Image decoding and encoding method and data transmission method for image

Abstract

Disclosed are an image decoding and encoding method and a data transmission method for an image. According to one embodiment of the present document, a decoded picture may be divided into sub-pictures. Information related to the sub-picture may be acquired by the decoding device, and a decoding process may be performed based on the information related to the sub-picture. In one embodiment, a decoding device may determine, based on information on a sub-picture, a position at which information related to a position of a virtual boundary for in-loop filtering is signaled.

Description

[0001] This application is a divisional application of the invention patent application with the original application number 202080097301.4 (International Application No.: PCT / KR2020 / 019012, filing date: December 23, 2020, invention title: Image coding apparatus and method based on picture partitioning). Technical Field

[0002] This document relates to an image coding apparatus and method based on picture partitioning. Background Art

[0003] Recently, the demand for high-resolution, high-quality images / videos such as 4K or 8K or higher ultra-high definition (UHD) images / videos has increased in various fields. As image / video data has high resolution and high quality, the amount of information or bits to be transmitted increases compared to existing image / video data. Therefore, transmitting image data using media such as existing wired / wireless broadband lines or existing storage media or storing image / video data using existing storage media increases the transmission cost and storage cost.

[0004] In addition, the interest and demand for immersive media such as virtual reality (VR) and artificial reality (AR) content or holograms have recently increased, and the broadcast of images / videos (e.g., game images) having characteristics different from real images has increased.

[0005] Therefore, a very efficient image / video compression technology is needed to effectively compress, transmit, store, and reproduce the information of high-resolution, high-quality images / videos having various characteristics as described above.

[0006] Specifically, a picture can be partitioned into specific units. For example, a picture can be divided into sub-pictures. To decode a picture composed of sub-pictures, a decoding device can signal sub-picture related information. Schemes for efficient signaling of sub-picture related information are being discussed. Summary of the Invention

[0007] Technical Solution

[0008] According to an embodiment of this document, a method and apparatus for increasing image coding efficiency are provided.

[0009] According to an embodiment of this document, an efficient filtering application method and apparatus are provided.

[0010] According to an embodiment of this document, a method and apparatus for effectively applying deblocking, sample adaptive offset (SAO), and adaptive loop filtering (ALF) are provided.

[0011] According to an embodiment of this document, in-loop filtering can be performed based on a virtual boundary.

[0012] According to an embodiment of this document, the decoded picture may be composed of sub-pictures.

[0013] According to an embodiment of this document, the signaling position of the information about the position of the virtual boundary may be determined based on the signaling of the information about the sub-pictures.

[0014] According to an embodiment of this document, the signaling of the information related to the virtual boundary may be performed based on the signaling of the information related to the sub-pictures.

[0015] According to an embodiment of this document, an encoding device for performing video / image encoding is provided.

[0016] According to an embodiment of this document, a computer-readable digital storage medium is provided, in which encoded video / image information generated according to the video / image encoding method disclosed in at least one embodiment of this document is stored.

[0017] According to an embodiment of this document, a computer-readable digital storage medium is provided, in which encoded information or encoded video / image information that causes a decoding device to execute the video / image decoding method disclosed in at least one embodiment of this document is stored.

[0018] Advantageous Effects

[0019] According to an embodiment of this document, the overall image / video compression efficiency may be improved.

[0020] According to an embodiment of this document, the subjective / objective visual quality may be improved through efficient filtering.

[0021] According to an embodiment of this document, efficient encoding may be achieved by omitting the process of rewriting the bitstream with signaling-based virtual boundary signaling through sub-pictures. Description of the Drawings

[0022] Figure 1 An example of a video / image encoding system to which an embodiment of this document can be applied is schematically shown.

[0023] Figure 2 is a diagram schematically showing the configuration of a video / image encoding device to which an embodiment of this document can be applied.

[0024] Figure 3 is a diagram schematically showing the configuration of a video / image decoding device to which an embodiment of this document can be applied.

[0025] Figure 4 An exemplary hierarchical architecture of an encoded video / image is shown.

[0026] Figure 5 Displays a screen according to an embodiment of this document.

[0027] Figure 6 Displays a sub - picture / slice / tile - based encoding method according to an embodiment of this document.

[0028] Figure 7 Displays a sub - picture / slice / tile - based decoding method according to an embodiment of this document.

[0029] Figure 8 Is a flowchart illustrating a filter - based encoding method in an encoding device.

[0030] Figure 9 Is a flowchart illustrating a filter - based decoding method in a decoding device.

[0031] Figure 10 and Figure 11 Schematically shows an example of a video / image encoding method and related components according to an embodiment of this document.

[0032] Figure 12 and Figure 13 Schematically shows an example of an image / video decoding method and related components according to an embodiment of this document.

[0033] Figure 14 Displays an example of a content stream system to which the embodiments disclosed in this document can be applied. Detailed implementation

[0034] Each configuration of the drawings described in this document is for independently illustrating functions as different features from each other, and does not mean that each configuration is implemented by mutually different hardware or different software. For example, two or more configurations can be combined to form one configuration, and one configuration can also be divided into multiple configurations. Embodiments in which configurations are combined and / or separated without departing from the gist of this document are included within the scope of the claims.

[0035] In addition, this document can be modified in various forms, and its specific embodiments will be described and shown in the drawings. However, these embodiments are not intended to limit this document. The terms used in the following description are only for describing specific embodiments and are not intended to limit this document. Singular expressions include plural expressions as long as they are clearly different in reading. Terms such as "including" and "having" are intended to indicate the presence of the features, numbers, steps, operations, elements, components, or combinations thereof used in the following description, and thus it should be understood that the possibility of the presence or addition of one or more different features, numbers, steps, operations, elements, components, or combinations thereof is not excluded.

[0036] Hereinafter, examples of the present embodiment will be described in detail with reference to the accompanying drawings. In addition, like reference numerals are used throughout the drawings to indicate like elements, and the same description of like elements will be omitted.

[0037] This document relates to video / image coding. For example, the methods / embodiments disclosed in this document may relate to the Versatile Video Coding (VVC) standard (ITU-T Rec. H.266), the next-generation video / image coding standard after VVC, or other video coding-related standards (e.g., the High Efficiency Video Coding (HEVC) standard (ITU-T Rec. H.265), the Essential Video Coding (EVC) standard, the AVS2 standard, etc.).

[0038] This document presents various embodiments of video / image coding, and unless otherwise specified, the above embodiments may also be executed in combination with each other.

[0039] In this document, video may refer to a series of images over time. A picture generally refers to a unit representing an image for a specific time range, and a slice / tile refers to a unit that constitutes a part of a picture in terms of coding. A slice / tile may include one or more Coding Tree Units (CTUs). A picture may be composed of one or more slices / titles. A picture may be composed of one or more tile groups. A tile group may include one or more tiles.

[0040] A pixel or picture element may mean the smallest unit that constitutes a picture (or image). In addition, "sample" may be used as a term corresponding to a pixel. A sample generally may represent a pixel or a pixel value, and may represent only the pixel / pixel value of the luminance component or only the pixel / pixel value of the chrominance component.

[0041] A unit may represent the 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 one luminance block and two chrominance (e.g., cb, cr) blocks. In some cases, a unit may be used interchangeably with terms such as a block or a region. In general, an M×N block may include an array of M columns and N rows of samples (or sample array) or a set (or array) of transform coefficients. Alternatively, a sample may mean a pixel value in the spatial domain, and when such a pixel value is transformed into the frequency domain, it may mean a transform coefficient in the frequency domain.

[0042] In this document, the terms " / " and "," should be interpreted as indicating "and / or". For example, the expression "A / B" may mean "A and / or B". In addition, "A,B" may mean "A and / or B". In addition, "A / B / C" may mean "at least one of A, B, and / or C". Additionally, "A / B / C" may mean "at least one of A, B, and / or C".

[0043] In addition, in this document, the term "or" should be interpreted as indicating "and / or". For example, the expression "A or B" may include 1) only A, 2) only B, and / or 3) both A and B. In other words, the term "or" in this document should be interpreted as indicating "additionally or alternatively".

[0044] In this specification, "at least one of A and B" may mean "only A", "only B", or "both A and B". In addition, in this specification, the expressions "at least one of A or B" or "at least one of A and / or B" may be interpreted in the same way as "at least one of A and B".

[0045] In addition, in this specification, "at least one of A, B, and C" may mean "only A", "only B", "only C", or "any combination of A, B, and C". In addition, "at least one of A, B, or C" or "at least one of A, B, and / or C" may mean "at least one of A, B, and C".

[0046] In addition, the parentheses used in this specification may mean "for example". Specifically, in the case of the expression "prediction (intra prediction)", it may indicate that "intra prediction" is proposed as an example of "prediction". In other words, the term "prediction" in this specification is not limited to "intra prediction", and it may indicate that "intra prediction" is proposed as an example of "prediction". In addition, even in the case of the expression "prediction (i.e., intra prediction)", it may indicate that "intra prediction" is proposed as an example of "prediction".

[0047] In this specification, the technical features described separately in one figure may be implemented separately or simultaneously.

[0048] Figure 1 An example of a video / image coding system of a document to which this document can be applied is shown.

[0049] Refer to Figure 1 , the video / image coding system may include a source device and a receiving device. The source device may send the encoded video / image information or data in the form of a file or a stream to the receiving device through a digital storage medium or a network.

[0050] The source device may include a video source, an encoding device, and a transmitter. The receiving device may include a receiver, a decoding device, and a renderer. The encoding device may be referred to as a video / image encoding device, and the decoding device may be referred to as a video / image decoding device. The transmitter may be included in the encoding device. The receiver may be included in the decoding device. The renderer may include a display, and the display may be configured as a separate device or an external component.

[0051] The video source can obtain video / images through processes such as capturing, synthesizing, or generating video / images. The video source can include a video / image capture device and / or a video / image generation device. For example, the video / image capture device can include one or more cameras, a video / image archive including previously captured video / images, etc. For example, the video / image generation device can include a computer, a tablet computer, and a smart phone, and can (electronically) generate video / images. For example, virtual video / images can be generated by a computer or the like. In this case, the video / image capture process can be replaced by a process of generating relevant data.

