WO2020259353A1 - 语法元素的熵编码/解码方法、装置以及编解码器 - Google Patents

语法元素的熵编码/解码方法、装置以及编解码器 Download PDF

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WO2020259353A1
WO2020259353A1 PCT/CN2020/096363 CN2020096363W WO2020259353A1 WO 2020259353 A1 WO2020259353 A1 WO 2020259353A1 CN 2020096363 W CN2020096363 W CN 2020096363W WO 2020259353 A1 WO2020259353 A1 WO 2020259353A1
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motion vector
candidate motion
value
video
syntax element
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PCT/CN2020/096363
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English (en)
French (fr)
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陈旭
杨海涛
张恋
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华为技术有限公司
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Publication of WO2020259353A1 publication Critical patent/WO2020259353A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/70—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by syntax aspects related to video coding, e.g. related to compression standards
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/103—Selection of coding mode or of prediction mode
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/124—Quantisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
    • H04N19/136—Incoming video signal characteristics or properties
    • H04N19/14—Coding unit complexity, e.g. amount of activity or edge presence estimation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H04N19/513—Processing of motion vectors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/80—Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation
    • H04N19/82—Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation involving filtering within a prediction loop
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/90—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals
    • H04N19/91—Entropy coding, e.g. variable length coding [VLC] or arithmetic coding

Definitions

  • This application relates to the field of video coding and decoding, and in particular to an entropy coding/decoding method, device and codec of syntax elements.
  • Digital video capabilities can be incorporated into a variety of devices, including digital televisions, digital live broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, Digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio telephones (so-called "smart phones"), video teleconferencing devices, video streaming devices and the like .
  • Digital video devices implement video compression technology, for example, in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4 Part 10 Advanced Video Coding (AVC), Video compression technology described in the video coding standard H.265/High Efficiency Video Coding (HEVC) standard and extensions of such standards.
  • Video devices can transmit, receive, encode, decode, and/or store digital video information more efficiently by implementing such video compression techniques.
  • Context-based adaptive binary arithmetic coding (Context-based Adaptive Binary Arithmetic Coding, CABAC) is a commonly used entropy coding (entropy coding) technology for the encoding and decoding of syntax element values.
  • the processing process of CABAC mainly includes binarization, context modeling and binary arithmetic coding.
  • binarization refers to binary processing of the input non-binary syntax element value, and unique conversion into a binary sequence (ie, binary string); context modeling refers to each bit in the binary string, according to the context Information (for example, the coding information in the reconstructed area around the corresponding node of the syntax element) determines the probability model of the bit; binary arithmetic coding refers to encoding the corresponding bit according to the probability value in the probability model, and according to the bit’s The value updates the probability value in the probability model.
  • context Information for example, the coding information in the reconstructed area around the corresponding node of the syntax element
  • CABAC technology is used to perform entropy encoding/decoding on the syntax element mmvd_cand_flag used in the merge with motion vector difference (Merge with Motion Vector Difference, MMVD) technology.
  • MMVD Merge with Motion Vector Difference
  • the embodiments of the present application provide an entropy encoding/decoding method, device, and codec of syntax elements, which reduce the complexity of encoding/decoding.
  • an embodiment of the present application provides an entropy coding method for syntax elements, including:
  • the bypass coding mode is used to perform entropy coding on the value of the first syntax element, so
  • the first syntax element is used to instruct to select the first candidate motion vector or the second candidate motion vector from the list of fusion candidate motion vectors as the basic motion vector for motion vector expansion, and the first candidate motion vector and the second candidate motion vector
  • the candidate motion vector is any two candidate motion vectors in the fusion candidate motion vector list.
  • the value of the first syntax element mmvd_cand_flag adopts the bypass coding mode to perform entropy coding, and there is no need to assign a specific probability model to the bits in the binary string of mmvd_cand_flag, which reduces the coding complexity.
  • a bypass coding mode to perform entropy coding on the value of the first syntax element, and further includes: If the length of the fusion candidate motion vector list is greater than the preset value, the switch flag indicating the bypass coding mode is set to the first value, and the value of the first syntax element is performed using the bypass coding mode. Entropy coding.
  • the switch identifier indicates whether to use the bypass coding mode to perform entropy coding on the value of the first syntax element, which can improve coding efficiency.
  • the first syntax element is mmvd_cand_flag.
  • an embodiment of the present application provides an entropy decoding method for syntax elements, including:
  • the bypass coding mode is used to entropy decode the value of the first syntax element, so The first syntax element is used to instruct to select the first candidate motion vector or the second candidate motion vector from the list of fusion candidate motion vectors as the basic motion vector for motion vector expansion, and the first candidate motion vector and the second candidate motion vector
  • the candidate motion vector is any two candidate motion vectors in the fusion candidate motion vector list.
  • the bypass decoding mode is adopted to perform entropy decoding on the value of the first syntax element mmvd_cand_flag, and there is no need to assign a specific probability model to the bits in the binary string of mmvd_cand_flag, which reduces the decoding complexity.
  • a bypass coding mode to perform entropy coding on the value of the first syntax element, and further includes: If the length of the fusion candidate motion vector list is greater than the preset value, the switch flag indicating the bypass coding mode is set to the first value, and the value of the first syntax element is performed using the bypass coding mode. Entropy decoding.
  • the switch identifier indicates whether to use the bypass decoding mode to perform entropy decoding on the value of the first syntax element, which can improve decoding efficiency.
  • the first syntax element is mmvd_cand_flag.
  • an entropy encoding device including:
  • the judging module is used for judging whether the length of the current fusion candidate motion vector list is greater than the preset value; the encoding module is used for if the length of the fusion candidate motion vector list is greater than the preset value, the bypass coding mode is used to Entropy coding is performed on the value of a syntax element, and the first syntax element is used to instruct to select the first candidate motion vector or the second candidate motion vector from the fusion candidate motion vector list as the basic motion vector for motion vector expansion, and The first candidate motion vector and the second candidate motion vector are any two candidate motion vectors in the fusion candidate motion vector list.
  • the encoding module is further configured to, if the length of the merged candidate motion vector list is greater than the preset value, set the switch flag indicating the bypass encoding mode to the first Value, using the bypass coding mode to perform entropy coding on the value of the first syntax element.
  • the first syntax element is mmvd_cand_flag.
  • an entropy decoding device including:
  • the judging module is used to judge whether the length of the current fusion candidate motion vector list is greater than the preset value; the decoding module is used to if the length of the fusion candidate motion vector list is greater than the preset value, use the bypass coding mode to Entropy decoding is performed on the value of a syntax element, and the first syntax element is used to instruct to select the first candidate motion vector or the second candidate motion vector from the list of fusion candidate motion vectors as the basic motion vector for motion vector expansion, and
  • the first candidate motion vector and the second candidate motion vector are any two candidate motion vectors in the fusion candidate motion vector list.
  • the decoding module is further configured to, if the length of the merged candidate motion vector list is greater than the preset value, set the switch flag indicating the bypass coding mode to the first Value, using the bypass coding mode to perform entropy decoding on the value of the first syntax element.
  • the first syntax element is mmvd_cand_flag.
  • an embodiment of the present application provides a video encoder, where the video encoder is used to encode image blocks and includes:
  • An inter-frame prediction device configured to predict the motion information of the currently encoded image block based on target candidate motion information, and determine the predicted pixel value of the currently encoded image block based on the motion information of the currently encoded image block;
  • the entropy encoding device configured to encode an index identifier of the target candidate motion information into a code stream, and the index identifier indicates the target candidate for the currently encoded image block Sports information
  • the reconstruction module is configured to reconstruct the currently coded image block based on the predicted pixel value.
  • embodiments of the present application provide a video decoder, where the video decoder is used to decode image blocks from a bitstream, including:
  • the entropy decoding device configured to decode an index identifier from a code stream, where the index identifier is used to indicate target candidate motion information of a currently decoded image block;
  • An inter-frame prediction device configured to predict the motion information of the currently decoded image block based on the target candidate motion information indicated by the index identifier, and determine the currently decoded image block based on the motion information of the currently decoded image block Predicted pixel value;
  • the reconstruction module is configured to reconstruct the currently decoded image block based on the predicted pixel value.
  • an embodiment of the present application provides a video encoding device, including: a non-volatile memory and a processor coupled with each other, the processor calls the program code stored in the memory to execute the first The method described in any one of the aspects.
  • an embodiment of the present application provides a video decoding device, including: a non-volatile memory and a processor coupled with each other, the processor calls the program code stored in the memory to execute the second The method described in any one of the aspects.
  • an embodiment of the present application provides a computer-readable storage medium, the computer-readable storage medium stores program code, wherein the program code includes a method for executing any one of the first or second aspects Instructions for some or all of the steps.
  • an embodiment of the present application provides a computer program product, which when the computer program product runs on a computer, causes the computer to execute part or all of the steps of any one of the first or second aspects.
  • the embodiment of the application adopts the bypass encoding/decoding mode to perform entropy encoding/decoding on the value of the first syntax element mmvd_cand_flag, and does not need to assign a specific probability model to the bits in the binary string of mmvd_cand_flag, thereby reducing encoding / Decoding complexity.
  • FIG. 1A is a block diagram of an example of a video encoding and decoding system 10 used to implement an embodiment of the present application;
  • FIG. 1B is a block diagram of an example of a video decoding system 40 used to implement an embodiment of the present application
  • FIG. 2 is a block diagram of an example structure of an encoder 20 used to implement an embodiment of the present application
  • FIG. 3 is a block diagram of an example structure of a decoder 30 used to implement an embodiment of the present application
  • FIG. 4 is a block diagram of an example of a video decoding device 400 used to implement an embodiment of the present application
  • Fig. 5 is a block diagram of another example of an encoding device or a decoding device for implementing an embodiment of the present application
  • Fig. 6 is a schematic flowchart of an entropy coding method for syntax elements used to implement an embodiment of the present application
  • FIG. 7 is another schematic flowchart of the method for entropy decoding of syntax elements used to implement an embodiment of the present application.
  • FIG. 8 is a structural block diagram of an entropy encoding device 800 used to implement an embodiment of the present application.
  • FIG. 9 is a structural block diagram of an entropy decoding device 900 used to implement an embodiment of the present application.
  • the corresponding device may include one or more units such as functional units to perform the described one or more method steps (for example, one unit performs one or more steps) , Or multiple units, each of which performs one or more of multiple steps), even if such one or more units are not explicitly described or illustrated in the drawings.
  • the corresponding method may include one step to perform the functionality of one or more units (for example, one step performs one or more units). The functionality, or multiple steps, each of which performs the functionality of one or more of the multiple units), even if such one or more steps are not explicitly described or illustrated in the drawings.
  • Video coding generally refers to processing a sequence of pictures that form a video or video sequence.
  • picture In the field of video coding, the terms “picture”, “frame” or “image” can be used as synonyms.
  • the video encoding used in this document means video encoding or video decoding.
  • Video encoding is performed on the source side and usually includes processing (for example, by compressing) the original video picture to reduce the amount of data required to represent the video picture, so as to store and/or transmit more efficiently.
  • Video decoding is performed on the destination side and usually involves inverse processing relative to the encoder to reconstruct the video picture.
  • the “encoding” of video pictures involved in the embodiments should be understood as involving “encoding” or “decoding” of a video sequence.
  • the combination of the encoding part and the decoding part is also called codec (encoding and decoding).
  • a video sequence includes a series of pictures, the pictures are further divided into slices, and the slices are divided into blocks.
  • Video coding is performed in units of blocks.
  • the concept of blocks is further expanded.
  • MB macroblock
  • the macroblock can be further divided into multiple prediction blocks (partitions) that can be used for predictive coding.
  • HEVC high-efficiency video coding
  • basic concepts such as coding unit (CU), prediction unit (PU), and transform unit (TU) are adopted, which are functionally
  • CU coding unit
  • PU prediction unit
  • TU transform unit
  • the CU can be divided into smaller CUs according to the quadtree, and the smaller CUs can be further divided to form a quadtree structure.
  • the CU is a basic unit for dividing and encoding the coded image.
  • PU can correspond to prediction block and is the basic unit of prediction coding.
  • the CU is further divided into multiple PUs according to the division mode.
  • the TU can correspond to the transform block and is the basic unit for transforming the prediction residual.
  • no matter CU, PU or TU they all belong to the concept of block (or image block) in nature.
  • a CTU is split into multiple CUs by using a quadtree structure represented as a coding tree.
  • a decision is made at the CU level whether to use inter-picture (temporal) or intra-picture (spatial) prediction to encode picture regions.
  • Each CU can be further split into one, two or four PUs according to the PU split type.
  • the same prediction process is applied in a PU, and relevant information is transmitted to the decoder on the basis of the PU.
  • the CU may be divided into transform units (TU) according to other quadtree structures similar to the coding tree used for the CU.
  • quad-tree and binary tree Quad-tree and binary tree (Quad-tree and Binary Tree, QTBT) are used to divide frames to divide coding blocks.
  • the CU may have a square or rectangular shape.
  • the image block to be encoded in the currently encoded image may be referred to as the current block.
  • a reference block is a block that provides a reference signal for the current block, where the reference signal represents the pixel value in the image block.
  • the block in the reference image that provides the prediction signal for the current block may be a prediction block, where the prediction signal represents the pixel value or sample value or sample signal in the prediction block. For example, after traversing multiple reference blocks, the best reference block is found. This best reference block will provide prediction for the current block, and this block is called a prediction block.
  • the original video picture can be reconstructed, that is, the reconstructed video picture has the same quality as the original video picture (assuming no transmission loss or other data loss during storage or transmission).
  • quantization is performed to perform further compression to reduce the amount of data required to represent the video picture, and the decoder side cannot completely reconstruct the video picture, that is, the quality of the reconstructed video picture is compared with the original video picture The quality is low or poor.
  • Video coding standards of H.261 belong to "lossy hybrid video coding and decoding” (that is, combining spatial and temporal prediction in the sample domain with 2D transform coding for applying quantization in the transform domain).
  • Each picture of a video sequence is usually divided into a set of non-overlapping blocks, and is usually coded at the block level.
  • the encoder side usually processes the video at the block (video block) level, that is, encodes the video.
  • the prediction block is generated by spatial (intra-picture) prediction and temporal (inter-picture) prediction, from the current block (currently processed or to be processed).
  • the processed block subtracts the prediction block to obtain the residual block, transforms the residual block in the transform domain and quantizes the residual block to reduce the amount of data to be transmitted (compressed), and the decoder side will process the inverse of the encoder Partially applied to the coded or compressed block to reconstruct the current block for representation.
  • the encoder duplicates the decoder processing loop, so that the encoder and the decoder generate the same prediction (for example, intra prediction and inter prediction) and/or reconstruction for processing, that is, to encode subsequent blocks.
  • FIG. 1A exemplarily shows a schematic block diagram of a video encoding and decoding system 10 applied in an embodiment of the present application.
  • the video encoding and decoding system 10 may include a source device 12 and a destination device 14.
  • the source device 12 generates encoded video data. Therefore, the source device 12 may be referred to as a video encoding device.
  • the destination device 14 can decode the encoded video data generated by the source device 12, and therefore, the destination device 14 can be referred to as a video decoding device.
  • Various implementations of source device 12, destination device 14, or both may include one or more processors and memory coupled to the one or more processors.
  • the memory may include, but is not limited to, RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program codes in the form of instructions or data structures accessible by a computer, as described herein.
  • the source device 12 and the destination device 14 may include various devices, including desktop computers, mobile computing devices, notebook (for example, laptop) computers, tablet computers, set-top boxes, telephone handsets such as so-called "smart" phones. Computers, televisions, cameras, display devices, digital media players, video game consoles, on-board computers, wireless communication equipment, or the like.
  • FIG. 1A shows the source device 12 and the destination device 14 as separate devices
  • the device embodiment may also include the source device 12 and the destination device 14 or the functionality of both, that is, the source device 12 or the corresponding The functionality of the destination device 14 or the corresponding functionality.
  • the same hardware and/or software may be used, or separate hardware and/or software, or any combination thereof may be used to implement the source device 12 or the corresponding functionality and the destination device 14 or the corresponding functionality .
  • the source device 12 and the destination device 14 may communicate with each other via a link 13, and the destination device 14 may receive encoded video data from the source device 12 via the link 13.
  • Link 13 may include one or more media or devices capable of moving encoded video data from source device 12 to destination device 14.
  • link 13 may include one or more communication media that enable source device 12 to transmit encoded video data directly to destination device 14 in real time.
  • the source device 12 may modulate the encoded video data according to a communication standard, such as a wireless communication protocol, and may transmit the modulated video data to the destination device 14.
  • the one or more communication media may include wireless and/or wired communication media, such as a radio frequency (RF) spectrum or one or more physical transmission lines.
  • RF radio frequency
  • the one or more communication media may form part of a packet-based network, such as a local area network, a wide area network, or a global network (e.g., the Internet).
  • the one or more communication media may include routers, switches, base stations, or other devices that facilitate communication from source device 12 to destination device 14.
  • the source device 12 includes an encoder 20, and optionally, the source device 12 may also include a picture source 16, a picture preprocessor 18, and a communication interface 22.
  • the encoder 20, the picture source 16, the picture preprocessor 18, and the communication interface 22 may be hardware components in the source device 12, or may be software programs in the source device 12. They are described as follows:
  • the picture source 16 which can include or can be any type of picture capture device, for example to capture real-world pictures, and/or any type of pictures or comments (for screen content encoding, some text on the screen is also considered to be encoded
  • a picture or part of an image) generating equipment for example, a computer graphics processor for generating computer animation pictures, or for acquiring and/or providing real world pictures, computer animation pictures (for example, screen content, virtual reality (virtual reality, VR) pictures), and/or any combination thereof (for example, augmented reality (AR) pictures).
  • the picture source 16 may be a camera for capturing pictures or a memory for storing pictures.
  • the picture source 16 may also include any type of (internal or external) interface for storing previously captured or generated pictures and/or acquiring or receiving pictures.
  • the picture source 16 When the picture source 16 is a camera, the picture source 16 may be, for example, a local or an integrated camera integrated in the source device; when the picture source 16 is a memory, the picture source 16 may be local or, for example, an integrated camera integrated in the source device. Memory.
  • the interface When the picture source 16 includes an interface, the interface may be, for example, an external interface for receiving pictures from an external video source.
  • the external video source is, for example, an external picture capturing device, such as a camera, an external memory, or an external picture generating device, such as It is an external computer graphics processor, computer or server.
  • the interface can be any type of interface according to any proprietary or standardized interface protocol, such as a wired or wireless interface, and an optical interface.
  • a picture can be regarded as a two-dimensional array or matrix of picture elements.
  • the pixel points in the array can also be called sampling points.
  • the number of sampling points of the array or picture in the horizontal and vertical directions (or axis) defines the size and/or resolution of the picture.
  • three color components are usually used, that is, pictures can be represented as or contain three sample arrays.
  • a picture includes corresponding red, green, and blue sample arrays.
  • each pixel is usually expressed in a luminance/chrominance format or color space.
  • a picture in the YUV format includes the luminance component indicated by Y (sometimes indicated by L) and the two indicated by U and V. Chrominance components.
  • the luma component Y represents brightness or gray level intensity (for example, the two are the same in a grayscale picture), and the two chroma components U and V represent chroma or color information components.
  • a picture in the YUV format includes a luminance sample array of luminance sample values (Y), and two chrominance sample arrays of chrominance values (U and V).
  • Pictures in RGB format can be converted or converted to YUV format, and vice versa. This process is also called color conversion or conversion. If the picture is black and white, the picture may only include the luminance sample array.
  • the picture transmitted from the picture source 16 to the picture processor may also be referred to as original picture data 17.
  • the picture preprocessor 18 is configured to receive the original picture data 17 and perform preprocessing on the original picture data 17 to obtain the preprocessed picture 19 or the preprocessed picture data 19.
