Chroma Intramode Derivation Encoder, Decoder, and Corresponding Method - Patent application

Abstract

To provide a method of coding executed by a decoding device.SOLUTION: A method of coding executed by a decoding device, includes: a step of acquiring a video bit stream; a step of acquiring an initial intra-prediction mode value corresponded to a chroma component of the current coding block by decoding the video bit stream; a step of determining whether or not a ratio between a width corresponded to a luma component of the current coding block and a width corresponded to a chroma component of the current coding block is equal to a threshold value; a step of acquiring the intra-mode prediction value to be mapped that is corresponded to a chroma component of the current coding block in accordance with the existed mapping relation and the initial intra-prediction mode value when it is determined that the ratio is equal to the threshold value; and a step of acquiring the prediction sample value corresponded to the chroma component of the current coding block in accordance with the intra-prediction mode value to be mapped.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] TECHNICAL FIELD Embodiments of the present disclosure relate generally to the field of picture processing, and more particularly to chroma intra prediction mode derivation. [Background technology]

[0002] Video coding (video encoding and video decoding) is used in a wide range of digital video applications, such as broadcast digital TV, video transmission over the Internet and mobile networks, real-time interactive applications such as video chat, video conferencing, DVD and Blu-ray® discs, video content collection and editing systems, and camcorders in security applications.

[0003] The amount of video data required to render even a relatively short video can be considerable, which can pose difficulties when the data is to be streamed or otherwise transmitted across communication networks with limited bandwidth capacity. Therefore, video data is generally compressed before being transmitted across modern telecommunications networks. Because memory resources may be limited, the size of the video can also be an issue when the video is stored in a storage device. Video compression devices often use software and / or hardware at the source to code the video data before transmission or storage, thereby reducing the amount of data needed to represent a digital video image. The compressed data is then received at the destination by a video decompression device, which decodes the video data. With limited network resources and an ever-increasing demand for higher video quality, improved compression and decompression techniques that improve compression ratios with little to no sacrifice in picture quality are desirable. Summary of the Invention [Means for solving the problem]

[0004] Embodiments of the present application provide apparatuses and methods for encoding and decoding according to the independent claims.

[0005] These and other objects are achieved by the subject matter of the independent claims. Further implementation forms are evident from the dependent claims, the description and the figures.

[0006] A first aspect of the present invention provides a coding method performed by a decoding device, the method comprising the steps of obtaining a video bitstream; decoding the video bitstream to obtain values ​​of chroma format display information for a current coding block; obtaining initial intra-prediction mode values ​​for chroma components of the current coding block; when the value of the chroma format display information for the current coding block is equal to a default value, obtaining mapped intra-prediction mode values ​​for the chroma components of the current coding block according to a default mapping relationship and the initial intra-prediction mode value; and obtaining predicted sample values ​​for the chroma components of the current coding block according to the mapped intra-prediction mode value.

[0007] According to an embodiment of the present invention, for a chroma subsampling format, the mapping relationship between intra prediction modes is derived more accurately, thereby improving coding efficiency.

[0008] As shown in FIG. 13, a coding method performed by a decoding device is disclosed, the method comprising:

[0009] S1301: Obtain a video bitstream.

[0010] The bit stream may be obtained according to a wireless or wired network, and may be transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, microwave, Wi-Fi, Bluetooth, LTE, or 5G.

[0011] In one embodiment, the bitstream is a sequence of bits in the form of a Network Abstraction Layer (NAL) unit stream or byte stream that forms a representation of a sequence of access units (AUs) that form one or more coded video sequences (CVSs).

[0012] In some embodiments, for the decoding process, a decoder side reads a bitstream and derives decoded pictures from the bitstream, and for the encoding process, an encoder side produces a bitstream.

[0013] Typically, a bitstream comprises syntax elements that are formed by a syntax structure.

[0014] Syntax element: An element of data that is represented within a bitstream.

[0015] Syntax structure: Zero or more syntax elements that occur together in a bitstream in a specified order.

[0016] In a particular example, a bitstream format specifies the relationship between a Network Abstraction Layer (NAL) unit stream and a byte stream, both of which are referred to as a bitstream.

[0017] A bitstream can be in one of two formats: NAL unit stream format or byte stream format. The NAL unit stream format is conceptually the more "basic" type. The NAL unit stream format comprises a sequence of syntax structures called NAL units. This sequence is ordered in decoding order. There are constraints imposed on the decoding order (and content) of the NAL units within a NAL unit stream.

[0018] A byte stream format can be constructed from the NAL unit stream format by ordering the NAL units in decoding order and prefixing each NAL unit with a start code prefix and zero or more zero-valued bytes to form a stream of bytes. The NAL unit stream format can be extracted from the byte stream format by locating unique start code prefix patterns within this stream of bytes.

[0019] This clause specifies the relationship between the source and decoded pictures provided via the bitstream.

[0020] The video source represented by the bitstream is a sequence of pictures in decoding order.

[0021] The source and decoded pictures each comprise one or more sample arrays. - Luma (Y) only (monochrome). - Luma and two chromas (YCbCr or YCgCo). - Green, Blue, and Red (GBR, also known as RGB). - Arrays representing other unspecified monochrome or tristimulus color sampling (e.g., also known as YZX, XYZ).

[0022] The variables and terms associated with these arrays are called luma (or L or Y) and chroma, where the two chroma arrays are called Cb and Cr regardless of the actual color representation method in use, which can be indicated in the syntax specified in VUI parameters as specified in ITU-T H.SEI | ISO / IEC23002-7.

[0023] The variables SubWidthC and SubHeightC are specified in Table 1 depending on the chroma format sampling structure specified through sps_chroma_format_idc and sps_separate_colour_plane_flag.

[0024] [Table 1]

[0025] In monochrome sampling, there is only one sample array, nominally considered the luma array.

[0026] In 4:2:0 sampling, each of the two chroma arrays has half the height and half the width of the luma array.

[0027] In 4:2:2 sampling, each of the two chroma arrays has the same height and half the width of the luma array.

[0028] For 4:4:4 sampling, the following applies depending on the value of sps_separate_colour_plane_flag: - If sps_separate_colour_plane_flag is equal to 0, then each of the two chroma arrays has the same height and width as the luma array. - Otherwise (sps_separate_colour_plane_flag equals 1), the three colour planes are processed separately as a monochrome sampled picture.

[0029] S1302: Obtain an initial intra prediction mode value for a chroma component of the current coding block.

[0030] The initial intra-prediction mode value may be obtained by parsing an index value coded within the video bitstream, or the initial intra-prediction mode value may be determined according to a syntax value parsed from the video bitstream.

[0031] In one implementation, the initial intra-prediction mode value for the chroma components of the current coding block is obtained based on the intra-prediction mode for the luma component of the current coding block.

[0032] In a particular example, the following process is used to obtain the initial intra-prediction mode values ​​for the chroma components of the current coding block.

[0033] The inputs to this process are: - A luma position ( xCb, yCb ) that specifies the top-left sample of the current chroma coding block relative to the top-left luma sample of the current picture. - The variable cbWidth that specifies the width of the current coding block in luma samples. - The variable cbHeight that specifies the height of the current coding block in luma samples. - The variable treeType, which specifies whether a single or a double tree is used.

[0034] In this process, the chrominance intra prediction mode IntraPredModeC[xCb][yCb] and the MIP chrominance direct mode flag MipChromaDirectFlag[xCb][yCb] are derived.

[0035] If treeType is equal to SINGLE_TREE, sps_chroma_format_idc is equal to 3, intra_chroma_pred_mode is equal to 4, and intra_mip_flag[ xCb ][ yCb ] is equal to 1, the following applies: - The MIP chroma direct mode flag MipChromaDirectFlag[ xCb ][ yCb ] is set equal to 1. - The chrominance intra-prediction mode IntraPredModeC[xCb][yCb] is set equal to IntraPredModeY[xCb][yCb].

[0036] Otherwise, the following applies: - The MIP chroma direct mode flag MipChromaDirectFlag[ xCb ][ yCb ] is set equal to 0. - The corresponding luma intra prediction mode lumaIntraPredMode is derived as follows: - If intra_mip_flag[ xCb + cbWidth / 2 ][ yCb + cbHeight / 2 ] is equal to 1, lumaIntraPredMode is set equal to INTRA_PLANAR. - Otherwise, if CuPredMode [ xCb + cbWidth / 2 ][ yCb + cbHeight / 2 ] is equal to MODE_IBC or MODE_PLT, lumaIntraPredMode is set equal to INTRA_DC. - Otherwise, lumaIntraPredMode is set equal to IntraPredModeY[ xCb + cbWidth / 2 ][ yCb + cbHeight / 2 ]. - The chrominance intra-prediction mode IntraPredModeC[ xCb ][ yCb ] is derived as follows: - If cu_act_enabled_flag[xCb][yCb] is equal to 1, the chroma intra prediction mode IntraPredModeC[xCb][yCb] is set equal to lumaIntraPredMode. - Otherwise, if BdpcmFlag[ xCb ][ yCb ]

[0001] is equal to 1, then IntraPredModeC[ xCb ][ yCb ] is set equal to BdpcmDir[ xCb ][ yCb ]

[0001] ? INTRA_ANGULAR50 : INTRA_ANGULAR18. Otherwise (cu_act_enabled_flag[xCb][yCb] is equal to 0 and BdpcmFlag[xCb][yCb] is equal to 0), the chrominance intra prediction mode IntraPredModeC[xCb][yCb] is derived using cclm_mode_flag, cclm_mode_idx, intra_chroma_pred_mode, and lumaIntraPredMode as specified in Table 20.

[0037] [Table 2]

[0038] S1303: Decode the video bitstream to obtain the value of the chroma format display information for the current coding block.

[0039] In one embodiment, the chroma format display information is the syntax sps_chroma_format_idc shown in Table 1. sps_chroma_format_idc specifies the chroma sampling relative to the luma sampling.

[0040] In one example, the syntax sps_chroma_format_idc is decoded from the sequence parameter set as follows:

[0041] [Table 3]

[0042] It may be understood that there is no particular order to step S1302 and step S1303, and that step S1302 may be performed before step S1303, or step S1303 may be performed before step S1302, or they may be performed in parallel.

[0043] S1304: When the value of the chroma format display information for the current coding block is equal to the default value, obtain mapped intra-prediction mode values ​​for the chroma components of the current coding block according to the default mapping relationship and the initial intra-prediction mode value.

[0044] In one embodiment, the default value is 2 or 1. A default value of 2 represents a chroma format of 4:2:2, and a default value of 1 represents a chroma format of 4:2:0.

[0045] In one example, when sps_chroma_format_idc is equal to 2, chroma intra prediction mode Y is derived using chroma intra prediction mode X, and then chroma intra prediction mode X is set equal to chroma intra prediction mode Y.

[0046] The mapping relationship between Mode X and Mode Y may be expressed according to Table 2, Table 3, Table 4, Table 5, Table 6, Table 8, Table 10, Table 12, Table 14, Table 15, or Table 18.

[0047] In one example, when sps_chroma_format_idc is equal to 2, chroma intra prediction mode Y is derived using chroma intra prediction mode X in Table 20 as specified in Table 21, and then chroma intra prediction mode X is set equal to chroma intra prediction mode Y.

[0048] [Table 4]

[0049] S1305: Obtain a predicted sample value for a chroma component of the current coding block according to the mapped intra prediction mode value.

[0050] The mapped intra-prediction mode value is used as the “intra-prediction mode value” to obtain the predicted sample value. For details of this process, refer to ITU H.264 or ITU H.265 or other documents.

[0051] As shown in FIG. 14, a second aspect of the present invention provides a decoding device 1400, which comprises: a receiving module 1401 configured to obtain a video bitstream; a parameter processing module 1402 configured to decode the video bitstream to obtain an initial intra-prediction mode value for a chroma component of a current coding block; The parameter process module 1402 is also configured to decode the video bitstream to obtain values ​​of chroma format display information for the current coding block; a mapping module 1403 configured to obtain mapped intra-prediction mode values ​​for chroma components of the current coding block according to a default mapping relationship and an initial intra-prediction mode value when a value of the chroma format display information for the current coding block is equal to a default value; The coding module 1404 is configured to obtain predicted sample values ​​for chroma components of the current coding block according to the mapped intra-prediction mode values.

[0052] The method according to the first aspect of the invention can be performed by an apparatus according to the second aspect of the invention. Further features and implementation forms of the method correspond to the features and implementation forms of the apparatus according to the second aspect of the invention.

[0053] In one embodiment, a third aspect of the present invention provides a coding method performed by an encoding device, comprising the steps of obtaining an initial intra-prediction mode value for a current coding block; determining whether a ratio between a width for a luma component of the current coding block and a width for a chroma component of the current coding block is equal to a threshold; when the ratio between the width for the luma component of the current coding block and the width for the chroma component of the current coding block is equal to the threshold, obtaining mapped intra-prediction mode values ​​for the chroma components of the current coding block according to a predefined mapping relationship and the initial intra-prediction mode value; and coding the current coding block according to the mapped intra-prediction mode value.

[0054] In one implementation, the method comprises: The method further comprises the step of encoding a value of chroma format display information for the current coding block into the bitstream, the value of the chroma format display information representing a ratio between a width for the luma component of the current coding block and a width for the chroma component of the current coding block.

[0055] In one implementation, the following table is used to represent the default mapping relationship:

[0056] [Table 5]

[0057] or

[0058] [Table 6]

[0059] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0060] In one implementation, the following table is used to represent the default mapping relationship:

[0061] [Table 7]

[0062] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0063] A further embodiment of the method according to the third aspect of the invention (encoding side) can be carried out correspondingly to the method according to the second aspect of the invention (decoding side).

[0064] In one embodiment, a decoder (30) or encoder (20) is disclosed that includes processing circuitry for performing a method according to any one of the above embodiments and implementations.

[0065] In one embodiment, a computer program product is disclosed comprising program code for performing a method according to any one of the above embodiments and implementations.

[0066] In one embodiment, a decoder or encoder comprising: one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring a decoder or encoder to perform a method according to any one of the above embodiments and implementations; A decoder or encoder is disclosed.

[0067] In one embodiment, a non-transitory storage medium is disclosed that includes an encoded bitstream that is decoded by an image decoding device, the bitstream being generated by dividing a frame of a video signal or an image signal into multiple blocks and including multiple syntax elements, the multiple syntax elements having an indicator (syntax sps_chroma_format_idc) according to any one of the above embodiments and implementations.

[0068] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description, drawings, and claims.

