Video encoding and decoding method, video codec and computer readable medium

Abstract

The embodiment of the present application provides a method for video coding, a video codec, and a computer-readable medium, including, for a current block encoded in an intra-frame prediction mode, deriving a candidate list of intra-frame prediction modes of multiple adjacent blocks adjacent to the current block. The candidate list includes a first candidate intra-frame prediction mode value (Mode1). The first candidate intra-frame prediction mode value corresponds to the intra-frame prediction mode of one of the multiple adjacent blocks. The candidate list also includes a second candidate intra-frame prediction mode value (Mode2) and a third candidate intra-frame prediction mode value (Mode3). The second candidate intra-frame prediction mode value (Mode2) and the third candidate intra-frame prediction mode value (Mode3) are determined according to the following formula: Mode2 = ((Mode1+61)%64)+2, Mode3 = ((Mode1‑1)%64)+2. The method also includes performing a reduction process to remove repeated intra-frame prediction modes in the candidate list, and determining the intra-frame prediction mode value of the current block according to the candidate list after the reduction process.

Description

[0001] This application is a divisional application of an actively modified version of a patent application with a filing date of July 5, 2019, Chinese patent application number 201980019756.1, and invention name “Video Coding and Decoding Method, Codec and Storage Medium”. Technical Field

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

[0003] The background description provided herein is for the purpose of generally presenting the context of the present application. To the extent described in this background section, the works of the presently named inventors and aspects of this description that may not otherwise qualify as prior art at the time of filing are neither explicitly nor implicitly admitted as prior art to the present invention.

[0004] Video encoding and decoding can be performed using inter-picture prediction with motion compensation. Uncompressed digital video can include a series of pictures, each picture having a spatial size of, for example, 1920x1080 luma samples and associated chroma samples. The series of pictures can have a fixed or variable picture rate (also informally referred to as a frame rate) of, for example, 60 pictures per second or 60Hz. Uncompressed video has very high bit rate requirements. For example, 1080p604:2:0 video with 8 bits per sample (1920x1080 luma sample resolution at 60Hz frame rate) requires a bandwidth of nearly 1.5Gbit / s. One hour of such video requires more than 600GB of storage space.

[0005] One purpose of video encoding and decoding can be to reduce redundancy in the input video signal through compression. Compression can help reduce the bandwidth or storage space requirements mentioned above, in some cases by two orders of magnitude or more. Lossless compression and lossy compression, as well as combinations thereof, can be employed. Lossless compression refers to techniques that can reconstruct an exact copy of the original signal from the compressed original signal. When lossy compression is used, the reconstructed signal may not be the same as the original signal, but the distortion between the original signal and the reconstructed signal is small enough to make the reconstructed signal usable for the intended application. In the case of video, lossy compression is widely used. The amount of tolerable distortion depends on the application, for example, users of some consumer streaming applications can tolerate higher distortion than users of television-type applications. The achievable compression rate can reflect that higher tolerable / acceptable distortion can produce higher compression rates.

[0006] Video encoders and video decoders may utilize a variety of broad categories of techniques including, for example, motion compensation, transforms, quantization, and entropy coding.

[0007] Video codec techniques may include a technique known as intra-coding. In intra-coding, sample values ​​are represented without reference to samples or other data from a previously reconstructed reference picture. In some video codecs, a picture is spatially subdivided into blocks of samples. When all blocks of samples are encoded in intra-mode, the picture may be an intra-picture. Intra-pictures and their derivatives such as independent decoder refresh pictures may be used to reset decoder states and may therefore be used as the first picture or still image in an encoded video stream and video session. Samples of an intra-block may be transformed and transform coefficients may be quantized prior to entropy coding. Intra-prediction may be a technique for minimizing sample values ​​in a domain prior to the transform. In some cases, the smaller the transformed direct current (DC) value and the smaller the alternating current (AC) coefficient, the fewer bits are required to represent a given quantization step size of an entropy-coded block.

[0008] Conventional intra-frame coding, such as known from, for example, MPEG-2 generation coding techniques, does not use intra-frame prediction. However, some newer video compression techniques include techniques that attempt to use, for example, surrounding sample data and / or metadata obtained during encoding / decoding of spatially adjacent, preceding data blocks in decoding order. Such techniques are hereinafter referred to as "intra-frame prediction" techniques. Note that, at least in some cases, intra-frame prediction uses only reference data from the reconstructed current picture, not reference pictures.

[0009] There can be many different forms of intra-frame prediction. When more than one such technique can be used in a given video coding technique, the technique in use can be encoded in the intra-frame prediction mode. In some cases, a mode can have sub-modes and / or parameters, and these sub-modes and / or parameters can be encoded separately or contained in a mode codeword. Which codeword is used in a given mode / sub-mode / parameter combination can have an impact on the coding efficiency gain through intra-frame prediction, so entropy coding techniques can be used to convert the codeword into a codestream.

[0010] In H.264, a certain intra-frame prediction mode was introduced, which was improved in H.265 and further improved in newer coding technologies such as the Joint Exploration Model (JEM), Next Generation Video Coding (VVC), and Benchmark Set (BMS). The prediction value block can be formed using the neighboring sample values ​​belonging to the existing sample. The sample values ​​of the neighboring samples are copied to the prediction value block according to the direction. The reference being used in the direction can be encoded in the code stream, or it can be predicted.

[0011] As video coding techniques have evolved, the number of possible directions has increased. In H.264 (2003), nine different directions could be represented. In H.265 (2013), that number increased to 33, 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 those possible directions with a small number of bits, allowing for some penalty for less likely directions. In addition, the direction itself can sometimes be predicted based on neighboring directions used in neighboring blocks that have already been decoded.

[0012] The mapping of the intra-frame prediction direction bits representing the direction in the encoded video bitstream can vary depending on the video coding technology, and can include, for example, a simple direct mapping from the prediction direction to the intra-frame prediction mode, a simple direct mapping to the codeword, and complex adaptive schemes involving the most likely mode and similar techniques. Those skilled in the art are readily familiar with those techniques. However, in all cases, there may be certain directions that are statistically less likely to appear in the video content than certain other directions. Since the goal of video compression is to reduce redundancy, in a well-functioning video coding technology, those unlikely directions will be represented by a larger number of bits than the likely directions.

[0013] VVC is the next generation video coding standard and is a further improvement of High Efficiency Video Coding (HEVC). The intra prediction mode in HEVC uses 33 directional modes, while the intra prediction mode in VVC uses 65 directional modes to improve the compression rate. However, the traditional HEVC intra prediction mode processing cannot handle the additional directional modes included in VVC. Summary of the invention

[0014] According to an embodiment of the present application, a method for video decoding is provided, including deriving a candidate list of intra-frame prediction modes of multiple adjacent blocks adjacent to the current block for a current block encoded in an intra-frame prediction mode. The candidate list includes a first candidate intra-frame prediction mode value (Mode1), and the first candidate intra-frame prediction mode value corresponds to the intra-frame prediction mode of one of the multiple adjacent blocks. The candidate list also includes a second candidate intra-frame prediction mode value (Mode2) and a third candidate intra-frame prediction mode value (Mode3). The second candidate intra-frame prediction mode value (Mode2) and the third candidate intra-frame prediction mode value (Mode3) are determined according to the following formulas: Mode2 = ((Mode1+61)%64)+2, Mode3 = ((Mode1-1)%64)+2. The method also includes performing a reduction process to remove repeated intra-frame prediction modes in the candidate list; and determining the intra-frame prediction mode value of the current block according to the candidate list after the reduction process.

[0015] According to an embodiment of the present application, a video decoder is provided, and the video decoder includes a processing circuit. The processing circuit is configured to derive a candidate list of intra-frame prediction modes of multiple adjacent blocks adjacent to the current block for a current block encoded in an intra-frame prediction mode. The candidate list includes a first candidate intra-frame prediction mode value (Mode1), and the first candidate intra-frame prediction mode value corresponds to the intra-frame prediction mode of one adjacent block among the multiple adjacent blocks. The candidate list also includes a second candidate intra-frame prediction mode value (Mode2) and a third candidate intra-frame prediction mode value (Mode3). The second candidate intra-frame prediction mode value (Mode2) and the third candidate intra-frame prediction mode value (Mode3) are determined according to the following formulas: Mode2 = ((Mode1+61)%64)+2, Mode3 = ((Mode1-1)%64)+2. The processing circuit is also configured to perform a reduction process to remove repeated intra-frame prediction modes in the candidate list; and determine the intra-frame prediction mode value of the current block according to the candidate list after the reduction process.

[0016] According to an embodiment of the present application, a non-temporary computer-readable medium storing instructions is provided, which, when executed by a processor in a video decoding device, causes the processor to perform a method, the method comprising, for a current block encoded in an intra-frame prediction mode, deriving a candidate list of intra-frame prediction modes of a plurality of neighboring blocks adjacent to the current block. The candidate list comprises a first candidate intra-frame prediction mode value (Mode1), the first candidate intra-frame prediction mode value corresponding to the intra-frame prediction mode of one of the plurality of neighboring blocks. The candidate list also comprises a second candidate intra-frame prediction mode value (Mode2) and a third candidate intra-frame prediction mode value (Mode3). The second candidate intra-frame prediction mode value (Mode2) and the third candidate intra-frame prediction mode value (Mode3) are determined according to the following formulas: Mode2 = ((Mode1 + 61)% 64) + 2, Mode3 = ((Mode1-1)% 64) + 2. The method also comprises performing a reduction process to remove repeated intra-frame prediction modes in the candidate list; and determining the intra-frame prediction mode value of the current block according to the candidate list after the reduction process.

