CN112135149B

CN112135149B - Entropy encoding/decoding method and device of syntax element and codec

Info

Publication number: CN112135149B
Application number: CN201910550626.2A
Authority: CN
Inventors: 陈旭; 杨海涛; 张恋
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2019-06-24
Filing date: 2019-06-24
Publication date: 2023-07-18
Anticipated expiration: 2039-06-24
Also published as: CN112135149A; WO2020259353A1

Abstract

The application discloses an entropy encoding/decoding method, device and codec of a syntax element, wherein the method comprises the following steps: judging whether the length of the current fusion candidate motion vector list is larger than a preset value or not; if the length of the fusion candidate motion vector list is greater than the preset value, entropy encoding/decoding is performed on the value of a first syntax element by adopting a bypass encoding mode, wherein the first syntax element is used for indicating that a first candidate motion vector or a second candidate motion vector is selected from the fusion candidate motion vector list to serve as a 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 implementation of the method can reduce the complexity of encoding/decoding.

Description

Entropy encoding/decoding method and device of syntax element and codec

Technical Field

The present disclosure relates to the field of video encoding and decoding, and in particular, to a method and apparatus for entropy encoding/decoding of syntax elements, and a codec.

Background

Digital video capabilities can be incorporated into a wide variety of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal Digital Assistants (PDAs), laptop or desktop computers, tablet computers, electronic book readers, digital cameras, digital recording devices, digital media players, video gaming devices, video game consoles, cellular or satellite radio telephones (so-called "smartphones"), video teleconferencing devices, video streaming devices, and the like. Digital video devices implement video compression techniques such as those described 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), the video coding standard H.265/High Efficiency Video Coding (HEVC) standard, and extensions of such standards. Video devices may more efficiently transmit, receive, encode, decode, and/or store digital video information by implementing such video compression techniques.

Context-based adaptive binary arithmetic coding (Context-based Adaptive Binary ArithmeticCoding, CABAC) is a commonly used entropy coding (entropy coding) technique for coding and decoding of syntax element values. The CABAC process mainly includes binarization (binarization), context modeling (context modeling), and binary arithmetic coding (binary arithmetic coding). Binarization refers to binary processing of input non-binary syntax element values, and unique conversion of the non-binary syntax element values into a binary sequence (namely binary strings); context modeling refers to determining, for each bit in a binary string, a probability model for the bit based on context information (e.g., syntax elements corresponding to coding information in reconstructed regions around nodes); binary arithmetic coding refers to coding corresponding bits according to probability values in a probability model and updating the probability values in the probability model according to the values of the bits.

The syntax element mmvd_cand_flag used in the fused motion vector difference (Merge with Motion Vector Difference, MMVD) technique is entropy-encoded/decoded using the CABAC technique described above in the related art. But the complexity of the entropy encoding/decoding is high.

Disclosure of Invention

The embodiment of the application provides an entropy coding/decoding method and device of a syntax element and a coder-decoder, which reduce the complexity of coding/decoding.

In a first aspect, an embodiment of the present application provides an entropy encoding method of a syntax element, including:

judging whether the length of the current fusion candidate motion vector list is larger than a preset value or not; if the length of the fusion candidate motion vector list is greater than the preset value, entropy coding is carried out on the value of a first syntax element by adopting a bypass coding mode, wherein the first syntax element is used for indicating that a first candidate motion vector or a second candidate motion vector is selected from the fusion candidate motion vector list to serve as a 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.

According to the method and the device, the value of the first syntax element mmvd_cand_flag is subjected to entropy coding in a bypass coding mode, a specific probability model is not required to be allocated to bits in a binary string of the mmvd_cand_flag, and coding complexity is reduced.

In one possible implementation manner, if the length of the fusion candidate motion vector list is greater than the preset value, entropy encoding the value of the first syntax element in the bypass encoding mode further includes: and if the length of the fusion candidate motion vector list is greater than the preset value, setting a switch mark indicating the bypass coding mode as a first value, and adopting the bypass coding mode to carry out entropy coding on the value of the first syntax element.

The coding efficiency can be improved by the switch identification indicating whether or not the value of the first syntax element is entropy coded using the bypass coding mode.

In one possible implementation, the first syntax element is mmvd_cand_flag.

In a second aspect, embodiments of the present application provide an entropy decoding method of a syntax element, including:

judging whether the length of the current fusion candidate motion vector list is larger than a preset value or not; if the length of the fusion candidate motion vector list is greater than the preset value, entropy decoding is carried out on the value of a first syntax element by adopting a bypass coding mode, wherein the first syntax element is used for indicating that a first candidate motion vector or a second candidate motion vector is selected from the fusion candidate motion vector list to serve as a 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 method and the device adopt the bypass decoding mode to carry out entropy decoding on the value of the first syntax element mmvd_cand_flag, a specific probability model is not required to be allocated for bits in the binary string of the mmvd_cand_flag, and decoding complexity is reduced.

In one possible implementation manner, if the length of the fusion candidate motion vector list is greater than the preset value, entropy encoding the value of the first syntax element in the bypass encoding mode further includes: and if the length of the fusion candidate motion vector list is greater than the preset value, setting a switch mark indicating the bypass coding mode as a first value, and adopting the bypass coding mode to carry out entropy decoding on the value of the first syntax element.

The decoding efficiency can be improved by the switch identification indicating whether or not to entropy-decode the value of the first syntax element using the bypass decoding mode.

In one possible implementation, the first syntax element is mmvd_cand_flag.

In a third aspect, an embodiment of the present application provides an entropy encoding apparatus, including:

the judging module is used for judging whether the length of the current fusion candidate motion vector list is larger than a preset value or not; the encoding module is configured to entropy encode a value of a first syntax element by using a bypass encoding mode if the length of the fused candidate motion vector list is greater than the preset value, where the first syntax element is used to indicate that a first candidate motion vector or a second candidate motion vector is selected from the fused candidate motion vector list as a 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 fused candidate motion vector list.

In a possible implementation manner, the encoding module is further configured to set a switch identifier indicating the bypass encoding mode to a first value if the length of the fusion candidate motion vector list is greater than the preset value, and entropy encode the value of the first syntax element by adopting the bypass encoding mode.

In one possible implementation, the first syntax element is mmvd_cand_flag.

In a fourth aspect, embodiments of the present application provide an entropy decoding apparatus, including:

the judging module is used for judging whether the length of the current fusion candidate motion vector list is larger than a preset value or not; the decoding module is configured to entropy decode a value of a first syntax element by using a bypass coding mode if the length of the fused candidate motion vector list is greater than the preset value, where the first syntax element is used to instruct that a first candidate motion vector or a second candidate motion vector is selected from the fused candidate motion vector list as a 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 fused candidate motion vector list.

In a possible implementation manner, the decoding module is further configured to set a switch identifier indicating the bypass coding mode to a first value if the length of the fusion candidate motion vector list is greater than the preset value, and entropy decode the value of the first syntax element using the bypass coding mode.

In one possible implementation, the first syntax element is mmvd_cand_flag.

In a fifth aspect, embodiments of the present application provide a video encoder for encoding an image block, including:

inter-frame prediction means for predicting motion information of a current encoded image block based on target candidate motion information, and determining a predicted pixel value of the current encoded image block based on the motion information of the current encoded image block;

entropy encoding means according to any of the third aspect above for encoding an index identification of the target candidate motion information into a bitstream, the index identification indicating the target candidate motion information for the current encoded image block;

a reconstruction module for reconstructing the current encoded image block based on the predicted pixel values.

In a sixth aspect, embodiments of the present application provide a video decoder for decoding an image block from a code stream, including:

Entropy decoding means according to any of the fourth aspect above for decoding an index identification from a bitstream, the index identification being indicative of target candidate motion information for a currently decoded image block;

inter-frame prediction means for predicting motion information of a current decoded image block based on target candidate motion information indicated by the index identification, and determining a predicted pixel value of the current decoded image block based on the motion information of the current decoded image block;

a reconstruction module for reconstructing the current decoded image block based on the predicted pixel values.

In a seventh aspect, embodiments of the present application provide a video encoding apparatus, including: a non-volatile memory and a processor coupled to each other, the processor invoking program code stored in the memory to perform the method as described in any of the first aspects above.

In an eighth aspect, embodiments of the present application provide a video decoding apparatus, including: a non-volatile memory and a processor coupled to each other, the processor invoking program code stored in the memory to perform a method as described in any of the second aspects above.

In a ninth aspect, embodiments of the present application provide a computer-readable storage medium storing program code, where the program code includes instructions for performing part or all of the steps of any one of the methods of the first or second aspects.

In a tenth aspect, embodiments of the present application provide a computer program product which, when run on a computer, causes the computer to perform part or all of the steps of any one of the methods of the first or second aspects.

It should be understood that, in the third to tenth aspects of the present application, the technical solutions of the first or second aspects of the present application are consistent, and the beneficial effects obtained by each aspect and the corresponding possible embodiments are similar, and are not repeated.

It can be seen that the embodiment of the present application reduces encoding/decoding complexity by entropy encoding/decoding the value of the first syntax element mmvd_cand_flag in the bypass encoding/decoding mode without assigning a specific probability model to the bits in the binary string of mmvd_cand_flag.

Drawings

In order to more clearly describe the technical solutions in the embodiments or the background of the present application, the following description will describe the drawings that are required to be used in the embodiments or the background of the present application.

FIG. 1A is a block diagram of an example of a video encoding and decoding system 10 for implementing embodiments of the present application;

FIG. 1B is a block diagram of an example of a video coding system 40 for implementing embodiments of the present application;

FIG. 2 is a block diagram of an example structure of an encoder 20 for implementing embodiments of the present application;

FIG. 3 is a block diagram of an example architecture of a decoder 30 for implementing embodiments of the present application;

fig. 4 is a block diagram of an example of a video coding apparatus 400 for implementing an embodiment of the present application;

FIG. 5 is a block diagram of another example encoding or decoding device for implementing embodiments of the present application;

fig. 6 is a flow diagram of an entropy encoding method for implementing syntax elements of an embodiment of the present application;

fig. 7 is another flow diagram of an entropy decoding method for implementing syntax elements of an embodiment of the present application;

fig. 8 is a block diagram of a structure of an entropy encoding apparatus 800 for implementing an embodiment of the present application;

fig. 9 is a block diagram of a structure of an entropy decoding device 900 for implementing an embodiment of the present application.

