Encoder, decoder and corresponding method using adaptive loop filters

Abstract

To provide an encoder, a decoder, and a corresponding method, using an adaptive loop filter.SOLUTION: The present disclosure provides a method of coding, implemented by a decoding device. The method includes the steps of: obtaining a bitstream, at least one bit in the bitstream representing a syntax element for a current block, the syntax element specifying the clipping index of a clipping value for an adaptive loop filter (ALF); parsing the bitstream to obtain a value of the syntax element for the current block, the syntax element being coded using a fixed length code; and applying adaptive loop filtering on the current block, based on the value of the syntax element for the current block. Herein the fixed length code means that all possible values of the syntax element are signaled using the same number of bits.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims priority to U.S. Provisional Patent Application No. 62 / 843,431, filed May 4, 2019. The disclosures of the aforementioned patent applications are incorporated herein by reference in their entireties.

[0002] Technical Field FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to the field of picture processing, and more particularly to filtering samples of blocks in a picture. [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 like video chat and video conferencing, DVDs and Blu-ray Discs, video content acquisition and editing systems, and camcorders in security applications.

[0004] The amount of video data required to represent a relatively short video can be substantial, which can create difficulties when the data is streamed or otherwise communicated over a communications network with limited bandwidth capacity. Thus, video data is typically compressed before being communicated over modern telecommunications networks. The size of the video can also be an issue when the video is stored in a storage device, since memory resources may be limited. Video compression devices often use software and / or hardware at the source to code the video data before transmission or storage, thereby reducing the amount of data required to represent a digital video image. The compressed data is then received at the destination by a video decompression device, which decodes the video data. With limited network resources and an ever-increasing demand for higher video quality, improved compression and decompression techniques that improve compression ratios with little or no sacrifice in picture quality are desirable. Summary of the Invention [Means for solving the problem]

[0005] Embodiments of the present application provide devices and methods for encoding and decoding according to the independent claims. These and other objects are achieved by the subject matter of the independent claims. Further implementations are evident from the dependent claims, the description and the drawings.

[0006] According to a first aspect of the present disclosure, there is provided a coding method implemented by a decoding device, the method comprising: The method includes obtaining a bitstream, where at least one bit in the bitstream represents a syntax element for a current block, the syntax element specifying a clipping index of a clipping value for an adaptive loop filter (ALF); parsing the bitstream to obtain a value of the syntax element for the current block, where the syntax element is coded using a fixed length code; and applying adaptive loop filtering to the current block based on the value of the syntax element for the current block, where a fixed length code means that all possible values ​​of a syntax element are signaled using the same number of bits. This provides a simpler way of signaling clipping parameters. Furthermore, coding efficiency is improved.

[0007] In one possible implementation of the method according to the first aspect itself, the value of the syntax element for the current block is obtained by using only said at least one bit.

[0008] In one possible implementation of the method according to any preceding implementation or the first aspect itself, said at least one bit is two bits.

[0009] In one possible implementation of the method according to any preceding implementation or the first aspect itself, the at least one bit in the bitstream represents a value of the syntax element.

[0010] In one possible implementation of the method according to any preceding implementation or the first aspect itself, the syntax element is for a chroma adaptive loop filter or a luma adaptive loop filter.

[0011] In one possible implementation of the method according to any preceding implementation or the first aspect itself, the clipping value is used to determine a clipping range used to limit (or clip) the difference between a target sample value and a neighboring sample value, and the limited sample value difference (or clipped sample value difference) is used to modify the target sample value in the ALF process.

[0012] In one possible implementation of the method according to any preceding implementation or the first aspect itself, the step of applying adaptive loop filtering to the current block based on the value of the syntax element includes the steps of obtaining a clipping value based on the value of the syntax element; limiting (or clipping) a difference between a target sample value and a neighboring sample value of the current block using the clipping value; multiplying the limited sample value difference (or clipped sample value difference) by an adaptive loop filter (ALF) coefficient; and modifying the target sample value using a result of the multiplication.

[0013] In one possible implementation of the method according to any preceding implementation or the first aspect itself, the clipping value is determined by using the clipping index specified by the syntax element and a mapping between clipping index and clipping value.

[0014] In one possible implementation of the method according to any preceding implementation or the first aspect itself, the fixed length code comprises a binary representation of an unsigned integer using the at least one bit, in other words, the at least one bit is a binary representation of a value of the syntax element, the value of the syntax element being an unsigned integer.

[0015] In one possible implementation of the method according to any preceding implementation or the first aspect itself, said syntax element is applied to a set of blocks, and the current block is one block in said set of blocks.

[0016] In one possible implementation of the method according to any preceding implementation or the first aspect itself, said syntax elements are at a slice level.

[0017] According to a second aspect of the present disclosure, there is provided a coding method implemented by a decoding device, the method comprising: The method includes: obtaining a bitstream, at least one bit in the bitstream representing a syntax element for a current block, the syntax element being an adaptive loop filter (ALF) clipping value index and / or an ALF coefficient parameter; parsing the bitstream to obtain a value of the syntax element for the current block, the value of the syntax element for the current block being obtained by using only the at least one bit of the syntax element; and applying adaptive loop filtering to the current block based on the value of the syntax element for the current block.

[0018] In one possible implementation of the method according to the second aspect itself, said syntax elements are coded using fixed length codes.

[0019] In one possible implementation of the method according to the immediately preceding implementation, the fixed length code includes a binary representation of an unsigned integer using the at least one bit, in other words, the at least one bit is a binary representation of a value of the syntax element, the value of the syntax element being an unsigned integer.

[0020] In one possible implementation of the method according to the second aspect itself or any preceding implementation thereof, the syntax element itself defines the value of the syntax element.

[0021] In one possible implementation of the method according to the second aspect itself or any preceding implementation thereof, the at least one bit in the bitstream represents a value of the syntax element.

[0022] In one possible implementation of the method according to the second aspect itself or any preceding implementation thereof, the ALF clipping value index specifies the clipping index of the clipping value for an adaptive loop filter (ALF).

[0023] In one possible implementation of the method according to the second aspect itself or any preceding implementation thereof, the ALF coefficient parameters are used to obtain the coefficients of the ALF.

[0024] In one possible implementation of the method according to the second aspect itself or any preceding implementation thereof, the value of the syntax element for the current block is obtained by using only the at least one bit of the syntax element, meaning that the value of the syntax element is defined by the syntax element itself.

[0025] In one possible implementation of the method according to the second aspect itself or any preceding implementation thereof, said syntax element is applied to a set of blocks, the current block being a block in said set of blocks.

[0026] In one possible implementation of the method according to the second aspect itself or any preceding implementation thereof, the syntax element is at a slice level.

[0027] In one possible implementation of the method according to the second aspect itself or any preceding implementation thereof, said ALF coefficient parameters are used to determine an ALF coefficient.

[0028] In one possible implementation form of the method according to the first or second aspect itself or any preceding implementation thereof, the syntax element is the ALF clipping value index and the at least one bit representing the syntax element is two bits.

[0029] In one possible implementation of the method according to the immediately preceding implementation, the ALF clipping value index identifies one clipping value out of four clipping values.

[0030] In one possible implementation of the method according to the first or second aspect itself or any preceding implementation thereof, the value of the ALF clipping value index is used to determine a clipping range, which is used in the adaptive loop filtering process.

[0031] According to a third aspect of the present disclosure, there is provided a coding method implemented by an encoding device, the method comprising: The method includes: determining a value of a syntax element for a current block, the syntax element specifying the clipping index of the clipping value for an adaptive loop filter (ALF); and generating a bitstream based on the value of the syntax element, at least one bit in the bitstream representing the syntax element, the syntax element being coded using a fixed length code.

[0032] In one possible implementation of the method according to the third aspect itself, said at least one bit of said syntax element is obtained by using only the value of said syntax element for the current block.

[0033] In one possible implementation of the method according to the third aspect itself or any preceding implementation thereof, the value of the syntax element corresponds to a minimum difference (e.g., mean squared error or rate-distortion cost) between a reconstructed block (or a filtered block) of a current block and an original signal of the current block, the reconstructed block (or the filtered block) being a result of using the value of the syntax element, the minimum difference being smaller than any other difference corresponding to any other possible value of the syntax element.

[0034] In one possible implementation of the method according to the third aspect itself or any preceding implementation thereof, at least one bit in the bitstream represents a value of the syntax element.

[0035] In one possible implementation of the method according to the third aspect itself or any preceding implementations thereof, the clipping value is used to determine a clipping range used to limit (or clip) the difference between a target sample value and a neighboring sample value, and the limited sample value difference (or clipped sample value difference) is used to modify the target sample value in the ALF process.

[0036] In one possible implementation of the method according to the third aspect itself or any preceding implementation thereof, the fixed length code comprises a binary representation of an unsigned integer using the at least one bit, in other words, the at least one bit is a binary representation of a value of the syntax element, the value of the syntax element being an unsigned integer.

[0037] In one possible implementation of the method according to the third aspect itself or any preceding implementation thereof, said syntax element is applied to a set of blocks and the current block is a block in said set of blocks.

[0038] In one possible implementation of the method according to the third aspect itself or any preceding implementation thereof, the syntax element is at a slice level.

[0039] According to a fourth aspect of the present disclosure, there is provided a coding method implemented by an encoding device, the method comprising: The method includes: determining a value of a syntax element for a current block, the syntax element being an adaptive loop filter (ALF) clipping value index and / or an ALF filter coefficient parameter; and generating a bitstream based on the value of the syntax element, at least one bit in the bitstream representing the syntax element, the at least one bit of the syntax element being obtained by using only the value of the syntax element for the current block.

[0040] In one possible implementation of the method according to the fourth aspect itself or any preceding implementation thereof, said syntax elements are coded using fixed length codes.

[0041] In one possible implementation of the method according to the immediately preceding implementation, the fixed length code comprises a binary representation of an unsigned integer using the at least one bit, in other words, the at least one bit is a binary representation of a value of the syntax element, the value of the syntax element being an unsigned integer.

[0042] In one possible implementation of the method according to the fourth aspect itself or any preceding implementation thereof, the at least one bit in the bitstream represents a value of the syntax element.

[0043] In one possible implementation of the method according to the fourth aspect itself or any preceding implementation thereof, said syntax element is applied to a set of blocks and the current block is a block in said set of blocks.

[0044] In one possible implementation of the method according to the fourth aspect itself or any preceding implementation thereof, the syntax element is at a slice level.

[0045] In one possible implementation of the method according to the fourth aspect itself or any preceding implementation thereof, said ALF coefficient parameters are used to determine an ALF coefficient.

[0046] In one possible implementation of the method according to the third or fourth aspect itself or any preceding implementation thereof, the syntax element is the ALF clipping value index and the at least one bit representing the syntax element is two bits.

[0047] In one possible implementation of a method according to the immediately preceding implementation of the fourth aspect, the ALF clipping value index identifies one clipping value out of four clipping values.

[0048] In one possible implementation of the method according to the third or fourth aspect itself or any preceding implementations thereof, the value of the ALF clipping value index is used to determine a clipping range, which is used in the adaptive loop filtering process.

[0049] According to a fifth aspect of the present disclosure, there is provided a decoder comprising processing circuitry for performing a method according to the first or second aspect or any implementation thereof.

[0050] According to a sixth aspect of the present disclosure, there is provided an encoder comprising processing circuitry for performing a method according to the third or fourth aspect or any implementation thereof.

[0051] According to a seventh aspect of the present disclosure there is provided a computer program product comprising program code for performing a method according to any of the first to fourth aspects or any implementation thereof.

[0052] According to an eighth aspect of the present disclosure, there is provided a non-transitory computer readable medium carrying program code which, when executed by a computing device, causes the computing device to perform a method according to any of the first to fourth aspects or any implementation thereof.

[0053] According to a ninth aspect of the present disclosure, there is provided a decoder having one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, the programming, when executed by the processor, configuring the decoder to perform a method according to either the first or second aspect or any implementation thereof.

[0054] According to a tenth aspect of the present disclosure, there is provided an encoder having one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, the programming, when executed by the processor, configuring the encoder to perform a method according to the third or fourth aspect or any implementation thereof.

