Method and apparatus for syntax signaling in video / image coding system

Abstract

Methods and apparatus are disclosed relating to syntax signaling in video / image coding systems. A decoding method performed by a decoding apparatus according to the present document includes: a decoding step of decoding a target object; a step for obtaining, from the bitstream, at least one of a CIIP availability flag indicating whether or not combined inter-picture merging and intra-picture prediction (CIIP) is available, and a partition mode availability flag indicating whether or not a partition mode for dividing the current block into two partitions and performing prediction is available; a step for determining a prediction mode of the current block on the basis of at least one of the CIIP available flag and the partition mode available flag; and a step for generating a prediction sample of the current block on the basis of the prediction mode, wherein the step for determining the prediction mode may include a step for obtaining a conventional merge flag from the bitstream on the basis of at least one of the CIIP available flag and the partition mode available flag.

Description

[0001] This application is a divisional application of a patent application with application number 202080045849.4 (PCT / KR2020 / 008153), which was submitted to the China Patent Office on December 22, 2021, with an international application date of June 23, 2020, and the invention name is “Method and device for syntax signaling in video / image coding system”. Technical Field

[0002] The technology relates to methods and apparatus for signaling syntax required for video / image reconstruction in a video / image coding system. Background Art

[0003] Recently, there is an increasing demand for high-resolution, high-quality images / videos such as 4K or 8K ultra high-definition (UHD) images / videos in various fields. As the image / video resolution or quality becomes higher, relatively more information or bits are transmitted compared to conventional image / video data. Therefore, if the image / video data is transmitted via a medium such as an existing wired / wireless broadband line or is stored in a conventional storage medium, the cost of transmission and storage is likely to increase.

[0004] Furthermore, there is growing interest and demand for virtual reality (VR) and artificial reality (AR) content and immersive media such as holograms; and there is also growing broadcasting of images / videos that exhibit image / video characteristics different from actual images / videos (e.g., game images / videos).

[0005] Therefore, efficient image / video compression technology is needed to effectively compress and transmit, store or play high-resolution, high-quality images / videos showing various characteristics as described above. Summary of the invention

[0006] Technical issues

[0007] One aspect of the present disclosure provides a method and apparatus for enhancing image coding efficiency.

[0008] Another aspect of the present disclosure provides a method and apparatus for efficiently performing inter prediction.

[0009] Yet another aspect of the present disclosure provides a method and apparatus for removing unnecessary signaling during inter-frame prediction.

[0010] Yet another aspect of the present disclosure provides a method and apparatus for efficiently signaling syntax associated with a merge mode during inter prediction.

[0011] Technical Solution

[0012] According to an embodiment of the present document, a decoding method performed by a decoding device includes: obtaining from a bitstream at least one of a combined inter-picture merging and intra-picture prediction (CIIP) enable flag indicating whether a CIIP is enabled and a partition mode enable flag indicating whether a partition mode in which prediction is performed by dividing a current block into two partitions is enabled; determining a prediction mode of a current block based on at least one of the CIIP enable flag or the partition mode enable flag; and generating a prediction sample of the current block based on the prediction mode, wherein the determination includes obtaining a regular merge flag from the bitstream based on at least one of the CIIP enable flag or the partition mode enable flag.

[0013] According to an embodiment of the present document, an encoding method performed by an encoding device includes: determining a prediction mode of a current block; deriving a prediction sample of the current block based on the prediction mode; deriving a residual sample based on the prediction sample; and encoding image information including information about the prediction mode generated based on the prediction mode and residual information generated based on the residual sample, wherein the information about the prediction mode includes at least one of a CIIP enable flag indicating whether CIIP is enabled and a partition mode enable flag indicating whether a partition mode in which prediction is performed by dividing the current block into two partitions is enabled, and wherein based on at least one of the CIIP enable flag or the partition mode enable flag, the image information includes a regular merge flag.

[0014] According to another embodiment of the present document, a computer-readable digital storage medium is provided, which contains information that enables a decoding device to perform a decoding method, the decoding method comprising: obtaining from a bitstream at least one of a CIIP enable flag indicating whether CIIP is enabled and a partition mode enable flag indicating whether a partition mode in which prediction is performed by dividing a current block into two partitions is enabled; determining a prediction mode of the current block based on at least one of the CIIP enable flag or the partition mode enable flag; and generating a prediction sample of the current block based on the prediction mode, wherein the determination comprises: obtaining a regular merge flag from the bitstream based on at least one of the CIIP enable flag or the partition mode enable flag.

[0015] Beneficial Effects

[0016] According to the embodiments of the present disclosure, the overall image / video compression efficiency may be enhanced.

[0017] According to the embodiments of the present disclosure, inter-frame prediction can be efficiently performed.

[0018] According to an embodiment of the present disclosure, signaling of unnecessary syntax may be effectively removed during inter-frame prediction.

[0019] According to an embodiment of the present disclosure, signaling of syntax related to merge mode may be efficiently performed during inter prediction.

[0020] According to an embodiment of the present disclosure, signaling of syntax related to merge mode may be efficiently performed during inter prediction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 An example of a video / image coding system to which embodiments of the present disclosure may be applied is schematically illustrated.

[0022] Figure 2 is a diagram schematically describing a configuration of a video / image encoding device to which an embodiment of the present disclosure can be applied.

[0023] Figure 3 is a diagram schematically describing a configuration of a video / image decoding device to which an embodiment of the present disclosure can be applied.

[0024] Figure 4 is a diagram showing a hierarchical structure of a compiled image.

[0025] Figure 5 An example of a video / image encoding method based on inter-frame prediction is shown.

[0026] Figure 6 An example of a video / image decoding method based on inter-frame prediction is shown.

[0027] Figure 7 A method of configuring a merge candidate list is schematically shown.

[0028] Figure 8 and 9 An example of a video / image encoding method including an inter-frame prediction method and associated components according to an embodiment of this document is schematically represented.

[0029] Fig.10 and 11 An example of a video / image decoding method including an inter-frame prediction method and associated components according to an embodiment of this document is schematically represented.

[0030] Fig.12 represents an example of a content streaming system to which the embodiments disclosed in this document can be applied. DETAILED DESCRIPTION

[0031] The disclosure of this document can be modified in various forms, and specific embodiments thereof will be described and illustrated in the accompanying drawings. However, the embodiments are not intended to limit the present disclosure. The terms used in this document are only used to describe specific embodiments, rather than to limit the embodiments of this document. Singular expressions include plural expressions as long as it is not clearly understood differently. Terms such as "including" and "having" are intended to indicate the presence of features, quantities, steps, operations, elements, components, or combinations thereof used in the document, and therefore it should be understood that the possibility of the presence or addition of one or more different features, quantities, steps, operations, elements, components, or combinations thereof is not excluded.

[0032] At the same time, each configuration of the drawings described in this document is an independent diagram for facilitating the description of functions as features that are different from each other, and does not mean that each configuration is implemented by different hardware or different software. For example, two or more configurations can be combined to form a configuration, and a configuration can also be divided into multiple configurations. Without departing from the gist of the present disclosure, embodiments of combined and / or separated configurations are included in the scope of the disclosure of this document.

[0033] This document relates to video / image coding. For example, the methods / embodiments disclosed in this document may be applied to methods disclosed in the Versatile Video Coding (VVC) standard. In addition, the methods / embodiments disclosed in this document may be applied to methods disclosed in the Essential Video Coding (EVC) standard, the AOMedia Video 1 (AV1) standard, the 2nd generation Audio Video Coding standard (AVS2), or next generation video / image coding standards (e.g., H.267, H.268, etc.).

[0034] This document proposes various embodiments of video / image coding, and unless otherwise specified, the above embodiments may also be performed in combination with each other.

[0035] In this document, video may refer to a series of images over time. A picture generally refers to a unit representing an image at a specific time frame, and a slice / tile refers to a unit that constitutes a part of a picture in terms of coding. A slice / tile may include one or more coding tree units (CTUs). A picture may be composed of one or more slices / tiles. A picture may be composed of one or more tile groups. A tile group may include one or more tiles. A tile may represent a rectangular area of ​​a CTU row within a tile in a picture (a tile may represent a rectangular area of ​​a CTU row within a tile in a picture). A tile may be partitioned into multiple tiles, each of which may be constructed using one or more CTU rows within a tile (a tile may be partitioned into multiple tiles, each of which may be constructed using one or more CTU rows within a tile). A tile that is not partitioned into multiple tiles may also be referred to as a tile. Tile scanning may represent a specific ordering of CTUs that partition a picture, where the CTUs may be ordered in a CTU raster scan within a tile, and tiles within a tile may be ordered contiguously in a raster scan of tiles of the tile, and tiles in a picture may be ordered contiguously in a raster scan of tiles of the picture (tile scanning is a specific ordering of CTUs that partition a picture, where the CTUs are ordered contiguously in a CTU raster scan within a tile, tiles within a tile are ordered contiguously in a raster scan of tiles of the tile, and tiles in a picture are ordered contiguously in a raster scan of tiles of the picture). A tile is a rectangular area of ​​a CTU within a specific tile column and a specific tile row (a tile is a rectangular area of ​​a CTU within a specific tile column and a specific tile row in a picture). A tile column is a rectangular area of ​​a CTU having a height equal to the height of the picture and a width that may be specified by a syntax element in a picture parameter set (a tile column is a rectangular area of ​​a CTU having a height equal to the height of the picture and a width specified by a syntax element in a picture parameter set). A tile row is a rectangular area of ​​a CTU having a width specified by a syntax element in a picture parameter set and a height that may be equal to the height of the picture (a tile row is a rectangular area of ​​a CTU having a height specified by a syntax element in a picture parameter set and a width equal to the width of the picture). A tile scan may represent a specific ordering of the CTUs that partition a picture, and the CTUs may be ordered contiguously in a CTU raster scan within a tile, and the tiles in a picture may be ordered contiguously in a raster scan of the tiles of the picture (a tile scan is a specific ordering of the CTUs that partition a picture, where the CTUs are ordered contiguously in a CTU raster scan within a tile and the tiles in a picture are ordered contiguously in a raster scan of the tiles of the picture). A slice may include an integer number of tiles of a picture, and this integer number of tiles may be included in a single NAL unit (a slice includes an integer number of tiles of a picture that may only be contained in a single NAL unit).A slice can be constructed from multiple complete tiles, or can be a contiguous sequence of complete tiles of a tile (a slice can consist of multiple complete tiles, or just a contiguous sequence of complete tiles of a tile). In this document, tileset and slice can be used instead of each other. For example, a tileset / tileset header can be called a slice / slice header in this document.

[0036] A pixel or a picture element (pel) may refer to the smallest unit constituting a picture (or image). In addition, "sample" may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, and may represent only a pixel / pixel value of a luminance component or only a pixel / pixel value of a chrominance component.

[0037] A unit may represent a basic unit of image processing. A unit may include at least one of a specific area of ​​a picture and information related to the area. A unit may include a luminance block and two chrominance (e.g., cb, cr) blocks. In some cases, a unit may be used interchangeably with terms such as a block or an area. In general, an M×N block may include a set (or array) of samples (or sample arrays) or transform coefficients of M columns and N rows.

[0038] In this document, the symbols " / " and "," should be interpreted as indicating "and / or". For example, the expression "A / B" is interpreted as "A and / or B", and the expression "A, B" is interpreted as "A and / or B". In addition, the expression "A / B / C" means "at least one of A, B, and / or C". In addition, the expression "A, B, C" also means "at least one of A, B, and / or C". (In this document, the terms " / " and "," should be interpreted as indicating "and / or". For example, the expression "A / B" may mean "A and / or B". In addition, "A, B" may mean "A and / or B". In addition, "A / B / C" may mean "at least one of A, B, and / or C". In addition, "A / B / C" may mean "at least one of A, B, and / or C".)

[0039] Furthermore, in this document, the term "or" should be interpreted as indicating "and / or". For example, the expression "A or B" may mean 1) only "A", 2) only "B", and / or 3) "both A and B". In other words, the term "or" in this document may mean "additional or alternative". (Furthermore, in this document, the term "or" should be interpreted as indicating "and / or". For example, the expression "A or B" may include 1) only A, 2) only B, and / or 3) both A and B. In other words, the term "or" in this document should be interpreted as indicating "additional or alternative".)

[0040] Hereinafter, examples of the present embodiment will be described in detail with reference to the accompanying drawings. In addition, in all drawings, the same reference numerals are used to indicate the same elements, and the same description of the same elements will be omitted.

[0041] Figure 1 An example of a video / image coding system to which the present disclosure can be applied is illustrated.

[0042] Reference Figure 1 The video / image coding system may include a source device and a receiving device. The source device may transmit the encoded video / image information or data in the form of a file or stream to the receiving device via a digital storage medium or a network.

[0043] The source device may include a video source, an encoding device, and a transmitter. The receiving device may include a receiver, a decoding device, and a renderer. The encoding device may be referred to as a video / image encoding device, and the decoding device may be referred to as a video / image decoding device. The transmitter may be included in the encoding device. The receiver may be included in the decoding device. The renderer may include a display, and the display may be configured as a separate device or an external component.

[0044] The video source may acquire the video / image by a process of capturing, synthesizing or generating the video / image. The video source may include a video / image capturing device and / or a video / image generating device. For example, the video / image capturing device may include one or more cameras, a video / image archive including previously captured videos / images, etc. For example, the video / image generating device may include a computer, a tablet computer, and a smart phone, and may (electronically) generate the video / image. For example, a virtual video / image may be generated by a computer, etc. In this case, the video / image capturing process may be replaced by a process of generating the relevant data.

[0045] The encoding device can encode the input video / image. For compression and coding efficiency, the encoding device can perform a series of processes such as prediction, transformation, and quantization. The encoded data (encoded video / image information) can be output in the form of a bit stream.

[0046] The transmitter may transmit the encoded image / image information or data output in the form of a bit stream to a receiver of a receiving device in the form of a file or stream through a digital storage medium or a network. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitter may include an element for generating a media file in a predetermined file format, and may include an element for transmitting through a broadcast / communication network. The receiver may receive / extract a bit stream and transmit the received bit stream to a decoding device.

