Image encoding / decoding method and apparatus based on adaptive slice scanning method, and recording medium storing bit stream

Abstract

Provided are an image encoding / decoding method and apparatus. An image decoding method according to the present disclosure comprises the steps of: determining a decoding order of a plurality of slices within a current picture; and decoding the plurality of slices based on the determined decoding order, in which a scanning order based on the plurality of slices is determined as an order different from a raster scanning order, a left adjacent slice located on the left side of the current slice and an upper adjacent slice located above the current slice in the current picture can be limited to be prior to the current slice based on the decoding order.

Description

Technical Field

[0001] The present disclosure relates to an image encoding / decoding method and apparatus and a recording medium for storing a bit stream, and more particularly, to an image encoding / decoding method and apparatus based on an adaptive slice scanning scheme, and a recording medium for storing a bit stream generated by the image encoding method / apparatus of the present disclosure. Background Art

[0002] Recently, the demand for high-resolution and high-quality images, such as high-definition (HD) images and ultra-high-definition (UHD) images, is increasing in various fields. As the resolution and quality of image data are improved, the amount of information or bit volume transmitted is relatively increased compared to existing image data. The increase in the amount of information or bit volume transmitted leads to an increase in transmission cost and storage cost.

[0003] Therefore, efficient image compression technology is needed to effectively transmit, store, and reproduce information about high-resolution and high-quality images. Summary of the invention

[0004] Technical issues

[0005] An object of the present disclosure is to provide an image encoding / decoding method and apparatus with improved encoding / decoding efficiency.

[0006] Another object of the present disclosure is to provide an encoding / decoding method and apparatus based on an adaptive slice scanning scheme according to the position and shape of a slice within a picture.

[0007] Another object of the present disclosure is to provide an encoding / decoding method and apparatus based on an adaptive slice scanning method according to whether subpicture across filtering is allowed.

[0008] Another object of the present disclosure is to provide an encoding / decoding method and device based on a flexible and arbitrary slice scanning scheme.

[0009] Another object of the present disclosure is to provide an encoding / decoding method and apparatus capable of performing in-loop filtering without decoding delay.

[0010] Another object of the present disclosure is to provide a non-transitory computer-readable recording medium for storing a bit stream generated by the image encoding method or apparatus according to the present disclosure.

[0011] Another object of the present disclosure is to provide a non-transitory computer-readable recording medium for storing a bit stream received and decoded by the image decoding apparatus according to the present disclosure and used to reconstruct an image.

[0012] Another object of the present disclosure is to provide a method of transmitting a bit stream generated by the image encoding method or apparatus according to the present disclosure.

[0013] The technical problems solved by the present disclosure are not limited to the above-mentioned technical problems, and other technical problems not described herein will be apparent to those skilled in the art through the following description.

[0014] Technical Solution

[0015] According to aspects of the present disclosure, an image decoding method may include: determining a decoding order of multiple slices within a current picture, and decoding the multiple slices based on the determined decoding order. Based on the decoding order of the multiple slices being determined as an order different from a raster scan order, a left adjacent slice located to the left of the current slice and an upper adjacent slice located above the current slice within the current picture may be restricted to precede the current slice in the decoding order.

[0016] According to another aspect of the present disclosure, an image decoding device may include a memory and at least one processor. The at least one processor may determine a decoding order of multiple slices within a current picture, and decode the multiple slices based on the determined decoding order. Based on the decoding order of the multiple slices being determined as an order different from a raster scan order, a left adjacent slice located to the left of the current slice and an upper adjacent slice located above the current slice within the current picture may be limited to precede the current slice in the decoding order.

[0017] According to another aspect of the present disclosure, an image encoding method may include: determining a coding order of multiple slices within a current picture, and encoding the multiple slices based on the determined coding order. Based on the coding order of the multiple slices being determined as an order different from a raster scan order, a left adjacent slice located to the left of the current slice and an upper adjacent slice located above the current slice within the current picture may be restricted to precede the current slice in the coding order.

[0018] In addition, a computer-readable recording medium according to another aspect of the present disclosure may store a bit stream generated by the image encoding apparatus or the image encoding method of the present disclosure.

[0019] In addition, a transmission method according to another aspect of the present disclosure may transmit a bit stream generated by the image encoding device or method of the present disclosure.

[0020] The features briefly summarized above with respect to the present disclosure are merely exemplary aspects of the following detailed description of the present disclosure and do not limit the scope of the present disclosure.

[0021] Beneficial Effects

[0022] According to the present disclosure, an image encoding / decoding method and apparatus with improved encoding / decoding efficiency can be provided.

[0023] Furthermore, according to the present disclosure, an encoding / decoding method and apparatus based on an adaptive slice scanning scheme according to the position and shape of a slice within a picture may be provided.

[0024] Furthermore, according to the present disclosure, an encoding / decoding method and apparatus based on an adaptive slice scanning method according to whether sub-picture cross filtering is allowed may be provided.

[0025] Furthermore, according to the present disclosure, a coding / decoding method and device based on a flexible and arbitrary slice scanning scheme may be provided.

[0026] Furthermore, according to the present disclosure, it is possible to provide an encoding / decoding method and apparatus capable of performing in-loop filtering without decoding delay.

[0027] Furthermore, according to the present disclosure, a non-transitory recording medium for storing a bit stream generated by the image encoding method or apparatus according to the present disclosure can be provided.

[0028] Furthermore, according to the present disclosure, it is possible to provide a non-transitory recording medium for storing a bit stream received and decoded by the image decoding device according to the present disclosure and used to reconstruct an image.

[0029] According to the present disclosure, a method of transmitting a bit stream generated by the image encoding method according to the present disclosure may be provided.

[0030] Those skilled in the art will understand that the effects that can be achieved through the present disclosure are not limited to what has been specifically described above, and other advantages of the present disclosure will be more clearly understood from the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 FIG. 4 is a diagram schematically showing a video encoding system to which an embodiment of the present disclosure is applicable.

[0032] Figure 2 is a view schematically showing an image encoding device to which an embodiment of the present disclosure is applicable.

[0033] Figure 3 is a view schematically showing an image decoding device to which an embodiment of the present disclosure is applicable.

[0034] Figures 4 to 7 is a diagram showing an example of a split screen.

[0035] Figure 8 is a schematic flowchart of an image decoding process applicable according to an embodiment of the present disclosure.

[0036] Fig. 9is a schematic flowchart of an image encoding process applicable according to an embodiment of the present disclosure.

[0037] Fig.10 is a diagram showing an example of a hierarchical structure for encoding an image / video.

[0038] Fig.11 A diagram for explaining a slice scanning scheme.

[0039] Figure 12 to Figure 14 is a diagram for explaining an adaptive slice scanning scheme according to an embodiment of the present disclosure.

[0040] Figures 15 to 19 is a diagram for explaining an adaptive slice scanning scheme according to an embodiment of the present disclosure.

[0041] Fig. 20 is a flowchart illustrating an image encoding method according to an embodiment of the present disclosure.

[0042] Fig.21 is a flowchart illustrating an image decoding method according to an embodiment of the present disclosure.

[0043] Fig. 22 is a diagram showing a content streaming system to which an embodiment of the present disclosure is applicable. DETAILED DESCRIPTION

[0044] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings to facilitate implementation by those skilled in the art. However, the present disclosure may be implemented in various forms and is not limited to the embodiments described herein.

[0045] When describing the present disclosure, if it is determined that the detailed description of related known functions or configurations makes the scope of the present disclosure unnecessarily ambiguous, the detailed description thereof will be omitted. In the drawings, parts irrelevant to the description of the present disclosure are omitted, and like reference numerals are given to like parts.

[0046] In the present disclosure, when a component is "connected", "coupled" or "linked" to another component, it may include not only a direct connection relationship but also an indirect connection relationship with intermediate components. In addition, when a component "includes" or "has" other components, unless otherwise specified, it means that other components may also be included, rather than excluding other components.

[0047] In the present disclosure, the terms first, second, etc. may be used only for the purpose of distinguishing one component from other components, and do not limit the order or importance of the components, unless otherwise specified. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

[0048] In the present disclosure, components that are distinguished from each other are intended to clearly describe each feature and do not mean that the components must be separated. That is, multiple components can be integrated and implemented in one hardware or software unit, or one component can be distributed and implemented in multiple hardware or software units. Therefore, even if not otherwise specified, these embodiments in which the components are integrated or the components are distributed are also included in the scope of the present disclosure.

[0049] In the present disclosure, the components described in each embodiment are not necessarily indispensable components, and some components may be optional components. Therefore, the embodiments consisting of a subset of the components described in the embodiments are also included in the scope of the present disclosure. In addition, the embodiments including other components in addition to the components described in the various embodiments are included in the scope of the present disclosure.

[0050] The present disclosure relates to encoding and decoding of images. Unless otherwise defined in the present disclosure, terms used in the present disclosure may have general meanings commonly used in the technical field to which the present disclosure belongs.

[0051] In this disclosure, a video may refer to a set of images that changes over time.

[0052] In the present disclosure, a "picture" generally refers to a unit representing an image within a specific time period, and a slice / tile is a coding unit constituting a part of a picture, and a picture may be composed of one or more slices / tiles. In addition, a slice / tile may include one or more coding tree units (CTUs).

