embodiments, determining whether the reference block is located in a CTU different from the current CTU is determined as follows:

[0115] Equation 5:

[0116] (xCb+(mvL[0]>>4))>>CtbLog2SizeY=(xCb>>CtbLog2SizeY)-1

[0117] According to some embodiments, when a reference block of a current block is located in a CTU different from a CTU of the current block, determining whether samples of the reference block are available in a reference memory is determined using the following items as inputs:

[0118] (i) the x and y coordinates of the current block (xCb, yCb); and

[0119] (ii) Adjacent luminance position ((xCb+(mvL[0]>>4)+(1<<CtbLog2SizeY),yCb+(mvL0[1]> >4)),

[0120] If the output is false, it is determined that the samples of the reference block are available. For example, for the current block at the current position (Cbx, Cby), inputs (i) and (ii) are used to determine whether the neighboring block (Nbx, Nby) is available for the current block. "Available" means that the block has been decoded and can be used for intra prediction (e.g., within the same tile).

[0121] According to some embodiments, when the reference block of the current block is located in a CTU different from the CTU of the current block, checking 2 M ×2 N area to determine whether samples of the reference block are available in the reference sample memory. M and N may be positive integers. According to some embodiments, determining whether samples of the reference block are available in the reference sample memory M ×2 N Whether a region is available is determined using the following as input:

[0122] (i) the x and y coordinates of the current block (xCb, yCb); and

[0123] (ii) Adjacent luminance position (((xCb+(mvL[0]>>4)+(1<<CtbLog2SizeY))> >(CtbLog2SizeY-1))<<(CtbLog2SizeY-1), ((yCb+(mvL0[1]>>4))>>(CtbLog2SizeY-1))<<(CtbLog2SizeY-1))

[0124] If the output is false, it is determined that the samples of the reference block are available (for example, the neighboring block is available for intra block copy use). For example, if M and N are equal to 8, and any sample of the 64×64 area in the current CTU (referred to as the current sample) has been reconstructed, the corresponding 64×64 area in the reference sample memory where the collocated sample of the current sample is located will not be available for IBC reference. In this way, the reference sample memory can be updated on a 64×64 basis.

[0125] In some embodiments, the CTUs in a picture have variable sizes, where the difference in width or height is doubled or halved. When the CTU size is halved, the reference sample memory that previously stored 1 CTU now stores 4 CTUs. Therefore, instead of two CTUs to the left of the current CTU, there will be four CTUs to the left of the current CTU, as shown in Figure 1. Fig.12As shown. In these cases, except for the leftmost CTU, all other previously coded samples of the 4 CTUs of reference data or the 2 CTUs of reference data in other CTUs to the left of the current CTU are fully available without using the conditional check in the above embodiment. For the leftmost CTU, the conditional check in the above embodiment is similar for the availability of reference samples, but when there are two CTUs for the leftmost CTU, the adjustment of the x-coordinate offset is 2*CTU width, and when there are four CTUs for the leftmost CTU, the adjustment of the x-coordinate offset is 4*CTU width.

[0126] Fig.13 and Fig.14 An embodiment of a process used when reconstructing a block encoded in intra mode to generate a prediction block for the block being reconstructed is shown. In various embodiments, the process is performed by a processing circuit, such as a processing circuit in a terminal device (110, 120, 130, and 140), a processing circuit that performs the functions of a video encoder (203), a processing circuit that performs the functions of a video decoder (210 and 310), a processing circuit that performs the functions of an intra prediction module (352), a processing circuit that performs the functions of a video encoder (403), a processing circuit that performs the functions of a predictor (435), a processing circuit that performs the functions of an intra encoder (522), a processing circuit that performs the functions of an intra decoder (672), etc. In some embodiments, the process is implemented in software instructions, so when the processing circuit executes the software instructions, the processing circuit performs the process.

[0127] The process generally begins at step S1300, where a coded video bitstream is received. The process proceeds to step S1302, where it is determined whether a reference block for a current block is located in a different CTU than a current CTU for the current block. If it is determined that the reference block is not located in a different CTU, the process proceeds to step S1304, where IBC is performed on the current block using the reference block.

[0128] According to one embodiment, the reference block and the current block are located in a picture included in the coded video bitstream.

[0129] If it is determined that the reference block is located in a different CTU, the process proceeds from step S1302 to step S1306, where it is determined whether the CTU of the current block and the reference sample memory have the same size. If the CTU of the current block and the reference sample memory are different sizes, the process proceeds to process A, which is described in further detail below. If the CTU of the current block and the reference sample memory are the same size, the process proceeds to step S1308, where a first region is determined for the current CTU. As an example, the first region may be a block collocated with the reference block, or a 2M ×2 N region, where M and N are positive integers.

