Image coding apparatus and method for controlling loop filtering

Abstract

To provide a decoding method by a decoding device.SOLUTION: In a decoding method by a decoding device according to an embodiment of this document, it can be determined whether signaling of information related to a virtual boundary exists in an SPS or picture header information on the basis of a virtual boundary availability flag.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] This document relates to an image coding apparatus and method for controlling loop filtering.

Background Art

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

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

[0004] Accordingly, there is a need for a highly efficient image / video compression technology to effectively compress, transmit, store, and reproduce information of high-resolution and high-quality images / videos having various characteristics as described above.

[0005] Specifically, loop filtering can be used for compression of images / videos. There is a discussion on a scheme for efficiently signaling information for controlling loop filtering.

Summary of the Invention

Means for Solving the Problems

[0006] According to an embodiment of this document, a method and apparatus for enhancing the efficiency of image / video coding are provided.

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

[0008] According to one embodiment of this 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 this document, in-loop filtering is performed based on a virtual boundary.

[0010] According to one embodiment of this document, the SPS (sequence parameter set) can include a virtual boundary availability flag of the SPS indicating whether in-loop filtering is executed across the virtual boundary.

[0011] According to one embodiment of this document, in-loop filtering can be executed across the virtual boundary based on the virtual boundary availability flag of the SPS.

[0012] According to one embodiment of this document, an encoding apparatus for performing video / image encoding is provided.

[0013] According to one embodiment of this document, a computer-readable digital storage medium storing encoded video / image information generated by the video / image encoding method disclosed in at least one of the embodiments of this document is provided.

[0014] According to one embodiment of this document, a computer-readable digital storage medium storing encoded information or encoded video / image information that causes a decoding apparatus to perform the video / image decoding method disclosed in at least one of the embodiments of this document is provided.

Advantages of the Invention

[0015] According to one embodiment of this document, the overall image / video compression efficiency can be increased.

[0016] According to one embodiment of this document, the subjective / objective visual quality can be enhanced through efficient filtering.

[0017] The in-loop filtering procedure based on virtual boundaries according to one embodiment of this document can save hardware resources.

[0018] According to one embodiment of this document, the in-loop filtering procedure based on virtual boundaries can be executed efficiently, and the filtering performance can be improved.

[0019] According to one embodiment of this document, the information for in-loop filtering based on virtual boundaries can be signaled efficiently.

Brief Description of the Drawings

[0020]

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Embodiments for Carrying Out the Invention

[0021] This document can be modified in various ways, can have various embodiments, and specific embodiments are illustrated in the drawings and will be described in detail. However, this is not intended to limit this document to specific embodiments. The terms commonly used in this specification are merely used to describe specific embodiments and are not used with the intention of limiting the technical idea of this document. Singular expressions include plural expressions unless the context clearly indicates otherwise. Terms such as "including" or "having" in this specification are intended to specify the existence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and it should be understood that the existence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof is not precluded in advance.

[0022] On the one hand, for the convenience of explaining the different characteristic functions of each component in the drawings described in this document, each component is independently illustrated, but this does not mean that each component is realized by separate hardware or separate software. For example, among the components, two or more components can be combined to form one component, and one component can also be divided into multiple components. As long as the implementation forms in which each component is integrated and / or separated do not deviate from the essence of this document, they are included in the scope of rights of this document.

[0023] Hereinafter, with reference to the accompanying drawings, the preferred embodiments of this document will be described in more detail. Hereinafter, the same reference numerals will be used for the same components in the drawings, and duplicate descriptions of the same components will be omitted.

[0024] This document relates to video / image coding. For example, the methods / embodiments disclosed in this document are related to the VVC (Versatile Video Coding) standard (ITU-T Rec.H.266), the next-generation video / image coding standard after VVC, or other video coding-related standards (such as the HEVC (High Efficiency Video Coding) standard (ITU-T Rec.H.265), the EVC (essential video coding) standard, the AVS2 standard, etc.).

[0025] This document presents various embodiments related to video / image coding. Unless otherwise mentioned, the above embodiments can also be executed in combination with each other.

[0026] In this document, "video" may mean a set of a series of "images" over time. "Picture" generally means a unit indicating one image in a specific time period, and "slice" / "tile" is a unit constituting a part of a picture in coding. A slice / tile may include one or more CTUs (Coding Tree Units). One picture may be composed of one or more slices / tiles. One picture may be composed of one or more tile groups. One tile group may include one or more tiles.

[0027] "Pixel" or "pel" may mean the smallest unit constituting one picture (or image). Also, the term "sample" may be used as a term corresponding to a pixel. A sample generally indicates a pixel or a pixel value, and may indicate only the pixel / pixel value of the luma component, or may indicate only the pixel / pixel value of the chroma component. Or, a sample may mean a pixel value in the spatial domain, and when such a pixel value is converted to the frequency domain, it may mean a conversion coefficient in the frequency domain.

[0028] "Unit" indicates a basic unit of image processing. A unit includes at least one of a specific region of a picture and information regarding the region. One unit includes one luma block and two chroma (e.g., cb, cr) blocks. A unit may, in some cases, be used interchangeably with terms such as "block" or "area". In a general case, an M×N block includes a set (or array) of samples (or sample array) or transform coefficients composed of M columns and N rows.

[0029] In this document, " / " and "," are interpreted as "and / or". For example, "A / B" is interpreted as "A and / or B", and "A, B" is interpreted as "A and / or B". Additionally, "A / B / C" means "at least one of A, B, and / or C". Also, "A, B, C" also means "at least one of A, B, and / or C".

[0030] Additionally, in this document, "or" is interpreted as "and / or". For example, "A or B" can mean 1) only "A", 2) only "B", or 3) "A and B". In other words, "or" in this document can mean "additionally or alternatively".

[0031] In this specification, "at least one of A and B" can mean "only A", "only B", or "both A and B". Also, in this specification, expressions such as "at least one of A or B" and "at least one of A and / or B" can be interpreted in the same way as "at least one of A and B".

[0032] Also, in this specification, "at least one of A, B, and C" can mean "only A", "only B", "only C", or "any combination of A, B, and C". Also, "at least one of A, B, or C" and "at least one of A, B, and / or C" can mean "at least one of A, B, and C".

[0033] Also, the parentheses used in this specification may mean "for example". Specifically, when it is displayed as "prediction (intra prediction)", "intra prediction" may be proposed as an example of "prediction". In other words, the "prediction" in this specification is not limited to "intra prediction", and "intra prediction" may be proposed as an example of "prediction". Also, when it is displayed as "prediction (that is, intra prediction)", "intra prediction" may be proposed as an example of "prediction".

[0034] The technical features separately described within one drawing in this specification may be realized separately or simultaneously.

[0035] FIG. 1 schematically shows an example of a video / image coding system to which this document can be applied.

[0036] As shown in FIG. 1, the video / image coding system can include a source device and a receiving device. The source device can transmit encoded video / image information or data in a file or streaming form to the receiving device via a digital storage medium or a network.

[0037] The source device can include a video source, an encoding device, and a transmitting unit. The receiving device can include a receiving unit, a decoding device, and a renderer. The encoding device can be called a video / image encoding device, and the decoding device can be called a video / image decoding device. A transmitter can be provided in the encoding device. A receiver can be provided in the decoding device. The renderer can include a display unit, and the display unit can also be composed of a separate device or an external component.

[0038] The video source can acquire video / images through processes such as video / image capture, synthesis, or generation. The video source can include a video / image capture device and / or a video / image generation device. The video / image capture device can include, for example, one or more cameras, a video / image archive containing previously captured video / images, etc. The video / image generation device can include, for example, a computer, a tablet, and a smartphone, etc., and can (electronically) generate video / images. For example, virtual video / images can be generated via a computer, etc., and in this case, the video / image capture process can be replaced by the process of generating related data.

[0039] The encoding device can encode the input video / image. The encoding device can perform a series of procedures such as prediction, transformation, quantization, etc. for compression and coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0040] The transmitting unit can transmit the encoded video / image information or data output in the form of a bitstream to the receiving unit of the receiving device via a digital storage medium or a network in file or streaming form. The digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitting unit can include elements for generating a media file via a predetermined file format and can include elements for transmission via a broadcast / communication network. The receiving unit can receive / extract the bitstream and transmit it to the decoding device.

[0041] The decoding device can decode the video / image by performing a series of procedures such as inverse quantization, inverse transformation, prediction, etc. corresponding to the operation of the encoding device.

[0042] The renderer can render the decoded video / image. The rendered video / image can be displayed via the display unit.

[0043] FIG. 2 is a drawing schematically explaining the configuration of a video / image encoding apparatus to which this document can be applied. Hereinafter, the video encoding apparatus can include an image encoding apparatus.

[0044] As shown in FIG. 2, the encoding apparatus 200 can 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 can include an inter-predictor 221 and an intra-predictor 222. The residual processor 230 can include a transformer 232, a quantizer 233, a dequantizer 234, and an inverse transformer 235. The residual processor 230 can further include a subtractor (231). The adder 250 can be called a reconstructor or a reconstructed block generator. The above-described image partitioner 210, predictor 220, residual processor 230, entropy encoder 240, adder 250, and filter 260 can be configured by one or more hardware components (for example, an encoder chipset or a processor) according to an embodiment. Also, the memory 270 can include a DPB (decoded picture buffer) and can also be configured by a digital storage medium. The hardware component can further include the memory 270 as an internal / external component.

[0045] The image segmentation unit 210 can divide an input image (or picture, frame) input to the encoding device 200 into one or more processing units. As an example, the processing unit can be called a coding unit (CU). In this case, the coding unit can be recursively divided from a coding tree unit (CTU) or a largest coding unit (LCU) by a QTBTTT (Quad-tree binary-tree ternary-tree) structure. For example, one coding unit can be divided into a plurality of coding units with 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 can be applied first, and then the binary-tree structure and / or the ternary structure can be applied. Or, the binary-tree structure can also be applied first. The coding procedure according to the present disclosure can be performed based on the final coding unit that is no longer divided. In this case, based on the coding efficiency according to the image characteristics, etc., the largest coding unit can be used as the final coding unit, or, if necessary, the coding unit can be recursively divided into coding units with a deeper depth so that the coding unit of the optimal size can be used as the final coding unit. Here, the coding procedure can include procedures such as prediction, transformation, and restoration, which will be described later. As another example, the processing unit can further include a prediction unit (PU: Prediction Unit) or a transform unit (TU: Transform Unit). In this case, the prediction unit and the transform unit can be divided or partitioned from the final coding unit described above, respectively.The prediction unit can be a unit of sample prediction, and the conversion unit can be a unit for deriving a conversion coefficient and / or a unit for deriving a residual signal from the conversion coefficient.

[0046] The unit can, in some cases, be used interchangeably with terms such as block or area. In general, an M×N block can represent a set of samples or transform coefficients, etc., consisting of M columns and N rows. A sample can generally represent a pixel or a pixel value, and can represent only the pixel / pixel value of the luma component, or can also represent only the pixel / pixel value of the chroma component. A sample can be used as a term corresponding to a pixel or a pel for one picture (or image).

[0047] The subtraction unit 231 can subtract the prediction signal (predicted block, predicted sample, or predicted sample array) output from the prediction unit 220 from the input image signal (original block, original sample, or original sample array) to generate a residual signal (residual block, residual sample, or residual sample array), and the generated residual signal is transmitted to the conversion unit 232. The prediction unit 220 can perform prediction on the processing target block (hereinafter referred to as the current block) and generate a predicted block including predicted samples for the current block. The prediction unit 220 can determine whether intra prediction or inter prediction is applied in units of the current block or CU. The prediction unit can generate various pieces of information related to prediction, such as prediction mode information, and transmit them to the entropy encoding unit 240 as described later in the description of each prediction mode. The information related to prediction can be encoded by the entropy encoding unit 240 and output in the form of a bitstream.

[0048] The intra prediction unit 222 can predict the current block by referring to samples within the current picture. The samples to be referred to can be located adjacent to the current block or can be located remotely, depending on the prediction mode. In intra prediction, the prediction mode can include a plurality of non-directional modes and a plurality of directional modes. The non-directional modes can include, for example, the DC mode and the Planar mode. The directional modes can include, for example, 33 directional prediction modes or 65 directional prediction modes, depending on the degree of detail of the prediction direction. However, this is an example, and more or fewer directional prediction modes can be used depending on the setting. The intra prediction unit 222 can also determine the prediction mode to be applied to the current block by using the prediction mode applied to the adjacent blocks.

[0049] 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, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between adjacent blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the adjacent blocks can include spatial neighboring blocks existing in the current picture and temporal neighboring blocks existing in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block can be the same or different. The temporal neighboring blocks can be called by names such as collocated reference blocks and collocated CUs (col CUs), and the reference picture including the temporal neighboring blocks can also be called a collocated picture (colPic). For example, the inter prediction unit 221 can construct a motion information candidate list based on adjacent 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 can be performed based on various prediction modes. For example, in the case of skip mode and merge mode, the inter prediction unit 221 can use the motion information of adjacent blocks as the motion information of the current block. In the case of skip mode, unlike merge mode, a residual signal may not be transmitted.In the case of the motion information prediction (motion vector prediction, MVP) mode, the motion vector of an adjacent block is used as a motion vector predictor, and the motion vector difference is signaled to indicate the motion vector of the current block.

[0050] The prediction unit 220 can generate a prediction signal based on various prediction methods described later. For example, the prediction unit can apply intra prediction or inter prediction, or both intra prediction and inter prediction simultaneously for the prediction of one block. This can be called combined inter and intra prediction (CIIP). In addition, the prediction unit can execute intra block copy (IBC) for the prediction of a block. The intra block copy can be used for content image / video coding such as games, for example, like SCC (screen content coding). IBC basically performs prediction within the current picture, but can be performed in the same way as inter prediction in terms of deriving a reference block within the current picture. That is, IBC can use at least one of the inter prediction techniques described in this document.

