Method and apparatus for removing redundant syntax from merged data syntax

Abstract

The invention relates to a method and apparatus for removing redundant syntax from merged data syntax. A decoding method performed by a decoding device according to the present document comprises the steps of: determining a prediction mode of a current block on the basis of information on the prediction mode obtained from a bitstream; constructing a merge candidate list based on the prediction mode; deriving motion information of the current block based on the merge candidate list; and generating a prediction sample of the current block based on the motion information, in which the bitstream includes a CIIP availability flag regarding whether combined inter-picture merge and intra-picture prediction (CIIP) are available, and the determining step may include obtaining a conventional merge flag from the bitstream based on the CIIP availability flag.

Description

[0001] This application is a divisional application of a patent application with the application number 202080045511.9 (PCT / KR2020 / 008154), an international filing date of June 23, 2020, and an invention title of "Method and Apparatus for Removing Redundant Syntax from Merged Data Syntax", which was filed on December 21, 2021. Technical Field

[0002] The technology relates to a method and apparatus for removing redundant syntax from merged data syntax in a video / image compilation system. Background Art

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

[0004] In addition, there has been a growing interest and demand for virtual reality (VR) and augmented reality (AR) content as well as immersive media such as holograms; and there has also been a growing broadcast of images / videos (e.g., game images / videos) that exhibit image / video characteristics different from actual images / videos.

[0005] Therefore, there is a need for efficient image / video compression technologies to effectively compress, transmit, store, or play high-resolution and high-quality images / videos that exhibit various characteristics as described above. Summary of the Invention

[0006] Technical Problem

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

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

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

[0010] Another aspect of the present disclosure provides a method and apparatus for effectively signaling information about a merge mode during inter-frame prediction.

[0011] Another aspect of this document provides a method and apparatus for removing redundant syntax from merged data syntax.

[0012] Technical Solution

[0013] According to an embodiment of this document, a decoding method performed by a decoding device includes: determining a prediction mode of a current block based on information about a prediction mode obtained from a bitstream; configuring a merge candidate list based on the prediction mode; deriving motion information of the current block based on the merge candidate list; and generating prediction samples of the current block based on the motion information, where the bitstream includes information about a CIIP availability flag indicating whether combined inter-picture merge and intra-picture prediction (CIIP) is available, and where the determining includes obtaining a regular merge flag from the bitstream based on the CIIP availability flag.

[0014] According to an embodiment of this document, an encoding method performed by an encoding device includes: determining a prediction mode of a current block; configuring a merge candidate list based on the prediction mode; deriving motion information of the current block based on the merge candidate list; deriving prediction samples of the current block based on the motion information; 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, where the image information includes a CIIP availability flag indicating whether CIIP is available, and where the image information includes a regular merge flag based on the CIIP availability flag.

[0015] According to another embodiment of this document, there is provided a computer-readable digital storage medium containing information that causes a decoding device to perform a decoding method, the decoding method including: determining a prediction mode of a current block based on information about a prediction mode obtained from a bitstream; configuring a merge candidate list based on the prediction mode; deriving motion information of the current block based on the merge candidate list; and generating prediction samples of the current block based on the motion information, where the bitstream includes information about a CIIP availability flag indicating whether combined inter-picture merge and intra-picture prediction (CIIP) is available, and where the determining includes obtaining a regular merge flag from the bitstream based on the CIIP availability flag.

[0016] Beneficial effects

[0017] According to an embodiment of the present disclosure, the overall image / video compression efficiency can be enhanced.

[0018] According to an embodiment of the present disclosure, inter-frame prediction can be effectively performed.

[0019] According to an embodiment of the present disclosure, unnecessary syntax signaling can be effectively removed during inter-frame prediction.

[0020] According to an embodiment of the present disclosure, information about the merge mode can be effectively signaled during inter-frame prediction.

[0021] According to an embodiment of the present disclosure, redundant syntax can be removed from the merged data syntax. Description of the Drawings

[0022] Figure 1 Schematically illustrates an example of a video / image compilation system to which embodiments of the present disclosure can be applied.

[0023] Figure 2 Is a diagram schematically depicting the configuration of a video / image encoding device to which embodiments of the present disclosure can be applied.

[0024] Figure 3 Is a diagram schematically depicting the configuration of a video / image decoding device to which embodiments of the present disclosure can be applied.

[0025] Figure 4 Is a diagram schematically representing an inter-frame predictor in an encoding device.

[0026] Figure 5 Is a diagram schematically representing an inter-frame predictor in a decoding device.

[0027] Figure 6 Is a diagram illustrating spatial candidates that can be used for inter-frame prediction.

[0028] Figure 7 Is a diagram illustrating temporal candidates that can be used for inter-frame prediction.

[0029] Figure 8 Is a diagram illustrating sub-block-based temporal motion vector prediction processing that can be used in inter-frame prediction.

[0030] Figure 9 Is a diagram illustrating partition patterns that can be applied to inter-frame prediction.

[0031] Figure 10 and 11 Schematically represents an example of a video / image encoding method including an inter-frame prediction method according to an embodiment of this document and associated components.

[0032] Figure 12 and 13 Schematically represents an example of a video / image decoding method including an inter-frame prediction method according to an embodiment of this document and associated components.

[0033] Figure 14 Illustrates an example of a content stream system to which embodiments disclosed in the present disclosure can be applied. Detailed Description of the Embodiments

[0034] 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 disclosure. The terms used in this document are only for describing specific embodiments and are not intended to limit the embodiments of this document. Expressions in the singular include expressions in the plural as long as they are 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 thus 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.

[0035] Meanwhile, each configuration of the accompanying drawings described in this document is for facilitating the independent illustration of functions as features different from each other, and does not mean that each configuration is implemented by mutually different hardware or different software. For example, two or more configurations can be combined to form one configuration, and one configuration can also be divided into multiple configurations. Embodiments of combining and / or separating configurations are included within the scope of the disclosure of this document without departing from the gist of the disclosure.

[0036] In this document, the symbols " / " and "," should be interpreted as "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". Additionally, the expression "A / B / C" means "at least one of A, B, and / or C". Furthermore, 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" can mean "A and / or B". Additionally, "A, B" can mean "A and / or B". Additionally, "A / B / C" can mean "at least one of A, B, and / or C". Additionally, "A / B / C" can mean "at least one of A, B, and / or C".)

[0037] Furthermore, in this document, the term "or" should be interpreted as "and / or". For example, the expression "A or B" can mean 1) only "A", 2) only "B", and / or 3) "both A and B". In other words, the term "or" in this document can mean "additionally or alternatively". (Furthermore, in the document, the term "or" should be interpreted as indicating "and / or". For example, the expression "A or B" can 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 "additionally or alternatively".)

[0038] This document relates to video / image coding. For example, the methods / embodiments disclosed in this document can be applied to the methods disclosed in the Versatile Video Coding (VVC) standard. In addition, the methods / embodiments disclosed in this document can be applied to the methods disclosed in the Essential Video Coding (EVC) standard, the AOMedia Video 1 (AV1) standard, the Second Generation Audio Video Coding Standard (AVS2), or the next-generation video / image coding standards (e.g., H.267, H.268, etc.).

[0039] This document presents various embodiments of video / image coding, and unless otherwise specified, the above embodiments can also be executed in combination with each other.

[0040] Hereinafter, examples of this embodiment will be described in detail with reference to the accompanying drawings. In addition, in all the 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 The figure illustrates an example of a video / image coding system to which the embodiments of the present disclosure can be applied.

[0042] Referring to Figure 1 , the video / image coding system may include a source device and a receiving device. The source device may transmit encoded video / image information or data in the form of a file or a 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 obtain video / images through processes such as capturing, synthesizing, or generating video / images. 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 video / images, etc. For example, the video / image generating device may include a computer, a tablet computer, and a smart phone, and may generate (electronically) video / images. For example, virtual video / images may be generated by a computer or the like. In this case, the video / image capturing process may be replaced by a process of generating relevant data.

[0045] The encoding device can encode the input video / image. For compression and compilation 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 bitstream.

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

[0047] The decoding device can decode the 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 can render the decoded video / image. The rendered video / image can be displayed through a display.

[0049] In this document, at least one of quantization / dequantization and / or transformation / inverse transformation can be omitted. In the case of omitting quantization / dequantization, the quantized transform coefficients can be referred to as transform coefficients. In the case of omitting transformation / inverse transformation, the transform coefficients can be referred to as coefficients or residual coefficients, or can still be referred to as transform coefficients in a unified expression.

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

[0051] 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 forms part of a picture in terms of compilation. A slice / tile may include one or more Compilation Tree Units (CTUs). A picture can consist of one or more slices / tiles. A picture can consist of one or more tile groups. A tile group can include one or more tiles. A brick can represent a rectangular region of CTU rows within a tile in a picture (a brick can represent a rectangular region of CTU rows within a tile in a picture). A tile can be partitioned into multiple bricks, and each brick can be constructed using one or more CTU rows within the tile (a tile can be partitioned into multiple bricks, and each brick can be constructed using one or more CTU rows within the tile). A tile that is not partitioned into multiple bricks can also be referred to as a brick. Tile scan can represent a specific order of sorting the CTUs that partition a picture, where the CTUs can be sorted in CTU raster scan order within a tile, and the bricks within a tile can be sorted continuously in the raster scan of the tile of the tile, and the tiles in a picture can be sorted continuously in the raster scan of the tile of the picture (tile scan is a specific order of sorting the CTUs that partition a picture, where the CTUs are sorted continuously in CTU raster scan order within a tile, the bricks within a tile are sorted continuously in the raster scan of the tile of the tile, and the tiles in a picture are sorted continuously in the raster scan of the tile of the picture). A tile is a rectangular region of CTUs within a specific tile column and a specific tile row in a picture (a tile is a rectangular region of CTUs within a specific tile column and a specific tile row in a picture). A tile column is a rectangular region of CTUs that has a height equal to the height of the picture and a width that can be specified by a syntax element in the picture parameter set (a tile column is a rectangular region of CTUs that has a height equal to the height of the picture and a width specified by a syntax element in the picture parameter set). A tile row is a rectangular region of CTUs that has a width specified by a syntax element in the picture parameter set and a height that can be equal to the height of the picture (a tile row is a rectangular region of CTUs that has a height specified by a syntax element in the picture parameter set and a width equal to the width of the picture). Tile scan can represent a specific order of sorting the CTUs that partition a picture, and the CTUs can be sorted continuously in CTU raster scan order within a tile, and the tiles in a picture can be sorted continuously in the raster scan of the tile of the picture (tile scan is a specific order of sorting the CTUs that partition a picture, where the CTUs are sorted continuously in CTU raster scan order within a tile while the tiles in a picture are sorted continuously in the raster scan of the tile of the picture). A slice can include an integer number of tiles of a picture, and this integer number of tiles can be included in a single NAL unit (a slice includes an integer number of tiles of a picture that can be contained in only a single NAL unit).A slice can be constructed using multiple complete tiles, or can be a sequence of consecutive complete tile blocks of a single tile (a slice can consist of multiple complete tile blocks, or only of a sequence of consecutive complete tile blocks of a single tile). In this document, tile groups and slices can be used interchangeably with each other. For example, in this document, a tile group / tile group header can be referred to as a slice / slice header.

[0052] A pixel or pel can mean the smallest unit that makes up a picture (or image). Additionally, the term "sample" can be used as a counterpart to a pixel. A sample can generally represent a pixel or a pixel value, and can represent only the pixel / pixel value of the luminance component or only the pixel / pixel value of the chrominance component.

[0053] A unit can represent the basic unit of image processing. A unit can include at least one of a specific region of a picture and information related to that region. A unit can include one luminance block and two chrominance (e.g., cb, cr) blocks. In some cases, a unit can be used interchangeably with terms such as a block or a region. In general, an M×N block can include a set (or array) of samples (or a sample array) or transform coefficients in M columns and N rows.

[0054] Figure 2 is a diagram schematically showing the configuration of a video / image coding device to which the present disclosure can be applied. Hereinafter, a device referred to as a video coding device can include an image coding device.

