Image encoding / decoding method and apparatus for performing deblocking filtering by determining boundary strength, and method for transmitting bit stream

Abstract

Provided are a method and apparatus for encoding / decoding an image. A method for decoding an image according to the present disclosure may comprise the steps of: obtaining a reconstructed image; determining a target boundary of deblocking filtering in the reconstructed image; determining the boundary strength of the target boundary; and applying deblocking filtering to the target boundary based on the boundary strength, in which when the target boundary is a transform block boundary and a color component of the reconstructed image is a chroma component, the boundary strength may be determined based on whether joint CbCr residual coding is performed on at least one of two blocks adjacent to the target boundary, and when the target boundary is a transform block boundary and the color component of the reconstructed image is a chroma component, the boundary strength may be determined based on whether joint CbCr residual coding is performed on at least one of the two blocks adjacent to the target boundary. And the joint CbCr residual encoding may correspond to encoding residual samples of the chroma Cb component and the chroma Cr component into a single transform block.

Description

Technical Field

[0001] The present disclosure relates to an image encoding / decoding method and apparatus, and more particularly, to an image encoding / decoding method and apparatus for performing deblocking filtering by determining a boundary strength, and a method of transmitting a bitstream generated by the image encoding method / apparatus of the present disclosure. Background Art

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

[0003] Therefore, there is a need for an efficient image compression technique to effectively transmit, store, and reproduce information on high-resolution and high-quality images. Summary of the Invention

[0004] Technical Problem

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

[0006] Another object of the present disclosure is to provide an image encoding / decoding method and apparatus for performing deblocking filtering.

[0007] Another object of the present disclosure is to provide an image encoding / decoding method and apparatus for determining a boundary strength of deblocking filtering to perform deblocking filtering.

[0008] Another object of the present disclosure is to provide a method of transmitting a bitstream generated by an image encoding method or apparatus according to the present disclosure.

[0009] Another object of the present disclosure is to provide a recording medium storing a bitstream generated by an image encoding method or apparatus according to the present disclosure.

[0010] Another object of the present disclosure is to provide a recording medium storing a bitstream received, decoded, and used for reconstructing an image by an image decoding apparatus according to the present disclosure.

[0011] The technical problems solved by the present disclosure are not limited to the above technical problems, and other technical problems not described herein will be apparent to those skilled in the art from the following description.

[0012] Technical Solution

[0013] An image decoding method according to an aspect of the present disclosure is performed by an image decoding device. The image decoding method includes: obtaining a reconstructed picture; determining a target boundary for deblocking filtering in the reconstructed picture; determining a boundary strength of the target boundary; and applying deblocking filtering to the target boundary based on the boundary strength. Based on the target boundary being a transform block boundary and a color component of the reconstructed picture being a chrominance component, the boundary strength may be determined based on whether joint CbCr residual coding is performed on at least one of two blocks adjacent to the target boundary, and the joint CbCr residual coding may correspond to coding residual samples of a chrominance Cb component and a chrominance Cr component as a single transform block.

[0014] In the image decoding method according to the present disclosure, it is determined whether joint CbCr residual coding can be performed on a block adjacent to the target boundary based on a first flag signaled for an adjacent block.

[0015] In the image decoding method according to the present disclosure, based on the target boundary being a transform block boundary and a color component of the reconstructed picture being a chrominance component, the boundary strength may also be determined based on whether at least one of two blocks adjacent to the target boundary includes a non - zero transform coefficient level.

[0016] In the image decoding method according to the present disclosure, it is determined whether a block adjacent to the target boundary includes at least one non - zero transform coefficient level based on a second flag signaled for an adjacent block.

[0017] In the image decoding method according to the present disclosure, based on the target boundary being a transform block boundary and a color component of the reconstructed picture being a chrominance component, the boundary strength may be determined based on a sum of two first flags and two second flags of two blocks adjacent to the target boundary.

[0018] In the image decoding method according to the present disclosure, it is determined that the boundary strength is 1 based on the sum being greater than 0.

[0019] In the image decoding method according to the present disclosure, based on the target boundary being a transform block boundary and a color component of the reconstructed picture being a luminance component, the boundary strength may be determined based on whether at least one of two blocks adjacent to the target boundary includes a non - zero transform coefficient level.

[0020] An image decoding device according to another embodiment of the present disclosure may include a memory and at least one processor. The at least one processor may obtain a reconstructed picture, determine a target boundary for deblocking filtering in the reconstructed picture, determine a boundary strength of the target boundary, and apply deblocking filtering to the target boundary based on the boundary strength. Based on the target boundary being a transform block boundary and the color component of the reconstructed picture being a chrominance component, the boundary strength may be determined based on whether joint CbCr residual coding is performed on at least one of two blocks adjacent to the target boundary, and the joint CbCr residual coding may correspond to encoding residual samples of chrominance Cb component and chrominance Cr component as a single transform block.

[0021] An image encoding method according to another aspect of the present disclosure may include the following steps: generating a reconstructed picture, determining a target boundary for deblocking filtering in the reconstructed picture, determining a boundary strength of the target boundary, and applying deblocking filtering to the target boundary based on the boundary strength. Based on the target boundary being a transform block boundary and the color component of the reconstructed picture being a chrominance component, the boundary strength may be determined based on whether joint CbCr residual coding is performed on at least one of two blocks adjacent to the target boundary, and the joint CbCr residual coding may correspond to encoding residual samples of chrominance Cb component and chrominance Cr component as a single transform block.

[0022] In the image encoding method according to the present disclosure, it is determined whether joint CbCr residual coding can be performed on a block adjacent to the target boundary based on a first flag signaled for an adjacent block.

[0023] In the image encoding method according to the present disclosure, based on the target boundary being a transform block boundary and the color component of the reconstructed picture being a chrominance component, the boundary strength may also be determined based on whether at least one of two blocks adjacent to the target boundary includes a non - zero transform coefficient level.

[0024] In the image encoding method according to the present disclosure, it may be determined whether a block adjacent to the target boundary includes at least one non - zero transform coefficient level based on a second flag signaled for an adjacent block.

[0025] In the image encoding method according to the present disclosure, based on the target boundary being a transform block boundary and the color component of the reconstructed picture being a chrominance component, the boundary strength may be determined based on the sum of two first flags and two second flags of two blocks adjacent to the target boundary.

[0026] In the image encoding method according to the present disclosure, it may be determined that the boundary strength is 1 based on the sum being greater than 0.

[0027] According to another aspect of the present disclosure, a transmission method can transmit a bitstream generated by the image encoding device or image encoding method of the present disclosure.

[0028] According to another aspect of the present disclosure, a computer-readable recording medium can store a bitstream generated by the image encoding device or image encoding method of the present disclosure.

[0029] The features briefly summarized above regarding 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.

[0030] Advantageous Effects

[0031] According to the present disclosure, an image encoding / decoding method and device with improved encoding / decoding efficiency can be provided.

[0032] According to the present disclosure, an image encoding / decoding method and device for performing deblocking filtering can be provided.

[0033] According to the present disclosure, an image encoding / decoding method and device for determining the boundary strength of deblocking filtering to perform deblocking filtering can be provided.

[0034] In addition, according to the present disclosure, a method for transmitting a bitstream generated by an image encoding method or device according to the present disclosure can be provided.

[0035] In addition, according to the present disclosure, a recording medium for storing a bitstream generated by an image encoding method or device according to the present disclosure can be provided.

[0036] In addition, according to the present disclosure, a recording medium can be provided that stores a bitstream received, decoded, and used for reconstructing an image by an image decoding device according to the present disclosure.

[0037] Those skilled in the art will understand that the effects achievable through the present disclosure are not limited to those specifically described above, and other advantages of the present disclosure will be more clearly understood from the detailed description. Brief Description of the Drawings

[0038] Figure 1 is a view schematically showing a video encoding system according to an embodiment of the present disclosure.

[0039] Figure 2 is a view schematically showing an image encoding device according to an embodiment of the present disclosure.

[0040] Figure 3 is a view schematically showing an image decoding device according to an embodiment of the present disclosure.

[0041] Figure 4It is a schematic flowchart of an image decoding process to which embodiments of the present disclosure can be applied.

[0042] Figure 5 It is a schematic flowchart of an image encoding process to which embodiments of the present disclosure can be applied.

[0043] Figure 6 It is a flowchart showing deblocking filtering according to the present disclosure.

[0044] Figure 7 It is a flowchart showing a method for determining the boundary strength of a target boundary according to an embodiment of the present disclosure.

[0045] Figure 8 It is a view showing the signaling of syntax elements in a transform block related to an embodiment of the present disclosure.

[0046] Figure 9 It is a flowchart showing a method for determining the boundary strength of a target boundary according to another embodiment of the present disclosure.