  • the pre-processing performed by the picture pre-processor 18 may include trimming, color format conversion (for example, conversion from RGB format to YUV format), toning, or denoising.
  • the encoder 20 (or video encoder 20) is configured to receive the pre-processed picture data 19, and process the pre-processed picture data 19 using a relevant prediction mode (such as the prediction mode in the various embodiments herein), thereby
  • the encoded picture data 21 is provided (the structure details of the encoder 20 will be described further based on FIG. 2 or FIG. 4 or FIG. 5).
  • the encoder 20 may be used to implement the various embodiments described below to realize the application of the chrominance block prediction method described in this application on the encoding side.
  • the communication interface 22 can be used to receive the encoded picture data 21, and can transmit the encoded picture data 21 to the destination device 14 or any other device (such as a memory) via the link 13 for storage or direct reconstruction, so The other device can be any device used for decoding or storage.
  • the communication interface 22 may be used, for example, to encapsulate the encoded picture data 21 into a suitable format, such as a data packet, for transmission on the link 13.
  • the destination device 14 includes a decoder 30, and optionally, the destination device 14 may also include a communication interface 28, a picture post processor 32, and a display device 34. They are described as follows:
  • the communication interface 28 may be used to receive the encoded picture data 21 from the source device 12 or any other source, for example, a storage device, and the storage device is, for example, an encoded picture data storage device.
  • the communication interface 28 can be used to transmit or receive the encoded picture data 21 via the link 13 between the source device 12 and the destination device 14 or via any type of network.
  • the link 13 is, for example, a direct wired or wireless connection.
  • the type of network is, for example, a wired or wireless network or any combination thereof, or any type of private network and public network, or any combination thereof.
  • the communication interface 28 may be used, for example, to decapsulate the data packet transmitted by the communication interface 22 to obtain the encoded picture data 21.
  • Both the communication interface 28 and the communication interface 22 can be configured as a one-way communication interface or a two-way communication interface, and can be used, for example, to send and receive messages to establish connections, confirm and exchange any other communication links and/or, for example, encoded picture data Information about the transmission of the transmitted data.
  • the decoder 30 (or referred to as the decoder 30) is used to receive the encoded picture data 21 and provide the decoded picture data 31 or the decoded picture 31 (below will further describe the decoder 30 based on Figure 3 or Figure 4 or Figure 5 Structural details).
  • the decoder 30 may be used to implement the various embodiments described below to realize the application of the chrominance block prediction method described in this application on the decoding side.
  • the picture post processor 32 is configured to perform post-processing on the decoded picture data 31 (also referred to as reconstructed picture data) to obtain post-processed picture data 33.
  • the post-processing performed by the picture post-processor 32 may include: color format conversion (for example, conversion from YUV format to RGB format), toning, trimming or resampling, or any other processing, and can also be used to convert post-processed picture data 33 is transmitted to the display device 34.
  • the display device 34 is configured to receive the post-processed image data 33 to display the image to, for example, users or viewers.
  • the display device 34 may be or may include any type of display for presenting reconstructed pictures, for example, an integrated or external display or monitor.
  • the display may include a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a plasma display, a projector, a micro LED display, a liquid crystal on silicon (LCoS), Digital light processor (digital light processor, DLP) or any other type of display.
  • FIG. 1A shows the source device 12 and the destination device 14 as separate devices
  • the device embodiment may also include the source device 12 and the destination device 14 or the functionality of both, that is, the source device 12 or Corresponding functionality and destination device 14 or corresponding functionality.
  • the same hardware and/or software may be used, or separate hardware and/or software, or any combination thereof may be used to implement the source device 12 or the corresponding functionality and the destination device 14 or the corresponding functionality .
  • the source device 12 and the destination device 14 may include any of a variety of devices, including any type of handheld or stationary device, for example, a notebook or laptop computer, mobile phone, smart phone, tablet or tablet computer, video camera, desktop Computers, set-top boxes, televisions, cameras, in-vehicle devices, display devices, digital media players, video game consoles, video streaming devices (such as content service servers or content distribution servers), broadcast receiver devices, broadcast transmitter devices And so on, and can not use or use any type of operating system.
  • a notebook or laptop computer mobile phone, smart phone, tablet or tablet computer
  • video camera desktop Computers
  • set-top boxes televisions, cameras, in-vehicle devices, display devices, digital media players, video game consoles, video streaming devices (such as content service servers or content distribution servers), broadcast receiver devices, broadcast transmitter devices And so on, and can not use or use any type of operating system.
  • Both the encoder 20 and the decoder 30 can be implemented as any of various suitable circuits, for example, one or more microprocessors, digital signal processors (digital signal processors, DSP), and application-specific integrated circuits (application-specific integrated circuits). circuit, ASIC), field-programmable gate array (FPGA), discrete logic, hardware, or any combination thereof.
  • the device can store the instructions of the software in a suitable non-transitory computer-readable storage medium, and can use one or more processors to execute the instructions in hardware to execute the technology of the present disclosure . Any of the foregoing (including hardware, software, a combination of hardware and software, etc.) can be regarded as one or more processors.
  • the video encoding and decoding system 10 shown in FIG. 1A is only an example, and the technology of this application can be applied to video encoding settings that do not necessarily include any data communication between encoding and decoding devices (for example, video encoding or video encoding). decoding).
  • the data can be retrieved from local storage, streamed on the network, etc.
  • the video encoding device can encode data and store the data to the memory, and/or the video decoding device can retrieve the data from the memory and decode the data.
  • encoding and decoding are performed by devices that do not communicate with each other but only encode data to the memory and/or retrieve data from the memory and decode the data.
  • FIG. 1B is an explanatory diagram of an example of a video coding system 40 including the encoder 20 of FIG. 2 and/or the decoder 30 of FIG. 3 according to an exemplary embodiment.
  • the video decoding system 40 can implement a combination of various technologies in the embodiments of the present application.
  • the video coding system 40 may include an imaging device 41, an encoder 20, a decoder 30 (and/or a video encoder/decoder implemented by the logic circuit 47 of the processing unit 46), and an antenna 42 , One or more processors 43, one or more memories 44 and/or display devices 45.
  • the imaging device 41, the antenna 42, the processing unit 46, the logic circuit 47, the encoder 20, the decoder 30, the processor 43, the memory 44, and/or the display device 45 can communicate with each other.
  • the encoder 20 and the decoder 30 are used to illustrate the video coding system 40, in different examples, the video coding system 40 may include only the encoder 20 or only the decoder 30.
  • antenna 42 may be used to transmit or receive an encoded bitstream of video data.
  • the display device 45 may be used to present video data.
  • the logic circuit 47 may be implemented by the processing unit 46.
  • the processing unit 46 may include application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, and so on.
  • the video decoding system 40 may also include an optional processor 43, and the optional processor 43 may similarly include application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, and the like.
  • the logic circuit 47 may be implemented by hardware, such as dedicated hardware for video encoding, and the processor 43 may be implemented by general software, an operating system, and the like.
  • the memory 44 may be any type of memory, such as volatile memory (for example, static random access memory (Static Random Access Memory, SRAM), dynamic random access memory (Dynamic Random Access Memory, DRAM), etc.) or non-volatile memory. Memory (for example, flash memory, etc.), etc.
  • volatile memory for example, static random access memory (Static Random Access Memory, SRAM), dynamic random access memory (Dynamic Random Access Memory, DRAM), etc.
  • Memory for example, flash memory, etc.
  • the memory 44 may be implemented by cache memory.
  • the logic circuit 47 may access the memory 44 (e.g., to implement an image buffer).
  • the logic circuit 47 and/or the processing unit 46 may include a memory (for example, a cache, etc.) for implementing an image buffer and the like.
  • the encoder 20 implemented by logic circuits may include an image buffer (e.g., implemented by the processing unit 46 or the memory 44) and a graphics processing unit (e.g., implemented by the processing unit 46).
  • the graphics processing unit may be communicatively coupled to the image buffer.
  • the graphics processing unit may include an encoder 20 implemented by a logic circuit 47 to implement various modules discussed with reference to FIG. 2 and/or any other encoder system or subsystem described herein.
  • Logic circuits can be used to perform the various operations discussed herein.
  • decoder 30 may be implemented by logic circuit 47 in a similar manner to implement the various modules discussed with reference to decoder 30 of FIG. 3 and/or any other decoder systems or subsystems described herein.
  • the decoder 30 implemented by logic circuits may include an image buffer (implemented by the processing unit 2820 or the memory 44) and a graphics processing unit (implemented by the processing unit 46, for example).
  • the graphics processing unit may be communicatively coupled to the image buffer.
  • the graphics processing unit may include a decoder 30 implemented by a logic circuit 47 to implement the various modules discussed with reference to FIG. 3 and/or any other decoder systems or subsystems described herein.
  • antenna 42 may be used to receive an encoded bitstream of video data.
  • the encoded bitstream may include data, indicators, index values, mode selection data, etc., related to the encoded video frame discussed herein, such as data related to coded partitions (e.g., transform coefficients or quantized transform coefficients). , (As discussed) optional indicators, and/or data defining code partitions).
  • the video coding system 40 may also include a decoder 30 coupled to the antenna 42 and used to decode the encoded bitstream.
  • the display device 45 is used to present video frames.
  • the decoder 30 may be used to perform the reverse process.
  • the decoder 30 can be used to receive and parse such syntax elements, and decode related video data accordingly.
  • the encoder 20 may entropy encode the syntax elements into an encoded video bitstream. In such instances, the decoder 30 can parse such syntax elements and decode related video data accordingly.
  • the entropy encoding/decoding method for syntax elements described in the embodiments of this application is mainly used in the entropy encoding/decoding process. This process exists in both the encoder 20 and the decoder 30.
  • decoder 30 can be, for example, the encoding/decoding corresponding to video standard protocols such as H.263, H.264, HEVV, MPEG-2, MPEG-4, VP8, VP9, or next-generation video standard protocols (such as H.266, etc.) Device.
  • Fig. 2 shows a schematic/conceptual block diagram of an example of an encoder 20 for implementing an embodiment of the present application.
  • the encoder 20 includes a residual calculation unit 204, a transformation processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transformation processing unit 212, a reconstruction unit 214, a buffer 216, and a loop filter.
  • Unit 220 a decoded picture buffer (DPB) 230, a prediction processing unit 260, and an entropy coding unit 270.
  • the prediction processing unit 260 may include an inter prediction unit 244, an intra prediction unit 254, and a mode selection unit 262.
  • the inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown).
  • the encoder 20 shown in FIG. 2 may also be referred to as a hybrid video encoder or a video encoder according to a hybrid video codec.
  • the residual calculation unit 204, the transform processing unit 206, the quantization unit 208, the prediction processing unit 260, and the entropy encoding unit 270 form the forward signal path of the encoder 20, and for example, the inverse quantization unit 210, the inverse transform processing unit 212, and the The structure unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, and the prediction processing unit 260 form the backward signal path of the encoder, wherein the backward signal path of the encoder corresponds to The signal path of the decoder (see decoder 30 in FIG. 3).
  • the encoder 20 receives the picture 201 or the image block 203 of the picture 201 through, for example, an input 202, for example, a picture in a picture sequence that forms a video or a video sequence.
  • the image block 203 may also be called the current picture block or the picture block to be encoded
  • the picture 201 may be called the current picture or the picture to be encoded (especially when the current picture is distinguished from other pictures in video encoding, the other pictures are for example the same video sequence). That is, the previous coded and/or decoded picture in the video sequence that also includes the current picture).
  • the embodiment of the encoder 20 may include a segmentation unit (not shown in FIG. 2) for segmenting the picture 201 into a plurality of blocks such as the image block 203, usually into a plurality of non-overlapping blocks.
  • the segmentation unit can be used to use the same block size and the corresponding grid defining the block size for all pictures in the video sequence, or to change the block size between pictures or subsets or groups of pictures, and divide each picture into The corresponding block.
  • the prediction processing unit 260 of the encoder 20 may be used to perform any combination of the aforementioned segmentation techniques.
  • the image block 203 is also or can be regarded as a two-dimensional array or matrix of sampling points with sample values, although its size is smaller than that of the picture 201.
  • the image block 203 may include, for example, one sampling array (for example, a luminance array in the case of a black-and-white picture 201) or three sampling arrays (for example, one luminance array and two chrominance arrays in the case of a color picture) or Any other number and/or type of array depending on the color format applied.
  • the number of sampling points in the horizontal and vertical directions (or axes) of the image block 203 defines the size of the image block 203.
  • the encoder 20 shown in FIG. 2 is used to encode the picture 201 block by block, for example, to perform encoding and prediction on each image block 203.
  • the residual calculation unit 204 is configured to calculate the residual block 205 based on the picture image block 203 and the prediction block 265 (other details of the prediction block 265 are provided below), for example, by subtracting the sample value of the picture image block 203 sample by sample (pixel by pixel). The sample value of the block 265 is de-predicted to obtain the residual block 205 in the sample domain.
  • the transform processing unit 206 is configured to apply a transform such as discrete cosine transform (DCT) or discrete sine transform (DST) on the sample values of the residual block 205 to obtain transform coefficients 207 in the transform domain.
  • a transform such as discrete cosine transform (DCT) or discrete sine transform (DST)
  • DCT discrete cosine transform
  • DST discrete sine transform
  • the transform coefficient 207 may also be referred to as a transform residual coefficient, and represents the residual block 205 in the transform domain.
  • the transform processing unit 206 may be used to apply an integer approximation of DCT/DST, such as the transform specified for HEVC/H.265. Compared with the orthogonal DCT transform, this integer approximation is usually scaled by a factor. In order to maintain the norm of the residual block processed by the forward and inverse transformation, an additional scaling factor is applied as part of the transformation process.
  • the scaling factor is usually selected based on certain constraints. For example, the scaling factor is a trade-off between the power of 2 used for the shift operation, the bit depth of the transform coefficient, accuracy, and implementation cost.
  • the inverse transformation processing unit 212 for the inverse transformation designate a specific scaling factor, and accordingly, the encoder The 20 side uses the transformation processing unit 206 to specify a corresponding scaling factor for the positive transformation.
  • the quantization unit 208 is used to quantize the transform coefficient 207 by applying scalar quantization or vector quantization, for example, to obtain the quantized transform coefficient 209.
  • the quantized transform coefficient 209 may also be referred to as a quantized residual coefficient 209.
  • the quantization process can reduce the bit depth associated with some or all of the transform coefficients 207. For example, n-bit transform coefficients can be rounded down to m-bit transform coefficients during quantization, where n is greater than m.
  • the degree of quantization can be modified by adjusting the quantization parameter (QP). For example, for scalar quantization, different scales can be applied to achieve finer or coarser quantization.
  • QP quantization parameter
  • a smaller quantization step size corresponds to a finer quantization
  • a larger quantization step size corresponds to a coarser quantization.
  • the appropriate quantization step size can be indicated by a quantization parameter (QP).
  • the quantization parameter may be an index of a predefined set of suitable quantization steps.
  • a smaller quantization parameter can correspond to fine quantization (smaller quantization step size)
  • a larger quantization parameter can correspond to coarse quantization (larger quantization step size)
  • Quantization may include division by a quantization step size and corresponding quantization or inverse quantization performed by, for example, inverse quantization 210, or may include multiplication by a quantization step size.
  • Embodiments according to some standards such as HEVC may use quantization parameters to determine the quantization step size.
  • the quantization step size can be calculated based on the quantization parameter using a fixed-point approximation of an equation including division. Additional scaling factors can be introduced for quantization and inverse quantization to restore the norm of the residual block that may be modified due to the scale used in the fixed-point approximation of the equations for the quantization step size and the quantization parameter.
  • the scales of inverse transform and inverse quantization may be combined.
  • a custom quantization table can be used and signaled from the encoder to the decoder in, for example, a bitstream. Quantization is a lossy operation, where the larger the quantization step, the greater the loss.
  • the inverse quantization unit 210 is configured to apply the inverse quantization of the quantization unit 208 on the quantized coefficients to obtain the inverse quantized coefficients 211, for example, based on or use the same quantization step size as the quantization unit 208, and apply the quantization scheme applied by the quantization unit 208 The inverse quantification scheme.
  • the inversely quantized coefficient 211 may also be referred to as the inversely quantized residual coefficient 211, which corresponds to the transform coefficient 207, although the loss due to quantization is usually different from the transform coefficient.
  • the inverse transform processing unit 212 is used to apply the inverse transform of the transform applied by the transform processing unit 206, for example, an inverse discrete cosine transform (DCT) or an inverse discrete sine transform (DST), so as to be in the sample domain Obtain the inverse transform block 213.
  • the inverse transformation block 213 may also be referred to as an inverse transformation and inverse quantization block 213 or an inverse transformation residual block 213.
  • the reconstruction unit 214 (for example, the summer 214) is used to add the inverse transform block 213 (that is, the reconstructed residual block 213) to the prediction block 265 to obtain the reconstructed block 215 in the sample domain, for example, The sample value of the reconstructed residual block 213 and the sample value of the prediction block 265 are added.
  • the buffer unit 216 (or “buffer” 216 for short) such as the line buffer 216 is used to buffer or store the reconstructed block 215 and the corresponding sample value, for example, for intra prediction.
  • the encoder can be used to use the unfiltered reconstructed block and/or the corresponding sample value stored in the buffer unit 216 to perform any type of estimation and/or prediction, such as intra-frame prediction.
  • the embodiment of the encoder 20 may be configured such that the buffer unit 216 is used not only for storing the reconstructed block 215 for intra prediction 254, but also for the loop filter unit 220 (not shown in FIG. 2 Out), and/or, for example, the buffer unit 216 and the decoded picture buffer unit 230 form one buffer.
  • Other embodiments may be used to use the filtered block 221 and/or blocks or samples from the decoded picture buffer 230 (neither shown in FIG. 2) as the input or basis for the intra prediction 254.
  • the loop filter unit 220 (or “loop filter” 220 for short) is used to filter the reconstructed block 215 to obtain the filtered block 221, thereby smoothly performing pixel conversion or improving video quality.
  • the loop filter unit 220 is intended to represent one or more loop filters, such as deblocking filters, sample-adaptive offset (SAO) filters or other filters, such as bilateral filters, auto Adaptive loop filter (ALF), or sharpening or smoothing filter, or collaborative filter.
  • the loop filter unit 220 is shown as an in-loop filter in FIG. 2, in other configurations, the loop filter unit 220 may be implemented as a post-loop filter.
  • the filtered block 221 may also be referred to as a filtered reconstructed block 221.
  • the decoded picture buffer 230 may store the reconstructed coded block after the loop filter unit 220 performs a filtering operation on the reconstructed coded block.
  • the embodiment of the encoder 20 may be used to output loop filter parameters (e.g., sample adaptive offset information), for example, directly output or by the entropy encoding unit 270 or any other
  • the entropy coding unit outputs after entropy coding, for example, so that the decoder 30 can receive and apply the same loop filter parameters for decoding.
  • the decoded picture buffer (DPB) 230 may be a reference picture memory that stores reference picture data for the encoder 20 to encode video data.
  • DPB 230 can be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM) (resistive RAM, RRAM)) or other types of memory devices.
  • DRAM dynamic random access memory
  • SDRAM synchronous DRAM
  • MRAM magnetoresistive RAM
  • RRAM resistive RAM
  • the DPB 230 and the buffer 216 may be provided by the same memory device or by separate memory devices.
  • a decoded picture buffer (DPB) 230 is used to store the filtered block 221.
  • the decoded picture buffer 230 may be further used to store other previous filtered blocks of the same current picture or different pictures such as the previously reconstructed picture, such as the previously reconstructed and filtered block 221, and may provide a complete previous Reconstruction is a decoded picture (and corresponding reference blocks and samples) and/or a partially reconstructed current picture (and corresponding reference blocks and samples), for example, for inter prediction.
  • a decoded picture buffer (DPB) 230 is used to store the reconstructed block 215.
