Image coding apparatus and method based on sub-picture

Abstract

To provide an image coding apparatus based on sub-picture in which signaling efficiency is increased.SOLUTION: According to embodiments of the present document, whether or not virtual boundary-related information (ex. virtual boundary location-related information) is signaled in a sequence parameter set may be determined on the basis of whether or not sub-picture information is present. For example, when the sub-picture information is present for a corresponding sequence, the virtual boundary-related information (ex. the virtual boundary location-related information) may be signaled in the sequence parameter set.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] This document relates to a sub-picture based video coding apparatus and method. [Background technology]

[0002] In recent years, the demand for high-resolution, high-quality images / videos such as 4K or 8K or higher UHD (Ultra High Definition) images / videos is increasing in various fields. As the image / video data has higher resolution and quality, the amount of information or bits to be transmitted increases relatively compared to existing image / video data, so that when image data is transmitted using a medium such as an existing wired or wireless broadband line or when image / video data is stored using an existing storage medium, the transmission cost and storage cost increase.

[0003] In addition, interest in and demand for immersive media such as virtual reality (VR), artificial reality (AR) content, and holograms has been increasing in recent years, and the broadcast of images / videos that have different image characteristics from real images, such as game images, is increasing.

[0004] Therefore, there is a demand for a highly efficient image / video compression technology to effectively compress and transmit, store, and play back high-resolution, high-quality image / video information having the above-mentioned various characteristics.

[0005] Specifically, in order to improve subjective / objective visual quality, pictures are composed of sub-pictures, and there are proposals for improving the efficiency of signaling sub-picture related information. Summary of the Invention [Means for solving the problem]

[0006] According to one embodiment of the present document, a method and apparatus for improving image / video coding efficiency is provided.

[0007] According to one embodiment of the present document, an efficient method and apparatus for applying filtering is provided.

[0008] According to one embodiment of the present document, a method and apparatus for efficiently applying deblocking, sample adaptive loop (SAO), and adaptive loop filtering (ALF) is provided.

[0009] According to one embodiment of this document, in-loop filtering is performed based on a virtual boundary.

[0010] According to one embodiment of the present document, the signaling of virtual border related information can be performed based on the signaling of sub-picture related information.

[0011] According to one embodiment of the present document, an encoding device for video / image encoding is provided.

[0012] According to one embodiment of the present document, there is provided a computer-readable digital storage medium having encoded video / image information generated by the video / image encoding method disclosed in at least one of the embodiments of the present document.

[0013] According to one embodiment of the present document, there is provided a computer-readable digital storage medium having encoded information or encoded video / image information stored thereon, which causes a decoding device to perform the video / image decoding method disclosed in at least one of the embodiments of the present document. Effect of the Invention

[0014] According to one embodiment of this document, the overall image / video compression efficiency can be increased.

[0015] According to one embodiment of this document, subjective / objective visual quality can be enhanced through efficient filtering.

[0016] According to one embodiment of this document, efficient coding can be achieved by omitting the bitstream rewriting procedure through signaling of virtual boundaries based on sub-picture signaling. [Brief description of the drawings]

[0017] [Figure 1] 1 illustrates generally an example of a video / image coding system to which embodiments of the present document may be applied; [Diagram 2] 1 is a diagram illustrating a schematic configuration of a video / image encoding device that can be applied to an embodiment of the present document. [Diagram 3] 1 is a diagram for illustrating a schematic configuration of a video / image decoding device that can be applied to an embodiment of the present document. [Figure 4] 1 shows an exemplary hierarchical structure for coded images / video. [Diagram 5] 1 shows a picture according to one embodiment of the present document. [Figure 6] 1 illustrates a sub-picture / slice / tile based encoding method according to one embodiment of the present document. [Figure 7] 1 illustrates a sub-picture / slice / tile based decoding method according to one embodiment of the present document. [Figure 8] 1 is a flowchart illustrating an encoding method based on filtering in an encoding device. [Figure 9] 1 is a flowchart illustrating a decoding method based on filtering in a decoding device. [Figure 10] 1 illustrates a schematic diagram of an example video / image encoding method and associated components according to embodiments of the present document; [Figure 11] 1 illustrates a schematic diagram of an example video / image encoding method and associated components according to embodiments of the present document; [Figure 12]1 illustrates a schematic diagram of an example of a picture / video decoding method and related components according to embodiments of the present document; [Figure 13] 1 illustrates a schematic diagram of an example of a picture / video decoding method and related components according to embodiments of the present document; [Figure 14] 1 illustrates an example of a content streaming system in which embodiments disclosed herein may be applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] This document may have various modifications and may have various embodiments, and a specific embodiment will be illustrated in the drawings and described in detail. However, this is not intended to limit this document to a specific embodiment. Terms commonly used in this specification are used merely to describe a specific embodiment, and are not intended to limit the technical ideas of this document. A singular expression includes a plural expression unless the context clearly indicates otherwise. In this specification, the terms "include" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0019] Meanwhile, each component in the drawings described in this document is illustrated independently for the convenience of explaining the different characteristic functions, and does not mean that each component is realized by separate hardware or software. For example, two or more components among the components may be combined to form one component, or one component may be divided into multiple components. An embodiment in which each component is integrated and / or separated is also included in the scope of the present document as long as it does not deviate from the essence of the present document.

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following, the same components in the drawings will be designated by the same reference numerals, and the duplicated description of the same components will be omitted.

[0021] 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 beyond 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.).

[0022] This document presents various embodiments related to video / image coding, which may also be implemented in combination with each other, unless otherwise stated.

[0023] In this document, video may mean a collection of a series of images over time. A picture generally means a unit that shows one image at a particular time, and a slice / tile is a unit that constitutes part of a picture in coding. A slice / tile may include one or more coding tree units (CTUs). A picture may be composed of one or more slices / tiles. A picture may be composed of one or more tile groups. A tile group may include one or more tiles.

[0024] A pixel or a pel may mean the smallest unit constituting one picture (or image). A term corresponding to a pixel may also be used as a "sample." A sample generally refers to a pixel or a pixel value, and may refer to only a pixel / pixel value of a luma component, or may refer to only a pixel / pixel value of a chroma component. Alternatively, a sample may refer to a pixel value in the spatial domain, or may refer to a transform coefficient in the frequency domain when such a pixel value is transformed into the frequency domain.

[0025] A unit refers to a basic unit of video processing. A unit includes at least one of a specific region of a picture and information about the region. One unit includes one luma block and two chroma (e.g., cb, cr) blocks. The term unit may be used interchangeably with terms such as block or area. In a general case, an M×N block includes a set (or array) of samples or transform coefficients consisting of M columns and N rows.

[0026] In this document, " / " and "," are interpreted as "and / or." For example, "A / B" is interpreted as "A and / or B," and "A, B" is interpreted as "A and / or B." Additionally, "A / B / C" means "at least one of A, B, and / or C." Also, "A, B, C" means "at least one of A, B, and / or C."

[0027] Additionally, in this document, "or" is to be interpreted as "and / or." For example, "A or B" can mean 1) "A" only, 2) "B" only, or 3) "A and B." In other words, in this document, "or" can mean "additionally or alternatively."

[0028] In this specification, "at least one of A and B" may mean "A only," "B only," or "both A and B." In addition, in this specification, the expressions "at least one of A or B" and "at least one of A and / or B" may be interpreted similarly to "at least one of A and B."

[0029] In addition, in this specification, "at least one of A, B and C" may mean "A only," "B only," "C only," or "any combination of A, B and C." Furthermore, "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."

[0030] In addition, parentheses used in this specification may mean "for example." Specifically, when "prediction (intra prediction)" is displayed, "intra prediction" may be proposed as an example of "prediction." In other words, "prediction" in this specification is not limited to "intra prediction," and "intra prediction" may be proposed as an example of "prediction." In addition, even when "prediction (i.e., intra prediction)" is displayed, "intra prediction" may be proposed as an example of "prediction."

[0031] Technical features described separately in one drawing in this specification may be realized separately or simultaneously.

[0032] FIG. 1 illustrates a schematic diagram of an example of a video / image coding system to which this document can be applied.

[0033] As shown in Figure 1, a video / image coding system may include a source device and a receiving device. The source device may transmit encoded video / image information or data in a file or streaming form to the receiving device via a digital storage medium or a network.

[0034] The source device may comprise a video source, an encoding device, and a sending unit. The receiving device may comprise a receiving unit, a decoding device, and a renderer. The encoding device may be referred to as a video / video encoding device, and the decoding device may be referred to as a video / video decoding device. The transmitter may be comprised in the encoding device. The receiver may be comprised in the decoding device. The renderer may comprise a display unit, which may be a separate device or an external component.

[0035] A video source may acquire video / images through a video / image capture, synthesis, or generation process, etc. A video source may include a video / image capture device and / or a video / image generation device. A video / image capture device may include, for example, one or more cameras, a video / image archive containing previously captured video / images, etc. A video / image generation device may include, for example, a computer, a tablet, a smartphone, etc., and may (electronically) generate video / images. For example, a virtual video / image may be generated via a computer, etc., in which case the video / image capture process may be replaced by a process in which related data is generated.

[0036] An encoding device can encode an input video / image. The encoding device can perform a series of procedures such as prediction, transformation, quantization, etc. for compression and coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0037] The transmitting unit may transmit the encoded video / image information or data output in the form of a bitstream to a receiving unit of a receiving device via a digital storage medium or a network in the form of a file or streaming. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitting unit may include elements for generating a media file through a predetermined file format and may include elements for transmission via a broadcasting / communication network. The receiving unit may receive / extract the bitstream and transmit it to a decoding device.

