Method, apparatus, and computer program for video coding

Abstract

To provide a method, apparatus, and computer program for video coding.SOLUTION: A processing circuitry in an apparatus decodes prediction information of a first block from a coded video bitstream. The first block is a non-square block and the prediction information for the first block is indicative of a first intra prediction mode in a first set of intra prediction modes for a square block. Then, the processing circuitry determines that the first intra prediction mode is within a subset of disabled intra prediction modes for the non-square block in the first set of intra prediction modes for the square block, remaps the first intra prediction mode to a second intra prediction mode in a second set of intra prediction modes that is used for the non-square block. Further, the processing circuitry reconstructs at least one sample of the first block according to the second intra prediction mode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 16 / 147,503, entitled "METHOD AND APPARATUS FOR VIDEO CODING," filed September 28, 2018 (now U.S. Patent No. 10,284,866), the entire contents of which are incorporated herein by reference, which in turn claims priority to U.S. Provisional Application No. 62 / 693,050, entitled "METHODS AND APPARATUS FOR WIDE ANGULAR INTRA PREDICTION IN VIDEO COMPRESSION," filed July 2, 2018.

[0002] Technical Field This disclosure describes embodiments that generally relate to video encoding. [Background technology]

[0003] The descriptions provided herein are intended to generally present the context for the present disclosure. Work described in this Background section, including work by currently designated inventors and aspects that may not qualify as prior art at the time of filing, is not admitted expressly or implicitly as prior art to the present disclosure.

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

[0005] One of the goals of video encoding and decoding is to reduce redundancy in a video input signal through compression. Compression can help reduce the bandwidth or storage space requirements mentioned above, sometimes by more than two orders of magnitude. Lossless compression, lossy compression, and combinations thereof can be employed. Lossless compression refers to techniques that reconstruct an exact replica of the original signal from a compressed version. When lossy compression is used, the reconstructed signal may differ from the original signal, but the distortion between the original and reconstructed signal is small enough to make the reconstructed signal useful for certain applications. In the case of video, lossy compression is widely used. The amount of acceptable distortion depends on the application; for example, users of certain consumer streaming applications tolerate higher distortion than users of television streaming applications. The achievable compression ratio can reflect the fact that the higher the allowable / tolerable distortion, the higher the achievable compression ratio.

[0006] Video encoders and decoders can use several broad types of techniques, including motion compensation, transforms, quantization, and entropy coding.

[0007] Video codec technology can include a technique called intra-coding. In intra-coding, sample values ​​are represented without reference to samples from previously reconstructed reference pictures or other data. In some video codecs, pictures are spatially subdivided into sample blocks. If all sample blocks are coded in intra mode, the picture may be an intra-picture. Intra-pictures and their derivatives (e.g., independent decoder refresh pictures) can be used to reset the decoder state and therefore can be used as the first picture or still image in a coded video bitstream and video session. Samples in intra-blocks can be transformed, and the transform coefficients can be quantized before entropy coding. Intra-prediction is a technique that minimizes sample values ​​in the pre-transform domain. In some cases, smaller transformed DC values ​​and smaller AC coefficients can require fewer bits to represent an entropy-coded block for a particular quantization step size.

[0008] Typically, intra-coding, as known from MPEG-2 generation encoding techniques, does not use intra-prediction. However, some new video compression techniques include techniques that rely on metadata and / or surrounding sample data obtained during encoding / decoding of spatially adjacent and preceding data blocks in decoding order. Hereinafter, such techniques will be referred to as "intra-prediction" techniques. Note that, at least in some cases, intra-prediction uses only reference data from the current picture being reconstructed, and not from a reference image.

[0009] Intra prediction may take many different forms. If a particular video coding technique can use one or more such techniques, the technique used can be coded as an intra prediction mode. In some cases, a mode may have sub-modes and / or parameters, which may be coded separately or included in a mode codeword. Because the codeword used for a particular mode / sub-mode / parameter combination can affect the coding efficiency gain from intra prediction, entropy coding techniques can be used to convert the codeword into a bitstream.

[0010] Certain modes of intra prediction were introduced via H.264, refined in H.265, and further refined in new coding techniques such as the Joint Search Model (JEM), Versatile Video Coding (VVC), and Benchmark Set (BMS). The predictor block can be formed using neighboring sample values ​​belonging to already available samples. Depending on the direction, the sample values ​​of the neighboring samples are copied into the predictor block. A reference to the direction in use can be coded into the bitstream, or it can be predicted itself. Summary of the Invention [Problem to be solved by the invention]

[0011] Referring to Figure 1, a subset of nine known prediction directions from the 35 possible prediction directions in H.265 is depicted in the lower right. The point where the arrows converge (101) represents the predicted sample. The arrows represent the direction in which the sample is predicted. For example, arrow (102) represents predicting sample (101) from one or more samples at the top right and at a 45-degree angle with the horizontal. Similarly, arrow (103) represents predicting sample (101) from one or more samples at a 22.5-degree angle with the horizontal to the lower right of sample (101).

[0012] Continuing with reference to FIG. 1, a square block (104) of 4×4 samples (indicated by a thick dashed line) is depicted in the upper right corner. The square block (104) contains 16 samples, each represented by "S," its position in the Y dimension (e.g., row index) and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample in the Y dimension (from the top) and the first sample in the X dimension (from the left). Similarly, sample S44 is the fourth sample in both the Y and X dimensions of the block (104). Because the block size is 4×4 samples, S44 is located in the lower right corner. Also depicted are reference samples, which follow a similar numbering scheme. The reference samples are represented by R, their Y position (e.g., row index) and X position (column index) relative to the block (104). In both H.264 and H.265, the predicted samples are adjacent to the block being reconstructed, so there is no need to use negative values.

[0013] Intra-picture prediction is performed by copying reference sample values ​​from neighboring samples according to the signaled prediction direction. For example, suppose the coded video bitstream includes signaling indicating that for a given block, samples are predicted from one or more prediction samples in the prediction direction consistent with arrow (102), i.e., in the upper right corner, at a 45-degree angle with the horizontal. In this case, samples S41, S32, S23, and S14 are predicted from the same R05. Next, sample S44 is predicted from 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 develops, the number of possible directions also increases. In H.264 (2003), nine different directions can be represented. This increased to 33 in H.265 (2013), and at the time of publication, JEM / VVC / BMS can support up to 65 directions. Experiments have been conducted to identify the most likely directions, and certain techniques in entropy coding are used to represent these possible directions using fewer bits, with certain penalties for relatively impossible directions. It may also be possible to predict the direction itself based on the neighboring directions used in neighboring decoded blocks.

[0016] FIG. 2 is a schematic diagram 201 showing the increase in the number of prediction directions over time based on the 65 intra prediction directions of JEM.

[0017] The mapping of intra-prediction direction bits to indicate directions in the coded video bitstream may vary among different video coding techniques, ranging from simple direct mappings involving prediction directions, intra-prediction modes, and codewords to complex adaptive schemes involving most-likely-occurring modes and similar techniques. Those skilled in the art will be readily familiar with these techniques. However, in all cases, there will be some directions that are statistically less likely to appear in the video content than certain other directions. Because video compression aims to reduce redundancy, a well-functioning video coding technique will represent these relatively impossible directions with a larger number of bits than the more likely directions. [Means for solving the problem]

[0018] Aspects of the present disclosure provide methods and apparatus for video encoding. In some examples, the apparatus includes a processing circuit. The processing circuit decodes prediction information for a first block from an encoded video bitstream. The first block is a non-square block, and the prediction information for the first block indicates a first intra-prediction mode in a first set of intra-prediction modes for square blocks. The processing circuit then determines that the first intra-prediction mode is within a subset of intra-prediction modes disabled for non-square blocks in the first set of intra-prediction modes for square blocks and remaps the first intra-prediction mode to a second intra-prediction mode in a second set of intra-prediction modes for non-square blocks. The second set of intra-prediction modes does not include the subset of disabled intra-prediction modes. The processing circuit also reconstructs at least one sample of the first block based on the second intra-prediction mode.

[0019] In some examples, the processing circuit determines an intra-prediction angle parameter associated with the second intra-prediction mode and reconstructs at least one sample of the first block based on the intra-prediction angle parameter. In examples, the second intra-prediction mode is not included in the first set of intra-prediction modes.

[0020] In some examples, the processing circuit determines the second set of intra prediction modes based on the shape of the first block. In some embodiments, the processing circuit calculates an aspect ratio of the first block and determines a subset of disabled intra prediction modes for the non-square block based on the aspect ratio of the first block. For example, if the ratio of the long side to the short side of the first block is less than or equal to 2, the subset of disabled intra prediction modes has a first number of disabled intra prediction modes, and if the ratio is greater than or equal to 4, the subset of disabled intra prediction modes has a second number of disabled intra prediction modes, the second number being greater than the first number.

[0021] In some embodiments, the processing circuit determines that the width of the first block is greater than the height of the first block and detects that the first intra-prediction mode is within a subset of disabled intra-prediction modes in the first set of intra-prediction modes starting with a left-bottom diagonal mode. In other embodiments, the processing circuit determines that the height of the first block is greater than the width of the first block and detects that the first intra-prediction mode is within a subset of disabled intra-prediction modes in the first set of intra-prediction modes starting with a right-bottom diagonal mode.

