Image decoding / encoding method and bit stream transmission method

Abstract

Provided are an image encoding / decoding method and apparatus. An image decoding method performed by an image decoding apparatus according to the present disclosure may include the following steps: acquiring size information indicating the size of a current slice corresponding to at least a portion of a current picture from a bitstream; and determining the size of the current slice based on the size information.

Description

Technical Field

[0001] The present disclosure relates to an image encoding / decoding method and apparatus, and more particularly, to an image encoding and decoding method and apparatus for selectively encoding size information of a slice, and a method of transmitting a bitstream generated by the image encoding method / apparatus of the present disclosure. Background Art

[0002] Recently, demand for high-resolution and high-quality images, such as high-definition (HD) and ultra-high-definition (UHD) images, is increasing across various fields. As the resolution and quality of image data improve, the amount of information or bits transmitted increases relative to existing image data. This increase in the amount of information or bits transmitted leads to increased transmission and storage costs.

[0003] Therefore, efficient image compression technology is needed to effectively transmit, store, and reproduce information about high-resolution and high-quality images. Summary of the Invention

[0004] Technical issues

[0005] An object of the present disclosure is to provide an image encoding / decoding method and apparatus with improved encoding / decoding efficiency.

[0006] Another object of the present disclosure is to provide an image encoding / decoding method and apparatus that improves encoding / decoding efficiency by selectively encoding size information of slices.

[0007] Another object of the present disclosure is to provide a method for transmitting a bitstream generated by the image encoding method or apparatus according to the present disclosure.

[0008] Another object of the present disclosure is to provide a recording medium storing a bit stream generated by the image encoding method or apparatus according to the present disclosure.

[0009] Another object of the present disclosure is to provide a recording medium storing a bit stream received and decoded by the image decoding apparatus according to the present disclosure and used to reconstruct an image.

[0010] The technical problems solved by the present disclosure are not limited to the above-mentioned technical problems, and those skilled in the art will understand other technical problems not described herein through the following description.

[0011] Technical Solution

[0012] According to one aspect of the present disclosure, an image decoding method performed by an image decoding device may include the following steps: obtaining size information indicating the size of a current slice corresponding to at least a portion of a current picture from a bitstream; and determining the size of the current slice based on the size information. Here, the size information may include width information indicating the width of the current slice in units of tile columns and height information indicating the height of the current slice in units of tile rows. The step of obtaining the size information from the bitstream may be performed based on whether the current slice belongs to the last tile column or last tile row of the current picture.

[0013] In addition, an image decoding device according to an aspect of the present disclosure may include a memory and at least one processor. The at least one processor may obtain size information indicating the size of a current slice corresponding to at least a portion of a current picture from a bitstream; and determine the size of the current slice based on the size information. Here, the size information may include width information indicating the width of the current slice in units of tile columns and height information indicating the height of the current slice in units of tile rows, and the size information may be obtained based on whether the current slice belongs to the last tile column or last tile row of the current picture.

[0014] According to another aspect of the present disclosure, an image encoding method performed by an image encoding device may include the following steps: determining a current slice corresponding to at least a portion of a current picture; and generating a bitstream including size information of the current slice. Here, the size information may include width information indicating the width of the current slice in units of tile columns and height information indicating the height of the current slice in units of tile rows. The step of generating the bitstream including the size information of the current slice may be performed based on whether the current slice belongs to the last tile column or the last tile row of the current picture.

[0015] In addition, a transmission method according to another aspect of the present disclosure may transmit a bit stream generated by the image encoding apparatus or the image encoding method of the present disclosure.

[0016] In addition, a computer-readable recording medium according to another aspect of the present disclosure may store a bitstream generated by the image encoding apparatus or the image encoding method of the present disclosure.

[0017] The features briefly summarized above with respect to the present disclosure are merely exemplary aspects of the following detailed description of the present disclosure and do not limit the scope of the present disclosure.

[0018] Beneficial effects

[0019] According to the present disclosure, it is possible to provide an image encoding / decoding method and apparatus with improved encoding / decoding efficiency.

[0020] Furthermore, according to the present disclosure, it is possible to provide an image encoding / decoding method and apparatus that improve encoding / decoding efficiency by selectively encoding size information of slices.

[0021] Furthermore, according to the present disclosure, a method of transmitting a bitstream generated by the image encoding method or apparatus according to the present disclosure may be provided.

[0022] Furthermore, according to the present disclosure, a recording medium storing a bit stream generated by the image encoding method or apparatus according to the present disclosure can be provided.

[0023] Furthermore, according to the present disclosure, there can be provided a recording medium storing a bit stream received and decoded by the image decoding apparatus according to the present disclosure and used to reconstruct an image.

[0024] Those skilled in the art will understand that the effects that can be achieved through the present disclosure are not limited to the contents that have been specifically described above, and other advantages of the present disclosure will be more clearly understood from the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 FIG. 1 is a diagram schematically illustrating a video encoding system to which embodiments of the present disclosure are applicable.

[0026] Figure 2 is a diagram schematically showing an image encoding device to which an embodiment of the present disclosure is applicable.

[0027] Figure 3 FIG. 1 is a diagram schematically showing an image decoding device to which an embodiment of the present disclosure is applicable.

[0028] Figure 4 is a diagram illustrating a segmentation structure of an image according to an embodiment.

[0029] Figure 5 is a view showing an embodiment of a partition type of a block according to a multi-type tree structure.

[0030] Figure 6 is a diagram illustrating a signaling mechanism of block partitioning information in a quadtree having a nested multi-type tree structure according to the present disclosure.

[0031] Figure 7 FIG. 1 is a diagram illustrating an embodiment of dividing a CTU into a plurality of CUs.

[0032] Figure 8 is a diagram illustrating neighboring reference samples according to an embodiment.

[0033] Figures 9 and 10 is a view illustrating intra prediction according to an embodiment.

[0034] Figure 11 is a view illustrating an encoding method using inter-frame prediction according to an embodiment.

[0035] Figure 12 is a view illustrating a decoding method using inter-frame prediction according to an embodiment.

[0036] Figure 13 is a block diagram of CABAC according to an embodiment for encoding one syntax element.

[0037] Figures 14 to 17 is a view illustrating entropy encoding and entropy decoding according to an embodiment.

[0038] Figure 18 and Figure 19 is a view showing an example of an image decoding and encoding process according to an embodiment.

[0039] Figure 20 is a diagram showing a layer structure of an encoded image according to an embodiment.

[0040] Figures 21 to 24 is a view illustrating an embodiment of dividing a screen using tiles, slices, and sub-pictures.

[0041] Figure 25 is a diagram showing an implementation of the syntax of a sequence parameter set.

[0042] Figure 26 is a view showing an embodiment of the syntax of a picture parameter set.

[0043] Figure 27 is a view showing an implementation of the syntax of the slice header.

[0044] Figure 28 and Figure 29 It is a view showing an embodiment of an encoding method and a decoding method.

[0045] Figure 30 and Figure 31 is a diagram illustrating another embodiment of a picture parameter set.

[0046] Figure 32 is a view showing an embodiment of a decoding method.

[0047] Figure 33 and Figure 34 is a view showing an algorithm for determining SliceTopLeftTileIdx.

[0048] Figure 35 is a view showing an embodiment of an encoding method.

[0049] Figure 36 is a diagram illustrating a content streaming system to which an embodiment of the present disclosure is applicable. DETAILED DESCRIPTION

[0050] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings to facilitate implementation by those skilled in the art. However, the present disclosure can be implemented in various forms and is not limited to the embodiments described herein.

[0051] When describing the present disclosure, if it is determined that the detailed description of related known functions or configurations makes the scope of the present disclosure unnecessarily ambiguous, its detailed description will be omitted. In the drawings, parts not related to the description of the present disclosure are omitted, and like reference numerals are given to like parts.

[0052] In the present disclosure, when a component is “connected,” “coupled,” or “linked” to another component, it may include not only a direct connection relationship but also an indirect connection relationship with intermediate components. In addition, when a component “includes” or “has” other components, unless otherwise specified, it means that other components may also be included, rather than excluding other components.

[0053] In the present disclosure, the terms first, second, etc. may be used only to distinguish one component from other components and do not limit the order or importance of the components unless otherwise specified. Accordingly, within the scope of the present disclosure, the first component in one embodiment may be referred to as the second component in another embodiment, and similarly, the second component in one embodiment may be referred to as the first component in another embodiment.

[0054] In this disclosure, components that are distinguished from each other are intended to clearly describe each feature and do not necessarily mean that the components must be separated. In other words, multiple components can be integrated and implemented in a single hardware or software unit, or a single component can be distributed and implemented in multiple hardware or software units. Therefore, even if not otherwise specified, embodiments in which components are integrated or distributed are also included in the scope of this disclosure.

[0055] In the present disclosure, the components described in the various embodiments are not necessarily essential components, and some components may be optional components. Therefore, embodiments consisting of a subset of the components described in the embodiments are also included in the scope of the present disclosure. In addition, embodiments that include other components in addition to the components described in the various embodiments are included in the scope of the present disclosure.

[0056] The present disclosure relates to encoding and decoding of images. Unless otherwise defined in the present disclosure, terms used in the present disclosure may have general meanings commonly used in the technical field to which the present disclosure belongs.

[0057] In the present disclosure, "video" may refer to a set of images over time. A picture generally refers to a unit representing an image at a specific time, while a slice / tile is a coding unit that constitutes a part of a picture during the encoding process. A picture may be composed of one or more slices / tiles. In addition, a slice / tile may include one or more coding tree units (CTUs). A picture may be composed of one or more slices / tiles. A picture may include one or more tile groups. A tile group may include one or more tiles. A tile may represent a rectangular area of ​​a CTU row within a tile in a picture. A tile may include one or more tiles. A tile may represent a rectangular area of ​​a CTU row within a tile. A tile may be divided into multiple tiles, and each tile may include one or more CTU rows belonging to a tile. A tile that is not divided into multiple tiles may also be considered a tile.

[0058] "Pixel" or "picture element (pel)" may refer to the smallest unit constituting a picture (or image). In addition, "sample" may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, or may represent only a pixel / pixel value of a luminance component or only a pixel / pixel value of a chrominance component.

[0059] In the present disclosure, a "unit" may refer to a basic unit of image processing. A unit may include at least one of a specific area of ​​a picture and information related to the area. A unit may include a luma block and two chroma blocks (e.g., Cb and Cr). In some cases, a unit may be used interchangeably with terms such as "sample array," "block," or "area." In general, an M×N block may include M columns and N rows of samples (or sample arrays) or a set (or array) of transform coefficients.

[0060] In the present disclosure, the term "current block" may refer to one of the following: "current coding block," "current coding unit," "encoding target block," "decoding target block," or "processing target block." When prediction is performed, the term "current block" may refer to either the "current prediction block" or the "prediction target block." When transform (inverse transform) / quantization (dequantization) is performed, the term "current block" may refer to either the "current transform block" or the "transform target block." When filtering is performed, the term "current block" may refer to the "filtering target block."

[0061] In addition, in the present disclosure, unless explicitly stated as a chroma block, "current block" may mean "luminance block of the current block." "Chroma block of the current block" may be expressed by including an explicit description of the chroma block such as "chroma block" or "current chroma block."

[0062] In this disclosure, the slash " / " or "," should be interpreted as indicating "and / or". For example, the expressions "A / B" and "A, B" may mean "A and / or B". In addition, "A / B / C" and "A / B / C" may mean "at least one of A, B, and / or C".

[0063] In the present disclosure, the term "or" should be interpreted as meaning "and / or". For example, the expression "A or B" may include 1) only "A", 2) only "B", and / or 3) both "A and B". In other words, in the present disclosure, the term "or" should be interpreted as meaning "additionally or alternatively".

[0064] Overview of Video Coding Systems

[0065] Figure 1 is a diagram illustrating a video encoding system according to the present disclosure.

[0066] The video encoding system according to an embodiment may include a source device 10 and a receiving device 20. The source device 10 may deliver encoded video and / or image information or data to the receiving device 20 via a digital storage medium or a network in the form of a file or a stream.

[0067] The source device 10 according to the embodiment may include a video source generator 11, an encoding device 12, and a transmitter 13. The receiving device 20 according to the embodiment may include a receiver 21, a decoding device 22, and a renderer 23. The encoding device 12 may be referred to as a video / image encoding device, and the decoding device 22 may be referred to as a video / image decoding device. The transmitter 13 may be included in the encoding device 12. The receiver 21 may be included in the decoding device 22. The renderer 23 may include a display, and the display may be configured as a separate device or an external component.

[0068] The video source generator 11 can obtain video / images by capturing, synthesizing, or generating video / images. The video source generator 11 may include a video / image capture device and / or a video / image generation device. The video / image capture device may include, for example, one or more cameras, a video / image archive including previously captured videos / images, etc. The video / image generation device may include, for example, a computer, a tablet computer, and a smartphone, and may generate videos / images (electronically). For example, a virtual video / image may be generated by a computer, etc. In this case, the video / image capture process may be replaced by a process for generating relevant data.

[0069] The encoding device 12 can encode the input video / image. For compression and coding efficiency, the encoding device 12 can perform a series of processes such as prediction, transformation, and quantization. The encoding device 12 can output the encoded data (encoded video / image information) in the form of a bitstream.

[0070] The transmitter 13 can transmit the encoded video / image information or data output in the form of a bitstream to the receiver 21 of the receiving device 20 in the form of a file or stream via a digital storage medium or a network. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitter 13 may include components for generating a media file in a predetermined file format and may also include components for transmitting via a broadcast / communication network. The receiver 21 may extract / receive the bitstream from the storage medium or network and transmit the bitstream to the decoding device 22.

[0071] The decoding device 22 may perform decoding on a video / image by performing a series of processes corresponding to the operations of the encoding device 12 , such as dequantization, inverse transformation, and prediction.

[0072] The renderer 23 may render the decoded video / image. The rendered video / image may be displayed on a display.

[0073] Overview of Image Coding Devices

[0074] Figure 2 is a diagram schematically showing an image encoding device to which an embodiment of the present disclosure is applicable.

[0075] like Figure 2 As shown, the image source device 100 may include an image segmenter 110, a subtractor 115, a transformer 120, a quantizer 130, a dequantizer 140, an inverse transformer 150, an adder 155, a filter 160, a memory 170, an inter-frame predictor 180, an intra-frame predictor 185, and an entropy encoder 190. The inter-frame predictor 180 and the intra-frame predictor 185 may be collectively referred to as a "predictor." The transformer 120, the quantizer 130, the dequantizer 140, and the inverse transformer 150 may be included in a residual processor. The residual processor may also include the subtractor 115.

[0076] In some embodiments, all or at least some of the components configuring the image source device 100 may be configured by one hardware component (eg, an encoder or a processor). In addition, the memory 170 may include a decoded picture buffer (DPB) and may be configured by a digital storage medium.

[0077] The image splitter 110 can split the input image (or picture or frame) input to the image source device 100 into one or more processing units. For example, a processing unit can be called a coding unit (CU). The coding unit can be obtained by recursively splitting a coding tree unit (CTU) or a maximum coding unit (LCU) according to a quadtree, binary tree, and ternary tree (QT / BT / TT) structure. For example, a coding unit can be split into multiple coding units of a deeper depth based on a quadtree structure, a binary tree structure, and / or a ternary tree structure. For the splitting of the coding unit, the quadtree structure can be applied first, and the binary tree structure and / or the ternary tree structure can be applied later. The encoding process according to the present disclosure can be performed based on the final coding unit that is no longer split. The maximum coding unit can be used as the final coding unit, and the coding unit of a deeper depth obtained by splitting the maximum coding unit can also be used as the final coding unit. Here, the encoding process may include the prediction, transformation, and reconstruction processes described later. As another example, the processing unit of the encoding process can be a prediction unit (PU) or a transform unit (TU). The prediction unit and the transform unit may be divided or partitioned from the final coding unit. The prediction unit may be a sample prediction unit, and the transform unit may be a unit for deriving a transform coefficient and / or a unit for deriving a residual signal from the transform coefficient.

[0078] The predictor (inter-frame predictor 180 or intra-frame predictor 185) can perform prediction on the block to be processed (current block) and generate a prediction block including prediction samples of the current block. The predictor can determine whether to apply intra-frame prediction or inter-frame prediction based on the current block or CU. The predictor can generate various information related to the prediction of the current block and send the generated information to the entropy encoder 190. The information about the prediction can be encoded in the entropy encoder 190 and output in the form of a bitstream.