[0038] The decoding device can decode the video / image by performing a series of steps such as inverse quantization, inverse transformation, prediction, etc., which correspond to the operations of the encoding device.

[0039] The renderer can render the decoded video / image. The rendered video / image can be displayed via a display unit.

[0040] 2 is a diagram for briefly explaining the configuration of a video / image encoding device to which the present document can be applied. Hereinafter, the video encoding device may include an image encoding device.

[0041] As shown in FIG. 2, the encoding device 200 may be configured to include an image partitioner 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 prediction unit 221 and an intra prediction unit 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 further include a subtractor 231. The adder 250 may be referred to as a reconstructor or a reconstructed block generator. The image division unit 210, the prediction unit 220, the residual processing unit 230, the entropy encoding unit 240, the addition unit 250, and the filtering unit 260 may be configured by one or more hardware components (e.g., an encoder chipset or a processor) according to an embodiment. Also, the memory 270 may include a decoded picture buffer (DPB) and may be configured by a digital storage medium. The hardware components may further include the memory 270 as an internal / external component.

[0042] The image division unit 210 may divide an input image (or a picture or a frame) input to the encoding device 200 into one or more processing units. As an example, the processing units may be called coding units (CUs). In this case, the coding units may be recursively divided from a coding tree unit (CTU) or a largest coding unit (LCU) according to a quad-tree binary-tree ternary-tree (QTBTTT) structure. For example, one coding unit may be divided into a plurality of coding units of a deeper depth based on a quad-tree structure, a binary tree structure, and / or a ternary structure. In this case, for example, the quad-tree structure may be applied first, and then the binary tree structure and / or the ternary structure may be applied. Alternatively, the binary tree structure may be applied first. The coding procedure according to the present disclosure may be performed based on a final coding unit that is not further divided. In this case, the largest coding unit may be used as the final coding unit based on coding efficiency according to image characteristics, or the coding unit may be recursively divided into coding units of lower depths as necessary, and a coding unit of an optimal size may be used as the final coding unit. Here, the coding procedure may include procedures such as prediction, transformation, and restoration, which will be described later. As another example, the processing unit may further include a prediction unit (PU) or a transform unit (TU). In this case, the prediction unit and the transform unit may each be divided or partitioned from the final coding unit described above.The prediction unit may be a unit of sample prediction, and the transform unit may be a unit for deriving transform coefficients and / or a unit for deriving a residual signal from the transform coefficients.

[0043] The unit may be used in combination with terms such as block or area depending on the case. In a general case, an M×N block may indicate a set of samples or transform coefficients consisting of M columns and N rows. A sample may generally indicate a pixel or a pixel value, may indicate only a pixel / pixel value of a luma component, or may indicate only a pixel / pixel value of a chroma component. A sample may be used as a term corresponding to a pixel or pel of one picture (or image).

[0044] The subtraction unit 231 may subtract a prediction signal (predicted block, prediction sample, or prediction sample array) output from the prediction unit 220 from an input image signal (original block, original sample, or original sample array) to generate a residual signal (residual block, residual sample, or residual sample array), and the generated residual signal is transmitted to the conversion unit 232. The prediction unit 220 may perform prediction on a processing target block (hereinafter, referred to as a current block) and generate a predicted block including a prediction sample for the current block. The prediction unit 220 may determine whether intra prediction or inter prediction is applied in units of a current block or a CU. The prediction unit may generate various information related to prediction, such as prediction mode information, and transmit the information to the entropy encoding unit 240, as described later in the description of each prediction mode. The prediction information may be encoded by the entropy encoding unit 240 and output in the form of a bitstream.

[0045] The intra prediction unit 222 may predict the current block by referring to samples in the current picture. The referenced samples may be located in the neighborhood of the current block or may be located away from the current block depending on the prediction mode. In the intra prediction, the prediction mode may include a plurality of non-directional modes and a plurality of directional modes. The non-directional modes may include, for example, a DC mode and a planar mode. The directional modes may include, for example, 33 directional prediction modes or 65 directional prediction modes depending on the fineness of the prediction direction. However, this is merely an example, and more or less directional prediction modes may be used depending on the settings. The intra prediction unit 222 may also determine the prediction mode to be applied to the current block using the prediction modes applied to the neighboring blocks.

[0046] The inter prediction unit 221 may derive a predicted block for a current block based on a reference block (reference sample array) identified by a motion vector on a reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring blocks may include a spatial neighboring block present in the current picture and a temporal neighboring block present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be called a collocated reference block, a collocated CU (col CU), etc., and the reference picture including the temporal neighboring block may be called a collocated picture (colPic). For example, the inter prediction unit 221 may generate information indicating which candidate is used to construct a motion information candidate list based on neighboring blocks and derive a motion vector and / or a reference picture index of the current block. Inter prediction may be performed based on various prediction modes, and for example, in the case of a skip mode and a merge mode, the inter prediction unit 221 may use motion information of a neighboring block as motion information of the current block. In the case of the skip mode, unlike the merge mode, a residual signal may not be transmitted.In the case of motion vector prediction (MVP) mode, the motion vector of the neighboring block can be used as a motion vector predictor, and the motion vector of the current block can be indicated by signaling the motion vector difference.

[0047] The prediction unit 220 may generate a prediction signal based on various prediction methods described later. For example, the prediction unit may apply intra prediction or inter prediction for prediction of one block, and may simultaneously apply intra prediction and inter prediction. This may be called combined inter and intra prediction (CIIP). The prediction unit may also perform intra block copy (IBC) for prediction of a block. The intra block copy may be used for content image / video coding such as games, for example, as in screen content coding (SCC). IBC basically performs prediction within a current picture, but may be performed similarly to inter prediction in deriving a reference block within the current picture. That is, IBC may use at least one of the inter prediction techniques described in this document.

[0048] The prediction signal generated through the inter prediction unit 221 and / or the intra prediction unit 222 may be used to generate a restored signal or may be used to generate a residual signal. The transform unit 232 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique may include a discrete cosine transform (DCT), a discrete sine transform (DST), a graph-based transform (GBT), or a conditionally non-linear transform (CNT). Here, the GBT refers to a transform obtained from a graph when the relationship information between pixels is expressed as a graph. The CNT refers to a transform obtained based on a prediction signal generated using all previously reconstructed pixels. In addition, the transform process may be applied to pixel blocks having the same square size, or may be applied to non-square variable-sized blocks.

[0049] The quantizer 233 quantizes the transform coefficients and transmits the quantized transform coefficients to the entropy encoder 240, which may encode the quantized signal (information on the quantized transform coefficients) and output the quantized signal to a bitstream. The information on the quantized transform coefficients may be referred to as residual information. The quantizer 233 may rearrange the quantized transform coefficients in a block form into a one-dimensional vector form based on a coefficient scan order, and may generate information on the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. The entropy encoder 240 may perform various encoding methods, such as exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy encoder 240 may encode information required for video / image restoration (e.g., values ​​of syntax elements, etc.) together with or separately from the quantized transform coefficients. The encoded information (e.g., encoded video / image information) may be transmitted or stored in the form of a bitstream in network abstraction layer (NAL) units. The video / image information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). The video / image information may further include general constraint information. Signaling / transmitted information and / or syntax elements described later in this document may be encoded through the encoding procedure described above and included in the bitstream. The bitstream may be transmitted via a network or stored in a digital storage medium.Here, the network may include a broadcasting network and / or a communication network, and the digital storage medium may include various storage media such as a USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitter (not shown) for transmitting the signal output from the entropy encoding unit 240 and / or a storage unit (not shown) for storing the signal may be configured as an internal / external element of the encoding device 200, or the transmitter may be included in the entropy encoding unit 240.

[0050] The quantized transform coefficients output from the quantizer 233 may be used to generate a prediction signal. For example, a residual signal (residual block or residual sample) may be reconstructed by applying inverse quantization and inverse transform to the quantized transform coefficients via the inverse quantizer 234 and the inverse transformer 235. The adder 155 may generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample, or reconstructed sample array) by adding the reconstructed residual signal to the prediction signal output from the predictor 220. When there is no residual for the current block, such as when a skip mode is applied, the predicted block may be used as the reconstructed block. The generated reconstructed signal may be used for intra prediction of the next current block in the current picture, and may also be used for inter prediction of the next picture after filtering, as described below.

[0051] Meanwhile, luma mapping with chroma scaling (LMCS) may be applied during picture encoding and / or reconstruction.

[0052] The filtering unit 260 may apply filtering to the reconstructed signal to improve subjective / objective image quality. For example, the filtering unit 260 may apply various filtering methods to the reconstructed picture to generate a modified reconstructed picture, and may store the modified reconstructed picture in the memory 270, specifically, in the DPB of the memory 270. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset (SAO), an adaptive loop filter, a bilateral filter, etc. The filtering unit 260 may generate various information related to filtering and transmit it to the entropy encoding unit 240, as will be described later in the description of each filtering method. The information related to filtering may be encoded by the entropy encoding unit 240 and output in the form of a bitstream.

[0053] The modified reconstructed picture transmitted to the memory 270 can be used as a reference picture in the inter prediction unit 221. When inter prediction is applied through this, the encoding apparatus can avoid prediction mismatch between the encoding apparatus 100 and the decoding apparatus, and can also improve encoding efficiency.