[0052] The encoding device can encode the input video / images. For compression and encoding efficiency, the encoding device can perform a series of processes such as prediction, transformation, and quantization. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0053] The transmitter can send the encoded image / image information or data output in the form of a bitstream to the receiver of the receiving device in the form of a file or a stream through a digital storage medium or a network. The digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitter can include elements for generating a media file in a predetermined file format and can include elements for transmitting through a broadcast / communication network. The receiver can receive / extract the bitstream and send the received bitstream to the decoding device.

[0054] The decoding device can decode the video / images by performing a series of processes such as dequantization, inverse transformation, and prediction corresponding to the operations of the encoding device.

[0055] The renderer can render the decoded video / images. The rendered video / images can be displayed through a display.

[0056] Figure 2 FIG. is a diagram schematically showing the configuration of a video / image encoding device to which the present document can be applied. Hereinafter, the so-called video encoding device can include an image encoding device.

[0057] Refer to Figure 2, the encoding device 200 may include and be configured with an image splitter 210, a predictor 220, a residual processor 230, an entropy encoder 240, an adder 250, a filter 260, and a memory 270. The predictor 220 may include an inter-frame predictor 221 and an intra-frame predictor 222. The residual processor 230 may include a transformer 232, a quantizer 233, a dequantizer 234, and an inverse transformer 235. The residual processor 230 may also include a subtractor 231. The adder 250 may be referred to as a reconstructor or a reconstruction block generator. According to an embodiment, the above-mentioned image splitter 210, predictor 220, residual processor 230, entropy encoder 240, adder 250, and filter 260 may be configured by one or more hardware components (e.g., an encoder chipset or a processor). Additionally, the memory 270 may include a decoded picture buffer (DPB) and may also be configured by a digital storage medium. The hardware components may also include the memory 270 as an internal / external component.

[0058] The image splitter 210 may divide an input image (or picture, frame) input to the encoding device 200 into one or more processing units. As an example, the processing unit may be referred to as a coding unit (CU). In this case, the coding unit may be recursively divided from a coding tree unit (CTU) or a largest coding unit (LCU) according to a quadtree binary tree ternary tree (QTBTTT) structure. For example, one coding unit may be divided into multiple coding units with a deeper depth based on a quadtree structure, a binary tree structure, and / or a ternary tree structure. In this case, for example, the quadtree structure is applied first, and then the binary tree structure and / or the ternary tree structure may be applied later. Alternatively, the binary tree structure may also be applied first. The encoding process according to this document may be performed based on the final coding unit that cannot be further divided. In this case, according to the encoding efficiency based on image characteristics, etc., the largest coding unit may be directly used as the final coding unit, or if necessary, the coding unit may be recursively divided into coding units with a deeper depth so that the coding unit with the optimal size can be used as the final coding unit. Here, the encoding process may include processes such as prediction, transformation, and reconstruction (described later). As another example, the processing unit may also include a prediction unit (PU) or a transformation unit (TU). In this case, each of the prediction unit and the transformation unit may be split or divided from the above-mentioned final coding unit. The prediction unit may be a unit for sample prediction, and the transformation unit may be a unit for deriving transformation coefficients and / or a unit for deriving a residual signal from the transformation coefficients.

[0059] In some cases, a unit may be used interchangeably with terms such as a block or a region. Generally, an M×N block may represent a sample or a set of transform coefficients consisting of M columns and N rows. A sample may generally represent a pixel or a pixel value, and may also represent only the pixel / pixel value of the luminance component, and may also represent only the pixel / pixel value of the chrominance component. A sample may be used as a term corresponding to a pixel or a pel configuring a picture (or an image).

[0060] The subtractor 231 may generate a residual signal (residual block, residual sample, or residual sample array) by subtracting the prediction signal (prediction block, prediction sample, or prediction sample array) output from the predictor 220 from the input image signal (original block, original sample, or original sample array), and the generated residual signal is sent to the transformer 232. The predictor 220 may perform prediction on a processing target block (hereinafter, referred to as "current block") and generate a prediction block including prediction samples of the current block. The predictor 220 may determine whether to apply intra prediction or inter prediction to the current block or in units of CUs. As will be described later in the description of each prediction mode, the predictor may generate various types of information related to prediction (e.g., prediction mode information) and transmit the generated information to the entropy encoder 240. Information about the prediction may be encoded in the entropy encoder 240 and output in the form of a bit stream.

[0061] The intra predictor 222 may predict the current block by referring to samples within the current picture. Depending on the prediction mode, the samples referred to may be located near the current block, or may also be far from the current block. The prediction modes in intra prediction may include a plurality of non-directional modes and a plurality of directional modes. For example, the non-directional modes may include a DC mode or a planar mode. For example, depending on the fineness of the prediction direction, the directional modes may include 33 directional prediction modes or 65 directional prediction modes. However, this is illustrative, and more or fewer directional prediction modes than the above numbers may be used according to the setting. The intra predictor 222 may also use the prediction mode applied to an adjacent block to determine the prediction mode applied to the current block.

[0062] The inter - frame predictor 221 can derive a predicted block of the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, in order to reduce the amount of motion information transmitted in the inter - frame prediction mode, the motion information can be predicted in units of blocks, sub - blocks, or samples based on the correlation of the motion information between neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can also include inter - frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter - frame prediction, neighboring blocks can include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block can be the same as each other, and can also be different from each other. The temporal neighboring block can be called by names such as a collocated reference block, a collocated CU (colCU), etc., and the reference picture including the temporal neighboring block can also be called a collocated picture (colPic). For example, the inter - frame predictor 221 can configure a motion information candidate list based on neighboring blocks and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter - frame prediction can be performed based on various prediction modes. For example, in the case of the skip mode and the merge mode, the inter - frame predictor 221 can use the motion information of neighboring blocks as the motion information of the current block. In the skip mode, different from the merge mode, the residual signal may not be transmitted. The motion vector prediction (MVP) mode can use the motion vector of a neighboring block as a motion vector predictor and signal a motion vector difference to indicate the motion vector of the current block.

[0063] The predictor 220 can generate a prediction signal based on various prediction methods described below. For example, the predictor can apply not only intra - frame prediction or inter - frame prediction to predict a block, but also apply both intra - frame prediction and inter - frame prediction at the same time. This can be called combined inter - frame and intra - frame prediction (CIIP). In addition, the predictor can perform intra - block copy (IBC) for predicting a block. Intra - block copy can be used for content image / motion image coding such as games, for example, screen content coding (SCC). IBC basically performs prediction in the current picture, but can be performed similarly to inter - frame prediction so that a reference block is derived in the current picture. That is, IBC can use at least one inter - frame prediction technique described in this document.

[0064] The prediction signal generated by the inter-frame predictor 221 and / or the intra-frame predictor 222 can be used to generate a reconstructed signal or to generate a residual signal. The transformer 232 can generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique can include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a graph-based transform (GBT), or a conditional non-linear transform (CNT). Here, GBT means 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. Additionally, the transform processing can be applied to a square pixel block of the same size or can be applied to a block of variable size other than square.

[0065] The quantizer 233 can quantize the transform coefficients and send them to the entropy encoder 240, and the entropy encoder 240 can encode the quantized signal (information about the quantized transform coefficients) and output a bitstream. The information about the quantized transform coefficients can be referred to as residual information. The quantizer 233 can rearrange the block-type quantized transform coefficients into a one-dimensional vector form based on the coefficient scan order, and generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. The entropy encoder 240 can perform various coding methods such as exponential Golomb, context-adaptive variable length coding (CAVLC), context-adaptive binary arithmetic coding (CABAC), etc. The entropy encoder 240 can encode the information required for video / image reconstruction together with or separately from the quantized transform coefficients (e.g., the value of a syntax element, etc.). The encoded information (e.g., the encoded video / image information) can be sent or stored in the form of a bitstream in units of network abstraction layer (NAL). The video / image information can also include information about various parameter sets, such as an adaptive parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). Additionally, the video / image information can also include general constraint information. In this document, the information and / or syntax elements signaled / sent later can be encoded by the above-mentioned encoding process and included in the bitstream. The bitstream can be sent through a network or can be stored in a digital storage medium. Here, the network can include a broadcast network and / or a communication network, and the digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitter (not shown) that sends the signal output from the entropy encoder 240 and / or the storage unit (not shown) that stores the signal can be configured as internal / external elements of the encoding device 200, and alternatively, the transmitter can be included in the entropy encoder 240.

[0066] The quantized transform coefficients output from the quantizer 233 can be used to generate a prediction signal. For example, a residual signal (residual block or residual sample) can be reconstructed by applying inverse quantization and inverse transformation to the quantized transform coefficients via the dequantizer 234 and the inverse transformer 235. The adder 250 adds the reconstructed residual signal to the prediction signal output from the predictor 220 to generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample, or reconstructed sample array). If there is no residual in the processing target block (e.g., in the case of applying the skip mode), the prediction block can be used as the reconstructed block. As described below, the generated reconstructed signal can be used for intra prediction of the next processing target block in the current picture and can be filtered for inter prediction of the next picture.

[0067] In addition, luminance mapping with chroma scaling (LMCS) can be applied during picture encoding and / or reconstruction processing.

[0068] The filter 260 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 260 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture and store the modified reconstructed picture in the memory 270 (specifically, the DPB of the memory 270). For example, various filtering methods can include deblocking filtering, sample adaptive offset (SAO), adaptive loop filter, bilateral filter, etc. The filter 260 can generate various types of information related to filtering and transmit the generated information to the entropy encoder 290, as will be described later in the description of each filtering method. The information related to filtering can be encoded by the entropy encoder 290 and output in the form of a bitstream.

[0069] The modified reconstructed picture sent to the memory 270 can be used as a reference picture in the inter predictor 221. When inter prediction is applied by the encoding device, prediction mismatch between the encoding device 200 and the decoding device 300 can be avoided and the encoding efficiency can be improved.

[0070] The DPB of the memory 270 can store the modified reconstructed picture used as a reference picture in the inter predictor 221. The memory 270 can store the motion information of the blocks that derive (or encode) the motion information in the current picture and / or the motion information of the blocks that have been reconstructed in the picture. The stored motion information can be transmitted to the inter predictor 221 to be used as the motion information of spatially adjacent blocks or temporally adjacent blocks. The memory 270 can store the reconstructed samples of the reconstructed blocks in the current picture and can transmit the reconstructed samples to the intra predictor 222.

