Method, device and medium for multi-reference line intra prediction in video decoding

Abstract

A method, apparatus and computer-readable storage medium for multi-reference line intra-frame prediction in video decoding. The method includes: receiving an encoded video stream of a current block by a device. The device includes a memory storing instructions and a processor communicating with the memory. The method also includes: extracting parameters from the encoded video stream by the device, the parameters indicating reference lines used for intra-frame prediction in the current block; dividing the current block by the device to obtain multiple sub-blocks; and in response to a sub-block of the multiple sub-blocks being located at the boundary of the current block, using the top adjacent reference line as the value of all top non-adjacent reference lines of the sub-block by the device.

Description

[0001] Related Applications

[0002] This application is based upon and claims the benefit of priority of U.S. Provisional Application No. 63 / 175,929, filed on April 16, 2021, and U.S. Non-Provisional Application No. 17 / 569,681, filed on January 6, 2022, both of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates to video encoding and / or decoding techniques, and in particular to an improved low memory design and signaling of a multiple reference row selection scheme. Background Art

[0004] The background description provided herein is for the purpose of presenting the present disclosure in general. The extent to which the work of the presently named inventors described in this background section and in various aspects of this specification is performed does not indicate that it qualifies as prior art at the time of filing this application, and it is never expressly or impliedly admitted that it is prior art to the present disclosure.

[0005] Video encoding and decoding may be performed using inter-picture prediction with motion compensation. An uncompressed digital video may include a series of pictures, each picture having a spatial size of, for example, 1920×1080 luma samples and associated full or subsampled chroma samples. The series of pictures may have a fixed or variable picture rate (alternatively referred to as a frame rate) of, for example, 60 pictures per second or 60 frames per second. For streaming or data processing, uncompressed video has specific bit rate requirements. For example, a video with a pixel resolution of 1920×1080, a frame rate of 60 frames per second, a chroma subsampling of 4:2:0, and 8 bits per pixel / color channel requires a bandwidth of nearly 1.5 Gbit / s. One hour of such video requires more than 600 GB of storage space.

[0006] One purpose of video encoding and decoding can be to reduce redundancy in an uncompressed input video signal by compression. Compression can help reduce the bandwidth and / or storage space requirements mentioned above, in some cases by two orders of magnitude or more. Lossless compression and lossy compression and their combinations can be used. Lossless compression refers to a technique that can reconstruct an exact copy of the original signal from the compressed original signal through a decoding process. Lossy compression refers to the following encoding / decoding process: the original video information is not completely preserved during encoding and cannot be completely restored during decoding. When lossy compression is used, the reconstructed signal may be different from the original signal, but the distortion between the original signal and the reconstructed signal is small enough to make the reconstructed signal usable for the intended application, despite the loss of some information. In the case of video, lossy compression is widely used in many applications. The amount of distortion that can be tolerated depends on the application. For example, users of some consumer video streaming applications can tolerate higher distortion than users of movie or television broadcast applications. The compression rate that can be achieved by a specific encoding algorithm can be selected or adjusted to reflect various distortion tolerances: higher tolerable distortion generally allows the encoding algorithm to produce higher losses and higher compression rates.

[0007] Video encoders and decoders may utilize techniques and steps from several broad categories including, for example, motion compensation, Fourier transforms, quantization, and entropy coding.

[0008] Video codec techniques may include a technique known as intra-coding. In intra-coding, sample values ​​are represented without reference to samples or other data from previously reconstructed reference pictures. In some video codecs, pictures are spatially subdivided into blocks of samples. When all blocks of samples are encoded in intra-mode, the picture may be referred to as an intra-picture. Intra-pictures and their derivatives (e.g., independent decoder refresh pictures) can be used to reset the decoder state and can therefore be used as the first picture in an encoded video stream and video session, or as a still image. The samples of the block after intra-prediction can then be transformed into the frequency domain, and the transform coefficients so generated can be quantized before entropy coding. Intra-prediction represents a technique that minimizes sample values ​​in the pre-transform domain. In some cases, the smaller the DC value after the transform and the smaller the AC coefficient, the fewer bits are required to represent the block after entropy coding at a given quantization step size.

[0009] Traditional intra-frame coding, such as known from coding techniques such as MPEG-2, does not use intra-frame prediction. However, some newer video compression techniques include techniques that attempt to encode / decode blocks based on, for example, surrounding sample data and / or metadata that are obtained during spatially adjacent encoding and / or decoding and that precede the data block being intra-coded or decoded in decoding order. Such techniques are hereinafter referred to as "intra-frame prediction" techniques. It should be noted that, at least in some cases, intra-frame prediction uses only reference data from the current picture being reconstructed, and does not use reference data from reference pictures.

[0010] Intra-frame prediction can take many different forms. When more than one such technique can be used in a given video coding technique, the technique in use may be referred to as an intra-frame prediction mode. One or more intra-frame prediction modes may be provided in a particular codec. In some cases, a mode may have sub-modes and / or may be associated with various parameters, and the mode / sub-mode information and the intra-frame coding parameters of a video block may be encoded separately or jointly contained in a mode codeword. Which codeword is used for a given mode, sub-mode, and / or parameter combination may affect the coding efficiency gain through intra-frame prediction, and therefore may affect the entropy coding technique used to convert the codeword into a bitstream.

[0011] H.264 introduced an intra prediction mode, which was refined in H.265 and further refined in newer coding techniques such as the Joint Exploration Model (JEM), Next Generation Video Coding (VVC), and Benchmark Set (BMS). Typically, for intra prediction, values ​​belonging to neighboring samples that have become available can be used to form a predictor block. For example, available values ​​for a particular set of neighboring samples can be copied to the prediction block along a certain direction and / or row. Reference to the direction of use can be encoded in the bitstream, or it can be predicted itself.

[0012] Referring to FIG. 1A , a subset of 9 prediction directions specified in the 33 possible intra-frame prediction directions of H.265 (corresponding to the 33 angular modes of the 35 intra-frame modes specified in H.265) is depicted at the bottom right. The point (101) where the arrows converge represents the sample being predicted. The arrows represent the direction along which the sample at 101 is predicted using neighboring samples. For example, arrow (102) indicates that sample (101) is predicted based on one or more neighboring samples at an angle of 45 degrees to the horizontal direction at the upper right. Similarly, arrow (103) indicates that sample (101) is predicted based on one or more neighboring samples at an angle of 22.5 degrees to the horizontal direction at the lower left of sample (101).

[0013] Still referring to FIG. 1A , a square block (104) of 4×4 samples is depicted at the upper left (indicated by the bold dashed line). The square block (104) includes 16 samples, each of which is labeled with “S”, its position in the Y dimension (e.g., row index), and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample in the Y dimension (starting from the top) and the first sample in the X dimension (starting from the left). Similarly, sample S44 is the fourth sample in the block (104) in both the Y and X dimensions. Since the size of the block is 4×4 samples, S44 is located in the lower right corner. An exemplary reference sample is also shown that follows a similar numbering scheme. The reference sample is labeled with R, its Y position (e.g., row index), and X position (column index) relative to the block (104). In H.264 and H.265, prediction samples adjacent to the block being reconstructed are used.

[0014] The intra picture prediction of block 104 may start by copying reference sample values ​​from neighboring samples according to a signaled prediction direction. For example, assume that the encoded video bitstream includes signaling indicating the prediction direction of arrow (102) for this block 104, i.e., predicting samples according to one or more prediction samples at the top right and at a 45 degree angle to the horizontal. In this case, samples S41, S32, S23, and S14 are predicted according to the same reference sample R05. Sample S44 is then predicted according to reference sample R08.

[0015] In some cases, the values ​​of multiple reference samples may be combined, such as by interpolation, to compute the reference sample; in particular, when the direction is not divisible by 45 degrees.

[0016] As video coding technology continues to develop, the number of possible directions increases. In H.264 (2003), for example, nine different directions can be used for intra-frame prediction. In H.265 (2013), this increased to 33 directions, and at the time of this disclosure, JEM / VVC / BMS can support up to 65 directions. Experimental studies have been conducted to help identify the most appropriate intra-frame prediction directions, and some techniques in entropy coding can be used to encode those most appropriate directions with small bits, accepting a certain bit cost for the direction. In addition, the direction itself can sometimes be predicted based on the adjacent directions used in the intra-frame prediction of decoded adjacent blocks.

[0017] FIG. 1B shows a schematic diagram ( 180 ) depicting 65 intra prediction directions according to JEM to illustrate the increase in the number of prediction directions in various encoding techniques developed over time.

[0018] The manner in which bits representing intra-prediction directions are mapped to the prediction directions in the coded video bitstream may vary from one video coding technique to another; for example, it may range from a simple direct mapping of prediction directions to intra-prediction modes, to mapping of prediction directions to codewords, to complex adaptive schemes involving most probable modes, and the like. However, in all cases, there may be certain intra-prediction directions that are statistically less likely to occur in the video content than certain other directions. Since the goal of video compression is to reduce redundancy, in a well-designed video coding technique, those less likely directions may be represented by more bits than more likely directions.

[0019] Inter-picture prediction or inter-prediction may be based on motion compensation. In motion compensation, sample data from a previously reconstructed picture or portion thereof (reference picture) may be used to predict a newly reconstructed picture or picture portion (e.g., block) after being spatially shifted in a direction indicated by a motion vector (hereinafter MV). In some cases, the reference picture may be the same as the picture currently being reconstructed. The MV may have two dimensions, X and Y, or three dimensions, with the third dimension being an indication of the reference picture being used (similar to the time dimension).

[0020] In some video compression techniques, the current MV applicable to a region of sample data may be predicted based on other MVs, for example, based on other MVs related to another region of sample data that is spatially adjacent to the region being reconstructed and that precede the current MV in decoding order. Doing so can greatly reduce the total amount of data required to encode the MV by eliminating redundancy in the related MVs, thereby increasing compression efficiency. MV prediction can work effectively, for example, because when encoding an input video signal obtained from a camera (called natural video), there is a statistical probability that a larger area than the area for which a single MV applies moves in a similar direction in the video sequence, so in some cases, similar motion vectors derived from MVs of neighboring areas can be used to predict the larger area. This makes the actual MV for a given region similar or identical to the MV predicted from the surrounding MVs. Further, after entropy coding, the MV can be represented using a smaller number of bits than would be used if the MV was encoded directly (rather than predicted from neighboring MVs). In some cases, MV prediction can be an example of losslessly compressing a signal (i.e., MV) derived from an original signal (i.e., a sample stream). In other cases, the MV prediction itself may be lossy, for example due to round-off errors when computing the prediction value from multiple surrounding MVs.

[0021] Various MV prediction mechanisms are described in H.265 / HEVC (ITU-T Recommendation H.265, "High Efficiency Video Coding", December 2016). Among the multiple MV prediction mechanisms specified by H.265, described below is a technique hereinafter referred to as "spatial merge".