[0055] According to an eleventh aspect of the present disclosure, there is provided a decoder having an entropy decoding unit configured to obtain a bitstream, at least one bit in the bitstream represents a syntax element for a current block, the syntax element specifying the clipping index of the clipping value for an adaptive loop filter (ALF); The entropy decoding unit is configured to parse the bitstream to obtain values ​​of the syntax elements for a current block, the syntax elements being coded using a fixed length code; and a filtering unit is configured to apply adaptive loop filtering to the current block based on the values ​​of the syntax elements for the current block.

[0056] According to a twelfth aspect of the present disclosure, there is provided a decoder having an entropy decoding unit configured to obtain a bitstream, at least one bit in the bitstream represents a syntax element for a current block, the syntax element being an adaptive loop filter (ALF) clipping value index or an ALF coefficient parameter; The entropy decoding unit is further configured to parse the bitstream to obtain a value of the syntax element for a current block, the value of the syntax element for the current block being obtained by using only the at least one bit of the syntax element; and a filtering unit is configured to apply adaptive loop filtering to the current block based on the value of the syntax element for the current block.

[0057] According to a thirteenth aspect of the present disclosure, there is provided an encoder, the encoder comprising: The method includes: a determination unit configured to determine a value of a syntax element for a current block, the syntax element specifying the clipping index of the clipping value for an adaptive loop filter (ALF); and an entropy encoding unit configured to generate a bitstream based on the value of the syntax element, where at least one bit in the bitstream represents the syntax element, and the syntax element is coded using a fixed length code.

[0058] According to a fourteenth aspect of the present disclosure, there is provided an encoder, the encoder comprising: The method includes: a determination unit configured to determine a value of a syntax element for a current block, the syntax element being an ALF clipping value index or an adaptive loop filter (ALF) coefficient parameter; and an entropy encoding unit configured to generate a bitstream based on the value of the syntax element, at least one bit in the bitstream representing the syntax element, the at least one bit of the syntax element being obtained by using only the value of the syntax element for the current block.

[0059] According to a fifteenth aspect of the present disclosure, there is provided a coding method implemented by a decoding device, the method comprising: obtaining a bitstream, wherein n bits in the bitstream represent a syntax element that specifies the clipping index of the clipping value for an adaptive loop filter (ALF), where n is an integer greater than or equal to 0; The method includes parsing the bitstream to obtain a value of the syntax element for a current block, the value of the syntax element being a binary representation of an unsigned integer using the n bits; and applying adaptive loop filtering to the current block based on the value of the syntax element for the current block.

[0060] In one possible implementation of the method according to the fifteenth aspect, the syntax elements may be slice level syntax elements.

[0061] According to a sixteenth aspect of the present disclosure, there is provided a coding method implemented by an encoding device, the coding method comprising: The method includes determining a value of a syntax element that specifies the clipping index of the clipping value for an adaptive loop filter (ALF), where n is an integer greater than or equal to 0; and generating a bitstream comprising n bits based on the value of the syntax element, where the binary representation of an unsigned integer using the n bits is the value of the syntax element.

[0062] In one possible implementation of the method according to the sixteenth aspect, the syntax elements may be slice-level syntax elements.

[0063] According to a seventeenth aspect of the present disclosure, there is provided a decoder, the decoder comprising: The present invention relates to an entropy decoding unit configured to obtain a bitstream, wherein n bits in the bitstream represent a slice-level syntax element that specifies the clipping index of the clipping value for an adaptive loop filter (ALF), where n is an integer greater than or equal to 0, and the entropy decoding unit is further configured to parse the bitstream to obtain a value of the syntax element for a current block, the value of the syntax element being a binary representation of an unsigned integer using the n bits; and a filtering unit configured to apply adaptive loop filtering to the current block based on the value of the syntax element for the current block.

[0064] According to an eighteenth aspect of the present disclosure, there is provided an encoder, the encoder comprising: The present invention includes a determination unit configured to determine a value of a slice-level syntax element that specifies the clipping index of the clipping value for an adaptive loop filter (ALF), where n is an integer greater than or equal to 0; and an entropy encoding unit configured to generate a bitstream comprising n bits based on the value of the syntax element, where the binary representation of an unsigned integer using the n bits is the value of the syntax element.

[0065] According to a nineteenth aspect of the present disclosure, there is provided a decoder comprising processing circuitry for performing a method according to the fifteenth aspect or any implementation thereof.

[0066] According to a twentieth aspect of the present disclosure, there is provided an encoder comprising processing circuitry for performing a method according to the sixteenth aspect or any implementation thereof.

[0067] According to a twenty-first aspect of the present disclosure there is provided a computer program product comprising program code for performing a method according to the fifteenth aspect, the sixteenth aspect, or any implementation thereof.

[0068] According to a twenty-second aspect of the present disclosure, there is provided a non-transitory computer readable medium carrying program code which, when executed by a computing device, causes the computing device to perform a method according to either the fifteenth aspect or the sixteenth aspect or any implementation thereof.

[0069] According to a twenty-third aspect of the present disclosure, there is provided a decoder having one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, the programming, when executed by the processor, configuring the decoder to perform a method according to the fifteenth aspect or any implementation thereof.

[0070] According to a twenty-fourth aspect of the present disclosure, there is provided an encoder having one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, the programming, when executed by the processor, configuring the encoder to perform a method according to the sixteenth aspect or any implementation thereof.

[0071] According to a twenty-fifth aspect of the present disclosure, there is provided a non-transitory storage medium comprising a bitstream comprising n bits, wherein the binary representation of an unsigned integer using the n bits is a value of a syntax element, the syntax element specifying the clipping index of the clipping value for an adaptive loop filter (ALF), where n is an integer greater than or equal to 0.

[0072] According to a twenty-sixth aspect of the present disclosure, a non-transitory storage medium is provided comprising a bitstream, at least one bit in the bitstream representing the syntax element, the syntax element being coded using a fixed length code and specifying the clipping index of the clipping value for an adaptive loop filter (ALF).

[0073] In an implementation of the method according to the twenty-sixth aspect itself, the syntax element itself defines the value of the syntax element.

[0074] According to a twenty-seventh aspect of the present disclosure, there is provided a non-transitory storage medium comprising a bitstream, at least one bit in the bitstream representing the syntax element, the syntax element being an adaptive loop filter (ALF) clipping value index or an ALF filter coefficient parameter, and the at least one bit of the syntax element being obtained by using only a value of the syntax element.

[0075] According to a twenty-eighth aspect of the present disclosure, there is provided a non-transitory storage medium including a bitstream encoded according to any aspect or any implementation thereof.

[0076] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims. [Brief description of the drawings]

[0077] In the following, embodiments of the invention are explained in more detail with reference to the accompanying drawings and figures. [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. [Diagram 2] FIG. 2 is a block diagram illustrating an example of a video encoder configured to implement embodiments of the present invention. [Diagram 3] FIG. 2 is a block diagram illustrating an exemplary structure of a video decoder configured to implement embodiments of the present invention. [Figure 4] FIG. 2 is a block diagram showing an example of an encoding device or a decoding device. [Diagram 5] FIG. 2 is a block diagram showing another example of an encoding device or a decoding device. [Figure 6] ALF filter shapes shown: Chroma 5x5 Diamond, Luma 7x7 Diamond. [Figure 7] 1 shows subsampled ALF block classification. [Figure 8] Signaling of VTM-5.0 ALF luma and chroma clipping parameters. [Figure 9] Modified VTM-5.0 ALF luma and chroma clipping parameter signaling is shown, where the clipping parameters are signaled using 2-bit fixed length codes. [Figure 10] FIG. 1 is a block diagram illustrating a method according to a first aspect of the present disclosure. [Figure 11] FIG. 4 is a block diagram illustrating a method according to a second aspect of the present disclosure. [Figure 12] FIG. 2 is a block diagram illustrating a method according to a third aspect of the present disclosure. [Figure 13] FIG. 11 is a block diagram illustrating a method according to a fourth aspect of the present disclosure. [Figure 14] FIG. 11 is a block diagram showing a decoder according to a fifth aspect of the present disclosure. [Figure 15] FIG. 13 is a block diagram showing an encoder according to a sixth aspect of the present disclosure. [Figure 16] FIG. 13 is a block diagram illustrating a decoder according to a ninth aspect of the present disclosure. [Figure 17] FIG. 13 is a block diagram illustrating an encoder according to a tenth aspect of the present disclosure. [Figure 18] FIG. 23 is a block diagram showing a decoder according to an eleventh aspect of the present disclosure. [Figure 19] FIG. 23 is a block diagram showing a decoder according to a twelfth aspect of the present disclosure. [Figure 20] FIG. 23 is a block diagram showing an encoder according to a thirteenth aspect of the present disclosure. [Figure 21] FIG. 23 is a block diagram showing an encoder according to a fourteenth aspect of the present disclosure. [Figure 22] FIG. 31 is a block diagram showing an exemplary structure of a content supply system 3100 for implementing a content distribution service. [Figure 23] FIG. 2 is a block diagram showing the structure of an example of a terminal device.

[0078] In the following, identical reference signs, unless expressly specified otherwise, refer to identical or at least functionally equivalent features. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0079] In the following description, reference is made to the accompanying drawings, which form a part of this disclosure and show, by way of example, 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 aspects and may include structural or logical changes not shown in the drawings. Thus, 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.

[0080] For example, it is understood that disclosure related to a described method may also hold for a corresponding apparatus or system configured to perform the method, and vice versa. For example, when one or more particular method steps are described, a corresponding apparatus may include one or more units, e.g., functional units, for performing the described one or more method steps (e.g., one unit performing the one or more steps, or multiple units performing one or more of the multiple steps, respectively), even if such one or more units are not explicitly described or illustrated. 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 a step for performing a function of the one or more units (e.g., one step for performing a function of the one or more units, or multiple steps for performing a function of one or more of the multiple units, respectively), even if such one or more steps are not explicitly described or illustrated. Furthermore, it is understood that features of various exemplary embodiments and / or aspects described herein may be combined with each other, unless otherwise specified.

[0081] Video coding typically refers to the processing of a series of pictures to form a video or a video sequence. Instead of the term "picture", the terms "frame" or "image" are sometimes used synonymously in the field of video coding. Video coding (or coding in general) includes two parts: video encoding and video decoding. Video encoding is performed at the source side and typically involves processing the original video picture (e.g., by compression) to reduce the amount of data required to represent the video picture (for more efficient storage and / or transmission). Video decoding is performed at the destination side and typically involves the reverse process, as compared to the encoder, to reconstruct the video picture. Any embodiment referring to "coding" a video picture (or pictures in general) is understood to relate to "encoding" or "decoding" a video picture or a respective video sequence. The combination of the encoding and decoding parts is also called a codec (coding and decoding).

[0082] In the case of lossless video coding, the original video picture can be reconstructed, i.e. the reconstructed video picture has the same quality as the original video picture (assuming there are no transmission losses or other data losses during storage or transmission). In the case of lossy video coding, further compression, e.g. by quantization, is performed to reduce the amount of data representing the video picture, and the video picture cannot be perfectly reconstructed at the decoder, i.e. the quality of the reconstructed video picture is lower or worse than the quality of the original video picture.

[0083] Some video coding standards belong to the group of "lossy hybrid video codecs" (i.e., they combine spatial and temporal prediction in the sample domain with 2D transform coding to apply quantization in the transform domain). Each picture of a video sequence is typically divided into a set of non-overlapping blocks, and coding is typically performed at the block level. In other words, at the encoder, the video is typically processed, i.e., encoded, at the block (video block) level, for example by generating a predictive block using spatial (intra-picture) and / or temporal (inter-picture) prediction, subtracting the predictive 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). At the decoder, on the other hand, the reverse process compared to the encoder is applied to the encoded or compressed block to reconstruct the current block for representation. Furthermore, the encoder replicates the decoder processing loop so that both generate the same prediction (eg, intra-prediction and inter-prediction) and / or reconstruction for processing, i.e., coding, subsequent blocks.

[0084] In the following, embodiments of a video coding system 10, a video encoder 20 and a video decoder 30 are described based on FIGS.