[0055] Referring to Figure 2 , the coding device 200 can include and be configured with an image splitter 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 can include an inter-frame predictor 221 and an intra-frame predictor 222. The residual processor 230 can include a transformer 232, a quantizer 233, an inverse quantizer 234, and an inverse transformer 235. The residual processor 230 can also include a subtractor 231. The adder 250 can be referred to as a reconstructor or a reconstructed block generator. According to an embodiment, the image splitter 210, the predictor 220, the residual processor 230, the entropy encoder 240, the adder 250, and the filter 260 described above can be configured by one or more hardware components (e.g., an encoder chipset or a processor). Additionally, the memory 270 can include a decoded picture buffer (DPB), and can also be configured by a digital storage medium. The hardware components can also include the memory 270 as an internal / external component.

[0056] The image splitter 210 may split an input image (or picture, frame) input to the encoding device 200 into one or more processing units. As an example, a processing unit may be referred to as a coding unit (CU). In this case, coding units may be recursively split from a coding tree unit (CTU) or a largest coding unit (LCU) according to a quadtree binary tree ternary tree (QTBTTT) structure. For example, a coding unit may be split into multiple 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 applied first, 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 units that are no longer split. In this case, based on the coding efficiency according to image characteristics, etc., the largest coding unit may be directly used as the final coding unit, or, as needed, the coding units may be recursively split into coding units with a deeper depth so that the coding units with the optimal size can be used as the final coding units. Here, the coding process may include processes such as prediction, transform, and reconstruction described later. As another example, a processing unit may also 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 units. The prediction unit may be a unit for sample prediction, and the transform unit may be a unit for deriving transform coefficients and / or a unit for deriving a residual signal from the transform coefficients.

[0057] In some cases, a unit may be used interchangeably with terms such as a block or a region. In general, an M×N block may represent a set of samples or transform coefficients consisting of M columns and N rows. Samples generally may represent pixels or pixel values, which may represent only the pixels / pixel values of the luminance component or only the pixels / pixel values of the chrominance component. Samples may be used as a term corresponding to pixels or pels of a picture (or image).

[0058] The encoding device 200 can generate a residual signal (residual block, residual sample array) by subtracting the prediction signal (prediction block, prediction sample array) output from the inter-frame predictor 221 or the intra-frame 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 encoder 200 can be referred to as the subtractor 231. The predictor can perform prediction on the block to be processed (hereinafter, referred to as the current block) and generate a prediction block including the prediction samples of the current block. The predictor can determine whether to apply intra-frame prediction or inter-frame prediction in units of the current block or CU. As will be 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. The information about the prediction can be encoded in the entropy encoder 240 and output in the form of a bitstream.

[0059] The intra-frame predictor 222 can predict the current block by referring to the samples in the current picture. Depending on the prediction mode, the samples referred to can be located near the current block or can be separated. In intra-frame prediction, the prediction mode can include a plurality of non-directional modes and a plurality of directional modes. For example, the non-directional modes can include the DC mode and the planar mode. For example, depending on the level of detail of the prediction direction, the directional modes can include 33 directional prediction modes or 65 directional prediction modes. However, this is only an example, and more or fewer directional prediction modes can be used according to the settings. The intra-frame predictor 222 can use the prediction mode applied to the neighboring block to determine the prediction mode applied to the current block.

[0060] The inter - frame predictor 221 can derive a prediction block of a 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 transmitted 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 neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can also include inter - frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter - frame prediction, neighboring blocks can 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 can be the same or different. The temporal neighboring block can be referred to as a collocated reference block, a collocated CU (colCU), etc., and the reference picture including the temporal neighboring block can be referred to as a collocated picture (colPic). For example, the inter - frame predictor 221 can configure a motion information candidate list based on 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 - frame prediction can be performed based on various prediction modes, and for example, in the skip mode and the merge mode, the inter - frame predictor 221 can use the motion information of neighboring blocks as the motion information of the current block. In the skip mode, different from the merge mode, the residual signal may not be sent. The motion vector prediction (MVP) mode can use the motion vector of a neighboring block as a motion vector predictor and signal the motion vector difference to indicate the motion vector of the current block.

[0061] The predictor 220 can generate a prediction signal based on various prediction methods described later. For example, the predictor can not only apply intra - frame prediction or inter - frame prediction to predict a block, but also apply both intra - frame prediction and inter - frame prediction simultaneously. This can be referred to as combined inter - frame and intra - frame prediction (CIIP). In addition, the predictor can be based on the intra - block copy (IBC) prediction mode or the palette mode to perform prediction on a block. The IBC prediction mode or the palette mode can be used for content image / video compilation such as games, for example, screen content compilation (SCC). IBC basically performs prediction in the current picture, but it can be performed similarly to inter - frame prediction because it derives a reference block in the current picture. That is, IBC can use at least one of the inter - frame prediction techniques described in this document. The palette mode can be regarded as an example of intra - frame compilation or intra - frame prediction. When the palette mode is applied, the sample values in the picture can be signaled based on the information about the palette table and the palette index.

[0062] The prediction signal generated by the predictor (including the inter - frame predictor 221 and / or the intra - frame predictor 222) can be used to generate a reconstructed signal or to generate a residual signal.

[0063] The transformer 232 can generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique can 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 the graph. CNT means a transform obtained based on a prediction signal generated by using all previously reconstructed pixels. Additionally, the transform process can also be applied to a pixel block of a square with the same size, and can also be applied to a block with a variable size other than a square. The quantizer 233 can quantize the transform coefficients to send the quantized transform coefficients to the entropy encoder 240, and the entropy encoder 240 can encode the quantized signal (information about the quantized transform coefficients) into a bitstream. The information about the quantized transform coefficients can be referred to as residual information.

[0064] The quantizer 233 can rearrange the quantized transform coefficients in block form into a one-dimensional vector based on the coefficient scan order, and also generate information about the quantized transform coefficients based on the quantized transform coefficients in one-dimensional vector form.

[0065] The entropy encoder 240 can 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 can also encode, together or separately, information necessary for the reconstructed video / image other than the quantized transform coefficients (e.g., values of syntax elements, etc.). The encoded information (e.g., encoded video / image information) can be sent or stored in the form of a bitstream in units of network abstraction layer (NAL). The video / image information can also include information about various parameter sets, such as adaptation parameter set (APS), picture parameter set (PPS), sequence parameter set (SPS), or video parameter set (VPS). Additionally, the video / image information can also include general constraint information. The information signaled / sent and / or syntax elements described later in this document can be encoded through the aforementioned encoding process and thus included in the bitstream. The bitstream can be sent through a network or can be stored in a digital storage medium. Here, the network can include a broadcast network and / or a communication network, etc., and the digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitter (not shown) for sending the signal output from the entropy encoder 240 and / or a storage unit (not shown) for storing the signal can be configured as internal / external elements of the encoding device 200, or the transmitter can also be included in the entropy encoder 240.

[0066] 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, enabling the reconstruction of the residual signal (residual block or residual sample). 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 enabling the generation of a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array). In the case of applying the skip mode, if there is no residual in the block to be processed, the predicted block can be used as the 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 within the current picture, and as will be described later, is also used for inter-frame prediction of the next picture through filtering.

[0067] Meanwhile, luminance mapping and chrominance scaling (LMCS) can also be applied during picture encoding and / or reconstruction.

[0068] 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 can 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 will be 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.

[0069] The modified reconstructed picture sent to the memory 270 can be used as a reference picture in the inter-frame predictor 221. If inter-frame prediction is applied through the inter-frame predictor, the encoding device can avoid prediction mismatch between the encoding device 200 and the decoding device and improve the compilation efficiency.

[0070] The DPB of the memory 270 can store the modified reconstructed picture used as a reference picture in the inter-frame predictor 221. The memory 270 can store the motion information of the block that derives (or encodes) the motion information in the current picture and / or the motion information of the block that has been reconstructed in the picture. The stored motion information can be sent to the inter-frame predictor 221 to be used as the motion information of spatially adjacent blocks or temporally adjacent blocks. The memory 270 can store the reconstructed samples of the reconstructed blocks in the current picture and can transfer the reconstructed samples to the intra-frame predictor 222.

[0071] Figure 3It is a diagram for schematically explaining the configuration of a video / image decoding device to which embodiments of the present disclosure can be applied.

[0072] Referring to 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-predictor 331 and an intra-predictor 332. 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 described above may be configured by one or more hardware components (e.g., a decoder chipset or a processor). Additionally, the memory 360 may include a decoded picture buffer (DPB) and may be configured by a digital storage medium. The hardware components may also include the memory 360 as an internal / external component.

[0073] When receiving a bitstream including video / image information, the decoding device 300 may reconstruct an image in response to the process of processing the video / image information in the Figure 2 encoding device shown. For example, the decoding device 300 may derive units / blocks based on block segmentation-related information obtained from the bitstream. The decoding device 300 may perform decoding using the processing units applied to the encoding device. Thus, the processing units for decoding may be, for example, compile units, and the compile units may be divided from the compile tree units or the largest compile units according to a quadtree structure, a binary tree structure, and / or a ternary tree structure. One or more transform units may be derived from the compile units. Additionally, the reconstructed image signal decoded and output by the decoding device 300 may be reproduced by a reproduction device.

[0074] The decoding device 300 may receive, in the form of a bitstream, from Figure 2The signal output by the encoding device shown in, 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 can also include information about various parameter sets, such as the Adaptive Parameter Set (APS), Picture Parameter Set (PPS), Sequence Parameter Set (SPS), or Video Parameter Set (VPS). Additionally, the video / image information can also include general constraint information. The decoding device can also decode pictures based on the information about the parameter sets and / or the general constraint information. The signaled / received information and / or syntax elements described later in this document can be decoded through the decoding process and obtained from the bitstream. For example, the entropy decoder 310 can decode the information within the bitstream based on coding methods such as exponential Golomb coding, CAVLC, or CABAC, and output the values of the syntax elements required for image reconstruction and the quantization values of the residual-related transform coefficients. More specifically, the CABAC entropy decoding method can receive the bins (binary bits) corresponding to each syntax element from the bitstream, determine the context model using the information of the syntax element to be decoded, the decoding information of neighboring blocks or the block to be decoded, or the information of the symbols / bins decoded in the previous stage, and perform arithmetic decoding on the bins by predicting the probability of generating the bins according to the determined context model to generate the symbols corresponding to the values of each syntax element. At this time, the CABAC entropy decoding method can determine the context model and then update the context model by using the information of the decoded symbols / bins for the context model of the next symbol / bin. The information related to prediction among the information decoded by the entropy decoder 310 can be provided to the predictors (inter-frame predictor 332 and intra-frame predictor 331), and the residual values (i.e., the quantized transform coefficients and the related parameter information) obtained by the entropy decoder 310 performing entropy decoding can be input to the residual processor 320.

[0075] The residual processor 320 may derive a residual signal (residual block, residual sample, residual sample array). Additionally, 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 component of the decoding device 300, or the receiver may be a component of the entropy decoder 310. Meanwhile, the decoding device according to this 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 the 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.

[0076] The dequantizer 321 may dequantize the quantized transform coefficients and output the transform coefficients. The dequantizer 321 may rearrange the quantized transform coefficients in a two-dimensional block form. In this case, the rearrangement may be performed based on the coefficient scan order executed in the encoding device. The dequantizer 321 may perform dequantization on the quantized transform coefficients using a quantization parameter (e.g., quantization step information) and obtain the transform coefficients.

[0077] The inverse transformer 322 inverse-transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

[0078] The predictor 330 may perform prediction on a current block and generate a prediction block including prediction samples of the current block. The predictor may determine whether to apply intra-frame prediction or inter-frame prediction to the current block based on the information about prediction output from the entropy decoder 310 and may determine a specific intra-frame / inter-frame prediction mode.