[0022] Specifically, referring to FIG. 2 , the current block ( 201 ) includes samples that have been found by the encoder during the motion search process, which can be predicted based on a previous block of the same size that has generated a spatial offset. Instead of encoding the MV directly, the MV can be derived from metadata associated with one or more reference pictures, such as using an MV associated with any of the five surrounding samples labeled A0, A1 and B0, B1, B2 (corresponding to 202 to 206, respectively), and the MV is derived from the nearest reference picture (in decoding order). In H.265, MV prediction can use prediction values ​​from the same reference picture that is being used by neighboring blocks. Summary of the invention

[0023] This disclosure describes various embodiments of methods, apparatus, and computer-readable storage media for video encoding and / or decoding.

[0024] According to one aspect, an embodiment of the present disclosure provides a method for multi-reference line intra-frame prediction in video decoding. The method includes: receiving an encoded video stream of a current block through a device. The device includes a memory storing instructions and a processor communicating with the memory. The method also includes: extracting parameters from the encoded video stream through a device, the parameters indicating a non-adjacent reference line used for intra-frame prediction in the current block; dividing the current block through a device to obtain a plurality of sub-blocks; and in response to a sub-block of the plurality of sub-blocks being located at a boundary of the current block, using a top adjacent reference line as a value of all top non-adjacent reference lines of the sub-block through a device.

[0025] According to another aspect, an embodiment of the present disclosure provides a device for video encoding and / or decoding. The device includes: a memory storing instructions; and a processor communicating with the memory. When the processor executes the instructions, the processor is configured to cause the device to perform the above-mentioned method for video decoding and / or encoding.

[0026] On the other hand, an embodiment of the present disclosure provides a non-transitory computer-readable medium storing instructions, which, when executed by a computer for video decoding and / or encoding, cause the computer to perform the above-mentioned method for video decoding and / or encoding.

[0027] The above and other aspects and implementations thereof are described in more detail in the drawings, the description and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further features, nature, and various advantages of the disclosed subject matter will become more apparent from the following detailed description and accompanying drawings.

[0029] FIG. 1A shows a schematic illustration of an exemplary subset of intra-prediction directional modes.

[0030] FIG. 1B shows a diagram of exemplary intra prediction directions.

[0031] FIG. 2 shows a schematic diagram of a current block and its surrounding spatial merging candidates for motion vector prediction in one example.

[0032] Figure 3 A schematic illustration of a simplified block diagram of a communication system (300) is shown according to an exemplary embodiment.

[0033] Figure 4 A schematic illustration of a simplified block diagram of a communication system (400) is shown according to an exemplary embodiment.

[0034] Figure 5 A schematic illustration of a simplified block diagram of a video decoder according to an exemplary embodiment is shown.

[0035] Figure 6 A schematic illustration of a simplified block diagram of a video encoder according to an exemplary embodiment is shown.

[0036] Figure 7 A block diagram of a video encoder according to another exemplary embodiment is shown.

[0037] Figure 8 A block diagram of a video decoder according to another exemplary embodiment is shown.

[0038] Fig. 9 A scheme of coding block division according to an exemplary embodiment of the present disclosure is shown.

[0039] Fig.10 Another scheme of coding block partitioning according to an exemplary embodiment of the present disclosure is shown.

[0040] Fig.11 Another scheme of coding block partitioning according to an exemplary embodiment of the present disclosure is shown.

[0041] Fig.12 Another scheme of coding block partitioning according to an exemplary embodiment of the present disclosure is shown.

[0042] Fig.13A scheme of dividing a coding block into a plurality of transform blocks and an encoding order of the transform blocks according to an exemplary embodiment of the present disclosure are shown.

[0043] Fig.14 Another scheme of dividing a coding block into a plurality of transform blocks and an encoding order of the transform blocks according to an exemplary embodiment of the present disclosure are shown.

[0044] Fig.15 Another scheme of dividing a coding block into a plurality of transform blocks according to an exemplary embodiment of the present disclosure is shown.

[0045] Fig.16 An intra prediction scheme based on respective reference lines according to an exemplary embodiment of the present disclosure is shown.

[0046] Fig.17 A flow chart of a method according to an exemplary embodiment of the present disclosure is shown.

[0047] Fig.18 An intra prediction scheme based on multiple reference lines according to an exemplary embodiment of the present disclosure is shown.

[0048] Fig.19 An intra prediction scheme based on multiple reference lines according to an exemplary embodiment of the present disclosure is shown.

[0049] Fig. 20 A schematic diagram of a computer system according to an exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0050] The present invention will now be described in detail hereinafter with reference to the accompanying drawings, which form a part hereof and show by way of illustration specific examples of embodiments. However, it is noted that the present invention may be embodied in a variety of different forms and, therefore, the subject matter covered or claimed is intended to be construed as not limited to any embodiment set forth below. It is also noted that the present invention may be embodied as a method, apparatus, component or system. Thus, embodiments of the present invention may, for example, take the form of hardware, software, firmware or any combination thereof.

[0051] Throughout the specification and claims, terms may have slightly different meanings revealed or implied by the context in addition to their explicitly stated meanings. The phrases "in one embodiment" or "in some embodiments" as used herein do not necessarily refer to the same embodiment, and the phrases "in another embodiment" or "in other embodiments" as used herein do not necessarily refer to different embodiments. Similarly, the phrases "in one implementation" or "in some implementations" as used herein do not necessarily refer to the same implementation, and the phrases "in another implementation" or "in other implementations" as used herein do not necessarily refer to different implementations. For example, it is intended that the subject matter claimed includes all or part of a combination of exemplary embodiments / implementations.

[0052] Typically, terms can be understood at least in part from usage in context. For example, terms such as "and", "or" or "and / or" as used herein may include various meanings, which may depend at least in part on the context in which such terms are used. Typically, if "or" is used for an association list (e.g., A, B, or C), "or" is intended to represent A, B, and C (used here in an inclusive sense) as well as A, B, or C (used here in an exclusive sense). In addition, the terms "one or more" or "at least one" as used herein depend at least in part on the context and may be used to describe any feature, structure, or characteristic in a singular sense, or may be used to describe a combination of features, structures, or characteristics in a plural sense. Similarly, terms such as "one", "an", or "the" may also be understood to convey singular usage or to convey plural usage, which may depend at least in part on the context. In addition, the term "based on" or "determined by..." may be understood to not necessarily be intended to convey a set of exclusive factors, but may allow for the presence of additional factors that are not necessarily explicitly described, which may depend at least in part on the context.

[0053] Figure 3 A simplified block diagram of a communication system (300) according to one embodiment of the present disclosure is shown. The communication system (300) includes a plurality of terminal devices that can communicate with each other via, for example, a network (350). For example, the communication system (300) includes a first pair of terminal devices (310) and (320) interconnected via the network (350). Figure 3In the example of , the first terminal device pair (310) and (320) can perform unidirectional data transmission. For example, the terminal device (310) can encode video data (for example, video data of a video picture stream collected by the terminal device (310)) for transmission to another terminal device (320) via the network (350). The encoded video data can be transmitted in the form of one or more encoded video code streams. The terminal device (320) can receive the encoded video data from the network (350), decode the encoded video data to restore the video picture, and display the video picture based on the restored video data. The unidirectional data transmission can be implemented in applications such as media services.

[0054] In another example, the communication system (300) includes a second terminal device pair (330) and (340) that performs bidirectional transmission of encoded video data, which can be implemented, for example, during a video conferencing application. For bidirectional data transmission, in one example, each of the terminal devices (330) and (340) can encode video data (e.g., video data of a video picture stream collected by the terminal device) for transmission to the other terminal device (330) and (340) via a network (350). Each of the terminal devices (330) and (340) can also receive the encoded video data transmitted by the other terminal device (330) and (340), and can decode the encoded video data to restore the video picture, and can display the video picture on an accessible display device based on the restored video data.

[0055] exist Figure 3 In the example of, terminal device (310), terminal device (320), terminal device (330) and terminal device (340) can be implemented as a server, a personal computer and a smart phone, but the applicability of the underlying principles of the present disclosure may not be limited to this. Embodiments of the present disclosure can be implemented in a desktop computer, a laptop computer, a tablet computer, a media player, a wearable computer, a dedicated video conferencing device, etc. Network (350) represents any number of networks that transmit encoded video data between terminal devices (310), terminal devices (320), terminal devices (330) and terminal devices (340), including, for example, wired (wired) and / or wireless communication networks. The communication network (350) can exchange data in a circuit switching channel, a packet switching channel and / or other types of channels. Representative networks include telecommunication networks, local area networks, wide area networks and / or the Internet. For the purpose of this discussion, unless explicitly stated herein, the architecture and topology of the network (350) may be irrelevant to the operation of the present disclosure.

[0056] As examples of applications for the disclosed subject matter, Figure 4The placement of the video encoder and video decoder in a video streaming environment is shown. The disclosed subject matter is equally applicable to other video applications, including, for example, video conferencing, digital TV, broadcasting, gaming, virtual reality, storing compressed video on digital media including CDs, DVDs, memory sticks, etc., and the like.

[0057] The video streaming system may include a video acquisition subsystem (413), which may include a video source (401), such as a digital camera, for creating an uncompressed video picture or image stream (402). In one example, the video picture stream (402) includes samples recorded by the digital camera of the video source 401. The video picture stream (402), which is depicted as a thick line to emphasize the high amount of data compared to the encoded video data (404) (or the encoded video bitstream), can be processed by an electronic device (420), which includes a video encoder (403) coupled to the video source (401). The video encoder (403) may include hardware, software, or a combination of hardware and software to implement or implement various aspects of the disclosed subject matter as described in more detail below. The encoded video data (404) (or the encoded video bitstream (404)), depicted as thin lines to emphasize the lower data volume compared to the uncompressed video picture stream (402), can be stored on the streaming server (405) for future use, or directly stored in a downstream video device (not shown). One or more streaming client subsystems, such as Figure 4 The client subsystem (406) and the client subsystem (408) in the streaming server (405) can access the streaming server (405) to retrieve the copy (407) and the copy (409) of the encoded video data (404). The client subsystem (406) may include, for example, a video decoder (410) in the electronic device (430). The video decoder (410) decodes the incoming copy (407) of the encoded video data and generates an uncompressed output video picture stream (411) that can be presented on a display (412) (e.g., a display screen) or other presentation device (not depicted). The video decoder 410 can be configured to perform some or all of the various functions described in the present disclosure. In some streaming systems, the encoded video data (404), (407) and (409) (e.g., video bitstreams) can be encoded according to certain video encoding / compression standards. Examples of these standards include ITU-T Recommendation H.265. In one example, the video coding standard under development is informally referred to as Next Generation Video Coding (VVC). The disclosed subject matter may be used in the context of VVC and other video coding standards.

[0058] It should be noted that the electronic device (420) and the electronic device (430) may include other components (not shown). For example, the electronic device (420) may include a video decoder (not shown), and the electronic device (430) may also include a video encoder (not shown).

[0059] In the following, Figure 5 A block diagram of a video decoder (510) according to any embodiment of the present disclosure is shown. The video decoder (510) may be included in an electronic device (530). The electronic device (530) may include a receiver (531) (e.g., a receiving circuit). The video decoder (510) may be used to replace Figure 4 A video decoder (410) in an example of FIG.

