Image coding device and method for controlling loop filtering

Abstract

To provide an image decoding method.SOLUTION: A method includes the steps of: acquiring image information; generating a residual sample; deriving a prediction sample; generating a reconstructed sample of a current picture based on the prediction sample and the residual sample; and generating a corrected reconstructed sample, the image information including SPS. Information related to a virtual boundary includes a virtual boundary enabled flag. The SPS includes an SPS virtual boundary present flag based on the virtual boundary enabled flag. Whether signaling of the information related to the virtual boundary is present in the SPS is determined based on the virtual boundary enabled flag. Whether an in-loop filtering process is performed across the virtual boundary is determined based on the virtual boundary enabled flag. The SPS includes information on the number of vertical virtual boundaries and the number of horizontal virtual boundaries, based on that a value of the SPS virtual boundary present flag is 1.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

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

[0003] In addition, in recent years, interest in and demand for immersive media such as VR (Virtual Reality), AR (Artificial Reality) content and holograms has increased, and broadcasts of images / videos with different image characteristics from real images, such as game images, are on the rise.

[0004] This necessitates the development of highly efficient image / video compression technologies to effectively compress and transmit, store, and play back high-resolution, high-quality image / video information that has the various characteristics described above.

[0005] In particular, there is a discussion of schemes for efficiently controlling loop filtering performed across virtual boundaries. Summary of the Invention [Means for solving the problem]

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

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

[0008] According to one embodiment of the present document, a method and apparatus for efficiently applying deblocking, SAO (Sample Adaptive Loop), and ALF (Adaptive Loop Filtering) is provided.

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

[0010] According to one embodiment of this document, a Sequence Parameter Set (SPS) may have a virtual boundary enable flag for the SPS that indicates whether in-loop filtering is performed across the virtual boundary.

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

[0012] According to one embodiment of the present document, there is provided an encoding device for performing video / image encoding.

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

[0014] According to one embodiment of the present document, there is provided a computer-readable digital storage medium having stored thereon encoded information or encoded video / image information that enables a decoding device to perform the video / image decoding method disclosed in at least one of the embodiments of the present document. [Effects 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, 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, an in-loop filtering procedure based on virtual boundaries can be performed efficiently and the filtering performance can be improved.

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

[0020] [Figure 1] FIG. 1 illustrates a schematic diagram of an example of a video / image coding system to which embodiments of the present document can be applied. [Figure 2] FIG. 1 is a diagram illustrating the configuration of a video / image encoding device that can be applied to embodiments of the present document. [Figure 3] FIG. 1 is a diagram illustrating the configuration of a video / image decoding device that can be applied to embodiments of the present document. [Figure 4] 1 is a diagram illustrating an exemplary hierarchical structure for coded images / videos. [Figure 5] FIG. 10 is a diagram illustrating an example of an ALF filter shape. [Figure 6] 1 is a flowchart illustrating an encoding method based on filtering in an encoding device. [Figure 7] 1 is a flowchart illustrating a filtering-based decoding method in a decoding device. [Figure 8] FIG. 1 illustrates a schematic diagram of an example of a video / image encoding method and associated components according to an embodiment of the present document. [Figure 9] FIG. 1 illustrates a schematic diagram of an example of a video / image encoding method and associated components according to an embodiment of the present document. [Figure 10] FIG. 1 illustrates a schematic diagram of an example of an image / video decoding method and associated components according to an embodiment of the present document. [Figure 11] FIG. 1 illustrates a schematic diagram of an example of an image / video decoding method and associated components according to an embodiment of the present document. [Figure 12] FIG. 1 illustrates an example of a content streaming system to which embodiments disclosed herein may be applied. DETAILED DESCRIPTION OF THE INVENTION

[0021] This document may be modified in various ways and may have various embodiments. Specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit this document to the specific embodiment. Common terms used in this document are used merely to describe specific embodiments and are not intended to limit the technical ideas of this document. A singular expression includes a plural expression unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0022] Meanwhile, each component in the drawings described in this document is illustrated independently for the convenience of explaining the different characteristic functions, and does not mean that each component is realized by separate hardware or software. For example, two or more components may be combined to form a single component, or a single component may be divided into multiple components. Embodiments in which each component is integrated and / or separated are also included within the scope of this document as long as they do not deviate from the essence of this document.

[0023] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Hereinafter, the same reference numerals will be used to refer to the same components in the drawings, and redundant descriptions of the same components will be omitted.

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

[0025] This document presents various embodiments relating to video / image coding, and unless otherwise stated, the embodiments may also be implemented in combination with each other.

[0026] In this document, video may refer to a collection of a series of images over time. A picture generally refers to a unit that shows one image at a specific time, and a slice / tile is a unit that constitutes part of a picture in coding. A slice / tile may include one or more Coding Tree Units (CTUs). A picture may be composed of one or more slices / tiles. A picture may be composed of one or more tile groups. A tile group may include one or more tiles.

[0027] A pixel or a pel may refer to the smallest unit constituting a picture (or an image). A "sample" may also be used as a term corresponding to a pixel. A sample generally refers to a pixel or a pixel value, and may refer to only a pixel / pixel value of a luma component, or may refer to only a pixel / pixel value of a chroma component. Alternatively, a sample may refer to a pixel value in the spatial domain, or, when such a pixel value is transformed into the frequency domain, may refer to a transform coefficient in the frequency domain.

[0028] A unit refers to a basic unit of image processing. A unit includes at least one of a specific region of a picture and information about that region. One unit includes one luma block and two chroma (e.g., cb, cr) blocks. The term unit may be mixed with terms such as block or area depending on the situation. In general, an M×N block includes a set (or array) of samples or transform coefficients consisting 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" 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, in this document, "or" can mean "additionally or alternatively."

[0031] As used herein, "at least one of A and B" can mean "A only," "B only," or "both A and B." Furthermore, as used herein, the expressions "at least one of A or B" and "at least one of A and / or B" can be interpreted similarly to "at least one of A and B."

[0032] Furthermore, in this specification, "at least one of A, B and C" can mean "A only," "B only," "C only," or "any combination of A, B and C." Furthermore, "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] Furthermore, parentheses used in this specification may mean "for example." Specifically, when "prediction (intra prediction)" is displayed, "intra prediction" may be proposed as an example of "prediction." In other words, "prediction" in this specification is not limited to "intra prediction," and "intra prediction" may be proposed as an example of "prediction." Furthermore, when "prediction (i.e., intra prediction)" is displayed, "intra prediction" may be proposed as an example of "prediction."

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

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

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

[0037] The source device may comprise a video source, an encoding device, and a transmitting unit. The receiving device may comprise a receiving unit, a decoding device, and a renderer. The encoding device may be referred to as a video / image encoding device, and the decoding device may be referred to as a video / image decoding device. The transmitter may be comprised in the encoding device. The receiver may be comprised in the decoding device. The renderer may comprise a display unit, which may be a separate device or an external component.

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

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

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

[0041] The decoding device can decode the video / image by performing a series of steps such as inverse quantization, inverse transform, prediction, etc., which correspond to the operations of the encoding device.

[0042] The renderer can render the decoded video / images, which can then be displayed via the display unit.

[0043] 2 is a diagram illustrating the configuration of a video / image encoding device to which this document can be applied. Hereinafter, the term "video encoding device" may include an image encoding device.

[0044] As shown in FIG. 2, the encoding device 200 may include an image partitioner 210, a predictor 220, a residual processor 230, an entropy encoder 240, an adder 250, a filter 260, and a memory 270. The predictor 220 may include an inter predictor 221 and an intra predictor 222. The residual processor 230 may include a transformer 232, a quantizer 233, a dequantizer 234, and an inverse transformer 235. The residual processor 230 may further include a subtractor 231. The adder 250 may be referred to as a reconstructor or a reconstructed block generator. The image dividing unit 210, the predicting unit 220, the residual processing unit 230, the entropy encoding unit 240, the adding unit 250, and the filtering unit 260 may be configured by one or more hardware components (e.g., an encoder chipset or a processor) depending on the embodiment. The memory 270 may include a decoded picture buffer (DPB) or may be configured by a digital storage medium. The above hardware components may further include the memory 270 as an internal / external component.

[0045] The image division unit 210 may divide an input image (or picture, frame) input to the encoding device 200 into one or more processing units. As an example, the processing units may be called coding units (CUs). In this case, the coding units may be recursively divided into coding tree units (CTUs) or largest coding units (LCUs) using a quad-tree, binary-tree, and ternary-tree (QTBTTT) structure. For example, one coding unit may be divided into multiple coding units of deeper depths based on a quad-tree structure, a binary tree structure, and / or a ternary tree structure. In this case, for example, the quad-tree structure may be applied first, and then the binary tree structure and / or the ternary tree structure may be applied. Alternatively, the binary tree structure may be applied first. The coding procedure according to the present disclosure may be performed based on a final coding unit that is not further divided. In this case, the largest coding unit may be used as the final coding unit based on coding efficiency according to image characteristics, or the coding unit may be recursively divided into coding units of lower depths as needed, and a coding unit of an optimal size may be used as the final coding unit. Here, the coding procedure may include procedures such as prediction, transformation, and restoration, which will be described later. As another example, the processing unit may further include a prediction unit (PU) or a transform unit (TU). In this case, the prediction unit and the transform unit may each be divided or partitioned from the final coding unit.The prediction unit may be a unit of sample prediction, and the transform unit may be a unit for deriving transform coefficients and / or a unit for deriving a residual signal from the transform coefficients.

[0046] The term "unit" may be used interchangeably with terms such as "block" or "area." In general, an MxN block may refer to a set of samples or transform coefficients consisting of M columns and N rows. A sample generally refers to a pixel or a pixel value, and may refer to only a pixel / pixel value of a luma component, or only a pixel / pixel value of a chroma component. A sample can be used as a term corresponding to a pixel or pel that constitutes one picture (or image).

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

[0048] The intra prediction unit 222 can predict the current block by referring to samples in the current picture. The referenced samples can be located in neighboring or distant locations from the current block depending on the prediction mode. In intra prediction, prediction modes can include a plurality of non-directional modes and a plurality of directional modes. The non-directional modes can include, for example, DC mode and planar mode. The directional modes can include, for example, 33 directional prediction modes or 65 directional prediction modes depending on the granularity of the prediction direction. However, this is merely an example, and more or less directional prediction modes may be used depending on the settings. The intra prediction unit 222 can also determine the prediction mode to be applied to the current block using the prediction modes applied to neighboring blocks.

[0049] The inter prediction unit 221 may derive a predicted block for the current block based on a reference block (reference sample array) identified by a motion vector on a reference picture. In this case, to reduce the amount of motion information transmitted in inter prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include information on an inter prediction direction (such as L0 prediction, L1 prediction, or Bi prediction). In the case of inter prediction, the neighboring blocks may include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be called a collocated reference block, a collocated CU (col CU), or the like, and the reference picture including the temporal neighboring block may be called a collocated picture (colPic). For example, the inter predictor 221 may construct a motion information candidate list based on neighboring blocks and generate information indicating which candidate is used to derive a motion vector and / or a reference picture index for the current block. Inter prediction may be performed based on various prediction modes, and for example, in the case of skip mode and merge mode, the inter predictor 221 may use motion information of neighboring blocks as motion information for 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 Vector Prediction (MVP) mode, the motion vector of the neighboring block can be used as the motion vector predictor, and the motion vector difference can be signaled to indicate the motion vector of the current block.