[0079] The predictor may generate a prediction signal based on various prediction methods described below. For example, the predictor may not only apply intra-frame prediction or inter-frame prediction to predict a block, but may also apply intra-frame prediction and inter-frame prediction simultaneously. This may be referred to as combined inter-frame and intra-frame prediction (CIIP). Additionally, the predictor may predict a block based on an intra-block copy (IBC) prediction mode or a palette mode. The IBC prediction mode or the palette mode may be used for content image / video compilation such as games, e.g., screen content compilation (SCC). IBC basically performs prediction in the current picture, but may be performed similarly to inter-frame prediction such that a reference block is derived in the current picture. That is, IBC may use at least one of the inter-frame prediction techniques described in this document. The palette mode may be regarded as an example of intra-frame compilation or intra-frame prediction. When the palette mode is applied, information about the palette table and the palette index may be included in the video / image information and signaled.

[0080] The intra predictor 331 can predict the current block by referring to samples in the current picture. Depending on the prediction mode, the samples referred to can be located near the current block or can be separated. In intra prediction, the prediction mode can include a plurality of non - directional modes and a plurality of directional modes. The intra predictor 331 can use the prediction mode applied to neighboring blocks to determine the prediction mode applied to the current block.

[0081] The inter predictor 332 can derive the predicted block of the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, in order to reduce the amount of motion information transmitted in the inter - 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 neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can also include inter - prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter - prediction, neighboring blocks can include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. For example, the inter predictor 332 can configure a motion information candidate list based on neighboring blocks and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter - prediction can be performed based on various prediction modes, and information about the prediction can include information indicating the mode of inter - prediction of the current block.

[0082] The adder 340 can generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the obtained residual signal to a prediction signal (predicted block, predicted sample array) output from a predictor (including the inter predictor 332 and / or the intra predictor 331). If there is no residual for the block to be processed, for example, when the skip mode is applied, the predicted block can be used as the reconstructed block.

[0083] The adder 340 can be referred to as a reconstructor or a reconstructed - block generator. The generated reconstructed signal can be used for intra - prediction of the next block to be processed in the current picture, can be output through filtering as described below, or can be used for inter - prediction of the next picture.

[0084] Meanwhile, luminance mapping and chroma scaling (LMCS) can be applied during picture decoding.

[0085] The filter 350 can apply filtering to the reconstructed signal, thereby improving the subjective / objective image quality. For example, the filter 350 can 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, various filtering methods can include de - blocking filtering, sample - adaptive offset, adaptive loop filter, bilateral filter, etc.

[0086] The (modified) reconstructed image stored in the DPB of the memory 360 can be used as a reference picture in the inter - predictor 332. The memory 360 can store the motion information of the blocks in which the motion information within the current picture is derived (decoded) and / or the motion information of the blocks within the previously reconstructed pictures. The stored motion information can be transmitted to the inter - predictor 260 to be used as the motion information of spatially neighboring blocks or temporally neighboring blocks. The memory 360 can store the reconstructed samples of the reconstructed blocks within the current picture and transmit the stored reconstructed samples to the intra - predictor 331.

[0087] In this specification, the exemplary embodiments described in the filter 260, the inter - predictor 221, and the intra - predictor 222 of the encoding device 200 can be equally applied to or respectively correspond to the filter 350, the inter - predictor 332, and the intra - predictor 331 of the decoding device 300.

[0088] The video / image compilation method according to the present disclosure can be performed based on the following partitioning structure. Specifically, the processes of prediction, residual processing ((inverse) transformation and (de)quantization), syntax element compilation, and filtering, which will be described later, can be performed based on CTUs and CUs (and / or TUs and PUs) derived based on the partitioning structure. The block partitioning process can be performed by the image splitter 210 of the above-described encoding device, the partitioning-related information can be processed (encoded) by the entropy encoder 240, 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 partitioning structure of the current picture based on the partitioning-related information obtained from the bitstream, and based on this, can perform a series of processes for image decoding (e.g., prediction, residual processing, block / picture reconstruction, in-loop filtering, etc.). The CU size and the TU size can be equal to each other, or multiple TUs can exist within the CU region. At the same time, the CU size can generally represent the luminance component (sample) compilation block (CB) size. The TU size can generally represent the luminance component (sample) transform block (TB) size. The chrominance 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 of the picture / image (chrominance format, e.g., 4:4:4, 4:2:2, 4:2:0, etc.). 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 the transformation / inverse transformation can be performed in units of TUs (TBs). In addition, for example, in the case of applying intra prediction, the intra prediction mode / type can be derived in units of CUs (or CBs), and the adjacent reference sample derivation and predicted sample generation processes can be performed in units of TUs (or TBs). In this case, one or more TUs (or TBs) can exist in one CU (or CB) region, and in this case, multiple TUs (or TBs) can share the same intra prediction mode / type.

[0089] In addition, in the video / image compilation according to the present disclosure, the image processing unit may have a hierarchical structure. A picture may be partitioned into one or more tiles, blocks, slices, and / or tile groups. A slice may include one or more blocks. A block may include one or more CTU rows within a tile. A slice may include an integer number of blocks in 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 region of CTUs within a specific tile column and a specific tile row in a picture. According to the raster scan of tiles in a picture, a tile group may include an integer number of tiles. A slice header may carry information / parameters that may be applied to the corresponding slice (blocks in the slice). In the case where the encoding / decoding device has a multi-core processor, the encoding / decoding processes for tiles, slices, blocks, and / or tile groups may be processed in parallel. In this document, a slice or a tile group may be used interchangeably. That is, a tile group header may be referred to as a slice header. Here, a slice may have one of slice types including an intra (I) slice, a predictive (P) slice, and a bi-predictive (B) slice. When predicting blocks in an I slice, inter-frame prediction may not be used, and only intra-frame prediction may be used. Of course, even in this case, signaling may be performed by compiling the original sample values without prediction. For blocks in a P slice, intra-frame prediction or inter-frame prediction may be used, and in the case of using inter-frame prediction, only one-way prediction may be used. Meanwhile, for blocks in a B slice, intra-frame prediction or inter-frame prediction may be used, and in the case of using inter-frame prediction, up to bi-prediction may be used.

[0090] The encoder may determine tile / tile group, block, slice, and maximum and minimum compilation unit sizes in consideration of compilation efficiency or parallel processing according to the characteristics of the video image (e.g., resolution), and information about them or information capable of deriving them may be included in the bitstream.

[0091] The decoder may obtain information indicating whether the CTUs in the tile / tile group, block, slice, and tile in the current picture have been partitioned into multiple compilation units. By obtaining (sending) such information only under specific conditions, efficiency may be enhanced.

[0092] The slice header (slice header syntax) may include information / parameters that can be commonly applied to slices. The APS (APS syntax) or PPS (PPS syntax) may include information / parameters that can be commonly applied to one or more pictures. The SPS (SPS syntax) may include information / parameters that can be commonly applied to one or more sequences. The VPS (VPS syntax) may include information / parameters that can be commonly applied to multiple layers. The DPS (DPS syntax) may include information / parameters that can be commonly applied to the entire video. The DPS may include information / parameters related to the concatenation of the compiled video sequence (CVS).

[0093] In this document, the higher-level syntax may include at least one of the APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, and slice header syntax.

[0094] In addition, for example, information on the partitioning and configuration of tiles / tile groups / tile slices can be configured by the encoding end through the higher-level syntax and transmitted to the decoding device in the form of a bitstream.

[0095] In image / video compilation, pictures constituting the image / video may be encoded / decoded according to the decoding order. The picture order corresponding to the output order of the decoded pictures may be set differently from the decoding order, and based on this picture order, backward prediction and forward prediction may also be performed in inter-frame prediction.

[0096] The picture decoding process may schematically include (by decoding) a process of obtaining image / video information from a bitstream, a picture reconstruction process, and an in-loop filtering process for the reconstructed picture. The picture reconstruction process may be performed based on residual samples and prediction samples obtained through the inter / intra prediction and residual processing processes (dequantization, inverse transform for quantized transform coefficients) described herein. Through the in-loop filtering process for the reconstructed picture that has been generated through the picture reconstruction process, a modified reconstructed picture may be generated, which may be output as a decoded picture and may also be stored in the decoded picture buffer or memory 360 of the decoding device and used as a reference picture in the inter prediction process of subsequent picture decoding. Depending on the situation, the in-loop filtering process may be omitted, and in this case, the reconstructed picture may be output as a decoded picture and may also be stored in the decoded picture buffer or memory 360 of the decoding device and used as a reference picture in the inter prediction process of subsequent picture decoding. The in-loop filtering process may include the deblocking filtering process, sample adaptive offset (SAO) process, adaptive loop filter (ALF) process, and / or bilateral filter process as described above, all or some of which may be omitted. In addition, one or some of the deblocking filtering process, sample adaptive offset (SAO) process, adaptive loop filter (ALF) process, and bilateral filtering process may be sequentially applied, or all of them may be sequentially applied. For example, after applying the deblocking process to the reconstructed picture, the SAO process may be performed on it. Optionally, for example, after applying the deblocking filtering process to the reconstructed picture, the ALF process may be performed on it. This may also be performed in the encoding device.

[0097] The picture encoding process may schematically include a process of generating a reconstructed picture for the current picture and an optional process of applying in-loop filtering to the reconstructed picture, and a process of encoding information for picture reconstruction (e.g., prediction information, residual information, partition information, etc.) and outputting the information in the form of a bitstream. The encoding device may derive (modified) residual samples from the quantized transform coefficients through a dequantizer 234 and an inverse transformer 235, and may generate a reconstructed picture based on the (modified) residual samples and prediction samples. The reconstructed picture generated in this way may be the same as the above-mentioned reconstructed picture generated in the decoding device. Through the in-loop filtering process for the reconstructed picture, a modified reconstructed picture may be generated, which may be stored in the decoded picture buffer or memory 270 and, similar to the case of the decoding device, used as a reference picture in the inter prediction process of subsequent picture encoding. As described above, all or part of the in-loop filtering process may be omitted depending on the situation. In the case of performing the in-loop filtering process, the (in-loop) filtering-related information (parameters) may be encoded in the entropy encoder 240 and output in the form of a bitstream, and the decoding device may perform the in-loop filtering process in the same manner as the encoding device based on the filtering-related information.

[0098] Through this in-loop filtering process, noise such as deblocking artifacts and ringing artifacts generated during image / video encoding can be reduced, and subjective / objective visual quality can be improved. In addition, since the in-loop filtering process is performed in both the encoding device and the decoding device, the encoding device and the decoding device can derive the same prediction result, enhance the reliability of picture encoding, and reduce the amount of data to be transmitted for picture encoding.

[0099] As described above, the picture reconstruction process can be performed in the encoding device and in the decoding device. Based on intra prediction / inter prediction for each block unit, a reconstructed block can be generated, and a reconstructed picture including the reconstructed block can be generated. In the case where the current picture / slice / tile group is an I picture / slice / tile group, the blocks included in the current picture / slice / tile group can be reconstructed based only on intra prediction. Meanwhile, in the case where the current picture / slice / tile group is a P or B picture / slice / tile group, the blocks included in the current picture / slice / tile group can be reconstructed based on intra prediction or inter prediction. In this case, inter prediction can be applied to some of the blocks in the current picture / slice / tile group, and intra prediction can be applied to some of the remaining blocks. The color components of a picture can include a luminance component and a chrominance component, and the methods and embodiments proposed in this document can be applied to the luminance component and the chrominance component, unless explicitly restricted by this document.

[0100] Meanwhile, as described above, when performing video encoding, prediction is performed to improve compression efficiency. Thus, a prediction block including prediction samples for a current block to be encoded (i.e., an encoding 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 way in the encoding device and the decoding device, and the encoding device can signal information about the residual between the original block and the prediction block (residual information) instead of the original sample values of the original block to the decoding device, thereby improving image encoding 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.

