Encoder, decoder, and corresponded method of chroma intra-mode derivation

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] Embodiments of the present application (disclosure) generally relate to the field of picture processing, and more particularly to chroma-intra prediction mode derivation.

Background Art

[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 conversational applications such as video chat, video conferencing, DVD and Blu-ray (registered trademark) disks, video content collection and editing systems, and camcorders for security applications.

[0003] The amount of video data required to depict even relatively short videos can be quite large, which can pose difficulties when the data is to be streamed or otherwise transmitted over a communication network with limited bandwidth capacity. Thus, video data is generally compressed before being transmitted over modern telecommunications networks. Since memory resources can be limited, the size of the video can also be a problem when the video is stored in a storage device. Video compression devices often code video data using software and / or hardware at the source, thereby reducing the amount of data required to represent the digital video image. The compressed data is then received at the destination by a video restoration device that decodes the video data. With limited network resources and an increasing demand for even higher video quality, improved compression and restoration techniques that improve the compression ratio with little to no sacrifice in picture quality are desirable.

Summary of the Invention

Means for Solving the Problems

[0004] Embodiments of the present application provide an apparatus and method for encoding and decoding according to independent claims.

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

[0006] A first aspect of the present invention provides a coding method executed by a decoding device. The method includes: 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; when the value of the chroma format display information for the current coding block is equal to a default value, obtaining a mapped intra prediction mode value for the chroma component of the current coding block according to a default mapping relationship and the initial intra prediction mode value; and obtaining a predicted sample value for the chroma component 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. The coding efficiency is improved.

[0008] As shown in FIG. 13, a coding method executed by a decoding device is disclosed. The method includes the following.

[0009] S1301: Obtain a video bitstream.

[0010] The bitstream can be obtained according to a wireless network or a wired network. The bitstream can be transmitted from a website, a server, or other remote sources using a coaxial cable, an optical fiber cable, a twisted pair, a digital subscriber line (DSL), or wireless technologies such as infrared, radio, microwave, WIFI, 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 a 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, the decoder side reads the bitstream and derives the decoded pictures from the bitstream, and for the encoding process, the encoder side creates the bitstream.

[0013] Generally, the bitstream comprises syntax elements formed by a syntax structure.

[0014] Syntax element: An element of data represented within the bitstream.

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

[0016] In a specific example, the bitstream format specifies the relationship between a network abstraction layer (NAL) unit stream and a byte stream, both of which are called bitstreams.

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

[0018] To form a byte stream, the NAL unit stream format can be constructed from the NAL unit stream format by ordering the NAL units in decode order and prefixing each NAL unit with a start code prefix and zero or more zero-valued bytes. The NAL unit stream format can be extracted from the byte stream format by searching for the position of the unique start code prefix pattern within this byte stream.

[0019] This section specifies the relationship between the source and decoded pictures given via the bitstream.

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

[0021] The source and decoded pictures each have one or more sample arrays. - Luma (Y) only (monochrome). - Luma and two chroma (YCbCr or YCgCo). - Green, blue, and red (also known as GBR, 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. The actual color representation method in use can be indicated in a syntax specified in VUI parameters as specified in ITU-T H.SEI | ISO / IEC 23002-7.

[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 that is 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 as the luma array and half the width.

[0028] In 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, each of the two chroma arrays has the same height and width as the luma array. - Otherwise (sps_separate_colour_plane_flag is equal to 1), the three color planes are processed separately as a monochrome sampled picture.

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

[0030] The initial intra prediction mode value can be obtained by syntax-analyzing the index value coded in the video bitstream, or the initial intra prediction mode value can be determined according to the syntax value syntax-analyzed from the video bitstream.

[0031] In one implementation, the initial intra prediction mode value for the chroma component 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 specific example, the following process is used to obtain the initial intra prediction mode value for the chroma component of the current coding block.

[0033] The input to this process is as follows. - The luma position (xCb, yCb) specifying the top-left sample of the current chroma coding block relative to the top-left luma sample of the current picture. - The variable cbWidth specifying the width of the current coding block in the luma sample. - The variable cbHeight specifying the height of the current coding block in the luma sample. - The variable treeType specifying whether a single tree or a double tree is used.

[0034] In this process, the chroma intra prediction mode IntraPredModeC[xCb][yCb] and the MIP chroma 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, then the following applies. - The MIP chroma direct mode flag MipChromaDirectFlag[xCb][yCb] is set equal to 1. - The chroma 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, then lumaIntraPredMode is set equal to INTRA_PLANAR. - Otherwise, if CuPredMode

[0000] [xCb + cbWidth / 2][yCb + cbHeight / 2] is equal to MODE_IBC or MODE_PLT, then lumaIntraPredMode is set equal to INTRA_DC. - Otherwise, lumaIntraPredMode is set equal to IntraPredModeY[xCb + cbWidth / 2][yCb + cbHeight / 2]. - The chroma 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, 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 ]

[0001] is equal to 0), the chroma 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 a sequence parameter set as follows.

[0041]

Table 3

[0042] There is no specific order for step S1302 and step S1303, it can be understood that step S1302 may be executed before step S1303, or step S1303 may be executed before step S1302, or they may be executed 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 the mapped intra prediction mode value for the chroma component 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. That the default value is 2 represents that the chroma format is 4:2:2, and that the default value is 1 represents that the chroma format is 4:2:0.

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

[0046] The mapping relationship between mode X and mode Y can be represented 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, the chroma intra prediction mode Y is derived using the chroma intra prediction mode X in Table 20 as specified in Table 21, and then the chroma intra prediction mode X is set equal to the chroma intra prediction mode Y.

[0048]

Table 4

[0049] S1305: Obtain the prediction sample value for the 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 prediction sample value. For details of this process, reference can be made to ITU H.264 or ITU H.265 or other documents.

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

[0052] The method according to the first aspect of the invention can be executed by the device according to the second aspect of the invention. Further features and implementation forms of the above method correspond to the features and implementation forms of the device according to the second aspect of the invention.

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

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

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

[0056]

Table 5

[0057] or

[0058]

Table 6

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

[0060] In one implementation, to represent the default mapping relationship, the following table, namely,

[0061]

Table 7

[0062] is used, 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 executed corresponding to the method according to the second aspect of the invention (decoding side).

[0064] In one embodiment, a decoder (30) or an encoder (20) comprising a processing circuit for executing the method according to any one of the above embodiments and implementations is disclosed.

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

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

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

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

[0069] Hereinafter, embodiments of the invention will be described in more detail with reference to the accompanying drawings and figures.

Brief Description of the Drawings

[0070]

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0071] Hereinafter, the same reference numerals refer to the same or at least functionally equivalent features unless otherwise specified explicitly.

[0072] In the following description, reference is made to the accompanying drawings, which form a part of the disclosure and illustrate specific aspects of embodiments of the invention or specific aspects in which embodiments of the invention may be used. It is understood that embodiments of the invention may be used in other aspects and may include structural or logical changes not depicted in the figures. Accordingly, the following detailed description should not be taken in a limiting sense, and the scope of the invention is defined by the appended claims.

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

[0074] Video coding typically refers to the processing of a sequence of pictures that form a video or video sequence. In the field of video coding, the terms "frame" or "image" may be used synonymously with the term "picture". Video coding (or generally coding) consists of two parts, video encoding and video decoding. Video encoding is performed on the source side and typically involves 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 on the destination side and typically involves performing the reverse process compared to the encoder to reconstruct the video picture. Embodiments that refer to the "coding" of a video picture (or generally a picture) are to be understood as relating to the "encoding" or "decoding" of the video picture or each video sequence. The combination of the encoding part and the decoding part is also called a 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 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 completely reconstructed at the decoder, i.e., the quality of the reconstructed video picture is lower or worse compared to the quality of the original video picture.

[0076] Some video coding standards belong to the group of "lossy hybrid video codecs" (i.e., they combine spatial and temporal prediction in the sample domain with 2D transform coding for applying 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, in the encoder, the video is typically processed, i.e., encoded, at the block (video block) level by generating a predicted block using, for example, spatial (intra-picture) prediction and / or temporal (inter-picture) prediction, subtracting the predicted block from the current block (the block being currently 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 in the decoder, the reverse process compared to the encoder is applied to the encoded or compressed block to reconstruct the current block for presentation. Further, the encoder duplicates the decoder processing loop so that both generate the same prediction (e.g., intra and inter prediction) and / or reconstruction for processing, i.e., coding, subsequent blocks.

[0077] Hereinafter, embodiments of a video coding system 10, a video encoder 20, and a video decoder 30 will be described with reference to FIGS. 1 through 3.

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

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

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

[0081] The picture source 16 may include any kind of picture capture device, for example, a camera for capturing real-world pictures, and / or any kind of picture generation device, for example, a computer graphics processor for generating computer-animated pictures, or may include or be 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). The picture source may be any kind of memory or storage device that stores any of the above-described pictures.

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

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

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

[0085] The communication interface 22 of the source device 12 is configured to receive the encoded picture data 21 and transmit the encoded picture data 21 (or any further processed version thereof) over the communication 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 in addition, i.e., optionally, a communication interface or communication unit 28, a post-processor 32 (or post-processing unit 32), and a display device 34.

