Method and apparatus for video coding and decoding

Abstract

An electronic device performs a method of decoding video data, including: receiving video data corresponding to a coding unit from a bitstream, where the coding unit is encoded in an inter prediction mode or an intra block copy mode; receiving a first syntax element from the video data, where the first syntax element indicates whether the coding unit has any non-zero residual; in accordance with a determination that the first syntax element has a non-zero value: receiving a second syntax element from the video data, where the second syntax element indicates whether the coding unit has been encoded using an adaptive color space transform (ACT); in accordance with a determination that the first syntax element has a zero value: assigning the zero value to the second syntax element; and determining whether to perform inverse ACT on the video data of the coding unit according to the value of the second syntax element.

Description

[0001] This application is a divisional application of patent application No. 202080050545.7, filed on September 23, 2020, entitled "Method and apparatus for video encoding and decoding in 4:4:4 chroma format". Related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 904,539, filed on September 23, 2019, entitled “METHODS AND APPARATUS OF VIDEO CODING IN 4:4:4 CHROMA FORMAT”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] In summary, this application relates to video data encoding, decoding, and compression, and more specifically, to methods and systems for improving the efficiency of video encoding and decoding. Background Technology

[0004] Digital video is supported by a variety of electronic devices, such as digital televisions, laptops or desktop computers, tablets, digital cameras, digital recording devices, digital media players, video game consoles, smartphones, video conferencing equipment, and video streaming devices. Electronic devices transmit, receive, encode, decode, and / or store digital video data by implementing video compression / decompression standards defined by: MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 (Part 10, Advanced Video Codec (AVC)), High Efficiency Video Codec (HEVC), and Universal Video Codec (VCC) standards. Video compression typically involves performing spatial (intra-frame) prediction and / or temporal (inter-frame) prediction to reduce or remove redundancy inherent in the video data. For block-based video codecs, video frames are divided into one or more stripes, each strip containing multiple video blocks, which may also be referred to as coding tree units (CTUs). Each CTU may contain one coding unit (CU), or be recursively split into smaller CUs until a predefined minimum CU size is reached. Each CU (also known as a leaf CU) contains one or more transform units (TUs), and each CU also contains one or more prediction units (PUs). Each CU can be encoded and decoded in intra-frame, inter-frame, or IBC modes. Video blocks in an intra-coded (I) strip of a video frame are encoded using spatial prediction relative to reference samples in adjacent blocks within the same video frame. Video blocks in an inter-coded (P or B) strip of a video frame can use spatial prediction relative to reference samples in adjacent blocks within the same video frame, or temporal prediction relative to reference samples in other previous and / or future reference video frames.

[0005] A prediction block for the current video block to be encoded is generated based on spatial or temporal predictions of previously encoded reference blocks (e.g., neighboring blocks). The process of finding reference blocks can be accomplished using a block-matching algorithm. The residual data representing the pixel difference between the current block to be encoded and the prediction block is called the residual block or prediction error. Inter-frame encoded blocks are encoded based on motion vectors pointing to reference blocks in the reference frames that form the prediction blocks, and the residual block. The process of determining motion vectors is often referred to as motion estimation. Intra-frame encoded blocks are encoded based on intra-frame prediction modes and the residual block. For further compression, the residual block is transformed from the pixel domain to the transform domain (e.g., the frequency domain), resulting in residual transform coefficients, which can then be quantized. The quantized transform coefficients, initially arranged in a two-dimensional array, can be scanned to produce a one-dimensional vector of transform coefficients, and then entropy-encoded into the video bitstream for even more 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 with digital video capabilities or transmitted directly to that device via wired or wireless means. The electronic device then performs video decompression (the reverse of the video compression process described above) by, for example, parsing the encoded video bitstream to obtain syntax elements from the bitstream and reconstructing the digital video data from the encoded video bitstream to its original format based at least in part on the syntax elements obtained from the bitstream, and presents the reconstructed digital video data on the display of the electronic device.

[0007] As digital video quality progresses from high definition to 4Kx2K or even 8Kx4K, the amount of video data to be encoded / decoded grows exponentially. Maintaining the image quality of decoded video data while encoding / decoding it more efficiently remains an ongoing challenge.

[0008] Some video content (e.g., screen content video) is encoded in a 4:4:4 chroma format, in which all three components (luminance component and two chroma components) have the same resolution. While the 4:4:4 chroma format includes more redundancy compared to the 4:2:0 and 4:2:2 chroma formats (which is detrimental to achieving good compression efficiency), it remains the preferred encoding format for many applications where high fidelity is required to preserve color information (such as sharp edges) in the decoded video. Given the redundancy present in 4:4:4 chroma format video, there is evidence that significant encoding and decoding improvements can be achieved by leveraging the correlations between the three color components of 4:4:4 video (e.g., Y, Cb, and Cr in the YCbCr domain; or G, B, and R in the RGB domain). Due to these correlations, the Adaptive Color Space Transformation (ACT) tool was employed during the development of the HEVC Screen Content Codec (SCC) extension to utilize the correlations between the three color components. Summary of the Invention

[0009] This application describes implementations related to video data encoding and decoding, and more specifically relates to systems and methods for improving the encoding and decoding efficiency of videos encoded in a specific chroma format.

[0010] According to a first aspect of this application, a method for decoding video data includes: receiving video data corresponding to a coding unit from a bitstream, wherein the coding unit is encoded in an inter-frame prediction mode or an intra-frame block copy mode; receiving a first syntax element from the video data, wherein the first syntax element indicates whether the coding unit has any non-zero residual; based on a determination that the first syntax element has a non-zero value: receiving a second syntax element from the video data, wherein the second syntax element indicates whether the coding unit has been encoded using an adaptive color space transformation (ACT); based on a determination that the first syntax element has a zero value: assigning the zero value to the second syntax element; and determining, based on the value of the second syntax element, whether to perform inverse ACT on the video data of the coding unit.

[0011] According to a second aspect of this application, an electronic device includes: one or more processing units; a memory; and a plurality of programs stored in the memory. When executed by the one or more processing units, the programs cause the electronic device to perform the method for decoding video data as described above.

[0012] According to a third aspect of this 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. When executed by the one or more processing units, the programs cause the electronic device to perform a method for decoding video data as described above.

[0013] According to a fourth aspect of this application, a method for encoding a coding unit within a video frame includes: performing inter-frame prediction or intra-frame block copy prediction on the coding unit; determining a value of a first syntax element, wherein the first syntax element indicates whether residual data exists for the coding unit, wherein the residual data has a transform tree structure; and determining a value of a second syntax element, wherein the second syntax element is used to indicate whether an adaptive color space transformation (ACT) has been applied to the coding unit if the first syntax element has a non-zero value.

[0014] According to a fifth aspect of this application, an electronic device includes: one or more processing units; a memory coupled to the one or more processing units; and a plurality of programs stored in the memory. When executed by the one or more processing units, the plurality of programs cause the electronic device to perform the method described above for encoding coding units within a video frame.

[0015] According to a sixth aspect of this application, a non-transitory computer-readable storage medium is provided for storing a plurality of programs for execution by an electronic device having one or more processing units, wherein the plurality of programs, when executed by the one or more processing units, cause the electronic device to perform a method as described above for encoding coding units within a video frame to generate a bitstream of encoded coding units within the video frame to be transmitted. Attached Figure Description

[0016] The accompanying drawings illustrate the described implementation and, together with the description, serve to explain the underlying principles. The drawings are included to provide a further understanding of the implementation and are incorporated herein by reference and form part of the specification. Similar reference numerals denote corresponding parts.

[0017] Figure 1 This is a block diagram illustrating an exemplary video encoding and decoding system according to some implementations of the present disclosure.

[0018] Figure 2 This is a block diagram illustrating an exemplary video encoder according to some implementations of this disclosure.

[0019] Figure 3 This is a block diagram illustrating an exemplary video decoder according to some implementations of this disclosure.

[0020] Figures 4A to 4EThis is a block diagram illustrating how, according to some implementations of this disclosure, a frame is recursively divided into multiple video blocks of different sizes and shapes.

[0021] Figures 5A to 5B This is a block diagram illustrating an example of applying adaptive color space transformation (ACT) techniques, according to some implementations of this disclosure, to transform the residual between the RGB color space and the YCgCo color space.

[0022] Figure 6 This is a block diagram illustrating a technique for applying luminance mapping with chroma scaling (LMCS) during exemplary video data decoding, based on some implementations of this disclosure.

[0023] Figure 7 This is a block diagram illustrating an exemplary video decoding process according to some implementations of the present disclosure, through which the video decoder implements the technique of inverse adaptive color space transformation (ACT).

[0024] Figure 8 This is a flowchart illustrating an exemplary process of some implementations of the present disclosure, in which a video decoder decodes video data by conditionally performing an inverse adaptive color space transformation. Detailed Implementation

[0025] Reference will now be made 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 can be implemented on many types of electronic devices with digital video capabilities.