[0079] The intra-frame predictor 185 can predict the current block by referring to samples in the current picture. Depending on the intra-frame prediction mode and / or intra-frame prediction technology, the reference samples can be located in the neighborhood of the current block or can be placed separately. The intra-frame prediction mode may include multiple non-directional modes and multiple directional modes. The non-directional mode may include, for example, a DC mode and a planar mode. Depending on the level of detail of the prediction direction, the directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes. However, this is merely an example, and more or fewer directional prediction modes may be used depending on the settings. The intra-frame predictor 185 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0080] The inter-frame predictor 180 can derive a prediction block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. In this case, to reduce the amount of motion information transmitted in inter-frame prediction mode, motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of motion information between neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can also include information about the inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter-frame prediction, neighboring blocks can include spatially neighboring blocks in the current picture and temporally neighboring blocks in the reference picture. The reference picture including the reference block and the reference picture including the temporally neighboring block can be the same or different. Temporally neighboring blocks can be referred to as collocated reference blocks, collocated CUs (colCUs), etc. A reference picture including temporally neighboring blocks can be referred to as collocated pictures (colPics). For example, the inter-frame predictor 180 can configure a motion information candidate list based on the neighboring blocks and generate information indicating which candidate to use to derive the motion vector and / or reference picture index for the current block. Inter-frame prediction can be performed based on various prediction modes. For example, in the case of skip mode and merge mode, the inter-frame predictor 180 can use the motion information of the neighboring block as the motion information of the current block. In the case of skip mode, unlike merge mode, a residual signal may not be transmitted. In the case of motion vector prediction (MVP) mode, the motion vector of the neighboring block can be used as a motion vector predictor, and the motion vector of the current block can be signaled by encoding a motion vector difference and an indicator of the motion vector predictor. The motion vector difference may mean the difference between the motion vector of the current block and the motion vector predictor.

[0081] The predictor can generate a prediction signal based on various prediction methods and prediction techniques described below. For example, the predictor can apply not only intra-frame prediction or inter-frame prediction, but also both intra-frame prediction and inter-frame prediction simultaneously to predict the current block. The prediction method that simultaneously applies both intra-frame prediction and inter-frame prediction to predict the current block is referred to as combined inter-frame and intra-frame prediction (CIIP). In addition, the predictor can perform intra-frame block copying (IBC) to predict the current block. Intra-frame block copying can be used for content image / video encoding such as gaming, such as screen content coding (SCC). IBC is a method that uses a previously reconstructed reference block in the current picture at a predetermined distance from the current block to predict the current picture. When IBC is applied, the position of the reference block in the current picture can be encoded as a vector (block vector) corresponding to the predetermined distance. IBC essentially performs prediction within the current picture, but can be performed similarly to inter-frame prediction because the reference block is derived within the current picture. That is, IBC can use at least one of the inter-frame prediction techniques described in this disclosure.

[0082] The prediction signal generated by the predictor can be used to generate a reconstructed signal or a residual signal. The subtractor 115 can generate a residual signal (residual block or residual sample array) by subtracting the prediction signal (prediction block or prediction sample array) output from the predictor from the input image signal (original block or original sample array). The generated residual signal can be sent to the transformer 120.

[0083] The transformer 120 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a Karhunen-Loève transform (KLT), a graph-based transform (GBT), or a conditional nonlinear transform (CNT). Here, GBT refers to a transform obtained from a graph when the relationship information between pixels is represented by a graph. CNT refers to a transform obtained based on a prediction signal generated using all previously reconstructed pixels. In addition, the transform process may be applied to square pixel blocks of the same size or to blocks of variable size other than square.

[0084] The quantizer 130 may quantize the transform coefficients and transmit them to the entropy encoder 190. The entropy encoder 190 may encode the quantized signal (information about the quantized transform coefficients) and output a bitstream. The information about the quantized transform coefficients may be referred to as residual information. The quantizer 130 may rearrange the quantized transform coefficients of the block type into a one-dimensional vector form based on the coefficient scanning order, and generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form.

[0085] The entropy encoder 190 can perform various encoding methods, such as exponential Golomb, context-adaptive variable length coding (CAVLC), context-adaptive binary arithmetic coding (CABAC), etc. The entropy encoder 190 can encode information required for video / image reconstruction other than quantized transform coefficients (e.g., values ​​of syntax elements, etc.) together or separately. The encoded information (e.g., encoded video / image information) can be transmitted or stored in the form of a bitstream in units of a network abstraction layer (NAL). The video / image information may also include information about various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may also include general constraint information. The signaled information, transmitted information, and / or syntax elements described in the present disclosure may be encoded through the above-mentioned encoding process and included in the bitstream.

[0086] The bitstream may be transmitted via a network or stored in a digital storage medium. The network may include a broadcast network and / or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitter (not shown) that transmits the signal output from the entropy encoder 190 and / or a storage unit (not shown) that stores the signal may be included as an internal / external element of the image source device 100. Alternatively, the transmitter may be provided as a component of the entropy encoder 190.

[0087] The quantized transform coefficients output from the quantizer 130 may be used to generate a residual signal. For example, the residual signal (residual block or residual sample) may be reconstructed by applying dequantization and inverse transform to the quantized transform coefficients through the dequantizer 140 and the inverse transformer 150.

[0088] The adder 155 adds the reconstructed residual signal to the prediction signal output from the inter-frame predictor 180 or the intra-frame predictor 185 to generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array). If the block to be processed has no residual, such as when skip mode is applied, the prediction block can be used as the reconstructed block. The adder 155 can be called a reconstructor or a reconstructed block generator. The generated reconstructed signal can be used for intra-frame prediction of the next block to be processed in the current picture, and can be used for inter-frame prediction of the next picture through filtering as described below.

[0089] The filter 160 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 160 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 170, specifically, in the DPB of the memory 170. Various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filtering, bilateral filtering, etc. The filter 160 can generate various information related to filtering and send the generated information to the entropy encoder 190, as described later in the description of each filtering method. The information related to filtering can be encoded by the entropy encoder 190 and output in the form of a bitstream.

[0090] The modified reconstructed picture transmitted to the memory 170 may be used as a reference picture in the inter predictor 180. When inter prediction is applied by the image source device 100, prediction mismatch between the image source device 100 and the image decoding apparatus may be avoided and encoding efficiency may be improved.

[0091] The DPB of the memory 170 can store the modified reconstructed picture for use as a reference picture in the inter-frame predictor 180. The memory 170 can store motion information of blocks used to derive (or encode) motion information in the current picture and / or motion information of reconstructed blocks in the picture. The stored motion information can be sent to the inter-frame predictor 180 and used as motion information of spatially adjacent blocks or motion information of temporally adjacent blocks. The memory 170 can store reconstructed samples of the reconstructed blocks in the current picture and can transmit the reconstructed samples to the intra-frame predictor 185.

[0092] Overview of Image Decoding Equipment

[0093] Figure 3 FIG. 1 is a diagram schematically showing an image decoding device to which an embodiment of the present disclosure is applicable.

[0094] like Figure 3 As shown, the image receiving apparatus 200 may include an entropy decoder 210, a dequantizer 220, an inverse transformer 230, an adder 235, a filter 240, a memory 250, an inter-frame predictor 260, and an intra-frame predictor 265. The inter-frame predictor 260 and the intra-frame predictor 265 may be collectively referred to as a "predictor." The dequantizer 220 and the inverse transformer 230 may be included in a residual processor.

[0095] According to an embodiment, all or at least some of the components configuring the image receiving apparatus 200 may be configured by hardware components (eg, a decoder or a processor). In addition, the memory 250 may include a decoded picture buffer (DPB) or may be configured by a digital storage medium.

[0096] The image receiving apparatus 200 having received a bit stream including video / image information can perform the same operation as that performed by Figure 2 The image source device 100 reconstructs the image using processing corresponding to the processing performed by the image receiving device 200. For example, the image receiving device 200 may perform decoding using a processing unit used in an image encoding device. Therefore, the decoding processing unit may be, for example, a coding unit. A coding unit may be obtained by dividing a coding tree unit or a maximum coding unit. The reconstructed image signal decoded and output by the image receiving device 200 may be reproduced by a reproduction device (not shown).

[0097] The image receiving apparatus 200 can receive the image in the form of a bit stream from Figure 2The received signal can be decoded by the entropy decoder 210. For example, the entropy decoder 210 can parse the bitstream to derive the information required for image reconstruction (or picture reconstruction) (for example, video / image information). The video / image information may also include information about various parameter sets, such as an adaptive parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may also include general constraint information. The image decoding device may also decode the picture based on the information about the parameter set and / or the general constraint information. The signaled / received information and / or syntax elements described in the present disclosure can be decoded and obtained from the bitstream through a decoding process. For example, the entropy decoder 210 decodes the information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and outputs the values ​​of the syntax elements required for image reconstruction and the quantized values ​​of the transform coefficients of the residual. More specifically, the CABAC entropy decoding method can receive a bin corresponding to each syntax element in the bitstream, use the decoding target syntax element information, the decoding information of the neighboring blocks and the decoding target block, or the information of the symbol / bin decoded at the previous stage to determine the context model, perform arithmetic decoding on the bin by predicting the probability of occurrence of the bin according to the determined context model, and generate a symbol corresponding to the value of each syntax element. In this case, after determining the context model, the CABAC entropy decoding method can update the context model by using the information of the decoded symbol / bin for the context model of the next symbol / bin. The information related to prediction among the information decoded by the entropy decoder 210 can be provided to the predictor (inter-frame predictor 260 and intra-frame predictor 265), and the residual value (that is, quantized transform coefficients and related parameter information) on which entropy decoding is performed in the entropy decoder 210 can be input to the dequantizer 220. In addition, the information about filtering among the information decoded by the entropy decoder 210 can be provided to the filter 240. In addition, a receiver (not shown) for receiving a signal output from the image encoding apparatus may be further configured as an internal / external element of the image receiving device 200 , or the receiver may be a component of the entropy decoder 210 .

[0098] In addition, the image decoding device according to the present disclosure may be referred to as a video / image / picture decoding device. The image decoding device may be divided into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder may include an entropy decoder 210. The sample decoder may include a dequantizer 220, an inverse transformer 230, an adder 235, a filter 240, a memory 250, an inter-frame predictor 260, or at least one of an intra-frame predictor 265.

[0099] The dequantizer 220 may dequantize the quantized transform coefficients and output the transform coefficients. The dequantizer 220 may rearrange the quantized transform coefficients in the form of two-dimensional blocks. In this case, the rearrangement may be performed based on the coefficient scanning order performed in the image encoding device. The dequantizer 220 may dequantize the quantized transform coefficients using quantization parameters (e.g., quantization step size information) and obtain the transform coefficients.

[0100] The inverse transformer 230 may perform inverse transformation on the transformation coefficients to obtain a residual signal (residual block, residual sample array).

[0101] The predictor may perform prediction on the current block and generate a prediction block including prediction samples of the current block. The predictor may determine whether to apply intra prediction or inter prediction to the current block based on the prediction information output from the entropy decoder 210, and may determine a specific intra / inter prediction mode (prediction technique).

[0102] As described in the predictor of the image source device 100 , the predictor can generate a prediction signal based on various prediction methods (techniques) to be described later.

[0103] The intra predictor 265 may predict the current block by referring to samples in the current picture. The description of the intra predictor 185 is also applicable to the intra predictor 265.

[0104] The inter-frame predictor 260 can derive a prediction block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. In this case, to reduce the amount of motion information transmitted in inter-frame prediction mode, motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of motion information between neighboring blocks and the current block. Motion information can include a motion vector and a reference picture index. Motion information can also include information on the inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter-frame prediction, neighboring blocks can include spatial neighboring blocks in the current picture and temporal neighboring blocks in the reference picture. For example, the inter-frame predictor 260 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 received candidate selection information. Inter-frame prediction can be performed based on various prediction modes, and information about the prediction can include information indicating the inter-frame prediction mode of the current block.

[0105] The adder 235 can generate a reconstruction signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the obtained residual signal to the prediction signal (prediction block, prediction sample array) output from the predictor (including the inter-frame predictor 260 and / or the intra-frame predictor 265). If the block to be processed has no residual, such as when the skip mode is applied, the prediction block can be used as the reconstructed block. The description of the adder 155 also applies to the adder 235. The adder 235 can be called a reconstructor or a reconstructed block generator. The generated reconstruction signal can be used for intra-frame prediction of the next block to be processed in the current picture, and can be used for inter-frame prediction of the next picture through filtering as described below.

[0106] The filter 240 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 240 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 250, specifically, in the DPB of the memory 250. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filtering, bilateral filtering, etc.

[0107] The (modified) reconstructed picture stored in the DPB of the memory 250 can be used as a reference picture in the inter-frame predictor 260. The memory 250 can store motion information of blocks for deriving (or decoding) motion information in the current picture and / or motion information of reconstructed blocks in the picture. The stored motion information can be sent to the inter-frame predictor 260 to be used as motion information of spatially adjacent blocks or motion information of temporally adjacent blocks. The memory 250 can store reconstructed samples of the reconstructed blocks in the current picture and transmit the reconstructed samples to the intra-frame predictor 265.

[0108] In the present disclosure, the embodiments described in the filter 160 , the inter predictor 180 , and the intra predictor 185 of the image source device 100 may be equally or correspondingly applied to the filter 240 , the inter predictor 260 , and the intra predictor 265 of the image receiving device 200 .

[0109] Overview of Image Segmentation

[0110] The video / image encoding method according to the present disclosure can be performed based on the following image segmentation structure. Specifically, the prediction, residual processing ((inverse) transform, (de)quantization, etc.), syntax element encoding and filtering processes described later can be performed based on the CTU, CU (and / or TU, PU) derived according to the image segmentation structure. The image can be segmented in block units and the block segmentation process can be performed in the image segmentor 110 of the encoding device. The segmentation related information can be encoded by the entropy encoder 190 and sent to the decoding device in the form of a bit stream. The entropy decoder 210 of the decoding device can derive the block segmentation structure of the current picture based on the segmentation related information obtained from the bit stream, and based on this, a series of processes (for example, prediction, residual processing, block / picture reconstruction, in-loop filtering, etc.) can be performed to perform image decoding.

[0111] A picture may be partitioned into a sequence of coding tree units (CTUs). Figure 4 An example of a picture being partitioned into CTUs is shown. A CTU may correspond to a coding tree block (CTB). Alternatively, a CTU may include a coding tree block of luma samples and two corresponding coding tree blocks of chroma samples. For example, for a picture containing three sample arrays, a CTU may include an N×N block of luma samples and two corresponding blocks of chroma samples. The maximum allowed size of a CTU for encoding and prediction may be different from the maximum allowed size of a CTU for transform. For example, even if the maximum size of a luma transform block is 64×64, the maximum allowed size of a luma block in a CTU may be 128×128.

[0112] Overview of CTU Segmentation

[0113] As described above, a coding unit (CTU) or a largest coding unit (LCU) may be obtained by recursively partitioning the coding tree unit (CTU) or the largest coding unit (LCU) according to a quadtree / binarytree / ternarytree (QT / BT / TT) structure. For example, the CTU may first be partitioned into a quadtree structure. Thereafter, the leaf nodes of the quadtree structure may be further partitioned using a multi-type tree structure.

[0114] Partitioning according to the quadtree means that the current CU (or CTU) is equally divided into four. By partitioning according to the quadtree, the current CU can be partitioned into four CUs with the same width and the same height. When the current CU is no longer partitioned into the quadtree structure, the current CU corresponds to a leaf node of the quadtree structure. The CU corresponding to the leaf node of the quadtree structure can no longer be partitioned and can be used as the final coding unit mentioned above. Alternatively, the CU corresponding to the leaf node of the quadtree structure can be further partitioned by a multi-type tree structure.

[0115] Figure 51 is a diagram illustrating an embodiment of a partition type of a block according to a multi-type tree structure. The partition according to the multi-type tree structure may include two types of partitions according to a binary tree structure and two types of partitions according to a ternary tree structure.

[0116] The two types of splits according to the binary tree structure may include vertical binary split (SPLIT_BT_VER) and horizontal binary split (SPLIT_BT_HOR). Vertical binary split (SPLIT_BT_VER) means that the current CU is equally split into two in the vertical direction. Figure 4 As shown in FIG, by vertical binary splitting, two CUs with the same height as the current CU and half the width of the current CU can be generated. Horizontal binary splitting (SPLIT_BT_HOR) means that the current CU is equally split into two in the horizontal direction. Figure 5 As shown, through horizontal binary partitioning, two CUs with a height half of the height of the current CU and the same width as the current CU can be generated.

[0117] The two types of splits according to the ternary tree structure may include vertical ternary split (SPLIT_TT_VER) and horizontal ternary split (SPLIT_TT_HOR). In vertical ternary split (SPLIT_TT_VER), the current CU is split in a vertical direction at a ratio of 1:2:1. Figure 5 As shown, through vertical trifurcated partitioning, two CUs with the same height as the current CU and a width of 1 / 4 of the current CU width and one CU with the same height as the current CU and a width of half the current CU width can be generated. In horizontal trifurcated partitioning (SPLIT_TT_HOR), the current CU is split in the horizontal direction at a ratio of 1:2:1. Figure 5 As shown, through horizontal trifurcated partitioning, two CUs with a height of 1 / 4 of the current CU and the same width as the current CU and one CU with a height of half the current CU and the same width as the current CU can be generated.

