Filtering-based image coding device and method

Abstract

A picture can be divided into subpictures / slices / tiles. For example, a picture can be divided into subpicture(s), and subpicture-related information can be used for coding. Subpicture-related information can be generated by an encoding device and transmitted to a decoding device. According to the embodiments of this document, signaling of subpicture-related information can be performed efficiently.

Description

Technology Field

[0001] This document relates to an in-loop filtering-based image coding device and method. Background Technology

[0002] Recently, the demand for high-resolution, high-quality video, such as 4K or 8K or higher UHD (Ultra High Definition) video, is increasing across various fields. As video data becomes higher resolution and higher quality, the amount of information or bits transmitted increases relative to existing video data; therefore, when transmitting video data using media such as existing wired or wireless broadband lines or storing video data using existing storage media, transmission and storage costs increase.

[0003] In addition, interest in and demand for immersive media such as VR (Virtual Reality), AR (Artificial Reality) content, and holograms have recently been increasing, and the broadcasting of video content with characteristics different from reality, such as game footage, is on the rise.

[0004] Accordingly, high-efficiency image / video compression technology is required to effectively compress, transmit, store, and play back high-resolution, high-quality image / video information having various characteristics as described above.

[0005] Specifically, an in-loop filtering procedure may be performed on the restored pictures (samples) to improve image quality. The decoding device signals information for the in-loop filtering procedure. There is discussion regarding efficient signaling methods for information related to in-loop filtering. means of solving the problem

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

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

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

[0009] According to one embodiment of the present document, in-loop filtering can be performed based on virtual boundaries.

[0010] According to one embodiment of the present document, the decoded picture may be composed of subpictures.

[0011] According to one embodiment of the present document, the signaling location of information regarding the locations of virtual boundaries can be determined based on the signaling of information regarding subpictures.

[0012] According to one embodiment of the present document, signaling of virtual boundary-related information can be performed based on signaling of subpicture-related information.

[0013] According to one embodiment of the present document, an encoding device for performing video / image encoding is provided.

[0014] According to one embodiment of the present document, a computer-readable digital storage medium is provided that stores encoded video / image information generated according to a video / image encoding method disclosed in at least one of the embodiments of the present document.

[0015] According to one embodiment of the present document, a computer-readable digital storage medium is provided that stores encoded information or encoded video / image information, which causes a video / image decoding method disclosed in at least one of the embodiments of the present document to be performed by a decoding device. Effects of the invention

[0016] According to one embodiment of the present document, overall image / video compression efficiency can be increased.

[0017] According to one embodiment of the present document, subjective / objective visual quality can be improved through efficient filtering.

[0018] According to one embodiment of the present document, efficient coding can be implemented by omitting the rewriting procedure of the bitstream through signaling-based virtual boundary signaling of subpictures. Brief explanation of the drawing

[0019] Figure 1 schematically illustrates an example of a video / image coding system that can be applied to embodiments of the present document. FIG. 2 is a diagram schematically illustrating the configuration of a video / image encoding device that can be applied to embodiments of the present document. FIG. 3 is a diagram schematically illustrating the configuration of a video / image decoding device that can be applied to embodiments of the present document. Figure 4 illustrates an exemplary hierarchical structure for a coded image / video. FIG. 5 illustrates a picture according to one embodiment of the present document. FIG. 6 illustrates a subpicture / slice / tile-based encoding method according to one embodiment of the present document. FIG. 7 illustrates a subpicture / slice / tile-based decoding method according to one embodiment of the present document. Figure 8 is a flowchart illustrating a filtering-based encoding method in an encoding device. FIG. 9 is a flowchart illustrating a filtering-based decoding method in a decoding device. FIGS. 10 and 11 schematically illustrate an example of a video / image encoding method and related components according to the embodiment(s) of the present document. FIGS. 12 and 13 schematically illustrate an example of an image / video decoding method and related components according to the embodiment(s) of the present document. FIG. 14 shows an example of a content streaming system to which the embodiments disclosed in this document can be applied. Specific details for implementing the invention

[0020] This document presents various embodiments regarding video / image coding, and unless otherwise noted, the embodiments may be performed in combination with one another.

[0021] In this document, "video" may refer to a set of images over time. "Picture" generally refers to a unit representing a single image at a specific time, and "slice" or "tile" are units that constitute a part of a picture in coding. A slice or tile may contain one or more CTUs (coding tree units). A single picture may consist of one or more slices or tiles. A single picture may consist of one or more tile groups. A tile group may contain one or more tiles.

[0022] Each component in the drawings described in this document is depicted independently for the convenience of describing different characteristic functions and does not imply that each component is implemented in separate hardware or software. For example, two or more components may be combined to form a single component, or a single component may be divided into multiple components. Embodiments in which each component is integrated and / or separated are also included within the scope of this document, provided that such integration and / or separation does not deviate from the essence of this document.

[0023] Meanwhile, as this document is subject to various modifications and may have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit this document to specific embodiments. Terms used in this specification are used merely to describe specific embodiments and are not intended to limit the technical scope of this document. Singular expressions include plural expressions unless the context clearly indicates otherwise. Terms such as "comprising" or "having" in this specification are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0024] Hereinafter, preferred embodiments of the present document will be described in more detail with reference to the attached drawings. In the following, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0025] This document relates to video / image coding. For example, the methods / executions disclosed in this document may relate to the VVC (Versatile Video Coding) standard (ITU-T Rec. H.266), next-generation video / image coding standards following VVC, or other video coding-related standards (e.g., HEVC (High Efficiency Video Coding) standard (ITU-T Rec. H.265), EVC (essential video coding) standard, AVS2 standard, etc.).

[0026] A pixel or pel can refer to the smallest unit that constitutes a picture (or image). Additionally, the term 'sample' may be used as a counterpart to pixel. Generally, a sample can represent a pixel or its value; it may represent only the pixel / pixel value of the luminance component, or only the pixel / pixel value of the chroma component. Alternatively, a sample may refer to a pixel value in the spatial domain, or it may refer to the transformation coefficient in the frequency domain when such pixel values ​​are converted to the frequency domain.

[0027] A unit may represent a basic unit of image processing. A unit may include at least one of a specific area of ​​a picture and information related to that area. A unit may include one luminance block and two chroma (e.g., cb, cr) blocks. Depending on the case, the term unit may be used interchangeably with terms such as block or area. In general, an MxN block may include samples (or sample arrays) or a set (or array) of transform coefficients consisting of M columns and N rows.

[0028] 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." Furthermore, "A, B, C" also means "at least one of A, B and / or C."

[0029] Additionally, in this document, "or" is interpreted as "and / or". For example, "A or B" may mean 1) "A" only, 2) "B" only, or 3) "A and B". Alternatively, "or" in this document may mean "additionally or alternatively".

[0030] In this specification, "at least one of A and B" may mean "only A," "only B," or "both A and B." Additionally, in this specification, the expressions "at least one of A or B" or "at least one of A and / or B" may be interpreted as synonymous with "at least one of A and B."

[0031] Additionally, in this specification, "at least one of A, B and C" may mean "only A," "only B," "only C," or "any combination of A, B and C." Also, "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."

[0032] Additionally, parentheses used in this specification may mean "for example." Specifically, where indicated as "prediction (intra-prediction)," "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." Furthermore, even where indicated as "prediction (i.e., intra-prediction)," "intra-prediction" may be proposed as an example of "prediction."

[0033] Technical features described individually within a single drawing in this specification may be implemented individually or simultaneously.

[0034] Figure 1 schematically illustrates an example of a video / image coding system to which this document can be applied.

[0035] Referring to FIG. 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 the form of a file or streaming to the receiving device via a digital storage medium or a network.

[0036] The source device may include a video source, an encoding device, and a transmission unit. The receiving device may include a receiving unit, a decoding device, and a renderer. The encoding device may be called a video / image encoding device, and the decoding device may be called a video / image decoding device. A transmitter may be included in the encoding device. A receiver may be included in the decoding device. The renderer may include a display unit, and the display unit may be composed of a separate device or an external component.

[0037] A video source may acquire video / images through processes such as video / image capture, synthesis, or generation. The video source may include a video / image capture device and / or a video / image generation device. The video / image capture device may include, for example, one or more cameras, a video / image archive containing previously captured video / images, etc. The video / image generation device may include, for example, a computer, a tablet, and a smartphone, etc., and may generate video / images (electronically). For example, virtual video / images may be generated through a computer, etc., in which case the video / image capture process may be replaced by a process in which related data is generated.

[0038] The encoding device can encode input video / images. The encoding device can perform a series of procedures, such as prediction, transformation, and quantization, for compression and coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0039] The transmission unit can transmit encoded video / image information or data output in the form of a bitstream to the 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, and SSD. The transmission unit may include elements for creating a media file through a predetermined file format and elements for transmission via a broadcasting / communication network. The receiving unit can receive / extract the bitstream and transmit it to a decoding device.

[0040] The decoding device can decode video / images by performing a series of procedures such as inverse quantization, inverse transform, and prediction corresponding to the operation of the encoding device.

[0041] The renderer can render the decoded video / image. The rendered video / image can be displayed through the display unit.

[0042] FIG. 2 is a diagram schematically illustrating the configuration of a video / image encoding device to which the present document may be applied. Hereinafter, the term "video encoding device" may include an image encoding device.

[0043] Referring to 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-predictor (221) and an intra-predictor (222). The residual processor (230) may include a transformer (232), a quantizer (233), a dequantizer (234), and an inverse transformer (235). The residual processor (230) may further include a subtractor (231). The addition unit (250) may be referred to as a reconstructor or a reconstructed block generator. The above-described image segmentation unit (210), prediction unit (220), residual processing unit (230), entropy encoding unit (240), addition unit (250), and filtering unit (260) may be configured by one or more hardware components (e.g., an encoder chipset or processor) according to the embodiment. Additionally, the memory (270) may include a decoded picture buffer (DPB) and may be configured by a digital storage medium. The hardware component may further include the memory (270) as an internal / external component.

