Cross-Component Sample Clipping

Abstract

Various implementations described herein include methods and systems for video coding. In one aspect, the method includes receiving video data including a current image frame having samples having a first color component and a second color component. The method further includes obtaining a first clipping range for pixel values ​​of the first color component in the samples based on syntax element values ​​in the received video data, and deriving a second clipping range for pixel values ​​of the second color component in the samples based on the first clipping range. The method further includes, in response to the pixel values ​​of the second color component exceeding the second clipping range, limiting the pixel values ​​to a minimum or maximum value corresponding to the second clipping range. The method further includes reconstructing the current non-monochrome image frame using the limited pixel values ​​for the samples.

Description

[Technical Field]

[0001] [Related Applications] This application claims priority to U.S. Provisional Patent Application No. 63 / 403,631, entitled "Cross Component Sample Clipping," filed September 2, 2022, and is a continuation of and claims priority to U.S. Patent Application No. 18 / 214,296, entitled "Cross Component Sample Clipping," filed June 26, 2023, the entire contents of all of which are incorporated by reference.

[0002] [Technical field] The disclosed embodiments relate generally to video coding and include, but are not limited to, systems and methods for jointly controlling clipping of color components of image frames during video coding. [Background technology]

[0003] Digital video is supported by a variety of electronic devices, such as digital televisions, laptop or desktop computers, tablet computers, digital cameras, digital recording devices, digital media players, video game consoles, smartphones, video conferencing devices, video streaming devices, etc. The electronic devices send and receive or otherwise communicate digital video data over communication networks and / or store the digital video data in storage devices. Due to the limited bandwidth capacity of communication networks and the limited memory resources of storage devices, video coding may be used to compress the video data according to one or more video coding standards before being communicated or stored.

[0004] Several video codec standards have been developed. For example, video coding standards include AV1 (AOMedia Video 1), VVC (Versatile Video Coding), JEM (Joint Exploration test Model), HEVC / H.265 (High-Efficiency Video Coding), AVC / H.264 (Advanced Video Coding), and MPEG (Moving Picture Expert Group) coding. Video coding generally uses prediction methods (e.g., inter-prediction, intra-prediction, etc.) that exploit the redundancy inherent in video data. The goal of video coding is to compress video data into a format that uses a lower bitrate while avoiding or minimizing degradation of video quality.

[0005] HEVC, also known as H.265, is a video compression standard designed as part of the MPEG-H project. ITU-T and ISO / IEC published the HEVC / H.265 standard in 2013 (Version 1), 2014 (Version 2), 2015 (Version 3), and 2016 (Version 4). Versatile Video Coding (VVC), also known as H.266, is a video compression standard intended as the successor to HEVC. ITU-T and ISO / IEC published the VVC / H.266 standard in 2020 (Version 1) and 2022 (Version 2). AV1 is an open video coding format designed as a replacement for HEVC. Approved version 1.0.0 with Errata 1 of the specification was released on January 8, 2019. Summary of the Invention

[0006] As mentioned above, encoding (compression) reduces bandwidth and / or storage space requirements. As described in more detail below, both lossless and lossy compression can be used. Lossless compression refers to a technique in which an exact copy of the original signal can be reconstructed from the compressed original signal through a decoding process. Lossy compression refers to an encoding / decoding process in which the original video information is not fully preserved during encoding and is not fully recoverable during decoding. When using lossy compression, the reconstructed signal may not be identical to the original signal, but the distortion between the original and reconstructed signal is small enough to make the reconstructed signal useful for the intended application. The amount of acceptable distortion depends on the application. For example, users of a particular consumer video streaming application may tolerate higher distortion than users of a movie or television broadcast application. The compression ratio achievable by a particular coding algorithm can be selected or adjusted to reflect different distortion tolerances. Higher tolerable distortion generally allows for coding algorithms that result in higher loss and higher compression ratios.

[0007] This disclosure describes jointly controlling clipping of color components of an image frame during video coding. Pixel values ​​of a color image are adaptively clipped at different pixel value ranges corresponding to different color components of the color image. For example, each sample is represented by three color components (e.g., red, green, and blue (RGB) color components and luma and chroma (YCbCr) components). Pixel values ​​of each color component have a respective clipping range within which the pixel values ​​of the respective color components are controlled. In some implementations, two color components of the same color image are co-located and correlated with each other. For example, a first color component and a second color component correspond to the same one or more pixels of the color image. For an image frame or a coding block of an image frame, a first clipping range for pixel values ​​of a first color component is associated with a second clipping range for pixel values ​​of a second color component. According to a pixel value of a first color component identified within the first clipping range, a corresponding pixel value of a second color component is identified within the second clipping range. Conversely, when a pixel value of the second color component is identified within the second clipping range, a pixel value of the corresponding first color component is identified within the first clipping range. One of the two clipping ranges is restored based at least in part on the other of the two clipping ranges. By these measures, information on one of the two clipping ranges does not need to be coded and transmitted in the video bitstream, or only needs to be coded and transmitted partially, thereby reducing the amount of video data to be coded and improving the efficiency of video data transmission.

[0008] According to some embodiments, a method of video decoding is provided. The method includes receiving video data including a current non-monochrome image frame having two or more color components. The current non-monochrome image frame includes samples having a first color component and a second color component, the second color component being different from the first color component. The method further includes obtaining a first clipping range for pixel values ​​of the first color component in the samples based on syntax element values ​​in the received video data, and deriving a second clipping range for pixel values ​​of the second color component in the samples based on the first clipping range for the pixel values ​​of the first color component. The method further includes, in response to the pixel values ​​of the second color component exceeding the second clipping range, limiting the pixel values ​​to a minimum or maximum value corresponding to the second clipping range. The method further includes reconstructing the current non-monochrome image frame using the limited pixel values ​​for the samples.

[0009] According to some embodiments, a computing system, such as a streaming system, a server system, a personal computer system, or other electronic device, is provided. The computing system includes control circuitry and a memory that stores one or more sets of instructions. The one or more sets of instructions include instructions for performing any of the methods described herein. In some embodiments, the computing system includes an encoder component and / or a decoder component.

[0010] According to some embodiments, a non-transitory computer-readable storage medium is provided that stores one or more sets of instructions for execution by a computing system, the one or more sets of instructions including instructions for performing any of the methods described herein.

[0011] Thus, disclosed are methods, as well as devices and systems, for coding video, which may complement or replace conventional methods, devices and systems for video coding.

[0012] The features and advantages described herein are not necessarily all-inclusive, and some additional features and advantages will become apparent to those skilled in the art, especially upon consideration of the drawings, specification, and claims provided in this disclosure. Furthermore, it should be noted that the language used herein has been chosen primarily for ease of reading and educational purposes, and not necessarily to delineate or limit the subject matter described herein. [Brief explanation of the drawings]

[0013] So that the present disclosure may be more fully understood, a more particular description can be had by reference to features of various embodiments, some of which are illustrated in the accompanying drawings. However, the accompanying drawings merely illustrate relevant features of the present disclosure and therefore should not be considered necessarily limiting, as the description may also recognize other useful features as those skilled in the art will recognize upon reading the present disclosure. [Figure 1] 1 is a block diagram illustrating an exemplary communication system according to some embodiments. [Figure 2A] FIG. 2 is a block diagram illustrating exemplary elements of an encoder component according to some embodiments. [Figure 2B] FIG. 2 is a block diagram illustrating exemplary elements of a decoder component according to some embodiments. [Figure 3] FIG. 1 is a block diagram illustrating an exemplary server system according to some embodiments. [Figure 4] 1 illustrates an exemplary process for clipping pixel values ​​of two color components of a current coding block of a current image frame, according to some embodiments. [Figure 5]4 illustrates another exemplary process for clipping two color components of a current coding block 404 of a current image frame, according to some embodiments. [Figure 6] FIG. 2 is a simplified block diagram illustrating exemplary elements of an encoder according to some embodiments. [Figure 7] 1 is a flow diagram of a method for coding video according to some embodiments.

[0014] According to common practice, the various features illustrated in the drawings are not necessarily drawn to scale and like reference numerals may be used to refer to like features throughout the specification and drawings. DETAILED DESCRIPTION OF THE INVENTION

[0015] This disclosure describes jointly controlling clipping of different color components of an image during video coding. Samples of a color image are adaptively clipped at different pixel value ranges corresponding to different color components of the color image. Each color component has a respective clipping range within which corresponding samples of the respective color component are controlled. In some implementations, two color components of the same color image are co-located and correlated with each other. Specifically, for an image frame or a coding block of an image frame, a first clipping range for pixel values ​​of a first color component is uniquely associated with a second clipping range for pixel values ​​of a second color component co-located with the first color component. If a pixel value of the first color component is identified within the first clipping range, the corresponding pixel value of the second color component is identified within the second clipping range. Conversely, if a pixel value of the second color component is identified within the second clipping range, the corresponding pixel value of the first color component is identified within the first clipping range. One of the two clipping ranges is restored based at least in part on the other of the two clipping ranges. By these measures, one of the two clipping ranges does not need to be coded and transmitted in the video bitstream, or only needs to be coded and transmitted partially, thereby reducing the amount of video data to be coded and increasing the efficiency of video data transmission.