[0017] The video decoding method provided by the embodiment of the present application derives a candidate list of intra-frame prediction modes for a current block encoded in an intra-frame prediction mode, and then uses a reduction process to remove repeated modes in the candidate list so that a unique mode is retained in the candidate list. Finally, based on the candidate list after the reduction process, the intra-frame prediction mode value of the current block is determined, thereby providing better prediction accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and the accompanying drawings, in which:

[0019] Figure 1 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment;

[0020] Figure 2 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment;

[0021] Figure 3 is a schematic diagram of a simplified block diagram of a decoder according to one embodiment;

[0022] Figure 4 is a schematic diagram of a simplified block diagram of an encoder according to one embodiment;

[0023] Figure 5 A block diagram showing an encoder according to another embodiment;

[0024] Figure 6 A block diagram showing a decoder according to another embodiment;

[0025] Figure 7 is a schematic diagram of an exemplary intra prediction mode;

[0026] Figure 8 (A) and Figure 8 (B) shows various angle modes for 35 prediction modes;

[0027] Fig. 9 (A) and Fig. 9 (B) shows various angle modes for 67 prediction modes;

[0028] Fig.10 is a schematic diagram of the current block and its surrounding neighbors;

[0029] Fig.11 An embodiment of a process performed by an encoder or a decoder is shown;

[0030] Fig.12 An embodiment of a process performed by an encoder or a decoder is shown;

[0031] Fig.13 An embodiment of a process performed by an encoder or a decoder is shown;

[0032] Fig.14 It is a schematic diagram of the current block and adjacent blocks;

[0033] Fig.15 is a schematic diagram of a computer system according to one embodiment. DETAILED DESCRIPTION

[0034] Figure 1 A simplified block diagram of a communication system (100) according to an embodiment disclosed in the present application is shown. The communication system (100) includes a plurality of terminal devices that can communicate with each other via, for example, a network (150). For example, the communication system (100) includes a first pair of terminal devices (110) and (120) interconnected via the network (150). Figure 1 In an embodiment, the first terminal device performs unidirectional data transmission between (110) and (120). For example, the terminal device (110) may encode video data (e.g., a video picture stream collected by the terminal device (110)) for transmission to another terminal device (120) via the network (150). The encoded video data is transmitted in the form of one or more encoded video code streams. The terminal device (120) may receive the encoded video data from the network (150), decode the encoded video data to restore the video data, and display the video picture based on the restored video data. Unidirectional data transmission is more common in applications such as media services.

[0035] In another example, a communication system (100) includes a pair of terminal devices (130) and (140) that perform bidirectional transmission of encoded video data, which bidirectional transmission may occur, for example, during a video conference. For bidirectional data transmission, in one example, each of the terminal devices (130) and (140) may encode video data (e.g., a video picture stream collected by the terminal device) for transmission to the other of the terminal devices (130) and (140) via a network (150). Each of the terminal devices (130) and (140) may also receive the encoded video data transmitted by the other of the terminal devices (130) and (140), and may decode the encoded video data to restore the video picture, and may display the video picture on an accessible display device based on the restored video data.

[0036] exist Figure 1In the example of, terminal device (110), terminal device (120), terminal device (130) and terminal device (140) may be shown as a server, a personal computer and a smart phone, but the principles disclosed in the present application may not be limited to this. The embodiments disclosed in the present application are applicable to laptop computers, tablet computers, media players and / or dedicated video conferencing devices. Network (150) represents any number of networks that transmit encoded video data between terminal devices (110), terminal devices (120), terminal devices (130) and terminal devices (140), including, for example, wired (wired) and / or wireless communication networks. Communication network (150) can exchange data in circuit switching and / or packet switching channels. Representative networks may include telecommunication networks, local area networks, wide area networks and / or the Internet. For the purposes of the present application, unless explained below, the architecture and topology of network (150) may be irrelevant to the operations disclosed in the present application.

[0037] As examples of applications of the disclosed subject matter, Figure 2 The placement of the video encoder and video decoder in a streaming environment is shown. The disclosed subject matter is equally applicable to other video-enabled applications including, for example, video conferencing, digital TV, storing compressed video on digital media including CDs, DVDs, memory sticks, etc., and the like.

[0038] The streaming system may include an acquisition subsystem (213), which may include a video source (201), such as a digital camera, that creates an uncompressed video picture stream (202). In an example, the video picture stream (202) includes samples captured by a digital camera. The video picture stream (202), depicted as thick lines to emphasize the high amount of data compared to the encoded video data (204) (or the encoded video bitstream), may be processed by an electronic device (220), which includes a video encoder (203) coupled to the video source (201). The video encoder (203) may include hardware, software, or a combination of hardware and software to implement or implement various aspects of the disclosed subject matter as described in more detail below. The encoded video data (204) (or the encoded video bitstream (204)), depicted as thin lines to emphasize the lower amount of data compared to the video picture stream (202), may be stored on a streaming server (205) for future use. One or more streaming client subsystems, such as Figure 2A client subsystem (206) and a client subsystem (208) in a streaming server (205) may access a streaming server (205) to retrieve a copy (207) and a copy (209) of encoded video data (204). The client subsystem (206) may include, for example, a video decoder (210) in an electronic device (230). The video decoder (210) decodes the incoming copy (207) of the encoded video data and generates an output video picture stream (211) that can be presented on a display (212) (e.g., a display screen) or another presentation device (not depicted). In some streaming systems, the encoded video data (204), the video data (207), and the video data (209) (e.g., a video bitstream) may be encoded according to certain video encoding / compression standards. Examples of such standards include ITU-T H.265. In an example, the video coding standard under development is informally referred to as Versatile Video Coding (VVC), and the disclosed subject matter may be used in the context of VVC. The VVC standard is described in “Versatile Video Coding (Draft 2)” published by JVET-K1001 in July 2018, the entire contents of which are incorporated herein by reference.

[0039] It should be noted that the electronic device (220) and the electronic device (230) may include other components (not shown). For example, the electronic device (220) may include a video decoder (not shown), and the electronic device (230) may also include a video encoder (not shown).

[0040] Figure 3 is a block diagram of a video decoder (310) according to an embodiment disclosed in the present application. The video decoder (310) may be included in an electronic device (330). The electronic device (330) may include a receiver (331) (e.g., a receiving circuit). The video decoder (310) may be used to replace Figure 2 A video decoder (210) in an example of FIG.

[0041] The receiver (331) may receive one or more encoded video sequences to be decoded by the video decoder (310); in the same or another embodiment, one encoded video sequence is received at a time, wherein the decoding of each encoded video sequence is independent of the other encoded video sequences. The encoded video sequence may be received from a channel (301), which may be a hardware / software link to a storage device storing the encoded video data. The receiver (331) may receive the encoded video data and other data, such as encoded audio data and / or auxiliary data streams, which may be forwarded to their respective consuming entities (not shown). The receiver (331) may separate the encoded video sequence from the other data. To prevent network jitter, a buffer memory (315) may be coupled between the receiver (331) and the entropy decoder / parser (320) (hereinafter referred to as "parser (320)"). In some applications, the buffer memory (315) is part of the video decoder (310). In other cases, the buffer memory (415) may be provided external to the video decoder (310) (not shown). In other cases, a buffer memory (not shown) is provided outside the video decoder (310) to prevent network jitter, for example, and another buffer memory (315) may be configured inside the video decoder (310) to handle broadcast timing, for example. When the receiver (331) receives data from a storage / forward device with sufficient bandwidth and controllability or from an isochronous network, it may not be necessary to configure the buffer memory (315), or the buffer memory may be made smaller. For use on a service packet network such as the Internet, a buffer memory (315) may also be required, which may be relatively large and may advantageously have an adaptive size, and may be at least partially implemented in an operating system or a similar element (not shown) outside the video decoder (310).

[0042] The video decoder (310) may include a parser (320) to reconstruct symbols (321) from the encoded video sequence. The types of symbols include information used to manage the operation of the video decoder (310) and potential information used to control a display device such as a display device (312) (e.g., a display screen) that is not an integral part of the electronic device (330) but can be coupled to the electronic device (330), such as Figure 3As shown in . The control information for the display device may be a parameter set fragment (not indicated) of Supplementary Enhancement Information (SEI message) or Video Usability Information (VUI). The parser (320) may parse / entropy decode the received coded video sequence. The encoding of the coded video sequence may be performed according to a video coding technique or standard, and may follow various principles, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, and the like. The parser (320) may extract a subgroup parameter set of at least one subgroup of the subgroups of pixels in the video decoder from the coded video sequence based on at least one parameter corresponding to the group. The subgroup may include a Group of Pictures (GOP), a picture, a tile, a slice, a macroblock, a Coding Unit (CU), a block, a Transform Unit (TU), a Prediction Unit (PU), and the like. The parser (320) may also extract information from the encoded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, and so on.

[0043] The parser (320) may perform entropy decoding / parsing operations on the video sequence received from the buffer memory (315) to create symbols (321).

[0044] Depending on the type of coded video picture or portion of coded video picture (e.g., inter- and intra-pictures, inter- and intra-blocks) and other factors, the reconstruction of the symbol (321) may involve multiple different units. Which units are involved and how they are involved may be controlled by subgroup control information parsed by the parser (320) from the coded video sequence. For the sake of brevity, such subgroup control information flow between the parser (320) and the multiple units below is not described.

[0045] In addition to the functional blocks already mentioned, the video decoder (310) can be conceptually subdivided into several functional units as described below. In a practical embodiment operating under commercial constraints, many of these units interact closely with each other and can be at least partially integrated with each other. However, for the purpose of describing the disclosed subject matter, the conceptual subdivision into the following functional units is appropriate.

[0046] The first unit is a sealer / inverse transform unit (351). The sealer / inverse transform unit (351) receives quantized transform coefficients as symbols (321) from the parser (320) and control information, including which transform method to use, block size, quantization factor, quantization scaling matrix, etc. The sealer / inverse transform unit (351) can output a block including sample values, which can be input into an aggregator (355).