[0044] The image segmentation unit (210) can divide an input image (or picture, frame) input to an encoding device (200) into one or more processing units. For example, the processing unit may be called a coding unit (CU). In this case, the coding unit may be recursively divided from a coding tree unit (CTU) or a largest coding unit (LCU) according to a QTBTTT (Quad-tree binary-tree ternary-tree) structure. For example, one coding unit may be divided into multiple 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 the binary-tree structure and / or ternary structure may be applied later. Or the binary-tree structure may be applied first. A coding procedure according to this document may be performed based on the final coding unit that is no longer divided. In this case, based on coding efficiency according to image characteristics, the maximum coding unit may be used directly as the final coding unit, or, if necessary, the coding unit may be recursively divided into lower-depth coding units so that a coding unit of the optimal size is used as the final coding unit. Here, the coding procedure may include procedures such as prediction, transformation, and restoration described later. As another example, the processing unit may further include a prediction unit (PU) or a transformation unit (TU). In this case, the prediction unit and the transformation unit may each be divided or partitioned from the final coding unit described above.The above prediction unit may be a unit of sample prediction, and the above transformation unit may be a unit that derives transformation coefficients and / or a unit that derives a residual signal from transformation coefficients.

[0045] The term "unit" may be used interchangeably with terms such as "block" or "area" depending on the context. In general, an MxN block may represent a set of samples or transform coefficients consisting of M columns and N rows. A sample can generally represent a pixel or a pixel value, and may represent only the pixel / pixel value of the luminance component or only the pixel / pixel value of the chroma component. A sample may be used to refer to a single picture (or image) as a term corresponding to a pixel or pel.

[0046] The subtraction unit (231) can generate a residual signal (residual block, residual samples, or residual sample array) by subtracting the predicted signal (predicted block, predicted samples, or predicted sample array) output from the prediction unit (220) from the input image signal (original block, original samples, or original sample array), and the generated residual signal is transmitted to the conversion unit (232). The prediction unit (220) can perform a prediction for a block to be processed (hereinafter referred to as the current block) and generate a predicted block (predicted block) containing predicted samples for the current block. The prediction unit (220) can determine whether intra prediction is applied or inter prediction is applied at the current block or CU unit. The prediction unit can generate various information regarding prediction, such as prediction mode information, as described later in the description of each prediction mode, and transmit it to the entropy encoding unit (240). Information regarding the prediction can be encoded in the entropy encoding unit (240) and output in the form of a bitstream.

[0047] The intra prediction unit (222) can predict the current block by referring to samples within the current picture. The referenced samples may be located near the current block or away from it, depending on the prediction mode. In intra prediction, the prediction modes 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 degree of fineness of the prediction direction. However, this is merely an example, and depending on the settings, more or fewer directional prediction modes may be used. The intra prediction unit (222) may also determine the prediction mode applied to the current block by using the prediction mode applied to the surrounding blocks.

[0048] The inter prediction unit (221) can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, to reduce the amount of motion information transmitted in the inter prediction mode, motion information can be predicted in 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 information on the inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, neighboring blocks may include spatial neighboring blocks existing within the current picture and temporal neighboring blocks existing in the reference picture. The reference picture containing the reference blocks and the reference picture containing the temporal neighboring blocks may be the same or different. The above temporal surrounding blocks may be referred to by names such as collocated reference block, collocated CU (colCU), etc., and the reference picture containing the above temporal surrounding blocks may be referred to as a collocated picture (colPic). For example, the inter prediction unit (221) may construct a list of motion information candidates based on surrounding blocks and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter prediction may be performed based on various prediction modes, for example, in the case of skip mode and merge mode, the inter prediction unit (221) may use the motion information of surrounding blocks as motion information of the current block. In the case of skip mode, unlike merge mode, a residual signal may not be transmitted.In the motion vector prediction (MVP) mode, the motion vector of surrounding blocks is used as a motion vector predictor, and the motion vector of the current block can be indicated by signaling the motion vector difference.

[0049] The prediction unit (220) can generate a prediction signal based on various prediction methods described below. For example, the prediction unit may apply intra prediction or inter prediction for a single block, and may also apply intra prediction and inter prediction simultaneously. This may be called combined inter and intra prediction (CIIP). Additionally, the prediction unit may perform intra block copy (IBC) for a block prediction. The intra block copy may be used for content video / video coding, such as in screen content coding (SCC), for example, games. IBC basically performs prediction within the current picture, but it may be performed similarly to inter prediction in that it derives a reference block within the current picture. That is, IBC may use at least one of the inter prediction techniques described in this document.

[0050] The prediction signal generated through the inter prediction unit (221) and / or intra prediction unit (222) can be used to generate a restoration signal or to generate a residual signal. The transformation unit (232) can generate transform coefficients by applying a transformation technique to the residual signal. For example, the transformation 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, GBT refers to a transformation obtained from a graph when the relationship information between pixels is represented as a graph. CNT refers to a transformation obtained based on generating a prediction signal using all previously reconstructed pixels. Additionally, the transformation process may be applied to a square pixel block of the same size, or to a non-square block of variable size.

[0051] The quantization unit (233) quantizes the transformation coefficients and transmits them to the entropy encoding unit (240), and the entropy encoding unit (240) can encode the quantized signal (information regarding the quantized transformation coefficients) and output it as a bitstream. The information regarding the quantized transformation coefficients may be called residual information. The quantization unit (233) can rearrange the block-shaped quantized transformation coefficients into a one-dimensional vector form based on the coefficient scan order, and can also generate information regarding the quantized transformation coefficients based on the one-dimensional vector-shaped quantized transformation coefficients. The entropy encoding unit (240) can perform various encoding methods such as, for example, exponential Golomb, CAVLC (context-adaptive variable length coding), CABAC (context-adaptive binary arithmetic coding), etc. The entropy encoding unit (240) may encode information necessary for video / image restoration (e.g., values ​​of syntax elements) together or separately, in addition to 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 units of NAL (network abstraction layer) units. The video / image information may further include information regarding 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). Additionally, the video / image information may further include general constraint information. The signaling / transmitting information and / or syntax elements described below in this document may be encoded through the encoding procedure described above and included in the bitstream.The above 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 USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmission unit (not shown) that transmits the signal output from the entropy encoding unit (240) and / or a storage unit (not shown) that stores it may be configured as internal / external elements of the encoding device (200), or the transmission unit may be included in the entropy encoding unit (240).

[0052] Quantized transform coefficients output from the quantization unit (233) can be used to generate a prediction signal. For example, a residual signal (residual block or residual samples) can be restored by applying inverse quantization and inverse transform to the quantized transform coefficients through the inverse quantization unit (234) and the inverse transform unit (235). An adder (250) can generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed samples, or reconstructed sample array) by adding the restored residual signal to the prediction signal output from the prediction unit (220). In cases where there is no residual for the block to be processed, such as when a skip mode is applied, the predicted block can be used as the reconstructed block. The generated reconstructed signal can be used for intra-prediction of the next block to be processed within the current picture, and can also be used for inter-prediction of the next picture after undergoing filtering as described below.

[0053] Meanwhile, LMCS (luma mapping with chroma scaling) may be applied during the picture encoding and / or restoration process.

[0054] The filtering unit (260) can improve subjective / objective image quality by applying filtering to the restored signal. For example, the filtering unit (260) can generate a modified restored picture by applying various filtering methods to the restored picture, and can store the modified restored picture in memory (270), specifically in the DPB of memory (270). The various filtering methods may include, for example, deblocking filtering, sample adaptive offset (SAO), adaptive loop filter, bilateral filter, etc. The filtering unit (260) can generate various information regarding filtering and transmit it to the entropy encoding unit (290), as described below in the description of each filtering method. The information regarding filtering can be encoded in the entropy encoding unit (290) and output in the form of a bitstream.

[0055] The modified restored picture transmitted to the memory (270) can be used as a reference picture in the inter-prediction unit (280). Through this, when inter-prediction is applied, the encoding device can avoid prediction mismatches between the encoding device (200) and the decoding device, and can also improve encoding efficiency.

[0056] The DPB of the memory (270) can store the modified restored picture to be used as a reference picture in the inter-prediction unit (221). The memory (270) can store motion information of blocks from which motion information is derived (or encoded) within the current picture and / or motion information of blocks within the picture that have already been restored. The stored motion information can be transmitted to the inter-prediction unit (221) to be used as motion information of spatially surrounding blocks or motion information of temporally surrounding blocks. The memory (270) can store restoration samples of the blocks restored within the current picture and transmit them to the intra-prediction unit (222).

[0057] Figure 3 is a diagram schematically illustrating the configuration of a video / image decoding device to which this document can be applied.

[0058] Referring to 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 aforementioned entropy decoding unit (310), residual processing unit (320), prediction unit (330), addition unit (340), and filtering unit (350) may be configured by a single hardware component (e.g., a decoder chipset or a processor) according to an embodiment. Additionally, the memory (360) may include a decoded picture buffer (DPB) and may be configured by a digital storage medium. The hardware component may further include the memory (360) as an internal / external component.

[0059] When a bitstream containing video / image information is input, the decoding device (300) can restore the image in correspondence with the process in which the video / image information is processed by the encoding device of FIG. 2. For example, the decoding device (300) can derive units / blocks based on block division information obtained from the bitstream. The decoding device (300) can perform decoding using a processing unit applied by the encoding device. Accordingly, the processing unit for decoding may be, for example, a coding unit, and the coding unit may be divided from a coding tree unit or a maximum coding unit according to a quad tree structure, a binary tree structure, and / or a binary tree structure. One or more conversion units may be derived from the coding unit. And, the restored image signal decoded and output through the decoding device (300) can be played back through a playback device.