[0060] The receiver (531) may receive one or more encoded video sequences to be decoded by the video decoder (510). In the same or another embodiment, one encoded video sequence may be decoded at a time, wherein the decoding of each encoded video sequence is independent of the other encoded video sequences. Each video sequence may be associated with multiple video frames or images. The encoded video sequence may be received from a channel (501), which may be a hardware / software link leading to a storage device storing the encoded video data or a streaming source transmitting the encoded video data. The receiver (531) may receive the encoded video data and other data, such as encoded audio data and / or auxiliary data streams, which may be forwarded to their respective processing circuits (not depicted). The receiver (531) may separate the encoded video sequence from the other data. To prevent network jitter, a buffer memory (515) may be provided between the receiver (531) and the entropy decoder / parser (520) (hereinafter referred to as "parser (520)"). In some applications, the buffer memory (515) may be implemented as part of the video decoder (510). In other applications, the buffer memory (515) may be located outside the video decoder (510) and separate from the video decoder (510) (not depicted). In still other applications, a buffer memory (not depicted) may be provided outside the video decoder (510) for the purpose of, for example, preventing network jitter, and another additional buffer memory (515) may be provided inside the video decoder (510) for, for example, processing playback timing. When the receiver (531) receives data from a storage / forward device with sufficient bandwidth and controllability or from an isochronous network, the buffer memory (515) may not be required, or the buffer memory may be made smaller. For use on a traffic packet network such as the Internet, a buffer memory (515) of sufficient size may be required, and the size of the buffer memory (515) may be relatively large. Such a buffer memory may be implemented to have an adaptive size and may be implemented at least in part in an operating system or similar element (not depicted) external to the video decoder (510).

[0061] The video decoder (510) may include a parser (520) to reconstruct symbols (521) from the encoded video sequence. The categories of these symbols include information for managing the operation of the video decoder (510) and potential information for controlling a presentation device such as a display (512) (e.g., a display screen), which may or may not be an integral part of the electronic device (530), but may be coupled to the electronic device (530), such as Figure 5 As shown. The control information for the rendering device may be in the form of auxiliary enhancement information (SEI message) or video usability information (VUI) parameter set fragments (not depicted). The parser (520) may parse / entropy decode the encoded video sequence received by the parser (520). The entropy encoding of the encoded video sequence may be performed according to a video coding technique or standard, and may follow various principles, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, etc. The parser (520) may extract a subgroup parameter set for at least one subgroup of the subgroups of pixels in the video decoder from the encoded video sequence based on at least one parameter corresponding to the subgroup. The subgroup may include a group of pictures (GOP), a picture, a tile, a slice, a macroblock, a coding unit (CU), a block, a transform unit (TU), a prediction unit (PU), etc. The parser (520) may also extract information such as transform coefficients (e.g., Fourier transform coefficients), quantizer parameter values, motion vectors, etc. from the encoded video sequence.

[0062] The parser (520) may perform entropy decoding / parsing operations on the video sequence received from the buffer memory (515), thereby creating symbols (521).

[0063] Depending on the type of coded video picture or portion of coded video picture (e.g., inter-picture and intra-picture, inter-block and intra-block) and other factors, the reconstruction of the symbol (521) may involve a number of different processing or functional units. The units involved and the manner in which the units are involved may be controlled by the parser (520) through subgroup control information parsed from the coded video sequence. For simplicity, such subgroup control information flow between the parser (520) and the various processing or functional units described below is not depicted.

[0064] In addition to the functional blocks already mentioned, the video decoder (510) can be conceptually subdivided into a number of functional units as described below. In actual implementations operating under commercial constraints, many of these functional units interact closely with each other and may be at least partially integrated with each other. However, for the purpose of clearly describing the various functions of the disclosed subject matter, the conceptual subdivision into multiple functions is adopted in the following of this disclosure.

[0065] The first unit may include a sealer / inverse transform unit (551). The sealer / inverse transform unit (551) may receive quantized transform coefficients as symbols (521) and control information from the parser (520), including information indicating which type of inverse transform to use, block size, quantization factors / parameters, quantization scaling matrices, etc. The sealer / inverse transform unit (551) may output a block including sample values, which may be input into an aggregator (555).

[0066] In some cases, the output samples of the scaler / inverse transform (551) may belong to an intra-coded block; that is, a block that does not use prediction information from a previously reconstructed picture, but may use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by an intra-picture prediction unit (552). In some cases, the intra-picture prediction unit (552) may use surrounding block information that has been reconstructed and stored in a current picture buffer (558) to generate a block of the same size and shape as the block being reconstructed. For example, the current picture buffer (558) buffers a partially reconstructed current picture and / or a fully reconstructed current picture. In some implementations, the aggregator (555) may add the prediction information generated by the intra-prediction unit (552) to the output sample information provided by the scaler / inverse transform unit (551) on a per-sample basis.

[0067] In other cases, the output samples of the scaler / inverse transform unit (551) may belong to a block that is inter-coded and potentially motion compensated. In this case, the motion compensated prediction unit (553) may access the reference picture memory (557) to extract samples for inter-picture prediction. After the extracted samples are motion compensated according to the symbols (521) belonging to the block, these samples may be added to the output of the scaler / inverse transform unit (551) by the aggregator (555) (the output of unit 551 may be referred to as residual samples or residual signals), thereby generating output sample information. The extraction of prediction samples by the motion compensated prediction unit (553) from the address in the reference picture memory (557) may be controlled by a motion vector, which may be provided to the motion compensated prediction unit (553) in the form of symbols (521), which may have, for example, an X component, a Y component (offset), and a reference picture component (time). Motion compensation may also include interpolation of sample values ​​retrieved from the reference picture memory (557) when using sub-sample accurate motion vectors, and may also be associated with motion vector prediction mechanisms, etc.

[0068] The output samples of the aggregator (555) may be subjected to various loop filtering techniques in a loop filter unit (556). The video compression techniques may include in-loop filter techniques controlled by parameters included in the coded video sequence (also referred to as a coded video bitstream) and available to the loop filter unit (556) as symbols (521) from the parser (520), however, the video compression techniques may also be responsive to meta information obtained during decoding of a previous (in decoding order) portion of the coded picture or coded video sequence, as well as to previously reconstructed and loop filtered sample values. A variety of types of loop filters may be included as part of the loop filter unit 556 in various orders, as will be described in further detail below.

[0069] The output of the loop filter unit (556) may be a sample stream that may be output to a rendering device (512) and stored in a reference picture memory (557) for future inter-picture prediction.

[0070] Once fully reconstructed, certain coded pictures may be used as reference pictures for future inter-picture prediction. For example, once the coded picture corresponding to the current picture is fully reconstructed, and the coded picture is identified as a reference picture (e.g., by the parser (520)), the current picture buffer (558) may become part of the reference picture memory (557), and a new current picture buffer may be reallocated before starting reconstruction of a subsequent coded picture.

[0071] The video decoder (510) may perform decoding operations according to a predetermined video compression technique employed in a standard such as ITU-T Recommendation H.265. The encoded video sequence may conform to the syntax specified by the video compression technique or standard used in the sense that the encoded video sequence follows the syntax of the video compression technique or standard and the profile recorded in the video compression technique or standard. Specifically, the profile may select certain tools from all the tools available in the video compression technique or standard as the only tools available for use under the profile. To conform to the standard, the complexity of the encoded video sequence may be within a range defined by the hierarchy of the video compression technique or standard. In some cases, the hierarchy limits the maximum picture size, the maximum frame rate, the maximum reconstruction sampling rate (measured in, for example, mega samples per second), the maximum reference picture size, etc. In some cases, the limits set by the hierarchy may be further defined by the hypothetical reference decoder (HRD) specification and metadata of the HRD buffer management signaled in the encoded video sequence.

[0072] In some exemplary embodiments, the receiver (531) may receive additional (redundant) data when receiving the encoded video. The additional data may be included as part of the encoded video sequence. The additional data may be used by the video decoder (510) to properly decode the data and / or more accurately reconstruct the original video data. The additional data may take the form of, for example, temporal, spatial or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0073] Figure 6 A block diagram of a video encoder (603) according to an exemplary embodiment of the present disclosure is shown. The video encoder (603) may be included in an electronic device (620). The electronic device (620) may further include a transmitter (640) (e.g., a transmission circuit). The video encoder (603) may be used to replace Figure 4 A video encoder (403) in an example.

[0074] The video encoder (603) can be used to obtain the video source (601) (not Figure 6 In an example of an electronic device (620) receiving video samples, a video source (601) can capture video images to be encoded by a video encoder (603). In another example, the video source (601) can be implemented as a part of the electronic device (620).

[0075] The video source (601) may provide a source video sequence in the form of a digital video sample stream to be encoded by a video encoder (603), the digital video sample stream may have any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 YCrCb, RGB, XYZ, ...), and any suitable sampling structure (e.g., YCrCb 4:2:0, YCrCb 4:4:4). In a media service system, the video source (601) may be a storage device capable of storing previously prepared videos. In a video conferencing system, the video source (601) may be a camera that captures local image information as a video sequence. The video data may be provided as a plurality of separate pictures or images that are given motion when viewed sequentially. The picture itself may be constructed as a spatial pixel array, wherein each pixel may include one or more samples depending on the sampling structure, color space, etc. used. A person of ordinary skill in the art may easily understand the relationship between pixels and samples. The following description focuses on the samples.

[0076] According to some exemplary embodiments, the video encoder (603) may encode and compress the pictures of the source video sequence into an encoded video sequence (643) in real time or under any other time constraints required by the application. Implementing an appropriate encoding speed constitutes a function of the controller (650). In some embodiments, the controller (650) may be functionally coupled to and control other functional units as described below. For simplicity, the coupling is not depicted in the figure. The parameters set by the controller (650) may include rate control related parameters (picture skipping, quantizer, lambda value of rate distortion optimization technology...), picture size, picture group (GOP) layout, maximum motion vector search range, etc. The controller (650) may be configured to have other suitable functions that are related to the video encoder (603) optimized for a certain system design.

[0077] In some exemplary embodiments, the video encoder (603) may be configured to operate in an encoding loop. As an oversimplified description, in one example, the encoding loop may include a source encoder (630) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be encoded and a reference picture) and a (local) decoder (633) embedded in the video encoder (603). The decoder (633) reconstructs the symbols to create sample data in a manner similar to how a (remote) decoder may create sample data, even though the embedded decoder 633 processes a video stream encoded by the source encoder 630 without entropy encoding (because in the video compression techniques considered in the disclosed subject matter, any compression between the entropy-encoded symbols and the encoded video bitstream may be lossless). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since the decoding of the symbol stream produces a bit-accurate result that is independent of the decoder location (local or remote), the contents of the reference picture memory (634) also correspond bit-accurately between the local encoder and the remote encoder. In other words, the reference picture samples "seen" by the prediction part of the encoder are exactly the same sample values ​​that the decoder will "see" when using the prediction during decoding. This basic principle of reference picture synchronization (and the drift that occurs when synchronization cannot be maintained, e.g. due to channel errors) is used to improve encoding quality.