[0022] In some embodiments, the processing circuit determines that the width of the first block is greater than the height of the first block and remaps the first intra-prediction mode to the second intra-prediction mode by adding a value to the mode number associated with the first intra-prediction mode. In some examples, the processing circuit determines that the height of the first block is greater than the width of the first block and converts the first intra-prediction mode to the second intra-prediction mode by subtracting a value from the mode number associated with the first intra-prediction mode.

[0023] Aspects of the present disclosure further provide a non-transitory computer-readable medium for storing instructions that, when executed by a computer for video decoding, cause the computer to perform a method for video encoding. [Brief explanation of the drawings]

[0024] Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and drawings. [Figure 1] 1 is a schematic diagram of a subset of intra-prediction modes according to H.265. [Figure 2] FIG. 10 is an explanatory diagram of the intra prediction direction using JEM. [Figure 3] FIG. 3 is a schematic diagram of a simplified block diagram of a communication system (300) according to an embodiment. [Figure 4]FIG. 4 is a schematic diagram of a simplified block diagram of a communication system (400) according to an embodiment. [Figure 5] FIG. 2 is a schematic diagram of a simplified block diagram of a decoder according to an embodiment; [Figure 6] FIG. 2 is a schematic diagram of a simplified block diagram of an encoder according to an embodiment; [Figure 7] 10 shows a block diagram of an encoder according to another embodiment. [Figure 8] 10 shows a block diagram of a decoder according to another embodiment; [Figure 9] A schematic diagram (900) is shown to explain an example of a wide-angle mode. [Figure 10] Some examples of remapping normal intra prediction modes to wide-angle modes are given below. [Figure 11] Some other examples of remapping normal intra prediction modes to wide-angle modes are shown. [Figure 12] 10A and 10B are schematic diagrams illustrating normal intra prediction directions and wide-angle intra prediction directions. [Figure 13] 13 shows a flowchart outlining a process (1300) according to an embodiment of the present disclosure. [Figure 14] FIG. 1 is a schematic diagram of a computer system according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] FIG. 3 illustrates a simplified block diagram of a communication system (300) according to an embodiment of the present disclosure. The communication system (300) includes multiple terminal devices that can communicate with each other, for example, via a network (350). For example, the communication system (300) includes a pair of terminal devices (310) and (320) connected to each other via the network (350). In the example of FIG. 3, the pair of terminal devices (310) and (320) perform unidirectional data transmission. For example, the terminal device (310) can encode video data (e.g., a video picture stream captured by the terminal device (310)) and transmit it to another terminal device (320) via the network (350). The encoded video data may be transmitted in the form of one or more encoded video bitstreams. The terminal device (320) can receive the encoded video data from the network (350), decode the encoded video data to reconstruct video pictures, and display the video pictures based on the reconstructed video data. One-way data transmission is common in media service applications, for example.

[0026] In another embodiment, the communication system (300) includes a second pair of terminal devices (330), (340) for performing bidirectional transmission of encoded video data, such as may occur during a video conference. For bidirectional data transmission, in an example, each of the terminal devices (330), (340) can encode and transmit video data (e.g., a video picture stream captured by the terminal device) to another of the terminal devices (330), (340) via the network (350). Each of the terminal devices (330), (340) can further receive encoded video data transmitted from another of the terminal devices (330), (340), decode the encoded video data to reconstruct video pictures, and display the video pictures on an accessible display device based on the reconstructed video data.

[0027] In the example of FIG. 3 , terminal devices 310, 320, 330, and 340 are shown as a server, a personal computer, and a smartphone, respectively, although the principles of the present disclosure are not limited thereto. Embodiments of the present disclosure apply to laptop computers, tablets, media players, and / or dedicated videoconferencing equipment. Network 350 represents any number of networks, including, for example, wired and / or wireless communication networks, for transmitting encoded video data between terminal devices 310, 320, 330, and 340. Communication network 350 may exchange data over circuit-switched and / or packet-switched channels. Exemplary networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of this description, unless otherwise noted below, the architecture and topology of network 350 may not be important to the operation of the present disclosure.

[0028] 4 illustrates the placement of video encoders and decoders in a streaming environment. As an example of application of the disclosed subject matter, the disclosed subject matter applies equally to other applications that support video, including video conferencing, digital television, and storing compressed video and the like on digital media, including CDs, DVDs, memory sticks, and the like.

[0029] The streaming system can include a capture subsystem (413), which can include a video source (401), such as a digital camera, for creating an uncompressed video picture stream (402). In an example, the video picture stream (402) includes captured samples from the digital camera. The video picture stream (402) is processed by electronics (420), which includes a video encoder (403) coupled to the video source (401). The video encoder (403) is depicted as a thick line to emphasize its large amount of data compared to the encoded video data (404) (or encoded video bitstream). The video encoder (403) can include hardware, software, or a combination thereof to implement or perform aspects of the disclosed subject matter, as described in detail below. The encoded video data (404) (or encoded video bitstream (404)) can be stored on the streaming server (405) for future use; the encoded video data is depicted as a thin line to emphasize its small amount of data compared to the video picture stream (402). One or more streaming client subsystems, such as the client subsystems (406) and (408) in FIG. 4, can access the streaming server (405) to retrieve replicas (407) and (409) of the encoded video data (404). The client subsystem (406) may include a video decoder (410), for example, in an electronic device (430). The video decoder (410) decodes the incoming replica of the encoded video data (407) and creates an outgoing video picture stream (411) that can be rendered on a display (412) (e.g., a screen) or other rendering device (not shown). In some streaming systems, the encoded video data 404, 407, and 409 (e.g., video bitstreams) may be encoded according to a particular video encoding / compression standard, examples of which include the ITU-T H.265 recommendation.In an example, a video coding standard under development is informally called Versatile Video Coding, or VVC, and the disclosed subject matter can be used in the context of VVC.

[0030] Note that the electronics 420 and 430 may include other components (not shown). For example, the electronics 420 may include a video decoder (not shown), and the electronics 430 may include a video encoder (not shown).

[0031] 5 shows a block diagram of a video decoder (510) according to an embodiment of the present disclosure. The video decoder (510) can be included in electronic equipment (530). The electronic equipment (530) can include a receiver (531) (e.g., receiving circuitry). The video decoder (510) can be used in place of the video decoder (410) in the example of FIG. 4.

[0032] The receiver (531) can receive one or more coded video sequences to be decoded by the video decoder (510), and in the same or another embodiment, can receive one coded video sequence at a time, with the decoding of each coded video sequence being independent of the other coded video sequences. The coded video sequences can be received from the channel (501), which can be a hardware / software link to a storage device for storing the coded video data. The receiver (531) can receive the coded video data accompanied by other data, such as coded audio data and / or auxiliary data streams that are forwarded to respective using entities (not shown). The receiver (531) can separate the coded video sequences from the other data. To prevent network jitter, a buffer memory (515) can be coupled between the receiver (531) and the entropy decoder / parser (520) (hereinafter referred to as "parser (520)"). In certain applications, the buffer memory (515) is part of the video decoder (510). In other applications, the buffer memory may be external to the video decoder 510 (not shown). In still other applications, there may be a buffer memory (not shown) external to the video decoder 510, for example, to prevent network jitter, and another buffer memory 515 internal to the video decoder 510, for example, to handle broadcast timing. The receiver 531 may not need the buffer memory 515, or the buffer memory 515 may be smaller, when receiving data from a store-and-forward device or an isochronous real-time network with sufficient bandwidth and controllability.For use in a best-effort packet network such as the Internet, a buffer memory (515) may be required, which may be relatively large and advantageously have an adaptive size, and may be implemented at least in part in an operator system or similar element (not shown) external to the video decoder (510).

[0033] The video decoder (510) may include a parser (520) to reconstruct symbols (521) based on the encoded video sequence. These symbol categories may include information for managing the operation of the video decoder (510) and information for controlling a display device, such as a display (512) (e.g., a screen), which may not be part of the electronic device (530) but may be coupled to it, as shown in FIG. 5. Control information for the display device may be in the form of a supplemental enhancement information (SEI) message or a video usability information (VUI) parameter set fragment (not shown). The parser (520) may parse / entropy decode the received encoded video sequence. The encoding of the encoded video sequence may conform to a video coding technology or standard and may follow various principles, including variable-length coding, Huffman coding, arithmetic coding with or without context-sensitive coding, etc. The parser (520) extracts a subgroup parameter set for at least one of the subgroups of pixels in the video decoder from the coded video sequence based on at least one parameter corresponding to the group, including a Group of Pictures (GOP), a picture, a tile, a slice, a macroblock, a coding unit (CU), a block, a transform unit (TU), a prediction unit (PU), etc. The parser (520) may also extract information from the coded video sequence, such as transform coefficients, quantizer parameter values, and motion vectors.

[0034] The parser (520) can create symbols (521) by performing entropy decoding / parsing operations on the video sequence received from the buffer memory (515).