[0050] The predictor 220 may generate a prediction signal based on various prediction methods, which will be described later. For example, the predictor may apply intra prediction or inter prediction for prediction of a block, or may simultaneously apply intra prediction and inter prediction. This may be referred to as combined inter and intra prediction (CIIP). The predictor may also perform intra block copy (IBC) for prediction of a block. The intra block copy may be used for content image / video coding, such as games, such as screen content coding (SCC). IBC basically performs prediction within a current picture, but may be similar to inter prediction in that it derives a reference block within the current picture. That is, IBC may use at least one of the inter prediction techniques described herein.

[0051] The prediction signal generated via (including) the inter prediction unit 221 and / or the intra prediction unit 222 may be used to generate a reconstructed signal or a residual signal. The transform unit 232 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique may include a discrete cosine transform (DCT), a discrete sine transform (DST), a graph-based transform (GBT), or a conditionally non-linear transform (CNT). Here, GBT refers to a transform obtained from a graph representing relationship information between pixels. CNT refers to a transform obtained based on a prediction signal generated using all previously reconstructed pixels. The transform process may be applied to pixel blocks having the same square size or non-square blocks of variable size.

[0052] The quantization unit 233 quantizes the transform coefficients and transmits the quantized signal to the entropy coding unit 240. The entropy coding unit 240 encodes the quantized signal (information about the quantized transform coefficients) and outputs the encoded signal as a bitstream. The information about the quantized transform coefficients may be referred to as residual information. The quantization unit 233 may rearrange the quantized transform coefficients in a block form into a one-dimensional vector form based on a coefficient scan order, and may generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. The entropy coding unit 240 may perform various encoding methods, such as exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). In addition to the quantized transform coefficients, the entropy coding unit 240 may also encode information required for video / image restoration (e.g., values of syntax elements) together with or separately from the quantized transform coefficients. The encoded information (e.g., encoded video / image information) may be transmitted or stored in the form of a bitstream in Network Abstraction Layer (NAL) units. The video / image information may further include information on various parameter sets, such as an Adaptation Parameter Set (APS), a Picture Parameter Set (PPS), a Sequence Parameter Set (SPS), or a Video Parameter Set (VPS). The video / image information may also include general constraint information. Signaling / transmitted information and / or syntax elements described later in this document may be encoded through the encoding procedure described above and included in the bitstream. The bitstream may be transmitted via a network or stored in a digital storage medium.Here, the network may include a broadcasting network and / or a communication network, and the digital storage medium may include various storage media such as a USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitting unit (not shown) for transmitting the signal output from the entropy encoding unit 240 and / or a storage unit (not shown) for storing the signal may be configured as an internal / external element of the encoding device 200, or the transmitting unit may be included in the entropy encoding unit 240.

[0053] The quantized transform coefficients output from the quantization unit 233 may be used to generate a prediction signal. For example, a residual signal (residual block or residual sample) may be reconstructed by applying inverse quantization and inverse transform to the quantized transform coefficients via the inverse quantization unit 234 and the inverse transform unit 235. The adder 155 may generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample, or reconstructed sample array) by adding the reconstructed residual signal to the prediction signal output from the prediction unit 220. When there is no residual for the current block, such as when skip mode is applied, the predicted block may be used as the reconstructed block. The generated reconstructed signal may be used for intra prediction of the next current block in the current picture, or may be used for inter prediction of the next picture after filtering, as described below.

[0054] Meanwhile, Luma Mapping with Chroma Scaling (LMCS) may be applied during picture encoding and / or restoration.

[0055] The filtering unit 260 may apply filtering to the reconstructed signal to improve subjective / objective image quality. For example, the filtering unit 260 may apply various filtering methods to the reconstructed picture to generate a modified reconstructed picture, and may store the modified reconstructed picture in the memory 270, specifically, in the DPB of the memory 270. The various filtering methods may include, for example, deblock filtering, sample adaptive offset (SAO), an adaptive loop filter, a bilateral filter, etc. The filtering unit 260 may generate various information related to filtering and transmit it to the entropy encoder 240, as will be described later in connection with each filtering method. The filtering information may be encoded by the entropy encoder 240 and output in the form of a bitstream.

[0056] The modified reconstructed picture transmitted to the memory 270 can be used as a reference picture in the inter prediction unit 221. When inter prediction is applied through this, the encoding apparatus can avoid prediction mismatch between the encoding apparatus 100 and the decoding apparatus, and can also improve encoding efficiency.

[0057] The DPB of the memory 270 may store the modified reconstructed picture to be used as a reference picture in the inter predictor 221. The memory 270 may store motion information of a block from which motion information in the current picture is derived (or encoded) and / or motion information of a block in an already reconstructed picture. The stored motion information may be transmitted to the inter predictor 221 to be used as motion information of a spatially neighboring block or a temporally neighboring block. The memory 270 may store reconstructed samples of reconstructed blocks in the current picture and transmit them to the intra predictor 222.

[0058] FIG. 3 is a diagram illustrating the configuration of a video / image decoding device to which this document can be applied.

[0059] As shown in FIG. 3, the decoding device 300 may include an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, a filter 350, and a memory 360. The predictor 330 may include an inter-predictor 331 and an intra-predictor 332. The residual processor 320 may include a dequantizer 321 and an inverse transformer 321. Depending on the embodiment, the entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filter 350 may be configured as a single hardware component (e.g., a decoder chipset or processor). The memory 360 may include a decoded picture buffer (DPB) or may be configured as a digital storage medium. The above hardware components may further include a memory 360 as an internal / external component.

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

[0061] The decoding device 300 may receive a signal output from the encoding device of FIG. 3 in the form of a bitstream, and the received signal may be decoded via the entropy decoding unit 310. For example, the entropy decoding unit 310 may parse the bitstream to derive information (e.g., video / image information) necessary for image reconstruction (or picture reconstruction). The video / image information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). The video / image information may also include general constraint information. The decoding device may further decode pictures based on the information on the parameter sets and / or the general constraint information. Signaling / received information and / or syntax elements, which will be described later in this document, may be decoded via the decoding procedure and obtained from the bitstream. For example, the entropy decoding unit 310 may decode information in a bitstream based on a coding method such as Exponential-Golomb coding, CAVLC, or CABAC, and output values of syntax elements required for image restoration and quantized values of transform coefficients related to the residual. More specifically, the CABAC entropy decoding method receives bins corresponding to each syntax element in the bitstream, determines a context model using information on the syntax element to be decoded and decoded information on neighboring and current blocks, or information on symbols / bins decoded in previous steps, predicts the occurrence probability of the bins based on the determined context model, and performs arithmetic decoding of the bins to generate symbols corresponding to the values of each syntax element. After determining the context model, the CABAC entropy decoding method may update the context model using information on the decoded symbols / bins for the context model of the next symbol / bin.Among the information decoded by the entropy decoding unit 310, information related to prediction is provided to the prediction unit 330, and residual information entropy-decoded by the entropy decoding unit 310, i.e., quantized transform coefficients and related parameter information, may be input to the inverse quantization unit 321. Among the information decoded by the entropy decoding unit 310, information related to filtering may be provided to the filtering unit 350. Meanwhile, a receiving unit (not shown) that receives a signal output from the encoding device may be further configured as an internal / external element of the decoding device 300, or the receiving unit may be a component of the entropy decoding unit 310. Meanwhile, the decoding device according to this document may be referred to as a video / image / picture decoding device, and the decoding device may be divided into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder may include the entropy decoding unit 310, and the sample decoder may include at least one of the inverse quantization unit 321, the inverse transform unit 322, the prediction unit 330, the addition unit 340, the filtering unit 350, and the memory 360.

[0062] The inverse quantization unit 321 may inverse quantize the quantized transform coefficients and output the transform coefficients. The inverse quantization unit 321 may rearrange the quantized transform coefficients in a two-dimensional block format. In this case, the rearrangement may be performed based on the coefficient scanning order performed in the encoding device. The inverse quantization unit 321 may inverse quantize the quantized transform coefficients using a quantization parameter (e.g., quantization step size information) to obtain transform coefficients.

[0063] The inverse transform unit 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

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

[0065] The predictor may generate a prediction signal based on various prediction methods, which will be described later. For example, the predictor may apply intra prediction or inter prediction for prediction of a block, or may simultaneously apply intra prediction and inter prediction. This may be referred to as combined inter and intra prediction (CIIP). The predictor may also perform intra block copy (IBC) for prediction of a block. The intra block copy may be used for content image / video coding, such as screen content coding (SCC), for games. IBC basically performs prediction within a current picture, but may be similar to inter prediction in deriving a reference block within the current picture. That is, IBC may utilize at least one of the inter prediction techniques described in this document. Palette mode may be considered an example of intra coding or intra prediction.

[0066] The intra prediction unit 331 can predict the current block by referring to samples in the current picture. The referenced samples can be located adjacent to the current block or can be located far away depending on the prediction mode. In intra prediction, prediction modes 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 modes applied to neighboring blocks.

[0067] The inter predictor 332 may derive a predicted block for the current block based on a reference block (reference sample array) identified by a motion vector on a reference picture. To reduce the amount of motion information transmitted in inter prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include information on the inter prediction direction (e.g., L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, the neighboring blocks may include spatial neighboring blocks in the current picture and temporal neighboring blocks in the reference picture. For example, the inter predictor 332 may construct a motion information candidate list based on the neighboring blocks and derive a motion vector and / or a reference picture index for the current block based on received candidate selection information. Inter prediction may be performed based on various prediction modes, and the prediction information may include information indicating the inter prediction mode for the current block.

[0068] The adder 340 may generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the obtained residual signal to the prediction signal (predicted block, predicted sample array) output from the prediction unit. When there is no residual for the current block, such as when skip mode is applied, the predicted block may be used as the reconstructed block.

[0069] The adder 340 may be referred to as a reconstruction unit or a reconstruction block generator. The generated reconstruction signal may be used for intra prediction of a next block to be processed in the current picture, may be output after filtering as described below, or may be used for inter prediction of a next picture.

[0070] Meanwhile, Luma Mapping with Chroma Scaling (LMCS) can be applied in the picture decoding process.

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

[0072] The (modified) reconstructed picture stored in the DPB of the memory 360 can be used as a reference picture in the inter predictor 332. The memory 360 can store motion information of a block from which motion information in the current picture is derived (or decoded) and / or motion information of a block in an already reconstructed picture. The stored motion information can be transmitted to the inter predictor 332 to be used as motion information of a spatially neighboring block or a temporally neighboring block. The memory 360 can store reconstructed samples of reconstructed blocks in the current picture and transmit them to the intra predictor 331.

[0073] In this specification, the embodiments described for the prediction unit 330, inverse quantization unit 321, inverse transform unit 322, and filtering unit 350 of the decoding device 300 can also be applied identically or correspondingly to the prediction unit 220, inverse quantization unit 234, inverse transform unit 235, and filtering unit 260 of the encoding device 200, respectively.

[0074] As described above, prediction is performed to improve compression efficiency when performing video coding. Through this, a predicted block including predicted samples for a current block, which is a block to be coded, can be generated. Here, the predicted block includes predicted samples in the spatial domain (or pixel domain). The predicted block is derived in the same way by an encoding device and a decoding device. The encoding device can improve image coding efficiency by signaling to a decoding device information (residual information) regarding the residual between the original block and the predicted block, rather than the original sample values of the original block themselves. The decoding device can derive a residual block including residual samples based on the residual information, combine the residual block with the predicted block to generate a reconstructed block including reconstructed samples, and generate a reconstructed picture including the reconstructed block.