[0047] In some cases, the output samples of the scaler / inverse transform unit (351) may belong to an intra-coded block; that is, a block that does not use predictive information from a previously reconstructed picture, but may use predictive information from a previously reconstructed portion of the current picture. Such predictive information may be provided by an intra-picture prediction unit (352). In some cases, the intra-picture prediction unit (352) generates a block of the same size and shape as the block being reconstructed using surrounding reconstructed information extracted from a current picture buffer (358). For example, the current picture buffer (358) buffers a partially reconstructed current picture and / or a fully reconstructed current picture. In some cases, the aggregator (355) adds the prediction information generated by the intra-prediction unit (352) to the output sample information provided by the scaler / inverse transform unit (351) on a per-sample basis.

[0048] In other cases, the output samples of the scaler / inverse transform unit (351) may belong to an inter-frame coded and potentially motion compensated block. In this case, the motion compensated prediction unit (353) may access the reference picture memory (357) to extract samples for prediction. After the extracted samples are motion compensated according to the symbols (321) belonging to the block, these samples may be added to the output of the scaler / inverse transform unit (351) (in this case referred to as residual samples or residual signals) by the aggregator (355) to generate output sample information. The acquisition of prediction samples by the motion compensated prediction unit (353) from the address in the reference picture memory (357) may be controlled by a motion vector, and the motion vector is provided to the motion compensated prediction unit (353) in the form of a symbol (321), which may have, for example, X, Y and reference picture components. Motion compensation may also include interpolation of sample values ​​extracted from the reference picture memory (357) when using sub-sample accurate motion vectors, motion vector prediction mechanisms, and the like.

[0049] The output samples of the aggregator (355) may be subjected to various loop filtering techniques in a loop filter unit (356). The video compression techniques may include in-loop filter techniques controlled by parameters included in the coded video sequence (also referred to as the coded video bitstream) and available to the loop filter unit (356) as symbols (321) from the parser (320), however, the video compression techniques may also be responsive to meta-information obtained during decoding of a coded picture or a previous (in decoding order) portion of the coded video sequence, as well as to previously reconstructed and loop filtered sample values.

[0050] The output of the loop filter unit (356) may be a sample stream that may be output to a display device (312) and stored in a reference picture memory (357) for subsequent inter-picture prediction.

[0051] Once fully reconstructed, certain coded pictures may be used as reference pictures for future prediction. For example, once the coded picture corresponding to the current picture is fully reconstructed, and the coded picture is identified as a reference picture (e.g., by the parser (320)), the current picture buffer (358) may become part of the reference picture memory (357), and a new current picture buffer may be reallocated before starting reconstruction of a subsequent coded picture.

[0052] The video decoder (310) may perform decoding operations according to a predetermined video compression technique, such as in the ITU-T H.265 standard. The encoded video sequence may conform to the syntax specified by the video compression technique or standard used in the sense that the encoded video sequence follows the syntax of the video compression technique or standard and the profile recorded in the video compression technique or standard. Specifically, the profile may select certain tools from all the tools available in the video compression technique or standard as the only tools available for use under the profile. For compliance, the complexity of the encoded video sequence is also required to be within the range defined by the hierarchy of the video compression technique or standard. In some cases, the hierarchy limits the maximum picture size, the maximum frame rate, the maximum reconstruction sampling rate (measured in, for example, mega samples per second), the maximum reference picture size, etc. In some cases, the limits set by the hierarchy may be further limited by the Hypothetical Reference Decoder (HRD) specification and metadata of the HRD buffer management signaled in the encoded video sequence.

[0053] In an embodiment, the receiver (331) may 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 may be used by the video decoder (310) to properly decode the data and / or more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0054] Figure 4 4 is a block diagram of a video encoder (403) according to an embodiment disclosed in the present application. The video encoder (403) is included in an electronic device (420). The electronic device (420) includes a transmitter (440) (e.g., a transmission circuit). The video encoder (403) can be used to replace Figure 2 A video decoder (203) in the example of FIG.

[0055] The video encoder (403) can be used to obtain the video source (401) (not Figure 4 In another embodiment, the video source (401) is a part of the electronic device (420) to receive video samples, and the video source can collect video images to be encoded by the video encoder (403). In another embodiment, the video source (401) is a part of the electronic device (420).

[0056] The video source (401) may provide a source video sequence in the form of a digital video sample stream to be encoded by the video encoder (403), which may have any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...), and any suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media service system, the video source (401) may be a storage device storing previously prepared videos. In a video conferencing system, the video source (401) may be a camera that captures local image information as a video sequence. The video data may be provided as a plurality of separate pictures that are given motion when viewed sequentially. The pictures themselves may be constructed as a spatial pixel array, where each pixel may include one or more samples depending on the sampling structure, color space, etc. used. The relationship between pixels and samples may be easily understood by those skilled in the art. The following description focuses on samples.

[0057] According to an embodiment, the video encoder (403) may encode and compress pictures of a source video sequence into an encoded video sequence (443) in real time or under any other time constraints required by the application. Implementing an appropriate encoding speed is a function of the controller (450). In some embodiments, the controller (450) controls other functional units as described below and is functionally coupled to the other functional units. For the sake of brevity, coupling is not indicated in the figure. The parameters set by the controller (450) may include rate control related parameters (picture skipping, quantizer, lambda value of rate distortion optimization technology, etc.), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. The controller (450) may be configured to have other suitable functions that are related to the video encoder (403) optimized for a certain system design.

[0058] In some embodiments, the video encoder (403) is configured to operate in an encoding loop. As a simple description, in an example, the encoding loop may include a source encoder (430) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be encoded and a reference picture) and a (local) decoder (433) embedded in the video encoder (403). The decoder (433) reconstructs the symbols to create sample data in a manner similar to that of the (remote) decoder (because in the video compression technology considered by the disclosed subject matter, any compression between the symbols and the encoded video code stream is lossless). The reconstructed sample stream (sample data) is input to a reference picture memory (434). Since the decoding of the symbol stream produces bit-accurate results that are independent of the decoder location (local or remote), the contents of the reference picture memory (434) are also bit-accurately corresponding between the local encoder and the remote encoder. In other words, the reference picture samples "seen" by the prediction part of the encoder are exactly the same as the sample values ​​that the decoder will "see" when using the prediction during decoding. This basic principle of reference picture synchronization (and the drift that occurs when synchronization cannot be maintained, eg due to channel errors) is also used in some related techniques.

[0059] The operation of the "local" decoder (433) may be combined with, for example, Figure 3 The "remote" decoder described in detail for the video decoder (310) is identical. However, additional brief reference is made to Figure 3 , when symbols are available and the entropy encoder (445) and parser (320) are capable of losslessly encoding / decoding the symbols into an encoded video sequence, the entropy decoding portion of the video decoder (310), including the buffer memory (315) and the parser (320), may not be fully implemented in the local decoder (433).

[0060] At this point, it can be observed that any decoder technology other than the parsing / entropy decoding present in the decoder must also be present in the corresponding encoder in substantially the same functional form. For this reason, the disclosed subject matter focuses on the decoder operation. The description of encoder technology can be simplified because encoder technology is mutually inverse to the decoder technology described comprehensively. A more detailed description is only needed in certain areas and is provided below.

[0061] During operation, in some examples, the source encoder (430) may perform motion compensated predictive coding. The motion compensated predictive coding predictively encodes an input picture with reference to one or more previously encoded pictures from a video sequence designated as "reference pictures." In this manner, the encoding engine (432) encodes the difference between a pixel block of the input picture and a pixel block of a reference picture that may be selected as a prediction reference for the input picture.

[0062] The local video decoder (433) may decode the encoded video data of the picture that may be designated as the reference picture based on the symbol created by the source encoder (430). The operation of the encoding engine (432) may advantageously be a lossy process. When the encoded video data is available at the video decoder ( Figure 4 When the video sequence is decoded at a remote video decoder (not shown), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (433) replicates the decoding process that may be performed by the video decoder on the reference picture and may cause the reconstructed reference picture to be stored in the reference picture cache (434). In this way, the video encoder (403) may store a copy of the reconstructed reference picture locally that has common content (absent transmission errors) with the reconstructed reference picture to be obtained by the remote video decoder.

[0063] The predictor (435) may perform a prediction search for the encoding engine (432). That is, for a new picture to be encoded, the predictor (435) may search the reference picture memory (434) for sample data (as candidate reference pixel blocks) or certain metadata, such as reference picture motion vectors, block shapes, etc., that may serve as appropriate prediction references for the new picture. The predictor (435) may operate on a pixel block by pixel block basis to find a suitable prediction reference. In some cases, as determined by the search results obtained by the predictor (435), the input picture may have prediction references taken from multiple reference pictures stored in the reference picture memory (434).

[0064] The controller (450) may manage encoding operations of the source encoder (430), including, for example, setting parameters and subgroup parameters for encoding video data.

[0065] The outputs of all the above functional units may be entropy encoded in an entropy encoder (445). The entropy encoder (445) performs lossless compression on the symbols generated by the various functional units according to techniques known to those skilled in the art, such as Huffman coding, variable length coding, arithmetic coding, etc., thereby converting the symbols into a coded video sequence.

[0066] The transmitter (440) may buffer the encoded video sequence created by the entropy encoder (445) in preparation for transmission over a communication channel (460), which may be a hardware / software link to a storage device where the encoded video data will be stored. The transmitter (440) may combine the encoded video data from the video encoder (403) with other data to be transmitted, such as encoded audio data and / or ancillary data streams (source not shown).

[0067] The controller (450) may manage the operation of the video encoder (403). During encoding, the controller (450) may assign a certain coded picture type to each coded picture, but this may affect the coding techniques that can be applied to the corresponding picture. For example, a picture may generally be assigned to any of the following picture types:

[0068] An intra picture (I picture) may be a picture that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs allow different types of intra pictures, including, for example, Independent Decoder Refresh ("IDR") pictures. Those skilled in the art are aware of the variations of I pictures and their corresponding applications and features.