[0085] 1A is a schematic block diagram illustrating an example coding system 10, such as video coding system 10 (or coding system 10 for short), that may employ techniques of the present application. A video encoder 20 (or encoder 20 for short) and a video decoder 30 (or decoder 30 for short) of video coding system 10 represent example devices that may be configured to perform techniques according to various examples described herein.

[0086] As shown in FIG. 1A, coding system 10 includes a source device 12 configured to provide encoded picture data 21 to a destination device 14, for example, which decodes the encoded picture data 13.

[0087] The source device 12 comprises an encoder 20 and may additionally, i.e. optionally, comprise a picture source 16 , a pre-processor (or pre-processing unit) 18 , for example a picture pre-processor 18 , and a communication interface or unit 22 .

[0088] Picture source 16 may comprise or be any kind of picture capture device, e.g., a camera for capturing real-world pictures, and / or any kind of picture generation device, e.g., a computer graphics processor for generating computer-animated pictures, or any kind of other device for obtaining and / or providing real-world pictures, computer-generated pictures (e.g., screen content, virtual reality (VR) pictures), and / or any combination thereof (e.g., augmented reality (AR) pictures). Picture source may also be any kind of memory or storage that stores any of the above pictures.

[0089] In distinction to the pre-processor 18 and the processing performed by the pre-processing unit 18 , the picture or picture data 17 may be referred to as raw picture or raw picture data 17 .

[0090] 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 can be understood that the pre-processing unit 18 may be an optional component.

[0091] A video encoder 20 is configured to receive the pre-processed picture data 19 and to provide encoded picture data 21 (as described in further detail below, eg, with reference to FIG. 2).

[0092] The communications interface 22 of the source device 12 may be configured to receive the encoded picture data 21 and to transmit the encoded picture data 21 (or any further processed version thereof) over the communications channel 13 to another device, such as a destination device 14 or any other device, for storage or direct reconstruction.

[0093] The destination device 14 has a decoder 30 (e.g., a video decoder 30) and may additionally, or optionally, have a communications interface or unit 28, a post-processor 32 (or post-processing unit 32), and a display device 34.

[0094] The communications interface 28 of the destination device 14 is configured to receive the encoded picture data 21 (or a further processed version thereof), e.g. directly from the source device 12, or from any other source, e.g. a storage device, e.g. an encoded picture data storage device, and to provide the encoded picture data 21 to a decoder 30.

[0095] Communications interface 22 and communications interface 28 may be configured to transmit or receive encoded picture data 21 or encoded data 13 via a direct communications link between source device 12 and 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.

[0096] The communications interface 22 may be configured, for example, to package the encoded picture data 21 in a suitable format, e.g., into packets, and / or process the encoded picture data using any type of transmission encoding or processing for transmission over a communications link or network.

[0097] The counterpart of the communication interface 22, the communication interface 28, may be configured, for example, to receive the transmitted data and process the transmitted data using any type of corresponding transmission decoding or processing and / or unpackaging to obtain the encoded picture data 21.

[0098] Both communication interface 22 and communication interface 28 may be configured as unidirectional communication interfaces, as indicated by the arrow for communication channel 13 pointing from source device 12 to destination device 14 in FIG. 1A, or as bidirectional communication interfaces, and may be configured, for example, to send and receive messages, for example, to set up a connection, to receive, acknowledge and exchange a communication link and / or any other information related to a data transmission, for example, an encoded picture data transmission.

[0099] The decoder 30 is configured to receive the encoded picture data 21 and to provide decoded picture data 31 or a decoded picture 31 (further details are described below, e.g. with reference to FIG. 3 or FIG. 5).

[0100] The post-processor 32 of the destination device 14 is configured to post-process the decoded picture data 31 (also called reconstructed picture data), e.g., a decoded picture 31, to obtain post-processed picture data 33, e.g., a post-processed picture 33. The post-processing performed by the 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., the decoded picture data 31 for display, e.g., by a display device 34.

[0101] A display device 34 of the destination device 14 is configured to receive the post-processed picture data 33 for displaying the picture, e.g., to a user or viewer. The display device 34 may be or include any type of display for presenting 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 micro LED display, a liquid crystal on silicon (LCoS), a digital light processor (DLP), or any other type of display.

[0102] 1A depicts source device 12 and destination device 14 as separate devices, an embodiment of the devices may include both or both functionality, source device 12 or corresponding functionality and destination device 14 or corresponding functionality. In such an embodiment, 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.

[0103] As will be apparent to one of ordinary skill in the art based on the above description, the presence and (exact) division of functions of different units or functions within source device 12 and / or destination device 14 as shown in FIG. 1A may vary depending on the actual device and application.

[0104] The encoder 20 (e.g., video encoder 20), or the decoder 30 (e.g., video decoder 30), or both the encoder 20 and the decoder 30, may be implemented via processing circuitry as shown in FIG. 1B, e.g., one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, hardware, dedicated video coding, or any combination thereof. The encoder 20 may be implemented via processing circuitry 46 to embody various modules discussed with respect to the encoder 20 of FIG. 2 and / or any other encoder system or subsystem described herein. The decoder 30 may be implemented via processing circuitry 46 to embody various modules discussed with respect to the decoder 30 of FIG. 3 and / or any other decoder system or subsystem described herein. The processing circuitry may be configured to perform various operations, as described below. As shown in FIG. 5. If the techniques are implemented partially in software, an apparatus may store instructions for the software on a suitable non-transitory computer-readable storage medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Either video encoder 20 or video decoder 30 may also be integrated within a single device as part of a combined encoder / decoder (codec), for example as shown in FIG. 1B.

[0105] The source device 12 and destination device 14 may include any of a wide range of devices, including any type of handheld or fixed device, such as a notebook or laptop computer, a mobile phone, a smart phone, 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 a content delivery server), a broadcast receiver device, a broadcast transmitter device, and the like, and may use no operating system or any type of operating system.

[0106] In some cases, source device 12 and destination device 14 may be equipped for wireless communication. Thus, source device 12 and destination device 14 may be wireless communication devices. In some cases, video coding system 10 shown in FIG. 1A is merely an example, and the techniques of the present application may be applied to video coding situations (e.g., video encoding or video decoding) that do not necessarily involve 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.

[0107] For ease of description, embodiments of the present invention are described herein with reference to, for example, High Efficiency Video Coding (HEVC) or Versatile Video Coding (VVC) reference software, the next generation video coding standards developed by the ITU-T Video Coding Experts Group (VCEG) and the ISO / IEC Moving Picture Experts Group (MPEG) Joint Collaboration Team on Video Coding (JCT-VC). Those skilled in the art will appreciate that embodiments of the present invention are not limited to HEVC or VVC.

[0108] Encoders and encoding methods 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 has an input 201 (or input interface 201), a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a loop filter unit 220, a decoded picture buffer (DPB) 230, a mode selection unit 260, an entropy encoding unit 270, and an output 272 (or output interface 272). The mode selection unit 260 may include an inter prediction unit 244, an intra prediction unit 254, and a partition division unit 262. The inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 shown in FIG. 2 may be referred to as a hybrid video encoder or a video encoder with a hybrid video codec.

[0109] The residual calculation unit 204, the transform processing unit 206, the quantization unit 208, and the mode selection unit 260 may be referred to as forming a forward signal path of the encoder 20, while the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 may be referred to as forming a backward signal path of the video encoder 20. The backward signal path of the video encoder 20 corresponds to the signal path of the decoder (see video decoder 30 of 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 referred to as forming an “embedded decoder” of the video encoder 20.

[0110] Picture and Picture Partitioning (Picture and Block) The encoder 20 may be configured to receive, for example, via an input 201, a picture 17 (or picture data 17), for example a picture of a sequence of pictures forming a video or a video sequence. The received picture or picture data may be a preprocessed picture 19 (or preprocessed picture data 19). For simplicity, the following description refers to the picture 17. The 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, for example previously encoded and / or decoded pictures of the same video sequence, i.e. a video sequence that also includes the current picture).

[0111] A (digital) picture is or can be considered as a two-dimensional array or matrix of intensity-valued samples. The samples in the array may be called pixels (short for picture element) or picture elements. The number of samples in the horizontal and vertical directions (or axes) of the array or picture defines the size and / or resolution of the picture. For color representation, typically three color components are used; that is, a picture is represented by or can contain three sample arrays. In an RBG format or color space, a picture contains corresponding red, green and blue sample arrays. However, in video coding, each pixel is typically represented in a luminance and chrominance format or color space, e.g. YCbCr, which contains a luminance component denoted Y (sometimes L is used instead), and two chrominance components denoted Cb and Cr. The luminance (or luma for short) component Y represents the brightness or gray level intensity (e.g., as in a grayscale picture), while the two chrominance (or chroma for short) components Cb and Cr represent the chromaticity or color information components. Thus, a picture in YCbCr format contains 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 can be converted or transformed into YCbCr format and vice versa. This process is also known as color conversion or transformation. If the picture is monochrome, the picture may contain only a luminance sample array. Thus, a picture can be an array of luma samples in monochrome format or an array of luma samples and two corresponding arrays of chroma samples in 4:2:0, 4:2:2, and 4:4:4 color formats, for example.

[0112] An embodiment of video encoder 20 may include a picture partitioning unit (not shown in FIG. 2) configured to partition picture 17 into multiple (typically non-overlapping) picture blocks 203. These blocks may also be referred to as 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 between pictures, or between subsets or groups of pictures, and to partition each picture into corresponding blocks.

[0113] In a further embodiment, the video encoder may be configured to directly receive a block 203 of picture 17, e.g., one, some, or all of the blocks forming picture 17. Picture block 203 may also be referred to as a current picture block or a picture block to be coded.

[0114] Similar to the picture 17, the picture block 203 is or can be considered as a two-dimensional array or matrix of samples with intensity values ​​(sample values), albeit with smaller dimensions than the picture 17. In other words, the block 203 can contain, for example, one sample array (e.g., a luma array in the case of a monochrome picture 17, or a luma or chroma array in the case of a color picture), or three sample arrays (e.g., a luma array and two chroma arrays in the case of a color picture 17), or any other number and / or type of arrays depending on the color format applied. The number of samples in the horizontal and vertical directions (or axes) of the block 203 defines the size of the block 203. Thus, the block may be, for example, an M×N (M columns×N rows) array of samples, or an M×N array of transform coefficients.

[0115] An embodiment of a video encoder 20 such as that shown in FIG. 2 may be configured to encode a picture 17 block by block, eg, encoding and prediction is performed for each block 203.

[0116] Residual calculation The residual calculation unit 204 may be configured to calculate a residual block 205 (also referred to as residual 205) based on the picture block 203 and a prediction block 265 (further details about the prediction block 265 will be described later), for example by sample-by-sample (pixel-by-pixel) subtraction of sample values ​​of the prediction block 265 from sample values ​​of the picture block 203 to obtain the residual block 205 in the sample domain.

[0117] conversion The transform processing unit 206 may be configured to apply a transform, such as a discrete cosine transform (DCT) or a discrete sine transform (DST), to the sample values ​​of the residual block 205 to obtain transform coefficients 207 in the transform domain. The transform coefficients 207 may be referred to as transform residual coefficients and represent the residual block 205 in the transform domain.

[0118] The transform processing unit 206 may be configured to apply an integer approximation of a DCT / DST, such as the transform specified for H.265 / HEVC. Compared to an orthogonal DCT transform, such an integer approximation is typically scaled by a factor. In order to preserve the norm of the residual blocks processed by the forward and inverse transforms, an additional scaling factor is applied as part of the transform process. The scaling factor is typically selected based on certain 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. A specific scaling factor may be specified, for example, for the inverse transform, for example by the inverse transform processing unit 212 (and the corresponding inverse transform, for example by the inverse transform processing unit 312 in the video decoder 30), and a corresponding scaling factor for the forward transform, for example by the transform processing unit 206 in the encoder 20, may be specified accordingly.

[0119] An embodiment of video encoder 20 (and individually transform processing unit 206) may be configured to output transform parameters, e.g., one or more types of transform, e.g., directly or encoded or compressed via entropy encoding unit 270, so that, for example, video decoder 30 may receive and use the transform parameters for decoding.

[0120] 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, which may also be referred to as quantized transform coefficients 209 or quantized residual coefficients 209.

