RU2785998C1 - Equipment and method for image encoding - Google Patents

Abstract

FIELD: images encoding and decoding.

SUBSTANCE: invention relates to equipment and methods for encoding/decoding an image. The effect is achieved by generating reconstructed samples based on predictive samples and residual samples, wherein the reconstructed samples include reconstructed luminance samples and reconstructed chrominance samples, then extracting adaptive loop filter (ALF) coefficients for the reconstructed chrominance sample ALF process, generating filtered reconstructed chrominance samples based on the reconstructed chrominance samples and ALF filter coefficients, extracting cross-component filter coefficients for cross-component filtering. At the same time, the image information includes a sequence parameter set (SPS) and slice header information, which includes an ALF activation flag, based on the value of which the cross-component adaptive contour filtering (CCALF) procedure for the filtered reconstructed chrominance samples is activated.

EFFECT: improving the efficiency of image/video encoding.

14 cl, 16 dwg, 30 tbl

Description

State of the art

The technical field to which the invention belongs

[1] The present disclosure relates to equipment and a method for encoding an image.

Description of the Prior Art

[2] Recently, the demand for high-quality high-definition image/video, such as 4K or 8K ultra-high definition (UHD) image/video or higher, is growing in various fields of technology. Since the image/video data has high resolution and high quality, the amount of information or bits to be transmitted increases with respect to the existing image/video data, and therefore the transmission of image data using a medium such as an existing wired/wireless broadband line or an existing storage media, or storing image/video data using an existing storage media increases transmission costs and storage costs.

[3] In addition, the interest and demand for immersive media such as virtual reality (VR) and artificial reality (AR) content or holograms is growing recently, and broadcasting for an image/video having characteristics different from reality images , such as game images, is enlarged.

[4] Accordingly, a high-performance image/video compression technology is required to efficiently compress, transmit, store, and reproduce high-quality, high-resolution image/video information having various characteristics as described above.

[5] In the encoding procedure for image/video compression, an in-loop filtering procedure may be performed. Recently, there has been a discussion about improving the filtering accuracy.

The essence of the invention

[6] The present disclosure provides a method and equipment for improving image/video coding efficiency.

[7] The present disclosure also provides a method and equipment for effectively applying filtration.

[8] The present disclosure also provides a method and equipment for efficient ALF application.

[9] According to an embodiment of the present disclosure, a filtering procedure may be performed on the recovered chrominance samples based on the recovered luminance samples.

[10] According to an embodiment of the present disclosure, the filtered reconstructed chrominance samples may be modified based on the reconstructed luminance samples.

[11] According to an embodiment of the present disclosure, information regarding whether or not CCALF is available may be signaled in the SPS.

[12] According to an embodiment of the present disclosure, information regarding the values of the coefficients of the cross-component filter can be extracted from ALF data (normal ALF data or CCALF data).

[13] According to an embodiment of the present disclosure, APS identification information including ALF data for extracting slice cross-component filter coefficients may be signaled.

[14] According to an embodiment of the present disclosure, information regarding the filter bank index for CCALF may be signaled in units of CTUs (blocks).

[15] According to an embodiment of the present disclosure, a video/image decoding method by means of decoding equipment is provided.

[16] According to an embodiment of the present disclosure, decoding equipment is provided to perform video/image decoding.

[17] According to an embodiment of the present disclosure, a video/image encoding method is provided by encoding equipment.

[18] According to an embodiment of the present disclosure, an encoding equipment for performing video/image encoding is provided.

[19] According to one embodiment of the present disclosure, a computer-readable digital storage medium is provided on which encoded video/image information generated according to the video/image coding method disclosed in at least one embodiment of the present disclosure is stored.

[20] According to an embodiment of the present disclosure, a computer-readable digital storage medium is provided on which encoded information or encoded video/image information is stored instructing a decoding equipment to perform a video/image decoding method disclosed in at least one embodiment of the present disclosure.

Positive Effects

[21] According to an embodiment of the present disclosure, the overall image/video compression efficiency can be improved.

[22] According to an embodiment of the present disclosure, subjective/objective visual quality can be improved by efficient filtering.

[23] According to an embodiment of the present disclosure, the ALF procedure can be efficiently performed and filtering performance can be improved.

[24] According to an embodiment of the present disclosure, the reconstructed chrominance samples filtered based on the reconstructed luminance samples may be modified to improve the frame quality and coding fidelity of the chrominance component of a decoded frame.

[25] According to an embodiment of the present disclosure, the CCALF procedure can be efficiently performed.

[26] According to an embodiment of the present disclosure, ALF related information can be efficiently signaled.

[27] According to an embodiment of the present disclosure, CCALF related information can be efficiently signaled.

[28] According to an embodiment of the present disclosure, ALF and/or CCALF may be adaptively applied in units of frames, slices, and/or coding units.

[29] According to an embodiment of the present disclosure, when CCALF is used in the encoding and decoding method and equipment for a still picture or video, the filter coefficients for CCALF and the on-off transmission method per unit of blocks or CTU can be improved, thereby improving encoding efficiency.

Brief description of the drawings

[30] FIG. 1 schematically shows an example of a video/image coding system that may be applied to embodiments of the present disclosure.

[31] FIG. 2 is a diagram principally illustrating a configuration of video/image coding equipment that may be applied to embodiments of the present disclosure.

[32] FIG. 3 is a diagram principally illustrating a configuration of video/image decoding equipment that may be applied to embodiments of the present disclosure.

[33] FIG. 4 roughly shows the hierarchical structure for an encoded picture/video.

[34] FIG. 5 is a flowchart illustrating a block recovery method based on intra prediction in decoding equipment.

[35] FIG. 6 is a flowchart illustrating a block recovery method based on inter prediction in coding equipment.

[36] FIG. 7 is a flowchart illustrating a block recovery method based on inter prediction in decoding equipment.

[37] FIG. 8 shows an example of an ALF filter shape.

[38] FIG. 9 is a diagram illustrating a virtual boundary applied to a filtering procedure according to an embodiment of the present disclosure.

[39] FIG. 10 shows an example of an ALF procedure using a virtual boundary according to an embodiment of the present disclosure.

[40] FIG. 11 is a diagram illustrating a cross-component adaptive loop filtering (CC-ALF) procedure according to an embodiment of the present disclosure.

[41] FIG. 12 and 13 schematically show an example of a video/image coding method and related components according to the embodiment(s) of the present disclosure.

[42] FIG. 14 and 15 schematically show an example of a method for decoding images/videos and related components according to the embodiment(s) of the present disclosure.

[43] FIG. 16 illustrates an example of a content streaming system to which the embodiments disclosed in the present disclosure may be applied.

Detailed description of embodiments

[44] The present disclosure may be modified in various forms, and specific embodiments thereof are described and shown in the drawings. However, these embodiments are not intended to limit the present disclosure. The terms used in the description below are used to simply describe specific embodiments, but are not intended to limit the present disclosure. The expression of the singular includes the expression of the plural as long as they are clearly treated differently. Terms such as "include" and "have" are intended to indicate that there are features, numbers, steps, operations, elements, components, or combinations of the foregoing used in the description below, and as such should be understood , which does not exclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations of the above.

[45] Meanwhile, each configuration in the drawings described in the present disclosure is shown independently for convenience of description with respect to various characteristic functions, and does not mean that each configuration is implemented as separate hardware or separate software. For example, two or more components for each component may be combined to form one component, or one component may be split into multiple components. Embodiments in which each component is integrated and/or separated are also included within the scope of this disclosure.

[46] The present disclosure relates to video/image coding. For example, the methods/embodiments disclosed in the present disclosure may apply to the methods disclosed in the Universal Video Coding (VVC) standard. In addition, the methods/embodiments disclosed in the present disclosure may be applied to the method disclosed in the Fundamental Video Coding (EVC) standard, the AOMedia Video 1 (AV1) standard, the second generation audio/video coding standard (AVS2), or the video coding standard. / next generation images (eg H.267 or H.268, etc.).

[47] The present disclosure presents various embodiments of video/image coding, and unless otherwise indicated, these embodiments may be performed in combination with each other.

[48] In the present disclosure, video can mean a sequence of images over time. A frame generally means a unit representing one image in a particular time domain, and a slice/tile (tile) is a unit constituting a frame when encoded. A slice/tile may include one or more coding tree units (CTUs). A frame may consist of one or more slices/blocks. A tile is a rectangular area of a CTU in a particular column of tiles and a particular row of tiles in a frame. The tile column is a rectangular area of CTUs having a height equal to the height of the frame and a width specified by syntax elements in the frame parameter set. The row of tiles is a rectangular area of CTUs having a height indicated by syntax elements in the frame parameter set and a width equal to the frame width. Tile scanning is a particular sequential ordering of CTUs segmenting a frame, whereby CTUs are ordered sequentially in a raster scan of the CTUs in a tile, while tiles in a frame are ordered sequentially in a raster scan of the frame's tiles. A slice includes an integer number of complete tiles or an integer number of consecutive completed CTU rows in a frame tile that can be contained solely in one NAL unit.

[49] Meanwhile, one frame may be divided into two or more subframes. A subframe may be a rectangular region of one or more slices in a frame.

[50] A pixel or pel can mean the smallest unit that makes up one frame (or image). In addition, "sample" can be used as a term corresponding to a pixel. A sample can generally represent a pixel or a pixel value, and can only represent a luminance component pixel/pixel value, or only a chrominance component pixel/pixel value.

[51] The unit may represent a basic image processing unit. The unit may include at least one of a particular area of the frame and information associated with the area. One unit may include one luminance block and two chrominance blocks (eg, Cb, Cr). The unit can be used interchangeably with terms such as block or zone in some cases. In general, an MxN block may include samples (or arrays of samples) or a set (or array) of transform coefficients of M columns and N rows. Alternatively, the sample may mean a pixel value in the spatial domain, and when such a pixel value is converted to the frequency domain, it can mean a transform factor in the frequency domain.

[52] In the present disclosure, "A or B (A or B)" can mean "only A", "only B", or "both A and B". In other words, "A or B (or B)" in the present disclosure may be interpreted as "A and/or B (A and/or B)". For example, in the present disclosure, "A, B, or C (A, B, or C)" means "A only", "B only", "C only", or "any combination of A, B and C".

[53] The slash (/) or comma used in the present disclosure may mean "and/or". For example, "A/B" could mean "A and/or B". Accordingly, "A/B" can mean "only A", "only B", or "both A and B". For example, "A, B, C" could mean "A, B, or C".

[54] In the present disclosure, "at least one of A and B" can mean "only A", "only B", or "both A and B". In addition, in the disclosure, the expression "at least one of A or B" or "at least one of A and/or B" can be interpreted equally as "at least one of A and B".

[55] In addition, in the present disclosure, "at least one of A, B and C" means "only A", "only B", "only C", or "any combination of A, B and C". In addition, "at least one of A, B or C" or "at least one of A, B and/or C" can mean "at least one of A, B and C".

[56] In addition, parentheses used in this disclosure may mean "for example". In particular, when "prediction (internal prediction)" is indicated, it may be referred to as "internal prediction" being suggested as an example of "prediction". In other words, "prediction" in the present disclosure is not limited to "internal prediction", and "internal prediction" may be offered as an example of "prediction". In addition, even when "prediction (ie, internal prediction)" is indicated, it may be referred to as "internal prediction" being offered as an example of "prediction".

[57] Technical features that are separately described in one drawing in this disclosure may be implemented separately or simultaneously.

[58] Hereinafter, embodiments of the present disclosure are described with reference to the accompanying drawings. Hereinafter in this document, identical numeral references may be used for identical components in the drawings, and repeated descriptions of identical components may be omitted.

[59] FIG. 1 illustrates an example of a video/image coding system to which the present disclosure may apply.

[60] Referring to FIG. 1, a video/image coding system may include a source device and a destination device. The source device may transmit the encoded information or video/image data to the receiving device via a digital storage medium or a network in the form of a file or streaming.

[61] The source device may include a video source, encoding equipment, and a transmitter. The receiver may include a receiver, decoding hardware, and a renderer. The encoding equipment may be referred to as "video/image coding equipment", and the decoding equipment may be referred to as "video/image decoding equipment". The transmitter may be included in the encoding equipment. The receiver may be included in decoding equipment. The renderer may include a display, and the display may be configured as a separate device or an external component.

[62] A video source may acquire a video/image through a process of capturing, synthesizing, or generating a video/image. The video source may include a video/image capture device and/or a video/image generation device. The video/image capture device may include, for example, one or more cameras, video/image archives including previously captured videos/images, and the like. The video/image generating apparatus may include, for example, computers, tablet computers, and smartphones, and may (electronically) generate video/images. For example, the virtual video/image may be generated via a computer or the like. In this case, the video/image capturing process may be replaced by a linked data generation process.

[63] The encoding equipment may encode the input video/image. The encoding equipment may perform a series of procedures such as prediction, transformation, and quantization for compression and encoding efficiency. Encoded data (encoded video/picture information) may be output in the form of a bit stream.

[64] The transmitter may transmit information or coded image/image data output in the form of a bit stream to the receiver of the receiving device via a digital storage medium or a network in the form of a file or streaming. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and the like. The transmitter may include an element for generating a media file via a predetermined file format and may include an element for transmission via a broadcast/communication network. The receiver may receive/retrieve the bitstream and transmit the received bitstream to the decoding equipment.

[65] The decoding equipment can decode the video/image by performing a sequence of procedures such as dequantization, inverse transformation, and prediction corresponding to the operation of the encoding equipment.

[66] The rendering module may prepare a decoded video/image by rendering. The rendered video/image can be displayed through the display.

[67] FIG. 2 is a diagram schematically illustrating the configuration of video/image coding equipment to which the present disclosure may apply. Hereinafter in this document, what is referred to as "video encoding equipment" may include image encoding equipment.

[68] Referring to FIG. 2, the encoding equipment 200 includes an image segmentation unit 210, a prediction unit 220, a residual processor 230 and an entropy encoder 240, an adder 250, a filter 260, and a memory 270. The prediction unit 220 may include an inter prediction unit 221 and an intra prediction unit 222. forecasting. Residual processor 230 may include a transformer 232, a quantizer 233, a dequantizer 234, and an inverse transformer 235. Residual processor 230 may further include a subtractor 231. Adder 250 may be referred to as a "rebuilder" or "recovered block generator". Image segmentation module 210, prediction module 220, residual processor 230, entropy encoder 240, adder 250, and filter 260 may be configured by at least one hardware component (eg, chipset or encoder processor) according to an embodiment. In addition, the memory 270 may include a decoded frame buffer (DPB) or may be configured by a digital storage medium. The hardware component may further include a storage device 270 as an internal/external component.

[69] The image segmentation module 210 may segment an input image (either a frame or a movie frame) input to the encoding equipment 200 into one or more processing units. For example, a processing unit may be referred to as a "coding unit (CU)". In this case, a coding unit may be recursively segmented according to a quadtree, binary tree, and ternary tree (QTBTTT) structure from a coding tree unit (CTU) or a largest coding unit (LCU). For example, one coding unit may be segmented into multiple deeper coding units based on a quadtree structure, a binary tree structure, and/or a ternary structure. In this case, for example, a quadtree structure may be applied first, and a binary tree structure and a ternary structure may subsequently be applied. Alternatively, a binary tree structure may be applied first. The encoding procedure according to the present disclosure may be performed based on a final encoding unit that is no longer segmented. In this case, the largest coding unit may be used as the final coding unit based on the coding efficiency according to the characteristics of the images, or if necessary, the coding unit may be recursively segmented into coding units of greater depth, and the coding unit having the optimal size may be used as the final coding units. Here, the encoding procedure may include a prediction, transformation, and restoration procedure, which is described below. As another example, the processing unit may further include a prediction unit (PU) or a transformation unit (TU). In this case, the prediction unit and the transformation unit may be split or segmented from the above final coding unit. The prediction unit may be a selective prediction unit, and the transform unit may be a unit for extracting a transform coefficient and/or a unit for extracting a residual signal from a transform coefficient.

[70] The unit can be used interchangeably with terms such as block or zone in some cases. In general, an MxN block may represent a set of samples or transform coefficients consisting of M columns and N rows. The sample, in general, may represent a pixel or pixel value, may represent only a pixel/pixel value of the luma component, or represent only a pixel/pixel value of the chroma component. Sampling can be used as a term corresponding to one frame (or image) for a pixel or pel.

[71] The subtractor 231 subtracts the prediction signal (predicted block, predictive samples, or array of predictive samples) output from prediction unit 220 from the input image signal (original block, original samples, or array of original samples) to obtain a remainder. A signal (residual block, residual samples, or an array of residual samples) may be generated, and the generated residual signal is provided to transformer 232. Prediction module 220 may perform prediction with respect to a target processing block (hereinafter referred to as the "current block") and generate a predicted a block that includes the predictive samples for the current block. Prediction module 220 may determine whether intra prediction or inter prediction is applied based on the current block or CU. As described below in the description of each prediction mode, the prediction module may generate various prediction-related information, such as prediction mode information, and pass the generated information to the entropy encoder 240. The prediction information may be encoded in the entropy encoder 240 and output in the form of a stream. bits.

[72] The intra prediction module 222 may predict the current block by referring to the samples in the current frame. The samples for the link may be located in the surroundings of the current block, or may be spaced apart according to the prediction mode. In intra prediction, the prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The non-directional mode may include, for example, a DC mode and a planar mode. The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes according to the granularity of the prediction direction. However, this is just an example, more or less directional prediction modes may be used depending on the setting. The intra prediction unit 222 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

[73] The inter prediction unit 221 may derive a predicted block for the current block based on a reference block (reference sample array) indicated by a motion vector for the reference frame. Here, in order to reduce the amount of motion information transmitted in the inter-prediction mode, motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of motion information between an adjacent block and a current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction direction information (L0 prediction, L1 prediction, bi-prediction, etc.). In the case of inter prediction, an adjacent block may include a spatial adjacent block present in the current frame and a temporal adjacent block present in the reference frame. The reference frame including the reference block and the reference frame including the temporal neighbor block may be the same or different. The temporal neighbor block may be referred to as a "collocated reference block", "collocated CU (colCU)" or the like, and a reference frame including the temporal neighbor block may be referred to as a "collocated frame (colPic)". For example, the inter prediction unit 221 may configure a motion information candidate list based on neighboring blocks, and generate information indicating which candidate is used to derive the motion vector and/or the reference frame index of the current block. Inter prediction may be performed based on various prediction modes. For example, in the case of the skip mode and the join mode, the inter prediction unit 221 may use the neighboring block motion information as the current block motion information. In the skip mode, unlike the merge mode, the residual signal may not be transmitted. In the case of a motion vector prediction (MVP) mode, the motion vector of an adjacent block may be used as a motion vector predictor, and the motion vector of the current block may be indicated by signaling a motion vector difference.