[0026] Figure 1 This is a block diagram illustrating an exemplary system 10 for encoding and decoding video blocks in parallel, according to some implementations of this disclosure. Figure 1 As shown, system 10 includes a source device 12 that generates and encodes video data to be decoded by a destination device 14 at a later time. The source device 12 and destination device 14 can include any of a variety of electronic devices, including desktop or laptop computers, tablet computers, smartphones, set-top boxes, digital televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, etc. In some implementations, the source device 12 and destination device 14 are equipped with wireless communication capabilities.

[0027] In some implementations, destination device 14 may receive encoded video data to be decoded via link 16. Link 16 may include 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 include a communication medium enabling source device 12 to send encoded video data directly to destination device 14 in real time. The encoded video data may be modulated according to communication standards, such as wireless communication protocols, and sent to destination device 14. The communication medium may include any wireless or wired communication medium, such as 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 such as the Internet. The communication medium may include a router, switch, base station, or any other device that may be used to facilitate communication from source device 12 to destination device 14.

[0028] In some other implementations, encoded video data can be sent from output interface 22 to storage device 32. Destination device 14 can then access the encoded video data in storage device 32 via input interface 28. Storage device 32 can include any of a variety of distributed or locally accessed data storage media, such as hard disk drives, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data. In another example, storage device 32 can correspond to a file server or another intermediate storage device that can hold the encoded video data generated by source device 12. Destination device 14 can access the stored video data from storage device 32 via streaming or downloading. The file server can be any type of computer capable of storing and sending encoded video data to destination device 14. Exemplary file servers include web servers (e.g., for websites), FTP servers, network attached storage (NAS) devices, or local disk drives. Destination device 14 can access the encoded video data via any standard data connection, including wireless channels (e.g., Wi-Fi connections), wired connections (e.g., DSL, cable modems, etc.), or combinations thereof, suitable for accessing encoded video data stored on a file server. Transmission of the encoded video data from storage device 32 can be streaming, downloading, or a combination of both.

[0029] like Figure 1As shown, source device 12 includes a video source 18, a video encoder 20, and an output interface 22. Video source 18 may include sources such as video capture devices (e.g., cameras), video archives containing previously captured video, video feed interfaces for receiving video from video content providers, and / or computer graphics systems for generating computer graphics data as source video, or combinations of such sources. As an example, if video source 18 is a camera in a security surveillance system, source device 12 and destination device 14 may form a camera phone or video phone. However, the implementation described in this application is generally applicable to video encoding and decoding and can be applied to wireless and / or wired applications.

[0030] Captured, pre-captured, or computer-generated video can be encoded by video encoder 20. The encoded video data can be sent directly to destination device 14 via output interface 22 of source device 12. The encoded video data can 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 also include a modem and / or transmitter.

[0031] 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 receives encoded video data via link 16. The encoded video data transmitted via 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 in encoded video data transmitted on a communication medium, stored on a storage medium, or stored on a file server.

[0032] In some implementations, destination device 14 may include 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 decoded video data to a user and may include 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.

[0033] Video encoder 20 and video decoder 30 can operate according to proprietary or industry standards, such as VVC, HEVC, MPEG-4 Part 10, Advanced Video Codec (AVC), or extensions of such standards. It should be understood that this application is not limited to any particular video encoding / decoding standard and can be applied to other video encoding / decoding standards. It is generally contemplated that the video encoder 20 of source device 12 can be configured to encode video data according to any of these current or future standards. Similarly, it is generally contemplated that the video decoder 30 of destination device 14 can be configured to decode video data according to any of these current or future standards.

[0034] The video encoder 20 and video decoder 30 can 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 in part in software, the electronic device may store instructions for the software in a suitable non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the video encoding / decoding operations disclosed in this disclosure. Each of the video encoder 20 and video decoder 30 may be included in one or more encoders or decoders, either of which may be integrated into the respective device as part of a combined encoder / decoder (CODEC).

[0035] Figure 2 This is a block diagram illustrating an exemplary video encoder 20 according to some implementations described in this disclosure. The video encoder 20 can perform intra-frame and inter-frame predictive coding of video blocks within a video frame. Intra-frame predictive coding relies on spatial prediction to reduce or remove spatial redundancy in the video data within a given video frame or picture. Inter-frame predictive coding relies on temporal prediction to reduce or remove temporal redundancy in the video data within neighboring video frames or pictures of a video sequence.

[0036] like Figure 2As shown, the video encoder 20 includes a video data memory 40, a prediction processing unit 41, a decoded picture buffer (DPB) 64, a summer 50, a transform processing unit 52, a quantization unit 54, and an entropy coding unit 56. The prediction processing unit 41 further includes a motion estimation unit 42, a motion compensation unit 44, a segmentation unit 45, an intra-frame prediction processing unit 46, and an intra-frame block copy (BC) unit 48. In some implementations, the video encoder 20 also includes an inverse quantization unit 58, an inverse transform processing unit 60, and a summer 62 for video block reconstruction. A deblocking filter (not shown) may be located between the summer 62 and the DPB 64 to filter block boundaries, thereby removing block artifacts from the reconstructed video. In addition to the deblocking filter, a loop filter (not shown) may be used to filter the output of the summer 62. The video encoder 20 may take the form of fixed or programmable hardware units, or may be partitioned among one or more of the fixed or programmable hardware units shown.

[0037] Video data memory 40 can store video data to be encoded by components of video encoder 20. The video data in video data memory 40 can be obtained, for example, from video source 18. DPB 64 is a buffer that stores reference video data for use when the video data is encoded by video encoder 20 (e.g., in intra-frame or inter-frame predictive coding modes). Video data memory 40 and DPB 64 can be formed from any of a variety of memory devices. In various examples, video data memory 40 can be on-chip with other components of video encoder 20, or off-chip relative to those components.

[0038] like Figure 2 As shown, after receiving video data, the segmentation unit 45 within the prediction processing unit 41 segments the video data into video blocks. This segmentation may also include segmenting the video frame into stripes, tiles, or other larger coding units (CUs) according to a predefined splitting structure associated with the video data (such as a quadtree structure). The video frame may be divided into multiple video blocks (or a set of video blocks referred to as tiles). The prediction processing unit 41 may select one of several possible predictive coding modes for the current video block based on error results (e.g., coding rate and distortion level), such as one of several intra-frame predictive coding modes or one of several inter-frame predictive coding modes. The prediction processing unit 41 may provide the resulting intra-frame or inter-frame predictive coded block to the summer 50 to generate a residual block, and to the summer 62 to reconstruct the encoded block for subsequent use as part of a reference frame. The prediction processing unit 41 also provides syntax elements, such as motion vectors, intra-frame mode indicators, partitioning information, and other such syntax information, to the entropy coding unit 56.

[0039] To select an appropriate intra-predictive coding mode for the current video block, the intra-predictive processing unit 46 within the 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 encoded to provide spatial prediction. The motion estimation unit 42 and motion compensation unit 44 within the prediction processing unit 41 perform inter-predictive coding of the current video block relative to one or more prediction blocks in one or more reference frames to provide temporal prediction. The video encoder 20 may execute multiple coding channels, for example, to select an appropriate coding mode for each block of video data.

[0040] In some implementations, motion estimation unit 42 determines the inter-frame prediction pattern for the current video frame by generating motion vectors based on a predetermined pattern within the video frame sequence. These motion vectors indicate the displacement of the prediction unit (PU) of a video block within the current video frame relative to a prediction block within a reference video frame. Motion estimation performed by motion estimation unit 42 is the process of generating motion vectors that estimate the motion of the video block. For example, the motion vectors may indicate the displacement of the PU of a video block within the current video frame or picture relative to a prediction block within a reference frame (or other coding unit) associated with the current block being encoded within the current frame (or other coding unit). The predetermined pattern may designate video frames in the sequence as P-frames or B-frames. Intra-frame BC unit 48 may determine vectors (such as block vectors) for intra-frame BC coding in a manner similar to how motion estimation unit 42 determines the motion vectors for inter-frame prediction, or it may utilize motion estimation unit 42 to determine the block vectors.

[0041] The prediction block is a block of the reference frame that is considered to be a close match to the PU of the video block to be encoded in terms of pixel differences, which can be determined by the sum of absolute differences (SAD), sum of squared differences (SSD), or other difference metrics. In some implementations, the video encoder 20 can compute the values ​​of sub-integer pixel positions of the reference frame stored in the DPB 64. For example, the video encoder 20 can interpolate the values ​​of quarter-pixel positions, eighth-pixel positions, or other fractional pixel positions of the reference frame. Therefore, the motion estimation unit 42 can perform motion search relative to full-pixel positions and fractional pixel positions and output motion vectors with fractional-pixel precision.

[0042] The motion estimation unit 42 calculates the motion vector of the PU in the inter-frame predictive coding frame by comparing the position of the PU with the position of the prediction block of a reference frame selected from the first reference frame list (list 0) or the second reference frame list (list 1). Each of the first or second reference frame lists identifies one or more reference frames stored in the DPB 64. The motion estimation unit 42 sends the calculated motion vector to the motion compensation unit 44, and then to the entropy coding unit 56.

