Enhanced coding in inter-component sample adaptive offsets.

Abstract

An electronic device performs a method for decoding video data, the method including: receiving from a video signal a picture frame including a first component and a second component in a first color space; determining a classifier for the second component in the first color space from a set of one or more samples of the first component associated with each sample of the second component in the first color space, where the set of one or more samples is located in the second color space; determining a sample offset for each sample of the second component in the first color space in accordance with the classifier; and modifying a value of each sample of the second component in the first color space based on the determined sample offset.

Description

[Technical Field]

[0001] Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 200,626, entitled "Cross-component Sample Adaptive Offset," filed March 18, 2021, and U.S. Provisional Patent Application No. 63 / 164,459, entitled "Cross-component Sample Adaptive Offset," filed March 22, 2021, which are incorporated by reference in their entireties.

[0002] This application relates generally to video coding and compression, and more particularly to methods and apparatus for improving both luma and chroma coding efficiency. [Background technology]

[0003] Digital video is supported by a variety of electronic devices, including digital televisions, laptop or desktop computers, tablet computers, digital cameras, digital recording devices, digital media players, video gaming consoles, smartphones, video teleconferencing devices, and video streaming devices. Electronic devices transmit, receive, encode, decode, and / or store digital video data by implementing video compression / decompression standards. Some well-known video coding standards include Versatile Video Coding (VVC), High Efficiency Video Coding (HEVC) (also known as H.265 or MPEG-H Part 2), and Advanced Video Coding (AVC) (also known as H.264 or MPEG-4 Part 10), which were jointly developed by ISO / IEC MPEG and ITU-T VCEG. AOMedia Video 1 (AV1) was developed by the Alliance for Open Media (AOM) as the successor to the predecessor standard VP9. Audio Video Coding (AVS) refers to digital audio and video compression standards, another series of video compression standards developed by the Audio and Video Coding Standard Workgroup.

[0004] Video compression typically involves performing spatial (intra-frame) prediction and / or temporal (inter-frame) prediction to reduce or remove redundancy inherent in video data. In block-based video coding, a video frame is divided into one or more slices, each having multiple video blocks, sometimes referred to as coding tree units (CTUs). Each CTU may contain one coding unit (CU) or may be recursively divided into smaller CUs until a predefined minimum CU size is reached. Each CU (also referred to as a leaf CU) contains one or more transform units (TUs), and each CU also contains one or more prediction units (PUs). Each CU may be coded in intra, inter, or IBC mode. Video blocks in an intra-coded (I) slice of a video frame are coded using spatial prediction with respect to reference samples in neighboring blocks within the same video frame. Video blocks in an inter-coded (P or B) slice of a video frame may use spatial prediction with respect to reference samples in neighboring blocks within the same video frame or temporal prediction with respect to reference samples in other previous and / or future reference video frames.

[0005] Spatial or temporal prediction based on previously coded reference blocks, e.g., neighboring blocks, yields a predicted block for the current video block to be coded. The process of finding the reference block may be achieved by a block matching algorithm. Residual data representing pixel differences between the current block to be coded and the predicted block is called a residual block or prediction error. Inter-coded blocks are coded according to motion vectors that point to reference blocks and residual blocks in a reference frame that form the predicted block. The process of determining the motion vector is typically called motion estimation. Intra-coded blocks are coded according to an intra-prediction mode and a residual block. For further compression, the residual block is transformed from the pixel domain to a transform domain, e.g., the frequency domain, to yield residual transform coefficients, which may then be quantized. The quantized transform coefficients are initially arranged in a two-dimensional array and can be scanned to yield a one-dimensional vector of transform coefficients, which can then be entropy coded into a video bitstream to achieve further compression.

[0006] The encoded video bitstream is then stored in a computer-readable storage medium (e.g., flash memory) for access by another electronic device having digital video capabilities, or transmitted directly to the electronic device via wired or wireless connection. The electronic device then performs video decompression (which is the reverse process of video compression described above), for example, by parsing the encoded video bitstream to obtain syntax elements from the bitstream, reconstructing digital video data from the encoded video bitstream to its original form based at least in part on the syntax elements obtained from the bitstream, and rendering the reconstructed digital video data on a display of the electronic device. Summary of the Invention [Problem to be solved by the invention]

[0007] As the quality of digital video goes from high definition to 4Kx2K or even 8Kx4K, the amount of video data to be encoded / decoded increases exponentially. How the video data can be encoded / decoded more efficiently while maintaining the image quality of the decoded video data is a constant challenge. [Means for solving the problem]

[0008] This application describes implementation examples relating to the encoding and decoding of video data, and more particularly, to methods and apparatus for improving the coding efficiency of both luma and chroma components, including improving coding efficiency by exploring inter-component relationships between the luma and chroma components.

[0009] According to a first aspect of the present application, a method for decoding a video signal includes receiving, from the video signal, a picture frame including a first component and a second component in a first color space; determining a classifier for the second component in the first color space from one or more samples of a first set of the first component associated with each sample of the second component in the first color space, wherein the one or more samples of the first set are transformed to the second color space; determining sample offsets for each sample of the second component in the first color space according to the classifier; and modifying values ​​of each sample of the second component in the first color space based on the determined sample offsets.

[0010] In some embodiments, the first component is a component selected from the group consisting of a luma component, a first chroma component, and a second chroma component, and the second component is a component selected from the group consisting of a luma component, a first chroma component, and a second chroma component.

[0011] In some embodiments, one or more samples of the first set are transformed to the second color space by a linear transformation.

[0012] According to a second aspect of the present application, an electronic device includes one or more processing units, a memory, and a plurality of programs stored in the memory, the programs, when executed by the one or more processing units, causing the electronic device to perform the method for encoding a video signal described above.

[0013] According to a third aspect of the present application, a non-transitory computer-readable storage medium stores a plurality of programs for execution by an electronic device having one or more processing units, the programs, when executed by the one or more processing units, causing the electronic device to perform the method for encoding a video signal as described above.

[0014] According to a fourth aspect of the present application, a computer-readable storage medium stores a bitstream containing video information generated by the above-described video encoding method.

[0015] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure.

[0016] The accompanying drawings, which are included to provide a further understanding of implementations and are incorporated in and constitute a part of this specification, illustrate implementations described and, together with the description, serve to explain the underlying principles, with like reference numerals referring to corresponding parts. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a block diagram illustrating an example video encoding and decoding system according to some implementations of the present disclosure. [Figure 2] FIG. 1 is a block diagram illustrating an example video encoder according to some implementations of the present disclosure. [Figure 3] FIG. 2 is a block diagram illustrating an example video decoder according to some implementations of the present disclosure. [Figure 4A]A block diagram showing how a frame is recursively divided into multiple video blocks of different sizes and shapes according to some implementations of this disclosure. [Figure 4B] A block diagram showing how a frame is recursively divided into multiple video blocks of different sizes and shapes according to some implementations of this disclosure. [Figure 4C] A block diagram showing how a frame is recursively divided into multiple video blocks of different sizes and shapes according to some implementations of this disclosure. [Figure 4D] A block diagram showing how a frame is recursively divided into multiple video blocks of different sizes and shapes according to some implementations of this disclosure. [Figure 4E] A block diagram showing how a frame is recursively divided into multiple video blocks of different sizes and shapes according to some implementations of this disclosure. [Figure 5] FIG. 1 is a block diagram illustrating four gradient patterns used in sample adaptive offset (SAO) according to some implementations of the present disclosure. [Figure 6A] FIG. 1 is a block diagram illustrating a CCSAO system and process applied to chroma samples by some implementations of the present disclosure, using DBF Y as input. [Figure 6B] FIG. 1 is a block diagram illustrating a CCSAO system and process applied to luma samples and chroma samples by some implementations of the present disclosure, using DBF Y / Cb / Cr as input. [Figure 6C] FIG. 1 is a block diagram illustrating a CCSAO system and process that can function independently according to some implementations of the present disclosure. [Figure 6D] FIG. 1 is a block diagram illustrating a CCSAO system and process that may be applied recursively (2 or N times) with the same or different offsets by some implementations of the present disclosure. [Figure 6E]FIG. 1 is a block diagram illustrating a CCSAO system and process applied in parallel to Enhanced Sample Adaptive Offset (ESAO) in the AVS standard according to some implementations of the present disclosure. [Figure 6F] FIG. 1 is a block diagram illustrating a CCSAO system and process applied after SAO according to some implementations of the present disclosure. [Figure 6G] FIG. 10 is a block diagram illustrating that some implementations of the present disclosure allow the CCSAO system and process to function independently without a CCALF. [Figure 6H] FIG. 1 is a block diagram illustrating a CCSAO system and process applied in parallel to a cross-component adaptive loop filter (CCALF) according to some implementations of the present disclosure. [Figure 7] FIG. 10 is a block diagram illustrating a sample process using a CCSAO according to some implementations of the present disclosure. [Figure 8] FIG. 10 is a block diagram illustrating how the CCSAO process is interleaved with vertical and horizontal deblocking filters (DBFs) according to some implementations of the present disclosure. [Figure 9] 1 is a flow diagram illustrating an example process for decoding a video signal using inter-component correlation according to some implementations of the present disclosure. [Figure 10A] FIG. 10 is a block diagram illustrating a classifier that uses different luma (or chroma) sample positions for C0 classification according to some implementations of the present disclosure. [Figure 10B] 10A-10C are diagrams illustrating several examples of different shapes for luma candidates according to some implementations of the present disclosure. [Figure 11] FIG. 10 is a block diagram of a sample process illustrating that all co-located and adjacent luma / chroma samples may be provided to CCSAO classification according to some implementations of the present disclosure. [Figure 12] FIG. 10 illustrates an example classifier by replacing a co-located luma sample value with a value obtained by weighting the co-located and neighboring luma samples, according to some implementations of the present disclosure. [Figure 13A] A block diagram showing that, according to some implementation examples of the present disclosure, CCSAO is not applied to the current chroma (luma) sample if any of the co-located and neighboring luma (chroma) samples used for classification are outside the current picture. [Figure 13B] FIG. 10 is a block diagram illustrating that, according to some implementations of the present disclosure, CCSAO is applied to a current luma or chroma sample when any of the co-located and neighboring luma or chroma samples used for classification are outside the current picture. [Figure 14] A block diagram showing that, according to some implementation examples of the present disclosure, CCSAO is not applied to the current chroma sample if the corresponding selected co-located or adjacent luma sample used for classification is outside the virtual space defined by the virtual boundary (VB). [Figure 15] 10A and 10B illustrate how repetition or mirror padding is applied to luma samples that fall outside the virtual boundary, according to some implementations of the present disclosure. [Figure 16] FIG. 10 illustrates that, according to some implementations of the present disclosure, an additional 1 luma line buffer is required when all 9 co-located and adjacent luma samples are used for classification. [Figure 17] FIG. 10 illustrates that in some implementations of the present disclosure, in AVS, the nine luma candidate CCSAOs intersecting the VB can be increased by two additional luma line buffers. [Figure 18A] FIG. 10 illustrates that in VVC, nine luma candidate CCSAOs intersecting a VB can be increased by one additional luma line buffer according to some implementation examples of the present disclosure. [Figure 18B] FIG. 10 illustrates that, according to some implementation examples of the present disclosure, when co-located or adjacent chroma samples are used to classify the current luma sample, the selected chroma candidate may cross the VB and require an additional chroma line buffer. [Figure 19A]A diagram showing that in some implementation examples of the present disclosure, in AVS and VVC, CCSAO is disabled for a chroma sample if any of the luma candidates for the chroma sample crosses VB (is outside the current chroma sample VB). [Figure 19B] A diagram showing that in some implementation examples of the present disclosure, in AVS and VVC, CCSAO is disabled for a chroma sample if any of the luma candidates for the chroma sample crosses VB (is outside the current chroma sample VB). [Figure 19C] A diagram showing that in some implementation examples of the present disclosure, in AVS and VVC, CCSAO is disabled for a chroma sample if any of the luma candidates for the chroma sample crosses VB (is outside the current chroma sample VB). [Figure 20A] A diagram showing that, in some implementation examples of the present disclosure, in AVS and VVC, CCSAO is enabled using repeated padding on chroma samples when any of the luma candidates for the chroma samples crosses the VB (is outside the current chroma sample VB). [Figure 20B] A diagram showing that, in some implementation examples of the present disclosure, in AVS and VVC, CCSAO is enabled using repeated padding on chroma samples when any of the luma candidates for the chroma samples crosses the VB (is outside the current chroma sample VB). [Figure 20C] A diagram showing that, in some implementation examples of the present disclosure, in AVS and VVC, CCSAO is enabled using repeated padding on chroma samples when any of the luma candidates for the chroma samples crosses the VB (is outside the current chroma sample VB). [Figure 21A] A diagram showing that, in some implementation examples of the present disclosure, in AVS and VVC, CCSAO is enabled using mirror padding on chroma samples when any of the luma candidates for the chroma sample crosses the VB (is outside the current chroma sample VB). [Figure 21B] A diagram showing that, in some implementation examples of the present disclosure, in AVS and VVC, CCSAO is enabled using mirror padding on chroma samples when any of the luma candidates for the chroma sample crosses the VB (is outside the current chroma sample VB). [Figure 21C] A diagram showing that, in some implementation examples of the present disclosure, in AVS and VVC, CCSAO is enabled using mirror padding on chroma samples when any of the luma candidates for the chroma sample crosses the VB (is outside the current chroma sample VB). [Figure 22A] FIG. 10 illustrates how CCSAO is enabled using two-sided symmetric padding for different CCSAO sample shapes according to some implementations of the present disclosure. [Figure 22B] FIG. 10 illustrates how CCSAO is enabled using two-sided symmetric padding for different CCSAO sample shapes according to some implementations of the present disclosure. [Figure 23] FIG. 10 illustrates a limitation of using a limited number of luma candidates for classification according to some implementations of the present disclosure. [Figure 24] A diagram showing that the CCSAO application region is not aligned to the coding tree block (CTB) / coding tree unit (CTU) boundary according to some implementation examples of the present disclosure. [Figure 25] A diagram showing that CCSAO application area frame partitioning can be fixed by CCSAO parameters according to some implementation examples of the present disclosure. [Figure 26] A diagram showing that, according to some implementation examples of the present disclosure, the CCSAO application area may be a binary tree (BT) / quadtree (QT) / ternary tree (TT) split from the frame / slice / CTB level. [Figure 27] FIG. 1 is a block diagram illustrating multiple classifiers used and switched at different levels within a picture frame according to some implementations of the present disclosure. [Figure 28]A block diagram showing that CCSAO application region partitioning is dynamic and can be switched at the picture level according to some implementations of the present disclosure. [Figure 29] FIG. 10 illustrates that some implementations of the present disclosure allow the CCSAO classifier to consider current or inter-component coding information. [Figure 30] FIG. 10 is a block diagram illustrating the SAO classification method disclosed in this disclosure acting as a post-prediction filter, according to some implementations of the present disclosure. [Figure 31] FIG. 10 is a block diagram illustrating that for a post-prediction SAO filter, each component can use the current sample and neighboring samples for classification, according to some implementations of the present disclosure. [Figure 32] 1 is a flow diagram illustrating an example process for decoding a video signal using inter-component correlation according to some implementations of the present disclosure. [Figure 33] FIG. 1 illustrates a computing environment coupled to a user interface according to some implementations of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] Reference will now be made in detail to specific implementations, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous non-limiting specific details are set forth to aid in understanding the subject matter presented herein. However, it will be apparent to those skilled in the art that various alternatives may be used without departing from the scope of the claims, and that the subject matter may be practiced without these specific details. For example, it will be apparent to those skilled in the art that the subject matter presented herein may be implemented in many types of electronic devices having digital video capabilities.

