Harmonized design for intra-bidirectional prediction and multiple reference line selection.

Abstract

The present invention provides a method, apparatus, and computer-readable storage medium for intra-bidirectional prediction and multiple reference line intra-prediction. [Solution] A method by a device including a memory for storing instructions and a processor for communicating with the memory includes the step of determining whether a unidirectional intra-prediction or an intra-bidirectional prediction is applied to a block based on the block's mode information. The block's mode information includes at least one of the block's reference line index, the block's intra-prediction mode, and the block's size. The method by the device also includes the step of performing a unidirectional intra-prediction on the block, depending on the determination that a unidirectional intra-prediction is applied to the block, and the step of performing an intra-bidirectional prediction on the block, depending on the determination that an intra-bidirectional prediction is applied to the block.

Description

Technical Field

[0001] [Related Applications] This application claims the benefit of priority based on U.S. Provisional Application No. 63 / 215,888, filed Jun. 28, 2021, and U.S. Non-Provisional Application No. 17 / 570,603, filed Jan. 7, 2022, and incorporates by reference the entire contents of both applications.

[0002] [Technical Field] The present disclosure relates to video encoding and / or decoding techniques, particularly improved designs and signaling for intra bidirectional prediction and multiple reference line selection schemes.

Background Art

[0003] The background description provided herein is for the purpose of generally presenting the context of the present disclosure. Work of the inventors named in the present application that is within the scope of what is described in this background section, and aspects of this description that may not be prior art as of the filing of the present application in other respects, are not admitted as prior art to the present disclosure, either expressly or implicitly.

[0004] Video encoding and decoding can be performed using interpicture prediction with motion compensation. Uncompressed digital video can contain a series of pictures, each picture having spatial dimensions of, for example, 1920 x 1080 luminance samples and associated full or subsampled chrominance samples. The series of pictures can have a fixed or variable picture rate (also called frame rate), for example, 60 pictures per second or 60 frames per second. Uncompressed video has specific bitrate requirements for streaming or data processing. For example, video with a pixel resolution of 1920 x 1080, a frame rate of 60 frames / second, and 4:2:0 chroma subsampling of 8 bits per color channel per pixel requires a bandwidth of nearly 1.5 Gbit / s. One hour of such video requires more than 600 GB of storage space.

[0005] One purpose of video encoding and decoding may be to reduce redundancy in uncompressed input video signals through compression. Compression can help reduce the bandwidth and / or storage space requirements mentioned above by more than two orders of magnitude, in some cases. Both lossless and lossy compression, as well as combinations thereof, can be used. Lossless compression refers to a technique in which, through the decoding process, an exact copy of the original signal can be reconstructed from the compressed original signal. Lossy compression refers to an encoding / decoding process in which the original video information is not sufficiently preserved during encoding and cannot be sufficiently recovered during decoding. When using lossy compression, the reconstructed signal may not be identical to the original signal, but the distortion between the original and reconstructed signals is small enough to render the reconstructed signal usefully for its intended use, despite some information loss. For video, lossy compression is widely used in many applications. The amount of acceptable distortion depends on the application. For example, users of certain consumer video streaming applications may tolerate higher distortion than users of film or television broadcast applications. The compression ratio achievable by a particular encoding algorithm can be selected or adjusted to reflect various distortion tolerances; generally, higher tolerable distortion allows for encoding algorithms that result in higher loss and higher compression ratios.

[0006] Video encoders and decoders can utilize techniques from several broad categories and steps, including, for example, motion compensation, Fourier transform, quantization, and entropy coding.

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

[0008] Traditional intra-encoding, such as that known from the MPEG-2 generation of encoding techniques, does not use intra-prediction. However, some newer video compression techniques include, for example, techniques that attempt to encode / decode blocks based on surrounding sample data and / or metadata that precede the block of data being intra-encoded or decoded in decoding order, acquired during the encoding and / or decoding of spatially adjacent ones. Such techniques are referred to below as “intra-prediction” techniques. Note that in at least some cases, intra-prediction uses only reference data from the current picture being reconstructed and not reference data from other reference pictures.

[0009] Various forms of intra-prediction can exist. If two or more such techniques are available in a given video coding technique, the techniques used can be called intra-prediction modes. One or more intra-prediction modes may be provided in a particular codec. In certain cases, a mode may have submodes and / or be associated with various parameters, and the mode / submode information and intra-coding parameters of a block of video may be coded individually or together included in a mode codeword. Which codeword is used for a given combination of mode, submode, and / or parameters may affect the coding efficiency gain through intra-prediction, and the entropy coding technique used to convert the codeword to a bitstream may similarly affect it.

[0010] Certain modes of intra-prediction were introduced in H.264, refined in H.265, and further sophisticated in newer coding techniques such as the joint exploration model (JEM), versatile video coding (VVC), and benchmark set (BMS). Generally, for intra-prediction, predictor blocks can be formed using available neighboring sample values. For example, available values ​​of a particular set of neighboring samples along a particular direction and / or line may be copied into the predictor block. References to the direction used can be encoded in the bitstream or predicted themselves.

[0011] Referring to Figure 1A, in the lower right, a subset of nine predictor directions is shown, specified by the 33 possible intra-predictor directions in H.265 (corresponding to 33 of the 35 intra-modes specified in H.265, or angular modes). The point where the arrows converge (101) represents the predicted sample. The arrows indicate the direction in which adjacent samples are used to predict the sample at 101. For example, arrow (102) indicates that sample (101) is predicted from the adjacent sample(s) to the upper right at an angle of 45 degrees from the horizontal. Similarly, arrow (103) indicates that sample (101) is predicted from the adjacent sample(s) to the lower left of sample (101) at an angle of 22.5 degrees from the horizontal.

[0012] Continuing to refer to Figure 1A, a 4x4 sample square block (104) is depicted in the upper left (indicated by a thick dashed line). The square block (104) contains 16 samples, each labeled with "S" and its position in the Y dimension (e.g., row index) and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample (from the top) in the Y dimension and the first sample (from the left) in the X dimension. Similarly, sample S44 is the fourth sample in block (104) in both the Y and X dimensions. Since the block is 4x4 sample size, S44 is in the lower right. Furthermore, an exemplary reference sample following a similar numbering scheme is shown. The reference sample is labeled with R and its Y position (e.g., row index) and X position (column index) relative to block (104). In both H.264 and H.265, adjacent predicted samples in the neighborhood of the block being reconstructed are used.

[0013] Intra-picture prediction in block 104 may begin by copying a reference sample value from an adjacent sample according to the signaled prediction direction. For example, suppose the encoded video bitstream includes signaling for this block 104, indicating the prediction direction by arrow (102). That is, the sample is predicted from the upper right prediction sample (one or more) at a 45-degree angle from the horizontal. In such a case, samples S41, S32, S23, and S14 are predicted from the same reference sample R05. Then, sample S44 is predicted from reference sample R08.

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

[0015] As video coding technology continues to advance, the number of possible directions has increased. In H.264 (2003), for example, nine different directions are available for intra-prediction. This increased to 33 in H.265 (2013), and as of the present disclosure, JEM / VVC / BMS can support up to 65 directions. Experiments have been conducted to help identify the most appropriate intra-prediction direction, and certain techniques may be used in entropy coding to encode these most appropriate directions with a small number of bits, while accepting a certain bit penalty for the direction. Furthermore, in some cases, the direction itself can be predicted from the adjacent direction used in the intra-prediction of the decoded adjacent block.

[0016] Figure 1B shows a schematic diagram (180) illustrating the 65 intra-prediction directions by JEM to illustrate the increasing number of prediction directions in various coding techniques developed over time.

[0017] The method of mapping intra-prediction direction bits to prediction directions in an encoded video bitstream may vary from video coding technique to video coding technique, ranging from simple direct mapping of prediction directions to intra-prediction modes to complex adaptive schemes involving codewords, most probable modes, and similar techniques. However, in all cases, there may be a particular direction of intra-prediction in video content that is statistically less likely than a given other direction. Since the goal of video compression is to reduce redundancy, in a well-designed video coding technique, these less likely directions may be represented by more bits than the more likely directions.

[0018] Interpicture prediction or interpretation may be based on motion compensation. In motion compensation, sample data from a previously reconstructed picture or a portion thereof (reference picture) may be used to predict a newly reconstructed picture or a portion thereof (e.g., a block) after being spatially shifted in the direction indicated by a motion vector (MV). In some cases, the reference picture may be the same as the picture currently being reconstructed. The MV may have two or three dimensions, X and Y, where the third dimension indicates the reference picture used (similar to the time dimension).

[0019] In some video compression techniques, the current motion vector (MV) applicable to a particular region of sample data can be predicted from other MVs, for example, from other MVs related to other regions of sample data that are spatially adjacent to the region being reconstructed and precede the current MV in decoding order. By doing so, the overall amount of data required to encode the MV can be substantially reduced by relying on reducing redundancy in the related MVs, thereby increasing compression efficiency. MV prediction can work effectively because, for example, when encoding an input video signal derived from a camera (known as natural video), there is statistical certainty that regions in the video sequence larger than the region to which a single MV is applicable are moving in a similar direction and, therefore, can be predicted using similar motion vectors derived from adjacent regions' MVs. As a result, the actual MV for a given region will be similar to or identical to the MV predicted from the surrounding MVs. Such an MV may then be represented with fewer bits than what would be used if the MV were encoded directly after entropy coding rather than being predicted from adjacent MVs. In some cases, MV prediction can be an example of lossless compression of a signal (i.e., MV) derived from the original signal (i.e., sample stream). In other cases, the MV prediction itself may be irreversible, for example, due to rounding errors when calculating the predictor from some surrounding MVs.

[0020] H.265 / HEVC (ITU-T Rec. H.265, "High Efficiency Video Coding", December 2016) describes various MV prediction mechanisms. Of the many MV prediction mechanisms specified by H.265, this specification will describe a technique hereafter referred to as "spatial merge".

