Method and device for video processing and medium

Abstract

Embodiments of the present disclosure provide a solution for video processing. A method for video processing is presented. The method comprises: for a conversion between a current video block of the video and a bitstream of the video, adjusting a prediction for the current video block, the prediction being determined based on a cross-component prediction scheme; and performing a conversion based on the adjusted prediction.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to video processing technologies, and more particularly, to cross-component prediction. Background Art

[0002] Nowadays, digital video capabilities are being applied to all aspects of people's lives. For video encoding / decoding, various types of video compression technologies have been proposed, such as MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 Part 10 Advanced Video Coding (AVC), ITU-T H.265 High Efficiency Video Coding (HEVC) standard, Versatile Video Coding (VVC) standard. However, there is an overall expectation to further improve the encoding / decoding quality of video encoding / decoding technologies. Summary of the Invention

[0003] Embodiments of the present disclosure provide a solution for video processing.

[0004] In a first aspect, a method for video processing is proposed. The method includes: adjusting a prediction for a current video block of a video for conversion between the current video block of the video and a bitstream of the video, the prediction being determined based on a cross-component prediction scheme; and performing the conversion based on the adjusted prediction.

[0005] According to the method of the first aspect of the present disclosure, the prediction for a video block determined based on a cross-component prediction scheme is adjusted before being further processed. Compared with traditional solutions, the proposed method can advantageously improve the encoding quality.

[0006] In a second aspect, an apparatus for video processing is proposed. The apparatus includes a processor and a non-transitory memory having instructions thereon. When the instructions are executed by the processor, the processor is caused to execute the method according to the first aspect of the present disclosure.

[0007] In a third aspect, a non-transitory computer-readable storage medium is proposed. The non-transitory computer-readable storage medium stores instructions that cause 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 proposed. The non-transitory computer-readable recording medium stores a bitstream generated by a method executed by an apparatus for video processing for a video. The method includes: adjusting a prediction for a current video block of the video, the prediction being determined based on a cross-component prediction scheme; and generating a bitstream based on the adjusted prediction.

[0009] In a fifth aspect, a method for storing a bitstream of a video is provided. The method includes: adjusting a prediction for a current video block of the video, the prediction being determined based on a cross-component prediction scheme; generating a bitstream based on the adjusted prediction; and storing the bitstream in a non-transitory computer-readable recording medium.

[0010] The present invention content is provided to introduce a selection of concepts further described below in the detailed implementation in a simplified form. The present invention content is not intended to identify the 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] Through the following detailed description with reference to the accompanying drawings, the above and other objects, features, and advantages of the example embodiments of the present disclosure will become more apparent. In the example 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 codec system according to some embodiments of the present disclosure is shown;

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

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

[0015] Figure 4 The nominal vertical and horizontal positions of 4:2:2 luma and chroma samples in a picture are shown;

[0016] Figure 5 An example of an encoder block diagram is shown;

[0017] Figure 6 67 intra prediction modes are shown;

[0018] Figure 7 Reference samples for wide-angle intra prediction are shown;

[0019] Figure 8 The problem of discontinuity in the case of a direction exceeding 45° is shown;

[0020] Figure 9 The positions of the samples for deriving α and β are shown;

[0021] Figure 10 An example of classifying neighboring samples into two groups is shown;

[0022] Figure 11AIt is a schematic diagram showing the definition of sample points used by PDPC applied to the diagonal upper-right pattern;

[0023] Figure 11B It is a schematic diagram showing the definition of sample points used by PDPC applied to the diagonal lower-left pattern;

[0024] Figure 11C It is a schematic diagram showing the definition of sample points used by PDPC applied to the adjacent diagonal upper-right pattern;

[0025] Figure 11D It is a schematic diagram showing the definition of sample points used by PDPC applied to the adjacent diagonal lower-left pattern;

[0026] Figure 12 It shows the gradient method for non-vertical / non-horizontal patterns;

[0027] Figure 13 It shows the nScale values regarding nTbH and the pattern number; for all cases of nScale < 0, the gradient method is used;

[0028] Figure 14 It shows the flowcharts of the current PDPC (left) and the proposed PDPC (right);

[0029] Figure 15 It shows the neighboring blocks (L, A, BL, AR, AL) used in the derivation of the general MPM list;

[0030] Figure 16 It shows an example of the proposed intra-frame reference mapping;

[0031] Figure 17 It shows an example of four reference lines adjacent to the prediction block;

[0032] Figure 18A It is a schematic diagram showing an example of the sub-division for 4×8 and 8×4 CUs;

[0033] Figure 18B It is a schematic diagram showing an example of the sub-division for CUs other than 4×8, 8×4, and 4×4;

[0034] Figure 19 It shows the matrix weighted intra-frame prediction process;

[0035] Figure 20 It shows the target sample points, template sample points, and reference sample points of the template used in DIMD;

[0036] Figure 21 It shows the proposed intra-frame block decoding process;

[0037] Figure 22Shows the HoG calculation from a template of width 3 pixels;

[0038] Figure 23 Shows the prediction fusion by weighted averaging of two HoG patterns and a plane;

[0039] Figure 24 Shows the spatial part of the convolutional filter;

[0040] Figure 25 Shows the reference region (with its padding) for deriving filter coefficients;

[0041] Figure 26 Shows four Sobel-based gradient patterns for GLM;

[0042] Figure 27 Shows the spatial samples for GL-CCCM;

[0043] Figure 28 Shows the non-downsampled luminance samples;

[0044] Figure 29 Shows the spatial GPM candidates;

[0045] Figure 30 Shows the GPM template;

[0046] Figure 31 Shows the GPM boundary;

[0047] Figure 32 Shows the binarization of the cross-component prediction mode in ECM;

[0048] Figure 33 Shows an example of a filter tap;

[0049] Figure 34 Shows an example of padding;

[0050] Figure 35A Shows an example of filtering using neighboring reconstruction samples;

[0051] Figure 35B Shows another example of filtering using neighboring reconstruction samples;

[0052] Figure 36 Shows an example of filtering using neighboring reconstruction samples and padding samples;

[0053] Figure 37A Shows an example of an encoding / decoding tree for encoding / decoding cross-component prediction modes;

[0054] Figure 37B Shows another example of an encoding / decoding tree for encoding / decoding cross-component prediction modes;

[0055] Figure 38 shows a flowchart of a method for video processing according to an embodiment of the present disclosure; and

[0056] Figure 39 shows a block diagram of a computing device in which various embodiments of the present disclosure may be implemented.

[0057] Throughout all the figures, the same or similar reference numerals generally refer to the same or similar elements. Detailed Description

[0058] The principles of the present disclosure will now be described with reference to some embodiments. It should be understood that the description of these embodiments is for illustrative purposes only and to assist those skilled in the art in understanding and implementing the present disclosure, and does not imply any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various ways other than those described below.

[0059] In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure pertains.

[0060] References herein to "one embodiment", "an embodiment", "example embodiment", etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but not every embodiment must include that particular feature, structure, or characteristic. Moreover, these phrases do not necessarily refer to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that such feature, structure, or characteristic, whether or not explicitly described, is within the knowledge of one of ordinary skill in the art in relation to other embodiments.

[0061] It should be understood that although terms such as "first" and "second" 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. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element, without departing from the scope of the example embodiments. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0062] The terms used in this disclosure are for the purpose of describing particular embodiments only and are not intended to limit the example embodiments. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprises", "comprising", "has", "having", "includes" and / or "including" when used herein specify the presence of the stated features, elements and / or components, etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. Example environment

[0063] Figure 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.

[0064] The video source 112 may include a source such as a video capture device. Examples of video capture devices 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.

[0065] 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 bitstream. The bitstream may include a sequence of bits that form an encoded representation of the video data. The bitstream may include encoded pictures and associated data. An encoded picture is an encoded representation of a picture. The associated data may include sequence parameter sets, picture parameter sets, and other syntax structures. The I / O interface 116 may include a modulator / demodulator and / or a transmitter. The encoded video data may be directly transmitted to the destination device 120 via the I / O interface 116 over a network 130A. The encoded video data may also be stored on a storage medium / server 130B for access by the destination device 120.

[0066] 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 a source device 110 or a 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 a user. The display device 122 may be integrated with the destination device 120 or may be external to the destination device 120, which is configured to interface with an external display device.

[0067] The video encoder 114 and the video decoder 124 may operate according to video compression standards such as the High Efficiency Video Coding (HEVC) standard, the Versatile Video Coding (VVC) standard, and other existing and / or future standards.

[0068] Figure 2 is a block diagram illustrating an example of a video encoder 200 according to some embodiments of the present disclosure. The video encoder 200 may be Figure 1 an example of the video encoder 114 in the system 100 shown.

[0069] The video encoder 200 may be configured to implement any or all of the techniques of the present disclosure. In Figure 2 an example, the video encoder 200 includes a plurality of functional components. The techniques described in the present disclosure may be shared among the various components of the video encoder 200. In some examples, a processor may be configured to execute any or all of the techniques described in the present disclosure.

[0070] In some embodiments, the video encoder 200 may include a segmentation 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. The prediction unit 202 may include a mode selection unit 203, a motion estimation unit 204, a motion compensation unit 205, and an intra prediction unit 206.

[0071] 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 in which at least one reference picture is the picture in which the current video block is located.

[0072] In addition, although some components such as the motion estimation unit 204 and the motion compensation unit 205 may be integrated, for purposes of explanation, these components are Figure 2is shown separately in the example of

[0073] The splitting unit 201 may split the picture into one or more video blocks. The video encoder 200 and the video decoder 300 may support various video block sizes.

[0074] The mode selection unit 203 may select, for example, one coding mode among multiple coding modes (intra coding or inter coding) based on an error result, and provide the resulting intra-coded block or inter-coded block to the residual generation unit 207 to generate residual block data, and provide it to the reconstruction unit 212 to reconstruct the coded block to be used as a reference picture. In some examples, the mode selection unit 203 may select the combined intra-inter prediction (CIIP) mode, in which 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 for the block (e.g., sub-pixel accuracy or integer pixel accuracy).

[0075] To perform inter prediction on the current video block, the motion estimation unit 204 may generate motion information for the current video block by comparing one or more reference frames from the cache 213 with the current video block. The motion compensation unit 205 may determine a predicted video block for the current video block based on the motion information and the decoded samples of a picture from the cache 213 other than the picture associated with the current video block.

[0076] The motion estimation unit 204 and the motion compensation unit 205 may perform different operations on the current video block, e.g., 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 composed of macroblocks, all of which are based on macroblocks within the same picture. Additionally, as used herein, in some aspects, a "P slice" and a "B slice" may refer to portions of a picture composed of macroblocks independent of the macroblocks in the same picture.

[0077] In some examples, the motion estimation unit 204 may perform uni-directional prediction on the current video block, and the motion estimation unit 204 may search the reference pictures in list 0 or list 1 to find a 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 that contains 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.

[0078] 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 to find a reference video block for the current video block, and may also search the reference pictures in list 1 to find another reference video block for the current video block. The motion estimation unit 204 may then generate a plurality of reference indices and a plurality of motion vectors, the plurality of reference indices indicating the plurality of reference pictures in list 0 and list 1 that contain the plurality of reference video blocks, and the plurality of motion vectors indicating the 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 indices and the plurality of motion vectors of the current video block 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 plurality of reference video blocks indicated by the motion information of the current video block.

[0079] In some examples, the motion estimation unit 204 may output a complete set of motion information for use in the decoding process of the decoder. Alternatively, in some embodiments, the motion estimation unit 204 may signal the motion information of the current video block by referring to the motion information of another video block. For example, the motion estimation unit 204 may determine that the motion information of the current video block is similar enough to the motion information of a neighboring video block.

[0080] In one example, the motion estimation unit 204 may indicate a value in the syntax structure associated with the current video block, the value indicating to the video decoder 300 that the current video block has the same motion information as another video block.

[0081] In another example, the motion estimation unit 204 may identify another video block and a motion vector difference (MVD) in the 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.

[0082] As discussed above, the video encoder 200 may signal motion vectors in a predictive manner. Two examples of predictive signaling techniques that may be implemented by the video encoder 200 include advanced motion vector prediction (AMVP) and Merge mode signaling.

[0083] 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 the decoded samples of other video blocks in the same picture. The prediction data for the current video block may include a predicted video block and various syntax elements.

[0084] The residual generation unit 207 can generate residual data for the current video block by subtracting (e.g., indicated by the minus sign) the (multiple) predicted video blocks of the current video block from the current video block. The residual data of the current video block can include residual video blocks corresponding to different sample components of the samples in the current video block.

[0085] In other examples, such as in the skip mode, there may be no residual data for the current video block, and the residual generation unit 207 may not perform the subtraction operation.

[0086] The transform processing unit 208 can generate one or more transform coefficient video blocks for the current video block by applying one or more transforms to the residual video block associated with the current video block.

[0087] After the transform processing unit 208 generates the transform coefficient video block associated with the current video block, the quantization unit 209 can 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.

[0088] The inverse quantization unit 210 and the inverse transform unit 211 can apply inverse quantization and inverse transform to the transform coefficient video block respectively to reconstruct the residual video block from the transform coefficient video block. The reconstruction unit 212 can add the reconstructed residual video block to the corresponding samples of one or more predicted video blocks generated by the prediction unit 202 to generate a reconstructed video block associated with the current video block for storage in the cache 213.

[0089] After the reconstruction unit 212 reconstructs the video block, a loop filtering operation can be performed to reduce the block effect artifacts in the video block.

[0090] The entropy coding unit 214 can 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 can perform one or more entropy coding operations to generate the entropy-coded data and output a bitstream including the entropy-coded data.

[0091] Figure 3 is a block diagram showing an example of a video decoder 300 according to some embodiments of the present disclosure. The video decoder 300 can be Figure 1 an example of the video decoder 124 in the system 100 shown.

[0092] The video decoder 300 can be configured to perform any or all of the techniques of the present disclosure. In Figure 3In the example of, the video decoder 300 includes multiple functional components. The techniques described in this disclosure can be shared among the various components of the video decoder 300. In some examples, the processor can be configured to perform any or all of the techniques described in this disclosure.

[0093] In Figure 3 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 cache 307. In some examples, the video decoder 300 can perform a decoding process generally opposite to the encoding process described with respect to the video encoder 200.

[0094] The entropy decoding unit 301 can retrieve the encoded bitstream. The encoded bitstream can include entropy-encoded video data (e.g., encoded blocks of video data). 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 indices, and other motion information. The motion compensation unit 302 can determine such information, for example, by performing AMVP and Merge mode. AMVP is used, including deriving several most likely candidates based on data from adjacent PBs and reference pictures. Motion information generally includes horizontal motion vector displacement values and vertical motion vector displacement values, one or two reference picture indices, and, in the case of a prediction region in a B slice, also an indication of which reference picture list is associated with each index. As used herein, in some aspects, "Merge mode" can refer to deriving motion information from spatially adjacent blocks or temporally adjacent blocks.

[0095] The motion compensation unit 302 can generate motion-compensated blocks, possibly performing interpolation based on an interpolation filter. An identifier for the interpolation filter used at sub-pixel precision can be included in the syntax element.

[0096] The motion compensation unit 302 can use the interpolation filter used by the video encoder 200 during the encoding of a video block to calculate interpolated values for sub-integer pixels of a reference block. The motion compensation unit 302 can determine the interpolation filter used by the video encoder 200 according to the received syntax information, and the motion compensation unit 302 can use the interpolation filter to generate a prediction block.

[0097] The motion compensation unit 302 may use at least part of the syntax information to determine the size of the blocks for encoding the (multiple) frames and / or (multiple) slices of the encoded video sequence, the partitioning information describing how each macroblock of the pictures of the encoded video sequence is partitioned, the mode indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter-frame encoded 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 / decoding, signal prediction, and residual signal reconstruction. A slice may be the entire picture or may also be a region of the picture.

[0098] The intra prediction unit 303 may use, for example, the intra prediction mode received in the bitstream to form a prediction block from spatially adjacent blocks. The inverse quantization unit 304 inverse 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 305 applies an inverse transform.

[0099] 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 302 or the intra prediction unit 303. If needed, a deblocking filter may also be applied to filter the decoded block to remove blocking artifact. The decoded video block is then stored in the cache 307, which provides reference blocks for subsequent motion compensation / intra prediction, and the cache 307 also produces the decoded video for presentation on a display device.