[0019] The first generation of AVS standards includes the Republic of China national standard "Information Technology, Advanced Audio Video Coding, Part 2: Video" (known as AVS1) and "Information Technology, Advanced Audio Video Coding Part 16: Radio Television Video" (known as AVS+). Compared with the MPEG-2 standard, this can provide approximately 50% bit rate savings with the same perceptual quality. The second generation of AVS standards includes a series of Republic of China national standards "Information Technology, Efficient Multimedia Coding" (known as AVS2), which primarily targets the transmission of additional HD TV programs. The coding efficiency of AVS2 is twice that of AVS+. Meanwhile, the video part of the AVS2 standard has been submitted by the Institute of Electrical and Electronics Engineers (IEEE) as an international standard for application. The AVS3 standard is a new generation video coding standard for UHD video that aims to surpass the coding efficiency of the latest international standard, HEVC, and provides approximately 30% bitrate savings compared to the HEVC standard. The AVS3-P2 baseline was completed at the 68th AVS Conference in March 2019, providing approximately 30% bitrate savings compared to the HEVC standard. Currently, a single reference software called the High Performance Model (HPM) is maintained by the AVS group to demonstrate a reference implementation of the AVS3 standard. Like HEVC, the AVS3 standard is built on a block-based hybrid video coding framework.

[0020] 1 is a block diagram illustrating an example system 10 for encoding and decoding video blocks in parallel according to some implementations of the present disclosure. As shown in FIG. 1, system 10 includes a source device 12, which generates and encodes video data for subsequent decoding by a destination device 14. Source device 12 and destination device 14 may comprise any of a wide variety of electronic devices, including desktop or laptop computers, tablet computers, smartphones, set-top boxes, digital televisions, cameras, display devices, digital media players, video gaming consoles, video streaming devices, etc. In some implementations, source device 12 and destination device 14 are equipped with wireless communication capabilities.

[0021] In some implementations, destination device 14 may receive encoded video data to be decoded via link 16. Link 16 may comprise any type of communication medium or device capable of moving encoded video data from source device 12 to destination device 14. In one example, link 16 may comprise a communication medium to enable source device 12 to transmit encoded video data directly to destination device 14 in real time. The encoded video data may be modulated according to a communication standard, such as a wireless communication protocol, and transmitted to destination device 14. The communication medium may include any wireless or wired communication medium, such as the radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network, such as a local area network, a wide area network, or a global network, e.g., the Internet. The communication medium may include routers, switches, base stations, or any other equipment that may be useful in facilitating communication from source device 12 to destination device 14.

[0022] In some other implementations, the encoded video data may be transmitted from output interface 22 to storage device 32. The encoded video data in storage device 32 may then be accessed by destination device 14 via input interface 28. Storage device 32 may include any of a variety of distributed or locally accessible data storage media, such as a hard drive, Blu-ray disc, DVD, CD-ROM, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data. In a further example, storage device 32 may correspond to a file server or another intermediate storage device capable of holding encoded video data generated by source device 12. Destination device 14 may access the stored video data via streaming or download from storage device 32. The file server may be any type of computer capable of storing encoded video data and transmitting the encoded video data to destination device 14. Exemplary file servers include a web server (e.g., for websites), an FTP server, a network-attached storage (NAS) device, or a local disk drive. Destination device 14 may access the encoded video data over any standard data connection suitable for accessing encoded video data stored on a file server, including a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., DSL, cable modem, etc.), or a combination of both. Transmission of the encoded video data from storage device 32 may be a streaming transmission, a download transmission, or a combination of both.

[0023] 1 , source device 12 includes video source 18, video encoder 20, and output interface 22. Video source 18 may include sources such as a video capture device, e.g., a video camera, a video archive containing previously captured video, a video feed interface for receiving video from a video content provider, and / or a computer graphics system for generating computer graphics data as source video, or a combination of such sources. As an example, if video source 18 is a video camera for a security surveillance system, source device 12 and destination device 14 may form a camera phone or video phone. However, implementations described herein may apply to video coding in general and may be applied to wireless and / or wired applications.

[0024] The captured, pre-captured, or computer-generated video may be encoded by video encoder 20. The encoded video data may be transmitted directly to destination device 14 via output interface 22 of source device 12. The encoded video data may also (or alternatively) be stored on storage device 32 for later access by destination device 14 or other devices for decoding and / or playback. Output interface 22 may further include a modem and / or a transmitter.

[0025] Destination device 14 includes an input interface 28, a video decoder 30, and a display device 34. Input interface 28 may include a receiver and / or a modem and may receive encoded video data over link 16. The encoded video data communicated over link 16 or provided on storage device 32 may include various syntax elements generated by video encoder 20 for use by video decoder 30 in decoding the video data. Such syntax elements may be included within the encoded video data transmitted over a communication medium, stored on a storage medium, or stored on a file server.

[0026] In some implementations, destination device 14 may include a display device 34, which may be an integrated display device or an external display device configured to communicate with destination device 14. Display device 34 displays the decoded video data to a user and may comprise any of a variety of display devices, such as a liquid crystal display (LCD), a plasma display, an organic light-emitting diode (OLED) display, or another type of display device.

[0027] Video encoder 20 and video decoder 30 may operate in accordance with proprietary or industry standards, such as VVC, HEVC, MPEG-4, Part 10, Advanced Video Coding (AVC), AVS, or extensions of such standards. It should be understood that the present application is not limited to any particular video coding / decoding standard and may apply to other video coding / decoding standards. It is generally contemplated that video encoder 20 of source device 12 may be configured to encode video data in accordance with any of these current or future standards. Similarly, it is generally contemplated that video decoder 30 of destination device 14 may be configured to decode video data in accordance with any of these current or future standards.

[0028] Video encoder 20 and video decoder 30 may each be implemented as any of a variety of suitable encoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When implemented partially in software, an electronic device can store instructions for the software on a suitable non-transitory computer-readable medium and execute these instructions in hardware using one or more processors to perform the video coding / decoding operations disclosed in this disclosure. Video encoder 20 and video decoder 30 may each be included in one or more encoders or decoders, any of which may be integrated as part of a combined encoder / decoder (CODEC) in the respective device.

[0029] 2 is a block diagram illustrating an example video encoder 20 according to some implementations described herein. Video encoder 20 can perform intra- and inter-predictive coding of video blocks within a video frame. Intra-predictive coding relies on spatial prediction to reduce or remove spatial redundancy in video data within a given video frame or picture. Inter-predictive coding relies on temporal prediction to reduce or remove temporal redundancy in video data within adjacent video frames or pictures of a video sequence.

[0030] As shown in FIG. 2, video encoder 20 includes video data memory 40, prediction processing unit 41, decoded picture buffer (DPB) 64, adder 50, transform processing unit 52, quantization unit 54, and entropy coding unit 56. Prediction processing unit 41 further includes motion estimation unit 42, motion compensation unit 44, partitioning unit 45, intra-prediction processing unit 46, and intra-block copy (BC) unit 48. In some implementations, video encoder 20 also includes inverse quantization unit 58 for video block reconstruction, inverse transform processing unit 60, and adder 62. An in-loop filter 63, such as a deblocking filter, may be placed between adder 62 and DPB 64 to filter block boundaries and remove block artifacts from the reconstructed video. In addition to the deblocking filter, another in-loop filter 63 may also be used to filter the output of adder 62. Further in-loop filters 63, such as sample adaptive offset (SAO) and adaptive in-loop filter (ALF), may be applied on the reconstructed CU before being placed in a reference picture store and used as a reference for encoding future video blocks. Video encoder 20 may take the form of a fixed or programmable hardware unit, or may be divided among one or more of the fixed or programmable hardware units shown.

[0031] Video data memory 40 may store video data to be encoded by components of video encoder 20. The video data in video data memory 40 may be obtained, for example, from video source 18. DPB 64 is a buffer that stores reference video data for use by video encoder 20 in encoding the video data (e.g., in intra- or inter-predictive coding modes). Video data memory 40 and DPB 64 may be formed by any of a variety of memory devices. In various examples, video data memory 40 may be on-chip with or off-chip relative to other components of video encoder 20.

[0032] As shown in FIG. 2, after receiving video data, partition unit 45 within prediction processing unit 41 partitions the video data into video blocks. This partitioning may also include dividing the video frame into slices, tiles, or other larger coding units (CUs) according to a predefined partitioning structure, such as a quadtree structure, associated with the video data. The video frame may be partitioned into multiple video blocks (or sets of video blocks called tiles). Prediction processing unit 41 may select one of multiple possible predictive coding modes, such as one of multiple intra-predictive coding modes or one of multiple inter-predictive coding modes, for the current video block based on error results (e.g., coding rate and distortion level). Prediction processing unit 41 may provide the resulting intra- or inter-predictive coded block to summer 50 to generate a residual block, or to summer 62 to reconstruct a coded block for later use as part of a reference frame. Prediction processing unit 41 also provides syntax elements, such as motion vectors, intra-mode indicators, partition information, and other such syntax information, to entropy coding unit 56.

[0033] To select an appropriate intra-predictive coding mode for the current video block, intra-prediction processing unit 46 within prediction processing unit 41 may perform intra-predictive coding of the current video block relative to one or more neighboring blocks in the same frame as the current block to be coded to provide spatial prediction. Motion estimation unit 42 and motion compensation unit 44 within prediction processing unit 41 perform inter-predictive coding of the current video block relative to one or more predictive blocks in one or more reference frames to provide temporal prediction. Video encoder 20 may perform multiple coding passes, e.g., to select an appropriate coding mode for each block of video data.

[0034] In some implementations, motion estimation unit 42 determines the inter-prediction mode for a current video frame by generating a motion vector indicating the displacement of a prediction unit (PU) of a video block in the current video frame relative to a predictive block in a reference video frame according to a predetermined pattern in a sequence of video frames. Motion estimation performed by motion estimation unit 42 is the process of generating motion vectors to estimate motion for video blocks. The motion vector may indicate, for example, the displacement of a PU of a video block in the current video frame or picture relative to a predictive block (or other coding unit) in a reference frame relative to the current block (or other coding unit) being coded in the current frame. The predetermined pattern may designate a video frame in the sequence as a P frame or a B frame. Similar to the determination of motion vectors by motion estimation unit 42 for inter prediction, intra BC unit 48 may determine a vector, e.g., a block vector, for intra BC coding, or may utilize motion estimation unit 42 to determine the block vector.

[0035] The predictive block is a block of the reference frame that is deemed to closely match the PU of the video block to be encoded in terms of pixel difference, which may be determined by sum of absolute differences (SAD), sum of squared differences (SSD), or other difference metric. In some implementations, video encoder 20 may calculate values ​​for sub-integer pixel locations of the reference frame stored in DPB 64. For example, video encoder 20 may interpolate values ​​for quarter-pixel locations, eighth-pixel locations, or other fractional pixel locations of the reference frame. Thus, motion estimation unit 42 may perform motion search for full pixel locations and fractional pixel locations and output motion vectors with fractional pixel accuracy.

[0036] Motion estimation unit 42 calculates a motion vector for a PU of a video block in an inter-predictively coded frame by comparing the position of the PU with the position of a predictive block of a reference frame selected from a first reference frame list (List0) or a second reference frame list (List1), each of which identifies one or more reference frames stored in DPB 64. Motion estimation unit 42 sends the calculated motion vector to motion compensation unit 44 and then to entropy coding unit 56.

[0037] Motion compensation performed by motion compensation unit 44 may involve fetching or generating a predictive block based on the motion vector determined by motion estimation unit 42. Upon receiving the motion vector for the PU of the current video block, motion compensation unit 44 may locate the predictive block to which the motion vector points in one of the reference frame lists, retrieve this predictive block from DPB 64, and forward this predictive block to adder 50. Adder 50 then forms a residual video block of pixel difference values ​​by subtracting pixel values ​​of the predictive block provided by motion compensation unit 44 from pixel values ​​of the current video block being coded. The pixel difference values ​​forming the residual video block may include luma or chroma difference components, or both. Motion compensation unit 44 may also generate syntax elements associated with the video blocks of the video frame for use by video decoder 30 in decoding the video blocks of the video frame. The syntax elements may include, for example, syntax elements defining the motion vector used to identify the predictive block, any flags indicating a prediction mode, or any other syntax information described herein. It should be noted that motion estimation unit 42 and motion compensation unit 44 may be highly integrated, but are shown separately for conceptual purposes.

[0038] In some implementations, the intra BC unit 48 can generate a vector and fetch a predictive block, similar to that described above with reference to the motion estimation unit 42 and the motion compensation unit 44, except that the predictive block is within the same frame as the current block being coded, and the vector is referred to as a block vector rather than a motion vector. In particular, the intra BC unit 48 can determine an intra prediction mode to use to code the current block. In some examples, the intra BC unit 48 can code the current block using various intra prediction modes, e.g., during separate coding passes, and test their performance through rate-distortion analysis. The intra BC unit 48 can then select a suitable intra prediction mode from among the various tested intra prediction modes and use and generate an intra mode indicator accordingly. For example, the intra BC unit 48 can calculate rate-distortion values ​​for the various tested intra prediction modes using rate-distortion analysis, and select and use the intra prediction mode with the best rate-distortion characteristics from among the tested modes as the suitable intra prediction mode. Rate-distortion analysis generally determines the amount of distortion (or error) between a coded block and the original uncoded block that was coded to result in the coded block, as well as the bit rate (i.e., number of bits) used to result in the coded block. Intra BC unit 48 can calculate ratios from the distortion and rate for various coded blocks to determine which intra-prediction mode exhibits the best rate-distortion value for that block.

[0039] In other examples, intra BC unit 48 may perform such functions for intra BC prediction, in whole or in part, using motion estimation unit 42 and motion compensation unit 44, depending on the implementation described herein. In either case, for intra block copying, the predictive block may be a block deemed to closely match the block to be coded in terms of pixel differences, which may be determined by sum of absolute differences (SAD), sum of squared differences (SSD), or other difference metric, and identification of the predictive block may include calculation of values ​​for sub-integer pixel locations.

[0040] Regardless of whether the predictive block is from the same frame according to intra prediction or from a different frame according to inter prediction, video encoder 20 may form a residual video block by subtracting pixel values ​​of the predictive block from pixel values ​​of the current video block being coded to form pixel difference values. The pixel difference values ​​that form the residual video block may include both luma and chroma component differences.

[0041] The intra-prediction processing unit 46 may intra-predict the current video block as an alternative to the inter-prediction performed by the motion estimation unit 42 and the motion compensation unit 44 or the intra-block copy prediction performed by the intra BC unit 48, as described above. In particular, the intra-prediction processing unit 46 may determine an intra-prediction mode to use to encode the current block. In doing so, the intra-prediction processing unit 46 may encode the current block using various intra-prediction modes, e.g., during separate encoding passes, and the intra-prediction processing unit 46 (or, in some examples, a mode selection unit) may select and use an appropriate intra-prediction mode from the tested intra-prediction modes. The intra-prediction processing unit 46 may provide information indicating the selected intra-prediction mode for the block to the entropy coding unit 56. The entropy coding unit 56 may encode the information indicating the selected intra-prediction mode in the bitstream.

[0042] After prediction processing unit 41 determines a predictive block for a current video block via inter- or intra-prediction, adder 50 forms a residual video block by subtracting the predictive block from the current video block. The residual video data in the residual block may be included in one or more transform units (TUs) and provided to transform processing unit 52. Transform processing unit 52 converts the residual video data into residual transform coefficients using a transform, such as a discrete cosine transform (DCT) or a conceptually similar transform.