[0101] Residual information can be generated through a transformation and quantization process. For example, an encoding device may derive a residual block between an original block and a prediction block, perform a transformation process on residual samples (residual sample array) included in the residual block to derive transform coefficients, perform a quantization process on the transform coefficients to derive quantized transform coefficients, and signal relevant residual information (through a bitstream) to a decoding device. Here, the residual information may include value information, position information, transformation technique, transformation kernel, quantization parameter, etc. of the quantized transform coefficients. The decoding device may perform an inverse quantization / inverse transformation process based on the residual information and derive residual samples (or a residual block). The decoding device may generate a reconstructed picture based on the prediction block and the residual block. In addition, for reference in inter prediction of subsequent pictures, the encoding device may also perform inverse quantization / inverse transformation on the quantized transform coefficients to derive a residual block and generate a reconstructed picture based on the residual block.

[0102] When inter - frame prediction is applied to a current block, a predictor of an encoding device / decoding device may derive prediction samples by performing inter - frame prediction on a per - block basis. Inter - frame prediction may 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. When inter - frame prediction is applied to the current block, a prediction block (prediction sample array) of the current block may be derived based on a reference block (reference sample array) specified by a motion vector on a reference picture indicated by a reference picture index. In this case, in order to reduce the amount of motion information transmitted in the inter - frame prediction mode, the motion information of the current block may be predicted on a per - block, per - sub - block, or per - sample basis based on the correlation of motion information between neighboring blocks and the current block. Motion information may include a motion vector and a reference picture index. Motion information may also include inter - frame prediction type (L0 prediction, L1 prediction, Bi - prediction, etc.) information. When inter - frame prediction is applied, 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. Temporal neighboring blocks may be referred to as collocated reference blocks or collocated CUs (colCUs), and the reference picture including the temporal neighboring blocks may be referred to as a collocated picture (colPic). For example, a motion information candidate list may be configured based on 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 the 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 skip mode, different from the merge mode, a residual signal may not be transmitted. In the case of the motion vector prediction (MVP) mode, the motion vector of the selected neighboring block may be used as a motion vector predictor, and a motion vector difference may be signaled. In this case, the sum of the motion vector predictor and the motion vector difference may be used to derive the motion vector of the current block.

[0103] The video / image encoding process based on inter - frame prediction may schematically include, for example, the following processes.

[0104] Figure 4 is a diagram schematically showing an inter - frame predictor in an encoding device.

[0105] Refer to Figure 4, the encoding device performs inter - frame prediction on the current block. The encoding device can derive the inter - frame prediction mode and motion information of the current block and generate prediction samples of the current block. Here, the processes of determining the inter - frame prediction mode, deriving the motion information, and generating the prediction samples can be executed simultaneously or one after another. For example, the inter - frame predictor 221 of the encoding device can include a prediction mode determiner 221_1, a motion information deriver 221_2, and a prediction sample deriver 221_3. The prediction mode determiner 221_1 can determine the prediction mode for the current block; the motion information deriver 221_2 can derive the motion information of the current block; and the prediction sample deriver 221_3 can derive the prediction samples of the current block. For example, the inter - frame predictor 221 of the encoding device can search for a block similar to the current block in a specific area (search area) of the reference picture through motion estimation and derive a reference block whose difference from the current block is the smallest or less than or equal to a specific level. Based on this, a reference picture index indicating the reference picture where the reference block is located can be derived, and a motion vector can be derived based on the position difference between the reference block and the current block. The encoding device can determine the mode applied to the current block from various prediction modes. The encoding device can compare the rate - distortion (RD) costs of various prediction modes and determine the best prediction mode for the current block.

[0106] For example, in the case where the skip mode or the merge mode is applied to the current block, the encoding device can configure a merge candidate list described later and can derive, among the reference blocks indicated by the merge candidates included in the merge candidate list, a reference block having the smallest difference from the current block or a difference equal to or less than a predetermined reference. In this case, the merge candidate associated with the derived reference block can be selected, and merge index information indicating the selected merge candidate can be generated and signaled to the decoding device. The motion information of the current block can be derived using the motion information of the selected merge candidate.

[0107] 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 among the motion vector predictors (mvps) included in the (A)MVP candidate list as the mvp of the current block. In this case, for example, the motion vector indicating the reference block derived by the above-described motion estimation may be used as the motion vector of the current block, and the mvp candidate having 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 the difference obtained by subtracting the mvp from the motion vector of the current block. In this case, information about the MVD may be signaled to the decoding device. Further, 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 signaled to the decoding device separately.

[0108] The encoding device may derive a residual sample based on the predicted sample. The encoding device may derive the residual sample by comparing the original sample of the current block with the predicted sample.

[0109] The encoding device encodes the image information including the prediction information and the residual information. The encoding device may 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 the prediction mode information (e.g., skip flag, merge flag, or mode index) and the motion information. The information about the motion information may include candidate selection information (e.g., merge index, mvp flag, or mvp index) as information for deriving the motion vector. Further, the information about the motion information may include information about the above MVD and / or reference picture index information. Further, the information about the motion information may include information indicating whether L0 prediction, L1 prediction, or bi-prediction is applied. The residual information is information related to the residual sample. The residual information may include information about the quantization transform coefficients for the residual sample.

[0110] The output bitstream may be stored in a (digital) storage medium to be transmitted to the decoding device or may be transmitted to the decoding device through a network.

[0111] Meanwhile, as described above, the encoding device may generate a reconstructed picture (including reconstructed samples and reconstructed blocks) 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 encoding efficiency can be enhanced. Accordingly, the encoding device may store the reconstructed picture (or reconstructed samples or reconstructed blocks) in the memory and may use the stored reconstructed picture as a reference picture for inter prediction. As described above, the in-loop filtering process may be further applied to the reconstructed picture.

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

[0113] Figure 5 It is a diagram schematically showing an inter-frame predictor in a decoding device.

[0114] Referring to Figure 5 , the decoding device may perform operations corresponding to those performed by the encoding device. The decoding device may perform prediction on a current block based on the received prediction information and may derive prediction samples.

[0115] Specifically, the decoding device may determine a prediction mode for the current block based on the received prediction information. The decoding device may determine which inter-frame prediction mode to apply to the current block based on the prediction mode information in the prediction information.

[0116] 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 candidates may include the skip mode, the merge mode, and / or the (A)MVP mode, or may include various inter-frame prediction modes described later.

[0117] The decoding device derives the motion information of the current block based on the determined inter-frame prediction mode. For example, when 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 selection information (merge index). The motion information of the selected merge candidate may be used to derive the motion information of the current block. The motion information of the selected merge candidate may be used as the motion information of the current block.

[0118] As another example, when the (A)MVP mode is applied to the current block, the decoding device may configure an (A)MVP candidate list described later and may use the motion vector of the mvp candidate selected from among the motion vector predictors (mvps) included in the (A)MVP candidate list as the mvp of the current block. Such selection may be performed based on the above 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 the 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 the reference picture, which is referenced for the inter-frame prediction of the current block.

[0119] Meanwhile, 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 candidate list configuration can be omitted.

[0120] The decoding device can generate a prediction sample for the current block based on the motion information of the current block. In this case, the reference picture can be derived based on the reference picture index of the current block, and the sample of the reference block indicated by the motion vector of the current block on the reference picture can be used to derive the prediction sample of the current block. In this case, as described later, the prediction sample filtering process for all or part of the prediction samples of the current block can be further performed in some cases.

[0121] For example, the inter - frame predictor (332) of the decoding device can include a prediction mode determination unit (332_1), a motion information derivation unit (332_2), and a prediction sample derivation unit (332_3). The prediction mode determination unit (332_1) can determine the prediction mode for the current block based on the received prediction mode information, the motion information derivation unit (332_2) can derive the motion information (motion vector and / or reference picture index) of the current block based on the information about the received motion information, and the prediction sample derivation unit (332_3) can derive the prediction sample of the current block.

[0122] The decoding device generates a residual sample for the current block based on the received residual information. The decoding device can generate a reconstructed sample for the current block based on the prediction sample and the residual sample, and based on this, the decoding device can generate a reconstructed picture. Thereafter, as described above, the in - loop filtering process can be further applied to the reconstructed picture.

[0123] As described above, the inter - frame prediction process can include steps of 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 can be performed by the encoding device and the decoding device. In this document, the compiling device can include the encoding device and / or the decoding device.

[0124] For the prediction of the current block in a 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 history motion vector prediction (HMVP) mode can be used. The decoder - side motion vector refinement (DMVR) mode, adaptive motion vector resolution (AMVR) mode, bi - prediction with CU - level weights (BCW), and bidirectional optical flow (BDOF) can be further used or alternatively used as side modes. The affine mode can be referred to as the affine motion prediction mode. The MVP mode can be referred to as the advanced motion vector prediction (AMVP) mode. In this document, a specific mode and / or a candidate of motion information 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 the merge / skip mode, or can be added as an mvp candidate for the MVP mode.

[0125] The prediction mode information indicating the inter - prediction mode for the current block can be signaled from the encoding device to the decoding device. The prediction mode information can be included in the bitstream and can be received at the decoding device. The prediction mode information can include index information indicating one of multiple candidate modes. In addition, the inter - prediction mode can be indicated by hierarchical signaling of flag information. In this case, the prediction mode information can include one or more flags. For example, whether to apply the skip mode can be indicated by signaling a skip flag, and in the case where the skip mode is not applied, whether to apply the merge mode can be indicated by signaling a merge flag, and in the case where the merge mode is not applied, it can be indicated to apply the MVP mode, or flags for additional partitions can be further signaled. The affine mode can be signaled as an independent mode, or can be signaled as a subordinate mode of the merge mode or the MVP mode. For example, the affine mode can include an affine merge mode and an affine MVP mode.

[0126] Meanwhile, information indicating whether the above-mentioned list 0 (L0) prediction, list 1 (L1) prediction, or dual prediction is used for the current block (current compilation unit) can be signaled. This information can be referred to as motion prediction direction information, inter-frame prediction direction information, or inter-frame prediction indication information, and can be configured / encoded / signaled in the form of, for example, the inter_pred_idc syntax element. That is, the inter_pred_idc syntax element can indicate whether the above-mentioned list 0 (L0) prediction, list 1 (L1) prediction, or dual prediction is used for the current block (current compilation 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 can be shown as the motion prediction direction. L0 prediction, L1 prediction, and dual prediction can be represented as pred_L0, pred_L1, and pred_BI, respectively. For example, the following prediction types can be represented according to the inter_pred_idc syntax element value.

[0127] As described above, a picture can include one or more slices. A slice can have one of the slice types including an intra (I) slice, a predictive (P) slice, and a bi-predictive (B) slice. The slice type can be indicated based on the slice type information. When predicting a block in an I slice, inter-frame prediction may not be used, and only intra-frame prediction may be used. Of course, even in this case, signaling can be performed by compiling the original sample values without prediction. For a block in a P slice, intra-frame prediction or inter-frame prediction can be used, and in the case of using inter-frame prediction, only one-way prediction can be used. Meanwhile, for a block in a B slice, intra-frame prediction or inter-frame prediction can be used, and in the case of using inter-frame prediction, up to dual prediction can be used at most.

[0128] L0 and L1 can include reference pictures encoded / decoded before the current picture. For example, L0 can include reference pictures before and / or after the current picture in the POC order, and L1 can include reference pictures after and / or before the current picture in the POC order. In this case, for L0, a relatively low reference picture index can be assigned to the reference picture before the current picture in the POC order, and for L1, a relatively low reference picture index can be assigned to the reference picture after the current picture in the POC order. In the case of a B slice, dual prediction can be applied, and even in this case, one-way dual prediction can be applied, or two-way dual prediction can be applied. Two-way dual prediction can be referred to as true dual prediction.

[0129] Specifically, for example, information about the inter-frame prediction mode of the current block can be compiled and signaled at the CU (CU syntax) level, or the information about the inter-frame prediction mode of the current block can be implicitly determined according to conditions. In this case, the information can be signaled explicitly for some modes, and the information can be derived implicitly for the remaining modes.

[0130] For example, the CU syntax can carry information about the (inter-frame) prediction modes in Table 1 below.