[0075] The residual information may be generated through a transform and quantization procedure. For example, an encoding device may derive a residual block between the original block and the predicted block, perform a transform procedure on residual samples (residual sample array) included in the residual block to derive transform coefficients, and perform a quantization procedure on the transform coefficients to derive quantized transform coefficients, and then signal the related residual information to a decoding device (via a bitstream). Here, the residual information may include information such as value information, position information, transform technique, transform kernel, and quantization parameter of the quantized transform coefficients. The decoding device may derive residual samples (or residual block) by performing an inverse quantization / inverse transform procedure based on the residual information. The decoding device may generate a reconstructed picture based on the predicted block and the residual block. The encoding device may also derive a residual block by inverse quantizing / inverse transforming quantized transform coefficients for reference for inter-prediction of a subsequent picture, and generate a reconstructed picture based on the residual block.

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

[0077] In this document, quantized transform coefficients and transform coefficients may be referred to as transform coefficients and scaled transform coefficients, respectively. In this case, residual information may include information about the transform coefficient(s), and the information about the transform coefficient(s) may be signaled via a residual coding syntax. Transform coefficients may be derived based on the residual information (or information about the transform coefficient(s)), and scaled transform coefficients may be derived through an inverse transform (scaling) on the transform coefficients. Residual samples may be derived based on an inverse transform (transform) on the scaled transform coefficients. This may be similarly applied / expressed in other parts of this document.

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

[0079] The motion information may include L0 motion information and / or L1 motion information depending on the inter prediction type (such as L0 prediction, L1 prediction, or Bi prediction). A motion vector in the L0 direction may be referred to as an L0 motion vector or MVL0, and a motion vector in the L1 direction may be referred to as an L1 motion vector or MVL1. Prediction based on an L0 motion vector may be referred to as L0 prediction, prediction based on an L1 motion vector may be referred to as L1 prediction, and prediction based on both the L0 motion vector and the L1 motion vector may be referred to as bi-prediction (Bi) prediction. Here, the L0 motion vector may indicate a motion vector associated with a reference picture list L0 (L0), and the L1 motion vector may indicate a motion vector associated with a reference picture list L1 (L1). The reference picture list L0 may include pictures that are earlier in output order than the current picture, and the reference picture list L1 may include pictures that are later in output order than the current picture. The previous picture may be called a forward (reference) picture, and the subsequent picture may be called a backward (reference) picture. The reference picture list L0 may further include, as reference pictures, pictures that are subsequent to the current picture in output order. In this case, the previous picture may be indexed first in the reference picture list L0, and the subsequent picture may be indexed thereafter. The reference picture list L1 may further include, as reference pictures, pictures that are subsequent to the current picture in output order. In this case, the subsequent picture may be indexed first in the reference picture list L1, and the previous picture may be indexed thereafter. Here, the output order may correspond to a POC (Picture Order Count) order.

[0080] FIG. 4 shows an exemplary hierarchical structure for coded images / videos.

[0081] As shown in Figure 4, coded images / videos are divided into a VCL (Video Coding Layer) that handles the image / video decoding process and itself, a lower system that transmits and stores the coded information, and a NAL (Network Abstraction Layer) that exists between the VCL and the lower system and is responsible for network adaptation functions.

[0082] The VCL can generate VCL data containing compressed image data (slice data), or parameter sets containing 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 for the image decoding process.

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

[0084] As shown in the above figures, NAL units can be classified into VCL NAL units and non-VCL NAL units according to the RBSP generated by the VCL. A VCL NAL unit can refer to a NAL unit that contains information about an image (slice data), and a non-VCL NAL unit can refer to a NAL unit that contains information necessary for decoding an image (parameter set or SEI message).

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

[0086] As mentioned above, the NAL unit type of an NAL unit can be identified by the RBSP data structure included in the NAL unit, and information about such NAL unit type can be stored and signaled in the NAL unit header.

[0087] For example, NAL units can be broadly classified into VCL NAL unit types and non-VCL NAL unit types depending on whether they contain information about an image (slice data). VCL NAL unit types can be classified according to the nature and type of pictures contained in the VCL NAL unit, and non-VCL NAL unit types can be classified according to the type of parameter set.

[0088] The following is an example of a NAL unit type identified by the type of parameter set included in the non-VCL NAL unit type.

[0089] -APS (Adaptation Parameter Set) NAL unit: Type for NAL units including APS

[0090] -DPS (Decoding Parameter Set) NAL unit: Type for NAL units 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 including SPS

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

[0094] -PH (Picture Header) NAL unit: Type for NAL unit including PH

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

[0096] Meanwhile, as described above, one picture may include multiple slices, and one slice may include a slice header and slice data. In this case, one picture header may be added to multiple slices (slice headers and slice data sets) in one picture. The picture header (picture header syntax) may include information / parameters commonly applicable to the picture. In this document, a slice may be mixed with or substituted for a tile group. Also, in this document, a slice header may be mixed with or substituted for a type group header.

[0097] The slice header (slice header syntax, slice header information) may include information / parameters commonly applicable to the slices. The APS (APS syntax) or PPS (PPS syntax) may include information / parameters commonly applicable to one or more slices or pictures. The SPS (SPS syntax) may include information / parameters commonly applicable to one or more sequences. The VPS (VPS syntax) may include information / parameters commonly applicable to multiple layers. The DPS (DPS syntax) may include information / parameters commonly applicable to video in general. The DPS may include information / parameters related to the concatenation of a Coded Video Sequence (CVS). In this document, the High Level Syntax (HLS) may include at least one of the APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, picture header syntax, and slice header syntax.

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

[0099] Meanwhile, to compensate for differences between an original image and a restored image due to errors that occur during the compression encoding process, such as quantization, an in-loop filtering procedure may be performed on the restored samples or pictures, as described above. As described above, the in-loop filtering may be performed in a filter unit of an encoding device and a filter unit of a decoding device, and a deblocking filter, SAO, and / or adaptive loop filter (ALF) may be applied. For example, the ALF procedure may be performed after the deblocking filtering procedure and / or SAO procedure are completed. However, in this case, the deblocking filtering procedure and / or SAO procedure may be omitted.

[0100] A detailed description of picture reconstruction and filtering will be given below. In image / video coding, a reconstructed block may be generated based on intra prediction / inter prediction for each block, and a reconstructed picture including the reconstructed block may be generated. If a current picture / slice is an I picture / slice, blocks included in the current picture / slice may be reconstructed based only on intra prediction. On the other hand, if the current picture / slice is a P or B picture / slice, blocks included in the current picture / slice may be reconstructed based on intra prediction or inter prediction. In this case, intra prediction may be applied to some blocks in the current picture / slice, and inter prediction may be applied to the remaining blocks.

[0101] Intra prediction may refer to a prediction that generates predicted samples for a current block based on reference samples in a picture to which the current block belongs (hereinafter referred to as the current picture). When intra prediction is applied to a current block, neighboring reference samples used for intra prediction of the current block may be derived. The neighboring reference samples of the current block may include samples adjacent to the left boundary and bottom-left neighboring samples of the current block having a size of nW×nH, a total of 2×nH samples, samples adjacent to the top boundary and top-right neighboring samples of the current block, a total of 2×nW samples, and one sample adjacent to the top-left neighboring sample of the current block. Alternatively, the neighboring reference samples of the current block may include upper neighboring samples of multiple columns and left neighboring samples of multiple rows. In addition, the neighboring reference samples of the current block may include a total of nH samples adjacent to the right boundary of the current block, which has a size of nW x nH, a total of nW samples adjacent to the bottom boundary of the current block, and one sample adjacent to the bottom-right of the current block.

[0102] However, some of the neighboring reference samples of the current block may not yet be decoded or may not be available. In this case, the decoder may construct neighboring reference samples to be used for prediction by substituting unavailable samples as available samples, or may construct neighboring reference samples to be used for prediction through interpolation of available samples.

[0103] When neighboring reference samples are derived, (i) a predicted sample may be derived based on an average or interpolation of neighboring reference samples of the current block, or (ii) the predicted sample may be derived based on a reference sample of the neighboring reference samples of the current block that exists in a specific (prediction) direction relative to the predicted sample. (i) This may be referred to as a non-directional mode or a non-angular mode, and (ii) this may be referred to as a directional mode or an angular mode. Alternatively, the predicted sample may be generated by interpolating the first and second neighboring samples, which are located in the opposite direction to the prediction direction of the intra prediction mode of the current block, based on the predicted sample of the neighboring reference samples of the current block. This may be referred to as Linear Interpolation Intra Prediction (LIP). Alternatively, a chroma predicted sample may be generated based on a luma sample using a linear model. This may be referred to as LM mode. In addition, a temporary (interim) predicted sample of the current block may be derived based on filtered neighboring reference samples, and a predicted sample of the current block may be derived by weighting the temporary predicted sample and at least one reference sample derived according to the intra prediction mode from the existing neighboring reference samples, i.e., non-filtered neighboring reference samples. This may be called Position Dependent Intra Prediction (PDPC). In addition, intra prediction coding may be performed by selecting a reference sample line with the highest prediction accuracy from multiple neighboring reference sample lines of the current block, deriving a predicted sample using a reference sample located in the prediction direction of the selected line, and signaling the reference sample line used to a decoding device.The above-described case may be referred to as Multi-Reference Line (MRL) intra prediction or MRL-based intra prediction. Furthermore, the current block may be divided into vertical or horizontal sub-partitions, and intra prediction may be performed based on the same intra prediction mode, with neighboring reference samples derived and used for each sub-partition. That is, in this case, the intra prediction mode for the current block is equally applied to the sub-partitions, and neighboring reference samples may be derived and used for each sub-partition, thereby improving intra prediction performance in some cases. This prediction method may be referred to as Intra Sub-Partitions (ISP) or ISP-based intra prediction. The above-described intra prediction method may be referred to as an intra prediction type, distinguished from the intra prediction modes in Tables of Contents (Sections 1 and 2). The intra prediction type may be referred to by various terms, such as an intra prediction technique or an additional intra prediction mode. For example, the intra prediction type (or additional intra prediction mode, etc.) may include at least one of the LIP, PDPC, MRL, and ISP. A general intra prediction method excluding specific intra prediction types such as LIP, PDPC, MRL, and ISP may be referred to as a normal intra prediction type. The normal intra prediction type may be generally applied when the specific intra prediction types are not applied, and prediction may be performed based on the intra prediction mode described above. Meanwhile, post-processing filtering may be performed on the derived prediction samples as needed.

[0104] Specifically, the intra prediction procedure may include an intra prediction mode / type determination step, a neighboring reference sample derivation step, and an intra prediction mode / type-based prediction sample derivation step. If necessary, a post-processing filtering step may be performed on the derived prediction samples.

[0105] A modified reconstructed picture is generated by the in-loop filtering procedure, and the modified reconstructed picture is output as a decoded picture from the decoding device and stored in a decoded picture buffer or memory of the encoding / decoding device for use as a reference picture in subsequent inter-prediction procedures when encoding / decoding pictures. The in-loop filtering procedure may include a deblocking filtering procedure, a sample adaptive offset (SAO) procedure, and / or an adaptive loop filter (ALF) procedure, as described above. In this case, one or some of the deblocking filtering procedure, the sample adaptive offset (SAO), the adaptive loop filter (ALF), and the bilateral filter procedure may be applied sequentially, or all of them may be applied sequentially. For example, the deblocking filtering procedure may be applied to the reconstructed picture before the SAO procedure. Alternatively, the deblocking filtering procedure may be applied to the reconstructed picture before the ALF procedure. This is also performed in the encoding device.

[0106] Deblock filtering is a filtering technique that removes distortions that occur at boundaries between blocks in a reconstructed picture. The deblock filtering procedure may, for example, derive a target boundary in a reconstructed picture, determine a boundary strength (bs) for the target boundary, and perform deblock filtering on the target boundary based on the bS. The bS may be determined based on the prediction modes of two blocks adjacent to the target boundary, a motion vector difference, whether the reference pictures are the same, whether there are significant non-zero coefficients, etc.