[0051] The prediction signal generated through the inclusion of the inter prediction unit 221 and / or the intra prediction unit 222 can be used to generate a restored signal or can be used to generate a residual signal. The conversion unit 232 can apply a conversion technique to the residual signal to generate transform coefficients. For example, the conversion technique can include DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), GBT (Graph-Based Transform), or CNT (Conditionally Non-linear Transform), etc. Here, GBT means the conversion obtained from this graph when expressing the relationship information between pixels in a graph. CNT means the conversion obtained based on generating a prediction signal using all previously reconstructed pixels. Also, the conversion process may be applied to a pixel block having the same size of a square or may be applied to a block of variable size that is not square.

[0052] The quantization unit 233 quantizes the transform coefficients and transmits them to the entropy encoding unit 240. The entropy encoding unit 240 can encode the quantized signal (information regarding the quantized transform coefficients) and output it as a bitstream. The information regarding the quantized transform coefficients can be referred to as residual information. The quantization unit 233 can reorder the block-form quantized transform coefficients in a one-dimensional vector form based on the coefficient scan order, and can also generate the information regarding the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. 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. In addition to the quantized transform coefficients, the entropy encoding unit 240 can also encode, together or separately, information necessary for video / image restoration (e.g., values of syntax elements, etc.). The encoded information (e.g., encoded video / image information) can be transmitted or stored in the form of a bitstream in units of NAL (network abstraction layer) units. The video / image information can 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), etc. Also, the video / image information can further include general constraint information. In this document, the signaling / transmitted information and / or syntax elements described later can be encoded via the above-described encoding procedure and included in the bitstream. The bitstream can be transmitted via a network or stored in a digital storage medium.Here, the network can include a broadcast network and / or a communication network, etc., and the digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The signal output from the entropy encoding unit 240 can be configured such that a transmission unit (not shown) for transmission and / or a storage unit (not shown) for storage are internal / external elements of the encoding device 200, or the transmission unit can also be included in the entropy encoding unit 240.

[0053] The quantized transform coefficients output from the quantization unit 233 can be used to generate a prediction signal. For example, by applying inverse quantization and inverse transformation to the quantized transform coefficients via the inverse quantization unit 234 and the inverse transformation unit 235, a residual signal (residual block or residual sample) can be restored. The addition unit 155 can generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample, or reconstructed sample array) by adding the restored residual signal to the prediction signal output from the prediction unit 220. When there is no residual for the processing target block, as in the case where the 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 processing target block within the current picture and, as will be described later, can also be used for inter prediction of the next picture after passing through filtering.

[0054] On the other hand, LMCS (luma mapping with chroma scaling) can also be applied during the picture encoding and / or restoration process.

[0055] The filtering unit 260 can apply filtering to the restored signal to improve the subjective / objective image quality. For example, the filtering unit 260 can apply various filtering methods to the restored picture to generate a modified restored picture, and store the modified restored picture in the memory 270, specifically, in the DPB of the memory 270. The various filtering methods can include, for example, deblocking filtering, sample adaptive offset (SAO), adaptive loop filter, bilateral filter, and the like. The filtering unit 260 can generate various information related to filtering and transmit it to the entropy encoding unit 240 as described later in the description of each filtering method. The information related to filtering can be encoded by the entropy encoding unit 240 and output in the form of a bit stream.

[0056] The modified restored picture transmitted to the memory 270 can be used as a reference picture in the inter prediction unit 221. Through this, when inter prediction is applied, the encoding device can avoid prediction mismatches between the encoding device 100 and the decoding device, and can also improve the encoding efficiency.

[0057] The DPB of the memory 270 can store the modified restored picture for use as a reference picture in the inter prediction unit 221. The memory 270 can store the motion information of the blocks in which the motion information in the current picture has been derived (or encoded) and / or the motion information of the blocks in the already restored picture. The stored motion information can be transmitted to the inter prediction unit 221 for utilization as the motion information of spatially adjacent blocks or temporally adjacent blocks. The memory 270 can store the restored samples of the restored blocks in the current picture and transmit them to the intra prediction unit 222.

[0058] FIG. 3 is a drawing schematically explaining the configuration of a video / image decoding apparatus to which this document can be applied.

[0059] As shown in FIG. 3, the decoding apparatus 300 can be configured to include an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, a filtering unit 350, and a memory 360. The predictor 330 can include an inter-prediction unit 331 and an intra-prediction unit 332. The residual processor 320 can include a dequantizer 321 and an inverse transformer 321. The entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filtering unit 350 described above can be configured by one hardware component (for example, a decoder chipset or a processor) according to an embodiment. Also, the memory 360 can include a DPB (decoded picture buffer) and can also be configured by a digital storage medium. The hardware component can further include the memory 360 as an internal / external component.

[0060] If a bitstream including video / image information is input, the decoding device 300 can restore an image corresponding to the process in which the video / image information is processed by the encoding device in FIG. 3. For example, the decoding device 300 can derive units / blocks based on the block division related information obtained from the bitstream. The decoding device 300 can perform decoding using the processing units applied in the encoding device. Therefore, the processing unit for decoding can be, for example, a coding unit, and the coding unit can be divided according to a quad-tree structure, a binary tree structure, and / or a ternary tree structure from a coding tree unit or a maximum coding unit. One or more transform units can be derived from the coding unit. Then, the restored image signal decoded and output via the decoding device 300 can be reproduced via a reproducing device.

[0061] The decoding device 300 can receive the signal output from the encoding device in FIG. 3 in the form of a bitstream, and the received signal can be decoded via the 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 can 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). Also, the video / image information can further include general constraint information. The decoding device can further decode a picture based on the information regarding the parameter set and / or the general constraint information. The signaling / received information and / or syntax elements described later in this document can be decoded via the decoding procedure and obtained from the bitstream. For example, the entropy decoding unit 310 can decode the information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and output the value of the syntax element necessary for image restoration and the quantized value of the transform coefficient regarding the residual. More specifically, the CABAC entropy decoding method receives the bin corresponding to each syntax element in the bitstream, determines a context model using the syntax element information to be decoded, the information adjacent to the decoding target block, and the decoding information of the decoding target block or the information of the symbol / bin decoded in the previous step, predicts the occurrence probability of the bin according to the determined context model, performs arithmetic decoding of the bin, and can generate a symbol corresponding to the value of each syntax element. At this time, after determining the context model, the CABAC entropy decoding method can update the context model using the information of the symbol / bin decoded for the context model of the next symbol / bin.Of the information decoded by the entropy decoding unit 310, the information related to prediction is provided to the prediction unit 330, and the residual information that has undergone entropy decoding in the entropy decoding unit 310, that is, the quantized transform coefficients and related parameter information, can be input to the inverse quantization unit 321. Also, among the information decoded by the entropy decoding unit 310, the information related to filtering can be provided to the filtering unit 350. On the other hand, a receiving unit (not shown) that receives the signal output from the encoding device can be further configured as an internal / external element of the decoding device 300, or the receiving unit can also be a component of the entropy decoding unit 310. On the other hand, the decoding device according to this document can be called a video / image / picture decoding device, and the decoding device can be classified into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder can include the entropy decoding unit 310, and the sample decoder can include at least one of the inverse quantization unit 321, the inverse transform unit 322, the prediction unit 330, the addition unit 340, the filtering unit 350, and the memory 360.

[0062] In the inverse quantization unit 321, the quantized transform coefficients can be inverse quantized to output the transform coefficients. The inverse quantization unit 321 can reorder the quantized transform coefficients in a two-dimensional block form. In this case, the reordering can be performed based on the coefficient scan order performed in the encoding device. The inverse quantization unit 321 can perform inverse quantization on the quantized transform coefficients using a quantization parameter (for example, quantization step size information) to obtain the transform coefficients.

[0063] In the inverse transform unit 322, the transform coefficients are inverse transformed to obtain a residual signal (residual block, residual sample array).

[0064] The prediction unit can perform prediction on the current block and generate a predicted block including a prediction sample for the current block. The prediction unit can determine whether intra prediction or inter prediction is applied to the current block based on the information regarding the prediction output from the entropy decoding unit 310, and can determine a specific intra / inter prediction mode.

[0065] The prediction unit can generate a prediction signal based on various prediction methods described later. For example, the prediction unit can not only apply intra prediction or inter prediction for the prediction of one block, but also apply intra prediction and inter prediction simultaneously. This can be called combined inter and intra prediction (CIIP). Also, the prediction unit can execute intra block copy (IBC) for the prediction of a block. The intra block copy can be used for content image / video coding such as games, for example, like SCC (screen content coding). IBC basically performs prediction within the current picture, but can be performed in the same way as inter prediction in terms of deriving a reference block within the current picture. That is, IBC can utilize at least one of the inter prediction techniques described in this document. The palette mode can be regarded as an example of intra coding or intra prediction.

[0066] The Intra prediction unit 331 can predict the current block by referring to samples within the current picture. The samples to be referred can be located adjacent to the current block or at a distance therefrom depending on the prediction mode. In intra prediction, the prediction mode can include a plurality of non-directional modes and a plurality of directional modes. The Intra prediction unit 331 can also determine the prediction mode to be applied to the current block using the prediction mode applied to an adjacent block.

[0067] The Inter prediction unit 332 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, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between an adjacent block and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the adjacent blocks can include spatial neighboring blocks existing within the current picture and temporal neighboring blocks existing in the reference picture. For example, the Inter prediction unit 332 can construct a motion information candidate list based on adjacent 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 the information regarding the prediction can include information indicating the mode of inter prediction for the current block.

[0068] The adder 340 can generate a restored signal (restored picture, restored block, restored sample array) by adding the acquired residual signal to the predicted signal (predicted block, predicted sample array) output from the predictor. When there is no residual for the block to be processed, such as when the skip mode is applied, the predicted block can be used as the restored block.

[0069] The adder 340 can be referred to as a restoration unit or a restored block generation unit. The generated restored signal can be used for intra prediction of the next block to be processed in the current picture, can be output after filtering as described later, or can also be used for inter prediction of the next picture.

[0070] On the other hand, LMCS (luma mapping with chroma scaling) can also be applied during the picture decoding process.

[0071] The filtering unit 350 can apply filtering to the restored signal to improve the subjective / objective image quality. For example, the filtering unit 350 can apply various filtering methods to the restored picture to generate a modified restored picture, and can send the modified restored picture to the memory 360, specifically, to the DPB of the memory 360. The various filtering methods can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0072] The (corrected) restored picture stored in the DPB of the memory 360 can be used as a reference picture in the inter prediction unit 332. The memory 360 can store the motion information of the block for which the motion information in the current picture has been derived (or decoded) and / or the motion information of the block in the already restored picture. The stored motion information can be transmitted to the inter prediction unit 332 for utilization as the motion information of spatially adjacent blocks or temporally adjacent blocks. The memory 360 can store the restored samples of the restored blocks in the current picture and can transmit them to the intra prediction unit 331.

[0073] In this specification, the embodiments described in the prediction unit 330, inverse quantization unit 321, inverse transform unit 322, filtering unit 350, etc. of the decoding device 300 can be applied to the prediction unit 220, inverse quantization unit 234, inverse transform unit 235, filtering unit 260, etc. of the encoding device 200 so as to be the same or corresponding respectively.

[0074] As described above, when performing video coding, prediction is performed to improve the compression efficiency. Through this, a predicted block including prediction samples for the current block which is the block to be coded can be generated. Here, the predicted block includes prediction samples in the spatial domain (or pixel domain). The predicted block is also derived in the encoding device and the decoding device, and the encoding device can improve the image coding efficiency by signaling information (residual information) regarding the residual between the original block and the predicted block which is not the original sample value of the original block to the decoding device. The decoding device can derive a residual block including residual samples based on the residual information, and can generate a restored block including restored samples by combining the residual block and the predicted block, and can generate a restored picture including the restored block.

[0075] The residual information can be generated via conversion and quantization procedures. For example, an encoding device can derive a residual block between the original block and the predicted block, execute a conversion procedure on the residual samples (residual sample array) included in the residual block to derive conversion coefficients, execute a quantization procedure on the conversion coefficients to derive quantized conversion coefficients, and thus signal the relevant residual information (via a bitstream) to a decoding device. Here, the residual information can include information such as the value information, position information, conversion technique, conversion kernel, and quantization parameter of the quantized conversion coefficients. A decoding device can execute an inverse quantization / inverse conversion procedure based on the residual information to derive residual samples (or a residual block). A decoding device can generate a restored picture based on the predicted block and the residual block. Also, an encoding device can inverse quantize / inverse convert the quantized conversion coefficients for reference in the inter prediction of subsequent pictures to derive a residual block and generate a restored picture based on this.

[0076] In this document, at least one of quantization / inverse quantization and / or conversion / inverse conversion can be omitted. When the quantization / inverse quantization is omitted, the quantized conversion coefficients can be called conversion coefficients. When the conversion / inverse conversion is omitted, the conversion coefficients can also be called coefficients or residual coefficients, or, for the sake of uniformity of expression, can still be called conversion coefficients.

[0077] In this document, the quantized transform coefficient and the transform coefficient can each be referred to as a transform coefficient and a scaled transform coefficient, respectively. In this case, the residual information can include information regarding the transform coefficient(s), and the information regarding the transform coefficient(s) can be signaled via a residual coding syntax. The transform coefficient can be derived based on the residual information (or the information regarding the transform coefficient(s)), and the scaled transform coefficient can be derived via an inverse transform (scaling) with respect to the transform coefficient. The residual sample can be derived based on an inverse transform (transformation) with respect to the scaled transform coefficient. This can be applied / expressed similarly in other parts of this document.