[0078] The operation of the "local" decoder (633) may be similar to that described above in conjunction with Figure 5 The "remote" decoder of the video decoder (510) described in detail is identical. However, additional brief reference is made to Figure 5, since the symbols are available and the entropy encoder (645) and the parser (520) are capable of losslessly encoding / decoding the symbols into the encoded video sequence, the entropy decoding portion of the video decoder (510) including the buffer memory (515) and the parser (520) may not be fully implemented in the local decoder (633) in the encoder.

[0079] At this point, it can be observed that any decoder technology other than parsing / entropy decoding, which can only exist in a decoder, must also be present in a corresponding encoder in substantially the same functional form. For this reason, the disclosed subject matter can sometimes focus on decoder operations, which are combined with the decoding portion of the encoder. Therefore, the description of encoder technology can be simplified because encoder technology is mutually inverse to the decoder technology described comprehensively. Hereinafter, only in certain areas or aspects, a more detailed description of the encoder is provided.

[0080] During operation, in some example implementations, the source encoder (630) may perform motion compensated predictive coding that predictively encodes an input picture by referencing one or more previously encoded pictures from a video sequence designated as "reference pictures." In this manner, the encoding engine (632) encodes the differences (or residuals) in color channels between pixel blocks of the input picture and pixel blocks of a reference picture that may be selected as a prediction reference for the input picture.

[0081] The local video decoder (633) may decode the encoded video data of the picture that may be designated as the reference picture based on the symbol created by the source encoder (630). The operation of the encoding engine (632) may advantageously be a lossy process. When the encoded video data may be decoded at the video decoder ( Figure 6 When decoded from a local video decoder (not shown), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (633) replicates the decoding process that may be performed by the video decoder on the reference picture and may cause the reconstructed reference picture to be stored in the reference picture cache (634). In this way, the video encoder (603) may store a copy of the reconstructed reference picture locally that has common content (absent transmission errors) with the reconstructed reference picture to be obtained by the far-end (remote) video decoder.

[0082] The predictor (635) may perform a prediction search for the encoding engine (632). That is, for a new picture to be encoded, the predictor (635) may search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or certain metadata, such as reference picture motion vectors, block shapes, etc., that may be used as appropriate prediction references for the new picture. The predictor (635) may operate on a pixel block by pixel block basis to find a suitable prediction reference. In some cases, as determined by the search results obtained by the predictor (635), the input picture may have prediction references taken from multiple reference pictures stored in the reference picture memory (634).

[0083] The controller (650) may manage encoding operations of the source encoder (630), including, for example, setting parameters and subgroup parameters for encoding video data.

[0084] The outputs of all the above functional units may be entropy encoded in an entropy encoder (645). The entropy encoder (645) performs lossless compression on the symbols generated by the various functional units according to techniques such as Huffman coding, variable length coding, arithmetic coding, etc., thereby converting the symbols into a coded video sequence.

[0085] The transmitter (640) can buffer the encoded video sequence created by the entropy encoder (645) in preparation for transmission over a communication channel (660), which can be a hardware / software link to a storage device that can store the encoded video data. The transmitter (640) can combine the encoded video data from the video encoder (603) with other data to be transmitted, such as encoded audio data and / or auxiliary data streams (source not shown).

[0086] The controller (650) may manage the operation of the video encoder (603). During encoding, the controller (650) may assign a certain coded picture type to each coded picture, but this may affect the coding techniques that can be applied to the corresponding picture. For example, a picture may generally be assigned to any of the following picture types:

[0087] An intra picture (I picture) may be a picture that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs allow for different types of intra pictures, including, for example, independent decoder refresh ("IDR") pictures. Those of ordinary skill in the art are aware of these variations of I pictures and their corresponding applications and features.

[0088] A predictive picture (P picture) may be a picture that can be encoded and decoded using intra prediction or inter prediction, which uses at most one motion vector and a reference index to predict sample values ​​for each block.

[0089] Bidirectional predictive pictures (B pictures), which can be pictures that can be encoded and decoded using intra-frame prediction or inter-frame prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple predictive pictures can use more than two reference pictures and associated metadata to reconstruct a single block.

[0090] The source picture may typically be spatially subdivided into a plurality of coding blocks of samples (e.g., blocks of 4×4, 8×8, 4×8, or 16×16 samples), and encoded block by block. These blocks may be predictively encoded with reference to other (already encoded) blocks, which are determined by the coding allocation applied to the corresponding picture of the block. For example, blocks of an I picture may be non-predictively encoded, or blocks of an I picture may be predictively encoded (spatial prediction or intra-frame prediction) with reference to already encoded blocks of the same picture. Blocks of pixels of a P picture may be predictively encoded by spatial prediction with reference to a previously encoded reference picture or by temporal prediction. Blocks of a B picture may be predictively encoded by spatial prediction with reference to one or two previously encoded reference pictures or by temporal prediction. For other purposes, source pictures or intermediately processed pictures may be subdivided into other types of blocks. The division of coding blocks and other types of blocks may or may not follow the same approach, as described in further detail below.

[0091] The video encoder (603) may perform encoding operations according to a predetermined video encoding technique or standard, such as ITU-T H.265 Recommendation. In operation, the video encoder (603) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancy in an input video sequence. Thus, the encoded video data may conform to the syntax specified by the video encoding technique or standard used.

[0092] In some exemplary embodiments, the transmitter (640) may transmit additional data when transmitting the encoded video. The source encoder (630) may include such data as part of the encoded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0093] The captured video may be taken as a plurality of source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often shortened to intra-prediction) exploits spatial correlations in a given picture, while inter-picture prediction exploits temporal or other correlations between pictures. For example, a particular picture being encoded / decoded may be divided into blocks, and the particular picture being encoded / decoded is referred to as the current picture. When a block in the current picture is similar to a reference block in a reference picture that was previously encoded in the video and is still buffered, the block in the current picture may be encoded by a vector called a motion vector. The motion vector points to a reference block in a reference picture, and in the case where multiple reference pictures are used, the motion vector may have a third dimension that identifies the reference picture.

[0094] In some exemplary embodiments, a bidirectional prediction technique may be used for inter-picture prediction. According to this bidirectional prediction technique, two reference pictures are used, such as a first reference picture and a second reference picture that precede the current picture in the video in decoding order (but may be in the past or future, respectively, in display order). A block in the current picture may be encoded by a first motion vector pointing to a first reference block in the first reference picture and a second motion vector pointing to a second reference block in the second reference picture. The block may be jointly predicted by a combination of the first reference block and the second reference block.

[0095] In addition, merge mode technology can be used for inter-picture prediction to improve coding efficiency.

[0096] According to some exemplary embodiments of the present disclosure, predictions such as inter-picture prediction and intra-picture prediction are performed in units of blocks. For example, a picture in a video picture sequence is divided into coding tree units (CTUs) for compression, and the CTUs in the picture may have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. Typically, a CTU may include three parallel coding tree blocks (CTBs): a luminance CTB and two chrominance CTBs. Each CTU may be recursively split into one or more coding units (CUs) in a quadtree. For example, a 64×64 pixel CTU may be split into a 64×64 pixel CU, or four 32×32 pixel CUs. Each of the one or more 32×32 blocks may be further split into four 16×16 pixel CUs. In some exemplary embodiments, each CU may be analyzed during encoding to determine a prediction type for the CU among a plurality of prediction types, such as an inter-prediction type or an intra-prediction type. A CU may be split into one or more prediction units (PUs) based on temporal and / or spatial predictability. Typically, each PU includes a luma prediction block (PB) and two chroma PBs. In one embodiment, the prediction operation in encoding (encoding / decoding) is performed in units of prediction blocks. Splitting a CU into PUs (or PBs of different color channels) can be performed in various spatial patterns. For example, a luma or chroma PB may include a matrix of values ​​(e.g., luma values) for samples, such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, etc.

[0097] Figure 7 A diagram of a video encoder (703) according to another exemplary embodiment of the present disclosure is shown. The video encoder (703) is configured to receive a processed block (e.g., a prediction block) of sample values ​​within a current video picture in a sequence of video pictures and encode the processed block into an encoded picture that is part of an encoded video sequence. In an example, the video encoder (703) may be used instead of Figure 4 A video encoder (403) in an example.

[0098] For example, the video encoder (703) receives a matrix of sample values ​​for a processing block, such as a prediction block of 8×8 samples, etc. The video encoder (703) then uses, for example, rate-distortion optimization (RDO) to determine whether to use intra mode, inter mode, or bidirectional prediction mode to best encode the processing block. When it is determined that the processing block is encoded in intra mode, the video encoder (703) may use intra prediction techniques to encode the processing block into an encoded picture; and when it is determined that the processing block is encoded in inter mode or bidirectional prediction mode, the video encoder (703) may use inter prediction or bidirectional prediction techniques to encode the processing block into an encoded picture, respectively. In some exemplary embodiments, merge mode may be used as a sub-mode of inter-picture prediction, in which motion vectors are derived from one or more motion vector predictors without the aid of encoded motion vector components external to the predictor. In some other exemplary embodiments, there may be motion vector components applicable to the subject block. Therefore, the video encoder (703) may include a sub-mode that is not in Figure 7 Components explicitly shown in, such as a mode decision module for determining a prediction mode for a processing block.

[0099] exist Figure 7 In the example of FIG. 7 , the video encoder ( 703 ) includes Figure 7 The exemplary arrangement shown in FIG. 1 includes an inter-frame encoder (730), an intra-frame encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721), and an entropy encoder (725) coupled together.

[0100] The inter-frame encoder (730) is configured to receive samples of a current block (e.g., a processing block), compare the block with one or more reference blocks in a reference picture (e.g., blocks in a previous picture and a subsequent picture in display order), generate inter-frame prediction information (e.g., redundant information description according to an inter-frame coding technique, motion vectors, merge mode information), and calculate an inter-frame prediction result (e.g., a predicted block) based on the inter-frame prediction information using any suitable technique. In some examples, the reference picture is based on coded video information, using a video code embedded in the video codec. Figure 6 The decoding unit 633 in the exemplary encoder 620 (eg Figure 7 The decoded reference picture is decoded by the residual decoder 728, as described in further detail below.

[0101] The intra encoder (722) is configured to receive samples of a current block (e.g., a processing block), compare the block with an encoded block in the same picture, and generate quantization coefficients after transformation, and in some cases also generate intra prediction information (e.g., intra prediction direction information according to one or more intra coding techniques). The intra encoder (722) can calculate an intra prediction result (e.g., a predicted block) based on the intra prediction information and a reference block in the same picture.

[0102] The general controller (721) can be configured to determine general control data and control other components of the video encoder (703) based on the general control data. In one example, the general controller (721) determines a prediction mode of a block and provides a control signal to a switch (726) based on the prediction mode. For example, when the prediction mode is an intra-frame mode, the general controller (721) controls the switch (726) to select an intra-frame mode result for use by the residual calculator (723), and controls the entropy encoder (725) to select intra-frame prediction information and include the intra-frame prediction information in the bitstream; and when the prediction mode of the block is an inter-frame mode, the general controller (721) controls the switch (726) to select an inter-frame prediction result for use by the residual calculator (723), and controls the entropy encoder (725) to select inter-frame prediction information and include the inter-frame prediction information in the bitstream.