[0121] 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 rounded to an m-bit transform coefficient during quantization, where n is greater than m. The degree of quantization may be modified by adjusting a quantization parameter (QP). For example, for scalar quantization, different scaling may be applied to achieve finer or coarser quantization. A smaller quantization step size corresponds to finer quantization, while a larger quantization step size corresponds to coarser quantization. The applicable quantization step sizes may be indicated by the quantization parameter (QP). The quantization parameter may, for example, be an index to 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 a division by the quantization step size, and corresponding and / or inverse dequantization, e.g., by the inverse quantization unit 210, may include a multiplication by the quantization step size. Some standards, e.g., HEVC, embodiments may be configured to use a quantization parameter to determine the quantization step size. In general, the quantization step size may be calculated based on the quantization parameter using a fixed-point approximation of an equation that includes a division. Additional scaling factors may be introduced for quantization and dequantization to restore the norm of the residual block that may be modified due to the scaling used in the fixed-point approximation of the equation for the quantization parameter and the quantization step size. In one example implementation, the scaling of the inverse transform and the dequantization may be combined. Alternatively, customized quantization tables may be used and signaled, e.g., in the bitstream, from the encoder to the decoder. Quantization is a lossy operation, and the loss increases with increasing quantization step size.

[0122] An embodiment of video encoder 20 (and specifically quantization unit 208) may be configured to output a quantization parameter (QP), e.g., directly or encoded via entropy encoding unit 270, so that video decoder 30, for example, can receive and apply the quantization parameter for decoding.

[0123] inverse quantization Inverse quantization unit 210 is configured to apply the inverse quantization of quantization unit 208 to the quantized coefficients, 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, to obtain dequantized coefficients 211. The dequantized coefficients 211 may also be referred to as dequantized residual coefficients 211, and correspond to transform coefficients 207, although they are typically not identical to the transform coefficients due to losses due to quantization.

[0124] Inverse transformation The inverse transform processing unit 212 is configured to apply an inverse transform of the transform applied by the transform processing unit 206, such as an inverse discrete cosine transform (DCT) or an inverse discrete sine transform (DST) or other inverse transform, to obtain a reconstructed residual block 213 (or corresponding dequantized coefficients 213) in the sample domain. The reconstructed residual block 213 may also be referred to as a transform block 213.

[0125] Reconstruction The reconstruction unit 214 (e.g., an adder or summator 214) is configured to add the transform block 213 (i.e., the reconstructed residual block 213) to the prediction block 265 to obtain a reconstructed block 215 in the sample domain, e.g., by adding sample values ​​of the reconstructed residual block 213 and the prediction block 265 sample by sample.

[0126] 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 in general, to filter the reconstructed samples to obtain filtered samples. The loop filter unit is configured, for example, to smooth pixel transitions or otherwise improve video quality. The loop filter unit 220 may include one or more loop filters, such as a deblocking filter, a sample adaptive offset (SAO) filter, or one or more other filters, such as a bilateral filter, an adaptive loop filter (ALF), a sharpening filter, a smoothing filter, or a collaborative filter, or any combination thereof. Although the loop filter unit 220 is illustrated as an in-loop filter in FIG. 2, in other configurations the loop filter unit 220 may be implemented as a post-loop filter. The filtered block 221 may also be referred to as a filtered reconstructed block 221.

[0127] Embodiments of video encoder 20 (and individually loop filter unit 220) may be configured to output loop filter parameters (such as sample adaptive offset information), e.g., directly or encoded via entropy encoding unit 270, so that, for example, decoder 30 can receive and apply the same loop filter parameters or respective loop filters for decoding.

[0128] Decode Picture Buffer The decoded picture buffer (DPB) 230 may be a memory that stores reference pictures or, in general, 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 previously filtered blocks, e.g., previously reconstructed and filtered blocks 221, of the same current picture or of a different picture, e.g., a previously reconstructed picture, and may provide a complete previously 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 be configured to store one or more unfiltered reconstructed blocks 215, for example if the reconstructed blocks 215 are not filtered by the loop filter unit 220, or unfiltered reconstructed samples in general, or any other further processed version of the reconstructed blocks or samples.

[0129] Mode Selection (Partitioning and Prediction) The mode selection unit 260 has a partitioning unit 262, an inter prediction unit 244 and an intra prediction unit 254 and is configured to receive or obtain original picture data, e.g., original block 203 (current block 203 of current picture 17) and reconstructed picture data, e.g., filtered and / or unfiltered reconstructed samples or blocks, of the same (current) picture and / or from one or more previously decoded pictures, e.g., from a decoded picture buffer 230 or other buffer (e.g., 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.

[0130] The mode selection unit 260 may be configured to determine or select a partitioning (including no partitioning) and a prediction mode (e.g., intra or inter prediction mode) for the current block prediction mode and generate a corresponding prediction block 265 used for calculation of the residual block 205 and reconstruction of the reconstruction block 215.

[0131] An embodiment of the mode selection unit 260 may be configured to select a partitioning and prediction mode (e.g., from those supported by or available to the mode selection unit 260) that provides the best match, i.e., 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 an overall “best”, “minimum”, “optimum”, etc., but may also refer to the termination, or achievement of a selection criterion, such as a value above or below a threshold, or other constraint, potentially leading to a “non-optimal selection”, but reducing complexity and processing time.

[0132] In other words, the partitioning unit 262 may be configured to partition the block 203 into smaller block partitions or sub-blocks (which still constitute blocks), e.g., using quad-tree partitioning (QT), binary partitioning (BT) or ternary tree partitioning (TT) or any combination thereof iteratively, and to perform, e.g., prediction on each of the block partitions or sub-blocks, where 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.

[0133] The partitioning (eg, by partitioning unit 260) and prediction processes (eg, by inter prediction unit 244 and intra prediction unit 254) performed by exemplary video encoder 20 are described in more detail below.

[0134] Partitioning The partitioning unit 262 may partition (or split) the current block 203 into smaller partitions, e.g., smaller blocks of square or rectangular size. These smaller blocks (which may also be called sub-blocks) may be further partitioned into even smaller partitions. This is also called tree partitioning or hierarchical tree partitioning, where e.g., 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 a next, lower tree level, e.g., nodes at tree level 1 (hierarchical level 1, depth 1), which may again be partitioned into two or more blocks at a next, lower level, e.g., tree level 2 (hierarchical level 2, depth 2), and so on, until the partitioning is terminated because 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 that uses a partitioning into two partitions is called a binary tree (BT), a tree that uses a partitioning into three partitions is called a ternary tree (TT), and a tree that uses a partitioning into four partitions is called a quad tree (QT).

[0135] As mentioned above, the term "block" as used herein may refer to a portion of a picture, particularly a square or rectangular portion. With reference to HEVC and VVC, for example, a block may be or correspond to a coding tree unit (CTU), a coding unit (CU), a prediction unit (PU), and a transform unit (TU), and / or a corresponding block, such as a coding tree block (CTB), a coding block (CB), a transform block (TB), or a prediction block (PB).

[0136] For example, a coding tree unit (CTU) may be or may include a CTB of luma samples for a picture having three sample arrays, two corresponding CTBs of chroma samples, or a CTB of samples for a picture coded using three separate color planes and syntax structures used to code a monochrome picture or sample. Correspondingly, a coding tree block (CTB) may be an N×N block of samples for some value of N such that the division of a component into CTBs is a partition division. A coding unit (CU) may be or may include a coding block of luma samples for a picture having three sample arrays, two corresponding coding blocks of chroma samples, or a coding block of samples for a picture coded using three separate color planes and syntax structures used to code a monochrome picture or sample. Correspondingly, a coding block (CB) may be an M×N block of samples for some value of M and N such that the division of a CTB into coding blocks is a partition division.

[0137] In an embodiment, for example according to HEVC, a coding tree unit (CTU) may be divided into CUs by using a quadtree structure, denoted as coding tree. The decision of whether to code a picture region using inter-picture (temporal) or intra-picture (spatial) prediction is made at the CU level. Each CU can be further divided into one, two, or four PUs according to a PU partition type. Within one PU, the same prediction process is applied, and related information is transmitted to the decoder for each PU. After obtaining a residual block by applying a prediction process based on the PU partition type, the CU can be partitioned into transform units (TUs) according to another quadtree structure similar to the coding tree for the CU.

[0138] In an embodiment, according to the latest video coding standard currently under development, for example referred to as Versatile Video Coding (VVC), quad-tree and binary tree (QTBT) partitioning is used to partition the coding blocks. In the QTBT block structure, the CUs can have either a square or rectangular shape. For example, the coding tree units (CTUs) are first partitioned by a quad-tree structure. The quad-tree leaf nodes are further partitioned by a binary or ternary tree (or tri-probe) structure. The partitioning tree leaf nodes are called coding units (CUs), and their segmentation is used for prediction and transformation processes without further partitioning. This means that in the QTBT coding block structure, CUs, PUs, and TUs have the same block size. In parallel, multi-partitioning, for example ternary tree partitioning, has also been proposed to be used with the QTBT block structure.

[0139] In one example, mode selection unit 260 of video encoder 20 may be configured to perform any combination of the partitioning techniques described herein.

[0140] As mentioned above, video encoder 20 may be configured to determine or select a best or optimal prediction mode from a (predetermined) set of prediction modes, which may include, for example, intra-prediction modes and / or inter-prediction modes.

[0141] Intra prediction The set of intra prediction modes may include, for example, 35 different intra prediction modes, e.g., non-directional modes such as DC (or average) mode and planar mode, or directional modes, as defined in HEVC, or may include, for example, 67 different intra prediction modes, e.g., non-directional modes such as DC (or average) mode and planar mode, or directional modes, as defined in VVC.

[0142] The intra prediction unit 254 is configured to use reconstructed samples of neighboring blocks of the same current picture to generate an intra prediction block 265 according to an intra prediction mode from a set of intra prediction modes.

[0143] Intra prediction unit 254 (or, generally, mode selection unit 260) is further configured to output the intra prediction parameters (or, generally, information indicative of the selected intra prediction mode for the block) in the form of syntax element 266 to entropy encoding unit 270 for inclusion in encoded picture data 21 so that, for example, video decoder 30 can receive and use the prediction parameters for decoding.

[0144] Inter Prediction The set (or possible) inter prediction modes depend on available reference pictures (i.e., previous, at least partially decoded pictures, e.g., stored in DBP 230) and other inter prediction parameters, such as whether the entire reference picture is used to look for the best matching reference block or only a portion of the reference picture is used, e.g., a search window area around that region of the current block, and / or whether pixel interpolation, e.g., half / semi-pixel and / or quarter-pixel interpolation, is applied.

[0145] In addition to the above prediction modes, skip mode and / or direct mode may be applied.

[0146] The inter prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (MC) unit (neither of which is shown in FIG. 2). The motion estimation unit may be configured to receive or obtain the picture block 203 (current picture block 203 of current picture 17) and the decoded picture 231, or at least one or more previously reconstructed blocks, e.g., reconstructed blocks of one or more other / different previously decoded pictures 231, for motion estimation. For example, a video sequence may include the current picture and the previously decoded picture 231, or in other words, the current picture and the previously decoded picture 231 may be part of or form a sequence of pictures forming a video sequence.

[0147] The encoder 20 may be configured to, for example, select a reference block from multiple reference blocks of the same or different ones of 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 also being called a motion vector (MV).

[0148] The motion compensation unit is configured to obtain, e.g., receive, inter prediction parameters and perform inter prediction based on or with the inter prediction parameters to obtain an inter prediction block 265. The motion compensation performed by the motion compensation unit may include performing interpolation, possibly to sub-pixel accuracy, based on the motion / block vectors determined by motion estimation to fetch or generate a prediction block. Interpolation filtering may generate additional pixel samples from known pixel samples, thus potentially increasing the number of candidate prediction blocks that can be used to code the picture block. Upon receiving a motion vector for the PU of the current picture block, the motion compensation unit may locate the prediction block to which the motion vector points in one of the reference picture lists.

[0149] 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.