[0107] SAO is a method of compensating for an offset difference between a reconstructed picture and an original picture on a sample-by-sample basis, and may be applied based on a type such as a band offset or an edge offset. According to SAO, samples are classified into different categories according to each SAO type, and an offset value may be added to each sample based on the category. Filtering information for SAO may include information on whether SAO is applicable, SAO type information, SAO offset value information, etc. SAO may also be applied to a reconstructed picture after the deblocking filtering is applied.

[0108] An adaptive loop filter (ALF) is a technique for filtering a reconstructed picture on a sample-by-sample basis based on filter coefficients according to a filter shape. An encoding apparatus can determine whether ALF is applicable, the ALF shape and / or ALF filtering coefficients, etc., by comparing a reconstructed picture with an original picture, and signal the determination to a decoding apparatus. That is, filtering information for ALF can include information on whether ALF is applicable, ALF filter shape information, ALF filtering coefficient information, etc. The ALF can also be applied to the reconstructed picture after the deblocking filtering is applied.

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

[0110] FIG. 5(a) shows a 7x7 diamond filter shape, and FIG. 5(b) shows a 5x5 diamond filter shape. Cn in the filter shape in FIG. 5 indicates a filter coefficient. When n is the same for Cn, this indicates that the same filter coefficient can be assigned. In this document, the position and / or unit to which filter coefficients are assigned according to the ALF filter shape may be referred to as a filter tab. One filter coefficient is assigned to each filter tab, and the arrangement of the filter tabs may correspond to the filter shape. The filter tab located at the center of the filter shape may be referred to as a center filter tab. Two filter tabs with the same n value that are located at corresponding positions based on the center filter tab may be assigned the same filter coefficient. For example, a 7x7 diamond filter shape includes 25 filter tabs, and filter coefficients C0 to C11 are assigned in a centrally symmetrical manner, so that filter coefficients can be assigned to the 25 filter tabs using only 13 filter coefficients. Also, for example, in the case of a 5x5 diamond filter shape, 13 filter tabs are included, and filter coefficients C0 to C5 are assigned in a centrally symmetric manner, so that filter coefficients can be assigned to the 13 filter tabs with only seven filter coefficients. For example, to reduce the amount of data related to the signaled filter coefficients, 12 of the 13 filter coefficients for a 7x7 diamond filter shape may be signaled (explicitly) and one filter coefficient may be derived (implicitly). Also, for example, 6 of the 7 filter coefficients for a 5x5 diamond filter shape may be signaled (explicitly) and one filter coefficient may be derived (implicitly).

[0111] 6 is a flowchart illustrating an encoding method based on filtering in an encoding device. The method of FIG. 6 may include steps S600 to S630.

[0112] In step S600, the encoding apparatus generates a reconstructed picture, which can be performed based on the above-described procedure for generating a reconstructed picture (or a reconstructed sample).

[0113] In step S610, the encoding device may determine whether in-loop filtering is applied (across the virtual boundary) based on the in-loop filtering-related information, where the in-loop filtering may include at least one of the above-mentioned deblocking filtering, SAO, or ALF.

[0114] In step S620, the encoding apparatus may generate a modified reconstructed picture (modified reconstructed sample) based on the determination in step S610, where the modified reconstructed picture (modified reconstructed sample) may be a filtered reconstructed picture (filtered reconstructed sample).

[0115] In step S630, the encoding device can encode the image / video information including the in-loop filtering related information based on the in-loop filtering procedure.

[0116] 7 is a flowchart illustrating a filtering-based decoding method in a decoding device. The method of FIG. 7 may include steps S700 to S730.

[0117] In step S700, the decoding device can obtain image / video information including in-loop filtering related information from a bitstream, where the bitstream can be based on encoded image / video information transmitted from an encoding device.

[0118] In step S710, the decoding device generates a reconstructed picture, which can be performed based on the above-described procedure for generating a reconstructed picture (or a reconstructed sample).

[0119] In step S720, the decoding device may determine whether in-loop filtering is applied (across the virtual boundary) based on the in-loop filtering-related information, where the in-loop filtering may include at least one of the above-mentioned deblocking filtering, SAO, or ALF.

[0120] In step S730, the decoding apparatus may generate a modified reconstructed picture (modified reconstructed sample) based on the determination in step S720, where the modified reconstructed picture (modified reconstructed sample) may be a filtered reconstructed picture (filtered reconstructed sample).

[0121] As described above, an in-loop filtering procedure can be applied to the reconstructed picture. In this case, a virtual boundary can be defined to further improve the subjective / objective visual quality of the reconstructed picture, and the in-loop filtering procedure can be applied across the virtual boundary. The virtual boundary can include, for example, a discontinuous edge of a 360-degree image, a VR image, or a picture-in-picture (PIP). For example, the virtual boundary can exist at a predetermined predetermined position, and its presence and / or position can be signaled. As an example, the virtual boundary can be located at the upper fourth sample line in a CTU row (specifically, for example, above the upper fourth sample line in the CTU row). As another example, information regarding the presence and / or position of the virtual boundary can be signaled via an HLS. As described above, the HLS can include an SPS, a PPS, a picture header, a slice header, etc.

[0122] The following describes the signaling and semantics of the high-level syntax for embodiments of this document.

[0123] One embodiment of this document may include a method for controlling a loop filter. This method for controlling a loop filter may be applied to a reconstructed picture. The in-loop filter (loop filter) may be used for decoding an encoded bitstream. The loop filter may include the deblocking, SAO, and ALF described above. The SPS may include flags associated with each of the deblocking, SAO, and ALF. The flags may indicate whether each tool is available for coding a Coded Layer Video Sequence (CLVS) or a Coded Video Sequence (CVS) that references the SPS.

[0124] If the loop filter is available for CVS, application of the loop filter can be controlled to avoid crossing certain boundaries. For example, it can be controlled whether the loop filter crosses sub-picture boundaries, whether the loop filter crosses tile boundaries, and whether the loop filter crosses virtual boundaries. Here, the virtual boundaries can be defined on the CTU based on the availability of line buffers.

[0125] In relation to whether an in-loop filtering procedure is performed across a virtual boundary, the in-loop filtering related information may include at least one of a virtual boundary enable flag of the SPS (a virtual boundary enable flag in the SPS), a virtual boundary present flag of the SPS, a virtual boundary present flag of the picture header, a virtual boundary present flag of the SPS picture header, and information regarding the location of the virtual boundary.

[0126] In the embodiments described herein, the information about the position of the virtual border may include information about the x-coordinate of the vertical virtual border and / or information about the y-coordinate of the horizontal virtual border. Specifically, the information about the position of the virtual border may include information about the x-coordinate of the vertical virtual border and / or information about the y-coordinate of the horizontal virtual border in luma sample units. The information about the position of the virtual border may also include information about the number of pieces of information (syntax elements) about the x-coordinate of the vertical virtual border present in the SPS. The information about the position of the virtual border may also include information about the number of pieces of information (syntax elements) about the y-coordinate of the horizontal virtual border present in the SPS. Alternatively, the information about the position of the virtual border may include information about the number of pieces of information (syntax elements) about the x-coordinate of the vertical virtual border present in the picture header. The information about the position of the virtual border may also include information about the number of pieces of information (syntax elements) about the y-coordinate of the horizontal virtual border present in the picture header.

[0127] The following table shows an example syntax and semantics of an SPS according to this embodiment.

[0128] [Table 1]

[0129] [Table 2]

[0130] The following table shows an example syntax and semantics of a Picture Parameter Set (PPS) according to this embodiment.

[0131] [Table 3]

[0132] [Table 4]

[0133] The following table shows an exemplary syntax and semantics of a picture header according to this embodiment.

[0134] [Table 5-1]

[0135] [Table 5-2]

[0136] [Table 6-1]

[0137] [Table 6-2]

[0138] The following table shows an example syntax and semantics of a slice header according to this embodiment.

[0139] [Table 7]

[0140] [Table 8]

[0141] The following describes the signaling of information about virtual boundaries that can be used in in-loop filtering.

[0142] In an existing design, to disable a loop filter that crosses virtual boundaries, i) the SPS virtual boundary presence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) is set to 0, and the PH virtual boundary presence flag (ph_loop_filter_across_virtual_boundaries_disabled_present_flag) is present and set to 0 for all picture headers, or ii) the SPS virtual boundary presence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) is set to 1, and information about the number of vertical virtual boundaries in the SPS (sps_num_ver_vertical_boudnaries) and information about the number of horizontal virtual boundaries in the SPS (sps_num_hor_vertical_boudnaries) can both be set to 0.

[0143] In existing designs, the above ii) causes the SPS virtual boundary present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) to be set to 1, which can cause problems in the decoding procedure as the decoder expects signaling for the location of the virtual boundary.

[0144] The embodiments described in the following paragraphs can provide solutions to solve the above-mentioned problems. The embodiments may be applied independently, or at least two or more embodiments may be applied in combination.

[0145] In one embodiment of this document, whether a syntax element for indicating virtual boundaries is included in an SPS may be controlled by a flag, for example, the number of the flags may be two (e.g., SPS virtual boundaries enabled flag, SPS virtual boundaries present flag).

[0146] In one example according to this embodiment, the virtual boundary enable flag of the SPS may be referred to as sps_loop_filter_across_virtual_boundaries_disabled_flag (or sps_virtual_boundaries_enabled_flag). The virtual boundary enable flag of the SPS may indicate whether a feature for disabling the loop filter across virtual boundaries is enabled.

[0147] In one example according to this embodiment, the virtual boundary presence flag of the SPS may be referred to as sps_loop_filter_across_virtual_boundaries_disabled_present_flag (or sps_virtual_boundaries_present_flag). The virtual boundary presence flag of the SPS may indicate whether signaling information for a virtual boundary is included in the SPS or a Picture Header (PH).

[0148] In one example according to this embodiment, when the virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1 and the virtual boundary present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is 0, signaling information to disable the loop filter across the virtual boundary may be included in the picture header.

[0149] In one example according to this embodiment, if information regarding the position of virtual boundaries (e.g., vertical virtual boundaries, horizontal virtual boundaries) 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.

[0150] In one example according to this embodiment, a variable may be derived that indicates whether filtering is disabled on virtual boundaries for the current picture. For example, the variable may include VirtualBoundairesDisabledFlag.

[0151] As one case in this example, if the virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is one and the virtual boundary present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is one, then VirtualBoundairesDisabledFlag may be one.

[0152] In another case in this example, if the virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1, the virtual boundary present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is 0, and the sum of information regarding the number of vertical virtual boundaries (e.g., ph_num_ver_virtual_boundaries) and information regarding the number of horizontal virtual boundaries (e.g., ph_num_hor_virtual_boundaries) is greater than 0, then VirtualBoundairesDisabledFlag may be 1.

[0153] In other cases in this example, VirtualBoundairesDisabledFlag may be 0.

[0154] The following table shows an example syntax of an SPS according to this embodiment.

[0155] [Table 9]

[0156] The following table provides example semantics for syntax elements included in the above syntax.

[0157] [Table 10]

[0158] The following table shows an exemplary syntax of the header information (picture header) according to this embodiment.

[0159] [Table 11]

[0160] The following table provides example semantics for syntax elements included in the above syntax.

[0161] [Table 12]

[0162] In embodiments related to Tables 9 to 12, image information encoded by an encoding device and / or image information obtained via a bitstream received by a decoding device from the encoding device may include a Sequence Parameter Set (SPS) and a Picture Header (PH). The SPS may include a virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag). The SPS may include a virtual boundary present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS based on the virtual boundary enable flag.