[0047] The decoding device may decode a video / image by performing a series of processes such as dequantization, inverse transformation, and prediction corresponding to the operations of the encoding device.

[0048] The renderer may render the decoded video / image. The rendered video / image may be displayed through a display.

[0049] In this document, at least one of quantization / dequantization and / or transform / inverse transform may be omitted. In the case where quantization / dequantization is omitted, the quantized transform coefficient may be referred to as a transform coefficient. In the case where transform / inverse transform is omitted, the transform coefficient may be referred to as a coefficient or a residual coefficient, or may still be referred to as a transform coefficient expressed uniformly.

[0050] In this document, quantized transform coefficients and transform coefficients may be referred to as transform coefficients and scaled transform coefficients, respectively. In this case, the residual information may include information about the transform coefficients, and the information about the transform coefficients may be signaled through residual coding syntax. The transform coefficients may be derived based on the residual information (or information about the transform coefficients), and the scaled transform coefficients may be derived by inverse transform (scaling) of the transform coefficients. The residual samples may be derived based on the inverse transform (transform) of the scaled transform coefficients. This may be applied / expressed in the same manner for other parts of this document.

[0051] Figure 2 is a diagram schematically showing a configuration of a video / image encoding device to which the present disclosure may be applied. Hereinafter, a device referred to as a video encoding device may include an image encoding device.

[0052] Reference Figure 2 , the encoding device 200 may include and be configured with an image segmenter 210, a predictor 220, a residual processor 230, an entropy encoder 240, an adder 250, a filter 260, and a memory 270. The predictor 220 may include an inter-frame predictor 221 and an intra-frame predictor 222. The residual processor 230 may include a transformer 232, a quantizer 233, a dequantizer 234, and an inverse transformer 235. The residual processor 230 may also include a subtractor 231. The adder 250 may be referred to as a reconstructor or a reconstructed block generator. According to an embodiment, the image segmenter 210, the predictor 220, the residual processor 230, the entropy encoder 240, the adder 250, and the filter 260 described above may be configured by one or more hardware components (e.g., an encoder chipset or processor). In addition, the memory 270 may include a decoded picture buffer (DPB) and may also be configured by a digital storage medium. The hardware component may also include a memory 270 as an internal / external component.

[0053] The image divider 210 may divide the input image (or picture, frame) input to the encoding device 200 into one or more processing units. As an example, the processing unit may be referred to as a coding unit (CU). In this case, the coding unit may be recursively divided from a coding tree unit (CTU) or a maximum coding unit (LCU) according to a quadtree binary tree ternary tree (QTBTTT) structure. For example, one coding unit may be divided into a plurality of coding units with a deeper depth based on a quadtree structure, a binary tree structure, and / or a ternary tree structure. In this case, for example, the quadtree structure is first applied, and the binary tree structure and / or the ternary tree structure may be applied later. Alternatively, the binary tree structure may also be applied first. The coding process according to this document may be performed based on the final coding unit that is no longer divided. In this case, based on the coding efficiency according to image characteristics, etc., the maximum coding unit may be directly used as the final coding unit, or, as required, the coding unit may be recursively divided into coding units with a deeper depth, so that the coding unit with the best size may be used as the final coding unit. Here, the coding process may include processes such as prediction, transformation, and reconstruction described later. As another example, the processing unit may further include a prediction unit (PU) or a transform unit (TU). In this case, each of the prediction unit and the transform unit may be split or partitioned from the above-mentioned final coding unit. The prediction unit may be a unit of sample prediction, and the transform unit may be a unit for deriving a transform coefficient and / or a unit for deriving a residual signal from the transform coefficient.

[0054] In some cases, a unit may be used interchangeably with terms such as a block or region. In general, an M×N block may represent a set of samples or transform coefficients consisting of M columns and N rows. A sample may generally represent a pixel or a pixel value, and may represent only a pixel / pixel value of a luminance component or only a pixel / pixel value of a chrominance component. A sample may be used as a term corresponding to one picture (or image) of a pixel or a pixel element.

[0055] The encoding device 200 can generate a residual signal (residual block, residual sample array) by subtracting a prediction signal (prediction block, prediction sample array) output from the inter predictor 221 or the intra predictor 222 from the input image signal (original block, original sample array), and the generated residual signal is sent to the transformer 232. In this case, as shown, the component that subtracts the prediction signal (prediction block, prediction sample array) from the input image signal (original block, original sample array) in the encoding device 200 can be referred to as a subtractor 231. The predictor can perform prediction on a block to be processed (hereinafter, referred to as a current block) and generate a prediction block including prediction samples of the current block. The predictor can determine whether to apply intra prediction or inter prediction in units of the current block or CU. As described later in the description of each prediction mode, the predictor can generate various information related to the prediction (such as prediction mode information) to send the generated information to the entropy encoder 240. Information about the prediction can be encoded in the entropy encoder 240 and output in the form of a bitstream.

[0056] The intra-frame predictor 222 can predict the current block with reference to samples in the current picture. Depending on the prediction mode, the referenced samples can be located near the current block or can be spaced apart. In intra-frame prediction, the prediction mode may include multiple non-directional modes and multiple directional modes. For example, the non-directional mode may include a DC mode and a plane mode. For example, depending on the level of detail of the prediction direction, the directional mode may include 33 directional prediction modes or 65 directional prediction modes. However, this is only an example, and more or fewer directional prediction modes may be used depending on the settings. The intra-frame predictor 222 may use the prediction mode applied to the neighboring blocks to determine the prediction mode applied to the current block.

[0057] The inter-frame predictor 221 may derive a prediction block of the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. Here, in order to reduce the amount of motion information sent in the inter-frame prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter-frame prediction, the neighboring blocks may include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be referred to as a collocated reference block, a collocated CU (colCU), etc., and the reference picture including the temporal neighboring block may be referred to as a collocated picture (colPic). For example, the inter-frame predictor 221 may configure a motion information candidate list based on the neighboring blocks and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter prediction may be performed based on various prediction modes, and for example, in the case of skip mode and merge mode, the inter predictor 221 may use motion information of a neighboring block as motion information of a current block. In skip mode, unlike merge mode, a residual signal may not be transmitted. A motion vector prediction (MVP) mode may indicate a motion vector of a current block by using a motion vector of a neighboring block as a motion vector predictor and signaling a motion vector difference.

[0058] The predictor 220 may generate a prediction signal based on various prediction methods described later. For example, the predictor may not only apply intra prediction or inter prediction to predict a block, but may also apply both intra prediction and inter prediction at the same time. This may be referred to as combined inter and intra prediction (CIIP). In addition, the predictor may be based on an intra block copy (IBC) prediction mode or a palette mode to perform prediction on a block. The IBC prediction mode or the palette mode may be used for content image / video coding of games, etc., such as screen content coding (SCC). IBC basically performs prediction in the current picture, but it may be performed similarly to inter prediction because it derives a reference block in the current picture. That is, IBC may use at least one of the inter prediction techniques described in this document. The palette mode may be considered an example of intra coding or intra prediction. When the palette mode is applied, the sample values ​​in the picture may be signaled based on information about the palette table and the palette index.

[0059] The prediction signal generated by the predictor (including the inter-frame predictor 221 and / or the intra-frame predictor 222 ) may be used to generate a reconstructed signal or to generate a residual signal.

[0060] The transformer 232 may generate a transform coefficient by applying a transform technique to a residual signal. For example, the transform technique may include at least one of the following: discrete cosine transform (DCT), discrete sine transform (DST), Karhunen–Loève transform (KLT), graph-based transform (GBT), or conditional nonlinear transform (CNT). Here, when the relationship information between pixels is illustrated as a graph, GBT means a transform obtained from a graph. CNT means a transform obtained based on a prediction signal generated by using all previously reconstructed pixels. In addition, the transform process may also be applied to pixel blocks of squares of the same size, and may also be applied to blocks of variable sizes other than squares. The quantizer 233 may quantize the transform coefficients to send the quantized transform coefficients to the entropy encoder 240, and the entropy encoder 240 may encode the quantized signal (information about the quantized transform coefficients) into a bitstream. Information about the quantized transform coefficients may be referred to as residual information.

[0061] The quantizer 233 may rearrange the quantized transform coefficients having the block form in a one-dimensional vector form based on a coefficient scanning order, and also generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form.

[0062] The entropy encoder 240 may perform various encoding methods such as exponential Golomb coding, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), etc. The entropy encoder 240 may also encode information necessary for reconstructing the video / image (e.g., the value of a syntax element, etc.) in addition to the quantized transform coefficients, together or separately. The encoded information (e.g., the encoded video / image information) may be transmitted or stored in units of a network abstraction layer (NAL) in the form of a bitstream. The video / image information may also include information about various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may also include general constraint information. The information and / or syntax elements signaled / transmitted described later in this document may be encoded by the aforementioned encoding process and thus included in the bitstream. The bitstream may be transmitted over a network or may be stored in a digital storage medium. Here, the network may include a broadcast network and / or a communication network, etc., and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitter (not shown) for transmitting a signal output from the entropy encoder 240 and / or a storage unit (not shown) for storing the signal may be configured as an internal / external element of the encoding device 200, or the transmitter may also be included in the entropy encoder 240.

[0063] The quantized transform coefficients output from the quantizer 233 can be used to generate a prediction signal. For example, the dequantizer 234 and the inverse transformer 235 apply dequantization and inverse transformation to the quantized transform coefficients so that the residual signal (residual block or residual sample) can be reconstructed. The adder 250 adds the reconstructed residual signal to the prediction signal output from the inter-frame predictor 221 or the intra-frame predictor 222, thereby generating a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array). As in the case of applying the skip mode, if there is no residual in the block to be processed, the prediction block can be used as a reconstructed block. The adder 250 can be referred to as a reconstructor or a reconstructed block generator. The generated reconstructed signal can be used for intra-frame prediction of the next block to be processed in the current picture, and as described later, it is also used for inter-frame prediction of the next picture through filtering.

[0064] Also, luminance mapping and chrominance scaling (LMCS) may be applied during picture encoding and / or reconstruction.

[0065] The filter 260 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 260 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture and store the modified reconstructed picture in the memory 270 (specifically, the DPB of the memory 270). For example, various filtering methods may include deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc. The filter 260 can generate various types of information related to filtering and send the generated information to the entropy encoder 240, as described later in the description of each filtering method. The information related to filtering can be encoded by the entropy encoder 240 and output in the form of a bitstream.

[0066] The modified reconstructed picture transmitted to the memory 270 may be used as a reference picture in the inter predictor 221. If inter prediction is applied through the inter predictor, the encoding apparatus may avoid prediction mismatch between the encoding apparatus 200 and the decoding apparatus and coding efficiency may be improved.

[0067] The DPB of the memory 270 may store a modified reconstructed picture used as a reference picture in the inter-frame predictor 221. The memory 270 may store motion information of a block for deriving (or encoding) motion information in the current picture and / or motion information of a reconstructed block in the picture. The stored motion information may be sent to the inter-frame predictor 221 to be used as motion information of a spatially adjacent block or motion information of a temporally adjacent block. The memory 270 may store reconstructed samples of a reconstructed block in the current picture and may transmit the reconstructed samples to the intra-frame predictor 222.

[0068] Figure 3 is a diagram for schematically explaining a configuration of a video / image decoding device to which an embodiment of the present disclosure can be applied.

[0069] Reference Figure 3 , the decoding device 300 may include and be configured with an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, a filter 350, and a memory 360. The predictor 330 may include an inter-frame predictor 332 and an intra-frame predictor 331. The residual processor 320 may include a dequantizer 321 and an inverse transformer 322. According to an embodiment, the entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filter 350, which have been described above, may be configured by one or more hardware components (e.g., a decoder chipset or a processor). In addition, the memory 360 may include a decoded picture buffer (DPB) and may be configured by a digital storage medium. The hardware component may also include the memory 360 as an internal / external component.

[0070] When a bit stream including video / image information is input, the decoding device 300 may respond to the Figure 2 The image can be reconstructed based on the process of processing video / image information in the encoding device shown. For example, the decoding device 300 can derive the unit / block based on the block segmentation related information obtained from the bit stream. The decoding device 300 can perform decoding using a processing unit applied to the encoding device. Therefore, the processing unit for decoding can be, for example, a coding unit, and the coding unit can be divided from the coding tree unit or the maximum coding unit according to a quadtree structure, a binary tree structure and / or a ternary tree structure. One or more transform units can be derived from the coding unit. In addition, the reconstructed image signal decoded and output by the decoding device 300 can be reproduced by a reproduction device.

[0071] The decoding device 300 may receive the bit stream from Figure 2The signal output by the encoding device shown in the figure, and the received signal can be decoded by the entropy decoder 310. For example, the entropy decoder 310 can derive the information (e.g., video / image information) required for image reconstruction (or picture reconstruction) by parsing the bitstream. The video / image information may also include information about various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may also include general constraint information. The decoding device may also decode the picture based on the information about the parameter set and / or the general constraint information. The information and / or syntax elements that are signaled / received and / or described later in this document may be decoded by a decoding process and obtained from the bitstream. For example, the entropy decoder 310 may decode the information within the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and output the values ​​of the syntax elements required for image reconstruction and the quantized values ​​of the residual-related transform coefficients. More specifically, the CABAC entropy decoding method may receive a bin (binary bit) corresponding to each syntax element from a bitstream, determine a context model using information of syntax elements to be decoded, information of decoded neighboring blocks or blocks to be decoded, or information of symbols / bins decoded in a previous stage, and generate symbols corresponding to the values ​​of each syntax element by predicting the probability of generating bins according to the determined context model to perform arithmetic decoding on the bins. At this time, the CABAC entropy decoding method may determine a context model and then update the context model by using the information of the decoded symbol / bin for the context model of the next symbol / bin. Information related to prediction among the information decoded by the entropy decoder 310 may be provided to a predictor (inter-frame predictor 332 and intra-frame predictor 331), and a residual value (ie, quantized transform coefficients and related parameter information) entropy-decoded by the entropy decoder 310 may be input to a residual processor 320.