[0053] "Pixel" or "pel" may refer to the smallest unit constituting a picture (or image). In addition, "sample" may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, or may represent only a pixel / pixel value of a luminance component or only a pixel / pixel value of a chrominance component.

[0054] In the present disclosure, a "unit" may refer to a basic unit of image processing. The unit may include at least one of a specific area of ​​a picture and information related to the area. In some cases, the unit may be used interchangeably with terms such as "sample array", "block" or "area". In general, an M×N block may include M columns and N rows of samples (or sample arrays) or a set (or array) of transform coefficients.

[0055] In the present disclosure, "current block" may mean one of "current coding block", "current coding unit", "coding target block", "decoding target block" or "processing target block". When prediction is performed, "current block" may mean "current prediction block" or "prediction target block". When transform (inverse transform) / quantization (dequantization) is performed, "current block" may mean "current transform block" or "transform target block". When filtering is performed, "current block" may mean "filtering target block".

[0056] In addition, in the present disclosure, unless explicitly stated as a chroma block, "current block" may mean a block including both a luma component block and a chroma component block or a "luminance block of the current block". The luma component block of the current block may be expressed by an explicit description including a luma component block such as "luminance block" or "current luma block". In addition, "chroma component block of the current block" may be expressed by an explicit description including a chroma component block such as "chroma block" or "current chroma block".

[0057] In the present disclosure, the slash " / " or "," should be interpreted as indicating "and / or". For example, the expressions "A / B" and "A, B" may mean "A and / or B". In addition, "A / B / C" and "A, B, C" may mean "at least one of A, B and / or C".

[0058] In the present disclosure, the term "or" should be interpreted as indicating "and / or". For example, the expression "A or B" may include 1) only "A", 2) only "B", and / or 3) both "A and B". In other words, in the present disclosure, the term "or" should be interpreted as indicating "additionally or alternatively".

[0059] In the present disclosure, "at least one of A, B, and C" may mean "only A", "only B", "only C", or "any and all combinations of A, B, and C". In addition, "at least one of A, B, or C" or "at least one of A, B and / or C" may mean "at least one of A, B, and C".

[0060] The brackets used in the present disclosure may mean "for example". For example, if "prediction (intra-frame prediction)" is indicated, "intra-frame prediction" may be proposed as an example of "prediction". In other words, "prediction" in the present disclosure is not limited to "intra-frame prediction", and "intra-frame prediction" may be proposed as an example of "prediction". In addition, even if "prediction (i.e., intra-frame prediction)" is indicated, "intra-frame prediction" may be proposed as an example of "prediction".

[0061] Overview of Video Coding Systems

[0062] Figure 1 is a diagram showing a video encoding system to which an embodiment of the present disclosure is applicable.

[0063] The video encoding system according to the embodiment may include an encoding device 10 and a decoding device 20. The encoding device 10 may deliver the encoded video and / or image information or data to the decoding device 20 via a digital storage medium or a network in the form of a file or a stream.

[0064] The encoding device 10 according to the embodiment may include a video source generator 11, an encoding unit 12, and a transmitter 13. The decoding device 20 according to the embodiment may include a receiver 21, a decoding unit 22, and a renderer 23. The encoding unit 12 may be referred to as a video / image encoding device, and the decoding unit 22 may be referred to as a video / image decoding device. The transmitter 13 may be included in the encoding unit 12. The receiver 21 may be included in the decoding unit 22. The renderer 23 may include a display and the display may be configured as a separate device or an external component.

[0065] The video source generator 11 can obtain the video / image by the process of capturing, synthesizing or generating the video / image. The video source generator 11 may include a video / image capturing device and / or a video / image generating device. The video / image capturing device may include, for example, one or more cameras, a video / image archive including previously captured videos / images, etc. The video / image generating device may include, for example, a computer, a tablet computer, and a smart phone, and may generate the video / image (electronically). For example, a virtual video / image may be generated by a computer, etc. In this case, the video / image capturing process may be replaced by a process of generating relevant data.

[0066] The encoding unit 12 may encode the input video / image. For compression and encoding efficiency, the encoding unit 12 may perform a series of processes such as prediction, transformation, and quantization. The encoding unit 12 may output the encoded data (encoded video / image information) in the form of a bitstream.

[0067] The transmitter 13 may transmit the encoded video / image information or data output in the form of a bit stream to the receiver 21 of the decoding device 20 in the form of a file or stream through a digital storage medium or a network. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitter 13 may include an element for generating a media file in a predetermined file format and may include an element for transmitting through a broadcast / communication network. The receiver 21 may extract / receive a bit stream from a storage medium or a network and transmit the bit stream to a decoding unit 22.

[0068] The decoding unit 22 may decode a video / image by performing a series of processes corresponding to the operations of the encoding unit 12 , such as dequantization, inverse transformation, and prediction.

[0069] The renderer 23 may render the decoded video / image. The rendered video / image may be displayed on a display.

[0070] Overview of Image Coding Equipment

[0071] Figure 2 is a view schematically showing an image encoding device to which an embodiment of the present disclosure is applicable.

[0072] like Figure 2 As shown, the image encoding device 100 may include an image segmenter 110, a subtractor 115, a transformer 120, a quantizer 130, a dequantizer 140, an inverse transformer 150, an adder 155, a filter 160, a memory 170, an inter-frame prediction unit 180, an intra-frame prediction unit 185, and an entropy encoder 190. The inter-frame prediction unit 180 and the intra-frame prediction unit 185 may be collectively referred to as a "prediction unit". The transformer 120, the quantizer 130, the dequantizer 140, and the inverse transformer 150 may be included in a residual processor. The residual processor may also include a subtractor 115.

[0073] In some embodiments, all or at least some of the components configuring the image encoding apparatus 100 may be configured by one hardware component (eg, an encoder or a processor). In addition, the memory 170 may include a decoded picture buffer (DPB) and may be configured by a digital storage medium.

[0074] The image segmenter 110 may segment the input image (or picture or frame) input to the image encoding device 100 into one or more processing units. For example, the processing unit may be referred to as a coding unit (CU). The coding unit may be obtained by recursively segmenting a coding tree unit (CTU) or a maximum coding unit (LCU) according to a quadtree binary tree ternary tree (QT / BT / TT) structure. For example, a coding unit may be segmented into a plurality of coding units of a deeper depth based on a quadtree structure, a binary tree structure, and / or a ternary tree structure. For the segmentation of the coding unit, the quadtree structure may be applied first, and the binary tree structure and / or the ternary tree structure may be applied later. The encoding process according to the present disclosure may be performed based on the final coding unit that is no longer segmented. The maximum coding unit may be used as the final coding unit, and the coding unit of a deeper depth obtained by segmenting the maximum coding unit may also be used as the final coding unit. Here, the encoding process may include the prediction, transformation, and reconstruction processes described later. As another example, the processing unit of the encoding process may be a prediction unit (PU) or a transformation unit (TU). The prediction unit and the transform unit may be divided or partitioned from the final coding unit. The prediction unit may be a sample prediction unit, and the transform unit may be a unit for deriving a transform coefficient and / or a unit for deriving a residual signal from the transform coefficient.

[0075] The prediction unit (inter prediction unit 180 or intra prediction unit 185) may perform prediction on the block to be processed (current block) and generate a prediction block including prediction samples of the current block. The prediction unit may determine whether to apply intra prediction or inter prediction based on the current block or CU. The prediction unit may generate various information related to the prediction of the current block and send the generated information to the entropy encoder 190. The information about the prediction may be encoded in the entropy encoder 190 and output in the form of a bitstream.

[0076] The intra prediction unit 185 can predict the current block by referring to the samples in the current picture. Depending on the intra prediction mode and / or the intra prediction technology, the reference samples can be located in the neighborhood of the current block or can be placed separately. The intra prediction mode may include multiple non-directional modes and multiple directional modes. The non-directional mode may include, for example, a DC mode and a plane mode. Depending on the level of detail of the prediction direction, the directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes. However, this is only an example, and more or fewer directional prediction modes may be used according to the setting. The intra prediction unit 185 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0077] The inter prediction unit 180 may derive a prediction block of the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. In this case, in order to reduce the amount of motion information sent in the inter prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring blocks may include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. 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 referred to as a collocated reference block, a collocated CU (colCU), etc. The reference picture including the temporal neighboring block may be referred to as a collocated picture (colPic). For example, the inter prediction unit 180 may configure a motion information candidate list based on the neighboring blocks and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter prediction may be performed based on various prediction modes. For example, in the case of skip mode and merge mode, the inter prediction unit 180 may use the motion information of the neighboring block as the motion information of the current block. In the case of skip mode, unlike the merge mode, a residual signal may not be sent. In the case of motion vector prediction (MVP) mode, the motion vector of the neighboring block may be used as a motion vector predictor, and the motion vector of the current block may be signaled by encoding the motion vector difference and an indicator of the motion vector predictor. The motion vector difference may mean the difference between the motion vector of the current block and the motion vector predictor.

