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: constructing at least one block vector (BV) candidate list for a video unit of a video for a conversion between the video unit and a bitstream of the video unit; utilizing one or more BVs in the at least one BV candidate list for chroma prediction of the video unit; and performing the conversion based on the chroma prediction of the video unit.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to video processing technologies, and more specifically, to intra-block copy for chrominance. Background Art

[0002] Nowadays, digital video capabilities are being applied to all aspects of people's lives. A variety of video compression technologies, 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 have been proposed for video encoding / decoding. However, it is generally desirable to further improve the encoding / decoding efficiency 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: constructing at least one block vector (BV) candidate list for a video unit for conversion between the video unit and a bitstream of the video unit; using one or more BVs in at least one BV candidate list for chrominance prediction of the video unit; and performing conversion based on the chrominance prediction of the video unit. In this way, the encoding / decoding efficiency and encoding / decoding performance can be improved.

[0005] In a second aspect, an apparatus for video processing is proposed. The apparatus includes: a processor and a non-transitory memory having instructions thereon. The instructions, when executed by the processor, cause the processor to execute the method according to the first aspect of the present disclosure.

[0006] 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.

[0007] In a fourth aspect, another non-transitory computer-readable recording medium is proposed. The non-transitory computer-readable recording medium stores a bitstream of a video generated by a method executed by an apparatus for video processing. The method includes: constructing at least one block vector (BV) candidate list for a video unit of the video; using one or more BVs in at least one BV candidate list for chrominance prediction of the video unit; and generating a bitstream based on the chrominance prediction of the video unit.

[0008] In a fifth aspect, a method for storing a bitstream of a video is provided. The method includes: constructing at least one block vector (BV) candidate list for video units of a video; utilizing one or more BVs from the at least one BV candidate list for chrominance prediction of a video unit; generating a bitstream based on the chrominance prediction of the video unit; and storing the bitstream in a non-transitory computer-readable medium.

[0009] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above and other objects, features, and advantages of the example embodiments of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. In the example embodiments of the present disclosure, the same reference numerals generally refer to the same components.

[0011] Figure 1 A block diagram showing an example video codec system according to some embodiments of the present disclosure is shown;

[0012] Figure 2 A block diagram showing a first example video encoder according to some embodiments of the present disclosure is shown;

[0013] Figure 3 A block diagram showing an example video decoder according to some embodiments of the present disclosure is shown;

[0014] Figure 4 The nominal vertical and horizontal positions of 4:2:2 luma samples and chroma samples in a picture are shown;

[0015] Figure 5 An example of an encoder block diagram is shown;

[0016] Figure 6 67 intra prediction modes are shown;

[0017] Figure 7 Reference samples for wide-angle intra prediction are shown;

[0018] Figure 8 The problem of discontinuity in the case of a direction exceeding 45° is shown;

[0019] Figure 9 An illustration of motion vector scaling for temporal Merge candidates is shown;

[0020] Figure 10 MMVD search points are shown;

[0021] Figure 11 Shows local illumination compensation;

[0022] Figure 12 Shows no subsampling for the short side;

[0023] Figure 13 Shows the IBC reference region depending on the current CU position;

[0024] Figure 14 Shows an example of symmetry in a screen content picture;

[0025] Figure 15A Shows an illustration of BV adjustment for horizontal flipping;

[0026] Figure 15B Shows an illustration of BV adjustment for vertical flipping;

[0027] Figure 16 Shows the in - frame template matching search region used;

[0028] Figure 17 Shows five positions in the reconstructed luminance samples;

[0029] Figure 18 Shows the prediction process of the DBV mode;

[0030] Figure 19 Shows a flowchart of a method for video processing according to an embodiment of the present disclosure;

[0031] Figure 20 Shows a block diagram of a computing device in which various embodiments of the present disclosure may be implemented.

[0032] Throughout the drawings, the same or similar reference numerals generally refer to the same or similar elements. Detailed Description

[0033] 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 illustration 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 may be implemented in various ways other than those described below.

[0034] 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 this disclosure belongs.

[0035] As used herein, the terms "one embodiment", "embodiment", "exemplary embodiment", etc. indicate that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment must include the specific feature, structure, or characteristic. Moreover, these phrases do not necessarily refer to the same embodiment. Further, when a specific feature, structure, or characteristic is described in connection with an exemplary embodiment, it is contended that such feature, structure, or characteristic, whether or not explicitly described, is within the knowledge of those skilled in the art in relation to other embodiments.

[0036] 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 exemplary embodiments. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0037] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the exemplary embodiments. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprises", "comprising", "has", "having", "includes", and / or "including" when used herein indicate 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. Exemplary Environment

[0038] Figure 1 is a block diagram showing an exemplary 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.

[0039] The video source 112 may include sources such as video capture devices. 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 combinations thereof.

[0040] 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 forming an encoded representation of the video data. The bitstream may include encoded pictures and associated data. The encoded pictures are the encoded representations of the pictures. 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 the network 130A. The encoded video data may also be stored on the storage medium / server 130B for access by the destination device 120.

[0041] 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 modulator. The I / O interface 126 may obtain the encoded video data from the source device 110 or the storage medium / server 130B. The video decoder 124 may decode the encoded video data. The display device 122 may display the decoded video data to the user. The display device 122 may be integrated with the destination device 120 or may be external to the destination device 120, which is configured to interface with an external display device.

[0042] 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.

[0043] Figure 2 is a block diagram showing 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.

[0044] The video encoder 200 may be configured to implement any or all of the techniques of the present disclosure. In Figure 2 the example, the video encoder 200 includes multiple 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.

[0045] 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 encoding 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.

[0046] 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.

[0047] 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 shown separately in Figure 2 the examples.

[0048] The segmentation unit 201 may segment a picture into one or more video blocks. The video encoder 200 and the video decoder 300 may support various video block sizes.

[0049] The mode selection unit 203 may select, for example, one coding mode (intra coding or inter coding) from a plurality of coding modes 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 for use as a reference picture. In some examples, the mode selection unit 203 may select a Combined Intra and 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).

[0050] 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 buffer 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 buffer 213 other than the picture associated with the current video block.

[0051] The motion estimation unit 204 and the motion compensation unit 205 can perform different operations on the current video block. For example, depending on whether the current video block is in an I-slice, a P-slice, or a B-slice. As used herein, an "I-slice" may refer to a part 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 parts of a picture composed of macroblocks that are independent of macroblocks within the same picture.

[0052] In some examples, the motion estimation unit 204 can perform uni-directional prediction on the current video block, and the motion estimation unit 204 can 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 can then generate a reference index and a motion vector, where the reference index indicates the reference picture in list 0 or list 1 that contains the reference video block, and the motion vector indicates the spatial displacement between the current video block and the reference video block. The motion estimation unit 204 can 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 can generate a predicted video block of the current video block based on the reference video block indicated by the motion information of the current video block.

[0053] Alternatively, in other examples, the motion estimation unit 204 can perform bi-directional prediction on the current video block. The motion estimation unit 204 can search the reference pictures in list 0 to find one reference video block for the current video block, and can also search the reference pictures in list 1 to find another reference video block for the current video block. The motion estimation unit 204 can then generate a plurality of reference indices and a plurality of motion vectors, where the plurality of reference indices indicate 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 indicate the plurality of spatial displacements between the plurality of reference video blocks and the current video block. The motion estimation unit 204 can 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 can generate a predicted video block of the current video block based on the plurality of reference video blocks indicated by the motion information of the current video block.

[0054] In some examples, the motion estimation unit 204 can output a complete set of motion information for the decoding process of the decoder. Alternatively, in some embodiments, the motion estimation unit 204 can 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 can determine that the motion information of the current video block is similar enough to the motion information of a neighboring video block.

[0055] In one example, the motion estimation unit 204 may indicate a value in a syntax structure associated with the current video block, and this value indicates to the video decoder 300 that the current video block has the same motion information as another video block.

[0056] In another example, the motion estimation unit 204 may identify another video block and a motion vector difference (MVD) in a syntax structure associated with the current video block. The motion vector difference indicates the difference between the motion vector of the current video block and the motion vector of the indicated video block. The video decoder 300 may use the motion vector of the indicated video block and the motion vector difference to determine the motion vector of the current video block.

[0057] 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.

[0058] 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.

[0059] The residual generation unit 207 may generate residual data for the current video block by subtracting (e.g., indicated by a 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 may include residual video blocks corresponding to different sample components of the samples in the current video block.

[0060] 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.

[0061] The transform processing unit 208 may 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.

[0062] After the transform processing unit 208 generates the transform coefficient video block associated with the current video block, the quantization unit 209 may quantize the transform coefficient video block associated with the current video block based on one or more quantization parameter (QP) values associated with the current video block.