[0047] Figure 10 It is a flowchart showing a method for determining the boundary strength of a target boundary according to another embodiment of the present disclosure.

[0048] Figure 11 It is a flowchart showing a method for determining the boundary strength of a target boundary according to another embodiment of the present disclosure.

[0049] Figure 12 It is a flowchart showing an encoding process based on deblocking filtering according to the present disclosure.

[0050] Figure 13 It is a flowchart showing a decoding process based on deblocking filtering according to the present disclosure.

[0051] Figure 14 It is a view showing two blocks and samples adjacent to a target boundary of deblocking filtering according to an embodiment of the present disclosure.

[0052] Figure 15 It is a view showing a content stream system to which embodiments of the present disclosure can be applied. Detailed Embodiments

[0053] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement them. However, the present disclosure can be implemented in various different forms and is not limited to the embodiments described herein.

[0054] In describing the present disclosure, detailed descriptions of related known functions or configurations will be omitted when such descriptions render the scope of the present disclosure unnecessarily obscure. In the drawings, parts irrelevant to the description of the present disclosure are omitted, and like reference numerals are attached to like parts.

[0055] 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 present. Additionally, 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.

[0056] In the present disclosure, terms such as first, second, etc. are only used 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, the first component in one embodiment may be referred to as the second component in another embodiment, and similarly, the second component in one embodiment may be referred to as the first component in another embodiment.

[0057] In the present disclosure, components that are mutually distinguishable are intended to clearly describe each feature and do not mean that the components must be separate. That is, multiple components may be integrated and implemented in one hardware or software unit, or one component may be distributed and implemented in multiple hardware or software units. Therefore, even without specific description, these embodiments of component integration or distribution are included within the scope of the present disclosure.

[0058] In the present disclosure, the components described in each embodiment are not necessarily essential components, and some components may be optional components. Therefore, embodiments consisting of a subset of the components described in the embodiments are also included within the scope of the present disclosure. In addition, embodiments that include other components in addition to the components described in the various embodiments are included within the scope of the present disclosure.

[0059] The present disclosure relates to the encoding and decoding of images. Unless redefined in the present disclosure, the terms used in the present disclosure may have the general meanings commonly used in the technical field to which the present disclosure pertains.

[0060] In the present disclosure, a "picture" generally refers to a unit representing an image within a specific time period, while a slice / tile / sub - picture is an encoding unit that forms part of a picture, and a picture may be composed of one or more slices / titles / sub - pictures. Additionally, a slice / tile / sub - picture may include one or more coding tree units (CTUs).

[0061] In the present disclosure, a "pixel" or "pel" may mean the smallest unit that constitutes a picture (or image). In addition, a "sample" may be used as a term corresponding to a pixel. A sample generally may 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.

[0062] In the present disclosure, a "unit" may represent 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 "region". In general, an M×N block may include a set (or array) of samples (or sample arrays) or transform coefficients having M columns and N rows.

[0063] In the present disclosure, a "current block" may mean one of a "current coding block", a "current coding unit", a "coding target block", a "decoding target block", or a "processing target block". When performing prediction, the "current block" may mean a "current prediction block" or a "prediction target block". When performing transform (inverse transform) / quantization (dequantization), the "current block" may mean a "current transform block" or a "transform target block". When performing filtering, the "current block" may mean a "filtering target block".

[0064] In addition, in the present disclosure, unless explicitly stated as a chrominance block, the "current block" may represent the luminance block of the "current block". The chrominance block of the "current block" may be expressed by including an explicit description of a chrominance block such as a "chrominance block" or a "current chrominance block".

[0065] In the present disclosure, the term " / " or "," may be interpreted as indicating "and / or". For example, "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.

[0066] In the present disclosure, the term "or" should be interpreted to indicate "and / or". For example, the expression "A or B" may include 1) only "A", 2) only "B", or 3) both "A and B". In other words, in the present disclosure, "or" should be interpreted to indicate "additionally or alternatively".

[0067] Overview of the video encoding system

[0068] Figure 1 is a view schematically showing a video coding system according to the present disclosure.

[0069] A video encoding system according to an embodiment may include an encoding device 10 and a decoding device 20. The encoding device 10 may deliver encoded video and / or image information or data in the form of a file or a stream to the decoding device 20 via a digital storage medium or a network.

[0070] The encoding device 10 according to an embodiment may include a video source generator 11, an encoding unit 12, and a transmitter 13. The decoding device 20 according to an 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 unit, and the decoding unit 22 may be referred to as a video / image decoding unit. 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.

[0071] The video source generator 11 may acquire video / images through a process of capturing, synthesizing, or generating video / images. 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 video / images, etc. The video / image generating device may include, for example, a computer, a tablet computer, and a smart phone, and may generate (electronically) video / images. For example, virtual video / images may be generated through a computer or the like. In this case, the video / image capturing process may be replaced by a process of generating relevant data.

[0072] The encoding unit 12 may encode the input video / images. 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 encoded data (encoded video / image information) in the form of a bitstream.

[0073] The transmitter 13 may transmit the encoded video / image information or data output in the form of a bitstream to the receiver 21 of the decoding device 20 in the form of a file or a stream via 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 via a broadcast / communication network. The receiver 21 may extract / receive the bitstream from the storage medium or the network and transmit the bitstream to the decoding unit 22.

[0074] The decoding unit 22 may decode the video / images by performing a series of processes corresponding to the operations of the encoding unit 12, such as dequantization, inverse transformation, and prediction.

[0075] The renderer 23 may render the decoded video / image. The rendered video / image may be displayed via a display.

[0076] Overview of the image encoding device

[0077] Figure 2 is a view schematically showing an image encoding device to which embodiments of the present disclosure are applicable.

[0078] As Figure 2 shown, the image encoding device 100 may include an image splitter 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 prediction unit 180, an intra prediction unit 185, and an entropy encoder 190. The inter prediction unit 180 and the intra 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 further include the subtractor 115.

[0079] In some embodiments, all or at least some of the multiple components configuring the image encoding device 100 may be configured by one hardware component (e.g., an encoder or a processor). Further, the memory 170 may include a decoded picture buffer (DPB) and may be configured by a digital storage medium.

[0080] The image splitter 110 may split an 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 splitting a coding tree unit (CTU) or a largest coding unit (LCU) according to a quadtree binary tree ternary tree (QT / BT / TT) structure. For example, one coding unit may be split into multiple coding units of a deeper depth based on a quadtree structure, a binary tree structure, and / or a ternary tree structure. For the splitting of the coding unit, the quadtree structure may be applied first, and then the binary tree structure and / or the ternary tree structure may be applied. The encoding process according to the present disclosure may be performed based on the final coding unit that is no longer split. The largest coding unit may be used as the final coding unit, or the coding unit of a deeper depth obtained by splitting the largest coding unit may be used as the final coding unit. Here, the encoding process may include processes of prediction, transformation, and reconstruction to be 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 transformation unit may be divided or split from the final coding unit. The prediction unit may be a sample prediction unit, and the transformation unit may be a unit for deriving transform coefficients and / or a unit for deriving a residual signal from the transform coefficients.

[0081] The prediction unit (inter-frame prediction unit 180 or intra-frame prediction unit 185) can perform prediction on a block to be processed (current block) and generate a prediction block including prediction samples of the current block. The prediction unit can determine whether to apply intra-frame prediction or inter-frame prediction based on the current block or CU. The prediction unit can generate various information related to the prediction of the current block and transmit the generated information to the entropy encoder 190. The information about the prediction can be encoded in the entropy encoder 190 and output in the form of a bitstream.

[0082] The intra-frame prediction unit 185 can predict the current block by referring to samples in the current picture. Depending on the intra-frame prediction mode and / or intra-frame prediction technique, the reference samples can be located among the neighbors of the current block or can be placed separately. The intra-frame prediction mode can include a plurality of non-directional modes and a plurality of directional modes. The non-directional modes can include, for example, the DC mode and the planar mode. Depending on the level of detail of the prediction direction, the directional modes can 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 can be used according to the settings. The intra-frame prediction unit 185 can determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0083] The inter-frame prediction unit 180 may derive a prediction block of a 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 transmitted in the inter-frame 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 neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter-frame prediction, 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-frame prediction unit 180 may configure a motion information candidate list based on neighboring blocks and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. The inter-frame prediction may be performed based on various prediction modes. For example, in the case of the skip mode and the merge mode, the inter-frame prediction unit 180 may use the motion information of neighboring blocks as the motion information of the current block. In the case of the skip mode, different from the merge mode, the residual signal may not be transmitted. In the case of the motion vector prediction (MVP) mode, the motion vector of a 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.