[0078] The prediction unit may generate a prediction signal based on various prediction methods and prediction techniques described below. For example, the prediction unit may apply not only intra prediction or inter prediction, but also both intra prediction and inter prediction at the same time to predict the current block. The prediction method of applying both intra prediction and inter prediction to predict the current block may be referred to as combined inter and intra prediction (CIIP). In addition, the prediction unit may perform intra block copying (IBC) to predict the current block. Intra block copying may be used for content image / video encoding of games, etc., such as screen content coding (SCC). IBC is a method of predicting the current picture using a previously reconstructed reference block in the current picture at a position separated by a predetermined distance from the current block. When IBC is applied, the position of the reference block in the current picture may be encoded as a vector (block vector) corresponding to a predetermined distance. IBC basically performs prediction in the current picture, but may be performed similarly to inter prediction because the reference block is derived within the current picture. That is, IBC may use at least one of the inter prediction techniques described in the present disclosure.

[0079] The prediction signal generated by the prediction unit can be used to generate a reconstruction signal or to generate a residual signal. The subtractor 115 can generate a residual signal (residual block or residual sample array) by subtracting the prediction signal (prediction block or prediction sample array) output from the prediction unit from the input image signal (original block or original sample array). The generated residual signal can be sent to the transformer 120.

[0080] The transformer 120 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a karhunen-loève transform (KLT), a graph-based transform (GBT), or a conditional nonlinear transform (CNT). Here, GBT refers to a transform obtained from a graph when relationship information between pixels is represented by a graph. CNT refers to a transform obtained based on a prediction signal generated using all previously reconstructed pixels. In addition, the transform process may be applied to square pixel blocks of the same size or may be applied to blocks of variable size rather than square.

[0081] The quantizer 130 may quantize the transform coefficients and send them to the entropy encoder 190. The entropy encoder 190 may encode the quantized signal (information about the quantized transform coefficients) and output a bitstream. The information about the quantized transform coefficients may be referred to as residual information. The quantizer 130 may rearrange the quantized transform coefficients of the block type into a one-dimensional vector form based on the coefficient scanning order, and generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form.

[0082] The entropy encoder 190 may perform various encoding methods, such as, for example, exponential Golomb, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), etc. The entropy encoder 190 may encode information required for video / image reconstruction other than quantized transform coefficients together or separately (e.g., values ​​of syntax elements, etc.). The encoded information (e.g., encoded video / image information) may be transmitted or stored in units of a network abstraction layer (NAL) in the form of a bitstream. The video / image information may also include information about various parameter sets, such as an adaptive parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may also include general constraint information. The signaled information, transmitted information, and / or syntax elements described in the present disclosure may be encoded and included in a bitstream through the above-described encoding process.

[0083] The bitstream may be transmitted through a network or may be stored in a digital storage medium. The network may include a broadcast network and / or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitter (not shown) that transmits a signal output from the entropy encoder 190 and / or a storage unit (not shown) that stores the signal may be included as an internal / external element of the image encoding device 100. Alternatively, a transmitter may be provided as a component of the entropy encoder 190.

[0084] The quantized transform coefficients output from the quantizer 130 may be used to generate a residual signal. For example, the residual signal (residual block or residual sample) may be reconstructed by applying dequantization and inverse transformation to the quantized transform coefficients through the dequantizer 140 and the inverse transformer 150.

[0085] The adder 155 adds the reconstructed residual signal to the prediction signal output from the inter-frame prediction unit 180 or the intra-frame prediction unit 185 to generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array). If the block to be processed has no residual, such as the case where the skip mode is applied, the prediction block can be used as a reconstructed block. The adder 155 can be called a reconstructor or a reconstructed block generator. The generated reconstructed signal can be used for intra-frame prediction of the next block to be processed in the current picture, and can be used for inter-frame prediction of the next picture by filtering as described below.

[0086] Furthermore, during picture coding and / or reconstruction, luminance mapping and chrominance scaling (LMCS) may be applied.

[0087] The filter 160 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 160 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 170, specifically, in the DPB of the memory 170. Various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filtering, bilateral filtering, etc. The filter 160 can generate various information related to filtering and send the generated information to the entropy encoder 190, as described later in the description of each filtering method. The information related to filtering can be encoded by the entropy encoder 190 and output in the form of a bit stream.

[0088] The modified reconstructed picture transmitted to the memory 170 may be used as a reference picture in the inter prediction unit 180. When inter prediction is applied by the image encoding device 100, prediction mismatch between the image encoding device 100 and an image decoding apparatus may be avoided and encoding efficiency may be improved.

[0089] The DPB of the memory 170 may store the modified reconstructed picture for use as a reference picture in the inter-frame prediction unit 180. The memory 170 may store the motion information of the block for deriving (or encoding) the motion information in the current picture and / or the motion information of the reconstructed block in the picture. The stored motion information may be sent to the inter-frame prediction unit 180 and used as the motion information of the spatial neighboring block or the motion information of the temporal neighboring block. The memory 170 may store the reconstructed samples of the reconstructed blocks in the current picture and may transmit the reconstructed samples to the intra-frame prediction unit 185.

[0090] Overview of Image Decoding Equipment

[0091] Figure 3 is a view schematically showing an image decoding device to which an embodiment of the present disclosure is applicable.

[0092] like Figure 3 As shown, the image decoding device 200 may include an entropy decoder 210, a dequantizer 220, an inverse transformer 230, an adder 235, a filter 240, a memory 250, an inter-frame prediction unit 260, and an intra-frame prediction unit 265. The inter-frame prediction unit 260 and the intra-frame prediction unit 265 may be collectively referred to as a "prediction unit". The dequantizer 220 and the inverse transformer 230 may be included in a residual processor.

[0093] According to an embodiment, all or at least some of the multiple components configuring the image decoding apparatus 200 may be configured by hardware components (eg, a decoder or a processor). In addition, the memory 170 may include a decoded picture buffer (DPB) or may be configured by a digital storage medium.

[0094] The image decoding apparatus 200 having received a bit stream including video / image information may perform the same operation as that performed by Figure 2 The image is reconstructed by processing corresponding to the processing performed by the image encoding device 100. For example, the image decoding device 200 can perform decoding using a processing unit applied in the image encoding device. Therefore, the processing unit of decoding can be, for example, a coding unit. The coding unit can be obtained by splitting the coding tree unit or the maximum coding unit. The reconstructed image signal decoded and output by the image decoding device 200 can be reproduced by a reproduction device (not shown).

[0095] The image decoding apparatus 200 may receive the image in the form of a bit stream from Figure 2The received signal may be decoded by the entropy decoder 210. For example, the entropy decoder 210 may parse the bitstream to derive information (e.g., video / image information) required for image reconstruction (or picture reconstruction). The video / image information may also include information about various parameter sets, such as an adaptive parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may also include general constraint information. The image decoding device may also decode the picture based on the information about the parameter set and / or the general constraint information. The signaled / received information and / or syntax elements described in the present disclosure may be decoded and obtained from the bitstream through a decoding process. For example, the entropy decoder 210 may decode the information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and output the values ​​of the syntax elements required for image reconstruction and the quantized values ​​of the transform coefficients of the residual. More specifically, the CABAC entropy decoding method can receive a bin corresponding to each syntax element in the bitstream, use the decoding target syntax element information, the decoding information of the neighboring block and the decoding target block, or the information of the symbol / bin decoded in the previous stage to determine the context model, perform arithmetic decoding on the bin by predicting the probability of occurrence of the bin according to the determined context model, and generate a symbol corresponding to the value of each syntax element. In this case, the CABAC entropy decoding method can update the context model by using the information of the decoded symbol / bin for the context model of the next symbol / bin after determining the context model. The information related to prediction among the information decoded by the entropy decoder 210 can be provided to the prediction unit (inter-frame prediction unit 260 and intra-frame prediction unit 265), and the residual value (ie, quantized transform coefficient and related parameter information) for which entropy decoding is performed in the entropy decoder 210 can be input to the dequantizer 220. In addition, the information about filtering among the information decoded by the entropy decoder 210 can be provided to the filter 240. In addition, a receiver (not shown) for receiving a signal output from the image encoding apparatus may be further configured as an internal / external element of the image decoding device 200 , or the receiver may be a component of the entropy decoder 210 .

[0096] In addition, the image decoding device according to the present disclosure may be referred to as a video / image / picture decoding device. The image 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 an entropy decoder 210. The sample decoder may include a dequantizer 220, an inverse transformer 230, an adder 235, a filter 240, a memory 250, an inter-frame prediction unit 260, or at least one of an intra-frame prediction unit 265.

[0097] The dequantizer 220 may dequantize the quantized transform coefficients and output the transform coefficients. The dequantizer 220 may rearrange the quantized transform coefficients in the form of two-dimensional blocks. In this case, the rearrangement may be performed based on the coefficient scanning order performed in the image encoding device. The dequantizer 220 may dequantize the quantized transform coefficients by using a quantization parameter (e.g., quantization step size information) and obtain the transform coefficients.

[0098] The inverse transformer 230 may perform an inverse transformation on the transformation coefficients to obtain a residual signal (residual block, residual sample array).

[0099] The prediction unit may perform prediction on the current block and generate a prediction block including prediction samples of the current block. The prediction unit may determine whether to apply intra prediction or inter prediction to the current block based on the information about prediction output from the entropy decoder 210, and may determine a specific intra / inter prediction mode (prediction technique).

[0100] The same as described in the prediction unit of the image encoding device 100 , the prediction unit can generate a prediction signal based on various prediction methods (techniques) to be described later.

[0101] The intra prediction unit 265 may predict the current block by referring to samples in the current picture. The description of the intra prediction unit 185 is also applicable to the intra prediction unit 265.