  • the prediction processing unit 260 also called the block prediction processing unit 260, is used to receive or obtain the image block 203 (the current image block 203 of the current picture 201) and reconstructed picture data, such as the same (current) picture from the buffer 216
  • the reference samples and/or the reference picture data 231 of one or more previously decoded pictures from the decoded picture buffer 230, and used to process such data for prediction, that is, the provision can be an inter-predicted block 245 or a The prediction block 265 of the intra prediction block 255.
  • the mode selection unit 262 may be used to select a prediction mode (for example, intra or inter prediction mode) and/or the corresponding prediction block 245 or 255 used as the prediction block 265 to calculate the residual block 205 and reconstruct the reconstructed block 215.
  • a prediction mode for example, intra or inter prediction mode
  • the corresponding prediction block 245 or 255 used as the prediction block 265 to calculate the residual block 205 and reconstruct the reconstructed block 215.
  • the embodiment of the mode selection unit 262 can be used to select a prediction mode (for example, from those supported by the prediction processing unit 260) that provides the best match or minimum residual (the minimum residual means Better compression in transmission or storage), or provide minimal signaling overhead (minimum signaling overhead means better compression in transmission or storage), or consider or balance both.
  • the mode selection unit 262 may be configured to determine a prediction mode based on rate distortion optimization (RDO), that is, select a prediction mode that provides the smallest rate-distortion optimization, or select a prediction mode whose related rate-distortion at least meets the prediction mode selection criteria .
  • RDO rate distortion optimization
  • the encoder 20 is used to determine or select the best or optimal prediction mode from a set of (predetermined) prediction modes.
  • the prediction mode set may include, for example, an intra prediction mode and/or an inter prediction mode.
  • the set of intra prediction modes may include 35 different intra prediction modes, for example, non-directional modes such as DC (or mean) mode and planar mode, or directional modes as defined in H.265, or may include 67 Different intra-frame prediction modes, for example, non-directional modes such as DC (or mean) mode and planar mode, or directional modes as defined in H.266 under development.
  • the set of inter-frame prediction modes depends on the available reference pictures (ie, for example, the aforementioned at least part of the decoded pictures stored in the DBP230) and other inter-frame prediction parameters, such as whether to use the entire reference picture or only use A part of the reference picture, such as the search window area surrounding the area of the current block, to search for the best matching reference block, and/or depending on whether pixel interpolation such as half pixel and/or quarter pixel interpolation is applied.
  • the set of inter prediction modes may include, for example, an advanced motion vector (Advanced Motion Vector Prediction, AMVP) mode and a merge mode.
  • AMVP Advanced Motion Vector Prediction
  • the set of inter-frame prediction modes may include the improved AMVP mode based on control points in the embodiments of the present application, and the improved merge mode based on control points.
  • the intra prediction unit 254 may be used to perform any combination of inter prediction techniques described below.
  • the embodiments of the present application may also apply skip mode and/or direct mode.
  • the prediction processing unit 260 may be further used to divide the image block 203 into smaller block partitions or sub-blocks, for example, by iteratively using quad-tree (QT) segmentation and binary-tree (BT) segmentation. Or triple-tree (TT) segmentation, or any combination thereof, and used to perform prediction, for example, for each of the block partitions or sub-blocks, where the mode selection includes selecting the tree structure of the segmented image block 203 and selecting the application The prediction mode for each of the block partitions or sub-blocks.
  • QT quad-tree
  • BT binary-tree
  • TT triple-tree
  • the inter prediction unit 244 may include a motion estimation (ME) unit (not shown in FIG. 2) and a motion compensation (MC) unit (not shown in FIG. 2).
  • the motion estimation unit is used to receive or obtain the picture image block 203 (the current picture image block 203 of the current picture 201) and the decoded picture 231, or at least one or more previously reconstructed blocks, for example, one or more other/different
  • the reconstructed block of the previously decoded picture 231 is used for motion estimation.
  • the video sequence may include the current picture and the previously decoded picture 31, or in other words, the current picture and the previously decoded picture 31 may be part of the picture sequence forming the video sequence, or form the picture sequence.
  • the encoder 20 may be used to select a reference block from multiple reference blocks of the same or different pictures among multiple other pictures, and provide the reference picture and/or provide a reference to the motion estimation unit (not shown in FIG. 2)
  • the offset (spatial offset) between the position of the block (X, Y coordinates) and the position of the current block is used as an inter prediction parameter. This offset is also called a motion vector (MV).
  • the motion compensation unit is used to obtain inter prediction parameters, and perform inter prediction based on or using the inter prediction parameters to obtain the inter prediction block 245.
  • the motion compensation performed by the motion compensation unit may include fetching or generating a prediction block based on a motion/block vector determined by motion estimation (interpolation of sub-pixel accuracy may be performed). Interpolation filtering can generate additional pixel samples from known pixel samples, thereby potentially increasing the number of candidate prediction blocks that can be used to encode picture blocks.
  • the motion compensation unit 246 can locate the prediction block pointed to by the motion vector in a reference picture list.
  • the motion compensation unit 246 may also generate syntax elements associated with the blocks and video slices for use by the decoder 30 when decoding picture blocks of the video slices.
  • the aforementioned inter-prediction unit 244 may transmit syntax elements to the entropy encoding unit 270, and the syntax elements include inter-prediction parameters (for example, after traversing multiple inter-prediction modes and selecting the inter-prediction mode used for prediction of the current block) Instructions).
  • the inter-frame prediction parameter may not be carried in the syntax element.
  • the decoder 30 can directly use the default prediction mode for decoding. It can be understood that the inter prediction unit 244 may be used to perform any combination of inter prediction techniques.
  • the intra prediction unit 254 is used to obtain, for example, receive a picture block 203 (current picture block) of the same picture and one or more previously reconstructed blocks, for example reconstructed adjacent blocks, for intra estimation.
  • the encoder 20 may be used to select an intra prediction mode from a plurality of (predetermined) intra prediction modes.
  • the embodiment of the encoder 20 may be used to select an intra prediction mode based on optimization criteria, for example, based on a minimum residual (for example, an intra prediction mode that provides a prediction block 255 most similar to the current picture block 203) or a minimum rate distortion.
  • a minimum residual for example, an intra prediction mode that provides a prediction block 255 most similar to the current picture block 203
  • a minimum rate distortion for example, an intra prediction mode that provides a prediction block 255 most similar to the current picture block 203
  • the intra prediction unit 254 is further configured to determine the intra prediction block 255 based on the intra prediction parameters of the selected intra prediction mode. In any case, after selecting the intra prediction mode for the block, the intra prediction unit 254 is also used to provide intra prediction parameters to the entropy encoding unit 270, that is, to provide an indication of the selected intra prediction mode for the block Information. In one example, the intra prediction unit 254 may be used to perform any combination of intra prediction techniques.
  • the aforementioned intra-prediction unit 254 may transmit syntax elements to the entropy encoding unit 270, and the syntax elements include intra-prediction parameters (for example, after traversing multiple intra-prediction modes, selecting the intra-prediction mode used for prediction of the current block) Instructions).
  • the intra prediction parameter may not be carried in the syntax element.
  • the decoder 30 can directly use the default prediction mode for decoding.
  • the entropy coding unit 270 is used to apply entropy coding algorithms or schemes (for example, variable length coding (VLC) scheme, context adaptive VLC (context adaptive VLC, CAVLC) scheme, arithmetic coding scheme, context adaptive binary arithmetic) Coding (context adaptive binary arithmetic coding, CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding or other entropy Encoding method or technique) applied to quantized residual coefficients 209, inter-frame prediction parameters, intra-frame prediction parameters and/or loop filter parameters, one or all (or not applied), to obtain the output 272
  • VLC variable length coding
  • CAVLC context adaptive VLC
  • CABAC context adaptive binary arithmetic
  • SBAC syntax-based context-adaptive binary arithmetic coding
  • PIPE probability interval partitioning entropy
  • encoded picture data 21 output in the form of encoded bitstream
  • the encoded bitstream can be transmitted to the video decoder 30, or archived for later transmission or retrieval by the video decoder 30.
  • the entropy encoding unit 270 may also be used for entropy encoding other syntax elements of the current video slice being encoded.
  • the non-transform-based encoder 20 may directly quantize the residual signal without the transform processing unit 206 for certain blocks or frames.
  • the encoder 20 may have a quantization unit 208 and an inverse quantization unit 210 combined into a single unit.
  • the encoder 20 may be used to implement the entropy coding method of syntax elements described in the following embodiments.
  • the video encoder 20 may directly quantize the residual signal without being processed by the transform processing unit 206, and accordingly does not need to be processed by the inverse transform processing unit 212; or, for some For image blocks or image frames, the video encoder 20 does not generate residual data, and accordingly does not need to be processed by the transform processing unit 206, quantization unit 208, inverse quantization unit 210, and inverse transform processing unit 212; or, the video encoder 20 may The reconstructed image block is directly stored as a reference block without being processed by the filter 220; or, the quantization unit 208 and the inverse quantization unit 210 in the video encoder 20 may be combined together.
  • the loop filter 220 is optional, and for lossless compression coding, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, and the inverse transform processing unit 212 are optional. It should be understood that, according to different application scenarios, the inter prediction unit 244 and the intra prediction unit 254 may be selectively activated.
  • FIG. 3 shows a schematic/conceptual block diagram of an example of a decoder 30 for implementing an embodiment of the present application.
  • the video decoder 30 is used to receive, for example, encoded picture data (for example, an encoded bit stream) 21 encoded by the encoder 20 to obtain a decoded picture 231.
  • video decoder 30 receives video data from video encoder 20, such as an encoded video bitstream and associated syntax elements that represent picture blocks of an encoded video slice.
  • the decoder 30 includes an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (such as a summer 314), a buffer 316, a loop filter 320, and The decoded picture buffer 330 and the prediction processing unit 360.
  • the prediction processing unit 360 may include an inter prediction unit 344, an intra prediction unit 354, and a mode selection unit 362.
  • video decoder 30 may perform decoding passes that are substantially reciprocal of the encoding passes described with video encoder 20 of FIG. 2.
  • the entropy decoding unit 304 is configured to perform entropy decoding on the encoded picture data 21 to obtain, for example, quantized coefficients 309 and/or decoded encoding parameters (not shown in FIG. 3), for example, inter prediction, intra prediction parameters , Loop filter parameters and/or any one or all of other syntax elements (decoded).
  • the entropy decoding unit 304 is further configured to forward the inter prediction parameters, intra prediction parameters and/or other syntax elements to the prediction processing unit 360.
  • the video decoder 30 may receive syntax elements at the video slice level and/or the video block level.
  • the inverse quantization unit 310 can be functionally the same as the inverse quantization unit 110
  • the inverse transformation processing unit 312 can be functionally the same as the inverse transformation processing unit 212
  • the reconstruction unit 314 can be functionally the same as the reconstruction unit 214
  • the buffer 316 can be functionally identical.
  • the loop filter 320 may be functionally the same as the loop filter 220
  • the decoded picture buffer 330 may be functionally the same as the decoded picture buffer 230.
  • the prediction processing unit 360 may include an inter prediction unit 344 and an intra prediction unit 354.
  • the inter prediction unit 344 may be functionally similar to the inter prediction unit 244, and the intra prediction unit 354 may be functionally similar to the intra prediction unit 254.
  • the prediction processing unit 360 is generally used to perform block prediction and/or obtain a prediction block 365 from the encoded data 21, and to receive or obtain (explicitly or implicitly) prediction-related parameters and/or information about the prediction from the entropy decoding unit 304, for example. Information about the selected prediction mode.
  • the intra-prediction unit 354 of the prediction processing unit 360 is used for the intra-prediction mode based on the signal and the previous decoded block from the current frame or picture. Data to generate a prediction block 365 for the picture block of the current video slice.
  • the inter-frame prediction unit 344 eg, motion compensation unit
  • the prediction processing unit 360 is used for the motion vector and the received from the entropy decoding unit 304
  • the other syntax elements generate a prediction block 365 for the video block of the current video slice.
  • a prediction block can be generated from a reference picture in a reference picture list.
  • the video decoder 30 may use the default construction technique to construct a list of reference frames based on the reference pictures stored in the DPB 330: list 0 and list 1.
  • the prediction processing unit 360 is configured to determine prediction information for the video block of the current video slice by parsing the motion vector and other syntax elements, and use the prediction information to generate the prediction block for the current video block being decoded.
  • the prediction processing unit 360 uses some syntax elements received to determine the prediction mode (for example, intra or inter prediction) and the inter prediction slice type ( For example, B slice, P slice or GPB slice), construction information for one or more of the reference picture list for the slice, motion vector for each inter-coded video block of the slice, The inter prediction status and other information of each inter-encoded video block of the slice to decode the video block of the current video slice.
  • the syntax elements received by the video decoder 30 from the bitstream include receiving adaptive parameter set (APS), sequence parameter set (sequence parameter set, SPS), and picture parameter set (picture parameter set). parameter set, PPS) or a syntax element in one or more of the slice headers.
  • APS adaptive parameter set
  • SPS sequence parameter set
  • PPS picture parameter set
  • the inverse quantization unit 310 may be used to inverse quantize (ie, inverse quantize) the quantized transform coefficients provided in the bitstream and decoded by the entropy decoding unit 304.
  • the inverse quantization process may include using the quantization parameter calculated by the video encoder 20 for each video block in the video slice to determine the degree of quantization that should be applied and also determine the degree of inverse quantization that should be applied.
  • the inverse transform processing unit 312 is used to apply an inverse transform (for example, an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process) to transform coefficients so as to generate a residual block in the pixel domain.
  • an inverse transform for example, an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process
  • the reconstruction unit 314 (for example, the summer 314) is used to add the inverse transform block 313 (that is, the reconstructed residual block 313) to the prediction block 365 to obtain the reconstructed block 315 in the sample domain, for example by adding The sample value of the reconstructed residual block 313 and the sample value of the prediction block 365 are added.
  • the loop filter unit 320 (during the encoding cycle or after the encoding cycle) is used to filter the reconstructed block 315 to obtain the filtered block 321, thereby smoothly performing pixel transformation or improving video quality.
  • the loop filter unit 320 may be used to perform any combination of the filtering techniques described below.
  • the loop filter unit 320 is intended to represent one or more loop filters, such as deblocking filters, sample-adaptive offset (SAO) filters or other filters, such as bilateral filters, auto Adaptive loop filter (ALF), or sharpening or smoothing filter, or collaborative filter.
  • the loop filter unit 320 is shown as an in-loop filter in FIG. 3, in other configurations, the loop filter unit 320 may be implemented as a post-loop filter.
  • the decoded video block 321 in a given frame or picture is then stored in a decoded picture buffer 330 that stores reference pictures for subsequent motion compensation.
  • the decoder 30 is used, for example, to output the decoded picture 31 through the output 332 for presentation or viewing by the user.
  • the decoder 30 may generate an output video stream without the loop filter unit 320.
  • the non-transform-based decoder 30 may directly inversely quantize the residual signal without the inverse transform processing unit 312 for certain blocks or frames.
  • the video decoder 30 may have an inverse quantization unit 310 and an inverse transform processing unit 312 combined into a single unit.
  • the decoder 30 is configured to implement the entropy decoding method of syntax elements described in the following embodiments.
  • the video decoder 30 may generate an output video stream without processing by the filter 320; or, for some image blocks or image frames, the entropy decoding unit 304 of the video decoder 30 does not decode the quantized coefficients, and accordingly does not It needs to be processed by the inverse quantization unit 310 and the inverse transform processing unit 312.
  • the loop filter 320 is optional; and for lossless compression, the inverse quantization unit 310 and the inverse transform processing unit 312 are optional.
  • the inter prediction unit and the intra prediction unit may be selectively activated.
  • the processing result for a certain link can be further processed and output to the next link, for example, in interpolation filtering, motion vector derivation or loop filtering, etc.
  • operations such as Clip or shift are further performed on the processing results of the corresponding link.
  • FIG. 4 is a schematic structural diagram of a video decoding device 400 (for example, a video encoding device 400 or a video decoding device 400) provided by an embodiment of the present application.
  • the video coding device 400 is suitable for implementing the embodiments described herein.
  • the video coding device 400 may be a video decoder (for example, the decoder 30 of FIG. 1A) or a video encoder (for example, the encoder 20 of FIG. 1A).
  • the video coding device 400 may be one or more components of the decoder 30 in FIG. 1A or the encoder 20 in FIG. 1A described above.
  • the video decoding device 400 includes: an entry port 410 for receiving data and a receiving unit (Rx) 420, a processor, logic unit or central processing unit (CPU) 430 for processing data, and a transmitter unit for transmitting data (Tx) 440 and outlet port 450, and a memory 460 for storing data.
  • the video decoding device 400 may further include a photoelectric conversion component and an electro-optical (EO) component coupled with the inlet port 410, the receiver unit 420, the transmitter unit 440, and the outlet port 450 for the outlet or inlet of optical signals or electrical signals.
  • EO electro-optical
  • the processor 430 is implemented by hardware and software.
  • the processor 430 may be implemented as one or more CPU chips, cores (for example, multi-core processors), FPGA, ASIC, and DSP.
  • the processor 430 communicates with the ingress port 410, the receiver unit 420, the transmitter unit 440, the egress port 450, and the memory 460.
  • the processor 430 includes a decoding module 470 (for example, an encoding module 470 or a decoding module 470).
  • the encoding/decoding module 470 implements the embodiments disclosed herein to implement the chroma block prediction method provided in the embodiments of the present application. For example, the encoding/decoding module 470 implements, processes, or provides various encoding operations.
  • the encoding/decoding module 470 provides a substantial improvement to the function of the video decoding device 400 and affects the conversion of the video decoding device 400 to different states.
  • the encoding/decoding module 470 is implemented by instructions stored in the memory 460 and executed by the processor 430.
  • the memory 460 includes one or more magnetic disks, tape drives, and solid-state hard disks, and can be used as an overflow data storage device for storing programs when these programs are selectively executed, and storing instructions and data read during program execution.
  • the memory 460 may be volatile and/or non-volatile, and may be read-only memory (ROM), random access memory (RAM), random access memory (ternary content-addressable memory, TCAM), and/or static Random Access Memory (SRAM).
  • FIG. 5 is a simplified block diagram of an apparatus 500 that can be used as either or both of the source device 12 and the destination device 14 in FIG. 1A according to an exemplary embodiment.
  • the device 500 can implement the technology of the present application.
  • FIG. 5 is a schematic block diagram of an implementation manner of an encoding device or a decoding device (referred to as a decoding device 500 for short) according to an embodiment of the application.
  • the decoding device 500 may include a processor 510, a memory 530, and a bus system 550.
  • the processor and the memory are connected through a bus system, the memory is used to store instructions, and the processor is used to execute instructions stored in the memory.
  • the memory of the decoding device stores program codes, and the processor can call the program codes stored in the memory to execute various video encoding or decoding methods described in this application, especially various new entropy encoding/decoding methods of syntax elements. To avoid repetition, it will not be described in detail here.
  • the processor 510 may be a central processing unit (Central Processing Unit, referred to as "CPU"), and the processor 510 may also be other general-purpose processors, digital signal processors (DSP), and dedicated integrated Circuit (ASIC), off-the-shelf programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc.
  • the general-purpose processor may be a microprocessor or the processor may also be any conventional processor or the like.
  • the memory 530 may include a read only memory (ROM) device or a random access memory (RAM) device. Any other suitable type of storage device can also be used as the memory 530.
  • the memory 530 may include code and data 531 accessed by the processor 510 using the bus 550.
  • the memory 530 may further include an operating system 533 and an application program 535.
  • the application program 535 includes at least one that allows the processor 510 to execute the video encoding or decoding method described in this application (especially the entropy encoding/decoding method of syntax elements described in this application). A program.
  • the bus system 550 may also include a power bus, a control bus, and a status signal bus. However, for clear description, various buses are marked as the bus system 550 in the figure.
  • the decoding device 500 may further include one or more output devices, such as a display 570.