[0069] In the following, embodiments of the invention will be explained in more detail with reference to the accompanying figures and drawings. [Brief explanation of the drawings]

[0070] [Figure 1A] 1 is a block diagram illustrating an example of a video coding system configured to implement embodiments of the invention. [Figure 1B] FIG. 2 is a block diagram illustrating another example of a video coding system configured to implement embodiments of the invention. [Figure 2] FIG. 1 is a block diagram illustrating an example of a video encoder configured to implement embodiments of the invention. [Figure 3] FIG. 2 is a block diagram illustrating an example structure of a video decoder configured to implement an embodiment of the invention. [Figure 4] FIG. 1 is a block diagram illustrating an example of an encoding or decoding device. [Figure 5] FIG. 10 is a block diagram illustrating another example of an encoding or decoding device. [Figure 6] An example for the chroma subsampling format 4:4:4. [Figure 7] An example for chroma subsampling format 4:2:0. [Figure 8] An example for chroma subsampling format 4:2:2. [Figure 9] FIG. 1 is a block diagram illustrating an example of a prediction mode. [Figure 10] An example of the original mode and the corresponding mode when chroma subsampling is applied in the horizontal direction using a 4:2:2 chroma subsampling format. [Figure 11] FIG. 31 is a block diagram illustrating an example structure of a content supply system 3100 that implements a content distribution service. [Figure 12] FIG. 2 is a block diagram illustrating the structure of an example of a terminal device. [Figure 13] 1 is a flow chart illustrating an embodiment of a method according to the present invention. [Figure 14] 1 is a block diagram illustrating an embodiment of an apparatus according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0071] In the following, the same reference signs refer to identical or at least functionally equivalent features, unless explicitly specified otherwise.

[0072] In the following description, reference is made to the accompanying figures which form part of the disclosure and which show, by way of illustration, certain aspects of embodiments of the invention or in which embodiments of the invention may be used. It is understood that embodiments of the invention may be used in other ways and may have structural or logical changes not depicted in the figures. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0073] For example, it is understood that disclosure regarding a described method may also apply to a corresponding device or system configured to perform that method, and vice versa. For example, if one or more particular method steps are described, a corresponding device may include one or more units, e.g., functional units, for performing the described one or more method steps, even if such one or more units are not explicitly described or illustrated in a figure. On the other hand, for example, if a particular apparatus is described based on one or more units, e.g., functional units, a corresponding method may include one step for performing the function of one or more units (e.g., one step for performing the function of one or more units, or multiple steps that each perform the function of one or more units), even if such one or more steps are not explicitly described or illustrated in a figure. Furthermore, it is understood that features of various exemplary embodiments and / or aspects described herein may be combined with each other, unless specifically noted otherwise.

[0074] Video coding typically refers to the processing of a sequence of pictures to form a video or a video sequence. Instead of the term "picture," the terms "frame" or "image" may be used synonymously in the field of video coding. Video coding (or, in general, coding) comprises two parts: video encoding and video decoding. Video encoding is performed at the source side and typically comprises processing the original video picture (e.g., by compression) to reduce the amount of data required to represent the video picture (for more efficient storage and / or transmission). Video decoding is performed at the destination side and typically comprises the reverse process compared to the encoder to reconstruct the video picture. Embodiments referring to "coding" of a video picture (or, in general, a picture) shall be understood to relate to "encoding" or "decoding" of the video picture or the respective video sequence. The combination of the encoding and decoding parts is also called CODEC (Coding and Decoding).

[0075] In the case of lossless video coding, the original video picture can be reconstructed, i.e., the reconstructed video picture has the same quality as the original video picture (assuming there is no transmission loss or other data loss during storage or transmission). In the case of lossy video coding, further compression is performed, e.g., by quantization, to reduce the amount of data representing the video picture, and the video picture cannot be perfectly reconstructed at the decoder, i.e., the quality of the reconstructed video picture is lower or worse than the quality of the original video picture.

[0076] Some video coding standards belong to the group of "lossy hybrid video codecs" (i.e., combine spatial and temporal prediction in the sample domain with 2D transform coding to apply quantization in the transform domain). Each picture of a video sequence is typically partitioned into a set of non-overlapping blocks, and coding is typically performed at the block level. In other words, at an encoder, video is typically processed, i.e., encoded, at the block (video block) level, for example, by generating a predictive block using spatial (intra-picture) prediction and / or temporal (inter-picture) prediction, subtracting the predictive block from a current block (the block currently being processed / to be processed) to obtain a residual block, transforming the residual block, and quantizing the residual block in the transform domain to reduce the amount of data to be transmitted (compression); while at a decoder, an inverse process compared to the encoder is applied to the encoded, or compressed, block to reconstruct the current block for representation. Additionally, the encoder duplicates the decoder processing loop so that both generate the same predictions (eg, intra and inter predictions) and / or reconstructions for processing, i.e., coding, subsequent blocks.

[0077] In the following, embodiments of a video coding system 10, a video encoder 20, and a video decoder 30 are described based on FIGS.

[0078] 1A is a schematic block diagram illustrating an example coding system 10, e.g., video coding system 10 (or coding system 10 for short), that may utilize the techniques of the present application. A video encoder 20 (or encoder 20 for short) and a video decoder 30 (or decoder 30 for short) of video coding system 10 represent examples of devices that may be configured to perform techniques according to various examples described in the present application.

[0079] As shown in FIG. 1A, coding system 10 includes, for example, a source device 12 configured to provide encoded picture data 21 to a destination device 14 for decoding the encoded picture data 13.

[0080] The source device 12 comprises an encoder 20, and may additionally, i.e. optionally, comprise a picture source 16, a preprocessor (or preprocessing unit) 18, for example a picture preprocessor 18, and a communication interface or unit 22.

[0081] Picture source 16 may comprise or be any kind of picture capture device, e.g., a camera for capturing real-world pictures, and / or any kind of picture generation device, e.g., a computer graphics processor for generating computer-animated pictures, or any kind of other device for obtaining and / or providing real-world pictures, computer-generated pictures (e.g., screen content, virtual reality (VR) pictures), and / or any combination thereof (e.g., augmented reality (AR) pictures). Picture source may be any kind of memory or storage device that stores any of the above-mentioned pictures.

[0082] To distinguish from the preprocessor 18 and the processing performed by the preprocessing unit 18, the picture or picture data 17 may also be referred to as an unprocessed picture or unprocessed picture data 17.

[0083] The pre-processor 18 is configured to receive (raw) picture data 17 and perform pre-processing on the picture data 17 to obtain a pre-processed picture 19 or pre-processed picture data 19. The pre-processing performed by the pre-processor 18 may comprise, for example, cropping, color format conversion (e.g., from RGB to YCbCr), color correction, or noise removal. It can be understood that the pre-processing unit 18 may be an optional component.

[0084] Video encoder 20 is configured to receive pre-processed picture data 19 and provide encoded picture data 21 (further details will be described below, eg, based on FIG. 2).

[0085] The communications interface 22 of the source device 12 may be configured to receive the encoded picture data 21 and transmit the encoded picture data 21 (or any further processed version thereof) over the communications channel 13 to another device, such as the destination device 14 or any other device, for storage or direct reconstruction.

[0086] The destination device 14 includes a decoder 30 (e.g., a video decoder 30), and may additionally, i.e. optionally, include a communication interface or communication unit 28, a post-processor 32 (or post-processing unit 32), and a display device 34.

[0087] The communications interface 28 of the destination device 14 is configured to receive the encoded picture data 21 (or any further processed version thereof), for example, directly from the source device 12 or from any other source, for example, a storage device, for example, an encoded picture data storage device, and to provide the encoded picture data 21 to the decoder 30.

[0088] The communication interface 22 and the communication interface 28 may be configured to transmit or receive the encoded picture data 21 or the encoded data 13 via a direct communication link between the source device 12 and the destination device 14, e.g., a direct wired or wireless connection, or via any type of network, e.g., a wired or wireless network or any combination thereof, or any type of private and public network, or any type of combination thereof.

[0089] The communications interface 22 may be configured, for example, to package the encoded picture data 21 in a suitable format, e.g., packets, and / or to process the encoded picture data using any type of transmission encoding or processing for transmission over a communications link or network.

[0090] Communications interface 28, which forms the counterpart to communications interface 22, may be configured, for example, to receive the transmitted data and process the transmitted data using any type of corresponding transmission decoding or processing and / or depackaging to obtain encoded picture data 21.

[0091] Both communication interface 22 and communication interface 28 may be configured as unidirectional communication interfaces, as indicated by the arrow for communication channel 13 in FIG. 1A pointing from source device 12 to destination device 14, or as bidirectional communication interfaces, and may be configured to send and receive messages, e.g., to set up a connection, to acknowledge and exchange any other information related to the communication link and / or data transmission, e.g., encoded picture data transmission.

[0092] The decoder 30 is configured to receive the encoded picture data 21 and provide decoded picture data 31 or decoded pictures 31 (further details will be described below, for example, based on Figure 3 or Figure 5).

[0093] Post-processor 32 of destination device 14 is configured to post-process decoded picture data 31 (also called reconstructed picture data), e.g., decoded picture 31, to obtain post-processed picture data 33, e.g., post-processed picture 33. The post-processing performed by post-processing unit 32 may comprise, e.g., color format conversion (e.g., from YCbCr to RGB), color correction, cropping, or resampling, or any other processing to prepare decoded picture data 31 for, e.g., display by display device 34.

[0094] A display device 34 of destination device 14 is configured to receive the post-processed picture data 33 for displaying the picture, for example, to a user or viewer. Display device 34 may be or comprise any type of display for presenting the reconstructed picture, for example, an integrated or external display or monitor. The display may comprise, for example, a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a plasma display, a projector, a micro-LED display, a liquid crystal on silicon (LCoS), a digital light processor (DLP), or any other type of display.

[0095] 1A depicts source device 12 and destination device 14 as separate devices, device embodiments may also include both source device 12 or corresponding functionality and destination device 14 or corresponding functionality. In such embodiments, source device 12 or corresponding functionality and destination device 14 or corresponding functionality may be realized using the same hardware and / or software, or by separate hardware and / or software, or any combination thereof.

[0096] As will be apparent to those skilled in the art based on the description, the functions of different units or the presence and (exact) division of functions within source device 12 and / or destination device 14 as depicted in FIG. 1A may vary depending on the actual device and application.

[0097] Encoder 20 (e.g., video encoder 20) or decoder 30 (e.g., video decoder 30), or both encoder 20 and decoder 30, may be implemented via processing circuitry as depicted in FIG. 1B , such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic, hardware, dedicated video coding, or any combination thereof. Encoder 20 may be implemented via processing circuitry 46 to implement various modules as discussed with respect to encoder 20 of FIG. 2 and / or any other encoder system or subsystem described herein. Decoder 30 may be implemented via processing circuitry 46 to implement various modules as discussed with respect to decoder 30 of FIG. 3 and / or any other decoder system or subsystem described herein. The processing circuitry may be configured to perform various operations as discussed below. 5, if the techniques are implemented partially in software, a device may store instructions for the software on a suitable non-transitory computer-readable storage medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Either video encoder 20 and video decoder 30 may be integrated within a single device as part of a combined encoder / decoder (CODEC), for example, as shown in FIG. 1B.

[0098] Source device 12 and destination device 14 may comprise any of a wide range of devices, including any type of handheld or fixed device, such as a notebook or laptop computer, a mobile phone, a smartphone, a tablet or tablet computer, a camera, a desktop computer, a set-top box, a television, a display device, a digital media player, a video game console, a video streaming device (such as a content service server or content distribution server), a broadcast receiver device, a broadcast transmitter device, or the like, and may use no operating system or any type of operating system. In some cases, source device 12 and destination device 14 may be equipped for wireless communication. Thus, source device 12 and destination device 14 may be wireless communication devices.

[0099] 1A is merely an example, and the techniques of the present application may be applied to a video coding setting (e.g., video encoding or video decoding) without necessarily including any data communication between the encoding and decoding devices. In other examples, data may be retrieved from local memory, streamed over a network, or the like. A video encoding device may encode data and store it in memory, and / or a video decoding device may retrieve data from memory and decode it. In some examples, encoding and decoding are performed by devices that do not communicate with each other, but simply encode data to memory and / or retrieve data from memory and decode it.

[0100] For ease of explanation, embodiments of the invention are described herein by reference to, for example, High-Efficiency Video Coding (HEVC) or to reference software for Versatile Video Coding (VVC), the next-generation video coding standard developed by the ITU-T Video Coding Experts Group (VCEG) and the ISO / IEC Joint Collaboration Team on Video Coding (JCT-VC) of the Motion Picture Experts Group (MPEG). Those skilled in the art will understand that embodiments of the invention are not limited to HEVC or VVC.

[0101] Encoders and encoding methods 2 illustrates a schematic block diagram of an exemplary video encoder 20 configured to implement the techniques of the present application. In the example of FIG. 2, the video encoder 20 includes an input 201 (or input interface 201), a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a loop filter unit 220, a decoded picture buffer (DPB) 230, a mode selection unit 260, an entropy encoding unit 270, and an output 272 (or output interface 272). The mode selection unit 260 may include an inter prediction unit 244, an intra prediction unit 254, and a partitioning unit 262. The inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 illustrated in FIG. 2 may also be referred to as a hybrid video encoder or a video encoder using a hybrid video codec.

[0102] The residual calculation unit 204, the transform processing unit 206, the quantization unit 208, and the mode selection unit 260 may be referred to as forming a forward signal path of the encoder 20, while the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 may be referred to as forming a backward signal path of the video encoder 20, which corresponds to the signal path of a decoder (see video decoder 30 in FIG. 3 ). The inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 are also referred to as forming a “built-in decoder” of the video encoder 20.

[0103] Pictures and picture divisions (pictures and blocks) Encoder 20 may be configured to receive picture 17 (or picture data 17), e.g., a picture of a sequence of pictures forming a video or a video sequence, e.g., via input 201. The received picture or picture data may also be preprocessed picture 19 (or preprocessed picture data 19). For purposes of brevity, the following description refers to picture 17. Picture 17 may also be called a current picture or a picture to be coded (particularly in video coding, to distinguish the current picture from other pictures of the same video sequence, i.e., a video sequence that also comprises the current picture, e.g., previously encoded and / or decoded pictures).