[74] The prediction module 220 may generate a prediction signal based on various prediction methods described below. For example, the prediction module may not only apply intra prediction or inter prediction to predict one block, but also apply both intra prediction and inter prediction at the same time. This may be referred to as "combined mutual and intra prediction (CIIP)". In addition, the prediction module may perform intra-block copy (IBC) to predict a block. The IBC prediction mode may be used for image/video coding of game content and the like, such as screen content coding (SCC). The IBC essentially performs prediction in the current frame, but may be performed similar to inter prediction in which the reference block is retrieved in the current frame. Thus, the IBC may use at least one of the inter-prediction technologies described in this disclosure.

[75] The prediction signal generated by the inter prediction unit 221 and/or the intra prediction unit 222 may be used to generate a recovered signal or generate a residual signal. Converter 232 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transform technology may include discrete cosine transform (DCT), discrete sine transform (DST), Karhunen-Loeve transform (KLT), graph-based transform (GBT), or conditionally non-linear transform (CNT). Here, GBT means a transformation obtained from a graph when relationship information between pixels is represented by a graph. CNT means a transform generated based on a predictive signal generated using all previously reconstructed pixels. In addition, the transformation process may be applied to square pixel blocks having the same size, or may be applied to blocks having a variable size rather than square.

[76] The quantizer 233 may quantize the transform coefficients and pass them to the entropy encoder 240, and the entropy encoder 240 may encode the quantized signal (information regarding the quantized transform coefficients) and output a bit stream. The information regarding the quantized transform coefficients may be referred to as "residual information". The quantizer 233 may repackage the block quantized transform coefficients into one-dimensional vector form based on the scan order of the coefficients, and generate information about the quantized transform coefficients based on the quantized transform coefficients in one-dimensional vector form. Information regarding transform coefficients may be generated. Entropy encoder 240 may implement various coding methods such as exponential Golomb coding, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and the like, for example. Entropy encoder 240 may encode information needed for video/image reconstruction other than quantized transform coefficients (eg, syntax element values, etc.) together or separately. Encoded information (eg, encoded video/image information) may be transmitted or stored in NAL (Network Abstraction Layer) units in the form of a bitstream. The video/image information may further include information regarding various parameter sets such as an adaptation parameter set (APS), a frame parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image information may further include general restriction information. In the present disclosure, the signaling/information to be transmitted and/or the syntax elements described later in the present disclosure may be encoded through the above encoding process and included in a bitstream. The bit stream may be transmitted over a network or may be stored on a digital storage medium. The network may include a broadcast network and/or a communications network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and the like. A transmitter (not shown), transmitting a signal output from the entropy encoder 240, and/or a storage module (not shown) storing the signal may be included as an internal/external member of the encoding equipment 200, and alternatively, a transmitter may be included in the entropy encoder 240 .

[77] The quantized transform coefficients output from quantizer 233 may be used to generate a predictive signal. For example, the residual signal (residual block or residual samples) may be recovered by applying dequantization and inverse transform to the quantized transform coefficients via dequantizer 234 and inverse transform 235. Summer 250 adds the recovered residual signal to the predictive signal output from predictor 220 to generate a reconstructed signal (recovered frame, recovered samples, or array of recovered samples). If there is no remainder for a block to be processed, such as in a case in which the skip mode is applied, the predicted block may be used as the reconstructed block. The generated recovered signal may be used to intra-predict the next block to be processed in the current frame, and may be used to inter-predict the next frame through filtering as described below.

[78] Meanwhile, luminance chrominance scaling (LMCS) transform may be applied during encoding and/or frame reconstruction.

[79] The filter 260 can improve subjective/objective image quality by applying filtering to the reconstructed signal. For example, filter 260 may generate a modified reconstructed frame by applying various filtering methods to the reconstructed frame and store the modified reconstructed frame in memory 270, namely the DPB of memory 270. Various filtering methods may include, for example, filtering to deblock , sampling based adaptive offset (SAO) filtering, adaptive loop filter, bilateral filter, and the like. The filter 260 may generate various filtering-related information and pass the generated information to the entropy encoder 240 as described below in the description of each filtering method. Filtering related information may be encoded by entropy encoder 240 and output in the form of a bitstream.

[80] The modified reconstructed frame transmitted to the memory 270 may be used as a reference frame in the inter prediction module 221 . When inter prediction is applied by the encoding equipment, prediction mismatch between the encoding equipment 200 and the decoding equipment 300 can be eliminated, and encoding efficiency can be improved.

[81] The DPB of the memory 270 may store the modified reconstructed frame for use as a reference frame in the inter prediction module 221 . The memory 270 may store block motion information from which motion information in the current frame is extracted (or encoded) and/or motion information of blocks in the frame that have already been recovered. The stored motion information may be transmitted to the inter-prediction unit 221 and used as spatial neighbor block motion information or temporal neighbor block motion information. The memory 270 may store the recovered samples of the recovered blocks in the current frame and may pass the recovered samples to the intra prediction module 222 .

[82] FIG. 3 is a diagram schematically illustrating the configuration of video/image decoding equipment to which the present disclosure may apply.

[83] Referring to FIG. 3, the decoding equipment 300 may include an entropy decoder 310, a residual processor 320, a prediction module 330, an adder 340, a filter 350, a memory 360. The prediction module 330 may include an inter prediction module 331 and an intra prediction module 332. Residual processor 320 may include a dequantizer 321 and inverse converter 321. Entropy decoder 310, residual processor 320, predictor 330, adder 340, and filter 350 may be configured by a hardware component (eg, a chipset or decoder processor) according to an embodiment. In addition, the storage device 360 may include a decoded frame buffer (DPB) or may be configured with a digital storage medium. The hardware component may further include a storage device 360 as an internal/external component.

[84] When a bitstream including video/image information is input, the decoding equipment 300 can reconstruct an image corresponding to the process in which the video/image information is processed in the encoding equipment of FIG. 2. For example, decoding equipment 300 may extract units/blocks based on block segmentation-related information obtained from the bit stream. The decoding equipment 300 may perform decoding using a processing unit used in the encoding equipment. Thus, the decoding processing unit, for example, may be a coding unit, and the coding unit may be segmented according to a quadtree structure, a binary tree structure, and/or a ternary tree structure from the coding tree unit or the largest coding unit. One or more transformation units may be derived from a coding unit. The reconstructed image signal decoded and output by the decoding equipment 300 can be reproduced by the playback equipment.

[85] The decoding equipment 300 may receive a signal output from the encoding equipment of FIG. 2 in the form of a bitstream, and the received signal may be decoded via entropy decoder 310. For example, entropy decoder 310 may parse the bitstream to extract information (eg, video/image information) needed for image recovery (or frame recovery). The video/image information may further include information regarding various parameter sets such as an adaptation parameter set (APS), a frame parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image information may further include general restriction information. The decoding equipment may further decode the frame based on the parameter set information and/or general constraint information. Signaling/receiving information and/or syntax elements described later in this disclosure may be decoded, may be decoded by a decoding procedure, and obtained from a bitstream. For example, entropy decoder 310 decodes information in the bitstream based on an encoding method such as Exponential Golomb, CAVLC, or CABAC coding and output syntax elements required for image reconstruction and quantized transform coefficient values for the remainder. More specifically, the CABAC entropy decoding method can receive a bin corresponding to each syntax element in the bit stream, determine a context model using the decoding target syntax element information, the decoding information of the decoding target block, or the symbol/bin information decoded in the previous step, and perform arithmetic decoding on the permission element by predicting the occurrence probability of the permission element according to the determined context model, and generating a character corresponding to the value of each syntax element. In this case, the CABAC entropy decoding method can update the context model by using the decoded symbol/bin information for the context model of the next symbol/bin after the context model is determined. Prediction-related information from the information decoded by the entropy decoder 310 may be provided to the prediction unit 330, and information regarding the residue for which entropy decoding is performed in the entropy decoder 310, i. quantized transform coefficients and related parameter information may be input to the dequantizer 321. In addition, information regarding filtering from the information decoded by the entropy decoder 310 may be provided to the filter 350. Meanwhile, a receiver (not shown) for receiving a signal output from the equipment encoding equipment may be further configured as an internal/external member of the decoding equipment 300, or the receiver may be a component of the entropy decoder 310. Meanwhile, the decoding equipment according to the present disclosure may be referred to as "video/image/frame decoding equipment", and the decoding equipment may be classified into an information decoder (video/image/frame information decoder) and a sample decoder (video/image/frame sample decoder). The information decoder may include an entropy decoder 310, and the selective decoder may include at least one of a dequantizer 321, an inverse transform 322, a predictor 330, an adder 340, a filter 350, and a memory 360.

[86] The dequantizer 321 may dequantize the quantized transform coefficients and output the transform coefficients. The dequantizer 321 may recompose the quantized transform coefficients into a two-dimensional block form. In this case, the reassembly may be performed based on the coefficient scan order performed in the encoding equipment. The dequantizer 321 may perform dequantization on the quantized transform coefficients by using a quantization parameter (eg, quantization step size information) and obtain the transform coefficients.

[87] The inverse transform 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, array of residual samples).

[88] Prediction module 230 may perform prediction for the current block and may generate a predicted block including prediction samples for the current block. The prediction module may determine whether intra prediction or inter prediction is applied to the current block based on the prediction information output from the entropy decoder 310, and may determine a specific intra/inter prediction mode.

[89] The prediction module may generate a prediction signal based on various prediction methods described below. For example, the prediction module may not only apply intra prediction or inter prediction in order to predict one block, but also apply intra prediction and inter prediction at the same time. This may be referred to as "combined mutual and intra prediction (CIIP)". In addition, the prediction module can perform intra-block copy (IBC). In-block copying can be used for image/video encoding of game content and the like, such as on-screen content coding (SCC). The IBC essentially performs prediction in the current frame, but may be performed similar to inter prediction in which the reference block is retrieved in the current frame. Thus, the IBC may use at least one of the inter-prediction technologies described in this disclosure.

[90] The intra prediction module 331 may predict the current block by referring to the samples in the current frame. The samples for the link may be located in the surroundings of the current block, or may be spaced apart according to the prediction mode. In intra prediction, the prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The intra prediction unit 331 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

[91] The inter prediction unit 332 may derive a predicted block for the current block based on a reference block (reference sample array) indicated by a motion vector for the reference frame. In this case, in order to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the adjacent block and the current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction direction information (L0 prediction, L1 prediction, bi-prediction, etc.). In the case of inter prediction, an adjacent block may include a spatial adjacent block present in the current frame and a temporal adjacent block present in the reference frame. For example, inter-prediction unit 332 may configure a motion information candidate list based on adjacent blocks, and derive the current block's motion vector and/or reference frame index based on the received candidate selection information. Inter prediction may be performed based on various prediction modes, and the prediction information may include information indicative of the inter prediction mode for the current block.

[92] The adder 340 may generate a reconstructed signal (recovered frame, reconstructed block, reconstructed sample array) by summing the obtained residual signal with the predictive signal (predicted block, predicted sample array) output from prediction module 330. If there is no remainder for the block to be processed, for example, when the skip mode is applied, the predicted block may be used as the reconstructed block.

[93] The adder 340 may be referred to as a "recovery module" or "recovered block generator". The generated recovered signal may be used for intra prediction of the next block to be processed in the current frame, may be output by filtering as described below, or may be used for inter prediction of the next frame.

[94] Meanwhile, luminance chrominance scaling (LMCS) transform may be applied in the frame decoding process.

[95] The filter 350 can improve subjective/objective image quality by applying filtering to the reconstructed signal. For example, filter 350 may generate a modified reconstructed frame by applying various filtering methods to the reconstructed frame and store the modified reconstructed frame in memory 360, namely the DPB of memory 360. Various filtering methods may include, for example, filtering to deblock , filtering based on a sampled adaptive bias, an adaptive loop filter, a bilateral filter, and the like.

[96] The (modified) reconstructed frame stored in the DPB of the storage device 360 may be used as a reference frame in the inter prediction module 332 . The memory 360 may store block motion information from which motion information in the current frame is extracted (or decoded) and/or motion information of blocks in the frame that have already been recovered. The stored motion information may be transmitted to the inter-prediction unit 260 so that it is used as spatial neighbor block motion information or temporal neighbor block motion information. The memory device 360 may store the reconstructed samples of the reconstructed blocks in the current frame and pass the reconstructed samples to the intra prediction module 331 .

[97] In this detailed description, the embodiments described in the prediction module 330, the dequantizer 321, the inverse converter 322, and the filter 350 of the decoding equipment 300 are the prediction module 220, the dequantizer 234, the inverse converter 235, and the filter 260, and can be applied identically or in the appropriate way.

[98] As described above, when encoding video, prediction is performed in order to improve compression efficiency. Through this, it is possible to generate a prediction block including the prediction samples for the current block, which is the block to be encoded. Here, the prediction block includes prediction samples in the spatial domain (or pixel domain). The predicted block is extracted equally from the encoding equipment and the decoding equipment, and the encoding equipment decodes information (residual information) about the residual between the original block and the predicted block, rather than the original sample value of the original block itself. By signaling to the device, image coding efficiency can be improved. The decoding equipment can extract a residual block including the residual samples based on the residual information, and generate a reconstructed block including the reconstructed samples by summing the residual block with the predicted block, and generate a reconstructed frame including the reconstructed blocks.

[99] Residual information may be generated through transformation and quantization processes. For example, the encoding equipment may extract the residual block between the original block and the predicted block, and perform a transform process on the residual samples (array of residual samples) included in the residual block to extract transform coefficients, and thereafter, by performing a quantization process on the transform coefficients, extract quantized transform coefficients to signal the residual associated information to the decoding equipment (via the bitstream). Here, the residual information may include location information, transform technology, transform kernel and quantization parameter, quantized transform coefficient value information, and so on. The decoding equipment may perform a dequantization/inverse transform process based on the residual information and extract residual samples (or residual blocks). The decoding equipment may generate a reconstructed frame based on the predicted block and the residual block. The encoding equipment may also dequantize/inversely transform the quantized transform coefficients for a later frame inter-prediction reference to extract the residual block and generate a reconstructed frame based on it.

[100] In the present disclosure, at least one of quantization/dequantization and/or transformation/inverse transformation may be omitted. When quantization/dequantization is omitted, the quantized transform coefficient may be referred to as a "transform coefficient". When the transform/inverse transform is omitted, the transform coefficients may be referred to as "coefficients" or "residual coefficients", or may still be referred to as "transform coefficients" for uniformity of expression.

[101] In the present disclosure, the quantized transform coefficient and the transform coefficient may be referred to as "transform coefficient" and "scaled transform coefficient", respectively. In this case, the residual information may include information on the transform coefficient(s), and information on the transform coefficient(s) may be signaled via the residual coding syntax. The transform coefficients may be derived based on the residual information (or information regarding the transform coefficient(s)), and the scaled transform coefficients may be derived via an inverse transform (scaling) of the transform coefficients. Residual samples may be derived based on an inverse transform (transform) of the scaled transform coefficients. This may also be applied/expressed in other parts of this disclosure.

[102] The prediction unit of the encoding equipment/decoding equipment can extract a predictive sample by performing inter prediction in units of blocks. Inter-prediction may be a prediction derived in a manner that depends on data elements (eg, sample values or motion information, etc.) of a frame(s) other than the current frame. When inter prediction is applied to a current block, a predicted block (predictive sample array) for the current block may be derived based on a reference block (reference sample array) indicated by a motion vector in a reference frame indicated by a reference frame index. Here, in order to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information of the current block may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring block and the current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction type information (L0 prediction, L1 prediction, bi-prediction, etc.). In the case of inter prediction, an adjacent block may include a spatial adjacent block present in the current frame and a temporal adjacent block present in the reference frame. The reference frame including the reference block and the reference frame including the temporal neighbor block may be the same or different. The temporal neighbor block may be referred to as a "collocated reference block", "collocated CU (colCU)" or the like, and a reference frame including the temporal neighbor block may be referred to as a "collocated frame (colPic)". For example, a list of motion information candidates may be configured based on adjacent blocks of the current block, and flag or index information indicating which candidate is selected (used) may be signaled to derive a motion vector and/or a reference frame index. current block. Inter prediction may be performed based on various prediction modes. For example, in the case of the skip mode and the join mode, the motion information of the current block may be identical to the motion information of the neighboring block. In the skip mode, unlike the combine mode, the residual signal may not be transmitted. In the case of a motion vector prediction (MVP) mode, the motion vector of a selected neighboring block may be used as a motion vector predictor, and the motion vector of the current block may be signaled. In this case, the motion vector of the current block may be extracted using the sum of the motion vector predictor and the motion vector difference.

[103] The motion information may include L0 motion information and/or L1 motion information according to the type of mutual prediction (L0 prediction, L1 prediction, bi-prediction, etc.). The motion vector in the L0 direction may be referred to as the "L0 motion vector" or "MVL0", and the motion vector in the L1 direction may be referred to as the "L1 motion vector" or "MVL1". Prediction based on the L0 motion vector may be referred to as "L0 prediction", prediction based on the L1 motion vector may be referred to as "L1 prediction", and prediction based on both the L0 motion vector and the L1 motion vector may be referred to as "biprediction". ". Here, the L0 motion vector may indicate a motion vector associated with the L0 list of reference frames (L0), and the L1 motion vector may indicate a motion vector associated with the L1 list of reference frames (L1). The reference frame list L0 may include frames that are earlier in the output order than the current frame as reference frames, and the reference frame list L1 may include frames that are later in the output order than the current frame. Previous frames may be referred to as "forward (reference) frames", and subsequent frames may be referred to as "reverse (reference) frames". The reference frame list L0 may further include frames that are later in the output order than the current frame as reference frames. In this case, previous frames may be indexed first in the reference frame list L0, and subsequent frames may be indexed later. The reference frame list L1 may further include previous frames in output order relative to the current frame as reference frames. In this case, subsequent frames may be indexed first in the reference frame list 1, and previous frames may be indexed later. The output order may correspond to the order of the numbers in the order of frames (POC).

[104] FIG. 4 roughly shows the hierarchical structure for an encoded picture/video.

[105] Referring to FIG. 4, the encoded image/video is divided into a video coding layer (VCL) that handles the process of decoding the image/video and itself, a subsystem that transmits and stores the encoded information, and a NAL (network abstraction layer) responsible for the function and present between the VCL. and subsystem.

[106] In the VCL, VCL data including compressed image data (slice data) is generated, or a parameter set including a frame parameter set (PSP), a sequence parameter set (SPS), and a video parameter set (VPS) may be generated. ), or a Supplemental Enhancement Information (SEI) message additionally required for the picture decoding process.

[107] In the NAL, a NAL unit may be generated by adding header information (NAL unit header) to a Primary Data Byte Sequence (RBSP) generated in the VCL. In this case, RBSP means slice data, parameter set, SEI message, etc. generated in the VCL. The NAL unit header may include NAL unit type information indicated according to the RBSP data included in the corresponding NAL unit.

[108] As shown in the drawing, a NAL unit can be classified into a VCL NAL unit and a non-VCL NAL unit according to the RBSP generated in the VCL. A VCL NAL unit may mean a NAL unit that includes information about an image (slice data) in an image, and a non-VCL NAL unit may mean a NAL unit that includes information (parameter set or SEI message) required for image decoding.