[0078] The prediction unit of the encoding / decoding device can derive a prediction sample by performing inter prediction in block units. Inter prediction can indicate a prediction derived in a method that depends on data elements (e.g., sample values or motion information) of pictures other than the current picture. When inter prediction is applied to the current block, a predicted block (prediction sample array) for the current block can be induced based on a reference block (reference sample array) specified by a motion vector on a reference picture indicated by the index of the reference picture. At this time, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information of the current block can be predicted in units of blocks, sub-blocks, or samples based on the correlation of motion information between adjacent blocks and the current block. The motion information can include a motion vector and an index of a reference picture. The motion information can further include information on the inter prediction type (L0 prediction, L1 prediction, Bi prediction, etc.). When inter prediction is applied, the adjacent blocks can include spatial neighboring blocks existing within the current picture and temporal neighboring blocks existing in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block can be called by names such as a collocated reference block or a collocated CU (colCU), and the reference picture including the temporal neighboring block may also be called a collocated picture (colPic). For example, a candidate list of motion information can be configured based on adjacent blocks of the current block, and flag or index information indicating which candidate is selected (used) can be signaled to derive the motion vector and / or the index of the reference picture of the current block. Inter prediction is performed based on various prediction modes. For example, in the case of the skip mode and the merge mode, the motion information of the current block can be the same as the motion information of the selected adjacent block.In the case of the skip mode, unlike the merge mode, the residual signal may not be transmitted. In the case of the motion vector prediction (MVP) mode, the motion vector of the selected adjacent 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 using the sum of the motion vector predictor and the motion vector difference.

[0079] The motion information can include L0 motion information and / or L1 motion information according to the inter prediction type (L0 prediction, L1 prediction, Bi prediction, etc.). The motion vector in the L0 direction can be called the L0 motion vector or MVL0, and the motion vector in the L1 direction can be called the L1 motion vector or MVL1. The prediction based on the L0 motion vector can be called L0 prediction, the prediction based on the L1 motion vector can be called L1 prediction, and the prediction based on both the L0 motion vector and the L1 motion vector can be called bi (Bi) prediction. Here, the L0 motion vector can indicate the motion vector related to the reference picture list L0 (L0), and the L1 motion vector can indicate the motion vector related to the reference picture list L1 (L1). The reference picture list L0 can include, as reference pictures, pictures that are earlier in the output order than the current picture, and the reference picture list L1 can include pictures that are later in the output order than the current picture. The earlier picture can be called a forward (reference) picture, and the later picture can be called a backward (reference) picture. The reference picture list L0 can further include, as reference pictures, pictures that are later in the output order than the current picture. In this case, the earlier picture can be indexed first within the reference picture list L0, and the later picture can be indexed thereafter. The reference picture list L1 can further include, as reference pictures, pictures that are earlier in the output order than the current picture. In this case, the later picture can be indexed first within the reference picture list 1, and the earlier picture can be indexed thereafter. Here, the output order can correspond to the POC (picture order count) order (order).

[0080] FIG. 4 exemplarily shows a hierarchical structure for a coded image / video.

[0081] As shown in FIG. 4, the coded image / video is divided into a VCL (video coding layer) that performs decoding processing of the image / video and handles itself, a lower-level system that transmits and stores the encoded information, and a NAL (network abstraction layer) that exists between the VCL and the lower-level system and is responsible for the network adaptation function.

[0082] In the VCL, VCL data including compressed image data (slice data) can be generated, or parameter sets including information such as a Picture Parameter Set (PPS), a Sequence Parameter Set (SPS), and a Video Parameter Set (VPS), or SEI (Supplemental Enhancement Information) messages that are additionally required in the decoding process of the image can be generated.

[0083] In the NAL, a NAL unit can be generated by adding header information (NAL unit header) to the RBSP (Raw Byte Sequence Payload) generated in the VCL. At this time, the RBSP means slice data, parameter sets, SEI messages, etc. generated in the VCL. The NAL unit header can include NAL unit type information specified by the RBSP data included in the corresponding NAL unit.

[0084] As shown in the above drawings, the NAL unit can be divided into a VCL NAL unit and a Non-VCL NAL unit according to the RBSP generated in the VCL. The VCL NAL unit can mean a NAL unit including information (slice data) for an image, and the Non-VCL NAL unit can mean a NAL unit including information (parameter set or SEI message) required for decoding the image.

[0085] The above-mentioned VCL NAL units and Non-VCL NAL units can be transmitted via a network with header information attached according to the data standard of the lower-level system. For example, the NAL unit can be transformed into a data form of a predetermined standard such as the H.266 / VVC file format, RTP (Real-time Transport Protocol), TS (Transport Stream), etc., and can be transmitted via various networks.

[0086] As described above, the NAL unit type can be specified by the RBSP data structure included in the corresponding NAL unit, and information about such NAL unit types can be stored in the NAL unit header and signaled.

[0087] For example, depending on whether the NAL unit contains information about an image (slice data), it can be roughly classified into a VCL NAL unit type and a Non-VCL NAL unit type. The VCL NAL unit type can be classified according to the nature and type of the picture included in the VCL NAL unit, and the Non-VCL NAL unit type can be classified according to the type of parameter set, etc.

[0088] The following is an example of the NAL unit type specified by the type of parameter set included in the Non-VCL NAL unit type, etc.

[0089] - APS (Adaptation Parameter Set) NAL unit: The type for the NAL unit containing APS

[0090] - DPS (Decoding Parameter Set) NAL unit: The type for the NAL unit containing DPS

[0091] -VPS (Video Parameter Set) NAL unit: Type for NAL unit containing VPS

[0092] -SPS (Sequence Parameter Set) NAL unit: Type for NAL unit containing SPS

[0093] -PPS (Picture Parameter Set) NAL unit: Type for NAL unit containing PPS

[0094] -PH (Picture header) NAL unit: Type for NAL unit containing PH

[0095] The above-mentioned NAL unit types have syntax information for the NAL unit type, and the syntax information can be stored in the NAL unit header and signaled. For example, the syntax information is nal_unit_type, and the NAL unit type can be specified by the nal_unit_type value.

[0096] On the other hand, as described above, one picture can include a plurality of slices, and one slice can include a slice header and slice data. In this case, one picture header can be further added for a plurality of slices (slice header and slice data set) within one picture. The picture header (picture header syntax) can include information / parameters that are commonly applicable to the picture. In this document, a slice can be mixed or replaced with a tile group. Also, in this document, a slice header can be mixed or replaced with a type group header.

[0097] The slice header (slice header syntax, slice header information) can include information / parameters that can be commonly applied to the slice. The APS (APS syntax) or PPS (PPS syntax) can include information / parameters that can be commonly applied to one or more slices or pictures. The SPS (SPS syntax) can include information / parameters that can be commonly applied to one or more sequences. The VPS (VPS syntax) can include information / parameters that can be commonly applied to multiple layers. The DPS (DPS syntax) can include information / parameters that can be commonly applied to the entire video. The DPS can include information / parameters related to the concatenation of the CVS (coded video sequence). In this document, the high level syntax (HLS) can include at least one of the APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, picture header syntax, and slice header syntax.

[0098] In this document, the image / video information encoded from the encoding device and signaled in the form of a bitstream to the decoding device can include not only information related to partitioning within the picture, intra / inter prediction information, residual information, in-loop filtering information, etc., but also the information included in the slice header, the information included in the picture header, the information included in the APS, the information included in the PPS, the information included in the SPS, the information included in the VPS, and / or the information included in the DPS. Further, the image / video information can further include the information of the NAL unit header.

[0099] On one hand, in order to compensate for the difference between the original image and the restored image due to errors occurring in the compression encoding process such as quantization, as described above, an in-loop filtering procedure can be executed on the restored sample or the restored picture. As described above, the in-loop filtering can be executed 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) can be applied. For example, the ALF procedure can be executed after the deblocking filtering procedure and / or the SAO procedure are completed. However, also in this case, the deblocking filtering procedure and / or the SAO procedure can be omitted.

[0100] Specific descriptions for picture restoration and filtering are described below. In image / video coding, a restored block can be generated based on intra prediction / inter prediction in each block unit, and a restored picture including the restored block can be generated. When the current picture / slice is an I picture / slice, the blocks included in the current picture / slice can be restored based on intra prediction only. On the other hand, when the current picture / slice is a P or B picture / slice, the blocks included in the current picture / slice can be restored based on intra prediction or inter prediction. In this case, intra prediction can be applied to some blocks within the current picture / slice, and inter prediction can also be applied to the remaining blocks.

[0101] Intra prediction can indicate a prediction that generates a prediction sample for the current block based on reference samples within the picture to which the current block belongs (hereinafter referred to as the current picture). When intra prediction is applied to the current block, adjacent reference samples used for intra prediction of the current block can be derived. The adjacent reference samples of the current block can include samples adjacent to the left boundary of the current block of size nW×nH and a total of 2×nH samples adjacent to the bottom-left, samples adjacent to the top boundary of the current block and a total of 2×nW samples adjacent to the top-right, and 1 sample adjacent to the top-left of the current block. Or, the adjacent reference samples of the current block can also include a plurality of columns of upper adjacent samples and a plurality of rows of left adjacent samples. Also, the adjacent reference samples of the current block can include a total of nH samples adjacent to the right boundary of the current block of size nW×nH, a total of nW samples adjacent to the bottom boundary of the current block, and 1 sample adjacent to the bottom-right of the current block.

[0102] However, some of the adjacent reference samples of the current block may not have been decoded yet or may not be available. In this case, the decoder can substitute samples that are not available with available samples to form adjacent reference samples used for prediction. Or, adjacent reference samples used for prediction can be formed through interpolation of available samples.

[0103] When an adjacent reference sample is derived, (i) a predicted sample can be derived based on the average or interpolation of the neighboring reference samples of the current block, and (ii) the predicted sample can also be derived based on the reference samples that exist in a specific (predicted) direction with respect to the predicted sample among the neighboring reference samples of the current block. In the case of (i), it is called a non-directional mode or a non-angle mode, and in the case of (ii), it can be called a directional mode or an angular mode. Also, among the adjacent reference samples, based on the predicted sample of the current block, the predicted sample can be generated through interpolation between the second adjacent sample and the first adjacent sample located in the opposite direction of the prediction direction of the intra prediction mode of the current block. The case described above can be called linear interpolation intra prediction (LIP). Also, a chroma predicted sample can be generated based on a luma sample using a linear model. In this case, it can be called the LM mode. Also, a temporary predicted sample of the current block is derived based on the filtered adjacent reference samples, and a predicted sample of the current block is derived by taking a weighted sum of at least one reference sample derived by the intra prediction mode among the existing adjacent reference samples, i.e., the non-filtered adjacent reference samples, and the temporary predicted sample. The case described above can be called PDPC (Position dependent intra prediction). Also, intra prediction coding can be performed by selecting the reference sample line with the highest prediction accuracy from among the adjacent multiple reference sample lines of the current block and using the reference sample located in the prediction direction on the corresponding line, and indicating (signaling) the reference sample line used at this time to the decoding device.In the above-described case, it can be called multi-reference line (MRL) intra prediction or MRL-based intra prediction. Also, the current block can be divided into vertical or horizontal sub-partitions, and intra prediction can be performed based on the same intra prediction mode, and adjacent reference samples can be derived and used in units of the sub-partitions. That is, in this case, the intra prediction mode for the current block is also applied to the sub-partitions, and by deriving and using adjacent reference samples in units of the sub-partitions, in some cases, the intra prediction performance can be improved. Such a prediction method can be called intra sub-partitions (ISP) or ISP-based intra prediction. The above-described intra prediction methods can be called intra prediction types when distinguished from the intra prediction modes in Tables of Contents 1 and 2. The intra prediction types can be called by various terms such as intra prediction techniques or additional intra prediction modes. For example, the intra prediction type (or, additional intra prediction mode, etc.) can include at least one of the above-described LIP, PDPC, MRL, and ISP. A general intra prediction method excluding specific intra prediction types such as LIP, PDPC, MRL, and ISP can be called a normal intra prediction type. The normal intra prediction type can be generally applied when the above-described specific intra prediction types are not applied, and prediction can be performed based on the above-described intra prediction modes. On the other hand, if necessary, post-processing filtering for the derived prediction samples can also be performed.

[0104] Specifically, the intra prediction procedure can include an intra prediction mode / type determination step, an adjacent reference sample derivation step, and an intra prediction mode / type-based prediction sample derivation step. Also, if necessary, a post-processing filtering step for the derived prediction samples can also be performed.

[0105] A restored picture modified by an in-loop filtering procedure is generated, and the modified restored picture is output as a decoded picture from the decoding device, and is also stored in a decoded picture buffer or memory of the encoding device / decoding device, and can be used as a reference picture in an inter-prediction procedure during picture encoding / decoding later. The in-loop filtering procedure includes, as described above, a deblocking filtering procedure, a SAO (sample adaptive offset) procedure, and / or an ALF (adaptive loop filter) procedure, etc. In this case, one or some of the deblocking filtering procedure, SAO (sample adaptive offset) procedure, ALF (adaptive loop filter) procedure, and bilateral filter procedure may be sequentially applied, or all of them may be sequentially applied. For example, after the deblocking filtering procedure is applied to the restored picture, the SAO procedure may be performed. Or, for example, after the deblocking filtering procedure is applied to the restored picture, the ALF procedure may be performed. This is also done in the same way in the encoding device.