[0087] The communication 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, such as a storage device, e.g., an encoded picture data storage device, and provide the encoded picture data 21 to the decoder 30.

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

[0089] Communication interface 22 may be configured to, for example, package the encoded picture data 21 in a suitable format, such as in a packet, and / or process the encoded picture data using any type of transmission encoding or processing for transmission over the communication link or communication network.

[0090] Communication interface 28, which forms the other side of communication interface 22, may be configured to, for example, receive the transmitted data and process the transmitted data using any type of corresponding transmission decoding or processing and / or packet removal to obtain the encoded picture data 21.

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

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

[0093] The post-processor 32 of the destination device 14 is configured to post-process the decoded picture data 31 (also referred to as the reconstructed picture data), for example, the decoded picture 31, to obtain the post-processed picture data 33, for example, the post-processed picture 33. The post-processing executed by the post-processing unit 32 may include, for example, color format conversion (e.g., from YCbCr to RGB), color correction, trimming, or resampling, or any other processing for preparing the decoded picture data 31 for display by the display device 34, for example.

[0094] The display device 34 of the destination device 14 is configured to receive the post-processed picture data 33 for displaying the picture to a user or viewer, for example. The display device 34 may be or include any type of display for representing the reconstructed picture, for example, an integrated or external display or monitor. The display may include, 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] FIG. 1A depicts source device 12 and destination device 14 as separate devices, but embodiments of the device may also include both or either the source device 12 or corresponding functionality and the destination device 14 or corresponding functionality. In such embodiments, the source device 12 or corresponding functionality and the destination device 14 or corresponding functionality may be implemented using the same hardware and / or software, or by separate hardware and / or software or any combination thereof.

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

[0097] The encoder 20 (e.g., video encoder 20) or decoder 30 (e.g., video decoder 30), or both the encoder 20 and decoder 30, may be implemented via a processing circuit 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, as represented in FIG. 1B. The encoder 20 may be implemented via the processing circuit 46 to embody various modules as discussed with respect to the encoder 20 of FIG. 2 and / or any other encoder system or subsystem described herein. The decoder 30 may be implemented via the processing circuit 46 to embody various modules as discussed with respect to the decoder 30 of FIG. 3 and / or any other decoder system or subsystem described herein. The processing circuit may be configured to perform various operations as discussed later. As represented in FIG. 5, if the techniques are implemented partially in software, the device may store instructions for the software in 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 the video encoder 20 or the video decoder 30 may be integrated within a single device, for example, as part of a combined encoder / decoder (CODEC) as represented in FIG. 1B.

[0098] Source device 12 and destination device 14 may comprise any kind of handheld or stationary device, such as a notebook or laptop computer, mobile phone, smartphone, tablet or tablet computer, camera, desktop computer, set-top box, television, display device, digital media player, video game console, video streaming device (such as a content service server or a content delivery server), broadcast receiver device, broadcast transmitter device, or the like, may not use an operating system, or may use any kind of operating system. In some cases, source device 12 and destination device 14 may be equipped for wireless communication. Accordingly, source device 12 and destination device 14 may be wireless communication devices.

[0099] In some cases, the video coding system 10 illustrated in FIG. 1A is merely an example, and the techniques of the present application do not necessarily include any data communication between the encoding and decoding devices and may be applied to video coding settings (e.g., video encoding or video decoding). In other examples, data may be retrieved from local memory, streamed over a network, or the like. The video encoding device may encode data and store it in memory and / or the 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 merely encode data in memory and / or retrieve and decode data from memory.

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

[0101] Encoder and encoding method FIG. 2 shows 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 conversion processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse conversion 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 division unit 262. The inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 as represented in FIG. 2 may also be referred to as a hybrid video encoder or a video encoder by a hybrid video codec.

[0102] The residual calculation unit 204, the conversion processing unit 206, the quantization unit 208, and the mode selection unit 260 may be referred to as forming the forward signal path of the encoder 20, while the inverse quantization unit 210, the inverse conversion 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 the reverse signal path of the video encoder 20, and the reverse signal path of the video encoder 20 corresponds to the signal path of the decoder (see the video decoder 30 in FIG. 3). The inverse quantization unit 210, the inverse conversion 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 the "built-in decoder" of the video encoder 20.

[0103] Picture and picture partition (picture and block) The encoder 20 may be configured to receive a picture 17 (or picture data 17), for example, a picture of a sequence of pictures forming a video or video sequence, via the input 201. The received picture or picture data may also be the pre-processed picture 19 (or pre-processed picture data 19). For the purpose of brevity, the following description refers to picture 17. Picture 17 may be the current picture, or (in video coding in particular, to distinguish the current picture from other pictures of the same video sequence, i.e., also pictures of the video sequence that also includes the current picture, for example, pictures that have been previously encoded and / or decoded) the picture to be coded.

[0104] (Digital) pictures can be, or can be regarded as, a two-dimensional array or matrix of samples having intensity values. Samples within the array can also be called pixels (short for picture elements) 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, typically three color components are employed, i.e., the picture can represent or include three sample arrays. In the RGB format or color space, the 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, e.g., 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 shortened to luma) component Y represents the luminance or gray level intensity (such as in a grayscale picture), while the two chrominance (or shortened to chroma) components Cb and Cr represent the chrominance or color information components. Thus, a picture in the 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 the RGB format can be converted or transformed to the YCbCr format and vice versa, and the process is also known as color conversion or transformation. If the picture is monochrome, the picture may comprise only a luminance sample array. Thus, the picture can be, for example, an array of luma samples in a 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] An embodiment of the video encoder 20 may comprise a picture partitioning unit (not depicted in FIG. 2) configured to partition picture 17 into a plurality of (typically non-overlapping) picture blocks 203. These blocks may also be referred to as root blocks, macroblocks (H.264 / AVC), or coding tree blocks (CTB) or coding tree units (CTU) (H.265 / HEVC and VVC). The picture partitioning unit may use the same block size and corresponding grid defining the block size for all pictures of the video sequence, or may vary the block size between pictures or subsets or groups of pictures and be configured to partition each picture into corresponding blocks.

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

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

[0108] An embodiment of the video encoder 20 as shown in FIG. 2 may be configured to encode picture 17 block by block. For example, encoding and prediction may be performed for each block 203.

[0109] An embodiment of the video encoder 20 as shown in FIG. 2 may be further configured to divide and / or encode a picture by using slices (also called video slices). The picture may be divided into one or more slices (typically non-overlapping), or encoded using those slices. Each slice may include one or more blocks (e.g., CTUs).

[0110] An embodiment of the video encoder 20 as shown in FIG. 2 may be further configured to divide and / or encode a picture by using tile groups (also called video tile groups) and / or tiles (also called video tiles). The picture may be divided into one or more tile groups (typically non-overlapping), or encoded using those tile groups. Each tile group may include, for example, one or more blocks (e.g., CTUs) or one or more tiles. Each tile may be, for example, rectangular in shape and may include one or more blocks (e.g., CTUs), for example, complete or fragmented blocks.

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

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

[0113] The conversion processing unit 206 may be configured to apply an integer approximation of DCT / DST, such as the conversion specified for H.265 / HEVC. Compared with the orthogonal DCT transform, such an integer approximation is typically scaled by a certain coefficient. To maintain the norm of the residual block processed by the forward and inverse transforms, an additional scaling coefficient is applied as part of the conversion process. The scaling coefficient is typically selected based on certain constraints, such as the scaling coefficient being a power of 2 for shift operations, the bit depth of the conversion coefficients, and the trade-off between accuracy and implementation cost. For example, specific scaling coefficients are specified for the inverse transform by the inverse transform processing unit 212 (and, for example, for the corresponding inverse transform by the inverse transform processing unit 312 in the video decoder 30), and the corresponding scaling coefficients for the forward transform by, for example, the conversion processing unit 206 in the encoder 20 may be specified accordingly.

[0114] Embodiments of the video encoder 20 (each, the conversion processing unit 206) may be configured to output conversion parameters, for example, one or more types of conversions, encoded or compressed, for example, directly or via the entropy encoding unit 270, whereby, for example, the video decoder 30 may receive and use the conversion parameters for decoding.

[0115] Quantization The quantization unit 208 can be configured to obtain the quantized coefficient 209 by quantizing the transform coefficient 207, for example, by applying scalar quantization or vector quantization. The quantized coefficient 209 may also be referred to as the quantized transform coefficient 209 or the quantized residual coefficient 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 (Quantization Parameter (QP)). For scalar quantization, for example, different scalings 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 be, for example, an index to a default set of applicable quantization step sizes. For example, a small quantization parameter may correspond to fine quantization (small quantization step size), a large quantization parameter may correspond to coarse quantization (large quantization step size), or vice versa. Quantization may include division by the quantization step size. For example, the corresponding and / or inverse dequantization by the inverse quantization unit 210 may include multiplication by the quantization step size. Some standards, such as embodiments according to HEVC, may be configured to determine the quantization step size using the quantization parameter. Generally, the quantization step size may be calculated based on the quantization parameter using a fixed-point approximation of an equation that includes 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 equations for the quantization step size and quantization parameter. In one exemplary implementation, the scaling of inverse transform and dequantization may be combined. Alternatively, a customized quantization table may be used and signaled, for example, 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 the video encoder 20 (each quantization unit 208) may be configured to output quantization parameters (QP) encoded, for example, directly or via the entropy encoding unit 270, whereby, for example, the video decoder 30 may receive and apply the quantization parameters for decoding.

