Clipping levels for nonlinear adaptive loop filters.

Abstract

To provide clipping levels for a non-linear adaptive loop filter.SOLUTION: There is provided a method for in-loop filtering by performing adaptive loop filtering on a reconstructed frame of a video stream, implemented by an encoding device or a decoding device. The method includes the steps of: forming differences between a pixel of the reconstructed frame and neighboring pixels in a connected area of the pixel; clipping the differences according to respective clipping levels; forming a weighted sum of the clipped differences; and adding the weighted sum to the pixel to determine a filtered pixel. The respective clipping levels are chosen from a same set of clipping levels for luma and chroma components.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority from International Patent Application No. PCT / RU2019 / 000454, filed June 24, 2019, with the Russian Patent Office; International Patent Application No. PCT / RU2019 / 000456, filed June 25, 2019, with the Russian Patent Office; International Patent Application No. PCT / RU2019 / 000476, filed July 3, 2019, with the Russian Patent Office; U.S. Provisional Application No. 62,871,200, filed July 7, 2019, with the United States Patent and Trademark Office; and International Patent Application No. PCT / RU2019 / 000483, filed July 8, 2019, with the Russian Patent and Trademark Office, the disclosures of which are incorporated by reference in their entireties.

[0002] [Technical field] Generally, this disclosure relates to the field of video coding. More specifically, this disclosure relates to filters (e.g., nonlinear in-loop filters) for video coding, methods for filtering reconstructed video frames, and encoding and decoding devices including filters for video coding. [Background technology]

[0003] Video coding (video encoding and / or decoding) is used in a wide range of digital video applications, such as broadcast digital TV, video transmission over the Internet and mobile networks, real-time conversation applications such as video chat, video conferencing, DVD and Blu-ray discs, video content acquisition and editing systems, and camcorders in security applications.

[0004] The amount of video data required to render even a relatively short video can be substantial, which can create difficulties when the data is streamed or communicated across communication networks with limited bandwidth capacity. Therefore, video data is typically compressed before being communicated across modern telecommunications networks. Video size can also be an issue when the video is stored on a storage device, as 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 needed to represent a digital video image. The compressed data is then received at the destination by a video decompression device, which decodes the video data. Due to limited network resources and ever-increasing demands for higher video quality, compression and decompression techniques that improve compression ratios with little or no sacrifice in picture quality are desirable.

[0005] The recently adopted ITU-T H.265 / HEVC standard (ISO / IEC 23008-2:2013, "Information technology - High efficiency coding and media delivery in heterogeneous environments - Part 2: High efficiency video coding", November 2013) proclaims a set of state-of-the-art video coding tools that offer a reasonable trade-off between coding efficiency and computational complexity.

[0006] An overview of the ITU-T H.265 / HEVC standard is given in Gary J. Sullivan, "Overview of the High Efficiency Video Coding (HEVC) Standard," IEEE Transactions on Circuits and Systems for Video Technology, Vol. 22, No. 12, December 2012, the entire contents of which are incorporated by reference.

[0007] One video coding tool from this standard is an adaptive loop filter that performs filtering on a reconstructed frame before using the frame for prediction. A conventional adaptive loop filter is described in Qian Chen, Yunfei Zheng, Peng Yin, Xiaoan Lu, Joel Sol'e, Qian Xu, Edouard Francois, and Dapeng Wu, "Classified Quadtree-based Adaptive Loop Filter," 2011 IEEE International Conference on Multimedia and Expo, pp. 1-6. In this filter, each pixel of the filtered reconstructed frame is a weighted sum of several pixels within a connected region of pixels from the reconstructed frame surrounding the location of the filtered pixel being generated. The connected region of a pixel is generally defined as the set of neighboring pixels of that pixel. The set may be symmetrically arranged around the pixel, and modifications may be applied near reconstructed frame boundaries or reconstructed block boundaries. Frequently used sets may have a diamond shape, such as a 7x7 diamond shape for the luma component or a 5x5 diamond shape for the chroma components, as shown in FIG. 12.

[0008] The filtering process of the (linear) adaptive loop filter is as follows:

number

[0009] The above equation can be reduced to the following equation (according to the nonlinear adaptive loop filter method described in JVET-M0385, publicly available at http: / / phenix.it-sudparis.eu / jvet / ) without any coding efficiency impact:

number

[0010] If the maximum weighting factor w(i,j) is an n-bit integer value, BitDepthLuma is the luma component bit depth (maximum number of bits for a luma pixel), and BitDepthChroma is the chroma component bit depth, then the implementation of the filter requires N integer multiplications of the n-bit value by a (BitDepthLuma+3)-bit value for luma component filtering and by a (BitDepthChroma+3)-bit value for chroma component filtering, where N is the filter length. Summary of the Invention

[0011] The method described below provides a low-complexity non-linear in-loop filter that requires N multiplications of n-bit filter coefficients by (BitDepthLuma+2)-bit values instead of N multiplications of n-bit filter coefficients by (BitDepthChroma+3)-bit values in state-of-the-art solutions for the luma component.For the chroma components, the method described below provides a low-complexity non-linear in-loop filter that requires N multiplications of n-bit filter coefficients by (BitDepthChroma+2)-bit values instead of N multiplications of n-bit filter coefficients by (BitDepthChroma+3)-bit values in state-of-the-art solutions.

[0012] Embodiments of the present disclosure provide an improved low-complexity in-loop filter for filtering reconstructed frames.

[0013] The embodiments of the present disclosure allow for a reduction in the complexity of the required multiplications without filtering degradation in quality.

[0014] These and other objects are achieved by the subject matter of the independent claims. Further realisation forms are evident from the dependent claims, the description and the drawings.

[0015] An embodiment of the present disclosure provides a method for in-loop filtering by performing adaptive loop filtering on reconstructed frames of a video stream, implemented by an encoding device or a decoding device, the method including the steps of forming / determining a difference between at least one of luma and chroma components of a pixel of the reconstructed frame and at least one of luma and chroma components of neighboring pixels within a connected region of the pixel, clipping the difference according to a respective clipping level, forming / determining a weighted sum of the clipped differences, and adding the weighted sum to at least one of the luma and chroma components of the pixel to determine a respective filtered component of the pixel, wherein the respective clipping levels are selected from the same set of clipping levels for the luma and chroma components.

[0016] According to the present disclosure, adaptive loop filtering can be applied to one or more of the luma and chroma components of a pixel of a reconstructed frame. When adaptive loop filtering is applied to more than one component, in particular to all of the luma and chroma components of a pixel, filtering is performed separately for each component. In other words, the steps of the above method, described in more detail below, are performed separately for each component submitted to adaptive loop filtering.

[0017] The adaptive loop filtering may be applied to a single pixel of the reconstructed frame, a group of pixels corresponding to a block such as a coding block, or to all of the pixels of the reconstructed frame.

[0018] As mentioned above, the connected region of a pixel may generally be defined as the set of neighboring pixels of that pixel. The set may be symmetrically arranged around the pixel, and the modification may be applied near a boundary of a reconstructed frame or a boundary of a reconstructed block. Frequently used sets may have a diamond shape, such as a 7x7 diamond shape for the luma component or a 5x5 diamond shape for the chroma components.

[0019] For each neighboring pixel in the connection region, a difference is determined between at least one of the luma and chroma components of the pixel of the reconstructed frame, i.e., the luma component or the chroma component, and at least one of the luma and chroma components of the neighboring pixel, i.e., the luma component or the respective chroma component. Each resulting difference is clipped according to its respective clipping level. In other words, each neighboring pixel in the connection region has an associated respective clipping level for each of the luma and chroma components. Thus, each clipping level depends on the component being filtered and the offset (i, j) of the coordinates (x+i, y+j) of the corresponding neighboring pixel with respect to the coordinates (x, y) of the pixel whose at least one of the luma and chroma components is being filtered.

[0020] Regardless of which component of a pixel is filtered, i.e., the luma component or one of the two chroma components, the respective clipping level is selected from a single set of clipping levels, which may in particular include all of the allowed or possible clipping levels for both the luma and chroma components.

[0021] Selecting clipping levels for the luma and chroma components from the same set of clipping levels may simplify the implementation of the nonlinear adaptive loop filter. In particular, determining the clipping levels, whether from a formula or a table, may be simplified.

[0022] Each clipping level may be selected according to a bit depth of at least one of the luma and chroma components. Alternatively or additionally, each clipping level may be selected according to a respective clipping index for each neighboring pixel in the connection region. In other words, for each neighboring pixel, a corresponding clipping level is selected according to a clipping index for that neighboring pixel, which may be different for different components of that neighboring pixel.

[0023] Selecting respective clipping levels from the same set of clipping levels for luma and chroma components may particularly imply that if the luma and chroma components have the same bit depth, the same clipping level is selected for the luma and chroma components for a particular clipping index. In other words, the bit depth and clipping index uniquely identify a clipping level within the set of clipping levels regardless of whether luma filtering or chroma filtering is performed. Thus, as long as the same clipping level is selected from the set of clipping levels for luma and chroma components of the same bit depth for the same clipping index, the set of clipping levels may be unified for the luma and chroma components. This does not exclude that different clipping levels may be selected for the luma and chroma components of neighboring pixels if the luma and chroma components of neighboring pixels have different bit depths and / or different clipping indexes.

[0024] Each clipping index may be signaled within the video stream.

[0025] Each clipping level is 2 BitDepth-1 Alternatively, each clipping level may be a positive clipping value below 2, where BitDepth indicates the bit depth of at least one of the luma and chroma components. BitDepth It may be a positive clipping value below, where BitDepth indicates the bit depth of at least one of the luma and chroma components.

[0026] A first restriction on the clipping level may allow the filtering multiplication bit depth to be reduced by one bit compared to the state of the art for each multiplication, saving hardware square footage.

[0027] According to the implementation, each filtered component O'(x,y) of a pixel having coordinates (x,y) in the reconstructed frame is calculated by the following equation:

number

[0028] Each clipping level may be a positive k-bit clipping value, where k<=BitDepth, where BitDepth indicates the bit depth of at least one of the luma and chroma components.

[0029] Each clipping level is, in particular, Lim(i,j)<=2 for the luma component. BitDepthLuma-1 is also acceptable, and Lim(i,j)<=2 for chrominance components BitDepthChroma Alternatively, each clipping level can be Lim(i,j)<=2, specifically for the luma component. BitDepthLuma Or, for chroma components, Lim(i,j)<=2 BitDepthChroma That's fine too.

[0030] Depending on the implementation, each clipping level may be selected from a look-up table (LUT) that represents a set of possible clipping levels for the luma and chroma components.

[0031] Providing clipping levels in the form of a LUT may further simplify the implementation of non-linear ALF: each clipping level may be determined at the decoder side from the respective bit depth and a clipping index clipIdx, which may be encoded in the bitstream and parsed from the bitstream.

[0032] The LUT may be defined as follows: [Table 1] Here, BitDepth indicates the bit depth of at least one of the luma and chroma components, and clipIdx indicates a clipping index.

[0033] Alternatively, the LUT may be defined as follows: [Table 2] Here, BitDepth indicates the bit depth of at least one of the luma and chroma components, and clipIdx indicates a clipping index.

[0034] The set of clipping levels Lim(i,j) for the luma and chroma components is determined through the change of the bit depths BitDepthLuma and BitDepthChroma of the luma and chroma components and the index Idx(i,j) according to the following equation:

number

[0035] Alternatively, the set of clipping levels Lim(i,j) for the luma and chroma components can be calculated through the change of the bit depths BitDepthLuma and BitDepthChroma of the luma and chroma components and the index Idx(i,j) according to the following equation:

number

[0036] Alternatively, the set of clipping levels Lim(i,j) for the luma and chroma components can be calculated through the change of the luma or component bit depth BitDepth and the index Idx(i,j) according to the following formula:

number

[0037] The LUT representing the set of clipping levels Lim(i,j) for the luma and chroma components is calculated through the change of the bit depths BitDepthLuma and BitDepthChroma of the luma and chroma components and the index Idx(i,j) according to the following equation:

number

[0038] Alternatively, the LUT representing the set of clipping levels Lim(i,j) for the luma and chroma components can be calculated through the change in the bit depths BitDepthLuma and BitDepthChroma of the luma and chroma components and the index Idx(i,j) using the following formula:

number

[0039] Alternatively, a LUT representing a set of clipping levels Lim(i,j) for luma and chroma components can be calculated through the change in the bit depth BitDepth of the luma or chroma component and the index Idx(i,j) using the following formula:

number

[0040] According to an implementation, for the set of clipping levels, the index Idx(i,j) is selected from the range of positive values from 0 to m, where m is a positive integer value. According to an implementation, for the set of possible clipping levels, Idx(i,j)=0,1,2,...,m, where m is a positive integer. m may be set equal to 3.

[0041] According to the realization scheme, the set of possible clipping levels Lim(i,j) for the luma and chroma components is determined through the change of the bit depths BitDepthLuma and BitDepthChroma of the luma and chroma components and the index Idx(i,j) according to the following equation:

number

[0042] In-loop filtering may be applied to the luma and chroma components of the reconstructed frame.

[0043] According to one aspect of an embodiment, there is provided an in-loop filtering apparatus for use in a video encoding or decoding apparatus, the in-loop filtering apparatus configured to process a reconstructed frame to generate a filtered reconstructed frame, the reconstructed frame comprising a plurality of pixels, each pixel associated with a pixel value, and the in-loop filtering apparatus comprising one or more processing circuits configured to perform any one of the methods according to the embodiment.

[0044] According to a further aspect of the embodiment, there is provided an encoder including processing circuitry for performing any one of the methods according to the embodiment.

[0045] According to a further aspect of the embodiments, there is provided a decoder including processing circuitry for performing any one of the methods according to the embodiments.

[0046] According to a further aspect of the embodiments, there is provided a computer program product comprising instructions which, when executed by a computer, cause the computer to perform any one of the methods according to the embodiments.

[0047] According to a further aspect of the embodiments, there is provided an encoder including one or more processors and a non-transitory computer-readable storage medium coupled to the one or more processors and storing instructions for execution by the one or more processors, the instructions, when executed by the one or more processors, configuring the encoder to perform any one of the methods according to the embodiments.

[0048] According to a further aspect of an embodiment, there is provided a decoder including one or more processors and a non-transitory computer-readable storage medium coupled to the one or more processors and storing instructions for execution by the one or more processors, the instructions, when executed by the one or more processors, configuring the decoder to perform any one of the methods according to the embodiment.

[0049] According to a further aspect of an embodiment, there is provided an encoder for processing a reconstructed frame to generate a filtered reconstructed frame, the reconstructed frame comprising a plurality of pixels, each pixel associated with a pixel value, the encoder comprising: a subtraction unit configured to form / determine a difference between at least one of luma and chroma components of a pixel of the reconstructed frame and at least one of luma and chroma components of neighboring pixels within a connected region of the pixel; a clipping unit configured to clip the difference according to a respective clipping level; a first addition unit configured to form / determine a weighted sum of the clipped differences; and a second addition unit configured to add the weighted sum to at least one of the luma and chroma components of the pixel to determine a respective filtered component of the pixel, the respective clipping level being selected from a same set of clipping levels for the luma and chroma components.

[0050] According to a further aspect of an embodiment, there is provided a decoder for processing a reconstructed frame to generate a filtered reconstructed frame, the reconstructed frame comprising a plurality of pixels, each pixel associated with a pixel value, the decoder comprising: a subtraction unit configured to form / determine a difference between at least one of luma and chroma components of a pixel of the reconstructed frame and at least one of luma and chroma components of neighboring pixels within a connected region of the pixel; a clipping unit configured to clip the difference according to a respective clipping level; a first addition unit configured to form / determine a weighted sum of the clipped differences; and a second addition unit configured to add the weighted sum to at least one of the luma and chroma components of the pixel to determine a respective filtered component of the pixel, wherein the respective clipping level is selected from a same set of clipping levels for the luma and chroma components.

[0051] In the above embodiment, a difference is formed between a pixel of the reconstructed frame (the filtered pixel or the pixel to be filtered) and neighboring pixels within a connected region of pixels on a line along one direction. In other words, a weighted sum of several pixels within a connected region of pixels from the reconstructed frame around the location of the filtered pixel is formed, and the neighboring pixels refer to several pixels around the filtered pixel in the reconstructed frame or block. In one example, a direction may be understood as a line going through m points (e.g., three points) with coordinates (x, y), (x+i, x+j), and (xi, xj). In other words, the filtered pixel corresponds to coordinates (x, y), and the neighboring pixels correspond to coordinates (x+i, x+j), (xi, xj), respectively. For each direction and offset (i, j), one clipped difference between the filtered pixel (x, y) and the neighboring pixel (x+i, x+j) and another clipped difference between the filtered pixel (x, y) and the neighboring pixel (xi, xj) are formed. Multiple directions may be considered to provide symmetric filtering. A frequently used example is a 7x7 diamond shape for luma filtering and a 5x5 diamond shape for chroma filtering, as shown in FIG.

[0052] According to a further aspect of the present disclosure, the above filtering method of the reconstructed frame can be used for the luma and chroma components at the encoder and decoder side.

[0053] According to a further aspect, the present disclosure relates to an apparatus for decoding a video stream, comprising a processor and a memory, the memory storing instructions for causing the processor to perform any one of the methods according to the embodiments.

