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 boundary strength, and a method of transmitting a bit stream generated by the image encoding method / apparatus of the present disclosure. Background Art

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

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

[0004] Technical issues

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

[0006] Another object of the present disclosure is to provide an 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 in order to perform deblocking filtering.

[0008] Another object of the present disclosure is to provide a method for transmitting a bit stream generated by the 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 bit stream generated by the 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 bit stream received and decoded by the image decoding apparatus according to the present disclosure and used to reconstruct an image.

[0011] The technical problems solved by the present disclosure are not limited to the above-mentioned technical problems, and other technical problems not described here will be clear to those skilled in the art through the following description.

[0012] Technical Solution

[0013] According to an aspect of the present disclosure, an image decoding method is performed by an image decoding device. The image decoding method includes: obtaining a reconstructed picture; determining a target boundary of 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 fact that the target boundary is a transform block boundary and the color component of the reconstructed picture is a chroma component, the boundary strength can 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 coding can correspond to encoding residual samples of the chroma Cb component and the chroma Cr component into 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 the adjacent block.

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

[0017] In the image decoding 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.

[0018] In the image decoding method according to the present disclosure, the boundary strength may be determined to be 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 the color component of the reconstructed picture being a luminance component, the boundary strength can be determined based on whether at least one of two blocks adjacent to the target boundary includes a non-zero transform coefficient level.

[0020] According to another embodiment of the present disclosure, an image decoding device may include a memory and at least one processor. The at least one processor may obtain a reconstructed picture, determine a target boundary of 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 fact that the target boundary is a transform block boundary and the color component of the reconstructed picture 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 coding may correspond to encoding residual samples of the chroma Cb component and the chroma Cr component into a single transform block.

[0021] According to another aspect of the present disclosure, an image encoding method may include the following steps: generating a reconstructed picture, determining a target boundary of 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 chroma component, the boundary strength may be determined based on whether joint CbCr residual encoding is performed on at least one of 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.

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

[0023] In the image encoding method according to the present disclosure, based on the fact that the target boundary is a transform block boundary and the color component of the reconstructed picture is a chrominance component, the boundary strength can also be determined based on whether at least one of the 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, whether a block adjacent to the target boundary includes at least one non-zero transform coefficient level may be determined based on a second flag signaled for the 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, the boundary strength may be determined to be 1 based on the sum being greater than 0.

[0027] A transmission method according to another aspect of the present disclosure may transmit a bit stream generated by the image encoding apparatus or the image encoding method of the present disclosure.

[0028] A computer-readable recording medium according to another aspect of the present disclosure may store a bit stream generated by the image encoding apparatus or the image encoding method of the present disclosure.

[0029] The features briefly summarized above with respect to the present disclosure are merely exemplary aspects of the following detailed description of the present disclosure and do not limit the scope of the present disclosure.

[0030] Beneficial Effects

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

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

[0033] According to the present disclosure, an image encoding / decoding method and apparatus for determining a boundary strength of deblocking filtering in order to perform deblocking filtering may be provided.

[0034] Furthermore, according to the present disclosure, it is possible to provide a method of transmitting a bit stream generated by the image encoding method or apparatus according to the present disclosure.

[0035] Furthermore, according to the present disclosure, it is possible to provide a recording medium storing a bit stream generated by the image encoding method or apparatus according to the present disclosure.

[0036] Furthermore, according to the present disclosure, it is possible to provide a recording medium that stores a bit stream received and decoded by the image decoding device according to the present disclosure and used to reconstruct an image.

[0037] Those skilled in the art will understand that the effects that can be achieved through the present disclosure are not limited to what has been specifically described above, and other advantages of the present disclosure will be more clearly understood from the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0043] Figure 6 is a flow chart illustrating deblocking filtering according to the present disclosure.

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

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

[0046] Fig. 9 is a flowchart illustrating a method of determining a boundary strength of a target boundary according to another embodiment of the present disclosure.

[0047] Fig.10 is a flowchart illustrating a method of determining a boundary strength of a target boundary according to another embodiment of the present disclosure.

[0048] Fig.11 is a flowchart illustrating a method of determining a boundary strength of a target boundary according to another embodiment of the present disclosure.

[0049] Fig.12 is a flow chart illustrating a deblocking filtering based encoding process according to the present disclosure.

[0050] Fig.13 is a flow chart illustrating a decoding process based on deblocking filtering according to the present disclosure.

[0051] Fig.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.

[0052] Fig.15 is a diagram showing a content streaming system to which an embodiment of the present disclosure can be applied. DETAILED DESCRIPTION

[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 may be implemented in various different forms and is not limited to the embodiments described herein.

[0054] When describing the present disclosure, if it is determined that the detailed description of related known functions or configurations makes the scope of the present disclosure unnecessarily vague, the detailed description thereof will be omitted. In the accompanying drawings, parts irrelevant to the description of the present disclosure are omitted, and similar reference numerals are attached to similar 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. In addition, when a component "includes" or "has" other components, unless otherwise specified, it means that other components may also be included, rather than excluding other components.

[0056] In the present disclosure, the terms first, second, etc. are used only for the purpose of distinguishing one component from other components, and do not limit the order or importance of the components unless otherwise specified. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

[0057] In the present disclosure, components that are distinguished from each other are intended to clearly describe each feature and do not mean that the components must be separated. That is, multiple components can be integrated and implemented in one hardware or software unit, or one component can be distributed and implemented in multiple hardware or software units. Therefore, even if not specifically stated, implementations in which these components are integrated or distributed are also included in the scope of the present disclosure.

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

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

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

[0061] In the present disclosure, "pixel" or "pel" may refer to the smallest unit constituting a picture (or image). In addition, "sample" may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, or may represent only a pixel / pixel value of a luminance component or only a pixel / pixel value of a chrominance component.