[0150] Entropy Coding The entropy encoding unit 270 is configured to, for example, apply an entropy encoding algorithm or scheme (e.g., a variable length coding (VLC) scheme, a context-adaptive VLC scheme (CAVLC), an arithmetic coding scheme, binarization, context-adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, or other entropy encoding method or technique) or bypass (non-compression) to the quantized coefficients 209, the inter-prediction parameters, the intra-prediction parameters, the loop filter parameters, and / or other syntax elements to obtain encoded picture data 21. The encoded picture data 21 can be output via an output 272, for example in the form of an encoded bitstream 21, so that, for example, the video decoder 30 can receive and use those parameters for decoding. The encoded bitstream 21 can be transmitted to the video decoder 30 or stored in a memory for later transmission or retrieval by the video decoder 30.

[0151] 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 quantize the residual signal directly for certain blocks or frames without the 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.

[0152] Decoder and decoding method 3 illustrates an example of a video decoder 30 configured to implement the techniques of the present application. The video decoder 30 is configured to receive encoded picture data 21 (e.g., encoded bitstream 21), e.g., encoded by encoder 20, to obtain a decoded picture 331. The encoded picture data or bitstream includes information for decoding the encoded picture data, e.g., data representing picture blocks and associated syntax elements of an encoded video slice.

[0153] In the example of FIG. 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, an inter prediction unit 344, and an intra prediction unit 354. Inter prediction unit 344 may be or may include a motion compensation unit. Video decoder 30, in some examples, may perform a decoding path that is generally inverse to the encoding path described with respect to video encoder 100 from FIG. 2.

[0154] As described with respect to encoder 20, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, loop filter 220, decoded picture buffer (DPB) 230, inter prediction unit 344, and intra prediction unit 354 are also referred to as forming an “embedded decoder” of video encoder 20. Thus, inverse quantization unit 310 may be functionally identical to inverse quantization unit 110, 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. Thus, the descriptions provided for the respective units and functions of video encoder 20 correspondingly apply to the respective units and functions of video decoder 30.

[0155] Entropy Decoding The entropy decoding unit 304 is configured to parse the bitstream 21 (or generally, the encoded picture data 21) and, for example, perform entropy decoding on the encoded picture data 21 to obtain, for example, quantized coefficients 309 and / or decoded coding parameters (not shown in FIG. 3 ), for example, any or all of inter prediction parameters (e.g., reference picture indexes 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 schemes mentioned with respect to the entropy encoding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide the inter prediction parameters, intra prediction parameters and / or other syntax elements to the mode selection unit 360 and other parameters to other units of the decoder 30. Video decoder 30 may receive syntax elements at the video slice level and / or at the video block level.

[0156] inverse quantization The inverse quantization unit 310 may be configured to receive a quantization parameter (QP) (or, in general, information regarding inverse quantization) and quantized coefficients from the encoded picture data 21 (e.g., by parsing and / or decoding by the entropy decoding unit 304) and apply inverse quantization based on the quantization parameter to the decoded quantized coefficients 309 to obtain dequantized coefficients 311. The dequantized coefficients 311 may also be referred to as transform coefficients 311. The inverse quantization process may use the quantization parameter determined by the video encoder 20 for each video block in a video slice to determine the degree of quantization, and similarly, the degree of inverse quantization to be applied.

[0157] Reverse 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 a reconstructed residual block 213 in the sample domain. The reconstructed residual block 213 may also be referred to as a transform block 313. The transform may be an inverse transform, e.g., an inverse DCT, an inverse DST, an inverse integer transform, or a conceptually similar inverse transform process. The inverse transform processing unit 312 may further be configured to receive transform parameters or corresponding information from the encoded picture data 21 (e.g., by parsing and / or decoding by the entropy decoding unit 304) to determine the transform to be applied to the dequantized coefficients 311.

[0158] Reconstruction The reconstruction unit 314 (e.g., an adder or summator 314) may be configured to add the reconstructed residual block 313 to the prediction block 365 to obtain a reconstructed block 315 in the sample domain, e.g., by adding sample values ​​of the reconstructed residual block 313 and the prediction block 365.

[0159] filtering Loop filter unit 320 (in coding loop or post coding loop) is configured to filter reconstructed block 315 to obtain filtered block 321, e.g., to smooth pixel transitions or otherwise improve video quality. Loop filter unit 320 may include one or more loop filters, such as a deblocking filter, a sample adaptive offset (SAO) filter, or one or more other filters, e.g., a bilateral filter, an adaptive loop filter (ALF), a sharpening filter, a smoothing filter, or a collaborative filter, or any combination thereof. Although loop filter unit 320 is illustrated as an in-loop filter in FIG. 3, in other configurations loop filter unit 320 may be implemented as a post-loop filter.

[0160] Decode Picture Buffer The decoded video blocks 321 of the picture are then stored in a decoded picture buffer 330. The decoded picture buffer 330 stores the decoded picture 331 as a reference picture for subsequent motion compensation for other pictures and / or for respective output or display.

[0161] The decoder 30 is configured to output the decoded picture 311 for presentation or viewing to a user, for example via an output 312.

[0162] prediction The inter prediction unit 344 may be identical to the inter prediction unit 244 (in particular the motion compensation unit), and the intra prediction unit 354 may be identical in function to the inter prediction unit 254 and performs the partitioning or partitioning decision and prediction based on partitioning and / or prediction parameters or respective information received (e.g. by parsing and / or decoding, e.g. by the entropy decoding unit 304) from the encoded picture data 21. The mode selection unit 360 may be configured to perform a block-wise prediction (intra prediction or inter prediction) based on the reconstructed picture, block or respective samples (filtered or unfiltered) to obtain a prediction block 365.

[0163] When a video slice is coded as an intra-coded (I) slice, intra prediction unit 354 of mode selection unit 360 is configured to generate a prediction block 365 for a picture block of the current video slice based on the signaled intra prediction mode and data from previously decoded blocks of the current picture. When a video picture is coded as an inter-coded (i.e., B or P) slice, inter prediction unit 344 (e.g., a motion compensation unit) of mode selection unit 360 is configured to generate a prediction block 365 for a video block of the current video slice based on the motion vector and other syntax elements received from entropy decode unit 304. For inter prediction, the prediction 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.

[0164] Mode selection unit 360 is configured to determine prediction information for the video blocks of the current video slice by parsing the motion vectors and other syntax elements, and use the prediction information to generate a predictive block for the current video block to be decoded. For example, mode selection unit 360 uses some of the received syntax elements to determine a prediction mode (e.g., intra prediction or inter prediction) to be used to code the video blocks of the video slice, an inter prediction slice type (e.g., a B slice, a P slice, or a GPB slice), construction information for one or more of the reference picture lists for the slice, motion vectors for each inter encoded video block of the slice, inter prediction status for each inter coded video block of the slice, and other information for decoding video blocks in the current video slice.

[0165] Other variations of the video decoder 30 may be used to decode the encoded picture data 21. For example, the decoder 30 may generate an output video stream without a loop filtering unit 320. For example, a non-transform-based decoder 30 may inverse quantize the residual signal directly for certain blocks or frames without the inverse transform processing unit 312. In another embodiment, the video decoder 30 may have the inverse quantization unit 310 and the inverse transform processing unit 312 combined into a single unit.

[0166] 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 the interpolation filtering, the motion vector derivation, or the loop filtering, further operations such as clipping or shifting may be performed on the processing result of the interpolation filtering, the motion vector derivation, or the loop filtering.

[0167] 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, sub-block motion vectors in affine, planar, ATMVP modes, temporal motion vectors, etc.). For example, the value of the motion vector is constrained to a predefined range according to its representation bits. If the representation bits of the motion vector are bitDepth, the range is -2^(bitDepth-1) to 2^(bitDepth-1)-1. For example, if bitDepth is set equal to 16, the range is -32768 to 32767, and if bitDepth is set equal to 18, the range is -131072 to 131071. For example, the value of the derived motion vector (e.g., MVs of four 4x4 sub-blocks in one 8x8 block) is constrained such that the maximum difference between the integer parts of the four 4x4 sub-block MVs is less than or equal to N pixels, e.g., less than or equal to 1 pixel. Here we provide two methods for constraining motion vectors according to bitDepth.

[0168] Method 1: Remove the overflow MSB (Most Significant Bit) by the following calculation:

number

number

[0169] Method 2: Remove the overflow MSB by clipping the value.

number

number

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

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

[0172] 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 ingress port 410, the receiver unit 420, the transmitter unit 440, the egress port 450, and the memory 460. The processor 430 has a coding module 470. The coding module 470 implements the above disclosed embodiments. For example, the coding module 470 implements, processes, prepares, or provides various coding operations. Thus, the inclusion of the coding module 470 substantially improves the functionality of the video coding device 400 and realizes the transformation of the video coding device 400 into different states. Alternatively, the coding module 470 is implemented as instructions stored in the memory 460 and executed by the processor 430.

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

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

[0175] The processor 502 in the device 500 may be a central processing unit. Alternatively, the processor 502 may be any other type of device or devices now existing or later developed that are capable of manipulating or processing information. Although the disclosed implementations can be practiced using a single processor as shown, such as processor 502, advantages in speed and efficiency can be achieved using multiple processors.

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

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

[0178] Though 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.

[0179] In-Loop Filter There are a total of three in-loop filters in VTM3. In addition to the deblocking filter and SAO (the two loop filters in HEVC), an adaptive loop filter (ALF) is also applied in VTM3. The filtering process order in VTM3 is deblocking filter, SAO, ALF.

[0180] ALF In VTM5, an Adaptive Loop Filter (ALF) with block-based filter adaptation is applied: for the luma component, one of 25 filters is selected for each 4x4 block based on the local gradient direction and function.

[0181] Filter Shape: In JEM, two diamond filter shapes (shown in Figure 6) are used for the luma component: for the luma component, a 7x7 diamond shape is applied, and for the chroma component, a 5x5 diamond shape is applied.

[0182] Block Classification: For the luma component, each 4x4 block is categorized into one of 25 classes. The classification index C is the quantized value of its directionality D and action.

number

number

number

[0183] To reduce the complexity of block classification, a subsampled 1-D Laplacian computation is applied. The same subsampled positions are used for the gradient computation in all directions, as shown in Figure 7.

[0184] The maximum and minimum values ​​of the horizontal and vertical gradients are then set as follows:

number

number

[0185] To derive the directional value D, these values ​​are compared with each other and with two thresholds t1 and t2:

number

[0186] The work value A is calculated as follows:

number

number

[0187] For the chroma components in a picture, no classification method is applied, i.e. for each chroma component, a single set of ALF coefficients is applied.

[0188] Geometric transformation of filter coefficients Before filtering each 4x4 luma block, a geometric transformation such as rotation or diagonal and vertical flip is applied to the filter coefficients f(k,l) depending on the gradient value calculated for that block. This is equivalent to applying these transformations to samples within the filter support region. The idea is to make different blocks to which ALF is applied more similar by aligning their orientation.

[0189] Three geometric transformations are introduced, including diagonal and vertical flips and rotations:

number

[0190] Signaling of filter parameters In VTM3, the ALF filter parameters are signaled in the slice header. Up to 25 sets of luma filter coefficients can be signaled. To reduce bit overhead, filter coefficients of different classes can be merged.

[0191] The filtering process can be controlled at the CTB level. A flag is always signaled indicating whether the ALF is applied to the luma CTB. For each chroma CTB, a flag may be signaled indicating whether the ALF is applied to the chroma CTB, which depends on the value of alf_chroma_ctb_present_flag.

[0192] The filter coefficients are quantized with a norm equal to 128. To further constrain the multiplication complexity, coefficient values ​​in central positions are bounded between 0 and 2. 8 , and the remaining positions have coefficient values ​​of -2 7 From 2 7 The bitstream conformance rule applies: the bitstream must be in the range -1 (inclusive). Filtering Process On the decoder side, when ALF is enabled for a CTB, each sample R(i,j) in the CU is filtered to obtain a sample value R'(i,j) as shown below, where L is the filter length and f m,n denote the filter coefficients, and f(k,l) denotes the decoded filter coefficients.

number

[0193] Alternatively, the filtering can be expressed as:

number

number

[0194] From VTM5 onwards (ITU JVET-N0242), the ALF is implemented in a non-linear manner. Equation 21 can be formulated as follows:

number

number

[0195] The filter is further modified by introducing nonlinearity to make the ALF more efficient by using a clipping function to reduce the influence of neighboring sample values ​​(I(x+i,y+j)) when they are too different from the current sample value (I(x,y)) being filtered.