[0060] The decoding device (300) can receive a signal output from the encoding device of FIG. 2 in the form of a bitstream, and the received signal can be decoded through an entropy decoding unit (310). For example, the entropy decoding unit (310) can parse the bitstream to derive information (e.g., video / image information) necessary for image restoration (or picture restoration). The video / image information may further include information regarding 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). Additionally, the video / image information may further include general constraint information. The decoding device can decode the picture based on information regarding the parameter sets and / or the general constraint information. The signaling / receiving information and / or syntax elements described below in this document can be obtained from the bitstream by being decoded through the decoding procedure. For example, the entropy decoding unit (310) can decode information within the bitstream based on coding methods such as exponential chording, CAVLC, or CABAC, and output values ​​of syntax elements required for image restoration and quantized values ​​of transformation coefficients regarding residuals. More specifically, the CABAC entropy decoding method can receive bins corresponding to each syntax element in the bitstream, determine a context model using information of the syntax element to be decoded and decoding information of surrounding and decoding target blocks or information of symbols / bins decoded in the previous step, predict the probability of occurrence of the bin according to the determined context model, and perform arithmetic decoding of the bin to generate symbols corresponding to the values ​​of each syntax element.At this time, the CABAC entropy decoding method can update the context model using the decoded symbol / bin information for the context model of the next symbol / bin after determining the context model. Among the information decoded in the entropy decoding unit (310), information regarding prediction is provided to the prediction unit (330), and information regarding the residual on which entropy decoding was performed in the entropy decoding unit (310), namely quantized transformation coefficients and related parameter information, can be input to the inverse quantization unit (321). Additionally, among the information decoded in the entropy decoding unit (310), information regarding filtering can be provided to the filtering unit (350). Meanwhile, a receiving unit (not shown) that receives a signal output from an 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), inverse transform unit (322), prediction unit (330), addition unit (340), filtering unit (350), and memory (360).

[0061] In the inverse quantization unit (321), the quantized transformation coefficients can be inversely quantized to output transformation coefficients. The inverse quantization unit (321) can rearrange the quantized transformation coefficients into a two-dimensional block form. In this case, the rearrangement can be performed based on the coefficient scan order performed by the encoding device. The inverse quantization unit (321) can perform inverse quantization on the quantized transformation coefficients using quantization parameters (e.g., quantization step size information) and obtain transformation coefficients.

[0062] In the inverse conversion unit (322), the conversion coefficients are inversely converted to obtain a residual signal (residual block, residual sample array).

[0063] The prediction unit performs a prediction for the current block and can generate a predicted block containing prediction samples for the current block. Based on information regarding the prediction output from the entropy decoding unit (310), the prediction unit can determine whether an intra prediction or an inter prediction is applied to the current block and can determine a specific intra / inter prediction mode.

[0064] The prediction unit may generate a prediction signal based on various prediction methods described below. For example, the prediction unit may apply intra prediction or inter prediction for the prediction of a single block, as well as apply intra prediction and inter prediction simultaneously. This may be referred to as combined inter and intra prediction (CIIP). Additionally, the prediction unit may perform intra block copy (IBC) for the prediction of a block. The intra block copy may be used for content video / video coding, such as in games, for example, screen content coding (SCC). IBC basically performs prediction within the current picture, but it may be performed similarly to inter prediction in that it derives a reference block within the current picture. That is, IBC may utilize at least one of the inter prediction techniques described in this document.

[0065] The intra prediction unit (332) can predict the current block by referring to samples within the current picture. The referenced samples may be located near the current block or away from it, depending on the prediction mode. In intra prediction, the prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The intra prediction unit (332) may determine the prediction mode applied to the current block by using the prediction mode applied to the surrounding blocks.

[0066] The inter prediction unit (331) can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, to reduce the amount of motion information transmitted in the inter prediction mode, motion information can be predicted in 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 information on the inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, neighboring blocks may include spatial neighboring blocks existing within the current picture and temporal neighboring blocks existing in the reference picture. For example, the inter prediction unit (331) may construct a motion information candidate list based on the neighboring blocks and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter-prediction can be performed based on various prediction modes, and information regarding the prediction may include information indicating the mode of inter-prediction for the current block.

[0067] The adder (340) can generate a restoration signal (restored picture, restored block, restored sample array) by adding the acquired residual signal to the prediction signal (predicted block, predicted sample array) output from the prediction unit (330). In cases where there is no residual for the block to be processed, such as when a skip mode is applied, the predicted block can be used as the restoration block.

[0068] The addition unit (340) may be called a restoration unit or a restoration block generation unit. The generated restoration signal may be used for intra-predicting the next block to be processed within the current picture, may be output after filtering as described below, or may be used for inter-predicting the next picture.

[0069] Meanwhile, LMCS (luma mapping with chroma scaling) may be applied during the picture decoding process.

[0070] The filtering unit (350) can improve subjective / objective image quality by applying filtering to the restored signal. For example, the filtering unit (350) can generate a modified restored picture by applying various filtering methods to the restored picture, and can transmit the modified restored picture to the DPB of the memory (60), specifically the memory (360). The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0071] The (modified) restored picture stored in the DPB of the memory (360) can be used as a reference picture in the inter-prediction unit (331). The memory (360) can store motion information of blocks from which motion information within the current picture has been derived (or decoded) and / or motion information of blocks within the picture that have already been restored. The stored motion information can be transmitted to the inter-prediction unit (331) to be used as motion information of spatially surrounding blocks or motion information of temporally surrounding blocks. The memory (360) can store restoration samples of the blocks restored within the current picture and transmit them to the intra-prediction unit (332).

[0072] In this specification, the embodiments described in the prediction unit (330), inverse quantization unit (321), inverse transformation unit (322), and filtering unit (350), etc. of the decoding device (300) may be applied to the prediction unit (220), inverse quantization unit (234), inverse transformation unit (235), and filtering unit (260), etc. of the encoding device (200) in the same or corresponding manner.

[0073] As described above, prediction is performed to increase compression efficiency during video coding. Through this, a predicted block containing predicted samples for the current block, which is the block to be coded, can be generated. Here, the predicted block includes predicted samples in the spatial domain (or pixel domain). The predicted block is derived identically by both the encoding device and the decoding device, and the encoding device can increase video coding efficiency by signaling information regarding the residual between the original block and the predicted block (residual information) to the decoding device, rather than the original sample value of the original block itself. The decoding device derives a residual block containing residual samples based on the residual information, can generate a restored block containing restored samples by combining the residual block and the predicted block, and can generate a restored picture containing the restored blocks.

[0074] The above residual information can be generated through transformation and quantization procedures. For example, an encoding device may derive a residual block between the original block and the predicted block, perform a transformation procedure on residual samples (residual sample array) included in the residual block to derive transformation coefficients, perform a quantization procedure on the transformation coefficients to derive quantized transformation coefficients, and signal the related residual information to a decoding device (via a bitstream). Here, the residual information may include information such as value information, position information, transformation technique, transformation kernel, and quantization parameters of the quantized transformation coefficients. The decoding device may perform an inverse quantization / inverse transformation procedure based on the residual information and derive residual samples (or residual blocks). The decoding device may generate a reconstructed picture based on the predicted block and the residual block. The encoding device can also derive a residual block by inversely quantizing / inversely transforming the quantized transform coefficients for reference to inter-predicting of the picture, and generate a restored picture based thereon.

[0075] In this document, at least one of quantization / inverse quantization and / or transformation / inverse transformation may be omitted. If the quantization / inverse quantization is omitted, the quantized transformation coefficients may be called transformation coefficients. If the transformation / inverse transformation is omitted, the transformation coefficients may be called coefficients or residual coefficients, or for the sake of consistency of expression, they may still be called transformation coefficients.

[0076] In this document, quantized transform coefficients and transform coefficients may be referred to as transform coefficients and scaled transform coefficients, respectively. In this case, residual information may include information regarding the transform coefficient(s), and information regarding said transform coefficient(s) may be signaled through residual coding syntax. Transform coefficients may be derived based on said residual information (or information regarding said transform coefficient(s), and scaled transform coefficients may be derived through inverse transform (scaling) of said transform coefficients. Residual samples may be derived based on the inverse transform (transform) of said scaled transform coefficients. This may be similarly applied / expressed in other parts of this document.

[0077] The prediction unit of the encoding / decoding device can derive prediction samples by performing inter-prediction on a block-by-block basis. Inter-prediction may represent a prediction derived in a manner dependent on data elements (e.g., sample values, or motion information, etc.) of picture(s) other than the current picture. When inter-prediction is applied to the current block, a predicted block (prediction sample array) for the current block can be derived based on a reference block (reference sample array) specified by a motion vector on the reference picture pointed to by the reference picture index. At this time, to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information of the current block can be predicted on a block, sub-block, or sample basis, based on the correlation of motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include information on the inter-prediction type (L0 prediction, L1 prediction, Bi prediction, etc.). When inter-prediction is applied, neighboring blocks may include spatial neighboring blocks existing within the current picture and temporal neighboring blocks existing in the reference picture. The reference picture containing the above reference block and the reference picture containing the above temporal surrounding block may be the same or different. The above temporal surrounding block may be called by names such as collocated reference block, collocated CU (colCU), etc., and the reference picture containing the above temporal surrounding block may be called collocated picture (colPic). For example, a list of motion information candidates may be constructed based on the surrounding blocks of the current block, and a flag or index information indicating which candidate is selected (used) to derive the motion vector and / or reference picture index of the current block may be signaled.Inter-prediction can be performed based on various prediction modes; 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 surrounding block. In the case of skip mode, unlike merge mode, a residual signal may not be transmitted. In the case of motion vector prediction (MVP) mode, the motion vector of the selected surrounding block is used as a motion vector predictor, and the motion vector difference can be signaled. In this case, the motion vector of the current block can be derived by using the sum of the motion vector predictor and the motion vector difference.