[0106] Deblocking filtering is a filtering technique that removes distortions occurring at the boundaries between blocks in the restored picture. The deblocking filtering procedure can, for example, derive a target boundary in the restored picture, determine the bS (boundary strength) for the target boundary, and perform deblocking filtering for the target boundary based on the bS. The bS can be determined based on the prediction mode of two adjacent blocks of the target boundary, the motion vector difference, whether the reference pictures are the same, the presence or absence of non-zero valid coefficients, etc.

[0107] SAO is a method for compensating the offset difference between the restored picture and the original picture in sample units, and can be applied based on types such as, for example, Band Offset and Edge Offset. According to SAO, samples can be classified into different categories by each SAO type, and an offset value can be added to each sample based on the category. The filtering information for SAO can include information on whether SAO can be applied, SAO type information, SAO offset value information, etc. SAO can also be applied to the restored picture after the deblocking filtering is applied.

[0108] ALF (Adaptive Loop Filter) is a technique for filtering in sample units based on filter coefficients according to the filter shape for the restored picture. The encoding device can determine, via comparison between the restored picture and the original picture, whether ALF can be applied, the ALF shape and / or the ALF filtering coefficient, etc., and can signal them to the decoding device. That is, the filtering information for ALF can include information on whether ALF can be applied, ALF filter shape information, ALF filtering coefficient information, etc. ALF can also be applied to the restored picture after the deblocking filtering is applied.

[0109] Figure 5 shows an example of the ALF filter shape.

[0110] Fig. 5(a) shows the filter shape of a 7x7 diamond, and (b) shows the filter shape of a 5x5 diamond. Cn within the filter shape in Fig. 5 indicates the filter coefficient. When n is the same for the said Cn, it indicates that the same filter coefficient can be assigned. In this document, the position and / or unit where the filter coefficient is assigned according to the filter shape of the ALF may be called a filter tab. At this time, one filter coefficient is assigned to each filter tab, and the form in which the filter tabs are arranged may correspond to the filter shape. The filter tab located at the center of the filter shape may be called the center filter tab. The same filter coefficient may be assigned to two filter tabs with the same n value that exist at corresponding positions with respect to the center filter tab. For example, in the case of the filter shape of a 7x7 diamond, it includes 25 filter tabs, and since the filter coefficients from C0 to C11 are assigned in a centrosymmetric form, the filter coefficients of only 13 filter coefficients can be assigned to the said 25 filter tabs. Also, for example, in the case of the filter shape of a 5x5 diamond, it includes 13 filter tabs, and since the filter coefficients from C0 to C5 are assigned in a centrosymmetric form, the filter coefficients of only 7 filter coefficients can be assigned to the said 13 filter tabs. For example, in order to reduce the data amount of the information regarding the filter coefficients to be signaled, 12 out of the 13 filter coefficients for the filter shape of a 7x7 diamond can be (explicitly) signaled, and 1 filter coefficient can be (implicitly) derived. Also, for example, 6 out of the 7 filter coefficients for the filter shape of a 5x5 diamond can be (explicitly) signaled, and 1 filter coefficient can be (implicitly) derived.

[0111] Fig. 6 shows an example of the ALF procedure using a virtual boundary according to an embodiment of this document.

[0112] The virtual boundary can be a line defined by shifting the horizontal CTU boundary by only N samples. In one example, N can be 4 for the luma component and / or N can be 2 for the chroma component.

[0113] The classification of the corrected blocks can be applied to the luma components. For the calculation of the 1D Laplacian gradient of a 4X4 block on the virtual boundary, only the samples on the virtual boundary can be used. Similarly, for the calculation of the 1D Laplacian gradient of a 4X4 block below the virtual boundary, only the samples below the virtual boundary can be used. The quantization of the activity value A can take into account the reduced number of samples used in the calculation of the 1D Laplacian gradient and can be scaled accordingly.

[0114] For the filtering procedure, a symmetric padding operation at the virtual boundary can be used for the luma and chroma components. Referring to FIG. 6, when samples filtered below the virtual boundary are located, the adjacent samples located above the virtual boundary can be padded. On the other hand, the other such samples can also be symmetrically padded.

[0115] The procedure described by FIG. 6 can also be used for the boundaries of slices, bricks, and / or tiles when filters are not available across the boundary. For the classification of ALF blocks, only the samples included in the same slice, brick, and / or tile can be used, and the activity value can be scaled accordingly. For ALF filtering, symmetric padding can be applied for each of the horizontal and / or vertical directions with respect to the horizontal and / or vertical boundaries.

[0116] FIG. 7 is a flowchart for explaining an encoding method based on filtering in an encoding device. The method of FIG. 7 can include steps S700 to S730.

[0117] In step S700, the encoding device can generate a reconstructed picture. The step S700 can be executed based on the above-described procedure for generating a reconstructed picture (or reconstructed samples).

[0118] In step S710, the encoding device can determine whether in-loop filtering is to be applied (across the virtual boundary) based on the in-loop filtering related information. Here, the in-loop filtering may include at least one of the deblocking filtering, SAO, or ALF described above.

[0119] In step S720, the encoding device can generate a modified reconstructed picture (modified reconstructed samples) based on the determination in step S710. Here, the modified reconstructed picture (modified reconstructed samples) can be a filtered reconstructed picture (filtered reconstructed samples).

[0120] In step S730, the encoding device can encode the image / video information including the in-loop filtering related information based on the in-loop filtering procedure.

[0121] FIG. 8 is a flowchart for explaining a decoding method based on filtering in a decoding device. The method of FIG. 8 can include steps S800 to S830.

[0122] In step S800, the decoding device can obtain the image / video information including the in-loop filtering related information from the bitstream. Here, the bitstream can be based on the encoded image / video information transmitted from the encoding device.

[0123] In step S810, the decoding device can generate a reconstructed picture. The step S810 can be executed based on the generation procedure of the reconstructed picture (or reconstructed samples) described above.

[0124] In step S820, the decoding device can determine whether in-loop filtering is to be applied (across the virtual boundary) based on the in-loop filtering related information. Here, the in-loop filtering may include at least one of the aforementioned deblocking filtering, SAO, or ALF.

[0125] In step S830, the decoding device can generate a modified reconstructed picture (modified reconstructed samples) based on the determination in step S820. Here, the modified reconstructed picture (modified reconstructed samples) can be a filtered reconstructed picture (filtered reconstructed samples).

[0126] As described above, the in-loop filtering procedure can be applied to the reconstructed picture. In this case, a virtual boundary can be defined to enhance the subjective / objective visual quality of the reconstructed picture, and the in-loop filtering procedure can also be applied across the virtual boundary. The virtual boundary may include discontinuous edges such as, for example, a 360-degree image, a VR image, or a PIP (picture in picture). For example, the virtual boundary may exist at a predetermined agreed-upon position, and its presence and / or position may be signaled. As an example, the virtual boundary may be located at the fourth sample line above in the CTU row (specifically, for example, above the fourth sample line above in the CTU row). As another example, information regarding its presence and / or position may also be signaled via HLS. The HLS may include, as described above, SPS, PPS, picture header, slice header, etc.

[0127] Hereinafter, the signaling and semantics of the high-level syntax related to the embodiments of this document will be described.

[0128] One embodiment of this document may include a method for controlling a loop filter. This method for controlling the loop filter can be applied to a reconstructed picture. The in-loop filter (loop filter) can be used for decoding an encoded bitstream. The loop filter may include the aforementioned deblocking, SAO, and ALF. The SPS may include flags associated with each of deblocking, SAO, and ALF. The flag can indicate whether each tool is available for coding a CLVS (coded layer video sequence) or a CVS (coded video sequence) that references the SPS.

[0129] When the loop filter is available for the CVS, the application of the loop filter can be controlled so as not to cross a specific boundary. For example, it can be controlled whether the loop filter crosses the boundary of a sub-picture. Also, it can be controlled whether the loop filter crosses the boundary of a tile. Along with this, it can be controlled whether the loop filter crosses a virtual boundary. Here, the virtual boundary can be defined on a CTU based on the availability of a line buffer.

[0130] Related to whether an in-loop filtering procedure is executed across a virtual boundary, the in-loop filtering related information may include at least one of a virtual boundary availability flag in the SPS (virtual boundary availability flag within the SPS), a virtual boundary existence flag in the SPS, a virtual boundary existence flag in the picture header, a virtual boundary existence flag in the SPS picture header, and information regarding the position of the virtual boundary.

[0131] In the embodiments included in this document, the information regarding the position of the virtual boundary may include information regarding the x coordinate of the vertical virtual boundary and / or information regarding the y coordinate of the horizontal virtual boundary. Specifically, the information regarding the position of the virtual boundary may include information regarding the x coordinate of the vertical virtual boundary and / or the y coordinate of the horizontal virtual boundary in terms of luma sample units. Also, the information regarding the position of the virtual boundary may include information regarding the number of information (syntax elements) regarding the x coordinate of the vertical virtual boundary existing in the SPS. Also, the information regarding the position of the virtual boundary may include information regarding the number of information (syntax elements) regarding the y coordinate of the horizontal virtual boundary existing in the SPS. Or, the information regarding the position of the virtual boundary may include information regarding the number of information (syntax elements) regarding the x coordinate of the vertical virtual boundary existing in the picture header. Also, the information regarding the position of the virtual boundary may include information regarding the number of information (syntax elements) regarding the y coordinate of the horizontal virtual boundary existing in the picture header.

[0132] The following table shows exemplary syntax and semantics of the SPS according to this embodiment.

[0133]

Table 1

[0134]

Table 2

[0135] The following table shows exemplary syntax and semantics of the PPS (picture parameter set) according to this embodiment.

[0136]

Table 3

[0137]

Table 4

[0138] The following table shows the exemplary syntax and semantics of the picture header according to this embodiment.

[0139]

Table 5-1

[0140]

Table 5-2

[0141]

Table 6-1

[0142]

Table 6-2

[0143] The following table shows the exemplary syntax and semantics of the slice header according to this embodiment.

[0144]

Table 7

[0145]

Table 8

[0146] The following describes the signaling of information for virtual boundaries that can be used in in-loop filtering.

[0147] In the existing design, in order to disable the loop filter across the virtual boundary, i) the virtual boundary existence flag of the SPS (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) is set to 0, and for all picture headers, the virtual boundary existence flag of the PH (ph_loop_filter_across_virtual_boundaries_disabled_present_flag) exists and is set to 0, or ii) the virtual boundary existence flag of the SPS (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) is set to 1, and both the information on the number of vertical virtual boundaries of the SPS (sps_num_ver_vertical_boudnaries) and the information on the number of horizontal virtual boundaries of the SPS (sps_num_hor_vertical_boudnaries) can be set to 0.

[0148] In the existing design, according to the above ii), when the virtual boundary existence flag of the SPS (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) is set to 1, problems in the decoding procedure may be caused by the decoder predicting the signaling for the position of the virtual boundary.

[0149] The embodiments described in the following paragraphs can propose solutions to solve the above-mentioned problems. The embodiments may be applied independently. Alternatively, at least two or more embodiments may be combined and applied.

[0150] In one embodiment of this document, whether a syntax element for indicating a virtual boundary is included in the SPS can be controlled by a flag. For example, the number of said flags can be two (e.g., SPS virtual boundaries enabled flag, SPS virtual boundaries present flag).

[0151] In an example according to this embodiment, the SPS virtual boundaries enabled flag may be referred to as sps_loop_filter_across_virtual_boundaries_disabled_flag (or sps_virtual_boundaries_enabled_flag). The SPS virtual boundaries enabled flag can indicate whether features for disabling the loop filter across the virtual boundary are enabled.

[0152] In an example according to this embodiment, the SPS virtual boundaries present flag may be referred to as sps_loop_filter_across_virtual_boundaries_disabled_present_flag (or sps_virtual_boundaries_present_flag). The SPS virtual boundaries present flag can indicate whether signaling information for the virtual boundary is included in the SPS or the picture header (PH).

[0153] In an example according to this embodiment, when the SPS virtual boundaries enabled flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) is 1 and the SPS virtual boundaries present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) is 0, signaling information for disabling the loop filter across the virtual boundary may be included in the picture header.

[0154] In an example according to this embodiment, when information regarding the position of a virtual boundary (e.g., a vertical virtual boundary, a horizontal virtual boundary) is included in the SPS, the sum of the number of vertical virtual boundaries and the number of horizontal virtual boundaries may be restricted to be greater than 0.

[0155] In an example according to this embodiment, a variable indicating whether a virtual boundary is filterable for the current picture may be derived. For example, the variable may include VirtualBoundairesDisabledFlag.

[0156] In one case of this illustration, when the virtual boundary availability flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1 and the virtual boundary presence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is 1, VirtualBoundairesDisabledFlag may be 1.

[0157] In another case of this illustration, when the virtual boundary availability flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1, the virtual boundary presence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is 0, and the sum of the information regarding the number of vertical virtual boundaries (e.g., ph_num_ver_virtual_boundaries) and the information regarding the number of horizontal virtual boundaries (e.g., ph_num_hor_virtual_boundaries) is greater than 0, VirtualBoundairesDisabledFlag may be 1.

[0158] In other cases of this illustration, VirtualBoundairesDisabledFlag may be 0.

[0159] The following table shows an exemplary syntax of SPS according to this embodiment.

[0160]

Table 9

[0161] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0162]

Table 10

[0163] The following table shows an exemplary syntax of header information (picture header) according to this embodiment.

[0164]

Table 11

[0165] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0166]

Table 12

[0167] In the embodiments related to Tables 9 to 12, the image information encoded by the encoding device and / or the image information obtained via the bitstream received from the encoding device by the decoding device may include a sequence parameter set (SPS) and a picture header (PH). The SPS may include a sps_loop_filter_across_virtual_boundaries_disabled_flag. The SPS may include a sps_loop_filter_across_virtual_boundaries_disabled_present_flag based on the sps_loop_filter_across_virtual_boundaries_disabled_flag.