[0043] Transform processing unit 52 may send the resulting transform coefficients to quantization unit 54. Quantization unit 54 quantizes the transform coefficients to further reduce the bit rate. The quantization process may also reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be modified by adjusting a quantization parameter. In some examples, quantization unit 54 may then perform a scan of a matrix containing the quantized transform coefficients. Alternatively, entropy coding unit 56 may perform the scan.

[0044] Following quantization, entropy coding unit 56 entropy codes the quantized transform coefficients into a video bitstream, using, for example, context-adaptive variable length coding (CAVLC), context-adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, or another entropy coding method or technique. The coded bitstream may then be transmitted to video decoder 30 or stored in storage device 32 for later transmission to or retrieval by video decoder 30. Entropy coding unit 56 may also entropy code motion vectors and other syntax elements for the current video frame being coded.

[0045] Inverse quantization unit 58 and inverse transform processing unit 60 apply inverse quantization and inverse transform, respectively, to reconstruct the residual video block in the pixel domain and generate reference blocks for prediction of other video blocks. As described above, motion compensation unit 44 may generate motion-compensated prediction blocks from one or more reference blocks of a frame stored in DPB 64. Motion compensation unit 44 may also apply one or more interpolation filters to the prediction block to calculate sub-integer pixel values ​​for use in motion estimation.

[0046] Adder 62 adds the reconstructed residual block to the motion compensated prediction block provided by motion compensation unit 44 to provide a reference block for storage in DPB 64. The reference block may then be used by intra BC unit 48, motion estimation unit 42, and motion compensation unit 44 as a prediction block for inter predicting another video block in a subsequent video frame.

[0047] 3 is a block diagram illustrating an example video decoder 30 according to some implementations of the present application. The video decoder 30 includes a video data memory 79, an entropy decoding unit 80, a prediction processing unit 81, an inverse quantization unit 86, an inverse transform processing unit 88, an adder 90, and a DPB 92. The prediction processing unit 81 further includes a motion compensation unit 82, an intra-prediction processing unit 84, and an intra-BC unit 85. The video decoder 30 may perform a decoding process that is generally reverse to the encoding process described above for the video encoder 20 in connection with FIG. 2. For example, the motion compensation unit 82 may generate prediction data based on a motion vector received from the entropy decoding unit 80, and the intra-prediction unit 84 may generate prediction data based on an intra-prediction mode indicator received from the entropy decoding unit 80.

[0048] In some examples, units of video decoder 30 may be tasked with performing implementations of the present application. Also, in some examples, implementations of the present disclosure may be divided among one or more of the units of video decoder 30. For example, intra BC unit 85 may perform implementations of the present application alone or in combination with other units of video decoder 30, such as motion compensation unit 82, intra prediction processing unit 84, and entropy decoding unit 80. In some examples, video decoder 30 may not include intra BC unit 85, and the functions of intra BC unit 85 may be performed by other components of prediction processing unit 81, such as motion compensation unit 82.

[0049] Video data memory 79 may store video data, such as an encoded video bitstream, to be decoded by other components of video decoder 30. The video data stored in video data memory 79 may be obtained, for example, from storage device 32, from a local video source such as a camera, via wired or wireless network communication of the video data, or by accessing a physical data storage medium (e.g., a flash drive or hard disk). Video data memory 79 may include a coded picture buffer (CPB) that stores coded video data from the coded video bitstream. A decoded picture buffer (DPB) 92 of video decoder 30 stores reference video data for use by video decoder 30 in decoding video data (e.g., in intra- or inter-predictive coding modes). Video data memory 79 and DPB 92 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. For illustrative purposes, video data memory 79 and DPB 92 are depicted in Figure 3 as two separate components of video decoder 30. However, it will be apparent to those skilled in the art that video data memory 79 and DPB 92 may be provided by the same memory device or by separate memory devices. In some examples, video data memory 79 may be on-chip with other components of video decoder 30 or off-chip with respect to those components.

[0050] During the decoding process, video decoder 30 receives an encoded video bitstream representing video blocks and associated syntax elements of encoded video frames. Video decoder 30 may receive the syntax elements at the video frame level and / or the video block level. Entropy decoding unit 80 of video decoder 30 entropy decodes the bitstream to generate quantized coefficients, motion vectors, or intra-prediction mode indicators, and other syntax elements. Entropy decoding unit 80 then forwards the motion vectors and other syntax elements to prediction processing unit 81.

[0051] When a video frame is coded as an intra-predictively coded (I) frame, or coded for intra-coded predictive blocks within other types of frames, intra-prediction processing unit 84 of prediction processing unit 81 can generate predictive data for video blocks of the current video frame based on the signaled intra-prediction mode and reference data from previously decoded blocks of the current frame.

[0052] When a video frame is coded as an inter-predictive (i.e., B or P) frame, motion compensation unit 82 of prediction processing unit 81 produces one or more prediction blocks for a video block of the current video frame based on the motion vectors and other syntax elements received from entropy decoding unit 80. Each of the prediction blocks may be produced from one reference frame in the reference frame lists. Video decoder 30 may construct reference frame lists List0 and List1 using a default construction technique based on the reference frames stored in DPB 92.

[0053] In some examples, when a video block is encoded according to the intra BC mode described herein, intra BC unit 85 of prediction processing unit 81 produces a predictive block for the current video block based on the block vectors and other syntax elements received from entropy decoding unit 80. The predictive block may be located within the same reconstructed region of the picture as the current video block as defined by video encoder 20.

[0054] Motion compensation unit 82 and / or intra BC unit 85 determine prediction information for video blocks of the current video frame by analyzing the motion vectors and other syntax elements, and then use the prediction information to produce a predictive block for the current video block being decoded. For example, motion compensation unit 82 uses some of the received syntax elements to determine the prediction mode (e.g., intra- or inter-prediction) used to encode the video blocks of the video frame, the inter-prediction frame type (e.g., B or P), construction information for one or more of the frame's reference frame lists, the motion vector for each inter-predictively coded video block of the frame, the inter-prediction state for each inter-predictively coded video block of the frame, and other information for decoding video blocks in the current video frame.

[0055] Similarly, intra BC unit 85 may use some of the received syntax elements, such as flags, to determine that the current video block was predicted using intra BC mode, construction information for the video blocks of the frame that are located within the reconstructed region and that should be stored in DPB 92, block vectors for each intra BC predicted video block of the frame, intra BC prediction states for each intra BC predicted video block of the frame, and other information for decoding video blocks in the current video frame.

[0056] Motion compensation unit 82 may also perform the interpolation using interpolation filters used by video encoder 20 during encoding of the video block to calculate interpolated values ​​for sub-integer pixels of the reference block. In this case, motion compensation unit 82 may determine the interpolation filters used by video encoder 20 from the received syntax elements and may use those interpolation filters to result in the predictive block.

[0057] Inverse quantization unit 86 inverse quantizes the quantized transform coefficients entropy decoded by entropy decoding unit 80 provided in the bitstream, using the same quantization parameters calculated by video encoder 20 for each video block in the video frame to determine the degree of quantization. Inverse transform processing unit 88 applies an inverse transform, e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process, to the transform coefficients to reconstruct residual blocks in the pixel domain.

[0058] After motion compensation unit 82 or intra BC unit 85 generates a predictive block for the current video block based on the vectors and other syntax elements, adder 90 reconstructs a decoded video block for the current video block by adding a residual block from inverse transform processing unit 88 and the corresponding predictive block generated by motion compensation unit 82 and intra BC unit 85. To further process the decoded video block, an in-loop filter 91 may be interposed between adder 90 and DPB 92. An in-loop filter 91, such as a deblocking filter, sample adaptive offset (SAO), and adaptive in-loop filter (ALF), may be applied on the reconstructed CU before being placed in the reference picture store. The decoded video blocks in a given frame are then stored in DPB 92, which stores reference frames used for motion compensation after the next video block. DPB 92, or a memory device separate from DPB 92, may also store decoded video for later presentation on a display device, such as display device 34 of FIG. 1.

[0059] In a typical video coding process, a video sequence typically includes an ordered set of frames or pictures. Each frame can include three sample arrays, denoted SL, SCb, and SCr. SL is a two-dimensional array of luma samples. SCb is a two-dimensional array of Cb chroma samples. SCr is a two-dimensional array of Cr chroma samples. In other cases, a frame may be monochromatic and therefore include only one two-dimensional array of luma samples.

[0060] Like HEVC, the AVS3 standard is built on a block-based hybrid video coding framework. The input video signal is processed in blocks (called coding units (CUs)). Unlike HEVC, which divides blocks solely based on quadtrees, AVS3 divides a single coding tree unit (CTU) into CUs based on quadtrees, binary trees, and extended quadtrees to adapt to varying local characteristics. In addition, the concept of multiple partitioning unit types in HEVC has been eliminated; that is, AVS3 does not separate CUs, prediction units (PUs), and transform units (TUs). Instead, each CU is always used as the basic unit for both prediction and transformation without further partitioning. In the AVS3 tree partitioning structure, a CTU is first partitioned based on a quadtree structure. Then, each quadtree leaf node can be further partitioned based on binary trees and extended quadtree structures.

[0061] As shown in FIG. 4A, video encoder 20 (or more specifically, partitioning unit 45) generates a coded representation of a frame by first dividing the frame into a set of coding tree units (CTUs). A video frame may contain an integer number of CTUs, sequentially ordered from left to right and top to bottom in raster scan order. Each CTU is the largest logical coding unit, and the width and height of the CTU are signaled by video encoder 20 in a sequence parameter set. All CTUs in a video sequence have the same size, which may be one of 128x128, 64x64, 32x32, or 16x16. However, it should be noted that the present application is not necessarily limited to a particular size. As shown in FIG. 4B, each CTU may comprise one coding tree block (CTB) for luma samples, two corresponding coding tree blocks for chroma samples, and syntax elements used to encode the samples in these coding tree blocks. The syntax elements describe the characteristics of different types of coding blocks of pixels and how a video sequence may be reconstructed at video decoder 30, including inter or intra prediction, intra prediction mode, motion vectors, and other parameters. For a monochrome picture or a picture with three distinct color planes, a CTU may comprise a single coding tree block and the syntax elements used to encode the samples of this coding tree block. A coding tree block may be an NxN block of samples.

[0062] To achieve better performance, video encoder 20 can recursively perform tree partitioning, such as binary tree partitioning, ternary tree partitioning, quad tree partitioning, or a combination thereof, on the coding tree blocks of a CTU to partition the CTU into smaller coding units (CUs). As illustrated in FIG. 4C, a 64×64 CTU 400 is first partitioned into four smaller CUs, each with a block size of 32×32. Among the four smaller CUs, CU 410 and CU 420 are each partitioned into four CUs with a block size of 16×16. Two 16×16 CUs, 430 and 440, are each further partitioned into four CUs with a block size of 8×8. FIG. 4D illustrates a quad tree data structure representing the end result of the partitioning process for CTU 400 illustrated in FIG. 4C, where each leaf node of the quad tree corresponds to one CU with a respective size ranging from 32×32 to 8×8. Similar to the CTU depicted in FIG. 4B, each CU may comprise a coding block (CB) of luma samples, two corresponding coding blocks of chroma samples for the same-sized frame, and syntax elements used to encode the samples of these coding blocks. In a monochrome picture or a picture with three distinct color planes, a CU may comprise a single coding block and syntax structures used to encode the samples of this coding block. Note that the quadtree partitioning depicted in FIGS. 4C and 4D is for illustrative purposes only, and a CTU may be partitioned into multiple CUs to adapt to varying local characteristics based on quadtree / ternary / binary tree partitioning. In multiple types of tree structures, a CTU is partitioned by a quadtree structure, and each quadtree leaf CU may be further partitioned by binary and ternary tree structures. As shown in FIG. 4E, AVS3 has five partitioning / partitioning types: quadtree, horizontal bisection, vertical bisection, horizontally extended quadtree partitioning, and vertically extended quadtree partitioning.

[0063] In some implementations, video encoder 20 may further divide the coding blocks of a CU into one or more M×N predictive blocks (PBs). A predictive block is a rectangular (square or non-square) block of samples to which the same inter or intra prediction is applied. A prediction unit (PU) of a CU may comprise a predictive block of luma samples, two corresponding predictive blocks of chroma samples, and syntax elements used to predict these predictive blocks. In a monochromatic picture or a picture with three separate color planes, a PU may comprise a single predictive block and syntax structures used to predict this predictive block. Video encoder 20 may generate predictive luma, Cb, and Cr blocks for the luma, Cb, and Cr predictive blocks of each PU of a CU.

[0064] Video encoder 20 may generate predictive blocks for a PU using intra prediction or inter prediction. If video encoder 20 uses intra prediction to generate predictive blocks for a PU, video encoder 20 may generate predictive blocks for the PU based on decoded samples of a frame associated with the PU. If video encoder 20 uses inter prediction to generate predictive blocks for the PU, video encoder 20 may generate predictive blocks for the PU based on decoded samples of one or more frames other than the frame associated with the PU.

[0065] After video encoder 20 generates predictive luma, Cb, and Cr blocks for one or more PUs of a CU, video encoder 20 may generate a luma residual block for the CU by subtracting the predictive luma block of the CU from its original luma coding block, where each sample in the luma residual block of the CU indicates a difference between a luma sample in one of the predictive luma blocks of the CU and a corresponding sample in the original luma coding block of the CU. Similarly, video encoder 20 may generate a Cb residual block and a Cr residual block for each CU, where each sample in the Cb residual block of the CU indicates a difference between a Cb sample in one of the predictive Cb blocks of the CU and a corresponding sample in the original Cb coding block of the CU, and each sample in the Cr residual block of the CU indicates a difference between a Cr sample in one of the predictive Cr blocks of the CU and a corresponding sample in the original Cr coding block of the CU.

[0066] Further, as shown in FIG. 4C , video encoder 20 may use quadtree partitioning to decompose the luma, Cb, and Cr residual blocks of a CU into one or more luma, Cb, and Cr transform blocks. A transform block is a rectangular (square or non-square) block of samples to which the same transform is applied. A transform unit (TU) of a CU may comprise a transform block of luma samples, two corresponding transform blocks of chroma samples, and syntax elements used to transform the transform block samples. Thus, each TU of a CU may be associated with a luma transform block, a Cb transform block, and a Cr transform block. In some examples, the luma transform block associated with a TU may be a sub-block of the luma residual block of the CU. The Cb transform block may be a sub-block of the Cb residual block of the CU. The Cr transform block may be a sub-block of the Cr residual block of the CU. In a monochrome picture or a picture with three separate color planes, a TU may comprise a single transform block and syntax structures used to transform the samples of the transform block.

[0067] Video encoder 20 may apply one or more transforms to a luma transform block of a TU to generate a luma coefficient block for the TU. The coefficient block may be a two-dimensional array of transform coefficients. The transform coefficients may be scalar quantities. Video encoder 20 may apply one or more transforms to a Cb transform block of a TU to generate a Cb coefficient block for the TU. Video encoder 20 may apply one or more transforms to a Cr transform block of the TU to generate a Cr coefficient block for the TU.