[0103] The residual calculator (723) may be configured to calculate the difference (residual data) between the received block and the prediction result of the block selected from the intra encoder (722) or the inter encoder (730). The residual encoder (724) may be configured to encode the residual data to generate a transform coefficient. For example, the residual encoder (724) may be configured to transform the residual data from the spatial domain to the frequency domain to generate the transform coefficient. The transform coefficient is then subjected to quantization to obtain a quantized transform coefficient. In various exemplary embodiments, the video encoder (703) further includes a residual decoder (728). The residual decoder (728) is configured to perform an inverse transform and generate decoded residual data. The decoded residual data may be appropriately used by the intra encoder (722) and the inter encoder (730). For example, the inter encoder (730) may generate a decoded block based on the decoded residual data and the inter prediction information, and the intra encoder (722) may generate a decoded block based on the decoded residual data and the intra prediction information. The decoded blocks are appropriately processed to generate decoded pictures, and the decoded pictures may be buffered in a memory circuit (not shown) and used as reference pictures.

[0104] The entropy encoder (725) may be configured to format the code stream to include the encoded blocks, and to perform entropy encoding. The entropy encoder (725) may be configured to include various information in the code stream. For example, the entropy encoder (725) may be configured to include general control data, selected prediction information (e.g., intra-frame prediction information or inter-frame prediction information), residual information, and other suitable information in the code stream. When the block is encoded in the merge sub-mode of the inter-frame mode or the bidirectional prediction mode, the residual information may not be present.

[0105] Figure 8 A diagram of an exemplary video decoder (810) according to another embodiment of the present disclosure is shown. The video decoder (810) is configured to receive an encoded picture as part of an encoded video sequence and decode the encoded picture to generate a reconstructed picture. In one example, the video decoder (810) may be used instead of Figure 4 A video decoder (410) in an example of FIG.

[0106] exist Figure 8 In the example of FIG. 8 , the video decoder ( 810 ) includes Figure 8 The exemplary arrangement shown in FIG. 8 is an entropy decoder (871), an inter-frame decoder (880), a residual decoder (873), a reconstruction module (874), and an intra-frame decoder (872) coupled together.

[0107] The entropy decoder (871) may be configured to reconstruct certain symbols from the encoded picture, the symbols representing syntax elements constituting the encoded picture. Such symbols may include, for example, a mode for encoding a block (e.g., intra mode, inter mode, bidirectional prediction mode, merge submode, or another submode), prediction information (e.g., intra prediction information or inter prediction information) that may identify certain samples or metadata used by an intra decoder (872) or an inter decoder (880) for prediction, residual information in the form of, for example, quantized transform coefficients, and the like. In one example, when the prediction mode is an inter or bidirectional prediction mode, the inter prediction information is provided to an inter decoder (880); and when the prediction type is an intra prediction type, the intra prediction information is provided to an intra decoder (872). The residual information may be subjected to inverse quantization and provided to a residual decoder (873).

[0108] The inter-frame decoder (880) may be configured to receive the inter-frame prediction information and generate an inter-frame prediction result based on the inter-frame prediction information.

[0109] The intra decoder (872) may be configured to receive intra prediction information and generate a prediction result based on the intra prediction information.

[0110] The residual decoder (873) may be configured to perform inverse quantization to extract dequantized transform coefficients, and process the dequantized transform coefficients to transform the residual from the frequency domain to the spatial domain. The residual decoder (873) may also utilize certain control information (to include quantizer parameters (QP)) that may be provided by the entropy decoder (871) (data path not depicted as this is only low data volume control information).

[0111] The reconstruction module (874) may be configured to combine the residual output by the residual decoder (873) with the prediction result (which may be output by the inter-frame prediction module or the intra-frame prediction module, as appropriate) in the spatial domain to form a reconstructed block, which forms part of a reconstructed picture, and the reconstructed picture is part of the reconstructed video. It should be noted that other suitable operations such as deblocking operations may also be performed to improve visual quality.

[0112] It should be noted that the video encoder (403), video encoder (603) and video encoder (703) and video decoder (410), video decoder (510) and video decoder (810) may be implemented using any suitable technology. In some exemplary embodiments, the video encoder (403), video encoder (603) and video encoder (703) and video decoder (410), video decoder (510) and video decoder (810) may be implemented using one or more integrated circuits. In another embodiment, the video encoder (403), video encoder (603) and video encoder (603) and video decoder (410), video decoder (510) and video decoder (810) may be implemented using one or more processors that execute software instructions.

[0113] Turning to coding block partitioning, in some exemplary implementations, a predetermined pattern may be applied. Fig. 9 As shown, an exemplary 4-way partitioning tree starting from a first predetermined level (e.g., a 64×64 block level) and descending to a second predetermined level (e.g., a 4×4 level) may be used. For example, a basic block may be subject to four partitioning options indicated by 902, 904, 906, and 908, where partitions marked as R may be allowed for recursive partitioning because Fig. 9 The same partition tree indicated may be repeated in small scales until the smallest level (e.g., 4×4 level). Fig. 9 Additional restrictions apply to the partitioning scheme. Fig. 9 In the implementation of , rectangular partitioning (e.g., 1:2 / 2:1 rectangular partitioning) may be allowed, but the rectangular partitioning may not be allowed to be recursive, but the square partitioning may be allowed to be recursive. If necessary, follow Fig. 9Recursively partitioning generates a final set of coded blocks. This scheme can be applied to one or more color channels.

[0114] Fig.10 Another exemplary predetermined partitioning pattern is shown, which allows recursive partitioning to form a partitioning tree. Fig.10 As shown, an exemplary 10-way partitioning structure or pattern may be predefined. A root block may start from a predetermined level (eg, from a 128×128 level or a 64×64 level). Fig.10 Exemplary partitioning structures include various 2:1 / 1:2 and 4:1 / 1:4 rectangular partitionings. Fig.10 The partition type with 3 sub-partitions indicated by 1002, 1004, 1006, and 1008 in the second row of can be referred to as a "T-type" partition. The "T-type" partitions 1002, 1004, 1006, and 1008 can be referred to as a left T-type, a top T-type, a right T-type, and a bottom T-type. In some implementations, further subdivisions are not allowed. Fig.10 The coding tree depth may be further defined to indicate the split depth from the root node or root block. For example, for the root node or root block (e.g., for a 128×128 block), the coding tree depth may be set to 0. Fig.10 After further splitting the root block, the coding tree depth increases by 1. In some implementations, only all square partitions in 1010 can be allowed to follow Fig.10 The pattern of 1002, 1004, 1006 and 1007 is recursively divided to become the next level of the partition tree. In other words, recursive partitioning may not be allowed for the square partitions with patterns 1002, 1004, 1006 and 1007. If necessary, follow Fig.10 Recursively partitioning generates a final set of coded blocks. This scheme can be applied to one or more color channels.

[0115] After following any of the above-mentioned partitioning processes or other processes to split or divide the basic block, the final partition set or coding block can be obtained again. Each of these partitions can be at one of various partitioning levels. Each partition can be called a coding block (CB). For the various exemplary partitioning implementations described above, each generated CB can have any allowed size and partitioning level. The partition is called a coding block because the partition can form a unit, some basic encoding / decoding decisions can be made for the unit, and the encoding / decoding parameters can be optimized, determined, and represented by a signal in the encoded video bitstream. The highest level in the final partition represents the depth of the coding block partition tree. The coding block can be a luminance coding block or a chrominance coding block.

[0116] In some other exemplary implementations, a quadtree structure may be used to recursively split the basic luma and chroma blocks into coding units. This split structure may be referred to as a coding tree unit (CTU), and the CTU is split into coding units (CUs) using a quadtree structure to adapt the partitioning to the various local characteristics of the basic CTU. In such an implementation, an implicit quadtree split may be performed at the picture boundary so that the block will remain quadtree split until the size fits the picture boundary. The term CU is used to collectively refer to the unit of luma coding blocks and chroma coding blocks (CBs).

[0117] In some implementations, the CB may be further divided. For example, the CB may be further divided into a plurality of prediction blocks (PBs) for intra-frame prediction or inter-frame prediction during the encoding and decoding process. In other words, the CB may be further divided into different sub-divisions in which independent prediction decisions / configurations may be made. In parallel, the CB may be further divided into a plurality of transform blocks (TBs) to describe the levels used to perform the transform or inverse transform of the video data. The partitioning schemes of the CB into PBs and TBs may be the same or may be different. For example, each partitioning scheme may be performed using its own process based on, for example, various characteristics of the video data. In some exemplary implementations, the PB partitioning scheme and the TB partitioning scheme may be irrelevant. In some other exemplary implementations, the PB partitioning scheme and the TB partitioning scheme and the boundaries may be interrelated. In some implementations, for example, the TB may be partitioned after the PB partitioning, in particular, after each PB is determined following the partitioning of the coding block, each PB may be further divided into one or more TBs. For example, in some implementations, the PB may be split into one TB, two TBs, four TBs, or other numbers of TBs.

[0118] In some implementations, in order to divide the basic block into coding blocks and further into prediction blocks and / or transform blocks, the luma channel and the chroma channel may be processed differently. For example, in some implementations, for the luma channel, it may be allowed to divide the coding block into prediction blocks and / or transform blocks, while for the chroma channel, it may not be allowed to divide the coding block into prediction blocks and / or transform blocks in this way. Therefore, in such an implementation, the transformation and / or prediction of the luma block may be performed only at the coding block level. For another example, the minimum transform block size of the luma channel and the chroma channel may be different, for example, compared with the chroma channel, the coding block of the luma channel may be allowed to be divided into smaller transform blocks and / or prediction blocks. For another example, the maximum depth of dividing the coding block into transform blocks and / or prediction blocks may be different between the luma channel and the chroma channel, for example, compared with the chroma channel, the coding block of the luma channel may be allowed to be divided into deeper transform blocks and / or prediction blocks. For a specific example, the luma coding block may be partitioned into transform blocks of multiple sizes, which may be represented by recursive partitioning down to up to 2 levels, and may allow transform block shapes such as square, 2:1 / 1:2, and 4:1 / 1:4, and transform block sizes from 4×4 to 64×64. However, for chroma blocks, only the largest possible transform block specified for the luma block may be allowed.

[0119] In some example implementations, to partition a coding block into PBs, the depth, shape and / or other characteristics of the PB partition may depend on whether the PB is intra-coded or inter-coded.

[0120] The partitioning of a coding block (or prediction block) into transform blocks may be implemented in various exemplary schemes, including but not limited to recursive or non-recursive quadtree splitting and predetermined pattern splitting, and additionally considering transform blocks located at the boundaries of the coding block or prediction block. In general, the resulting transform blocks may be at different splitting levels, may not have the same size, and their shape may not need to be square (e.g., the transform block may be rectangular with some allowed size and aspect ratio).