[0130] The process continues to step S1310, where it is determined whether a memory location for a reference block is available. For example, a first region located in a current CTU may be collocated with a second region in a different CTU, where the second region includes a reference block. If the first region has been at least partially reconstructed, it is determined that a memory location for the reference block in the reference sample memory is not available. If it is determined that a memory location for the reference block in the reference sample memory is not available, the process continues to step S1312, where a default process is performed, such as selecting another reference block. In another approach, if it is determined that a memory location for a reference block in the reference sample memory is not available, the default process may be to place a predetermined value to form a reference block for the current block, such as 1<<(bit_depth-1), where bit_depth is the bit depth used for each sample. If a memory location for a reference block in the reference sample memory is available, the process continues from step S1310 to step S1314, where one or more samples are retrieved from a memory location corresponding to the reference block to decode the current block.

[0131] According to some embodiments, the first region is collocated with the second region in a different CTU, and the first region has first position coordinates in the CTU of the current block, and the first position coordinates are the same as second position coordinates of the second region in a different CTU of the reference block.

[0132] According to some embodiments, the first region is a current block and the second region is a reference block. For example, the size of each of the first region and the second region is 2 M ×2 N , where M=6 and N=6.

[0133] Process A may generally begin at step S1400, where it is determined whether the size of the CTU of the current block is smaller than the size of the reference sample memory. If the size of the CTU of the current block is not smaller than the size of the reference sample memory, the process proceeds to step S1402 to determine whether to perform a memory location in the reference sample memory corresponding to the reference block. For example, steps S1308 to S1312 may be repeated at step S1402 as described above.

[0134] If, at step S1400, it is determined that the size of the CTU of the current block is smaller than the size of the reference sample memory, the process proceeds to step S1404, where it is determined whether the distance between the different CTU where the reference block is located and the current CTU where the current block is located is less than a threshold. As an example, the distance between the reference block and the current block may be determined based on the difference between the X coordinates of these blocks. As an example, the threshold may be defined as:

[0135] ((Size of reference sample memory / Size of CTU)-1)*(CTU width).

[0136] If the distance between the different CTU of the reference block and the CTU of the current block is less than the threshold, the process continues to step S1406 to retrieve one or more samples from the memory location corresponding to the reference block to decode the current block. At this point, when the distance between the reference block of the different CTU and the current block is less than the threshold, no decoding is performed. Fig.13 If the distance between the reference block of the different CTU and the current block is greater than or equal to the threshold, the process returns from step S1404 to step S1402. Fig.14 The process shown ends after step S1402 or S1404.

[0137] For example, if it is determined that the distance between the reference block of the different CTU and the current block is greater than or equal to a threshold, then (i) a first region in the CTU of the current block that is juxtaposed with a second region in the different CTU is determined, the first region having position coordinates in the CTU of the current block, which are the same as the position coordinates of the second region in the different CTU of the reference block; (ii) based on the decoding status of the first region, determining whether a memory location for the reference block in the reference sample memory is available; and (iii) in response to determining that the memory location for the reference block is available, retrieving one or more samples from the memory location corresponding to the reference block to decode the current block.

[0138] Fig.12 Depicted Fig.14 , where the size of the reference sample memory is twice as large as the size of the current CTU. If the reference block is located in CTU 1202, the distance between CTU 1202 and the current CTU will be less than the threshold. Therefore, in this case, the memory location corresponding to the reference block in the reference sample memory will be available, and therefore, there is no need to perform a memory check of the reference sample memory. If the reference block is located in CTU 1204, the distance between CTU 1204 and the current CTU will be greater than or equal to the threshold. Therefore, in this case, a memory check of the reference sample memory is performed. Fig.13The memory check described in steps S1308 to S1312 in FIG. 10A determines whether the memory location is available.

[0139] The above techniques may be implemented as computer software using computer-readable instructions and physically stored in one or more computer-readable media. Fig.15 A computer system (1500) suitable for implementing certain embodiments of the disclosed subject matter is shown.

[0140] Computer software may be encoded using any suitable machine code or computer language that may be subjected to assembly, compilation, linking or similar mechanisms to create code comprising instructions that may be executed directly by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., or through interpretation, microcode execution, etc.

[0141] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, IoT devices, etc.