[0078] The above motion information may include L0 motion information and / or L1 motion information depending on the inter-prediction type (L0 prediction, L1 prediction, Bi prediction, etc.). A motion vector in the L0 direction may be called an L0 motion vector or MVL0, and a motion vector in the L1 direction may be called an L1 motion vector or MVL1. A prediction based on an L0 motion vector may be called an L0 prediction, a prediction based on an L1 motion vector may be called an L1 prediction, and a prediction based on both the L0 motion vector and the L1 motion vector may be called a pair (Bi) prediction. Here, the L0 motion vector may represent a motion vector associated with reference picture list L0 (L0), and the L1 motion vector may represent a motion vector associated with reference picture list L1 (L1). Reference picture list L0 may include pictures that are prior to the current picture in output order as reference pictures, and reference picture list L1 may include pictures that are subsequent to the current picture in output order. The aforementioned previous pictures may be referred to as forward (reference) pictures, and the aforementioned subsequent pictures may be referred to as reverse (reference) pictures. The reference picture list L0 may include additional pictures that are output later than the current picture as reference pictures. In this case, within the reference picture list L0, the previous pictures may be indexed first, and the subsequent pictures may be indexed next. The reference picture list L1 may include additional pictures that are output earlier than the current picture as reference pictures. In this case, within the reference picture list L1, the subsequent pictures may be indexed first, and the previous pictures may be indexed next. Here, the output order may correspond to the POC (picture order count) order.

[0079] Figure 4 illustrates an exemplary hierarchical structure for a coded image / video.

[0080] Referring to Figure 4, the coded image / video is divided into a VCL (video coding layer) that handles the decoding processing of the image / video and the image / video itself, a subsystem that transmits and stores the encoded information, and a NAL (network abstraction layer) that exists between the VCL and the subsystem and is responsible for network adaptation functions.

[0081] In VCL, VCL data containing compressed image data (slice data) can be generated, or parameter sets containing information such as Picture Parameter Set (PPS), Sequence Parameter Set (SPS), and Video Parameter Set (VPS), or SEI (Supplemental Enhancement Information) messages that are additionally required in the decoding process of the image can be generated.

[0082] In NAL, a NAL unit can be created by adding header information (NAL unit header) to the Raw Byte Sequence Payload (RBSP) generated in VCL. In this case, the RBSP refers to slice data, parameter sets, SEI messages, etc. generated in VCL. The NAL unit header may include NAL unit type information specified according to the RBSP data included in the NAL unit.

[0083] As illustrated in the figure above, NAL units can be classified into VCL NAL units and Non-VCL NAL units depending on the RBSP generated in VCL. A VCL NAL unit may refer to a NAL unit containing information about an image (slice data), and a Non-VCL NAL unit may refer to a NAL unit containing information necessary to decode an image (parameter set or SEI message).

[0084] The aforementioned VCL NAL unit and Non-VCL NAL unit can be transmitted over a network by attaching header information according to the data specifications of the underlying system. For example, the NAL unit can be transformed into a data format of a specified specification, such as H.266 / VVC file format, RTP (Real-time Transport Protocol), TS (Transport Stream), etc., and transmitted over various networks.

[0085] As described above, the NAL unit type can be determined according to the RBSP data structure included in the NAL unit, and information about this NAL unit type can be stored in the NAL unit header and signaled.

[0086] For example, NAL units can be broadly classified into VCL NAL unit types and Non-VCL NAL unit types depending on whether they contain information about the image (slice data). VCL NAL unit types can be classified according to the properties and types of the picture included in the VCL NAL unit, while Non-VCL NAL unit types can be classified according to the types of parameter sets.

[0087] The following is an example of a NAL unit type specified according to the type of parameter set included in the Non-VCL NAL unit type.

[0088] - APS (Adaptation Parameter Set) NAL unit: Type for the NAL unit containing the APS

[0089] - DPS (Decoding Parameter Set) NAL unit: Type for the NAL unit containing the DPS

[0090] - VPS (Video Parameter Set) NAL unit: Type for the NAL unit containing the VPS

[0091] - SPS (Sequence Parameter Set) NAL unit: Type for the NAL unit containing the SPS

[0092] - PPS(Picture Parameter Set) NAL unit: Type for the NAL unit containing the PPS

[0093] - PH (Picture header) NAL unit: Type for NAL unit containing PH

[0094] The above-described NAL unit types have syntax information for the NAL unit type, and said syntax information can be stored in the NAL unit header and signaled. For example, said syntax information may be nal_unit_type, and NAL unit types may be specified by the nal_unit_type value.

[0095] Meanwhile, as described above, a single picture may include multiple slices, and a single slice may include a slice header and slice data. In this case, a picture header may be additionally added for multiple slices (slice header and slice data set) within a single picture. The picture header (picture header syntax) may include information / parameters that can be commonly applied to the picture. In this document, a slice may be used interchangeably or replaced with a tile group. Additionally, in this document, a slice header may be used interchangeably or replaced with a type group header.

[0096] The slice header (slice header syntax, slice header information) may include information / parameters that can be commonly applied to the slice. The APS (APS syntax) or PPS (PPS syntax) may include information / parameters that can be commonly applied to one or more slices or pictures. The SPS (SPS syntax) may include information / parameters that can be commonly applied to one or more sequences. The VPS (VPS syntax) may include information / parameters that can be commonly applied to multiple layers. The DPS (DPS syntax) may include information / parameters that can be commonly applied to the entire video. The DPS may include information / parameters related to the concatenation of a CVS (coded video sequence). In this document, the term High level syntax (HLS) may include at least one of the above APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, picture header syntax, and slice header syntax.

[0097] In this document, the video information encoded from an encoding device to a decoding device and signaled in the form of a bitstream includes not only information related to picture partitioning, intra / inter prediction information, residual information, and in-loop filtering information, but may also include 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. Additionally, the video information may further include information from the NAL unit header.

[0098] Meanwhile, to compensate for the difference between the original image and the restored image caused by errors occurring during compression encoding processes such as quantization, an in-loop filtering procedure may be performed on the restored samples or restored pictures as described above. As described above, in-loop filtering may be performed in the filter section of the encoding device and the filter section of the 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 SAO procedure are completed. However, even in this case, the deblocking filtering procedure and / or SAO procedure may be omitted.

[0099] A detailed explanation regarding picture restoration and filtering will be provided below. In video coding, restoration blocks may be generated based on intra prediction and inter prediction on a block-by-block basis, and a restored picture containing the restoration blocks may be generated. If the current picture / slice is I picture / slice, the blocks included in the current picture / slice may be restored based solely on intra prediction. Meanwhile, if the current picture / slice is P or B picture / slice, the blocks included in the current picture / slice may be restored based on either intra prediction or inter prediction. In this case, intra prediction may be applied to some blocks within the current picture / slice, while inter prediction may be applied to the remaining blocks.

[0100] Intra prediction may represent a prediction that generates prediction samples for the current block based on reference samples within the picture to which the current block belongs (hereinafter, the current picture). When intra prediction is applied to the current block, surrounding reference samples to be used for the intra prediction of the current block may be derived. The surrounding reference samples of the current block may include a sample adjacent to the left boundary of the current block of size nWxnH and a total of 2xnH samples adjacent to the bottom-left, a sample adjacent to the top boundary of the current block and a total of 2xnW samples adjacent to the top-right, and one sample adjacent to the top-left of the current block. Alternatively, the surrounding reference samples of the current block may include multiple columns of upper surrounding samples and multiple rows of left surrounding samples. Additionally, the surrounding reference samples of the current block may include a total of nH samples adjacent to the right boundary of the current block of size nWxnH, 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.

[0101] However, some of the surrounding reference samples of the current block may not yet be decoded or may not be available. In this case, the decoder may construct the surrounding reference samples to be used for prediction by substituting the unavailable samples with available samples. Alternatively, the surrounding reference samples to be used for prediction may be constructed through the interpolation of available samples.

[0102] When neighboring reference samples are derived, a prediction sample can be derived based on the average or interpolation of the neighboring reference samples of the current block, and (ii) the prediction sample can also be derived based on a reference sample existing in a specific (prediction) direction with respect to the prediction sample among the neighboring reference samples of the current block. Case (i) may be called a non-directional mode or non-angular mode, and case (ii) may be called a directional mode or angular mode. Additionally, the prediction sample may be generated through interpolation between the first neighboring sample and the second neighboring sample located in the opposite direction of the prediction direction of the intra prediction mode of the current block relative to the prediction sample of the current block among the neighboring reference samples. The above case may be called Linear Interpolation Intra Prediction (LIP). Furthermore, chroma prediction samples may be generated based on luminance samples using a linear model. This case may be called LM mode. In addition, a provisional prediction sample of the current block may be derived based on filtered surrounding reference samples, and a prediction sample of the current block may be derived by performing a weighted sum of the provisional prediction sample and at least one reference sample derived according to the intra prediction mode among the existing surrounding reference samples, i.e., unfiltered surrounding reference samples. The above case may be called PDPC (Position dependent intra prediction).In addition, intra-prediction coding can be performed by selecting the reference sample line with the highest prediction accuracy among the surrounding multiple reference sample lines of the current block, deriving a prediction sample using a reference sample located in the prediction direction from that line, and signaling the used reference sample line to a decoding device. The above-described case may be referred to as multi-reference line (MRL) intra prediction or MRL-based intra prediction. Furthermore, the current block may be divided into vertical or horizontal subpartitions to perform intra prediction based on the same intra prediction mode, while deriving and utilizing surrounding reference samples at the subpartition level. That is, in this case, the intra prediction mode for the current block is applied identically to the subpartitions, but intra prediction performance can be improved depending on the circumstances by deriving and utilizing surrounding reference samples at the subpartition level. This prediction method may be referred to as intra sub-partitions (ISP) or ISP-based intra prediction. The above-described intra prediction methods may be referred to as intra prediction types to distinguish them from the intra prediction mode in Section 1.2. The above-mentioned intra-prediction type may be referred to by various terms, such as intra-prediction technique or additional intra-prediction mode. For example, the above-mentioned intra-prediction type (or additional intra-prediction mode, etc.) may include at least one of the aforementioned LIP, PDPC, MRL, and ISP. A general intra-prediction method excluding specific intra-prediction types such as LIP, PDPC, MRL, and ISP may be referred to as a normal intra-prediction type. The normal intra-prediction type may be generally applied when specific intra-prediction types such as the above are not applied, and prediction may be performed based on the aforementioned intra-prediction mode. Meanwhile, post-processing filtering may be performed on the derived prediction samples as necessary.

