Encoders, decoders, and corresponding methods

Abstract

To provide a method of decoding a coded video bitstream.SOLUTION: A decoding method comprises steps of: obtaining a picture-level syntax element included in a picture header of a current picture, the picture-level syntax element being used to specify whether an adaptive loop filter (ALF) is enabled for the current picture; in the case where the picture-level syntax element specifies that the adaptive loop filter is enabled for the current picture, obtaining a parameter set identifier included in the picture header, the parameter set identifier being used to indicate a first parameter set comprising a set of ALF parameters, and a temporal identifier of the first parameter set being less than or equal to a temporal identifier of the current picture; and performing the adaptive loop filter on at least one slice of the current picture based on the first parameter set.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0002] FIELD Embodiments of the present disclosure relate generally to the field of picture processing, and more particularly to high-level syntax elements. [Background technology]

[0003] Video coding (video encoding and 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 conversation applications such as video chat, video conferencing, DVD and Blu-ray discs, video content acquisition and editing systems, and camcorders in security applications.

[0004] The amount of video data required to render even a relatively short video can be significant, which can pose challenges when the data is to be streamed or otherwise transmitted over communication networks with limited bandwidth capacity. Therefore, video data is generally compressed before being transmitted over modern communication networks. Because memory resources may be limited, video size can also be an issue when the video is stored on a storage device. Often, video compression devices use software and / or hardware at the source to code the video data before transmission or storage, thereby reducing the amount of data needed to represent a digital video image. The compressed data is then received at the destination by a video decompression device, which decodes the video data. With limited network resources and an ever-increasing demand for higher video quality, improved compression and decompression techniques that increase compression ratios with little or no sacrifice in picture quality are desirable. Summary of the Invention [Means for solving the problem]

[0005] Embodiments of the present application provide apparatus and methods for encoding and decoding according to the independent claims.

[0006] These and other objects are achieved by the subject matter of the independent claims. Further implementation forms are evident from the dependent claims, the description and the drawings.

[0007] According to a first aspect, the present disclosure relates to a method for decoding a video bitstream performed by a decoding device, the video bitstream including data representing a current picture, the decoding method including: obtaining, by parsing the video bitstream, a picture level syntax element included in a picture header of the current picture, the picture level syntax element being used to specify whether an adaptive loop filter (ALF) is enabled for the current picture; if the picture level syntax element specifies that an adaptive loop filter is enabled for the current picture, obtaining a parameter set identifier included in the picture header, the parameter set identifier being used to indicate a first parameter set including a set of ALF parameters, wherein a temporal identifier of the first parameter set is less than or equal to a temporal identifier of the current picture; and performing an adaptive loop filter on at least one slice of the current picture based on the first parameter set.

[0008] A picture header is a syntax structure that contains syntax elements that apply to all slices of a coded picture. A syntax structure is zero or more syntax elements that exist together in a specified order in the bitstream, and syntax elements are elements of data that are represented in the bitstream.

[0009] The first parameter set is an adaptation parameter set (APS), which is a syntax structure.

[0010] The current picture is a coded picture contained in a picture unit (PU), where a PU is a set of NAL units that are related to each other according to specified classification rules and are consecutive in decoding order.

[0011] A network abstraction layer (NAL) unit is a syntax structure that contains an indication of the type of data that follows and bytes containing data or part of data of the current picture, a picture header, or a parameter set containing a set of ALF parameters, where each NAL unit has a temporal identifier.

[0012] If the temporal identifier of a first NAL unit is less than the temporal identifier of a second NAL unit in the same layer, the data encapsulated by the first NAL unit may be decoded without reference to the data encapsulated by the second NAL unit. The temporal identifier may also be used in a sub-bitstream extraction process, which is a process in which NAL units in a bitstream that do not belong to a target set determined by a target highest temporal identifier are removed from the bitstream, and the output sub-bitstream consists of NAL units in the bitstream that belong to the target set. Thus, the temporal identifier of a first parameter set being less than or equal to the temporal identifier of the current picture may enable the first parameter set to be referenced when decoding the current picture, or may enable a sub-bitstream extraction process for the current picture.

[0013] The time identifier may be related to the decoding order.

[0014] In a possible implementation form of the method according to the first aspect itself, the step of performing an adaptive loop filter on at least one slice of the current picture based on the first parameter set includes performing an adaptive loop filter on a luma component of the at least one slice of the current picture based on the first parameter set.

[0015] In any of the above-mentioned implementations of the first aspect or a possible implementation form of the method according to the first aspect itself, the method further includes, if the picture level syntax element specifies that an adaptive loop filter is enabled for the current picture, a step of obtaining another parameter set identifier included in the picture header, wherein the parameter set identifier is used to indicate a second parameter set including a set of ALF parameters, and a temporal identifier of the second parameter set is less than or equal to the temporal identifier of the current picture, and a step of performing an adaptive loop filter on chroma components of at least one slice of the current picture based on the second parameter set.

[0016] The second parameter set is the Adaptation Parameter Set (APS), which is a syntax structure.

[0017] According to a second aspect, the present disclosure relates to a method for encoding a video bitstream performed by an encoding device, the video bitstream including data representing a current picture, the encoding method including: determining whether an adaptive loop filter (ALF) is enabled for the current picture; encoding a picture level syntax element into a picture header of the current picture based on determining whether the adaptive loop filter (ALF) is enabled for the current picture, the picture level syntax element being used to specify whether the adaptive loop filter (ALF) is enabled for the current picture; and if the adaptive loop filter is enabled for the current picture, encoding a parameter set identifier into the picture header, the parameter set identifier being used to indicate a first parameter set including a set of ALF parameters for the adaptive loop filter, and a temporal identifier of the first parameter set being set equal to or less than the temporal identifier of the current picture.

[0018] The step of determining whether an adaptive loop filter (ALF) is enabled for the current picture may include comparing a cost of running the adaptive loop filter (ALF) on at least one block of the current picture with a cost of not running the adaptive loop filter (ALF) on the current picture, and determining that the adaptive loop filter (ALF) is disabled for the current picture if the cost of running the adaptive loop filter (ALF) on at least one block of the current picture is equal to or greater than the cost of running the adaptive loop filter (ALF) on at least one block of the current picture, and otherwise determining that the adaptive loop filter (ALF) is enabled for the current picture. The cost may be a rate-distortion cost.

[0019] In a possible implementation form of the method according to the second aspect itself, the method further comprises a step of encoding the temporal identifier of the first parameter set and the temporal identifier of the current picture into the video bitstream.

[0020] In any of the above-mentioned implementations of the second aspect or in a possible implementation form of a method according to the second aspect itself, the first parameter set includes a set of ALF parameters of an adaptive loop filter performed on the luma component of at least one slice of the current picture.

[0021] In any of the above-mentioned implementations of the second aspect or a possible implementation form of the method according to the second aspect itself, the method further includes, if the picture level syntax element specifies that an adaptive loop filter is enabled for the current picture, a step of encoding another parameter set identifier in the picture header, wherein the parameter set identifier is used to indicate a second parameter set including a set of ALF parameters of an adaptive loop filter to be performed on chroma components of at least one slice of the current picture, and wherein a temporal identifier of the second parameter set is set to be less than or equal to the temporal identifier of the current picture.

[0022] According to a third aspect, the present disclosure relates to an apparatus for decoding a coded video bitstream. The apparatus includes: an acquisition unit configured to acquire a picture level syntax element included in a picture header of a current picture by parsing the video bitstream, the picture level syntax element being used to specify whether an adaptive loop filter (ALF) is enabled for the current picture. If the picture level syntax element specifies that the adaptive loop filter is enabled for the current picture, the acquisition unit is further configured to acquire a parameter set identifier included in the picture header, the parameter set identifier being used to indicate a first parameter set including a set of ALF parameters, a temporal identifier of the first parameter set being less than or equal to a temporal identifier of the current picture, and a filtering unit configured to perform an adaptive loop filter on at least one slice of the current picture based on the first parameter set.

[0023] In a form of possible implementation of the apparatus according to the third aspect itself, the filtering unit is configured to perform an adaptive loop filter on the luma component of at least one slice of the current picture based on the first parameter set.

[0024] In a possible implementation form of the device according to any of the above-mentioned implementations of the third aspect or the third aspect itself, the obtaining unit is further configured to obtain another parameter set identifier included in the picture header when the picture level syntax element specifies that an adaptive loop filter is enabled for the current picture, the parameter set identifier being used to indicate a second parameter set including a set of ALF parameters, a temporal identifier of the second parameter set being less than or equal to a temporal identifier of the current picture, and the filtering unit is configured to perform an adaptive loop filter on chroma components of at least one slice of the current picture based on the second parameter set.

[0025] According to a fourth aspect, the present disclosure relates to an apparatus for encoding a coded video bitstream, the apparatus including: a determining unit configured to determine whether an adaptive loop filter (ALF) is enabled for a current picture; and an encoding unit configured to encode a picture-level syntax element into a picture header of the current picture based on determining whether the adaptive loop filter (ALF) is enabled for the current picture, the picture-level syntax element being used to specify whether the adaptive loop filter (ALF) is enabled for the current picture, the encoding unit being further configured to encode a parameter set identifier into the picture header if the adaptive loop filter is enabled for the current picture, the parameter set identifier being used to indicate a first parameter set including a set of ALF parameters of the adaptive loop filter, and a temporal identifier of the first parameter set being set equal to or less than the temporal identifier of the current picture.

[0026] In a possible implementation form of the apparatus according to the fourth aspect itself, the encoding unit is further configured to encode the temporal identifier of the first parameter set and the temporal identifier of the current picture into the video bitstream.

[0027] In any of the above-mentioned implementations of the fourth aspect or a possible implementation form of an apparatus according to the fourth aspect itself, the first parameter set includes a set of ALF parameters of an adaptive loop filter performed on the luma component of at least one slice of the current picture.

[0028] In a possible implementation form of the device according to any of the above-mentioned implementations of the fourth aspect or the fourth aspect itself, the encoding unit is further configured, if the picture level syntax element specifies that an adaptive loop filter is enabled for the current picture, to encode another parameter set identifier in the picture header, where the parameter set identifier is used to indicate a second parameter set including a set of ALF parameters of the adaptive loop filter to be performed on chroma components of at least one slice of the current picture, and where a temporal identifier of the second parameter set is set to be less than or equal to the temporal identifier of the current picture.

[0029] The method according to the first aspect of the present disclosure may be performed by an apparatus according to the third aspect of the present disclosure. Further features and modes of implementation of the method according to the first aspect of the present disclosure correspond to the features and modes of implementation of the apparatus according to the third aspect of the present disclosure.

[0030] The method according to the second aspect of the present disclosure may be performed by an apparatus according to the fourth aspect of the present disclosure. Further features and modes of implementation of the method according to the second aspect of the present disclosure correspond to the features and modes of implementation of the apparatus according to the fourth aspect of the present disclosure.

[0031] The method according to the second aspect may be extended to an implementation form corresponding to an implementation form of the method according to the first aspect, and therefore, the implementation form of the method includes the features of the corresponding implementation form of the first aspect.

[0032] The advantages of the method according to the second aspect are the same as those of the corresponding implementation of the method according to the first aspect.

[0033] According to a fifth aspect, the present disclosure relates to an apparatus for decoding a video stream, including a processor and a memory, the memory storing instructions for causing the processor to perform a method according to the first aspect or any implementation thereof.

[0034] According to a sixth aspect, the present disclosure relates to an apparatus for encoding a video stream, including a processor and a memory, the memory storing instructions for causing the processor to perform a method according to the second aspect or any implementation of the second aspect.

[0035] According to a seventh aspect, a computer-readable storage medium is proposed having stored thereon instructions that, when executed, cause one or more processors to code video data, the instructions causing the one or more processors to perform a method according to the first or second aspect or any implementation of the first or second aspect.

[0036] According to an eighth aspect, the present disclosure relates to a computer program comprising a program code for performing the method according to the first or second aspect or any implementation of the first or second aspect when the program is run on a computer.

[0037] According to a ninth aspect, the present disclosure relates to a decoder including a processing circuit for performing a method according to the first aspect or any implementation of the first aspect.

[0038] According to a tenth aspect, the present disclosure relates to an encoder including a processing circuit for performing a method according to the second aspect or any implementation of the second aspect.

[0039] According to an eleventh aspect, the present disclosure relates to a non-transitory storage medium including an encoded bitstream decoded by an image decoding device, wherein the bitstream is generated by dividing a current picture of a video signal or an image signal into a plurality of blocks and includes a plurality of syntax elements, the plurality of syntax elements including a picture-level syntax element included in a picture header of the current picture by parsing the video bitstream, the picture-level syntax element being used to specify whether an adaptive loop filter (ALF) is enabled for the current picture, and if the picture-level syntax element specifies that the adaptive loop filter is enabled for the current picture, the bitstream further includes a parameter set identifier included in the picture header, the parameter set identifier being used to indicate a first parameter set including a set of ALF parameters, and a temporal identifier of the first parameter set being set to be equal to or less than the temporal identifier of the current picture.

[0040] Particular embodiments are set out in the accompanying independent claims, with further embodiments set out in the dependent claims.

[0041] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description, drawings, and claims.

[0042] Furthermore, the following embodiments are provided:

[0043] In one embodiment, a bitstream for video coding is provided, and the DPS occurs at most once in the bitstream.

[0044] In one embodiment, the DPS is not required in the bitstream.

[0045] In one embodiment, when a bitstream includes a DPS, only one DPS is in the bitstream.

[0046] In one embodiment, all DPS NAL units with a particular value of dps_decoding_parameter_set_id in a bitstream have the same content.

[0047] In one embodiment, one DPS ID cannot hook into the content of more than one DPS.

[0048] In one embodiment, a bitstream for video coding is provided in which the level signaled in the DPS is constrained to be greater than or equal to the level signaled in the SPS.

[0049] In one embodiment, there is provided a method of coding performed by a decoding device, comprising the step of parsing a bitstream according to any one of the above embodiments.

[0050] In one embodiment, there is provided a method of coding performed by an encoding device, comprising generating a bitstream according to any one of the above-mentioned embodiments.

[0051] In one embodiment, an encoder (20) is provided that includes processing circuitry for performing a method according to any one of the above embodiments.

[0052] In one embodiment, a decoder (30) is provided that includes processing circuitry for performing a method according to any one of the above embodiments.

[0053] In one embodiment, there is provided a computer program product comprising program code for performing a method according to any one of the above embodiments when the program code is run on a computer or processor.

[0054] In one embodiment, one or more processors; and a non-transitory computer-readable storage medium coupled to a processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform a method according to any one of the preceding embodiments.

[0055] In one embodiment, one or more processors; An encoder is provided, the encoder comprising: a non-transitory computer-readable storage medium coupled to a processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the encoder to perform a method according to any one of the preceding embodiments.

[0056] In one embodiment, a non-transitory computer readable medium is provided that carries program code that, when executed by a computing device, causes the computing device to perform a method according to any one of the above-described embodiments.

[0057] In one embodiment, a method for decoding a video bitstream performed by a decoding device, the video bitstream including data representing a coded picture including a sequence of tiles, the decoding method comprising: obtaining a syntax element (e.g., tile_column_width_minus1) by parsing the video bitstream, where the syntax element is used to derive a width of a tile column, and the sum of the widths of the tile columns is less than or equal to the width of the coded picture; and predicting the coded picture according to the width of the tile column.

[0058] In one embodiment, the value of each syntax element plus one is the width of the tile column within the tile column.

[0059] In one embodiment, the width of a tile column has an index i in the range from 0 to num_exp_tile_columns_minus1 - 1.

[0060] In one embodiment, the width of a tile column has an index i in the range from 0 to num_exp_tile_columns_minus1.

[0061] In one embodiment, a method for decoding a video bitstream performed by a decoding device, the video bitstream including data representing a coded picture including a sequence of tiles, the decoding method comprising: obtaining a syntax element (e.g., tile_column_width_minus1) by parsing the video bitstream, the syntax element being used to derive a tile column width value, the tile column width value being uniform and being less than or equal to the coded picture width; and predicting the coded picture according to the width of the tile column.

[0062] In one embodiment, the value of the syntax element plus one is the width value of the tile column.

[0063] In one embodiment, the width of a tile column has index i equal to num_exp_tile_columns_minus1.

[0064] In one embodiment, a method for decoding a video bitstream performed by a decoding device, the video bitstream including data representing a coded picture including tile rows, the decoding method comprising: obtaining a syntax element (e.g., tile_row_height_minus1) by parsing the video bitstream, where the syntax element is used to derive a height of a tile row, and the sum of the heights of the tile rows is less than or equal to the height of the coded picture; A method is provided that includes predicting a coded picture by tile row height.

[0065] In one embodiment, the value of each syntax element plus one is the height of the tile row within the tile row.

[0066] In one embodiment, the height of a tile row has an index i in the range from 0 to num_exp_tile_rows_minus1 - 1.

[0067] In one embodiment, the height of a tile row has an index i ranging from 0 to num_exp_tile_rows_minus1.

[0068] In one embodiment, a method for decoding a video bitstream performed by a decoding device, the video bitstream including data representing a coded picture including tile rows, the decoding method comprising: obtaining a syntax element (e.g., tile_row_height_minus1) by parsing the video bitstream, where the syntax element is used to derive a tile row height value, where the tile row height value is uniform and is less than or equal to the height of the coded picture; and predicting the coded picture by the height of the tile rows.

[0069] In one embodiment, the value of the syntax element plus one is the height value of the tile row.

[0070] In one embodiment, the height of a tile row has index i equal to num_exp_tile_rows_minus1.

[0071] In one embodiment, an encoder (20) is provided that includes processing circuitry for performing a method according to any one of the above embodiments.

[0072] In one embodiment, a decoder (30) is provided that includes processing circuitry for performing a method according to any one of the above embodiments.

[0073] In one embodiment, there is provided a computer program product comprising program code for performing a method according to any one of the above embodiments when the program code is run on a computer or processor.

[0074] In one embodiment, one or more processors; and a non-transitory computer-readable storage medium coupled to a processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform a method according to any one of the preceding embodiments.

[0075] In one embodiment, one or more processors; An encoder is provided, the encoder comprising: a non-transitory computer-readable storage medium coupled to a processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the encoder to perform a method according to any one of the preceding embodiments.

