Method, apparatus and computer program for decoding video

Abstract

To provide a method and apparatus for encoding / decoding a moving picture.SOLUTION: The apparatus comprises processing circuitry that stores reconstructed samples of a reconstructed block in a memory. When a current sub-block in the current block is reconstructed using intra block copy (IBC) based on a reference sub-block in the reconstructed block, the processing circuitry determines, based on a position of the current sub-block, whether a reconstructed sample of the reference sub-block stored in the memory is indicated as overwritten; When it is determined that the reconstructed samples of the reference subblock stored in the memory are indicated as not overwritten, the reconstructed samples of the current subblock are generated based on the reconstructed samples of the reference subblock, and the reconstructed samples of the collocated subblock in the reconstructed block stored in the memory are overwritten with the generated reconstructed samples of the current subblock.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This disclosure claims the benefit of priority to U.S. patent application Ser. No. 16 / 419,235, entitled "METHOD AND APPARATUS FOR VIDEO CODING," filed May 22, 2019, which claims the benefit of priority to U.S. provisional patent application Ser. No. 62 / 735,002, entitled "Reference search," filed September 21, 2018. This application claims the benefit of priority to "Range Optimization for Intra Picture Block Compensation," the entire contents of which are incorporated herein by reference.

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

[0003] The discussion of the background art provided herein is intended to generally provide a context for the present disclosure. Work by the inventors described in this application is not admitted expressly or impliedly as prior art to the present disclosure, to the extent that the work is described in this background art section, as well as aspects of this application that may not be considered prior art at the time of filing.

[0004] Video encoding and decoding can be performed using inter-image prediction with motion compensation. Uncompressed digital video can include a series of images, each having spatial dimensions of, for example, 1920 x 1080 luminance samples and associated chrominance samples. The series of images can have a fixed or variable image rate (informally known as a frame rate), for example, 60 images per second or 60 Hz. Uncompressed video has significant bitrate requirements. For example, 1080p60 4:2:0 video (1920 x 1080 luminance sample resolution at a 60 Hz frame rate) with 8 bits per sample requires nearly 1.5 gigabits per second of bandwidth. One hour of such video requires more than 600 gigabytes of storage space.

[0005] One goal of video encoding and decoding can be to reduce redundancy in the input video signal through compression. Compression can help reduce the aforementioned bandwidth or storage space requirements by a factor of 100 or more, in some cases. Both lossless and lossy compression, as well as combinations of these, may be used. Lossless compression refers to techniques that can reconstruct an exact copy of an original signal from a compressed version of the original signal. With lossy compression, the reconstructed signal may not be identical to the original signal, but the distortion between the original and reconstructed signal is small enough that the reconstructed signal is sufficiently useful for its intended application. For video, lossy compression is widely used. The amount of distortion tolerable depends on the application; for example, users of some consumer streaming applications may tolerate higher-order distortion than users of television distribution applications. The achievable compression ratio may reflect that the higher the possible / acceptable distortion, the higher the compression ratio.

[0006] Motion compensation may be a lossy compression technique and may refer to a technique in which blocks of sample data from a previously reconstructed image, or portion thereof (reference image), are spatially shifted in a direction indicated by a motion vector (hereafter referred to as MV) and then used to predict a newly reconstructed image or image portion. In some cases, the reference image may be the same as the image currently being reconstructed. MV may have two dimensions, X and Y, or three dimensions, with the third dimension indicating the reference image in use (which may indirectly be a temporal dimension).

[0007] In some video compression techniques, the MV applicable to some regions of sample data can be predicted from other MVs, e.g., MVs for other regions of sample data that are spatially adjacent to the region being reconstructed, and that MV is prioritized in the decoding order. In this way, the amount of data required to encode the MVs can be substantially reduced, thereby removing redundancy and increasing compression ratios. MV prediction can work efficiently, for example, when encoding input video signals obtained from a camera (known as natural video), because there is a statistical likelihood that regions larger than the region to which a single MV can be applied will move in a similar direction and, therefore, can potentially be predicted using similar motion vectors derived from MVs of neighboring regions. As a result, the MV found for a given region will be similar or identical to the MV predicted from the surrounding MVs, and after entropy coding, can be represented using fewer bits than would be used to directly encode the MVs. In some cases, MV prediction may be an example of lossless compression of a signal (i.e., MV) derived from the source signal (i.e., sample stream). In other cases, MV prediction itself may be lossy, for example, due to rounding errors when calculating a predictor from several surrounding MVs.

[0008] Various MV prediction mechanisms are described in H.265 / HEVC (ITU-T Rec. H.265, “High Efficiency Video Coding”, December 2016). Among the many MV prediction mechanisms proposed by H.265, this specification describes a technique hereafter referred to as “spatial merging.”

[0009] Referring to Figure 1, a current block (101) contains spatially shifted samples that the encoder found to be predictable from a previous block of the same size during the motion search process. Rather than directly encoding its MV, the MV can be derived from metadata associated with one or more reference pictures, e.g., the last reference picture (in decoding order), using MVs associated with any one of five surrounding samples, denoted A0, A1, and B0, B1, and B2 (102-106, respectively). In H.265, MV prediction can use predictors from the same reference picture used by neighboring blocks. Summary of the Invention

[0010] Aspects of the present disclosure provide a method and apparatus for encoding / decoding moving images. In some examples, the apparatus includes a processing circuit that stores reconstructed samples of a reconstructed block of an image in a memory. The reconstructed samples of the reconstructed block are reconstructed according to an encoded video bitstream. When a current sub-block in a current block of the image is reconstructed based on a reference sub-block in the reconstructed block using intra block copy (IBC), the processing circuit determines, based on a position of the current sub-block, whether the reconstructed sample of the reference sub-block stored in the memory indicates that it has been overwritten. If it is determined that the reconstructed sample of the reference sub-block stored in the memory indicates that it has not been overwritten, the processing circuit generates a reconstructed sample of the current sub-block to output based on the reconstructed sample of the reference sub-block, and overwrites the reconstructed sample of the collocated sub-block in the reconstructed block stored in the memory with the generated reconstructed sample of the current sub-block.

[0011] In some embodiments, the current block includes one or more non-overlapping partitions, the non-overlapping partitions including the current partition in which the current sub-block is located, and the reconstructed block includes one or more non-overlapping partitions that are respectively co-located with one or more partitions of the current block. In some embodiments, the processing circuit determines that a partition in the reconstructed block that includes the reference sub-block is co-located with one of the partitions in the current block that has not been reconstructed indicates that the reconstructed sample of the reference sub-block stored in memory has not been overwritten.

[0012] In some embodiments, the current block has a size of 128x128 luma samples, and the one or more non-overlapping partitions of the current block include four partitions each having a size of 64x64 luma samples.

[0013] In some embodiments, the one or more non-overlapping partitions of the current block include only one partition that is the size of the current block, and in some embodiments, each of the one or more non-overlapping partitions of the current block has a size that is equal to or greater than the maximum reference sub-block size used in IBC.

[0014] In some embodiments, the current block includes an upper-left, upper-right, lower-left, and lower-right section, and the reconstructed block includes an upper-left, upper-right, lower-left, and lower-right section. In some embodiments, the processing circuit determines that the reconstructed samples of the reference sub-block stored in memory indicate not being overwritten if the current sub-block is located in the upper-left section of the current block and the reference sub-block is located in one of the upper-right, lower-left, and lower-right sections within the reconstructed block. In some embodiments, the processing circuit determines that the reconstructed samples of the reference sub-block stored in memory indicate not being overwritten if the current sub-block is located in one of the upper-left, upper-right, and lower-left section of the current block and the reference sub-block is located in the lower-right section of the reconstructed block.

[0015] Aspects of the present disclosure further provide a non-transitory computer-readable medium storing instructions that, when executed by a computer to decode video, cause the computer to perform a method for decoding video.

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

[0017] [Figure 1] FIG. 1 is a schematic diagram of a current block and its surrounding spatial merge candidates in one example. [Figure 2] 2 is a simplified block diagram schematic of a communication system (200), according to an embodiment. [Figure 3]1 is a simplified block diagram schematic of a communication system (300), according to an embodiment. [Figure 4] FIG. 2 is a schematic diagram of a simplified block diagram of a decoder according to an embodiment; [Figure 5] FIG. 2 is a simplified block diagram schematic of an encoder according to an embodiment; [Figure 6] 1 shows a block diagram of an encoder according to another embodiment. [Figure 7] 1 shows a block diagram of a decoder according to another embodiment. [Figure 8] 1 is a schematic diagram of a current block in a current image that is coded using intra block copy (IBC) according to an embodiment; [Figure 9] 1 is a schematic diagram of a current block and neighboring blocks in a current image using IBC, according to an embodiment; [Figure 10A] FIG. 10 is a schematic diagram illustrating how reconstructed samples in neighboring blocks are overwritten based on the position of a current sub-block coded using IBC, according to one embodiment. [Figure 10B] FIG. 10 is a schematic diagram of how reconstructed samples in neighboring blocks are shown to be overwritten based on the position of a current sub-block coded using IBC, according to another embodiment. [Figure 11] 1 is a schematic diagram of a current block, a first reference block, and a second reference block between the current block and the first reference block in a current image using IBC, according to an embodiment; [Figure 12] 13 shows a flowchart outlining a decoding process (1300) according to an embodiment of the present disclosure. [Figure 13] 14 shows a flowchart outlining an encoding process (1400) according to an embodiment of the present disclosure. [Figure 14] FIG. 1 is a schematic diagram of a computer system, according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] FIG. 2 illustrates a simplified block diagram of a communication system (200) according to an embodiment of the present disclosure. The communication system (200) includes multiple terminal devices that can communicate with each other, e.g., via a network (250). For example, the communication system (200) includes a first pair of terminal devices (210) and (220) interconnected via the network (250). In the example of FIG. 2, the first pair of terminal devices (210) and (220) perform unidirectional data transmission. For example, the terminal device (210) may encode video data (e.g., a stream of video captured by the terminal device (210)) for transmission to the other terminal device (220) via the network (250). The encoded video data may be transmitted in the form of one or more coded video bitstreams. The terminal device (220) may receive the coded video data from the network (250), decode the coded video data to recover the video, and display the video according to the recovered video data. One-way data transmission may be common in media serving applications, etc.