[0072] The residual processor 320 may derive a residual signal (residual block, residual sample, residual sample array). In addition, information about filtering among the information decoded by the entropy decoder 310 may be provided to the filter 350. Meanwhile, a receiver (not shown) for receiving a signal output from the encoding device may also be configured as an internal / external element of the decoding device 300, or the receiver may be a component of the entropy decoder 310. Meanwhile, the decoding device according to the present document may be referred to as a video / image / picture decoding device, and the decoding device may be classified into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder may include an entropy decoder 310, and the sample decoder may include at least one of the following: a dequantizer 321, an inverse transformer 322, an adder 340, a filter 350, a memory 360, an inter-frame predictor 332, and an intra-frame predictor 331.

[0073] The dequantizer 321 may dequantize the quantized transform coefficient and output the transform coefficient. The dequantizer 321 may rearrange the quantized transform coefficient in a two-dimensional block form. In this case, the rearrangement may be performed based on the coefficient scanning order performed in the encoding device. The dequantizer 321 may perform dequantization on the quantized transform coefficient using a quantization parameter (e.g., quantization step size information) and obtain the transform coefficient.

[0074] The inverse transformer 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

[0075] The predictor 330 may perform prediction on the current block and generate a prediction block including prediction samples of the current block. The predictor may determine whether to apply intra prediction or inter prediction to the current block based on the information on prediction output from the entropy decoder 310 and may determine a specific intra / inter prediction mode.

[0076] The predictor can generate a prediction signal based on various prediction methods described below. For example, the predictor can not only apply intra prediction or inter prediction to predict a block, but also apply intra prediction and inter prediction at the same time. This can be called combined inter and intra prediction (CIIP). In addition, the predictor can predict blocks based on intra block copy (IBC) prediction mode or palette mode. IBC prediction mode or palette mode can be used for content image / video coding of games, such as screen content coding (SCC). IBC basically performs prediction in the current picture, but can be performed similarly to inter prediction so that a reference block is derived in the current picture. That is, IBC can use at least one inter prediction technique described in this document. The palette mode can be regarded as an example of intra coding or intra prediction. When the palette mode is applied, information about the palette table and the palette index can be included in the video / image information and notified with a signal.

[0077] The intra-frame predictor 331 can predict the current block with reference to samples in the current picture. Depending on the prediction mode, the referenced samples can be located near the current block or can be spaced apart. In intra-frame prediction, the prediction mode can include multiple non-directional modes and multiple directional modes. The intra-frame predictor 331 can use the prediction mode applied to the neighboring block to determine the prediction mode applied to the current block.

[0078] The inter-frame predictor 332 can derive the prediction block of the current block based on the reference block (reference sample array) specified by the motion vector on the reference picture. At this time, in order to reduce the amount of motion information sent in the inter-frame prediction mode, the motion information can be predicted in units of blocks, sub-blocks or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter-frame prediction, the neighboring blocks may include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. For example, the inter-frame predictor 332 may configure a motion information candidate list based on the neighboring blocks and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter-frame prediction may be performed based on various prediction modes, and the information about the prediction may include information indicating the mode of inter-frame prediction of the current block.

[0079] The adder 340 can generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the obtained residual signal to the prediction signal (prediction block, prediction sample array) output from the predictor (including the inter-frame predictor 332 and / or the intra-frame predictor 331). If there is no residual in the block to be processed, for example, when the skip mode is applied, the prediction block can be used as the reconstructed block.

[0080] The adder 340 may be referred to as a reconstructor or a reconstructed block generator. The generated reconstructed signal may be used for intra prediction of the next block to be processed in the current picture, may be output through filtering as described below, or may be used for inter prediction of the next picture.

[0081] At the same time, luminance mapping and chroma scaling (LMCS) can be applied during the picture decoding process.

[0082] The filter 350 may apply filtering to the reconstructed signal, thereby improving the subjective / objective image quality. For example, the filter 350 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture and send the modified reconstructed picture to the memory 360 (specifically, the DPB of the memory 360). For example, the various filtering methods may include deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0083] The (modified) reconstructed image stored in the DPB of the memory 360 can be used as a reference picture in the inter-frame predictor 332. The memory 360 can store the motion information of the block in which the motion information in the current picture is derived (decoded) and / or the motion information of the block in the previously reconstructed picture. The stored motion information can be transmitted to the predictor 260 to be used as the motion information of the spatial neighboring block or the motion information of the temporal neighboring block. The memory 360 can store the reconstructed samples of the reconstructed block in the current picture and transmit the stored reconstructed samples to the intra-frame predictor 331.

[0084] In the present specification, the exemplary embodiments described in the filter 260, the inter-frame predictor 221, and the intra-frame predictor 222 of the encoding device 200 may be equally applied to or correspond to the filter 350, the inter-frame predictor 332, and the intra-frame predictor 331 of the decoding device 300, respectively.

[0085] The video / image coding method according to the present disclosure can be performed based on the following partition structure. Specifically, the prediction, residual processing ((inverse) transform and (de)quantization), syntax element coding and filtering processes described later can be performed based on the CTU and CU (and / or TU and PU) derived based on the partition structure. The block partition process can be performed by the image segmenter 210 of the above-mentioned encoding device, and the partition related information can be processed by the entropy encoder 240 (encoding) and can be transmitted to the decoding device in the form of a bitstream. The entropy decoder 310 of the decoding device can derive the block partition structure of the current picture based on the partition related information obtained from the bitstream, and based on this, a series of processes for image decoding (e.g., prediction, residual processing, block / picture reconstruction, in-loop filtering, etc.) can be performed. The CU size and the TU size can be equal to each other, or multiple TUs can exist within the CU area. At the same time, the CU size can generally represent the brightness component (sample) coding block (CB) size. The TU size can generally represent the brightness component (sample) transform block (TB) size. The chroma component (sample) CB or TB size can be derived based on the luminance component (sample) CB or TB size according to the component ratio according to the color format (chroma format, for example, 4:4:4, 4:2:2, 4:2:0, etc.) of the picture / image. The TU size can be derived based on maxTbSize. For example, if the size of the CU is larger than maxTbSize, multiple TUs (TBs) of maxTbSize can be derived from the CU, and transform / inverse transform can be performed in units of TU (TB). In addition, for example, in the case of applying intra-frame prediction, the intra-frame prediction mode / type can be derived in units of CU (or CB), and the adjacent reference sample derivation and prediction sample generation process can be performed in units of TU (or TB). In this case, one or more TUs (or TBs) may exist in one CU (or CB) area, and in this case, multiple TUs (or TBs) may share the same intra-frame prediction mode / type.

[0086] In addition, in the video / image coding according to the present disclosure, the image processing unit may have a hierarchical structure. A picture may be partitioned into one or more tiles, tiles, slices and / or tile groups. A slice may include one or more tiles. A tile may include one or more CTU rows within a tile. A slice may include an integer number of tiles of a picture. A tile group may include one or more tiles. A tile may include one or more CTUs. A CTU may be partitioned into one or more CUs. A tile represents a rectangular area of ​​a CTU within a specific tile column and a specific tile row in a picture. According to the tile raster scan in the picture, a tile group may include an integer number of tiles. A slice header may carry information / parameters that may be applied to a corresponding slice (a block in a slice). In the case where the encoding / decoding device has a multi-core processor, the encoding / decoding process for tiles, slices, tiles and / or tile groups may be processed in parallel. In this document, slices or tile groups may be used interchangeably. That is, a tile group header may be referred to as a slice header. Here, the slice may have one of slice types including intra (I) slice, prediction (P) slice, and bi-prediction (B) slice. When predicting a block in an I slice, inter prediction may not be used, but only intra prediction may be used. Of course, even in this case, signaling may be performed by coding the original sample value without prediction. For a block in a P slice, intra prediction or inter prediction may be used, and in the case of using inter prediction, only unidirectional prediction may be used. Meanwhile, for a block in a B slice, intra prediction or inter prediction may be used, and in the case of using inter prediction, up to bi-prediction may be used.

[0087] The encoder may determine tiles / tile groups, tiles, slices, and maximum and minimum coding unit sizes in consideration of coding efficiency or parallel processing according to characteristics of a video image (eg, resolution), and information about them or information capable of deriving them may be included in a bitstream.

[0088] The decoder can obtain information indicating whether a tile / tile group, a tile, a slice, and a CTU in a tile of the current picture have been partitioned into multiple coding units. By making such information available (sent) only under certain conditions, efficiency can be enhanced.

[0089] The slice header (Slice Header Syntax) may include information / parameters that may be commonly applied to slices. The APS (APS Syntax) or PPS (PPS Syntax) may include information / parameters that may be commonly applied to one or more pictures. The SPS (SPS Syntax) may include information / parameters that may be commonly applied to one or more sequences. The VPS (VPS Syntax) may include information / parameters that may be commonly applied to multiple layers. The DPS (DPS Syntax) may include information / parameters that may be commonly applied to the entire video. The DPS may include information / parameters related to the concatenation of a coded video sequence (CVS).

[0090] In this document, the higher-level syntax may include at least one of APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, and slice header syntax.

[0091] In addition, for example, information on partitioning and configuration of tiles / tile groups / tiles / slices may be configured by the encoding end through a higher-level syntax and may be transmitted to the decoding device in the form of a bitstream.

[0092] Figure 4 is a diagram showing a hierarchical structure of a compiled image.

[0093] The coded image is divided into a video coding layer (VCL) that processes the image itself and the decoding process of the image, a subsystem that transmits and stores coding information, and a network abstraction layer (NAL) that exists between the VCL and the subsystem and is responsible for network adaptation functions.

[0094] VCL can create VCL data including compressed image data (slice data), or can generate a parameter set such as a picture parameter set (Picture Parameter Set: PPS), a sequence parameter set (Sequence Parameter Set: SPS), a video parameter set (Video Parameter Set: VPS), etc., or a supplemental enhancement information (SEI) message additionally required for the decoding process of the image.

[0095] In NAL, a NAL unit can be generated by adding header information (NAL unit header) to a raw byte sequence payload (RBSP) generated in the VCL. In this case, RBSP refers to slice data, parameter sets, SEI messages, etc. that have been generated in the VCL. The NAL unit header can include NAL unit type information specified according to the RBSP data included in the corresponding NAL unit.

[0096] like Figure 4As shown, the NAL unit can be divided into VCL NAL unit and non-VCL NAL unit according to the RBSP generated in the VCL. The VCL NAL unit may mean a NAL unit including information about the image (slice data), and the non-VCL NAL unit may mean a NAL unit including information required for decoding the image (parameter set or SEI message).

[0097] The above-mentioned VCL NAL unit and non-VCL NAL unit can be sent through the network by adding header information according to the data standard of the subsystem. For example, the NAL unit can be converted into a predetermined standard data form such as H.266 / VVC file format, real-time transport protocol (RTP), transport stream (TS), etc., and sent through various networks.

[0098] As described above, for a NAL unit, a NAL unit type may be specified according to an RBSP data structure included in a corresponding NAL unit, wherein information on such a NAL unit type may be stored in a NAL unit header and signaled.

[0099] For example, NAL units can be roughly classified into VCL NAL unit types and non-VCL NAL unit types depending on whether the NAL unit includes information about an image (slice data). VCL NAL unit types can be classified according to the attributes and types of pictures included in the VCL NAL unit, and non-VCL NAL unit types can be classified according to the types of parameter sets, etc.

[0100] The following are examples of NAL unit types specified according to the kind of parameter sets included in the non-VCL NAL unit type and the like.

[0101] -APS (Adaptation Parameter Set) NAL unit: Type of NAL unit that includes APS

[0102] -DPS (Decoding Parameter Set) NAL unit: the type of NAL unit that includes the DPS

[0103] -VPS (Video Parameter Set) NAL unit: the type of NAL unit that includes the VPS

[0104] -SPS (Sequence Parameter Set) NAL unit: the type of NAL unit that includes SPS

[0105] -PPS (Picture Parameter Set) NAL unit: Type of NAL unit that includes PPS

[0106] The above-mentioned NAL unit type has syntax information of the NAL unit type, and the syntax information may be stored and signaled in the NAL unit header. For example, the syntax information may be nal_unit_type, and the NAL unit type may be specified by the nal_unit_type value.

[0107] A slice header (slice header syntax) may include information / parameters that may be commonly applied to slices. APS (APS syntax) or PPS (PPS syntax) may include information / parameters that may be commonly applied to one or more slices or pictures. SPS (SPS syntax) may include information / parameters that may be commonly applied to one or more sequences. VPS (VPS syntax) may include information / parameters that may be commonly applied to multiple layers. DPS (DPS syntax) may include information / parameters that may be commonly applied to the entire video. DPS may include information / parameters related to the concatenation of a coded video sequence (CVS). In this document, a high-level syntax (HLS) may include at least one of the following: APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, and slice header syntax.

[0108] In this article, the image / video information encoded in the form of a bit stream and notified by a signal from the encoding device to the decoding device may include not only information related to intra-picture partitions, intra-frame / inter-frame prediction information, residual information, in-loop filtering information, etc., but also information included in the slice header, information included in the APS, information included in the PPS, information included in the SPS and / or information included in the VPS.

[0109] At the same time, as described above, when performing video coding, prediction is performed to improve compression efficiency. Thus, a prediction block including prediction samples for a current block as a block to be coded (ie, a coding target block) can be generated. Here, the prediction block includes prediction samples in the spatial domain (or pixel domain). The prediction block is derived in the same manner in the encoding device and the decoding device, and the encoding device can signal the information about the residual between the original block and the prediction block (residual information) instead of the original sample value of the original block to the decoding device, thereby improving the image coding efficiency. The decoding device can derive a residual block including residual samples based on the residual information, add the residual block and the prediction block to generate a reconstructed block including reconstructed samples, and generate a reconstructed picture including the reconstructed block.