[0100] Some exemplary embodiments of the present disclosure will be described in detail below. It should be noted that the use of section headings in this document is for ease of understanding and does not limit the embodiments disclosed in the section to that section. In addition, although some embodiments are described with reference to the multi-functional video coding or other specific video codecs, the disclosed techniques are also applicable to other video coding techniques. In addition, although some embodiments describe the video encoding steps in detail, it should be understood that the corresponding decoding steps of decoding will be implemented by the decoder. In addition, the term video processing includes video encoding 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 bitrates. 1. Brief Overview Embodiments relate to video coding and decoding techniques. Specifically, they relate to chrominance coding and decoding. Embodiments may be applied to existing video coding and decoding standards such as HEVC or multi-functional video coding (VVC). Embodiments are also applicable to future video coding and decoding standards or video codecs. 2. Introduction Video coding standards have mainly evolved from the well-known ITU-T and ISO / IEC standards. ITU-T developed H.261 and H.263, and ISO / IEC developed MPEG-1 and MPEG-4 Visual. The two organizations jointly developed the H.264 / MPEG-2 video, H.264 / MMPEG-4 Advanced Video Coding (AVC), and H.264 / HEVC standards. Since H.262, video coding standards have been based on a hybrid video coding structure that utilizes temporal prediction plus transform coding. To explore future video coding technologies beyond HEVC, VCEG and MPEG jointly established the Joint Video Exploration Team (JVET) in 2015. Since then, JVET has adopted many new methods and incorporated them into a reference software called the Joint Exploration Model (JEM). In April 2018, the Joint Video Exploration Team (JVET) between VCEG (Q6 / 16) and ISO / IEC JTC1 SC29 / WG11 (MPEG) was created to work on the VVC standard, with the goal of reducing the bitrate by 50% compared to HEVC. 2.1 Color Space and Chroma Subsampling A color space (also known as a color model (or color system)) is an abstract mathematical model that simply describes a color range as a digital tuple, typically 3 or 4 values or color components (such as RGB). Basically, a color space is a refinement of a coordinate system and subspace. For video compression, the most frequently used color spaces are YCbCr and RGB. YCbCr, Y'CbCr, or Y Pb / Cb Pr / Cr (also written as YCBCR or Y'CBCR) is a family of color spaces that are used as part of the color image pipeline in video and digital photography systems. Y' is the luminance component, and CB and CR are the blue-difference and red-difference chrominance components. Y' (with the superscript symbol) is different from Y, which is luminance, meaning that the light intensity is non-linearly encoded based on gamma-corrected RGB primaries. Chroma subsampling is the practice of encoding an image by achieving less resolution for chrominance information than for luminance information, taking advantage of the fact that the human visual system has lower sharpness for color differences than for luminance. 2.1.1. 4:4:4 Each of the three Y'CbCr components has the same sampling rate, so there is no chroma subsampling. This scheme is sometimes used in high-end film scanners and film post-production. 2.1.2. 4:2:2 Sample the two chrominance components at half the sampling rate of luminance: the horizontal chrominance resolution is halved while the vertical chrominance resolution remains unchanged. This reduces the bandwidth of the uncompressed video signal by one third with little visual difference. Examples of the nominal vertical and horizontal positions for the 4:2:2 color format are depicted in the VVC working draft Figure 4 in the 2.1.3.4:2:0 In 4:2:0, the horizontal sampling is doubled compared to 4:1:1, but since the Cb and Cr channels are only sampled on every other line in this scheme, the vertical resolution is halved. Thus, the data rate is the same. Cb and Cr are each downsampled by a factor of 2 both horizontally and vertically. There are three variants of the 4:2:0 scheme which have different horizontal and vertical positioning. · In MPEG-2, Cb and Cr are horizontally co-located. Cb and Cr are placed between the pixels in the vertical direction (placed with a gap). · In JPEG / JFIF, H261 and MPEG-1, Cb and Cr are placed with a gap, at the mid-position between alternating luminance samples. · In 4:2:0 DV, Cb and Cr are horizontally co-located. In the vertical direction, they are co-located on alternating lines. Table 2-1 SubWidthC and SubHeightC values derived from chroma_format_idc and separate_colour_plane_flag 2.2 Encoding process of typical video codecs Figure 5 An example of the encoder block diagram of VVC is shown, which contains three loop filter blocks: deblocking filter (DF), sample adaptive offset (SAO) and ALF. Different from the DF which uses predefined filters, SAO and ALF utilize the original samples of the current picture to reduce the mean square error between the original samples and the reconstructed samples by adding offsets and applying finite impulse response (FIR) filters respectively, where the encoding side information is signaled by the offsets and filter coefficients. ALF is located at the last processing stage of each picture and can be regarded as a tool to attempt to capture and fix the artifacts generated in the previous stage. 2.3 Intra-mode codec with 67 intra prediction modes To capture any edge direction presented in natural videos, the number of directional intra modes is extended from 33 used in HEVC to 65, as Figure 6As shown, the planar mode and the DC mode remain unchanged. These dense direction-based intra prediction modes are applicable to all block sizes and apply to both luma intra prediction and chroma intra prediction. In HEVC, each intra-coded block has a square shape, and the length of each of its sides is a power of 2. Therefore, no division operation is required to generate an intra prediction value using the DC mode. In VVC, a block can have a rectangular shape, which generally requires a division operation for each block. To avoid the division operation for DC prediction, only the longer side is used to calculate the average value of a non-square block. 2.3.1 Wide-angle intra prediction Although 67 modes are defined in VVC, the exact prediction direction for a given intra prediction mode index further depends on the block shape. The traditional angular intra prediction directions are defined as from 45 degrees to -135 degrees in the clockwise direction. In VVC, several traditional angular intra prediction modes are adaptively replaced with wide-angle intra prediction modes for non-square blocks. The original mode index is used to signal the replaced mode, and the original mode index 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 coding and decoding method remains unchanged. To support these prediction directions, a top reference of length 2W+1 and a left reference of length 2H+1 are defined, as Figure 9 shown. The number of modes replaced in the wide-angle direction mode depends on the aspect ratio of the block. The replaced intra prediction modes are shown in Table 2-2. Table 2-2 Intra prediction modes replaced by wide-angle modes As Figure 8 shown, in the case of wide-angle intra prediction, two vertically adjacent prediction samples can use two non-adjacent reference samples. Therefore, a low-pass reference sample filter and side smoothing are applied to wide-angle prediction to reduce the increased gap Δp α brought about by the negative impact. If the wide-angle mode represents a non-fractional offset. There are 8 modes in the wide-angle mode that meet this condition, and they are [-14, -12, -10, -6, 72, 76, 78, 80]. When predicting a block through these modes, the samples in the reference buffer are directly copied without applying any interpolation. With this modification, the number of samples that need to be smoothed is reduced. In addition, it aligns the design of non-fractional modes in traditional prediction modes and wide-angle modes. In VVC, 4:2:2 and 4:4:4 chroma formats as well as 4:2:0 chroma format are supported. The chroma derivation mode (DM) derivation table for the 4:2:2 chroma format was initially ported from HEVC, and the number of entries was extended from 35 to 67 to align with the extension of the intra prediction mode. Since the HEVC specification does not support prediction angles below -135 degrees and above 45 degrees, the luma intra prediction modes in the range from 2 to 5 are mapped to 2. Therefore, the chroma DM derivation table for the 4:2:2 chroma format is updated by replacing some values of the entries in the mapping table to more precisely transform the prediction angles of chroma blocks. 2.4 Intra Prediction Mode Coding and Decoding for Chrominance Components For the chrominance components of an intra PU, the encoder selects the best chroma prediction mode among 5 modes including plane, DC, horizontal, vertical, and direct copy for the intra prediction mode of the luma component. The mapping between the intra prediction direction for chroma and the intra prediction mode number is shown in Table 2-3. When the intra prediction mode number for the chrominance component is 4, the intra prediction direction for the luma component is used for intra prediction sample generation for the chrominance component. When the intra prediction mode number for the chrominance component is not 4 and is the same as the intra prediction mode number for the luma component, intra prediction direction 66 is used for intra prediction sample generation for the chrominance component. 2.5 Inter Prediction For each inter prediction CU, the motion parameters include the motion vector, reference picture index and reference picture list use index, and additional information required for the new coding features of VVC that will be used for inter prediction sample generation. The motion parameters can be signaled in an explicit or implicit manner. When a CU is encoded in skip mode, the CU is associated with a PU and has no significant residual coefficients, no coded motion vector difference or reference picture index. A Merge mode is specified, whereby the motion parameters of the current CU, including spatial candidates and temporal candidates, and additional scheduling introduced in VVC, are obtained from neighboring CUs. The Merge mode can be applied to any inter prediction CU, not just limited to skip mode. The alternative to the Merge mode is the explicit transmission of motion parameters, where the motion vector, the corresponding reference picture index and reference picture list use flag for each reference picture list, and other required information are signaled explicitly for each CU. 2.6 Intra Block Copy (IBC) Intra Block Copy (IBC) is a tool adopted in the HEVC extension on SCC. As is well known, it significantly improves the encoding and decoding efficiency of screen content materials. Since the IBC mode is implemented as a block-level encoding and decoding mode, block matching (BM) is performed at the encoder to find the best block vector (or motion vector) for each CU. Here, the block vector is used to indicate the displacement from the current block to the reference block that has been reconstructed within the current picture. The luminance block vector of the CU encoded and decoded by IBC has integer precision. The chrominance block vector is also rounded to integer precision. When used in combination with AMVR, the IBC mode can switch between 1-pixel and 4-pixel motion vector precisions. The CU encoded and decoded by IBC is regarded as a third prediction mode in addition to the intra or inter prediction modes. The IBC mode is applicable to CUs with a width and height less than or equal to 64 luminance samples. On the encoder side, hash-based motion estimation is performed for IBC. The encoder performs RD checks on blocks with a width or height not greater than 16 luminance samples. For non-Merge modes, a block vector search is first performed using hash-based search. If the hash search does not return a valid candidate, a block-matching based local search will be performed. In the hash-based search, the hash key match (32-bit CRC) between the current block and the reference block is extended to all allowed block sizes. The hash key calculation for each position in the current picture is based on 4×4 sub-blocks. For a larger-sized current block, the hash key is determined to match the hash key of the reference block when the hash keys of all 4×4 sub-blocks match the hash keys in the corresponding reference positions. If the hash keys of multiple reference blocks are found to match the hash key of the current block, the block vector cost of each matching reference is calculated, and the one with the minimum cost is selected. In the block-matching search, the search range is set to cover the previous CTU and the current CTU. At the CU level, the IBC mode uses flags to signal that it can be signaled as the IBC AMVP mode or the IBC Skip / Merge mode, as follows: - IBC Skip / Merge mode: The Merge candidate index is used to indicate which block vector from the list of neighboring candidate IBC-encoded blocks is used to predict the current block. The Merge list includes spatial candidates, HMVP candidates, and paired candidates. - IBC AMVP mode: The block vector difference is encoded in the same way as the motion vector difference. The block vector prediction method uses two candidates as prediction values, one from the left neighbor and one from the upper neighbor (if it is IBC-encoded). When either neighbor is not available, the default block vector is used as the prediction value. A flag is signaled to indicate the block vector prediction value index. 2.7 Cross-Component Linear Model Prediction To reduce cross-component redundancy, the cross-component linear model (CCLM) prediction mode is used in VVC. For this CCLM prediction mode, the following linear model is used to predict chroma samples based on the reconstructed luma samples of the same CU: pred C (i,j) = α·rec L ′(i,j) + β (2-1) where pred C (i,j) represents the predicted chroma sample in the CU, and rec L (i,j) represents the downsampled reconstructed luma sample of the same CU. The CCLM parameters (α and β) are derived using 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 as follows: – When the LM mode is applied, W’ = W, H’ = H; – When the LM_T mode is applied, W’ = W + H; – When the 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]…S[-1, H’-1]. Then, four samples are selected as follows: – When the LM mode is applied and both the upper neighboring sample and the left neighboring sample are available, S[W’ / 4, -1], S[3*W’ / 4, -1], S[-1, H’ / 4], S[-1, 3*H’ / 4]; – When the LM-T mode is applied or only the upper neighboring sample is available, S[W’ / 8, -1], S[3*W’ / 8, -1], S[5*W’ / 8, -1], S[7*W’ / 8, -1]; – When the LM-L mode is applied or only the left neighboring sample is available, S[-1, H’ / 8], S[-1, 3*H’ / 8], S[-1, 5*H’ / 8], S[-1, 7*H’ / 8]. The four neighboring luma samples at the selected positions are downsampled and compared four times to find two larger values: x 0 A and x 1 A , and two smaller values: x 0 B and x 1 B . Their corresponding chroma sample values are denoted as y 0 A , y 1A , y 0 B and y 1 B . Then x A , x B , y A and y B are deduced as follows: X a = (x 0 A + x 1 A + 1) >> 1; X b = (x 0 B + x 1 B + 1) >> 1; Y a = (y 0 A + y 1 A + 1) >> 1; Y b = (y 0 B + y 1 B + 1) >> 1 (2 - 2) Finally, the linear model parameters α and β are obtained according to the following formula. β = Y b - α·X b (2 - 4) Figure 9 Shows an example of the positioning of the left and upper samples involved in the CCLM mode and the samples of the current block. A lookup table is used to implement the division operation to calculate the parameters. 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 exponentially. For example, diff is approximated with 4 significant bits and an exponent. Therefore, the table for 1 / diff is reduced to 16 elements for 16 values of the significant bits as follows: DivTable[ ] = {0, 7, 6, 5, 5, 4, 4, 3, 3, 2, 2, 1, 1, 1, 1, 0} (2 - 5) This will help reduce the computational complexity and the memory size required to store the required table. In addition to the upper and left templates being used together to calculate the linear model coefficients, they can also be used alternately in two other LM modes, called the LM_T and LM_L modes. In the LM_T mode, only the upper template is used to calculate the linear model coefficients. To obtain more samples, the upper template is extended to (W + H) samples. In the LM_L mode, only the left template is used to calculate the linear model coefficients. To obtain more samples, the left template is extended to (H + W) samples. In the LM mode, the left template and the upper template are used to calculate the linear model coefficients. To match the chrominance 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 the horizontal and vertical directions. The selection of the downsampling filter is specified by the SPS level flag. The two downsampling filters are as follows, corresponding to "type-0" and "type-2" content respectively. Note that when the upper reference line is at the CTU boundary, only one luma line (the general line buffer in intra prediction) is used for the downsampled luma samples. This parameter calculation is performed as part of the decoding process, not just as an encoder search operation. Therefore, no syntax is used to convey the α and β values to the decoder. For chrominance intra mode coding and decoding, a total of 8 intra modes are allowed for chrominance intra coding and decoding. These modes include five traditional intra modes and three cross-component linear model modes (LM, LM_T, and LM_L). The chrominance mode signaling and derivation process are shown in Table 2-3. The chrominance mode coding and decoding directly depend on the intra prediction mode of the corresponding luma block. Since a separate block partitioning structure for luma and chrominance components is enabled in the I slice, one chrominance block can correspond to multiple luma blocks. Therefore, for the chrominance DM mode, the intra prediction mode of the corresponding luma block covering the center position of the current chrominance block is directly inherited. Table 2-3 Deriving Chrominance Prediction Modes from Luma Modes when CCLM is Enabled As shown in Table 2-4, a single binarization table is used regardless of the value of sps_cclm_enabled_flag. Table 2-4 Unified Binarization Table for Chrominance Prediction Modes Value of intra_chroma_pred_mode Binary string 4 00 0 0100 1 0101 2 0110 3 0111 5 10 6 110 7 111 In Table 2-4, the first binary bit indicates whether it is in the normal mode (0) or the LM mode (1). If it is in the 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_T (1). For this case, when the sps_cclm_enabled_flag is 0, the first binary bit of the binary table corresponding to the intra_chroma_pred_mode can be discarded before entropy encoding / decoding. Or, in other words, the first binary bit is presumed to be 0 and thus not encoded / decoded. This single binary table is used for both cases where the sps_cclm_enabled_flag is equal to 0 and 1. The first two binary bits in Table 2-4 are context-encoded using their own context model, and the remaining binary bits are bypass-encoded. In addition, to reduce the luminance-chrominance delay in the dual tree, when the 64×64 luminance encoding / decoding tree node is split using Not Split (and ISP is not used for the 64×64 CU) or QT, the chroma CUs in the 32×32 / 32×16 chroma encoding / decoding tree nodes are allowed to use CCLM in the following ways: - If the 32×32 chroma node is not split or split using QT split, all chroma CUs in the 32×32 node can use CCLM. - If the 32×32 chroma node is split using horizontal BT and the 32×16 child node is not split or split using vertical BT, all chroma CUs in the 32×16 chroma node can use CCLM. Under all other luminance and chroma encoding / decoding tree partitioning conditions, CCLM is not allowed for chroma CUs. 2.8 Multiple Model Linear Model (MMLM) For MMLM, there can be more than one linear model between the luminance samples and chroma samples in a CU. In this method, the neighboring luminance samples and neighboring chroma samples of the current block are classified into several groups, and each group is used as a training set to derive a linear model (i.e., specific α and β are derived for a specific group). In addition, the samples of the current luminance block are also classified based on the same rule as the classification of the neighboring luminance samples. The neighboring samples can be classified into M groups, where M is 2 or 3. In the cases of M = 2 and M = 3, the MMLM method is designed with two additional chroma prediction modes in addition to the original LM mode, called MMLM2 and MMLM3. The encoder selects the best mode during the RDO process and signals this mode. When M is equal to 2, Figure 10An example of classifying neighboring samples into two groups is shown. The threshold is calculated as the average of neighboring reconstructed luminance samples. Rec’L[x,y]<=threshold Rec' L Neighboring samples where [x, y]≤Threshold are classified into Group 1; while Rec’L[x,y]>threshold Rec′ L Neighboring samples where [x,y]>Threshold are classified into Group 2. Similar to CCLM, there are 3 modes in MMLM, namely MMLM, MMLM_T, and MMLM_L. Two models are derived as follows. The threshold is the average of neighboring samples for luminance reconstruction. The linear model for each category is derived by using the least mean square (LMS) method (if enabled) or the minimum / maximum method of VVC. 2.9 Position-dependent Intra Prediction Combination In VVC, the intra prediction results of DC, Planar, and several angular modes are further modified by the position-dependent intra prediction combination (PDPC) method. PDPC is an intra prediction method that calls a combination of boundary reference samples and HEVC-style intra prediction with filtered boundary reference samples. PDPC is applied to the following intra modes without signaling: Planar, DC, intra angles less than or equal to horizontal, and intra angles greater than or equal to vertical and less than or equal to 80. If the current block is in BDPCM mode or the MRL index is greater than 0, PDPC is not applied. According to Equation 2-8 below, the predicted sample pred(x’,y’) is predicted using a linear combination of reference samples and the intra prediction mode (DC, Planar, Angular): pred(x’,y’)=Clip(0,(1<<BitDepth)-1,(wL×R -1，y’ +wT×R x’-1 +(64-wL-wT)×pred(x’,y’) +32)>>6) (2-9) where R x,-1 ,R -1,y represent the reference samples located at the top and left boundaries of the current sample (x, y), respectively. If PDPC is applied to DC, planar, horizontal, and vertical intra modes, no additional boundary filtering is required, as is the case for HEVC DC mode boundary filtering or horizontal / vertical mode edge filtering. The PDPC process for DC mode and planar mode is the same. For angular modes, if the current angular mode is HOR_IDX or VER_IDX, the left or top reference sample is not used, respectively. The PDPC weights and scale factors depend on the prediction mode and block size. PDPC is applied to blocks with width and height both greater than or equal to 4. Figures 11A to 11D Shows the definition of reference samples (R x,-1 and R -1,y ) for PDPC applied in various prediction modes. The predicted sample pred(x’,y’) is located at (x’,y’) within the prediction block. For example, for the angular mode, the x coordinate of reference sample R x,-1 is given by: x = x’ + y’ + 1, and the y coordinate of reference sample R -1,y is similarly given by: y = x’ + y’ + 1. For other angular modes, the reference samples R x,-1 and R -1,y can be at fractional sample positions. In this case, the sample value at the nearest integer sample position will be used. 2.10 Gradient PDPC As Figure 12 shown, the gradient-based method is extended to non-vertical / non-horizontal modes. Here, the gradient is calculated as r(-1,y) – r(-1 + d,-1), where d is the horizontal displacement depending on the angular direction. The following points need to be noted here: The gradient term r(-1,y) – r(-1 + d,-1) needs to be calculated once per row as it does not depend on the x position. The calculation of d is already part of the original intra prediction process that can be reused, so d does not need to be calculated separately. Thus, the precision of d is 1 / 32 pixel. When d is at a fractional position, two-tap (linear) filtering is already used, i.e., if dPos is the displacement with 1 / 32 pixel precision, dInt is the (rounded down) integer part (dPos >> 5), and dFract is the fractional part with 1 / 32 pixel precision (dPos & 31), then r(-1 + d) is calculated as: r(-1 + d) = (32 – dFrac)*r(-1 + dInt) + dFrac*r(-1 + dInt + 1). As described in a, this two-tap filtering is performed once per row (if needed). Finally, the predicted signal is calculated: p(x,y) = Clip(((64 – wL(x)) * p(x,y) + wL(x) * (r(-1,y) - r(-1 + d,-1)) + 32) >> 6) where wL(x) = 32 >> ((x << 1) >> nScale2), and nScale2 = (log2(nTbH) + log2(nTbW) – 2) >> 2, which are the same as in the vertical / horizontal mode. In short, the same process is applied as in the vertical / horizontal mode (in fact, d = 0 represents the vertical / horizontal mode). Second, in the case of non-vertical / non-horizontal mode, when (nScale < 0) or PDPC cannot be applied due to the unavailability of the auxiliary reference samples, the gradient-based method is activated. The values of nScale related to the TB size and angle mode have been shown in Figure 13 to better visualize the situation of using the gradient method. In addition, in Figure 14 the flowcharts for the current PDPC and the proposed PDPC are shown. 