[0019] In another example, the communication system 200 includes a second pair of terminal devices 230 and 240 that engage in bidirectional transmission of encoded video data, such as may occur during a video conference. In the example, in the bidirectional transmission of data, each of the terminal devices 230 and 240 may encode video data (e.g., a stream of video captured by the terminal device) for transmission to the other of the terminal devices 230 and 240 over the network 250. Each of the terminal devices 230 and 240 may receive the encoded video data transmitted by the other of the terminal devices 230 and 240, decode the encoded video data to recover the video, and display the video on an accessible display device in accordance with the recovered video data.

[0020] In the example of FIG. 2 , the terminal devices 210, 220, 230, and 240 may be depicted as a server, a personal computer, and a smartphone, although the principles of the present disclosure need not be so limited. Embodiments of the present disclosure also apply to laptops, tablet computers, media players, and / or dedicated videoconferencing equipment. The network 250 represents any number of networks, including wired and / or wireless communication networks, that transmit encoded video data between the terminal devices 210, 220, 230, and 240. The communication network 250 may exchange data over circuit-switched and / or packet-switched channels. Exemplary networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of this discussion, the architecture and topology of the network 250 may be irrelevant to the operation of the present disclosure, unless otherwise described below.

[0021] 3 illustrates the placement of a video encoder and decoder in a streaming environment as an example application of the disclosed subject matter, which is equally applicable to other video uses including, for example, video conferencing, digital television, and storage of compressed video on digital media such as CDs, DVDs, memory sticks, etc.

[0022] The streaming system may include a capture subsystem (313), which may include, for example, a video source (301), such as a digital camera, that creates an uncompressed video stream (302). In the example, the video stream (302) includes samples captured by the digital camera. The video stream (302), shown in bold to emphasize its large amount of data compared to the encoded video data (304) (or encoded video bitstream), may be processed by electronics (320) that includes a video encoder (303) coupled to the video source (301). As described in more detail below, the video encoder (303) may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter. The encoded video data (304) (or encoded video bitstream (304)), shown in thin to emphasize its small amount of data compared to the video stream (302), may be stored on a streaming server (305) for later use. One or more streaming client subsystems, such as the client subsystems 306 and 308 of FIG. 3, can access the streaming server 305 to retrieve copies 307 and 309 of the encoded video data 304. The client subsystem 306 may include a video decoder 310, for example, within an electronic device 330. The video decoder 310 decodes the incoming copy of the encoded video data 307 to generate an outgoing video stream 311 that can be displayed on a display device 312 (e.g., a display screen) or other display device (not shown). In some streaming systems, the encoded video data 304, 307, and 309 (e.g., a video bitstream) may be encoded according to several video encoding / compression standards. Examples of such standards include ITU-T Recommendation H.265. In one example, a developing video encoding standard is informally known as Versatile Video Coding (VVC).The disclosed subject matter can be used in connection with VVC.

[0023] It should be noted that the electronics 320 and 330 may include other components (not shown). For example, the electronics 320 may include a video decoder (not shown), and the electronics 330 may similarly include a video encoder (not shown).

[0024] 4 shows a block diagram of a video decoder (410) according to an embodiment of the present disclosure. The video decoder (410) may be included in an electronic device (430). The electronic device (430) may include a receiver (431) (e.g., receiving circuitry). The video decoder (410) may be used in place of the video decoder (310) in the example of FIG. 3.

[0025] The receiver (431) may receive one or more coded video sequences to be decoded by the video decoder (410), and in the same or different embodiments, may receive one coded video sequence simultaneously, with the decoding of each coded video sequence being independent of the other coded video sequences. The coded video sequences may be received from a channel (401), which may be hardware / software coupled to a storage device that stores the coded video data. The receiver (431) may receive the coded video data along with other data, such as coded audio data and / or auxiliary data streams, which may be forwarded to respective entities (not shown). The receiver (431) may separate the coded video sequences from other data. To combat network jitter, a buffer memory (415) may be coupled between the receiver (431) and the entropy decoder / parser (420) (hereinafter referred to as "parser (420)"). In some applications, the buffer memory (415) is part of the video decoder (410). In other applications, it may be external to the video decoder (410) (not shown). In still other applications, there may be a buffer memory (not shown) external to the video decoder (410), for example, to combat network jitter, and there may be another buffer memory (415) internal to the video decoder (410), for example, to address playout timing. When the receiver (431) is receiving data from a storage / transmission device with sufficient bandwidth and controllability, or from an isosynchronous network, the buffer memory (415) may not be necessary or may be small. The buffer memory (415), which may be required for use with best-effort packet networks such as the Internet, may be relatively large, preferably of adaptable size, and may be implemented, at least in part, in an operating system or similar element (not shown) external to the video decoder (410).

[0026] The video decoder (410) may include a parser (420) to reconstruct symbols (421) from the encoded video sequence. Such symbol classification includes information used to manage the operation of the video decoder (410) and potential information for controlling a display device, such as a display device (412) (e.g., a display screen), which, as shown in FIG. 4, is not an integral part of the electronics (430), but may be coupled to the electronics (430). Control information for one or more display devices may be included in Supplemental Enhancement Information (SEI) messages, or Video Usability Information (VU). The parser (420) may parse / entropy decode the received coded video sequence. The code of the coded video sequence may conform to a video coding technique or standard and may follow various principles, including variable length coding, Huffman coding, context-dependent or context-independent arithmetic coding, etc. The parser (420) may extract a set of subgroup parameters for at least one subgroup of pixels in the video decoder based on at least one parameter corresponding to the group from the coded video sequence. The subgroup may include a group of pictures (GOP), image, tile, slice, macroblock, coding unit (CU), block, transform unit (TU), prediction unit (PU), etc. The parser (420) may also extract information from the coded video sequence, such as transform coefficients, quantizer parameter values, and motion vectors.

[0027] The parser (420) may perform entropy decoding / parsing operations on the video sequence received from the buffer memory (415) to generate symbols (421).

[0028] The reconstruction of the symbols (421) can include several different units, depending on the type of coded video or portion thereof (e.g., inter-picture and intra-picture, inter-block and intra-block), as well as other factors. Which units are included and how can be controlled by subgroup control information parsed from the coded video sequence by the parser (420). The flow of such subgroup control information between the parser (420) and the following units is not shown for clarity.

[0029] In addition to the functional blocks already described, the video decoder (410) may be conceptually subdivided into several functional units, as described below. In actual implementations operating under commercial constraints, many of these units may interact closely with each other and may be at least partially integrated with each other. However, for purposes of describing the disclosed subject matter, a conceptual subdivision into the following functional units is appropriate:

[0030] The first unit is a scalar / inverse transform unit (451), which receives quantized transform coefficients as well as control information, including the transform to use, block size, quantization factor, quantization scaling matrix, etc., as symbol(s) (421) from the parser (420). The scalar / inverse transform unit (451) can output blocks containing sample values, which can be input to an aggregator (455).

[0031] In some cases, the output samples of the scaler / inverse transform (451) may relate to intra-coded blocks, i.e., blocks that do not use prediction information from a previously reconstructed image may use prediction information from a previously reconstructed portion of the current image. Such prediction information may be provided by an intra-image prediction unit (452). In some cases, the intra-image prediction unit (452) generates blocks of the same size and shape as the block being reconstructed using surrounding, already reconstructed information retrieved from a current image buffer (458). The current image buffer (458), for example, buffers a partially reconstructed and / or fully reconstructed current image. The aggregator (455) may optionally add the prediction information generated by the intra-prediction unit (452) to the output sample information provided by the scaler / inverse transform unit (451) on a sample-by-sample basis.

[0032] In other cases, the output samples of the scalar / inverse transform unit (451) may relate to an inter-coded and potentially motion-compensated block. In such cases, the motion-compensated prediction unit (453) may access a reference picture memory (457) to retrieve samples for use in prediction. After motion-compensating the retrieved samples according to the symbols (421) associated with the block, these samples may be added to the output of the scalar / inverse transform unit (451) (called residual samples or residual signals in this case) by an aggregator (455) to generate output sample information. The addresses in the reference picture memory (457) from which the motion-compensated prediction unit (453) retrieves prediction samples may be controlled by a motion vector, available to the motion-compensated prediction unit (453) in the form of a symbol (421), and may have, for example, X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​retrieved from the reference picture memory (457) when sub-sample accurate motion vectors are used, motion vector prediction mechanisms, and the like.

[0033] The output samples of the aggregator (455) can be subjected to various loop filtering techniques in a loop filter unit (456). Video compression techniques can include in-loop filtering techniques controlled by parameters included in the coded video sequence (also called a coded video bitstream) and made available to the loop filter unit (456) as symbols (421) from the parser (420), but can also be responsive to meta-information obtained during decoding of previous (in decoding order) portions of the coded image or coded video sequence, as well as to previously reconstructed loop-filtered sample values.

[0034] The output of the loop filter unit (456) may be a sample stream that can be output to a display device (412) and stored in a reference picture memory (457) for use in subsequent inter-picture prediction.

[0035] Some coded images, once fully reconstructed, can be used as reference images for subsequent prediction. For example, if a coded image corresponding to a current image is fully reconstructed and the coded image has been identified as a reference image (e.g., by the parser (420)), the current image buffer (458) can become part of the reference image memory (457), and a new current image buffer can be reallocated before starting the reconstruction of a subsequent coded image.

[0036] The video decoder (410) may perform decoding operations according to a predetermined video compression technique in a certain standard, such as ITU-T Rec. H.265. A coded video sequence is said to conform to the syntax specified by the video compression technique or standard used in the sense that the coded video sequence conforms to both the syntax of the video compression technique or standard and the profile specified in the video compression technique or standard. Specifically, a profile may select only some tools from all tools available in the video compression technique or standard as tools usable under that profile. A further requirement for compliance may be that the complexity of the coded video sequence be within a range specified by the level of the video compression technique or standard. In some cases, the level may impose limits on the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limits set by the level may be further constrained in some cases by a Hypothetical Reference Decoder (HRD) specification and HRD buffer management metadata signaled in the coded video sequence.

[0037] In embodiments, the receiver (431) may receive additional (redundant) data along with the encoded video. The additional data may be included as part of one or more encoded video sequences. The additional data may be used by the video decoder (410) to properly decode the data and / or to more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant images, forward error correction codes, etc.