[0102] The inter-frame prediction unit 260 can derive the prediction block of the current block based on the reference block (reference sample array) specified by the motion vector on the reference picture. In this case, in order to reduce the amount of motion information sent in the inter-frame prediction mode, the motion information can be predicted in units of blocks, sub-blocks or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter-frame prediction, the neighboring blocks may include spatial neighboring blocks existing in the current picture and temporal neighboring blocks existing in the reference picture. For example, the inter-frame prediction unit 260 may configure a motion information candidate list based on the neighboring blocks, and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter-frame prediction may be performed based on various prediction modes, and information about the prediction may include information indicating the inter-frame prediction mode of the current block.

[0103] The adder 235 can generate a reconstruction signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the obtained residual signal to the prediction signal (prediction block, prediction sample array) output from the prediction unit (including the inter-frame prediction unit 260 and / or the intra-frame prediction unit 265). If the block to be processed has no residual, such as when the skip mode is applied, the prediction block can be used as the reconstructed block. The description of the adder 155 also applies to the adder 235. The adder 235 can be called a reconstructor or a reconstructed block generator. The generated reconstruction signal can be used for intra-frame prediction of the next block to be processed in the current picture, and can be used for inter-frame prediction of the next picture by filtering as described below.

[0104] The filter 240 can improve the subjective / objective image quality by applying filtering to the reconstructed signal. For example, the filter 240 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 250, specifically, in the DPB of the memory 250. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filtering, bilateral filtering, etc.

[0105] The (modified) reconstructed picture stored in the DPB of the memory 250 can be used as a reference picture in the inter-frame prediction unit 260. The memory 250 can store the motion information of the block for deriving (or decoding) the motion information in the current picture and / or the motion information of the reconstructed block in the picture. The stored motion information can be sent to the inter-frame prediction unit 260 to be used as the motion information of the spatial neighboring block or the motion information of the temporal neighboring block. The memory 250 can store the reconstructed samples of the reconstructed block in the current picture and transmit the reconstructed samples to the intra-frame prediction unit 265.

[0106] In the present disclosure, the embodiments described in the filter 160 , the inter-frame prediction unit 180 , and the intra-frame prediction unit 185 of the image encoding device 100 may be equally or correspondingly applied to the filter 240 , the inter-frame prediction unit 260 , and the intra-frame prediction unit 265 of the image decoding device 200 .

[0107] Overview of Image Segmentation

[0108] The video / image encoding / decoding method according to the present disclosure may be performed based on the following image segmentation structure. Specifically, processes such as prediction, residual processing ((inverse) transform, (de)quantization, etc.), syntax element encoding and filtering may be performed based on CTU, CU (and / or TU, PU) derived based on the image segmentation structure. The block segmentation process may be performed in the image segmentor 110 of the encoding device. The segmentation related information may be encoded by the entropy encoder 190 and transmitted to the decoding device 200 in the form of a bitstream. The entropy decoder 210 of the decoding device may derive the block segmentation structure of the current picture based on the segmentation related information obtained from the bitstream, and based on this, a series of processes (e.g., prediction, residual processing, block / picture reconstruction, in-loop filtering, etc.) may be performed for image decoding. The CU size may be equal to the TU size, or there may be multiple TUs in the CU region. In addition, the CU size may generally indicate the luminance component (sample) CB size. The TU size may generally indicate the luminance component (sample) TB size. The chroma component (sample) CB or TB size can be derived based on the luminance component (sample) CB or TB size according to the component ratio according to the color format (chroma format, for example, 4:4:4, 4:2:2, 4:2:0, etc.) of the picture / image. The TU size can be derived based on maxTbSize. For example, when the CU size is larger than maxTbSize, multiple TUs (TBs) with maxTbSize can be derived from the CU, and transform / inverse transform can be performed in units of TU (TB). In addition, for example, when intra prediction is applied, the intra prediction mode / type can be derived in units of CU (or CB), and the neighboring reference sample derivation and prediction sample generation process can be performed in units of TU (or TB). In this case, one or more TUs (or TBs) may exist in the CU (or CB) area. In this case, multiple TUs (or TBs) can share the same intra prediction mode / type.

[0109] In addition, in the image encoding / decoding according to the present disclosure, the image processing unit may have a hierarchical structure. For example, a picture may be divided into one or more tiles, tiles, slices, or tile groups. A slice may include one or more tiles. A tile may include one or more CTU rows in a tile. A slice may include an integer number of tiles of a picture. A tile group may include one or more tiles. A tile may include one or more CTUs. A CTU may be divided into one or more CUs as described above. A tile may be composed of a rectangular area of ​​a CTU within a specific row and a specific column in a picture. A tile group may include an integer number of tiles within a picture according to a tile-raster scan. A slice header may signal information / parameters applicable to a slice (a block within a slice). When the encoding / decoding device has a multi-core processor, the encoding / decoding process of a tile, slice, tile, or tile group may be performed in parallel. In the present disclosure, slices or tile groups may be used interchangeably. That is, a tile group header may be referred to as a slice header. Here, the slice may have one of the slice types including intra (I) slice, prediction (P) slice, and bidirectional prediction (B) slice. For blocks in the I slice, inter prediction may not be used, and only intra prediction may be used for prediction. Of course, even in this case, the original sample values ​​may be encoded and signaled without prediction. For blocks in the P slice, intra prediction or inter prediction may be used, and when inter prediction is used, only unidirectional prediction may be used. In addition, for blocks in the B slice, intra prediction or inter prediction may be used, and when inter prediction is used, up to bidirectional prediction may be used.

[0110] In the encoding device, the patch / patchwork group, tile, slice, maximum and minimum coding unit sizes can be determined based on the characteristics of the image (e.g., resolution) or considering coding efficiency or parallel processing, and information thereon or information that can derive the information can be included in the bitstream.

[0111] In a decoding device, information indicating whether a tile / tile group, a tile, or a CTU in a slice of a current picture is partitioned into a plurality of coding units may be obtained. When such information is obtained (sent) only under certain conditions, efficiency is improved.

[0112] The slice header (slice header syntax) may include information / parameters that are generally applicable to slices. APS (APS syntax) or PPS (PPS syntax) may include information / parameters that are generally applicable to one or more pictures. SPS (SPS syntax) may include information / parameters that are generally applicable to one or more sequences. VPS (VPS syntax) may include information / parameters that are generally applicable to multiple layers. DPS (DPS syntax) may include information / parameters that are generally applicable to the entire video. DPS may include information / parameters related to the concatenation of a coded video sequence (CVS). In the present disclosure, the high-level syntax may include at least one of APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, or slice header syntax.

[0113] Furthermore, for example, information on the partitioning and configuration of tiles / tile groups / tiles / slices may be constructed by a high-level syntax in an encoding device and transmitted to a decoding device in the form of a bitstream.

[0114] Split structure

[0115] A picture may be partitioned into a sequence of coding tree units (CTUs). A CTU may correspond to a coding tree block (CTB). Alternatively, a CTU may include a coding tree block of luma samples and two coding tree blocks of chroma samples corresponding thereto. For example, for a picture containing three sample arrays, a CTU may include an N×N block of luma samples and two corresponding blocks of chroma samples. Figure 4 An example is shown in which one picture is divided into a plurality of CTUs.

[0116] The maximum allowed size of a CTU for coding and prediction may be different from the maximum allowed size of a CTU for transform. For example, even if the maximum allowed size of a CTU for transform is 64×64, the maximum allowed size of a luma block in a CTU for coding and prediction may be 128×128.

[0117] In addition, the picture may be partitioned into one or more tile rows and one or more tile columns. A tile may be a sequence of CTUs covering a rectangular area of ​​the picture. The CTUs of a tile may be scanned in a raster scan order within the tile.

[0118] A slice may consist of an integer number of complete tiles or an integer number of consecutive complete CTU rows of a picture within a tile. Two slicing modes may be supported: one is a raster scan slicing mode and the other is a rectangular slicing mode.

[0119] In the raster scan slice mode, a slice may include a complete sequence of tiles of a picture along a tile raster scan. In the present disclosure, a slice according to the raster scan slice mode may be referred to as a raster scan slice.

[0120] In the rectangular slice mode, a slice may include a plurality of complete tiles that together form a rectangular area of ​​a picture or a plurality of continuous complete CTU rows that together form a tile of a rectangular area of ​​a picture. In the present disclosure, a slice according to the rectangular slice mode may be referred to as a rectangular slice. The tiles included in the rectangular slice may be scanned in a tile raster scan order within the rectangular area corresponding to the slice.

[0121] Furthermore, one or more slices may constitute a sub-picture. That is, a sub-picture may include one or more slices that together cover a rectangular area of ​​the picture.

[0122] Figure 5a to Figure 5c is a diagram illustrating an example of splitting the screen.

[0123] First refer to Figure 5a In raster scan slice mode, the picture can be divided into 12 tiles and 3 raster scan slices.

[0124] Reference Figure 5b In the rectangular slice mode, the picture can be divided into 24 tiles (ie, 6 tile rows and 4 tile columns) and 9 rectangular slices.

[0125] Reference Figure 5c , the picture can be divided into 4 tiles (ie, 2 tile rows and 2 tile columns) and 4 rectangular slices.

[0126] Figure 6 is a diagram showing an example of dividing a screen into sub-screens.

[0127] Reference Figure 6 , the picture can be divided into 28 sub-pictures with varying sizes.