[0035] The reconstruction of the symbols (521) involves several different units, depending on the type of coded video picture or part thereof (e.g., inter-picture vs. intra-picture, inter-block vs. intra-block) and other factors. The units involved and the type of involvement can be controlled by subgroup control information parsed by the parser (520) from the coded video sequence. For simplicity, the flow of such subgroup control information between the parser (520) and the following units is not shown:

[0036] In addition to the functional blocks already mentioned, the video decoder (510) can be conceptually subdivided into the following functional units. In an actual implementation operating under business constraints, several of these units may interact closely with each other and may be at least partially integrated with each other. However, for purposes of illustrating the disclosed subject matter, a conceptual subdivision into the following functional units is appropriate:

[0037] The first unit is a scalar / inverse transform unit (551). The scalar / inverse transform unit (551) receives quantized transform coefficients and control information as symbols (521) from the parser (520), including the transform scheme to be used, block size, quantization factor, quantization scaling matrix, etc. The scalar / inverse transform unit (551) can output blocks containing sample values ​​that can be input to an aggregator (555).

[0038] In some cases, the output samples of the scaler / inverse transform unit (551) may relate to intra-coded blocks, i.e., blocks that do not use prediction information from a previously reconstructed picture but can use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by the intra-picture prediction unit (552). In some cases, the intra-picture prediction unit (552) generates blocks of the same size and shape as the block being reconstructed using surrounding, already reconstructed information obtained from the current picture buffer (558). For example, the current picture buffer (558) buffers a partially reconstructed and / or fully reconstructed current picture. In some cases, the aggregator (555) adds, on a sample-by-sample basis, the prediction information generated by the intra-prediction unit (552) to the output sample information provided by the scaler / inverse transform unit (551).

[0039] In other cases, the output samples of the scalar / inverse transform unit (551) may relate to an inter-coded, potentially motion-compensated block. In such cases, the motion-compensated prediction unit (553) may access a reference picture memory (557) to obtain samples for prediction. After motion-compensating the obtained samples based on the symbols (521) for the block, these samples are added by the aggregator (555) to the output of the scalar / inverse transform unit (551) (referred to as residual samples or residual signals in such cases) to generate output sample information. The addresses in the reference picture memory (557) from which the motion-compensated prediction unit (553) obtains the prediction samples are controlled by motion vectors, which are obtained by the motion-compensated prediction unit (553) and have the form of symbols (521) with X, Y, and reference picture components, for example. Motion compensation may also include interpolation of sample values ​​extracted from the reference picture memory (557) when sub-sample accurate motion vectors are used, motion vector prediction mechanisms, and so on.

[0040] The output samples of the aggregator (555) are processed by various loop filtering techniques in a loop filter unit (556). The video compression techniques can include in-loop filtering techniques, but they can also be responsive to meta-information obtained during decoding of previous portions of the coded picture or coded video sequence (in decoding order), and to previously reconstructed loop-filtered sample values. The in-loop filtering techniques are controlled by parameters contained in the coded video sequence (also called the coded video bitstream) and provided to the loop filter unit (556) as symbols (521) from the parser (520).

[0041] The output of the loop filter unit (556) may be a sample stream that can be output to a display device (512) and stored in a reference picture memory (557) for use in future inter-picture prediction.

[0042] Once a coded picture is fully reconstructed, it can be used as a reference picture for future prediction. For example, once the coded picture corresponding to the current picture is fully reconstructed and the coded picture is recognized as a reference picture (e.g., via the parser (520)), the current picture buffer (558) can become part of the reference picture memory (557), and a new current picture buffer can be reallocated before starting reconstruction of a subsequent coded picture.

[0043] The video decoder (510) can perform decoding operations according to a predetermined video compression technology, for example, in the ITU-T H.265 Recommendation. The encoded video sequence can comply with the syntax specified by the video compression technology or standard being used, in the sense that the encoded video sequence conforms to both the syntax of the video compression technology or standard and the profile recorded in the video compression technology or standard. Specifically, the profile can select specific tools from all tools available in the video compression technology or standard as the only tools available according to this profile. Compliance also requires that the complexity of the encoded video sequence be within a range limited by the level of the video compression technology or standard. In some cases, the level limits 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 imposed by the level can be further limited, in some cases, by metadata for managing the HRD buffer signaled in the encoded video sequence and by the specifications of a hypothetical reference decoder (HRD).

[0044] In embodiments, the receiver (531) can receive additional (redundant) data along with the encoded video. The additional data may be included as part of the encoded video sequence. The additional data can be used by the video decoder (510) to properly decode the data and / or more accurately reconstruct the original video data. The additional data can be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0045] 6 shows a block diagram of a video encoder (603) according to an embodiment of the present disclosure. The video encoder (603) is included in an electronic device (620). The electronic device (620) includes a transmitter (640) (e.g., a transmission circuit). The video encoder (603) may be used in place of the video encoder (403) in the example of FIG. 4.

[0046] The video encoder (603) receives video samples from a video source (601) (which is not part of the electronic device (620) in the example of FIG. 6), which can capture video images that are encoded by the video encoder (603). In another example, the video source (601) is part of the electronic device (620).

[0047] The video source (601) can provide a source video sequence in the form of a digital video sample stream to be encoded by the video encoder (603). The digital video sample stream can have any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, etc.), any suitable color space (e.g., BT.601 Y CrCB, RGB, etc.), and any suitable sampling configuration (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media services system, the video source (601) can be a storage device for storing pre-prepared video. In a video conferencing system, the video source (601) can be a camera for capturing local image information as a video sequence. The video data can be provided as multiple individual pictures that, when viewed sequentially, convey motion. The pictures themselves can be organized as a spatial pixel array, with each pixel containing one or more samples, depending on the sampling configuration, color space, etc. used. The relationship between pixels and samples is readily apparent to those skilled in the art. The following discussion focuses on samples.

[0048] According to an embodiment, the video encoder (603) can encode and compress pictures of a source video sequence into an encoded video sequence (643) in real time or under any other time constraints required by the application. Running at an appropriate encoding rate is one of the functions of the controller (650). In some embodiments, the controller (650) controls and is operatively coupled to other functional units described below. For simplicity, coupling is not shown. Parameters set by the controller (650) may include rate control-related parameters (e.g., picture skip, quantizer, lambda value for rate-distortion optimization techniques), picture size, group of pictures (GOP) placement, maximum motion vector search range, etc. The controller (650) may be configured to have other suitable functions, which are associated with optimizing the video encoder (603) for a particular system design.

[0049] In some embodiments, the video encoder (603) is configured to operate in an encoding loop. As a highly simplified example, the encoding loop may include a source encoder (630) (e.g., responsible for creating a symbol-like symbol stream based on an input picture to be encoded and a reference picture) and a (local) decoder (633) embedded in the video encoder (603). The decoder (633) reconstructs the symbols to create sample data in the same way that a (remote) decoder creates sample data (because any compression between symbols and the encoded video bitstream is lossless in the video compression techniques considered in the disclosed subject matter). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Because decoding the symbol stream produces bit-exact results independent of the location (local or remote) of the decoder, the contents of the reference picture memory (634) are bit-exact between the local and remote encoders. In other words, the predictive part of the encoder sees as reference picture samples exactly the same sample values ​​that the decoder "sees" when using prediction during decoding. This basic principle of reference picture synchrony (and the drift that occurs when synchrony cannot be maintained, e.g., from channel error) also applies to several related fields.

[0050] The operation of the "local" decoder (633) may be the same as the operation of the "remote" decoder (e.g., the video decoder (510)) described in detail above in conjunction with Figure 5. However, with further brief reference to Figure 5, if symbols are available and the entropy encoder (645) and parser (520) losslessly encode / decode the symbols into an encoded video sequence, the entropy decoding portion of the video decoder (510), including the buffer memory (515) and parser (520), may not be fully implemented in the local decoder (633).

[0051] In this case, it is understood that in addition to the analysis / entropy decoding present in the decoder, any decoder techniques necessarily exist in the corresponding encoder in essentially the same functional form. For this reason, the disclosed subject matter focuses on the operation of the decoder. The description of the encoder technique can be simplified because the encoder technique and the fully described decoder technique are mutually inverse. Further description is only necessary in certain areas and is provided below.

[0052] During operation, in some examples, the source encoder (630) may perform motion-compensated predictive encoding, i.e., perform predictive encoding on an input picture with reference to one or more previously encoded pictures from a video sequence designated as “reference pictures.” In this manner, the encoding engine (632) encodes differences between pixel blocks of the input picture and pixel blocks of reference pictures that can be selected as predictive references for the input picture.

[0053] The local video decoder (633) can decode the encoded video data of pictures that can be designated as reference pictures based on symbols created 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 a video decoder (not shown in FIG. 6), the reconstructed video sequence can generally be a replica of the source video sequence with some error. The local video decoder (633) can replicate the decoding process performed by the video decoder on the reference pictures and store the reconstructed reference pictures in a reference picture cache (634). In this way, as reconstructed reference pictures obtained from a remote video decoder (without transmission error), the video encoder (603) can locally store replicas of reconstructed reference pictures that have common content.

[0054] The predictor (635) performs a prediction search for the coding engine (632). That is, for a new picture to be coded, the predictor (635) can search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or metadata, such as reference picture motion vectors and block shapes, that can be used as suitable prediction references for the new picture. The predictor (635) can find suitable prediction references by operating pixel block by pixel block on the sample blocks. In some cases, as determined by the search results obtained by the predictor (635), the input picture can have prediction references derived from multiple reference pictures stored in the reference picture memory (634).

[0055] The controller (650) can manage the encoding operations of the source encoder (630), including, for example, setting parameters and subgroup parameters for encoding the video data.