[109] The above VCL NAL unit and non-VCL NAL unit can be transmitted through the network by attaching header information according to the subsystem data standard. For example, the NAL unit can be converted to a data format of a predetermined standard such as H.266/VVC file format, Real Time Transport Protocol (RTP), Transport Stream (TS), etc., and transmitted through various networks.

[110] As described above, the NAL unit may be indicated with the type of the NAL unit according to the RBSP data structure included in the corresponding NAL unit, and information regarding the type of the NAL unit may be stored and signaled in the header of the NAL unit.

[111] For example, a NAL unit may be classified into a VCL type of a NAL unit and a non-VCL NAL unit type according to whether or not the NAL unit includes information (slice data) about an image. The VCL type of the NAL unit may be classified according to the nature and type of frames included in the VCL NAL unit, and the non-VCL type of the NAL unit may be classified according to parameter set types.

[112] The following is an example of a NAL unit type specified according to a parameter set type included in a non-VCL NAL unit type.

[113] - APS (Adaptation Parameter Set) NAL Unit: A type for a NAL unit including an APS

[114] - DPS (Decoding Parameter Set) NAL Unit: A type for a NAL unit including a DPS

[115] - VPS (Video Parameter Set) NAL Unit: A type for a NAL unit including a VPS

[116] - SPS (Sequence Parameter Set) NAL Unit: A type for a NAL unit including an SPS

[117] - PPS (Frame Parameter Set) NAL Unit: A type for a NAL unit including a PPS

[118] - PH (Frame Header) NAL Unit: A type for a NAL unit including a PH

[119] The above NAL unit types may have syntax information for the NAL unit type, and the syntax information may be stored and signaled in the NAL unit header. For example, the syntax information may be nal_unit_type and the types of NAL units may be indicated by the value of nal_unit_type.

[120] Meanwhile, as described above, one frame may include a plurality of slices, and one slice may include a slice header and slice data. In this case, one frame header may additionally be added to a plurality of slices (a slice header and a slice data set) in one frame. The frame header (frame header syntax) may include information/parameters generally applicable to the frame. In the present disclosure, a slice may be mixed or replaced by a group of tiles. In addition, in the present disclosure, the slice header may be mixed with or replaced with a tile group header.

[121] The slice header (slice header syntax, slice header information) may include information/parameters that may be applied generically to the slice. APS (APS Syntax) or PPS (PPS Syntax) may include information/parameters that may be applied generically to one or more slices or frames. SPS (SPS syntax) may include information/parameters that may be applied generically to one or more sequences. VPS (VPS Syntax) may include information/parameters that may be applied generically to multiple layers. DPS (DPS Syntax) may include information/parameters that may be applied generically to the full video. The DPS may include information/parameters related to coded video sequence (CVS) concatenation. The High Level Syntax (HLS) in the present disclosure may include at least one of APS Syntax, PPS Syntax, SPS Syntax, VPS Syntax, DPS Syntax, and Slice Header Syntax.

[122] In the present disclosure, the image/image information encoded from the encoding equipment and signaled to the decoding equipment in the form of a bit stream includes not only segmentation-related information in a frame, intra/inter prediction information, residual information, in-loop filtering information and the like, but also information included in the slice header, information included in the APS, information included in the PPS, information included in the SPS, and/or information included in the VPS.

[123] Meanwhile, in order to compensate for the difference between the original image and the reconstructed image due to an error occurring in a compression encoding process such as quantization, an in-loop filtering process may be performed on the reconstructed samples or reconstructed frames as described above. As described above, in-loop filtering may be performed by an encoding equipment filter and a decoding equipment filter, and a deblocking filter, SAO, and/or an adaptive loop filter (ALF) may be applied. For example, the ALF process may be executed after the deblocking filtering process and/or the SAO process is completed. However, even in this case, the deblocking filtering process and/or the SAO process may be omitted.

[124] Later in this document, a detailed description of frame recovery and filtering is provided. In image/video coding, a reconstructed block may be generated based on intra-prediction/inter-prediction for each block, and a reconstructed frame including the reconstructed blocks may be generated. When the current frame/slice is an I-frame/slice, blocks included in the current frame/slice can only be reconstructed based on intra prediction. Meanwhile, when the current frame/slice is a P or B frame/slice, blocks included in the current frame/slice may be reconstructed based on intra prediction or inter prediction. In this case, intra prediction may be applied to some blocks in the current frame/slice, and inter prediction may be applied to the remaining blocks.

[125] Intra prediction may mean prediction that generates predictive samples for a current block based on reference samples in a frame to which the current block belongs (hereinafter referred to as "current frame"). When intra prediction is applied to the current block, adjacent reference samples to be used for intra prediction of the current block may be extracted. Adjacent reference samples of the current block may include samples adjacent to the left border relative to the current block having size nWxnH and a total of 2xnH samples bordering the bottom left, samples adjacent to the upper border relative to the current block and a total of 2xnW samples , bordering the top right, and one selection bordering the top left, relative to the current box. Alternatively, the adjacent reference samples of the current block may include a plurality of upper neighbor samples and a plurality of left neighbor samples. In addition, the adjacent reference samples of the current block may include a sum of nH samples adjacent to the right boundary with respect to the current block having size nWxnH, a sum of nW samples adjacent to the lower boundary with respect to the current block, and one sample adjacent to the lower right with respect to current block.

[126] However, some adjacent reference samples of the current block may not yet be decoded or may not be available. In this case, the decoder may configure adjacent reference samples to be used for prediction by substituting available samples for samples that are not available. Alternatively, adjacent reference samples to be used for prediction may be configured through interpolation of the available samples.

[127] When adjacent reference samples are extracted, a predictive sample may be derived based on an average or interpolation of adjacent reference samples of the current block and (ii) prediction from adjacent reference samples of the current block. The predictive sample may be derived based on a reference sample present in a particular direction (prediction) relative to the sample. Case (i) may be referred to as "non-directional mode" or "non-angular mode", and case (ii) may be referred to as "directional mode" or "angular mode". In addition, based on the prediction sample of the current block from the neighboring reference samples, the second neighboring sample located in the opposite direction from the prediction direction of the intra prediction mode of the current block and the first neighboring sample are interpolated. A predictive sample can be formed. The above case may be referred to as "linear interpolation intra prediction (LIP)". In addition, the chrominance signal prediction samples may be generated based on the luminance signal samples using a linear model. This case may be referred to as "LM mode". In addition, the temporal prediction sample of the current block may be derived based on the filtered neighboring reference samples and at least one reference sample derived according to the intra prediction mode from the existing neighboring reference samples, i. e. the unfiltered adjacent reference samples and the temporal prediction sample may be added with weighting to derive the current block prediction sample. The above case may be referred to as "position dependent intra prediction (PDPC)". In addition, a reference sample line having the highest prediction accuracy of the adjacent multiple reference sample lines of the current block may be selected to derive a prediction sample by using a reference sample located in the prediction direction on the corresponding line, and then the reference sample line used herein , may be indicated (signaled) to the decoding equipment, thereby performing intra predictive coding. The above case may be referred to as "multiple reference line (MRL) intra prediction" or "MRL intra prediction". In addition, intra prediction may be performed based on the same intra prediction mode by dividing the current block into vertical or horizontal sub-segments, and adjacent reference samples may be extracted and used in a unit of sub-segments. Thus, in this case, the intra prediction mode for the current block is equally applied to the sub-segments, and the performance of the intra prediction can be improved in some cases by extracting and using neighboring reference samples in a unit of sub-segments. Such a prediction method may be referred to as "intra-sub-segment prediction (ISP) or ISP-based". The above-described intra prediction methods may be referred to as "intra prediction type" apart from the intra prediction mode. The type of intra prediction may be referred to by various terms such as "intra prediction technology" or "additional intra prediction mode". For example, the intra prediction type (or additional intra prediction mode) may include at least one of LIP, PDPC, MRL, and ISP described above. The general intra prediction method except for a specific type of intra prediction such as LIP, PDPC, MRL, or ISP may be referred to as "normal intra prediction type". The normal intra prediction type may generally be applied when a particular type of intra prediction is not applied, and prediction may be performed based on the intra prediction mode described above. Meanwhile, post-filtering can be performed on the predicted sample, drawn as needed.

[128] Specifically, the intra prediction procedure may include an intra prediction mode/type determination step, an adjacent reference sample extraction step, and a prediction sample extraction step based on the intra prediction mode/type. In addition, the post-filtering step may be performed on the predicted sample, drawn as needed.

[129] Hereinafter, this document describes intra prediction in the coding equipment. The encoding equipment may extract the intra prediction mode for the current block, extract adjacent reference samples of the current block, and generate prediction samples in the current block based on the intra prediction mode and adjacent reference samples. Here, the procedures for determining the intra prediction mode, extracting the peripheral reference samples, and generating the prediction samples may be performed simultaneously, or one procedure may be performed before the other procedure. For example, the encoder intra prediction module 222 may include a prediction mode/type determination module, a reference sample extraction module, and a prediction sample extraction module, and the prediction mode/type determination module may determine the intra prediction mode/type for the current block, the reference sample extraction module samples may extract adjacent reference samples of the current block, and a predictive sample extractor may extract motion samples of the current block. Meanwhile, although not shown when the above-described prediction sample filtering procedure is performed, the intra prediction module 222 may further include a prediction sample filter (not shown). The encoding equipment may determine the mode applied to the current block from the plurality of intra prediction modes. The encoding equipment can compare the RD costs for the intra prediction modes and determine the optimal intra prediction mode for the current block.

[130] Meanwhile, the encoding equipment may perform a filtering procedure on the predictive samples. Filtering predictive samples may be referred to as "post-filtering". Some or all of the prediction samples may be filtered by a prediction sample filtering procedure. In some cases, the filtering procedure for predictive samples may be omitted.

[131] The encoding equipment extracts residual samples for the current block based on the predictive samples (S510). The encoding equipment may compare the predictive samples in the original samples of the current block on a phase basis and extract the residual samples.

[132] The encoding equipment may transform/quantize the residual samples to extract quantized transform coefficients (S520), and thereafter dequantize/inversely transform the quantized transform coefficients again to extract (modified) residual samples (S530). The reason for performing the dequantization/inverse transformation again after the transformation/quantization is to extract residual samples identical to the residual samples extracted from the decoding equipment as described above.

[133] The encoding equipment may generate a reconstructed block including reconstructed samples for the current block based on the predictive samples and the (modified) residual samples (S540). The reconstructed frame for the current frame may be generated based on the reconstructed block.

[134] The encoding equipment may encode image information including prediction information about intra prediction (for example, prediction mode information indicating a prediction mode) and residual information about intra and residual samples, and output the encoded image information in the form of a bitstream, as described. above. The residual information may include a residual encoding syntax. The encoding equipment may transform/quantize the residual samples so as to extract the quantized transform coefficients. The residual information may include information regarding the quantized transform coefficients.

[135] FIG. 5 is a flowchart illustrating a block recovery method based on intra prediction in decoding equipment. The method according to FIG. 5 may include steps S500, S510, S520, S530, and S540. The decoding equipment may perform an operation corresponding to the operation performed in the encoding equipment.

[136] S500-S520 may be executed by the intra prediction unit 331 of the decoding equipment, and prediction information of S500 and residual information of S530 may be obtained from the bitstream by the entropy decoder 310 of the decoding equipment. The decoding hardware residual processor 320 may derive residual samples for the current block based on the residual information. Specifically, the dequantizer 321 of the residual processor 320 extracts the transform coefficients by performing dequantization based on the quantized transform coefficients derived based on the residual information, and the inverse transform 322 of the residual processor can extract the residual samples for the current block by performing an inverse transform on the transform coefficients. S540 may be performed by adder 340 or decode hardware recovery module.

[137] Specifically, the decoding equipment may derive the intra prediction mode for the current block based on the received prediction mode information (S500). The decoding equipment may extract the peripheral reference samples of the current block (S510). The decoding equipment generates prediction samples in the current block based on the intra prediction mode and neighboring reference samples (S520). In this case, the image decoding equipment may perform a prediction sample filtering procedure. Filtering predictive samples may be referred to as "post-filtering". Some or all of the prediction samples may be filtered by a prediction sample filtering procedure. In some cases, the filtering procedure for predictive samples may be omitted.

[138] The decoding equipment generates residual samples for the current block based on the received residual information (S530). The decoding equipment may generate reconstructed samples for the current block based on the predictive samples and the residual samples, and extract a reconstructed block including the reconstructed samples (S540). The reconstructed frame for the current frame may be generated based on the reconstructed block.

[139] Here, the decoding equipment intra prediction unit 331 may include a prediction mode/type determination unit, a reference sample extraction unit, and a prediction sample extraction unit, and the prediction mode/type determination unit may determine the intra prediction mode for the current block based on the information of the prediction mode obtained by the entropy decoder 310 of the decoding equipment, the reference sample extractor may extract the peripheral reference samples of the current block, and the prediction sample extractor may extract the prediction samples of the current block. Meanwhile, although not shown, when the prediction sample filtering procedure described above is performed, the intra prediction unit 331 may further include a prediction sample filter (not shown).

[140] The prediction information may include intra prediction mode information and/or intra prediction type information. The intra prediction mode information may include, for example, flag information (eg, intra_luma_mpm_flag) indicating whether or not the most likely mode (MPM) is applied to the current block, or the remaining mode is applied, and when the MPM is applied to the current block, the mode information The prediction may further include index information (eg, intra_luma_mpm_idx) indicating one of the possible intra prediction modes (MPM candidates). Intra prediction mode candidates (MPM candidates) may include an MPM candidate list or an MPM list. In addition, when MPM is not applied to the current block, the intra prediction mode information may further include remaining mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra prediction modes except for intra prediction mode options (MPM options) . The decoding equipment may determine the intra prediction mode of the current block based on the intra prediction mode information. A separate MPM list can be configured for the above MIP.

[141] In addition, the intra-prediction type information may be implemented in various forms. For example, the intra prediction type information may include intra prediction type index information indicating one of the intra prediction types. As another example, the intra prediction type information may include at least one of reference sample line information (e.g., intra_luma_ref_idx) indicating whether or not an MRL is applied to the current block, and if so, which reference sample line is being used. , ISP flag information (eg, intra_subpartitions_mode_flag) indicating whether or not ISP is applied to the current block, ISP type information (eg, intra_subpartitions_split_flag) indicating the sub-partition splitting type when ISP is applied, flag information indicating whether or not PDCP, or flag information indicating whether or not LIP is applied. In addition, the intra prediction type information may include a MIP flag indicating whether or not MIP is applied to the current block.

[142] The intra prediction mode information and/or the intra prediction type information may be encoded/decoded via the coding method described in the present disclosure. For example, the intra prediction mode information and/or the intra prediction type information may be coded/decoded by entropy coding (eg, CABAC, CAVLC) based on a truncated binary code (Rice).

[143] The prediction module of the encoding equipment/decoding equipment can extract predictive samples by performing inter-prediction on a block-by-block basis. Inter-prediction may be a prediction derived in a manner that depends on data elements (eg, sample values or motion information) of a frame(s) other than the current frame. When inter prediction is applied to a current block, a predicted block (predictive sample array) for the current block may be derived based on a reference block (reference sample array) indicated by a motion vector in a reference frame indicated by a reference frame index. In this case, in order to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information of the current block may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the adjacent block and the current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction type information (L0 prediction, L1 prediction, bi-prediction, etc.). When inter prediction is applied, the neighbor block may include a spatial neighbor block that is present in the current frame and a temporal neighbor block that is present in the reference frame. The reference frame including the reference block and the reference frame including the temporal neighbor block may be identical to each other or different from each other. The temporal neighbor block may be referred to as "collocated reference block", "collocated CU (colCU)", etc., and a reference frame including the temporal neighbor block may be referred to as "collocated frame ( colpic)". For example, a list of motion information candidates may be configured based on neighboring blocks of the current block, and flag or index information indicating which candidate is selected (used) in order to derive the motion vector and/or index of the reference frame of the current block may transmitted in service signals. Inter-prediction may be performed based on different prediction modes and, for example, in the case of the skip mode and the join mode, the motion information of the current block may be identical to the motion information of the adjacent block. In the case of the skip mode, the residual signal may not be transmitted, in contrast to the combine mode. In the case of the motion vector prediction (MVP) mode, the motion vector of the selected neighboring block is used as a motion vector predictor, and the motion vector difference may be signaled. In this case, the motion vector of the current block may be extracted using the sum of the motion vector predictor and the motion vector difference.

[144] FIG. 6 is a flowchart illustrating a block recovery method based on inter prediction in coding equipment. The method according to FIG. 7 may include steps S600, S610, S620, S630, and S640.

[145] S600 may be performed by the coding equipment inter-prediction unit 221, and S610-S630 may be performed by the coding equipment residual processor 230. Specifically, S610 may be performed by the encoding equipment subtractor 231, S620 may be performed by the encoding equipment converter 232 and quantizer 233, and S630 may be performed by the encoding equipment dequantizer 234 and inverse converter 235. At S600, prediction information may be extracted by inter-prediction unit 221 and encoded by entropy encoder 240. Residual information may be extracted through S610 and S620 and encoded by entropy encoder 240. Residual information is information regarding residual samples. The residual information may include information regarding quantized transform coefficients for the residual samples. As described above, the residual samples may be extracted as transform coefficients via the coding equipment transform 232, and the transform coefficients may be extracted as quantized transform coefficients via the quantizer 233. Information regarding the quantized transform coefficients may be encoded by the entropy encoder 240 via a residual encoding procedure.

[146] The encoding equipment performs inter prediction for the current block (S600). The encoding equipment may extract the inter-prediction mode and motion information of the current block, and generate prediction samples of the current block. Here, the procedures for determining the inter-prediction mode, extracting motion information, and generating prediction samples may be performed simultaneously, or one procedure may be performed before another procedure. For example, the coding equipment inter-prediction unit 221 may include a prediction mode determination unit, a motion information extraction unit, and a prediction sample extraction unit, and the prediction mode determination unit may determine the prediction mode for the current block, the motion information extraction unit may extract the motion information of the current block. , and the prediction sample extractor may extract motion samples of the current block. For example, the coding equipment inter-prediction unit 221 may search for a block similar to the current block in a predetermined area (search area) of reference frames through motion estimation, and may extract a reference block in which the difference with respect to the current block is the minimum or is a predetermined reference value or less. Based on this, a reference frame index indicating a reference frame in which the reference block is located may be extracted, and a motion vector may be extracted based on a position difference between the reference block and the current block. The encoding equipment may determine the mode applied to the current block from among various prediction modes. The encoding equipment can compare the rate-dependent distortion cost (RD) functions for different prediction modes and determine the optimal prediction mode for the current block.

[147] For example, when the skip mode or merge mode is applied to the current block, the encoding equipment may construct a merge candidate list, which is described below, and extract a reference block in which the difference with respect to the current block is minimal or is a predetermined reference value or less , from the reference blocks indicated by the join candidates included in the join candidate list. In this case, the combining candidate associated with the extracted reference block may be selected, and combining index information indicating the selected combining candidate may be generated and signaled to the decoding equipment. The motion information of the current block may be extracted using the motion information of the selected join candidate.