[0054] According to a further aspect, the present disclosure relates to an apparatus for encoding a video stream, comprising a processor and a memory, the memory storing instructions for causing the processor to perform any one of the methods according to the embodiments.

[0055] According to a further aspect, a computer-readable storage medium is proposed having stored thereon instructions that, when executed, cause one or more processors configured to code video data to perform any one of the methods according to the embodiments.

[0056] According to a further aspect, the present disclosure relates to a computer program comprising a program code for performing any one of the methods according to the embodiments when the computer program is executed on a computer.

[0057] Thus, for the luma component, the described in-loop filter may require N multiplications of an n-bit filter coefficient by a (BitDepthLuma+2)-bit value of the sum of two clipped differences between the pixel to be filtered and a neighboring pixel lying in a line along one direction, instead of N multiplications of an n-bit filter coefficient by a (BitDepthLuma+3)-bit value as in state-of-the-art solutions. For the chroma components, the in-loop filter may require N multiplications of an n-bit filter coefficient by a (BitDepthChroma+2)-bit value of the sum of two clipped differences between the pixel to be filtered and a neighboring pixel lying in a line along one direction, instead of N multiplications of an n-bit filter coefficient by a (BitDepthChroma+3)-bit value as in state-of-the-art solutions.

[0058] The details of one or more embodiments are set forth in the accompanying drawings and the detailed description below. Other features, objects, and advantages will become apparent from the detailed description, the drawings, and the claims. [Brief explanation of the drawings]

[0059] In the following, embodiments of the invention will be described in more detail with reference to the accompanying figures and drawings. [Figure 1A]1 is a block diagram illustrating an example of a video coding system configured to implement embodiments of the present disclosure. [Figure 1B] FIG. 2 is a block diagram illustrating another example of a video coding system configured to implement embodiments of the present disclosure. [Figure 2] 1 shows a schematic diagram illustrating an encoding device including a filter according to an embodiment of the present disclosure; [Figure 3] 1 shows a schematic diagram illustrating a decoding device including a filter according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a block diagram illustrating an example of an encoding device or a decoding device. [Figure 5] FIG. 10 is a block diagram showing another example of an encoding device or a decoding device. [Figure 6] FIG. 1 is a schematic diagram showing changes in clipping levels for the state of the art. [Figure 7] FIG. 1 is a schematic diagram illustrating an exemplary mechanism of an exemplary process according to an embodiment of the present disclosure. [Figure 8] 1 shows a flowchart of a video encoding / decoding method according to an embodiment of the present disclosure. [Figure 9] 1 shows a block diagram illustrating an example of an encoding / decoding device according to an embodiment of the present disclosure. [Figure 10] 1 is a block diagram illustrating an exemplary structure of a content supply system for implementing a content distribution service. [Figure 11] FIG. 2 is a block diagram illustrating the structure of an example terminal device. [Figure 12] 1 shows exemplary 7×7 and 5×5 diamond-shaped filter taps for ALF.

[0060] In the following, identical reference signs, unless expressly specified otherwise, denote identical or at least functionally equivalent features. DETAILED DESCRIPTION OF THE INVENTION

[0061] In the following description, reference is made to the accompanying drawings which form a part of this disclosure and which show, by way of illustration, specific aspects of embodiments of the present disclosure or in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other ways and may include structural or logical changes not shown in the drawings. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

[0062] For example, it is understood that disclosure related to a described method may also apply to a corresponding device or system configured to perform the method, and vice versa. For example, when one or more particular method steps are described, a corresponding device may include one or more units, e.g., functional units, for performing the described one or more method steps, even if such one or more units are not explicitly described or shown in the drawings (e.g., one unit performs one or more steps, or multiple units each perform one or more of the steps). 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 the function of one or more units, even if such one or more steps are not explicitly described or shown in the drawings (e.g., one step performs the function of one or more units, or multiple steps each perform the function of one or more of the units). Furthermore, it is understood that features of various exemplary embodiments and / or aspects described herein may be combined with each other, unless otherwise specified.

[0063] The following terms are used throughout this disclosure. Coding block: An M×N block of samples for positive integer values of M and N, and the division of a coding tree block (CTB) into coding blocks is called a partition. coding tree block (CTB): An L×L block of samples for positive integer values of L, and the division of a component frame into CTBs is called a partition. Coding tree unit (CTU): Contains the CTBs of luma samples and two corresponding CTBs of chroma samples of a picture with a three sample arrangement, or the CTBs of samples of a picture coded using three separate color planes and syntax structures used to code a monochrome picture or sample. Coding unit (CU): Contains a coding block of luma samples and two corresponding coding blocks of chroma samples for a picture with a three sample arrangement, or a coding block of samples for a picture coded using three separate color planes and syntax structures used to code a monochrome picture or sample. - Component: an array or a single sample from one of the three arrays (luma and two chroma) that make up a picture in 4:2:0, 4:2:2 or 4:4:4 color format, or an array or a single sample from an array that makes up a picture in monochrome format. Picture: an array of luma samples for monochrome formats, or an array of luma samples and two corresponding arrays of chroma samples for 4:2:0, 4:2:2 and 4:4:4 color formats.

[0064] Typically, video coding refers to the processing of a sequence of pictures forming a video or a video sequence. Instead of the term "picture," the terms "frame" or "image" may be used synonymously in the field of video coding. Video coding (or coding in general) includes two parts: video encoding and video decoding. Video encoding is performed on the source side and typically involves processing the original video picture (e.g., by compression) to reduce the amount of data needed to represent the video picture (for more efficient storage and / or transmission). Video decoding is performed on the destination side and typically involves the reverse processing compared to the encoder to reconstruct the video picture. Embodiments referring to "coding" of a video picture (or pictures in general) shall be understood to relate to "encoding" or "decoding" of the video picture or the respective video sequence. The combination of the encoder and decoder is also called a CODEC (Coding and Decoding).

[0065] In the case of lossless video coding, the original video picture can be reconstructed, i.e., the reconstructed video picture has the same quality as the original video picture (assuming no transmission losses or other data losses occur 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, which cannot be fully reconstructed at the decoder, i.e., the quality of the reconstructed video picture is low or poor compared to the quality of the original video picture.

[0066] 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 partitioned into a set of non-overlapping blocks, and coding is typically performed at the block level. In other words, at an encoder, video is typically processed, i.e., encoded, at the block (video block) level, for example, by generating a predictive block using spatial (intra-picture) prediction and / or temporal (inter-picture) prediction, subtracting the predictive block from a current block (the block currently being processed / to be processed) to obtain a residual block, transforming the residual block, and quantizing the residual block in the transform domain to reduce the amount of data to be transmitted (compression). Meanwhile, at a decoder, an inverse process compared to the encoder is applied to the coded or compressed block to reconstruct the current block for representation. Furthermore, the encoder replicates the decoder processing loop, so that both generate the same predictions (e.g., intra- and inter-predictions) and / or reconstructions for processing, i.e., coding, subsequent blocks.

[0067] In the following embodiment of the video coding system 10, a video encoder 20 and a video decoder 30 will be described with reference to FIGS.

[0068] 1A is a schematic block diagram illustrating an example coding system 10, e.g., video coding system 10 (or coding system 10 for short), that may utilize the techniques of the present application. A video encoder 20 (or encoder 20 for short) and a video decoder 30 (or decoder 30 for short) of video coding system 10 represent examples of devices that may be configured to perform techniques according to various examples described herein.

[0069] As shown in FIG. 1A, coding system 10 includes a source device 12 configured to provide encoded picture data 21 to, for example, a destination device 14 for decoding encoded picture data 13.

[0070] The source device 12 includes an encoder 20 and may further, i.e. optionally, include 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 .

[0071] Picture source 16 may be or include 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.

[0072] In contrast to the pre-processor 18 and the processing performed by the pre-processing unit 18 , the pictures or picture data 17 may also be referred to as raw pictures or raw picture data 17 .

[0073] The pre-processor 18 may be 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 will be understood that the pre-processing unit 18 may be an optional component.

[0074] Video encoder 20 may be configured to receive pre-processed picture data 19 and provide encoded picture data 21 (described in further detail below, eg, with reference to FIG. 2).

[0075] The communication interface 22 of the source device 12 may be configured to receive the encoded picture data 21 and transmit the encoded picture data 21 (or any further processed version thereof) over the communication channel 13 to another device, such as the destination device 14 or any other device, for storage or direct reconstruction.

[0076] The destination device 14 includes a decoder 30 (e.g., a video decoder 30), and may further, i.e. optionally, include a communication interface or communication unit 28, a post-processor 32 (or post-processing unit 32), and a display device 34.

[0077] The communications interface 28 of the destination device 14 may be configured to receive the coded picture data 21 (or any further processed version thereof), for example, directly from the source device 12 or from any other source, for example, a storage device such as a coded picture data storage device, and to provide the coded picture data 21 to the decoder 30.

[0078] The communication interface 22 and the communication interface 28 may be configured to transmit or receive the encoded picture data 21 or the encoded data 13 via a direct communication link between the source device 12 and the destination device 14, e.g., a direct wired or wireless connection, or via any type of network, e.g., a wired or wireless network or any combination thereof, or any type of private and public network, or any combination thereof.

[0079] The communications interface 22 may be configured to package the coded picture data 21 in a suitable format, for example into packets, and / or process the coded picture data using any type of transmission coding or processing for transmission over a communications link or network.

[0080] The communications interface 28, which forms the counterpart of the communications interface 22, may be configured to receive the transmitted data and process it using any type of corresponding transmission decoding or processing and / or unpackaging to obtain the coded picture data 21.

[0081] 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 to send and receive messages to acknowledge and exchange any other information related to a communication link and / or data transmission, such as coded picture data transmission, for example, to set up a connection.

[0082] The decoder 30 may be configured to receive the coded picture data 21 and to provide decoded picture data 31 or decoded pictures 31 (further details are described below, for example with reference to Figure 3 or Figure 5).

[0083] A post-processor 32 of destination device 14 may be configured to post-process decoded picture data 31 (also called reconstructed picture data), e.g., decoded picture 31, to obtain post-processed picture data 33, such as post-processed picture 33. The post-processing performed by post-processing unit 32 may include any one or more of color format conversion (e.g., from YCbCr to RGB), color correction, cropping or resampling, or any other processing, e.g., to prepare decoded picture data 31 for display by, e.g., display device 34.

[0084] A display device 34 of destination device 14 may be configured to receive the post-processed picture data 33 and display the picture to, for example, a user or viewer. Display device 34 may be or include any type of display that presents the reconstructed picture, such as an integrated or external display or monitor. The display may be a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a plasma display, a projector, a microLED display, a liquid crystal on silicon (LCoS), a digital light processor (DLP), or any other type of display.

[0085] 1A depicts source device 12 and destination device 14 as separate devices, an embodiment of the devices may also include both devices or both functionality, i.e., 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.

[0086] As will be apparent to those skilled in the art based on the description, the presence and (exact) division 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.

[0087] Encoder 20 (e.g., video encoder 20) or decoder 30 (e.g., video decoder 30), or both encoder 20 and decoder 30, may be implemented via processing circuitry as shown in FIG. 1B , such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic, hardware, dedicated video coding, or any combination thereof. Encoder 20 may be implemented via processing circuitry 46 to embody various modules as described with respect to encoder 20 of FIG. 2 and / or any other encoder system or subsystem described herein. Decoder 30 may be implemented via processing circuitry 46 to embody various modules as described with respect to decoder 30 of FIG. 3 and / or any other decoder system or subsystem described herein. The processing circuitry may be configured to perform various operations as described below. 5, where the techniques are implemented partially in software, a device may store instructions for the software in a suitable non-transitory computer-readable storage medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Video encoder 20 and video decoder 30 may be integrated as part of a combined encoder / decoder (CODEC) in a single device, for example, as shown in FIG. 1B.

[0088] 1B includes processing circuitry that implements both video encoder 20 and video decoder 30. Additionally, one or more imaging devices 41, such as a camera for capturing real-world pictures, an antenna 42, one or more memory stores 44, one or more processors 43, and / or a display device 45, such as display device 34 described above, may be provided as part of video coding system 40.

[0089] Source device 12 and destination device 14 may include any of a wide variety of devices, including any type of handheld or stationary device, e.g., a notebook or laptop computer, a mobile phone, a smartphone, a tablet or tablet computer, a camera, a desktop computer, a set-top box, a television, a display device, a digital media player, a video game console, a video streaming device (such as a content service server or content distribution server), a broadcast receiver device, a broadcast transmitter device, etc., and may or may not use any type of operating system. In some cases, source device 12 and destination device 14 may be equipped for wireless communication. Thus, source device 12 and destination device 14 may be wireless communication devices.

[0090] 1A is merely an example, and the techniques of the present application may be applied to video coding systems (e.g., video encoding or video decoding) that do not necessarily include any data communication between the encoding device and the 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.

[0091] For ease of explanation, embodiments of the present disclosure 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 Joint Collaboration Team on Video Coding (JCT-VC) of the ISO / IEC Motion Picture Experts Group (MEPEG). Those skilled in the art will understand that embodiments of the present disclosure are not limited to HEVC or VVC.

[0092] Encoder and encoding method FIG. 2 shows a schematic block diagram of an exemplary video encoder 20 configured to implement the techniques of the present application. In the example of FIG. 2, the video encoder 20 includes an input 201 (or input interface 201), a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a loop filter unit 220, a decoded picture buffer (DPB) 230, a mode selection unit 260, an entropy coding unit 270, and an output 272 (or output interface 272). The mode selection unit 260 may include an inter prediction unit 244, an intra prediction processing unit 254, and a partition unit 262. The inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 shown in FIG. 2 may also be referred to as a hybrid video encoder or a video encoder using a hybrid video codec.

[0093] 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. Meanwhile, 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 be referred to as forming a backward signal path of the video encoder 20, which corresponds to the signal path of the decoder (see decoder 30 in FIG. 3 ). The inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 may also be referred to as forming a “built-in decoder” of the video encoder 20.

[0094] Pictures and picture partitions (pictures and blocks) The encoder 20 may be configured to receive, for example, via input 201, a picture 17 (or picture data 17), e.g., a picture of a video or a sequence of pictures forming a video sequence. The received picture or picture data may also be a preprocessed picture 19 (preprocessed picture data 19). For simplicity, the following description refers to the picture 17. The picture 17 may also be called a current picture or a picture to be coded (particularly in video coding, to distinguish the current picture from other pictures, e.g., pictures that have been previously coded and / or decoded in the same video sequence, i.e., the video sequence that also includes the current picture).

[0095] A (digital) picture can be thought of as or be a two-dimensional array or matrix of samples with intensity values. The samples in the array may also be called pixels (short for picture element) or pels. The number of samples in the horizontal and vertical directions (or axes) of the array or picture defines the size and / or resolution of the picture. For color representation, three color components are typically used, i.e., a picture may be represented as or 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 by Y (sometimes L is used instead) and two chrominance components denoted by Cb and Cr. The luminance (or luma for short) component Y represents brightness or gray-level intensity (e.g., as in a grayscale picture). On the other hand, the two chrominance (or chroma for short) components Cb and Cr represent chromaticity or color information components. Thus, a picture in YCbCr format includes a luminance sample array of luminance sample values (Y) and two chrominance sample arrays of chrominance values (Cb and Cr). A picture in RGB format may be converted or transformed into YCbCr format, or vice versa. The process is also known as color conversion or translation. If a picture is monochrome, the picture may include only a luminance sample array. Thus, a picture may be, for example, an array of luma samples in 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.

[0096] Embodiments of video encoder 20 may include a picture partition unit (not shown in FIG. 2) configured to partition picture 17 into multiple (typically non-overlapping) picture blocks 203. These blocks may also be called root blocks, macroblocks (H.264 / AVC) or coding tree blocks (CTBs) or coding tree units (CTUs) (in H.265 / HEVC and VVC). The picture partition unit may be configured to use the same block size for all pictures of a video sequence and a corresponding grid that defines the block size, or to vary the block size among pictures or subsets or groups of pictures and partition each picture into corresponding blocks.

[0097] In further embodiments, the video encoder may be configured to directly receive blocks 203 of picture 17, e.g., one, some, or all of the blocks that form picture 17. Picture blocks 203 may also be referred to as current picture blocks or picture blocks to be coded.

[0098] Similar to picture 17, picture block 203 can again be considered as or be a two-dimensional array or matrix of samples having intensity values (sample values), but with smaller dimensions than picture 17. In other words, block 203 may, for example, include one sample array (e.g., a luma array in the case of a monochrome picture 17, or a luma or chroma array in the case of a color picture) or three sample arrays (e.g., a luma and two chroma arrays in the case of a color picture 17), or any other number and / or type of arrays depending on the applied color format. The number of samples in the horizontal and vertical directions (or axes) of block 203 defines the size of block 203. Thus, a block may, for example, include an M×N (M columns by N rows) array of samples, or an M×N array of transform coefficients.

[0099] An embodiment of video encoder 20 such as that shown in FIG. 2 may be configured to encode picture 17 on a block-by-block basis, eg, encoding and prediction is performed on a block-by-block basis.

[0100] Embodiments of video encoder 20 such as that shown in FIG. 2 may be further configured to partition and / or encode pictures using slices (also called video slices), where a picture may be partitioned into or encoded using one or more (typically non-overlapping) slices, each of which may include one or more blocks (e.g., CTUs) or groups of one or more blocks (e.g., tiles (H.265 / HEVC or VVC) or bricks (VVC)).