[0142] Fig.15 The components of the computer system (1500) shown are exemplary in nature and are not intended to suggest any limitation on the scope of use or functionality of computer software implementing embodiments of the present disclosure. The configuration of components should also not be interpreted as having any dependencies or requirements with respect to any one or combination of components shown in the exemplary embodiment of the computer system (1500).

[0143] The computer system (1500) may include certain human-machine interface input devices. Such human-machine interface input devices may be responsive to input from one or more human users through, for example, tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), olfactory input (not depicted). The human-machine interface device may also be used to capture certain media that are not necessarily directly related to human conscious input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, photographic images obtained from a still image camera), and videos (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

[0144] The input human-machine interface device may include one or more of the following (only one of each item is shown): keyboard (1501), mouse (1502), touch pad (1503), touch screen (1510), data gloves (not shown), joystick (1505), microphone (1506), scanner (1507), camera (1508).

[0145] The computer system (1500) may also include certain human-computer interface output devices. Such human-computer interface output devices may stimulate one or more human user senses, for example, through tactile output, sound, light, and smell / taste. Such human-computer interface output devices may include tactile output devices (e.g., tactile feedback of a touch screen (1510), a data glove (not shown), or a joystick (1505), but may also be a tactile feedback device that is not used as an input device), audio output devices (e.g., speakers (1509), headphones (not depicted)), visual output devices (e.g., screens (1510) including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capabilities, each with or without tactile feedback capabilities - some of which are capable of outputting two-dimensional visual outputs or outputs in more than three dimensions through devices such as stereoscopic image output, virtual reality glasses (not depicted), holographic displays and smoke boxes (not depicted), and printers (not depicted).

[0146] The computer system (1500) may also include human-accessible storage devices and their associated media, such as optical media including CD / DVD ROM / RW (1520) with CD / DVD and other media (1521), thumb drives (1522), removable hard drives or solid-state drives (1523), traditional magnetic media such as tapes and floppy disks (not depicted), dedicated ROM / ASIC / PLD-based devices such as security dongles (not depicted), etc.

[0147] Those skilled in the art should also understand that the term "computer-readable media" used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

[0148] The computer system (1500) may also include an interface to one or more communication networks. The network may be, for example, a wireless network, a wired network, an optical network. The network may further be a local network, a wide area network, a metropolitan area network, a vehicle and industrial network, a real-time network, a delay-tolerant network, etc. Examples of networks include local area networks such as Ethernet, wireless LANs, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., television wired or wireless wide area digital networks including cable television, satellite television, and terrestrial broadcast television, vehicle and industrial television including CANBus, etc. Some networks typically require an external network interface adapter (e.g., a USB port of the computer system (1500)), which is connected to some universal data port or peripheral bus (1549); as described below, other network interfaces are typically integrated into the kernel of the computer system (1500) by connecting to the system bus (e.g., connected to an Ethernet interface in a PC computer system or connected to a cellular network interface in a smartphone computer system). The computer system (1500) can use any of these networks to communicate with other entities. Such communications may be one-way receive only (e.g., broadcast television), one-way send only (e.g., a CANbus connected to certain CANbus devices), or bidirectional, for example, using a local or wide area digital network to connect to other computer systems. As described above, certain protocols and protocol stacks may be used on each of the above-mentioned networks and network interfaces.

[0149] The above-mentioned human-machine interface device, human-machine accessible storage device, and network interface may be attached to the kernel (1540) of the computer system (1500).

[0150] The core (1540) may include one or more central processing units (CPUs) (1541), graphics processing units (GPUs) (1542), dedicated programmable processing units in the form of field programmable gate arrays (FPGAs) (1543), hardware accelerators (1544) for certain tasks, etc. These devices, as well as read-only memory (ROM) (1545), random access memory (1546), internal mass storage (1547) such as internal non-user accessible hard drives, SSDs, etc., may be connected via a system bus (1548). In some computer systems, the system bus (1548) may be accessed in the form of one or more physical plugs to enable expansion with additional CPUs, GPUs, etc. Peripheral devices may be connected directly to the core's system bus (1548) or connected to the core's system bus (1548) via a peripheral bus (1549). The architecture of the peripheral bus includes PCI, USB, etc.

[0151] The CPU (1541), GPU (1542), FPGA (1543) and accelerator (1544) can execute certain instructions, which can be combined to form the above-mentioned computer code. The computer code can be stored in ROM (1545) or RAM (1546). Transient data can also be stored in RAM (1546), while permanent data can be stored in, for example, internal mass storage (1547). Fast storage and retrieval to any storage device can be enabled by using a cache, which can be closely associated with the following: one or more CPUs (1541), GPUs (1542), mass storage (1547), ROM (1545), RAM (1546), etc.