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

[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 (or corresponding dequantized coefficients 213) in the sample domain. The reconstructed residual block 213 may also be referred to as the transform block 213.

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

[0121] Filter processing The loop filter unit 220 (or, abbreviated as "loop filter" 220) 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 to, for example, smooth pixel transitions or otherwise improve video quality. The loop filter unit 220 may comprise a deblocking filter, a Sample-Adaptive Offset (SAO) filter, or one or more other filters, such as a bilateral filter, an Adaptive Loop Filter (ALF), a sharpening, a smoothing filter, or a collaborative filter, or any combination thereof. Although the loop filter unit 220 is depicted in FIG. 2 as 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 the filtered reconstructed block 221.

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

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

[0124] Mode Selection (Partitioning and Prediction) The mode selection unit 260 includes a classification unit 262, an inter prediction unit 244, and an intra prediction unit 254, and is configured to receive or obtain original picture data, for example, the original block 203 (the current block 203 of the current picture 17), and reconstructed picture data from the same (current) picture and / or from one or more previously decoded pictures, for example, from the decoded picture buffer 230 or other buffer (e.g., an unrepresented line buffer), such as filtered and / or unfiltered reconstructed samples or blocks. The reconstructed picture data is used as reference picture data for prediction, for example, inter prediction or intra prediction, to obtain the prediction block 265 or predictor 265.

[0125] The mode selection unit 260 may be configured to classify for the current block prediction mode (without classification) and determine or select a prediction mode (e.g., an intra or inter prediction mode), and generate a corresponding prediction block 265 that is used for the calculation of the residual block 205 and for the reconstruction of the reconstructed block 215.

[0126] Embodiments of the mode selection unit 260 may be configured to select the segmentation and prediction modes (e.g., from those supported by or available to the mode selection unit 260) that provide the best match, or in other words the smallest residue (the smallest residue implies better compression for transmission or storage), or the smallest signaling overhead (the smallest signaling overhead implies better compression for transmission or storage), or both, or a trade-off, or a balance. The mode selection unit 260 may be configured to determine the segmentation and prediction modes based on Rate Distortion Optimization (RDO), i.e., to select the prediction mode that provides the smallest rate distortion. Terms such as "best," "smallest," "optimal," etc. in this context do not necessarily refer to an overall "best," "smallest," "optimal," etc., but may refer to the fulfillment of a criterion for termination or selection, such as a value above or below a threshold or other constraint, potentially leading to a "sub-optimal selection," but reducing complexity and processing time.

[0127] In other words, the segmentation unit 262 may be configured to repeatedly use, for example, quad-tree-partitioning (QT), binary partitioning (BT), or triple-tree-partitioning (TT), or any combination thereof, to partition the block 203 into smaller block segments or sub-blocks (which again form blocks), and for example, to perform prediction for each of the block segments or sub-blocks. The mode selection may include the selection of the tree structure of the block 203 to be segmented, and the prediction mode is applied to each of the block segments or sub-blocks.

[0128] The segmentation and prediction processing (e.g., by the segmentation unit 260) performed by the exemplary video encoder 20 will be described in more detail below.

[0129] Classification The classification unit 262 can classify (or divide) the current block 203 into smaller classifications, for example, smaller blocks in the size of a square or a rectangle. These smaller blocks (which can also be called sub-blocks) can be further classified into even smaller classifications. This is also called a tree classification or a hierarchical tree classification. For example, the root block at the root tree level 0 (hierarchical level 0, depth 0) can be recursively classified, for example, into two or more blocks at the next lower tree level, for example, nodes at tree level 1 (hierarchical level 1, depth 1), and these blocks can again be classified into two or more blocks at the next lower level, for example, tree level 2 (hierarchical level 2, depth 2), etc., until the termination criterion is met, for example, until the maximum tree depth or the minimum block size is reached and the classification ends. The blocks that are not further classified are also called the leaf blocks or leaf nodes of the tree. A tree using classification into two classifications is called a binary tree (BT), a tree using classification into three classifications is called a ternary tree (TT), and a tree using classification into four classifications is called a quadtree (QT).

[0130] As described above, the term "block" as used herein may be a portion of a picture, particularly a square or rectangular portion. For example, referring to HEVC and VVC, a block may be 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), or may correspond thereto.

[0131] For example, a coding tree unit (CTU) may be a CTB of luma samples of a picture having three sample arrays, two corresponding CTBs of chroma samples, or a CTB of samples of a picture coded using a monochrome picture or three separate color planes, and a syntax structure used to code the samples, or may comprise them. 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 in segments. A coding unit (CU) may be a coding block of luma samples of a picture having three sample arrays, two corresponding coding blocks of chroma samples, or a coding block of samples of a picture coded using a monochrome picture or three separate color planes, and a syntax structure used to code the samples, or may comprise them. 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 in segments.

[0132] For example, in an embodiment according to HEVC, a coding tree unit (CTU) can be divided into coding units (CUs) by using a quadtree structure represented as a coding tree. The decision as to whether to code a picture area using (temporal) inter-picture prediction or (spatial) intra-picture prediction is made at the CU level. Each CU can be further divided into one, two, or four prediction units (PUs) according to the PU division type. Inside one PU, the same prediction process is applied, and the relevant information is transmitted to the decoder for each PU. After obtaining a residual block by applying a prediction process based on the PU division type, the CU can be divided 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 quadtree and binary tree (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 quadtree structure. A quadtree leaf node is further partitioned by a binary tree or a 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 the CU, PU, and TU have the same block size in the QTBT coding block structure. In parallel, multiple partitions, for example, ternary tree partitions, can be used together with the QTBT block structure.

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

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

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

[0137] The intra prediction unit 254 is configured to use the reconstructed samples of adjacent blocks of the same current picture to generate an intra prediction block 265 according to the 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 the information indicating the selected intra prediction mode for a block) in the form of a syntax element 266 to the entropy encoding unit 270 for inclusion in the encoded picture data 21, whereby, 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., previously decoded pictures that are at least partially stored in, for example, 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 only a part of the reference picture, for example, the search window area around the area of the current block, and / or, for example, whether pixel interpolation, such as half / semi - pel and / or quarter - pel interpolation, is applied or not.

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

[0141] The inter prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (MC) unit (neither of which is shown in FIG. 2). The motion estimation unit may be configured to receive or acquire, for motion estimation, the picture block 203 (the current picture block 203 of the current picture 17) and the decoded picture 231, or at least one or more previously reconstructed blocks, for example, the reconstructed blocks of one or more other / different previously decoded pictures 231. For example, the 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 the sequence of pictures forming the video sequence or may form them.

[0142] The encoder 20 may be configured to select a reference block from among a plurality of reference blocks of the same or different pictures of a plurality of other pictures, and provide a 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 an inter-prediction parameter. This offset is also called a motion vector (MV).

[0143] The motion compensation unit is configured to obtain, for example, receive, an inter-prediction parameter, and perform inter-prediction based on or using the inter-prediction parameter to obtain an inter-prediction block 265. The motion compensation performed by the motion compensation unit may involve fetching or generating a prediction block based on the motion / block vector determined by motion estimation, and perhaps performing interpolation to sub-pixel accuracy. The interpolation filtering process may generate additional pixel samples from known pixel samples, thus potentially increasing the number of candidate prediction blocks that can be used to code a picture block. When receiving a motion vector for a PU of the current picture block, the motion compensation unit may locate the prediction block indicated by the motion vector within one of the reference picture lists.

[0144] The motion compensation unit may also generate syntax elements associated with the block and the video slice for use by the video decoder 30 when decoding the picture block of the video slice. In addition to or instead of the slice and its 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 applies, for example, an entropy encoding algorithm or method (e.g., variable length coding (VLC) method, context adaptive VLC scheme (CAVLC), arithmetic coding method, binarization, context adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, or another entropy encoding methodology or technique), or bypass (no compression) to the quantized coefficients 209, inter prediction parameters, intra prediction parameters, loop filter parameters, and / or other syntax elements, and is configured to obtain encoded picture data 21 that can be output via output 272, for example, in the form of an encoded bitstream 21, whereby, for example, the video decoder 30 can receive and use the parameters for decoding. The encoded bitstream 21 can be transmitted to the video decoder 30 or stored in memory for later transmission or retrieval by the 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 directly quantize the residual signal for a block or frame without the transform processing unit 206. In another implementation, the encoder 20 can have a quantization unit 208 and an inverse quantization unit 210 combined in a single unit.