[0168] For example, the SPS may include the sps_loop_filter_across_virtual_boundaries_disabled_present_flag when the value of the sps_loop_filter_across_virtual_boundaries_disabled_flag is 1. Based on the sps_loop_filter_across_virtual_boundaries_disabled_flag and the sps_loop_filter_across_virtual_boundaries_disabled_present_flag, the SPS may include information on the number of vertical virtual boundaries of the SPS (sps_num_ver_virtual_boundaries), information on the positions of the vertical virtual boundaries of the SPS (sps_virtual_boundaries_pos_x[i]), information on the number of horizontal virtual boundaries of the SPS (sps_num_hor_virtual_boundaries), and information on the positions of the horizontal virtual boundaries of the SPS (sps_virtual_boundaries_pos_y[i]). For example, the SPS may include information on the number of vertical virtual boundaries of the SPS, information on the positions of the vertical virtual boundaries of the SPS, information on the number of horizontal virtual boundaries of the SPS, and information on the positions of the horizontal virtual boundaries of the SPS when the value of the sps_loop_filter_across_virtual_boundaries_disabled_flag is 1 and the value of the sps_loop_filter_across_virtual_boundaries_disabled_present_flag is 1.

[0169] In one example, the number of information regarding the position of the vertical virtual boundary of the SPS can be determined based on the information regarding the number of vertical virtual boundaries of the SPS, and the number of information regarding the position of the horizontal virtual boundary of the SPS can be determined based on the information regarding the number of horizontal virtual boundaries of the SPS. The picture header may include information (ph_num_ver_virtual_boundaries) regarding the number of vertical virtual boundaries of the PH, information (ph_virtual_boundaries_pos_x[i]) regarding the position of the vertical virtual boundary of the PH, information (ph_num_hor_virtual_boundaries) regarding the number of horizontal virtual boundaries of the PH, and information (ph_virtual_boundaries_pos_y[i]) regarding the position of the horizontal virtual boundary of the PH, based on the virtual boundary availability flag and the virtual boundary presence flag of the SPS.

[0170] For example, when the value of the virtual boundary availability flag is 1 and the value of the virtual boundary presence flag of the SPS is 0, the picture header may include information regarding the number of vertical virtual boundaries of the PH, information regarding the position of the vertical virtual boundary of the PH, information regarding the number of horizontal virtual boundaries of the PH, and information regarding the position of the horizontal virtual boundary of the PH. In one example, the number of information regarding the position of the vertical virtual boundary of the PH can be determined based on the information regarding the number of vertical virtual boundaries of the PH, and the number of information regarding the position of the horizontal virtual boundary of the PH can be determined based on the information regarding the number of horizontal virtual boundaries of the PH.

[0171] In another embodiment of this document, each of the header information (picture header) of the pictures referring to the SPS may include the virtual boundary existence flag ph_loop_filter_across_virtual_boundaries_disabled_present_flag (or ph_virtual_boundaries_present_flag) of the PH. This embodiment can also be described together with the virtual boundary availability flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS and the virtual boundary existence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS as in the previous embodiments.

[0172] In an example according to this embodiment, when the virtual boundary availability flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1 and the virtual boundary existence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is 0, each of the header information (picture header) of the pictures referring to the SPS may include the virtual boundary existence flag ph_loop_filter_across_virtual_boundaries_disalbed_present_flag (or ph_virtual_boundaries_present_flag) of the PH.

[0173] In an example according to this embodiment, when information regarding the position of the virtual boundary (for example, vertical virtual boundary, horizontal virtual boundary) is included in the SPS, the sum of the number of vertical virtual boundaries and the number of horizontal virtual boundaries may be restricted to be greater than 0.

[0174] In an example according to this embodiment, a variable indicating whether a filter is disabled by a virtual boundary for the current picture can be derived. For example, the variable may include VirtualBoundairesDisabledFlag.

[0175] As one case in this illustration, when the virtual boundary available flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1 and the virtual boundary existence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is 1, VirtualBoundairesDisabledFlag can be 1.

[0176] As another case in this illustration, when the virtual boundary available flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1 and the virtual boundary existence flag (ph_loop_filter_across_virtual_boundaries_disabled_present_flag) of the PH is 1, VirtualBoundairesDisabledFlag can be 1.

[0177] In other cases in this illustration, VirtualBoundairesDisabledFlag can be 0.

[0178] The following table shows an exemplary syntax of the SPS according to this embodiment.

[0179]

Table 13

[0180] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0181]

Table 14

[0182] The following table shows an exemplary syntax of the header information (picture header) according to this embodiment.

[0183]

Table 15

[0184] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0185]

Table 16-1

[0186]

Table 16-2

[0187] In the embodiments related to Tables 13 to 16, the image information encoded by the encoding device and / or the image information obtained via the bitstream received from the encoding device by the decoding device may include a sequence parameter set (SPS) and a picture header (PH). The SPS may include a sps_loop_filter_across_virtual_boundaries_disabled_flag. The SPS may include a sps_loop_filter_across_virtual_boundaries_disabled_present_flag based on the sps_loop_filter_across_virtual_boundaries_disabled_flag. For example, the SPS may include the sps_loop_filter_across_virtual_boundaries_disabled_present_flag when the value of the sps_loop_filter_across_virtual_boundaries_disabled_flag is 1. The SPS may include information about the number of vertical virtual boundaries of the SPS (sps_num_ver_virtual_boundaries), information about the positions of the vertical virtual boundaries of the SPS (sps_virtual_boundaries_pos_x[i]), information about the number of horizontal virtual boundaries of the SPS (sps_num_hor_virtual_boundaries), and information about the positions of the horizontal virtual boundaries of the SPS (sps_virtual_boundaries_pos_y[i]) based on the sps_loop_filter_across_virtual_boundaries_disabled_flag and the sps_loop_filter_across_virtual_boundaries_disabled_present_flag.

[0188] For example, when the value of the virtual boundary availability flag is 1 and the value of the virtual boundary existence flag of the SPS is 1, the SPS may include information on the number of vertical virtual boundaries of the SPS, information on the positions of the vertical virtual boundaries of the SPS, information on the number of horizontal virtual boundaries of the SPS, and information on the positions of the horizontal virtual boundaries of the SPS. In one example, the number of information on the positions of the vertical virtual boundaries of the SPS can be determined based on the information on the number of vertical virtual boundaries of the SPS, and the number of information on the positions of the horizontal virtual boundaries of the SPS can be determined based on the information on the number of horizontal virtual boundaries of the SPS. The picture header may include a virtual boundary existence flag of the PH based on the virtual boundary availability flag and the virtual boundary existence flag of the SPS.

[0189] For example, when the value of the virtual boundary availability flag is 1 and the value of the virtual boundary existence flag of the SPS is 0, the picture header may include the virtual boundary existence flag of the PH. The picture header may include information on the number of vertical virtual boundaries of the PH (ph_num_ver_virtual_boundaries), information on the positions of the vertical virtual boundaries of the PH (ph_virtual_boundaries_pos_x[i]), information on the number of horizontal virtual boundaries of the PH (ph_num_hor_virtual_boundaries), and information on the positions of the horizontal virtual boundaries of the PH (ph_virtual_boundaries_pos_y[i]) based on the virtual boundary existence flag of the PH.

[0190] For example, when the value of the virtual boundary existence flag of the picture header is 1, the picture header may include information regarding the number of vertical virtual boundaries of the PH, information regarding the positions of the vertical virtual boundaries of the PH, information regarding the number of horizontal virtual boundaries of the PH, and information regarding the positions of the horizontal virtual boundaries of the PH. In one example, the number of information regarding the positions of the vertical virtual boundaries of the PH can be determined based on the information regarding the number of vertical virtual boundaries of the PH, and the number of information regarding the positions of the horizontal virtual boundaries of the PH can be determined based on the information regarding the number of horizontal virtual boundaries of the PH.

[0191] In another embodiment of this document, whether a syntax element for indicating a virtual boundary is included in the SPS can be controlled by a flag. For example, the number of the flags can be two (e.g., SPS virtual boundaries present flag, SPS PH virtual boundaries present flag).

[0192] In one example according to this embodiment, the SPS virtual boundary existence flag may be referred to as sps_loop_filter_across_virtual_boundaries_disabled_present_flag (or sps_virtual_boundaries_present_flag). The SPS virtual boundary existence flag can indicate whether virtual boundary information is included in the SPS.

[0193] In one example according to this embodiment, the SPS PH virtual boundary existence flag may be referred to as sps_ph_loop_filter_across_virtual_boundaries_disabled_present_flag. The SPS PH virtual boundary existence flag can indicate whether virtual boundary information is included in the picture header (PH).

[0194] In one example according to this embodiment, when the virtual boundary existence flag of the SPS (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) is 1, the virtual boundary existence flag of the SPS PH (sps_ph_loop_filter_across_virtual_boundaries_disabled_present_flag) does not exist and can be restricted to be inferred as 0.

[0195] In one example according to this embodiment, when the virtual boundary existence flag of the SPS PH (sps_ph_loop_filter_across_virtual_boundaries_disabled_present_flag) is 1, signaling information for disabling the loop filter across the virtual boundary may be included in the picture header.

[0196] The following table shows an exemplary syntax of the SPS according to this embodiment.

[0197]

Table 17

[0198] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0199]

Table 18

[0200] The following table shows an exemplary syntax of the header information (picture header) according to this embodiment.

[0201]

Table 19

[0202] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0203] [Table 20-1]

[0204] [Table 20-2]

[0205] In the embodiments related to Tables 17 to 20, the image information encoded by the encoding device and / or the image information obtained via the bitstream received from the encoding device by the decoding device may include a sequence parameter set (SPS) and a picture header (PH). The SPS may include a virtual boundary existence flag of the SPS (sps_loop_filter_across_virtual_boundaries_disabled_present_flag). Based on the virtual boundary existence flag of the SPS, the SPS may include information regarding the number of vertical virtual boundaries of the SPS (sps_num_ver_virtual_boundaries), information regarding the positions of the vertical virtual boundaries of the SPS (sps_virtual_boundaries_pos_x[i]), information regarding the number of horizontal virtual boundaries of the SPS (sps_num_hor_virtual_boundaries), and information regarding the positions of the horizontal virtual boundaries of the SPS (sps_virtual_boundaries_pos_y[i]).

[0206] For example, when the value of the virtual boundary existence flag of the SPS is 1, the SPS may include information on the number of vertical virtual boundaries of the SPS, information on the positions of the vertical virtual boundaries of the SPS, information on the number of horizontal virtual boundaries of the SPS, and information on the positions of the horizontal virtual boundaries of the SPS. In one example, the number of information on the positions of the vertical virtual boundaries of the SPS can be determined based on the information on the number of vertical virtual boundaries of the SPS, and the number of information on the positions of the horizontal virtual boundaries of the SPS can be determined based on the information on the number of horizontal virtual boundaries of the SPS. The SPS may include a virtual boundary existence flag of the SPS PH based on the virtual boundary existence flag of the SPS.

[0207] For example, when the value of the virtual boundary existence flag of the SPS is 0, the SPS may include a virtual boundary existence flag of the SPS PH. The picture header may include a virtual boundary existence flag of the PH based on the virtual boundary existence flag of the SPS PH. For example, when the value of the virtual boundary existence flag of the SPS PH is 1, the picture header may include the virtual boundary existence flag of the PH. The picture header may include information on the number of vertical virtual boundaries of the PH (ph_num_ver_virtual_boundaries), information on the positions of the vertical virtual boundaries of the PH (ph_virtual_boundaries_pos_x[i]), information on the number of horizontal virtual boundaries of the PH (ph_num_hor_virtual_boundaries), and information on the positions of the horizontal virtual boundaries of the PH (ph_virtual_boundaries_pos_y[i]) based on the virtual boundary existence flag of the PH.

[0208] For example, when the value of the virtual boundary existence flag of the picture header is 1, the picture header may include information regarding the number of vertical virtual boundaries of the PH, information regarding the positions of the vertical virtual boundaries of the PH, information regarding the number of horizontal virtual boundaries of the PH, and information regarding the positions of the horizontal virtual boundaries of the PH. In one example, the number of information regarding the positions of the vertical virtual boundaries of the PH can be determined based on the information regarding the number of vertical virtual boundaries of the PH, and the number of information regarding the positions of the horizontal virtual boundaries of the PH can be determined based on the information regarding the number of horizontal virtual boundaries of the PH.

[0209] In another embodiment of this document, when gradual decoding refresh (GDR) is available (i.e., when the value of gdr_enabled_flag is 1), the feature that the loop filter is disabled at the virtual boundary is enabled, and the information of the virtual boundary can be signaled (can be included) in the picture header.

[0210] In another embodiment of this document, when the function of disabling the loop filter across the virtual boundary is enabled, the information regarding the signaling of the position of the virtual boundary can be included in one or more parameter sets. For example, when the function of disabling the loop filter across the virtual boundary is enabled, the information regarding the signaling of the position of the virtual boundary can be included in the SPS and the picture header.

[0211] In this embodiment, when the virtual boundary availability flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1 and the signaling information regarding the position of the virtual boundary is included in one or more parameter sets, the following is the case.

[0212] a) The signaling information regarding the position of the virtual boundary can be included only in the SPS, only in the picture header, or in both the SPS and the picture header.

[0213] b) The derivation of the VirtualBoundariesDisabledFlag for each picture is as follows.

[0214] - If sps_loop_filter_across_virtual_boundaries_disabled_flag is 0, the VirtualBoundariesDisabledFlag can be set to 0.