[0196] In VTM5, the ALF filter is modified as follows:

number

[0197] To limit signaling costs and encoder complexity, the evaluation of clipping values ​​is reduced to a small set of possible values: in VTM5, only four possible fixed values ​​are used, which are the same for inter and intra tile groups.

[0198] Since the variance of local differences is often larger for "luma" than for "chroma", two different sets of clipping values ​​are used: for the "luma" and "chroma" filters. The clipping values ​​also include the maximum sample value in each set (here 1024 for a 10-bit bit depth), so clipping can be disabled if not needed.

[0199] The set of clipping values ​​used in VTM5 is given in Table 2. The four values ​​were chosen by approximately evenly dividing, in the logarithmic domain, the full range of sample values ​​(coded with 10 bits) for luma and the range from 4 to 1024 for chroma. More precisely, the luma table of clipping values ​​is obtained by the following formula:

number

number

[0200] Another in-loop filter There are a total of three in-loop filters in VVC. Besides the deblocking filter and SAO (the two loop filters in HEVC), an adaptive loop filter (ALF) is applied. The ALF includes luma ALF, chroma ALF and cross-component ALF (CC-ALF). The ALF filtering process is designed so that the luma ALF, chroma ALF and CC-ALF can run in parallel. The filtering process order in VVC is deblocking filter, SAO, ALF. The SAO in VVC is the same as in HEVC.

[0201] In VVC, a new process called luma mapping with chroma scaling has been added (previously known as adaptive in-loop reshaper). LMCS modifies the pre-encoded and reconstructed sample values ​​by redistributing the codewords across the dynamic range. This new process is performed before deblocking.

[0202] Adaptive Loop Filter In VVC, an Adaptive Loop Filter (ALF) with block-based filter adaptation is applied: for the luma component, one of 25 filters is selected for each 4x4 block based on its direction and performance on local gradients.

[0203] Filter Shape: Two diamond filter shapes (shown in Figure 6) are used: for the luma component a 7x7 diamond shape is applied, and for the chroma component a 5x5 diamond shape is applied.

[0204] Block Classification: For the luma component, each 4x4 block is categorized into one of 25 classes. The classification index C is derived based on its directionality D and the quantized value of the action ^A as follows:

number

[0205] To calculate D and ^A, first the horizontal, vertical, and two diagonal gradients are calculated using the 1-D Laplacian:

number

[0206] To reduce the complexity of block classification, a subsampled 1-D Laplacian computation is applied. The same subsampled positions are used for the gradient computation in all directions, as shown in Figure 7.

[0207] Then, the Dmax and Dmin values ​​of the horizontal and vertical gradients are set as follows:

number

number

[0208] To derive the directional value D, these values ​​are compared with each other and with two thresholds t1 and t2:

number

[0209] The work value A is calculated as follows:

number

number

[0210] For the chroma components in a picture, no classification method is applied, i.e. for each chroma component, a single set of ALF coefficients is applied.

[0211] Geometric transformation of filter coefficients and clipping values Before filtering each 4x4 luma block, a geometric transformation such as a rotation or a diagonal and vertical flip is applied to the filter coefficients f(k,l) and the corresponding filter clipping values ​​c(k,l) depending on the gradient value calculated for that block. This is equivalent to applying these transformations to samples within the filter support region. The idea is to make different blocks to which ALF is applied more similar by aligning their orientation.

[0212] Three geometric transformations are introduced, including diagonal, vertical flip, and rotation:

number

[0213] Signaling of filter parameters The ALF filter parameters are signaled in Adaptation Parameter Sets (APS). In one APS, up to 25 sets of luma filter coefficients and clipping value indices and up to 8 sets of chroma filter coefficients and clipping value indices can be signaled. To reduce bit overhead, filter coefficients of different classes for the luma component can be merged. In the slice header, the indexes of the APSs used for the current slice are signaled.

[0214] The clipping value index decoded from the APS allows to determine 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 given by the following formula:

number

[0215] In 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 indicating whether ALF is applied to the luma CTB. The luma CTB can select a filter set from among 16 fixed filter sets and the filter sets from APSs. 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 the decoder.

[0216] For chroma components, an APS index is signaled in the slice header to indicate the chroma filter sets used for the current slice. At the CTB level, if an APS has multiple chroma filter sets, a filter index is signaled for each chroma CTB.

[0217] The filter coefficients are quantized with a norm equal to 128. To constrain the multiplication complexity, coefficient values ​​at non-central positions are scaled by −2 7 From 2 7The bitstream conformance is enforced such that the coefficients must be in the range of −1 (inclusive). The central position coefficient is not signaled in the bitstream and is assumed to be equal to 128.

[0218] Filtering Process On the decoder side, when ALF is enabled for a CTB, each sample R(i,j) in the CU is filtered, resulting in a sample value R'(i,j) as shown below.

number

[0219] The selected clipping value is coded in the "alf_data" syntax element using a Golomb encoding that corresponds to the clipping value's index in Table 1 above. This encoding is the same as for the filter index. The alf_data may be in an adaptation_parameter_set_rbsp(), which may be referenced by the slice header.

[0220] The syntax details are given in the table below. [Table 4-1] [Table 4-2] [Table 4-3]

[0221] The semantics of the newly introduced syntax elements are as follows: alf_luma_clip equal to 0 specifies that a linear adaptive loop filter is applied to the luma component. alf_luma_clip equal to 1 specifies that a non-linear adaptive loop filter may be applied to the luma component.

[0222] Alf_chroma_clip equal to 0 specifies that a linear adaptive loop filter is applied to the chroma components, and alf_chroma_clip equal to 1 specifies that a non-linear adaptive loop filter is applied to the chroma components. If not present, alf_chroma_clip is inferred to be 0.

[0223] alf_luma_clip_min_eg_order_minus1 plus 1 specifies the minimum order of the exponential-Golomb code for luma clipping index signaling. The value of alf_luma_clip_min_eg_order_minus1 shall be in the range 0 to 6, inclusive.

[0224] alf_luma_clip_eg_order_increase_flag[i] equal to 1 specifies that the minimum order of the exponential-Golomb code for luma clipping index signaling is incremented by 1. alf_luma_clip_eg_order_increase_flag[i] equal to 0 specifies that the minimum order of the exponential-Golomb code for luma clipping index signaling is not incremented by 1. The order of the Exponential-Golomb code expGoOrderYClip[i] used to decode the value of alf_luma_clip_idx[sigFiltIdx][j] is derived as follows: expGoOrderYClip[i]=alf_luma_clip_min_eg_order_minus1+1+alf_luma_clip_eg_order_increase_flag[i]

[0225] alf_luma_clip_idx[sigFiltIdx][j] specifies the clipping index of the clipping value to use before multiplying the jth coefficient of the luma filter signaled by sigFiltIdx. If alf_luma_clip_idx[sigFiltIdx][j] is not present, it is inferred to be equal to 0 (no clipping). The order k of the exponential-Golomb binarization uek(v) is derived as follows: golombOrderIdxYClip[]={0,0,1,0,0,1,2,1,0,0,1,2} k=expGoOrderYClip[golombOrderIdxYClip[j]]

[0226] For sigFiltIdx=0..alf_luma_num_filters_signalled_minus1, j=0..11, the variable filterClips[signFiltIdx][j] is initialized as follows: [Table 5] Element AlfClip, with filtIdx=0..NumAlfFilters-1 and j=0..11 L Luma filter clipping value AlfClip with [filtIdx][j] L is derived as follows: AlfClip L [filtIdx][j]=filterClips[alf_luma_coeff_delta_idx[filtIdx]][j]

[0227] alf_chroma_clip_min_eg_order_minus1 plus 1 specifies the minimum order of the exponential-Golomb code for chroma clipping index signaling. The value of alf_chroma_clip_min_eg_order_minus1 shall be in the range 0 to 6, inclusive.

[0228] alf_chroma_clip_eg_order_increase_flag[i] equal to 1 specifies that the minimum order of the exponential-Golomb code for chroma clipping index signaling is incremented by 1. alf_chroma_clip_eg_order_increase_flag[i] equal to 0 specifies that the minimum order of the exponential-Golomb code for chroma clipping index signaling is not incremented by 1. The order of the Exponential-Golomb code expGoOrderC[i] used to decode the value of alf_chroma_clip_idx[j] is derived as follows: expGoOrderC[i]=alf_chroma_clip_min_eg_order_minus1+1+alf_chroma_clip_eg_order_increase_flag[i]

[0229] alf_chroma_clip_idx[j] specifies the clipping index of the clipping value to use before multiplying the jth coefficient of the chroma filter. If alf_chroma_clip_idx[j] is not present, it is inferred to be 0 (no clipping). The order k of the exponential-Golomb binarization uek(v) is derived as follows: golombOrderIdxC[]={0,0,1,0,0,1} k=expGoOrderC[golombOrderIdxC[j]] Element AlfClip for j=0..5 C Chroma filter clipping value AlfClip with [j] C is derived as follows: [Table 6]

[0230] ALF syntax specification according to VVC specifications Adaptive Loop Filter Process 1.1 General The inputs of this process are the reconstructed picture sample arrays recPictureL, recPictureCb and recPictureCr prior to the adaptive loop filter. The output of this process is the modified reconstructed picture sample arrays alfPictureL, alfPictureCb, and alfPictureCr after the adaptive loop filter.

[0231] The sample values ​​in the modified reconstructed picture sample arrays alfPictureL, alfPictureCb, and alfPictureCr after the adaptive loop filter are initially set equal to the sample values ​​in the reconstructed picture sample arrays recPictureL, recPictureCb, and recPictureCr prior to the adaptive loop filter, respectively.

[0232] If the value of tile_group_alf_enabled_flag is equal to 1, then for every coding tree unit with luma coding tree block position (rx, ry), where rx=0..PicWidthInCtbs-1 and ry=0..PicHeightInCtbs-1, the following process is applied: When the value of alf_ctb_flag[0][rx][ry] is equal to 1, the coding tree block filtering process for the luma samples specified in section 1.2 is called. The luma coding tree block position (xCtb, yCtb) set equal to recPictureL, alfPictureL, and (rx<<CtbLog2SizeY, ry<<CtbLog2SizeY) is input, and the output is the modified filtered picture alfPictureL. When the value of alf_ctb_flag[1][rx][ry] is equal to 1, the coding tree block filtering process for the chroma samples specified in section 1.1 is called. The recPicture set equal to recPictureCb, the alfPicture set equal to alfPictureCb, and the chroma coding tree block position (xCtbC, yCtbC) set equal to (rx<<(CtbLog2SizeY-1), ry<<(CtbLog2SizeY-1)) are input, and the output is the modified filtered picture alfPictureCb. When the value of alf_ctb_flag[2][rx][ry] is equal to 1, the coding tree block filtering process for the chroma samples specified in section 1.4 is called. The recPicture set equal to recPictureCr, the alfPicture set equal to alfPictureCr, and the chroma coding tree block position (xCtbC, yCtbC) set equal to (rx<<(CtbLog2SizeY-1), ry<<(CtbLog2SizeY-1)) are input, and the output is the modified filtered picture alfPictureCr.

[0233] 1.2 Coding Tree Block Filtering Process on Luma Samples The input to this process is as follows: the reconstructed luma picture sample array recPictureL prior to the adaptive loop filtering process; the filtered reconstructed luma picture sample array alfPictureL, The luma position (xCtb, yCtb) that specifies the top-left sample of the current luma coding tree block relative to the top-left sample of the current picture.

[0234] The output of this process is the modified filtered reconstructed luma picture sample array alfPictureL.

[0235] The derivation process for the filter indices in Section 1.3 is invoked. The reconstructed luma picture sample array recPictureL with positions (xCtb, yCtb) is taken as input, and filtIdx[x][y] and transposeIdx[x][y], for x,y = 0..CtbSizeY-1, are the outputs.