[0056] The output of all of the functional units can be entropy coded by an entropy coder (645), which converts the symbols produced by each functional unit into an encoded video sequence by losslessly compressing the symbols according to techniques known to those skilled in the art (e.g., Huffman coding, variable length coding, arithmetic coding, etc.).

[0057] The transmitter (640) can buffer the encoded video sequence created by the entropy encoder (645) in preparation for transmission over a communication channel (660), which may be a hardware / software link to a storage device for storing the encoded video data. The transmitter (640) can merge the encoded video data from the video encoder (603) with other data to be transmitted, such as encoded audio data and / or auxiliary data streams (sources not shown).

[0058] The controller (650) can manage the operation of the video encoder (603). During encoding, the controller (650) assigns each encoded picture a particular encoding picture type, which can affect the encoding technique applied to the corresponding picture. For example, pictures are typically assigned as one of the following picture types:

[0059] An intra picture (I-picture) may be a picture that is coded and decoded without using any other picture in a sequence as a source of prediction. Some video codecs allow different types of intra pictures, including, for example, independent decoder refresh ("IDR") pictures. Those skilled in the art are aware of these variations of I-pictures and their corresponding uses and characteristics.

[0060] A predicted picture (P picture) may be a picture that is coded and decoded using intra- or inter-prediction, which uses at most one motion vector and reference index to predict sample values ​​for each block.

[0061] A bidirectionally predicted picture (B-picture) may be a picture that is encoded and decoded using intra- or inter-prediction, which uses at most two motion vectors and reference indices to predict sample values ​​for each block. Similarly, multiple predicted pictures apply more than two reference pictures and associated metadata to the reconstruction of a single block.

[0062] A source picture is typically spatially subdivided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and can be coded block by block. These blocks can be predictively coded with reference to other (coded) blocks, which are determined by the coding assignment applied to the block's corresponding picture. For example, blocks of an I-picture can be non-predictively coded, or they can be predictively coded (spatial prediction or intra prediction) with reference to coded blocks of the same picture. Pixel blocks of a P-picture can be predictively coded via spatial or temporal prediction with reference to one previously coded reference picture. Blocks of a B-picture can be predictively coded via spatial or temporal prediction with reference to one or two previously coded reference pictures.

[0063] The video encoder (603) may perform encoding operations based on a given video encoding technique or standard, such as the ITU-T H.265 recommendation. In doing so, the video encoder (603) may perform various compression operations, including predictive encoding operations that use temporal and spatial redundancies in the input video sequence. Thus, the encoded video data conforms to the syntax specified by the video encoding technique or standard being used.

[0064] In an embodiment, the transmitter (640) transmits 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, Supplemental Enhancement Information (SEI) messages, Video Usability Information (VUI) parameter set fragments, etc.

[0065] Video may be captured as multiple source pictures (video pictures) in a time sequence. Intra-picture prediction (commonly abbreviated to intra-prediction) uses spatial correlation within a particular picture, while inter-picture prediction uses correlation (temporal or otherwise) between pictures. In an example, a particular picture being coded / decoded, called the current picture, is divided into blocks. If a block in the current picture is similar to a reference block in a previously coded and still buffered reference picture in the video, the block in the current picture can be coded 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 for identifying the reference picture when multiple reference pictures are used.

[0066] In some embodiments, inter-picture prediction can use bidirectional prediction techniques. Bidirectional prediction techniques use two reference pictures, a first reference picture and a second reference picture, that are earlier in decoding order than the current picture in the video (but potentially earlier and later in display order, respectively). A block in the current picture can be coded with a first motion vector that points to a first reference block in the first reference picture and a second motion vector that points to a second reference block in the second reference picture. A block can be predicted by a combination of the first and second reference blocks.

[0067] In addition, to improve coding efficiency, a merge mode technique is used for inter-picture prediction.

[0068] According to some embodiments of the present disclosure, prediction such as inter-picture prediction and intra-picture prediction is performed for each block. For example, according to the HEVC standard, pictures in a video picture sequence are divided into coding tree units (CTUs) for compression, and the CTUs in a picture have the same size, such as 64x64 pixels, 32x32 pixels, or 16x16 pixels. A CTU typically includes three coding tree blocks (CTBs): one luma CTB and two chroma CTBs. Each CTU can be recursively divided into one or more coding units (CUs) using a quadtree. For example, a 64x64 pixel CTU may be divided into one 64x64 pixel CU, four 32x32 pixel CUs, or sixteen 16x16 pixel CUs. In an example, each CU is analyzed to determine a prediction type for the CU, such as an inter-prediction type or an intra-prediction type. The CU is divided into one or more prediction units (PUs) according to temporal and / or spatial predictability. Each PU generally includes a luma prediction block (PB) and two chroma PBs. In an embodiment, a prediction operation in coding (encoding / decoding) is performed for each prediction block. When using a luma prediction block as an example of a prediction block, the prediction block includes a matrix of pixel values ​​(e.g., luma values) of 8x8 pixels, 16x16 pixels, 8x16 pixels, 16x8 pixels, etc.

[0069] 7 shows a diagram of a video encoder (703) according to another embodiment of this disclosure. The video encoder (703) is arranged to receive a processed block of sample values ​​(e.g., a predictive block) in a current video picture in a video picture sequence and to encode the processed block into a coded picture that is part of the coded video sequence. In an example, the video encoder (703) is used in place of the video encoder (403) in the example of FIG. 4.

[0070] In an HEVC example, the video encoder (703) receives a matrix of sample values ​​for a processing block, the processing block being, for example, a predicted block of 8x8 samples. The video encoder (703) determines, for example, by rate-distortion optimization, whether to optimally encode the processing block using intra mode, inter mode, or bidirectional prediction mode. If the processing block is encoded in intra mode, the video encoder (703) encodes the processing block into a coded picture using intra prediction techniques. If the processing block is encoded in inter mode or bidirectional prediction mode, the video encoder (703) can encode the processing block into a coded picture using inter prediction or bidirectional prediction techniques, respectively. In some video encoding techniques, the merge mode may be an inter-picture prediction submode, which does not use coded motion vector components outside the predictor but obtains motion vectors from one or more motion vector predictors. In other video encoding techniques, there may be motion vector components applied to the theme block. In some examples, the video encoder (703) includes other components, such as a mode decision module (not shown) for determining the mode of the processing block.

[0071] In the example of FIG. 7, the video encoder (703) includes an inter encoder (730), an intra encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721), and an entropy encoder (725), concatenated as shown in FIG. 7.

[0072] The inter encoder (730) is configured to receive samples of a current block (e.g., a processing block), compare the block with one or more reference blocks in a reference picture (e.g., blocks in a previous picture and a subsequent picture), generate inter prediction information (e.g., redundant information description according to an inter coding technique, motion vectors, merge mode information), and calculate an inter prediction result (e.g., a predicted block) based on the inter prediction information using any suitable technique. In some examples, the reference picture is a decoding reference picture decoded based on the coded video information.

[0073] The intra encoder (722) is configured to receive samples of a current block (e.g., a processing block), optionally compare the current block with coded blocks in the same picture, generate transformed quantized coefficients, and optionally further generate intra prediction information (e.g., intra prediction direction information according to one or more intra coding techniques).

[0074] The general-purpose controller (721) is configured to determine general-purpose control data and control other components of the video encoder (703) based on the general-purpose control data. In an example, the general-purpose controller (721) determines the mode of a block and provides a control signal to the switch (726) based on the mode. For example, if the mode is intra-mode, the general-purpose controller (721) controls the switch (726) to select intra-mode results for use by the residual calculator (723) and controls the entropy encoder (725) to select intra-prediction information for inclusion in the bitstream; if the mode is inter-mode, the general-purpose controller (721) controls the switch (726) to select inter-prediction results for use by the residual calculator (723) and controls the entropy encoder (725) to select inter-prediction information for inclusion in the bitstream.

[0075] The residual calculator (723) is configured to calculate the difference (residual data) between the received block and a prediction result selected from the intra-encoder (722) or the inter-encoder (730). The residual encoder (724) operates on the residual data and is configured to encode the residual data to generate transform coefficients. In an example, the residual encoder (724) is configured to transform the residual data in the frequency domain to generate transform coefficients. The transform coefficients are then quantized to obtain quantized transform coefficients.

[0076] The entropy encoder (725) is configured to format the bitstream to include the coded block. The entropy encoder (725) is configured to include various information in accordance with an appropriate standard, such as the HEVC standard. In an example, the entropy encoder (725) is configured to include general control data, selected prediction information (e.g., intra-prediction information or inter-prediction information), residual information, and other appropriate information in the bitstream. Note that, according to the disclosed subject matter, there is no residual information when coding a block in a bi-prediction mode or a merged sub-mode of an inter mode.

[0077] 8 shows a diagram of a video decoder (810) according to another embodiment of this disclosure. The video decoder (810) is configured to receive coded pictures that are part of a coded video sequence and decode the coded pictures to generate reconstructed pictures. In an example, the video decoder (810) is used in place of the video decoder (410) in the example of FIG. 4.

[0078] In the example of FIG. 8, the video decoder (810) includes an entropy decoder (871), an inter decoder (880), a residual decoder (873), a reconstruction module (874), and an intra decoder (872), concatenated as shown in FIG.