[0076] In one embodiment, a non-transitory computer readable medium is provided that carries program code that, when executed by a computing device, causes the computing device to perform a method according to any one of the above-described embodiments.

[0077] In the following, embodiments of the invention will be explained in more detail with reference to the accompanying figures and drawings. [Brief explanation of the drawings]

[0078] [Figure 1A] 1 is a block diagram illustrating an example of a video coding system configured to implement embodiments of the present invention. [Figure 1B] FIG. 2 is a block diagram illustrating another example of a video coding system configured to implement embodiments of the present invention. [Figure 2] 1 is a block diagram illustrating an example of a video encoder configured to implement embodiments of the present invention. [Figure 3] 1 is a block diagram illustrating an exemplary structure of a video decoder configured to implement embodiments of the present invention. [Figure 4] FIG. 1 is a block diagram illustrating an example of an encoding device or a decoding device. [Figure 5] FIG. 10 is a block diagram showing another example of an encoding device or a decoding device. [Figure 6] 31 is a block diagram illustrating an exemplary structure of a content supply system 3100 for implementing a content distribution service. [Figure 7] FIG. 2 is a block diagram illustrating the structure of an example terminal device. [Figure 8] 1 is a flow diagram of a decoding method according to one embodiment. [Figure 9] 1 is a flow diagram of an encoding method according to one embodiment; [Figure 10] FIG. 2 is a schematic diagram of an encoder according to one embodiment. [Figure 11] FIG. 2 is a schematic diagram of a decoder according to one embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0079] In the following, the same reference signs, unless otherwise specified, refer to identical or at least functionally equivalent features.

[0080] In the following description, reference is made to the accompanying drawings which form a part of this disclosure and which show, by way of illustration, specific aspects of embodiments of the invention or in which embodiments of the invention may be used. It is understood that embodiments of the invention may be used in other ways and may include structural or logical changes not shown in the drawings. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0081] For example, it is understood that disclosure related to a described method may also apply to a corresponding device or system configured to perform the method, and vice versa. For example, when one or more particular method steps are described, a corresponding device may include one or more units, e.g., functional units, for performing the described one or more method steps (e.g., one unit that performs one or more steps, or multiple units that each perform one or more of the steps), even if such one or more units are not explicitly described or shown in a figure. On the other hand, for example, when a particular apparatus is described based on one or more units, e.g., functional units, a corresponding method may include one step for performing the function of the one or more units (e.g., one step that performs the function of one or more units, or multiple steps that each perform one or more functions of multiple units), even if such one or more steps are not explicitly described or shown in a figure. Furthermore, it is understood that features of various exemplary embodiments and / or aspects described herein may be combined with each other unless expressly stated otherwise.

[0082] Video coding generally refers to the processing of a sequence of pictures that form a video or a video sequence. Instead of the term "picture," the terms "frame" or "image" may be used synonymously in the field of video coding. Video coding (or generally coding) includes two parts: video encoding and video decoding. Video encoding is performed at the source side and generally involves processing the original video picture (e.g., by compression) to reduce the amount of data needed to represent the video picture (for more efficient storage and / or transmission). Video decoding is performed at the destination side and generally involves the reverse processing compared to the encoder to reconstruct the video picture. Embodiments that refer to "coding" a video picture (or generally pictures) are understood to relate to "encoding" or "decoding" the video picture or respective video sequence. The combination of the encoding and decoding parts is also called a codec (coding and decoding).

[0083] In the case of lossless video coding, the original video picture can be reconstructed (assuming there is no transmission loss or other data loss during storage or transmission), i.e., the reconstructed video picture has the same quality as the original video picture. In the case of lossy video coding, further compression, for example by quantization, is performed to reduce the amount of data representing the video picture, which cannot be perfectly reconstructed at the decoder, i.e., the quality of the reconstructed video picture is lower or worse than the quality of the original video picture.

[0084] Some video coding standards belong to the group of "lossy hybrid video codecs" (i.e., combine spatial and temporal prediction in the sample domain with 2D transform coding for applying quantization in the transform domain). Each picture of a video sequence is generally partitioned into a set of non-overlapping blocks, and coding is generally performed at the block level. In other words, at an encoder, video is generally processed, i.e., encoded, at the block (video block) level, for example, by generating a prediction block using spatial (intra-picture) prediction and / or temporal (inter-picture) prediction, subtracting the prediction block from a current block (the block currently being / 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); whereas at a decoder, an inverse process is applied to the coded or compressed block compared to the encoder to reconstruct the current block for representation. Furthermore, the encoder replicates the decoder's processing loop so that both generate the same prediction (eg, intra and inter prediction) and / or reconstruction for processing, i.e., coding, subsequent blocks.

[0085] In the following, embodiments of a video coding system 10, a video encoder 20 and a video decoder 30 are described based on FIGS.

[0086] 1A is a schematic block diagram illustrating an example coding system 10, e.g., video coding system 10 (or coding system 10 for short), that may utilize techniques of the present application. A video encoder 20 (or encoder 20 for short) and a video decoder 30 (or decoder 30 for short) of video coding system 10 illustrate examples of devices that may be configured to perform techniques according to various examples described in the present application.

[0087] As shown in FIG. 1A, coding system 10 includes a source device 12 configured to provide encoded picture data 21 to, for example, a destination device 14 for decoding the encoded picture data 13.

[0088] The source device 12 includes an encoder 20 and may additionally, i.e., optionally, 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.

[0089] Picture source 16 may include or be any kind of picture capture device, e.g., a camera for capturing real-world pictures, and / or any kind of picture generation device, e.g., a computer graphics processor for generating computer-animated pictures, or any kind of other device for obtaining and / or providing real-world pictures, computer-generated pictures (e.g., screen content, virtual reality (VR) pictures), and / or any combination thereof (e.g., augmented reality (AR) pictures). Picture source may be any kind of memory or storage for storing any of the above-mentioned pictures.

[0090] To distinguish from the preprocessor 18 and the processing performed by the preprocessing unit 18, the picture or picture data 17 may also be referred to as a raw picture or raw picture data 17.

[0091] The pre-processor 18 is configured to receive (raw) picture data 17 and perform pre-processing on the picture data 17 to obtain a pre-processed picture 19 or pre-processed picture data 19. The pre-processing performed by the pre-processor 18 may include, for example, cropping, color format conversion (e.g., from RGB to YCbCr), color correction, or noise removal. It may be understood that the pre-processing unit 18 may be an optional component.

[0092] Video encoder 20 is configured to receive pre-processed picture data 19 and provide encoded picture data 21 (further details are described below, eg, with reference to FIG. 2).

[0093] The communication interface 22 of the source device 12 may be configured to receive the encoded picture data 21 and transmit the encoded picture data 21 (or any further processed version thereof) via the communication channel 13 to another device, e.g., the destination device 14 or any other device, for storage or direct reconstruction.

[0094] The destination device 14 includes a decoder 30 (e.g., a video decoder 30) and may additionally, i.e., optionally, include a communication interface or communication unit 28, a post-processor 32 (or post-processing unit 32), and a display device 34.

[0095] The communications interface 28 of the destination device 14 is configured to receive the encoded picture data 21 (or any further processed version thereof), for example directly from the source device 12 or from any other source, for example a storage device, for example a storage device for encoded picture data, and to provide the encoded picture data 21 to the decoder 30.

[0096] The communication interface 22 and the communication interface 28 may be configured to transmit or receive the encoded picture data 21 or the encoded data 13 via a direct communication link between the source device 12 and the destination device 14, e.g., a direct wired or wireless connection, or via any type of network, e.g., a wired or wireless network or any combination thereof, or any type of private and public network, or any type of combination thereof.

[0097] The communications interface 22 may be configured to process the encoded picture data 21 using any type of transmission encoding or processing, for example, packaging the encoded picture data 21 into a suitable format, e.g., packets, and / or for transmission over a communications link or network.

[0098] The communications interface 28 forming the counterpart of the communications interface 22 may for example be configured to receive the transmitted data and process the transmitted data using any type of corresponding transmission decoding or processing and / or depackaging to obtain the encoded picture data 21.

[0099] Both communication interface 22 and communication interface 28 may be configured as unidirectional communication interfaces, as indicated by the arrows for communication channel 13 in FIG. 1A pointing from source device 12 toward destination device 14, or as bidirectional communication interfaces, and may be configured, for example, to send and receive messages, for example, to set up connections and to confirm and exchange communications links and / or any other information related to data transmission, e.g., transmission of encoded picture data.

[0100] The decoder 30 is configured to receive encoded picture data 21 and provide decoded picture data 31 or decoded pictures 31 (further details are described below, for example, based on Figure 3 or Figure 5).

[0101] Post-processor 32 of destination device 14 is configured to post-process decoded picture data 31 (also called reconstructed picture data), e.g., decoded picture 31, to obtain post-processed picture data 33, e.g., post-processed picture 33. The post-processing performed by post-processing unit 32 may include, e.g., color format conversion (e.g., from YCbCr to RGB), color correction, cropping, or resampling, or any other processing to prepare, e.g., decoded picture data 31, for display by, e.g., display device 34.

[0102] Display device 34 of destination device 14 is configured to receive post-processed picture data 33, for example, to display the picture to a user or viewer. Display device 34 may be or include any type of display for showing the reconstructed picture, e.g., 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 microLED display, a liquid crystal on silicon (LCoS), a digital light processor (DLP), or any other type of display.

[0103] 1A depicts source device 12 and destination device 14 as separate devices, embodiments of the devices may include both or both functionality: source device 12 or corresponding functionality and destination device 14 or corresponding functionality. In such embodiments, source device 12 or corresponding functionality and destination device 14 or corresponding functionality may be implemented using the same hardware and / or software or by separate hardware and / or software or any combination thereof.

[0104] As will be clear to those skilled in the art based on the description, the presence and (exact) division of functions of different units or functions within source device 12 and / or destination device 14 shown in FIG. 1A may vary depending on the actual device and application.

[0105] Encoder 20 (e.g., video encoder 20) or decoder 30 (e.g., video decoder 30), or both encoder 20 and decoder 30, may be implemented by processing circuitry shown in FIG. 1B , such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, hardware, dedicated to video coding, or any combination thereof. Encoder 20 may be implemented by processing circuitry 46 to embody various modules discussed in connection with encoder 20 of FIG. 2 and / or any other encoder system or subsystem described herein. Decoder 30 may be implemented by processing circuitry 46 to embody various modules discussed in connection with decoder 30 of FIG. 3 and / or any other decoder system or subsystem described herein. The processing circuitry may be configured to perform various operations discussed below. 5, where the techniques are implemented partially in software, a device may store instructions for the software on a suitable non-transitory computer-readable storage medium and may execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Either video encoder 20 and video decoder 30 may be incorporated as part of a combined encoder / decoder (codec) in a single device, for example, as shown in FIG. 1B.

[0106] The source device 12 and the destination device 14 may include any of a wide range of devices, including any type of handheld or fixed device, e.g., a notebook or laptop computer, a mobile phone, a smartphone, a tablet or tablet computer, a camera, a desktop computer, a set-top box, a television, a display device, a digital media player, a video game console, a video streaming device (such as a content service server or content distribution server), a broadcast receiver device, a broadcast transmitter device, etc., and may use no operating system or any type of operating system. In some cases, the source device 12 and the destination device 14 may be capable of wireless communication. Thus, the source device 12 and the destination device 14 may be wireless communication devices.

[0107] In some cases, the video coding system 10 shown in FIG. 1A is merely an example, and the techniques of this disclosure may be applied to video coding situations (e.g., video encoding or video decoding) that do not necessarily involve any data communication between an encoding device and a decoding device. In other examples, data may be retrieved from local memory, streamed over a network, etc. A video encoding device may encode data and store it in memory, and / or a video decoding device may retrieve data from memory and decode it. In some examples, encoding and decoding are performed by devices that do not communicate with each other but simply encode data to memory and / or retrieve data from memory and decode it.

[0108] For ease of explanation, embodiments of the present invention are described herein with reference to reference software, e.g., High-Efficiency Video Coding (HEVC), or Versatile Video Coding (VVC), the next-generation video coding standard developed by the ITU-T Video Coding Experts Group (VCEG) and the ISO / IEC Joint Collaboration Team on Video Coding (JCT-VC) of the Motion Picture Experts Group (MPEG). Those skilled in the art will understand that embodiments of the present invention are not limited to HEVC or VVC.

[0109] 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 transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a loop filter unit 220, a decoded picture buffer (DPB) 230, a mode selection unit 260, an entropy coding unit 270, and an output 272 (or output interface 272). The mode selection unit 260 may include an inter prediction unit 244, an intra prediction unit 254, and a partitioning unit 262. The inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 shown in FIG. 2 may also be referred to as a hybrid video encoder or a video encoder using a hybrid video codec.

[0110] The residual calculation unit 204, the transform processing unit 206, the quantization unit 208, and the mode selection unit 260 may be considered to form a forward signal path of the encoder 20, while the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 may be considered to form a backward signal path of the video encoder 20, which corresponds to the signal path of a decoder (see video decoder 30 in FIG. 3 ). The inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 may also be considered to form a “built-in decoder” of the video encoder 20.

[0111] Picture & Picture Division (Picture & Block) Encoder 20 may, for example, be configured to receive via input 201 picture 17 (or picture data 17), e.g., a picture of a sequence of pictures forming a video or a video sequence. The received picture or picture data may also be preprocessed picture 19 (or preprocessed picture data 19). For simplicity, the following description refers to picture 17. Picture 17 may also be referred to as a current picture or a picture to be coded (particularly in video coding, to distinguish the current picture from other pictures, e.g., already coded and / or decoded pictures of the same video sequence, i.e., the video sequence that also includes the current picture).

[0112] A (digital) picture is or can be considered as a two-dimensional array or matrix of samples having intensity values. The samples of the array may also be called pixels (short for picture element) or pels. The number of samples in the horizontal and vertical directions (or axes) of the array or picture defines the size and / or resolution of the picture. For color representation, three color components are generally used, i.e., a picture may be represented or include three sample arrays. In an RBG format or color space, a picture includes corresponding red, green, and blue sample arrays. However, in video coding, each pixel is generally represented in a luminance and chrominance format or color space, e.g., YCbCr, which includes a luminance component denoted by Y (although L may be used instead) and two chrominance components denoted by Cb and Cr. The luminance (or luma for short) component Y represents brightness or gray level intensity (e.g., similar to a grayscale picture), while the two chrominance (or chroma for short) components Cb and Cr represent chromaticity or color information components. Thus, a picture in YCbCr format includes a luminance sample array of luminance sample values ​​(Y) and two chrominance sample arrays of chrominance values ​​(Cb and Cr). A picture in RGB format may be converted or transformed to YCbCr format, or vice versa; the process is also known as color transformation or conversion. If a picture is monochrome, the picture may include only a luminance sample array. Thus, a picture may 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.

[0113] An embodiment of video encoder 20 may include a picture partitioning unit (not shown in FIG. 2 ) configured to partition picture 17 into multiple (usually non-overlapping) picture blocks 203. These blocks may also be called root blocks, macroblocks (H.264 / AVC), or coding tree blocks (CTBs) or coding tree units (CTUs) (H.265 / HEVC and VVC). The picture partitioning unit may be configured to use the same block size for all pictures of a video sequence and a corresponding grid defining the block size, or to vary the block size among pictures or subsets or groups of pictures, and to partition each picture into corresponding blocks.

[0114] In further embodiments, the video encoder may be configured to directly receive blocks 203 of picture 17, e.g., one, some, or all of the blocks that form picture 17. Picture blocks 203 may also be referred to as current picture blocks or picture blocks to be coded.

[0115] Similar to picture 17, picture block 203 has smaller dimensions than picture 17, but is also considered or can be considered a two-dimensional array or matrix of samples having intensity values ​​(sample values). In other words, block 203 may include, for example, one sample array (e.g., a luma array for a monochrome picture 17, or a luma or chroma array for a color picture), or three sample arrays (e.g., a luma and two chroma arrays for a color picture 17), or any other number and / or type of array, depending on the applied color format. The number of samples in the horizontal and vertical directions (or axes) of block 203 defines the size of block 203. Thus, a block may be, for example, an MxN (M columns by N rows) array of samples or an MxN array of transform coefficients.

[0116] The embodiment of video encoder 20 shown in FIG. 2 may be configured to encode picture 17 block by block, eg, encoding and prediction is performed for each block 203.

[0117] The embodiment of video encoder 20 shown in FIG. 2 may be further configured to partition and / or encode a picture by using slices (also referred to as video slices), where a picture may be partitioned into or encoded using one or more (generally non-overlapping) slices, each of which may include one or more blocks (e.g., CTUs) or one or more groups of blocks (e.g., tiles (H.265 / HEVC and VVC) or bricks (VVC)).

[0118] The embodiment of video encoder 20 shown in FIG. 2 may be further configured to partition and / or encode a picture by using slices / tile groups (also referred to as video tile groups) and / or tiles (also referred to as video tiles), where a picture may be partitioned into or encoded using one or more (generally non-overlapping) slices / tile groups, where each slice / tile group may, for example, include one or more blocks (e.g., CTUs) or one or more tiles, where each tile may, for example, be rectangular in shape and may include one or more blocks (e.g., CTUs), e.g., full or fractional blocks.

[0119] Calculating residuals The residual calculation unit 204 may be configured to calculate the residual block 205 (also referred to as the residual 205) based on the picture block 203 and the prediction block 265 (further details about the prediction block 265 are provided later), for example, by subtracting the sample values ​​of the prediction block 265 from the sample values ​​of the picture block 203 on a sample-by-sample (pixel-by-pixel) basis to obtain the residual block 205 in the sample domain.

[0120] conversion The transform processing unit 206 may be configured to apply a transform, for example, a discrete cosine transform (DCT) or a discrete sine transform (DST), to the sample values ​​of the residual block 205 to obtain transform coefficients 207 in a transform domain. The transform coefficients 207, also referred to as transform residual coefficients, may represent the residual block 205 in the transform domain.