[0068] After generating a coefficient block (e.g., a luma coefficient block, a Cb coefficient block, or a Cr coefficient block), the video encoder 20 may quantize the coefficient block. Quantization generally refers to a process by which transform coefficients are quantized, possibly to reduce the amount of data used to represent the transform coefficients and provide further compression. After the video encoder 20 quantizes the coefficient block, the video encoder 20 may entropy encode syntax elements indicating the quantized transform coefficients. For example, the video encoder 20 may perform context-adaptive binary arithmetic coding (CABAC) on the syntax elements indicating the quantized transform coefficients. Finally, the video encoder 20 may output a bitstream including a sequence of bits and associated data that form a representation of the encoded frame, which may be stored in storage device 32 or transmitted to destination device 14.

[0069] After receiving the bitstream generated by video encoder 20, video decoder 30 can parse the bitstream to obtain syntax elements from the bitstream. Video decoder 30 can reconstruct frames of video data based at least in part on the syntax elements obtained from the bitstream. The process of reconstructing video data is generally reverse to the encoding process performed by video encoder 20. For example, video decoder 30 can perform an inverse transform on coefficient blocks associated with TUs of a current CU to reconstruct residual blocks associated with the TUs of the current CU. Video decoder 30 also reconstructs coding blocks of the current CU by adding samples of predictive blocks for PUs of the current CU to corresponding samples of transform blocks of TUs of the current CU. After reconstructing the coding blocks for each CU of a frame, video decoder 30 can reconstruct the frame.

[0070] SAO is a process that modifies decoded samples, after the application of a deblocking filter, by conditionally adding an offset value to each sample based on values ​​in a lookup table transmitted by the encoder. SAO filtering is performed region-by-region based on the filtering type selected for each CTB by the syntax element sao-type-idx. A value of 0 for sao-type-idx indicates that no SAO filter is applied to the CTB, while values ​​1 and 2 signal the use of the band-offset and edge-offset filtering types, respectively. In band-offset mode, specified by sao-type-idx equal to 1, the selected offset value depends directly on the sample amplitude. In this mode, the complete sample amplitude range is uniformly divided into 32 segments called bands, and sample values ​​belonging to four of these bands (consecutive within the 32 bands) are modified by adding a transmitted value, denoted as band-offset, which can be positive or negative. The main reason for using four consecutive bands is that in smooth areas where banding artifacts may appear, the sample amplitudes of the CTB tend to be concentrated in only a few of these bands. Additionally, the design choice of using four offsets unifies with the edge offset operation mode, which also uses four offset values. In the edge offset mode specified by sao-type-idx equal to 2, the syntax element sao-eo-class, with a value between 0 and 3, signals whether horizontal, vertical, or one of the two diagonal gradient directions is used for edge offset classification in the CTB.

[0071] Figure 5 is a block diagram illustrating four gradient patterns used in SAO according to some implementations of the present disclosure. Four gradient patterns 502, 504, 506, and 508 are for each sao-eo-class in edge offset mode. The sample labeled "p" indicates the center sample to be considered. Two samples labeled "n0" and "n1" designate two adjacent samples along the following gradient patterns: (a) horizontal (sao-eo-class=0), (b) vertical (sao-eo-class=1), (c) 135° diagonal (sao-eo-class=2), and (d) 45° diagonal (sao-eo-class=3). Each sample in the CTB is classified into one of five EdgeIdx categories by comparing the sample value p located at a certain position with the values ​​n0 and n1 of two adjacent samples, as shown in Figure 5. This classification is performed for each sample based on the decoded sample value; therefore, no additional signaling for EdgeIdx classification is required. For EdgeIdx categories 1 through 4, an offset value from the transmitted lookup table is added to the sample value depending on the EdgeIdx category at the sample location. The offset value is always positive for categories 1 and 2, and negative for categories 3 and 4. Thus, the filter generally has a smoothing effect in edge offset mode. Table 1 below shows sample EdgeIdx categories for SAO edge classes.

[0072] [Table 1] Table 1: Sample EdgeIdx categories in SAO edge classes For SAO types 1 and 2, a total of four amplitude offset values ​​are transmitted to the decoder for each CTB. For type 1, a sign is also encoded. The offset values ​​and associated syntax elements, such as sao-type-idx and sao-eo-class, are determined by the encoder, typically using criteria that optimize rate-distortion performance. For efficient signaling, SAO parameters can be indicated as inherited from the left or top CTB using a merge flag. In summary, SAO is a nonlinear filtering operation that allows additional refinement of the reconstructed signal, enhancing the signal representation both in smooth areas and around edges.

[0073] In some embodiments, methods and systems are disclosed herein for improving coding efficiency or reducing the complexity of sample adaptive offset (SAO) by introducing inter-component information. SAO is used in the HEVC, VVC, AVS2, and AVS3 standards. In the following description, the existing SAO design in the HEVC, VVC, AVS2, and AVS3 standards is used as the basic SAO method for those skilled in the art of video coding. However, the inter-component method described in this disclosure may also be applied to other loop filter designs or other coding tools with similar design spirit. For example, in the AVS3 standard, SAO is replaced by a coding tool called enhanced sample adaptive offset (ESAO). However, the CCSAO disclosed herein may be applied in parallel to the ESAO. In another example, the CCSAO may be applied in parallel to the Constrained Directional Enhancement Filter (CDEF) in the AV1 standard.

[0074] For existing SAO designs in the HEVC, VVC, AVS2, and AVS3 standards, the luma Y, chroma Cb, and chroma Cr sample offset values ​​are determined independently, i.e., the current chroma sample offset is determined only by the current chroma sample value and adjacent chroma sample values, same positionAlternatively, adjacent luma samples may not be considered. However, luma samples maintain more original picture detail than chroma samples and can benefit from the current chroma sample offset determination. Furthermore, because chroma samples typically lose high-frequency detail after RGB-to-YCbCr color conversion or after quantization and deblocking filters, introducing luma samples with preserved high-frequency detail for chroma offset determination can benefit from chroma sample reconstruction. Therefore, further gains can be expected by exploring inter-component correlations, for example, by using inter-component sample adaptive offset (CCSAO) methods and systems. In some embodiments, this correlation not only includes inter-component sample values ​​but also includes picture / coding information such as prediction / residual coding mode, transform type, and quantization / deblocking / SAO / ALF parameters from the inter-component sample values.

[0075] Another example is that in the case of SAO, the luma sample offset is determined by the luma sample only. However, for example, luma samples with the same band offset (BO) classification may be assigned different offsets. same position and neighboring chroma samples, thereby obtaining a more effective classification. SAO classification can be obtained as a shortcut to compensate for sample differences between the original picture and the reconstructed picture. Therefore, an effective classification is desired.

[0076] 6A is a block diagram illustrating a CCSAO system and process applied on chroma samples by some implementations of this disclosure, using DBF Y as an input. The luma sample after the luma deblocking filter (DBF Y) is used to determine additional offsets for chroma Cb and Cr after SAO Cb and SAO Cr. For example, the current chroma sample 602 is first same positionThe luma sample 604 and the adjacent (white) luma sample 606 are used to classify the current luma sample, and the corresponding CCSAO offset value of the corresponding class is added to the current chroma sample value. Figure 6B is a block diagram illustrating a CCSAO system and process applied on the luma sample and chroma sample by some implementations of the present disclosure and using DBF Y / Cb / Cr as input. Figure 6C is a block diagram illustrating a CCSAO system and process that can function independently by some implementations of the present disclosure. Figure 6D is a block diagram illustrating a CCSAO system and process that can be applied recursively (2 or N times) with the same or different offsets at the same codec stage or repeated at different stages by some implementations of the present disclosure. In summary, in some embodiments, to classify the current luma sample, information of the current luma sample and the adjacent luma samples, same position and information of neighboring chroma samples (Cb and Cr) may be used. In some embodiments, to classify the current chroma sample (Cb or Cr), same position and adjacent luma samples, same position and adjacent cross-chroma samples, as well as the current chroma sample and adjacent chroma samples, may be used. In some embodiments, the CCSAO may be cascaded (1) after DBF Y / Cb / Cr, (2) after pre-DBF reconstructed image Y / Cb / Cr, or (3) after SAO Y / Cb / Cr, or (4) after ALF Y / Cb / Cr.

[0077] In some embodiments, the CCSAO may also be applied in parallel to other coding tools, such as the ESAO in the AVS standard or the CDEF in the AV1 standard. Figure 6E is a block diagram illustrating a CCSAO system and process applied in parallel to the ESAO in the AVS standard according to some implementations of the present disclosure.

[0078] 6F is a block diagram illustrating a CCSAO system and process applied after the SAO according to some implementations of the present disclosure. In some embodiments, FIG. 6F shows that the location of the CCSAO can be after the SAO, i.e., in the place of the cross-component adaptive loop filter (CCALF) in the VVC standard. FIG. 6G is a block diagram illustrating that the CCSAO system and process can function independently without the CCALF according to some implementations of the present disclosure. In some embodiments, the SAO Y / Cb / Cr can be replaced with ESAO, for example, in the AVS3 standard.

[0079] FIG. 6H is a block diagram illustrating a CCSAO system and process applied in parallel to CCALF according to some implementations of the present disclosure. In some embodiments, FIG. 6H illustrates that CCSAO may be applied in parallel to CCALF. In some embodiments, the locations of CCALF and CCSAO may be switched in FIG. 6H. In some embodiments, in FIGS. 6A-6H or throughout this disclosure, the SAO Y / Cb / Cr blocks may be swapped with ESAO Y / Cb / Cr (AVS3) or CDEF (AV1). Note that Y / Cb / Cr may also be referred to as RGB in the video coding domain.

[0080] In some embodiments, the current chroma sample classification is: same position The SAO type (Edge Offset (EO) or BO), class, and category of the luma sample are reused. The corresponding CCSAO offset can be signaled or derived from the decoder itself. For example, h_Y can be same position Let h_Cb be the luma SAO offset, and h_Cb and h_Cr be the CCSAO Cb and Cr offsets, respectively. h_Cb (or h_Cr) = w*h_Y, where w can be selected from a restricted table, e.g., ±1 / 4, ±1 / 2, 0, ±1, ±2, ±4..., etc., where |w| includes only values ​​that are powers of 2.

[0081] In some embodiments, same positionThe comparison scores of the luma sample (Y0) and the eight adjacent luma samples [-8,8] are used, resulting in a total of 17 classes.

[0082] Initial Class=0 Loop through 8 adjacent luma samples (Yi, i=1~8) if Y0>Yi Class+=1 else if Y0 <Yi Class-=1 In some embodiments, the classification methods described above may be combined. For example, to increase diversity, the comparison scores combined with SAO BO (32-band classification) are used, resulting in a total of 17*32 classes. In some embodiments, Cb and Cr may use the same class to reduce complexity or save bits.

[0083] 7 is a block diagram illustrating a sample process using a CCSAO according to some implementations of the present disclosure. Specifically, FIG. 7 illustrates that the input of the CCSAO can introduce vertical and horizontal DBF inputs to simplify class determination or increase flexibility. For example, Y0_DBF_V, Y0_DBF_H, and Y0 can be respectively used as DBF_V, DBF_H, and Y0 in the input of the SAO. same position Let Yi_DBF_V, Yi_DBF_H, and Yi be the 8 adjacent luma samples at the input of DBF_V, DBF_H, and SAO, respectively, where i = 1 to 8.

[0084] Max Y0=max(Y0_DBF_V,Y0_DBF_H,Y0_DBF) Max Yi=max(Yi_DBF_V,Yi_DBF_H,Yi_DBF) max Y0 and max Yi are given as CCSAO classifications.

[0085] Figure 8 is a block diagram illustrating how the CCSAO process is interleaved into vertical and horizontal DBFs according to some example implementations of the present disclosure. In some embodiments, the CCSAO blocks in Figures 6, 7, and 8 may be optional. For example, using the DBF_V luma sample input as the CCSAO input, while using Y0_DBF_V and Yi_DBF_V for the first CCSAO_V, which applies the same sample processing as in Figure 6.

[0086] In some embodiments, the CCSAO syntax implemented is shown in Table 2 below.

[0087] [Table 2] Table 2: An example of CCSAO syntax In some embodiments, when one additional chroma offset is signaled to signal the CCSAO Cb and Cr offset values, the other chroma component offset can be derived by a positive or negative sign or by weighting to save bit overhead. For example, let h_Cb and h_Cr be the offsets of the CCSAO Cb and Cr, respectively. By explicitly signaling w, when w=±|w| and the |w| candidates are limited, h_Cr can be derived from h_Cb without explicitly signaling h_Cr itself.

[0088] h_Cr=w*h_Cb FIG. 9 is a flow diagram illustrating an example process 900 for decoding a video signal using inter-component correlation according to some implementations of the present disclosure.

[0089] Video decoder 30 receives a video signal including a first component and a second component (910). In some embodiments, the first component is a luma component and the second component is a chroma component of the video signal.

[0090] Video decoder 30 also receives a plurality of offsets associated with the second component (920).

[0091] Video decoder 30 then utilizes the characteristic measure of the first component to obtain a classification category associated with the second component (930). For example, in FIG. 6, current chroma sample 602 is first same position The luma sample 604 and the adjacent (white) luma sample 606 are used to sort and the corresponding CCSAO offset value is added to the current chroma sample.

[0092] Video decoder 30 further selects a first offset from the plurality of offsets for the second component according to the classification category (940).

[0093] Video decoder 30 additionally modifies the second component based on the selected first offset (950).

[0094] In some embodiments, obtaining a classification category associated with the second component using the characteristic measurement of the first component (930) includes obtaining a classification category for each sample of the second component using a respective sample of the first component, wherein the respective sample of the first component is a classification category for each sample of the second component. same position For example, the current chroma sample classification is same position It reuses the SAO type (EO or BO), class, and category from the Luma sample.

[0095] In some embodiments, obtaining a classification category associated with the second component using characteristic measurements of the first component (930) includes obtaining a classification category for each sample of the second component using each sample of the first component, where each sample of the first component is reconstructed before being deblocked or reconstructed after being deblocked. In some embodiments, the first component is deblocked with a deblocking filter (DBF). In some embodiments, the first component is deblocked with a luma deblocking filter (DBF Y). For example, as an alternative to FIG. 6 or FIG. 7, the CCSAO input may be before DBF Y.

[0096] In some embodiments, the characteristic measure is derived by dividing the range of sample values ​​of the first component into bands and selecting bands based on the intensity values ​​of the samples in the first component. In some embodiments, the characteristic measure is derived from a band offset (BO).

[0097] In some embodiments, the characteristic measure is derived based on the direction and intensity of edge information of the samples in the first component. In some embodiments, the characteristic measure is derived from edge offset (EO).

[0098] In some embodiments, modifying (950) the second component includes adding the selected first offset directly to the second component, e.g., adding a corresponding CCSAO offset value to the current chroma component sample.

[0099] In some embodiments, modifying (950) the second component includes mapping the selected first offset to a second offset and adding the mapped second offset to the second component. For example, if one additional chroma offset is signaled to signal the CCSAO Cb and Cr offset values, the other chroma component offset can be derived by using a positive or negative sign or by weighting to save bit overhead.

[0100] In some embodiments, receiving 910 the video signal includes receiving a syntax element indicating whether decoding the video signal using CCSAO is enabled for the video signal in a sequence parameter set (SPS). In some embodiments, cc_sao_enabled_flag indicates whether CCSAO is enabled at the sequence level.

[0101] In some embodiments, receiving (910) the video signal includes receiving a syntax element indicating whether decoding the video signal using CCSAO is enabled for the second component at the slice level. In some embodiments, slice_cc_sao_cb_flag or slice_cc_sao_cr_flag indicates whether CCSAO is enabled within the slice for Cb or Cr, respectively.

[0102] In some embodiments, receiving 920 multiple offsets associated with the second component includes receiving different offsets for different coding tree units (CTUs), where for a CTU, cc_sao_offset_sign_flag indicates a sign for the offset and cc_sao_offset_abs indicates the CCSAO Cb and Cr offset values ​​for the current CTU.