[0079] The entropy decoder (871) is configured to reconstruct specific symbols based on the coded picture, which indicate the syntax elements that make up the coded picture. Such symbols may include, for example, a mode for coding a block (e.g., intra mode, inter mode, bidirectional prediction mode, merge submode, or the latter two in another submode), prediction information (e.g., intra prediction information or inter prediction information) that identifies some samples or metadata used for prediction by the intra decoder (872) or inter decoder (880), respectively, residual information in the form of, for example, quantized transform coefficients, etc. In an example, if the prediction mode is an inter or bidirectional prediction mode, the inter prediction information is provided to the inter decoder (880), and if the prediction type is an intra prediction type, the intra prediction information is provided to the intra decoder (872). The residual information is dequantized and provided to the residual decoder (873).

[0080] The inter decoder (880) is configured to receive the inter prediction information and to generate an inter prediction result based on the inter prediction information.

[0081] The intra decoder (872) is configured to receive the intra prediction information and to generate a prediction result based on the intra prediction information.

[0082] The residual decoder (873) is configured to perform inverse quantization to extract dequantized transform coefficients, and process the dequantized transform coefficients to transform the residual from the frequency domain to the spatial domain. The residual decoder (873) may also require some control information (to include quantizer parameters (QP)), which can be provided from the entropy decoder (871) (datapath not shown as this is only low-volume control information).

[0083] The reconstruction module (874) is arranged to combine, in the spatial domain, the residual output from the residual decoder (873) with the prediction result (output from the inter-prediction module or the intra-prediction module, as the case may be), to form a reconstructed block, which may be part of a reconstructed picture, which may in turn be part of a reconstructed video, although other suitable operations, such as a deblocking operation, may be performed to improve visual quality.

[0084] It should be noted that any suitable technology may be used to implement the video encoders (403), (603), (703) and video decoders (410), (510), (810). In some embodiments, the video encoders (403), (603), (703) and video decoders (410), (510), (810) may be implemented by one or more integrated circuits. In other embodiments, the video encoders (403), (603), (703) and video decoders (410), (510), (810) may be implemented by one or more processors executing software instructions. According to some aspects of the present disclosure, in the case of intra prediction, a wide-angle mode may be used to compress the video and reduce bandwidth or storage space requirements.

[0085] 9 shows a schematic diagram (900) for explaining an example of a wide-angle mode. Generally, intra-prediction ranges from a 45-degree direction in the upper right corner (corresponding to the arrow pointing to 34 in FIG. 9, indicating mode 34) to a 45-degree direction in the lower left corner (corresponding to the arrow pointing to 2 in FIG. 9, indicating mode 2), and is referred to as a normal intra-prediction mode. When applying the 35 HEVC intra-prediction mode, mode 2 is referred to as a bottom-left diagonal mode, and mode 34 is referred to as a top-right diagonal mode. Wide angles beyond the prediction direction range covered by the normal intra-prediction mode correspond to wide-angle intra-prediction modes.

[0086] In some examples, a wide-angle intra-prediction direction is associated with one normal intra-prediction direction. For example, the wide-angle intra-prediction direction and the associated intra-prediction direction capture the same directionality but use reference samples on the opposite side (left column or top row). In examples, a wide-angle intra-prediction mode is signaled by transmitting a one-bit flag for the associated direction that has a wide-angle "inverted mode" enabled. In the example of Figure 9, the first direction with an arrow pointing to 35 is the wide-angle intra-prediction direction and is associated with the second direction with an arrow pointing to 03. Therefore, the first direction can be signaled by transmitting a one-bit flag for the second direction.

[0087] In an embodiment, for 33-directional angular intra prediction, the availability of new modes is limited to the 10 directional modes closest to the 45-degree diagonal top-right mode (i.e., mode 34 when using 35 normal intra modes) and the bottom-left mode (i.e., mode 2 when using 35 normal intra modes). The actual sample prediction process follows the prediction process in HEVC or VVC.

[0088] The example of FIG. 9 shows 33 intra-prediction directions associated with modes 2 to 34. In the example, if the width of a block is greater than the height of the block, the directions associated with modes 35 and 36 can be used as wide-angle intra-prediction directions. Modes 3 and 4 then have an extra flag indicating whether to use the indicated mode or the inverted wide-angle directions of modes 35 and 36. Some examples (e.g., Global Video Coding Test Model 1 (VTM1)) support square and non-square blocks with partition structures such as quadtree, binary tree, and ternary tree (QT+BT+TT). If intra-prediction for square and non-square blocks is designed to use the same intra-prediction mode (e.g., modes 2 to 34) as for square blocks, the intra-prediction modes (e.g., modes 2 to 34 in the example of FIG. 9) are not efficient for non-square blocks. Wide-angle prediction modes (e.g., modes 35 and 36 in the example of FIG. 9) can be used to more efficiently encode non-square blocks.

[0089] In some examples, the signaling of wide-angle intra-prediction depends on the intra-prediction mode, so there is a parsing dependency problem when parsing the wide-angle control flag (the intra-prediction mode must be reconstructed in the parsing process).

[0090] In some embodiments, some intra-prediction modes for square blocks are remapped to wide-angle prediction modes for non-square blocks. In an example, the remapping process removes some intra-prediction modes for square blocks from the set of intra-prediction modes originally used for the square blocks, and adds the same number of wide-angle prediction modes to this set of intra-prediction modes to form a new set of intra-prediction modes for the particular non-square block. Thus, a certain number of modes in the intra-prediction mode set are changed, while other modes remain the same. In some examples, the certain number of changed modes depends on the shape of the block, for example, the aspect ratio of the block.

[0091] For square blocks, a set of normal intra prediction modes is applied for intra prediction, and the number of modes in the set of normal intra prediction modes may be 35, 67, etc. For non-square blocks, some modes may be removed from the set of normal intra prediction modes and the same number of wide-angle modes (as the removed modes) may be added to the remaining normal intra prediction modes to form a new set of intra prediction modes. Thus, in the example, the signaled mode indices for non-square blocks and square blocks are the same, and the non-square blocks and square blocks share the same mode encoding algorithm. For 35 normal intra prediction modes, the indices of the added top-right wide-angle modes are mode 35, mode 36, mode 37, mode 38, etc., and the indices of the added bottom-left wide-angle modes are mode -1, mode -2, mode -3, mode -4, etc.

[0092] 10 and 11 show two examples of remapping some normal intra prediction modes to wide-angle modes. In FIG. 10, modes 2 through 34 relate to the intra prediction directions shown in FIG. 10. Modes 2 through 34, together with modes 0 and 1, form a set of normal intra prediction modes for a square block. In the example of FIG. 10, modes 2 and 3 (indicated by dashed lines) are removed from the set of normal intra prediction modes. Wide-angle modes 35 and 36 (indicated by dotted lines) are also added, with the direction of mode 35 opposite that of mode 3 (indicated by (1001)) and the direction of mode 36 opposite that of mode 4 (indicated by (1002)). Thus, modes 4 through 36, together with modes 0 and 1, form a new set of intra prediction modes for a particular non-square block.

[0093] 11, modes 33 and 34 (shown in dashed lines) are removed, and wide-angle modes 1 and 2 (shown in dotted lines) are added. The direction of mode 1 is opposite to that of mode 33 (shown in (1101)), and the direction of mode 2 is opposite to that of mode 32 (shown in (1102)). Thus, modes 2, 1, and 2 through 32, along with modes 0 and 1, form a new set of intra-prediction modes for a particular non-square block.

[0094] In one embodiment, the angular distance between the removed normal mode and the added wide-angle mode is greater than 90 degrees and less than or equal to 180 degrees. For example, if there are 35 normal intra prediction modes and the width is greater than the height, modes 2 through 5 are removed and wide-angle modes 35 through 38 are added. If the height is greater than the width, modes 31 through 34 are removed and modes -1 through -4 are added. In another example, if there are 67 normal intra prediction modes and the width is greater than the height, modes 2 through 9 are removed and modes 67 through 74 are added. If the height is greater than the width, modes 59 through 66 are removed and modes -1 through -8 are added.

[0095] In an alternative embodiment, the normal modes removed and the wide-angle modes added are in opposite directions. For example, if there are 35 normal intra-prediction modes and the width is greater than the height, modes 3 to 6 are removed and wide-angle modes 35 to 38 are added. If the height is greater than the width, modes 30 to 33 are removed and modes -1 to -4 are added. Alternatively, if there are 67 normal intra-prediction modes and the width is greater than the height, modes 3 to 10 are removed and wide-angle modes 67 to 74 are added. If the height is greater than the width, modes 58 to 65 are removed and wide-angle modes -1 to -8 are added.

[0096] In an alternative embodiment, if the width is greater than the height, remove some normal modes in the bottom-left direction and add an equal number of wide-angle modes in the top-right direction; otherwise, if the height is greater than the width, remove some modes in the top-right direction and add an equal number of wide-angle modes in the bottom-left direction.

[0097] For example, if there are 35 normal intra prediction modes and the width is greater than the height, modes 2 to 5 are removed and wide-angle modes 35 to 38 are added; if the height is greater than the width, modes 31 to 34 are removed and wide-angle modes -1 to -4 are added.

[0098] In an alternative embodiment, the number of removed normal intra prediction modes is fixed for all non-square block shapes. For all non-square blocks, N normal intra prediction modes are removed and N wide-angle modes are added accordingly. For example, when using 35 normal modes, N may be between 1 and 7; when using 67 normal modes, N may be between 2 and 14; and when using 129 normal intra prediction modes, N may be between 4 and 28.