[148] As another example, when the (A)MVP mode is applied to the current block, the encoding equipment constructs an (A)MVP candidate list, which is described below, and uses the motion vector of the selected MVP candidate from the predictor candidates motion vectors (MVP) included in the list of possible (A)MVP options as the MVP of the current block. In this case, for example, a motion vector indicating a reference block derived by the motion estimation described above can be used as the motion vector of the current block, and an MVP candidate having a motion vector having the smallest difference relative to the motion vector of the current block, of possible MVPs may be the selected MVP candidate. A motion vector difference (MVD), which is a difference obtained by subtracting the MVP from the motion vector of the current block, can be extracted. In this case, information regarding the MVD may be signaled to the decoding equipment. In addition, when the (A)MVP mode is applied, the index value of the reference frame may be configured as reference frame index information and separately signaled to the decoding equipment.

[149] The encoding equipment may derive residual samples based on the predictive samples (S610). The encoding equipment can extract residual samples by comparing the original samples of the current block with the predictive samples.

[150] The encoding equipment transforms/quantizes the residual samples to extract quantized transform coefficients (S620), and then dequantizes/inversely transforms the quantized transform coefficients again to extract (modified) residual samples (S630). The reason for performing the dequantization/inverse transformation again after the transformation/quantization is to extract residual samples identical to the residual samples extracted from the decoding equipment as described above.

[151] The encoding equipment may generate a reconstructed block including reconstructed samples for the current block based on the predictive samples and the (modified) residual samples (S640). The reconstructed frame for the current frame may be generated based on the reconstructed block.

[152] Although not shown as described above, the encoding equipment 100 can encode video information including prediction information and residual information. The encoding equipment 100 may output encoded image information in the form of a bit stream. The prediction information may be information related to the prediction procedure and may include prediction mode information (eg, skip flag, merge flag, or mode index) and motion information. The motion information may include candidate selection information (eg, merge index, MVP flag, or MVP index), which is information for extracting a motion vector. In addition, information regarding motion information may include the above MVD information and/or reference frame index information. In addition, the information on the motion information may include information indicating whether or not L0 prediction, L1 prediction, or bi-prediction is applied. The residual information is information about the residual samples. The residual information may include information regarding quantized transform coefficients for the residual samples.

[153] The output bitstream may be stored on a (digital) storage medium and transmitted to the decoding equipment, or may be transmitted to the decoding equipment via a network.

[154] FIG. 7 is a flowchart illustrating a block recovery method based on inter prediction in decoding equipment. The method according to FIG. 7 may include steps S700, S710, S720, S730, and S740. The decoding equipment may perform an operation corresponding to the operation performed by the encoding equipment.

[155] S700-S720 may be performed by the decoding equipment mutual prediction unit 332, and prediction information on S700 and residual information on S730 may be obtained from the bitstream by the entropy decoder 310 of the decoding equipment. The decoding hardware residual processor 320 may derive residual samples for the current block based on the residual information. In particular, the dequantizer 321 of the residual processor 320 may extract the transform coefficients by performing dequantization based on the quantized transform coefficients derived based on the residual information, and the dequantizer 322 of the residual processor may extract the residual samples for the current block by performing an inverse transform on the transform coefficients. S740 may be performed by adder 340 or decode hardware recovery module.

[156] In particular, the decoding equipment may determine the prediction mode for the current block based on the received prediction information (S700). The decoding equipment can determine which inter prediction mode is applied to the current block based on the prediction mode information in the prediction information.

[157] For example, it may be determined whether or not the merge mode is applied to the current block, or whether or not the (A)MVP mode is determined based on the merge flag. Alternatively, one of the various possible inter-prediction modes may be selected based on the mode index. Possible options for the inter prediction mode may include skip mode, merge mode, and/or (A)MVP mode, or may include various inter prediction modes, which are described below.

[158] The decoding equipment extracts motion information of the current block based on the determined inter-prediction mode (S710). For example, when the skip mode or merge mode is applied to the current block, the decoding equipment may configure a merge candidate list, which is described below, and select one merge candidate from among the merge candidates included in the merge candidate list. The selection may be performed based on the above selection information (combination index). The motion information of the current block may be extracted using the motion information of the selected join candidate. The motion information of the selected join candidate may be used as the motion information of the current block.

[159] As another example, when the (A)MVP mode is applied to the current block, the decoding equipment may construct the (A)MVP candidate list, which is described below, and use the motion vector of the selected MVP candidate from among the candidates motion vector predictors (MVP) included in the list of possible (A)MVP options as the MVP of the current block. The selection may be performed based on the selection information (MVP flag or MVP index) described above. In this case, the MVD of the current block may be derived based on the information regarding the MVD, and the motion vector of the current block may be derived based on the MVP of the current block and the MVD. In addition, the index of the key frame of the current block may be derived based on the information of the index of the key frame. The frame indicated by the reference frame index in the reference frame list for the current block may be retrieved as the reference frame referenced for inter-prediction of the current block.

[160] Meanwhile, as described below, the motion information of the current block can be retrieved without configuring the candidate list. In this case, the motion information of the current block may be extracted according to the procedure disclosed in the prediction mode, which is described below. In this case, the option list configuration as described above may be omitted.

[161] The decoding equipment may generate prediction samples for the current block based on motion information of the current block (S720). In this case, the reference frame may be derived based on the reference frame index of the current block, and the prediction samples of the current block may be derived using the reference block samples indicated by the motion vector of the current block in the reference frame. In this case, as described below, the filtering procedure of the prediction samples for all or some of the prediction samples of the current block may further be performed depending on the case.

[162] For example, the decoding equipment inter-prediction unit 332 may include a prediction mode determination unit, a motion information extraction unit, and a prediction sample extraction unit, and the prediction mode determination unit may determine the prediction mode for the current block based on the received prediction mode information, the unit the motion information extractor may extract the motion information (motion vector and/or reference frame index, etc.) of the current block based on the received information regarding the motion information, and the prediction sample extractor may extract the prediction samples of the current block.

[163] The decoding equipment generates residual samples for the current block based on the received residual information (S730). The decoding equipment may generate reconstructed samples for the current block based on the predictive samples and the residual samples, and may extract a reconstructed block including the reconstructed samples (S740). The reconstructed frame for the current frame may be generated based on the reconstructed block.

[164] Various inter-prediction modes may be used to predict the current block in a frame. For example, various modes such as merge mode, skip mode, motion vector prediction (MVP) mode, affine mode, sub-block based merge mode, and MVD merge mode (MMVD), and the like, may be used. Decoder side motion vector detail mode (DMVR), adaptive motion vector resolution (AMVR) mode, CU layer weighting biprediction (BCW), bidirectional optical flow (BDOF), and the like. can also be used as additional modes in addition or instead. The affine mode may be referred to as "affine motion prediction mode". The MVP mode may be referred to as "Advanced Motion Vector Prediction (AMVP) mode". In the present disclosure, some modes and/or motion information candidates retrieved by some modes may be included as one of the motion information candidates of other modes. For example, an HMVP candidate may be added as a merge candidate in merge/skip mode, or may be added as an MVP candidate in MVP mode.

[165] Prediction mode information indicating the inter-prediction mode of the current block may be signaled from the encoding equipment to the decoding equipment. The prediction mode information may be included in the bitstream and received by the decoding equipment. The prediction mode information may include index information indicating one of the plurality of possible modes. Alternatively, the inter-prediction mode may be indicated via hierarchical signaling of flag information. In this case, the prediction mode information may include one or more flags. For example, a skip flag may be signaled to indicate whether or not the skip mode is applied, and if the skip mode is not applied, a merge flag may be signaled to indicate whether or not the merge mode is applied, and if the merge mode is not applied. applied, the need to apply the MVP mode is indicated, or a flag for additional classification may optionally be signaled. The affine mode may be signaled in an independent mode, or may be signaled in a mode dependent on the combining mode or the MVP mode. For example, an affine mode may include an affine join mode and an affine MVP mode.

[166] Meanwhile, information indicating whether or not the list 0 (L0) prediction, list 1 (L1) prediction, or bi-prediction described above is used in the current block (current coding unit) may be transmitted overhead. signals in the current block. The information may be referred to as "motion prediction direction information", "inter prediction direction information", or "inter prediction indicator information", and may be configured/encoded/transmitted in signaling, for example, in the form of an inter_pred_idc syntax element. Thus, the inter_pred_idc syntax element may indicate whether or not the above list 0 (L0) prediction, list 1 (L1) prediction, or bi-prediction for the current block (current coding unit) is used. In the present disclosure, for convenience of description, an inter-prediction type (L0 prediction, L1 prediction, or bi-prediction) indicated by the inter_pred_idc syntax element may be indicated as a motion prediction direction. L0 prediction may be represented as pred_L0, L1 prediction as pred_L1, and pair prediction as pred_BI. For example, the following prediction types may be determined according to the value of the inter_pred_idc syntax element.

[167] Tab. one

[168] As described above, one frame may include one or more slices. The slice may have one of the types of slices, including an inner (I) slice, a predictive (P) slice, and a bi-predictive (B) slice. The slice type may be indicated based on the slice type information. For blocks in an I-slice, inter prediction may not be used for prediction, and only intra prediction may be used. Of course, even in this case, the original sample value may be encoded and signaled without prediction. Intra-prediction or inter-prediction can be used for blocks in a P-slice, and only uni-prediction can be used when inter-prediction is used. Meanwhile, intra-prediction or inter-prediction may be used for blocks in a B-slice, and up to bi-prediction may be used when inter prediction is used.

[169] L0 and L1 may include reference frames that are previously encoded/decoded prior to the current frame. For example, L0 may include reference frames before and/or after the current frame in POC order, and L1 may include reference frames after and/or before the current frame in POC order. In this case, L0 may be assigned a smaller key frame index with respect to previous key frames in the POC order than with respect to the current key frames, and L1 may be assigned a smaller key frame index with respect to previous key frames in the POC order than with respect to the current frame. In the case of a B-slice, biprediction may be applied, in which case, unidirectional biprediction may be applied, or bidirectional biprediction may be applied. Bidirectional biprediction may be referred to as "true biprediction".

[170] As described above, the residual block (residual samples) may be derived based on the predicted block (predictive samples) derived through prediction in the coding stage, and the residual samples transformed/quantized by the residual information may be generated. The residual information may include information regarding the quantized transform coefficients. The residual information may be included in the video/image information, and the video/image information may be encoded and transmitted to the decoding equipment in the form of a bitstream. The decoding equipment may obtain residual information from the bitstream and may extract residual samples based on the residual information. In particular, the decoding equipment can extract quantized transform coefficients based on the residual information, and can extract residual blocks (residual samples) through a dequantization/inverse transform procedure.

[171] Meanwhile, at least one (inverse) transformation and/or (de)-quantization procedure may be omitted.

[172] Hereinafter, this document describes the in-loop filtering procedure performed on the reconstructed frame. The modified reconstructed sample, block, frame (or modified filtered sample, block, frame) may be generated through an in-loop filtering procedure, and the modified (modified and filtered) reconstructed frame may be output as a decoded frame in the decoding equipment, and may also be stored in a decoded frame buffer. or storage device of the encoding equipment/decoding equipment and used as a reference frame in the inter prediction procedure during encoding/decoding of the frame thereafter. The in-loop filtering procedure may include a deblocking filtering procedure, a sampled adaptive offset (SAO) filtering procedure, and/or an adaptive loop filtering (ALF) procedure as described above. In this case, one or more of the deblocking filter procedure, the sampled adaptive offset (SAO) filter procedure, the adaptive loop filter (ALF) procedure, and the bilateral filter procedure may be sequentially applied, or all may be sequentially applied. For example, the SAO procedure may be executed after the deblocking filter procedure is applied to the reconstructed frame. Alternatively, for example, the ALF procedure may be performed after the deblocking filter procedure is applied to the reconstructed frame. This can also be done in the coding equipment.

[173] Deblocking filtering is a filtering technique that removes distortion at boundaries between blocks in a reconstructed frame. The deblocking filtering procedure, for example, may extract the target boundary from the reconstructed frame, determine the boundary intensity (bS) for the target boundary, and perform deblocking filtering for the target boundary based on bS; bS may be determined based on the prediction mode, motion vector difference, whether or not the reference frame is identical, whether or not a non-zero significant coefficient exists, etc., for two blocks adjacent to the target boundary.

[174] SAO is a method for compensating for an offset difference between a reconstructed frame and an original frame based on samples. For example, SAO may be applied based on the type, such as band offset, edge offset, and the like. According to SAO, samples can be classified into different categories according to each SAO type, and a bias value can be added to each sample based on the category. The filtering information for SAO may include information regarding whether or not SAO is applied, SAO type information, and SAO offset value information. SAO may be applied to the reconstructed frame after deblocking filtering is applied.

[175] An adaptive loop filter (ALF) is a technique for filtering a reconstructed frame based on samples based on filter coefficients according to a filter shape. The encoding equipment may determine whether or not to apply the ALF, the ALF shape and/or the ALF filter factor, and so on. by comparing the reconstructed frame and the original frame, and may be signaled to the decoding equipment. Thus, the filtering information for the ALF may include information regarding whether or not ALF is applied, ALF filter shape information, ALF filter coefficient information, and the like. ALF may be applied to the reconstructed frame after deblocking filtering is applied.

[176] FIG. 8 shows an example of an ALF filter shape.

[177] FIG. 8, (a) shows the shape of a 7×7 diamond filter, (b) shows the shape of a 5×5 diamond filter. In FIG. 8, Cn in the filter form represents the filter coefficient. When n in Cn is identical, this indicates that identical filter coefficients may be assigned. In the present disclosure, the position and/or unit to which filter coefficients are assigned according to the form of the ALF filter may be referred to as a "filter tap". In this case, one filter coefficient may be assigned to each filter tap, and the arrangement of the filter taps may correspond to the shape of the filter. The filter tap located in the center of the filter shape may be referred to as the "centre filter tap". Identical filter coefficients may be assigned to two filter taps having the same value of n, existing at positions corresponding to each other relative to the center filter tap. For example, in the case of a 7×7 diamond-shaped filter, 25 filter taps are included, and since the filter coefficients C0-C11 are assigned in a centrally symmetrical form, the filter coefficients can be assigned to 25 filter taps using only 13 filter coefficients. Further, for example, in the case of a 5×5 diamond filter, 13 filter taps are included, and since filter coefficients C0-C5 are assigned in a centrally symmetrical form, filter coefficients are assigned to 13 filter taps using only 7 filter coefficients. For example, in order to reduce the data amount of information regarding signaling filter coefficients, 12 of the 13 filter coefficients for a 7×7 diamond filter may be signaled (explicitly) and 1 filter coefficient may (implicitly) be extracted. In addition, for example, 6 out of 7 filter coefficients for a 5×5 diamond filter may be signaled (explicitly) and 1 filter coefficient may be extracted (implicitly).

[178] According to an embodiment of the present disclosure, an ALF parameter used for an ALF procedure may be signaled via an adaptation parameter set (APS). The ALF parameter may be derived from filter information or ALF data for ALF.

[179] ALF is a type of in-loop filtering technology that can be applied in video/image coding as described above. ALF can be performed using an adaptive Wiener filter. This may serve to minimize the mean square error (MSE) between the original samples and the decoded samples (or reconstructed samples). The high-level design for an ALF tool may include syntax elements available in the SPS and/or in the slice header (or tile group header).

[180] In an example, before filtering for each block of 4x4 luminance signals, geometric transformations such as rotation or diagonal and vertical flipping may be applied to the filter coefficients f(k, l) depending on the gradient values computed for the block, and corresponding cut-off values c(k, l) in the filter. This is equivalent to applying these transformations to the samples in the filter media zone. The creation of other blocks to which ALF is applied may be similar to the placement of these blocks according to their orientation.

[181] For example, three transformations, diagonal, vertical flip and rotation, can be performed based on the following equations.

[182] Equation 1

Diagonal: f_D(k, l)=f(l, k), c_D(k, l)=c(l, k)

[183] Equation 2

Vertical flip: f_V(k, l)=f(k, K-l-1), c_V(k, l)=c(k, K-l-1)

[184] Equation 3

Rotation: f_R(k, l)=f(K-l-1, k), c_R(k, l)=c(K-l-1, k)

[185] In Equations 1-3, K may be a filter size. 0≤k and 1≤K-1 may represent coefficient coordinates. For example, (0, 0) may represent a left upper corner coordinate, and/or (K-1, K-1) may represent a lower right corner coordinate. The relationship between transformations and four gradients in four directions can be summarized in the following table.

[186] Tab. 2

Gradient values transformation g _d2 <g _d1 and g _h <g _v Lack of conversion g _d2< g _d1 and g _v< g _h Diagonal g _d1< g _d2 and g _h< g _v Vertical flip g _d1< g _d2 and g _v< g _h Rotation

[187] The ALF filter parameters may be signaled in the APS and the slice header. In one APS, up to 25 luma filter coefficients and cutoff indexes can be signaled. In one APS, up to 8 chrominance filter coefficients and cutoff indexes can be signaled. To reduce the extra number of bits, the filter coefficients of different classifications for the luma component may be combined. In the slice header, the APS indices (referenced by the current slice) used for the current slice may be signaled.

[188] The clip value indices decoded from the APS may allow clip values to be determined using the clip value luma table and the clip value chrominance table. These clipping values may depend on the internal bit depth. More specifically, the luminance signal table of the clipping values and the chrominance signal table of the clipping values can be derived based on the following equations.

[189] Equation 4

AlfClipL={round(2^(B(N-n+1)/N)) for n∈[1...N]}

[190] Equation 5

AlfClipC={round(2^((B-8)+8((N-n))/(N-1))) for n∈[1...N]}

[191] In the above

equations, B may be the internal bit depth, and N may be the number of allowed clipping values (a predetermined number). For example, N might be 4.

[192] In the slice header, up to 7 APS indices may be signaled to indicate the luminance filter sets used for the current slice. The filtering procedure can additionally be controlled at the CTB level. For example, a flag indicating whether or not ALF is applied to the CTB of luma signals may be signaled. The luminance CTB can select from 16 fixed filter sets and APS filter sets. The filter bank index may be signaled for the luminance CTB to indicate which filter bank is applied. The 16 fixed filter sets can be predefined and hardcoded in the encoder and decoder.

[193] For the chroma component, an APS index may be signaled in a slice header to indicate the chrominance filter sets used for the current slice. At the CTB level, when there are two or more chrominance filter sets in an APS, a filter index may be signaled for each chrominance CTB.

[194] The filter coefficients may be quantized with 128 as the norm. To limit the complexity of the multiplication, bitstream matching may be applied such that the non-center position coefficient values may range from 0 to 28, and/or the coefficient values of the remaining positions may range from -27 to 27-1. The center position coefficient may not be signaled in the bitstream, and may be predetermined (considered) to be 128.

[195] When ALF is available for the current block, each sample R(i, j) may be filtered, and the filtered result R'(i, j) may be expressed by the following equation.

[196] Equation 6

[197] In the above equation, f(k, l) may be the decoded filter coefficients, K(x, y) may be a clipping function, and c(k, l) may be the decoded clipping parameters. For example, the variables k and/or l may range from -L/2 to L/2. Here, L may represent the length of the filter. The clipping function K(x, y)=min (y, max(-y, x)) can correspond to the Clip3(-y, y, x) function.