[0103] In some embodiments, receiving 920 multiple offsets associated with the second component includes receiving a syntax element indicating whether the received offset of the CTU is the same as one of the CTU's neighboring CTUs, where the neighboring CTU is a left or upper neighboring CTU. For example, cc_sao_merge_up_flag indicates whether the CCSAO offset is merged from a left or upper CTU.

[0104] In some embodiments, the video signal further includes a third component, and the method of decoding the video signal using the CCSAO further includes receiving a second plurality of offsets associated with the third component, utilizing characteristic measurements of the first component to obtain a second classification category associated with the third component, selecting a third offset from the second plurality of offsets for the third component according to the second classification category, and modifying the third component based on the selected third offset.

[0105] FIG. 11 illustrates all the configurations according to some implementations of the present disclosure. same position 6A, 6B, and 11 show the inputs of the CCSAO classification. In FIG. 11, the current chroma sample is 1104, and the inter-component same position The chroma sample is 1102, same position The luma samples are 1106.

[0106] In some embodiments, an exemplary classifier (C0) is same position The luma or chroma sample value (Y0) (Y4 / U4 / V4 in Figure 6B and Figure 6C) is used for classification. If band_num is the number of equally divided bands of the luma or chroma dynamic range and bit_depth is the sequence bit depth, an example class index for the current chroma sample is:

[0107] class(C0)=(Y0*band_num)>>bit_depth In some embodiments, this classification takes into account rounding, for example:

[0108] class(C0)=((Y0*band_num)+(1<<bit_depth))> >bit_depth Some band_num and bit_depth examples are listed below in Table 3. Table 3 shows three classification examples when the number of bands for each classification example is different.

[0109] [Table 3] Table 3: Example band_num and bit_depth for each class index In some embodiments, the classifier uses a different luma sample location for the C0 classification. Figure 10A is a block diagram showing a classifier that uses a different luma (or chroma) sample location for the C0 classification, for example, using neighboring Y7 instead of Y0 for the C0 classification, according to some implementations of the present disclosure.

[0110] In some embodiments, different classifiers can be switched at the Sequence Parameter Set (SPS) / Adaptation Parameter Set (APS) / Picture Parameter Set (PPS) / Picture Header (PH) / Slice Header (SH) / Region / Coding Tree Unit (CTU) / Coding Unit (CU) / Sub-block / Sample level. For example, in Figure 10, Y0 is used for POC0 but Y7 is used for POC1, as shown in Table 4 below.

[0111] [Table 4] Table 4: Different classifiers are applied to different pictures In some embodiments, FIG. 10B shows some examples of different shapes for luma candidates according to some implementations of the present disclosure. For example, constraints may be applied to the shapes. In some cases, the total number of luma candidates must be a power of two, as shown in FIG. 10B(b), (c), and (d). In some cases, the number of luma candidates must be horizontally and vertically symmetric about the chroma sample (center), as shown in FIG. 10B(a), (c), (d), and (e). In some embodiments, the power of two constraint and the symmetry constraint may also be applied to the chroma candidates. The U / V portions of FIG. 6B and FIG. 6C show an example for the symmetry constraint. In some embodiments, different color formats may have different classifier "constraints." For example, the 420 color format uses the luma / chroma candidate selection shown in Figures 6B and 6C (one candidate is selected from a 3x3 shape), while the 444 color format uses Figure 10B(f) for luma and chroma candidate selection, and the 422 color format uses Figure 10B(g) for luma (two chroma samples share four luma candidates) and Figure 10B(f) for chroma candidates.

[0112] In some embodiments, C0 position and C0 band_num may be combined and switched at SPS / APS / PPS / PH / SH / region / CTU / CU / subblock / sample level. Different combinations may result in different classifiers, as shown in Table 5 below.

[0113] [Table 5] Table 5: Different classifier and band number combinations applied to different pictures In some embodiments, same position The luma sample value (Y0) is same position and a value (Yp) obtained by weighting adjacent luma samples. same position The luma sample value is same positionand replacing it with a value obtained by weighting adjacent luma samples. same position The luma sample value (Y0) may be replaced with a phase correction value (Yp) obtained by weighting adjacent luma samples. Different Yp may be different classifiers.

[0114] In some embodiments, different Yp are applied to different chroma formats, for example, in Figure 12, Yp in (a) is used for 420 chroma format, Yp in (b) is used for 422 chroma format, and Y0 is used for 444 chroma format.

[0115] In some embodiments, another classifier (C1) is: same position The comparison score of the luma sample (Y0) and its eight adjacent luma samples is [-8,8], resulting in a total of 17 classes, as shown below.

[0116] Initial class (C1) = 0, loop through 8 adjacent luma samples (Yi,i = 1 to 8) if Y0>Yi Class+=1 else if Y0 <Yi Class-=1 In some embodiments, an example of C1 is equal to the following function, where the threshold th is 0:

[0117] ClassIdx=Index2ClassTable(f(C,P1)+f(C,P2)+...+f(C,P8)) if xy>th,f(x,y)=1;if xy=th,f(x,y)=0;if xy <th,f(x,y)=-1 where Index2ClassTable is a lookup table (LUT) and C is the current sample or same position P1 to P8 are adjacent samples.

[0118] In some embodiments, similar to the C4 classifier, one or more thresholds may be predefined (e.g., maintained in a LUT) or signaled at the SPS / APS / PPS / PH / SH / region / CTU / CU / subblock / sample level to aid in classification (quantization) of the differences.

[0119] In some embodiments, the variation (C1') only counts the comparison score [0,8], which results in 8 classes. (C1, C1') is the classifier group, and the PH / SH level flag can be signaled to switch between C1 and C1'.

[0120] Initial class (C1') = 0, loop through 8 adjacent luma samples (Yi,i = 1 to 8) if Y0>Yi Class+=1 In some embodiments, the variation (C1) selectively uses N neighbors out of M neighboring samples to calculate the comparison score. An M-bit bitmask may be signaled at the SPS / APS / PPS / PH / SH / region / CTU / CU / subblock / sample level to indicate which neighboring samples were selected to calculate the comparison score. Using FIG. 6B as an example for the luma classifier, eight neighboring luma samples are candidates, and an 8-bit bitmask (01111110) is signaled at PH, indicating that six samples Y1 through Y6 are selected. Therefore, the comparison score is [-6, 6], resulting in an offset of 13. The selective classifier C1 gives the encoder more options for trading off offset signaling overhead and classification granularity.

[0121] Like C1, variation (C1') counts only the comparison score [0,+N], so the previous example bitmask 01111110 gives a comparison score of [0,6], resulting in an offset of 7.

[0122] In some embodiments, different classifiers are combined to result in a generic classifier, for example, different classifiers are applied to different pictures (different POC values), as shown in Table 6-1 below.

[0123] [Table 6] Table 6-1: Different generic classifiers apply to different pictures In some embodiments, another exemplary classifier (C3) uses a bit mask for classification, as shown in Table 6-2. To indicate this classifier, a 10-bit bit mask is signaled at the SPS / APS / PPS / PH / SH / region / CTU / CU / subblock / sample level. For example, a bit mask of 11 1100 0000 means that for a given 10-bit luma sample value, only the most significant bits (MSBs): 4 bits are used for classification, resulting in a total of 16 classes. Another exemplary bit mask of 10 0100 0001 means that only 3 bits are used for classification, resulting in a total of 8 classes.

[0124] In some embodiments, the bit mask length (N) may be fixed or may be switched at the SPS / APS / PPS / PH / SH / region / CTU / CU / sub-block / sample level. For example, for a 10-bit sequence, a 4-bit bit mask 1110 is signaled in the PH in the picture, with the three most significant bits b9, b8, and b7 used for classification. Another example is a 4-bit bit mask 0011 on the least significant bits, with b0 and b1 used for classification. The bit mask classifier may correspond to luma or chroma classification. Whether the most significant bit or least significant bit is used for the bit mask N may be fixed or may be switched at the SPS / APS / PPS / PH / SH / region / CTU / CU / sub-block / sample level.

[0125] In some embodiments, the luma position and C3 bitmask may be combined and switched at the SPS / APS / PPS / PH / SH / region / CTU / CU / sub-block / sample level. Different combinations may result in different classifiers.

[0126] In some embodiments, a "max number of ones" bit mask restriction may be applied to limit the number of corresponding offsets. For example, limiting the "max number of ones" bit mask to 4 in an SPS results in a maximum offset of 16 in the sequence. The bit masks for different POCs may be different, but the "max number of ones" shall not exceed 4 (and shall not exceed 16 for all classes). The "max number of ones" value may be signaled and can be switched at the SPS / APS / PPS / PH / SH / region / CTU / CU / sub-block / sample level.

[0127] [Table 7] Table 6-2: Example classifier uses bitmasks for classification (bitmask positions are underlined) In some embodiments, as shown in FIG. 11 , other inter-component chroma samples, such as chroma sample 1102 and its neighboring samples, may also be provided to the CCSAO classification, e.g., for the current chroma sample 1104. For example, the Cr chroma sample may be provided to the CCSAO Cb classification. The Cb chroma sample may be provided to the CCSAO Cr classification. The classifier for the inter-component chroma sample may be the same as the luma inter-component classifier or may have its own classifier, as described in this disclosure. The two classifiers may be combined to form a joint classifier for classifying the current chroma sample. For example, a joint classifier combining the inter-component luma and chroma samples results in a total of 16 classes, as shown in Table 6-3 below.

[0128] [Table 8] Table 6-3: Example classifier using a joint classifier combining inter-component luma and chroma samples (bitmask positions are underlined) All the above mentioned classifiers (C0, C1, C1', C2, C3) can be combined. See for example Table 6-4 below.

[0129] [Table 9] Table 6-4: Different classifiers are combined In some embodiments, the exemplary classifier (C2) is: same position and the difference of adjacent luma samples (Yn). Figure 12(c) shows an example of Yn, which has a dynamic range of [-1024, 1023] when the bit depth is 10. Let band_num in C2 be the number of equally divided bands of the Yn dynamic range.

[0130] Class(C2)=(Yn+(1<<bit_depth)*band_num)> >(bit_depth+1).

[0131] In some embodiments, C0 and C2 are combined to yield a generic classifier, for example, different classifiers are applied to different pictures (different POCs), as shown in Table 7 below.

[0132] [Table 10] Table 7: Different generic classifiers are applied to different pictures In some embodiments, all the above-mentioned classifiers (C0, C1, C1', C2) are combined, for example, different classifiers are applied to different pictures (different POCs), as shown in Table 8-1 below.

[0133] [Table 11] Table 8-1: Different generic classifiers apply to different pictures In some embodiments, an exemplary classifier (C4) uses the difference between the CCSAO input value and the sample value to be compensated for classification, as shown in Table 8-2 below. For example, if CCSAO is applied in the ALF stage, the difference between the pre-ALF and post-ALF sample values ​​of the current component is used for classification. To aid in the classification (quantization) of the difference, one or more thresholds may be predefined (e.g., maintained in a look-up table (LUT)) or signaled at the SPS / APS / PPS / PH / SH / region / CTU / CU / sub-block / sample level. The C4 classifier can be combined with the Y / U / VbandNum of C0 to form a joint classifier (e.g., exemplary POC1, as shown in Table 8-2).

[0134] [Table 12] Table 8-2: Example classifier uses the difference between the CCSAO input value and the sample value to be compensated for classification In some embodiments, because different coding modes may introduce different distortion statistics into the reconstructed image, an exemplary classifier (C5) uses "coding information" to aid in sub-block classification. For example, as shown in Table 8-3 below, a CCSAO sample may be classified by its previous coding information, and the combination of coding information may form a classifier. Figure 30 below shows another example of different stages of coding information for C5.

[0135] [Table 13] Table 8-3: CCSAO samples are classified by the previous coding information of that sample, and the combination of coding information can form a classifier In some embodiments, the exemplary classifier (C6) uses YUV color transform values ​​for classification. For example, to classify the current Y component, use 1 / 1 / 1. same positionAlternatively, adjacent Y / U / V samples are selected to be color converted to RGB, and the bandNum of C3 is used to quantize the R value to become the current Y component classifier.

[0136] In some embodiments, other exemplary classifiers that use only current component information for the current component classification may be used as inter-component classification. For example, as shown in FIG. 5 and Table 1, luma sample information and eo-class are used to derive EdgeIdx and classify the current chroma sample. Other "non-inter-component" classifiers that may also be used as inter-component classifiers include edge direction, pixel intensity, pixel variance, pixel variance, sum of pixel Laplacian, Sobel operator, Compass operator, high-pass filter value, low-pass filter value, etc.

[0137] In some embodiments, multiple classifiers are used in the same POC. The current frame is divided into several regions, and each region uses the same classifier. For example, three different classifiers are used in POC0, and which classifier (0, 1, or 2) is used is signaled at the CTU level, as shown in Table 9 below.

[0138] [Table 14] Table 9: Different generic classifiers are applied to different regions in the same picture In some embodiments, the maximum number of multiple classifiers (which may also be referred to as alternative offset sets) may be fixed or signaled at the SPS / APS / PPS / PH / SH / region / CTU / CU / subblock / sample level. In one example, the fixed (predefined) maximum number of multiple classifiers is four. In that case, four different classifiers are used in POC0, and which classifier (0, 1, or 2) is used is signaled at the CTU level. Abbreviated unary (TU) codes may be used to indicate the classifier used for each luma or chroma CTB. For example, as shown in Table 10 below, when the TU code is 0, no CCSAO is applied; when the TU code is 10, set 0 is applied; when the TU code is 110, set 1 is applied; when the TU code is 1110, set 2 is applied; and when the TU code is 1111, set 3 is applied. To indicate the classifier for the CTB (offset set index), fixed-length codes, Golomb-Rice codes, and exponential-Golomb codes may be used. Three different classifiers are used in POC1.

[0139] [Table 15] Table 10: Abbreviated unary (TU) codes are used to indicate the classifier used for each chroma CTB An example of CTB offset set indexes for Cb and Cr is given in the 1280x720 sequence POC0 (when the CTU size is 128x128, the number of CTUs in a frame is 10x6). Cb of POC0 uses four offset sets and Cr uses one offset set. As shown in Table 11-1 below, when the offset set index is 0, CCSAO is not applied; when the offset set index is 1, set 0 is applied; when the offset set index is 2, set 1 is applied; when the offset set index is 3, set 2 is applied; and when the offset set index is 4, set 3 is applied. The type is selected same positionIt means the position of the luma sample (Yi). Different offset sets can have different types, band_num, and corresponding offsets.

[0140] [Table 16] Table 11-1: An example of CTB offset set index for Cb and Cr is given in 1280x720 sequence POC0 (if CTU size is 128x128, the number of CTUs in the frame is 10x6) In some embodiments, same position An example of jointly using current and adjacent Y / U / V samples for classification is given in Table 11-2 below (three-component joint bandNum classification for each Y / U / V component). At POC0, {2,4,1} offset sets are used for {Y,U,V}, respectively. Each offset set can be adaptively switched at SPS / APS / PPS / PH / SH / region / CTU / CU / sub-block / sample level. Different offset sets can have different classifiers. For example, to classify the current Y4 luma sample as the candidate position (candPos) shown in Figures 6B and 6C, Y set0 is used for {current Y4, same position U4, same position V4} are selected as candidates, with different bandNum{Y,U,V}={16,1,2}. When {candY,candU,candV} are used as the sample values ​​of the selected {Y,U,V} candidates, the total number of classes is 32, and the class index derivation can be shown as follows:

[0141] bandY=(candY*bandNumY)>>BitDepth; bandU=(candU*bandNumU)>>BitDepth; bandV=(candV*bandNumV)>>BitDepth; classIdx=bandY*bandNumU*bandNumV +bandU*bandNumV +bandV; Another example is the component V set1 classification in POC1, where candPos={neighbor Y8, neighbor U3, neighbor V0} is used with bandNum={4,1,2}, resulting in 8 classes.