[0063] The inverse quantization unit 210 and the inverse transform unit 211 may apply inverse quantization and inverse transform to the transformed coefficient video block, respectively, to reconstruct the residual video block from the transformed coefficient video block. The reconstruction unit 212 may add the reconstructed residual video block to 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 buffer 213.

[0064] After the reconstruction unit 212 reconstructs the video block, a loop filtering operation may be performed to reduce block effect artifacts in the video block.

[0065] The entropy encoding unit 214 may receive data from other functional components of the video encoder 200. When the entropy encoding unit 214 receives the data, the entropy encoding unit 214 may perform one or more entropy encoding operations to generate entropy encoded data and output a bitstream including the entropy encoded data.

[0066] Figure 3 is a block diagram illustrating an example of a video decoder 300 according to some embodiments of the present disclosure. The video decoder 300 may be Figure 1 an example of the video decoder 124 in the system 100 shown.

[0067] The video decoder 300 may be configured to perform any or all of the techniques of the present disclosure. In Figure 3 an example, the video decoder 300 includes a plurality of functional components. The techniques described in the present disclosure may be shared among the various components of the video decoder 300. In some examples, a processor may be configured to perform any or all of the techniques described in the present disclosure.

[0068] In Figure 3 an example, the video decoder 300 includes an entropy decoding unit 301, a motion compensation unit 302, an intra prediction unit 303, an inverse quantization unit 304, an inverse transform unit 305, and a reconstruction unit 306 and a buffer 307. In some examples, the video decoder 300 may perform a decoding process generally opposite to the encoding process described with respect to the video encoder 200.

[0069] The entropy decoding unit 301 may retrieve the encoded bitstream. The encoded bitstream may include entropy-coded video data (e.g., encoded blocks of video data). The entropy decoding unit 301 may decode the entropy-coded video data, and the motion compensation unit 302 may 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 may 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. The motion information generally includes a horizontal motion vector displacement value and a vertical motion vector displacement value, 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" may refer to deriving motion information from spatially adjacent blocks or temporally adjacent blocks.

[0070] The motion compensation unit 302 may generate motion-compensated blocks, possibly performing interpolation based on an interpolation filter. An identifier for the interpolation filter used at sub-pixel precision may be included in the syntax element.

[0071] The motion compensation unit 302 may use the interpolation filter used by the video encoder 200 during the encoding of a video block to compute interpolated values for sub-integer pixels of a reference block. The motion compensation unit 302 may determine the interpolation filter used by the video encoder 200 according to received syntax information, and the motion compensation unit 302 may use the interpolation filter to generate a prediction block.

[0072] 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 a picture 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, "slice" may refer to a data structure that can be decoded independently of other slices of the same picture in terms of entropy coding, signal prediction, and residual signal reconstruction. A slice may be the entire picture, or it may also be a region of the picture.

[0073] The intra prediction unit 303 may use, for example, an 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.

[0074] The reconstruction unit 306 can obtain the decoded block, for example, by adding a residual block to the corresponding prediction block generated by the motion compensation unit 302 or the intra prediction unit 303. If necessary, a deblocking filter can also be applied to filter the decoded block to remove block effect artifacts. The decoded video block is then stored in the buffer 307, which provides reference blocks for subsequent motion compensation / intra prediction, and the buffer 307 also produces the decoded video for presentation on a display device.