2.11 Auxiliary MPM The existing primary MPM (PMPM) list includes 6 entries, while the auxiliary MPM (SMPM) list includes 16 entries. First, a general MPM list with 22 entries is constructed, and then the first 6 entries in this general MPM table are included in the PMPM list, and the remaining entries form the SMPM list. The first entry in the general MPM list is the planar mode. As Figure 15 shown, the remaining entries are composed of the intra modes of the left (L), above (A), bottom-left (BL), top-right (AR), and top-left (AL) neighboring blocks, the band direction mode with an offset added from the first two available band direction modes of the neighboring blocks, and the default mode. If the CU block is vertically oriented, the order of the neighboring blocks is A, L, BL, AR, AL; otherwise, it is L, A, BL, AR, AL. First, the PMPM flag is parsed. If it is equal to 1, the PMPM index is parsed to determine which entry in the PMPM list is selected. Otherwise, the SPMPM flag is parsed to determine whether to parse the SMPM index or the remaining modes. 2.12 6-Tap Intra Interpolation Filter To improve the prediction accuracy, it is proposed to replace the 4-tap cubic interpolation filter with a 6-tap interpolation filter. The filter coefficients are derived based on the same polynomial regression model, but the polynomial order is 6. The filter coefficients are as follows:[[]] {0,0,256,0,0,0}, / / 0 / 32 position {0,-4,253,9,-2,0}, / / 1 / 32 position {1, -7, 249, 17, -4, 0}, / / 2 / 32 position {1, -10, 245, 25, -6, 1}, / / 3 / 32 position {1, -13, 241, 34, -8, 1}, / / 4 / 32 position {2, -16, 235, 44, -10, 1}, / / 5 / 32 position {2, -18, 229, 53, -12, 2}, / / 6 / 32 position {2, -20, 223, 63, -14, 2}, / / 7 / 32 position {2, -22, 217, 72, -15, 2}, / / 8 / 32 position {3, -23, 209, 82, -17, 2}, / / 9 / 32 position {3, -24, 202, 92, -19, 2}, / / 10 / 32 position {3, -25, 194, 101, -20, 3}, / / 11 / 32 position {3, -25, 185, 111, -21, 3}, / / 12 / 32 position {3, -26, 178, 121, -23, 3}, / / 13 / 32 position {3, -25, 168, 131, -24, 3}, / / 14 / 32 position {3, -25, 159, 141, -25, 3}, / / 15 / 32 position {3, -25, 150, 150, -25, 3}, / / Half - pixel position The reference samples for interpolation are from the reconstructed samples or the filled samples in HEVC, so that no conditional check for the availability of reference samples is required. It is recommended to use a 4 - tap cubic interpolation filter instead of using a nearest - rounding operation to derive the extended intra - reference samples. As Figure 16 shown in the example in, to derive the value of the reference sample P, a four - tap interpolation filter is used, while in JEM - 3.0 or HM, P is directly set to X1. 2.13 Multiple - reference - line (MRL) intra prediction Multiple - reference - line (MRL) intra prediction uses more reference lines for intra prediction. In Figure 17In [the figure], an example of 4 reference lines is depicted, where the samples of segment A and segment F are not taken from the reconstructed neighboring samples, but are filled with the closest samples from segment B and segment E respectively. HEVC intra picture prediction uses the closest reference line (i.e., reference line 0). In MRL, 2 additional lines (reference line 1 and reference line 2) are used. The index (mrl_idx) of the selected reference line is signaled and used to generate the intra prediction value. For reference line indices greater than 0, only additional reference line modes are included in the MPM list, and only the MPM index is signaled without the remaining modes. The reference line index is signaled before the intra prediction mode, and in the case where a non-zero reference line index is signaled, the planar mode is excluded from the intra prediction modes. MRL is disabled for the first line of blocks within a CTU to prevent the use of extended reference samples outside the current CTU row. Additionally, PDPC will be disabled when additional lines are used. For the MRL mode, the derivation of the DC value in the DC intra prediction mode with a non-zero reference line index is aligned with the derivation for reference line index 0. MRL requires using 3 neighboring luma reference lines stored in the CTU to generate predictions. The cross-component linear model (CCLM) tool also requires 3 neighboring luma reference lines for its downsampling filter. The definition of MRL using the same 3 lines is aligned with CCLM to reduce the storage requirements of the decoder. 2.14 Intra Sub-Partitioning (ISP) Intra Sub-Partitioning (ISP) divides the luma intra prediction block vertically or horizontally into 2 or 4 sub-partitions according to the block size. For example, the minimum block size for ISP is 4×8 (or 8×4). If the block size is greater than 4×8 (or 8×4), the corresponding block will be divided into 4 sub-partitions. It has been noted that M×128 (N≤64) and 128×N (N≤64) ISP blocks may cause potential problems when using a 64×64 VDPU. For example, in the case of a single tree, an M×128 CU has an M×128 luma TB and two corresponding chroma TBs. If the CU uses ISP, then the luma TB will be divided into 4 M×32 TBs (only horizontal division is possible), each of which is smaller than a 64×64 block. However, in the current ISP design, the chroma blocks are not divided. Therefore, the sizes of both chroma components will be greater than 32×32 blocks. Similarly, using ISP with a 128×N CU can create a similar situation. Therefore, these two cases are problems for the 64×64 decoder pipeline. Thus, the CU size for which ISP can be used is limited to a maximum of 64×64. Figures 18A to 18B Examples of two possibilities are shown. All sub-partitions satisfy the condition of having at least 16 samples. In the ISP, it is not allowed that the 1×N / 2×N sub-block prediction depends on the reconstructed values of the previously decoded 1×N / 2×N sub-blocks of the coded block, so that the minimum prediction width of the sub-block becomes four samples. For example, an 8×N (N>4) coded block encoded and decoded by the ISP with vertical partitioning is divided into two prediction regions, each with a size of 4×N, and the size of the four transforms is 2×N. Similarly, a 4×N coded block encoded and decoded by the ISP with vertical partitioning is predicted using the complete 4×N block; four transforms are used, each of 1×N. Although transform sizes of 1×N and 2×N are allowed, it can be asserted that the transforms of these blocks within the 4×N region can be executed in parallel. For example, when the 4×N prediction region contains four 1×N transforms, there is no transform in the horizontal direction; the transforms in the vertical direction can be executed as a single 4×N transform in the vertical direction. Similarly, when the 4×N prediction region contains two 2×N transform blocks, the transform operations of the two 2×N blocks can be performed in parallel in each direction (horizontal and vertical). Therefore, compared with processing the intra block of the 4×4 conventional coding and decoding, no additional latency is added when processing these smaller blocks. Table 2-5 Entropy Coding Coefficient Group Sizes Block size Coefficient array size 1×N, N≥16 1×16 N×1, N≥16 16×1 2×N, N≥8 2×8 N×2, N≥8 8×2 All other possible M×N cases 4×4 For each sub-partition, the reconstructed samples are obtained by adding the residual signal to the prediction signal. Here, the residual signal is generated through processes such as entropy decoding, inverse quantization, and inverse transform. Therefore, the reconstructed sample values of each sub-partition can be used to generate the prediction of the next sub-partition, and each sub-partition is processed repeatedly. In addition, the first sub-partition to be processed is the word partition that contains the top-left sample of the CU and then continues downward (horizontal partitioning) or to the right (vertical partitioning). Therefore, the reference samples used to generate the sub-partition prediction signal are only located on the left and above the row. All sub-partitions share the same intra mode. The following is a summary of the interaction between the ISP and other coding and decoding tools. – Multiple Reference Lines (MRL): If the MRL index of the block is not 0, the ISP coding and decoding mode will be presumed to be 0, so the ISP mode information will not be sent to the decoder. – Entropy Coding Coefficient Group Sizes: As shown in Table 2-5, the size of the entropy coding sub-block has been modified so that there are 16 samples in all possible cases. It is worth noting that the new size only affects the blocks generated by the ISP, where one size is less than 4 samples. In all other cases, the coefficient group remains at a 4×4 size. – CBF Coding and Decoding: Assume that at least one sub-partition has a non-zero CBF. Therefore, if n is the number of sub-partitions and the first n-1 sub-partitions have produced zero CBF, the CBF of the nth sub-partition is presumed to be 1. – Transform Size Constraint: All ISP transforms with a length greater than 16 points use DCT-II. – MTS flag: If the CU uses the ISP coding / decoding mode, the MTS CU flag will be set to 0 and will not be sent to the decoder. Therefore, the encoder will not perform RD tests on the different available transforms for each resulting sub-partition. The transform selection for the ISP mode will be changed to be fixed and selected according to the intra mode used, the processing order, and the block size. Therefore, signaling is not required. For example, let t H and t V be the horizontal transform and the vertical transform selected for a w×h sub-partition respectively, where w is the width and h is the height. Then the transform is selected according to the following rules: – If w = 1 or h = 1, there is no horizontal transform or vertical transform respectively. – If w≥4 and w≤16, t H = DST-VII, otherwise t H = DCT-II. – If h≥4 and h≤16, t V = DST-VII, otherwise t V = DCT-II. In the ISP mode, all 67 intra prediction modes are allowed. If the corresponding width and height are at least 4 samples long, PDPC is also applied. In addition, the reference sample filtering process (reference smoothing) and the conditions for the selection of the intra interpolation filter no longer exist, and in the ISP mode, the cubic (DCT-IF) filter is always applied to fractional position interpolation. 2.15 Matrix weighted intra prediction (MIP) The matrix weighted intra prediction (MIP) method is a new intra prediction technique added in VVC. To predict the samples of a rectangular block with width W and height H, the matrix weighted intra prediction (MIP) takes as input a row of H reconstructed neighboring boundary samples on the left side of the block and a row of W reconstructed neighboring boundary samples above the block. If the reconstructed samples are not available, they are generated as in traditional intra prediction. As Figure 19 shown, the generation of the prediction signal is based on the following three steps, namely averaging, matrix-vector multiplication, and linear interpolation. 2.15.1 Averaging neighboring samples Among the boundary samples, four samples or eight samples are selected by averaging based on the block size and shape. Specifically, according to a predefined rule depending on the block size, by averaging the neighboring boundary samples, the input boundaries bdry top and bdry left are reduced to smaller boundaries and Then, the two reduced boundaries and Spliced to the reduced boundary vector bdry red , for a 4×4 shaped block, its size is 4, while for all other shaped blocks, its size is 8. If mode refers to the MIP mode, this splicing is defined as follows: 2.15.2 Matrix Multiplication Taking the averaged samples as input, perform matrix-vector multiplication and then add an offset. The result is a reduced prediction signal on the downsampled set of samples in the original block. From the reduced input vector bdry red , generate the reduced prediction signal pred red , which is a signal on the downsampled block with width W red and height H red . Here, W red and H red are defined as: Calculate the reduced prediction signal pred by computing the matrix-vector product and adding an offset red : pred red = A·bdry red + b (2-13) Here, A is a matrix that has W red ·H red rows, and if W = H = 4, it has 4 columns, and in all other cases it has 8 columns. b is a vector with size W red ·H red . The matrix A and the offset vector b are taken from one of the sets S0, S1, S2. Define the index idx = idx(W,H) as follows: Here, each coefficient of the matrix A is represented with 8-bit precision. The set S0 consists of 16 matrices , each matrix having 16 rows and 4 columns, and 16 offset vectors , each offset vector having a size of 16. The matrices and offset vectors of this set are used for blocks of size 4×4. The set S1 consists of 8 matrices and 8 offset vectors , each matrix having 16 rows and 8 columns, and each offset vector having a size of 16. The set S2 consists of 6 matrices and 6 offset vectors , each matrix having 64 rows and 8 columns, and each offset vector having a size of 64. 2.15.3 Interpolation The prediction signals at the remaining positions are generated from the prediction signals on the downsampled set by linear interpolation, which is a single-step linear interpolation in each direction. The interpolation is first performed in the horizontal direction and then in the vertical direction, independent of the shape or size of the block. 2.15.4. Signaling of MIP Mode and Coordination with Other Coding Tools For each coding unit (CU) in the intra mode, a flag indicating whether to apply the MIP mode is sent. If the MIP mode is to be applied, the MIP mode (predModeIntra) is signaled. For the MIP mode, the transpose flag (isTransposed) (which determines whether the mode is transposed) and the MIP mode Id (modeId) (which determines which matrix is to be used for a given MIP mode) are derived as follows. isTransposed = predModeIntra & 1 modeId = predModeIntra >> 1 (2 - 15) The MIP coding mode is coordinated with other coding tools by considering the following aspects: – Enable LFNST for MIP on large blocks. The LFNST transform in the planar mode is used here. – The reference sample derivation for MIP is performed entirely as the reference sample derivation for the traditional intra prediction mode. – For the upsampling step used in MIP prediction, the original reference samples are used instead of the downsampled samples. – Clipping is performed before upsampling instead of after upsampling. – MIP is allowed to reach 64×64 regardless of the maximum transform size. The number of MIP modes is 32 for sizeId = 0, 16 for sizeId = 1, and 12 for sizeId = 2. 2.16 Intra Mode Derivation on the Decoder Side In JEM - 2.0, the intra mode is extended from 35 modes in HEVC to 67 modes, and they are derived at the encoder and explicitly signaled to the decoder. In JEM - 2.0, a large amount of overhead is spent on intra mode coding. For example, in all intra coding configurations, the intra mode signaling overhead can be as high as 5% - 10% of the total bitrate. This paper proposes an intra mode derivation method on the decoder side to reduce the intra mode coding overhead while maintaining the prediction accuracy. To reduce the overhead of intra mode signaling, this paper proposes a decoder-side intra mode derivation (DIMD) method. In the proposed method, instead of explicitly signaling the intra mode, information is derived from the neighboring reconstructed samples of the current block at both the encoder and the decoder. There are two ways to use the intra mode derived by DIMD: 1) For a 2N×2N CU, when the corresponding CU-level DIMD flag is enabled, the DIMD mode is used as the intra mode for intra prediction; 2) For an N×N CU, the DIMD mode is used to replace a candidate in the existing MPM list to improve the efficiency of intra mode encoding and decoding. 2.16.1 Template-based intra mode derivation As Figure 20 shown, the target represents the current block (block size is N) for which the intra prediction mode is to be estimated. The template (represented by the pattern area in Figure 20 ) specifies a set of reconstructed samples that are used to derive the intra mode. The template size is expressed as the number of samples extending above and to the left of the target block within the template, i.e., L. In the current implementation, the template size used for 4×4 and 8×8 blocks is 2 (i.e., L = 2), and the template size used for 16×16 and larger blocks is 4 (i.e., L = 4). As defined in JEM-2.0, the reference of the template (represented by the dotted area in Figure 20 ) refers to the set of neighboring samples above and to the left of the template. Different from the template samples that always come from the reconstructed area, the reference samples of the template may not have been reconstructed when encoding / decoding the target block. In this case, the existing reference sample replacement algorithm of JEM-2.0 is used to replace the unavailable reference samples with available reference samples. For each intra prediction mode, DIMD calculates the sum of absolute differences (SAD) between the reconstructed template samples and their predicted samples obtained from the reference samples of the template. The intra prediction mode that produces the minimum SAD is selected as the final intra prediction model for the target block. 2.16.2 DIMD for intra 2N×2N CU For an intra 2N×2N CU, DIMD is used as an additional intra mode, which is adaptively selected by comparing the DIMD intra mode with the best normal intra mode (i.e., explicitly signaled). For each intra 2N×2N CU, a flag is signaled to indicate the usage of DIMD. If the flag is 1, the intra mode derived by DIMD is used to predict the CU; otherwise, DIMD is not applied, and the intra mode explicitly signaled in the bitstream is used to predict the CU. When DIMD is enabled, the chrominance components always reuse the same intra mode derived for the luminance component, i.e., the DM mode. In addition, for each CU decoded and encoded by DIMD, the blocks in the CU can adaptively select to derive their intra modes at the PU level or the TU level. Specifically, when the DIMD flag is 1, another CU-level DIMD control flag is signaled to indicate at which level DIMD is performed. If this flag is 0, it means that DIMD is performed at the PU level, and all TUs in the PU use the same derived intra mode for intra prediction; otherwise (i.e., the DIMD control flag is 1), it means that DIMD is performed at the TU level, and each TU in the PU derives its own intra mode. In addition, when DIMD is enabled, the number of angular directions increases to 129, and the DC mode and the planar mode remain unchanged. To accommodate the increased granularity of the angular intra modes, the accuracy of the intra interpolation filtering for DIMD-encoded / decoded CUs is increased from 1 / 32 pixel to 1 / 64 pixel. In addition, to use the derived intra mode of the DIMD-encoded / decoded CU as an MPM candidate for neighboring intra blocks, before using the 129 directions of the DIMD-encoded / decoded CU as MPMs, they are converted to "normal" intra modes (i.e., 65 angular intra directions). 2.16.3 DIMD for Intra N×N CUs In the proposed method, the intra mode of the intra N×N CU is always signaled. However, to improve the efficiency of intra mode encoding / decoding, the intra mode derived from DIMD is used as an MPM candidate for predicting the intra modes of the four PUs in the CU. To avoid increasing the overhead of MPM index signaling, the DIMD candidate is always placed at the first position in the MPM list, and the last existing MPM candidate mode is removed. In addition, a deduplication operation is performed so that if the DIMD candidate is redundant, it is not added to the MPM list. 2.16.4 Intra Mode Search Algorithm for DIMD To reduce the encoding / decoding complexity, a direct and fast intra mode search algorithm is used for DIMD. First, an initial estimation process is performed to provide a good starting point for the intra mode search. Specifically, an initial candidate list is created by selecting N fixed modes from the allowed intra modes. Then, the SAD is calculated for all candidate intra modes, and the intra mode that minimizes the SAD is selected as the starting intra mode. To achieve a good complexity / performance trade-off, the initial candidate list consists of 11 intra modes, including DC, planar, and every 4th mode among the 33 angular intra directions defined in HEVC, i.e., intra modes 0, 1, 2, 6, 10…30, 34. If the intra mode in the start frame is DC mode or planar mode, it is used as the DIMD mode. Otherwise, based on the start intra mode, a refinement process is then applied, where the best intra mode is identified through a single iteration search. It works by comparing the SAD values of three intra modes separated by a given search interval at each iteration and keeping the intra mode that minimizes the SAD. The search interval is then reduced to half, and the intra mode selected from the previous iteration is used as the center intra mode for the current iteration. For the current DIMD implementation with 129 angular intra directions, up to 4 iterations are used in the refinement process to find the best DIMD intra mode. 2.17 Intra mode derivation at the decoder side by calculating gradients of neighboring samples Three angular modes are selected from the gradient histogram (HoG) calculated from the neighboring pixels of the current block. Once these three modes are selected, their prediction values are calculated normally, and then their weighted average is used as the final prediction value of the block. To determine the weights, the corresponding magnitudes in the HoG are used for each of the three modes. The DIMD mode is used as an alternative prediction mode and is always checked in the FullRD mode. Some aspects of the current version of DIMD have been modified in signaling, HoG calculation, and prediction fusion. The purpose of this modification is to improve the codec performance and address the complexity issues (i.e., throughput of 4×4 blocks) raised during the last meeting. The following sections describe the modifications in each aspect. 2.17.1 Signaling Figure 21 Shows the order of parsing flags / indexes integrated with the proposed DIMD in VTM5. It can be seen that a single CABAC context is first used to parse the DIMD flag of the block, which is initialized to the default value 154. If flag == 0, the parsing continues normally. Otherwise (if the flag == 1), only the ISP index is parsed, and the following flags / indexes are presumed to be zero: BDPCM flag, MIP flag, MRL index. In this case, the entire IPM parsing is also skipped. During the parsing phase, when a regular non-DIMD block queries the IPM of its DIMD neighbor, the mode PLANAR_IDX is used as the virtual IPM of the DIMD block. 2.17.2 Texture analysis The texture analysis of DIMD includes gradient histogram (HoG) calculation ( Figure 22 ). The HoG calculation is performed by applying horizontal and vertical Sobel filters to the pixels in a template of width 3 around the block. However, if the upper template pixels fall into a different CTU, then they will not be used for texture analysis. Once computed, the IPMs corresponding to the two highest histogram bins are selected for the block. In the previous version, all pixels in the middle row of the template participated in the HoG computation. However, the current version improves the throughput of the process by applying the Sobel filter more sparsely over 4x4 blocks. To this end, only one pixel to the left and one pixel above are used. This is as Figure 22 shown. In addition to reducing the number of operations for gradient computation, this feature also simplifies the selection of the best 2 modes from the HoG, since the resulting HoG cannot have more than two non-zero magnitudes. 