[198] In an example, to reduce the linear ALF buffer requirement, modified block classification and filtering may be applied to samples adjacent to horizontal CTU boundaries. To this end, virtual boundaries may be defined.

[199] FIG. 9 is a diagram illustrating a virtual boundary applied to a filtering procedure according to an embodiment of the present document. Fig. 10 illustrates an example of an ALF procedure using a virtual boundary according to an embodiment of the present disclosure. In the following, FIG. 10 in combination with FIG. nine.

[200] Referring to FIG. 9, the virtual boundary may be a line defined by shifting the horizontal CTU boundary by N samples. In an example, N may be equal to 4 for the luminance signal component, and/or N may be equal to 2 for the chrominance signal component.

[201] FIG. 9, the modified block classification may be applied to the luma component. For a one-dimensional Laplacian gradient computation of a 4×4 block at a virtual boundary, only samples above the virtual boundary can be used. Likewise, to calculate the 1D Laplace gradient of a 4×4 block below the virtual boundary, only samples below the virtual boundary can be used. The quantization of the activity value A can be scaled accordingly to account for the reduced number of samples used in the one-dimensional Laplace gradient calculation.

[202] For the filtering procedure, a symmetrical addition operation on virtual boundaries can be used for the luminance and chrominance signal components. Referring to FIG. 9, when the filtered sample is located below the virtual boundary, adjacent samples located above the virtual boundary may be padded. Meanwhile, corresponding samples on the other side can also be symmetrically padded.

[203] The procedure described in accordance with FIG. 10 can also be used for slice, brick and/or tile borders when no filter is available on the borders. To classify ALF blocks, only the samples contained in the identical slice, brick, and/or tile can be used, and the activity value can be scaled accordingly. For ALF filtering, symmetrical padding may be applied for each of the horizontal and/or vertical directions relative to the horizontal and/or vertical boundaries.

[204] FIG. 11 is a diagram illustrating a cross-component adaptive loop filtering (CC-ALF) procedure according to an embodiment of the present document. The CC-ALF procedure may be referred to as the "cross-component filtering procedure".

[205] In an aspect, the ALF procedure may include a general ALF procedure and a CC-ALF procedure. Thus, CC-ALF-procedure can mean some of the procedures from the ALF-procedure. In another aspect, the filtering procedure may include a deblocking procedure, an SAO procedure, an ALF procedure, and/or a CC-ALF procedure.

[206] CC-ALF may detail each component of the chrominance signals using sampled values of the luminance signals. The CC-ALF is controlled by bitstream information (images) that includes (a) information regarding filter coefficients for each chroma component and (b) information regarding a mask that controls the application of filtering to blocks of samples. The filter coefficients may be signaled at the APS, and the block size and mask may be signaled at the slice layer.

[207] Referring to FIG. 11, CC-ALF can be operated by applying a linear diamond filter ((b) of FIG. 11) to the luma channel for each chroma component. The filter coefficients are passed to APS, scaled by a factor of 210, and rounded up for fixed point representation. The application of the filter may be controlled at a variable block size and signaled by a context encoding flag received for the blocks of each sample. The block size along with the CC-ALF activation flag may be received at the slice level for each chroma component. The block size (for chrominance samples) may be 16x16, 32x32, 64x64, or 128x128.

[208] In the following embodiments, a method is provided for re-filtering or modifying recovered chrominance samples filtered by ALF based on the recovered luma samples.

[209] An embodiment of the present disclosure relates to filtering on-off transmission and filtering coefficient transmission in CC-ALF. As described above, the information (syntax element) in the syntax table disclosed in the present disclosure may be included in image/video information, may be configured/encoded in an encoder, and transmitted to a decoder in the form of a bit stream. The decoding equipment can parse/decode the information (syntax element) in the corresponding syntax table. The decoding equipment may perform a frame/picture/video decoding procedure (specifically, for example, a CC-ALF procedure) based on the decoded information. This applies later in this document to other embodiments.

[210] The following table shows some syntax of slice header information according to an embodiment of the present disclosure.

[211] Tab. 3

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

[213] Tab. 4

slice_cross_component_alf_cb_enabled_flag equal to 0 indicates that the Cb cross-component filter is not applied to the Cb color component; slice_cross_component_alf_cb_enabled_flag equal to 1 indicates that the Cb cross-component filter is applied to the Cb color component.

slice_cross_component_alf_cr_enabled_flag equal to 0 indicates that the Cr cross-component filter is not applied to the chrominance Cr component; slice_cross_component_alf_cb_enabled_flag equal to 1 indicates that a cross-component Cr filter is applied to the chrominance Cr component.

slice_cross_component_alf_cb_reuse_temporal_layer_filter equal to 1 indicates that the coefficients of the cross-component Cb filter, j=0...13 inclusive, are set equal to AlfCCTemporalCoeffcb[TemporalId][j].

slice_cross_component_alf_cb_reuse_temporal_layer_filter equal to 0 and slice_cross_component_alf_cb_enabled_flag equal to 1 indicate that the slice_cross_component_alf_cb_aps_id syntax element is present in the slice header.

When slice_cross_component_alf_cb_enabled_flag is 1 and slice_cross_component_alf_cb_reuse_temporal_layer_filter is 0, the elements of AlfCCTemporalCoeffcb[TemporalId][j] with j=0...13 are extracted as follows:

AlfCCTemporalCoeffcb[TemporalId][j]=AlfCCCoeffcb[slice_cross_component_alf_cb_aps_id][j]

slice_cross_component_alf_cr_reuse_temporal_layer_filter equal to 1 indicates that the coefficients of the cross-component Cr filter, j=0...13 inclusive, are set to AlfCCTemporalCoeffcr[TemporalId][j].

slice_cross_component_alf_cr_reuse_temporal_layer_filter equal to 0 and slice_cross_component_alf_cr_enabled_flag equal to 1 indicate that the slice_cross_component_alf_cr_aps_id syntax element is present in the slice header.

When slice_cross_component_alf_cr_enabled_flag is 1 and slice_cross_component_alf_cr_reuse_temporal_layer_filter is 0, the elements of AlfCCTemporalCoeffcr[TemporalId][j] with j=0...13 are extracted as follows:

AlfCCTemporalCoeffcr[TemporalId][j]=AlfCCCoeffcr[slice_cross_component_alf_cr_aps_id][j]

slice_cross_component_alf_cb_aps_id indicates the adaptation_parameter_set_id referenced by the Cb color component of the slice for the cross-component Cb filter. When slice_cross_component_alf_cb_aps_id is not present, it is logically inferred to be slice_alf_aps_id_luma[0]. The TemporalId ALF APS of a NAL unit having an adaptation_parameter_set_id equal to slice_cross_component_alf_cb_aps_id shall be less than or equal to the TemporalId of the encoded slice NAL unit.

slice_cross_component_alf_cr_aps_id indicates the adaptation_parameter_set_id referenced by the Cr color component of the slice for the cross-component Cr filter. When slice_cross_component_alf_cr_aps_id is not present, it is logically inferred to be slice_alf_aps_id_luma[0]. The TemporalId ALF APS of a NAL unit having an adaptation_parameter_set_id equal to slice_cross_component_alf_cr_aps_id shall be less than or equal to the TemporalId of the encoded slice NAL unit.

slice_cross_component_alf_cb_log2_control_size_minus4 indicates the value of the square block sizes in the number of samples as follows:

AlfCCSamplesCbW=AlfCCSamplesCbH=2(slice_cross_component_alf_cb_log2_control_size_minus4 | 4)

slice_cross_component_alf_cb_log2_control_size_minus4 must be in the range 0-3, inclusive.

slice_cross_component_alf_cr_log2_control_size_minus4 indicates the value of the square block sizes in the number of samples as follows:

AlfCCSamplesCrW=AlfCCSamplesCrH=2(slice_cross_component_alf_cr_log2_control_size_minus4 | 4)

slice_cross_component_alf_cr_log2_control_size_minus4 must be in the range 0-3, inclusive.

[214] Referring to the above two tables, when sps_cross_component_alf_enabled_flag is equal to 1 in the slice header, slice_cross_component_alf_cb_enabled_flag parsing may be performed to determine whether or not Cb CC-ALF is applied in the slice. When slice_cross_component_alf_cb_enabled_flag is 1, CC-ALF is applied to the corresponding Cb slice, and when slice_cross_component_alf_cb_reuse_temporal_layer_filter is 1, an identical existing temporal layer filter can be reused. When slice_cross_component_alf_cb_enabled_flag is equal to 0, CC-ALF may be applied using a filter on the corresponding adaptation parameter set (APS) identifier via parsing slice_cross_component_alf_cb_aps_id. Slice_cross_component_alf_cb_log2_control_size_minus4 may mean that CC-ALF applies the block unit in the Cb slice.

[215] For example, when the value of slice_cross_component_alf_cb_log2_control_size_minus4 is 0, then whether or not CC-ALF is applied is determined in units of 16x16. When the value of slice_cross_component_alf_cb_log2_control_size_minus4 is 1, then whether or not CC-ALF is applied is determined in units of 32×32. When the value of slice_cross_component_alf_cb_log2_control_size_minus4 is 2, then whether or not CC-ALF is applied is determined in units of 64x64. When the value of slice_cross_component_alf_cb_log2_control_size_minus4 is 3, then whether or not CC-ALF is applied is determined in units of 128×128. In addition, a structure syntax identical to that described above is used for Cr CC-ALF.

[216] The following table shows an exemplary syntax for ALF data.

[217] Tab. five

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

[219] Tab. 6

alf_luma_filter_signal_flag equal to 1 indicates that the luma signal filter bank is signaled; alf_luma_filter_signal_flag equal to 0 indicates that the luma signal filter bank is not signaled. When alf_luma_filter_signal_flag is not present, it is logically inferred to be 0.

alf_chroma_filter_signal_flag equal to 1 indicates that the chroma signal filter is signaled; alf_chroma_filter_signal_flag equal to 0 indicates that the chroma signal filter is not signaled. When alf_chroma_filter_signal_flag is not present, it is logically inferred to be 0.

alf_cross_component_cb_filter_signal_flag equal to 1 indicates that the Cb cross-component filter set is signaled; alf_cross_component_cb_filter_signal_flag equal to 0 indicates that the Cb cross-component filter set is not signaled. When alf_cross_component_cb_filter_signal_flag is not present, it is logically inferred to be 0.

alf_cross_component_cr_filter_signal_flag equal to 1 indicates that the Cr cross-component filter set is signaled; alf_cross_component_cb_filter_signal_flag equal to 0 indicates that the Cr cross-component filter bank is not signaled. When alf_cross_component_cr_filter_signal_flag is not present, it is logically inferred to be 0,

alf_cross_component_cb_min_eg_order_minusl plus 1 specifies the minimum exponential Golomb code order to signal cross-component Cb filter coefficients. The value alf_cross_component_cb_min_eg_order_minus1 must be in the range 0-9, inclusive.

alf_cross_component_cr_min_eg_order_minus1 plus 1 specifies the minimum exponential Golomb code order to signal cross-component Cr filter coefficients. The value alf_cross_component_cb_min_eg_order_minus1 must be in the range 0-9, inclusive.

alf_cross_component_cb_eg_order_increase_flag [i], equal to 1, indicates that the minimum exponential Golomb order for signaling the coefficients of the cross-component Cb filter is progressively increased by 1; alf_cross_component_cb_eg_order_increase_flag[i] equal to 0 indicates that the minimum exponential Golomb order for signaling the coefficients of the cross-component Cb filter does not incrementally increase by 1.

The order expGoOrderCb[i] of the Exponential Golomb code used to decode the values alf_cross_component_cb_coeff_abs[j] is extracted as follows:

expGoOrdcrCb[i]=(i==0?alf_cross_component_cb_min_eg_order_minus1+1:expGoOrderCb [i-1])+alf_cross_component_cb_eg_order_increase_flag[i]

alf_cross_component_cr_eg_order_increase_flag [i], equal to 1, indicates that the minimum exponential Golomb order for signaling the coefficients of the cross-component Cr filter is progressively increased by 1; alf_cross_component_cr_eg_order_increase_flag[i] equal to 0 indicates that the minimum exponential Golomb code order for signaling the coefficients of the cross-component Cr filter does not incrementally increase by 1.

The order expGoOrderCr[i] of the Exponential Golomb code used to decode the values alf_cross_component_cb_coeff_abs[j] is extracted as follows:

expGoOrderCr[i]=(i==0?alf_cross_component_cr_min_eg_order_minus1+1:expGoOrderCr [i-1])+alf_cross_component_cr_eg_order_increase_flag[i]

alf_cross_component_cb_coeff_abs [j] indicates the absolute value of the j-th signaling coefficient of the Cb cross-component filter. When alf_cross_component_cb_coeff_abs[j] is not present, it is logically inferred to be 0.

The order k of the exponential Golomb binarization uek(v) is extracted as follows:

golombOrderIdxCb[]={0,2,2,2,1,2,2,2,2,2,2,1,2,1} [this can represent a classification of the coefficient into 3 categories, each category uses an identical exponential code Golomb order k]

k=expGoOrderCb[golombOrderIdxCb[j]]

[220]

alf_cross_component_cr_coeff_abs [j] indicates the absolute value of the j-th signaling coefficient of the Cr cross-component filter. When alf_cross_component_cr_coeff_abs[j] is not present, it is logically inferred to be 0.

The order k of the exponential Golomb binarization uck(v) is extracted as follows:

golombOrderIdxCr[]={0,1,2,1,0,1,2,2,2,2,2,1,2,1} [this can represent a classification of the coefficient into 3 categories, each category uses an identical exponential code Golomb order k]

k=expGoOrderCr [golombOrderIdxCr[j]]

alf_cross_component_cb_coeff_sign [j] indicates the sign of the j-th coefficient of the Cb cross-component filter as follows:

- If alf_cross_component_cb_coeff_sign[j] is 0, the corresponding Cb cross-component filter coefficient is positive.

- Otherwise (alf_cross_component_cb_coeff_sign[j] is equal to 1), the corresponding coefficient of the Cb cross-component filter has a negative value.

When alf_cross_component_cb_coeff_sign[j] is not present, it is logically inferred to be 0.

The coefficients AlfCCCoeffcb[adaptation_parameter_set_id] of the cross-component Cb filter with elements AlfCCCoeffcb[adaptation_parameter_set_id][j], with j=0...13, are extracted as follows:

AlfCCCoeffcb[adaptation_parameter_set_id][j]=alf_cross_component_cb_coeff_abs[j]*(l-2*alf_cross_component_cb_coeff_sign[j])

The bitstream matching requirement is that the values of AlfCCCoeffcb[adaptation_parameter_set_id][j], with j=0...13, must be in the range from -2 ¹⁰ -1 to 2 ¹⁰ -1, inclusive.

alf_cross_component_cr_coeff_sign [j] specifies the sign of the j-th coefficient of the Cr cross-component filter as follows:

- If alf_cross_component_cr_coeff_sign[j] is 0, the corresponding cross-component Cr filter coefficient is positive.

- Otherwise (alf_cross_component_cr_coeff_sign[j] is equal to 1), the corresponding coefficient of the cross-component Cr filter has a negative value.

When alf_cross_component_cr_coeff_sign[j] is not present, it is logically inferred to be 0.

The coefficients AlfCCCoeffcr[adaptation_parameter_set_id] of the cross-component Cr filter with elements AlfCCCoeffcr[adaptation_parameter_set_id][j], with j=0...13, are extracted as follows:

AlfCCCoeffcr[adaptation_parameter_set_id][j]=alf_cross_component_cr_coeff_abs[j]*(l-2*alf_cross_component_cr_coeff_sign[j])

The bitstream matching requirement is that the values of AlfCCCoeffcr[adaptation_parameter_set_id][j], with j=0...13, must be in the range from -2 ¹⁰ -1 to 2 ¹⁰ -1, inclusive.

TemporalId is the temporary identifier of the current NAL unit.

[221] Referring to the above two tables, the CC-ALF syntax elements do not adhere to the existing (common) ALF syntax structure, but are transmitted independently and configured to be applied independently. Thus, CC-ALF can be applied even when the ALF tool in the SPS is turned off. A new hardware pipeline design is required as the CC-ALF must be able to operate independently of the existing ALF structure. This results in increased hardware implementation costs and increased hardware latency.

[222] In addition, in ALF, whether or not images based on luminance signals and chrominance signals are applied is determined in units of CTU, and the result of the determination is transmitted to the decoder by signaling. However, whether or not the CC-ALF variable is applied is determined in units of 16×16-128×128, and this application may cause a collision between the existing ALF structure and the CC-ALF. This causes problems in the hardware implementation and at the same time causes an increase in line buffers for various CC-ALF application variables.

[223] In the present disclosure, the above problems in the CC-ALF hardware implementation are resolved by integrally applying the CC-ALF syntactic structure to the ALF syntactic structure.

[224] According to an embodiment of the present disclosure, to determine whether or not CC-ALF is used, a sequence parameter set (SPS) may include a CC-ALF enable flag (sps_ccalf_enable_flag). The CC-ALF activation flag may be transmitted independently of the ALF activation flag (sps_alf_enabled_flag) to determine whether ALF is used (applied) or not.

[225] The following table shows a portion of an exemplary SPS syntax according to the present embodiment.

[226] Tab. 7

[227] Referring to the above table, CC-ALF can only be applied when ALF is always running. Thus, only when the ALF enable flag (sps_alf_enabled_flag) is 1, the CC-ALF enable flag (sps_ccalf_enabled_flag) can be parsed. CC-ALF and ALF can be combined according to the table above. The CC-ALF-activation flag may indicate (and may be associated with) whether or not CC-ALF is available.

[228] The following table shows part of an exemplary syntax for slice headers.

[229] Tab. eight

[230] Referring to the above table, the parsing of sps_ccalf_enabled_flag can only be performed when sps_alf_enabled_flag is equal to 1. Syntax elements included in the table can be described based on Table 4. In the example, image information encoded by encoding equipment or obtained (received) by the decoding equipment, may include slice header information (slice_header). Based on determining that the value of the CC-ALF activation flag (sps_ccalf_flag) is 1, the slice header information includes a first flag (slice_cross_component_alf_cb_enabeld_flag) related to whether or not CC-ALF is available for the Cb color component of the filtered recovered signal samples. chroma, and a second flag (slice_cross_component_alf_cr_enabeld_flag) related to whether or not CC-ALF is available for the chrominance Cr component of the filtered reconstructed chrominance samples.

[231] In an example, based on determining that the value of the first flag (slice_cross_component_alf_cb_enabeld_flag) is 1, the slice header information may include identification information (slice_cross_component_alf_cb_aps_id) of the first APS to extract cross-component filter coefficients for the Cb color component. Based on determining that the value of the second flag (slice_cross_component_alf_cr_enabeld_flag) is 1, the slice header information may include the identification information (slice_cross_component_alf_cr_aps_id) of the second APS to extract the cross-component filter coefficients for the Cr color component.