  • the display 570 may be a touch-sensitive display that merges the display with a touch-sensitive unit operable to sense touch input.
  • the display 570 may be connected to the processor 510 via the bus 550.
  • Fig. 6 is a schematic flowchart of an entropy coding method for syntax elements used to implement an embodiment of the present application.
  • This process 600 may be performed by the video encoder 20.
  • the process 600 is described as a series of steps or operations. It should be understood that the process 600 may be executed in various orders and/or occur simultaneously, and is not limited to the execution order shown in FIG. 6.
  • the entropy coding method of syntax elements includes:
  • Step 601 Determine whether the length of the current fusion candidate motion vector list is greater than a preset value.
  • the length of the fusion candidate motion vector list refers to the number of candidate motion vectors (Motion Vector, MV) included in the fusion candidate motion vector list (the number is represented by MaxNumMergeCand, for example).
  • MMVD technology utilizes a list of fusion candidate motion vectors. First, a candidate MV is selected from the list of fusion candidate motion vectors as the basic MV, and then the MV is extended and expressed based on the basic MV.
  • the MV extended expression has three elements, namely the MV starting point and the movement step. Length (Distance) and movement direction (Direction).
  • the selected candidate MV is the MV starting point.
  • the selected candidate MV is used to determine the initial position of the MV.
  • the base candidate index (Base candidate IDX) is used to indicate the index of the candidate MV in the merged candidate motion vector list
  • Nth MVP is used to indicate the Nth MV in the merged candidate motion vector list.
  • Base candidate IDX can be used to indicate its corresponding candidate MV. If the number of candidate MVs available for selection in the fusion candidate motion vector list is 1, the Base candidate IDX may not be used.
  • the step identifier (Distance IDX) is used to indicate the offset distance of the MV.
  • Distance IDX is used to indicate the index of the pixel distance offset from the initial position
  • Pixel distance is used to indicate the pixel distance offset from the initial position (MV starting point).
  • Distance IDX 2
  • the corresponding pixel distance is 1-pel (ie one pixel)
  • the corresponding pixel distance can be represented by Distance IDX.
  • the direction IDX is used to indicate the offset direction of the MV. See Table 3.
  • Direction IDX is used to indicate the MV offset direction based on the initial position (MV starting point)
  • x-axis is used to indicate the component of the offset direction on the x axis
  • y-axis is used to indicate the offset direction The component of the y axis.
  • the corresponding offset direction can be indicated by Direction IDX.
  • the process of using MMVD technology to determine the predicted pixel value of the current block includes: first determining the MV starting point according to Basecandidate IDX, then determining the offset direction based on the MV starting point according to Direction IDX, and finally determining the offset indicated in Direction IDX according to Distance IDX
  • the syntax element mmvd_cand_flag[x0][y0] is used to indicate from any two candidate MVs in the fusion candidate motion vector list (for example, the first candidate MV and the second candidate MV in the fusion candidate motion vector list).
  • mmvd_cand_flag[x0][y0] 0 by default.
  • (x0, y0) represents the position of the current block in the current image, that is, the coordinate position of the pixel point of the upper left vertex of the current block relative to the pixel point of the upper left vertex of the current image.
  • the first syntax element mmvd_cand_flag is used to indicate that the first candidate MV or the second candidate MV is selected from the list of fusion candidate motion vectors as the basic MV for motion vector expansion.
  • the first candidate MV and the second candidate MV are fusion candidates. Any two candidate MVs in the motion vector list.
  • the first syntax element mmvd_cand_flag only has meaning when the number of candidate MVs available for selection in the fusion candidate motion vector list is greater than a preset value (for example, 1), so this application first determines the current fusion candidate motion vector list Whether the length is greater than the preset value.
  • N 3 and the indexes of any N candidate MVs are 0, 1, and 2, respectively, the value of mmvd_cand_flag can be any one of 0-2.
  • Step 602 If the length of the fusion candidate motion vector list is greater than the preset value, use the bypass coding mode to perform entropy coding on the value of the first syntax element.
  • CABAC is a commonly used entropy coding technology for the coding and decoding of syntax element values.
  • the processing process of CABAC mainly includes binarization, context modeling and binary arithmetic coding.
  • binarization refers to binary processing of the input non-binary syntax element value and unique conversion into a binary sequence (ie, binary string); context modeling refers to every bit (bin) in the binary string , Determine the probability model of the bit according to the context information (for example, the coding information in the reconstructed area around the corresponding node of the syntax element); binary arithmetic coding means to code the corresponding bit according to the probability value in the probability model, and according to The value of the bit updates the probability value in the probability model.
  • the basic principle of arithmetic coding is: according to the occurrence probability of different values (ie 0 or 1) of the bits in the binary string, the [0,1) interval is divided into non-overlapping sub-intervals, and the width of the sub-intervals is exactly the same as each The probability of the value, so that the different bits of the binary string will correspond to each sub-interval one-to-one, and then the interval mapping is performed recursively, and finally a cell is obtained. A representative decimal number from the cell is selected as the actual Encoding output. Statistically, the closer the probability of a bit to 1 is to 0.5, the more bits are needed to encode the bit; the closer the probability of a bit to 1 is to 0 or 1, the more bits are needed to encode the bit. less.
  • Regular coding mode and bypass coding mode include context modeling and binary arithmetic coding, which are two different entropy coding methods.
  • the probability of occurrence of binary symbols 0 and 1 is fixed at 0.5, which is compared with the conventional coding mode:
  • the probability estimation and update process of the bypass coding mode is omitted, that is, no context modeling is required , There is no need to update the context model;
  • the probability interval subdivision operation process of the bypass coding mode is simplified, that is, only the probability interval needs to be divided equally, while the conventional coding mode needs to subdivide the current based on the estimated probability Probability interval. It can be seen that the bypass coding mode can be regarded as a special case of the conventional coding mode.
  • the process of entropy encoding the value of the first syntax element (mmvd_cand_flag) in the bypass encoding mode includes:
  • Binary transformation is performed on the value of the first syntax element mmvd_cand_flag in the syntax elements to obtain a binary string, and the binary string includes one or more bins.
  • the value of mmvd_cand_flag is 0 or 1, so a binary bit can be obtained by binarizing it.
  • a bit of 0 indicates that the value of mmvd_cand_flag is 0, and a bit of 1 indicates that the value of mmvd_cand_flag is 1.
  • binarization of mmvd_cand_flag can also obtain two binary bits.
  • Binarization of mmvd_cand_flag can also obtain one or more binary bits.
  • a bit of 0 indicates that the value of mmvd_cand_flag is 0, and a bit of 10 indicates that the value of mmvd_cand_flag is 1. It should be noted that this application may also adopt other methods to perform binary transformation on the value of mmvd_cand_flag, which is not specifically limited.
  • the binarization process can be omitted.
  • the interval is [0,28)
  • This application obtains the code string of the binary string according to the first probability interval and the second probability interval. For example, this application can perform a renormalization operation when the length of the probability interval is less than half of the left boundary value of the probability interval, shift the length of the probability interval to the left by one bit, and extend it to the left boundary value of the probability interval. More than one-half, and then shift the left boundary of the probability interval by one bit to the left and output the most significant bit to obtain the code string of mmvd_cand_flag.
  • This is the code string that takes the value 0 of mmvd_cand_flag.
  • the entropy encoding of the first syntax element mmvd_cand_flag in the syntax element in this application can be understood as encoding the bits in the binary string of the value of mmvd_cand_flag, specifically, in the binary string based on the value of mmvd_cand_flag The probability value of the bit is encoded.
  • the switch flag (byPassFlag) indicating the bypass coding mode is set to the first value, and the bypass coding mode is used for the first value.
  • the value of the syntax element is entropy coded.
  • the background operation step of the encoder starting the bypass encoding mode to perform entropy encoding on the value of the first syntax element is that the encoder reads that the switch identifier of the bypass encoding mode is set to the first value.
  • Fig. 7 is another schematic flow chart for implementing the method for entropy decoding of syntax elements in an embodiment of the present application.
  • This process 700 may be performed by the video decoder 30.
  • the process 700 is described as a series of steps or operations. It should be understood that the process 700 may be executed in various orders and/or occur simultaneously, and is not limited to the execution order shown in FIG. 7.
  • the entropy decoding method of syntax elements includes:
  • Step 701 Determine whether the length of the current fusion candidate motion vector list is greater than a preset value.
  • the length of the fusion candidate motion vector list refers to the number of candidate MVs included in the fusion candidate motion vector list (the number is represented by MaxNumMergeCand, for example).
  • Step 702 If the length of the merged candidate motion vector list is greater than the preset value, use the bypass decoding mode to perform entropy decoding on the encoded string of the first syntax element.
  • the first syntax element is used to indicate to select the first candidate motion vector or the second candidate motion vector from the list of fusion candidate motion vectors as the basic motion vector for motion vector expansion.
  • the first candidate motion vector and the second candidate motion vector are fusion candidate motions Any two candidate motion vectors in the vector list.
  • this embodiment adopts the bypass decoding mode to perform entropy decoding on mmvd_cand_flag, so there is no need to assign specific bits in the binary string of mmvd_cand_flag.
  • the probability model reduces the decoding complexity.
  • this embodiment is to perform entropy decoding on the code string of mmvd_cand_flag in the bitstream to obtain the value of mmvd_cand_flag.
  • the process of performing entropy decoding on the encoded string of the first syntax element (mmvd_cand_flag) in the bypass decoding mode in this application includes:
  • the first engine parameter is used to indicate the length of the probability interval
  • the second engine parameter is used to indicate the left boundary of the probability interval.
  • the first engine parameter is ivlCurrRange
  • the second engine parameter is ivlOffset.
  • the encoding string of the first syntax element mmvd_cand_flag adopts the bypass decoding mode to perform entropy decoding, and there is no need to assign a specific probability model to the bits in the binary string of mmvd_cand_flag, which reduces the decoding complexity.
  • the switch flag (byPassFlag) indicating the bypass decoding mode is set to the first value, and the bypass decoding mode is used for the first value.
  • the value of the syntax element is entropy.
  • the background operation step of the decoder initiating the bypass decoding mode to perform entropy decoding on the value of the first syntax element is that the decoder reads that the switch identifier of the bypass decoding mode is set to the first value.
  • Y, U and V respectively represent the three components of the video data format (Y represents the luminance component, U and V represent the chrominance component), corresponding to different test sequence categories (for example, Class A1, Class A2, Class B, Class C, Class E etc.)
  • the performance gain results of the encoding/decoding using the bypass encoding/decoding mode compared to the conventional encoding/decoding mode can be obtained by simulation, and it can be seen that the overall display performance of the average simulation result (Overall) is basically unchanged.
  • the encoding time (EncT) and decoding time (DecT) also correspond to different test sequence categories, and simulation results can be obtained using the bypass encoding/decoding mode compared to the conventional encoding/decoding mode.
  • the average simulation results also show that the processing time is reduced.
  • the three components of the video signal represented by Y, U, and V, corresponding to different test sequence categories, can be simulated using bypass encoding/decoding mode compared to conventional encoding/
  • the average simulation result shows a certain improvement in performance.
  • Encoding time (EncT) and decoding time (DecT) also corresponding to different test sequence categories, can be simulated to obtain the comparison result of the time required for encoding/decoding in the bypass encoding/decoding mode compared to the conventional encoding/decoding mode, which can be seen
  • the average simulation results also show a reduction in processing time.
  • FIG. 8 is a structural block diagram of an entropy encoding device 800 used to implement an embodiment of the present application.
  • the entropy encoding device 800 includes a judgment module 801 and an encoding module 802, wherein:
  • the judging module 801 is used to judge whether the length of the current merged candidate motion vector list is greater than a preset value; the encoding module 802 is used to adopt the bypass coding mode if the length of the merged candidate motion vector list is greater than the preset value Entropy coding the value of the first syntax element, where the first syntax element is used to instruct to select the first candidate motion vector or the second candidate motion vector from the list of fused candidate motion vectors as the basic motion vector for motion vector expansion, The first candidate motion vector and the second candidate motion vector are any two candidate motion vectors in the fusion candidate motion vector list.
  • the encoding module 802 is further configured to, if the length of the merged candidate motion vector list is greater than the preset value, set the switch identifier indicating the bypass encoding mode to the first One value, using the bypass coding mode to perform entropy coding on the value of the first syntax element.
  • the first syntax element is mmvd_cand_flag.
  • the above judgment module 801 and encoding module 802 can be applied to the entropy encoding process at the encoding end. Specifically, at the encoding end, these modules can be applied to the entropy encoding unit 270 of the aforementioned encoder 20.
  • FIG. 9 is a structural block diagram of an entropy decoding device 900 used to implement an embodiment of the present application.
  • the entropy decoding device 900 includes a judgment module 901 and a decoding module 902, wherein:
  • the judging module 901 is used to judge whether the length of the current fusion candidate motion vector list is greater than a preset value; the decoding module 902 is used to adopt the bypass coding mode if the length of the fusion candidate motion vector list is greater than the preset value Entropy decoding the value of the first syntax element, the first syntax element being used to instruct to select the first candidate motion vector or the second candidate motion vector from the fusion candidate motion vector list as the basic motion vector for motion vector expansion,
  • the first candidate motion vector and the second candidate motion vector are any two candidate motion vectors in the fusion candidate motion vector list.
  • the decoding module 902 is further configured to, if the length of the merged candidate motion vector list is greater than the preset value, set the switch identifier indicating the bypass encoding mode to the first One value, using the bypass coding mode to perform entropy decoding on the value of the first syntax element.
  • the first syntax element is mmvd_cand_flag.
  • the above judgment module 901 and decoding module 902 can be applied to the entropy decoding process at the decoding end. Specifically, at the decoding end, these modules can be applied to the entropy decoding unit 304 of the aforementioned decoder 30.
  • the computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium, or a communication medium that includes any medium that facilitates the transfer of a computer program from one place to another (for example, according to a communication protocol) .
  • computer-readable media may generally correspond to (1) non-transitory tangible computer-readable storage media, or (2) communication media, such as signals or carrier waves.
  • Data storage media can be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, codes, and/or data structures for implementing the techniques described in this application.
  • the computer program product may include a computer-readable medium.
  • such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, flash memory, or structures that can be used to store instructions or data Any other media that can be accessed by the computer in the form of desired program code. And, any connection is properly termed a computer-readable medium.
  • any connection is properly termed a computer-readable medium.
  • coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave to transmit instructions from a website, server, or other remote source
  • coaxial cable Wire, fiber optic cable, twisted pair, DSL or wireless technologies such as infrared, radio and microwave are included in the definition of media.
  • the computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other temporary media, but are actually directed to non-transient tangible storage media.
  • magnetic disks and optical disks include compact disks (CDs), laser disks, optical disks, digital versatile disks (DVD) and Blu-ray disks, where disks usually reproduce data magnetically, while optical disks use lasers to reproduce data optically data. Combinations of the above should also be included in the scope of computer-readable media.
  • DSP digital signal processors
  • ASIC application-specific integrated circuits
  • FPGA field programmable logic arrays
  • processor may refer to any of the foregoing structure or any other structure suitable for implementing the techniques described herein.
  • DSP digital signal processors
  • ASIC application-specific integrated circuits
  • FPGA field programmable logic arrays
  • the term "processor” as used herein may refer to any of the foregoing structure or any other structure suitable for implementing the techniques described herein.
  • the functions described by the various illustrative logical blocks, modules, and steps described herein may be provided in dedicated hardware and/or software modules configured for encoding and decoding, or combined Into the combined codec.
  • the technology may be fully implemented in one or more circuits or logic elements.
  • the technology of this application can be implemented in a variety of devices or devices, including wireless handsets, integrated circuits (ICs), or a set of ICs (for example, chipsets).
  • ICs integrated circuits
  • a set of ICs for example, chipsets.
  • Various components, modules, or units are described in this application to emphasize the functional aspects of the device for performing the disclosed technology, but they do not necessarily need to be implemented by different hardware units.
  • various units can be combined with appropriate software and/or firmware in the codec hardware unit, or by interoperating hardware units (including one or more processors as described above). provide.