[0071] Figure 3 is a diagram for schematically illustrating the configuration of a video / image decoding device of a document to which this document can be applied.

[0072] Refer to Figure 3, the decoding device 300 may include and be configured with an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, a filter 350, and a memory 360. The predictor 330 may include an inter-frame predictor 331 and an intra-frame predictor 332. The residual processor 320 may include a dequantizer 321 and an inverse transformer 322. According to an embodiment, the entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filter 350 described above may be configured by one or more hardware components (e.g., a decoder chipset or a processor). Additionally, the memory 360 may include a decoded picture buffer (DPB) and may be configured by a digital storage medium. The hardware components may also include the memory 360 as an internal / external component.

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

[0074] The decoding device 300 may receive from Figure 2The signal output by the encoding device in the form of a bitstream, and the received signal can be decoded by the entropy decoder 310. For example, the entropy decoder 310 can parse the bitstream to derive the information (e.g., video / image information) required for image reconstruction (or picture reconstruction). The video / image information may also include information about various parameter sets, such as the Adaptive Parameter Set (APS), Picture Parameter Set (PPS), Sequence Parameter Set (SPS), or Video Parameter Set (VPS). Additionally, the video / image information may also include general constraint information. The decoding device can also decode the picture based on the information about the parameter sets and / or the general constraint information. The signaled / received information and / or syntax elements described later in this document can be decoded through the decoding process and obtained from the bitstream. For example, the entropy decoder 310 decodes the information in the bitstream based on an encoding method such as exponential Golomb coding, CAVLC, or CABAC, and outputs the syntax elements required for image reconstruction and the quantization values of the transform coefficients of the residuals. More specifically, the CABAC entropy decoding method can receive the bins corresponding to the respective syntax elements in the bitstream, use the information of the syntax element to be decoded, the decoding information of the block to be decoded, or the information of the symbols / bins decoded in the previous stage to determine the context model, and perform arithmetic decoding on the bins by predicting the probability of the bin occurrence according to the determined context model, and generate the symbols corresponding to the values of the respective syntax elements. In this case, the CABAC entropy decoding method can update the context model by using the information of the decoded symbols / bins for the context model of the next symbol / bin after determining the context model. Among the information decoded by the entropy decoder 310, the information related to prediction can be provided to the predictor 330, and the information about the residuals for which entropy decoding has been performed in the entropy decoder 310 (i.e., the quantized transform coefficients and related parameter information) can be input to the dequantizer 321. Additionally, the information about filtering among the information decoded by the entropy decoder 310 can be provided to the filter 350. Furthermore, a receiver (not shown) for receiving the signal output by the encoding device can also be configured as an internal / external component of the decoding device 300, or the receiver can be a constituent component of the entropy decoder 310. Additionally, the decoding device according to this document can be referred to as a video / image / picture decoding device, and the decoding device can be classified into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder may include the entropy decoder 310, and the sample decoder may include at least one of the dequantizer 321, inverse transformer 322, predictor 330, adder 340, filter 350, and memory 360.

[0075] The dequantizer 321 can dequantize the quantized transform coefficients to output the transform coefficients. The dequantizer 321 can rearrange the quantized transform coefficients in a two-dimensional block form. In this case, the rearrangement can be performed based on the coefficient scanning order executed by the encoding device. The dequantizer 321 can perform dequantization on the quantized transform coefficients using quantization parameters (e.g., quantization step information) and obtain the transform coefficients.

[0076] The inverse transformer 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

[0077] The predictor 330 can perform prediction of the current block and generate a prediction block including the prediction samples of the current block. The predictor can determine whether to apply intra prediction or inter prediction to the current block and determine a specific intra / inter prediction mode based on the information about prediction output from the entropy decoder 310.

[0078] The predictor can generate a prediction signal based on various prediction methods described below. For example, the predictor can not only apply intra prediction or inter prediction to predict a block, but also apply intra prediction and inter prediction simultaneously. This can be referred to as combined inter and intra prediction (CIIP). Additionally, the predictor can perform intra block copy (IBC) for the prediction block. Intra block copy can be used for content image / motion image coding such as games, e.g., screen content coding (SCC). IBC basically performs prediction in the current picture, but can be performed similarly to inter prediction so that a reference block is derived in the current picture. That is, IBC can use at least one of the inter prediction techniques described in this document.

[0079] The intra predictor 332 can predict the current block by referring to the samples in the current picture. Depending on the prediction mode, the samples referred to can be located near the current block or can be far from the current block. In intra prediction, the prediction mode can include multiple non - directional modes and multiple directional modes. The intra predictor 332 can use the prediction mode applied to the neighboring block to determine the prediction mode to be applied to the current block.

[0080] The inter - frame predictor 331 can derive a predicted block of the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter - frame prediction mode, the motion information can be predicted in units of blocks, sub - blocks, or samples based on the correlation of the motion information between neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can also include 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 spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. For example, the inter - frame predictor 331 can construct a candidate list of motion information based on neighboring blocks and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter - frame prediction can be performed based on various prediction modes, and the information about the prediction can include information indicating the inter - frame prediction mode of the current block.

[0081] The adder 340 can generate a reconstructed signal (reconstructed picture, reconstructed block, and reconstructed sample array) by adding the obtained residual signal to the predicted signal (predicted block or predicted sample array) output from the predictor 330. If there is no residual for the processing target block, for example, in the case of applying the skip mode, the predicted block can be used as the reconstructed block.

[0082] The adder 340 can be referred to as a reconstructor or a reconstructed - block generator. The generated reconstructed signal can be used for intra - frame prediction of the next block to be processed in the current picture and, as described later, can also be output through filtering or can be used for inter - frame prediction of the next picture.

[0083] In addition, luminance mapping with chroma scaling (LMCS) can also be applied in the picture decoding process.

[0084] The filter 350 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 350 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture and store the modified reconstructed picture in the memory 360 (specifically, the DPB of the memory 360). For example, various filtering methods can include de - blocking filtering, sample - adaptive offset, adaptive loop filter, bilateral filter, etc.

[0085] The (modified) reconstructed picture stored in the DPB of the memory 360 can be used as a reference picture in the inter - frame predictor 331. The memory 360 can store the motion information of the block that derives (or decodes) the motion information in the current picture and / or the motion information of the blocks that have been reconstructed in the picture. The stored motion information can be transmitted to the inter - frame predictor 331 to be used as the motion information of spatial neighboring blocks or temporal neighboring blocks. The memory 360 can store the reconstructed samples of the reconstructed blocks in the current picture and transmit the reconstructed samples to the intra - frame predictor 332.

[0086] In this specification, the embodiments described in the predictor 330, dequantizer 321, inverse transformer 322, and filter 350 of the decoding device 300 can also be applied in the same or corresponding manner as the predictor 220, dequantizer 234, inverse transformer 235, and filter 260 of the encoding device 200.

[0087] In addition, as described above, when performing video encoding, prediction is performed to improve the compression efficiency. Thus, a prediction block including prediction samples of a current block (i.e., an encoding target block) to be encoded can be generated. Here, the prediction block includes prediction samples in the spatial domain (or pixel domain). The prediction block is derived in the same manner in the encoding device and the decoding device, and the encoding device can signal to the decoding device information (residual information) about the residual between the original block and the prediction block instead of the original sample values of the original block, thereby increasing the image encoding efficiency. The decoding device can derive a residual block including residual samples based on the residual information, add the residual block and the prediction block to generate a reconstructed block including reconstructed samples, and generate a reconstructed picture including the reconstructed block.

[0088] The residual information can be generated through transformation and quantization processing. For example, the encoding device can derive a residual block between the original block and the prediction block, perform transformation processing on the residual samples (residual sample array) included in the residual block to derive transform coefficients, perform quantization processing on the transform coefficients to derive quantized transform coefficients, and signal the relevant residual information (through the bitstream) to the decoding device. Here, the residual information can include value information, position information, transformation technique, transformation kernel, quantization parameter, etc. of the quantized transform coefficients. The decoding device can perform dequantization / inverse transformation processing based on the residual information and derive residual samples (or a residual block). The decoding device can generate a reconstructed picture based on the prediction block and the residual block. Additionally, as a reference for inter-frame prediction of a later picture, the encoding device can also dequantize / inverse transform the quantized transform coefficients to derive a residual block and generate a reconstructed picture based on it.

[0089] In this document, at least one of quantization / dequantization and / or transformation / inverse transformation can be omitted. When quantization / dequantization is omitted, the quantized transform coefficients can be referred to as transform coefficients. When transformation / inverse transformation is omitted, the transform coefficients can be referred to as coefficients or residual coefficients, or for the sake of consistency of expression, they can still be referred to as transform coefficients.

[0090] In this document, the quantized transform coefficients and the transform coefficients may be referred to as transform coefficients and scaled transform coefficients, respectively. In this case, the residual information may include information about the transform coefficients, and the information about the transform coefficients may be signaled by the residual coding syntax. The transform coefficients may be derived based on the residual information (or the information about the transform coefficients), and the scaled transform coefficients may be derived by an inverse transform (scaling) of the transform coefficients. The residual samples may be derived based on an inverse transform (transformation) of the scaled transform coefficients. This may also be applied / expressed in other parts of this document.

[0091] The predictor of an encoding device / decoding device may derive a predicted sample by performing inter prediction on a block-by-block basis. The inter prediction may be a prediction derived in a manner depending on data elements (e.g., sample values or motion information) of pictures other than the current picture. When inter prediction is applied to a current block, a predicted block (predicted sample array) of the current block may be derived based on a reference block (reference sample array) specified by a motion vector on a reference picture pointed to by a reference picture index. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information of the current block may be predicted on a block, sub-block, or sample basis based on the correlation between the motion information of 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 about an inter prediction type (L0 prediction, L1 prediction, Bi prediction, etc.). When inter prediction is applied, the neighboring blocks may include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring blocks may be the same or different. The temporal neighboring blocks may be referred to as co-located reference blocks, co-located CUs (colCUs), etc., and the reference picture including the temporal neighboring blocks may be referred to as a co-located picture (colPic). For example, a motion information candidate list may be constructed based on neighboring blocks of the current block, and a flag or index information indicating which candidate is selected (used) to derive the motion vector and / or reference picture index of the current block may be signaled. The inter prediction may be performed based on various prediction modes. For example, in the skip mode and the merge mode, the motion information of the current block may be the same as the motion information of the selected neighboring block. In the skip mode, different from the merge mode, the residual signal may not be sent. In the case of the motion vector prediction (MVP) mode, the motion vector of the selected neighboring block may be used as a motion vector predictor, and 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.