[0121] The transform processing unit 206 may be configured to apply an integer approximation of a DCT / DST, such as the transform specified for H.265 / HEVC. Compared to an orthogonal DCT transform, such an integer approximation is generally scaled by a particular factor. To maintain the norm of the residual blocks processed by the forward and inverse transforms, an additional scaling factor is applied as part of the transform process. The scaling factor is generally selected based on particular constraints, such as the scaling factor being a power of two for shift operations, the bit depth of the transform coefficients, a trade-off between accuracy and implementation cost, etc. For example, a particular scaling factor may be specified for the inverse transform, e.g., by the inverse transform processing unit 212 (and the corresponding inverse transform, e.g., by the inverse transform processing unit 312 in the video decoder 30), and a corresponding scaling factor for the forward transform, e.g., by the transform processing unit 206 of the encoder 20, may be specified accordingly.

[0122] An embodiment of the video encoder 20 (respectively, the transform processing unit 206) may be configured to output transform parameters, e.g., a certain transform or transforms, either as is or encoded or compressed by the entropy coding unit 270, such that the video decoder 30 may receive the transform parameters and use them for decoding.

[0123] Quantization The quantization unit 208 may be configured to quantize the transform coefficients 207, for example, by applying scalar quantization or vector quantization, to obtain quantized coefficients 209. The quantized coefficients 209 may also be referred to as quantized transform coefficients 209 or quantized residual coefficients 209.

[0124] The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, an n-bit transform coefficient may be truncated to an m-bit transform coefficient during quantization, where n is greater than m. The degree of quantization may be modified by adjusting a quantization parameter (QP). For example, with respect to scalar quantization, different scaling may be applied to achieve finer or coarser quantization. A smaller quantization step size corresponds to finer quantization, while a larger quantization step size corresponds to coarser quantization. The applicable quantization step size may be indicated by the quantization parameter (QP). The quantization parameter may, for example, be an index into a predefined set of applicable quantization step sizes. For example, a small quantization parameter may correspond to fine quantization (small quantization step size) and a large quantization parameter may correspond to coarse quantization (large quantization step size), or vice versa. Quantization may include division by a quantization step size, and corresponding and / or inverse dequantization by, for example, the inverse quantization unit 210 may include multiplication by the quantization step size. Some standards, for example, HEVC, embodiments may be configured to determine the quantization step size using a quantization parameter. Generally, the quantization step size may be calculated based on the quantization parameter using a fixed-point approximation of an equation involving division. Additional scaling factors may be introduced for quantization and dequantization to restore the norm of the residual block, which may be modified due to scaling used in the fixed-point approximation of the equation for the quantization step size and the quantization parameter. In one exemplary implementation, the scaling of the inverse transform and dequantization may be combined. Alternatively, customized quantization tables may be used, e.g., signaled from the encoder to the decoder in the bitstream.Quantization is a lossy operation and the loss increases as the quantization step size increases.

[0125] An embodiment of video encoder 20 (respectively, quantization unit 208) may be configured to output a quantization parameter (QP), e.g., as is or encoded by entropy encoding unit 270, such that video decoder 30 may receive and apply the quantization parameter for decoding.

[0126] inverse quantization Inverse quantization unit 210 is configured to apply the inverse quantization of quantization unit 208 to the quantized coefficients to obtain dequantized coefficients 211, e.g., by applying the inverse of the quantization scheme applied by quantization unit 208, based on or using the same quantization step size as quantization unit 208. The dequantized coefficients 211, also referred to as dequantized residual coefficients 211, may correspond to transform coefficients 207—although they are generally not identical to the transform coefficients due to loss due to quantization.

[0127] 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, for example, 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 a transform block 213.

[0128] Rebuild The reconstruction unit 214 (e.g., an adder or summator 214) is configured to add the transform block 213 (i.e., the reconstructed residual block 213) to the prediction block 265, for example, by adding the sample values ​​of the reconstructed residual block 213 and the sample values ​​of the prediction block 265—sample by sample—to obtain a reconstructed block 215 in the sample domain.

[0129] filtering The loop filter unit 220 (or "loop filter" 220 for short) is configured to filter the reconstructed block 215 to obtain a filtered block 221, or generally, to filter the reconstructed samples to obtain filtered sample values. The loop filter unit is configured, for example, to smooth pixel transitions or otherwise improve video quality. The loop filter unit 220 may include one or more loop filters, such as a deblocking filter, a sample-adaptive offset (SAO) filter, or one or more other filters, for example, an adaptive loop filter (ALF), a noise suppression filter (NSF), or any combination thereof. In an example, the loop filter unit 220 may include a deblocking filter, an SAO filter, and an ALF filter. The order of the filtering process may be: deblocking filter, SAO, and ALF. In another example, a process called luma mapping with chroma scaling (LMCS) (i.e., adaptive in-loop reshaper) is added. This process is performed before deblocking. In another example, the deblocking filter process may also be applied to internal sub-block edges, such as affine sub-block edges, ATMVP sub-block edges, sub-block transform (SBT) edges, and intra sub-partition (ISP) edges. Although loop filter unit 220 is shown in FIG. 2 as being an in-loop filter, in other configurations, loop filter unit 220 may be implemented as a post-loop filter. Filtered block 221 may also be referred to as filtered reconstructed block 221.

[0130] Embodiments of video encoder 20 (respectively, loop filter unit 220) may be configured to output loop filter parameters (such as SAO filter parameters, or ALF filter parameters (ALF parameters), or LMCS parameters) either as is or encoded by entropy coding unit 270, e.g., such that decoder 30 may receive and apply the same or respective loop filter parameters for decoding. Here, entropy coding unit 270 may encode a picture-level syntax element into the picture header of the current picture, where the picture-level syntax element is used to specify whether an adaptive loop filter (ALF) is enabled for the current picture.

[0131] Decoded Picture Buffer The decoded picture buffer (DPB) 230 may be a memory that stores 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 a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The decoded picture buffer (DPB) 230 may be configured to store one or more filtered blocks 221. The decoded picture buffer 230 may further be configured to store other already-filtered blocks, e.g., already-reconstructed filtered blocks 221, of the same current picture or a different picture, e.g., an already-reconstructed picture, and may provide a complete already-reconstructed, i.e., decoded, picture (and corresponding reference blocks and samples) and / or a partially-reconstructed current picture (and corresponding reference blocks and samples), e.g., for inter-prediction. The decoded picture buffer (DPB) 230 may also be configured to store one or more unfiltered reconstructed blocks 215 or generally unfiltered reconstructed samples, for example, if the reconstructed blocks 215 are not filtered by the loop filter unit 220, or to store any other further processed version of the reconstructed blocks or samples.

[0132] Mode selection (classification & prediction) The mode selection unit 260 includes a partitioning unit 262, an inter prediction unit 244, and an intra prediction unit 254, and is configured to receive or obtain original picture data, e.g., original block 203 (current block 203 of current picture 17), and reconstructed picture data, e.g., filtered and / or unfiltered reconstructed samples or blocks of the same (current) picture and / or from one or more already decoded pictures, for example, from the decoded picture buffer 230 or other buffer (e.g., a line buffer, not shown). The reconstructed picture data is used as reference picture data for prediction, e.g., inter prediction or intra prediction, to obtain a prediction block 265 or predictor 265.

[0133] The mode selection unit 260 may be configured to determine or select a partitioning and prediction mode (e.g., intra or inter prediction mode) for the prediction mode of the current block (which does not include partitioning) and generate a corresponding prediction block 265 used for calculating the residual block 205 and reconstructing the reconstructed block 215.

[0134] Embodiments of the mode selection unit 260 may be configured to select a partitioning and prediction mode (e.g., from partitioning and prediction modes supported by or available to the mode selection unit 260) that provides the best match, or in other words, the smallest residual (smallest residual means better compression for transmission or storage), or the smallest signaling overhead (smallest signaling overhead means better compression for transmission or storage), or that considers or balances both. The mode selection unit 260 may be configured to determine the partitioning and prediction mode based on rate-distortion optimization (RDO), i.e., to select the prediction mode that provides the smallest rate-distortion. Terms such as “best,” “minimum,” “optimum,” etc. in this context do not necessarily refer to the overall “best,” “minimum,” “optimum,” etc., but may also refer to satisfying termination or selection criteria such as values ​​above or below a threshold, or other constraints that potentially lead to a “suboptimal selection,” but that reduce complexity and processing time.

[0135] In other words, the partitioning unit 262 may be configured to partition the pictures of the video sequence into a sequence of coding tree units (CTUs), and the CTUs 203 may be partitioned using, for example, quadtree partitioning (QT), bipartitioning, tree The block may be further partitioned into smaller block partitions or sub-blocks (again forming blocks) using iterative tree partitioning (BT), or ternary tree partitioning (TT), or any combination thereof, and the partitioning unit 262 may be configured, for example, to perform prediction on each of the block partitions or sub-blocks, and the mode selection includes selecting a tree structure of the partitioned block 203, and a prediction mode is applied to each of the block partitions or sub-blocks.

[0136] Below, the partitioning (eg, by partitioning unit 260) and prediction processes (by inter-prediction unit 244 and intra-prediction unit 254) performed by exemplary video encoder 20 are described in more detail.

[0137] Classification The partitioning unit 262 may be configured to partition a picture of a video sequence into a sequence of coding tree units (CTUs), and the partitioning unit 262 may partition (or divide) the coding tree units (CTUs) 203 into smaller sections, for example, smaller blocks of square or rectangular size. For a picture with a three-sample arrangement, a CTU consists of an N×N block of luma samples and two corresponding blocks of chroma samples. The maximum allowed size of a luma block of a CTU is specified to be 128×128 in the developing Versatile Video Coding (VVC) standard, but may be specified to be a value larger than 128×128, for example, 256×256, in the future. The CTUs of a picture may be clustered / grouped as slices / tile groups, tiles, or bricks. A tile encompasses a rectangular region of a picture, and a tile may be divided into one or more bricks. A brick consists of several rows of CTUs within the tile. A tile that is not partitioned into multiple bricks may be called a brick. However, a brick is a pure subset of a tile and is not called a tile. There are two modes of tile groups supported in VVC: raster scan slice / tile group mode and rectangular slice mode. In raster scan tile group mode, a slice / tile group contains a sequence of tiles that raster scan the tiles of a picture. In rectangular slice mode, a slice contains several bricks of a picture that collectively form a rectangular region of the picture. The bricks within a rectangular slice are in the raster scan order of the bricks of the slice. These smaller blocks (which may also be called sub-blocks) may be further partitioned into even smaller divisions.This is also called tree partitioning or hierarchical tree partitioning; for example, a root block at root tree level 0 (hierarchical level 0, depth 0) may be recursively partitioned, e.g., into two or more blocks at the next lower tree level, e.g., a node at tree level 1 (hierarchical level 1, depth 1); these blocks may be partitioned again into two or more blocks at the next lower level, e.g., tree level 2 (hierarchical level 2, depth 2); and so on until partitioning is terminated because, e.g., a termination criterion is met, e.g., a maximum tree depth or a minimum block size is reached. Blocks that are not further partitioned are also called leaf blocks or leaf nodes of the tree. A tree using a partition into two partitions is called a binary tree (BT), a tree using a partition into three partitions is called a ternary tree (TT), and a tree using a partition into four partitions is called a quad tree (QT).

[0138] For example, a coding tree unit (CTU) could be or include a CTB of luma samples, two corresponding CTBs of chroma samples for a picture with a three-sample arrangement, or a CTB of samples for a picture coded using three separate color planes and a syntax structure used to code a monochrome picture or sample. Correspondingly, a coding tree block (CTB) could be an N×N block of samples for some value of N such that the division of the components into CTBs is a partition. A coding unit (CU) could be or include a coding block of luma samples, two corresponding coding blocks of chroma samples for a picture with a three-sample arrangement, or a coding block of samples for a picture coded using three separate color planes and a syntax structure used to code a monochrome picture or sample. Correspondingly, a coding block (CB) could 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 a partition.

[0139] For example, in an HEVC embodiment, a coding tree unit (CTU) may be divided into CUs by using a quadtree structure represented as a coding tree. The decision of whether to code a picture area using inter-picture (temporal) prediction or intra-picture (spatial) prediction is made at the leaf CU level. Each leaf CU may be further divided into one, two, or four PUs according to a PU partition type. Within one PU, the same prediction process is applied, and related information is transmitted to the decoder based on the PU. After obtaining residual blocks by applying a prediction process based on the PU partition type, the leaf CU may be partitioned into transform units (TUs) by another quadtree structure similar to the coding tree for CUs.

[0140] For example, in an embodiment according to the latest video coding standard currently under development, called Versatile Video Coding (VVC), a nested multitype tree of a combined quadtree using, for example, a bisection and trisection segmentation structure is used to partition a coding tree unit. In the coding tree structure within a coding tree unit, a CU may have either a square or rectangular shape. For example, a coding tree unit (CTU) is first partitioned by a quadtree. Then, the leaf nodes of the quadtree may be further partitioned by a multitype tree structure. There are four partition types in the multitype tree structure: vertical bisection (SPLIT_BT_VER), horizontal bisection (SPLIT_BT_HOR), vertical trisection (SPLIT_TT_VER), and horizontal trisection (SPLIT_TT_HOR). The leaf nodes of the multitype tree are called coding units (CUs), and this segmentation is used for prediction and transform processing without any further partitioning, as long as the CU is not too long with respect to the maximum transform length. This means that in most cases, CUs, PUs, and TUs have the same block size within a quadtree with a nested multi-type tree coding block structure. An exception occurs when the maximum supported transform length is smaller than the width or height of a CU's color components. VVC develops a unique signaling mechanism for partitioning information within a quadtree with a nested multi-type tree coding tree structure. In the signaling mechanism, the coding tree unit (CTU) is treated as the root of the quadtree and is first partitioned by the quadtree structure. The leaf nodes of each quadtree (when large enough to allow it) are further partitioned by the multi-type tree structure.In a multi-type tree structure, a first flag (mtt_split_cu_flag) is signaled to indicate whether the node is further partitioned; when the node is further partitioned, a second flag (mtt_split_cu_vertical_flag) is signaled to indicate the split direction; and then a third flag (mtt_split_cu_binary_flag) is signaled to indicate whether the split is bipartite or tripartite. Based on the values ​​of mtt_split_cu_vertical_flag and mtt_split_cu_binary_flag, the multi-type tree split mode (MttSplitMode) of the CU can be derived by the decoder based on a predefined rule or table. Specific designs, for example, 64x64 luma blocks and 32x32 chroma in a VVC hardware decoder. block Regarding the pipeline design, note that TT partitioning is prohibited when either the width or height of a luma coding block is greater than 64, as shown in FIG. 6. TT partitioning is also prohibited when either the width or height of a chroma coding block is greater than 32. The pipeline design divides a picture into virtual pipeline data units (VPDUs), which are defined as non-overlapping units within a picture. In a hardware decoder, consecutive VPDUs are processed simultaneously by multiple pipeline stages. The size of a VPDU is roughly proportional to the buffer size of most pipeline stages, and therefore, it is important to keep the size of a VPDU small. In most hardware decoders, the size of a VPDU can be set to the maximum transform block (TB) size. However, in VVC, ternary tree (TT) and binary tree (BT) partitioning can lead to an increase in the size of a VPDU.

[0141] Furthermore, when any part of a tree node block exceeds the picture boundary below or to the right, the tree node block is forced to split until all samples of every coded CU are within the picture boundary.

[0142] As an example, an intra sub-partition (ISP) tool may divide a luma intra-predicted block vertically or horizontally into two or four sub-partitions depending on the block size.

[0143] In one example, mode select unit 260 of video encoder 20 may be configured to perform any combination of the partitioning techniques described herein.

[0144] As mentioned above, video encoder 20 is configured to determine or select a best or optimal prediction mode from a set of (e.g., predetermined) prediction modes, which may include, for example, intra-prediction modes and / or inter-prediction modes.

[0145] Intra prediction The set of intra prediction modes may include, for example, 35 different intra prediction modes defined in HEVC, e.g., non-directional modes such as DC (or average) mode and planar mode, or directional modes, or 67 different intra prediction modes defined for VVC, e.g., non-directional modes such as DC (or average) mode and planar mode, or directional modes. As an example, some conventional directional intra prediction modes are adaptively replaced by wide-angle intra prediction modes for non-square blocks, e.g., defined in VVC. As another example, to avoid a split operation for DC prediction, only the long side is used to calculate the average for non-square blocks. Also, the results of intra prediction for planar modes may be further modified by a position-dependent intra prediction combination (PDPC) method.

[0146] The intra prediction unit 254 is configured to generate the intra prediction block 265 using reconstructed samples of neighboring blocks of the same current picture according to an intra prediction mode from a set of intra prediction modes.

[0147] The intra prediction unit 254 (or generally the mode selection unit 260) is further configured to output the intra prediction parameters (or generally information indicating the selected intra prediction mode for the block) to the entropy encoding unit 270 in the form of syntax elements 266 for inclusion in the encoded picture data 21, for example, so that the video decoder 30 may receive the prediction parameters and use them for decoding.

[0148] Inter Prediction The set (or possible) inter prediction modes depends on the available reference pictures (i.e., for example, previous at least partially decoded pictures stored in DBP230) as well as other inter prediction parameters, such as whether the entire reference picture is used to search for the best matching reference block or only a portion of the reference picture, for example, a search window area around the area of ​​the current block, and / or whether pixel interpolation, for example, half / semi-pel, quarter-pel and / or 1 / 16-pel interpolation, is applied.

[0149] In addition to the prediction modes mentioned above, skip mode, direct mode, and / or other inter prediction modes may be applied.

[0150] For example, in extended merge prediction, the merge candidate list for such a mode is constructed by sequentially including the following five types of candidates: spatial MVPs from spatially neighboring CUs, temporal MVPs from co-located CUs, history-based MVPs from a FIFO table, pair-averaged MVPs, and zero MVs. Also, decoder-side motion vector refinement (DMVR) based on bidirectional matching may be applied to improve the accuracy of MVs in the merge mode. The merge mode with MVD (MMVD) is derived from the merge mode with motion vector difference. An MMVD flag is signaled immediately after sending the skip and merge flags to specify whether the MMVD mode is used for a CU. Also, a CU-level adaptive motion vector resolution (AMVR) scheme may be applied. AMVR allows the MVD of a CU to be coded with different precisions. The MVD of the current CU may be adaptively selected depending on the prediction mode for the current CU. When a CU is coded in merge mode, the combined inter / intra prediction (CIIP) mode may be applied to the current CU. A weighted average of the inter and intra prediction signals is performed to obtain the CIIP prediction. In affine motion compensation prediction, the affine motion field of a block is described by motion information of two control points (four parameters) or three control point motion vectors (six parameters). Subblock-based temporal motion vector prediction (SbTMVP) is similar to HEVC's temporal motion vector prediction (TMVP), but predicts the motion vectors of lower CUs within the current CU.Bidirectional optical flow (BDOF), formerly called BIO, is a simpler version that requires much less computation, especially in terms of the number of multiplications and the size of the multipliers. Regarding triangular partitioning modes, in such modes, a CU is evenly divided into two triangular partitions using either diagonal or anti-diagonal partitioning. Furthermore, bi-prediction mode is extended from simple averaging to allow for weighted averaging of two prediction signals.