[0084] The prediction unit may generate a prediction signal based on various prediction methods and prediction techniques described below. For example, the prediction unit may not only apply intra-frame prediction or inter-frame prediction, but also apply intra-frame prediction and inter-frame prediction simultaneously to predict the current block. The prediction method of applying both intra-frame prediction and inter-frame prediction simultaneously to predict the current block may be referred to as combined intra and inter prediction (CIIP). In addition, the prediction unit may perform intra-block copy (IBC) to predict the current block. Intra-block copy may be used for content image / video coding such as games, for example, 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 from the current block by a predetermined distance. When IBC is applied, the position of the reference block in the current picture may be encoded as a vector (block vector) corresponding to the predetermined distance. In IBC, the prediction is basically performed in the current picture, but the prediction may be performed similarly to inter-frame prediction because the reference block is derived within the current picture. That is, IBC may use at least one of the inter-frame prediction techniques described in the present disclosure.

[0085] The prediction signal generated by the prediction unit can be used to generate a reconstructed signal or 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 transmitted to the transformer 120.

[0086] The transformer 120 can generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique can include at least one of discrete cosine transform (DCT), discrete sine transform (DST), karhunen-loève transform (KLT), graph-based transform (GBT), or conditional non-linear transform (CNT). Here, GBT refers to a transform obtained from a graph when the 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 can be applied to square pixel blocks of the same size or can be applied to blocks with variable sizes rather than squares.

[0087] The quantizer 130 can quantize the transform coefficients and transmit them to the entropy encoder 190. The entropy encoder 190 can encode the quantized signal (information about the quantized transform coefficients) and output a bitstream. The information about the quantized transform coefficients can be referred to as residual information. The quantizer 130 can rearrange the quantized transform coefficients in block form into a one-dimensional vector form based on the coefficient scan order and generate information about the quantized transform coefficients based on the quantized transform coefficients in one-dimensional vector form.

[0088] The entropy encoder 190 can perform various coding methods, such as exponential Golomb, context-adaptive variable length coding (CAVLC), context-adaptive binary arithmetic coding (CABAC), etc. The entropy encoder 190 can encode information required for video / image reconstruction other than the quantized transform coefficients (e.g., values of syntax elements, etc.) together or separately. The encoded information (e.g., encoded video / image information) can be transmitted or stored in the form of a bitstream in units of network abstraction layer (NAL). The video / image information can also include information about various parameter sets, such as adaptive parameter set (APS), picture parameter set (PPS), sequence parameter set (SPS), or video parameter set (VPS). In addition, the video / image information can also include general constraint information. The signaling information, transmitted information, and / or syntax elements described in this disclosure can be encoded through the above encoding process and included in the bitstream.

[0089] The bitstream can be transmitted over a network or stored in a digital storage medium. The network can include a broadcast network and / or a communication network, and the digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmitter (not shown) for transmitting the signal output from the entropy encoder 190 and / or a storage unit (not shown) for storing the signal can be included as internal / external elements of the image encoding device 100. Alternatively, a transmitter can be provided as a component of the entropy encoder 190.

[0090] The quantized transform coefficients output from the quantizer 130 can be used to generate a residual signal. For example, the quantized transform coefficients can be dequantized and inverse-transformed by the dequantizer 140 and the inverse-transformer 150 to reconstruct the residual signal (residual block or residual samples).

[0091] 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). In the case where there is no residual in the block to be processed, for example, when the skip mode is applied, the predicted block can be used as the reconstructed block. The adder 155 can be referred to as 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 through filtering as described below.

[0092] 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 can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filtering, bilateral filtering, etc. The filter 160 can generate various information related to the filtering and transmit the generated information to the entropy encoder 190, as described later in the description of each filtering method. The information related to the filtering can be encoded by the entropy encoder 190 and output in the form of a bitstream.

[0093] The modified reconstructed picture transmitted to the memory 170 can be used as a reference picture in the inter-frame prediction unit 180. When inter-frame prediction is applied by the image encoding device 100, prediction mismatch between the image encoding device 100 and the image decoding device can be avoided and the encoding efficiency can be improved.

[0094] The DPB of the memory 170 may store the modified reconstructed picture to be used as a reference picture in the inter prediction unit 180. The memory 170 may store the motion information of the blocks from which the motion information in the current picture is derived (or encoded) and / or the motion information of the blocks that have been reconstructed in the picture. The stored motion information may be transmitted to the inter prediction unit 180 and used as the motion information of spatially neighboring blocks or temporally neighboring blocks. 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 prediction unit 185.

[0095] Overview of the image decoding device

[0096] Figure 3 is a view schematically showing an image decoding apparatus to which embodiments of the present disclosure are applicable.

[0097] As Figure 3 shown, the image decoding apparatus 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 prediction unit 260, and an intra prediction unit 265. The inter prediction unit 260 and the intra 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.

[0098] According to an embodiment, all or at least some of the plurality of components configuring the image decoding apparatus 200 may be configured by hardware components (e.g., a decoder or a processor). Further, the memory 250 may include a decoded picture buffer (DPB) or may be configured by a digital storage medium.

[0099] The image decoding apparatus 200 that has received a bitstream including video / image information may reconstruct an image by performing a process corresponding to the process performed by the Figure 2 image encoding apparatus 100. For example, the image decoding apparatus 200 may perform decoding using the processing units applied in the image encoding apparatus. Thus, the decoding processing units may be, for example, encoding units. The encoding units may be obtained by dividing a coding tree unit or a maximum coding unit. The reconstructed image signal decoded and output by the image decoding apparatus 200 may be reproduced by a reproducing apparatus (not shown).

[0100] The image decoding apparatus 200 may receive, in the form of a bitstream, from Figure 2The signal output by the image encoding device. The received signal can be decoded by the entropy decoder 210. For example, the entropy decoder 210 can parse the bitstream to derive the information (e.g., video / image information) required for image reconstruction (or picture reconstruction). The video / image information can also include information about various parameter sets, such as adaptive parameter set (APS), picture parameter set (PPS), sequence parameter set (SPS), or video parameter set (VPS). In addition, the video / image information can also include general constraint information. The image decoding device can 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 can be decoded through the decoding process and obtained from the bitstream. For example, the entropy decoder 210 decodes the information in the bitstream based on an encoding method such as exponential Golomb coding, CAVLC, or CABAC, and outputs the values of the syntax elements required for image reconstruction and the quantization values of the transform coefficients of the residuals. More specifically, the CABAC entropy decoding method can receive the bins corresponding to each syntax element in the bitstream, use the decoding target syntax element information, neighboring blocks, and the decoding information of the decoding target block or the information of the symbols / bins decoded in the previous stage to determine the context model, perform arithmetic decoding on the bins by predicting the occurrence probability of the bins according to the determined context model, and generate the symbols corresponding to the values of each syntax element. In this case, after determining the context model, the CABAC entropy decoding method can update the context model by using the information of the decoded symbols / bins for the context model of the next symbol / bin. The information related to prediction in the information decoded by the entropy decoder 210 can be provided to the prediction units (inter-frame prediction unit 260 and intra-frame prediction unit 265), and the residual values for which entropy decoding is performed in the entropy decoder 210, that is, the quantized transform coefficients and the related parameter information, 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. Furthermore, the receiver (not shown) for receiving the signal output by the image encoding device can be further configured as an internal / external element of the image decoding device 200, or the receiver can be a component of the entropy decoder 210.

[0101] In addition, the image decoding device according to the present disclosure can be referred to as a video / image / picture decoding device. The image decoding device can be divided into an information decoder (video / image / picture information decoder) and a sample decoder (video / image / picture sample decoder). The information decoder can include the entropy decoder 210. The sample decoder can include at least one of the dequantizer 220, inverse transformer 230, adder 235, filter 240, memory 250, inter-frame prediction unit 260, or intra-frame prediction unit 265.

[0102] 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 scan order executed in the image coding device. The dequantizer 220 may dequantize the quantized transform coefficients by using a quantization parameter (e.g., quantization step information) and obtain the transform coefficients.

[0103] The inverse transformer 230 may perform an inverse transform on the transform coefficients to obtain a residual signal (residual block, residual sample array).

[0104] The prediction unit may perform prediction on the current block and generate a prediction block including the 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).

[0105] Similar to that described in the prediction unit of the image coding device 100, the prediction unit may generate a prediction signal based on various prediction methods (techniques) described later.

[0106] The intra prediction unit 265 may predict the current block by referring to the samples in the current picture. The description of the intra prediction unit 185 is equally applicable to the intra prediction unit 265.

[0107] The inter prediction unit 260 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 transmitted in the inter prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include information about an inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter 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 prediction unit 260 may configure a motion information candidate list based on neighboring blocks, and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. The inter prediction may be performed based on various prediction modes, and the information about prediction may include information indicating the inter prediction mode of the current block.