[0131] [Table 1]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144]

[0145] Here, the cu_skip_flag can indicate whether the skip mode is applied to the current block (CU).

[0146] The pred_mode_flag being equal to 0 specifies that the current compilation unit is compiled in the inter-frame prediction mode. The pred_mode_flag being equal to 1 specifies that the current compilation unit is compiled in the intra-frame prediction mode.

[0147] The pred_mode_ibc_flag being equal to 1 specifies that the current compilation unit is compiled in the IBC prediction mode. The pred_mode_ibc_flag being equal to 0 specifies that the current compilation unit is not compiled in the IBC prediction mode.

[0148] pcm_flag [x0][y0] being equal to 1 specifies the existence of the pcm_sample() syntax structure and the non-existence of the transform_tree() syntax structure in the compilation unit that includes the luminance coding block at the position (x0, y0). pcm_flag [x0][y0] being equal to 0 specifies the non-existence of the pcm_sample() syntax structure. That is to say, pcm_flag can indicate whether the Pulse Code Modulation (PCM) mode is applied to the current block. If the PCM mode is applied to the current block, prediction, transformation, and quantization may not be applied, and the original sample values in the current block can be compiled and signaled.

[0149] intra_mip_flag[x0][y0] being equal to 1 specifies that the intra prediction type of the luminance sample is matrix-based intra prediction (MIP). intra_mip_flag[x0][y0] being equal to 0 specifies that the intra prediction type of the luminance sample is not matrix-based intra prediction. That is to say, intra_mip_flag can indicate whether the MIP prediction mode (type) is applied to the current block (the luminance samples of the current block).

[0150] intra_chroma_pred_mode[x0][y0] specifies the intra prediction mode of the chroma samples in the current block.

[0151] general_merge_flag[x0][y0] specifies whether to infer the inter prediction parameters of the current compilation unit from adjacent inter prediction partitions. That is to say, general_merge_flag can indicate the enabling of general merge, and when the general_merge_flag value is 1, the general 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 encoded video / image information (or bitstream), and the merge data syntax can be configured / compiled to include the information shown in Table 2 below.

[0152] [Table 2]

[0153]

[0154]

[0155]

[0156] Here, regular_merge_flag[x0][y0] being equal to 1 specifies that the regular merge mode is used to generate the inter-prediction parameters for the current coding unit. That is, regular_merge_flag indicates whether the merge mode (regular merge mode) is applied to the current block.

[0157] mmvd_merge_flag[x0][y0] being equal to 1 specifies that the merge mode with motion vector difference is used to generate the inter-prediction parameters for the current coding unit. That is, mmvd_merge_flag indicates whether MMVD is applied to the current block.

[0158] mmvd_cand_flag [x0][y0] specifies whether the first (0) or second (1) candidate in the merge candidate list is used together with the motion vector difference derived from mmvd_distance_idx [x0][y0] and mmvd_direction_idx[x0][y0].

[0159] mmvd_distance_idx [x0][y0] specifies the index used to derive MmvdDistance [x0][y0].

[0160] mmvd_direction_idx [x0][y0] specifies the index used to derive MmvdSign[x0][y0].

[0161] merge_subblock_flag[x0][y0] specifies whether the sub-block-based inter-prediction parameters are used for the current coding. That is, merge_subblock_flag can indicate whether the sub-block merge mode (or affine merge mode) is applied to the current block.

[0162] merge_subblock_idx[x0][y0] specifies the merge candidate index of the sub-block-based merge candidate list.

[0163] ciip_flag[x0][y0] specifies whether combined inter-picture merge and intra-picture prediction are applied to the current coding unit.

[0164] merge_triangle_idx0[x0][y0] specifies the first merge candidate index of the triangle-shaped motion compensation candidate list.

[0165] merge_triangle_idx1[x0][y0] specifies the second merge candidate index of the triangle-shaped motion compensation candidate list.

[0166] merge_idx [x0][y0] specifies the merge candidate index of the merge candidate list.

[0167] Meanwhile, referring again to the CU syntax in Table 1, mvp_l0_flag [x0][y0] specifies the motion vector predictor index of list 0. That is, in the case of applying the MVP mode, mvp_l0_flag can represent the candidate selected from the MVP candidate list for the MVP derivation of the current block.

[0168] ref_idx_l1[x0][y0] has the same semantics as ref_idx_l0, where l0, L0, and list 0 are replaced by l1, L1, and list 1 respectively.

[0169] inter_pred_idc[x0][y0] specifies whether list 0, list 1, or bi-prediction is used for the current coding unit.

[0170] sym_mvd_flag [x0][y0] being 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 do not exist. That is, sym_mvd_flag indicates whether symmetric MVD is used for mvd coding.

[0171] ref_idx_l0[x0][y0] specifies the list 0 reference picture index for the current coding unit.

[0172] ref_idx_l1[x0][y0] has the same semantics as ref_idx_l0, where l0, L0, and list 0 are replaced by l1, L1, and list 1 respectively.

[0173] inter_affine_flag[x0][y0] being equal to 1 specifies that for the current coding unit, when decoding a P or B slice, motion compensation based on an affine model is used to generate the prediction samples of the current coding unit.

[0174] cu_affine_type_flag[x0][y0] being 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 the prediction samples of the current coding unit. cu_affine_type_flag[x0][y0] being equal to 0 specifies that motion compensation based on a 4-parameter affine model is used to generate the prediction samples of the current coding unit.

[0175] The amvr_flag [x0][y0] specifies the resolution of the motion vector difference. The array indices x0, y0 specify the position (x0, y0) of the top-left luma sample of the coded block under consideration relative to the top-left luma sample of the picture. amvr_flag [x0][y0] being equal to 0 specifies that the resolution of the motion vector difference is 1 / 4 of a luma sample. amvr_flag [x0][y0] being equal to 1 specifies that the resolution of the motion vector difference is further specified by amvr_precision_flag [x0][y0].

[0176] If inter_affine_flag [x0][y0] is equal to 0, amvr_precision_flag[x0][y0] being equal to 0 specifies that the resolution of the motion vector difference is an integer luma sample, otherwise 1 / 16 of a luma sample. If inter_affine_flag[x0][y0] is equal to 0, amvr_precision_flag [x0][y0] being equal to 1 specifies that the resolution of the motion vector difference is four luma samples, otherwise an integer luma sample. The array indices x0, y0 specify the position (x0, y0) of the top-left luma sample of the coded block under consideration relative to the top-left luma sample of the picture.

[0177] bcw_idx [x0][y0] specifies the weight index for bi-prediction with CU weights.

[0178] The coding device may perform inter prediction based on the motion information of the current block. The coding device may derive the optimal motion information of the current block through a motion estimation process. For example, the coding device may search for a similar reference block with high correlation in terms of fractional pixels within the search range determined in the reference picture using the original block in the original picture of the current block, and through this, the coding device may derive the motion information. The block similarity may be derived based on the difference between the sample values based on the phase. For example, the block similarity may 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, the motion information may be derived based on the reference block with the minimum SAD in the search area. The derived motion information may be signaled to the decoding device according to several methods based on the inter prediction mode.

[0179] The coding device may derive the predicted samples of the current block based on the motion information. The current block including the predicted samples may be referred to as the predicted block.

[0180] A 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 units in the reference picture. In the case where affine inter prediction is applied to the current block, the encoding device may generate prediction samples based on the motion vector (MV) in units of samples / sub-blocks. In the case of applying dual prediction, the prediction samples derived through the weighted sum or weighted average (depending on the phase) of the prediction samples derived based on L0 prediction (i.e., prediction using the reference pictures in reference picture list L0 and MVL0) and the prediction samples derived based on L1 prediction (i.e., prediction using the reference pictures in reference picture list L1 and MVL1) may be used as the prediction samples of the current block. If, when applying dual prediction (i.e., in the case corresponding to dual prediction and bi-directional prediction), the reference pictures for L0 prediction and the reference pictures for L1 prediction are in different temporal directions based on the current picture, they may be referred to as true dual prediction.

[0181] Reconstruction samples and a reconstructed picture may be generated based on the derived prediction samples, and thereafter, processes such as in-loop filtering may be performed.

[0182] Figure 6 is a diagram explaining the spatial candidates that can be used for inter prediction.

[0183] In the case where the merge mode is applied during inter prediction, the motion information of the current block is not directly sent, and the motion information of the current block is derived using the motion information of adjacent prediction blocks. Therefore, the encoding device may represent the motion information of the current block by sending flag information indicating the use of the merge mode and a merge index indicating which adjacent prediction block is used. The merge mode may be referred to as the regular merge mode.

[0184] The encoding device searches for merge candidate blocks for deriving the motion information of the current block in order to perform the merge mode. For example, up to 5 merge candidate blocks may be used, but in this 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 the slice header or tile group header, but this embodiment is not limited thereto. After finding the merge candidate blocks, the encoding device may generate a merge candidate list, and may select the merge candidate block with the minimum cost as the final merge candidate block.

[0185] This document provides various embodiments of merge candidate blocks for constructing a merge candidate list.

[0186] 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 6The blocks A0, A1, B0, B1, and B2 shown in can be used as spatial merge candidates. Hereinafter, the spatial merge candidates or spatial MVP candidates described later can be referred to as SMVPs, and the temporal merge candidates or temporal MVP candidates described later can be referred to as TMVPs.

[0187] For example, the merge candidate list for the current block can be configured based on the following process.

[0188] First, the compiling device (encoding device / decoding device) can insert the spatial merge candidates derived by searching for the spatial neighboring blocks of the current block into the merge candidate list. For example, the spatial neighboring blocks can include the lower-left neighboring block A0, the left neighboring block A1, the upper-left neighboring block B0, the upper neighboring block B1, and the upper-right 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, and the lower-right neighboring block can further be used as spatial neighboring blocks. The compiling device can detect the enabled blocks by searching for the spatial neighboring blocks based on the priority, and can derive the motion information of the detected blocks as spatial merge candidates. For example, the encoding device and / or the decoding device can search for the 5 blocks shown in Figure 6 in the order of A1, B1, B0, A0, and B2, and can configure the merge candidate list by sequentially indexing the enabled candidates.

[0189] In addition, the compiling device can insert the temporal merge candidates derived by searching for the temporal neighboring blocks of the current block into the merge candidate list. The temporal neighboring blocks can be located on a reference picture, which is a picture different from the current picture on which the current block is located. The reference picture on which the temporal neighboring blocks are located can be referred to as the collocated picture or col picture. The temporal neighboring blocks can be searched in the order of the lower-right neighboring block and the lower-right center block of the collocated block for the current block on the col picture.

[0190] Meanwhile, the compiling device can identify whether the number of current merge candidates is less than the number of maximum merge candidates. The number of maximum merge candidates can be predefined or can be signaled from the encoding device to the decoding device. For example, the encoding device can 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.

[0191] If, as a result of recognition, the number of current merge candidates is less than the number of maximum merge candidates, the compiling device may insert additional merge candidates into the merge candidate list. For example, the additional merge candidates may include at least one of a history-based merge candidate, a pairwise average merge candidate, an ATMVP, a combined dual-prediction merge candidate (in the case where the slice / tile group type of the current slice / tile group is of type B), and / or a zero vector merge candidate.

[0192] If, as a result of recognition, the number of current merge candidates is not less than the number of maximum merge candidates, the compiling device may end the configuration of the merge candidate list. In this case, the encoding device may select the best merge candidate among the merge candidates constituting the merge candidate list based on 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.

[0193] The motion information of the selected merge candidate may be used as the motion information of the current block, and as described above, the predicted samples of the current block may be derived based on the motion information of the current block. The encoding device may derive the residual samples of the current block based on the predicted samples, and may signal the residual information regarding the residual samples to the decoding device. As described above, the decoding device may generate reconstructed samples based on the residual samples and the predicted samples derived according to the residual information, and based on this, the decoding device may generate a reconstructed picture.