[0215] - In another case in this exemplification, if the information regarding the position of the virtual boundary is not signaled in all of the SPS or the picture header associated with the picture, the VirtualBoundariesDisabledFlag can be set to 0.

[0216] - In other cases in this exemplification (where the position of the virtual boundary is signaled only in the SPS, only in the picture header, or in both the SPS and the picture header), the VirtualBoundariesDisabledFlag can be set to 1.

[0217] c) The virtual boundaries applied to a picture can include the union of the virtual boundaries signaled in the parameter sets that the picture directly or indirectly references. For example, the virtual boundaries can include the virtual boundaries signaled in the SPS (if they exist). For example, the virtual boundaries can include the virtual boundaries signaled in the picture header associated with the picture (if they exist).

[0218] d) Restrictions can be applied so as not to exceed the maximum number of virtual boundaries per picture or pre-defined values. For example, the pre-defined value can be 8.

[0219] e) The information regarding the position of the virtual boundaries signaled in the picture header (if any) can be restricted so as not to be the same as the information regarding the position of the virtual boundaries included in other parameter sets (e.g., SPS or PPS).

[0220] - As an alternative, for a position of a certain virtual boundary currently applied to a picture, the position of the virtual boundary (e.g., the same position of the virtual boundary signaled in a picture header related to the SPS and the picture) may be included in two different parameter sets.

[0221] f) If the virtual boundary existence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is 1, the virtual boundary existence flag (sps_ph_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS PH does not exist and may be restricted to be inferred as 0.

[0222] The following table shows an exemplary syntax of the SPS according to this embodiment.

[0223]

Table 21

[0224] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0225]

Table 22

[0226] The following table shows an exemplary syntax of the header information (picture header) according to this embodiment.

[0227]

Table 23

[0228] The following table shows exemplary semantics for the syntax elements included in the syntax.

[0229]

Table 24-1

[0230]

Table 24-2

[0231] In embodiments related to Tables 21 to 24, the image information encoded by the encoding device and / or the image information obtained via the bitstream received from the encoding device by the decoding device may include a sequence parameter set (SPS) and a picture header (PH). The SPS may include a sps_loop_filter_across_virtual_boundaries_disabled_flag. The SPS may include a sps_loop_filter_across_virtual_boundaries_disabled_present_flag based on the sps_loop_filter_across_virtual_boundaries_disabled_flag. For example, the SPS may include the sps_loop_filter_across_virtual_boundaries_disabled_present_flag when the value of the sps_loop_filter_across_virtual_boundaries_disabled_flag is 1. The SPS may include information regarding the number of vertical virtual boundaries of the SPS (sps_num_ver_virtual_boundaries), information regarding the positions of the vertical virtual boundaries of the SPS (sps_virtual_boundaries_pos_x[i]), information regarding the number of horizontal virtual boundaries of the SPS (sps_num_hor_virtual_boundaries), and information regarding the positions of the horizontal virtual boundaries of the SPS (sps_virtual_boundaries_pos_y[i]) based on the sps_loop_filter_across_virtual_boundaries_disabled_flag and the sps_loop_filter_across_virtual_boundaries_disabled_present_flag.

[0232] For example, when the value of the virtual boundary availability flag is 1 and the value of the virtual boundary existence flag of the SPS is 1, the SPS may include information regarding the number of vertical virtual boundaries of the SPS, information regarding the positions of the vertical virtual boundaries of the SPS, information regarding the number of horizontal virtual boundaries of the SPS, and information regarding the positions of the horizontal virtual boundaries of the SPS. In one example, the number of information regarding the positions of the vertical virtual boundaries of the SPS can be determined based on the information regarding the number of vertical virtual boundaries of the SPS, and the number of information regarding the positions of the horizontal virtual boundaries of the SPS can be determined based on the information regarding the number of horizontal virtual boundaries of the SPS. The picture header may include a virtual boundary existence flag of the PH based on the virtual boundary availability flag.

[0233] For example, when the value of the virtual boundary availability flag is 1, the picture header may include a virtual boundary existence flag of the PH. The picture header may include information regarding the number of vertical virtual boundaries of the PH (ph_num_ver_virtual_boundaries), information regarding the positions of the vertical virtual boundaries of the PH (ph_virtual_boundaries_pos_x[i]), information regarding the number of horizontal virtual boundaries of the PH (ph_num_hor_virtual_boundaries), and information regarding the positions of the horizontal virtual boundaries of the PH (ph_virtual_boundaries_pos_y[i]) based on the virtual boundary existence flag of the PH. For example, when the value of the virtual boundary existence flag of the PH is 1, the picture header may include information regarding the number of vertical virtual boundaries of the PH, information regarding the positions of the vertical virtual boundaries of the PH, information regarding the number of horizontal virtual boundaries of the PH, and information regarding the positions of the horizontal virtual boundaries of the PH. In one example, the number of information regarding the positions of the vertical virtual boundaries of the PH can be determined based on the information regarding the number of vertical virtual boundaries of the PH, and the number of information regarding the positions of the horizontal virtual boundaries of the PH can be determined based on the information regarding the number of horizontal virtual boundaries of the PH.

[0234] In another embodiment of this document, although based on the foregoing embodiments, loop filtering can be performed by not imposing the limitation that the sum of the number of vertical virtual boundaries and the number of horizontal virtual boundaries is greater than zero.

[0235] In another embodiment of this document, information regarding virtual boundaries can be signaled in both SPS and PH. In an example of this embodiment, when the virtual boundary available flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) in SPS is 1, information regarding the number of vertical virtual boundaries, information regarding the number of horizontal virtual boundaries, and / or information regarding the position of virtual boundaries can be included in SPS. Along with this, when the virtual boundary available flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) in SPS is 1, information regarding the number of vertical virtual boundaries, information regarding the number of horizontal virtual boundaries, and / or information regarding the delta value of the position of virtual boundaries (delta value of the position of virtual boundaries) can be included in the picture header. The delta value of the position of virtual boundaries can refer to the difference between the positions of virtual boundaries. The picture header can also include information regarding the sign of the position of virtual boundaries.

[0236] According to an example for this embodiment, in order to derive the position of virtual boundaries for each picture, when the delta value of the position of virtual boundaries does not exist in the picture header, the information regarding the position of virtual boundaries signaled in SPS can be used for loop filtering. When the delta value of the position of virtual boundaries exists in the picture header, the position of virtual boundaries can be derived based on the sum of the information regarding the position of virtual boundaries signaled in SPS and the associated delta values.

[0237] The following table shows an exemplary syntax of SPS according to this embodiment.

[0238]

Table 25

[0239] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0240] [Table 26]

[0241] The following table shows the exemplary syntax of the header information (picture header) according to this embodiment.

[0242] [Table 27]

[0243] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0244] [Table 28-1]

[0245] [Table 28-2]

[0246] In the embodiments related to Tables 25 to 28, the image information encoded by the encoding device and / or the image information obtained via the bitstream received from the encoding device by the decoding device may include a sequence parameter set (SPS) and a picture header (PH). The SPS may include a sps_loop_filter_across_virtual_boundaries_disabled_flag. Based on the sps_loop_filter_across_virtual_boundaries_disabled_flag, the SPS may include information on the number of vertical virtual boundaries of the SPS (sps_num_ver_virtual_boundaries), information on the positions of the vertical virtual boundaries of the SPS (sps_virtual_boundaries_pos_x[i]), information on the number of horizontal virtual boundaries of the SPS (sps_num_hor_virtual_boundaries), and information on the positions of the horizontal virtual boundaries of the SPS (sps_virtual_boundaries_pos_y[i]). For example, when the value of the sps_loop_filter_across_virtual_boundaries_disabled_flag is 1, the SPS may include information on the number of horizontal virtual boundaries of the SPS, information on the positions of the horizontal virtual boundaries of the SPS, information on the number of vertical virtual boundaries of the SPS, and information on the positions of the vertical virtual boundaries of the SPS.

[0247] In one example, the number of information regarding the position of the horizontal virtual boundary of the SPS can be determined based on the information regarding the number of horizontal virtual boundaries of the SPS, and the number of information regarding the position of the vertical virtual boundary of the SPS can be determined based on the information regarding the number of vertical virtual boundaries of the SPS. The picture header may include a virtual boundary existence flag of the PH based on the virtual boundary availability flag. For example, when the value of the virtual boundary availability flag is 1, the picture header may include the virtual boundary existence flag of the PH. The picture header may include information regarding the delta value of the position of the horizontal virtual boundary of the PH (ph_virtual_boundaries_pos_x_delta[i]), information regarding the sign of the position of the horizontal virtual boundary of the PH (ph_virtual_boundaries_pos_x_sign[i]), information regarding the delta value of the position of the vertical virtual boundary of the PH (ph_virtual_boundaries_pos_y_delta[i]), and information regarding the sign of the position of the vertical virtual boundary of the PH (ph_virtual_boundaries_pos_y_sign[i]) based on the virtual boundary existence flag of the PH.

[0248] For example, when the value of the virtual boundary existence flag of the PH is 1, the picture header may include information regarding the delta value of the position of the vertical virtual boundary of the PH, information regarding the sign of the position of the vertical virtual boundary of the PH, information regarding the delta value of the position of the horizontal virtual boundary of the PH, and information regarding the sign of the position of the horizontal virtual boundary of the PH. In one example, based on the information regarding the number of vertical virtual boundaries of the SPS, the number of information regarding the delta value of the position of the vertical virtual boundary of the PH and the number of information regarding the sign of the position of the vertical virtual boundary of the PH can be determined, and based on the information regarding the number of horizontal virtual boundaries of the SPS, the number of information regarding the delta value of the position of the horizontal virtual boundary of the PH and the number of information regarding the sign of the position of the horizontal virtual boundary of the PH can be determined.

[0249] In yet another embodiment of this document, the signaling of information regarding the position of the virtual boundary for each picture is described. In one example, if the information regarding the position of the virtual boundary is included in the SPS and the information regarding the delta value of the position of the virtual boundary is not included in the picture header, the information regarding the position of the virtual boundary included in the SPS may be used for loop filtering. If the information regarding the position of the virtual boundary is not included in the SPS and the information regarding the delta value of the position of the virtual boundary is included in the picture header, the information regarding the position of the virtual boundary included in the picture header may be used for loop filtering. If the information regarding the position of the virtual boundary is included in the SPS and the information regarding the delta value of the position of the virtual boundary is included in the picture header, the position of the virtual boundary may be derived based on the sum of the information regarding the position of the virtual boundary signaled in the SPS and the associated delta value. If the information regarding the position of the virtual boundary is not included in the SPS and the information regarding the delta value of the position of the virtual boundary is not included in the picture header, the virtual boundary may not be applied to the picture.

[0250] The following table shows an exemplary syntax of the SPS according to this embodiment.

[0251]

Table 29

[0252] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0253]

Table 30

[0254] The following table shows an exemplary syntax of the header information (picture header) according to this embodiment.

[0255]

Table 31

[0256] The following table shows exemplary semantics regarding the syntax elements included in the syntax.

[0257] [Table 32-1]

[0258] [Table 32-2]

[0259] In embodiments related to Tables 29 to 32, the image information encoded by the encoding device and / or the image information obtained via the bitstream received from the encoding device by the decoding device may include a sequence parameter set (SPS) and a picture header (PH).

[0260] The SPS may include a virtual boundary availability flag (sps_loop_filter_across_virtual_boundaries_disabled_flag). The SPS may include an SPS virtual boundary presence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) based on the virtual boundary availability flag. For example, the SPS may include the SPS virtual boundary presence flag when the value of the virtual boundary availability flag is 1. The SPS may include information regarding the number of SPS vertical virtual boundaries (sps_num_ver_virtual_boundaries), information regarding the positions of the SPS vertical virtual boundaries (sps_virtual_boundaries_pos_x[i]), information regarding the number of SPS horizontal virtual boundaries (sps_num_hor_virtual_boundaries), and information regarding the positions of the SPS horizontal virtual boundaries (sps_virtual_boundaries_pos_y[i]) based on the virtual boundary availability flag and the SPS virtual boundary presence flag.

[0261] For example, the SPS may include information regarding the number of the horizontal virtual boundaries, information regarding the positions of the horizontal virtual boundaries, information regarding the number of the vertical virtual boundaries, and information regarding the positions of the vertical virtual boundaries when the value of the virtual boundary availability flag is 1 and the value of the SPS virtual boundary presence flag is 1. In one example, the number of the information regarding the positions of the horizontal virtual boundaries can be determined based on the information regarding the number of the horizontal virtual boundaries, and the number of the information regarding the positions of the vertical virtual boundaries can be determined based on the information regarding the number of the vertical virtual boundaries. The picture header may include a PH virtual boundary presence flag based on the virtual boundary availability flag.

[0262] For example, when the value of the virtual boundary available flag is 1, the picture header may include the virtual boundary existence flag of the PH. The picture header may include information on the number of vertical virtual boundaries of the PH (ph_num_ver_virtual_boundaries) based on the virtual boundary existence flag of the PH and information on the number of vertical virtual boundaries of the SPS. For example, when the value of the virtual boundary existence flag of the PH is 1 and the value of the information on the number of vertical virtual boundaries of the SPS is 0, the picture header may include information on the number of vertical virtual boundaries of the PH. In one example, the picture header may include information on the delta value of the position of the vertical virtual boundary of the PH (ph_virtual_boundaries_pos_x_delta[i]) and information on the sign of the position of the vertical virtual boundary of the PH (ph_virtual_boundaries_pos_x_sign[i]) based on the information on the number of vertical virtual boundaries of the PH. In one example, based on the information on the number of vertical virtual boundaries of the PH, the number of information on the delta value of the position of the vertical virtual boundary of the PH and the number of information on the sign of the position of the vertical virtual boundary of the PH can be determined. The picture header may include information on the number of horizontal virtual boundaries of the PH (ph_num_hor_virtual_boundaries) based on the virtual boundary existence flag of the PH and information on the number of horizontal virtual boundaries of the SPS.