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

[0148] In the example of Figure 3, the 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., an adder 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. The inter prediction unit 344 may be or include a motion compensation unit. The video decoder 30 may execute a decoding path that is generally complementary to the encoding path described with respect to the video encoder 100 from Figure 2 in some examples.

[0149] As described with respect to the encoder 20, 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 344, and the intra prediction unit 354 are also referred to as forming the "built-in decoder" of the video encoder 20. Thus, the inverse quantization unit 310 may be identical in function to the inverse quantization unit 110, the inverse transform processing unit 312 may be identical in function to the inverse transform processing unit 212, the reconstruction unit 314 may be identical in function to the reconstruction unit 214, the loop filter 320 may be identical in function to the loop filter 220, and the decoded picture buffer 330 may be identical in function to the decoded picture buffer 230. Thus, the description provided for each unit and function of the video 20 encoder applies correspondingly to each unit and function of the video decoder 30.

[0150] Entropy decoding The entropy decoding unit 304 syntax-analyzes the bitstream 21 (or generally the encoded picture data 21), and for example, performs entropy decoding on the encoded picture data 21 to obtain, for example, the quantized coefficients 309 and / or the decoded coding parameters (not shown in FIG. 3), for example, the inter-prediction parameters (e.g., reference picture index and motion vector), the intra-prediction parameters (e.g., intra-prediction mode or index), the transform parameters, the quantization parameters, the loop filter parameters, and / or any or all of the other syntax elements. The entropy decoding unit 304 may be configured to apply a decoding algorithm or method corresponding to the encoding method as described for the entropy encoding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide the inter-prediction parameters, the intra-prediction parameters, and / or the other syntax elements to the mode application unit 360 and other parameters to the other units of the decoder 30. The video decoder 30 may receive syntax elements at the video slice level and / or the video block level. In addition to or instead of the slice and its respective syntax elements, tile groups and / or tiles and their respective syntax elements may be received and / or used.

[0151] Inverse quantization The inverse quantization unit 310 receives the quantization parameter (quantization parameter (QP)) (or generally information regarding inverse quantization) and the quantized coefficients from the encoded picture data 21 (e.g., by the entropy decoding unit 304, e.g., by syntax analysis and / or decoding), and based on the quantization parameter, applies inverse quantization to the decoded quantized coefficients 309 to obtain the dequantized coefficients 311, which may also be referred to as transform coefficients 311. The inverse quantization process may include the use of the quantization parameter determined by the 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 transformation processing unit 312 receives the dequantized coefficients 311, which may also be referred to as transform coefficients 311, and may be configured to apply a transformation to the dequantized coefficients 311 to obtain the reconstructed residual block 213 in the sample region. The reconstructed residual block 213 may also be referred to as the transform block 313. The transformation may be an inverse transformation, e.g., an inverse DCT, an inverse DST, an inverse integer transformation, or a conceptually similar inverse transformation process. The inverse transformation processing unit 312 may be further configured to receive the transformation parameter or corresponding information from the encoded picture data 21 (e.g., by the entropy decoding unit 304, e.g., by syntax analysis and / or decoding) to determine the transformation to be applied to the dequantized coefficients 311.

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

[0154] Filter processing (Either within or after the coding loop) The loop filter unit 320, for example, is configured to filter the reconstructed block 315 to obtain a filtered block 321 in order to smooth pixel transitions or otherwise improve video quality. The loop filter unit 320 may comprise a deblocking filter, a sample-adaptive offset (SAO) filter, or one or more other filters, such as a bilateral filter, an adaptive loop filter (ALF), a sharpening, a smoothing filter, or a collaborative filter, or any combination thereof. Although the loop filter unit 320 is shown in FIG. 3 as an in-loop filter, in other configurations, the loop filter unit 320 may be implemented as a post-loop filter.

[0155] Decoded picture buffer The decoded video block 321 of the picture is then stored in a decoded picture buffer 330 that stores the decoded picture 331 as a reference picture for subsequent motion compensation for other pictures and / or for each output display to be output.

[0156] The decoder 30 is configured to output the decoded picture 311, for example, via output 312, for presentation or viewing by the user.

[0157] Prediction The inter prediction unit 344 may be the same as the inter prediction unit 244 (especially the motion compensation unit), and the intra prediction unit 354 may be the same as the inter prediction unit 254 in function, and based on each piece of information received from the division and / or prediction parameters, or the encoded picture data 21 (for example, by the entropy decoding unit 304, for example, by syntax analysis and / or decoding), perform division or division determination and prediction. 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 each sample to obtain the prediction block 365.

[0158] When a video slice is coded as an intracoded (I) slice, the intra prediction unit 354 of the mode application unit 360 is configured to generate a prediction 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 intercoded (i.e., B or P) slice, the inter prediction unit 344 (e.g., motion compensation unit) of the mode application unit 360 is configured to create a prediction block 365 for a video block of the current video slice based on a motion vector and other syntax elements received from the entropy decoding unit 304. For inter prediction, the prediction block may be created from one of the reference pictures in one of the reference picture lists. The video decoder 30 may configure the reference frame lists, list 0 and list 1, using default construction techniques based on the reference pictures stored in the DPB 330. In addition to or instead of a slice (e.g., a video slice), the same or similar may apply for embodiments that use a tile group (e.g., a video tile group) and / or a tile (e.g., a video tile), e.g., the video may be coded using I, P, or B tile groups and / or tiles.

[0159] The mode application unit 360 is configured to determine prediction information for video blocks of the current video slice by parsing the motion vectors or related information and other syntax elements, and to create a prediction block for the currently decoded video block using the prediction information. For example, the 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), the configuration information for one or more of the reference picture lists for the slice, the motion vector for each inter-coded video block of the slice, the inter prediction status for each inter-coded video block of the slice, and other information for decoding the video blocks within the current video slice. In addition to or instead of a slice (e.g., a video slice), the same or similar may apply to embodiments that use tile groups (e.g., video tile groups) and / or tiles (e.g., video tiles), e.g., the video may be coded using I, P, or B tile groups and / or tiles.

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

[0161] An embodiment of video decoder 30, as represented 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 one or more tile groups (typically non-overlapping) or decoded using the same, and each tile group 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., complete or partial blocks.

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

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

[0164] It should be noted that further operations can be applied to the derived motion vectors of the current block (including, but not limited to, the control point motion vectors in affine mode, affine, planar, sub-block motion vectors in ATMVP mode, temporal motion vectors, etc.). For example, the value of the motion vector is restricted to a predefined range according to its representation bits. If the representation bits of the 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 the derived motion vector (e.g., the MV of 4 4×4 sub-blocks within one 8×8 block) is restricted such that the maximum difference between the integer parts of the 4 4×4 sub-block MVs is not greater than N pixels, where N is not greater than 1 pixel. Here, two methods are provided for restricting the motion vector according to bitDepth.

[0165] Method 1: Remove the overflow MSB (Most Significant Bit) by a 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) Here, 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 represent intermediate values.

[0166] For example, if the value of mvx is -32769, after applying equations (1) and (2), the resulting value is 32767. In a computer system, decimal numbers are stored as two's complements. The two's complement of -32769 is 1,0111,1111,1111,1111 (17 bits), and 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) (32767 in decimal). 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 represented by 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) Here, vx is the horizontal component of the motion vector of an image block or sub-block, vy is the vertical component of the motion vector of an image block or sub-block, x, y, and z respectively correspond to the three input values of the MV clipping process, and the definition of the function Clip3 is as follows.

[0169]

Equation

[0170] Figure 4 is a schematic diagram of a video coding device 400 according to an 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] The video coding device 400 includes an inlet 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 data, a transmitter unit (Tx) 440 and an outlet port 450 (or output port 450) for transmitting data, and a memory 460 for storing data. The video coding device 400 may also include optical-to-electrical (OE) components and electrical-to-optical (EO) components coupled to the inlet port 410, the receiver unit 420, the transmitter unit 440, and the outlet port 450 for the outlet or inlet of optical or electrical signals.

[0172] Processor 430 is implemented by hardware and software. Processor 430 can be implemented as one or more CPU chips, cores (e.g., as a multi-core processor), FPGAs, ASICs, and DSPs. Processor 430 communicates with an input port 410, a receiver unit 420, a transmitter unit 440, an output port 450, and a memory 460. Processor 430 includes a coding module 470. Coding module 470 implements the disclosed embodiments described above. For example, coding module 470 implements, processes, prepares, or provides various coding operations. Accordingly, the inclusion of coding module 470 provides a significant improvement to the functionality of video coding device 400 and results in a conversion of video coding device 400 to different states. Alternatively, coding module 470 is implemented as instructions stored in memory 460 and executed by 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 to store programs when such a program is selected for execution and to store 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 can be used as either or both of the source device 12 and the destination device 14 from FIG. 1 according to an exemplary embodiment.

[0175] The processor 502 within the apparatus 500 can be a central processing unit. Alternatively, the processor 502 can be any other type of device or devices capable of manipulating or processing information, existing or to be developed in the future. The disclosed implementation can be carried out using a single processor, e.g., the processor 502, as represented, but advantages in terms of speed and efficiency can be achieved using more than one processor.