[0021] Specifically, referring to Figure 2, the current block (201) contains samples found by the encoder during the motion search process that are predictable from the previous block of the same size, which has been spatially shifted. Instead of directly encoding its MV, the MV can be derived from metadata associated with one or more reference pictures, for example, from the most recent reference picture (in decoding order), using the MV associated with one of the five surrounding samples labeled A0, A1, and B0, B1, B2 (202-206, respectively). In H.265, the MV prediction can use predictors from the same reference pictures used by the adjacent blocks. [Overview of the project]

[0022] This disclosure describes various embodiments of methods, apparatus, and computer-readable storage media for video encoding and / or decoding.

[0023] In one aspect, embodiments of the present disclosure provide methods for intra-bidirectional prediction and multiple-reference-line intra-prediction in video decoding. The method includes a step of a device receiving an encoded video bitstream of a block. The device includes a memory for storing instructions and a processor for communicating with the memory. The method also includes a step of the device determining whether unidirectional intra-prediction or intra-bidirectional prediction is applied to a block based on the block's mode information, wherein the block's mode information includes at least one of the block's reference line index, the block's intra-prediction mode, and the block's size; a step of the device performing unidirectional intra-prediction on the block if it has been determined that unidirectional intra-prediction is applied to the block; and a step of the device performing intra-bidirectional prediction on the block if it has been determined that intra-bidirectional prediction is applied to the block.

[0024] According to another aspect, one embodiment of the present disclosure provides an apparatus for video encoding and / or decoding. The apparatus includes a memory for storing instructions and a processor communicating with the memory. When the processor executes the instructions, the processor is configured to cause the apparatus to execute the above method for video decoding and / or encoding.

[0025] In another aspect, one embodiment of the present disclosure provides a non-transitory computer-readable medium storing instructions that, when executed by a computer for video decoding and / or encoding, cause the computer to execute the above method for video decoding and / or encoding.

[0026] The above and other aspects and their implementations are described in more detail in the drawings, the detailed description, and the claims.

Brief Description of the Drawings

[0027] Further features, properties, and various advantages of the disclosed subject matter will become more apparent from the following detailed description and the accompanying drawings. [Figure 1A] A schematic diagram of an exemplary subset of intra prediction direction modes is shown. [Figure 1B] An explanatory diagram of an exemplary intra prediction direction is shown. [Figure 2] A schematic diagram of a current block and its surrounding spatial merge candidates for motion vector prediction in one example is shown. [Figure 3] A schematic diagram of a simplified block diagram of a communication system according to an exemplary embodiment is shown. [Figure 4] A schematic diagram of a simplified block diagram of a communication system (400) according to an exemplary embodiment is shown. [Figure 5] A schematic diagram of a simplified block diagram of a video decoder according to an exemplary embodiment is shown. [Figure 6] A schematic diagram of a simplified block diagram of a video encoder according to an exemplary embodiment is shown. [Figure 7]A block diagram of a video encoder according to an exemplary embodiment is shown. [Figure 8] A block diagram of a video decoder according to an exemplary embodiment is shown. [Figure 9] This disclosure illustrates an exemplary embodiment of a directional intra-prediction mode. [Figure 10] This disclosure illustrates an exemplary embodiment of a non-directional intra-predictive mode. [Figure 11] This disclosure illustrates a recursive intra-prediction mode according to an exemplary embodiment. [Figure 12] This disclosure illustrates various reference line-based intra-prediction methods according to exemplary embodiments. [Figure 13A] This disclosure illustrates an exemplary embodiment of intra-bidirectional prediction. [Figure 13B] Another intra-bidirectional prediction is shown by an exemplary embodiment of the present disclosure. [Figure 14] A flowchart of the method according to an exemplary embodiment of this disclosure is shown. [Figure 15] This disclosure illustrates an exemplary embodiment of intra-bidirectional prediction based on multiple reference lines. [Figure 16] An exemplary embodiment of this disclosure demonstrates another intra-bidirectional prediction based on multiple reference lines. [Figure 17] A schematic diagram of a computer system according to an exemplary embodiment of the present disclosure is shown. [Modes for carrying out the invention]

[0028] The present invention will be described in detail below with reference to the accompanying drawings, which constitute a part of the present invention and illustrate specific examples of embodiments. However, it should be noted that the present invention may be embodied in various different forms. Therefore, it is intended that the subject matter covered or claimed subject matter is not limited to any of the embodiments shown below. It should also be noted that the present invention may be embodied as a method, device, component, or system. Therefore, embodiments of the present invention may take the form of, for example, hardware, software, firmware, or any combination thereof.

[0029] Throughout the specification and claims, terms may have nuances implied or suggested in context beyond their explicitly stated meaning. As used herein, the phrases “in one embodiment” or “in some embodiments” do not necessarily refer to the same embodiment, and the phrases “in another embodiment” or “in other embodiments” do not necessarily refer to different embodiments. Similarly, the phrases “in one implementation” or “in some implementations” do not necessarily refer to the same implementation, and the phrases “in another implementation” or “in other implementations” do not necessarily refer to different implementations. For example, the subject matter of the claims is intended to include combinations of embodiments / implementations that are entirely or partially exemplary.

[0030] In general, terms may be understood at least partially from their usage in context. For example, terms such as “and,” “or,” or “and / or” as used herein may have various meanings that may depend at least partially on the context in which such terms are used. Typically, when “or” is used to relate a list such as A, B, or C, it is intended to mean A, B, and C, used here in an inclusive sense, and A, B, or C, used here in an exclusive sense. Furthermore, the terms “one or more” or “at least one” as used herein may be used at least partially on context to describe any feature, structure, or characteristic in a single sense, or to describe a combination of features, structures, or characteristics in multiple senses. Similarly, singular terms (such as “a,” “an,” or “the”) may also be understood, at least partially on context, to convey either a singular or plural usage. Furthermore, the terms “based on” or “determined by” may be understood not necessarily to convey an exclusive set of factors, and instead, depending at least partially on the context, may allow for the presence of further factors that are not necessarily explicitly described.

[0031] Figure 3 shows a simplified block diagram of a communication system (300) according to one embodiment of the present disclosure. The communication system (300) includes a plurality of terminal devices that can communicate with each other, for example, over a network (350). For example, the communication system (300) includes a first pair of terminal devices (310) and (320) interconnected over the network (350). In the example of Figure 3, the first pair of terminal devices (310) and (320) may perform one-way transmission of data. For example, terminal device (310) may encode video data (e.g., a stream of video pictures captured by terminal device (310)) for transmission to the other terminal device (320) over the network (350). The encoded video data may be transmitted in the form of one or more encoded video bitstreams. Terminal device (320) may receive the encoded video data from the network (350), decode the encoded video data to restore the video pictures, and display the video pictures according to the restored video data. One-way data transmission may be implemented in media service applications, etc.

[0032] In another example, the communication system (300) includes a second pair of terminal devices (330) and (340) that perform bidirectional transmission of encoded video data, which may be performed, for example, during a video conferencing application. For bidirectional transmission of data, in one example, each terminal device of terminal devices (330) and (340) may encode video data (e.g., a stream of video pictures captured by the terminal device) for transmission over the network (350) to the other terminal device of terminal devices (330) and (340). Each terminal device of terminal devices (330) and (340) may receive encoded video data transmitted by the other terminal device of terminal devices (330) and (340), decode the encoded video data to restore the video pictures, and display the video pictures on an accessible display device according to the restored video data.

[0033] In the example in Figure 3, terminal devices (310), (320), (330), and (340) may be implemented as servers, personal computers, and smartphones, but the applicability of the underlying principles of this disclosure is not limited to these. Embodiments of this disclosure may be implemented in desktop computers, laptop computers, tablet computers, media players, wearable computers, and / or dedicated video conferencing equipment. Network (350) represents any number or type of network that transmits encoded video data between terminal devices (310), (320), (330), and (340), including, for example, wired and / or wireless communication networks. Communication network (350) may exchange data in circuit-switched, packet-switched, and / or other types of channels. Typical networks include telecommunication networks, local area networks, wide area networks, and / or the Internet. For the purposes of this discussion, the architecture and topology of network (350) may not be important to the operation of this disclosure unless expressly described below.

[0034] Figure 4 shows the arrangement of a video encoder and video decoder in a video streaming environment as an example of an application for the disclosed subject matter. The disclosed subject matter may be equally applicable to other video applications, such as video conferencing, digital television broadcasting, games, virtual reality, and storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0035] The video streaming system may include a video source (401), such as a digital camera, and may also include a video capture subsystem (413) that generates, for example, 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 drawn as a thick line to emphasize its high data volume compared to encoded video data (404) (or encoded video bitstream), may be processed by an electronic device (420) including a video encoder (403) coupled to the video source (401). The video encoder (403) may include hardware, software, or a combination thereof to enable or realize aspects of the subject disclosed below. The encoded video data (404) (or encoded video bitstream (404)), which is drawn as a thin line to highlight its lower data volume compared to the uncompressed video picture stream (402), can be stored in a streaming server (405) for future use, or directly in a downstream video device (not shown). One or more streaming client subsystems, such as client subsystems (406) and (408) in Figure 4, can access the streaming server (405) to retrieve copies (407) and (409) of the encoded video data (404). The client subsystem (406) may include a video decoder (410) within, for example, an electronic device (430). The video decoder (410) decodes the input copy (407) of the encoded video data and generates an output stream (411) of an uncompressed video picture that can be rendered on a display (412) (e.g., a display screen) or other rendering device (not shown). The video decoder 410 may be configured to perform some or all of the various functions described herein.In some streaming systems, encoded video data (404), (407), and (409) (e.g., video bitstream) can be encoded according to specific video encoding / compression standards. Examples of these standards include ITU-T Recommendation H.265. For example, a video encoding standard under development is informally known as the Multipurpose Video Coding (VVC). The disclosed subject matter may be used in the context of VVC and other video encoding standards.

[0036] It should be noted that electronic devices (420) and (430) may include other components (not shown). For example, electronic device (420) may include a video decoder (not shown), and electronic device (430) may also include a video encoder (not shown).

[0037] Figure 5 shows a block diagram of a video decoder (510) according to any embodiment of the present disclosure described below. 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) can be used in place of the video decoder (310) in the example of Figure 4.