[232] The following table shows a portion of the SPS syntax according to another example of the present embodiment.

[233] Tab. nine

[234] The following table roughly shows part of the slice header syntax.

[235] Tab. 10

[236] Referring to Table 9, when ChromaArrayType is not equal to 0 and the ALF activation flag (sps_alf_enabled_flag) is 1, the SPS may include a CC-ALF activation flag (sps_ccalf_enabled_flag). For example, if ChromaArrayType is not equal to 0, the chrominance format may not be monochrome, and the CC-ALF activation flag may be transmitted through the SPS based on the case in which the chrominance format is not monochrome.

[237] Referring to Table 9, based on the case in which ChromaArrayType is not equal to 0, information regarding CC-ALF (slice_cross_component_alf_cb_enabled_flag, slice_cross_component_alf_cb_aps_id, slice_cross_component_alf_cr_enabled_flag, slice_cross_component_alf_cr) may be included in slice header information.

[238] In an example, image information encoded by encoding equipment or obtained by decoding equipment may include SPS. The SPS may include a first ALF enable flag (sps_alf_enabled_flag) related to whether ALF is available or not. For example, based on determining that the value of the first ALF activation flag is 1, the SPS may include a CC-ALF activation flag related to whether cross-component filtering is available or not. In another example, if sps_ccalf_enabled_flag is not used and sps_alf_enabled_flag is 1, CC-ALF may always be applied (sps_ccalf_enabled_flag==1).

[239] The following table shows a portion of the slice header syntax according to another example of this embodiment.

[240] Tab. eleven

[241] Referring to the above table, parsing of the CC-ALF activation flag (sps_ccalf_enabled_flag) can only be performed when the ALF activation flag (sps_alf_enabled_flag) is equal to 1.

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

[243] Tab. 12

slice_ccalf_enabled_flag equal to 1 indicates that the cross-component adaptive loop filter is enabled and can be applied to the Cb or Cr color component in the slice; slice_ccalf_enabled_flag equal to 0 indicates that the cross-component adaptive contour filter is disabled for all color components in the slice.

slice_ccalf_chroma_idc equal to 0 indicates that the cross-component adaptive contour filter is not applied to the Cb and Cr chrominance components, slice_calf_chroma_idc equal to 1 indicates that the cross-component adaptive contour filter is applied to the Cb chrominance component; slice_ccalf_chroma_idc equal to 2 indicates that the cross-component adaptive contour filter is applied to the chrominance Cr component, slice_ccalf_chroma_idc equal to 3 indicates that the cross-component adaptive contour filter is applied to the chrominance Cb and Cr components. When slice_calf_chroma_idc is not present, it is logically inferred to be 0.

slice_ccalf_aps_id_chroma indicates the adaptation_parameter_set_id of the CCALF APS referenced by the slice chroma component. The TemporalId of an APS NAL unit having aps_params_type equal to CC_ALF_APS and an adaptation_parameter_set_id equal to slice_calf_aps_id_chroma shall be less than or equal to the TemporalId of the encoded slice NAL unit.

For internal slices and slices in an IRAP frame, slice_ccalf_aps_id_chroma shall not refer to a CCALF APS associated with other frames other than the frame containing the internal slices or the IRAP frame.

[244] The slice_ccalf_chroma_idc of the above table may be described by the semantics of the table below.

[245] Tab. 13

slice_calf_chroma_idc equal to 0 indicates that the cross-component adaptive contour filter is applied to the Cb chroma component; slice_calf_chroma_idc equal to 1 indicates that the cross-component adaptive contour filter is applied to the Cr chroma component; slice_calf_chroma_idc equal to 2 indicates that the cross-component adaptive contour filter is applied to the Cb and Cr chrominance components. When slice_calf_chroma_idc is not present, it is logically inferred to be 0.

[246] The following table shows a portion of the slice header syntax according to another example of this embodiment.

[247] Tab. fourteen

[248] The syntax elements included in the table may be described according to Table 12 or Table 13. In addition, when the chrominance signal format is not monochrome, CCALF-related information may be included in a slice header.

[249] The following table shows a portion of the slice header syntax according to another example of this embodiment.

[250] Tab. fifteen

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

[252] Tab. 16

slice_calf_chroma_idc equal to 0 indicates that the cross-component adaptive contour filter is not applied to the Cb and Cr chrominance components; slice_calf_chroma_idc equal to 1 indicates that the cross-component adaptive contour filter is applied to the Cb chroma component; slice_calf_chroma_idc equal to 2 indicates that the cross-component adaptive contour filter is applied to the Cr chroma component; slice_calf_chroma_idc equal to 3 indicates that the cross-component adaptive contour filter is applied to the Cb and Cr chrominance components. When slicc_ccalf_chroma_idc is not present, it is logically inferred to be 0.

slice_ccalf_aps_id_chroma indicates the adaptation_parameter_sct_id of the CCALF APS referenced by the slice chroma component. The TemporalId of an APS NAL unit having aps_params_type equal to CC_ALF_APS and an adaptation_parameter_set_id equal to slice_calf_aps_id_chroma shall be less than or equal to the TemporalId of the encoded slice NAL unit.

For internal slices and slices in an IRAP frame, slice_ccalf_aps_id_chroma shall not refer to a CCALF APS associated with other frames other than the frame containing the internal slices or the IRAP frame.

[253] The following table shows a portion of the slice header syntax according to another example of this embodiment. The syntax elements included in the following table may be described according to table 12 or table 13.

[254] Tab. 17

[255] Referring to the above table, whether or not ALF and CCALF based on slice units are applied can be determined immediately via slice_alf_enabled_flag. After parsing slice_alf_chroma_idc, when the first ALF activation flag (sps_alf_enabled_flag) is 1, slice_ccalf_chroma_idc may be parsed.

[256] Referring to the above table, whether or not sps_ccalf_enabeld_flag is equal to 1 in the slice header information may be determined only when slice_alf_enabled_flag is equal to 1. The slice header information may include a second ALF activation flag (slice_alf_enabled_flag) related to whether ALF is available or not. Based on the determination that the value of the second ALF activation flag (slice_alf_enabled_flag) is 1, CCALF may be enabled for the slice.

[257] The following table roughly shows part of the APS syntax. The adaptation_parameter_set_id syntax element may indicate identifier information (identification information) of the APS.

[258] Tab. eighteen

[259] The following table shows an exemplary syntax for ALF data.

[260] Tab. nineteen

[261] Referring to the above two tables, APS may include ALF data (alf_data). An APS including ALF data may be referred to as "ALF APS" ("ALF-type APS"). Thus, an APS type including ALF data may be an ALF type. The APS type may be defined as information regarding an APS type or a syntax element (aps_params_type). The ALF data may include a Cb filter signaling flag (alf_cross_component_cb_filter_signal_flag or alf_cc_cb_filter_signal_flag) related to whether or not cross-component filters for the Cb color component are signaled. The ALF data may include a Cr signaling signaling flag (alf_cross_component_cr_filter_signal_flag or alf_cc_cr_filter_signal_flag) related to whether or not cross-component filters for the Cr color component are signaled.

[262] In an example, based on the transmit flag in the signaling of the Cr filters, the ALF data may include information (alf_cross_component_cr_coeff_abs) about the absolute values of the cross-component filter coefficients for the Cr color component and information about the signs (alf_cross_component_cr_coeff_sign) about the signs of the cross-component coefficients filter for the color Cr component. Based on information regarding the absolute values of the cross-component filter coefficients for the chrominance Cr component and information regarding the signs of the cross-component filter coefficients for the chrominance Cr component, the cross-component filter coefficients for the chrominance Cr component can be extracted.

[263] In an example, the ALF data may include information (alf_cross_component_cb_coeff_abs) regarding the absolute values of the cross-component filter coefficients for the Cb color component and information (alf_cross_component_cb_coeff_sign) regarding the signs of the cross-component filter coefficients for the Cb color component. Based on information regarding the absolute values of the cross-component filter coefficients for the Cb color component and information regarding the signs of the cross-component filter coefficients for the Cb color component, the cross-component filter coefficients for the Cb color component can be extracted.

[264] The following table shows the syntax associated with ALF data according to another example.

[265] Tab. twenty

[266] Referring to the above table, after transmitting alf_cross_component_filter_signal_flag first, when alf_cross_component_filter_signal_flag is equal to 1, a transmission flag in Cb/Cr filter signaling may be transmitted. Thus, alf_cross_component_filter_signal_flag integrates Cb/Cr to determine whether or not the CCALF filter coefficients should be transmitted.

[267] The following table shows the syntax associated with ALF data according to another example.

[268] Tab. 21

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

[270] Tab. 22

alf_cross_component_cb_filter_signal_flag equal to 1 indicates that the Cb cross-component filter set is signaled; alf_cross_component_cb_filter_signal_flag equal to 0 indicates that the Cb cross-component filter set is not signaled. When alf_cross_component_cb_filter_signal_flag is not present, it is logically inferred to be 0.

alf_cross_component_cr_filter_signal_flag equal to 1 indicates that the Cr cross-component filter set is signaled; alf_cross_component_cr_filler_signal_nag equal to 0 indicates that the Cr cross-component filter bank is not signaled. When alf_cross_component_cr_filter_signal_flag is not present, it is logically inferred to be 0.

alf_cross_component_cb_coeff_abs [j] indicates the absolute value of the j-th signaling coefficient of the Cb cross-component filter. When alf_cross_component_cb_coeff_abs[j] is not present, it is logically inferred to be 0.

The order k of the exponential transformation of uek(v) to binary Golomb form is set to 3.

alf_cross_component_cb_coeff_sign [j] indicates the sign of the j-th coefficient of the Cb cross-component filter as follows:

- If alf_cross_component_cb_cocff_sign[j] is 0, the corresponding Cb cross-component filter coefficient is positive.

- Otherwise (alf_cross_component_cb_coeff_sign[j] is equal to 1), the corresponding coefficient of the Cb cross-component filter has a negative value.

When alf_cross_component_cb_coeff_sign[j] is not present, it is logically inferred to be 0.

The coefficients AlfCCCoeffCb[adaptation_parameter_set_id] of the cross-component Cb filter with elements AlfCCCoeffCb[adaptation_parameter_set_id][j], with j=0...13, are extracted as follows:

AlfCCCoeffCb[adaptation_parameter_set_id][j]=alf_cross_component_cb_coeff_abs[j]*(l-2*alf_cross_component_cb_coeff_sign[j])

The bitstream matching requirement is that the values of AlfCCCoeffCb[adaptation_parameter_set_id][j], with j=0...13, must be in the range from -2 ¹⁰ -1 to 2 ¹⁰ -1, inclusive.

alf_cross_component_cr_coeff_abs [j] indicates the absolute value of the j-th signaling coefficient of the Cr cross-component filter. When alf_cross_component_cr_coeff_abs[j] is not present, it is logically inferred to be 0.

The order k of the exponential transformation of uek(v) to binary Golomb form is set to 3.

[271]

alf_cross_component_cr_coeff_sign [j] specifies the sign of the j-th coefficient of the Cr cross-component filter as follows:

- If alf_cross_component_cr_coeff_sign[j] is 0, the corresponding cross-component Cr filter coefficient is positive.

- Otherwise (alf_cross_component_cr_coeff_sign[j] is equal to 1), the corresponding coefficient of the cross-component Cr filter has a negative value.

When alf_cross_component_cr_coeff_sign[j] is not present, it is logically inferred to be 0.

The coefficients AlfCCCoeffCr[adaplalion_parameter_set_id] of the cross-component Cr filter with elements AlfCCCoeffcr[adaptation_parameter_set_id][j], with j=0...13, are extracted as follows:

AlfCCCoeffcr[adaptation_parameter_set_id][j]=alf_cross_component_cr_coeff_abs[j]*(l-2*alf_cross_component_cr_coeff_sign[j])

The bitstream matching requirement is that the values of AlfCCCoeffCr[adaptation_parameter_set_id][j], with j=0...13, must be in the range from -2 ¹⁰ -1 to 2 ¹⁰ -1, inclusive.

[272] The following table shows the syntax associated with ALF data according to another example.

[273] Tab. 23

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

[275] Tab. 24

alf_cross_component_cb_filter_signal_flag equal to i indicates that the Cb cross-component filter set is signaled; alf_cross_componenl_cb_filter_signal_flag equal to 0 indicates that the Cb cross-component filter bank is not signaled. When alf_cross_component_cb_filter_signal_flag is not present, it is logically inferred to be 0.

alf_cross_cotnponent_cr_filter_signal_flag equal to 1 indicates that the cross component Cr filter bank is signaled, alf_cross_component_cr_filter_signal_flag equal to 0 indicates that the cross component Cr filter bank is not signaled. When alf_cross_component_cr_filter_signal_flag is not present, it is logically inferred to be 0.

alf_cb_num_alt_filters_minus1 plus 1 indicates the number of alternative cross-component adaptive loop filters for the Cb components.

alf_cross_component_cb_coeff_abs [j] indicates the absolute value of the j-th signaling coefficient of the Cb cross-component filter. When alf_cross_component_cb_coeff_abs[j] is not present, it is logically inferred to be 0.

The order k of the exponential transformation of uek(v) to binary Golomb form is set to 3.

alf_cross_component_cb_coeff_sign [j] indicates the sign of the j-th coefficient of the Cb cross-component filter as follows:

- If alf_cross_component_cb_cocff_sign[j] is 0, the corresponding Cb cross-component filter coefficient is positive.

- Otherwise (alf_cross_component_cb_coeff_sign[j] is equal to 1), the corresponding coefficient of the Cb cross-component filter has a negative value.

When alf_cross_component_cb_coeff_sign[j] is not present, it is logically inferred to be 0.

The coefficients AlfCCCoeffCb[adaptation_parameter_set_id] of the cross-component Cb filter with elements AlfCCCoeffCb[adaptation_parameter_set_id][j], with j=0...13, are extracted as follows:

AlfCCCoeffCb[adaptation_parameter_set_id][j]=alf_cross_component_cb_coeff_abs[j]*(l-2*alf_cross_component_cb_coeff_sign[j])

The bitstream matching requirement is that the values of AlfCCCoeffCb[adaptation_parameter_sel_id][j], with j=0...13, must be in the range from -2 ¹⁰ -1 to 2 ¹⁰ -1, inclusive.

alf_cr_num_alt_filters_minus1 plus 1 indicates the number of alternative cross-component adaptive loop filters for the Cr components.

alf_cross_component_cr_coeff_abs [j] indicates the absolute value of the j-th signaling coefficient of the Cr cross-component filter. When alf_cross_component_cr_coeff_abs[j] is not present, it is logically inferred to be 0.

The order k of the exponential transformation of uek(v) to binary Golomb form is set to 3.

[276]

alf_cross_component_cr_coeff_sign [j] specifies the sign of the j-th coefficient of the Cr cross-component filter as follows:

- If alf_cross_component_cr_coeff_sign[j] is 0, the corresponding cross-component Cr filter coefficient is positive.

- Otherwise (alf_cross_component_cr_coeff_sign[j] is equal to 1), the corresponding coefficient of the cross-component Cr filter has a negative value.

When alf_cross_component_cr_coeff_sign[j] is not present, it is logically inferred to be 0.

The coefficients AlfCCCocffCr[adaptation_parameter_set_id] of the cross-component Cr filter with elements AlfCCCoeffCr[adaptation_parameter_set_id][j], with j=0...13, are extracted as follows:

AffCCCoeffCr[adaptation_parameter_set_id][j]=alf_cross_component_cr_coeff_abs[j]*(l-2*alf_cross_component_cr_coeff_sign[j])

The bitstream matching requirement is that the values of AlfCCCoeffCr[adaptation_parameter_set_id][j], with j=0...13, must be in the range from -2 ¹⁰ -1 to 2 ¹⁰ -1, inclusive.

[277] In the above two tables, the exponential Golomb binarization order for parsing the syntax alf_cross_component_cb_coeff_abs[j] and alf_cross_component_cr_coeff_abs[j] may be specified by one of 0-9 values.

[278] Referring to the above two tables, the ALF data may include a Cb filter signaling signaling flag (alf_cross_component_cb_filter_signal_flag or alf_cc_cb_filter_signal_flag) related to whether or not cross-component filters for the Cb color component are signaled. Based on the Cb signaling signaling transmit flag (alf_cross_component_cb_filter_signal_flag), the ALF data may include information (ccalf_cb_num_alt_filters_minus1) related to the number of cross component filters for the Cb color component. Based on information related to the number of cross-component filters for the Cb color component, the ALF data may include information (alf_cross_component_cb_coeff_abs) about the absolute values of the cross-component filter coefficients for the Cb color component and information (alf_cross_component_cr_coeff_sign) about the signs of the cross-component filter coefficients for the Cb color -component. Based on information regarding the absolute values of the cross-component filter coefficients for the Cb color component and information regarding the signs of the cross-component filter coefficients for the Cb color component, the cross-component filter coefficients for the Cb color component can be extracted.

[279] In an example, the ALF data may include a Cr signaling signaling flag (alf_cross_component_cr_filter_signal_flag or alf_cc_cr_filter_signal_flag) related to whether or not cross-component filters for the Cr color component are signaled. Based on the Cr signaling signaling transmit flag (alf_cross_component_cr_filter_signal_flag), the ALF data may include information (ccalf_cr_num_alt_filters_minus1) related to the number of cross component filters for the Cr color component. Based on information related to the number of cross-component filters for the chrominance Cr component, the ALF data may include information (alf_cross_component_cr_coeff_abs) regarding the absolute values of the cross-component filter coefficients for the chrominance Cr component and information (alf_cross_component_cr_coeff_sign) regarding the signs of the cross-component filter coefficients for the chroma Cr -component. Based on information regarding the absolute values of the cross-component filter coefficients for the chrominance Cr component and information regarding the signs of the cross-component filter coefficients for the chrominance Cr component, the cross-component filter coefficients for the chrominance Cr component can be extracted.

[280] The following table shows the syntax regarding the coding tree unit according to an embodiment of the present disclosure.

[281] Tab. 25

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

[283] Tab. 26

calf_ctb_flag [chromaIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] equal to 1 indicates that a cross-component adaptive loop filter is applied to the chroma component coding tree block indicated by chromaIdx equal to 0 for Cb and equal to 1 for Cr , for the unit of the coding tree at the location (xCtb, yCtb) of the luminance signal; calf_ctb_flag[chromaIdx][xCtb>>CtbLog2SizeY][yCtb>>, CtbLog2SizeY] equal to 0 indicates that the adaptive loop filter is not applied to the chroma component coding tree block indicated by the chromaIdx coding tree unit at location (xCtb, yCtb ) of the luminance signal.

When calf_ctb_flag[cIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is not present, it is logically inferred to be 0.

[284] The following table shows the syntax of coding tree units according to another example of this embodiment.