[0062] In the present disclosure, a "unit" may refer to a basic unit of image processing. The unit may include at least one of a specific area of ​​a picture and information related to the area. In some cases, the unit may be used interchangeably with terms such as "sample array", "block" or "area". In general, an M×N block may include M columns and N rows of samples (or sample arrays) or a set (or array) of transform coefficients.

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

[0064] In addition, in the present disclosure, unless explicitly stated as a chroma block, "current block" may mean "luminance block of the current block." "Chroma block of the current block" may be expressed by including an explicit description of a chroma block such as "chroma block" or "current chroma 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 Video Coding Systems

[0068] Figure 1 is a diagram schematically illustrating a video encoding system according to the present disclosure.

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

[0070] The encoding device 10 according to the embodiment may include a video source generator 11, an encoding unit 12, and a transmitter 13. The decoding device 20 according to the embodiment may include a receiver 21, a decoding unit 22, and a renderer 23. The encoding unit 12 may be called a video / image encoding unit, and the decoding unit 22 may be called 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 can obtain the video / image by the process of capturing, synthesizing or generating the video / image. The video source generator 11 may include a video / image capturing device and / or a video / image generating device. The video / image capturing device may include, for example, one or more cameras, a video / image archive including previously captured videos / images, etc. The video / image generating device may include, for example, a computer, a tablet computer, and a smart phone, and may generate the video / image (electronically). For example, a virtual video / image may be generated by a computer, etc. In this case, the video / image capturing process may be replaced by a process of generating relevant data.

[0072] The encoding unit 12 may encode the input video / image. For compression and encoding efficiency, the encoding unit 12 may perform a series of processes such as prediction, transformation, and quantization. The encoding unit 12 may output encoded data (encoded video / image information) in the form of a bitstream.

[0073] The transmitter 13 transmits the encoded video / image information or data output in the form of a bit stream to the receiver 21 of the decoding device 20 in the form of a file or stream through a digital storage medium or a network. The digital storage medium may include various storage media, such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmitter 13 may include an element for generating a media file in a predetermined file format and may include an element for transmission through a broadcast / communication network. The receiver 21 may extract / receive a bit stream from a storage medium or a network and transmit the bit stream to the decoding unit 22.

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

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

[0076] Overview of Image Coding Equipment

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

[0078] like Figure 2 As shown, the image encoding device 100 may include an image segmenter 110, a subtractor 115, a transformer 120, a quantizer 130, a dequantizer 140, an inverse transformer 150, an adder 155, a filter 160, a memory 170, an inter-frame prediction unit 180, an intra-frame prediction unit 185, and an entropy encoder 190. The inter-frame prediction unit 180 and the intra-frame prediction unit 185 may be collectively referred to as a "prediction unit". The transformer 120, the quantizer 130, the dequantizer 140, and the inverse transformer 150 may be included in a residual processor. The residual processor may also include a subtractor 115.

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

[0080] The image segmenter 110 may segment the input image (or picture or frame) input to the image encoding device 100 into one or more processing units. For example, the processing unit may be referred to as a coding unit (CU). The coding unit may be obtained by recursively segmenting a coding tree unit (CTU) or a maximum coding unit (LCU) according to a quadtree binary tree ternary tree (QT / BT / TT) structure. For example, a coding unit may be segmented into a plurality of coding units of a deeper depth based on a quadtree structure, a binary tree structure, and / or a ternary tree structure. For the segmentation of the coding unit, the quadtree structure may be applied first, and 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 segmented. The maximum coding unit may be used as the final coding unit, and the coding unit of a deeper depth obtained by segmenting the maximum coding unit may also be used as the final coding unit. Here, the encoding process may include the prediction, transformation, and reconstruction processes described later. As another example, the processing unit of the encoding process may be a prediction unit (PU) or a transformation unit (TU). The prediction unit and the transform unit may be divided or partitioned from the final coding unit. The prediction unit may be a sample prediction unit, and the transform unit may be a unit for deriving a transform coefficient and / or a unit for deriving a residual signal from the transform coefficient.

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

[0082] The intra prediction unit 185 can predict the current block by referring to the samples in the current picture. Depending on the intra prediction mode and / or the intra prediction technology, the reference samples can be located in the neighbors of the current block or can be placed separately. The intra prediction mode may include multiple non-directional modes and multiple directional modes. The non-directional mode may include, for example, a DC mode and a plane mode. Depending on the level of detail of the prediction direction, the directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes. However, this is only an example, and more or fewer directional prediction modes may be used according to the settings. The intra prediction unit 185 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0083] The inter prediction unit 180 may derive a prediction block of the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. In this case, in order to reduce the amount of motion information 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 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 inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring blocks may include spatial neighboring blocks present in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be referred to as a collocated reference block, a collocated CU (colCU), etc. The reference picture including the temporal neighboring block may be referred to as a collocated picture (colPic). For example, the inter prediction unit 180 may configure a motion information candidate list based on the neighboring blocks and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter prediction may be performed based on various prediction modes. For example, in the case of skip mode and merge mode, the inter prediction unit 180 may use the motion information of the neighboring block as the motion information of the current block. In the case of skip mode, unlike the merge mode, the residual signal may not be transmitted. In the case of motion vector prediction (MVP) mode, the motion vector of the neighboring block may be used as a motion vector predictor, and the motion vector of the current block may signal the motion vector of the current block by encoding the motion vector difference and the 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 prediction or inter prediction, but may also apply intra prediction and inter prediction simultaneously to predict the current block. The prediction method of applying both intra prediction and inter prediction simultaneously to predict the current block may be referred to as combined inter and intra prediction (CIIP). In addition, the prediction unit may perform intra block copying (IBC) to predict the current block. Intra block copying may be used for content image / video encoding of games, etc., such as screen content coding (SCC). IBC is a method of predicting the current picture using a previously reconstructed reference block in the current picture at a position separated by a predetermined distance from the current block. When IBC is applied, the position of the reference block in the current picture may be encoded as a vector (block vector) corresponding to a predetermined distance. In IBC, prediction is basically performed in the current picture, but prediction may be performed similarly to inter prediction because the reference block is derived within the current picture. That is, IBC may use at least one of the inter prediction techniques described in the present disclosure.