[0108] The adder 235 can generate a reconstructed 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). The description of the adder 155 is equally applicable to the adder 235. In the case where there is no residual for the block to be processed, such as when the skip mode is applied, the prediction block can be used as the reconstructed block. The description of the adder 155 is equally applicable to the adder 235. The adder 235 can be referred to as 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.

[0109] 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 can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filtering, bilateral filtering, etc.

[0110] 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 blocks from which the motion information in the current picture is derived (or decoded) and / or the motion information of the blocks that have been reconstructed in the picture. The stored motion information can be transmitted to the inter-frame prediction unit 260 to be used as the motion information of spatially neighboring blocks or temporally neighboring blocks. The memory 250 can store the reconstructed samples of the reconstructed blocks in the current picture and transmit the reconstructed samples to the intra-frame prediction unit 265.

[0111] 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 can 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.

[0112] Overview of the image decoding / encoding process

[0113] In image / video coding, the pictures constituting the image / video can be encoded / decoded according to a series of decoding orders. The picture order corresponding to the output order of the decoded pictures can be set differently from the above decoding order, and based on this, not only forward prediction but also backward prediction can be performed during inter-frame prediction.

[0114] Figure 4FIG. 0 is a schematic flowchart of an image decoding process to which embodiments of the present disclosure can be applied.

[0115] Figure 4 Each process shown in Figure 3 can be executed by an image decoding device. For example, step S410 can be executed by the entropy decoder 210 of the image decoding device, step S420 can be executed by the prediction units 260 and 265, step S430 can be executed by the residual processors 220 and 230, step S440 can be executed by the adder 235, and step S450 can be executed by the filter 240. Step S410 can include an information decoding (parsing) process described in the present disclosure, step S420 can include an inter / intra prediction process described in the present disclosure, step S430 can include a residual processing process described in the present disclosure, step S440 can include a block / picture reconstruction process described in the present disclosure, and step S450 can include an in-loop filtering process described in the present disclosure.

[0116] Referring to Figure 4 , the picture decoding process can schematically include a process (by decoding) for obtaining video / image information from a bitstream (S410), an image (picture) reconstruction process (S420 to S440), and an in-loop filtering process (S450) for reconstructing an image (picture). The image reconstruction process can be performed based on prediction samples obtained through inter / intra prediction (S420) and residual samples obtained through residual processing (S430) (inverse quantization and inverse transformation of quantization transform coefficients). For a reconstructed picture generated through the image reconstruction process, a modified reconstructed picture can be generated through the in-loop filtering process (S450), and the modified reconstructed picture can be output as a decoded picture, stored in the memory or decoded picture buffer (DPB) 250 of the image decoding device, and used as a reference picture in the inter prediction process when decoding a later picture. In some cases, the in-loop filtering process can be omitted. In this case, the reconstructed picture can be output as a decoded picture, stored in the DPB 250 or memory of the image decoding device, and used as a reference picture in the inter prediction process when decoding a later picture. The in-loop filtering process (S450) can include a deblocking filtering process, a sample adaptive offset (SAO) process, an adaptive loop filter (ALF) process, and / or a bilateral filter process, and some or all of them can be omitted as described above. Additionally, one or some of the deblocking filtering process, the sample adaptive offset (SAO) process, the adaptive loop filter (ALF) process, and / or the bilateral filter process can be applied in sequence, or all of them can be applied in sequence. For example, after the deblocking filtering process is applied to the reconstructed image, the SAO process can be executed. Alternatively, after the deblocking filtering process is applied to the reconstructed image, the ALF process can be executed. This can even be similarly executed in an image encoding device.

[0117] Figure 5 is a schematic flowchart of an image encoding process to which embodiments of the present disclosure can be applied.

[0118] Figure 5 Each process shown in Figure 2 can be executed by an image encoding device. For example, step S510 can be executed by prediction units 180 and 185 of the image encoding device, step S520 can be executed by residual processors 115, 120, and 130, and step S530 can be executed in entropy encoder 190. Step S510 can include the inter / intra prediction processes described in the present disclosure, step S520 can include the residual processing processes described in the present disclosure, and step S530 can include the information encoding processes described in the present disclosure.

[0119] Referring to Figure 5 , the image encoding process can schematically 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 of the current picture and a process for applying in-loop filtering to the reconstructed picture (optional). The image encoding device can derive (modified) residual samples from the quantized transform coefficients through dequantizer 140 and inverse transformers 150, and generate a reconstructed picture based on the prediction samples output in step S510 and the (modified) residual samples. The reconstructed picture generated in this way can be equal to the reconstructed picture generated in the image decoding device. Similar to the image decoding device, the modified reconstructed picture can be generated through an in-loop filtering process for the reconstructed picture, and can be stored in decoded picture buffer (DPB) 170 or a memory, and can be used as a reference picture in the inter prediction process when encoding a later picture. As described above, in some cases, some or all of the in-loop filtering processes can be omitted. When the in-loop filtering process is executed, the (in-loop) filtering related information (parameters) can be encoded in entropy encoder 190 and output in the form of a bitstream, and the image decoding device can execute the in-loop filtering process using the same method as the image encoding device based on the filtering related information.

[0120] Through such an in-loop filtering process, noise (e.g., blocking effect and ringing effect) that appears during video / image encoding can be reduced, and subjective / objective visual quality can be improved. In addition, by executing 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 sent for picture encoding can be reduced.

[0121] 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. Reconstructed blocks can be generated based on intra prediction / inter prediction on a block-by-block basis, and a reconstructed picture including the reconstructed blocks 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 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 prediction or inter prediction. In this case, inter prediction can be applied to some blocks in the current picture / slice / tile group and intra prediction can be applied to the remaining blocks. The color components of a picture can include a luminance component and a chrominance component, and unless explicitly restricted in the present disclosure, the methods and embodiments of the present disclosure can be applied to both the luminance component and the chrominance component.

[0122] Figure 6 is a flowchart showing deblocking filtering according to the present disclosure. Figure 6 The deblocking filtering shown can correspond to the deblocking filtering of the in-loop filtering described above. Figure 6 The deblocking filtering shown can be performed, for example, by Figure 2 filter 160 of Figure 3 or filter 240 of

[0123] Deblocking filtering can correspond to a filtering technique for removing distortions occurring at the boundaries between blocks in a reconstructed picture. A target boundary can be derived from the reconstructed picture through a deblocking filtering process (S610). Additionally, the boundary strength of the derived target boundary can be determined (S620). Deblocking filtering for the target boundary can be performed based on the determined boundary strength (S630). The boundary strength can be determined based on the prediction mode, motion vector difference, whether the reference pictures are the same, and / or the presence / absence of non-zero valid coefficients of two blocks adjacent to the target boundary.

[0124] Deblocking filtering can be applied to the reconstructed picture. Deblocking filtering can be performed in the same order as the decoding process for each CU of the reconstructed picture. First, vertical edges can be filtered (horizontal filtering). Thereafter, horizontal edges can be filtered (vertical filtering). Deblocking filtering can be applied to all coded block (or sub-block) edges and transform block edges.

[0125] As described above, in-loop filtering may include SAO. SAO may correspond to a method of compensating for the offset difference between the reconstructed picture and the original picture on a sample-by-sample basis. For example, SAO may be applied based on types such as band offset or edge offset. According to SAO, samples may be classified into different categories according to each SAO type. An offset value may be added to each sample based on the classified category. The filtering information of SAO may include information on whether SAO is applied, SAO type information, and / or SAO offset value information. SAO may be applied to the reconstructed picture after applying deblocking filtering.

[0126] In addition, in-loop filtering may include ALF. ALF may correspond to a technique for performing filtering on a sample-by-sample basis of a reconstructed picture based on filter coefficients according to a filter shape. The encoding device may determine whether to apply ALF, the ALF shape, and / or the ALF filter coefficients by comparing between the reconstructed picture and the original picture. In addition, this may be signaled to the decoding device. The filtering information of ALF may include information on whether ALF is applied, ALF filter shape information, and / or ALF filter coefficient information. ALF may be applied to the reconstructed picture after applying deblocking filtering.

[0127] According to some embodiments of the present disclosure, the boundary strength may be determined according to the conditions of two blocks adjacent to a target boundary. In the present disclosure, the boundary strength and the boundary filtering strength may be used interchangeably.

[0128] Figure 14 is a view showing two blocks and samples adjacent to a target boundary of deblocking filtering according to an embodiment of the present disclosure.

[0129] In Figure 14 the boundary represented by the thick solid line may be the target boundary of deblocking filtering.

[0130] As Figure 14 shown in, when the target boundary is a vertical boundary, the left block may be defined as a P block based on the target boundary, and the right block may be defined as a Q block. In addition, when the target boundary is a horizontal boundary, the upper block may be defined as a P block based on the target boundary, and the lower block may be defined as a Q block.