[0163] For example, the SPS may include a virtual boundary presence flag for the SPS when the value of the virtual boundary enable flag is 1. The SPS may include, based on the virtual boundary enable flag and the virtual boundary presence flag for the SPS, 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]). For example, when the value of the virtual boundary enable flag is 1 and the value of the virtual boundary presence flag for the SPS is 1, the SPS may include information about the number of vertical virtual boundaries of the SPS, information about the positions of the vertical virtual boundaries of the SPS, information about the number of horizontal virtual boundaries of the SPS, and information about the positions of the horizontal virtual boundaries of the SPS.

[0164]

[0066] In one example, the amount of information regarding the positions of vertical virtual boundaries of the SPS can be determined based on information regarding the number of vertical virtual boundaries of the SPS, and the amount of information regarding the positions of horizontal virtual boundaries of the SPS can be determined based on information regarding the number of horizontal virtual boundaries of the SPS. The picture header may include, based on the virtual boundary enable flag and the virtual boundary presence flag of the SPS, 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]).

[0165] For example, the picture header may include information regarding the number of vertical virtual borders of the PH, information regarding the positions of the vertical virtual borders of the PH, information regarding the number of horizontal virtual borders of the PH, and information regarding the positions of the horizontal virtual borders of the PH when the value of the virtual border enable flag is 1 and the value of the virtual border presence flag of the SPS is 0. In one example, the amount of information regarding the positions of the vertical virtual borders of the PH can be determined based on the information regarding the number of vertical virtual borders of the PH, and the amount of information regarding the positions of the horizontal virtual borders of the PH can be determined based on the information regarding the number of horizontal virtual borders of the PH.

[0166] In another embodiment of this document, each of the header information (picture headers) of pictures that reference an SPS may include a PH virtual boundary present flag ph_loop_filter_across_virtual_boundaries_disabled_present_flag (or ph_virtual_boundaries_present_flag). This embodiment can also be described with an SPS virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) and an SPS virtual boundary present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) as in the previous embodiment.

[0167] In one example according to this embodiment, when the virtual boundary enable 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 0, each of the header information (picture headers) of pictures that reference the SPS may include the virtual boundary presence flag ph_loop_filter_across_virtual_boundaries_disalbed_present_flag (or ph_virtual_boundaries_present_flag) of the PH.

[0168] In one example according to this embodiment, if information regarding the position of virtual boundaries (e.g., vertical virtual boundaries, horizontal virtual boundaries) 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.

[0169] In one example according to this embodiment, a variable may be derived that indicates whether filtering is disabled on virtual boundaries for the current picture. For example, the variable may include VirtualBoundairesDisabledFlag.

[0170] As one case in this example, if the virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is one and the virtual boundary present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is one, then VirtualBoundairesDisabledFlag may be one.

[0171] As another case in this example, if the virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1 and the virtual boundary present flag (ph_loop_filter_across_virtual_boundaries_disabled_present_flag) of the PH is 1, then VirtualBoundairesDisabledFlag may be 1.

[0172] In other cases in this example, VirtualBoundairesDisabledFlag may be 0.

[0173] The following table shows an example syntax of an SPS according to this embodiment.

[0174] [Table 13]

[0175] The following table provides example semantics for syntax elements included in the above syntax.

[0176] [Table 14]

[0177] The following table shows an exemplary syntax of the header information (picture header) according to this embodiment.

[0178] [Table 15]

[0179] The following table provides example semantics for syntax elements included in the above syntax.

[0180] [Table 16-1]

[0181] [Table 16-2]

[0182] In embodiments related to Tables 13 to 16, image information encoded by an encoding device and / or image information obtained via a bitstream received by a decoding device from the encoding device may include a sequence parameter set (SPS) and a picture header (PH). The SPS may include a virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag). The SPS may include a virtual boundary present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) based on the virtual boundary enable flag. For example, the SPS may include the virtual boundary present flag when the value of the virtual boundary enable flag is 1. Based on the virtual boundary enable flag and the virtual boundary presence 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 position 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 position of the horizontal virtual boundaries of the SPS (sps_virtual_boundaries_pos_y[i]).

[0183] For example, when the virtual border enable flag has a value of 1 and the virtual border presence flag of the SPS has a value of 1, the SPS may include information regarding the number of vertical virtual borders of the SPS, information regarding the positions of the vertical virtual borders of the SPS, information regarding the number of horizontal virtual borders of the SPS, and information regarding the positions of the horizontal virtual borders of the SPS. In one example, the amount of information regarding the positions of the vertical virtual borders of the SPS may be determined based on the information regarding the number of vertical virtual borders of the SPS, and the amount of information regarding the positions of the horizontal virtual borders of the SPS may be determined based on the information regarding the number of horizontal virtual borders of the SPS. The picture header may include a virtual border presence flag of the PH based on the virtual border enable flag and the virtual border presence flag of the SPS.

[0184] For example, the picture header may include a virtual boundary presence flag for the PH when the value of the virtual boundary enable flag is 1 and the value of the virtual boundary presence flag for the SPS is 0. Based on the virtual boundary presence flag for the PH, the picture header may include information on the number of vertical virtual boundaries for the PH (ph_num_ver_virtual_boundaries), information on the positions of the vertical virtual boundaries for the PH (ph_virtual_boundaries_pos_x[i]), information on the number of horizontal virtual boundaries for the PH (ph_num_hor_virtual_boundaries), and information on the positions of the horizontal virtual boundaries for the PH (ph_virtual_boundaries_pos_y[i]).

[0185] For example, the picture header may include information regarding the number of vertical virtual borders of the PH, information regarding the positions of the vertical virtual borders of the PH, information regarding the number of horizontal virtual borders of the PH, and information regarding the positions of the horizontal virtual borders of the PH when the value of the virtual border presence flag of the PH is 1. In one example, the amount of information regarding the positions of the vertical virtual borders of the PH can be determined based on the information regarding the number of vertical virtual borders of the PH, and the amount of information regarding the positions of the horizontal virtual borders of the PH can be determined based on the information regarding the number of horizontal virtual borders of the PH.

[0186] In another embodiment of this document, whether a syntax element for indicating virtual boundaries is included in an SPS may be controlled by a flag, for example, the number of flags may be two (e.g., SPS virtual boundaries present flag, SPS PH virtual boundaries present flag).

[0187] In one example according to this embodiment, the virtual boundary presence flag of the SPS may be referred to as sps_loop_filter_across_virtual_boundaries_disabled_present_flag (or sps_virtual_boundaries_present_flag). The virtual boundary presence flag of the SPS may indicate whether information about the virtual boundary is included in the SPS.

[0188] In one example according to this embodiment, the virtual boundary present flag of the SPS PH may be referred to as sps_ph_loop_filter_across_virtual_boundaries_disabled_present_flag. The virtual boundary present flag of the SPS PH may indicate whether virtual boundary information is included in the Picture Header (PH).

[0189] In one example according to this embodiment, if the virtual boundary presence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is 1, the virtual boundary presence flag (sps_ph_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS PH does not exist and may be limited to be inferred to 0.

[0190] In one example according to this embodiment, when the virtual boundary present flag (sps_ph_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS PH is 1, signaling information for disabling the loop filter across the virtual boundary may be included in the picture header.

[0191] The following table shows an example syntax of an SPS according to this embodiment.

[0192] [Table 17]

[0193] The following table provides example semantics for syntax elements included in the above syntax.

[0194] [Table 18]

[0195] The following table shows an exemplary syntax of the header information (picture header) according to this embodiment.

[0196] [Table 19]

[0197] The following table provides example semantics for syntax elements included in the above syntax.

[0198] [Table 20-1]

[0199] [Table 20-2]

[0200] In embodiments related to Tables 17 to 20, image information encoded by an encoding device and / or image information obtained via a bitstream received by a decoding device from the encoding device may include a sequence parameter set (SPS) and a picture header (PH). The SPS may include a virtual boundary presence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) for the SPS. The SPS may include, based on the virtual boundary presence flag, 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]).

[0201] For example, when the value of the virtual boundary presence 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 amount of information regarding the positions of the vertical virtual boundaries of the SPS may be determined based on the information regarding the number of vertical virtual boundaries of the SPS, and the amount of information regarding the positions of the horizontal virtual boundaries of the SPS may be determined based on the information regarding the number of horizontal virtual boundaries of the SPS. The SPS may include a virtual boundary presence flag of an SPS PH based on the virtual boundary presence flag of the SPS.

[0202] For example, if the value of the virtual boundary presence flag of the SPS is 0, the SPS may include a virtual boundary presence flag of the SPS PH. The picture header may include a virtual boundary presence flag of the PH based on the virtual boundary presence flag of the SPS PH. For example, if the value of the virtual boundary presence flag of the SPS PH is 1, the picture header may include a virtual boundary presence flag of the PH. The picture header may include, based on the virtual boundary presence flag of the PH, 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]).

[0203] For example, the picture header may include information regarding the number of vertical virtual borders of the PH, information regarding the positions of the vertical virtual borders of the PH, information regarding the number of horizontal virtual borders of the PH, and information regarding the positions of the horizontal virtual borders of the PH when the value of the virtual border presence flag of the PH is 1. In one example, the amount of information regarding the positions of the vertical virtual borders of the PH can be determined based on the information regarding the number of vertical virtual borders of the PH, and the amount of information regarding the positions of the horizontal virtual borders of the PH can be determined based on the information regarding the number of horizontal virtual borders of the PH.

[0204] In another embodiment of this document, when Gradual Decoding Refresh (GDR) is enabled (i.e., the value of gdr_enabled_flag is 1), the feature of disabling the loop filter at the virtual boundary is enabled, and information about the virtual boundary may be signaled in (included in) the picture header.

[0205] In another embodiment of this document, when the functionality for disabling the loop filter across a virtual boundary is enabled, information regarding signaling of the location of the virtual boundary may be included in one or more parameter sets. For example, when the functionality for disabling the loop filter across a virtual boundary is enabled, information regarding signaling of the location of the virtual boundary may be included in the SPS and picture header.

[0206] In this embodiment, when the virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1 and signaling information regarding the location of the virtual boundary is included in one or more parameter sets, the following applies.

[0207] a) Signaling information regarding the location of the virtual boundary may be included only in the SPS, only in the picture header, or in both the SPS and the picture header.

[0208] b) The derivation of VirtualBoundariesDisabledFlag for each picture is as follows:

[0209] - If sps_loop_filter_across_virtual_boundaries_disabled_flag is 0, VirtualBoundariesDisabledFlag may be set to 0.

[0210] In another case in this example, if no information about the location of the virtual boundaries is signaled in the SPS or in any of the picture headers associated with the picture, then VirtualBoundariesDisabledFlag may be set to 0.

[0211] In other cases in this example (when the location of the virtual boundaries is signaled only in the SPS, or only in the picture header, or both in the SPS and the picture header), VirtualBoundariesDisabledFlag may be set to 1.

[0212] c) The virtual boundary applied to a picture may include the union of virtual boundaries signaled in parameter sets to which the picture directly or indirectly refers. For example, the virtual boundary may include the virtual boundary signaled in the SPS, if present. For example, the virtual boundary may include the virtual boundary signaled in the picture header associated with the picture, if present.

[0213] d) A limit may be applied such that the maximum number of virtual borders per picture does not exceed a pre-defined value, for example, the pre-defined value may be 8.

[0214] e) The information about the location of the virtual border signaled in the picture header (if any) may be restricted so that it is not the same as the information about the location of the virtual border contained in other parameter sets (e.g., SPS or PPS).