[0043] Motion compensation performed by motion compensation unit 44 may involve obtaining or generating prediction blocks based on motion vectors determined by motion estimation unit 42. Upon receiving motion vectors from the PU for the current video block, motion compensation unit 44 may locate the prediction block pointed to by the motion vector in one of the reference frame lists, retrieve the prediction block from DPB 64, and forward the prediction block to summer 50. Summer 50 then forms a residual video block of pixel differences by subtracting the pixel values ​​of the prediction block provided by motion compensation unit 44 from the pixel values ​​of the current video block being encoded. The pixel differences forming the residual video block may include a luminance difference component or a chrominance difference component, or both. Motion compensation unit 44 may also generate syntax elements associated with video blocks of a video frame for use by video decoder 30 when decoding video blocks of a video frame. Syntax elements may include, for example, syntax elements defining motion vectors for identifying prediction blocks, any flags indicating prediction modes, 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.

[0044] In some implementations, the intra-BC unit 48 can generate vectors and obtain prediction blocks in a manner similar to that described above in conjunction with the motion estimation unit 42 and the motion compensation unit 44, but where the prediction blocks are in the same frame as the current block being encoded, and where the vector is referred to as the block vector in contrast to the motion vector. Specifically, the intra-BC unit 48 can determine the intra-prediction mode to be used for encoding the current block. In some examples, the intra-BC unit 48 can encode the current block using various intra-prediction modes (e.g., during separate encoding channels) and test their performance through rate-distortion analysis. Next, the intra-BC unit 48 can select the appropriate intra-prediction mode to use from the various tested intra-prediction modes and generate an intra-mode indicator accordingly. For example, the intra-BC unit 48 can use rate-distortion analysis for various tested intra-prediction modes to calculate rate-distortion values ​​and select the intra-prediction mode with the best rate-distortion characteristics from the tested modes as the appropriate intra-prediction mode to use. Rate-distortion analysis typically determines the amount of distortion (or error) between an encoded block and the original uncoded block (which is encoded to produce the encoded block), as well as the bit rate (i.e., the number of bits) used to produce the encoded block. Intra-frame BC unit 48 can calculate the ratio based on the distortion and rate for various encoded blocks to determine which intra-frame prediction mode exhibits the optimal rate-distortion value for that block.

[0045] In other examples, intra-BC unit 48 may use, in whole or in part, motion estimation unit 42 and motion compensation unit 44 to perform such functions for intra-BC prediction according to the implementation described herein. In either case, for intra-block copying, the predicted block may be a block that is considered to closely match the block to be encoded in terms of pixel differences, which may be determined by sum of absolute differences (SAD), sum of squared differences (SSD), or other difference metrics, and the identification of the predicted block may include calculating values ​​for sub-integer pixel positions.

[0046] Regardless of whether the predicted block comes from the same frame predicted intra-frame or from different frames predicted inter-frame, the video encoder 20 can form a residual video block by subtracting the pixel values ​​of the predicted block from the pixel values ​​of the current video block being encoded, thus forming a pixel difference. The pixel difference forming the residual video block can include both luma component difference and chroma component difference.

[0047] Intra-prediction processing unit 46 can perform intra-prediction on the current video block as an alternative to inter-prediction performed by motion estimation unit 42 and motion compensation unit 44, or intra-block copy prediction performed by intra-BC unit 48, as described above. Specifically, intra-prediction processing unit 46 can determine the intra-prediction mode to be used for encoding the current block. To this end, intra-prediction processing unit 46 can encode the current block using various intra-prediction modes (e.g., during a separate encoding channel), and intra-prediction processing unit 46 (or mode selection unit in some examples) can select the appropriate intra-prediction mode to use from the tested intra-prediction modes. Intra-prediction processing unit 46 can provide information to entropy coding unit 56 indicating the intra-prediction mode selected for the block. Entropy coding unit 56 can encode the information indicating the selected intra-prediction mode into the bitstream.

[0048] After prediction processing unit 41 determines the prediction block for the current video block via inter-frame prediction or intra-frame prediction, summer 50 forms a residual video block by subtracting the prediction 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 uses a transform (such as discrete cosine transform (DCT) or a conceptually similar transform) to transform the residual video data into residual transform coefficients.

[0049] The transform processing unit 52 can send the obtained transform coefficients to the quantization unit 54. The quantization unit 54 quantizes the transform coefficients to further reduce the bit rate. The quantization process can also reduce the bit depth associated with some or all of the coefficients. The degree of quantization can be modified by adjusting the quantization parameters. In some examples, the quantization unit 54 can then perform a scan of the matrix that includes the quantized transform coefficients. Alternatively, the entropy coding unit 56 can perform the scan.

[0050] After quantization, entropy coding unit 56 uses, for example, context-adaptive variable-length codec (CAVLC), context-adaptive binary arithmetic codec (CABAC), syntax-based context-adaptive binary arithmetic codec (SBAC), probabilistic interval partitioned entropy (PIPE) codec, or other entropy coding methods or techniques to entropy encode the quantized transform coefficients into the video bitstream. The encoded bitstream can then be sent to video decoder 30, or archived in storage device 32 for later transmission to or retrieval by video decoder 30. Entropy coding unit 56 can also entropy encode the motion vectors and other syntax elements used for the current video frame being encoded.

[0051] The inverse quantization unit 58 and the inverse transform processing unit 60 apply inverse quantization and inverse transform, respectively, to reconstruct the residual video block in the pixel domain to generate a reference block for predicting other video blocks. As described above, the motion compensation unit 44 can generate motion-compensated prediction blocks from one or more reference blocks of the frame stored in the DPB 64. The motion compensation unit 44 can also apply one or more interpolation filters to the prediction block to calculate sub-integer pixel values ​​for use in motion estimation.

[0052] The summer 62 adds the reconstructed residual block to the motion-compensated prediction block generated by the motion compensation unit 44 to produce a reference block for storage in the DPB 64. The reference block can then be used as a prediction block by the intra-frame BC unit 48, the motion estimation unit 42, and the motion compensation unit 44 for inter-frame prediction of another video block in subsequent video frames.

[0053] Figure 3 This is a block diagram illustrating an exemplary video decoder 30 according to some implementations of this 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, a summer 90, and a DPB 92. The prediction processing unit 81 further includes a motion compensation unit 82, an intra-frame prediction processing unit 84, and an intra-frame prediction (BC) unit 85. The video decoder 30 can perform tasks generally combined with the above. Figure 2 The decoding process is the opposite of the encoding process described for video encoder 20. For example, motion compensation unit 82 can generate prediction data based on motion vectors received from entropy decoding unit 80, while intra-frame prediction unit 84 can generate prediction data based on intra-frame prediction mode indicators received from entropy decoding unit 80.

[0054] In some examples, a unit of the video decoder 30 may be assigned to perform the task of implementing the present application. Furthermore, in some examples, the implementation of the present disclosure may be divided among one or more units of the video decoder 30. For example, the intra-frame BC unit 85 may perform the implementation of the present application independently, or in combination with other units of the video decoder 30 (such as the motion compensation unit 82, the intra-frame prediction processing unit 84, and the entropy decoding unit 80). In some examples, the video decoder 30 may not include the intra-frame BC unit 85, and the functionality of the intra-frame BC unit 85 may be performed by other components of the prediction processing unit 81 (such as the motion compensation unit 82).

[0055] Video data memory 79 may store video data, such as encoded video bitstreams, to be decoded by other components of video decoder 30. The video data stored in video data memory 79 may be obtained from storage device 32, or from a local video source (such as a camera), for example, via wired or wireless network communication of video data, or by accessing a physical data storage medium (e.g., a flash drive or hard disk). Video data memory 79 may include an encoded picture buffer (CPB) that stores encoded video data from the encoded video bitstream. Decoded picture buffer (DPB) 92 of video decoder 30 stores reference video data for use by video decoder 30 when decoding video data (e.g., in intra-frame predictive coding mode or inter-frame predictive coding mode). Video data memory 79 and DPB 92 may be formed of 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... Figure 3 The video data memory 79 and DPB 92 are depicted as two distinct components of the video decoder 30. However, it will be apparent to those skilled in the art that the video data memory 79 and DPB 92 may be provided by the same memory device or separate memory devices. In some examples, the video data memory 79 may be on-chip with other components of the video decoder 30, or off-chip relative to those components.

[0056] During the decoding process, the video decoder 30 receives an encoded video bitstream representing video blocks of encoded video frames and associated syntax elements. The video decoder 30 may receive syntax elements at the video frame level and / or the video block level. The entropy decoding unit 80 of the video decoder 30 performs entropy decoding on the bitstream to generate quantization coefficients, motion vectors or intra-frame prediction mode indicators, and other syntax elements. The entropy decoding unit 80 then forwards the motion vectors and other syntax elements to the prediction processing unit 81.

[0057] When a video frame is encoded as an intra-predictive coded (I) frame or for intra-coded prediction blocks in other types of frames, the intra-predictive processing unit 84 of the prediction processing unit 81 can generate prediction data for the video block of the current video frame based on the intra-predictive mode notified by a signal and reference data from previously decoded blocks of the current frame.

[0058] When a video frame is encoded as an inter-frame predictive coded (i.e., B or P) frame, the motion compensation unit 82 of the prediction processing unit 81 generates one or more prediction blocks for the video block of the current video frame based on the motion vectors and other syntax elements received from the entropy decoding unit 80. Each of the prediction blocks can be generated from reference frames within one of the reference frame lists. The video decoder 30 can construct the reference frame list (list 0 and list 1) using the default construction technique based on the reference frames stored in the DPB 92.