[0110] The residual information can be generated by a transformation and quantization process. For example, the encoding device can derive a residual block between the original block and the prediction block, perform a transformation process on the residual samples (residual sample array) included in the residual block to derive the transformation coefficient, perform a quantization process on the transformation coefficient to derive the quantized transformation coefficient, and signal the relevant residual information (through the bitstream) to the decoding device. Here, the residual information may include value information, position information, transformation technology, transformation kernel, quantization parameter, etc. of the quantized transformation coefficient. The decoding device can perform a dequantization / inverse transformation process based on the residual information and derive residual samples (or residual blocks). The decoding device can generate a reconstructed picture based on the prediction block and the residual block. In addition, for reference to the inter-frame prediction of the subsequent picture, the encoding device can also dequantize / inverse transform the quantized transformation coefficient to derive the residual block, and generate a reconstructed picture based on the residual block.

[0111] In the case where inter-frame prediction is applied to the current block, the predictor of the encoding device / decoding device can derive prediction samples by performing inter-frame prediction in units of blocks. Inter-frame prediction can be a prediction derived in a manner that depends on data elements (e.g., sample values ​​or motion information) of pictures other than the current picture. In the case where inter-frame prediction is applied to the current block, the prediction block (prediction sample array) of the current block can be derived based on the reference block (reference sample array) specified by the motion vector on the reference picture indicated by the reference picture index. In this case, in order to reduce the amount of motion information sent in the inter-frame prediction mode, the motion information of the current block can be predicted in units of blocks, sub-blocks or samples based on the correlation of motion information between neighboring blocks and the current block. The motion information may include motion vectors and reference picture indexes. The motion information may also include inter-frame prediction type (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of applying inter-frame prediction, the neighboring blocks may include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be equal to or different from each other. A temporally neighboring block may be referred to as a collocated reference block or collocated CU (colCU), and a reference picture including a temporally neighboring block may be referred to as a collocated picture (colPic). For example, a motion information candidate list may be configured based on the neighboring blocks of the current block, and a flag or index information indicating which candidate is selected (used) to derive the motion vector and / or reference picture index of the current block may be signaled. Inter-frame prediction may be performed based on various prediction modes, for example, in the case of skip mode and (normal) merge mode, the motion information of the current block may be equal to the motion information of the selected neighboring block. In the case of skip mode, unlike merge mode, a residual signal may not be sent. In the case of motion vector prediction (MVP) mode, the motion vector of the selected neighboring block may be used as a motion vector predictor, and the motion vector difference may be signaled. In this case, the motion vector of the current block may be derived using the sum of the motion vector predictor and the motion vector difference.

[0112] The video / image encoding process based on inter-frame prediction may schematically include, for example, the following process.

[0113] Figure 5 An example of a video / image encoding method based on inter-frame prediction is shown.

[0114] The encoding device performs inter prediction on the current block (S500). The encoding device may derive an inter prediction mode and motion information for the current block, and may generate a prediction sample of the current block. Here, the processes of inter prediction mode determination, motion information derivation, and prediction sample generation may be performed simultaneously, or any one process may be performed before the other processes. For example, the inter predictor of the encoding device may include a prediction mode determination unit, a motion information derivation unit, and a prediction sample derivation unit. The prediction mode determination unit may determine a prediction mode for the current block, the motion information derivation unit may derive motion information of the current block, and the prediction sample derivation unit may derive a prediction sample of the current block. For example, the inter predictor of the encoding device may search for a block similar to the current block in a specific area (search area) of the reference picture through motion estimation, and may derive a reference block having a minimum difference or a difference equal to or less than a predetermined reference with the current block. Based on this, the inter predictor of the encoding device may derive a reference picture index indicating a reference picture where the reference block is located, and may derive a motion vector based on the position difference between the reference block and the current block. The encoding device may determine a mode applied to the current block among various prediction modes. The encoding apparatus may compare rate-distortion (RD) costs of various prediction modes, and may determine an optimal prediction mode for a current block.

[0115] For example, in the case where the skip mode or merge mode is applied to the current block, the encoding device may configure a merge candidate list described later, and may derive a reference block having a minimum difference or a difference equal to or less than a predetermined reference from the current block among the reference blocks indicated by the merge candidates included in the merge candidate list. In this case, a merge candidate related to the derived reference block may be selected, and merge index information indicating the selected merge candidate may be generated and signaled to the decoding device. The motion information of the current block may be derived using the motion information of the selected merge candidate.

[0116] As another example, in the case where the (A)MVP mode is applied to the current block, the encoding device may configure the (A)MVP candidate list described later, and may use the motion vector of the MVP candidate selected from the motion vector predictor (MVP) candidates included in the (A)MVP candidate list as the MVP of the current block. In this case, for example, the motion vector of the reference block derived by the above-mentioned motion estimation may be used as the motion vector of the current block, and the MVP candidate having the motion vector with the smallest difference from the motion vector of the current block among the MVP candidates may become the selected MVP candidate. A motion vector difference (MVD) may be derived, which is a difference obtained by subtracting the MVP from the motion vector of the current block. In this case, information about the MVD may be notified to the decoding device by a signal. In addition, in the case where the (A)MVP mode is applied, the reference picture index value may be configured as reference picture index information, and may be separately notified to the decoding device by a signal.

[0117] The encoding apparatus may induce residual samples based on the prediction samples (S510). The encoding apparatus may induce residual samples by comparing original samples of the current block with the prediction samples.

[0118] The encoding device encodes the image information including prediction information and residual information (S520). The encoding device can output the encoded image information in the form of a bitstream. The prediction information may be information related to the prediction process, and may include information about prediction mode information (e.g., a skip flag, a merge flag, or a mode index) and motion information. The information about the motion information may include candidate selection information (e.g., a merge index, an mvp flag, or an mvp index) as information for deriving a motion vector. In addition, the information about the motion information may include information about the above-mentioned MVD and / or reference picture index information. In addition, the information about the motion information may include information indicating whether L0 prediction, L1 prediction, or dual prediction is applied. The residual information is information related to the residual sample. The residual information may include information about the quantized transform coefficients used for the residual sample.

[0119] The output bitstream may be stored in a (digital) storage medium to be transmitted to a decoding device or may be transmitted to a decoding device over a network.

[0120] At the same time, as described above, the encoding device can generate a reconstructed picture (including a reconstructed sample and a reconstructed block) based on the reference sample and the residual sample. This is to enable the encoding device to derive the same prediction result as the prediction result performed by the decoding device, and by doing so, the coding efficiency can be enhanced. Therefore, the encoding device can store the reconstructed picture (or reconstructed sample or reconstructed block) in a memory, and can use the stored reconstructed picture as a reference picture for inter-frame prediction. As described above, the in-loop filtering process can be further applied to the reconstructed picture.

[0121] The video / image decoding process based on inter-frame prediction may schematically include, for example, the following process.

[0122] Figure 6 An example of a video / image decoding method based on inter-frame prediction is shown.

[0123] Reference Figure 6 The decoding device may perform an operation corresponding to the operation performed by the encoding device. The decoding device may perform prediction on the current block based on the received prediction information and may derive a prediction sample.

[0124] Specifically, the decoding apparatus may determine a prediction mode for the current block based on the received prediction information (S600). The decoding apparatus may determine which inter prediction mode to apply to the current block based on prediction mode information in the prediction information.

[0125] For example, the decoding device may determine whether to apply the merge mode or determine the (A) MVP mode with respect to the current block based on the merge flag. In addition, the decoding device may select one of various inter-frame prediction mode candidates based on the mode index. The inter-frame prediction mode candidate may include a skip mode, a merge mode, and / or an (A) MVP mode, or may include various inter-frame prediction modes described later.

[0126] The decoding device derives motion information of the current block based on the determined inter prediction mode (S610). For example, in the case where the skip mode or the merge mode is applied to the current block, the decoding device may configure a merge candidate list described later, and may select one of the merge candidates included in the merge candidate list. Such selection may be performed based on the above-mentioned selection information (merge index). The motion information of the current block may be derived using the motion information of the selected merge candidate. The motion information of the selected merge candidate may be used as the motion information of the current block.

[0127] As another example, in the case where the (A)MVP mode is applied to the current block, the decoding device may configure the (A)MVP candidate list described later, and may use the motion vector of the MVP candidate selected from the motion vector predictor (MVP) candidates included in the (A)MVP candidate list as the MVP of the current block. This selection may be performed based on the above-mentioned selection information (MVP flag or MVP index). In this case, the MVD of the current block may be derived based on the information about the MVD, and the motion vector of the current block may be derived based on the MVP and MVD of the current block. In addition, the reference picture index of the current block may be derived based on the reference picture index information. The picture indicated by the reference picture index in the reference picture list of the current block may be derived as a reference picture, which is referenced for inter-frame prediction of the current block.

[0128] At the same time, as described later, the motion information of the current block can be derived without configuring the candidate list, and in this case, the motion information of the current block can be derived according to the process disclosed in the prediction mode described later. In this case, the above-mentioned candidate list configuration can be omitted.

[0129] The decoding device may generate a prediction sample of the current block based on the motion information of the current block (S620). In this case, a reference picture may be derived based on a reference picture index of the current block, and a sample of the reference block indicated by the motion vector of the current block on the reference picture may be used to derive the prediction sample of the current block. In this case, as described later, a prediction sample filtering process for all or part of the prediction samples of the current block may be further performed in some cases.

[0130] For example, the inter-frame predictor of the decoding device may include a prediction mode determination unit, a motion information derivation unit, and a prediction sample derivation unit. The prediction mode determination unit may determine a prediction mode for a current block based on the received prediction mode information, the motion information derivation unit may derive motion information (motion vector and / or reference picture index) of the current block based on information about the received motion information, and the prediction sample derivation unit may derive a prediction sample of the current block.

[0131] The decoding device generates residual samples for the current block based on the received residual information (S630). The decoding device can generate reconstructed samples for the current block based on the predicted samples and the residual samples, and based on this, can generate a reconstructed picture (S640). Thereafter, as described above, the in-loop filtering process can be further applied to the reconstructed picture.

[0132] As described above, the inter-frame prediction process may include inter-frame prediction mode determination, motion information derivation according to the determined prediction mode, and prediction execution (prediction sample generation) based on the derived motion information. As described above, the inter-frame prediction process may be performed by an encoding device and a decoding device. In this document, a coding device may include an encoding device and / or a decoding device.

[0133] For the prediction of the current block in the picture, various inter prediction modes can be used. For example, various modes such as merge mode, skip mode, motion vector prediction (MVP) mode, affine mode, sub-block merge mode, merge with MVD (MMVD) mode, and historical motion vector prediction (HMVP) mode can be used. Decoder-side motion vector refinement (DMVR) mode, adaptive motion vector resolution (AMVR) mode, dual prediction with CU-level weights (BCW), and bidirectional optical flow (BDOF) can be further used or used as incidental modes instead. Affine mode can be referred to as affine motion prediction mode. MVP mode can be referred to as advanced motion vector prediction (AMVP) mode. In this document, a specific mode and / or a motion information candidate derived from a specific mode can be included as one of the candidates related to the motion information of another mode. For example, an HMVP candidate can be added as a merge candidate for a merge / skip mode, or can be added as an MVP candidate for an MVP mode.

[0134] Prediction mode information indicating an inter prediction mode for a current block may be signaled from an encoding device to a decoding device. The prediction mode information may be included in a bitstream and may be received in a decoding device. The prediction mode information may include index information indicating one of a plurality of candidate modes. In addition, the inter prediction mode may be indicated by hierarchical signaling of flag information. In this case, the prediction mode information may include one or more flags. For example, whether a skip mode is applied may be indicated by signaling a skip flag, and in the case where the skip mode is not applied, whether a merge mode is applied may be indicated by signaling a merge flag, and in the case where the merge mode is not applied, the application of the MVP mode may be indicated, or a flag for additional partitioning may be further signaled. The affine mode may be signaled as an independent mode, or may be signaled as a subordinate mode of the merge mode or the MVP mode. For example, the affine mode may include an affine merge mode and an affine MVP mode.

[0135] At the same time, information indicating whether the above-mentioned list 0 (L0) prediction, list 1 (L1) prediction or dual prediction is used for the current block (current coding unit) may be signaled. This information may be referred to as motion prediction direction information, inter-frame prediction direction information or inter-frame prediction indication information, and may be configured / encoded / signaled in the form of, for example, an inter_pred_idc syntax element. That is, the inter_pred_idc syntax element may indicate whether the above-mentioned list 0 (L0) prediction, list 1 (L1) prediction or dual prediction is used for the current block (current coding unit). In this document, for ease of explanation, the inter-frame prediction type (L0 prediction, L1 prediction or BI prediction) indicated by the inter_pred_idc syntax element may be displayed as a motion prediction direction. L0 prediction, L1 prediction and dual prediction may be represented as pred_L0, pred_L1 and pred_BI, respectively. For example, the following prediction types may be represented according to the inter_pred_idc syntax element value.

[0136] As described above, a picture may include one or more slices. A slice may have one of slice types including an intra (I) slice, a predictive (P) slice, and a bidirectional predictive (B) slice. The slice type may be indicated based on slice type information. When predicting a block in an I slice, inter prediction may not be used, but only intra prediction may be used. Of course, even in this case, signaling may be performed by coding the original sample values ​​without prediction. For blocks in P slices, intra prediction or inter prediction may be used, and when inter prediction is used, only unidirectional prediction may be used. At the same time, for blocks in B slices, intra prediction or inter prediction may be used, and when inter prediction is used, up to bi-prediction may be used.

[0137] L0 and L1 may include reference pictures encoded / decoded before the current picture. For example, L0 may include reference pictures before and / or after the current picture in POC order, and L1 may include reference pictures after and / or before the current picture in POC order. In this case, for L0, a relatively low reference picture index may be assigned to a reference picture before the current picture in POC order, and for L1, a relatively low reference picture index may be assigned to a reference picture after the current picture in POC order. In the case of a B slice, bi-prediction may be applied, and even in this case, unidirectional bi-prediction may be applied, or bi-directional bi-prediction may be applied. Bi-directional bi-prediction may be referred to as true bi-prediction.