[0236] To derive the filtered reconstructed luma sample alfPictureL[x][y], each reconstructed luma sample in the current luma coding tree block recPictureL[x][y], for x,y=0..CtbSizeY-1, is filtered as follows: The array of luma filter coefficients f[j] corresponding to the filter specified by filtIdx[x][y], for j=0..12, is derived as follows: f[j]=AlfCoeffL[filtIdx[x][y]][j] The array of luma filter clipping values ​​c[j] corresponding to the filter specified by filtIdx[x][y], for j=0..11, is derived as follows: c[j]=AlfClipL[filtIdx[x][y]][j]

[0237] The luma filter coefficient filterCoeff is derived depending on transposeIdx[x][y] as follows: [Table 7]

[0238] For a given array of luma samples, recPicture, the location (hx,vy) of each corresponding luma sample (x,y) in the array is derived as follows: [Table 8]

[0239] The variable sum is derived as follows: [Table 9-1] [Table 9-2]

[0240] The modified filtered reconstructed luma picture samples alfPictureL[xCtb+x][yCtb+y] are derived as follows: [Table 10]

[0241] 1.3 ALF transposition of luma samples and derivation process of filter index The inputs for this process are: The luma position (xCtb, yCtb) that specifies the top-left sample of the current luma coding tree block relative to the top-left sample of the current picture. The reconstructed luma picture sample array recPictureL prior to the adaptive loop filtering process

[0242] The output of this process is: Classification filter index array filtIdx[x][y], where x,y=0..CtbSizeY-1 Transpose index array, transposeIdx[x][y], where x,y=0..CtbSizeY-1

[0243] For a given array of luma samples, recPicture, the location (hx,vy) of each corresponding luma sample (x,y) in the array is derived as follows: hx=Clip3(0,pic_width_in_luma_samples-1,x) vy=Clip3(0,pic_height_in_luma_samples-1,y)

[0244] The classification filter index array filtIdx and the transpose index array transposeIdx are derived by the following ordered steps: For x,y=-2..CtbSizeY+1, the variables filtH[x][y], filtV[x][y], filtD0[x][y], and filtD1[x][y] are derived as follows: If both x and y are even numbers or both x and y are uneven numbers, the following applies: [Table 11] Otherwise, filtH[x][y], filtV[x][y], filtD0[x][y], and filtD1[x][y] are set to 0.

[0245] As x,y=0..(CtbSizeY-1)>>2, the variables varTempH1[x][y], varTempV1[x][y], varTempD01[x][y], varTempD11[x][y] and varTemp[x][y] are derived as follows: [Table 12]

[0246] The variables hv1, hv0 and dirHV are derived as follows: [Table 13]

[0247] The variables d1, d0 and dirD are derived as follows: [Table 14]

[0248] The variables hvd1, hvd0 are derived as follows: [Table 15]

[0249] The variables dirS[x][y], dir1[x][y] and dir2[x][y] are derived as follows: [Table 16]

[0250] For x,y=0..CtbSizeY-1, the variable avgVar[x][y] is derived as follows: [Table 17]

[0251] For x=y=0..CtbSizeY-1, the classification filter index array filtIdx[x][y] and the transpose index array transposeIdx[x][y] are derived as follows: [Table 18] If dirS[x][y] is not equal to 0, filtIdx[x][y] is modified as follows: [Table 19]

[0252] 1.4 Coding Tree Block Filtering Process on Chroma Samples The inputs for this process are: the reconstructed chroma picture sample array recPicture prior to the adaptive loop filtering process; the filtered reconstructed chroma picture sample array alfPicture, The chroma position (xCtbC, yCtbC) that specifies the top-left sample of the current chroma coding tree block relative to the top-left sample of the current picture.

[0253] The output of this process is the modified filtered reconstructed chroma picture sample array alfPicture.

[0254] The size of the current chroma coding tree block ctbSizeC is derived as follows: ctbSizeC=CtbSizeY / SubWidthC

[0255] To derive the filtered reconstructed chroma sample alfPicture[x][y], each reconstructed chroma sample in the current chroma coding tree block recPicture[x][y], for x,y=0..ctbSizeC-1, is filtered as follows:

[0256] For each corresponding chroma sample (x,y) in a given array of chroma samples, recPicture, the position (hx,vy) is derived as follows: [Table 20]

[0257] The variable sum is derived as follows: [Table 21]

[0258] The modified filtered reconstructed chroma picture samples alfPicture[xCtbC+x][yCtbC+y] are derived as follows: [Table 22]

[0259] As described above and shown in FIG. 8, the ALF luma and chroma clipping parameters are transmitted using order-K exponential-Golomb codes similar to the ALF filter coefficients.

[0260] The use of exponential-Golomb codes of order K for clipping parameters may not be efficient in terms of coding efficiency, because the signaled clipping parameters are simply indices into a table of clipping values ​​(see Table 2 above). The index values ​​range from 0 to 3. Thus, signaling index values ​​from 0 to 3 using exponential-Golomb codes of order K as with the ALF filter coefficients would require the use of additional syntax elements alf_luma_clip_min_eg_order_min_minus1, alf_luma_clip_eg_order_increase_flag[i] to determine the value K (the order of exponential-Golomb codes used), and then the syntax element alf_luma_clip_idx is signaled using exponential-Golomb codes of order K. This signaling method is therefore complex and not efficient in terms of coding efficiency. Thus, a simpler method of signaling clipping parameters is desired.

[0261] In one embodiment of the proposed solution (Solution 1), as shown in Fig. 9, the clipping parameters are signaled using a fixed length code, and thus the syntax elements alf_luma_clip_min_eg_order_minus1, alf_luma_clip_eg_order_increase_flag[i] are not used. The syntax element alf_luma_clip_idx is signaled using a 2-bit fixed length code. This method has the advantage that the clipping parameters are signaled in a very simple manner and the coding efficiency is improved, since most of the syntax elements related to K-th order exponential-Golomb codes are not signaled anymore.

[0262] The corrected alf_data syntax is: [Table 23-1] [Table 23-2] [Table 23-3]

[0263] As an embodiment of an alternative solution (Solution 2), truncated unary coding may be used to signal the clipping parameter index.

[0264] As an embodiment of the alternative solution (Solution 3), if the number of clipping parameters is changed from a fixed value of 4 to a different number greater than 4, the fixed length code (v) "value v" is correspondingly increased. For example, if the number of clipping parameters is increased from 4 to 5 or 6, the fixed length code uses 3 bits to signal the clipping parameters.

[0265] As an embodiment of an alternative solution (Solution 4), the ALF filter coefficients are signaled using a fixed length code instead of a Kth order exponential-Golomb code.

[0266] 10 is a block diagram illustrating a method according to a first aspect of the present disclosure, the method including obtaining a bitstream, where at least one bit in the bitstream represents a syntax element for a current block (1001), the syntax element being an adaptive loop filter (ALF) clipping value index that specifies a clipping index of a clipping value to use before multiplying an ALF coefficient, parsing the bitstream to obtain a value of the syntax element for the current block, the syntax element being coded using a fixed length code (1002), and applying adaptive loop filtering to the current block based on the value of the syntax element for the current block (1003).

[0267] 11 is a block diagram illustrating a method according to a second aspect of the present disclosure. According to the second aspect, a coding method implemented by a decoding device is provided. The method includes obtaining a bitstream, where at least one bit in the bitstream represents a syntax element for a current block (1101), the syntax element being an adaptive loop filter (ALF) clipping value index or an ALF coefficient parameter; parsing the bitstream to obtain a value of the syntax element for the current block, where the value of the syntax element for the current block is obtained by using only the at least one bit of the syntax element (1102); and applying adaptive loop filtering to the current block based on the value of the syntax element for the current block (1103).

[0268] 12 is a block diagram illustrating a method according to a third aspect of the present disclosure. According to the third aspect, a coding method is provided implemented by an encoding device. The method includes: determining (1201) a value of a syntax element for a current block, the syntax element specifying the clipping index of the clipping value to be used before multiplying a coefficient of an adaptive loop filter (ALF); and generating (1202) a bitstream based on the value of the syntax element, at least one bit in the bitstream representing the syntax element, the syntax element being coded using a fixed length code.

[0269] 13 is a block diagram illustrating a method according to a fourth aspect of the present disclosure. According to the fourth aspect, a coding method is provided implemented by an encoding device, the method including: determining (1301) a value of a syntax element for a current block, the syntax element being an adaptive loop filter (ALF) clipping value or an ALF filter coefficient parameter; and generating a bitstream based on the value of the syntax element, at least one bit in the bitstream representing the syntax element, the at least one bit of the syntax element being obtained by using only the value of the syntax element for the current block.

[0270] 14 is a block diagram illustrating a decoder according to a fifth aspect of the present disclosure. According to the fifth aspect of the present disclosure, there is provided a decoder 1400 comprising a processing circuit 1401 for performing a method according to the first or second aspect or any implementation thereof.

[0271] 15 is a block diagram illustrating an encoder according to a sixth aspect of the present disclosure. According to the sixth aspect of the present disclosure, there is provided an encoder 1500 comprising a processing circuit 1501 for performing a method according to the third or fourth aspect or any implementation thereof.

[0272] 16 is a block diagram illustrating a decoder according to a ninth aspect of the present disclosure. According to the ninth aspect of the present disclosure, a decoder 1600 is provided, comprising one or more processors 1601; and a non-transitory computer-readable storage medium 1602 coupled to the processors 1601 and storing programming for execution by the processors 1601, the programming, when executed by the processors 1601, configuring the decoder 1600 to perform a method according to the first or second aspect or any implementation thereof.

[0273] 17 is a block diagram illustrating an encoder according to a tenth aspect of the present disclosure. According to the tenth aspect of the present disclosure, an encoder 1700 is provided, comprising one or more processors 1701; and a non-transitory computer-readable storage medium 1702 coupled to the processors 1701 and storing programming for execution by the processors 1701, the programming, when executed by the processors 1701, configuring the encoder 1700 to perform a method according to the third or fourth aspect or any implementation thereof.

[0274] 18 is a block diagram illustrating a decoder according to an eleventh aspect of the present disclosure. According to the eleventh aspect of the present disclosure, a decoder 1800 is provided, comprising an entropy decoding unit 1801 (which may be the entropy decoding unit 304) configured to obtain a bitstream 1811, where at least one bit in the bitstream 1811 represents a syntax element for a current block, the syntax element specifying the clipping index of the clipping value to be used before multiplying coefficients of an adaptive loop filter (ALF); the entropy decoding unit 1801 is further configured to parse the bitstream 1811 to obtain a value 1812 of the syntax element for the current block, where the syntax element is coded using a fixed length code; and a filtering unit 1803 (which may be the loop filter 320) configured to apply adaptive loop filtering to the current block based on the value 1812 of the syntax element for the current block.

[0275] 19 is a block diagram illustrating a decoder according to a twelfth aspect of the present disclosure. According to the twelfth aspect of the present disclosure, a decoder 1900 is provided, comprising an entropy decoding unit 1901 (which may be the entropy decoding unit 304) configured to obtain a bitstream 1911, where at least one bit in the bitstream 1911 represents a syntax element for a current block, the syntax element being an ALF clipping value index or an ALF coefficient parameter, the entropy decoding unit 1801 further configured to parse the bitstream to obtain a value 1912 of the syntax element for the current block, where the value of the syntax element for the current block is obtained by using only the at least one bit of the syntax element; and a filtering unit (which may be the loop filter 320) configured to apply adaptive loop filtering to the current block based on the value 1912 of the syntax element for the current block.

[0276] 20 is a block diagram illustrating an encoder according to a thirteenth aspect of the present disclosure. According to a thirteenth aspect of the present disclosure, an encoder 2000 is provided, which comprises: The entropy encoding unit includes: a determination unit 2001 (which may be a loop filter 220) configured to determine a value 2012 of a syntax element for a current block, the syntax element specifying the clipping index of the clipping value to be used before multiplying coefficients of an adaptive loop filter (ALF); and an entropy encoding unit 2002 (which may be an entropy encoding unit 270) configured to generate a bitstream 2011 based on the value 2012 of the syntax element, the entropy encoding unit comprising: at least one bit in the bitstream 2011 representing the syntax element, the syntax element being coded using a fixed length code.