[0054] The DPB of the memory 270 may store the modified reconstructed picture to be used as a reference picture in the inter prediction unit 221. The memory 270 may store motion information of a block from which motion information in the current picture is derived (or encoded) and / or motion information of a block in an already reconstructed picture. The stored motion information may be transmitted to the inter prediction unit 221 to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory 270 may store reconstructed samples of reconstructed blocks in the current picture and transmit them to the intra prediction unit 222.

[0055] FIG. 3 is a diagram illustrating a schematic configuration of a video / image decoding device to which the present document can be applied.

[0056] As shown in FIG. 3, the decoding device 300 may be configured to include an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, a filter 350, and a memory 360. The predictor 330 may include an inter predictor 331 and an intra predictor 332. The residual processor 320 may include a dequantizer 321 and an inverse transformer 321. The entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filter 350 may be configured as one hardware component (e.g., a decoder chipset or processor) according to an embodiment. In addition, the memory 360 may include a decoded picture buffer (DPB) and may be configured as a digital storage medium. The hardware components may further include a memory 360 as an internal / external component.

[0057] If a bitstream including video / image information is input, the decoding apparatus 300 can restore an image corresponding to a process in which the video / image information is processed by the encoding apparatus of FIG. 3. For example, the decoding apparatus 300 can derive units / blocks based on block division related information obtained from the bitstream. The decoding apparatus 300 can perform decoding using a processing unit applied in the encoding apparatus. Thus, the processing unit for decoding can be, for example, a coding unit, and the coding unit can be divided from a coding tree unit or a maximal coding unit according to a quad tree structure, a binary tree structure, and / or a ternary tree structure. One or more transform units can be derived from the coding unit. Then, the restored image signal decoded and output by the decoding apparatus 300 can be reproduced by a reproduction device.

[0058] The decoding device 300 may receive a signal output from the encoding device of FIG. 3 in the form of a bitstream, and the received signal may be decoded via the entropy decoding unit 310. For example, the entropy decoding unit 310 may derive information (e.g., video / image information) required for image restoration (or picture restoration) by parsing the bitstream. The video / image information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may further include general constraint information. The decoding device may further decode pictures based on information on the parameter set and / or the general constraint information. Signaling / received information and / or syntax elements described later in this document may be decoded via the decoding procedure and obtained from the bitstream. For example, the entropy decoding unit 310 may decode information in a bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and output values ​​of syntax elements required for image restoration and quantized values ​​of transform coefficients related to residuals. More specifically, the CABAC entropy decoding method may receive bins corresponding to each syntax element in the bitstream, determine a context model using syntax element information to be decoded and decode information of adjacent and to-be-decoded blocks or information of symbols / bins decoded in a previous step, predict the occurrence probability of a bin according to the determined context model, and perform arithmetic decoding of the bins to generate a symbol corresponding to the value of each syntax element. In this case, the CABAC entropy decoding method may update the context model using information of the decoded symbol / bin for the context model of the next symbol / bin after determining the context model.Among the information decoded by the entropy decoding unit 310, information related to prediction is provided to the prediction unit 330, and residual information entropy decoded by the entropy decoding unit 310, i.e., quantized transform coefficients and related parameter information, may be input to the inverse quantization unit 321. Among the information decoded by the entropy decoding unit 310, information related to filtering may be provided to the filtering unit 350. Meanwhile, a receiving unit (not shown) for receiving a signal output from the encoding device may be further configured as an internal / external element of the decoding device 300, or the receiving unit may be a component of the entropy decoding unit 310. Meanwhile, the decoding device according to the present document may be called a video / image / picture decoding device, and the decoding device may be divided into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder may include the entropy decoding unit 310, and the sample decoder may include at least one of the inverse quantization unit 321, the inverse transform unit 322, the prediction unit 330, the addition unit 340, the filtering unit 350, and the memory 360.

[0059] The inverse quantization unit 321 may inverse quantize the quantized transform coefficients and output the transform coefficients. The inverse quantization unit 321 may rearrange the quantized transform coefficients in a two-dimensional block form. In this case, the rearrangement may be performed based on a coefficient scan order performed in the encoding device. The inverse quantization unit 321 may perform inverse quantization on the quantized transform coefficients using a quantization parameter (e.g., quantization step size information) to obtain transform coefficients.

[0060] The inverse transform unit 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

[0061] The prediction unit may perform prediction on a current block and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied to the current block based on the prediction information output from the entropy decoding unit 310, and may determine a specific intra / inter prediction mode.

[0062] The prediction unit may generate a prediction signal based on various prediction methods described later. For example, the prediction unit may apply intra prediction or inter prediction for prediction of one block, and may simultaneously apply intra prediction and inter prediction. This may be called combined inter and intra prediction (CIIP). The prediction unit may also perform intra block copy (IBC) for prediction of a block. The intra block copy may be used for content image / video coding such as games, for example, as in screen content coding (SCC). IBC basically performs prediction within a current picture, but may be performed similarly to inter prediction in deriving a reference block within the current picture. That is, IBC may utilize at least one of the inter prediction techniques described in this document. Palette mode may be considered as an example of intra coding or intra prediction.

[0063] The intra prediction unit 331 may predict a current block by referring to samples in a current picture. The referenced samples may be located in the neighborhood of the current block or may be located far away depending on a prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The intra prediction unit 331 may also determine a prediction mode to be applied to the current block using a prediction mode applied to a neighboring block.

[0064] The inter prediction unit 332 may derive a predicted block for the current block based on a reference block (reference sample array) identified by a motion vector on a reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on correlation of motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring blocks may include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. For example, the inter prediction unit 332 may construct a motion information candidate list based on the neighboring blocks and derive a motion vector and / or a reference picture index for the current block based on received candidate selection information. Inter prediction may be performed based on various prediction modes, and the information on the prediction may include information indicating a mode of inter prediction for the current block.

[0065] The adder 340 may generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the acquired residual signal to the prediction signal (predicted block, predicted sample array) output from the prediction unit. When there is no residual for the current block, such as when the skip mode is applied, the predicted block may be used as the reconstructed block.

[0066] The adder 340 may be referred to as a reconstruction unit or a reconstruction block generator. The generated reconstruction signal may be used for intra prediction of a next block to be processed in a current picture, may be output through filtering as described below, or may be used for inter prediction of a next picture.

[0067] Meanwhile, LMCS (luma mapping with chroma scaling) can be applied during the picture decoding process.

[0068] The filtering unit 350 may apply filtering to the reconstructed signal to improve subjective / objective image quality. For example, the filtering unit 350 may apply various filtering methods to the reconstructed picture to generate a modified reconstructed picture, and may transmit the modified reconstructed picture to the memory 360, specifically, to the DPB of the memory 360. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, an adaptive loop filter, a bilateral filter, etc.

[0069] The (modified) reconstructed picture stored in the DPB of the memory 360 may be used as a reference picture in the inter prediction unit 332. The memory 360 may store motion information of a block from which motion information in the current picture is derived (or decoded) and / or motion information of a block in an already reconstructed picture. The stored motion information may be transmitted to the inter prediction unit 332 to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory 360 may store reconstructed samples of reconstructed blocks in the current picture and transmit them to the intra prediction unit 331.

[0070] In this specification, the embodiments described for the prediction unit 330, inverse quantization unit 321, inverse transform unit 322, and filtering unit 350 of the decoding device 300 can be applied identically or correspondingly to the prediction unit 220, inverse quantization unit 234, inverse transform unit 235, and filtering unit 260 of the encoding device 200, respectively.

[0071] As described above, prediction is performed to improve compression efficiency when performing video coding. Through this, a predicted block including predicted samples for a current block, which is a block to be coded, can be generated. Here, the predicted block includes predicted samples in a spatial domain (or a pixel domain). The predicted block is derived in the same manner by an encoding device and a decoding device, and the encoding device can improve video coding efficiency by signaling information (residual information) on the residual between the original block and the predicted block, which is not an original sample value of the original block, to a decoding device. The decoding device can derive a residual block including residual samples based on the residual information, combine the residual block with the predicted block to generate a reconstructed block including reconstructed samples, and generate a reconstructed picture including the reconstructed block.

[0072] The residual information may be generated through a transform and quantization procedure. For example, the encoding apparatus may derive a residual block between the original block and the predicted block, perform a transform procedure on the residual samples (residual sample array) included in the residual block to derive transform coefficients, and perform a quantization procedure on the transform coefficients to derive quantized transform coefficients, and then signal the related residual information (through a bitstream) to the decoding apparatus. Here, the residual information may include information such as value information, position information, transform technique, transform kernel, and quantization parameter of the quantized transform coefficients. The decoding apparatus may derive a residual sample (or a residual block) by performing an inverse quantization / inverse transform procedure based on the residual information. The decoding apparatus may generate a reconstructed picture based on the predicted block and the residual block. Also, the encoding apparatus may derive a residual block by inverse quantizing / inverse transforming the quantized transform coefficients for reference for inter-prediction of a future picture, and generate a reconstructed picture based on the residual block.

[0073] In this document, at least one of quantization / dequantization and / or transform / inverse transform may be omitted. When the quantization / dequantization is omitted, the quantized transform coefficients may be referred to as transform coefficients. When the transform / inverse transform is omitted, the transform coefficients may also be referred to as coefficients or residual coefficients, or may still be referred to as transform coefficients for uniformity of representation.