[0151] The inter prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (MC) unit (neither of which are shown in FIG. 2). The motion estimation unit may be configured to receive or obtain, 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 already reconstructed blocks, e.g., reconstructed blocks of one or more other / different already decoded pictures 231. For example, a video sequence may include the current picture and the already decoded picture 231, or in other words, the current picture and the already decoded picture 231 may be part of or form a sequence of pictures that form a video sequence.

[0152] The encoder 20 may be configured to, for example, select a reference block from multiple reference blocks of the same or different pictures among multiple other pictures, and provide the reference picture (or reference picture index) and / or an offset (spatial offset) between the position (x, y coordinates) of the reference block and the position of the current block as an inter-prediction parameter to the motion estimation unit. This offset is also called a motion vector (MV).

[0153] The motion compensation unit is configured to obtain, e.g., receive, inter prediction parameters and perform inter prediction based on or using the inter prediction parameters to obtain the inter prediction block 265. The motion compensation performed by the motion compensation unit may include fetching or generating a prediction block based on a motion / block vector determined by motion estimation, possibly performing interpolation with sub-pixel accuracy. Interpolation filtering may generate additional pixel samples from known pixel samples, thus potentially increasing the number of candidate prediction blocks that may be used to code the picture block. Upon receiving a motion vector for the PU of the current picture block, the motion compensation unit may find the prediction block to which the motion vector points in one of the reference picture lists.

[0154] The motion compensation unit may also generate syntax elements associated with the blocks and video slices for use by video decoder 30 in decoding picture blocks of the video slices. In addition to, or as an alternative to, slices and their respective syntax elements, tile groups and / or tiles and their respective syntax elements may be generated or used.

[0155] Entropy Coding The entropy coding unit 270 is configured to apply, for example, an entropy coding algorithm or scheme (e.g., a variable length coding (VLC) scheme, a context adaptive VLC scheme (CAVLC), an arithmetic coding scheme, binarization, context adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, or another entropy coding method or technique) or bypass (uncompressed) to the quantized coefficients 209, the inter-prediction parameters, the intra-prediction parameters, the loop filter parameters (such as a set of ALF parameters), and / or other syntax elements to obtain coded picture data 21 that may be output via an output 272, for example, in the form of coded bitstream 21, such that, for example, video decoder 30 may receive the parameters and use them for decoding. The encoded bitstream 21 may be transmitted to the video decoder 30 or stored in memory for later transmission or retrieval by the video decoder 30 .

[0156] Other structural variations of the video encoder 20 may be used to encode the video stream. For example, a non-transform-based encoder 20 may directly quantize the residual signal for a particular block or frame without a transform processing unit 206. In another implementation, the encoder 20 may have the quantization unit 208 and the inverse quantization unit 210 combined into a single unit.

[0157] Decoder and decoding method 3 shows an example of a video decoder 30 configured to implement the techniques of the present application. The video decoder 30 is configured to receive coded picture data 21 (e.g., coded bitstream 21), e.g., coded by encoder 20, to obtain a decoded picture 331. The coded picture data or bitstream includes information for decoding the coded picture data, e.g., data representing picture blocks of coded video slices (and / or tile groups or tiles) and associated syntax elements.

[0158] 3, decoder 30 includes an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (e.g., summer 314), a loop filter 320, a decoded picture buffer (DBP) 330, a mode application unit 360, an inter prediction unit 344, and an intra prediction unit 354. Inter prediction unit 344 may be or include a motion compensation unit. Video decoder 30, in some examples, may perform a decoding path that is generally the reverse of the encoding path described in connection with video encoder 100 of FIG. 2.

[0159] As described in connection with encoder 20, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, loop filter 220, decoded picture buffer (DPB) 230, inter prediction unit 344, and intra prediction unit 354 are also considered to form a “built-in decoder” of video encoder 20. Thus, inverse quantization unit 310 210, inverse transform processing unit 312 may be functionally identical to inverse transform processing unit 212, reconstruction unit 314 may be functionally identical to reconstruction unit 214, loop filter 320 may be functionally identical to loop filter 220, and decoded picture buffer 330 may be functionally identical to decoded picture buffer 230. Accordingly, the descriptions given with respect to the respective units and functions of video 20 encoder apply mutatis mutandis to the respective units and functions of video decoder 30.

[0160] Entropy Decoding The entropy decoding unit 304 is configured to parse the bitstream 21 (or generally the coded picture data 21) and, e.g., perform entropy decoding on the coded picture data 21 to obtain, e.g., quantized coefficients 309 and / or decoded coding parameters (not shown in FIG. 3 ), e.g., any or all of inter-prediction parameters (e.g., reference picture indices and motion vectors), intra-prediction parameters (e.g., intra-prediction modes or indices), transform parameters, quantization parameters, loop filter parameters, and / or other syntax elements. The entropy decoding unit 304 may be configured to apply a decoding algorithm or scheme corresponding to the encoding scheme described in connection with the entropy coding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide the inter-prediction parameters, intra-prediction parameters, and / or other syntax elements to the mode application unit 360 and to provide other parameters to 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 as an alternative to slices and their respective syntax elements, tile groups and / or tiles and their respective syntax elements may be received and / or used.

[0161] inverse quantization Inverse quantization unit 310 may be configured to receive a quantization parameter (QP) (or information generally related to inverse quantization) and quantized coefficients from encoded picture data 21 (e.g., by parsing and / or decoding by entropy decoding unit 304), and apply inverse quantization to the decoded quantized coefficients 309 based on the quantization parameter to obtain dequantized coefficients 311, which may also be referred to as transform coefficients 311. The inverse quantization process may include using the quantization parameter determined by video encoder 20 for each video block within a video slice (or tile or tile group) to determine the degree of quantization and, similarly, the degree of inverse quantization to be applied.

[0162] Inverse transformation The inverse transform processing unit 312 may be configured to receive the dequantized coefficients 311, also referred to as transform coefficients 311, and apply a transform to the dequantized coefficients 311 to obtain reconstructed residual blocks 213 in the sample domain. The reconstructed residual blocks 213 may also be referred to as transform blocks 213. The transform may be an inverse transform, e.g., an inverse DCT, an inverse DST, an inverse integer transform, or a conceptually similar inverse transform process. The inverse transform processing unit 312 may further be configured to receive transform parameters or corresponding information from the coded picture data 21 (e.g., by parsing and / or decoding, e.g., by the entropy decoding unit 304) to determine the transform to apply to the dequantized coefficients 311.

[0163] Rebuild The reconstruction unit 314 (e.g., an adder or summer 314) may be configured to add the reconstructed residual block 313 to the prediction block 365, for example, by adding the sample values ​​of the reconstructed residual block 313 and the sample values ​​of the prediction block 365, to obtain a reconstructed block 315 in the sample domain.

[0164] filtering A loop filter unit 320 (either in the coding loop or after the coding loop) is configured to filter the reconstructed block 315 to obtain a filtered block 321, for example, to smooth pixel transitions or otherwise improve video quality. The loop filter unit 320 may include one or more loop filters, such as a deblocking filter, a sample adaptive offset (SAO) filter, or one or more other filters, for example, an adaptive loop filter (ALF), a noise suppression filter (NSF), or any combination thereof. In an example, the loop filter unit 220 may include a deblocking filter, an SAO filter, and an ALF filter. The order of the filtering processes may be deblocking filter, SAO, and ALF. In another example, a process called luma mapping with chroma scaling (LMCS) (i.e., adaptive in-loop reshaper) is added. This process is performed before deblocking. In another example, the deblocking filter process may also be applied to interior sub-block edges, e.g., affine sub-block edges, ATMVP sub-block edges, sub-block transform (SBT) edges, and intra-sub-partition (ISP) edges. Although loop filter unit 320 is shown in FIG. 3 as being an in-loop filter, in other configurations, loop filter unit 320 may be implemented as a post-loop filter.

[0165] Decoded Picture Buffer The decoded video blocks 321 of the picture are then stored in a decoded picture buffer 330, which stores the decoded picture 331 as a reference picture for subsequent motion compensation with respect to other pictures and / or for output on a display, respectively.

[0166] The decoder 30 is configured to output the decoded pictures 311 for presentation or viewing to a user, for example via an output 312.

[0167] prediction The inter prediction unit 344 may be identical to the inter prediction unit 244 (especially the motion compensation unit), and the intra prediction unit 354 may be functionally identical to the inter prediction unit 254, and performs the partitioning or partitioning decision and prediction based on the partitioning and / or prediction parameters or respective information received from the decoded picture data 21 (e.g., by analyzing and / or decoding by the entropy decoding unit 304). The mode application unit 360 may be configured to perform prediction (intra or inter prediction) for each block based on the (filtered or unfiltered) reconstructed picture, block, or respective sample to obtain a prediction block 365.

[0168] When a video slice is coded as an intra-coded (I) slice, intra prediction unit 354 of mode application unit 360 is configured to generate a predictive block 365 for a picture block of the current video slice based on the signaled intra prediction mode and data from already decoded blocks of the current picture. When a video picture is coded as an inter-coded (i.e., B or P) slice, inter prediction unit 344 (e.g., a motion compensation unit) of mode application unit 360 is configured to generate a predictive block 365 for a video block of the current video slice based on the motion vector and other syntax elements received from entropy decoding unit 304. For inter prediction, the predictive block may be generated from one of the reference pictures in one of the reference picture lists. Video decoder 30 may construct the reference frame lists, List 0 and List 1, using a default construction technique based on the reference pictures stored in DPB 330. The same or similar may apply for or by embodiments that use tile groups (e.g., video tile groups) and / or tiles (e.g., video tiles) in addition to or as an alternative to slices (e.g., video slices); for example, video may be coded using I, P, or B tile groups and / or tiles.

[0169] Mode application unit 360 is configured to determine prediction information for video blocks of the current video slice by parsing motion vectors or related information and other syntax elements, and to use the prediction information to generate a predictive block for the current video block being decoded. For example, mode application unit 360 uses some of the received syntax elements to determine the prediction mode (e.g., intra or inter prediction) used to code the video blocks of the video slice, the slice type for inter prediction (e.g., B slice, P slice, or GPB slice), construction information for one or more of the reference picture lists for the slice, motion vectors for each inter-coded video block of the slice, the status of inter prediction for each inter-coded video block of the slice, and other information for decoding video blocks in the current video slice. The same or similar may apply for or by embodiments that use tile groups (e.g., video tile groups) and / or tiles (e.g., video tiles) in addition to or as an alternative to slices (e.g., video slices); e.g., video may be coded using I, P, or B tile groups and / or tiles.

[0170] The embodiment of video decoder 30 shown in FIG. 3 may be configured to partition and / or decode pictures by using slices (also referred to as video slices), where a picture may be partitioned into or decoded using one or more (generally non-overlapping) slices, each of which may include one or more blocks (e.g., CTUs) or one or more groups of blocks (e.g., tiles (H.265 / HEVC and VVC) or bricks (VVC)).

[0171] The embodiment of video decoder 30 shown in FIG. 3 may be configured to partition and / or decode a picture by using slices / tile groups (also referred to as video tile groups) and / or tiles (also referred to as video tiles), where a picture may be partitioned into or decoded using one or more (generally non-overlapping) slice / tile groups, where each slice / tile group may include, for example, one or more blocks (e.g., CTUs) or one or more tiles, where each tile may, for example, be rectangular in shape and may include one or more blocks (e.g., CTUs), e.g., full or fractional blocks.

[0172] Other variations of video decoder 30 may be used to decode encoded picture data 21. For example, decoder 30 may generate an output video stream without loop filtering unit 320. For example, a non-transform-based decoder 30 may directly inverse quantize the residual signal for a particular block or frame without inverse transform processing unit 312. In another implementation, video decoder 30 may have inverse quantization unit 310 and inverse transform processing unit 312 combined into a single unit.

[0173] It should be understood that in the encoder 20 and the decoder 30, the processing result of the current step may be further processed and then output to the next step. For example, after interpolation filtering, motion vector derivation, or loop filtering, further operations such as clip or shift may be performed on the processing result of the interpolation filtering, motion vector derivation, or loop filtering.

[0174] It should be noted that further operations may be applied to the derived motion vector of the current block (including, but not limited to, control point motion vectors in affine mode, lower-block motion vectors in affine, planar, and ATMVP modes, temporal motion vectors, etc.). For example, the value of a motion vector is constrained to a predetermined range according to its representation bits. If the representation bits of a motion vector are bitDepth, the range is -2^(bitDepth-1) to 2^(bitDepth-1)-1, where "^" means exponentiation. For example, if bitDepth is set equal to 16, the range is -32768 to 32767, and if bitDepth is set equal to 18, the range is -131072 to 131071. For example, the values ​​of the derived motion vectors (e.g., the MVs of four 4x4 sub-blocks in one 8x8 block) are constrained so that the maximum difference between the integer parts of the MVs of the four 4x4 sub-blocks is no more than N pixels, such as no more than 1 pixel. Here, we provide two methods for constraining the motion vectors according to bitDepth.

[0175] 4 is a schematic diagram of a video coding device 400 according to an embodiment of the present disclosure. The video coding device 400 is suitable for implementing the disclosed embodiments as described herein. In an 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.

[0176] Video coding device 400 includes an incoming 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 outgoing port 450 (or output port 450) for transmitting data, and a memory 460 for storing data. Video coding device 400 may also include optical-electrical (OE) and electrical-optical (EO) components coupled to the incoming port 410, receiver unit 420, transmitter unit 440, and outgoing port 450 for emitting or receiving optical or electrical signals.

[0177] The processor 430 is implemented by hardware and software. The processor 430 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor), FPGA, ASIC, and DSP. The processor 430 communicates with the incoming port 410, the receiver unit 420, the transmitter unit 440, the outgoing port 450, and the memory 460. The processor 430 includes a coding module 470. The coding module 470 implements the disclosed embodiments described above. For example, the coding module 470 implements, processes, prepares, or provides various coding operations. Thus, the inclusion of the coding module 470 significantly improves the functionality of the video coding device 400 and results in the transition of the video coding device 400 to different states. Alternatively, the coding module 470 is implemented as instructions stored in the memory 460 and executed by the processor 430.

[0178] Memory 460 may include one or more disks, tape drives, and solid-state drives, and may be used to store programs when such programs are selected for execution, as well as an overflow data storage device for storing instructions and data read during execution of the programs. 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).

[0179] FIG. 5 is a simplified block diagram of an apparatus 500 that may be used as either or both of source device 12 and destination device 14 of FIG. 1, according to an example embodiment.

[0180] Processor 502 of apparatus 500 may be a central processing unit. Alternatively, processor 502 may be any other type of device or devices, existing or later developed, that are capable of manipulating or processing information. While the disclosed implementations may be performed by a single processor, e.g., processor 502, as shown, speed and efficiency advantages may be realized by using two or more processors.

[0181] The memory 504 of the apparatus 500 may, in implementation, be a read-only memory (ROM) device or a random-access memory (RAM) device. Any other suitable type of storage device may be used as the memory 504. The memory 504 may include code and data 506 accessed by the processor 502 using a bus 512. The memory 504 may further include an operating system 508 and application programs 510, which include at least one program that enables the processor 502 to perform the methods described herein. For example, the application programs 510 may include applications 1 through N, further including a video coding application that performs the methods described herein.

[0182] The apparatus 500 may also include one or more output devices, such as a display 518. The display 518, in one example, may be a touch-sensitive display that combines a display with touch-sensing elements operable to sense touch input. The display 518 may be coupled to the processor 502 via the bus 512.

[0183] Although shown here as a single bus, bus 512 of device 500 may be comprised of multiple buses. Additionally, secondary storage 514 may be directly coupled to other components of device 500 or may be accessed over a network, and may include a single integrated unit such as a memory card or multiple units such as multiple memory cards. Thus, device 500 may be implemented in a wide variety of configurations.

[0184] Decoder Parameter Set (DPS) A syntax structure is proposed to include the maximum number of sub-layers (similar to HEVC) and a profile_level( ) syntax structure that indicates the profile and level of decoders that can decode the bitstream and contains constraints that apply to the bitstream.

[0185] An example syntax table for DPS is shown below.

[0186] [Table 1]

[0187] The DPS raw byte sequence payload (RBSP) is made available to the decoding process before it is referenced and is contained in at least one AU with a temporal identifier (TemporalId) equal to 0 or is provided by external means. NOTE 1 - DPS NAL units are required to be available to the decoding process (either in the bitstream or by external means) before they can be referenced. However, DPS RBSPs contain information that is not necessary for the operation of the decoding process as specified in Sections 2 through 9 of this specification.

[0188] dps_decoding_parameter_set_id identifies the DPS for reference by other syntax elements. The value of dps_decoding_parameter_set_id shall be greater than 0.

[0189] dps_max_sublayers_minus1 plus 1 specifies the maximum number of temporal sublayers that may exist in each CVS layer that references the DPS. The value of dps_max_sublayers_minus1 is in the range 0 to 6, inclusive.

[0190] dps_reserved_zero_5bits is equal to 0 in bitstreams conforming to this version of this specification. Other values ​​of dps_reserved_zero_5bits are reserved for future use by ITU-T | ISO / IEC.

[0191] dps_num_ptls_minus1 plus 1 specifies the number of profile_tier_level() syntax structures in the DPS.

[0192] When two or more profile_tier_level( ) syntax structures exist in a DPS, it is a requirement of bitstream conformance that each CVS in the bitstream conforms to at least one of the profile_tier_level( ) syntax structures.

[0193] dps_extension_flag equal to 0 specifies that the dps_extension_data_flag syntax element is not present in the DPS RBSP syntax structure. dps_extension_flag equal to 1 specifies that the dps_extension_data_flag syntax element is present in the DPS RBSP syntax structure.