[0085] The prediction signal generated by the prediction unit can be used to generate a reconstruction signal or to generate a residual signal. The subtractor 115 can generate a residual signal (residual block or residual sample array) by subtracting the prediction signal (prediction block or prediction sample array) output from the prediction unit from the input image signal (original block or original sample array). The generated residual signal can be transmitted to the transformer 120.

[0086] The transformer 120 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technique may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a karhunen-loève transform (KLT), a graph-based transform (GBT), or a conditional nonlinear transform (CNT). Here, GBT refers to a transform obtained from a graph when relationship information between pixels is represented by a graph. CNT refers to a transform obtained based on a prediction signal generated using all previously reconstructed pixels. In addition, the transform process may be applied to square pixel blocks of the same size or may be applied to blocks of variable size rather than square.

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

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

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

[0090] The quantized transform coefficients output from the quantizer 130 may be used to generate a residual signal. For example, the residual signal (residual block or residual sample) may be reconstructed by applying dequantization and inverse transformation to the quantized transform coefficients through the dequantizer 140 and the inverse transformer 150.

[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 the block to be processed has no residual, such as when the skip mode is applied, the prediction block can be used as a reconstructed block. The adder 155 can be called a reconstructor or a reconstructed block generator. The generated reconstructed signal can be used for intra-frame prediction of the next block to be processed in the current picture, and can be used for inter-frame prediction of the next picture by filtering as described below.

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

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

[0094] The DPB of the memory 170 may store the modified reconstructed picture for use as a reference picture in the inter-frame prediction unit 180. The memory 170 may store the motion information of the block from which the motion information in the current picture is derived (or encoded) and / or the motion information of the reconstructed block in the picture. The stored motion information may be transmitted to the inter-frame prediction unit 180 and used as the motion information of the spatial neighboring block or the motion information of the temporal neighboring block. The memory 170 may store the reconstructed samples of the reconstructed blocks in the current picture and may transmit the reconstructed samples to the intra-frame prediction unit 185.

[0095] Overview of Image Decoding Equipment

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

[0097] like Figure 3 As shown, the image decoding device 200 may include an entropy decoder 210, a dequantizer 220, an inverse transformer 230, an adder 235, a filter 240, a memory 250, an inter-frame prediction unit 260, and an intra-frame prediction unit 265. The inter-frame prediction unit 260 and the intra-frame prediction unit 265 may be collectively referred to as a "prediction unit". The dequantizer 220 and the inverse transformer 230 may be included in a residual processor.

[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 (eg, a decoder or a processor). In addition, the memory 250 may include a decoded picture buffer (DPB) or may be configured by a digital storage medium.

[0099] The image decoding device 200 having received a bit stream including video / image information may perform the same Figure 2 The image encoding device 100 may reconstruct the image by processing corresponding to the processing performed by the image encoding device 100. For example, the image decoding device 200 may perform decoding using a processing unit applied in the image encoding device. Therefore, the processing unit of decoding may be, for example, a coding unit. The coding unit may be obtained by partitioning the coding tree unit or the maximum coding unit. The reconstructed image signal decoded and output by the image decoding device 200 may be reproduced by a reproduction device (not shown).

[0100] The image decoding device 200 may receive the image in the form of a bit stream from Figure 2The received signal may be decoded by the entropy decoder 210. For example, the entropy decoder 210 may parse the bitstream to derive information (e.g., video / image information) required for image reconstruction (or picture reconstruction). The video / image information may also include information about various parameter sets, such as an adaptive parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may also include general constraint information. The image decoding device may also decode the picture based on the information about the parameter set and / or the general constraint information. The signaled / received information and / or syntax elements described in the present disclosure may be decoded and obtained from the bitstream through a decoding process. For example, the entropy decoder 210 may decode the information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and output the values ​​of the syntax elements required for image reconstruction and the quantized values ​​of the transform coefficients of the residual. More specifically, the CABAC entropy decoding method can receive a bin corresponding to each syntax element in the bitstream, use the decoding target syntax element information, the decoding information of the neighboring block and the decoding target block, or the information of the symbol / bin decoded in the previous stage to determine the context model, perform arithmetic decoding on the bin by predicting the probability of occurrence of the bin according to the determined context model, and generate a symbol corresponding to the value of each syntax element. In this case, the CABAC entropy decoding method can update the context model by using the information of the decoded symbol / bin for the context model of the next symbol / bin after determining the context model. The information related to the prediction in the information decoded by the entropy decoder 210 can be provided to the prediction unit (inter-frame prediction unit 260 and intra-frame prediction unit 265), and the residual value of the entropy decoding performed on it in the entropy decoder 210, that is, the quantized transform coefficient and the related parameter information can be input to the dequantizer 220. In addition, the information about filtering in the information decoded by the entropy decoder 210 can be provided to the filter 240. In addition, a receiver (not shown) for receiving a signal output from the image encoding apparatus may be further configured as an internal / external element of the image decoding apparatus 200 , or the receiver may be a component of the entropy decoder 210 .