Detailed Description

Embodiments of the present application are described below with reference to the accompanying drawings in the embodiments of the present application. In the following description, reference is made to the accompanying drawings which form a part hereof and which show by way of illustration specific aspects in which embodiments of the application may be practiced. It is to be understood that the embodiments of the present application may be used in other respects and may include structural or logical changes not depicted in the drawings. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present application is defined by the appended claims. For example, it should be understood that the disclosure in connection with the described methods may be equally applicable to a corresponding apparatus or system for performing the methods, and vice versa. For example, if one or more specific method steps are described, the corresponding apparatus may comprise one or more units, such as functional units, to perform the one or more described method steps (e.g., one unit performing one or more steps, or multiple units each performing one or more of the multiple steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, if a specific apparatus is described based on one or more units such as a functional unit, for example, the corresponding method may include one step to perform the functionality of the one or more units (e.g., one step to perform the functionality of the one or more units, or multiple steps each to perform the functionality of one or more units, even if such one or more steps are not explicitly described or illustrated in the figures). Further, it is to be understood that features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless explicitly stated otherwise.

The technical scheme related to the embodiment of the application can be applied to the existing video coding standards (such as H.264, HEVC and the like) and future video coding standards (such as H.266). The terminology used in the description section of the present application is for the purpose of describing particular embodiments of the present application only and is not intended to be limiting of the present application. Some concepts that may be related to embodiments of the present application are briefly described below.

Video coding generally refers to processing a sequence of pictures that form a video or video sequence. In the field of video coding, the terms "picture", "frame" or "image" may be used as synonyms. Video encoding as used herein refers to video encoding or video decoding. Video encoding is performed on the source side, typically including processing (e.g., by compression) the original video picture to reduce the amount of data required to represent the video picture, thereby more efficiently storing and/or transmitting. Video decoding is performed on the destination side, typically involving inverse processing with respect to the encoder to reconstruct the video pictures. The embodiment relates to video picture "encoding" is understood to relate to "encoding" or "decoding" of a video sequence. The combination of the encoding portion and the decoding portion is also called codec (encoding and decoding).

A video sequence comprises a series of pictures (pictures) which are further divided into slices (slices) which are further divided into blocks (blocks). Video coding performs coding processing in units of blocks, and in some new video coding standards, the concept of blocks is further extended. For example, in the h.264 standard, there are Macro Blocks (MBs), which can be further divided into a plurality of prediction blocks (partition) that can be used for predictive coding. In the high performance video coding (high efficiency video coding, HEVC) standard, basic concepts such as a Coding Unit (CU), a Prediction Unit (PU), and a Transform Unit (TU) are adopted, and various block units are functionally divided and described by using a brand new tree-based structure. For example, a CU may be divided into smaller CUs according to a quadtree, and the smaller CUs may continue to be divided, thereby forming a quadtree structure, where a CU is a basic unit for dividing and encoding an encoded image. Similar tree structures exist for PUs and TUs, which may correspond to prediction blocks, being the basic unit of predictive coding. The CU is further divided into a plurality of PUs according to a division pattern. The TU may correspond to a transform block, which is a basic unit for transforming a prediction residual. However, whether CU, PU or TU, essentially belongs to the concept of blocks (or picture blocks).

In HEVC, for example, CTUs are split into multiple CUs by using a quadtree structure denoted as coding tree. A decision is made at the CU level whether to encode a picture region using inter-picture (temporal) or intra-picture (spatial) prediction. Each CU may be further split into one, two, or four PUs depending on the PU split type. The same prediction process is applied within one PU and the relevant information is transmitted to the decoder on a PU basis. After the residual block is obtained by applying the prediction process based on the PU split type, the CU may be partitioned into Transform Units (TUs) according to other quadtree structures similar to the coding tree for the CU. In a recent development of video compression technology, a Quad tree and a binary tree (qd-tree and binary tree, QTBT) partition frames are used to partition the encoded blocks. In QTBT block structures, a CU may be square or rectangular in shape.

Herein, for convenience of description and understanding, an image block to be encoded in a current encoded image may be referred to as a current block, for example, in encoding, a block currently being encoded; in decoding, a block currently being decoded is referred to. A decoded image block in a reference image used for predicting a current block is referred to as a reference block, i.e. a reference block is a block providing a reference signal for the current block, wherein the reference signal represents pixel values within the image block. A block in the reference picture that provides a prediction signal for the current block may be referred to as a prediction block, where the prediction signal represents pixel values or sample signals within the prediction block. For example, after traversing multiple reference blocks, the best reference block is found, which will provide prediction for the current block, which is referred to as the prediction block.

In the case of lossless video coding, the original video picture may be reconstructed, i.e., 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). In the case of lossy video coding, the amount of data needed to represent a video picture is reduced by performing further compression, e.g. quantization, whereas the decoder side cannot reconstruct the video picture completely, i.e. the quality of the reconstructed video picture is lower or worse than the quality of the original video picture.

Several video coding standards of h.261 belong to the "lossy hybrid video codec" (i.e. spatial and temporal prediction in the sample domain is combined with 2D transform coding in the transform domain for applying quantization). Each picture of a video sequence is typically partitioned into non-overlapping sets of blocks, typically encoded at the block level. In other words, the encoder side typically processes, i.e. encodes, video at the block (video block) level, e.g. generates a prediction block by spatial (intra-picture) prediction and temporal (inter-picture) prediction, subtracts the prediction block from the current block (currently processed or to-be-processed block) to obtain a 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), while the decoder side applies the inverse processing part of the relative encoder to the encoded or compressed block to reconstruct the current block for representation. In addition, the encoder replicates the decoder processing loop so that the encoder and decoder generate the same predictions (e.g., intra-prediction and inter-prediction) and/or reconstructions for processing, i.e., encoding, the subsequent blocks.

The system architecture to which the embodiments of the present application apply is described below. Referring to fig. 1A, fig. 1A schematically illustrates a block diagram of a video encoding and decoding system 10 to which embodiments of the present application are applied. As shown in fig. 1A, video encoding and decoding system 10 may include a source device 12 and a destination device 14, source device 12 generating encoded video data, and thus source device 12 may be referred to as a video encoding apparatus. Destination device 14 may decode encoded video data generated by source device 12, and thus destination device 14 may be referred to as a video decoding apparatus. Various implementations of source apparatus 12, destination apparatus 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 the desired program code in the form of instructions or data structures that can be accessed by a computer, as described herein. The source device 12 and the destination device 14 may include a variety of devices including desktop computers, mobile computing devices, notebook (e.g., laptop) computers, tablet computers, set-top boxes, telephone handsets such as so-called "smart" phones, televisions, cameras, display devices, digital media players, video game consoles, vehicle mount computers, wireless communication devices, or the like.

Although fig. 1A depicts source device 12 and destination device 14 as separate devices, device embodiments may also include the functionality of both source device 12 and destination device 14, or both, i.e., source device 12 or corresponding functionality and destination device 14 or corresponding functionality. In such embodiments, the source device 12 or corresponding functionality and the destination device 14 or corresponding functionality may be implemented using the same hardware and/or software, or using separate hardware and/or software, or any combination thereof.

A communication connection may be made between source device 12 and destination device 14 via link 13, and destination device 14 may receive encoded video data from source device 12 via 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. In one example, 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. In this example, source apparatus 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 destination apparatus 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. 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 equipment that facilitate communication from source apparatus 12 to destination apparatus 14.

Source device 12 includes an encoder 20 and, alternatively, source device 12 may also include a picture source 16, a picture preprocessor 18, and a communication interface 22. In a specific implementation, 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. The descriptions are as follows:

the picture source 16 may include or be any type of picture capture device for capturing, for example, real world pictures, and/or any type of picture or comment (for screen content encoding, some text on the screen is also considered part of the picture or image to be encoded), for example, a computer graphics processor for generating computer animated pictures, or any type of device for capturing and/or providing real world pictures, computer animated pictures (e.g., screen content, virtual Reality (VR) pictures), and/or any combination thereof (e.g., real scene (AR) pictures). Picture source 16 may be a camera for capturing pictures or a memory for storing pictures, picture source 16 may also include any type of (internal or external) interface for storing previously captured or generated pictures and/or for capturing or receiving pictures. When picture source 16 is a camera, picture source 16 may be, for example, an integrated camera, either local or integrated in the source device; when picture source 16 is memory, picture source 16 may be local or integrated memory integrated in the source device, for example. When the picture source 16 comprises an interface, the interface may for example be an external interface receiving pictures from an external video source, for example an external picture capturing device, such as a camera, an external memory or an external picture generating device, for example an external computer graphics processor, a computer or a server. The interface may be any kind of interface according to any proprietary or standardized interface protocol, e.g. a wired or wireless interface, an optical interface.

Wherein a picture can be regarded as a two-dimensional array or matrix of pixel elements. The pixels in the array may also be referred to as sampling points. The number of sampling points of the array or picture in the horizontal and vertical directions (or axes) defines the size and/or resolution of the picture. To represent color, three color components are typically employed, i.e., a picture may be represented as or contain three sample arrays. For example, in RBG format or color space, the picture includes corresponding red, green, and blue sample arrays. However, in video coding, each pixel is typically represented in a luminance/chrominance format or color space, e.g., for a picture in YUV format, comprising a luminance component indicated by Y (which may sometimes also be indicated by L) and two chrominance components indicated by U and V. The luminance (luma) component Y represents the luminance or grayscale level intensity (e.g., the same in a grayscale picture), while the two chrominance (chroma) components U and V represent the chrominance or color information components. Accordingly, a picture in 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 may be converted or transformed into YUV format and vice versa, a process also known as color transformation or conversion. If the picture is black and white, the picture may include only an array of luma samples. In the present embodiment, the picture transmitted by the picture source 16 to the picture processor may also be referred to as the original picture data 17.

A picture preprocessor 18 for receiving the original picture data 17 and performing preprocessing on the original picture data 17 to obtain a preprocessed picture 19 or preprocessed picture data 19. For example, the preprocessing performed by the picture preprocessor 18 may include truing, color format conversion (e.g., from RGB format to YUV format), toning, or denoising.

Encoder 20 (or video encoder 20) receives pre-processed picture data 19, and processes pre-processed picture data 19 using an associated prediction mode (e.g., a prediction mode in various embodiments herein) to provide encoded picture data 21 (details of the structure of encoder 20 will be described further below based on fig. 2 or fig. 4 or fig. 5). In some embodiments, encoder 20 may be configured to perform various embodiments described below to implement the application of the chroma block prediction method described herein on the encoding side.

Communication interface 22 may be used to receive encoded picture data 21 and may transmit encoded picture data 21 over link 13 to destination device 14 or any other device (e.g., memory) for storage or direct reconstruction, which may be any device for decoding or storage. Communication interface 22 may be used, for example, to encapsulate encoded picture data 21 into a suitable format, such as a data packet, for transmission over link 13.