[0277] 21 is a block diagram illustrating an encoder according to a fourteenth aspect of the present disclosure. According to the fourteenth aspect of the present disclosure, an encoder 2100 is provided, comprising: a determining unit 2101 (which may be a loop filter 220) configured to determine a value 2112 of a syntax element for a current block, the syntax element being an ALF clipping value index or an ALF coefficient parameter; and an entropy encoding unit 2102 (which may be an entropy encoding unit 270) configured to generate a bitstream 2111 based on the value 2112 of the syntax element, the at least one bit in the bitstream 2111 representing the syntax element, the at least one bit of the syntax element being obtained by using only the value of the syntax element for the current block.

[0278] The present disclosure provides the following further embodiments.

[0279] Embodiment 1. A method of coding implemented by a decoding device, comprising: obtaining a bitstream, where at least one bit in the bitstream corresponds to a syntax element for a current block (or a set of blocks, one block of which is the current block); parsing the bitstream to obtain a value of the syntax element for the current block, where the value of the syntax element for the current block only refers to the at least one bit; and filtering the current block based on the value of the syntax element for the current block.

[0280]

[0023] Embodiment 2. The method of embodiment 1, wherein the values ​​of the syntax elements are coded according to a fixed length code, which means that all possible values ​​of the syntax elements are signaled using the same number of bits.

[0281]

[0023] Embodiment 3. The method of embodiment 1, wherein the values ​​of the syntax elements are coded according to a truncated unary code, which means that the most frequently occurring value of the given syntax element is signaled using the least number of bits and the least occurring value of the syntax element is signaled using the most number of bits.

[0282]

[0021] Embodiment 4. The method of any one of embodiments 1-3, wherein the syntax element is an adaptive loop filter clipping index parameter.

[0283]

[0023] Embodiment 5. The method of any one of embodiments 1-3, wherein the syntax elements are adaptive loop filter coefficient parameters.

[0284]

[0023] Embodiment 6. The method of any one of embodiments 1 to 5, wherein the values ​​of the syntax elements are used to determine filter coefficients, and the filter coefficients are used in the filtering process.

[0285]

[0023] Embodiment 7. The method of any one of embodiments 1 to 5, wherein the value of the syntax element is used to determine a clipping range, which is used in the filtering process (the clipping range is used to limit the amount of modification allowed for a given sample by its neighboring samples).

[0286] Embodiment 8. A decoder (30) comprising processing circuitry for carrying out the method according to any one of embodiments 1 to 7.

[0287] Embodiment 9. A computer program product comprising program code for carrying out the method according to any one of embodiments 1 to 7.

[0288] Embodiment 10. one or more processors; A decoder having a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform a method according to any one of embodiments 1 to 7.

[0289] The following is a description of the encoding and decoding methods and systems using them as illustrated in the above embodiments.

[0290] 22 is a block diagram showing a content delivery system 3100 for implementing a content delivery service. The content delivery system 3100 includes a capture device 3102, a terminal device 3106, and optionally a display 3126. The capture device 3102 communicates with the terminal device 3106 through a communication link 3104. The communication link may include the communication channel 13 described above. The communication link 3104 includes, but is not limited to, WIFI, Ethernet, cable, wireless (3G / 4G / 5G), USB, or any type of combination thereof.

[0291] The capture device 3102 may generate data and encode the data by the encoding method as shown in the above embodiments. Alternatively, the capture device 3102 may deliver the data to a streaming server (not shown), which encodes the data and transmits the encoded data to the terminal device 3106. The capture device 3102 may include, but is not limited to, a camera, a smartphone or pad, a computer or laptop, a video conferencing system, a PDA, a vehicle mounted device, or any combination thereof. For example, the capture device 3102 may include a source device 12 as described above. If the data includes video, a video encoder 20 included in the capture device 3102 may actually perform the video encoding process. If the data includes audio (i.e., voice), an audio encoder included in the capture device 3102 may actually perform the audio encoding process. For some practical scenarios, the capture device 3102 delivers the encoded video and audio data by multiplexing them together. In other practical scenarios, for example in a videoconferencing 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.

[0292] In the content delivery system 3100, the terminal device 310 receives and plays the encoded data. The terminal device 3106 may be a device having data receiving and restoring capabilities, such as a smartphone or pad 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video recorder (DVR) 3112, a TV 3114, a set-top box (STB) 3116, a video conferencing system 3118, a video surveillance system 3120, a personal digital assistant (PDA) 3122, a vehicle mounted device 3124, or any combination of these, that can decode the encoded data described above. For example, the terminal device 3106 may include the destination device 14 described above. If the encoded data includes video, the video decoder 30 included in the terminal device is prioritized to perform video decoding. If the encoded data includes audio, the audio decoder included in the terminal device is prioritized to perform audio decoding processing.

[0293] For a terminal device having a display, such as a smartphone or pad 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video recorder (DVR) 3112, a TV 3114, a personal digital assistant (PDA) 3122, or a vehicle mounted device 3124, the terminal device can provide the decoded data to its display. For a terminal device without a display, such as a STB 3116, a video conferencing system 3118, or a video surveillance system 3120, an external display 3126 is contacted thereto to receive and display the decoded data.

[0294] When each device in this system performs encoding or decoding, the picture encoding device or picture decoding device shown in the above-mentioned embodiments can be used.

[0295] 23 is a diagram showing the structure of an example of the terminal device 3106. After the terminal device 3106 receives the stream from the capture device 3102, the protocol progression unit 3202 analyzes the transmission protocol of the stream. The protocol includes, but is 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 kind of combination thereof.

[0296] After the protocol proceeding 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, for some practical scenarios, for example in a video conferencing system, the encoded audio data and the encoded video data are not multiplexed. In this situation, the encoded data is sent to the video decoder 3206 and the audio decoder 3208 without passing through the demultiplexing unit 3204.

[0297] Through the demultiplexing process, a video elementary stream (ES), an audio ES, and optionally subtitles are generated. A video decoder 3206 including the video decoder 30 as described in the above-mentioned embodiments decodes the video ES by the decoding method as shown in the above-mentioned embodiments to generate video frames, and provides the data to a synchronization unit 3212. An audio decoder 3208 decodes the audio ES to generate audio frames, and provides the data to a synchronization unit 3212. Alternatively, the video frames may be stored in a buffer (not shown in FIG. 23) before being provided to the synchronization unit 3212. Similarly, the audio frames may be stored in a buffer (not shown in FIG. 23) before being provided to the synchronization unit 3212.

[0298] The synchronization unit 3212 synchronizes the 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. Information may be coded in the syntax using timestamps for the presentation of the coded audio and visual data and for the delivery of the data stream itself.

[0299] If subtitles are included in the stream, the subtitle decoder 3210 decodes the subtitles, synchronizes them with the video and audio frames, and provides the video / audio / subtitles to the video / audio / subtitle display 3216.

[0300] The present invention is not limited to the above-mentioned system, and any of the picture encoding devices or picture decoding devices in the above-mentioned embodiments can be incorporated into other systems, for example, an automobile system.

[0301] Although the embodiments of the present disclosure have been described primarily in terms of video coding, it should be noted that the 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, as in video coding. In general, when picture processing coding is limited to a single picture 17, only inter prediction units 244 (encoder) and 344 (decoder) may not be available. All other features (also referred to as tools or techniques) of video encoder 20 and video decoder 30 may be used equally for still picture processing. The other functions are, for example, 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.

[0302] The embodiments of, for example, the encoder 20 and the decoder 30, and the functions described herein with reference to, for example, the encoder 20 and the decoder 30, may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on a computer-readable medium or transmitted over a communication medium as one or more instructions or code and executed by a hardware-based processing unit. The computer-readable medium may include a computer-readable storage medium corresponding to a tangible medium, such as a data storage medium, or a communication medium including any medium that facilitates transfer of a computer program from one place to another, for example according to a communication protocol. Thus, the computer-readable medium may generally correspond to (1) a tangible computer-readable storage medium that is non-transitory, or (2) a communication medium, such as a signal or carrier wave. The data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0303] 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 referred to as 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 waves, and microwaves, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio waves, and microwaves are included within the definition of media. 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 are instead directed to non-transitory, tangible storage media. As used herein, disk and disc include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks and Blu-ray discs, where disks typically reproduce data magnetically while discs reproduce data optically using lasers. Combinations of the above should also be included within the scope of computer readable media.

[0304] 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. Thus, the term "processor" as used herein may refer to any of the foregoing structures, or any other structure suitable for implementation of the techniques described herein. Furthermore, in some aspects, the functionality described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding, or may be incorporated into a combined codec. Also, these techniques may be implemented entirely in one or more circuit or logic elements.

[0305] 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). In this disclosure, various components, modules, or units are described to highlight functional aspects of an apparatus configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, the various units may be combined in a codec hardware unit or may be provided by a collection of interoperating hardware units that include one or more processors as described above in association with suitable software and / or firmware.

Claims

1. A coding method implemented by a decoding device, the method comprising: obtaining a bitstream, at least one bit in the bitstream representing a syntax element, the syntax element being an ALF coefficient parameter; parsing the bitstream to obtain values ​​of the syntax elements, wherein the ALF coefficient parameters are used to determine ALF coefficients; applying adaptive loop filtering based on the ALF coefficients; the syntax element applies to a set of blocks, method.

2. A coding method implemented by a decoding device, the method comprising: obtaining a bitstream, at least one bit in the bitstream representing a syntax element, the syntax element being an ALF coefficient parameter; parsing the bitstream to obtain values ​​of the syntax elements, wherein the ALF coefficient parameters are used to determine ALF coefficients; applying adaptive loop filtering based on the ALF coefficients; the syntax elements are at a slice level, method.

3. A coding method implemented by a decoding device, the method comprising: obtaining a bitstream, at least one bit in the bitstream representing a syntax element, the syntax element being an ALF coefficient parameter; parsing the bitstream to obtain values ​​of the syntax elements, wherein the ALF coefficient parameters are used to determine ALF coefficients; applying adaptive loop filtering based on the ALF coefficients; the value of the syntax element is an unsigned integer. method.

4. 1. A coding method implemented by an encoding device, the method comprising: determining a value of a syntax element for a current block, the syntax element being an ALF coefficient parameter; generating a bitstream based on the value of the syntax element, wherein at least one bit in the bitstream represents the syntax element, and the ALF coefficient parameters are used to determine an ALF coefficient; the syntax element applies to a set of blocks, method.

5. A coding method implemented by an encoding device, the method comprising: determining a value of a syntax element for a current block, the syntax element being an ALF coefficient parameter; generating a bitstream based on the value of the syntax element, wherein at least one bit in the bitstream represents the syntax element, and the ALF coefficient parameters are used to determine an ALF coefficient; the syntax elements are at a slice level, method.

6. A coding method implemented by an encoding device, the method comprising: determining a value of a syntax element for a current block, the syntax element being an ALF coefficient parameter; generating a bitstream based on the value of the syntax element, wherein at least one bit in the bitstream represents the syntax element, and the ALF coefficient parameters are used to determine an ALF coefficient; the value of the syntax element is an unsigned integer. method.

7. A decoder (30) having processing circuitry for carrying out the method according to any one of claims 1 to 3.

8. An encoder (20) having processing circuitry for carrying out the method according to any one of claims 4 to 6.

9. A non-transitory computer readable medium carrying instruction code which, when executed by a computing device, causes the computing device to perform the method of any one of claims 1 to 6.

10. one or more processors; A decoder comprising: a non-transitory computer readable storage medium coupled to said processor and storing programming for execution by said processor, said programming, when executed by said processor, configuring said decoder to perform a method according to any one of claims 1 to 3. decoder.

11. one or more processors; and a non-transitory computer readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the encoder to perform the method of any one of claims 4 to 6. Encoder.

12. 1. A coding method implemented by an encoding device, the method comprising: obtaining a value of a syntax element, the syntax element being an ALF coefficient parameter, the ALF coefficient parameter being used to determine an ALF coefficient; applying adaptive loop filtering based on the values ​​of the syntax elements; encoding the syntax elements into a bitstream; the syntax element applies to a set of blocks, method.

13. A method of decoding a bitstream by a decoder, the bitstream including syntax elements, a processor of the decoder decodes the bitstream to obtain syntax elements, the syntax elements being ALF coefficient parameters, the ALF coefficient parameters being used to determine ALF coefficients; the processor is configured to apply adaptive loop filtering based on the ALF coefficients; the syntax element applies to a set of blocks, method.

Images