[0038] 5 shows a block diagram of a video encoder (503) according to an embodiment of the present disclosure. The video encoder (503) is included in an electronic device (520). The electronic device (520) includes a transmitter (540) (e.g., a transmission circuit). The video encoder (503) can be used in place of the video encoder (303) in the example of FIG. 3.

[0039] The video encoder (503) may receive video samples from a video source (501) (which, in the example of FIG. 5, is not part of the electronic device (520)) that may capture the video(s) to be encoded by the video encoder (503). In another example, the video source (501) is part of the electronic device (520).

[0040] The video source (501) may provide a source video sequence to be encoded by the video encoder (503) in the form of a digital video sample stream, which may be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, etc.), any suitable 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 delivery system, the video source (501) may be a storage device storing previously prepared video. In a video conferencing system, the video source (501) may be a camera capturing local image information as a video sequence. The video data may be provided as multiple individual images that convey motion when viewed in sequence. The images themselves may be organized as a spatial array of pixels, each of which may contain one or more samples, depending on the sampling structure, color space, etc., used. Those skilled in the art will readily understand the relationship between pixels and samples. The following discussion will focus on samples.

[0041] According to embodiments, the video encoder (503) may encode and compress images of a source video sequence into an encoded video sequence (543) in real time or under other time constraints required by the application. Achieving an appropriate encoding rate is one function of the controller (550). In some embodiments, the controller (550) controls and is operatively coupled to other functional units, as described below. For clarity, coupling is not shown. Parameters set by the controller (550) may include rate control-related parameters (e.g., picture skip, quantization, lambda values ​​for rate-distortion optimization techniques), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. The controller (550) may be configured to have other appropriate functions associated with the video encoder (503) optimized for certain system designs.

[0042] In some embodiments, the video encoder (503) is configured to operate in an encoding loop. In a simplified example, the encoding loop may include a source encoder (530) (e.g., responsible for generating symbols, such as a symbol stream, based on an input image to be encoded and one or more reference images) and a (local) decoder (533) embedded in the video encoder (503). The decoder (533) reconstructs the symbols to generate sample data in a manner similar to that generated by the (remote) decoder (since the compression between the symbols and the encoded video bitstream is both lossless in the video compression techniques considered in this disclosure). The reconstructed sample stream (sample data) is input to a reference image memory (534). Since decoding of the symbol stream results in bit-perfect decoding, regardless of the location (local or remote) of the decoder, the contents of the reference image memory (534) are also bit-perfect between the local and remote encoders. In other words, the predictor of the encoder "sees" the exact same sample values ​​as the reference image samples that the decoder "sees" when using prediction during decoding. This basic principle of reference image synchronicity (and the resulting drift if synchronicity cannot be maintained, e.g., due to channel errors) is used in some related art as well.

[0043] The operation of the "local" decoder (533) may be the same as a "remote" decoder, such as the video decoder (410), which has already been described in detail above in connection with Figure 4. However, referring also momentarily to Figure 4, the entropy decoding portion of the video decoder (410), including the buffer memory (415), and the parser (420), need not be entirely implemented in the local decoder (533), since symbols are available and can be losslessly encoded / decoded into an encoded video sequence by the entropy encoder (545) and parser (420).

[0044] It should be noted at this point that the decoder technology present in the decoder, with the exception of parsing / entropy decoding, naturally requires that it also be present in the corresponding encoder in nearly identical functional form. For this reason, the disclosed subject matter focuses on the operation of the decoder. A description of the encoder technology can be omitted, since it is the reverse of the decoder technology, which is described generically. Only in a few areas is more detailed explanation required, as described below.

[0045] In some examples, during operation, the source encoder (530) may perform motion-compensated predictive encoding, predictively encoding an input image with respect to one or more previously encoded images from a video sequence designated as “reference images.” In this method, the encoding engine (532) encodes differences between pixel blocks of the input image and pixel blocks of one or more reference images that may be selected as the predictive reference(s) for the input image.

[0046] The local video decoder (533) may decode the encoded video data of images that may be designated as reference images based on symbols generated by the source encoder (530). The operation of the encoding engine (532) may preferably be a lossy process. When the encoded video data is decoded by a video decoder (not shown in FIG. 5), the reconstructed video sequence may be a copy of the source video sequence, typically with some errors. The local video decoder (533) may replicate the decoding process that may be performed on the reference images by the video decoder and may cause the reconstructed reference images to be stored in a reference image cache (534). In this way, the video encoder (503) may locally store copies of reconstructed reference images that have content in common with reconstructed reference images obtained by a far-end video decoder (free of transmission errors).

[0047] The predictor (535) may perform a prediction search for the coding engine (532). That is, for a new image to be coded, the predictor (535) may search the reference image memory (534) for sample data (as candidate reference pixel blocks) or some metadata, such as reference image motion vectors, block shapes, etc., which serve as suitable prediction references for the new image. The predictor (535) may operate on a sample block-by-pixel block basis to find suitable prediction references. In some cases, as determined by the search results obtained by the predictor (535), the input image may have prediction references drawn from multiple reference images stored in the reference image memory (534).

[0048] The controller (550) may manage the encoding operations of the source encoder (530), including, for example, setting parameters and subgroup parameters used to encode the video data.

[0049] The output of all the aforementioned functional units may be entropy coded by an entropy coder (545), which converts the symbols, as produced by the various functional units, into an encoded video sequence by losslessly compressing the symbols with techniques such as Huffman coding, variable length coding, or arithmetic coding.

[0050] The transmitter (540) may buffer the encoded video sequence(s) as they are generated by the entropy encoder (545) in preparation for transmission over the communication channel (560), which may be a hardware / software link to a storage device that stores the encoded video data. The transmitter (540) may merge the encoded video data of the video encoder (503) with other data to be transmitted, such as encoded audio data and / or auxiliary data streams (sources not shown).

[0051] A controller (550) may manage the operation of the video encoder (503). During encoding, the controller (550) may assign several encoding image types to each encoded image, which may affect the encoding technique that may be applied to each image. For example, images are often assigned to one of the following image types:

[0052] An intra-picture (I-picture) is one that can be coded and decoded without using other pictures in the sequence as a source of prediction. Some video codecs allow different types of intra-pictures, including, for example, Independent Decoder Refresh ("IDR") pictures. Those skilled in the art are aware of such variations of I-pictures, as well as their respective uses and characteristics.

[0053] A predicted image (P picture) can be coded and decoded using intra or inter prediction, using at most one motion vector and reference index to predict the sample values ​​of each block.

[0054] Bidirectionally predicted images (B-pictures) can be coded and decoded using intra- or inter-prediction, using up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multi-predicted images can use more than two reference images and associated metadata to reconstruct a block.

[0055] A source image may be subdivided, typically spatially, into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks, as determined by the code assignment applied to each image of the block. For example, blocks of an I-picture may be coded non-predictively or predictively with reference to previously coded blocks of the same image (spatial prediction or intra-prediction). Pixel blocks of a P-picture may be predictively coded by spatial prediction or by temporal prediction with reference to one previously coded reference image. Blocks of a B-picture may be predictively coded by spatial prediction or by temporal prediction with reference to one or two previously coded reference images.

[0056] The video encoder (503) may perform encoding operations in accordance with a predetermined video encoding technique or standard, such as ITU-T Rec. H.265. In doing so, the video encoder (503) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancies in the input video sequence. The encoded video data may therefore conform to a syntax specified by the video encoding technique or standard used.

[0057] In an embodiment, the transmitter (540) may transmit additional data along with the encoded video. The source encoder (530) may include such data as part of the encoded video sequence. The additional data may include other types of redundant data, such as temporal / spatial / SNR enhancement layers, redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0058] Video may be captured as multiple source images (videos) in a time sequence. Intra-image prediction (often abbreviated to intra-prediction) uses spatial correlation within a given image, while inter-image prediction uses correlation (temporal or otherwise) between images. In an example, a particular image being encoded / decoded, called the current image, is divided into blocks. When a block in the current image is similar to a reference block in a previously encoded and still buffered reference image in the video, the block in the current image can be coded by a vector called a motion vector. The motion vector points to a reference block in the reference image and can have a third dimension that identifies the reference image; in some cases, multiple reference images are used.

[0059] In some embodiments, inter-image prediction can use bidirectional prediction techniques. Bidirectional prediction techniques use two reference images, such as a first reference image and a second reference image, both of which precede the current image in decoding order (but may precede and follow the current image in display order), respectively. A block in the current image can be coded with a first motion vector that points to a first reference block in the first reference image and a second motion vector that points to a second reference block in the second reference image. A block can be predicted using a combination of the first and second reference blocks.

[0060] Also, merge mode techniques can be used for inter-image prediction to improve coding efficiency.

[0061] According to some embodiments of the present disclosure, prediction, such as inter-image prediction and intra-image prediction, is performed within a block unit. For example, according to the HEVC standard, images in a video sequence are divided into coding tree units (CTUs) for compression, and the CTUs within an image have the same size, such as 64x64 pixels, 32x32 pixels, or 16x16 pixels. Generally, a CTU includes three coding tree blocks (CTBs), one luma CTB and two chroma CTBs. Each CTU can be recursively quadtree-decomposed into one or more coding units (CUs). For example, a 64x64 pixel CTU can be divided into one 64x64 pixel CU, four 32x32 pixel CUs, or sixteen 16x16 pixel CUs. In an example, each CU is analyzed to determine the prediction type of the CU, such as inter prediction type or intra prediction type. The CU is then divided into one or more prediction units (PUs) according to temporal and / or spatial predictability. Generally, each PU includes one luma prediction block (PB) and two chroma PBs. In an embodiment, prediction operations in coding (encoding / decoding) are performed in units of prediction blocks. Using a luma prediction block as an example of a prediction block, the prediction block includes a matrix of pixel values ​​(e.g., luma values) of 8x8 pixels, 16x16 pixels, 8x16 pixels, 16x8 pixels, etc.

[0062] 6 shows a diagram of a video encoder (603) according to another embodiment of the present disclosure. The video encoder (603) is configured to receive a processed block of sample values ​​(e.g., a predictive block) in a current picture of a video sequence and to encode the processed block into an encoded image that is part of the encoded video sequence. In an example, the video encoder (603) is used in place of the video encoder (303) in the example of FIG. 3.