[0131] In the present disclosure, the samples in the P block may be represented by p n and the samples in the Q block may be represented by q n That is, p n and q n may be samples facing the boundary (target boundary) between the P block and the Q block. In this case, n may be an integer greater than or equal to 0 and may represent the distance from the target boundary. p 0 may be a sample in the P block adjacent to the target boundary, and q 0can represent samples in the Q block adjacent to the target boundary. For example, p 0 can be a sample in the left or upper block adjacent to the target boundary, q 0 can be a sample in the right or lower block adjacent to the target boundary. Alternatively, as Figure 14 shown, the samples in the P block can be represented by p n，m and the samples in the Q block can be represented by q n，m In this case, n is an integer greater than or equal to 0 as described above and can represent the distance from the target boundary. Additionally, m can be an index for distinguishing samples located at the same distance from the target boundary in one block (P block or Q block).

[0132] Furthermore, in the following description, the first value, second value, and third value of the boundary strength can represent 0, 1, and 2 respectively, but the scope of the present disclosure is not limited by such a definition.

[0133] The image encoding device and the image decoding device can perform deblocking filtering based on the boundary strength. For example, when the boundary strength is the first value (e.g., 0), filtering may not be applied to the corresponding target boundary. Deblocking filtering can be applied based on the filter strength (strong filter / weak filter) and / or the filter length.

[0134] In the present disclosure, deblocking filtering can be performed by obtaining information related to deblocking filtering from the bitstream. For example, the information related to deblocking filtering can include a flag specifying whether deblocking filtering is available. Additionally, the information related to deblocking filtering can include information for deriving the boundary strength.

[0135] The deblocking filtering process can be performed separately according to the color components (luminance component (Y) and chrominance components (cb, cr)) of the reconstructed picture. For example, the boundary strength bS can be derived differently according to the color components (luminance component (Y) and chrominance components (cb, cr)). Additionally, for example, the target boundary can be derived separately according to the color components (luminance component (Y) and chrominance components (cb, cr)). In the present disclosure, the color component can be specified by the component index cIdx. For example, when cIdx is 0, it can specify the luminance component. Additionally, when cIdx is 1, it can specify the chrominance component cb, and when cIdx is 2, it can specify the chrominance component cr.

[0136] Figure 7 is a flowchart showing a method for determining the boundary strength of a target boundary according to an embodiment of the present disclosure.

[0137] Referring to Figure 7 it can be determined whether the current block is a luminance component block (e.g., cIdx = 0) and the samples p 0 and q 0Whether both are included in an encoded block to which block-based quantization residual domain differential pulse code modulation (BDPCM) is applied (e.g., intra_bdpcm_luma_flag = 1) (S710). When the above conditions are satisfied (S710 is yes), the boundary strength corresponding to the target boundary can be determined as a first value (e.g., 0).

[0138] When the conditions of step S710 are not satisfied (S710 is no), step S720 can be determined. Specifically, it can be determined whether the current block is a chrominance component block (e.g., cIdx > 0) and samples p 0 and q 0 Whether both are included in an encoded block to which BDPCM is applied (e.g., intra_bdpcm_chroma_flag = 1) (S720). When the above conditions are satisfied (S720 is yes), the boundary strength corresponding to the target boundary can be determined as a first value (e.g., 0).

[0139] When the conditions of step S720 are not satisfied (S720 is no), step S730 can be determined. Specifically, it can be determined whether sample p 0 or sample q 0 is included in an encoded block encoded in an intra prediction mode (S730). When the above conditions are satisfied (S730 is yes), the boundary strength corresponding to the target boundary can be determined as a third value (e.g., 2).

[0140] When the conditions of step S730 are not satisfied (S730 is no), step S740 can be determined. Specifically, it can be determined that the target boundary is the boundary of an encoded block and whether sample p 0 or sample q 0 is included in an encoded block to which combined inter and intra prediction (CIIP) is applied (e.g., ciip_flag = 1) (S740). When the above conditions are satisfied (S740 is yes), the boundary strength corresponding to the target boundary can be determined as a third value (e.g., 2).

[0141] When the conditions of step S740 are not satisfied (S740 is no), step S750 can be determined. Specifically, it can be determined that the target boundary is the boundary of a transform block and whether sample p 0 or sample q 0 is included in a transform block having one or more non-zero transform coefficient levels (S750). When the above conditions are satisfied (S750 is yes), the boundary strength corresponding to the target boundary can be determined as a second value (e.g., 1).

[0142] When the conditions of step S750 are not satisfied (S750 is no), step S760 can be determined. Specifically, it can be determined that the sample p 0The prediction mode of the coded block and the sample q included 0 Whether the prediction modes of the coded blocks including the sample q are different (S760). When the above conditions are satisfied (S760 is YES), the boundary strength corresponding to the target boundary can be determined as a second value (e.g., 1). For example, when one of the two coded blocks located on both sides of the target boundary is coded in the IBC prediction mode and the other is coded in the inter prediction mode, the boundary strength of the corresponding target boundary can be determined as the second value (e.g., 1).

[0143] When the conditions of step S760 are not satisfied (S760 is NO), step S770 can be determined. Specifically, in step S770, it can be determined whether the color component is a luminance component (e.g., cIdx = 0), whether the target boundary is the boundary of a sub-block (e.g., edgeFlags = 2), and whether at least one of various other conditions described below is satisfied (S770). In step S770, when the color component is a luminance component, the target boundary is the boundary of a sub-block, and at least one of the other conditions (Condition 1 to Condition 5) described below is satisfied (S770 is YES), the boundary strength corresponding to the target boundary can be determined as the second value (e.g., 1).

[0144] - Condition 1: The coded block including the sample p 0 and the coded block including the sample q 0 are both coded, and the difference between the horizontal component or the vertical component of the block vector of each block is greater than or equal to 8 units in units of 1 / 16 luminance samples.

[0145] - Condition 2: The coded block including the sample p 0 and the coded block including the sample q 0 refer to different reference pictures or have different numbers of motion vectors. In Condition 2, it is determined whether the reference pictures are the same by only considering whether the pictures for inter prediction reference are the same, and the corresponding reference pictures belonging to reference picture list 0 or reference picture list 1 are not considered. In addition, the index values specifying the corresponding reference pictures are not considered. In addition, the prediction direction flag (PredFlagL0, PredFlagL1) values can be used to determine the number of motion vectors. For example, the number of motion vectors can be derived as PredFlagL0 + PredFlagL1.

[0146] - Condition 3: One motion vector is used to predict the coded block including the sample p 0 and the coded block including the sample q 0 and the difference between the horizontal component or the vertical component of the motion vector of each block can be greater than or equal to 8 units in units of 1 / 16 luminance samples.

[0147] - Condition 4: Use two motion vectors and two different reference pictures to predict an encoded sub-block including the same p 0 and use two motion vectors and two identical reference pictures to predict an encoded sub-block including sample q 0 and the difference between the horizontal or vertical components of the motion vectors of the same reference picture can be greater than or equal to 8 unit values in units of 1 / 16 luma samples.

[0148] - Condition 5: Use two motion vectors of the same reference picture to predict an encoded sub-block including sample p 0 and use two motion vectors of the same reference picture to predict an encoded sub-block including sample q 0 and satisfy the following two conditions (Condition 5-1 and Condition 5-2).

[0149] - Condition 5-1: The difference between the horizontal or vertical components of the list 0 motion vectors used to predict each encoded sub-block can be greater than or equal to 8 unit values in units of 1 / 16 luma samples, and the difference between the horizontal or vertical components of the list 1 motion vectors used to predict each encoded sub-block can be greater than or equal to 8 unit values in units of 1 / 16 luma samples.

[0150] - Condition 5-2: The difference between the horizontal or vertical components between the list 0 motion vectors used to predict the encoded sub-block including sub-block p 0 and the list 1 motion vectors used to predict the encoded sub-block including sample q 0 can be greater than or equal to 8 unit values in units of 1 / 16 luma samples, or the difference between the horizontal or vertical components between the list 1 motion vectors used to predict the encoded sub-block including sub-block p 0 and the list 0 motion vectors used to predict the encoded sub-block including sample q 0 can be greater than or equal to 8 unit values in units of 1 / 16 luma samples.

[0151] In the above Conditions 1 to 5, the difference between the vertical (or horizontal) components of the motion vectors can mean the absolute value of the difference between the vertical (or horizontal) components of the motion vectors.

[0152] When the condition of step S770 is not satisfied (S770 is NO), the boundary strength of the corresponding target boundary can be determined as a first value (for example, 0).