[0103] Specifically, the intra-prediction procedure may include an intra-prediction mode / type determination step, a peripheral reference sample derivation step, and an intra-prediction mode / type-based prediction sample derivation step. Additionally, a post-filtering step for the derived prediction samples may be performed as needed.

[0104] A modified restored picture may be generated through an in-loop filtering procedure, and the modified restored picture may be output as a decoded picture from a decoding device, or stored in the decoded picture buffer or memory of an encoding / decoding device to be used as a reference picture in an inter-prediction procedure during subsequent encoding / decoding of the picture. As described above, the in-loop filtering procedure may include a deblocking filtering procedure, a sample adaptive offset (SAO) procedure, and / or an adaptive loop filter (ALF) procedure. In this case, one or some of the deblocking filtering procedure, the sample adaptive offset (SAO) procedure, the adaptive loop filter (ALF) procedure, and the bilateral filter procedure may be applied sequentially, or all of them may be applied sequentially. For example, the SAO procedure may be performed after the deblocking filtering procedure is applied to the restored picture. Or, for example, the ALF procedure may be performed after the deblocking filtering procedure is applied to the restored picture. This can be done in the same way in the encoding device.

[0105] Deblocking filtering is a filtering technique that removes distortion occurring at the boundaries between blocks in a restored picture. The deblocking filtering procedure may, for example, derive a target boundary in the 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 the prediction mode of two blocks adjacent to the target boundary, the difference in motion vectors, whether the reference picture is identical, the existence of non-zero valid coefficients, etc.

[0106] SAO is a method that compensates for the offset difference between the restored picture and the original picture on a sample-by-sample basis, and can be applied based on types such as band offset and edge offset. According to SAO, samples are classified into different categories based on each SAO type, and an offset value can be added to each sample based on the category. Filtering information for SAO may include information regarding whether SAO is applied, SAO type information, and SAO offset value information. SAO may also be applied to the restored picture after the deblocking filtering described above has been applied.

[0107] Adaptive Loop Filter (ALF) is a technique that filters a restored picture on a sample-by-sample basis using filter coefficients determined by the filter shape. An encoding device can determine whether to apply ALF, the ALF shape, and / or ALF filtering coefficients by comparing the restored picture with the original picture, and can signal this information to a decoding device. In other words, the filtering information for ALF may include information regarding whether to apply ALF, information on the ALF filter shape, and information on the ALF filtering coefficients. ALF may also be applied to the restored picture after the aforementioned deblocking filtering has been applied.

[0108] FIG. 5 illustrates a picture according to one embodiment of the present document. The exemplary picture of FIG. 5 may be divided into subpictures, slices, and tiles.

[0109] Referring to FIG. 5, the picture can be divided into subpictures. For example, a subpicture may include one or more slices. A slice may represent a rectangular area of ​​the picture. Additionally, the picture may be divided into tiles. For example, a rectangular slice may include only a subset of a single tile. That is, in FIG. 5, two rectangular slices share the same tile, and the two rectangular slices may each belong to different subpictures. Problems that may arise from a case like FIG. 5 and solutions thereto will be described later.

[0110] In one example, a picture / subpicture can be coded based on subpicture(s) / slice(s) / tile(s). An encoding device can encode the current picture based on a subpicture / slice / tile structure, or the encoding device can encode one or more subpictures (including slices / tiles) of the current picture and output a (sub)bitstream containing (encoded) information regarding the subpictures. A decoding device can decode one or more subpictures within the current picture based on a (sub)bitstream containing (encoded) information regarding the subpicture(s) / slice(s) / tile(s).

[0111] FIG. 6 illustrates a subpicture / slice / tile-based encoding method according to one embodiment of the present document.

[0112] The encoder may divide the (input) picture into multiple (or one or more) subpicture(s) / slice(s) / tile(s). Each subpicture may be encoded individually / independently, and a bitstream may be output. Here, the bitstream for a subpicture may be referred to as a substream, subset, or sub-bitstream. Information regarding a subpicture / slice / tile may include the information / syntax element(s) described in this document. For example, information regarding a slice may include information related to the number of slices signaled for each picture / subpicture, the width / height of slices within a tile, etc. For example, information regarding a tile may include information related to the number of tiles (e.g., number of tile columns and / or rows) and information related to the size of each tile (e.g., width and / or height).

[0113] The encoder can encode one or more subpictures using information about the subpictures. The encoder can encode one or more slices / tiles using information about the slices / tiles.

[0114] FIG. 7 illustrates a subpicture / slice / tile-based decoding method according to one embodiment of the present document.

[0115] The decoder can decode one or more subpictures (including slices / tiles) and output one or more decoded subpicture(s) or output a current picture containing subpictures. The bitstream may include sub-stream(s) or sub-bitstream(s) for the subpicture(s). As described above, information regarding subpictures / slices / tiles may be constructed within the high-level syntax (HLS) contained in the bitstream. The decoder can derive one or more subpictures based on information regarding subpictures. The decoder can derive one or more slices / tiles based on information regarding slices / tiles. The decoder can decode all or part of the subpictures. The decoder can decode subpictures (including the current block (or CU)), CTUs, slices, and / or tiles based on CABAC, prediction, residual processing (transform, quantization), in-loop filtering, etc. Accordingly, decoded subpicture(s) may be output. The decoded subpicture(s) may include restored / decoded block(s). Decoded subpictures within an output subpicture set (OPS) may also be output. For example, if the picture is related to a 360-degree or omnidirectional image / video, some of it may be rendered, in which case only some of the total subpictures 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 is available indicating whether in-loop filtering is available across subpicture boundaries, the decoder may apply an in-loop filtering procedure (e.g., deblocking filtering) to the subpicture boundary located between two subpictures.For example, if the subpicture boundary is the same as the picture boundary, the in-loop filtering procedure for the subpicture boundaries may not be applied / performed.

[0116] In the embodiments of this document, image / video information may include HLS, and HLS may include information regarding subpicture(s) / slice(s) / tile(s). Information regarding subpicture(s) may include information representing one or more subpictures within the current picture. Information regarding slice(s) may include information representing one or more slices within the current picture, subpicture, or tile. Information regarding tile(s) may include information representing one or more tiles within the current picture, subpicture, or slice. A picture may include a tile containing one or more slices, and / or a slice containing one or more tiles. Additionally, a picture may include a subpicture containing one or more slices / tiles.

[0117] The following tables represent the syntax related to the picture divisions (subpictures / slices / tiles) described above. Information regarding subpicture(s) / slice(s) / tile(s) may include the syntax elements within the following tables.

[0118] The following table shows the syntax of a sequence parameter set (SPS) based on picture segmentation (subpicture / slice / tile).

[0119]

[0120] The following table shows the syntax of a picture parameter set (PPS) based on picture segmentation (subpicture / slice / tile).

[0121]

[0122] The following table shows the syntax of a picture splitting (subpicture / slice / tile) based slice header.

[0123]

[0124] FIG. 8 is a flowchart illustrating a filtering-based encoding method in an encoding device. The method of FIG. 8 may include steps S800 to S830.

[0125] In step S800, the encoding device can generate a restored picture. Step S800 can be performed based on the procedure for generating a restored picture (or restored samples) described above.

[0126] In step S810, the encoding device may determine whether in-loop filtering is applied (across virtual boundaries) based on information related to in-loop filtering. Here, the in-loop filtering may include at least one of the aforementioned deblocking filtering, SAO, or ALF.

[0127] In step S820, the encoding device may generate a modified restored picture (modified restored samples) based on the decision of step S810. Here, the modified restored picture (modified restored samples) may be a filtered restored picture (filtered restored samples).

[0128] In step S830, the encoding device can encode image / video information containing in-loop filtering related information based on an in-loop filtering procedure.

[0129] FIG. 9 is a flowchart illustrating a filtering-based decoding method in a decoding device. The method of FIG. 9 may include steps S900 to S930.

[0130] In step S900, the decoding device can obtain image / video information including in-loop filtering related information from the bitstream. Here, the bitstream may be based on encoded image / video information transmitted from the encoding device.

[0131] In step S910, the decoding device can generate a restored picture. Step S910 can be performed based on the procedure for generating a restored picture (or restored samples) described above.

[0132] In step S920, the decoding device can determine whether in-loop filtering is applied (across virtual boundaries) based on information related to in-loop filtering. Here, the in-loop filtering may include at least one of the aforementioned deblocking filtering, SAO, or ALF.

[0133] In step S930, the decoding device may generate a modified restored picture (modified restored samples) based on the decision of step S920. Here, the modified restored picture (modified restored samples) may be a filtered restored picture (filtered restored samples).