[0016] 1 is a block diagram illustrating a communication system 100 according to some embodiments. Communication system 100 includes a source device 102 and multiple electronic devices 120 (e.g., electronic devices 120-1 through 120-m) communicatively coupled to each other via one or more networks. In some embodiments, communication system 100 is a streaming system for use with video-enabled applications, such as, for example, videoconferencing applications, digital TV applications, and media storage and / or distribution applications.

[0017] Source device 102 includes a video source 104 (e.g., a camera component or media storage) and an encoder component 106. In some embodiments, video source 104 is a digital camera (e.g., configured to create an uncompressed video sample stream). Encoder component 106 generates one or more encoded video bitstreams from the video stream. The video stream from video source 104 may have a higher data volume compared to encoded video bitstream 108 generated by encoder component 106. Because encoded video bitstream 108 has a lower data volume (less data) compared to the video stream from the video source, encoded video bitstream 108 requires less bandwidth to transmit and less storage space to store compared to the video stream from video source 104. In some embodiments, source device 102 does not include encoder component 106 (e.g., configured to transmit uncompressed video data to network 110).

[0018] The one or more networks 110 represent any number of networks that carry information between the source device 102, the server system 112, and / or the electronic device 120, including, for example, wired and / or wireless communication networks. The one or more networks 110 may exchange data over circuit-switched and / or packet-switched channels. Exemplary networks include telecommunications networks, local area networks, wide area networks, and / or the Internet.

[0019] One or more networks 110 include a server system 112 (e.g., a distributed / cloud computing system). In some embodiments, server system 112 is or includes a streaming server (e.g., configured to store and / or distribute video content, such as an encoded video stream from source device 102). Server system 112 includes a coder component 114 (e.g., configured to encode and / or decode video data). In some embodiments, coder component 114 includes an encoder component and / or a decoder component. In various embodiments, coder component 114 is instantiated as hardware, software, or a combination thereof. In some embodiments, coder component 114 is configured to decode encoded video bitstream 108 and re-encode the video data using a different encoding standard and / or methodology to generate encoded video data 116. In some embodiments, server system 112 is configured to generate multiple video formats and / or encodings from encoded video bitstream 108.

[0020] In some embodiments, server system 112 functions as a Media-Aware Network Element (MANE). For example, server system 112 may be configured to prune encoded video bitstream 108 to accommodate potentially different bitstreams for one or more of electronic devices 120. In some embodiments, a MANE is provided separate from server system 112.

[0021] Electronic device 120-1 includes a decoder component 122 and a display 124. In some embodiments, decoder component 122 is configured to decode encoded video data 116 to generate an output video stream that can be rendered on a display or other type of rendering device. In some embodiments, one or more of electronic devices 120 does not include a display component (e.g., is communicatively coupled to an external display device and / or includes media storage). In some embodiments, electronic device 120 is a streaming client. In some embodiments, electronic device 120 is configured to access server system 112 to obtain encoded video data 116.

[0022] The source device and / or the plurality of electronic devices 120 are sometimes referred to as “terminal devices” or “user devices.” In some embodiments, the source device 120 and / or one or more of the electronic devices 102 are instances of a server system, a personal computer, a portable device (e.g., a smartphone, tablet, or laptop), a wearable device, a videoconferencing device, and / or other types of electronic devices.

[0023] In an exemplary operation of communication system 100, source device 102 transmits encoded video bitstream 108 to server system 112. For example, source device 102 may code a stream of pictures captured by the source device. Server system 112 may receive encoded video bitstream 108 and decode and / or encode encoded video bitstream 108 using coder component 114. For example, server system 112 may apply a coding to the video data that is more optimal for network transmission and / or storage. Server system 112 may transmit encoded video data 116 (e.g., one or more coded video bitstreams) to one or more of electronic devices 120. Each electronic device 120 may decode encoded video data 116 to recover and optionally display video pictures.

[0024] In some embodiments, the transmission described above is a unidirectional data transmission. Unidirectional data transmission is sometimes used in media serving applications, etc. In some embodiments, the transmission described above is a bidirectional data transmission. Bidirectional data transmission is sometimes used in video conferencing applications, etc. In some embodiments, the coded video bitstream 108 and / or the coded video data 116 are encoded and / or decoded according to any of the video coding / compression standards described herein, such as HEVC, VVC, and / or AV1.

[0025] 2A is a block diagram illustrating exemplary elements of encoder component 106 according to some embodiments. Encoder component 106 receives a source video sequence from video source 104. In some embodiments, the encoder component includes a receiver (e.g., transceiver) component configured to receive the source video sequence. In some embodiments, encoder component 106 receives a video sequence from a remote video source (e.g., a video source that is a component of a device different from encoder component 106). Video source 104 may provide the source video sequence in the form of a digital video sample stream that can be of any suitable bit depth (e.g., 8-bit, 10-bit, or 12-bit), any color space (e.g., B.601 Y CrCb or RGB), and any suitable sampling structure (e.g., Y CrCb 4:2:0 or Y CrCb 4:4:4). In some embodiments, video source 104 is a storage device that stores previously captured / prepared video. In some embodiments, video source 104 is a camera that captures local image information as a video sequence. Video data may be provided as multiple individual pictures that, when viewed sequentially, impart motion. The pictures themselves may be organized as a spatial array of pixels, each of which may contain one or more samples, depending on the sampling structure, color space, etc., in use. Those skilled in the art will readily understand the relationship between pixels and samples. The following discussion will focus on samples.

[0026] The encoder component 106 is configured to code and / or compress pictures of a source video sequence into a coded video sequence 216 in real time or under other time constraints required by the application. Enforcing an appropriate coding rate is one function of the controller 204. In some embodiments, the controller 204 controls and is operatively coupled to other functional units, as described below. Parameters set by the controller 204 may include rate control-related parameters (e.g., picture skip, quantizer, and / or lambda value for rate-distortion optimization techniques), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. Those skilled in the art will readily identify other functions of the controller 204, as they may be associated with the encoder component 106 being optimized for a particular system design.

[0027] In some embodiments, the encoder component 106 is configured to operate in a coding loop. In a simplified example, the coding loop includes a source coder 202 (e.g., responsible for creating a symbol-like symbol stream based on an input picture to be coded and a reference picture) and a (local) decoder 210. The decoder 210 reconstructs the symbols to create sample data in a manner similar to a (remote) decoder (when the compression between the symbols and the coding video bitstream is lossless). The reconstructed sample stream (sample data) is input to a reference picture memory 208. Because decoding the symbol stream produces bit-accurate results independent of the location (local or remote) of the decoder, the contents in the reference picture memory 208 are also bit-accurate between the local and remote encoders. In this way, the prediction portion of the encoder interprets the same sample values ​​as reference picture samples as the decoder interprets when using prediction during decoding. This principle of reference picture synchronization (and the resulting drift if synchronization cannot be maintained, e.g., due to channel errors) is known to those skilled in the art.

[0028] The operation of decoder 210 may be the same as that of a remote decoder, such as decoder component 122, described in detail below in connection with Figure 2B. However, with brief reference to Figure 2B, because symbols are available and the encoding / decoding of symbols into a coded video sequence by entropy coder 214 and parser 254 may be lossless, the entropy decoding portion of decoder component 122, including buffer memory 252 and parser 254, may not be fully implemented in local decoder 210.

[0029] An observation that can be made at this point is that any decoder technology, with the exception of analysis / entropy decoding, present in the decoder must necessarily exist in substantially the same functional form in the corresponding encoder. For this reason, the subject matter of the disclosure focuses on decoder operation. A description of the encoder technology can be omitted, as it is the reverse of the decoder technology, which is described generically. Only in certain areas is a more detailed description required, which is provided below.

[0030] As part of its operation, source coder 202 may perform motion-compensated predictive coding, which predictively codes an input frame with reference to one or more previously coded frames from the video sequence designated as reference frames. In this manner, coding engine 212 codes differences between pixel blocks of the input frame and pixel blocks of reference frames that may be selected as prediction references for the input frame. Controller 204 may manage the coding operations of source coder 202, including, for example, setting parameters and subgroup parameters used to encode the video data.

[0031] The decoder 210 decodes the coded video data of frames that may be designated as reference frames based on symbols created by the source coder 202. The operation of the coding engine 212 may advantageously be a lossy process. When the coded video data is decoded in a video decoder (not shown in FIG. 2A), the reconstructed video sequence may be a replica of the source video sequence with some errors. The decoder 210 may replicate the decoding process that may be performed by a remote video decoder on the reference frames and store the reconstructed reference frames in the reference picture memory 208. In this way, the encoder component 106 locally stores copies of reconstructed reference frames that have content in common with the reconstructed reference frames (without transmission errors) obtained by the remote video decoder.