[0092] According to 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. The motion vector in the L0 direction may be referred to as the L0 motion vector or MVL0, and the motion vector in the L1 direction may be referred to as the L1 motion vector or MVL1. The prediction based on the L0 motion vector may be referred to as L0 prediction, the prediction based on the L1 motion vector may be referred to as L1 prediction, and the 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 indicate the motion vector associated with the reference picture list L0 (L0), and the L1 motion vector may indicate the motion vector associated with the reference picture list L1 (L1). The reference picture list L0 may include pictures that are earlier than the current picture in the output order as reference pictures, and the reference picture list L1 may include pictures that are later than the current picture in the output order. The previous picture may be referred to as the forward (reference) picture, and the subsequent picture may be referred to as the backward (reference) picture. The reference picture list L0 may also include pictures that are later than the current picture in the output order as reference pictures. In this case, in the reference picture list L0, the previous picture may be indexed first, and the subsequent picture may be indexed next. The reference picture list L1 may also include pictures that are earlier than the current picture in the output order as reference pictures. In this case, the subsequent picture may be indexed first in the reference picture list 1, and the previous picture may be indexed next. Here, the output order may correspond to the picture order count (POC) order.

[0093] Figure 4 Exemplarily shows the hierarchical structure of the encoded image / video.

[0094] Refer to Figure 4 , the encoded image / video is divided into the VCL (Video Coding Layer) for processing the image / video decoding process and itself, the subsystem for transmitting and storing the encoded information, and the network abstraction layer (NAL) that exists between the VCL and the subsystem and is responsible for the network adaptation function.

[0095] The VCL may generate VCL data including compressed image data (slice data), or generate parameter sets including Picture Parameter Set (PSP), Sequence Parameter Set (SPS), Video Parameter Set (VPS), etc., or Supplementary Enhancement Information (SEI) messages that are additionally required for the decoding process of the image.

[0096] In the NAL, a NAL unit can be generated by adding header information (NAL unit header) to the raw byte sequence payload (RBSP) generated in the VCL. In this case, the RBSP refers to slice data, parameter sets, SEI messages, etc. 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.

[0097] As shown in the figure, NAL units can be divided into VCL NAL units and non-VCL NAL units according to the RBSP generated in the VCL. A VCL NAL unit can mean a NAL unit including information about an image (slice data), and a non-VCL NAL unit can mean a NAL unit containing information required for decoding the image (parameter set or SEI message).

[0098] The above VCL NAL units and non-VCL NAL units can be sent over the network by attaching header information according to the data standard of the subsystem. For example, NAL units can be transformed into a data form of a predetermined standard such as the H.266 / VVC file format, Real-Time Transport Protocol (RTP), Transport Stream (TS), etc. and sent over various networks.

[0099] As described above, in a NAL unit, the NAL unit type can be specified according to the RBSP data structure included in the corresponding NAL unit, and information about the NAL unit type can be stored in the NAL unit header and signaled.

[0100] For example, NAL units can be roughly classified into a VCL NAL unit type and a non-VCL NAL unit type according to whether the NAL unit includes information about an image (slice data). The VCL NAL unit type can be classified according to the nature and type of the pictures included in the VCL NAL unit, and the non-VCL NAL unit type can be classified according to the type of the parameter set.

[0101] The following are examples of NAL unit types specified according to the type of the parameter set included in the non-VCL NAL unit type.

[0102] - APS (Adaptive Parameter Set) NAL unit: The type of the NAL unit including APS

[0103] - DPS (Decoding Parameter Set) NAL unit: The type of the NAL unit including DPS

[0104] - VPS (Video Parameter Set) NAL unit: The type of the NAL unit including VPS

[0105] - SPS (Sequence Parameter Set) NAL unit: The type of the NAL unit including SPS

[0106] -PPS (Picture Parameter Set) NAL unit: The type of the NAL unit including PPS

[0107] -PH (Picture Header) NAL unit: The type of the NAL unit including PH

[0108] The above NAL unit types have the syntax information of the NAL unit type, and the syntax information can be stored in the NAL unit header and signaled. For example, the syntax information can be nal_unit_type, and the NAL unit type can be specified by the nal_unit_type value.

[0109] 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 multiple slices (slice header and slice data sets) in a picture. The picture header (picture header syntax) may include information / parameters generally applicable to the picture. In this document, slices may be mixed with tile groups or replaced by tile groups. Additionally, in this document, slice headers may be mixed with tile group headers or replaced by type group headers.

[0110] The slice header (slice header syntax or slice header information) may include information / parameters generally applicable to the slice. APS (APS syntax) or PPS (PPS syntax) may include information / parameters generally applicable to one or more slices or pictures. SPS (SPS syntax) may include information / parameters generally applicable to one or more sequences. VPS (VPS syntax) may include information / parameters generally applicable to multiple layers. DPS (DPS syntax) may include information / parameters generally applicable to the entire video. DPS may include information / parameters related to the concatenation of coded video sequences (CVS). In this document, the high-level syntax (HLS) may include at least one of APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, picture header syntax, and slice header syntax.

[0111] In this document, 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 the segmentation-related information, intra / inter prediction information, residual information, loop filter information, etc. in the picture, but also the information included in the slice header, the information included in the picture header, the information included in APS, the information included in PPS, the information included in SPS, the information included in VPS, and / or the information included in DPS. Additionally, the image / video information may further include the information of the NAL unit header.

[0112] In addition, in order to compensate for the difference between the original image and the reconstructed image caused by errors in compression encoding processing such as quantization, loop filtering processing may be performed on the reconstructed samples or the reconstructed picture as described above. As described above, loop filtering may be performed by the filter of the encoding device and the filter of the decoding device, and a deblocking filter, SAO, and / or an adaptive loop filter (ALF) may be applied. For example, the ALF process may be performed after the deblocking filtering process and / or the SAO process. However, even in this case, the deblocking filtering process and / or the SAO process may be omitted.

[0113] Hereinafter, a detailed description of picture reconstruction and filtering will be given. In image / video coding, reconstructed blocks may be generated in units of blocks based on intra prediction / inter prediction, and a reconstructed picture including the reconstructed blocks may be generated. If the current picture / slice is an I picture / slice, the blocks included in the current picture / slice may be reconstructed only based on intra prediction. In addition, if the current picture / slice is a P or B picture / slice, the blocks included in the current picture / slice may be reconstructed based on intra prediction or inter prediction. In this case, intra prediction may be applied to some of the blocks in the current picture / slice, and inter prediction may be applied to the remaining blocks.

[0114] Intra prediction may represent a prediction for generating a prediction sample of a current block based on reference samples in the picture (hereinafter, the current picture) to which the current block belongs. In the case where intra prediction is applied to the current block, neighboring reference samples to be used for the intra prediction of the current block may be derived. The neighboring reference samples of the current block may include samples adjacent to the left boundary of the current block having a size of nW×nH, a total of 2×nH samples adjacent to the lower left, samples adjacent to the upper boundary of the current block, a total of 2×nW samples adjacent to the upper right, and one sample adjacent to the upper left of the current block. Alternatively, the neighboring reference samples of the current block may include upper neighboring samples in multiple columns and left neighboring samples in multiple rows. Alternatively, the neighboring reference samples of the current block may include a total of nH samples adjacent to the right boundary of the current block having a size of nW×nH, a total of nH samples adjacent to the right boundary of the current block, a total of nW samples adjacent to the lower boundary of the current block, and one sample adjacent to the lower right of the current block.

[0115] However, some of the neighboring reference samples of the current block may not have been decoded yet or may be unavailable. In this case, the decoder may configure the neighboring reference samples to be used for prediction by replacing the unavailable samples with available samples. Alternatively, the neighboring reference samples to be used for prediction may be configured by interpolation of available samples.

[0116] In the case of deriving neighboring reference samples, (i) a predicted sample may be derived based on an average or interpolation of neighboring reference samples of a current block, and (ii) a predicted sample may be derived based on reference samples among the neighboring reference samples of the current block that are present in a specific (predicted) direction of the predicted sample. The case of (i) may be referred to as a non-directional mode or non-corner mode, and the case of (ii) may be referred to as a directional mode or corner mode. Further, a predicted sample may be generated by interpolation between a first neighboring sample and a second neighboring sample among the neighboring reference samples, where the predicted sample of the current block is located in a direction opposite to the predicted direction of the intra prediction mode of the current block. The above case may be referred to as linear interpolation intra prediction (LIP). Further, a chrominance prediction sample may be generated based on luminance samples using a linear model. This case may be referred to as the LM mode. Further, a temporal prediction sample of the current block may be derived based on filtered neighboring reference samples, and a predicted sample of the current block may be derived by calculating a weighted sum of the temporal prediction sample and at least one reference sample derived according to the intra prediction mode among existing neighboring reference samples (i.e., unfiltered neighboring reference samples). The above case may be referred to as position-dependent intra prediction (PDPC). Further, a predicted sample may be derived by selecting a reference sample line having the highest prediction accuracy among a plurality of neighboring reference sample lines of the current block and using the reference samples on the corresponding line that are in the predicted direction, and in this case, intra prediction coding may be performed in a method of indicating (signaling) the used reference sample line to a decoding device. The above case may be referred to as multi-reference line (MRL) intra prediction or MRL-based intra prediction. Further, intra prediction may be performed based on the same intra prediction mode by dividing the current block into vertical sub-partitions or horizontal sub-partitions, and neighboring reference samples may be derived and used in units of sub-partitions. That is, in this case, since the intra prediction mode of the current block is equally applied to the sub-partitions, and neighboring reference samples are derived and used in units of sub-partitions, the intra prediction performance may be enhanced in some cases. This prediction method may be referred to as intra sub-partition (ISP) or ISP-based intra prediction. The above intra prediction methods may be referred to as intra prediction types different from the intra prediction modes in Content 1.2. Intra prediction types may be referred to by various terms such as intra prediction techniques or additional intra prediction modes. For example, an intra prediction type (or additional intra prediction mode) may include at least one of the above LIP, PDPC, MRL, or ISP. A general intra prediction method other than a specific intra prediction type such as LIP, PDPC, MRL, or ISP may be referred to as a normal intra prediction type. In the case where a specific intra prediction type is not applied, the normal intra prediction type may generally be applied, and prediction may be performed based on the above intra prediction modes. Further, if necessary, post-filtering may be performed on the derived predicted samples.

