Method and device for video processing and medium

Abstract

The embodiment of the invention provides a video processing scheme. A method for video processing is proposed. The method comprises: for a conversion between a video unit of a video and a bitstream of the video unit, generating a sample value of a first color component of the video unit corresponding to a sample of a second color component by applying a plurality of filters to at least one sample of the first color component; and performing a conversion based on the generated sample values.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 358,442 filed on July 5, 2022 and U.S. Provisional Application No. 63 / 367,623 filed on July 4, 2022, both of which have been assigned to the assignee of this application, and the entire contents of the two applications are incorporated by reference into this application. Technical Field

[0002] Embodiments of the present disclosure relate generally to video processing techniques, and more particularly, to self-perceptual filter estimation for cross-component prediction in image / video codecs. Background Art

[0003] Nowadays, digital video capabilities are being used in all aspects of people's lives. Various types of video compression technologies, such as MPEG-2, MPEG-4, ITU-TH.263, ITU-TH.264 / MPEG-4 Part 10 Advanced Video Codec (AVC), ITU-TH.265 High Efficiency Video Codec (HEVC) standard, and Versatile Video Codec (VVC) standard have been proposed for video encoding / decoding. However, it is generally expected to further improve the encoding and decoding efficiency of video encoding and decoding technologies. Summary of the invention

[0004] An embodiment of the present disclosure provides a solution for video processing.

[0005] In a first aspect, a method for video processing is proposed. The method includes: for conversion between a video unit of a video and a bitstream of the video unit, by applying multiple filters to at least one sample of the first color component, generating a sample value of a first color component of the video unit corresponding to a sample of a second color component; and performing conversion bitstream based on the generated sample value. In this way, filtering can be efficient, improving encoding and decoding efficiency.

[0006] In a second aspect, a device for video processing is provided. The device includes a processor and a non-volatile memory having instructions thereon. The instructions, when executed by the processor, cause the processor to perform the method according to the first aspect of the present disclosure.

[0007] In a third aspect, a non-transitory computer-readable storage medium is provided, wherein the non-transitory computer-readable storage medium stores instructions for causing a processor to execute the method according to the first aspect of the present disclosure.

[0008] In a fourth aspect, another non-transitory computer-readable recording medium is provided. The non-transitory computer-readable recording medium stores a bitstream of a video generated by a method performed by an apparatus for video processing. The method includes: generating sample values ​​of a first color component of a video unit corresponding to a sample of a second color component by applying multiple filters to at least one sample of the first color component; and generating a bitstream based on the generated sample values.

[0009] In a fifth aspect, a method for storing a bitstream of a video is provided. The method comprises: generating sample values ​​of a first color component of a video unit corresponding to samples of a second color component by applying a plurality of filters to at least one sample of the first color component; generating a bitstream based on the generated sample values; and storing the bitstream in a non-transitory computer-readable recording medium.

[0010] This disclosure is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This disclosure is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become more apparent through the following detailed description with reference to the accompanying drawings.In the exemplary embodiments of the present disclosure, the same reference numerals generally refer to the same components.

[0012] Figure 1 A block diagram showing an example video encoding and decoding system according to some embodiments of the present disclosure is shown;

[0013] Figure 2 A block diagram of a first example video encoder according to some embodiments of the present disclosure is shown;

[0014] Figure 3 A block diagram of an example video decoder according to some embodiments of the present disclosure is shown;

[0015] Figure 4 67 intra prediction modes are shown;

[0016] Figure 5 Reference samples for wide-angle intra prediction are shown;

[0017] Figure 6 The problem of discontinuity is shown in the case of orientations exceeding 45°;

[0018] Figure 7 The locations of the samples used for the derivation of α and β are shown;

[0019] Figure 8Luminance sample downsampling is shown;

[0020] Fig.9A and Fig. 9B The flow charts of AFE-CCL are shown respectively;

[0021] Fig.10 A flowchart showing a method for video processing according to an embodiment of the present disclosure; and

[0022] Fig.11 A block diagram of a computing device is shown in which various embodiments of the present disclosure may be implemented.

[0023] Throughout the drawings, the same or similar reference numbers generally refer to the same or similar elements. DETAILED DESCRIPTION

[0024] The principle of the present disclosure is now described in conjunction with some embodiments. It should be understood that these embodiments are described only for illustrative purposes to help those skilled in the art understand and implement the present disclosure without any limitation to the scope of the present disclosure. The disclosure described herein can be implemented in various ways except for the manner described below.

[0025] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0026] References in this disclosure to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an example embodiment, it is considered to be within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in other embodiments, whether or not explicitly described.

[0027] It should be understood that although the terms "first" and "second" etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the exemplary embodiments, a first element may be referred to as a second element, and similarly a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0028] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms as well. It should also be understood that when used herein, the terms "comprises", "comprising", "has", "having", "includes", and / or "including" specify the presence of stated features, elements, and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Example Environment

[0029] Figure 1 1 is a block diagram illustrating an example video codec system 100 that may utilize the techniques of the present disclosure. As shown, the video codec system 100 may include a source device 110 and a destination device 120. The source device 110 may also be referred to as a video encoding device, and the destination device 120 may also be referred to as a video decoding device. In operation, the source device 110 may be configured to generate encoded video data, and the destination device 120 may be configured to decode the encoded video data generated by the source device 110. The source device 110 may include a video source 112, a video encoder 114, and an input / output (I / O) interface 116.

[0030] The video source 112 may include a source such as a video capture device. Examples of a video capture device include, but are not limited to, an interface for receiving video data from a video content provider, a computer graphics system for generating video data, and / or a combination thereof.

[0031] The video data may include one or more pictures. The video encoder 114 encodes the video data from the video source 112 to generate a bit stream. The bit stream may include a bit sequence that forms a coded representation of the video data. The bit stream may include coded pictures and associated data. The coded pictures are coded representations of pictures. The associated data may include sequence parameter sets, picture parameter sets, and other grammatical structures. The I / O interface 116 may include a modulator / demodulator and / or a transmitter. The coded video data may be directly transmitted to the destination device 120 via the network 130A via the I / O interface 116. The coded video data may also be stored on a storage medium / server 130B for access by the destination device 120.

[0032] The destination device 120 may include an I / O interface 126, a video decoder 124, and a display device 122. The I / O interface 126 may include a receiver and / or a modem. The I / O interface 126 may obtain encoded video data from the source device 110 or the storage medium / server 130B. The video decoder 124 may decode the encoded video data. The display device 122 may display the decoded video data to the user. The display device 122 may be integrated with the destination device 120, or may be outside the destination device 120, which is configured to be connected to an external display device interface.

[0033] The video encoder 114 and the video decoder 124 may operate according to a video compression standard, such as the High Efficiency Video Codec (HEVC) standard, the Versatile Video Codec (VVC) standard, and other existing and / or future standards.

[0034] Figure 2 is a block diagram showing an example of a video encoder 200 according to some embodiments of the present disclosure, which may be Figure 1 An example of a video encoder 114 in the system 100 is shown.

[0035] Video encoder 200 may be configured to implement any or all of the techniques of this disclosure. Figure 2 In the example of , video encoder 200 includes multiple functional components. The techniques described in this disclosure can be shared between the various components of video encoder 200. In some examples, a processor can be configured to perform any or all of the techniques described in this disclosure.

[0036] In some embodiments, the video encoder 200 may include a partitioning unit 201, a prediction unit 202, a residual generation unit 207, a transformation unit 208, a quantization unit 209, an inverse quantization unit 210, an inverse transformation unit 211, a reconstruction unit 212, a buffer 213 and an entropy coding unit 214, and the prediction unit 202 may include a mode selection unit 203, a motion estimation unit 204, a motion compensation unit 205 and an intra-frame prediction unit 206.

[0037] In other examples, the video encoder 200 may include more, fewer, or different functional components. In one example, the prediction unit 202 may include an intra-block copy (IBC) unit. The IBC unit may perform prediction in an IBC mode, where at least one reference picture is a picture where the current video block is located.

[0038] Furthermore, although some components (such as the motion estimation unit 204 and the motion compensation unit 205) may be integrated, for the purpose of explanation, these components are described in detail below. Figure 2 are shown separately in the example.

[0039] The partitioning unit 201 may partition a picture into one or more video blocks. The video encoder 200 and the video decoder 300 may support various video block sizes.

[0040] The mode selection unit 203 may select one of a plurality of coding modes (intra or inter) based on the error result, for example, and provide the resulting intra-coded block or inter-coded block to the residual generation unit 207 to generate residual block data, and to the reconstruction unit 212 to reconstruct the coded block for use as a reference picture. In some examples, the mode selection unit 203 may select a combination of intra and inter prediction (CIIP) modes, where the prediction is based on an inter prediction signal and an intra prediction signal. In the case of inter prediction, the mode selection unit 203 may also select a resolution for the motion vector (e.g., sub-pixel precision or integer pixel precision) for the block.

[0041] To perform inter-frame prediction on the current video block, the motion estimation unit 204 may generate motion information for the current video block by comparing the current video block with one or more reference frames from the buffer 213. The motion compensation unit 205 may determine a predicted video block for the current video block based on the motion information and decoded samples of pictures from the buffer 213 other than the picture associated with the current video block.

[0042] The motion estimation unit 204 and the motion compensation unit 205 may perform different operations on the current video block, for example, depending on whether the current video block is in an I slice, a P slice, or a B slice. As used herein, an "I slice" may refer to a portion of a picture consisting of macroblocks, all of which are based on macroblocks within the same picture. Furthermore, as used herein, in some aspects, a "P slice" and a "B slice" may refer to a portion of a picture consisting of macroblocks that are independent of macroblocks in the same picture.

[0043] In some examples, the motion estimation unit 204 may perform unidirectional prediction on the current video block, and the motion estimation unit 204 may search the reference pictures of list 0 or list 1 to find the reference video block for the current video block. The motion estimation unit 204 may then generate a reference index and a motion vector, the reference index indicating the reference picture in list 0 or list 1 containing the reference video block, and the motion vector indicating the spatial displacement between the current video block and the reference video block. The motion estimation unit 204 may output the reference index, the prediction direction indicator, and the motion vector as the motion information of the current video block. The motion compensation unit 205 may generate a predicted video block for the current video block based on the reference video block indicated by the motion information of the current video block.

[0044] Alternatively, in other examples, the motion estimation unit 204 may perform bidirectional prediction on the current video block. The motion estimation unit 204 may search the reference pictures in list 0 for a reference video block for the current video block, and may also search the reference pictures in list 1 for another reference video block for the current video block. The motion estimation unit 204 may then generate a plurality of reference indexes and a plurality of motion vectors, the plurality of reference indexes indicating a plurality of reference pictures in list 0 and list 1 containing a plurality of reference video blocks, and the plurality of motion vectors indicating a plurality of spatial displacements between the plurality of reference video blocks and the current video block. The motion estimation unit 204 may output the plurality of reference indexes and the plurality of motion vectors of the current video block as motion information of the current video block. The motion compensation unit 205 may generate a predicted video block for the current video block based on the plurality of reference video blocks indicated by the motion information of the current video block.

[0045] In some examples, motion estimation unit 204 may output a complete set of motion information for use in a decoding process by a decoder. Alternatively, in some embodiments, motion estimation unit 204 may signal motion information of a current video block with reference to motion information of another video block. For example, motion estimation unit 204 may determine that motion information of a current video block is sufficiently similar to motion information of an adjacent video block.

[0046] In one example, motion estimation unit 204 may indicate to video decoder 300 a value in a syntax structure associated with the current video block that indicates that the current video block has the same motion information as another video block.

[0047] In another example, the motion estimation unit 204 may identify another video block and a motion vector difference (MVD) in a syntax structure associated with the current video block. The motion vector difference indicates the difference between the motion vector of the current video block and the motion vector of the indicated video block. The video decoder 300 may use the motion vector of the indicated video block and the motion vector difference to determine the motion vector of the current video block.

[0048] As discussed above, the video encoder 200 may signal motion vectors in a predictive manner.Two examples of prediction signaling techniques that may be implemented by the video encoder 200 include Advanced Motion Vector Prediction (AMVP) and merge mode signaling.

[0049] The intra prediction unit 206 may perform intra prediction on the current video block. When the intra prediction unit 206 performs intra prediction on the current video block, the intra prediction unit 206 may generate prediction data for the current video block based on decoded samples of other video blocks in the same picture. The prediction data for the current video block may include a prediction video block and various syntax elements.

[0050] The residual generation unit 207 may generate residual data for the current video block by subtracting (e.g., indicated by a minus sign) the prediction video block(s) of the current video block from the current video block. The residual data of the current video block may include residual video blocks corresponding to different sample portions of samples in the current video block.

[0051] In other examples, such as in skip mode, there may be no residual data for the current video block, and the residual generation unit 207 may not perform a subtraction operation.

[0052] Transform processing unit 208 may generate one or more transform coefficient video blocks for a current video block by applying one or more transforms to the residual video block associated with the current video block.

[0053] After transform processing unit 208 generates a transform coefficient video block associated with the current video block, quantization unit 209 may quantize the transform coefficient video block associated with the current video block based on one or more quantization parameter (QP) values ​​associated with the current video block.

[0054] The inverse quantization unit 210 and the inverse transform unit 211 may apply inverse quantization and inverse transform to the transform coefficient video block, respectively, to reconstruct a residual video block from the transform coefficient video block. The reconstruction unit 212 may add the reconstructed residual video block to corresponding samples from one or more prediction video blocks generated by the prediction unit 202 to generate a reconstructed video block associated with the current video block for storage in the buffer 213.

[0055] After reconstruction unit 212 reconstructs the video block, a loop filtering operation may be performed to reduce video blocking artifacts in the video block.

[0056] The entropy coding unit 214 may receive data from other functional components of the video encoder 200. When the entropy coding unit 214 receives the data, the entropy coding unit 214 may perform one or more entropy coding operations to generate entropy-coded data and output a bitstream including the entropy-coded data.

[0057] Figure 3 is a block diagram showing an example of a video decoder 300 according to some embodiments of the present disclosure, which may be Figure 1 An example of a video decoder 124 in the system 100 is shown.

[0058] Video decoder 300 may be configured to perform any or all of the techniques of this disclosure. Figure 3In the example of , video decoder 300 includes multiple functional components. The techniques described in this disclosure can be shared between the various components of video decoder 300. In some examples, a processor can be configured to perform any or all of the techniques described in this disclosure.

[0059] exist Figure 3 In the example of , the video decoder 300 includes an entropy decoding unit 301, a motion compensation unit 302, an intra prediction unit 303, an inverse quantization unit 304, an inverse transform unit 305, and a reconstruction unit 306 and a buffer 307. In some examples, the video decoder 300 can perform a decoding process that is generally opposite to the encoding process described with respect to the video encoder 200.

[0060] The entropy decoding unit 301 can retrieve the encoded bitstream. The encoded bitstream may include entropy-encoded video data (e.g., encoded video data blocks). The entropy decoding unit 301 can decode the entropy-encoded video data, and the motion compensation unit 302 can determine motion information from the entropy-decoded video data, the motion information including motion vectors, motion vector precision, reference picture list indexes, and other motion information. The motion compensation unit 302 can determine the information, for example, by performing AMVP and merge mode. AMVP is used, including deriving several most likely candidates based on data and reference pictures from adjacent PBs. The motion information typically includes horizontal and vertical motion vector displacement values, one or two reference picture indexes, and in the case of prediction areas in B strips, also includes an identification of which reference picture list is associated with each index. As used herein, in some aspects, "merge mode" may refer to deriving motion information from blocks that are adjacent in the spatial or temporal domain.