[0194] dps_extension_data_flag may have any value. The presence and value of dps_extension_data_flag does not affect a decoder's conformance with the profile specified in Appendix A. Decoders conforming to this version of this specification ignore all dps_extension_data_flag syntax elements.

[0195] Sequence Parameter Set RBSP Syntax

[0196] [Table 2]

[0197] sps_ptl_dpb_hrd_params_present_flag equal to 1 specifies that the profile_tier_level() and dpb_parameters() syntax structures are present in the SPS, and that the general_hrd_parameters() and ols_hrd_parameters() syntax structures may also be present in the SPS. sps_ptl_dpb_hrd_params_present_flag equal to 0 specifies that none of these four syntax structures are present in the SPS. The value of sps_ptl_dpb_hrd_params_present_flag is equal to vps_independent_layer_flag[ GeneralLayerIdx[ nuh_layer_id ] ].

[0198] If vps_independent_layer_flag[ GeneralLayerIdx[ nuh_layer_id ] ] is equal to 1, the variable MaxDecPicBuffMinus1 is set equal to max_dec_pic_buffering_minus1[ sps_max_sublayers_minus1 ] of the dpb_parameters() syntax structure in the SPS. Otherwise, MaxDecPicBuffMinus1 is set equal to max_dec_pic_buffering_minus1[ sps_max_sublayers_minus1 ] of the layer_nonoutput_dpb_params_idx[ GeneralLayerIdx[ nuh_layer_id ] ]th dpb_parameters() syntax structure in the VPS.

[0199] General Profile, Tier, and Level Syntax

[0200] [Table 3]

[0201] General Profile, Tier, and Level Semantics The profile_tier_level( ) syntax structure provides level information and, optionally, profile, tier, subprofile, and general constraint information.

[0202] When the profile_tier_level() syntax structure is included in a DPS, OlsInScope is an OLS that includes all layers in the entire bitstream that references the DPS. When the profile_tier_level() syntax structure is included in a VPS, OlsInScope is one or more OLSs specified by the VPS. When the profile_tier_level() syntax structure is included in an SPS, OlsInScope is an OLS that includes only the layer that is the lowest layer among the layers that reference the SPS, and this lowest layer is an independent layer.

[0203] general_profile_idc indicates the profile to which OlsInScope conforms as specified in Appendix A. The bitstream shall not contain values ​​of general_profile_idc other than those specified in Appendix A. Other values ​​of general_profile_idc are reserved for future use by ITU-T | ISO / IEC.

[0204] general_tier_flag specifies the tier context for the interpretation of general_level_idc as specified in Appendix A.

[0205] general_level_idc indicates the level to which OlsInScope conforms as specified in Annex A. The bitstream shall not contain values ​​of general_level_idc other than those specified in Annex A. Other values ​​of general_level_idc are reserved for future use by ITU-T | ISO / IEC. NOTE 1 -- A larger value of general_level_idc indicates a higher level. The maximum level signaled in the DPS for an OlsInScope may be higher than the level signaled in the SPS for a CVS contained in the OlsInScope. NOTE 2 - When OlsInScope conforms to multiple profiles, general_profile_idc should indicate the profile that provides the preferred decoded result or preferred bitstream identification information, as determined by the encoder (in a manner not specified herein). NOTE 3 - When the --profile_tier_level() syntax structure is included in the DPS and the CVS of OlsInScope conforms to different profiles, the general_profile_idc and level_idc should indicate the profile and level of the decoder that can decode the OlsInScope.

[0206] num_sub_profiles specifies the number of general_sub_profile_idc[ i ] syntax elements.

[0207] general_sub_profile_idc[ i ] indicates the ith interoperability metadata registered as specified by Rec. ITU-T T.35, the content of which is not specified by this specification.

[0208] sublayer_level_present_flag[ i ] equal to 1 specifies that level information is present in the profile_tier_level( ) syntax structure for the sublayer representation with TemporalId equal to i. sublayer_level_present_flag[ i ] equal to 0 specifies that level information is not present in the profile_tier_level( ) syntax structure for the sublayer representation with TemporalId equal to i.

[0209] ptl_alignment_zero_bit is equal to 0.

[0210] The semantics of the syntax element sublayer_level_idc[ i ] is the same as the syntax element general_level_idc, except that it specifies the inference of non-current values, but applies to sublayer representations whose TemporalId is equal to i.

[0211] When not present, the value of sublayer_level_idc[ i ] is inferred as follows: - sublayer_level_idc[ maxNumSubLayersMinus1 ] is inferred to be equal to general_level_idc in the same profile_tier_level() structure. - for i from maxNumSubLayersMinus1 - 1 to 0, inclusive (in descending order of i values), sublayer_level_idc[ i ] is inferred to be equal to sublayer_level_idc[ i + 1 ].

[0212] Picture Header RBSP Syntax

[0213] [Table 4]

[0214] pic_alf_enabled_present_flag equal to 1 specifies that pic_alf_enabled_flag, pic_num_alf_aps_ids_luma, pic_alf_aps_id_luma[ i ], pic_alf_chroma_idc, and pic_alf_aps_id_chroma are present in the PH. pic_alf_enabled_present_flag equal to 0 specifies that pic_alf_enabled_flag, pic_num_alf_aps_ids_luma, pic_alf_aps_id_luma[ i ], pic_alf_chroma_idc, and pic_alf_aps_id_chroma are not present in the PH. When pic_alf_enabled_present_flag is not present, pic_alf_enabled_present_flag is inferred to be equal to 0.

[0215] pic_alf_enabled_flag equal to 1 specifies that the adaptive loop filter is enabled for all slices associated with the PH and may be applied to the Y, Cb, or Cr color components within the slice. pic_alf_enabled_flag equal to 0 specifies that the adaptive loop filter may be disabled for one, more than one, or all slices associated with the PH. When not present, pic_alf_enabled_flag is inferred to be equal to 0.

[0216] pic_num_alf_aps_ids_luma specifies the number of ALF APSs referenced by the slice associated with the PH.

[0217] pic_alf_aps_id_luma[ i ] specifies the adaptation_parameter_set_id of the i-th ALF APS referenced by the luma component of the slice associated with the PH.

[0218] The value of alf_luma_filter_signal_flag is equal to 1 for APS NAL units with aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to pic_alf_aps_id_luma[ i ].

[0219] pic_alf_chroma_idc equal to 0 specifies that no adaptive loop filter is applied to the Cb and Cr color components. pic_alf_chroma_idc equal to 1 indicates that an adaptive loop filter is applied to the Cb color component. pic_alf_chroma_idc equal to 2 indicates that an adaptive loop filter is applied to the Cr color component. pic_alf_chroma_idc equal to 3 indicates that an adaptive loop filter is applied to the Cb and Cr color components. When pic_alf_chroma_idc is not present, pic_alf_chroma_idc is inferred to be equal to 0.

[0220] pic_alf_aps_id_chroma specifies the adaptation_parameter_set_id of the ALF APS referenced by the chroma component of the slice associated with the PH.

[0221] The value of alf_chroma_filter_signal_flag is equal to 1 for APS NAL units with aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to pic_alf_aps_id_chroma.

[0222] PPS

[0223] [Table 5A] [Table 5B]

[0224] pps_subpic_id_signalling_present_flag equal to 1 specifies that subpicture ID mapping is signaled in the PPS. pps_subpic_id_signalling_present_flag equal to 0 specifies that subpicture ID mapping is not signaled in the PPS. When sps_subpic_id_present_flag is 0 or sps_subpic_id_signalling_present_flag is equal to 1, pps_subpic_id_signalling_present_flag is equal to 0.

[0225] pps_num_subpics_minus1 plus 1 specifies the number of subpictures in the coded picture that reference the PPS.

[0226] It is a bitstream compliance requirement that the value of pps_num_subpic_minus1 be equal to sps_num_subpics_minus1.

[0227] The value of pps_subpic_id_len_minus1 plus 1 specifies the number of bits used to represent the syntax element pps_subpic_id[ i ]. The value of pps_subpic_id_len_minus1 is in the range 0 to 15, inclusive.

[0228] It is a bitstream compliance requirement that the value of pps_subpic_id_len_minus1 be the same for all PPSs referenced by coded pictures within a CLVS.

[0229] pps_subpic_id[ i ] specifies the subpicture ID of the ith subpicture. The length of the pps_subpic_id[ i ] syntax element is pps_subpic_id_len_minus1 + 1 bits.

[0230] no_pic_partition_flag equal to 1 specifies that picture partitioning is not applied to each picture that references a PPS. no_pic_partition_flag equal to 0 specifies that each picture that references a PPS may be partitioned into two or more tiles or slices.

[0231] It is a bitstream compliance requirement that the value of no_pic_partition_flag be the same for all PPSs referenced by coded pictures within a CLVS.

[0232] When the value of sps_num_subpics_minus1 + 1 is greater than 1, it is a requirement for bitstream compliance that the value of no_pic_partition_flag not be equal to 1.

[0233] pps_log2_ctu_size_minus5 plus 5 specifies the luma coding tree block size of each CTU. pps_log2_ctu_size_minus5 is equal to sps_log2_ctu_size_minus5.

[0234] The value of num_exp_tile_columns_minus1 plus 1 specifies the number of tile column widths explicitly provided. The value of num_exp_tile_columns_minus1 is in the range 0 to PicWidthInCtbsY - 1, inclusive. When no_pic_partition_flag is equal to 1, the value of num_exp_tile_columns_minus1 is inferred to be equal to 0.

[0235] The value of num_exp_tile_rows_minus1 plus 1 specifies the number of tile row heights explicitly provided. The value of num_exp_tile_rows_minus1 is in the range 0 to PicHeightInCtbsY - 1, inclusive. When no_pic_partition_flag is equal to 1, the value of num_tile_rows_minus1 is inferred to be equal to 0.

[0236] The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0237] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1.

[0238] rect_slice_flag equal to 0 specifies that the tiles in each slice are in raster scan order and slice information is not signaled in the PPS. rect_slice_flag equal to 1 specifies that the tiles in each slice cover a rectangular area of ​​the picture and slice information is signaled in the PPS. When not present, rect_slice_flag is inferred to be equal to 1. When subpics_present_flag is equal to 1, the value of rect_slice_flag is equal to 1.

[0239] single_slice_per_subpic_flag equal to 1 specifies that each subpicture consists of only one rectangular slice. single_slice_per_subpic_flag equal to 0 specifies that each subpicture may consist of one or more rectangular slices. When subpics_present_flag is equal to 0, single_slice_per_subpic_flag is equal to 0. When single_slice_per_subpic_flag is equal to 1, num_slices_in_pic_minus1 is inferred to be equal to sps_num_subpics_minus1.

[0240] The value of num_slices_in_pic_minus1 plus 1 specifies the number of rectangular slices in each picture that refer to the PPS. The value of num_slices_in_pic_minus1 lies in the range of 0 to MaxSlicesPerPicture - 1, inclusive, where MaxSlicesPerPicture is specified in Appendix A. When no_pic_partition_flag is equal to 1, the value of num_slices_in_pic_minus1 is inferred to be equal to 0.

[0241] A tile_idx_delta_present_flag equal to 0 specifies that no tile_idx_delta values ​​are present in the PPS and all rectangular slices in the picture referencing the PPS are specified in raster order according to the process defined in Section 6.5.1. A tile_idx_delta_present_flag equal to 1 specifies that tile_idx_delta values ​​may be present in the PPS and all rectangular slices in the picture referencing the PPS are specified in the order indicated by the values ​​of tile_idx_delta.

[0242] The value of slice_width_in_tiles_minus1[ i ] plus 1 specifies the width of the i-th rectangular slice in units of tile columns. The value of slice_width_in_tiles_minus1[ i ] lies in the range 0 to NumTileColumns - 1, inclusive. When absent, the value of slice_width_in_tiles_minus1[ i ] is inferred as specified in Section 6.5.1.

[0243] The value of slice_height_in_tiles_minus1[ i ] plus 1 specifies the height of the ith rectangular slice in units of tile rows. The value of slice_height_in_tiles_minus1[ i ] lies in the range 0 to NumTileRows - 1, inclusive. When absent, the value of slice_height_in_tiles_minus1[ i ] is inferred as specified in Section 6.5.1.

[0244] The value of num_slices_in_tile_minus1[ i ] plus 1 specifies the number of slices in the current tile, where the i-th slice contains a subset of CTU rows from a single tile. The value of num_slices_in_tile_minus1[ i ] is in the range 0 to RowHeight[ tileY ] - 1, inclusive, where tileY is the index of the tile row containing the i-th slice. When not present, the value of num_slices_in_tile_minus1[ i ] is inferred to be equal to 0.

[0245] The value of slice_height_in_ctu_minus1[ i ] plus 1 specifies the height of the i-th rectangular slice in units of CTU rows, when the i-th slice contains a subset of CTU rows from a single tile. The value of slice_height_in_ctu_minus1[ i ] is in the range 0 to RowHeight[ tileY ] - 1, inclusive, where tileY is the index of the tile row containing the i-th slice.

[0246] tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When absent, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0.

[0247] 6.5.1 CTB Raster Scan, Tile Scan, and Subpicture Scan Processes The variable NumTileColumns, which specifies the number of tile columns, and the list ColWidth[ i ], for i in the range 0 to NumTileColumn - 1, inclusive, which specifies the width of the ith tile column in CTB units, are derived as follows: remainingWidthInCtbsY = PicWidthInCtbsY for( i = 0; i < num_exp_tile_columns_minus1; i++ ) { colWidth[ i ] = tile_column_width_minus1[ i ] + 1 remainingWidthInCtbsY -= colWidth[ i ] } uniformTileColWidth = tile_column_width_minus1[ num_exp_tile_columns_minus1 ] + 1 (23) while( remainingWidthInCtbsY >= uniformTileColWidth ) { colWidth[ i++ ] = uniformTileColWidth remainingWidthInCtbsY -= uniformTileColWidth } if( remainingWidthInCtbsY > 0 ) colWidth[ i++ ] = remainingWidthInCtbsY NumTileColumns = i

[0248] The variable NumTileRows, which specifies the number of tile rows, and the list RowHeight[ j ], for j ranging from 0 to NumTileRows - 1 inclusive, which specifies the height of the j-th tile row in CTB units, are derived as follows: remainingHeightInCtbsY = PicHeightInCtbsY for( j = 0; j < num_exp_tile_rows_minus1; j++ ) { RowHeight[ j ] = tile_row_height_minus1[ j ] + 1 remainingHeightInCtbsY -= RowHeight[ j ] } uniformTileRowHeight = tile_row_height_minus1[ num_exp_tile_rows_minus1 ] + 1 (24) while( remainingHeightInCtbsY >= uniformTileRowHeight ) { RowHeight[ j++ ] = uniformTileRowHeight remainingHeightInCtbsY -= uniformTileRowHeight } if( remainingHeightInCtbsY > 0 ) RowHeight[ j++ ] = remainingHeightInCtbsY NumTileRows = j

[0249] The variable NumTilesInPic is set equal to NumTileColumns * NumTileRows.

[0250] The list tileColBd[ i ], for i ranging from 0 to NumTileColumns inclusive, specifying the position of the boundary of the ith tile column in CTB units, is derived as follows: for( tileColBd

[0000] = 0, i = 0; i < NumTileColumns; i++ ) tileColBd[ i + 1 ] = tileColBd[ i ] + colWidth[ i ] (25)

[0251] A list tileRowBd[ j ] for j ranging from 0 to NumTileRows inclusive, specifying the position of the boundary of the j-th tile row in CTB units, is derived as follows: for( tileRowBd

[0000] = 0, j = 0; j < NumTileRows; j++ ) tileRowBd[ j + 1 ] = tileRowBd[ j ] + RowHeight[ j ] (26)

[0252] The list CtbToTileColBd[ctbAddrX] for ctbAddrX ranging from 0 to PicWidthInCtbsY inclusive, which specifies the conversion from horizontal CTB addresses to the left tile column boundary in CTB units, is derived as follows: tileX = 0 for( ctbAddrX = 0; ctbAddrX <= PicWidthInCtbsY; ctbAddrX++ ) { if( ctbAddrX == tileColBd[ tileX + 1 ] ) (27) tileX++ CtbToTileColBd[ ctbAddrX ] = tileColBd[ tileX ] }

[0253] The list CtbToTileRowBd[ctbAddrY] for ctbAddrY ranging from 0 to PicHeightInCtbsY inclusive, which specifies the conversion from vertical CTB addresses to the upper tile row boundary in CTB units, is derived as follows: tileY = 0 for( ctbAddrY = 0; ctbAddrY <= PicHeightInCtbsY; ctbAddrY++ ) { if( ctbAddrY == tileRowBd[ tileY + 1 ] ) (28) tileY++ CtbToTileRowBd[ ctbAddrY ] = tileRowBd[ tileY ] } For rectangular slices, a list NumCtuInSlice[i] for i ranging from 0 to num_slices_in_pic_minus1, inclusive, specifying the number of CTUs in the i-th slice, and a matrix CtbAddrInSlice[i][j] for i ranging from 0 to num_slices_in_pic_minus1, inclusive, and j ranging from 0 to NumCtuInSlice[i] - 1, inclusive, specifying the picture raster scan address of the j-th CTB in the i-th slice are derived as follows: if( subpics_present_flag && single_slice_per_subpic_flag ) { for( i = 0; i <= sps_num_subpics_minus1; i++ ) NumCtuInSlice[ i ] = 0 for( i = 0; i < PicSizeInCtbsY; i ++ ) { sliceIdx = CtbToSubPicIdx[ i ] CtbAddrInSlice[ sliceIdx ][ NumCtuInSlice[ sliceIdx ] ] = i NumCtuInSlice[ sliceIdx ]++ } } else { tileIdx = 0 for( i = 0; i <= num_slices_in_pic_minus1; i++ ) NumCtuInSlice[ i ] = 0 for( i = 0; i <= num_slices_in_pic_minus1; i++ ) { tileX = tileIdx % NumTileColumns tileY = tileIdx / NumTileColumns if( i == num_slices_in_pic_minus1 ) { slice_width_in_tiles_minus1[ i ] = NumTileColumns - 1 - tileX slice_height_in_tiles_minus1[ i ] = NumTileRows - 1 - tileY num_slices_in_tile_minus1[ i ] = 0 } if( slice_width_in_tiles_minus1[ i ] == 0 && slice_height_in_tiles_minus1[ i ] == 0 ) { (29) ctbY = tileRowBd[ tileY ] for( j = 0; j < num_slices_in_tile_minus1[ i ]; j++ ) { AddCtbsToSlice( i, tileColBd[ tileX ], tileColBd[ tileX + 1 ], ctbY, ctbY + slice_height_in_ctu_minus1[ i ] + 1 ) ctbY += slice_height_in_ctu_minus1[ i ] + 1 i++ } AddCtbsToSlice( i, tileColBd[ tileX ], tileColBd[ tileX + 1 ], ctbY, tileRowBd[ tileY + 1 ] ) ; } else for( j = 0; j <= slice_height_in_tiles_minus1[ i ]; j++ ); for( k = 0; k <= slice_width_in_tiles_minus1[ i ]; k++ ); AddCtbsToSlice( i, tileColBd[ tileX + k ], tileColBd[ tileX + k + 1 ], tileRowBd[ tileY + j ], tileRowBd[ tileY + j + 1 ] ) ; if( tile_idx_delta_present_flag ) tileIdx += tile_idx_delta[ i ] else { tileIdx += slice_width_in_tiles_minus1[ i ] + 1 if ( tileIdx % NumTileColumns == 0 ) ; tileIdx += slice_height_in_tiles_minus1[ i ] * NumTileColumns }} }} }}

[0254] The key AddCtbsToSlice( sliceIdx, startX, stopX, startY, stopY ) is one of these. for( ctbY = startY ; ctbY < stopY ; ctbY ++ ) ; for( ctbX = startX ; ctbX < stopX ; ctbX++ ) { ; CtbAddrInSlice[ sliceIdx ][ NumCtuInSlice[ sliceIdx ] ] = ctbY * PicWidthInCtbsY + ctbX (30) NumCtuInSlice[ sliceIdx ]++ }

[0255] It is a requirement for a bitstream to be compliant that the value of NumCtuInSlice[ i ] for i in the range 0 to num_slices_in_pic_minus1, inclusive, be greater than 0. It is also a requirement for a bitstream to be compliant that the matrix CtbAddrInSlice[ i ][ j ] for i in the range 0 to num_slices_in_pic_minus1, inclusive, and j in the range 0 to NumCtuInSlice[ i ] - 1, inclusive, contain every CTB address in the range 0 to PicSizeInCtbsY - 1 exactly once.