[0128] When a picture is coded using three separate color planes (i.e., separate_colour_plane_flag=1), a slice may contain only CTUs of one color component identified by the corresponding value of color_plane_id, and each color component array of the picture may consist of slices with the same colour_plane_id value. Coded slices with different colour_plane_id values ​​within a picture may be interleaved with each other under the following constraint: For each colour_plane_id value, the coded slice NAL units with the corresponding colour_plane_id value must be present in increasing order of CTU addresses in tile scan order for the first CTU of each coded slice NAL unit.

[0129] When separate_colour_plane_flag is 0, each CTU of the picture may be included in exactly one slice. In contrast, when separate_colour_plane_flag is 1, each CTU of a color component may be included in exactly one slice (ie, information about each CTU of the picture exists in exactly three slices, and the three slices have different colour_plane_id values).

[0130] Tiling can change the order of CTUs within a picture. For example, if a picture is divided into two or more tiles, the order of CTUs within each tile can follow the raster scan order, such as Figure 7 In the example of , the picture is partitioned into two tiles and each tile contains eight CTUs.

[0131] Overview of the Image Decoding / Decoding Process

[0132] In image / video coding, the pictures constituting the image / video can be encoded / decoded according to the decoding order. The picture order corresponding to the output order of the decoded pictures can be set differently from the decoding order, and based on this, not only forward prediction but also backward prediction can be performed during inter-frame prediction.

[0133] Figure 8 is a schematic flowchart of an image decoding process applicable according to an embodiment of the present disclosure.

[0134] Figure 8 Each process shown can be represented by Figure 3 For example, step S810 may be performed by the entropy decoder 210 of the image decoding device, step S820 may be performed by the prediction units 265 and 260, step S830 may be performed by the residual processors 220 and 230, step S840 may be performed by the adder 235, and step S850 may be performed by the filter 240. Step S810 may include the information decoding (parsing) process described in the present disclosure, step S820 may include the inter / intra prediction process described in the present disclosure, step S830 may include the residual processing process described in the present disclosure, step S840 may include the block / picture reconstruction process described in the present disclosure, and step S850 may include the in-loop filtering process described in the present disclosure.

[0135] Reference Figure 8, the image decoding process may schematically include a process (S810) for obtaining image / video information from a bit stream (by decoding), an image (picture) reconstruction process (S820 to S840), and an in-loop filtering process (S850) for the reconstructed picture. The picture reconstruction process may be performed based on the prediction samples obtained by inter / intra prediction (S820) and the residual samples (dequantization and inverse transformation of quantized transform coefficients) obtained by residual processing (S830). For the reconstructed picture generated by the picture reconstruction process, a modified reconstructed picture may be generated by an in-loop filtering process, and the modified reconstructed picture may be output as a decoded picture, which is stored in a decoded picture buffer (DPB) or a memory 250 of an image decoding device, and is used as a reference picture in an inter prediction process when the picture is decoded later. The in-loop filtering process (S850) may be omitted. In this case, the reconstructed picture can be output as a decoded picture, which is stored in the DPB or memory 250 of the image decoding device and used as a reference picture in the inter-frame prediction process when the picture is decoded later. The in-loop filtering process (S850) may include a deblocking filtering process, a sample adaptive offset (SAO) process, an adaptive loop filtering (ALF) process, and / or a bilateral filtering process, etc. as described above, and some or all of them may be omitted. In addition, one or some of the deblocking filtering process, the sample adaptive offset (SAO) process, the adaptive loop filtering (ALF) process, and / or the bilateral filtering process may be applied sequentially or all of them may be applied sequentially. For example, after applying the deblocking filtering process to the reconstructed picture, the SAO process may be performed. Alternatively, after applying the deblocking filtering process to the reconstructed picture, the ALF process may be performed. Even in an image encoding device, this may be performed similarly.

[0136] Fig. 9 is a schematic flowchart of an image encoding process applicable according to an embodiment of the present disclosure.

[0137] Fig. 9 Each process shown can be represented by Figure 2 For example, step S910 may be performed by the prediction units 180 and 185 of the image decoding device, step S920 may be performed by the residual processors 115, 120 and 130, and step S930 may be performed in the entropy encoder 190. Step S910 may include the inter-frame prediction / intra-frame prediction process described in the present disclosure, step S920 may include the residual processing process described in the present disclosure, and step S930 may include the information encoding process described in the present disclosure.

[0138] Reference Fig. 9, schematically, the image encoding process may include not only a process for encoding and outputting information for picture reconstruction (e.g., prediction information, residual information, segmentation information, etc.) in the form of a bitstream, but also a process for generating a reconstructed picture for the current picture and a process for applying in-loop filtering to the reconstructed picture (optional). The image encoding device may derive (modify) residual samples from the quantized transform coefficients through the dequantizer 140 and the inverse transformer 150, and generate a reconstructed picture based on the prediction samples and (modified) residual samples as the output of step S910. The reconstructed picture generated in this way may be equal to the reconstructed picture generated in the image decoding device. The modified reconstructed picture may be generated by an in-loop filtering process for the reconstructed picture, and the modified reconstructed picture may be stored in a decoded picture buffer or memory 170, and similar to the decoding device, may be used as a reference picture in an inter-frame prediction process when the picture is encoded later. As described above, in some cases, some or all of the in-loop filtering process may be omitted. When an in-loop filtering process is performed, (in-loop) filtering-related information (parameters) can be encoded in the entropy encoder 190 and output in the form of a bit stream, and the image decoding device can perform the in-loop filtering process based on the filtering-related information using the same method as the image encoding device.

[0139] By such an in-loop filtering process, noise (e.g., block artifacts and ringing artifacts) occurring during image / video encoding can be reduced, and subjective / objective visual quality can be improved. In addition, by performing the in-loop filtering process in both the image encoding device and the image decoding device, the image encoding device and the image decoding device can derive the same prediction result, the picture encoding reliability can be increased, and the amount of data to be transmitted for picture encoding can be reduced.

[0140] As described above, the image (picture) reconstruction process can be performed not only in an image decoding device, but also in an image encoding device. A reconstructed block can be generated based on intra-frame prediction / inter-frame prediction in block units, and a reconstructed picture including the reconstructed block can be generated. When the current picture / slice / tile group is an I picture / slice / tile group, the blocks included in the current picture / slice / tile group can be reconstructed based only on intra-frame prediction. On the other hand, when the current picture / slice / tile group is a P or B picture slice / tile group, the blocks included in the current picture / slice / tile group can be reconstructed based on intra-frame prediction or inter-frame prediction. In this case, inter-frame prediction can be applied to some blocks in the current picture / slice / tile group, and intra-frame prediction can be applied to the remaining blocks. The color components of the picture may include luminance components and chrominance components, and unless explicitly defined in the present disclosure, the methods and embodiments of the present disclosure are applicable to both luminance components and chrominance components.

[0141] Example of coding layer structure

[0142] The encoded video / image according to the present disclosure may be processed, for example, according to the encoding layers and structures to be described later.

[0143] Fig.10 is an example of a layer structure for encoding images / videos.

[0144] The coded image / video is classified into a video coding layer (VCL) for image decoding processing and processing itself, a lower system for transmitting and storing coded information, and a network abstraction layer (NAL) existing between the VCL and the lower system and responsible for network adaptation functions.

[0145] In the VCL, VCL data including compressed image data (slice data) can be generated, or a parameter set or a supplemental enhancement information (SEI) message including information such as a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS) which is additionally required for the decoding process of the image can be generated.

[0146] In NAL, header information (NAL unit header) may be added to a raw byte sequence payload (RBSP) generated in a VCL to generate a NAL unit. In this case, the RBSP involves slice data, parameter sets, SEI messages generated in the VCL. The NAL unit header may include NAL unit type information specified according to the RBSP data included in the corresponding NAL unit.

[0147] like Figure 6 As shown, according to the type of RBSP generated in VCL, NAL units can be classified into VCL NAL units and non-VCL NAL units. A VCL NAL unit may refer to a NAL unit including information about an image (slice data), while a non-VCL NAL unit may refer to a NAL unit including information required for decoding an image (parameter set or SEI message).

[0148] The VCL NAL unit and the non-VCL NAL unit may be attached with header information and sent over the network according to the data format of the underlying system. For example, the NAL unit may be modified into data having a predetermined data format (e.g., H.266 / VVC file format, RTP (Real-time Transport Protocol) or TS (Transport Stream)) and sent over various networks.

[0149] As described above, in the NAL unit, the NAL unit type can be specified according to the RBSP data structure included in the corresponding NAL unit, and information about the NAL unit type can be stored in the NAL unit header and signaled. For example, this can be broadly classified into VCL NAL unit types and non-VCL NAL unit types based on whether the NAL unit includes information about the image (slice data). VCL NAL unit types can be classified according to the characteristics and types of the picture, and non-VCL NAL unit types can be classified according to the type of parameter set.

[0150] Listed below are examples of NAL unit types specified according to the type of parameter sets / information included in the non-VCL NAL unit type.