[0038] The receiver (531) may receive one or more encoded video sequences to be decoded by the video decoder (510). In the same or different embodiments, one encoded video sequence may be decoded at a time, and the decoding of each encoded video sequence is independent of other encoded video sequences. Each video sequence may be associated with multiple video frames or images. The encoded video sequences may be received from a channel (501), which may be a storage device storing encoded video data or a hardware / software link to a streaming source transmitting encoded video data. The receiver (531) may receive the encoded video data together with other data such as encoded audio data and / or auxiliary data streams, which may be transferred to their respective processing circuits (not shown). The receiver (531) can isolate the encoded video sequences from other data. As a measure against network jitter, a buffer memory (515) may be placed between the receiver (531) and the entropy decoder / parser (520) (hereinafter referred to as the "parser"). In certain applications, the buffer memory (515) may be implemented as part of the video decoder (510). In other applications, it may exist separately outside the video decoder (510) (not shown). In yet other applications, for example to counter network jitter, the buffer memory (not shown) may exist outside the video decoder (510), and further, for example to handle playback timing, another additional buffer memory (515) may exist inside the video decoder (510). If the receiver (531) is receiving data from a storage / transfer device with sufficient bandwidth and controllability, or from an isochronous network, the buffer memory (515) may not be necessary or may be small. For use in best-effort packet networks such as the Internet, a sufficiently large buffer memory (515) may be required, and that size may be relatively large.Such buffer memory may be implemented with an adaptive size and may be implemented at least partially outside the video decoder (510) in the operating system or a similar element (not shown).

[0039] The video decoder (510) may include a parser (520) for reconstructing symbols (521) from the encoded video sequence. These categories of symbols may include information used to manage the operation of the video decoder (510) and potentially information for controlling a rendering device such as a display (512) (e.g., a display screen). The display may be an integral part of or not an integral part of an electronic device (530), as shown in Figure 5, and may be coupled to the electronic device (530). Control information for the rendering device(s) may be in the form of Supplementary Enhancement Information (SEI messages) or Video Usability Information (VUI) parameter set fragments (not shown). The parser (520) can parse / entropy decode the encoded video sequence received by the parser (520). The entropy coding of the encoded video sequence can follow video coding techniques or standards, and can follow various principles, including variable-length coding, Huffman coding, context-sensitive or insensitive arithmetic coding, etc. The parser (520) can extract from the encoded video sequence a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder, based on at least one parameter corresponding to the subgroup. Subgroups can include Group of Pictures (GOP), pictures, tiles, slices, macroblocks, coding units (CU), blocks, transform units (TU), prediction units (PU), etc. The parser (520) can also extract information from the encoded video sequence such as transformation coefficients (e.g., Fourier transform coefficients), quantizer parameter values, and motion vectors.

[0040] The parser (520) can perform an entropy decoding / parse operation on the video sequence received from the buffer memory (515), thereby generating a symbol (521).

[0041] The reconstruction of the symbol (521) may involve multiple different processing or functional units, depending on the type of the encoded video picture or its portion (e.g., inter and intra picture, inter and intra block) and other factors. The units involved and how they are involved may be controlled by subgroup control information parsed from the encoded video sequence by the parser (520). The flow of such subgroup control information between the parser (520) and the multiple processing or functional units described below is not depicted for brevity.

[0042] In addition to the functional blocks already described, the video decoder (510) can be conceptually divided into several functional units, as described below. In a practical implementation operating under commercial constraints, many of these functional units can interact closely with each other and be at least partially integrated. However, for the purpose of clearly describing the various functions of the disclosed subject, a conceptual subdivision into functional units is adopted in the following disclosure.

[0043] The first unit may include a scaler / inverse unit (551). The scaler / inverse unit (551) may receive quantized transformation coefficients and control information from the parser (520) as symbols (singular or plural) (521). The control information includes information indicating which type of inverse transformation to use, block size, quantization coefficients / parameters, quantization scaling matrix, etc. The scaler / inverse unit (551) can output a block containing sample values ​​that can be input to the tallyer (555).

[0044] In some cases, the output samples of the scaler / inverse transform (551) may relate to intra-encoded blocks, i.e., blocks that do not use prediction information from previously reconstructed pictures but can use prediction information from previously reconstructed portions 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 already been reconstructed and stored in the current picture buffer (558) to generate blocks of the same size and shape as the block being reconstructed. The current picture buffer (558) buffers, for example, partially reconstructed current pictures and / or fully reconstructed current pictures. Depending on the implementation, the aggregater (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) for each sample.

[0045] In other cases, the output samples of the scaler / inverse unit (551) may relate to inter-encoded and potentially motion-compensated blocks. In such cases, the motion-compensated prediction unit (553) may access the reference picture memory (557) to retrieve samples to be used for inter-picture prediction. After the retrieved samples have been motion-compensated according to symbols (521) relating to the blocks, these samples can be added by the aggregater (555) to the output of the scaler / inverse unit (the output of unit 551 may be called residual samples or residual signals) to generate output sample information. The address in the reference picture memory (557) from which the motion-compensated unit (553) retrieves the predicted samples can be controlled by motion vectors available to the motion-compensated unit (553) in the form of symbols (521). These symbols may, for example, have X, Y components (shift), and a reference picture component (time). Motion compensation may include interpolation of sample values ​​taken from reference picture memory (557) when accurate motion vectors less than or equal to the sample are used, and may also be related to a motion vector prediction mechanism, etc.

[0046] The output samples from the tallyer (555) can be subjected to various loop filtering techniques within the loop filter unit (556). The video compression technique may include in-loop filtering techniques. The in-loop filtering techniques are controlled by parameters contained in the encoded video sequence (also called the encoded video bitstream) and made available to the loop filter unit (556) as symbols (521) from the parser (520), but can also respond to metadata obtained during decoding of earlier parts (in decoding order) of the encoded picture or encoded video sequence, as well as to previously reconstructed and loop-filtered sample values. Several types of loop filters may be included as part of the loop filter unit 556 in various orders, as will be described in more detail below.

[0047] The output of the loop filter unit (556) can be a sample stream, which can be output to the rendering device (512) and can also be stored in the reference picture memory (557) for use in future interpicture prediction.

[0048] A particular encoded picture, once fully reconstructed, can be used as a reference picture for future interpicture prediction. For example, once the encoded picture corresponding to the current picture is fully reconstructed and that encoded picture is identified as a reference picture (e.g., by the parser (520)), the current picture buffer (558) can become part of the reference picture memory (557), and a fresh current picture buffer can be reallocated before the reconstruction of subsequent encoded pictures begins.

[0049] The video decoder (510) can perform decoding operations according to a predetermined video compression technique adopted in a standard such as ITU-T Recommendation H.265. The encoded video sequence can conform to the syntax defined by the video compression technique or standard used, in the sense that the encoded video sequence conforms to the syntax and profile documented in the video compression technique or standard. Specifically, a profile can select specific tools from all the tools available in the video compression technique or standard, as tools that are only available for use under that profile. To conform to the standard, the complexity of the encoded video sequence may be within the range defined by the level of the video compression technique or standard. In some cases, the level constrains the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limits set by the level may, in some cases, be further constrained through the Hypothetical Reference Decoder (HRD) specification and metadata for HRD buffer management, which are signaled in the encoded video sequence.

[0050] In some exemplary embodiments, the receiver (531) may receive additional (redundant) data along with the encoded video. The additional data may be included as part of the encoded video sequence(s) or sequence(s). The additional data may be used by the video decoder (510) to properly decode the data and / or to more accurately reconstruct the original video data. The additional data may take the form of, for example, a temporal, spatial, or signal-to-noise ratio (SNR) enhancement layer, redundant slices, redundant pictures, forward error correction codes, etc.

[0051] Figure 6 shows a block diagram of a video encoder (603) according to an exemplary embodiment of the present disclosure. 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 transmitting circuit). The video encoder (603) can be used in place of the video encoder (403) in the example of Figure 4.

[0052] The video encoder (603) can receive video samples from a video source (601) (which is not part of the electronic device (620) in the example in Figure 6) that can capture video images to be encoded by the video encoder (603). In another example, the video source (601) may be implemented as part of the electronic device (620).

[0053] The video source (601) can provide a source video sequence to be encoded by the video encoder (603) in the form of a digital video sample stream, which can be of any preferred bit depth (e.g., 8 bits, 10 bits, 12 bits, ...), any color space (e.g., BT.601 YCrCB, RGB, XYZ, ...), and any preferred sampling structure (e.g., YCrCb 4:2:0, YCrCb 4:4:4). In a media service system, the video source (601) may also be a storage device capable of storing pre-prepared video. In a video conferencing system, the video source (601) may also be a camera that captures local image information as a video sequence. The video data may be provided as a plurality of individual pictures or images that give motion when viewed in sequence. The picture itself may be organized as a spatial array of pixels, and each pixel may contain one or more samples, depending on the sampling structure, color space, etc., in use. Those skilled in the art will readily understand the relationship between pixels and samples. The following description will focus on samples.

[0054] According to some exemplary embodiments, the video encoder (603) can encode and compress the pictures of a source video sequence in real time or under any other temporal constraints required by the application to obtain an encoded video sequence (643). Enforcing an appropriate encoding rate constitutes one function of the controller (650). In some embodiments, the controller (650) may be functionally coupled to and control other functional units, such as those described below. Such couplings are not depicted for brevity. Parameters set by the controller (650) may include parameters related to rate control (picture skip, quantizer, lambda value of rate-distortion optimization technique, ...), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. The controller (650) may be configured to have other preferred functions of the video encoder (603) optimized for a particular system design.