[0118] Figure 6 is a diagram illustrating a signaling mechanism of block partitioning information in a quadtree having a nested multi-type tree structure according to the present disclosure.

[0119] Here, the CTU is regarded as the root node of the quadtree and is first split into a quadtree structure. Information (e.g., qt_split_flag) indicating whether quadtree partitioning is performed on the current CU (CTU or node (QT_node) of the quadtree) can be signaled. For example, when qt_split_flag has a first value (e.g., "1"), the current CU can be quadtree split. In addition, when qt_split_flag has a second value (e.g., "0"), the current CU is not quadtree split, but becomes a leaf node (QT_leaf_node) of the quadtree. Each quadtree leaf node can then be further split into a multi-type tree structure. That is, the leaf node of the quadtree can become a node (MTT_node) of a multi-type tree. In the multi-type tree structure, a first flag (e.g., Mtt_split_cu_flag) can be signaled to indicate whether the current node is additionally split. If the corresponding node is additionally split (for example, if the first flag is 1), the second flag (for example, Mtt_split_cu_vertical_flag) can be signaled to indicate the split direction. For example, the split direction can be a vertical direction when the second flag is 1, and a horizontal direction when the second flag is 0. Then, a third flag (for example, Mtt_split_cu_binary_flag) can be signaled to indicate whether the split type is a binary split type or a ternary split type. For example, the split type can be a binary split type when the third flag is 1, and a ternary split type when the third flag is 0. The nodes of the multi-type tree obtained by binary splitting or ternary splitting can be further split into a multi-type tree structure. However, the nodes of the multi-type tree may not be split into a quadtree structure. If the first flag is 0, the corresponding node of the multi-type tree is no longer split, but becomes a leaf node (MTT_leaf_node) of the multi-type tree. The CU corresponding to the leaf node of the multi-type tree can be used as the above-mentioned final coding unit.

[0120] Based on mtt_split_cu_vertical_flag and mtt_split_cu_binary_flag, a multi-type tree partition mode (MttSplitMode) of a CU may be derived as shown in the following Table 1. In the following description, a multi-type tree partition mode may be referred to as a multi-tree partition type or a partition type.

[0121] [Table 1]

[0122] MttSplitMode mtt_split_cu_vertical_flag mtt_split_cu_binary_flag SPLIT_TT_HOR 0 0 SPLIT_BT_HOR 0 1 SPLIT_TT_VER 1 0 SPLIT_BT_VER 1 1

[0123] Figure 7 is a diagram showing an example of partitioning a CTU into a plurality of CUs by applying a multi-type tree after applying a quadtree. Figure 7 , the bold block edge 710 represents quadtree partitioning, while the remaining edges 720 represent multi-type tree partitioning. The CU may correspond to a coding block (CB). In an embodiment, the CU may include a coding block of luma samples and two coding blocks of chroma samples corresponding to the luma samples. The chroma component (sample) CB or TB size may be derived based on the luma component (sample) CB or TB size based on the component ratio according to the color format (chroma format, e.g., 4:4:4, 4:2:2, 4:2:0, etc.) of the picture / image. In the case of a 4:4:4 color format, the chroma component CB / TB size may be set to be equal to the luma component CB / TB size. In the case of a 4:2:2 color format, the width of the chroma component CB / TB may be set to half the width of the luma component CB / TB and the height of the chroma component CB / TB may be set to the height of the luma component CB / TB. In the case of a 4:2:0 color format, the width of the chroma component CB / TB may be set to half the width of the luma component CB / TB and the height of the chroma component CB / TB may be set to half the height of the luma component CB / TB.

[0124] In an embodiment, when the size of the CTU is based on a luma sample unit of 128, the size of the CU may be from 128×128 to 4×4, which is the same size as the CTU. In an embodiment, in the case of a 4:2:0 color format (or chroma format), the chroma CB size may be from 64×64 to 2×2.

[0125] Furthermore, in an embodiment, the CU size and the TU size may be the same. Alternatively, there may be multiple TUs in a CU region. The TU size may generally represent the luma component (sample) transform block (TB) size.

[0126] The TU size can be derived based on the maximum allowed TB size maxTbSize as a predetermined value. For example, when the CU size is larger than maxTbSize, multiple TUs (TBs) with maxTbSize can be derived from the CU, and transform / inverse transform can be performed in units of TU (TB). For example, the maximum allowed luma TB size can be 64×64 and the maximum allowed chroma TB size can be 32×32. If the width or height of the CB split according to the tree structure is larger than the maximum transform width or height, the CB can be automatically (or implicitly) split until the TB size limits in the horizontal and vertical directions are met.

[0127] In addition, for example, when intra prediction is applied, the intra prediction mode / type can be derived in units of CU (or CB), and the neighboring reference sample derivation and prediction sample generation process can be performed in units of TU (or TB). In this case, there can be one or more TUs (or TBs) in one CU (or CB) area, and in this case, multiple TUs or (TBs) can share the same intra prediction mode / type.

[0128] In addition, for a quadtree coding tree scheme with nested multi-type trees, the following parameters may be signaled from the encoding device to the decoding device as SPS syntax elements. For example, at least one of the following parameters may be signaled: a CTU size representing the size of the root node of the quadtree, a MinQTSize representing the minimum allowed quadtree leaf node size, a MaxBtSize representing the maximum allowed binary tree root node size, a MaxTtSize representing the maximum allowed ternary tree root node size, a MaxMttDepth representing the maximum allowed hierarchical depth of multi-type tree partitioning from a quadtree leaf node, a MinBtSize representing the minimum allowed binary leaf node size, or a MinTtSize representing the minimum allowed ternary leaf node size.

[0129] As an embodiment using a 4:2:0 chroma format, the CTU size can be set to 128×128 luminance blocks and two 64×64 chroma blocks corresponding to these luminance blocks. In this case, MinOTSize can be set to 16×16, MaxBtSize can be set to 128×128, MaxTtSzie can be set to 64×64, MinBtSize and MinTtSize can be set to 4×4, and MaxMttDepth can be set to 4. Quadtree partitioning can be applied to the CTU to generate quadtree leaf nodes. Quadtree leaf nodes can be referred to as leaf QT nodes. The size of the quadtree leaf node can range from 16×16 size (e.g., MinOTSize) to 128×128 size (e.g., CTU size). If the leaf QT node is 128×128, it may not be additionally partitioned into a binary tree / ternary tree. This is because, in this case, even if partitioned, it exceeds MaxBtsize and MaxTtszie (e.g., 64×64). In other cases, the leaf QT node may be further split into a multi-type tree. Therefore, the leaf QT node is the root node of the multi-type tree, and the leaf QT node may have a multi-type tree depth (mttDepth) value of 0. If the multi-type tree depth reaches MaxMttdepth (for example, 4), further splitting may not be considered. If the width of the multi-type tree node is equal to MinBtSize and is less than or equal to 2×MinTtSize, further horizontal splitting may not be considered. If the height of the multi-type tree node is equal to MinBtSize and is less than or equal to 2×MinTtSize, further vertical splitting may not be considered. When splitting is not considered, the encoding device may skip signaling of the splitting information. In this case, the decoding device may derive splitting information with a predetermined value.

[0130] In addition, one CTU may include a coding block of luma samples (hereinafter referred to as "luminance block") and two coding blocks of chroma samples corresponding thereto (hereinafter referred to as "chroma blocks"). The above-mentioned coding tree scheme may be applied equally or separately to the luma blocks and chroma blocks of the current CU. Specifically, the luma blocks and chroma blocks in one CTU may be partitioned into the same block tree structure, and in this case, the tree structure may be represented as SINGLE_TREE. Alternatively, the luma blocks and chroma blocks in one CTU may be partitioned into separate block tree structures, and in this case, the tree structure may be represented as DUAL_TREE. That is, when the CTU is partitioned into dual trees, the block tree structure for the luma block and the block tree structure for the chroma block may exist separately. In this case, the block tree structure for the luma block may be referred to as DUAL_TREE_LUMA, and the block tree structure for the chroma component may be referred to as DUAL_TREE_CHROMA. For P and B slices / tile groups, the luma blocks and chroma blocks in one CTU may be restricted to have the same coding tree structure. However, for I slices / patch groups, luma blocks and chroma blocks can have separate block tree structures. If a separate block tree structure is applied, luma CTBs can be split into CUs based on a specific coding tree structure, and chroma CTBs can be split into chroma CUs based on another coding tree structure. That is, this means that a CU in an I slice / patch group to which a separate block tree structure is applied can include coding blocks for the luma component or coding blocks for two chroma components, and a CU in a P or B slice / patch group can include blocks for three color components (one luma component and two chroma components).

[0131] Although a quadtree coding tree structure with nested multi-type trees has been described, the structure for partitioning a CU is not limited thereto. For example, the BT structure and the TT structure may be interpreted as concepts included in a multi-partition tree (MPT) structure, and the CU may be interpreted as being partitioned using the QT structure and the MPT structure. In an example where a CU is partitioned using the QT structure and the MPT structure, a syntax element (e.g., MPT_split_type) including information about how many blocks a leaf node of the QT structure is partitioned into and a syntax element (e.g., MPT_split_mode) including information about which direction a leaf node of the QT structure is partitioned into, may be signaled to determine the partition structure.

[0132] In another example, the CU may be split in a manner different from the QT structure, the BT structure, or the TT structure. That is, instead of splitting a CU of a lower depth into 1 / 4 of a CU of a higher depth according to the QT structure, splitting a CU of a lower depth into 1 / 2 of a CU of a higher depth according to the BT structure, or splitting a CU of a lower depth into 1 / 4 or 1 / 2 of a CU of a higher depth according to the TT structure, in some cases the CU of a lower depth may be split into 1 / 5, 1 / 3, 3 / 8, 3 / 5, 2 / 3, or 5 / 8 of a CU of a higher depth, and the method of splitting the CU is not limited thereto.

[0133] The quadtree coding block structure with multiple tree types can provide a very flexible block segmentation structure. Due to the supported segmentation types in the multi-type tree, different segmentation patterns can potentially produce the same coding block structure in some cases. By limiting the occurrence of such redundant segmentation patterns in encoding and decoding devices, the amount of segmentation information data can be reduced.

[0134] In addition, in the encoding and decoding of videos / images according to the present disclosure, the image processing unit may have a hierarchical structure. A picture may be divided into one or more tiles, tiles, slices and / or tile groups. A slice may include one or more tiles. A tile may include one or more CTU rows in a tile. A slice may include an integer number of tiles of a picture. A tile group may include one or more tiles. A tile may include one or more CTUs. A CTU may be divided into one or more CUs. A tile may be a rectangular area including a specific tile row and a specific tile column consisting of multiple CTUs in a picture. According to the tile raster scan in the picture, a tile group may include an integer number of tiles. The slice header may carry information / parameters applicable to the corresponding slice (block in the slice). When the encoding device or decoding device has a multi-core processor, the encoding / decoding process for tiles, slices, tiles and / or tile groups may be performed in parallel.

[0135] In the present disclosure, the names or concepts of slice or patch group can be used interchangeably. That is, the patch group header can be called a slice header. Here, the slice can have one of the slice types including intra-frame (I) slice, predicted (P) slice and bi-predicted (B) slice. For blocks in I slices, inter-frame prediction is not used for prediction, and only intra-frame prediction can be used. Of course, even in this case, the original sample values ​​can be encoded and signaled without prediction. For blocks in P slices, intra-frame prediction or inter-frame prediction can be used. When inter-frame prediction is used, only single prediction can be used. In addition, for blocks in B slices, intra-frame prediction or inter-frame prediction can be used. When inter-frame prediction is used, at most bi-prediction can be used.

[0136] The encoding device may determine the size of a tile / tile group, tile, slice, and maximum and minimum coding units according to the characteristics of the video image (e.g., resolution) or considering coding efficiency and parallel processing. In addition, information about this or information that can derive this may be included in the bitstream.

[0137] The decoding device can obtain information indicating whether a CTU in a patch or a patch / patch group, tile, or slice of the current picture is divided into multiple coding units. The encoding device and the decoding device can improve coding efficiency by signaling this information under specific conditions.

[0138] The slice header (slice header syntax) may include information / parameters that may be commonly applied to a slice. The APS (APS syntax) or PPS (PPS syntax) may include information / parameters that may be commonly applied to one or more pictures. The SPS (SPS syntax) may include information / parameters that may be commonly applied to one or more sequences. The VPS (VPS syntax) may include information / parameters that may be commonly applied to multiple layers. The DPS (DPS syntax) may include information / parameters that may be commonly applied to the entire video. The DPS may include information / parameters associated with a combination of coded video sequences (CVSs).

[0139] In addition, for example, information on the partitioning and configuration of tiles / tile groups / tiles / slices may be structured at the encoding level through a high-level syntax and transmitted to a decoding device in the form of a bitstream.

[0140] Overview of Intra Prediction

[0141] Hereinafter, intra prediction performed by the above encoding and decoding devices will be described in more detail. Intra prediction may refer to prediction for generating prediction samples of a current block based on reference samples in a picture to which the current block belongs (hereinafter referred to as the current picture).

[0142] Will refer to Figure 8 A description is given. When intra prediction is applied to the current block 801, neighboring reference samples to be used for intra prediction of the current block 801 can be derived. The neighboring reference samples of the current block may include: a total of 2×nh samples including a sample 811 of size nW×nH adjacent to the left boundary of the current block and a sample 812 adjacent to the lower left, a total of 2×nW samples including a sample 821 adjacent to the upper boundary of the current block and a sample 822 adjacent to the upper right, and one sample 831 adjacent to the upper left of the current block. Alternatively, the neighboring reference samples of the current block may include multiple columns of upper neighboring samples and multiple rows of left neighboring samples.

[0143] In addition, the neighboring reference samples of the current block may include: a total of nH samples 841 of size nW×nH adjacent to the right boundary of the current block, a total of nW samples 851 adjacent to the bottom boundary of the current block, and one sample 842 adjacent to the bottom right of the current block.

[0144] However, some neighboring reference samples of the current block have not yet been decoded or may be unavailable. In this case, the decoding device can construct neighboring reference samples to be used for prediction by replacing unavailable samples with available samples. Alternatively, the neighboring reference samples to be used for prediction can be constructed by interpolation of available samples.

[0145] When deriving neighboring reference samples, (i) the prediction sample can be derived based on an average or interpolation of the neighboring reference samples of the current block, and (ii) the prediction sample can be derived based on a reference sample located in a specific (prediction) direction relative to the prediction sample among the neighboring reference samples of the current block. Case (i) can be referred to as a non-directional mode or non-angular mode, while case (ii) can be referred to as a directional mode or angular mode. Alternatively, the prediction sample can be generated based on the prediction sample of the current block among the neighboring reference samples by interpolating between a first neighboring sample and a second neighboring sample located in a direction opposite to the prediction direction of the intra-frame prediction mode of the current block. This case can be referred to as linear interpolated intra-frame prediction (LIP). Alternatively, a linear model can be used to generate chroma prediction samples based on luma samples. This case can be referred to as LM mode. Alternatively, a temporary prediction sample for the current block can be derived based on filtered neighboring reference samples, and the prediction sample for the current block can be derived by weighted summing the temporary prediction sample with at least one reference sample derived according to the intra-frame prediction mode among existing neighboring reference samples (that is, unfiltered neighboring reference samples). This case can be referred to as position-dependent intra-frame prediction (PDPC). In addition, a reference sample row with the highest prediction accuracy can be selected from multiple neighboring reference sample rows of the current block, and the prediction sample can be derived using reference samples on the corresponding row located in the prediction direction. In this case, intra-frame prediction coding can be performed by indicating (signaling) the reference sample row to be used to the decoding device. The above situation can be referred to as multiple reference line (MRL) intra-frame prediction or MRL-based intra-frame prediction. In addition, the current block can be divided into vertical or horizontal sub-partitions, intra-frame prediction can be performed based on the same intra-frame prediction mode, and neighboring reference samples can be derived and used in units of sub-partitions. That is, in this case, the intra-frame prediction mode of the current block is applied equally to the sub-partitions, and neighboring reference samples can be derived and used in units of sub-partitions, thereby improving intra-frame prediction performance in some cases. This prediction method can be referred to as intra sub-partitioning (ISP) or ISP-based intra-frame prediction. This intra-frame prediction method can be referred to as an intra-frame prediction type to distinguish it from an intra-frame prediction mode (e.g., DC mode, planar mode, or directional mode). Intra-frame prediction types can be referred to by various terms, such as intra-frame prediction technique or additional intra-frame prediction mode. For example, the intra prediction type (or additional intra prediction mode, etc.) may include at least one of the above-mentioned LIP, PDPC, MRL, and ISP. A general intra prediction method that excludes specific intra prediction types such as LIP, PDPC, MRL, and ISP may be referred to as a general intra prediction type. The general intra prediction type may refer to a case where a specific intra prediction type is not applied, and prediction may be performed based on the above-mentioned intra prediction mode. In addition, post-filtering may be performed on the derived prediction sample as needed.