Abstract

本申请公开了语法元素的熵编码/解码方法、装置以及编解码器，该方法包括：判断当前融合候选运动矢量列表的长度是否大于预设值；若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵编码/解码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。实施本申请能够减少编码/解码的复杂度。

Description

语法元素的熵编码/解码方法、装置以及编解码器
本申请要求于2019年6月24日提交中国专利局、申请号为201910550626.2、申请名称为“语法元素的熵编码/解码方法、装置以及编解码器”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及视频编解码领域，尤其涉及一种语法元素的熵编码/解码方法、装置以及编解码器。
背景技术
数字视频能力可并入到多种多样的装置中，包含数字电视、数字直播系统、无线广播系统、个人数字助理(PDA)、膝上型或桌上型计算机、平板计算机、电子图书阅读器、数码相机、数字记录装置、数字媒体播放器、视频游戏装置、视频游戏控制台、蜂窝式或卫星无线电电话(所谓的“智能电话”)、视频电话会议装置、视频流式传输装置及其类似者。数字视频装置实施视频压缩技术，例如，在由MPEG-2、MPEG-4、ITU-T H.263、ITU-T H.264/MPEG-4第10部分高级视频编码(AVC)定义的标准、视频编码标准H.265/高效视频编码(HEVC)标准以及此类标准的扩展中所描述的视频压缩技术。视频装置可通过实施此类视频压缩技术来更有效率地发射、接收、编码、解码和/或存储数字视频信息。
基于上下文自适应的二进制算术编码(Context-based Adaptive Binary Arithmetic Coding，CABAC)是一种常用的熵编码(entropy coding)技术，用于语法元素值的编码和解码处理。CABAC的处理过程主要包括二进制化(binarization)、上下文建模(context modeling)和二进制算术编码(binary arithmetic coding)。其中，二进制化是指对输入的非二进制语法元素值进行二进制处理，将其唯一的转换为一个二进制序列(即二进制串)；上下文建模是指对二进制串中的每一个位元，根据上下文信息(例如，语法元素对应节点周围已重建区域内的编码信息)决定该位元的概率模型；二进制算术编码是指根据概率模型中的概率值对对应的位元进行编码，并根据位元的值更新概率模型中的概率值。
相关技术中采用上述CABAC技术对融合运动矢量差(Merge with Motion Vector Difference，MMVD)技术中用到的语法元素mmvd_cand_flag进行熵编码/解码。但是该熵编码/解码的复杂度较高。
发明内容
本申请实施例提供一种语法元素的熵编码/解码方法、装置以及编解码器，减少了编码/解码的复杂度。
第一方面，本申请实施例提供了一种语法元素的熵编码方法，包括：
判断当前融合候选运动矢量列表的长度是否大于预设值；若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵编码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选 运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。
本申请通过对第一语法元素mmvd_cand_flag的值采用旁路编码模式进行熵编码，不需要为mmvd_cand_flag的二进制串中的位元分配特定的概率模型，减少了编码复杂度。
在一种可能的实现方式中，所述若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵编码，还包括：若所述融合候选运动矢量列表的长度大于所述预设值，则将指示所述旁路编码模式的开关标识设置为第一值，采用所述旁路编码模式对所述第一语法元素的值进行熵编码。
通过开关标识指示是否对第一语法元素的值采用旁路编码模式进行熵编码，可以提高编码效率。
在一种可能的实现方式中，所述第一语法元素为mmvd_cand_flag。
第二方面，本申请实施例提供了一种语法元素的熵解码方法，包括：
判断当前融合候选运动矢量列表的长度是否大于预设值；若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵解码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。
本申请通过对第一语法元素mmvd_cand_flag的值采用旁路解码模式进行熵解码，不需要为mmvd_cand_flag的二进制串中的位元分配特定的概率模型，减少了解码复杂度。
在一种可能的实现方式中，所述若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵编码，还包括：若所述融合候选运动矢量列表的长度大于所述预设值，则将指示所述旁路编码模式的开关标识设置为第一值，采用所述旁路编码模式对所述第一语法元素的值进行熵解码。
通过开关标识指示是否对第一语法元素的值采用旁路解码模式进行熵解码，可以提高解码效率。
在一种可能的实现方式中，所述第一语法元素为mmvd_cand_flag。
第三方面，本申请实施例提供了一种熵编码装置，包括：
判断模块，用于判断当前融合候选运动矢量列表的长度是否大于预设值；编码模块，用于若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵编码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。
在一种可能的实现方式中，所述编码模块，还用于若所述融合候选运动矢量列表的长度大于所述预设值，则将指示所述旁路编码模式的开关标识设置为第一值，采用所述旁路编码模式对所述第一语法元素的值进行熵编码。
在一种可能的实现方式中，所述第一语法元素为mmvd_cand_flag。
第四方面，本申请实施例提供了一种熵解码装置，包括：
判断模块，用于判断当前融合候选运动矢量列表的长度是否大于预设值；解码模块， 用于若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵解码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。
在一种可能的实现方式中，所述解码模块，还用于若所述融合候选运动矢量列表的长度大于所述预设值，则将指示所述旁路编码模式的开关标识设置为第一值，采用所述旁路编码模式对所述第一语法元素的值进行熵解码。
在一种可能的实现方式中，所述第一语法元素为mmvd_cand_flag。
第五方面，本申请实施例提供了一种视频编码器，所述视频编码器用于编码图像块，包括：
帧间预测装置，用于基于目标候选运动信息预测当前编码图像块的运动信息，基于所述当前编码图像块的运动信息确定所述当前编码图像块的预测像素值；
如上述第三方面任一项所述的熵编码装置，用于将所述目标候选运动信息的索引标识编入码流，所述索引标识指示用于所述当前编码图像块的所述目标候选运动信息；
重建模块，用于基于所述预测像素值重建所述当前编码图像块。
第六方面，本申请实施例提供了一种视频解码器，所述视频解码器用于从码流中解码出图像块，包括：
如上述第四方面任一项所述的熵解码装置，用于从码流中解码出索引标识，所述索引标识用于指示当前解码图像块的目标候选运动信息；
帧间预测装置，所述帧间预测装置用于基于所述索引标识指示的目标候选运动信息预测当前解码图像块的运动信息，基于所述当前解码图像块的运动信息确定所述当前解码图像块的预测像素值；
重建模块，用于基于所述预测像素值重建所述当前解码图像块。
第七方面，本申请实施例提供了一种视频编码设备，包括：相互耦合的非易失性存储器和处理器，所述处理器调用存储在所述存储器中的程序代码以执行如上述第一方面任一项所描述的方法。
第八方面，本申请实施例提供了一种视频解码设备，包括：相互耦合的非易失性存储器和处理器，所述处理器调用存储在所述存储器中的程序代码以执行如上述第二方面任一项所描述的方法。
第九方面，本申请实施例提供一种计算机可读存储介质，所述计算机可读存储介质存储了程序代码，其中，所述程序代码包括用于执行第一或二方面的任意一种方法的部分或全部步骤的指令。
第十方面，本申请实施例提供一种计算机程序产品，当所述计算机程序产品在计算机上运行时，使得所述计算机执行第一或二方面的任意一种方法的部分或全部步骤。
应当理解的是，本申请的第三至十方面与本申请的第一或二方面的技术方案一致，各方面及对应的可行实施方式所取得的有益效果相似，不再赘述。
可以看到，本申请实施例通过对第一语法元素mmvd_cand_flag的值采用旁路编码/解 码模式进行熵编码/解码，不需要为mmvd_cand_flag的二进制串中的位元分配特定的概率模型，减少了编码/解码复杂度。
附图说明
为了更清楚地说明本申请实施例或背景技术中的技术方案，下面将对本申请实施例或背景技术中所需要使用的附图进行说明。
图1A是用于实现本申请实施例的视频编码及解码系统10实例的框图；
图1B是用于实现本申请实施例的视频译码系统40实例的框图；
图2是用于实现本申请实施例的编码器20实例结构的框图；
图3是用于实现本申请实施例的解码器30实例结构的框图；
图4是用于实现本申请实施例的视频译码设备400实例的框图；
图5是用于实现本申请实施例的另一种编码装置或解码装置实例的框图；
图6是用于实现本申请实施例的语法元素的熵编码方法的一个流程示意图；
图7是用于实现本申请实施例的语法元素的熵解码方法的另一个流程示意图；
图8是用于实现本申请实施例的熵编码装置800的结构框图；
图9是用于实现本申请实施例的熵解码装置900的结构框图。
具体实施方式
下面结合本申请实施例中的附图对本申请实施例进行描述。以下描述中，参考形成本公开一部分并以说明之方式示出本申请实施例的具体方面或可使用本申请实施例的具体方面的附图。应理解，本申请实施例可在其它方面中使用，并可包括附图中未描绘的结构或逻辑变化。因此，以下详细描述不应以限制性的意义来理解，且本申请的范围由所附权利要求书界定。例如，应理解，结合所描述方法的揭示内容可以同样适用于用于执行所述方法的对应设备或系统，且反之亦然。例如，如果描述一个或多个具体方法步骤，则对应的设备可以包含如功能单元等一个或多个单元，来执行所描述的一个或多个方法步骤(例如，一个单元执行一个或多个步骤，或多个单元，其中每个都执行多个步骤中的一个或多个)，即使附图中未明确描述或说明这种一个或多个单元。另一方面，例如，如果基于如功能单元等一个或多个单元描述具体装置，则对应的方法可以包含一个步骤来执行一个或多个单元的功能性(例如，一个步骤执行一个或多个单元的功能性，或多个步骤，其中每个执行多个单元中一个或多个单元的功能性)，即使附图中未明确描述或说明这种一个或多个步骤。进一步，应理解的是，除非另外明确提出，本文中所描述的各示例性实施例和/或方面的特征可以相互组合。
本申请实施例所涉及的技术方案不仅可能应用于现有的视频编码标准中(如H.264、HEVC等标准)，还可能应用于未来的视频编码标准中(如H.266标准)。本申请的实施方式部分使用的术语仅用于对本申请的具体实施例进行解释，而非旨在限定本申请。下面先对本申请实施例可能涉及的一些概念进行简单介绍。
视频编码通常是指处理形成视频或视频序列的图片序列。在视频编码领域，术语“图片(picture)”、“帧(frame)”或“图像(image)”可以用作同义词。本文中使用的视频编 码表示视频编码或视频解码。视频编码在源侧执行，通常包括处理(例如，通过压缩)原始视频图片以减少表示该视频图片所需的数据量，从而更高效地存储和/或传输。视频解码在目的地侧执行，通常包括相对于编码器作逆处理，以重构视频图片。实施例涉及的视频图片“编码”应理解为涉及视频序列的“编码”或“解码”。编码部分和解码部分的组合也称为编解码(编码和解码)。
视频序列包括一系列图像(picture)，图像被进一步划分为切片(slice)，切片再被划分为块(block)。视频编码以块为单位进行编码处理，在一些新的视频编码标准中，块的概念被进一步扩展。比如，在H.264标准中有宏块(macroblock，MB)，宏块可进一步划分成多个可用于预测编码的预测块(partition)。在高性能视频编码(high efficiency video coding，HEVC)标准中，采用编码单元(coding unit，CU)，预测单元(prediction unit，PU)和变换单元(transform unit，TU)等基本概念，从功能上划分了多种块单元，并采用全新的基于树结构进行描述。比如CU可以按照四叉树进行划分为更小的CU，而更小的CU还可以继续划分，从而形成一种四叉树结构，CU是对编码图像进行划分和编码的基本单元。对于PU和TU也有类似的树结构，PU可以对应预测块，是预测编码的基本单元。对CU按照划分模式进一步划分成多个PU。TU可以对应变换块，是对预测残差进行变换的基本单元。然而，无论CU，PU还是TU，本质上都属于块(或称图像块)的概念。
例如在HEVC中，通过使用表示为编码树的四叉树结构将CTU拆分为多个CU。在CU层级处作出是否使用图片间(时间)或图片内(空间)预测对图片区域进行编码的决策。每个CU可以根据PU拆分类型进一步拆分为一个、两个或四个PU。一个PU内应用相同的预测过程，并在PU基础上将相关信息传输到解码器。在通过基于PU拆分类型应用预测过程获取残差块之后，可以根据类似于用于CU的编码树的其它四叉树结构将CU分割成变换单元(transform unit，TU)。在视频压缩技术最新的发展中，使用四叉树和二叉树(Quad-tree and binary tree，QTBT)分割帧来分割编码块。在QTBT块结构中，CU可以为正方形或矩形形状。
本文中，为了便于描述和理解，可将当前编码图像中待编码的图像块称为当前块，例如在编码中，指当前正在编码的块；在解码中，指当前正在解码的块。将参考图像中用于对当前块进行预测的已解码的图像块称为参考块，即参考块是为当前块提供参考信号的块，其中，参考信号表示图像块内的像素值。可将参考图像中为当前块提供预测信号的块为预测块，其中，预测信号表示预测块内的像素值或者采样值或者采样信号。例如，在遍历多个参考块以后，找到了最佳参考块，此最佳参考块将为当前块提供预测，此块称为预测块。
无损视频编码情况下，可以重构原始视频图片，即经重构视频图片具有与原始视频图片相同的质量(假设存储或传输期间没有传输损耗或其它数据丢失)。在有损视频编码情况下，通过例如量化执行进一步压缩，来减少表示视频图片所需的数据量，而解码器侧无法完全重构视频图片，即经重构视频图片的质量相比原始视频图片的质量较低或较差。
H.261的几个视频编码标准属于“有损混合型视频编解码”(即，将样本域中的空间和时间预测与变换域中用于应用量化的2D变换编码结合)。视频序列的每个图片通常分割成不重叠的块集合，通常在块层级上进行编码。换句话说，编码器侧通常在块(视频块)层级处理亦即编码视频，例如，通过空间(图片内)预测和时间(图片间)预测来产生预 测块，从当前块(当前处理或待处理的块)减去预测块以获取残差块，在变换域变换残差块并量化残差块，以减少待传输(压缩)的数据量，而解码器侧将相对于编码器的逆处理部分应用于经编码或经压缩块，以重构用于表示的当前块。另外，编码器复制解码器处理循环，使得编码器和解码器生成相同的预测(例如帧内预测和帧间预测)和/或重构，用于处理亦即编码后续块。
下面描述本申请实施例所应用的系统架构。参见图1A，图1A示例性地给出了本申请实施例所应用的视频编码及解码系统10的示意性框图。如图1A所示，视频编码及解码系统10可包括源设备12和目的地设备14，源设备12产生经编码视频数据，因此，源设备12可被称为视频编码装置。目的地设备14可对由源设备12所产生的经编码的视频数据进行解码，因此，目的地设备14可被称为视频解码装置。源设备12、目的地设备14或两个的各种实施方案可包含一或多个处理器以及耦合到所述一或多个处理器的存储器。所述存储器可包含但不限于RAM、ROM、EEPROM、快闪存储器或可用于以可由计算机存取的指令或数据结构的形式存储所要的程序代码的任何其它媒体，如本文所描述。源设备12和目的地设备14可以包括各种装置，包含桌上型计算机、移动计算装置、笔记型(例如，膝上型)计算机、平板计算机、机顶盒、例如所谓的“智能”电话等电话手持机、电视机、相机、显示装置、数字媒体播放器、视频游戏控制台、车载计算机、无线通信设备或其类似者。
虽然图1A将源设备12和目的地设备14绘示为单独的设备，但设备实施例也可以同时包括源设备12和目的地设备14或同时包括两者的功能性，即源设备12或对应的功能性以及目的地设备14或对应的功能性。在此类实施例中，可以使用相同硬件和/或软件，或使用单独的硬件和/或软件，或其任何组合来实施源设备12或对应的功能性以及目的地设备14或对应的功能性。
源设备12和目的地设备14之间可通过链路13进行通信连接，目的地设备14可经由链路13从源设备12接收经编码视频数据。链路13可包括能够将经编码视频数据从源设备12移动到目的地设备14的一或多个媒体或装置。在一个实例中，链路13可包括使得源设备12能够实时将经编码视频数据直接发射到目的地设备14的一或多个通信媒体。在此实例中，源设备12可根据通信标准(例如无线通信协议)来调制经编码视频数据，且可将经调制的视频数据发射到目的地设备14。所述一或多个通信媒体可包含无线和/或有线通信媒体，例如射频(RF)频谱或一或多个物理传输线。所述一或多个通信媒体可形成基于分组的网络的一部分，基于分组的网络例如为局域网、广域网或全球网络(例如，因特网)。所述一或多个通信媒体可包含路由器、交换器、基站或促进从源设备12到目的地设备14的通信的其它设备。
源设备12包括编码器20，另外可选地，源设备12还可以包括图片源16、图片预处理器18、以及通信接口22。具体实现形态中，所述编码器20、图片源16、图片预处理器18、以及通信接口22可能是源设备12中的硬件部件，也可能是源设备12中的软件程序。分别描述如下：
图片源16，可以包括或可以为任何类别的图片捕获设备，用于例如捕获现实世界图片，和/或任何类别的图片或评论(对于屏幕内容编码，屏幕上的一些文字也认为是待编 码的图片或图像的一部分)生成设备，例如，用于生成计算机动画图片的计算机图形处理器，或用于获取和/或提供现实世界图片、计算机动画图片(例如，屏幕内容、虚拟现实(virtual reality，VR)图片)的任何类别设备，和/或其任何组合(例如，实景(augmented reality，AR)图片)。图片源16可以为用于捕获图片的相机或者用于存储图片的存储器，图片源16还可以包括存储先前捕获或产生的图片和/或获取或接收图片的任何类别的(内部或外部)接口。当图片源16为相机时，图片源16可例如为本地的或集成在源设备中的集成相机；当图片源16为存储器时，图片源16可为本地的或例如集成在源设备中的集成存储器。当所述图片源16包括接口时，接口可例如为从外部视频源接收图片的外部接口，外部视频源例如为外部图片捕获设备，比如相机、外部存储器或外部图片生成设备，外部图片生成设备例如为外部计算机图形处理器、计算机或服务器。接口可以为根据任何专有或标准化接口协议的任何类别的接口，例如有线或无线接口、光接口。
其中，图片可以视为像素点(picture element)的二维阵列或矩阵。阵列中的像素点也可以称为采样点。阵列或图片在水平和垂直方向(或轴线)上的采样点数目定义图片的尺寸和/或分辨率。为了表示颜色，通常采用三个颜色分量，即图片可以表示为或包含三个采样阵列。例如在RBG格式或颜色空间中，图片包括对应的红色、绿色及蓝色采样阵列。但是，在视频编码中，每个像素通常以亮度/色度格式或颜色空间表示，例如对于YUV格式的图片，包括Y指示的亮度分量(有时也可以用L指示)以及U和V指示的两个色度分量。亮度(luma)分量Y表示亮度或灰度水平强度(例如，在灰度等级图片中两者相同)，而两个色度(chroma)分量U和V表示色度或颜色信息分量。相应地，YUV格式的图片包括亮度采样值(Y)的亮度采样阵列，和色度值(U和V)的两个色度采样阵列。RGB格式的图片可以转换或变换为YUV格式，反之亦然，该过程也称为色彩变换或转换。如果图片是黑白的，该图片可以只包括亮度采样阵列。本申请实施例中，由图片源16传输至图片处理器的图片也可称为原始图片数据17。
图片预处理器18，用于接收原始图片数据17并对原始图片数据17执行预处理，以获取经预处理的图片19或经预处理的图片数据19。例如，图片预处理器18执行的预处理可以包括整修、色彩格式转换(例如，从RGB格式转换为YUV格式)、调色或去噪。
编码器20(或称视频编码器20)，用于接收经预处理的图片数据19，采用相关预测模式(如本文各个实施例中的预测模式)对经预处理的图片数据19进行处理，从而提供经编码图片数据21(下文将进一步基于图2或图4或图5描述编码器20的结构细节)。在一些实施例中，编码器20可以用于执行后文所描述的各个实施例，以实现本申请所描述的色度块预测方法在编码侧的应用。
通信接口22，可用于接收经编码图片数据21，并可通过链路13将经编码图片数据21传输至目的地设备14或任何其它设备(如存储器)，以用于存储或直接重构，所述其它设备可为任何用于解码或存储的设备。通信接口22可例如用于将经编码图片数据21封装成合适的格式，例如数据包，以在链路13上传输。
目的地设备14包括解码器30，另外可选地，目的地设备14还可以包括通信接口28、图片后处理器32和显示设备34。分别描述如下：
通信接口28，可用于从源设备12或任何其它源接收经编码图片数据21，所述任何其它源例如为存储设备，存储设备例如为经编码图片数据存储设备。通信接口28可以用于 藉由源设备12和目的地设备14之间的链路13或藉由任何类别的网络传输或接收经编码图片数据21，链路13例如为直接有线或无线连接，任何类别的网络例如为有线或无线网络或其任何组合，或任何类别的私网和公网，或其任何组合。通信接口28可以例如用于解封装通信接口22所传输的数据包以获取经编码图片数据21。