[0055] In some exemplary embodiments, the video encoder (603) may be configured to operate in an encoding loop. In a drastically simplified explanation, in one example, the encoding loop may include a source encoder (630) (for example, responsible for generating symbols such as a symbol stream based on the input picture and reference picture(s) to be encoded) and an embedded (local) decoder (633) in the video encoder (603). Even if the embedded decoder 633 processes the encoded video stream without entropy coding by the source encoder 630, the decoder (633) reconstructs the symbols to generate sample data in a similar manner to what a (remote) decoder would also generate (in the video compression techniques considered in the disclosed subject, any compression between the symbols in entropy coding and the encoded video bitstream can be lossless). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Symbol stream decoding yields bit-accurate results regardless of the decoder location (local or remote), so the contents of the reference picture memory (634) are also bit-accurate between the local and remote encoders. In other words, the encoder's predictive unit "sees" the exact same sample values ​​as the reference picture samples that the decoder "sees" when using the predictions during decoding. This fundamental principle of reference picture synchronization (and the resulting drift, for example, when synchronization cannot be maintained due to channel errors) is used to improve encoding quality.

[0056] The operation of the "local" decoder (633) may be the same as that of the "remote" decoder, such as the video decoder (410), which has already been described in detail above in relation to Figure 5. However, referring briefly to Figure 5, since symbols are available and the encoding / decoding of symbols to an encoded video sequence by the entropy encoder (645) and parser (420) may be reversible, the entropy decoding section of the video decoder (410), which includes the buffer memory (415) and parser (420), does not need to be fully implemented in the encoder's local decoder (633).

[0057] An observation that can be made at this point is that any decoder technique, except for parse / entropy decoding which can exist only within the decoder, may need to exist in substantially the same functional form within the corresponding encoder. For this reason, the subject matter disclosed may sometimes focus on the decoder operation, as is the case with the decoding portion of the encoder. Therefore, the description of the encoder technique can be omitted, as it is the inverse of the comprehensively described decoder technique. A more detailed description is provided below only for specific areas or aspects of the encoder.

[0058] In operation, in some exemplary implementations, the source encoder (630) may perform motion-compensated predictive coding, predictively coding the input picture by referencing one or more previously coded pictures from a video sequence designated as “reference pictures”. In this way, the coding engine (632) codes the difference (or residual) in the color channels between the pixel blocks of the input picture and the pixel blocks of the reference picture(s) that may be selected as predictive references for the input picture.

[0059] The local video decoder (633) can decode the encoded video data of a picture that may be designated as a reference picture based on the symbols generated by the source encoder (630). The operation of the encoding engine (632) can, advantageously, be a lossy process. When the encoded video data can be decoded by the video decoder (not shown in Figure 6), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (633) can replicate the decoding process that the video decoder may perform on the reference picture and have the reconstructed reference picture stored in the reference picture cache (634). In this way, the video encoder (603) can locally store a copy of the reconstructed reference picture that has common content (unless there are transmission errors) as the reconstructed reference picture that would be obtained by the far-end (remote) video decoder.

[0060] The predictor (635) can perform a predictive search on the encoding engine (632). That is, for a new picture to be encoded, the predictor (635) can search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or specific metadata, such as reference picture motion vectors, block shapes, etc., that can function as appropriate predictive references for the new picture. The predictor (635) may operate on a sample block-by-pixel-block basis to find appropriate predictive references. In some cases, the input picture may have predictive references drawn from multiple reference pictures stored in the reference picture memory (634), as determined by the search results obtained by the predictor (635).

[0061] The controller (650) may manage the encoding operation of the source encoder (630), including, for example, setting parameters and subgroup parameters used to encode the video data.

[0062] The outputs of all the above functional units can undergo entropy coding in the entropy encoder (645). The entropy encoder (645) converts the symbols generated by the various functional units into coded video sequences by lossless compression of the symbols according to techniques such as Huffman coding, variable-length coding, and arithmetic coding.

[0063] The transmitter (640) can buffer the encoded video sequence generated by the entropy encoder (645) and prepare it for transmission over the communication channel (660). The communication channel (660) may be a hardware / software link to a storage device that stores the encoded video data. The transmitter (640) can merge the encoded video data from the video encoder (630) with other data to be transmitted, such as encoded audio data and / or auxiliary data streams (sources not shown).

[0064] The controller (650) may manage the operation of the video encoder (603). During encoding, the controller (650) may assign a certain encoded picture type to each encoded picture. The encoded picture type may affect the encoding technique that can be applied to each picture. For example, a picture may often be assigned as one of the following picture types:

[0065] An intra-picture (I-picture) may be something that can be encoded and decoded without using other pictures in the sequence as a source for prediction. Some video codecs allow different types of intra-pictures, including, for example, Independent Decoder Refresh ("IDR") pictures. Those skilled in the art will recognize these variations of I-pictures, as well as their respective uses and characteristics.

[0066] A predictive picture (P-picture) may be encoded and decoded using intra-prediction or inter-prediction, which uses up to one motion vector and reference index to predict the sample values ​​of each block.

[0067] A bidirectional predictive picture (B-picture) may be encoded and decoded using intra-prediction or inter-prediction, employing up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, a multi-predictive picture may use three or more reference pictures and associated metadata for the reconstruction of a single block.

[0068] A source picture is typically divided spatially into multiple sample-encoded blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each), and each block can be encoded. Blocks can be predictively encoded by referencing other (already encoded) blocks, as determined by the encoding assignment applied to each picture in the block. For example, a block of picture I may be non-predictively encoded, or it may be predictively encoded by referencing an already encoded block of the same picture (spatial prediction or intra-prediction). A pixel block of picture P may be predictively encoded via spatial prediction or temporal prediction by referencing one previously encoded reference picture. A block of picture B may be predictively encoded via spatial prediction or temporal prediction by referencing one or two previously encoded reference pictures. The source picture or intermediate processing picture may be subdivided into other types of blocks for other purposes. The division of encoded blocks and other types of blocks may or may not follow the same scheme, as will be described in more detail below.

[0069] The video encoder (603) can perform encoding operations in accordance with a specified video encoding technique or standard, such as ITU-T Recommendation H.265. In this operation, the video encoder (603) can perform various compression operations, including predictive encoding operations that utilize temporal and spatial redundancy in the input video sequence. Thus, the encoded video data may conform to the syntax specified by the video encoding technique or standard used.

[0070] In some exemplary embodiments, the transmitter (640) may transmit additional data along with the encoded video. The source encoder (630) may include such data as part of the encoded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, and the like.

[0071] A video may be captured as multiple source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often abbreviated as intra-prediction) utilizes spatial correlations within a given picture, while inter-picture prediction utilizes temporal or other correlations between pictures. For example, a particular picture to be encoded / decoded, called the current picture, may be divided into blocks. If a block in the current picture is analogous to a reference block in a previously encoded and still-buffered reference picture in the video, it may be encoded by a vector called a motion vector. The motion vector points to a reference block in the reference picture and may have a third dimension that identifies the reference picture if multiple reference pictures are used.

[0072] In some exemplary embodiments, a bidirectional prediction technique can be used in interpicture prediction. According to such a bidirectional prediction technique, two reference pictures are used, such as a first reference picture and a second reference picture, both of which precede the current picture in decoding order in the video (but may be past or future in display order, respectively). A block in the current picture can 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 can be predicted together by the combination of the first and second reference blocks.

[0073] Furthermore, merge mode techniques may be used in interpicture prediction to improve coding efficiency.

[0074] According to some exemplary embodiments of this disclosure, predictions such as interpicture prediction and intrapicture prediction are performed in units of blocks. For example, a picture in a sequence of video pictures is divided into coding tree units (CTUs) for compression, and those CTUs in a picture may have the same size, such as 64x64 pixels, 32x32 pixels, or 16x16 pixels. Generally, a CTU may include three parallel coding tree blocks (CTBs), which are one lumen CTB and two chromen CTBs. Each CTU can be recursively quadtree-divided into one or more coding units (CUs). For example, a 64x64 pixel CTU can be divided into one 64x64 pixel CU or four 32x32 pixel CUs. Each of the one or more 32x32 blocks may be further divided into four 16x16 pixel CUs. In some exemplary embodiments, each CU may be analyzed during coding to determine the prediction type for that CU among various prediction types, such as inter-prediction type or intra-prediction type. A CU may be divided into one or more prediction units (PUs) depending on its temporal and / or spatial predictability. Generally, each PU includes a luma prediction block (PB) and two chroma PBs. In some embodiments, the prediction operation in coding (encoding / decoding) is performed in units of prediction blocks. The division of CUs into PUs (or PBs for different color channels) may be performed in various division patterns. For example, the luma or chroma PB may include a matrix of values ​​(e.g., luma values) for pixels, such as 8x8 pixels, 16x16 pixels, 8x16 pixels, 16x8 pixels, etc.

[0075] Figure 7 shows a diagram of a video encoder (703) according to another exemplary embodiment of the present disclosure. The video encoder (703) is configured to receive a processing block (e.g., a prediction block) of sample values ​​in the current video picture within a sequence of video pictures, and to encode the processing block into an encoded picture which is part of an encoded video sequence. The exemplary video encoder (703) may be used instead of the video encoder (403) in the example of Figure 4.

[0076] For example, the video encoder (703) receives a matrix of sample values ​​for a processing block, such as a prediction block with 8x8 samples. The video encoder (703) then determines, for example using rate-distortion optimization (RDO), which mode—intra-mode, inter-mode, or bidirectional prediction—best suits the processing block for encoding. If it is determined that the processing block is encoded in intra-mode, the video encoder (703) may use the intra-prediction technique to encode the processing block into an encoded picture. If it is determined that the processing block is encoded in inter-mode or bidirectional prediction mode, the video encoder (703) may use the inter-prediction technique or the bidirectional prediction technique, respectively, to encode the processing block into an encoded picture. In some exemplary embodiments, merge mode may be used as a submode of interpicture prediction in which the motion vector is derived from one or more motion vector predictors, but without benefit from encoded motion vector components outside of the predictors. In some exemplary embodiments, there may be motion vector components applicable to the target block. Therefore, the video encoder (703) may include components not explicitly shown in Figure 7, such as a mode determination module (not shown) for determining the prediction mode of the processing block.

[0077] In the example in Figure 7, the video encoder (703) includes an interencoder (730), an intraencoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721), and an entropy encoder (725), all coupled together as shown in the exemplary arrangement in Figure 7.