[0032] The predictor 206 may perform the prediction search for the coding engine 212. That is, for a new frame to be coded, the predictor 206 may search the reference picture memory 208 for sample data (as candidate reference pixel blocks) or specific metadata such as reference picture motion vectors, block shapes, etc., that can serve as suitable prediction references for the new picture. The predictor 206 may operate on a sample block / pixel block basis to find suitable prediction references. In some cases, as determined by the search results obtained by the predictor 206, the input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory 208.

[0033] The output of all the above functional units may be entropy coded in entropy coder 214. Entropy coder 214 converts the symbols produced by the various functional units into a coded video sequence by losslessly compressing the symbols according to techniques known to those skilled in the art (e.g., Huffman coding, variable length coding, and / or arithmetic coding).

[0034] In some embodiments, the output of the entropy coder 214 is coupled to a transmitter. The transmitter may be configured to buffer coded video sequences created by the entropy coder 214 and prepare them for transmission over a communication channel 218, which may be a hardware / software link to a storage device that stores the coded video data. The transmitter may be configured to merge the coded video data from the source coder 202 with other data to be transmitted, such as coded audio data and / or an auxiliary data stream (source not shown). In some embodiments, the transmitter may transmit additional data along with the coded video. The source coder 202 may include such data as part of the coded video sequence. The additional data may include other forms of redundant data, such as temporal / spatial / SNR enhancement layers, redundant pictures and slices, Supplementary Enhancement Information (SEI) messages, Visual Usability Information (VUI) parameter set fragments, etc.

[0035] The controller 204 may manage the operation of the encoder component 106. During coding, the controller 204 may assign each coded picture a specific coded picture type, which may affect the coding technique applied to the respective picture. For example, a picture may be assigned as an intra picture (I picture), a predicted picture (P picture), or a bidirectionally predicted picture (B picture). An intra picture may be encoded and decoded without using other frames in the sequence as a source of prediction. Some video codecs allow different types of intra pictures, including, for example, Independent Decoder Refresh (IDR) pictures. Those skilled in the art will recognize these variations of I pictures and their respective uses and characteristics, and therefore will not be repeated here. A predicted picture may be encoded and decoded using intra prediction or inter prediction, which uses at most one motion vector and reference index to predict sample values ​​for each block. A bidirectionally predicted picture may be encoded and decoded using intra prediction or inter prediction, which uses at most two motion vectors and reference indexes to predict sample values ​​for each block. Similarly, a multi-predicted picture can use more than two reference pictures and associated metadata for the reconstruction of a single block.

[0036] A source picture is typically spatially subdivided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and may be coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks, as determined by the coding assignment applied to the block's respective picture. For example, blocks of an I-picture may be non-predictively coded or predictively coded with reference to already coded blocks of the same picture (spatial prediction or intra-prediction). Pixel blocks of a P-picture may be non-predictively coded via spatial prediction or via temporal prediction with reference to one previously coded reference picture. Blocks of a B-picture may be non-predictively coded via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

[0037] Video may be captured as multiple source pictures (video pictures) in a time sequence. Intra-picture prediction (often abbreviated as intra-prediction) exploits spatial correlation within a given picture, while inter-picture prediction exploits correlation (temporal or other) between pictures. In one example, a particular picture being encoded / decoded, called the current picture, is partitioned into blocks. When a block in the current picture is similar to a reference block in a previously coded and still buffered reference picture in the video, the block in the current picture can be coded by a vector called a motion vector. A motion vector points to a reference block within the reference picture and may have a third dimension that identifies the reference picture if multiple reference pictures are used.

[0038] Encoder component 106 may perform coding operations in accordance with a given video coding technique or standard, such as any of those described herein. In doing so, encoder component 106 may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancy in the input video sequence. Thus, the coded video data may conform to a syntax specified by the video coding technique or standard being used.

[0039] 2B is a block diagram illustrating exemplary elements of a decoder component 122 according to some embodiments. The decoder component 122 of FIG. 2B is coupled to a channel 218 and a display 124. In some embodiments, the decoder component 122 includes a transmitter coupled to a loop filter 256 and configured to transmit data to the display 124 (e.g., via a wired or wireless connection).

[0040] In some embodiments, decoder component 122 includes a receiver coupled to channel 218 and configured to receive data from channel 218 (e.g., via a wired or wireless connection). The receiver may be configured to receive one or more coded video sequences to be decoded by decoder component 122. In some embodiments, the decoding of each coded video sequence is independent of the other coded video sequences. Each coded video sequence may be received from channel 218, which may be a hardware / software link to a storage device that stores the coded video data. The receiver may receive the coded video data along with other data, such as coded audio data and / or auxiliary data streams, which may be forwarded to a respective usage entity (not shown). The receiver may separate the coded video sequences from the other data. In some embodiments, the receiver receives additional (redundant) data along with the coded video. The additional data may be included as part of the coded video sequence. The additional data may be used by decoder component 122 to decode the data and / or to more accurately reconstruct the original video data. The further data may be in the form of, for example, temporal, spatial or SNR enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0041] According to some embodiments, the decoder component 122 includes a buffer memory 252, a parser 254 (sometimes referred to as an entropy decoder), a scaler / inverse transform unit 258, an intra-picture prediction unit 262, a motion compensated prediction unit 260, an aggregator 268, a loop filter unit 256, a reference picture memory 266, and a current picture memory 264. In some embodiments, the decoder component 122 is implemented as an integrated circuit, a series of integrated circuits, and / or other electronic circuitry. In some embodiments, the decoder component 122 is implemented at least partially in software.

[0042] Buffer memory 252 is coupled between channel 218 and parser 254 (e.g., to address network jitter). In some embodiments, buffer memory 252 is separate from decoder component 122. In some embodiments, a separate buffer memory is provided between the output of channel 218 and decoder component 122. In some embodiments, in addition to buffer memory 252 within decoder component 122 (e.g., configured to handle playback timing), a separate buffer memory is provided external to decoder component 122 (e.g., to address network jitter). When receiving data from a storage / forwarding device with sufficient bandwidth and controllability or from an isochronous network, buffer memory 252 may not be required or may be small. For use over best-effort packet networks such as the Internet, buffer memory 252 may be required and may be relatively large, advantageously adaptively sized, and implemented, at least in part, in an operating system or similar element (not shown) external to decoder component 122.

[0043] Parser 254 is configured to reconstruct symbols 270 from the coded video sequence. The symbols may include, for example, information used to manage the operation of decoder component 122 and / or information for controlling a rendering device such as display 124. The control information for the rendering device may be in the form of, for example, a Supplementary Enhancement Information (SEI) message or a Video Usability Information (VUI) parameter set fragment (not shown). Parser 254 parses (entropy decodes) the coded video sequence. The coding of the coded video sequence may follow a video coding technique or standard and may follow principles well known to those skilled in the art, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, etc. Parser 254 may extract a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder from the coded video sequence based on at least one parameter corresponding to the group. The subgroups may include a group of pictures (GOP), a picture, a tile, a slice, a macroblock, a coding unit (CU), a block, a transform unit (TU), a prediction unit (PU), etc. Parser 254 may also extract information from the coded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, etc.

[0044] The reconstruction of symbols 270 may involve several different units, depending on the type of coded video picture or portion thereof (inter-picture and intra-picture, inter-block and intra-block, etc.), and other factors. Which units are involved and how they are involved can be controlled by subgroup control information parsed from the coded video sequence by parser 254. The flow of such subgroup control information between parser 254 and the following units is not shown for clarity.

[0045] In addition to the above functional blocks, the decoder component 122 can be conceptually subdivided into a number of functional units, as described below. In an actual implementation operating under commercial constraints, many of these units will interact closely with each other and may be at least partially integrated with each other. However, for purposes of describing the disclosed subject matter, the conceptual subdivision into the following functional units will be maintained.

[0046] The scaler / inverse transform unit 258 receives the quantized transform coefficients and control information (such as which transform to use, block size, quantization coefficients and / or quantization scaling matrix) from the parser 254 as symbols 270. The scaler / inverse transform unit 258 can output blocks containing sample values ​​that can be input to the aggregator 268.

[0047] In some cases, the output samples of the scaler / inverse transform unit 258 relate to intra-coded blocks, i.e., blocks that do not use prediction information from a previously reconstructed picture but can use prediction information from a previously reconstructed portion of the current picture. Such prediction information can be provided by the intra-picture prediction unit 262. The intra-picture prediction unit 262 may generate blocks of the same size and shape as the block being reconstructed using surrounding already reconstructed information retrieved from the current (partially reconstructed) picture from the current picture memory 264. The aggregator 268 may add, on a sample-by-sample basis, the prediction information generated by the intra-picture prediction unit 262 to the output sample information provided by the scaler / inverse transform unit 258.

[0048] In other cases, the output samples of the scaler / inverse transform unit 258 relate to an inter-coded, potentially motion-compensated, block. In such cases, the motion-compensated prediction unit 260 may access the reference picture memory 266 to retrieve samples used for prediction. After motion-compensating the retrieved samples according to symbols 270 associated with the block, these samples may be added by an aggregator 268 to the output of the scaler / inverse transform unit 258 (in this case, referred to as residual samples or a residual signal) to generate output sample information. The addresses in the reference picture memory 266 from which the motion-compensated prediction unit 260 retrieves prediction samples may be controlled by a motion vector. The motion vector may be made available to the motion-compensated prediction unit 260 in the form of a symbol 270, which may have, for example, X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​retrieved from the reference picture memory 266 when sub-sample accurate motion vectors are used, motion vector prediction mechanisms, etc.