[0075] 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 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 coding steps in detail, it should be understood that the corresponding decoding steps of the decoding will be implemented by the decoder. In addition, the term video processing includes video coding or compression, video decoding or decompression, and video transcoding, in which video pixels are represented from one compression format to another compression format or at different compression bit rates. 1. Brief Overview The present disclosure relates to video coding techniques. Specifically, it relates to intra block copy (IBC), how and / or whether to use IBC for chrominance prediction, and other coding tools in image / video coding. It can be applied to existing video coding standards such as HEVC, or multi-functional video coding (VVC). It can also be applicable to future video coding standards or video codecs. 2. Introduction Video coding standards have mainly evolved from the well-known ITU-T standards and ISO / IEC standards. ITU-T developed H.261 and H.263, ISO / IEC developed MPEG-1 and MPEG-4 Visual, and the two organizations jointly developed H.262 / MPEG-2 Video and H.264 / MPEG-4 Advanced Video Coding (AVC) as well as the H.265 / HEVC standard. 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. As a result, 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 Experts Team (JVET) between VCEG (Q6 / 16) and ISO / IEC JTC1 SC29 / WG11 (MPEG) was created, working 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 a 3-value or 4-value or color components (such as RGB). Basically, a color space is an elaboration of a coordinate system and subspaces. 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 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 chrominance component and red-difference chrominance component. Y’ (with a prime) is distinguished 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 at a lower resolution for chrominance information than for luminance information, taking advantage of the fact that the human visual system is less sensitive to color differences than to 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 post-production for movies. 2.1.2. 4∶2∶2 The two chrominance components are sampled at half the sampling rate of the 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. An example of the nominal vertical and horizontal positions of the 4:2:2 color format is depicted in Figure 4 the VVC working draft. 2.1.3. 4:2:0 In 4:2:0, compared to 4:1:1, the horizontal sampling is doubled, but since the Cb channel and the Cr channel are sampled only on every alternate line in this scheme, the vertical resolution is halved. Thus, the data rate is the same. Cb and Cr are each subsampled horizontally and vertically by a factor of 2. There are three variants of the 4:2:0 scheme, which have different horizontal and vertical positions. · In MPEG-2, Cb and Cr are placed together horizontally. Cb and Cr are placed (spaced) between the pixels in the vertical direction. · In JPEG / JFIF, H261, and MPEG-1, Cb and Cr are placed together with a gap, at the midpoint between the alternate luminance samples. · In 4:2:0 DV, Cb and Cr are placed together horizontally. Vertically, they are placed together on alternate lines. Table 2-1. SubWidthC and SubHeightC values derived from chroma_format_idc and separate_colour_plane_flag 2.2. Encoding and decoding streams of typical video codecs Figure 5 An example of the encoder block diagram of VVC is shown, which includes three loop filter blocks: the deblocking filter (DF), sample adaptive offset (SAO), and ALF. Different from the DF that 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 an offset and by applying a finite impulse response (FIR) filter respectively, where the encoded and decoded side information signals the offset and the filter coefficients. ALF is located at the last processing stage of each picture and can be regarded as a tool that attempts to capture and fix the artifacts created by the previous stages. 2.3. Intra-mode encoding and decoding 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 Figure 6as shown in , and the planar mode and the DC mode remain the same. These denser intra prediction modes in the direction frame are applicable to all block sizes and both luma intra prediction and chroma intra prediction. In HEVC, each intra-coded block has a square shape, and the length of each side is a power of 2. Therefore, no division operation is required to generate the intra prediction value using the DC mode. In VVC, in general, a block can have a rectangular shape that 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 also depends on the block shape. The conventional angular intra prediction directions are defined as from 45 degrees to -135 degrees in the clockwise direction. In VVC, several conventional angular intra prediction modes are adaptively replaced by wide-angle intra prediction modes for non-square blocks. The replaced modes are signaled using the original mode index, which is remapped to the index of the wide-angle mode after parsing. The total number of intra prediction modes remains the same, i.e., 67, and the intra mode coding and decoding method remains unchanged. To support these prediction directions, as Figure 7 shown, a top reference of length 2W + 1 and a left reference of length 2H + 1 are defined. The number of replaced modes for 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 edge smoothing are applied to wide-angle prediction to reduce the negative impact on the increased gap Δp α . If the wide-angle mode represents a non-fractional offset. There are 8 modes in the wide-angle mode that satisfy this condition, and these 8 modes are [-14, -12, -10, -6, 72, 76, 78, 80]. When a block is predicted by these modes, the samples in the reference buffer are directly copied without applying any interpolation. By this modification, the number of samples that need to be smoothed is reduced. In addition, it aligns the design of non-fractional modes in the conventional prediction mode and the wide-angle mode. In VVC, 4∶2∶2 chroma format, 4∶4∶4 chroma format, and 4∶2∶0 are supported. The chroma derivation mode (DM) derivation table for the 4∶2∶2 chroma format was originally 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 mode changing from 2 to 5 is mapped to 2. Therefore, the chroma DM derivation table for the 4∶2∶2 chroma format is updated by replacing some values of the mapping table entries to more accurately transform the prediction angles of chroma blocks. 2.4. Inter - frame prediction For each inter - frame predicted CU, motion parameters including motion vectors, reference picture indices, and reference picture list - used indices, as well as additional information required by the new decoding features of VVC are used for inter - frame predicted sample generation. The motion parameters can be signaled in an explicit or implicit manner. When a CU is coded / decoded in skip mode, the CU is associated with a PU and has no significant residual coefficients, no coded / decoded motion vector delta, or reference picture index. The Merge mode is specified, whereby the motion parameters for the current CU are obtained from neighboring CUs, including spatial candidates and temporal candidates, as well as additional scheduling introduced in VVC. The Merge mode can be applied to any inter - frame predicted CU, not only for skip mode. An alternative to the Merge mode is the explicit transmission of motion parameters, where for each reference picture list and for each CU, the motion vectors, corresponding reference picture indices, using flags and other required information for the reference picture list are explicitly signaled. 2.5. 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 coding / decoding efficiency of screen content materials. Since the IBC mode is implemented as a block - level coding / 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 luma block vectors of CUs coded / decoded by IBC are of integer precision. The chroma block vectors are also rounded to integer precision. When combined with AMVR, the IBC mode can switch between 1 - pixel motion vector precision and 4 - pixel motion vector precision. CUs coded / decoded by IBC are regarded as a third prediction mode different from intra or inter - frame prediction modes. The IBC mode is applicable to CUs with both width and height less than or equal to 64 luma 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 luma samples. For non-Merge modes, 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 current block of a larger size, the hash key is determined to match the hash key of the reference block when all 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 for each matching reference is calculated, and the block vector cost with the minimum cost is selected. In the block-matching search, the search range is set to cover both the previous CTU and the current CTU. At the CU level, the IBC mode utilization flag is signaled, and it can be signaled as the following IBC AMVP mode or IBC skip / Merge mode: - IBC skip / Merge mode: The Merge candidate index is used to indicate which block vectors from the list of IBC-encoded blocks of neighboring candidates are used to predict the current block. The Merge list consists of spatial, HMVP, and pairwise 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 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. 2.6. Merge Mode with MVD (MMVD) In addition to the Merge mode, in the case where implicitly derived motion information is directly used for the prediction sample generation of the current CU, the Merge mode with motion vector difference (MMVD) is introduced in VVC. The MMVD flag is signaled immediately after the regular Merge flag is sent to specify whether the MMVD mode is used for the CU. In MMVD, after selecting a Merge candidate, it is further refined by MVD information transmitted via signals. The further information includes a Merge candidate flag, an index for specifying a motion dimension, and an index for indicating a motion direction. In the MMVD mode, one of the first two candidates in the Merge list is selected to be used as the MV basis. The MMVD candidate flag is transmitted via signals to specify which one is used between the first Merge candidate and the second Merge candidate. Figure 9 is an illustration of motion vector scaling for time-domain Merge candidates. The distance index specifies the motion dimension information and indicates a predefined offset from the starting point. As Figure 10 shown, the offset is added to the horizontal or vertical component of the starting MV. The relationship between the distance index and the predefined offset is specified in Table 2-3. Table 2-3 - Relationship between distance index and predefined offset The direction index indicates the direction of the MVD relative to the starting point. The direction index can represent four directions as shown in Table 2-4. It should be noted that the meaning of the MVD sign can vary according to the information of the starting MV. When the starting MV is a uni-directional prediction MV or a bi-directional prediction MV where both lists point to the same side of the current picture (i.e., the POCs of both references are greater than the POC of the current picture, or both are less than the POC of the current picture), the signs in Table 2-4 specify the signs of the MV offsets added to the starting MV. When the starting MV is a bi-directional prediction MV with two MVs pointing to different sides of the current picture (i.e., the POC of one reference is greater than the POC of the current picture, and the POC of the other reference is less than the POC of the current picture), and the POC difference in List 0 is greater than the POC difference in List 1, the signs in Table 2-4 specify the signs of the MV offsets added to the List 0 MV component of the starting MV, and the sign of the List 1 MV has the opposite value. Otherwise, if the POC difference in List 1 is greater than List 0, the signs in Table 2-4 specify the signs of the MV offsets added to the List 1 MV component of the starting MV, and the sign of the List 0 MV has the opposite value. The MVD is scaled according to the POC differences in each direction. If the POC differences in the two lists are the same, no scaling is required. Otherwise, if the POC difference in List 0 is greater than the one in List 1, the MVD of List 1 is scaled by defining the POC difference of L0 as td and the POC difference of L1 as tb, as described in Figure 9 . If the POC difference of L1 is greater than L0, the MVD of List 0 is scaled in the same way. If the starting MV is uni-directional prediction, the MVD is added to the available MV. Table 2-4 - Signs of MV offsets specified by the direction index Direction Index 00 01 10 11 x-axis + - N / A NA y-axis N / A N / A + - 2.7. Local Illumination Compensation (LIC) Local Illumination Compensation (LIC) is a codec tool used to address the problem of local illumination changes between the current picture and its temporal reference picture. LIC is based on a linear model, where scaling factors and offsets are applied to reference samples to obtain the predicted samples of the current block. Specifically, LIC can be mathematically modeled by the following equation: P(x, y) = α·P r (x + v x , y + v y ) + β where P(x, y) is the predicted signal of the current block at coordinates (x, y); P r (x + v x , y + v y ) is the reference block pointed to by the motion vector (v x , v y ); and α and β are the corresponding scaling factor and offset applied to the reference block. Figure 11 Fig. shows the LIC process. In Figure 11 , when LIC is applied to a block, the Least Mean Square Error (LMSE) method is adopted to derive the values of the LIC parameters (i.e., α and β) by minimizing the difference between the neighboring samples of the current block (i.e., the template T in Figure 11 ) and their corresponding reference samples in the temporal reference picture (i.e., T0 or T1 in Figure 11 ). Additionally, to reduce the computational complexity, both the template samples and the reference template samples are downsampled (adaptive downsampling) to derive the LIC parameters, i.e., only the shaded samples in Figure 11 are used to derive α and β. To improve the codec performance, no downsampling is performed on the short side as shown in Figure 12 . 