[285] Tab. 27

[286] Referring to the above table, CCALF may be applied in CTU units. In an example, the image information may include information (coding_tree_unit()) regarding a coding tree unit. The information regarding the coding tree unit may include information (ccalf_ctb_flag[0) regarding whether or not a cross-component filter is applied to the current Cb color component block, and/or information (ccalf_ctb_flag[1]) regarding whether or not a cross-component filter is applied to to the current block of the color Cr-component. In addition, information regarding a coding tree unit may include information (ccalf_ctb_filter_alt_idx[0) regarding a filterbank index for a cross-component filter applied to the current Cb chroma component block and/or information (ccalf_ctb_filter_alt_idx[1]) regarding a filterbank index for cross-component filter applied to the current Cr-color block. The syntax may be adaptively transmitted according to the syntax of slice_ccalf_enabled_flag and slice_ccalf_chroma_idc.

[287] The following table shows the syntax of coding tree units according to another example of this embodiment.

[288] Tab. 28

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

[290] Tab. 29

calf_ctb_flag [chromaIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] equal to 1 indicates that a cross-component adaptive loop filter is applied to the chroma component coding tree block indicated by chromaIdx equal to 0 for Cb and equal to 1 for Cr , for the unit of the coding tree at the location (xCtb, yCtb) of the luminance signal; calf_ctb_flag[cIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] equal to 0 indicates that the adaptive loop filter is not applied to the chroma component coding tree block indicated by the chromaIdx coding tree unit at location (xCtb, yCtb) brightness signal.

When calf_ctb_flag[cIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is not present, it is logically inferred to be 0.

calf_ctb_filter_alt_idx [chromaIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] specifies the index of the alternative cross-component adaptive loop filter applied to the chroma component coding tree block, where chromaIdx is 0 for Cb and chromaIdx is 1 for Cr, for unity coding tree at location (xCtb, yCtb) of the luminance signal. When calf_ctb_filter_alt_idx[chromaIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is not present, it is logically inferred to be zero.

[291] The following table shows the syntax of coding tree units according to another example of this embodiment. The syntax elements included in the table below may be described according to table 29.

[292] Tab. thirty

[293] In an example, the image information may include information regarding a coding tree unit (coding_tree_unit()). Information regarding a coding tree unit may include information regarding whether or not a cross-component filter is applied to the current Cb color component block (ccalf_ctb_flag[0)] and/or information (ccalf_ctb_flag[1]) regarding whether or not a cross-component filter is applied to to the current block of the color Cr-component. In addition, information regarding a coding tree unit may include information (ccalf_ctb_filter_alt_idx[0) regarding a filterbank index for a cross-component filter applied to the current Cb chroma component block and/or information (ccalf_ctb_filter_alt_idx[1]) regarding a filterbank index for cross-component filter applied to the current Cr-color block.

[294] FIG. 12 and 13 schematically show an example of a video/image coding method and related components according to the embodiment(s) of the present disclosure. The method disclosed in FIG. 12 may be performed by the encoding equipment disclosed in FIG. 2 or fig. 13. In particular, for example, S1200 and S1210 of FIG. 12 can be performed by the coding equipment predictor 220, and S1220-S1240 of FIG. 12 may be performed by the residual processor 230 of the encoding hardware. S1250 may be performed by the coding equipment adder 250, S1260 may be performed by the coding equipment filter 260, and S1270 may be performed by the coding equipment entropy encoder 240. The method disclosed in FIG. 12 may include the embodiments described above in this disclosure.

[295] Referring to FIG. 12, the encoding equipment may extract predictive samples (S1200). Predictive samples may include luminance predictive samples and chrominance predictive samples. The encoding equipment may extract the prediction samples of the current block based on the prediction mode. In this case, various prediction methods disclosed in the present disclosure, such as inter prediction or intra prediction, may be applied.

[296] The encoding equipment may generate prediction related information (S1210). The encoding equipment may generate prediction-related information based on the prediction samples and/or the mode applied to them. The prediction-related information may include information regarding various prediction modes (eg, pooling mode, MVP mode, etc.), MVD information, and the like.

[297] The encoding equipment may generate residual samples (S1220). The residual samples may include luma residual samples and chrominance residual samples. The encoding equipment may derive residual samples for the current block, and residual samples for the current block may be derived based on the original samples of the current block and the predictive samples.

[298] The encoding equipment may extract (quantized) transform coefficients (S1230). The encoding equipment may derive transform coefficients based on the transform procedure for the residual samples. The transform coefficients may include luminance signal transform coefficients and chrominance signal transform coefficients. For example, luminance transform coefficients may be derived based on the residual luminance samples, and chrominance transform coefficients may be derived based on the residual chrominance samples. For example, the conversion procedure may include at least one of DCT, DST, GBT, or CNT. The encoding equipment may extract the quantized transform coefficients. The encoding equipment may derive quantized transform coefficients based on a quantization procedure for the transform coefficients. The quantized transform coefficients may be in one-dimensional vector form based on the scan order of the coefficients.

[299] The encoding equipment may generate residual information (S1240). The encoding equipment may generate residual information indicative of the quantized transform coefficients. The residual information may be generated through various coding methods such as exponential Golomb code, CAVLC, CABAC, and the like.

[300] The encoding equipment may generate reconstructed samples (S1250). The reconstructed samples may include reconstructed luma samples (luma components of the reconstructed samples) and/or reconstructed chrominance samples (chrominance components of the reconstructed samples). The encoding equipment may generate reconstructed samples based on the residual information. The reconstructed samples may be generated by summing the residual samples based on the residual information with the predictive sample.

[301] The encoding equipment may generate ALF related information and/or CCALF related information (S1260). The encoding equipment may generate ALF related information and/or CCALF related information for the recovered samples. The encoding hardware extracts the ALF-related parameter that can be used to filter the reconstructed samples and generates the ALF-related information. For example, ALF related information may include ALF related information described above in this disclosure. The encoding equipment may generate CCALF related information for the reconstructed chrominance samples from the reconstructed samples.

[302] The encoding equipment may encode video/image information (S1270). The image information may include residual information and/or ALF related information. The encoded video/image information may be output in the form of a bitstream. The bit stream may be transmitted to the decoding equipment via a network or a storage medium.

[303] In an example, the CCALF-related information may include a CCALF activation flag, a flag related to whether or not CCALF is available for the Cb- (or Cr-) color component, a transmission flag in the Cb- (or Cr -) filters related to whether or not cross-component filters for the Cb (or Cr-) color component are signaled, information related to the number of cross-component filters for the Cb- (or Cr-) color component, information regarding the values of the coefficients of the cross-component filter for the Cb (or Cr) color component, information regarding the absolute values of the cross-component filter coefficients for the Cb (or Cr-) color component, information regarding the signs of the cross-component filter coefficients for the Cb (or Cr-) color component, and/or information regarding whether or not a cross-component filter is applied to the current block of the Cb- (or Cr-) color component in the information (coding tree unit syntax) regarding the tree unit wa coding.

[304] The image/video information may include various types of information according to an embodiment of the present document. For example, the image/video information may include information disclosed in at least one of Tables 1-30 described above.

[305] In an embodiment, the image information may include a sequence parameter set (SPS). The SPS may include a CCALF activation flag related to whether cross-component filtering is available or not. Based on the CCALF-availability flag, identification information (identifier information) of adaptation parameter sets (APS) including ALF data used to extract cross-component filter coefficients for CCALF can be extracted.

[306] In an embodiment, the SPS may include an ALF activation flag (sps_alf_enabled_flag) related to whether ALF is available or not. Based on the determination that the value of the ALF activation flag (sps_alf_enabled_flag) is 1, the SPS may include a CCALF activation flag related to whether cross-component filtering is available or not.

[307] In an embodiment, the image information may include slice header information and an adaptation parameter set (APS). The header information may include information associated with the APS identifier, including ALF data. For example, cross-component filter coefficients may be derived from ALF data.

[308] In an embodiment, the slice header information may include an ALF activation flag (slice_alf_enabled_flag) related to whether ALF is available or not. Sps_alf_enabled_flag and slice_alf_enabled_flag may be referred to as "first ALF activation flag" and "second ALF activation flag", respectively. Based on determining that the value of the second ALF enable flag (slice_alf_enabled_flag) is 1, it may be determined whether or not the value of the CCALF enable flag is 1. In the example, based on determining that the value of the second ALF enable flag is 1, CCALF may be available for cutting.

[309] In an embodiment, the header information (slice header information) may include a first flag related to whether or not CCALF is available for the Cb color component of the filtered recovered chrominance samples, and a second flag related to whether or not no CCLF for the chrominance Cr component of the filtered reconstructed chrominance samples. In another example, based on determining that the value of the ALF enable flag (slice_alf_enabled_flag) is 1, the header information (slice header information) may include a first flag related to whether or not CCALF is available for the Cb color component of the filtered reconstructed chrominance samples, and a second flag related to whether or not CCLF is available for the chrominance Cr component of the filtered reconstructed chrominance samples.

[310] In an embodiment, based on determining that the value of the first flag is 1, the slice header information may include identification information (information associated with the second APS ID) of the first APS to extract cross-component filter coefficients for the Cb color component. Based on the determination that the value of the second flag is 1, the slice header information may include identification information (information associated with the second APS ID) of the second APS to extract cross-component filter coefficients for the chrominance Cr component.

[311] In an embodiment, the first ALF data included in the first APS may include a Cb filter signaling signaling flag related to whether cross-component filters for the Cb color component are signaled. Based on the transmit flag in the Cb filter signaling, the first ALF data may include information related to the number of cross-component filters for the Cb color component. Based on information related to the number of cross-component filters for the Cb color component, the first ALF data may include information on the absolute values of the cross-component filter coefficients for the Cb color component and information on the signs of the cross-component filter coefficients for the Cb color component. Based on information regarding information regarding absolute values of the Cb color component cross-filter coefficients and information regarding the signs of the Cb color component cross-component filter coefficients, the cross-component filter coefficients for the Cb color component can be extracted.

[312] In an embodiment, information related to the number of cross-component filters for the Cb color component may be encoded with a zero-order exponential Golomb code (zero EG).

[313] In an embodiment, the second ALF data included in the second APS may include a Cr signaling signaling flag related to whether or not cross-component filters for the Cr color component are signaled. Based on the transmit flag in the Cr signaling, the second ALF data may include information related to the number of cross filters for the Cr color component. Based on information related to the number of cross-component filters for the chrominance Cr component, the second ALF data may include information regarding the absolute values of the cross-component filter coefficients for the chrominance Cr component and information regarding the signs of the cross-component filter coefficients for the chrominance Cr component. Based on the absolute values of the cross-component filter coefficients for the Cr color component and information regarding the signs of the cross-component filter coefficients for the Cr color component, the cross-component filter coefficients for the Cr color component can be extracted.

[314] In an embodiment, information related to the number of cross-component filters for the chrominance Cr component may be encoded with a zero-order exponential Golomb code (zero EG).

[315] In an embodiment, the image information may include information regarding a coding tree unit. Information regarding a coding tree unit may include information regarding whether or not a cross-component filter is applied to the current Cb chroma component block and/or information regarding whether or not a cross-component filter is applied to the current Cr chroma component.

[316] In an embodiment, information regarding a coding tree unit may include information regarding a filterbank index for a cross-component filter applied to the current block of the Cb color component and/or information regarding a filterbank index for a cross-component filter applied to the current block. color Cr-component.

[317] FIG. 14 and 15 schematically show an example of a method for decoding video/images and related components according to the embodiment(s) of the present disclosure.

[318] The method disclosed in FIG. 14 may be performed by the decoding equipment illustrated in FIG. 3 or 15. In particular, for example, the S1400 of FIG. 14 may be performed by the entropy decoder 310 of the decoding equipment, S1410 and S1420 may be performed by the residual processor 320 of the decoding equipment, S1430 may be performed by the decoding equipment prediction unit 330, S1440 may be performed by the adder 340 of the decoding equipment, and S1450-S1480 may be performed by the filter 350 decoding equipment. The method disclosed in FIG. 14 may include the embodiments described above in this disclosure.

[319] Referring to FIG. 14, the decoding equipment can receive/acquire video/image information (S1400). The video/image information may include prediction related information and/or residual information. The decoding equipment can receive/receive image/video information via a bitstream. In an example, the video/image information may further include CCAL related information. For example, in an example, the CCALF related information may include a CCALF activation flag, a flag related to whether or not CCALF is available for the Cb- (or Cr-) color component, a transmit flag in the Cb- (or Cr-) signaling. ) filters related to whether or not cross-component filters for the Cb- (or Cr-) color component are signaled, information related to the number of cross-component filters for the Cb- (or Cr-) color component, information regarding the absolute values of the coefficients of the cross-component filter for the Cb- (or Cr-) color component, information regarding the signs of the cross-component filter coefficients for the Cb- (or Cr-) color component, and/or information regarding whether or not the cross-component filter is applied to the current Cb- (or Cr-) color block. )component in the information (syntax of coding tree units) relative to the coding tree unit.

[320] The image/video information may include various types of information according to an embodiment of the present document. For example, the image/video information may include information disclosed in at least one of Tables 1-30 described above.

[321] The decoding equipment may extract transform coefficients (S1410). In particular, the decoding equipment may derive quantized transform coefficients based on the residual information. The transform coefficients may include luminance signal transform coefficients and chrominance signal transform coefficients. The quantized transform coefficients may be in one-dimensional vector form based on the scan order of the coefficients. The decoding equipment may derive transform coefficients based on a dequantization procedure for the quantized transform coefficients.

[322] The decoding equipment may extract residual samples (S1420). The decoding hardware may extract residual samples based on the transform coefficients. The residual samples may include luma residual samples and chrominance residual samples. For example, luminance residual samples may be derived based on luminance transform coefficients, and chrominance residual samples may be derived based on chrominance transform coefficients. In addition, the residual samples for the current block may be derived based on the original samples and the prediction samples of the current block.

[323] The decoding equipment may perform prediction based on the image/video information and extract prediction samples of the current block (S1430). The decoding equipment may derive the prediction samples of the current block based on the prediction related information. The prediction related information may include prediction mode information. The decoding equipment may determine whether or not inter prediction or intra prediction is applied to the current block based on the prediction mode information, and may perform prediction based on this. Predictive samples may include luminance predictive samples and/or chrominance predictive samples.

[324] The decoding equipment may generate/retrieve recovered samples (S1440). The reconstructed samples may include reconstructed luma samples and/or reconstructed chrominance samples. The decoding hardware may generate reconstructed luma (or chrominance) samples based on the residual samples. The luminance components of the reconstructed samples may correspond to the reconstructed luminance samples, and the chrominance components of the reconstructed samples may correspond to the reconstructed chrominance samples.

[325] The decoding equipment may extract the ALF filter coefficients for the recovered chrominance samples ALF procedure (S1450). In addition, the decoding hardware can extract the ALF filter coefficients for the ALF procedure of the reconstructed luminance samples. The ALF filter coefficients may be derived based on the ALF parameters included in the ALF data in the APS.

[326] The decoding equipment may generate filtered reconstructed chrominance samples (S1460). The decoding hardware may generate filtered reconstructed samples based on the reconstructed chrominance samples and ALF filter coefficients.

[327] The decoding equipment may extract cross-component filter coefficients for cross-component filtering (S1470). The cross-component filter coefficients may be derived based on the CCALF-related information in the ALF data included in the above APS, and the identification information of the corresponding APS may be included in (may be signaled through) the slice header.

[328] The decoding equipment may generate modified filtered chrominance reconstructed samples (S1480). The decoding equipment may generate modified and filtered chrominance reconstructed samples based on the luminance reconstructed samples, filtered chrominance reconstructed samples, and cross-component filter coefficients. In an example, the decoding hardware may extract the difference between the two samples from the reconstructed luminance samples and multiply the difference by one filter coefficient from the cross-component filter coefficients. Based on the result of the multiplication and the filtered chrominance reconstructed samples, the decoding equipment may generate modified filtered chrominance reconstructed samples. For example, the decoding hardware may generate modified filtered chrominance reconstructed samples based on the sum of the product and one of the filtered chrominance reconstructed samples.

[329] In an embodiment, the image information may include a sequence parameter set (SPS). The SPS may include a CCALF activation flag related to whether cross-component filtering is available or not. Based on the CCALF-availability flag, identification information (identifier information) of adaptation parameter sets (APS) including ALF data used to extract cross-component filter coefficients for CCALF can be extracted.

[330] In an embodiment, the SPS may include an ALF activation flag (sps_alf_enabled_flag) related to whether ALF is available or not. Based on the determination that the value of the ALF activation flag (sps_alf_enabled_flag) is 1, the SPS may include a CCALF activation flag related to whether cross-component filtering is available or not.

[331] In an embodiment, the image information may include slice header information and an adaptation parameter set (APS). The header information may include information associated with the APS identifier, including ALF data. For example, cross-component filter coefficients may be derived from ALF data.

[332] In an embodiment, the slice header information may include an ALF activation flag (slice_alf_enabled_flag) related to whether ALF is available or not. Sps_alf_enabled_flag and slice_alf_enabled_flag may be referred to as "first ALF activation flag" and "second ALF activation flag", respectively. Based on determining that the value of the second ALF enable flag (slice_alf_enabled_flag) is 1, it may be determined whether or not the value of the CCALF enable flag is 1. In the example, based on determining that the value of the second ALF enable flag is 1, CCALF may be available for cutting.

[333] In an embodiment, the header information (slice header information) may include a first flag related to whether or not CCALF is available for the Cb color component of the filtered recovered chrominance samples, and a second flag related to whether or not no CCLF for the chrominance Cr component of the filtered reconstructed chrominance samples. In another example, based on determining that the value of the ALF enable flag (slice_alf_enabled_flag) is 1, the header information (slice header information) may include a first flag related to whether or not CCALF is available for the Cb color component of the filtered reconstructed chrominance samples, and a second flag related to whether or not CCLF is available for the chrominance Cr component of the filtered reconstructed chrominance samples.

[334] In an embodiment, based on determining that the value of the first flag is 1, the slice header information may include identification information (information associated with the second APS ID) of the first APS to extract cross-component filter coefficients for the Cb color component. Based on the determination that the value of the second flag is 1, the slice header information may include identification information (information associated with the second APS ID) of the second APS to extract cross-component filter coefficients for the chrominance Cr component.

[335] In an embodiment, the first ALF data included in the first APS may include a Cb filter signaling signaling flag related to whether or not cross-component filters for the Cb color component are signaled. Based on the transmit flag in the Cb filter signaling, the first ALF data may include information related to the number of cross-component filters for the Cb color component. Based on information related to the number of cross-component filters for the Cb color component, the first ALF data may include information on the absolute values of the cross-component filter coefficients for the Cb color component and information on the signs of the cross-component filter coefficients for the Cb color component. Based on information regarding information regarding absolute values of the Cb color component cross-filter coefficients and information regarding the signs of the Cb color component cross-component filter coefficients, the cross-component filter coefficients for the Cb color component can be extracted.

[336] In an embodiment, information related to the number of cross-component filters for the Cb color component may be encoded with a zero-order exponential Golomb code (zero EG).