[0104] A (digital) picture is, or can be considered as, a two-dimensional array or matrix of samples with intensity values. The samples in the array may also be called pixels (a short form of picture element) or pels. The number of samples in the horizontal and vertical directions (or axes) of the array or picture defines the size and / or resolution of the picture. For color representation, three color components are typically employed, i.e., a picture may be represented as or contain three sample arrays. In an RBG format or color space, a picture comprises corresponding red, green, and blue sample arrays. However, in video coding, each pixel is typically represented in a luminance and chrominance format or color space, such as YCbCr, which comprises a luminance component denoted by Y (sometimes L is also used instead) and two chrominance components denoted by Cb and Cr. The luminance (or luma for short) component Y represents brightness or gray-level intensity (e.g., as in a grayscale picture), while the two chrominance (or chroma for short) components Cb and Cr represent chromaticity or color information components. Thus, a picture in YCbCr format comprises a luminance sample array of luminance sample values ​​(Y) and two chrominance sample arrays of chrominance values ​​(Cb and Cr). A picture in RGB format may be converted or transformed to YCbCr format, or vice versa, a process also known as color conversion or transformation. If the picture is monochrome, the picture may comprise only a luminance sample array. Thus, a picture may be, for example, an array of luma samples in monochrome format, or an array of luma samples and two corresponding arrays of chroma samples in 4:2:0, 4:2:2, and 4:4:4 color formats.

[0105] Embodiments of video encoder 20 may comprise a picture partition unit (not depicted in FIG. 2 ) configured to partition picture 17 into multiple (typically non-overlapping) picture blocks 203. These blocks may also be called root blocks, macroblocks (H.264 / AVC), or coding tree blocks (CTBs) or coding tree units (CTUs) (H.265 / HEVC and VVC). The picture partition unit may be configured to use the same block size for all pictures of a video sequence and a corresponding grid defining the block sizes, or to vary the block size among pictures or subsets or groups of pictures, and to partition each picture into corresponding blocks.

[0106] In further embodiments, the video encoder may be configured to directly receive blocks 203 of picture 17, e.g., one, some, or all of the blocks that form picture 17. Picture blocks 203 may also be referred to as current picture blocks or picture blocks to be coded.

[0107] Like picture 17, picture block 203 again can be considered as a two-dimensional array or matrix of samples having intensity values ​​(sample values), but with smaller dimensions than picture 17. In other words, block 203 may comprise, for example, one sample array (e.g., a luma array in the case of a monochrome picture 17, or a luma or chroma array in the case of a color picture), or three sample arrays (e.g., a luma and two chroma arrays in the case of a color picture 17), or any other number and / or type of arrays depending on the applied color format. The number of samples in the horizontal and vertical directions (or axes) of block 203 defines the size of block 203. Thus, a block may be, for example, an M×N (M columns by N rows) array of samples, or an M×N array of transform coefficients.

[0108] An embodiment of video encoder 20 such as that depicted in FIG. 2 may be configured to encode picture 17 block by block, eg, encoding and prediction is performed for each block 203.

[0109] An embodiment of video encoder 20 such as that depicted in FIG. 2 may be further configured to partition and / or encode pictures by using slices (also referred to as video slices), where a picture may be partitioned into or encoded using one or more (typically non-overlapping) slices, each of which may comprise one or more blocks (e.g., CTUs).

[0110] An embodiment of video encoder 20 as depicted in FIG. 2 may further be configured to partition and / or encode a picture by using tile groups (also referred to as video tile groups) and / or tiles (also referred to as video tiles), where a picture may be partitioned into or encoded using one or more (typically non-overlapping) tile groups, each of which may comprise, for example, one or more blocks (e.g., CTUs) or one or more tiles, and each tile may be, for example, rectangular in shape and may comprise one or more blocks (e.g., CTUs), e.g., full or fragmentary blocks.

[0111] Residual calculation The residual calculation unit 204 may be configured to calculate the residual block 205 (also referred to as the residual 205) based on the picture block 203 and the prediction block 265 (further details about the prediction block 265 will be provided later), for example, by subtracting the sample values ​​of the prediction block 265 from the sample values ​​of the picture block 203 on a sample-by-sample (pixel-by-pixel) basis to obtain the residual block 205 in the sample domain.

[0112] conversion The transform processing unit 206 may be configured to apply a transform, such as a discrete cosine transform (DCT) or a discrete sine transform (DST), on the sample values ​​of the residual block 205 to obtain transform coefficients 207 in the transform domain. The transform coefficients 207, also called transform residual coefficients, may represent the residual block 205 in the transform domain.

[0113] The transform processing unit 206 may be configured to apply an integer approximation of a DCT / DST, such as the transform specified for H.265 / HEVC. Compared to an orthogonal DCT transform, such an integer approximation is typically scaled by a factor. To maintain the norm of the residual blocks processed by the forward and inverse transforms, an additional scaling factor is applied as part of the transform process. The scaling factor is typically chosen based on certain constraints, such as the scaling factor being a power of two due to shift operations, the bit depth of the transform coefficients, a trade-off between accuracy and implementation cost, etc. For example, a particular scaling factor may be specified for, e.g., the inverse transform by the inverse transform processing unit 212 (and the corresponding inverse transform by, e.g., the inverse transform processing unit 312 in the video decoder 30), and a corresponding scaling factor for the forward transform by, e.g., the transform processing unit 206 in the encoder 20 may be specified accordingly.

[0114] An embodiment of video encoder 20 (respectively, transform processing unit 206) may be configured to output transform parameters, e.g., one or more types of transform, encoded or compressed, e.g., directly or via entropy encoding unit 270, so that, for example, video decoder 30 may receive and use the transform parameters for decoding.

[0115] quantization The quantization unit 208 may be configured to quantize the transform coefficients 207, for example, by applying scalar quantization or vector quantization, to obtain quantized coefficients 209. The quantized coefficients 209 may also be referred to as quantized transform coefficients 209 or quantized residual coefficients 209.

[0116] The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, an n-bit transform coefficient may be truncated to an m-bit transform coefficient during quantization, where n is greater than m. The degree of quantization may be modified by adjusting a Quantization Parameter (QP). For example, for scalar quantization, different scaling may be applied to achieve finer or coarser quantization. A smaller quantization step size corresponds to finer quantization, while a larger quantization step size corresponds to coarser quantization. The applicable quantization step size may be indicated by the quantization parameter (QP). The quantization parameter may, for example, be an index into a predefined set of applicable quantization step sizes. For example, a small quantization parameter may correspond to fine quantization (small quantization step size) and a large quantization parameter may correspond to coarse quantization (large quantization step size), or vice versa. Quantization may involve division by a quantization step size, and corresponding and / or inverse dequantization, e.g., by the inverse quantization unit 210, may involve multiplication by the quantization step size. Some standards, e.g., HEVC, embodiments may be configured to determine the quantization step size using a quantization parameter. Generally, the quantization step size may be calculated based on the quantization parameter using a fixed-point approximation of a formula involving division. Additional scaling factors may be introduced for quantization and dequantization to restore the norm of the residual block, which may be modified due to the scaling used in the fixed-point approximation of the formula for the quantization step size and quantization parameter. In one example implementation, the scaling of the inverse transform and dequantization may be combined. Alternatively, customized quantization tables may be used and signaled, e.g., in the bitstream, from the encoder to the decoder. Quantization is a lossy operation, and the loss increases with increasing quantization step size.

[0117] Embodiments of video encoder 20 (respectively, quantization unit 208) may be configured to output a quantization parameter (QP), e.g., encoded directly or via entropy encoding unit 270, so that, for example, video decoder 30 may receive and apply the quantization parameter for decoding.

[0118] inverse quantization Inverse quantization unit 210 is configured to apply the inverse quantization of quantization unit 208 on the quantized coefficients to obtain dequantized coefficients 211, e.g., by applying the inverse of the quantization scheme applied by quantization unit 208, based on or using the same quantization step size as quantization unit 208. The dequantized coefficients 211, also referred to as dequantized residual coefficients 211, may correspond to transform coefficients 207, although they are typically not identical to the transform coefficients due to loss due to quantization.

[0119] Inverse transformation The inverse transform processing unit 212 is configured to apply an inverse transform of the transform applied by the transform processing unit 206, such as an inverse discrete cosine transform (DCT) or an inverse discrete sine transform (DST), or other inverse transform, to obtain a reconstructed residual block 213 in the sample domain (or corresponding dequantized coefficients 213). The reconstructed residual block 213 may also be referred to as a transform block 213.

[0120] Reconstruction The reconstruction unit 214 (e.g., an adder or summator 214) is configured to add the transform block 213 (i.e., the reconstructed residual block 213) to the prediction block 265 to obtain a reconstructed block 215 in the sample domain, for example, by adding the sample values ​​of the reconstructed residual block 213 and the sample values ​​of the prediction block 265, sample by sample.

[0121] Filtering The loop filter unit 220 (or “loop filter” 220 for short) is configured to filter the reconstructed block 215 to obtain a filtered block 221, or generally, to filter the reconstructed samples to obtain filtered samples. The loop filter unit is configured, for example, to smooth pixel transitions or otherwise improve video quality. The loop filter unit 220 may comprise one or more loop filters, such as a deblocking filter, a Sample-Adaptive Offset (SAO) filter, or one or more other filters, e.g., a bilateral filter, an Adaptive Loop Filter (ALF), a sharpening filter, a smoothing filter, or a collaborative filter, or any combination thereof. Although the loop filter unit 220 is depicted in FIG. 2 as being an in-loop filter, in other configurations, the loop filter unit 220 may be implemented as a post-loop filter. The filtered block 221 may also be referred to as a filtered reconstructed block 221.

[0122] Embodiments of video encoder 20 (respectively, loop filter unit 220) may be configured to output loop filter parameters (such as sample adaptive offset information), e.g., directly or encoded via entropy encoding unit 270, such that decoder 30 may receive and apply the same loop filter parameters or respective loop filters for decoding, for example.

[0123] Decoded Picture Buffer Decoded picture buffer (DPB) 230 may be a memory that stores reference pictures, or reference picture data in general, for encoding video data by video encoder 20. DPB 230 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Decoded picture buffer (DPB) 230 may be configured to store one or more filtered blocks 221. The decoded picture buffer 230 may further be configured to store other previously filtered blocks, e.g., previously reconstructed, filtered blocks 221, e.g., previously reconstructed pictures, of the same current picture or of a different picture, and may provide, for example, for inter-prediction, a previously reconstructed, i.e., decoded, complete picture (and corresponding reference blocks and samples) and / or a partially reconstructed current picture (and corresponding reference blocks and samples). For example, if the reconstructed blocks 215 are not filtered by the loop filter unit 220 or are any other further processed versions of the reconstructed blocks or samples, the decoded picture buffer (DPB) 230 may also be configured to store one or more unfiltered reconstructed blocks 215, or in general, unfiltered reconstructed samples.

[0124] Mode Selection (Segmentation and Prediction) The mode selection unit 260 includes a partitioning unit 262, an inter prediction unit 244, and an intra prediction unit 254, and is configured to receive or obtain original picture data, e.g., original block 203 (current block 203 of current picture 17), and reconstructed picture data, e.g., filtered and / or unfiltered reconstructed samples or blocks, of the same (current) picture and / or from one or more previously decoded pictures, e.g., from the decoded picture buffer 230 or other buffers (e.g., line buffers, not shown). The reconstructed picture data is used as reference picture data for prediction, e.g., inter prediction or intra prediction, to obtain a prediction block 265 or predictor 265.

[0125] The mode selection unit 260 may be configured to determine or select a partition and a prediction mode (e.g., intra or inter prediction mode) for the current block prediction mode (which does not include partitions) and generate a corresponding prediction block 265 that is used for calculating the residual block 205 and for reconstructing the reconstructed block 215.

[0126] Embodiments of the mode selection unit 260 may be configured to select a partition and prediction mode (e.g., from those supported by or available to the mode selection unit 260) that provides the best match, or in other words, the smallest residual (smallest residual means better compression for transmission or storage), or the smallest signaling overhead (smallest signaling overhead means better compression for transmission or storage), or that considers or balances both. The mode selection unit 260 may be configured to determine the partition and prediction mode based on Rate Distortion Optimization (RDO), i.e., select a prediction mode that provides the smallest rate distortion. Terms such as “best,” “minimum,” “optimal,” etc. in this context do not necessarily refer to an overall “best,” “minimum,” “optimal,” etc., but may refer to the satisfaction of a termination or selection criterion, such as a value above or below a threshold or other constraint, potentially leading to a “suboptimal selection,” but reducing complexity and processing time.

[0127] In other words, the partitioning unit 262 may be configured to partition the block 203 into smaller block partitions or sub-blocks (which again form blocks), for example using quad-tree partitioning (QT), binary partitioning (BT), or triple-tree partitioning (TT), or any combination thereof, iteratively, and to perform prediction for each of the block partitions or sub-blocks, for example, wherein the mode selection comprises selecting a tree structure of the partitioned block 203, and a prediction mode is applied to each of the block partitions or sub-blocks.

[0128] Below, the partitioning (eg, by partitioning unit 260) and prediction processes (by inter-prediction unit 244 and intra-prediction unit 254) performed by example video encoder 20 will be described in more detail.

[0129] classification The partitioning unit 262 may partition (or divide) the current block 203 into smaller partitions, e.g., smaller blocks of square or rectangular size. These smaller blocks (which may also be called sub-blocks) may be further partitioned into even smaller partitions. This is also called tree partitioning or hierarchical tree partitioning; for example, a root block at root tree level 0 (hierarchical level 0, depth 0) may be recursively partitioned, e.g., into two or more blocks at the next lower tree level, e.g., nodes at tree level 1 (hierarchical level 1, depth 1), which may again be partitioned into two or more blocks at the next lower level, e.g., tree level 2 (hierarchical level 2, depth 2), etc., until, e.g., a termination criterion is met, e.g., the maximum tree depth or minimum block size is reached, and partitioning is terminated. Blocks that are not further partitioned are also called leaf blocks or leaf nodes of the tree. A tree that uses a partition into two partitions is called a Binary-Tree (BT), a tree that uses a partition into three partitions is called a Ternary-Tree (TT), and a tree that uses a partition into four partitions is called a Quad-Tree (QT).

[0130] As previously mentioned, the term "block" as used herein may refer to a portion of a picture, particularly a square or rectangular portion. For example, with reference to HEVC and VVC, a block may be or correspond to a coding tree unit (CTU), a coding unit (CU), a prediction unit (PU), and a transform unit (TU), and / or a corresponding block, such as a coding tree block (CTB), a coding block (CB), a transform block (TB), or a prediction block (PB).