[0049] The output samples of aggregator 268 may be subjected to various loop filtering techniques in loop filter unit 256. Video compression techniques may include in-loop filter techniques controlled by parameters contained in the coded video bitstream and made available to loop filter unit 256 as symbols 270 from parser 254, but may also be responsive to meta-information obtained during decoding of previous portions (in decoding order) of the coded picture or coded video sequence, or may be responsive to previously reconstructed loop-filtered sample values.

[0050] The output of the loop filter unit 256 may be a stream of samples that may be output to a rendering device such as the display 124 and stored in a reference picture memory 266 for use in future inter-picture prediction.

[0051] Once a particular coded picture is fully reconstructed, it can be used as a reference picture for future prediction. Once a coded picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by parser 254), the current reference picture can become part of reference picture memory 266, and a new current picture memory can be reallocated before beginning reconstruction of a subsequent coded picture.

[0052] Decoder component 122 may perform decoding operations according to a given video compression technique, which may be documented in a standard, such as any of the standards described herein. The coded video sequence may conform to the syntax specified by the video compression technique or standard being used, in the sense of conforming to the syntax of the video compression technique or standard, as specified in the video compression technique document or standard, particularly the profile document therein. Also, to conform to some video compression techniques or standards, the complexity of the coded video sequence may be within a range defined by the level of the video compression technique or standard. In some cases, the level limits the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. In some cases, the limits set by the level can be further limited through a Hypothetical Reference Decoder (HRD) specification and metadata for HRD buffer management signaled within the coded video sequence.

[0053] 3 is a block diagram illustrating a server system 112 according to some embodiments. The server system 112 includes a control circuit 302, one or more network interfaces 304, a memory 314, a user interface 306, and one or more communication buses 312 for interconnecting these components. In some embodiments, the control circuit 302 includes one or more processors (e.g., a CPU, a GPU, and / or a DPU). In some embodiments, the control circuit includes one or more field-programmable gate arrays (FPGAs), hardware accelerators, and / or one or more integrated circuits (e.g., application-specific integrated circuits).

[0054] The network interface 304 may be configured to interface with one or more communications networks (e.g., wireless, wired, and / or optical networks). The communications networks may be local, wide-area, metropolitan, vehicular and industrial, real-time, delay-tolerant, etc. Examples of communications networks include local area networks such as Ethernet, WLAN, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., TV wired or wireless wide area digital networks including cable TV, satellite TV, and terrestrial broadcast TV, vehicular and industrial networks including CANBus, etc. Such communications may be unidirectional, receive only (e.g., broadcast TV), unidirectional transmit only (e.g., CANbus to a specific CANbus device), or bidirectional (e.g., to other computer systems using local or wide area digital networks). Such communications may include communications to one or more cloud computing networks.

[0055] The user interface 306 includes one or more output devices 308 and / or one or more input devices 310. The input devices 310 may include one or more of a keyboard, a mouse, a trackpad, a touchscreen, a data glove, a joystick, a microphone, a scanner, a camera, etc. The output devices 308 may include one or more of an audio output device (e.g., a speaker), a visual output device (e.g., a display or monitor), etc.

[0056] Memory 314 may include high-speed random-access memory (such as DRAM, SRAM, DDR RAM, and / or other random-access solid-state memory devices) and / or non-volatile memory (such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, and / or other non-volatile solid-state storage devices). Memory 314 optionally includes one or more storage devices located remotely from control circuitry 302. Memory 314, or alternatively, a non-volatile solid-state memory device within memory 314, comprises a non-transitory computer-readable storage medium. In some embodiments, memory 314 or the non-transitory computer-readable storage medium of memory 314 stores the following programs, modules, instructions, and data structures, or a subset or superset thereof: an operating system 316 that handles various basic system services and contains procedures for performing hardware-dependent tasks; A network communications module 318 used to connect the server system 112 to other computing devices via one or more network interfaces 304 (e.g., via wired and / or wireless connections). A coding module 320 for performing various functions related to encoding and / or decoding data, such as video data. In some embodiments, the coding module 320 is an instance of the coder component 114. The coding module 320 includes, but is not limited to, one or more of the following: a decoding module 322 for performing various functions related to decoding the encoded data, such as those previously described with respect to the decoder component 122; and An encoding module 340 for performing various functions related to encoding data, such as those previously described with respect to the encoder component 106. A picture memory 352 for storing pictures and picture data, e.g., for use with coding module 320. In some embodiments, picture memory 352 includes one or more of reference picture memory 208, buffer memory 252, current picture memory 264, and reference picture memory 266.

[0057] In some embodiments, the decoding module 322 includes a parsing module 324 (e.g., configured to perform various functions previously described with respect to the parser 254), a transform module 326 (e.g., configured to perform various functions previously described with respect to the scalar / inverse transform unit 258), a prediction module 328 (e.g., configured to perform various functions previously described with respect to the motion compensation prediction unit 260 and / or the intra-picture prediction unit 262), and a filter module 330 (e.g., configured to perform various functions previously described with respect to the loop filter 256).

[0058] In some embodiments, encoding module 340 includes a code module 342 (e.g., configured to perform various functions previously described with respect to source coder 202 and / or coding engine 212) and a prediction module 344 (e.g., configured to perform various functions previously described with respect to predictor 206). In some embodiments, decoding module 322 and / or encoding module 340 include a subset of the modules shown in Figure 3. For example, a shared prediction module is used by both decoding module 322 and encoding module 340.

[0059] Each of the above-identified modules stored in memory 314 corresponds to a set of instructions for performing functions described herein. The above-identified modules (e.g., sets of instructions) need not be implemented as separate software programs, procedures, or modules; thus, various subsets of these modules may be combined or otherwise rearranged in various embodiments. For example, coding module 320 optionally does not include separate decoding and encoding modules, but rather uses the same set of modules to perform both sets of functions. In some embodiments, memory 314 stores a subset of the above-identified modules and data structures. In some embodiments, memory 314 stores additional modules and data structures not described above, such as an audio processing module.

[0060] In some embodiments, server system 112 includes a web or Hypertext Transfer Protocol (HTTP) server, a File Transfer Protocol (FTP) server, and web pages and applications implemented using Common Gateway Interface (CGI) scripts, PHP Hyper-text Preprocessor (PHP), Active Server Pages (ASP), Hypertext Markup Language (HTML), Extensible Markup Language (XML), Java, JavaScript, Asynchronous JavaScript and XML (AJAX), XHP, Javelin, Wireless Universal Resource File (WURFL), etc.

[0061] While FIG. 3 illustrates a server system 112 according to some embodiments, FIG. 3 is not intended as an architectural schematic diagram of the embodiments described herein, but rather as a functional description of various features that may be present in one or more server systems. In practice, items shown separately may be combined, and some items may be separated, as will be recognized by those skilled in the art. For example, some items shown separately in FIG. 3 may be implemented on a single server, and single items may be implemented by one or more servers. The actual number of servers used to implement server system 112, and how functionality is allocated among them, will vary from implementation to implementation and, optionally, depend in part, on the amount of data traffic the server system handles during peak and average usage periods.

[0062] FIG. 4 illustrates an exemplary process 400 for clipping pixel values ​​of two color components of a current coding block 404 of a current image frame 402, according to some embodiments. A GOP includes a sequence of image frames. The sequence of image frames includes a current image frame 402, which further includes a current coding block 404. The current image frame 402 includes a color image, i.e., a non-monochrome image frame. The current coding block 404 is coded based on prediction data of one or more coding blocks 408 of one or more reference images 406 within the GOP. In some embodiments, bilateral matching is applied to code the current coding block 404. For example, the current coding block 404 is coded based on prediction data of two reference prediction blocks 408 of two reference frames 406 within the GOP. In some embodiments, adaptive sample clipping is applied in JCTVC-C0146 and JVET-C0040, where for samples of each color component (e.g., luma samples and chroma samples), a respective clipping range is determined and applied by the decoder 122 during clipping operations following prediction, reconstruction, deblocking, and / or adaptive loop filtering in video encoding and decoding. Specifically, in some embodiments, the decoder 122 obtains video data of a current image frame 402 including samples 410 having a first color component 412 (e.g., a blue component) and a second color component 422 (e.g., a red component). The first color component 412 is different from the second color component 422. For pixel values ​​of the first color component 412, a first clipping range 414 is determined and used to determine a second clipping range 424 for pixel values ​​of the second color component 422. The decoder 122 reconstructs the current image frame 402, including clipping the pixel values ​​of the second color component 422 according to the second clipping range 424. For ease of reference, each of the color components 412 and 422 of the current image frame 402 is represented by a respective color plot 430 or 440 showing the relationship between the time of occurrence of each pixel value and the pixel value of the respective color component (e.g., in the range 0 to 255).