[0059] In some examples, when a video block is encoded according to the intra-BC mode described herein, the intra-BC unit 85 of the prediction processing unit 81 generates a prediction block for the current video block based on the block vector and other syntax elements received from the entropy decoding unit 80. The prediction block can be located within a reconstructed region of the same image as the current video block defined by the video encoder 20.

[0060] Motion compensation unit 82 and / or intra-frame BC unit 85 determine prediction information for video blocks in the current video frame by parsing motion vectors and other syntax elements, and then use this prediction information to generate prediction blocks 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-frame or inter-frame prediction) for decoding video blocks in the video frame, the inter-frame prediction frame type (e.g., B or P), construction information for one or more reference frame lists for the frame, motion vectors for each inter-frame prediction encoded video block in the frame, the inter-frame prediction state for each inter-frame prediction encoded video block in the frame, and other information for decoding video blocks in the current video frame.

[0061] Similarly, the intra-BC unit 85 can use some of the syntax elements (e.g., flags) among the received syntax elements to determine whether the current video block was predicted using the intra-BC mode, which video blocks of the frame are in the reconstructed region and should be stored in the DPB 92, the block vector for each intra-BC predicted video block of the frame, the intra-BC prediction state for each intra-BC predicted video block of the frame, and other information for decoding video blocks in the current video frame.

[0062] The motion compensation unit 82 can also perform interpolation using an interpolation filter, such as that used by the video encoder 20 during the encoding of video blocks, to calculate the interpolated values ​​for sub-integer pixels of the reference block. In this case, the motion compensation unit 82 can determine the interpolation filter used by the video encoder 20 from the received syntax elements and use the interpolation filter to generate the prediction block.

[0063] The inverse quantization unit 86 uses the same quantization parameters calculated by the video encoder 20 for each video block in the video frame to inverse quantize the quantization transform coefficients provided in the bitstream and entropy decoded by the entropy decoding unit 80 to determine the degree of quantization. The inverse transform processing unit 88 applies an inverse transform (e.g., inverse DCT, inverse integer transform, or a conceptually similar inverse transform process) to the transform coefficients to reconstruct the residual block in the pixel domain.

[0064] After the motion compensation unit 82 or the intra-frame BC unit 85 generates a prediction block for the current video block based on vectors and other syntax elements, the summer 90 reconstructs the decoded video block for the current video block by adding the residual block from the inverse transform processing unit 88 to the corresponding prediction block generated by the motion compensation unit 82 and the intra-frame BC unit 85. A loop filter (not shown) may be located between the summer 90 and the DPB 92 to further process the decoded video block. The decoded video block in a given frame is then stored in the DPB 92, which stores a reference frame for subsequent motion compensation for the next video block. The DPB 92 or a separate memory device may also store the decoded video for later display on a display device (such as...). Figure 1 It is displayed on the display device 34).

[0065] In a typical video encoding and decoding process, a video sequence usually consists of an ordered set of frames or images. Each frame may include three sample arrays, denoted as SL, SCb, and SCr. SL is a two-dimensional array of luma samples. SCb is a two-dimensional array of chroma samples (Cb). SCr is a two-dimensional array of chroma samples (Cr). In other instances, a frame may be monochromatic and therefore consist of only a two-dimensional array of luma samples.

[0066] like Figure 4A As shown, the video encoder 20 (or more specifically, the segmentation unit 45) generates a coded representation of a frame by first segmenting the frame into a set of Code Tree Units (CTUs). A video frame may include an integer number of CTUs ordered sequentially 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 the video encoder 20 in a sequence parameter set such that all CTUs in the video sequence have the same size (one of 128×128, 64×64, 32×32, and 16×16). However, it should be noted that this application is not necessarily limited to a specific size. Figure 4BAs shown, each CTU may include a coding tree block (CTB) for luma samples, two corresponding coding tree blocks for chroma samples, and syntax elements for decoding the samples of the coding tree blocks. The syntax elements describe the characteristics of different types of units in the encoded pixel block and how the video sequence is reconstructed at the video decoder 30, including inter-frame or intra-frame prediction, intra-frame prediction mode, motion vectors, and other parameters. In monochrome images or images with three separate color planes, the CTU may include a single coding tree block and syntax elements for decoding the samples of the coding tree block. The coding tree block may be an NxN sample block.

[0067] To achieve better performance, the video encoder 20 can recursively perform tree splitting (such as binary tree splitting, ternary tree splitting, quadtree splitting, or a combination of both) on the coding tree blocks of the CTU, and divide the CTU into smaller coding units (CUs). Figure 4C As depicted, the 64x64 CTU 400 was first divided into four smaller CUs, each with a block size of 32x32. Of these four smaller CUs, CU 410 and CU 420 were each divided into four 16x16 CUs according to their block size. The two 16x16 CUs, 430 and 440, were further divided into four 8x8 CUs according to their block size. Figure 4D A quadtree data structure is described, which shows, as follows: Figure 4C The final result of the CTU 400 partitioning process depicted in the diagram is that each leaf node of the quadtree corresponds to a CU of a corresponding size ranging from 32x32 to 8x8. (Compared to...) Figure 4B Similar to the CTU depicted, each CU can include a coded block (CB) of the same size frame's luma samples and two corresponding coded blocks of chroma samples, as well as syntax elements for decoding the samples of the coded blocks. In monochrome images or images with three separate color planes, the CU can include a single coded block and a syntax structure for decoding the samples of the coded block. It should be noted that in Figure 4C and 4D The quadtree partitioning depicted is for illustrative purposes only, and a CTU can be split into CUs based on quadtree / tritree / binary tree partitioning to accommodate different local characteristics. In multi-type tree structures, a CTU is partitioned by a quadtree structure, and each quadtree leaf CU can be further partitioned by binary and ternary tree structures. Figure 4E As shown, there are five types of segmentation: quadrilateral segmentation, horizontal binary segmentation, vertical binary segmentation, horizontal ternary segmentation, and vertical ternary segmentation.

[0068] In some implementations, the video encoder 20 can also segment the coded blocks of the CU into one or more MxN prediction blocks (PBs). A prediction block is a rectangular (square or non-square) block of samples to which the same prediction (inter-frame or intra-frame) is applied. A prediction unit (PU) of the CU may include a prediction block of luma samples, two corresponding prediction blocks of chroma samples, and syntax elements for predicting the prediction blocks. In a monochrome image or an image with three separate color planes, a PU may include a single prediction block and a syntax structure for predicting the prediction block. The video encoder 20 can generate predicted luma, Cb, and Cr blocks for each PU of the CU.

[0069] Video encoder 20 can use intra-frame prediction or inter-frame prediction to generate prediction blocks for the PU. If video encoder 20 uses intra-frame prediction to generate prediction blocks for the PU, then video encoder 20 can generate prediction blocks for the PU based on decoded samples of the frame associated with the PU. If video encoder 20 uses inter-frame prediction to generate prediction blocks for the PU, then video encoder 20 can generate prediction blocks for the PU based on decoded samples of one or more frames different from the frame associated with the PU.

[0070] After the video encoder 20 generates predicted luminance, Cb, and Cr blocks for one or more PUs of the CU, the video encoder 20 can generate a luminance residual block for the CU by subtracting the predicted luminance block of the CU from its original luminance coding block, such that each sample in the luminance residual block of the CU indicates the difference between a luminance sample in one of the predicted luminance blocks of the CU and a corresponding sample in the original luminance coding block of the CU. Similarly, the video encoder 20 can generate Cb residual blocks and Cr residual blocks for the CU, respectively, such that each sample in the Cb residual block of the CU indicates the difference between a Cb sample in one of the predicted 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 the difference between a Cr sample in one of the predicted Cr blocks of the CU and a corresponding sample in the original Cr coding block of the CU.

[0071] In addition, such as Figure 4CAs shown, the video encoder 20 can use quadtree partitioning to decompose the luminance, Cb, and Cr residual blocks of the CU into one or more luminance, 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 the CU can include a transform block of luminance samples, two corresponding transform blocks of chrominance samples, and syntax elements for transforming the transform block samples. Therefore, each TU of the CU can be associated with a luminance transform block, a Cb transform block, and a Cr transform block. In some examples, the luminance transform block associated with a TU can be a sub-block of the CU's luminance residual block. A Cb transform block can be a sub-block of the CU's Cb residual block. A Cr transform block can be a sub-block of the CU's Cr residual block. In a monochrome image or an image with three separate color planes, a TU can include a single transform block and a syntax structure of samples for transforming the transform block.

[0072] The video encoder 20 can apply one or more transforms to the luminance transform block of the TU to generate a luminance coefficient block for the TU. The coefficient block can be a two-dimensional array of transform coefficients. The transform coefficients can be scalars. The video encoder 20 can apply one or more transforms to the Cb transform block of the TU to generate a Cb coefficient block for the TU. The video encoder 20 can apply one or more transforms to the Cr transform block of the TU to generate a Cr coefficient block for the TU.