[0063] In an HEVC example, the video encoder (603) receives a matrix of sample values ​​for a processing block, such as a predictive block of 8x8 samples. The video encoder (603) determines, using, for example, rate-distortion optimization, whether the processing block is best coded using intra-mode, inter-mode, or bidirectional predictive mode. When the processing block is coded in intra-mode, the video encoder (603) may use intra-prediction techniques to code the processing block into a coded image, and when the processing block is coded in inter-mode or bidirectional predictive mode, the video encoder (603) may use inter-prediction or bidirectional predictive techniques, respectively, to code the processing block into a coded image. In some video coding techniques, the merge mode may be an inter-image prediction submode, in which motion vectors are derived from one or more motion vector predictors and do not utilize coded motion vector components outside the predictors. In some other video coding techniques, there may be motion vector components applicable to the current block. In examples, the video encoder (603) includes other elements, such as a mode decision module (not shown), to determine the mode of the processing blocks.

[0064] In the example of FIG. 6, the video encoder (603) includes an inter encoder (630), an intra encoder (622), a residual calculator (623), a switch (626), a residual encoder (624), an overall controller (621), and an entropy encoder (625), which are coupled together as shown in FIG. 6.

[0065] The inter encoder (630) 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 image (e.g., blocks in previous and subsequent images), generate inter prediction information (e.g., a description of redundant information through inter coding techniques, motion vectors, merge mode information), and calculate an inter prediction result (e.g., a predicted block) based on the inter prediction information using any suitable technique. In some examples, the reference image is a decoded reference image that is decoded based on coded video information.

[0066] The intra encoder (622) is configured to receive samples of a current block (e.g., a processing block), possibly compare the block with blocks already coded in the same image, and generate transformed quantized coefficients and possibly also intra prediction information (e.g., intra prediction direction information according to one or more intra coding techniques). In an example, the intra encoder (622) further calculates an intra prediction result (e.g., a predicted block) based on the intra prediction information and reference blocks in the same image.

[0067] The overall controller (621) is configured to determine overall control data and control other elements of the video encoder (603) based on the overall control data. In an example, the overall controller (621) determines the mode of the block and provides a control signal to the switch (626) based on the mode. For example, when the mode is intra-mode, the overall controller (621) controls the switch (626) to select intra-mode results to be used by the residual calculator (623) and controls the entropy encoder (625) to select intra-prediction information and include the intra-prediction information in the bitstream. When the mode is inter-mode, the overall controller (621) controls the switch (626) to select inter-prediction results to be used by the residual calculator (623) and controls the entropy encoder (625) to select inter-prediction information and include the inter-prediction information in the bitstream.

[0068] The residual calculator (623) is configured to calculate the difference (residual data) between the received block and a prediction result selected from the intra encoder (622) or the inter encoder (630). The residual encoder (624) is configured to operate on the residual data to encode the residual data and generate transform coefficients. In an example, the residual encoder (624) is configured to transform the residual data from the spatial domain to the frequency domain to generate transform coefficients. The transform coefficients are then quantized to obtain quantized transform coefficients. In various embodiments, the video encoder (603) further includes a residual decoder (628). The residual decoder (628) is configured to perform an inverse transform to generate decoded residual data. The decoded residual data can be used by the intra encoder (622) and the inter encoder (630), as appropriate. For example, the inter encoder (630) can generate decoded blocks based on the decoded residual data and inter prediction information, and the intra encoder (622) can generate decoded blocks based on the decoded residual data and intra prediction information. The decoded blocks are processed accordingly to generate decoded images, which can be buffered in a memory circuit (not shown) and used as reference images in some examples.

[0069] The entropy encoder (625) is configured to format a bitstream to include the coded blocks. The entropy encoder (625) is configured to include various information in accordance with an appropriate standard, such as the HEVC standard. For example, the entropy encoder (625) is configured to include overall control data, selected prediction information (e.g., intra-prediction information or inter-prediction information), residual data, and other appropriate information in the bitstream. Note that, according to the disclosed subject matter, there is no residual information when coding a block in an inter mode or a merge submode of either a bi-prediction mode.

[0070] 7 shows a diagram of a video decoder (710) according to another embodiment of the present disclosure. The video decoder (710) is configured to receive coded images that are part of a coded video sequence and decode the coded images to generate reconstructed images. In an example, the video decoder (710) is used in place of the video decoder (310) in the example of FIG. 3.

[0071] In the example of FIG. 7, the video decoder (710) includes an entropy decoder (771), an inter decoder (780), a residual decoder (773), a reconstruction module (774), and an intra decoder (772), coupled together as shown in FIG. 7.

[0072] The entropy decoder (771) can be configured to reconstruct from the coded image several symbols representing the syntax elements from which the coded image is created. Such symbols can include, for example, residual information in the form of prediction information (e.g., intra-mode, inter-mode, bi-prediction mode, merged submode, or inter-mode and bi-prediction mode of another submode) that can identify the mode in which the block is coded (e.g., intra-mode, inter-mode, bi-prediction mode), several samples or metadata used for prediction by the intra decoder (772) or the inter decoder (780), respectively, quantized transform coefficients, etc. In an example, when the prediction mode is an inter-mode or bi-prediction mode, the inter decoder (780) is provided with inter-prediction information, and when the prediction type is an intra-prediction type, the intra decoder (772) is provided with intra-prediction information. The residual information can be dequantized and provided to the residual decoder (773).

[0073] The inter decoder (780) is configured to receive the inter prediction information and to generate inter prediction results based on the inter prediction information.

[0074] The intra decoder (772) is configured to receive intra prediction information and to generate a prediction result based on the intra prediction information.

[0075] The residual decoder (773) is configured to extract the unquantized transform coefficients and perform inverse quantization to process the unquantized transform coefficients and transform the residual from the frequency domain to the spatial domain. The residual decoder (773) may further require some control information (to include quantizer parameters (QP)), which may be provided by the entropy decoder (771) (data path not shown for this, as there may only be low-volume control information).

[0076] The reconstruction module (774) is configured to combine the residual as output of the residual decoder (773) and the prediction result (possibly as output by an inter- or intra-prediction module) in the spatial domain to form a reconstructed block, which may become part of the reconstructed image and then part of the reconstructed video. It should be noted that other suitable operations, such as deblocking operations, may be performed to improve visual quality.

[0077] It should be noted that the video encoders (303), (503), and (603) and the video decoders (310), (410), and (710) may be implemented using any suitable technology. In an embodiment, the video encoders (303), (503), and (603) and the video decoders (310), (410), and (710) may be implemented using one or more integrated circuits. In another embodiment, the video encoders (303), (503), and (503) and the video decoders (310), (410), and (710) may be implemented using one or more processors executing software instructions.

[0078] FIG. 8 is a schematic diagram of a current block (810) in a current image (800) that is coded using intra block copying (IBC), according to an embodiment.

[0079] In some examples, a block may be coded using a reference block from a different image, which is also called motion compensation. In some examples, a block may be coded using a reference block from a previously reconstructed region within the same image, which is also called intra-image block compensation, current-image referencing (CPR), or intra-block copying (IBC). A displacement vector indicating the offset between the current block and the reference block is called a block vector (or BV for short). Unlike the motion vectors of motion compensation, which can take any value (positive or negative, in both the x- and y-dimensions), constraints are imposed on the block vector to ensure that the reference block has already been reconstructed and its reconstructed samples are usable. In some embodiments, taking into account parallelism constraints, some reference regions that cross tile boundaries or wavefront ladder-shaped boundaries are further excluded.

[0080] The coding of block vectors can be explicit or implicit. In explicit mode, the difference between a block vector and its predictor can be signaled in a manner similar to AMVP mode in inter coding. In implicit mode, the block vector can be recovered from the predictor in a manner similar to motion vectors in merge mode. The resolution of block vectors is set to integer positions in some implementations, or in some examples, fractional positions.

[0081] The use of IBC at the block level can be signaled using a block-level flag. In some examples, this flag can signal when the current block is not coded in merge mode. In some examples, this flag can be signaled by a reference index approach. This is done by treating the currently decoded picture as a reference picture. In HEVC Screen Content Coding (HEVC SCC), such a reference picture is placed at the last position in the list. This special reference picture, together with other temporal reference pictures, is also further managed in the Decoded Picture Buffer (DPB).

[0082] There are several variations in the implementation of IBC, such as inverted intra block copy (where the reference block is flipped horizontally or vertically before being used to predict the current block), or line-based intra block copy (where each compensation unit within an MxN coding block is an Mx1 or 1xN line).

[0083] An example using IBC is shown in Figure 8, where a current image (800) includes 15 blocks arranged in 3 rows and 5 columns. In some examples, each block corresponds to a coding tree unit (CTU). The current block (810) includes a sub-block (812) (e.g., a coded block within a CTU) with a block vector (822) that points to a reference sub-block (832) within the current image (800).

[0084] The reconstructed samples of the current image can be stored in a dedicated memory. Considering implementation costs, the reference region in which the reconstructed samples of the reference block are available may not be as large as the entire frame, but depends on the memory size of the dedicated memory. Therefore, for a current sub-block using IBC, in some examples, the IBC reference sub-block may be limited to only a few adjacent regions rather than the entire image.

[0085] In some examples, a memory dedicated to storing reference samples of previously coded CUs for later intra block copy reference is called a reference sample memory. In one example, the memory size is one CTU, for example, storing up to one previously coded CTU or one left CTU. In another example, the memory size is two CTUs, for example, two previously coded CTUs, or two left CTUs, or one current CTU and one left CTU combined. In some embodiments, each CTU requires memory size to store 128x128 luma samples together with corresponding chroma samples. If the reference block is outside the stored and reconstructed area, the reference block cannot be used for IBC.

[0086] In some embodiments, when starting a new CTU (i.e., the current CTU), the reference sample memory allocates space to store reconstructed samples for the entire current CTU. In some embodiments, the memory size is one CTU, and the space allocated to the current CTU can still be partially used to store reconstructed samples from previously coded CTUs, so the allocation of space for the current CTU is not completed at the start of the current CTU. Thus, a portion (or location) of the reference sample memory that stores reconstructed samples from a previously coded CTU can be used in IBC mode to predict the current coded block in the current CTU until this portion is updated by the reconstructed samples of the current coded block in the current CTU. After that, the data of this portion can still be used for IBC reference to provide reconstructed samples from the current CTU, but cannot be used to provide reconstructed samples from the previously coded CTU that was just overwritten.