[0152] The computer readable medium may have thereon computer code for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of the present disclosure, or the medium and computer code may be of a type well known and available to those skilled in the art of computer software.

[0153] As a non-limiting example, as a result of a processor (including a CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media, a computer system having an architecture (1500), in particular a kernel (1540), is able to provide functionality. Such computer-readable media may be media associated with a user-accessible mass storage as described above, as well as memories of certain non-temporary kernels (1540), such as a kernel internal mass storage (1547) or ROM (1545). Software implementing the various embodiments of the present disclosure may be stored in such devices and executed by the kernel (1540). Depending on specific needs, the computer-readable medium may include one or more storage devices or chips. The software may enable the kernel (1540), in particular the processor in the kernel (including a CPU, GPU, FPGA, etc.), to perform a specific process or a specific part of a specific process described herein, including defining a data structure stored in RAM (1546) and modifying such a data structure according to a process defined by the software. Additionally or alternatively, the computer system may be enabled to provide functionality due to logic hardwired or otherwise embodied in circuitry (e.g., accelerator (1544)) that may replace software or operate in conjunction with software to perform a particular process or a particular portion of a particular process described herein. Portions involving software may include logic or, where appropriate, may not include logic. Portions involving computer-readable media may include circuitry (e.g., an integrated circuit (IC)) storing software for execution, circuitry embodying logic for execution, or both, where appropriate. The present disclosure includes any suitable combination of hardware and software.

[0154] Appendix A: Abbreviations

[0155] JEM: Joint Exploration Model

[0156] VVC: Versatile Video Coding

[0157] BMS: Benchmark Set

[0158] MV: Motion Vector

[0159] HEVC: High Efficiency Video Coding

[0160] SEI: Supplemental Enhancement Information

[0161] VUI: Video Availability Information

[0162] GOP: Group of Pictures

[0163] TU: Transform Unit

[0164] PU: prediction unit

[0165] CTU: Coding Tree Unit

[0166] CTB: Coding Tree Block

[0167] PB: prediction block

[0168] HRD: Hypothetical Reference Decoder

[0169] SNR: Signal to Noise Ratio

[0170] CPU: Central Processing Unit

[0171] GPU: Graphics Processing Unit

[0172] CRT: cathode ray tube

[0173] LCD: Liquid Crystal Display

[0174] OLED: Organic Light Emitting Diode

[0175] CD: compact disc

[0176] DVD: Digital Video Disc

[0177] ROM: Read Only Memory

[0178] RAM: Random Access Memory

[0179] ASIC: Application-Specific Integrated Circuit

[0180] PLD: Programmable Logic Device

[0181] LAN: Local Area Network

[0182] GSM: Global System for Mobile Communications

[0183] LTE: Long Term Evolution

[0184] CANBus: Controller Area Network Bus

[0185] USB: Universal Serial Bus

[0186] PCI: Programmable Communications Interface

[0187] FPGA: Field Programmable Gate Array

[0188] SSD: Solid State Drive

[0189] IC: Integrated Circuit

[0190] CU: Coding Unit

[0191] Although the present application has described a number of exemplary embodiments, there are modifications, permutations, and various replacement equivalents that fall within the scope of the present application. Therefore, it should be understood that those skilled in the art can design a variety of systems and methods that, although not explicitly shown or described herein, embody the principles of the present application and therefore fall within the spirit and scope of the present application.

Claims

1. A video decoding method, the method comprising: receiving an encoded video bitstream; Determine whether a size of a first coding tree unit CTU where a current block in the coded video bitstream is located is smaller than a size of a reference sample memory, and determine a second CTU where a reference block of the current block is located, the reference block is located in a CTU different from the first CTU, and the reference block and the current block are located in a picture included in the coded video bitstream; In response to determining that the size of the first CTU is smaller than the size of the reference sample memory, determining whether a distance between the second CTU and the first CTU is smaller than a threshold, wherein the threshold is calculated according to a ratio of the size of the reference sample memory to the size of the first CTU, and the threshold is determined according to the following formula: ((size of reference sample memory / size of first CTU)-1)*(width of first CTU); In response to determining that the distance is less than the threshold, one or more samples are retrieved from a memory location corresponding to the reference block to decode the current block.