[0061] The motion compensation unit 302 may generate a motion compensated block, possibly performing interpolation based on interpolation filtering.An identifier for the interpolation filter used with sub-pixel precision may be included in the syntax element.

[0062] The motion compensation unit 302 may calculate interpolated values ​​for sub-integer pixels of a reference block using interpolation filtering used by the video encoder 200 during encoding of the video block. The motion compensation unit 302 may determine the interpolation filter used by the video encoder 200 based on received syntax information, and the motion compensation unit 302 may use the interpolation filter to generate a prediction block.

[0063] The motion compensation unit 302 may use at least part of the syntax information to determine the size of blocks used to encode (multiple) frames and / or (multiple) slices of the encoded video sequence, partition information describing how each macroblock of a picture of the encoded video sequence is partitioned, a mode indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter-coded block, and other information for decoding the encoded video sequence. As used herein, in some aspects, a "slice" may refer to a data structure that can be decoded independently of other slices of the same picture in terms of entropy coding and decoding, signal prediction, and residual signal reconstruction. A slice may be an entire picture, or it may be a region of a picture.

[0064] The intra prediction unit 303 may use, for example, an intra prediction mode received in the bitstream to form a prediction block from spatially neighboring blocks. The inverse quantization unit 303 inversely quantizes (i.e., dequantizes) the quantized video block coefficients provided in the bitstream and decoded by the entropy decoding unit 301. The inverse transform unit 303 applies an inverse transform.

[0065] The reconstruction unit 306 may obtain the decoded block, for example, by adding the residual block to the corresponding prediction block generated by the motion compensation unit 202 or the intra prediction unit 303. If necessary, a deblocking filter may also be applied to filter the decoded block in order to remove blocking artifacts. The decoded video block is then stored in a buffer 307, which provides reference blocks for subsequent motion compensation / intra prediction, and the buffer 307 also generates the decoded video for presentation on a display device.