[0117] Specifically, the intra prediction process may include steps of intra prediction mode / type determination, neighboring reference sample derivation, and prediction sample derivation based on the intra prediction mode / type. Additionally, if necessary, a post-filtering step may be performed on the derived prediction samples.

[0118] A reconstructed picture modified through in-loop filtering processing may be generated, and the modified reconstructed picture may be output as a decoded picture from the decoding device. Additionally, the modified reconstructed picture may be stored in a decoded picture buffer or memory of the encoding device / decoding device and then used as a reference picture in the inter prediction process when encoding / decoding a picture. As described above, the in-loop filtering processing may include deblocking filtering processing, sample adaptive offset (SAO) processing, and / or adaptive loop filter (ALF) processing. In this case, one or some of deblocking filtering processing, sample adaptive offset (SAO) processing, adaptive loop filter (ALF) processing, and bilateral filtering processing may be applied sequentially, or all the processing may be applied sequentially. For example, after applying deblocking filtering processing to the reconstructed picture, SAO processing may be performed. Additionally, for example, after applying deblocking filtering processing to the reconstructed picture, ALF processing may be performed. This may even be performed by the encoding device in the same manner.

[0119] Deblocking filtering is a filtering technique for removing distortions that occur at the boundaries between blocks in the reconstructed picture. For example, the deblocking filtering processing may derive a target boundary from the reconstructed picture, determine the boundary strength (bS) of the target boundary, and perform deblocking filtering on the target boundary based on bS. bS may be determined based on the prediction mode of two blocks adjacent to the target boundary, the motion vector difference, whether the reference pictures are the same, and the presence of non-0 valid coefficients.

[0120] SAO is a method for compensating the offset difference between the reconstructed picture and the original picture on a sample-by-sample basis, and may be applied based on types such as band offset, edge offset, etc., for example. According to SAO, samples are classified into different categories according to the SAO type, and an offset value may be added to each sample based on the category. The filtering information of SAO may include information on whether SAO is applied, SAO type information, and SAO offset value information. SAO may be applied to the reconstructed picture after applying deblocking filtering.

[0121] The adaptive loop filter (ALF) is a filtering technique for filtering the reconstructed picture on a sample-by-sample basis based on filter coefficients according to the filter shape. The encoding device may determine whether to apply ALF, the ALF shape, and / or the ALF filter coefficients by comparing the reconstructed picture and the original picture with each other, and may signal it to the decoding device. That is, the filtering information of ALF may include information on whether ALF is applied, ALF filter shape information, and ALF filter coefficient information. ALF may also be applied to the reconstructed picture after applying deblocking filtering.

[0122] Figure 5 Displays a screen according to an embodiment of this document. Figure 5 The exemplary screen can be divided into sub - screens, slices, and tiles.

[0123] Referring to Figure 5 , the screen can be divided into sub - screens. For example, a sub - screen can include one or more slices. A slice can represent a rectangular area of the screen. In addition, the screen can be divided into tiles. For example, a rectangular slice can include only a part (subset) of one tile. That is, in Figure 5 , two rectangular slices are within the same tile, and these two rectangular slices can belong to different sub - screens. The problems caused by the situation of Figure 5 and their solutions will be described later.

[0124] In an example, the screen / sub - screen can be encoded based on sub - screens / slices / tiles. The encoding device can encode the current screen based on the sub - screen / slice / tile structure, or the encoding device can encode one or more sub - screens (including slices / tiles) of the current screen and can output a (sub) bit - stream including (encoded) information about the sub - screen. The decoding device can decode one or more sub - screens in the current screen based on the (sub) bit - stream including (encoded) information about the sub - screen / slice / tile.

[0125] Figure 6 Displays a sub - screen / slice / tile - based encoding method according to an embodiment of this document.

[0126] The encoder can divide the (input) screen into multiple (or one or more) sub - screens / slices / tiles. Each sub - screen can be encoded individually / independently and a bit - stream can be output. Here, the bit - stream for the sub - screen can be referred to as a sub - stream, subset, or sub - bit - stream. The information about the sub - screen / slice / tile can include the information / syntax elements described in this document. For example, the information about a slice can include information related to the number of slices signaled for each screen / sub - screen and the width / height of the slices in the tile. For example, the information about a tile can include information related to the number of tiles (e.g., the number of tile columns and / or the number of tile rows) and information related to the size of each tile (e.g., width and / or height).

[0127] The encoder can encode one or more sub - screens as information about the sub - screen. The encoder can encode one or more slices / tiles as information about the slice / tile.

[0128] Figure 7 Displays a sub - screen / slice / tile - based decoding method according to an embodiment of this document.

[0129] The decoder can decode one or more sub - pictures (including slices / tile - parts), and can output one or more decoded sub - pictures or the current picture including sub - pictures. The bitstream can include sub - streams or sub - bitstreams for sub - pictures. As described above, information about sub - pictures / slices / tile - parts can be configured in the High - Level Syntax (HLS) included in the bitstream. The decoder can derive one or more sub - pictures based on the information about sub - pictures. The decoder can derive one or more slices / tile - parts based on the information about slices / tile - parts. The decoder can decode all or some of the sub - pictures. The decoder can decode sub - pictures (including the current block (or CU)), CTUs, slices, and / or tile - parts based on CABAC, prediction, residual processing (transformation and quantization), and in - loop filtering. Thus, decoded sub - pictures can be output. The decoded sub - pictures can include reconstructed / decoded blocks. The decoded sub - pictures in the Output Picture Set (OPS) can be output together. As an example, if the picture is related to a 360 - degree or omnidirectional image / video, some of them can be rendered, and in this case, only some of all the sub - pictures can be decoded, and some or all of the decoded sub - pictures can be rendered according to the user's viewport or viewing position. Additionally, if the information indicating (representing) whether in - loop filtering is enabled across sub - picture boundaries is enabled, the decoder can apply in - loop filtering processing (e.g., de - blocking filtering) for the sub - picture boundary located between two sub - pictures. For example, if the sub - picture boundary is the same as the picture boundary, the in - loop filtering processing for the sub - picture boundary can be applied or not performed.

[0130] In an embodiment of this document, the image / video information can include HLS, and the HLS can include information about sub - pictures / slices / tile - parts. The information about sub - pictures can include information representing one or more sub - pictures in the current picture. The information about slices can include information representing one or more slices in the current picture, sub - picture, or tile - part. The information about tile - parts can include information representing one or more tile - parts in the current picture, sub - picture, or slice. The picture can include tile - parts containing one or more slices and / or slices containing one or more tile - parts. In addition, the picture can include sub - pictures containing one or more slices / tile - parts.

[0131] The following table represents the syntax related to the above - mentioned picture partitioning (sub - pictures / slices / tile - parts). The information about sub - pictures / slices / tile - parts can include the syntax elements in the following table.

[0132] The following table represents the syntax of the Sequence Parameter Set (SPS) based on the picture partitioning (sub - pictures / slices / tile - parts).

[0133] [Table 1]

[0134]

[0135] The following table shows the syntax of the Picture Parameter Set (PPS) based on picture partitioning (sub - picture / slice / tile).

[0136] [Table 2]

[0137]

[0138] The following table shows the syntax of the slice header based on picture partitioning (sub - picture / slice / tile).

[0139] [Table 3]

[0140]

[0141] Figure 8 is a flowchart illustrating the filter - based encoding method in an encoding device. Figure 8 The method may include steps S800 to S830.

[0142] In step S800, the encoding device may generate a reconstructed picture. Step S800 may be performed based on the above - mentioned process of generating a reconstructed picture (or reconstructed samples).

[0143] In step S810, the encoding device may determine whether to apply in - loop filtering (across virtual boundaries) based on in - loop filtering - related information. Here, in - loop filtering may include at least one of the above - mentioned de - blocking filtering, SAO, or ALF.

[0144] In step S820, the encoding device may generate a modified reconstructed picture (modified reconstructed samples) based on the determination in step S810. Here, the modified reconstructed picture (modified reconstructed samples) may be a filtered reconstructed picture (filtered reconstructed samples).

[0145] In step S830, the encoding device may encode the image / video information including in - loop filtering - related information based on the in - loop filtering process.

[0146] Figure 9 is a flowchart illustrating the filter - based decoding method in a decoding device. Figure 9 The method may include steps S900 to S930.

[0147] In step S900, the decoding device may obtain the image / video information including in - loop filtering - related information from the bitstream. Here, the bitstream may be based on the encoded image / video information sent from the encoding device.

[0148] In step S910, the decoding device may generate a reconstructed picture. Step S910 may be performed based on the above - mentioned process of generating a reconstructed picture (or reconstructed samples).

[0149] In step S920, the decoding device may determine whether to apply in-loop filtering (across virtual boundaries) based on in-loop filtering related information. Here, the in-loop filtering may include at least one of the aforementioned deblocking filtering, SAO, or ALF.

[0150] In step S930, the decoding device may generate a modified reconstructed picture (modified reconstructed samples) based on the determination in step S920. Here, the modified reconstructed picture (modified reconstructed samples) may be a filtered reconstructed picture (filtered reconstructed samples).

[0151] As described above, in-loop filtering processing may be applied to the reconstructed picture. In this case, in order to further enhance the subjective / objective visual quality of the reconstructed picture, virtual boundaries may be defined, and in-loop filtering processing may be applied across the virtual boundaries. For example, the virtual boundaries may include discontinuous edges such as 360-degree images, VR images, or picture-in-picture (PIP). For example, the virtual boundaries may exist at predetermined stitching positions, and their presence / absence and / or positions may be signaled. As an example, the virtual boundary may be located on the fourth sample line above the CTU row (specifically, for example, above the fourth sample line of the CTU row). As another example, information about the presence / absence and / or position of the virtual boundary may be signaled by HLS. As described above, HLS may include SPS, PPS, picture header, and slice header.