[0121] In some exemplary implementations, a coding partition tree scheme or structure may be used. The coding partition tree schemes for the luma channel and the chroma channel may not need to be the same. In other words, the luma channel and the chroma channel may have different coding tree structures. In addition, whether the luma channel and the chroma channel use the same or different coding partition tree structures, and the actual coding partition tree structure to be used, may depend on whether the slice being encoded is a P slice, a B slice, or an I slice. For example, for an I slice, the chroma channel and the luma channel may have different coding partition tree structures or coding partition tree structure patterns, while for a P slice or a B slice, the luma channel and the chroma channel may share the same coding partition tree scheme. When different coding partition tree structures or patterns are applied, the luma channel may be divided into CBs by one coding partition tree structure, and the chroma channel may be divided into chroma CBs by another coding partition tree structure.

[0122] A specific exemplary implementation of coding block and transform block partitioning is described below. In this exemplary implementation, the basic coding block can be split into coding blocks using the above-mentioned recursive quadtree splitting. At each level, whether further quadtree splitting of a specific partition should be continued can be determined by local video data characteristics. The generated CB can be at various quadtree splitting levels of various sizes. A decision can be made at the CB level (or CU level, for all three color channels) whether to use inter-frame picture (time) prediction or intra-frame picture (spatial) prediction to encode the picture area. Depending on the PB splitting type, each CB can be further split into one PB, two PBs, four PBs, or other number of PBs. Within a PB, the same prediction process can be applied, and relevant information is sent to the decoder based on the PB. After obtaining the residual block by applying the prediction process based on the PB splitting type, the CB can be divided into TBs according to another quadtree structure similar to the coding tree of the CB. In this specific implementation, the CB or TB can be limited to a square, but it is not necessary to be limited to a square. Furthermore, in this particular example, for inter prediction, the PB can be either square or rectangular, whereas for intra prediction, the PB can only be square. For example, the coding block can be further split into four square TBs. Each TB can be further recursively split (using quadtree splitting) into smaller TBs, which are called residual quadtrees (RQTs).

[0123] Another specific example of dividing a basic coding block into CB and other PBs and / or TBs is described below. Fig.10Instead of the multi-partition unit type shown, a quadtree with nested multi-type trees can be used, which uses a binary and ternary split segment structure. The separation of CB, PB, and TB concepts (i.e., dividing CB into PB and / or TB, and dividing PB into TB) can be abandoned unless the CB is required to have a size that is too large for the maximum transform length (in this case, further splitting of such CB may be required). This exemplary splitting scheme can be designed to support greater flexibility in the shape of CB partitions, so that prediction and transformation can be performed at the CB level without further partitioning. In this coding tree structure, the CB can be square or rectangular. Specifically, the coding tree block (CTB) can first be divided by a quadtree structure. Then, the quadtree leaf nodes can be further divided by a multi-type tree structure. Fig.11 An example of a multi-type tree structure is shown in FIG. Fig.11 The exemplary multi-type tree architecture includes four split types, which are called vertical binary split (Split_BT_VER) (1102), horizontal binary split (Split_BT_HOR) (1104), vertical ternary split (Split_TT_VER) (1106) and horizontal ternary split (Split_TT_HOR) (1108). The CB then corresponds to the leaves of the multi-type tree. In this exemplary implementation, unless the CB is too large for the maximum transform length, the segment is used for prediction and transform processing without any further partitioning. This means that in most cases, CB, PB and TB have the same block size in a quadtree with a nested multi-type tree coding block structure. An exception occurs when the maximum supported transform length is less than the width or height of the CB color component.

[0124] exist Fig.12 An example of a quadtree with a nested multi-type tree coding block structure for a block partition of a CTB is shown in FIG. Fig.12 The CTB 1200 is shown as a quadtree split into four square partitions 1202, 1204, 1206 and 1208. For each quadtree split partition, further use is made Fig.11 The multi-type tree structure is used to make split decisions. Fig.12 In the example of , partition 1204 is not further split. Partitions 1202 and 1208 are both split using another quadtree. For partition 1202, the upper left partition, upper right partition, lower left partition, and lower right partition of the second level quadtree split are split using the third level quadtree, Fig.11 1104, do not split and Fig.11 1108. The partition 1208 uses another quadtree partition, and the upper left partition, upper right partition, lower left partition and lower right partition of the second level quadtree partition are respectively Fig.11The third level split 1106, no split, no split and Fig.11 The two subdivisions of the third level upper left division of 1208 are further split according to 1104 and 1108. The division 1206 adopts the following Fig.11 The second level split pattern of 1102 is split into two partitions, which are further divided according to Fig.11 1108 and 1102 are split at the third level. Fig.11 At 1104, the fourth level split is further applied to one of the partitions.

[0125] For the specific example above, the maximum luma transform size may be 64×64, and the maximum supported chroma transform size may be different from luma, for example at 32×32. When the width or height of a luma coding block or a chroma coding block is greater than the maximum transform width or height, the luma coding block or the chroma coding block may be automatically split along the horizontal direction and / or the vertical direction to meet the transform size limit along that direction.

[0126] In a specific example, in order to divide the basic coding block into the above-mentioned CBs, the coding tree scheme may support the ability of luma and chroma to have different block tree structures. For example, for P slices and B slices, the luma CTB and chroma CTB in one CTU may share the same coding tree structure. For example, for I slices, luma and chroma may have different coding block tree structures. When different block tree modes are applied, the luma CTB may be divided into luma CBs by one coding tree structure, and the chroma CTB may be divided into chroma CBs by another coding tree structure. This means that a CU in an I slice may consist of coding blocks of a luma component or coding blocks of two chroma components, and a CU in a P slice or a B slice may always consist of coding blocks of all three color components unless the video is monochrome.

[0127] Exemplary implementations of partitioning a coding block or prediction block into transform blocks and the encoding order of the transform blocks are described in further detail below. In some exemplary implementations, transform partitioning may support transform blocks of various shapes such as 1:1 (square), 1:2 / 2:1, and 1:4 / 4:1, where the size of the transform block ranges from, for example, 4×4 to 64×64. In some implementations, if the coding block is less than or equal to 64×64, the transform block partitioning may only be applied to the luma component, so that for the chroma block, the transform block size is the same as the coding block size. Otherwise, if the coding block width or height is greater than 64, the luma coding block and the chroma coding block may be implicitly split into multiple min(W, 64)×min(H, 64) transform blocks and min(W, 32)×min(H, 32) transform blocks, respectively.

[0128] In some exemplary implementations, for intra-coded blocks and inter-coded blocks, the coded blocks may be further divided into multiple transform blocks, where the division depth may be up to a predetermined number of levels (e.g., 2 levels). The transform block division depth and size may be related. An exemplary mapping from the transform size of the current depth to the transform size of the next depth is shown in Table 1 below.

[0129] Table 1: Transform partition size settings

[0130]

[0131] According to the exemplary mapping of Table 1, for a 1:1 square block, the next level transform splitting may create four 1:1 square sub-transform blocks. The transform splitting may stop at 4×4, for example. Therefore, the transform size 4×4 at the current depth corresponds to the same size 4×4 at the next depth. In the example of Table 1, for a 1:2 / 2:1 non-square block, the next level transform splitting will create two 1:1 square sub-transform blocks, and for a 1:4 / 4:1 non-square block, the next level transform splitting will create two 1:2 / 2:1 sub-transform blocks.

[0132] In some exemplary implementations, for the luma component of intra coded blocks, additional restrictions may be applied. For example, for each transform partitioning level, all sub-transform blocks may be constrained to be of equal size. For example, for a 32×16 coding block, a level 1 transform split creates two 16×16 sub-transform blocks and a level 2 transform split creates eight 8×8 sub-transform blocks. In other words, the second level split must be applied to all first level sub-blocks to keep the transform units of equal size. Fig.13 1 shows an example of transform block partitioning for intra-coded square blocks following Table 1, and the coding order indicated by arrows. Specifically, 1302 shows a square coding block. A first level splitting into 4 equal-sized transform blocks according to Table 1 is shown at 1304, where the coding order is indicated by arrows. A second level splitting of all first-level equal-sized blocks into 16 equal-sized transform blocks according to Table 1 is shown at 1306, where the coding order is indicated by arrows.

[0133] In some exemplary implementations, the above-mentioned restrictions on intra-frame coding may not apply to the luminance component of inter-frame coded blocks. For example, after the first level transform split, any sub-transform block can be further split into another level independently. Therefore, the resulting transform blocks can be of the same size or of different sizes. Fig.14 An example of splitting an inter-frame coding block into transform blocks and the coding order of the transform blocks are shown in FIG. Fig.14In the example of FIG. 1402 , according to Table 1, the inter-frame coding block 1402 is split into transform blocks at two levels. At the first level, the inter-frame coding block is split into four transform blocks of equal size. Then, only one of the four transform blocks (but not all transform blocks) is further split into four sub-transform blocks, resulting in a total of 7 transform blocks, and the 7 transform blocks have two different sizes, as shown in 1404. The exemplary coding order of the 7 transform blocks is as follows: Fig.14 As shown by the arrow in 1404.

[0134] In some exemplary implementations, for chroma components, some additional restrictions may be applied to transform blocks. For example, for chroma components, the transform block size may be as large as the coding block size, but may not be smaller than a predetermined size, such as 8×8.

[0135] In some other exemplary implementations, for coding blocks with width (W) or height (H) greater than 64, the luma coding blocks and chroma coding blocks may be implicitly split into blocks that are multiples of min(W, 64)×min(H, 64) transform units and min(W, 32)×min(H, 32) transform units, respectively.

[0136] Fig.15 Another exemplary alternative for dividing a coding block or prediction block into transform blocks is further shown. Fig.15 As shown, instead of using recursive transform partitioning, a predetermined set of partition types may be applied to a coding block according to the transform type of the coding block. Fig.15 In the specific example shown, one of six exemplary partitioning types can be applied to split the coding block into various numbers of transform blocks. This scheme can be applied to either the coding block or the prediction block.

[0137] In more detail, Fig.15 As shown, Fig.15 The partitioning scheme of provides up to 6 partitioning types for any given transform type. In this scheme, a transform type can be assigned to each coding block or prediction block based on, for example, rate-distortion cost. In one example, the partitioning type assigned to a coding block or prediction block can be determined based on the transform partitioning type of the coding block or prediction block. A specific partitioning type can correspond to a transform block partition size and mode (or partitioning type), such as Fig.15 The four partition types shown are shown. The correspondence between various transform types and various partition types can be predefined. An exemplary correspondence is shown below, where the capital letter label indicates the transform type that can be assigned to the coding block or prediction block based on the rate-distortion cost:

[0138] PARTITION_NONE: Allocate a transform size equal to the block size.

[0139] PARTITION_SPLIT: Allocates a transform size that is 1 / 2 the width of the block size and 1 / 2 the height of the block size.

[0140] PARTITION_HORZ: Allocates a transform size that has the same width as the block size and is 1 / 2 the height of the block size.

[0141] PARTITION_VERT: Allocates a transform size that is 1 / 2 the width of the block size and has the same height as the block size.