[0078] The interencoder (730) is configured to receive a sample of the current block (e.g., a processing block), compare the block to one or more reference blocks in the reference picture (e.g., blocks in earlier and later pictures in display order), generate interprediction information (e.g., a description of redundant information by the intercoding technique, motion vectors, merge mode information), and, based on the interprediction information, compute an interprediction result (e.g., a predicted block) using any preferred technique. In some examples, the reference picture is a decoded reference picture, decoded based on encoded video information using a decoding unit 633 embedded in the exemplary encoder 620 in Figure 6 (shown as a residual decoder 728 in Figure 7, as will be described in more detail below).

[0079] The intra encoder (722) is configured to receive a sample of the current block (e.g., a processing block), compare the block to a block already encoded in the same picture, generate quantized coefficients after conversion, and optionally also generate intra prediction information (e.g., intra prediction direction information by one or more intra coding techniques). The intra encoder (722) may also calculate an intra prediction result (e.g., a predicted block) based on the intra prediction information and a reference block in the same picture.

[0080] The general controller (721) may be configured to determine general control data and control other components of the video encoder (703) based on the general control data. For example, the general controller (721) determines the prediction mode of a block and provides control signals to the switch (726) based on that prediction mode. For example, if the prediction mode is intra-mode, the general controller (721) controls the switch (726) to select the intra-mode result for use by the residual calculator (723), select the intra-prediction information, and control the entropy encoder (725) to include the intra-prediction information in the bitstream. If the prediction mode of the block is inter-mode, the general controller (721) controls the switch (726) to select the inter-prediction result for use by the residual calculator (723), select the inter-prediction information, and control the entropy encoder (725) to include the inter-prediction information in the bitstream.

[0081] The residual calculator (723) may be configured to calculate the difference (residual data) between a received block and the prediction result of that block selected from an intra-encoder (722) or inter-encoder (730). The residual encoder (724) may be configured to encode the residual data to generate conversion coefficients. For example, the residual encoder (724) may be configured to convert the residual data from the spatial domain to the frequency domain to generate conversion coefficients. The conversion coefficients are then subjected to a quantization process to obtain quantized conversion coefficients. In various exemplary embodiments, the video encoder (703) also includes a residual decoder (728). The residual decoder (728) is configured to perform an inverse transform to generate decoded residual data. The decoded residual data can be suitably used by the intra-encoder (722) and inter-encoder (730). For example, an interencoder (730) can generate a decoded block based on decoded residual data and interprediction information, and an intraencoder (722) can generate a decoded block based on decoded residual data and intraprediction information. The decoded block is suitably processed to generate a decoded picture, which is buffered in a memory circuit (not shown) and can be used as a reference picture.

[0082] The entropy encoder (725) is configured to format the bitstream to include the encoded blocks and to perform entropy encoding. The entropy encoder (725) is configured to include various types of information in the bitstream. For example, the entropy encoder (725) may be configured to include general control data, selected prediction information (e.g., intra-prediction information or inter-prediction information), residual information, and other suitable information in the bitstream. Residual information may not be present when encoding blocks in either inter-mode or bidirectional prediction mode merge submodes.

[0083] Figure 8 shows a diagram of an exemplary video decoder (810) according to another embodiment of the present disclosure. The video decoder (810) is configured to receive an encoded picture which is part of an encoded video sequence, decode the encoded picture, and produce a reconstructed picture. In one example, the video decoder (810) may be used instead of the video decoder (410) in the example of Figure 4.

[0084] In the example shown in Figure 8, the video decoder (810) includes an entropy decoder (871), an interdecoder (880), a residual decoder (873), a reconfiguration module (874), and an intradecoder (872) coupled together as shown in the exemplary configuration of Figure 8.

[0085] The entropy decoder (871) can be configured to reconstruct specific symbols from an encoded picture that represent the syntax elements comprising the encoded picture. Such symbols may include, for example, the mode in which the block is encoded (e.g., intra-mode, inter-mode, bidirectional prediction mode, merge sub-mode, or another sub-mode), prediction information (e.g., intra-prediction information or inter-prediction information) that can identify specific samples or metadata used for prediction by the intra-decoder (872) or inter-decoder (880), residual information in the form of quantized transformation coefficients, etc. In one example, if the prediction mode is inter or bidirectional prediction mode, inter-prediction information is provided to the inter-decoder (880). If the prediction type is intra-prediction type, intra-prediction information is provided to the intra-decoder (872). The residual information may undergo inverse quantization and be provided to the residual decoder (873).

[0086] The interdecoder (880) may be configured to receive interprediction information and generate interprediction results based on the interprediction information.

[0087] The intra decoder (872) may be configured to receive intra prediction information and generate prediction results based on the intra prediction information.

[0088] The residual decoder (873) may be configured to perform inverse quantization to extract the dequantized conversion coefficients, process the dequantized conversion coefficients, and convert the residual from the frequency domain to the spatial domain. The residual decoder (873) may also utilize certain control information, including quantizer parameters (QP), which may be provided by the entropy decoder (871) (this is only low-data-volume control information, so no data path is drawn).

[0089] The reconstruction module (874) may be configured to combine the residuals output by the residual decoder (873) and the prediction results (which may be output by an intra or interprediction module, depending on the case) in the spatial domain to form a reconstructed block that forms part of the reconstructed picture as part of the reconstructed video. Note that other preferred operations, such as deblocking operations, may also be performed to improve visual quality.

[0090] The video encoders (403), (603), (703), and video decoders (410), (510), (810) can be implemented using any preferred technique. In some exemplary embodiments, the video encoders (403), (603), (703), and video decoders (410), (510), (810) can be implemented using one or more integrated circuits. In another embodiment, the video encoders (403), (603), (703), and video decoders (410), (510), (810) can be implemented using one or more processors that execute software instructions.

[0091] Returning to the intra-prediction process, samples within a block (e.g., luma or chroma prediction blocks, or encoded blocks if not further subdivided into prediction blocks) are predicted by adjacent lines, next adjacent lines, other lines, or multiple lines, or combinations thereof, to generate prediction blocks. The residuals between the actual encoded blocks and the prediction blocks may then be processed through transformation and subsequent quantization. Various intra-prediction modes become available, and parameters related to intra-mode selection and other parameters may be signaled in a bitstream. For example, the various intra-prediction modes may relate to line positions or multiple positions for predicting samples, the direction in which prediction samples are selected from prediction lines or multiple lines, and other special intra-prediction modes.

[0092] For example, a set of intra-prediction modes (also called "intra-modes") may include a predetermined number of directional intra-prediction modes. As described above in relation to the exemplary implementation in Figure 1, these intra-prediction modes may correspond to a predetermined number of directions in which samples outside a block are selected as predictions for samples predicted within a particular block. In another particular exemplary implementation, eight principal directional modes corresponding to angles from 45° to 207° with respect to the horizontal axis may be supported and predefined.

[0093] In some other implementations of intra prediction, the directional intra modes may be further extended to angles set at a finer granularity to further leverage greater spatial redundancy in directional textures. For example, the above implementation of eight angles may be configured to provide eight nominal angles called V_PRED, H_PRED, D45_PRED, D135_PRED, D113_PRED, D157_PRED, D203_PRED, and D67_PRED, as shown in Figure 9. For each nominal angle, a predetermined number (e.g., seven) finer angles may be added. Such extensions may make a larger total number (e.g., 56 in this example) of directional angles available for intra prediction, corresponding to the same number of predetermined directional intra modes. The predicted angle may be expressed as the nominal intra angle plus an angle delta. In the particular example above with seven finer angular directions for each nominal angle, the angle delta may be multiplied by a step size of 3° from -3 to 3.

[0094] The directional intra-prediction described above may also be called unidirectional intra-prediction and is distinct from bidirectional intra-prediction (also called intra-bidirectional prediction), which will be described later in this disclosure.

[0095] In some implementations, a predetermined number of non-directional intra-prediction modes may be predefined and available in place of or in addition to the directional intra-modes described above. For example, five non-directional intra-modes may be specified, called smooth intra-prediction modes. These non-directional intra-mode prediction modes may be specifically called DC, PAETH, SMOOTH, SMOOTH_V, and SMOOTH_H intra-modes. The prediction of samples for a particular block in these exemplary non-directional modes is shown in Figure 10. As an example, Figure 10 shows that a 4x4 block 1002 is predicted by samples from the upper adjacent line and / or left adjacent line. A particular sample 1010 in block 1002 may correspond to the direct upper sample 1004 of sample 1010 in the upper adjacent line of block 1002, the upper left sample 1006 of sample 1010 as the intersection of the upper and left adjacent lines, and the direct left sample 1008 of sample 1010 in the left adjacent line of block 1002. In an exemplary DC intra-prediction mode, the average of left and upper neighbor samples 1008 and 1004 may be used as the predictor for sample 1010. In an exemplary PAETH intra-prediction mode, upper, left, and upper-left reference samples 1004, 1008, and 1006 are taken, and then the value of these three reference samples closest to (upper + left - upper-left) may be set as the predictor for sample 1010. In an exemplary SMOOTH_V intra-prediction mode, sample 1010 may be predicted by quadratic interpolation in the vertical direction of upper-left neighbor sample 1006 and left neighbor sample 1008. In an exemplary SMOOTH_H intra-prediction mode, sample 1010 may be predicted by quadratic interpolation in the horizontal direction of upper-left neighbor sample 1006 and upper neighbor sample 1004. In an exemplary SMOOTH intra-prediction mode, sample 1010 may be predicted by the average of the vertical and horizontal quadratic interpolations. The above implementations of non-directional intra-modes are shown merely as non-limiting examples. Non-directional selection of other adjacent lines and other samples, as well as methods for combining predictive samples to predict specific samples within a prediction block, are also considered.

[0096] At various encoding levels (picture, slice, block, unit, etc.), the encoder's selection of a particular intra-prediction mode from the directional or non-directional modes described above may be signaled in the bitstream. In some exemplary implementations, eight exemplary nominal directional modes (13 choices in total) may be signaled first, along with five non-angle smooth modes. Then, if the signaled mode is one of the eight nominal angle intra-modes, an index is further signaled to indicate the selected angle delta for the corresponding signaled nominal angle. In some other exemplary implementations, all intra-prediction modes may be indexed together for signaling (e.g., 56 directional modes plus 5 non-directional modes to generate 61 intra-prediction modes).