[0063] In some embodiments, the second clipping range 424 is defined by a second upper limit 424U and a second lower limit 424L. The first clipping range 414 is defined by a first upper limit 414U that differs from the second upper limit 424U by a first deviation d1, and a first lower limit 414L that differs from the second lower limit 424L by a second deviation d2. Furthermore, in some embodiments, the first clipping range 414, the first deviation d1, and the second deviation d2 are transmitted from the encoder 106 to the decoder 122. The decoder 122 determines the second clipping range 424 by determining the second upper limit 424U based on the first upper limit 414U and the first deviation d1, and determining the second lower limit 424L based on the first lower limit 414L and the second deviation d1. For example, second upper limit 424U is the sum of first upper limit 414U and first deviation d1, and second lower limit 424L is the sum of first lower limit 414L and second deviation d2. Furthermore, in some embodiments, each of first deviation d1 and second deviation d2 is represented and signaled in a quantized form of a respective integer power of 2. In one example, first deviation d1 is signaled in a quantized form of a power of 2 (e.g., a quantized form of 4), and d1 is signaled as an approximation of 0, 4, 8, 12, 16, etc.

[0064] In some embodiments, the current image frame 402 follows a previous image 428 in the GOP. The previous image 428 includes a previous sample having a first color component 412 and a second color component 422. The first color component 412 of the previous sample corresponds to a third clipping range 416 defined by a third upper limit 416U and a third lower limit 416L, and the second color component 422 of the previous sample corresponds to a fourth clipping range 426 defined by a fourth upper limit 426U that differs from the third upper limit 416U by a third deviation d3 and a fourth lower limit 426L that differs from the third lower limit 416L by a fourth deviation d4. The encoder 126 determines a first deviation d1 between the first upper limit 414U and the second upper limit 424U based on the third deviation d3 of the previous image 428, and determines a second deviation d2 between the first lower limit 414L and the second lower limit 424L based on the fourth deviation d4.

[0065] In some embodiments, the second color component 422 and the first color component 412 correspond to the same current coding block 404 of the current image frame 402. The second color component 422 and the first color component 412 are co-located with each other. The first color component 412 corresponding to the sample 410 is co-located with the second color component 422 corresponding to the sample 410 in the current image frame 402. For example, the first color component 412 includes a luma component, and the second color component 422 includes chroma components (e.g., Cb, Cr) that are co-located with the luma component. In some embodiments, the encoder 126 downsamples one or more pixel values ​​420 of the first color component 412 corresponding to the sample 410 to generate a down-sampled second sample. The second clipping range 424 of the sample 410 is determined based on the second clipping range of the down-sampled second sample.

[0066] In some embodiments, data of the current image frame 402 transmitted from the encoder 106 to the decoder 122 includes information of the first clipping range 414 (e.g., limits 414U and 414L) of the first color component 412 within a high-level syntax associated with the current image frame 402. The high-level syntax corresponds to a data level above the block level and is embedded in one of the group consisting of a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (AP), a slice header, a picture header, a tile header, and a coding tree unit (CTU) header. In other words, the information of the first clipping range 414 (e.g., limits 414U and 414L) of the first color component 412 is optionally coded at a coding block level, an image slice level, an image tile level, an image frame level, or a higher level. In some embodiments, the current image frame 402 includes an image region, which may further include one or more coding blocks, one or more image slices, one or more image tiles, an entire image, or a combination thereof. The samples 410 of the second color component 422 and the first color component 412 are located in the image region. A second clipping range 424 is applied to the image region of the current image frame 402.

[0067] In some embodiments, the decoder 122 determines whether a luma mapping with chroma scaling (LMCS) filter is applied. Following the determination that an LMCS filter is applied, the decoder 122 determines a second clipping range 424 based on the bit depth of the video coding. In some embodiments, the decoder 122 determines that an LMCS filter is not applied. The first clipping range 414 is determined based on a predetermined clipping range 418. The first clipping range 414 is determined by an upper deviation d from a predetermined upper limit 418U. U The first upper limit 414U and the predetermined lower limit 418L differ by a lower deviation d D The decoder 122 determines the upper deviation d in the video data of the current image frame 402 by U and lower deviation d D The first clipping range 414 is obtained by the upper deviation d U and lower deviation d D In some embodiments, the upper deviation d U and lower deviation d D are represented and signaled in quantized form as respective integer powers of 2. In some embodiments, the second clipping range 424 is defined by a second upper limit 424U that differs from the predetermined upper limit 418U by a fifth deviation and a second lower limit 424L that differs from the predetermined lower limit 418L by a sixth deviation. The decoder 122 obtains the fifth deviation and the sixth deviation and determines the second clipping range 424 based on the fifth deviation and the sixth deviation.

[0068] 5 shows another exemplary process 500 for clipping two color components of a current coding block 404 of a current image frame 402, according to some embodiments. A sequence of image frames of a GOP includes the current image frame 402, which further includes the current coding block 404. In some embodiments, the decoder 122 obtains video data of the current image frame 402, including samples 410 having a first color component 412 (e.g., a blue component) and a second color component 422 (e.g., a red component). For pixel values ​​of the first color component 412, a first clipping range 414 is determined and used to determine a second clipping range 424 for the samples 410. The decoder 122 reconstructs the current image frame 402, including clipping pixel values ​​of the second color component 422 according to the second clipping range. Each of the color components 412 and 422 of the current image frame 402 is represented by a respective color plot 430 or 440 that shows the relationship between the time of occurrence of each pixel value and the pixel value (e.g., in the range of 0 to 255). First and second clipping ranges 414 and 424 correspond to the range of pixel values ​​of the color components 412 and 422 on the x-axis of the color plots 430 and 440.

[0069] In some embodiments, the second clipping range 424 is selected from a plurality of second discontinuous data ranges 524. Based on the first clipping range 414 for the pixel values ​​of the first color component 412, the decoder selects a second clipping range 424 corresponding to the sample 410 from the plurality of second discontinuous data ranges 524. Furthermore, in some embodiments, each second discontinuous data range 524 corresponds (e.g., uniquely) to a first data range 514 of the first color component 412. The decoder 122 compares the pixel values ​​of the first color component 412 of the sample 410 with the first data ranges 514 corresponding to each subset (e.g., all, less than all) of the second discontinuous data ranges 524. According to the comparison result, a first clipping range 414 is identified from the first data ranges 514 corresponding to the subset of the second discontinuous data ranges 524. The second clipping range 424 corresponds to the identified first clipping range 414. 5, in one example, the second discrete data ranges 524-1, 524-2, 524-3, and 524-4 correspond to the first data ranges 514-1, 514-2, 514-3, and 514-4, respectively. The pixel values ​​of the first color component 412 of the sample 410 are compared to a subset or all of the first data ranges 514-1, 514-2, 514-3, and 514-4 to determine that the second clipping range 514C of the second color component 422 includes the first data range 514-4 corresponding to the second discrete data range 524-2. Therefore, the second discrete data range 524-2 is selected as the second clipping range 424 of the second color component 412.

[0070] In some embodiments, the second clipping range 424 of the second color component 422 includes a plurality of consecutive data intervals 502, each of which corresponds (e.g., uniquely) to a data interval 504 of the first clipping range 414 of the first color component 412. The bitstream transmitted by the encoder 106 to the decoder 122 conveys information about the plurality of consecutive data intervals 502, information about a data interval 502 of the first clipping range 414 corresponding to each of the plurality of consecutive data intervals 504, or both. As described above, the second clipping range 424 includes samples 410 of the second color component 422. In some embodiments, pixel values ​​of the second color component 422 are shifted by an offset to determine an interval index representing one of the plurality of consecutive data intervals 502 in the second clipping range 424. In some embodiments, the plurality of consecutive data intervals 502 includes a first number of data intervals, the first number being predefined or signaled within syntax associated with the current image frame 402. Alternatively, in some embodiments, the plurality of consecutive data intervals 502 have a fixed interval size. In some embodiments, each consecutive data interval 502 has a size within a predetermined substantially small size range (e.g., between 20 and 40).

[0071] In some embodiments, pixel values ​​420 of the first color component 412 are shifted by an offset to determine an interval index that represents one of the plurality of data intervals 504 within the first clipping range 414. In some embodiments, the plurality of data intervals 504 includes a second number of data intervals, where the second number is predefined or signaled within syntax associated with the current image frame 402. Alternatively, in some embodiments, the plurality of data intervals 504 have a fixed interval size. In some embodiments, each data interval 504 has a size within a predetermined substantially small size range (e.g., between 20 and 40). In one example, pixel values ​​of the samples 410 are shifted by 6 bits (i.e., divided by 64) to determine an integer value corresponding to the interval index. Each interval has a fixed size of 64. Furthermore, in some embodiments, the interval index used to identify one of the data intervals 504 within the first clipping range 414 is also used to identify one of the data intervals 502 within the second clipping range 424.