[0263] For example, when the value of the virtual boundary existence flag of the PH is 1 and the value of the information regarding the number of horizontal virtual boundaries of the SPS is 0, the picture header may include the information regarding the number of horizontal virtual boundaries of the PH. In one example, based on the information regarding the number of horizontal virtual boundaries of the PH, the picture header may include information (ph_virtual_boundaries_pos_y_delta[i]) regarding the delta value of the position of the horizontal virtual boundaries of the PH and information (ph_virtual_boundaries_pos_y_sign[i]) regarding the sign of the position of the horizontal virtual boundaries of the PH. In one example, based on the information regarding the number of horizontal virtual boundaries of the PH, the number of information regarding the delta value of the position of the horizontal virtual boundaries of the PH and the number of information regarding the sign of the position of the horizontal virtual boundaries of the PH can be determined.

[0264] According to the embodiments of the present document together with the table, the information necessary to control in-loop filtering performed across virtual boundaries can be efficiently signaled by the coding device. In one example, information related to whether in-loop filtering is available across virtual boundaries can be signaled.

[0265] FIG. 9 and FIG. 10 schematically show an example of a video / image encoding method and related components according to the embodiments of the present document.

[0266] The method disclosed in FIG. 9 can be executed by the encoding device disclosed in FIG. 2 or FIG. 10. Specifically, for example, S900 to S920 in FIG. 9 can be executed by the residual processing unit 230 of the encoding device in FIG. 10, S930 and S940 in FIG. 9 can be executed by the prediction unit 220 of the encoding device in FIG. 10, S950 in FIG. 9 can be executed by the filtering unit 260 of the encoding device in FIG. 10, and S960 in FIG. 9 can be executed by the entropy encoding unit 240 of the encoding device in FIG. 10. The method disclosed in FIG. 9 may include the embodiments described above in the present document.

[0267] Referring to FIG. 9, the encoding device can derive residual samples (S900). The encoding device can derive the residual samples for the current block, and the residual samples for the current block can be derived based on the original samples and the predicted samples of the current block. Specifically, the encoding device can derive the predicted samples of the current block based on the prediction mode. In this case, various prediction methods disclosed in this document, such as inter prediction or intra prediction, can be applied. The residual samples can be derived based on the predicted samples and the original samples.

[0268] The encoding device can derive transform coefficients (S910). The encoding device can derive the transform coefficients based on the transform procedure for the residual samples. For example, the transform procedure may include at least one of DCT, DST, GBT, or CNT.

[0269] The encoding device can derive quantized transform coefficients. The encoding device can derive the quantized transform coefficients based on the quantization procedure for the transform coefficients. The quantized transform coefficients may have a form of a one-dimensional vector based on the coefficient scan order.

[0270] The encoding device can generate residual information (S920). The encoding device can generate the residual information based on the transform coefficients. The encoding device can generate the residual information indicating the quantized transform coefficients. The residual information can be generated through various encoding methods such as exponential Golomb, CAVLC, CABAC, etc.

[0271] The encoding device can derive a prediction sample (S930). The encoding device can derive the prediction sample of the current block based on the prediction mode. The encoding device can derive the prediction sample of the current block based on the prediction mode. In this case, various prediction methods disclosed in this document, such as inter prediction or intra prediction, can be applied.

[0272] The encoding device can generate prediction-related information (S940). The encoding device can generate prediction-related information based on the prediction sample and / or the mode applied thereto. The prediction-related information may include information for various prediction modes (e.g., merge mode, MVP mode, etc.), MVD information, etc.

[0273] The encoding device can generate a restored sample. The encoding device can generate a restored sample based on the residual information. The restored sample can be generated by adding the residual sample based on the residual information to the prediction sample. Specifically, the encoding device can perform a prediction (intra or inter prediction) on the current block and generate a restored sample based on the original sample and the prediction sample generated from the prediction.

[0274] The restored sample may include a restored luma sample and a restored chroma sample. Specifically, the residual sample may include a residual luma sample and a residual chroma sample. The residual luma sample can be generated based on the original luma sample and the predicted luma sample. The residual chroma sample can be generated based on the original chroma sample and the predicted chroma sample. The encoding device can derive a conversion coefficient (luma conversion coefficient) for the residual luma sample and / or a conversion coefficient (chroma conversion coefficient) for the residual chroma sample. The quantized conversion coefficient may include a quantized luma conversion coefficient and / or a quantized chroma conversion coefficient.

[0275] The encoding device can generate in-loop filtering related information for the restoration samples of the current picture (S950). The encoding device can execute an in-loop filtering procedure on the restoration samples and generate in-loop filtering related information based on the in-loop filtering procedure. For example, the in-loop filtering related information may include information regarding the virtual boundary described above in this document (such as the virtual boundary available flag in the SPS, the virtual boundary available flag in the picture header, the virtual boundary existence flag in the SPS, the virtual boundary existence flag in the picture header, information regarding the position of the virtual boundary, etc.).

[0276] The encoding device can encode video / image information (S960). The encoding device can encode video / image information including the residual information, prediction related information, and the in-loop filtering related information. The encoded video / image information can be output in the form of a bitstream. The bitstream can be transmitted to a decoding device via a network or a storage medium.

[0277] The image / video information can include various information according to the embodiments of this document. For example, the image / video information may include information disclosed in at least one of Tables 1 to 32 described above.

[0278] In one embodiment, the image information may include the SPS and picture header information referring to the SPS. The SPS may include a virtual boundary available flag (the virtual boundary available flag in the SPS) related to whether signaling of information related to the virtual boundary exists (or is available) in the SPS or the picture header information. The in-loop filtering procedure can be executed across the virtual boundary based on the virtual boundary available flag (or may not be executed across the virtual boundary). For example, the virtual boundary available flag can indicate whether a disable of the in-loop filtering procedure across the virtual boundary is available.

[0279] In one embodiment, the SPS may include a virtual boundary existence flag for the SPS. For example, based on the virtual boundary existence flag for the SPS, it can be determined whether information regarding the position of the virtual boundary and information regarding the number of the virtual boundaries are included in the SPS.

[0280] In one embodiment, based on the value of the virtual boundary existence flag for the SPS being 1, the SPS may include information regarding the number of vertical virtual boundaries.

[0281] In one embodiment, the SPS may include information regarding the position of vertical virtual boundaries. Also, based on the information regarding the number of the vertical virtual boundaries, the number of the information regarding the position of the vertical virtual boundaries can be determined.

[0282] In one embodiment, based on the value of the virtual boundary existence flag for the SPS being 1, the SPS may include information regarding the number of horizontal virtual boundaries.

[0283] In one embodiment, the SPS may include information regarding the position of horizontal virtual boundaries. Also, based on the information regarding the number of the horizontal virtual boundaries, the number of the information regarding the position of the horizontal virtual boundaries can be determined.

[0284] In one embodiment, based on the value of the virtual boundary availability flag (virtual boundary availability flag for the SPS) being 1 and the value of the virtual boundary existence flag being 0, the picture header information may include a virtual boundary existence flag for the picture header.

[0285] In one embodiment, based on the value of the virtual boundary existence flag for the picture header being 1, the picture header information may include information regarding the number of vertical virtual boundaries.

[0286] In one embodiment, the picture header information may include information regarding the position of vertical virtual boundaries. Also, based on the information regarding the number of the vertical virtual boundaries, the number of the information regarding the position of the vertical virtual boundaries can be determined.

[0287] In one embodiment, based on the value of the virtual boundary presence flag of the picture header being 1, the picture header information may include information regarding the number of horizontal virtual boundaries.

[0288] In one embodiment, the picture header information may include information regarding the position of the horizontal virtual boundary. Also, based on the information regarding the number of the horizontal virtual boundaries, the number of the information regarding the position of the horizontal virtual boundary can be determined.

[0289] In one embodiment, based on the SPS including information regarding the position of the vertical virtual boundary and information regarding the position of the horizontal virtual boundary, the sum of the number of the vertical virtual boundaries and the number of the horizontal virtual boundaries may be greater than 0.

[0290] In one embodiment, the image information (and / or in-loop filtering related information, virtual boundary related information) may further include a virtual boundary presence flag of the SPS, a virtual boundary presence flag of the picture header, and a gradual decoding refresh (GDR) availability flag. For example, based on the value of the GDR availability flag being 1, the value of the virtual boundary availability flag (the virtual boundary availability flag of the SPS) may be 1, the value of the virtual boundary presence flag of the SPS may be 0, and the value of the virtual boundary presence flag of the picture header may be 1 (the signaling of the virtual boundary information may exist in the picture header).

[0291] FIGS. 11 and 12 schematically show an example of a video / image decoding method and related components according to an embodiment of the present document.

[0292] The method disclosed in FIG. 11 can be executed by the decoding device disclosed in FIG. 3 or FIG. 12. Specifically, for example, S1100 in FIG. 11 can be executed by the entropy decoding unit 310 of the decoding device, S1110 and S1120 can be executed by the residual processing unit 320 of the decoding device, S1130 can be executed by the prediction unit 330 of the decoding device, S1140 can be executed by the addition unit 340 of the decoding device, and S1150 can be executed by the filtering unit 350 of the decoding device. The method disclosed in FIG. 11 may include the embodiments described above in this document.

[0293] Referring to FIG. 11, the decoding device can receive / acquire video / image information (S1100). The video / image information may include residual information, prediction-related information, and / or in-loop filtering-related information (and / or virtual boundary-related information). The decoding device can receive / acquire the image / video information via a bitstream.

[0294] The image / video information may include various information according to the embodiments of this document. For example, the image / video information may include the information disclosed in at least one of Tables 1 to 32 described above.

[0295] The decoding device can derive quantized transform coefficients. The decoding device can derive quantized transform coefficients based on the residual information. The quantized transform coefficients may have a form of a one-dimensional vector based on the coefficient scan order. The quantized transform coefficients may include quantized luma transform coefficients and / or quantized chroma transform coefficients.

[0296] The decoding device can derive the conversion coefficients (S1110). The decoding device can derive the conversion coefficients based on the inverse quantization procedure for the quantized conversion coefficients. The decoding device can derive the luma conversion coefficients via inverse quantization based on the quantized luma conversion coefficients. The decoding device can derive the chroma conversion coefficients via inverse quantization based on the quantized chroma conversion coefficients.

[0297] The decoding device can generate / derive residual samples (S1120). The decoding device can derive the residual samples based on the inverse transformation procedure for the conversion coefficients. The decoding device can derive the residual luma samples via the inverse transformation procedure based on the luma conversion coefficients. The decoding device can derive the residual chroma samples via the inverse transformation procedure based on the chroma conversion coefficients.

[0298] The decoding device can generate prediction samples (S1130). The decoding device can generate prediction samples for the current block based on the prediction-related information. The decoding device can perform prediction based on the image / video information and derive the prediction samples of the current block. The prediction-related information may include prediction mode information. The decoding device can determine whether inter prediction or intra prediction is applied to the current block based on the prediction mode information, and perform prediction based on this. The prediction samples may include prediction luma samples and / or prediction chroma samples.

[0299] The decoding device can generate / derive restored samples (S1140). For example, the decoding device can generate / derive restored luma samples and / or restored chroma samples. The decoding device can generate restored luma samples and / or restored chroma samples based on the residual information. The decoding device can generate restored samples based on the residual information. The restored samples may include restored luma samples and / or restored chroma samples. The luma component of the restored sample may correspond to the restored luma sample, and the chroma component of the restored sample may correspond to the restored chroma sample. The decoding device can generate predicted luma samples and / or predicted chroma samples through a prediction procedure. The decoding device can generate a restored luma sample based on the predicted luma sample and the residual luma sample. The decoding device can generate a restored chroma sample based on the predicted chroma sample and the residual chroma sample.

[0300] The decoding device can generate modified (filtered) restored samples (S1150). The decoding device can generate modified restored samples by performing an in-loop filtering procedure on the restored samples of the current picture. The decoding device can generate modified restored samples based on in-loop filtering related information (and / or virtual boundary related information). The decoding device can use a deblocking procedure, an SAO procedure, and / or an ALF procedure to generate modified restored samples.

[0301] In one example, the step of S1150 can include a step of determining whether the in-loop filtering procedure is to be performed across a virtual boundary. That is, the decoding device can determine whether the in-loop filtering procedure is to be performed across a virtual boundary. The decoding device can determine whether the in-loop filtering procedure is to be performed based on in-loop filtering related information (and / or virtual boundary related information).

[0302] In one embodiment, the image information may include SPS and picture header information referring to the SPS. The SPS may include a virtual boundary availability flag (virtual boundary existence flag of the SPS). Based on the virtual boundary availability flag, it can be determined whether (or is available) signaling of information related to the virtual boundary exists in the SPS or the picture header information. Based on the determination, the step of generating the corrected restored sample (S1150) may include the step of performing the in-loop filtering procedure across the virtual boundary (or may include the step of performing the in-loop filtering procedure without crossing the virtual boundary). For example, the virtual boundary availability flag can indicate whether a disable of the in-loop filtering procedure across the virtual boundary is available.

[0303] In one embodiment, the SPS may include a virtual boundary existence flag of the SPS. For example, based on the virtual boundary existence flag of the SPS, it can be determined whether the SPS includes information regarding the position of the virtual boundary and information regarding the number of the virtual boundaries.

[0304] In one embodiment, based on the value of the virtual boundary existence flag of the SPS being 1, the SPS may include information regarding the number of vertical virtual boundaries.