[0138] Specifically, for example, information about the inter prediction mode of the current block may be compiled and signaled at the CU (CU syntax) level, or information about the inter prediction mode of the current block may be implicitly determined according to conditions. In this case, the information may be explicitly signaled with respect to some modes, and the information may be implicitly derived with respect to the remaining modes.

[0139] For example, the CU syntax may carry information about the (inter) prediction mode as in Table 1 below.

[0140] [Table 1]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154] Here, cu_skip_flag may indicate whether the skip mode is applied to the current block (CU).

[0155] pred_mode_flag equal to 0 specifies that the current coding unit is coded in inter prediction mode. pred_mode_flag equal to 1 specifies that the current coding unit is coded in intra prediction mode.

[0156] pred_mode_ibc_flag equal to 1 specifies that the current coding unit is coded in IBC prediction mode. pred_mode_ibc_flag equal to 0 specifies that the current coding unit is not coded in IBC prediction mode.

[0157] pcm_flag [x0][y0] equal to 1 specifies that the pcm_sample() syntax structure is present and the transform_tree() syntax structure is not present in the coding unit including the luma coding block at position (x0, y0). pcm_flag [x0][y0] equal to 0 specifies that the pcm_sample() syntax structure is not present. That is, pcm_flag can indicate whether a pulse code modulation (PCM) mode is applied to the current block. If the PCM mode is applied to the current block, prediction, transform, and quantization may not be applied, and the original sample values ​​in the current block may be encoded and signaled.

[0158] intra_mip_flag[x0][y0] equal to 1 specifies that the intra prediction type for luma samples is matrix-based intra prediction (MIP). intra_mip_flag[x0][y0] equal to 0 specifies that the intra prediction type for luma samples is not matrix-based intra prediction. That is, intra_mip_flag can indicate whether the MIP prediction mode (type) is applied to the current block (the luma samples of the current block).

[0159] intra_chroma_pred_mode[x0][y0] specifies the intra prediction mode for chroma samples in the current block.

[0160] general_merge_flag[x0][y0] specifies whether to infer the inter prediction parameters of the current coding unit from the adjacent inter prediction partitions. That is, general_merge_flag can indicate that regular merging is enabled, and when the general_merge_flag value is 1, regular merge mode, mmvd mode, and merge sub-block mode (sub-block merge mode) are enabled. For example, when the general_merge_flag value is 1, the merge data syntax can be parsed from the coded video / image information (or bitstream), and the merge data syntax can be configured / compiled to include information as shown in Table 2 below.

[0161] [Table 2]

[0162]

[0163]

[0164]

[0165] Here, regular_merge_flag[x0][y0] equal to 1 specifies that the regular merge mode is used to generate the inter prediction parameters of the current coding unit. That is, regular_merge_flag indicates whether the merge mode (regular merge mode) is applied to the current block.

[0166] mmvd_merge_flag[x0][y0] equal to 1 specifies that the merge mode with motion vector difference is used to generate the inter prediction parameters of the current coding unit. That is, mmvd_merge_flag indicates whether MMVD is applied to the current block.

[0167] mmvd_cand_flag[x0][y0] specifies whether the first (0) or second (1) candidate in the merge candidate list is used with the motion vector difference derived from mmvd_distance_idx[x0][y0] and mmvd_direction_idx[x0][y0].

[0168] mmvd_distance_idx [x0][y0] specifies the index used to derive MmvdDistance [x0][y0].

[0169] mmvd_direction_idx[x0][y0] specifies the index used to derive MmvdSign[x0][y0].

[0170] merge_subblock_flag[x0][y0] specifies whether subblock-based inter prediction parameters are used for current coding. That is, merge_subblock_flag can indicate whether subblock merge mode (or affine merge mode) is applied to the current block.

[0171] merge_subblock_idx[x0][y0] specifies a merge candidate index of a sub-block based merge candidate list.

[0172] ciip_flag[x0][y0] specifies whether combined inter-picture merging and intra-picture prediction is applied to the current coding unit.

[0173] merge_triangle_idx0[x0][y0] specifies the first merge candidate index of the triangle shape based motion compensation candidate list.

[0174] merge_triangle_idx1[x0][y0] specifies the second merge candidate index of the triangle shape based motion compensation candidate list.

[0175] merge_idx[x0][y0] specifies the merge candidate index of the merge candidate list.

[0176] Meanwhile, referring again to the CU syntax of Table 1, mvp_l0_flag [x0][y0] specifies the motion vector predictor index of list 0. That is, in the case where the MVP mode is applied, mvp_l0_flag may indicate a candidate in the MVP candidate list selected for MVP derivation of the current block.

[0177] ref_idx_l1[x0][y0] has the same semantics as ref_idx_l0, where l0, L0, and list0 are replaced by l1, L1, and list1, respectively.

[0178] inter_pred_idc[x0][y0] specifies whether list 0, list 1, or bi-prediction is used for the current coding unit.

[0179] sym_mvd_flag[x0][y0] equal to 1 specifies that the syntax elements ref_idx_l0[x0][y0] and ref_idx_l1[x0][y0] and the mvd_coding(x0, y0, refList, cpIdx) syntax structure for refList equal to 1 are not present. In other words, sym_mvd_flag indicates whether symmetric MVD is used for mvd coding.

[0180] ref_idx_l0[x0][y0] specifies the list 0 reference picture index for the current coding unit.

[0181] ref_idx_l1[x0][y0] has the same semantics as ref_idx_l0, where l0, L0, and list0 are replaced by l1, L1, and list1, respectively.

[0182] inter_affine_flag[x0][y0] equal to 1 specifies that, for the current coding unit, when decoding a P or B slice, affine model-based motion compensation is used to generate prediction samples for the current coding unit.

[0183] cu_affine_type_flag[x0][y0] equal to 1 specifies that, for the current coding unit, when decoding a P or B slice, motion compensation based on a 6-parameter affine model is used to generate prediction samples for the current coding unit. cu_affine_type_flag[x0][y0] equal to 0 specifies that motion compensation based on a 4-parameter affine model is used to generate prediction samples for the current coding unit.

[0184] amvr_flag [x0][y0] specifies the resolution of the motion vector difference. The array index x0, y0 specifies the position (x0, y0) of the top left luma sample of the considered coding block relative to the top left luma sample of the picture. amvr_flag [x0][y0] equal to 0 specifies that the resolution of the motion vector difference is 1 / 4 of the luma sample. amvr_flag [x0][y0] equal to 1 specifies that the resolution of the motion vector difference is further specified by amvr_precision_flag [x0][y0].

[0185] If inter_affine_flag[x0][y0] is equal to 0, then amvr_precision_flag[x0][y0] is equal to 0 to specify that the resolution of motion vector differences is one integer luma sample, otherwise it is 1 / 16 of a luma sample. If inter_affine_flag[x0][y0] is equal to 0, then amvr_precision_flag[x0][y0] is equal to 1 to specify that the resolution of motion vector differences is four luma samples, otherwise it is one integer luma sample. The array index x0, y0 specifies the position (x0, y0) of the top-left luma sample of the considered coding block relative to the top-left luma sample of the picture.

[0186] bcw_idx[x0][y0] specifies the weight index of bi-prediction with CU weight.

[0187] The coding device can perform inter-frame prediction using the motion information of the current block. The coding device can derive the best motion information of the current block through a motion estimation process. For example, the coding device can use the original block in the original picture of the current block to search for a similar reference block with high correlation in units of fractional pixels within a search range determined in the reference picture, and through this, the coding device can derive motion information. Block similarity can be derived based on the difference between phase-based sample values. For example, block similarity can be calculated based on the SAD between the current block (or the template of the current block) and the reference block (or the template of the reference block). In this case, motion information can be derived based on the reference block with the smallest SAD in the search area. The derived motion information can be signaled to the decoding device according to several methods based on the inter-frame prediction mode.

[0188] The coding device may derive a prediction sample of the current block based on the motion information. The current block including the prediction sample may be referred to as a prediction block.

[0189] The prediction block may include prediction samples (prediction sample array) of the current block. In the case where the motion vector of the current block indicates a fractional sample unit, an interpolation process may be performed, and through this process, the prediction samples of the current block may be derived based on the reference samples of the fractional sample unit in the reference picture. In the case where affine inter prediction is applied to the current block, the coding device may generate prediction samples based on the motion vector (MV) in units of samples / sub-blocks. In the case where bi-prediction is applied, the prediction samples derived by the weighted sum or weighted average (according to the phase) of the prediction samples derived based on the L0 prediction (i.e., prediction using the reference pictures in the reference picture list L0 and MVL0) and the prediction samples derived based on the L1 prediction (i.e., prediction using the reference pictures in the reference picture list L1 and MVL1) may be used as the prediction samples of the current block. If, when bi-prediction is applied (i.e., in the case corresponding to bi-prediction and bidirectional prediction), the reference pictures for L0 prediction and the reference pictures for L1 prediction are located in different time directions based on the current picture, they may be referred to as true bi-prediction.

[0190] Reconstructed samples and reconstructed pictures may be generated based on the derived prediction samples, and thereafter, processes such as in-loop filtering may be performed.

[0191] Figure 7 A method of configuring a merge candidate list is schematically shown.

[0192] In the case where the merge mode is applied during inter-frame prediction, the motion information of the current block is not directly transmitted, and the motion information of the neighboring prediction block is used to derive the motion information of the current block. Therefore, the encoding device can indicate the motion information of the current block by transmitting flag information indicating the use of the merge mode and a merge index indicating which neighboring prediction block is used. The merge mode may be referred to as a normal merge mode.

[0193] The coding device searches for a merge candidate block for deriving motion information of the current block in order to perform a merge mode. For example, up to 5 merge candidate blocks may be used, but in the present embodiment, the number of merge candidate blocks is not limited thereto. In addition, information about the maximum number of merge candidate blocks may be sent in a slice header or a tile group header, but the present embodiment is not limited thereto. After finding the merge candidate block, the coding device may generate a merge candidate list, and may select the merge candidate block with the minimum cost as the final merge candidate block.

[0194] This document provides various embodiments of merge candidate blocks for constructing a merge candidate list.

[0195] The merge candidate list may include, for example, 5 merge candidate blocks. For example, 4 spatial merge candidates and one temporal merge candidate may be used. As a specific example, in the case of spatial merge candidates, Figure 6Blocks A0, A1, B0, B1, and B2 shown in FIG. 4 may be used as spatial merge candidates. Hereinafter, a spatial merge candidate or spatial MVP candidate to be described later may be referred to as SMVP, and a temporal merge candidate or temporal MVP candidate to be described later may be referred to as TMVP.

[0196] For example, the merge candidate list for the current block may be configured based on the following process.

[0197] First, the coding device (coding device / decoding device) may insert a spatial merge candidate derived by searching the spatial neighboring blocks of the current block into the merge candidate list (S700). For example, the spatial neighboring blocks may include the lower left neighboring block A0, the left neighboring block A1, the upper right neighboring block B0, the upper neighboring block B1, and the upper left neighboring block B2 of the current block. However, this is exemplary, and in addition to the above-mentioned spatial neighboring blocks, additional neighboring blocks such as the right neighboring block, the lower neighboring block, the lower right neighboring block, etc. may be further used as spatial neighboring blocks. The coding device may detect available blocks by searching the spatial neighboring blocks based on priority, and may derive the motion information of the detected blocks as spatial merge candidates. For example, the coding device and / or the decoding device may search 5 blocks in the order of A1, B1, B0, A0, and B2, and may configure the merge candidate list by sequentially indexing the available candidates.

[0198] In addition, the coding device may insert a temporal merge candidate derived by searching for temporal neighboring blocks of the current block into the merge candidate list (S710). The temporal neighboring block may be located on a reference picture that is a picture different from the current picture where the current block is located. The reference picture where the temporal neighboring block is located may be referred to as a collocated picture or a col picture. The temporal neighboring blocks may be searched in the order of a lower right corner neighboring block and a lower right center block of a collocated block for the current block on the col picture.

[0199] At the same time, the coding device may identify whether the number of current merge candidates is less than the number of maximum merge candidates (S720). The number of maximum merge candidates may be predefined or may be signaled from the encoding device to the decoding device. For example, the encoding device may generate information about the number of maximum merge candidates, encode the information, and transmit the encoded information to the decoding device in the form of a bitstream. If the number of maximum merge candidates is filled, the subsequent candidate addition process may not be performed.

[0200] If, as a result of the identification, the number of current merge candidates is less than the number of maximum merge candidates, the coding device may insert an additional merge candidate into the merge candidate list (S730). For example, the additional merge candidate may include at least one of a history-based merge candidate, a pairwise average merge candidate, an ATMVP, a combined bi-prediction merge candidate (in the case where the slice / tile group type of the current slice / tile group is a B type), and / or a zero vector merge candidate.

[0201] If, as a result of the identification, the number of current merge candidates is not less than the number of maximum merge candidates, the coding device may end the configuration of the merge candidate list (S740). In this case, the encoding device may select the best merge candidate among the merge candidates constituting the merge candidate list based on the rate-distortion (RD) cost, and may signal selection information (e.g., a merge index) indicating the selected merge candidate to the decoding device. The decoding device may select the best merge candidate based on the merge candidate list and the selection information.

[0202] The motion information of the selected merge candidate may be used as the motion information of the current block, and as described above, the prediction sample of the current block may be derived based on the motion information of the current block. The encoding device may derive the residual sample of the current block based on the prediction sample, and may signal the residual information about the residual sample to the decoding device. As described above, the decoding device may generate a reconstructed sample based on the residual sample and the prediction sample derived from the residual information, and based on this, the decoding device may generate a reconstructed picture.

[0203] When skip mode is applied during inter prediction, motion information of the current block can be derived in the same manner as when merge mode is applied. However, when skip mode is applied, the residual signal of the corresponding block can be omitted, so the prediction sample can be immediately used as the reconstructed sample.

[0204] The temporal candidate may represent the temporal merge candidate described above. In addition, the motion vector included in the temporal candidate may correspond to the temporal MVP candidate.