[0072] In some embodiments, the second clipping range 424 of the first color component includes a plurality of consecutive data intervals 502, further including a first data interval 502A and a second data interval 502B. The first data interval 502A is defined by two interval limits. The second data interval 502B is defined and signaled using a deviation of the first data interval 502A from the two interval limits. In some embodiments, the first clipping range 414 of the second color component includes a plurality of data intervals 504, further including a third data interval 504A and a fourth data interval 504B. The third data interval 504A is defined by two interval limits. The fourth data interval 504B is defined and signaled using a deviation of the third data interval 504A from the two interval limits.

[0073] In some embodiments, a first range of data ranges 514 is determined based on a second range of data ranges 514. For example, the upper and lower bounds of data range 514-2 are known, and the upper and lower bounds of data range 514-4 are determined based on deviations from the known upper and lower bounds of data range 514-2. One or two deviations are signaled for data range 514-4 to determine its upper and lower bounds based on the known upper and lower bounds of data range 514-2 during decoding.

[0074] 6 is a simplified block diagram illustrating exemplary elements of the encoder 106 according to some embodiments. For controlled clipping of different color components 422 and 412, information of two clipping ranges 424 and 414 of a pixel in the current image frame 102 is encoded into the bitstream 216 (also referred to as the coded video sequence 216), which is transmitted to the decoder 122. For example, the first clipping range 414 is represented by a minimum value 414L (min_value) and a maximum value 412U (max_value) of the first color component 414 of a sample 410 in the current image frame 102. If the pixel value of the first color component 412 is outside the first clipping range 414 after reconstruction (in the encoder 106 or the decoder 122), the pixel value of the first color component 412 is clipped to the first clipping range 414 based on the minimum value 414L or the maximum value 414U of the first clipping range 414. The second clipping range 424 and the first clipping range 414 are predicted during encoding and before transmission. In some embodiments, controlled clipping is implemented as a Clip3 function shown as the following equation: clipped_value=Clip3(min_value,max_value,orig_value) (1) where orig_value and clipped_value represent the original and clipped values ​​of the color sample, respectively. The Clip3 function limits the original and clipped values ​​to within the clipping range 424 or 414 of [min_value, max_value].

[0075] In some embodiments, controlled clipping is applied during multiple encoding stages (e.g., four encoding stages) in the encoder 106 and multiple decoding stages (e.g., four decoding stages) in the decoder 122. For example, the four encoding stages are post-prediction clipping 602, post-reconstruction clipping 604, post-deblocking clipping 606, and post-adaptive loop filtering (ALF) clipping 608. Prediction reference buffers 610A and 610B for both intra-prediction and inter-prediction are used to store predictions and generate a residual 612 relative to the original sequence of images, and post-prediction clipping 602 is applied to reduce the error level of the residual 612. Prior to reconstruction, the residual 612 is quantized for transmission. The residual 612 is dequantized during reconstruction 614, which expands the dynamic range of the residual 612 and also changes the dynamic range of the reconstructed pixel values. The dynamic range of the reconstructed pixel values ​​can be limited by post-reconstruction clipping 604 if the range is known a priori. While the reconstructed pixel values ​​are outside the limited range, pixel errors are reduced. Deblocking 616 and ALF 618 modify the reconstructed pixel values ​​by filtering, optionally modifying the dynamic range of the pixel values. Post-deblocking clipping 606 and post-ALF clipping 608 are applied to limit pixel values ​​within the clipping ranges 414 and 424.

[0076] The control clipping minimum values ​​414L and 424L and maximum values ​​414U and 424U are defined at the picture parameter set (PPS) level or at the slice level. In some embodiments, PPS-level adaptation is used, and the minimum and maximum values ​​are transmitted in the PPS or are predefined by setting the broadcast legal flag to 1. In some embodiments, slice-level adaptation is enabled separately for the luma and chroma components. The minimum and maximum values ​​signaled in the PPS are used for these predictions in the slice header.

[0077] In some embodiments, during encoding or decoding, the data of the current image frame 402 includes one or more of a coding block of predicted samples, a coding block of reconstructed samples, and one or more reconstructed coding blocks that are processed and output by a loop filter selected from the group consisting of a deblocking filter, a CDEF filter, a CCSO filter, a loop reconstruction filter, an SAO filter, an adaptive loop filter, a cross-component ALF, and a cross-component SAO filter.

[0078] 7 is a flow diagram illustrating a method 700 for coding video according to some embodiments. Method 700 may be performed in a computing system (e.g., server system 112, source device 102, or electronic device 120) having control circuitry and memory storing instructions for execution by the control circuitry. In some embodiments, method 700 is performed by executing instructions stored in memory of the computing system (e.g., coding module 320 of memory 314). A clipping operation is applied to pixel values ​​410 of a second color component 422 using pixel values ​​420 of a first color component 412. In some embodiments, each of the second color component 422 and the first color component 412 corresponds to a separate color component of the red, green, and blue primaries. Alternatively, in some embodiments, the second color component 422 is one of two chroma components (Cb and Cr), and the first color component 412 is a luma component corresponding to one of the two chroma components. The clipping operation is based on one or more clipping parameters (e.g., a minimum or maximum value of a clipping range of the first or second color component) identified on a data level corresponding to one of a VPS, SPS, PPS, APS, slice header, picture header, tile header, or CTU header. In some embodiments, the block is one of a coding block, a prediction block, and a transform block.

[0079] In some embodiments, multiple clipping ranges (e.g., first discontinuous data range 512 in FIG. 5 ) are signaled for the second color component 422, and the selection of the second clipping range 424 depends on pixel values ​​of another color component (e.g., first color component 412). In one example, the clipping range of the second color component (e.g., Y component) is divided into multiple data intervals 504. For each data interval 502, a corresponding data interval 502 of the second clipping range 424 is signaled for the first color component (e.g., Cb component or Cr component). In another example, an interval index identifying the corresponding data interval within the second clipping range 424 or first clipping range 414 is determined by pixel values ​​shifted by an offset. In some embodiments, the number of intervals is predefined or signaled in a high-level syntax, where the high-level syntax indicates any data level above the block level, optionally one of VPS, SPS, PPS, APS, slice header, picture header, tile header, or CTU header. In some situations, the block indicates a coding block, a prediction block, or a transform block. In some embodiments, the data intervals 502 have equal sizes. In some embodiments, the data intervals 504 have equal sizes. In some embodiments, the data intervals 502 have sizes that are controlled within a substantially small range (e.g., within ±20 pixel values). In some embodiments, the data intervals 504 have sizes that are controlled within a substantially small range (e.g., within ±10 pixel values).

[0080] In some embodiments, pixel values ​​420 of the first color component 412 are co-located with samples 410 of the second color component 422. In some embodiments, downsampling is first applied to the first color component 412, and then the downsampled samples 420, which are co-located with samples 410 of the second color component 422, are used to identify a second clipping range 424 for the samples 410 of the second color component 422. Alternatively, in some embodiments, when applying sample clipping to the second color component 422, the reconstructed pixel values ​​of the first color component 412 are examined, and a clipping range index is determined for the first color component 412. Based on the clipping range index, a clipping range or index for performing sample clipping on the second color component 422 is selected.

[0081] In some embodiments, when applying sample clipping to a second color component 422 (e.g., Cb or Cr), the already determined clipping range 414 of the first color component 412 (e.g., Y) is used. A delta value d1 or d2 is signaled for each of the lower limit 424L(min) and upper limit 424U(max) of the second clipping range 424. In some embodiments, the delta value d1 or d2 is signaled directly. In some situations, the second clipping range 424 of the second color component 422 (e.g., Cb) is determined based on the first clipping range 414 of the first color component 412 (e.g., Y). The second clipping range 424 is expressed based on a second upper limit 424U (e.g., max_Cb) and a second lower limit 424L (e.g., min_Cb), and the first clipping range 414 is expressed based on a first upper limit 414U (e.g., max_Y) and a first lower limit 414L (e.g., min_Y). The limits 424U and 424L are expressed based on a first deviation d1 (delta_max_Y_Cb) and a second deviation d2 (delta_min_Y_Cb) as follows: min_Cb=min_Y+delta_min_Y_Cb (2) max_Cb=max_Y-delta_max_Y_Cb (3)

[0082] In some situations, the first deviation d1 (delta_max_Y_Cb) and the second deviation d2 (delta_min_Y_Cb) are signaled in a quantized form of 2 to the power N (or a bit shift of N). The limits 424U and 424L of the second clipping range 424 are expressed as follows: min_Cb=min_Y+(1< <delta_min_Y_Cb_shift) (4) max_Cb=max_Y-(1< <delta_max_Y_Cb_shift) (5)

[0083] In some embodiments, when applying sample clipping to a second color component 422 (e.g., Cb or Cr) for a pixel value 420 of a first color component 412, the first clipping range 414 previously determined for the second pixel value 420 of the first color component 412 is applied to determine a first clipping range for the second color component 422. A first deviation d1 is signaled for a second upper limit 424U of the second clipping range 424, and a second deviation d2 is signaled for a second lower limit 424L of the second clipping range 424.