[0066] Some exemplary embodiments of the present disclosure will be described in detail below. It should be noted that the section titles used in this document are for ease of understanding, rather than limiting the embodiments disclosed in the section to that section. In addition, although some embodiments are described with reference to general video codecs or other specific video codecs, the disclosed technology is also applicable to other video codec technologies. In addition, although some embodiments describe the video coding and decoding steps in detail, it should be understood that the corresponding decoding steps of the cancellation codec will be implemented by the decoder. In addition, the term video processing includes video coding or compression, video decoding or decompression, and video transcoding, in which video pixels are represented from one compression format to another compression format or at different compression bit rates. 1 Brief Overview The present disclosure relates to video coding techniques. Specifically, it relates to intra-frame prediction in video coding. These ideas can be applied to any image / video coding standard or non-standard image / video codec, such as the next generation image / video coding standard, either alone or in various combinations. 2 Introduction Video codec standards have developed mainly through the development of the well-known ITU-T and ISO / IEC standards. ITU-T developed H.261 and H.263, ISO / IEC developed MPEG-1 and MPEG-4 Visual, and the two organizations jointly developed H.262 / MPEG-2 Video and H.264 / MPEG-4 Advanced Video Codec (AVC) and H.265 / HEVC standards. Since H.262, video codec standards have been based on a hybrid video codec structure, in which temporal prediction plus transform codec is utilized. In order to explore future video codec technologies beyond HEVC, VCEG and MPEG jointly established the Joint Video Exploration Team (JVET) in 2015. JVET meetings are also held quarterly, and the new video codec standard was officially named Versatile Video Codec (VVC) at the April 2018 JVET meeting, and the first version of the VVC Test Model (VTM) was released at this time. Then the VVC working draft and test model VTM are updated after each meeting. The VVC project achieved technical completion (FDIS) in July 2020. 2.1 Intra Prediction in VVC v1 (Extracted from JVET-R2002-v2) 2.1.1 Intra-mode codec with 67 intra-prediction modes To capture arbitrary edge directions present in natural videos, the number of directional intra modes in VVC is extended from 33 to 65, as used in HEVC. Figure 4 The new directional modes that are not in HEVC are depicted as arrow 3 in , and the planar and DC modes remain the same. These more intensive directional intra prediction modes apply to all block sizes and both luma and chroma intra prediction. In VVC, wide-angle intra prediction mode for non-square blocks is used to adaptively replace several normal-angle intra prediction modes. Wide-angle intra prediction is described in 3.3.1.2. In HEVC, each intra-coded block has a square shape with the length of each side being a power of 2. Therefore, no division operation is required to generate intra predictors using DC mode. In VVC, in general, blocks can have a rectangular shape requiring the use of division operations for each block. To avoid division operations for DC prediction, only the longer sides are used to calculate the average for non-square blocks. 2.1.1.1 Intra-mode encoding and decoding In order to keep the complexity of the most probable mode (MPM) list generation low, an intra-mode codec with 6 MPM modes is used, considering two available adjacent intra modes. The following three aspects are considered in constructing the MPM list: – Default intra mode – Neighboring intra mode – Intra-mode for export Regardless of whether the MRL and ISP codecs are applied, a unified 6-MPM list is used for intra blocks. The MPM list is constructed based on the intra modes of the left and above neighboring blocks. Assuming that the mode of the left neighboring block is denoted as Left and the mode of the above neighboring block is denoted as Above, the unified MPM list is constructed as follows: – When a neighboring block is not available, its intra mode is set to planar by default. – If both mode Left and mode Above are non-angle modes: –MPM list {Planar,DC,V,H,V-4,V+4} – If one of the modes Left and Above is an angle mode and the other is a non-angle mode: – Set mode Max to the larger mode between Left and Above –MPM list {Planar,Max,DC,Max-1,Max+1,Max-2} – If both mode Left and mode Above are angle modes and they are different: – Set mode Max to the larger mode between Left and Above – If the difference between the modes Left and Above is in the range of 2 to 62, inclusive –MPM list {Planar,Left,Above,DC,Max-1,Max+1} -otherwise –MPM list {Planar,Left,Above,DC,Max-2,Max+2} – If both Mode Left and Mode Above are angle modes and they are the same: –MPM list {Planar,Left,Left-1,Left+1,DC,Left-2} In addition, the first binary bit of the MPM index codeword is CABAC context coded. A total of three contexts are used, corresponding to whether the current intra block is MRL enabled, ISP enabled, or a normal intra block. During the generation of the 6 MPM lists, pruning is used to remove repeated patterns so that only unique patterns can be included in the MPM lists. For entropy coding and decoding of the 61 non-MPM patterns, truncated binary code (TBC) is used. 2.1.1.2 Wide-angle intra prediction for non-square blocks Although 67 modes are defined in VVC, the exact prediction direction for a given intra prediction mode index also depends on the block shape. The normal angle intra prediction direction is defined to be from 45 degrees to -135 degrees in the clockwise direction. In VVC, several normal angle intra prediction modes are adaptively replaced with the wide angle intra prediction mode for non-square blocks. The replaced mode is signaled using the original mode index, which is remapped to the index of the wide angle mode after parsing. The total number of intra prediction modes remains unchanged, i.e. 67, and the intra mode encoding and decoding method remains unchanged. To support these prediction directions, an upper reference of length 2W+1 and a left reference of length 2H+1 are defined as Figure 5 The number of replaced modes in the wide-angle direction mode depends on the aspect ratio of the block. The replaced intra prediction modes are shown in Table 2-1. Table 2-1 - Intra-prediction modes replaced by wide-angle mode like Figure 6 As shown, in the case of wide-angle intra prediction, two vertically adjacent predicted samples can use two non-adjacent reference samples. Therefore, a low-pass reference sample filter and edge smoothing are applied to wide-angle prediction to reduce the negative impact of the increased gap Δpα. If the wide-angle mode represents a non-fractional offset. There are 8 modes in the wide-angle mode that meet this condition, and these modes are [-14, -12, -10, -6, 72, 76, 78, 80]. When a block is predicted by these modes, the samples in the reference buffer are directly copied without applying any interpolation. Through this modification, the number of samples that need to be smoothed is reduced. In addition, it aligns the design of non-fractional modes in conventional prediction mode and wide-angle mode. In VVC, 4:2:2 and 4:4:4 as well as 4:2:0 chroma formats are supported. The chroma derivation mode (DM) derivation table for the 4:2:2 chroma format was originally ported from HEVC, expanding the number of entries from 35 to 67 to align with the expansion of intra prediction modes. Since the HEVC specification does not support prediction angles below -135 degrees and above 45 degrees, the luma intra prediction modes ranging from 2 to 5 are mapped to 2. Therefore, the chroma DM derivation table for the 4:2:2: chroma format is updated to more accurately convert the prediction angles for chroma blocks by replacing some values ​​of the entries of the mapping table. . 2.1.1.3 Mode Dependent Intra-Frame Smoothing (MDIS) A four-tap intra-frame interpolation filter is used to improve the accuracy of directional intra-frame prediction. In HEVC, a two-tap linear interpolation filter has been used to generate intra-frame prediction blocks in directional prediction mode (i.e., outside planar and DC predictors). In VVC, a simplified 6-bit 4-tap Gaussian interpolation filter is used only for directional intra-frame mode. The non-directional intra-frame prediction process is unmodified. The selection of the 4-tap filter is performed according to the MDIS condition for the directional intra-frame prediction mode, which provides non-fractional displacement, i.e., all the following directional modes are excluded: 2, HOR_IDX, DIA_IDX, VER_IDX, 66. Depending on the intra prediction mode, the following reference sample processing is performed: – Directional intra prediction modes are classified into one of the following groups: – vertical or horizontal mode (HOR_IDX, VER_IDX), – diagonal mode (2, DIA_IDX, VDIA_IDX) expressing angles as multiples of 45 degrees, – other directional modes; – if the directional intra prediction mode is classified as belonging to group A, no filter is applied to the reference samples to generate the predicted samples; – Otherwise, if the mode falls into group B, then a [1,2,1] reference sample filter may be applied (depending on the MDIS condition) to the reference samples to further copy these filtered values ​​into the intra predictor according to the selected direction, but no interpolation filter is applied; Otherwise, if the mode is classified as belonging to group C, then only the intra reference sample interpolation filter is applied to the reference samples to generate prediction samples falling in fractional or integer positions between the reference samples according to the selected direction (no reference sample filtering is performed). 2.1.2 Cross-component linear model prediction 2.1.2.1 Single Model Cross-Component Linear Model Prediction In order to reduce cross-component redundancy, the cross-component linear model (CCLM) prediction mode is used in VVC to predict the chroma samples based on the reconstructed luma samples of the same CU using the following linear model: pred C (i,j)=α·rec L ′(i,j)+ β (3-1) where pred C (i, j) represents the predicted chroma samples in the CU and rec L ′(i,j) represents the downsampled reconstructed luma samples of the same CU. The CCLM parameters (α and β) are derived from at most four neighboring chroma samples and their corresponding downsampled luma samples. Assuming the current chroma block size is W×H, W' and H' are set to – W'=W, H'=H when LM mode is applied; – When LM-A mode is applied, W'=W+H; – When LM-L mode is applied, H'=H+W; The upper neighboring positions are denoted as S[0,1], S[W'-1,-1] and the left neighboring positions are denoted as S[1,0] and S[-1,H'-1]. Then four samples were selected as – When LM mode is applied and both upper and left neighboring samples are available, S[W' / 4,-1], S[3*W' / 4,-1], S[-1,H' / 4], S[-1,3*H' / 4]; – When LM-A mode is applied or only upper neighbor samples are available, S[W' / 8,-1], S[3*W' / 8,-1], S[5*W' / 8,-1], S[7*W' / 8,-1]; – When LM-L mode is applied or only left neighbor samples are available, S[-1,H' / 8], S[-1,3*H' / 8], S[-1,5*H' / 8], S[-1,7*H' / 8]; The four neighboring brightness samples at the selected position are downsampled and compared four times to find the smaller of the two values ​​x 0 A and dx 1 A , and two larger values ​​x 0 B and x 1 B Their corresponding chrominance sample values ​​are recorded as y 0 A ,y 1 A ,y 0 B and 1 B . And x A , x B ,y A and B is exported as: X a =(x 0 A +x 1 A +1)>>1;X b =(x 0 B +x1 B +1)>>1;Y a =(y 0 A +y 1 A +1)>>1;Y b =(y 0 B +y 1 B +1)>>1(3- 2) Finally, the linear model parameters α and β are obtained according to the following equations. β=Y b -α·X b (3-4) Figure 7 An example of the positions of the left and above samples involved in the CCLM mode and the samples of the current block is shown. The division operation is performed using a lookup table to calculate the parameter α. In order to reduce the memory required to store the table, the diff value (the difference between the maximum and minimum values) and the parameter α are represented by exponential notation. For example, diff is approximated with a 4-bit significand and an exponent. Therefore, for 16 values ​​of the significand, the table for 1 / diff is reduced to 16 elements as follows: DivTable[]={0,7,6,5,5,4,4,3,3,2,2,1,1,1,1,0}(3-5) This will have the benefit of reducing the computational complexity as well as the memory size required to store the required tables. In addition to the upper and left templates being used together to compute the linear model coefficients, they can also be used alternatively in other 2LM modes, referred to as LM_A and LM_L modes. In LM_A mode, only the upper template is used to calculate the linear model coefficients. In order to obtain more samples, the upper template is expanded to (W+H). In LM_L mode, only the left template is used to calculate the linear model coefficients. In order to obtain more samples, the left template is expanded to (H+W). For non-square blocks, expand the upper template to W+W and the left template to H+H. To match the chroma sample positions for 4:2:0 video sequences, two types of downsampling filters are applied to the luma samples to achieve a 2:1 downsampling ratio in both horizontal and vertical directions. The choice of downsampling filter is specified by the SPS level flag. The two downsampling filters corresponding to "type 0" and "type 2" content, respectively, are as follows. Note that when the upper reference line is at a CTU boundary, only one luma line (common line buffer in intra prediction) is used to make the downsampled luma samples. This parameter calculation is performed as part of the decoding process and is not simply an encoder search operation. Therefore, no syntax is used to convey the α and β values ​​to the decoder. For chroma intra mode coding and decoding, a total of 8 intra modes are allowed for chroma intra mode coding and decoding. These modes include five traditional intra modes and three cross-component linear model modes (CCLM, LM_A, and LM_L). The chroma mode signaling and derivation process are shown in Table 3-3. Chroma mode coding and decoding depends directly on the intra prediction mode of the corresponding luminance block. Since separate block partitioning structures for luminance and chrominance components are enabled in the I stripe, one chroma block can correspond to multiple luminance blocks. Therefore, for the chroma DM mode, the intra prediction mode of the corresponding luminance block covering the center position of the current chroma block is directly inherited. Table 3-3 - Derivation of chroma prediction modes from luma mode when ccm_ is enabled Regardless of the value of sps_cclm_enabled_flag, a single binarization table is used, as shown in Table 3-4. Table 3-4- Unified binarization table of chroma prediction mode In Table 3-4, the first binary bit indicates whether it is normal (0) or LM mode (1). If it is LM mode, the next binary bit indicates whether it is LM_CHROMA (0). If it is not LM_CHROMA, the next 1 binary bit indicates whether it is LM_L (0) or LM_A (1). For this case, when sps_cclm_enabled_flag is 0, the first binary bit of the binarization table for the corresponding intra_chroma_pred_mode can be discarded before entropy coding. Or, in other words, the first binary bit is inferred to be 0 and therefore not coded. This single binary table is used for both cases where sps_cclm_enabled_flag is equal to 0 and 1. The first two binary bits in Table 3-4 are context coded with their own context model, and the remaining binary bits are bypass coded. Additionally, to reduce luma-chroma latency in dual trees, when a 64x64 luma codec tree node is partitioned as unsplit (and ISP is not used for 64x64 CUs) or QT, chroma CUs in 32x32 / 32x16 chroma codec tree nodes are allowed to use CCLM in the following manner: – If a 32x32 chroma node is unpartitioned or partitioned QT partitioned, all chroma CUs in the 32x32 node may use CCLM; – If a 32x32 chroma node is split using horizontal BT, and the 32x16 child node is not split or uses vertical BT split, then all chroma CUs in the 32x16 chroma node can use CCLM. Under all other luma and chroma codec tree partitioning conditions, CCLM is not allowed for chroma CUs. 2.1.2.2 Multi-model cross-component linear model prediction The above section gives the unimodal cross-component linear model prediction in the VVC specification, which considers all luma and chroma samples of the current codec block and its neighborhood as the entire group, and uses a single linear function to modulate the similarity between all those luma and chroma samples. Compared with a single model that classifies luma and chroma samples into one group, multi-model cross-component linear model prediction has also been studied by researchers. Here, "multi-model" is named to indicate a cross-component method that classifies luma and chroma samples into more than one group and uses more than one function to modulate the similarity between luma samples and chroma samples of a codec block. For example, for a codec block, it can be encoded and decoded by dual-model based cross-component prediction, which divides all luma and chroma samples of the codec block into two groups, and then each group has one model / function to modulate the similarity between luma and chroma samples belonging to the group. 3 Questions Existing designs for cross-component prediction have the following problems: 1) Luma samples should be downsampled to obtain corresponding luma sample values ​​for chroma samples. Fixed downsampling filters may not be efficient. 4 Detailed solutions In order to solve the above problems and some unmentioned problems, the following method is disclosed. The embodiments should be considered as examples to explain the general concept and should not be interpreted in a narrow way. In addition, these embodiments can be applied individually or in combination in any way. In the following discussion, W and H represent the width and height of the current block, respectively. CCLM may refer to any kind of CCLM mode, such as CCLM-L, CCLM-T, CCLM-LT or multi-model CCLM. CCLM may also refer to any other prediction method that uses reconstructed samples of the first component to predict at least one sample in the second component, not limited to conventional CCLM as defined in JEM or VVC, or CCLM-L, or CCLM-LT, or CCLM-LT, or multi-model CCLM. 1. Having multiple filters to generate sample values ​​of a first color component (eg, Y) corresponding to samples of a second color component (eg, Cb / Cr). 1) In one example, multiple filters may be used in the CCLM process. 2) In one example, a filter among the plurality of filters (denoted as F(Y)) where {L} represents a sample set of the first color component can be derived as F(Y)=(c 0 ×S 0 +c 1 ×S 1 +…c n ×S n + offset)>>K, where n is the number of taps of F, c i is the filter coefficient of filter tap i, S i is the value of the i-th sample of the sample of the first component involved in the filter F, and the offset and K are integers. a. Alternatively, at least one nonlinear term may be involved in the filter, expressed as F(Y)=(c 0 ×S 0 +c 1 ×S 1 +… c n ×S n +g(S 0 ,S 1 ,…,S n )+offset)>>K, where g is a nonlinear function. For example, g(S)=log(S)orS 2 or S 3 or S w ,or wait. b. In one example, the filtered result may be clipped. 3) For example, c i is an integer which can be positive, negative, or zero. 4) In one example, c i or |c i The sum of | can be a fixed number, such as 2 K . 5) In one example, the offset may be equal to 2 K-1 . 6) In one example, the positions of the samples of the first component involved in the filter F may depend on the positions of the samples of the second component. 7) In one example, the positions of the samples of the first component involved in the filter F may depend on the color format, such as 4:4:4 or 4:2:0 or 4:2:2. 8) For K samples of the second component, filter F will generate K corresponding samples of the first component. a. For a color format such as 4:2:0 or 4:2:2, when the first component is Y and the second component is Cb or Cr, the filter F may include a downsampling or downscaling process. 9) Assume that the position of a particular sample in the second component is (xC, yC), and the position of the i-th sample in the first component involved in F, which is used to generate the sample value corresponding to the particular sample, is (xL, yL). a. In one example, xL=scaleX*xC+OffX. b. In one example, yL=scaleY*yC+OffY. c. In one example, scaleX and scaleY may depend on the color format. i. For example, for 4:2:0 format, scaleX=scaleY=2. ii. For example, for 4:2:2 format, scaleX=2, scaleY=1. iii. For example, for 4:4:4 format, scaleX=scaleY=1. d. In one example, OffX and OffY are integers, and they may depend on i. e. In one example, the sample in the first component involved in F corresponding to a particular sample in the second component may be In the following position: i.P0:(scaleX*xC,scaleY*yC) ii.P1:(scaleX*xC,scaleY*yC+1) iii.P2:(scaleX*xC,scaleY*yC-1) iv.P3:(scaleX*xC+1,scaleY*yC) v.P4:(scaleX*xC+1,scaleY*yC+1) vi.P5:(scaleX*xC+1,scaleY*yC-1) vii.P6:(scaleX*xC-1,scaleY*yC) viii.P7:(scaleX*xC-1,scaleY*yC+1) ix.P8:(scaleX*xC-1,scaleY*yC-1). f. In one example, the samples of the first component involved in F (with 6 taps) corresponding to a particular sample in the second component may be at positions P0, P1, P3, P4, P6, P7. g. In one example, the positions of the samples involved in F may depend on the color format. h. In one example, the positions of the samples involved in F may depend on the first color component and / or the second color component. i. In one example, the positions of the samples involved in F may depend on the position of the current block (eg, whether the current block is at the boundary of a picture / slice / tile / CTU row / CTU). j. In one example, the location of the samples involved in F may depend on the type of CCLM, such as conventional CCLM, or CCLM-L, or CCLM-T, or CCLM-LT, or multi-model CCLM, etc. k. In one example, the filter coefficient of a filter tap at a position may be set to 0 as an alternative to removing the tap at that position. 1. In one example, if the samples involved in F are not available (eg, outside the current picture / slice / tile / CTU row / CTU), the samples involved in F may be removed from the filtering process. i. In one example, if the sample involved in F is not available (e.g., in the current picture / slice / tile / CTU row / CTU), the samples involved in F can be filled from the filtering process. a) For example, it is filled with the value of its most recent available sample. a. For example, the most recent available sample must be involved in F. 10) In one example, the candidate filter set Ψ={F 0 , F 1 , F 2 , …F M} may be predefined, and at least one of the candidate filters may be used to filter the samples of the first component. 11) In one example, coefficients of at least one filter candidate may be indicated from the encoder to the decoder, for example in an SPS / PPS / slice header / picture header / CTU, etc. a. The coefficients can be signaled in a predictive manner. b. The coefficients can be binarized into fixed length codes / / (truncated) unary codes / exponential Golomb codes / etc. c. The coefficients for Cb and Cr may be different and signaled separately for Cb / Cr. d. The coefficients for Cb and Cr may be the same and signaled together. 12) In one example, coefficients of at least one of the filter candidates may be derived online. a. For example, the coefficients may be derived by a minimum mean square error (LMSE) method using the decoded sample values. b. Online export can be performed for Cb and Cr separately, or can be shared by Cb and Cr. 13) The candidate filter set can be the same to encode and decode different color components such as Cb and Cr. 14) The candidate filter sets can be different to encode and decode different color components such as Cb and Cr. 15) The candidate filter set may depend on codec information, such as codec mode / slice or picture type / W and H / color format / color component / etc. 2. Filter selection can be derived at both the encoder and the decoder. a. In one example, costs corresponding to filters may be calculated, and filter selection may be applied based on the cost of each filter. i. For example, the filter with the minimum cost may be selected. b. In one example, the cost of filter F can be derived as the sum of absolute differences (SAD) or the sum of squared differences (SSD) or the sum of absolute transformed differences (SATD) or mean removed SAD (MR-SAD) between the reconstructed samples of the second component at the first set of positions and the corresponding predicted values ​​at the first set of positions. i. In one example, the first set of positions may include sample positions adjacent to the current block. a) “Adjacent to” may include “left” and / or “above” and / or “upper left” and / or “upper right” and / or “lower left”. b) The first set of positions may depend on the availability of neighboring samples. a. For example, a set may include only available samples. b. For example, if the left neighboring block is available, the set may include samples to the left of the current block. c. For example, if an upper neighboring block is available, the set may include samples above the current block. c) The neighboring samples may be adjacent to the current block or not adjacent to the current block. a. For example, the neighboring samples may include K rows of samples above the current block. b. For example, the neighboring samples may include K columns of samples to the left of the current block. ii. In one example, a filter F may be used to derive a predicted value. a) In one example, a filter F may be used to generate samples of the first component (denoted S) corresponding to reconstructed samples of the second component (denoted R) at a second set of positions. b) In one example, S and R can be used to derive one or more linear models for filter F. a. In one example, the model may be generated using the LMSE method as defined in JEM or the min-max method as defined in VVC. b. In one example, the method proposed in MMLM can be used to generate multiple models (such as two). c) In one example, one or more linear models may be applied to generate a predicted value for a sample of the second component at position (x, y) of aP(x,y)=a*S(x,y)+b, where P(x,y) is the predicted value and S(x,y) is the corresponding brightness sample. (a,b) represents a linear model. b. For example, additional operations such as shifting or clipping may be applied to derive predictions using a linear model. d) In one example, whether to derive / use one model or multiple models may depend on the encoding / decoding mode. a. For example, when applying CCLM mode, derive / use a model to generate forecast values. b. For example, when the MMLM model is applied, a model is derived / used to generate forecast values. iii. The first set of positions and the second set of positions may be the same. iv. The first set of positions and the second set of positions may be different. a) In one example, the first position set may include two rows of samples above the current block and / or two columns of samples to the left of the current block. b) In one example, the second position set may include a row of samples above the current block and / or a column of samples to the left of the current block. v. The first set of positions and / or the second set of positions may depend on the codec mode. a) For example, if the current coding mode is CCLM-L, the first position set and / or the second position set may only include samples on the left side of the current block. b) For example, if the current coding mode is CCLM-T, the first position set and / or the second position set may only include samples above the current block. 3. Filter selection information can be signaled from the encoder to the decoder. a. In one example, a syntax element SE (eg, filter index) may be signaled in a CU / TU / PU / CTU / slice / picture to indicate the selected filter. i. SE can be coded and decoded with at least one codec context in arithmetic codec. ii.SE can be encoded and decoded using bypass codec. iii. SE can be binarized into fixed length code / (truncated) unary code / exponential Golomb code / etc. iv. SE can be encoded and decoded in a predictive manner, such as predicted by SE from at least one neighboring block. v. For example, SE may be signaled separately for at least two components (e.g., Cb and Cr). The two components of Cb and Cr may have different SEs. vi. For example, X_flag may be signaled for at least two components, such as Cb and Cr. That is, two components such as Cb and Cr may have the same SE. 4. In one example, multiple stages of filters may be applied. a. In one example, samples of a first component (denoted as S) may be filtered by a first filter (denoted as F1) to produce filtered samples (denoted as S'). And S' may be filtered by a second filter (denoted as F2) to generate filtered samples S". i. In one example, S" can be used in the CCLM process as 'samples of the first component corresponding to samples in the second component. ii. In one example, S" may be further filtered by a third filter (denoted as F3) to generate filtered samples S'', a) S'' can be used in the CCLM process as samples of the first component corresponding to samples in the second component. b) S' can be further 'filtered. b. If the color format is not 4:4:4, ie, the resolution of the first component and the resolution of the second component are different, a resampling (eg, downsampling) process may be associated with any stage of the filter. c. In one example, S involving the nth filter stage (n) The samples in can be located in the following locations: i.P0:(scaleX (n) *xC,scaleY (n) *yC) ii.P1:(scaleX (n) *xC,scaleY (n) *yC+1) iii.P2:(scaleX (n) *xC,scaleY (n) *yC-1) iv.P3:(scaleX (n) *xC+1,scaleY (n) *yC) v.P4:(scaleX (n) *xC+1,scaleY (n) *yC+1) vi.P5:(scaleX (n) *xC+1,scaleY (n) *yC-1) vii.P6:(scaleX (n) *xC-1,scaleY (n) *yC) viii.P7:(scaleX (n) *xC-1,scaleY (n) *yC+1) ix.P8:(scaleX (n) *xC-1,scaleY (n) *yC-1) where scaleX (n) and scaleY (n) Indicates the scaling ratio of the sample before the nth filtering and the sample of the second component. For example, if the sample before the nth filtering and the sample of the second component have the same resolution, scaleX (n) =scaleY (n) =1. d. In one example, the filters in a stage (such as the first stage) may be fixed. e. In one example, the filter in a stage (such as the second stage) may be adaptive. i. For example, a filter may be selected from a set of candidate filters. ii. For example, filters can be exported online. iii. For example, the filter may be signaled from the encoder to the decoder. f. In one example, two stages of filtering are applied. i. In the first stage, the luma samples are filtered and downsampled using the filtering method defined in VVC, i.e., when the color format is 4:2:0, corresponding to the position (i, j) of the chroma component, we have ii. In the second stage, S' is further filtered adaptively. g. In one example, any of the methods on filters disclosed in this document can be applied to filters in any stage of multi-stage filtering. 5. In one example, when luma mapping with chroma scaling (LMCS) is applied, the samples of the first component to be filtered may be in the original domain, or they may be in a converted (mapped) domain. 6. In one example, when samples of the first component are used as samples of the first component corresponding to samples in different components in the process of CCLM, the samples of the first component may be filtered in different ways. a. For example, a first filter (denoted as F1) may be applied to a second component such as Cb, and a second filter (denoted as F2) may be applied to a third component such as Cr. i. In one example, the filter derivation process may be performed separately for the Cb component and the Cr component. ii. In one example, the filter index may be signaled separately for the Cb component and the Cr component. 7. In one example, when samples of the first component are used in the process of CCLM as samples of the first component corresponding to samples in a different component, the samples of the first component may be filtered in the same manner. a. For example, a first filter (denoted as F1) may be applied to a second component, such as Cb, and the first filter F1 may also be applied to a third component, such as Cr. i. In one example, the filter derivation process may be performed once for both the Cb component and the Cr component. a) In one example, samples are derived that may depend on one of the two components (eg, Cb). b) In one example, samples are derived that may depend on both components. ii. In one example, the filter index may be signaled once for both the Cb component and the Cr component. 8. Codec mode X may be applied, which has a multi-filter approach for cross-component prediction. a. In one example, it is possible to signal from the encoder to the decoder whether codec mode X is allowed, such as in SPS / PPS / picture header / slice header / CTU row / CTU / CU, etc. b. In one example, whether codec mode X is allowed may depend on codec information. i. For example, codec mode X is allowed (only) when a specific mode is applied, such as conventional CCLM and / or CCLM-L and / or CCLM-T and / or CCLM-LT and / or multi-model CCLM. ii. For example, if W and / or H satisfy one or more conditions, such as: W*H<=T1 and / or W*H>=T2 and / or max(W,H)<=T3, and / or min(W,H)>=T4, then codec mode X is allowed. a) For example, codec mode X is allowed only when W*H>8; iii. For example, decoding mode X is allowed (only) for certain kinds of slice / picture types (eg I-slices). iv. For example, decoding mode X is allowed (only) for certain kinds of color formats (such as 4:2:0). v. For example, decoding mode X is allowed for (only) certain color components (eg Cb and / or Cr). vi. For example, decoding mode X is allowed (only) for a certain profile / level of the standard. vii. For example, decoding mode X is allowed (only) if at least K neighboring samples are available. (e.g. K=1, 2, 3, 4...) c. In one example, a syntax element X_flag may be signaled to indicate whether codec mode X is used. i. For example, X_flag is signaled only if mode X is allowed. ii. For example, if mode X is not allowed, X_flag is set to a default value (eg, 0 means mode X is not used). iii. For example, X_flag may be signaled for a picture or a slice or a CTU or a CU or a PU or a TU. iv. For example, X_flag may be signaled separately for at least two components such as Cb and Cr. That is, two components such as Cb and Cr may have different X_flags, and they are processed differently as to whether to perform a multi-filter method. v. For example, X_flag may be signaled for at least two components such as Cb and Cr. That is, two components such as Cb and Cr may have the same X_flag, and they are processed in the same way as to whether the multi-filter method is performed. vi. X_flag can be coded with at least one codec context in arithmetic codec. vii.X_flag can be encoded and decoded using bypass codec. d. In one example, a second syntax element related to a multi-filter method for cross-component prediction may be signaled after X_flag. i. In one example, the second syntax element may be signaled only if it indicates that a multi-filter method is to be applied. ii. In one example, the second syntax element may indicate a filter to be used. iii. In one example, the second syntax element may indicate a method of deriving the filter. General claims 9. Whether and / or how to apply the above disclosed method can be signaled at the sequence level / picture group level / picture level / slice level / tile group level, for example in the sequence header / picture header / SPS / VPS / DPS / DCI / PPS / PPS / slice header / tile group header. 10. Whether and / or how to apply the above disclosed methods may be signaled at a PB / TB / CB / PU / TU / CU / VPDU / CTU / CTU row / slice / tile / sub-picture / other kind of area containing more than one sample or pixel. 11. Whether and / or how to apply the above disclosed method may depend on the coded information, such as block size, color format, single / dual tree partitioning, color component, slice / picture type. 5. Embodiment 5.1 Example 1 A self-aware filter estimation CCLM (SAFE-CCLM) method is proposed to explore the advantages of multiple downsampling filters without signaling the filter index. Using SAFE-CCLM, N candidate brightness downsampling filters are predefined. Figure 8 As shown, the downsampling filtering process for the 4:2:0 color format is performed as follows: Among them, Rec L (x,y) and Rec' L (x, y) are the reconstructed luma samples before and after downsampling filtering at position (x, y), and {c 0 ,c 1 ,c 2 ,c 3 ,c 4 ,c 5} is the filter coefficient. It should be noted that in the current ECM, {c 0 ,c 1 ,c 2 ,c 3 ,c 4 ,c 5N candidate luma sampling filters with different coefficients are predefined by SAFE-CCLM. Fig.9A and Fig. 9B A flow chart of SAFE-CCLM is shown. First, when SAFE-CCLM is applied, a linear model between luminance and chrominance components is derived in the same manner as in the ECM for each candidate filter. Second, the linear model is used to calculate the prediction value on a test area including a column of left neighboring samples and a row of upper neighboring samples. Third, the SAD cost between the reconstructed chrominance samples and their corresponding prediction values ​​is calculated for each filter candidate. Finally, the filter candidate with the minimum SAD cost is selected as the downsampling filter to perform CCLM prediction on the current block. When CCLM is indicated to be used for a block, a SAFE-CCLM flag is signaled to further indicate whether SAFE-CCLM is applied. In this embodiment, N=32, and the candidate set is filtered as follows: or