[0073] After generating coefficient blocks (e.g., luma coefficient blocks, Cb coefficient blocks, or Cr coefficient blocks), video encoder 20 can quantize the coefficient blocks. Quantization generally refers to the process of quantizing transform coefficients to potentially reduce the amount of data used to represent the transform coefficients, thereby providing further compression. After quantizing the coefficient blocks, video encoder 20 can entropy-encode the syntax elements indicating the quantized transform coefficients. For example, video encoder 20 can perform context-adaptive binary arithmetic coding (CABAC) on the syntax elements indicating the quantized transform coefficients. Finally, video encoder 20 can output a bitstream comprising bit sequences that form representations of encoded frames and associated data, which is either stored in storage device 32 or sent to destination device 14.

[0074] After receiving the bitstream generated by the video encoder 20, the video decoder 30 can parse the bitstream to obtain syntax elements from it. The video decoder 30 can then reconstruct frames of video data, at least in part, based on the syntax elements obtained from the bitstream. The process of reconstructing the video data is generally the reverse of the encoding process performed by the video encoder 20. For example, the video decoder 30 can perform an inverse transform on the coefficient block associated with the TU of the current CU to reconstruct the residual block associated with the TU of the current CU. The video decoder 30 also reconstructs the coded blocks of the current CU by adding the samples of the prediction block for the PU of the current CU to the corresponding samples of the transform block of the TU of the current CU. After reconstructing the coded blocks for each CU of the frame, the video decoder 30 can reconstruct the frame.

[0075] As mentioned above, video encoding and decoding primarily use two modes to achieve video compression: intra-frame prediction and inter-frame prediction. Palette-based encoding and decoding is another encoding and decoding scheme adopted by many video encoding and decoding standards. In palette-based encoding and decoding (which may be particularly suitable for encoding and decoding screen-generated content), the video codec (e.g., video encoder 20 or video decoder 30) forms a palette table representing the colors of a given block of video data. The palette table includes the most important (e.g., frequently used) pixel values ​​in the given block. Pixel values ​​that are not frequently represented in the video data of a given block are not included in the palette table, or are included in the palette table as escape colors.

[0076] Each entry in the palette table includes an index for the corresponding pixel value in the palette table. The palette indexes for samples within a block can be encoded to indicate which entry in the palette table will be used to predict or reconstruct which sample. This palette pattern begins with the process of generating palette predictions for the first block, strip, tile, or other such groupings of a picture. As will be explained below, palette predictions for subsequent video blocks are typically generated by updating previously used palette predictions. For illustrative purposes, it is assumed that palette predictions are defined at the picture level. In other words, a picture may include multiple coded blocks, each with its own palette table, but there is only one palette prediction for the entire picture.

[0077] To reduce the number of bits required to signal palette entries in the video bitstream, the video decoder can utilize palette prediction values ​​to determine new palette entries in the palette table for reconstructing video blocks. For example, palette prediction values ​​can include palette entries from previously used palette tables, or even be initialized to have a recently used palette table by including all entries from the most recently used palette table. In some implementations, palette prediction values ​​can include fewer entries than all entries in the most recently used palette table, and then incorporate some entries from other previously used palette tables. Palette prediction values ​​can have the same size as the palette table used to encode different blocks, or they can be larger or smaller than the palette table used to encode different blocks. In one example, the palette prediction values ​​are implemented as a first-in-first-out (FIFO) table containing 64 palette entries.

[0078] To generate a palette table for video data blocks from palette prediction values, the video decoder can receive a one-bit flag for each entry of the palette prediction values ​​from the encoded video bitstream. The one-bit flag can have a first value (e.g., binary 1) indicating that the associated entry of the palette prediction value will be included in the palette table, or a second value (e.g., binary 0) indicating that the associated entry of the palette prediction value will not be included in the palette table. If the size of the palette prediction values ​​is larger than the palette table for video data blocks, the video decoder can stop receiving more flags once the maximum size for the palette table is reached.

[0079] In some implementations, certain entries in the palette table can be signaled directly in the encoded video bitstream, rather than determined using palette prediction values. For such entries, the video decoder can receive three separate m-bit values ​​from the encoded video bitstream, indicating the pixel values ​​associated with the entry's luminance and two chrominance components, where m represents the bit depth of the video data. Those palette entries derived from palette prediction values ​​require only one bit of flag, compared to the multiple m-bit values ​​needed for directly signaled palette entries. Therefore, using palette prediction values ​​to signal some or all palette entries can significantly reduce the number of bits required to signal entries in the new palette table, thereby improving the overall encoding / decoding efficiency of palette pattern encoding / decoding.

[0080] In many cases, the palette prediction value for a block is determined based on the palette table used to decode one or more previously encoded blocks. However, when encoding the first coding tree unit in a picture, strip, or tile, the palette table for the previously encoded block may be unavailable. Therefore, entries from the previously used palette table cannot be used to generate the palette prediction value. In such cases, the sequence of the palette prediction value initializer can be signaled in the Sequence Parameter Set (SPS) and / or Picture Parameter Set (PPS), which are the values ​​used to generate the palette prediction value when the previously used palette table is unavailable. The SPS typically refers to the syntax structure of syntax elements applicable to a series of consecutive encoded video pictures (referred to as an encoded video sequence (CVS)) as determined by the content of syntax elements found in the PPS, which is referenced by syntax elements in the header of each strip segment. The PPS typically refers to the syntax structure of syntax elements applicable to one or more individual pictures within a CVS as determined by syntax elements in the header of each strip segment. Therefore, SPS is generally considered to be a more advanced syntax structure than PPS, which means that the syntax elements included in SPS are generally less frequently changed compared to those included in PPS, and are applicable to a larger portion of video data.

[0081] Figures 5A to 5B This is a block diagram illustrating an example of applying Adaptive Color Space Transformation (ACT) technology to transform the residual between the RGB color space and the YCgCo color space according to some implementations of this disclosure.

[0082] In the HEVC screen content codec extension, ACT is applied to adaptively transform residuals from one color space (e.g., RGB) to another (e.g., YCgCo), significantly reducing the correlation (e.g., redundancy) between the three color components (e.g., R, G, and B) in the YCgCo color space. Furthermore, in existing ACT designs, a flag is used to signal each TU. tu_act_enabled_flag Adaptation of different color spaces is performed at the Transform Unit (TU) level. When the flag... tu_act_enabled_flag When the value equals 1, it indicates that the residual of the current TU is encoded in the YCgCo space; otherwise (i.e., the flag equals 0), it indicates that the residual of the current TU is encoded in the original color space (i.e., no color space conversion). Furthermore, different color space transformation formulas are applied depending on whether the current TU is encoded in a lossless or lossy mode. Specifically, in Figure 5A Formulas for forward and inverse color space transformation between the RGB and YCgCo color spaces for lossy modes are defined.

[0083] For lossless mode, a reversible version of the RGB-YCgCo transform (also known as YCgCo-LS) is used. The reversible version of the RGB-YCgCo transform is based on... Figure 5B This is achieved through the lifting operations and related descriptions depicted in the text.

[0084] like Figure 5A As shown, the forward and inverse color transformation matrices used in lossy mode are not normalized. Therefore, after applying the color transformation, the amplitude of the YCgCo signal is smaller than the amplitude of the original signal. To compensate for the amplitude reduction caused by the forward color transformation, an adjusted quantization parameter is applied to the residual in the YCgCo domain. Specifically, when applying the color space transformation, the QP value QP used to quantize the YCgCo domain residual is... Y QP Cg and QP Co They are set to QP-5, QP-5, and QP-3 respectively, where QP is the quantization parameter used in the original color space.

[0085] Figure 6 This is a block diagram illustrating the application of a luminance mapping technique with chroma scaling (LMCS) during exemplary video data decoding, based on some implementations of this disclosure.

[0086] In VVC, LMCS is used as a novel encoding / decoding tool preceding loop filters (e.g., deblocking filters, SAO, and ALF). Typically, LMCS has two main modules: 1) Luminance component loop mapping based on an adaptive piecewise linear model; and 2) Luminance-dependent chroma residual scaling. Figure 6 The modified decoding process in which LMCS is applied is shown. Figure 6 In the mapped domain, the decoding modules include an entropy decoding module, an inverse quantization module, an inverse transform module, a luma intra-frame prediction module, and a luma sample reconstruction module (i.e., the sum of luma prediction samples and luma residual samples). In the original (i.e., unmapped) domain, the decoding modules include a motion compensation prediction module, a chroma intra-frame prediction module, a chroma sample reconstruction module (i.e., the sum of chroma prediction samples and chroma residual samples), and all loop filter modules (such as a deblocking module, a SAO module, and an ALF module). New operation modules introduced by LMCS include a luma sample forward mapping module 610, a luma sample inverse mapping module 620, and a chroma residual scaling module 630.

[0087] The loop mapping of LMCS can adjust the dynamic range of the input signal to improve encoding and decoding efficiency. In existing LMCS designs, the loop mapping of luminance samples is established based on two mapping functions: one is the forward mapping function. FwdMap and a corresponding reverse mapping function InvMapThe forward mapping function is signaled from the encoder to the decoder using a piecewise linear model with 16 equally sized segments. The inverse mapping function can be derived directly from the forward mapping function and therefore does not require signaling.