Destination device 14 includes a decoder 30, and alternatively destination device 14 may also include a communication interface 28, a picture post-processor 32, and a display device 34. The descriptions are as follows:

communication interface 28 may be used to receive encoded picture data 21 from source device 12 or any other source, such as a storage device, such as an encoded picture data storage device. The communication interface 28 may be used to transmit or receive encoded picture data 21 via a link 13 between the source device 12 and the destination device 14, such as a direct wired or wireless connection, or via any type of network, such as a wired or wireless network or any combination thereof, or any type of private and public networks, or any combination thereof. Communication interface 28 may, for example, be used to decapsulate data packets transmitted by communication interface 22 to obtain encoded picture data 21.

Both communication interface 28 and communication interface 22 may be configured as unidirectional communication interfaces or bidirectional communication interfaces and may be used, for example, to send and receive messages to establish connections, to acknowledge and to exchange any other information related to the communication link and/or to the transmission of data, for example, encoded picture data transmissions.

Decoder 30 (or referred to as decoder 30) for receiving encoded picture data 21 and providing decoded picture data 31 or decoded picture 31 (details of the structure of decoder 30 will be described below further based on fig. 3 or fig. 4 or fig. 5). In some embodiments, decoder 30 may be configured to perform various embodiments described below to implement the application of the chroma block prediction method described herein on the decoding side.

A picture post-processor 32 for performing post-processing on the decoded picture data 31 (also referred to as reconstructed slice data) to obtain post-processed picture data 33. The post-processing performed by the picture post-processor 32 may include: color format conversion (e.g., from YUV format to RGB format), toning, truing, or resampling, or any other process, may also be used to transmit post-processed picture data 33 to display device 34.

A display device 34 for receiving the post-processed picture data 33 for displaying pictures to, for example, a user or viewer. The display device 34 may be or include any type of display for presenting reconstructed pictures, for example, an integrated or external display or monitor. For example, the display may include a liquid crystal display (liquid crystal display, LCD), an organic light emitting diode (organic light emitting diode, OLED) display, a plasma display, a projector, a micro LED display, a liquid crystal on silicon (liquid crystal on silicon, LCoS), a digital light processor (digital light processor, DLP), or any other type of display.

It will be apparent to those skilled in the art from this description that the functionality of the different units or the existence and (exact) division of the functionality of the source device 12 and/or destination device 14 shown in fig. 1A may vary depending on the actual device and application. Source device 12 and destination device 14 may comprise any of a variety of devices, including any type of handheld or stationary device, such as a notebook or laptop computer, mobile phone, smart phone, tablet or tablet computer, video camera, desktop computer, set-top box, television, camera, in-vehicle device, display device, digital media player, video game console, video streaming device (e.g., content service server or content distribution server), broadcast receiver device, broadcast transmitter device, etc., and may not use or use any type of operating system.

Encoder 20 and decoder 30 may each be implemented as any of a variety of suitable circuits, such as, for example, one or more microprocessors, digital signal processors (digital signal processor, DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic, hardware or any combinations thereof. If the techniques are implemented in part in software, an apparatus may store instructions of the software in a suitable non-transitory computer-readable storage medium and may execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Any of the foregoing (including hardware, software, a combination of hardware and software, etc.) may be considered one or more processors.

In some cases, the video encoding and decoding system 10 shown in fig. 1A is merely an example, and the techniques of this disclosure may be applicable to video encoding settings (e.g., video encoding or video decoding) that do not necessarily involve any data communication between encoding and decoding devices. In other examples, the data may be retrieved from local memory, streamed over a network, and the like. The video encoding device may encode and store data to the memory and/or the video decoding device may retrieve and decode data from the memory. In some examples, encoding and decoding are performed by devices that do not communicate with each other, but instead only encode data to memory and/or retrieve data from memory and decode data.

Referring to fig. 1B, fig. 1B is an illustration of an example of a video coding system 40 including encoder 20 of fig. 2 and/or decoder 30 of fig. 3, according to an example embodiment. Video coding system 40 may implement a combination of the various techniques of the embodiments of the present application. In the illustrated embodiment, video coding system 40 may include an imaging device 41, an encoder 20, a decoder 30 (and/or a video codec implemented by logic circuitry 47 of a processing unit 46), an antenna 42, one or more processors 43, one or more memories 44, and/or a display device 45.

As shown in fig. 1B, 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. As discussed, although video coding system 40 is depicted with encoder 20 and decoder 30, in different examples, video coding system 40 may include only encoder 20 or only decoder 30.

In some examples, antenna 42 may be used to transmit or receive an encoded bitstream of video data. Additionally, in some examples, display device 45 may be used to present video data. In some examples, logic 47 may be implemented by processing unit 46. The processing unit 46 may comprise application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, or the like. The video coding system 40 may also include an optional processor 43, which optional processor 43 may similarly include application-specific integrated circuit (ASIC) logic, a graphics processor, a general purpose processor, or the like. In some examples, logic 47 may be implemented in hardware, such as video encoding dedicated hardware, processor 43 may be implemented in general purpose software, an operating system, or the like. In addition, the memory 44 may be any type of memory, such as volatile memory (e.g., static random access memory (StaticRandom Access Memory, SRAM), dynamic random access memory (Dynamic Random Access Memory, DRAM), etc.) or non-volatile memory (e.g., flash memory, etc.), and the like. In a non-limiting example, the memory 44 may be implemented by an overspeed cache. In some examples, logic circuitry 47 may access memory 44 (e.g., for implementing an image buffer). In other examples, logic 47 and/or processing unit 46 may include memory (e.g., a cache, etc.) for implementing an image buffer, etc.

In some examples, encoder 20 implemented by logic circuitry may include an image buffer (e.g., implemented by processing unit 46 or memory 44) and a graphics processing unit (e.g., implemented by processing unit 46). The graphics processing unit may be communicatively coupled to the image buffer. The graphics processing unit may include encoder 20 implemented by logic circuitry 47 to implement the various modules discussed with reference to fig. 2 and/or any other encoder system or subsystem described herein. Logic circuitry may be used to perform various operations discussed herein.

In some examples, decoder 30 may be implemented in a similar manner by logic circuit 47 to implement the various modules discussed with reference to decoder 30 of fig. 3 and/or any other decoder system or subsystem described herein. In some examples, decoder 30 implemented by logic circuitry may include an image buffer (implemented by processing unit 2820 or memory 44) and a graphics processing unit (e.g., implemented by processing unit 46). The graphics processing unit may be communicatively coupled to the image buffer. The graphics processing unit may include decoder 30 implemented by logic circuit 47 to implement the various modules discussed with reference to fig. 3 and/or any other decoder system or subsystem described herein.

In some examples, antenna 42 may be used to receive an encoded bitstream of video data. As discussed, the encoded bitstream may include data related to the encoded video frame, indicators, index values, mode selection data, etc., discussed herein, such as data related to the encoded partitions (e.g., transform coefficients or quantized transform coefficients, optional indicators (as discussed), and/or data defining the encoded partitions). Video coding system 40 may also include a decoder 30 coupled to antenna 42 and used to decode the encoded bitstream. The display device 45 is used to present video frames.

It should be understood that for the example described with reference to encoder 20 in the embodiments of the present application, decoder 30 may be used to perform the reverse process. Regarding signaling syntax elements, decoder 30 may be configured to receive and parse such syntax elements and decode the associated video data accordingly. In some examples, encoder 20 may entropy encode the syntax elements into an encoded video bitstream. In such examples, decoder 30 may parse such syntax elements and decode the relevant video data accordingly.

It should be noted that, the entropy encoding/decoding method of the syntax element described in the embodiment of the present application is mainly used in the entropy encoding/decoding process, where the entropy encoding/decoding process exists in both the encoder 20 and the decoder 30, and the encoder 20 and the decoder 30 in the embodiment of the present application may be, for example, an encoder/decoder corresponding to a video standard protocol such as h.263, h.264, HEVV, MPEG-2, MPEG-4, VP8, VP9, or a next-generation video standard protocol (such as h.266, etc.).

Referring to fig. 2, fig. 2 shows a schematic/conceptual block diagram of an example of an encoder 20 for implementing an embodiment of the present application. In the example of fig. 2, encoder 20 includes a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a buffer 216, a loop filter unit 220, a decoded picture buffer (decoded picture buffer, DPB) 230, a prediction processing unit 260, and an entropy encoding 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.

For example, 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 a forward signal path of the encoder 20, whereas for example the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (decoded picture buffer, DPB) 230, the prediction processing unit 260 form a 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).

Encoder 20 receives picture 201 or an image block 203 of picture 201, e.g., a picture in a sequence of pictures forming a video or video sequence, through, e.g., input 202. Image block 203 may also be referred to as a current picture block or a picture block to be encoded, and picture 201 may be referred to as a current picture or a picture to be encoded (especially when distinguishing the current picture from other pictures in video encoding, such as previously encoded and/or decoded pictures in the same video sequence, i.e., a video sequence that also includes the current picture).

An embodiment of encoder 20 may comprise a partitioning unit (not shown in fig. 2) for partitioning picture 201 into a plurality of blocks, e.g. image blocks 203, typically into a plurality of non-overlapping blocks. The segmentation unit may be used to use the same block size for all pictures in the video sequence and a corresponding grid defining the block size, or to alter the block size between pictures or subsets or groups of pictures and to segment each picture into corresponding blocks.

In one example, prediction processing unit 260 of encoder 20 may be used to perform any combination of the above-described partitioning techniques.

Like picture 201, image block 203 is also or may be considered as a two-dimensional array or matrix of sampling points having sampling values, albeit of smaller size than picture 201. In other words, the image block 203 may comprise, for example, one sampling array (e.g., a luminance array in the case of a black-and-white picture 201) or three sampling arrays (e.g., one luminance array and two chrominance arrays in the case of a color picture) or any other number and/or class of arrays 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 as shown in fig. 2 is used for encoding a picture 201 block by block, for example, performing encoding and prediction for each image block 203.

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

The transform processing unit 206 is configured to apply a transform, such as a discrete cosine transform (discretecosine transform, DCT) or a discrete sine transform (discrete sine transform, DST), on the sample values of the residual block 205 to obtain transform coefficients 207 in the transform domain. The transform coefficients 207 may also be referred to as transform residual coefficients and represent the residual block 205 in the transform domain.