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

[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 scanning order performed in the image encoding device. The dequantizer 220 may dequantize the quantized transform coefficients by using a quantization parameter (e.g., quantization step size information) and obtain the transform coefficients.

[0103] The inverse transformer 230 may inversely transform 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 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] The same as described in the prediction unit of the image encoding device 100 , the prediction unit can generate a prediction signal based on various prediction methods (techniques) described later.

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

[0107] The inter-frame prediction unit 260 can derive the prediction block of the current block based on the reference block (reference sample array) specified by the motion vector on the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter-frame prediction mode, the motion information can be predicted in units of blocks, sub-blocks or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may also include inter-frame prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter-frame prediction, the neighboring blocks may include spatial neighboring blocks existing in the current picture and temporal neighboring blocks existing in the reference picture. For example, the inter-frame prediction unit 260 may configure a motion information candidate list based on the neighboring blocks, and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter-frame prediction may be performed based on various prediction modes, and information about the prediction may include information indicating the inter-frame prediction mode of the current block.

[0108] The adder 235 can generate a reconstruction signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the obtained residual signal to the prediction signal (prediction block, prediction sample array) output from the prediction unit (including the inter-frame prediction unit 260 and / or the intra-prediction unit 265). The description of the adder 155 is also 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 a reconstructed block. The description of the adder 155 is also applicable to the adder 235. The adder 235 can be referred to as a reconstructor or a reconstructed block generator. The generated reconstruction signal can be used for intra-frame prediction of the next block to be processed in the current picture, and can be used for inter-frame prediction of the next picture through 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 may 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 may be used as a reference picture in the inter-frame prediction unit 260. The memory 250 may store the motion information of the block from which the motion information in the current picture is derived (or decoded) and / or the motion information of the reconstructed block in the picture. The stored motion information may be transmitted to the inter-frame prediction unit 260 to be used as the motion information of the spatial neighboring block or the motion information of the temporal neighboring block. The memory 250 may store the reconstructed samples of the reconstructed block in the current picture and transmit the reconstructed samples to the intra-frame prediction unit 265.

[0111] In the present disclosure, the implementations 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 4is a schematic flowchart of an image decoding process to which embodiments of the present disclosure may be applied.

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

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

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

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

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

[0120] By such an in-loop filtering process, noise (e.g., block effect and ringing effect) occurring during video / image encoding can be reduced, and subjective / objective visual quality can be improved. In addition, by performing the in-loop filtering process in both the image encoding device and the image decoding device, the image encoding device and the image decoding device can derive the same prediction result, the picture encoding reliability can be increased, and the amount of data to be 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. A reconstructed block can be generated based on intra prediction / inter prediction in block units, and a reconstructed picture including the reconstructed block can be generated. When the current picture / slice / tile group is an I picture / slice / tile group, the blocks included in the current picture / slice / tile group can be reconstructed based only on intra 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 the picture may include a luminance component and a chrominance component, and unless explicitly limited in the present disclosure, the methods and embodiments of the present disclosure may be applied to both luminance components and chrominance components.

[0122] Figure 6 is a flow chart illustrating deblocking filtering according to the present disclosure. Figure 6 The deblocking filtering shown may correspond to the deblocking filtering of the in-loop filtering described above. Figure 6 The deblocking filter shown can be, for example, Figure 2 Filter 160 or Figure 3 The filter 240 is executed.

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

[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, the vertical edges can be filtered (horizontal filtering). Thereafter, the horizontal edges can be filtered (vertical filtering). Deblocking filtering can be applied to all coding block (or sub-block) edges and transform block edges.

[0125] As described above, the in-loop filtering may include SAO. SAO may correspond to a method of compensating the offset difference between the reconstructed picture and the original picture in units of samples. 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 filter 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 deblocking filtering is applied.

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

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

[0128] Fig.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] exist Fig.14 , the boundary indicated by the thick solid line may be a target boundary for deblocking filtering.

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

[0131] In the present disclosure, the samples in a P block may be represented by p n Represented by, and the samples in the Q block can be represented by q n In other words, p n and q nmay 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 a distance from the target boundary. p0 may be a sample in a P block adjacent to the target boundary, and q0 may represent a sample in a Q block adjacent to the target boundary. For example, p0 may be a sample of a left block or an upper block adjacent to the target boundary, and q0 may be a sample of a right block or a lower block adjacent to the target boundary. Alternatively, as Fig.14 As shown in , the samples in P block can be represented by p n，m Represented by, 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 may represent a distance from a target boundary. In addition, m may be an index for distinguishing samples located at the same distance from a target boundary in one block (P block or Q block).

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

[0133] The image encoding device and the image decoding device may perform deblocking filtering based on boundary strength. For example, when the boundary strength is a first value (e.g., 0), no filtering may be applied to the corresponding target boundary. Deblocking filtering may be applied based on filter strength (strong filter / weak filter) and / or filter length.

[0134] In the present disclosure, deblocking filtering can be performed by obtaining information related to deblocking filtering from a bitstream. For example, the information related to deblocking filtering can include a flag that specifies whether deblocking filtering is available. In addition, the information related to deblocking filtering can include information for deriving 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)). In addition, 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. In addition, 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 illustrating a method of determining a boundary strength of a target boundary according to an embodiment of the present disclosure.

[0137] Reference Figure 7, it can be determined whether the current block is a luminance component block (e.g., cIdx=0) and whether both samples p0 and q0 are included in a coding 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 met (S710 is yes), the boundary strength of the corresponding target boundary can be determined as a first value (e.g., 0).