[0142] [Table 17] Table 11-2: same position An example of using current and adjacent Y / U / V samples jointly for classification In some embodiments, for example, as shown in Table 11-3 below: same position Here is an example where adjacent Y / U / V samples are jointly used to classify the current Y / U / V sample (three-component joint edgeNum(C1) and bandNum classification for each Y / U / V component). Edge CandPos is the center position used for the C1 classifier, edge bitMask is the C1 adjacent sample activation indicator, and edgeNum is the number of the corresponding C1 class. In this example, C1 is only applied to the Y classifier (hence edgeNum is equal to edgeNumY), and edge candPos is always Y4 (current / same position However, C1 may be applied to a Y / U / V classifier with edge candPos as the adjacent sample position.

[0143] If diff denotes the C1 comparison score of Y, then the classIdx derivation can be:

[0144] bandY=(candY*bandNumY)>>BitDepth; bandU=(candU*bandNumU)>>BitDepth; bandV=(candV*bandNumV)>>BitDepth; edgeIdx=diff+(edgeNum>>1); bandIdx=bandY*bandNumU*bandNumV +bandU*bandNumV +bandV; classIdx=bandIdx*edgeNum+edgeIdx;

[0145] [Table 18] Table 11-3 (Part 1): same position An example of using current and adjacent Y / U / V samples jointly for classification

[0146] [Table 19] Table 11-3 (Part 2): same position An example of using current and adjacent Y / U / V samples jointly for classification

[0147] [Table 20] Table 11-3 (Part 3): same position An example of using current and adjacent Y / U / V samples jointly for classification In some embodiments, max band_num (bandNumY, bandNumU, or bandNumV) may be fixed or signaled at the SPS / APS / PPS / PH / SH / region / CTU / CU / sub-block / sample level. For example, if the decoder fixes max band_num=16 for each frame, 4 bits are signaled to indicate the band_num of C0 in the frame. Some other max band_num examples are listed in Table 12 below.

[0148] [Table 21] Table 12: Examples of maximum band_num and band_num bits In some embodiments, the maximum number of classes or offsets (combinations of multiple classifiers used jointly, e.g., C1 edgeNum*C1 bandNumY*bandNumU*bandNumV) for each set (or all added sets) may be fixed or signaled at the SPS / APS / PPS / PH / SH / region / CTU / CU / subblock / sample level. For example, max could be fixed at class_num=256*4 for all added sets, and an encoder conformance check or decoder norm check could be used to verify the constraint.

[0149] In some embodiments, restrictions may be applied to the C0 classification, for example restricting band_num (bandNumY, bandNumU, or bandNumV) to only power-of-two values. Instead of explicitly signaling band_num, the syntax band_num_shift is signaled. The decoder can use shift operations to avoid multiplications. Different band_num_shifts may be used for different components.

[0150] class(C0)=(Y0>>band_num_shift)>>bit_depth Another example operation considers rounding to reduce error.

[0151] class(C0)=((Y0+(1<<(band_num_shift-1)))>>band_num_shift)>>bit_depth For example, if band_num_max (Y, U, or V) is 16, then the possible band_num_shift candidates are 0, 1, 2, 3, 4, corresponding to band_num=1, 2, 4, 8, 16, as shown in Table 13.

[0152] [Table 22]

[0153] [Table 23] Table 13: band_num and corresponding band_num_shift candidates In some embodiments, the classifiers applied to Cb and Cr are different. The Cb and Cr offsets for all classes can be signaled separately. For example, different offsets are signaled and applied to different chroma components, as shown in Table 14 below.

[0154] [Table 24] Table 14: Cb and Cr offsets for all classes can be signaled separately In some embodiments, the maximum offset value is fixed or signaled at the sequence parameter set (SPS), adaptive parameter set (APS), picture parameter set (PPS), picture header (PH), slice header (SH), region, CTU, CU, sub-block, or sample level. For example, the maximum offset is [-15, 15]. Different components can have different maximum offset values.

[0155] In some embodiments, the offset signaling may use differential pulse code modulation (DPCM), for example, an offset of {3, 3, 2, 1, -1} may be signaled as {3, 0, -1, -1, -2}.

[0156] In some embodiments, the offsets may be stored in an APS or memory buffer for reuse for the next picture / slice, and an index may be signaled to indicate which stored previous frame offset is to be used for the current picture.

[0157] In some embodiments, the classifiers for Cb and Cr are the same. The Cb and Cr offsets for all classes may be jointly signaled, for example as shown in Table 15 below.

[0158] [Table 25] Table 15: Cb and Cr offsets for all classes can be jointly signaled In some embodiments, the classifiers for Cb and Cr may be the same. For example, the Cb and Cr offsets for all classes may be jointly signaled by a sign flag difference, as shown in Table 16 below. According to Table 16, when the Cb offset is (3, 3, 2, -1), the derived Cr offset is (-3, -3, -2, 1).

[0159] [Table 26] Table 16: Cb and Cr offsets for all classes can be jointly signaled by sign flag differences In some embodiments, a sign flag may be signaled for each class, for example, as shown in Table 17 below: According to Table 17, when the Cb offset is (3, 3, 2, -1), the derived Cr offset is (-3, 3, 2, 1) according to the respective sign flags.

[0160] [Table 27] Table 17: Cb and Cr offsets for all classes can be jointly signaled by the sign flag signaled for each class In some embodiments, the classifiers for Cb and Cr may be the same. For example, as shown in Table 18 below, the Cb and Cr offsets for all classes may be jointly signaled by weight differences. The weights (w) may be selected in a restricted table, e.g., ±¼, ±½, 0, ±1, ±2, ±4..., where |w| includes only values ​​that are powers of 2. According to Table 18, when the Cb offset is (3, 3, 2, -1), the derived Cr offset is (-6, -6, -4, 2) depending on the respective sign flags.

[0161] [Table 28] Table 18: Cb and Cr offsets for all classes can be jointly signaled by weight differences In some embodiments, weights may be signaled for each class, for example, as shown in Table 19 below: According to Table 19, when the Cb offset is (3, 3, 2, -1), the derived Cr offset is (-6, 12, 0, -1) according to the respective sign flags.

[0162] [Table 29] Table 19: Cb and Cr offsets for all classes can be jointly signaled with weights signaled for each class In some embodiments, when multiple classifiers are used in the same POC, different offset sets are signaled separately or jointly.

[0163] In some embodiments, previously decoded offsets may be stored for use in future frames. To reduce the overhead of offset signaling, an index may be signaled to indicate which previously decoded offset set is used for the current frame. For example, as shown in Table 20 below, the POC0 offset may be reused by POC2 by signaling offset set idx=0.

[0164] [Table 30] Table 20: An index can be signaled to indicate which previously decoded offset set is used for the current frame In some embodiments, the reuse offsets set idx for Cb and Cr may be different, for example as shown in Table 21 below.

[0165] [Table 31] Table 21: An index may be signaled to indicate which previously decoded offset set is used for the current frame, and the index may be different for the Cb and Cr components In some embodiments, offset signaling can use additional syntax including start and length to reduce signaling overhead. For example, when band_num=256, only offsets for band_idx=37-44 are signaled. In the example in Table 22-1 below, the syntax for start and length are both 8-bit fixed length codes that should align to the band_num bits.

[0166] [Table 32] Table 22-1: Offset signaling uses additional syntax including start and length In some embodiments, when CCSAO is applied to all YUV triplets: same position and adjacent YUV samples may be used jointly for classification, and all of the offset signaling methods described above for Cb / Cr may be extended to Y / Cb / Cr. In some embodiments, different component offset sets may be stored and used separately (each component has its own stored set) or jointly (each component shares / reuses the same stored set). Examples of separate sets are shown in Table 22-2 below.

[0167] [Table 33] JPEG0007762213000034.jpg12168 Table 22-2: An example showing that different component offset sets may be stored and used separately (each component has its own stored set) or jointly (each component shares / reuses the same stored set) In some embodiments, when the sequence bit depth is greater than 10 (or a specific bit depth), the offset can be quantized before signaling. On the decoder side, as shown in Table 23 below, the decoded offset is inverse quantized before application. For example, in the case of a 12-bit sequence, the decoded offset is left-shifted (inverse quantized) by 2.

[0168] [Table 34] Table 23: The decoded offset is inverse quantized before application In some embodiments, the offset can be calculated as CcSaoOffsetVal = (1 - 2 * ccsao_offset_sign_flag) * (ccsao_offset_abs << (BitDepth - Min(10, BitDepth))).

[0169] In some embodiments, the sample processing is described below. Let R(x, y) be the input luma or chroma sample value before CCSAO, and R'(x, y) be the output luma or chroma sample value after CCSAO.

[0170] offset = ccsao_offset[[class_index of R(x, y)]] R'(x, y) = Clip3(0, (1 << bit_depth) - 1, R(x, y) + offset) According to the above equations, each luma or chroma sample value R(x, y) is classified using the classifier indicated by the current picture and / or the current offset set idx. The corresponding offset of the derived class index is added to each luma or chroma sample value R(x, y). The clip function Clip3 is applied to (R(x, y) + offset) to create an output luma or chroma sample value R'(x, y) within the bit depth dynamic range, e.g., in the range from 0 to (1 << bit_depth) - 1.

[0171] In some embodiments, boundary processing is described below. same position If any of the adjacent luma (chroma) samples is located outside the current picture, the CCSAO is not applied to the current chroma (luma) sample. same position 13A(b) is a block diagram showing that if any of the adjacent luma (chroma) samples is located outside the current picture, the CCSAO is not applied to the current chroma (luma) sample. For example, in FIG. 13A(a), when a classifier is used, the CCSAO is not applied to the chroma components in the leftmost column of the current picture. For example, when C1' is used, as shown in FIG. 13A(b), the CCSAO is not applied to the chroma components in the leftmost column and the top row of the current picture.

[0172] FIG. 13B illustrates a method for classification used by some implementations of the present disclosure. same position 13B(b) is a block diagram showing that if any of the adjacent luma or chroma samples is located outside the current picture, the CCSAO is applied to the current luma or chroma sample. In some embodiments, the variations are used for classification, as shown in FIG. 13B(b). same position If any of the adjacent luma or chroma samples is located outside the current picture, the missing sample may be repeated or mirror-padded to create a sample for classification, as shown in Figure 13B(a), and the CCSAO may be applied to the current luma or chroma sample. In some embodiments, the picture boundary processing method by invalidation / repetition / mirror disclosed herein may also be used for classification. same position and may be applied to the subpicture / slice / tile / CTU / 360 virtual boundary if any of the adjacent luma (chroma) samples are located outside the current subpicture / slice / tile / patch / CTU / 360 virtual boundary.

[0173] For example, a picture is divided into one or more tile rows and one or more tile columns. A tile is a series of CTUs that cover a rectangular area of ​​the picture.

[0174] A slice consists of an integer number of complete tiles or an integer number of contiguous complete CTU rows within a tile of a picture.

[0175] A subpicture contains one or more slices that collectively cover a rectangular area of ​​the picture.

[0176] In some embodiments, 360-degree video is captured on a sphere, which inherently has no "boundaries," and reference samples located outside the boundaries of the reference picture in the projected domain can always be obtained from neighboring samples in the spherical domain. For projection formats consisting of multiple surfaces, discontinuities appear between two or more adjacent surfaces in the frame-packed picture, regardless of the type of compact frame packing arrangement used. VVC introduces vertical and / or horizontal virtual boundaries where in-loop filtering operations are disabled, and the location of these boundaries is signaled in the SPS or picture header. Compared to using two tiles, one for each pair of consecutive surfaces, the use of 360 virtual boundaries is more flexible because it does not require the surface size to be a multiple of the CTU size. In some embodiments, the maximum number of vertical 360 virtual boundaries is three, and the maximum number of horizontal 360 virtual boundaries is also three. In some embodiments, the distance between two virtual boundaries is greater than or equal to the CTU size, and the granularity of the virtual boundaries is 8 luma samples, e.g., an 8x8 sample grid.

[0177] FIG. 14 illustrates a corresponding selected image used for classification, according to some implementations of the present disclosure. same position14(a) is a block diagram showing that CCSAO is not applied to the current chroma sample if the adjacent luma sample is outside the virtual space defined by the virtual boundary. In some embodiments, the virtual boundary (VB) is a virtual line separating spaces within a picture frame. In some embodiments, when the virtual boundary (VB) is applied within the current frame, CCSAO is not applied to chroma samples that select corresponding luma positions that are outside the virtual space defined by the virtual boundary. FIG. 14 shows an example of virtual boundaries for a C0 classifier with nine luma position candidates. For each CTU, CCSAO is not applied to chroma samples whose corresponding selected luma positions are outside the virtual space encompassed by the virtual boundary. For example, in FIG. 14(a), when the selected Y7 luma sample position is on the opposite side of the horizontal virtual boundary 1406, which is located four pixels from the bottom of the frame, CCSAO is not applied to chroma sample 1402. For example, in FIG. 14(b), when the selected Y5 luma sample position is located on the opposite side of the vertical virtual boundary 1408 located y pixels from the right edge of the frame, CCSAO is not applied to the chroma sample 1404.

[0178] FIG. 15 illustrates that, in some implementation examples of the present disclosure, repetition or mirror padding may be applied to luma samples outside the virtual boundary. FIG. 15(a) illustrates an example of repetition padding. If the original Y7 is selected to be the classifier located at the bottom of VB1502, the Y4 luma sample value is used for classification (copied to the Y7 position) rather than the original Y7 luma sample value. FIG. 15(b) illustrates an example of mirror padding. If Y7 is selected to be the classifier located at the bottom of VB1504, the Y1 luma sample value, which is symmetrical to the Y7 value with respect to the Y0 luma sample, is used for classification rather than the original Y7 luma sample value. The padding method allows the possibility of applying CCSAO to more chroma samples, and therefore more coding gain may be realized.

[0179] In some embodiments, restrictions may be applied to reduce the line buffer required by the CCSAO and simplify boundary processing condition checks. Figure 16 shows the results of some implementations of the present disclosure for all nine same position and adjacent luma samples are used for classification, an additional 1 luma line buffer may be required, i.e., full line luma samples of line -5 above the current VB1602. Figure 10B(a) shows an example where only 6 luma candidates are used for classification, which reduces the line buffer and does not require any additional boundary checks in Figures 13A and 13B.

[0180] In some embodiments, using luma samples for CCSAO classification may increase the luma line buffer and therefore decoder hardware implementation costs. Figure 17 illustrates how, in some implementations of the present disclosure, nine luma candidate CCSAOs crossing VB 1702 in AVS may increase two additional luma line buffers. For luma and chroma samples above the virtual boundary (VB) 1702, DBF / SAO / ALF are processed in the current CTU row. For luma and chroma samples below VB 1702, DBF / SAO / ALF are processed in the next CTU row. In the AVS decoder hardware design, the pre-DBF samples for luma lines -4 to -1, the pre-SAO samples for line -5, and the pre-DBF samples for chroma lines -3 to -1, and the pre-SAO samples for line -4 are stored as line buffers for DBF / SAO / ALF processing of the next CTU row. When processing the next CTU row, luma and chroma samples that are not in the line buffer are unavailable. However, for example, at chroma line -3(b), chroma samples are processed in the next CTU row, but CCSAO requires SAO pre-luma sample lines -7, -6, and -5 for classification. SAO pre-luma sample lines -7 and -6 are not in the line buffer and therefore unavailable. Adding SAO pre-luma sample lines -7 and -6 to the line buffer increases decoder hardware implementation costs. In some examples, luma VB (line -4) and chroma VB (line -3) may be different (not aligned).