[0256] The list CtbToSubPicIdx[ctbAddrRs] for ctbAddrRs ranging from 0 to PicSizeInCtbsY - 1, inclusive, which specifies the conversion from CTB addresses to subpicture indices in a picture raster scan, is derived as follows: for( ctbAddrRs = 0; ctbAddrRs < PicSizeInCtbsY; ctbAddrRs++ ) { posX = ctbAddrRs % PicWidthInCtbsY posY = ctbAddrRs / PicWidthInCtbsY CtbToSubPicIdx[ ctbAddrRs ] = -1 for( i = 0; CtbToSubPicIdx[ ctbAddrRs ] < 0 && i <= sps_num_subpics_minus1; i++ ) { (31) if( ( posX >= subpic_ctu_top_left_x[ i ] ) && ( posX < subpic_ctu_top_left_x[ i ] + subpic_width_minus1[ i ] + 1 ) && ( posY >= subpic_ctu_top_left_y[ i ] ) && ( posY < subpic_ctu_top_left_y[ i ] + subpic_height_minus1[ i ] + 1 ) ) CtbToSubPicIdx[ ctbAddrRs ] = i } }

[0257] The lists NumSlicesInSubpic[ i ] and SliceSubpicToPicIdx[ i ][ k ] specifying the number of rectangular slices in the ith subpicture and the picture-level slice index of the kth slice in the ith subpicture are derived as follows: for( j = 0; j <= sps_num_subpics_minus1; j++ ) NumSlicesInSubpic[ j ] = 0 for( i = 0; i <= num_slices_in_pic_minus1; i++ ) { posX = CtbAddrInSlice[ i ]

[0000] % PicWidthInCtbsY posY = CtbAddrInSlice[ i ]

[0000] / PicWidthInCtbsY for( j = 0; j <= sps_num_subpics_minus1; j++ ) { if( ( posX >= subpic_ctu_top_left_x[ j ] ) && (32) ( posX < subpic_ctu_top_left_x[ j ] + subpic_width_minus1[ j ] + 1 ) && ( posY >= subpic_ctu_top_left_y[ j ] ) && ( posY < subpic_ctu_top_left_y[ j ] + subpic_height_minus1[ j ] + 1 ) ) { SliceSubpicToPicIdx[ j ][ NumSlicesInSubpic[ j ] ] = i NumSlicesInSubpic[ j ]++ } } }

[0258] Currently, the DPS has a DPS ID, and there is no restriction on the corresponding relationship between the contents of the DPS NAL units and the ID values.

[0259] Also, there is no restriction on the number of times a DPS may be in the bitstream: if there are many DPSs in the bitstream and they have the same DPS ID, the decoder does not know which DPS to select.

[0260] The level signaled in the DPS should be the worst-case capability of the entire bitstream, and therefore should not be less than the level signaled in the SPS.

[0261] Currently, there are no constraints on the TemporalId of an APS NAL unit and the TemporalId of a picture associated with a picture header (PH). However, when nal_unit_type is equal to PPS_NUT, PREFIX_APS_NUT, or SUFFIX_APS_NUT, the TemporalId is greater than or equal to the TemporalId of the PU that contains the NAL unit, and in bitstream subtraction scenarios, there should be constraints on the TemporalId of an APS NAL unit and the TemporalId of a picture associated with a PH.

[0262] The tile relative variables tile_column_width_minus1[i], tile_row_height_minus1[i], tile_idx_delta[i] should have some constraints applied to them to ensure proper values, as none of these variables for any tile can exceed the extents of the picture. Also, tile column and tile height should be greater than 0.

[0263] Embodiments: Option A: Add the constraint that a DPS can only occur at most once in a bitstream, i.e., a DPS is not required in a bitstream, and if a bitstream contains a DPS, only one DPS can occur in the bitstream.

[0264] The DPS RBSP is made available to the decoding process before it is referenced, and is either contained in at least one AU with TemporalId equal to 0, or is provided by external means.

[0265] NOTE 1 – At most one DPS NAL unit is present in the bitstream.

[0266] NOTE 2 - DPS NAL units are required to be available to the decoding process (either in the bitstream or by external means) before they can be referenced. However, DPS RBSPs contain information that is not necessary for the operation of the decoding process as specified in Sections 2 through 9 of this specification.

[0267] Option B: Add the constraint that all DPS NAL units with a particular value of dps_decoding_parameter_set_id in the bitstream have the same content, in which case one DPS ID cannot hook (correspond) to the content of more than one DPS.

[0268] for example, The DPS RBSP is made available to the decoding process before it is referenced, and is either contained in at least one AU with TemporalId equal to 0, or is provided by external means. NOTE 1 - DPS NAL units are required to be available to the decoding process (either in the bitstream or by external means) before they can be referenced. However, DPS RBSPs contain information that is not necessary for the operation of the decoding process as specified in Sections 2 through 9 of this specification.

[0269] All DPS NAL units with a particular value of dps_decoding_parameter_set_id in a bitstream have the same content.

[0270] Add the constraint that the level signaled in the DPS should be equal to or greater than the level signaled in the SPS.

[0271] general_level_idc indicates the level to which OlsInScope conforms as specified in Annex A. The bitstream shall not contain values ​​of general_level_idc other than those specified in Annex A. Other values ​​of general_level_idc are reserved for future use by ITU-T | ISO / IEC. (1) NOTE 1 -- A larger value of general_level_idc indicates a higher level. The maximum level signaled in the DPS for an OlsInScope is not less than the level signaled in the SPS for a CVS contained in the OlsInScope. (2) NOTE 2 - When OlsInScope conforms to multiple profiles, general_profile_idc should indicate the profile that provides the preferred decoded result or preferred bitstream identification information, as determined by the encoder (in a manner not specified herein). (3) NOTE 3--When the profile_tier_level() syntax structure is included in the DPS and the CVS of OlsInScope conforms to different profiles, the general_profile_idc and level_idc should indicate the profile and level of the decoder that can decode OlsInScope.

[0272] Constraints on ALF NAL units pic_alf_aps_id_luma[ i ] specifies the adaptation_parameter_set_id of the i-th ALF APS referenced by the luma component of the slice associated with the PH.

[0273] The value of alf_luma_filter_signal_flag is equal to 1 for APS NAL units with aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to pic_alf_aps_id_luma[ i ].

[0274] The TemporalId of an APS NAL unit with aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to pic_alf_aps_id_luma[ i ] is less than or equal to the TemporalId of the picture associated with the PH.

[0275] pic_alf_aps_id_chroma specifies the adaptation_parameter_set_id of the ALF APS referenced by the chroma component of the slice associated with the PH.

[0276] The value of alf_chroma_filter_signal_flag is equal to 1 for APS NAL units with aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to pic_alf_aps_id_chroma.

[0277] The TemporalId of an APS NAL unit with aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to pic_alf_aps_id_chroma is less than or equal to the TemporalId of the picture associated with the PH.

[0278] Constraints on tile-relative variables The tile relative variables tile_column_width_minus1[ i ], tile_row_height_minus1[ i ], tile_idx_delta[ i ] should have some constraints placed on these variables to ensure proper values ​​of these variables.

[0279] Option A: The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in units of CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with indices greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. The value of tile_column_width_minus1[ i ] is in the range 0 to PicWidthInCtbsY - 1, inclusive. When not present, a value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0280] For i in the range 0 to num_exp_tile_columns_minus1 - 1, the sum of tile_column_width_minus1[ i ] is less than PicWidthInCtbsY.

[0281] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. The value of tile_row_height_minus1[ i ] is in the range 0 to PicHeightInCtbsY - 1, inclusive. When not present, a value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, the sum of tile_row_height_minus1[ i ] is less than PicHeightInCtbsY.

[0282] Option A': The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0283] For i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY.

[0284] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY.

[0285] Option B: tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When not present, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0. For i in the range of 0 to num_slices_in_pic_minus1 - 1, inclusive, the sum of tile_idx_delta[ i ] is less than NumTilesInPic.

[0286] Option C: Option A + Option B The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in units of CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with indices greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. The value of tile_column_width_minus1[ i ] is in the range 0 to PicWidthInCtbsY - 1, inclusive. When not present, a value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0287] For i in the range 0 to num_exp_tile_columns_minus1 - 1, the sum of tile_column_width_minus1[ i ] is less than PicWidthInCtbsY.

[0288] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. The value of tile_row_height_minus1[ i ] is in the range 0 to PicHeightInCtbsY - 1, inclusive. When not present, a value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, the sum of tile_row_height_minus1[ i ] is less than PicHeightInCtbsY.

[0289] tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When not present, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0. For i in the range of 0 to num_slices_in_pic_minus1 - 1, inclusive, the sum of tile_idx_delta[ i ] is less than NumTilesInPic.

[0290] Option C': Option A' + Option B The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0291] For i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY.

[0292] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY.

[0293] tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When not present, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0. For i in the range of 0 to num_slices_in_pic_minus1 - 1, inclusive, the sum of tile_idx_delta[ i ] is less than NumTilesInPic.

[0294] Option D: (Alternative to Option A') The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0295] For i in the range 0 to num_exp_tile_columns_minus1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY.

[0296] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY.

[0297] Option E: Option D + Option B The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0298] For i in the range 0 to num_exp_tile_columns_minus1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY.

[0299] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY.

[0300] tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When not present, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0. For i in the range of 0 to num_slices_in_pic_minus1 - 1, inclusive, the sum of tile_idx_delta[ i ] is less than NumTilesInPic.

[0301] Option F: (Alternative to Option A') The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0302] For i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY. The value of tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is less than PicWidthInCtbsY.

[0303] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY. The value of tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is less than PicHeightInCtbsY.

[0304] Option G: Option F + Option B The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0305] For i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY. The value of tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is less than PicWidthInCtbsY.

[0306] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY. The value of tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is less than PicHeightInCtbsY.

[0307] tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When not present, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0. For i in the range of 0 to num_slices_in_pic_minus1 - 1, inclusive, the sum of tile_idx_delta[ i ] is less than NumTilesInPic.

[0308] In the above, the statement regarding two values ​​M and N that "M is less than or equal to N" can also be interpreted as "M does not exceed N."

[0309] The different implementations of this application are as follows:

[0310] First embodiment [DPS ID] Currently, the DPS has a DPS ID, and there are no restrictions on the corresponding relationship between the contents of the DPS NAL units and the ID values.

[0311] Also, there is no restriction on the number of times a DPS may be in the bitstream: if there are many DPSs in the bitstream and they have the same DPS ID, the decoder does not know which DPS to select.

[0312] To deal with this problem, two options are provided.

[0313] Option A: Add the constraint that a DPS can only be present at most once in a bitstream, i.e., a DPS is not required in a bitstream, and if a bitstream contains a DPS, only one DPS can be present in the bitstream.

[0314] The DPS RBSP is made available to the decoding process before it is referenced, and is either contained in at least one AU with TemporalId equal to 0, or is provided by external means.

[0315] NOTE 1 – At most one DPS NAL unit is present in the bitstream.

[0316] NOTE 2 - DPS NAL units are required to be available to the decoding process (either in the bitstream or by external means) before they can be referenced. However, DPS RBSPs contain information that is not necessary for the operation of the decoding process as specified in Sections 2 through 9 of this specification.

[0317] Option B: Add the constraint that all DPS NAL units with a particular value of dps_decoding_parameter_set_id in the bitstream have the same content, in which case one DPS ID cannot hook (correspond) to the content of more than one DPS.

[0318] for example, The DPS RBSP is made available to the decoding process before it is referenced, and is either contained in at least one AU with TemporalId equal to 0, or is provided by external means. NOTE 1 - DPS NAL units are required to be available to the decoding process (either in the bitstream or by external means) before they can be referenced. However, DPS RBSPs contain information that is not necessary for the operation of the decoding process as specified in Sections 2 through 9 of this specification.

[0319] All DPS NAL units with a particular value of dps_decoding_parameter_set_id in a bitstream have the same content.

[0320] Second embodiment [DPS level] The level signaled in the DPS should be or represent the worst-case capacity of the entire bitstream, and therefore should be equal to or greater than the level signaled in the SPS. A constraint may be imposed that the level signaled in the DPS should not be less than the level signaled in the SPS.

[0321] general_level_idc indicates the level to which OlsInScope conforms as specified in Annex A. The bitstream shall not contain values ​​of general_level_idc other than those specified in Annex A. Other values ​​of general_level_idc are reserved for future use by ITU-T | ISO / IEC. NOTE 1 -- A larger value of general_level_idc indicates a higher level. The maximum level signaled in the DPS for an OlsInScope is not less than the level signaled in the SPS for a CVS contained in the OlsInScope. NOTE 2 - When OlsInScope conforms to multiple profiles, general_profile_idc should indicate the profile that provides the preferred decoded result or preferred bitstream identification information, as determined by the encoder (in a manner not specified herein). NOTE 3 - When the --profile_tier_level() syntax structure is included in the DPS and the CVS of OlsInScope conforms to different profiles, the general_profile_idc and level_idc should indicate the profile and level of the decoder that can decode the OlsInScope.

[0322] Third embodiment [ALF nalu's tid] Currently, there are no constraints on the TemporalId of an APS NAL unit and the TemporalId of a picture associated with a PH. However, when nal_unit_type is equal to PPS_NUT, PREFIX_APS_NUT, or SUFFIX_APS_NUT, the TemporalId must be greater than or equal to the TemporalId of the PU that contains the NAL unit, and in a bitstream subtraction scenario, there should be constraints on the TemporalId of an APS NAL unit and the TemporalId of a picture associated with a PH.

[0323] Constraints on ALF NAL units pic_alf_aps_id_luma[ i ] specifies the adaptation_parameter_set_id of the i-th ALF APS referenced by the luma component of the slice associated with the PH.

[0324] The value of alf_luma_filter_signal_flag is equal to 1 for APS NAL units with aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to pic_alf_aps_id_luma[ i ].

[0325] The TemporalId of an APS NAL unit with aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to pic_alf_aps_id_luma[ i ] is less than or equal to the TemporalId of the picture associated with the PH.

[0326] pic_alf_aps_id_chroma specifies the adaptation_parameter_set_id of the ALF APS referenced by the chroma component of the slice associated with the PH.

[0327] The value of alf_chroma_filter_signal_flag is equal to 1 for APS NAL units with aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to pic_alf_aps_id_chroma.

[0328] The TemporalId of an APS NAL unit with aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to pic_alf_aps_id_chroma is less than or equal to the TemporalId of the picture associated with the PH.

[0329] Fourth embodiment [tile] The tile relative variables tile_column_width_minus1[ i ], tile_row_height_minus1[ i ], tile_idx_delta[ i ] should have some constraints placed on these variables to ensure proper values ​​of these variables.

[0330] This is because these variables for any tile cannot exceed the extents of the picture. Also, tile columns and tile height should be greater than 0.

[0331] Option A: The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in units of CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with indices greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. The value of tile_column_width_minus1[ i ] is in the range 0 to PicWidthInCtbsY - 1, inclusive. When not present, a value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1. For i in the range 0 to num_exp_tile_columns_minus1 - 1, the sum of tile_column_width_minus1[ i ] is less than PicWidthInCtbsY.

[0332] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. The value of tile_row_height_minus1[ i ] is in the range 0 to PicHeightInCtbsY - 1, inclusive. When not present, a value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, the sum of tile_row_height_minus1[ i ] is less than PicHeightInCtbsY.

[0333] Option A': The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1. For i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY.

[0334] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY.

[0335] Option B: Verify that a rectangular slice should be included in the picture.

[0336] tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When not present, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0. For i in the range of 0 to num_slices_in_pic_minus1 - 1, inclusive, the sum of tile_idx_delta[ i ] is less than NumTilesInPic.