[0069] A predictive picture (P picture) may be a picture that can be encoded and decoded using intra prediction or inter prediction, which uses at most one motion vector and a reference index to predict sample values ​​for each block.

[0070] Bidirectional predictive pictures (B pictures), which can be pictures that can be encoded and decoded using intra prediction or inter prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple predictive pictures can use more than two reference pictures and associated metadata for reconstructing a single block.

[0071] The source picture may typically be spatially subdivided into blocks of samples (e.g., blocks of 4×4, 8×8, 4×8, or 16×16 samples), and coded block by block. These blocks may be predictively coded with reference to other (already coded) blocks, which are determined by the coding allocation applied to the block's corresponding picture. For example, a block of an I picture may be non-predictively coded, or the block may be predictively coded (spatial prediction or intra-frame prediction) with reference to an already coded block of the same picture. A block of a P picture may be non-predictively coded by spatial prediction with reference to one previously coded reference picture or by temporal prediction. A block of a B picture may be non-predictively coded by spatial prediction with reference to one or two previously coded reference pictures or by temporal prediction.

[0072] The video encoder (403) may perform encoding operations according to a predetermined video encoding technique or standard, such as ITU-T H.265 Recommendation. In operation, the video encoder (403) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancy in an input video sequence. Thus, the encoded video data may conform to the syntax specified by the video encoding technique or standard used.

[0073] In an embodiment, the transmitter (440) may transmit additional data when transmitting the encoded video. The source encoder (430) may include such data as part of the encoded video sequence. The additional data may include other forms of redundant data such as temporal / spatial / SNR enhancement layers, redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0074] The captured video may be taken as a plurality of source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often simplified to intra-prediction) exploits spatial correlations in a given picture, while inter-picture prediction exploits (temporal or other) correlations between pictures. In an example, a particular picture being encoded / decoded is divided into blocks, and the particular picture being encoded / decoded is referred to as the current picture. When a block in the current picture is similar to a reference block in a reference picture that was previously encoded in the video and is still buffered, the block in the current picture may be encoded by a vector called a motion vector. The motion vector points to a reference block in a reference picture, and in the case where multiple reference pictures are used, the motion vector may have a third dimension that identifies the reference picture.

[0075] In some embodiments, bidirectional prediction techniques may be used in inter-picture prediction. According to the bidirectional prediction technique, two reference pictures are used, for example, a first reference picture and a second reference picture that are both before the current picture in the video in decoding order (but may be in the past and future in display order, respectively). A block in the current picture may be encoded by a first motion vector pointing to a first reference block in the first reference picture and a second motion vector pointing to a second reference block in the second reference picture. Specifically, the block may be predicted by a combination of the first reference block and the second reference block.

[0076] In addition, merge mode technology can be used in inter-picture prediction to improve coding efficiency. In merge mode, a block in the current picture can inherit the motion vector of an adjacent block in the current picture (e.g., share a border with an adjacent block and be located in a larger partition area with the adjacent block).

[0077] According to some embodiments disclosed in the present application, predictions such as inter-picture prediction and intra-picture prediction are performed in units of blocks. 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 the pictures have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. The HEVC standard is described in H.265 / HEVC (ITU-T H.265 Recommendation, "High Efficiency Video Coding", December 2016), the entire contents of which are incorporated herein by reference (hereinafter referred to as the "HEVC standard"). In general, a CTU includes three coding tree blocks (CTBs), which are one luminance CTB and two chrominance CTBs. Each CTU can also be recursively split into one or more coding units (CUs) using a quadtree. For example, a 64×64 pixel CTU can be split into a 64×64 pixel CU, or 4 32×32 pixel CUs, or 16 16×16 pixel CUs. In the example, each CU is analyzed to determine the prediction type for the CU, such as an inter-frame prediction type or an intra-frame prediction type. Depending on the temporal and / or spatial predictability, the CU is split into one or more prediction units (PUs). Typically, each PU includes a luma prediction block (PB) and two chroma PBs. In an embodiment, the prediction operation in encoding (encoding / decoding) is performed in units of prediction blocks. Taking the luma prediction block as an example of a prediction block, the prediction block includes a matrix of values ​​(e.g., luma values) for pixels, such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

[0078] Figure 5 1 is a diagram of a video encoder (503) according to another embodiment disclosed in the present application. The video encoder (503) is configured to receive a processed block (e.g., a prediction block) of sample values ​​within a current video picture in a video picture sequence, and encode the processed block into an encoded picture that is part of an encoded video sequence. In this embodiment, the video encoder (503) is used to replace Figure 2 A video encoder (203) in an embodiment.

[0079] In an HEVC embodiment, a video encoder (503) receives a matrix of sample values ​​for a processing block, such as a prediction block of 8×8 samples. The video encoder (503) uses, for example, rate-distortion (RD) optimization to determine whether to use intra mode, inter mode, or bidirectional prediction mode to best encode the processing block. When encoding the processing block in intra mode, the video encoder (503) may use intra prediction techniques to encode the processing block into an encoded picture; and when encoding the processing block in inter mode or bidirectional prediction mode, the video encoder (503) may use inter prediction or bidirectional prediction techniques to encode the processing block into an encoded picture, respectively. "Merge mode" is a sub-mode of inter prediction and bidirectional prediction, respectively, and can be used to perform reconstruction on prediction samples with or without using residuals. In other words, a coding block encoded in merge mode includes one or more references in the form of motion vectors, and may include control information unrelated to the disclosed subject matter, and may or may not include coefficients of residuals. In some video encoding techniques, the merge mode may be an inter-picture prediction sub-mode, in which motion vectors are derived from one or more motion vector predictors without the aid of encoded motion vector components external to the predictor. In some other video encoding techniques, there may be motion vector components applicable to the subject block. In an embodiment, the video encoder (503) includes other components, such as a mode decision module (not shown) for determining a processing block mode.

[0080] exist Figure 5 In the example of FIG. 5 , the video encoder ( 503 ) includes: Figure 5 Shown are an inter-frame encoder (530), an intra-frame encoder (522), a residual calculator (523), a switch (526), ​​a residual encoder (524), a general controller (521), and an entropy encoder (525) coupled together.

[0081] The inter-frame encoder (530) is configured to receive a sample of a current block (e.g., a processing block), compare the block with one or more reference blocks in a reference picture (e.g., blocks in a previous picture and a subsequent picture), generate inter-frame prediction information (e.g., redundant information description, motion vector, merge mode information according to the inter-frame coding technology), and calculate an inter-frame prediction result (e.g., a predicted block) based on the inter-frame prediction information using any suitable technology.

[0082] The intra encoder (522) is configured to receive samples of a current block (e.g., a processing block), compare the block to an already encoded block in the same picture in some cases, generate quantized coefficients after transformation, and in some cases also generate intra prediction information (e.g., intra prediction direction information according to one or more intra coding techniques).

[0083] The general controller (521) is configured to determine general control data and control other components of the video encoder (503) based on the general control data. In an example, the general controller (521) determines the mode of the block and provides a control signal to the switch (526) based on the mode. For example, when the mode is intra mode, the general controller (521) controls the switch (526) to select the intra mode result for use by the residual calculator (523), and controls the entropy encoder (525) to select intra prediction information and add the intra prediction information to the bitstream; and when the mode is inter mode, the general controller (521) controls the switch (526) to select the inter prediction result for use by the residual calculator (523), and controls the entropy encoder (525) to select the inter prediction information and add the inter prediction information to the bitstream.

[0084] The residual calculator (523) is configured to calculate the difference (residual data) between the received block and the prediction result selected from the intra-frame encoder (522) or the inter-frame encoder (530). The residual encoder (524) is configured to operate based on the residual data to encode the residual data to generate transform coefficients. In an example, the residual encoder (524) is configured to convert the residual data in the frequency domain and generate transform coefficients. The transform coefficients are then subjected to a quantization process to obtain quantized transform coefficients.

[0085] The entropy encoder (525) is configured to format the codestream to produce an encoded block. The entropy encoder (525) includes various information according to a suitable standard, such as the HEVC standard. In an example, the entropy encoder (525) is configured to include general control data, selected prediction information (such as intra-frame prediction information or inter-frame prediction information), residual information, and other suitable information in the codestream. It should be noted that according to the disclosed subject matter, when the block is encoded in the inter-frame mode or the merge sub-mode of the bidirectional prediction mode, there is no residual information.

[0086] Figure 6 is a diagram of a video decoder (610) according to another embodiment disclosed in the present application. The video decoder (610) is configured to receive an encoded image as part of an encoded video sequence and decode the encoded image to generate a reconstructed picture. In an example, the video decoder (610) is used to replace Figure 2 A video decoder (210) is shown in an example.

[0087] exist Figure 6 In the example of FIG. 6 , the video decoder ( 610 ) includes Figure 6 An entropy decoder (671), an inter-frame decoder (680), a residual decoder (673), a reconstruction module (674) and an intra-frame decoder (672) coupled together are shown in FIG.

[0088] The entropy decoder (671) may be configured to reconstruct certain symbols from the encoded picture, which represent syntax elements constituting the encoded picture. Such symbols may include, for example, a mode for encoding the block (e.g., intra mode, inter mode, bidirectional prediction mode, a merged submode of the latter two, or another submode), prediction information (e.g., intra prediction information or inter prediction information) that can identify certain samples or metadata for prediction by the intra decoder (672) or the inter decoder (680), respectively, residual information in the form of, for example, quantized transform coefficients, and the like. In an example, when the prediction mode is inter or bidirectional prediction mode, the inter prediction information is provided to the inter decoder (680); and when the prediction type is an intra prediction type, the intra prediction information is provided to the intra decoder (672). The residual information may be subjected to inverse quantization and provided to the residual decoder (673).

[0089] The inter-frame decoder (680) is configured to receive inter-frame prediction information and generate an inter-frame prediction result based on the inter-frame prediction information.