通信接口28和通信接口22都可以配置为单向通信接口或者双向通信接口，以及可以用于例如发送和接收消息来建立连接、确认和交换任何其它与通信链路和/或例如经编码图片数据传输的数据传输有关的信息。
解码器30(或称为解码器30)，用于接收经编码图片数据21并提供经解码图片数据31或经解码图片31(下文将进一步基于图3或图4或图5描述解码器30的结构细节)。在一些实施例中，解码器30可以用于执行后文所描述的各个实施例，以实现本申请所描述的色度块预测方法在解码侧的应用。
图片后处理器32，用于对经解码图片数据31(也称为经重构图片数据)执行后处理，以获得经后处理图片数据33。图片后处理器32执行的后处理可以包括：色彩格式转换(例如，从YUV格式转换为RGB格式)、调色、整修或重采样，或任何其它处理，还可用于将将经后处理图片数据33传输至显示设备34。
显示设备34，用于接收经后处理图片数据33以向例如用户或观看者显示图片。显示设备34可以为或可以包括任何类别的用于呈现经重构图片的显示器，例如，集成的或外部的显示器或监视器。例如，显示器可以包括液晶显示器(liquid crystal display，LCD)、有机发光二极管(organic light emitting diode，OLED)显示器、等离子显示器、投影仪、微LED显示器、硅基液晶(liquid crystal on silicon，LCoS)、数字光处理器(digital light processor，DLP)或任何类别的其它显示器。
虽然，图1A将源设备12和目的地设备14绘示为单独的设备，但设备实施例也可以同时包括源设备12和目的地设备14或同时包括两者的功能性，即源设备12或对应的功能性以及目的地设备14或对应的功能性。在此类实施例中，可以使用相同硬件和/或软件，或使用单独的硬件和/或软件，或其任何组合来实施源设备12或对应的功能性以及目的地设备14或对应的功能性。
本领域技术人员基于描述明显可知，不同单元的功能性或图1A所示的源设备12和/或目的地设备14的功能性的存在和(准确)划分可能根据实际设备和应用有所不同。源设备12和目的地设备14可以包括各种设备中的任一个，包含任何类别的手持或静止设备，例如，笔记本或膝上型计算机、移动电话、智能手机、平板或平板计算机、摄像机、台式计算机、机顶盒、电视机、相机、车载设备、显示设备、数字媒体播放器、视频游戏控制台、视频流式传输设备(例如内容服务服务器或内容分发服务器)、广播接收器设备、广播发射器设备等，并可以不使用或使用任何类别的操作系统。
编码器20和解码器30都可以实施为各种合适电路中的任一个，例如，一个或多个微处理器、数字信号处理器(digital signal processor，DSP)、专用集成电路(application-specific integrated circuit，ASIC)、现场可编程门阵列(field-programmable gate array，FPGA)、离散逻辑、硬件或其任何组合。如果部分地以软件实施所述技术，则设备可将软件的指令存储于合适的非暂时性计算机可读存储介质中，且可使用一或多个处理器以硬件执行指令从而执行本公开的技术。前述内容(包含硬件、软件、硬件与软件的组合等)中的任一者 可视为一或多个处理器。
在一些情况下，图1A中所示视频编码及解码系统10仅为示例，本申请的技术可以适用于不必包含编码和解码设备之间的任何数据通信的视频编码设置(例如，视频编码或视频解码)。在其它实例中，数据可从本地存储器检索、在网络上流式传输等。视频编码设备可以对数据进行编码并且将数据存储到存储器，和/或视频解码设备可以从存储器检索数据并且对数据进行解码。在一些实例中，由并不彼此通信而是仅编码数据到存储器和/或从存储器检索数据且解码数据的设备执行编码和解码。
参见图1B，图1B是根据一示例性实施例的包含图2的编码器20和/或图3的解码器30的视频译码系统40的实例的说明图。视频译码系统40可以实现本申请实施例的各种技术的组合。在所说明的实施方式中，视频译码系统40可以包含成像设备41、编码器20、解码器30(和/或藉由处理单元46的逻辑电路47实施的视频编/解码器)、天线42、一个或多个处理器43、一个或多个存储器44和/或显示设备45。
如图1B所示，成像设备41、天线42、处理单元46、逻辑电路47、编码器20、解码器30、处理器43、存储器44和/或显示设备45能够互相通信。如所论述，虽然用编码器20和解码器30绘示视频译码系统40，但在不同实例中，视频译码系统40可以只包含编码器20或只包含解码器30。
在一些实例中，天线42可以用于传输或接收视频数据的经编码比特流。另外，在一些实例中，显示设备45可以用于呈现视频数据。在一些实例中，逻辑电路47可以通过处理单元46实施。处理单元46可以包含专用集成电路(application-specific integrated circuit，ASIC)逻辑、图形处理器、通用处理器等。视频译码系统40也可以包含可选的处理器43，该可选处理器43类似地可以包含专用集成电路(application-specific integrated circuit，ASIC)逻辑、图形处理器、通用处理器等。在一些实例中，逻辑电路47可以通过硬件实施，如视频编码专用硬件等，处理器43可以通过通用软件、操作系统等实施。另外，存储器44可以是任何类型的存储器，例如易失性存储器(例如，静态随机存取存储器(Static Random Access Memory，SRAM)、动态随机存储器(Dynamic Random Access Memory，DRAM)等)或非易失性存储器(例如，闪存等)等。在非限制性实例中，存储器44可以由超速缓存内存实施。在一些实例中，逻辑电路47可以访问存储器44(例如用于实施图像缓冲器)。在其它实例中，逻辑电路47和/或处理单元46可以包含存储器(例如，缓存等)用于实施图像缓冲器等。
在一些实例中，通过逻辑电路实施的编码器20可以包含(例如，通过处理单元46或存储器44实施的)图像缓冲器和(例如，通过处理单元46实施的)图形处理单元。图形处理单元可以通信耦合至图像缓冲器。图形处理单元可以包含通过逻辑电路47实施的编码器20，以实施参照图2和/或本文中所描述的任何其它编码器系统或子系统所论述的各种模块。逻辑电路可以用于执行本文所论述的各种操作。
在一些实例中，解码器30可以以类似方式通过逻辑电路47实施，以实施参照图3的解码器30和/或本文中所描述的任何其它解码器系统或子系统所论述的各种模块。在一些实例中，逻辑电路实施的解码器30可以包含(通过处理单元2820或存储器44实施的)图像缓冲器和(例如，通过处理单元46实施的)图形处理单元。图形处理单元可以通信 耦合至图像缓冲器。图形处理单元可以包含通过逻辑电路47实施的解码器30，以实施参照图3和/或本文中所描述的任何其它解码器系统或子系统所论述的各种模块。
在一些实例中，天线42可以用于接收视频数据的经编码比特流。如所论述，经编码比特流可以包含本文所论述的与编码视频帧相关的数据、指示符、索引值、模式选择数据等，例如与编码分割相关的数据(例如，变换系数或经量化变换系数，(如所论述的)可选指示符，和/或定义编码分割的数据)。视频译码系统40还可包含耦合至天线42并用于解码经编码比特流的解码器30。显示设备45用于呈现视频帧。
应理解，本申请实施例中对于参考编码器20所描述的实例，解码器30可以用于执行相反过程。关于信令语法元素，解码器30可以用于接收并解析这种语法元素，相应地解码相关视频数据。在一些例子中，编码器20可以将语法元素熵编码成经编码视频比特流。在此类实例中，解码器30可以解析这种语法元素，并相应地解码相关视频数据。
需要说明的是，本申请实施例描述的语法元素的熵编码/解码方法主要用于熵编码/解码过程，此过程在编码器20和解码器30均存在，本申请实施例中的编码器20和解码器30可以是例如H.263、H.264、HEVV、MPEG-2、MPEG-4、VP8、VP9等视频标准协议或者下一代视频标准协议(如H.266等)对应的编/解码器。
参见图2，图2示出用于实现本申请实施例的编码器20的实例的示意性/概念性框图。在图2的实例中，编码器20包括残差计算单元204、变换处理单元206、量化单元208、逆量化单元210、逆变换处理单元212、重构单元214、缓冲器216、环路滤波器单元220、经解码图片缓冲器(decoded picture buffer，DPB)230、预测处理单元260和熵编码单元270。预测处理单元260可以包含帧间预测单元244、帧内预测单元254和模式选择单元262。帧间预测单元244可以包含运动估计单元和运动补偿单元(未图示)。图2所示的编码器20也可以称为混合型视频编码器或根据混合型视频编解码器的视频编码器。
例如，残差计算单元204、变换处理单元206、量化单元208、预测处理单元260和熵编码单元270形成编码器20的前向信号路径，而例如逆量化单元210、逆变换处理单元212、重构单元214、缓冲器216、环路滤波器220、经解码图片缓冲器(decoded picture buffer，DPB)230、预测处理单元260形成编码器的后向信号路径，其中编码器的后向信号路径对应于解码器的信号路径(参见图3中的解码器30)。
编码器20通过例如输入202，接收图片201或图片201的图像块203，例如，形成视频或视频序列的图片序列中的图片。图像块203也可以称为当前图片块或待编码图片块，图片201可以称为当前图片或待编码图片(尤其是在视频编码中将当前图片与其它图片区分开时，其它图片例如同一视频序列亦即也包括当前图片的视频序列中的先前经编码和/或经解码图片)。
编码器20的实施例可以包括分割单元(图2中未绘示)，用于将图片201分割成多个例如图像块203的块，通常分割成多个不重叠的块。分割单元可以用于对视频序列中所有图片使用相同的块大小以及定义块大小的对应栅格，或用于在图片或子集或图片群组之间更改块大小，并将每个图片分割成对应的块。
在一个实例中，编码器20的预测处理单元260可以用于执行上述分割技术的任何组合。
如图片201，图像块203也是或可以视为具有采样值的采样点的二维阵列或矩阵，虽然其尺寸比图片201小。换句话说，图像块203可以包括，例如，一个采样阵列(例如黑白图片201情况下的亮度阵列)或三个采样阵列(例如，彩色图片情况下的一个亮度阵列和两个色度阵列)或依据所应用的色彩格式的任何其它数目和/或类别的阵列。图像块203的水平和垂直方向(或轴线)上采样点的数目定义图像块203的尺寸。
如图2所示的编码器20用于逐块编码图片201，例如，对每个图像块203执行编码和预测。
残差计算单元204用于基于图片图像块203和预测块265(下文提供预测块265的其它细节)计算残差块205，例如，通过逐样本(逐像素)将图片图像块203的样本值减去预测块265的样本值，以在样本域中获取残差块205。
变换处理单元206用于在残差块205的样本值上应用例如离散余弦变换(discrete cosine transform，DCT)或离散正弦变换(discrete sine transform，DST)的变换，以在变换域中获取变换系数207。变换系数207也可以称为变换残差系数，并在变换域中表示残差块205。
变换处理单元206可以用于应用DCT/DST的整数近似值，例如为HEVC/H.265指定的变换。与正交DCT变换相比，这种整数近似值通常由某一因子按比例缩放。为了维持经正变换和逆变换处理的残差块的范数，应用额外比例缩放因子作为变换过程的一部分。比例缩放因子通常是基于某些约束条件选择的，例如，比例缩放因子是用于移位运算的2的幂、变换系数的位深度、准确性和实施成本之间的权衡等。例如，在解码器30侧通过例如逆变换处理单元212为逆变换(以及在编码器20侧通过例如逆变换处理单元212为对应逆变换)指定具体比例缩放因子，以及相应地，可以在编码器20侧通过变换处理单元206为正变换指定对应比例缩放因子。
量化单元208用于例如通过应用标量量化或向量量化来量化变换系数207，以获取经量化变换系数209。经量化变换系数209也可以称为经量化残差系数209。量化过程可以减少与部分或全部变换系数207有关的位深度。例如，可在量化期间将n位变换系数向下舍入到m位变换系数，其中n大于m。可通过调整量化参数(quantization parameter，QP)修改量化程度。例如，对于标量量化，可以应用不同的标度来实现较细或较粗的量化。较小量化步长对应较细量化，而较大量化步长对应较粗量化。可以通过量化参数(quantization parameter，QP)指示合适的量化步长。例如，量化参数可以为合适的量化步长的预定义集合的索引。例如，较小的量化参数可以对应精细量化(较小量化步长)，较大量化参数可以对应粗糙量化(较大量化步长)，反之亦然。量化可以包含除以量化步长以及例如通过逆量化210执行的对应的量化或逆量化，或者可以包含乘以量化步长。根据例如HEVC的一些标准的实施例可以使用量化参数来确定量化步长。一般而言，可以基于量化参数使用包含除法的等式的定点近似来计算量化步长。可以引入额外比例缩放因子来进行量化和反量化，以恢复可能由于在用于量化步长和量化参数的等式的定点近似中使用的标度而修改的残差块的范数。在一个实例实施方式中，可以合并逆变换和反量化的标度。或者，可以使用自定义量化表并在例如比特流中将其从编码器通过信号发送到解码器。量化是有损操作，其中量化步长越大，损耗越大。
逆量化单元210用于在经量化系数上应用量化单元208的逆量化，以获取经反量化系 数211，例如，基于或使用与量化单元208相同的量化步长，应用量化单元208应用的量化方案的逆量化方案。经反量化系数211也可以称为经反量化残差系数211，对应于变换系数207，虽然由于量化造成的损耗通常与变换系数不相同。
逆变换处理单元212用于应用变换处理单元206应用的变换的逆变换，例如，逆离散余弦变换(discrete cosine transform，DCT)或逆离散正弦变换(discrete sine transform，DST)，以在样本域中获取逆变换块213。逆变换块213也可以称为逆变换经反量化块213或逆变换残差块213。
重构单元214(例如，求和器214)用于将逆变换块213(即经重构残差块213)添加至预测块265，以在样本域中获取经重构块215，例如，将经重构残差块213的样本值与预测块265的样本值相加。
可选地，例如线缓冲器216的缓冲器单元216(或简称“缓冲器”216)用于缓冲或存储经重构块215和对应的样本值，用于例如帧内预测。在其它的实施例中，编码器可以用于使用存储在缓冲器单元216中的未经滤波的经重构块和/或对应的样本值来进行任何类别的估计和/或预测，例如帧内预测。
例如，编码器20的实施例可以经配置以使得缓冲器单元216不只用于存储用于帧内预测254的经重构块215，也用于环路滤波器单元220(在图2中未示出)，和/或，例如使得缓冲器单元216和经解码图片缓冲器单元230形成一个缓冲器。其它实施例可以用于将经滤波块221和/或来自经解码图片缓冲器230的块或样本(图2中均未示出)用作帧内预测254的输入或基础。
环路滤波器单元220(或简称“环路滤波器”220)用于对经重构块215进行滤波以获取经滤波块221，从而顺利进行像素转变或提高视频质量。环路滤波器单元220旨在表示一个或多个环路滤波器，例如去块滤波器、样本自适应偏移(sample-adaptive offset，SAO)滤波器或其它滤波器，例如双边滤波器、自适应环路滤波器(adaptive loop filter，ALF)，或锐化或平滑滤波器，或协同滤波器。尽管环路滤波器单元220在图2中示出为环内滤波器，但在其它配置中，环路滤波器单元220可实施为环后滤波器。经滤波块221也可以称为经滤波的经重构块221。经解码图片缓冲器230可以在环路滤波器单元220对经重构编码块执行滤波操作之后存储经重构编码块。
编码器20(对应地，环路滤波器单元220)的实施例可以用于输出环路滤波器参数(例如，样本自适应偏移信息)，例如，直接输出或由熵编码单元270或任何其它熵编码单元熵编码后输出，例如使得解码器30可以接收并应用相同的环路滤波器参数用于解码。
经解码图片缓冲器(decoded picture buffer，DPB)230可以为存储参考图片数据供编码器20编码视频数据之用的参考图片存储器。DPB 230可由多种存储器设备中的任一个形成，例如动态随机存储器(dynamic random access memory，DRAM)(包含同步DRAM(synchronous DRAM，SDRAM)、磁阻式RAM(magnetoresistive RAM，MRAM)、电阻式RAM(resistive RAM，RRAM))或其它类型的存储器设备。可以由同一存储器设备或单独的存储器设备提供DPB 230和缓冲器216。在某一实例中，经解码图片缓冲器(decoded picture buffer，DPB)230用于存储经滤波块221。经解码图片缓冲器230可以进一步用于存储同一当前图片或例如先前经重构图片的不同图片的其它先前的经滤波块，例如先前经重构和经滤波块221，以及可以提供完整的先前经重构亦即经解码图片(和对 应参考块和样本)和/或部分经重构当前图片(和对应参考块和样本)，例如用于帧间预测。在某一实例中，如果经重构块215无需环内滤波而得以重构，则经解码图片缓冲器(decoded picture buffer，DPB)230用于存储经重构块215。
预测处理单元260，也称为块预测处理单元260，用于接收或获取图像块203(当前图片201的当前图像块203)和经重构图片数据，例如来自缓冲器216的同一(当前)图片的参考样本和/或来自经解码图片缓冲器230的一个或多个先前经解码图片的参考图片数据231，以及用于处理这类数据进行预测，即提供可以为经帧间预测块245或经帧内预测块255的预测块265。
模式选择单元262可以用于选择预测模式(例如帧内或帧间预测模式)和/或对应的用作预测块265的预测块245或255，以计算残差块205和重构经重构块215。
模式选择单元262的实施例可以用于选择预测模式(例如，从预测处理单元260所支持的那些预测模式中选择)，所述预测模式提供最佳匹配或者说最小残差(最小残差意味着传输或存储中更好的压缩)，或提供最小信令开销(最小信令开销意味着传输或存储中更好的压缩)，或同时考虑或平衡以上两者。模式选择单元262可以用于基于码率失真优化(rate distortion optimization，RDO)确定预测模式，即选择提供最小码率失真优化的预测模式，或选择相关码率失真至少满足预测模式选择标准的预测模式。
下文将详细解释编码器20的实例(例如，通过预测处理单元260)执行的预测处理和(例如，通过模式选择单元262)执行的模式选择。
如上文所述，编码器20用于从(预先确定的)预测模式集合中确定或选择最好或最优的预测模式。预测模式集合可以包括例如帧内预测模式和/或帧间预测模式。
帧内预测模式集合可以包括35种不同的帧内预测模式，例如，如DC(或均值)模式和平面模式的非方向性模式，或如H.265中定义的方向性模式，或者可以包括67种不同的帧内预测模式，例如，如DC(或均值)模式和平面模式的非方向性模式，或如正在发展中的H.266中定义的方向性模式。
在可能的实现中，帧间预测模式集合取决于可用参考图片(即，例如前述存储在DBP230中的至少部分经解码图片)和其它帧间预测参数，例如取决于是否使用整个参考图片或只使用参考图片的一部分，例如围绕当前块的区域的搜索窗区域，来搜索最佳匹配参考块，和/或例如取决于是否应用如半像素和/或四分之一像素内插的像素内插，帧间预测模式集合例如可包括先进运动矢量(Advanced Motion Vector Prediction，AMVP)模式和融合(merge)模式。具体实施中，帧间预测模式集合可包括本申请实施例改进的基于控制点的AMVP模式，以及，改进的基于控制点的merge模式。在一个实例中，帧内预测单元254可以用于执行下文描述的帧间预测技术的任意组合。
除了以上预测模式，本申请实施例也可以应用跳过模式和/或直接模式。
预测处理单元260可以进一步用于将图像块203分割成较小的块分区或子块，例如，通过迭代使用四叉树(quad-tree，QT)分割、二进制树(binary-tree，BT)分割或三叉树(triple-tree，TT)分割，或其任何组合，以及用于例如为块分区或子块中的每一个执行预测，其中模式选择包括选择分割的图像块203的树结构和选择应用于块分区或子块中的每一个的预测模式。
帧间预测单元244可以包含运动估计(motion estimation，ME)单元(图2中未示出) 和运动补偿(motion compensation，MC)单元(图2中未示出)。运动估计单元用于接收或获取图片图像块203(当前图片201的当前图片图像块203)和经解码图片231，或至少一个或多个先前经重构块，例如，一个或多个其它/不同先前经解码图片231的经重构块，来进行运动估计。例如，视频序列可以包括当前图片和先前经解码图片31，或换句话说，当前图片和先前经解码图片31可以是形成视频序列的图片序列的一部分，或者形成该图片序列。
例如，编码器20可以用于从多个其它图片中的同一或不同图片的多个参考块中选择参考块，并向运动估计单元(图2中未示出)提供参考图片和/或提供参考块的位置(X、Y坐标)与当前块的位置之间的偏移(空间偏移)作为帧间预测参数。该偏移也称为运动向量(motion vector，MV)。
运动补偿单元用于获取帧间预测参数，并基于或使用帧间预测参数执行帧间预测来获取帧间预测块245。由运动补偿单元(图2中未示出)执行的运动补偿可以包含基于通过运动估计(可能执行对子像素精确度的内插)确定的运动/块向量取出或生成预测块。内插滤波可从已知像素样本产生额外像素样本，从而潜在地增加可用于编码图片块的候选预测块的数目。一旦接收到用于当前图片块的PU的运动向量，运动补偿单元246可以在一个参考图片列表中定位运动向量指向的预测块。运动补偿单元246还可以生成与块和视频条带相关联的语法元素，以供解码器30在解码视频条带的图片块时使用。