[0131] For example, a coding tree unit (CTU) may be or comprise a CTB of luma samples for a picture having three sample arrays, two corresponding CTBs of chroma samples, or a CTB of samples for a monochrome picture or a picture coded using three separate color planes, and a syntax structure used to code the samples. Correspondingly, a coding tree block (CTB) may be an N×N block of samples for some values ​​of N such that the division of the components into CTBs is partitioned. A coding unit (CU) may be or comprise a coding block of luma samples for a picture having three sample arrays, two corresponding coding blocks of chroma samples, or a coding block of samples for a monochrome picture or a picture coded using three separate color planes, and a syntax structure used to code the samples. Correspondingly, a coding block (CB) may be an M×N block of samples for some values ​​of M and N such that the division of the CTB into coding blocks is partitioned.

[0132] For example, in an HEVC embodiment, a coding tree unit (CTU) may be divided into CUs by using a quadtree structure denoted as a coding tree. The decision of whether a picture area should be coded using (temporal) inter-picture prediction or (spatial) intra-picture prediction is made at the CU level. Each CU may be further divided into one, two, or four PUs according to a PU partition type. Within one PU, the same prediction process is applied, and related information is transmitted to the decoder for each PU. After obtaining residual blocks by applying a prediction process based on the PU partition type, the CU may be partitioned into transform units (TUs) according to another quadtree structure similar to the coding tree for the CU.

[0133] For example, in an embodiment according to the latest video coding standard currently under development, called Versatile Video Coding (VVC), a combined quad-tree and binary tree (QTBT) partitioning is used, for example, to partition coding blocks. In the QTBT block structure, a CU can have either a square or rectangular shape. For example, a coding tree unit (CTU) is first partitioned by a quad-tree structure. The quad-tree leaf node is further partitioned by a binary tree or ternary tree (or triple tree) structure. The partitioning tree leaf node is called a coding unit (CU), and its segmentation is used for prediction and transform processing without further partitioning. This means that CUs, PUs, and TUs have the same block size in the QTBT coding block structure. In parallel, multiple partitions, for example, triple tree partitioning, can be used with the QTBT block structure.

[0134] In one example, mode select unit 260 of video encoder 20 may be configured to perform any combination of the partitioning techniques described herein.

[0135] As described above, video encoder 20 is configured to determine or select a best or optimal prediction mode from a (e.g., predetermined) set of prediction modes, which may comprise, for example, intra-prediction modes and / or inter-prediction modes.

[0136] Intra prediction The set of intra prediction modes may, for example, comprise 35 different intra prediction modes, e.g., non-directional modes such as DC (or average) mode and planar mode, or directional modes, as defined in HEVC, or may, for example, comprise 67 different intra prediction modes, e.g., non-directional modes such as DC (or average) mode and planar mode, or directional modes, as defined for VVC.

[0137] The intra prediction unit 254 is configured to use reconstructed samples of neighboring blocks of the same current picture to generate an intra prediction block 265 according to an intra prediction mode of the set of intra prediction modes.

[0138] The intra prediction unit 254 (or generally the mode selection unit 260) is further configured to output the intra prediction parameters (or generally information indicating the selected intra prediction mode for the block) in the form of syntax elements 266 to the entropy encoding unit 270 for inclusion in the encoded picture data 21, so that, for example, the video decoder 30 may receive and use the prediction parameters for decoding.

[0139] Inter Prediction The set of inter prediction modes (or possible inter prediction modes) depends on the available reference pictures (i.e., previous pictures that have been at least partially decoded, e.g., stored in DBP 230) and other inter prediction parameters, such as whether the entire reference picture is used to search for the best matching reference block or whether only a portion of the reference picture, e.g., a search window area around the area of ​​the current block, is used, and / or whether pixel interpolation, e.g., half / semi-pel and / or quarter-pel interpolation, is applied.

[0140] In addition to the above prediction modes, skip mode and / or direct mode may be applied.

[0141] The inter prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (MC) unit (both not shown in FIG. 2). The motion estimation unit may be configured to receive or obtain a picture block 203 (current picture block 203 of current picture 17) and a decoded picture 231, or at least one or more previously reconstructed blocks, e.g., reconstructed blocks of one or more other / different previously decoded pictures 231, for motion estimation. For example, a video sequence may comprise the current picture and the previously decoded picture 231, or in other words, the current picture and the previously decoded picture 231 may be part of or form a sequence of pictures that form a video sequence.

[0142] The encoder 20 may be configured to, for example, select a reference block from multiple reference blocks of the same or different pictures among multiple other pictures, and provide the reference picture (or reference picture index) and / or an offset (spatial offset) between the position (x, y coordinates) of the reference block and the position of the current block to the motion estimation unit as inter-prediction parameters. This offset is also called a motion vector (MV).

[0143] The motion compensation unit is configured to obtain, e.g., receive, inter prediction parameters and perform inter prediction based on or using the inter prediction parameters to obtain inter prediction block 265. The motion compensation performed by the motion compensation unit may involve fetching or generating a predictive block based on motion / block vectors determined by motion estimation, possibly performing interpolation to sub-pixel precision. Interpolation filtering may generate additional pixel samples from known pixel samples, thus potentially increasing the number of candidate predictive blocks that can be used to code the picture block. Upon receiving a motion vector for the PU of the current picture block, the motion compensation unit may locate the predictive block to which the motion vector points in one of the reference picture lists.

[0144] The motion compensation unit may also generate syntax elements associated with the blocks and video slices for use by video decoder 30 in decoding picture blocks of the video slices. In addition to, or as an alternative to, slices and their respective syntax elements, tile groups and / or tiles and their respective syntax elements may be generated or used.

[0145] Entropy Coding The entropy encoding unit 270 may encode the quantized coefficients 209, the inter-prediction parameters, the intra-prediction parameters, the loop filter parameters, and / or other syntax elements using, for example, an entropy encoding algorithm or scheme (e.g., a variable length coding (VLC) scheme, a context adaptive VLC scheme (CAVLC)), an arithmetic coding scheme, binarization, context adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy, etc. 2. The video decoder 30 may be configured to apply a compression algorithm (e.g., a PIPE (High Entropy Encoding) coding, or another entropy encoding methodology or technique), or bypass (no compression) to obtain encoded picture data 21, which may be output via output 272, e.g., in the form of encoded bitstream 21, whereby, for example, video decoder 30 may receive and use the parameters for decoding. Encoded bitstream 21 may be transmitted to video decoder 30 or stored in memory for later transmission or retrieval by video decoder 30.

[0146] Other structural variations of the video encoder 20 can be used to encode the video stream. For example, a non-transform-based encoder 20 can quantize the residual signal directly for a block or frame without the transform processing unit 206. In another implementation, the encoder 20 can have the quantization unit 208 and the inverse quantization unit 210 combined into a single unit.

[0147] Decoder and decoding method 3 illustrates an example of a video decoder 30 configured to implement the techniques of the present application. The video decoder 30 is configured to receive encoded picture data 21 (e.g., encoded bitstream 21), for example, encoded by encoder 20, to obtain a decoded picture 331. The encoded picture data or bitstream comprises information for decoding the encoded picture data, for example, data representing picture blocks of an encoded video slice (and / or tile group or tile), and associated syntax elements.

[0148] 3, decoder 30 includes an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (e.g., summer 314), a loop filter 320, a decoded picture buffer (DBP) 330, a mode application unit 360, an inter prediction unit 344, and an intra prediction unit 354. Inter prediction unit 344 may be or may include a motion compensation unit. Video decoder 30 may, in some examples, perform a decoding path that is generally complementary to the encoding path described with respect to video encoder 100 from FIG. 2.

[0149] As described with respect to encoder 20, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, loop filter 220, decoded picture buffer (DPB) 230, inter prediction unit 344, and intra prediction unit 354 are also referred to as forming a “built-in decoder” of video encoder 20. Accordingly, inverse quantization unit 310 may be identical in function to inverse quantization unit 110, inverse transform processing unit 312 may be identical in function to inverse transform processing unit 212, reconstruction unit 314 may be identical in function to reconstruction unit 214, loop filter 320 may be identical in function to loop filter 220, and decoded picture buffer 330 may be identical in function to decoded picture buffer 230. Accordingly, the descriptions provided for the respective units and functions of video encoder 20 apply correspondingly to the respective units and functions of video decoder 30.

[0150] Entropy Decoding The entropy decoding unit 304 is configured to parse the bitstream 21 (or encoded picture data 21 in general), e.g., perform entropy decoding on the encoded picture data 21, e.g., to obtain quantized coefficients 309 and / or decoded coding parameters (not shown in FIG. 3 ), e.g., any or all of inter-prediction parameters (e.g., reference picture indices and motion vectors), intra-prediction parameters (e.g., intra-prediction modes or indices), transform parameters, quantization parameters, loop filter parameters, and / or other syntax elements. The entropy decoding unit 304 may be configured to apply a decoding algorithm or scheme corresponding to an encoding scheme such as described with respect to the entropy encoding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide the inter-prediction parameters, intra-prediction parameters, and / or other syntax elements to the mode application unit 360 and other parameters to other units of the decoder 30. The video decoder 30 may receive syntax elements at a video slice level and / or a video block level. In addition to or as an alternative to slices and their respective syntax elements, tile groups and / or tiles and their respective syntax elements may be received and / or used.

[0151] inverse quantization Inverse quantization unit 310 may be configured to receive a quantization parameter (QP) (or generally, information regarding inverse quantization) and quantized coefficients from encoded picture data 21 (e.g., by parsing and / or decoding by entropy decoding unit 304), and apply inverse quantization on decoded quantized coefficients 309 based on the quantization parameter to obtain dequantized coefficients 311, which may also be referred to as transform coefficients 311. The inverse quantization process may involve use of a quantization parameter determined by video encoder 20 for each video block in a video slice (or tile or tile group) to determine the degree of quantization, and similarly, the degree of inverse quantization to be applied.

[0152] Inverse transformation The inverse transform processing unit 312 may be configured to receive the dequantized coefficients 311, also referred to as transform coefficients 311, and apply a transform to the dequantized coefficients 311 to obtain the reconstructed residual block 213 in the sample domain. The reconstructed residual block 213 may also be referred to as the transform block 313. The transform may be an inverse transform, e.g., an inverse DCT, an inverse DST, an inverse integer transform, or a conceptually similar inverse transform process. The inverse transform processing unit 312 may further be configured to receive transform parameters or corresponding information from the encoded picture data 21 (e.g., by parsing and / or decoding by the entropy decoding unit 304) to determine the transform to be applied to the dequantized coefficients 311.

[0153] Reconstruction The reconstruction unit 314 (e.g., an adder or summator 314) may be configured to add the reconstructed residual block 313 to the prediction block 365, for example, by adding the sample values ​​of the reconstructed residual block 313 and the sample values ​​of the prediction block 365, to obtain a reconstructed block 315 in the sample domain.

[0154] Filtering Loop filter unit 320 (either in the coding loop or after the coding loop) is configured to filter reconstructed block 315 to obtain filtered block 321, e.g., to smooth pixel transitions or otherwise improve video quality. Loop filter unit 320 may comprise one or more loop filters, such as a deblocking filter, a sample-adaptive offset (SAO) filter, or one or more other filters, e.g., a bilateral filter, an adaptive loop filter (ALF), a sharpening filter, a smoothing filter, or a collaborative filter, or any combination thereof. Although loop filter unit 320 is depicted in FIG. 3 as being an in-loop filter, in other configurations, loop filter unit 320 may be implemented as a post-loop filter.

[0155] Decoded Picture Buffer The decoded video blocks 321 of the picture are then stored in a decoded picture buffer 330, which stores the decoded picture 331 as a reference picture for subsequent motion compensation for other pictures and / or for output respective display.

[0156] The decoder 30 is arranged to output the decoded pictures 311, for example via output 312, for presentation or viewing to a user.

[0157] prediction The inter prediction unit 344 may be identical to the inter prediction unit 244 (especially the motion compensation unit), and the intra prediction unit 354 may be identical in function to the inter prediction unit 254, performing the partition or partition decision and prediction based on the partition and / or prediction parameters or respective information received (e.g., by parsing and / or decoding by the entropy decoding unit 304) from the encoded picture data 21. The mode application unit 360 may be configured to perform prediction (intra or inter prediction) for each block based on the (filtered or unfiltered) reconstructed picture, block, or respective sample to obtain a prediction block 365.

[0158] When a video slice is coded as an intra-coded (I) slice, intra prediction unit 354 of mode application unit 360 is configured to generate predictive block 365 for a picture block of the current video slice based on the signaled intra prediction mode and data from previously decoded blocks of the current picture. When a video picture is coded as an inter-coded (i.e., B or P) slice, inter prediction unit 344 (e.g., a motion compensation unit) of mode application unit 360 is configured to produce predictive block 365 for a video block of the current video slice based on motion vectors and other syntax elements received from entropy decoding unit 304. For inter prediction, the predictive block may be produced from one of the reference pictures in one of the reference picture lists. Video decoder 30 may construct the reference frame lists, List 0 and List 1, using a default construction technique based on the reference pictures stored in DPB 330. The same or similar may apply to or with embodiments that use tile groups (e.g., video tile groups) and / or tiles (e.g., video tiles) in addition to or as an alternative to slices (e.g., video slices), e.g., video may be coded using I, P, or B tile groups and / or tiles.

[0159] Mode application unit 360 is configured to determine prediction information for video blocks of a current video slice by parsing motion vectors or related information and other syntax elements, and use the prediction information to produce predictive blocks for the current video block being decoded. For example, mode application unit 360 uses some of the received syntax elements to determine the prediction mode (e.g., intra- or inter-prediction) used to code the video blocks of the video slice, the inter-prediction slice type (e.g., B slice, P slice, or GPB slice), configuration information for one or more of the reference picture lists for the slice, motion vectors for each inter-encoded video block of the slice, inter-prediction status for each inter-coded video block of the slice, and other information to decode the video blocks in the current video slice. The same or similar may apply for or with embodiments that use tile groups (e.g., video tile groups) and / or tiles (e.g., video tiles) in addition to, or as an alternative to, slices (e.g., video slices); e.g., video may be coded using I, P, or B tile groups and / or tiles.

[0160] An embodiment of the video decoder 30 as depicted in FIG. 3 may be configured to partition and / or decode a picture by using slices (also referred to as video slices), where a picture may be partitioned into or decoded using one or more (typically non-overlapping) slices, each of which may comprise one or more blocks (e.g., CTUs).

[0161] An embodiment of video decoder 30 such as that depicted in FIG. 3 may be configured to partition and / or decode a picture by using tile groups (also referred to as video tile groups) and / or tiles (also referred to as video tiles), where a picture may be partitioned into or decoded using one or more (typically non-overlapping) tile groups, each of which may comprise, for example, one or more blocks (e.g., CTUs) or one or more tiles, and each tile may be, for example, rectangular in shape and may comprise one or more blocks (e.g., CTUs), e.g., full or fractional blocks.