[0084] In some embodiments, sample clipping may be applied to predicted samples, reconstructed samples after adding residual samples and predicted samples, and reconstructed samples after applying certain loop filtering, including, but not limited to, a subset of deblocking, constrained directional enhancement filtering (CDEF) in AV1 and the like, cross-component sample offsetting (CCSO) in AVM and the like, loop reconstruction in AV1, sample adaptive offset (SAO) filtering, adaptive loop filtering, cross-component ALF, and cross-component SAO.

[0085] In some embodiments, the dynamic ranges of multiple color components are associated with and coded in a first image region of the current image frame 402. The first image region is optionally the entire picture, an image slice, or a given partition of the current image frame 402. The clipping ranges of the multiple color components of the first image region are used as predictors when performing range clipping of a second image region that is coded and decoded after the first image region. In one example, the current image frame has a second clipping range 424 of the second color component 422 and a first clipping range 414 of the first color component 412. For sample clipping, a second upper limit 424U(max_Cb) and a second lower limit 424L(min_Cb) are determined based on a first deviation d1(delta_max_Y_Cb) and a second deviation d2(delta_min_Y_Cb) as follows: min_Cb=min_Y+delta_min_Y_Cb (6) max_Cb=max_Y-delta_max_Y_Cb (7)

[0086] In some situations, the first deviation d1(delta_max_Y_Cb) and the second deviation d2(delta_min_Y_Cb) are predicted or derived based on range information of a previously coded picture (e.g., the previous image frame 428 in FIG. 4). In one example, the first deviation d1(delta_max_Y_Cb) and the second deviation d2(delta_min_Y_Cb) remain unchanged between the previous image frame 428 and the current image frame 402. The second clipping range 424 of the second color component 422 of the image frame 428 has a second upper limit 424U(max_Cb′) and a second lower limit 424L(min_Cb′), and the first clipping range 414′ of the first color component 412 of the reference image 406 has a first upper limit 414U(max_Y′) and a first lower limit 414L(min_Y′). The first deviation d1 (delta_max_Y_Cb) and the second deviation d2 (delta_min_Y_Cb) of the current image frame 402 are determined as follows: delta_min_Y_Cb=min_Cb'-min_Y (8) delta_max_Y_Cb=max_Y'-max_Cb' (9)

[0087] In some embodiments, different clipping ranges are applied based on whether a luma mapping with chroma scaling (LMCS) filter is applied to the current block. The LMCS filter is added as a new processing block between the reconstruction 614 and the loop filtering 616-618 (FIG. 6). The LMCS has two main components: 1) in-loop mapping of the luma component based on an adaptive piecewise linear model, and 2) luma-dependent chroma residual scaling is applied to the chroma components. In some embodiments, the LMCS filter is applied. The second clipping range 424 or the first clipping range 414 is determined by the bit depth applied for encoding and decoding. Alternatively, in some embodiments, the LMCS filter is not applied, and the second clipping range 424 of the second color component 422 or the first clipping range 414 of the first color component 412 is determined based on a predetermined clipping range 418 having a predetermined upper limit 418U (max_Y_0) and a predetermined lower limit 418L (min_Y_0). For the first clipping range 414, the upper deviation d U (max_Y_slice_delta) and lower deviation d D (min_Y_slice_delta) is optionally signaled in 2N (or N bit-shifted) quantized form to save bitrate. In one example, the first color component 412 corresponds to the luma component (Y). A slice-level first clipping range 414 is determined as follows: min_Y_slice=min_Y_0+(1< <min_Y_slice_delta_shift) (10) max_Y_slice=max_Y_0-max_Y_slice_delta_shift (11)

[0088] 7 depicts some logical steps in a particular order, but steps that are not order-dependent may be reordered and other steps may be combined or separated. Some reordering or other groupings not specifically mentioned will be apparent to those skilled in the art, and the order and grouping presented herein is not exhaustive. Furthermore, it should be recognized that these steps may be implemented in hardware, firmware, software, or any combination thereof.

[0089] Next, some exemplary embodiments will be described.

[0090] (A1) In one aspect, some embodiments include a method 700 for coding video data. The method 700 includes receiving (702) video data including a current non-monochrome image frame having two or more color components. The current non-monochrome image frame includes samples having a first color component and a second color component (704), the second color component being different from the first color component. The method 700 further includes obtaining (706) a first clipping range for pixel values ​​of the first color component in the samples based on syntax element values ​​in the received video data; deriving (708) a second clipping range for pixel values ​​of the second color component in the samples based on the first clipping range for the pixel values ​​of the first color component; limiting (710) the pixel values ​​to a minimum or maximum value corresponding to the second clipping range in response to the pixel values ​​of the second color component exceeding the second clipping range; and reconstructing (712) the current non-monochrome image frame using the limited pixel values ​​for the samples.

[0091] (A2) In some embodiments of A1, the second clipping range is selected from a plurality of second discontinuous data ranges for the second color component, and deriving the second clipping range further includes selecting a second clipping range corresponding to the second color component from the plurality of second discontinuous data ranges based on the first clipping range for pixel values ​​of the first color component.

[0092] (A3) In some embodiments of A1 or A2, each second discrete data range corresponds to a first data range of a first color component. Selecting a second clipping range further includes comparing pixel values ​​of the first color component with first data ranges corresponding to each subset of the second discrete data ranges, and identifying a first clipping range from the first data ranges corresponding to the subset of the second discrete data ranges according to a comparison result. The second clipping range corresponds to the first clipping range.

[0093] (A4) In some embodiments of any of A1 to A3, the second clipping range is defined by a second upper limit corresponding to a maximum value and a second lower limit corresponding to a minimum value. The first clipping range is defined by a first upper limit that differs from the second upper limit by a first deviation, and a first lower limit that differs from the second lower limit by a second deviation. The step of determining the second clipping range further includes the steps of (1) determining the second upper limit based on the first upper limit and the first deviation, and (2) determining the second lower limit based on the first lower limit and the second deviation.

[0094] (A5) In some embodiments of A4, each of the first deviation and the second deviation is represented and signaled in a quantized form of a respective integer power of two.

[0095] (A6) In some embodiments of A4, the current non-monochrome image frame follows a previous image in a group of pictures (GOP). The previous image includes a previous sample having a first color component and a second color component. Pixel values ​​of the first color component of the previous sample correspond to a third clipping range defined by a third upper limit and a third lower limit, and pixel values ​​of the second color component of the previous sample correspond to a fourth clipping range defined by a fourth upper limit that differs from the third upper limit by a third deviation and a fourth lower limit that differs from the third lower limit by a fourth deviation. Obtaining video data of the current non-monochrome image frame further includes determining a first deviation between the first upper limit and the second upper limit based on the third deviation and determining a second deviation between the first lower limit and the second lower limit based on the fourth deviation.

[0096] (A7) In some embodiments of any of A1-A6, the second clipping range for pixel values ​​of the second color component includes a plurality of consecutive data intervals, each consecutive data interval corresponding to a data interval of the first clipping range for pixel values ​​of the first color component. The method 700 further includes obtaining a bitstream including information of the plurality of consecutive data intervals and information of a data interval of the first clipping range corresponding to each of the plurality of consecutive data intervals.

[0097] (A8) In some embodiments of any of A7, the second clipping range includes pixel values ​​of a first color component of the sample, and the method 700 further includes shifting the pixel values ​​of the first color component of the sample by an offset to determine an interval index that represents one of a plurality of consecutive data intervals within the second clipping range.

[0098] (A9) In some embodiments of A7 or A8, the plurality of consecutive data intervals includes a first number of data intervals, the first number being predefined or signaled within syntax associated with the current non-monochrome image frame.

[0099] (A10) In some embodiments of any of A7-A9, the plurality of consecutive data intervals have a fixed interval size.

[0100] (A11) In some embodiments of any of A1-A10, the second clipping range of the second color component includes a plurality of consecutive data intervals, further including a first data interval and a second data interval. The first data interval is defined by two interval limits. The second data interval is defined and signaled using a deviation of the first data interval from the two interval limits.

[0101] (A12) In some embodiments of any of A1-A11, the second color component is currently co-located with the first color component in the non-monochrome image frame.

[0102] (A13) In some embodiments of any of A1 to A12, method 700 further includes obtaining first clipping range information for pixel values ​​of the first color component in a high-level syntax associated with the current non-monochrome image frame, the high-level syntax corresponding to a data level above the block level and embedded in one of the group consisting of: VPS, SPS, PPS, APS, slice header, picture header, tile header, CTU header.

[0103] (A14) In some embodiments of any of A1-A13, the video data currently including the non-monochrome image frame includes one or more of a coding block of predicted samples, a coding block of reconstructed samples, and one or more reconstructed coding blocks that are processed by and output by a loop filter (720).

[0104] (A15) In some embodiments of A14, the loop filter is selected from the group consisting of a deblocking filter, a CDEF filter, a CCSO filter, a loop recovery filter, an SAO filter, an adaptive loop filter, a cross-component ALF, and a cross-component SAO filter.