[0067] As used herein, the term "video unit" or "video block" may be a sequence, a picture, a slice, a tile, a block, a sub-picture, a codec tree unit (CTU) / codec tree block (CTB), a CTU / CTB row, one or more codec units (CU) / codec blocks (CB), one or more CTU / CTBs, one or more virtual pipeline data units (VPDU), a sub-region within a picture / slice / tile / block. The term "around motion compensation (WAMC)" as used herein may refer to a codec method in which, when a motion vector refers to samples beyond one or more picture boundaries of a reference picture, instead of padding the boundaries (e.g., repeat padding, mirror padding, motion compensated padding, or other padding methods) to derive the value of the out-of-bounds samples, the motion vector is adjusted within the picture with one or more surrounding offsets.

[0068] In the following discussion, W and H represent the width and height of the current block, respectively. The term "CCLM" as used herein may refer to any kind of CCLM mode, such as CCLM-L, CCLM-T, CCLM-LT, or multi-model CCLM. The term "CCLM" as used herein may also refer to any other prediction method that uses reconstructed samples of a first component to predict at least one sample in a second component, not limited to conventional CCLM as defined in JEM or VVC, or CCLM-L, or CCLM-LT, or CCLM-LT, or multi-model CCLM.

[0069] Fig.10 A flow chart of a method 1000 for video processing according to an embodiment of the present disclosure is shown. The method 4700 is implemented during conversion between a video unit of a video and a bitstream of the video.

[0070] At block 1010, for conversion between a video unit of a video and a bitstream of the video unit, sample values ​​of a first color component of the video unit corresponding to samples of a second color component are generated by applying a plurality of filters to at least one sample of the first color component. In some embodiments, the plurality of filters are applied during cross-component linear model prediction of the video unit.

[0071] At block 1020, a conversion is performed based on the generated sample values. In some embodiments, the conversion may include encoding the video unit into a bitstream. Alternatively or in addition, the conversion may include decoding the video unit from the bitstream. In this way, codec efficiency and codec performance may be improved.

[0072] In some embodiments, the table filter in the plurality of filters is derived as F(Y)=(c 0 ×S 0 +c 1 ×S 1 +…c n ×S n + offset)>>K, where F(Y) represents the target filter, {Y} represents the sample set of the first color component, n represents the number of taps of the target filter, c i represents the filter coefficient of filter tap i, S i represents the value of the i-th sample of the first color component involved in the representation, i is an integer, and the offset and K are integers respectively. In some embodiments, at least one nonlinear term involved in a target filter in the plurality of filters is represented as: F(Y)=(c 0 ×S 0 +c 1 ×S 1 +…c n ×S n +g(S 0 , S 1 , …, S n )+offset)>>K, where F(Y) represents the target filter, {Y} represents the sample set of the first color component, n represents the number of taps of the target filter, c i represents the filter coefficient of filter tap i, S i represents the value of the i-th sample of the first color component involved in the representation, and offset and K are integers respectively, and g represents a nonlinear function. In some embodiments, g(S) is one of the following: log(S) or S2 or S 3 or S w ,or and wherein w is an integer. In some embodiments, the filtered results after the plurality of filters are clipped.

[0073] In some embodiments, the filter coefficients of the filter taps are integers, and the filter coefficients of the filter taps are positive, negative, or zero. i or |c i The sum of | is a fixed number, where c i represents the filter coefficient for filter tap i.

[0074] In some embodiments, the sum is 2 K , where K is an integer. In some embodiments, the offset is equal to 2 K-1 , where K is an integer.

[0075] In some embodiments, the position of the samples of the first color component involved in the target filter of the plurality of filters depends on the position of the samples of the second color component. In some embodiments, the position of the samples of the first color component involved in the target filter of the plurality of filters depends on the color format. In some embodiments, the color format is one of: 4:4:4 or 4:2:0 or 4:2:2.

[0076] In some embodiments, for K samples of the second color component, a target filter in the plurality of filters generates K corresponding samples of the first color component, where K is an integer. In some embodiments, for a color format of 4:2:0 or 4:2:2, the target filter includes a downsampling or downscaling process when the first color component is Y and the second color component is Cb or Cr.

[0077] In some embodiments, xL=scaleX*xC+OffX, and / or yL=scaleY*yC+OffY, and wherein xC, yC represent the position of a specific sample in the second color component, xL, yL represent the position of the i-th sample in the first color component involved in the target filter in the plurality of filters corresponding to the specific sample, respectively, and scaleX and scaleY are scaling factors, respectively. In some embodiments, scaleX and scaleY depend on the color format. In some embodiments, scaleX and scaleY are equal to 2 for a color format of 4:2:0, or scaleX is equal to 2 and scaleY is equal to 1 for a color format of 4:2:2, or scaleX and scaleY are equal to 1 for a color format of 4:4:4.

[0078] In some embodiments, OffX and OffY depend on the sequence value (i) of the sample and are integers. In some embodiments, the samples in the first color component involved in the target filter corresponding to a particular sample in the second color component are in one or more of the following positions: P0: (scaleX*xC, scaleY*yC), P1: (scaleX*xC, scaleY*yC+1), P2: (scaleX*xC, scaleY*yC-1), P3: (scaleX*xC+1, scaleY*yC), P4: (scaleX*xC+1, scaleY*yC+1), P5: (scaleX*xC+1, scaleY*yC-1 ), P6:(scaleX*xC-1,scaleY*yC), P7:(scaleX*xC-1,scaleY*yC+1), and P8:(scaleX*xC-1,scaleY*yC-1), and wherein P0, P1, P2, P3, P4, P5, P6, P7 and P8 represent positions, xC, yC represent positions of specific samples in the second color component, xL, yL represent positions of the i-th sample in the first color component involved in the target filter among the multiple filters corresponding to the specific sample, and scaleX and scaleY are respectively scaling factors.

[0079] In some embodiments, the samples in the first color component involved in the target filter with 6 taps corresponding to a particular sample in the second color component are at positions P0, P1, P3, P4, P6, P7. In some embodiments, the positions of the samples involved in the target filter depend on the color format. In some embodiments, the positions of the samples involved in the target filter depend on at least one of the first color component or the second color component. In some embodiments, the positions of the samples involved in the target filter depend on the position of the current block.

[0080] In some embodiments, the position of the current block is at a boundary of one of a picture, a slice, a tile, a codec tree unit (CTU), or a CTU row. In some embodiments, the position of the samples involved in the target filter depends on the type of a cross-component linear model (CCLM) of the video unit. In some embodiments, the type of CCLM includes at least one of the following: conventional CCLM, CCLM-L, CCLM-T, CCLM-LT, or multi-model CCLM.

[0081] In some embodiments, the filter coefficients of the filter taps at a position are set to 0 to remove the filter taps at the position. In some embodiments, if the samples are not available (such as outside the current picture / slice / tile / CTU row / CTU), the samples involved in the target filter can be removed from the filtering process.

[0082] In some embodiments, if the sample is not available (e.g., outside the current picture / slice / tile / CTU row / CTU), the sample involved in the target filter can be filled from the filtering process. In some embodiments, the sample is filled with the value of the nearest available sample of the sample. In some embodiments, the nearest available sample is involved in the target filter.

[0083] In some embodiments, a set of candidate filters is predefined (e.g., Ψ={F0, F1, F2, ... FM}), and at least one candidate filter from the set of candidate filters is used to filter samples of the first color component. In some embodiments, the coefficients of at least one filter candidate may be indicated from the encoder to the decoder, for example in an SPS / PPS / slice header / picture header / CTU, etc.

[0084] In some embodiments, the coefficients are indicated in a predictive manner. In some embodiments, the coefficients are binarized as one of the following: a fixed length code, a unary code, a truncated unary code, or an exponential Golomb code. In some embodiments, the coefficients for Cb and Cr are different and are indicated separately. In some embodiments, the coefficients for Cb and Cr are the same and are indicated together.

[0085] In some embodiments, the coefficients of at least one filter candidate are derived online. For example, the coefficients are derived by a minimum mean square error (LMSE) method using decoded sample values. In some embodiments, the online derivation of the coefficients is performed separately for Cb and Cr, or the online derivation of the coefficients is shared by Cb and Cr.

[0086] In some embodiments, the set of candidate filters used to encode and decode different color components is the same. In some embodiments, the set of candidate filters used to encode and decode different color components is different.

[0087] In some embodiments, the candidate filter set depends on the codec information of the video unit. For example, the codec information includes at least one of the following: codec mode, slice type, picture type, width of the video unit, height of the video unit, color format of the video unit, or color component of the video unit.

[0088] In some embodiments, filter selection information about a plurality of filters is indicated from an encoder to a decoder. In some embodiments, a syntax element indicating the selected filter is indicated in one of the following: a coding unit (CU), a prediction unit (PU), a transform unit (TU), a CTU, a slice, or a picture.

[0089] In some embodiments, the syntax element is encoded and decoded by at least one codec context in arithmetic coding. In some embodiments, the syntax element is encoded and decoded by bypass coding. In some embodiments, the syntax element is binarized into one of the following: a fixed length code, a unary code, a truncated unary code, or an exponential Golomb code. In some embodiments, the syntax element is encoded and decoded in a predictive manner. In some embodiments, the syntax element is indicated separately for at least two components, or wherein the syntax element is indicated for at least two components.

[0090] In some embodiments, the method further comprises determining whether the codec mode is applied during the multi-filter method for cross-component prediction of the video unit. In some embodiments, whether the codec mode is allowed is indicated from the encoder to the decoder in one of the following: sequence parameter set (SPS), picture parameter set (PPS), picture header, slice header, CTU row, CTU, or CU.

[0091] In some embodiments, whether the codec mode is allowed depends on the codec information. In some embodiments, if the specific mode is applied to the video unit, the codec mode is allowed. In some embodiments, the specific mode includes at least one of the following: conventional CCLM, CCLM-L, CCLM-T, CCLM-LT, or multi-model CCLM.

[0092] In some embodiments, if the width of the video unit and the height of the video unit meet one or more conditions, the codec mode is allowed. In some embodiments, the one or more conditions include at least one of the following: W*H<=T1, W*H>=T2, max(W,H)<=T3, min(W,H)>=T4, or W*H is greater than a predetermined number, and wherein W represents the width of the video unit, H represents the height of the video unit, and T1, T2, T3, and T4 are integers.

[0093] In some embodiments, codec mode X is allowed for a specific kind of slice type or picture type (e.g., I slice). In some embodiments, codec mode X is allowed for a specific kind of color format. In some embodiments, codec mode X is allowed for a specific color component. In some embodiments, codec mode X is allowed for a specific profile or level of the standard. In some embodiments, codec mode X is allowed if at least K neighboring samples are available, where K is an integer, such as 1, 2, 3, 3, 4, etc.

[0094] In some embodiments, whether to indicate a syntax element (e.g., X_flag) depends on whether a codec mode is applied. In some embodiments, if the codec mode is allowed, the syntax element is indicated. In some embodiments, if the codec mode is not allowed, the syntax element is set to a default value (e.g., 0, meaning that the codec mode is not used). In some embodiments, the syntax element is indicated for one of the following: picture, slice, CTU, CU, PU, ​​or TU.