[0146] Specifically, the intra prediction process may include an intra prediction mode / type determination step, a neighboring reference sample derivation step, and a prediction sample derivation step based on the intra prediction mode / type. In addition, post-filtering may be performed on the derived prediction samples as needed.

[0147] In addition to the above-mentioned intra prediction types, affine linear weighted intra prediction (ALWIP) can be used. ALWIP can be referred to as linear weighted intra prediction (LWIP), matrix weighted intra prediction (MIP), or matrix-based intra prediction. When MIP is applied to the current block, i) neighboring reference samples that have undergone an averaging process are used, ii) a matrix-vector multiplication process can be performed, and iii) a horizontal / vertical interpolation process can be further performed as needed to derive the prediction samples of the current block. The intra prediction mode used for MIP can be constructed differently from the intra prediction mode used in the above-mentioned LIP, PDPC, MRL, ISP intra prediction, or ordinary intra prediction. The intra prediction mode of MIP can be referred to as MIP intra prediction mode, MIP prediction mode, or MIP mode. For example, the matrix and offset used in the matrix-vector multiplication can be set differently according to the intra prediction mode of MIP. Here, the matrix can be referred to as a (MIP) weight matrix, and the offset can be referred to as a (MIP) offset vector or a (MIP) bias vector. The detailed MIP method will be described below.

[0148] The block reconstruction process based on intra-frame prediction and intra-frame prediction units in an encoding device may illustratively include, for example, the following. S910 may be performed by the intra-frame predictor 185 of the encoding device, and S920 may be performed by a residual processor of the encoding device, which includes at least one of the subtractor 115, the transformer 120, the quantizer 130, the dequantizer 140, and the inverse transformer 150. Specifically, S920 may be performed by the subtractor 115 of the encoding device. In S930, prediction information may be derived by the intra-frame predictor 185 and encoded by the entropy encoder 190. In S930, residual information may be derived by the residual processor and encoded by the entropy encoder 190. Residual information is information about residual samples. The residual information may include information about quantized transform coefficients of the residual samples. As described above, the residual samples may be derived into transform coefficients by the transformer 120 of the encoding device, and the transform coefficients may be derived into quantized transform coefficients by the quantizer 130. Information about the quantized transform coefficients may be encoded by the entropy encoder 190 through a residual encoding process.

[0149] The encoding device may perform intra prediction for the current block (S910). The encoding device may derive an intra prediction mode / type for the current block, derive neighboring reference samples for the current block, and generate prediction samples in the current block based on the intra prediction mode / type and the neighboring reference samples. Here, the process for determining the intra prediction mode / type, the process for deriving neighboring reference samples, and the process for generating prediction samples may be performed simultaneously, or any one process may be performed before the other. For example, although not shown, the intra predictor 185 of the encoding device may include an intra prediction mode / type determination unit, a reference sample derivation unit, and a prediction sample derivation unit. The intra prediction mode / type determination unit may determine the intra prediction mode / type for the current block, the reference sample derivation unit may derive neighboring reference samples for the current block, and the prediction sample derivation unit may derive prediction samples for the current block. In addition, when performing the prediction sample filtering process described below, the intra predictor 185 may further include a prediction sample filter. The encoding device may determine the mode / type to be applied to the current block from among multiple intra prediction modes / types. The encoding device may compare RD costs of intra prediction modes / types and determine an optimal intra prediction mode / type for the current block.

[0150] In addition, the encoding device may perform a prediction sample filtering process. Prediction sample filtering may be referred to as post-filtering. Some or all of the prediction samples may be filtered by the prediction sample filtering process. In some cases, the prediction sample filtering process may be omitted.

[0151] The encoding apparatus may generate residual samples of the current block based on the (filtered) prediction samples (S920).The encoding apparatus may compare the prediction samples with the original samples of the current block based on the phase and derive the residual samples.

[0152] The encoding device may encode image information including information about intra-frame prediction (prediction information) and residual information of residual samples (S930). The prediction information may include intra-frame prediction mode information and intra-frame prediction type information. The encoding device may output the encoded image information in the form of a bitstream. The output bitstream may be sent to a decoding device via a storage medium or a network.

[0153] The residual information may include the following residual coding syntax. The encoding device may transform / quantize the residual samples to derive quantized transform coefficients. The residual information may include information about the quantized transform coefficients.

[0154] In addition, as described above, the encoding device can generate a reconstructed picture (including reconstructed samples and reconstructed blocks). To this end, the encoding device can perform dequantization / inverse transformation on the quantized transform coefficients again to derive (modified) residual samples. The residual samples are transformed / quantized and then dequantized / inverse transformed to derive residual samples that are the same as the residual samples derived in the decoding device as described above. The encoding device can generate a reconstructed block including reconstructed samples of the current block based on the predicted samples and the (modified) residual samples. A reconstructed picture of the current picture can be generated based on the reconstructed block. As described above, the in-loop filtering process is further applied to the reconstructed picture.

[0155] For example, a video / image decoding process based on intra prediction and an intra predictor in a decoding device may illustratively include the following: The decoding device may perform operations corresponding to those performed in the encoding device.

[0156] S1010 to S1030 may be performed by the intra-frame predictor 265 of the decoding device, and the prediction information of S1010 and the residual information of S1040 may be obtained from the bitstream by the entropy decoder 210 of the decoding device. A residual processor of the decoding device, including at least one of the dequantizer 220 and the inverse transformer 230, may derive residual samples of the current block based on the residual information. Specifically, the dequantizer 220 of the residual processor may perform dequantization based on the quantized transform coefficients derived from the residual information to derive transform coefficients, and the dequantizer 220 of the residual processor may perform inverse transform on the transform coefficients to derive residual samples of the current block. S1050 may be performed by the adder 235 or the reconstructor of the decoding device.

[0157] Specifically, the decoding device may derive the intra prediction mode / type of the current block based on the received prediction information (intra prediction mode / type information) (S1010). The decoding device may derive the neighboring reference samples of the current block (S1020). The decoding device may generate prediction samples in the current block based on the intra prediction mode / type and the neighboring reference samples (S1030). In this case, the encoding device may perform a prediction sample filtering process. Prediction sample filtering may be referred to as post-filtering. Some or all of the prediction samples may be filtered through the prediction sample filtering process. In some cases, the prediction sample filtering process may be omitted.

[0158] The decoding device may generate residual samples of the current block based on the received residual information. The decoding device may generate reconstructed samples of the current block based on the predicted samples and the residual samples, and derive reconstructed samples including the reconstructed samples (S1040). A reconstructed picture of the current picture may be generated based on the reconstructed block. As described above, the in-loop filtering process is further applicable to the reconstructed picture.

[0159] Here, although not shown, the intra-frame predictor 265 of the decoding device may include an intra-frame prediction mode / type determination unit, a reference sample derivation unit, and a prediction sample derivation unit. The intra-frame prediction mode / type determination unit may determine the intra-frame prediction mode / type of the current block based on the intra-frame prediction mode / type information obtained by the entropy decoder 210, the reference sample derivation unit may derive neighboring reference samples of the current block, and the prediction sample derivation unit may derive the prediction sample of the current block. In addition, when performing the above-mentioned prediction sample filtering process, the intra-frame predictor 265 may further include a prediction sample filter.

[0160] The intra-frame prediction mode information may include flag information (e.g., intra_luma_mpm_flag) indicating whether the most probable mode (MPM) or the residual mode is applied to the current block, and when MPM is applied to the current block, the prediction mode information may further include index information (e.g., intra_luma_mpm_idx) indicating one of the intra-frame prediction mode candidates (MPM candidates). The intra-frame prediction mode candidates (MPM candidates) may be configured as an MPM candidate list or an MPM list. In addition, when MPM is not applied to the current block, the intra-frame prediction mode information may further include residual mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra-frame prediction modes other than the intra-frame prediction mode candidates (MPM candidates). The decoding device may determine the intra-frame prediction mode of the current block based on the intra-frame prediction mode information. A separate MPM list may be configured for the above-mentioned MIP.

[0161] In addition, the intra-frame prediction type information can be implemented in various forms. For example, the intra-frame prediction type information may include intra-frame prediction type index information indicating one of the intra-frame prediction types. As another example, the intra-frame prediction type information may include reference sample row information (e.g., intra_luma_ref_idx) indicating whether MRL is applied to the current block and, if so, which reference sample row is used, ISP flag information (e.g., intra_subpartitions_mode_flag) indicating whether ISP is applied to the current block, ISP type information (e.g., intra_subpartitions_split_flag) indicating the type of sub-partition division when ISP is applied, flag information indicating whether PDCP is applied, or flag information indicating whether LIP is applied. In addition, the intra-frame prediction type information may include at least one of a MIP flag indicating whether MIP is applied to the current block.

[0162] The intra-frame prediction mode information and / or the intra-frame prediction type information may be encoded / decoded by the encoding method described in the present disclosure. For example, the intra-frame prediction mode information and / or the intra-frame prediction type information may be encoded / decoded by entropy encoding (e.g., CABAC or CAVLC) based on a truncated (Rice) binary code.

[0163] Overview of Inter-frame Prediction

[0164] Hereinafter, reference will be described Figure 2 and Figure 3 The detailed techniques of inter-frame prediction are described in the following description of encoding and decoding. In the case of a decoding device, the video / image decoding method based on inter-frame prediction and the inter-frame predictor in the decoding device can operate according to the following description. In the case of an encoding device, the video / image encoding method based on inter-frame prediction and the inter-frame predictor in the encoding device can operate according to the following description. In addition, in the following description, the data encoded by the following description can be stored in the form of a bitstream.

[0165] A predictor in an encoding / decoding device can perform inter-frame prediction on a block-by-block basis to derive prediction samples. Inter-frame prediction may refer to prediction derived using a method that relies on data elements (e.g., sample values, motion information, etc.) from pictures other than the current picture. When inter-frame prediction is applied to the current block, the prediction block (prediction sample array) of the current block can 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, to reduce the amount of motion information transmitted in inter-frame prediction mode, the motion information of the current block can be predicted on a block, sub-block, or sample basis based on the correlation of motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include information on the inter-frame prediction type (L0 prediction, L1 prediction, Bi prediction, etc.). When inter-frame prediction is applied, neighboring blocks may include spatially neighboring blocks in the current picture and temporally neighboring blocks in the reference picture. The reference picture comprising the reference block and the reference picture comprising the temporally neighboring blocks may be the same or different. A temporally neighboring block may be referred to as a collocated reference block or collocated CU or colCU, and a reference picture including the temporally neighboring block may be referred to as a collocated picture (colPic). For example, a motion information candidate list may be configured based on the neighboring blocks of the current block, and a flag or index information indicating which candidate is selected (used) to derive the motion vector and / or reference picture index of the current block may be signaled. Inter-frame prediction may be performed based on various prediction modes, and for example, in the case of skip mode and merge mode, the motion information of the current block may be equal to the motion information of the selected neighboring block. In the case of skip mode, unlike merge mode, a residual signal may not be sent. In the case of motion vector prediction (motion vector prediction, MVP) mode, the motion vector of the selected neighboring block may be used as a motion vector predictor, and the motion vector difference may be signaled. In this case, the motion vector of the current block may be derived using the sum of the motion vector predictor and the motion vector difference.

[0166] Depending on the inter-frame prediction type (L0 prediction, L1 prediction, Bi prediction, etc.), the motion information may include L0 motion information and / or L1 motion information. A motion vector in the L0 direction may be referred to as an L0 motion vector or MVL0, and a motion vector in the L1 direction may be referred to as an L1 motion vector or MVL1. Prediction based on the L0 motion vector may be referred to as L0 prediction, prediction based on the L1 motion vector may be referred to as L1 prediction, and prediction based on both the L0 motion vector and the L1 motion vector may be referred to as Bi prediction. Here, the L0 motion vector may represent a motion vector associated with reference picture list L0 (L0), and the L1 motion vector may represent a motion vector associated with reference picture list L1 (L1). Reference picture list L0 may include pictures preceding the current picture in output order as reference pictures, and reference picture list L1 may include pictures following the current picture in output order. Pictures preceding the current block may be referred to as forward (reference) pictures, and pictures following the current block may be referred to as backward (reference) pictures. Reference picture list L0 may also include pictures following the current picture in output order as reference pictures. In this case, in reference picture list L0, pictures before the current block are indexed first, and pictures after the current block are indexed. Reference picture list L1 may also include pictures before the current picture in output order as reference pictures. In this case, in reference picture list 1, pictures after the current block may be indexed first, and pictures before the current block may be indexed. Here, the output order may correspond to the picture order count (POC) order.

[0167] For example, the video / image encoding process based on inter-frame prediction and inter-frame predictor in the encoding device can be schematically described as follows. Figure 11A description is given. The encoding device performs inter-frame prediction for the current block (S1110). The encoding device can derive the inter-frame prediction mode and motion information of the current block, and generate prediction samples for the current block. Here, the inter-frame prediction mode determination, motion information derivation, and prediction sample derivation processes can be performed simultaneously, and any process can be performed before another process. For example, the inter-frame predictor of the encoding device may include a prediction mode determination unit, a motion information derivation unit, and a prediction sample derivation unit. The prediction mode determination unit can determine the prediction mode of the current block, the motion information derivation unit can derive the motion information of the current block, and the prediction sample derivation unit can derive the prediction samples of the current block. For example, the inter-frame predictor of the encoding device can search for a block similar to the current block in a specific area (search area) of a reference picture through motion estimation, and derive a reference block whose difference with the current block is the smallest or less than or equal to a specific criterion. 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 a mode to be applied to the current block among various prediction modes. The encoding device may compare RD costs of various prediction modes and determine an optimal prediction mode for the current block.

[0168] For example, when skip mode or merge mode is applied to the current block, the encoding device may construct a merge candidate list (described below) and derive a reference block whose difference with the current block is the smallest or less than or equal to a specific criterion among the reference blocks indicated by the merge candidates included in the merge candidate list. In this case, a merge candidate associated with the derived reference block may be selected, and merge index information indicating the selected merge candidate may be generated and signaled to the decoding device. The motion information of the selected merge candidate may be used to derive the motion information of the current block.

[0169] As another example, when the (A)MVP mode is applied to the current block, the encoding device may construct an (A)MVP candidate list to be described below, and use the motion vector of a motion vector predictor (MVP) candidate selected from among the MVP candidates included in the (A)MVP candidate list as the MVP of the current block. In this case, the motion vector indicating the reference block derived by motion estimation may be used as the motion vector of the current block, and the MVP candidate having the smallest difference with the motion vector of the current block among the MVP candidates may be the selected MVP candidate. A motion vector difference (MVD) obtained by subtracting the MVP from the motion vector of the current block may be derived. In this case, information about the MVD may be signaled to the decoding device. In addition, when the (A)MVP mode is applied, the value of the reference picture index may be constructed as reference picture index information and signaled to the decoding device.

[0170] The encoding apparatus may derive residual samples based on the predicted samples (S1120). The encoding apparatus may derive residual samples by comparing the original samples of the current block with the predicted samples.

[0171] The encoding device encodes the image information including prediction information and residual information (S1130). The encoding device can output the encoded image information in the form of a bitstream. The prediction information may include prediction mode information (e.g., skip flag, merge flag, mode index, etc.) and motion information as information related to the prediction process. The motion information may include candidate selection information (e.g., merge index, mvp flag or mvp index) as information for deriving a motion vector. In addition, the motion information may include information about the above-mentioned MVD and / or reference picture index information. In addition, the motion information may include information indicating whether L0 prediction, L1 prediction or bi prediction is applied. The residual information is information about the residual sample. The residual information may include information about the quantized transform coefficients of the residual sample.

[0172] The output bitstream may be stored in a (digital) storage medium and sent to the decoding device, or may be sent to the decoding device via a network.

[0173] In addition, as described above, the encoding device can generate a reconstructed picture (including reconstructed samples and reconstructed blocks) based on the reference samples and the residual samples. This enables the decoding device to derive the same prediction result as the prediction result performed in the encoding device, thereby improving encoding efficiency. Therefore, the encoding device can store the reconstructed picture (or reconstructed sample or reconstructed block) in a memory and use it as a reference picture for inter-frame prediction. As described above, the in-loop filtering process can further be applied to the reconstructed picture.

[0174] For example, a video / image decoding process based on inter-frame prediction and an inter-frame predictor in a decoding device may schematically include the following contents.