2.8. IBC Using Template Matching The proposal also uses template matching with IBC for both the IBC Merge mode and the IBC AMVP mode. The IBC-TM Merge list has been modified compared to the list used by the regular IBC Merge mode, such that candidates are selected according to the motion distances between candidates in the same way as in the regular TM Merge mode using a deduplication method. The end-zero motion fulfillment (which is meaningless for intra-frame coding) has been replaced by the motion vectors of the left (-W, 0) CU, top (0, -H) CU, and top-left (-W, -H) CU, and then, if necessary, the left CU fulfillment list is used without deduplication. In the IBC-TM Merge mode, a template matching method is utilized to refine the selected candidates before the RDO or decoding process. The IBC-TM Merge mode has competed with the regular IBC Merge mode and signals the TM-Merge flag. In the IBC-TM AMVP mode, up to 3 candidates are selected from the IBC Merge list. The template matching method is used to refine each of these 3 selected candidates, and they are sorted according to their resulting template matching costs. Then, typically only the first two candidates are considered during the motion estimation process. The template matching refinement for both the IBC-TM Merge mode and the AMVP mode is very simple because the IBC motion vectors are constrained to be integers and are within the reference region as Figure 13 shown. Thus, in the IBC-TM Merge mode, all refinements are performed with integer precision, and in the IBC-TM AMVP mode, it is performed with integer or 4-pixel precision. In both cases, the refined motion vectors in each refinement step must comply with the constraints of the reference region. 2.9. IBC Merge Mode with Block Vector Difference The IBC Merge mode with block vector difference is as follows. The distance set is {1-pixel, 2-pixel, 4-pixel, 8-pixel, 12-pixel, 16-pixel, 24-pixel, 32-pixel, 40-pixel, 48-pixel, 56-pixel, 64-pixel, 72-pixel, 80-pixel, 88-pixel, 96-pixel, 104-pixel, 112-pixel, 120-pixel, 128-pixel}, and the BVD directions are two horizontal directions and two vertical directions. The base candidate is selected from the first five candidates in the reordered IBC Merge list. And for all possible MBVD refinement positions (20×4) of each base candidate, they are reordered based on the SAD cost between the template (one row above the current block and one column to the left of the current block) and the reference at each refinement position. Finally, the first 8 refinement positions with the lowest template SAD cost are kept as available positions and thus used for MBVD index coding and decoding. 2.10. Reconstruction Reordered IBC (RR-IBC) Screen content coding and decoding tools similar to Intra Block Copy (IBC) generate predicted blocks by directly copying previously decoded reference regions in the same picture. Symmetry is often observed in video content, especially in text character regions and computer-generated graphics in screen content sequences, as Figure 14 shown. Therefore, specific screen content coding and decoding tools that consider symmetry will effectively compress such video content. A reconstructed reordering IBC (RR-IBC) mode for screen content video coding and decoding is proposed. When applied, samples in the reconstructed block are flipped according to the flip type of the current block. On the encoder side, the original block is flipped before motion search and residual calculation, while the prediction block is derived without flipping. On the decoder side, the reconstructed block is flipped to restore the original block. For blocks coded and decoded by RR-IBC, two flipping methods are supported, horizontal flipping and vertical flipping. First, for blocks coded and decoded by IBC AMVP, a syntax flag is signaled to indicate whether the reconstruction is flipped, and if it is flipped, another flag specifying the flip type is further signaled. For IBC Merge, without syntax signaling, the flip type is inherited from neighboring blocks. Considering horizontal symmetry or vertical symmetry, the current block and the reference block are usually horizontally or vertically aligned. Therefore, when horizontal flipping is applied, the vertical component of the BV is not signaled and is presumed to be equal to 0. Similarly, when vertical flipping is applied, the horizontal component of the BV is not signaled and is presumed to be equal to 0. To better utilize the symmetry property, a flip-aware BV adjustment method is applied to refine the block vector candidates. For example, as Figure 15A and Figure 15B shown, (x nbr , y nbr ) and (x cur , y cur ) represent the coordinates of the center samples of the neighboring block and the current block respectively, and BV nbr and BV cur represent the BV of the neighboring block and the current block respectively. Instead of directly inheriting the BV from the neighboring block, when the neighboring block is coded with horizontal flipping, the horizontal component of BV cur (denoted as BV nbr h ) is calculated by adding the motion shift to it to obtain the horizontal component of BV cur , that is, BV cur h = 2(x nbr - x cur ) + BV nbr h . Similarly, when the neighboring block is coded with vertical flipping, the vertical component of BV nbr (denoted as BV nbr v ) is calculated by adding the motion shift to it to obtain the vertical component of BV cur , that is, BV cur v = 2(y nbr - y cur ) + BV nbrv 。 2.11. Intra-frame Template Matching Intra-frame template matching prediction (intra-TMP) is a special intra-frame prediction mode that copies the best prediction block from the reconstructed part of the current frame, and its L-shaped template matches the current template. For a predefined search range, the encoder searches for the template in the reconstructed part of the current frame that is most similar to the current template and uses the corresponding block as the prediction block. The encoder then signals the use of this mode, and the same prediction operation is performed on the decoder side. By matching the L-shaped causal neighbors of the current block with another block in the predefined search area consisting of Figure 16 to generate a prediction signal: R1: the current CTU R2: the top-left CTU R3: the upper CTU R4: the left CTU. SAD is used as the cost function. Within each region, the decoder searches for the template that has the minimum SAD relative to the current one and uses its corresponding block as the prediction block. The sizes of all regions (SearchRange_w, SearchRange_h) are set proportionally to the block sizes (BlkW, BlkH) for which a fixed number of SAD comparisons are made per pixel. That is: SearchRange_w = a * BlkW SearchRange_h = a * BlkH where 'a' is a constant that controls the gain / complexity trade-off. In fact, 'a' is equal to 5. For CUs with dimensions less than or equal to 64 in width and height, the intra-frame template matching tool is enabled. This maximum CU size for intra-frame template matching is configurable. When DIMD is not used for the current CU, the intra-frame template matching prediction mode is signaled at the CU level through a dedicated flag. 2.12. Direct Block Vector (DBV) Mode for Chroma Prediction In ECM-6.0, the intra-frame prediction modes for the chroma components include 6 cross-component linear model (LM) modes, convolutional cross-component model (CCCM) mode, gradient linear model (GLM) mode, DIMD mode, direct mode (DM), and four default intra-frame prediction modes. In the signaling of the chroma intra-frame mode, intra_chroma_pred_mode is signaled to indicate a specific codec mode, as shown in Table 2-5. Binary processing of intra_chroma_pred_mode in ECM6.0 ECM6.0 includes a method of performing chrominance prediction using block vectors in MODE_IBC. In single-tree segmentation, the prediction process of IBC is applied to both the luminance component and the chrominance component, and the chrominance block vector is derived from the corresponding luminance block vector according to the chrominance format sampling structure. In double-tree segmentation, the prediction process of IBC is only applied to the luminance component. This contribution proposes a method to improve the coding efficiency of chrominance intra prediction for screen content, namely the direct block vector (DBV) mode. For the chrominance component, when the chrominance double-tree is activated in an intra slice, if one of the luminance blocks ( Figure 17 at the following five positions) in the luminance block is coded using MODE_IBC, its block vector bvL is used and scaled to derive the chrominance block vector bvC. The scaling factor depends on the chrominance format sampling structure. Then, by using the position of the current chrominance block (xCb, yCb) and its bvC, the corresponding offset position (xCb + bvC[0], yCb + bvC[1]) is determined, and block copy prediction is performed as Figure 18 shown. The proposed DBV mode is signaled at the CU level by a flag to indicate whether it is applied, as shown in Table 2-6. Table 2-6 - Binary processing of intra_chroma_pred_mode in the proposed method 2.13. Extension of intra block copy Several coding tools that combine inter prediction and intra prediction have been proposed to improve the coding performance of VTM and ECM, such as combined intra-inter prediction (CIIP), geometric partitioning mode with inter and intra prediction (GPM-intra). Similarly, intra block copy (IBC) can be improved by considering intra prediction. In addition, LIC in ECM-6.0 is an inter prediction technique for modeling the local illumination change between the current block and its predicted block. However, the illumination change within a picture has not been studied. In this contribution, three aspects of extending the use of IBC are proposed: Aspect #1: Combining IBC and intra prediction (IBC-CIIP); Aspect #2: IBC with geometric partitioning (IBC-GPM); Aspect #3: IBC with local illumination compensation (IBC-LIC). 2.13.1. Combining IBC and Intra Prediction (IBC-CIIP) When IBC-CIIP is applied to a CU, two prediction signals are obtained using IBC and intra prediction. The two prediction signals are weighted and summed to generate the final prediction. IBC-CIIP can be applied to the IBC AMVP mode and the IBC Merge mode. The use of IBC-CIIP is indicated by signaling a CU flag. 2.13.2. IBC with Geometric Partitioning (IBC-GPM) When IBC GPM is applied to a CU, the CU is geometrically partitioned into two sub-partitions. Prediction signals for the two sub-partitions are generated using IBC and intra prediction. IBC-GPM can be applied to the IBC Merge mode. The use of IBC-GPM is indicated by signaling a CU flag. 2.13.3. IBC with Local Illumination Compensation (IBC-LIC) When IBC-LIC is applied to a CU, the local illumination change between the CU and its prediction block is modeled as a linear equation. The parameters of the linear equation are derived similar to those for LIC for inter prediction. IBC-LIC can be applied to the IBC AMVP mode and the IBC Merge mode. For the IBC AMVP mode, the use of IBC-LIC is indicated by signaling an IBC-LIC flag. For the IBC Merge mode, the IBC-LIC flag is deduced from the Merge candidates. 3. Problem In the current design of the dual-tree partitioning in ECM, the prediction process of IBC is only applied to the luma component. In 2.12, a method called the Direct Block Vector (DBV) mode is used to enable IBC for the chroma component. However, only the first available luma block vector from five positions is scaled and used as the chroma block vector, which may limit the coding performance. 