[0095] In some embodiments, for at least two components, the syntax element is indicated separately, and the at least two components are handled differently with respect to whether to perform a multi-filter method. For example, X_flag can be signaled separately for at least two components such as Cb and Cr. That is, two components such as Cb and Cr can have different X_flags, and they are handled differently with respect to whether to perform a multi-filter method.

[0096] In some embodiments, where for at least two components, the syntax element is indicated, and the at least two components are handled in the same way as to whether a multi-filter method is performed. For example, X_flag may be signaled for at least two components such as Cb and Cr. That is, two components such as Cb and Cr may have the same X_flag, and they are handled in the same way as to whether a multi-filter method is performed.

[0097] In some embodiments, the syntax element is encoded using at least one codec context in arithmetic codec, or wherein the syntax element is encoded using bypass codec.

[0098] In some embodiments, after the syntax element, another syntax element related to the multi-filter method for cross-component prediction is indicated. In some embodiments, the other syntax element is indicated only when the multi-filter method is indicated to be applied. In some embodiments, the further syntax element indicates that the target filter is to be used. In some embodiments, the further syntax element indicates the method used to derive the target filter.

[0099] In some embodiments, filter selection for multiple filters is derived at both the encoder and the decoder. In some embodiments, the cost corresponding to the target filter is calculated, and the target filter selection is applied according to the cost of each filter. In some embodiments, the target filter with the minimum cost is selected.

[0100] In some embodiments, the cost of the target filter is derived as one of the following: the sum of absolute differences (SAD), the sum of squared differences (SSD), the sum of absolute transformed differences (SATD), or the mean removed SAD (MR-SAD) of the reconstructed samples of the second color component at the first set of positions and the corresponding predicted values ​​at the first set of positions.

[0101] In some embodiments, the first set of positions includes sample positions of adjacent video units. In some embodiments, the sample position is to the left of the video unit, and / or the sample position is above the video unit, the sample position is to the upper left of the video unit, the sample position is to the upper right of the video unit, or the sample position is to the lower left of the video unit. In some embodiments, the first set of sample positions depends on the availability of adjacent samples. In some embodiments, the sample set includes available samples, or if a left adjacent block is available, the sample set includes samples to the left of the video unit, or if an upper adjacent block is available, the sample set includes samples above the video unit.

[0102] In some embodiments, the neighboring samples are adjacent to the video unit or are not adjacent to the video unit. In some embodiments, herein, the neighboring samples include K rows of samples above the video unit, where K is an integer. In some embodiments, the neighboring samples include K columns of samples to the left of the video unit, where K is an integer.

[0103] In some embodiments, a target filter is used to derive a prediction value. In some embodiments, the target filter is used to generate samples of the first color component corresponding to the reconstructed samples of the second color component at a second set of positions. In some embodiments, the generated samples and the reconstructed samples are used to derive at least one linear model for the target filter. In some embodiments, at least one linear model is generated using an LMSE method or a minimum-maximum method. In some embodiments, at least one linear model is generated using a method in a multi-model-based cross-component linear model chrominance intra-frame prediction (MMLM) for video coding.

[0104] In some embodiments, at least one linear model is applied to generate predicted values ​​for samples of the second color component at positions in the first set of positions. In some embodiments, the predicted values ​​are derived as: P(x,y)=a*S(x,y)+b, and wherein (x,y) represents the position, P(x,y) represents the predicted value, S(x,y) represents the corresponding luma sample, and (a,b) represents at least one linear model.

[0105] In some embodiments, additional operations are applied to derive prediction values ​​using at least one linear model. In some embodiments, the additional operations include at least one of shifting or clipping.

[0106] In some embodiments, whether to derive or use at least one linear model depends on the codec mode of the video unit. In some embodiments, if CCLM mode is applied, one mode is derived / used to generate prediction values. In some embodiments, if MMLM mode is applied, one mode is derived / used to generate prediction values.

[0107] In some embodiments, the first set of positions and the second set of positions are the same. In some embodiments, the first set of positions and the second set of positions are different. In some embodiments, the first set of positions includes at least one of the following: two rows of samples above the video unit, or two columns of samples to the left of the video unit. In some embodiments, the second set of positions includes at least one of the following: a row of samples above the video unit, or a column of samples to the left of the video unit.

[0108] In some embodiments, at least one of the first set of positions or the second set of positions depends on a codec mode of the video unit. In some embodiments, if the codec mode is CCLM-L, at least one of the first set of positions or the second set of positions includes samples to the left of the video unit. In some embodiments, where the codec mode is CCLM-T, at least one of the first set of positions or the second set of positions includes samples above the video unit.

[0109] In some embodiments, a multi-stage filter is applied. In some embodiments, samples of the first color component are filtered by a first filter to generate a first set of filtered samples, and the filtered samples of the first set are filtered by a second filter to generate a second set of filtered samples. In some embodiments, the filtered samples of the second set are used as samples of the first color component corresponding to samples in the second color component during the CCLM process. In some embodiments, the filtered samples of the second set are further filtered by a third filter to generate a third set of filtered samples. In some embodiments, the filtered samples of the third set are used as samples of the first color component corresponding to samples in the second color component during the CCLM process. In some embodiments, the filtered samples of the third set are further filtered.

[0110] In some embodiments, if the color format is not 4:4:4, the resampling process is associated with any stage of the plurality of filters. If the color format is not 4:4:4, i.e., the resolution of the first component and the resolution of the second component are different, the resampling (e.g., downsampling) process can be associated with any stage of the filter.

[0111] In some embodiments, the samples involved in the nth filtering stage are at one or more of the following positions: P0: (scale X (n) *xC,scaleY(n) *yC), P1:(scaleX (n) *xC,scaleY (n) *yC+1), P2:(scaleX (n) *xC,scaleY (n) *yC-1), P3:(scaleX (n) *xC+1,scaleY (n) *yC), P4:(scaleX (n) *xC+1,scaleY (n) *yC+1), P5:(scaleX (n) *xC+1,scaleY (n) *yC-1), P6:(scaleX (n) *xC-1,scaleY (n) *yC), P7:(scaleX (n) *xC-1,scaleY (n) *yC+1), P8:(scaleX (n) *xC-1,scaleY (n) *yC-1), where scaleX (n) and scaleY (n) represents the scaling ratio of the sample before the nth filtering and the sample of the second color component, (xC, yC) represents the position of the sample in the second color component, and n is an integer. In some embodiments, if the sample before the nth filtering and the sample of the second color component have the same resolution, scaleX (n) and scaleY (n) is equal to 1.

[0112] In some embodiments, the target filter in one stage is fixed. In some embodiments, the target filter in one stage is adaptive. In some embodiments, the filter is selected from a group of candidate filters. In some embodiments, the filter is derived online. In some embodiments, the filter is indicated to the decoder from the encoder.

[0113] In some embodiments, two stages of filtering are applied. In some embodiments, in the first stage, the luma samples corresponding to the positions of the chroma components are filtered and downsampled. In some embodiments, in the first stage, the luma samples are filtered and downsampled using the filtering method defined in VVC, i.e., corresponding to the position (i, j) of the chroma component, when the color format is 4:2:0, the filtered luma samples are obtained by: Where S′(i,j) represents the filtered brightness and (i,j) represents the position.

[0114] In some embodiments, the filtered luminance samples are further filtered adaptively. In some embodiments, the target filter is a filter in a stage of multi-stage filtering. In one example, any method on the filter disclosed in this document can be applied to filters in any stage of multi-stage filtering.

[0115] In some embodiments, if Luma Mapping with Chroma Scaling (LMCS) is applied, the samples of the first color component to be filtered are in the original domain. In some embodiments, such as where if LMCS is applied, the samples of the first color component to be filtered are in the converted domain.

[0116] In some embodiments, if samples of the first color component are used in the CCLM process, the samples are filtered in a different manner. In some embodiments, the first filter is applied to the second color component, and the second filter is applied to the third component. In some embodiments, the derivation process of the target filter is performed separately for the Cb component and the Cr component. In some embodiments, the derivation process of the target filter is performed separately for the Cb component and the Cr component.

[0117] In some embodiments, if samples of the first color component are used in the process of CCLM, the samples of the first color component are filtered in the same manner. In some embodiments, the first filter is applied to the second color component, and the first filter is applied to the third component. In some embodiments, the derivation process of the target filter is performed for both the Cb component and the Cr component. In some embodiments, the derivation process depends on samples of one of the Cb component and the Cr component. In some embodiments, the derivation process depends on samples of both the Cb component and the Cr component. In some embodiments, the filter index of the target filter is indicated for both the Cb component and the Cr component.

[0118] In some embodiments, an indication of whether and / or how to generate sample values ​​in a first color component by applying multiple filters is indicated at one of the following: sequence level, picture group level, picture level, slice level, or tile group level. In some embodiments, an indication of whether and / or how to generate sample values ​​in a first color component by applying multiple filters is indicated in one of the following: sequence header, picture header, sequence parameter set (SPS), video parameter set (VPS), dependency parameter set (DPS), decoding capability information (DCI), picture parameter set (PPS), adaptation parameter set (APS), slice header, or tile group header. In some embodiments, an indication of whether and / or how to generate sample values ​​in a first color component by applying multiple filters is included in one of the following: prediction block (PB), transform block (TB), codec block (CB), prediction unit (PU), transform unit (TU), codec unit (CU), virtual pipeline data unit (VPDU), codec tree unit (CTU), CTU row, slice, tile, sub-picture; or a region containing more than one sample or pixel.

[0119] In some embodiments, the method further includes determining whether and / or how to generate sample values ​​in the first color component by applying multiple filters based on encoded information of the video unit, the encoded information including at least one of the following: block size, color format, single tree and / or dual tree partitioning, color component, slice type, or picture type.

[0120] According to another embodiment of the present disclosure, a non-transitory computer-readable recording medium is provided. The non-transitory computer-readable recording medium stores a bitstream of a video generated by a method performed by a device for video processing. The method includes: generating sample values ​​of a first color component of a video unit of the video corresponding to a sample of a second color component by applying multiple filters to at least one sample of the first color component; and generating a bitstream based on the generated sample values.

[0121] According to some other embodiments of the present disclosure, a method for storing a bitstream of a video is provided. The method includes: generating sample values ​​of a first color component of a video unit of the video corresponding to a sample of a second color component by applying multiple filters to at least one sample of the first color component; generating a bitstream based on the generated sample values; and storing the bitstream in a non-transitory computer-readable recording medium.

[0122] Embodiments of the present disclosure may be described according to the following clauses, features of which may be combined in any reasonable way.

[0123] Item 1. A method of video processing, comprising: for conversion between a video unit of a video and a bitstream of the video unit, generating sample values ​​of a first color component of the video unit corresponding to samples of a second color component by applying multiple filters to at least one sample of the first color component; and performing the conversion based on the generated sample values.

[0124] Clause 2. The method of clause 1, wherein the plurality of filters are applied during cross-component linear model prediction of the video unit.

[0125] Clause 3. A method according to clause 1, wherein a target filter among a plurality of filters is derived as: F(Y) = (c0×S0+c1×S1+…cn×Sn+offset)>>K, and wherein F(Y) represents the target filter, {Y} represents a set of samples of a first color component, n represents the number of taps of the target filter, ci represents the filter coefficient of filter tap i, Si represents the value of the i-th sample of the first color component involved in the representation, i is an integer, and offset and K are respectively integers.

[0126] Clause 4. A method according to clause 1, wherein at least one nonlinear term involved in a target filter among a plurality of filters is expressed as: F(Y) = (c0×S0+c1×S1+…cn×Sn+g(S0, S1,…, Sn)+offset)>>K, and wherein F(Y) represents the target filter, {Y} represents a sample set of a first color component, n represents the number of taps of the target filter, ci represents the filter coefficient of filter tap i, Si represents the value of the i-th sample of the first color component involved in the representation, and offset and K are integers respectively, and g represents a nonlinear function.

[0127] Clause 5. The method according to clause 4. wherein g(S) is one of: log(S) or S2 or S3 or Sw, or √(W&S), and wherein w is an integer.

[0128] Clause 6. The method of clause 1, wherein the filtered results after the plurality of filters are clipped.

[0129] Clause 7. A method according to clause 3 or 4, wherein the filter coefficients of the filter taps are integers, and the filter coefficients of the filter taps are positive, negative or zero.

[0130] Clause 8. A method according to clause 3 or 4, wherein the sum of ci or |ci| is a fixed number, where ci represents the filter coefficient of filter tap i.

[0131] Clause 9. The method of clause 8, wherein the sum is 2K, where K is an integer.

[0132] Clause 10. The method of clause 3 or 4, wherein the offset is equal to 2K-1, where K is an integer.

[0133] Clause 11. The method of clause 1, wherein the positions of samples of the first color component involved in a target filter of the plurality of filters depend on the positions of samples of the second color component.

[0134] Clause 12. The method of clause 1, wherein the positions of the samples of the first color component involved in a target filter of the plurality of filters depend on a color format.

[0135] Clause 13. The method of clause 12, wherein the color format is one of: 4:4:4 or 4:2:0 or 4:2:2.

[0136] Clause 14. The method of clause 1, wherein for K samples of the second color component, the target filter in the plurality of filters generates K corresponding samples of the first color component, where K is an integer.

[0137] Clause 15. The method of clause 14, wherein for a color format that is 4:2:0 or 4:2:2, the target filter comprises a downsampling or downscaling process when the first color component is Y and the second color component is Cb or Cr.

[0138] Clause 16. A method according to clause 1, wherein xL=scaleX*xC+OffX, and / or yL=scaleY*yC+OffY, and wherein xC, yC represent the position of a specific sample in the second color component, xL, yL respectively represent the position of the i-th sample in the first color component involved in a target filter among a plurality of filters corresponding to the specific sample, and scaleX and scaleY are respectively scaling factors.

[0139] Clause 17. The method of clause 16, wherein scaleX and scaleY depend on a color format.

[0140] Clause 18. A method according to clause 17, wherein for a color format of 4:2:0, scaleX and scaleY are equal to 2, or for a color format of 4:2:2, scaleX is equal to 2 and scaleY is equal to 1, or for a color format of 4:4:4, scaleX and scaleY are equal to 1.

[0141] Clause 19. The method of clause 16, wherein OffX and OffY depend on the sequence value (i) of the sample and are integers.

[0142] Clause 20. A method according to clause 16, wherein the sample in the first color component involved in the target filter corresponding to the specific sample in the second color component is in one or more of the following positions: P0: (scaleX*xC, scaleY*yC), P1: (scaleX*xC, scaleY*yC+1), P2: (scaleX*xC, scaleY*yC-1), P3: (scaleX*xC+1, scaleY*yC), P4: (scaleX*xC+1, scaleY*yC+1), P5: (scaleX*xC+1, scaleY* yC-1), P6:(scaleX*xC-1,scaleY*yC), P7:(scaleX*xC-1,scaleY*yC+1), and P8:(scaleX*xC-1,scaleY*yC-1), and wherein P0, P1, P2, P3, P4, P5, P6, P7 and P8 represent positions, xC, yC represent positions of specific samples in the second color component, xL, yL represent positions of the i-th sample in the first color component involved in the target filter among the multiple filters corresponding to the specific sample, and scaleX and scaleY are respectively scaling factors.