[0101] An embodiment of video encoder 20 such as that shown in FIG. 2 may be further configured to partition and / or encode a picture using slice / tile groups (also referred to as video tile groups) and / or tiles (also referred to as video tiles), where a picture may be partitioned into or encoded using one or more (typically non-overlapping) slice / tile groups, each of which may include one or more blocks (e.g., CTUs) or one or more tiles, and each tile may be rectangular in shape and include one or more blocks (e.g., CTUs), e.g., full or partial blocks.

[0102] Residual calculation The residual calculation unit 204 is configured to calculate the residual block 205 based on the picture block 203 and the prediction block 265 (further details regarding the prediction block 265 are provided below), for example, by subtracting sample values of the prediction block 265 from sample values of the picture block 203 on a sample-by-sample (pixel-by-pixel) basis to obtain the residual block 205 in the sample domain.

[0103] conversion The transform processing unit 206 is 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 in a transform domain 207. The transform coefficients 207 may also be called transform residual coefficients and represent the residual block 205 in the transform domain.

[0104] 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 specific factor. To maintain the norm of the residual block 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 specific constraints, such as the scaling factor being a power of two due to shift operations, the bit depth of the transform coefficients, a trade-off between accuracy and implementation cost, etc. A specific scaling factor may be specified, for example, for the inverse transform by the inverse transform processing unit 212 (and the corresponding inverse transform by, e.g., the inverse transform processing unit 312 in the video decoder 30), and a corresponding scaling factor for the forward transform by, e.g., the transform processing unit 206 in the encoder 20 may be specified accordingly.

[0105] An embodiment of video encoder 20 (respectively, transform processing unit 206) may be configured to output transform parameters, e.g., a type of transform or multiple transforms, that are encoded or compressed, e.g., directly or via entropy coding unit 270, so that, for example, video decoder 30 may receive and use the transform parameters for decoding.

[0106] Quantization The quantization unit 208 may be configured to quantize the transform coefficients 207, for example by applying scalar quantization or vector quantization, to obtain quantized coefficients 209. The quantized coefficients 209 may also be referred to as quantized transform coefficients 209 or quantized residual coefficients 209.

[0107] The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, an n-bit transform coefficient may be truncated to an m-bit transform coefficient during quantization, where n is greater than m. The degree of quantization may be changed by adjusting a quantization parameter (QP). For example, in 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 may be indicated by the quantization parameter (QP). The quantization parameter may, for example, be an index of a predetermined set of applicable quantization step sizes. For example, a small quantization parameter may correspond to finer quantization (smaller quantization step size), and a large quantization parameter may correspond to coarser quantization (larger quantization step size), or vice versa. Quantization may involve division by a quantization step size, while the corresponding and / or inverse dequantization by, for example, the inverse quantization unit 210 may involve multiplication by the quantization step size. Some standards, such as HEVC, may be configured to use a quantization parameter to determine the quantization step size. Generally, the quantization step size may be calculated based on the quantization parameter using a fixed-point approximation of a formula that includes division. Due to the scaling used in the fixed-point approximation of the formula for the quantization step size and the quantization parameter, additional scaling factors for quantization and dequantization may be introduced to restore the norm of the residual block, which may change. In one exemplary implementation, the scaling of the inverse transform and dequantization may be combined. Alternatively, customized quantization tables may be used, e.g., signaled from the encoder to the decoder in the bitstream. Quantization is a lossy operation, and loss increases with increasing quantization step size.

[0108] Embodiments of video encoder 20 (respectively, quantization unit 208) may be configured to output a quantization parameter (QP), e.g., encoded directly or via entropy coding unit 270, so that, for example, video decoder 30 may receive and apply the quantization parameter for decoding.

[0109] inverse quantization The inverse quantization unit 210 is configured to apply the inverse quantization of the quantization unit 208 to the quantized coefficients, e.g., by applying the inverse of the quantization scheme applied by the quantization unit 208, based on or using the same quantization step size as the quantization unit 208, to obtain dequantized coefficients 211. The dequantized coefficients 211 are also referred to as dequantized residual coefficients 211 and may correspond to the transform coefficients 207, although they are typically not identical to the transform coefficients due to loss due to quantization.

[0110] 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.

[0111] Reconstruction The reconstruction unit 214 (e.g., an adder or summer 214) is configured to add the transform block 213 (i.e., the reconstructed residual block 213) to the prediction block 265, e.g., by adding the sample values of the reconstructed residual block 213 and the sample values of the prediction block 265 sample by sample, to obtain the reconstructed block 215 in the sample domain.

[0112] filtering The loop filter unit 220 (or "loop filter" 220 for short) is configured to filter the reconstructed block 215 to obtain a filtered block 221, or generally, to filter reconstructed samples to obtain filtered samples. The loop filter unit may be configured to smooth pixel transitions or 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, an adaptive loop filter (ALF), a noise suppression filter (NSF), or any combination thereof. In one example, the loop filter unit 220 may include a deblocking filter, an SAO filter, and an ALF filter. The order of the filtering processes may be deblocking filter, SAO, and ALF. In another example, a process called luma mapping with chroma scaling (LMCS) (i.e., adaptive in-loop reshaper) is added. This process is performed before deblocking. In other examples, the deblocking filter process may also be applied to internal sub-block edges, such as affine sub-block edges, ATMVP sub-block edges, sub-block transform (SBT) edges, and intra sub-partition (ISP) edges. Although loop filter unit 220 is shown in FIG. 2 as being an in-loop filter, in other configurations, loop filter unit 220 may be implemented as a post-loop filter. Filtered block 221 may also be referred to as filtered reconstruction block 221.

[0113] An embodiment of video encoder 20 (respectively, loop filter unit 220) may be configured to output loop filter parameters (such as SAO filter parameters or ALF filter parameters or LMCS parameters), which may be encoded, for example, directly or via entropy encoding unit 220, so that, for example, decoder 30 may receive and apply the same loop filter parameters or respective loop filters for decoding.

[0114] Decoded Picture Buffer The decoded picture buffer (DPB) 230 may be a memory that stores reference pictures, or reference picture data in general, for encoding video data by the video encoder 20. The DPB 230 may be formed from 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 be further configured to store other previously filtered blocks, e.g., previously reconstructed filtered blocks 221, of the same current picture or 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 also be configured to store one or more unfiltered reconstructed blocks 215, or in general, unfiltered reconstructed samples, e.g., if the reconstructed blocks 215 are not filtered by the loop filter unit 220, or other further processed versions of any of the reconstructed blocks or samples.

[0115] Mode selection (partition and prediction) The mode select unit 260 includes a partition unit 262, an inter prediction unit 244, and an intra prediction unit 254, and is configured to receive or obtain original picture data, such as original block 203 (current block 203 of current picture 17), and reconstructed picture data, such as filtered and / or unfiltered reconstructed samples or blocks of the same (current) picture and / or from one or more previously decoded pictures, for example, from the decoded picture buffer 230 or another buffer (e.g., a line buffer, not shown). The reconstructed picture data is used as reference picture data for prediction, for example, inter prediction or intra prediction, to obtain a prediction block 265 or predictor 265.

[0116] The mode selection unit 260 may be configured to determine or select a partition (including no partition) 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 calculating the residual block 205 and for reconstructing the reconstruction block 215.

[0117] Embodiments of mode selection unit 260 may be configured to select partitions and prediction modes (e.g., from those supported or available by mode selection unit 260) that provide the best fit, or in other words, the smallest residual (smallest residual means better compression for transmission or storage) or the smallest signaling overhead (smallest signaling overhead means better compression for transmission or storage), or that consider or balance both. Mode selection unit 260 may also be configured to determine partitions and prediction modes based on rate distortion optimization (RDO), i.e., to select a prediction mode that provides the smallest rate distortion. Terms such as “best,” “minimum,” “optimum,” etc. in this context do not necessarily indicate an overall “best,” “minimum,” “optimum,” etc., but may indicate the satisfaction of termination or selection criteria, such as values above or below a threshold, or other constraints that potentially result in a “suboptimal selection,” but reduce complexity and processing time.

[0118] In other words, the partition unit 262 may be configured to partition pictures from a video sequence into a sequence of coding tree units (CTUs), and the CTUs 203 may be further partitioned into smaller block partitions or sub-blocks (which again form blocks), for example using quad-tree partitioning (QT), binary-tree partitioning (BT) or triple-tree partitioning (TT) or any combination thereof repeatedly, and perform prediction for 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.

[0119] The partitioning (eg, by partition unit 262) and prediction processes (by inter prediction unit 244 and intra prediction unit 254) performed by exemplary video encoder 20 are described in further detail below.

[0120] partition The partition unit 262 may be configured to partition a picture from a video sequence into a sequence of coding tree units (CTUs), and the partition unit 262 may partition (or divide) the coding tree units (CTUs) 203 into smaller partitions, e.g., smaller blocks of square or rectangular size. For a picture with a three-sample arrangement, a CTU contains an N×N block of luma samples along with two corresponding blocks of chroma samples. The maximum allowable size of a luma block in a CTU is currently specified as 128×128 in the versatile video coding (VVC) specification, but may be specified as a value different from 128×128, e.g., 256×256, in the future. CTUs of a picture may be clustered / grouped as slices / tile groups, tiles, or bricks. A tile covers a rectangular area of the picture, and a tile can be divided into one or more bricks. A brick consists of multiple rows of CTUs within the tile. A tile that is not partitioned into multiple bricks can be called a brick. However, a brick is a true subset of a tile and is not called a tile. There are two modes of tile groups supported by VVC: raster scan slice / tile group mode and rectangular slice mode. In raster scan tile group mode, a slice / tile group contains a sequence of tiles in the tile raster scan of a picture. In rectangular slice mode, a slice contains multiple bricks of a picture that collectively form a rectangular region of the picture. The bricks within a rectangular slice are in the order of the brick raster scan of the slice.

[0121] Smaller blocks (which may also be called sub-blocks) may be further partitioned into even smaller partitions. This is also called tree partitioning or hierarchical tree partitioning; for example, a root block at root tree level 0 (hierarchical level 0, depth 0) may be recursively partitioned, e.g., into two or more blocks at the next lower tree level, e.g., into nodes at tree level 1 (hierarchical level 1, depth 1); these blocks may again be partitioned into two or more blocks at the next lower tree level, e.g., tree level 2 (hierarchical level 2, depth 2), until partitioning is terminated, e.g., because a termination criterion is met, e.g., because a maximum tree depth or a minimum block size is reached. Further, unpartitioned blocks are also called leaf blocks or leaf nodes of the tree. A tree using partitions into two partitions is called a binary tree (BT), a tree using partitions into three partitions is called a ternary tree (TT), and a tree using partitions into four partitions is called a quad tree (QT).

[0122] For example, a coding tree unit (CTU) may be or may include a CTB of luma samples and two corresponding CTBs of chroma samples for a picture having a three-sample arrangement, or a CTB of samples for a picture coded using a syntax structure used for coding a monochrome picture or three separate color planes and samples. Correspondingly, a coding tree block (CTB) may be an N×N block of samples, for some value of N, whereby the division of the components into CTBs is a partition. A coding unit (CU) may be or may include a coding block of luma samples and two corresponding coding blocks of chroma samples for a picture having a three-sample arrangement, or a coding block of samples for a monochrome picture or a picture coded using a syntax structure used for coding three separate color planes and samples. Correspondingly, a coding block (CB) may be an M×N block of samples, for some values of M and N, whereby the division of the CTB into coding blocks is a partition.

[0123] For example, in some embodiments according to HEVC, coding tree units (CTUs) may be divided into CUs by using a quadtree structure, denoted as a coding tree. The decision of whether to code a picture region using inter-picture (temporal) prediction or intra-picture (spatial) prediction is made at the leaf CU level. Each leaf 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 sent to the decoder for each PU. After obtaining residual blocks by applying the prediction process based on the PU partition type, the leaf CUs can be partitioned into transform units (TUs) according to another quadtree structure similar to the coding tree for CUs.

[0124] For example, in an embodiment according to the latest video coding standard currently under development, called Versatile Video Coding (VVC), a combined quadtree nested multitype tree using bisection and trisection segmentation structures is used to partition the coding tree units, for example. In the coding tree structure within a coding tree unit, the CUs can have either a square or rectangular shape. For example, a coding tree unit (CTU) is first partitioned by a quadtree. The quadtree leaf nodes can then be further partitioned by a multitype tree structure. There are four split types in the multitype tree structure: vertical bisection (SPLIT_BT_VER), horizontal bisection (SPLIT_BT_HOR), vertical trisection (SPLIT_TT_VER), and horizontal trisection (SPLIT_TT_HOR). The multitype tree leaf nodes are called coding units (CUs), and this segmentation is used for prediction and transform processes without further partitioning, as long as the CUs are not too large for the maximum transform length. This means that in most cases, the CU, prediction unit (PU) and transform unit (TU) have the same block size in a quadtree with a nested multi-type tree coding block structure. An exception occurs when the maximum supported transform length is smaller than the width or height of the color components of the CU.

[0125] VVC defines a unique signaling mechanism for partitioning information in a quadtree with a nested multitype tree coding tree structure. In this signaling mechanism, a coding tree unit (CTU) is treated as the root of the quadtree and is first partitioned according to the quadtree structure. Then, each quadtree leaf node (if large enough to allow it) is further partitioned according to the multitype tree structure. In the multitype tree structure, a first flag (mtt_split_cu_flag) is signaled to indicate whether the node is to be further partitioned. If the node is to be further partitioned, a second flag (mtt_split_cu_vertical_flag) is signaled to indicate the split direction, and then a third flag (mtt_split_cu_binary_flag) is signaled to indicate whether the split is bipartitioned or tripartite. Based on the values of mtt_split_cu_vertical_flag and mtt_split_cu_binary_flag, the multi-type tree splitting mode (MttSplitMode) of the CU can be derived by the decoder based on a predetermined rule or table. In certain designs, such as a 64x64 luma block and 32x32 chroma pipeline design in a VVC hardware decoder, TT splitting is prohibited when either the width or height of the luma coding block is greater than 64. TT splitting is also prohibited when either the width or height of the chroma coding block is greater than 32. The pipeline design divides a picture into virtual pipeline data units (VPDUs), which are defined as non-overlapping units within a picture. In a hardware decoder, consecutive VPDUs are processed simultaneously by multiple pipeline stages. Because the VPDU size is roughly proportional to the buffer size in most pipeline stages, it is important to keep the VPDU size small. In most hardware decoders, the VPDU size can be set to the maximum transform block (TB) size.However, in VVC, ternary tree (TT) and binary tree (BT) partitions can result in an increase in the size of the VPDU.

[0126] Furthermore, it should be noted that when part of a tree node block exceeds the bottom or right picture boundary, the tree node block is forced to be split until all samples of all coded CUs are located within the picture boundary.

[0127] As an example, an Intra Sub-Partitions (ISP) tool may divide a luma intra-prediction block vertically or horizontally into two or four sub-partitions, depending on the block size.

[0128] In one example, mode select unit 260 of video encoder 20 may be configured to perform any combination of the partitioning techniques described herein.

[0129] As described above, video encoder 20 is configured to determine or select a best or optimal prediction mode from a (e.g., predetermined) set of prediction modes, which may include intra-prediction modes and / or inter-prediction modes.

[0130] Intra prediction The set of intra prediction modes may include 35 different intra prediction modes, such as non-directional modes like DC (or average) mode and planar mode, or directional modes as defined in HEVC, or may include 67 different intra prediction modes, such as non-directional modes like DC (or average) mode and planar mode, or directional modes as defined in VVC. As an example, some conventional angular intra prediction modes are adaptively replaced with wide-angle intra prediction modes for non-square blocks, such as those defined in VVC. As another example, to avoid a split operation for DC prediction, only the long side is used to calculate the average for non-square blocks. In addition, the results of planar mode intra prediction may be further modified by a position-dependent intra prediction combination (PDPC) method.

[0131] The intra prediction unit 254 is configured to use reconstructed samples of neighboring blocks of the same current picture to generate an (intra) predicted block 265 according to an intra prediction mode from a set of intra prediction modes.

[0132] The intra prediction unit 254 (or generally the mode selection unit 260) may further be configured to output intra prediction parameters (or generally information indicating the selected intra prediction mode for the block) to the entropy coding unit 270 in the form of a syntax element 226 for inclusion in the coded picture data 21, so that, for example, the video decoder 30 may receive and use the prediction parameters for decoding.

[0133] Inter Prediction The set (or possibilities) of inter prediction modes depends on the 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 search for the best matching reference block, or whether only a portion of the reference picture, e.g., a search window area around the area of the current block, is used, and / or whether pixel interpolation is applied, such as, for example, half / semi-pel and / or quarter-pel and / or 1 / 16-pel interpolation.

[0134] In addition to the prediction modes mentioned above, skip mode, direct mode and / or other inter prediction modes may also be applied.

[0135] For example, for enhanced merge prediction, the merge candidate list for such a mode is constructed by including the following five types of candidates in order: spatial MVP from spatially neighboring CUs, temporal MVP from co-located CUs, history-based MVP from a FIFO table, pairwise average MVP, and zero MV. Also, bilateral matching-based decoder-side motion vector refinement (DMVR) may be applied to improve the accuracy of MVs for merge modes.