[0175] The decoding device may perform an operation corresponding to the operation performed by the encoding device. The decoding device may perform prediction on the current block based on the received prediction information and derive a prediction sample.

[0176] Specifically, the decoding apparatus may determine a prediction mode of the current block based on the received prediction information (S1210).The decoding apparatus may determine which inter prediction mode to apply to the current block based on prediction mode information in the prediction information.

[0177] For example, whether merge mode or (A)MVP mode is applied to the current block can be determined based on a merge flag. Alternatively, one of various inter-frame prediction mode candidates can be selected based on a mode index. Inter-frame prediction mode candidates may include skip mode, merge mode, and / or (A)MVP mode, or may include various inter-frame prediction modes described below.

[0178] The decoding device derives motion information of the current block based on the determined inter-frame prediction mode (S1220). For example, when the skip mode or merge mode is applied to the current block, the decoding device may construct the following merge candidate list and select one of the merge candidates included in the merge candidate list. The selection may be performed based on the above-mentioned 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.

[0179] As another example, when the (A)MVP mode is applied to the current block, the decoding device may construct an (A)MVP candidate list to be described below, and use the motion vector of a motion vector predictor (MVP) candidate selected from among the MVP candidates included in the (A)MVP candidate list as the MVP of the current block. The selection may be performed based on the above-mentioned selection information (MVP flag or MVP index). In this case, the MVD of the current block may be derived based on the information about the MVD, and the motion vector of the current block may be derived based on the MVD and MVP 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 for inter-frame prediction reference of the current block.

[0180] In addition, as described above, the motion information of the current block can be derived without constructing a candidate list. In this case, the motion information of the current block can be derived according to the process in the prediction mode described below. In this case, the construction of the candidate list as described above can be omitted.

[0181] The decoding device may generate prediction samples of the current block based on the motion information of the current block (S1230). In this case, a reference picture may be derived based on a reference picture index of the current block, and the prediction samples of the current block may be derived using samples of the reference block indicated by the motion vector of the current block on the reference picture. In this case, as described above, in some cases, a prediction sample filtering process may be further performed for all or some prediction samples of the current block.

[0182] For example, the inter-frame predictor of the decoding device may include a prediction mode determination unit, a motion information derivation unit and a prediction sample derivation unit. The prediction mode determination unit can determine the prediction mode of the current block based on the received prediction mode information, the motion information derivation unit can derive the motion information (motion vector and / or reference picture index) of the current block based on the received motion information, and the prediction sample derivation unit can derive the prediction sample of the current block.

[0183] The decoding device generates residual samples of the current block based on the received residual information (S1240). The decoding device can generate reconstructed samples of the current block based on the predicted samples and the residual samples, and generate a reconstructed picture based on the samples (S1250). As described above, the in-loop filtering process can be further applied to the reconstructed picture.

[0184] As described above, the inter-frame prediction process may include the steps of determining an inter-frame prediction mode, deriving motion information according to the determined prediction mode, and performing prediction (prediction sample generation) based on the derived motion information. As described above, the inter-frame prediction process may be performed in an encoding device and a decoding device.

[0185] Quantization / Dequantization

[0186] As described above, the quantizer of the encoding device may derive quantized transform coefficients by applying quantization to the transform coefficients, and the dequantizer of the encoding device or the dequantizer of the decoding device may derive transform coefficients by applying dequantization to the quantized transform coefficients.

[0187] In the encoding and decoding of moving images / still images, the quantization ratio can be changed, and the compression ratio can be adjusted using the changed quantization ratio. From the perspective of implementation, taking into account the complexity, instead of directly using the quantization ratio, a quantization parameter (QP) can be used. For example, a quantization parameter with an integer value from 0 to 63 can be used, and each quantization parameter value can correspond to an actual quantization ratio. In addition, the quantization parameter QP of the luminance component (luminance sample) can be set differently. Y and the quantization parameter QP of the chroma component (chroma samples) C .

[0188] During the quantization process, a transform coefficient C can be received and divided by a quantization ratio Qstep to obtain a quantized transform. In this case, considering computational complexity, the quantization ratio can be multiplied by a scale to make it an integer, and a shift operation can be performed according to a value corresponding to the scale value. Based on the product of the quantization ratio and the scale value, a quantization scale can be derived. In other words, the quantization scale can be derived based on the QP. By applying the quantization scale to the transform coefficient C, the quantized transform coefficient C' can be derived.

[0189] The dequantization process is the inverse process of the quantization process. By multiplying the quantized transform coefficient C' by the quantization ratio Qstep, the reconstructed transform coefficient C" can be obtained. In addition, the level scale can be derived from the quantization parameter, and the level scale can be applied to the quantized transform coefficient C' to derive the reconstructed transform coefficient C". Due to losses in the transformation and / or quantization process, the reconstructed transform coefficient C" may be slightly different from the original transform coefficient C. Therefore, even in the encoding device, dequantization can be performed in the same manner as the decoding device.

[0190] In addition, an adaptive frequency-weighted quantization technique that adjusts the quantization strength according to frequency can be applied. Adaptive frequency-weighted quantization refers to a method that applies quantization strength differently according to frequency. In adaptive frequency-weighted quantization, a predefined quantization scaling matrix can be used to apply quantization strength differently according to frequency. That is, the quantization / dequantization process described above can be performed based on the quantization scaling matrix. For example, different quantization scaling matrices can be used depending on the size of the current block and / or whether the prediction mode applied to the current block is inter-frame prediction or intra-frame prediction to generate the residual signal of the current block. The quantization scaling matrix can be referred to as a quantization matrix or a scaling matrix. The quantization scaling matrix can be predefined. In addition, for frequency-adaptive scaling, frequency quantization scaling information for the quantization scaling matrix can be constructed / encoded in the encoding device and signaled to the decoding device. The frequency quantization scaling information can be referred to as quantization scaling information. The frequency quantization scaling information can include scaling list data, scaling_list_data. The quantization scaling matrix can be derived (modified) based on the scaling list data. In addition, the frequency quantization scaling information can include a flag indicating whether the scaling list data exists. Alternatively, when the scaling list data is signaled at a higher level (eg, SPS), information indicating whether the scaling list data is modified at a lower level (eg, PPS or tile group header, etc.) may also be included.

[0191] Transformation / Inverse Transformation

[0192] As described above, the encoding device can derive a residual block (residual samples) based on a block predicted by intra / inter / IBC prediction (prediction block), and derive quantized transform coefficients by applying transform and quantization to the derived residual samples. Information about the quantized transform coefficients (residual information) can be included and encoded in the residual coding syntax and output in the form of a bitstream. The decoding device can obtain and decode the information about the quantized transform coefficients (residual information) from the bitstream to derive the quantized transform coefficients. The decoding device can derive residual samples based on the quantized transform coefficients by dequantization / inverse transform. As described above, either quantization / dequantization or transform / inverse transform can be skipped. When the transform / inverse transform is skipped, the transform coefficient can be referred to as a coefficient or a residual coefficient, or for consistency of expression, it can still be referred to as a transform coefficient. Whether the transform / inverse transform is skipped can be signaled based on a transform skip flag (e.g., transform_skip_flag).

[0193] Transformation / inverse transformation can be performed based on a transform kernel. For example, a multiple transform selection (MTS) scheme for performing transform / inverse transformation can be applied. In this case, some of a plurality of transform kernel sets can be selected and applied to the current block. The transform kernel can be referred to by various terms such as a transform matrix or a transform type. For example, a transform kernel set can indicate a combination of a transform kernel in the vertical direction (vertical transform kernel) and a transform kernel in the horizontal direction (horizontal transform kernel).

[0194] Transformation / inverse transformation can be performed in units of CU or TU. That is, transformation / inverse transformation can be applied to residual samples in a CU or residual samples in a TU. The CU size can be equal to the TU size, or multiple TUs can exist in a CU area. In addition, the CU size can generally indicate the luminance component (sample) CB size. The TU size can generally indicate the luminance component (sample) 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 of the color format (chrominance format) (for example, 4:4:4, 4:4:4, 4:2:2, 4:2:0, etc.). The TU size can be derived based on maxTbSize. For example, when the CU size is greater than maxTbSize, multiple TUs (TBs) with maxTbSize can be derived from the CU, and transformation / inverse transformation can be performed in units of TU (TB). maxTbSize can be considered to determine whether to apply various intra prediction types (such as ISP). The information about the maxTbSize may be predetermined, or the information about the maxTbSize may be generated and encoded in the encoding device and signaled to the encoding device.

[0195] Entropy Coding

[0196] As referenced above Figure 2 As described above, all or some of the video / image information may be entropy encoded by the entropy encoder 190, see Figure 3 All or some of the described video / image information may be entropy decoded by the entropy decoder 310. In this case, the video / image information may be encoded / decoded in units of syntax elements. In the present disclosure, encoding / decoding the information may include encoding / decoding by the method described in this paragraph.

[0197] Figure 13 This is a block diagram of CABAC for encoding a syntax element. During the CABAC encoding process, first, when the input signal is a syntax element rather than a binary value, the input signal can be converted to a binary value through binarization. When the input signal is already a binary value, binarization can be bypassed. Here, the binary numbers 0 or 1 that constitute the binary value can be referred to as bins. For example, when the binary string (bin string) after binarization is 110, each of 1, 1, and 0 can be referred to as a bin. The bin of a syntax element can represent the value of the corresponding syntax element.

[0198] The binarized bin can be input to a conventional coding engine or a bypass coding engine. The conventional coding engine can assign a context model that reflects the probability value to the corresponding bin, and encode the corresponding bin based on the assigned context model. The conventional coding engine can encode each bin and then update the probability model of the corresponding bin. The bin encoded in this way can be called a context coding bin. The bypass coding engine can bypass the process for estimating the probability for the input bin and the process for updating the probability model applied to the corresponding bin after encoding. The bypass coding engine can encode the input bin by applying a uniform probability distribution (e.g., 50:50) instead of assigning a context, thereby increasing the encoding speed. The bin encoded in this way can be called a bypass bin. The context model can be assigned and updated for each context coding (conventional coding) bin, and the context model can be indicated based on ctxidx or ctxInc. ctxidx can be derived based on ctxInc. Specifically, for example, the context index ctxidx indicating the context model of each conventionally coded bin can be derived as the sum of the context index increment (ctxInc) and the context index offset (ctxIdxOffset). Here, ctxInc can be derived differently for each bin. ctxIdxOffset can be represented by the lowest value of ctxIdx. The lowest value of ctxIdx can be called the initial value initValue of ctxIdx. ctxIdxOffset is a value generally used to distinguish the context model from other syntax elements, and the context model of a syntax element can be distinguished / derived based on ctxinc.

[0199] During the entropy encoding process, it can be determined whether encoding is performed by a regular encoding engine or a bypass encoding engine, and the encoding path can be switched. Entropy decoding can be performed in the reverse order of the same process as entropy encoding.

[0200] For example, the above entropy coding can be done as Figure 14 and Figure 15 Execute as in . Figure 14 and Figure 15 The encoding device (entropy encoder) may perform an entropy encoding process on the image / video information. The image / video information may include segmentation-related information, prediction-related information (e.g., inter-frame / intra-frame prediction distinction information, intra-frame prediction mode information, inter-frame prediction mode information, etc.), residual information, in-loop filtering-related information, etc., or may include various syntax elements related thereto. Entropy encoding may be performed in units of syntax elements. Figure 14 Steps S1410 to S1420 can be performed by Figure 2 The encoding is performed by the entropy encoder 190 of the encoding device.

[0201] The encoding device may perform binarization on the target syntax element (S1410). Here, the binarization may be based on various binarization methods such as a truncated Rice binarization process, a fixed-length binarization process, and the like, and the binarization method of the target syntax element may be predefined. The binarization process may be performed by the binarization unit 191 in the entropy encoder 190.

[0202] The encoding device may perform entropy encoding on the target syntax element (S1420). The encoding device may perform encoding based on conventional encoding (based on context) or bypass encoding on the bin string of the target syntax element based on an entropy encoding technique such as CABAC (context adaptive arithmetic coding) or CAVLC (context adaptive variable length coding), and its output may be included in the bitstream. The entropy encoding process may be performed by the entropy encoding processor 192 in the entropy encoder 190. As described above, the bitstream may be sent to the decoding device via a (digital) storage medium or a network.

[0203] refer to Figure 16 and Figure 17 , the decoding device (entropy decoder) can decode the encoded image / video information. The image / video information may include segmentation related information, prediction related information (for example, inter-frame / intra-frame prediction distinction information, intra-frame prediction mode information, inter-frame prediction mode information, etc.), residual information, in-loop filtering related information, etc., or may include various syntax elements related thereto. Entropy coding can be performed in units of syntax elements. Steps S1610 to S1620 may be performed by Figure 3 The entropy decoder 210 of the decoding device is executed.

[0204] The decoding device may perform binarization on the target syntax element (S1610). Here, binarization may be performed based on various binarization methods such as a truncated Rice binarization process, a fixed-length binarization process, and the binarization method of the target syntax element may be predefined. The decoding device may derive an available bin string (bin string candidate) for an available value of the target syntax element through the binarization process. The binarization process may be performed by the binarization unit 211 in the entropy decoder 210.

[0205] The decoding device can perform entropy decoding (S1620) for the target syntax element. When the bins of the target syntax element are sequentially decoded and parsed from the input bits in the bitstream, the decoding device can compare the derived bin string with the available bin string of the corresponding syntax element. If the derived bin string is equal to one of the available bin strings, the value corresponding to the corresponding bin string can be derived as the value of the corresponding syntax element. If not, the above process can be performed again after further parsing the next bit in the bitstream. Through this process, the start bit or end bit of specific information (specific syntax element) in the bitstream is not used, but variable length bits are used to signal the corresponding information. In this way, relatively few bits can be assigned low values, and the overall coding efficiency can be improved.

[0206] The decoding device can perform context-based or bypass-based decoding for a bin in a bin string from a bitstream based on an entropy coding technique such as CABAC or CAVLC. The entropy decoding process can be performed by an entropy decoding processor 212 in the entropy decoder 210. The bitstream may include various information for image / video decoding as described above. As described above, the bitstream may be sent to the decoding device via a (digital) storage medium or a network.

[0207] In the present disclosure, a table including syntax elements (syntax table) can be used to signal information from an encoding device to a decoding device. The order of syntax elements in the table including syntax elements used in the present disclosure can indicate the order in which the syntax elements are parsed from a bitstream. The encoding device can construct and encode the syntax table so that the decoding device parses the syntax elements in the parsing order. The decoding device can parse and decode the syntax elements corresponding to the syntax table from the bitstream according to the parsing order and obtain the values ​​of the syntax elements.

[0208] General image / video encoding process

[0209] In image / video coding, the pictures constituting the image / video can be encoded / decoded according to the decoding order. The picture order corresponding to the output order of the decoded pictures can be set to be different from the decoding order, and based on this, during inter-frame prediction, not only forward prediction but also backward prediction can be performed.

[0210] Figure 18 An example of a schematic picture decoding process to which the embodiments of the present disclosure are applicable is shown. Figure 18In the embodiment of the present invention, S1810 may be performed in the entropy decoder 210 of the decoding device, S1820 may be performed in the predictor including the intra predictor 265 and the inter predictor 260, S1830 may be performed in the residual processor including the dequantizer 220 and the inverse transformer 230, S1840 may be performed in the adder 235, and S1850 may be performed in the filter 240. S1810 may include the information decoding process described in the present disclosure, S1820 may include the inter / intra prediction process described in the present disclosure, S1830 may include the residual processing process described in the present disclosure, S1840 may include the block / picture reconstruction process described in the present disclosure, and S1850 may include the in-loop filtering process described in the present disclosure.

[0211] refer to Figure 18 , the picture decoding process can illustratively include a process of obtaining image / video information from a bitstream (by decoding) (S1810), a picture reconstruction process (S1820 to S1840), and an in-loop filtering process (S1850) of the reconstructed picture. The picture reconstruction process can be performed based on the prediction samples and residual samples obtained by the inter / intra prediction (S1820) and residual processing (S1830) (dequantization and inverse transformation of quantized transform coefficients) described in the present disclosure. For the reconstructed picture generated by the picture reconstruction process, a modified reconstructed picture can be generated by the in-loop filtering process, and the modified reconstructed picture can be output as a decoded picture, stored in the decoded picture buffer or memory 250 of the decoding device, and used as a reference picture in the inter-frame prediction process when the picture is later decoded. In some cases, the in-loop filtering process can be omitted. In this case, the reconstructed picture can be output as a decoded picture, stored in the decoded picture buffer or memory 250 of the decoding device, and used as a reference picture in the inter-frame prediction process when the picture is later decoded. The in-loop filtering process (S1850) may include a deblocking filtering process, a sample adaptive offset (SAO) process, an adaptive loop filter (ALF) process, and / or a bilateral filtering process, some or all of which may be omitted as described above. In addition, one or some of the deblocking filtering process, the sample adaptive offset (SAO) process, the adaptive loop filter (ALF) process, and / or the bilateral filter process may be applied sequentially, or all of them may be applied sequentially. For example, after applying the deblocking filtering process to the reconstructed picture, the SAO process may be performed. Alternatively, for example, after applying the deblocking filtering process to the reconstructed picture, the ALF process may be performed. This may also be performed similarly in the encoding device.