[0088] At the strip level, the parameters of the luminance mapping model are signaled. First, an existence flag is signaled to indicate whether the luminance mapping model will be signaled for the current strip. If a luminance mapping model exists in the current strip, the corresponding piecewise linear model parameters are further signaled. Additionally, at the strip level, another LMCS control flag is signaled to enable / disable the LMCS for that strip.

[0089] The chroma residual scaling module 630 is designed to compensate for the interaction of quantization precision between the luminance signal and its corresponding chroma signal when loop mapping is applied to the luminance signal. A signal in the strip header also indicates whether chroma residual scaling is enabled or disabled for the current strip. If luminance mapping is enabled, an additional flag is signaled to indicate whether luminance-dependent chroma residual scaling is applied. When luminance mapping is not used, luminance-dependent chroma residual scaling is always disabled and no additional flag is required. Furthermore, chroma residual scaling is always disabled for CUs containing four or fewer chroma samples.

[0090] Figure 7 This is a block diagram illustrating an exemplary video decoding process according to some implementations of the present disclosure, through which the video decoder implements the Inverse Adaptive Color Space Transform (ACT) technique.

[0091] Similar to the ACT design in HEVC SCC, ACT in VVC converts the intra / inter-frame prediction residuals of a CU with a 4:4:4 chroma format from the original color space (e.g., RGB color space) to the YCgCo color space. As a result, redundancy between the three color components can be reduced for better encoding and decoding efficiency. Figure 7 A flowchart illustrating how inverse ACT is applied to the decoding process within the VVC framework by adding the inverse ACT module 710 is provided. When processing a CU encoded with ACT enabled, entropy decoding, inverse quantization, and inverse DCT / DST-based transform are first applied to the CU. Following this, as... Figure 7 As described, the inverse ACT is invoked to convert the decoded residual from the YCgCo color space to the original color space (e.g., RGB and YCbCr). Furthermore, since the ACT in lossy mode is not normalized, a QP adjustment of (-5, -5, -3) is applied to the Y, Cg, and Co components to compensate for the magnitude of the variation in the transformed residual.

[0092] In some embodiments, the ACT method reuses the same ACT core transform of HEVC to perform color conversion between different color spaces. Specifically, depending on whether the current CU is encoded in a lossy or lossless manner, two different versions of the color transform are applied. For the lossy case, the forward and inverse color transforms use an irreversible YCgCo transform matrix, such as... Figure 5A As described in [the text]. For the non-destructive case, the application is as follows: Figure 5B The reversible color transformation YCgCo-LS is shown in the figure. Furthermore, unlike existing ACT designs, the proposed ACT scheme introduces the following changes to handle its interaction with other codec tools in the VVC standard.

[0093] For example, since the residual of a CU in HEVC can be divided into multiple TUs, the ACT control flag is individually signaled for each TU to indicate whether color space conversion needs to be applied. However, as described above... Figure 4E As described, a quadtree with nested binary and ternary partitioning structures is applied in VVC to replace the multi-partition type concept, thereby removing the separate CU, PU, ​​and TU partitions in HEVC. This means that, in most cases, a CU leaf node is also used as a unit for prediction and transform processing without further partitioning, unless the maximum supported transform size is smaller than the width or height of a component of the CU. Based on this partitioning structure, this disclosure proposes adaptively enabling and disabling ACT at the CU level. Specifically, a flag is signaled for each CU. cu_act_enabled_flag This flag allows selection between the original color space and the YCgCo color space to decode the residuals of the CU. If the flag is equal to 1, it indicates that the residuals of all TUs within the CU are encoded in the YCgCo color space. Otherwise, if the flag... cu_act_enabled_flag If the value is 0, then all residuals of the CU are encoded in the original color space.

[0094] Figure 8 This is a flowchart 800 illustrating an exemplary process according to some implementations of the present disclosure, through which a video decoder decodes video data by conditionally performing an inverse adaptive color space transformation (ACT) technique.

[0095] As in Figure 5A and Figure 5B As described, when the current CU contains at least one non-zero coefficient, the ACT can only affect the decoded residual. If all coefficients obtained from entropy decoding are zero, the reconstructed residual remains zero with or without the application of the inverse ACT. For inter-frame mode and intra-block copy (IBC) mode, information about whether a CU contains non-zero coefficients is obtained from the CU root coding block flag (CBF) (i.e., cu_cbfThe flag is indicated by a CBF flag. When the flag is equal to 1, it means that a residual syntax element for the current CU exists in the video bitstream. Otherwise (i.e., the flag is equal to 0), it means that the residual syntax element of the current CU will not be signaled or indicated differently in the video bitstream, and all residuals of the CU are inferred to be zero. Therefore, in some embodiments, it is proposed to only use the root CBF flag of the current CU. cu_cbf The signal notification flag is only used when the inter-frame mode and IBC mode are both equal to 1. cu_act_enabled_flag Otherwise (i.e., the flag) cu_cbf (equal to 0), no signal notification flag. cu_act_enabled_flag Furthermore, ACT is disabled for decoding the residual of the current CU. On the other hand, unlike inter-frame mode and IBC mode, for intra-frame mode, the root CBF flag is not signaled; that is, the flag can be omitted. cu_cbf To adjust the flags used for intra-frame CU cu_act_enabled_flag The existence of . Conversely, when ACT is applied to an intra CU, it is proposed to use the ACT flag to conditionally enable / disable CBF signaling for the luma component. For example, for an intra CU using ACT, the decoder assumes that at least one component contains non-zero coefficients. Therefore, when ACT is enabled for an intra CU and there are no non-zero residuals in its transform blocks except for its exact last transform block, the CBF for its exact last transform block is inferred to be 1 without signaling. For an intra CU containing only one TU, if the CBF for its two chroma components (as by tu_cbf_cb and tu_cbf_cr If the indicated value is zero, then in the absence of signaling, the CBF flag of the last component (i.e., tu_cbf_luma The value is always inferred as 1. In one embodiment, such an inference rule for luminance CBF is enabled only for intra-frame CUs that contain only a single TU for residual decoding.

[0096] In order to conditionally perform inverse ACT on the coding unit, the video decoder first receives video data corresponding to the coding unit from the bitstream (e.g., encoded in 4:4:4 format), where the coding unit is encoded in inter-frame prediction mode or intra-frame block copy mode (810).

[0097] Next, the video decoder receives the first syntax element (e.g., the CU root coding block flag) from the video data. cu_ cbf ), where the first syntax element indicates whether the coding unit has any non-zero residual (820).

[0098] If the first syntax element has a non-zero value (e.g., 1, which indicates the presence of a residual syntax element for the encoding / decoding unit in the bitstream) (830): then the video decoder receives the second syntax element (e.g., ...) from the video data. cu_act_ enabled_fla The second syntax element indicates whether the encoding unit has been encoded using Adaptive Color Space Transformation (ACT) (830-1).

[0099] On the other hand, if the first syntax element has a zero value (e.g., 0, which indicates that there is no residual syntax element for the coding unit in the bitstream) (840): the video decoder assigns a zero value to the second syntax element (e.g., assigns a zero value to the second syntax element). cu_act_ enabled_flag Set to 0)(840-1).

[0100] Then, the video decoder determines whether to perform the inverse ACT on the video data of the coding unit based on the value of the second syntax element (e.g., if the second syntax element has a zero value, the inverse ACT is abandoned; if the second syntax element has a non-zero value, the inverse ACT is performed). The value of the second syntax element can be received from the video data or assigned based on the above logic (850).

[0101] In some embodiments, the encoding units are encoded in a 4:4:4 chroma format, wherein each of these components (e.g., luminance and both chroma) has the same sample rate.

[0102] In some embodiments, a first syntax element having a zero value indicates that there is no residual syntax element for a coding unit in the bitstream, and a first syntax element having a non-zero value indicates that there is a residual syntax element for a coding unit in the bitstream.

[0103] In some embodiments, the first syntax element includes cu_cbf The flag, and the second syntax element includes cu_act_ enabled Logo.

[0104] In some embodiments, when the coding unit is encoded in intra-frame prediction mode, the video decoder conditionally receives syntax elements (e.g., for decoding the luma component of the coding unit) for decoding the luma component of the coding unit. tu_cbf_y ).

[0105] In order to conditionally receive the syntax elements used for decoding the luma component, the video decoder first receives video data corresponding to the coding unit from the bitstream. The coding unit is encoded in intra-frame prediction mode and includes a first chroma component, a second chroma component, and a luma component. In some embodiments, the coding unit includes only one transform unit.

[0106] Next, the video decoder receives the first syntax element (e.g., ...) from the video data. cu_act_enabled_ flag The first syntax element indicates whether the encoding unit has been encoded using ACT. For example, cu_act_enabled_ flag An expression equal to "1" indicates that the encoding unit has been encoded using ACT, and cu_act_enabled_flag A value of "0" indicates that the encoding unit is not encoded using ACT (e.g., so there is no need to perform inverse ACT).