[0136] Merge mode with MVD (MMVD) is a merge mode with motion vector difference (MVD). To specify whether the MMVD mode is used for a CU, an MMVD flag is signaled immediately after sending the skip flag and merge flag. Also, a CU-level adaptive motion vector resolution (AMVR) scheme may be applied. AMVR allows the MVD of a CU to be coded with different precision. Depending on the prediction mode for the current CU, the MVD of the current CU can be adaptively selected.

[0137] When a CU is coded in merge mode, the combined inter / intra prediction (CIIP) mode may be applied to the current CU. To obtain the CIIP prediction, a weighted average of the inter and intra prediction signals is performed. In affine motion compensation prediction, the affine motion field of a block is described by motion information of two control points (four parameters) or three control points (six parameters) motion vectors. Sub-block-based temporal motion vector prediction (SbTMVP) is similar to temporal motion vector prediction (TMVP) in HEVC, but predicts the motion vectors of sub-CUs within the current CU. Bidirectional optical flow (BDOF), formerly known as BIO, is a simpler version that requires significantly less computational effort, especially in terms of the number of multiplications and the size of the multipliers. In triangular partition mode, the CU is evenly divided into two triangular-shaped partitions using either diagonal or non-diagonal partitioning. Furthermore, bi-prediction mode is extended beyond simple averaging to allow weighted averaging of two prediction signals.

[0138] The inter prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (ME) unit (both not shown in FIG. 2 ). The motion estimation unit may be configured to receive or obtain at least one or more previously reconstructed blocks, such as picture block 203 (current block 203 of current picture 17) and decoded picture 231, or a reconstructed block of one or more other / different previous decoded pictures 231, for motion estimation. As an example, a video sequence may include the current picture and the previous decoded picture 231, or in other words, the current picture and the previous decoded picture 231 may be part of or form a sequence of pictures that form a video sequence.

[0139] The encoder 20 may be configured to select a reference block from multiple reference blocks of the same or different ones of multiple previously decoded pictures, and provide the reference picture (or reference picture index) and / or an offset (spatial offset) between the position (x, y coordinates) of the reference block and the position of the current block to the motion estimation unit as inter prediction parameters. This offset is also called a motion vector (MV).

[0140] The motion compensation unit may be configured to obtain, for example, receive inter-prediction parameters and perform inter-prediction based on or using the inter-prediction parameters to obtain an (inter) prediction block 265. The motion compensation performed by the motion compensation unit may include fetching or generating a prediction block based on motion / block vectors determined by motion estimation, possibly performing interpolation to sub-pixel precision. Interpolation filtering may generate additional pixel samples from known pixel samples, thus potentially increasing the number of candidate prediction blocks that can be used to code the picture block. Upon receiving the motion vector of the PU of the current picture block, the motion compensation unit may find the prediction block to which the motion vector points in one of the reference picture lists.

[0141] The motion compensation unit may also generate syntax elements associated with the blocks and video slices for use by video decoder 30 in decoding picture blocks of the video slices. In addition to or as an alternative to slices and their respective syntax elements, tile groups and / or tiles and their respective syntax elements may be generated or used.

[0142] Entropy Coding The entropy coding unit 270 is configured to, for example, apply or bypass (uncompress) an entropy coding algorithm or scheme (e.g., a variable length coding (VLC) scheme, a context adaptive VLC (CAVLC) scheme, 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 coding method or technique) to the quantized coefficients 209, the inter-prediction parameters, the intra-prediction parameters, the loop filter parameters, and / or other syntax elements to obtain coded picture data 21 that can be output via output 272, for example, in the form of coded bitstream 21, so that, for example, video decoder 30 may receive and use the parameters for decoding. Encoded bitstream 21 may be transmitted to video decoder 39 or may be stored in memory for later transmission or retrieval by video decoder 30 .

[0143] Other structural variations of the video encoder 20 can be used to encode the video stream. For example, a non-transform-based encoder 20 can directly quantize the residual signal for a particular block or frame, without the transform processing unit 206. In other implementations, the encoder 20 can have the quantization unit 208 and the inverse quantization unit 210 combined into a single unit.

[0144] Decoder and decoding method 3 shows an example of a video decoder 30 configured to implement the techniques of the present application. The video decoder 30 is configured to receive coded picture data 21 (e.g., coded bitstream 21), for example, coded by encoder 20, to obtain a decoded picture 331. The decoded picture data or bitstream includes information for decoding the coded picture data, for example, data representing picture blocks of coded video slices (and / or tile groups or tiles) and associated syntax elements.

[0145] 3, decoder 30 includes an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (e.g., summer 314), a loop filter 320, a decoded picture buffer (DBP) 330, a mode application unit 360, an inter prediction unit 344, and an intra prediction unit 354. Inter prediction unit 344 may be or include a motion compensation unit. Video decoder 30, in some examples, may perform a decoding path that is generally inverse to the encoding path described with respect to video encoder 20 from FIG. 2.

[0146] 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 244, and intra prediction unit 254 may also be referred to as forming a “built-in decoder” of video encoder 20. Accordingly, inverse quantization unit 310 may be functionally identical to inverse quantization unit 210, inverse transform processing unit 312 may be functionally identical to inverse transform processing unit 212, reconstruction unit 314 may be functionally identical to reconstruction unit 214, loop filter 320 may be functionally identical to loop filter 220, and decoded picture buffer 330 may be functionally identical to decoded picture buffer 230. Accordingly, the descriptions provided for the respective units and functions of video encoder 20 apply correspondingly to the respective units and functions of video decoder 30.

[0147] Entropy Decoding The entropy decoding unit 304 is configured to parse the bitstream 21 (or coded picture data 21 in general) and, e.g., perform entropy decoding on the coded picture data 21 to obtain quantized coefficients 309 and / or decoded coding parameters 366, such as, e.g., any or all of inter-prediction parameters (e.g., reference picture indices and motion vectors), intra-prediction parameters (e.g., intra-prediction modes or indices), transform parameters, quantization parameters, loop filter parameters, and / or other syntax elements. The entropy decoding unit 304 may be configured to apply a decoding algorithm or scheme corresponding to an encoding scheme such as those described with respect to the entropy coding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide the inter-prediction parameters, intra-prediction parameters, and / or other syntax elements to the mode application unit 360 and to provide other parameters to other units of the decoder 30. The video decoder 30 may receive video slice-level and / or video block-level syntax elements. In addition to or as an alternative to slices and their respective syntax elements, tile groups and / or tiles and their respective syntax elements may be received and / or used.

[0148] inverse quantization Inverse quantization unit 310 may be configured to receive a quantization parameter (QP) (or generally, information regarding inverse quantization) and quantized coefficients from coded picture data 21 (e.g., by parsing and / or decoding by entropy decoding unit 304, for example), and to apply inverse quantization to decoded quantized coefficients 309 based on the quantization parameter to obtain dequantized coefficients 311, which may also be referred to as transform coefficients 311. The inverse quantization process may involve using the quantization parameter determined by video encoder 20 for each video block within a video slice (or tile or tile group) to determine the degree of quantization, and similarly the degree of inverse quantization, to be applied.

[0149] Inverse transformation The inverse transform processing unit 312 may be configured to receive the dequantized coefficients 311, also referred to as transform coefficients 311, and apply a transform to the dequantized coefficients 311 to obtain reconstructed residual blocks 313 in the sample domain. The reconstructed residual blocks 313 may also be referred to as transform blocks 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 coded 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.

[0150] Reconstruction The reconstruction unit 314 (e.g., an adder or summer 314) may be configured to add the reconstructed residual block 313 to the prediction block 365, e.g., by adding sample values of the reconstructed residual block 313 and sample values of the prediction block 365, to obtain a reconstructed block 315 in the sample domain.

[0151] filtering The loop filter unit 320 (either in the coding loop or after the coding loop) is configured to filter the reconstructed block 315 to obtain a filtered block 321, e.g., to smooth pixel transitions or improve video quality. The loop filter unit 320 may include one or more loop filters, such as a deblocking filter, a sample-adaptive offset (SAO) filter, or one or more other filters, e.g., an adaptive loop filter (ALF), a noise suppression filter (NSF), or any combination thereof. In one example, the loop filter unit 320 may include a deblocking filter, an SAO filter, and an ALF filter. The order of the filtering processes may be deblocking filter, SAO, and ALF. In another example, a process called luma mapping with chroma scaling (LMCS) (i.e., adaptive in-loop reshaper) is added. This process is performed before deblocking. In other examples, the deblocking filter process may also be applied to internal sub-block edges, e.g., affine sub-block edges, ATMVP sub-block edges, sub-block transform (SBT) edges, and intra sub-partition (ISP) edges. Although loop filter unit 320 is shown in FIG. 3 as being an in-loop filter, in other configurations, loop filter unit 320 may be implemented as a post-loop filter.

[0152] Decoded Picture Buffer The decoded video blocks 321 of the picture are then stored in a decoded picture buffer 330, which stores the decoded picture as a reference picture for later motion compensation for other pictures and / or for output or respective display.

[0153] The decoder 30 is arranged to output the decoded pictures 331, for example via output 312, for presentation or viewing to a user.

[0154] 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 functionally identical to the intra prediction unit 254, and performs the division or partition decision and prediction based on the partition and / or prediction parameters or respective information received from the coded picture data 21 (e.g., by parsing and / or decoding by the entropy decoding unit 304). The mode application unit 360 may be configured to perform prediction (intra or inter prediction) for each block based on the reconstructed picture, block or respective (filtered or unfiltered) samples to obtain a prediction block 365.

[0155] When a video slice is coded as an intra-coded (I) slice, intra prediction unit 354 of mode application unit 360 is configured to generate predictive block 365 for a picture block of the current video slice based on the signaled intra prediction mode and data from a previously decoded block of the current picture. When a video picture is coded as an inter-coded (i.e., B or P) slice, inter prediction unit 344 (e.g., a motion compensation unit) of mode application unit 360 is configured to generate predictive block 365 for a video block of the current video slice based on the motion vector and other syntax elements received from entropy decoding unit 304. In inter prediction, the predictive block may be generated from one of the reference pictures in one of the reference picture lists. Video decoder 30 may construct the reference picture lists, List 0 and List 1, using a default construction technique based on the reference pictures stored in DPB 330. The same or similar techniques may be applied to or by embodiments that use tile groups (e.g., video tile groups) and / or tiles (e.g., video tiles) in addition to or as an alternative to slices (e.g., video slices), e.g., video may be coded using I, P, or B tile groups and / or tiles.

[0156] Mode application unit 360 is configured to determine prediction information for video / picture blocks of the current video slice by parsing the motion vectors or related information and other syntax elements, and use the prediction information to generate predictive blocks for the current video block being decoded. For example, mode application unit 360 uses some of the received syntax elements to determine the prediction mode (e.g., intra or inter prediction) used to code the video blocks of the video slice, the inter-prediction slice type (e.g., B slice, P slice, or GPB slice), configuration information for one or more of the slice's reference picture lists, motion vectors for each inter-coded video block of the slice, inter-prediction states for each inter-coded video block of the slice, and other information for decoding video blocks in the current video slice. The same or similar techniques may be applied to or with embodiments that use tile groups (e.g., video tile groups) and / or tiles (e.g., video tiles) in addition to or as an alternative to slices (e.g., video slices), e.g., video may be coded using I, P, or B tile groups and / or tiles.

[0157] Embodiments of video decoder 30 such as that shown in FIG. 3 may be configured to partition and / or decode pictures using slices (also called video slices), where a picture may be partitioned into or decoded using one or more (typically non-overlapping) slices, each of which may include one or more blocks (e.g., CTUs) or groups of one or more blocks (e.g., tiles (H.265 / HEVC and VVC or bricks (VVC)).

[0158] An embodiment of video decoder 30 such as that shown in FIG. 3 may be configured to partition and / or decode a picture using slice / tile groups (also referred to as video tile groups) and / or tiles (also referred to as video tiles), where a picture may be partitioned into or decoded using one or more (typically non-overlapping) slice / tile groups, where each slice / tile group may include one or more blocks (e.g., CTUs) or one or more tiles, where each tile may be rectangular in shape and include one or more blocks (e.g., CTUs), e.g., full or partial blocks.

[0159] Other variations of the video decoder 30 may be used to decode the coded picture data 21. For example, the decoder 30 may generate the output video stream without the loop filter unit 320. For example, a non-transform-based decoder 30 may directly inverse quantize the residual signal for a particular block or frame without the inverse transform processing unit 312. In other implementations, the video decoder 30 may have the inverse quantization unit 310 and the inverse transform processing unit 312 combined into a single unit.

[0160] It should be understood that in the encoder 20 and the decoder 30, the processing result of the current step may be further processed and then output to the next step. For example, after interpolation filtering, motion vector derivation or loop filtering, further operations such as clipping or shifting may be performed on the processing result of the interpolation filtering, motion vector derivation or loop filtering.

[0161] 4 is a schematic diagram of a video coding device 400 according to an embodiment of the present disclosure. Video coding device 400 is suitable for implementing embodiments of the disclosure as described below. In an embodiment, video coding device 400 may be a decoder, such as video decoder 30 of FIG. 1A, or an encoder, such as video encoder 20 of FIG. 1A.

[0162] Video coding device 400 may include an ingress port 410 (or input port 410) and one or more receiver units (Rx) 420 for receiving data, a processor, logic unit, or central processing unit (CPU) 430 for processing data, one or more transmitter units (Tx) 440 and egress ports 450 (or output ports 450) for transmitting data, and memory 460 for storing data. Video coding device 400 may also include optical-to-electrical (OE) and electrical-to-optical (EO) components coupled to ingress port 410, receiver units 420, transmitter units 440, and egress ports 450 for the egress or ingress of optical or electrical signals.

[0163] The processor 430 may be implemented in hardware and software. The processor 430 may be implemented as one or more CPU chips, cores (e.g., multi-core processors), FPGAs, ASICs, and DSPs. The processor 430 may communicate with the ingress port 410, the receiver unit 420, the transmitter unit 440, the egress port 450, and the memory 460. The processor 430 may include a coding module 470. The coding module 470 implements the disclosed embodiments described above and below. For example, the coding module 470 may implement, process, prepare, or provide various coding operations. Thus, what is included in the coding module 470 may provide substantial improvements to the functionality of the video coding device 400 and result in the transformation of the video coding device 400 into a different state. Alternatively, the coding module 470 may be implemented as instructions stored in the memory 460 and executed by the processor 430.

[0164] Memory 460 may include one or more disks, tape drives, and solid-state drives, and may be used for storing programs when such programs are selected for execution and as an overflow data storage device for storing instructions and data read during the execution of the programs. Memory 460 may be, for example, volatile and / or non-volatile, and may be read-only memory (ROM), random access memory (RAM), ternary content-addressable memory (TCAM), and / or static random-access memory (SRAM).

[0165] FIG. 5 is a simplified block diagram of an apparatus 500 that may be used as one or both of source device 12 and destination device 14 from FIG. 1A according to an example embodiment.

[0166] Processor 502 in device 500 may be a central processing unit. Alternatively, processor 502 may be any other type of device or devices, now existing or later developed, that can manipulate or process information. While the disclosed implementations may be implemented with a single processor, such as processor 502, as shown, advantages in speed and efficiency may be achieved using more than one processor.

[0167] The memory 504 in the apparatus 500 may, in implementation, be a read only memory (ROM) device or a random access memory (RAM) device. Any other suitable type of storage device may be used as the memory 504. The memory 504 may include code and data 506 that is accessed by the processor 502 using a bus 512. The memory 504 may further include an operating system 508 and application programs 510, which include at least one program that enables the processor 502 to perform methods described herein. For example, the application programs 510 may include applications 1-N, which may further include a video coding application that performs methods described herein.

[0168] The apparatus 500 may also include one or more output devices, such as a display 518. The display 518 may, in one example, be a touch-sensitive display that combines a display with a touch-sensitive element operable to sense touch input. The display 518 may be coupled to the processor 502 via the bus 512.

[0169] Although shown here as a single bus, bus 512 of device 500 may be comprised of multiple buses. Additionally, secondary storage (not shown) may be directly coupled to other components of device 500 or may be accessible 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.

[0170] Nonlinear Adaptive Loop Filter This disclosure provides various improvements to nonlinear adaptive loop filters (ALFs) such as those described in JVET-M0385, publicly available at http: / / phenix.it-sudparis.eu / jvet / . As described in the introduction to this disclosure, the nonlinear ALF may be implemented in loop filter unit 220 of encoder 20 shown in Figure 2 and correspondingly in loop filter unit 320 of decoder 30 shown in Figure 3. The nonlinear ALF may perform filtering on a reconstructed frame before using this frame for prediction.

[0171] Generally, a method for in-loop filtering by performing adaptive loop filtering on reconstructed frames of a video stream, implemented by an encoding device or a decoding device according to the present disclosure, may be implemented by the following steps, as shown in FIG. 8.

[0172] Step 1310: Form / determine a difference between at least one of the luma and chroma components of a pixel of a reconstructed frame and at least one of the luma and chroma components of neighboring pixels within a connected region of the pixel. The connected region of a pixel is generally defined as a set of neighboring pixels of the pixel. The set may be symmetrically arranged around the pixel, and the modification may be applied near a boundary of the reconstructed frame or a boundary of a reconstructed block. A frequently used set may have a diamond shape, such as a 7x7 diamond shape for the luma component or a 5x5 diamond shape for the chroma components. In-loop filtering may be performed separately for the luma and chroma components of the reconstructed frame. The differences entering each filtering process are determined between each component of the pixel. In other words, the difference between the luma components of the pixel is determined to perform nonlinear ALF filtering on the luma component. Similarly, for each chroma component, the difference between each chroma component of the pixel is determined to perform nonlinear ALF filtering on the respective chroma component.