2.17.3. Prediction Fusion The current method uses the fusion of three prediction values for each block. However, the selection of the prediction modes is different, and the combined intra prediction method proposed in [2] is used, where the planar mode is considered for combination with other modes when computing the candidates for intra prediction. In the current version, the two IPMs corresponding to the two highest HoG bins are combined with the planar mode. The prediction fusion is applied as a weighted average of the above three prediction values. To this end, the weight of the plane is fixed to 21 / 64 (~1 / 3). Then, the remaining 43 / 64 (~2 / 3) of the weight is shared proportionally between the two HoG IPMs according to the magnitude of their HoG bins. Figure 23 This shows the process. 2.18 Template-based Intra-mode Derivation (TIMD) This paper proposes a template-based intra-mode derivation (TIMD) method using the MPM, where the TIMD modes are derived from the MPM using neighboring templates. The TIMD modes are used as an additional intra prediction method for the CU. 2.18.1 TIMD Mode Derivation For each intra prediction mode in the MPM, the SATD between the prediction of the template and the reconstructed samples is computed. The intra prediction mode with the minimum SATD is selected as the TIMD mode and is used for the intra prediction of the current CU. The position-dependent intra prediction combination (PDPC) is included in the derivation of the TIMD mode. 2.18.2 TIMD Signaling A flag is signaled in the sequence parameter set (SPS) to enable / disable the proposed method. When the flag is true, a CU-level flag is signaled to indicate whether the proposed TIMD method is used. The TIMD flag is signaled after the MIP flag. If the TIMD flag is equal to true, the remaining syntax elements related to the luma intra prediction mode, including MRL, ISP, and the normal parsing stage for the luma intra prediction mode, are skipped. 2.18.3 Interaction with New Coding Tools The planar DIMD method with prediction fusion is integrated into EE2. When the EE2 DIMD flag is true, the proposed TIMD flag is not signaled through and is set to false. Similar to PDPC, gradient PDPC is also included in the derivation of the TIMD mode. When the secondary MPM is enabled, both the primary MPM and the secondary MPM are used to derive the TIMD mode. The 6-tap interpolation filter is not used in the derivation of the TIMD mode. 2.18.4 Modifications to the MPM list construction in the derivation of the TIMD mode During the construction of the MPM list, the intra prediction mode of neighboring blocks is derived as planar when they are inter-coded. To improve the accuracy of the MPM list, when neighboring blocks are inter-coded, the propagated intra prediction mode is derived using the motion vector and the reference picture and is used in the construction of the MPM list. This modification is only used in the derivation of the TIMD mode. 2.18.5 TIMD with fusion This paper proposes that for the intra modes derived using the TIMD method, instead of only selecting the mode with the minimum SATD cost, the top two modes with the minimum SATD cost are selected, then they are fused through weights, and this weighted intra prediction is used to encode and decode the current CU. The costs of the two selected modes are compared with a threshold, and the cost factor 2 is applied in the test as follows: costMode2 < 2 * costMode1. If this condition is true, fusion is applied; otherwise, only mode1 is used. The weights of the modes are calculated according to their SATD costs as follows: weight1 = costMode2 / (costMode1 + costMode2), weight2 = 1 - weight1. 2.19 Convolutional cross-component model (CCCM) for intra prediction It is proposed to apply the convolutional cross-component model (CCCM) to predict chroma samples from the reconstructed luma samples in a similar spirit to that accomplished by the current CCLM mode. Similar to CCLM, when chroma subsampling is used, the reconstructed luma samples are downsampled to match the lower-resolution chroma grid. Similarly, similar to CCLM, there is an option to use a single model or multi-model variant of CCCM. The multi-model variant uses two models, one model derived for samples above the average luminance reference value, and the other model derived for the remaining samples (following the spirit of the CCLM design). The multi-model CCCM mode can be selected for a PU with at least 128 available reference samples. 2.19.1 Convolution Filter The proposed convolutional 7-tap filter consists of a 5-tap plus-shaped spatial domain component, a non-linear term, and a bias term. The input of the 5-tap spatial domain component of the filter consists of the central (C) luminance sample, which is co-located with the chrominance sample to be predicted and its upper / north (N), lower / south (S), left / west (W), and right / east (E) neighbors, as follows Figure 24 shown below. The non-linear term P is represented as a power of 2 of the central luminance sample C and is scaled to the range of the sample values of the content: P = (C * C + midVal) >> bitDepth. That is, for 10-bit content, it is calculated as: P = (C * C + 512) >> 10. The bias term B represents a scalar offset between the input and the output (similar to the offset term in CCLM) and is set to the middle chrominance value (512 for 10-bit content). The output of the filter is calculated as the convolution between the filter coefficients c i and the input values, and is clipped to the range of valid chrominance samples: predChromaVal = c0C + c1N + c2S + c3E + c4W + c5P + c6B. 2.19.2 Calculation of Filter Coefficients The filter coefficients c i are calculated by minimizing the MSE between the predicted chrominance samples and the reconstructed chrominance samples in the reference region. Figure 25 The reference region consisting of 6 rows of chrominance samples above and to the left of the PU is shown. The reference region extends one PU width to the right and one PU height below the PU boundary. The region is adjusted to include only the available samples. The extension of the region needs to be shown in blue to support the "side samples" of the plus-shaped spatial filter, and the extension is filled when in the unavailable region. MSE minimization is performed by computing the autocorrelation matrix for the luminance input and the cross-correlation vector between the luminance input and the chrominance output. The autocorrelation matrix is LDL-factorized, and the final filter coefficients are computed using back substitution. This process generally follows the computation of the ALF filter coefficients in ECM, but LDL-factorization is chosen instead of Cholesky factorization to avoid using square root operations. The proposed method uses only integer arithmetic. 2.19.3 Bitstream Signaling The use of this mode is signaled by a PU-level flag encoded / decoded by CABAC. A new CABAC context is included to support this. When entering the signaling, CCCM is considered a sub-mode of CCLM. That is, the CCCM flag is signaled only when the intra prediction mode is LM_CHROMA_IDX (to enable single-mode CCCM) or MMLM_CHROMA_IDX (to enable multi-model CCCM). 2.20 Gradient Linear Model (GLM) Compared with CCLM, instead of the downsampled luminance values, GLM uses the luminance sample gradients to derive the linear model. Specifically, when applying GLM, the input to the CCLM process (i.e., the downsampled luminance sample L) is replaced by the luminance sample gradient G. The other parts of CCLM (e.g., parameter derivation, prediction sample linear transformation) remain unchanged. C = α·G + β For signaling, when the CCLM mode is enabled for the current CU, two flags are signaled separately for the Cb and Cr components to indicate whether GLM is enabled for each component; if GLM is enabled for a component, then a syntax element is further signaled to select one of the 4 gradient filters for gradient calculation. · Four gradient filters are enabled for GLM, as Figure 26 shown. 2.21 Gradient and Location Based Convolutional Cross-Component Model for Intra Prediction (GL-CCCM) The proposed GL-CCCM method uses gradient and location information instead of the 4 spatially adjacent samples in the CCCM filter. The GL-CCCM filter for prediction is: predChromaVal = c0C + c1G y + c2G x + c3Y + c4X + c5P + c6B where G y and G x are the vertical and horizontal gradients, respectively, and are computed as: G y=(2N + NW + NE)-(2S + SW + SE) G x =(2W + NW + SW)-(2E + NE + SE) In addition, the Y and X parameters are the vertical and horizontal positions of the central luma sample, and they are calculated relative to the upper-left coordinate of the block. The remaining parameters are the same as those of the CCCM tool. The reference region for parameter calculation is the same as that of the CCCM method. Bitstream signaling Use CABAC encoding and decoding to signal the PU basic flag through the use of the signaling mode. Include a new CABAC context to support this. When entering the signaling, GL-CCCM is considered a sub-mode of CCCM. That is, the GL-CCCM flag is signaled only when the original CCCM flag is true. Encoder operation The encoder performs two new RD checks in the chroma prediction mode loop, one for checking the single-model GL-CCCM mode and one for checking the multi-model GL-CCCM mode. 2.22 CCCM using non-downsampled luma samples 2.22.1 Block level In this paper, a CCCM using non-downsampled luma samples is proposed, where the chroma samples are directly predicted from the original reconstructed luma samples, i.e., without downsampling. As Figure 28 shown, the proposed CCCM filter consists of a 6-tap spatial domain term, two non-linear terms, and a bias term. The 6-tap spatial domain term corresponds to 6 neighboring luma samples (i.e., L0, L1, …, L5) of the chroma sample to be predicted (i.e., C). where α i is the coefficient associated with L i and β is the offset. Similar to the existing CCCM design, up to 6 rows / columns of chroma samples above and to the left of the current CU are applied to derive the filter coefficients. The filter coefficients are derived based on the same LDL decomposition method used in CCCM. In this paper, in addition to the existing CCCM model, the proposed method is signaled as an additional CCCM model. For signaling, when CCCM is selected, a single flag is signaled and used for both chroma components to indicate whether the default CCCM model or the proposed CCCM model is applied. 2.22.2 High-level control Downsampling of the luminance component may not be optimal for CCCM model derivation for content with sharp details such as SCC content. In this paper, it is proposed to disable luminance downsampling and directly derive and apply the model to the non-downsampled samples. If downsampling is not applied, the CCCM model shape is a rhombus 5×5. The SPS flag is signaled to indicate whether luminance downsampling is applied for CCCM. 2.23 Spatial GPM (SGPM) In spatial GPM, a candidate list including partition divisions and two intra prediction modes is constructed. Up to 11 MPMs of the intra prediction modes are used to form combinations, and the length of the candidate list is set to be equal to 16. The selected candidate index is signaled. Figure 29 Spatial GPM candidates are shown. Use Figure 29 The list is reordered using the template shown. The GPM blending process is not used in the template, and the SAD between the prediction and reconstruction of the template is used for sorting. Figure 30 The GPM template is shown. Figure 31 GPM blending is shown. The SGPM mode is applied to blocks whose width and height satisfy the same constraints as in inter-frame GPM. Consider the following items: ● Spatial GPM partition mode: 26 predefined modes. Adaptive derivation algorithm based on horizontal and vertical gradient ratios. ● Intra prediction mode selection: IPM lists with and without TIMD: For each partition mode, an IPM list is derived for each part using the intra-inter GPM list derivation. The IPM list size is 3. In the list, the TIMD derivation mode is replaced by 2 derivation modes with horizontal and vertical orientations (using the top or left template) or the TIMD derivation mode is excluded. MPM list: A unified MPM list (up to 11 elements) is used for all partition modes. ● Template size (left and above): 1 or 4 ● Extended block size: Spatial GPM is extended to be further applied to 4x8, 8x4, 4x16, and 16x4 blocks, which can be described as 4 <= width <= 64, 4 <= height <= 64, width < height * 8, height < width * 8, width * height >= 32. ● Adaptive blending: Adaptive blending is tested for spatial GPM, where the blending depth τ is derived as follows: ■ If min(width, height) == 4, select 1 / 2τ; ■ Otherwise, if min(width, height) == 8, select τ; ■ Otherwise, if min(width, height) == 16, select 2τ; ■ Otherwise, if min(width, height) == 32, select 4τ; ■ Otherwise, select 8τ. 2.24 Signaling of Cross-Component Prediction Modes in ECM Figure 32 Shows the binarization of cross-component prediction modes in ECM. Figure 32 "CCLM" in can be replaced by "CCCM". In ECM-7, cross-component modes include CCLM, CCLM-L, CCLM-T, MM-CCLM, MM-CCLM-L, MM-CCLM-T and CCCM, CCCM-L, CCCM-T, MM-CCCM, MM-CCCM-L, MM-CCCM-T. A flag is signaled to determine whether it is a CCCM mode or a CCLM mode. Truncated unary code is applied to indicate Figure 32 the CCLM mode or CCCM mode shown in. CCLM or CCCM: 0; MM-CCLM or MM-CCCM: 10; CCLM-L or CCCM-L: 110; CCLM-T or CCCM-T: 1110; MM-CCLM-L or MM-CCCM-L: 11110; MM-CCLM-T or MM-CCCM-T: 11110. 3. Problems 1. Cross-component prediction may introduce discontinuities. 2. The signaling of cross-component prediction may not be efficient. 4. Detailed Solutions The following solutions should be considered as examples to explain general concepts. These solutions should not be interpreted in a narrow sense. In addition, these solutions can be combined in any way. In the following discussion, CCCM may refer to the original CCCM mode, or may refer to a variant of CCCM, such as CCCM-L, CCCM-T, MM-CCCM, MM-CCCM-L, MM-CCCM-T. In the following discussion, CCLM can refer to the original CCLM mode, or can refer to variants of CCLM, such as CCLM-L, CCLM-T, MM-CCLM, MM-CCLM-L, MM-CCLM-T, etc. Filtering for cross-component prediction 1. It is proposed that cross-component prediction in a block (such as MM-CCLM or MM-CCCM) can be modified before being further processed. a. In one example, cross-component prediction in a block can be filtered before being further processed. 1) In one example, the predicted sample points represented as F(x,y) after filtering can be derived as a weighted average of n predicted sample points, represented as P(x’,y’), before filtering. In equation form, where W k is the weighting value on the kth sample point. a) In one example, where W k , offset, and S are integers. 2) In one example, F(x,y) = (8P(x,y) + P(x-1,y-1) + P(x,y-1) + P(x+1,y-1) + P(x-1,y) + P(x+1,y) + P(x-1,y+1) + P(x,y+1) + P(x+1,y+1) + 8) >> 4. 3) In one example, F(x,y) = (4P(x,y) + P(x,y-1) + P(x-1,y) + P(x+1,y) + P(x,y+1) + 4) >> 3. 4) In one example, F(x,y) = (2P(x,y) + P(x,y-1) + P(x,y+1) + 2) >> 2. 5) In one example, F(x,y) = (2P(x,y) + P(x-1,y) + P(x+1,y) + 2) >> 2. 6) Figure 33 Several examples of filter taps are shown. b. In one example, the same modification method (such as filtering) can be applied to different color components, such as Cb and Cr. c. In one example, different modification methods (such as different filtering methods) can be applied to different color components, such as Cb and Cr. d. In one example, sample point filling can be performed at the block boundary. i. For example, repetitive filling can be applied at the boundary. Figure 34An example of repeated filling is shown. The shaded samples are filled. The "arrow" indicates "copy". e. In one example, filtering may not be performed on samples outside the current block for at least one tap sample. f. In one example, an alternative filter shape may be applied to samples outside the current block for at least one tap sample of the original filter shape. With the alternative filter shape, samples outside the current block are excluded as filter tap samples. 2. It is proposed that cross-component prediction in a block can be modified depending on at least one reconstructed sample before being further processed. a. In one example, at least one reconstructed sample can be used to filter cross-component prediction samples in a block. b. In one example, the reconstructed sample can be an adjacent neighboring sample or a non-adjacent neighboring sample. c. In one example, the reconstructed sample can be a temporal reference sample in a reference block. d. In one example, the reconstructed sample can have the same color component or different color components. e. In one example, samples in the first N (e.g., N = 1) rows of the current block can be filtered using neighboring reconstructed samples above the current block. i. For example, F(x,0) = (3P(x,0) + R(x,-1)) >> 2, where R(x,-1) is the reconstructed sample. f. In one example, samples in the first N (e.g., N = 1) columns of the current block can be filtered using neighboring reconstructed samples to the left of the current block. i. For example, F(0,y) = (3P(0,y) + R(-1,y)) >> 2, where R(-1,y) is the reconstructed sample. g. Figures 35A to 35B Two examples of filtering with neighboring reconstructed samples are shown. The "arrow" indicates "filtering". h. In one example, the prediction samples are filtered using the reconstructed samples only when the reconstructed samples are available. i. In one example, if the reconstructed sample is not available, the prediction samples are filtered with filled samples. ii. In one example, if the reconstructed sample is not available, the taps associated with the reconstructed sample are not used to filter the prediction samples. i. In one example, the prediction samples can be filtered using the reconstructed samples and / or prediction samples and / or filled samples. j. Figure 36 An example of filtering a prediction block is shown. The filter window is 3×3, as Figure 33As shown, depending on the sample position, reconstructing samples, predicted samples, and filled samples may involve a filtering process for the samples. 3. In one example, a modified (e.g., filtered) predicted sample can be used to modify (e.g., filter) another predicted sample that has not been modified (e.g., filtered). 4. In one example, position-dependent prediction combination (PDPC) can be applied to chrominance intra-coded blocks. a. PDPC is applied if the block is coded using a cross-component prediction mode. 5. In one example, whether to modify (e.g., filter) cross-component prediction in a block can be signaled as a syntax element (SE). a. For example, the SE is signaled in a conditional manner. i. For example, the SE is signaled only when the mode of the current block is a cross-component prediction mode. SE. ii. For example, the SE is signaled only when the mode of the current block is MM-CCLM or MM-CCCM. iii. For example, the SE is signaled only when the mode of the current block is MM-CCLM, MM-CCLM-L, MM- CCLM-T or MM-CCCM, MM-CCCM-T, MM-CCCM-L. 6. In one example, when cross-component prediction is used in a merge mode, cross-component prediction can be modified (e.g., filtered). a. For the merge mode, the predicted value can be generated by at least two prediction methods, where at least one prediction method is cross-component prediction, such as CCLM or CCCM. More fusion modes for cross-component prediction 7. It is proposed that the predicted value can be generated by at least two prediction methods, where at least one prediction method is cross-component prediction, such as CCLM or CCCM, and at least one of them is inter-frame prediction. a. In one example, the predicted value can be generated as a weighted sum of at least two prediction methods. b. In one example, the predicted value of a chrominance block can be generated by at least two prediction methods, where at least one of the prediction methods is cross-component prediction, such as CCLM or CCCM or MM-CCLM or MM-CCCM, and when the block is coded using the combined intra-inter prediction (CIIP) mode, at least one of the prediction methods is inter-frame prediction. 8. It is proposed that the predicted value can be generated by at least two prediction methods, where at least two are cross-component prediction, such as CCLM or CCCM. a. In one example, the predicted value can be generated as a weighted sum of at least two prediction methods. b. The two prediction methods can be any combination of {CCLM, MM-CCLM, CCLM-L, CCLM-T, MM-CCLM-L, MM-CCLM-T, CCCM, MM-CCCM, CCCM-L, CCCM-T, MM-CCCM-L, MM-CCCM-T}. 9. It is proposed that SGPM can be applied to chrominance components, such as Cb / Cr. a. In one example, the partitioning method (or weighting method) can be the same for Cb and Cr. b. In one example, the partitioning method (or weighting method) can be different for Cb and Cr. c. In one example, the partitioning method (or weighting method) for Cb and / or Cr can share the same method with luminance. d. In one example, the partitioning method (or weighting method) for Cb and / or Cr can be different from the partitioning method of luminance. i. The partitioning method (or weighting method) for Cb and / or Cr can be signaled using at least one syntax element (SE). ii. The partitioning method (or weighting method) for Cb and / or Cr can be derived without signaling the SE. e. In one example, at least one prediction method used for chrominance in SGPM can be cross-component prediction, such as CCLM / CCCM / MM-CCLM / MM-CCCM / etc. Signaling for cross-component prediction 10. It is proposed that CCLM-L, CCLM-T, MM-CCLM-L, and MM-CCLM-T (or CCCM-L, CCCM-T, MM-CCCM-L, and MM-CCCM-T) can be signaled differently from the way of rounding-based unary coding. a. In one example, a first flag can be signaled to indicate whether to use the left mode (CCLM-L, MM-CCLM-L, or CCCM-L, MM-CCCM-L) or the above mode (CCLM-T, MM-CCLM-T, or CCCM-T, MM-CCCM-T). b. In one example, a second flag can be signaled to indicate whether to use the single model mode (CCLM-L, CCLM-T, or CCCM-L, CCCM-T) or the multi-model mode (MM-CCLM-L, MM-CCLM-T, or MM-CCCM-L, MM-CCCM-T). c. In one example, the first flag or the second flag can be encoded and decoded using at least one context model. i. In one example, the context model can be determined by encoding and decoding information of neighboring blocks (such as the mode information of neighboring blocks). ii. In one example, the context model for the second flag can depend on the first flag. iii. In one example, the context model for the first flag can depend on the second flag. d. In one example, the first flag or the second flag can be encoded and decoded using bypass encoding and decoding. e. In one example, the first flag can be encoded and decoded before the second flag. f. In one example, the second flag can be encoded and decoded before the first flag. g. Figures 37A to 37B Two examples of the proposed encoding and decoding tree are shown. Figures 37A to 37B "CCLM" in can be replaced by "CCCM". h. In one example, the first flag or the second flag can be signaled in a conditional manner. i. Only when the indication mode is CCLM-L, CCLM-T, MM-CCLM-L, and MM- CCLM-T (or CCCM-L, CCCM-T, MM-CCCM-L, and MM-CCCM-T) is the first flag or the second flag signaled. ii. The first flag is signaled only when both the left neighboring block and the upper neighboring block are available. iii. The second flag is signaled only when either the left neighboring block or the upper neighboring block is available. General aspects 11. The above-disclosed syntax elements can be binarized into flags, fixed-length codes, EG(x) codes, unary codes, truncated unary codes, truncated binary codes, etc. It can be signed or unsigned. 12. The above-disclosed syntax elements can be encoded and decoded using at least one context model. Or it can be bypass encoded and decoded. 13. The above-disclosed syntax elements can be signaled in a way. a. The SE is signaled only when the corresponding function is applicable. 14. The syntax elements disclosed above can be signaled at the block level / sequence base / group of pictures base / picture level / strip level / slice group level, for example, in the coding / decoding structures of CTU / CU / TU / PU / CTB / CB / TB / PB or sequence header / picture header / SPS / VPS / DPS / DCI / PPS / APS / strip header / slice group header. 15. Whether and / or how to apply the methods disclosed above can be signaled at the block level / sequence level / group of pictures level / picture level / strip level / slice group level, for example, in the coding / decoding structures of CTU / CU / TU / PU / CTB / CB / TB / PB or sequence header / picture header / SPS / VPS / DPS / DCI / PPS / APS / strip header / slice group header. 16. Whether and / or how to apply the methods disclosed above can depend on the information to be coded / decoded, such as block size, color format, single-tree / double-tree partitioning, color component, strip / picture type. 17. The proposed methods disclosed in this document can be used in other coding / decoding tools that require chroma fusion.