[0138] When the condition of step S710 is not satisfied (S710 is no), step S720 may be determined. Specifically, it may be determined whether the current block is a chroma component block (e.g., cIdx>0) and whether both samples p0 and q0 are included in a coding block to which BDPCM is applied (e.g., intra_bdpcm_chroma_flag=1) (S720). When the above condition is satisfied (S720 is yes), the boundary strength of the corresponding target boundary may be determined as a first value (e.g., 0).

[0139] When the condition of step S720 is not met (S720 is no), step S730 may be determined. Specifically, it may be determined that sample p0 or sample q0 is included in a coding block encoded in an intra prediction mode (S730). When the above condition is met (S730 is yes), the boundary strength of the corresponding target boundary may be determined as a third value (e.g., 2).

[0140] When the condition of step S730 is not met (S730 is no), step S740 may be determined. Specifically, it may be determined whether the target boundary is a boundary of a coding block and whether sample p0 or sample q0 is included in a coding block to which combined inter-frame and intra-frame prediction (CIIP) is applied (e.g., ciip_flag=1) (S740). When the above condition is met (S740 is yes), the boundary strength of the corresponding target boundary may be determined as a third value (e.g., 2).

[0141] When the condition of step S740 is not satisfied (S740 is no), step S750 may be determined. Specifically, it may be determined whether the target boundary is a boundary of a transform block and whether sample p0 or sample q0 is included in a transform block having one or more non-zero transform coefficient levels (S750). When the above condition is satisfied (S750 is yes), the boundary strength corresponding to the target boundary may be determined as a second value (e.g., 1).

[0142] When the condition of step S750 is not satisfied (S750 is no), step S760 may be determined. Specifically, it may be determined whether the prediction mode of the coding subblock containing sample p0 and the prediction mode of the coding subblock containing sample q0 are different (S760). When the above condition is satisfied (S760 is yes), the boundary strength of the corresponding target boundary may be determined as a second value (e.g., 1). For example, when one of the two coding subblocks located on both sides of the target boundary is encoded in the IBC prediction mode and the other is encoded in the inter-frame prediction mode, the boundary strength of the corresponding target boundary may be determined as a second value (e.g., 1).

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

[0144] - Condition 1: Both the coded subblock containing sample p0 and the coded subblock containing sample q0 are encoded in IBC prediction mode, and the difference between the horizontal component or the vertical component of the block vector of each subblock is greater than or equal to an 8-unit value in units of 1 / 16 luma samples.

[0145] - Condition 2: The coding subblock containing sample p0 and the coding subblock containing sample q0 refer to different reference pictures or have different numbers of motion vectors. In condition 2, whether the reference pictures are the same is determined by considering only whether the pictures referenced for inter-frame prediction are the same, and whether the corresponding reference pictures belong to reference picture list 0 or reference picture list 1 is not considered. In addition, whether the index values ​​specifying the corresponding reference pictures are the same is not considered. In addition, the number of motion vectors can be determined using the prediction direction flag (PredFlagL0, PredFlagL1) value. For example, the number of motion vectors can be derived as PredFlagL0+PredFlagL1.

[0146] - Condition 3: A motion vector is used to predict a coding subblock containing sample p0 and a coding subblock containing sample q0, and the difference between the horizontal component or the vertical component of the motion vector of each subblock can be greater than or equal to an 8-unit value in units of 1 / 16 luma samples.

[0147] -Condition 4: Two motion vectors and two different reference pictures are used to predict a coding subblock including the same p0, and two motion vectors and two same reference pictures are used to predict a coding subblock including sample q0, and the difference between the horizontal component or the vertical component of the motion vector 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: Two motion vectors of the same reference picture are used to predict the coded subblock containing sample p0, two motion vectors of the same reference picture are used to predict the coded subblock containing sample q0, and the following two conditions (Condition 5-1 and Condition 5-2) are met.

[0149] -Condition 5-1: The difference between the horizontal component or the vertical component of the list 0 motion vector used to predict each coding 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 component or the vertical component of the list 1 motion vector used to predict each coding 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 component or the vertical component between the list 0 motion vector used to predict the coding subblock including subblock p0 and the list 1 motion vector used to predict the coding subblock including sample q0 can be greater than or equal to 8 unit values ​​in units of 1 / 16 luma samples, or the difference between the horizontal component or the vertical component between the list 1 motion vector used to predict the coding subblock including subblock p0 and the list 0 motion vector used to predict the coding subblock including sample q0 can be greater than or equal to 8 unit values ​​in units of 1 / 16 luma samples.

[0151] In the above-mentioned Conditions 1 to 5, the difference between the vertical (or horizontal) components of the motion vectors may 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 : No), the boundary strength corresponding to the target boundary may be determined as a first value (eg, 0).

[0153] Reference 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 For example, you can omit Figure 7 In addition to the steps shown in Figure 7 Steps other than those shown may be added to Figure 7 In addition, Figure 7 Some of the steps shown in the drawings may be performed simultaneously with other steps, or the order of the steps may be changed.

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

[0155] However, when the residual samples of two chrominance components (e.g., Cb component and Cr component) are encoded as a single transform block, in relation to the determination of step S750, a problem of inaccurate determination of the boundary strength of the block boundary may occur. For example, in the present disclosure, "joint CbCr residual encoding" may mean a technique of encoding the residual samples of two chrominance components (e.g., Cb component and Cr component) as a single transform block. Whether joint CbCr residual encoding is applied for the current block may be determined based on information (e.g., a flag) signaled by a bitstream. That is, the image encoding device may determine whether joint CbCr residual encoding is performed on the current block, and based on this, encode the flag information into a bitstream. In addition, the image decoding device may determine whether joint CbCr residual encoding is performed (has been performed) 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 may be tu_joint_cbcr_residual_flag.