[0151] -APS (Adaptation Parameter Set) NAL unit: the type of NAL unit that includes APS

[0152] -DPS (Decoding Parameter Set) NAL unit: the type of NAL unit that includes the DPS

[0153] -VPS (Video Parameter Set) NAL unit: the type of NAL unit that contains the VPS

[0154] -SPS (Sequence Parameter Set) NAL unit: the type of NAL unit that includes SPS

[0155] -PPS (Picture Parameter Set) NAL unit: the type of NAL unit that includes the PPS

[0156] The above-mentioned NAL unit type may have syntax information about the NAL unit type, and the syntax information may be stored in the NAL unit header and signaled. For example, the syntax information may include nal_unit_type, and the NAL unit type may be specified by the nal_unit_type value.

[0157] In addition, as described above, a picture may include multiple slices, and a slice may include a slice header and slice data. In this case, a picture header may also be added to multiple slices (slice headers and slice data sets) in a picture. The picture header (picture header syntax) may include information / parameters that are generally applicable to the picture. The slice header (slice header syntax) may include information / parameters that are generally applicable to the slice. APS (APS syntax) or PPS (PPS syntax) may include information / parameters that are generally applicable to one or more slices or pictures. SPS (SPS syntax) may include information / parameters that are generally applicable to one or more sequences. VPS (VPS syntax) may include information / parameters that are generally applicable to multiple layers. DPS (DPS syntax) may include information / parameters that are generally applicable to the entire video. DPS may include information / parameters related to the concatenation of CVS (coded video sequence). In the present disclosure, the high-level syntax (HLS) may include at least one of APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, or slice header syntax.

[0158] In the present disclosure, the image / video information encoded by the encoding device and signaled to the decoding device in the form of a bit stream may include not only intra-screen segmentation related information, intra-frame / inter-frame prediction information, residual information, in-loop filtering information, but also information included in the slice header, APS, PPS, SPS and / or VPS.

[0159] Problems with existing technology

[0160] In most existing video codecs, only raster scan order is usually applied to slices within a picture, and arbitrary slice ordering has been proposed in some video codecs. Specific examples of raster scan order and arbitrary slice ordering are as follows: Fig.11 shown.

[0161] Reference Fig.11 , one picture may include three slices (slice #1 to slice #3) having different sizes.

[0162] If the slices within the frame follow the raster scan order ( Fig.11 (a)), the slice NAL units of the picture can be encoded / decoded in the order of the first slice (slice #1), the second slice (slice #2), and the third slice (slice #3).

[0163] In contrast, if the slices within the frame follow an arbitrary slice order ( Fig.11 (b)), the slice NAL units of the picture can be encoded / decoded in any order, such as the second slice (slice #2), the third slice (slice #3), and the first slice (slice #1).

[0164] In the case of following arbitrary slice ordering, since the slices within the picture can be reordered according to specific criteria (e.g., slice importance), it can have advantages in error recovery. However, since the existing method does not take into account the in-loop filtering process, several problems may arise for the implementation of the in-loop filter. For example, according to the existing method, since the order of slices received by the image decoding device may be in an arbitrary order, it is difficult to implement a block-based in-loop filter. In other words, as long as the image decoding device decodes / reconstructs each coding block, it cannot perform in-loop filtering on the corresponding coding block, and has the constraint that the reconstruction of all slices within the corresponding picture for in-loop filtering must be completed. In addition, the above constraints cause delays in encoding / decoding.

[0165] In order to solve this problem, the present disclosure proposes a more efficient slice scanning solution.The embodiments of the present disclosure described below are intended to explain representative aspects of the present disclosure and may be applied independently or in combination of two or more.

[0166] Implementation Method 1

[0167] According to embodiment 1 of the present disclosure, an adaptive (or flexible) slice scanning scheme based on the position and shape of the slice within the picture can be provided. Specifically, a raster scanning scheme or an arbitrary slice scanning scheme can be selectively applied to the slice within the picture. When the arbitrary slice scanning scheme is applied to the slice within the picture, the left adjacent slice and the upper adjacent slice can be restricted to precede the current slice in the decoding order. In addition, when the slice within the picture is not a rectangular slice, the raster scanning scheme should be applied to the slice.

[0168] Embodiment 1 of the present disclosure may be implemented based on at least one of the following aspects: The following aspects may be applied alone or in combination of two or more.

[0169] - (Aspect 1): The order of slices of a picture may not be the raster scan order.

[0170] - (Aspect 2): If the order of the slices of a picture does not follow the raster scan order, the following constraints may apply.

[0171] a) If a particular slice A has a left neighboring slice B within the same picture, then slice B should precede slice A in decoding order. Here, slice B does not need to immediately precede slice A in decoding order, since there may be one or more (left neighboring) slices between slice B and slice A.

[0172] b) If a particular slice A has an upper neighboring slice B within the same picture, then slice B should precede slice A in decoding order. Here, since there may be one or more (upper neighboring) slices between slice B and slice A, slice B does not need to immediately precede slice A in decoding order.

[0173] - (Aspect 3): If the coded slices are not rectangular slices, the order of the slices shall follow the raster scan order. In contrast, if the coded slices are rectangular slices, the order of the slices may be the raster scan order, or may be any order other than the raster scan order, for example, any slice scan order according to Aspect 2 above.

[0174] Figure 12 to Figure 14 is a diagram for explaining an adaptive slice scanning scheme according to an embodiment of the present disclosure. Figure 12 to Figure 14 In the example, it is assumed that a picture includes 16 rectangular slices.

[0175] First, refer to Fig.12 Since the slices in the picture are rectangular slices, the raster scanning scheme can be applied according to the above aspect 3 for the slices. Therefore, the slices in the bitstream can have a raster scanning order from slice #0 to slice #15, and can be encoded / decoded sequentially according to this order.

[0176] In contrast, when applying an arbitrary slice scanning scheme to slices within a picture, the constraints of aspect 2 above may be applied. Fig.13 , assuming that the current slice is slice #10, slices #8 and #9 as left adjacent slices can be restricted to precede slice #10 in the bitstream. In addition, slices #2 and #6 as upper adjacent slices can be restricted to precede slice #10 in the bitstream. It goes without saying that the application result of the above constraints can change according to the position of the current slice. For example, assuming that the current slice is slice #0, because there is no left adjacent slice and upper adjacent slice, therefore, slice #0 can precede all other slices (i.e., slices #1 to #15) in the bitstream. In addition, assuming that the current slice is slice #3, because there is only a left adjacent slice and there is no upper adjacent slice, therefore, slice #3 can precede all other slices (i.e., slices #7, #11 and #15) of the corresponding slice column in the bitstream. In addition, assuming that the current slice is slice #12, because there is only an upper adjacent slice and there is no left adjacent slice, therefore, slice #12 can precede all other slices (i.e., slices #13 to #15) of the corresponding slice row in the bitstream.

[0177] A specific example of the above arbitrary slice scan order is as follows Fig.14 See Fig.14, any slice scanning scheme according to aspect 2 above can be applied to slices within a picture. Therefore, the slices within the bitstream can have any order of slices #0, #4, #1, #8, #5, #2, #3, #12, #6, #9, #10, #7, #13, #11, #14 and #15, and can be encoded / decoded in sequence according to the order. In the above example, since the left adjacent slice (i.e., slice #4) and the upper adjacent slice (i.e., slice #1) can be used to decode / reconstruct slice #5, for example, slice #5 can precede slice #3 in the decoding order, which satisfies the constraint of aspect 2 above.

[0178] As described above, according to Embodiment 1 of the present disclosure, a raster scanning scheme or an arbitrary slice scanning scheme can be selectively applied to slices within a picture. When the arbitrary slice scanning scheme is applied to slices within a picture, the left adjacent slice and the upper adjacent slice can be limited to precede the current slice in the decoding order. Therefore, in-loop filtering for the current slice can be performed without reconstructing all slices within the picture, thereby preventing encoding / decoding delays and further improving efficiency.

[0179] Implementation Method 2

[0180] When a picture is divided into multiple sub-pictures, in-loop filtering can be performed across sub-picture boundaries, or can be performed only within each sub-picture without crossing sub-picture boundaries. Hereinafter, in-loop filtering performed across sub-picture boundaries will be referred to as "sub-picture cross filtering".

[0181] When sub-picture cross filtering is performed, in-loop filtering may be performed on the current slice with reference to a slice included in another sub-picture, and thus, the constraint of aspect 2 described above in embodiment 1 may be applicable to all slices within the picture. However, when sub-picture cross filtering is not performed, in-loop filtering is performed on the current slice without reference to a neighboring slice included in another sub-picture, and thus, the constraint of aspect 2 described above in embodiment 1 may be applicable only to slices included in the same sub-picture. Thus, if sub-picture cross filtering is not performed, there is no dependency related to the in-loop filter between slices belonging to different sub-pictures, and thus, it is necessary to limit the constraint of the aspect described above in embodiment 1 to slices included in the same sub-picture.

[0182] Therefore, according to Embodiment 2 of the present disclosure, an adaptive (or flexible) slice scanning scheme based on whether sub-picture cross filtering is allowed can be provided. Specifically, a raster scanning scheme or an arbitrary slice scanning scheme can be selectively applied to slices within a picture. When an arbitrary slice scanning scheme is applied to slices within a picture, the range of the left adjacent slice and the upper adjacent slice that are restricted to precede the current slice in the decoding order can be determined as the same picture range or the same sub-picture range, depending on whether sub-picture cross filtering is allowed.

[0183] Embodiment 2 of the present disclosure may be implemented based on at least one of the following aspects: The following aspects may be applied alone or in combination of two or more.