[0212] Figure 19 An example of a schematic picture encoding process to which the embodiments of the present disclosure are applicable is shown. Figure 19 For S1910, please refer to the above reference. Figure 2 The described encoding device may be performed in a predictor including the intra predictor 185 or the inter predictor 180, S1920 may be performed in a residual processor including the transformer 120 and / or the quantizer 130, and S1930 may be performed in the entropy encoder 190. S1910 may include the inter / intra prediction process described in the present disclosure, S1920 may include the residual processing process described in the present disclosure, and S1930 may include the information encoding process described in the present disclosure.

[0213] refer to Figure 19 , the picture encoding process may illustratively include not only a process for encoding information for picture reconstruction (e.g., prediction information, residual information, segmentation information, etc.) and outputting the information in the form of a bitstream, but also a process for generating a reconstructed picture of the current picture and an (optional) process for applying in-loop filtering to the reconstructed picture, as described in relation to Figure 2 As described. The encoding device can derive (modified) residual samples from the quantized transform coefficients through the dequantizer 140 and the inverse transformer 150, and generate a reconstructed picture based on the predicted samples and the (modified) residual samples as the output of S1910. The reconstructed picture generated in this way can be equal to the reconstructed picture generated in the decoding device. The modified reconstructed picture can be generated by an in-loop filtering process for the reconstructed picture, can be stored in the decoded picture buffer or the memory 170, and can be used as a reference picture in the inter-frame prediction process when the picture is later encoded, which is similar to the situation in the decoding device. As described above, in some cases, some or all of the in-loop filtering process can be omitted. When the in-loop filtering process is performed, the (in-loop) filtering related information (parameters) can be encoded in the entropy encoder 190 and output in the form of a bitstream, and the decoding device can perform the in-loop filtering process based on the filtering related information using the same method as the encoding device.

[0214] This in-loop filtering process can reduce noise (such as blocking artifacts and ringing artifacts) generated during image / video encoding, and can improve subjective / objective visual quality. In addition, by performing the in-loop filtering process in the encoding device and the decoding device, the encoding device and the decoding device can derive the same prediction result, which can increase the reliability of picture encoding and reduce the amount of data transmitted for picture encoding.

[0215] As described above, the picture reconstruction process can be performed not only in the decoding device but also in the encoding device. A reconstructed block can be generated based on intra-frame prediction / inter-frame prediction in block units, and a reconstructed picture including the reconstructed block can be generated. When the current picture / slice / patchwork group is an I picture / slice / patchwork group, the blocks included in the current picture / slice / patchwork group can be reconstructed based only on intra-frame prediction. In addition, when the current picture / slice / patchwork group is a P or B picture / slice / patchwork group, the blocks included in the current picture / slice / patchwork group can be reconstructed based on intra-frame prediction or inter-frame prediction. In this case, inter-frame prediction can be applied to some blocks in the current picture / slice / patchwork group, and intra-frame prediction can be applied to the remaining blocks. The color components of the picture may include luminance components and chrominance components, and unless otherwise explicitly defined in the present disclosure, the methods and embodiments of the present disclosure may be applied to luminance components and chrominance components.

[0216] Examples of coding layers and structures

[0217] The encoded video / image according to the present disclosure may be processed, for example, according to the coding layers and structures to be described below.

[0218] Figure 20 This diagram shows the layer structure of coded images. Coded images can be categorized into the Video Coding Layer (VCL), which handles the image decoding process and its own processing, lower layers for transmitting and storing coded information, and the Network Abstraction Layer (NAL), which exists between the VCL and lower layers and is responsible for network adaptation functions.

[0219] In the VCL, VCL data including compressed image data (slice data) can be generated, or a parameter set including information such as a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS) or a supplemental enhancement information (SEI) message additionally required for the decoding process of the image can be generated.

[0220] In NAL, header information (NAL unit header) can be added to the raw byte sequence payload (RBSP) generated in the VCL to generate a NAL unit. In this case, RBSP refers to slice data, parameter sets, and SEI messages generated in the VCL. The NAL unit header can include NAL unit type information specified according to the RBSP data included in the corresponding NAL unit.

[0221] As shown in the figure, NAL units can be classified into VCL NAL units and non-VCL NAL units according to the RBSP generated in the VCL. VCL NAL units can refer to NAL units that include information about images (slice data), and non-VCL NAL units can refer to NAL units that include information required for decoding images (parameter sets or SEI messages).

[0222] VCL NAL units and non-VCL NAL units can be attached with header information and transmitted over a network according to the data standard of a lower system. For example, the NAL unit can be modified into a predetermined standard data form such as the H.266 / VVC file format, RTP (Real-time Transport Protocol), or TS (Transport Stream) and transmitted over various networks.

[0223] As described above, in a NAL unit, a NAL unit type may be specified according to an RBSP data structure included in a corresponding NAL unit, and information on the NAL unit type may be stored in a NAL unit header and signaled.

[0224] For example, depending on whether the NAL unit includes information about the image (slice data), it can be roughly classified into VCL NAL unit type and non-VCL NAL unit type. VCL NAL unit type can be classified according to the characteristics and type of the picture included in the VCL NAL unit, and non-VCL NAL unit type can be classified according to the type of parameter set.

[0225] Examples of NAL unit types specified according to the types of parameter sets / information included in the non-VCL NAL unit type will be listed below.

[0226] -DCI (Decoding Capability Information) NAL unit: Type of NAL unit containing DCI

[0227] -VPS (Video Parameter Set) NAL unit: Type of NAL unit containing VPS

[0228] -SPS (Sequence Parameter Set) NAL unit: the type of NAL unit that includes the SPS

[0229] -PPS (Picture Parameter Set) NAL unit: type of NAL unit including PPS

[0230] -APS (Adaptation Parameter Set) NAL unit: type of NAL unit including APS

[0231] - PH (Picture Header) NAL unit: type of NAL unit including PH

[0232] The above-mentioned NAL unit type may have syntax information for the NAL unit type, and the syntax information may be stored in the NAL unit header and signaled. For example, the syntax information may be nal_unit_type, and the NAL unit type may be specified as a nal_unit_type value.

[0233] In addition, as described above, a picture may include multiple slices, and a slice may include a slice header and slice data. In this case, a picture header may be further added to the multiple slices (slice header and slice data set) in a picture. The picture header (picture header syntax) may include information / parameters that are generally applicable to the picture.

[0234] The slice header (slice header syntax) may include information / parameters that are commonly applicable to the slice. APS (APS syntax) or PPS (PPS syntax) may include information / parameters that are commonly applicable to one or more slices or pictures. SPS (SPS syntax) may include information / parameters that are commonly applicable to one or more sequences. VPS (VPS syntax) may include information / parameters that are commonly applicable to multiple layers. DCI (DCI syntax) may include information / parameters that are commonly applicable to the entire video. DCI may include information / parameters related to decoding capabilities. In the present disclosure, the high-level syntax (HLS) may include at least one of APS syntax, PPS syntax, SPS syntax, VPS syntax, DCI syntax, picture header syntax, or slice header syntax. In addition, in the present disclosure, the low-level syntax (LLS) may, for example, include slice data syntax, CTU syntax, coding unit syntax, transform unit syntax, etc.

[0235] In the present disclosure, the image / video information encoded in the encoding device and signaled to the decoding device in the form of a bitstream may include not only information related to intra-frame segmentation, intra-frame / inter-frame prediction information, residual information, and in-loop filtering information, but also information about slice headers, picture headers, APS, PPS, SPS, VPS, and / or DCI. In addition, the image / video information may also include general constraint information and / or information about NAL unit headers.

[0236] Split the screen using sprites, slices, and tiles

[0237] A picture can be divided into at least one tile row and at least one tile column. A tile can be composed of a CTU sequence and can cover a rectangular area of ​​a picture.

[0238] A slice can consist of an integer number of complete tiles or an integer number of consecutive complete CTU rows in a picture.

[0239] For slicing, two modes may be supported: one mode may be referred to as raster scan slicing mode, and the other mode may be referred to as rectangular slicing mode. In raster scan slicing mode, a slice may include a sequence of complete tiles that exist in a picture in a tile raster scan order. In rectangular slicing mode, a slice may include multiple complete tiles assembled to form a rectangular area of ​​the picture, or multiple consecutive complete CTU rows assembled to form a tile of a rectangular area of ​​the picture. Tiles in a rectangular slice may be scanned in a tile raster scan order in the rectangular area corresponding to the slice. A sub-picture may include at least one slice that is assembled to cover a rectangular area of ​​the picture.

[0240] To describe the split relationship of the screen in more detail, refer to Figures 21 to 24 Give a description. Figures 21 to 24 An embodiment of partitioning a picture using tiles, slices, and sub-pictures is shown. Figure 21 An example of a picture divided into 12 tiles and three raster scan slices is shown. Figure 22 An example of a picture divided into 24 tiles (6 tile columns and 4 tile rows) and 9 rectangular slices is shown. Figure 23 An example of a picture partitioned into four tiles (two tile columns and two tile rows) and four rectangular slices is shown.

[0241] Figure 24 An example of dividing a screen into sub-screens is shown. Figure 24 In , a picture can be divided into 12 left tiles covering one slice composed of 4×4 CTUs and 6 right tiles covering two slices vertically assembled by 2×2 CTUs, so that one picture is divided into 24 slices and 24 sub-pictures with different areas. Figure 24 In the example of , individual slices correspond to individual sprites.

[0242] HLS (High Level Syntax) signaling and semantics

[0243] As described above, HLS can be encoded and / or signaled for video and / or image encoding. As described above, in the present disclosure, video / image information can be included in HLS. In addition, image / video encoding methods can be performed based on such image / video information.

[0244] Picture header and slice header

[0245] A coded picture can be composed of at least one slice. Parameters describing the coded picture can be signaled in a picture header (PH), or parameters describing the slice can be signaled in a slice header (SH). The PH can be sent as a NAL unit type. The SH can be provided at the start of a NAL unit that configures the payload of the slice (e.g., slice data).

[0246] Screen split signaling

[0247] In one embodiment, a picture may be partitioned into multiple sub-pictures, tiles, and / or slices. Signaling of sub-pictures may be provided in a sequence parameter set. Signaling of tiles and rectangular slices may be provided in a picture parameter set. Additionally, signaling of raster scan slices may be provided in a slice header.

[0248] Figure 25 The syntax of the sequence parameter set is shown in FIG. Figure 25 In the syntax of , the syntax elements are as follows.

[0249] The subpic_info_present_flag syntax element may indicate whether sub-picture information is present. For example, a first value of subpic_info_present_flag (e.g., 0) may indicate that sub-picture information for a coded layer video sequence (CLVS) is not present in the bitstream and that only one sub-picture exists in an individual picture of the CLVS. A second value of subpic_info_present_flag (e.g., 1) may indicate that sub-picture information for a coded layer video sequence (CLVS) is present in the bitstream and that at least one sub-picture may exist in an individual picture of the CLVS.

[0250] Here, CLVS may mean a layer of a coded video sequence. CLVS may be a PU sequence having the same nuh_layer_id as a prediction unit (PU) of a gradual decoding refresh (GDR) picture or an intra random access point (IRAP) picture, which is not output until a reconstructed signal is generated.

[0251] The syntax element sps_num_subpics_minus1 may indicate the number of sub-pictures. For example, the value obtained by adding 1 to this value may represent the number of sub-pictures belonging to an individual picture of the CLVS. The value of sps_num_subpics_minus1 may have a value from 0 to Ceil(pic_width_max_in_luma_samples ÷ CtbSizeY)*Ceil(pic_height_max_in_luma_samples ÷ CtbSizeY)-1. When the value of sps_num_subpics_minus1 does not exist, the value of sps_num_subpics_minus1 may be derived as 0.

[0252] A value of 1 for the syntax element sps_independent_subpics_flag may indicate that intra prediction is not performed, inter prediction is not performed, and in-loop filtering operations are not performed outside the boundaries of a sub-picture in a CLVS.

[0253] A value of 0 for the syntax element sps_independent_subpics_flag may indicate that inter prediction or in-loop filtering operations may be performed outside the boundaries of a sub-picture in a CLVS. When the value of sps_independent_subpics_flag is not present, the value of sps_independent_subpics_flag may be derived to be 0.

[0254] The syntax element subpic_ctu_top_left_x[i] may indicate the horizontal position of the top left CTU of the i-th sub-picture in units of CtbSizeY. The length of the subpic_ctu_top_left_x[i] syntax element may be Ceil(Log2((pic_width_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)) bits. When subpic_ctu_top_left_x[i] does not exist, its value may be derived as 0. Here, pic_width_max_in_luma_samples may be a variable indicating the maximum width of a picture expressed in units of luma samples. CtbSizeY may be a variable indicating the size of a luma sample unit size of a CTB. CtbLog2SizeY may be a variable indicating a value obtained by taking log2 of the luma sample unit size of the CTB.

[0255] The syntax element subpic_ctu_top_left_y[i] may indicate the vertical position of the top left CTU of the i-th sub-picture in units of CtbSizeY. The length of the subpic_ctu_top_left_x[i] syntax element may be Ceil(Log2((pic_height_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)) bits. Here, pic_height_max_in_luma_samples may be a variable indicating the maximum height of the picture expressed in units of luma samples. When subpic_ctu_top_left_y[i] does not exist, its value may be derived as 0.

[0256] The value obtained by adding 1 to the syntax element subpic_width_minus1[i] may indicate the width of the first sub-picture, and its unit may be CtbSizeY. The length of subpic_width_minus1[i] may be Ceil(Log2((pic_width_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)) bits. When the value of subpic_width_minus1[i] does not exist, the value of subpic_width_minus1[i] may be calculated as ((pic_width_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)-subpic_ctu_top_left_x[i]-1.

[0257] The value obtained by adding 1 to the syntax element subpic_height_minus1[i] may indicate the height of the first sub-picture, and its unit may be CtbSizeY. The length of subpic_height_minus1[i] may be Ceil(Log2((pic_height_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)) bits. When subpic_height_minus1[i] does not exist, the value of subpic_height_minus1[i] may be calculated as ((pic_height_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)-subpic_ctu_top_left_y[i]-1.

[0258] A value of 1 for the syntax element subpic_treated_as_pic_flag[i] indicates that the i-th sub-picture of each coded picture in the CLVS is treated as a picture except for in-loop filtering operations. A value of 0 for subpic_treated_as_pic_flag[i] indicates that the i-th sub-picture of each coded picture in the CLVS is not treated as a picture except for in-loop filtering operations. When subpic_treated_as_pic_flag[i] is not present, the value of subpic_treated_as_pic_flag[i] may be set to the value of sps_independent_subpics_flag.

[0259] A value of 1 for the syntax element loop_filter_across_subpic_enabled_flag[i] may indicate that in-loop filtering may be performed outside the boundaries of the i-th sub-picture in each coded picture in the CLVS. A value of 0 for loop_filter_across_subpic_enabled_flag[i] may indicate that in-loop filtering is not performed outside the boundaries of the i-th sub-picture in each coded picture in the CLVS. When the value of loop_filter_across_subpic_enabled_flag[i] is not present, the value of loop_filter_across_subpic_enabled_flag[i] may be determined as 1-sps_independent_subpics_flag.

[0260] Figure 26 is a diagram showing an embodiment of the syntax of a picture parameter set. Figure 26 In the syntax of , the syntax elements are as follows.

[0261] A first value (eg, 0) of the syntax element no_pic_partition_flag may indicate that each picture of the reference PPS may be partitioned into two or more tiles or slices. A second value (eg, 1) of the no_pic_partition_flag may indicate that picture partitioning is not applied to each picture of the reference PPS.

[0262] The value obtained by adding 5 to the syntax element pps_log2_ctu_size_minus5 may indicate the luma coding block size of each CTU. The value of pps_log2_ctu_size_minus5 may be limited to be equal to sps_log2_ctu_size_minus5, which indicates the same value in the sequence parameter set.

[0263] The value obtained by adding 1 to the syntax element num_exp_tile_columns_minus1 indicates the number of explicitly provided tile column widths. The value of num_exp_tile_columns_minus1 can have a value from 0 to PicWidthInCtbsY-1. When the value of no_pic_partition_flag is 1, the value of num_exp_tile_columns_minus1 can be derived as 0.