4. Detailed Solutions The following detailed solutions should be considered as examples to explain the general concepts. These solutions should not be interpreted in a narrow way. In addition, these solutions can be combined in any way. In the present disclosure, Intra Block Copy (IBC) may not be limited to current IBC techniques, but may be interpreted as a technique in which a reference (or prediction) block is obtained using samples in the current strip / slice / sub-picture / picture / other video unit (e.g., CTU row), excluding conventional intra prediction methods. In the following discussion, IBC may be replaced by other coding tools (e.g., palette, intra-template matching) that depend on the coded / decoded / reconstructed information within the same region. Determination of Block Vectors for Chrominance Prediction 1. It is proposed to construct at least one block vector (BV) candidate list for a video unit, and one or more block vectors in the list can be used for chrominance prediction of the video unit. a. In one example, the (multiple) lists can be constructed in different ways for a single-tree structure and a dual-tree structure. i. In one example, if the dual-tree structure is applied, different lists can be constructed for the luminance component and the chrominance component. ii. In one example, if the single-tree structure is applied, the (multiple) lists can be shared by the luminance component and the chrominance component. b. In one example, different chrominance components (such as Cb and Cr) can share the same BV. c. In one example, different chrominance components (such as Cb and Cr) can have different BVs. i. For example, the BVs for the two components can be refined separately. 1) The refinement can be template matching. d. In one example, one or more BVs of the list for the (multiple) chrominance components can be derived from the luminance component. i. In one example, the BV of the co-located luminance video unit can be used. 1) In one example, the co-located luminance video is located by the luminance position P L (x, y)), where the luminance position is obtained by the chrominance position P C (x, y)) and the downsampling rates for luminance and chrominance in different color formats. a) In one example, P L (x, y) = P C (x * SubWidthC, y * SubHeightC). 2) In one example, (P C (x, y)) can refer to the center position of the chrominance video unit. Denote the width and height of the chrominance video unit as W and H, and x is in the range from 0 to W - 1 (including 0 and W - 1), and y is in the range from 0 to H - 1 (including 0 and H - 1). a) In one example, (P C (x, y)) = (W / 2 - 1, H / 2 + 1). b) In one example, (P C (x, y)) = (W / 2 + 1, H / 2 - 1). c) In one example, (P C (x, y)) = (W / 2 - 1, H / 2 + 1). d) In one example, (P C (x, y)) = (W / 2 + 1, H / 2 + 1). 3) In one example, (P C (x, y)) may refer to the upper - left / upper - right / lower - left / lower - right position of a chrominance video unit. ii. In one example, one or more BVs of the spatial neighboring video units (adjacent and / or non - adjacent) of a co - located luma video unit may be used. iii. In one example, one or more BVs in the history - based block vector prediction (HBVP) table for IBC of the luma component may be used. 1) For example, the BV for a previously decoded and knitted block may be inserted into the HBVP table. iv. In one example, when encoding / decoding the neighboring video units of a co - located luma video unit using a specific mode, one or more BVs derived from the neighboring video units may be used. 1) For example, the specific mode may be intra - TMP. 2) For example, the specific mode may be IBC. v. In one example, the BV derived from the luma component may be scaled before being used to construct the BV candidate list for the chrominance component. 1) In one example, whether and / or how to scale the BV may depend on the color format. Denote bvLx, bvLy, bvCx, bvCy as the two components of the luma BV and the two components of the scaled chrominance BV. a) In one example, bvCx = bvLx >> (SubWidthC - 1). b) In one example, bvCy = bvLy >> (SubHeightC - 1). e. In one example, one or more BVs in the list may be derived from the chrominance component. i. In one example, one or more BVs of the spatial neighboring video units (neighboring and / or non - adjacent) of the current video unit may be used. ii. In one example, for the chrominance component, an HBVP table may be constructed. 1) In one example, how to generate / update / fill / define the HBVP table for chrominance may be the same as that for luma. a) Alternatively, how to generate / update / fill / define the HBVP table for chrominance may be different from that for luma. 2) In one example, how to use the HBVP table for chrominance may be the same as that for luma. a) Alternatively, how to use the HBVP table for chrominance may be different from that for luma. 3) In one example, one or more BVs in the HBVP table for chrominance can be used. iii. In one example, when coding / decoding neighboring video units using a specific mode, one or more BVs derived from the neighboring video units can be used. 1) For example, the specific mode can be intra TMP. 2) For example, the specific mode can be IBC. f. In one example, one or more default BVs can be used. g. In one example, one or more BVs can be added to the BV candidate list with different priorities. i. In one example, the BV from the co-located luma video can be added first. ii. In one example, the BV from the first candidate type can be added before the BV from the second candidate type, and the first candidate type is different from the second candidate type. 1) In one example, the first / second candidate type can refer to adjacent spatial neighboring video units or non-adjacent spatial neighboring video units or HBVP, or video units coded / decoded by intra TMP. iii. In one example, the default BV can be added to the last position of the BV candidate list. h. In one example, the BV candidate list can be reordered. i. In one example, the template matching (TM) cost or bilateral matching (BM) cost can be used for reordering. ii. In one example, the BV candidate list can be divided into different subgroups, and reordering can be applied within the subgroups. iii. In one example, the BV indices in the reordered list can be signaled in the bitstream. iv. In one example, the BV within the minimum TM / BV cost (e.g., at the first order in the reordered list) can be implicitly used for the video unit without signaling. i. In one example, the BVs in the list can be refined. i. In one example, TM can be used to refine the BV. ii. In one example, BM can be used to refine the BV. j. In one example, an index can be signaled in the bitstream to indicate which BV in the BV candidate list is used for chrominance prediction. i. Alternatively, the index can be derived instead of being signaled. k. In one example, the first available BV in the BV candidate list can be used for chrominance prediction. l. In one example, BV candidates can be constructed by using at least one BV derived from the luminance component and at least one BV derived from the chrominance component. i. For example, BV candidates can be constructed by averaging one BV derived from the luminance component and one BV derived from the chrominance component. 2. It is proposed that a BV offset can be added to the BV used for chrominance prediction. a. In one example, an offset or an (multiple) index indicating the offset in the offset set can be signaled in the bitstream or derived. i. In one example, the offset set can be predefined or signaled in the bitstream. ii. In one example, the offset set can be reordered. In one example, the combination of the BVs in the candidate list and the BV offsets in the offset set can be reordered. iii. In one example, the offset set can be defined as a distance table and a direction table (for example, examples are shown in Tables 2-3 and 2-4). 1) In one example, the first index in the distance table and the second index in the direction table can be coded and decoded separately. iv. In one example, the offset set can be defined as a single table (for example, containing both distance information and direction information). 1) In one example, one index in the offset set can be coded and decoded. v. In one example, the index can be context-coded. vi. In one example, the index in the reordered list can be coded and decoded using a Rice parameter. vii. In one example, the offset set can depend on the coding information. viii. In one example, the offset can be derived using a TM- or BM-based method. 1) In one example, the offset can be shared by different color components. 2) In one example, the offset can be different for different color components. b. In one example, whether to add a BV offset can be signaled in the bitstream. i. In one example, a syntax element can be signaled to indicate whether the BV offset is used. ii. In one example, one or more syntax elements can be signaled to indicate the BV offset. 1) In one example, the BV offset can be equal to zero. 2) In one example, reordering can be used to derive a BV offset through signal transmission. c. In one example, the offset of one component (such as Cb or Cr) can be predicted by the BV offset of another component (such as Y). 3. In one example, chrominance prediction using BV derivation is fused with other coding and decoding methods. a. In one example, other coding and decoding methods can refer to conventional intra prediction modes, or CCLM, or MMLM, or CCCM, or GLM, or DIMD, or TIMD, or intra TMP. b. In one example, chrominance prediction using BV derivation can be fused with the following: inter prediction modes (e.g., CIIP (e.g., CIIP-plane, CIIP-TIMD, CIIP-TM), BCW (e.g., BCW index derived by TM), MMVD (e.g., MMVD or TM-based reordering for MMVD), template matching (TM), IBC (e.g., IBC-TM, IBC with block vector difference, IBC with reconstructed reordering), affine (e.g., affine MMVD, TM-based reordering for affine MMVD), DMVR / multi-pass DMVR, PROF, BDOF / sample-based BDOF, adaptive decoder-side motion vector refinement (ADMVR), OBMC, or TM-based OBMC, MHP, GPM (e.g., GPM, GPM-TM, GPM-MMVD, GPM-intra), bilateral / template matching AMVP-Merge mode. c. In one example, chrominance prediction using BV derivation can be fused with luma prediction / reconstruction. d. In one example, the weights for fusion can be predefined, or signaled in the bitstream, or derived depending on the coding and decoding information. e. In one example, whether and / or how to fuse chrominance prediction can be signaled. i. Alternatively, whether and / or how to fuse chrominance prediction can depend on the coding and decoding information. 1) In one example, it can depend on whether fusion is used for collocated luma video units. 2) In one example, it can depend on the sequence content, such as fusion not being used for SCC sequences. ii. In one example, high-level syntax (HLS) can be signaled to indicate whether fusion can be used. f. In one example, whether and / or how to fuse chrominance prediction can be derived. i. In one example, TM-based methods can be used. 4. In one example, the chrominance BV of the current video unit can be used for subsequent video units. a. In one example, the chrominance BV of the current video unit can be stored. b. In one example, the chrominance BV of the current video unit can be added to the HBVP table for chrominance. c. In one example, the chrominance BV of the current video unit can be used for the processing of the current block (e.g., transform, MTS, LFNST, deblocking, loop filtering, etc.). d. Alternatively, the chrominance BV of the current video unit may not be used for subsequent video units. 5. In one example, when IBC is used for chrominance prediction, specific codec tools may be allowed to be used. a. In one example, specific codec tools may refer to IBC-TM, IBC-MBVD, RR-IBC, or IBC-IBC, or IBC-GPM, or IBC-CIIP. i. In one example, syntax elements may be signaled in the bitstream to indicate whether specific codec tools are used for chrominance prediction. b. In one example, the flip type of the chrominance RR-IBC block may be inherited from the flip type of the luminance block. i. For example, the luminance block may be: the co-located luminance block and / or its spatial (adjacent / non-adjacent) neighboring blocks, and / or a luminance block having a different position from the co-located luminance block. ii. Alternatively, the flip type of the chrominance RR-IBC block may be determined independently (e.g., the flip type of the chrominance block may be different from that of the luminance block). c. Alternatively, specific codec tools may not be allowed to be used. d. In one example, it is used in a dual tree. e. In one example, it is used in a single tree. General Aspects 6. In the above examples, a video unit may refer to a color component / sub-picture / strip / slice / coding tree unit (CTU) / CTU row / CTU group / coding unit (CU) / prediction unit (PU) / transformation unit (TU) / coding tree block (CTB) / coding block (CB) / prediction block (PB) / transformation block (TB) / block / sub-block of a block / sub-region within a block / any other region containing more than one sample or pixel. 7. Whether and / or how to apply the methods disclosed above can be signaled at the sequence level / picture group level / picture level / strip level / slice group level, such as in the sequence header / picture header / SPS / VPS / DPS / DCI / PPS / APS / strip header / slice group header. 8. Whether and / or how to apply the methods disclosed above can be signaled at PB / TB / CB / PU / TU / CU / VPDU / CTU / CTU row / strip / slice / sub-picture / other types of regions containing more than one sample or pixel. 9. Whether and / or how to apply the methods disclosed above can depend on transcoded information, such as block size, color format, mono / double tree segmentation, color component, strip / picture type.