[0194] In the case where the skip mode is applied during inter prediction, the motion information of the current block may be derived in the same manner as in the case where the merge mode is applied. However, in the case where the skip mode is applied, the residual signal of the corresponding block may be omitted, and thus the predicted samples may be immediately used as the reconstructed samples. For example, the skip mode may be applied when the value of the CU skip flag (cu_skip_flag) is 1.

[0195] Figure 7 is a diagram explaining the temporal candidates that can be used for inter prediction.

[0196] Here, the temporal candidates may represent the temporal merge candidates described above. In addition, the motion vectors included in the temporal candidates may correspond to the temporal mvp candidates.

[0197] 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 CUs belonging to the collocated reference picture (which may be referred to as colPic). The reference picture list to be used for deriving the collocated CUs is explicitly signaled in the slice header. As Figure 7As shown by the dashed line in [description], scaled motion vectors for temporal merge candidates are obtained, and the motion vectors are scaled from the motion vectors of the collocated CUs 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 to be equal to zero.

[0198] In addition to the merge mode, where the implicitly derived motion information is directly used for the prediction sample generation of the current CU, a merge mode with motion vector difference (MMVD) is introduced in VVC. Since a similar motion information derivation method is used for the skip mode and the merge mode, MMVD can be applied to the skip mode. The MMVD flag (e.g., mmvd_flag) can be signaled immediately after the skip flag and the merge flag are sent to specify whether the MMVD mode is used for the CU.

[0199] In MMVD, after the merge candidates are selected, the merge candidates are further refined by the signaled MVD information. When MMVD is applied to the current block (i.e., when mmvd_flag is equal to 1), further information of MMVD can be signaled.

[0200] The 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 together with the motion vector difference, an index (e.g., mmvd_distance_idx) specifying the motion amplitude, and an index (e.g., mmvd_direction_idx) for indicating the motion direction. In the MMVD mode, one of the first two candidates in the merge list is selected as the MV basis. The merge candidate flag is signaled to specify which one is used.

[0201] The distance index specifies the motion amplitude information and indicates a predefined offset from the starting point.

[0202] The offset is added to the horizontal component or the vertical component of the starting MV. The relationship between the distance index and the predefined offset is specified in Table 3.

[0203] [Table 3]

[0204]

[0205] Here, slice_fpel_mmvd_enabled_flag being equal to 1 specifies that the merge mode with motion vector difference uses integer sample precision in the current slice. slice_fpel_mmvd_enabled_flag being equal to 0 specifies that the merge mode with motion vector difference may use fractional sample precision in the current slice. When absent, the value of slice_fpel_mmvd_enabled_flag is inferred to be 0. The slice_fpel_mmvd_enabled_flag syntax element may be signaled (and may be included) through the slice header.

[0206] The direction index indicates the direction of the MVD relative to the starting point. The direction index may indicate the four directions as shown in Table 4. Note that the meaning of the MVD sign may vary according to the information of the starting MV. When the starting MV is a non-predicted MV or a bi-predicted MV where both lists point to the same side of the current picture (i.e., both reference POCs are greater than the POC of the current picture, or both are less than the POC of the current picture), the signs in Table 4 specify the signs of the MV offsets added to that starting MV. When the starting MV is a bi-predicted MV where the two MVs point to different sides of the current picture (i.e., one reference POC is greater than the POC of the current picture and the other reference POC is less than the POC of the current picture), the signs in Table 4 specify the signs of the MV offsets added to the list 0 MV component of the starting MV and the signs of the list 1 MV have opposite values.

[0207] [Table 4 ]

[0208]

[0209] The two merged components plus the MVD offset MmvdOffset[x0][y0] are derived as follows.

[0210] [Equation 1]

[0211]

[0212] Figure 8 is a diagram explaining the sub-block based temporal motion vector prediction process that can be used during inter prediction.

[0213] 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 CUs in the current picture. The same collocated pictures used by TMVP are used for SbTVMP. The differences between SbTMVP and TMVP are in the following two main aspects.

[0214] 1. TMVP predicts the motion at the CU level, while SbTMVP predicts the motion at the sub-CU level.

[0215] 2. TMVP extracts the temporal motion vector from the collocated block in the collocated picture (the collocated block is the bottom-right or center (bottom-right center) block relative to the current CU), while SbTMVP applies a motion shift before extracting the temporal motion information from the collocated picture, where the motion shift is obtained from the motion vector of one of the spatial neighboring blocks of the current CU.

[0216] Figure 8 The figure shows the SbTVMP process. SbTMVP predicts the motion vector of the sub-CUs within the current CU in two steps. In the first step, the spatial neighbor A1 is checked. If A1 has a motion vector using the collocated picture when its reference picture is identified, then this 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).

[0217] 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 the sub-CU level motion information (motion vector and reference index) from the collocated picture as Figure 8 shown. Figure 8 The example in assumes that the motion shift is set to the motion of block A1. Then, for each sub-CU, the motion information of its corresponding block (the smallest motion grid covering the central sample) in the collocated picture is used to derive the motion information for the sub-CU. When the sub-block has an even length, width, and height, the central sample (bottom-right central sample) can correspond to the bottom-right sample among the 4 central samples in the sub-CU.

[0218] After identifying the motion information of the collocated sub-CUs, 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.

[0219] A sub-block-based merge list containing a combination of both SbTVMP candidates and affine merge candidates can be used for signaling in the affine merge mode (which can be called the (sub-block-based) merge mode). The SbTVMP mode is enabled / disabled by a sequence parameter set (SPS) flag. If the SbTMVP mode is enabled, the SbTMVP prediction sub is added as the first entry in the sub-block merge candidate list, followed by the affine merge candidates. The maximum allowed size of the affine merge candidate list can be 5.

[0220] The size of the sub-CUs used in SbTMVP can be fixed to 8×8, and the SbTMVP mode can only be applied to CUs where both the width and height are greater than or equal to 8, as done in the affine merge mode.

[0221] The encoding logic for additional SbTMVP merge candidates is the same as that for other merge candidates. That is, for each CU in a P or B slice, an additional RD check can be performed to decide whether to use the SbTMVP candidate.

[0222] Figure 9 is a diagram explaining the partitioning modes that can be applied to inter-frame prediction.

[0223] The triangular partitioning mode can be used for inter-frame prediction. The triangular partitioning mode can only be applied to CUs of 8x8 or larger. A CU-level flag is used as a merge mode together with other merge modes to signal the triangular partitioning mode, and the other merge modes include the regular merge mode, the MMVD mode, the CIIP mode, and the sub-block merge mode.

[0224] When using this mode, a CU can be evenly divided into two triangular partitions using diagonal splitting or anti-diagonal splitting, as Figure 9 shown. Each triangular partition in the CU is inter-frame predicted using its own motion; only single prediction is allowed for each partition, that is, each partition has one motion vector and one reference index. A single-prediction motion constraint is applied to ensure that, as with regular dual prediction, only two motion-compensated predictions are required for each CU.

[0225] If the triangular partitioning mode is used for the current CU, a flag indicating the direction (diagonal or anti-diagonal) of the triangular partition and two merge indices (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 for specifying the TMP merge index is binary-coded. After predicting each of the triangular partitions, a hybrid process with adaptive weights is used to adjust the sample values along the diagonal or anti-diagonal edge. This is the prediction signal for the entire CU, and the transform and quantization processes will be applied to the entire CU, as in other prediction modes. Finally, the motion field of the CU predicted using the triangular partitioning mode is stored in 4×4 units. The triangular partitioning mode is not used in combination with SBT, that is, when the signaled triangular mode is equal to 1, the cu_sbt_flag is inferred to be 0 without signaling.

[0226] The single-prediction candidate list is directly derived from the merge candidate list constructed as described above.

[0227] After predicting each triangular partition using its own motion, a blend is applied to two prediction signals to derive samples around diagonal or anti-diagonal edges.

[0228] Combined inter and intra prediction can be applied to the current block. An additional flag (e.g., ciip_flag) is signaled to indicate whether the combined inter / intra prediction (CIIP) mode is applied to the current CU. For example, when compiling a CU in merge mode, if the CU includes at least 64 luma samples (i.e., CU width multiplied by CU height is equal to or greater than 64), and if both the CU width and CU height are less than 128 luma samples, then an additional flag is signaled to indicate whether the combined inter / intra prediction (CIIP) mode is applied to the current CU. As its name indicates, CIIP prediction combines an inter prediction signal with an intra prediction signal. The same inter prediction processing applied to the regular merge mode is used to derive the inter prediction signal in CIIP mode P_inter; while the intra prediction signal P_intra follows the regular intra prediction processing with planar mode to be derived. Then, a weighted average is used to combine the intra and inter prediction signals, where the weight values are calculated as follows according to the compilation modes of the upper neighboring block and the left neighboring block.

[0229] If the upper neighbor is available and is intra-compiled, set isIntrantop to 1, otherwise set isIntrantop to 0.

[0230] If the left neighbor is available and is intra-compiled, set isIntraLeft to 1, otherwise set isIntraLeft to 0.

[0231] If (isIntraLeft + isIntraLeft) equals 2, set wt to 3.

[0232] Otherwise, if (isIntraLeft + isIntraLeft) equals 1, set wt to 2.

[0233] Otherwise, set wt to 1.

[0234] CIIP prediction is formed as follows.

[0235] [Equation 2]

[0236]

[0237] Meanwhile, to generate prediction blocks, the encoding device may derive motion information based on the above-mentioned conventional merge mode, skip mode, SbTMVP mode, MMVD mode, triangle partitioning mode (partitioning mode), and / or CIIP mode. Each mode can be enabled / disabled through the on / off flag of each mode included in the sequence parameter set (SPS). If the on / off flag for a specific mode is disabled, the encoding device does not signal the explicitly sent syntax for the corresponding prediction mode in units of CU or PU.

[0238] In this document, to remove the signaling of redundant syntax, a method for signaling syntax is disclosed considering the on / off of the merge / skip mode and the application method.

[0239] For example, in the case of regular_merge_flag, under the conditions where MMVD, sub-block merge, CIIP merge, and triangle merge are not allowed, there are no possible candidates other than the conventional merge mode, and thus there is no need to signal the flag (e.g., the conventional merge flag).

[0240] In addition, under the conditions where sub-block merge, CIIP merge, and triangle merge are not allowed, there is no need to signal the mmvd-related flag (e.g., mmvd_merge_flag).

[0241] Under the conditions where CIIP merge and triangle merge are not allowed, there is no need to signal the sub-block-related flag (e.g., merge_subblock_flag).

[0242] Under the conditions where triangle merge is not allowed, there is no need to signal the CIIP-related flag (e.g., CIIP_flag).

[0243] According to the merge data syntax in Table 2, when all or part of the specific modes for the merge / skip mode are disabled, redundant signaling of the on / off flag occurs. Therefore, in this document, the following method can be used to prevent redundant signaling of the same information (flag) during the process of selecting the merge mode applied to the current block.

[0244] 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 presented exemplarily, the technical features of this specification are not limited to the specific names used in the following drawings.

[0245] Figure 10 and Figure 11 Schematically shows 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.

[0246] Figure 10The encoding method disclosed in Figure 2 can be executed by the encoding device 200 disclosed in Figure 10 . Specifically, for example, S1000 to S1030 of Figure 10 can be executed by the predictor 220 of the encoding device 200, S1040 can be executed by the residual processor 230 of the encoding device 200, and S1050 can be executed by the entropy encoder 240 of the encoding device 200.

[0247] Specifically, referring to Figure 10 and Figure 11 , the predictor of the encoding device can determine the prediction mode of the current block (S1000). As an example, in the case where inter-frame prediction is applied to the current block, the predictor of the encoding device can determine any one of the regular merge mode, skip mode, MMVD mode, sub-block merge mode, partition mode, and CIIP mode as the prediction mode of the current block.

[0248] Here, the regular merge mode can be defined as a mode for deriving the motion information of the current block by using the motion information of neighboring blocks. The skip mode can be defined as a mode in which the predicted block is used as the reconstructed block. The MMVD mode can be applied to the merge mode or the skip mode, and can be defined as a merge (or skip) mode using the motion vector difference. The sub-block merge mode can be defined as a merge mode based on sub-blocks. The partition mode can be defined as a mode for performing prediction by dividing the current block into two partitions (diagonal or anti-diagonal). The CIIP mode can be defined as a mode in which inter-picture merge and intra-picture prediction are combined with each other.