具体的，上述帧间预测单元244可向熵编码单元270传输语法元素，所述语法元素包括帧间预测参数(比如遍历多个帧间预测模式后选择用于当前块预测的帧间预测模式的指示信息)。可能应用场景中，如果帧间预测模式只有一种，那么也可以不在语法元素中携带帧间预测参数，此时解码端30可直接使用默认的预测模式进行解码。可以理解的，帧间预测单元244可以用于执行帧间预测技术的任意组合。
帧内预测单元254用于获取，例如接收同一图片的图片块203(当前图片块)和一个或多个先前经重构块，例如经重构相相邻块，以进行帧内估计。例如，编码器20可以用于从多个(预定)帧内预测模式中选择帧内预测模式。
编码器20的实施例可以用于基于优化标准选择帧内预测模式，例如基于最小残差(例如，提供最类似于当前图片块203的预测块255的帧内预测模式)或最小码率失真。
帧内预测单元254进一步用于基于如所选择的帧内预测模式的帧内预测参数确定帧内预测块255。在任何情况下，在选择用于块的帧内预测模式之后，帧内预测单元254还用于向熵编码单元270提供帧内预测参数，即提供指示所选择的用于块的帧内预测模式的信息。在一个实例中，帧内预测单元254可以用于执行帧内预测技术的任意组合。
具体的，上述帧内预测单元254可向熵编码单元270传输语法元素，所述语法元素包括帧内预测参数(比如遍历多个帧内预测模式后选择用于当前块预测的帧内预测模式的指示信息)。可能应用场景中，如果帧内预测模式只有一种，那么也可以不在语法元素中携带帧内预测参数，此时解码端30可直接使用默认的预测模式进行解码。
熵编码单元270用于将熵编码算法或方案(例如，可变长度编码(variable length coding，VLC)方案、上下文自适应VLC(context adaptive VLC，CAVLC)方案、算术编码方案、上下文自适应二进制算术编码(context adaptive binary arithmetic coding，CABAC)、基于语法的上下文自适应二进制算术编码(syntax-based context-adaptive binary arithmetic  coding，SBAC)、概率区间分割熵(probability interval partitioning entropy，PIPE)编码或其它熵编码方法或技术)应用于经量化残差系数209、帧间预测参数、帧内预测参数和/或环路滤波器参数中的单个或所有上(或不应用)，以获取可以通过输出272以例如经编码比特流21的形式输出的经编码图片数据21。可以将经编码比特流传输到视频解码器30，或将其存档稍后由视频解码器30传输或检索。熵编码单元270还可用于熵编码正被编码的当前视频条带的其它语法元素。
视频编码器20的其它结构变型可用于编码视频流。例如，基于非变换的编码器20可以在没有针对某些块或帧的变换处理单元206的情况下直接量化残差信号。在另一实施方式中，编码器20可具有组合成单个单元的量化单元208和逆量化单元210。
具体的，在本申请实施例中，编码器20可用于实现后文实施例中描述的语法元素的熵编码方法。
应当理解的是，视频编码器20的其它的结构变化可用于编码视频流。例如，对于某些图像块或者图像帧，视频编码器20可以直接地量化残差信号而不需要经变换处理单元206处理，相应地也不需要经逆变换处理单元212处理；或者，对于某些图像块或者图像帧，视频编码器20没有产生残差数据，相应地不需要经变换处理单元206、量化单元208、逆量化单元210和逆变换处理单元212处理；或者，视频编码器20可以将经重构图像块作为参考块直接地进行存储而不需要经滤波器220处理；或者，视频编码器20中量化单元208和逆量化单元210可以合并在一起。环路滤波器220是可选的，以及针对无损压缩编码的情况下，变换处理单元206、量化单元208、逆量化单元210和逆变换处理单元212是可选的。应当理解的是，根据不同的应用场景，帧间预测单元244和帧内预测单元254可以是被选择性的启用。
参见图3，图3示出用于实现本申请实施例的解码器30的实例的示意性/概念性框图。视频解码器30用于接收例如由编码器20编码的经编码图片数据(例如，经编码比特流)21，以获取经解码图片231。在解码过程期间，视频解码器30从视频编码器20接收视频数据，例如表示经编码视频条带的图片块的经编码视频比特流及相关联的语法元素。
在图3的实例中，解码器30包括熵解码单元304、逆量化单元310、逆变换处理单元312、重构单元314(例如求和器314)、缓冲器316、环路滤波器320、经解码图片缓冲器330以及预测处理单元360。预测处理单元360可以包含帧间预测单元344、帧内预测单元354和模式选择单元362。在一些实例中，视频解码器30可执行大体上与参照图2的视频编码器20描述的编码遍次互逆的解码遍次。
熵解码单元304用于对经编码图片数据21执行熵解码，以获取例如经量化系数309和/或经解码的编码参数(图3中未示出)，例如，帧间预测、帧内预测参数、环路滤波器参数和/或其它语法元素中(经解码)的任意一个或全部。熵解码单元304进一步用于将帧间预测参数、帧内预测参数和/或其它语法元素转发至预测处理单元360。视频解码器30可接收视频条带层级和/或视频块层级的语法元素。
逆量化单元310功能上可与逆量化单元110相同，逆变换处理单元312功能上可与逆变换处理单元212相同，重构单元314功能上可与重构单元214相同，缓冲器316功能上可与缓冲器216相同，环路滤波器320功能上可与环路滤波器220相同，经解码图片缓冲 器330功能上可与经解码图片缓冲器230相同。
预测处理单元360可以包括帧间预测单元344和帧内预测单元354，其中帧间预测单元344功能上可以类似于帧间预测单元244，帧内预测单元354功能上可以类似于帧内预测单元254。预测处理单元360通常用于执行块预测和/或从经编码数据21获取预测块365，以及从例如熵解码单元304(显式地或隐式地)接收或获取预测相关参数和/或关于所选择的预测模式的信息。
当视频条带经编码为经帧内编码(I)条带时，预测处理单元360的帧内预测单元354用于基于信号表示的帧内预测模式及来自当前帧或图片的先前经解码块的数据来产生用于当前视频条带的图片块的预测块365。当视频帧经编码为经帧间编码(即B或P)条带时，预测处理单元360的帧间预测单元344(例如，运动补偿单元)用于基于运动向量及从熵解码单元304接收的其它语法元素生成用于当前视频条带的视频块的预测块365。对于帧间预测，可从一个参考图片列表内的一个参考图片中产生预测块。视频解码器30可基于存储于DPB 330中的参考图片，使用默认建构技术来建构参考帧列表：列表0和列表1。
预测处理单元360用于通过解析运动向量和其它语法元素，确定用于当前视频条带的视频块的预测信息，并使用预测信息产生用于正经解码的当前视频块的预测块。在本申请的一实例中，预测处理单元360使用接收到的一些语法元素确定用于编码视频条带的视频块的预测模式(例如，帧内或帧间预测)、帧间预测条带类型(例如，B条带、P条带或GPB条带)、用于条带的参考图片列表中的一个或多个的建构信息、用于条带的每个经帧间编码视频块的运动向量、条带的每个经帧间编码视频块的帧间预测状态以及其它信息，以解码当前视频条带的视频块。在本公开的另一实例中，视频解码器30从比特流接收的语法元素包含接收自适应参数集(adaptive parameter set，APS)、序列参数集(sequence parameter set，SPS)、图片参数集(picture parameter set，PPS)或条带标头中的一个或多个中的语法元素。
逆量化单元310可用于逆量化(即，反量化)在比特流中提供且由熵解码单元304解码的经量化变换系数。逆量化过程可包含使用由视频编码器20针对视频条带中的每一视频块所计算的量化参数来确定应该应用的量化程度并同样确定应该应用的逆量化程度。
逆变换处理单元312用于将逆变换(例如，逆DCT、逆整数变换或概念上类似的逆变换过程)应用于变换系数，以便在像素域中产生残差块。
重构单元314(例如，求和器314)用于将逆变换块313(即经重构残差块313)添加到预测块365，以在样本域中获取经重构块315，例如通过将经重构残差块313的样本值与预测块365的样本值相加。
环路滤波器单元320(在编码循环期间或在编码循环之后)用于对经重构块315进行滤波以获取经滤波块321，从而顺利进行像素转变或提高视频质量。在一个实例中，环路滤波器单元320可以用于执行下文描述的滤波技术的任意组合。环路滤波器单元320旨在表示一个或多个环路滤波器，例如去块滤波器、样本自适应偏移(sample-adaptive offset，SAO)滤波器或其它滤波器，例如双边滤波器、自适应环路滤波器(adaptive loop filter，ALF)，或锐化或平滑滤波器，或协同滤波器。尽管环路滤波器单元320在图3中示出为环内滤波器，但在其它配置中，环路滤波器单元320可实施为环后滤波器。
随后将给定帧或图片中的经解码视频块321存储在存储用于后续运动补偿的参考图片的经解码图片缓冲器330中。
解码器30用于例如，藉由输出332输出经解码图片31，以向用户呈现或供用户查看。
视频解码器30的其它变型可用于对压缩的比特流进行解码。例如，解码器30可以在没有环路滤波器单元320的情况下生成输出视频流。例如，基于非变换的解码器30可以在没有针对某些块或帧的逆变换处理单元312的情况下直接逆量化残差信号。在另一实施方式中，视频解码器30可以具有组合成单个单元的逆量化单元310和逆变换处理单元312。
具体的，在本申请实施例中，解码器30用于实现后文实施例中描述的语法元素的熵解码方法。
应当理解的是，视频解码器30的其它结构变化可用于解码经编码视频位流。例如，视频解码器30可以不经滤波器320处理而生成输出视频流；或者，对于某些图像块或者图像帧，视频解码器30的熵解码单元304没有解码出经量化的系数，相应地不需要经逆量化单元310和逆变换处理单元312处理。环路滤波器320是可选的；以及针对无损压缩的情况下，逆量化单元310和逆变换处理单元312是可选的。应当理解的是，根据不同的应用场景，帧间预测单元和帧内预测单元可以是被选择性的启用。
应当理解的是，本申请的编码器20和解码器30中，针对某个环节的处理结果可以经过进一步处理后，输出到下一个环节，例如，在插值滤波、运动矢量推导或环路滤波等环节之后，对相应环节的处理结果进一步进行Clip或移位shift等操作。
参见图4，图4是本申请实施例提供的视频译码设备400(例如视频编码设备400或视频解码设备400)的结构示意图。视频译码设备400适于实施本文所描述的实施例。在一个实施例中，视频译码设备400可以是视频解码器(例如图1A的解码器30)或视频编码器(例如图1A的编码器20)。在另一个实施例中，视频译码设备400可以是上述图1A的解码器30或图1A的编码器20中的一个或多个组件。
视频译码设备400包括：用于接收数据的入口端口410和接收单元(Rx)420，用于处理数据的处理器、逻辑单元或中央处理器(CPU)430，用于传输数据的发射器单元(Tx)440和出口端口450，以及，用于存储数据的存储器460。视频译码设备400还可以包括与入口端口410、接收器单元420、发射器单元440和出口端口450耦合的光电转换组件和电光(EO)组件，用于光信号或电信号的出口或入口。
处理器430通过硬件和软件实现。处理器430可以实现为一个或多个CPU芯片、核(例如，多核处理器)、FPGA、ASIC和DSP。处理器430与入口端口410、接收器单元420、发射器单元440、出口端口450和存储器460通信。处理器430包括译码模块470(例如编码模块470或解码模块470)。编码/解码模块470实现本文中所公开的实施例，以实现本申请实施例所提供的色度块预测方法。例如，编码/解码模块470实现、处理或提供各种编码操作。因此，通过编码/解码模块470为视频译码设备400的功能提供了实质性的改进，并影响了视频译码设备400到不同状态的转换。或者，以存储在存储器460中并由处理器430执行的指令来实现编码/解码模块470。
存储器460包括一个或多个磁盘、磁带机和固态硬盘，可以用作溢出数据存储设备， 用于在选择性地执行这些程序时存储程序，并存储在程序执行过程中读取的指令和数据。存储器460可以是易失性和/或非易失性的，可以是只读存储器(ROM)、随机存取存储器(RAM)、随机存取存储器(ternary content-addressable memory，TCAM)和/或静态随机存取存储器(SRAM)。
参见图5，图5是根据一示例性实施例的可用作图1A中的源设备12和目的地设备14中的任一个或两个的装置500的简化框图。装置500可以实现本申请的技术。换言之，图5为本申请实施例的编码设备或解码设备(简称为译码设备500)的一种实现方式的示意性框图。其中，译码设备500可以包括处理器510、存储器530和总线系统550。其中，处理器和存储器通过总线系统相连，该存储器用于存储指令，该处理器用于执行该存储器存储的指令。译码设备的存储器存储程序代码，且处理器可以调用存储器中存储的程序代码执行本申请描述的各种视频编码或解码方法，尤其是各种新的语法元素的熵编码/解码方法。为避免重复，这里不再详细描述。
在本申请实施例中，该处理器510可以是中央处理单元(Central Processing Unit，简称为“CPU”)，该处理器510还可以是其他通用处理器、数字信号处理器(DSP)、专用集成电路(ASIC)、现成可编程门阵列(FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件等。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。
该存储器530可以包括只读存储器(ROM)设备或者随机存取存储器(RAM)设备。任何其他适宜类型的存储设备也可以用作存储器530。存储器530可以包括由处理器510使用总线550访问的代码和数据531。存储器530可以进一步包括操作系统533和应用程序535，该应用程序535包括允许处理器510执行本申请描述的视频编码或解码方法(尤其是本申请描述的语法元素的熵编码/解码方法)的至少一个程序。
该总线系统550除包括数据总线之外，还可以包括电源总线、控制总线和状态信号总线等。但是为了清楚说明起见，在图中将各种总线都标为总线系统550。
可选的，译码设备500还可以包括一个或多个输出设备，诸如显示器570。在一个示例中，显示器570可以是触感显示器，其将显示器与可操作地感测触摸输入的触感单元合并。显示器570可以经由总线550连接到处理器510。
下面详细阐述本申请实施例的方案：
图6是用于实现本申请实施例的语法元素的熵编码方法的一个流程示意图。该过程600可由视频编码器20执行。过程600描述为一系列的步骤或操作，应当理解的是，过程600可以以各种顺序执行和/或同时发生，不限于图6所示的执行顺序。如图6所示，语法元素的熵编码方法包括：
步骤601、判断当前融合候选运动矢量列表的长度是否大于预设值。
融合候选运动矢量列表的长度是指该融合候选运动矢量列表包括的候选运动矢量(Motion Vector，MV)的数量(该数量例如用MaxNumMergeCand表示)。MMVD技术利用了融合候选运动矢量列表，先从融合候选运动矢量列表中选取一个候选MV作为基础MV，然后基于该基础MV进行MV拓展表达，MV拓展表达有三个要素，即MV起始点、 运动步长(Distance)和运动方向(Direction)。
(1)选取候选MV
利用已有的融合候选运动矢量列表，所选用的候选MV即为MV起始点，换言之，所选用的候选MV用于确定MV的初始位置。参见表1，基本候选索引(Base candidate IDX)用于表示融合候选运动矢量列表中的候选MV的索引，Nth MVP用于表示融合候选运动矢量列表中的第N个MV。其中，Base candidate IDX＝0对应融合候选运动矢量列表中的第一个MV，Base candidate IDX＝1对应融合候选运动矢量列表中的第二个MV，Base candidate IDX＝2对应融合候选运动矢量列表中的第三个MV，Base candidate IDX＝3对应融合候选运动矢量列表中的第四个MV。可以通过Base candidate IDX表示其对应的候选MV，如果融合候选运动矢量列表中可供选取的候选MV的个数为1，则可以不用Base candidate IDX。
表1
Base candidate IDX 0 1 2 3
N th MVP 1 st MVP 2 nd MVP 3 rd MVP 4 th MVP
(2)确定步长
步长标识(Distance IDX)用于表示MV的偏移距离。参见表2，Distance IDX用于表示偏移初始位置的像素距离的索引，Pixel distance用于表示偏移初始位置(MV起始点)的像素距离。其中，Distance IDX＝0对应的像素距离为1/4-pel(即1/4像素)，Distance IDX＝1对应的像素距离为1/2-pel(即1/2像素)，Distance IDX＝2对应的像素距离为1-pel(即一个像素)，Distance IDX＝3对应的像素距离为2-pel(即两个像素)，Distance IDX＝4对应的像素距离为4-pel(即四个像素)，Distance IDX＝5对应的像素距离为8-pel(即八个像素)，Distance IDX＝6对应的像素距离为16-pel(即十六个像素)，Distance IDX＝7对应的像素距离为32-pel(即三十二个像素)。可以通过Distance IDX表示其对应的像素距离。
表2
Distance IDX 0 1 2 3 4 5 6 7
Pixel distance 1/4-pel 1/2-pel 1-pel 2-pel 4-pel 8-pel 16-pel 32-pel
(3)确定方向
方向标识(Direction IDX)用于表示MV的偏移方向。参见表3，Direction IDX用于表示基于初始位置(MV起始点)的MV偏移方向，x-axis用于表示该偏移方向在x轴的分量，y-axis用于表示该偏移方向在y轴的分量。其中，Direction IDX＝00，表示偏向x轴正向，y轴不限定，Direction IDX＝01，表示偏向x轴反向，y轴不限定，Direction IDX＝10，表示偏向y轴正向，x轴不限定，Direction IDX＝11，表示偏向y轴反向，x轴不限定。可以通过Direction IDX表示其对应的偏移方向。
表3
Direction IDX 00 01 10 11
x-axis + – N/A N/A
y-axis N/A N/A + –
采用MMVD技术确定当前块的预测像素值的过程包括：首先根据Base candidate IDX确定MV起始点，然后根据Direction IDX确定基于MV起始点的偏移方向，最后根据Distance IDX确定在Direction IDX指示的偏移方向上偏移MV起始点的像素距离。例如，Base candidate IDX＝0，Direction IDX＝00，Distance IDX＝2，表示以融合候选运动矢量列表中的第一个MV为MV起始点，向x轴正向偏移一个像素的MV运动矢量为当前块的MV，用以预测或获取当前块的预测像素值。
在现有的VVC草案中，采用语法元素mmvd_cand_flag[x0][y0]表示从融合候选运动矢量列表中的任意两个候选MV中(例如，融合候选运动矢量列表中的第一个候选MV和第二个候选MV，或者第一个候选MV和第三个候选VM，或者第三个候选MV和第六个候选MV等)选取哪一个候选MV作为基础MV，通常mmvd_cand_flag[x0][y0]＝0表示选取该任意两个候选MV中的第一个候选MV，mmvd_cand_flag[x0][y0]＝1表示选取该任意两个候选MV中的第二个候选MV。但如果码流中不出现该语法元素的值时，默认mmvd_cand_flag[x0][y0]＝0。(x0,y0)表示当前块在当前图像中的位置，即当前块左上顶点的像素点相对于当前图像左上顶点的像素点的坐标位置。
如上所述，第一语法元素mmvd_cand_flag用于指示从融合候选运动矢量列表中选取第一候选MV或第二候选MV作为运动矢量拓展的基础MV，该第一候选MV和第二候选MV是融合候选运动矢量列表中的任意两个候选MV。可见第一语法元素mmvd_cand_flag需要在融合候选运动矢量列表中可供选取的候选MV的个数大于预设值(例如1)时才有存在的意义，因此本申请先判断当前融合候选运动矢量列表的长度是否大于预设值。
需要说明的是，第一语法元素mmvd_cand_flag还可以用于指示从融合候选运动矢量列表中的任意N个候选MV中选取任一候选MV作为运动矢量拓展的基础MV，N>1且N<＝MaxNumMergeCand。例如，融合候选运动矢量列表中包括的候选MV的数量为6，即MaxNumMergeCand＝6，这六个候选MV的索引分别是0、1、2、……、5。当N＝6，则mmvd_cand_flag的值可以为0-5中的任意一个。当N＝3，任意N个候选MV的索引分别是0、1和2，则mmvd_cand_flag的值可以为0-2中的任意一个。
步骤602、若融合候选运动矢量列表的长度大于预设值，则采用旁路编码模式对第一语法元素的值进行熵编码。
CABAC是一种常用的熵编码技术，用于语法元素值的编码和解码处理。CABAC的处理过程主要包括二进制化(binarization)、上下文建模(context modeling)和二进制算术编码(binary arithmetic coding)。其中，二进制化是指对输入的非二进制语法元素值进行二进制处理，将其唯一的转换为一个二进制序列(即二进制串)；上下文建模是指对二进制串中的每一个位元(bin)，根据上下文信息(例如，语法元素对应节点周围已重建区域内的编码信息)决定该位元的概率模型；二进制算术编码是指根据概率模型中的概率值对对应的位元进行编码，并根据位元的值更新概率模型中的概率值。