[0090] The intra decoder (672) is configured to receive intra prediction information and generate a prediction result based on the intra prediction information.

[0091] The residual decoder (673) is configured to perform inverse quantization to extract dequantized transform coefficients, and process the dequantized transform coefficients to convert the residual from the frequency domain to the spatial domain. The residual decoder (673) may also require certain control information (including quantizer parameters QP), and this information may be provided by the entropy decoder (671) (the data path is not indicated because this is only low-volume control information).

[0092] The reconstruction module (674) is configured to combine the residual output by the residual decoder (673) with the prediction result (which may be output by the inter-frame prediction module or the intra-frame prediction module) in the spatial domain to form a reconstructed block, which may be part of a reconstructed picture, which in turn may be part of a reconstructed video. It should be noted that other suitable operations such as deblocking operations may be performed to improve visual quality.

[0093] It should be noted that the video encoder (203), video encoder (403) and video encoder (503) and video decoder (210), video decoder (310) and video decoder (610) may be implemented using any suitable technology. In an embodiment, the video encoder (203), video encoder (403) and video encoder (503) and video decoder (210), video decoder (310) and video decoder (610) may be implemented using one or more integrated circuits. In another embodiment, the video encoder (203), video encoder (403) and video encoder (403) and video decoder (210), video decoder (310) and video decoder (610) may be implemented using one or more processors that execute software instructions.

[0094] Figure 7 An embodiment of an exemplary angle mode for intra prediction is shown. Figure 7 Depicted in the lower right center is a subset of 9 prediction directions from the 35 possible prediction directions that may be from H.265. The point (701) where the arrows converge represents the sample being predicted. The arrows represent the direction from which the sample is predicted. For example, arrow (702) indicates that sample (701) is predicted from one or more samples to the upper right at an angle of 45 degrees to the horizontal axis. Similarly, arrow (703) indicates that sample (701) is predicted from one or more samples to the lower left of sample (701) at an angle of 22.5 degrees to the horizontal axis.

[0095] Still refer to Figure 7, a square block (704) of 4×4 samples is depicted in the upper right (indicated by the bold dashed line). The square block (704) includes 16 samples, each sample is labeled with "S" and its position in the Y dimension (e.g., row index) and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample in the Y dimension (starting from the top) and the first sample in the X dimension (starting from the left). Similarly, sample S44 is the fourth sample in the Y dimension and X dimension of block (704). Since the size of the block is 4×4 samples, S44 is in the lower right corner. Reference samples following a similar numbering strategy are also shown. Relative to block (704), the reference samples are labeled with R and their Y position (e.g., row index) and X position (column index). Intra-picture prediction can operate by appropriately copying reference sample values ​​from neighboring samples using the prediction direction indicated by the signal. For example, assume that the encoded video bitstream includes signaling that indicates a prediction direction consistent with arrow (702) for the block, that is, the sample is predicted based on one or more prediction samples to the upper right at a 45 degree angle to the horizontal direction. In this case, samples S41, S32, S23, and S14 are predicted based on the same R05. Sample S44 is then predicted based on R08.

[0096] In some cases, the values ​​of multiple reference samples may be combined, such as by interpolation, in order to compute a reference sample; in particular when the directions cannot be divided by 45 degrees.

[0097] According to some embodiments, intra prediction uses blocks that are spatially adjacent to previously decoded boundary samples to predict a new prediction block (PB). In some embodiments, angular intra prediction is employed to effectively model the different directional structures present in video and image content. The set of available prediction directions can be selected to provide a good trade-off between coding complexity and coding efficiency.

[0098] According to some embodiments, intra prediction may be performed according to a predetermined number (X) of intra prediction modes. Each intra prediction mode may be identified by an integer, where mode 0 represents a plane intra prediction mode and mode 1 represents a direct current (DC) intra prediction mode. The plane intra prediction mode (i.e., mode 0) may be a plane prediction mode for texture images and may be used to maintain continuity along block edges. The DC intra prediction mode (i.e., mode 1) may be used to predict planar regions of smoothly varying content such as flat surfaces.

[0099] Mode 2 to Mode X-1 may indicate angular intra prediction modes, each angular mode indicating a direction. In a video image, horizontal and vertical patterns may appear more frequently than patterns with other directivities. Therefore, in some embodiments, an angular intra mode that is closer to a horizontal mode or a vertical mode may have a smaller displacement parameter than displacement parameters in other directions. For example, the displacement parameter difference may become larger when closer to a diagonal direction to reduce the density of prediction modes for less frequently occurring patterns.

[0100] Figure 8 (A) and Figure 8 (B) shows an embodiment of a total of 35 intra prediction modes including 33 angle modes. Mode 0 is a plane intra (INTRA_PLANAR) mode, and mode 1 is a direct current (DC) intra (INTRA_DC) mode. In addition, modes 2 to 34 represent intra angle modes. Mode 10 is a horizontal angle mode, and mode 26 is a vertical mode. Fig. 9 (A) and Fig. 9 (B) shows an embodiment of a total of 67 intra prediction modes including 65 angle modes. Mode 0 is INTRA_PLANAR mode, and mode 1 is INTRA_DC mode. In addition, modes 2 to 66 represent angle intra modes (INTRA_ANGULAR) INTRA_ANGULAR2 to INTRA_ANGULAR66, respectively. Mode 18 is a horizontal mode, and mode 50 is a vertical mode.

[0101] exist Fig. 9 (A) and Fig. 9 The embodiment shown in (B) enables the capture of arbitrary edge directions present in natural videos. Figure 8 (A) and Figure 8 Compared with the embodiment shown in (B), Fig. 9 (A) and Fig. 9 The embodiment shown in (B) provides better prediction accuracy due to the increase in the number of modes. However, during the most probable mode (MPM) derivation process, when additional modes are obtained by adding -1 or +1 to the angle modes already included in the MPM list, a %65 modulo operation needs to be performed. The %65 operation is disadvantageous because it is different from the %2 N Compared to the operation of %65, the operation of %65 is more complex to implement in hardware (such as an encoder or decoder). In this regard, the complexity of the modulus operation is similar to the complexity of the division operation, which is undesirable when performing video encoding and decoding by ordinary technicians in the field. However, it can be implemented in the same way as &(2 N ) Different ways to 2 N Perform a modulo operation, which is simpler than division.

[0102] According to some embodiments, when deriving neighboring modes for a given angular mode, a modulo % M operation is used, where M is a power of 2, but may not be equal to 32. This may be done during the MPM derivation process, during the auxiliary MPM derivation process, or during the P th The adjacent mode is exported during the MPM list export process. Examples of M include, but are not limited to, 2, 4, 8, 16, 64, 128, 256, etc.

[0103] According to some embodiments, the total number of angular intra modes is K=1+2 N , the value of modulo M is 2 N , and the angle mode index ranges from A0 to A K-1 The -d mode can be derived by the following formula:

[0104] Formula 1: M_0 = ((mode + 2 N -A0-d)%2 N )+A0

[0105] The +d mode can be derived by the following formula:

[0106] Formula 2: M_1 = ((mode - A0 + d) % 2 N )+A0

[0107] For example, when M is equal to 64 (eg, N=6), the total number of angle intra modes K is 1+2 6 =65, where A0 is 2, and A K-1 is 64. The -d mode can be derived by the following formula:

[0108] M_0=((mode+62-d)%64)+2

[0109] In addition, the +d mode is derived by the following formula:

[0110] M_1=((mode-2+d)%64)+2

[0111] According to some embodiments, M is the sum of multiple (X) powers of 2. Example values ​​of M include, but are not limited to, 32+64, 32+16, 16+64, etc. Example values ​​of X include, but are not limited to, 2, 3, 4, etc. When M is the sum of multiple (X) powers of 2, the total number of angular intra modes is K=1+2 N0 +2 N1 , where M is 2 N0 +2 N1 , and the angle mode index ranges from A0 to A K-1 .

[0112] The -d mode can be derived by the following formula:

[0113] Formula 3: M_0=((mode+2 N0 +2 N1 -A0-d)%(2 N0 +2 N1 ))+A0

[0114] The +d mode can be derived by the following formula:

[0115] Formula 4: M_1=((mode+2 N0 +2 N1 -A0+d)%(2 N0 +2 N1 ))+A0

[0116] According to some embodiments, in order to adapt to the increase in the number of directional intra-frame modes, the intra-frame mode encoding method derives a candidate list including a predetermined number of most probable modes (MPMs). In some embodiments, the predetermined number is 6, but as understood by a person skilled in the art, the predetermined number is not limited to the number of MPMs. The modes included in the candidate list can be classified into (1) adjacent intra-frame modes, (2) derived intra-frame modes, and (3) default intra-frame modes.

[0117] In some embodiments, five neighboring intra prediction modes are used to form an initial candidate list. Fig.10 A current block 1001 is shown, which is surrounded by (i) a lower left (BL) neighboring block 1002, (ii) a left side neighboring block 1003, (iii) an upper right (AR) neighboring block 1004, (iv) an upper (A) neighboring block 1005, and (v) an upper left (AL) neighboring block 1006. The order of these blocks in the initial candidate list is left, upper, plane, DC, lower left, upper right, and upper left.

[0118] In some embodiments, when using Fig.10 After forming the initial candidate list with the patterns of the adjacent blocks shown in , a reduction process is used to remove repeated patterns so that unique patterns remain in the candidate list. For example, if the left block (1003) and the lower left block (1002) are both in INTRA_DC mode, one of these blocks is removed from the candidate list.

[0119] If the candidate list is not full after the reduction process (e.g., there are less than 6 MPM candidates in the candidate list), the derived mode is added to the candidate list. The derived mode can be obtained by adding -1 or +1 to each angle intra node included in the candidate list. For example, for d=1, K=66, N=6, Formula 1 or Formula 3 can be used to derive the -1 mode, and Formula 2 or Formula 4 can be used to derive the +1 mode. For example, when Formula 1 is used, the -d mode is:

[0120] M_0=((mode+62-d)%64)+2

[0121] Furthermore, when using Equation 2, the +d mode is:

[0122] M_1=((mode-2+d)%64)+2

[0123] In the above examples, d may be a positive integer, such as d=1, d=2, d=3, etc.