[0162] Other variations of the video decoder 30 may be used to decode the encoded picture data 21. For example, the decoder 30 may produce an output video stream without a loop filtering unit 320. For example, a non-transform-based decoder 30 may inverse quantize the residual signal directly for a block or frame without an inverse transform processing unit 312. In another implementation, the video decoder 30 may have the inverse quantization unit 310 and the inverse transform processing unit 312 combined into a single unit.

[0163] It should be understood that the processing result of the current step may be further processed and then output to the next step in the encoder 20 and the decoder 30. For example, after the interpolation filtering, motion vector derivation, or loop filtering, further operations such as clipping or shifting may be performed on the processing result of the interpolation filtering, motion vector derivation, or loop filtering.

[0164] It should be noted that further operations may be applied to the derived motion vectors of the current block (including, but not limited to, control point motion vectors in affine mode, sub-block motion vectors in affine, planar, and ATMVP modes, temporal motion vectors, etc.). For example, the value of a motion vector is constrained to a predetermined range according to its representation bits. If the representation bits of a motion vector are bitDepth, the range is -2^(bitDepth-1) to 2^(bitDepth-1)-1, where "^" means exponentiation. For example, if bitDepth is set equal to 16, the range is -32768 to 32767, and if bitDepth is set equal to 18, the range is -131072 to 131071. For example, the value of a derived motion vector (e.g., the MVs of four 4x4 sub-blocks in one 8x8 block) is constrained so that the maximum difference between the integer parts of the four 4x4 sub-block MVs is not greater than N pixels, such as not greater than 1 pixel. Here, we provide two methods for constraining motion vectors according to bitDepth.

[0165] Method 1: Remove the overflow MSB (Most Significant Bit) by flow operation. ux = ( mvx + 2 bitDepth ) % 2 bitDepth (1) mvx = ( ux >= 2 bitDepth-1 ) ? ( ux - 2 bitDepth ) : ux (2) uy = ( mvy + 2 bitDepth ) % 2 bitDepth (3) mvy = ( uy >= 2 bitDepth-1 ) ? ( uy - 2 bitDepth ) : uy (4) where mvx is the horizontal component of the motion vector of the image block or sub-block, mvy is the vertical component of the motion vector of the image block or sub-block, and ux and uy denote intermediate values.

[0166] For example, if the value of mvx is -32769, then after applying equations (1) and (2), the resulting value is 32767. In computer systems, decimal numbers are stored as two's complement numbers. The two's complement of -32769 is 1, 0111, 1111, 1111, 1111 (17 bits), then the MSB is discarded, so the resulting two's complement is 0111, 1111, 1111, 1111, which is the same as the output by applying equations (1) and (2) (decimal number is 32767). ux = ( mvpx + mvdx +2 bitDepth ) % 2 bitDepth (5) mvx = ( ux >= 2 bitDepth-1 ) ? ( ux - 2 bitDepth ) : ux (6) uy = ( mvpy + mvdy +2 bitDepth ) % 2 bitDepth (7) mvy = ( uy >= 2 bitDepth-1 ) ? ( uy - 2 bitDepth ) : uy (8)

[0167] As shown in equations (5) to (8), the operation can be applied between the sums of mvp and mvd.

[0168] Method 2: Remove the overflow MSB by clipping the value. vx = Clip3(-2 bitDepth-1 , 2 bitDepth-1 -1, vx) vy = Clip3(-2 bitDepth-1 , 2 bitDepth-1 -1, vy) where vx is the horizontal component of the motion vector of the image block or sub-block, vy is the vertical component of the motion vector of the image block or sub-block, x, y, and z correspond to the three input values ​​of the MV clipping process, respectively, and the definition of the function Clip3 is as follows:

[0169]

number

[0170] 4 is a schematic diagram of a video coding device 400 according to one embodiment of the disclosure. The video coding device 400 is suitable for implementing the disclosed embodiments as described herein. In one embodiment, the video coding device 400 may be a decoder, such as the video decoder 30 of FIG. 1A, or an encoder, such as the video encoder 20 of FIG. 1A.

[0171] Video coding device 400 comprises an ingress port 410 (or input port 410) and a receiver unit (Rx) 420 for receiving data, a processor, logic unit, or central processing unit (CPU) 430 for processing the data, a transmitter unit (Tx) 440 and an egress port 450 (or output port 450) for transmitting the data, and a memory 460 for storing the data. Video coding device 400 may also comprise optical-to-electrical (OE) and electrical-to-optical (EO) components coupled to ingress port 410, receiver unit 420, transmitter unit 440, and egress port 450 for the egress or ingress of optical or electrical signals.

[0172] The processor 430 is implemented in hardware and software. The processor 430 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor), FPGA, ASIC, and DSP. The processor 430 is in communication with the ingress port 410, the receiver unit 420, the transmitter unit 440, the egress port 450, and the memory 460. The processor 430 includes a coding module 470. The coding module 470 implements the disclosed embodiments described above. For example, the coding module 470 implements, processes, prepares, or provides various coding operations. Thus, the inclusion of the coding module 470 provides significant improvements to the functionality of the video coding device 400 and results in the transformation of the video coding device 400 into different states. Alternatively, the coding module 470 is implemented as instructions stored in the memory 460 and executed by the processor 430.

[0173] Memory 460 may comprise one or more disks, tape drives, and solid-state drives, and may be used as an overflow data storage device for storing programs when such programs are selected for execution and for storing instructions and data read during program execution. Memory 460 may be, for example, volatile and / or non-volatile, and may be read-only memory (ROM), random access memory (RAM), ternary content-addressable memory (TCAM), and / or static random-access memory (SRAM).

[0174] FIG. 5 is a simplified block diagram of an apparatus 500 that may be used as either or both of source device 12 and destination device 14 from FIG. 1, according to an example embodiment.

[0175] The processor 502 in the apparatus 500 may be a central processing unit. Alternatively, the processor 502 may be any other type of device or devices, now existing or later developed, capable of manipulating or processing information. While the disclosed implementations may be implemented using a single processor, e.g., processor 502, as shown, advantages in speed and efficiency may be achieved using more than one processor.

[0176] The memory 504 in the apparatus 500 may be a read-only memory (ROM) device or a random access memory (RAM) device in one implementation. Any other suitable type of storage device may be used as the memory 504. The memory 504 may include code and data 506 that is accessed by the processor 502 using a bus 512. The memory 504 may further include an operating system 508 and application programs 510, which include at least one program that enables the processor 502 to perform the methods described herein. For example, the application programs 510 may include applications 1 through N, which further include a video coding application that performs the methods described herein.

[0177] The apparatus 500 may also include one or more output devices, such as a display 518. The display 518, in one example, may be a touch-sensitive display that combines a display with touch-sensitive elements operable to sense touch input. The display 518 may be coupled to the processor 502 via the bus 512.

[0178] Although depicted here as a single bus, bus 512 of device 500 may be comprised of multiple buses. Additionally, secondary storage 514 may be directly coupled to other components of device 500 or may be accessed over a network, and may comprise a single integrated unit such as a memory card, or multiple units such as multiple memory cards. Thus, device 500 may be implemented in a wide variety of configurations.

[0179] Chroma Component Subsampling In video coding, there is typically one luminance component (Y) and two chrominance components (Cb and Cr) for the input video. In practice, the chrominance components are typically subsampled to reduce storage and transition bandwidth for the video.

[0180] There are several chroma subsampling formats. In some examples, there is one chroma subsampling format that does not require chroma subsampling for video, for example, chroma subsampling format 4:4:4. In chroma subsampling format 4:4:4, the three components Y, U, and V are equally distributed within the frame, as shown in the example in Figure 6. In one example, assuming the size of the luma component is 1 in the video, the total size of the video is 3.

[0181] In practice, one chroma subsampling format, 4:2:0, is widely used, in which the chroma components are subsampled by half the horizontal and vertical equivalents to the luma component, and the size of Cb or Cr is 1 / 4 of the size of the luma component, as shown in the example in Figure 7. Therefore, in the 4:2:0 format, the total size of the video is 1(Y) + 0.25(Cb) + 0.25(Cr) = 1.5 of the size of the luma component. Compared with the 4:4:4 chroma subsampling format, the 4:2:0 format saves half of the size required for video stream storage or transition.

[0182] In another example, a chroma subsampling format 4:2:2 is disclosed, in which the chroma components are horizontally subsampled as shown in the example in FIG. 8. In this case, the size of Cb or Cr is half that of the luma component. Therefore, the total size of the video in this format is 1(Y) + 0.5(Cb) + 0.5(Cr) = 2 times the size of the luma component. Compared with the 4:4:4 chroma subsampling format, the 4:2:2 format saves 1 / 3 of the size required for storage or transition.

[0183] In these examples, the luma component size is assumed to be 1 in the video.

[0184] In one example expressed in ITU-T JVET O2001 (the link is http: / / phenix.it-sudparis.eu / jvet / doc_end_user / documents / 15_Gothenburg / wg11 / JVET-O2001-v14.zip), the variables and terms associated with these arrays are called luma (or L or Y) and chroma, where the two chroma arrays are called Cb and Cr.

[0185] The variables SubWidthC and SubHeightC are specified in Table 1 below depending on the chroma format sampling structure specified through chroma_format_idc and separate_colour_plane_flag. Other values ​​for chroma_format_idc, SubWidthC, and SubHeightC may be specified in the future by ITU-T | ISO / IEC.

[0186] [Table 8]

[0187] chroma_format_idc specifies the chroma sampling relative to the luma sampling (as expressed in Table 1 and the associated paragraph). The value of chroma_format_idc shall be in the inclusive range of 0 to 3.

[0188] In monochrome sampling, there is only one sample array, nominally considered the luma array.

[0189] In 4:2:0 sampling, each of the two chroma arrays has half the height and half the width of the luma array.

[0190] In 4:2:2 sampling, each of the two chroma arrays has the same height and half the width of the luma array.

[0191] For 4:4:4 sampling, the following applies depending on the value of separate_colour_plane_flag: - If separate_colour_plane_flag is equal to 0, then each of the two chroma arrays has the same height and width as the luma array. - Otherwise (separate_colour_plane_flag equals 1), the three colour planes are processed separately as a monochrome sampled picture.

[0192] The number of bits required to represent each of the samples in the luma and chroma arrays in a video sequence is in the inclusive range of 8 to 16, and the number of bits used in the luma array may differ from the number of bits used in the chroma array.

[0193] When the value of chroma_format_idc is equal to 1, the nominal relative vertical and horizontal positions of luma and chroma samples within a picture are represented in Figure 7. Alternative relative chroma sample positions may be indicated within the video utility information.

[0194] When the value of chroma_format_idc is equal to 2, the chroma samples are co-located with the corresponding luma samples, and their nominal positions within the picture are as shown in Figure 8.

[0195] When the value of chroma_format_idc is equal to 3, all array samples are co-located for all instances of the picture, and their nominal positions within the picture are as shown in FIG.

[0196] Angular intra-prediction modes and their corresponding directional interpretations In the example shown in Figure 9, solid lines (2 to 66) with arrows are used to represent the angular intra-prediction modes. Among them, modes 18 and 50 correspond to horizontal and vertical prediction directions, respectively. Relative to the horizontal direction, modes 2 and 34 correspond to 45° and -45°, respectively. Relative to the vertical direction, modes 66 and 34 correspond to 45° and -45°.

[0197] In some examples, as represented in Table 2, which has modes as inputs and distances as outputs, the angles of these modes (eg, inputs 2, 18, 34, 50, 66) are implicitly defined using the distance values.

[0198] [Table 9]

[0199] The corresponding degree of Mode X is degree = arctan(output(x) / 32) It can be derived as:

[0200] In one example, input mode 2 will output a value of 32, and the corresponding degrees for mode 2 is 45°. Similarly, modes 18, 34, 50, and 66 will output values ​​of 0, -32, 0, and 32, and the corresponding degrees are 0, -45°, 0, and 45°, respectively. It is noted that modes 18 (horizontal prediction) and 50 (vertical prediction) both correspond to 0 degrees, and mode 34 corresponds to an overlapping -45° relative to the two 0-degree modes.

[0201] As shown in Figure 10, for modes 0 through 34, adjacent sides of the desired angle are parallel to the horizontal direction, while opposite sides of the desired angle are parallel to the vertical direction. The desired angle corresponding to mode 8 is shown on the left side of Figure 10. For modes 34 through 66, adjacent sides of the desired angle are parallel to the vertical direction, while opposite sides of the desired angle are parallel to the horizontal direction.

[0202] In some instances, some modes (e.g., modes 3, 4, 6...26) do not have outputs that are multiples of 32. Among modes 2, 18, 34, 50, 66, the corresponding degrees for these modes are not uniformly distributed among 45 degrees. As illustrated in Figure 9, modes are more tightly defined when their corresponding angles are closer to horizontal (mode 18) and vertical (mode 50) degrees.

[0203] In some examples, some intra prediction modes (e.g., 8, 28, 40, and 60...) will output values ​​that are multiples of 16 (but not 32), corresponding to angles whose opposite sides are half adjacent (the tangent function of these angles is 0.5 or -0.5).

[0204] In some examples, there are wide angle modes from -1 to -14, and from 67 to 80. When the block aspect ratio is not 1:1, these modes are not directly coded but are mapped.

[0205] The mapping rule is defined as the following process, with input nW as the width of the block, nH as the height of the block, and predModeIntra as the input angle mode:

[0206] The variable whRatio is set equal to Abs(Log2(nW / nH)).

[0207] For non-square blocks (nW not equal to nH), the intra prediction mode predModeIntra is modified as follows: If all of the following conditions (which are used to determine whether or not to apply the wide-angle mapping process) are true, then predModeIntra is set equal to ( predModeIntra +65 ). - nW is greater than nH, - predModeIntra is greater than or equal to 2, - predModeIntra is less than ( whRatio > 1 ) ? ( 8 + 2 * whRatio ) : 8. - Otherwise, if all of the following conditions (which are used to determine whether to apply the wide-angle mapping process) are true, then predModeIntra is set equal to (predModeIntra - 67): - nH is greater than nW, - predModeIntra is less than or equal to 66, - predModeIntra is greater than ( whRatio > 1 ) ? ( 60 - 2 * whRatio ) : 60.

[0208] Taking a block with an aspect ratio of 1:2 (block width is half its height) as an example, predModeIntra modes 61 to 66 will be mapped to -6 to -1 when the following conditions are met: - nH is greater than nW, - predModeIntra is less than or equal to 66, - predModeIntra is greater than ( whRatio > 1 ) ? ( 60 - 2 * whRatio ) : 60, where whRatio = Abs( Log2( nW / nH ) ) = 1.