[0076] Figure 19 A flowchart of a method 1900 for video processing according to an embodiment of the present disclosure is shown. Method 1900 is implemented during the conversion between a target video block of a video and the bitstream of the video.

[0077] At block 2010, at least one block vector (BV) candidate list is constructed for a video unit of the video for the conversion between the video unit of the video and the bitstream of the video unit.

[0078] At block 2020, one or more BVs in at least one BV candidate list are used for chrominance prediction of the video unit. In some embodiments, one or more default BVs in at least one BV candidate list are used for chrominance prediction of the video unit.

[0079] At block 2030, the conversion is performed based on the chrominance prediction of the video unit. In some embodiments, the conversion may include encoding the video unit into the bitstream. Alternatively, the conversion may include decoding the video unit from the bitstream. In this way, the encoding / decoding efficiency and encoding / decoding performance can be improved.

[0080] In some embodiments, different chrominance components may share the same BV in at least one BV candidate list. For example, different chrominance components include the Cb component and the Cr component.

[0081] In some embodiments, one or more BVs in at least one BV candidate list are derived from chrominance components. In some embodiments, one or more BVs of spatially neighboring video units of the video unit are used for chrominance prediction of the video unit. For example, the spatially neighboring video units may be adjacent and / or non-adjacent.

[0082] In some embodiments, a history-based block vector prediction (HBVP) table is constructed for the chrominance component. In some embodiments, the scheme for generating (updating / populating / defining) the HBVP table for the chrominance component is the same as the scheme for generating the HBVP table for the luminance component. Alternatively, the scheme for generating the HBVP table for the chrominance component is different from the scheme for generating the HBVP table for the luminance component.

[0083] In some embodiments, the scheme for using the HBVP table for the chrominance component is the same as the scheme for using the HBVP table for the luminance component. Alternatively, the scheme for using the HBVP table for the chrominance component is different from the scheme for using the HBVP table for the luminance component.

[0084] In some embodiments, one or more BVs in the HBVP table for chrominance are used for chrominance prediction. In some embodiments, when neighboring video units are encoded / decoded using a target mode, one or more BVs derived from the neighboring video units are used for chrominance prediction. In some embodiments, the target mode is one of the following: intra-template matching (intra-TMP) mode or intra-block copy (IBC) mode.

[0085] In some embodiments, one or more BVs of at least one BV candidate list for the chrominance component are derived from the luminance component. In some embodiments, the BV of the co-located luminance video unit is used. In some embodiments, the co-located luminance video is located by the luminance position P L (x, y). The luminance position can be obtained by the chrominance position P C (x, y) and the downsampling ratios of luminance and chrominance in different color formats. In some embodiments, P L (x, y) = P C (x * SubWidthC, y * SubHeightC).

[0086] In some embodiments, the chrominance position P C (x, y) is the center position of the chrominance video unit. In some embodiments, (P C (x, y)) = (W / 2 - 1, H / 2 + 1), or (P C (x, y)) = (W / 2 + 1, H / 2 - 1), or (P C (x, y)) = (W / 2 - 1, H / 2 + 1), or (P C (x, y)) = (W / 2 + 1, H / 2 + 1). W may represent the width of the chrominance video unit, H may represent the height of the chrominance video unit, x may range from 0 to W - 1, and y may range from 0 to H - 1. In some other embodiments, the chrominance position PC (x, y)) is one of the following: the upper left position of the chrominance video unit, the upper right position of the chrominance video unit, the lower left position of the chrominance video unit, or the lower right position of the chrominance video unit.

[0087] In some embodiments, one or more BVs of the spatial neighboring video units of the co-located luma video unit are used for chrominance prediction. In one example, one or more BVs of the spatial neighboring video units (adjacent and / or non-adjacent) of the co-located luma video unit may be used.

[0088] In some embodiments, one or more BVs in the HBVP table for IBC of the luma component are used for chrominance prediction. In some embodiments, BVs for previously decoded and encoded blocks are inserted into the HBVP table.

[0089] In some embodiments, when the neighboring video units of the co-located luma video unit are encoded and decoded using the target mode, one or more BVs derived from the neighboring video units are used for chrominance prediction. In some embodiments, the target mode is one of the following: the intra TMP mode or the IBC mode. In some embodiments, one or more BVs derived from the luma component are scaled before being used to construct at least one BV candidate list.

[0090] In some embodiments, whether and / or how to scale one or more BVs depends on the color format. In some embodiments, bvCx = bvLx >> (SubWidthC - 1), or where bvCy = bvLy >> (SubHeightC - 1), and where bvLx and bvLy represent two components of the luma BV, and bvCx and bvCy represent two components of the scaled chrominance BV.

[0091] In some embodiments, one or more BVs are added to at least one BV candidate list with different priorities. In some embodiments, the BV from the co-located luma video is added first.

[0092] In some embodiments, the BV from the first candidate type is added before the BV from the second candidate type, and where the first candidate type is different from the second candidate type. In some embodiments, the first candidate type or the second candidate type is one of the following: an adjacent spatial neighboring video unit, a non-adjacent spatial neighboring video unit, HBVP, or a video unit encoded and decoded by intra TMP. In some embodiments, the default BV is added to the last position of at least one BV candidate list.

[0093] In some embodiments, at least one BV candidate list is reordered. In some embodiments, template matching (TM) cost or bilateral matching (BM) cost is used to reorder at least one BV candidate list. In some embodiments, at least one BV candidate list is divided into different subgroups, and the reordering of at least one BV candidate list is applied within the subgroups. In some embodiments, the BV indices in the reordered BV candidate list are indicated in the bitstream. In some embodiments, the BV within the minimum TM cost or BM cost (e.g., at the first order in the reordered list) is implicitly used for the video unit without signaling.

[0094] In some embodiments, at least one BV candidate list is constructed in different ways for the single-tree structure and the dual-tree structure. In some embodiments, if the dual-tree structure is applied, different BV candidate lists are constructed for the luminance component and the chrominance component. In some embodiments, if the single-tree structure is applied, at least one BV candidate list is shared by the luminance component and the chrominance component.

[0095] In some embodiments, different chrominance components have different BVs. For example, the BVs for two components are refined separately. In some embodiments, the refinement of the BV is template matching.

[0096] In some embodiments, the BVs in at least one BV candidate list are refined. In some embodiments, TM is used to refine the BV. Alternatively, BM is used to refine the BV.

[0097] In some embodiments, an index is indicated in the bitstream to indicate which BV in at least one BV candidate list is used for chrominance prediction. In some embodiments, an index is indicated in the bitstream to indicate which BV in at least one BV candidate list is derived.

[0098] In some embodiments, the first available BV in at least one BV candidate list is used for chrominance prediction. In some embodiments, the BV candidate is constructed by using at least one BV derived from the luminance component and at least one BV derived from the chrominance component. In some embodiments, the BV candidate is constructed by averaging one BV derived from the luminance component and one BV derived from the chrominance component.

[0099] In some embodiments, a BV offset is added to one or more BVs used for chrominance prediction. In some embodiments, the BV offset or an index indicating the BV offset in the offset set is indicated in the bitstream. Alternatively, the BV offset or an index indicating the BV offset in the offset set is derived.

[0100] In some embodiments, the BV offset set is predefined. Alternatively, the BV offset is indicated in the bitstream. In some embodiments, the BV offset set is reordered. In some embodiments, the combination of the BV in at least one BV candidate list and the BV offset in the offset set is reordered.

[0101] In some embodiments, the offset set is defined as a distance table and a direction table (e.g., examples are shown in Tables 2-3 and 2-4). In some embodiments, the first index in the distance table and the second index in the direction table are separately coded and decoded.

[0102] In some embodiments, the offset set is defined as a single table. For example, the single table can include both distance information and direction information. In some embodiments, the index indicating the BV offset in the offset set is coded and decoded.

[0103] In some embodiments, the index indicating the BV offset is context-coded. In some embodiments, the index indicating the BV offset in the reordered BV candidate list is coded using a Rice parameter. In some embodiments, the offset set depends on the coded information.