[0173] Step 1320: Clip the difference according to the respective clipping level. Each neighboring pixel, and therefore each difference, may have its own clipping level. In other words, the clipping level may depend on the offset (i, j) of each neighboring pixel relative to the coordinates (x, y) of the pixel to be filtered.

[0174] Step 1330: Form / determine a weighted sum of the clipped differences. The weighting factors may be defined separately for each difference. In other words, the weighting factors or weights may depend on the offset (i,j) of each neighboring pixel with respect to the coordinates (x,y) of the pixel to be filtered.

[0175] Step 1340: Determine a filtered respective component of the pixel, ie, the luma component or the respective chroma component, by adding a weighted sum to at least one of the luma and chroma components of the pixel.

[0176] According to one aspect of the present disclosure, each clipping level may be selected from the same set of possible clipping levels for the luma and chroma components. In other words, a single set of clipping levels may be provided, from which all of the clipping levels used in the above method are derived. Different clipping levels may be applied to the luma and chroma components, particularly according to the different bit depths of the luma and chroma components, but the same set of possible clipping levels is provided for all components. This approach also provides consistent clipping for RGB coding of video.

[0177] The set of possible clipping levels may be predefined or may be determined according to one or more predefined formulas. The set of possible clipping levels may be predefined in the form of a table, in particular a look-up table (LUT). The set of possible clipping levels, in particular a LUT, may be determined as a result of one or more parameter formulas. In other words, one or more formulas having parameters may be used to determine the set of possible clipping values. The parameters may include a bit depth and an index. Through variation of the parameters, the set of possible clipping values may be determined in the form of a table with parameters indicating the rows and columns of the table.

[0178] The present disclosure further provides a simplification of the nonlinear adaptive loop filter employed in VVC Test Model 5.0 (VTM5.0), in which an adaptive clipping operation is applied during the filtering process. In the worst-case scenario, the nonlinear adaptive loop filter requires 12 multiplications of an 8-bit filter coefficient by a (BitDepth+3)-bit value equal to the sum of the clipped differences between the filtered sample and neighboring samples.

[0179] A method according to an embodiment of the present disclosure modifies the formula for calculating clipping values and applies secondary clipping to guarantee the bit depth of the multiplication operations after addition. This method allows for a 2-bit saving of multiplication bit depth from 8×(BitDepth+3) to 8×(BitDepth+1) for each of 12 multiplications in the worst-case scenario. As mentioned above, the same clipping level formulas for luma and chroma components may be used to unify the calculations. The simplification shows negligible performance changes, i.e., 0.00% / −0.02% / −0.01% and 0.02% / −0.04% / −0.04% (Y / Cb / Cr) in All-Intra (AI) and Random-Access (RA) configurations, respectively.

[0180] This disclosure broadly provides three aspects for simplification of the nonlinear portion of an adaptive loop filter (ALF). 1. Modify the clipping level formula to ensure the clipped difference is in the 11-bit range. 2. Apply secondary clipping to ensure that the clipped sum of the differences is still in the 11-bit range. 3. The same set of possible clipping levels, and in particular the same formulas, are used to calculate luma and chroma clipping values.

[0181] These modifications allow reducing the filtering multiplication bit depth from 8×(BitDepth+3) to 8×(BitDepth+1) for each of the 12 multiplications saving hardware square area.

[0182] Aspect 1: Modify the formula for calculating clipping values As a first aspect of the present disclosure, it is proposed to modify the formulas for calculating clipping values to ensure that the output after clipping with negative and positive values of Lim(i,j) is in the 11-bit range (for an internal BitDepth of 10 bits). An example set of formulas for clipping levels for luma and chroma components may be as follows:

number

[0183] Other values for Idx are possible, especially fractional values.

[0184] In the text of the VVC specification, the following modifications may be implemented:

number

[0185] This modification saves one bit of the filtering multiplication bit depth.

[0186] Aspect 2: Secondary Clipping According to a second aspect, it is proposed to add a secondary clipping of the clipped difference sum between the filtering sample, i.e. the sample to be filtered and the neighboring samples, to ensure that the clipped difference sum is still in the 11-bit range (for an internal BitDepth of 10 bits).

number

[0187] A possible modification of the VVC specification that realizes the above formula may be as follows:

number

[0188] The chroma components are as follows:

number

[0189] Aspect 3: Using the same formula to calculate luma and chroma clipping values According to a third aspect, it is proposed to use the same formula for calculating clipping values for both luma and chroma.

number

[0190] The following changes may be implemented in the VVC specification:

number

[0191] 6 is a schematic diagram illustrating the above-mentioned exemplary changes in clipping levels for the state of the art. Clipping levels AlfClip for luma and chroma components according to this aspect of the present disclosure L [adaptation_parameter_set_id][filtIdx][j] and AlfClip C[adaptation_parameter_set_id][j] is determined using the same formula, where the bit depth (BitDepthY and BitDepthC) and the clipping index (alf_luma_clip_idx and alf_chroma_clip_idx) are parameters that determine the possible clipping levels. Therefore, the set of possible clipping levels may be provided in the form of a table, such as a look-up table, and the entries in the table may be generated according to the above formula. The clipping index (alf_luma_clip_idx and alf_chroma_clip_idx) depends on sfIdx and j, and therefore on the offset (i, j) of the respective neighboring pixels. It will be understood that other formulas may be used to determine the clipping levels, in particular the set of possible clipping levels. In particular, the subtraction of 1 that implements aspect 1 as described above may be omitted.

[0192] 7 is a schematic diagram illustrating the above-mentioned exemplary changes in clipping levels related to the state of the art in mathematical terms. The same formula is used to determine clipping levels for luma and chroma components. As a result, only a single set of possible clipping levels may be used for both luma and chroma components, and the respective bit depths and clipping indices may be used as parameters indicating the clipping levels to be applied. In other words, the clipping levels actually applied depend on the bit depths and indices of the respective components, which may themselves depend on the offsets (i, j) of the neighboring pixels, but the clipping levels are obtained from the same set of possible clipping levels defined by the ranges of possible bit depths and indices of the components. Therefore, for the same bit depths and neighboring pixels, the same clipping levels are applied to the luma and chroma components. Using the same set of clipping levels for luma and chroma components makes the filtering process consistent with RGB coding.

[0193] In general, a single set of possible clipping levels may be used for the luma and chroma components. The clipping levels may be determined using the same formula for the luma and chroma components as described above. The calculation yields a set of possible clipping levels with BitDepthLuma / BitDepthChroma and Idx representing the parameters that determine the set of possible clipping levels. Since the set is determined based on two parameters, it can be represented by a table. As described above, the rows of the table may be associated with different values of BitDepthLuma / BitDepthChroma, while the columns may be associated with different values of the index Idx.

[0194] The entries in the table may be calculated according to either the formula above or the formula described below, starting from a set of allowed values for BitDepthLuma / BitDepthChroma and Idx. Alternatively, the table may be predefined.

[0195] The third aspect provides a further simplification due to the unification of the clipping values or levels, in particular their calculation, for the luma and chroma components.

[0196] According to this aspect (luma / chroma matching), in other implementations, tables may be used instead of formulas, which may also be combined with the first aspect (10-bit bit depth in clipping formulas), as explained below.

[0197] To avoid floating-point operations in the calculation of clipping levels according to some of the embodiments of the present disclosure, a table definition may be used instead, which specifies integer outputs (4×9=36 entries) in an exemplary embodiment for bit depths 8, 9, 10, ... 16 and four clipping indices Idx. According to a third aspect, the same table may be used for luma and chroma components, and in particular may be calculated using the following luma formula:

number

[0198] In VTM-5.0, the clipping values of the adaptive loop filter are calculated using floating-point arithmetic. In the present disclosure, the clipping value calculation can be simplified by using integer arithmetic. Compared to VTM-5.0, the disclosed method achieves similar coding efficiency and encoding / decoding time under common test conditions.

[0199] As already described above, the in-loop filter 320, 220 is configured to process reconstructed frames from the decoded reconstructed video stream to generate filtered reconstructed frames.

[0200] 8 shows a flowchart of a video encoding / decoding method according to an embodiment of the present disclosure. The illustrated method performs in-loop filtering by performing adaptive loop filtering on a reconstructed frame of a video stream as follows: In step 1310, a difference between at least one of the luma and chroma components of a pixel of the reconstructed frame and at least one of the luma and chroma components of neighboring pixels within a connected region of the pixel is determined. In step 1320, the determined difference is clipped according to a respective clipping level. In step 1330, a weighted sum of the clipped differences is formed. Finally, in step 1340, the weighted sum is added to at least one of the luma and chroma components of the pixel to determine a respective filtered component of the pixel. The respective clipping level is selected from the same set of possible clipping levels for the luma and chroma components.

[0201] 9 shows a block diagram illustrating an example of an encoding / decoding device according to an embodiment of the present disclosure. The encoding / decoding device 20 / 30 includes a subtraction unit 1410 configured to form a difference between at least one of luma and chroma components of a pixel of a reconstructed frame and at least one of luma and chroma components of neighboring pixels in a connected region of the pixel, a clipping unit 1420 configured to clip the difference according to a respective clipping level, a first addition unit 1430 configured to form a weighted sum of the clipped differences, and a second addition unit 1440 configured to add the weighted sum to at least one of the luma and chroma components of the pixel to determine a respective filtered component of the pixel, where the respective clipping levels are selected from the same set of possible clipping levels for the luma and chroma components.

[0202] Addition units 1430 and 1440, subtraction unit 1410, and clipping unit 1420 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 communications medium as one or more instructions or code for execution by a hardware-based processing unit. 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 circuits. Accordingly, the term "processor" as used herein may refer to any of the above structures or any other structure suitable for implementing the techniques described herein. 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. Alternatively, the techniques may be implemented entirely in one or more circuits or logic elements.

[0203] The present disclosure provides the following implementation of a nonlinear ALF according to one or more of the above aspects.

[0204] In the following embodiment and implementation, the limit value m for the range of index Idx(i,j) can be set to 3.

[0205] According to a first realization, a reconstructed frame (e.g., each reconstructed frame) is divided into a set of blocks (superpixels), each block is filtered by an adaptive loop filter, and each pixel of the filtered reconstructed frame is calculated according to the following equation:

number

[0206] where I(x+i,y+j) is a positive BitDepthLuma bit value for the luma component or BitDepthChroma bit value for the chroma component corresponding to the pixel value (or pixel luminance) at the point with coordinates (x+i,y+j) in the reconstructed frame, O'(x,y) is the filtered pixel with coordinates (x,y) in the reconstructed frame, w(i,j) denotes an n-bit integer filter coefficient corresponding to the pixel location with offset (i,j) relative to the filtered pixel, and Lim(i,j) is a positive k-bit clipping value, k<=BitDepth, where Lim(i,j)<=2 for the luma component. BitDepthLuma -1 and Lim(i,j)<=2 for chroma components BitDepthChroma -1, and the index Idx(i,j) can be selected from the range of positive values from 0 to m, where m is a positive integer value. A floating point value or fraction may be used for Idx to generate an integer exponent in the above formula for clipping level.

[0207] According to a second realization, the clipping level Lim(i,j) is calculated using the same formula for the luma and chroma components:

number

[0208] A floating point value or fraction may be used for Idx to generate an integer exponent in the above formula for clipping level.

[0209] According to the third implementation, for luma component filtering, when BitDepthLuma is equal to 10, the maximum clipping level is Lim(i,j)=1023, and when BitDepthLuma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0210] According to the fourth implementation, for chroma component filtering, when BitDepthChroma is equal to 10, the maximum clipping level is Lim(i,j)=1023, and when BitDepthChroma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0211] According to a fifth realization, the clipping level Lim(i,j) is calculated using the same formula for the luma and chroma components:

number

[0212] In this implementation, the clipping level Lim(i,j) is a positive k-bit clipping value, k<=BitDepth+1, and Lim(i,j)<=2 for the luma component. BitDepthLuma and Lim(i,j)<=2 for the chroma components. BitDepthChroma is.

[0213] A floating point value or fraction may be used for Idx to generate an integer exponent in the above formula for clipping level.

[0214] According to a sixth realization, the clipping level Lim(i,j) is calculated using the same formula for the luma and chroma components:

number

[0215] A floating point value or fraction may be used for Idx to generate an integer exponent in the above formula for clipping level.

[0216] According to a seventh realization, the clipping level Lim(i,j) is calculated for the luma and chroma components according to the following formula:

number

[0217] A floating point value or fraction may be used for Idx to generate an integer exponent in the above formula for clipping level.

[0218] The fifth to seventh implementations provide a single set of possible clipping levels Lim(i,j), from which the clipping level for each neighboring pixel with offset (i,j) is determined according to the values of BitDepthLuma / BitDepthChroma and Idx(i,j). Only one set of clipping levels is provided for both the luma and chroma components, thereby simplifying the ALF process.

[0219] According to the eighth realization, the set of possible clipping levels Lim(i,j) can be determined by a table representation according to one of the formulas of the fifth to seventh realizations.

[0220] In this disclosure, the clipping levels Lim(i,j) for luma and chroma component filtering may have a table representation.

[0221] In this disclosure, the following two example table representations are provided herein, and it is noted that the table representation of the clipping level Lim(i,j) may include, but is not limited to, the following two example table representations:

[0222] In one example, the clipping level Lim(i,j) may be determined by using a table representation. If idx = Idx(i,j) = 0, 1, 2 or 3, If BitDepthLuma is equal to 8, then the clipping level Lim(idx)=[255,63,15,3]. If BitDepthLuma is equal to 9, then the clipping level Lim(idx)=[511,107,22,4]. If BitDepthLuma is equal to 10, the clipping level Lim(idx) = [1023,180,31,5]. If BitDepthLuma is equal to 11, the clipping level Lim(idx) = [2047,303,44,6]. If BitDepthLuma is equal to 12, the clipping level Lim(idx) = [4095,511,63,7]. If BitDepthLuma is equal to 13, the clipping level Lim(idx)=[8191,860,90,9]. If BitDepthLuma is equal to 14, the clipping level Lim(idx) = [16383,1447,127,10]. If BitDepthLuma is equal to 15, then the clipping level Lim(idx)=[32767,2434,180,12], and / or If BitDepthLuma is equal to 16, then the clipping level Lim(idx)=[65535,4095,255,15].

[0223] In other examples, the clipping level Lim(i,j) may be determined by using other table representations. If idx = Idx(I,j) = 0, 1, 2 or 3, If BitDepthLuma is equal to 8, then the clipping level Lim(idx)=[255,64,16,4]. If BitDepthLuma is equal to 9, the clipping level Lim(idx) = [511,108,23,5]. If BitDepthLuma is equal to 10, the clipping level Lim(idx) = [1023,181,32,6]. If BitDepthLuma is equal to 11, the clipping level Lim(idx) = [2047,304,45,7]. If BitDepthLuma is equal to 12, the clipping level Lim(idx) = [4095,512,64,8]. If BitDepthLuma is equal to 13, the clipping level Lim(idx)=[8191,861,91,10]. If BitDepthLuma is equal to 14, the clipping level Lim(idx) = [16383,1448,128,11]. If BitDepthLuma is equal to 15, then the clipping level Lim(idx)=[32767,2435,181,13], and / or If BitDepthLuma is equal to 16, then the clipping level Lim(idx)=[65535,4096,256,16].

[0224] According to a ninth realization scheme, the above filtering method of the reconstructed frame can be used for the luma and chroma components at the encoder and decoder side.

[0225] Therefore, the maximum clipping level for the luma component Lim(i,j)<=2 BitDepthLuma -1 and Lim(i,j)<=2 for chroma components BitDepthChroma The described in-loop filter with BitDepthLuma -1 may require, for the luma component, N multiplications of an n-bit filter coefficient by a (BitDepthLuma + 2)-bit value of the sum of two clipped differences between the filtered pixel and neighboring pixels in the pixel's connected region, instead of N multiplications of an n-bit filter coefficient by a (BitDepthChroma + 3)-bit value in state-of-the-art solutions. For the chroma components, the in-loop filter may require N multiplications of an n-bit filter coefficient by a (BitDepthChroma + 2)-bit value of the sum of two clipped differences between the filtered pixel and neighboring pixels in the connected region, instead of N multiplications of an n-bit filter coefficient by a (BitDepthChroma + 3)-bit value in state-of-the-art solutions. As in the art, the connected region may be different for filtering of the luma and chroma components.

[0226] Some specific embodiments are outlined below: In the following embodiments, the reconstructed frame is filtered by an adaptive loop filter (such as a nonlinear ALF).