[0337] Option C: Option A + Option B The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in units of CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with indices greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. The value of tile_column_width_minus1[ i ] is in the range 0 to PicWidthInCtbsY - 1, inclusive. When not present, a value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1. For i in the range 0 to num_exp_tile_columns_minus1 - 1, the sum of tile_column_width_minus1[ i ] is less than PicWidthInCtbsY.

[0338] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. The value of tile_row_height_minus1[ i ] is in the range 0 to PicHeightInCtbsY - 1, inclusive. When not present, a value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, the sum of tile_row_height_minus1[ i ] is less than PicHeightInCtbsY.

[0339] tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When not present, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0. For i in the range of 0 to num_slices_in_pic_minus1 - 1, inclusive, the sum of tile_idx_delta[ i ] is less than NumTilesInPic.

[0340] Option C': Option A' + Option B The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1. For i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY.

[0341] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY.

[0342] tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When not present, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0. For i in the range of 0 to num_slices_in_pic_minus1 - 1, inclusive, the sum of tile_idx_delta[ i ] is less than NumTilesInPic.

[0343] Option D: (Alternative to Option A') The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0344] For i in the range 0 to num_exp_tile_columns_minus1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY.

[0345] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY.

[0346] Option E: Option D + Option B The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0347] For i in the range 0 to num_exp_tile_columns_minus1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY.

[0348] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY.

[0349] tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When not present, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0. For i in the range of 0 to num_slices_in_pic_minus1 - 1, inclusive, the sum of tile_idx_delta[ i ] is less than NumTilesInPic.

[0350] Option F: (Alternative to Option A') The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0351] For i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY. The value of tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is less than PicWidthInCtbsY.

[0352] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY. The value of tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is less than PicHeightInCtbsY.

[0353] Option G: Option F + Option B The value of tile_column_width_minus1[ i ] plus 1 specifies the width of the ith tile column in CTBs, for i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive. tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is used to derive the width of tile columns with index greater than or equal to num_exp_tile_columns_minus1 as specified in Section 6.5.1. When not present, the value of tile_column_width_minus1

[0000] is inferred to be equal to PicWidthInCtbsY - 1.

[0354] For i in the range 0 to num_exp_tile_columns_minus1 - 1, inclusive, the sum of (tile_column_width_minus1[ i ] + 1) is less than or equal to PicWidthInCtbsY. The value of tile_column_width_minus1[ num_exp_tile_columns_minus1 ] is less than PicWidthInCtbsY.

[0355] The value of tile_row_height_minus1[ i ] plus 1 specifies the height of the ith tile row in CTBs, for i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive. tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is used to derive the height of tile rows with index greater than or equal to num_exp_tile_rows_minus1 as specified in Section 6.5.1. When not present, the value of tile_row_height_minus1

[0000] is inferred to be equal to PicHeightInCtbsY - 1. For i in the range 0 to num_exp_tile_rows_minus1 - 1, inclusive, the sum of (tile_row_height_minus1[ i ] + 1) is less than or equal to PicHeightInCtbsY. The value of tile_row_height_minus1[ num_exp_tile_rows_minus1 ] is less than PicHeightInCtbsY.

[0356] tile_idx_delta[ i ] specifies the tile index difference between the ith and (i + 1)th rectangular slices. The value of tile_idx_delta[ i ] is in the range of -NumTilesInPic + 1 to NumTilesInPic - 1, inclusive. When not present, the value of tile_idx_delta[ i ] is inferred to be equal to 0. In all other cases, the value of tile_idx_delta[ i ] is not equal to 0. For i in the range of 0 to num_slices_in_pic_minus1 - 1, inclusive, the sum of tile_idx_delta[ i ] is less than NumTilesInPic.

[0357] In the above, the statement regarding two values ​​M and N that "M is less than or equal to N" can also be interpreted as "M does not exceed N."

[0358] (1) The constraint that a DPS can occur at most once in a bitstream, and the mechanism by which all DPS NAL units with a particular value of dps_decoding_parameter_set_id in a bitstream have the same content when the bitstream can have more than one DPS, reduce or eliminate ambiguity at the decoder.

[0359] (2) The level signaled in the DPS should be the worst-case capability of the entire bitstream, and therefore should not be less than the level signaled in the SPS. Otherwise, the parameters in the DPS are meaningless.

[0360] (3) Restrictions on the TID of ALF NALUs are added to ensure that bitstream subtraction works properly depending on the TID of the NALU.

[0361] (4) From a compliance perspective, tile-relative variables should be constrained to valid ranges to ensure that each tile has at least one CTU, each tile should be contained by a picture, and rectangular slices should be contained by a picture.

[0362] The following is a description of the application of the encoding and decoding methods shown in the above embodiments and the systems that use them.

[0363] 6 is a block diagram showing a content supply system for realizing a content distribution service. The content supply system 3100 includes a capture device 3102, a terminal device 3106, and optionally a display 3126. The capture device 3102 communicates with the terminal device 3106 via a communication link 3104. The communication link may include the communication channel 13 described above. Examples of the communication link 3104 include, but are not limited to, WIFI, Ethernet, cable, wireless (3G / 4G / 5G), USB, or any combination thereof.

[0364] The capture device 3102 may generate data and encode the data according to the encoding method described in the above embodiment. Alternatively, the capture device 3102 may deliver the data to a streaming server (not shown), which encodes the data and transmits the encoded data to the terminal device 3106. Examples of the capture device 3102 include, but are not limited to, a camera, a smartphone or smart pad, a computer or laptop, a video conferencing system, a PDA, an in-vehicle device, or any combination thereof. For example, the capture device 3102 may include the source device 12 described above. When the data includes video, a video encoder 20 included in the capture device 3102 may actually perform the video encoding process. When the data includes audio (i.e., voice), an audio encoder included in the capture device 3102 may actually perform the audio encoding process. In some practical scenarios, the capture device 3102 delivers the encoded video and audio data by multiplexing them together. In other practical scenarios, for example, in a video conferencing system, the encoded audio data and the encoded video data are not multiplexed. The capture device 3102 delivers the encoded audio data and the encoded video data separately to the terminal device 3106 .

[0365] In the content supply system 3100, a terminal device 3106 receives and plays the encoded data. The terminal device 3106 can be a device having data reception and restoration capabilities, such as a smartphone or smart pad 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video recorder (DVR) 3112, a TV 3114, a set-top box (STB) 3116, a video conferencing system 3118, a video surveillance system 3120, a personal digital assistant (PDA) 3122, an in-vehicle device 3124, or any combination thereof, that can decode the above-mentioned encoded data. For example, the terminal device 3106 can include the above-mentioned destination device 14. 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.

[0366] For terminal devices with a display, such as a smartphone or smart pad 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video recorder (DVR) 3112, a TV 3114, a personal digital assistant (PDA), or an in-vehicle device 3124, the terminal device can provide the decoded data to its display. For terminal devices without a display, such as an STB 3116, a video conferencing system 3118, or a video surveillance system 3120, an external display 3126 is contacted to receive and show the decoded data.

[0367] When each device in this system performs encoding or decoding, the picture encoding device or picture decoding device shown in the above embodiments may be used.

[0368] 7 is a diagram illustrating the structure of an example of a terminal device 3106. After the terminal device 3106 receives a stream from the capture device 3102, a protocol progression unit 3202 analyzes the transmission protocol of the stream. Examples of protocols include, but are not limited to, Real Time Streaming Protocol (RTSP), Hypertext Transfer Protocol (HTTP), HTTP Live Streaming Protocol (HLS), MPEG-DASH, Real Time Transport Protocol (RTP), Real Time Messaging Protocol (RTMP), or any type of combination thereof.

[0369] After the protocol progression unit 3202 processes the stream, a stream file is generated. The file is output to the demultiplexing unit 3204. The demultiplexing unit 3204 can separate the multiplexed data into encoded audio data and encoded video data. As mentioned above, in some scenarios, for example, in a video conferencing system, the encoded audio data and encoded video data are not multiplexed. In this situation, the encoded data is sent to the video decoder 3206 and the audio decoder 3208 without passing through the demultiplexing unit 3204.

[0370] The demultiplexing process generates a video elementary stream (ES), an audio ES, and optionally subtitles. A video decoder 3206, which includes the video decoder 30 described in the above embodiment, decodes the video ES using the decoding method shown in the above embodiment to generate video frames, and supplies this data to a synchronization unit 3212. An audio decoder 3208 decodes the audio ES to generate audio frames, and supplies this data to the synchronization unit 3212. Alternatively, the video frames may be stored in a buffer (not shown in FIG. 7) before being supplied to the synchronization unit 3212. Similarly, the audio frames may be stored in a buffer (not shown in FIG. 7) before being supplied to the synchronization unit 3212.

[0371] The synchronization unit 3212 synchronizes video and audio frames and provides 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 a syntax that uses timestamps for the presentation of the coded audio and visual data as well as timestamps for the delivery of the data stream itself.

[0372] If subtitles are included in the stream, the subtitle decoder 3210 decodes the subtitles, synchronizes the subtitles with the video and audio frames, and provides the video / audio / subtitles to the video / audio / subtitle display 3216.

[0373] The embodiments of the present invention are not limited to the above-mentioned systems, and either the picture encoding device or the picture decoding device of the above-mentioned embodiments may be incorporated into other systems, for example, a system in an automobile.

[0374] Mathematical Operators The mathematical operators used in this application are similar to those used in the C programming language. However, the results of integer division and arithmetic shift operations are more strictly defined, and additional operations such as exponentiation and division of real values ​​are defined. The numbering and counting rules generally start from 0; for example, "first" is equivalent to number 0, "second" is equivalent to number 1, and so on.

[0375] 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 yExponentiation. Specifies x to the yth power. In other contexts, such notation is used to write superscripts that are not intended to be interpreted as powers. / Integer division with result truncation towards zero. For example, 7 / 4 and -7 / -4 round down to 1, and -7 / 4 and 7 / -4 round down to -1. ÷ Used to represent division in mathematical equations where truncation or rounding is not intended.

[0376]

number

[0377] Used to represent division in mathematical equations where truncation or rounding is not intended.

[0378]

number

[0379] The sum of f(i) for all integer values ​​of i from x to y inclusive. x % y modulo. The remainder of x divided by y, defined only for integers x and y, where x >= 0 and y > 0.

[0380] Logical operators The following logical operators are defined as follows: x && y The Boolean logic "intersection" of x and y x || y Boolean logic "union" of x and y Boolean logic "negation" x ? y : zIf x is true or not equal to 0, evaluates to the value y, otherwise evaluates to the value z.

[0381] Relational operators The following relational operators are defined as follows: > Greater than >= Greater than or equal to < Less than <= The following == Equal != Not equal

[0382] 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 distinct value with respect to the syntax element or variable. The value "na" is considered not equal to any other value.

[0383] Bit operators The following bit operators are defined as follows. & Bitwise "logical AND". When operating on integer arguments, it acts on the two's complement representation of the integer value. When operating on a binary argument containing fewer bits than the other argument, the shorter argument is extended by adding leading bits equal to 0. | Bitwise "logical OR". When operating on integer arguments, it acts on the two's complement representation of the integer value. When operating on a binary argument containing fewer bits than the other argument, the shorter argument is extended by adding leading bits equal to 0. ^ Bitwise "exclusive OR". When operating on integer arguments, it acts on the two's complement representation of the integer value. When operating on a binary argument containing fewer bits than the other argument, the shorter argument is extended by adding leading bits equal to 0. x>>y Arithmetic right shift of the two's complement representation of the integer x by y bits. 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 the same value as the MSB of x before the shift operation. x<<y Arithmetic left shift of the two's complement representation of the integer x by y bits. 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.

[0384] 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, is evaluated 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).

[0385] Range notation The following notation is used to specify a range of values: x = y..zx takes the integer values ​​from y to z inclusive, where x, y, and z are integers and z is greater than y.

[0386] Mathematical Functions The following mathematical functions are defined:

[0387]

number

[0388] Asin( x ) The trigonometric arc sine function, operating on an argument x in the range of -1.0 to 1.0, inclusive, and with an output value in radians ranging from -π÷2 to π÷2, inclusive. Atan(x) The trigonometric arctangent function that operates on the argument x and has an output value in the range -π÷2 to π÷2, inclusive, in radians.

[0389]

number

[0390] 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 )

[0391]

number

[0392] Cos( x ) The trigonometric cosine function acting on the argument x in radians. Floor(x) The largest integer less than or equal to x.

[0393]

number

[0394] Ln( x ) The natural logarithm of x (the logarithm to the base e, where e is the constant base of natural logarithms, 2.718281828...). Log2( x ) The base 2 logarithm of x. Log10( x ) The base 10 logarithm of x.

[0395]

number

[0396]

number

[0397] Round( x ) = Sign( x ) * Floor( Abs( x ) + 0.5 )

[0398]

number

[0399] Sin(x) The trigonometric sine function acting on the argument x in radians

[0400]

number

[0401] Swap( x, y ) = ( y, x ) Tan( x ) The trigonometric tangent function acting on the argument x in radians

[0402] Operation precedence When precedence within an expression is not made explicit using parentheses, the following rules apply: An operation with a higher priority is evaluated before any operation with a lower priority. Operations of equal precedence are evaluated in order from left to right.

[0403] The table below specifies the precedence of operations from highest to lowest, with higher positions in the table indicating higher precedence.

[0404] With respect to operators that are also used in the C programming language, the precedence used herein is the same as that used in the C programming language.

[0405] Table: Precedence of operations from highest (top of table) to lowest (bottom of table)

[0406] [Table 6]

[0407] Text description of logical operations In the text, in the following form: if( condition 0 ) Statement 0 else if( condition1 ) Statement 1 ... else / * Comment giving information about remaining conditions * / Statement n A statement of logical operation, mathematically written in the form: may be written as follows: As follows... / ...the following applies: - If condition 0, then statement 0 - Otherwise, if condition 1, then statement 1 - ... - otherwise (comment conveying information about the remaining conditions), statement n

[0408] Each "if ..., otherwise ..., then ..., otherwise" statement in the text is introduced by "as follows ..." or "...the following applies" immediately followed by "if ..., then ...". The final condition of an "if ..., otherwise ..., then ..., otherwise ..." is always "otherwise ...". Alternately inserted "if ..., otherwise ..., then ..., otherwise ..." statements can be identified by matching the "as follows ..." or "...the following applies" with the closing "otherwise ...".

[0409] In the text, in the following form: if( condition0a && condition0b ) Statement 0 else if( condition 1a || condition 1b ) Statement 1 ... else Statement n A statement of logical operation, mathematically written in the form: may be written as follows: As follows... / ...the following applies: - Statement 0 if all of the following conditions are true: - Condition 0a - Condition 0b - Otherwise, if one or more of the following conditions are true, then statement 1 - Condition 1a - Condition 1b - ... - otherwise, statement n

[0410] In the text, in the following form: if( condition 0 ) Statement 0 if( condition1 ) Statement 1 A statement of logical operation, mathematically written in the form: may be written as follows: If condition 0, then statement 0 If condition 1, then statement 1

[0411] While embodiments of the present invention have been described primarily in terms of video coding, it should be noted that embodiments of coding system 10, encoder 20, and decoder 30 (and correspondingly, system 10), as well as other embodiments described herein, may be configured for processing or coding of still pictures, i.e., processing or coding of individual pictures independent of any preceding or subsequent pictures, similar to video coding. Generally, when picture processing or coding is limited to a single picture 17, only inter prediction units 244 (encoder) and 344 (decoder) may not be available. All other functions (also called tools or technologies) of the video encoder 20 and the video decoder 30, such as residual calculation 204 / 304, transform 206, quantization 208, inverse quantization 210 / 310, (inverse) transform 212 / 312, partitioning 262 / 362, intra prediction 254 / 354, and / or loop filtering 220, 320, and entropy coding 270, and entropy decoding 304, may be used equally for processing still pictures.

[0412] For example, embodiments of the encoder 20 and decoder 30 and the functionality described herein in connection with, for example, the encoder 20 and decoder 30 may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on a computer-readable medium or transmitted over a communication medium as one or more instructions or code and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium such as a data storage medium, or a communication medium, which includes any medium that facilitates transfer of a computer program from one place to another, for example via a communication protocol. Thus, generally, a computer-readable medium may correspond to (1) a tangible computer-readable storage medium that is non-transitory or (2) a communication medium such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementing the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0413] In particular, a method for decoding a coded video bitstream is provided, which is implemented in a decoder as shown in FIG. 8, and includes: S801, by parsing the video bitstream, obtaining a picture level syntax element included in a picture header of a current picture, wherein the picture level syntax element (e.g., pic_alf_enabled_flag) is used to specify whether an adaptive loop filter (ALF) is enabled for the current picture; S802, if the picture level syntax element specifies that an adaptive loop filter is enabled for the current picture, obtaining a parameter set identifier (e.g., pic_alf_aps_id_luma[i]) included in the picture header, wherein the parameter set identifier is used to indicate a first parameter set (e.g., APS) including a set of ALF parameters, and a temporal identifier (e.g., TemporalId) of the first parameter set is less than or equal to the temporal identifier of the current picture; and S803, performing an adaptive loop filter on at least one slice of the current picture based on the first parameter set.

[0414] The current picture is a coded picture contained in a picture unit (PU), where a PU is a set of NAL units that are related to each other according to specified classification rules and are consecutive in decoding order.

[0415] A Network Abstraction Layer (NAL) unit is a syntax structure that contains an indication of the type of data that follows and bytes containing all or part of the coded data of the current picture, a picture header, or a parameter set containing a set of ALF parameters, where each NAL unit has a temporal identifier.

[0416] The temporal identifier (e.g., TemporalId) of the first parameter set is the TemporalId of an APS NAL unit with aps_params_type equal to ALF_APS. aps_params_type equal to ALF_APS means that the ALF parameters are carried within an APS. An APS NAL unit is a NAL unit that contains an APS.

[0417] If the temporal identifier of a first NAL unit is less than the temporal identifier of a second NAL unit of the same layer, the data encapsulated by the first NAL unit may be decoded without reference to the data encapsulated by the second NAL unit. The temporal identifier may also be used in a sub-bitstream extraction process, which is a process in which NAL units in a bitstream that do not belong to a target set determined by a target highest temporal identifier are removed from the bitstream, and the output sub-bitstream consists of NAL units in the bitstream that belong to the target set.

[0418] The time identifier may be related to the decoding order.