[0143] Clause 21. The method of clause 20, wherein the samples in the first color component involved by the target filter with 6 taps corresponding to the particular sample in the second color component are at positions P0, P1, P3, P4, P6, P7.

[0144] Clause 22. The method of clause 16, wherein the positions of samples involved in the target filter depend on the color format.

[0145] Clause 23. The method of clause 16, wherein the position of samples involved in the target filter depends on at least one of the first color component or the second color component.

[0146] Clause 24. The method of clause 16, wherein the positions of samples involved in the target filter depend on the position of the current block.

[0147] Clause 25. The method of clause 24, wherein the position of the current block is at a boundary of one of a picture, a slice, a tile, a codec tree unit (CTU), or a CTU row.

[0148] Clause 26. The method of clause 16, wherein the locations of samples involved in the target filter depend on the type of cross-component linear model (CCLM) of the video unit.

[0149] Clause 27. The method according to clause 26, wherein the type of CCLM includes at least one of the following: conventional CCLM, CCLM-L, CCLM-T, CCLM-LT, or multi-model CCLM.

[0150] Clause 28. The method of clause 16, wherein a filter coefficient of a filter tap at a position is set to 0 to remove the filter tap at the position.

[0151] Clause 29. The method of clause 16, wherein if a sample involved in a target filter is not available, the sample is removed from the filtering process.

[0152] Clause 30. The method of clause 29, wherein if samples referred to in the target filter are not available, samples are filled in from the filtering process.

[0153] Clause 31. The method of clause 30, wherein the sample is filled with the value of the sample's most recent available sample.

[0154] Clause 32. The method of clause 31, wherein the most recent available sample is involved in the target filter.

[0155] Clause 33. The method of clause 1, wherein a set of candidate filters is predefined and at least one candidate filter from the set of candidate filters is used to filter samples of the first color component.

[0156] Clause 34. The method of clause 33, wherein coefficients of at least one filter candidate are indicated from the encoder to the decoder.

[0157] Clause 35. The method of clause 34, wherein the coefficients are indicated in a predictive manner.

[0158] Clause 36. The method of clause 34, wherein the coefficients are binarized as one of: a fixed length code, a unary code, a truncated unary code, or an exponential Golomb code.

[0159] Clause 37. The method of clause 34, wherein the coefficients for Cb and Cr are different and are indicated separately.

[0160] Clause 38. The method of clause 34, wherein the coefficients for Cb and Cr are the same and are indicated together.

[0161] Clause 39. The method of clause 33, wherein coefficients of at least one filter candidate are derived online.

[0162] Clause 40. The method of clause 39, wherein the coefficients are derived by a minimum mean square error (LMSE) method using the decoded sample values.

[0163] Clause 41. The method according to clause 39, wherein the online derivation of coefficients is performed separately for Cb and Cr, or the online derivation of coefficients is shared by Cb and Cr.

[0164] Clause 42. The method of clause 33, wherein the sets of candidate filters used to encode and decode different color components are the same.

[0165] Clause 43. The method of clause 33, wherein the sets of candidate filters used to encode and decode different color components are different.

[0166] Clause 44. The method of clause 33, wherein the set of candidate filters depends on codec information of the video unit.

[0167] Clause 45. The method according to clause 44, wherein the codec information comprises at least one of the following: a codec mode, a slice type, a picture type, a width of the video unit, a height of the video unit, a color format of the video unit, or a color component of the video unit.

[0168] Clause 46. The method of clause 1, wherein filter selection information regarding the plurality of filters is indicated from the encoder to the decoder.

[0169] Clause 47. The method of clause 46, wherein the syntax element indicating the selected filter is indicated in one of: a coding unit (CU), a prediction unit (PU), a transform unit (TU), a CTU, a slice, or a picture.

[0170] Clause 48. The method of clause 46, wherein the syntax element is encoded by at least one codec context in arithmetic coding.

[0171] Clause 49. The method of clause 46, wherein the syntax element is encoded by bypass encoding.

[0172] Clause 50. The method of clause 46, wherein the syntax element is binarized into one of: a fixed length code, a unary code, a truncated unary code, or an exponential Golomb code.

[0173] Clause 51. The method of clause 46, wherein the syntax elements are encoded and decoded in a predictive manner.

[0174] Clause 52. The method of clause 46, wherein the syntax element is indicated for at least two components separately, or wherein the syntax element is indicated for at least two components.

[0175] Clause 53. The method of clause 1, further comprising: determining whether a codec mode is applied during a multi-filter method for cross-component prediction of a video unit.

[0176] Clause 54. A method according to clause 53, wherein whether the codec mode is allowed is indicated from the encoder to the decoder in one of the following: sequence parameter set (SPS), picture parameter set (PPS), picture header, slice header, CTU line, CTU, or CU.

[0177] Clause 55. The method according to clause 53, wherein whether the codec mode is allowed depends on the codec information.

[0178] Clause 56. The method of clause 55, wherein the codec mode is allowed if the specific mode is applied to the video unit.

[0179] Clause 57. A method according to clause 56, wherein the specific mode includes at least one of the following: conventional CCLM, CCLM-L, CCLM-T, CCLM-LT, or multi-model CCLM.

[0180] Clause 58. The method of Clause 55, wherein the codec mode is allowed if a width of the video unit and a height of the video unit satisfy one or more conditions.

[0181] Clause 59. A method according to Clause 58, wherein one or more conditions include at least one of the following: W*H<=T1, W*H>=T2, max(W,H)<=T3, min(W,H)>=T4, or W*H is greater than a predetermined number, and wherein W represents the width of the video unit, H represents the height of the video unit, and T1, T2, T3 and T4 are integers.

[0182] Clause 60. A method according to clause 55, wherein codec mode X is allowed for a specific kind of slice type or picture type, and / or the codec mode is allowed for a specific kind of color format, and / or the codec mode is allowed for a specific color component, and / or the codec mode is allowed for a specific profile or level of the standard, and / or the codec mode is allowed if at least K neighboring samples are available, where K is an integer.

[0183] Clause 61. A method according to clause 53, wherein whether the syntax element is indicated depends on whether codec mode X is applied.

[0184] Clause 62. The method of clause 61, wherein the syntax element is indicated if the codec mode is allowed.

[0185] Clause 63. The method of clause 61, wherein if the codec mode is not allowed, the syntax element is set to a default value.

[0186] Clause 64. The method of clause 61, wherein the syntax element is indicated for one of the following: a picture, a slice, a CTU, a CU, a PU, or a TU.

[0187] Clause 65. The method according to clause 61, wherein for at least two components the syntax elements are indicated separately and the at least two components are handled differently with respect to whether a multi-filter method is performed.

[0188] Clause 66. The method according to clause 61, wherein for at least two components the syntax element is indicated, and the at least two components are handled in the same way with respect to whether a multi-filter method is performed.

[0189] Clause 67. The method of clause 61, wherein the syntax element is encoded using at least one codec context in arithmetic coding, or wherein the syntax element is encoded using bypass coding.

[0190] Clause 68. The method of clause 61, wherein following the syntax element another syntax element related to a multi-filter method for cross-component prediction is indicated.

[0191] Clause 69. A method according to clause 68, wherein the further syntax element is indicated only when a multi-filter method is indicated to be applied.

[0192] Clause 70. The method of clause 68, wherein another syntax element indicates a target filter to be used.

[0193] Clause 71. The method of clause 68, wherein the further syntax element indicates a method to derive the target filter.

[0194] Clause 72. The method of clause 1, wherein filter selection regarding the plurality of filters is derived at both the encoder and the decoder.

[0195] Clause 73. The method of clause 72, wherein costs corresponding to target filters are calculated and target filter selection is applied based on the costs of each filter.

[0196] Clause 74. The method of clause 73, wherein the target filter having the smallest cost is selected.

[0197] Clause 75. A method according to clause 72, wherein the cost of the target filter is derived as one of the following: the sum of absolute differences (SAD), the sum of squared differences (SSD), the sum of absolute transformed differences (SATD), or the mean removed SAD (MR-SAD) of the reconstructed samples of the second color component at the first set of positions and the corresponding predicted values ​​at the first set of positions.

[0198] Clause 76. The method of clause 75, wherein the first set of positions comprises sample positions of adjacent video units.

[0199] Clause 77. A method according to clause 76, wherein the sample position is on the left side of the video unit, and / or the sample position is above the video unit, the sample position is on the upper left of the video unit, the sample position is on the upper right of the video unit, or the sample position is on the lower left of the video unit.

[0200] Clause 78. The method of clause 76, wherein the first set of sample positions depends on the availability of neighboring samples.

[0201] Clause 79. The method of clause 78, wherein the sample set comprises available samples, or the sample set comprises samples to the left of the video unit if a left neighboring block is available, or the sample set comprises samples above the video unit if an above neighboring block is available.

[0202] Clause 80. The method of clause 78, wherein the neighboring samples are adjacent to the video unit or are not adjacent to the video unit.

[0203] Clause 81. The method of clause 80, wherein the neighboring samples include K rows of samples above the video unit, where K is an integer.

[0204] Clause 82. The method of clause 80, wherein the neighboring samples include K columns of samples to the left of the video unit, where K is an integer.

[0205] Clause 83. The method of clause 75, wherein the prediction value is derived using a target filter.

[0206] Clause 84. The method of clause 83, wherein the target filter is used to generate samples of the first color component corresponding to reconstructed samples of the second color component at the second set of positions.

[0207] Clause 85. The method of clause 84, wherein the generated samples and the reconstructed samples are used to derive at least one linear model for a target filter.

[0208] Clause 86. The method of clause 85, wherein at least one linear model is generated using a LMSE method or a min-max method.

[0209] Clause 87. The method of clause 85, wherein the at least one linear model is generated using a method in multi-model based cross-component linear model chroma intra prediction (MMLM) for video codec.

[0210] Clause 88. The method of clause 85, wherein at least one linear model is applied to generate predicted values ​​for samples of the second color component at locations in the first set of locations.

[0211] Clause 89. A method according to clause 88, wherein the prediction value is derived as: P(x,y) = a*S(x,y) + b, and wherein (x,y) represents the position, P(x,y) represents the prediction value, S(x,y) represents the corresponding brightness sample, and (a,b) represents at least one linear model.

[0212] Clause 90. The method of clause 88, wherein additional operations are applied to derive prediction values ​​using at least one linear model.

[0213] Clause 91. The method of clause 90, wherein the additional operation comprises at least one of shifting or clipping.

[0214] Clause 92. The method of clause 85, wherein whether to derive or use at least one linear model depends on a coding mode of the video unit.

[0215] Clause 93. The method of clause 92, wherein if the CCLM model is applied, a model is derived / used to generate the predicted value.

[0216] Clause 94. The method of clause 92, wherein if the MMLM model is applied, a model is derived / used to generate the predicted value.

[0217] Clause 95. The method of clause 75, wherein the first set of positions and the second set of positions are the same.

[0218] Clause 96. The method of clause 75, wherein the first set of positions and the second set of positions are different.

[0219] Clause 97. The method of clause 96, wherein the first set of positions includes at least one of: two rows of samples above the video unit, or two columns of samples to the left of the video unit.

[0220] Clause 98. The method of clause 96, wherein the second set of positions includes at least one of: a row of samples above the video unit, or a column of samples to the left of the video unit.

[0221] Clause 99. The method of clause 75, wherein at least one of the first set of positions or the second set of positions depends on a codec mode of the video unit.

[0222] Clause 100. The method of clause 99, wherein if the codec mode is CCLM-L, at least one of the first set of positions or the second set of positions includes samples to the left of the video unit.

[0223] Clause 101. The method of clause 99, wherein if the codec mode is CCLM-T, at least one of the first set of positions or the second set of positions includes samples above the video unit.

[0224] Clause 102. The method of clause 1, wherein a multi-stage filter is applied.

[0225] Clause 103. The method of clause 102, wherein the samples of the first color component are filtered by a first filter to generate a first set of filtered samples, and the first set of filtered samples are filtered by a second filter to generate a second set of filtered samples.

[0226] Clause 104. The method of clause 103, wherein the filtered samples of the second set are used in the process of CCLM as samples of the first color component corresponding to samples in the second color component.

[0227] Clause 105. The method of clause 103, wherein the second set of filtered samples are further filtered by a third filter to generate a third set of filtered samples.

[0228] Clause 106. The method of clause 105, wherein the filtered samples of the third set are used in the process of CCLM as samples of the first color component corresponding to samples in the second color component.

[0229] Clause 107. The method of clause 105, wherein the third set of filtered samples are further filtered.

[0230] Clause 108. The method of clause 102, wherein if the color format is not 4:4:4, a resampling process is associated with any stage of the plurality of filters.

[0231] Clause 109. A method according to clause 102, wherein the samples involved in the nth filtering stage are at one or more of the following positions: P0: (scaleX(n)*xC, scaleY(n)*yC), P1: (scaleX(n)*xC, scaleY(n)*yC+1), P2: (scaleX(n)*xC, scaleY(n)*yC-1), P3: (scaleX(n)*xC+1, scaleY(n)*yC), P4: (scaleX(n)*xC+1, scaleY(n)*yC+1), P5 :(scaleX(n)*xC+1,scaleY(n)*yC-1), P6:(scaleX(n)*xC-1,scaleY(n)*yC), P7:(scaleX(n)*xC-1,scaleY(n)*yC+1), P8:(scaleX(n)*xC-1,scaleY(n)*yC-1), where scaleX(n) and scaleY(n) represent the scaling ratio of the samples before the nth filtering and the samples of the second color component, (xC, yC) represents the position of the sample in the second color component, and n is an integer.

[0232] Clause 110. The method of clause 109, wherein scaleX(n) and scaleY(n) are equal to 1 if the samples before the nth filtering and the samples of the second color component have the same resolution.

[0233] Clause 111. The method of clause 102, wherein the target filter in one stage is fixed.

[0234] Clause 112. The method of clause 102, wherein the target filter in one stage is adaptive.

[0235] Clause 113. The method of clause 112, wherein the filter is selected from a set of candidate filters, or wherein the filter is derived online, or wherein the filter is indicated from an encoder to a decoder.

[0236] Clause 114. The method of clause 102, wherein two stages of filtering are applied.

[0237] Clause 115. The method of clause 114, wherein in the first stage, luma samples corresponding to positions of chroma components are filtered and downsampled.

[0238] Clause 116. A method according to clause 115, wherein if the color format is 4:2:0, the filtered brightness sample is obtained by: S'(i,j) = [(S(2i-1,2j-1)+2·S(2i-1,2j-1)+S(2i+1,2j-1)+@〖S(2i-1,2j)+2·S〗_(2i,2j)+S(2i+1,2j)+4)]>>3 wherein S'(i,j) represents the filtered brightness and (i,j) represents the position. wherein S'(i,j) represents the filtered brightness and (i,j) represents the position.

[0239] Clause 117. The method of clause 115, wherein the filtered luma samples are further filtered adaptively.

[0240] Clause 118. The method of any one of clauses 1-117, wherein the target filter is a filter in a stage of multi-stage filtering.