[0101] More details of embodiments of the present disclosure related to cross-component prediction will be described below. The embodiments of the present disclosure should be considered as examples for explaining the general concepts and should not be interpreted in a narrow sense. In addition, these embodiments can be applied individually or in combination in any way.

[0102] As used herein, the term "block" can represent a color component, sub-picture, picture, strip, slice, coding tree unit (CTU), CTU row, CTU group, coding unit (CU), prediction unit (PU), transform unit (TU), coding tree block (CTB), coding block (CB), prediction block (PB), transform block (TB), sub-block of a video block, sub-region within a video block, a video processing unit including a plurality of samples / pixels, etc. The block can be rectangular or non-rectangular.

[0103] Figure 38 A flowchart of a method 3800 for video processing according to some embodiments of the present disclosure is shown. Method 3800 can be implemented during the conversion between the current video block of a video and the bitstream of the video. As Figure 38 shown, method 3800 starts at 3802, where the prediction for the current video block is adjusted. The prediction is determined based on a cross-component prediction scheme.

[0104] In some embodiments, the prediction for the current video block can be adjusted by filtering the prediction. Alternatively, the prediction for the current video block can be adjusted by upsampling the prediction. In some embodiments, the prediction for the current video block can be adjusted by downsampling the prediction. It should be understood that the possible implementations of the adjustments described herein are merely illustrative and should not be construed as limiting the present disclosure in any way.

[0105] In some embodiments, the cross-component prediction scheme can include a cross-component linear model (CCLM) and / or a variant of the CCLM, such as a multi-model CCLM (MM-CCLM), CCLM left (CCLM-L), CCLM top (CCLM-T), MM-CCLM-L, MM-CCLM-T, etc. Additionally or alternatively, the cross-component prediction scheme can include a convolutional cross-component model (CCCM) and / or a variant of the CCCM, such as a multi-model CCCM (MM-CCCM), CCCM left (CCCM-L), CCCM top (CCCM-T), MM-CCCM-L, MM-CCCM-T, etc.

[0106] At 3804, a transformation is performed based on the adjusted prediction. In some embodiments, the transformation can include encoding the current video block into a bitstream. Alternatively or additionally, the transformation can include decoding the current video block from the bitstream. It should be understood that the above description and / or examples are described for illustrative purposes only. The scope of the present disclosure is not limited in this regard.

[0107] In view of the above, the prediction for a video block determined based on a cross-component prediction scheme is adjusted before being further processed. Compared with traditional solutions, the proposed method can advantageously improve the coding and decoding quality.

[0108] In some embodiments, the prediction for the current video block can include a first prediction sample, and the adjusted prediction can include a filtered first prediction sample, which is obtained by filtering the first prediction sample. By way of example and not limitation, the filtered first prediction sample can be determined based on a weighted sum of multiple prediction samples in the prediction for the current video block. By means of the filtering process described herein, the discontinuities introduced by the cross-component prediction scheme can be reduced, and thus the coding and decoding quality can be improved.

[0109] In an example embodiment, the filtered first prediction sample can be determined based on: where F(x,y) represents the filtered first prediction sample at coordinates (x,y), L represents the number of multiple prediction samples, P(x k ,yk ) represents the k-th prediction sample among a plurality of prediction samples, and W k represents the weighting value for the k-th prediction sample.

[0110] In another exemplary embodiment, the filtered first prediction sample may be determined based on the following: where F(x, y) represents the filtered first prediction sample at coordinates (x, y), L represents the number of prediction samples, and P(x k , y k ) represents the k-th prediction sample among a plurality of prediction samples, and W k represents the weighting value for the k-th prediction sample, and each of offset and S is an integer.

[0111] In one example, the filtered first prediction sample may be determined based on the following: F(x, y) = (8P(x, y) + P(x - 1, y - 1) + P(x, y - 1) + P(x + 1, y - 1) + P(y - 1, y) + P(x + 1, y) + P(x - 1, y + 1) + P(x, y + 1) + P(x + 1, y + 1) + 8) >> 4 where F(x, y) represents the filtered first prediction sample at coordinates (x, y), and P(s, t) represents the prediction sample at coordinates (s, t) among a plurality of prediction samples.

[0112] In another example, the filtered first prediction sample may be determined based on the following: F(x, y) = (4P(x, y) + P(x, y - 1) + P(x - 1, y) + P(x + 1, y) + P(x, y + 1) + 4) >> 3 where F(x, y) represents the filtered first prediction sample at coordinates (x, y), and P(s, t) represents the prediction sample at coordinates (s, t) among a plurality of prediction samples.

[0113] In another example, the filtered first prediction sample may be determined based on the following: F(x, y) = (2P(x, y) + P(x, y - 1) + P(x, y + 1) + 2) >> 2 where F(x, y) represents the filtered first prediction sample at coordinates (x, y), and P(s, t) represents the prediction sample at coordinates (s, t) among a plurality of prediction samples.

[0114] In yet another example, the filtered first prediction sample may be determined based on the following: F(x,y) = (2P(x,y) + P(x - 1,y) + P(x + 1,y) + 2) >> 2 where F(x,y) represents the filtered first prediction sample at coordinate (x,y), and P(s,t) represents the prediction sample at coordinate (s,t) among a plurality of prediction samples.

[0115] In some embodiments, the shape of the filter for filtering predictions can be square, as shown in sub - figure 3301 of Figure 33 Shown. Alternatively, the shape of the filter for filtering predictions can be cross - shaped, as shown in sub - figure 3302 of Figure 33 Shown. In some other embodiments, the shape of the filter for filtering predictions can be a vertical line, as shown in sub - figure 3303 of Figure 33 Shown. In still some other embodiments, the shape of the filter for filtering predictions can be a horizontal line, as shown in sub - figure 3304 of Figure 33 Shown.

[0116] In some embodiments, different color components of the current video block can be adjusted (e.g., filtered) based on the same adjustment scheme. Alternatively, different color components of the current video block can be adjusted based on different adjustment schemes (e.g., different filtering schemes). By way of example and not limitation, different color components can include the Cb component and the Cr component. For example, the Cb component can represent the blue - difference chrominance component, while the Cr component can represent the red - difference chrominance component. In another example, the Cb component and the Cr component can be replaced by the U component and the V component. It should be understood that the Cb component and / or the Cr component can represent any other suitable color component. The scope of the present disclosure is not limited in this regard.

[0117] In some embodiments, a padding process can be applied to at least one sample at the boundary of the current video block. By way of example, the padding process can include repetitive padding. In repetitive padding, the value for one of the at least one sample can be determined as the value for a sample in the current video block (e.g., the nearest sample, etc.). It should be understood that any other suitable padding process (e.g., mirror padding, etc.) can also be applied.