[0099] In a subembodiment, N may be signaled as an advanced syntax element (e.g., in a sequence parameter set (SPS), picture parameter set (PPS), slice header) or as a common syntax element or parameter for a region of the picture.

[0100] In one example, if there are 35 normal intra prediction modes, 4 normal intra modes are removed, and if there are 67 normal intra prediction modes, 8 normal intra modes are removed.

[0101] In an alternative embodiment, the number of removed regular intra prediction modes depends on the shape of the non-square block.

[0102] In some examples, when width / height ≤ 2 or height / width ≤ 2 (aspect ratio = width / height, 1 < aspect ratio ≤ 2, or 1 / 2 ≤ aspect ratio < 1), M normal intra prediction modes are removed. Also, when width / height ≥ 4 or height / width ≥ 4 (aspect ratio ≥ 4 or aspect ratio ≤ 1 / 4), N normal intra prediction modes are removed. Also, in the example, when 2 < aspect ratio < 4 or 1 / 4 ≤ aspect ratio < 1 / 2, P normal intra prediction modes are removed. In the example, M is not equal to N. In one example, when there are 35 normal intra prediction modes, M is equal to 3, N is equal to 5, when there are 67 normal intra prediction modes, M is equal to 6, N is equal to 10. P may be the same as M or N, or may be different from both M and N.

[0103] In a sub - embodiment, M and N can be signaled as advanced syntax elements (e.g., in a sequence parameter set (SPS), a picture parameter set (PPS), a slice header), or as common syntax elements and parameters for a region of a picture. In another example, the number of normal intra prediction modes removed depends on the encoded information, including, but not limited to, the width of the block, the height of the block, and the ratio of the width to the height of the block, and the size of the block area.

[0104] In an alternative embodiment, the removed normal intra prediction modes start from the bottom - left diagonal mode (i.e., mode 2 when using 35 modes) or the top - right diagonal mode (i.e., mode 34 when using 35 modes), and the added wide - angle modes start from the nearest corner beyond the bottom - left diagonal mode or the top - right diagonal mode (i.e., mode 1 or mode 35).

[0105] In some examples, the removed normal modes and added wide-angle modes may be contiguous or non-contiguous. In one example, if there are 35 normal intra-prediction modes and the width is greater than the height, modes 2 through 5 are removed and wide-angle modes 35 through 38 are added. In another example, if there are 35 normal intra-prediction modes and the width is greater than the height, modes 2 through 5 are removed and wide-angle modes 35, 37, 38, and 39 are added.

[0106] In an alternative embodiment, the used / removed normal intra-prediction modes are used to indicate the added wide-angle modes. As a result, the unused normal intra-prediction modes are still signaled, but the meaning of these unused normal intra-prediction modes is converted to the added wide-angle modes. For example, if the width is greater than the height, mode 2 is removed but still signaled. For one non-square block, if the decoder decodes mode 2 and the width is greater than the height, the decoder converts mode 2 to mode 35.

[0107] In an alternative embodiment, to obtain the most probable mode (MPM) of the current block, if the intra prediction of a neighboring block exceeds the intra prediction direction range of the current block, the mode of the neighboring block is mapped to the closest direction covered by the intra prediction direction range of the current block. For example, the current block is a square block, and the block to its left is a non-square block, and the mode number of the left block is 35. Mode 35 is not covered by the mode range of the current block. Therefore, the mode of the left block is mapped to mode 34, which is the closest mode covered by the mode range of the current block.

[0108] In some embodiments, an intra prediction process is performed on a rectangular block using wide-angle prediction. The intra prediction process receives inputs such as an intra prediction mode (represented by predModeIntra), the width of the current block (represented by nWidth), the height of the block (represented by nHeight), neighboring samples (represented by p[x][y], where x=-1, y=-1 to nWidth+nHeight-1) (x=0 to nWidth+nHeight-1, y=-1), and a variable cIdx that specifies the color components of the current block. The intra prediction process can generate prediction samples predSamples[x][y], where x=0 to nWidth-1, y=0 to nHeight-1.

[0109] In some embodiments, the intra prediction process is performed based on a mapping between the intra prediction mode predModeIntra and the angle parameter intraPredAngle.

[0110] 12 is a schematic diagram illustrating 43 intra prediction directions. The 43 intra prediction directions include 33 normal intra prediction directions corresponding to normal intra prediction modes, modes 2 to 34, as well as five wide-angle directions extending beyond mode 34 (as shown in modes 35 to 39) and five wide-angle directions extending beyond mode 2 (as shown in modes -1 to -5).

[0111] 12 further shows a top staff (upper staff) and a left staff (left staff). In some examples, the angle parameter intraPredAngle is measured by the top staff or the left staff. Table 1 specifies a mapping table between the intra prediction mode predModeIntra and the angle parameter intraPredAngle. [Table 1]

[0112] In the example, the incoming intra prediction mode predModeIntra is one of the removed normal intra prediction modes, and the incoming intra prediction mode predModeIntra is converted to a wide mode based on the aspect ratio (nWidth / nHeight) of the current block.

[0113] For example, if nWidth / nHeight=2 and 2≦predModeIntra≦4, then predModeIntra←predModeIntra+33. Specifically, if the block width nWidth is twice the block height nHeight, three normal intra prediction modes (modes 2, 3, and 4) are removed from the set of normal intra prediction modes, and three wide-angle modes (modes 35, 36, and 37) are added to the remaining normal intra prediction modes to form a new set of intra prediction modes for the block. If the input intra prediction mode predModeIntra corresponds to one of the removed modes, the intra prediction mode predModeIntra is converted to the wide-angle mode.

[0114] Furthermore, if nWidth / nHeight≧4 and 2≦predModeIntra≦6, predModeIntra←predModeIntra+33. Specifically, if the block width nWidth is greater than or equal to four times the block height nHeight, five normal intra prediction modes (mode 2, mode 3, mode 4, mode 5, and mode 6) are removed from the set of normal intra prediction modes, and five wide-angle modes (mode 35, mode 36, mode 37, mode 38, and mode 39) are added to the remaining normal intra prediction modes to form a new set of intra prediction modes for the block. If the input intra prediction mode predModeIntra corresponds to one of the removed modes, the intra prediction mode predModeIntra is converted to the wide-angle mode.

[0115] Also, if nHeight / nWidth=2 and 32≦predModeIntra≦34, predModeIntra←predModeIntra-35. Specifically, if the block height nHeight is twice the block width nWidth, three normal intra prediction modes (mode 34, mode 33, and mode 32) are removed from the set of normal intra prediction modes, and three wide-angle modes (mode-1, mode-2, and mode-3) are added to the remaining normal intra prediction modes to form a new set of intra prediction modes for the block. If the input intra prediction mode predModeIntra corresponds to one of the removed modes, the intra prediction mode predModeIntra is converted to a wide-angle mode.

[0116] Furthermore, if nHeight / nWidth≧4 and 30≦predModeIntra≦34, predModeIntra←predModeIntra-35. Specifically, if the block height nHeight is greater than or equal to four times the block width nWidth, five normal intra prediction modes (mode 34, mode 33, mode 32, mode 31, and mode 30) are removed from the set of normal intra prediction modes, and five wide-angle modes (mode-1, mode-2, mode-3, mode-4, and mode-5) are added to the remaining normal intra prediction modes to form a new set of intra prediction modes for the block. If the input intra prediction mode predModeIntra corresponds to one of the removed modes, the intra prediction mode predModeIntra is converted to the wide-angle mode.

[0117] Then, according to the intra prediction mode predModeIntra, a corresponding angle parameter intraPredAngle can be determined, for example, based on Table 1. According to an appropriate video coding standard (e.g., the HEVC standard), prediction samples predSamples[x][y] can be calculated based on the angle parameter intraPredAngle.

[0118] In another example, 65 normal intra prediction directions are applied to intra prediction of square blocks. For example, as shown in FIG. 2, the 65 normal intra prediction directions correspond to Mode 2 to Mode 66 as normal intra prediction modes. Mode 2 to Mode 66, Mode 0 (planar mode), and Mode 1 (DC mode) form a set of 67 intra prediction modes for square blocks. In some embodiments, a certain number of normal intra prediction modes are removed and the same number of wide-angle modes are added to a new set of intra prediction modes for rectangular blocks, where the number depends on the aspect ratio of the rectangular block.

[0119] In some embodiments, an intra prediction process is performed on a rectangular block (current block) using wide-angle prediction. The intra prediction process receives inputs such as an intra prediction mode predModeIntra, a width nWidth of the current block, a height nHeight of the block, and neighboring samples (represented as p[x][y], where x=-1, y=-1 to nWidth+nHeight-1) (x=0 to nWidth+nHeight-1, y=-1). The intra prediction process can generate prediction samples predSamples[x][y], where x=0 to nWidth-1 and y=0 to nHeight-1.

[0120] In the example, the variable whRatio is constrained to be equal to min(abs(Log2(nWidth / nHeight)),2). If nWidth is greater than nHeight but less than twice nHeight, whRatio is less than 1. If nWidth is equal to twice nHeight, whRatio is equal to 1. If nWidth is greater than twice nHeight but less than four times nHeight, whRatio is in the range (1, 2). If nWidth is four times nHeight, whRatio is equal to 2. If nWidth is greater than four times nHeight, whRatio is equal to 2.