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

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

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

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

[0160] exist Figure 8In the example shown, tu_joint_cbcr_residual_flag[x][y] may specify whether the residual samples of the Cb component and the residual samples of the Cr component are encoded as a single transform block for a transform block whose coordinates of the upper left sample are (x, y). For example, when tu_joint_cbcr_residual_flag is a 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. In addition, when tu_joint_cbcr_residual_flag is a first value (e.g., 0), the transform coefficient levels of the chroma components may be encoded / 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 level of the Cb transform block can be encoded / decoded, and when tu_cb_coded_flag is 0, the transform coefficient level of the Cb transform block can be inferred to be 0 without encoding / decoding. Similarly, when tu_cr_coded_flag is 1, the transform coefficient level of the Cr transform block can be encoded / decoded, and when tu_cr_coded_flag is 0, the transform coefficient level of the Cr transform block can be inferred to be 0 without encoding / decoding. When tu_joint_cbcr_residual_flag is not present in the bitstream, its value can be inferred to be the first value.

[0161] like Figure 8 As shown in , the transmission of 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. Figure 8 It can be clearly seen from the figure that the signaling conditions of the residual information are not limited to tu_y_coded_flag, tu_cb_coded_flag, and tu_cr_coded_flag. However, in the present disclosure, as the signaling conditions of the residual information, only tu_y_coded_flag, tu_cb_coded_flag, tu_cr_coded_flag and / or some conditions may be mentioned. This is for the convenience 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, or may include Figure 8 Additional signaling conditions not shown in Figure 8As shown in , for example, when tu_y_coded_flag is 1, residual information of the luma transform block may be signaled. Similarly, residual information of the Cb transform block and the Cr transform block may be signaled based on tu_cb_coded_flag and tu_cr_coded_flag.

[0162] However, if Figure 8 As 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 tu_cb_coded_flag and tu_joint_cbcr_residual_flag are both 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, transform_skip_flag and 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 may be derived as 0. Therefore, based on the determination of step S750, the boundary strength of the target boundary of the Cb component may be derived as 1, and the boundary strength of the target boundary of the Cr component may 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 may be derived as a value other than 1.

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

[0169] In the following, the above-mentioned problem improvement by considering the application of joint CbCr residual coding will be described. Figure 7 Various implementations of implementations.

[0170] Fig. 9 is a flowchart illustrating a method of determining a boundary strength of a target boundary according to another embodiment of the present disclosure.

[0171] Fig. 9 To improve the reference Figure 7 The boundary strength determination method described in Figure 7 Methods and Fig. 9 The methods can be the same or overlapping. Figure 7 Methods and Fig. 9 In the method, repeated descriptions of the same or overlapping steps may be omitted. For example, Figure 7 Steps S710 to S750 may correspond to Fig. 9 Steps S910 to S950. In addition, Figure 7 Steps S760 to S770 may correspond to Fig. 9 The steps S970 to S980 are described in detail. The repeated description of the corresponding steps will be omitted. Figure 7 Compared with the method based on Fig. 9 The boundary strength determination method further includes step S960.

[0172] Specifically, refer to Fig. 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 two conditions described below 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 (e.g., 1).

[0173] - Condition S960 - 1 : The current block is a chroma Cb component block (eg, cIdx=1), and the sample p0 or the sample q0 is included in a transform block on which joint CbCr residual coding is performed (eg, tu_joint_cbcr_residual_flag=1).

[0174] - Condition S960-2: The current block is a chroma Cr component block (eg, cIdx=2), and the sample p0 or the sample q0 is included in a transform block on which joint CbCr residual coding is performed (eg, tu_joint_cbcr_residual_flag=1).

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

[0176] - S960 Merge condition: The current block is a chroma block (eg, cIdx>0), and sample p0 or sample q0 is included in a transform block on which joint CbCr residual coding is performed (eg, tu_joint_cbcr_residual_flag=1).

[0177] Reference Fig. 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 Fig. 9 For example, you can omit Fig. 9 In addition to the steps shown in Fig. 9 Steps other than those shown may be added to Fig. 9 In addition, Fig. 9 Some of the steps shown in the drawings may be performed simultaneously with other steps, or the order of the steps may be changed.

[0178] For example, since tu_joint_cbcr_residual_flag may mean that at least one of tu_cu_coded_flag or tu_cr_coded_flag is 1, for a Cb transform block or a Cr transform block, it may be changed to omit the residual flag according to Fig. 9 Step S950 in the boundary strength determination method.

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

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

[0181] Fig.10 To improve the reference Figure 7 The boundary strength determination method described in Figure 7 Methods and Fig.10 The methods can be the same or overlapping. Figure 7 Methods and Fig.10 In the method, repeated descriptions of the same or overlapping steps may be omitted. For example, Figure 7 Steps S710 to S740 may correspond to Fig.10 Steps S1010 to S1040. In addition, Figure 7 Steps S760 to S770 may correspond to Fig.10The steps S1060 to S1070 are described in detail. The repeated description of the corresponding steps will be omitted. Figure 7 Compared with the method based on Fig.10 The boundary strength determination method further includes step S1050 instead of step S750.

[0182] Specifically, refer to Fig.10 , when the condition of step S1040 is not met (S1040 is no), step S1050 may be determined. Specifically, it may be determined whether the target boundary is a boundary of a transform block and whether at least one of the three conditions described below is met (S1050). When the above conditions are met (S1050 is yes), the boundary strength corresponding to the target boundary may be determined as a second value (e.g., 1).

[0183] - Condition S1050 - 1 : The current block is a luma component block (eg, cIdx=0), and the sample p0 or the sample q0 is included in a luma transform block (eg, tu_y_coded_flag=1) including one or more non-zero transform coefficient levels.