[0118] In some embodiments, if at least one sample used for filtering a second sample in the current video block is outside the current video block, the second sample may not be filtered. Alternatively, if at least one sample for the filter shape used for filtering the second sample in the current video block is outside the current video block, an additional filter shape can be used to filter the second sample. In this case, if one or more samples for the additional filter shape are outside the current video block, the one or more samples are excluded from use.

[0119] In some embodiments, the prediction for the current video block may be adjusted based on at least one reconstructed sample of at least one neighboring block of the current video block. For example, the prediction for the current video block may be adjusted by filtering the prediction using at least one reconstructed sample.

[0120] In some embodiments, one of the at least one reconstructed samples may be adjacent to the current video block. Alternatively or additionally, one of the at least one reconstructed samples may not be adjacent to the current video block. In some other embodiments, one of the at least one reconstructed samples may be a temporal reference sample in a reference block of the current video block.

[0121] In some embodiments, at least one of the reconstructed samples may have the same color component as the prediction sample to be adjusted. Alternatively, at least one of the reconstructed samples may have a different color component from the prediction sample to be adjusted.

[0122] In some embodiments, at least one of the reconstructed samples may include a neighboring reconstructed sample above the current video block. Additionally, the first N rows of prediction samples of the current video block may be filtered using the neighboring reconstructed sample, and N may be an integer, such as 1, 2, etc.

[0123] For example, the topmost row (e.g., the uppermost row) of prediction samples of the current video block may include a third prediction sample, and the third prediction sample may be filtered based on the following: F(x,0) = (3P(x,0) + R(x,-1)) >> 2 where F(x,0) represents the filtered third prediction sample at coordinate (x,0), P(x,0) represents the third prediction sample, and R(x,-1) represents the neighboring reconstructed sample above the third prediction sample.

[0124] In some embodiments, at least one of the reconstructed samples may include a neighboring reconstructed sample to the left of the current video block. Additionally, the first M columns of prediction samples of the current video block may be filtered using the neighboring reconstructed sample. M may be an integer, such as 1, 2, etc.

[0125] In some embodiments, the leftmost column (e.g., the leftmost column) of prediction samples of the current video block may include a fourth prediction sample, and the fourth prediction sample may be filtered based on the following: F(0,y) = (3P(0,y) + R(-1,y)) >> 2 where F(0,y) represents the filtered fourth prediction sample at coordinate (0,y), P(0,y) represents the fourth prediction sample, and R(-1,y) represents the neighboring reconstructed sample to the left of the fourth prediction sample.

[0126] In some embodiments, if a first reconstructed sample among at least one reconstructed sample is available, the predicted samples of the current video block can be filtered using the first reconstructed sample. If the first reconstructed sample is not available, the predicted samples of the current video block can be filtered without the first reconstructed sample. In such a case, the predicted samples of the current video block can be filtered using padding samples instead of the first reconstructed sample.

[0127] In some embodiments, the predicted samples of the current video block can be filtered using reconstructed samples, additional predicted samples, and / or padding samples, as Figure 36 shown. In Figure 36 it, the hollow circles can represent the predicted samples of the current video block. For example, based on the positions of the predicted samples, reconstructed samples, additional predicted samples, and / or padding samples can be used to filter the predicted samples of the current video block.

[0128] In some embodiments, the bitstream can include a syntax element indicating whether to adjust the prediction for the current video block. Alternatively, the syntax element indicating whether to adjust the prediction for the current video block can be indicated in the bitstream in a conditional manner. In one example, if the mode of the current video block includes a cross-component prediction mode, the syntax element can be indicated in the bitstream.

[0129] Alternatively, if the mode of the current video block includes one of the following, the syntax element can be indicated in the bitstream: multi-model cross-component linear model (MM-CCLM), or multi-model convolutional cross-component model (MM-CCCM). In another example, if the mode of the current video block includes one of the following, the syntax element can be indicated in the bitstream: MM-CCLM, MM-CCLM-L, MM-CCLM-T, MM-CCCM, MM-CCCM-T, or MM-CCCM-L. It should be understood that the above examples are described for illustrative purposes only. The scope of the present disclosure is not limited in this regard.

[0130] In some embodiments, if the prediction for the current video block is used in a fusion mode, the prediction for the current video block can be adjusted. For example, the target prediction for the current video block in the fusion mode can be determined by fusing the adjusted prediction with at least one additional prediction for the current video block. By way of example and not limitation, the at least one additional prediction can be determined based on one or more prediction schemes of a cross-component prediction scheme.

[0131] In some embodiments, the adjusted prediction samples in the adjusted prediction for the current video block are used to adjust additional prediction samples. In some other embodiments, the first video block of the video is a chrominance intra-coded block, and position-dependent prediction combination (PDPC) may be applied to the chrominance intra-coded block. Additionally, the first video block may be coded using a cross-component prediction scheme. That is, if the block is coded using a cross-component prediction mode, PDPC is applied.

[0132] In some embodiments, the target prediction for a second video block of the video may be generated based on multiple prediction schemes. By way of example and not limitation, the target prediction for the second video block may be generated based on a weighted sum of multiple candidate predictions for the second video block. The multiple predictions may be determined based on multiple schemes.

[0133] In some embodiments, the multiple prediction schemes may include at least one cross-component prediction scheme and at least one inter-frame prediction scheme. Additionally, the second video block may be a chrominance block coded using a combined intra-inter prediction (CIIP) mode.

[0134] In some alternative embodiments, the multiple prediction schemes may include at least two cross-component prediction schemes. By way of example and not limitation, the at least two cross-component prediction schemes may include a combination of at least two of the following: CCLM, MM-CCLM, CCLM-L, CCLM-T, MM-CCLM-L, MM-CCLM-T, CCCM, MM-CCCM, CCCM-L, CCCM-T, MM-CCCM-L, or MM-CCCM-T.

[0135] In some embodiments, a spatial geometry partitioning mode (SGPM) may be applied to at least one chrominance component of a third video block of the video. For example, the at least one chrominance component may include a Cb component and / or a Cr component. Additionally, at least one prediction scheme used in the SGPM may include a cross-component prediction scheme.

[0136] In some embodiments, the partitioning scheme or the weighting scheme of the SGPM for the Cb component may be the same as that for the Cr component. Alternatively, the partitioning scheme or the weighting scheme of the SGPM for the Cb component may be different from that for the Cr component.

[0137] In some embodiments, the partitioning scheme or the weighting scheme of the SGPM for one chrominance component in the at least one chrominance component may be the same as that for the luminance component. Alternatively, the partitioning scheme or the weighting scheme of the SGPM for one chrominance component in the at least one chrominance component may be different from that for the luminance component.

[0138] In some embodiments, the bitstream may include at least one syntax element that indicates a partitioning scheme or a weighting scheme for an SGPM for one of at least one chrominance component. Alternatively, the partitioning scheme or the weighting scheme for an SGPM for one of at least one chrominance component may be determined and not present in the bitstream.

[0139] In some embodiments, multiple cross-component prediction schemes may be indicated in the bitstream in a manner different from truncation-unary coding / decoding. In one example, the multiple cross-component prediction schemes may include CCLM-L, CCLM-T, MM-CCLM-L, and MM-CCLM-T. In another example, the multiple cross-component prediction schemes may include CCCM-L, CCCM-T, MM-CCCM-L, and MM-CCCM-T. It should be understood that the above examples are described for illustrative purposes only. The scope of the present disclosure is not limited in this regard.

[0140] In some embodiments, the bitstream may include at least one of the following: a first indication indicating whether a left mode or an above mode is used; or a second indication indicating whether a single-model mode or a multi-model mode is used. The first indication and / or the second indication may be coded / decoded using at least one context model. In one example, the at least one context model may be determined based on coding / decoding information of neighboring blocks of a current video block. Alternatively, the context model for coding / decoding the first indication may depend on the context model for coding / decoding the second indication, or the context model for coding / decoding the second indication may depend on the context model for coding / decoding the first indication.

[0141] In some alternative embodiments, the first indication or the second indication may be coded / decoded using bypass coding / decoding. In some embodiments, the first indication may be coded / decoded before the second indication. Alternatively, the second indication may be coded / decoded before the first indication.

[0142] In some embodiments, each of the first indication and the second indication may be a bit in a bit string that indicates one of the multiple cross-component prediction schemes. In Figure 37A the example shown, CCLM may be indicated by the bit string 0, MM_CCLM may be indicated by the bit string 10, CCLM-L may be indicated by the bit string 1100, CCLM-T may be indicated by the bit string 1101, MM-CCLM-L may be indicated by the bit string 1110, and MM-CCLM-T may be indicated by the bit string 1111. In this example, the third bit in the bit string corresponds to the second indication, and the fourth bit in the bit string corresponds to the first indication.

[0143] In Figure 37BIn another example shown, CCLM can be indicated by bit string 0, MM_CCLM can be indicated by bit string 10, CCLM-L can be indicated by bit string 1100, MM-CCLM-L can be indicated by bit string 1101, CCLM-T can be indicated by bit string 1110, and MM-CCLM-T can be indicated by bit string 1111. In this example, the third bit in the bit string corresponds to the first indication, and the fourth bit in the bit string corresponds to the second indication.

[0144] In some embodiments, the first indication and / or the second indication may be indicated in a conditional manner in the bitstream. For example, if a predetermined cross-component prediction scheme is indicated, the first indication or the second indication may be indicated in the bitstream. By way of example, the first indication or the second indication is signaled only when the indication mode is CCLM-L, CCLM-T, MM-CCLM-L, and MM-CCLM-T (or CCCM-L, CCCM-T, MM-CCCM-L, and MM-CCCM-T).

[0145] In some embodiments, if both the left neighboring block and the upper neighboring block of the current video block are available, the first indication may be indicated in the bitstream. Alternatively, if at least one of the left neighboring block or the upper neighboring block of the current video block is available, the second indication may be indicated in the bitstream. In some embodiments, the first indication and / or the second indication may be implemented as a flag, a syntax element, etc.

[0146] By means of the above signaling method, the signaling of cross-component prediction can be advantageously more efficient than conventional truncation-unary coding and decoding schemes.

[0147] In some embodiments, a syntax element can be binarized into: a flag, a fixed-length code, an exponential Golomb (EG) code, a unary code, a truncation-unary code, a truncation-binary code, and so on. Additionally or alternatively, a syntax element can be signed or unsigned.

[0148] In some embodiments, a syntax element can be coded and decoded using at least one context model. Alternatively, a syntax element can be bypassed coded and decoded. In some other embodiments, a syntax element can be indicated in the bitstream in a conditional manner. For example, if the corresponding function is applicable, the syntax element can be indicated in the bitstream.

[0149] In some embodiments, a syntax element may be indicated at: the block level, the sequence level, the group of pictures level, the picture level, the slice level, the slice group level, etc. Additionally or alternatively, the syntax element may be indicated in: the coding structure of a coding tree unit (CTU), the coding structure of a coding unit (CU), the coding structure of a transform unit (TU), the coding structure of a prediction unit (PU), the coding structure of a coding tree block (CTB), the coding structure of a coding block (CB), the coding structure of a transform block (TB), the coding structure of a prediction block (PB), a sequence header, a picture header, a sequence parameter set (SPS), a video parameter set (VPS), a dependent parameter set (DPS), decoding capability information (DCI), a picture parameter set (PPS), an adaptive parameter set (APS), a slice header, or a slice group header.

[0150] In some embodiments, whether and / or how to apply a method may be indicated at: the block level, the sequence level, the group of pictures level, the picture level, the slice level, the slice group level, etc. Additionally or alternatively, whether and / or how to apply the method may be indicated in: the coding structure of a CTU, the coding structure of a CU, the coding structure of a TU, the coding structure of a PU, the coding structure of a CTB, the coding structure of a CB, the coding structure of a TB, the coding structure of a PB, a sequence header, a picture header, a sequence parameter set (SPS), a video parameter set (VPS), a dependent parameter set (DPS), decoding capability information (DCI), a picture parameter set (PPS), an adaptive parameter set (APS), a slice header, or a slice group header.

[0151] In some embodiments, whether and / or how to apply a method may depend on the coded information of the current video block. By way of example and not limitation, the coded information may include: block size, color format, single-tree segmentation, dual-tree segmentation, color component, slice type, picture type, etc. In some other embodiments, the method may be applicable to coding tools that require chroma fusion.

[0152] It should be understood that the above first, second, and / or third video blocks may be the current video block itself or other video blocks different from the current video block. The scope of the present disclosure is not limited in this regard.

[0153] 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 generated by a method executed by a device for video processing for a video. In the method, the prediction for the current video block of the video is adjusted. The prediction is determined based on a cross-component prediction scheme. Additionally, a bitstream is generated based on the adjusted prediction.

[0154] According to still other embodiments of the present disclosure, a method for storing a bitstream of a video is provided. In this method, the prediction for the current video block of the video is adjusted. The prediction is determined based on a cross-component prediction scheme. In addition, a bitstream is generated based on the adjusted prediction, and the bitstream is stored in a non-transitory computer-readable recording medium.

[0155] The implementation of the present disclosure can be described according to the following items, and the features can be combined in any reasonable manner.

[0156] Item 1. A method for video processing, comprising: adjusting a prediction for a current video block of a video for conversion between the current video block of the video and a bitstream of the video, the prediction being determined based on a cross-component prediction scheme; and performing the conversion based on the adjusted prediction.

[0157] Item 2. The method according to Item 1, wherein the prediction for the current video block is adjusted by filtering the prediction.

[0158] Item 3. The method according to Item 2, wherein the prediction for the current video block includes a first prediction sample, the adjusted prediction includes the filtered first prediction sample, and the filtered first prediction sample is determined based on a weighted sum of a plurality of prediction samples in the prediction for the current video block.

[0159] Item 4. The method according to Item 3, wherein the filtered first prediction sample is determined based on: where F(x,y) represents the filtered first prediction sample at coordinates (x,y), L represents the number of the plurality of prediction samples, P(x k ,y k ) represents the kth prediction sample among the plurality of prediction samples, and W k represents the weighting value for the kth prediction sample.

[0160] Item 5. The method according to Item 3, wherein the filtered first prediction sample is determined based on: where F(x,y) represents the filtered first prediction sample at coordinates (x,y), L represents the number of the plurality of prediction samples, P(x k ,y k ) represents the kth prediction sample among the plurality of prediction samples, W k represents the weighting value for the kth prediction sample, and each of offset and S is an integer.

[0161] Item 6. The method according to item 3, wherein the filtered first prediction sample is determined based on the following: F(x,y) = (8P(x,y) + P(x - 1,y - 1) + P(x,y - 1) + P(x + 1,y - 1) + P(x - 1,y) + P(x + 1,y) + P(x - 1,y + 1) + P(x,y + 1) + P(x + 1,y + 1) + 8) >> 4 where F(x,y) represents the filtered first prediction sample at the coordinates (x,y), and P(s,t) represents the prediction sample at the coordinates (s,t) among the plurality of prediction samples.

[0162] Item 7. The method according to item 3, wherein the filtered first prediction sample is determined based on the following: F(x,y) = (4P(x,y) + P(x,y - 1) + P(x - 1,y) + P(x + 1,y) + P(x,y + 1) + 4) >> 3 where F(x,y) represents the filtered first prediction sample at the coordinates (x,y), and P(s,t) represents the prediction sample at the coordinates (s,t) among the plurality of prediction samples.

[0163] Item 8. The method according to item 3, wherein the filtered first prediction sample is determined based on the following: F(x,y) = (2P(x,y) + P(x,y - 1) + P(x,y + 1) + 2) >> 2 where F(x,y) represents the filtered first prediction sample at the coordinates (x,y), and P(s,t) represents the prediction sample at the coordinates (s,t) among the plurality of prediction samples.

[0164] Item 9. The method according to item 3, wherein the filtered first prediction sample is determined based on the following: F(x,y) = (2P(x,y) + P(x - 1,y) + P(x + 1,y) + 2) >> 2 where F(x,y) represents the filtered first prediction sample at the coordinates (x,y), and P(s,t) represents the prediction sample at the coordinates (s,t) among the plurality of prediction samples.

[0165] Item 10. The method according to any one of items 2 to 5, wherein the shape of the filter for filtering the prediction includes one of the following: square, cross, vertical line, or horizontal line.

[0166] Item 11. The method according to any one of Items 1 to 10, wherein different color components of the current video block are adjusted based on the same adjustment scheme.

[0167] Item 12. The method according to any one of Items 1 to 10, wherein different color components of the current video block are adjusted based on different adjustment schemes.

[0168] Item 13. The method according to any one of Items 11 to 12, wherein the different color components include the Cb component and the Cr component.

[0169] Item 14. The method according to any one of Items 1 to 13, wherein a filling process is applied to at least one sample point at the boundary of the current video block.

[0170] Item 15. The method according to Item 14, wherein the filling process includes repeated filling.

[0171] Item 16. The method according to Item 15, wherein in the repeated filling, the value of one sample point among the at least one sample point is determined as the value of a sample point in the current video block.

[0172] Item 17. The method according to any one of Items 2 to 16, wherein if at least one sample point used for filtering a second sample point in the current video block is outside the current video block, the second sample point is not filtered.

[0173] Item 18. The method according to any one of Items 2 to 16, wherein if at least one sample point for a filter shape used for filtering a second sample point in the current video block is outside the current video block, another filter shape is used to filter the second sample point.

[0174] Item 19. The method according to Item 18, wherein if one or more sample points for the another filter shape are outside the current video block, the one or more sample points are excluded from use.

[0175] Item 20. The method according to Item 1, wherein the prediction for the current video block is adjusted based on at least one reconstructed sample point of at least one neighboring block of the current video block.

[0176] Item 21. The method according to Item 20, wherein the prediction for the current video block is adjusted by filtering the prediction by using the at least one reconstructed sample point.