[0134] As described above, an in-loop filtering procedure may be applied to the restored picture. In this case, to further enhance the subjective / objective visual quality of the restored picture, a virtual boundary may be defined, and the in-loop filtering procedure may be applied across said virtual boundary. The said virtual boundary may include discontinuous edges, such as those in 360-degree images, VR images, or PIP (picture in picture). For example, said virtual boundary may exist at a predetermined agreed-upon location, and its existence and / or location may be signaled. As an example, said virtual boundary may be located at the upper 4th sample line of the CTU row (specifically, for example, above the upper 4th sample line of said CTU row). As another example, information regarding the existence and / or location of said virtual boundary may be signaled via HLS. As described above, said HLS may include SPS, PPS, Pick the header, Slice header, etc.

[0135] High-level syntax signaling and semantics regarding the embodiments of this document will be described below.

[0136] One embodiment of this document may include a method for controlling loop filters. This method for controlling loop filters may be applied to a restored picture. In-loop filters (loop filters) may be used for decoding encoded bitstreams. Loop filters may include the deblocking, SAO, and ALF described above. SPS may include flags associated with deblocking, SAO, and ALF, respectively. The flags may indicate whether each tool is available for coding CLVS (coded layer video sequence) and CVS (coded video sequence) that reference the SPS.

[0137] If the loop filters are available for CVS, the application of the loop filters can be controlled so as not to cross specific boundaries. For example, whether the loop filters cross subpicture boundaries can be controlled. Additionally, whether the loop filters cross tile boundaries can be controlled. Furthermore, whether the loop filters cross virtual boundaries can be controlled. Here, virtual boundaries can be defined on CTUs based on the availability of line buffers.

[0138] Regarding whether an in-loop filtering procedure is performed across a virtual boundary, the in-loop filtering information may include at least one of an SPS virtual boundary availability flag (virtual boundary availability flag within SPS), an SPS virtual boundary existence flag, a picture header virtual boundary existence flag, an SPS picture header virtual boundary existence flag, and information regarding the location of the virtual boundary.

[0139] In the embodiments included in this document, information regarding the location of a virtual boundary may include information regarding the x-coordinate of a vertical virtual boundary and / or information regarding the y-coordinate of a horizontal virtual boundary. Specifically, information regarding the location of a virtual boundary may include information regarding the x-coordinate of a vertical virtual boundary and / or the y-coordinate of a horizontal virtual boundary in units of luma samples. Additionally, information regarding the location of a virtual boundary may include information regarding the number of information (syntax elements) regarding the x-coordinate of a vertical virtual boundary existing in the SPS. Additionally, information regarding the location of a virtual boundary may include information regarding the number of information (syntax elements) regarding the y-coordinate of a horizontal virtual boundary existing in the SPS. Alternatively, information regarding the location of a virtual boundary may include information regarding the number of information (syntax elements) regarding the x-coordinate of a vertical virtual boundary existing in the picture header. Additionally, information regarding the location of a virtual boundary may include information regarding the number of information (syntax elements) regarding the y-coordinate of a horizontal virtual boundary existing in the picture header.

[0140] The following tables show exemplary syntax and semantics of the sequence parameter set (SPS) according to the present embodiment.

[0141]

[0142]

[0143] The following tables show exemplary syntax and semantics of the picture parameter set (PPS) according to the present embodiment.

[0144]

[0145]

[0146] The following tables show exemplary syntax and semantics of a picture header according to the present embodiment.

[0147]

[0148]

[0149]

[0150]

[0151] The following tables show exemplary syntax and semantics of a slice header according to the present embodiment.

[0152]

[0153]

[0154] Below, information related to sub-pictures, information related to virtual boundaries that can be used in in-loop filtering, and their signaling will be explained.

[0155] In one example, two different rectangular slices can belong to different subpictures while sharing the same tile. In this case, a problem may arise where the complexity of coding increases.

[0156] To simplify picture segmentation, one embodiment of this document may include examples of conditions for a picture that is segmented into two or more subpictures. In one example, all CTUs within a single tile may belong to the same subpictures. In another example, all CTUs within a subpicture may belong to the same tile. These two examples may be applied individually, sequentially, or in combination for image / video coding. Additionally, in one embodiment of this document, if a subpicture includes CTUs that are a subset of all CTUs within a single tile, said subpicture may not include CTUs belonging to another tile.

[0157] In signaling for the current picture, if the value of subpic_present_flag is 1, the number of subpictures within each picture referencing the SPS can be 1 (the value of sps_num_subpics_minus1 is 0). This condition was created to support a subpicture extraction use case where a subpicture coded independently from the bitstream can be extracted to form a different bitstream without changing values ​​lower than the parameter sets. 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] still exist. In this situation, the existence of these syntax elements is not only redundant, but if an incorrect value is signaled for the corresponding syntax element, it can make the decoder's behavior unpredictable. For example, if the value of subpics_present_flag is 1 and the value of sps_num_subpics_minus1 is 0, this means there is only one subpicture (the picture itself), and the value of subpic_treat_as_pic_flag[0] is equal to 1. In this case, if the corresponding value is signaled as 0, a contradictory problem may occur during the decoding process.

[0158] To address the problem described in the paragraph above, one embodiment of this document includes examples of conditions that can be applied when subpicture signaling exists (e.g., the value of subpic_present_flag is 1) and only one subpicture exists within the picture (e.g., the value of sps_num_subpics_minus1 is 0). The examples of conditions may be as shown in the following table.

[0159]

[0160] In one example, if subpicture signaling exists and the locations of virtual boundaries are present in the picture header, there is a problem in that the picture header must be rewritten to verify the correct signaling of the virtual boundary locations in subpicture extraction and merging scenarios. This may contradict the design objective of subpicture extraction / merging, which does not require bitstream rewriting for NAL units at a lower level than the parameter sets.

[0161] To address the problem described in the above paragraph, in one embodiment of this document, when subpicture signaling exists (e.g., when subpicture signaling exists in the SPS), signaling of virtual boundary locations may not be included in the picture header. In one example, when subpicture signaling exists, information regarding the locations of virtual boundaries may be included in the high-level parameter set. For example, when subpicture signaling exists, information regarding the locations of virtual boundaries may be included in the SPS. Alternatively, when subpicture signaling exists, information regarding the locations of virtual boundaries may be included in the PPS.

[0162] In one embodiment of the present document, if subpicture ID signaling is present (value of sps_subpic_id_present_flag is 1), all subpictures may be independently coded subpictures (value of subpic_treated_as_pic_flag[i] is 1). In this case, the location of the subpicture ID signaling (e.g., SPS, PPS, or picture header) may be irrelevant.

[0163] According to the embodiments of this document in conjunction with the tables above, whether virtual boundary-related information (e.g., virtual boundary location information) is signaled in the sequence parameter set can be determined based on whether sub-picture information exists. For example, if sub-picture information exists for the sequence, virtual boundary-related information (e.g., virtual boundary location information) can be signaled in the sequence parameter set. Accordingly, the virtual boundary-based coding method according to the embodiments of this document can be efficiently performed without rewriting or modifying high-level syntax.

[0164] Additionally, according to embodiments of this document, a (decoded) picture may be composed of subpictures. Information regarding said subpictures may be obtained by a decoding device, and a decoding procedure may be performed based on the information regarding said subpictures. In one example, based on the information regarding said subpictures, the decoding device may determine a location (e.g., SPS) where information regarding the locations of virtual boundaries for in-loop filtering is signaled.

[0165] FIGS. 10 and 11 schematically illustrate an example of a video / image encoding method and related components according to the embodiment(s) of the present document.

[0166] The method disclosed in FIG. 10 may be performed by the encoding device disclosed in FIG. 2 or FIG. 11. Specifically, for example, S1000 to S1020 of FIG. 10 may be performed by the residual processing unit (230) of the encoding device of FIG. 11, S1040 of FIG. 10 may be performed by the filtering unit (260) of the encoding device of FIG. 11, and S1050 of FIG. 10 may be performed by the entropy encoding unit (240) of the encoding device of FIG. 11. Additionally, although not shown in FIG. 10, prediction samples 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 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.

[0167] The encoding device can derive subpictures. The encoding device can divide the current picture into subpictures. The encoding device can determine the size (e.g., height / width) of the subpictures. Additionally, the encoding device can determine the number of subpicture(s) included in the current picture.

[0168] The encoding device may generate subpicture-related information. For example, the encoding device may generate subpicture-related information based on the number of subpicture(s) included in the current picture, the size of the subpictures (e.g., height / width), and / or the boundaries of the subpictures. The subpicture-related information may include information regarding the existence of a subpicture, information regarding whether a subpicture is treated as a picture, information regarding the number of subpicture(s) included in the current picture, information regarding the size of the subpictures (e.g., height / width), information regarding whether the boundaries of the subpictures match the boundaries of the current picture, and / or information regarding the IDs of the subpictures.

[0169] Referring to FIG. 10, the encoding device can derive residual samples (S1000). The encoding device can derive residual samples for the current block, and the residual samples for the current block can be derived based on the original samples and predicted samples of the current block. Specifically, the encoding device can derive predicted samples of 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. Residual samples can be derived based on the predicted samples and original samples.

[0170] The encoding device can derive transformation coefficients (S1010). The encoding device can derive transformation coefficients based on a transformation procedure for the residual samples. For example, the transformation procedure may include at least one of DCT, DST, GBT, or CNT.

[0171] The encoding device can derive quantized transformation coefficients (S1020). The encoding device can derive quantized transformation coefficients based on a quantization procedure for the transformation coefficients. The quantized transformation coefficients may have a one-dimensional vector form based on the coefficient scan order.