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

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

[0178] Although depicted here as a single bus, the bus 512 of the apparatus 500 can consist of multiple buses. Further, the secondary storage device 514 can be directly coupled to other components of the apparatus 500 or can be accessed via a network and can comprise a single integrated unit such as a memory card or multiple units such as multiple memory cards. Accordingly, the apparatus 500 can be implemented in a wide variety of configurations.

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

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

[0181] In practice, one chroma subsampling format 4:2:0 is widely used, where the chrominance components are subsampled to half horizontally and vertically corresponding to the luma component as represented in the example in FIG. 7, and the size of Cb or Cr is 1 / 4 of the size of the luma component. Thus, in the 4:2:0 format, the total size of the video is 1 (Y) + 0.25 (Cb) + 0.25 (Cr) = 1.5 times 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 storage or transition of the video stream.

[0182] In another example, a chroma subsampling format 4:2:2 is disclosed, where the chroma components are horizontally subsampled as represented in the example in FIG. 8. In this case, the size of Cb or Cr is half of the luma component. Thus, 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 transfer.

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

[0184] In an example presented 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 of 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 luma sampling (as represented in Table 1 and the associated paragraphs). The value of chroma_format_idc shall be in the range including all of 0 to 3.

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

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

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

[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, each of the two chroma arrays has the same height and width as the luma array. - Otherwise (separate_colour_plane_flag is equal to 1), the three colour planes are processed separately as a monochrome sampled picture.

[0192] The number of bits required for the representation of each sample in the luma and chroma arrays within a video sequence shall be in the range including all of 8 to 16, and the number of bits used within the luma array may be different from the number of bits used within the chroma array.

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

[0194] When the value of chroma_format_idc is equal to 2, the chroma samples are placed at the same location as the corresponding luma samples, and the nominal positions within the picture are as shown in Figure 8.

[0195] When the value of chroma_format_idc is equal to 3, for all cases of the picture, all array samples are placed at the same location, and the nominal positions within the picture are as shown in Figure 6.

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

[0197] In some examples, as shown in Table 2 having modes as input and distances as output, the angles of these modes (e.g., input 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) can be derived as.

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

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

[0202] In some examples, 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 shown in Figure 9, the modes are more densely defined when their corresponding angles are closer to the 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 where the opposite side is half of the adjacent side (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 follows using the input nW as the block width, nH as the block height, and predModeIntra as the input angle mode.

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

[0207] For non-square blocks (where nW is 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 to apply the wide-angle mapping process) are true, 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, 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 (where the block width is half the 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, - The predModeIntra is greater than (60 - 2 * whRatio) when (whRatio > 1), where whRatio = Abs(Log2(nW / nH)) = 1.

[0209] Chroma Intra Prediction Mode Derivation When Chroma Components are Subsampled Horizontally or Vertically 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 a ratio changed due to subsampling.

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

[0211] In this case, due to chroma subsampling, the aspect ratio of the chroma block is 1:2. Therefore, the original mode is adjusted (mapped) according to the horizontally subsampled chroma components. In this case, mode 2 is mapped to 61 to adjust for a 50% reduction in the horizontal direction. Since the aspect ratio of the subsampled block is 1:2 and 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) It is as follows.

[0213] The tangent value of this angle is twice the tangent value of Mode 2, which reflects that the adjacent side of Mode 2 is halved due to chroma subsampling.

[0214] (As shown on the left in FIG. 10) Since the position with half the width corresponds to Mode 8, Mode 8 is mapped to Mode 2, 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, the horizontal and vertical prediction modes with a degree of 0 are not mapped to other modes, that is, the horizontal / vertical mode is still mapped to the same mode.

[0215] To map the intra prediction mode when the chroma component is subsampled (for example, in the chroma subsampling format 4:2:2), the mapping table is defined as follows.

[0216]

Table 10

[0217] In one implementation of the present invention, as defined in Table 4, it is proposed to replace the mapping from Modes 2 to 7 with 60 to 65.

[0218]

Table 11

[0219] In the above example, Mode 2 will be mapped to 61. In this embodiment, Mode 2 will be mapped to Mode 60 as shown in FIG. 10.

[0220] In one implementation of the present invention, as defined in Table 5, it is proposed to replace the mappings for modes 2 to 7 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, as defined in Table 6, it is proposed to map modes 8 to 18 with the following modes.

[0223]

Table 13

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

[0225]

Table 14

[0226] The left side represents the input modes from 2 to 18, and each mode corresponds to a tangent value and an angle. In the case of no subsampling, the angles of these modes can be defined as follows. degree = arctan(output(x) / 32)

[0227] For modes 2 through 34, the scaling factor 32 may be regarded as the width represented in FIG. 10. For those modes, the adjacent sides of the desired angle are parallel to the horizontal direction, while the opposite sides of the desired angle are parallel to the vertical direction. The desired angle corresponding to mode 8 is represented in the left subfigure of FIG. 10. In contrast, for modes 34 through 66, since (the angle corresponding to mode 34 is a duplicate angle (-45 degrees) related to both the horizontal and vertical directions) the adjacent sides of the desired angle are parallel to the vertical direction, while the opposite sides of the desired angle are parallel to the horizontal direction.

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

[0229] In one example, the doubled tangent values are listed for each mode on the right side of Table 7. However, the angle is not linearly proportional to the tangent value. 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, to find the corresponding mapping mode, the reference table is first generated using the following steps with the input mode X. · Obtain the output value according to Table 2. · Alternatively or in addition, calculate the tangent value of this mode as output(X) / 32. · Alternatively or in addition, calculate the angle using the derived tangent value, for example, arctan (output(x) / 32). ·As an alternative or in addition, use the range of input mode X to generate a reference table using the three steps above. As shown on the left side of Table 7, which includes columns for tangent values, angle values, and input mode, X belongs to 2..18.

[0231] The following steps are applied to derive the mode mapped using input mode X. ·As an alternative or in addition, double the tangent value of mode X as 2*output(X) / 32. ·As an alternative or in addition, use the doubled tangent value to calculate the angle in the chroma subsampling format 4:2:2, e.g., arctan(2*output(x) / 32). ·As an alternative or in addition, find the closest angle in the reference table (e.g., the angle list without chroma subsampling in Table 7) according to the calculated angle value in the chroma subsampling format 4:2:2. ·As an alternative or in addition, pick up the corresponding output mode according to the closest angle in the reference table.

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

[0233] In one example, after the reference table is generated, input mode 10 derives its output mode as follows. ·Double the tangent value of mode 10 as 2*12 / 32 = 0.75. ·Use the doubled tangent value to calculate the angle in the chroma subsampling format 4:2:2, e.g., arctan(0.75) = 36.8699°. ·Find the closest angle 35.70669° in the reference table according to the calculated angle value 36.8699°. ·Pick up the corresponding output mode 5 according to the closest angle 35.70669° in the reference table.

[0234] Therefore, 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 to the following modes as defined in Table 8.

[0236] [Table 15]

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

[0238]

Table 16

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

[0240] In one implementation of the present invention, it is proposed to map modes 29 to 34 to 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 the output mode as defined in the previous embodiment, except for the following aspects. · When generating the reference table, input modes from 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 less than -45° (i.e., the absolute value of the angle is greater than 45°). Since the smallest angle that can be derived is -45°, these (less than -45°) angles cannot be directly used. In this case, their complementary angles are used, and the mapped angle faces the upper boundary of the current block (instead of the current left boundary). Therefore, the adjacent side and the opposite side of the mapped angle are swapped, and thus the tangent value of their complementary angles, 1 / 2 * tangent(output(x) / 32), is used to derive the correct angle to find the closest angle within the reference table.

[0245] In one implementation of the present invention, it is proposed to map modes 35 to 50 in 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 represent how the mapped mode is derived.

[0248] [Table 20]

[0249] Table 13 can be derived using the process for deriving the output mode, but the following aspects are changed. · When generating the reference table, input modes from 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, since the opposite sides are halved using the 4:2:2 chroma subsampling format, the corresponding tangent values are halved (instead of being doubled as in Table 7).

[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, the opposite side of the corresponding angle is parallel to the horizontal direction, and the adjacent side of the corresponding angle is parallel to the vertical direction. Due to chroma subsampling, the horizontal direction is reduced by half, that is, the opposite side of the corresponding angle is reduced by half. This is equivalent to reducing its output value by half, which means its output value is now -26 / 2 = -13. Since -13 has two equivalent closest 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, 49 can be mapped to either 43 or 44, 44 or 45, 45 or 46, 48 or 49, 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 in 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 represent how the mapped modes are derived.

[0258] [Table 24]

[0259] Similar to Table 13, Table 16 can be derived using the process for deriving the output mode, but the following aspects are changed. · When generating the reference table, input modes from 50 to 66 are used. · Modes 51 to 66 correspond to the angles whose opposite sides are the upper boundaries of the current block. After chroma subsampling, since the opposite sides are halved using the 4:2:2 chroma subsampling format, the corresponding tangent values are halved (instead of being doubled as in Table 7).