[0104] In some embodiments, the BV offset is derived using a TM- or BM-based scheme. In some embodiments, the BV offset is shared by different color components. Alternatively, the BV offset is different for different color components.

[0105] In some embodiments, whether to add the BV offset is indicated in the bitstream. In some embodiments, a syntax element is signaled to indicate whether the BV offset is used.

[0106] In some embodiments, one or more syntax elements are signaled to indicate the BV offset. In some embodiments, the BV offset is equal to zero. In some embodiments, reordering is used to signal or derive the BV offset. In some embodiments, the BV offset of one component (such as Cb or Cr) is predicted by the BV offset of another component (such as Y).

[0107] In some embodiments, the chrominance prediction derived using the one or more BVs is combined with other coding methods. In some embodiments, the other coding methods can include at least one of the following: conventional intra prediction mode, cross-component linear mode (CCLM), multi-mode learner mode (MMLM), convolutional cross-component model (CCCM), general linear mode (GLM), decoder-side intra mode derivation (DIMD), template-based intra mode derivation (TIMD), or intra TMP.

[0108] In some embodiments, one or more BV-derived chrominance predictions are combined with at least one of the following: an inter prediction mode (e.g., CIIP, CII-plane, CII-TIMD, CIIP-TM), bi-directional prediction with codec unit-level weights (BCW) (e.g., BCW index derived from TM), Merge mode with motion vector difference (MMVD) (e.g., MMVD or TM-based reordering for MMVD), template matching (TM), IBC (e.g., IBC-TM, IBC with block vector difference, IBC with reconstruction reordering), affine (e.g., affine MMVD, TM-based reordering for affine MMVD), decoder-side motion vector refinement (DMVR), multi-pass DMVR, prediction refinement using optical flow (PROF), bi-directional optical flow (BDOF), sample-based BDOF, adaptive decoder-side motion vector refinement (ADMVR), overlapped block motion compensation (OBMC), TM-based OBMC, multi-hypothesis prediction (MHP), geometric partitioning mode (GPM) (e.g., GPM, GPM-TM, GPM-MMVD, GPM-intra), bilateral AMVP-Merge mode or template matching AMVP-Merge mode. In some embodiments, one or more BV-derived chrominance predictions are combined with luminance prediction or luminance reconstruction.

[0109] In some embodiments, the weights for combination are predefined. Alternatively, the weights are signaled in the bitstream. In some other embodiments, the weights are derived depending on the codec information.

[0110] In some embodiments, whether to combine chrominance prediction and / or the scheme for combining chrominance prediction is signaled. In some embodiments, whether to combine chrominance prediction and / or the scheme for combining chrominance prediction depends on the codec information. In some embodiments, whether to combine chrominance prediction and / or the scheme for combining chrominance prediction depends on whether the combination is used for co-located luma video units. In some embodiments, whether to combine chrominance prediction and / or the scheme for combining chrominance prediction depends on the sequence content, such as the fusion not being used for SCC sequences.

[0111] In some embodiments, high-level syntax (HLS) is signaled to indicate whether the combination is used. In some embodiments, whether to combine chrominance prediction and / or the scheme for combining chrominance prediction is derived. In some embodiments, TM-based methods are used for combining chrominance prediction.

[0112] In some embodiments, the chrominance BV of a video unit is used for subsequent video units. In some embodiments, the chrominance BV of a video unit is stored. In some embodiments, the chrominance BV of the current video unit is added to the HBVP table for chrominance. In some embodiments, the chrominance BV of a video unit is used for the processing of the current block (e.g., transform, MTS, LFNST, deblocking, loop filtering, etc.). In some embodiments, the chrominance BV of a video unit is not used for subsequent video units.

[0113] In some embodiments, when IBC is used for chrominance prediction, the target codec tool is allowed to be used. For example, the target codec tool includes at least one of the following: IBC-TM, IBC with Merge mode having block vector difference (IBC-MBVD), reconstructed reordered IBC (RR-IBC), IBC-IBC, IBC-GPM, or IBC-intra / inter joint prediction (IBC-CIIP). In some embodiments, a syntax element is signaled in the bitstream to indicate whether the target codec tool is used for chrominance prediction.

[0114] In some embodiments, the flip type of a chrominance RR-IBC block is inherited from the flip type of a luminance block. For example, the luminance block is at least one of the following: a co-located luminance block, a spatial (adjacent / non-adjacent) neighboring block of a co-located luminance block, or a luminance block having a different position from the co-located luminance block.

[0115] In some embodiments, the flip type of a chrominance RR-IBC block is determined independently. For example, the flip type of a chrominance block can be different from that of a luminance block.

[0116] In some embodiments, the target codec tool is used in a dual tree, or where the target codec tool is used in a single tree. In some embodiments, when IBC is used for chrominance prediction, the target codec tool is not allowed to be used. In some embodiments, a video unit includes at least one of the following: a color component, a prediction block (PB), a transform block (TB), a codec block (CB), a prediction unit (PU), a transform unit (TU), a codec tree block (CTB), a codec unit (CU), a codec tree unit (CTU), a CTU row, a CTU group, a slice, a picture, a sub-picture, a block, a sub-region within a block, or a region containing more than one sample or pixel.

[0117] In some embodiments, an indication of whether and / or how to utilize one or more BVs from at least one BV candidate list for chrominance prediction of a video unit is indicated at one of the following: sequence level, picture group level, picture level, slice level, or slice group level.

[0118] In some embodiments, an indication of whether and / or how to utilize one or more block vectors (BVs) from at least one BV candidate list for chrominance prediction of a video unit is indicated in one of the following: sequence header, picture header, sequence parameter set (SPS), video parameter set (VPS), dependency parameter set (DPS), decoding capability information (DCI), picture parameter set (PPS), adaptive parameter set (APS), slice header, or slice group header.

[0119] In some embodiments, an indication of whether and / or how to utilize one or more BVs from at least one BV candidate list for chrominance prediction of a video unit is included in one of the following: prediction block (PB), transform block (TB), codec block (CB), prediction unit (PU), transform unit (TU), codec unit (CU), virtual pipeline data unit (VPDU), codec tree unit (CTU), CTU row, slice, picture, sub-picture; or a region containing more than one sample or pixel.

[0120] In some embodiments, method 1900 further includes: determining whether and / or how to utilize one or more BVs from at least one BV candidate list for chrominance prediction of a video unit based on the decoded information of the video unit, where the decoded information includes at least one of the following: block size, color format, single-tree and / or dual-tree segmentation, color component, slice type, or picture type.

[0121] According to further embodiments of the present disclosure, a non-transitory computer-readable recording medium is provided. The non-transitory computer-readable recording medium stores a bitstream of a video generated by a method executed by a device for video processing. The method includes: constructing at least one block vector (BV) candidate list for a video unit of a video; utilizing one or more BVs from at least one BV candidate list for chrominance prediction of the video unit; and generating a bitstream based on the chrominance prediction of the video unit.

[0122] According to still further embodiments of the present disclosure, a method for storing a bitstream of a video is provided. The method includes: constructing at least one block vector (BV) candidate list for a video unit of a video; utilizing one or more BVs from at least one BV candidate list for chrominance prediction of the video unit; generating a bitstream based on the chrominance prediction of the video unit; and storing the bitstream in a non-transitory computer-readable medium.

[0123] The embodiments of the present disclosure may be described according to the following clauses, and the features may be combined in any reasonable manner.

[0124] Item 1. A method for video processing, comprising: constructing at least one block vector (BV) candidate list for a video unit for conversion between the video unit and a bitstream of the video unit; using one or more BVs in the at least one BV candidate list for chrominance prediction of the video unit; and performing the conversion based on the chrominance prediction of the video unit.

[0125] Item 2. The method according to Item 1, wherein different chrominance components share the same BV in the at least one BV candidate list.

[0126] Item 3. The method according to Item 2, wherein the different chrominance components include a Cb component and a Cr component.

[0127] Item 4. The method according to Item 1, wherein one or more default BVs in the at least one BV candidate list are used for the chrominance prediction of the video unit.

[0128] Item 5. The method according to Item 1, wherein one or more BVs in the at least one BV candidate list are derived from chrominance components.

[0129] Item 6. The method according to Item 5, wherein one or more BVs of a spatial neighboring video unit of the video unit are used for the chrominance prediction of the video unit.

[0130] Item 7. The method according to Item 5, wherein a history-based block vector prediction (HBVP) table is constructed for chrominance components.

[0131] Item 8. The method according to Item 7, wherein the scheme for generating the HBVP table for chrominance components is the same as the scheme for generating the HBVP table for luminance components, or wherein the scheme for generating the HBVP table for chrominance components is different from the scheme for generating the HBVP table for luminance components.