[0264] The value obtained by adding 1 to the syntax element num_exp_tile_rows_minus1 may indicate the number of explicitly provided tile row heights. The value of num_exp_tile_rows_minus1 may have a value from 0 to PicHeightInCtbsY-1. When the value of no_pic_partition_flag is 1, the value of num_exp_tile_rows_minus1 may be derived as 0.

[0265] The value obtained by adding 1 to the syntax element tile_column_width_minus1[i] may indicate the width of the i-th tile column in units of CTBs. Here, i may have a value from 0 to num_exp_tile_columns_minus1-1. tile_column_width_minus1[num_exp_tile_columns_minus1] may be used to derive the width of a tile having an index of a tile column equal to or greater than num_exp_tile_columns_minus1. The value of tile_column_width_minus1[i] may have a value from 0 to PicWidthInCtbsY-1. When tile_column_width_minus1[i] is not provided from the bitstream, the value of tile_column_width_minus1[0] may be set to the value of PicWidthInCtbsY-1.

[0266] The value obtained by adding 1 to the syntax element tile_row_height_minus1[i] may indicate the height of the i-th tile row in units of CTBs. Here, i may have a value from 0 to num_exp_tile_rows_minus1-1. tile_row_height_minus1[num_exp_tile_rows_minus1] may be used to derive the height of a tile having an index of a tile row equal to or greater than num_exp_tile_rows_minus1. The value of tile_row_height_minus1[i] may have a value from 0 to PicHeightInCtbsY-1. When tile_row_height_minus1[i] is not provided from the bitstream, the value of tile_row_height_minus1[0] may be set to the value of PicHeightInCtbsY-1.

[0267] A value of 0 for the syntax element rect_slice_flag may indicate that the tiles in each slice are scanned in raster scan order and that slice information is not signaled through the picture parameter set. A value of 1 for rect_slice_flag may indicate that the tiles in each slice cover a rectangular area of ​​the picture and that slice information is signaled through the picture parameter set. Here, the variable NumTilesInPic may represent the number of tiles present in the picture. When rect_slice_flag is not present in the bitstream, the value of rect_slice_flag may be derived as 1. Additionally, when the value of subpic_info_present_flag is 1, the value of rect_slice_flag may be forced to 1.

[0268] The syntax element single_slice_per_subpic_flag with a value of 1 may indicate that each sub-picture consists of only one rectangular slice. The syntax element single_slice_per_subpic_flag with a value of 0 may indicate that each sub-picture consists of at least one rectangular slice. When single_slice_per_subpic_flag is not present in the bitstream, the value of single_slice_per_subpic_flag may be derived as 0.

[0269] The value obtained by adding 1 to the syntax element num_slices_in_pic_minus1 may indicate the number of slices in a picture. A value of 0 for the syntax element tile_idx_delta_present_flag may indicate that the tile_idx_delta[i] syntax element is not present in the picture parameter set and that all pictures of the reference picture parameter set are partitioned into rectangular slice rows and rectangular slice columns according to a slice raster scan order. A value of 1 for tile_idx_delta_present_flag may indicate that the tile_idx_delta[i] syntax element may be present in the picture parameter set and that all rectangular slices of the pictures belonging to the reference picture parameter set are specified according to increasing values ​​of i in the order indicated by the value of tile_idx_delta[i]. When tile_idx_delta_present_flag is not present, the value of tile_idx_delta_present_flag may be derived to be 0.

[0270] The value obtained by adding 1 to the syntax element slice_width_in_tiles_minus1[i] may indicate the width of the i-th rectangular slice in units of tile columns. The value of slice_width_in_tiles_minus1[i] may have a value from 0 to NumTileColumns-1. Here, when i is less than num_slices_in_pic_minus1 and the value of NumTileColumns is 1, the value of slice_width_in_tiles_minus1[i] may be derived as 0. Here, the variable NumTileColumns may indicate the number of tile columns present in the current picture. Here, the variable NumTileRows may indicate the number of tile rows present in the current picture.

[0271] When the value of num_exp_slices_in_tile[i] is 0, the value obtained by adding 1 to the syntax element slice_height_in_tiles_minus1[i] may indicate the height of the i-th rectangular slice in tile rows. The value of slice_height_in_tiles_minus1[i] may have a value from 0 to NumTileRows-1. When the value of i is less than num_slices_in_pic_minus1 and the value of slice_height_in_tiles_minus1[i] is not obtained from the bitstream, the value of slice_height_in_tiles_minus1[i] may be derived from the following equation.

[0272] [Formula 1]

[0273] slice_height_in_tiles_minus1[i]=NumTileRows==1?0:slice_height_in_tiles_minus1[i-1]

[0274] SliceTopLeftTileIdx may be a variable indicating the index of the top left tile of the slice.

[0275] The syntax element num_exp_slices_in_tile[i] may indicate the number of heights of slices explicitly provided relative to slices in a tile including the i-th slice (e.g., a tile with the same tile index as SliceTopLeftTileIdx[i]. The value of num_exp_slices_in_tile[i] may have a value from 0 to RowHeight[SliceTopLeftTileIdx[i] / NumTileColumns]-1. When num_exp_slices_in_tile[i] is not provided from the bitstream, the value of num_exp_slices_in_tile[i] may be derived as 0. Here, RowHight[i] may be a variable indicating the height of the i-th tile in units of CTBs. Here, when the value of num_exp_slices_in_tile[i] is 0, the tile including the i-th slice may not be split into multiple tiles.

[0276] The value obtained by adding 1 to the syntax element exp_slice_height_in_ctus_minus1[i][j] may indicate the height of the j-th rectangular slice in the tile including the i-th slice in units of CTUs. The value of exp_slice_height_in_ctus_minus1[i][j] may have a value from 0 to RowHeight[SliceTopLeftTileIdx[i] / NumTileColumns]-1.

[0277] The variable NumSlicesInTile[i] may indicate the number of slices present in the tile including the i-th slice.

[0278] The syntax element tile_idx_delta[i] may indicate the difference between the tile index of the tile including the first CTU in the (i+1)th rectangular slice and the tile index of the tile including the first CTU in the i-th rectangular slice. The value of tile_idx_delta[i] may have a value from -NumTilesInPic+1 to NumTilesInPic-1. When the value of tile_idx_delta[i] is not present in the bitstream, the value of tile_idx_delta[i] may be derived as 0. When the value of tile_idx_delta[i] is present, the value of tile_idx_delta[i] may be forced to a non-zero value.

[0279] A value of 1 for the syntax element loop_filter_across_tiles_enabled_flag may indicate that in-loop filtering operations may be performed outside tile boundaries in pictures of the reference picture parameter set. A value of 0 for loop_filter_across_tiles_enabled_flag may indicate that in-loop filtering operations may not be performed outside tile boundaries in pictures of the reference picture parameter set.

[0280] The in-loop filtering operation may include any of a deblocking filter, a sample adaptive offset (SAO) filter, or an adaptive loop filter (ALF).When loop_filter_across_tiles_enabled_flag is not present in the bitstream, the value of loop_filter_across_tiles_enabled_flag may be derived as 1.

[0281] A value of 1 for the syntax element loop_filter_across_slices_enabled_flag may indicate that in-loop filtering operations may be performed outside of slice boundaries in the pictures of the reference picture parameter set. A value of 0 for the loop_filter_across_slice_enabled_flag may indicate that in-loop filtering operations are not performed outside of slice boundaries in the pictures of the reference picture parameter set. The in-loop filtering operations may include any of a deblocking filter, a sample adaptive offset (SAO) filter, or an adaptive loop filter (ALF). When loop_filter_across_slice_enabled_flag is not present in the bitstream, the value of loop_filter_across_slice_enabled_flag may be derived as 1.

[0282] Figure 27 is a diagram showing an implementation of the syntax of the slice header. Figure 27In the syntax of , the syntax elements are as follows.

[0283] The syntax element slice_subpic_id may indicate the sub-picture ID of the sub-picture that includes the slice. When the value of slice_subpic_id exists in the bitstream, the value of the variable CurrSubpicIdx may be derived as the value of CurrSubpicIdx using the value of SubpicIdVal[CurrSubpicIdx] of slice_subpic_id. Otherwise (slice_subpic_id does not exist in the bitstream), the value of CurrSubpicIdx may be derived as 0. The length of slice_subpic_id may be sps_subpic_id_len_minus1+1 bits. Here, NumSlicesInSubpic[i] may be a variable indicating the number of slices in the i-th sub-picture. The variable CurrSubpicIdx may indicate the index of the current sub-picture.

[0284] The syntax element slice_address indicates the slice address of the slice. When slice_address is not provided, the value of slice_address can be derived as 0.

[0285] In addition, when the value of rect_slice_flag is 0, slice_address may be equal to the raster scan tile index of the first tile in the slice, and the length of the slice_address syntax element may be Ceil(Log2(NumTilesInPic)) bits, and slice_address may have a value from 0 to NumTilesInPic-1. Otherwise, (if the value of rect_slice_flag is non-zero, e.g., 1), the address of the slice may be the sub-picture level slice index of the slice, and the length of the slice_address syntax element may be Ceil(Log2(NumSlicesInSubpic[CurrSubpicIdx])) bits, and the slice_address syntax element may have a value from 0 to NumSlicesInSubpic[CurrSubpicIdx]-1.

[0286] The syntax element sh_extra_bit[i] can have a value of 0 or 1. The decoding device can perform decoding regardless of the value of sh_extra_bit[i]. To do this, the encoding device needs to generate a bitstream so that decoding is performed regardless of the value of sh_extra_bit[i]. Here, NumExtraShBits can be a variable indicating the number of bits required to further signal information in the slice header.

[0287] The value obtained by adding 1 to the syntax element num_tiles_in_slice_minus1 may indicate the number of tiles in the slice (if any).The value of num_tiles_in_slice_minus1 may have a value from 0 to NumTilesInPic-1.

[0288] A variable NumCtusInCurrSlice indicating the number of CTUs in a current slice and a list CtbAddrInCurrSlice[i] indicating the picture raster scan address of the i-th CTB in the slice (where i has a value from 0 to NumCtusInCurrSlice-1) may be derived as follows.

[0289] [Table 2]

[0290]

[0291] The variables SubpicLeftBoundaryPos, SubpicTopBoundaryPos, SubpicRightBoundaryPos, and SubpicBotBoundaryPos can be derived according to the following algorithm.

[0292] [Table 3]

[0293]

[0294] Improvements in screen split signaling

[0295] The above-mentioned signaling related to picture segmentation has the problem of signaling unnecessary information when the slice is a rectangular slice. For example, when the slice is a quadrilateral (e.g., rectangular) slice, the width of the individual slices can be signaled in tile units. However, when the top left tile of the slice is the tile of the last tile column, the width of the slice may not be a value other than one tile unit. For example, in this case, the width of the slice may only have a width value derived in one tile unit. Therefore, the width of such a slice may not be signaled or may be limited to one tile unit.

[0296] Similarly, when the slice is a quadrilateral (e.g., rectangular) slice, the width of the individual slice may be signaled in tile units. However, when the tile at the top left position of the slice is the tile of the last tile row, the height of the slice may not be a value other than one tile unit. Therefore, the height of such a slice may not be signaled or may be limited to one tile unit.

[0297] To address the above issues, the following method may be applied. When the slices are quadrilateral (e.g., rectangular) slices and the width and / or height of the individual slices are signaled in tile units, the following embodiment is applicable. The following method may be applied alone or in combination with at least one other embodiment.

[0298] Method 1: When the first tile of a rectangular slice (e.g., the tile in the upper left corner) is the tile located at the last tile column of the picture, the width of the slice may not be signaled. In this case, the width of the slice may be derived as one tile unit.

[0299] For example, the syntax element slice_width_in_tiles_minus1[i] may not be present in the bitstream. The value of the syntax element slice_width_in_tiles_minus1[i] may be derived to be 0.

[0300] Method 2: Even when the first tile of a rectangular slice (e.g., the tile in the upper left corner) is the tile located in the last tile column of the picture, the width of the slice may be signaled. However, in this case, the width of the slice may be limited to one tile unit.

[0301] For example, the syntax element slice_width_in_tiles_minus1[i] may be present in the bitstream and thus parsed. However, the value of the syntax element slice_width_in_tiles_minus1[i] may be limited to 0.

[0302] Method 3: When the first tile of a rectangular slice (e.g., the tile in the upper left corner) is located in the last tile row of the picture, the height of the slice may not be signaled. In this case, the height of the slice may be derived as one tile unit.

[0303] For example, the syntax element slice_height_in_tiles_minus1[i] may not be present in the bitstream. The value of the syntax element slice_height_in_tiles_minus1[i] may be derived to be 0.

[0304] Method 4: When the first tile of a rectangular slice (eg, the tile in the upper left corner) is the tile located in the last tile row of the picture, the height of the slice may be signaled. However, in this case, the height of the slice may be limited to one tile unit.

[0305] For example, the syntax element slice_height_in_tiles_minus1[i] may be present in the bitstream and thus parsed. However, the value of the syntax element slice_height_in_tiles_minus1[i] may be restricted to be equal to 0.

[0306] In one embodiment, the above embodiment is applicable to Figure 28 and Figure 29 The encoding method and decoding method shown in FIG. According to one embodiment, the encoding device may derive slices and / or patches in the current picture ( S2810 ). In addition, the encoding device may encode the current picture based on the derived slices and / or patches ( S2820 ).

[0307] Similarly, the decoding device according to the embodiment can obtain video / image information from the bitstream (S2910). In addition, the decoding device can derive slices and / or patches present in the current picture based on the video / image information (including information about slices and / or patches) (S2920). In addition, the decoding device can reconstruct and / or decode the current picture based on the slices and / or patches (S2930).

[0308] For the above-mentioned processing of the encoding device and the decoding device, the information about the slice and / or patch may include the above-mentioned information and syntax. The video or image information may include an HLS. The HLS may include information about the slice and / or information about the patch. The HLS may also include information about sub-pictures. The information about the slice may include information specifying at least one slice belonging to the current picture. In addition, the information about the patch may include information specifying at least one patch belonging to the current picture. The information about the sub-picture may include information specifying at least one sub-picture belonging to the current picture. A patch including at least one slice may exist in a single picture.

[0309] For example, in Figure 29 At S2930, the current picture may be reconstructed and / or decoded based on the derived slices and / or patches. By splitting a picture, encoding and decoding efficiency may be improved in various aspects.

[0310] For example, the picture can be segmented for parallel processing and error recovery. In the case of parallel processing, some embodiments executed in a multi-core CPU may need to segment the source picture into tiles and / or slices. Individual slices and / or tiles can be processed in parallel in different cores. This is very efficient for performing high-resolution real-time video encoding that cannot be performed by other methods. In addition, by reducing the information shared between tiles, this segmentation has the advantage of reducing memory constraints. Since the tiles are distributed to different threads while performing parallel processing, the parallel architecture is useful due to its segmentation mechanism. For example, in the process of deriving motion information in inter-frame prediction, neighboring blocks present in different slices and / or tiles can be restricted to not be used. Context information for encoding information and / or syntax elements can be initialized for each slice and / or tile.

[0311] Error resilience may be achieved by applying unequal error protection (UEP) to the coded patches and / or slices.

[0312] Implementation Method 1

[0313] Hereinafter, embodiments based on the above-mentioned methods 1 and 3 will be described. The following embodiments may be applied to improve encoding / decoding technologies such as the VVC specification.

[0314] In one embodiment, the Figure 30 In another embodiment, the syntax table for signaling the picture parameter set may be set as shown in FIG. Figure 31 The shown arrangement is used to signal a syntax table for a picture parameter set.

[0315] exist Figure 30 In an embodiment, for i with a value from 0 to num_slices_in_pic_minus1-1, when the value of NumTileColumns is greater than 1 and the value of SliceTopLeftTileIdx[i]%NumTileColumns is not NumTileColumns-1, the syntax element slice_width_in_tile_minus1[i] can be obtained sequentially with respect to i.

[0316] In addition, for i having a value from 0 to num_slices_in_pic_minus1-1, when the value of NumTileRows is greater than 1, the value of tile_idx_delta_present_flag is 1, or the value of SliceTopLeftTileIdx[i]%NumTileColumns is 0 and the value of SliceTopLeftTileIdx[i] / NumTileColumns is not NumTileRows-1, the syntax element slice_height_in_tiles_minus1[i] can be obtained sequentially with respect to i.

[0317] exist Figure 30 and Figure 31 In an embodiment, the syntax element slice_width_in_tiles_minus1[i] may be a syntax element indicating the width of the i-th rectangular slice. For example, a value obtained by adding 1 to slice_width_in_tiles_minus1[i] may indicate the width of the i-th rectangular slice in tile columns. The value of slice_width_in_tiles_minus1[i] may have a value from 0 to NumTileColumns-1. When slice_width_in_tiles_minus1[i] is not obtained from the bitstream, the value of slice_width_in_tiles_minus1[i] may be derived as 0.