2. The method according to claim 1, wherein: The method further comprises: In response to determining that the size of the first CTU is equal to the size of the reference sample memory, determining a first area in the first CTU, the first area being juxtaposed with a second area in the second CTU, the first area having a first position coordinate in the first CTU, the second area having a second position coordinate in the second CTU, the first position coordinate being the same as the second position coordinate in a y-coordinate direction, the first position coordinate being different from the second position coordinate in an x-coordinate direction by a width of an integer number of CTUs, and the second area being an area where the reference block is located; determining, based on a decoding status of samples in the first region, whether a memory location for the reference block is available in a reference sample memory; and In response to determining that the memory location for the reference block is available, one or more samples are retrieved from the memory location corresponding to the reference block to decode the current block.

3. The method according to claim 2, wherein: The determining, based on the decoding status of the samples in the first region, whether a memory location for the reference block in the reference sample memory is available comprises: Input the x and y coordinates of the current block (xCb, yCb), and input the adjacent luminance position (((xCb+(mvL0[0]>>4)+(1<<CtbLog2SizeY))> >(CtbLog2SizeY-1))<<(CtbLog2SizeY-1), ((yCb+(mvL0[1]>>4))>>(CtbLog2SizeY-1))<<(CtbLog2SizeY-1)), where CtbLog2SizeY refers to the CTU size in the Log2 domain; mvL0[0], mvL0[1] refer to the x and y components of the block vector mvL0, respectively; If the output is false, it is determined that samples of the reference block are available.

4. The method according to claim 2, wherein: The first region is the current block, and the second region is the reference block.

5. The method according to claim 2, wherein: The size of each of the first region and the second region is 2 M ×2 N .

6. The method according to claim 5, wherein: M=6 and N=6.

7. The method according to any one of claims 2 to 6, wherein: The method further comprises: In response to determining that the decoding status of the first region indicates that the first region does not include at least one at least partially decoded block, the memory location corresponding to the reference block is determined to be available.

8. The method according to any one of claims 2 to 6, wherein: The method further comprises: In response to determining that the distance is greater than or equal to the threshold, performing the following processing: (i) determining the first region in the first CTU of the current block; (ii) determining whether a memory location for the reference block in the reference sample memory is available based on a decoding status of the first region; and (iii) in response to determining that the memory location for the reference block is available, retrieving one or more samples from the memory location corresponding to the reference block to decode the current block.

9. A video decoder comprising: A processing circuit configured to execute the video decoding method according to any one of claims 1 to 8.

10. A video encoding method, the method comprising: receiving video data; Determine whether a size of a first coding tree unit CTU where a current block in the video data is located is smaller than a size of a reference sample memory, and determine a second CTU where a reference block of the current block is located, the reference block is located in a CTU different from the first CTU, and the reference block and the current block are located in a picture included in a coded video bitstream; In response to determining that the size of the first CTU is smaller than the size of the reference sample memory, determining whether a distance between the second CTU and the first CTU is smaller than a threshold, wherein the threshold is calculated according to a ratio of the size of the reference sample memory to the size of the first CTU, and the threshold is determined according to the following formula: ((size of reference sample memory / size of first CTU)-1)*(width of first CTU); In response to determining that the distance is less than the threshold, one or more samples are retrieved from a memory location corresponding to the reference block to encode the current block.

11. A video encoder, comprising: A processing circuit configured to: receiving video data; Determine whether a size of a first coding tree unit CTU where a current block in the video data is located is smaller than a size of a reference sample memory, and determine a second CTU where a reference block of the current block is located, the reference block is located in a CTU different from the first CTU, and the reference block and the current block are located in a picture included in a coded video bitstream; In response to determining that the size of the first CTU is smaller than the size of the reference sample memory, determining whether a distance between the second CTU and the first CTU is smaller than a threshold, wherein the threshold is calculated according to a ratio of the size of the reference sample memory to the size of the first CTU, and the threshold is determined according to the following formula: ((size of reference sample memory / size of first CTU)-1)*(width of first CTU); In response to determining that the distance is less than the threshold, one or more samples are retrieved from a memory location corresponding to the reference block to encode the current block.

12. A non-transitory computer-readable medium storing instructions, wherein when the instructions are executed by a processor in a video decoder, the processor is caused to execute the video decoding method according to any one of claims 1 to 8, or the video encoding method according to claim 10.

13. A computer device, comprising a memory and a processor, wherein the memory stores instructions, and when the instructions are executed by the processor, the processor executes the video decoding method according to any one of claims 1 to 8, or the video encoding method according to claim 10.

14. A method for processing a video bitstream, characterized in that: The video bit stream is decoded based on the video decoding method according to any one of claims 1 to 8, or is generated by the video encoding method according to claim 10.

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