[0153] Refer to Figure 7 The method for determining the boundary strength bS described is exemplary, and the boundary strength determination method according to the present disclosure is not limited to Figure 7 the example shown. For example, some steps shown in Figure 7 can be omitted, and in addition toFigure 7 Steps other than the steps shown can be added to Figure 7 any position in the flowchart of Figure 7 Some of the steps shown in

[0154] In Figure 7 the example shown, step S750 determines whether two transform blocks adjacent to a target boundary include non-zero transform coefficient levels. Additionally, when the condition of step S750 is satisfied, the boundary strength corresponding to the target boundary can be determined as a second value (e.g., 1).

[0155] However, when encoding the residual samples of two chrominance components (e.g., the Cb component and the Cr component) as a single transform block, related to the determination of step S750, there may be a problem of inaccurate determination of the boundary strength of the block boundary. For example, in the present disclosure, "joint CbCr residual coding" may refer to a technique of encoding the residual samples of two chrominance components (e.g., the Cb component and the Cr component) as a single transform block. It can be determined whether to apply joint CbCr residual coding to the current block based on the information signaled through the bitstream (e.g., a flag). That is, the image coding device can determine whether to perform joint CbCr residual coding on the current block and encode the flag information as a bitstream based on this. Additionally, the image decoding device can determine whether to perform (has performed) joint CbCr residual coding on the current block by parsing the flag information from the bitstream and reconstruct the current block based on this. For example, in the present disclosure, the flag information can be tu_joint_cbcr_residual_flag.

[0156] Figure 8 is a view showing the signaling of syntax elements in a transform block related to an embodiment of the present disclosure.

[0157] In Figure 8 the example shown, tu_cb_coded_flag[x][y] can specify whether the transform block of the Cb component (hereinafter referred to as "Cb transform block") with the coordinates of the upper left sample being (x, y) includes one or more non-zero transform coefficient levels. For example, tu_cb_coded_flag with a second value (e.g., 1) can specify that the Cb transform block includes one or more non-zero transform coefficient levels. Additionally, tu_cb_coded_flag with a first value (e.g., 0) can specify that the Cb transform block does not include one or more non-zero transform coefficient levels. When tu_cb_coded_flag is the first value, all transform coefficient levels in the Cb transform block can be set to 0. Additionally, when tu_cb_coded_flag does not exist in the bitstream, its value can be inferred as the first value.

[0158] In Figure 8 the example shown, tu_cr_coded_flag[x][y] can specify whether the transform block (hereinafter referred to as "Cr transform block") of the Cr component with the coordinates of the upper left sample being (x, y) includes one or more non-zero transform coefficient levels. For example, tu_cr_coded_flag with a second value (e.g., 1) can specify that the Cr transform block contains one or more non-zero transform coefficient levels. Additionally, tu_cr_coded_flag with a first value (e.g., 0) can specify that the Cr transform block does not include one or more non-zero transform coefficient levels. When tu_cr_coded_flag is the first value, all transform coefficient levels in the Cr transform block can be set to 0. Additionally, when tu_cr_coded_flag does not exist in the bitstream, its value can be inferred as the first value.

[0159] In Figure 8 the example shown, tu_y_coded_flag[x][y] can specify whether the transform block (hereinafter referred to as "luma transform block") of the luma component with the coordinates of the upper left sample being (x, y) includes one or more non-zero transform coefficient levels. For example, tu_y_coded_flag with a second value (e.g., 1) can specify that the luma transform block contains one or more non-zero transform coefficient levels. Additionally, tu_y_coded_flag with a first value (e.g., 0) can specify that the luma transform block does not include one or more non-zero transform coefficient levels. When tu_y_coded_flag is the first value, all transform coefficient levels in the luma transform block can be set to 0. When tu_y_coded_flag does not exist in the bitstream, its value can be inferred as the first value or the second value based on various other syntax elements and / or variables.

[0160] In Figure 8In the example shown, tu_joint_cbcr_residual_flag[x][y] can specify whether the residual samples of the Cb component and the residual samples of the Cr component are coded as a single transform block for a transform block with coordinates (x, y) of the top-left sample. For example, when tu_joint_cbcr_residual_flag is the second value (e.g., 1), the transform unit may include transform coefficient levels for a single transform block, and the residual samples of the Cb component and the Cr component may be derived from the single transform block. Additionally, when tu_joint_cbcr_residual_flag is the first value (e.g., 0), the transform coefficient levels of the chrominance components may be coded / decoded as specified by tu_cb_coded_flag and tu_cr_coded_flag. For example, when tu_cb_coded_flag is 1, the transform coefficient levels of the Cb transform block may be coded / decoded, and when tu_cb_coded_flag is 0, the transform coefficient levels of the Cb transform block may be inferred as 0 without coding / decoding. Similarly, when tu_cr_coded_flag is 1, the transform coefficient levels of the Cr transform block may be coded / decoded, and when tu_cr_coded_flag is 0, the transform coefficient levels of the Cr transform block may be inferred as 0 without coding / decoding. When tu_joint_cbcr_residual_flag is not present in the bitstream, its value may be inferred as the first value.

[0161] As Figure 8 shown in, the transmission of the residual information (transform_skip_flag, residual_coding(), and / or residual_ts_coding()) of each color component (luminance (Y), chrominance (Cb and Cr)) can be determined based on various parameters and / or conditions. As Figure 8 is apparent from, the signaling conditions of the residual information are not limited to tu_y_coded_flag, tu_cb_coded_flag, and tu_cr_coded_ilag. However, in the present disclosure, as the signaling conditions of the residual information, only tu_y_coded_flag, tu_cb_coded_flag, tu_cr_codedflag, and / or some conditions may be mentioned. This is for ease of description, and the signaling conditions of the residual information are not limited thereto. That is, the signaling conditions of the residual information may include Figure 8 all or part of the signaling conditions shown in, or may include Figure 8 additional signaling conditions not shown in. As Figure 8As shown, for example, when tu_y_coded_flag is 1, the residual information of the luminance transform block can be signaled. Similarly, the residual information of the Cb transform block and the Cr transform block can be signaled based on tu_cb_coded_flag and tu_cr_coded_flag.

[0162] However, as Figure 8 shown, the residual information for the Cr transform block can be signaled only when the following conditions are met.

[0163] !(tu_cb_coded_flag && tu_joint_cbcr_residual_flag)

[0164] According to the above conditions, when both tu_cb_coded_flag and tu_joint_cbcr_residual_flag are 1, the residual information of the Cr transform block is not signaled. That is, when both tu_cb_coded_flag and tu_joint_cbcr_residual_flag are 1, although tu_cr_coded_flag is 1, the transform_skip_flag and the residual syntax for the Cr component are not signaled. In this case, all transform coefficient levels in the Cr transform block can be derived as 0.

[0165] In the above example, when tu_cb_coded_flag is 1, the Cb transform block includes at least one non-zero transform coefficient level, and although tu_cr_coded_flag is 1, all transform coefficient levels in the Cr transform block can be derived as 0. Therefore, based on the determination in step S750, the boundary strength of the target boundary of the Cb component can be derived as 1, and the boundary strength of the target boundary of the Cr component can be derived as a value other than 1.

[0166] Therefore, by applying joint CbCr residual coding, the following two problems may occur in the boundary strength determination process.

[0167] First, in step S750, although tu_cr_coded_flag is 1, the boundary strength of the target boundary of the Cr component can also be derived as a value other than 1.

[0168] Second, although tu_cr_coded_flag is 0, when tu_joint_cbcr_flag is 1, the Cr transform block can include one or more non-zero transform coefficient levels. However, in step S750, the boundary strength of the target boundary of the Cr component can also be derived as a value other than 1.

[0169] In the following, various embodiments of an embodiment that is improved by considering the above problems according to the application of joint CbCr residual coding will be described. Figure 7

[0170] Figure 9 FIG. is a flowchart showing a method for determining the boundary strength of a target boundary according to another embodiment of the present disclosure.

[0171] Figure 9 is for improving the boundary strength determination method described with reference to Figure 7 Figure 7 Figure 9 The method and Figure 7 Figure 9 The method may be the same or overlapping. In Figure 7 Figure 9 Figure 7 Figure 9 The steps S710 to S750 of Figure 7 Figure 9 The boundary strength determination method according to

[0172] Specifically, referring to Figure 9 , when the condition of step S950 is not satisfied (S950 is NO), step S960 may be determined. More specifically, it may be determined whether the target boundary is a boundary of a transform block and whether at least one of the following two conditions is satisfied (S960). When the above conditions are satisfied (S960 is YES), the boundary strength corresponding to the target boundary may be determined as a second value (for example, 1).

[0173] -Condition S960-1: The current block is a chrominance Cb component block (for example, cIdx = 1), and sample p 0 or sample q 0 is included in a transform block in which joint CbCr residual coding has been performed (for example, tu_joint_cbcr_residual_flag = 1).