[0184] - (Aspect 4): The order of slices of a picture and / or sub-picture may not be in raster scan order. This may mean that when a picture is partitioned into multiple sub-pictures, the encoding / decoding order of slices within the picture may be determined separately for each sub-picture.

[0185] - (Aspect 5): When there are two or more sub-pictures within a picture, sub-picture cross filtering is allowed, and the order of slices within the picture does not follow the raster scan order, the following constraints may apply.

[0186] a) If a particular slice A has a left neighboring slice B within the "same picture", then slice B should precede slice A in decoding order. Here, since there may be one or more (left neighboring) slices between slice B and slice A, slice B does not need to immediately precede slice A in decoding order.

[0187] b) If a particular slice A has an upper neighboring slice B within the "same picture", then slice B should precede slice A in decoding order. Here, since there may be one or more (upper neighboring) slices between slice B and slice A, slice B does not need to immediately precede slice A in decoding order.

[0188] - (Aspect 6): If there are two or more sub-pictures within a picture, sub-picture cross filtering is not allowed, and the order of slices in the picture does not follow the raster scan order, the following constraints may apply:

[0189] a) If a particular slice A has a left neighboring slice B within the "same sub-picture", then slice B should precede slice A in decoding order. Here, slice B does not need to immediately precede slice A in decoding order, since there may be one or more (left neighboring) slices between slice B and slice A.

[0190] b) If a particular slice A has an upper neighboring slice B within the "same sub-picture", then slice B must precede slice A in decoding order. Here, since there may be one or more (upper neighboring) slices between slice B and slice A, slice B does not need to immediately precede slice A in decoding order.

[0191] - (Aspect 7): If two slices (e.g., slice A and slice B) within the same picture belong to different sub-pictures and sub-picture cross filtering is not allowed, slice A may precede slice B in the decoding order, or may follow slice B. In other words, the decoding order of slice A and slice B may be determined regardless of the sub-picture to which each slice belongs.

[0192] Figures 15 to 19 is a diagram for explaining an adaptive slice scanning scheme according to an embodiment of the present disclosure. Figures 15 to 19 In the embodiment, it is assumed that a picture includes 16 rectangular slices, and the picture is vertically divided into two sub-pictures (Subpic0 and Subpic1).

[0193] First, refer to Fig.15 , a raster scan scheme may be applied to the slices of each sub-picture according to the above aspect 4. Therefore, the slices may have a raster scan order from slice #0 to slice #7 of the first sub-picture (SubPic0) and then from slice #8 to slice #15 of the second sub-picture (SubPic1) within the bitstream, and may be encoded / decoded sequentially according to the order.

[0194] In contrast, when an arbitrary slice scanning scheme is applied to slices within a picture, the constraints of aspect 5 or 6 described above may be applied based on whether sub-picture cross filtering is allowed.

[0195] Specifically, refer to Fig.16 , when sub-picture cross filtering is allowed, the constraints of aspect 5 may be applied. For example, assuming that the current slice is slice #13, the left neighboring slices #4, #5, and #12 within the same picture may be constrained to precede slice #13 within the bitstream. In addition, the top neighboring slices #9 and #11 within the same picture may be constrained to precede slice #13 within the bitstream. As with aspect 2 of embodiment 1, the result of applying aspect 5 may change depending on the position of the current slice within the picture.

[0196] A specific example of any of the above slice sorting is Fig.17 See Fig.17, the arbitrary slice scanning scheme according to aspect 5 can be applied to slices within a picture. Therefore, the slices within the bitstream can have an arbitrary order of slices #0, #1, #8, #2, #9, #3, #4, #10, #5, #11, #6, #12, #7, #13, #14 and #15, and can be encoded / decoded sequentially according to the order.

[0197] Next, refer to Fig.18 , when sub-picture cross filtering is not allowed, the constraints of aspect 6 may be applied. For example, assuming that the current slice is slice #13, only slice #12, which is the left neighboring slice within the same sub-picture, may be constrained to precede slice #13 within the bitstream. In addition, slices #9 and #11, which are the upper neighboring slices within the same sub-picture, may be constrained to precede slice #13 within the bitstream. As with aspect 2 of embodiment 1, the result of applying aspect 6 may change depending on the position of the current slice within the sub-picture.

[0198] A specific example of the above arbitrary slice scan order is as follows Fig.19 See Fig.19 , the arbitrary slice scanning scheme according to aspect 6 can be applied to slices within a picture. Therefore, the slices within the bitstream can have an arbitrary order such as slices #0, #8, #2, #9, #4, #10, #6, #11, #1, #12, #3, #13, #5, #14, #15 and #7, and can be encoded / decoded sequentially according to the order.

[0199] Furthermore, if each slice within a picture carries a NAL unit, the constraints of aspects 5 and 6 above can be described as follows:

[0200] For two coded slice NAL units A and B of a coded picture, assuming that subpicIdxA and subpicIdxB are sub-picture level index values ​​indicating the sub-picture to which each slice belongs, the order of VCL NAL units within the coded picture may be restricted as follows.

[0201] - (Constraint 1): If sub-picture cross filtering is allowed, and coded slice NAL unit A is the left neighbor of coded slice NAL unit B, and subpicIdxA is equal to or different from subpicIdxB, then slice NAL unit A should precede slice NAL unit B in decoding order.

[0202] - (Constraint 2): If sub-picture cross filtering is allowed, and coded slice NAL unit A is an upper neighbor of coded slice NAL unit B, and subpicIdxA is equal to or different from subpicIdxB, then slice NAL unit A should precede slice NAL unit B in decoding order.

[0203] - (Constraint 3): If sub-picture cross filtering is not allowed, and coded slice NAL unit A is the left neighbor of coded slice NAL unit B, and subpicIdxA is equal to subpicIdxB, then slice NAL unit A shall precede slice NAL unit B in decoding order.

[0204] - (Constraint 4): If sub-picture cross filtering is not allowed, and coded slice NAL unit A is an upper neighbor of coded slice NAL unit B, and subpicIdxA is equal to subpicIdxB, then slice NAL unit A shall precede slice NAL unit B in decoding order.

[0205] As described above, according to Embodiment 2 of the present disclosure, a raster scanning scheme or an arbitrary slice scanning scheme can be selectively applied to slices within a picture. When the arbitrary slice scanning scheme is applied to slices within a picture, the range of adjacent slices whose decoding order is restricted can be determined as the same picture range or the same sub-picture range based on whether sub-picture cross filtering is allowed. Therefore, since the slice scanning order can be determined by considering the characteristics of the sub-picture cross filter, encoding / decoding delay can be prevented and efficiency can be further improved.

[0206] In the following, reference will be made to Fig. 20 and Fig.21 An image encoding / decoding method according to an embodiment of the present disclosure is described in detail.

[0207] Fig. 20 is a flowchart illustrating an image encoding method according to an embodiment of the present disclosure. Fig. 20 The image encoding method can be Figure 2 The image encoding device is executed.

[0208] Reference Fig. 20 , the image encoding device may determine the encoding order of multiple slices in the current picture (S2010). The encoding order may be determined by a raster scan order or an arbitrary slice scan order. When determining the encoding order, at least one of aspects 1 to 3 of the above-mentioned embodiment 1 may be applied, or at least one of aspects 4 to 7 of the above-mentioned embodiment 2 may be applied.

[0209] In one embodiment, based on the coding order of the plurality of slices being determined to be an order different from the raster scan order (e.g., an arbitrary slice scan order), a left adjacent slice located to the left of the current slice and an upper adjacent slice located above the current slice within the current picture may be restricted to precede the current slice in the coding order. In this case, the left adjacent slice need not immediately precede the current slice in the coding order. Additionally, the upper adjacent slice need not immediately precede the current slice in the coding order.

[0210] In one embodiment, based on the fact that the slices are not rectangular slices, the encoding order of the plurality of slices may be restricted to a raster scan order.

[0211] In one implementation, based on the current picture including multiple sub-pictures, the coding order of multiple slices may be determined separately for each sub-picture.

[0212] In one embodiment, based on the current picture including multiple sub-pictures, the coding order of multiple slices is determined based on whether in-loop filtering across the boundaries of the sub-pictures is allowed. For example, based on the fact that in-loop filtering is allowed for the current picture and the coding order of multiple slices is determined to be an order different from the raster scan order, the above-mentioned coding order restrictions of adjacent slices can be applied to all slices within the current picture. In contrast, based on the fact that in-loop filtering is not allowed for the current picture and the coding order of multiple slices is determined to be an order different from the raster scan order, the above-mentioned coding order restrictions of adjacent slices can be applied to each sub-picture individually. In addition, based on the fact that in-loop filtering is not allowed for the current picture, the coding order of slices belonging to different sub-pictures within the current picture can be determined regardless of the sub-picture to which each slice belongs.

[0213] In addition, the image encoding device can generate a bitstream by encoding multiple slices based on the determined encoding order (S2020). In this case, the encoded data of the multiple slices (eg, slice NAL units) can be sorted in the bitstream according to the determined encoding order.

[0214] Fig.21 is a flowchart illustrating an image decoding method according to an embodiment of the present disclosure. Fig.21 The image decoding method can be Figure 3 The image decoding device is executed.