[0249] The predictor of the encoding device can configure a merge candidate list based on the prediction mode of the current block (S1010). For example, in the case where the prediction mode of the current block is determined to be the (regular) merge mode, the predictor of the encoding device can configure a merge candidate list (or motion information candidate list) based on the spatial neighboring blocks and temporal neighboring blocks of the current block, and based on this, the predictor of the encoding device can generate motion information.

[0250] The predictor of the encoding device may derive the motion information of the current block based on the merge candidate list (S1020). The motion information may include a motion vector and a reference picture index. For example, when the prediction mode of the current block is determined to be the (regular) 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. In this case, the predictor of the encoding device may search for a block similar to the current block in a specific region (search region) of the reference picture through motion estimation to derive a reference block having the smallest difference or a difference equal to or less than a predetermined reference with respect to the current block, and based on this, the predictor of the encoding device may derive a reference picture index indicating the reference picture in which the reference block is located. In addition, the predictor of the encoding device may derive a motion vector based on the positional difference between the reference block and the current block.

[0251] The predictor of the encoding device may derive the predicted sample (predicted block) of the current block based on the prediction mode of the current block and the motion information of the current block (S1030). 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 this information.

[0252] The residual processor of the encoding device may derive the residual sample based on the original sample (original block) for the current block and the predicted sample (predicted block) for the current block (S1040). In addition, the residual processor of the encoding device may derive information about the residual sample based on the residual sample.

[0253] 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 (S1050). 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 bitstream. The bitstream may be sent to the decoding device through a network or a storage medium.

[0254] For example, the picture information may include information on 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). Additionally, the picture information may include information on the prediction mode of the current block, such as the Compilation Unit syntax and the Merge Data syntax. Here, the Sequence Parameter Set may include a Combined Inter-Inter and Intra-Prediction (CIIP) enable flag (ciip enable flag) and an enable flag for the partitioning mode. The Compilation Unit syntax may include a CU skip flag indicating whether the skip mode is applied to the current block.

[0255] According to an embodiment, as an example, in order to prevent duplicate transmission of the same syntax, the encoding device may apply some or all of the regular_merge_flag signaling conditions and related semantics, the MMVD_merge_flag signaling conditions and related semantics, the merge_subblock_flag signaling conditions and related semantics, and / or the CIIP flag signaling conditions and related semantics based on the condition that allows MMVD (MMVD mode) (MMVDAllowed), the condition that allows merging of sub-blocks (sub-block merge mode) (MergeSubBlockAllowed), the condition that allows merging of CIIP (CIIP mode) (MergeCIIPAllowed), and / or the condition that allows merging of triangles (partitioning mode) (MergeTriangleAllowed).

[0256] To this end, as an example, the Merge Data syntax may be configured as shown in Table 5 below.

[0257] [Table 5 ]

[0258]

[0259]

[0260] In Table 5, general_merge_flag[x0][y0] specifies whether the inter-frame prediction parameters for the current compilation unit are inferred from the inter-frame prediction partitions of adjacent frames. The array indices x0, y0 specify the position (x0, y0) of the top-left luma sample of the considered compilation block relative to the top-left luma sample of the picture.

[0261] When general_merge_flag[x0][y0] does not exist, the following inference is made.

[0262] - If cu_skip_flag[x0][y0] is equal to 1, then general_merge_flag[x0][y0] is inferred to be equal to 1.

[0263] - Otherwise, general_merge_flag[x0][y0] is inferred to be equal to 0.

[0264] In Table 5, the conditions for allowing MMVD (MMVD mode) (MMVDAllowed), the conditions for allowing merging of sub-blocks (sub-block merge mode) (MergeSubBlockAllowed), the conditions for allowing merging of CIIP (CIIP mode) (MergeCIIPAllowed), and / or the conditions for allowing merging of triangles (partition mode) (MergeTriangleAllowed) can be derived based on the following conditions.

[0265] If all of the following conditions are true, then the variable MMVDAllowed is set to be equal to true.

[0266] - general_merge_flag[x0][y0] is equal to 1

[0267] - sps_mmvd_enabled_flag is equal to 1

[0268] - cbWidth * CbHeight is greater than 32

[0269] If all of the following conditions are true, then the variable MergeSubblockAllowed is set to be equal to true.

[0270] - general_merge_flag[x0][y0] is equal to 1

[0271] - MaxNumSubblockMergeCand > 0

[0272] cbWidth is greater than or equal to 8, and cbHeight is greater than or equal to 8

[0273] If all of the following conditions are true, then the variable MergeCIIPAllowed is set to be equal to true.

[0274] - general_merge_flag[x0][y0] is equal to 1

[0275] - sps_ciip_enabled_Flag is equal to 1

[0276] - cu_skip_flag[x0][y0] is equal to 0

[0277] - cbWidth * cbHeight is greater than or equal to 64

[0278] - cbWidth is less than 128 and cbHeight is less than 128

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

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

[0281] - sps_triangle_enalbed_Flag is equal to 1, and slice_type is equal to B

[0282] - NaxNumTriangleMergeCand is greater than or equal to 2

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

[0284] In the above conditions, MMVDAllowed indicates the condition where MMVD is allowed, 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 4x8 blocks and / or 8x4 blocks, the compression efficiency can be improved, and thus the MMVDAllowed condition can be changed as follows.

[0285] If all of the following conditions are true, set the variable MMVDAllowed equal to true.

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

[0287] - sps_mmvd_enabled_flag is equal to 1

[0288] Meanwhile, regular_merge_flag[x0][y0] being equal to 1 specifies the regular merge mode for generating the inter-prediction parameters of the current coding unit. The array indices x0, y0 specify the position (x0, y0) of the top-left luminance sample of the coding block under consideration relative to the top-left luminance sample of the picture.

[0289] Referring to Table 5, the regular merge flag can be included in the image information, and in the case where at least one of the values of the condition based on the MMVD mode (MMVDAllowed), 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 regular merge flag can be signaled in the form of a bitstream.

[0290] As an example, when CIIP is enabled, the regular merge flag may be included in 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, when the general merge flag value is 1, the CIIP enable flag value is 1, the product of the height and width of the current block is equal to or greater than 64, the height or width of the current block is less than 128, or the skip flag value is 0, the regular merge flag may be included in the bitstream. Additionally, when all conditions based on the general merge flag, the CIIP enable flag, the current block size, and the CU skip flag are satisfied, the regular merge flag can be included in the bitstream.

[0291] As another example, when the partition mode is enabled, the regular merge flag may be included in the bitstream. The case where the partition mode is enabled can 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, when the general merge flag value is 1, the partition mode enable flag value is 1, the product of the height and 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 can be included in the bitstream. Additionally, when all of the above conditions are satisfied, the regular merge flag can be included in the bitstream.

[0292] When regular_merge_flag[x0][y0] does not exist in the merge data syntax, the following inference is made.

[0293] If all of the following conditions are true, then regular_merge_flag[x0][y0] is inferred to be equal to 1.

[0294] - MMVDAllowed is equal to 0

[0295] - MergeSubBlockAllowed is equal to 0

[0296] - MergeCIIPAllowd is equal to 0

[0297] - MergeTriangleAllowed is equal to 0

[0298] - Otherwise, regular_merge_flag[x0][y0] is inferred to be equal to 0.

[0299] Meanwhile, mmvd_merge_flag[x0][y0] being equal to 1 specifies that a merge mode with a motion vector difference is used to generate the inter-prediction parameters of the current coding unit. The array indices x0, y0 specify the position (x0, y0) of the top-left luma sample of the coding block under consideration relative to the top-left luma sample of the picture.

[0300] Referring to Table 5, the MMVD merge flag may be included in the picture information and signaled in the bitstream when at least one of the values in the condition based on the MMVD mode (MMVDAllowed), the condition based on the sub-block merge mode (MergeSubBlockAllowed), the condition based on the CIIP mode (MergeCIIPAllowd), and the condition based on the partition mode (MergeTriangleAllowed) is equal to 1.

[0301] When mmvd_merge_flag[x0][y0] is not present in the merge data syntax, it is inferred as follows.

[0302] If all of the following conditions are true, then mmvd_merge_flag[x0][y0] is inferred to be equal to 1.

[0303] - regular_merge_flag[x0][y0] is equal to 0

[0304] - MMVDAllowed is equal to 0

[0305] - MergeSubBlockAllowed is equal to 0

[0306] - MergeCIIPAllowd is equal to 0

[0307] - MergeTriangleAllowed is equal to 0

[0308] - Otherwise, mmvd_merge_flag[x0][y0] is inferred to be equal to 0.

[0309] mmvd_cand_flag[x0][y0] specifies whether the first (0) or second (1) candidate in the merge candidate list is used together with the motion vector difference derived from mmvd_distance_idx[x0][y0] and mmvd_direction_idx[x0][y0]. The array indices x0, y0 specify the position (x0, y0) of the top-left luma sample of the coding block under consideration 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.

[0310] mmvd_distance_idx[x0][y0] specifies the index used to derive MmvdDistance[x0][y0], as specified in Table 3. The array indices x0, y0 specify the position (x0, y0) of the upper-left luminance sample of the coding block under consideration relative to the upper-left luminance sample of the picture.

[0311] mmvd_direction_idx[x0][y0] specifies the index used to derive MmvdSign[x0][y0], as specified in Table 4. The array indices x0, y0 specify the position (x0, y0) of the upper-left luminance sample of the coding block under consideration relative to the upper-left luminance sample of the picture.

[0312] The two components of the merged plus MVD offset MmvdOffset[x0][y0] are derived as in Equation 1.

[0313] merge_subblock_flag[x0][y0] specifies whether to infer sub-block based inter prediction parameters for the current coding unit from neighboring blocks. The array indices x0, y0 specify the position (x0, y0) of the upper-left luminance sample of the coding block under consideration relative to the upper-left luminance sample of the picture.

[0314] Referring to Table 5, in the case where at least one of the values in the sub-block merge mode condition (MergeSubBlockAllowed), the CIIP mode condition (MergeCIIPAllowwed), and the partition mode condition (MergeTriangleAllowed) is 1, the merge sub-block flag may be included in the picture information and signaled in the form of a bitstream.

[0315] When merge_subblock_flag[x0][y0] does not exist in the merge data syntax, the following inference is made.

[0316] If all of the following conditions are true, then merge_subblock_flag[x0][y0] is inferred to be equal to 1.

[0317] - regular_merge_flag[x0][y0] is equal to 0

[0318] - mmvd_merge_flag[x0][y0] is equal to 0

[0319] - MergeSubBlockAllowed is equal to 0

[0320] - MergeCIIPAllowed is equal to 0

[0321] - MergeTriangleAllowed is equal to 0

[0322] - Otherwise, merge_subblock_flag[x0][y0] is inferred to be equal to 0.

[0323] merge_subblock_idx[x0][y0] specifies the merge candidate index based on the sub-block-based merge candidate list, where x0, y0 specify the position (x0, y0) of the upper-left luminance sample of the considered compilation block relative to the upper-left luminance sample of the picture.

[0324] When merge_subblock_idx[x0][y0] does not exist, it is inferred to be equal to 0.

[0325] Meanwhile, ciip_flag[x0][y0] specifies whether to apply combined inter-picture merge and intra-picture prediction to the current compilation unit. The array indices x0, y0 specify the position (x0, y0) of the upper-left luminance sample of the considered compilation block relative to the upper-left luminance sample of the picture.

[0326] Referring to Table 5, the CIIP flag can be included in the image information and can be signaled in the bitstream in the case where at least one of the conditions based on the CIIP mode (MergeCIIPAllowed) and the conditions based on the partition mode (MergeTriangleAllowed) has a value of 1.