[0227] According to a first embodiment, the present disclosure relates to an in-loop filtering apparatus for use in a video encoding or decoding apparatus, the in-loop filtering apparatus being configured to process a reconstructed frame to generate a filtered reconstructed frame, the reconstructed frame comprising a plurality of pixels, each pixel associated with a pixel value, the in-loop filtering apparatus comprising: The one or more processing circuits configured to filter pixels (i.e., filtered pixels, such as each pixel) from the reconstructed frame, wherein the filtered pixels (e.g., each pixel) of the filtered reconstructed frame are calculated by subtracting a weighted sum of the filtered pixel (e.g., I(x,y)) from the clipped pixel and a clipped difference between the filtered pixel and neighboring pixels (Σ (i,j)≠(0,0) w(i,j)×{Clip[Δ(x,y,i,j),Lim(i,j)]+Clip[Δ(x,y,-i,-j),Lim(i,j)]} etc.), or the filtered pixels of the filtered reconstructed frame are based on this sum.

[0228] Clipping level is 2 BitDepth BitDepth can be less than or equal to -1, where BitDepth is the bit depth of the filtered component (luma component or one of the two chroma components) of a pixel (e.g., I(x,y)) of the reconstructed frame, or BitDepth is the maximum number of bits in a sample (pixel) of each component of the reconstructed frame.

[0229] In particular, the filtered pixels are calculated using the following formula:

number

[0230] In particular, the clipping level (or clipping value) Lim(i,j) may be a positive k-bit clipping value, where k<=BitDepth.

[0231] The clipping levels Lim(i,j) for the luma and chroma component filtering may have a tabular representation, in particular in the form of a look-up table (LUT).

[0232] The clipping levels Lim(i,j) for the luma and chroma component filtering may be obtained from or determined by a tabular representation, in particular in the form of a look-up table (LUT).

[0233] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated according to the following formula:

number

[0234] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated according to the following formula:

number

[0235] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated according to the following formula:

number

[0236] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated according to the following formula:

number

[0237] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated according to the following formula:

number

[0238] According to the implementation scheme of the first embodiment, the clipping level Lim(i,j) may be determined by the same formula for the luma and chroma components of the filtered pixel (such as I(x,y)) of the reconstructed frame, or the same clipping level Lim(i,j) may be applied to the luma and chroma components of the filtered pixel (such as I(x,y)) of the reconstructed frame.

[0239] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0240] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0241] According to the implementation of the first embodiment, the clipping level Lim(i,j) may be obtained or determined from a table representation, which has the same formula for the luma and chroma components:

number

[0242] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0243] According to the implementation of the first embodiment, the clipping level Lim(i,j) may be obtained or determined from a table representation, which has the same formula for the luma and chroma components:

number

[0244] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0245] According to the implementation of the first embodiment, the luma component filtering is as follows: If BitDepthLuma is equal to 10, the maximum clipping level may be Lim(i,j)=1023, and / or If BitDepthLuma is equal to 8, the maximum clipping level may be Lim(i,j)=255.

[0246] According to the implementation of the first embodiment, the luma component filtering is as follows: If BitDepthLuma is equal to 10, the maximum clipping level is Lim(i,j)=1023, and / or If BitDepthLuma is equal to 9, the maximum clipping level is Lim(i,j)=511. If BitDepthLuma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0247] According to the implementation of the first embodiment, the luma component filtering is as follows: If BitDepthLuma is equal to 16, the maximum clipping level is Lim(i,j)=65535. If BitDepthLuma is equal to 15, the maximum clipping level is Lim(i,j)=32767. If BitDepthLuma is equal to 14, the maximum clipping level is Lim(i,j)=16383. If BitDepthLuma is equal to 13, the maximum clipping level is Lim(i,j)=8191. If BitDepthLuma is equal to 12, the maximum clipping level is Lim(i,j)=4095. If BitDepthLuma is equal to 11, the maximum clipping level is Lim(i,j)=2047. If BitDepthLuma is equal to 10, the maximum clipping level is Lim(i,j)=1023. If BitDepthLuma is equal to 9, the maximum clipping level is Lim(i,j)=511, and / or If BitDepthLuma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0248] According to the implementation method of the first embodiment, for chroma component filtering, If BitDepthChroma is equal to 10, the maximum clipping level may be Lim(i,j)=1023, and / or If BitDepthChroma is equal to 8, the maximum clipping level may be Lim(i,j)=255.

[0249] According to the implementation method of the first embodiment, for chroma component filtering, If BitDepthChroma is equal to 16, the maximum clipping level is Lim(i,j)=65535. If BitDepthChroma is equal to 15, the maximum clipping level is Lim(i,j)=32767. If BitDepthChroma is equal to 14, the maximum clipping level is Lim(i,j)=16383. If BitDepthChroma is equal to 13, the maximum clipping level is Lim(i,j)=8191. If BitDepthChroma is equal to 12, the maximum clipping level is Lim(i,j)=4095. If BitDepthChroma is equal to 11, the maximum clipping level is Lim(i,j)=2047. If BitDepthChroma is equal to 10, the maximum clipping level is Lim(i,j)=1023. If BitDepthChroma is equal to 9, the maximum clipping level is Lim(i,j)=511, and / or If BitDepthChroma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0250] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0251] According to the implementation of the first embodiment, the clipping level Lim(i,j) may be selected from the same set of possible values for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame.

[0252] According to the implementation of the first embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0253] In this implementation, the clipping level Lim(i,j) is a positive k-bit clipping value, k<=BitDepth+1, and Lim(i,j)<=2 for the luma component. BitDepthLuma and Lim(i,j)<=2 for the chroma components. BitDepthChroma is.

[0254] According to the implementation of the first embodiment, the clipping level (or clipping value) Lim(i,j) may be determined for the luma and chroma components of the reconstructed frame by the same table representation below: If idx = Idx(i,j) = 0, 1, 2 or 3, If BitDepthLuma is equal to 8, then the clipping level Lim(idx)=[255,63,15,3]. If BitDepthLuma is equal to 9, then the clipping level Lim(idx)=[511,107,22,4]. If BitDepthLuma is equal to 10, the clipping level Lim(idx) = [1023,180,31,5]. If BitDepthLuma is equal to 11, the clipping level Lim(idx) = [2047,303,44,6]. If BitDepthLuma is equal to 12, the clipping level Lim(idx) = [4095,511,63,7]. If BitDepthLuma is equal to 13, the clipping level Lim(idx)=[8191,860,90,9]. If BitDepthLuma is equal to 14, the clipping level Lim(idx) = [16383,1447,127,10]. If BitDepthLuma is equal to 15, then the clipping level Lim(idx)=[32767,2434,180,12], and / or If BitDepthLuma is equal to 16, then the clipping level Lim(idx)=[65535,4095,255,15].

[0255] According to the implementation of the first embodiment, the clipping level (or clipping value) Lim(i,j) may be determined for the luma and chroma components of the reconstructed frame by the same table representation below: If idx = Idx(i,j) = 0, 1, 2 or 3, If BitDepthLuma is equal to 8, then the clipping level Lim(idx)=[255,64,16,4]. If BitDepthLuma is equal to 9, the clipping level Lim(idx) = [511,108,23,5]. If BitDepthLuma is equal to 10, the clipping level Lim(idx) = [1023,181,32,6]. If BitDepthLuma is equal to 11, the clipping level Lim(idx) = [2047,304,45,7]. If BitDepthLuma is equal to 12, the clipping level Lim(idx) = [4095,512,64,8]. If BitDepthLuma is equal to 13, the clipping level Lim(idx)=[8191,861,91,10]. If BitDepthLuma is equal to 14, the clipping level Lim(idx) = [16383,1448,128,11]. If BitDepthLuma is equal to 15, then the clipping level Lim(idx)=[32767,2435,181,13], and / or If BitDepthLuma is equal to 16, then the clipping level Lim(idx)=[65535,4096,256,16].

[0256] According to an implementation scheme of the first embodiment, for use in a video encoding or decoding device, the above-mentioned in-loop filter may be configured to process a current reconstructed block, the current reconstructed block including a plurality of pixels from a reconstructed frame.

[0257] According to an implementation of the first embodiment, an in-loop filter may be applied to the luma and chroma components of the reconstructed frame.

[0258] According to an implementation scheme of the first embodiment, the filtered reconstructed frames may be used to generate encoded video data for the video signal for transmission or storage, or may be used to decode the video signal for display on a display device.

[0259] According to one aspect of the first embodiment, there is provided an encoding device for encoding a current frame from an input video stream, the encoding device including an in-loop filter device according to any one of the implementation manners of the first embodiment.

[0260] According to a further aspect of the first embodiment, there is provided a decoding device for decoding an encoded frame, the decoding device including an in-loop filter device according to any one of the implementation manners of the first embodiment.

[0261] According to the implementation of the first embodiment, the clipping level Lim(i,j) may be obtained from or determined by a table representation, and the same table representation may be used for the luma and chroma components.

[0262] According to the implementation of the first embodiment, the clipping level is 2 BitDepth BitDepth can be less than or equal to -1, where BitDepth is the bit depth of the filtered component (luma component or one of the two chroma components) of a pixel (e.g., I(x,y)) of the reconstructed frame, or BitDepth is the maximum number of bits in a sample (pixel) of each component of the reconstructed frame.

[0263] According to a second embodiment, the present disclosure relates to an in-loop filtering method for processing reconstructed frames from a decoded video stream to generate filtered reconstructed frames, the reconstructed frames including a plurality of pixels, each pixel associated with a pixel value, the in-loop filtering method comprising: The method includes filtering pixels (i.e., filtering pixels such as each pixel) from the reconstructed frame, wherein the filtered pixel of the filtered reconstructed frame is a sum of the filtered pixel and a weighted sum of clipped differences between the filtered pixel and neighboring pixels, or the filtered pixel of the filtered reconstructed frame is based on the sum.

[0264] Clipping level is 2 BitDepthBitDepth can be less than or equal to -1, where BitDepth is the bit depth of the filtered component (luma component or one of the two chroma components) of a pixel (e.g., I(x,y)) of the reconstructed frame, or BitDepth is the maximum number of bits in a sample (pixel) of each component of the reconstructed frame.

[0265] In particular, the method may include processing a current reconstructed block, the current reconstructed block including a plurality of pixels from a reconstructed frame.

[0266] In particular, the filtered pixels are calculated using the following formula:

number

[0267] In one example, a pixel brightness or pixel value may be a value corresponding to the brightness of a pixel on a screen or display. In other words, a pixel brightness is a value corresponding to a pixel.

[0268] In one example, the luma samples have picture coordinates such as (x, y), which are the picture coordinates of the specified luma sample.

[0269] In one example, the chroma samples have picture coordinates such as (x,y) which are the picture coordinates of the specified chroma sample.

[0270] It can be understood that before or during the filtering process, a pixel (e.g., I(x,y)) can be understood as a pixel to be filtered or a filtered pixel, and after the filtering process is performed, the value of the pixel (e.g., I(x,y)) can be changed and can be understood as a filtered pixel (e.g., O'(x,y)).

[0271] In particular, the clipping level Lim(i,j) may be a positive k-bit clipping value, where k<=BitDepth.

[0272] The clipping levels Lim(i,j) for the luma and chroma component filtering may have a tabular representation, in particular in the form of a look-up table (LUT).

[0273] The clipping levels Lim(i,j) for the luma and chroma component filtering may be obtained from or determined by a tabular representation, in particular in the form of a look-up table (LUT).

[0274] According to the realization of the second embodiment, the clipping level Lim(i,j) is calculated in particular by the following formula:

number

[0275] According to the realization of the second embodiment, the clipping level Lim(i,j) is calculated in particular by the following formula:

number

[0276] In this implementation, the clipping level Lim(i,j) is a positive k-bit clipping value, k<=BitDepth+1, and Lim(i,j)<=2 for the luma component. BitDepthLuma and Lim(i,j)<=2 for the chroma components. BitDepthChroma is.

[0277] According to the realization of the second embodiment, the clipping level Lim(i,j) is calculated in particular by the following formula:

number

[0278] According to the implementation of the second embodiment, the clipping level Lim(i,j) or clipping value Lim(i,j) of a table representation (such as a table or LUT table) is calculated using the following formula:

number

[0279] According to the implementation of the second embodiment, the clipping level Lim(i,j) is calculated according to the following formula:

number

[0280] According to the implementation scheme of the second embodiment, the clipping level Lim(i,j) may be determined by the same formula for the luma and chroma components of the filtered pixel (such as I(x,y)) of the reconstructed frame, or the same clipping level Lim(i,j) may be applied to the luma and chroma components of the filtered pixel (such as I(x,y)) of the reconstructed frame.

[0281] According to the implementation of the second embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0282] According to the implementation of the second embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0283] According to the realization of the second embodiment, the clipping level Lim(i,j) may be obtained or determined from a table representation, which has the same formula for the luma and chroma components:

number

[0284] According to the implementation of the second embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0285] According to the realization of the second embodiment, the clipping level Lim(i,j) may be obtained or determined from a table representation, which has the same formula for the luma and chroma components:

number

[0286] According to the implementation of the second embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0287] According to the implementation of the second embodiment, the clipping level (or clipping value) Lim(i,j) may be determined for the luma and chroma components of the reconstructed frame by the same table representation below: If idx = Idx(i,j) = 0, 1, 2 or 3, If BitDepthLuma is equal to 8, then the clipping level Lim(idx)=[255,63,15,3]. If BitDepthLuma is equal to 9, then the clipping level Lim(idx)=[511,107,22,4]. If BitDepthLuma is equal to 10, the clipping level Lim(idx) = [1023,180,31,5]. If BitDepthLuma is equal to 11, the clipping level Lim(idx) = [2047,303,44,6]. If BitDepthLuma is equal to 12, the clipping level Lim(idx) = [4095,511,63,7]. If BitDepthLuma is equal to 13, the clipping level Lim(idx)=[8191,860,90,9]. If BitDepthLuma is equal to 14, the clipping level Lim(idx) = [16383,1447,127,10]. If BitDepthLuma is equal to 15, then the clipping level Lim(idx)=[32767,2434,180,12], and / or If BitDepthLuma is equal to 16, then the clipping level Lim(idx)=[65535,4095,255,15].

[0288] According to the implementation of the second embodiment, the clipping level (or clipping value) Lim(i,j) may be determined for the luma and chroma components of the reconstructed frame by the same table representation below: If idx = Idx(i,j) = 0, 1, 2 or 3, If BitDepthLuma is equal to 8, then the clipping level Lim(idx)=[255,64,16,4]. If BitDepthLuma is equal to 9, the clipping level Lim(idx) = [511,108,23,5]. If BitDepthLuma is equal to 10, the clipping level Lim(idx) = [1023,181,32,6]. If BitDepthLuma is equal to 11, the clipping level Lim(idx) = [2047,304,45,7]. If BitDepthLuma is equal to 12, the clipping level Lim(idx) = [4095,512,64,8]. If BitDepthLuma is equal to 13, the clipping level Lim(idx)=[8191,861,91,10]. If BitDepthLuma is equal to 14, the clipping level Lim(idx) = [16383,1448,128,11]. If BitDepthLuma is equal to 15, then the clipping level Lim(idx)=[32767,2435,181,13], and / or If BitDepthLuma is equal to 16, then the clipping level Lim(idx)=[65535,4096,256,16].

[0289] According to the implementation of the second embodiment, the luma component filtering is as follows: If BitDepthLuma is equal to 10, the maximum clipping level may be Lim(i,j)=1023, and / or If BitDepthLuma is equal to 8, the maximum clipping level may be Lim(i,j)=255.

[0290] According to the implementation of the second embodiment, the luma component filtering is as follows: If BitDepthLuma is equal to 16, the maximum clipping level is Lim(i,j)=65535. If BitDepthLuma is equal to 15, the maximum clipping level is Lim(i,j)=32767. If BitDepthLuma is equal to 14, the maximum clipping level is Lim(i,j)=16383. If BitDepthLuma is equal to 13, the maximum clipping level is Lim(i,j)=8191. If BitDepthLuma is equal to 12, the maximum clipping level is Lim(i,j)=4095. If BitDepthLuma is equal to 11, the maximum clipping level is Lim(i,j)=2047. If BitDepthLuma is equal to 10, the maximum clipping level is Lim(i,j)=1023. If BitDepthLuma is equal to 9, the maximum clipping level is Lim(i,j)=511, and / or If BitDepthLuma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0291] According to the implementation method of the second embodiment, for chroma component filtering, If BitDepthChroma is equal to 10, the maximum clipping level may be Lim(i,j)=1023, and / or If BitDepthChroma is equal to 8, the maximum clipping level may be Lim(i,j)=255.

[0292] According to the implementation method of the second embodiment, for chroma component filtering, If BitDepthChroma is equal to 16, the maximum clipping level is Lim(i,j)=65535. If BitDepthChroma is equal to 15, the maximum clipping level is Lim(i,j)=32767. If BitDepthChroma is equal to 14, the maximum clipping level is Lim(i,j)=16383. If BitDepthChroma is equal to 13, the maximum clipping level is Lim(i,j)=8191. If BitDepthChroma is equal to 12, the maximum clipping level is Lim(i,j)=4095. If BitDepthChroma is equal to 11, the maximum clipping level is Lim(i,j)=2047. If BitDepthChroma is equal to 10, the maximum clipping level is Lim(i,j)=1023. If BitDepthChroma is equal to 9, the maximum clipping level is Lim(i,j)=511, and / or If BitDepthChroma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0293] According to the implementation of the second embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0294] According to the implementation of the second embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) of the reconstructed frame using the same formula:

number

[0295] In this implementation, the clipping level Lim(i,j) is a positive k-bit clipping value, k<=BitDepth+1, and Lim(i,j)<=2 for the luma component. BitDepthLuma and Lim(i,j)<=2 for the chroma components. BitDepthChroma is.