[0124] If the candidate list is still not full after adding the export mode to the candidate list, the default mode can be added in the following order: vertical mode, horizontal mode, mode 2, and diagonal mode. As a result of this process, a unique candidate list of 6 MPM modes will be generated.

[0125] According to some embodiments, truncated unary binarization is used for entropy coding of selected modes using 6 MPMs. The first three items can be encoded using a context that depends on the MPM mode associated with the item currently being signaled. MPM modes can be divided into one of three categories: (a) primarily horizontal modes (i.e., the MPM mode number is less than or equal to the mode number in the diagonal direction), (b) primarily vertical modes (i.e., the MPM mode is greater than the mode number in the diagonal direction), and (c) non-angular (DC and planar) classes. Therefore, based on this classification, three contexts can be used to signal the MPM index.

[0126] According to some embodiments, the encoding for selecting the remaining 61 non-MPMs can be performed in the following manner. The 61 non-MPMs can first be divided into two sets: a selected mode set and a non-selected mode set. The selected mode set can contain 16 modes, and the remaining modes (45 modes) can be assigned to the non-selected mode set. The mode set to which the current mode belongs can be indicated by a flag in the code stream. If the mode to be indicated is within the selected mode set, the selected mode can be represented by a signal of a 4-bit fixed length code, and if the mode to be indicated is from the non-selected set, the selected mode can be represented by a signal of a truncated binary code.

[0127] Fig.11 An embodiment of a process performed by an encoder or decoder, such as the intra encoder 522 or the intra decoder 672, respectively, is shown. Fig.11 The process shown can be used to derive a candidate list for determining an intra prediction mode for a current block. The process can start with step S1100 in the case of an empty candidate list, in which, for the current block, neighboring intra modes are added to the candidate mode list. For example, referring to Fig.10, for the current block 1001, the intra modes of the neighboring blocks 1002 to 1006 are added to the candidate list. The process proceeds to step S1102, in which the repeated intra modes are removed from the candidate list. For example, if both modes in the candidate list include the mode INTRA_DC, one of these modes will be removed.

[0128] The process proceeds to step S1104, in which it is determined whether the number of modes in the candidate mode list is less than a predetermined number. For example, the predetermined number may be set to 6. If the number of nodes in the candidate list is equal to the predetermined number, the candidate list is completed, and the process proceeds to step S1112, in which the intra mode of the current block is determined for the current block using the candidate list.

[0129] If the number of modes in the candidate list is less than the predetermined number, the process proceeds to step S1106 to determine the derived intra mode. For example, for each angle intra mode included in the candidate list, the -1 mode is determined using Formula 1 or Formula 3 with d=1, and the +1 mode is determined using Formula 2 or Formula 4 with d=1.

[0130] The process proceeds to step S1108 to determine whether the number of patterns in the candidate list is less than the predetermined number. If the number of patterns in the candidate list is still less than the predetermined number, the process proceeds to step S1110, in which a default node is added to the candidate list. For example, the default mode may include a vertical mode, a horizontal mode, a mode 2, and a diagonal mode. The process proceeds from step S1110 to step S1112. Returning to step S1108, if the number of patterns in the candidate list is equal to the predetermined number, the step proceeds to step S1112.

[0131] Fig.12 An embodiment of a process performed by an encoder or decoder, such as the intra encoder 522 or the intra decoder 672, respectively, is shown for determining a luma intra prediction mode for a current block. Fig. 9 The intra prediction mode shown performs Fig.12 In the process shown, there are 67 intra-frame prediction modes in total, and the intra-frame angle modes of the 67 intra-frame prediction modes are numbered 2-66. Fig.12 The process shown may start at step S1200, where neighboring positions are set for the current block. For example, if the current block has position coordinates (xPb, yPb), the neighboring position (xNbA, yNba) and the neighboring position (xNbB, yNbB) are set as follows:

[0132] (xNbA,yNba)=(xPb-1,yPb),

[0133] (xNbB,yNbB)=(xPb,yPb-1).

[0134] Fig.14 An example of a neighboring position (xNbA, yNbA) and a neighboring position (xNbB, yNbB) is shown. For example, block A represents a neighboring position (xNbA, yNba) because the neighboring position is on the left side of the current block (xPb, yPb). In addition, block B represents a neighboring position (xNbB, yNbB) because the neighboring position is on the upper side of the current block (xPb, yPb).

[0135] The process proceeds to step S1202, in which the intra prediction mode for the neighboring position is determined. For example, the intra prediction mode for the neighboring position (xNbA, yNba) and the neighboring position (xNbB, yNbB) can be assigned to variables candIntraPredModeA and candIntraPredModeB, respectively. In this regard, candIntraPredModeA can represent the intra prediction mode of block A ( Fig.14 ), and candIntraPredModeB can represent the intra prediction mode of block B ( Fig.14 ). The variables candIntraPredModeA and candIntraPredModeB may generally be referred to as candIntraPredModeX. The following steps (i) and (ii)(a) to (ii)(d) describe an example process for determining the variable candIntraPredModeX, where for the case where X is replaced by A or B, the variable candIntraPredModeX (e.g., candIntraPredModeA or candIntraPredModeB) is derived in the following manner.

[0136] (i) The process begins by assigning a value to the parameters (xCurr, yCurr) as the current position of the current block, and then determining whether a reference sample is available for the current block. For example, the availability derivation process for blocks in z-scan order specified in Section 6.4.1 of the HEVC standard is called with a position (xCurr, yCurr) set equal to (xPb, yPb) and a neighboring position (xNbY, yNbY) set equal to (xNbX, yNbX) as input, and the output is assigned to a Boolean parameter availableX, which is used to indicate whether the reference sample of the current block is available.

[0137] (ii) The candidate intra prediction mode candIntraPredModeX is derived in the following way:

[0138] (a) If availableX is FALSE (i.e., the reference sample is not available), then set candIntraPredModeX to be equal to INTRA_DC,

[0139] (b) Otherwise (i.e., the reference sample is available), if CuPredMode[xNbX][yNbX] is not equal to MODE_INTRA or pcm_flag[xNbX][yNbX] is equal to 1, then set candIntraPredModeX to INTRA_DC,

[0140] (c) Otherwise, if X is equal to B and yPb-1 is less than ((yPb >> CtbLog2SizeY) << CtbLog2SizeY), then set candIntraPredModeB to INTRA DC.

[0141] (d) Otherwise, set candIntraPredModeX to be equal to IntraPredModeY[xNbX][yNbX]

[0142] In the above example, the variable CuPredMode can represent the intra prediction mode of the current block, the variable pcm_flag can represent whether the differential pulse code modulation (DPCM) mode is enabled, and the variable CtbLog2SizeY can represent the Log2 value of the block height.

[0143] The process proceeds to step S1204, in which a candidate list of the most probable mode (MPM) is determined. An example process for determining the candidate list of the MPM is shown in Fig.13 . In Fig.13 , the variable A represents candIntraPredModeA and the variable B represents candIntraPredModeB.

[0144] Fig.13 The process shown can start at step S1300, in which it is determined whether A = B. If A = B (i.e., A and B have the same intra prediction mode), then the process proceeds to step S1302 to determine whether A < 2 (i.e., A is a non - angular intra prediction mode). If A < 2, then the process proceeds to step S1304, in which the candidate list is determined as follows:

[0145] Candidate list[0] = Intra_Planar

[0146] Candidate list[1] = Intra_DC

[0147] Candidate list [2] = Intra_Angular50.

[0148] If A is not less than 2, the process proceeds from step S1302 to step S1306, in which the candidate list is determined as follows:

[0149] Candidate List[0] = A

[0150] Candidate list [1] = 2 + ((A + 61) % 64)

[0151] Candidate list [2] = 2 + ((A-2 + 1) % 64).

[0152] As described above, the first item in the candidate list (e.g., candidate list [0]) is set to the inter prediction mode corresponding to block A ( Fig.14 ), determine the second item in the candidate list (e.g., candidate list [1]) according to Formula 1, and determine the third item in the candidate list (e.g., candidate list [2]) according to Formula 2, where d=1, N=6 and A0=2.

[0153] Returning to step S1300, if A is not equal to B, the process proceeds to step S1308, in which the first item in the candidate list (e.g., candidate list [0]) is set to A, and the second item in the candidate list (e.g., candidate list [1]) is set to B. The process proceeds to step S1310, in which it is determined whether both A and B are not planar intra-frame modes. If neither A nor B is a planar intra-frame mode, the process proceeds to step S1312, in which the third item in the candidate list (e.g., candidate list [2]) is set to a planar intra-frame mode.

[0154] Returning to step S1310, if A or B is a planar intra mode (e.g., mode 0), the process proceeds to step S1314, in which it is determined whether neither A nor B is a DC intra mode (e.g., mode 1). If neither A nor B is a DC intra mode, the process proceeds to step S1316, in which the third item in the candidate list (e.g., candidate list [2]) is set to a DC intra mode. However, if A or B is a DC intra mode, the process proceeds from step S1314 to step S1318, in which the third item in the candidate list (e.g., candidate list [2]) is set to a vertical intra prediction mode (e.g., mode 50).

[0155] After creating the candidate list of MPMs, Fig.13 The process shown is complete. Return Fig.12, the process proceeds from step S1204 to step S1206, in which the intra prediction mode of the current block is determined. The intra prediction mode of the current block can be represented by a variable IntraPredModeY[xPb][yPb], which can be determined according to steps (i) and steps (ii)(a) to (ii)(e) as described below. In particular, in step (i), it is determined whether the intra prediction mode of the current block is included in the candidate list (e.g., the Boolean parameter prev_intra_luma_pred_flag is true). For example, if the luma intra prediction mode of the current block is one of the three candidates included in the candidate list (which can be represented by the variable mpm_idx), the variable prev_intra_luma_pred_flag[xPb][yPb] can be set to 1 by the encoder. The encoder can indicate the variables prev_intra_luma_pred_flag and mpm_idx to the decoder through a signal in the video bitstream.