[0205] In this step, only one candidate is added to the candidate list. In particular, when deriving the temporal merge candidate, the scaled motion vector is derived based on the collocated CU belonging to the collocated reference picture (which may be referred to as colPic). The reference picture list to be used for deriving the collocated CU is explicitly signaled in the slice header. Figure 8As shown by the dotted line in , the scaled motion vector of the temporal merge candidate is obtained, which is scaled from the motion vector of the collocated CU using the POC distances tb and td, where tb is defined as the POC difference between the reference picture of the current picture and the current picture, and td is defined as the POC difference between the reference picture of the collocated picture and the collocated picture. The reference picture index of the temporal merge candidate is set equal to zero.

[0206] The position for the temporal candidate is selected between candidates C0 and C1. If the CU of position C0 is not available, is intra-coded, or is outside the row of the current CTU, then position C1 is used. Otherwise, position C0 is used to derive the temporal merge candidate.

[0207] In addition to the merge mode, in which the implicitly derived motion information is directly used for prediction sample generation of the current CU, a merge mode with motion vector difference (MMVD) is introduced in VVC. Because similar motion information derivation methods are used for skip mode and merge mode, MMVD can be applied to skip mode. An MMVD flag (e.g., mmvd_flag) can be signaled immediately after sending the skip flag and the merge flag to specify whether the MMVD mode is used for a CU.

[0208] In MMVD, after a merge candidate is selected, the merge candidate is further refined by signaled MVD information. When MMVD is applied to the current block (ie, when mmvd_flag is equal to 1), further information of MMVD may be signaled.

[0209] Further information includes a merge candidate flag (e.g. mmvd_merge_flag) indicating whether the first candidate (0) or the second candidate (1) in the merge candidate list is used with the motion vector difference, an index specifying the magnitude of the motion (e.g. mmvd_distance_idx), and an index indicating the direction of the motion (e.g. mmvd_direction_idx). In MMVD mode, one of the first two candidates in the merge list is selected to be used as the MV basis. The merge candidate flag is signaled to specify which one is used.

[0210] The distance index specifies motion magnitude information and indicates a predefined offset from a starting point.

[0211] The offset is added to the horizontal or vertical component of the starting MV. The relationship between the distance index and the predefined offset is specified in Table 3.

[0212] [Table 3]

[0213]

[0214] Here, slice_fpel_mmvd_enabled_flag equal to 1 specifies that merge mode with motion vector difference uses integer sample precision in the current slice. slice_fpel_mmvd_enabled_flag equal to 0 specifies that merge mode with motion vector difference can use fractional sample precision in the current slice. When not present, the value of slice_fpel_mmvd_enabled_flag is inferred to be 0. The slice_fpel_mmvd_enabled_flag syntax element may be signaled via (and may be included in) the slice header.

[0215] The direction index indicates the direction of the MVD relative to the starting point. The direction index can indicate four directions as shown in Table 4. Note that the meaning of the MVD symbol can change depending on the information of the starting MV. When the starting MV is a non-predicted MV or a dual-predicted MV in which both lists point to the same side of the current picture (i.e., the POCs of both references are greater than the POC of the current picture, or are less than the POC of the current picture), the symbol in Table 4 specifies the sign of the MV offset added to the starting MV. When the starting MV is a dual-predicted MV in which two MVs point to different sides of the current picture (i.e., the POC of one reference is greater than the POC of the current picture, and the POC of the other reference is less than the POC of the current picture), the symbol in Table 4 specifies the sign of the MV offset added to the list 0 MV component of the starting MV and the sign of the list 1 MV has the opposite value.

[0216] [Table 4]

[0217]

[0218] The combined two components plus the MVD offset MmvdOffset[x0][y0] are derived as follows.

[0219] [Equation 1]

[0220]

[0221] The sub-block based temporal motion vector prediction (SbTMVP) method can be used for inter prediction. Similar to the temporal motion vector prediction (TMVP), SbTMVP uses the motion field in the collocated picture to improve the motion vector prediction and merge mode of the CU in the current picture. The same collocated pictures used by TMVP are used for SbTVMP. SbTMVP differs from TMVP in the following two main aspects.

[0222] 1. TMVP predicts motion at CU level, but SbTMVP predicts motion at sub-CU level.

[0223] 2. TMVP extracts the temporal motion vector from a collocated block in a collocated picture (a collocated block is a bottom-right or center (bottom-right-center) block relative to the current CU), while SbTMVP applies a motion shift before extracting temporal motion information from the collocated picture, where the motion shift is obtained from a motion vector from one of the spatially neighboring blocks of the current CU.

[0224] SbTMVP predicts the motion vector of a sub-CU within the current CU in two steps. In the first step, the spatial neighbor A1 is checked. If A1 has a motion vector that uses a collocated picture when its reference picture is identified, then that motion vector (which can be called the temporal MV (tempVM)) is selected as the motion shift to be applied. If no such motion is identified, the motion shift is set to (0, 0).

[0225] In the second step, the motion shift identified in step 1 is applied (i.e., added to the coordinates of the current block) to obtain sub-CU level motion information (motion vector and reference index) from the collocated picture. Next, for each sub-CU, the motion information for the sub-CU is derived using the motion information of its corresponding block in the collocated picture (the smallest motion grid covering the center sample). When the sub-block has an even length, width, and height, the center sample (the lower right center sample) can correspond to the lower right sample among the 4 center samples in the sub-CU.

[0226] After the motion information of the collocated sub-CU is identified, it is converted to the motion vector and reference index of the current sub-CU in a manner similar to the TMVP process, where temporal motion scaling can be applied to align the reference picture of the temporal motion vector with the reference picture of the current CU.

[0227] A sub-block based merge list containing a combination of both SbTVMP candidates and affine merge candidates can be used for signaling of affine merge mode (which can be referred to as (sub-block based) merge mode). SbTVMP mode is enabled / disabled by a sequence parameter set (SPS) flag. If SbTMVP mode is enabled, the SbTMVP predictor is added as the first entry in the sub-block merge candidate list, followed by the affine merge candidate. The maximum allowed size of the affine merge candidate list can be 5.

[0228] The sub-CU size used in SbTMVP may be fixed to 8×8, and as done in affine merge mode, the SbTMVP mode may only be applied to CUs whose width and height are both greater than or equal to 8.

[0229] The encoding logic of the additional SbTMVP merge candidate is the same as that of other merge candidates, that is, for each CU in a P or B slice, an additional RD check may be performed to decide whether to use the SbTMVP candidate.

[0230] Triangle partition mode can be used for inter prediction. Triangle partition mode can be applied only to CUs of 8x8 or larger. A CU level flag is used as a merge mode to signal triangle partition mode, along with other merge modes, including normal merge mode, MMVD mode, CIIP mode, and sub-block merge mode.

[0231] When this mode is used, the CU can be evenly split into two triangular partitions using diagonal or anti-diagonal partitioning. Each triangular partition in the CU is inter-predicted using its own motion; only uni-prediction is allowed for each partition, i.e., each partition has one motion vector and one reference index. Uni-prediction motion constraints are applied to ensure that, as with conventional bi-prediction, only two motion compensated predictions are required for each CU.

[0232] If triangle partition mode is used for the current CU, a flag indicating the direction of the triangle partition (diagonal or anti-diagonal) and two merge indexes (one merge index for each partition) are further signaled. The number of maximum TPM candidate sizes is explicitly signaled at the slice level, and the syntax specifying the TMP merge index is binarized. After predicting each of the triangle partitions, a blending process with adaptive weights is used to adjust the sample values ​​along the diagonal or anti-diagonal edges. This is the prediction signal for the entire CU, and the transform and quantization process will be applied to the entire CU as in other prediction modes. Finally, the motion field of the CU predicted using the triangle partition mode is stored in 4×4 units. The triangle partition mode is not used in combination with SBT, that is, when the signaled triangle mode is equal to 1, cu_sbt_flag is inferred to be 0 without signaling.

[0233] The single prediction candidate list is directly derived from the merged candidate list constructed as described above.

[0234] After predicting each triangle partition using its own motion, blending is applied to the two prediction signals to derive samples around diagonal or anti-diagonal edges.

[0235] Combined inter-frame and intra-frame prediction can be applied to the current block. An additional flag (e.g., ciip_flag) can be signaled to indicate whether the combined inter-frame / intra-frame prediction (CIIP) mode is applied to the current CU. For example, when a CU is encoded in merge mode, if the CU includes at least 64 luma samples (i.e., the CU width multiplied by the CU height is equal to or greater than 64), and if both the CU width and the CU height are less than 128 luma samples, an additional flag is signaled to indicate whether the combined inter-frame / intra-frame prediction (CIIP) mode is applied to the current CU. As its name indicates, CIIP prediction combines an inter-frame prediction signal with an intra-frame prediction signal. The inter-frame prediction signal in the CIIP mode P_inter is derived using the same inter-frame prediction process applied to the conventional merge mode; while the intra-frame prediction signal P_intra follows the conventional intra-frame prediction process with the planar mode to derive. Then, the intra-frame and inter-frame prediction signals are combined using weighted averaging, where the weight values ​​are calculated according to the coding modes of the upper neighboring block and the left neighboring block as follows.

[0236] If the upper neighbor is available and is intra compiled, isIntrantop is set to 1, otherwise isIntrantop is set to 0.

[0237] If the left neighbor is available and is intra-coded, isIntraLeft is set to 1, otherwise isIntraLeft is set to 0.

[0238] If (isIntraLeft + isIntraLeft) equals 2, then set wt to 3.

[0239] Otherwise, if (isIntraLeft + isIntraLeft) equals 1, set wt to 2.

[0240] Otherwise, set wt to 1.

[0241] The CIIP forecast is formed as follows.

[0242] [Equation 2]

[0243]

[0244] At the same time, in order to generate a prediction block, the coding device can derive motion information based on the above-mentioned conventional merge mode, skip mode, SbTMVP mode, MMVD mode, triangle partition mode (partition mode) and / or CIIP mode. Each mode can be enabled / disabled by an on / off flag of each mode included in a sequence parameter set (SPS). If the on / off flag for a particular mode is disabled, the encoding device does not signal the syntax for explicit transmission of the corresponding prediction mode in units of CU or PU.

[0245] In this document, in order to remove signaling of redundant syntax, a method for signaling syntax considering on / off of merge / skip mode and an application method is disclosed.

[0246] For example, in case of regular_merge_flag, under the condition that MMVD, subblock merging, CIIP merging, and triangle merging are not allowed, there are no possible candidates other than the regular merge mode, and thus there is no need to signal a flag (eg, regular merge flag).

[0247] Furthermore, under the condition that sub-block merging, CIIP merging, and triangle merging are not allowed, mmvd related flags (eg, mmvd_merge_flag) do not need to be signaled.

[0248] Under the condition that CIIP merging and triangle merging are not allowed, the sub-block related flag (eg, merge_subblock_flag) does not need to be signaled.

[0249] Under the condition that triangle merging is not allowed, the CIIP related flag (eg, CIIP_flag) does not need to be signaled.

[0250] According to the merge data syntax of Table 2, redundant signaling of the on / off flag occurs when a specific mode for the merge / skip mode is fully or partially disabled. Therefore, in this document, the following method can be used to prevent redundant signaling of the same information (flag) in the process of selecting the merge mode applied to the current block.

[0251] The following drawings are prepared to explain specific examples of this document. Since the names of specific devices and signals / information described in the drawings are exemplarily presented, the technical features of this specification are not limited to the specific names used in the following drawings.

[0252] Figure 8 and Fig. 9 An example of a video / image encoding method including an inter-frame prediction method and associated components according to an embodiment of the present disclosure is schematically shown.

[0253] Figure 8 The encoding method disclosed in can be Figure 2 Specifically, for example, Figure 8 S800 to S810 may be performed by the predictor 220 of the encoding apparatus 200 , S820 may be performed by the residual processor 230 of the encoding apparatus 200 , and S830 may be performed by the entropy encoder 240 of the encoding apparatus 200 . Figure 8The encoding method disclosed in may include the above-mentioned embodiments of this document.

[0254] Specifically, refer to Figure 8 and Fig. 9 , the predictor of the encoding device may determine a prediction mode of the current block (S800). As an example, in the case where inter prediction is applied to the current block, the predictor of the encoding device may determine any one of a normal merge mode, a skip mode, an MMVD mode, a sub-block merge mode, a partition mode, and a CIIP mode as the prediction mode of the current block.

[0255] Here, the conventional merge mode may be defined as a mode for deriving the motion information of the current block using the motion information of the neighboring blocks. The skip mode may be defined as a mode in which the prediction block is used as the reconstructed block. The MMVD mode may be applied to the merge mode or the skip mode, and may be defined as a merge (or skip) mode using a motion vector difference. The sub-block merge mode may be defined as a merge mode based on a sub-block. The partition mode may be defined as a mode in which prediction is performed by dividing the current block into two partitions (diagonal or anti-diagonal). The CIIP mode may be defined as a mode in which inter-picture merging and intra-picture prediction are combined with each other.

[0256] The predictor of the encoding device may derive a prediction sample of the current block based on the prediction mode of the current block (S810). For example, in the case where the prediction mode for the current block is determined to be a (conventional) merge mode, the predictor of the encoding device may configure a merge candidate list (or a motion information candidate list) based on the spatial neighboring blocks and the temporal neighboring blocks of the current block, and based on this, the predictor of the encoding device may generate motion information. The motion information may include a motion vector and a reference picture index. The predictor of the encoding device may derive a reference block having a minimum difference or a difference equal to or less than a predetermined reference with the current block by searching for a block similar to the current block in a specific area (search area) of the reference picture through motion estimation, and based on this, the predictor of the encoding device may derive a reference picture index indicating the reference picture where the reference block is located. In addition, the predictor of the encoding device may derive a motion vector based on the position difference between the reference block and the current block.