[0209] Chroma intra prediction mode derivation when chroma components are horizontally or vertically subsampled In some examples, for a 4:2:2 chroma subsampling format, a mapping table may be defined to derive the final chroma intra angle mode, where the original chroma angle prediction mode is adjusted based on the ratio changed due to subsampling.

[0210] In one example, as shown in Figure 10, blocks without chroma subsampling (left side) have the same width and height. Modes 2, 8, 18, 34, 50, and 66 are labeled with their prediction directions. When the 4:2:2 chroma subsample format is applied (i.e., the chroma components are subsampled only horizontally and chroma samples are aligned with luma samples every two columns, as shown in Figure 8), the width of the chroma components is half that of the luma components.

[0211] In this case, the aspect ratio of the chroma block is 1:2 due to the chroma subsampling. Therefore, the original modes are adjusted (mapped) according to the horizontally subsampled chroma components. In this case, mode 2 is mapped to 61 to adjust for the half reduction in the horizontal direction. Because the aspect ratio of the subsampled block is 1:2, and if the mapped mode 61 meets the conditions for the wide-angle mapping process, the mapped mode 61 will be further mapped to mode -6 according to the wide-angle mapping process.

[0212] Mode-6 corresponds to an output value of 64 according to Table 2. Therefore, the corresponding degree of the final angle after chroma subsampling is degree = arctan(64 / 32) is.

[0213] The tangent of this angle is twice that of mode 2, reflecting that the adjacent side of mode 2 has been halved due to chroma subsampling.

[0214] Mode 8 is mapped to mode 2 because the half-width position corresponds to mode 8 (as represented on the left in FIG. 10), and mode 8 corresponds to an angle of 45° due to the width in the horizontal direction. Similarly, modes 34 and 60 are mapped to 40 and 60, respectively. In these examples, horizontal and vertical prediction modes whose degree is 0 are not mapped to other modes, i.e., the horizontal / vertical modes are still mapped to the same mode.

[0215] To map intra prediction modes when the chroma components are subsampled (eg, chroma subsampling format 4:2:2), a mapping table is defined as follows:

[0216] [Table 10]

[0217] One implementation of the present invention proposes replacing the mapping of modes 2 to 7 with 60 to 65, as defined in Table 4.

[0218] [Table 11]

[0219] In the above example, mode 2 would map to 61. In this embodiment, mode 2 would map to mode 60 as depicted in FIG.

[0220] One implementation of the present invention proposes replacing the mapping of modes 2 to 7, as defined in Table 5, with 61 to 66, which are the same as modes 2 to 7 in Table 3.

[0221] [Table 12]

[0222] In one implementation of the present invention, it is proposed to map modes 8 to 18 with the following modes, as defined in Table 6:

[0223] [Table 13]

[0224] In one implementation of the present invention, Table 7 below is used to show how the mapped modes are derived.

[0225] [Table 14]

[0226] The left side represents input modes 2 to 18, each corresponding to a tangent value and an angle. In the case without subsampling, the angles of these modes can be defined as follows: degree = arctan(output(x) / 32)

[0227] For modes 2 through 34, scaling factor 32 may be considered as a width as depicted in FIG. 10. For those modes, adjacent sides of the desired angle are parallel to the horizontal direction, while opposite sides of the desired angle are parallel to the vertical direction. The desired angle corresponding to mode 8 is depicted in the left sub-view of FIG. 10. In contrast, for modes 34 through 66 (because the angle corresponding to mode 34 is an overlapping angle (-45 degrees) associated with both the horizontal and vertical directions), adjacent sides of the desired angle are parallel to the vertical direction, while opposite sides of the desired angle are parallel to the horizontal direction.

[0228] Due to chroma subsampling, for modes 2 to 34 the subsampled tangent value is doubled since the adjacent side (parallel to the width) is halved, and for modes 34 to 66 the subsampled tangent value is halved since the opposite side is halved.

[0229] In one example, doubled tangent values ​​are listed for each mode on the right side of Table 7. However, the angles are not linearly proportional to the tangent values. Therefore, these doubled tangent values ​​need to be converted back to angle values. Using the converted angle values ​​on the right side with chroma subsampling, the mode with the closest angle on the left side of Table 7 is the output mode.

[0230] In summary, a lookup table is first generated using the following steps with an input mode X to find the corresponding mapping mode. Obtain the output value according to Table 2. Alternatively or additionally, calculate the tangent value of this mode as output(X) / 32. Alternatively or additionally, calculate the angle using the derived tangent value, e.g., arctan(output(x) / 32). Alternatively or additionally, use the range of input mode X to generate a lookup table using the three steps above, with X ranging from 2..18, as represented on the left side of Table 7, which contains columns for tangent value, angle value, and input mode.

[0231] To derive the mapped modes using the input mode X, the following steps are applied: Alternatively or additionally, double the tangent value for X mode as 2*output(X) / 32. Alternatively or additionally, calculate the angle in chroma subsampling format 4:2:2 using a doubled tangent value, e.g. arctan(2*output(x) / 32). Alternatively or additionally, according to the calculated angle value in the chroma subsampling format 4:2:2, find the closest angle in a lookup table (for example, the angle list without chroma subsampling in Table 7). Alternatively or additionally, pick up the corresponding output mode according to the closest angle in the look-up table.

[0232] For the sake of brevity, the above process will be referred to as the process for deriving the output mode.

[0233] In one example, the input mode 10 derives its output mode as follows after the look-up table is generated: ·Double the tangent value of the 10th mode: 2*12 / 32 = 0.75. · Calculate the angle in chroma subsampling format 4:2:2 using doubled tangent value, e.g. arctan(0.75) = 36.8699°. According to the calculated angle value 36.8699°, find the closest angle 35.70669° in the lookup table. According to the closest angle 35.70669° in the lookup table, pick up the corresponding output mode 5.

[0234] Thus, input mode 10 is mapped to mode 5.

[0235] In one implementation of the present invention, it is proposed to map modes 19 to 28 with the following modes, as defined in Table 8:

[0236] [Table 15]

[0237] In one implementation of the present invention, Table 9 below is used to show how the mapped modes are derived.

[0238] [Table 16]

[0239] Table 9 can be similarly derived using the process for deriving output modes as defined in the previous embodiment. In this example, input modes 19 through 34 are used when generating the lookup table (left side of Table 9).

[0240] In one implementation of the present invention, it is proposed to map modes 29 to 34 with the following modes, as defined in Table 10:

[0241] [Table 17]

[0242] In one implementation of the present invention, the following Table 11 is used to show how the mapped modes are derived.

[0243] [Table 18]

[0244] In one example, Table 11 can be derived using the process for deriving output modes as defined in the previous embodiment, except for the following aspects. · When generating lookup tables, input modes 29 to 40 are used. For modes 29 to 34, one more step is required to derive the output mode. The angle corresponding to the value of 2*tangent(output(x) / 32) is smaller than -45° (i.e., the absolute value of the angle is greater than 45°). These angles (smaller than -45°) cannot be used directly because the smallest angle that can be derived is -45°. In this case, their complement is used, and the mapped angle faces the top boundary of the current block (instead of the current left boundary). Therefore, the adjacent and opposite sides of the mapped angle are swapped, and the tangent value of their complement, 1 / 2*tangent(output(x) / 32), is used to derive the correct angle, which is used to find the closest angle in the lookup table.

[0245] In one implementation of the present invention, it is proposed to map modes 35 to 50 with the following modes, as defined in Table 12:

[0246] [Table 19]

[0247] In one implementation of the present invention, the following Table 13 is used to show how the mapped modes are derived.

[0248] [Table 20]

[0249] Table 13 may be derived using the process for deriving output modes, but with the following modifications. · When generating lookup tables, input modes 35 to 50 are used. Modes 35 to 50 correspond to angles whose opposite sides are the upper boundary of the current block. After chroma subsampling, the corresponding tangent values ​​are halved (instead of doubled in Table 7) because the opposite sides are halved using the 4:2:2 chroma subsampling format.

[0250] In one example, mode 36 can also be mapped to 42 by considering the following mapping table, as shown in Table 2:

[0251] [Table 21]

[0252] From the perspective of mode 36, opposite sides of corresponding angles are parallel to the horizontal direction, and adjacent sides of corresponding angles are parallel to the vertical direction. Due to chroma subsampling, the horizontal direction is reduced by half, i.e., opposite sides of corresponding angles are reduced by half. This is equivalent to reducing its output value by half, which means that its output value is now -26 / 2 = -13. Since -13 has two equivalent nearest output values, -12 and -14, it can be mapped to either mode 41 or 42.

[0253] For the same reason, modes 39, 41, 43, 47, and 49 can be mapped to either 43 or 44, 44 or 45, 45 or 46, 48 or 49, and 49 or 50, respectively. Table 14 summarizes the possible mapping modes and how they are derived.

[0254] [Table 22]

[0255] In one implementation of the present invention, it is proposed to map modes 51 to 66 with the following modes, as defined in Table 15:

[0256] [Table 23]

[0257] In one implementation of the present invention, the following Table 16 is used to show how the mapped modes are derived.

[0258] [Table 24]

[0259] Similar to Table 13, Table 16 may be derived using the process for deriving output modes, but with the following modifications. · When generating lookup tables, input modes 50 to 66 are used. Modes 51 to 66 correspond to angles whose opposite sides are the upper boundary of the current block. After chroma subsampling, the corresponding tangent values ​​are halved (instead of doubled in Table 7) because the opposite sides are halved using the 4:2:2 chroma subsampling format.

[0260] Similar to Table 14, as shown in Table 17, some of the modes among modes 51 to 66 may have alternative mapped modes.

[0261] [Table 25]

[0262] In the above embodiments, many embodiments are represented as chroma subsampling mode 4:2:2, i.e., a mapping mode for subsampling of the chroma components by half in the horizontal direction. It is noted that a similar approach can be proposed for chroma subsampling formats in which the chroma components are subsampled vertically.

[0263] In some examples, it is not necessary to perform intra-prediction mode mapping for chroma subsampling formats that result in no change in block aspect, for example, with a 4:2:0 chroma subsampling format, the chroma components are subsampled in both the horizontal and vertical directions, so the block aspect does not change and therefore no mode mapping needs to be performed.

[0264] In some examples, the above embodiments can be combined as long as one input mode X has one output mode Y. For example, the following Table 18 is one of the proposed combinations of embodiments.

[0265] [Table 26]

[0266] In some examples, one or any combination of the modes disclosed in the above embodiments (eg, Tables 2 to 18) may be combined to form a mode mapping relationship.

[0267] Example 1. A method of coding performed by a decoding device, comprising: obtaining a video bitstream; decoding the video bitstream to obtain an initial intra-prediction mode value for a chroma component of the current coding block; determining whether a ratio between a width for the luma component of the current coding block and a width for the chroma component of the current coding block is equal to a threshold value (or determining whether a ratio between a height for the luma component of the current coding block and a height for the chroma component of the current coding block is equal to a threshold value); when it is determined that the ratio is equal to the threshold value, obtaining mapped intra-prediction mode values ​​for the chroma components of the current coding block according to a predefined mapping relationship and the initial intra-prediction mode value; and obtaining predicted sample values ​​for the chroma components of the current coding block according to the mapped intra-prediction mode values.

[0268] Example 2. The method of Example 1, with the threshold being 2 or 0.5.

[0269] Example 3. The following table is used to represent the default mapping relationship:

[0270] [Table 27]

[0271] or

[0272] [Table 28]

[0273] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0274] Example 4. The following table is used to represent the default mapping relationship:

[0275] [Table 29]

[0276] 4. The method of any one of Examples 1 to 3, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0277] Example 5. The following table is used to represent the default mapping relationship:

[0278] [Table 30]

[0279] 5. The method of any one of Examples 1 to 4, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0280] Example 6. The following table is used to represent the default mapping relationship:

[0281] [Table 31]

[0282] 6. The method of any one of Examples 1 to 5, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0283] Example 7. The following table is used to represent the default mapping relationship:

[0284] [Table 32]

[0285] 7. The method of any one of Examples 1 to 6, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0286] Example 8. The following table is used to represent the default mapping relationship:

[0287] [Table 33]

[0288] 7. The method of any one of Examples 1 to 6, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0289] Example 9. The following table is used to represent the default mapping relationship:

[0290] [Table 34]

[0291] 7. The method of any one of Examples 1 to 6, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0292] Example 10. The following table is used to represent the default mapping relationship:

[0293] [Table 35]

[0294] 10. The method of any one of Examples 1 to 6, 8, and 9, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0295] Example 11. The following table is used to represent the default mapping relationships:

[0296] [Table 36]

[0297] 10. The method of any one of Examples 1 to 6, 8, and 9, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0298] Example 12. The following table is used to represent the default mapping relationships:

[0299] [Table 37]

[0300] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0301] Example 13. The following table is used to represent the default mapping relationships:

[0302] [Table 38]

[0303] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0304] Example 14. The following table is used to represent the default mapping relationships:

[0305] [Table 39]

[0306] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0307] Example 15. The following table is used to represent the default mapping relationships:

[0308] [Table 40]

[0309] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0310] Example 16. The following table is used to represent the default mapping relationships:

[0311] [Table 41]

[0312] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0313] Example 17. The following table is used to represent the default mapping relationships:

[0314] [Table 42]

[0315] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0316] Example 18. The following table is used to represent the default mapping relationships:

[0317] [Table 43]

[0318] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0319] Example 19. The following table is used to represent the default mapping relationships:

[0320] [Table 44]

[0321] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0322] Example 20. The following table is used to represent the default mapping relationships:

[0323] [Table 45]

[0324] 20. The method of any one of Examples 1 to 19, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0325] Example 21. The following table is used to represent the default mapping relationships:

[0326] [Table 46]

[0327] 20. The method of any one of Examples 1 to 19, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0328] Example 22. The following table is used to represent the default mapping relationships:

[0329] [Table 47]

[0330] 20. The method of any one of Examples 1 to 19, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0331] Example 23. The following table is used to represent the default mapping relationships:

[0332] [Table 48]

[0333] 23. The method of any one of Examples 1 to 19 and 21 to 22, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0334] Example 24. The following table is used to represent the default mapping relationships:

[0335] [Table 49]

[0336] 23. The method of any one of Examples 1 to 19 and 21 to 22, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0337] Example 25. The following table is used to represent the default mapping relationships:

[0338] [Table 50]

[0339] 25. The method of any one of Examples 1 to 19 and 21 to 24, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0340] Example 26. The following table is used to represent the default mapping relationships:

[0341] [Table 51]

[0342] 25. The method of any one of Examples 1 to 19 and 21 to 24, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0343] Example 27. The following table is used to represent the default mapping relationships:

[0344] [Table 52]

[0345] 27. The method of any one of Examples 1 to 19 and 21 to 26, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0346] Example 28. The following table is used to represent the default mapping relationships:

[0347] [Table 53]

[0348] 27. The method of any one of Examples 1 to 19 and 21 to 26, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0349] Example 29. The following table is used to represent the default mapping relationships:

[0350] [Table 54]

[0351] 29. The method of any one of Examples 1 to 19 and 21 to 28, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0352] Example 30. The following table is used to represent the default mapping relationships:

[0353] [Table 55]

[0354] 29. The method of any one of Examples 1 to 19 and 21 to 28, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0355] Example 31. The following table is used to represent the default mapping relationships:

[0356] [Table 56]

[0357] 31. The method of any one of Examples 1 to 19 and 21 to 30, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0358] Example 32. The following table is used to represent the default mapping relationships:

[0359] [Table 57]

[0360] 31. The method of any one of Examples 1 to 19 and 21 to 30, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0361] Example 33. A coding method performed by a decoding device, comprising: obtaining a video bitstream; decoding the video bitstream to obtain an initial intra-prediction mode value for a chroma component of the current coding block; decoding the video bitstream to obtain a value of chroma format display information for the current coding block; When the value of the chroma format display information for the current coding block is equal to a default value, obtaining mapped intra-prediction mode values ​​for the chroma components of the current coding block according to the default mapping relationship and the initial intra-prediction mode value; and obtaining predicted sample values ​​for the chroma components of the current coding block according to the mapped intra-prediction mode values.