[0087] In some embodiments, the current CTU is divided into partitions based on one or more predefined grid patterns, such as 64x64 partitions, 32x32 partitions, etc. If the position of the current coding block within the current CTU falls within one of the predefined partitions, the reconstructed samples for the entire corresponding partition stored in the reference sample memory are updated with reconstructed samples from the current CTU, indicating that older reconstructed samples from previously coded CTUs in that partition in the reference sample memory cannot be used for IBC reference purposes. In some examples, the size of the partitions is at least as large as the maximum possible IBC code block size. For example, if the maximum reference block size for IBC is 64x64, the CTU can be divided into as few as 64x64 partitions.

[0088] In some alternative embodiments, when a reference block in a previously coded CTU and its co-located block in the current CTU share the same location in the reference sample memory, the memory location is updated with data from the current CTU when the co-located block in the current CTU is coded. During the coding process of the current CTU, for a coded block in IBC mode, the reference block in the previously coded CTU is found and its reference samples are stored in the reference sample memory. For this reference block, if no samples in the co-located block in the current CTU have been coded, the location in the reference sample memory is not updated with data from the current CTU, and this reference block containing reference samples from the previously coded CTU can still be used for IBC. Alternatively, according to an embodiment, if at least one sample of the co-located block in the current CTU has been reconstructed, this reference block in the previously coded CTU can be marked as overwritten and cannot be used for IBC reference.

[0089] In some embodiments, the memory size is two CTUs. When starting a new CTU (i.e., the current CTU), the reconstructed samples of the last-coded CTU may be left untouched, and the space allocated to the current CTU can be partially used to store reconstructed samples from previously-coded CTUs that were coded before the last-coded CTU. Thus, depending on the coding order, the partition structure of the block, and the availability of reconstructed samples in memory, the allowable range of reference samples used in IBC mode can extend to the reconstructed part of the current CTU, the entire last-coded CTU, and / or the part of the previously-coded CTU that can be indicated as not being overwritten by the reconstructed samples of the current block.

[0090] In another embodiment, the memory size is two CTUs. When starting a new CTU (i.e., the current CTU), the reconstructed samples from the last coded CTU may be left as they are. Thus, depending on the coding order, the partition structure of the block, and the availability of reconstructed samples in memory, the allowable range of reference samples used in IBC mode can be extended to the reconstructed part of the current CTU and the entire last coded CTU.

[0091] In some examples, the size of an IBC reference sub-block can be the same as a certain inter-coded block. To use reference sample memory more efficiently, the size of an IBC reference sub-block can be limited to not exceed 64 luma samples on either the width or height edge, and depending on the color format, corresponding size constraints are applied to the chroma samples. For example, in a 4:2:0 format, the size of a chroma block in IBC mode can be limited to not exceed 32 samples on each side. In some embodiments, a lower limit such as 32 luma samples on each side can be used.

[0092] In the following non-limiting examples, for purposes of illustrating various embodiments, the maximum IBC reference sub-block size is set to 64x64 luma samples. Therefore, with a CTU size of 128x128 luma samples, sub-blocks of 128x128, 128x64, 64x128, 128x32, 32x128, etc. cannot use intra block copy mode for luma samples. For chroma samples, the corresponding size for chroma samples applies, similar to the constraints for luma samples, depending on the color format.

[0093] FIG. 9 is a schematic diagram of a current block (CTU, 910) and neighboring blocks (CTU, 960) in a current image using IBC, according to an embodiment.

[0094] In some embodiments, two sub-blocks from different CTUs are called co-located sub-blocks if they have the same size and the same position offset value relative to the upper-left corner of each CTU. Figure 9 shows a current sub-block (912) in a current block (i.e., CTU) (910) and three of its possible reference sub-blocks (962, 964, and 966) in a previously coded block (960) on the left, identifiable by their respective block vectors (922, 924, and 926). In this example, for a reference sample memory size of one CTU, the reference sub-block (966) can be found in memory because its co-located sub-block (936) in the current block (910) has not yet been reconstructed (white area). Therefore, that location in the reference sample memory still stores a reference sample from the previously coded block (960). In contrast, reference subblock (962) cannot be used because its co-located subblock (932) in the current block (910) has been reconstructed (gray area). The reference sample memory location for reference subblock (962) has been overwritten with reconstructed samples from subblock (932) in the current block (910). Similarly, reference subblock (964) cannot be a valid reference subblock because a portion of its co-located subblock (934) in the current block (910) has been reconstructed, and therefore that portion of memory has been partially overwritten with data in the current block (910).

[0095] To efficiently use the stored reconstructed samples while sharing memory space between CTUs, the encoder or decoder may determine whether a reference sub-block from a previously coded block has been (or is believed to have been) overwritten based on the partition structure, coding order, and / or the position of the current sub-block within the current block.

[0096] For example, if a reference sub-block in a previously coded block and its co-located sub-block in the current block share the same location in the reference sample memory, when any portion of this co-located sub-block in the current block is coded, that location in the memory can be indicated as being updated (e.g., overwritten or considered to be overwritten) with data in the current block. During the coding process of the current block, for a sub-block in IBC mode, its reference sub-block in the previously coded block is found, and its reference samples are stored in the reference sample memory. For this reference sub-block, if a sample in its co-located sub-block in the current block has not been coded, its location in the reference sample memory has not been updated with data from the current block, and this reference sub-block containing reference samples from the previously coded block can be used for IBC reference. Otherwise, if at least one sample of the co-located sub-block in the current block has been coded, the corresponding location in the reference sample memory has been updated with data in the current block, and this reference sub-block cannot be used for IBC reference.

[0097] The general solution described above is based on checking the availability of different positions during the encoding and / or decoding process of the current block. In some examples, this availability checking process can be simplified to only checking the availability of a few preset positions. In some examples, the determination of the availability of a 64x64 luma block from a previously coded block may be based on whether any portion of the 64x64 block at that same position in the current block is coded. In this case, only the top-left position of each 64x64 block in the current block may need to be checked. In other embodiments, other positions may be checked. The proposed method / solution can be extended to smaller block sizes, such as evaluation based on 32x32 blocks.

[0098] Different determination factors for different partition structures are further described based on the following two partitioning scenarios: Based on different partition structures, such availability determination may be performed by checking individual samples unlimitedly or with limitations to increase the availability reference range and improve IBC performance without using extra reference sample memory.

[0099] In the first scenario, each of the four 64x64 luma partitions (32x32 chroma partitions in 4:2:0 format) in the current CTU is completely contained within a coding block (also called a sub-block), or each coding block in the current CTU is completely contained within one of the four 64x64 luma partitions (32x32 chroma partitions in 4:2:0 format).

[0100] According to the first scenario, at the 128x128 CTU level, this block can be coded as is (128x128), or it can be split into four 64x64 blocks and further split, or it can be split into two 128x64 blocks and further split, or it can be split into two 64x128 blocks and further split.

[0101] In some variants, ternary tree division is not allowed for blocks with any edge (width or height) larger than 64 luma samples, or the resulting block is not contained within one of the four 64x64 partitions, or entirely contains one of the four 64x64 partitions.

[0102] In one example, if the size of a coding block is 128x128 and the maximum IBC block size is 64x64, then this 128x128 block will not be coded in IBC mode.

[0103] In one example, when the coding block is four 64x64 blocks, the availability of reference samples can be explained with reference to Figure 10A.

[0104] FIG. 10A is a schematic diagram illustrating how reconstructed samples in neighboring blocks are overwritten based on the position of a current sub-block coded using IBC, according to one embodiment.

[0105] In FIG. 10A, the current block (1010) corresponds to the current CTU, which includes four 64x64 partitions (1012, 1014, 1016, and 1018). The previously coded block (1060) corresponds to the left CTU, which includes four 64x64 partitions (1062, 1064, 1066, and 1068). The coding order for processing the coding blocks in the current block (1010) starts with the upper-left partition (1012), then the upper-right partition (1014), then the lower-left partition (1016), and finally the lower-right partition (1018). The 64x64 partition with vertical stripes is where the current coding block will be located (the current coding block may be smaller in size than 64x64). The shaded gray blocks are reconstructed blocks. Blocks marked with an "X" must be overwritten with a reconstructed sample from the current block at the corresponding location, or have been overwritten and therefore cannot be used for IBC lookup.

[0106] Thus, if the current coding block is within the top-left 64x64 partition (1012) of the current block (1010), then in addition to the already reconstructed samples in the current CTU, the reconstructed samples in the top-right, bottom-left, and bottom-right 64x64 partitions (1064, 1066, and 1068) of the left CTU (block 1060) can be referenced using IBC mode. Partition (1062) is shown as being overwritten and unavailable.

[0107] In an embodiment, if the current coding block is within the upper right 64x64 partition (1014) of the current block (1010), then in addition to the already reconstructed samples in the current CTU, the reconstructed samples in the lower left and lower right 64x64 partitions (1066 and 1068) of the left CTU (block 1060) can be referenced using IBC mode. Partitions (1062 and 1064) are shown as overwritten and unavailable.

[0108] In an embodiment, if the current coding block is within the 64x64 partition (1016) to the lower left of the current block (1010), then in addition to the already reconstructed samples in the current CTU, reference samples in the 64x64 partition to the lower right of the left CTU (block 1060) can be referenced using IBC mode. Partitions (1062, 1064, and 1066) are shown as overwritten and unavailable.

[0109] In an embodiment, only already reconstructed samples in the current CTU can be referenced using IBC mode if the current coding block is within the 64x64 partition (1018) to the bottom right of the current block (1010). Partitions (1062, 1064, 1066, and 1068) are shown as overwritten and unavailable.

[0110] The above assumptions work in cases where the CTU is split into a quadtree at the first level (if there is any split at the 128x128 level), such as when separate luma / chroma coding trees (parallel trees) are used.

[0111] In one example, if the coding block is two 128x64 blocks, it is not allowed to apply horizontal binary tree partitioning at the next level. Otherwise, the resulting 128x32 block would be contained in two 64x64 partitions, which would violate the premise of the first scenario. Therefore, each 128x64 block may be coded as is, or may be partitioned into two 64x64 blocks, or may be partitioned into four 64x16 blocks by a quadtree.