[0121] Similarly, if nHeight is greater than nWidth but less than twice nWidth, whRatio is less than 1. If nHeight is equal to twice nWidth, whRatio is equal to 1. If nHeight is greater than twice nWidth but less than four times nWidth, whRatio is in the range (1, 2). If nHeight is four times nWidth, whRatio is equal to 2. If nHeight is greater than four times nWidth, whRatio is equal to 2. Thus, whRatio is a function of the block shape and is independent of the block's orientation.

[0122] In the example, the incoming intra-prediction mode predModeIntra is one of the removed normal intra-prediction modes, and the incoming intra-prediction mode predModeIntra is converted to a wide-angle mode based on the whRatio of the current block.

[0123] For example, if nWidth is greater than nHeight but less than twice nHeight, whRatio is less than 1, and six normal intra prediction modes (modes 2 to 7) are removed from the set of normal intra prediction modes, and six wide-angle modes (modes 67 to 72) are added to the remaining normal intra prediction modes to form a new set of intra prediction modes for the block. If the input intra prediction mode predModeIntra corresponds to one of the removed modes (greater than or equal to 2 and less than 8), 65 is added to convert the intra prediction mode predModeIntra to a wide-angle mode.

[0124] Also, if nWidth is four or more times greater than nHeight, a new set of intra prediction modes for the block is formed by removing 10 normal intra prediction modes (modes 2 to 11) from the set of normal intra prediction modes and adding 10 wide-angle modes (modes 67 to 76) to the remaining normal intra prediction modes. If the input intra prediction mode predModeIntra corresponds to one of the removed modes (greater than or equal to 2 and less than 12), 65 is added to convert the intra prediction mode predModeIntra to a wide-angle mode.

[0125] Also, if nHeight is greater than nWidth but less than twice nWidth, whRatio is less than 1, and six normal intra prediction modes (modes 61 to 66) are removed from the set of normal intra prediction modes, and six wide-angle modes (modes -1 to -6) are added to the remaining normal intra prediction modes to form a new set of intra prediction modes for the block. If the input intra prediction mode predModeIntra corresponds to one of the removed modes (greater than or equal to 61 and less than 67), 67 is subtracted to convert the intra prediction mode predModeIntra to a wide-angle mode.

[0126] Also, if nHeight is four or more times greater than nWidth, 10 normal intra prediction modes (modes 57 to 66) are removed from the set of normal intra prediction modes, and 10 wide-angle modes (modes -1 to -10) are added to the remaining normal intra prediction modes to form a new set of intra prediction modes for the block. If the input intra prediction mode predModeIntra corresponds to one of the removed modes (greater than or equal to 57 and less than 67), 67 is subtracted to convert the intra prediction mode predModeIntra to a wide-angle mode.

[0127] Then, according to the intra-prediction mode predModeIntra, a corresponding angle parameter intraPredAngle can be determined, for example, based on a lookup table. Then, according to an appropriate video coding standard (e.g., the HEVC standard), prediction samples predSamples[x][y] can be calculated based on the angle parameter intraPredAngle.

[0128] FIG. 13 shows a flowchart outlining a process (1300) according to an embodiment of the present disclosure. The process (1300) can be used to reconstruct a block coded in intra-mode and generates a prediction block for the block being reconstructed. In various embodiments, the process (1300) is performed by a processing circuit, such as a processing circuit in a terminal device (310), (320), (330), or (340), a processing circuit that performs the functions of the video encoder (403), a processing circuit that performs the functions of the video decoder (410), a processing circuit that performs the functions of the video decoder (510), a processing circuit that performs the functions of the intra prediction module (552), a processing circuit that performs the functions of the video encoder (603), a processing circuit that performs the functions of the predictor (635), a processing circuit that performs the functions of the intra encoder (722), or a processing circuit that performs the functions of the intra decoder (872). In some embodiments, the process (1300) is implemented by software instructions, such that the processing circuit performs the process (1300) when executing the software instructions. The process starts from (S1301) and proceeds to (S1310).

[0129] At (S1310), prediction information for the block is decoded. In examples, the processing circuit decodes the prediction information for the block from the encoded video bitstream. In some examples, the block is a non-square block, and the prediction information for the block indicates a first intra-prediction mode, and the first intra-prediction mode is included in a first set of intra-prediction modes for square blocks.

[0130] At (S1320), the processing circuit determines whether the first intra-prediction mode is within the subset of intra-prediction modes disabled for non-square blocks. If the first intra-prediction mode is within the subset of intra-prediction modes disabled for non-square blocks, processing proceeds to (S1330); otherwise, processing proceeds to (S1350).

[0131] At (S1330), the first intra prediction mode is remapped to a second intra prediction mode in a second set of intra prediction modes for non-square blocks, the second intra prediction mode being a wide-angle intra prediction mode that is not in the first set of intra prediction modes for square blocks, and the second set of intra prediction modes not including the subset of disabled intra prediction modes.

[0132] At (S1340), samples of the block are reconstructed based on the second intra-prediction mode. In some examples, corresponding angle parameters can be determined according to the second intra-prediction mode, for example, based on a lookup table. Then, samples of the block can be calculated based on the angle parameters according to an appropriate video coding standard (e.g., the HEVC standard). Then, processing proceeds to S1399, where it ends.

[0133] At (1350), samples of the block are reconstructed based on the first intra-prediction mode. In some examples, corresponding angle parameters can be determined according to the first intra-prediction mode, for example, based on a lookup table. Then, samples of the block can be calculated based on the angle parameters according to an appropriate video coding standard (e.g., the HEVC standard). Processing proceeds to S1399, where it ends.

[0134] The techniques described above may be implemented as computer software by computer-readable instructions physically stored on one or more computer-readable media. For example, Figure 14 illustrates a computer system (1400) suitable for implementing some embodiments of the disclosed subject matter.

[0135] Computer software can be encoded in any suitable machine code or computer language, and can be, through mechanisms such as assembling, compiling, linking, etc., created to create code including instructions that can be executed directly by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., or that can be interpreted, executed by microcode, etc.

[0136] The instructions may be executed by various types of computers or components thereof, including, for example, personal computers, tablets, servers, smartphones, gaming devices, Internet of Things devices, etc.

[0137] The components of computer system 1400 illustrated in Figure 14 are exemplary in nature and are not intended to imply any limitation on the scope or functionality of the computer software used to implement embodiments of the present disclosure. The arrangement of components should not be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary embodiment of computer system 1400.

[0138] The computer system (1400) may include several human interface input devices. Such human interface input devices may respond to one or more human user inputs, for example, via tactile input (e.g., keystrokes, slides, data glove movements), audio input (e.g., voice, claps), visual input (e.g., posture), and olfactory input (not shown). Human interface devices may also be used to capture certain media not necessarily directly related to conscious human input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, photographic images obtained from static image capture devices), and video (e.g., two-dimensional video, three-dimensional video including stereo video).

[0139] The human interface input devices may include one or more of a keyboard (1401), a mouse (1402), a touchpad (1403), a touch panel (1410), a data glove (not shown), a joystick (1405), a microphone (1406), a scanner (1407), and an image capture device (1408) (only one of each is shown).

[0140] The computer system (1400) may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the human user's senses, for example, through haptic output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touchscreen (1410), data gloves (not shown), or joystick (1405), although some haptic feedback devices may not be used as input devices), audio output devices (e.g., speakers (1409), headphones (not shown)), visual output devices (e.g., a screen (1410), including CRT screens, LCD screens, plasma screens, and OLED screens, each with or without touchscreen input capabilities and with or without haptic feedback capabilities, some of which may be capable of providing two-dimensional visual output or three-dimensional or higher-dimensional output, such as by means of stereo output), virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown), and printers (not shown).

[0141] The computer system (1400) may also include human-accessible storage devices and associated media, such as optical media such as CD / DVD ROM / RW (1420) with media such as CD / DVD (1421), thumb drives (1422), removable hard drives or solid state drives (1423), conventional magnetic media (e.g., magnetic tape and floppy disks (not shown)), dedicated ROM / ASIC / PLD based devices (e.g., dongles (not shown)), and the like.

[0142] Additionally, those skilled in the art should understand that the term "computer-readable medium" as used in connection with the presently disclosed subject matter does not include transmission media, carrier waves, or other transitory signals.

[0143] The computer system 1400 may further include an interface to one or more communications networks. The network may be, for example, a wireless, wired, optical, etc. network. The network may also be a local, wide-area, metropolitan, in-vehicle, industrial, real-time, delay-tolerant, etc. network. Examples of networks include, for example, local area networks such as Ethernet, wireless LANs, cellular networks (including GSM, 3G, 4G, 5G, LTE, etc.), television wired or wireless wide-area digital network television (including cable, satellite, and terrestrial television), in-vehicle and industrial networks (including CAN Bus), etc. Some networks typically require an external network interface adapter connected to a general-purpose data port or peripheral bus 1449 (e.g., a USB port on the computer system 1400), while other networks are typically integrated into the core of the computer system 1400 by connecting to a system bus (e.g., an Ethernet interface on a PC computer system or a cellular network interface on a smartphone computer system), as described below. Using any of these networks, the computer system 1400 can communicate with other entities. Such communication may be one-way, receive only (e.g., broadcast television), one-way transmit only (e.g., a CANbus to a CANbus device), or two-way (e.g., using a local area or wide area digital network to reach another computer system). Specific protocols and protocol stacks may be used for each of these networks and network interfaces as described above.