[0215] Alternatively, for the position of a virtual boundary applied to the current picture, the position of the virtual boundary (e.g., the position of the same virtual boundary signaled in the SPS and the picture header associated with the picture) may be included in two different parameter sets.

[0216] f) If the virtual boundary present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS is 1, the virtual boundary present flag (sps_ph_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS PH is not present and may be limited to be inferred to 0.

[0217] The following table shows an example syntax of an SPS according to this embodiment.

[0218] [Table 21]

[0219] The following table provides example semantics for syntax elements included in the above syntax.

[0220] [Table 22]

[0221] The following table shows an exemplary syntax of the header information (picture header) according to this embodiment.

[0222] [Table 23]

[0223] The following table provides example semantics for syntax elements included in the above syntax.

[0224] [Table 24-1]

[0225] [Table 24-2]

[0226] In embodiments related to Tables 21 to 24, image information encoded by an encoding device and / or image information obtained via a bitstream received by a decoding device from the encoding device may include a Sequence Parameter Set (SPS) and a Picture Header (PH). The SPS may include a virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag). The SPS may include a virtual boundary present flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) based on the virtual boundary enable flag. For example, the SPS may include the virtual boundary present flag when the value of the virtual boundary enable flag is 1. Based on the virtual boundary enable flag and the virtual boundary presence 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 position 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 position of the horizontal virtual boundaries of the SPS (sps_virtual_boundaries_pos_y[i]).

[0227] For example, when the virtual border enable flag has a value of 1 and the virtual border presence flag of the SPS has a value of 1, the SPS may include information regarding the number of vertical virtual borders of the SPS, information regarding the positions of the vertical virtual borders of the SPS, information regarding the number of horizontal virtual borders of the SPS, and information regarding the positions of the horizontal virtual borders of the SPS. In one example, the amount of information regarding the positions of the vertical virtual borders of the SPS may be determined based on the information regarding the number of vertical virtual borders of the SPS, and the amount of information regarding the positions of the horizontal virtual borders of the SPS may be determined based on the information regarding the number of horizontal virtual borders of the SPS. The picture header may include a virtual border presence flag of the PH based on the virtual border enable flag.

[0228] For example, when the value of the virtual boundary enable flag is 1, the picture header may include a virtual boundary presence flag for the PH. Based on the virtual boundary presence flag for the PH, the picture header may include information on the number of vertical virtual boundaries for the PH (ph_num_ver_virtual_boundaries), information on the positions of the vertical virtual boundaries for the PH (ph_virtual_boundaries_pos_x[i]), information on the number of horizontal virtual boundaries for the PH (ph_num_hor_virtual_boundaries), and information on the positions of the horizontal virtual boundaries for the PH (ph_virtual_boundaries_pos_y[i]). For example, when the value of the virtual boundary presence flag for the PH is 1, the picture header may include information on the number of vertical virtual boundaries for the PH, information on the positions of the vertical virtual boundaries for the PH, information on the number of horizontal virtual boundaries for the PH, and information on the positions of the horizontal virtual boundaries for the PH. In one example, the amount of information regarding the position of the vertical virtual border of the PH can be determined based on information regarding the number of vertical virtual borders of the PH, and the amount of information regarding the position of the horizontal virtual border of the PH can be determined based on information regarding the number of horizontal virtual borders of the PH.

[0229] In another embodiment of this document, loop filtering can be performed according to the embodiment described above, but by not restricting the number of vertical virtual borders plus the number of horizontal virtual borders to be greater than zero.

[0230] In another embodiment of this document, information about virtual boundaries may be signaled in both the SPS and the PH. In one example of this embodiment, when the virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1, information about the number of vertical virtual boundaries, information about the number of horizontal virtual boundaries, and / or information about the positions of the virtual boundaries may be included in the SPS. Additionally, when the virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag) of the SPS is 1, information about the number of vertical virtual boundaries, information about the number of horizontal virtual boundaries, and / or information about a delta value of the virtual boundary positions (delta value of the virtual boundary positions) may be included in the picture header. The delta value of the virtual boundary positions may refer to the difference between the positions of the virtual boundaries. The picture header may also include information about the sign of the virtual boundary positions.

[0231] According to one example related to this embodiment, to derive the position of the virtual boundary for each picture, if the delta value of the virtual boundary position is not present in the picture header, the information about the virtual boundary position signaled in the SPS may be used for loop filtering.If the delta value of the virtual boundary position is present in the picture header, the position of the virtual boundary may be derived based on a summation between the information about the virtual boundary position signaled in the SPS and the associated delta value.

[0232] The following table shows an example syntax of an SPS according to this embodiment.

[0233] [Table 25]

[0234] The following table provides example semantics for syntax elements included in the above syntax.

[0235] [Table 26]

[0236] The following table shows an exemplary syntax of the header information (picture header) according to this embodiment.

[0237] [Table 27]

[0238] The following table provides example semantics for syntax elements included in the above syntax.

[0239] [Table 28-1]

[0240] [Table 28-2]

[0241] In embodiments related to Tables 25 to 28, image information encoded by an encoding device and / or image information obtained via a bitstream received by a decoding device from the encoding device may include a sequence parameter set (SPS) and a picture header (PH). The SPS may include a virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag). Based on the virtual boundary enable 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 virtual border enable flag is 1, the SPS may include information regarding the number of horizontal virtual borders of the SPS, information regarding the position of the horizontal virtual borders of the SPS, information regarding the number of vertical virtual borders of the SPS, and information regarding the position of the vertical virtual borders of the SPS.

[0242] In one example, the amount of information regarding the position of the horizontal virtual boundary of the SPS may be determined based on information regarding the number of horizontal virtual borders of the SPS, and the amount of information regarding the position of the vertical virtual border of the SPS may be determined based on information regarding the number of vertical virtual borders of the SPS. The picture header may include a virtual boundary presence flag for the PH based on the virtual boundary enable flag. For example, if the value of the virtual boundary enable flag is 1, the picture header may include the virtual boundary presence flag for the PH. The picture header may include, based on the virtual boundary presence flag for the PH, information regarding a delta value of the position of the horizontal virtual boundary for the PH (ph_virtual_boundaries_pos_x_delta[i]), information regarding the sign of the position of the horizontal virtual boundary for the PH (ph_virtual_boundaries_pos_x_sign[i]), information regarding a delta value of the position of the vertical virtual boundary for the PH (ph_virtual_boundaries_pos_y_delta[i]), and information regarding the sign of the position of the vertical virtual boundary for the PH (ph_virtual_boundaries_pos_y_sign[i]).

[0243] For example, the picture header may include information on a delta value of the position of the vertical virtual border of the PH, information on the sign of the position of the vertical virtual border of the PH, information on a delta value of the position of the horizontal virtual border of the PH, and information on the sign of the position of the horizontal virtual border of the PH when the value of the virtual border presence flag of the PH is 1. In one example, the number of pieces of information on the delta value of the position of the vertical virtual border of the PH and the number of pieces of information on the sign of the position of the vertical virtual border of the PH can be determined based on the information about the number of vertical virtual borders of the SPS, and the number of pieces of information on the delta value of the position of the horizontal virtual border of the PH and the number of pieces of information on the sign of the position of the horizontal virtual border of the PH can be determined based on the information about the number of horizontal virtual borders of the SPS.

[0244] In yet another embodiment of this document, signaling of information regarding the position of a virtual boundary for each picture is described. In one example, when information regarding the position of a virtual boundary is included in an SPS and information regarding a delta value of the position of the virtual boundary is not included in a picture header, the information regarding the position of the virtual boundary included in the SPS may be used for loop filtering. When information regarding the position of a virtual boundary is not included in an SPS and information regarding a delta value of the position of the virtual boundary is included in a picture header, the information regarding the position of the virtual boundary included in the picture header may be used for loop filtering. When information regarding the position of a virtual boundary is included in an SPS and information regarding a delta value of the position of the virtual boundary is included in a picture header, the position of the virtual boundary may be derived based on a summation between the information regarding the position of the virtual boundary signaled in the SPS and the associated delta value. When information regarding the position of the virtual boundary is not included in an SPS and information regarding a delta value of the position of the virtual boundary is not included in a picture header, a virtual boundary may not be applied to a picture.

[0245] The following table shows an example syntax of an SPS according to this embodiment.

[0246] [Table 29]

[0247] The following table provides example semantics for syntax elements included in the above syntax.

[0248] [Table 30]

[0249] The following table shows an exemplary syntax of the header information (picture header) according to this embodiment.

[0250] [Table 31]

[0251] The following table provides example semantics for syntax elements included in the above syntax.

[0252] [Table 32-1]

[0253] [Table 32-2]

[0254] In embodiments related to Tables 29 to 32, image information encoded by an encoding device and / or image information obtained via a bitstream received by a decoding device from the encoding device may include a Sequence Parameter Set (SPS) and a Picture Header (PH).

[0255] The SPS may include a virtual boundary enable flag (sps_loop_filter_across_virtual_boundaries_disabled_flag). The SPS may include a virtual boundary presence flag (sps_loop_filter_across_virtual_boundaries_disabled_present_flag) of the SPS based on the virtual boundary enable flag. For example, the SPS may include a virtual boundary presence flag of the SPS when the value of the virtual boundary enable flag is 1. The SPS may include, based on the virtual boundary enable flag and the virtual boundary presence flag of the SPS, 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]).

[0256] For example, when the virtual border enable flag is 1 and the virtual border presence flag of the SPS is 1, the SPS may include information regarding the number of horizontal virtual borders, information regarding the positions of the horizontal virtual borders, information regarding the number of vertical virtual borders, and information regarding the positions of the vertical virtual borders. In one example, the amount of information regarding the positions of the horizontal virtual borders can be determined based on the information regarding the number of horizontal virtual borders, and the amount of information regarding the positions of the vertical virtual borders can be determined based on the information regarding the number of vertical virtual borders. The picture header may include a virtual border presence flag of a PH based on the virtual border enable flag.

[0257] For example, if the value of the virtual boundary enable flag is 1, the picture header may include a virtual boundary presence flag for the PH. The picture header may include information about the number of vertical virtual boundaries for the PH (ph_num_ver_virtual_boundaries) based on the virtual boundary presence flag for the PH and information about the number of vertical virtual boundaries for the SPS. For example, if the value of the virtual boundary presence flag for the PH is 1 and the value of the information about the number of vertical virtual boundaries for the SPS is 0, the picture header may include information about the number of vertical virtual boundaries for the PH. In one example, the picture header may include information about a delta value of the position of the vertical virtual boundary for the PH (ph_virtual_boundaries_pos_x_delta[i]) and information about the sign of the position of the vertical virtual boundary for the PH (ph_virtual_boundaries_pos_x_sign[i]) based on the information about the number of vertical virtual boundaries for the PH. In one example, the number of pieces of information about the delta value of the position of the vertical virtual boundary for the PH and the number of pieces of information about the sign of the position of the vertical virtual boundary for the PH can be determined based on the information about the number of vertical virtual boundaries for the PH. The picture header may include information about the number of horizontal virtual boundaries of the PH (ph_num_hor_virtual_boundaries) based on the virtual boundary presence flag of the PH and information about the number of horizontal virtual boundaries of the SPS.

[0258] For example, if the value of the virtual boundary presence flag of the PH is 1 and the value of the information about the number of horizontal virtual boundaries of the SPS is 0, the picture header may include information about the number of horizontal virtual boundaries of the PH. In one example, the picture header may include, based on the information about the number of horizontal virtual boundaries of the PH, information about a delta value of the position of the horizontal virtual boundary of the PH (ph_virtual_boundaries_pos_y_delta[i]) and information about the sign of the position of the horizontal virtual boundary of the PH (ph_virtual_boundaries_pos_y_sign[i]). In one example, based on the information about the number of horizontal virtual boundaries of the PH, the amount of information about the delta value of the position of the horizontal virtual boundary of the PH and the amount of information about the sign of the position of the horizontal virtual boundary of the PH can be determined.