[0181] 17, FIG. 18A illustrates that in VVC, nine luma candidate CCSAOs intersecting VB 1802 may increase one additional luma line buffer according to some implementations of the present disclosure. VB may be different in different standards. In VVC, luma VB is line -4 and chroma VB is line -2, and therefore nine candidate CCSAOs may increase one luma line buffer.

[0182] In some embodiments, in the first solution, if any of the luma candidates for a chroma sample crosses VB (outside the current chroma sample VB), the CCSAO is disabled for that chroma sample. Figures 19A-19C show that, according to some implementation examples of the present disclosure, if any of the luma candidates for a chroma sample crosses VB1902 (outside the current chroma sample VB), the CCSAO is disabled for that chroma sample in AVS and VVC. Figure 14 also shows some examples of this implementation.

[0183] In some embodiments, in the second solution, for "cross-VB" luma candidates, repeat padding is used in the CCSAO from a luma line close to and opposite VB, e.g., luma line -4. In some embodiments, repeat padding from the luma closest to the adjacent luma below VB is implemented for the "cross-VB" chroma candidates. Figures 20A-20C show that, in AVS and VVC, CCSAO is enabled using repeat padding for chroma samples if any of the luma candidates for the chroma samples crosses VB2002 (is outside the current chroma sample VB) according to some implementation examples of this disclosure. Figure 14(a) also shows some examples of this implementation example.

[0184] In some embodiments, in the third solution, for "cross-VB" luma candidates, mirror padding is used for CCSAO from below the luma VB. Figures 21A-21C show that some implementation examples of the present disclosure enable CCSAO using mirror padding for chroma samples in AVS and VVC when any of the luma candidates for a chroma sample crosses VB 2102 (is outside the current chroma sample VB). Figures 14(b) and 13B(b) also show some examples of this implementation. In some embodiments, in the fourth solution, "double-sided symmetric padding" is used to apply CCSAO. Figures 22A-22B show that some implementation examples of the present disclosure enable CCSAO using double-sided symmetric padding for some examples of different CCSAO shapes (e.g., 9 luma candidates (Figure 22A) and 8 luma candidates (Figure 22B)). Same position For a luma sample set with a central luma sample, if one side of the luma sample set is outside VB2 202, double-sided symmetric padding is applied to both sides of the luma sample set. For example, in Figure 22A, luma samples Y0, Y1, and Y2 are outside VB2 202, so both Y0, Y1, Y2 and Y6, Y7, Y8 are padded using Y3, Y4, and Y5. For example, in Figure 22B, luma sample Y0 is outside VB2 202, so Y0 is padded using Y2 and Y7 is padded using Y5.

[0185] 18B illustrates a diagram in which, according to some implementations of the present disclosure, co-located or adjacent chroma samples are used to classify the current luma sample, and the selected chroma candidate may cross VB and require additional chroma line buffers. Solutions 1-4 similar to those described above may be applied to address this issue.

[0186] Solution 1 is to disable CCSAO for luma samples when any of its chroma candidates may cross VB.

[0187] Solution 2 is to use repeated padding from the chroma closest to the adjacent chroma below VB for the "cross VB" chroma candidate.

[0188] Solution 3 is to use mirror padding from below chroma VB for the "crossed VB" chroma candidate.

[0189] Solution 4 is to use "double-sided symmetric padding". same position For a candidate set centered on a chroma sample, if one side of the candidate set is outside the VB, double-sided symmetric padding is applied on both sides.

[0190] The padding method provides the possibility to apply the CCSAO to more luma or chroma samples, and therefore more coding gain can be realized.

[0191] In some embodiments, in a bottom picture (or slice, tile, brick) boundary CTU row, samples below the VB are processed in the current CTU row, and therefore the above special treatment (solutions 1, 2, 3, and 4) does not apply to this bottom picture (or slice, tile, brick) boundary CTU row. For example, a 1920x1080 frame is divided into 128x128 CTUs. The frame contains 15x9 CTUs (rounded up). The bottom CTU row is the 15th CTU row. The decoding process is performed CTU-by-CTU for each CTU row. Deblocking needs to be applied along the horizontal CTU boundary between the current CTU row and the next CTU row. Inside one CTU, in the bottom 4 / 2 luma / chroma lines, the VB of the CTB is applied to each CTU row because the DBF samples (in the case of VVC) are processed in the next CTU row and are not available for the CCSAO of the current CTU row. However, in the bottom CTU row of the picture frame, there is no next CTU row remaining, so the bottom 4 / 2 luma / chroma line DBF samples are available in the current CTU row and are DBF processed in the current CTU row.

[0192] In some embodiments, the VBs shown in Figures 13-22 may be swapped with the boundaries of the subpicture / slice / tile / patch / CTU / 360 virtual boundary. In some embodiments, the positions of the chroma and luma samples in Figures 13-22 may be switched. In some embodiments, the positions of the chroma and luma samples in Figures 13-22 may be swapped with the positions of the first chroma sample and the second chroma sample. In some embodiments, the VBs of the ALFs in the CTU may be generally horizontal. In some embodiments, the boundaries of the subpicture / slice / tile / patch / CTU / 360 virtual boundary may be horizontal or vertical.

[0193] In some embodiments, restrictions may be applied to reduce the line buffer required by the CCSAO and simplify boundary processing condition checks, as illustrated in Figure 16. Figure 23 illustrates restrictions to use a limited number of luma candidates for classification according to some implementations of the present disclosure. Figure 23(a) illustrates restrictions to use only six luma candidates for classification. Figure 23(b) illustrates restrictions to use only four luma candidates for classification.

[0194] In some embodiments, an application region is implemented. The CCSAO application region unit can be based on a CTB, i.e., the on / off control, CCSAO parameters (offset used for classification offset set index, luma candidate position, band_num, bitmask, etc.) are the same within one CTB.

[0195] In some embodiments, the application region may not be aligned to the CTB boundary. For example, the application region may be shifted rather than aligned to the chroma CTB boundary. While the syntax (on / off control, CCSAO parameters) is still shown for each CTB, the actual application region is not aligned to the CTB boundary. Figure 24 illustrates that, according to some implementations of the present disclosure, the CCSAO application region is not aligned to the CTB / CTU boundary 2406. For example, the application region is not aligned to the chroma CTB / CTU boundary 2406, but is shifted (4,4) samples up and left relative to the VB 2408. This unaligned CTB boundary design benefits the deblocking process because the same deblocking parameters are used for each 8x8 deblocking process region.

[0196] In some embodiments, the CCSAO application region unit (mask size) may be variable (larger or smaller than the CTB size), as shown in Table 24. The mask size may be different for different components. The mask size may be switched at the SPS / APS / PPS / PH / SH / region / CTU / CU / sub-block / sample level. For example, in the PH, a series of mask on / off flags and offset set indexes are shown to indicate each CCSAO region information.

[0197] [Table 35] Table 24: CCSAO application area units (mask size) may be variable In some embodiments, the CCSAO applicability region frame partition may be fixed, for example, by dividing the frame into N regions. Figure 25 illustrates that, according to some implementations of the present disclosure, the CCSAO applicability region frame partition may be fixed by a CCSAO parameter.

[0198] In some embodiments, each region can have its own region on / off control flag and CCSAO parameters. Also, if the region size is larger than the CTB size, it can have both a CTB on / off control flag and a region on / off control flag. Figures 25(a) and 25(b) show some examples of dividing a frame into N regions. Figure 25(a) shows a vertical division consisting of four regions. Figure 25(b) shows a square division consisting of four regions. In some embodiments, similar to the picture-level CTB on all-on control flag (ph_cc_sao_cb_ctb_control_flag / ph_cc_sao_cr_ctb_control_flag), if the region on / off control flag is off, a CTB on / off flag can be further signaled. Otherwise, CCSAO is applied to all CTBs within this region without further signaling of a CTB flag.

[0199] In some embodiments, different CCSAO application regions can share the same region on / off control and CCSAO parameters. For example, in Figure 25(c), regions 0-2 share the same parameters, and regions 3-15 share the same parameters. Figure 25(c) also shows that the region on / off control flags and CCSAO parameters can be signaled in Hilbert scan order.

[0200] In some embodiments, the CCSAO application area unit can be a quadtree / binarytree / ternarytree split from the picture / slice / CTB level. Similar to CTB splitting, a series of split flags are signaled to indicate the CCSAO application area division. Figure 26 shows that in some implementations of the present disclosure, the CCSAO application area can be a binary tree (BT) / quadtree (QT) / ternary tree (TT) split from the frame / slice / CTB level.

[0201] Figure 27 is a block diagram illustrating multiple classifiers used and switched at different levels within a picture frame according to some implementations of this disclosure. In some embodiments, when multiple classifiers are used in a frame, the method of applying the classifier set index may be switched at the SPS / APS / PPS / PH / SH / region / CTU / CU / sub-block / sample level. For example, as shown in Table 25 below, four classifier sets are used within a frame and switched at the PH. Figures 27(a) and 27(c) show the default fixed region classifier. Figure 27(b) shows the classifier set index signaled at the mask / CTB level, where 0 means CCSAO off for this CTB and 1-4 means set index.

[0202] [Table 36] Table 25: Four classifier sets are used within a frame and switched with PH In some embodiments, for a default region, the region level flag may be signaled if the CTB in this region does not use the default set index (e.g., the region level flag is 0), but uses other classifier sets in this frame. For example, if the default set index is used, the region level flag will be 1. For example, in four regions of a square partition, the following classifier sets are used, as shown in Table 26 below:

[0203] [Table 37] Table 26: A region-level flag can be signaled to indicate whether CTBs in this region do not use the default set index. Figure 28 is a block diagram illustrating that, in some implementations of the present disclosure, CCSAO application region division can be dynamic and can be switched at the picture level. For example, Figure 28(a) shows that three CCSAO offset sets are used in this POC (set_num=3), thus dividing the picture frame vertically into three regions. Figure 28(b) shows that four CCSAO offset sets are used in this POC (set_num=4), thus dividing the picture frame horizontally into four regions. Figure 28(c) shows that three CCSAO offset sets are used in this POC (set_num=3), thus dividing the picture frame horizontally into three regions. Each region can have its own region all-on flag to save CTB on / off control bits. The number of regions depends on the picture set_num being signaled.

[0204] The CCSAO application area can be a specific area according to the coding information within the block (sample position, sample coding mode, loop filter parameters, etc.). For example, 1) the CCSAO application area may be applied only when the sample is coded in skip mode, or 2) the CCSAO application area may include only N samples along the CTU boundary, or 3) the CCSAO application area may include only samples on an 8x8 grid within a frame, or 4) the CCSAO application area may include only DBF filter samples, or 5) the CCSAO application area may include only the top M and left N rows within a CU. Different application areas can use different classifiers. For example, in a CTU, skip mode uses C1, an 8x8 grid uses C2, and both skip mode and an 8x8 grid use C3. For example, in a CTU, skip mode coded samples use C1, CU-centered samples use C2, and CU-centered skip mode coded samples use C3. Figure 29 illustrates that, in some implementations of the present disclosure, the CCSAO classifier can take into account current or inter-component coding information. For example, different coding modes / parameters / sample positions can form different classifiers. Different coding information can be combined to form a joint classifier. Different regions can use different classifiers. Figure 29 also illustrates another example of an application area.

[0205] In some embodiments, the CCSAO syntax implemented is shown in Table 27 below. In some instances, the binarization of each syntax element may be changed. In AVS3, the term patch is similar to slice, and patch header is similar to slice header. FLC stands for fixed length code. TU stands for shortened unary code. EGk stands for exponential-Golomb code with degree k, where k may be fixed. SVLC stands for signed EG0. UVLC stands for unsigned EG0.

[0206] [Table 38] JPEG0007762213000040.jpg249152 JPEG0007762213000041.jpg217158 Table 27: Example CCSAO syntax If a high-order flag is off, the low-order flags may be inferred from the off state of the flags and do not need to be signaled. For example, if ph_cc_sao_cb_flag is false in this picture, then ph_cc_sao_cb_band_num_minus1, ph_cc_sao_cb_luma_type, cc_sao_cb_offset_sign_flag, cc_sao_cb_offset_abs, ctb_cc_sao_cb_flag, cc_sao_cb_merge_left_flag, and cc_sao_cb_merge_up_flag are inferred to be not present and false.

[0207] In some embodiments, the ccsao_enabled_flag of the SPS is adjusted with the SAO enable flag of the SPS, as shown in Table 28 below.

[0208] [Table 39] Table 28: SPS ccsao_enabled_flag is adjusted by SPS SAO enable flag In some embodiments, ph_cc_sao_cb_ctb_control_flag, ph_cc_sao_cr_ctb_control_flag indicate whether to enable the granularity of CTB on / off control for Cb / Cr. If ph_cc_sao_cb_ctb_control_flag and ph_cc_sao_cr_ctb_control_flag are enabled, ctb_cc_sao_cb_flag and ctb_cc_sao_cr_flag may be further signaled. Otherwise, whether CCSAO is applied to the current picture depends on ph_cc_sao_cb_flag, ph_cc_sao_cr_flag, and ctb_cc_sao_cb_flag and ctb_cc_sao_cr_flag are not further signaled at the CTB level.

[0209] In some embodiments, for ph_cc_sao_cb_type and ph_cc_sao_cr_type, a central is in the same position A flag may be further signaled to distinguish whether the luma position (Y0 position in FIG. 10) is used for classification for chroma samples. Similarly, if cc_sao_cb_type and cc_sao_cr_type are signaled at the CTB level, a flag may be further signaled by the same mechanism. For example, if the number of C0 luma position candidates is 9, then the center position may be used for classification as shown in Table 29 below. is in the same position cc_sao_cb_type0_flag is further signaled to distinguish whether luma position is used or not. is in the same position If the luma position is not used, cc_sao_cb_type_idc is used to indicate which of the remaining 8 neighboring luma positions is used.

[0210] [Table 40] Table 29: Center are in the same position cc_sao_cb_type0_flag is signaled to distinguish whether luma position is used or not Table 30 below shows an example where a single (set_num=1) or multiple (set_num>1) classifiers are used within a frame in AVS. The syntax notation can be mapped to the notation used above.

[0211] [Table 41]

[0212] [Table 42] Table 30: An example of how single (set_num=1) or multiple (set_num>1) classifiers are used in a picture frame in AVS When combined with Figure 25 or Figure 27, where each region has its own set, an example syntax may include region on / off control flags (picture_ccsao_lcu_control_flag[compIdx][setIdx]), as shown in Table 31 below.

[0213] [Table 43] Table 31: Each region has its own set, and an example syntax can include region on / off control flags (picture_ccsao_lcu_control_flag[compIdx][setIdx]) In some embodiments, extensions to intra- and inter-prediction post-SAO filters are further illustrated below. In some embodiments, the SAO classification method disclosed in this disclosure can act as a post-prediction filter, and the prediction can be intra, inter, or other prediction tools, such as intra-block copy. Figure 30 is a block diagram illustrating the SAO classification method disclosed in this disclosure acting as a post-prediction filter according to some implementations of the present disclosure.