[0296] According to the implementation of the second embodiment, the rounding procedure is as follows:

number

[0297] According to the implementation of the second embodiment, the clipping level Lim(i,j) may be obtained from or determined by a table representation, and the same table representation may be used for the luma and chroma components.

[0298] According to the implementation of the second embodiment, the clipping level is 2 BitDepthBitDepth can be less than or equal to -1, where BitDepth is the bit depth of the filtered component (luma component or one of the two chroma components) of a pixel (e.g., I(x,y)) of the reconstructed frame, or BitDepth is the maximum number of bits in a sample (pixel) of each component of the reconstructed frame.

[0299] According to a third embodiment, the present disclosure relates to an in-loop filtering apparatus for use in a video encoding or decoding apparatus, the in-loop filtering apparatus being configured to process a reconstructed frame to generate a filtered reconstructed frame, the reconstructed frame comprising a plurality of pixels, each pixel associated with a pixel value, the in-loop filtering apparatus comprising: one or more processing circuits configured to filter pixels (i.e., filtered pixels, such as each pixel) from the reconstructed frame, wherein the filtered pixels (i.e., each pixel) of the filtered reconstructed frame are determined according to the following equation:

number

[0300] According to the implementation of the third embodiment, the clipping level Lim(i,j) is calculated for the luma and chroma components of the filtered pixel (e.g., I(x,y)) using the same formula:

number

[0301] According to a fourth embodiment, the present disclosure relates to an in-loop filtering apparatus for use in a video encoding or decoding apparatus, the in-loop filtering apparatus being configured to process a reconstructed frame to generate a filtered reconstructed frame, the reconstructed frame comprising a plurality of pixels, each pixel associated with a pixel value, the in-loop filtering apparatus comprising: one or more processing circuits configured to filter pixels (i.e., filtered pixels, such as each pixel) from the reconstructed frame, wherein the filtered pixels (i.e., each pixel) of the filtered reconstructed frame are determined according to the following equation:

number

[0302] The same clipping level (or clipping value) Lim(i,j) may be applied to the luma and chroma components of the current pixel. The same clipping level table may be used for luma and chroma component filtering.

[0303] According to the implementation scheme of the fourth embodiment, the same clipping level (or clipping value) for the luma and chroma components may be determined from the same table based on the bit depth of the luma and chroma components of a pixel (such as I(x,y)) of the reconstructed frame and clipIdx, which may be a signaling element used to determine which clipping level from the possible clipping levels can be used for the current tap in the current filter.

[0304] According to an implementation of the fourth embodiment, the clipping levels (or clipping values) for the luma and chroma components may be determined from a single LUT table defined as follows: [Table 3] The value of the column clipIdx=0 is the following formula for the clipping level Lim(i,j) for Idx(i,j)=0:

number

[0305] According to an implementation of the fourth embodiment, the clipping levels (or clipping values) for the luma and chroma components may be determined from a single LUT table defined as follows: [Table 4]

[0306] According to an implementation of the fourth embodiment, the clipping levels (or clipping values) for the luma and chroma components may be determined from a single LUT table defined as follows: [Table 5]

[0307] According to a fifth embodiment, the present disclosure relates to an in-loop filtering method for processing reconstructed frames from a decoded video stream to generate filtered reconstructed frames, the reconstructed frames including a plurality of pixels, each pixel associated with a pixel value, the in-loop filtering method comprising: filtering pixels (i.e., filtering pixels such as each pixel) from the reconstructed frame, wherein the filtered pixels (i.e., each pixel) of the filtered reconstructed frame are filtered according to the following formula:

number

[0308] According to the implementation scheme of the fifth embodiment, I(x+i,y+j) is a positive BitDepthLuma bit value for the luma component or a BitDepthChroma bit value for the chroma component corresponding to the pixel value (or pixel luminance) at a point with coordinates (x+i,y+j) in the reconstructed frame, O'(x,y) is a filtered pixel with coordinates (x,y) in the reconstructed frame, w(i,j) denotes an n-bit integer filter coefficient corresponding to a pixel position with offset (i,j) with respect to the filtered pixel, and Lim(I,j) is a positive or non-negative clipping value (e.g., Lim(i,j)=b in the table).

[0309] According to the implementation method of the fifth embodiment, for the luma component, Lim(i,j)<=2 BitDepthLuma -1 and Lim(i,j)<=2 for chroma components BitDepthChroma It is -1.

[0310] According to the implementation of the fifth embodiment, the clipping levels Lim(i,j) may be obtained from or determined by a table representation (such as a table or a LUT table), which follows the same formula for the luma and chroma components:

number

[0311] According to the implementation of the fifth embodiment, the clipping levels Lim(i,j) may be obtained from or determined by a table representation (such as a table or a LUT table), which is based on the following formula for the luma and chroma components:

number

[0312] According to the implementation of the fifth embodiment, the clipping level Lim(i,j) may be obtained from or determined by a table representation (such as a table or a LUT table), and the same table representation may be used for the luma and chroma components.

[0313] According to the implementation of the fifth embodiment, the clipping level is 2 BitDepth BitDepth can be less than or equal to -1, where BitDepth is the bit depth of the filtered component (luma component or one of the two chroma components) of a pixel (e.g., I(x,y)) of the reconstructed frame, or BitDepth is the maximum number of bits in a sample (pixel) of each component of the reconstructed frame.

[0314] According to the implementation of the fifth embodiment, the clipping level Lim(i,j) may be obtained from or determined by the following table representation: If idx = Idx(i,j) = 0, 1, 2 or 3, If BitDepthLuma is equal to 8, then the clipping level Lim(idx)=[255,63,15,3]. If BitDepthLuma is equal to 9, then the clipping level Lim(idx)=[511,107,22,4]. If BitDepthLuma is equal to 10, the clipping level Lim(idx) = [1023,180,31,5]. If BitDepthLuma is equal to 11, the clipping level Lim(idx) = [2047,303,44,6]. If BitDepthLuma is equal to 12, the clipping level Lim(idx) = [4095,511,63,7]. If BitDepthLuma is equal to 13, the clipping level Lim(idx)=[8191,860,90,9]. If BitDepthLuma is equal to 14, the clipping level Lim(idx) = [16383,1447,127,10]. If BitDepthLuma is equal to 15, then the clipping level Lim(idx)=[32767,2434,180,12], and / or If BitDepthLuma is equal to 16, then the clipping level Lim(idx)=[65535,4095,255,15].

[0315] According to the implementation of the fifth embodiment, the clipping level Lim(i,j) may be obtained from or determined by the following table representation: If idx = Idx(I,j) = 0, 1, 2 or 3, If BitDepthLuma is equal to 8, then the clipping level Lim(idx)=[255,64,16,4]. If BitDepthLuma is equal to 9, the clipping level Lim(idx) = [511,108,23,5]. If BitDepthLuma is equal to 10, the clipping level Lim(idx) = [1023,181,32,6]. If BitDepthLuma is equal to 11, the clipping level Lim(idx) = [2047,304,45,7]. If BitDepthLuma is equal to 12, the clipping level Lim(idx) = [4095,512,64,8]. If BitDepthLuma is equal to 13, the clipping level Lim(idx)=[8191,861,91,10]. If BitDepthLuma is equal to 14, the clipping level Lim(idx) = [16383,1448,128,11]. If BitDepthLuma is equal to 15, then the clipping level Lim(idx)=[32767,2435,181,13], and / or If BitDepthLuma is equal to 16, then the clipping level Lim(idx)=[65535,4096,256,16].

[0316] According to the implementation of the fifth embodiment, the luma component filtering is as follows: If BitDepthLuma is equal to 16, the maximum clipping level is Lim(i,j)=65535. If BitDepthLuma is equal to 15, the maximum clipping level is Lim(i,j)=32767. If BitDepthLuma is equal to 14, the maximum clipping level is Lim(i,j)=16383. If BitDepthLuma is equal to 13, the maximum clipping level is Lim(i,j)=8191. If BitDepthLuma is equal to 12, the maximum clipping level is Lim(i,j)=4095. If BitDepthLuma is equal to 11, the maximum clipping level is Lim(i,j)=2047. If BitDepthLuma is equal to 10, the maximum clipping level is Lim(i,j)=1023. If BitDepthLuma is equal to 9, the maximum clipping level is Lim(i,j)=511, and / or If BitDepthLuma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0317] According to the implementation method of the fifth embodiment, for chroma component filtering, If BitDepthChroma is equal to 16, the maximum clipping level is Lim(i,j)=65535. If BitDepthChroma is equal to 15, the maximum clipping level is Lim(i,j)=32767. If BitDepthChroma is equal to 14, the maximum clipping level is Lim(i,j)=16383. If BitDepthChroma is equal to 13, the maximum clipping level is Lim(i,j)=8191. If BitDepthChroma is equal to 12, the maximum clipping level is Lim(i,j)=4095. If BitDepthChroma is equal to 11, the maximum clipping level is Lim(i,j)=2047. If BitDepthChroma is equal to 10, the maximum clipping level is Lim(i,j)=1023. If BitDepthChroma is equal to 9, the maximum clipping level is Lim(i,j)=511, and / or If BitDepthChroma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0318] According to a sixth embodiment, the present disclosure relates to an in-loop filtering apparatus for use in a video encoding or decoding apparatus, the in-loop filtering apparatus being configured to process a reconstructed frame to generate a filtered reconstructed frame, the reconstructed frame comprising a plurality of pixels, each pixel associated with a pixel value, the in-loop filtering apparatus comprising: one or more processing circuits configured to filter pixels (i.e., filtered pixels, such as each pixel) from the reconstructed frame, wherein the filtered pixels (i.e., each pixel) of the filtered reconstructed frame are filtered according to the following formula:

number

[0319] According to the implementation scheme of the sixth embodiment, I(x+i,y+j) is a positive BitDepthLuma bit value for the luma component or a BitDepthChroma bit value for the chroma component corresponding to the pixel value (or pixel luminance) at a point with coordinates (x+i,y+j) in the reconstructed frame, O'(x,y) is a filtered pixel with coordinates (x,y) in the reconstructed frame, w(i,j) denotes an n-bit integer filter coefficient corresponding to a pixel position with offset (i,j) with respect to the filtered pixel, and Lim(I,j) is a positive or non-negative clipping value (e.g., Lim(i,j)=b in the table).

[0320] According to the implementation of the sixth embodiment, for the luma component, Lim(i,j)<=2 BitDepthLuma -1 and Lim(i,j)<=2 for chroma components BitDepthChroma It is -1.

[0321] According to the implementation of the sixth embodiment, the clipping levels Lim(i,j) may be obtained from or determined by a table representation (such as a table or a LUT table), which follows the same formula for the luma and chroma components:

number

[0322] According to the implementation of the sixth embodiment, the clipping levels Lim(i,j) may be obtained from or determined by a table representation (such as a table or a LUT table), which is based on the following formula for the luma and chroma components:

number

[0323] According to the implementation of the sixth embodiment, the clipping level Lim(i,j) may be obtained from or determined by a table representation (such as a table or a LUT table), and the same table representation may be used for the luma and chroma components.

[0324] According to the implementation of the sixth embodiment, the clipping level is 2 BitDepth BitDepth can be less than or equal to -1, where BitDepth is the bit depth of the filtered component (luma component or one of the two chroma components) of a pixel (e.g., I(x,y)) of the reconstructed frame, or BitDepth is the maximum number of bits in a sample (pixel) of each component of the reconstructed frame.

[0325] According to the implementation of the sixth embodiment, the clipping level Lim(i,j) may be obtained from or determined by the following table representation: If idx = Idx(i,j) = 0, 1, 2 or 3, If BitDepthLuma is equal to 8, then the clipping level Lim(idx)=[255,63,15,3]. If BitDepthLuma is equal to 9, then the clipping level Lim(idx)=[511,107,22,4]. If BitDepthLuma is equal to 10, the clipping level Lim(idx) = [1023,180,31,5]. If BitDepthLuma is equal to 11, the clipping level Lim(idx) = [2047,303,44,6]. If BitDepthLuma is equal to 12, the clipping level Lim(idx) = [4095,511,63,7]. If BitDepthLuma is equal to 13, the clipping level Lim(idx)=[8191,860,90,9]. If BitDepthLuma is equal to 14, the clipping level Lim(idx) = [16383,1447,127,10]. If BitDepthLuma is equal to 15, then the clipping level Lim(idx)=[32767,2434,180,12], and / or If BitDepthLuma is equal to 16, then the clipping level Lim(idx)=[65535,4095,255,15].

[0326] According to the implementation of the sixth embodiment, the clipping level Lim(i,j) may be obtained from or determined by the following table representation: If idx = Idx(I,j) = 0, 1, 2 or 3, If BitDepthLuma is equal to 8, then the clipping level Lim(idx)=[255,64,16,4]. If BitDepthLuma is equal to 9, the clipping level Lim(idx) = [511,108,23,5]. If BitDepthLuma is equal to 10, the clipping level Lim(idx) = [1023,181,32,6]. If BitDepthLuma is equal to 11, the clipping level Lim(idx) = [2047,304,45,7]. If BitDepthLuma is equal to 12, the clipping level Lim(idx) = [4095,512,64,8]. If BitDepthLuma is equal to 13, the clipping level Lim(idx)=[8191,861,91,10]. If BitDepthLuma is equal to 14, the clipping level Lim(idx) = [16383,1448,128,11]. If BitDepthLuma is equal to 15, then the clipping level Lim(idx)=[32767,2435,181,13], and / or If BitDepthLuma is equal to 16, then the clipping level Lim(idx)=[65535,4096,256,16].

[0327] According to the implementation of the sixth embodiment, the luma component filtering is as follows: If BitDepthLuma is equal to 16, the maximum clipping level is Lim(i,j)=65535. If BitDepthLuma is equal to 15, the maximum clipping level is Lim(i,j)=32767. If BitDepthLuma is equal to 14, the maximum clipping level is Lim(i,j)=16383. If BitDepthLuma is equal to 13, the maximum clipping level is Lim(i,j)=8191. If BitDepthLuma is equal to 12, the maximum clipping level is Lim(i,j)=4095. If BitDepthLuma is equal to 11, the maximum clipping level is Lim(i,j)=2047. If BitDepthLuma is equal to 10, the maximum clipping level is Lim(i,j)=1023. If BitDepthLuma is equal to 9, the maximum clipping level is Lim(i,j)=511, and / or If BitDepthLuma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0328] According to the implementation method of the sixth embodiment, for chroma component filtering, If BitDepthChroma is equal to 16, the maximum clipping level is Lim(i,j)=65535. If BitDepthChroma is equal to 15, the maximum clipping level is Lim(i,j)=32767. If BitDepthChroma is equal to 14, the maximum clipping level is Lim(i,j)=16383. If BitDepthChroma is equal to 13, the maximum clipping level is Lim(i,j)=8191. If BitDepthChroma is equal to 12, the maximum clipping level is Lim(i,j)=4095. If BitDepthChroma is equal to 11, the maximum clipping level is Lim(i,j)=2047. If BitDepthChroma is equal to 10, the maximum clipping level is Lim(i,j)=1023. If BitDepthChroma is equal to 9, the maximum clipping level is Lim(i,j)=511, and / or If BitDepthChroma is equal to 8, the maximum clipping level is Lim(i,j)=255.

[0329] According to a seventh embodiment, the present disclosure relates to a computer program product comprising a program code for performing any one of the methods according to the second and fifth embodiments when the program code is executed on a computer or processor.

[0330] According to an eighth embodiment, the present disclosure relates to a decoder including 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 processors, configuring the decoder to perform any one of the methods according to the second and fifth embodiments.

[0331] According to a ninth embodiment, the present disclosure relates to an encoder including 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 processors, configuring the encoder to perform any one of the methods according to the second and fifth embodiments.

[0332] According to a tenth embodiment, the present disclosure relates to a non-transitory computer-readable medium carrying program code that, when executed by a computing device, causes the computing device to perform any one of the methods according to the second and fifth embodiments.

[0333] The following is a description of the application of the encoding and decoding methods shown in the above embodiments and a system using them.

[0334] 10 is a block diagram showing a content supply system 3100 for realizing a content distribution service. The content supply system 3100 includes a capture device 3102, a terminal device 3106, and optionally a display 3126. The capture device 3102 communicates with the terminal device 3106 over a communication link 3104. The communication link may include the above-mentioned communication channel 13. The communication link 3104 includes, but is not limited to, WIFI, Ethernet, cable, wireless (3G / 4G / 5G), USB, or any combination thereof.

[0335] The capture device 3102 may generate data and encode the data using the encoding method described in the above embodiment. Alternatively, the capture device 3102 may deliver the data to a streaming server (not shown in the drawings), which then 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, an in-vehicle device, or any combination thereof. For example, the capture device 3102 may include the source device 12 described above. When the data includes video, the video encoder 20 included in the capture device 3102 may actually perform video encoding processing. When the data includes audio (i.e., voice), the audio encoder included in the capture device 3102 may actually perform audio encoding processing. In some practical scenarios, the capture device 3102 delivers the encoded video and audio data by multiplexing them together. In other practical scenarios, for example, in a video conferencing system, the encoded audio data and the encoded video data are not multiplexed. The capture device 3102 delivers the encoded audio data and the encoded video data separately to the terminal device 3106 .