The transform processing unit 206 may be used to apply integer approximations of DCT/DST, such as the transforms specified for HEVC/H.265. Such integer approximations are typically scaled by some factor compared to the orthogonal DCT transform. To maintain the norms of the forward and inverse transformed processed residual blocks, an additional scaling factor is applied as part of the transformation process. The scaling factor is typically selected based on certain constraints, e.g., the scaling factor is a tradeoff between power of 2, bit depth of transform coefficients, accuracy, and implementation cost for shift operations, etc. For example, a specific scaling factor is specified for inverse transformation by, for example, the inverse transformation processing unit 212 on the decoder 30 side (and for corresponding inverse transformation by, for example, the inverse transformation processing unit 212 on the encoder 20 side), and accordingly, a corresponding scaling factor may be specified for positive transformation by the transformation processing unit 206 on the encoder 20 side.

The quantization unit 208 is for quantizing the transform coefficients 207, for example by applying scalar quantization or vector quantization, to obtain quantized transform coefficients 209. The quantized transform coefficients 209 may also be referred to as quantized residual coefficients 209. The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, n-bit transform coefficients may be rounded down to m-bit transform coefficients during quantization, where n is greater than m. The quantization level may be modified by adjusting quantization parameters (quantization parameter, QP). For example, for scalar quantization, different scales may be applied to achieve finer or coarser quantization. Smaller quantization step sizes correspond to finer quantization, while larger quantization step sizes correspond to coarser quantization. The appropriate quantization step size may be indicated by a quantization parameter (quantization parameter, QP). For example, the quantization parameter may be an index of a predefined set of suitable quantization steps. For example, smaller quantization parameters may correspond to fine quantization (smaller quantization step size) and larger quantization parameters may correspond to coarse quantization (larger quantization step size) and vice versa. Quantization may involve division by a quantization step size and corresponding quantization or inverse quantization, e.g., performed by inverse quantization 210, or may involve multiplication by a quantization step size. Embodiments according to some standards, such as HEVC, may use quantization parameters to determine quantization step sizes. In general, the quantization step size may be calculated based on quantization parameters using a fixed-point approximation of an equation that includes division. Additional scaling factors may be introduced for quantization and inverse quantization to recover norms of residual blocks that may be modified due to the scale used in the fixed point approximation of the equation for quantization step size and quantization parameters. In one example embodiment, the inverse transformed and inverse quantized scales may be combined. Alternatively, a custom quantization table may be used and signaled from the encoder to the decoder, e.g., in a bitstream. Quantization is a lossy operation, where the larger the quantization step size, the larger the loss.

The inverse quantization unit 210 is configured to apply inverse quantization of the quantization unit 208 on the quantized coefficients to obtain inverse quantized coefficients 211, e.g., apply an inverse quantization scheme of the quantization scheme applied by the quantization unit 208 based on or using the same quantization step size as the quantization unit 208. The dequantized coefficients 211 may also be referred to as dequantized residual coefficients 211, correspond to the transform coefficients 207, although the losses due to quantization are typically different from the transform coefficients.

The inverse transform processing unit 212 is configured to apply an inverse transform of the transform applied by the transform processing unit 206, for example, an inverse discrete cosine transform (discrete cosine transform, DCT) or an inverse discrete sine transform (discrete sine transform, DST), to obtain an inverse transform block 213 in the sample domain. The inverse transform block 213 may also be referred to as an inverse transformed inverse quantized block 213 or an inverse transformed residual block 213.

A reconstruction unit 214 (e.g., a summer 214) is used to add the inverse transform block 213 (i.e., the reconstructed residual block 213) to the prediction block 265 to obtain the reconstructed block 215 in the sample domain, e.g., to add sample values of the reconstructed residual block 213 to sample values of the prediction block 265.

Optionally, a buffer unit 216, e.g. a line buffer 216 (or simply "buffer" 216), is used to buffer or store the reconstructed block 215 and the corresponding sample values for e.g. intra prediction. In other embodiments, the encoder may be configured to use the unfiltered reconstructed block and/or the corresponding sample values stored in the buffer unit 216 for any kind of estimation and/or prediction, such as intra prediction.

For example, embodiments of encoder 20 may be configured such that buffer unit 216 is used not only to store reconstructed blocks 215 for intra prediction 254, but also for loop filter unit 220 (not shown in fig. 2), and/or such that buffer unit 216 and decoded picture buffer unit 230 form one buffer, for example. Other embodiments may be used to use the filtered block 221 and/or blocks or samples (neither shown in fig. 2) from the decoded picture buffer 230 as an input or basis for the intra prediction 254.

The loop filter unit 220 (or simply "loop filter" 220) is used to filter the reconstructed block 215 to obtain a filtered block 221, which facilitates pixel transitions or improves video quality. 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, adaptive loop filters (adaptive loop filter, ALF), or sharpening or smoothing filters, or collaborative filters. Although loop filter unit 220 is shown in fig. 2 as an in-loop filter, in other configurations 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. Decoded picture buffer 230 may store the reconstructed encoded block after loop filter unit 220 performs a filtering operation on the reconstructed encoded block.

Embodiments of encoder 20 (and correspondingly loop filter unit 220) may be configured to output loop filter parameters (e.g., sample adaptive offset information), e.g., directly or after entropy encoding by entropy encoding unit 270 or any other entropy encoding unit, e.g., such that decoder 30 may receive and apply the same loop filter parameters for decoding.

Decoded picture buffer (decoded picture buffer, DPB) 230 may be a reference picture memory that stores reference picture data for use by encoder 20 in encoding video data. DPB 230 may be formed of any of a variety of memory devices, such as dynamic random access memory (dynamic random access memory, DRAM) (including Synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM)), or other types of memory devices. DPB 230 and buffer 216 may be provided by the same memory device or separate memory devices. In a certain example, a decoded picture buffer (decoded picture buffer, DPB) 230 is used to store the filtered block 221. The decoded picture buffer 230 may further be used to store the same current picture or other previously filtered blocks, e.g., previously reconstructed and filtered blocks 221, of different pictures, e.g., previously reconstructed pictures, and may provide complete previously reconstructed, i.e., decoded pictures (and corresponding reference blocks and samples) and/or partially reconstructed current pictures (and corresponding reference blocks and samples), e.g., for inter prediction. In a certain example, if the reconstructed block 215 is reconstructed without in-loop filtering, the decoded picture buffer (decoded picture buffer, DPB) 230 is used to store the reconstructed block 215.

The prediction processing unit 260, also referred to as block prediction processing unit 260, is adapted to receive or obtain image blocks 203 (current image blocks 203 of a current picture 201) and reconstructed slice data, e.g. reference samples of the same (current) picture from the buffer 216 and/or reference picture data 231 of one or more previously decoded pictures from the decoded picture buffer 230, and to process such data for prediction, i.e. to provide a prediction block 265, which may be an inter-predicted block 245 or an intra-predicted block 255.

The mode selection unit 262 may be used to select a prediction mode (e.g., intra or inter prediction mode) and/or a corresponding prediction block 245 or 255 used as the prediction block 265 to calculate the residual block 205 and reconstruct the reconstructed block 215.

Embodiments of mode selection unit 262 may be used to select the prediction mode (e.g., from those supported by prediction processing unit 260) that provides the best match or minimum residual (minimum residual meaning better compression in transmission or storage), or that provides the minimum signaling overhead (minimum signaling overhead meaning better compression in transmission or storage), or both. The mode selection unit 262 may be adapted to determine a prediction mode based on a rate-distortion optimization (rate distortion optimization, RDO), i.e. to select the prediction mode that provides the least rate-distortion optimization, or to select a prediction mode for which the associated rate-distortion at least meets a prediction mode selection criterion.

The prediction processing performed by an instance of encoder 20 (e.g., by prediction processing unit 260) and the mode selection performed (e.g., by mode selection unit 262) will be explained in detail below.

As described above, the encoder 20 is configured to determine or select the best or optimal prediction mode from a (predetermined) set of prediction modes. The set of prediction modes may include, for example, intra prediction modes and/or inter prediction modes.

The set of intra prediction modes may include 35 different intra prediction modes, for example, a non-directional mode such as a DC (or mean) mode and a planar mode, or a directional mode as defined in h.265, or 67 different intra prediction modes, for example, a non-directional mode such as a DC (or mean) mode and a planar mode, or a directional mode as defined in h.266 under development.

In a possible implementation, the set of inter prediction modes depends on the available reference pictures (i.e. at least part of the decoded pictures stored in the DBP230 as described above, for example) and other inter prediction parameters, e.g. on whether the entire reference picture is used or only a part of the reference picture is used, e.g. a search window area surrounding an area of the current block, to search for the best matching reference block, and/or on whether pixel interpolation like half-pixel and/or quarter-pixel interpolation is applied, e.g. the set of inter prediction modes may comprise advanced motion vector (Advanced Motion Vector Prediction, AMVP) mode and fusion (merge) mode, for example. In particular implementations, the set of inter prediction modes may include an improved control point-based AMVP mode of an embodiment of the present application, and an improved control point-based merge mode. In one example, intra-prediction unit 254 may be used to perform any combination of the inter-prediction techniques described below.

In addition to the above prediction modes, the present embodiments may also apply skip mode and/or direct mode.

The prediction processing unit 260 may be further operative to partition the image block 203 into smaller block partitions or sub-blocks, for example, by iteratively using a quad-tree (QT) partition, a binary-tree (BT) partition, or a ternary-tree (TT) partition, or any combination thereof, and to perform prediction for each of the block partitions or sub-blocks, for example, wherein the mode selection includes selecting a tree structure of the partitioned image block 203 and selecting a prediction mode applied to each of the block partitions or sub-blocks.

The inter prediction unit 244 may include a motion estimation (motion estimation, ME) unit (not shown in fig. 2) and a motion compensation (motion compensation, MC) unit (not shown in fig. 2). The motion estimation unit is used to receive or obtain a picture image block 203 (current picture image block 203 of current picture 201) and a decoded picture 231, or at least one or more previously reconstructed blocks, e.g. reconstructed blocks of one or more other/different previously decoded pictures 231, for motion estimation. For example, the video sequence may include a current picture and a previously decoded picture 31, or in other words, the current picture and the previously decoded picture 31 may be part of, or form, a sequence of pictures that form the video sequence.

For example, encoder 20 may be configured to select a reference block from a plurality of reference blocks of the same or different pictures of a plurality of other pictures, and provide the reference picture and/or an offset (spatial offset) between a position (X, Y coordinates) of the reference block and a position of a current block to a motion estimation unit (not shown in fig. 2) as an inter prediction parameter. This offset is also called Motion Vector (MV).