[0257] For example, in the case where the prediction mode for the current block is determined to be a (conventional) merge mode, the predictor of the encoding device may configure a merge candidate list (or a motion information candidate list) based on the spatial neighboring blocks and the temporal neighboring blocks of the current block, and based on this, the predictor of the encoding device may generate motion information. The predictor of the encoding device may derive the prediction sample (prediction block) of the current block based on the prediction mode of the current block and the motion information of the current block. In addition, the predictor of the encoding device may generate information about the prediction mode based on the prediction mode. Here, the information about the prediction mode may include inter / intra prediction classification information and inter prediction mode information, and may include various syntax elements related to the information.

[0258] The residual processor of the encoding device may generate residual samples based on original samples for the current block (original block) and predicted samples for the current block (prediction block) (S820). In addition, the residual processor of the encoding device may derive information about the residual samples based on the residual samples.

[0259] The encoder of the encoding device may encode the image information including the information about the residual sample and the information about the prediction mode (S830). The image information may include partition related information, prediction mode related information, residual information, and in-loop filtering related information, and may include various syntax elements related to the information. The information encoded by the encoder of the encoding device may be output in the form of a bit stream. The bit stream may be sent to the decoding device via a network or a storage medium.

[0260] For example, the image information may include information about various parameter sets, such as an adaptive parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the image information may include information about the prediction mode of the current block, such as a coding unit syntax and a merge data syntax. Here, the sequence parameter set may include a combined inter-picture merging and intra-picture prediction (CIIP) enable flag (ciip enable flag) and an enable flag for a partition mode. The coding unit syntax may include a CU skip flag indicating whether a skip mode is applied to the current block.

[0261] According to an embodiment, as an example, in order to prevent repeated transmission of the same syntax, the encoding device may apply part or all of the regular_merge_flag signaling condition and related semantics, the MMVD_merge_flag signaling condition and related semantics, the merge_subblock_flag signaling condition and related semantics, and / or the CIIP flag signaling condition and related semantics based on the condition (MMVDAllowed) of allowing MMVD (MMVD mode), the condition (MergeSubBlockAllowed) of allowing the merging of sub-blocks (sub-block merge mode), the condition (MergeCIIPAllowed) of allowing the merging of CIIP (CIIP mode) and / or the condition (MergeTriangleAllowed) of allowing the merging of triangles (partition mode).

[0262] To this end, as an example, the merge data syntax may be configured as shown in Table 5 below.

[0263] [Table 5]

[0264]

[0265]

[0266] In Table 5, general_merge_flag[x0][y0] specifies whether inter prediction parameters for the current coding unit are inferred from neighboring inter prediction partitions. Array index x0, y0 specifies the position (x0, y0) of the top left luma sample of the considered coding block relative to the top left luma sample of the picture.

[0267] When general_merge_flag[x0][y0] does not exist, it is inferred as follows.

[0268] - If cu_skip_flag[x0][y0] is equal to 1, general_merge_flag[x0][y0] is inferred to be equal to 1.

[0269] Otherwise, general_merge_flag[x0][y0] is inferred to be equal to 0.

[0270] In Table 5, the condition (MMVDAllowed) for allowing MMVD (MMVD mode), the condition (MergeSubBlockAllowed) for allowing merging sub-blocks (sub-block merge mode), the condition (MergeCIIPAllowed) for allowing merging CIIP (CIIP mode) and / or the condition (MergeTriangleAllowed) for allowing merging triangles (partition mode) can be derived according to the following conditions.

[0271] If all of the following conditions are true, then the variable MMVDAllowed is set equal to true.

[0272] -general_merge_flag[x0][y0] is equal to 1

[0273] -sps_mmvd_enabled_flag equal to 1

[0274] -cbWidth*CbHeight is greater than 32

[0275] If all of the following conditions are true, then the variable MergeSubblockAllowed is set equal to true.

[0276] -general_merge_flag[x0][y0] is equal to 1

[0277] -MaxNumSubblockMergeCand>0

[0278] cbWidth is greater than or equal to 8, and cbHeight is greater than or equal to 8

[0279] If all of the following conditions are true, the variable MergeCIIPAllowed is set equal to true.

[0280] -general_merge_flag[x0][y0] is equal to 1

[0281] -sps_ciip_enabled_Flag equals 1

[0282] -cu_skip_flag[x0][y0] is equal to 0

[0283] -cbWidth * cbHeight greater than or equal to 64

[0284] -cbWidth is less than 128 and cbHeight is less than 128

[0285] If all of the following conditions are true, then MergeTriangleAllowed is set equal to true.

[0286] -general_merge_flag[x0][y0] is equal to 1

[0287] -sps_triangle_enalbed_Flag is equal to 1 and slice_type is equal to B

[0288] -NaxNumTriangleMergeCand is greater than or equal to 2

[0289] -cbWidth * cbHeight greater than or equal to 64

[0290] In the above conditions, MMVDAllowed indicates that MMVD is an allowable condition, and in this case, when the current block is not a 4×8 block or an 8×4 block, the condition based on the block size is satisfied. However, in the case where single-prediction MMVD is allowed in a 4×8 block and / or an 8×4 block, compression efficiency can be improved, and therefore the MMVDAllowed condition can be changed as follows.

[0291] If all of the following conditions are true, then the variable MMVDAllowed is set equal to true.

[0292] -general_merge_flag[x0][y0] is equal to 1

[0293] -sps_mmvd_enabled_flag equal to 1

[0294] Meanwhile, regular_merge_flag[x0][y0] equal to 1 specifies that the regular merge mode is used to generate inter prediction parameters for the current coding unit. Array index x0, y0 specifies the position (x0, y0) of the top left luma sample of the considered coding block relative to the top left luma sample of the picture.

[0295] Referring to Table 5, a normal merge flag may be included in the image information, and when at least one of the conditions based on the MMVD mode (MMVDAllowed), the conditions based on the sub-block merge mode (MergeSubBlockAllowed), the conditions based on the CIIP mode (MergeCIIPAllowed), and the conditions based on the partition mode (MergeTriangleAllowed) is 1, the normal merge flag may be signaled in the form of a bitstream.

[0296] As an example, in the case where CIIP is enabled, a regular merge flag may be included in the bitstream. The case where CIIP is enabled may be determined based on at least one of a general merge flag, a CIIP enable flag, a current block size, and a CU skip flag. For example, in the case where the general merge flag value is 1, the CIIP enable flag value is 1, the product of the height of the current block and the width of the current block is equal to or greater than 64, the height of the current block or the width of the current block is less than 128, or the skip flag value is 0, a regular merge flag may be included in the bitstream. In addition, in the case where all conditions based on the general merge flag, the CIIP enable flag, the current block size, and the CU skip flag are met, a regular merge flag may be included in the bitstream.

[0297] As another example, in the case where the partition mode is enabled, a regular merge flag may be included in the bitstream. The case where the partition mode is enabled may be determined based on at least one of a general merge flag, a partition mode enable flag indicating whether the partition mode is enabled, and information about the current block. For example, in the case where the general merge flag value is 1, the partition mode enable flag value is 1, the product of the height of the current block and the width of the current block is equal to or greater than 64, the slice type of the current block is a B slice, or the maximum number of partition mode candidates is equal to or greater than 2, the regular merge flag may be included in the bitstream. In addition, in the case where all of the above conditions are met, the regular merge flag may be included in the bitstream.

[0298] When regular_merge_flag[x0][y0] is not present in the merge data syntax, it is inferred as follows.

[0299] If all of the following conditions are true, regular_merge_flag[x0][y0] is inferred to be equal to 1.

[0300] -MMVDAllowed is equal to 0

[0301] -MergeSubBlockAllowed is equal to 0

[0302] -MergeCIIPAllowd equals 0

[0303] -MergeTriangleAllowed is equal to 0

[0304] Otherwise, regular_merge_flag[x0][y0] is inferred to be equal to 0.

[0305] Meanwhile, mmvd_merge_flag[x0][y0] equal to 1 specifies that merge mode with motion vector difference is used to generate inter prediction parameters for the current coding unit. Array index x0, y0 specifies the position (x0, y0) of the top left luma sample of the considered coding block relative to the top left luma sample of the picture.

[0306] Referring to Table 5, when at least one value of the MMVD mode-based condition (MMVDAllowed), the sub-block merge mode-based condition (MergeSubBlockAllowed), the CIIP mode-based condition (MergeCIIPAllowd), and the partition mode-based condition (MergeTriangleAllowed) is 1, the MMVD merge flag may be included in the image information and may be signaled in the form of a bitstream.

[0307] When mmvd_merge_flag[x0][y0] is not present in the merge data syntax, it is inferred as follows.

[0308] mmvd_merge_flag[x0][y0] is inferred to be equal to 1 if all of the following conditions are true.

[0309] -regular_merge_flag[x0][y0] is equal to 0

[0310] -MMVDAllowed is equal to 0

[0311] -MergeSubBlockAllowed is equal to 0

[0312] -MergeCIIPAllowd equals 0

[0313] -MergeTriangleAllowed is equal to 0

[0314] Otherwise, mmvd_merge_flag[x0][y0] is inferred to be equal to 0.

[0315] mmvd_cand_flag[x0][y0] specifies whether the first (0) or second (1) candidate in the merge candidate list is used with the motion vector difference derived from mmvd_distance_idx[x0][y0] and mmvd_direction_idx[x0][y0]. The array index x0, y0 specifies the position (x0, y0) of the top-left luma sample of the considered coding block relative to the top-left luma sample of the picture. When mmvd_cand_flag[x0][y0] is not present, it is inferred to be equal to 0.

[0316] mmvd_distance_idx[x0][y0] specifies the index used to derive MmvdDistance[x0][y0], as specified in Table 3. The array index x0, y0 specifies the position (x0, y0) of the top-left luma sample of the considered coding block relative to the top-left luma sample of the picture.

[0317] mmvd_direction_idx[x0][y0] specifies the index used to derive MmvdSign[x0][y0], as specified in Table 4. The array index x0, y0 specifies the position (x0, y0) of the top-left luma sample of the considered coding block relative to the top-left luma sample of the picture.

[0318] The two components of the combined MVD offset MmvdOffset[x0][y0] are derived as in Equation 1.

[0319] merge_subblock_flag[x0][y0] specifies whether subblock-based inter prediction parameters for the current coding unit are inferred from neighboring blocks. Array index x0, y0 specifies the position (x0, y0) of the top-left luma sample of the considered coding block relative to the top-left luma sample of the picture.

[0320] Referring to Table 5, when at least one value of the condition based on the sub-block merge mode (MergeSubBlockAllowed), the condition based on the CIIP mode (MergeCIIPAllowwed), and the condition based on the partition mode (MergeTriangleAllowed) is 1, the merge sub-block flag may be included in the image information and may be signaled in the form of a bitstream.

[0321] When merge_subblock_flag[x0][y0] is not present in the merge data syntax, the inference is as follows.

[0322] merge_subblock_flag[x0][y0] is inferred to be equal to 1 if all of the following conditions are true.

[0323] -regular_merge_flag[x0][y0] is equal to 0

[0324] -mmvd_merge_flag[x0][y0] is equal to 0

[0325] -MergeSubBlockAllowed is equal to 0

[0326] -MergeCIIPAllowed equals 0

[0327] -MergeTriangleAllowed is equal to 0

[0328] Otherwise, merge_subblock_flag[x0][y0] is inferred to be equal to 0.

[0329] merge_subblock_idx[x0][y0] specifies the merge candidate index of the sub-block based merge candidate list, where x0, y0 specifies the position (x0, y0) of the top-left luma sample of the considered coding block relative to the top-left luma sample of the picture.

[0330] When merge_subblock_idx[x0][y0] does not exist, it is inferred to be equal to 0.

[0331] Meanwhile, ciip_flag[x0][y0] specifies whether combined inter-picture merging and intra-picture prediction is applied to the current coding unit. Array index x0, y0 specifies the position (x0, y0) of the top left luma sample of the considered coding block relative to the top left luma sample of the picture.

[0332] Referring to Table 5, the CIIP flag may be included in the image information, and in the case where at least one value of a CIIP mode-based condition (MergeCIIPAllowed) and a partition mode-based condition (MergeTriangleAllowed) is 1, the CIIP flag may be signaled in the form of a bitstream.

[0333] For example, in the case where the partition mode is enabled, the CIIP flag may be included in the bitstream. The case where the partition mode is enabled may be determined based on at least one of a general merge flag, a partition mode enable flag indicating whether the partition mode is enabled, and information about the current block. For example, in the case where the general merge flag value is 1, the partition mode enable flag value is 1, the product of the height of the current block and the width of the current block is equal to or greater than 64, the slice type of the current block is a B slice, or the maximum number of partition mode candidates is equal to or greater than 2, the CIIP flag may be included in the bitstream. In addition, in the case where all of the above conditions are met, the CIIP flag may be included in the bitstream.

[0334] When ciip_flag[x0][y0] does not exist, the inference is as follows.

[0335] If all of the following conditions are true, ciip_flag[x0][y0] is set equal to 1.

[0336] -MergeCIIPAllowed equals 0

[0337] -MergeTriangleAllowed is equal to 0

[0338] - Otherwise, ciip_flag[x0][y0] is set equal to 0.

[0339] When ciip_flag[x0][y0] is equal to 1, the variable IntraPredModeY[x][y] is set equal to INTRA_PLANAR, where x = xCb..xCb + cbWidth − 1 and y = yCb..yCb + cbHeight - 1.

[0340] The variable MergeTriangleFlag[x0][y0] specifies whether triangle-based motion compensation is used to generate prediction samples for the current coding unit when decoding a B slice, which is derived as follows.

[0341] If all of the following conditions are true, MergeTriangleFlag[x0][y0] is set equal to 1.

[0342] -MergeTriangleAllowed is equal to 1

[0343] -regular_merge_flag[x0][y0] is equal to 0

[0344] -mmvd_merge_flag[x0][y0] is equal to 0

[0345] -merge_subblock_flag[x0][y0] is equal to 0

[0346] -ciip_flag[x0][y0] is equal to 0

[0347] Otherwise, MergeTriangleFlag[x0][y0] is equal to 0.

[0348] Fig.10 and Fig.11 An example of a video / image decoding method including an inter-frame prediction method and associated components according to an embodiment of this document is schematically shown.