[0362] Example 34. The method of Example 33, with the default value being 2 or 1.

[0363] Example 35. The following table is used to represent the default mapping relationships:

[0364] [Table 58]

[0365] or

[0366] [Table 59]

[0367] 33. The method of Example 31 or 32, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0368] Example 36. The following table is used to represent the default mapping relationships:

[0369] [Table 60]

[0370] 36. The method of any one of Examples 33 to 35, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0371] Example 37. The following table is used to represent the default mapping relationships:

[0372] [Table 61]

[0373] 37. The method of any one of Examples 33-36, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0374] Example 38. The following table is used to represent the default mapping relationships:

[0375] [Table 62]

[0376] 38. The method of any one of Examples 33-37, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0377] Example 39. The following table is used to represent the default mapping relationships:

[0378] [Table 63]

[0379] 39. The method of any one of Examples 33-38, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0380] Example 40. The following table is used to represent the default mapping relationships:

[0381] [Table 64]

[0382] 39. The method of any one of Examples 33-38, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0383] Example 41. The following table is used to represent the default mapping relationships:

[0384] [Table 65]

[0385] 39. The method of any one of Examples 33-38, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0386] Example 42. The following table is used to represent the default mapping relationships:

[0387] [Table 66]

[0388] 42. The method of any one of Examples 33-38, 40, and 41, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0389] Example 43. The following table is used to represent the default mapping relationships:

[0390] [Table 67]

[0391] 42. The method of any one of Examples 33-38, 40, and 41, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0392] Example 44. The following table is used to represent the default mapping relationships:

[0393] [Table 68]

[0394] 44. The method of any one of Examples 33-38 and 40-43, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0395] Example 45. The following table is used to represent the default mapping relationships:

[0396] [Table 69]

[0397] 44. The method of any one of Examples 33-38 and 40-43, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0398] Example 46. The following table is used to represent the default mapping relationships:

[0399] [Table 70]

[0400] 46. ​​The method of any one of Examples 33-38 and 40-45, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0401] Example 47. The following table is used to represent the default mapping relationships:

[0402] [Table 71]

[0403] 46. ​​The method of any one of Examples 33-38 and 40-45, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0404] Example 48. The following table is used to represent the default mapping relationships:

[0405] [Table 72]

[0406] 48. The method of any one of Examples 33-38 and 40-47, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0407] Example 49. The following table is used to represent the default mapping relationships:

[0408] [Table 73]

[0409] 48. The method of any one of Examples 33-38 and 40-47, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0410] Example 50. The following table is used to represent the default mapping relationships:

[0411] [Table 74]

[0412] 49. The method of any one of Examples 33-38 and 40-49, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0413] Example 51. The following table is used to represent the default mapping relationships:

[0414] [Table 75]

[0415] 49. The method of any one of Examples 33-38 and 40-49, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0416] Example 52. The following table is used to represent the default mapping relationships:

[0417] [Table 76]

[0418] 52. The method of any one of Examples 33-51, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0419] Example 53. The following table is used to represent the default mapping relationships:

[0420] [Table 77]

[0421] 52. The method of any one of Examples 33-51, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0422] Example 54. The following table is used to represent the default mapping relationships:

[0423] [Table 78]

[0424] 52. The method of any one of Examples 33-51, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0425] Example 55. The following table is used to represent the default mapping relationships:

[0426] [Table 79]

[0427] 55. The method of any one of Examples 33-51 and 53-54, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0428] Example 56. The following table is used to represent the default mapping relationships:

[0429] [Table 80]

[0430] 55. The method of any one of Examples 33-51 and 53-54, wherein mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0431] Example 57. The following table is used to represent the default mapping relationships:

[0432] [Table 81]

[0433] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0434] Example 58. The following table is used to represent the default mapping relationships:

[0435] [Table 82]

[0436] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0437] Example 59. The following table is used to represent the default mapping relationships:

[0438] [Table 83]

[0439] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0440] Example 60. The following table is used to represent the default mapping relationships:

[0441] [Table 84]

[0442] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0443] Example 61. The following table is used to represent the default mapping relationships:

[0444] [Table 85]

[0445] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0446] Example 62. The following table is used to represent the default mapping relationships:

[0447] [Table 86]

[0448] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0449] Example 63. The following table is used to represent the default mapping relationships:

[0450] [Table 87]

[0451] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0452] Example 64. The following table is used to represent the default mapping relationships:

[0453] [Table 88]

[0454] is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

[0455] Example 65. A decoder (30) comprising processing circuitry for performing the method according to any one of examples 1 to 64.

[0456] Example 66. A computer program product comprising program code for performing the method according to any one of Examples 1 to 64.

[0457] Example 67. A decoder comprising: one or more processors; and a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform a method according to any one of Examples 1 to 64.

[0458] The following is a description of the encoding method and the decoding method as presented in the above-mentioned embodiments, and the application of the system using them.

[0459] 11 is a block diagram illustrating a content delivery system 3100 for implementing a content distribution service. The content delivery system 3100 includes a capture device 3102, a terminal device 3106, and optionally a display 3126. The capture device 3102 communicates with the terminal device 3106 over a communication link 3104. The communication link may include the communication channel 13 described above. The communication link 3104 includes, but is not limited to, WIFI, Ethernet, cable, wireless (3G / 4G / 5G), USB, or any type of combination thereof, or the like.

[0460] The capture device 3102 may generate data and encode the data by the encoding method as described in the above embodiment. Alternatively, the capture device 3102 may deliver the data to a streaming server (not shown), which encodes the data and transmits the encoded data to the terminal device 3106. The capture device 3102 may include, but is not limited to, a camera, a smartphone or pad, a computer or laptop, a video conferencing system, a PDA, a vehicle-mounted device, or any combination thereof, or the like. For example, the capture device 3102 may include the source device 12 described above. When the data includes video, a video encoder 20 included in the capture device 3102 may actually perform the video encoding process. When the data includes audio (i.e., voice), an audio encoder included in the capture device 3102 may actually perform the audio encoding process. For some practical scenarios, the capture device 3102 delivers the encoded video and audio data by multiplexing them together. In other practical scenarios, for example, in a video conferencing system, the encoded audio data and the encoded video data are not multiplexed, and the capture device 3102 delivers the encoded audio data and the encoded video data to the terminal device 3106 separately.

[0461] In the content delivery system 3100, a terminal device 3106 receives and plays the encoded data. The terminal device 3106 can be a device having data reception and recovery capabilities, such as a smartphone or pad 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video recorder (DVR) 3112, a TV 3114, a set top box (STB) 3116, a video conferencing system 3118, a video surveillance system 3120, a personal digital assistant (PDA) 3122, a vehicle-mounted device 3124, or any combination thereof, capable of decoding the encoded data described above. For example, the terminal device 3106 may include the destination device 14 described above. When the encoded data includes video, the video decoder 30 included in the terminal device is prioritized to perform video decoding. When the encoded data includes audio, an audio decoder included within the terminal device is prioritized to perform the audio decoding process.

[0462] For a terminal device having a display, such as a smartphone or pad 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video recorder (DVR) 3112, a TV 3114, a personal digital assistant (PDA) 3122, or a vehicle-mounted device 3124, the terminal device can provide the decoded data to its display. For a terminal device not equipped with a display, such as an STB 3116, a video conferencing system 3118, or a video surveillance system 3120, an external display 3126 is contacted thereto to receive and display the decoded data.

[0463] When each device in this system performs encoding or decoding, a picture encoding device or a picture decoding device can be used as shown in the above-mentioned embodiments.

[0464] 12 is a diagram illustrating the structure of an example of the terminal device 3106. After the terminal device 3106 receives a stream from the capture device 3102, a protocol progression unit 3202 analyzes the transmission protocol of the stream. The protocol may include, but is not limited to, Real Time Streaming Protocol (RTSP), Hyper Text Transfer Protocol (HTTP), HTTP Live streaming protocol (HLS), MPEG-DASH, Real-time Transport protocol (RTP), Real Time Messaging Protocol (RTMP), or any type of combination thereof, or the like.

[0465] After the protocol progression unit 3202 processes the stream, a stream file is generated. The file is output to the demultiplexing unit 3204. The demultiplexing unit 3204 can separate the multiplexed data into encoded audio data and encoded video data. As described above, in some practical scenarios, for example, in a video conferencing system, the encoded audio data and encoded video data are not multiplexed. In this situation, the encoded data is transmitted to the video decoder 3206 and the audio decoder 3208 without passing through the demultiplexing unit 3204.

[0466] Through the demultiplexing process, a video elementary stream (ES), an audio ES, and optionally subtitles are generated. The video decoder 3206, which includes the video decoder 30 as described in the above-mentioned embodiment, decodes the video ES by the decoding method as described in the above-mentioned embodiment to generate video frames and supplies this data to the synchronization unit 3212. The audio decoder 3208 decodes the audio ES to generate audio frames and supplies this data to the synchronization unit 3212. Alternatively, the video frames may be stored in a buffer (not shown in FIG. 12) before being supplied to the synchronization unit 3212. Similarly, the audio frames may be stored in a buffer (not shown in FIG. 12) before being supplied to the synchronization unit 3212.

[0467] The synchronization unit 3212 synchronizes the video and audio frames and provides the video / audio to the video / audio display 3214. For example, the synchronization unit 3212 synchronizes the presentation of video and audio information. The information may be coded in the syntax using timestamps related to the presentation of the coded audio and visual data and timestamps related to the delivery of the data stream itself.

[0468] If subtitles are included in the stream, a subtitle decoder 3210 decodes the subtitles, synchronizes them with the video and audio frames, and provides the video / audio / subtitles to a video / audio / subtitle display 3216 .

[0469] The present invention is not limited to the above-described system, and either the picture encoding device or the picture decoding device in the above-described embodiments can be incorporated into other systems, for example, automobile systems.

[0470] Mathematical Operators The mathematical operators used in this application are similar to those used in the C programming language. However, the results of integer division and arithmetic shift operations are more precisely defined, and additional operations such as exponentiation and real division are defined. Numbering and counting conventions generally start at 0, e.g., "first" is equivalent to 0th, "second" is equivalent to 1st, etc.

[0471] Arithmetic operators The following arithmetic operators are defined as follows: + Addition. - Subtraction (as an operator of two arguments) or negation (as a unary prefix operator). * Multiplication, including matrix multiplication. x y Exponentiation. Specifies x to the yth power. In other contexts, such notation is used to make a superscript not intended for interpretation as a power. / Integer division with truncation of the result towards 0. For example, 7 / 4 and -7 / -4 round down to 1, and -7 / 4 and 7 / -4 round down to -1. ÷ Used to denote division in mathematical expressions, where no truncation or rounding is intended.

[0472]

number

[0473] Used to denote division in mathematical expressions where no truncation or rounding is intended.

[0474]

number

[0475] The sum of f(i) for all integer values ​​of i from x to y inclusive. x % y modulo. The remainder when x is divided by y, defined only for integers x and y, with x>=0 and y>0.

[0476] Logical operators The following logical operators are defined as follows: x && y The Boolean logic "connection" of x and y. x || y The Boolean logic "disjunction" of x and y. ! "Not" in Boolean logic. x ? y : zIf x is TRUE, i.e. not equal to 0, evaluates to the value of y, otherwise evaluates to the value of z.

[0477] Relational operators The following relational operators are defined as follows: > Greater than. >= Greater than or equal to. < Less than. <= Less than or equal to. == Equal to. != Not equal to.

[0478] When a relational operator is applied to a syntax element or variable that has been assigned the value "na" (not applicable), the value "na" is treated as a special value for that syntax element or variable. The value "na" is not considered equal to any other value.

[0479] Bitwise Operators The following bitwise operators are defined as follows: & Bitwise "and". When operating on integer arguments, it operates on the two's complement representation of the integer value. When operating on a binary argument that contains fewer bits than another argument, the shorter argument is extended by appending the more significant bits equal to 0. Bitwise "logical or". When operating on integer arguments, it operates on the two's complement representation of the integer values. When operating on a binary argument that contains fewer bits than another argument, the shorter argument is extended by appending its more significant bits equal to 0. ^ Bitwise "exclusive or". When operating on integer arguments, it operates on the two's complement representation of the integer value. When operating on a binary argument that contains fewer bits than another argument, the shorter argument is extended by appending more significant bits equal to 0. x >> y Arithmetic right shift of the two's complement integer representation of x by y binary places. This function is defined only for non-negative integer values ​​of y. The bit shifted into the most significant bit (MSB) as a result of the right shift has a value equal to the MSB of x before the shift operation. x << y: Arithmetic left shift of the two's complement integer representation of x by y binary places. This function is defined only for non-negative integer values ​​of y. The bit that is shifted into the least significant bit (LSB) as a result of the left shift has value equal to 0.