[0336] In the content delivery system 3100, a terminal device 3106 receives and plays encoded data. The terminal device 3106 may be a device capable of receiving and restoring data, 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, an in-vehicle device 3124, or any combination thereof, capable of decoding the encoded data. For example, the terminal device 3106 may include the destination device 14 described above. When the encoded data includes video, the video decoder 30 included in the terminal device is prioritized to perform video decoding. When the encoded data includes audio, the audio decoder included in the terminal device is prioritized to perform audio decoding.

[0337] In a terminal device having its own display, such as a smartphone or pad 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video decoder (DVR) 3112, a TV 3114, a personal digital assistant (PDA) 3122 or an in-vehicle device 3124, the terminal device can provide the decoded data to its own display. In a terminal device without a display, such as an STB 3116, a video conferencing system 3118 or a video surveillance system 3120, an external display 3126 is brought into contact with it to receive and display the decoded data.

[0338] When each device in this system performs encoding or decoding, it can use a picture encoding device or a picture decoding device as shown in the above embodiment.

[0339] 11 is a diagram illustrating an example structure of the terminal device 3106. After the terminal device 3106 receives a stream from the capture device 3102, the protocol processing unit 3202 analyzes the transmission protocol of the stream. The protocol may include, but is not limited to, Real Time Streaming Protocol (RTSP), Hyper Text Transfer Protocol (HTTP), HTTP Live Streaming Protocol (HLS), MPEG-DASH, Real-time Transport Protocol (RTP), Real Time Messaging Protocol (RTMP), or any type of combination thereof.

[0340] After the protocol processing unit 3202 processes the stream, a stream file is generated. The file is output to the demultiplexing unit 3204. The demultiplexing unit 3204 can separate the multiplexed data into encoded audio data and encoded video data. As mentioned above, in some practical scenarios, for example, in a video conferencing system, the encoded audio data and encoded video data are not multiplexed. In this situation, the encoded data is sent to the video decoder 3206 and the audio decoder 3208 without passing through the demultiplexing unit 3204.

[0341] Through the demultiplexing process, a video elementary stream (ES), an audio ES, and optional subtitles are generated. A video decoder 3206, which includes the video decoder 30 as described in the above embodiment, decodes the video ES using the decoding method as shown in the above embodiment to generate video frames and supplies this data to a synchronization unit 3212. An audio decoder 3208 decodes the audio ES to generate audio frames and supplies this data to the synchronization unit 3212. Alternatively, the video frames may be stored in a buffer (not shown in FIG. 11) before being supplied to the synchronization unit 3212. Similarly, the audio frames may be stored in a buffer (not shown in FIG. 11) before being supplied to the synchronization unit 3212.

[0342] The synchronization unit 3212 synchronizes the video and audio frames and provides the video / audio to the video / audio display 3214. For example, the synchronization unit 3212 synchronizes the presentation of video and audio information. The information may be coded in the syntax using timestamps for the presentation of the coded audio and visual data and timestamps for the delivery of the data stream itself.

[0343] 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 .

[0344] The present invention is not limited to the above system, and either the picture encoding device or the picture decoding device in the above embodiments can be incorporated into other systems, for example, vehicle systems.

[0345] Mathematical Operators The mathematical operators used in this application are similar to those used in the C programming language. However, the results of integer division and arithmetic shift operations are more precisely defined, and additional operators such as exponentiation and division of real values are defined. Numbering and counting conventions generally start from 0, i.e., "first" is equivalent to 0th, "second" is equivalent to 1st, etc.

[0346] Logical operators The following logical operators are defined as follows: [Table 6] Logical operators The following logical operators are defined as follows:

[0347] x&&y The Boolean logic "product" of x and y x||y Boolean logic "union" of x and y Boolean logic "negation" x?y:z Evaluates to the value of y if x is true or not equal to 0, otherwise evaluates to the value of z Relational operators The following relational operators are defined as follows:

[0348] > greater than >= Greater than or equal to < Less than <= Less than or equal to == Equal != Not equal to When a relational operator is applied to a syntax element or variable that has been assigned the value "na" (not applicable), the value "na" is treated as a separate value of the syntax element or variable. The value "na" is considered not equal to any other value.

[0349] Bitwise Operators The following bitwise operators are defined as follows:

[0350] & Bitwise "product". When operating on integer arguments, the operation is performed on the two's complement representation of the integer values. When operating on a binary argument that contains fewer bits than the other argument, the shorter argument is extended by adding higher-order bits equal to 0.

[0351] | Bitwise "sum". When operating on integer arguments, the operation is performed on the two's complement representation of the integer values. When operating on a binary argument that contains fewer bits than the other argument, the shorter argument is extended by adding higher-order bits equal to 0.

[0352] ^ Bitwise "exclusive sum". When operating on integer arguments, the operation is performed on the two's complement representation of the integer values. When operating on a binary argument that contains fewer bits than the other argument, the shorter argument is extended by adding higher-order bits equal to 0.

[0353] x>>y Arithmetic right shift of the two's complement integer representation of x by y binary digits. This function is defined only for non-negative integer values of y. The bit shifted into the most significant bit (MSB) as a result of the right shift has the same value as the MSB of x before the shift operation.

[0354] x<<y Arithmetic left shift of the two's complement integer representation of x by y binary digits. This function is defined only for non-negative integer values of y. The bit shifted into the least significant bit (LSB) as a result of the left shift has a value equal to 0.

[0355] Assignment operators The following assignment operators are defined as follows.

[0356] = Assignment operator ++ Increment. That is, x++ is equal to x=x+1. When used in an array index, it is evaluated to the value of the variable before the increment operation.

[0357] -- Decrement, i.e. x-- is equal to x=x-1. When used in an array index, evaluates to the value of the variable before the decrement operation.

[0358] += increment by the specified amount, i.e. x+=3 is equal to x=x+3, and x+=(-3) is equal to x=x+(-3).

[0359] -= Decrement by the specified amount, i.e. x-=3 is equal to x=x-3, and x-=(-3) is equal to x=x-(-3).

[0360] Range Notation The following notation is used to specify a range of values:

[0361] x=y..zx takes an integer value greater than or equal to y and less than or equal to z, where x, y, and z are integers and z is greater than y.

[0362] Mathematical Functions The following mathematical functions are defined:

number

[0363] Atan(x) The trigonometric arctangent function, operated on the argument x, with output values in the range -π÷2 to π÷2 inclusive, in radians.

number

[0364] Clip1 Y (x)=Clip3(0,(1< <BitDepth Y )-1,x) Clip1 C (x)=Clip3(0,(1< <BitDepthC )-1,x)

number

[0365] Floor(x) The largest integer less than or equal to x.

number

[0366] Log2(x) The base 2 logarithm of x.

[0367] Log10(x) The base 10 logarithm of x.

number

number

number

[0368] Sqrt(x)=√x Swap(x,y)=(y,x) Tan(x) The trigonometric tangent function, operating on the argument x in radians.

[0369] Operation precedence When the precedence of an expression is not explicitly indicated by the use of parentheses, the following rules apply:

[0370] An operation with a higher priority is evaluated before any operation with a lower priority.

[0371] -Operations of equal precedence are evaluated sequentially from left to right.

[0372] The table below specifies the priority of operations from highest to lowest, with higher positions in the table indicating higher priority.

[0373] For operators that are also used in the C programming language, the precedence used herein is the same as the precedence used in the C programming language. [Table 7] Text description of logical operations In text, the format is: if(condition0) Statement 0 else(condition 1) Statement 1 ... else / *Reference notes for remaining conditions* / Statement n A statement of logical operation such as mathematically described in may be written in the following manner:

[0374] ...as / ...the following applies: -If condition 0, then statement 0 - Otherwise, if condition 1, then statement 1 -... - Otherwise (reference notes for the remaining conditions), statement n Each "if... otherwise, if... otherwise" statement in the text is introduced by "as" or "the following applies" immediately followed by "if...". The final condition of an "if... otherwise, if... otherwise" may always be "otherwise". Alternating "if... otherwise, if... otherwise, if..." statements can be identified by matching a "as" or "the following applies" that ends with an "otherwise".

[0375] In text, the following format: if(condition0a&&condition0b) Statement 0 else if(condition 1a||condition 1b) Statement 1 ... else Statement n A statement of logical operation such as mathematically described in may be written in the following manner:

[0376] ...as / ...the following applies: -Statement 0 if all of the following conditions are true: -Condition 0a -condition 0b - Otherwise, if one or more of the following conditions are true, then statement 1: -Condition 1a -Condition 1b -… - Otherwise, statement n In text, the following format: if(condition0) Statement 0 if(condition1) Statement 1 A statement of logical operation such as mathematically described in may be written in the following manner:

[0377] If condition 0, then statement 0 If condition 1 is true, then statement 1 Although embodiments of the present disclosure have been described primarily in the context of video coding, it should be noted that embodiments of coding system 10, encoder 20, and decoder 30 (and correspondingly, system 10), as well as other embodiments described herein, may also be configured for still picture processing or coding, i.e., processing or coding of individual pictures independent of any previous or subsequent pictures, as in video coding. Generally, when picture processing coding is limited to a single picture 17, only the inter-prediction units 244 (encoder) and 344 (decoder) may not be available. All other functions (also referred to as tools or techniques) of video encoder 20 and video decoder 30 may equally be used for still picture processing, e.g., residual calculation 204 / 304, transform 206, quantization 208, inverse quantization 210 / 310, (inverse) transform 212 / 312, partition 262, intra prediction 254 / 354, and / or loop filtering 220, 320, as well as entropy coding 270 and entropy decoding 304.

[0378] For example, embodiments of the encoder 20 and the decoder 30, and the functions described herein with respect to the encoder 20 and the decoder 30, may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on a computer-readable medium or transmitted over a communication medium as one or more instructions or code and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which correspond to tangible media such as data storage media, or communication media, including any medium that facilitates transfer of a computer program from one place to another, for example, according to a communication protocol. Thus, computer-readable media may generally correspond to (1) tangible computer-readable storage media that are non-transitory, or (2) communication media such as a signal or carrier wave. Data storage media may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementing the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0379] By way of example, and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included within the definition of medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but instead cover non-transitory tangible storage media. As used herein, disk and disc include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically and discs reproduce data optically with a laser. Combinations of the above should also be included within the scope of computer-readable media.

[0380] The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor," as used herein, may refer to any of the above structures or any other structure suitable for implementing the techniques described herein. 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. Alternatively, the techniques may be implemented entirely in one or more circuit or logic elements.

[0381] The techniques of this disclosure may be implemented in a wide range of devices or apparatuses, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the techniques of the disclosure, but do not necessarily require implementation by different hardware units. Rather, as noted above, the various units may be combined with a codec hardware unit in combination with appropriate software and / or firmware, or may be provided by a collection of interoperating hardware units including one or more processors as described above.

Claims

1. 1. A method for in-loop filtering by performing adaptive loop filtering on reconstructed frames of a video stream, implemented by an encoding device, comprising: forming a difference between a chroma component of a pixel of the reconstructed frame and a chroma component of a neighboring pixel within a connected region of the pixel; clipping the difference according to a respective clipping level, the clipping level being determined by a clipping index; forming a weighted sum of the clipped differences; adding the weighted sum to the chroma components of the pixel to determine a filtered respective component of the pixel; encoding the clipping index into a bitstream; Including, The set of clipping levels Lim(i,j) for the chroma components is calculated through the change of the bit depth BitDepthChroma of the chroma components and the index Idx(i,j) according to the following formula: [Equation 1] Determined in accordance with the method.

2. The method of claim 1 , wherein the respective clipping levels are selected according to the bit depth of the chroma components of the pixel.

3. The method of claim 1 or 2, wherein the respective clipping levels are selected according to respective clipping indices for respective neighboring pixels within the connected region.

4. The method of claim 3 , wherein the respective clipping indexes are signaled within the video stream.

5. The clipping levels for each of the above are 2 BitDepth A positive clipping value less than or equal to -1, or the respective clipping level is 2 BitDepth 3. The method of claim 1, wherein the positive clipping values are: BitDepth=0, BitDepth=1, BitDepth=2, BitDepth=3, BitDepth=4, BitDepth=5, BitDepth=6, BitDepth=7, BitDepth=8, BitDepth=9, BitDepth=10, BitDepth=11, BitDepth=12, BitDepth=13, BitDepth=14

6. 3. The method of claim 1, wherein each said clipping level is a positive k-bit clipping value, k<=BitDepth, where BitDepth indicates the bit depth of said chroma component.

7. The clipping levels of each of the chrominance components are Lim(i,j)<=2 BitDepthChroma -1 or The clipping levels of each of the chrominance components are Lim(i,j)<=2 BitDepthChroma The method according to claim 1 or 2, wherein

8. The method of claim 1 or 2, wherein the respective clipping levels are selected from a look-up table (LUT) representing the set of clipping levels for the chroma components.

9. The LUT is defined as follows: 【Table 1】 The method of claim 8 , wherein BitDepth indicates a bit depth of the chroma component and clipIdx indicates a clipping index.

10. The method of claim 1 or 2, wherein in-loop filtering is applied to chroma components of the reconstructed frame.

11. 1. A method for in-loop filtering by performing adaptive loop filtering on reconstructed frames of a video stream, implemented by a decoding device, comprising: parsing a clipping index from the bitstream; forming a difference between a chroma component of a pixel of the reconstructed frame and a chroma component of a neighboring pixel within a connected region of the pixel; clipping the difference according to a respective clipping level, the clipping level being determined by the clipping index; forming a weighted sum of the clipped differences; adding the weighted sum to the chroma components of the pixel to determine a filtered respective component of the pixel; Including, The set of clipping levels Lim(i,j) for the chroma components is calculated through the change of the bit depth BitDepthChroma of the chroma components and the index Idx(i,j) according to the following formula: [Equation 1] Determined in accordance with the method.

12. An in-loop filtering device (320, 220) for use in a video encoding device, comprising: The in-loop filtering device (320, 220) is configured to process a reconstructed frame to generate a filtered reconstructed frame, the reconstructed frame including a plurality of pixels, each pixel associated with a pixel value, and the in-loop filtering device (320, 220) includes one or more processing circuits configured to perform the method of claim 1 or 2.

13. An encoder (20) including processing circuitry for carrying out the method of claim 1 or 2.

14. A decoder (30) including processing circuitry for performing the method of claim 11.

15. A computer program comprising: A computer program comprising instructions that, when executed by a computer, cause the computer to carry out the method according to claim 1 or 2 or 11.

16. An encoder (20), one or more processors; a non-transitory computer-readable storage medium coupled to the one or more processors, the non-transitory computer-readable storage medium storing instructions for execution by the one or more processors; Including, The instructions, when executed by the one or more processors, configure the encoder to perform the method of claim 1 or 2.

17. A decoder (30), one or more processors; a non-transitory computer-readable storage medium coupled to the one or more processors, the non-transitory computer-readable storage medium storing instructions for execution by the one or more processors; Including, The instructions, when executed by the one or more processors, configure the decoder to perform the method of claim 11.

18. 1. An encoder for processing a reconstructed frame to generate a filtered reconstructed frame, the reconstructed frame including a plurality of pixels, each pixel associated with a pixel value, the encoder comprising: a parsing unit configured to parse clipping indices from the bitstream; a subtraction unit configured to form a difference between a chroma component of a pixel of the reconstructed frame and a chroma component of a neighboring pixel within a connected region of the pixel; a clipping unit configured to clip the difference according to a respective clipping level, the clipping level being determined by the clipping index; a first summation unit configured to form a weighted sum of the clipped differences; Including, The set of clipping levels Lim(i,j) for the chroma components is calculated through the change of the bit depth BitDepthChroma of the chroma components and the index Idx(i,j) according to the following formula: [Equation 1] Determined according to the encoder.

19. 1. A decoder for processing a reconstructed frame to generate a filtered reconstructed frame, the reconstructed frame including a plurality of pixels, each pixel associated with a pixel value, the decoder comprising: a subtraction unit configured to form a difference between a chroma component of a pixel of the reconstructed frame and a chroma component of a neighboring pixel within a connected region of the pixel; a clipping unit configured to clip said difference according to a respective clipping level; a first summation unit configured to form a weighted sum of the clipped differences; a second summation unit configured to add the weighted sum to the chroma components of the pixel to determine a filtered respective component of the pixel; Including, The set of clipping levels Lim(i,j) for the chroma components is calculated through the change of the bit depth BitDepthChroma of the chroma components and the index Idx(i,j) according to the following formula: [Equation 1] ,decoder,determined according to

20. 1. A device for storing and decoding video or image bitstreams, comprising a communications interface, a processor, and a storage medium, the communication interface is configured to receive and / or transmit a bitstream, the storage medium is configured to store the bitstream, the bitstream includes clipping indices, the clipping indices are used to determine clipping levels, the clipping levels are used to clip a difference, the difference is formed between a chroma component of a pixel of a reconstructed frame and a chroma component of a neighboring pixel in a connected region of the pixel, the clipped difference is a weighted sum, and adding the weighted sum to the chroma component of the pixel to determine a filtered respective component of the pixel; The set of clipping levels Lim(i,j) for the chroma components is calculated through the change of the bit depth BitDepthChroma of the chroma components and the index Idx(i,j) according to the following formula: [Equation 1] Determined in accordance with the device.

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