[0152] Hereinafter, the high-level syntax signaling and semantics according to the embodiments of this document will be described.

[0153] The embodiments of this document may include a method for controlling an in-loop filter. The method for controlling an in-loop filter may be applied to the reconstructed picture. The in-loop filter (loop filter) may be used to decode the encoded bit rate. The loop filter may include the aforementioned deblocking, SAO, and ALF. The SPS may include flags related to deblocking, SAO, and ALF respectively. The flags may indicate whether each tool is enabled for encoding of the coded layer video sequence (CLVS) and coded video sequence (CVS) that refer to the SPS.

[0154] If the loop filter is enabled for the CVS, it may be controlled not to apply the loop filter across specific boundaries. For example, it may be controlled whether the loop filter crosses the sub-picture boundary. In addition, it may be controlled whether the loop filter crosses the tile boundary. Additionally, it may be controlled whether the loop filter crosses the virtual boundary. Here, the virtual boundary may be defined on the CTU based on the availability of the line buffer.

[0155] Regarding whether to perform in-loop filtering across virtual boundaries, the in-loop filtering related information may include at least one of the SPS virtual boundary enable flag (virtual boundary enable flag in SPS), SPS virtual boundary presence flag, picture header virtual boundary presence flag, SPS picture header virtual boundary presence flag, and information about the position of the virtual boundary.

[0156] In the embodiments included in this document, the information about the position of the virtual boundary may include information about the x coordinate of the vertical virtual boundary and information about the y coordinate of the horizontal virtual boundary. Specifically, the information about the position of the virtual boundary may include information about the x coordinate of the vertical virtual boundary and / or the y coordinate of the horizontal virtual boundary in units of luminance samples. In addition, the information about the position of the virtual boundary may include information about the number of information (syntactic elements) of the x coordinate of the vertical virtual boundary existing in the SPS. In addition, the information about the virtual boundary may include information about the number of information (syntactic elements) of the y coordinate of the horizontal virtual boundary existing in the SPS. In addition, the information about the position of the virtual boundary may include information about the number of information (syntactic elements) of the x coordinate of the vertical virtual boundary existing in the picture header. In addition, the information about the position of the virtual boundary may include information about the number of information (syntactic elements) of the y coordinate of the horizontal virtual boundary existing in the picture header.

[0157] The following table shows the exemplary syntax and semantics of the sequence parameter set (SPS) according to this embodiment.

[0158] [Table 4]

[0159]

[0160] [Table 5]

[0161]

[0162]

[0163] The following table shows the exemplary syntax and semantics of the picture parameter set (PPS) according to this embodiment.

[0164] [Table 6]

[0165]

[0166] [Table 7]

[0167]

[0168] The following table shows the exemplary syntax and semantics of the picture header according to this embodiment.

[0169] [Table 8]

[0170]

[0171]

[0172] [Table 9]

[0173]

[0174]

[0175] The following table shows the exemplary syntax and semantics of the slice header according to this embodiment.

[0176] [Table 10]

[0177]

[0178] [Table 11]

[0179]

[0180]

[0181] Next, information related to sub - pictures, information related to virtual boundaries available for in - loop filtering, and their signaling will be described.

[0182] In an example, two different rectangular slices can belong to different sub - pictures while sharing the same tile. In this case, a problem of increased coding complexity may occur.

[0183] To simplify picture partitioning, embodiments of this document may include conditional examples where a picture is divided into two or more sub - pictures. In an example, all CTUs in a tile can belong to the same sub - picture. In another example, all CTUs in a sub - picture can belong to the same tile. The above two examples can be applied separately to image / video coding, applied sequentially, or applied in combination. Further, in embodiments of this document, in the case where a sub - picture includes CTUs that are a subset of all CTUs in a tile, the sub - picture may not include CTUs belonging to another tile.

[0184] In the signaling for the current picture, if the value of subpic_present_flag is 1, the number of sub-pictures in each picture of the reference SPS can be 1 (the value of sps_num_subpics_minus1 is 0). Such conditions are already available to support the use case of sub-picture extraction, where the sub-pictures are independently encoded from the bitstream to form another bitstream, without even changing the values of the parameters less than the parameter set. Therefore, even if the value of subpic_present_flag is 1 and the value of sps_num_subpics_minus1 is 0, there are still subpic_ctu_top_left_x[0], subpic_ctu_top_left_y[0], subpic_width_minus1[0], subpic_height_minus1[0], subpic_treated_as_pic_flag[i], and / or loop_filter_across_subpic_enabled_flag[i]. In this case, these syntax elements may overlap with each other, and if an incorrect value is signaled in the corresponding syntax element, it may also make the operation of the decoder unpredictable. For example, if the value of subpics_present_flag is 1 and the value of sps_num_subpics_minus1 is 0, this means that there is only one sub-picture (the picture itself), and the value of subpic_treat_as_pic_flag[0] is equal to 1. In this case, if the corresponding value is signaled as 0, a contradiction problem may occur in the decoding process.

[0185] To solve the above problems, the embodiments of this document include conditional examples that can be applied when there is sub-picture signaling (e.g., the value of subpic_present_flag is 1) and there is only one sub-picture in the picture (e.g., the value of sps_num_subpics_minus1 is 0). The above conditional examples can be as shown in the following table.

[0186] [Table 12]

[0187]

[0188] In the example, when there is sub-picture signaling and the position of the virtual boundary exists in the picture header, there is a problem of whether the signaling for rewriting the picture header to identify the position of the virtual boundary is correct in the sub-picture extraction and sub-picture merging scenarios. This may violate the design purpose of sub-picture extraction / merging, where there is no need to rewrite the bitstream for NAL units of layers lower than the parameter set.

[0189] To solve the above problems, according to the embodiments of this document, if there is sub-picture signaling (for example, if there is sub-picture signaling in the SPS), the signaling of the virtual boundary position may not be included in the picture header. As an example, if there is sub-picture signaling, the information about the position of the virtual boundary may be included in the high-level parameter set. For example, if there is sub-picture signaling, the information about the position of the virtual boundary may be included in the SPS. In addition, if there is sub-picture signaling, the information about the position of the virtual boundary may be included in the PPS.

[0190] In the embodiments of this document, if there is sub-picture ID signaling (if the value of sps_subpic_id_present_flag is 1), all sub-pictures may be independently encoded sub-pictures (the value of subpic_treated_as_pic_flag[i] is 1). In this case, the position of the sub-picture ID signaling (for example, SPS, PPS, or picture header) may not matter.

[0191] According to the embodiments of this document and the above table, it is possible to determine whether to signal virtual boundary-related information (for example, information related to the virtual boundary position) in the sequence parameter set based on the presence or absence of sub-picture information. For example, in the case where there is sub-picture information in the corresponding sequence, virtual boundary-related information (for example, information related to the virtual boundary position) may be signaled in the sequence parameter set. Therefore, it is possible to effectively perform the virtual boundary-based coding method according to the embodiments of this document without rewriting or changing the high-level syntax.

[0192] In addition, according to the embodiments of this document, a (decoded) picture may be composed of sub-pictures. Information about the sub-pictures may be obtained by the decoding device, and based on the information about the sub-pictures, decoding processing may be performed. In an example, based on the information about the sub-pictures, the decoding device may determine the position (for example, SPS) that signals the information about the position of the virtual boundary for in-loop filtering.

[0193] Figure 10 and Figure 11 Schematically shows an example of a video / image coding method and related components according to the embodiments of this document.

[0194] Figure 10 The method disclosed in Figure 2 or Figure 11 may be executed by the coding device disclosed in Figure 10 Specifically, for example, Figure 11 S1000 and / or S1010 of Figure 10 may be executed by the predictor 220, residual processor 230, adder 250, and / or filter 260 of the coding device of Figure 11is executed by the residual processor 230 of the encoding device, Figure 10 S1040 of Figure 11 is executed by the filter 260 of the encoding device, Figure 10 S1050 of Figure 11 is executed by the entropy encoder 240 of the encoding device. In addition, although Figure 10 is not shown in Figure 10 the method disclosed in

[0195] With reference to Figure 10 , the encoding device may derive a sub-picture (S1000). The encoding device may divide the current picture into sub-pictures. The encoding device may determine the size (e.g., height / width) of the sub-picture. In addition, the encoding device may determine the number of sub-pictures included in the current picture.

[0196] The encoding device may generate sub-picture related information (S1010). For example, the encoding device may generate sub-picture related information based on the number of sub-pictures included in the current picture, the size (e.g., height / width) of the sub-picture, and / or the boundary of the sub-picture. The sub-picture related information may include information on whether there is a sub-picture, information on whether the sub-picture is regarded as a picture, information on the number of sub-pictures included in the current picture, information on the size (e.g., height / width) of the sub-picture, information on whether the boundary of the sub-picture coincides with the boundary of the current picture, and / or information on the ID of the sub-picture.

[0197] The encoding device may derive residual samples (S1020). The encoding device may derive the residual samples of the current block, and the residual samples of the current block may be derived based on the original samples and the predicted samples of the current block. Specifically, the encoding device may derive the predicted samples of the current block based on the prediction mode. In this case, various prediction methods disclosed in this document, such as inter-frame prediction or intra-frame prediction, may be applied. The residual samples may be derived based on the predicted samples and the original samples.

[0198] The encoding device may derive transform coefficients. The encoding device may derive transform coefficients based on the transform processing of the residual samples. For example, the transform processing may include at least one of DCT, DST, GBT, or CNT.

[0199] The encoding device may derive quantized transform coefficients. The encoding device may derive quantized transform coefficients based on the quantization processing of the transform coefficients. Based on the coefficient scan order, the quantized transform coefficients may have a one-dimensional vector form.

[0200] The encoding device may generate residual information (S1030). The encoding device may generate residual information based on the residual samples of the current block. The encoding device may generate residual information representing quantized transform coefficients. The residual information may be generated by various coding methods such as exponential Golomb, CAVLC, and CABAC.