[0112] In one example, if the coding block is two 64x128 blocks, applying vertical binary tree partitioning at the next level is not allowed. Otherwise, the resulting 32x128 block would be contained in two 64x64 partitions, which would violate the premise of the first scenario. Therefore, each 64x128 block may be coded as is, or may be partitioned into two 64x64 blocks, or may be partitioned into four 16x64 blocks by a quadtree.

[0113] In some examples, the VVC standard allows flexible block partitioning strategies using quadtrees, binary trees, and ternary trees. If the first level partitioning is not a quadtree, such as when a parallel tree is not used, it may still be a binary tree partition (rather than a ternary tree partitioning). If a vertical binary tree partitioning is applied at the first level from the CTU, such as having two 128x64 blocks or two 64x128 blocks, the second and third coding orders of the four 64x64 partitions in Figure 10A may be different.

[0114] 10B is a schematic diagram of how reconstructed samples in neighboring blocks are indicated as overwritten based on the position of a current sub-block coded using IBC, according to another embodiment. In FIG. 10B, the availability of reference samples for the upper right 64×64 partition and the lower left 64×64 partition is shown when vertical binary tree partitioning is applied at the 128×128 level from the CTU. When horizontal binary tree partitioning is applied at the 128×128 level from the CTU, the coding order and availability of reference samples for the upper right 64×64 block and the lower left 64×64 block are the same as in FIG. 10A.

[0115] Thus, according to an embodiment, if the current coding block is within the top-left 64x64 partition (1012) of the current block (1010), then in addition to the already reconstructed samples in the current CTU, the reconstructed samples in the top-right, bottom-left, and bottom-right 64x64 partitions (1064, 1066, and 1068) of the left CTU (block 1060) can be referenced using IBC mode. Partition (1062) is shown as being overwritten and unavailable.

[0116] According to an embodiment, if the current coding block is within the bottom-left 64x64 partition (1016) of the current block (1010), then in addition to the already reconstructed samples in the current CTU, the reconstructed samples in the top-right and bottom-right 64x64 partitions (1064 and 1068) of the left CTU (block 1060) can be referenced using IBC mode. Partitions (1062 and 1066) are shown as overwritten and unavailable.

[0117] If the current coding block is within the upper right 64x64 partition (1016) of the current block (1010), then in addition to the already reconstructed samples in the current CTU, reference samples in the lower right 64x64 partition of the left CTU (block 1060) can be referenced using IBC mode. Partitions (1062, 1064, and 1066) are shown as overwritten and unavailable.

[0118] According to an embodiment, only already reconstructed samples in the current CTU can be referenced using IBC mode if the current coding block is within the 64x64 partition (1018) to the bottom right of the current block (1010). Partitions (1062, 1064, 1066, and 1068) are shown as overwritten and unavailable.

[0119] Two exemplary solutions are outlined below for discussion with reference to Figures 10A and 10B.

[0120] A first exemplary solution is to completely reuse the reference sample memory when possible. More specifically, depending on the position of the current sub-block (e.g., coding block) relative to the current block (e.g., CTU), the following can be applied: If the current sub-block is within the upper-left 64x64 block of the current block, in addition to the already reconstructed samples in the current block, the reconstructed samples in the upper-right, lower-left, and lower-right 64x64 blocks of the left block can be further referenced using IBC mode. If the current sub-block is within the upper right 64x64 block of the current block, in addition to the already reconstructed samples in the current block, it can also reference the reconstructed samples in the lower right 64x64 block of the left block using IBC mode. Also, if the luma position (0,64) for the current block has not yet been reconstructed, the current sub-block can also reference the reconstructed samples in the lower left 64x64 block of the left block using IBC mode. If the current sub-block is within the bottom-left 64x64 block of the current block, in addition to the already reconstructed samples in the current block, it can further reference reconstructed samples in the bottom-right 64x64 block of the left block using IBC mode.If the luma position (64,0) for the current block has not yet been reconstructed, the current sub-block can further reference reconstructed samples in the top-right 64x64 block of the left block using IBC mode. Only already reconstructed samples within the current block can be referenced using IBC mode if the current block is within the 64x64 cell to the lower right of the current block.

[0121] Table I below summarizes the availability of reconstructed samples from the left block for the first exemplary solution. UL, UR, LL, and LR refer to the upper left, upper right, lower left, and lower right, respectively. An "X" sign means unavailable, and a "Y" sign means available.

[0122] [Table 1]

[0123] The second exemplary solution is to simplify the process, regardless of the block division strategy adopted. More specifically, depending on the position of the current sub-block (e.g., coding block) relative to the current block (e.g., CTU), the following can be applied: If the current sub-block is within the upper-left 64x64 block of the current block, in addition to the already reconstructed samples in the current block, the reconstructed samples in the upper-right, lower-left, and lower-right 64x64 blocks of the left block can be further referenced using IBC mode. If the current sub-block is within the upper right 64x64 block of the current block, in addition to the already reconstructed samples in the current block, the reconstructed samples in the lower right 64x64 block of the left block can be further referenced using IBC mode. If the current sub-block is within the lower-left 64x64 block of the current block, in addition to the already reconstructed samples in the current block, the reconstructed samples in the lower-right 64x64 block of the left block can be further referenced using IBC mode. Only already reconstructed samples within the current block can be referenced using IBC mode if the current block is within the 64x64 cell to the lower right of the current block.

[0124] Table II below summarizes the availability of reconstructed samples from the left block for the second exemplary solution. UL, UR, LL, and LR refer to the upper left, upper right, lower left, and lower right, respectively. An "X" sign means unavailable, and a "Y" sign means available.

[0125] [Table 2]

[0126] In the second scenario, only quadtree and binary tree partitioning is allowed at the CTU root (128x128 luma samples), after which binary or ternary tree partitioning can be applied to either side of the 64x128, 128x64, or 64x64 blocks, respectively.

[0127] According to the second scenario, if the current sub-block in CPR mode falls within the upper-left 64x64 partition, it is only guaranteed that all coding units in the upper-left 64x64 partition are coded before the coding blocks in the lower-right 64x64 partition. In this case, during the processing of the coding units in the upper-left 64x64 partition of the current block, the lower-right 64x64 partition of the left block has not yet been updated. The reconstructed samples in this reference area (the lower-right 64x64 partition of the left block) can be used for CPR reference.

[0128] For coding blocks located in the other three 64x64 partitions of the current block, there is no guarantee that the complete 64x64 partition containing the reference samples of the left block will not be updated during the processing of the coding unit within the corresponding 64x64 partition. In some cases, no special action is suggested.

[0129] In the second scenario, two exemplary solutions are outlined below.

[0130] In a third exemplary solution, if the current sub-block is within the top-left 64x64 partition of the current block, it is allowed to use the bottom-right 64x64 partition of the left block as a reference for CPR mode. Sub-blocks within the other three 64x64 partitions of the current block are only allowed to reference reconstructed samples within the current block.

[0131] Table III below summarizes the availability of reconstructed samples from the left block for the third exemplary solution. UL, UR, LL, and LR refer to the upper left, upper right, lower left, and lower right, respectively. An "X" sign means unavailable, and a "Y" sign means available.

[0132] [Table 3]

[0133] To further improve the third exemplary solution, the availability of each 64x64 partition in the left block can be evaluated for each sub-block in the current block by checking the availability of the upper left corner of each 64x64 partition in the current block. For example, if the upper left corner of the lower left 64x64 partition in the current block has not yet been reconstructed when the current sub-block is in the upper right 64x64 partition of the current block, this means that the upper left and upper right 64x64 partitions of the current block are processed before the lower left and lower right 64x64 partitions of the current block. Therefore, the reference sample memory locations storing reference samples in the lower left and lower right 64x64 partitions of the left block have not yet been updated. These can be used as references for the current sub-block in CPR mode. A similar check is applied to the upper left corner of the upper right 64x64 partition.

[0134] Therefore, the fourth exemplary solution allows for more complete reuse of the reference sample memory when possible. More specifically, depending on the position of the current sub-block relative to the current block, the following can be applied: If the current sub-block is within the top-left 64x64 block of the current block, in addition to the already reconstructed samples in the current block, it can further reference reconstructed samples in the bottom-right 64x64 block of the left block using IBC mode. Also, if the luma position (0,64) for the current block has not yet been reconstructed, the current sub-block can further reference reconstructed samples in the bottom-left 64x64 block of the left block using IBC mode. If the luma position (64,0) for the current block has not yet been reconstructed, the current sub-block can further reference reconstructed samples in the top-right 64x64 block of the left block using IBC mode. If the current sub-block is within the upper right 64x64 block of the current block, in addition to the already reconstructed samples in the current block, if the luma position (0,64) for the current block has not been reconstructed, the current sub-block can further refer to reconstructed samples in the lower left 64x64 block and the lower right 64x64 block of the left block using IBC mode. If the current sub-block is within the bottom-left 64x64 block of the current block, in addition to the already reconstructed samples in the current block, if the luma position (64,0) for the current block has not been reconstructed, the current sub-block can further refer to reconstructed samples in the top-left 64x64 block and bottom-right 64x64 block of the left block using IBC mode. Only already reconstructed samples within the current block can be referenced using IBC mode if the current block is within the 64x64 cell to the lower right of the current block.

[0135] Table IV below summarizes the availability of reconstructed samples from the left block for the fourth exemplary solution. UL, UR, LL, and LR refer to the upper left, upper right, lower left, and lower right, respectively. An "X" sign means unavailable, and a "Y" sign means available.

[0136] [Table 4]

[0137] In the above solution, the reconstructed samples of the left block are divided into four 64x64 partitions, and each of the 64x64 partitions is considered as a whole unit for determining whether the reconstructed samples in this partition can be used for coding the current sub-block in CPR mode. The proposed solution as described above can also be applied to a finer division setting, for example, to evaluate each 32x32 partition in the reference sample memory.

[0138] Furthermore, an evaluation of whether the reference sub-block for the current sub-block in IBC mode is in the left block can be performed by determining (a) whether all samples in the reference sub-block are from the left block, and (b) whether all reconstructed samples in the reference sub-block are from the left block.

[0139] The block vector constraint example based on the fourth solution described above is used as an unrestricted example below. In the example below, the CTU has a size of 128x128, and the reference sample memory has a size to store one CTU. In the example below, there is no chroma interpolation for IBC mode.