[0074] 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 on the transform coefficient(s), and the information on the transform coefficient(s) may be signaled via a residual coding syntax. Transform coefficients may be derived based on the residual information (or information on the transform coefficient(s)), and scaled transform coefficients may be derived via an inverse transform (scaling) on ​​the transform coefficients. Residual samples may be derived based on an inverse transform (transform) on the scaled transform coefficients. This may be similarly applied / expressed in other parts of this document.

[0075] A prediction unit of an encoding device / decoding device may perform inter prediction on a block basis to derive a prediction sample. Inter prediction may indicate a prediction derived in a manner dependent on data elements (e.g., sample values ​​or motion information) of pictures other than the current picture. When inter prediction is applied to the current block, a predicted block (prediction sample array) for the current block may be derived based on a reference block (reference sample array) specified by a motion vector on a reference picture indicated by an index of the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, motion information of the current block may be predicted on a block, sub-block, or sample basis based on correlation of motion information between a neighboring block and the current block. The motion information may include a motion vector and an index of a reference picture. The motion information may further include information on an inter prediction type (L0 prediction, L1 prediction, Bi prediction, etc.). When inter prediction is applied, the neighboring block may include a spatial neighboring block present in the current picture and a temporal neighboring block present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be called a collocated reference block, a collocated CU (colCU), etc., and the reference picture including the temporal neighboring block may be called a collocated picture (colPic). For example, a candidate list of motion information may be constructed based on neighboring blocks of the current block, and flag or index information indicating which candidate is selected (used) to derive the motion vector and / or reference picture index of the current block may be signaled. Inter prediction is performed based on various prediction modes, and for example, in the case of skip mode and merge mode, the motion information of the current block may be the same as the motion information of the selected neighboring block.In the case of skip mode, unlike the merge mode, the residual signal may not be transmitted. In the case of motion vector prediction (MVP) mode, the motion vector of the selected neighboring block is used as a motion vector predictor, and a 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.

[0076] The motion information may include L0 motion information and / or L1 motion information depending on an inter prediction type (L0 prediction, L1 prediction, Bi prediction, etc.). A motion vector in the L0 direction may be referred to as an L0 motion vector or MVL0, and a motion vector in the L1 direction may be referred to as an L1 motion vector or MVL1. A prediction based on an L0 motion vector may be referred to as an L0 prediction, a prediction based on an L1 motion vector may be referred to as an L1 prediction, and a prediction based on both the L0 motion vector and the L1 motion vector may be referred to as a bi-prediction (Bi) prediction. Here, the L0 motion vector may indicate a motion vector associated with a reference picture list L0 (L0), and the L1 motion vector may indicate a motion vector associated with a reference picture list L1 (L1). The reference picture list L0 may include pictures that are earlier in output order than the current picture, and the reference picture list L1 may include pictures that are later in output order than the current picture. The previous picture may be referred to as a forward (reference) picture, and the subsequent picture may be referred to as a backward (reference) picture. The reference picture list L0 may further include a picture subsequent to the current picture in output order as a reference picture. In this case, the previous picture may be indexed earlier in the reference picture list L0, and the subsequent picture may be indexed thereafter. The reference picture list L1 may further include a picture subsequent to the current picture in output order as a reference picture. In this case, the subsequent picture may be indexed earlier in the reference picture list 1, and the previous picture may be indexed thereafter. Here, the output order may correspond to a picture order count (POC) order.

[0077] FIG. 4 shows an exemplary hierarchical structure for coded images / video.

[0078] Referring to Figure 4, the coded image / video is divided into a VCL (video coding layer) that handles the image / video decoding process and the video itself, a lower system that transmits and stores the coded information, and a NAL (network abstraction layer) that exists between the VCL and the lower system and is responsible for network adaptation functions.

[0079] In VCL, it is possible to generate VCL data including compressed video data (slice data), or to generate parameter sets including information such as a Picture Parameter Set (PPS), a Sequence Parameter Set (SPS), and a Video Parameter Set (VPS), or a Supplemental Enhancement Information (SEI) message that is additionally required for the video decoding process.

[0080] In NAL, NAL units can be generated by adding header information (NAL unit header) to RBSP (Raw Byte Sequence Payload) generated in VCL. In this case, RBSP means slice data, parameter set, SEI message, etc. generated in VCL. NAL unit header can include NAL unit type information specified by RBSP data included in the corresponding NAL unit.

[0081] As shown in the drawing, NAL units can be classified into VCL NAL units and non-VCL NAL units according to the RBSP generated by the VCL. The VCL NAL unit can refer to a NAL unit that includes information (slice data) on an image, and the non-VCL NAL unit can refer to a NAL unit that includes information (parameter set or SEI message) required for decoding an image.

[0082] The VCL NAL unit and the non-VCL NAL unit can be transmitted over a network with header information according to the data standard of the lower system. For example, the NAL unit can be transformed into a data format of a predetermined standard such as H.266 / VVC file format, RTP (Real-time Transport Protocol), TS (Transport Stream), etc., and transmitted over various networks.

[0083] As mentioned above, the NAL unit type of a NAL unit can be identified by the RBSP data structure included in the corresponding NAL unit, and information on such NAL unit type can be stored and signaled in the NAL unit header.

[0084] For example, NAL units can be broadly classified into VCL NAL unit types and non-VCL NAL unit types depending on whether the NAL unit includes information on a video (slice data). The VCL NAL unit types can be classified according to the nature and type of a picture included in the VCL NAL unit, and the non-VCL NAL unit types can be classified according to the type of a parameter set.

[0085] The following is an example of a NAL unit type specified by the type of parameter set that the Non-VCL NAL unit type includes.

[0086] -APS (Adaptation Parameter Set) NAL unit: Type for NAL units containing APS

[0087] -DPS (Decoding Parameter Set) NAL unit: Type for NAL units containing DPS

[0088] -VPS (Video Parameter Set) NAL unit: Type for NAL units containing VPS

[0089] -SPS (Sequence Parameter Set) NAL unit: Type for NAL units containing SPS

[0090] -PPS (Picture Parameter Set) NAL unit: Type for NAL units containing PPS

[0091] -PH (Picture header) NAL unit: Type for NAL unit containing PH

[0092] The above-mentioned NAL unit type has syntax information for the NAL unit type, and the syntax information can be stored in a 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.

[0093] Meanwhile, as described above, one picture may include multiple slices, and one slice may include a slice header and slice data. In this case, one picture header may be further added for multiple slices (slice header and slice data set) in one picture. The picture header (picture header syntax) may include information / parameters commonly applicable to the pictures. In this document, slices may be mixed with or replaced by tile groups. Also, in this document, slice headers may be mixed with or replaced by type group headers.

[0094] The slice header (slice header syntax, slice header information) may include information / parameters commonly applicable to the slices. The APS (APS syntax) or PPS (PPS syntax) may include information / parameters commonly applicable to one or more slices or pictures. The SPS (SPS syntax) may include information / parameters commonly applicable to one or more sequences. The VPS (VPS syntax) may include information / parameters commonly applicable to multiple layers. The DPS (DPS syntax) may include information / parameters commonly applicable to videos in general. The DPS may include information / parameters related to concatenation of coded video sequences (CVSs). In this document, a high level syntax (HLS) may include at least one of the APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, picture header syntax, and slice header syntax.

[0095] In this document, image / video information encoded from an encoding device to a decoding device and signaled in the form of a bitstream may include information related to partitioning in a picture, intra / inter prediction information, residual information, in-loop filtering information, etc., as well as information included in the slice header, information included in the picture header, information included in the APS, information included in the PPS, information included in the SPS, information included in the VPS, and / or information included in the DPS. In addition, the image / video information may further include information of a NAL unit header.

[0096] Meanwhile, in order to compensate for the difference between an original image and a reconstructed image due to an error occurring during a compression encoding process such as quantization, an in-loop filtering procedure may be performed on the reconstructed samples or pictures as described above. As described above, the in-loop filtering may be performed in a filter unit of an encoding device and a filter unit of a decoding device, and a deblocking filter, SAO and / or an adaptive loop filter (ALF) may be applied. For example, the ALF procedure may be performed after the deblocking filtering procedure and / or the SAO procedure is completed. However, in this case, the deblocking filtering procedure and / or the SAO procedure may be omitted.

[0097] A detailed description of picture reconstruction and filtering will be given below. In image / video coding, a reconstruction block may be generated based on intra prediction / inter prediction for each block, and a reconstruction picture including the reconstruction block may be generated. If a current picture / slice is an I picture / slice, blocks included in the current picture / slice may be reconstructed based only on intra prediction. Meanwhile, if a current picture / slice is a P or B picture / slice, 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 blocks in the current picture / slice, and inter prediction may be applied to the remaining blocks.

[0098] Intra prediction may refer to a prediction that generates a prediction sample for a current block based on a reference sample in a picture to which the current block belongs (hereinafter, referred to as a current picture). When intra prediction is applied to a current block, neighboring reference samples used for intra prediction of the current block may be derived. The neighboring reference samples of the current block may include a sample adjacent to the left boundary of the current block having a size of nW×nH and a total of 2×nH samples adjacent to the bottom-left side, a sample adjacent to the top boundary of the current block and a total of 2×nW samples adjacent to the top-right side, and one sample adjacent to the top-left side of the current block. Alternatively, the neighboring reference samples of the current block may include upper neighboring samples of multiple columns and left neighboring samples of multiple rows. In addition, 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 nW samples adjacent to the bottom boundary of the current block, and one sample adjacent to the bottom-right of the current block.

[0099] However, some of the neighboring reference samples of the current block may not yet be decoded or may not be available. In this case, the decoder may substitute the unavailable samples as available samples to construct the neighboring reference samples to be used for prediction. Alternatively, the decoder may construct the neighboring reference samples to be used for prediction through interpolation of available samples.