[0174] -Condition S960-2: The current block is a chrominance Cr component block (for example, cIdx = 2), and sample p 0 or sample q 0 is included in a transform block in which joint CbCr residual coding has been performed (for example, tu_joint_cbcr_residual_flag = 1).

[0175] The above conditions S960-1 and S960-2 can be combined into one condition, for example, as follows.

[0176] - S960 combined condition: The current block is a chrominance block (e.g., cIdx > 0), and sample p 0 or sample q 0 is included in a transform block that has performed joint CbCr residual coding (e.g., tu_joint_cbcr_residual_flag = 1).

[0177] Referring to Figure 9 the method for determining the boundary strength bS described is exemplary, and the boundary strength determination method according to the present disclosure is not limited to Figure 9 the example shown. For example, some steps shown in Figure 9 can be omitted, and steps other than those shown in Figure 9 can be added at any position in the flowchart of Figure 9 . Additionally, Figure 9 some steps shown in

[0178] can be executed simultaneously with other steps, or the order of the steps can be changed. For example, since tu_joint_cbcr_residual_flag can mean that at least one of tu_cu_coded_flag or tu_cr_coded_flag is 1, for the Cb transform block or the Cr transform block, the steps in the boundary strength determination method according to Figure 9 can be changed to be omitted.

[0179] According to the boundary strength determination method described with reference to Figure 9 , the above two problems that may occur by applying joint CbCr residual coding can be solved. That is, when joint CbCr residual coding is applied, the boundary strength of the deblocking filter for the transform block boundary can be determined as a non-zero value (e.g., 1).

[0180] Figure 10 is a flowchart showing a method for determining the boundary strength of a target boundary according to another embodiment of the present disclosure.

[0181] Figure 10 is for improving the boundary strength determination method described with reference to Figure 7 , Figure 7 the method of Figure 10 and the method of Figure 7 can be the same or overlapping. In Figure 10 the method of Figure 7 the steps S710 to S740 can respectively correspond to Figure 10Steps S1010 to S1040. Additionally, Figure 7 Steps S760 to S770 can respectively correspond to Figure 10 Steps S1060 to S1070. Repeated descriptions of the corresponding steps will be omitted. Compared with Figure 7 the method of Figure 10 the boundary strength determination method of

[0182] Specifically, referring to Figure 10 , when the condition of step S1040 is not satisfied (S1040 is NO), step S1050 can be determined. Specifically, it can be determined whether the target boundary is the boundary of the transform block and whether at least one of the three conditions described below is satisfied (S1050). When the above conditions are satisfied (S1050 is YES), the boundary strength corresponding to the target boundary can be determined as the second value (for example, 1).

[0183] - Condition S1050-1: The current block is a luminance component block (for example, cIdx = 0), and sample p 0 or sample q 0 is included in the luminance transform block including one or more non-zero transform coefficient levels (for example, tu_y_coded_flag = 1).

[0184] - Condition S1050-2: The current block is a chrominance Cb component block (for example, cIdx = 1), and sample p 0 or sample q 0 is included in the Cb transform block including one or more non-zero transform coefficient levels (for example, tu_cb_coded_flag = 1).

[0185] - Condition S1050-3: The current block is a chrominance Cr component block (for example, cIdx = 2), and sample p 0 or sample q 0 is included in the Cr transform block including one or more non-zero transform coefficient levels (for example, tu_cr_codedflag = 1).

[0186] The method for determining the boundary strength bS described with reference to Figure 10 is exemplary, and the boundary strength determination method according to the present disclosure is not limited to Figure 10 the example shown. For example, some steps shown in Figure 10 can be omitted, and steps other than those shown in Figure 10 can be added to any position of the flowchart of Figure 10 . Additionally, Figure 10Some of the steps shown can be performed simultaneously with other steps, or the order of other steps can be changed.

[0187] According to the boundary strength determination method referred to Figure 10 above, the above two problems that may occur by applying joint CbCr residual coding can be solved. That is, since Figure 10 the method determines whether a transform block includes one or more non-zero transform coefficient levels for each color component, even when applying joint CbCr residual coding, the boundary strength of the deblocking filter for the transform block boundary can be accurately determined.

[0188] Figure 11 is a flowchart showing a method for determining the boundary strength of a target boundary according to another embodiment of the present disclosure.

[0189] Figure 11 is to improve the boundary strength determination method referred to Figure 7 above, Figure 7 the method of Figure 11 and the method of Figure 7 can be the same or overlapping. In Figure 11 the method of Figure 7 and the method of Figure 11 the repetitive description of the same or overlapping steps can be omitted. For example, Figure 7 steps S710 to S740 of Figure 11 can respectively correspond to steps S1110 to S1140 of Figure 7 . In addition, Figure 11 steps S760 to S770 of

[0190] can respectively correspond to steps S1160 to S1170 of Figure 11 . The repetitive description of the corresponding steps will be omitted. Compared with the method of

[0191] -Condition S1150-1: The current block is a luminance component block (e.g., cIdx = 0), and sample p 0 or sample q 0 is included in a luminance transform block including one or more transform coefficient levels (e.g., tu_y_coded_flag = 1).

[0192] -Condition S1150-2: The current block is a chrominance Cb component block (e.g., cIdx = 1), and sample p 0 or sample q 0 is included in a Cb transform block that includes one or more non-zero transform coefficient levels (e.g., tu_cb coded_flag = 1).

[0193] -Condition S1150-3: The current block is a chrominance Cr component block (e.g., cIdx = 2), and sample p 0 or sample q 0 is included in a Cr transform block that includes one or more non-zero transform coefficient levels (e.g., tu_cr_coded_flag = 1).

[0194] -Condition S1150-4: The current block is not a luminance component block (e.g., cIdx ≠ 0), and sample p 0 or sample q 0 is included in a transform block in which joint CbCr residual coding has been performed (e.g., tu_joint_cbcr_residual_flag = 1).

[0195] Reference Figure 11 The method for determining the boundary strength bS described is exemplary, and the boundary strength determination method according to the present disclosure is not limited to Figure 11 the example shown. For example, some steps shown in Figure 11 may be omitted, and steps other than those shown in Figure 11 may be added at any position in the flowchart of Figure 11 . Additionally, Figure 11 some steps shown in

[0196] Figure 11 Figure 11 Figure 11

[0197] Figures 7 to 11 ​​​​​In the described embodiments, the determination of the boundary strength determined based on whether the transform block includes one or more non-zero transform coefficient levels can be variably changed by considering the application of joint CbCr residual coding.

[0198] For example, as described above, when joint CbCr residual coding is applied to at least one of two blocks (P block and Q block) adjacent to the target boundary (tu_joint_cbcr_residual_flag is 1), the boundary strength can be determined as a second value (e.g., 1). Additionally, when at least one of two blocks (P block and Q block) adjacent to the target boundary includes a non-zero transform coefficient level (the coding flag of the corresponding color component is 1), the boundary strength can be determined as a second value (e.g., 1).

[0199] Therefore, according to another embodiment of the present disclosure, the condition of step S750 can be changed as follows.

[0200] For the luminance component (e.g., cIdx = 0), when the sum of the tu_y_coded_flag values of the P block and the Q block is greater than 0, the corresponding boundary strength can be determined as a second value (e.g., 1).

[0201] For the Cb component (e.g., cIdx = 1), when the tu_cb_coded_flag values, tu_joint_cbcr_residual_flag values, tu_cb_coded_flag values, and tu_joint_cbcr_residual_flag values of the P block and the Q block are greater than 0, the corresponding boundary strength can be determined as a second value (e.g., 1).

[0202] For the Cr component (e.g., cIdx = 2), when the tu_cr_coded_flag values, tu_joint_cbcr_residual_flag values, tu_cr_coded_flag values, and tu_joint_cbcr_residual_flag values of the P block and the Q block are greater than 0, the corresponding boundary strength can be determined as a second value (e.g., 1).

[0203] As described above, according to the changed example, when at least one of the P block or the Q block includes a non-zero transform coefficient level or joint CbCr residual coding is applied to at least one of the P block or the Q block, the corresponding boundary strength can be determined as a second value (e.g., 1).

[0204] Figure 12 is a flowchart showing an encoding process based on deblocking filtering according to the present disclosure.

[0205] Refer toFigure 12 An image encoding device can generate a reconstructed picture (S1210). The image encoding device can generate a reconstructed picture by encoding and reconstructing an input image to be encoded.

[0206] The image encoding device can derive deblocking filter related information of the reconstructed picture (S1220).

[0207] As described above, the deblocking filter related information may include a flag specifying whether the deblocking filter is available. Additionally, the deblocking filter related information may include various information for deriving boundary strength. The boundary strength may be derived differently according to the luminance component (Y) and the chrominance components (cb, cr). The target boundaries to which deblocking filtering is applied may be derived separately according to the luminance component (Y) and the chrominance components (cb, cr).