[0184] - Condition S1050 - 2 : The current block is a chroma Cb component block (eg, cIdx=1), and sample p0 or sample q0 is included in a Cb transform block (eg, tu_cb_coded_flag=1) including one or more non-zero transform coefficient levels.

[0185] - Condition S1050 - 3 : The current block is a chroma Cr component block (eg, cIdx=2), and the sample p0 or the sample q0 is included in a Cr transform block including one or more non-zero transform coefficient levels (eg, tu_cr_coded_flag=1).

[0186] Reference Fig.10 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 Fig.10 For example, you can omit Fig.10 In addition to the steps shown in Fig.10 Steps other than those shown may be added to Fig.10 In addition, Fig.10 Some of the steps shown in the drawings may be performed simultaneously with other steps, or the order of other steps may be changed.

[0187] According to reference Fig.10 The boundary strength determination method described in the above can solve the above two problems that may occur by applying joint CbCr residual coding. Fig.10The method of determining whether a transform block includes one or more non-zero transform coefficient levels for each color component can accurately determine the boundary strength of deblocking filtering for transform block boundaries even when joint CbCr residual coding is applied.

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

[0189] Fig.11 To improve the reference Figure 7 The boundary strength determination method described in Figure 7 Methods and Fig.11 The methods can be the same or overlapping. Figure 7 Methods and Fig.11 In the method, repeated descriptions of the same or overlapping steps may be omitted. For example, Figure 7 Steps S710 to S740 may correspond to Fig.11 Steps S1110 to S1140. In addition, Figure 7 Steps S760 to S770 may correspond to Fig.11 The steps S1160 to S1170 are described in detail. The repeated description of the corresponding steps will be omitted. Figure 7 Compared with the method based on Fig.11 The boundary strength determination method further includes step S1150 instead of step S750.

[0190] Reference Fig.11 , when the condition of step S1140 is not met (S1140 is no), step S1150 may be determined. Specifically, it may be determined whether the target boundary is a boundary of a transform block and whether at least one of the four conditions described below is met (S1150). When the above conditions are met (S1150 is yes), the boundary strength corresponding to the target boundary may be determined as a second value (e.g., 1).

[0191] - Condition S1150 - 1 : The current block is a luma component block (eg, cIdx=0), and the sample p0 or the sample q0 is included in a luma transform block including one or more transform coefficient levels (eg, tu_y_coded_flag=1).

[0192] - Condition S1150 - 2 : The current block is a chroma Cb component block (eg, cIdx=1), and sample p0 or sample q0 is included in a Cb transform block (eg, tu_cb_coded_flag=1) including one or more non-zero transform coefficient levels.

[0193] - Condition S1150 - 3 : The current block is a chroma Cr component block (eg, cIdx=2), and the sample p0 or the sample q0 is included in a Cr transform block including one or more non-zero transform coefficient levels (eg, tu_cr_coded_flag=1).

[0194] - Condition S1150 - 4: The current block is not a luma component block (eg, cIdx≠0), and sample p0 or sample q0 is included in a transform block on which joint CbCr residual coding is performed (eg, tu_joint_cbcr_residual_flag=1).

[0195] Reference Fig.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 Fig.11 For example, you can omit Fig.11 In addition to the steps shown in Fig.11 Steps other than those shown may be added to Fig.11 In addition, Fig.11 Some of the steps shown in the drawings may be performed simultaneously with other steps, or the order of the steps may be changed.

[0196] According to reference Fig.11 The boundary strength determination method described in the above can solve the above two problems that may occur by applying joint CbCr residual coding. Fig.11 The method of determining whether a transform block includes one or more non-zero transform coefficient levels for each color component can accurately determine the boundary strength of deblocking filtering for transform block boundaries even when joint CbCr residual coding is applied. Fig.11 According to the method, 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).

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

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

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

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

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

[0202] For the Cr component (eg, cIdx=2), when the value of tu_cr_coded_flag, the value of tu_joint_cbcr_residual_flag of the P block, the value of tu_cr_coded_flag, and the value of tu_joint_cbcr_residual_flag of the Q block are greater than 0, the corresponding boundary strength may be determined to be a second value (eg, 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] Fig.12 is a flow chart illustrating a deblocking filtering based encoding process according to the present disclosure.

[0205] Reference Fig.12 , the image encoding apparatus may generate a reconstructed picture (S1210). The image encoding apparatus may generate a reconstructed picture by encoding an input image to be encoded and reconstructing it.

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

[0207] As described above, the deblocking filter related information may include a flag that specifies whether the deblocking filter is available. In addition, 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 component (cb, cr). The target boundary for applying the deblocking filter may be derived separately according to the luminance component (Y) and the chrominance component (cb, cr).

[0208] The image encoding apparatus may 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 for use as a reference picture for inter-frame prediction.

[0209] The image encoding apparatus may encode the image data including the deblocking filter related information (S1240). For example, the deblocking filter related information may be transmitted to the entropy encoder 190 and encoded by the entropy encoder 190, thereby being output in the form of a bit stream.

[0210] Fig.13 is a flow chart illustrating a decoding process based on deblocking filtering according to the present disclosure.

[0211] Reference Fig.13 , the image decoding apparatus may obtain image data including deblocking filter related information from a bit stream (S1310).

[0212] Figure 3 The image decoding device 200 may receive the image in the form of a bit stream from Figure 2 The entropy decoder 210 may obtain information (eg, video / image information) required for image reconstruction (or picture reconstruction) by parsing the bit stream.