[0241] Clause 119. A method according to clause 1, wherein if a luminance mapping with chroma scaling (LMCS) is applied, the samples of the first color component to be filtered are in the original domain, or wherein if LMCS is applied, the samples of the first color component to be filtered are in the converted domain.

[0242] Clause 120. The method of clause 1, wherein if samples of the first color component are used in a CCLM process, the samples are filtered in a different manner.

[0243] Clause 121. The method of clause 120, wherein the first filter is applied on the second color component and the second filter is applied on the third component.

[0244] Clause 122. The method of clause 120, wherein the derivation process of the target filter is performed separately for the Cb component and the Cr component.

[0245] Clause 123. The method of clause 120, wherein the filter index of the target filter is indicated separately for the Cb component and the Cr component.

[0246] Clause 124. The method of clause 1, wherein the samples of the first color component are filtered in the same manner if the samples of the first color component are used in the process of CCLM.

[0247] Clause 125. The method of clause 124, wherein the first filter is applied to the second color component and the first filter is applied to the third component.

[0248] Clause 126. The method of clause 124, wherein the derivation process of the target filter is performed for both the Cb component and the Cr component.

[0249] Clause 127. The method of clause 126, wherein the derivation process depends on samples of one of the Cb component and the Cr component, or wherein the derivation process depends on samples of both the Cb component and the Cr component.

[0250] Clause 128. The method of clause 124, wherein a filter index of a target filter is indicated for both a Cb component and a Cr component.

[0251] Clause 129. A method according to any of clauses 1-128, wherein an indication of whether and / or how sample values ​​are generated in a first color component by applying multiple filters is indicated at one of: a sequence level, a picture group level, a picture level, a slice level, or a tile group level.

[0252] Clause 130. A method according to any of clauses 1-128, wherein an indication of whether and / or how sample values ​​are generated in a first color component by applying multiple filters is indicated in one of: a sequence header, a picture header, a sequence parameter set (SPS), a video parameter set (VPS), a dependency parameter set (DPS), decoding capability information (DCI), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, or a tile group header.

[0253] Clause 131. A method according to any of clauses 1-128, wherein an indication of whether and / or how sample values ​​are generated in a first color component by applying multiple filters is included in one of the following: a prediction block (PB), a transform block (TB), a codec block (CB), a prediction unit (PU), a transform unit (TU), a codec unit (CU), a virtual pipeline data unit (VPDU), a codec tree unit (CTU), a CTU row, a slice, a tile, a sub-picture; or a region containing more than one sample or pixel.

[0254] Clause 132. The method according to any one of clauses 1-128 further includes: determining whether and / or how to generate sample values ​​in a first color component by applying multiple filters based on encoded and decoded information of the video unit, the encoded and decoded information including at least one of the following: block size, color format, single tree and / or dual tree partitioning, color component, slice type, or picture type.

[0255] Clause 133. The method of any of clauses 1-132, wherein converting comprises encoding the video unit into a bitstream.

[0256] Clause 134. The method of any of clauses 1-132, wherein converting comprises decoding the video unit from a bitstream.

[0257] Clause 135. An apparatus for video processing, comprising a processor and a non-transitory memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform a method according to any of clauses 1-134.

[0258] Clause 136. A non-transitory computer-readable storage medium storing instructions that cause a processor to perform a method according to any of clauses 1-134.

[0259] Item 137. A non-transitory computer-readable storage medium storing a bitstream of a video generated by a method performed by a device for video processing, the method comprising: generating sample values ​​of a first color component of a video unit of the video corresponding to samples of a second color component by applying multiple filters to at least one sample of the first color component; and generating a bitstream based on the generated sample values.

[0260] Item 138. A method for storing a bitstream of a video, comprising: generating sample values ​​of a first color component of a video unit of the video corresponding to samples of a second color component by applying multiple filters to at least one sample of the first color component; and generating a bitstream based on the generated sample values; and storing the bitstream in a non-transitory computer-readable recording medium. Example Device

[0261] Fig.11 A block diagram of a computing device 1100 in which various embodiments of the present disclosure may be implemented is shown. The computing device 1100 may be implemented as a source device 110 (or video encoder 114 or 200) or a destination device 120 (or video decoder 124 or 300), or may be included in a source device 110 (or video encoder 114 or 200) or a destination device 120 (or video decoder 124 or 300).

[0262] It should be understood that Fig.11 The computing device 1100 shown in FIG. 1 is for illustrative purposes only and is not intended to in any way imply any limitation on the functionality and scope of the embodiments of the present disclosure.

[0263] like Fig.11 As shown, computing device 1100 includes a general computing device 1100. Computing device 1100 may include at least one or more processors or processing units 1110, memory 1120, storage unit 1130, one or more communication units 1140, one or more input devices 1150, and one or more output devices 1160.

[0264] In some embodiments, the computing device 1100 can be implemented as any user terminal or server terminal with computing power. The server terminal can be a server provided by a service provider, a large computing device, etc. The user terminal can be, for example, any type of mobile terminal, fixed terminal or portable terminal, including a mobile phone, a station, a unit, a device, a multimedia computer, a multimedia tablet computer, an Internet node, a communicator, a desktop computer, a laptop computer, a notebook computer, a netbook computer, a personal communication system (PCS) device, a personal navigation device, a personal digital assistant (PDA), an audio / video player, a digital camera / camcorder, a positioning device, a television receiver, a radio broadcast receiver, an electronic book device, a gaming device, or any combination thereof, and includes accessories and peripherals of these devices, or any combination thereof. It is conceivable that the computing device 1100 can support any type of interface to the user (such as a "wearable" circuit device, etc.).

[0265] The processing unit 1110 may be a physical processor or a virtual processor and may implement various processes based on a program stored in the memory 1120. In a multi-processor system, multiple processing units execute computer executable instructions in parallel to improve the parallel processing capability of the computing device 1100. The processing unit 1110 may also be referred to as a central processing unit (CPU), a microprocessor, a controller, or a microcontroller.

[0266] The computing device 1100 typically includes various computer storage media. Such media can be any media accessible by the computing device 1100, including but not limited to volatile media and non-volatile media, or removable media and non-removable media. The memory 1120 can be a volatile memory (e.g., a register, a cache, a random access memory (RAM)), a non-volatile memory (such as a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM) or flash memory) or any combination thereof. The storage unit 1130 can be any removable or non-removable medium, and can include machine-readable media, such as a memory, a flash drive, a disk, or other media that can be used to store information and / or data and can be accessed in the computing device 1100.

[0267] The computing device 1100 may also include additional removable / non-removable storage media, volatile / non-volatile storage media. Fig.11 Although not shown in the figure, a magnetic disk drive for reading from and / or writing to a removable nonvolatile magnetic disk and an optical disk drive for reading from and / or writing to a removable nonvolatile optical disk may be provided. In this case, each drive may be connected to the bus (not shown) via one or more data medium interfaces.

[0268] The communication unit 1140 communicates with another computing device via a communication medium. In addition, the functionality of the components in the computing device 1100 can be implemented by a single computing cluster or multiple computing machines that can communicate via a communication connection. Therefore, the computing device 1100 can operate in a networked environment using logical connections to one or more other servers, networked personal computers (PCs), or other general network nodes.

[0269] The input device 1150 may be one or more of various input devices, such as a mouse, keyboard, trackball, voice input device, etc. The output device 1160 may be one or more of various output devices, such as a display, a speaker, a printer, etc. With the help of the communication unit 1140, the computing device 1100 may also communicate with one or more external devices (not shown), such as storage devices and display devices, and the computing device 1100 may also communicate with one or more devices that enable a user to interact with the computing device 1100, or any device that enables the computing device 1100 to communicate with one or more other computing devices (e.g., a network card, a modem, etc.), if necessary. Such communication may be performed via an input / output (I / O) interface (not shown).

[0270] In some embodiments, some or all components of the computing device 1100 may also be arranged in a cloud computing architecture rather than being integrated in a single device. In a cloud computing architecture, components may be provided remotely and work together to implement the functions described in the present disclosure. In some embodiments, cloud computing provides computing, software, data access and storage services, which will not require the end user to know the physical location or configuration of the system or hardware that provides these services. In various embodiments, cloud computing provides services via a wide area network (e.g., the Internet) using a suitable protocol. For example, a cloud computing provider provides applications via a wide area network, which can be accessed through a web browser or any other computing component. The software or components of the cloud computing architecture and the corresponding data may be stored on a remote server. The computing resources in a cloud computing environment may be merged or distributed at the location of a remote data center. Cloud computing infrastructures may provide services through a shared data center, although they appear as a single access point for users. Therefore, cloud computing architectures may be used to provide components and functions described herein from a service provider at a remote location. Alternatively, they may be provided by a conventional server, or installed directly or otherwise on a client device.

[0271] In an embodiment of the present disclosure, the computing device 1100 may be used to implement video encoding / decoding. The memory 1120 may include one or more video encoding / decoding modules 1125 having one or more program instructions. These modules can be accessed and executed by the processing unit 1110 to perform the functions of the various embodiments described herein.

[0272] In an example embodiment performing video encoding, input device 1150 may receive video data as input 1170 to be encoded. The video data may be processed by, for example, video codec module 1125 to generate an encoded bitstream. The encoded bitstream may be provided as output 1180 via output device 1160.

[0273] In an example embodiment performing video decoding, input device 1150 may receive an encoded bitstream as input 1170. The encoded bitstream may be processed by, for example, video codec module 1125 to generate decoded video data. The decoded video data may be provided as output 1180 via output device 1160.

[0274] Although the present disclosure has been specifically shown and described with reference to the preferred embodiments of the present disclosure, it will be understood by those skilled in the art that various changes can be made in form and detail without departing from the spirit and scope of the present application as defined by the appended claims. These changes are intended to be encompassed by the scope of the present application. Therefore, the foregoing description of the embodiments of the present application is not intended to be limiting.

Claims

1. A video processing method, comprising: For conversion between a video unit of a video and a bitstream of the video unit, generating sample values ​​of a first color component of the video unit corresponding to samples of a second color component by applying a plurality of filters to at least one sample of the first color component; and The conversion is performed based on the generated sample values.

2. The method of claim 1, wherein the plurality of filters are applied in a process of cross-component linear model prediction of the video unit.

3. The method according to claim 1, wherein the target filter among the plurality of filters is derived as: F(Y)=(c0×S0+c1×S1+…c n ×S n + offset) >> K, and Wherein F(Y) represents the target filter, {Y} represents the sample set of the first color component, n represents the number of taps of the target filter, c i represents the filter coefficient of filter tap i, S i represents the value of the i-th sample of the first color component involved in the representation, i is an integer, and offset and K are respectively integers.

4. The method according to claim 1, wherein at least one nonlinear term involved in a target filter among the plurality of filters is expressed as: F(Y)=(c0×S0+c1×S1+…c n ×S n +g(S0,S1,…,S n )+offset)>>K, and Wherein F(Y) represents the target filter, {Y} represents the sample set of the first color component, n represents the number of taps of the target filter, c i represents the filter coefficient of filter tap i, S i represents the value of the i-th sample of the first color component involved in the representation, and offset and K are respectively integers, and g represents a nonlinear function.

5. The method according to claim 4. wherein g(S) is one of the following: log(S) or S 2 or S 3 or S w ,or And where w is an integer. The method of claim 1 , wherein filtered results after the plurality of filters are clipped.

7. The method according to claim 3 or 4, wherein the filter coefficients of the filter taps are integers, and The filter coefficients of the filter taps are positive, negative or zero.

8. The method according to claim 3 or 4, wherein c i or |c i The sum of | is a fixed number, where c i represents the filter coefficient for filter tap i.

9. The method according to claim 8, wherein the sum is 2 K , where K is an integer.

10. The method according to claim 3 or 4, wherein the offset is equal to 2 K-1 , where K is an integer.

11. The method of claim 1, wherein positions of samples of the first color component involved in a target filter of the plurality of filters depend on positions of the samples of the second color component. 12 . The method of claim 1 , wherein positions of samples of the first color component involved in a target filter of the plurality of filters depend on a color format.

13. The method of claim 12, wherein the color format is one of: 4:4:4 or 4:2:0 or 4:2:

2.

14. The method of claim 1, wherein for K samples of the second color component, a target filter in the plurality of filters generates K corresponding samples of the first color component, where K is an integer.

15. The method of claim 14, wherein for a color format of 4:2:0 or 4:2:2, the target filter comprises a downsampling or downscaling process when the first color component is Y and the second color component is Cb or Cr.

16. The method of claim 1, wherein xL=scaleX*xC+OffX, and / or yL = scaleY * yC + OffY, and Wherein xC, yC represent the position of a specific sample in the second color component, xL, yL respectively represent the position of the i-th sample in the first color component involved in the target filter in the multiple filters corresponding to the specific sample, and scaleX and scaleY are respectively scaling factors. The method of claim 16 , wherein scaleX and scaleY depend on a color format.

18. The method of claim 17, wherein for a color format of 4:2:0, scaleX and scaleY are equal to 2, or For a 4:2:2 color format, scaleX equals 2 and scaleY equals 1, or For a 4:4:4 color format, scaleX and scaleY are equal to 1.

19. The method of claim 16, wherein OffX and OffY depend on the sequence value (i) of the sample and are integers.

20. The method of claim 16, wherein the sample in the first color component involved by the target filter corresponding to the particular sample in the second color component is in one or more of the following positions: P0: (scaleX*xC, scaleY*yC), P1: (scaleX*xC, scaleY*yC+1), P2: (scaleX*xC, scaleY*yC-1), P3: (scaleX*xC+1, scaleY*yC), P4:(scaleX*xC+1,scaleY*yC+1), P5:(scaleX*xC+1,scaleY*yC-1), P6: (scaleX*xC-1, scaleY*yC), P7: (scaleX*xC-1, scaleY*yC+1), and P8: (scaleX*xC-1, scaleY*yC-1), and Wherein P0, P1, P2, P3, P4, P5, P6, P7 and P8 represent positions, xC, yC represent positions of specific samples in the second color component, xL, yL represent positions of the i-th sample in the first color component involved in the target filter among the multiple filters corresponding to the specific sample, and scaleX and scaleY are respectively scaling factors.

21. The method of claim 20, wherein the samples in the first color component involved in the target filter with 6 taps corresponding to the specific samples in the second color component are at the positions P0, P1, P3, P4, P6, P7.

22. The method of claim 16, wherein the locations of samples involved in the target filter depend on a color format.

23. The method of claim 16, wherein the positions of samples involved in the target filter depend on at least one of the first color component or the second color component.

24. The method of claim 16, wherein the positions of samples involved in the target filter depend on the position of the current block.

25. The method of claim 24, wherein the position of the current block is at a boundary of one of a picture, a slice, a tile, a codec tree unit (CTU), or a CTU row.

26. The method of claim 16, wherein the locations of samples involved in the target filter depend on a type of a cross-component linear model (CCLM) of the video unit.

27. The method according to claim 26, wherein the type of the CCLM comprises at least one of the following: Conventional CCLM, CCLM-L, CCLM-T, CCLM-LT, or Multi-model CCLM.

28. The method of claim 16, wherein a filter coefficient of a filter tap at a position is set to 0 to remove the filter tap at the position.

29. The method of claim 16, wherein if a sample involved in the target filter is not available, the sample is removed from the filtering process.

30. The method of claim 29, wherein if the samples referred to in the target filter are not available, the samples are filled in from the filtering process.