[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 presented as a mapping mode for chroma subsampling mode 4:2:2, i.e., subsampling only half of the chroma components 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 where the block aspect does not change. For example, using the 4:2:0 chroma subsampling format, the chroma components are subsampled in both the horizontal and vertical directions, so the block aspect will not change, and thus it is not necessary to perform mode mapping.

[0264] In some examples, as long as one input mode X has one output mode Y, the above embodiments can be combined. For example, Table 18 below 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 (e.g., from Table 2 to Table 18) may be combined to form a mode mapping relationship.

[0267] Example 1. A coding method executed by a decoding device, comprising: obtaining a video bitstream; decoding the video bitstream to obtain an initial intra prediction mode value for the chroma component of the current coding block; Determining whether the ratio between the width of the current coding block with respect to the luma component and the width of the current coding block with respect to the chroma component is equal to a threshold value (alternatively, determining whether the ratio between the height of the current coding block with respect to the luma component and the height of the current coding block with respect to the chroma component is equal to a threshold value), and When it is determined that the ratio is equal to the threshold value, obtaining a mapped intra prediction mode value for the chroma component of the current coding block according to a predetermined mapping relationship and an initial intra prediction mode value; and Obtaining predicted sample values for the chroma component of the current coding block according to the mapped intra prediction mode value. A method comprising the steps.

[0268] Example 2. The method of Example 1, where the threshold value is 2 or 0.5.

[0269] Example 3. The following table for representing a predetermined mapping relationship, that is,

[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. The method of Example 1 or 2.

[0274] Example 4. The following table for representing a predetermined mapping relationship, that is,

[0275]

Table 29

[0276] One of the methods of Examples 1 to 3, in which is used, 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, i.e.,

[0278] [Table 30]

[0279] One of the methods of Examples 1 to 4, in which is used, 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, i.e.,

[0281] [Table 31]

[0282] One of the methods of Examples 1 to 5, in which is used, 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, i.e.,

[0284] [Table 32]

[0285] One of the methods of Examples 1 to 6, in which is used, mode X represents the initial intra prediction mode value, and mode Y represents the mapped intra prediction mode value.

[0286] Example 8. To represent a given mapping relationship, the following table, i.e.,

[0287]

Table 33

[0288] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, by any one of the methods of Examples 1 to 6.

[0289] Example 9. To represent a given mapping relationship, the following table, i.e.,

[0290]

Table 34

[0291] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, by any one of the methods of Examples 1 to 6.

[0292] Example 10. To represent a given mapping relationship, the following table, i.e.,

[0293]

Table 35

[0294] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, by any one of the methods of Examples 1 to 6, 8, and 9.

[0295] Example 11. To represent a given mapping relationship, the following table, i.e.,

[0296]

Table 36

[0297] One of the methods of Examples 1 to 6, 8, and 9, in which is used, mode X represents an initial intra prediction mode value, and mode Y represents a mapped intra prediction mode value.

[0298] Example 12. The following table, i.e.,

[0299] [Table 37]

[0300] One of the methods of Examples 1 to 6 and 8 to 11, in which is used, mode X represents an initial intra prediction mode value, and mode Y represents a mapped intra prediction mode value.

[0301] Example 13. The following table, i.e.,

[0302] [Table 38]

[0303] One of the methods of Examples 1 to 6 and 8 to 11, in which is used, mode X represents an initial intra prediction mode value, and mode Y represents a mapped intra prediction mode value.

[0304] Example 14. The following table, i.e.,

[0305] [Table 39]

[0306] One of the methods of Examples 1 to 6 and 8 to 13, in which is used, mode X represents an initial intra prediction mode value, and mode Y represents a mapped intra prediction mode value.

[0307] Example 15. The following table, i.e.,

[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, in any one of the methods of Examples 1 to 6 and 8 to 13.

[0310] Example 16. The following table, i.e.,

[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, in any one of the methods of Examples 1 to 6 and 8 to 15.

[0313] Example 17. The following table, i.e.,

[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, in any one of the methods of Examples 1 to 6 and 8 to 15.

[0316] Example 18. The following table, i.e.,

[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, one of the methods of Examples 1 to 6 and 8 to 17.

[0319] Example 19. The following table, i.e.,

[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, one of the methods of Examples 1 to 6 and 8 to 17.

[0322] Example 20. The following table, i.e.,

[0323] [Table 45]

[0324] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods of Examples 1 to 19.

[0325] Example 21. The following table, i.e.,

[0326] [Table 46]

[0327] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods of Examples 1 to 19.

[0328] Example 22. A method according to any one of Examples 1 to 19, wherein the following table, i.e.,

[0329] [Table 47]

[0330] is used, mode X represents an initial intra prediction mode value, and mode Y represents a mapped intra prediction mode value.

[0331] Example 23. A method according to any one of Examples 1 to 19 and 21 to 22, wherein the following table, i.e.,

[0332] [Table 48]

[0333] is used, mode X represents an initial intra prediction mode value, and mode Y represents a mapped intra prediction mode value.

[0334] Example 24. A method according to any one of Examples 1 to 19 and 21 to 22, wherein the following table, i.e.,

[0335] [Table 49]

[0336] is used, mode X represents an initial intra prediction mode value, and mode Y represents a mapped intra prediction mode value.

[0337] Example 25. A method according to any one of Examples 1 to 19 and 21 to 22, wherein the following table, i.e.,

[0338] [Table 50]

[0339] One of the methods from Examples 1 to 19 and 21 to 24 is used, where 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 a predefined mapping relationship, that is,

[0341] [Table 51]

[0342] One of the methods from Examples 1 to 19 and 21 to 24 is used, where 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 a predefined mapping relationship, that is,

[0344] [Table 52]

[0345] One of the methods from Examples 1 to 19 and 21 to 26 is used, where 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 a predefined mapping relationship, that is,

[0347] [Table 53]

[0348] One of the methods from Examples 1 to 19 and 21 to 26 is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value.

[0349] Example 29. To represent a given mapping relationship, the following table, i.e.,

[0350] [Table 54]

[0351] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, in any one of the methods of Examples 1 to 19 and 21 to 28.

[0352] Example 30. To represent a given mapping relationship, the following table, i.e.,

[0353] [Table 55]

[0354] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, in any one of the methods of Examples 1 to 19 and 21 to 28.

[0355] Example 31. To represent a given mapping relationship, the following table, i.e.,

[0356] [Table 56]

[0357] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, in any one of the methods of Examples 1 to 19 and 21 to 30.

[0358] Example 32. To represent a given mapping relationship, the following table, i.e.,

[0359] [Table 57]

[0360] One of the methods from Example 1 to 19 and 21 to 30 is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value.

[0361] Example 33. A method of coding executed by a decoding device, obtaining a video bitstream; decoding the video bitstream to obtain an initial intra prediction mode value for the 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 a mapped intra prediction mode value for the chroma component of the current coding block according to a default mapping relationship and the initial intra prediction mode value; obtaining predicted sample values for the chroma component of the current coding block according to the mapped intra prediction mode value.

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

[0363] Example 35. The following table for representing the default mapping relationship, that is,

[0364] [Table 58]

[0365] or

[0366] [Table 59]

[0367] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, the method of Example 31 or 32.

[0368] Example 36. The following table is used to represent a predefined mapping relationship, i.e.,

[0369] [Table 60]

[0370] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, any one of the methods of Examples 33 to 35.

[0371] Example 37. The following table is used to represent a predefined mapping relationship, i.e.,

[0372] [Table 61]

[0373] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, any one of the methods of Examples 33 to 36.

[0374] Example 38. The following table is used to represent a predefined mapping relationship, i.e.,

[0375] [Table 62]

[0376] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, any one of the methods of Examples 33 to 37.

[0377] Example 39. To represent a given mapping relationship, the following table, i.e.,

[0378] [Table 63]

[0379] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods from Examples 33 to 38.

[0380] Example 40. To represent a given mapping relationship, the following table, i.e.,

[0381] [Table 64]

[0382] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods from Examples 33 to 38.

[0383] Example 41. To represent a given mapping relationship, the following table, i.e.,

[0384] [Table 65]

[0385] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods from Examples 33 to 38.

[0386] Example 42. To represent a given mapping relationship, the following table, i.e.,

[0387] [Table 66]

[0388] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods of Examples 33 to 38, 40, and 41.

[0389] Example 43. The following table is used to represent a predefined mapping relationship, i.e.,

[0390] [Table 67]

[0391] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods of Examples 33 to 38, 40, and 41.

[0392] Example 44. The following table is used to represent a predefined mapping relationship, i.e.,

[0393] [Table 68]

[0394] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods of Examples 33 to 38 and 40 to 43.

[0395] Example 45. The following table is used to represent a predefined mapping relationship, i.e.,

[0396] [Table 69]

[0397] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods of Examples 33 to 38 and 40 to 43.

[0398] Example 46. To represent a given mapping relationship, the following table, i.e.,

[0399] [Table 70]

[0400] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods from Examples 33 to 38 and 40 to 45.

[0401] Example 47. To represent a given mapping relationship, the following table, i.e.,

[0402] [Table 71]

[0403] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods from Examples 33 to 38 and 40 to 45.