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

[0214] For example, Figure 3 The 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 apparatus may 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 the sake of clarity of description, the exemplary method of the present disclosure described above is represented as a series of operations, it is not intended to limit the order of executing the steps, and these steps can be performed simultaneously or in different orders when necessary. In order to implement the method according to the present invention, the steps described may further include other steps, may include the remaining steps except some steps, or may include other additional steps except some steps.

[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 an execution condition or situation 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 met, the image encoding device or the image decoding device may perform the predetermined operation after determining whether the predetermined condition is met.

[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 matters described in the various embodiments may be applied independently or in combination of two or more.

[0220] Various embodiments of the present disclosure may be implemented in hardware, firmware, software or a combination thereof. In the case of implementing the present disclosure in hardware, the present disclosure may be implemented in an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a general purpose processor, a controller, a microcontroller, a microprocessor, etc.

[0221] In addition, the image decoding device and the image encoding device of the embodiment of the present disclosure can be included in a multimedia broadcast transmission and reception device, a mobile communication terminal, a home theater video device, a digital theater video device, a surveillance camera, a video chat device, a real-time communication device such as video communication, a mobile streaming device, a storage medium, a camera, a video on demand (VoD) service provider, an OTT video (over the top video) device, an Internet streaming service provider, a three-dimensional (3D) video device, a video phone video device, a medical video device, etc., and can be used to process a video signal or a data signal. For example, an OTT video device may include a game console, a Blu-ray player, an Internet access TV, a home theater system, a smart phone, a tablet PC, a digital video recorder (DVR), etc.

[0222] Fig.15 is a diagram showing a content streaming system to which an embodiment of the present disclosure can be applied.

[0223] like Fig.15 As shown in , a content streaming system to which the embodiments of the present disclosure are applied may mainly include an encoding server, a streaming server, a network server, a media storage device, a user device, and a multimedia input device.

[0224] The encoding server compresses the content input from a multimedia input device such as a smart phone, camera, or camcorder 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, camera, or camcorder directly generates a bitstream, the encoding server can be omitted.

[0225] The bitstream may be generated by the image encoding method or the image encoding device to which the embodiments of the present disclosure are applied, and the streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

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

[0227] The streaming server may receive content from a media storage device and / or an encoding server. For example, when receiving content from an encoding server, the content may be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bitstream within a predetermined time.

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

[0229] Each server in the content streaming system may operate as a distributed server, in which case 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 operations of methods according to various embodiments to be performed on a device or computer, and non-transitory computer-readable media having such software or commands stored thereon and executable on a device or computer.

[0231] Industrial Applicability

[0232] The embodiments of the present disclosure may be used to encode or decode an image.

Claims

1. An image decoding method performed by an image decoding device, the image decoding method comprising the following steps: Obtaining a first flag, a second flag, a third flag, and a fourth flag from a bitstream, wherein the first flag specifies whether to perform joint CbCr residual coding on a first block adjacent to a target boundary of deblocking filtering, the second flag specifies whether to perform joint CbCr residual coding on a second block adjacent to the target boundary, the third flag specifies whether the first block includes a non-zero transform coefficient, and the fourth flag indicates whether the second block includes a non-zero transform coefficient; obtaining a reconstructed image; determining the object boundary in the reconstructed image; determining a boundary strength of the target boundary; and applying a deblocking filter to the object boundary based on the boundary strength, Wherein, based on the fact that the target boundary is a transform block boundary and the color component of the reconstructed image is a chrominance component, the boundary strength is determined based on the first flag, the second flag, the third flag, and the fourth flag.

2. The image decoding method according to claim 1, wherein: The boundary strength is determined to be 1 based on one or more of the first flag, the second flag, the third flag, and the fourth flag being equal to 1.

3. The image decoding method according to claim 1, wherein: The boundary strength is determined based on whether at least one of the first block and the second block includes a non-zero transform coefficient, based on the target boundary being a transform block boundary and the color component of the reconstructed image being a luminance component.

4. The image decoding method according to claim 1, wherein: The joint CbCr residual coding corresponds to encoding the residual samples of the chroma Cb component and the chroma Cr component into a single transform block.

5. An image encoding method performed by an image encoding device, the image encoding method comprising the following steps: generating a reconstructed image; Determining a target boundary for deblocking filtering in the reconstructed image; determining a boundary strength of the target boundary; as well as applying a deblocking filter to the object boundary based on the boundary strength, Wherein, based on the target boundary being a transform block boundary and the color component of the reconstructed image being a chrominance component, the boundary strength is determined based on a first flag, a second flag, a third flag, and a fourth flag, wherein the first flag specifies whether to perform joint CbCr residual encoding on a first block adjacent to the target boundary, the second flag specifies whether to perform joint CbCr residual encoding on a second block adjacent to the target boundary, the third flag specifies whether the first block includes a non-zero transform coefficient, and the fourth flag indicates whether the second block includes a non-zero transform coefficient.

6. The image encoding method according to claim 5, wherein: The boundary strength is determined to be 1 based on one or more of the first flag, the second flag, the third flag, and the fourth flag being equal to 1.

7. The image encoding method according to claim 5, wherein: The boundary strength is determined based on whether at least one of the first block and the second block includes a non-zero transform coefficient, based on the target boundary being a transform block boundary and the color component of the reconstructed image being a luminance component.

8. The image encoding method according to claim 5, wherein: The joint CbCr residual coding corresponds to encoding the residual samples of the chroma Cb component and the chroma Cr component into a single transform block.

9. An image decoding device, comprising: a memory having machine executable instructions stored thereon; as well as at least one processor, 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 encoding device, the image encoding device comprising: a memory having machine executable instructions stored thereon; as well as at least one processor, The at least one processor is configured to execute the machine executable instructions to implement the image encoding method according to any one of claims 5-8.

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

Images