[0177] Item 22. The method according to any one of Items 20 to 21, wherein one of the at least one reconstructed sample points is adjacent to the current video block, or one of the at least one reconstructed sample points is not adjacent to the current video block.

[0178] Item 23. The method according to any one of Items 20 to 22, wherein one of the at least one reconstructed sample points is a temporal reference sample point in a reference block of the current video block.

[0179] Item 24. The method according to any one of Items 20 to 23, wherein the at least one reconstructed sample point has the same color component as the prediction sample point to be adjusted, or the at least one reconstructed sample point has a different color component from the prediction sample point to be adjusted.

[0180] Item 25. The method according to any one of Items 21 to 24, wherein the at least one reconstructed sample point includes a neighboring reconstructed sample point above the current video block, and the first N rows of prediction sample points of the current video block are filtered using the neighboring reconstructed sample point, and N is an integer.

[0181] Item 26. The method according to Item 25, wherein the first row of prediction sample points of the current video block includes a third prediction sample point, and the third prediction sample point is filtered based on the following: F(x,0) = (3P(x,0) + R(x,-1)) >> 2 where F(x,0) represents the filtered third prediction sample point at the coordinate (x,0), P(x,0) represents the third prediction sample point, and R(x,-1) represents the neighboring reconstructed sample point above the third prediction sample point.

[0182] Item 27. The method according to any one of Items 21 to 26, wherein the at least one reconstructed sample point includes a neighboring reconstructed sample point to the left of the current video block, and the first M columns of prediction sample points of the current video block are filtered using the neighboring reconstructed sample point, and M is an integer.

[0183] Item 28. The method according to Item 27, wherein the first column of prediction sample points of the current video block includes a fourth prediction sample point, and the fourth prediction sample point is filtered based on the following: F(0,y) = (3P(0,y) + R(-1,y)) >> 2 where F(0,y) represents the filtered fourth prediction sample point at the coordinate (0,y), P(0,y) represents the fourth prediction sample point, and R(-1,y) represents the neighboring reconstructed sample point to the left of the fourth prediction sample point.

[0184] Item 29. The method according to any one of Items 21 to 28, wherein if a first reconstructed sample among the at least one reconstructed sample is available, the predicted samples of the current video block are filtered using the first reconstructed sample, or if the first reconstructed sample is not available, the predicted samples of the current video block are filtered without the first reconstructed sample.

[0185] Item 30. The method according to Item 29, wherein if the first reconstructed sample is not available, the predicted samples of the current video block are filtered using padding samples.

[0186] Item 31. The method according to Item 2, wherein the predicted samples of the current video block are filtered using at least one of the following: reconstructed samples, additional predicted samples, or padding samples.

[0187] Item 32. The method according to Item 2, wherein the predicted samples of the current video block are filtered using at least one of the following: reconstructed samples, additional predicted samples, or padding samples based on the position of the predicted samples.

[0188] Item 33. The method according to any one of Items 1 to 32, wherein the bitstream includes a syntax element indicating whether to adjust the prediction for the current video block.

[0189] Item 34. The method according to any one of Items 1 to 32, wherein the syntax element indicating whether to adjust the prediction for the current video block is indicated in the bitstream in a conditional manner.

[0190] Item 35. The method according to Item 34, wherein if the mode of the current video block includes a cross-component prediction mode, the syntax element is indicated in the bitstream.

[0191] Item 36. The method according to Item 34, wherein if the mode of the current video block includes one of the following, the syntax element is indicated in the bitstream: multi-model cross-component linear model (MM-CCLM), or multi-model convolutional cross-component model (MM-CCCM).

[0192] Item 37. The method according to Item 34, wherein if the mode of the current video block includes one of the following, the syntax element is indicated in the bitstream: MM-CCLM, MM-CCLM-L, MM-CCLM-T, MM-CCCM, MM-CCCM-T, or MM-CCCM-L.

[0193] Item 38. The method according to any one of Items 1 to 32, wherein if the prediction for the current video block is used in a merge mode, the prediction for the current video block is adjusted.

[0194] Item 39. The method according to Item 38, wherein the target prediction for the current video block is determined in the merge mode by merging the adjusted prediction with at least one additional prediction for the current video block.

[0195] Item 40. The method according to any one of Items 1 to 39, wherein the adjusted prediction samples in the adjusted prediction for the current video block are used to adjust additional prediction samples.

[0196] Item 41. The method according to any one of Items 1 to 40, wherein a first video block of the video is an intra chroma coded block, and a position-dependent prediction combination (PDPC) is applied to the intra chroma coded block.

[0197] Item 42. The method according to Item 41, wherein the first video block is coded and decoded using a cross-component prediction scheme.

[0198] Item 43. The method according to any one of Items 1 to 42, wherein the target prediction for a second video block of the video is generated based on a plurality of prediction schemes.

[0199] Item 44. The method according to Item 43, wherein the target prediction for the second video block is generated according to a weighted sum of a plurality of candidate predictions of the second video block determined based on the plurality of prediction schemes.

[0200] Item 45. The method according to any one of Items 43 to 44, wherein the plurality of prediction schemes includes at least one cross-component prediction scheme and at least one inter prediction scheme.

[0201] Item 46. The method according to Item 45, wherein the second video block is a chroma block coded and decoded using an intra-inter combined prediction (CIIP) mode.

[0202] Item 47. The method according to any one of Items 43 to 44, wherein the plurality of prediction schemes includes at least two cross-component prediction schemes.

[0203] Item 48. The method according to Item 47, wherein the at least two cross-component prediction schemes include a combination of at least two of the following: CCLM, MM-CCLM, CCLM-L, CCLM-T, MM-CCLM-L, MM-CCLM-T, CCCM, MM-CCCM, CCCM-L, CCCM-T, MM-CCCM-L or MM-CCCM-T.

[0204] Item 49. The method according to any one of Items 1 to 48, wherein a spatial geometry partitioning mode (SGPM) is applied to at least one chrominance component of a third video block of the video.

[0205] Item 50. The method according to Item 49, wherein the at least one chrominance component includes at least one of a Cb component and a Cr component.

[0206] Item 51. The method according to Item 50, wherein a partitioning scheme or a weighting scheme of the SGPM for the Cb component is the same as that for the Cr component, or a partitioning scheme or a weighting scheme of the SGPM for the Cb component is different from that for the Cr component.

[0207] Item 52. The method according to any one of Items 49 to 51, wherein a partitioning scheme or a weighting scheme of the SGPM for one chrominance component among the at least one chrominance component is the same as that for a luminance component, or a partitioning scheme or a weighting scheme of the SGPM for one chrominance component among the at least one chrominance component is different from that for the luminance component.

[0208] Item 53. The method according to any one of Items 49 to 51, wherein the bitstream includes at least one syntax element indicating a partitioning scheme or a weighting scheme of the SGPM for one chrominance component among the at least one chrominance component.

[0209] Item 54. The method according to any one of Items 49 to 51, wherein a partitioning scheme or a weighting scheme of the SGPM for one chrominance component among the at least one chrominance component is determined and does not exist in the bitstream.

[0210] Item 55. The method according to any one of Items 49 to 54, wherein at least one prediction scheme used in the SGPM includes a cross-component prediction scheme.

[0211] Item 56. The method according to any one of Items 1 to 55, wherein a plurality of cross-component prediction schemes are indicated in the bitstream in a manner different from rounding-unary coding.

[0212] Item 57. The method according to Item 56, wherein the plurality of cross-component prediction schemes include CCLM-L, CCLM-T, MM-CCLM-L, and MM-CCLM-T, or the plurality of cross-component prediction schemes include CCCM-L, CCCM-T, MM-CCCM-L, and MM-CCCM-T.

[0213] Item 58. The method according to any one of Items 56 to 57, wherein the bitstream includes at least one of the following: a first indication indicating whether a left mode or an above mode is used; or a second indication indicating whether a single-model mode or a multi-model mode is used.

[0214] Item 59. The method according to Item 58, wherein the first indication or the second indication is coded and decoded using at least one context model.

[0215] Item 60. The method according to Item 59, wherein the at least one context model is determined based on coding and decoding information of neighboring blocks of the current video block.

[0216] Item 61. The method according to Item 59, wherein the context model for coding and decoding the first indication depends on the context model for coding and decoding the second indication, or the context model for coding and decoding the second indication depends on the context model for coding and decoding the first indication.

[0217] Item 62. The method according to Item 58, wherein the first indication or the second indication is coded and decoded using bypass coding.

[0218] Item 63. The method according to any one of Items 58 to 62, wherein the first indication is coded and decoded before the second indication, or the second indication is coded and decoded before the first indication.

[0219] Item 64. The method according to any one of Items 58 to 62, wherein each of the first indication and the second indication is a bit in a bit string indicating one cross-component prediction scheme among the plurality of cross-component prediction schemes.

[0220] Item 65. The method according to any one of Items 56 to 57, wherein at least one of the following is indicated in the bitstream in a conditional manner: a first indication indicating whether a left mode or an above mode is used, or a second indication indicating whether a single-model mode or a multi-model mode is used.

[0221] Item 66. The method according to Item 65, wherein if a predetermined cross-component prediction scheme is indicated, the first indication or the second indication is indicated in the bitstream.

[0222] Item 67. The method according to Item 65, wherein if both the left neighboring block and the upper neighboring block of the current video block are available, the first indication is indicated in the bitstream.

[0223] Item 68. The method according to Item 65, wherein if at least one of the left neighboring block or the upper neighboring block of the current video block is available, the second indication is indicated in the bitstream.

[0224] Item 69. The method according to any one of Items 33 to 37 or 53, wherein the syntax element is binarized into one of the following: flag, fixed - length code, exponential Golomb (EG) code, unary code, truncated unary code, or truncated binary code.

[0225] Item 70. The method according to any one of Items 33 to 37, 53, or 69, wherein the syntax element is signed or unsigned.

[0226] Item 71. The method according to any one of Items 33 to 37, 53, or 69 to 70, wherein the syntax element is coded or decoded using at least one context model, or the syntax element is bypass - coded.

[0227] Item 72. The method according to any one of Items 33 to 37, 53, or 69 to 71, wherein the syntax element is indicated in the bitstream in a conditional manner.

[0228] Item 73. The method according to Item 72, wherein if the corresponding function is applicable, the syntax element is indicated in the bitstream.

[0229] Item 74. The method according to any one of Items 33 to 37, 53, or 69 to 73, wherein the syntax element is indicated at one of the following: block level, sequence level, group - of - pictures level, picture level, slice level, or slice - group level.

[0230] Item 75. The method according to any one of Items 33 to 37, 53, or 69 to 73, wherein the syntax element is indicated in one of the following: the coding structure of a coding tree unit (CTU), the coding structure of a coding unit (CU), the coding structure of a transform unit (TU), the coding structure of a prediction unit (PU), the coding structure of a coding tree block (CTB), the coding structure of a coding block (CB), the coding structure of a transform block (TB), the coding structure of a prediction block (PB), sequence header, picture header, sequence parameter set (SPS), video parameter set (VPS), dependency parameter set (DPS), decoding capability information (DCI), picture parameter set (PPS), adaptive parameter set (APS), slice header, or slice - group header.

[0231] Item 76. The method according to any one of Items 1 to 75, wherein whether and / or how to apply the method is indicated at one of the following: block level, sequence level, group of pictures level, picture level, strip level, or slice group level.

[0232] Item 77. The method according to any one of Items 1 to 75, wherein whether and / or how to apply the method is indicated in one of the following: the coding and decoding structure of CTU, the coding and decoding structure of CU, the coding and decoding structure of TU, the coding and decoding structure of PU, the coding and decoding structure of CTB, the coding and decoding structure of CB, the coding and decoding structure of TB, the coding and decoding structure of PB, 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 slice group header.

[0233] Item 78. The method according to any one of Items 1 to 77, wherein whether and / or how to apply the method depends on the encoded and decoded information of the current video block.

[0234] Item 79. The method according to Item 78, wherein the encoded and decoded information includes at least one of the following: block size, color format, single-tree segmentation, double-tree segmentation, color component, strip type, or picture type.

[0235] Item 80. The method according to any one of Items 1 to 79, wherein the method is applicable to coding and decoding tools that require chroma fusion.

[0236] Item 81. The method according to any one of Items 1 to 80, wherein the conversion includes encoding the current video block into the bitstream.

[0237] Item 82. The method according to any one of Items 1 to 80, wherein the conversion includes decoding the current video block from the bitstream.

[0238] Item 83. 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 execute the method according to any one of Items 1 to 82.

[0239] Item 84. A non-transitory computer-readable storage medium storing instructions that cause a processor to execute the method according to any one of Items 1 to 82.

[0240] Item 85. A non-transitory computer-readable recording medium stores a bitstream generated by a method executed by a device for video processing for a video, wherein the method includes: adjusting a prediction for a current video block of the video, the prediction being determined based on a cross-component prediction scheme; and generating the bitstream based on the adjusted prediction.

[0241] Item 86. A method for storing a bitstream of a video includes: adjusting a prediction for a current video block of the video, the prediction being determined based on a cross-component prediction scheme; generating the bitstream based on the adjusted prediction; and storing the bitstream in a non-transitory computer-readable recording medium. Example device

[0242] Figure 39 FIG. shows a block diagram of a computing device 3900 in which various embodiments of the present disclosure may be implemented. The computing device 3900 may be implemented as the source device 110 (or the video encoder 114 or 200) or the destination device 120 (or the video decoder 124 or 300), or may be included in the source device 110 (or the video encoder 114 or 200) or the destination device 120 (or the video decoder 124 or 300).

[0243] It should be understood that Figure 39 the computing device 3900 shown in FIG. is for illustrative purposes only and does not imply any limitation to the functionality and scope of the embodiments of the present disclosure in any way.

[0244] As Figure 39 shown, the computing device 3900 includes a general-purpose computing device 3900. The computing device 3900 may include at least one or more processors or processing units 3910, a memory 3920, a storage unit 3930, one or more communication units 3940, one or more input devices 3950, and one or more output devices 3960.

[0245] In some embodiments, computing device 3900 may be implemented as any user terminal or server terminal having computing capabilities. The server terminal may be a server provided by a service provider, a large computing device, etc. The user terminal may be, for example, any type of mobile terminal, fixed terminal, or portable terminal, including mobile phones, stations, units, devices, multimedia computers, multimedia tablet computers, Internet nodes, communicators, desktop computers, laptop computers, notebook computers, netbook computers, tablet computers, personal communication system (PCS) devices, personal navigation devices, personal digital assistant (PDA), audio / video players, digital cameras / video cameras, positioning devices, television receivers, radio broadcast receivers, e-book devices, gaming devices, or any combination thereof, including accessories and peripherals of these devices or any combination thereof. It is contemplated that computing device 3900 may support any type of interface to the user (such as "wearable" circuitry, etc.).

[0246] Processing unit 3910 may be a physical processor or a virtual processor, and may implement various processes based on programs stored in memory 3920. In a multi-processor system, multiple processing units execute computer-executable instructions in parallel to improve the parallel processing ability of computing device 3900. Processing unit 3910 may also be referred to as a central processing unit (CPU), microprocessor, controller, or microcontroller.

[0247] Computing device 3900 generally includes various computer storage media. Such media may be any media accessible by computing device 3900, including but not limited to volatile media and non-volatile media, or removable media and non-removable media. Memory 3920 may be volatile memory (e.g., registers, caches, random access memory (RAM)), non-volatile memory (such as read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), or flash memory), or any combination thereof. Storage unit 3930 may be any removable or non-removable media, and may include machine-readable media, such as memory, flash drive, disk, or other media that can be used to store information and / or data and can be accessed in computing device 3900.

[0248] Computing device 3900 may also include additional removable / non-removable storage media, volatile / non-volatile storage media. Although not shown in Figure 39 a disk drive for reading from and / or writing to a removable non-volatile disk, and an optical disk drive for reading from and / or writing to a removable non-volatile optical disk may be provided. In this case, each drive may be connected to a bus (not shown) via one or more data media interfaces.

[0249] The communication unit 3940 communicates with another computing device via a communication medium. Additionally, the functionality of the components in the computing device 3900 can be implemented by a single computing cluster or multiple computer machines, which can communicate via a communication connection. Thus, the computing device 3900 can operate in a networked environment using a logical connection to one or more other servers, networked personal computers (PCs), or other general network nodes.

[0250] The input device 3950 can be one or more of a variety of input devices, such as a mouse, keyboard, trackball, voice input device, and so on. The output device 3960 can be one or more of a variety of output devices, such as a display, speaker, printer, and so on. With the aid of the communication unit 3940, the computing device 3900 can also communicate with one or more external devices (not shown), such as storage devices and display devices, the computing device 3900 can also communicate with one or more devices that enable a user to interact with the computing device 3900, or if needed, the computing device 3900 can also communicate with any device (such as a network card, modem, etc.) that enables the computing device 3900 to communicate with one or more other computing devices. Such communication can be carried out via an input / output (I / O) interface (not shown).

[0251] In some embodiments, some or all of the components of the computing device 3900 can also be arranged in a cloud computing architecture rather than being integrated in a single device. In a cloud computing architecture, the components can be provided remotely and work together to achieve the functions described in this disclosure. In some embodiments, cloud computing provides computing, software, data access, and storage services, which will not require the end user to be aware of the physical location or configuration of the system or hardware providing these services. In various embodiments, cloud computing uses appropriate protocols to provide services via a wide area network (such as the Internet). For example, a cloud computing provider provides an application via a wide area network, and the application can be accessed via a web browser or any other computing component. The software or components of the cloud computing architecture and the corresponding data can be stored on a server at a remote location. The computing resources in a cloud computing environment can be consolidated or distributed at the locations of remote data centers. The cloud computing infrastructure can provide services through a shared data center, although to the user, they appear as a single access point. Thus, a cloud computing architecture can be used to provide the components and functions described herein from a service provider at a remote location. Alternatively, the components and functions described herein can be provided by a conventional server or directly or otherwise installed on a client device.