[0201] The encoding device may generate reconstructed samples. The encoding device may generate reconstructed samples based on the residual information. The reconstructed samples may be generated by adding the residual samples based on the residual information to the predicted samples. Specifically, the encoding device may perform prediction (intra-frame or inter-frame prediction) on the current block, and may generate reconstructed samples based on the predicted samples generated by the prediction and the original samples.

[0202] The reconstructed samples may include reconstructed luminance samples and reconstructed chrominance samples. Specifically, the residual samples may include residual luminance samples and residual chrominance samples. The residual luminance samples may be generated based on the original luminance samples and the predicted luminance samples. The residual chrominance samples may be generated based on the original chrominance samples and the predicted chrominance samples. The encoding device may derive the transform coefficients (luminance transform coefficients) of the residual luminance samples and / or the transform coefficients (chrominance transform coefficients) of the residual chrominance samples. The quantized transform coefficients may include quantized luminance transform coefficients and / or quantized chrominance transform coefficients.

[0203] The encoding device may determine whether to perform in-loop filtering processing across virtual boundaries (S1040). Based on the above determination, the encoding device may generate information about the number and position of the virtual boundaries. For example, the encoding device may generate information about the number and position of the virtual boundaries. For example, the encoding device may generate information about the number of vertical virtual boundaries, information about the position of the vertical virtual boundaries, information about the number of horizontal virtual boundaries, and information about the position of the horizontal virtual boundaries.

[0204] The encoding device may generate in-loop filtering related information for the reconstructed samples of the current picture. The encoding device may perform in-loop filtering processing on the reconstructed samples, and may generate in-loop filtering related information based on the in-loop filtering processing. For example, the in-loop filtering related information may include the information about virtual boundaries described above in this document (SPS virtual boundary enable flag, picture header virtual boundary enable flag, SPS virtual boundary presence flag, picture header virtual boundary presence flag, and information about the position of the virtual boundaries). In an example, the encoding device may generate in-loop filtering related information based on the information about the number of vertical virtual boundaries, information about the position of the vertical virtual boundaries, information about the number of horizontal virtual boundaries, and information about the position of the horizontal virtual boundaries.

[0205] The encoding device may encode video / image information (S1050). The image information may include residual information, prediction-related information, sub-picture-related information, and / or in-loop filtering-related information. The encoded video / image information may be output in the form of a bitstream. The bitstream may be transmitted to the decoding device via a network or a storage medium.

[0206] The image / video information may include various information according to the embodiments of this document. For example, the image / video information may include the information disclosed in at least one of Tables 1 to 12 above.

[0207] In an embodiment, the image information may include a sequence parameter set (SPS) and picture header information referring to the SPS. Based on whether the SPS includes sub-picture-related information, it may be determined whether additional information related to the virtual boundary is included in the SPS and the picture header.

[0208] In an embodiment, the additional information related to the virtual boundary may include the number of virtual boundaries and the positions of the virtual boundaries.

[0209] In an embodiment, the additional virtual boundary-related information may include information about the number of vertical virtual boundaries, information about the positions of the vertical virtual boundaries, information about the number of horizontal virtual boundaries, and information about the positions of the horizontal virtual boundaries.

[0210] In an embodiment, the image information may include a sub-picture presence flag (e.g., subpic_present_flag). It may be determined whether the SPS includes sub-picture-related information based on the sub-picture presence flag.

[0211] In an embodiment, the image information may include a sub-picture ID presence flag. Based on the value of the sub-picture ID presence flag being 1, the sub-picture in the current picture may be an independently encoded sub-picture.

[0212] In an embodiment, the current picture may include sub-pictures and tiles. The coding tree units (CTUs) in one tile may belong to the same sub-picture.

[0213] In an embodiment, the current picture may include sub-pictures and tiles. The coding tree units (CTUs) in one sub-picture may belong to the same tile.

[0214] In an embodiment, the SPS may include an SPS virtual boundary presence flag related to whether the SPS includes additional information related to the virtual boundary. Based on the SPS including sub-picture-related information, the value of the SPS virtual boundary presence flag may be determined to be 1.

[0215] In an embodiment, based on the SPS including sub-picture-related information, the additional information related to the virtual boundary may not be included in the picture header.

[0216] In an embodiment, based on the SPS including sub-picture related information, the SPS may include additional information related to virtual boundaries.

[0217] Figure 12 and Figure 13 Schematically shows an example of a video / image decoding method and related components according to an embodiment of this document.

[0218] Figure 12 The method disclosed in Figure 12 or Figure 13 may be executed by the decoding device disclosed in. Specifically, for example, Figure 12 S1200 of Figure 12 may be executed by the entropy decoder 310 of the decoding device, Figure 12 S1210 of

[0219] may be executed by the residual processor 320 and / or the predictor 330 of the decoding device, S1220 may be executed by the residual processor 320 and / or the adder 340 of the decoding device, and S1220 may be executed by the filter 350 of the decoding device. Figure 12 Referring to

[0220] the decoding device may receive / acquire video / image information (S1200). The video / image information may include residual information, prediction-related information, sub-picture related information, and / or in-loop filtering related information. The decoding device may receive / acquire image / video information through a bitstream.

[0221] The decoding device may derive sub-pictures of the current picture (S1210). The decoding device may derive sub-pictures according to the sub-picture related information obtained based on the bitstream. Based on the sub-picture related information, the number of sub-pictures, the size of the sub-pictures, and whether the sub-pictures are regarded as pictures may be determined. Residual samples and / or prediction samples to be described later may be generated based on the sub-pictures.

[0222] The decoding device may derive quantized transform coefficients. The decoding device may derive quantized transform coefficients based on the residual information. Based on the coefficient scan order, the quantized transform coefficients may have a one-dimensional vector form. The quantized transform coefficients may include quantized luminance transform coefficients and / or quantized chrominance transform coefficients.

[0223] The decoding device can derive transform coefficients. The decoding device can derive transform coefficients based on the dequantization process of the quantized transform coefficients. The decoding device can derive the luminance transform coefficients by dequantizing the quantized luminance transform coefficients. The decoding device can derive the chrominance transform coefficients by dequantizing the quantized chrominance transform coefficients.

[0224] The decoding device can generate / derive residual samples. The decoding device can derive residual samples based on the inverse transform process of the transform coefficients. The decoding device can derive the residual luminance samples by inverse transform processing based on the luminance transform coefficients. The decoding device can derive the residual chrominance samples by inverse transform processing based on the chrominance transform coefficients.

[0225] The decoding device can generate / derive reconstructed samples (S1220). For example, the decoding device can generate / derive reconstructed luminance samples and / or reconstructed chrominance samples. The decoding device can generate the reconstructed luminance samples and / or the reconstructed chrominance samples based on the residual information. The decoding device can generate the reconstructed samples based on the residual information. The reconstructed samples can include the reconstructed luminance samples and / or the reconstructed chrominance samples. The luminance component of the reconstructed samples can correspond to the reconstructed luminance samples, and the chrominance component of the reconstructed samples can correspond to the reconstructed chrominance samples. The decoding device can generate predicted luminance samples and / or predicted chrominance samples through prediction processing. The decoding device can generate the reconstructed luminance samples based on the predicted luminance samples and the residual luminance samples. The decoding device can generate the reconstructed chrominance samples based on the predicted chrominance samples and the residual chrominance samples. Additionally, the decoding device can generate the reconstructed samples of the current picture based on the residual samples, the predicted samples, and / or the sub-picture.

[0226] The decoding device can generate modified (filtered) reconstructed samples (S1230). The decoding device can generate the modified reconstructed samples based on the in-loop filtering process for the reconstructed samples. The decoding device can generate the modified reconstructed samples based on the in-loop filtering related information. To generate the modified reconstructed samples, the decoding device can use deblocking processing, SAO processing, and / or ALF processing.

[0227] In an embodiment, the image information may include the sequence parameter set (SPS) and the picture header information of the reference SPS. Based on whether the SPS includes sub-picture related information, it can be determined whether the SPS or the picture header includes additional information related to the virtual boundary.

[0228] In an embodiment, the additional information related to the virtual boundary may include the number of virtual boundaries and the positions of the virtual boundaries.

[0229] In an embodiment, the additional information related to the virtual boundary may include information about the number of vertical virtual boundaries, information about the positions of the vertical virtual boundaries, information about the number of horizontal virtual boundaries, and information about the positions of the horizontal virtual boundaries.

[0230] In an embodiment, the picture information may include a sub-picture presence flag (e.g., subpic_present_flag). Whether the SPS includes sub-picture related information may be determined based on the sub-picture presence flag.

[0231] In an embodiment, the picture information may include a sub-picture ID presence flag. Based on the value of the sub-picture ID presence flag being 1, the sub-picture in the current picture may be an independently coded sub-picture.

[0232] In an embodiment, the current picture may include sub-pictures and tiles. Coding tree units (CTUs) in one tile may belong to the same sub-picture.

[0233] In an embodiment, the current picture may include sub-pictures and tiles. Coding tree units (CTUs) in one sub-picture may belong to the same tile.

[0234] In an embodiment, the SPS may include an SPS virtual boundary presence flag related to whether the SPS includes additional information related to virtual boundaries. Based on the SPS including sub-picture related information, the value of the SPS virtual boundary presence flag may be determined to be 1.

[0235] In an embodiment, based on the SPS including sub-picture related information, the picture header may not include additional information related to virtual boundaries.

[0236] If there are residual samples of the current block, the decoding device may receive information about the residual of the current block. The information about the residual may include transform coefficients of the residual samples. The decoding device may derive the residual samples (or residual sample array) of the current block based on the residual information. Specifically, the decoding device may derive the quantized transform coefficients based on the residual information. Based on the coefficient scan order, the quantized transform coefficients may have a one-dimensional vector form. The decoding device may derive the transform coefficients based on the dequantization process of the quantized transform coefficients. The decoding device may derive the residual samples based on the transform coefficients.

[0237] The decoding device may generate reconstructed samples based on (intra) prediction samples and residual samples, and may derive a reconstructed block or a reconstructed picture based on the reconstructed samples. Specifically, the decoding device may generate reconstructed samples based on the sum of (intra) prediction samples and residual samples. Thereafter, as described above, if necessary, in order to improve the subjective / objective picture quality, the decoding device may apply in-loop filtering processes, such as deblocking filtering and / or SAO processing, to the reconstructed picture.