[0404] Example 48. To represent a given mapping relationship, the following table, i.e.,

[0405] [Table 72]

[0406] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods from Examples 33 to 38 and 40 to 47.

[0407] Example 49. To represent a given mapping relationship, the following table, i.e.,

[0408] [Table 73]

[0409] One of the methods from Examples 33 to 38 and 40 to 47, where is used, 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, i.e.,

[0411] [Table 74]

[0412] One of the methods from Examples 33 to 38 and 40 to 49, where is used, 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, i.e.,

[0414] [Table 75]

[0415] One of the methods from Examples 33 to 38 and 40 to 49, where is used, 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, i.e.,

[0417] [Table 76]

[0418] One of the methods from Examples 33 to 51 is used, where 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, i.e.,

[0420] [Table 77]

[0421] One of the methods from Examples 33 to 51 is used, where 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, i.e.,

[0423] [Table 78]

[0424] One of the methods from Examples 33 to 51 is used, where 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, i.e.,

[0426] [Table 79]

[0427] One of the methods from Examples 33 to 51 and 53 to 54 is used, where Mode X represents the initial intra prediction mode value and Mode Y represents the mapped intra prediction mode value.

[0428] Example 56. To represent a given mapping relationship, the following table, i.e.,

[0429]

Table 80

[0430] is used, where mode X represents the initial intra prediction mode value and mode Y represents the mapped intra prediction mode value, one of the methods from Examples 33 to 51 and 53 to 54.

[0431] Example 57. To represent a given mapping relationship, the following table, i.e.,

[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, one of the methods from Examples 33 to 51 and 53 to 56.

[0434] Example 58. To represent a given mapping relationship, the following table, i.e.,

[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, one of the methods from Examples 33 to 51 and 53 to 56.

[0437] Example 59. To represent a given mapping relationship, the following table, i.e.,

[0438]

Table 83

[0439] One of the methods from Examples 33 to 51 and 53 to 58, where is used, 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, i.e.,

[0441] [Table 84]

[0442] One of the methods from Examples 33 to 51 and 53 to 58, where is used, 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, i.e.,

[0444] [Table 85]

[0445] One of the methods from Examples 33 to 51 and 53 to 60, where is used, 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, i.e.,

[0447] [Table 86]

[0448] One of the methods from Examples 33 to 51 and 53 to 60 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. To represent the predefined mapping relationship, the following table, i.e.,

[0450] [Table 87]

[0451] One of the methods from Examples 33 to 51 and 53 to 62 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. To represent the predefined mapping relationship, the following table, i.e.,

[0453] [Table 88]

[0454] One of the methods from Examples 33 to 51 and 53 to 62 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 a processing circuit 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, one or more processors, A non-transitory computer-readable storage medium coupled to a processor and storing programming for execution by the processor, the programming configuring a decoder to perform a method by any one of Examples 1 to 64 when executed by the processor, the decoder.

[0458] The following is an explanation of an encoding method, a decoding method as represented in the above-described embodiments, and the application of systems using them.

[0459] FIG. 11 is a block diagram showing a content supply system 3100 for realizing a content distribution service. This content supply system 3100 includes a capture device 3102 and a terminal device 3106, and optionally includes 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 combination of these types, or the like.

[0460] The capture device 3102 can generate data and encode the data by the encoding method as represented in the above embodiments. Alternatively, the capture device 3102 may deliver the data to a streaming server (not shown in the figure), and the server encodes the data and transmits the encoded data to the terminal device 3106. The capture device 3102 includes, but is not limited to, a camera, a smartphone or a tablet, a computer or a 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 as described above. When the data includes video, the video encoder 20 included in the capture device 3102 can actually perform video encoding processing. When the data includes audio (i.e., voice), the audio encoder included in the capture device 3102 can actually perform audio encoding processing. For some practical scenarios, the capture device 3102 distributes the encoded video and audio data by multiplexing them together. For other practical scenarios, for example, in a video conferencing system, the encoded audio data and the encoded video data are not multiplexed. The capture device 3102 distributes the encoded audio data and the encoded video data to the terminal device 3106 separately.

[0461] In the content supply system 3100, the terminal device 310 receives and plays back the encoded data. The terminal device 3106 can be a smartphone or tablet 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, or a device having data reception and restoration capabilities such as the like. For example, the terminal device 3106 may include the destination device 14 as 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, the audio decoder included in the terminal device is prioritized to perform audio decoding processing.

[0462] For the terminal device having the display, such as a smartphone or tablet 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 supply the decoded data to the display. For the 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 there to receive and display the decoded data.

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

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

[0465] After the protocol progress 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 the 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 inverse multiplexing processing, a video elementary stream (ES), an audio ES, and optionally subtitles are generated. A video decoder 3206 including a video decoder 30 as described in the above-described embodiments decodes the video ES by a decoding method as represented in the above-described embodiments to generate a video frame, and supplies this data to a synchronization unit 3212. An audio decoder 3208 decodes the audio ES to generate an audio frame, and supplies this data to the synchronization unit 3212. Alternatively, the video frame may be stored in a buffer (not shown in FIG. 12) before supplying it to the synchronization unit 3212. Similarly, the audio frame may be stored in a buffer (not shown in FIG. 12) before supplying it to the synchronization unit 3212.

[0467] The synchronization unit 3212 synchronizes the video frame and the audio frame, and supplies the video / audio to a 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 time stamps related to the presentation of the coded audio and visual data, and time stamps 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 frame and the audio frame, and supplies the video / audio / subtitle to a video / audio / subtitle display 3216.

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

[0470] Mathematical operator 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-valued division are defined. The numbering and counting conventions generally start from 0. For example, "the first" is equivalent to the 0th, "the second" is equivalent to the 1st, and so on.

[0471] Arithmetic operators The following arithmetic operators are defined as follows. + Addition. - Subtraction (as a two-argument operator) or negation (as a unary prefix operator). * Multiplication, including matrix multiplication. x y Exponentiation. Specifies x to the power of y. In other contexts, such notation is used to make superscripts that are not intended for interpretation as exponents. / Integer division with truncation of the result to zero. For example, 7 / 4 and -7 / -4 are truncated to 1, and -7 / 4 and 7 / -4 are truncated to -1. ÷ Used to denote division in a mathematical expression where truncation or rounding is not intended.

[0472]

Number

[0473] Used to denote division in a mathematical expression where truncation or rounding is not intended.

[0474]

Number

[0475] The sum of f(i) where i takes on all integer values from x to y, including y. x % y Modulo. The remainder when x is divided by y, defined only for integers x and y such that x >= 0 and y > 0.

[0476] Logical operators The following logical operators are defined as follows. x && y The Boolean logical "AND" of x and y. x || y The Boolean logical "OR" of x and y. ! Boolean logical "NOT". x? y : z If x is TRUE, i.e., not equal to 0, evaluate to the value of y, otherwise evaluate 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 to which the value "na" (not applicable) is assigned, the value "na" is treated as a special value for that syntax element or variable. The value "na" is considered not 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 values. When operating on a binary argument containing fewer bits than the other argument, the shorter argument is extended by adding higher-order bits equal to 0. | Bitwise "OR". When operating on integer arguments, it operates on the two's complement representation of the integer values. When operating on a binary argument containing fewer bits than the other argument, the shorter argument is extended by adding higher-order bits equal to 0. ^ Bitwise "exclusive 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 the other argument, the shorter argument is extended by adding higher-order bits equal to 0. x >> y An arithmetic right shift of the two's complement integer representation of x by y binary digits. 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 An arithmetic left shift of the two's complement integer representation of x by y binary digits. This function is defined only for non-negative integer values of y. The bit shifted into the least significant bit (LSB) as a result of the left shift has a value equal to 0.

[0480] Assignment operators 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..z x takes an integer value that includes all from y to z, where x, y, and z are integers and z is greater than y.

[0482] Mathematical function The following mathematical functions are defined.

[0483]

Number

[0484] Asin(x) Performs the operation on an argument x within the range including all from -1.0 to 1.0, and has an output value within the range including all from -π÷2 to π÷2 in radians, which is the inverse sine function of trigonometry. Atan(x) Performs the operation on an argument x and has an output value within the range including all from -π÷2 to π÷2 in radians, which is the inverse tangent function of trigonometry.

[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) Performs the operation on an argument x in radians, which is the cosine function of trigonometry. Floor(x) The largest integer less than or equal to x.

[0489] [Number]

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

[0491] [Number]

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

[0493] [Number]

[0494] Sin(x) The sine function of trigonometry that operates on the argument x in radians.

[0495] [Number]

[0496] Swap( x, y ) = ( y, x ) Tan(x) The tangent function of trigonometry that operates 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. - Operations with higher precedence are evaluated before any operations with lower precedence. - Operations with the same 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 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] Text description of logical operations In the text, logical operation statements that will be mathematically described in the following form, i.e., if(condition 0) Statement 0 else if(condition 1) Statement 1 ... else / * Explanatory note for the 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 for the remaining conditions), statement n

[0502] Each of the "if... then, else if... then, else..." statements in this document is introduced, immediately following it, with "if... then", "as follows" or "the following applies". The last condition of the "if... then, else if... then, else..." is always "else...". Alternately arranged "if... then, else if... then, else..." statements can be identified by aligning "as follows" or "the following applies" with the final "else...".