The motion compensation unit is used to acquire inter prediction parameters and perform inter prediction based on or using the inter prediction parameters to acquire the inter prediction block 245. The motion compensation performed by the motion compensation unit (not shown in fig. 2) may involve fetching or generating a prediction block based on motion/block vectors determined by motion estimation (possibly performing interpolation of sub-pixel accuracy). Interpolation filtering may generate additional pixel samples from known pixel samples, potentially increasing the number of candidate prediction blocks available for encoding a picture block. Upon receiving the motion vector for the PU of the current picture block, motion compensation unit 246 may locate the prediction block to which the motion vector points in a reference picture list. Motion compensation unit 246 may also generate syntax elements associated with the blocks and video slices for use by decoder 30 in decoding the picture blocks of the video slices.

Specifically, the inter prediction unit 244 may transmit a syntax element including inter prediction parameters (e.g., indication information of an inter prediction mode selected for current block prediction after traversing a plurality of inter prediction modes) to the entropy encoding unit 270. In a possible application scenario, if the inter prediction mode is only one, the inter prediction parameter may not be carried in the syntax element, and the decoding end 30 may directly use the default prediction mode for decoding. It is appreciated 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, a picture block 203 (current picture block) that receives the same picture and one or more previously reconstructed blocks, for example, reconstructed neighboring blocks, for intra estimation. For example, encoder 20 may be configured to select an intra-prediction mode from a plurality of (predetermined) intra-prediction modes.

Embodiments of encoder 20 may be used to select an intra-prediction mode based on optimization criteria, such as based on a minimum residual (e.g., the intra-prediction mode that provides a prediction block 255 most similar to current picture block 203) or minimum rate distortion.

The intra prediction unit 254 is further adapted to determine an intra prediction block 255 based on intra prediction parameters like the selected intra prediction mode. In any case, after the intra-prediction mode for the block is selected, the intra-prediction unit 254 is also configured to provide the intra-prediction parameters, i.e., information indicating the selected intra-prediction mode for the block, to the entropy encoding unit 270. In one example, intra-prediction unit 254 may be used to perform any combination of intra-prediction techniques.

Specifically, the intra-prediction unit 254 may transmit a syntax element including an intra-prediction parameter (such as indication information of an intra-prediction mode selected for the current block prediction after traversing a plurality of intra-prediction modes) to the entropy encoding unit 270. In a possible application scenario, if there is only one intra prediction mode, the intra prediction parameter may not be carried in the syntax element, and the decoding end 30 may directly use the default prediction mode for decoding.

The entropy encoding unit 270 is configured to apply an entropy encoding algorithm or scheme (e.g., a variable length coding (variable length coding, VLC) scheme, a Context Adaptive VLC (CAVLC) scheme, an arithmetic coding scheme, a context adaptive binary arithmetic coding (context adaptive binary arithmetic coding, CABAC), a syntax-based context-based binary arithmetic coding (SBAC), a probability interval partitioning entropy (probability interval partitioning entropy, PIPE) coding, or other entropy encoding methods or techniques) to one or all of the quantized residual coefficients 209, inter-prediction parameters, intra-prediction parameters, and/or loop filter parameters (or not) to obtain encoded picture data 21 that may be output by the output 272 in the form of, for example, an encoded bitstream 21. The encoded bitstream may be transmitted to video decoder 30 or archived for later transmission or retrieval by video decoder 30. Entropy encoding unit 270 may also be used to entropy encode other syntax elements of the current video slice being encoded.

Other structural variations of video encoder 20 may be used to encode the video stream. For example, the non-transform based encoder 20 may directly quantize the residual signal without a transform processing unit 206 for certain blocks or frames. In another embodiment, encoder 20 may have quantization unit 208 and inverse quantization unit 210 combined into a single unit.

Specifically, in the present embodiment, the encoder 20 may be used to implement the entropy encoding method of the syntax element described in the later embodiments.

It should be appreciated that other structural variations of video encoder 20 may be used to encode the video stream. For example, for some image blocks or image frames, video encoder 20 may directly quantize the residual signal without processing by transform processing unit 206, and accordingly without processing by inverse transform processing unit 212; alternatively, for some image blocks or image frames, video encoder 20 does not generate residual data and accordingly does not need to be processed by transform processing unit 206, quantization unit 208, inverse quantization unit 210, and inverse transform processing unit 212; alternatively, video encoder 20 may store the reconstructed image block directly as a reference block without processing via filter 220; alternatively, quantization unit 208 and inverse quantization unit 210 in video encoder 20 may be combined together. The loop filter 220 is optional, and in the case of lossless compression encoding, the transform processing unit 206, quantization unit 208, inverse quantization unit 210, and inverse transform processing unit 212 are optional. It should be appreciated that inter-prediction unit 244 and intra-prediction unit 254 may be selectively enabled depending on the different application scenarios.

Referring to fig. 3, fig. 3 shows a schematic/conceptual block diagram of an example of a decoder 30 for implementing an embodiment of the present application. Video decoder 30 is operative to receive encoded picture data (e.g., encoded bitstream) 21, e.g., encoded by encoder 20, to obtain decoded picture 231. During the decoding process, video decoder 30 receives video data, such as an encoded video bitstream representing picture blocks of an encoded video slice and associated syntax elements, from video encoder 20.

In the example of fig. 3, decoder 30 includes entropy decoding unit 304, inverse quantization unit 310, inverse transform processing unit 312, reconstruction unit 314 (e.g., summer 314), buffer 316, loop filter 320, decoded picture buffer 330, and 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. In some examples, video decoder 30 may perform a decoding pass that is substantially reciprocal to the encoding pass described with reference to video encoder 20 of fig. 2.

Entropy decoding unit 304 is used to perform entropy decoding on encoded picture data 21 to obtain, for example, quantized coefficients 309 and/or decoded encoding parameters (not shown in fig. 3), e.g., any or all of inter-prediction, intra-prediction parameters, loop filter parameters, and/or other syntax elements (decoded). Entropy decoding unit 304 is further configured to forward inter-prediction parameters, intra-prediction parameters, and/or other syntax elements to prediction processing unit 360. Video decoder 30 may receive syntax elements at the video stripe level and/or the video block level.

Inverse quantization unit 310 may be functionally identical to inverse quantization unit 110, inverse transform processing unit 312 may be functionally identical to inverse transform processing unit 212, reconstruction unit 314 may be functionally identical to reconstruction unit 214, buffer 316 may be functionally identical to buffer 216, loop filter 320 may be functionally identical to loop filter 220, and decoded picture buffer 330 may be functionally identical to decoded picture buffer 230.

The prediction processing unit 360 may include an inter prediction unit 344 and an intra prediction unit 354, where the inter prediction unit 344 may be similar in function to the inter prediction unit 244 and the intra prediction unit 354 may be similar in function to the intra prediction unit 254. The prediction processing unit 360 is typically used to perform block prediction and/or to obtain a prediction block 365 from the encoded data 21, as well as to receive or obtain prediction related parameters and/or information about the selected prediction mode (explicitly or implicitly) from, for example, the entropy decoding unit 304.

When a video slice is encoded as an intra-coded (I) slice, the intra-prediction unit 354 of the prediction processing unit 360 is used to generate a prediction block 365 for a picture block of the current video slice based on the signaled intra-prediction mode and data from a previously decoded block of the current frame or picture. When a video frame is encoded as an inter-coded (i.e., B or P) slice, an inter-prediction unit 344 (e.g., a motion compensation unit) of prediction processing unit 360 is used to generate a prediction block 365 for a video block of the current video slice based on the motion vector and other syntax elements received from entropy decoding unit 304. For inter prediction, a prediction block may be generated from one reference picture within one reference picture list. Video decoder 30 may construct a reference frame list based on the reference pictures stored in DPB 330 using default construction techniques: list 0 and list 1.

The prediction processing unit 360 is configured to determine prediction information for a video block of a current video slice by parsing the motion vector and other syntax elements, and generate a prediction block for the current video block being decoded using the prediction information. In an example of the present application, prediction processing unit 360 uses some syntax elements received to determine a prediction mode (e.g., intra or inter prediction) for encoding video blocks of a video slice, an inter prediction slice type (e.g., B slice, P slice, or GPB slice), construction information for one or more of the reference picture lists of the slice, motion vectors for each inter-encoded video block of the slice, inter prediction state for each inter-encoded video block of the slice, and other information to decode video blocks of the current video slice. In another example of the present disclosure, the syntax elements received by video decoder 30 from the bitstream include syntax elements received in one or more of an adaptive parameter set (adaptive parameter set, APS), a sequence parameter set (sequence parameter set, SPS), a picture parameter set (picture parameter set, PPS), or a slice header.

Inverse quantization unit 310 may be used to inverse quantize (i.e., inverse quantize) the quantized transform coefficients provided in the bitstream and decoded by entropy decoding unit 304. The inverse quantization process may include using quantization parameters calculated by video encoder 20 for each video block in a video stripe to determine the degree of quantization that should be applied and likewise the degree of inverse quantization that should be applied.

The inverse transform processing unit 312 is configured to apply an inverse transform (e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process) to the transform coefficients in order to generate a residual block in the pixel domain.

A reconstruction unit 314 (e.g., a summer 314) is used to add the inverse transform block 313 (i.e., the reconstructed residual block 313) to the prediction block 365 to obtain a reconstructed block 315 in the sample domain, e.g., by adding sample values of the reconstructed residual block 313 to sample values of the prediction block 365.

Loop filter unit 320 is used (during or after the encoding cycle) to filter reconstructed block 315 to obtain filtered block 321, to smooth pixel transitions or improve video quality. In one example, loop filter unit 320 may be used to perform any combination of the filtering techniques described below. Loop filter unit 320 is intended to represent one or more loop filters, such as a deblocking filter, a sample-adaptive offset (SAO) filter, or other filters, such as a bilateral filter, an adaptive loop filter (adaptive loop filter, ALF), or a sharpening or smoothing filter, or a collaborative filter. Although loop filter unit 320 is shown in fig. 3 as an in-loop filter, in other configurations loop filter unit 320 may be implemented as a post-loop filter.

The decoded video blocks 321 in a given frame or picture are then stored in a decoded picture buffer 330 that stores reference pictures for subsequent motion compensation.

Decoder 30 is for outputting decoded picture 31, e.g., via output 332, for presentation to a user or for viewing by a user.

Other variations of video decoder 30 may be used to decode the compressed bitstream. For example, decoder 30 may generate the output video stream without loop filter unit 320. For example, the non-transform based decoder 30 may directly inverse quantize the residual signal without an inverse transform processing unit 312 for certain blocks or frames. In another embodiment, the video decoder 30 may have an inverse quantization unit 310 and an inverse transform processing unit 312 combined into a single unit.