[0318] When the definition of slice_width_in_tiles_minus1[i] is changed as described above, the constraint that “when i is less than num_slices_in_pic_minus1 and the value of NumTileColumns is equal to 1, the value of slice_width_in_tiles_minus1[i] is derived to be 0” can be omitted. Therefore, as in Figure 31 In an implementation manner, the constraint "NumTileColumns>1" may be removed from the picture parameter set syntax.

[0319] slice_height_in_tiles_minus1[i] may be a syntax element indicating the height of the i-th rectangular slice. For example, when the value of num_exp_slices_in_tile[i] is 0, the value obtained by adding 1 to slice_height_in_tiles_minus1[i] may indicate the height of the i-th rectangular slice in tile rows. The value of slice_height_in_tiles_minus1[i] may have a value from 0 to NumTileRows-1.

[0320] When slice_height_in_tiles_minus1[i] is not obtained from the bitstream, the value of slice_height_in_tiles_minus1[i] may be derived as follows.

[0321] First, when the value of NumTileRow is 1 or the value of SliceTopLeftTileIdx[i] % NumTileColumns is NumTileColumns-1, the value of slice_height_in_tiles_minus1[i] can be derived as 0.

[0322] Otherwise (e.g., when the value of NumTileRow is not 1 and the value of SliceTopLeftTileIdx[i] % NumTileColumns is not NumTileColumns-1), the value of slice_height_in_tiles_minus1[i] may be derived as slice_height_in_tiles_minus1[i-1]. For example, the value of slice_height_in_tiles_minus1[i] may be set to slice_height_in_tiles_minus1[i-1], which is the height value of the previous slice. For example, the value of slice_height_in_tiles_minus1[i] may be set identically for all slices in a tile.

[0323] When the definition of slice_height_in_tiles_minus1[i] is changed as described above, the existing constraint that “when i is less than num_slices_in_pic_minus1 and the value of NumTileRows is equal to 1, the value of slice_width_in_tiles_minus1[i] is derived to be 0” can be omitted. Therefore, as in Figure 31In an embodiment, the constraint "NumTileRows>1" may be removed from the picture parameter set syntax.

[0324] Implementation Method 2

[0325] Hereinafter, embodiments based on the above-mentioned methods 2 and 4 will be described. The following embodiments may be applied to improve encoding / decoding technologies such as the VVC specification.

[0326] In one embodiment, slice_width_in_tiles_minus1[i] may be a syntax element indicating the width of the i-th rectangular slice. For example, a value obtained by adding 1 to slice_width_in_tiles_minus1[i] may indicate the width of the i-th rectangular slice in tile columns. The value of slice_width_in_tiles_minus1[i] may have a value from 0 to NumTileColumns-1. When slice_width_in_tiles_minus1[i] is not obtained from the bitstream, the value of slice_width_in_tiles_minus1[i] may be derived as 0.

[0327] At this time, when i is less than num_slices_in_pic_minus1 and the value of NumTileColumns is equal to 1, the value of slice_width_in_tiles_minus1[i] can be derived to 0. In addition, for bitstream consistency, when the first tile of the i-th rectangular slice is the last tile in the tile column, the value of slice_width_in_tiles_minus1[i] can be forced to 0.

[0328] slice_height_in_tiles_minus1[i] may be a syntax element indicating the height of the i-th rectangular slice. For example, when the value of num_exp_slices_in_tile[i] is 0, the value obtained by adding 1 to slice_height_in_tiles_minus1[i] may indicate the height of the i-th rectangular slice in tile rows. The value of slice_height_in_tiles_minus1[i] may have a value from 0 to NumTileRows-1.

[0329] At this time, when i is less than num_slices_in_pic_minus1 and the value of slice_height_in_tiles_minus1[i] is not obtained from the bitstream, the value of slice_height_in_tiles_minus1[i] can be determined according to the value of NumTileRows. For example, this can be determined as shown in the following formula.

[0330] [Formula 2]

[0331] slice_height_in_tiles_minus1[i]=NumTileRows==1?0:slice_height_in_tiles_minus1[i-1]

[0332] In addition, for bitstream consistency, when the first tile of the i-th rectangular slice is the last tile of a tile row, the value of slice_height_in_tiles_minus1[i] may be forced to 0.

[0333] Encoding and decoding methods

[0334] Hereinafter, an image encoding method performed by an image encoding apparatus and an image decoding method performed by an image decoding apparatus according to an embodiment will be described.

[0335] First, the operation of the decoding device will be described. The image decoding device according to the embodiment may include a memory and a processor, and the decoding device may perform decoding through the operation of the processor. Figure 32 is a view showing an implementation of a decoding method according to an embodiment.

[0336] The decoding apparatus according to the embodiment may acquire the syntax element no_pic_partition_flag indicating the availability of partition of the current picture from the bitstream. As described above, the decoding apparatus may determine the availability of partition of the current picture based on the value of no_pic_partition_flag (S3210).

[0337] When partitioning of the current picture is available, the decoding apparatus may obtain a syntax element num_exp_tile_rows_minus1 indicating the number of tile rows partitioning the current picture and a syntax element num_exp_tile_columns_minus1 indicating the number of tile columns from the bitstream and determine the number of tile rows and tile columns therefrom as described above ( S3220 ).

[0338] Based on the number of tile columns, the decoding apparatus may acquire a syntax element tile_column_width_minus1 indicating the width of each tile column partitioning the current picture from the bitstream and determine the width of each tile column therefrom as described above ( S3230 ).

[0339] Based on the number of tile rows, the decoding device can obtain a syntax element tile_row_height_minus1[i] indicating the height of each tile row that partitions the current picture from the bitstream, and determine the height of each tile row therefrom (S3240). In addition, the decoding device can calculate the number of tiles that partition the current picture by multiplying the number of tile columns by the number of tile rows.

[0340] Next, the decoding apparatus may obtain a syntax element rect_slice_flag indicating whether the current picture is partitioned into rectangular slices based on whether the number of tiles partitioning the current picture is greater than 1, and determine whether the current picture is partitioned into rectangular slices from its value as described above ( S3250 ).

[0341] Next, the decoding apparatus may acquire a syntax element num_slices_in_pic_minus1 indicating the number of slices partitioning the current picture from a bitstream based on whether the current picture is partitioned into rectangular slices, and determine the number of slices partitioning the current picture therefrom as described above ( S3260 ).

[0342] Next, the decoding apparatus may acquire size information indicating the size of each of the slices partitioning the current picture from the bitstream as many as the number of slices partitioning the current picture from the bitstream ( S3270 ).

[0343] Here, the size information may include a syntax element slice_width_in_tiles_minus1[i] as width information indicating the width of the slice and a syntax element slice_height_in_tiles_minus1[i] as height information indicating the height of the slice. Slice_width_in_tiles_minus1[i] may indicate the width of the slice in tile columns, and slice_height_in_tiles_minus1[i] may indicate the height of the slice in tile rows.

[0344] Here, when the decoding device obtains size information of the current slice (e.g., the i-th slice) from the bitstream, the decoding device can obtain slice_width_in_tiles_minus1[i] from the bitstream based on whether the upper left tile of the current slice belongs to the last tile column of the current picture.

[0345] For example, when the top left tile index of the current slice (e.g., SliceTopLeftTileIdx) is not the tile index corresponding to the last column of the tile column belonging to the current picture, slice_width_in_tiles_minus1[i] may be obtained from the bitstream. However, when the top left tile index of the current slice is the tile index corresponding to the last column of the tile column belonging to the current picture, slice_width_in_tiles_minus1[i] may not be obtained from the bitstream and may be determined to be 0.

[0346] Similarly, the decoding device may obtain slice_height_in_tiles_minus1[i] from the bitstream based on whether the upper left tile of the current slice belongs to the last tile row of the current picture.

[0347] For example, when the top left tile index of the current slice is not the tile index corresponding to the last row of tile rows belonging to the current picture, slice_height_in_tiles_minus1[i] may be obtained from the bitstream. However, when the top left tile index of the current slice is the tile index corresponding to the last row of tile rows belonging to the current picture, slice_height_in_tiles_minus1[i] may not be obtained from the bitstream and may be determined to be 0.

[0348] Next, the decoding device may determine the size of each slice for partitioning the current picture based on the size information, and decode the determined slice, thereby decoding the image. For example, the CTU included in the slice having the determined size may be decoded using inter-frame prediction or intra-frame prediction, thereby decoding the slice (S3280).

[0349] In addition, SliceTopLeftTileIdx may be a variable indicating the top left tile of the slice and may be accessed through Figure 33 and Figure 34 algorithm to determine. Figure 33 and Figure 34 The algorithm is a continuous algorithm.

[0350] Next, the operation of the encoding device will be described. The image encoding device according to the embodiment may include a memory and a processor, and the encoding device may perform encoding in a manner corresponding to the decoding of the decoding device through the operation of the processor. For example, Figure 35As shown, the encoding device can encode the current picture. First, the encoding device can determine the tile columns and tile rows of the current picture (S3510). Next, the slices of the segmented image can be determined (S3520). Next, the encoding device can generate a bitstream including predetermined information (S3530), the predetermined information including the size information of the slice. For example, the encoding device can generate a bitstream including no_pic_partition_flag, num_exp_tile_rows_minus1, num_exp_tile_columns_minus1, tile_column_width_minus1, tile_row_height_minus1[i], rect_slice_flag, num_slices_in_pic_minus1, slice_width_in_tiles_minus1[i], and slice_height_in_tiles_minus1[i] as syntax elements obtained from the bitstream by the decoding device.

[0351] At this time, the size information may be included in the bitstream based on whether the current slice belongs to the last tile column or last tile row of the current picture. For example, the encoding device may encode the bitstream based on whether the top left tile of the current slice is the last tile column and / or last tile row, so that slice_width_in_tiles_minus1[i] and slice_height_in_tiles_minus1[i] correspond to the description of the decoding device. Here, the current slice may be a rectangular slice.

[0352] Application Implementation

[0353] Although the exemplary methods of the present disclosure are shown as a series of operations for clarity of description, it is not intended to limit the order in which the steps are performed, and the steps may be performed simultaneously or in a different order if necessary. To implement the methods according to the present disclosure, the steps described may further include other steps, may include the remaining steps in addition to some steps, or may include other additional steps in addition to some steps.

[0354] In the present disclosure, an image encoding device or image decoding device that performs a predetermined operation (step) may perform an operation (step) of confirming the execution conditions or circumstances of the corresponding operation (step). For example, if it is described that a predetermined operation is performed when a predetermined condition is satisfied, the image encoding device or image decoding device may perform the predetermined operation after determining whether the predetermined condition is satisfied.

[0355] The various embodiments of the present disclosure are not a list of all possible combinations and are intended to describe representative aspects of the present disclosure, and matters described in the various embodiments may be applied independently or in combinations of two or more.

[0356] Various embodiments of the present disclosure may be implemented in hardware, firmware, software, or a combination thereof. In the case of implementing the present disclosure in hardware, the present disclosure may be implemented in an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a general purpose processor, a controller, a microcontroller, a microprocessor, or the like.

[0357] In addition, the image decoding device and the image encoding device to which the embodiments of the present disclosure are applied may be included in multimedia broadcast transmission and reception devices, mobile communication terminals, home theater video devices, digital theater video devices, surveillance cameras, video chat devices, real-time communication devices such as video communication, mobile streaming devices, storage media, cameras, video on demand (VoD) service providers, OTT video (over the top video) devices, Internet streaming service providers, three-dimensional (3D) video devices, video phone video devices, medical video devices, etc., and may be used to process video signals or data signals. For example, OTT video devices may include game consoles, Blu-ray players, Internet-connected TVs, home theater systems, smart phones, tablet PCs, digital video recorders (DVRs), etc.

[0358] Figure 36 is a diagram illustrating a content streaming system to which embodiments of the present disclosure can be applied.

[0359] like Figure 36 As shown, the content streaming system applying the embodiments of the present disclosure may mainly include an encoding server, a streaming server, a network server, a media storage device, a user device, and a multimedia input device.

[0360] The encoding server compresses content input from a multimedia input device such as a smartphone, a camera, or a camcorder into digital data to generate a bitstream and transmits the bitstream to the streaming server. As another example, when a multimedia input device such as a smartphone, a camera, or a camcorder directly generates a bitstream, the encoding server may be omitted.

[0361] A bitstream may be generated by applying the image encoding method or the image encoding apparatus according to the embodiment of the present disclosure, and a streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

[0362] A streaming server transmits multimedia data to a user device based on a user's request via a network server. The network server acts as an intermediary to inform users of services. When a user requests a desired service from the network server, the network server delivers it to the streaming server, which then transmits the multimedia data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server is used to control commands and responses between devices in the content streaming system.

[0363] The streaming server can receive content from a media storage device and / or an encoding server. For example, when receiving content from an encoding server, the content can be received in real time. In this case, in order to provide a smooth streaming service, the streaming server can store the bitstream for a predetermined time.

[0364] Examples of user devices may include mobile phones, smart phones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, tablet computers, tablet PCs, ultrabooks, wearable devices (e.g., smart watches, smart glasses, head-mounted displays), digital televisions, desktop computers, digital signage, etc.

[0365] The various servers in the content streaming system may operate as distributed servers, in which case data received from the various servers may be distributed.

[0366] The scope of the present disclosure includes software or machine-executable commands (e.g., operating systems, applications, firmware, programs, etc.) for enabling operations according to the methods of various embodiments to be performed on a device or computer, and non-transitory computer-readable media having such software or commands stored thereon and executable on a device or computer.

[0367] Industrial Applicability

[0368] The embodiments of the present disclosure may be used to encode or decode an image.

Claims

1. An image decoding method performed by an image decoding device, the image decoding method comprising the following steps: obtaining, from a bitstream, size information indicating a size of a current slice corresponding to at least a portion of a current picture; as well as determining the size of the current slice based on the size information, The current slice is a rectangular slice and includes at least one tile, The size information includes width information indicating the width of the current slice in units of tile columns and height information indicating the height of the current slice in units of tile rows, and Wherein, obtaining the width information of the current slice from the bitstream is skipped based on that the upper left patch of the current slice belongs to the last patch column of the current picture.

2. The image decoding method according to claim 1, wherein: Based on the fact that the upper left patch of the current slice belongs to the last patch column of the current picture, obtaining the width information of the current slice from the bitstream is skipped, and the width information is determined to be a predetermined value, the predetermined value being 0, and The predetermined value indicates a tile column.

3. The image decoding method according to claim 1, wherein: Obtaining the height information of the current slice from the bitstream is skipped based on the top left patch of the current slice belonging to the last patch row of the current picture.

4. The image decoding method according to claim 1, wherein: The height information of the current slice is obtained from the bitstream based on that the upper left patch of the current slice does not belong to the last patch row of the current picture.

5. The image decoding method according to claim 1, wherein: Based on the fact that the upper left patch of the current slice belongs to the last patch row of the current picture, obtaining the height information of the current slice from the bitstream is skipped, and the height information is determined to be a predetermined value, the predetermined value being 0, and The predetermined value indicates a tile row.

6. The image decoding method according to claim 1, in, The step of obtaining the size information is performed based on the number of slices into which the current picture is divided, The number of slices for dividing the current picture is determined by: determining availability of partitioning of the current picture based on partitioning information obtained from the bitstream; determining, based on the availability of the segmentation of the current picture, a number of tile rows and a number of tile columns for segmenting the current picture; determining the width of each tile column that divides the current picture based on the number of tile columns; determining the height of each tile row that divides the current picture based on the number of tile rows; determining whether the current picture is divided into rectangular slices based on the number of slices that divide the current picture; and The number of slices into which the current picture is partitioned is obtained from the bitstream based on whether the current picture is partitioned into rectangular slices.

7. An image encoding method performed by an image encoding device, the image encoding method comprising the following steps: determining a current slice corresponding to at least a portion of a current picture; as well as Encoding the size information of the current slice into the bitstream, The current slice is a rectangular slice and includes at least one tile, The size information includes width information indicating the width of the current slice in units of tile columns and height information indicating the height of the current slice in units of tile rows, and Wherein, encoding the width information of the current slice in the bitstream is skipped based on that the upper left patch of the current slice belongs to the last patch column of the current picture.

8. A method for transmitting a bit stream generated by an image encoding method, the image encoding method comprising the steps of: determining a current slice corresponding to at least a portion of a current picture; as well as Encoding the size information of the current slice into the bitstream, The current slice is a rectangular slice and includes at least one tile, The size information includes width information indicating the width of the current slice in units of tile columns and height information indicating the height of the current slice in units of tile rows, and Wherein, encoding the width information of the current slice in the bitstream is skipped based on that the upper left patch of the current slice belongs to the last patch column of the current picture.

Images