[337] In an embodiment, the second ALF data included in the second APS may include a Cr signaling signaling flag related to whether cross-component filters for the Cr color component are signaled. Based on the transmit flag in the Cr signaling, the second ALF data may include information related to the number of cross filters for the Cr color component. Based on information related to the number of cross-component filters for the chrominance Cr component, the second ALF data may include information regarding the absolute values of the cross-component filter coefficients for the chrominance Cr component and information regarding the signs of the cross-component filter coefficients for the chrominance Cr component. Based on the absolute values of the cross-component filter coefficients for the Cr color component and information regarding the signs of the cross-component filter coefficients for the Cr color component, the cross-component filter coefficients for the Cr color component can be extracted.

[338] In an embodiment, information related to the number of cross-component filters for the chrominance Cr component may be encoded with a zero-order exponential Golomb code (zero EG).

[339] In an embodiment, the image information may include information regarding a coding tree unit. Information regarding a coding tree unit may include information regarding whether or not a cross-component filter is applied to the current Cb chroma component block and/or information regarding whether or not a cross-component filter is applied to the current Cr chroma component.

[340] In an embodiment, information regarding a coding tree unit may include information regarding a filterbank index for a cross-component filter applied to the current block of the Cb color component and/or information regarding a filterbank index for a cross-component filter applied to the current block. color Cr-component.

[341] When there is a residual sample for the current block, the decoding equipment may receive information regarding the residual for the current block. The residual information may include transform coefficients for the residual samples. The decoding hardware may derive residual samples (or an array of residual samples) for the current block based on the residual information. In particular, the decoding equipment may derive quantized transform coefficients based on the residual information. The quantized transform coefficients may be in one-dimensional vector form based on the scan order of the coefficients. The decoding equipment may derive transform coefficients based on a dequantization procedure for the quantized transform coefficients. The decoding hardware may extract residual samples based on the transform coefficients.

[342] The decoding equipment may generate reconstructed samples based on the (mutual) predictive samples and residual samples, and may extract a reconstructed block or a reconstructed frame based on the reconstructed samples. More specifically, the decoding hardware may generate reconstructed samples based on the sum of (inner) predictive samples and residual samples. Thereafter, as described above, the decoding equipment may apply an in-loop filtering procedure, eg, a deblocking and/or SAO filtering procedure, to the reconstructed frame to improve the subjective/objective quality of the frames, if necessary.

[343] For example, the decoding equipment can obtain image information including all or part of the above information (or syntax elements) by decoding the bit stream or encoded information. In addition, the bitstream information or encoded information may be stored in a computer-readable storage medium and may cause the above decoding method to be performed.

[344] In the above embodiment, the methods are described based on a flowchart having a sequence of steps or blocks. The present disclosure is not limited to the order of the above steps or blocks. Some steps or blocks may occur simultaneously or in a different order than other steps or blocks, as described above. Additionally, those skilled in the art should understand that the steps shown in the above flowchart are not exhaustive, and other steps may be included, or one or more steps in the flowchart may be removed without affecting scope of this disclosure.

[345] The method according to the above embodiments of the present disclosure may be implemented in software form, and the encoding equipment and/or decoding equipment according to the present disclosure, for example, may be included in equipment that performs image processing for a TV, computer, smartphone, set-top box, display devices, etc.

[346] When the embodiments in the present disclosure are implemented in software, the above method may be implemented as a module (process, function, etc.) that performs the above function. The module may be stored in a storage device and executed by a processor. The storage device may be internal or external to the processor and may be connected to the processor through various known means. The processor may include an application specific integrated circuit (ASIC), other chipsets, logic circuits, and/or data processing devices. The storage device may include Read Only Memory (ROM), Random Access Memory (RAM), flash memory, memory cards, storage media, and/or other data storage devices. Thus, the embodiments described in this disclosure may be performed by implementation on a processor, microprocessor, controller, or chip. For example, the functional modules shown in each figure may be implemented and executed on a computer, processor, microprocessor, controller, or chip. In this case, information regarding the instructions or algorithm to be implemented may be stored in the digital storage medium.

[347] In addition, the decoding equipment and encoding equipment to which this disclosure applies can be included in multimedia broadcast transceiver equipment, mobile communication terminal, home theater system video equipment, digital cinema system video equipment, surveillance camera, video chat equipment, real-time communications, such as video communications, mobile streaming equipment, storage media, video recording equipment, VoD service equipment, video equipment over networks (OTT), Internet streaming service equipment, 3D video equipment, video teleconferencing equipment , transport UE (i.e., UE in a vehicle, UE in an aircraft, UE in a ship, etc.) and medical video equipment, and can be used to process video and data signals. For example, video over network (OTT) equipment may include a game console, Blu-ray player, Internet access TV, home theater system, smartphone, tablet PC, digital video recorder (DVR), and the like.

[348] Additionally, the processing method to which the present disclosure applies may be created in the form of a program to be executed by a computer and may be stored in a computer-readable recording medium. Multimedia data having a data structure according to the present disclosure may also be stored on computer-readable recording media. Computer-readable recording media includes all types of data storage devices that store data readable by a computer system. Computer-readable recording media, for example, may include BD, Universal Serial Bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical storage. In addition, computer-readable recording media includes media implemented in the form of carrier waves (ie, as transmission over the Internet). In addition, the bit stream generated by the encoding method may be stored in a computer-readable recording medium, or may be transmitted over wired/wireless communication networks.

[349] In addition, embodiments of the present disclosure may be implemented with a computer program product according to program codes, and the program codes may be executed on a computer through embodiments of the present disclosure. The program codes may be stored on a medium that can be read by a computer.

[350] FIG. 17 shows an example of a content streaming system to which the embodiments disclosed in the present disclosure may be applied.

[351] Referring to FIG. 17, the content streaming system to which the embodiment(s) of the present disclosure applies may mainly include an encoding server, a streaming server, a web server, a media storage, a user device, and a media input device.

[352] The encoding server compresses content input from media input devices such as a smartphone, a camera, a camcorder, etc. into digital data to form a bit stream and transmit the bit stream to the stream server. As another example, when media input devices such as smartphones, cameras, camcorders, etc. In order to generate the bitstream directly, the encoding server may be omitted.

[353] The bit stream may be generated by the encoding method or the bit stream generation method to which the embodiment(s) of the present disclosure applies, and the stream server may temporarily store the bit stream in the process of transmitting or receiving the bit stream.

[354] The streaming server transmits media data to the user device based on the user's request through the web server, and the web server serves as a medium for informing the user about the service. When a user requests a desired service from a web server, the web server delivers it to the streaming server, and the streaming server transmits media data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server serves to manage the command/response between devices in the content streaming system.

[355] The streaming server may receive content from a media store and/or an encoding server. For example, when content is received 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 keep the bitstream for a predetermined time.

[356] Examples of a user device may include a mobile phone, smartphone, laptop computer, digital broadcast terminal, personal digital assistant (PDA), portable media player (PMP), navigation device, stylus tablet PC, tablet PCs, ultrabooks, wearable devices (e.g., smart watches, smart glasses, head-mounted displays), digital TVs, desktop computers, digital signage system, etc. Each server in the content streaming system may operate as a distributed server, in which case the data received from each server may be distributed.

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

[358] The claims described herein may be combined in various ways. For example, the technical features of the claims for the method of the present disclosure may be combined and implemented as an equipment, and the technical features of the claims for the equipment of the present disclosure may be combined and implemented as a method. In addition, the technical features of the method claim of the present disclosure and the technical features of the equipment claim can be combined to be implemented as equipment, and the technical features of the method claim of the present disclosure and the technical features of the equipment claim can be combined and implemented. as a way.

Claims (105)

1. A method for decoding images carried out by means of decoding equipment, the method comprising the steps of: obtaining image information including prediction-related information and residual information via a bitstream; extracting the transform coefficients based on the residual information; - form the residual samples based on the coefficients of the transformation; - forming forecast samples on the basis of information related to forecasting; and generating recovered samples based on the predictive samples and the residual samples, the recovered samples including recovered luminance samples and recovered chrominance samples; extracting adaptive loop filter (ALF) coefficients for the ALF process of the reconstructed chrominance samples; - generating filtered reconstructed chrominance samples based on the reconstructed chrominance samples and ALF filter coefficients; - extract the coefficients of the cross-component filter for cross-component filtering; and - generating modified filtered reconstructed chrominance samples based on reconstructed luminance samples, filtered reconstructed chrominance samples and cross-component filter coefficients, - wherein the image information includes sequence parameter set (SPS) and slice header information, - SPS includes an ALF activation flag related to whether the ALF process is activated or not, - based on the ALF activation flag value of 1, the SPS includes a cross-component adaptive loop filter (CCALF) activation flag related to whether or not cross-component filtering is available, - based on determining that the value of the ALF activation flag in the SPS is 1, the slice header information includes an ALF activation flag related to whether ALF is activated or not, - based on determining that the value of the ALF activation flag included in the slice header information is 1 and the value of the CCALF activation flag included in the SPS is 1, the slice header information includes information as to whether or not CCALF is activated for filtered reconstructed chrominance samples, and - based on the value of information regarding whether or not CCALF for filtered chrominance reconstructed samples is enabled or not equal to 1, the slice header information includes identification information (ID) of an adaptation parameter set (APS) associated with CCALF for filtered chrominance reconstructed samples, - ALF data included in the APS includes information related to the number of cross-component filters for the Cb color component and information related to the number of cross-component filters for the Cr component, - based on information related to the number of cross-component filters for the Cb color component, the ALF data includes information on the absolute values of the cross-component filter coefficients for the Cb color component and information on the signs of the cross-component filter coefficients for the Cb color component, and - based on information related to the number of cross-component filters for the chrominance Cr component, ALF data includes information regarding the absolute values of the cross-component filter coefficients for the chrominance Cr component and information regarding the signs of the cross-component filter coefficients for the chrominance Cr component. 2. The method of claim 1, wherein, based on determining that the value of the CCALF activation flag is 1, the slice header information includes a first flag related to whether or not CCALF is activated for the Cb color component of the filtered recovered signal samples. chrominance, and a second flag related to whether or not CCALF is enabled for the chrominance Cr component of the filtered recovered chrominance samples. 3. The method according to claim 2, in which: - based on the value of the first flag equal to 1, the slice header information includes the first APS identification information including the first ALF data used to extract the cross-component filter coefficients for the Cb color component of the filtered recovered chrominance samples, and - based on the value of the first flag equal to 1, the slice header information includes the identification information of the second APS, including the second ALF data used to extract the coefficients of the cross-component filter for the color Cr component of the filtered reconstructed chrominance samples. 4. The method according to claim 1, in which: - the cross-component filter coefficients for the Cb color component are derived based on information regarding the absolute values of the cross-component filter coefficients for the Cb color component and information regarding the signs of the cross-component filter coefficients for the Cb color component, and The cross-component filter coefficients for the chrominance Cr component are derived based on information regarding the absolute values of the cross-component filter coefficients for the chrominance Cr component and information regarding the signs of the cross-component filter coefficients for the chrominance Cr component. 5. The method according to claim 1, in which: - the image information includes information regarding the unit of the coding tree, and - information regarding the coding tree unit includes: - information as to whether or not a cross-component filter is applied to the current block of the Cb color component; and - information as to whether or not a cross-component filter is applied to the current Cr-color block. 6. The method according to claim 1, in which: - the image information includes information regarding the unit of the coding tree, and - information regarding the coding tree unit includes: - information regarding the index of the filter bank for the cross-component filter applied to the current block of the Cb color component; and - information regarding the filter bank index for the cross-component filter applied to the current Cr-color block. 7. An image encoding method carried out by means of encoding equipment, the method comprising the steps of: - extract predictive samples for the current block; generating prediction-related information based on the prediction samples; - form residual samples for the current block; - extract the transformation coefficients based on the transformation process for the residual samples; - form the residual information based on the conversion coefficients; generating reconstructed samples based on residual samples and predictive samples, the reconstructed samples including reconstructed luma samples and reconstructed chrominance samples; generating adaptive loop filter (ALF) related information and cross-component ALF (CCALF) related information for the reconstructed samples; and encoding image information including residual information, prediction-related information, ALF-related information, and CCALF-related information, - wherein - the image information includes sequence parameter set (SPS) and slice header information, - SPS includes an ALF activation flag related to whether the ALF process is activated or not, - based on the ALF activation flag value of 1, the SPS includes a CCALF activation flag related to whether CCALF is available or not, - based on determining that the value of the ALF activation flag in the SPS is 1, the slice header information includes an ALF activation flag related to whether ALF is activated or not, - based on determining that the value of the ALF activation flag included in the slice header information is 1 and the value of the CCALF activation flag included in the SPS is 1, the slice header information includes information as to whether or not CCALF is activated for filtered reconstructed chrominance samples, and - based on the value of information regarding whether or not CCALF for filtered chrominance reconstructed samples is enabled or not equal to 1, the slice header information includes identification information (ID) of an adaptation parameter set (APS) associated with CCALF for filtered chrominance reconstructed samples, - ALF data included in the APS includes information related to the number of cross-component filters for the Cb color component and information related to the number of cross-component filters for the Cr component, - based on information related to the number of cross-component filters for the Cb color component, the ALF data includes information on the absolute values of the cross-component filter coefficients for the Cb color component and information on the signs of the cross-component filter coefficients for the Cb color component, and - based on information related to the number of cross-component filters for the chrominance Cr component, ALF data includes information regarding the absolute values of the cross-component filter coefficients for the chrominance Cr component and information regarding the signs of the cross-component filter coefficients for the chrominance Cr component. 8. The method of claim 7, wherein, based on determining that the value of the CCALF activation flag is 1, the slice header information includes a first flag related to whether or not CCALF is activated for the Cb color component of the filtered recovered signal samples. chroma, and a second flag related to whether or not CCALF is enabled for the chrominance Cr component of the filtered recovered chrominance samples. 9. The method according to claim 8, in which: - based on the value of the first flag equal to 1, the slice header information includes the first APS identification information including the first ALF data used to extract the cross-component filter coefficients for the Cb color component of the filtered recovered chrominance samples, and - based on the value of the second flag equal to 1, the slice header information includes identification information of the second APS, including the second ALF data used to extract the coefficients of the cross-component filter for the color Cr component of the filtered reconstructed chrominance samples. 10. The method according to claim 9, in which: - the cross-component filter coefficients for the Cb color component are derived based on information regarding the absolute values of the cross-component filter coefficients for the Cb color component and information regarding the signs of the cross-component filter coefficients for the Cb color component, and - the cross-component filter coefficients for the color Cr component are derived based on information regarding the absolute values of the coefficients of the cross-component filter for the color Cr component and information regarding the signs of the coefficients of the cross-component filter for the color Cr component 11. The method according to claim 7, in which: - the image information includes information regarding the unit of the coding tree, and - information regarding the coding tree unit includes: - information as to whether or not a cross-component filter is applied to the current block of the Cb color component; and - information as to whether or not a cross-component filter is applied to the current Cr-color block. 12. The method according to claim 7, in which: - the image information includes information regarding the unit of the coding tree, and - information regarding the coding tree unit includes: - information regarding the index of the filter bank for the cross-component filter applied to the current block of the Cb color component; and - information regarding the filter bank index for the cross-component filter applied to the current Cr-color block. 13. A non-volatile computer-readable storage medium that stores a bit stream generated by an image encoding method, wherein the image encoding method comprises: - extraction of predictive samples for the current block; - formation of information related to forecasting based on forecast samples; - formation of residual samples for the current block; - extracting the transformation coefficients based on the transformation process for the residual samples; - formation of residual information based on the conversion coefficients; - generating reconstructed samples based on residual samples and predictive samples, the reconstructed samples including reconstructed luma samples and reconstructed chrominance samples; - generation of adaptive loop filter (ALF) related information and cross-component ALF (CCALF) related information for the reconstructed samples; and encoding image information to form a bit stream, wherein the image information includes residual information, prediction-related information, ALF-related information, and CCALF-related information, - wherein - the image information includes a sequence parameter set (SPS) and slice header information, - SPS includes an ALF activation flag related to whether the ALF process is activated or not, - based on the ALF activation flag value of 1, the SPS includes a CCALF activation flag related to whether CCALF is available or not, - based on determining that the value of the ALF activation flag in the SPS is 1, the slice header information includes an ALF activation flag related to whether ALF is activated or not, - based on determining that the value of the ALF activation flag included in the slice header information is 1 and the value of the CCALF activation flag included in the SPS is 1, the slice header information includes information as to whether or not CCALF is activated for the filtered reconstructed chrominance samples, and - based on the value of information regarding whether or not CCALF for filtered chrominance reconstructed samples is enabled or not equal to 1, the slice header information includes identification information (ID) of an adaptation parameter set (APS) associated with CCALF for filtered chrominance reconstructed samples, - ALF data included in the APS includes information related to the number of cross-component filters for the Cb color component and information related to the number of cross-component filters for the Cr component, - based on information related to the number of cross-component filters for the Cb color component, the ALF data includes information on the absolute values of the cross-component filter coefficients for the Cb color component and information on the signs of the cross-component filter coefficients for the Cb color component, and - based on information related to the number of cross-component filters for the chrominance Cr component, ALF data includes information regarding the absolute values of the cross-component filter coefficients for the chrominance Cr component and information regarding the signs of the cross-component filter coefficients for the chrominance Cr component. 14. A method for transmitting data for an image, the method comprising the steps of: - get a bit stream for the image, wherein the bit stream is generated based on extracting the prediction samples for the current block, generating prediction related information based on the predictive samples, generating residual samples for the current block, extracting transform coefficients based on the transform process for the residual samples, generating residual information based on transform coefficients, generation of reconstructed samples based on residual samples and predictive samples, wherein the reconstructed samples include reconstructed luminance samples and reconstructed chrominance samples, generation of adaptive loop filter (ALF) related information, and information related to with cross-component ALF (CCALF) for recovered samples, and encoding image information including residual information, prediction-related information, ALF-related information, and CCALF-related information; and - transmit data containing a stream of bits, - wherein - the image information includes a sequence parameter set (SPS) and slice header information, - SPS includes an ALF activation flag related to whether the ALF process is activated or not, - based on the ALF activation flag value of 1, the SPS includes a CCALF activation flag related to whether CCALF is available or not, - based on determining that the value of the ALF activation flag in the SPS is 1, the slice header information includes an ALF activation flag related to whether ALF is activated or not, - based on determining that the value of the ALF activation flag included in the slice header information is 1 and the value of the CCALF activation flag included in the SPS is 1, the slice header information includes information as to whether or not CCALF is activated for filtered reconstructed chrominance samples, and - based on the value of information regarding whether or not CCALF for filtered chrominance reconstructed samples is enabled or not equal to 1, the slice header information includes identification information (ID) of an adaptation parameter set (APS) associated with CCALF for filtered chrominance reconstructed samples, - ALF data included in the APS includes information related to the number of cross-component filters for the Cb color component and information related to the number of cross-component filters for the Cr component, - based on information related to the number of cross-component filters for the Cb color component, the ALF data includes information on the absolute values of the cross-component filter coefficients for the Cb color component and information on the signs of the cross-component filter coefficients for the Cb color component, and - based on information related to the number of cross-component filters for the chrominance Cr component, ALF data includes information regarding the absolute values of the cross-component filter coefficients for the chrominance Cr component and information regarding the signs of the cross-component filter coefficients for the chrominance Cr component.

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