[0140] In this non-limiting example, the following is assumed: Luma position (xCb, yCb) of the top-left sample of the current luma coding block (e.g., current sub-block) relative to the top-left luma sample of the current picture The variable cbWidth specifies the width of the current coding block in luma samples. The variable cbHeight specifies the height of the current coding block in luma samples. The variable ctuSize specifies the size (width or height) of the coding tree block (e.g., the current block) in luma samples. The luma block vector (bVx,bVy) for the current luma coding block, in integer precision.

[0141] Therefore, the top-left position of the current sub-block is (xCb, yCb), the bottom-right position of the current sub-block is (xCb+cbWidth-1, yCb+cbHeight-1), and the top-left position of the reference sub-block is (xCb+bVx, yCb+bVy), and the bottom-right position of the reference sub-block is (xCb+bVx+cbWidth-1, yCb+bVy+cbHeight-1).

[0142] In this non-limiting example, a valid block vector satisfies the following conditions: The entire reference subblock is reconstructed before the current subblock, The entire reference sub-block is in the same tile / slice as the current sub-block, bVx+cbWidth+xCb<=0 or bVy+cbHeight+yCb<=0, ·(yCb+bVy) / ctuSize=yCb / ctuSize, ·(yCb+bVy+cbHeight=1) / ctuSize=yCb / ctuSize, (xCb+bVx) / ctuSize>=(xCb / ctuSize)―1, (xCb+bVx+cbWidth-1) / ctuSize<=xCb / ctuSize.

[0143] If (xCb+bVx) / ctuSize is equal to (xCb / ctuSize)−1, it means that at least a part of the reference sub-block is within the left block, and the following applies: ·The condition (xCb%ctuSize>=64&&yCb%ctuSize>=64) is not true, If xCb%ctuSize<64&&yCb%ctuSize<64, If position ((xCb / ctuSize)+64,(yCb / ctuSize)) is unavailable (i.e., the sample at this position has not been reconstructed), and if position ((xCb / ctuSize),(yCb / ctuSize)+64) is unavailable, then either (xCb+bVx)%ctuSize>64 or (yCb+bVy)%ctuSize>64 is true, If position ((xCb / ctuSize)+64, (yCb / ctuSize)) is unavailable, then (xCb+bVx)%ctuSize>64 is true, (If position ((xCb / ctuSize), (yCb / ctuSize)+64) is unavailable) (yCb+bVy)%ctuSize>64 is true, If xCb%ctuSize>=64&&xCb%ctuSize<64, Position ((xCb / ctuSize), (yCb / ctuSize)+64) is unavailable and (yCb+bVy)%ctuSize>64 is true, If xCb%ctuSize<64&&xCb%ctuSize>=64, The position ((xCb / ctuSize)+64, (yCb / ctuSize)) is unavailable and (xCb+bVx)%ctuSize>64 is true.

[0144] The proposed solution as described above can be extended to other configurations of the reference sample memory. Also, it should be noted that while the determination of which reconstructed samples are available is described above for several processing orders and partition sizes (e.g., from left to right or from top to bottom), the determination can be changed according to other processing orders and / or partition sizes in other embodiments.

[0145] 11 is a schematic diagram of a current block (CTU, 1110), a first reference block (CTU, 1160), and a second reference block (CTU, 1140) located between the current block (CTU, 1110) and the first reference block (CTU, 1160) in a current image using IBC, according to an embodiment. FIG. 11 shows a current sub-block (1112) in the current block (i.e., CTU) (1110), a first possible reference sub-block (1166) in the first reference block (1160) that can be identified by a block vector (1126), and a second possible reference sub-block (1142) in the second reference block (1140) that can be identified by a block vector (1122). When generating the reconstructed samples for the current block (1110), the memory space for storing the reconstructed samples for the block (1140) remains, so that all reconstructed samples of the second reference block (1140) can be used to determine the reference sub-block for the current sub-block (1112) in IBC mode. However, the memory space for storing the reconstructed samples for the first reference block (1160) is allocated to store the reconstructed samples for the current block (1110), and the availability of the reference sub-block in the first reference block (1160) depends on whether the co-located block in the current block (1110) has been reconstructed, in a manner similar to that described above with reference to Figures 9-11.

[0146] 12 shows a flowchart outlining a decoding process (1200) according to an embodiment of the present disclosure. The process (1200) can be used to reconstruct a block (i.e., the current block) of an image coded using IBC mode. In some embodiments, one or more operations are performed before or after the process (1200), and some of the operations shown in FIG. 12 may be reordered or omitted.

[0147] In various embodiments, step 1200 is performed by a processing circuit, such as the processing circuitry in terminal devices 210, 220, 230, and 240, or the processing circuitry that performs the functions of video decoders 310, 410, or 710. In some embodiments, step 1200 is implemented by software instructions, such that the processing circuitry performs step 1200 when it executes the software instructions. The process begins at step S1201 and proceeds to step S1210.

[0148] At (S1210), reconstructed samples of a reconstructed block of an image are stored in a memory. The reconstructed samples of the reconstructed block are reconstructed according to the encoded video bitstream. In some examples, the reconstructed block corresponds to block (960) of FIG. 9 or block (1160) of FIG. 11. In some examples, the reconstructed samples of the reconstructed block can be generated using the systems or decoders shown in FIGS. 3, 4, and 7.

[0149] In (S1220), it is determined whether the current sub-block in the current block of the image is reconstructed using intra block copy (IBC) based on the reference sub-block in the reconstruction block. If it is determined that the current sub-block is reconstructed using IBC, the process proceeds to (S1230). Otherwise, the current sub-block can be reconstructed using another process and is coded using IBC mode, and the process proceeds to (S1299) and ends.

[0150] At (S1230), it is determined whether the reconstructed samples of the reference sub-block stored in memory have been overwritten (or are indicated as being overwritten) based on the position of the current sub-block. In some examples, it is determined that the reconstructed samples of the reference sub-block stored in memory have been overwritten, for example, as described above with reference to FIGS. 9-11. If it is determined that the reconstructed samples of the reference sub-block stored in memory indicate that they have been overwritten, the process proceeds to (S1240). Otherwise, the current sub-block is reconstructed without using the reconstructed samples of the reference sub-block, or by another process, and coded using IBC mode, and the process proceeds to (S1299) and ends. In some examples, the reconstructed samples of the reconstructed block can be generated using the systems or decoders shown in FIGS. 3, 4, and 7.

[0151] In (S1240), when it is determined that the reconstructed samples of the reference sub-block stored in memory indicate that they have not been overwritten, reconstructed samples of the current sub-block are generated for output based on the reconstructed samples of the reference sub-block. In (S1250), the reconstructed samples of the co-located sub-block in the reconstructed block stored in memory are overwritten with the generated reconstructed samples of the current sub-block. In some examples, the reconstructed samples of the reconstructed block can be generated using the systems or decoders shown in Figures 3, 4, and 7.

[0152] After step (S1250), the process proceeds to step (S1299) and ends.

[0153] 13 shows a flowchart outlining an encoding process (1300) according to an embodiment of the present disclosure. The process (1300) may be used to encode a block of an image (i.e., the current block) using IBC mode. In some embodiments, one or more operations may be performed before or after the process (1300), and some of the operations shown in FIG. 13 may be reordered or omitted.

[0154] In various embodiments, step 1300 is performed by a processing circuit, such as the processing circuitry in terminal devices 210, 220, 230, and 240, or the processing circuitry performing functions such as video encoders 303, 503, or 603. In some embodiments, step 1300 is implemented by software instructions, such that the processing circuitry performs step 1300 when it executes the software instructions. The process begins at step S1301 and proceeds to step S1310.

[0155] At (S1310), reconstructed samples of a reconstructed block of an image are stored in a memory. The reconstructed samples of the reconstructed block are reconstructed according to the coded prediction information. In some examples, the reconstructed block corresponds to block (960) of FIG. 9 or block (1160) of FIG. 11. In some examples, the reconstructed samples of the reconstructed block can be generated using the systems or encoders shown in FIGS. 3, 5, and 6.

[0156] At (S1320), it is determined whether a current sub-block in a current block of an image is coded using intra block copying (IBC) based on a reference sub-block in a reconstructed block. If it is determined that the current sub-block is coded using IBC, the process proceeds to (S1330). Otherwise, the current sub-block may be coded using processes not fully described in this disclosure, and for coding using IBC mode, the process proceeds to (S1399) and ends.

[0157] At (S1330), a range of reconstructed samples stored in memory that have not been overwritten (or are not indicated as being overwritten) is determined based on at least the position of the current sub-block. In some examples, it may be determined whether a range of reconstructed samples stored in memory has been overwritten or not, for example, as described above with reference to Figures 9-11. In some examples, the reconstructed samples of the reconstructed block may be generated using the systems or encoders shown in Figures 3, 5, and 6.

[0158] At (S1340), reference sub-blocks within the range of reconstructed samples that are not marked as being overwritten are determined. At (S1350), reconstructed samples of the current sub-block are generated based on the reconstructed samples of the reference sub-blocks. At (S1360), reconstructed samples of the co-located sub-blocks within the reconstructed block stored in memory are overwritten with the generated reconstructed samples of the current sub-block. In some examples, the reconstructed samples of the reconstructed block can be generated using the systems or encoders shown in Figures 3, 5, and 6.

[0159] After step (S1360), the process proceeds to step (S1399) and ends.

[0160] The techniques described above can be implemented as computer software using computer-readable instructions and physically stored on one or more computer-readable media. For example, Figure 14 illustrates a computer system (1400) suitable for implementing some embodiments of the disclosed subject matter.

[0161] Computer software can be encoded using any suitable machine code or computer language, which may follow mechanisms such as assembly, compilation, linking, etc. to create code containing instructions that can be executed by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., directly, or via interpretation, microcode execution, etc.

[0162] The instructions may be executed by various types of computers or components thereof, such as personal computers, tablet computers, servers, smartphones, game consoles, and Internet of Things (IoT) devices.

[0163] 14 is exemplary in nature and is not intended to suggest any limitation on the scope of use or functionality of the computer software implementing embodiments of the present disclosure. The arrangement of components should not be interpreted as having any dependency or requirement regarding any one or combination of components illustrated in the exemplary embodiment of computer system (1400).