[0327] For example, in the case where the partition mode is enabled, the CIIP flag can be included in the bitstream. The case where the partition mode is enabled can 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, in the case where the general merge flag value is 1, the partition mode enable flag value is 1, the product of the height and 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 can be included in the bitstream. Additionally, in the case where all of the above conditions are satisfied, the CIIP flag can be included in the bitstream.

[0328] When ciip_flag[x0][y0] does not exist, the following inference is made.

[0329] If all of the following conditions are true, then ciip_flag[x0][y0] is set to be equal to 1.

[0330] - MergeCIIPAllowed is equal to 0

[0331] -MergeTriangleAllowed is equal to 0

[0332] - Otherwise, ciip_flag[x0][y0] is set equal to 0.

[0333] 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.

[0334] 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.

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

[0336] -MergeTriangleAllowed is equal to 1

[0337] -regular_merge_flag[x0][y0] is equal to 0

[0338] -mmvd_merge_flag[x0][y0] is equal to 0

[0339] -merge_subblock_flag[x0][y0] is equal to 0

[0340] -ciip_flag[x0][y0] is equal to 0

[0341] Otherwise, MergeTriangleFlag[x0][y0] is equal to 0.

[0342] Figure 12 and Figure 13 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.

[0343] Figure 12 The decoding method disclosed in can be Figure 3 and Figure 13 Specifically, for example, Figure 12 S1200 to S1230 of may be performed by the predictor 330 of the decoding device 300. In this document, Figure 12 The decoding method disclosed in may include the above embodiments.

[0344] Referring to Figure 12 and Figure 13 , the decoding device can obtain information about the prediction mode for the current block from the bitstream, and based on this information, the decoding device can determine the prediction mode for the current block (S1200). Specifically, the entropy decoder 310 of the decoding device can derive residual information and information about the prediction mode from the signal received from the Figure 2 encoding device in the form of a bitstream. Here, the information about the prediction mode can be referred to as prediction-related information. The information about the prediction mode can include inter-frame / intra-frame prediction classification information and inter-frame prediction mode information, and can include various syntax elements related to this information.

[0345] In the bitstream, image information can be included, which includes 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). The image information can also include information about the prediction mode for the current block, such as Compilation Unit syntax and Merge Data syntax. The Sequence Parameter Set can include a CIIP enable flag and an enable flag for the partitioning mode. The Compilation Unit syntax can include a CU skip flag indicating whether the skip mode is applied to the current block.

[0346] The predictor 320 of the decoding device can configure a motion information candidate list (or merge candidate list) for the current block based on the prediction mode for the current block (S1210). In addition, the predictor 320 of the decoding device can select a merge candidate from the motion information candidate list based on the candidate selection information (merge index) obtained from the bitstream, and can use the motion information of the selected merge candidate to derive the motion information of the current block (S1220).

[0347] When the motion information of the current block is derived, the predictor of the decoding device can generate a prediction sample for the current block based on the motion information of the current block (S1230).

[0348] Meanwhile, the residual processor 320 of the decoding device can generate residual samples based on the residual information obtained from the bitstream.

[0349] The adder 340 of the decoding device can 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 can be generated based on the reconstructed sample. Thereafter, if necessary, in order to improve the subjective / objective picture quality, an in-loop filtering process such as deblocking filtering, SAO, and / or ALF process can be applied to the reconstructed picture.

[0350] As an example, when determining the prediction mode of the current block, if at least one value among the condition based on the MMVD mode (MMVDAllowed), 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 may obtain or parse a regular merge flag from the bitstream.

[0351] As an example, when CIIP is enabled, the decoding device may parse a regular merge flag from the bitstream. The situation where CIIP is enabled may 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, when the general merge flag value is 1, the CIIP enable flag value is 1, the product of the height and width of the current block is equal to or greater than 64, the height or width of the current block is less than 128, or the skip flag value is 0, the decoding device may determine that CIIP is enabled. In addition, when all the conditions based on the general merge flag, the CIIP enable flag, the current block size, and the CU skip flag are satisfied, the decoding device may determine that CIIP is enabled.

[0352] As another example, when the partition mode is enabled, the decoding device may parse a regular merge flag from the bitstream. The situation where the partition mode is enabled 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 and width of the current block is equal to or greater than 64, the slice type of the current block is B slice, or the maximum number of partition mode candidates is equal to or greater than 2. In addition, when all the above conditions are satisfied, the decoding device may determine that the partition mode is enabled.

[0353] Meanwhile, when determining the prediction mode for the current block, if at least one value among the condition based on the MMVD mode (MMVDAllowed), 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 may obtain or parse an MMVD merge flag from the bitstream.

[0354] In addition, when determining the prediction mode of the current block, if at least one value among the condition based on the sub-block merge mode (MergeSubBlockAllowed), the condition based on the CIIP mode (MergeCIIPAllowed), and the condition based on the partitioning mode (MergeTriangleAllowed) is 1, the predictor of the decoding device can obtain or parse the merge sub-block flag from the bitstream.

[0355] In addition, when determining the prediction mode for the current block, if at least one value among the condition based on the CIIP mode (MergeCIIPAllowed) and the condition based on the partitioning mode (MergeTriangleAllowed) is 1, the predictor of the decoding device can obtain or parse the CIIP flag from the bitstream. As an example, when the partitioning mode is enabled, the decoding device can parse the CIIP flag from the bitstream. The case where the partitioning mode is enabled can be determined based on at least one of the general merge flag, the partitioning mode enable flag indicating whether the partitioning mode is enabled, and the information about the current block. For example, the decoding device can determine that the partitioning mode is enabled when the general merge flag value is 1, the partitioning mode enable flag value is 1, the product of the height 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 partitioning mode candidates is equal to or greater than 2. In addition, when all of the above conditions are satisfied, the decoding device can determine that the partitioning mode is enabled.

[0356] Although the above exemplary system has been described with reference to a flowchart listing steps or blocks in sequence, 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 a different step, in a different order, or simultaneously. In addition, those of ordinary skill in the art will understand that the steps of the flowchart are not exclusive. On the contrary, within the scope of the present disclosure, another step can be included therein, or one or more steps can be deleted.

[0357] The above method according to the present disclosure can be in the form of software, and the encoding device and / or decoding device according to the present disclosure can be included in a device for performing image processing (such as a TV, a computer, a smart phone, a set-top box, a display device, etc.).

[0358] When an embodiment is implemented in software in the present disclosure, modules (procedures, functions, etc.) that perform the above functions may be used to implement the above method. The modules may be stored in a memory and executed by a processor. The memory may 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 chip sets, logic circuits, and / or a data processor. The memory may include a read-only memory (ROM), a random access memory (RAM), a 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 drawing may be implemented and executed on a computer, a processor, a microprocessor, a controller, or a chip. In this case, the information for implementation (e.g., information about instructions) or algorithms may be stored in a digital storage medium.

[0359] In addition, the decoding device and the encoding device to which the present disclosure is applied may include a multimedia broadcast transceiver, a mobile communication terminal, a home theater video device, a digital cinema video device, a surveillance camera, a video chat device, and real-time communication devices such as video communication, a mobile streaming device, a storage medium, a camera, a video-on-demand (VoD) service provider, an over-the-top (OTT) video device, an Internet streaming service provider, a 3D video device, a virtual reality (VR) device, an augmented reality (AR) device, an image phone video device, a vehicle terminal (e.g., a vehicle (including an autonomous vehicle) terminal, an aircraft terminal, or a ship terminal), and a medical video device, etc., and may be used to process image signals or data signals. For example, the OTT video device may include a game console, a Blu-ray player, an Internet-connected TV, a home theater system, a smart phone, a tablet PC, and a digital video recorder (DVR), etc.

[0360] In addition, the processing method to which the present disclosure is applied may be generated in the form of a program executed by a computer and may be stored in a computer-readable recording medium. Multimedia data having a data structure according to the present disclosure may also be stored in a computer-readable recording medium. The computer-readable recording medium includes all kinds of storage devices and distributed storage devices in which computer-readable data is stored. The computer-readable recording medium may 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. The computer-readable recording medium also includes a medium embodied in the form of a carrier wave (e.g., transmission through the Internet). In addition, the bit stream generated by an encoding method may be stored in a computer-readable recording medium or transmitted through a wired or wireless communication network.

[0361] In addition, embodiments of the present disclosure can be implemented as a computer program product based on program code, and the program code can be executed by a computer in embodiments of the present disclosure document. The program code can be stored on a computer-readable carrier.

[0362] Figure 14 An example of a content streaming system to which the embodiments disclosed in this document can be applied is shown.

[0363] Referring to Figure 14 , a content streaming system to which the embodiments of this document are applied can generally include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0364] The encoding server compresses the content input from a multimedia input device (such as a smart phone, a camera, and a video camera, etc.) into digital data to generate a bitstream and sends the bitstream to the streaming server. As another example, when the multimedia input device (such as a smart phone, a camera, and a video camera, etc.) directly generates a bitstream, the encoding server can be omitted.

[0365] The bitstream can be generated by applying an encoding method or a bitstream generation method of the embodiments of this document, and the streaming server can temporarily store the bitstream during the process of sending or receiving the bitstream.

[0366] The streaming server sends multimedia data to the user device through the web server based on a user request, and the web server serves as a medium for informing the user of available services. When the user requests a 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 can include a separate control server. In this case, the control server is used to control commands / responses between devices within the content streaming system.

[0367] The streaming server can receive content from the media storage and / or the encoding server. For example, when receiving content from the 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.

[0368] Examples of user devices can include mobile phones, smart phones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, tablet PCs, tablet PCs, ultrabooks, wearable devices (such as smart watches, smart glasses, head-mounted displays), digital TVs, desktop computers, digital signage, etc.

[0369] Each server in the content stream system can operate as a distribution server, in which case the data received from each server can be distributed.

Claims

1. A decoding method performed by a decoding device, the method comprising: Determining a prediction mode of a current block from a bitstream; Configuring a merge candidate list based on the prediction mode; Deriving motion information of the current block based on the merge candidate list; And Generating a prediction sample of the current block based on the motion information, Wherein the bitstream includes an enable flag indicating whether to apply combined inter-picture prediction and intra-picture prediction, Wherein determining the prediction mode of the current block includes: Obtaining a merge flag from the bitstream based on the enable flag indicating application of the combined inter-picture prediction and intra-picture prediction, the merge flag indicating that a merge mode is used to generate inter-frame prediction parameters of the current block; and Determining the merge mode indicated by the merge flag as the prediction mode of the current block.

2. An encoding method performed by an encoding device, the method comprising: Determining a prediction mode of a current block; Configuring a merge candidate list based on the prediction mode; Deriving motion information of the current block based on the merge candidate list; Generating a prediction sample of the current block based on the motion information, Deriving residual samples based on the prediction sample; And Encoding image information based on the residual samples, Wherein the image information includes an enable flag indicating whether to apply combined inter-picture prediction and intra-picture prediction, Wherein the image information further includes a merge flag based on the enable flag indicating application of the combined inter-picture prediction and intra-picture prediction, the merge flag indicating that a merge mode is used to generate inter-frame prediction parameters of the current block; and Wherein the prediction mode of the current block is configured to be determined based on the merge mode indicated by the merge flag.

3. A transmission method for image data, the transmission method comprising: Generating a bitstream, wherein the bitstream is generated by: Determining a prediction mode of a current block; Configuring a merge candidate list based on the prediction mode; Deriving motion information of the current block based on the merge candidate list; Deriving a prediction sample of the current block based on the motion information, Deriving residual samples based on the prediction sample; and Generating the bitstream by encoding image information based on the residual samples; and Transmitting the data including the bitstream, Wherein the image information includes an enable flag indicating whether to apply combined inter-picture prediction and intra-picture prediction, Wherein the image information further includes a merge flag based on the enable flag indicating application of combined inter-picture prediction and intra-picture prediction, the merge flag indicating that a merge mode is used to generate inter-frame prediction parameters of the current block; and Wherein the prediction mode of the current block is configured to be determined based on the merge mode indicated by the merge flag.

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