Specifically, in the present embodiment, the decoder 30 is used to implement the entropy decoding method of the syntax element described in the later embodiments.

It should be appreciated that other structural variations of video decoder 30 may be used to decode the encoded video bitstream. For example, video decoder 30 may generate an output video stream without processing by filter 320; alternatively, for some image blocks or image frames, the entropy decoding unit 304 of the video decoder 30 does not decode quantized coefficients, and accordingly does not need to be processed by the inverse quantization unit 310 and the inverse transform processing unit 312. Loop filter 320 is optional; and for the case of lossless compression, the inverse quantization unit 310 and the inverse transform processing unit 312 are optional. It should be appreciated that the inter prediction unit and the intra prediction unit may be selectively enabled according to different application scenarios.

It should be understood that, in the encoder 20 and the decoder 30 of the present application, the processing result for a certain link may be further processed and then output to a next link, for example, after the links such as interpolation filtering, motion vector derivation or loop filtering, the processing result for the corresponding link is further processed by performing operations such as Clip or shift.

Referring to fig. 4, fig. 4 is a schematic structural diagram of a video decoding apparatus 400 (e.g., a video encoding apparatus 400 or a video decoding apparatus 400) provided in an embodiment of the present application. The video coding apparatus 400 is adapted to implement the embodiments described herein. In one embodiment, video coding device 400 may be a video decoder (e.g., decoder 30 of fig. 1A) or a video encoder (e.g., encoder 20 of fig. 1A). In another embodiment, video coding apparatus 400 may be one or more of the components described above in decoder 30 of fig. 1A or encoder 20 of fig. 1A.

The video coding apparatus 400 includes: an ingress port 410 and a receiving unit (Rx) 420 for receiving data, a processor, logic unit or Central Processing Unit (CPU) 430 for processing data, a transmitter unit (Tx) 440 and an egress port 450 for transmitting data, and a memory 460 for storing data. The video decoding apparatus 400 may further include a photoelectric conversion component and an electro-optical (EO) component coupled to the inlet port 410, the receiver unit 420, the transmitter unit 440, and the outlet port 450 for the outlet or inlet of optical or electrical signals.

The processor 430 is implemented in hardware and software. Processor 430 may be implemented as one or more CPU chips, cores (e.g., multi-core processors), FPGAs, ASICs, and DSPs. Processor 430 is in communication with inlet port 410, receiver unit 420, transmitter unit 440, outlet port 450, and memory 460. The processor 430 includes a coding module 470 (e.g., an encoding module 470 or a decoding module 470). The encoding/decoding module 470 implements embodiments disclosed herein to implement the chroma block prediction methods provided by embodiments of the present application. For example, the encoding/decoding module 470 implements, processes, or provides various encoding operations. Thus, substantial improvements are provided to the functionality of the video coding device 400 by the encoding/decoding module 470 and affect the transition of the video coding device 400 to different states. Alternatively, the encoding/decoding module 470 is implemented in instructions stored in the memory 460 and executed by the processor 430.

Memory 460 includes one or more disks, tape drives, and solid state drives, and may be used as an overflow data storage device for storing programs when selectively executing such programs, as well as storing instructions and data read during program execution. Memory 460 may be volatile and/or nonvolatile and may be Read Only Memory (ROM), random Access Memory (RAM), random access memory (TCAM) and/or Static Random Access Memory (SRAM).

Referring to fig. 5, fig. 5 is a simplified block diagram of an apparatus 500 that may be used as either or both of the source device 12 and the destination device 14 in fig. 1A, according to an example embodiment. The apparatus 500 may implement the techniques of this application. In other words, fig. 5 is a schematic block diagram of one implementation of an encoding device or decoding device (simply referred to as decoding device 500) of an embodiment of the present application. The decoding device 500 may include, among other things, a processor 510, a memory 530, and a bus system 550. The processor is connected with the memory through the bus system, the memory is used for storing instructions, and the processor is used for executing the instructions stored by the memory. The memory of the decoding device stores program code, and the processor may invoke the program code stored in the memory to perform the various video encoding or decoding methods described herein, particularly the entropy encoding/decoding methods of the various new syntax elements. To avoid repetition, a detailed description is not provided herein.

In the present embodiment, the processor 510 may be a central processing unit (Central Processing Unit, abbreviated as "CPU"), and the processor 510 may also be other general purpose processors, digital Signal Processors (DSPs), application Specific Integrated Circuits (ASICs), off-the-shelf programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may 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 may also be used as memory 530. Memory 530 may include code and data 531 accessed by processor 510 using bus 550. The memory 530 may further include an operating system 533 and an application 535, the application 535 including at least one program that allows the processor 510 to perform the video encoding or decoding methods described herein (particularly the entropy encoding/decoding methods of syntax elements described herein).

The bus system 550 may include a power bus, a control bus, a status signal bus, and the like in addition to a data bus. For clarity of illustration, the various buses are labeled in the figure as bus system 550.

Optionally, the decoding device 500 may also include one or more output devices, such as a display 570. In one example, the display 570 may be a touch sensitive display that incorporates a display with a touch sensitive unit operable to sense touch input. A display 570 may be connected to processor 510 via bus 550.

The following details the scheme of the embodiments of the present application:

Fig. 6 is a flow chart illustrating an entropy encoding method for implementing syntax elements of an embodiment of the present application. The process 600 may be performed by video encoder 20. Process 600 is described as a series of steps or operations, it being understood that process 600 may be performed in various orders and/or concurrently, and is not limited to the order of execution as depicted in fig. 6. As shown in fig. 6, the entropy encoding method of the syntax element includes:

and 601, judging whether the length of the current fusion candidate motion vector list is larger than a preset value.

The length of the fusion candidate Motion Vector list refers to the number of candidate Motion Vectors (MVs) included in the fusion candidate Motion Vector list (the number is represented by MaxNumMergeCand, for example). The MMVD technology utilizes a fusion candidate motion vector list, firstly selects a candidate MV from the fusion candidate motion vector list as a basic MV, and then carries out MV expansion expression based on the basic MV, wherein the MV expansion expression has three elements, namely an MV starting point, a motion step length (Distance) and a motion Direction (Direction).

(1) Selecting candidate MVs

The selected candidate MV is the MV starting point, in other words, the selected candidate MV is used to determine the initial position of the MV, by using the existing fusion candidate motion vector list. Referring to table 1, a basic candidate index (Base candidate IDX) is used to represent an index of candidate MVs in the fusion candidate motion vector list, and Nth MVP is used to represent an Nth MV in the fusion candidate motion vector list. Wherein Base candidate IDX =0 corresponds to a first MV in the fusion candidate motion vector list, base candidate IDX =1 corresponds to a second MV in the fusion candidate motion vector list, base candidate IDX =2 corresponds to a third MV in the fusion candidate motion vector list, base candidate IDX =3 corresponds to a fourth MV in the fusion candidate motion vector list. The corresponding candidate MVs can be represented by Base candidate IDX, and Basecandidate IDX can be omitted if the number of candidate MVs available for selection in the fusion candidate motion vector list is 1.

TABLE 1

Base candidate IDX	0	1	2	3
					N ^th MVP	1 ^st MVP	2 ^nd MVP	3 ^rd MVP	4 ^th MVP

(2) Determining step size

A step identity (Distance IDX) is used to represent the offset Distance of the MV. Referring to table 2, distance IDX is used for an index indicating a Pixel distance of the offset initial position, and Pixel distance is used for an index indicating a Pixel distance of the offset initial position (MV start point). Wherein, the Distance idx=0 corresponds to a pixel Distance of 1/4-pel (i.e., 1/4 pixels), the Distance idx=1 corresponds to a pixel Distance of 1/2-pel (i.e., 1/2 pixels), the Distance idx=2 corresponds to a pixel Distance of 1-pel (i.e., one pixel), the Distance idx=3 corresponds to a pixel Distance of 2-pel (i.e., two pixels), the Distance idx=4 corresponds to a pixel Distance of 4-pel (i.e., four pixels), the Distance idx=5 corresponds to a pixel Distance of 8-pel (i.e., eight pixels), the Distance idx=6 corresponds to a pixel Distance of 16-pel (i.e., sixteen pixels), and the Distance idx=7 corresponds to a pixel Distance of 32-pel (i.e., thirty-two pixels). Its corresponding pixel Distance may be represented by Distance IDX.

TABLE 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) Determining direction

A Direction identification (Direction IDX) is used to indicate the offset Direction of the MV. Referring to table 3, direction IDX is used to represent the MV offset direction based on the initial position (MV start point), x-axis is used to represent the component of the offset direction in the x-axis, and y-axis is used to represent the component of the offset direction in the y-axis. The Direction idx=00 indicates that the Direction is biased toward the x-axis, the y-axis is not limited, the Direction idx=01 indicates that the Direction is biased toward the x-axis, the y-axis is not limited, the Direction idx=10 indicates that the Direction is biased toward the y-axis, the x-axis is not limited, the Direction idx=11 indicates that the Direction is biased toward the y-axis, and the x-axis is not limited. Its corresponding offset Direction may be represented by Direction IDX.

TABLE 3 Table 3

Direction IDX	00	01	10	11
					x-axis	+	–	N/A	N/A
y-axis	N/A	N/A	+	–

The process of determining the predicted pixel value of the current block using MMVD techniques includes: the MV starting point is first determined according to Base candidate IDX, then the offset Direction based on the MV starting point is determined according to the Direction IDX, and finally the pixel Distance for offsetting the MV starting point in the offset Direction indicated by the Direction IDX is determined according to the Distance IDX. For example, base candidate IDX =0, direction idx=00, distance idx=2, which indicates that the MV motion vector forward shifted by one pixel to the x-axis is used as the MV of the current block with the first MV in the fusion candidate motion vector list as the MV start point, so as to predict or obtain the predicted pixel value of the current block.

In the existing VVC draft, a syntax element mmvd_cand_flag [ x0] [ y0] is used to indicate which candidate MV is selected as the base MV from any two candidate MVs in the merged candidate motion vector list (for example, the first candidate MV and the second candidate MV in the merged candidate motion vector list, or the first candidate MV and the third candidate VM, or the third candidate MV and the sixth candidate MV, etc.), typically mmvd_cand_flag [ x0] [ y0] =0 indicates that the first candidate MV of the any two candidate MVs is selected, and mmvd_cand_flag [ x0] =1 indicates that the second candidate MV of the any two candidate MVs is selected. But default mmvd_cand_flag x0 y 0=0 if the value of the syntax element does not appear in the bitstream. (x 0, y 0) represents the position of the current block in the current image, i.e., the coordinate position of the pixel point of the top-left vertex of the current block with respect to the pixel point of the top-left vertex of the current image.