算术编码的基本原理是：根据二进制串中位元的不同取值(即0或1)的出现概率把[0,1)区间划分为互不重叠的子区间，子区间的宽度恰好是各取值的概率，这样二进制串的不同位元将与各子区间一一对应，然后递归地进行区间映射，最后得到一个小区间，从该小区间内选取一个代表性的小数做二进制变换后作为实际的编码输出。统计意义上，一个位元为1的概率越接近于0.5，则编码该位元需要的比特越多；一个位元为1的概率越接 近于0或1，则编码该位元需要的比特越少。
常规编码模式(regular coding mode)和旁路编码模式(Bypass coding mode)包括上下文建模(context modeling)和二进制算术编码(binary arithmetic coding)，是两种不同的熵编码的方法。
在旁路编码模式中，假定二进制符号0和1发生的概率都固定是0.5，其与常规编码模式相比：首先，旁路编码模式的概率估计和更新过程被省略，即无需进行上下文建模，也无需进行上下文模型的更新；其次，旁路编码模式的概率区间子分操作过程被简化，即只需要对概率区间等分即可，而常规编码模式需要根据估计的概率来子分当前的概率区间。可见旁路编码模式可以看做是常规编码模式的一种特殊情况。
本申请采用旁路编码模式对第一语法元素(mmvd_cand_flag)的值进行熵编码的过程包括：
(1)二进制化
对语法元素中的第一语法元素mmvd_cand_flag的值进行二进制变换得到二进制串，该二进制串包括一个或多个位元(bin)。例如，mmvd_cand_flag的值为0或1，因此对其进行二进制化可以得到一个二值的位元，该位元为0表示mmvd_cand_flag的值为0，该位元为1表示mmvd_cand_flag的值为1。或者，对mmvd_cand_flag进行二进制化也可以得到两个二值的位元，该两个位元为00表示mmvd_cand_flag的值为0，该位元为01表示mmvd_cand_flag的值为1。对mmvd_cand_flag进行二进制化也可以得到一个或多个二值的位元，位元为0表示mmvd_cand_flag的值为0，位元为10表示mmvd_cand_flag的值为1。需要说明的是，本申请还可以采用其他方法对mmvd_cand_flag的值进行二进制变换，对此不做具体限定。
在另一种实施方式中，该二进制化过程可以省略。
(2)采用旁路编码模式进行熵编码
a、确定位元的概率值
本申请中由于采用的是旁路编码模式，因此无需对上一步骤得到的二进制串中的每个位元分配特定的概率模型，而是认为每个位元上取值为0和1的概率相等，即各为0.5。
b、根据概率划分概率区间
示例性的，初始概率区间为[0,1)，根据概率为0.5，可以将初始概率区间分为两个子概率区间：第一概率区间[0,0.5)和第二概率区间[0.5,1)，mmvd_cand_flag＝0对应第一概率区间，mmvd_cand_flag＝1对应第二概率区间。
示例性的，可以对上述概率区间进行扩展，将初始概率区间[0,1)的长度扩展到510，用9位二进制数表示，即[0,29)，这样mmvd_cand_flag＝0对应的第一概率区间为[0,28)，mmvd_cand_flag＝1对应的第二概率区间为[28,29)。
c、编码处理
本申请根据第一概率区间和第二概率区间获取二进制串的编码串。例如，本申请可以在概率区间的长度小于概率区间的左边界值的二分之一时，进行重归一化操作，将概率区间的长度左移一位，扩展到概率区间的左边界值的二分之一以上，然后对概率区间的左边界左移一个比特后输出最高位比特，得到mmvd_cand_flag的编码串。
示例性的，mmvd_cand_flag＝0的二进制串为0，将第一概率区间的左边界000000000 左移一个比特后输出最高位比特0，这就是对mmvd_cand_flag的0取值的编码串。mmvd_cand_flag＝1的二进制串为1，将第二概率区间的左边界11111111加上第二概率区间的长度28后得到111111111，将其左移一个比特后输出最高位比特1，这就是对mmvd_cand_flag的1取值的编码串。
需要说明的是，本申请对语法元素中的第一语法元素mmvd_cand_flag的熵编码可以理解为是对mmvd_cand_flag的值的二进制串中的位元进行编码，具体的，是根据mmvd_cand_flag的值的二进制串中的位元的概率值对该位元的进行编码。
本申请，通过对第一语法元素mmvd_cand_flag的值采用旁路编码模式进行熵编码，不需要为mmvd_cand_flag的二进制串中的位元分配特定的概率模型，减少了编码复杂度。
在一种可能的是实现方式中，若融合候选运动矢量列表的长度大于预设值，则将指示旁路编码模式的开关标识(byPassFlag)设置为第一值，采用旁路编码模式对第一语法元素的值进行熵编码。
编码器启动旁路编码模式对第一语法元素的值进行熵编码的后台的操作步骤是，编码器读到旁路编码模式的开关标识被设置为了第一值。byPassFlag可以类似于是否采用旁路编码模式进行熵编码的开关，例如byPassFlag的值为0或1，byPassFlag＝0表示不采用旁路编码模式进行熵编码，byPassFlag＝1表示采用旁路编码模式进行熵编码。因此只有byPassFlag＝1，才会采用旁路编码模式对mmvd_cand_flag的值进行熵编码，byPassFlag＝0则不采用旁路编码模式对mmvd_cand_flag的值进行熵编码，例如可以采用常规编码模式对mmvd_cand_flag的值进行熵编码。
图7是用于实现本申请实施例的语法元素的熵解码方法的另一个流程示意图。该过程700可由视频解码器30执行。过程700描述为一系列的步骤或操作，应当理解的是，过程700可以以各种顺序执行和/或同时发生，不限于图7所示的执行顺序。如图7所示，语法元素的熵解码方法包括：
步骤701、判断当前融合候选运动矢量列表的长度是否大于预设值。
融合候选运动矢量列表的长度是指该融合候选运动矢量列表包括的候选MV的数量(该数量例如用MaxNumMergeCand表示)。
步骤702、若融合候选运动矢量列表的长度大于预设值，则采用旁路解码模式对第一语法元素的编码串进行熵解码。
第一语法元素用于指示从融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，第一候选运动矢量和第二候选运动矢量是融合候选运动矢量列表中的任意两个候选运动矢量。
与图6所示方法实施例相似之处在于，对于第一语法元素mmvd_cand_flag的情况，本实施例采用旁路解码模式对mmvd_cand_flag进行熵解码，这样不需要为mmvd_cand_flag的二进制串中的位元分配特定的概率模型，减少了解码复杂度。
而与图6所示方法实施例不同之处在于，本实施例是要对码流中的mmvd_cand_flag的编码串进行熵解码，得到mmvd_cand_flag的值。
示例性的，本申请采用旁路解码模式对第一语法元素(mmvd_cand_flag)的编码串进行熵解码的过程包括：
(1)获取第一引擎参数和第二引擎参数
第一引擎参数用于表示概率区间的长度，第二引擎参数用于表示概率区间的左边界。示例性的，第一引擎参数为ivlCurrRange，第二引擎参数为ivlOffset，如上所述，对概率区间[0,1)进行扩展，将其长度扩展到510，用9位二进制数表示，即为[0,29)。可以得到ivlCurrRange＝510，ivlOffset＝000000000(即ivlOffset为根据read_bit(9)获取得到的无符号整数对应的9位二进制数)。
(2)更新ivlOffset的值，并得到binVal(即mmvd_cand_flag)的值
a、将ivlOffset的值乘以2，即左移一位，然后通过使用read_bits(1)得到1bit的二进制数，将该二进制数和ivlOffset按位与，得到新的ivlOffset的值。
b、将新的ivlOffset的值和ivlCurrRange的值进行比较：
若新的ivlOffset的值比ivlCurrRange大，则将binVal的值设置为1，并用ivlOffset的值减去ivlCurrRange的值；
否则，binVal的值设置为0。
本申请，通过对第一语法元素mmvd_cand_flag的编码串采用旁路解码模式进行熵解码，不需要为mmvd_cand_flag的二进制串中的位元分配特定的概率模型，减少了解码复杂度。
在一种可能的是实现方式中，若融合候选运动矢量列表的长度大于预设值，则将指示旁路解码模式的开关标识(byPassFlag)设置为第一值，采用旁路解码模式对第一语法元素的值进行熵。
解码器启动旁路解码模式对第一语法元素的值进行熵解码的后台的操作步骤是，解码器读到旁路解码模式的开关标识被设置为了第一值。byPassFlag可以类似于是否采用旁路解码模式进行熵解码的开关，例如byPassFlag的值为0或1，byPassFlag＝0表示不采用旁路解码模式进行熵解码，byPassFlag＝1表示采用旁路解码模式进行熵解码。因此只有byPassFlag＝1，才会采用旁路解码模式对mmvd_cand_flag的值进行熵解码，byPassFlag＝0则不采用旁路解码模式对mmvd_cand_flag的值进行熵解码，例如可以采用常规解码模式对mmvd_cand_flag的值进行熵解码。
示例性的，在VTM-5.0参考软件上进行本申请技术方案的仿真实验，结果如表4和表5所示。通过实验表明，对mmvd_cand_flag的值进行熵编码/解码的过程中，采用旁路编码/解码模式相较于常规编码/解码模式，其在视频序列采用随机存取(Random Access)配置下，Y、U和V分别表示的视频数据格式的三个分量(Y表示亮度分量，U和V表示色度分量)，对应不同的测试序列类别(例如，Class A1、Class A2、Class B、Class C、Class E等)可仿真得到采用旁路编码/解码模式相较于常规编码/解码模式的编码/解码的性能增益结果，可见其平均仿真结果(Overall)显示性能是基本不变的。而编码时间(EncT)和解码时间(DecT)，同样对应不同的测试序列类别可仿真得到采用旁路编码/解码模式相较于常规编码/解码模式的编码/解码所需时长的比较结果，可见其平均仿真结果也显示处理时长减小。
在视频序列采用低延迟(Low Delay)配置下，Y、U和V分别表示的视频信号的三个分量，对应不同的测试序列类别可仿真得到采用旁路编码/解码模式相较于常规编码/解码模式的编码/解码的性能增益结果，可见其平均仿真结果(Overall)显示性能是有一定的提升的。编码时间(EncT)和解码时间(DecT)，同样对应不同的测试序列类别可仿 真得到采用旁路编码/解码模式相较于常规编码/解码模式的编码/解码所需时长的比较结果，可见其平均仿真结果也显示处理时长减小。
表4
Figure PCTCN2020096363-appb-000001
表5
Figure PCTCN2020096363-appb-000002
需要说明的是，以上仿真结果是针对第一语法元素mmvd_cand_flag采用旁路编码/解码模式后，对视频序列进行熵编码/解码的一种示例性的举例描述，其并不能作为本申请技术方案的实现效果的唯一证明。
基于与上述方法相同的发明构思，本申请实施例还提供了一种熵编码装置。图8是用于实现本申请实施例的熵编码装置800的结构框图，该熵编码装置800包括判断模块801和编码模块802，其中：
判断模块801，用于判断当前融合候选运动矢量列表的长度是否大于预设值；编码模块802，用于若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵编码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。
在一种可能的实现方式中，所述编码模块802，还用于若所述融合候选运动矢量列表的长度大于所述预设值，则将指示所述旁路编码模式的开关标识设置为第一值，采用所述旁路编码模式对所述第一语法元素的值进行熵编码。
在一种可能的实现方式中，所述第一语法元素为mmvd_cand_flag。
需要说明的是，上述判断模块801和编码模块802可应用于编码端的熵编码过程。具体的，在编码端，这些模块可应用于前述编码器20的熵编码单元270。
还需要说明的是，判断模块801和编码模块802的具体实现过程可参考图6实施例的详细描述，为了说明书的简洁，这里不再赘述。
基于与上述方法相同的发明构思，本申请实施例还提供了一种熵解码装置。图9是用于实现本申请实施例的熵解码装置900的结构框图，该熵解码装置900包括判断模块901和解码模块902，其中：
判断模块901，用于判断当前融合候选运动矢量列表的长度是否大于预设值；解码模块902，用于若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵解码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。
在一种可能的实现方式中，所述解码模块902，还用于若所述融合候选运动矢量列表的长度大于所述预设值，则将指示所述旁路编码模式的开关标识设置为第一值，采用所述旁路编码模式对所述第一语法元素的值进行熵解码。
在一种可能的实现方式中，所述第一语法元素为mmvd_cand_flag。
需要说明的是，上述判断模块901和解码模块902可应用于解码端的熵解码过程。具体的，在解码端，这些模块可应用于前述解码器30的熵解码单元304。
还需要说明的是，判断模块901和解码模块902的具体实现过程可参考图7实施例的详细描述，为了说明书的简洁，这里不再赘述。
本领域技术人员能够领会，结合本文公开描述的各种说明性逻辑框、模块和算法步骤所描述的功能可以硬件、软件、固件或其任何组合来实施。如果以软件来实施，那么各种说明性逻辑框、模块、和步骤描述的功能可作为一或多个指令或代码在计算机可读媒体上存储或传输，且由基于硬件的处理单元执行。计算机可读媒体可包含计算机可读存储媒体，其对应于有形媒体，例如数据存储媒体，或包括任何促进将计算机程序从一处传送到另一处的媒体(例如，根据通信协议)的通信媒体。以此方式，计算机可读媒体大体上可对应于(1)非暂时性的有形计算机可读存储媒体，或(2)通信媒体，例如信号或载波。数据存储媒体可为可由一或多个计算机或一或多个处理器存取以检索用于实施本申请中描述的技术的指令、代码和/或数据结构的任何可用媒体。计算机程序产品可包含计算机可读媒体。
作为实例而非限制，此类计算机可读存储媒体可包括RAM、ROM、EEPROM、CD-ROM或其它光盘存储装置、磁盘存储装置或其它磁性存储装置、快闪存储器或可用来存储指令或数据结构的形式的所要程序代码并且可由计算机存取的任何其它媒体。并且，任何连接被恰当地称作计算机可读媒体。举例来说，如果使用同轴缆线、光纤缆线、双绞线、数字订户线(DSL)或例如红外线、无线电和微波等无线技术从网站、服务器或其它远程源传输指令，那么同轴缆线、光纤缆线、双绞线、DSL或例如红外线、无线电和微波等无线技术 包含在媒体的定义中。但是，应理解，所述计算机可读存储媒体和数据存储媒体并不包括连接、载波、信号或其它暂时媒体，而是实际上针对于非暂时性有形存储媒体。如本文中所使用，磁盘和光盘包含压缩光盘(CD)、激光光盘、光学光盘、数字多功能光盘(DVD)和蓝光光盘，其中磁盘通常以磁性方式再现数据，而光盘利用激光以光学方式再现数据。以上各项的组合也应包含在计算机可读媒体的范围内。
可通过例如一或多个数字信号处理器(DSP)、通用微处理器、专用集成电路(ASIC)、现场可编程逻辑阵列(FPGA)或其它等效集成或离散逻辑电路等一或多个处理器来执行指令。因此，如本文中所使用的术语“处理器”可指前述结构或适合于实施本文中所描述的技术的任一其它结构中的任一者。另外，在一些方面中，本文中所描述的各种说明性逻辑框、模块、和步骤所描述的功能可以提供于经配置以用于编码和解码的专用硬件和/或软件模块内，或者并入在组合编解码器中。而且，所述技术可完全实施于一或多个电路或逻辑元件中。
本申请的技术可在各种各样的装置或设备中实施，包含无线手持机、集成电路(IC)或一组IC(例如，芯片组)。本申请中描述各种组件、模块或单元是为了强调用于执行所揭示的技术的装置的功能方面，但未必需要由不同硬件单元实现。实际上，如上文所描述，各种单元可结合合适的软件和/或固件组合在编码解码器硬件单元中，或者通过互操作硬件单元(包含如上文所描述的一或多个处理器)来提供。
在上述实施例中，对各个实施例的描述各有侧重，某个实施例中没有详述的部分，可以参见其他实施例的相关描述。
以上所述，仅为本申请示例性的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到的变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应该以权利要求的保护范围为准。

Claims (16)

  1. 一种语法元素的熵编码方法，其特征在于，包括：
    判断当前融合候选运动矢量列表的长度是否大于预设值；
    若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵编码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。
  2. 根据权利要求1所述的方法，其特征在于，所述若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵编码，还包括：
    若所述融合候选运动矢量列表的长度大于所述预设值，则将指示所述旁路编码模式的开关标识设置为第一值，采用所述旁路编码模式对所述第一语法元素的值进行熵编码。
  3. 根据权利要求1或2所述的方法，其特征在于，所述第一语法元素为mmvd_cand_flag。
  4. 一种语法元素的熵解码方法，其特征在于，包括：
    判断当前融合候选运动矢量列表的长度是否大于预设值；
    若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵解码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。
  5. 根据权利要求4所述的方法，其特征在于，所述若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵编码，还包括：
    若所述融合候选运动矢量列表的长度大于所述预设值，则将指示所述旁路编码模式的开关标识设置为第一值，采用所述旁路编码模式对所述第一语法元素的值进行熵解码。
  6. 根据权利要求4或5所述的方法，其特征在于，所述第一语法元素为mmvd_cand_flag。
  7. 一种熵编码装置，其特征在于，包括：
    判断模块，用于判断当前融合候选运动矢量列表的长度是否大于预设值；
    编码模块，用于若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵编码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。
  8. 根据权利要求7所述的装置，其特征在于，所述编码模块，还用于若所述融合候选运动矢量列表的长度大于所述预设值，则将指示所述旁路编码模式的开关标识设置为第一值，采用所述旁路编码模式对所述第一语法元素的值进行熵编码。
  9. 根据权利要求7或8所述的装置，其特征在于，所述第一语法元素为 mmvd_cand_flag。
  10. 一种熵解码装置，其特征在于，包括：
    判断模块，用于判断当前融合候选运动矢量列表的长度是否大于预设值；
    解码模块，用于若所述融合候选运动矢量列表的长度大于所述预设值，则采用旁路编码模式对第一语法元素的值进行熵解码，所述第一语法元素用于指示从所述融合候选运动矢量列表中选取第一候选运动矢量或第二候选运动矢量作为运动矢量拓展的基础运动矢量，所述第一候选运动矢量和所述第二候选运动矢量是所述融合候选运动矢量列表中的任意两个候选运动矢量。
  11. 根据权利要求10所述的装置，其特征在于，所述解码模块，还用于若所述融合候选运动矢量列表的长度大于所述预设值，则将指示所述旁路编码模式的开关标识设置为第一值，采用所述旁路编码模式对所述第一语法元素的值进行熵解码。
  12. 根据权利要求10或11所述的装置，其特征在于，所述第一语法元素为mmvd_cand_flag。
  13. 一种视频编码器，其特征在于，所述视频编码器用于编码图像块，包括：
    帧间预测装置，用于基于目标候选运动信息预测当前编码图像块的运动信息，基于所述当前编码图像块的运动信息确定所述当前编码图像块的预测像素值；
    如权利要求7-9任一项所述的熵编码装置，用于将所述目标候选运动信息的索引标识编入码流，所述索引标识指示用于所述当前编码图像块的所述目标候选运动信息；
    重建模块，用于基于所述预测像素值重建所述当前编码图像块。
  14. 一种视频解码器，其特征在于，所述视频解码器用于从码流中解码出图像块，包括：
    如权利要求10-12任一项所述的熵解码装置，用于从码流中解码出索引标识，所述索引标识用于指示当前解码图像块的目标候选运动信息；
    帧间预测装置，所述帧间预测装置用于基于所述索引标识指示的目标候选运动信息预测当前解码图像块的运动信息，基于所述当前解码图像块的运动信息确定所述当前解码图像块的预测像素值；
    重建模块，用于基于所述预测像素值重建所述当前解码图像块。
  15. 一种视频编码设备，包括：相互耦合的非易失性存储器和处理器，所述处理器调用存储在所述存储器中的程序代码以执行如权利要求1-3任一项所描述的方法。
  16. 一种视频解码设备，包括：相互耦合的非易失性存储器和处理器，所述处理器调用存储在所述存储器中的程序代码以执行如权利要求4-6任一项所描述的方法。
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