[0097] In some exemplary implementations, the exemplary 56 directional intra-prediction modes or any other number of directional intra-prediction modes may be implemented using an integrated directional predictor that projects each sample in a block onto a reference subsample position and interpolates the reference sample by a two-tap bilinear filter.

[0098] In some implementations, additional filter modes, called FILTER INTRA modes, may be designed to capture attenuating spatial correlations with references on edges. In these modes, in addition to out-of-block samples, in-block prediction samples may be used as intra-predictive reference samples for some patches within the block. For example, these modes may be predefined and available for intra-prediction for at least Luma blocks (or Luma blocks only). A predetermined number (e.g., five) of filter-intra modes may be predesigned, each represented by a set of n-tap filters (e.g., 7-tap filters) that reflect the correlation between a sample in a 4x2 patch and its n adjacent neighbors. In other words, the weight coefficients of the n-tap filters may be position-dependent. Taking an 8x8 block, 4x2 patch, and 7-tap filtering as an example, the 8x8 block 1102 may be divided into eight 4x2 patches, as shown in Figure 11. These patches are indicated in Figure 11 by B0, B1, B1, B3, B4, B5, B6, and B7. For each patch, its seven neighborhoods, indicated by R0 to R7 in Figure 11, may be used to predict the samples within the current patch. In patch B0, all neighborhoods may have already been reconstructed. However, in other patches, some neighborhoods may be currently within the block and not yet reconstructed. In that case, the predicted values ​​of the nearest neighborhood are used as a reference. For example, as shown in Figure 11, not all neighborhoods in patch B7 are reconstructed, so predicted samples from some neighborhoods of B4, B5 and / or B6 are used instead.

[0099] In some implementations of intra prediction, one color component may be predicted using one or more other color components. The color components may be any one of the color components in the YCrCb, RGB, XYZ color space, etc. For example, prediction of chroma components (e.g., chroma blocks) from luma components (e.g., luma reference samples), called CfL (Chroma from Luma), may be implemented. In some exemplary implementations, cross-color prediction may only be allowed from luma to chroma. For example, chroma samples within a chroma block may be modeled as a linear function of matching reconstructed luma samples. CfL prediction may be implemented as follows: CfL(α) = α × LAC + DC (1)

[0100] Here, LAC represents the AC contribution of the luma component, α represents the parameter of the linear model, and DC represents the DC contribution of the chroma component. For example, the AC component is obtained for each sample in a block, while the DC component is obtained for the entire block. Specifically, the reconstructed luma samples may be subsampled to the chroma resolution, and then the average luma value (DC of luma) may be subtracted from each luma value to form the AC contribution in luma. The AC contribution of luma is then used in the linear mode of equation (1) to predict the AC value of the chroma component. Instead of requiring the decoder to calculate a scaling parameter to approximate or predict the chroma AC component from the luma AC contribution, exemplary CfL implementations may determine the parameter α based on the original chroma samples and signal it in the bitstream. This reduces the complexity of the decoder and results in more accurate predictions. With respect to the DC contribution of the chroma component, some exemplary implementations may use an intra-DC mode within the chroma component to calculate it.

[0101] Returning to intra-prediction, in some exemplary implementations, the prediction of a sample within a coding block or prediction block may be based on one of a set of reference lines. In other words, instead of always using the nearest adjacent line (e.g., the nearest upper adjacent line or nearest left adjacent line of the prediction block shown in Figure 1 above), multiple reference lines may be provided as options for selection of the intra-prediction. Such an implementation of intra-prediction may be called Multiple Reference Line Selection (MRLS). In these implementations, the encoder signals which of the multiple reference lines will be used to generate the intra-predictor. On the decoder side, after parsing the reference line index, the intra-prediction for the current intra-prediction block can be generated by identifying the reconstructed reference sample by searching for the specified reference line according to the intra-prediction mode (directional, non-directional, and other intra-prediction modes, etc.). In some implementations, the reference line index may be signaled at the coding block level, and only one of multiple reference lines may be selected and used for the intra-prediction of a single coding block. In some examples, more than one reference line may be selected simultaneously for intra-prediction. For example, more than one reference line may be combined, weighted or unweighted, averaged, interpolated, or otherwise combined to generate a prediction. In some exemplary implementations, MRLS may be applied only to the luminal component and not to the chromal component.

[0102] Figure 12 shows an example of a four-reference-line MRLS. As shown in the example in Figure 12, the intra-coded block 1202 may be predicted based on any one of four horizontal reference lines 1204, 1206, 1208, and 1210 and four vertical reference lines 1212, 1214, 1216, and 1218. Of these reference lines, 1210 and 1218 are the nearest neighbor reference lines. The reference lines may be indexed according to their distance from the coded block. For example, reference lines 1210 and 1218 may be called zero reference lines, and the other reference lines may be called non-zero reference lines. Specifically, reference lines 1208 and 1216 may be called first reference lines, reference lines 1206 and 1214 may be called second reference lines, and reference lines 1204 and 1212 may be called third reference lines.

[0103] In addition to the unidirectional intra-prediction described in the preceding parts of this disclosure, two reference pixels may be used in combination along the prediction direction to realize a direction predictor, which may be called bidirectional intra-prediction or intra-bidirectional prediction (IBP).

[0104] In some implementations, for a current block (e.g., an encoded block or an encoded block), IBP may also be applicable to directional modes where the directional mode has an angle less than 90°, such as, but not limited to, D67_PRED and D45_PRED in Figure 9. In some other implementations, IBP may also be applicable to directional modes where the directional mode has an angle greater than 180°, such as, but not limited to, D203_PRED in Figure 9.

[0105] When intra-bidirectional prediction is applied, two reference pixels are selected along the direction of the directional mode. One reference pixel is currently from the top or upper right of the block, and the other pixel is currently from the left or lower left of the block. A weighted average of the two reference pixels may be calculated to achieve the predictor.

[0106] Figure 13A shows an example of IBP for an encoded block (1330) in directional mode with a prediction direction (1340) from A(1322) to B(1312). A and B are two reference samples / values, also called the first and second predictors. A is at the intersection of the direction (1340) and the upper reference line (1320), and B is at the intersection of the direction (1340) and the left reference line (1310). The prediction for pixel (x,y)(1332), which is a pixel in encoded block (1330), is shown as pred(x,y). pred(x,y) may be generated as a weighted combination of the two predictors A and B, as shown in equation (2). Pred(x,y)=w*A+(1-w)*B (2)

[0107] A and / or B may be derived in a direction prediction process that includes interpolation for fractional pixel references. Figure 13B shows another example of IBP for an encoded block (1330) in different direction modes with different prediction directions (1350) from A(1314) to B(1324).

[0108] In some implementations where IBP is applied, two reference pixels located in adjacent upper reference lines and adjacent left references along the direction are weighted to realize the predictor. Both IBP and multiple reference line selection (MRLS) may be applied to encoded blocks, resulting in several problems / challenges. For example, one problem / challenge may involve how to apply IBP to the current block when one or more reference samples in one or more non-adjacent reference lines are selected.

[0109] This disclosure describes various embodiments for signal transmission and / or determination of multiple reference line intra-predictions in video coding and / or decoding, addressing at least one of the problems / challenges described above.

[0110] In various embodiments, with reference to Figure 14, a method 1400 for intra-bidirectional prediction and multiple-reference-line intra-prediction in video decoding is provided. The method 1400 may include, in whole or in part, the steps of: receiving a block of encoded video bitstream by a device including a memory for storing instructions and a processor communicating with the memory; determining by the device whether unidirectional intra-prediction or intra-bidirectional prediction is applied to a block based on the block's mode information, wherein the block's mode information includes at least one of the block's reference line index, the block's intra-prediction mode, and the block's size; and, depending on the determination that unidirectional intra-prediction is applied to the block, the device performing unidirectional intra-prediction on the block; and, depending on the determination that intra-bidirectional prediction is applied to the block, the device performing intra-bidirectional prediction on the block. In some implementations, step 1420 may include a step in which the device determines whether unidirectional intra-prediction or intra-bidirectional prediction is applied to a block based on the block's mode information, wherein the block's mode information includes at least one of the block's reference line index, the block's intra-prediction mode, or the block's size.

[0111] In some implementations, if an intra-prediction mode does not belong to one of the smooth modes described above, or if the intra-prediction mode generates one or more prediction samples according to a given prediction direction, this intra-prediction mode may be classified as one of the directional modes, and / or this intra-prediction mode may be called a directional intra-prediction mode (or directional mode).

[0112] In various embodiments of this disclosure, the size of a block (e.g., an encoding block, a prediction block, or a transformation block, for example, not limited to these) may represent the width or height of the block. The width or height of the block may also be an integer value in units of pixels.

[0113] In various embodiments of this disclosure, the size of a block (e.g., an encoding block, a prediction block, or a transformation block, for example, but not limited to these) may refer to the area size of the block. The area size of a block may also be an integer value calculated by multiplying the width of the block by the height of the block in units of pixels.

[0114] In some of the various embodiments of this disclosure, the size of a block (e.g., an encoding block, a prediction block, or a transformation block, for example, not limited to these) may represent the maximum width or height of the block, the minimum width or height of the block, or the aspect ratio of the block. The aspect ratio of the block may be calculated as the width divided by the height of the block, or as the height divided by the width of the block.

[0115] In this disclosure, a reference line index indicates a reference line among multiple reference lines. In various embodiments, a reference line index of 0 for a block may indicate an adjacent reference line to the block, which is also the reference line closest to the block. For example, referring to block (1202) in Figure 12, the upper reference line (1210) is the upper adjacent reference line to block (1202) and is also the upper reference line closest to the block. The left reference line (1218) is the left adjacent reference line to block (1202) and is also the left reference line closest to the block. A reference line index greater than 0 for a block indicates a non-adjacent reference line to the block, which is also the reference line not closest to the block. For example, referring to block (1202) in Figure 12, a reference line index of 1 may indicate the upper reference line (1208) and / or the left reference line (1216), a reference line index of 2 may indicate the upper reference line (1206) and / or the left reference line (1214), and / or a reference line index of 3 may indicate the upper reference line (1204) and / or the left reference line (1212).