[0100] When the neighboring reference sample is derived, (i) the prediction sample may be derived based on an average or an interpolation of neighboring reference samples of the current block, and (ii) the prediction sample may be derived based on a reference sample that exists in a specific (prediction) direction with respect to the prediction sample among the neighboring reference samples of the current block. The case (i) may be called a non-directional mode or a non-angular mode, and the case (ii) may be called a directional mode or an angular mode. In addition, the prediction sample may be generated through an interpolation between the second neighboring sample and the first neighboring sample that are located in the opposite direction to the prediction direction of the intra prediction mode of the current block based on the prediction sample of the current block among the neighboring reference samples. The above case may be called a linear interpolation intra prediction (LIP). In addition, a chroma prediction sample may be generated based on a luma sample using a linear model. In this case, it may be called a LM mode. Also, a temporary prediction sample of the current block may be derived based on the filtered neighboring reference sample, and a prediction sample of the current block may be derived by weighting the temporary prediction sample and at least one reference sample derived according to the intra prediction mode among the existing neighboring reference samples, i.e., non-filtered neighboring reference samples. The above case may be called PDPC (Position Dependent Intra Prediction). Also, intra prediction coding may be performed by selecting a reference sample line with the highest prediction accuracy from the neighboring multiple reference sample lines of the current block, deriving a prediction sample using a reference sample located in the prediction direction of the corresponding line, and signaling the reference sample line used at this time to a decoding device.The above case may be referred to as multi-reference line (MRL) intra prediction or MRL-based intra prediction. In addition, the current block may be divided into vertical or horizontal sub-partitions, and intra prediction may be performed based on the same intra prediction mode, and adjacent reference samples may be derived and used in units of the sub-partitions. That is, in this case, the intra prediction mode for the current block is equally applied to the sub-partitions, and adjacent reference samples may be derived and used in units of the sub-partitions, thereby improving intra prediction performance in some cases. Such a prediction method may be referred to as intra sub-partitions (ISP) or ISP-based intra prediction. The above-mentioned intra prediction method may be called an intra prediction type, distinguished from the intra prediction modes in Tables 1 and 2. The intra prediction type may be referred to by various terms, such as an intra prediction technique or an additional intra prediction mode. For example, the intra prediction type (or additional intra prediction mode, etc.) may include at least one of the above-mentioned LIP, PDPC, MRL, and ISP. A general intra prediction method excluding specific intra prediction types such as LIP, PDPC, MRL, and ISP may be called a normal intra prediction type. The normal intra prediction type may be generally applied when the specific intra prediction type is not applied, and prediction may be performed based on the intra prediction mode described above. Meanwhile, post-processing filtering may be performed on the derived prediction samples as necessary.

[0101] Specifically, the intra prediction procedure may include an intra prediction mode / type determination step, a neighboring reference sample derivation step, and an intra prediction mode / type-based prediction sample derivation step. If necessary, a post-processing filtering step may be performed on the derived prediction sample.

[0102] A modified reconstructed picture is generated by the in-loop filtering procedure, and the modified reconstructed picture is output from the decoding device as a decoded picture and stored in a decoded picture buffer or memory of the encoding device / decoding device, so that it can be used as a reference picture in an inter-prediction procedure when encoding / decoding a picture thereafter. The in-loop filtering procedure includes a deblocking filtering procedure, a sample adaptive offset (SAO) procedure, and / or an adaptive loop filter (ALF) procedure, as described above. In this case, one or a part of the deblocking filtering procedure, the sample adaptive offset (SAO), the adaptive loop filter (ALF), and the bi-lateral filter procedure may be applied sequentially, or all of them may be applied sequentially. For example, the deblocking filtering procedure may be applied to the reconstructed picture, and then the SAO procedure may be performed. Or, for example, the deblocking filtering procedure may be applied to the reconstructed picture, and then the ALF procedure may be performed. This is also performed in the encoding device.

[0103] Deblocking filtering is a filtering technique that removes distortions occurring at boundaries between blocks in a restored picture. The deblocking filtering procedure may, for example, derive a target boundary in a restored picture, determine a boundary strength (bS) for the target boundary, and perform deblocking filtering on the target boundary based on the bS. The bS may be determined based on prediction modes of two blocks adjacent to the target boundary, motion vector difference, whether the reference picture is the same, whether there is a non-zero valid coefficient, etc.

[0104] SAO is a method of compensating for an offset difference between a reconstructed picture and an original picture in sample units, and may be applied based on a type such as a band offset or an edge offset. According to SAO, samples may be classified into different categories according to each SAO type, and an offset value may be added to each sample based on the category. Filtering information for SAO may include information on whether SAO is applicable, SAO type information, SAO offset value information, etc. SAO may also be applied to a reconstructed picture after the deblocking filtering is applied.

[0105] An adaptive loop filter (ALF) is a technique for filtering a reconstructed picture on a sample-by-sample basis based on a filter coefficient according to a filter shape. An encoding apparatus can determine whether or not to apply ALF, an ALF shape and / or an ALF filtering coefficient, etc., by comparing a reconstructed picture with an original picture, and can signal the same to a decoding apparatus. That is, filtering information for ALF can include information on whether or not to apply ALF, ALF filter shape information, ALF filtering coefficient information, etc. An ALF can also be applied to a reconstructed picture after the deblocking filtering is applied.

[0106] Figure 5 shows a picture according to one embodiment of this document. The example picture of Figure 5 can be divided into sub-pictures, slices, and tiles.

[0107] Referring to FIG. 5, a picture may be divided into sub-pictures. For example, a sub-picture may include one or more slices. A slice may represent a rectangular region of a picture. A picture may also be divided into tiles. For example, a rectangular slice may include only a subset of a tile. That is, in FIG. 5, two rectangular slices may be within the same tile, and each of the two rectangular slices may belong to a different sub-picture. Problems that may arise in a case such as FIG. 5 and solutions therefor will be described later.

[0108] In one example, a picture / sub-picture can be coded based on a sub-picture / slice / tile. An encoding device can encode a current picture based on a sub-picture / slice / tile structure, or an encoding device can encode one or more sub-pictures (including slices / tiles) of a current picture and output a (sub)bitstream containing (encoded) information about the sub-pictures. A decoding device can decode one or more sub-pictures in a current picture based on a (sub)bitstream containing (encoded) information about the sub-pictures / slice / tile.

[0109] FIG. 6 illustrates a sub-picture / slice / tile based encoding method according to one embodiment of this document.

[0110] An encoder can split an (input) picture into multiple (or one or more) sub-pictures / slices / tiles. Each sub-picture can be encoded separately / independently and a bitstream can be output. Here, a bitstream for a sub-picture can be referred to as a sub-stream, a subset, or a sub-bitstream. The information for the sub-pictures / slices / tiles can include information / syntax elements described in this document. For example, the information for slices can include information related to the number of slices signaled for each picture / sub-picture, width / height of slices within a tile, etc. For example, the information for tiles can include information related to the number of tiles (e.g., number of columns and / or rows of the tile) and the size (e.g., width and / or height) of each tile.

[0111] The encoder may encode one or more subpictures with information for the subpictures, and the encoder may encode one or more slices / tiles with information for the slices / tiles.

[0112] FIG. 7 illustrates a sub-picture / slice / tile based decoding method according to one embodiment of this document.

[0113] The decoder may decode one or more sub-pictures (including slices / tiles) and may output one or more decoded sub-pictures or a current picture including the sub-pictures. The bitstream may include a sub-stream or sub-bitstream for the sub-picture. As described above, information about the sub-picture / slice / tile may be configured in a high level syntax (HLS) included in the bitstream. The decoder may derive one or more sub-pictures based on information about the sub-picture. The decoder may derive one or more slices / tiles based on information about the slices / tiles. The decoder may decode all or a part of the sub-picture. The decoder may decode the sub-picture (including the current block (or CU)), CTU, slice, and / or tile based on CABAC, prediction, residual processing (transform, quantization), in-loop filtering, etc. Thus, a decoded sub-picture may be output. The decoded sub-picture may include a reconstructed / decoded block. The decoded subpictures in an output subpicture set (OPS) may also be output together. As an example, when a picture is associated with a 360-degree or omnidirectional image / video, some of them may be rendered, in which case only some of the subpictures of the entire subpicture may be decoded, and some or all of the decoded subpictures may be rendered depending on the user viewport or viewing position. In addition, if information indicating whether in-loop filtering is available across the subpicture boundaries is available, the decoder may apply an in-loop filtering procedure (e.g., deblocking filtering) to the boundaries of the subpictures located between two subpictures.For example, if the sub-picture boundaries are the same as the picture boundaries, then the in-loop filtering procedure on the sub-picture boundaries may not be applied / performed.

[0114] In an embodiment of this document, the image / video information may include HLS, which may include information about subpictures / slices / tiles. The information about subpictures may include information indicating one or more subpictures in a current picture. The information about slices may include information indicating one or more slices in a current picture, subpicture, or tile. The information about tiles may include information indicating one or more tiles in a current picture, subpicture, or slice. A picture may include tiles that include one or more slices and / or slices that include one or more tiles. A picture may also include subpictures that include one or more slices / tiles.

[0115] The following table shows syntax associated with the picture divisions (sub-pictures / slices / tiles) discussed above: Information regarding sub-pictures / slices / tiles may include the syntax elements in the following table.