[0172] The encoding device can generate residual information (S1030). The encoding device can generate residual information based on the residual samples for the current block. The encoding device can generate residual information representing the quantized transform coefficients. The residual information can be generated through various encoding methods such as exponential Golomb, CAVLC, CABAC, etc.

[0173] The encoding device can generate restoration samples. The encoding device can generate restoration samples based on the residual information. The restoration samples can be generated by adding residual samples based on the residual information with prediction samples. Specifically, the encoding device performs a prediction (intra or inter prediction) for the current block and can generate restoration samples based on the original samples and the prediction samples generated from the prediction.

[0174] Reconstructed samples may include reconstructed luminance samples and reconstructed chroma samples. Specifically, residual samples may include residual luminance samples and residual chroma samples. Residual luminance samples may be generated based on original luminance samples and predicted luminance samples. Residual chroma samples may be generated based on original chroma samples and predicted chroma samples. An encoding device may derive transformation coefficients (luma transformation coefficients) for the residual luminance samples and / or transformation coefficients (chroma transformation coefficients) for the residual chroma samples. Quantized transformation coefficients may include quantized luminance transformation coefficients and / or quantized chroma transformation coefficients.

[0175] The encoding device can determine whether an in-loop filtering procedure is performed across virtual boundaries (S1040). Based on the determination, the encoding device can generate information regarding the number of virtual boundaries and the locations of the virtual boundaries. For example, the encoding device can generate information regarding the number of vertical virtual boundaries, information regarding the locations of the vertical virtual boundaries, information regarding the number of horizontal virtual boundaries, and information regarding the locations of the horizontal virtual boundaries.

[0176] The encoding device can generate in-loop filtering information for the restoration samples of the current picture. The encoding device can perform an in-loop filtering procedure for the restoration samples and can generate in-loop filtering information based on said in-loop filtering procedure. For example, the in-loop filtering information may include information regarding virtual boundaries described in detail in this document (SPS virtual boundary availability flag, picture header virtual boundary availability flag, SPS virtual boundary presence flag, picture header virtual boundary presence flag, information regarding the locations of virtual boundaries, etc.). In one example, the encoding device can generate in-loop filtering information based on information regarding the number of vertical virtual boundaries, information regarding the locations of vertical virtual boundaries, information regarding the number of horizontal virtual boundaries, and information regarding the locations of horizontal virtual boundaries.

[0177] An encoding device can encode video / image information (S1050). The image information may include residual information, prediction-related information, subpicture-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.

[0178] The above image / video information may include various information according to embodiments of the present document. For example, the above image / video information may include information disclosed in at least one of Tables 1 to 12 described above.

[0179] In one embodiment, the image information may include a sequence parameter set (SPS). Based on whether the SPS includes information related to a subpicture, it may be determined whether the SPS includes additional information related to a virtual boundary.

[0180] In one embodiment, additional information related to the virtual boundaries may include the number of virtual boundaries and the locations of the virtual boundaries.

[0181] In one embodiment, additional information related to the virtual boundaries may include information regarding the number of vertical virtual boundaries, information regarding the locations of the vertical virtual boundaries, information regarding the number of horizontal virtual boundaries, and information regarding the locations of the horizontal virtual boundaries.

[0182] In one embodiment, the image information may include a subpicture present flag (e.g., subpic_present_flag). Based on the subpicture present flag, it may be determined whether the SPS includes information related to the subpicture.

[0183] In one embodiment, the image information may include a subpicture ID presence flag. Based on the value of the subpicture ID presence flag being 1, the subpictures within the current picture may be independently-coded subpictures.

[0184] In one embodiment, the current picture may include subpictures and tiles. Coding tree units (CTUs) within a single tile may belong to the same subpicture.

[0185] In one embodiment, the current picture may include subpictures and tiles. Coding tree units (CTUs) within a single subpicture may belong to the same tile.

[0186] In one embodiment, the SPS may include an SPS virtual boundary presence flag related to whether the SPS includes additional information related to the virtual boundaries. Based on whether the SPS includes information related to the subpicture, the value of the SPS virtual boundary presence flag may be determined to be 1.

[0187] In one embodiment, the image information may include picture header information. Based on the fact that the SPS includes subpicture-related information, additional information related to the virtual boundaries may not be included in the picture header.

[0188] In one embodiment, based on the fact that the SPS includes information related to the subpicture, the SPS may include additional information related to the virtual boundaries.

[0189] FIGS. 12 and 13 schematically illustrate an example of a video / image decoding method and related components according to the embodiment(s) of the present document.

[0190] The method disclosed in FIG. 12 may be performed by the decoding device disclosed in FIG. 12 or FIG. 13. Specifically, for example, S1200 of FIG. 12 may be performed by the entropy decoding unit (310) of the decoding device, S1210 to S1230 of FIG. 12 may be performed by the residual processing unit (320) of the decoding device, S1240 may be performed by the residual processing unit (320) and / or the addition unit (340) of the decoding device, and S1250 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.

[0191] Referring to FIG. 12, a decoding device can receive / acquire video / image information (S1200). The video / image information may include residual information, prediction-related information, subpicture-related information, and / or in-loop filtering-related information. The decoding device can receive / acquire the video / image information through a bitstream.

[0192] The above image / video information may include various information according to embodiments of the present document. For example, the above image / video information may include information disclosed in at least one of Tables 1 to 12 described above.

[0193] The decoding device can derive subpicture(s) for the current picture. The decoding device can derive subpicture(s) based on subpicture-related information obtained based on the bitstream. Based on the subpicture-related information, the number of subpicture(s), the size of the subpicture(s), and whether the subpicture(s) are treated as pictures can be determined. The residual samples and / or prediction samples described below can be generated based on the subpicture(s).

[0194] The decoding device can derive quantized transformation coefficients (S1210). The decoding device can derive quantized transformation coefficients based on the residual information. The quantized transformation coefficients may have a one-dimensional vector form based on the coefficient scan order. The quantized transformation coefficients may include quantized luminance transformation coefficients and / or quantized chroma transformation coefficients.

[0195] The decoding device can derive transformation coefficients (S1220). The decoding device can derive transformation coefficients based on an inverse quantization procedure for the quantized transformation coefficients. The decoding device can derive luminance transformation coefficients through inverse quantization based on the quantized luminance transformation coefficients. The decoding device can derive chroma transformation coefficients through inverse quantization based on the quantized chroma transformation coefficients.

[0196] The decoding device can generate / derive residual samples (S1230). The decoding device can derive residual samples based on an inverse transform procedure for the transformation coefficients. The decoding device can derive residual luminance samples through an inverse transform procedure based on the luminance transformation coefficients. The decoding device can derive residual chroma samples through an inverse transform procedure based on the chroma transformation coefficients.

[0197] The decoding device can generate / derive reconstructed samples (S1240). For example, the decoding device can generate / derive reconstructed luminance samples and / or reconstructed chroma samples. The decoding device can generate reconstructed luminance samples and / or reconstructed chroma samples based on the residual information. The decoding device can generate reconstructed samples based on the residual information. The reconstructed samples may include reconstructed luminance samples and / or reconstructed chroma samples. The luminance component of the reconstructed samples may correspond to the reconstructed luminance samples, and the chroma component of the reconstructed samples may correspond to the reconstructed chroma samples. The decoding device can generate predicted luminance samples and / or predicted chroma samples through a prediction procedure. The decoding device can generate reconstructed luminance samples based on the predicted luminance samples and the residual luminance samples. The decoding device can generate reconstructed chroma samples based on the predicted chroma samples and the residual chroma samples. In addition, the decoding device can generate restoration samples of the current picture based on residual samples, prediction samples, and / or subpicture(s).

[0198] The decoding device can generate modified (filtered) restored samples (S1250). The decoding device can generate modified restored samples based on an in-loop filtering procedure for the restored samples. The decoding device can generate modified restored 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 modified restored samples.

[0199] In one embodiment, the image information may include a sequence parameter set (SPS). Based on whether the SPS includes information related to a subpicture, it may be determined whether the SPS includes additional information related to a virtual boundary.

[0200] In one embodiment, additional information related to the virtual boundaries may include the number of virtual boundaries and the locations of the virtual boundaries.

[0201] In one embodiment, additional information related to the virtual boundaries may include information regarding the number of vertical virtual boundaries, information regarding the locations of the vertical virtual boundaries, information regarding the number of horizontal virtual boundaries, and information regarding the locations of the horizontal virtual boundaries.

[0202] In one embodiment, the image information may include a subpicture present flag (e.g., subpic_present_flag). Based on the subpicture present flag, it may be determined whether the SPS includes information related to the subpicture.

[0203] In one embodiment, the image information may include a subpicture ID presence flag. Based on the value of the subpicture ID presence flag being 1, the subpictures within the current picture may be independently-coded subpictures.

[0204] In one embodiment, the current picture may include subpictures and tiles. Coding tree units (CTUs) within a single tile may belong to the same subpicture.

[0205] In one embodiment, the current picture may include subpictures and tiles. Coding tree units (CTUs) within a single subpicture may belong to the same tile.

[0206] In one embodiment, the SPS may include an SPS virtual boundary presence flag related to whether the SPS includes additional information related to the virtual boundaries. Based on whether the SPS includes information related to the subpicture, the value of the SPS virtual boundary presence flag may be determined to be 1.

[0207] In one embodiment, the image information may include picture header information. Based on the fact that the SPS includes subpicture-related information, additional information related to the virtual boundaries may not be included in the picture header.

[0208] In one embodiment, based on the fact that the SPS includes information related to the subpicture, the SPS may include additional information related to the virtual boundaries.