[0252] In an embodiment of the present disclosure, the computing device 3900 may be used to implement video encoding / decoding. The memory 3920 may include one or more video codec modules 3925 having one or more program instructions. These modules are accessible and executable by the processing unit 3910 to perform the functions of the various embodiments described herein.

[0253] In an example embodiment of performing video encoding, the input device 3950 may receive video data as the input 3970 to be encoded. The video data may be processed, for example, by the video codec module 3925 to generate an encoded bitstream. The encoded bitstream may be provided as the output 3980 via the output device 3960.

[0254] In an example embodiment of performing video decoding, the input device 3950 may receive the encoded bitstream as the input 3970. The encoded bitstream may be processed, for example, by the video codec module 3925 to generate decoded video data. The decoded video data may be provided as the output 3980 via the output device 3960.

[0255] Although the present disclosure has been specifically shown and described with reference to preferred embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope of the present application as defined by the appended claims. These variations are intended to be covered 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 method for video processing, comprising: For conversion between a current video block of a video and a bitstream of the video, adjusting a prediction for the current video block, the prediction determined based on a cross-component prediction scheme; as well as The converting is performed based on the adjusted prediction.

2. The method of claim 1, wherein the prediction for the current video block is adjusted by filtering the prediction.

3. The method of claim 2 , wherein the prediction for the current video block comprises a first prediction sample, the adjusted prediction comprises a filtered first prediction sample, and the filtered first prediction sample is determined based on a weighted sum of a plurality of prediction samples in the prediction for the current video block.

4. The method of claim 3 , wherein the filtered first prediction sample is determined based on: where F(x, y) represents the filtered first prediction sample at coordinates (x, y), L represents the number of the plurality of prediction samples, P(x k , y k ) represents the k-th prediction sample among the plurality of prediction samples, and W k represents the weighting value for the k-th prediction sample.

5. The method of claim 3 , wherein the filtered first prediction sample is determined based on: Where F(x,y) represents the filtered first prediction sample at the coordinate (x,y), L represents the number of the plurality of prediction samples, P(x k ,y k ) represents the kth prediction sample point among the multiple prediction sample points, W k represents the weighted value for the k-th prediction sample point, and each of offset and S is an integer.

6. The method of claim 3 , wherein the filtered first prediction sample is determined based on: F(x,y)=(8P(x,y)+P(x-1,y-1)+P(x,y-1)+P(x+1,y-1)+P(x-1,y)+P(x+1,y)+P(x-1,y+1)+P(x,y+1)+P(x+1,y+1)+8)>>4 Wherein F(x,y) represents the filtered first prediction sample at coordinates (x,y), and P(s,t) represents the prediction sample at coordinates (s,t) among the plurality of prediction samples.

7. The method of claim 3 , wherein the filtered first prediction sample is determined based on: F(x,y)=(4P(x,y)+P(x,y-1)+P(x-1,y)+P(x+1,y)+P(x,y+1)+4)>>3 Wherein F(x,y) represents the filtered first prediction sample at coordinates (x,y), and P(s,t) represents the prediction sample at coordinates (s,t) among the plurality of prediction samples.

8. The method of claim 3 , wherein the filtered first prediction sample is determined based on: F(x,y)=(2P(x,y)+P(x,y-1)+P(x,y+1)+2)>>2 Wherein F(x,y) represents the filtered first prediction sample at coordinates (x,y), and P(s,t) represents the prediction sample at coordinates (s,t) among the plurality of prediction samples.

9. The method of claim 3, wherein the filtered first prediction sample is determined based on: F(x,y)=(2P(x,y)+P(x-1,y)+P(x+1,y)+2)>>2 Wherein F(x,y) represents the filtered first prediction sample at coordinates (x,y), and P(s,t) represents the prediction sample at coordinates (s,t) among the plurality of prediction samples.

10. The method according to any one of claims 2 to 5, wherein the shape of the filter for filtering the prediction includes one of the following: a square, a cross, a vertical line, or a horizontal line.

11. The method according to any one of claims 1 to 10, wherein different color components of the current video block are adjusted based on the same adjustment scheme.

12. The method according to any one of claims 1 to 10, wherein different color components of the current video block are adjusted based on different adjustment schemes.

13. The method according to any one of claims 11 to 12, wherein the different color components include a Cb component and a Cr component.

14. The method according to any one of claims 1 to 13, wherein a filling process is applied to at least one sample point at the boundary of the current video block.

15. The method according to claim 14, wherein the filling process includes repeated filling.

16. The method according to claim 15, wherein in the repeated filling, the value of one sample point among the at least one sample point is determined as the value of a sample point in the current video block.

17. The method according to any one of claims 2 to 16, wherein if at least one sample point for filtering a second sample point in the current video block is outside the current video block, the second sample point is not filtered.

18. The method according to any one of claims 2 to 16, wherein if at least one sample point for the filter shape used to filter a second sample point in the current video block is outside the current video block, another filter shape is used to filter the second sample point.

19. The method according to claim 18, wherein if one or more sample points for the another filter shape are outside the current video block, the one or more sample points are excluded from use.

20. The method according to claim 1, wherein the prediction for the current video block is adjusted based on at least one reconstructed sample point of at least one neighboring block of the current video block.

21. The method according to claim 20, wherein the prediction for the current video block is adjusted by filtering the prediction by using the at least one reconstructed sample point.

22. The method according to any one of claims 20 to 21, wherein one of the at least one reconstructed sample points is adjacent to the current video block, or one of the at least one reconstructed sample points is not adjacent to the current video block.

23. The method according to any one of claims 20 to 22, wherein one of the at least one reconstructed sample points is a temporal reference sample point in a reference block of the current video block.

24. The method according to any one of claims 20 to 23, wherein the at least one reconstructed sample point has the same color component as the prediction sample point to be adjusted, or the at least one reconstructed sample point has a different color component from the prediction sample point to be adjusted.

25. The method according to any one of claims 21 to 24, wherein the at least one reconstructed sample includes a neighboring reconstructed sample above the current video block, and the first N rows of predicted samples of the current video block are filtered using the neighboring reconstructed sample, and N is an integer.

26. The method according to claim 25, wherein the topmost row of predicted samples of the current video block includes a third predicted sample, and the third predicted sample is filtered based on the following: F(x,0) = (3P(x,0) + R(x, -1)) >> 2 where F(x,0) represents the filtered third predicted sample at the coordinate (x,0), P(x,0) represents the third predicted sample, and R(x, -1) represents the neighboring reconstructed sample above the third predicted sample.

27. The method according to any one of claims 21 to 26, wherein the at least one reconstructed sample includes a neighboring reconstructed sample to the left of the current video block, and the first M columns of predicted samples of the current video block are filtered using the neighboring reconstructed sample, and M is an integer.

28. The method according to claim 27, wherein the leftmost column of predicted samples of the current video block includes a fourth predicted sample, and the fourth predicted sample is filtered based on the following: F(0,y) = (3P(0,y) + R(-1,y)) >> 2 where F(0,y) represents the filtered fourth predicted sample at the coordinate (0,y), P(0,y) represents the fourth predicted sample, and R(-1,y) represents the neighboring reconstructed sample to the left of the fourth predicted sample.

29. The method according to any one of claims 21 to 28, wherein if a first reconstructed sample in the at least one reconstructed sample is available, the predicted samples of the current video block are filtered using the first reconstructed sample, or if the first reconstructed sample is not available, the predicted samples of the current video block are filtered without the first reconstructed sample.

30. The method according to claim 29, wherein if the first reconstructed sample is not available, the predicted samples of the current video block are filtered using padding samples.

31. The method according to claim 2, wherein the predicted samples of the current video block are filtered using at least one of the following: reconstructed samples, additional predicted samples, or padding samples.

32. The method according to claim 2, wherein the predicted samples of the current video block are filtered using at least one of the following based on the position of the predicted samples: reconstructed samples, additional predicted samples, or padding samples.

33. The method according to any one of claims 1 to 32, wherein the bitstream includes a syntax element indicating whether to adjust the prediction for the current video block.

34. The method according to any one of claims 1 to 32, wherein the syntax element indicating whether to adjust the prediction for the current video block is indicated in the bitstream in a conditional manner.

35. The method of claim 34, wherein the syntax element is indicated in the bitstream if a mode of the current video block comprises an inter-component prediction mode.

36. The method of claim 34, wherein the syntax element is indicated in the bitstream if the mode of the current video block comprises one of: Multi-model cross-component linear model (MM-CCLM), or Multi-Model Convolutional Cross-Component Model (MM-CCCM).

37. The method of claim 34, wherein the syntax element is indicated in the bitstream if the mode of the current video block comprises one of: MM-CCLM, MM-CCLM-L, MM-CCLM-T, MM-CCCM, MM-CCCM-T, or MM-CCCM-L.

38. The method of any one of claims 1 to 32, wherein the prediction for the current video block is adjusted if the prediction for the current video block is used in a merge mode.

39. The method of claim 38, wherein a target prediction for the current video block is determined in the merge mode by fusing the adjusted prediction with at least one additional prediction for the current video block.

40. The method of any one of claims 1 to 39, wherein adjusted prediction samples in the adjusted prediction for the current video block are used to adjust further prediction samples.

41. The method of any one of claims 1 to 40, wherein a first video block of the video is a chroma intra-coded block, and position-dependent prediction combining (PDPC) is applied to the chroma intra-coded block.

42. The method of claim 41, wherein the first video block is encoded using a cross-component prediction scheme.

43. The method of any one of claims 1 to 42, wherein a target prediction for a second video block of the video is generated based on a plurality of prediction schemes.

44. The method of claim 43, wherein the target prediction for the second video block is generated according to a weighted sum of a plurality of candidate predictions for the second video block determined based on the plurality of prediction schemes.

45. The method of any one of claims 43 to 44, wherein the plurality of prediction schemes comprises at least one cross-component prediction scheme and at least one inter-frame prediction scheme.

46. The method of claim 45, wherein the second video block is a chroma block encoded using a joint intra and inter prediction (CIIP) mode.

47. The method of any one of claims 43 to 44, wherein the plurality of prediction schemes comprises at least two cross-component prediction schemes.

48. The method according to claim 47, wherein the at least two cross-component prediction schemes include a combination of at least two of the following: CCLM, MM-CCLM, CCLM-L, CCLM-T, MM-CCLM-L, MM-CCLM-T, CCCM, MM-CCCM, CCCM-L, CCCM-T, MM-CCCM-L, or MM-CCCM-T.

49. The method according to any one of claims 1 to 48, wherein a spatial geometry partitioning mode (SGPM) is applied to at least one chrominance component of a third video block of the video.

50. The method according to claim 49, wherein the at least one chrominance component includes at least one of a Cb component and a Cr component.

51. The method according to claim 50, wherein a partitioning scheme or a weighting scheme of the SGPM for the Cb component is the same as that for the Cr component, or the partitioning scheme or the weighting scheme of the SGPM for the Cb component is different from that for the Cr component.

52. The method according to any one of claims 49 to 51, wherein a partitioning scheme or a weighting scheme of the SGPM for one chrominance component of the at least one chrominance component is the same as that for a luminance component, or the partitioning scheme or the weighting scheme of the SGPM for one chrominance component of the at least one chrominance component is different from that for the luminance component.

53. The method according to any one of claims 49 to 51, wherein the bitstream includes at least one syntax element indicating a partitioning scheme or a weighting scheme of the SGPM for one chrominance component of the at least one chrominance component.

54. The method according to any one of claims 49 to 51, wherein a partitioning scheme or a weighting scheme of the SGPM for one chrominance component of the at least one chrominance component is determined and is not present in the bitstream.

55. The method according to any one of claims 49 to 54, wherein at least one prediction scheme used in the SGPM includes a cross-component prediction scheme.

56. The method according to any one of claims 1 to 55, wherein a plurality of cross-component prediction schemes are indicated in the bitstream in a manner different from rounding-based unary coding.

57. The method according to claim 56, wherein the plurality of cross-component prediction schemes include CCLM-L, CCLM-T, MM-CCLM-L, and MM-CCLM-T, or the plurality of cross-component prediction schemes include CCCM-L, CCCM-T, MM-CCCM-L, and MM-CCCM-T.

58. The method according to any one of claims 56 to 57, wherein the bitstream includes at least one of the following: a first indication indicating whether a left mode or an above mode is used; or a second indication indicating whether a single-model mode or a multi-model mode is used.

59. The method according to claim 58, wherein the first indication or the second indication is coded and decoded using at least one context model.

60. The method according to claim 59, wherein the at least one context model is determined based on the coding and decoding information of neighboring blocks of the current video block.

61. The method according to claim 59, wherein the context model for coding and decoding the first indication depends on the context model for coding and decoding the second indication, or the context model for coding and decoding the second indication depends on the context model for coding and decoding the first indication.

62. The method according to claim 58, wherein the first indication or the second indication is coded and decoded using bypass coding.

63. The method according to any one of claims 58 to 62, wherein the first indication is coded and decoded before the second indication, or the second indication is coded and decoded before the first indication.

64. The method according to any one of claims 58 to 62, wherein each of the first indication and the second indication is a bit in a bit string indicating one of the plurality of cross-component prediction schemes.

65. The method according to any one of claims 56 to 57, wherein at least one of the following is indicated in the bitstream in a conditional manner: a first indication indicating whether a left mode or an above mode is used, or a second indication indicating whether a single model mode or a multi-model mode is used.

66. The method according to claim 65, wherein if a predetermined cross-component prediction scheme is indicated, the first indication or the second indication is indicated in the bitstream.

67. The method according to claim 65, wherein if both the left neighboring block and the above neighboring block of the current video block are available, the first indication is indicated in the bitstream.

68. The method according to claim 65, wherein if at least one of the left neighboring block or the above neighboring block of the current video block is available, the second indication is indicated in the bitstream.

69. The method according to any one of claims 33 to 37 or 53, wherein a syntax element is binarized into one of the following: a flag, a fixed-length code, an exponential Golomb (EG) code, a unary code, a truncated unary code, or a truncated binary code.

70. The method according to any one of claims 33 to 37, 53 or 69, wherein the syntax element is signed or unsigned.

71. The method according to any one of claims 33 to 37, 53 or 69 to 70, wherein the syntax element is coded and decoded using at least one context model, or the syntax element is bypass-coded.

72. The method according to any one of claims 33 to 37, 53 or 69 to 71, wherein the syntax element is indicated in the bitstream in a conditional manner.

73. The method according to claim 72, wherein if the corresponding function is applicable, the syntax element is indicated in the bitstream.

74. The method according to any one of claims 33 to 37, 53 or 69 to 73, wherein the syntax element is indicated at one of the following: block level, sequence level, group of pictures level, picture level, Strip level, or Slice group level.

75. The method according to any one of claims 33 to 37, 53 or 69 to 73, wherein the syntax element is indicated in one of the following: The coding structure of a coding tree unit (CTU), The coding structure of a coding unit (CU), The coding structure of a transform unit (TU), The coding structure of a prediction unit (PU), The coding structure of a coding tree block (CTB), The coding structure of a coding block (CB), The coding structure of a transform block (TB), The coding structure of a prediction block (PB), Sequence header, Picture header, Sequence parameter set (SPS), Video parameter set (VPS), Dependency parameter set (DPS), Decoding capability information (DCI), Picture parameter set (PPS), Adaptive parameter set (APS), Strip header, or Slice group header.

76. The method according to any one of claims 1 to 75, wherein whether and / or how to apply the method is indicated at one of the following: Block level, Sequence level, Group of pictures level, Picture level, Strip level, or Slice group level.

77. The method according to any one of claims 1 to 75, wherein whether and / or how to apply the method is indicated in one of the following: The coding structure of a CTU, The coding structure of a CU, The coding structure of a TU, The coding structure of a PU, The coding structure of a CTB, The coding structure of a CB, The coding structure of a TB, The coding structure of a PB, Sequence header, Picture header, Sequence parameter set (SPS), Video parameter set (VPS), Dependency parameter set (DPS), Decoding capability information (DCI), Picture parameter set (PPS), Adaptive parameter set (APS), Strip header, or Slice group header.

78. The method according to any one of claims 1 to 77, wherein whether and / or how to apply the method depends on the coded information of the current video block.

79. The method according to claim 78, wherein the coded information includes at least one of the following: Block size, Color format, Single tree segmentation, Dual tree segmentation, Color component, Strip type, or Picture type.

80. The method according to any one of claims 1 to 79, wherein the method is applicable to coding tools that require chroma fusion.

81. The method according to any one of claims 1 to 80, wherein the transformation includes encoding the current video block into the bitstream.

82. The method according to any one of claims 1 to 80, wherein the transformation includes decoding the current video block from the bitstream.

83. 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 the method according to any one of claims 1 to 82.

84. A non-transitory computer-readable storage medium storing instructions that cause a processor to perform the method according to any one of claims 1 to 82.

85. A non-transitory computer-readable recording medium storing a bitstream of a video generated by a method performed by an apparatus for video processing, wherein the method comprises: adjusting a prediction for a current video block of the video, the prediction determined based on a cross-component prediction scheme; as well as The bitstream is generated based on the adjusted prediction.

86. A method for storing a bitstream of a video, comprising: adjusting a prediction for a current video block of the video, the prediction determined based on a cross-component prediction scheme; generating the bitstream based on the adjusted prediction; as well as The bitstream is stored in a non-transitory computer-readable recording medium.

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