As described above, the first syntax element mmvd_cand_flag is used to indicate that a first candidate MV or a second candidate MV, which are any two candidate MVs in the fusion candidate motion vector list, is selected from the fusion candidate motion vector list as a base MV for motion vector expansion. It can be seen that the first syntax element mmvd_cand_flag needs to have meaning only 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 the present application firstly determines whether the length of the current fusion candidate motion vector list is greater than the preset value.

It should be noted that, the first syntax element mmvd_cand_flag may also be used to indicate that any candidate MV is selected from any N candidate MVs in the fusion candidate motion vector list as a base MV for motion vector expansion, where N >1 and N < = MaxNumMergeCand. For example, the number of candidate MVs included in the fusion candidate motion vector list is 6, i.e., maxnummergecand=6, and the indexes of the six candidate MVs are 0, 1, 2, … …, 5, respectively. When n=6, the value of mmvd_cand_flag may be any one of 0 to 5. When n=3, indexes of any N candidate MVs are 0, 1, and 2, respectively, the value of mmvd_cand_flag may be any one of 0 to 2.

Step 602, if the length of the fusion candidate motion vector list is greater than a preset value, entropy encoding is performed on the value of the first syntax element by adopting a bypass encoding mode.

CABAC is a commonly used entropy coding technique for coding and decoding syntax element values. The CABAC process mainly includes binarization (binarization), context modeling (context modeling), and binary arithmetic coding (binary arithmetic coding). Binarization refers to binary processing of input non-binary syntax element values, and unique conversion of the non-binary syntax element values into a binary sequence (namely binary strings); context modeling refers to determining, for each bit (bin) in a binary string, a probability model of the bit based on context information (e.g., syntax elements corresponding to coding information in a reconstructed region around a node); binary arithmetic coding refers to coding corresponding bits according to probability values in a probability model and updating the probability values in the probability model according to the values of the bits.

The basic principle of arithmetic coding is: dividing the [0,1 ] interval into mutually non-overlapping subintervals according to the occurrence probability of different values (namely 0 or 1) of bits in the binary string, wherein the width of each subinterval is exactly the probability of each value, so that the different bits in the binary string correspond to each subinterval one by one, then performing interval mapping recursively, finally obtaining a cell interval, and selecting a representative decimal from the cell interval to perform binary transformation and then outputting the binary transformation as actual coding. Statistically, the closer a probability that a bit is 1 is to 0.5, the more bits are needed to encode that bit; the closer to 0 or 1 the probability that a bit is 1, the fewer bits are needed to encode the bit.

The regular coding mode (regular coding mode) and the bypass coding mode (Bypass coding mode) include context modeling (context modeling) and binary arithmetic coding (binary arithmetic coding), are two different methods of entropy coding.

In the bypass coding mode, it is assumed that the probability of occurrence of both binary symbols 0 and 1 is fixed to 0.5, which is compared to the conventional coding mode: firstly, the probability estimation and updating process of the bypass coding mode is omitted, namely, the context modeling is not needed, and the updating of the context model is not needed; secondly, the probability interval sub-dividing operation process of the bypass coding mode is simplified, namely, only the probability interval is required to be equally divided, and the conventional coding mode is required to sub-divide the current probability interval according to the estimated probability. It can be seen that the bypass coding mode can be seen as a special case of the regular coding mode.

The process of entropy encoding a value of a first syntax element (mmvd_cand_flag) using a bypass encoding mode includes:

(1) Binarization of

Binary transforming the value of the first syntax element mmvd_cand_flag in the syntax elements results in a binary string comprising one or more bits (bins). For example, the value of mmvd_cand_flag is 0 or 1, so binarizing it may result in a binary bit, where 0 represents 0 for mmvd_cand_flag and 1 represents 1 for mmvd_cand_flag. Alternatively, binarizing the mmvd_cand_flag may also result in two binary bits, where a value of 00 indicates that the value of mmvd_cand_flag is 0 and a value of 01 indicates that the value of mmvd_cand_flag is 1. Binarizing the mmvd_cand_flag may also result in one or more binary bits, a bit of 0 indicating a value of 0 for the mmvd_cand_flag and a bit of 10 indicating a value of 1 for the mmvd_cand_flag. It should be noted that, in the present application, other methods may be used to binary-transform the value of mmvd_cand_flag, which is not limited specifically.

In another embodiment, the binarization process may be omitted.

(2) Entropy coding using bypass coding mode

a. Determining probability values for bits

In the present application, since the bypass coding mode is adopted, it is not necessary to assign a specific probability model to each bit in the binary string obtained in the previous step, but the probabilities of taking the values of 0 and 1 on each bit are considered to be equal, that is, 0.5.

b. Dividing probability intervals according to probabilities

Illustratively, the initial probability interval is [0,1 ], and according to the probability of 0.5, the initial probability interval can be divided into two sub-probability intervals: a first probability interval [0, 0.5) and a second probability interval [0.5, 1), mmvd_cand_flag=0 corresponds to the first probability interval and mmvd_cand_flag=1 corresponds to the second probability interval.

The probability interval may be extended, for example, by extending the length of the initial probability interval [0,1 ] to 510, represented by a 9-bit binary number, i.e., [0,2 ] ⁹ ) So that the first probability interval corresponding to mmvd_cand_flag=0 is [0,2 ⁸ ) The second probability interval corresponding to mmvd_cand_flag=1 is [2 ] ⁸ ,2 ⁹ )。

c. Encoding process

The method and the device acquire the coding string of the binary string according to the first probability interval and the second probability interval. For example, when the length of the probability interval is less than one half of the left boundary value of the probability interval, the renormalization operation can be performed, the length of the probability interval is shifted one bit to the left and is extended to be more than one half of the left boundary value of the probability interval, and then the left boundary of the probability interval is shifted one bit to output the highest bit, so that the code string of mmvd_cand_flag is obtained.

For example, the binary string with mmvd_cand_flag=0 is 0, and the left boundary 000000000 of the first probability interval is shifted left by one bit to output the most significant bit 0, which is the encoding string with the value of 0 for mmvd_cand_flag. The binary string mmvd_cand_flag=1 is 1, and the left boundary 11111111 of the second probability interval is added to the length 2 of the second probability interval ⁸ Then 111111111 is obtained, and the highest bit 1 is output after the left shift of the value is one bit, namely, the code string with the value of 1 of mmvd_cand_flag.

It should be noted that, the entropy encoding of the first syntax element mmvd_cand_flag in the syntax elements may be understood as encoding a bit in a binary string of values of mmvd_cand_flag, specifically, encoding the bit according to a probability value of the bit in the binary string of values of mmvd_cand_flag.

According to the method and the device, the value of the first syntax element mmvd_cand_flag is subjected to entropy coding in a bypass coding mode, a specific probability model is not required to be allocated to bits in the binary string of the mmvd_cand_flag, and coding complexity is reduced.

In one possible implementation, if the length of the fusion candidate motion vector list is greater than a preset value, a switch flag (byPassFlag) indicating a bypass coding mode is set to a first value, and the value of the first syntax element is entropy coded using the bypass coding mode.

The operation step of the encoder in the background of starting the bypass coding mode to entropy code the value of the first syntax element is that the switch flag of the bypass coding mode is set to the first value. The byPassFlag may be similar to a switch whether or not entropy encoding is performed using the bypass encoding mode, for example, the value of byPassFlag is 0 or 1, bypassflag=0 indicates that entropy encoding is not performed using the bypass encoding mode, and bypassflag=1 indicates that entropy encoding is performed using the bypass encoding mode. Therefore, only by passflag=1, the value of mmvd_cand_flag is entropy-encoded in the bypass encoding mode, and by passflag=0, the value of mmvd_cand_flag is not entropy-encoded in the bypass encoding mode, for example, the value of mmvd_cand_flag may be entropy-encoded in the conventional encoding mode.

Fig. 7 is another flow diagram of an entropy decoding method for implementing syntax elements of an embodiment of the present application. The process 700 may be performed by video decoder 30. Process 700 is described as a series of steps or operations, it being understood that process 700 may be performed in various orders and/or concurrently, and is not limited to the order of execution as depicted in fig. 7. As shown in fig. 7, the entropy decoding method of the syntax element includes:

Step 701, judging whether the length of the current fusion candidate motion vector list is larger than a preset value.

The length of the fusion candidate motion vector list refers to the number of candidate MVs (the number is represented by MaxNumMergeCand, for example) included in the fusion candidate motion vector list.

Step 702, if the length of the fusion candidate motion vector list is greater than a preset value, entropy decoding is performed on the encoded string of the first syntax element by adopting a bypass decoding mode.

The first syntax element is used for indicating that a first candidate motion vector or a second candidate motion vector is selected from the fusion candidate motion vector list and used as a 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.

Similar to the method embodiment shown in fig. 6, in the case of the first syntax element mmvd_cand_flag, the present embodiment adopts the bypass decoding mode to perform entropy decoding on the mmvd_cand_flag, so that a specific probability model does not need to be allocated to bits in the binary string of mmvd_cand_flag, and decoding complexity is reduced.

The difference from the method embodiment shown in fig. 6 is that the present embodiment is to entropy decode the encoding string of mmvd_cand_flag in the code stream to obtain the value of mmvd_cand_flag.

Illustratively, the entropy decoding of the encoded string of the first syntax element (mmvd_cand_flag) using the bypass decoding mode includes:

(1) Acquiring first engine parameters and second engine parameters

The first engine parameter is used to represent the length of the probability interval and the second engine parameter is used to represent the left boundary of the probability interval. Illustratively, the first engine parameter is ivlCurrRange and the second engine parameter is ivlOffset, and the probability interval [0,1 ] is extended to 510, as described above, and represented by a 9-bit binary number, namely [0,2 ] ⁹ ). An ivlcurrrange=510 can be obtained, and an ivloffset=000000000 (i.e., the ivlOffset is a 9-bit binary number corresponding to an unsigned integer obtained from the read_bit (9)).

(2) Updating the value of ivlOffset and obtaining the value of binVal (i.e. mmvd_cand_flag)

a. The value of ivlo offset is multiplied by 2, i.e. shifted one bit to the left, then a 1bit binary number is obtained by using read_bits (1), and the binary number and ivlo offset are bitwise and, resulting in a new value of ivlo offset.

b. The new value of ivlOffset is compared with the value of ivlCurrRange:

if the new ivlOffset value is greater than the ivlCurrRange, setting the value of the binVal to 1 and subtracting the value of the ivlCurrRange from the value of the ivlOffset;

Otherwise, the value of binVal is set to 0.