[0105] (A16) In some embodiments of any of A1 to A15, the method 700 further includes determining whether a luma mapping with chroma scaling (LMCS) filter is applied, and determining a second clipping range based on a bit depth of the video coding according to a determination that the LMCS filter is applied.

[0106] (A17) In some embodiments of any of A1-A16, method 700 further includes determining that an LMCS filter is not applied. The first clipping range is defined by a first upper limit that differs from a predetermined upper limit by an upper deviation and a first lower limit that differs from a predetermined lower limit by a lower deviation. Acquiring video data including the current non-monochrome image frame further includes acquiring an upper deviation and a lower deviation. Acquiring the first clipping range further includes determining the first clipping range based on the upper deviation and the lower deviation.

[0107] (A18) In some embodiments of any of A1 to A17, the first color component is a luma component corresponding to one of two chroma components, and the second color component is one of two chroma components (Cb and Cr).

[0108] (A19) In some embodiments of any of A1-A17, the first color component includes a first primary color of red, green, and blue primaries, and the second color component includes a second primary color of red, green, and blue primaries.

[0109] In another aspect, some embodiments include a computing system (e.g., server system 112) including control circuitry (e.g., control circuitry 302) and a memory (e.g., memory 314) coupled to the control circuitry, wherein the memory stores one or more sets of instructions configured to be executed by the control circuitry, the one or more sets of instructions including instructions for performing any of the methods described herein (e.g., A1-A21 above).

[0110] In yet another aspect, some embodiments include a non-transitory computer-readable storage medium storing one or more sets of instructions for execution by control circuitry of a computing system, the one or more sets of instructions including instructions for performing any of the methods described herein (e.g., A1-A21 above).

[0111] In this specification, terms such as "first," "second," etc. may be used to describe various elements, but it is understood that these elements should not be limited by these terms. These terms are used only to distinguish one element from another.

[0112] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the claims. When used in the description of the embodiments and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. The term "and / or," as used herein, is also understood to indicate and encompass any and all possible combinations of one or more of the associated listed items. It is further understood that, as used herein, the terms "comprises" and / or "comprising" specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0113] As used herein, the term "if" can be interpreted to mean "when" or "upon" or "upon determining" or "according to determining" or "upon detecting" the stated condition is true, depending on the context. Similarly, the phrase "if [the stated condition is determined to be true]" or "if [the stated condition is true]" or "when [the stated condition is true]" can be interpreted to mean "upon determining" or "according to determining" or "upon detecting" or "upon detecting" the stated condition is true, depending on the context.

[0114] The above description has been described with reference to specific embodiments for purposes of explanation. However, the exemplary discussion above is not intended to be exhaustive or to limit the scope of the claims to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described to best explain the principles of operation and practical application, thereby enabling others skilled in the art.

Claims

1. 1. A method for decoding video data, comprising: receiving video data including a current non-monochrome image frame having two or more color components, the current non-monochrome image frame including samples having a first color component and a second color component, the second color component being different from the first color component; obtaining a first clipping range for pixel values ​​of the first color component in the sample based on syntax element values ​​in the received video data; deriving a second clipping range for pixel values ​​of the second color component in the sample based on the first clipping range for pixel values ​​of the first color component; limiting the pixel value of the second color component to a minimum or maximum value corresponding to the second clipping range in response to the pixel value exceeding the second clipping range; reconstructing the current non-monochrome image frame using the limited pixel values ​​for the samples; A method comprising:

2. the second clipping range is selected from a plurality of second discontinuous data ranges of the second color component; The step of deriving the second clipping range includes:

2. The method of claim 1, further comprising selecting the second clipping range corresponding to the second color component from the plurality of second discontinuous data ranges based on the first clipping range for the pixel values ​​of the first color component.

3. each second discrete data range corresponds to a first data range of the first color component; The step of selecting the second clipping range includes: comparing the pixel values ​​of the first color component to the first data ranges corresponding to each subset of a second discontinuous data range; identifying the first clipping range from a first data range corresponding to a subset of the second discontinuous data range according to a comparison result, wherein the second clipping range corresponds to the first clipping range; The method of claim 2 further comprising:

4. the second clipping range is defined by a second upper limit corresponding to the maximum value and a second lower limit corresponding to the minimum value; the first clipping range is defined by a first upper limit that differs from the second upper limit by a first deviation and a first lower limit that differs from the second lower limit by a second deviation; The step of determining the second clipping range includes: (1) determining the second upper limit based on the first upper limit and the first deviation; (2) determining the second lower limit based on the first lower limit and the second deviation; The method of claim 1 further comprising:

5. The method of claim 4 , wherein each of the first deviation and the second deviation is represented and signaled in a quantized form of a respective integer power of two.

6. the current non-monochrome image frame follows a previous image in a group of pictures (GOP); the previous image includes a previous sample having the first color component and the second color component; a pixel value of the first color component of the previous sample corresponds to a third clipping range defined by a third upper limit and a third lower limit, and a pixel value of the second color component of the previous sample corresponds to a fourth clipping range defined by a fourth upper limit that differs from the third upper limit by a third deviation and a fourth lower limit that differs from the third lower limit by a fourth deviation; The step of obtaining the video data of the current non-monochrome image frame includes: determining the first deviation between the first upper limit and the second upper limit based on the third deviation; determining the second deviation between the first lower limit and the second lower limit based on the fourth deviation; The method of claim 4 further comprising:

7. the second clipping range for the pixel values ​​of the second color component includes a plurality of consecutive data intervals, each consecutive data interval corresponding to a data interval of the first clipping range for the pixel values ​​of the first color component; The method comprises:

2. The method of claim 1, further comprising: obtaining a bitstream including information about the plurality of consecutive data intervals and information about the data intervals of the first clipping range corresponding to each of the plurality of consecutive data intervals.

8. the second clipping range includes pixel values ​​of the first color component of the sample; The method comprises:

8. The method of claim 7, further comprising shifting the pixel values ​​of the first color component of the sample by an offset to determine an interval index representing one of the plurality of consecutive data intervals within the second clipping range.

9. 8. The method of claim 7, wherein the plurality of consecutive data intervals comprises a first number of data intervals, the first number being predefined or signaled within syntax associated with the current non-monochrome image frame.

10. The method of claim 7 , wherein the plurality of consecutive data intervals have a fixed interval size.

11. the second clipping range of the second color component includes a plurality of consecutive data intervals, further including a first data interval and a second data interval; the first data interval is defined by two interval limits; The method of claim 1 , wherein the second data interval is defined and signaled using a deviation of the first data interval from the two interval limits.

12. The method of claim 1 , wherein the second color component is co-located with the first color component in the current non-monochrome image frame.

13. The method comprises:

2. The method of claim 1, further comprising obtaining the first clipping range information for the pixel values ​​of the first color component in a high-level syntax associated with the current non-monochrome image frame, the high-level syntax corresponding to a data level above the block level and embedded in one of the group consisting of a VPS, an SPS, a PPS, an APS, a slice header, a picture header, a tile header, and a CTU header.

14. 2. The method of claim 1, wherein the video data comprising the current non-monochrome image frame includes one or more of a coding block of predicted samples, a coding block of reconstructed samples, and one or more reconstructed coding blocks that are processed and output by a loop filter.

15. 15. The method of claim 14, wherein the loop filter is selected from the group consisting of a deblocking filter, a CDEF filter, a CCSO filter, a loop reconstruction filter, a SAO filter, an adaptive loop filter, a cross-component ALF, and a cross-component SAO filter.

16. The method comprises: determining whether a luma mapping with chroma scaling (LMCS) filter is applied; determining the second clipping range based on a bit depth of video coding according to the determination that the LMCS filter is applied; The method of claim 1 further comprising:

17. The method comprises: determining that no LMCS filter is applied; the first clipping range is defined by a first upper limit that differs from a predetermined upper limit by an upper deviation and a first lower limit that differs from a predetermined lower limit by a lower deviation; obtaining video data including the current non-monochrome image frame further comprises obtaining the upper deviation and the lower deviation; The method of claim 1 , wherein obtaining the first clipping range further comprises determining the first clipping range based on the upper deviation and the lower deviation.

18. 2. The method of claim 1, wherein the first color component is a luma component corresponding to one of two chroma components, and the second color component is one of two chroma components (Cb and Cr).

19. 1. An apparatus comprising: control circuitry; and a memory storing one or more programs configured to be executed by the control circuitry, 19. Apparatus, wherein the one or more programs cause the control circuitry to perform a method according to any one of claims 1 to 18.

20. A program causing a computer to carry out the method according to any one of claims 1 to 18.

21. 1. A method for encoding video data, comprising: determining a first clipping range for pixel values ​​of the first color component in samples for encoding video data including a current non-monochrome image frame having samples having a first color component and a second color component; determining a second clipping range for pixel values ​​of the second color component in the sample based on the first clipping range for pixel values ​​of the first color component; limiting the pixel value of the second color component to a minimum or maximum value corresponding to the second clipping range in response to the pixel value exceeding the second clipping range; encoding the current non-monochrome image frame using the limited pixel values ​​for the samples; A method comprising:

Images