[0215] Reference Fig.21 , the image decoding device may determine the decoding order of multiple slices in the current picture (S2110). The decoding order may be determined as one of a raster scan order or an arbitrary slice scan order. When determining the decoding order, at least one of aspects 1 to 3 of the above-mentioned embodiment 1 may be applied, or at least one of aspects 4 to 7 of the above-mentioned embodiment 2 may be applied.

[0216] In one embodiment, based on the decoding order of the plurality of slices being determined to be an order different from the raster scan order (e.g., an arbitrary slice scan order), a left adjacent slice located to the left of the current slice and an upper adjacent slice located above the current slice within the current picture may be restricted to precede the current slice in the decoding order. In this case, the left adjacent slice need not immediately precede the current slice in the decoding order. Additionally, the upper adjacent slice need not immediately precede the current slice in the decoding order.

[0217] In one embodiment, based on the fact that the slices are not rectangular slices, the decoding order of the plurality of slices may be restricted to a raster scan order.

[0218] In one implementation, based on the current picture including multiple sub-pictures, the decoding order of multiple slices may be determined separately for each sub-picture.

[0219] In one embodiment, based on the current picture including multiple sub-pictures, the decoding order of multiple slices is determined based on whether in-loop filtering across the boundaries of the sub-pictures is allowed. For example, based on the fact that in-loop filtering is allowed for the current picture and the decoding order of multiple slices is determined to be an order different from the raster scan order, the above-mentioned decoding order restriction of adjacent slices can be applied to all slices within the current picture. In contrast, based on the fact that in-loop filtering is not allowed for the current picture and the decoding order of multiple slices is determined to be an order different from the raster scan order, the above-mentioned decoding order restriction of adjacent slices can be applied to each sub-picture individually. In addition, based on the fact that in-loop filtering is not allowed for the current picture, the decoding order of slices belonging to different sub-pictures within the current picture can be determined regardless of the sub-picture to which each slice belongs.

[0220] In addition, the image decoding device can decode multiple slices based on the determined decoding order (S2020). In this case, when performing in-loop filtering on the decoded current slice, the left adjacent slice and the upper adjacent slice that have been decoded according to the above-mentioned decoding order restriction can be used, thereby preventing encoding / decoding delays and further improving efficiency.

[0221] Although for the sake of clarity of description, the exemplary method of the present disclosure described above is represented as a series of operations, it is not intended to limit the order of executing the steps, and these steps can be performed simultaneously or in different orders when necessary. In order to implement the method according to the present disclosure, the steps described may further include other steps, may include the remaining steps except some steps, or may include other additional steps except some steps.

[0222] In the present disclosure, an image encoding device or an image decoding device that performs a predetermined operation (step) may perform an operation (step) of confirming an execution condition or situation of the corresponding operation (step). For example, if it is described that a predetermined operation is performed when a predetermined condition is met, the image encoding device or the image decoding device may perform the predetermined operation after determining whether the predetermined condition is met.

[0223] The various embodiments of the present disclosure are not a list of all possible combinations and are intended to describe representative aspects of the present disclosure, and matters described in the various embodiments may be applied independently or in combination of two or more.

[0224] Various embodiments of the present disclosure may be implemented in hardware, firmware, software or a combination thereof. In the case of implementing the present disclosure in hardware, the present disclosure may be implemented in an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a general purpose processor, a controller, a microcontroller, a microprocessor, etc.

[0225] In addition, the image decoding device and the image encoding device to which the embodiments of the present disclosure are applied may be included in a multimedia broadcast sending and receiving device, a mobile communication terminal, a home theater video device, a digital theater video device, a surveillance camera, a video chat device, a real-time communication device such as video communication, a mobile streaming device, a storage medium, a camera, a video on demand (VoD) service provider, an OTT video (over the top video) device, an Internet streaming service provider, a three-dimensional (3D) video device, a video phone video device, a medical video device, etc., and may be used to process a video signal or a data signal. For example, an OTT video device may include a game console, a Blu-ray player, an Internet access TV, a home theater system, a smart phone, a tablet PC, a digital video recorder (DVR), etc.

[0226] Fig. 22 is a diagram showing a content streaming system to which an embodiment of the present disclosure is applicable.

[0227] like Fig. 22 As shown, the content streaming system to which the embodiments of the present disclosure are applied may mainly include an encoding server, a streaming server, a network server, a media storage device, a user device, and a multimedia input device.

[0228] The encoding server compresses the content input from the multimedia input device such as a smart phone, a camera, a camcorder, etc. into digital data to generate a bit stream and sends the bit stream to the streaming server. As another example, when the multimedia input device such as a smart phone, a camera, a camcorder, etc. directly generates a bit stream, the encoding server can be omitted.

[0229] A bitstream may be generated by an image encoding method or an image encoding device to which an embodiment of the present disclosure is applied, and a streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

[0230] The streaming server sends multimedia data to the user device based on the user's request through the network server, and the network server is used as a medium to inform the user of the service. When the user requests the required service from the network server, the network server can deliver it to the streaming server, and the streaming server can send the multimedia data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server is used to control the command / response between the devices within the content streaming system.

[0231] The streaming server may receive content from a media storage device and / or an encoding server. For example, when receiving content from an encoding server, the content may be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bitstream within a predetermined time.

[0232] Examples of user devices may include mobile phones, smart phones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smart watches, smart glasses, head-mounted displays), digital televisions, desktop computers, digital signage, etc.

[0233] Each server in the content streaming system may operate as a distributed server, in which case data received from each server may be distributed.

[0234] The scope of the present disclosure includes software or machine-executable commands (e.g., operating systems, applications, firmware, programs, etc.) for enabling operations of methods according to various embodiments to be performed on a device or computer, and non-transitory computer-readable media having such software or commands stored thereon and executable on a device or computer.

[0235] Industrial Applicability

[0236] The embodiments of the present disclosure may be used to encode or decode an image.

Claims

1. An image decoding method performed by an image decoding device, the image decoding method comprising the following steps: Determine the decoding order of multiple slices in the current picture; as well as decoding the plurality of slices based on the determined decoding order, The decoding order based on the multiple slices is determined to be an order different from the raster scan order, and in the decoding order, the left adjacent slice located on the left side of the current slice and the upper adjacent slice located above the current slice in the current picture are restricted to precede the current slice.

2. The image decoding method according to claim 1, wherein: Based on the plurality of slices not being rectangular slices, the decoding order of the plurality of slices is restricted to the raster scan order.

3. The image decoding method according to claim 1, wherein: Based on the current picture including a plurality of sub-pictures, the decoding order of the plurality of slices is determined separately for each sub-picture.

4. The image decoding method according to claim 1, wherein: Based on the current picture including a plurality of sub-pictures, the decoding order of the plurality of slices is determined according to whether in-loop filtering across boundaries of the sub-pictures is allowed.

5. The image decoding method according to claim 4, wherein: Based on the in-loop filtering being enabled for the current picture and the decoding order of the plurality of slices being determined to be an order different from the raster scan order, a restriction is applied to all slices within the current picture.

6. The image decoding method according to claim 4, wherein: Based on the in-loop filtering not being allowed for the current picture and the decoding order of the plurality of slices being determined to be an order different from the raster scan order, restrictions are applied to each sub-picture individually.

7. The image decoding method according to claim 4, wherein: The decoding order of slices belonging to different sub-pictures within the current picture is determined regardless of a sub-picture to which each slice belongs, based on the in-loop filtering not being allowed for the current picture.

8. An image encoding method performed by an image encoding device, the image encoding method comprising the following steps: Determine the encoding order of multiple slices in the current picture; as well as encoding the plurality of slices based on the determined coding order, Wherein, the encoding order based on the multiple slices is determined to be an order different from the raster scanning order, and in the encoding order, the left adjacent slice located on the left side of the current slice and the upper adjacent slice located above the current slice in the current picture are restricted to precede the current slice.

9. The image encoding method according to claim 8, wherein: Based on the slice not being a rectangular slice, the encoding order of the plurality of slices is restricted to the raster scan order.

10. The image encoding method according to claim 8, wherein: Based on the current picture including a plurality of sub-pictures, the encoding order of the plurality of slices is determined separately for each sub-picture.

11. The image encoding method according to claim 8, wherein: Based on the fact that the current picture includes a plurality of sub-pictures, the coding order of the plurality of slices is determined according to whether in-loop filtering across boundaries of the sub-pictures is allowed.

12. The image encoding method according to claim 11, wherein: Based on the in-loop filtering being enabled for the current picture and the coding order of the plurality of slices being determined to be an order different from the raster scan order, a restriction is applied to all slices within the current picture.

13. The image encoding method according to claim 11, wherein: Based on the in-loop filtering not being allowed for the current picture and the coding order of the plurality of slices being determined to be an order different from the raster scan order, restrictions are applied to each sub-picture individually.

14. The image encoding method according to claim 11, wherein: Based on the in-loop filtering not being allowed for the current picture, the coding order of slices belonging to different sub-pictures within the current picture is determined regardless of the sub-picture to which each slice belongs.

15. A computer-readable recording medium for storing a bit stream generated by an image encoding method, the image encoding method comprising the steps of: Determine the encoding order of multiple slices in the current picture; as well as encoding the plurality of slices based on the determined coding order, Wherein, the encoding order based on the multiple slices is determined to be an order different from the raster scanning order, and in the encoding order, the left adjacent slice located on the left side of the current slice and the upper adjacent slice located above the current slice in the current picture are restricted to precede the current slice.

Images