[0142] PARTITION_HORZ4: Allocates a transform size that has the same width as the block size and is 1 / 2 the height of the block size.

[0143] PARTITION_VERT4: Allocates a transform size that is 1 / 4 the width of the block size and has the same height as the block size.

[0144] In the above example, for the divided transform blocks, such as Fig.15 The partition types shown all include a uniform transform size. This is merely an example and not a limitation. In some other exemplary implementations, in a specific partition type (or mode), a mixed transform block size may be used for the transform blocks of the partition.

[0145] Returning to intra prediction, in some exemplary implementations, the prediction of samples in a coding block or prediction block may be based on one reference row in a set of reference rows. In other words, instead of always using the nearest neighbor row (e.g., the neighbor row just above or the neighbor row just to the left of the prediction block, as shown in FIG. 1 above), multiple reference rows may be provided as selection options for intra prediction. Such intra prediction implementations may be referred to as multiple reference row selection (MRLS). In these implementations, the encoder determines and signals which reference row of multiple reference rows is used to generate intra predictions. On the decoder side, after parsing the reference row index, the reconstructed reference sample may be identified by looking up the specified reference row according to an intra prediction mode (e.g., directional intra prediction mode, non-directional intra prediction mode, and other intra prediction modes), thereby generating an intra prediction for the current intra prediction block. In some implementations, the reference row index may be signaled at the coding block level, and only one reference row among multiple reference rows may be selected for intra prediction of a coding block. In some examples, more than one reference row may be selected together for intra prediction. For example, more than one reference row may be combined (with or without weights), averaged, interpolated, or processed in any other manner to generate a prediction.In some exemplary implementations, MRLS may only be applicable to luma components, and not to chroma components.

[0146] exist Fig.16 An example of a 4-reference-row MRLS is depicted in FIG. Fig.16 As shown in the example of , the intra-frame coding block 1602 can be predicted based on one of the four horizontal reference lines 1604, 1606, 1608 and 1610 and one of the four vertical reference lines 1612, 1614, 1616 and 1618. Among these reference lines, 1610 and 1618 are directly adjacent reference lines. The reference lines can be indexed according to their distance from the coding block. For example, reference lines 1610 and 1618 can be called zero reference lines, and other reference lines can be called non-zero reference lines. Specifically, reference lines 1608 and 1616 can be called first reference lines; reference lines 1606 and 1614 can be called second reference lines; and reference lines 1604 and 1612 can be called third reference lines.

[0147] There may be some issues / problems associated with implementing a multiple reference line selection (MRLS) scheme. In some implementations without multiple reference line selection, only the nearest (or neighboring) top (or above) and / or left reference lines are relevant, and only samples from the nearest (or neighboring) top (or above) and / or left reference lines need to be buffered / stored for intra prediction of the current block. When MRLS is applied to intra-coded blocks, 4 top (or above) reference lines and 4 left reference lines can be used for intra prediction. Therefore, the buffer for storing adjacent reference samples needs to be increased by 3 times. In addition, for super blocks, the length of the buffer may be as long as the length of the reference line located at the boundary of the super block, and in some cases, may be equal to the picture width in the hardware decoder, so the 3-fold increase in the buffer size is a large burden for the hardware decoder.

[0148] The present disclosure describes various embodiments for improving low memory design and / or signaling of multiple reference row selection schemes for intra prediction in video encoding and / or decoding, thereby addressing at least one of the problems / problems discussed above.

[0149] In various embodiments, reference Fig.17 , a method 1700 for multi-reference line intra prediction in video decoding. The method 1700 may include some or all of the following steps: step 1710, receiving an encoded video stream of a current block by a device including a memory storing instructions and a processor communicating with the memory; step 1720, extracting a parameter from the encoded video stream by the device, the parameter indicating a non-adjacent reference line for intra prediction in the current block; step 1730, dividing the current block by the device to obtain a plurality of sub-blocks; and / or step 1740, in response to a sub-block of the plurality of sub-blocks being located at a boundary of the current block, using a top adjacent reference line as a value of all top non-adjacent reference lines of the sub-block by the device.

[0150] In some implementations, the current block may be referred to as a block, and the multiple sub-blocks obtained by dividing the current block may be referred to as multiple coding blocks. In some other implementations, step 1720 may include: extracting a parameter from the encoded video bitstream by a device, the parameter indicating a reference row for intra-frame prediction in the current block.

[0151] In various embodiments of the present disclosure, the size of a block (such as but not limited to a coding block, a prediction block, or a transform block) may refer to the width or height of the block. The width or height of the block may be an integer in pixels.

[0152] In various embodiments of the present disclosure, the size of a block (such as but not limited to a coding block, a prediction block, or a transform block) may refer to the area size of the block. The area size of the block may be an integer in pixels calculated by multiplying the width of the block by the height of the block.

[0153] In some different embodiments of the present disclosure, the size of a block (such as but not limited to a coding block, a prediction block, or a transform block) may refer to the minimum value of the width or height of the block, the minimum value of the height or width of the block, or the aspect ratio of the block. The width ratio of the block may be calculated by dividing the width of the block by the height, or by dividing the height of the block by the width.

[0154] In the present disclosure, a reference row index indicates a reference row among a plurality of reference rows. In various embodiments, if the reference row index of a block is 0, it may indicate an adjacent reference row of the block, and the adjacent reference row is also the nearest reference row of the block. Fig.16 For a block (1602) in FIG. 1 , the top reference row (1610) is the top adjacent reference row of the block (1602) and is also the top nearest reference row of the block; the left reference row (1618) is the left adjacent reference row of the block (1602) and is also the left nearest reference row of the block. If the reference row index of a block is greater than 0, it indicates a non-adjacent reference row of the block, and a non-adjacent reference row is also a non-nearest reference row of the block. For example, the reference row index of the block is greater than 0. Fig.16 In the block (1602), if the reference row index is 1, it may indicate the top reference row (1608) and / or the left reference row (1616); if the reference row index is 2, it may indicate the top reference row (1606) and / or the left reference row (1614); and / or if the reference row index is 3, it may indicate the top reference row (1604) and / or the left reference row (1612).

[0155] Referring to step 1710, the device may be Figure 5 An electronic device (530) or Figure 8 In some implementations, the device may be a video decoder (810) in Figure 6 In other implementations, the device may be Figure 5 a portion of an electronic device (530) in Figure 8 a portion of a video decoder (810) in, or Figure 6 The encoded video code stream may be a part of the decoder (633) in the encoder (620) in FIG. Figure 8 A coded video sequence in Figure 6 or Figure 7 The intermediate coded data in .

[0156] In some implementations, a block may be referred to as a super block. A super block may refer to a largest coding block, such as, but not limited to, a coding tree block (CTB) and / or a largest coding unit (LCU). In some other implementations, a super block may refer to a predetermined block size, such as, but not limited to, 32×32, 64×64, 128×128, and / or 256×256.

[0157] Referring to step 1720, the device may extract parameters from the encoded video bitstream, the parameters being usable for MRLS and indicating a reference row in the block for intra prediction. In some implementations, the reference row indicated by the parameters may be one of N reference rows, where N is an integer greater than 1. In some other implementations, the reference row indicated by the parameters may be one of N non-adjacent reference rows.

[0158] In some implementations, the method 1700 may further include: using, by the device, a left adjacent reference row of the block. In some other implementations, the left adjacent reference row may be one of N left reference rows of the block.

[0159] Referring to step 1730, the device may partition the block to obtain a plurality of coding blocks. In some implementations, the device may partition the block to obtain a coding block partition tree. The coding block partition tree may include a plurality of coding blocks.

[0160] Referring to step 1740, for a coding block from a plurality of coding blocks, when the coding block is located at a block boundary, the device may use the top adjacent reference row as a value of all top non-adjacent reference rows of the coding block. In some implementations, the boundary (or boundaries) of a block (e.g., a super block) may refer to only the top boundary of the block, or only the left boundary of the block, or both the left boundary and the top boundary of the block.

[0161] In various embodiments, in order to reduce the memory size for storing samples from multiple reference rows, when the current intra-frame coding block is located at the boundary of a super-block, samples in the N left reference rows (columns) can be used for intra-frame prediction, and samples in the nearest (or adjacent) above (or top) reference row can be used for intra-frame prediction.

[0162] N is a positive integer greater than 1, such as 2, 3, or 4. For example, when N=3, for a coding block located at the boundary of a super block, three left reference lines and an adjacent top reference line may be used for intra prediction. In some implementations, the three left reference lines may be the three nearest left reference lines of the block, such as Fig.16 Reference lines (1618, 1616 and 1614) in.

[0163] In some implementations, the reference row index may be signaled and encoded into the bitstream regardless of whether the current intra-coded block is located at a super-block boundary.

[0164] Referring again to step 1740, the step of using the top adjacent reference row as the value of all top non-adjacent reference rows of the coding block may include copying samples from the top adjacent reference row to all other top non-adjacent reference rows, thereby significantly reducing the memory size for storing samples from all other top non-adjacent reference rows.

[0165] In some implementations, if the current intra-frame coded block is located at a block (e.g., super-block) boundary and the reference row index indicates that a non-zero (or non-adjacent) reference row is used for intra-frame prediction of the current coded block, samples in the top (or above) non-zero reference row are derived by copying from the nearest top (or above) reference row.

[0166] As an example, in Fig.18 In FIG. 1 , a coding block (also referred to as a coded block or code block) (1802) is located at the top boundary (1830) and the left boundary (1840) of a block (eg, a superblock). Fig.18 As shown, the top boundary (1830) and the left boundary (1840) of the super block may be indicated by bold lines. The top left sample (A-4, A-3, A-2 and / or A-1) and the top sample (A+0, ..., A+N) in the nearest upper reference row (1810) of the coding block (1802) are copied to the upper non-zero reference row (1808, 1806 and / or 1804). In some implementations, multiple left reference rows (1818, 1816, 1814 and / or 1812) may be allowed to store their own samples respectively.

[0167] In the various implementations described above, taking the top adjacent reference row as an example, a similar scheme may be applicable to the left adjacent reference row, wherein, in order to improve the low storage design, the samples in the left non-zero reference row may be derived from the nearest (or adjacent) left reference row, for example, by copying the left adjacent reference row.

[0168] In various embodiments, optionally, method 1700 may further include: partitioning the coding block by a device to obtain a plurality of transform blocks. In some implementations, the device may partition the coding block to obtain a transform block partition tree including a plurality of transform blocks. In some implementations, optionally, method 1700 may include: in response to a first transform block among the plurality of transform blocks being located at a top boundary of the coding block, using a top adjacent reference row as a value of all top non-adjacent reference rows of the first transform block by a device; and / or in response to a second transform block among the plurality of transform blocks not being located at a top boundary of the coding block, using a reference row indicated by a parameter of the second transform block for the second transform block by a device. In some implementations, the reference row indicated by the parameter may be one of the N top reference rows of the second transform block.