According to the method and the device, the encoding string of the first syntax element mmvd_cand_flag is subjected to entropy decoding in a bypass decoding mode, a specific probability model is not required to be allocated to bits in the binary string of the mmvd_cand_flag, and decoding complexity is reduced.

In one possible implementation, if the length of the fusion candidate motion vector list is greater than a preset value, a switch flag (byPassFlag) indicating a bypass decoding mode is set to a first value, and the value of the first syntax element is entropy-used in the bypass decoding mode.

The operation step of the decoder in the background of initiating the bypass decoding mode to entropy decode the value of the first syntax element is that the switch flag of the bypass decoding mode that the decoder reads is set to the first value. The byPassFlag may be similar to a switch whether or not to perform entropy decoding in the bypass decoding mode, for example, the value of byPassFlag is 0 or 1, bypassflag=0 indicates that entropy decoding is not performed in the bypass decoding mode, and bypassflag=1 indicates that entropy decoding is performed in the bypass decoding mode. Therefore, only by passflag=1, the value of mmvd_cand_flag is entropy-decoded in the bypass decoding mode, and by passflag=0, the value of mmvd_cand_flag is not entropy-decoded in the bypass decoding mode, for example, the value of mmvd_cand_flag may be entropy-decoded in the normal decoding mode.

For example, simulation experiments of the technical scheme of the present application were performed on VTM-5.0 reference software, and the results are shown in Table 4 and Table 5. Experiments show that in the process of entropy encoding/decoding the mmvd_cand_flag value, compared with the conventional encoding/decoding mode, the bypass encoding/decoding mode is adopted, three components (Y represents a luminance component, U and V represent chrominance components) of a video data format respectively represented by Y, U and V under the Random Access (Random Access) configuration of a video sequence, and the performance gain result of encoding/decoding in comparison with the conventional encoding/decoding mode can be obtained through simulation corresponding to different test sequence categories (for example, class A1, class A2, class B, class C, class E and the like), so that the average simulation result (Overall) of the performance gain result is basically unchanged. The encoding time (EncT) and decoding time (DecT) can be simulated to obtain the comparison result of the encoding/decoding time length of the bypass encoding/decoding mode compared with the conventional encoding/decoding mode according to different test sequence categories, and the average simulation result can be seen to also display the reduction of the processing time length.

Under the condition that a video sequence adopts Low Delay (Low Delay) configuration, the three components of the video signals respectively represented by Y, U and V can be simulated to obtain performance gain results of encoding/decoding by adopting a bypass encoding/decoding mode compared with a conventional encoding/decoding mode corresponding to different test sequence types, and the average simulation result (over) display performance of the performance gain results is improved to a certain extent. The encoding time (EncT) and decoding time (DecT) can be simulated to obtain the comparison result of the encoding/decoding time length of the bypass encoding/decoding mode compared with the conventional encoding/decoding mode according to different test sequence categories, and the average simulation result can also show that the processing time length is reduced.

TABLE 4 Table 4

TABLE 5

It should be noted that, the above simulation result is an exemplary description of entropy encoding/decoding a video sequence after the bypass encoding/decoding mode is adopted for the first syntax element mmvd_cand_flag, which is not the only proof of the implementation effect of the technical solution of the present application.

Based on the same inventive concept as the above method, the embodiment of the application also provides an entropy encoding device. Fig. 8 is a block diagram of an entropy encoding apparatus 800 for implementing an embodiment of the present application, where the entropy encoding apparatus 800 includes a judging module 801 and an encoding module 802, where:

a judging module 801, configured to judge whether a length of the current fusion candidate motion vector list is greater than a preset value; the encoding module 802 is configured to entropy encode a value of a first syntax element by using a bypass encoding mode if the length of the fused candidate motion vector list is greater than the preset value, where the first syntax element is used to indicate that a first candidate motion vector or a second candidate motion vector is selected from the fused candidate motion vector list as a 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 fused candidate motion vector list.

In a possible implementation manner, the encoding module 802 is further configured to set a switch identifier indicating the bypass encoding mode to a first value if the length of the fusion candidate motion vector list is greater than the preset value, and entropy encode the value of the first syntax element in the bypass encoding mode.

In one possible implementation, the first syntax element is mmvd_cand_flag.

It should be noted that, the above-mentioned judging module 801 and the encoding module 802 may be applied to the entropy encoding process of the encoding end. In particular, at the encoding end, these modules may be applied to the entropy encoding unit 270 of the aforementioned encoder 20.

It should be further noted that, the specific implementation process of the determining module 801 and the encoding module 802 may refer to the detailed description of the embodiment of fig. 6, and for brevity of the description, the description is omitted here.

Based on the same inventive concept as the above method, the embodiment of the application also provides an entropy decoding device. Fig. 9 is a block diagram of an entropy decoding device 900 for implementing an embodiment of the present application, where the entropy decoding device 900 includes a judging module 901 and a decoding module 902, where:

the judging module 901 is configured to judge whether the length of the current fusion candidate motion vector list is greater than a preset value; the decoding module 902 is configured to entropy decode a value of a first syntax element by using a bypass coding mode if a length of the fused candidate motion vector list is greater than the preset value, where the first syntax element is used to indicate that a first candidate motion vector or a second candidate motion vector is selected from the fused candidate motion vector list as a 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 fused candidate motion vector list.

In a possible implementation manner, the decoding module 902 is further configured to set a switch identifier indicating the bypass coding mode to a first value if the length of the fusion candidate motion vector list is greater than the preset value, and entropy decode the value of the first syntax element using the bypass coding mode.

In one possible implementation, the first syntax element is mmvd_cand_flag.

It should be noted that the above-mentioned judging module 901 and decoding module 902 may be applied to the entropy decoding process at the decoding end. Specifically, at the decoding end, these modules may be applied to the entropy decoding unit 304 of the aforementioned decoder 30.

It should be further noted that, the specific implementation process of the judging module 901 and the decoding module 902 may refer to the detailed description of the embodiment of fig. 7, and for brevity of the description, the description is omitted here.

Those of skill in the art will appreciate that the functions described in connection with the various illustrative logical blocks, modules, and algorithm steps described in connection with the disclosure herein may be implemented as hardware, software, firmware, or any combination thereof. If implemented in software, the functions described by the various illustrative logical blocks, modules, and steps may be stored on a computer readable medium or transmitted as one or more instructions or code and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media corresponding to tangible media, such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another (e.g., according to a communication protocol). In this manner, a computer-readable medium may generally correspond to (1) a non-transitory tangible computer-readable storage medium, or (2) a communication medium, such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementing the techniques described herein. The computer program product may include a computer-readable medium.

By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that the computer-readable storage medium and data storage medium do not include connections, carrier waves, signals, or other transitory media, but are actually directed to non-transitory tangible storage media. Disk and disc, as used herein, includes Compact Disc (CD), laser disc, optical disc, digital Versatile Disc (DVD), and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The instructions may be executed by one or more processors, such as one or more Digital Signal Processors (DSPs), general purpose microprocessors, application Specific Integrated Circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Thus, the term "processor" as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. Additionally, in some aspects, the functions described by the various illustrative logical blocks, modules, and steps described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated in a combination codec. Moreover, the techniques may be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses including a wireless handset, an Integrated Circuit (IC), or a set of ICs (e.g., a chipset). The various components, modules, or units are described in this application to emphasize functional aspects of the devices for performing the disclosed techniques but do not necessarily require realization by different hardware units. Indeed, as described above, the various units may be combined in a codec hardware unit in combination with suitable software and/or firmware, or provided by an interoperable hardware unit (including one or more processors as described above).

In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to related descriptions of other embodiments.

The foregoing is merely illustrative of specific embodiments of the present application, and the scope of the present application is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An entropy encoding method of a syntax element, comprising:

judging whether the length of the current fusion candidate motion vector list is larger than a preset value or not;

if the length of the fusion candidate motion vector list is greater than the preset value, setting a switch mark indicating a bypass coding mode as a first value, and adopting the bypass coding mode to carry out entropy coding on the value of a first syntax element, wherein the first syntax element is used for indicating that a first candidate motion vector or a second candidate motion vector is selected from the fusion candidate motion vector list to serve as a 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.

2. The method of claim 1, wherein the first syntax element is mmvd_cand_flag.

3. A method of entropy decoding of syntax elements, comprising:

if the length of the fusion candidate motion vector list is greater than the preset value, setting a switch mark indicating a bypass coding mode as a first value, and adopting the bypass coding mode to carry out entropy decoding on the value of a first syntax element, wherein the first syntax element is used for indicating that a first candidate motion vector or a second candidate motion vector is selected from the fusion candidate motion vector list to serve as a 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.

4. The method of claim 3, wherein the first syntax element is mmvd_cand_flag.

5. An entropy encoding device, comprising:

the judging module is used for judging whether the length of the current fusion candidate motion vector list is larger than a preset value or not;

The encoding module is configured to set a switch flag indicating a bypass encoding mode to a first value if the length of the fusion candidate motion vector list is greater than the preset value, and entropy encode a value of a first syntax element by using the bypass encoding mode, where the first syntax element is used to indicate that a first candidate motion vector or a second candidate motion vector is selected from the fusion candidate motion vector list as a 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.

6. The apparatus of claim 5, wherein the first syntax element is a mmvd_cand_flag.

7. An entropy decoding device, comprising:

the decoding module is configured to set a switch flag indicating a bypass coding mode to a first value if the length of the fusion candidate motion vector list is greater than the preset value, and entropy decode a value of a first syntax element by using the bypass coding mode, where the first syntax element is used to indicate that a first candidate motion vector or a second candidate motion vector is selected from the fusion candidate motion vector list as a 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.

8. The apparatus of claim 7, wherein the first syntax element is a mmvd_cand_flag.

9. A video encoder for encoding image blocks, comprising:

entropy encoding means according to claim 5 or 6, for encoding an index identification of the target candidate motion information into a bitstream, the index identification indicating the target candidate motion information for the current encoded image block;

10. A video decoder for decoding image blocks from a bitstream, comprising:

entropy decoding means according to claim 7 or 8, for decoding an index identification from the bitstream, the index identification being indicative of target candidate motion information of a currently decoded image block;

11. A video encoding apparatus comprising: a non-volatile memory and a processor coupled to each other, the processor invoking program code stored in the memory to perform the method as described in claim 1 or 2.

12. A video decoding apparatus comprising: a non-volatile memory and a processor coupled to each other, the processor invoking program code stored in the memory to perform the method as described in claim 3 or 4.