[0144] The human interface devices, human accessible storage devices, and network interfaces may be attached to a core (1440) of the computer system (1400).

[0145] The core (1440) may include one or more central processing units (CPUs) (1441), graphics processing units (GPUs) (1442), dedicated programmable processing units in the form of field programmable gate arrays (FPGAs) (1443), hardware accelerators for specific tasks (1444), etc. These devices, along with read-only memory (ROM) (1445), random access memory (1446), and internal mass storage (e.g., internal non-user-accessible hard disk drives, SSDs, etc.) (1447), may be connected via a system bus (1448). In some computer systems, the system bus (1448) may be accessible in the form of one or more physical plugs, allowing expansion with additional CPUs, GPUs, etc. Peripheral devices may be connected to the core's system bus (1448) directly or via a peripheral bus (1449). Peripheral bus architectures include PCI, USB, etc.

[0146] The CPU (1441), GPU (1442), FPGA (1443), and accelerator (1444) can execute specific instructions that combine to make up the computer code. The computer code can be stored in ROM (1445) or RAM (1446). Temporary data can also be stored in RAM (1446), while permanent data is stored, for example, in internal mass storage (1447). Cache memory can be used to enable fast storage and retrieval of any memory in the memory, and can be closely associated with one or more of the CPU (1441), GPU (1442), mass storage (1447), ROM (1445), RAM (1446), etc.

[0147] The computer-readable medium can contain computer code for performing various computer-implemented operations, and the medium and computer code may be specially designed and constructed for the purposes of the present disclosure, or they may be of the type well known and available to those skilled in the art of computer software.

[0148] By way of example and not limitation, a computer system having the architecture (1400), and in particular the core (1440), can provide functionality realized by a processor (including a CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media may include user-accessible mass storage media, as described above, as well as specific storage devices with the core (1440), such as the core's internal mass storage device (1447) or ROM (1445). Software for implementing various embodiments of the present disclosure can be stored on such devices and executed by the core (1440). Depending on particular needs, the computer-readable media may include one or more storage devices or chips. The software may cause the core (1440), and in particular the processor (including a CPU, GPU, FPGA, etc.) therein, to perform specific processes or portions of specific processes described herein, including defining data structures stored in RAM (1446) and modifying such data structures through software-defined operations. Additionally or alternatively, a computer system may provide functionality through logic hardwired or otherwise implemented in circuitry (e.g., accelerator (1444)), which may operate in place of or in conjunction with software to perform particular operations or portions of particular operations described herein. Where appropriate, references to software may include logic, and conversely, references to logic may include software. Where appropriate, references to computer-readable media may include circuitry (e.g., integrated circuits (ICs)) on which software is stored for execution, circuitry embodying logic for execution, or both. The present disclosure includes any appropriate combination of hardware and software.

[0149] While this disclosure has described several exemplary embodiments, there are alterations, substitutions, and various substitute equivalents that fall within the scope of this disclosure. It should thus be understood that those skilled in the art will be able to devise many systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and are therefore within its spirit and scope. [Appendix A] Acronyms JEM: Joint exploration model (JEM) VVC: Versatile video coding (VVC) BMS: benchmark set (BMS) HEVC: High Efficiency Video Coding (HEVC) SEI: Supplementary Enhancement Information (SEI) VUI: Video Usability Information (VUI) GOP: Groups of Pictures TU: Transform Units PU: Prediction Unit CTU: Coding Tree Unit CTB: Coding Tree Block (CTB) PB: Prediction Block (PB) HRD: Hypothetical Reference Decoder (HRD) SNR: Signal-to-Noise Ratio CPU: Central Processing Unit GPU: Graphics Processing Unit CRT: Cathode Ray Tube (CRT) LCD: Liquid-Crystal Display OLED: Organic Light-Emitting Diode CD: Compact Disc DVD: Digital Video Disc (DVD) ROM: Read-Only Memory RAM: Random Access Memory ASIC: Application-Specific Integrated Circuit (ASIC) PLD: Programmable Logic Device (PLD) LAN: Local Area Network GSM: Global System for Mobile communications LTE: Long-Term Evolution CANBus: Controller Area Network Bus USB: Universal Serial Bus PCI: Peripheral Component Interconnect FPGA: Field Programmable Gate Array SSD: Solid-state drive (SSD) IC: Integrated Circuit CU: Coding Unit (CU)

Claims

1. A method for decoding a video bitstream using a decoder, the method being: Currently, the stage is to determine if the block is a non-square block; A step of decoding prediction information from the bitstream, wherein the prediction information indicates a candidate intra-prediction mode number that identifies a corresponding intra-prediction mode; The steps include determining whether the candidate intra-prediction mode number belongs to a subset of invalid intra-prediction mode numbers; If the candidate intra-prediction mode number belongs to the subset of invalidated intra-prediction mode numbers: The method involves directly remapping the candidate intra-prediction mode numbers to derive final intra-prediction mode numbers belonging to a first set of intra-prediction mode numbers for non-square blocks, wherein the first set includes a first number of wide-angle intra-prediction mode numbers not present in the second set of intra-prediction mode numbers for square blocks, and excludes a second number of invalidated intra-prediction mode numbers present in the second set from the first set; The sample of the non-square block is reconstructed according to the final intra-prediction mode number; If the candidate intra-prediction mode number does not belong to the subset of invalid intra-prediction mode numbers: The steps include: Reconstructing the sample of the non-square block according to the candidate intra-prediction mode identified by the candidate intra-prediction mode number; Methods that include...

2. The method according to claim 1, wherein the subset of invalidated intra-prediction mode numbers is determined based on at least one of the width, height, and width-to-height ratio of the non-square block, and is independent of the prediction direction angle associated with each invalidated intra-prediction mode number.

3. The method according to claim 1, wherein the remapping of the candidate intra-prediction mode number to the final intra-prediction mode number does not include deriving the prediction direction of the final intra-prediction mode by subtracting the prediction direction of the candidate intra-prediction mode from 180 degrees.

4. The remapping is: If the width of the non-square block is greater than the height of the non-square block, a first predetermined number is added to the first intra-prediction mode to obtain a second intra-prediction mode corresponding to the upper right wide-angle direction; If the height of the non-square block is greater than the width, the method includes subtracting a second predetermined number from the first intra-prediction mode to obtain a second intra-prediction mode corresponding to the lower left wide-angle direction. The method according to claim 1.

5. The method according to claim 1, wherein the second number of disabled intra-prediction modes includes one or more intra-prediction modes numbered sequentially from the lower left or upper right side of the second set depending on the aspect ratio of the non-square block.

6. The method according to claim 1, wherein the first set of intra-predictive modes is defined as a result of a wide-angle remapping performed on the second set for the non-square blocks.

7. The method according to claim 1, wherein the initial intra prediction mode is signaled in the bitstream using the same syntactic elements used for the square blocks.

8. A method of encoding video using an encoder, the method being: A step of selecting a candidate intra-prediction mode number to identify the corresponding intra-prediction mode for the current non-square block from a first set of intra-prediction mode numbers for the non-square block, wherein the first set includes a first number of wide-angle intra-prediction mode numbers that are not in a second set of intra-prediction mode numbers for the square block, and a second number of disabled intra-prediction mode numbers that are in the second set are excluded from the first set; The step of determining whether the candidate intra-prediction mode number is one of the wide-angle intra-prediction mode numbers; If the candidate intra-prediction mode number is one of the wide-angle intra-prediction mode numbers: Performing a reverse remapping directly on the candidate intra-prediction mode numbers to derive a mapped intra-prediction mode number belonging to the second set, wherein the mapped intra-prediction mode number is one of the invalidated intra-prediction mode numbers excluded from the first set; The process involves generating prediction information indicating the mapped intra-prediction mode number; If the candidate intra-prediction mode number is not one of the wide-angle intra-prediction mode numbers: The steps include generating prediction information indicating the candidate intra-prediction mode number, and Methods that include...

9. A method for storing a bitstream by an encoder, the method being: A step of selecting a candidate intra-prediction mode number to identify the corresponding intra-prediction mode for the current non-square block from a first set of intra-prediction mode numbers for the non-square block, wherein the first set includes a first number of wide-angle intra-prediction mode numbers that are not in a second set of intra-prediction mode numbers for the square block, and a second number of disabled intra-prediction mode numbers that are in the second set are excluded from the first set; The step of determining whether the candidate intra-prediction mode number is one of the wide-angle intra-prediction mode numbers; If the candidate intra-prediction mode number is one of the wide-angle intra-prediction mode numbers: Performing a reverse remapping directly on the candidate intra-prediction mode numbers to derive a mapped intra-prediction mode number belonging to the second set, wherein the mapped intra-prediction mode number is one of the invalidated intra-prediction mode numbers excluded from the first set; The process involves generating prediction information indicating the mapped intra-prediction mode number; If the candidate intra-prediction mode number is not one of the wide-angle intra-prediction mode numbers: The steps include: generating prediction information indicating the candidate intra-prediction mode number; A step of storing a bitstream containing the aforementioned prediction information. Methods that include...

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