[0238] For example, the decoding device may obtain picture information including all or part of the above information (or syntax elements) by decoding a bitstream or coded information. In addition, the bitstream or coded information may be stored in a computer-readable storage medium and may cause the above decoding method to be executed.

[0239] Although the method is described in the above embodiments based on a flowchart listing steps or blocks in sequence, the steps of this document are not limited to a specific order, and specific steps may be performed in different steps, in a different order, or simultaneously relative to the above. In addition, those of ordinary skill in the art will understand that the steps of the flowchart are not exclusive, and another step may be included therein, or one or more steps in the flowchart may be deleted without affecting the scope of this document.

[0240] The above method according to this document may be in the form of software, and the encoding device and / or decoding device according to this document may be included in a device for image processing (e.g., TV, computer, smart phone, set-top box, display device, etc.).

[0241] When the embodiments of this document are implemented by software, the above method may be implemented by modules (processes or functions) that execute the above functions. The modules may be stored in a memory and executed by a processor. The memory may be installed inside or outside the processor and may be connected to the processor via various well-known means. The processor may include an application-specific integrated circuit (ASIC), other chip sets, logic circuits, and / or data processing devices. The memory may include a read-only memory (ROM), a random access memory (RAM), a flash memory, a memory card, a storage medium, and / or other storage devices. In other words, the embodiments according to this document may be implemented and executed on a processor, a microprocessor, a controller, or a chip. For example, the functional units shown in each figure may be implemented and executed on a computer, a processor, a microprocessor, a controller, or a chip. In this case, information about the implementation (e.g., information about instructions) or algorithms may be stored in a digital storage medium.

[0242] In addition, the decoding device and the encoding device to which the embodiments of this document are applied may be included in a multimedia broadcast transceiver, a mobile communication terminal, a home theater video device, a digital cinema video device, a surveillance camera, a video chat device, and a real-time communication device (e.g., video communication), a mobile streaming device, a storage medium, a camera, a video-on-demand (VoD) service provider, an over-the-top (OTT) video device, an Internet streaming service provider, a 3D video device, a virtual reality (VR) device, an augmented reality (AR) device, an image phone video device, a vehicle terminal (e.g., a vehicle (including an autonomous vehicle) terminal, an aircraft terminal, or a ship terminal), and a medical video device; and may be used to process image signals or data. For example, an OTT video device may include a game console, a Blu-ray player, an Internet-connected TV, a home theater system, a smart phone, a tablet PC, and a digital video recorder (DVR).

[0243] In addition, the processing method according to an embodiment of this document can be generated in the form of a program executed by a computer and can be stored in a computer-readable recording medium. Multimedia data having a data structure according to an embodiment of this document can also be stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices and distributed storage devices that store computer-readable data. For example, the computer-readable recording medium can include Blu-ray Disc (BD), Universal Serial Bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices. The computer-readable recording medium also includes a medium specifically implemented in the form of a carrier wave (e.g., transmission via the Internet). In addition, the bitstream generated by this encoding method can be stored in a computer-readable recording medium or transmitted via a wired or wireless communication network.

[0244] In addition, an embodiment of this document can be specifically implemented as a computer program product based on program code, and the program code can be executed on a computer according to an embodiment of this document. The program code can be stored on a computer-readable carrier.

[0245] Figure 14 An example of a content stream system to which an embodiment of this document can be applied is shown.

[0246] Refer to Figure 14 , a content stream system to which an embodiment of this document is applied generally includes an encoding server, a streaming server, a network server, a media storage device, a user device, and a multimedia input device.

[0247] The encoding server is used to compress the content input from a multimedia input device (e.g., a smart phone, a camera, a video camera, etc.) into digital data to generate a bitstream and send it to the streaming server. As another example, in the case where the multimedia input device (e.g., a smart phone, a camera, a video camera, etc.) directly generates a bitstream, the encoding server can be omitted.

[0248] The bitstream can be generated by an encoding method or a bitstream generation method according to an embodiment of this document. And, during the process of sending or receiving the bitstream, the streaming server can temporarily store the bitstream.

[0249] The streaming server sends multimedia data to a user device via the network server based on a user's request. The network server serves as an instrument to inform the user of what services are available. When the user requests a service that the user wants, the network server transmits the request to the streaming server, and the streaming server sends the multimedia data to the user. In this regard, the content stream system can include a separate control server, and in this case, the control server is used to control the commands / responses between various devices in the content stream system.

[0250] The streaming server may receive content from a media storage device and / or an encoding server. For example, in the case of receiving content from the encoding server, the content may be received in real time. In this case, the streaming server may store the bitstream for a predetermined period of time to smoothly provide the streaming service.

[0251] For example, the user equipment may include a mobile phone, a smart phone, a laptop computer, a digital broadcast terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation device, a tablet computer, a tablet PC, a ultrabook, a wearable device (e.g., a watch-type terminal (smart watch), a glasses-type terminal (smart glasses), a head-mounted display (HMD)), a digital TV, a desktop computer, a digital signage, etc.

[0252] Each server in the content streaming system may operate as a distributed server, and in this case, the data received by each server may be processed in a distributed manner.

[0253] The claims in this specification may be combined in various ways. For example, the technical features in the method claims of this specification may be combined to be implemented or executed in a device, and the technical features in the device claims may be combined to be implemented or executed in a method. In addition, the technical features in the method claims and the device claims may be combined to be implemented or executed in a device. In addition, the technical features in the method claims and the device claims may be combined to be implemented or executed in a method.

Claims

1. An image decoding method performed by a decoding device, the image decoding method comprising the following steps: Obtaining image information including residual information and sub-picture related information from a bitstream; Deriving at least one sub-picture for a current picture based on the sub-picture related information; Deriving quantized transform coefficients based on the residual information; Deriving transform coefficients based on the quantized transform coefficients; Generating residual samples based on the transform coefficients; Generating reconstructed samples for the current picture based on the residual samples and the sub-picture; and Generating modified reconstructed samples based on in-loop filtering processing of the reconstructed samples, wherein the image information includes a sequence parameter set (SPS) and picture header information referring to the SPS, wherein, based on whether the SPS includes the sub-picture related information, it is determined whether information about the position of a virtual boundary is included in the SPS or in the picture header information, wherein, based on there being multiple sub-pictures in the current picture, the sub-picture related information includes information about the positions of the sub-pictures, and wherein, based on there being one sub-picture in the current picture, the information about the position of the sub-picture is determined as a predetermined value.

2. The image decoding method according to claim 1, wherein, The information about the position of the virtual boundary includes information about the position of a vertical virtual boundary and information about the position of a horizontal virtual boundary.

3. The image decoding method according to claim 1, wherein, The image information includes a sub-picture presence flag, and wherein, based on the sub-picture presence flag, it is determined whether the SPS includes the sub-picture related information.

4. The image decoding method according to claim 1, wherein, The SPS includes an SPS virtual boundary presence flag related to whether the SPS includes the information about the position of the virtual boundary, and wherein, based on the SPS including the sub-picture related information, the value of the SPS virtual boundary presence flag is determined as 1.

5. The image decoding method according to claim 1, wherein, Based on the SPS including the sub-picture related information, the information about the position of the virtual boundary is not included in the picture header.

6. The image decoding method according to claim 5, wherein, Based on the SPS including the sub-picture related information, the SPS includes the information about the position of the virtual boundary.

7. An image encoding method performed by an encoding device, the image encoding method comprising the following steps: Deriving at least one sub-picture for a current picture; Generating sub-picture related information based on the sub-picture; Deriving residual samples for a current block; Deriving transform coefficients based on the residual samples; Deriving quantized transform coefficients based on the transform coefficients; Generating residual information based on the quantized transform coefficients; Determining whether in-loop filtering processing is performed across a virtual boundary; and Encoding image information based on the sub-picture related information, the residual information, and determining whether in-loop filtering processing is performed across a virtual boundary, wherein the image information includes a sequence parameter set (SPS) and picture header information referring to the SPS, wherein, based on whether the SPS includes the sub-picture related information, it is determined whether information about the position of a virtual boundary is included in the SPS or in the picture header information, and Among them, based on the fact that there are multiple sub - pictures in the current picture only, the sub - picture related information includes information about the position of the sub - picture.

8. The image encoding method according to claim 7, wherein, The information about the position of the virtual boundary includes information about the position of the vertical virtual boundary and information about the position of the horizontal virtual boundary.

9. The image encoding method according to claim 7, wherein, The image information includes a sub - picture presence flag, and Among them, based on the sub - picture presence flag, it is determined whether the SPS includes the sub - picture related information.

10. The image encoding method according to claim 7, wherein, The image information includes a sub - picture ID presence flag, and Among them, based on the value of the sub - picture ID presence flag being 1, the sub - pictures in the current picture are independently encoded.

11. The image encoding method according to claim 7, wherein, The SPS includes an SPS virtual boundary presence flag related to whether the SPS includes the information about the position of the virtual boundary, and Among them, based on the SPS including the sub - picture related information, the value of the SPS virtual boundary presence flag is determined to be 1.

12. The image encoding method according to claim 7, wherein, Based on the SPS including the sub - picture related information, the information about the position of the virtual boundary is not included in the picture header.

13. The image encoding method according to claim 12, wherein, Based on the SPS including the sub - picture related information, the SPS includes the information about the position of the virtual boundary.

14. A method for transmitting data of an image, the transmission method comprising the following steps: Obtain a bitstream for the image, wherein the bitstream is generated based on the following steps: derive at least one sub - picture for the current picture, generate sub - picture related information based on the sub - picture, derive residual samples for the current block, derive transform coefficients based on the residual samples, derive quantized transform coefficients based on the transform coefficients, generate residual information based on the quantized transform coefficients, determine whether to perform in - loop filtering processing across the virtual boundary, and encode the image information based on the sub - picture related information, the residual information, and the determination of whether to perform in - loop filtering processing across the virtual boundary; and Transmit the data including the bitstream, wherein the image information includes a sequence parameter set SPS and picture header information referring to the SPS, wherein, based on whether the SPS includes the sub - picture related information, it is determined whether the information about the position of the virtual boundary is included in the SPS or in the picture header information, and wherein, based on the fact that there are multiple sub - pictures in the current picture only, the sub - picture related information includes information about the position of the sub - picture.

Images