[0156] If the inter prediction mode is not included in the candidate list (e.g., prev_intra_luma_pred_flag[xPb][yPb]=0), in step (ii), the candidate list is arranged in order from lowest to highest (e.g., steps (a) to (c)), and then the inter prediction mode of the current block is set to a non-MPM mode (e.g., rem_intra_luma_pred_mode) and derived according to the derived candidate list (e.g., steps (d) and (e)).

[0157] The process for determining the intra prediction mode (eg, IntraPredModeY[xPb][yPb]) of the current block can be described as follows:

[0158] (i) If prev_intra_luma_pred_flag[xPb][yPb]=1, set IntraPredModeY[xPb][yPb] equal to candModeList[mpm_idx[xPb][yPb]],

[0159] (ii) Otherwise, derive IntraPredModeY[xPb][yPb] by performing the following steps in order:

[0160] (a) When candModeList[0] is greater than candModeList[1], the two values ​​are swapped as follows:

[0161] (candModeList[0],candModeList[1])=Swap(candModeList[0],candModeList[1]),

[0162] (b) When candModeList[0] is greater than candModeList[2], the two values ​​are swapped as follows:

[0163] (candModeList[0],candModeList[2])=Swap(candModeList[0],candModeList[2]),

[0164] (c) When candModeList[1] is greater than candModeList[2], the two values ​​are swapped as follows:

[0165] (candModeList[1],candModeList[2])=Swap(candModeList[1],candModeList[2]),

[0166] (d) Set IntraPredModeY[xPb][yPb] equal to rem_intra_luma_pred_mode[xPb][yPb],

[0167] (e) For i equal to 0 to 2 (inclusive), when IntraPredModeY[xPb][yPb] is greater than or equal to candModeList[i], the value of IntraPredModeY[xPb][yPb] is increased by 1.

[0168] The above techniques and processes may be implemented as computer software using computer-readable instructions and physically stored in one or more computer-readable media. Fig.15 A computer system (1500) suitable for implementing certain embodiments of the disclosed subject matter is shown.

[0169] Computer software may be encoded using any suitable machine code or computer language that may be subjected to assembly, compilation, linking or similar mechanisms to create code comprising instructions that may be executed directly by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., or through interpretation, microcode, etc.

[0170] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, IoT devices, etc.

[0171] Fig.15 The components of the computer system (1500) shown are exemplary in nature and are not intended to suggest any limitation on the scope of use or functionality of computer software implementing embodiments of the application. Nor should the configuration of components be interpreted as having any dependency or requirement relating to any one or combination of components shown in the exemplary embodiment of the computer system (1500).

[0172] The computer system (1500) may include certain human-machine interface input devices. Such human-machine interface input devices may respond to input from one or more human users, for example, through: tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), olfactory input (not depicted). The human-machine interface device may also be used to capture certain media that are not necessarily directly related to human conscious input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, photographic images obtained from a still image camera), video (e.g., two-dimensional video, three-dimensional video including stereoscopic video), etc.

[0173] The input human-machine interface device may include one or more of the following (only one of each is shown): keyboard (1501), mouse (1502), touch pad (1503), touch screen (1510), data gloves (not shown), joystick (1505), microphone (1506), scanner (1507), camera (1508).

[0174] The computer system (1500) may also include certain human-machine interface output devices. Such human-machine interface output devices may stimulate one or more human user senses, for example, through tactile output, sound, light, and smell / taste. Such human-machine interface output devices may include tactile output devices (e.g., tactile feedback of a touch screen (1510), a data glove (not shown), or a joystick (1505), but may also be a tactile feedback device that is not an input device), audio output devices (e.g., speakers (1509), headphones (not shown)), visual output devices (e.g., screens (1510) including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capabilities, each with or without tactile feedback capabilities - some of which are capable of outputting two-dimensional visual outputs or more than three-dimensional outputs through devices such as stereoscopic image output, virtual reality glasses (not depicted), holographic displays and smoke boxes (not depicted), and printers (not depicted).

[0175] The computer system (1500) may also include human-accessible storage devices and their associated media: for example, optical media including CD / DVD ROM / RW (1520) with CD / DVD etc. media (1521), thumb drives (1522), removable hard drives or solid-state drives (1523), traditional magnetic media such as tapes and floppy disks (not shown), dedicated ROM / ASIC / PLD based devices such as security dongles (not shown), etc.

[0176] Those skilled in the art should also understand that the term "computer-readable media" used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transient signals.

[0177] The computer system (1500) may also include an interface to one or more communication networks. The network may be, for example, a wireless network, a wired network, an optical network. The network may further be a local network, a wide area network, a metropolitan area network, a vehicle and industrial network, a real-time network, a delay-tolerant network, etc. Examples of networks include local area networks such as Ethernet, wireless LANs, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., television wired or wireless wide area digital networks including cable television, satellite television, and terrestrial broadcast television, vehicle and industrial television including CANBus, etc. Some networks typically require an external network interface adapter (e.g., a USB port of the computer system (1500)) connected to some general data port or peripheral bus (1549); as described below, other network interfaces are typically integrated into the kernel of the computer system (1500) by connecting to the system bus (e.g., connecting to an Ethernet interface in a PC computer system or connecting to a cellular network interface in a smartphone computer system). The computer system (1500) can use any of these networks to communicate with other entities. Such communications may be one-way receive only (e.g., broadcast television), one-way send only (e.g., a CANbus connected to certain CANbus devices), or bidirectional, for example, using a LAN or WAN digital network to connect to other computer systems. As described above, certain protocols and protocol stacks may be used on each of those networks and network interfaces.

[0178] The above-mentioned human-machine interface device, human-machine accessible storage device, and network interface may be attached to the kernel ( 1540 ) of the computer system ( 1500 ).

[0179] The core (1540) may include one or more central processing units (CPUs) (1541), graphics processing units (GPUs) (1542), dedicated programmable processing units in the form of field programmable gate arrays (FPGAs) (1543), hardware accelerators (1544) for certain tasks, etc. These devices, as well as read-only memory (ROM) (1545), random access memory (1546), internal mass storage (1547) such as internal non-user accessible hard drives, SSDs, etc., may be connected via a system bus (1548). In some computer systems, the system bus (1548) may be accessed in the form of one or more physical plugs to enable expansion by additional CPUs, GPUs, etc. Peripheral devices may be connected directly to the core's system bus (1548) or to the core's system bus (1848) via a peripheral bus (1549). The architecture of the peripheral bus includes PCI, USB, etc.

[0180] The CPU (1541), GPU (1542), FPGA (1543) and accelerator (1544) can execute certain instructions, which can be combined to constitute the above-mentioned computer code. The computer code can be stored in ROM (1545) or RAM (1546). Transition data can also be stored in RAM (1546), while permanent data can be stored, for example, in internal mass storage (1547). Fast storage and retrieval to any storage device can be performed by using a cache, which can be closely associated with the following: one or more CPUs (1541), GPUs (1542), mass storage (1547), ROM (1545), RAM (1546), etc.

[0181] The computer readable medium may have thereon computer code for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of this application, or the medium and computer code may be of a type well known and available to those skilled in the art of computer software.

[0182] As a non-limiting example, a computer system having an architecture (1500), particularly a kernel (1540), can provide functionality due to one or more processors (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software contained in one or more tangible computer-readable media. Such computer-readable media can be media associated with user-accessible mass storage as described above, as well as certain non-temporary memories of the kernel (1540), such as kernel internal mass storage (1547) or ROM (1545). Software implementing various embodiments of the present application can be stored in such devices and executed by the kernel (1540). Depending on specific needs, the computer-readable medium may include one or more storage devices or chips. The software can cause the kernel (1540), particularly the processors therein (including CPUs, GPUs, FPGAs, etc.) to perform specific processes or specific parts of specific processes described herein, including defining data structures (1546) stored in RAM and modifying such data structures according to processes defined by the software. Additionally or alternatively, the computer system may provide functionality due to logic hardwired or otherwise embodied in circuitry (e.g., accelerator (1544)) that may replace software or operate in conjunction with software to perform a particular process or a particular portion of a particular process described herein. Where appropriate, references to portions of software may include logic and vice versa. Where appropriate, references to portions of computer-readable media may include circuitry (e.g., integrated circuits (ICs)) storing software for execution, circuitry embodying logic for execution, or both. The present application includes any suitable combination of hardware and software.

[0183] Appendix A: Abbreviations

[0184] MV: Motion Vector

[0185] HEVC: High Efficiency Video Coding

[0186] SEI: Supplemental Enhancement Information

[0187] VUI: Video Availability Information

[0188] GOP: Group of Pictures

[0189] TU: Transformation Unit

[0190] PU: prediction unit

[0191] CTU: Coding Tree Unit

[0192] CTB: Coding Tree Block

[0193] PB: prediction block

[0194] HRD: Hypothesized Reference Decoder

[0195] SNR: Signal to Noise Ratio

[0196] CPU: Central Processing Unit

[0197] GPU: Graphics Processing Unit

[0198] CRT: cathode ray tube

[0199] LCD: Liquid Crystal Display

[0200] OLED: Organic Light Emitting Diode

[0201] CD: compact disc

[0202] DVD: Digital Video Disc

[0203] ROM: Read Only Memory

[0204] RAM: Random Access Memory

[0205] ASIC: Application-Specific Integrated Circuit

[0206] PLD: Programmable Logic Device

[0207] LAN: Local Area Network

[0208] GSM: Global System for Mobile Communications

[0209] LTE: Long Term Evolution

[0210] CANBus: Controller Area Network Bus

[0211] USB: Universal Serial Bus

[0212] PCI: Peripheral Component Interconnect

[0213] FPGA: Field Programmable Gate Array

[0214] SSD: Solid State Drive

[0215] IC: Integrated Circuit

[0216] CU: Coding Unit

[0217] Although the present application has described a number of exemplary embodiments, there are modifications, permutations, and various replacement equivalents that fall within the scope of the present application. Therefore, it should be understood that those skilled in the art will be able to design many systems and methods that, although not explicitly shown or described herein, embody the principles of the present application and therefore fall within the spirit and scope of the present application.