[0107] After receiving the first syntax element from the video data, the video decoder receives the second syntax element from the video data (e.g., tu_cbf_cb ) and third syntactic elements (e.g., tu_cbf_cr The second syntax element indicates whether the first chromaticity component has any non-zero residuals, and the third syntax element indicates whether the second chromaticity component has any non-zero residuals. For example, tu_cbf_cb or tu_cbf_cr The value "1" indicates that either the first chromaticity component or the second chromaticity component has at least one non-zero residual, and tu_cbf_cb or tu_cbf_cr A value of "0" indicates that the first chromaticity component or the second chromaticity component does not have any non-zero residuals.

[0108] If the first syntax element has a non-zero value (e.g., 1, indicating that the inverse ACT should be performed), and at least one of the two chroma components includes a non-zero residual (e.g., ... tu_cbf_cb == 1 or tu_cbf_cr ==1): The video decoder receives the fourth syntax element (e.g., from the video data) from the video data. tu_cbf_y ), where the fourth syntax element indicates whether the luminance component has any non-zero residuals.

[0109] On the other hand, if the first syntax element has a non-zero value, and the two chroma components have only zero residuals (e.g., tu_cbf_cb == 0 and tu_cbf_cr ==0: The video decoder assigns a default value (e.g., a non-zero value) to the fourth syntax element, indicating that the luminance component has a non-zero residual. As a result, the video decoder no longer receives the value of the fourth syntax element from the video data.

[0110] After determining the value of the fourth syntax element (e.g., by receiving the value from the video data, or by assigning a default non-zero value to the fourth syntax element), the video decoder determines whether to reconstruct the coding unit from the video data based on the fourth syntax element.

[0111] In some embodiments, the encoding unit includes only one transformation unit (TU).

[0112] In some embodiments, determining whether to reconstruct the coding unit from the video data based on the fourth syntax element includes: reconstructing the residual of the luminance component based on the determination that the fourth syntax element has a non-zero value; and abandoning the reconstruction of the residual of the luminance component based on the determination that the fourth syntax element has a zero value.

[0113] Given the strong correlation among the three components of 4:4:4 video, the intra-frame mode used to predict the luma and chroma components is often the same for a given coded block. Therefore, it is proposed that ACT be enabled only for the chroma component of an intra-frame CU when it uses the same intra-frame prediction mode (i.e., DM mode) as the luma component, to reduce ACT signaling overhead. In some embodiments, there are two methods for conditionally signaling the ACT enable / disable flag and the chroma intra-frame prediction mode. In one embodiment of this disclosure, it is proposed to signal the ACT enable / disable flag before the intra-frame prediction mode signaling of an intra-frame CU. In other words, when the ACT flag (i.e., DM mode) is used, the ACT is enabled only for the chroma component. cu_act_enabled_flag When ) equals 1, the intra-prediction mode of the chroma component is not notified by a signal; instead, it is inferred as the DM mode (i.e., the same intra-prediction mode of the luma component is reused). Otherwise (i.e., cu_act_enabled_flag Even if the value is zero, the intra-prediction mode of the chroma component is still signaled. In another embodiment of this disclosure, it is proposed to signal the ACT enable / disable flag after the signaling of the intra-prediction mode. In this case, it is only necessary to signal the ACT flag if the resolved value of the chroma intra-prediction mode is DM mode. cu_act_enabled_flag Otherwise (i.e., the chroma intra-prediction mode is not equal to DM), there is no need to use a signal notification flag. cu_act_enabled_flag And it is inferred to be 0. In yet another embodiment, it is proposed to enable ACT for all possible chroma intra-frame modes. If such an approach is applied, a signaling flag will always be used regardless of the chroma intra-frame prediction mode. cu_act_enabled_flag .

[0114] In order to conditionally signal the ACT enable / disable flag and chroma intra-prediction mode, the video decoder first receives video data corresponding to the coding unit from the bitstream, wherein the coding unit is encoded in intra-prediction mode and includes two chroma components and one luma component.

[0115] Then, the video decoder receives the first syntax element (e.g., ...) from the video data. cu_act_enabled_flag ), which indicates that the encoding unit has been encoded using ACT.

[0116] The video decoder then receives a second syntax element from the video data, where the second syntax element represents the intra-prediction parameters of the luminance component of the coding unit (e.g., it represents one of 67 intra-prediction directions).

[0117] If the second syntax element has a non-zero value indicating that the coding unit has been encoded using ACT: the video decoder reconstructs the two chroma components of the coding unit by applying the same intra-prediction parameters to the two chroma components of the coding unit as to the luminance component of the coding unit.

[0118] In some embodiments, the intra-prediction parameters indicate the intra-prediction direction applied to generate intra-prediction samples of coding units.

[0119] When ACT is enabled for a CU, the residuals of all three components need to be accessed for color space conversion. However, as mentioned earlier, VVC design cannot guarantee that each CU always contains information for all three components. In some embodiments of this disclosure, ACT should be disabled when the CU does not contain information for all three components.

[0120] First, when applying a split-tree (also known as a "dual-tree") partitioning structure, the luma and chroma samples within a CTU are divided into CUs based on the split partitioning structure. As a result, the CUs in the luma partitioning tree contain only the coding information for the luma component, and the CUs in the chroma partitioning tree contain only the coding information for the two chroma components. Switching between single-tree and split-tree partitioning structures occurs at various levels, such as sequence level, picture level, stripe level, and coding unit group level. Therefore, when a split-tree is applied to a region, the ACT (Active Activation Control) is inferred to be disabled for all CUs (both luma and chroma CUs) within that region, without signaling the replacement of the inferred zero ACT flag.

[0121] Secondly, when ISP mode is enabled, TU partitions are applied only to luma samples, while chroma samples are encoded without further splitting into multiple TUs. Assuming N is the number of ISP sub-partitions (i.e., TUs) used for an intra-frame CU, according to the current ISP design, only the last TU contains both luma and chroma components, while the first N-1 ISP TUs consist only of luma components. According to one embodiment of this disclosure, ACT is disabled in ISP mode. There are two ways to disable ACT for ISP mode. In the first approach, it is proposed to signal the ACT enable / disable flag (i.e., before signaling the ISP mode syntax) before signaling the ACT enable / disable flag. cu_act_enabled_flag In such a case, when the sign cu_act_enabled_flagWhen the value is 1, the ISP mode will not be signaled in the bitstream; instead, it will always be inferred as zero (i.e., off). In the second approach, it is proposed to use ISP mode signaling to bypass the signaling of the ACT flag. Specifically, in this method, in the flag... cu_act_ enabled_flag Previously, a signal was used to notify the ISP mode. When ISP mode is selected, the signal notification flag is no longer needed. cu_act_ enabled_flag And it will be inferred as zero. Otherwise (ISP mode not selected), the flag will still be notified by a signal. cu_act_ enabled_flag To adaptively select the color space for residual coding of the CU.

[0122] In addition to disabling ACT for CUs where the luma and chroma partitioning structures are misaligned, this disclosure also proposes disabling LMCS for CUs where ACT is applied. In one embodiment, it is proposed to disable both luma mapping and chroma residual scaling when a CU selects the YCgCo color space to encode its residuals (i.e., ACT is one). In another embodiment, when ACT is enabled for a CU, it is proposed to disable only chroma residual scaling, while luma mapping can still be applied to adjust the dynamic range of the output luma samples. In a final embodiment, it is proposed to enable both luma mapping and chroma residual scaling for CUs that apply ACT to encode their residuals.

[0123] In order to disable ACT signaling due to the dual-tree partitioning structure, the video decoder receives information from the bitstream indicating whether the coding units in the video data are encoded by a single-tree partition or a dual-tree partition.

[0124] If a single-tree partitioning method is used to encode coding units, where each coding unit contains both luminance and chrominance components: the video decoder receives a second syntax element (e.g., ...) from the video data. cu_act_enabled_flag ), where the value of the first syntax element indicates whether to perform an inverse adaptive color space transformation (ACT) for each coding unit.

[0125] On the other hand, if a dual-tree partition is used to encode the coding unit, the video decoder assigns a zero value to the second syntax element, wherein the coding unit in the luminance partition tree of the dual-tree partition only includes coding information related to the luminance component of the coding unit, and the coding unit in the chrominance partition tree of the dual-tree partition only includes coding information related to the chrominance component of the coding unit.

[0126] Then, the video decoder determines whether to perform the inverse ACT for each coding unit in the coding tree unit based on the second syntax element.

[0127] In some embodiments, determining whether to perform inverse ACT on each coding unit in the coding tree unit based on the second syntax element includes: performing inverse ACT on each coding unit based on the determination that the second syntax element has a non-zero value; and abandoning the performance of inverse ACT on each coding unit based on the determination that the second syntax element has a zero value.