[0503] In this document, logical operation statements that will be mathematically described in the following form, namely, if(condition 0a && condition 0b) Statement 0 else if(condition 1a || condition 1b) Statement 1 ... else Statement n can be described in the following form. ...as follows / ...the following applies - If all of the following conditions are true, then Statement 0: - condition 0a - condition 0b - Otherwise, if one or more of the following conditions are true, then Statement 1: - condition 1a - condition 1b -... - Otherwise, then Statement n

[0504] In this document, logical operation statements that will be mathematically described in the following form, namely, if(condition 0) Statement 0 if(condition 1) Statement 1 It can be described in the following form. When condition 0 is met, statement 0 When condition 1 is met, statement 1

[0505] Although the embodiments of the invention are mainly described based on video coding, it should be noted that the embodiments of the coding system 10, the encoder 20, and the decoder 30 (and the corresponding system 10), and other embodiments described herein can also be configured for still picture processing or coding, that is, the processing or coding of individual pictures independent of any preceding or consecutive pictures as in video coding. Generally, when picture processing coding is limited to a single picture 17, only the 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 can be equally used for still picture processing, for example, residual calculation 204 / 304, transformation 206, quantization 208, inverse quantization 210 / 310, (inverse) transformation 212 / 312, segmentation 262 / 362, intra prediction 254 / 354, and / or loop filter processing 220, 320, and entropy coding 270 and entropy decoding 304.

[0506] For example, the embodiments of the encoder 20 and the decoder 30, and the functions described herein with reference to, for example, 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 in a computer-readable medium as one or more instructions or codes, or transmitted over a communication medium and executed by a processing unit based on hardware. The computer-readable medium may include a computer-readable storage medium corresponding to a tangible medium such as a data storage medium, or a communication medium including any medium that facilitates the transfer of a computer program from one location to another, for example, in accordance with 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 a 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, codes, and / or data structures for implementing the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0507] By way of example and without limitation, such computer-readable storage media can include 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 the desired program code in the form of instructions or data structures and that is accessible by a computer. Also, any connection can be properly termed a computer-readable medium. For example, if the 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, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but instead are directed to non-transient tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where disk typically magnetically reproduces data, while disc optically reproduces data using a laser. Combinations of the above should also be included within the scope of computer-readable media.

[0508] The commands can 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 logic circuits or discrete logic circuits. Thus, the term "processor" as used herein can refer to either the foregoing structures or any other structure suitable for implementation of the techniques described herein. Additionally, in some aspects, the functions described herein can be provided within dedicated hardware and / or software modules configured to encode and decode, or incorporated within a combined codec. Also, the techniques can be fully realized within one or more circuits or logic elements.

[0509] The techniques of this disclosure can be implemented in a wide variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs), or sets of ICs (e.g., chip sets). Various components, modules, or units are described in this disclosure to emphasize functional aspects of a device configured to execute the disclosed techniques, but do not necessarily require implementation by different hardware units. Rather, as described above, various units can be combined within a codec hardware unit, or provided by a set of interoperable hardware units including one or more processors as described above, along with suitable software and / or firmware.

Description of the Reference Numerals

[0510] 10 Video coding system 12 Source device 13 Communication channel 14 Destination device 16 Picture source 17 Picture, picture data, raw picture, raw picture data 18 Preprocessor, preprocessing unit 19 Pre-processed picture, pre-processed 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 device 46 Processing circuit 201 Input, input interface 203 Picture block 204 Residual calculation unit 205 Residual block, residual 206 Transformation processing unit 207 Transformation coefficient 208 Quantization unit 209 Quantized coefficient, quantized transformation coefficient, quantized residual coefficient 210 Inverse quantization unit 211 Dequantized coefficient, inverse quantized residual coefficient 212 Inverse transformation processing unit 213 Reconstructed residual block, corresponding dequantized coefficient, transformation block 214 Reconstruction unit 215 Reconstructed block 220 Loop filter unit 221 Filtered block, filtered reconstructed block 230 Decoded picture buffer 231 Decoded picture 244 Inter prediction unit 254 Intra prediction unit 260 Mode selection unit 262 Partitioning unit 265 Prediction block, predictor 266 Syntax element 270 Entropy encoding unit 272 Output, output interface 304 Entropy decoding unit 309 Quantized coefficient 310 Inverse quantization unit 311 Transform coefficient, dequantized coefficient 312 Inverse transform processing unit 313 Reconstructed residual block, transform block 314 Reconstruction unit, adder 315 Reconstructed block 320 Loop filter unit 321 Filtered block, decoded video block of picture 330 Decoded picture buffer (DPB) 331 Decoded picture 332 Output 344 Inter prediction unit 354 Intra prediction unit 360 Mode application unit 365 Prediction block 400 Video coding device 410 Inlet port, input port 420 Receiver unit 430 Processor, logic unit, central processing unit 440 Transmitter unit 450 Outlet port, output port 460 Memory 470 Coding module 500 Device 502 Processor 504 Memory 506 Code and data 508 Operating system 510 Application program 512 Bus 514 Secondary storage 518 Display 1400 Decoding device 1401 Receiving module 1402 Parameter processing module 1403 Mapping module 1404 Prediction module 3100 Content supply system 3102 Capture device 3104 Communication link 3106 Terminal device 3108 Smartphone / Tablet 3110 Computer / Laptop 3112 Network video recorder / Digital video recorder 3114 TV 3116 Set-top box 3118 Video conferencing system 3120 Video surveillance system 3122 Portable information terminal 3124 Vehicle-mounted device 3126 Display 3202 Protocol progress unit 3204 Demultiplexing unit 3206 Video decoder 3208 Audio decoder 3210 Subtitle decoder 3212 Synchronization 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; obtaining mapped intra-prediction mode values ​​for chroma components of the current coding block according to a default mapping relationship and the initial intra-prediction mode value when the value of chroma format display information for the current coding block is equal to a default value; obtaining a predicted sample value for a chrominance component of the current coding block according to the mapped intra-prediction mode value; A method for providing the above.

2. 2. The method of claim 1, wherein the default value is 2 or 1, the default value being 2 representing a chroma format of 4:2:2, and the default value being 1 representing a chroma format of 4:2:

0.

3. The method of claim 1 or 2, wherein the initial intra-prediction mode value for a chroma component of the current coding block is obtained based on an intra-prediction mode for a luma component of the current coding block.

4. The following table is used to represent the predefined mapping relationship: 【Table 1】 or 【Table 2】 4. The method according to claim 1 , wherein mode X represents the initial intra-prediction mode values ​​and mode Y represents the mapped intra-prediction mode values.

5. The following table is used to represent the predefined mapping relationship: 【Table 3】 5. The method according to claim 1 , wherein mode X represents the initial intra-prediction mode values ​​and mode Y represents the mapped intra-prediction mode values.

6. The following table is used to represent the predefined mapping relationship: 【Table 4】 6. The method according to claim 1, wherein mode X represents the initial intra-prediction mode values ​​and mode Y represents the mapped intra-prediction mode values.

7. The following table is used to represent the predefined mapping relationship: 【Table 5】 7. The method according to claim 1, wherein mode X represents the initial intra-prediction mode values ​​and mode Y represents the mapped intra-prediction mode values.

8. The following table is used to represent the predefined mapping relationship: 【Table 6】 4. The method according to claim 1 , wherein mode X represents the initial intra-prediction mode values ​​and mode Y represents the mapped intra-prediction mode values.

9. A decoder (30) comprising processing circuitry for carrying out the method according to any one of claims 1 to 8.

10. 1. A method of coding performed by an encoding device, comprising: 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; obtaining a mapped intra-prediction mode value for a chroma component of the current coding block according to a predefined mapping relationship and the initial intra-prediction mode value when the ratio between the width for a luma component of the current coding block and the width for a chroma component of the current coding block is equal to the threshold value; coding the current coding block according to the mapped intra-prediction mode value; A method for providing the above.

11. The method further comprising:

11. The method of claim 10, further comprising: encoding a value of chroma format display information for the current coding block into a bitstream, the value of chroma format display information representing the ratio between the width for a luma component of the current coding block and the width for a chroma component of the current coding block.

12. The following table is used to represent the predefined mapping relationship: 【Table 7】 or 【Table 8】 12. The method of claim 10 or 11, wherein mode X represents the initial intra-prediction mode values ​​and mode Y represents the mapped intra-prediction mode values.

13. The following table is used to represent the predefined mapping relationship: 【Table 9】 12. The method of claim 10 or 11, wherein mode X represents the initial intra-prediction mode values ​​and mode Y represents the mapped intra-prediction mode values.

14. A computer program product comprising program code for carrying out the method according to any one of claims 1 to 8 and 10 to 13.

15. 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 the method of any one of claims 1 to 8.

16. 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 10 to 13.

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