[0259] In conjunction with the above table, embodiments of this document allow the coding device to efficiently signal information necessary to control in-loop filtering performed across virtual boundaries. In one example, information related to whether in-loop filtering is available across virtual boundaries can be signaled.

[0260] 8 and 9 show a schematic diagram of an example of a video / image encoding method and related components according to an embodiment of this document.

[0261] The method disclosed in FIG. 8 may be performed by the encoding device disclosed in FIG. 2 or FIG. 9. Specifically, for example, S800 and S810 of FIG. 8 may be performed by the residual processing unit 230 of the encoding device of FIG. 9, S820 and / or S830 of FIG. 8 may be performed by the filtering unit 260 of the encoding device of FIG. 9, and S840 of FIG. 8 may be performed by the entropy coding unit 240 of the encoding device of FIG. 9. Also, although not shown in FIG. 8, prediction samples or prediction-related information may be derived by the prediction unit 220 of the encoding device of FIG. 8, and a bitstream may be generated from the residual information or prediction-related information by the entropy coding unit 240 of the encoding device. The method disclosed in FIG. 8 may include the embodiments described above in this document.

[0262] Referring to FIG. 8, an encoding apparatus may derive residual samples (S800). The encoding apparatus may derive residual samples for a current block, and the residual samples for the current block may be derived based on original samples and predicted samples of the current block. Specifically, the encoding apparatus may derive predicted samples for the current block based on a prediction mode. In this case, various prediction methods disclosed herein, such as inter prediction or intra prediction, may be applied. Residual samples may be derived based on the predicted samples and original samples.

[0263] The encoding device may derive transform coefficients. The encoding device may derive the transform coefficients based on a transform procedure on the residual samples. For example, the transform procedure may include at least one of a DCT, a DST, a GBT, or a CNT.

[0264] The encoding device may derive quantized transform coefficients. The encoding device may derive the quantized transform coefficients based on a quantization procedure for the transform coefficients. The quantized transform coefficients may have the form of a one-dimensional vector based on a coefficient scanning order.

[0265] The encoding apparatus may generate residual information (S810) based on the residual samples for the current block. The encoding apparatus may generate residual information indicating the quantized transform coefficients. The residual information may be generated through various encoding methods such as Exponential-Golomb, CAVLC, and CABAC.

[0266] The encoding device may generate reconstructed samples based on the residual information. The reconstructed samples may be generated by adding residual samples based on the residual information to predicted samples. Specifically, the encoding device may perform prediction (intra- or inter-prediction) on the current block and generate reconstructed samples based on the original samples and predicted samples generated from the prediction.

[0267] The reconstructed samples may include reconstructed luma samples and reconstructed chroma samples. Specifically, the residual samples may include residual luma samples and residual chroma samples. The residual luma samples may be generated based on the original luma samples and the predicted luma samples. The residual chroma samples may be generated based on the original chroma samples and the predicted chroma samples. The encoding device may derive transform coefficients for the residual luma samples (luma transform coefficients) and / or transform coefficients for the residual chroma samples (chroma transform coefficients). The quantized transform coefficients may include quantized luma transform coefficients and / or quantized chroma transform coefficients.

[0268] The encoding device may determine whether the in-loop filtering procedure is performed across a virtual boundary (S820). Here, the virtual boundary may be the same as the virtual boundary described above. Also, the in-loop filtering procedure may include at least one of a deblocking procedure, an SAO procedure, or an ALF procedure.

[0269] The encoding device may generate virtual boundary-related information (S830). The encoding device may generate the virtual boundary-related information based on the determination in step S820. The virtual boundary-related information may be included in in-loop filtering-related information. Here, the in-loop filtering-related information may refer to information used to perform the in-loop filtering procedure. For example, the virtual boundary-related information may include information about the virtual boundary described above in this document (such as the virtual boundary enable flag in the SPS, the virtual boundary enable flag in the picture header, the virtual boundary present flag in the SPS, the virtual boundary present flag in the picture header, and information about the position of the virtual boundary).

[0270] The encoding device may encode video / image information (S840). The image information may include residual information, prediction-related information, and / or in-loop filtering-related information. The encoded video / image information may be output in the form of a bitstream. The bitstream may be transmitted to a decoding device via a network or a storage medium.

[0271] The image / video information may include various information according to embodiments of this document, for example, the image / video information may include information disclosed in at least one of Tables 1 to 32 above.

[0272] In one embodiment, the image information may include a Sequence Parameter Set (SPS) and picture header information referencing the SPS. The virtual boundary-related information may include a virtual boundary enable flag (or a virtual boundary enable flag of an SPS). Based on the virtual boundary enable flag, it can be determined whether signaling of the virtual boundary-related information exists in the SPS or the picture header information. The in-loop filtering procedure can be performed across a virtual boundary (or may not be performed across a virtual boundary) based on the virtual boundary enable flag. For example, the virtual boundary enable flag can indicate whether disabling of the in-loop filtering procedure across a virtual boundary is possible.

[0273] In one embodiment, the SPS includes the virtual boundary enable flag and a virtual boundary presence flag of the SPS, and based on the virtual boundary presence flag, it can be determined whether information regarding the position of the virtual boundary and information regarding the number of the virtual boundaries is included in the SPS.

[0274] In one embodiment, based on the value of the virtual border presence flag of the SPS being 1, the SPS may include information regarding the number of vertical virtual borders.

[0275] In one embodiment, the SPS may include information about the positions of vertical virtual boundaries, and the number of pieces of information about the positions of the vertical virtual boundaries may be determined based on the information about the number of vertical virtual boundaries.

[0276] In one embodiment, based on the value of the virtual boundary presence flag of the SPS being 1, the SPS may include information regarding the number of horizontal virtual boundaries.

[0277] In one embodiment, the SPS may include information about the positions of horizontal virtual boundaries, and the number of pieces of information about the positions of the horizontal virtual boundaries may be determined based on the information about the number of horizontal virtual boundaries.

[0278] In one embodiment, based on the value of the virtual boundary enable flag being 1 and the value of the virtual boundary present flag of the SPS being 0, the picture header information may include a virtual boundary present flag of the picture header.

[0279] In one embodiment, based on the value of the virtual border presence flag of the picture header being 1, the picture header information may include information regarding the number of vertical virtual borders.

[0280] In one embodiment, the picture header information may include information about the positions of vertical virtual borders, and the number of pieces of information about the positions of the vertical virtual borders may be determined based on the information about the number of vertical virtual borders.

[0281] In one embodiment, based on the value of the virtual border presence flag of the picture header being 1, the picture header information may include information regarding the number of horizontal virtual borders.

[0282] In one embodiment, the picture header information may include information about the positions of horizontal virtual borders, and the number of pieces of information about the positions of the horizontal virtual borders may be determined based on the information about the number of horizontal virtual borders.

[0283] In one embodiment, the sum of the number of vertical virtual borders and the number of horizontal virtual borders may be greater than 0, based on the SPS including information regarding the position of vertical virtual borders and information regarding the position of horizontal virtual borders.

[0284] In one embodiment, the in-loop filtering-related information (and / or virtual boundary-related information) may further include a virtual boundary presence flag of an SPS, a virtual boundary presence flag of a picture header, and a Gradual Decoding Refresh (GDR) enable flag. For example, based on the value of the GDR enable flag being 1, the value of the virtual boundary enable flag of the SPS (virtual boundary enable flag) 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 (signaling of virtual boundary information may be present in the picture header).

[0285] 10 and 11 show a schematic diagram of an example of a video / image decoding method and related components according to an embodiment of the present document.

[0286] The method disclosed in Fig. 10 may be performed by the decoding device disclosed in Fig. 3 or Fig. 11. Specifically, for example, S1000 in Fig. 10 may be performed by the entropy decoding unit 310 of the decoding device, S1010 may be performed by the residual processing unit 320 and / or the adding unit 340 of the decoding device, and S1020 may be performed by the filtering unit 350 of the decoding device. The method disclosed in Fig. 10 may include the embodiments described above in this document.

[0287] 10, a decoding device may receive / acquire video / image information (S1000). The video / image information may include residual information, prediction-related information, and / or in-loop filtering-related information. The decoding device may receive / acquire the image / video information via a bitstream.

[0288] The image / video information may include various information according to embodiments of this document, for example, the image / video information may include information disclosed in at least one of Tables 1 through 32 above.

[0289] The decoding device may derive quantized transform coefficients. The decoding device may derive the quantized transform coefficients based on the residual information. The quantized transform coefficients may have the form of a one-dimensional vector based on the coefficient scanning order. The quantized transform coefficients may include quantized luma transform coefficients and / or quantized chroma transform coefficients.

[0290] The decoding device can derive transform coefficients. The decoding device can derive transform coefficients based on an inverse quantization procedure for the quantized transform coefficients. The decoding device can derive luma transform coefficients through inverse quantization based on the quantized luma transform coefficients. The decoding device can derive chroma transform coefficients through inverse quantization based on the quantized chroma transform coefficients.

[0291] The decoding device may generate / derive residual samples. The decoding device may derive residual samples based on an inverse transform procedure on the transform coefficients. The decoding device may derive residual luma samples via an inverse transform procedure based on luma transform coefficients. The decoding device may derive residual chroma samples via an inverse transform procedure based on chroma transform coefficients.

[0292] The decoding device may generate / derive reconstructed samples (S1010). For example, the decoding device may generate / derive reconstructed luma samples and / or reconstructed chroma samples. The decoding device may generate reconstructed luma samples and / or reconstructed chroma samples based on the residual information. The decoding device may generate reconstructed samples based on the residual information. The reconstructed samples may include reconstructed luma samples and / or reconstructed chroma samples. The luma components of the reconstructed samples may correspond to the reconstructed luma samples, and the chroma components of the reconstructed samples may correspond to the reconstructed chroma samples. The decoding device may generate predicted luma samples and / or predicted chroma samples through a prediction procedure. The decoding device may generate reconstructed luma samples based on the predicted luma samples and the residual luma samples. The decoding device may generate reconstructed chroma samples based on the predicted chroma samples and the residual chroma samples.

[0293] The decoding device may generate modified (filtered) reconstructed samples (S1020). The decoding device may generate the modified reconstructed samples based on an in-loop filtering procedure on the reconstructed samples. The decoding device may generate the modified reconstructed samples based on in-loop filtering-related information. The decoding device may use a deblocking procedure, an SAO procedure, and / or an ALF procedure to generate the modified reconstructed samples.

[0294] In one embodiment, the image information may include an SPS and picture header information that references the SPS. The virtual boundary-related information may include a virtual boundary enable flag (or a virtual boundary presence flag of an SPS). Based on the virtual boundary enable flag, it can be determined whether signaling of the virtual boundary-related information exists in the SPS or the picture header information. The in-loop filtering procedure can be performed across a virtual boundary (or may not be performed without crossing it) based on the virtual boundary enable flag. For example, the virtual boundary enable flag can indicate whether disabling of the in-loop filtering procedure across a virtual boundary is possible.

[0295] In one embodiment, the SPS may include a virtual boundary enable flag and / or a virtual boundary presence flag of the SPS, and based on the virtual boundary presence flag of the SPS, it can be determined whether the SPS includes information about the location of the virtual boundary and information about the number of the virtual boundaries.

[0296] In one embodiment, based on the value of the virtual border presence flag of the SPS being 1, the SPS may include information regarding the number of vertical virtual borders.