[0116] The following table shows the syntax of sequence parameter set (SPS) based on picture division (sub-picture / slice / tile).

[0117] [Table 1]

[0118] The following table shows the syntax of picture parameter set (PPS) based on picture division (sub-picture / slice / tile).

[0119] [Table 2]

[0120] The following table shows the slice header syntax based on picture division (subpicture / slice / tile).

[0121] [Table 3]

[0122] 8 is a flow chart for explaining an encoding method based on filtering in an encoding device. The method of FIG. 8 may include steps S800 to S830.

[0123] In step S800, the encoding apparatus can generate a reconstructed picture, which can be performed based on the above-described reconstructed picture (or reconstructed sample) generating procedure.

[0124] In step S810, the encoding device may determine whether in-loop filtering is applied (across the virtual boundary) based on the in-loop filtering related information, where the in-loop filtering may include at least one of the above-mentioned deblocking filtering, SAO, or ALF.

[0125] In step S820, the encoding apparatus may generate a modified reconstructed picture (modified reconstructed sample) based on the determination in step S810, where the modified reconstructed picture (modified reconstructed sample) may be a filtered reconstructed picture (filtered reconstructed sample).

[0126] In step S830, the encoding apparatus may encode image / video information including in-loop filtering related information based on the in-loop filtering procedure.

[0127] 9 is a flow chart for explaining a decoding method based on filtering in a decoding device. The method of FIG. 9 may include steps S900 to S930.

[0128] In step S900, the decoding device can obtain image / video information including in-loop filtering related information from a bitstream, where the bitstream can be based on encoded image / video information transmitted from an encoding device.

[0129] In step S910, the decoding device can generate a reconstructed picture, which can be performed according to the above-mentioned reconstructed picture (or reconstructed sample) generating procedure.

[0130] In step S920, the decoding device may determine whether in-loop filtering is applied (across the virtual boundary) based on the in-loop filtering related information, where the in-loop filtering may include at least one of the above-mentioned deblocking filtering, SAO, or ALF.

[0131] In step S930, the decoding apparatus may generate a modified reconstructed picture (modified reconstructed sample) based on the determination in step S920, where the modified reconstructed picture (modified reconstructed sample) may be a filtered reconstructed picture (filtered reconstructed sample).

[0132] As described above, an in-loop filtering procedure can be applied to the reconstructed picture. In this case, a virtual boundary can be defined to further improve the subjective / objective visual quality of the reconstructed picture, and the in-loop filtering procedure can be applied across the virtual boundary. The virtual boundary can include, for example, a discontinuous edge of a 360-degree image, a VR image, or a picture in picture (PIP). For example, the virtual boundary can be present at a predetermined promised position, and its presence and / or position can be signaled. As an example, the virtual boundary can be located at the fourth sample line at the top of a CTU row (specifically, for example, above the fourth sample line at the top of the CTU row). As another example, information regarding the presence and / or position of the virtual boundary can be signaled via an HLS. The HLS can include an SPS, a PPS, a picda header, a slice header, etc., as described above.

[0133] The following describes the signaling and semantics of the high-level syntax for the embodiments of this document.

[0134] An embodiment of this document may include a method for controlling a loop filter. The method for controlling a loop filter may be applied to a reconstructed picture. An in-loop filter (loop filter) may be used for decoding an encoded bitstream. The loop filter may include the above-mentioned deblocking, SAO, and ALF. The SPS may include flags associated with each of the deblocking, SAO, and ALF. The flags may indicate whether each tool is available for coding a coded layer video sequence (CLVS) or coded video sequence (CVS) that references the SPS.

[0135] If the loop filter is available to the CVS, application of the loop filter may be controlled to avoid crossing certain boundaries. For example, it may be controlled whether the loop filter crosses sub-picture boundaries. It may also be controlled whether the loop filter crosses tile boundaries. In addition, it may be controlled whether the loop filter crosses virtual boundaries. Here, virtual boundaries may be defined on a CTU based on line buffer availability.

[0136] In relation to whether an in-loop filtering procedure is performed across a virtual boundary, the in-loop filtering related information may include at least one of a virtual boundary availability flag of the SPS (a virtual boundary availability flag in the SPS), a virtual boundary present flag of the SPS, a virtual boundary present flag of the picture header, a virtual boundary present flag of the SPS picture header, and information regarding the location of the virtual boundary.

[0137] In the embodiment included in this document, the information about the position of the virtual border may include information about the x-coordinate of the vertical virtual border and / or information about the y-coordinate of the horizontal virtual border. Specifically, the information about the position of the virtual border may include information about the x-coordinate of the vertical virtual border and / or information about the y-coordinate of the horizontal virtual border in luma sample units. Also, the information about the position of the virtual border may include information about the number of pieces of information (syntax elements) about the x-coordinate of the vertical virtual border present in the SPS. Also, the information about the position of the virtual border may include information about the number of pieces of information (syntax elements) about the y-coordinate of the horizontal virtual border present in the SPS. Or, the information about the position of the virtual border may include information about the number of pieces of information (syntax elements) about the x-coordinate of the vertical virtual border present in the picture header. Also, the information about the position of the virtual border may include information about the number of pieces of information (syntax elements) about the y-coordinate of the horizontal virtual border present in the picture header.

[0138] The following table shows an example syntax and semantics of a sequence parameter set (SPS) according to this embodiment.

[0139] [Table 4]

[0140] [Table 5]

[0141] The following table shows an example syntax and semantics of a picture parameter set (PPS) according to this embodiment.

[0142] [Table 6]

[0143] [Table 7]

[0144] The following table shows an example syntax and semantics of a picture header according to this embodiment.

[0145] [Table 8-1]

[0146] [Table 8-2]

[0147] [Table 9-1]

[0148] [Table 9-2]

[0149] The following table shows an example syntax and semantics of a slice header according to this embodiment.

[0150] [Table 10]

[0151] [Table 11]

[0152] In the following, information related to sub-pictures, information related to virtual boundaries that can be used in in-loop filtering, and their signaling are described.

[0153] In one example, two different rectangular slices may belong to different sub-pictures while sharing the same tile, which may cause problems of increased coding complexity.

[0154] For the simplification of picture division, an embodiment of this document may include examples of conditions for a picture to be divided into two or more sub-pictures. In one example, all CTUs in a tile may belong to the same sub-picture. In another example, all CTUs in a sub-picture may belong to the same tile. Both examples may be applied separately, sequentially, or in combination for image / video coding. Also, in one embodiment of this document, if a sub-picture includes a CTU that is a subset of all CTUs in a tile, the sub-picture may not include CTUs that belong to other tiles.

[0155] In the signaling for the current picture, if the value of subpic_present_flag is 1, the number of subpictures in each picture that refer to the SPS may be 1 (the value of sps_num_subpics_minus1 is 0). This condition is made to support an example of a subpicture extraction use, where an independently coded subpicture may be extracted from a bitstream to form another bitstream without changing the lower value of the parameter set. Thus, even if the value of subpic_present_flag is 1 and the value of sps_num_subpics_minus1 is 0, 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] are still present. In such a situation, the presence of such syntax elements is not only redundant, but can also make the decoder's operation unpredictable if an incorrect value is signaled for the syntax element. For example, if subpics_present_flag has a value of 1 and sps_num_subpics_minus1 has a value of 0, this means that there is only one subpicture (the picture itself), and subpic_treat_as_pic_flag[0] has a value of 1. In this case, if the value is signaled to a value of 0, inconsistency problems may occur in the decoding procedure.

[0156] To solve the problem described in the previous paragraph, one embodiment of this document includes examples of conditions that may be applied when sub-picture signaling is present (e.g., subpic_present_flag has a value of 1) and there is only one sub-picture in the picture (e.g., sps_num_subpics_minus1 has a value of 0). The examples of the conditions are as follows:

[0157] [Table 12]

[0158] In one example, if sub-picture signaling is present and the virtual border location is present in the picture header, there is a problem that the picture header must be re-created to ensure that the virtual border location signaling is correct in sub-picture extraction and sub-picture merging scenarios, which may violate the design objective of sub-picture extraction / merging, which is that no rewriting of the bitstream is required for NAL units of layers lower than the parameter set.

[0159] To solve the problem in the above paragraph, in one embodiment of this document, when sub-picture signaling is present (e.g., when sub-picture signaling is present in the SPS), the signaling of the virtual border position may not be included in the picture header. In one example, when sub-picture signaling is present, information on the virtual border position may be included in a higher level parameter set. For example, when sub-picture signaling is present, information on the virtual border position may be included in the SPS. Alternatively, when sub-picture signaling is present, information on the virtual border position may be included in the PPS.

[0160] In one embodiment of this document, if subpicture ID signaling is present (sps_subpic_id_present_flag has a value of 1), all subpictures may be independently coded subpictures (subpic_treated_as_pic_flag[i] has a value of 1). In this case, the location of the subpicture ID signaling (e.g., SPS, PPS, or picture header) is irrelevant.

[0161] In conjunction with the above table, according to an embodiment of the present document, it can be determined whether virtual border related information (e.g., virtual border position related information) is signaled in a sequence parameter set based on whether sub-picture information is present. For example, if sub-picture information is present for the sequence, virtual border related information (e.g., virtual border position related information) can be signaled in the sequence parameter set. This allows the coding method based on virtual borders according to the embodiment of the present document to be efficiently performed without rewriting or modifying higher level syntax.

[0162] 10 and 11 show a schematic diagram of an example of a video / image encoding method and associated components according to an embodiment of the present document.