[0169] In some implementations, the current coding block may be split into more than one transform block (TB) and / or more than one transform unit (TU). When the current coding block is located at the boundary of a super block and the reference row index indicates that a non-zero reference row is used for the current coding block, only the samples in the nearest upper reference row can be used for intra-frame prediction of the TU located at the boundary of the super block; when the current coding block is located at the boundary of the super block and the reference row index indicates that a non-zero reference row is used for the current coding block, the samples in the upper non-zero reference row can still be used for the TU not located at the boundary of the super block.

[0170] As an example, see Fig.19 , the thick solid line (1930) indicates the top boundary of the super block. Multiple transform units (TU1, TU2, TU3 and / or TU4) (1904, 1906, 1908 and 1910) are located in one coding block. TU1 (1904) and TU2 (1906) are located at the boundary of the super block (indicated by the horizontal thick solid line (1930)), while TU3 (1908) and TU4 (1910) are not located at the top boundary of the super block. Therefore, only samples in the nearest reference row above are available for TU1 and TU2, while samples in non-zero reference rows are still available for TU3 and TU4. Similarly, in some other implementations, when a transform block within a coding block is located at the left boundary of a super block, only samples in the nearest reference row on the left are available for the transform block.

[0171] The embodiments of the present disclosure may be used individually or in any order. In addition, each method (or embodiment), encoder and decoder may be implemented by a processing circuit (e.g., one or more processors or one or more integrated circuits). In one example, one or more processors execute a program stored in a non-transitory computer-readable medium. The embodiments of the present disclosure may be applied separately to more than one color component, or may be applied together to more than one color component.

[0172] The above techniques may be implemented as computer software using computer-readable instructions and physically stored in one or more computer-readable media. Fig. 20 A computer system (2600) suitable for implementing certain embodiments of the disclosed subject matter is shown.

[0173] Computer software may be encoded using any suitable machine code or computer language that may be subjected to assembly, compilation, linking or similar mechanisms to create code comprising instructions that may be executed directly by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., or through interpretation, microcode execution, etc.

[0174] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, Internet of Things devices, and the like.

[0175] Fig. 20 The components of the computer system (2600) shown are exemplary in nature and are not intended to suggest any limitation on the scope of use or functionality of computer software implementing embodiments of the present disclosure. Neither should the configuration of components be interpreted as having any dependency or requirement relating to any one or combination of components shown in the exemplary embodiment of the computer system (2600).

[0176] The computer system (2600) may include certain human-machine interface input devices. Such human-machine interface input devices may be responsive to input from one or more human users through, for example, tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), olfactory input (not depicted). Human-machine interface devices may also be used to capture certain media that are not necessarily directly related to human conscious input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, captured images obtained from a still image camera), and videos (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

[0177] The human-machine interface input device may include one or more of the following (only one of each is shown): keyboard (2601), mouse (2602), touchpad (2603), touch screen (2610), data gloves (not shown), joystick (2605), microphone (2606), scanner (2607), camera (2608).

[0178] The computer system (2600) may also include certain human-machine interface output devices. Such human-machine interface output devices may stimulate one or more human user senses through, for example, tactile output, sound, light, and smell / taste. Such human-machine interface output devices may include tactile output devices (e.g., tactile feedback of a touch screen (2610), a data glove (not shown), or a joystick (2605), but may also be a tactile feedback device that is not an input device), audio output devices (e.g., speakers (2609), headphones (not depicted)), visual output devices (e.g., screens (2610) including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capabilities, each with or without tactile feedback capabilities, some of which are capable of outputting two-dimensional visual outputs or outputs in more than three dimensions through devices such as stereoscopic image output, virtual reality glasses (not depicted), holographic displays and smoke boxes (not depicted), and printers (not depicted).

[0179] The computer system (2600) may also include human-accessible storage devices and their associated media, such as optical media including CD / DVD ROM / RW (2620) with CD / DVD etc. media (2621), thumb drives (2622), removable hard drives or solid-state drives (2623), traditional magnetic media such as tapes and floppy disks (not depicted), dedicated ROM / ASIC / PLD based devices such as security dongles (not depicted), and the like.

[0180] Those skilled in the art should also understand that the term "computer-readable media" used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

[0181] The computer system (2600) may also include an interface (2654) to one or more communication networks (2655). The network may be, for example, a wireless network, a wired network, an optical network. The network may further be a local network, a wide area network, a metropolitan area network, a vehicle and industrial network, a real-time network, a delay-tolerant network, etc. Examples of networks include local area networks such as Ethernet, wireless LANs, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., television wired or wireless wide area digital networks including cable television, satellite television, and terrestrial broadcast television, vehicle and industrial networks including CAN buses, etc. Some networks typically require an external network interface adapter attached to some general data port or peripheral bus (2649) (e.g., a USB port of the computer system (2600)); as described below, other network interfaces are typically integrated into the kernel of the computer system (2600) by attaching to the system bus (e.g., connected to an Ethernet interface in a PC computer system or connected to a cellular network interface in a smartphone computer system). The computer system (2600) can use any of these networks to communicate with other entities. Such communications may be one-way receive only (e.g., broadcast television), one-way send only (e.g., CANBus connected to certain CANBus devices), or bidirectional, for example, using a LAN or WAN digital network to connect to other computer systems. As described above, certain protocols and protocol stacks may be used on each of those networks and network interfaces.

[0182] The above-mentioned human interface device, human-accessible storage device, and network interface may be attached to the kernel (2640) of the computer system (2600).

[0183] The kernel (2640) may include one or more central processing units (CPUs) (2641), graphics processing units (GPUs) (2642), dedicated programmable processing units in the form of field programmable gate arrays (FPGAs) (2643), hardware accelerators (2644) for certain tasks, graphics adapters (2650), and the like. These devices, as well as read-only memory (ROM) (2645), random access memory (2646), internal mass storage (2647) such as internal non-user accessible hard drives, SSDs, and the like, may be connected via a system bus (2648). In some computer systems, the system bus (2648) may be accessed in the form of one or more physical plugs to enable expansion by additional CPUs, GPUs, and the like. Peripheral devices may be attached directly to the kernel's system bus (2648) or to the kernel's system bus (2648) via a peripheral bus (2649). In one example, a screen (2610) may be connected to a graphics adapter (2650). The architecture of the peripheral bus includes PCI, USB, and the like.

[0184] The CPU (2641), GPU (2642), FPGA (2643) and accelerator (2644) can execute certain instructions, which can be combined to form the above-mentioned computer code. The computer code can be stored in ROM (2645) or RAM (2646). Transition data can also be stored in RAM (2646), while permanent data can be stored, for example, in internal mass storage (2647). Fast storage and retrieval to any storage device can be performed by using a cache, which can be closely associated with the following: one or more CPUs (2641), GPUs (2642), mass storage (2647), ROM (2645), RAM (2646), etc.

[0185] The computer readable medium may have thereon computer codes for performing various computer-implemented operations. The medium and computer codes may be those specially designed and constructed for the purposes of the present disclosure, or the medium and computer codes may be of a type well known and available to those skilled in the art of computer software.

[0186] As a non-limiting example, a computer system having an architecture (2600), particularly a kernel (2640), may provide functionality due to one or more processors (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software contained in one or more tangible computer-readable media. Such computer-readable media may be media associated with user-accessible mass storage as described above, as well as memories of certain non-temporary kernels (2640), such as kernel internal mass storage (2647) or ROM (2645). Software implementing various embodiments of the present disclosure may be stored in such devices and executed by the kernel (2640). Depending on specific needs, the computer-readable medium may include one or more storage devices or chips. The software may enable the kernel (2640), particularly the processors therein (including CPUs, GPUs, FPGAs, etc.), to perform specific processes or specific parts of specific processes described herein, including defining data structures stored in RAM (2646) and modifying such data structures according to processes defined by the software. In addition or in the alternative, a computer system may provide functionality due to logic hardwired or otherwise embodied in circuitry (e.g., accelerator (2644)) that may replace software or operate in conjunction with software to perform specific processes or specific portions of specific processes described herein. Where appropriate, references to portions of software may include logic and vice versa. Where appropriate, references to portions of computer-readable media may include circuitry (e.g., integrated circuits (ICs)) storing software for execution, circuitry embodying logic for execution, or both. The present disclosure includes any suitable combination of hardware and software.

[0187] Although a particular invention has been described with reference to illustrative embodiments, this description is not meant to be limiting. Based on this description, various modifications to the illustrative embodiments and additional embodiments of the present invention will be apparent to those of ordinary skill in the art. Those skilled in the art will readily recognize that these and various other modifications may be made to the exemplary embodiments illustrated and described herein without departing from the spirit and scope of the present invention. Therefore, it is contemplated that the appended claims will cover any such modifications and alternative embodiments. Certain proportions illustrated may be exaggerated, while other proportions may be minimized. Therefore, the disclosure and the accompanying drawings should be considered illustrative, not limiting.

Claims

1. A method for multi-reference line intra prediction in video decoding, characterized in that: The method comprises: Receiving an encoded video code stream of a current block by a device, the device comprising a memory storing instructions and a processor communicating with the memory; Determining to apply multiple reference row selection to the current block; Extracting, by the device, a parameter from the encoded video bitstream, the parameter indicating a non-adjacent reference row for intra-frame prediction in the current block; Dividing the current block by the device to obtain a plurality of sub-blocks; and In response to a sub-block among the multiple sub-blocks being located at the boundary of the current block and the multiple reference row selection being applied to the current block, the device replaces the upper left value of the non-adjacent reference row corresponding to the non-adjacent reference row index of the sub-block with the upper left value corresponding to the adjacent reference row.

2. The method according to claim 1, characterized in that The method further comprises: The left adjacent reference line of the sub-block is used by the device.

3. The method according to claim 1, characterized in that The current block includes at least one of the following: a super block, a maximum coding block, a coding tree block CTB, a maximum coding unit LCU, and a predetermined block with a predetermined size.

4. The method according to claim 1, characterized in that The boundary of the current block includes one of the following: a top boundary of the current block, a left boundary of the current block, or a left boundary and a top boundary of the current block.

5. The method according to claim 1, characterized in that The method further comprises: The samples from the top adjacent reference row are copied to all other top non-adjacent reference rows.

6. The method according to claim 5, characterized in that The method further comprises: The sub-block is divided by the device to obtain a plurality of transform blocks.

7. The method according to claim 6, characterized in that The method further comprises: In response to a first transform block of the plurality of transform blocks being located at a top boundary of the sub-block, using, by the device, the top adjacent reference row as a value for all top non-adjacent reference rows of the first transform block; and In response to a second transform block of the plurality of transform blocks not being located at a top boundary of the subblock, using, by the apparatus, a reference row indicated by a parameter of the second transform block for the second transform block.

8. A device for multi-reference line intra prediction in video decoding, characterized in that: The device comprises: a memory for storing instructions; and A processor in communication with the memory, wherein when the processor executes the instructions, the processor is configured to cause the apparatus to perform the method according to any one of claims 1 to 7.

9. A non-transitory computer-readable storage medium storing instructions, characterized in that: When the instructions are executed by a processor, the instructions are configured to cause the processor to perform the method according to any one of claims 1 to 7.

10. A method for storing a video code stream, characterized in that: The video code stream is decoded based on the method according to any one of claims 1 to 7.

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