[0128] In some embodiments, to disable ISP mode due to ACT signaling, the video decoder first receives video data corresponding to the coding unit from the bitstream. Next, the video decoder receives a first syntax element (e.g., ...) from the video data. cu_act_enabled_flag The first syntax element indicates whether the coding unit is encoded using ACT. If the first syntax element has a zero value, the video decoder receives a second syntax element from the video data, where the second syntax element indicates whether the coding unit is encoded using ISP mode. If the first syntax element has a non-zero value: the video decoder assigns a zero value to the second syntax element, indicating that the coding unit is not encoded using ISP mode. The video decoder then determines whether to reconstruct the coding unit from the video data using ISP mode based on the second syntax element. In current VVC, when ISP mode is enabled, TU partitions are applied only to luma samples, while chroma samples are encoded without further splitting into multiple TUs. According to embodiments of this disclosure, due to the rich texture information in the chroma plane, it is proposed to also enable ISP mode for chroma encoding in 4:4:4 video. Different methods can be used based on this embodiment. In one method, an additional ISP index is signaled and shared by the two chroma components. In another method, it is proposed to separately signal two additional ISP indices, one for Cb / B and the other for Cr / R. In the third approach, it is proposed to reuse the ISP index used for the luminance component for ISP prediction of the two chrominance components.

[0129] Matrix-weighted intra-frame prediction (MIP) is an intra-frame prediction technique. It is used to predict the width... W and height H For a rectangular block of samples, MIP takes H reconstructed adjacent boundary samples in a row to the left of the block and W reconstructed adjacent boundary samples in a row above the block as input. If reconstructed samples are unavailable, reconstructed samples are generated as in conventional intra-frame prediction. The generation of the predicted signal is based on three steps: averaging, matrix-vector multiplication, and linear interpolation.

[0130] In the current VVC, MIP mode is enabled only for the luma component. For the same reasons as enabling ISP mode for the chroma component, in one embodiment, it is proposed to enable MIP for the chroma components of 444 videos. Two signaling methods can be applied. In the first method, it is proposed to signal the two MIP modes separately, one for the luma component and the other for both chroma components. In the second method, it is proposed to signal only a single MIP mode shared by both the luma and chroma components.

[0131] To enable MIP for chroma components with a 4:4:4 chroma format, the video decoder receives video data from the bitstream corresponding to coding units, where each coding unit is encoded in intra-frame prediction mode and comprises two chroma components and one luma component, with the chroma and luma components having the same resolution. Next, the video decoder receives a first syntax element (e.g., ...) from the video data. intra_mip_flag The first syntax element indicates that the luminance component of the coding unit has been encoded using the MIP tool. If the first syntax element has a non-zero value, that non-zero value indicates that the luminance component of the coding unit has been encoded using the MIP tool: the video decoder receives the second syntax element from the video data (e.g., intra_mip_mode The second syntax element indicates the MIP mode applied to the luma component of the coding unit; and the two chroma components of the coding unit are reconstructed by applying the MIP mode of the luma component to the two chroma components of the coding unit. The following shows the syntax design specification for decoding video data using ACT in VVC.

[0132] First, add an extra syntax element to the Sequence Parameter Set (SPS) (e.g., sps_act_enabled_ flag This indicates whether ACT is enabled at the sequence level. In some embodiments, if color space conversion is applied to video content whose luminance and chrominance components have the same resolution, a bitstream conformance requirement needs to be added so that ACT can be enabled only for 4:4:4 chroma formats. Table 1 shows the modified SPS syntax table with the above syntax added. Table 1. Modified SPS Syntax Table

[0133] logo sps_act_enabled_flag A value of 1 indicates that adaptive color space transformation is enabled. (Flag) sps_act_ enabled_flag A value of 0 indicates that adaptive color space transformation is disabled, and no signal notification flag is used for CUs that reference SPS. cu_act_enabled_flagAnd it is inferred to be 0. When ChromaArrayType is not equal to 3, the value of sps_act_enabled_flag should be equal to 0 as a requirement for bitstream consistency.

[0134] logo cu_act_enabled_flag A value of 1 indicates that the residual of the encoding unit is encoded in the YCgCo color space. (Marker) cu_act_enabled_flag A value of 0 indicates that the residual of the encoding unit is encoded in the original color space. When no flag is present... cu_act_enabled_flag When it is, it is inferred to be equal to 0.

[0135] In one or more examples, the described functionality can be implemented using hardware, software, firmware, or any combination thereof. If implemented in software, the functionality can 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. A computer-readable medium can include a computer-readable storage medium (which corresponds to a tangible medium such as a data storage medium) or a communication medium that includes, for example, any medium facilitating the transfer of a computer program from one place to another according to a communication protocol. In this way, a computer-readable medium can generally correspond to (1) a non-transitory tangible computer-readable storage medium or (2) a communication medium such as a signal or carrier wave. A data storage medium can 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 used to implement the implementations described in this application. A computer program product can include a computer-readable medium.

[0136] The terminology used in the description of the implementations herein is for the purpose of describing a particular implementation only and is not intended to limit the scope of the claims. As used in the description of the 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. It will also be understood that the term “and / or,” as used herein, refers to and includes any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “comprise” and / or “comprising,” when used in this specification, specify the presence of the 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.

[0137] It will also be understood that although the terms first, second, etc., may be used in this document to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of implementation, a first electrode may be referred to as a second electrode, and similarly, a second electrode may be referred to as a first electrode. Both the first electrode and the second electrode are electrodes, but they are not the same electrode.

[0138] The description of this application has been given for purposes of illustration and description, and is not intended to be exhaustive or to limit the invention to a disclosed form. Many modifications, variations, and alternative implementations will be apparent to those skilled in the art who benefit from the teachings presented in the foregoing description and the associated drawings. Embodiments were chosen and described in order to best explain the principles of the invention, its practical application, and to enable others skilled in the art to understand the invention for various implementations and to best utilize the basic principles and various implementations with various modifications suited to the particular purpose contemplated. Therefore, it will be understood that the scope of the claims will not be limited to the specific examples of the disclosed implementations, and that modifications and other implementations are intended to be included within the scope of the appended claims.

Claims

1. A method for decoding video data, comprising: Receive a first syntax element from the bitstream, the first syntax element indicating whether the coding unit in the video data is encoded by a single-tree partition or a dual-tree partition, wherein each coding unit contains both a luminance component and a chrominance component; Based on the determination that the encoding unit uses single-tree partitioning for encoding: A second syntax element is determined from the video data, wherein the second syntax element indicates whether the coding unit has been subjected to an adaptive color space transformation (ACT); and The inverse ACT is performed on the residual data of the encoding unit based on the non-zero value of the second syntax element.

2. The method according to claim 1, further comprising: Based on the determination that the encoding unit is encoded using a dual-tree partition, a zero value is assigned to the second syntax element, wherein the encoding unit in the luminance partition tree of the dual-tree partition includes only the encoding information related to the luminance component of the encoding unit, and the encoding unit in the chrominance partition tree of the dual-tree partition includes only the encoding information related to the chrominance component of the encoding unit.

3. The method according to claim 1, further comprising: Based on the determination that the second syntax element has a zero value, the inverse ACT is abandoned for the encoding unit.

4. The method according to claim 1, wherein, The switching between single-tree partitioning and dual-tree partitioning structures occurs at the sequence level, image level, stripe level, or coding unit level.

5. The method according to claim 1, wherein, The encoding unit is encoded in a 4:4:4 chroma format.

6. A method for encoding coding units within a video frame, comprising: Determine the value of a first syntax element, which indicates whether the coding unit is encoded by a single-tree partition or a dual-tree partition, wherein each coding unit contains both a luminance component and a chrominance component; Determine the value of the second syntax element, wherein the second syntax element indicates whether the encoding unit has been subjected to the adaptive color space transformation (ACT); and Based on the determination of the value of the first syntax element, indicating that the encoding unit is encoded using a single tree partition, a signal is sent to notify the value of the determined second syntax element.

7. The method according to claim 6, further comprising: Based on the determination that the value of the first syntax element indicates that the encoding unit is encoded using a dual-tree partition, the value of the second syntax element is determined to be zero, wherein the encoding unit in the luminance partition tree of the dual-tree partition only includes encoding information related to the luminance component of the encoding unit, and the encoding unit in the chrominance partition tree of the dual-tree partition only includes encoding information related to the chrominance component of the encoding unit.

8. The method according to claim 6, wherein, The second syntax element with a non-zero value indicates that ACT is performed on the residual data of the encoded unit.

9. The method according to claim 6, wherein, The second syntax element with a value of zero indicates that ACT should not be performed on the encoded unit.

10. The method according to claim 6, wherein, The switching between single-tree partitioning and dual-tree partitioning structures occurs at the sequence level, image level, stripe level, or coding unit level.

11. The method according to claim 6, wherein, The encoding unit is encoded in a 4:4:4 chroma format.

12. An electronic device comprising: One or more processing units; Memory coupled to the one or more processing units; as well as A plurality of programs stored in the memory, which, when executed by the one or more processing units, cause the electronic device to perform the method according to any one of claims 1-11.

13. A computer-readable storage medium for storing a bit stream formed by instructions, which, when executed by a computing device having one or more processors, cause the one or more processors to perform the encoding method according to any one of claims 6-10.

14. The computer-readable storage medium according to claim 13, wherein, The encoding unit is encoded in a 4:4:4 chroma format.

15. A method for storing a bit stream, comprising: Perform the encoding method according to any one of claims 6-10 to generate a bitstream; as well as Store the bit stream.

16. The method according to claim 15, wherein, The encoding unit is encoded in a 4:4:4 chroma format.

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