[0305] In one embodiment, the SPS may include information regarding the position of the vertical virtual boundaries. Also, based on the information regarding the number of the vertical virtual boundaries, the number of the information regarding the position of the vertical virtual boundaries can be determined.

[0306] In one embodiment, based on the value of the virtual boundary existence flag of the SPS being 1, the SPS may include information regarding the number of horizontal virtual boundaries.

[0307] In one embodiment, the SPS may include information regarding the position of a horizontal virtual boundary. Also, based on the information regarding the number of the horizontal virtual boundaries, the number of the information regarding the position of the horizontal virtual boundary can be determined.

[0308] In one embodiment, the image information includes picture header information, and based on that the value of the virtual boundary available flag (the virtual boundary available flag of the SPS) is 1 and the value of the virtual boundary existence flag of the SPS is 0, the picture header information may include a virtual boundary existence flag of the picture header.

[0309] In one embodiment, based on that the value of the virtual boundary existence flag of the picture header is 1, the picture header information may include information regarding the number of vertical virtual boundaries.

[0310] In one embodiment, the picture header information may include information regarding the position of vertical virtual boundaries. Also, based on the information regarding the number of the vertical virtual boundaries, the number of the information regarding the position of the vertical virtual boundary can be determined.

[0311] In one embodiment, based on that the value of the virtual boundary existence flag of the picture header is 1, the picture header information may include information regarding the number of horizontal virtual boundaries.

[0312] In one embodiment, the picture header information may include information regarding the position of horizontal virtual boundaries. Also, based on the information regarding the number of the horizontal virtual boundaries, the number of the information regarding the position of the horizontal virtual boundary can be determined.

[0313] In one embodiment, based on that the SPS includes information regarding the position of vertical virtual boundaries and information regarding the position of horizontal virtual boundaries, the sum of the number of the vertical virtual boundaries and the number of the horizontal virtual boundaries may be greater than 0.

[0314] In one embodiment, the image information (and / or in-loop filtering related information, virtual boundary related information) may further include a virtual boundary presence flag in the SPS, a virtual boundary presence flag in the picture header, and a gradual decoding refresh (GDR) availability flag. For example, based on the value of the GDR availability flag being 1, the value of the virtual boundary availability flag (virtual boundary availability flag in the SPS) may be 1, the value of the virtual boundary presence flag in the SPS may be 0, and the value of the virtual boundary presence flag in the picture header may be 1 (signaling of virtual boundary information may be present in the picture header).

[0315] When there are residual samples for the current block, the decoding device can receive information regarding the residual for the current block. The information regarding the residual can include transform coefficients regarding the residual samples. The decoding device can derive residual samples (or, a residual sample array) for the current block based on the residual information. Specifically, the decoding device can derive quantized transform coefficients based on the residual information. The quantized transform coefficients can have a one-dimensional vector form based on the coefficient scan order. The decoding device can derive transform coefficients based on an inverse quantization procedure for the quantized transform coefficients. The decoding device can derive residual samples based on the transform coefficients.

[0316] The decoding device can generate restored samples based on (intra) prediction samples and residual samples, and can derive a restored block or a restored picture based on the restored samples. Specifically, the decoding device can generate restored samples based on the sum of the (intra) prediction samples and the residual samples. Thereafter, as described above, the decoding device can apply in-loop filtering procedures such as deblocking filtering and / or SAO procedures to the restored picture, if necessary, to improve subjective / objective image quality.

[0317] For example, the decoding device can decode a bitstream or encoded information and obtain image information including all or part of the aforementioned information (or syntax elements). Further, the bitstream or encoded information can be stored in a computer-readable storage medium and can be caused to perform the aforementioned decoding method.

[0318] In the foregoing embodiments, the method has been described based on a flowchart as a series of steps or blocks, but the corresponding embodiments are not limited to the order of the steps, and a certain step can occur in a different order from the steps described above or simultaneously. Also, those skilled in the art can understand that the steps shown in the flowchart are not exclusive, and different steps can be included, or one or more steps of the flowchart can be deleted without affecting the scope of the embodiments of this document.

[0319] The method according to the foregoing embodiments of this document can be implemented in the form of software, and the encoding device and / or decoding device according to this document can be included in, for example, a device that performs image processing such as a TV, a computer, a smartphone, a set-top box, a display device, etc.

[0320] In this document, when an embodiment is realized by software, the above-described method can be realized by modules (processes, functions, etc.) that perform the above-described functions. The modules can be stored in a memory and executed by a processor. The memory may be inside or outside the processor and may be connected to the processor by various well-known means. The processor can include an ASIC (application-specific integrated circuit), other chip sets, logic circuits, and / or data processing devices. The memory can include a ROM (read-only memory), a RAM (random access memory), a flash memory, a memory card, a storage medium, and / or other storage devices. That is, the embodiments described in this document can be realized and performed on a processor, a microprocessor, a controller, or a chip. For example, the functional units shown in each drawing can be realized and performed on a computer, a processor, a microprocessor, a controller, or a chip. In this case, information for realization (e.g., information on instructions) or an algorithm can be stored in a digital storage medium.

[0321] In addition, the decoding device and encoding device to which the embodiments of this document are applied may include a multimedia broadcast transmission / reception device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video conferencing device, a real-time communication device such as video communication, a mobile streaming device, a storage medium, a camcorder, an on-demand video (VoD) service providing device, an OTT video (Over the top video) device, an Internet streaming service providing device, a three-dimensional (3D) video device, a VR (virtual reality) device, an AR (augmented reality) device, a picture phone video device, a transportation means terminal (e.g., a vehicle terminal including an autonomous driving vehicle terminal, an airplane terminal, a ship terminal, etc.) and a medical video device, etc., and may be used to process video signals or data signals. For example, the OTT video (Over the top video) device may include a game console, a Blu-ray player, an Internet access TV, a home theater system, a smartphone, a tablet PC, a DVR (Digital Video Recoder), etc.

[0322] In addition, the processing method to which the embodiments of this document are applied can be produced in the form of a program executed by a computer and can be stored in a recording medium readable by the computer. Multimedia data having a data structure according to the embodiments of this document can also be stored in a recording medium readable by the computer. The recording medium readable by the computer includes all types of storage devices and distributed storage devices in which data readable by the computer is stored. The recording medium readable by the computer can include, for example, Blu-ray Disc (BD), Universal Serial Bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices. Further, the recording medium readable by the computer includes a medium realized in the form of a carrier wave (for example, transmission via the Internet). Also, a bitstream generated by an encoding method can be stored in a recording medium readable by the computer or transmitted via a wired or wireless communication network.

[0323] In addition, the embodiments of this document can be realized by a computer program product with program code, and the program code can be executed by a computer according to the embodiments of this document. The program code can be stored on a carrier readable by a computer.

[0324] FIG. 13 shows an example of a content streaming system to which the embodiments disclosed in this document can be applied.

[0325] Referring to FIG. 13, the content streaming system to which the embodiments of this document are applied can generally include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0326] The encoding server compresses the content input from a multimedia input device such as a smartphone, camera, camcorder, etc. into digital data to generate a bitstream, and plays the role of transmitting this to the streaming server. As another example, when a multimedia input device such as a smartphone, camera, camcorder, etc. directly generates a bitstream, the encoding server can be omitted.

[0327] The bitstream can be generated by an encoding method or a method for generating a bitstream to which the embodiments of this document are applied, and the streaming server can temporarily store the bitstream in the process of transmitting or receiving the bitstream.

[0328] The streaming server transmits multimedia data to a user device based on a user request via a web server, and the web server plays the role of a medium for informing the user of what services are available. If the user requests a desired service from the web server, the web server transmits this to the streaming server, and the streaming server transmits multimedia data to the user. At this time, the content streaming system can include another control server, and in this case, the control server plays the role of controlling commands / responses between each device in the content streaming system.

[0329] The streaming server can receive content from a media repository and / or an encoding server. For example, when it comes to receiving content from the encoding server, the content can be received in real time. In this case, in order to provide a smooth streaming service, the streaming server can store the bitstream for a certain period of time.

[0330] In the example of the user device, there may be a mobile phone, a smart phone, a laptop computer, a digital broadcast terminal, a PDA (personal digital assistants), a PMP (portable multimedia player), a navigation device, a slate PC, a tablet PC, an ultrabook, a wearable device (for example, a smartwatch, a smart glass, an HMD (head mounted display)), a digital TV, a desktop computer, a digital signage, etc.

[0331] Each server in the content streaming system can be operated as a distributed server. In this case, the data received by each server can be distributedly processed.

[0332] The claims described in this specification can be combined in various ways. For example, the technical features of the method claims in this specification can be combined and realized as an apparatus, and the technical features of the apparatus claims in this specification can be combined and realized as a method. Also, the technical features of the method claims in this specification and the technical features of the apparatus claims can be combined and realized as an apparatus, and the technical features of the method claims in this specification and the technical features of the apparatus claims can be combined and realized as a method.

Claims

1. In an image decoding method executed by a decoding apparatus, obtaining image information including residual information, prediction-related information, and in-loop filtering-related information via a bitstream; deriving transform coefficients based on the residual information; generating residual samples based on the transform coefficients; generating prediction samples based on the prediction-related information; generating restored samples based on the residual samples and the prediction samples; generating modified restored samples based on the in-loop filtering-related information, comprising: the image information includes an SPS (sequence parameter set) and picture header information referring to the SPS; the SPS includes a virtual boundary availability flag and an SPS virtual boundary existence flag; the step of generating the modified restored samples includes: executing an in-loop filtering procedure for the restored samples; determining, based on the SPS virtual boundary existence flag, whether (i) information related to a virtual boundary exists in the SPS or (ii) information related to a virtual boundary exists in the picture header information; determining, based on the virtual boundary availability flag, whether the in-loop filtering procedure across the virtual boundary is enabled; whether information regarding the position of the virtual boundary and information regarding the number of the virtual boundaries are included in the SPS is determined based on the SPS virtual boundary existence flag; based on the value of the SPS virtual boundary existence flag being 1, the SPS includes the information regarding the number of the virtual boundaries; An image decoding method, wherein based on the information regarding the number of the virtual boundaries, the SPS includes the information regarding the position of the virtual boundaries.

2. In an image encoding method executed by an encoding apparatus, deriving residual samples for a current block; deriving transform coefficients based on the residual samples for the current block; generating residual information based on the transform coefficients; generating prediction samples for the current block based on the residual samples; generating prediction-related information based on the prediction sample; generating loop filtering-related information for the in-loop filtering procedure of the restored sample; encoding image information including the residual information, the prediction-related information, and the loop filtering-related information; wherein the image information includes an SPS (sequence parameter set) and picture header information referring to the SPS; the SPS includes a virtual boundary availability flag and an SPS virtual boundary existence flag related to whether (i) information related to the virtual boundary exists in the SPS or (ii) information related to the virtual boundary exists in the picture header information; the value of the virtual boundary availability flag is related to whether the in-loop filtering procedure is enabled across the virtual boundary; the value of the SPS virtual boundary existence flag is related to whether information regarding the position of the virtual boundary and information regarding the number of the virtual boundaries are included in the SPS; based on the value of the SPS virtual boundary existence flag being 1, the SPS includes the information regarding the number of the virtual boundaries; based on the information regarding the number of the virtual boundaries, the SPS includes the information regarding the position of the virtual boundary, an image encoding method. **Claim 3**: A method for generating a bitstream, the method comprising: deriving a residual sample for a current block; deriving transform coefficients based on the residual sample for the current block; generating residual information based on the transform coefficients; generating a prediction sample for the current block based on the residual sample; generating prediction-related information based on the prediction sample; generating loop filtering-related information for the in-loop filtering procedure of the restored sample; generating the bitstream by encoding image information including the residual information, the prediction-related information, and the loop filtering-related information; wherein the image information includes an SPS (sequence parameter set) and picture header information referring to the SPS; The SPS includes a virtual boundary availability flag and an SPS virtual boundary existence flag related to (i) whether information related to the virtual boundary exists in the SPS or (ii) whether information related to the virtual boundary exists in the picture header information. The value of the virtual boundary availability flag is related to whether the in-loop filtering procedure is enabled across the virtual boundary. The value of the SPS virtual boundary existence flag is related to whether the SPS contains information regarding the position of the virtual boundary and information regarding the number of the virtual boundaries. Based on the value of the SPS virtual boundary existence flag being 1, the SPS includes the information regarding the number of the virtual boundaries. Based on the information regarding the number of the virtual boundaries, the SPS includes the information regarding the position of the virtual boundary.

4. A method for transmitting data for an image, comprising: obtaining a bitstream for the image, the bitstream being generated based on encoding image information including residual samples for a current block, deriving transform coefficients based on the residual samples for the current block, generating residual information based on the transform coefficients, generating prediction samples for the current block based on the residual samples, generating prediction-related information based on the prediction samples, generating in-loop filtering-related information for an in-loop filtering procedure of restored samples, and the residual information, the prediction-related information, and the in-loop filtering-related information; transmitting the data including the bitstream. The image information includes an SPS (sequence parameter set) and picture header information referring to the SPS. The SPS includes a virtual boundary availability flag and an SPS virtual boundary existence flag related to (i) whether information related to the virtual boundary exists in the SPS or (ii) whether information related to the virtual boundary exists in the picture header information. The value of the virtual boundary availability flag is related to whether the in-loop filtering procedure is enabled across the virtual boundary. The value of the SPS virtual boundary existence flag is related to whether information regarding the position of the virtual boundary and information regarding the number of the virtual boundaries are included in the SPS, Based on the fact that the value of the SPS virtual boundary existence flag is 1, the SPS includes the information regarding the number of the virtual boundaries, Based on the information regarding the number of the virtual boundaries, the SPS includes the information regarding the position of the virtual boundary, a method.

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