[0208] The image encoding device can generate a modified reconstructed picture by applying deblocking filtering to the reconstructed picture based on the derived deblocking filter related information (S1230). The modified reconstructed picture may be sent to the memory 170 and may be used as a reference picture in the inter-frame prediction unit 180. The DPB in the memory 170 may store the modified reconstructed picture to be used as a reference picture for inter-frame prediction.

[0209] The image encoding device can encode the image data including the deblocking filter related information (S1240). For example, the deblocking filter related information may be sent to the entropy encoder 190 and encoded by the entropy encoder 190, and output in the form of a bitstream.

[0210] Figure 13 is a flowchart showing a decoding process based on deblocking filtering according to the present disclosure.

[0211] Referring to Figure 13 the image decoding device can obtain image data including deblocking filter related information from the bitstream (S1310).

[0212] Figure 3 the image decoding device 200 can receive a signal output in the form of a bitstream from Figure 2 the image encoding device 100. The entropy decoder 210 can obtain information (e.g., video / image information) required for image reconstruction (or picture reconstruction) by parsing the bitstream.

[0213] The image decoding device can generate a reconstructed picture based on the obtained image information (S1320).

[0214] For example, Figure 3The adder 235 of the image decoding device 200 can generate a reconstructed picture by adding the obtained residual signal to the prediction signal (prediction block, prediction sample array) output from the prediction unit (inter-frame prediction unit 260 and / or intra-frame prediction unit 265).

[0215] The image decoding device can generate a modified reconstructed picture by applying deblocking filtering to the reconstructed picture (S1330).

[0216] Figure 3 The filter 240 of the image decoding device 200 can improve the subjective / objective image quality by applying filtering to the reconstructed picture. For example, the filter 240 can generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture. The modified reconstructed picture can be stored in the memory 250, specifically, in the DPB of the memory 250. 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.

[0217] Although for clarity of description, the above exemplary methods of the present disclosure are represented as a series of operations, it is not intended to limit the order of execution of the steps, and these steps can be executed simultaneously or in a different order when necessary. To implement the method according to the present invention, the described steps may further include other steps, may include the remaining steps except for some steps, or may include other additional steps except for some steps.

[0218] 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 the execution conditions or circumstances of the corresponding operation (step). For example, in the case where it is described that a predetermined operation is performed when a predetermined condition is satisfied, the image encoding device or the image decoding device may perform the predetermined operation after determining whether the predetermined condition is satisfied.

[0219] 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 the matters described in the various embodiments can be applied independently or in combinations of two or more.

[0220] The various embodiments of the present disclosure can be implemented in hardware, firmware, software, or a combination thereof. In the case where the present disclosure is implemented by hardware, the present disclosure can be implemented by 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.

[0221] In addition, the image decoding device and the image encoding device according to the embodiments of the present disclosure may be included in a multimedia broadcast transmission and reception device, a mobile communication terminal, a home theater video device, a digital cinema 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 providing device, an over-the-top (OTT) video device, an Internet streaming service providing device, a three-dimensional (3D) video device, a video phone video device, a medical video device, etc., and may be used to process video signals or data signals. For example, the 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.

[0222] Figure 15 is a view showing a content stream system to which the embodiments of the present disclosure can be applied.

[0223] As Figure 15 shown, the content stream 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.

[0224] The encoding server compresses the content input from a multimedia input device such as a smart phone, a camera, a video camera, etc. into digital data to generate a bitstream and sends the bitstream to the streaming server. As another example, when a multimedia input device such as a smart phone, a camera, a video camera, etc. directly generates a bitstream, the encoding server may be omitted.

[0225] The bitstream may be generated by the image encoding method or the image encoding device according to the embodiments of the present disclosure, and the streaming server may temporarily store the bitstream during the process of sending or receiving the bitstream.

[0226] The streaming server sends multimedia data to the user device based on a request from the user through the network server, and the network server serves as a medium for informing the user of the service. When the user requests a required service from the network server, the network server may deliver it to the streaming server, and the streaming server may send the multimedia data to the user. In this case, the content stream system may include a separate control server. In this case, the control server is used to control commands / responses between the devices in the content stream system.

[0227] The streaming server may receive content from the media storage device and / or the encoding server. For example, when receiving content from the 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 for a predetermined time.

[0228] Examples of user devices may include mobile phones, smartphones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, head-mounted displays), digital TVs, desktop computers, digital signage, and the like.

[0229] Each server in the content streaming system may operate as a distributed server, in which case the data received from each server may be distributed.

[0230] The scope of the present disclosure includes software or machine-executable commands (e.g., operating systems, applications, firmware, programs, etc.) for enabling the operation of methods according to various embodiments to be executed on a device or computer, and non-transitory computer-readable media having such software or commands stored thereon and executable on the device or computer.

[0231] Industrial Applicability

[0232] Embodiments of the present disclosure may be used to encode or decode images.

Claims

1. An image decoding method performed by an image decoding device, the image decoding method comprises the following steps: Obtain a reconstructed image; Determine a target boundary of deblocking filtering in the reconstructed image; Determine a boundary strength of the target boundary; and Apply deblocking filtering to the target boundary based on the boundary strength, wherein, based on that the target boundary is a transform block boundary and a color component of the reconstructed image is a chrominance component, the boundary strength is determined based on whether at least one of two blocks adjacent to the target boundary includes non-zero transform coefficients and whether joint CbCr residual coding is performed on at least one of the two blocks adjacent to the target boundary.

2. The image decoding method according to claim 1, wherein, Based on that the target boundary is a transform block boundary and a color component of the reconstructed image is a chrominance component, it is determined that the boundary strength is equal to 1 based on that at least one of the two blocks adjacent to the target boundary includes non-zero transform coefficients and joint CbCr residual coding is performed on at least one of the two blocks adjacent to the target boundary.

3. The image decoding method according to claim 1, further comprises: Parse a bitstream to obtain a first flag, a second flag, a third flag, and a fourth flag, wherein, the first flag specifies whether a first block of the two blocks includes non-zero transform coefficients, the second flag specifies whether a second block of the two blocks includes non-zero transform coefficients, the third flag specifies whether joint CbCr residual coding is performed on the first block, and the fourth flag specifies whether joint CbCr residual coding is performed on the second block.

4. The image decoding method according to claim 1, wherein, Based on that the target boundary is a transform block boundary and a color component of the reconstructed image is a luminance component, the boundary strength is determined based on whether at least one of the two blocks adjacent to the target boundary includes non-zero transform coefficients.

5. An image encoding method performed by an image encoding device, the image encoding method comprises the following steps: Generate a reconstructed image; Determine a target boundary of deblocking filtering in the reconstructed image; Determine a boundary strength of the target boundary; and Apply deblocking filtering to the target boundary based on the boundary strength, wherein, based on that the target boundary is a transform block boundary and a color component of the reconstructed image is a chrominance component, the boundary strength is determined based on whether at least one of two blocks adjacent to the target boundary includes non-zero transform coefficients and whether joint CbCr residual coding is performed on at least one of the two blocks adjacent to the target boundary.

6. The image encoding method according to claim 5, wherein, Based on that the target boundary is a transform block boundary and a color component of the reconstructed image is a chrominance component, it is determined that the boundary strength is equal to 1 based on that at least one of the two blocks adjacent to the target boundary includes non-zero transform coefficients and joint CbCr residual coding is performed on at least one of the two blocks adjacent to the target boundary.

7. The image encoding method according to claim 5, further Comprising: Generating a first flag, a second flag, a third flag, and a fourth flag, wherein the first flag specifies whether the first of the two blocks includes non-zero transform coefficients, the second flag specifies whether the second of the two blocks includes non-zero transform coefficients, the third flag specifies whether joint CbCr residual coding is performed on the first block, and the fourth flag specifies whether joint CbCr residual coding is performed on the second block.

8. The image coding method according to claim 5, wherein Based on the target boundary being a transform block boundary and the color component of the reconstructed image being a luminance component, the boundary strength is determined based on whether at least one of the two blocks adjacent to the target boundary includes non-zero transform coefficients.

9. An image decoding device, Comprising: A memory storing machine-executable instructions thereon; And At least one processor, wherein the at least one processor is configured to execute the machine-executable instructions to implement the image decoding method according to any one of claims 1-4.

10. An image coding device, the image coding device Comprising: A memory storing machine-executable instructions thereon; And At least one processor, wherein the at least one processor is configured to execute the machine-executable instructions to implement the image coding method according to any one of claims 5-8.

11. A computer-readable storage medium storing a bitstream, wherein The bitstream is decoded according to the image decoding method according to any one of claims 1-4, or the bitstream is generated according to the image coding method according to any one of claims 5-8.

Images