[0218] The above disclosure also includes the following embodiments:

[0219] (1) A method for video decoding in a decoder, comprising deriving a candidate list for a block encoded in an intra-frame prediction mode. The candidate list includes a first candidate intra-frame prediction mode value (Mode1). The first candidate intra-frame prediction mode value corresponds to an intra-frame prediction mode of a neighboring block adjacent to the encoding block as the first intra-frame prediction mode among multiple intra-frame prediction modes. The candidate list also includes a second candidate intra-frame prediction mode value (Mode2) and a third candidate intra-frame prediction mode value (Mode3). The second candidate intra-frame prediction mode value (Mode2) and the third candidate intra-frame prediction mode value (Mode3) are determined based on a predetermined offset from the first candidate intra-frame prediction mode value and a modulo M operation, where M is a power of 2 and M is not equal to 32. The method also includes determining the intra-frame prediction mode value of the encoding block based on the derived candidate list.

[0220] (2) A method according to feature (1), wherein Mode2 is determined according to the following formula: ((Mode1+M-A0-d)%M)+A0, wherein N is a positive integer, d is a positive integer, and the total number of modes within the angle frame is K=1+2 N , M is equal to 2 N , and the angle mode index ranges from A0 to A k-1 .

[0221] (3) A method according to feature (2), wherein Mode3 is determined according to the formula ((Mode1-A0+d)%M)+A0.

[0222] (4) A video decoder comprising a processing circuit, the processing circuit being configured to derive a candidate list for a block encoded in an intra-frame prediction mode. The candidate list includes a first candidate intra-frame prediction mode value (Mode1). The first candidate intra-frame prediction mode value corresponds to an intra-frame prediction mode of a neighboring block adjacent to the encoding block as the first intra-frame prediction mode among multiple intra-frame prediction modes. The candidate list also includes a second candidate intra-frame prediction mode value (Mode2) and a third candidate intra-frame prediction mode value (Mode3). The second candidate intra-frame prediction mode value (Mode2) and the third candidate intra-frame prediction mode value (Mode3) are determined based on a predetermined offset from the first candidate intra-frame prediction mode value and a modulo M operation, where M is a power of 2 and M is not equal to 32. The processing circuit is also configured to determine the intra-frame prediction mode value of the encoding block based on the derived candidate list.

[0223] (5) A video decoder according to feature (4), wherein Mode2 is determined according to the following formula: ((Mode1+M-A0-d)%M)+A0, wherein N is a positive integer, d is a positive integer, and the total number of angle intra modes is K=1+2 N , M is equal to 2N , and the angle mode index ranges from A0 to A k-1 .

[0224] (6) A video decoder according to feature (5), wherein Mode3 is determined according to the following formula: ((Mode1-A0+d)%M)+A0.

[0225] (7) A non-temporary computer-readable medium storing instructions, which, when executed by a processor in a video decoding device, causes the processor to perform a method, the method comprising deriving a candidate list for a block encoded in an intra-frame prediction mode. The candidate list comprises a first candidate intra-frame prediction mode value (Mode1). The first candidate intra-frame prediction mode value corresponds to an intra-frame prediction mode of a neighboring block adjacent to the encoding block as the first intra-frame prediction mode among multiple intra-frame prediction modes. The candidate list also comprises a second candidate intra-frame prediction mode value (Mode2) and a third candidate intra-frame prediction mode value (Mode3). The second candidate intra-frame prediction mode value (Mode2) and the third candidate intra-frame prediction mode value (Mode3) are determined based on a predetermined offset from the first candidate intra-frame prediction mode value and a modulo M operation, wherein M is a power of 2 and M is not equal to 32. The method also comprises determining the intra-frame prediction mode value of the encoding block based on the derived candidate list.

[0226] (8) The non-transitory computer-readable medium of feature (7), wherein Mode2 is determined according to the following formula:

[0227] ((Mode1+M-A0-d)%M)+A0,

[0228] Where N is a positive integer, d is a positive integer, and the total number of angle intra modes is K = 1 + 2 N , M is equal to 2 N , and the angle mode index ranges from A0 to A k-1 .

[0229] (9) The non-transitory computer readable medium of feature (8), wherein Mode1 is determined according to the following formula:

[0230] ((Mode1-A0+d)%M)+A0.

Claims

1. A method for video decoding, comprising: For a current block encoded in an intra prediction mode, a candidate list of intra prediction modes including a plurality of neighboring blocks adjacent to the current block is derived, wherein the candidate list includes: a first candidate intra-frame prediction mode value Mode1, wherein the first candidate intra-frame prediction mode value corresponds to an intra-frame prediction mode of one of the plurality of neighboring blocks, and The second candidate intra prediction mode value Mode2 and the third candidate intra prediction mode value Mode3, wherein the second candidate intra prediction mode value Mode2 and the third candidate intra prediction mode value Mode3 are determined according to the following formula: Mode2=((Mode1+61)%64)+2, Mode3 = ((Mode1-1)%64)+2; An intra prediction mode value of the current block is determined according to the candidate list.

2. The method according to claim 1, characterized in that: The total number of intra prediction modes is 67, and the total number of angular intra modes is K=65.

3. The method according to claim 1, characterized in that The multiple neighboring blocks include a first neighboring block located on the left side of the current block, a second neighboring block located on the lower left side of the current block, a third neighboring block located on the upper left side of the current block, a fourth neighboring block located on the upper side of the current block, and a fifth neighboring block located on the upper right side of the current block.

4. The method according to claim 1, characterized in that: The method further comprises: In response to the number of modes in the candidate list being less than a predetermined number, at least one default mode is added to the candidate list, wherein the at least one default mode is added to the candidate list in the following order: vertical mode, horizontal mode, mode 2, diagonal mode, and mode 2 represents one of the intra-frame angle modes.

5. A video decoder comprising: A processing circuit, the processing circuit being configured to: For a current block encoded in an intra prediction mode, a candidate list of intra prediction modes including a plurality of neighboring blocks adjacent to the current block is derived, wherein the candidate list includes: a first candidate intra-frame prediction mode value Mode1, wherein the first candidate intra-frame prediction mode value corresponds to an intra-frame prediction mode of one of the plurality of neighboring blocks, and The second candidate intra prediction mode value Mode2 and the third candidate intra prediction mode value Mode3, wherein the second candidate intra prediction mode value Mode2 and the third candidate intra prediction mode value Mode3 are determined according to the following formula: Mode2=((Mode1+61)%64)+2, Mode3 = ((Mode1-1)%64)+2; An intra prediction mode value of the current block is determined according to the candidate list.

6. The video decoder according to claim 5, characterized in that The total number of intra prediction modes is 67, and the total number of angular intra modes is K=65.

7. The video decoder according to claim 5, characterized in that The multiple neighboring blocks include a first neighboring block located on the left side of the current block, a second neighboring block located on the lower left side of the current block, a third neighboring block located on the upper left side of the current block, a fourth neighboring block located on the upper side of the current block, and a fifth neighboring block located on the upper right side of the current block.

8. The video decoder according to claim 5, characterized in that In response to the number of modes in the candidate list being less than a predetermined number, at least one default mode is added to the candidate list, wherein the at least one default mode is added to the candidate list in the following order: vertical mode, horizontal mode, mode 2, diagonal mode, and mode 2 represents one of the intra-frame angle modes.

9. A video encoding method, comprising: For a current block encoded in an intra prediction mode, a candidate list of intra prediction modes including a plurality of neighboring blocks adjacent to the current block is derived, wherein the candidate list includes: a first candidate intra-frame prediction mode value Mode1, wherein the first candidate intra-frame prediction mode value corresponds to an intra-frame prediction mode of one of the plurality of neighboring blocks, and The second candidate intra prediction mode value Mode2 and the third candidate intra prediction mode value Mode3, wherein the second candidate intra prediction mode value Mode2 and the third candidate intra prediction mode value Mode3 are determined according to the following formula: Mode2=((Mode1+61)%64)+2, Mode3 = ((Mode1-1)%64)+2; An intra prediction mode value of the current block is determined according to the candidate list.

10. A video encoder, comprising: A processing unit, the processing unit being configured to: For a current block encoded in an intra prediction mode, a candidate list of intra prediction modes including a plurality of neighboring blocks adjacent to the current block is derived, wherein the candidate list includes: a first candidate intra-frame prediction mode value Mode1, wherein the first candidate intra-frame prediction mode value corresponds to an intra-frame prediction mode of one of the plurality of neighboring blocks, and The second candidate intra prediction mode value Mode2 and the third candidate intra prediction mode value Mode3, wherein the second candidate intra prediction mode value Mode2 and the third candidate intra prediction mode value Mode3 are determined according to the following formula: Mode2=((Mode1+61)%64)+2, Mode3 = ((Mode1-1)%64)+2; An intra prediction mode value of the current block is determined according to the candidate list.

11. A non-transitory computer-readable medium storing instructions, wherein when the instructions are executed by a processor in a video decoding device, the processor executes the video decoding method according to any one of claims 1 to 4 or the video encoding method according to claim 9.

12. A method for processing a video code stream, characterized in that: The video code stream is decoded based on the decoding method according to any one of claims 1 to 4, or is generated according to the encoding method according to claim 9.

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