[0164] The computer system (1400) may include several human interface input devices. Such human interface input devices may respond to input by one or more users, for example, by tactile input (e.g., pressing a key, swiping, moving a data glove), audio input (e.g., voice, clapping), visual input (e.g., gestures), or olfactory input (not shown). The human interface devices may further be used to capture several media that do not necessarily involve direct conscious human input, such as audio (e.g., speech, music, ambient sounds), images (e.g., scanned images, photographic images captured by a still camera), and video (e.g., two-dimensional video, three-dimensional video, including stereoscopic video).

[0165] The input human interface devices may include one or more of a keyboard (1401), a mouse (1402), a trackpad (1403), a touchscreen (1410), a data glove (not shown), a joystick (1405), a microphone (1406), a scanner (1407), and a camera (1408) (only one of each is shown).

[0166] The computer system (1400) may include several human interface output devices. Such human interface output devices may stimulate one or more of the user's senses, such as haptic output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touchscreen (1410), data gloves (not shown), or joystick (1405), although some haptic feedback devices may not function as input devices), audio output devices (speakers (1409), headphones (not shown)), visual output devices (such as screens (1410) including CRT screens, LCD screens, plasma screens, and OLED screens, each with or without touchscreen input capability and each with or without haptic feedback capability, some of which may be capable of outputting two-dimensional video output or output in excess of three dimensions by means of stereoscopic output, VR glasses (not shown), holographic displays, smoke generating devices (smoke tanks (not shown)), and printers (not shown)).

[0167] The computer system (1400) may further include human-accessible storage devices and their associated media, such as optical media, including media (1421) such as CD / DVD ROM / RW (1420), USB thumb-drives (1422), removable hard drives or solid-state drives (1423), legacy magnetic media (not shown) such as tape and floppy disks, and specialized ROM / ASIC / PLD-based devices (not shown) such as security dongles.

[0168] Those skilled in the art will further appreciate that the term "computer-readable medium" as used with respect to the subject matter disclosed herein does not include transmission media, carrier waves or other transitory signals.

[0169] The computer system 1400 may further include an interface to one or more communication networks. The network may be, for example, wireless, wired, or optical. The network may also be local, wide-area, metropolitan, in-vehicle, industrial, real-time, delay-tolerant, or the like. Examples of networks include local area networks such as Ethernet; cellular networks including WLAN, GSM, 3G, 4G, 5G, LTE, and the like; wide-area digital networks for cable or wireless television, including cable, satellite, and terrestrial television; and industrial networks including in-vehicle and CANbus. Some networks typically require an external network interface adapter attached to some general-purpose data port or peripheral bus 1449 (e.g., a USB port on the computer system 1400); other networks typically are integrated into the core of the computer system 1400 by attaching to a system bus (e.g., an Ethernet interface on a PC computer system or a cellular network interface on a smartphone computer system), as described below. Using any such network, the computer system 1400 can communicate with other entities. Such communication may be one-way, receive-only (e.g., television broadcast), one-way transmit-only (e.g., CANbus to device transmitting to CANbus), or two-way communication to other computer systems, for example, using local or wide area digital networks. As previously mentioned, several protocols and protocol stacks may be used for each such network and each network interface.

[0170] The aforementioned human interface devices, human-accessible storage devices, and network interfaces may be attached to the core 1440 of the computer system 1400 .

[0171] The core (1440) may include one or more central processing units (CPUs) (1441), graphics processing units (GPUs) (1442), specialized programmable processing units (1443) in the form of field programmable gate areas (FPGAs), hardware accelerators (1444) for some tasks, etc. Such devices may be connected via a system bus (1448), along with read-only memory (ROM) (1445), random access memory (1446), and internal mass storage such as an internal non-user-accessible hard drive, SSD, etc. (1447). In some computer systems, the system bus (1448) may be accessible in the form of one or more physical plugs, allowing expansion with additional CPUs, GPUs, etc. Peripheral devices may be attached directly to the core's system bus (1448) or via a peripheral bus (1449). Peripheral bus architectures include PCI, USB, etc.

[0172] The CPU (1441), GPU (1442), FPGA (1443), and accelerator (1444) may combine and execute several instructions that may make up the aforementioned computer code. The computer code may be stored in ROM (1445) or RAM (1446). Transient data may also be stored in RAM (1446), whereas persistent data may be stored, for example, in internal mass storage (1447). Cache memory may be used to allow quick storage and retrieval in any memory device, and may be closely associated with one or more of the CPU (1441), GPU (1442), mass storage (1447), ROM (1445), RAM (1446), etc.

[0173] The computer-readable medium may bear computer code for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of the present disclosure, or they may be of the kind well known and available to those skilled in the computer software arts.

[0174] By way of example and not limitation, a computer system having the architecture (1400), and specifically the core (1440), can provide functionality as a result of processor(s) (e.g., CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media may be user-accessible mass storage devices, as previously introduced, as well as media associated with some storage of the core (1440) that are non-transitory in nature, such as the core's internal mass storage device (1447) or ROM (1445). Software implementing various embodiments of the present disclosure can be stored on such devices and executed by the core (1440). The computer-readable media may include one or more memory devices or chips, depending on particular needs. The software can cause the core (1440), and specifically the processors therein (including the CPU, GPU, FPGA, etc.), to perform certain operations, or portions of certain operations, described herein, including defining data structures stored in RAM (1446) and modifying such data structures according to software-defined operations. Additionally or alternatively, a computer system may provide functionality as a result of logic hardwired into or embodied in circuitry (e.g., accelerator (1444)), which may operate in place of or in conjunction with software to perform specific operations, or portions of specific operations, described herein. References to software may encompass logic where appropriate, and vice versa. References to computer-readable media may encompass circuitry (such as an integrated circuit (IC)) that stores software for execution where appropriate, circuitry embodying logic for execution, or both. The present disclosure encompasses any suitable combination of hardware and software. Appendix: Acronyms JEM: Joint Exploration Model VVC: versatile video coding BMS: benchmark set MV: Motion Vector HEVC: High Efficiency Video Coding SEI: Supplementary Enhancement Information VUI:Video Usability Information GOP: Group of Pictures TU: Transform Unit PU: Prediction Unit CTU: Coding Tree Unit CTB: Coding Tree Block PB: Prediction Block HRD: Hypothetical Reference Decoder SNR: Signal Noise Ratio CPU: Central Processing Unit GPU: Graphics Processing Unit CRT: Cathode Ray Tube LCD: Liquid-Crystal Display OLED: Organic Light-Emitting Diode CD: Compact Disc DVD: Digital Video Disc ROM: Read-Only Memory RAM: Random Access Memory ASIC: Application-Specific Integrated Circuit PLD: Programmable Logic Device LAN: Local Area Network GSM: Global System for Mobile communications LTE: Long-Term Evolution CANBus: Controller Area Network Bus USB: Universal Serial Bus PCI: Peripheral Component Interconnect FPGA: Field Programmable Gate Array SSD: Solid-state drive IC: Integrated Circuit CU: Coding Unit IBC: Intra Block Copy CPR: Current Picture Referencing BV: Block Vector AMVP: Advanced Motion Vector Prediction HEVC SCC: HEVC Screen Content Coding DPB: Decoded Picture Buffer

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

[0176] 200 Communication Systems 210 Terminal Equipment 220 Terminal Equipment 230 Terminal Equipment 240 Terminal Equipment 250 Network 300 Communication Systems 301 Video Source 302 Video Stream 303 Video Encoder 304 Video data, encoded video bitstream 305 Streaming Server 306 Client Subsystem 307 Copying of encoded video data 308 Client Subsystem 309 Copying of encoded video data 310 Video decoder 311 Outgoing Video Stream 312 Display device 313 Acquisition Subsystem 320 Electronic equipment 330 Electronic equipment 401 Channel 410 Video Decoder 412 Display device 415 Buffer Memory 420 Parser 421 Symbol 430 Electronic equipment 431 Receiver 451 Scaler / Descaler Unit 452 Intra-Image Prediction Unit 453 Motion Compensation Prediction Unit 455 Aggregation Device 456 Loop Filter Unit 457 Reference Image Memory 458 Current Image Buffer 501 Video Source 503 Video Encoder 520 Electronic equipment 530 Source Encoder 532 encoding engine 533 Local Decoder 534 Reference Image Memory 535 Predictor 540 Transmitter 543 Video Sequences 545 Entropy Encoder 550 Controller 560 Communication Channels 603 Video Encoder 621 General Controller 622 Intra Encoder 623 Residual Calculator 624 Residual Encoder 625 Entropy Encoder 626 Switch 628 Residual Decoder 630 Intercoder 710 Video Decoder 771 Entropy Decoder 772 Intra Decoder 773 Residual Decoder 774 Reconstruction Module 780 Inter Decoder 1400 Computer Systems 1401 keyboard 1402 Mouse 1403 Trackpad 1405 Joystick 1406 Mike 1407 Scanner 1408 Camera 1409 Audio output device 1410 Touchscreen 1420 CD / DVD ROM / RW 1421 Medium 1422 USB memory 1423 Solid State Drive 1440 cores 1441 Central Processing Unit (CPU) 1442 Graphics Processing Unit (GPU) 1443 FPGA 1444 Accelerator 1445 Read-Only Memory (ROM) 1446 Random Access Memory (RAM) 1447 Internal mass storage 1448 System Bus 1449 Peripheral Bus 1450 graphics adapter 1454 Network Interface

Claims

[Claim 1] A video decoding method executed by a decoder, comprising: The decoder: storing reconstructed samples of a reconstructed block of an image in a memory, the reconstructed samples of the reconstructed block being reconstructed according to an encoded video bitstream; identifying a reference sub-block for a current sub-block in a current block of the image if the current sub-block is reconstructed using intra block copying (IBC) based on a reference sub-block in the reconstructed block; After the reference sub-block is identified, determining whether the reconstructed samples of the reference sub-block stored in the memory indicate that they have been overwritten based on the position of the current sub-block; generating reconstructed samples of the current sub-block to output based on the reconstructed samples of the reference sub-block when determining that the reconstructed samples of the reference sub-block stored in the memory indicate that they have not been overwritten; overwriting the reconstructed samples of the co-located sub-block in the reconstructed block stored in the memory with the generated reconstructed samples of the current sub-block; A method comprising:

Images