[0163] The method disclosed in FIG. 10 may be performed by the encoding device disclosed in FIG. 2 or FIG. 11. Specifically, for example, S1000 and S1010 in FIG. 10 may be performed by the residual processing unit 230 of the encoding device in FIG. 11, S1020 in FIG. 10 may be performed by the filtering unit 260 of the encoding device in FIG. 11, and S1030 in FIG. 10 may be performed by the entropy encoding unit 240 of the encoding device in FIG. 11. Also, although not shown in FIG. 10, a prediction sample or prediction related information may be derived by the prediction unit 220 of the encoding device in FIG. 10, and a bitstream may be generated from the residual information or prediction related information by the entropy encoding unit 240 of the encoding device. The method disclosed in FIG. 10 may include the embodiments described above in this document.

[0164] Referring to FIG. 10, an encoding apparatus may derive a residual sample (S1000). The encoding apparatus may derive a residual sample for a current block, and the residual sample for the current block may be derived based on an original sample and a predicted sample of the current block. Specifically, the encoding apparatus may derive a predicted sample for the current block based on a prediction mode. In this case, various prediction methods disclosed in this document, such as inter prediction or intra prediction, may be applied. A residual sample may be derived based on the predicted sample and the original sample.

[0165] The encoding device may derive the transform coefficients. The encoding device may derive the transform coefficients based on a transform procedure on the residual samples. For example, the transform procedure may include at least one of DCT, DST, GBT, or CNT.

[0166] The encoding device may derive quantized transform coefficients. The encoding device may derive the quantized transform coefficients based on a quantization procedure for the transform coefficients. The quantized transform coefficients may have a form of a one-dimensional vector based on a coefficient scanning order.

[0167] An encoding apparatus may generate residual information (S1010). The encoding apparatus may generate residual information based on the residual samples for the current block. The encoding apparatus may generate residual information indicating the quantized transform coefficients. The residual information may be generated through various encoding methods such as Exponential Golomb, CAVLC, CABAC, etc.

[0168] The encoding apparatus may generate a reconstructed sample. The encoding apparatus may generate a reconstructed sample based on the residual information. The reconstructed sample may be generated by adding a residual sample based on the residual information to a predicted sample. Specifically, the encoding apparatus may perform prediction (intra- or inter-prediction) on a current block and generate a reconstructed sample based on an original sample and a predicted sample generated from the prediction.

[0169] The reconstructed sample may include a reconstructed luma sample and a reconstructed chroma sample. Specifically, the residual sample may include a residual luma sample and a residual chroma sample. The residual luma sample may be generated based on an original luma sample and a predicted luma sample. The residual chroma sample may be generated based on an original chroma sample and a predicted chroma sample. The encoding apparatus may derive a transform coefficient for the residual luma sample (luma transform coefficient) and / or a transform coefficient for the residual chroma sample (chroma transform coefficient). The quantized transform coefficient may include a quantized luma transform coefficient and / or a quantized chroma transform coefficient.

[0170] The encoding apparatus may generate in-loop filtering related information for reconstructed samples of a current picture (S1020). The encoding apparatus may perform an in-loop filtering procedure on the reconstructed samples and may generate in-loop filtering related information based on the in-loop filtering procedure. For example, the in-loop filtering related information may include information on the virtual boundary described above in this document (such as a virtual boundary available flag in the SPS, a virtual boundary available flag in the picture header, a virtual boundary present flag in the SPS, a virtual boundary present flag in the picture header, and information on the position of the virtual boundary).

[0171] An encoding device may encode video / image information (S1030). The image information may include residual information, prediction-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 a decoding device via a network or a storage medium.

[0172] The image / video information may include various information according to embodiments of this document, for example, the image / video information may include at least one of the information disclosed in Tables 1-12 above.

[0173] In one embodiment, the image information may include a sequence parameter set (SPS). Based on whether the SPS includes sub-picture related information, it may be determined whether the SPS includes further information related to a virtual boundary.

[0174] In one embodiment, the further information associated with the virtual boundaries may include the number of the virtual boundaries and the locations of the virtual boundaries.

[0175] In one embodiment, further information associated with the virtual borders may include information regarding the number of vertical virtual borders, information regarding the position of the vertical virtual borders, information regarding the number of horizontal virtual borders, and information regarding the position of the horizontal virtual borders.

[0176] In one embodiment, the video information may include a sub-picture present flag (eg, subpic_present_flag). Based on the sub-picture present flag, it may be determined whether the SPS includes the sub-picture related information.

[0177] In an embodiment, the video information may include a sub-picture ID presence flag, where if the sub-picture ID presence flag has a value of 1, the sub-picture in the current picture may be an independently-coded sub-picture.

[0178] In one embodiment, the current picture may include sub-pictures and tiles, and coding tree units (CTUs) in a tile may belong to the same sub-picture.

[0179] In one embodiment, the current picture may include sub-pictures and tiles, and coding tree units (CTUs) in one sub-picture may belong to the same tile.

[0180] In one embodiment, the SPS may include an SPS virtual border present flag associated with whether the SPS includes further information related to the virtual border. Based on the SPS including the sub-picture related information, a value of the SPS virtual border present flag may be determined to be 1.

[0181] In one embodiment, the video information may include picture header information. Based on the SPS including the sub-picture related information, further information related to the virtual border may not be included in the picture header.

[0182] In one embodiment, based on the SPS including the sub-picture related information, the SPS may include further information related to the virtual boundary.

[0183] 12 and 13 show a schematic diagram of an example of a video / image decoding method and related components according to an embodiment of the present document.

[0184] The method disclosed in Fig. 12 may be performed by the decoding device disclosed in Fig. 12 or Fig. 13. Specifically, for example, S1200 in Fig. 12 may be performed by the entropy decoding unit 310 of the decoding device, S1210 may be performed by the residual processing unit 320 and / or the addition unit 340 of the decoding device, and S1220 may be performed by the filtering unit 350 of the decoding device. The method disclosed in Fig. 12 may include the embodiments described above in this document.

[0185] Referring to FIG 12, a decoding device may receive / acquire video / image information (S1200). The video / image information may include residual information, prediction-related information, and / or in-loop filtering-related information. The decoding device may receive / acquire the video / image information via a bitstream.

[0186] The image / video information may include various information according to embodiments of this document, for example, the image / video information may include at least one of the information disclosed in Tables 1 to 12 above.

[0187] The decoding device may derive quantized transform coefficients. The decoding device may derive quantized transform coefficients based on the residual information. The quantized transform coefficients may have a form of a one-dimensional vector based on a coefficient scanning order. The quantized transform coefficients may include quantized luma transform coefficients and / or quantized chroma transform coefficients.

[0188] A decoding device may derive transform coefficients. The decoding device may derive transform coefficients based on an inverse quantization procedure for the quantized transform coefficients. The decoding device may derive luma transform coefficients through inverse quantization based on the quantized luma transform coefficients. The decoding device may derive chroma transform coefficients through inverse quantization based on the quantized chroma transform coefficients.

[0189] The decoding apparatus may generate / derive a residual sample. The decoding apparatus may derive a residual sample based on an inverse transform procedure on the transform coefficients. The decoding apparatus may derive a residual luma sample through an inverse transform procedure based on a luma transform coefficient. The decoding apparatus may derive a residual chroma sample through an inverse transform procedure based on a chroma transform coefficient.

[0190] The decoding apparatus may generate / derive a reconstructed sample (S1210). For example, the decoding apparatus may generate / derive a reconstructed luma sample and / or a reconstructed chroma sample. The decoding apparatus may generate a reconstructed luma sample and / or a reconstructed chroma sample based on the residual information. The decoding apparatus may generate a reconstructed sample based on the residual information. The reconstructed sample may include a reconstructed luma sample and / or a reconstructed chroma sample. A luma component of the reconstructed sample may correspond to the reconstructed luma sample, and a chroma component of the reconstructed sample may correspond to the reconstructed chroma sample. The decoding apparatus may generate a predicted luma sample and / or a predicted chroma sample through a prediction procedure. The decoding apparatus may generate a reconstructed luma sample based on the predicted luma sample and the residual luma sample. The decoding apparatus may generate a reconstructed chroma sample based on the predicted chroma sample and the residual chroma sample.

[0191] The decoding device may generate modified (filtered) reconstructed samples (S1220). The decoding device may generate the modified reconstructed samples based on an in-loop filtering procedure on the reconstructed samples. The decoding device may generate the modified reconstructed samples based on in-loop filtering related information. The decoding device may use a deblocking procedure, an SAO procedure, and / or an ALF procedure to generate the modified reconstructed samples.

[0192] In one embodiment, the image information may include a sequence parameter set (SPS). Based on whether the SPS includes sub-picture related information, it may be determined whether the SPS includes further information related to a virtual boundary.

[0193] In one embodiment, the further information associated with the virtual boundaries may include the number of the virtual boundaries and the locations of the virtual boundaries.

[0194] In one embodiment, the further information associated with the virtual borders may include information regarding the number of vertical virtual borders, information regarding the position of the vertical virtual borders, information regarding the number of horizontal virtual borders, and information regarding the position of the horizontal virtual borders.

[0195] In one embodiment, the video information may include a sub-picture present flag (eg, subpic_present_flag). Based on the sub-picture present flag, it may be determined whether the SPS includes the sub-picture related information.

[0196] In one embodiment, the video information may include a sub-picture ID presence flag, where if the sub-picture ID presence flag has a value of 1, the sub-picture in the current picture may be an independently-coded sub-picture.