[0349] Fig.10 The decoding method disclosed in can be Figure 3 and Fig.11 Specifically, for example, the entropy decoder 310 of the decoding device may be used to perform Fig.10 S1000 of the decoding device 300, and S1010 to S1020 may be performed in the predictor 330 of the decoding device 300. In this document, Fig.10 The decoding method disclosed in may include the above-mentioned embodiments.

[0350] The decoding device may obtain at least one of a CIIP enable flag, a CU skip flag, and a partition mode enable flag from a bitstream (S1000). In addition, the prediction mode of the current block may be determined based on the CIIP enable flag, the CU skip flag, and the partition mode enable flag (S1010). Specifically, the entropy decoder 310 of the decoding device may obtain at least one of a CIIP enable flag, a CU skip flag, and a partition mode enable flag from a bitstream. Figure 2 The residual information and the information about the prediction mode are derived from the signal received by the encoding device. Here, the information about the prediction mode may be referred to as prediction related information. The information about the prediction mode may include inter / intra prediction distinction information, inter prediction mode information, etc., and may include various syntax elements related thereto.

[0351] In the bitstream, image information may be included, which includes information about various parameter sets such as adaptive parameter set (APS), picture parameter set (PPS), sequence parameter set (SPS) or video parameter set (VPS). The image information may also include information about the prediction mode for the current block, such as coding unit syntax and merge data syntax. The sequence parameter set may include a CIIP enable flag and an enable flag for partition mode. The coding unit syntax may include a CU skip flag indicating whether the skip mode is applied to the current block.

[0352] The predictor 330 of the decoding device may configure the motion information of the current block based on the prediction mode for the current block. For example, the predictor 330 of the decoding device may configure a motion information candidate list (or a merge candidate list) for the current block based on information about the prediction mode obtained from the bitstream. In addition, the predictor 330 of the decoding device may select a merge candidate from the motion information candidate list based on candidate selection information (merge index) obtained from the bitstream, and may use the motion information of the selected merge candidate to derive the motion information of the current block.

[0353] When deriving the motion information of the current block, the predictor of the decoding device may generate a prediction sample of the current block based on the prediction mode of the current block and the motion information of the current block, etc. ( S1020 ).

[0354] Meanwhile, the residual processor 320 of the decoding device may generate residual samples based on residual information obtained from the bitstream.

[0355] The adder 340 of the decoding device may generate a reconstructed sample based on the prediction sample generated by the predictor 330 and the residual sample generated by the residual processor 320. A reconstructed picture may be generated based on the reconstructed sample. Thereafter, as needed, in order to improve the subjective / objective picture quality, an in-loop filtering process such as deblocking filtering, SAO and / or ALF process may be applied to the reconstructed picture.

[0356] As an embodiment, when determining the prediction mode of the current block, when at least one of the conditions based on the MMVD mode (MMVDAllowed), the conditions based on the sub-block merge mode (MergeSubBlockAllowed), the conditions based on the CIIP mode (MergeCIIPAllowed), and the conditions based on the partition mode (MergeTriangleAllowed) is 1, the predictor of the decoding device can obtain or parse a regular merge flag from the bitstream.

[0357] As an example, in the case where CIIP is enabled, the decoding device can parse the conventional merge flag from the bitstream. The case where CIIP is enabled can be determined based on at least one of the general merge flag, the CIIP enable flag, the current block size, and the CU skip flag. For example, in the case where the general merge flag value is 1, the CIIP enable flag value is 1, the product of the height of the current block and the width of the current block is equal to or greater than 64, the height of the current block or the width of the current block is less than 128, or the skip flag value is 0, the decoding device can determine that CIIP is enabled. In addition, in the case where all conditions based on the general merge flag, the CIIP enable flag, the current block size, and the CU skip flag are met, the decoding device can determine that CIIP is enabled.

[0358] As another example, in the case where the partition mode is enabled, the decoding device may parse a regular merge flag from the bitstream. The case where the partition mode is enabled may be determined based on at least one of a general merge flag, a partition mode enable flag indicating whether the partition mode is enabled, and information about the current block. For example, the decoding device may determine that the partition mode is enabled when the general merge flag value is 1, the partition mode enable flag value is 1, the product of the height of the current block and the width of the current block is equal to or greater than 64, the slice type of the current block is a B slice, or the maximum number of partition mode candidates is equal to or greater than 2. In addition, when all of the above conditions are met, the decoding device may determine that the partition mode is enabled.

[0359] At the same time, when determining the prediction mode for the current block, when at least one value of the MMVD mode-based condition (MMVDAllowed), the sub-block merge mode-based condition (MergeSubBlockAllowed), the CIIP mode-based condition (MergeCIIPAllowed), and the partition mode-based condition (MergeTriangleAllowed) is 1, the predictor of the decoding device can obtain or parse the MMVD merge flag from the bitstream.

[0360] In addition, when determining the prediction mode of the current block, when at least one value of the condition based on the sub-block merge mode (MergeSubBlockAllowed), the condition based on the CIIP mode (MergeCIIPAllowed), and the condition based on the partition mode (MergeTriangleAllowed) is 1, the predictor of the decoding device can obtain or parse the merge sub-block flag from the bitstream.

[0361] In addition, when determining the prediction mode for the current block, the predictor of the decoding device may obtain or parse the CIIP flag from the bitstream when at least one of the conditions based on the CIIP mode (MergeCIIPAllowed) and the conditions based on the partition mode (MergeTriangleAllowed) is 1. As an example, when the partition mode is enabled, the decoding device may parse the CIIP flag from the bitstream. The case of enabling the partition mode may be determined based on at least one of the general merge flag, the partition mode enable flag indicating whether the partition mode is enabled, and the information about the current block. For example, the decoding device may determine that the partition mode is enabled when the general merge flag value is 1, the partition mode enable flag value is 1, the product of the height of the current block and the width of the current block is equal to or greater than 64, the slice type of the current block is a B slice, or the maximum number of partition mode candidates is equal to or greater than 2. In addition, when all of the above conditions are met, the decoding device may determine that the partition mode is enabled.

[0362] Although the above exemplary system has been described based on a flowchart that lists steps or blocks in order, the steps of the present disclosure are not limited to a specific order. Therefore, relative to the above steps, a certain step can be performed in different steps or in a different order or simultaneously. In addition, it will be understood by those of ordinary skill in the art that the steps of the flowchart are not exclusive. On the contrary, within the scope of the present disclosure, another step can be included, or one or more steps can be deleted.

[0363] The above-mentioned method according to the present disclosure may be in the form of software, and the encoding device and / or decoding device according to the present disclosure may be included in a device for performing image processing (eg, a TV, a computer, a smart phone, a set-top box, a display device, etc.).

[0364] When the embodiments are implemented in software in the present disclosure, the above methods can be implemented using modules (processes, functions, etc.) that perform the above functions. The module can be stored in a memory and executed by a processor. The memory can be arranged internally or externally to the processor and connected to the processor using various well-known means. The processor may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and / or data processors. The memory may include a read-only memory (ROM), a random access memory (RAM), flash memory, a memory card, a storage medium, and / or other storage devices. That is, the embodiments described herein may be implemented and executed on a processor, a microprocessor, a controller, or a chip. For example, the functional units shown in each of the accompanying drawings may be implemented and executed on a computer, a processor, a microprocessor, a controller, or a chip. In this case, information (e.g., information about instructions) or algorithms for implementation may be stored in a digital storage medium.

[0365] In addition, the decoding device and encoding device to which the present disclosure is applied may include multimedia broadcast transceivers, mobile communication terminals, home theater video devices, digital theater video devices, surveillance cameras, video chat devices, and real-time communication devices such as video communication, mobile streaming devices, storage media, cameras, video on demand (VoD) service providers, over-the-top (OTT) video devices, Internet streaming service providers, 3D video devices, virtual reality (VR) devices, augmented reality (AR) devices, image phone video devices, vehicle terminals (e.g., vehicle (including autonomous vehicle) terminals, aircraft terminals, or ship terminals) and medical video devices, and can be used to process image signals or data signals. For example, OTT video devices may include game consoles, Blu-ray players, TVs connected to the Internet, home theater systems, smart phones, tablet PCs, and digital video recorders (DVRs), etc.

[0366] In addition, the processing method to which the present disclosure is applied can be generated in the form of a program executed by a computer and can be stored in a computer-readable recording medium. Multimedia data having a data structure according to the present disclosure can also be stored in a computer-readable recording medium. Computer-readable recording media include all kinds of storage devices and distributed storage devices in which computer-readable data is stored. Computer-readable recording media can be, for example, a Blu-ray disc (BD), a universal serial bus (USB), a ROM, a PROM, an EPROM, an EEPROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device. Computer-readable recording media also include media embodied in the form of a carrier wave (e.g., transmission via the Internet). In addition, the bit stream generated by the encoding method can be stored in a computer-readable recording medium or sent via a wired or wireless communication network.

[0367] In addition, the embodiments of the present disclosure may be implemented as a computer program product based on a program code, and the program code may be executed on a computer by the embodiments of the present disclosure document. The program code may be stored on a computer-readable carrier.

[0368] Fig.12 An example of a content streaming system to which the embodiments disclosed in this document can be applied is shown.

[0369] Reference Fig.12 , a content streaming system to which the embodiments of this document are applied may basically include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0370] The encoding server compresses the content input from the multimedia input device (such as a smart phone, camera, and camcorder, etc.) into digital data to generate a bit stream and sends the bit stream to the streaming server. As another example, when the multimedia input device (such as a smart phone, camera, and camcorder, etc.) directly generates the bit stream, the encoding server can be omitted.

[0371] A bitstream may be generated by an encoding method or a bitstream generation method to which an embodiment of this document is applied, and a streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

[0372] The streaming server sends multimedia data to the user device based on the user request through the web server, and the web server is used as a medium to inform the user which services are available. When the user requests the desired service from the web server, the web server delivers the user's request to the streaming server, and the streaming server sends the multimedia data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server is used to control the command / response between the devices in the content streaming system.

[0373] The streaming server can receive content from a media storage and / or encoding server. For example, when receiving content from an encoding server, the content can be received in real time. In this case, in order to provide a smooth streaming service, the streaming server can store the bitstream for a predetermined time.

[0374] Examples of user devices may include mobile phones, smart phones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation, tablet PCs, tablet PCs, ultrabooks, wearable devices (e.g., smart watches, smart glasses, head-mounted displays), digital TVs, desktop computers, digital signage, etc.

[0375] Each server in the content streaming system may operate as a distribution server, in which case data received from each server may be distributed.

Claims

1. A decoding method performed by a decoding device, the method comprising: obtain, from a bitstream, a combined inter-picture merging and intra-picture prediction (CIIP) enable flag indicating whether a CIIP is enabled and a partition mode enable flag indicating whether a partition mode in which prediction is performed by partitioning a current block into two partitions is enabled; Determining a prediction mode of the current block based on the CIIP enable flag and the partition mode enable flag; as well as generating a prediction sample of the current block based on the prediction mode, It is characterized in that The determining comprises obtaining a normal merge flag from the bitstream based on the CIIP enable flag and the partition mode enable flag, wherein the normal merge flag is obtained from the bitstream based on the case where the value of the CIIP enable flag is equal to 1 and the value of the partition mode enable flag is equal to 1, and Therein, the conventional merge flag is included in the merge data syntax.

2. A coding method performed by a coding device, the method comprising: Determine the prediction mode of the current block; deriving a prediction sample of the current block based on the prediction mode; deriving residual samples based on the prediction samples; as well as encoding image information including information about the prediction mode generated based on the prediction mode and residual information generated based on the residual samples, wherein the information about the prediction mode includes a combined inter-picture merging and intra-picture prediction (CIIP) enable flag indicating whether a CIIP is enabled and a partition mode enable flag indicating whether a partition mode in which prediction is performed by dividing the current block into two partitions is enabled, It is characterized in that The image information includes a conventional merge flag based on the CIIP enable flag and the partition mode enable flag, wherein, based on the case where the value of the CIIP enable flag is equal to 1, or the value of the partition mode enable flag is equal to 1, the normal merge flag is included in the image information, and Therein, the conventional merge flag is included in the merge data syntax.

3. A non-transitory computer-readable digital storage medium storing a bitstream generated by a method, the method comprising: Determine the prediction mode of the current block; deriving a prediction sample of the current block based on the prediction mode; deriving residual samples based on the prediction samples; as well as encoding image information including information about the prediction mode generated based on the prediction mode and residual information generated based on the residual samples, wherein the information about the prediction mode includes a combined inter-picture merging and intra-picture prediction (CIIP) enable flag indicating whether a CIIP is enabled and a partition mode enable flag indicating whether a partition mode in which prediction is performed by dividing the current block into two partitions is enabled, It is characterized in that The image information includes a conventional merge flag based on the CIIP enable flag and the partition mode enable flag, wherein, based on the case where the value of the CIIP enable flag is equal to 1, or the value of the partition mode enable flag is equal to 1, the normal merge flag is included in the image information, and Therein, the conventional merge flag is included in the merge data syntax.

4. A method for transmitting image data, the method comprising: Obtaining a bitstream, wherein the bitstream is generated based on: determining a prediction mode of a current block, deriving prediction samples of the current block based on the prediction mode, deriving residual samples based on the prediction samples; and encoding image information including information about the prediction mode generated based on the prediction mode and residual information generated based on the residual samples; and sending said data comprising said bit stream, wherein the information about the prediction mode includes a combined inter-picture merging and intra-picture prediction (CIIP) enable flag indicating whether a CIIP is enabled and a partition mode enable flag indicating whether a partition mode in which prediction is performed by dividing the current block into two partitions is enabled, It is characterized in that The image information includes a conventional merge flag based on the CIIP enable flag and the partition mode enable flag, wherein, based on the case where the value of the CIIP enable flag is equal to 1, or the value of the partition mode enable flag is equal to 1, the normal merge flag is included in the image information, and Therein, the conventional merge flag is included in the merge data syntax.

Images