[0116] Referring to step 1410, the device may be the electronic device (530) in Figure 5 or the video decoder (810) in Figure 8. In some implementations, the device may be the decoder (633) within the encoder (620) in Figure 6. In other implementations, the device may be part of the electronic device (530) in Figure 5, part of the video decoder (810) in Figure 8, or part of the decoder (633) within the encoder (620) in Figure 6. The encoded video bitstream may be the encoded video sequence in Figure 8, or the intermediate encoded data in Figure 6 or Figure 7. Blocks may indicate blocks being encoded or blocks that have been encoded.

[0117] In some implementations, when a directional intra-prediction mode is selected for a block to generate an intra-predictor from samples of non-adjacent reference lines, it may be determined whether unidirectional intra-prediction or intra-bidirectional intra-prediction is applied to the block, and this determination may depend on the block's mode information. In some implementations, the block's mode information may include, but is not limited to, a reference line index (e.g., indicating which of several reference lines it is), one or more intra-prediction angles (e.g., indicating which of several directional intra-prediction modes it is), and / or the size of the block.

[0118] Referring to step 1420, the device may determine whether unidirectional intra-prediction or intra-bidirectional prediction is applied to the block based on the block's mode information. In some implementations, step 1420 may include determining that unidirectional intra-prediction is applied to the block depending on whether the block's reference line index indicates a non-adjacent reference line. As an example, unidirectional intra-prediction may be applied to a non-adjacent reference line regardless of the current intra-prediction angle of the block.

[0119] In various embodiments, step 1420 may include determining whether intra-bidirectional prediction is applied to a block depending on whether the block's reference line index indicates an adjacent reference line. As an example, intra-bidirectional prediction may now be applied only to the block's adjacent reference lines.

[0120] In various embodiments, step 1420 may include determining whether unidirectional intra-prediction is applied to a block depending on whether the block's reference line index is greater than a predetermined threshold, and / or whether intra-bidirectional prediction is applied to a block depending on whether the block's reference line index is less than or equal to a predetermined threshold. For example, the decision of whether unidirectional intra-prediction or intra-bidirectional prediction is applied to a non-adjacent reference line also depends on whether the value of the reference line index is greater than a predetermined value N, where N is a non-negative integer (e.g., 0, 1, 2, 3, or 4).

[0121] In one example, the predetermined value N is 0. If the value of the block's reference line index is greater than 0, i.e., any non-adjacent reference line (e.g., any of lines 1212, 1214, 1216, 1204, 1206 and / or 1208 in Figure 12) is used in the block, unidirectional intra-prediction is applied to the block, and / or if the value of the block's reference line index is 0 or less, i.e., an adjacent reference line (e.g., any of lines 1218 and / or 1210 in Figure 12) is used in the block, intra-bidirectional prediction is applied to the block.

[0122] In another example, the given value N is 1. If the value of the block's reference line index is greater than 1, i.e., if any of the first subset of non-adjacent reference lines (e.g., any of lines 1212, 1214, 1204 and / or 1206 in Figure 12) is used for the block, then unidirectional intra-prediction is applied to the block, and / or if the value of the block's reference line index is 1 or less, i.e., if any of the adjacent reference lines (e.g., any of lines 1218 and / or 1210 in Figure 12) and / or any of the second subset of non-adjacent reference lines (e.g., any of lines 1218 and / or 1210 in Figure 12) is used for the block, then intra-bidirectional prediction is applied to the block.

[0123] In various embodiments, step 1420 may also include determining that intra-bidirectional prediction is applied to a block depending on whether the block's intra-prediction mode belongs to a first selection set of intra-prediction modes and the reference line index indicates an adjacent reference line; determining that unidirectional intra-prediction is applied to a block depending on whether the block's intra-prediction mode belongs to a first selection set of intra-prediction modes and the reference line index indicates a non-adjacent reference line; and / or determining that intra-bidirectional prediction is applied to a block depending on whether the block's intra-prediction mode belongs to a second selection set of intra-prediction modes. In some implementations, the first selection set of intra-prediction modes does not overlap with the second selection set of intra-prediction modes. In some other implementations, the second selection set of intra-prediction modes may include diagonal intra-prediction modes.

[0124] In some implementations, for a selected set of intra-prediction modes, IBP is applied to both adjacent and non-adjacent reference lines, but for the remaining set of intra-prediction modes, IBP is applied only to adjacent reference lines. In some other implementations, the selected set of intra-prediction modes may include several intra-prediction modes with certain specific directional angles, and therefore only integer samples are used as reference values ​​for the intra-prediction. In one example, only integer samples are used as reference values ​​for several intra-prediction modes that have diagonal directions (i.e., 45° or 225°). In another example, when intra-prediction is applied by using only integer samples for diagonal intra-prediction modes, IBP may also be applied to non-adjacent reference lines, and the diagonal intra-prediction modes are intra-prediction modes that have diagonal directions (i.e., 45° or 225°).

[0125] In various embodiments, step 1420 may include determining that unidirectional intra prediction is applied to a block depending on whether the block's reference line index is odd and / or whether the reference line index indicates a non-adjacent reference line, and / or determining that intra-bidirectional prediction is applied to a block depending on whether the block's reference line index is even and / or whether the reference line index indicates an adjacent reference line.

[0126] In some implementations, the decision of whether to apply unidirectional intra-prediction or intra-bidirectional prediction to a non-adjacent reference line depends on whether the reference line index value is even or odd. For example, if the reference line index value of a block is odd, unidirectional intra-prediction is applied to the block, and / or if the reference line index value of a block is even, intra-bidirectional prediction is applied to the block. Another example is that if the reference line index value of a block is even, unidirectional intra-prediction is applied to the block, and / or if the reference line index value of a block is odd, intra-bidirectional prediction is applied to the block.

[0127] In various embodiments, there may be only one reference line index for a block. During encoding, the reference line index of a block may be encoded in the encoded bitstream, and / or, during decoding, the reference line index of a block may be decoded / extracted from the encoded bitstream. Step 1440 may include determining a first predictor based on the reference line index of a block, determining a second predictor based on the reference line index of a block, and / or determining a final predictor of a block according to a weighting calculation between the first and second predictors.

[0128] In some implementations, intra-bidirectional prediction is applied, and if the block's reference line index indicates that non-adjacent reference lines should be used for intra-prediction, then both predictor A and predictor B are generated from the samples in the non-adjacent reference lines to generate intra-predictors from the samples in the non-adjacent reference lines. A weighting calculation is then performed based on predictor A and predictor B to generate the final IBP predictor.

[0129] In various embodiments, there may be more than one reference line index for a given block. The first reference line index may indicate a reference line used among multiple upper reference lines, and the second reference line index may indicate a reference line used among multiple left reference lines, or vice versa, where the first reference line index indicates a reference line used among multiple left reference lines, and the second reference line index indicates a reference line used among multiple upper reference lines. During encoding, more than one reference line index of a block may be encoded into the encoded bitstream, and / or, during decoding, more than one reference line index of a block may be decoded / extracted from the encoded bitstream.

[0130] In some implementations, step 1440 may include determining a first predictor based on a first reference line index of the block, determining a second predictor based on a second reference line index of the block, and / or determining a final predictor of the block according to a weighting calculation between the first and second predictors.

[0131] In some other implementations, the first reference line index indicates a non-adjacent reference line, the first predictor is generated from the first sample in the non-adjacent reference line, and / or the second reference line index indicates an adjacent reference line, the second predictor is generated from the second sample in the adjacent reference line.

[0132] In one example referring to Figure 15, when intra-bidirectional prediction is applied to the coded block (1530), an intra predictor (1532) is generated from samples in two reference lines, including one non-adjacent reference line and / or one or more adjacent reference lines. As shown in Figure 15, the coded block has a left adjacent reference line (1510), an upper adjacent reference line (1520), and at least one upper adjacent reference line (1521 and / or 1522). For example, but not limited to, a first reference line index of 2 may indicate an upper non-adjacent reference line (1522), and thus the predictor (1528) is generated from samples in the non-adjacent reference line (1522) selected by MRLS according to the prediction direction (1550). In some implementations, a second reference line index of 0 may indicate a left adjacent reference line (1510). In some other implementations, the left neighbor reference line (1510) may be indicated / implied without a second reference line index. Predictor B (1514) is generated from samples of the neighbor reference line (1510) according to the prediction direction (1550). Predictors A and B are then weighted and combined to generate an intra-predictor (1532) according to the IBP scheme, for example, according to the equation in equation (2). In some implementations, the weight (w) may depend on the distance between the intra-predictor (1532) and either predictor A or predictor B. In equation (2), the smaller the distance between the intra-predictor (1532) and predictor A (1528) (i.e., the closer predictor (1532) is to predictor A (1528)), the larger the weight (w). Similarly, in equation (2), the greater the distance between the intra predictor (1532) and predictor A (1528) (i.e., the further predictor (1532) is from predictor A (1528)), the smaller the weight (w).

[0133] Figure 15 shows an example with a single left reference line and multiple upper reference lines. Similarly, in another example, when intra-bidirectional prediction is applied to a coding block, a single upper reference line and multiple left reference lines may be applied to the coding block.

[0134] In various embodiments, there may be more than one reference line index for a given block. A first reference line index may indicate a reference line used among multiple upper reference lines, and a second reference line index may indicate more than one reference line used among multiple left reference lines, or vice versa, where the first reference line index indicates a reference line used among multiple left reference lines, and the second reference line index indicates more than one reference line used among multiple upper reference lines. During encoding, more than one reference line index of a block may be encoded into the encoded bitstream, and / or, during decoding, more than one reference line index of a block may be decoded / extracted from the encoded bitstream.