[0297] In one embodiment, the SPS may include information about the positions of vertical virtual boundaries, and the number of pieces of information about the positions of the vertical virtual boundaries may be determined based on the information about the number of vertical virtual boundaries.

[0298] In one embodiment, based on the value of the virtual boundary presence flag of the SPS being 1, the SPS may include information regarding the number of horizontal virtual boundaries.

[0299] In one embodiment, the SPS may include information about the positions of horizontal virtual boundaries, and the number of pieces of information about the positions of the horizontal virtual boundaries may be determined based on the information about the number of horizontal virtual boundaries.

[0300] In one embodiment, based on the value of the virtual boundary enable flag being 1 and the value of the virtual boundary present flag of the SPS being 0, the picture header information may include a virtual boundary present flag of the picture header.

[0301] In one embodiment, based on the value of the virtual border presence flag of the picture header being 1, the picture header information may include information regarding the number of vertical virtual borders.

[0302] In one embodiment, the picture header information may include information about the positions of vertical virtual borders, and the number of pieces of information about the positions of the vertical virtual borders may be determined based on the information about the number of vertical virtual borders.

[0303] In one embodiment, based on the value of the virtual border presence flag of the picture header being 1, the picture header information may include information regarding the number of horizontal virtual borders.

[0304] In one embodiment, the picture header information may include information about the positions of horizontal virtual borders, and the number of pieces of information about the positions of the horizontal virtual borders may be determined based on the information about the number of horizontal virtual borders.

[0305] In one embodiment, the sum of the number of vertical virtual borders and the number of horizontal virtual borders may be greater than 0, based on the SPS including information regarding the position of vertical virtual borders and information regarding the position of horizontal virtual borders.

[0306] In one embodiment, the in-loop filtering-related information (and / or virtual boundary-related information) may further include a virtual boundary presence flag of an SPS, a virtual boundary presence flag of a picture header, and a Gradual Decoding Refresh (GDR) enable flag. For example, based on the value of the GDR enable flag being 1, the value of the virtual boundary enable flag of the SPS (virtual boundary enable flag) 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 (signaling of virtual boundary information may be present in the picture header).

[0307] If residual samples for the current block exist, the decoding device may receive information about the residual for the current block. The information about the residual may include transform coefficients related to the residual samples. The decoding device may derive residual samples (or a residual sample array) for the current block based on the residual information. Specifically, the decoding device may derive quantized transform coefficients based on the residual information. The quantized transform coefficients may have a one-dimensional vector form based on a coefficient scanning order. The decoding device may derive the transform coefficients based on an inverse quantization procedure for the quantized transform coefficients. The decoding device may derive the residual samples based on the transform coefficients.

[0308] The decoding apparatus may generate reconstructed samples based on (intra) predicted samples and residual samples, and derive reconstructed blocks or pictures based on the reconstructed samples. Specifically, the decoding apparatus may generate reconstructed samples based on the sum of the (intra) predicted samples and residual samples. As described above, the decoding apparatus may then apply an in-loop filtering procedure, such as a deblocking filtering and / or SAO procedure, to the reconstructed pictures as needed to improve subjective / objective image quality.

[0309] For example, a decoding device can decode the bitstream or encoded information to obtain image information including all or part of the above-described information (or syntax elements). The bitstream or encoded information can be stored in a computer-readable storage medium, and the above-described decoding method can be performed.

[0310] In the above-described embodiments, the method is described based on a flowchart as a series of steps or blocks, but the embodiment is not limited to the order of the steps, and a step may occur in a different order or simultaneously with a different step than described above. Also, a person skilled in the art will understand that the steps shown in the flowchart are not exclusive, and different steps may be included, or one or more steps of the flowchart may be deleted without affecting the scope of the embodiments herein.

[0311] The methods according to the embodiments of the present document described above can be implemented in the form of software, and the encoding device and / or decoding device according to the present document can be included in devices that perform image processing, such as TVs, computers, smartphones, set-top boxes, display devices, etc.

[0312] When an embodiment of this document is implemented in software, the method described above may be implemented with modules (processes, functions, etc.) that perform the functions described above. The modules may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor in various well-known ways. The processor may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, a memory card, a storage medium, and / or other storage devices. That is, the embodiments described herein may be implemented and performed on a processor, microprocessor, controller, or chip. For example, the functional units illustrated in each figure may be implemented and performed on a computer, processor, microprocessor, controller, or chip. In this case, information (e.g., information on instructions) or algorithms for implementation may be stored on a digital storage medium.

[0313] In addition, the decoding device and encoding device to which the embodiments of this document are applied may be included in a multimedia broadcast transmitting / receiving device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video interactive device, a real-time communication device such as video communication, a mobile streaming device, a storage medium, a camcorder, a video-on-demand (VoD) service providing device, an over-the-top (OTT) video (over-the-top) device, an internet streaming service providing device, a three-dimensional (3D) video device, a virtual reality (VR) device, an augmented reality (AR) device, an image telephone video device, a transportation terminal (e.g., a vehicle terminal (including an autonomous vehicle), an airplane terminal, a ship terminal, etc.), a medical video device, etc., and may be used to process video signals or data signals. For example, an over-the-top (OTT) video (over-the-top) device may include a game console, a Blu-ray player, an internet access TV, a home theater system, a smartphone, a tablet PC, a digital video recorder (DVR), etc.

[0314] Furthermore, a processing method to which an embodiment of this document is applied can be produced in the form of a computer-executable program and stored in a computer-readable recording medium. Multimedia data having a data structure according to an embodiment of this document can also be stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices and distributed storage devices in which computer-readable data is stored. The computer-readable recording medium may include, for example, a Blu-ray Disc (BD), a Universal Serial Bus (USB), a ROM, a PROM, an EPROM, an EEPROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device. The computer-readable recording medium also includes media realized in the form of a carrier wave (e.g., transmission via the Internet). The bitstream generated by the encoding method can be stored in a computer-readable recording medium or transmitted via a wired or wireless communication network.

[0315] Furthermore, the embodiments of the present document may be implemented in a computer program product by program code, which may be executed by a computer in accordance with the embodiments of the present document. The program code may be stored on a computer-readable carrier.

[0316] FIG. 12 illustrates an example of a content streaming system in which the embodiments disclosed herein can be applied.

[0317] Referring to FIG. 12, a content streaming system to which the embodiments of this document are applied may broadly include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0318] The encoding server compresses content input from a multimedia input device such as a smartphone, camera, camcorder, etc. into digital data to generate a bitstream and transmits the bitstream to the streaming server. As another example, if a multimedia input device such as a smartphone, camera, camcorder, etc. directly generates a bitstream, the encoding server may be omitted.

[0319] The bitstream can be generated by an encoding method or a bitstream generation method to which an embodiment of this document is applied, and the streaming server can temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[0320] The streaming server transmits multimedia data to a user device based on a user request via a web server, and the web server acts as an intermediary that informs the user of available services. When a user requests a desired service from the web server, the web server transmits the request to the streaming server, which then transmits the multimedia data to the user. In this case, the content streaming system may include a separate control server, which controls commands and responses between devices in the content streaming system.

[0321] The streaming server can receive content from a media storage device (storage) and / or an encoding server. For example, when receiving content from the encoding server, the content can be received in real time. In this case, the streaming server can store the bitstream for a certain period of time to provide a smooth streaming service.

[0322] Examples of the user device include a mobile phone, a smartphone, a laptop computer, a digital broadcasting terminal, a PDA (Personal Digital Assistant), a PMP (Portable Multimedia Player), a navigation system, a slate PC, a tablet PC, an ULTRABOOK (registered trademark), a wearable device (e.g., a smartwatch, smart glass, or a head mounted display (HMD)), a digital TV, a desktop computer, and a digital signature.

[0323] Each server in the content streaming system can be operated as a distributed server, and in this case, data received by each server can be processed in a distributed manner.

[0324] The claims described in this specification may be combined in various ways. For example, the technical features of the method claims herein may be combined to be realized as an apparatus, and the technical features of the apparatus claims herein may be combined to be realized as a method. Furthermore, the technical features of the method claims herein and the technical features of the apparatus claims herein may be combined to be realized as an apparatus, and the technical features of the method claims herein and the technical features of the apparatus claims herein may be combined to be realized as a method.

Claims

1. 1. An image decoding method executed by a decoding device, comprising: obtaining image information via a bitstream, the image information including residual information, information related to a virtual boundary, and prediction-related information; generating residual samples based on the residual information; deriving a prediction sample based on the prediction-related information; generating reconstructed samples of a current picture based on the predicted samples and the residual samples; generating modified reconstruction samples based on an in-loop filtering procedure on the reconstruction samples; the image information includes an SPS (Sequence Parameter Set) and picture header information that references the SPS, the information related to the virtual boundary includes a virtual boundary enable flag; The SPS includes an SPS virtual boundary presence flag based on the virtual boundary enable flag; determining whether signaling of the information related to the virtual boundary is present in the SPS or the picture header information based on the virtual boundary enable flag; determining whether the in-loop filtering procedure is enabled across the virtual boundary based on the virtual boundary enable flag; The method of claim 1, wherein the SPS includes information regarding the position of a vertical virtual boundary and information regarding the position of a horizontal virtual boundary based on the value of the SPS virtual boundary presence flag being 1.

2. 1. An image encoding method performed by an encoding device, comprising: deriving prediction-related information for the current block; generating a predicted sample for the current block based on the prediction-related information; deriving residual samples for the current block based on the prediction samples; generating residual information based on the residual samples for the current block; generating reconstructed samples for a current picture based on the predicted samples and the residual samples; determining whether an in-loop filtering procedure is enabled across a virtual boundary; generating information related to the virtual boundary based on the determination; encoding image information including the prediction-related information, the residual information, and the information related to the virtual boundary; the image information includes an SPS (Sequence Parameter Set) and picture header information that references the SPS, the information related to the virtual boundary includes a virtual boundary enable flag; The SPS includes an SPS virtual boundary presence flag based on the virtual boundary enable flag; determining whether signaling of the information related to the virtual boundary is present in the SPS or the picture header information based on the virtual boundary enable flag; determining a value of the virtual boundary enable flag based on whether the in-loop filtering procedure is enabled across the virtual boundary; The method, wherein a value of the SPS virtual boundary present flag is determined to be equal to 1 based on if information regarding a position of a vertical virtual boundary and information regarding a position of a horizontal virtual boundary are included in the SPS.

3. A method for transmitting data relating to an image, comprising: obtaining a bitstream of the image, the bitstream comprising: deriving prediction-related information for the current block; generating a predicted sample for the current block based on the prediction-related information; deriving residual samples for the current block based on the prediction samples; generating residual information based on the residual samples for the current block; generating reconstructed samples for a current picture based on the predicted samples and the residual samples; determining whether an in-loop filtering procedure is enabled across a virtual boundary; generating information related to the virtual boundary based on the determination; encoding image information including the prediction-related information, the residual information, and the information related to the virtual boundary; transmitting the data including the bitstream; the image information includes an SPS (Sequence Parameter Set) and picture header information that references the SPS, the information related to the virtual boundary includes a virtual boundary enable flag; The SPS includes an SPS virtual boundary presence flag based on the virtual boundary enable flag; determining whether signaling of the information related to the virtual boundary is present in the SPS or the picture header information based on the virtual boundary enable flag; determining a value of the virtual boundary enable flag based on whether the in-loop filtering procedure is enabled across the virtual boundary; The method, wherein a value of the SPS virtual boundary present flag is determined to be equal to 1 based on if information regarding a position of a vertical virtual boundary and information regarding a position of a horizontal virtual boundary are included in the SPS.

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