[0214] In some embodiments, a corresponding classifier is selected for each Y, U, and V component. For each component prediction sample, the corresponding classifier is first classified and a corresponding offset is added. For example, each component can use the current sample and neighboring samples for classification. As shown in Table 32 below, Y uses the current Y sample and neighboring Y samples, and U / V uses the current U / V sample for classification. Figure 31 is a block diagram illustrating that, for a post-prediction SAO filter, each component can use the current sample and neighboring samples for classification, according to some implementations of the present disclosure.

[0215] [Table 44] Table 32: For each Y, U, and V component the corresponding classifier is selected In some embodiments, the refined prediction samples (Ypred', Upred', Vpred') are updated by adding the corresponding class offsets and are then used for intra, inter, or other prediction.

[0216] Ypred'=clip3(0,(1< <bit_depth)-1,Ypred+h_Y[i]) Upred'=clip3(0,(1< <bit_depth)-1,Upred+h_U[i]) Vpred'=clip3(0,(1< <bit_depth)-1,Vpred+h_V[i]) In some embodiments, in addition to the current chroma component, for the chroma U and V components, an inter-component offset (Y) may be used for further offset classification. For example, as shown below in Table 33, an additional inter-component offset (h'_U, h'_V) may be added with the current component offset (h_U, h_V).

[0217] [Table 45] Table 33: In addition to the current chroma components, for the chroma U and V components, the inter-component (Y) can be used for further offset classification In some embodiments, the improved prediction samples (Upred”, Vpred”) are updated by adding the corresponding class offset and are then used for intra, inter, or other prediction.

[0218] Upred”=clip3(0,(1< <bit_depth)-1,Upred’+h’_U[i]) Vpred”=clip3(0,(1< <bit_depth)-1,Vpred’+h’_V[i]) In some embodiments, intra and inter predictions may use different SAO filter offsets.

[0219] FIG. 32 is a flow diagram illustrating an example process 3200 for decoding a video signal using inter-component correlation according to some implementations of the present disclosure.

[0220] Video decoder 30 (shown in FIG. 3) receives (3210) a picture frame from a video signal, the picture frame including a first component and a second component in a first color space.

[0221] Video decoder 30 determines (3220) a classifier for the second component in the first color space from one or more samples of a first set of the first component in the second color space associated with each sample of the second component in the first color space.

[0222] Video decoder 30 determines (3230) sample offsets for each sample of the second component in the first color space according to the classifier.

[0223] Video decoder 30 modifies (3240) the value of each sample of the second component in the first color space based on the determined sample offset.

[0224] In some embodiments, the first component is a component selected from the group consisting of a luma component, a first chroma component, and a second chroma component, and the second component is a component selected from the group consisting of a luma component, a first chroma component, and a second chroma component.

[0225] In some embodiments, the first set of one or more samples is obtained by transforming one or more samples of the first component associated with each sample of the second component from the first color space to the second color space using a linear transform.

[0226] In some embodiments, the linear transformation is O1=a×I1+b×I2+c×I3 O2=d×I1+e×I2+f×I3 O3=g×I1+h×I2+i×I3 where a, b, c, d, e, f, g, h, and i are predetermined constants, I1, I2, and I3 are sample values ​​of the first component, the second component, and the third component, respectively, in the first color space, and O1, O2, and O3 are sample values ​​of the first component, the second component, and the third component, respectively, in the second color space.

[0227] In some embodiments, the first color space is a YUV color space and the second color space is an RGB color space.

[0228] In some embodiments, the first color space is an RGB color space and the second color space is a YUV color space.

[0229] In some embodiments, the first set of one or more samples is obtained by transforming one or more samples of the first component associated with each sample of the second component from the first color space to the second color space using a nonlinear transform.

[0230] In some embodiments, determining the classifier (3220) further includes determining a classifier for the second component in the first color space from one or more samples of a second set of the second component associated with a respective sample of the second component, wherein the one or more samples of the second set are located within the first color space or the second color space.

[0231] In some embodiments, the picture frame further includes a third component, and determining the classifier (3220) further includes determining a classifier for the second component in the first color space from one or more samples of a third set of the third component associated with each sample of the second component, the third component being a second chroma component, and the one or more samples of the third set being located in the first color space or the second color space.

[0232] In some embodiments, the classifier is determined by at least one of a first sub-classifier and / or a second sub-classifier, where the first sub-classifier is determined by dividing a first dynamic range of values ​​of one or more samples of a first set of first components into a first number of bands and selecting bands based on intensity values ​​of one or more samples of the first set of first components, and the second sub-classifier is determined based on the direction and intensity of edge information of a first sub-group of one or more samples of a second set of second components.

[0233] In some embodiments, the first component is a first chroma component and the second component is a luma component, and one or more samples of the first set of the first component associated with each sample of the second component are same position and one or more of the adjacent samples.

[0234] In some embodiments, one or more samples of a second set of the second component associated with each sample of the second component are selected from one or more of the current sample and adjacent samples of the second component for each sample of the second component.

[0235] In some embodiments, determining the classifier (3220) further includes determining a classifier for the second component in the first color space from one or more samples of a fourth set of one or more of the first, second, and third components associated with each sample of the second component, wherein the one or more samples of the fourth set are located within the first color space or within the second color space.

[0236] In some embodiments, determining the classifier (3220) further includes determining a classifier for the second component in the first color space from previous encoding information of the one or more samples of the fourth set.

[0237] In some embodiments, determining the classifier (3220) sets the class index of the classifier to ClassIdx = Index2ClassTable(f(C, P1)+f(C, P2)+...+f(C, P8)) where C is the value of the current sample or same position the value of the sample, P1, P2,...P8 are the values of adjacent samples, Index2ClassTable is a predefined table of index classes, th is a threshold, f(x, y)=1 when x - y>th, f(x, y)=0 when x - y = th, and f(x, y)=-1 when x - y<th.

[0238] 33 shows a computing environment 3310 coupled to a user interface 3350. The computing environment 3310 may be part of a data processing server. The computing environment 3310 includes a processor 3320, a memory 3330, and an input / output (I / O) interface 3340.

[0239] The processor 3320 typically controls the overall operation of the computing environment 3310, such as operations associated with display, data acquisition, data communication, and image processing. The processor 3320 may include one or more processors to execute instructions for performing all or some of the steps in the methods described above. Additionally, the processor 3320 may include one or more modules that facilitate interaction between the processor 3320 and other components. The processor may be a central processing unit (CPU), a microprocessor, a single-chip machine, a graphical processing unit (GPU), etc.

[0240] The memory 3330 is configured to store various types of data to support the operation of the computing environment 3310. The memory 3330 may include predefined software 3332. Examples of such data include instructions for any application or method operated on the computing environment 3310, video data sets, image data, etc. The memory 3330 may be implemented using any type of volatile or non-volatile memory device, or combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic or optical disks.

[0241] The I / O interface 3340 provides an interface between the processor 3320 and a peripheral interface module, such as a keyboard, a click wheel, buttons, etc. The buttons may include, but are not limited to, a home button, a start scan button, and a stop scan button. The I / O interface 3340 may be coupled to an encoder and a decoder.

[0242] In one embodiment, a non-transitory computer-readable storage medium is also provided, comprising, for example, in memory 3330, a plurality of programs executable by processor 3320 in computing environment 3310 to perform the aforementioned methods. Alternatively, the non-transitory computer-readable storage medium may store a bitstream or datastream including encoded video information (e.g., video information including one or more syntax elements), the bitstream or datastream generated by an encoder (e.g., video encoder 20 of FIG. 2) using, for example, the encoding method described above for use by a decoder (e.g., video decoder 30 of FIG. 3) in decoding the video data. The non-transitory computer-readable storage medium may be, for example, a ROM, a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, etc.

[0243] In one embodiment, a computing device is also provided that includes one or more processors (e.g., processor 3320) and a non-transitory computer-readable storage medium or memory 3330 having stored thereon a plurality of programs executable by the one or more processors, the one or more processors being configured to, upon execution of the plurality of programs, perform the aforementioned method.

[0244] In one embodiment, a computer program product is also provided that includes a plurality of programs executable by the processor 3320 in the computing environment 3310 to perform the methods described above, e.g., in the memory 3330. For example, the computer program product may include a non-transitory computer-readable storage medium.

[0245] In one embodiment, the computing environment 3310 may be implemented by one or more ASICs, DSPs, digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs, GPUs, controllers, microcontrollers, microprocessors, or other electronic components to perform the methods described above.

[0246] Further embodiments also include various subsets of the above embodiments combined or otherwise rearranged in various other embodiments.

[0247] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted via a computer-readable 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 communications protocol. In this manner, computer-readable media may generally correspond to (1) tangible computer-readable storage media that is non-transitory, or (2) a communication medium 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 implementations described herein. A computer program product may include computer-readable media.

[0248] The terminology used in the description of implementations herein is for the purpose of describing particular implementations only and is not intended to limit the scope of the claims. When used in the description of implementations and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and / or" will also be understood to refer to and include any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms "comprises" and / or "comprising," as used herein, specify the presence of stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or groups thereof.

[0249] In this specification, terms such as "first," "second," etc. may be used to describe various elements, but it should be understood that these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first electrode may be referred to as a second electrode, and a second electrode may be referred to as a first electrode, without departing from the scope of the implementation. The first electrode and the second electrode are both electrodes, but are not the same electrode.

[0250] Throughout this specification, references to "in one example," "example," "illustrative," etc., mean that one or more particular features, structures, or characteristics described in connection with an example are included in at least one example of the disclosure. Thus, the appearances of the phrases "in one example," "in an example," "illustratively," etc. in various places throughout this specification do not necessarily all refer to the same example. Furthermore, particular features, structures, or characteristics in one or more examples may include being combined in any suitable manner.

[0251] The description in this application has been presented for purposes of illustration and description and is not intended to be exhaustive or to be limited to the invention in the form disclosed. Many modifications, variations, and alternative implementations will be apparent to those skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. The embodiments have been chosen and described to best explain the principles of the invention, its practical application, and to enable others skilled in the art to understand the invention in relation to various implementations and to best utilize the underlying principles and various implementations, along with various modifications suited to the particular use contemplated. It is therefore to be understood that the scope of the claims is not limited to the particular implementations disclosed, but that modifications and other implementations are intended to be included within the scope of the appended claims.

Claims

1. 1. A method for decoding a video signal, comprising: receiving a picture frame from the video signal, the picture frame including a first component and a second component in a first color space; determining a classifier for the second component in the first color space from one or more samples of a first set of the first component associated with a respective sample of the second component in the first color space, wherein the first set of one or more samples is transformed to a second color space; determining sample offsets for the respective samples of the second component in the first color space according to the classifier; and modifying values ​​of the respective samples of the second component in the first color space based on the determined sample offsets.

2. the first component is a component selected from the group consisting of a luma component, a first chroma component, and a second chroma component; the second component is a component selected from the group consisting of the luma component, the first chroma component, and the second chroma component; The method of claim 1.

3. The method of claim 1 , wherein one or more samples of the first set are transformed from the first color space to the second color space using a linear transformation.

4. The linear transformation is O １ =a7I １ +b×I ２ + × I ３ O ２ =d×I １ +exI ２ +f×I ３ O ３ =g×I １ +h×I ２ + × I ３ where a, b, c, d, e, f, g, h, and i are predetermined constants, and I １ , I ２ , I ３ are in the first color space and are values ​​of samples of the first component, the second component, and the third component, respectively; １ , O ２ , O ３ 4. The method of claim 3, wherein x, y ...

5. The method of claim 1 , wherein the first color space is a YUV color space and the second color space is an RGB color space.

6. The method of claim 1 , wherein the first color space is an RGB color space and the second color space is a YUV color space.

7. The method of claim 1 , wherein one or more samples of the first set are transformed from the first color space to the second color space using a nonlinear transformation.

8. 2. The method of claim 1 , wherein determining the classifier further comprises determining the classifier for the second component in the first color space from a second set of one or more samples of the second component associated with the respective sample of the second component, wherein the one or more samples of the second set are located in the first color space or transformed into the second color space.

9. 9. The method of claim 8, wherein the picture frame further includes a third component, and wherein determining the classifier further includes determining the classifier for the second component in the first color space from one or more samples of a third set of the third component associated with the respective samples of the second component, the third component being a second chroma component, and one or more samples of the third set being located in the first color space or transformed into the second color space.

10. 9. The method of claim 8, wherein the classifier is determined by at least one of a first sub-classifier and / or a second sub-classifier, wherein the first sub-classifier is determined by dividing a first dynamic range of values ​​of one or more samples of the first set of the first component into a first number of bands and selecting bands based on intensity values ​​of one or more samples of the first set of the first component, and the second sub-classifier is determined based on direction and intensity of edge information of a first sub-group of one or more samples of the second set of the second component.

11. 2. The method of claim 1, wherein the first component is a first chroma component and the second component is a luma component, and wherein one or more samples of the first set of the first component associated with the respective sample of the second component are selected from one or more of co-located and adjacent samples of the first component with respect to the respective sample of the second component.

12. 9. The method of claim 8, wherein one or more samples of the second set of second components associated with the respective sample of the second component are selected from one or more of a current sample and adjacent samples of the second component relative to the respective sample of the second component.

13. The method of claim 1, wherein the picture frame further includes a third component, and determining the classifier further includes determining the classifier for the second component in the first color space from one or more samples of a fourth set of one or more of the first, second, and third components associated with the respective samples of the second component, and wherein one or more samples of the fourth set are located in the first color space or transformed into the second color space.

14. determining the classifier further comprises determining the classifier for the second component in the first color space from previous encoding information of one or more samples of the fourth set; 14. The method of claim 13, wherein the coding information includes at least one or more of picture order count (POC) information, component information, offset information, prediction information, transform information, quantization information, residual coding information, luma mapping with chroma scaling (LMCS) information, deblocking information, sample adaptive offset (SAO) information, adaptive in-loop filter (ALF) information, or offset number information.

15. Determining the classifier comprises: ClassIdx=Index2ClassTable(f(C,P1)+f(C,P2)+...+f(C,P8)) 14. The method of claim 13, further comprising determining f(x, y) as: where C is a value of the current sample or the co-located sample, P1, P2, ... P8 are values ​​of the neighboring samples, Index2ClassTable is a predefined table of index classes, th is a threshold, and if x - y > th, f(x, y) = 1, if x - y = th, f(x, y) = 0, and if x - y < th, f(x, y) = -1.

16. one or more processing units; a memory coupled to the one or more processing units; a plurality of programs stored in the memory, the plurality of programs, when executed by the one or more processing units, causing the electronic device to perform the method of any one of claims 1 to 15. electronic equipment.

17. 16. A non-transitory computer-readable storage medium storing a plurality of programs for execution by an electronic device having one or more processing units, the plurality of programs, when executed by the one or more processing units, causing the electronic device to perform the method of any one of claims 1 to 15.

18. 16. A computer program comprising instructions for execution by an electronic device having one or more processing units, the instructions, when executed by the one or more processing units, causing the electronic device to perform the method of any one of claims 1 to 15.

19. 1. A method for transmitting a bitstream, comprising: performing an encoding method to generate a bitstream; transmitting the bitstream to a decoding device; The encoding method comprises: determining a picture frame including a first component and a second component in a first color space; determining a classifier for the second component in the first color space from one or more samples of a first set of first components associated with respective samples of the second component in the first color space, wherein the first set of one or more samples is transformed to a second color space; determining sample offsets for the respective samples of the second component in the first color space according to the classifier; modifying values ​​of the respective samples of the second component in the first color space based on the determined sample offsets.

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