[0197] In one embodiment, the current picture may include sub-pictures and tiles, and coding tree units (CTUs) in a tile may belong to the same sub-picture.

[0198] In one embodiment, the current picture may include sub-pictures and tiles, and coding tree units (CTUs) in one sub-picture may belong to the same tile.

[0199] In one embodiment, the SPS may include an SPS virtual border present flag associated with whether the SPS includes further information related to the virtual border. Based on the SPS including the sub-picture related information, a value of the SPS virtual border present flag may be determined to be 1.

[0200] In one embodiment, the video information may include picture header information. Based on the SPS including the sub-picture related information, further information related to the virtual border may not be included in the picture header.

[0201] In one embodiment, based on the SPS including the sub-picture related information, the SPS may include further information related to the virtual boundary.

[0202] The decoding apparatus may receive information about a residual for a current block if a residual sample for the current block exists. The information about the residual may include a transform coefficient related to the residual sample. The decoding apparatus may derive a residual sample (or a residual sample array) for the current block based on the residual information. Specifically, the decoding apparatus may derive a quantized transform coefficient based on the residual information. The quantized transform coefficient may have a one-dimensional vector form based on a coefficient scan order. The decoding apparatus may derive the transform coefficient based on a dequantization procedure for the quantized transform coefficient. The decoding apparatus may derive a residual sample based on the transform coefficient.

[0203] The decoding apparatus may generate a reconstructed sample based on an (intra) predicted sample and a residual sample, and may derive a reconstructed block or a reconstructed picture based on the reconstructed sample. Specifically, the decoding apparatus may generate a reconstructed sample based on a sum of an (intra) predicted sample and a residual sample. As described above, the decoding apparatus may then apply an in-loop filtering procedure, such as a deblocking filtering and / or an SAO procedure, to the reconstructed picture, if necessary, to improve subjective / objective image quality.

[0204] For example, a decoding device may decode a bitstream or encoded information to obtain video information including all or part of the above-mentioned information (or syntax elements). Also, the bitstream or encoded information may be stored in a computer-readable storage medium and may be triggered to perform the above-mentioned decoding method.

[0205] In the above-described embodiments, the method is described based on a flowchart as a series of steps or blocks, but the embodiment is not limited to the order of steps, and some steps may occur in a different order or simultaneously with other steps than those described above. Also, those skilled in the art can understand that the steps shown in the flowchart are not exclusive, and different steps may be included, or one or more steps of the flowchart may be deleted without affecting the scope of the embodiments of this document.

[0206] The methods according to the embodiments of the present document described above may be embodied in the form of software, and the encoding device and / or decoding device according to the present document may be included in a device that performs image processing, such as a TV, a computer, a smartphone, a set-top box, a display device, etc.

[0207] In this document, when the embodiments are implemented in software, the methods described above may be implemented with modules (processes, functions, etc.) performing the functions described above. The modules may be stored in a memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor in various well-known ways. The processor may include an application-specific integrated circuit (ASIC), other chipsets, 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. That is, the embodiments described in this document may be implemented and performed on a processor, microprocessor, controller, or chip. For example, the functional units shown in each drawing may be implemented and performed on a computer, processor, microprocessor, controller, or chip. In this case, information on instructions or algorithms for implementation may be stored on a digital storage medium.

[0208] In addition, the decoding device and the encoding device to which the embodiments of the present document are applied may be included in a multimedia broadcast transmitting / receiving device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video interactive device, a real-time communication device such as a video communication, a mobile streaming device, a storage medium, a camcorder, a customized video (VoD) service providing device, an over-the-top video (OTT) device, an internet streaming service providing device, a three-dimensional (3D) video device, a virtual reality (VR) device, an argument reality (AR) device, a video telephone video device, a transportation means terminal (e.g., a vehicle (including an autonomous vehicle) terminal, an airplane terminal, a ship terminal, etc.), and a medical video device, etc., and may be used to process a video signal or a data signal. For example, an over-the-top video (OTT) device may include a game console, a Blu-ray player, an internet access TV, a home theater system, a smartphone, a tablet PC, a digital video recorder (DVR), etc.

[0209] In addition, the processing method to which the embodiment of this document is applied may be produced in the form of a program executed by a computer and may be stored in a computer-readable recording medium. Multimedia data having a data structure according to the embodiment of this document may also be stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices and distributed storage devices in which computer-readable data is stored. The computer-readable recording medium may include, for example, a Blu-ray Disc (BD), a Universal Serial Bus (USB), a ROM, a PROM, an EPROM, an EEPROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device. The computer-readable recording medium may also include a medium embodied in the form of a carrier wave (e.g., transmission via the Internet). In addition, a bit stream generated by the encoding method may be stored in a computer-readable recording medium or transmitted via a wired or wireless communication network.

[0210] Furthermore, the embodiments of the present document may be embodied in a computer program product with program code, the program code being executable by a computer in accordance with the embodiments of the present document. The program code may be stored on a carrier readable by a computer.

[0211] FIG. 14 illustrates an example of a content streaming system in which the embodiments disclosed herein can be applied.

[0212] Referring to FIG. 14, a content streaming system to which the embodiments of this document are applied may broadly include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0213] The encoding server compresses content input from a multimedia input device such as a smartphone, camera, camcorder, etc. into digital data to generate a bitstream and transmits the bitstream to the streaming server. As another example, if a multimedia input device such as a smartphone, camera, camcorder, etc. directly generates a bitstream, the encoding server may be omitted.

[0214] The bitstream may be generated by an encoding method or a bitstream generation method to which an embodiment of this document is applied, and the streaming server may temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[0215] The streaming server transmits multimedia data to a user device based on a user request via a web server, and the web server acts as a medium to inform the user of available services. When a user requests a desired service from the web server, the web server transmits the request to the streaming server, and the streaming server transmits multimedia data to the user. In this case, the content streaming system may include a separate control server, and in this case, the control server controls commands / responses between devices in the content streaming system.

[0216] The streaming server may receive content from a media repository and / or an encoding server. For example, when the content is received from the encoding server, the content may be received in real time. In this case, the streaming server may store the bitstream for a certain period of time in order to provide a smooth streaming service.

[0217] Examples of the user devices include mobile phones, smart phones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation systems, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glass, head mounted displays (HMDs)), digital TVs, desktop computers, digital signage, etc.

[0218] Each server in the content streaming system can be operated as a distributed server, in which case data received by each server can be processed in a distributed manner.

[0219] The claims described herein may be combined in various ways. For example, the technical features of the method claims herein may be combined and embodied as an apparatus, and the technical features of the apparatus claims herein may be combined and embodied as a method. In addition, the technical features of the method claims herein and the technical features of the apparatus claims herein may be combined and embodied as an apparatus, and the technical features of the method claims herein and the technical features of the apparatus claims herein may be combined and embodied as a method.

Claims

1. A video decoding method executed by a decoding device, comprising: obtaining video information including residual information via a bitstream; generating a reconstructed sample of a current picture based on the residual information; generating modified reconstructed samples based on an in-loop filtering procedure on the reconstructed samples; The video information includes a sequence parameter set (SPS); the SPS includes a sub-picture present flag indicating whether sub-picture related information is included in the SPS; the sub-picture related information includes information regarding the number of sub-pictures in a picture; A video decoding method, wherein if the sub-picture presence flag indicates that the sub-picture related information is included in the SPS, it is determined that the number of sub-pictures in the current picture is 1, and information regarding the position of a virtual border is included in the SPS.

2. The video decoding method of claim 1 , wherein the information regarding the position of the virtual border includes information regarding the position of a vertical virtual border and information regarding the position of a horizontal virtual border.

3. the current picture includes a subpicture and a tile; The video decoding method of claim 1 , wherein all coding tree units (CTUs) in one tile belong to the same sub-picture.

4. the current picture includes a subpicture and a tile; The video decoding method of claim 1 , wherein all coding tree units (CTUs) in one sub-picture belong to the same tile.

5. The video information includes a picture header; The video decoding method of claim 1 , wherein if the sub-picture present flag indicates that the sub-picture related information is included in the SPS, information regarding the location of the virtual border is not included in the picture header.

6. A video encoding method performed by an encoding device, comprising: generating a residual sample for the current block; generating residual information based on the residual samples for the current block; generating in-loop filtering related information for reconstructed samples of a current picture; encoding video information including the residual information and the in-loop filtering related information; The video information includes a sequence parameter set (SPS); the SPS includes a sub-picture present flag indicating whether sub-picture related information is included in the SPS; the sub-picture related information includes information regarding the number of sub-pictures in a picture; A video encoding method, wherein if the sub-picture presence flag indicates that the sub-picture related information is included in the SPS, it is determined that the number of sub-pictures in the current picture is 1, and information regarding the location of a virtual boundary is included in the SPS.

7. In a method of transmitting data for video, obtaining a bitstream for the video, the bitstream being generated based on generating residual samples for a current block, generating residual information based on the residual samples for the current block, generating in-loop filtering related information for reconstructed samples of a current picture, and encoding video information including the residual information and the in-loop filtering related information; transmitting the data including the bitstream; The video information includes a sequence parameter set (SPS); the SPS includes a sub-picture present flag indicating whether sub-picture related information is included in the SPS; the sub-picture related information includes information regarding the number of sub-pictures in a picture; A data transmission method, wherein if the sub-picture presence flag indicates that the sub-picture related information is included in the SPS, it is determined that the number of sub-pictures in the current picture is 1 and information regarding the position of a virtual border is included in the SPS.

Images