31. The method of claim 30, wherein the sample is filled with the value of the nearest available sample of the sample.

32. The method of claim 31, wherein the most recent available sample is involved in the target filter.

33. The method of claim 1, wherein a set of candidate filters is predefined and at least one candidate filter from the set of candidate filters is used to filter samples of the first color component.

34. The method of claim 33, wherein coefficients of at least one filter candidate are indicated from an encoder to a decoder.

35. The method of claim 34, wherein the coefficients are indicated in a predictive manner.

36. The method of claim 34, wherein the coefficients are binarized as one of: Solid long code, Unary code, truncate the unary code, or Exponential Columbus code.

37. The method of claim 34, wherein the coefficients for Cb and Cr are different and are indicated separately.

38. The method of claim 34, wherein the coefficients for Cb and Cr are the same and are indicated together.

39. The method of claim 33, wherein coefficients of at least one filter candidate are derived online.

40. The method of claim 39, wherein the coefficients are derived by a minimum mean square error (LMSE) method using decoded sample values.

41. The method of claim 39, wherein the online derivation of the coefficients is performed separately for Cb and Cr, or The on-line derivation of the coefficients is shared by Cb and Cr.

42. The method of claim 33, wherein the candidate filter sets used to encode and decode different color components are the same.

43. The method of claim 33, wherein the candidate filter sets used to encode and decode different color components are different.

44. The method of claim 33, wherein the candidate filter set depends on codec information of the video unit.

45. The method according to claim 44, wherein the codec information comprises at least one of the following: Codec mode, Strip type, Image type, the width of the video unit, The height of the video unit, the color format of the video unit, or The color components of the video unit.

46. ​​The method of claim 1, wherein filter selection information regarding the plurality of filters is indicated from an encoder to a decoder.

47. The method of claim 46, wherein the syntax element indicating the selected filter is indicated in one of: Codec Unit (CU), Prediction Unit (PU), Transformation Unit (TU), CTU, Strip, or picture.

48. The method of claim 46, wherein the syntax element is coded by at least one codec context in arithmetic coding.

49. The method of claim 46, wherein the syntax elements are encoded by bypass encoding.

50. The method of claim 46, wherein the syntax element is binarized into one of: Solid long code, Unary code, truncate the unary code, or Exponential Columbus code.

51. The method of claim 46, wherein the syntax elements are encoded in a predictive manner.

52. The method of claim 46, wherein the syntax element is indicated separately for at least two components, or Wherein the syntax element is indicated for at least two components.

53. The method of claim 1, further comprising: A determination is made as to whether a codec mode is applied during a multi-filter method for cross-component prediction for the video unit.

54. The method of claim 53, wherein whether the codec mode is allowed is indicated from the encoder to the decoder in one of the following: Sequence Parameter Set (SPS), Picture Parameter Set (PPS), Picture header, Strip head, CTU line, CTU, or CU.

55. The method of claim 53, wherein whether the codec mode is allowed depends on codec information.

56. The method of claim 55, wherein the codec mode is allowed if a specific mode is applied to the video unit.

57. The method of claim 56, wherein the specific mode comprises at least one of the following: Conventional CCLM, CCLM-L, CCLM-T, CCLM-LT, or Multi-model CCLM.

58. The method of claim 55, wherein the codec mode is allowed if a width of the video unit and a height of the video unit satisfy one or more conditions.

59. The method of claim 58, wherein the one or more conditions include at least one of the following: W*H<=T1, W*H>=T2, max(W,H)<=T3, min(W,H)>=T4, or W*H is greater than a predetermined number, and Wherein W represents the width of the video unit, H represents the height of the video unit, and T1, T2, T3 and T4 are integers.

60. The method of claim 55, wherein the codec mode X is allowed for a specific kind of slice type or picture type, and / or The codec mode is allowed for a particular kind of color format, and / or For a particular color component, the codec mode is allowed, and / or The codec modes that are allowed for a particular profile or level of the standard, and / or The codec mode is allowed if at least K neighboring samples are available, where K is an integer.

61. The method of claim 53, wherein whether a syntax element is indicated depends on whether the codec mode X is applied.

62. The method of claim 61, wherein the syntax element is indicated if the codec mode is allowed.

63. The method of claim 61, wherein if the codec mode is not allowed, the syntax element is set to a default value.

64. The method of claim 61, wherein the syntax element is indicated for one of: a picture, a slice, a CTU, a CU, a PU, or a TU.

65. The method of claim 61, wherein the syntax element is indicated separately for at least two components, and the at least two components are handled differently with respect to whether to perform the multi-filter method.

66. The method of claim 61, wherein the syntax element is indicated for at least two components, and the at least two components are handled in the same way with respect to whether the multi-filter method is performed.

67. The method of claim 61, wherein the syntax element is coded using at least one codec context in arithmetic coding, or The syntax elements are encoded and decoded using bypass coding.

68. The method of claim 61, wherein following the syntax element another syntax element related to the multi-filter method for the cross-component prediction is indicated.

69. The method of claim 68, wherein the further syntax element is indicated only if the multi-filter method is indicated to be applied.

70. The method of claim 68, wherein the another syntax element indicates a target filter to be used.

71. The method of claim 68, wherein the another syntax element indicates a method used to derive a target filter.

72. The method of claim 1, wherein filter selection with respect to the plurality of filters is derived at both an encoder and a decoder.

73. The method of claim 72, wherein costs corresponding to target filters are calculated and the target filter selection is applied based on the costs of each filter.

74. A method according to claim 73, wherein the target filter with the smallest cost is selected.

75. The method of claim 72, wherein the cost of the target filter is derived as one of the following: reconstructed samples of the second color component at a first set of positions and corresponding predicted values ​​at the first set of positions: Sum of Absolute Differences (SAD), The sum of squared differences (SSD), The sum of absolute transformation differences (SATD), or Mean removed SAD (MR-SAD).

76. The method of claim 75, wherein the first set of positions comprises sample positions adjacent to the video unit.

77. The method of claim 76, wherein the sample position is to the left of the video unit, and / or The sample position is above the video unit, The sample position is at the upper left of the video unit, The sample position is at the upper right of the video unit, or The sample position is at the lower left of the video unit.

78. The method of claim 76, wherein the first set of sample locations is dependent on the availability of neighboring samples.

79. The method of claim 78, wherein the sample set comprises available samples, or If a left neighboring block is available, the sample set includes samples to the left of the video unit, or If an above neighboring block is available, the sample set includes samples above the video unit.

80. The method of claim 78, wherein the neighboring samples are adjacent to the video unit or are not adjacent to the video unit.

81. The method of claim 80, wherein the neighboring samples comprise K rows of samples above the video unit, where K is an integer.

82. The method of claim 80, wherein the neighboring samples comprise K columns of samples to the left of the video unit, where K is an integer.

83. The method of claim 75, wherein the prediction value is derived using a target filter.

84. The method of claim 83, wherein the target filter is used to generate samples of the first color component at a second set of positions that correspond to reconstructed samples of the second color component.

85. The method of claim 84, wherein the generated samples and the reconstructed samples are used to derive at least one linear model for the target filter.

86. The method of claim 85, wherein the at least one linear model is generated using a LMSE method or a min-max method.

87. The method of claim 85, wherein the at least one linear model is generated using a method in Multi-Model-Based Cross-Component Linear Model Chroma Intra Prediction (MMLM) for video codec.

88. The method of claim 85, wherein the at least one linear model is applied to generate predicted values ​​for samples of the second color component at locations in the first set of locations.

89. The method of claim 88, wherein the predicted value is derived as: P(x,y)=a*S(x,y)+b, and Wherein (x, y) represents the position, P(x, y) represents the predicted value, S(x, y) represents the corresponding brightness sample, and (a, b) represents the at least one linear model.

90. The method of claim 88, wherein additional operations are applied to derive the predicted values ​​using the at least one linear model.

91. The method of claim 90, wherein the additional operation comprises at least one of shifting or clipping.

92. The method of claim 85, wherein whether to derive or use the at least one linear model depends on a coding mode of the video unit.

93. A method according to claim 92, wherein if the CCLM model is applied, a model is derived / used to generate predicted values.

94. The method of claim 92, wherein if the MMLM model is applied, a model is derived / used to generate the predicted value.

95. The method of claim 75, wherein the first set of positions and the second set of positions are the same.

96. The method of claim 75, wherein the first set of positions and the second set of positions are different.

97. The method of claim 96, wherein the first set of positions includes at least one of: two rows of samples above the video unit, or two columns of samples to the left of the video unit.

98. The method of claim 96, wherein the second set of positions includes at least one of: a row of samples above the video unit, or a column of samples to the left of the video unit.

99. The method of claim 75, wherein at least one of the first set of positions or the second set of positions depends on a codec mode of the video unit.

100. The method of claim 99, wherein if the codec mode is CCLM-L, at least one of the first set of positions or the second set of positions includes samples to the left of the video unit.

101. The method of claim 99, wherein if the codec mode is CCLM-T, at least one of the first set of positions or the second set of positions includes samples above the video unit.

102. The method of claim 1, wherein a multi-stage filter is applied.

103. The method of claim 102, wherein samples of the first color component are filtered by a first filter to generate a first set of filtered samples, and the first set of filtered samples are filtered by a second filter to generate a second set of filtered samples.

104. The method of claim 103, wherein the second set of filtered samples are used in a CCLM process as the samples of the first color component corresponding to samples in the second color component.

105. The method of claim 103, wherein the second set of filtered samples are further filtered by a third filter to generate a third set of filtered samples.

106. The method of claim 105, wherein the third set of filtered samples are used in a CCLM process as the samples of the first color component corresponding to samples in the second color component.

107. The method of claim 105, wherein the third set of filtered samples are further filtered.

108. The method of claim 102, wherein a resampling process is associated with any stage of the plurality of filters if the color format is not 4:4:

4.

109. The method of claim 102, wherein the samples involved in the nth filtering stage are located in one or more of the following positions: P0:(scaleX (n) *xC,scaleY (n) *yC), P1:(scaleX (n) *xC,scaleY (n) *yC+1), P2:(scaleX (n) *xC,scaleY (n) *yC-1), P3:(scaleX (n) *xC+1,scaleY (n) *yC), P4:(scaleX (n) *xC+1,scaleY (n) *yC+1), P5:(scaleX (n) *xC+1,scaleY (n) *yC-1), P6:(scaleX (n) *xC-1,scaleY (n) *yC), P7:(scaleX (n) *xC-1,scaleY (n) *yC+1), P8:(scaleX (n) *xC-1,scaleY (n) *yC-1), where scaleX (n) and scaleY (n) represents the scaling ratio between the sample before the nth filtering and the sample of the second color component, (xC, yC) represents the position of the sample in the second color component, and n is an integer.

110. The method of claim 109, wherein if the samples before the n-th filtering and the samples of the second color component have the same resolution, scaleX (n) and scaleY (n) is equal to 1.

111. The method of claim 102, wherein the target filter in one stage is fixed.

112. The method of claim 102, wherein the target filter in one stage is adaptive.

113. The method of claim 112, wherein the filter is selected from a set of candidate filters, or where the filter is derived online, or Wherein the filters are indicated from the encoder to the decoder.

114. The method of claim 102, wherein two stages of filtering are applied.

115. The method of claim 114, wherein in a first stage, luma samples corresponding to positions of chroma components are filtered and downsampled.

116. The method of claim 115, wherein if the color format is 4:2:0, the filtered luma samples are obtained by: in, S′(i,j) represents the filtered brightness, and (i,j) represents the position.

117. The method of claim 115, wherein the filtered luma samples are further filtered adaptively.

118. A method according to any one of claims 1-117, wherein the target filter is a filter in a stage of multi-stage filtering.

119. The method of claim 1, wherein if Luma Mapping with Chroma Scaling (LMCS) is applied, the samples of the first color component to be filtered are in the original domain, or Wherein if LMCS is applied, the samples of the first color component to be filtered are in the converted domain.

120. The method of claim 1, wherein samples of the first color component are filtered differently if the samples are used in the CCLM process.

121. A method according to claim 120, wherein a first filter is applied to the second color component and a second filter is applied to the third component.

122. The method according to claim 120, wherein the derivation process of the target filter is performed separately for the Cb component and the Cr component.

123. The method according to claim 120, wherein the filter index of the target filter is indicated separately for the Cb component and the Cr component.

124. The method of claim 1, wherein the samples of the first color component are filtered in the same manner as if the samples of the first color component were used in a CCLM process.

125. The method of claim 124, wherein a first filter is applied to a second color component and the first filter is applied to a third component.

126. The method of claim 124, wherein the derivation process of the target filter is performed for both the Cb component and the Cr component.

127. The method of claim 126, wherein the derivation process depends on samples of one of the Cb component and the Cr component, or The derivation process depends on samples of both the Cb component and the Cr component.

128. The method of claim 124, wherein a filter index of the target filter is indicated for both a Cb component and a Cr component.

129. The method of any one of claims 1-128, wherein an indication of whether and / or how the sample values ​​in the first color component are generated by applying the plurality of filters is indicated at one of: Sequence level, Picture group level, Picture level, Stripe level, or Tile group level.

130. The method of any one of claims 1-128, wherein the indication of whether and / or how the sample values ​​in the first color component are generated by applying the plurality of filters is indicated in one of: Sequence header, Picture header, Sequence Parameter Set (SPS), Video Parameter Set (VPS), Dependent Parameter Set (DPS), Decoding Capability Information (DCI), Picture Parameter Set (PPS), Adaptive Parameter Set (APS), Strip header, or Tile group header.

131. The method of any one of claims 1-128, wherein the indication of whether and / or how the sample values ​​in the first color component are generated by applying the plurality of filters is comprised in one of: Prediction Block (PB), Transform Block (TB), Codec Block (CB), Prediction Unit (PU), Transformation Unit (TU), Codec Unit (CU), Virtual Pipeline Data Unit (VPDU), Codec Tree Unit (CTU), CTU line, Strips, Tile, sub-image; or An area that contains more than one sample or pixel.

132. The method of any one of claims 1-128, further comprising: determining whether and / or how to generate the sample values ​​in the first color component by applying the plurality of filters based on encoded information of the video unit, the encoded information comprising at least one of: Block size, Color format, Single-tree and / or dual-tree partitioning, Color components, Strip type, or Image type.

133. The method of any one of claims 1-132, wherein the converting comprises encoding the video unit into the bitstream.

134. The method of any one of claims 1-132, wherein the converting comprises decoding the video unit from the bitstream.

135. A device for video processing, comprising a processor and a non-volatile memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform a method according to any one of claims 1-134.

136. A non-transitory computer-readable storage medium storing instructions that cause a processor to perform the method of any one of claims 1-134.

137. A non-transitory computer-readable storage medium storing a bitstream of a video generated by a method performed by an apparatus for video processing, the method comprising: generating sample values ​​of the first color component of a video unit of the video corresponding to samples of the second color component by applying a plurality of filters to at least one sample of the first color component; and The bitstream is generated based on the generated sample values.

138. A method for storing a bitstream of a video, comprising: generating sample values ​​of the first color component of a video unit of the video corresponding to samples of the second color component by applying a plurality of filters to at least one sample of the first color component; as well as generating the bitstream based on the generated sample values; as well as The bit stream is stored in a non-transitory computer-readable recording medium.

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