[0480] assignment operator The following arithmetic operators are defined as follows: = assignment operator. ++ increment, i.e., x++ is equivalent to x = x + 1, and when used in an array index, evaluates to the value of the variable before the increment operation. -- Decrement, i.e., x--, is equivalent to x = x - 1, and when used in an array index, evaluates to the value of the variable before the decrement operation. += Increment by the specified amount, i.e., x += 3 is equivalent to x = x + 3 and x += (-3) is equivalent to x = x + (-3). -= Decrement by the specified amount, i.e., x -= 3 is equivalent to x = x - 3, and x -= (-3) is equivalent to x = x - (-3).

[0481] Range Notation The following notation is used to specify a range of values: x=y..zx takes integer values ​​starting from y up to and including z, where x, y, and z are integers and z is greater than y.

[0482] Mathematical Functions The following mathematical functions are defined:

[0483]

number

[0484] Asin(x) The trigonometric arc sine function, operating on an argument x in the inclusive range of -1.0 to 1.0, and with an output value in the inclusive range of -π÷2 to π÷2 in radians. Atan(x) The trigonometric arctangent function, operating on the argument x, with output values ​​in the range -π÷2 to π÷2 inclusive, in radians.

[0485]

number

[0486] Ceil(x) The smallest integer greater than or equal to x. Clip1 Y ( x ) = Clip3( 0, ( 1 << BitDepth Y ) - 1, x ) Clip1 C ( x ) = Clip3( 0, ( 1 << BitDepth C ) - 1, x )

[0487]

number

[0488] Cos(x) The trigonometric cosine function, operating on the argument x in radians. Floor(x) The largest integer less than or equal to x.

[0489]

number

[0490] Ln(x) The natural logarithm of x (logarithm to base e, where e is the base constant of the natural logarithm, 2.718 281 828...). Log2(x) The base 2 logarithm of x. Log10(x) The base 10 logarithm of x.

[0491]

number

[0492] Round( x ) = Sign( x ) * Floor( Abs( x ) + 0.5 )

[0493]

number

[0494] Sin(x) The trigonometric sine function, operating on the argument x in radians.

[0495]

number

[0496] Swap( x, y ) = ( y, x ) Tan(x) The trigonometric tangent function, operating on the argument x in radians.

[0497] Order of operation precedence When the order of precedence in an expression is not explicitly indicated by the use of parentheses, the following rules apply: - An operation with higher precedence is evaluated before any operation with lower precedence. - Operations of equal precedence are evaluated sequentially from left to right.

[0498] The following table specifies the precedence of operations from highest to lowest, with higher positions in the table indicating higher precedence.

[0499] For those operators that are also used in the C programming language, the order of precedence used in this specification is the same as that used in the C programming language.

[0500] [Table 89]

[0501] Logical operations in text In the text, statements of logical operations that are to be written mathematically in the following form: if(condition 0) Statement 0 else if(condition 1) Statement 1 ... else / * explanatory notes for remaining conditions * / Statement n can be explained in the following form: ...as follows / ...the following applies - If condition 0, then statement 0 - Otherwise, if condition 1, then statement 1 - ... - Otherwise (explanatory note in the remaining condition), statement n

[0502] Each "if, otherwise, then, otherwise" statement in the text is introduced with "as follows" or "the following applies", followed immediately by an "if." The final condition of an "if, otherwise, then, otherwise" is always "otherwise." Interleaved "if, otherwise, then, otherwise" statements can be identified by matching the "as follows" or "the following applies" with the closing "otherwise."

[0503] In the text, statements of logical operations that are to be written mathematically in the following form: if(condition0a && condition0b) Statement 0 else if(condition 1a || condition 1b) Statement 1 ... else Statement n can be explained in the following form: ...as follows / ...the following applies - Statement 0 if all of the following conditions are true: - Condition 0a - Condition 0b - Otherwise, if one or more of the following conditions are true, then statement 1: - Condition 1a - Condition 1b - ... - Otherwise, statement n

[0504] In the text, statements of logical operations that are to be written mathematically in the following form: if(condition 0) Statement 0 if(condition1) Statement 1 can be explained in the following form: If condition 0, then statement 0 If condition 1, then statement 1

[0505] Although embodiments of the invention are primarily described based on video coding, it should be noted that embodiments of coding system 10, encoder 20, and decoder 30 (and correspondingly, system 10), as well as other embodiments described herein, may also be configured for still picture processing or coding, i.e., processing or coding of individual pictures independent of any preceding or successive pictures, as in video coding. Generally, when picture processing coding is limited to a single picture 17, only inter prediction units 244 (encoder) and 344 (decoder) may not be available. All other functions (also called tools or techniques) of the video encoder 20 and the video decoder 30 may be equally used for still picture processing, e.g., residual calculation 204 / 304, transform 206, quantization 208, inverse quantization 210 / 310, (inverse) transform 212 / 312, partitioning 262 / 362, intra prediction 254 / 354, and / or loop filtering 220, 320, and entropy coding 270 and entropy decoding 304.

[0506] For example, embodiments of the encoder 20 and the decoder 30, and functions described herein with reference to the encoder 20 and the decoder 30, may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on a computer-readable medium or transmitted over a communication medium as one or more instructions or code and executed by a hardware-based processing unit. The computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium such as a data storage medium, or a communication medium, which includes any medium that facilitates transfer of a computer program from one place to another, for example, according to a communication protocol. In this form, the computer-readable medium may generally correspond to (1) a tangible computer-readable storage medium that is non-transitory, or (2) a communication medium such as a signal or carrier wave. The data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementing the techniques described in this disclosure. A computer program product may include the computer-readable medium.

[0507] By way of example, and not limitation, such computer-readable storage media may comprise RAM, ROM, EEPROM, CD-ROM, or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included within the definition of medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but instead cover non-transitory tangible storage media. As used herein, disk and disc include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically while discs reproduce data optically using lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0508] The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor" as used herein may refer to any of the above structures or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a combined codec. Also, the techniques may be fully implemented within one or more circuits or logic elements.

[0509] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to highlight functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require implementation by different hardware units. Rather, as described above, the various units may be combined in a codec hardware unit or provided by a collection of interoperable hardware units, including one or more processors as described above, along with suitable software and / or firmware. [Explanation of symbols]

[0510] 10. Video Coding System 12 Source Devices 13 Communication Channels 14 Destination Device 16 Picture Source 17 Picture, Picture Data, Raw Picture, Raw Picture Data 18 Preprocessor, preprocessing unit 19 Preprocessed Picture, Preprocessed Picture Data 20 Video Encoder 21 Encoded Picture Data 22 Communication interface, communication unit 28 Communication interface, communication unit 30 Video decoder, short decoder 31 Decoded Picture, Decoded Picture Data 32 Post-processor, post-processing unit 33 Post-Processed Picture, Post-Processed Picture Data 34 Display Devices 46 Processing Circuit 201 Input, input interface 203 Picture Block 204 Residual Calculation Unit 205 Residual Block, Residual 206 Conversion Processing Unit 207 Conversion Factor 208 quantization units 209 quantized coefficients, quantized transform coefficients, quantized residual coefficients 210 Inverse Quantization Unit 211 Dequantized coefficients, dequantized residual coefficients 212 Inverse Transformation Processing Unit 213 reconstructed residual block, corresponding dequantized coefficients, transform block 214 Reconstruction Unit 215 reconstructed blocks 220 Loop Filter Unit 221 filtered blocks, filtered reconstructed blocks 230 Decoded Picture Buffer 231 decoded pictures 244 Inter Prediction Units 254 intra prediction units 260 Mode Selection Unit 262 division units 265 prediction block, predictor 266 Syntax Elements 270 Entropy Encoding Unit 272 Output, Output Interface 304 Entropy Decoding Unit 309 Quantized Coefficients 310 Inverse Quantization Unit 311 transform coefficients, dequantized coefficients 312 Inverse Transformation Processing Unit 313 Reconstructed residual block, transform block 314 Reconstruction Unit, Adder 315 reconstructed blocks 320 Loop Filter Unit 321 filtered blocks, decoded video blocks of a picture 330 Decoded Picture Buffer (DPB) 331 Decoded Picture 332 Output 344 Inter Prediction Unit 354 intra prediction units 360 mode application unit 365 predicted blocks 400 Video Coding Device 410 inlet port, input port 420 receiver unit 430 Processors, Logic Units, Central Processing Units 440 transmitter unit 450 outlet port, output port 460 memory 470 Coding Module 500 devices 502 processor 504 memory 506 Code and Data 508 Operating Systems 510 Application Program 512 Bus 514 Secondary Storage 518 Display 1400 Decoding Device 1401 Receiver Module 1402 Parameter Process Module 1403 Mapping Module 1404 Prediction Module 3100 Contents Supply System 3102 Capture Device 3104 Communication Links 3106 Terminal Device 3108 Smartphone / Pad 3110 Computer / Laptop 3112 Network Video Recorder / Digital Video Recorder 3114 TV 3116 Set-top Box 3118 Video Conference System 3120 Video Surveillance System 3122 Mobile Information Terminals 3124 Vehicle-mounted devices 3126 Display 3202 Protocol Progression Unit 3204 Demultiplexing Unit 3206 Video Decoder 3208 Audio Decoder 3210 Subtitle Decoder 3212 Synchronous Unit 3214 Video / Audio Display 3216 Video / Audio / Subtitle Display

Claims

1. A method of coding performed by a decoding device, comprising: obtaining a video bitstream; decoding the video bitstream to obtain a value of chroma format display information for a current coding block; obtaining an initial intra-prediction mode value for a chroma component of the current coding block based on at least one syntax element parsed from the video bitstream; When the value of the chroma format display information is equal to 2, obtaining mapped intra-prediction mode values ​​for chroma components of the current coding block according to a predefined mapping relationship and the initial intra-prediction mode value; obtaining a prediction block of the current coding block according to the mapped intra-prediction mode value; obtaining quantized residual coefficients according to the video bitstream; performing inverse quantization on the quantized residual coefficients to obtain dequantized residual coefficients; obtaining a reconstructed residual block based on the dequantized residual coefficients; adding the reconstructed residual block to the prediction block to obtain a reconstructed block; Equipped with The following table is used to represent the predetermined mapping relationship: Table 1 is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

2. The method of claim 1 , wherein the value of chroma format display information equal to 2 represents that the chroma format is 4:2:

2.

3. The method of claim 1 or 2, wherein the at least one syntax element comprises cclm_mode_flag and cclm_mode_idx.

4. 4. The method of claim 1, wherein the initial intra-prediction mode value for a chroma component of the current coding block is obtained based on the at least one syntax element and an intra-prediction mode for a luma component of the current coding block.

5. A decoder (30) comprising processing circuitry for carrying out the method according to any one of claims 1 to 4.

6. 1. A method of coding performed by an encoding device, comprising: obtaining an initial intra-prediction mode value for the current coding block based on the at least one syntax element; encoding the at least one syntax element into a video bitstream; encoding values ​​of chroma format display information for a current coding block into the video bitstream; When the value of the chroma format display information is equal to 2, obtaining mapped intra-prediction mode values ​​for chroma components of the current coding block according to a predefined mapping relationship and the initial intra-prediction mode value; obtaining a prediction block of the current coding block according to the mapped intra-prediction mode value; obtaining a residual block based on the current coding block and the predicted block; quantizing residual coefficients corresponding to the residual block to obtain quantized residual coefficients; encoding the quantized residual coefficients into the video bitstream; Equipped with The following table is used to represent the predetermined mapping relationship: Table 2 is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

7. The method of claim 6 , wherein the value of chroma format display information equal to 2 represents that the chroma format is 4:2:

2.

8. 8. The method of claim 6 or 7, wherein the at least one syntax element comprises cclm_mode_flag and cclm_mode_idx.

9. 9. The method of claim 6, wherein the initial intra-prediction mode value for a chroma component of the current coding block is obtained based on the at least one syntax element and an intra-prediction mode for a luma component of the current coding block.

10. A computer program comprising a program code for performing the method according to any one of claims 1 to 4 or any one of claims 6 to 9.

11. A decoder comprising: one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform the method of any one of claims 1 to 4.

12. 1. An encoder comprising: one or more processors; and a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the encoder to perform the method of any one of claims 6 to 9.

13. A device for storing a bitstream, comprising at least one memory and at least one receiver; the at least one receiver configured to receive one or more bitstreams; the at least one memory configured to store the one or more bitstreams; the bitstream comprises values ​​of chroma format display information for a current coding block, the bitstream further comprising at least one syntax element used to determine an initial intra-prediction mode value for a chroma component of the current coding block; when the value of the chroma format display information is equal to 2, causing an encoder or decoder to obtain mapped intra-prediction mode values ​​for chroma components of the current coding block according to a predefined mapping relationship and the initial intra-prediction mode value; The following table is used to represent the predetermined mapping relationship: Table 3 is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

14. The device of claim 13 , wherein the at least one syntax element comprises cclm_mode_flag and cclm_mode_idx.

15. 1. A method for storing a bitstream, comprising: receiving one or more bitstreams through at least one receiver; storing the bitstream in one or more storage devices, the bitstream comprising values ​​of chroma format display information for a current coding block, the bitstream further comprising at least one syntax element used to determine an initial intra-prediction mode value for a chroma component of the current coding block; Equipped with when the value of the chroma format display information is equal to 2, causing an encoder or decoder to obtain mapped intra-prediction mode values ​​for chroma components of the current coding block according to a predefined mapping relationship and the initial intra-prediction mode value; The following table is used to represent the predetermined mapping relationship: Table 4 is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

16. The method of claim 15 , wherein the at least one syntax element comprises cclm_mode_flag and cclm_mode_idx.

17. 1. A system for processing a bitstream, comprising: an encoding device, one or more storage devices, and a decoding device; the encoding device is configured to obtain a video signal and encode the video signal to obtain one or more bitstreams, the bitstream comprising values ​​of chroma format display information for a current coding block, the bitstream further comprising at least one syntax element used to determine an initial intra-prediction mode value for a chroma component of the current coding block; when the value of the chroma format display information is equal to 2, causing an encoder or decoder to obtain mapped intra-prediction mode values ​​for chroma components of the current coding block according to a predefined mapping relationship and the initial intra-prediction mode value; the one or more storage devices are used to store the one or more bitstreams; the decoding device is used to decode the one or more bitstreams; The following table is used to represent the predetermined mapping relationship: Table 5 is used, where mode X represents the initial intra-prediction mode value and mode Y represents the mapped intra-prediction mode value.

18. 20. The system of claim 17, wherein the at least one syntax element comprises cclm_mode_flag and cclm_mode_idx.

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