[0209] If residual samples for the current block exist, the decoding device may receive information regarding residuals for the current block. The information regarding residuals may include transformation coefficients regarding residual samples. The decoding device may derive residual samples (or a residual sample array) for the current block based on the residual information. Specifically, the decoding device may derive quantized transformation coefficients based on the residual information. The quantized transformation coefficients may have a one-dimensional vector form based on the coefficient scan order. The decoding device may derive transformation coefficients based on an inverse quantization procedure for the quantized transformation coefficients. The decoding device may derive residual samples based on the transformation coefficients.

[0210] The decoding device can generate reconstructed samples based on (intra) prediction samples and residual samples, and can derive a reconstructed block or a reconstructed picture based on said reconstructed samples. Specifically, the decoding device can generate reconstructed samples based on the sum between the (intra) prediction samples and the residual samples. As previously described, the decoding device may then apply in-loop filtering procedures, such as deblocking filtering and / or SAO procedures, to said reconstructed picture to improve subjective / objective image quality as needed.

[0211] For example, a decoding device can decode a bitstream or encoded information to obtain image information containing all or part of the information (or syntax elements) described above. Additionally, the bitstream or encoded information may be stored in a computer-readable storage medium and may cause the decoding method described above to be performed.

[0212] In the embodiments described above, methods are described based on flowcharts as a series of steps or blocks; however, the embodiments are not limited to the order of the steps, and some steps may occur in a different order or simultaneously with other steps as described above. Furthermore, those skilled in the art will understand that the steps shown in the flowcharts are not exclusive, and other steps may be included, or one or more steps of the flowcharts may be omitted without affecting the scope of the embodiments of this document.

[0213] The method according to the embodiments of the present document described above may be implemented 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, computer, smartphone, set-top box, display device, etc.

[0214] When the embodiments described in this document are implemented in software, the method described above may be implemented as a module (process, function, etc.) that performs the function described above. The module may be stored in memory and executed by a processor. The memory may be located inside or outside the processor and may be connected to the processor by various well-known means. The processor may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices. That is, the embodiments described in this document may be implemented and executed on a processor, microprocessor, controller, or chip. For example, the functional units illustrated in each figure may be implemented and executed 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.

[0215] In addition, the decoding device and encoding device to which the embodiment(s) of this document apply may be included in multimedia broadcasting transmission and reception devices, mobile communication terminals, home cinema video devices, digital cinema video devices, surveillance cameras, video conversation devices, real-time communication devices such as video communication, mobile streaming devices, storage media, camcorders, Video on Demand (VoD) service providers, Over-the-top video (OTT) devices, internet streaming service providers, 3D video devices, virtual reality (VR) devices, augmented reality (AR) devices, video phone video devices, transportation terminals (e.g., vehicle terminals (including autonomous vehicles), airplane terminals, ship terminals, etc.), and medical video devices, and may be used to process video signals or data signals. For example, Over-the-top video (OTT) devices may include game consoles, Blu-ray players, internet-connected TVs, home theater systems, smartphones, tablet PCs, Digital Video Recorders (DVRs), etc.

[0216] Additionally, the processing method to which the embodiment(s) of this document are applied may be produced in the form of a program that is executed by a computer and may be stored on a computer-readable recording medium. Multimedia data having a data structure according to the embodiment(s) of this document may also be stored on 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. Additionally, the computer-readable recording medium includes a medium implemented in the form of a carrier wave (e.g., transmission over the Internet). Additionally, a bitstream generated by an encoding method may be stored on a computer-readable recording medium or transmitted via a wired or wireless communication network.

[0217] Additionally, the embodiment(s) of this document may be implemented as a computer program product by program code, and said program code may be executed on a computer by the embodiment(s) of this document. said program code may be stored on a computer-readable carrier.

[0218] FIG. 14 shows an example of a content streaming system to which the embodiments disclosed in this document can be applied.

[0219] Referring to FIG. 14, a content streaming system to which embodiments of the present document are applied may largely include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0220] The above encoding server compresses content input from multimedia input devices, such as smartphones, cameras, and camcorders, into digital data to generate a bitstream and transmits it to the streaming server. As another example, if multimedia input devices, such as smartphones, cameras, and camcorders, generate the bitstream directly, the encoding server may be omitted.

[0221] The bitstream above may be generated by an encoding method or a bitstream generation method to which the embodiments of the present document are applied, and the streaming server may temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[0222] 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 it to the streaming server, and the streaming server transmits the multimedia data to the user. At this time, the content streaming system may include a separate control server, and in this case, the control server plays the role of controlling commands and responses between each device within the content streaming system.

[0223] The streaming server may receive content from a media storage and / or an encoding server. For example, when receiving content from the encoding server, the content may be received in real time. In this case, to provide a seamless streaming service, the streaming server may store the bitstream for a certain period of time.

[0224] Examples of the above user devices may include mobile phones, smartphones, laptop computers, digital broadcasting terminals, PDAs (personal digital assistants), PMPs (portable multimedia players), navigation systems, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, HMDs (head-mounted displays)), digital TVs, desktop computers, digital signage, etc.

[0225] Each server within the above-mentioned content streaming system can be operated as a distributed server, and in this case, data received from each server can be processed in a distributed manner.

[0226] The claims described in this specification may be combined in various ways. For example, the technical features of the method claims in this specification may be combined to be implemented as a device, and the technical features of the device claims in this specification may be combined to be implemented as a method. Furthermore, the technical features of the method claims and the technical features of the device claims in this specification may be combined to be implemented as a device, and the technical features of the method claims and the technical features of the device claims in this specification may be combined to be implemented as a method.

Claims

Claim 1 A video decoding method performed by a decoding device, comprising: acquiring video information including residual information through a bitstream; deriving quantized transform coefficients based on the residual information; deriving transform coefficients based on an inverse quantization procedure for the quantized transform coefficients; deriving residual samples based on an inverse transform procedure for the transform coefficients; generating restoration samples of a current picture based on the residual samples; and generating modified restoration samples based on an in-loop filtering procedure for the restoration samples of the current picture, wherein the in-loop filtering procedure is determined to determine whether the in-loop filtering procedure is performed across virtual boundaries, wherein the video information includes a sequence parameter set (SPS), and information regarding the position of the subpicture is determined as a predetermined value based on the existence of one subpicture in the current picture. Claim 2 delete Claim 3 An image decoding method according to claim 1, characterized in that the information regarding the number of virtual boundaries includes information regarding the number of vertical virtual boundaries and information regarding the number of horizontal virtual boundaries. Claim 4 A video decoding method according to claim 1, wherein the video information includes a subpicture existence flag, and based on the subpicture existence flag, whether the SPS includes subpicture-related information is determined. Claim 5 delete Claim 6 delete Claim 7 A video decoding method according to claim 1, wherein the SPS includes an SPS virtual boundary existence flag related to whether the SPS includes information regarding the number of virtual boundaries, and the value of the SPS virtual boundary existence flag is determined to be 1 based on whether the SPS includes subpicture-related information. Claim 8 A video decoding method according to claim 1, characterized in that the video information includes picture header information, and based on the fact that the SPS includes sub-picture related information, information regarding the number of virtual boundaries is not included in the picture header. Claim 9 An image decoding method according to claim 8, characterized in that, based on the fact that the SPS includes information related to the subpicture, the SPS includes information regarding the number of virtual boundaries. Claim 10 A video encoding method performed by an encoding device, comprising: a step of deriving residual samples for a current block; a step of deriving transformation coefficients based on a transformation procedure for the residual samples; a step of deriving quantized transformation coefficients based on a quantization procedure for the transformation coefficients; a step of generating residual information based on the quantized transformation coefficients; a step of determining whether an in-loop filtering procedure is performed on the restored samples of the current picture across virtual boundaries; and a step of encoding video information based on the residual information and the determination, wherein the video information includes a sequence parameter set (SPS), and the signaling subpicture-related information includes information regarding the location of at least one subpicture, based solely on the existence of a plurality of subpictures in the current picture. Claim 11 delete Claim 12 An image encoding method according to claim 10, characterized in that the information regarding the number of virtual boundaries includes information regarding the number of vertical virtual boundaries and information regarding the number of horizontal virtual boundaries. Claim 13 A video encoding method according to claim 10, wherein the video information includes a subpicture existence flag, and based on the subpicture existence flag, whether the SPS includes subpicture-related information is determined. Claim 14 A video encoding method according to claim 10, wherein the video information includes a subpicture ID existence flag, and based on the value of the subpicture ID existence flag being 1, the subpictures within the current picture are independently coded. Claim 15 delete Claim 16 delete Claim 17 A video encoding method according to claim 10, wherein the SPS includes an SPS virtual boundary existence flag related to whether the SPS includes information regarding the number of virtual boundaries, and the value of the SPS virtual boundary existence flag is determined to be 1 based on whether the SPS includes information related to the subpicture. Claim 18 A video encoding method according to claim 10, characterized in that the above video information includes picture header information, and based on the fact that the above SPS includes subpicture-related information, the above information regarding the number of virtual boundaries is not included in the picture header. Claim 19 A video encoding method according to claim 18, characterized in that, based on the fact that the above SPS includes information related to the above subpicture, the above SPS includes information regarding the number of the above virtual boundaries. Claim 20 delete Claim 21 A method for transmitting a bitstream generated by a video encoding method, wherein the video encoding method comprises: a step of deriving residual samples for a current block; a step of deriving transformation coefficients based on a transformation procedure for the residual samples; a step of deriving quantized transformation coefficients based on a quantization procedure for the transformation coefficients; a step of generating residual information based on the quantized transformation coefficients; a step of determining whether an in-loop filtering procedure is performed on the restored samples of the current picture across virtual boundaries; and a step of encoding video information based on the residual information and the determination, wherein the video information includes a sequence parameter set (SPS), and the signaling subpicture-related information includes information regarding the location of at least one subpicture, based solely on the existence of a plurality of subpictures in the current picture.

Images