[0135] In some implementations, step 1440 may include the first reference line index representing a non-adjacent reference line and the first predictor being generated from a first sample in the non-adjacent reference line, and / or the second reference line index representing multiple reference lines and the second predictor being generated as a linearly weighted average of samples obtained from each of the multiple reference lines, each along the prediction angle.

[0136] In some other implementations, when intra-bidirectional prediction is applied to generate intra-predictions from samples of non-adjacent reference lines, one or both predictors are generated using multiple (more than one) samples of reference lines.

[0137] In one example, referring to Figure 16, the predictor is generated using a linear weighted sum of one or more samples from multiple reference lines along the prediction angle (1650) (the first sample (1626) from the first reference line (1620), the second sample (1627) from the second reference line (1621), and the third sample (1628) from the third reference line (1622). The weight of each sample may be predefined according to the relative position of the sample (across the multiple reference lines) involved in the derivation of the predictor.

[0138] In various embodiments, Method 1400 may further include determining that intra-bidirectional prediction is applied to a block and, in response that the block's reference line index indicates a non-adjacent reference line, disabling the reference sample filtering process, using a reference sample for intra-bidirectional prediction in response that a reference sample from a non-adjacent reference is available, and / or using an available adjacent reference sample for intra-bidirectional prediction in response that a reference sample from a non-adjacent reference is unavailable.

[0139] In some implementations, the reference sample filtering process may be disabled when bidirectional intra-prediction is applied to one or more non-adjacent reference lines. Therefore, one or more reference samples may be taken from one or more non-adjacent (or non-zero) reference lines and used directly for intra-bidirectional prediction. If one or more reference samples from one or more non-adjacent (or non-zero) reference lines are unavailable, they may be padded with one or more available adjacent reference samples. In some other implementations, padding for unavailable reference samples may include copying from available adjacent reference samples.

[0140] The embodiments of this disclosure may be used individually or in any order. Furthermore, each of the methods (or embodiments), encoders and decoders 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 on a non-temporary computer-readable medium. The embodiments of this disclosure may be applied to a lumina block or a chroma block, in which case the embodiments may be applied individually to one or more color components or to one or more color components together.

[0141] The techniques described above can be implemented as computer software using computer-readable instructions and can be physically stored on one or more computer-readable media. For example, Figure 17 shows a computer system (2600) suitable for carrying out a particular embodiment of the disclosed subject matter.

[0142] Computer software can be coded using any suitable machine code or computer language, and can be subjected to assembly, compilation, linking, or similar mechanisms to create code containing instructions that can be executed directly or through interpretation, microcode execution, etc., by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc.

[0143] The instructions can be executed on various types of computers or their components, including, for example, personal computers, tablet computers, servers, smartphones, gaming devices, and Internet of Things devices.

[0144] The components shown in Figure 17 for the computer system (2600) are illustrative and not intended to imply any limitation on the scope of use or functionality of computer software implementing embodiments of the present disclosure. The configuration of the components should not be construed as having any dependency or requirement on any one or combination of components shown in the exemplary embodiments of the computer system (2600).

[0145] The computer system (2600) may include certain human interface input devices. Such human interface input devices may respond to input from one or more human users through, for example, haptic input (e.g., keystrokes, swipes, data glove movements), voice input (e.g., voice, clapping), visual input (e.g., gestures), or olfactory input (not shown). The human interface devices may also be used to capture certain media that are not necessarily directly related to conscious human input, such as sound (e.g., speech, music, ambient sounds), images (e.g., scanned images, photographic images obtained from a still image camera), or video (e.g., 2D video, 3D video including stereoscopic video).

[0146] The input human interface device may include one or more of the following (only one of each is shown): keyboard (2601), mouse (2602), trackpad (2603), touchscreen (2610), data glove (not shown), joystick (2605), microphone (2606), scanner (2607), and camera (2608).

[0147] The computer system (2600) may also include certain human interface output devices. Such human interface output devices may stimulate the senses of one or more human users, for example, through tactile output, sound, light, and smell / taste. Such human interface output devices may include tactile output devices (e.g., tactile feedback via a touchscreen (2610), data glove (not shown), or joystick (2605); however, there may also be tactile feedback devices that do not function as input devices), audio output devices (e.g., speakers (2609), headphones (not shown)), visual output devices (e.g., screens (2610) including CRT screens, LCD screens, plasma screens, and OLED screens; each may or may not have touchscreen input functionality, each may or may not have tactile feedback functionality, and some of them may output two-dimensional visual output or higher-than-three-dimensional output through means such as stereoscopic output; virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0148] The computer system (2600) may also include human-accessible storage devices and associated media, such as optical media including CD / DVD ROM / RW (2620) along with CD / DVD or similar media (2621), thumb drives (2622), removable hard drives or solid-state drives (2623), legacy magnetic media such as tapes and floppy disks (not shown), and specialized ROM / ASIC / PLD-based devices such as security dongles (not shown).

[0149] Those skilled in the art should also understand that the term “computer-readable medium” as used in relation to the subject matter currently disclosed does not include a transmission medium, carrier wave, or other transient signal.

[0150] The computer system (2600) may also include an interface (2654) to one or more communication networks (2655). The networks may be, for example, wireless, wired, or optical. The networks may further be local, wide-area, metropolitan, automotive, and industrial, real-time, latency-tolerant, etc. Examples of networks include cellular networks such as Ethernet®, Wi-Fi, GSM, 3G, 4G, 5G, LTE, etc.; wide-area digital networks for wired or wireless TV, including cable television, satellite television, and terrestrial television; and automotive and industrial networks including CAN Bus. Certain networks typically require an external network interface adapter attached to a specific general-purpose data port or peripheral bus (2649) (e.g., a USB port on the computer system (2600)). Others are typically integrated into the core of the computer system (2600) by attachment to a system bus, as described later (e.g., an Ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks, the computer system (2600) may communicate with other entities. Such communications may be one-way, receive-only (e.g., broadcast television), one-way transmit-only (e.g., CANbus to a specific CANbus device), or bidirectional to other computer systems using local or wide-area digital networks, for example. Specific protocols and protocol stacks may be used on each of these networks and network interfaces as described above.

[0151] The aforementioned human interface device, human-accessible memory device, and network interface can be attached to the core (2640) of the computer system (2600).

[0152] The core (2640) may include one or more central processing units (CPUs) (2641), graphics processing units (GPUs) (2642), specialized programmable processing units in the form of field-programmable gate arrays (FPGAs) (2643), hardware accelerators for specific tasks (2644), graphics adapters (2650), etc. These devices may be connected via a system bus (2648) along with read-only memory (ROM) (2645), random access memory (2646), internal mass storage devices such as internal non-user-accessible hard drives and solid-state drives (SSDs) (2647). In some computer systems, the system bus (2648) may be accessible in the form of one or more physical plugs to allow expansion with additional CPUs, GPUs, etc. Peripheral devices may be connected directly to the core's system bus (2648) or via a peripheral bus (2649). For example, a screen (2610) may be connected to the graphics adapter (2650). The architecture for peripheral buses includes PCI, USB, etc.

[0153] The CPU (2641), GPU (2642), FPGA (2643), and accelerator (2644) can execute specific instructions that can be combined to form the aforementioned computer code. This computer code can be stored in ROM (2645) or RAM (2646). Temporary data can also be stored in RAM (2646), while persistent data can be stored, for example, in an internal mass storage device (2647). High-speed storage and retrieval to any of the memory devices can be enabled by using cache memory that can be closely associated with one or more CPUs (2641), GPUs (2642), mass storage devices (2647), ROMs (2645), RAM (2646), etc.

[0154] A computer-readable medium may have computer code thereon for performing various computer-implemented operations. The medium and computer code may be specifically designed and constructed for the purposes of this disclosure, or they may be of a type that is well known and available to those skilled in the computer software field.

[0155] As a non-limiting example, a computer system having architecture (2600), specifically a core (2640), can provide functionality as a result of a processor (including CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media can be user-accessible mass storage as described above, as well as media related to specific storage of the core (2640) of a non-transient nature, such as a mass storage device (2647) or ROM (2645) within the core. Software implementing various embodiments of this disclosure can be stored in such devices and executed by the core (2640). The computer-readable media can include one or more memory devices or chips, depending on the specific needs. The software can cause the core (2640) and specifically the processor (including CPU, GPU, FPGA, etc.) within it to execute specific processes or specific parts described herein, including defining data structures stored in RAM (2646) and modifying such data structures according to processes defined by the software. Additionally or alternatively, a computer system may provide functionality as a result of logic wired within a circuit (e.g., an accelerator (2644)) or otherwise embodied, which may operate in place of, or in conjunction with, software for performing a particular process or a particular part of a particular process as described herein. References to software include logic, and vice versa as appropriate. References to computer-readable media may, as appropriate, include circuits for storing software for execution (e.g., integrated circuits (ICs)), circuits for embodying logic for execution, or both. This disclosure encompasses any preferred combination of hardware and software.

[0156] While a particular invention has been described with reference to exemplary embodiments, this description is not intended to be limiting. Various modifications of exemplary and further embodiments of the invention will be apparent to those skilled in the art from this description. Those skilled in the art will readily recognize that various modifications above and to the exemplary embodiments described herein can be made without departing from the spirit and scope of the invention. Accordingly, the appended claims are intended to cover any such modifications and alternative embodiments. Certain proportions in the drawings may be exaggerated, and other proportions may be minimized. Accordingly, the disclosure and drawings are to be considered exemplary and not limiting.

Claims

[Claim 1] A method for intra-bidirectional prediction and multiple reference line intra-prediction performed by a video decoder, The video decoder receives the encoded video bitstream of a block, A step of determining whether unidirectional intra-prediction or intra-bidirectional prediction is applied to a block based on the mode information of the block, wherein the mode information of the block includes at least one of the reference line index of the block, the intra-prediction mode of the block, and the size of the block. The video decoder performs the unidirectional intra-prediction on the block, in accordance with the determination that the unidirectional intra-prediction is applied to the block. In response to the determination that the intra-bidirectional prediction is applied to the block, the video decoder performs the intra-bidirectional prediction on the block. A method that includes this.

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