[0419] The step of performing an adaptive loop filter on at least one slice of the current picture based on the first parameter set includes performing an adaptive loop filter on a luma component of the at least one slice of the current picture based on the first parameter set.

[0420] When ALF is enabled for a CTB, each sample R(i, j) in the CU is filtered using ALF to produce a sample value R'(i, j), as shown below:

[0421]

number

[0422] where f(k, l) denotes the decoded filter coefficients, K(x, y) is the clipping function, and c(k, l) denotes the decoded clipping parameters. The variables k and l vary between -L / 2 and L / 2, and L denotes the filter length. The clipping function K(x, y) = min(y, max(-y, x)), which corresponds to the function Clip3(-y, y, x). The clipping operation introduces nonlinearity to make the ALF more efficient by reducing the influence of neighboring sample values ​​that are too different from the current sample value.

[0423] The ALF filter parameters (or ALF parameters) are signaled within an adaptive parameter set (APS). Within one APS, up to 25 pairs of luma filter coefficients and clipping value indices and up to 8 pairs of chroma filter coefficients and clipping value indices may be signaled. To reduce bit overhead, different classifications of filter coefficients for the luma component may be merged. In the picture header, the index of the APS used for the current picture is signaled.

[0424] The clipping value index decoded from the APS allows determining the clipping values ​​using a table of clipping values ​​for both the luma and chroma components. These clipping values ​​depend on the internal bit depth. More precisely, the clipping values ​​are calculated using the following formula: AlfClip = {round(2 B-α*n )} for n ∈ [0..N - 1]} where B is equal to the internal bit depth, α is a predefined constant value equal to 2.35, and N is equal to 4, which is the number of allowed clipping values ​​in VVC. Then, AlfClip is rounded to the nearest value in the form of a power of two.

[0425] Within the slice header, up to seven APS indices can be signaled to specify the luma filter set to be used for the current slice. The filtering process can be further controlled at the CTB level. A flag is always signaled to indicate whether an ALF is applied to the luma CTB. The luma CTB can select a filter set among 16 fixed filter sets and a filter set from an APS. A filter set index is signaled for the luma CTB to indicate which filter set is applied. The 16 fixed filter sets are predefined and hard-coded in both the encoder and decoder.

[0426] For chroma components, an APS index is signaled in the slice header to indicate the chroma filter set being used for the current slice. At the CTB level, if there is more than one chroma filter set in an APS, a filter index is signaled for each chroma CTB.

[0427] The filter coefficients are quantized with a norm equal to 128. To limit the complexity of multiplications, bitstream compliance is applied such that coefficient values ​​in non-central positions are in the range of -27 to 27 - 1, inclusive. Coefficients in central positions are not signaled in the bitstream and are assumed to be equal to 128.

[0428] The method may further include, if a picture-level syntax element (e.g., pic_alf_enabled_flag) specifies that an adaptive loop filter is enabled for the current picture, obtaining another parameter set identifier included in the picture header, where the parameter set identifier (e.g., pic_alf_aps_id_chroma) is used to indicate a second parameter set (e.g., APS) including a set of ALF parameters, and a temporal identifier of the second parameter set is less than or equal to the temporal identifier of the current picture; and performing an adaptive loop filter on chroma components of at least one slice of the current picture based on the second parameter set.

[0429] Similarly, there is provided a method for encoding a video bitstream including coded data, implemented in an encoder as shown in Figure 9. The method includes the steps of: S901, determining whether an adaptive loop filter (ALF) is enabled for a current picture; S902 based on determining whether an adaptive loop filter (ALF) is enabled for the current picture, encoding a picture level syntax element (e.g., pic_alf_enabled_flag) in a picture header of the current picture, the picture level syntax element being used to specify whether an adaptive loop filter (ALF) is enabled for the current picture; S903 and if the adaptive loop filter is enabled for the current picture, encoding a parameter set identifier (e.g., pic_alf_aps_id_luma[i]) into the picture header, wherein the parameter set identifier is used to indicate a first parameter set (e.g., APS) including a set of ALF parameters for the adaptive loop filter, and wherein a temporal identifier (e.g., TemporalId) of the first parameter set is set to be less than or equal to the temporal identifier of the current picture.

[0430] The method may further include encoding the temporal identifier of the first parameter set and the temporal identifier of the current picture into a video bitstream.

[0431] The first parameter set includes a set of ALF parameters for an adaptive loop filter performed on the luma component of at least one slice of the current picture.

[0432] The method may further include, if the picture level syntax element specifies that an adaptive loop filter is enabled for the current picture, encoding another parameter set identifier in the picture header, wherein the parameter set identifier (e.g., pic_alf_aps_id_chroma) is used to indicate a second parameter set (e.g., APS) including a set of ALF parameters of an adaptive loop filter to be performed on chroma components of at least one slice of the current picture, and wherein a temporal identifier of the second parameter set is set to be less than or equal to the temporal identifier of the current picture.

[0433] 10 shows a decoder 1000 configured to decode a video bitstream including coded data for multiple pictures. The decoder 1000 according to the illustrated example includes an acquisition unit 1010 configured to acquire a picture-level syntax element included in a picture header of a current picture by parsing the video bitstream, the picture-level syntax element being used to specify whether an adaptive loop filter (ALF) is enabled for the current picture. If the picture-level syntax element specifies that the adaptive loop filter is enabled for the current picture, the acquisition unit 1010 is further configured to acquire a parameter set identifier included in the picture header, the parameter set identifier being used to indicate a first parameter set including a set of ALF parameters, a temporal identifier of the first parameter set being less than or equal to a temporal identifier of the current picture, and a filtering unit 1020 configured to perform an adaptive loop filter on at least one slice of the current picture based on the first parameter set.

[0434] The obtaining unit 1010 may be the entropy decoding unit 304. The filtering unit 1020 may be the loop filter 320. The decoder 1000 may be the destination device 14, the decoder 30, the apparatus 500, the video decoder 3206, or the terminal device 3106.

[0435] Similarly, an encoder 1100 configured to encode a video bitstream including coded data for a plurality of pictures is provided, as shown in Figure 11. The encoder 1100 includes a determining unit 1110 configured to determine whether an adaptive loop filter (ALF) is enabled for a current picture, and an encoding unit 1120 configured to encode a picture-level syntax element into a picture header of the current picture based on determining whether the adaptive loop filter (ALF) is enabled for the current picture, the picture-level syntax element being used to specify whether the adaptive loop filter (ALF) is enabled for the current picture. If the adaptive loop filter is enabled for the current picture, the encoding unit 1120 is further configured to encode a parameter set identifier into the picture header, the parameter set identifier being used to indicate a first parameter set including a set of ALF parameters for the adaptive loop filter, and a temporal identifier of the first parameter set being set equal to or less than the temporal identifier of the current picture.

[0436] The encoding unit 1120 may be the entropy encoding unit 270. The decision unit 1110 may be the loop filter 220. The encoder 1100 may be the source device 12, the encoder 20, or the apparatus 500.

[0437] By way of example, and not limitation, such computer-readable storage media may 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 desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio wave, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio wave, and microwave are included within the definition of medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but instead cover non-transitory, tangible storage media. As used herein, disk and disc include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically while discs reproduce data optically using a laser. Combinations of the above should also be included within the scope of computer-readable media.

[0438] The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor," as used herein, may refer to any of the above structures or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a combined codec. Also, the techniques may be implemented entirely in one or more circuits or logic elements.

[0439] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to highlight functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as noted above, the various units may be combined in a codec hardware unit or provided by a collection of interoperable hardware units including one or more processors as described above in conjunction with suitable software and / or firmware. [Explanation of symbols]

[0440] 10 Video coding system, coding system 12 Source Device 13 Encoded picture data, communication channel 14 Destination Device 16 Picture Source 17 Picture, Picture Data, Raw Picture, Raw Picture Data, Monochrome Picture, Color Picture, Current Picture 18 Preprocessor, preprocessing unit, picture preprocessor 19 Preprocessed Picture, Preprocessed Picture Data 20 Video Encoder, Encoder 21 Encoded picture data, encoded bitstream 22 Communication interface, communication unit 28 Communication interface, communication unit 30 decoder, video decoder 31 Decoded Picture Data, Decoded Picture 32 Post-processor, post-processing unit 33 Post-processed picture data, post-processed picture 34 Display Devices 46 Processing Circuit 100 Video Encoder 201 Input, input interface 203 Picture Block, Original Block, Current Block, Current Picture Block, CTU 204 Residual Calculation Unit, Residual Calculation 205 Residual Block, Residual 206 Conversion Processing Unit, Conversion 207 Conversion Factor 208 Quantization Unit, Quantization 209 Quantized Coefficients, Quantized Transform Coefficients, Quantized Residual Coefficients 210 Inverse quantization unit, inverse quantization 211 Dequantized coefficients, dequantized residual coefficients 212 Inverse Transform Processing Unit, (Inverse) Transform 213 Reconstructed residual block, dequantized coefficients, transform block 214 Reconstruction Unit, Adder, Summer 215 reconstructed blocks 216 buffers 220 Loop filter unit, loop filter 221 filtered blocks, filtered reconstructed blocks 230 Decoded Picture Buffer (DPB) 231 decoded pictures 244 Inter Prediction Unit (Encoder) 254 Intra prediction unit, Inter prediction unit, Intra prediction 260 Mode Selection Unit 262 Division Unit, Division 265 prediction block, predictor 266 Syntax Elements 270 Entropy Coding Unit, Entropy Coding 272 Output, Output Interface 304 Residual Calculation, Entropy Decoding, Entropy Decoding Unit 309 Quantized Coefficients 310 Inverse Quantization Unit, Inverse Quantization 311 Dequantized Coefficients, Transform Coefficients 312 Inverse Transform Processing Unit, Output, (Inverse) Transform 313 Reconstructed Residual Blocks 314 Reconstruction Unit, Summer, Adder 315 reconstructed blocks 320 Loop filter, loop filter unit, loop filtering unit 321 filtered blocks, decoded video blocks 330 Decoded Picture Buffer (DPB) 331 decoded pictures 344 Inter Prediction Unit (Decoder) 354 Intra prediction unit, Intra prediction 360 mode application unit 362 Division 365 predicted blocks 400 Video Coding Device 410 Incoming port, input port 420 Receiver Unit (Rx) 430 Processor, Logic Unit, Central Processing Unit (CPU) 440 Transmitter Unit (Tx) 450 outgoing and outgoing ports 460 memory 470 Coding Module 500 devices 502 processor 504 memory 506 Data 508 Operating Systems 510 Application Program 512 Bus 514 Secondary Storage 518 Display 1000 decoders 1010 Acquisition Units 1020 Filtering Unit 1100 Encoder 1110 Judgment Unit 1120 coding units 3100 Contents Supply System 3102 Capture Device 3104 Communication Links 3106 Terminal Device 3108 Smartphones, smart pads 3110 Computers, Laptops 3112 Network Video Recorder (NVR) / Digital Video Recorder (DVR) 3114 TV 3116 Set-top box (STB) 3118 Video Conference System 3120 Video Surveillance System 3122 Personal Digital Assistant (PDA) 3124 In-Vehicle Devices 3126 Display 3202 Protocol Progression Unit 3204 Demultiplexing Unit 3206 Video Decoder 3208 Audio Decoder 3210 Subtitle Decoder 3212 Synchronous Unit 3214 Video / Audio Display 3216 Video / Audio / Subtitle Display

Claims

1. parsing a picture level syntax element from a picture header of a current picture, the picture level syntax element being used to specify whether an adaptive loop filter (ALF) is enabled for the current picture; when the picture level syntax element specifies that the ALF is enabled for the current picture, parsing a first parameter set identifier from the picture header, wherein the first parameter set identifier specifies an adaptation_parameter_set_id of an ALF adaptation parameter set (APS) to which a luma component of a slice in the current picture refers, and a temporal identifier of an APS Network Abstraction Layer (NAL) unit having an aps_params_type equal to ALF_APS and an adaptation_parameter_set_id equal to the first parameter set identifier is less than or equal to a temporal identifier of the current picture; a decoding method in which the value of alf_luma_filter_signal_flag of the APS NAL unit having aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to the first parameter set identifier is equal to 1.

2. 2. The method of claim 1, further comprising: performing an adaptive loop filter on the luma component of at least one slice of the current picture based on the ALF APS specified by the first parameter set identifier.

3. 3. The method of claim 1, further comprising: when the picture level syntax element specifies that the ALF is enabled for the current picture, obtaining a second parameter set identifier from the picture header, wherein the second parameter set identifier specifies an adaptation_parameter_set_id of an ALF APS to which a chroma component of the slice in the current picture refers, and a temporal identifier of an APS NAL unit having an aps_params_type equal to ALF_APS and an adaptation_parameter_set_id equal to the second parameter set identifier is less than or equal to the temporal identifier of the current picture.

4. 4. The method of claim 3, wherein the value of alf_chroma_filter_signal_flag of the APS NAL unit having aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to the second parameter set identifier is equal to 1.

5. 5. The method of claim 1, wherein the picture level syntax element is pic_alf_enable_flag.

6. 6. The method according to claim 1, wherein the first parameter set identifier is pic_alf_aps_id_luma[i].

7. 5. The method of claim 3, wherein the second parameter set identifier is pic_alf_aps_id_chroma.

8. encoding a picture level syntax element in a picture header of a current picture, the picture level syntax element being used to specify whether an adaptive loop filter (ALF) is enabled for the current picture; and when the ALF is enabled for the current picture, encoding a first parameter set identifier in the picture header, the first parameter set identifier specifying an adaptation_parameter_set_id of an ALF adaptation parameter set (APS) to which a luma component of a slice in the current picture refers, and a temporal identifier of an APS Network Abstraction Layer (NAL) unit having an aps_params_type equal to ALF_APS and an adaptation_parameter_set_id equal to the first parameter set identifier is less than or equal to a temporal identifier of the current picture; a coding method in which the value of alf_luma_filter_signal_flag of the APS NAL unit having aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to the first parameter set identifier is set to 1.

9. The method of claim 8 , further comprising encoding the temporal identifier of the ALF APS specified by the first parameter set identifier and the temporal identifier of the current picture into a video bitstream.

10. 10. The method of claim 8, further comprising: when the picture level syntax element specifies that the ALF is enabled for the current picture, encoding a second parameter set identifier in the picture header, wherein the second parameter set identifier specifies an adaptation_parameter_set_id of an ALF APS to which a chroma component of the slice in the current picture refers, and a temporal identifier of an APS NAL unit having an aps_params_type equal to ALF_APS and an adaptation_parameter_set_id equal to the second parameter set identifier is less than or equal to the temporal identifier of the current picture.

11. 11. The method of claim 10, wherein the value of alf_chroma_filter_signal_flag of the APS NAL unit having aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to the second parameter set identifier is set to 1.

12. 12. The method according to claim 8, wherein the picture level syntax element is pic_alf_enable_flag.

13. 13. The method according to claim 8, wherein the first parameter set identifier is pic_alf_aps_id_luma[i].

14. 12. The method according to claim 10 or 11, wherein the second parameter set identifier is pic_alf_aps_id_chroma.

15. An encoder comprising processing circuitry for carrying out the method of any one of claims 8 to 14.

16. A decoder comprising processing circuitry for carrying out the method of any one of claims 1 to 7.

17. A computer program comprising program code for causing a computer or processor to perform the method of any one of claims 1 to 14.

18. one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, Parsing a picture level syntax element from a picture header of a current picture, the picture level syntax element being used to specify whether an adaptive loop filter (ALF) is enabled for the current picture; and a non-transitory computer-readable storage medium that configures a decoder to parse a first parameter set identifier from the picture header when the picture level syntax element specifies that the ALF is enabled for the current picture, the first parameter set identifier specifying an adaptation_parameter_set_id of an ALF adaptation parameter set (APS) to which a luma component of a slice in the current picture refers, and a temporal identifier of an APS Network Abstraction Layer (NAL) unit having an aps_params_type equal to ALF_APS and an adaptation_parameter_set_id equal to the first parameter set identifier is less than or equal to a temporal identifier of the current picture; a decoder in which the value of alf_luma_filter_signal_flag is equal to 1 for the APS NAL unit having aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to the first parameter set identifier.

19. one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, encoding a picture level syntax element in a picture header of a current picture, the picture level syntax element being used to specify whether an adaptive loop filter (ALF) is enabled for the current picture; and and a non-transitory computer-readable storage medium that configures an encoder to, when the ALF is enabled for the current picture, encode in the picture header a first parameter set identifier, the first parameter set identifier specifying an adaptation_parameter_set_id of an ALF adaptation parameter set (APS) to which a luma component of a slice in the current picture refers, and wherein a temporal identifier of an APS Network Abstraction Layer (NAL) unit having an aps_params_type equal to ALF_APS and an adaptation_parameter_set_id equal to the first parameter set identifier is less than or equal to a temporal identifier of the current picture; the encoder setting the value of alf_luma_filter_signal_flag equal to 1 for the APS NAL units having aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to the first parameter set identifier.

20. A non-transitory computer readable storage medium comprising program code which, when executed by a computing device, causes the computing device to perform the method of any one of claims 1 to 14.

21. a non-transitory memory storage configured to store video data in the form of a bitstream; A video data decoding device comprising: a decoder configured to perform any of the methods of any one of claims 1 to 7.

22. a non-transitory memory storage configured to store video data in the form of a bitstream; and an encoder configured to perform any of the methods according to any one of claims 8 to 14.

23. 1. A device for storing a bitstream, comprising: at least one memory configured to store the bitstream; A device, wherein the device is configured to generate the bitstream according to the method of any one of claims 8 to 14.

24. 24. The device of claim 23, wherein when the ALF is enabled for the current picture, the picture header further includes a second parameter set identifier, the second parameter set identifier specifies an adaptation_parameter_set_id of an ALF APS to which a chroma component of the slice in the current picture refers, and a temporal identifier of an APS NAL unit having an aps_params_type equal to ALF_APS and an adaptation_parameter_set_id equal to the second parameter set identifier is less than or equal to the temporal identifier of the current picture.

25. 25. The device of claim 24, wherein a value of alf_chroma_filter_signal_flag of the APS NAL unit having aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to the second parameter set identifier is equal to 1.

26. A method for storing a bitstream by a device, comprising: generating a bitstream according to a method according to any one of claims 8 to 14; and storing the bitstream in one or more memories.

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