[0132] Item 9. The method according to Item 7, wherein the scheme for using the HBVP table for chrominance components is the same as the scheme for using the HBVP table for luminance components, or wherein the scheme for using the HBVP table for chrominance components is different from the scheme for using the HBVP table for luminance components.

[0133] Item 10. The method according to Item 7, wherein one or more BVs in the HBVP table for chrominance are used for the chrominance prediction.

[0134] Item 11. The method according to Item 5, wherein when neighboring video units are encoded or decoded using a target mode, one or more BVs derived from the neighboring video units are used for the chrominance prediction.

[0135] Item 12. The method according to Item 11, wherein the target mode is one of the following: an intra-template matching (intra-TMP) mode or an intra-block copy (IBC) mode.

[0136] Item 13. The method according to Item 1, wherein one or more BVs of the at least one BV candidate list for the chrominance component are derived from the luminance component.

[0137] Item 14. The method according to Item 13, wherein the BV of the co-located luminance video unit is used.

[0138] Item 15. The method according to Item 14, wherein the co-located luminance video is located by a luminance position P L (x, y)), where the luminance position is obtained by a chrominance position P C (x, y)) and a downsampling ratio for luminance and chrominance in different color formats.

[0139] Item 16. The method according to Item 15, wherein P L (x, y) = P C (x * SubWidthC, y * SubHeightC).

[0140] Item 17. The method according to Item 15, wherein the chrominance position P C (x, y)) is the center position of the chrominance video unit.

[0141] Item 18. The method according to Item 17, wherein (P C (x, y)) = (W / 2 - 1, H / 2 + 1), or wherein (P C (x, y)) = (W / 2 + 1, H / 2 - 1), or wherein (P C (x, y)) = (W / 2 - 1, H / 2 + 1), or wherein (P C (x, y)) = (W / 2 + 1, H / 2 + 1), and wherein W represents the width of the chrominance video unit, H represents the height of the chrominance video unit, x is in the range of 0 to W - 1, and y is in the range of 0 to H - 1.

[0142] Item 19. The method according to Item 15, wherein the chrominance position P C(x, y)) is one of the following: the upper left position of the chrominance video unit, the upper right position of the chrominance video unit, the lower left position of the chrominance video unit, or the lower right position of the chrominance video unit.

[0143] Item 20. The method according to Item 13, wherein one or more BVs of the spatial neighboring video units of the co-located luma video unit are used for the chrominance prediction.

[0144] Item 21. The method according to Item 13, wherein one or more BVs in the HBVP table for IBC of the luma component are used for the chrominance prediction.

[0145] Item 22. The method according to Item 21, wherein the BV for the previously transcoded block is inserted into the HBVP table.

[0146] Item 23. The method according to Item 13, wherein when the neighboring video units of the co-located luma video unit are coded using the target mode, one or more BVs derived from the neighboring video units are used for the chrominance prediction.

[0147] Item 24. The method according to Item 23, wherein the target mode is one of the following: intra TMP mode or IBC mode.

[0148] Item 25. The method according to Item 13, wherein one or more BVs derived from the luma component are scaled before being used to construct the at least one BV candidate list.

[0149] Item 26. The method according to Item 25, wherein whether and / or how to scale the one or more BVs depends on the color format.

[0150] Item 27. The method according to Item 26, wherein bvCx = bvLx>>(SubWidthC - 1), or wherein bvCy = bvLy >> (SubHeightC - 1), and wherein bvLx and bvLy represent two components of the luma BV, and bvCx and bvCy represent two components of the scaled chrominance BV.

[0151] Item 28. The method according to Item 1, wherein the one or more BVs are added to the at least one BV candidate list with different priorities.

[0152] Item 29. The method according to Item 28, wherein the BV from the co-located luma video is added first.

[0153] Item 30. The method according to Item 28, wherein the BV from the first candidate type is added before the BV from the second candidate type, and wherein the first candidate type is different from the second candidate type.

[0154] Item 31. The method according to Item 30, wherein the first candidate type or the second candidate type is one of the following: an adjacent spatial neighborhood video unit, a non-adjacent spatial neighborhood video unit, an HBVP, or a video unit encoded / decoded by intra-TMP.

[0155] Item 32. The method according to Item 28, wherein the default BV is added to the last position of the at least one BV candidate list.

[0156] Item 33. The method according to Item 1, wherein the at least one BV candidate list is reordered.

[0157] Item 34. The method according to Item 33, wherein a template matching (TM) cost or a bilateral matching (BM) cost is used to reorder the at least one BV candidate list.

[0158] Item 35. The method according to Item 33, wherein the at least one BV candidate list is divided into different subgroups, and the reordering of the at least one BV candidate list is applied within the subgroups.

[0159] Item 36. The method according to Item 33, wherein the BV indices in the reordered BV candidate list are indicated in the bitstream.

[0160] Item 37. The method according to Item 33, wherein the BV within the minimum TM cost or BM cost is implicitly used for the video unit without signaling.

[0161] Item 38. The method according to Item 1, wherein the at least one BV candidate list is constructed in different ways for a single-tree structure and a dual-tree structure.

[0162] Item 39. The method according to Item 38, wherein if a dual-tree structure is applied, different BV candidate lists are constructed for the luminance component and the chrominance component.

[0163] Item 40. The method according to Item 38, wherein if a single-tree structure is applied, the at least one BV candidate list is shared by the luminance component and the chrominance component.

[0164] Item 41. The method according to Item 1, wherein different chrominance components have different BVs.

[0165] Item 42. The method according to item 41, wherein the BV for two components is refined separately.

[0166] Item 43. The method according to item 41, wherein the refinement of the BV is template matching.

[0167] Item 44. The method according to item 1, wherein the BV in the at least one BV candidate list is refined.

[0168] Item 45. The method according to item 44, wherein TM is used to refine the BV, or wherein BM is used to refine the BV.

[0169] Item 46. The method according to item 1, wherein an index is indicated in the bitstream to indicate which BV in the at least one BV candidate list is used for chrominance prediction.

[0170] Item 47. The method according to item 1, wherein an index is indicated in the bitstream to indicate which BV in the at least one BV candidate list is derived.

[0171] Item 48. The method according to item 1, wherein the first available BV in the at least one BV candidate list is used for the chrominance prediction.

[0172] Item 49. The method according to item 1, wherein BV candidates are constructed by using at least one BV derived from the luminance component and at least one BV derived from the chrominance component.

[0173] Item 50. The method according to item 1, wherein BV candidates are constructed by averaging one BV derived from the luminance component and one BV derived from the chrominance component.

[0174] Item 51. The method according to any one of items 1 to 50, wherein a BV offset is added to the one or more BVs used for the chrominance prediction.

[0175] Item 52. The method according to item 51, wherein the BV offset or an index indicating the BV offset in the offset set is indicated in the bitstream, or wherein the BV offset or the index indicating the BV offset in the offset set is derived.

[0176] Item 53. The method according to item 52, wherein the BV offset set is predefined, or wherein the BV offset is indicated in the bitstream.

[0177] Item 54. The method according to item 52, wherein the BV offset set is reordered.

[0178] Item 55. The method according to item 52, wherein the combination of the BV in the at least one BV candidate list and the BV offset in the offset set is reordered.

[0179] Item 56. The method according to item 52, wherein the offset set is defined as a distance table and a direction table.

[0180] Item 57. The method according to item 56, wherein the first index in the distance table and the second index in the direction table are separately encoded and decoded.

[0181] Item 58. The method according to item 52, wherein the offset set is defined as a single table.

[0182] Item 59. The method according to item 58, wherein the index indicating the BV offset in the offset set is encoded and decoded.

[0183] Item 60. The method according to item 52, wherein the index indicating the BV offset is contextually encoded.

[0184] Item 61. The method according to item 52, wherein the index indicating the BV offset in the reordered BV candidate list is encoded and decoded using a Rice parameter.

[0185] Item 62. The method according to item 52, wherein the offset set depends on the encoding and decoding information.

[0186] Item 63. The method according to item 52, wherein the BV offset is derived using a TM or BM based scheme.

[0187] Item 64. The method according to item 63, wherein the BV offset is shared by different color components, or wherein the BV offset is different for different color components.

[0188] Item 65. The method according to item 51, wherein whether to add the BV offset is indicated in the bitstream.

[0189] Item 66. The method according to item 65, wherein a syntax element is signaled to indicate whether the BV offset is used.

[0190] Item 67. The method according to item 65, wherein one or more syntax elements are signaled to indicate the BV offset.

[0191] Item 68. The method according to item 67, wherein the BV offset is equal to zero.

[0192] Item 69. The method according to Item 67, wherein reordering is used to transmit or derive the BV offset by a signal.

[0193] Item 70. The method according to Item 51, wherein the BV offset of one component is predicted by the BV offset of another component.

[0194] Item 71. The method according to any one of Items 1 to 70, wherein the chrominance prediction using the one or more BV derivations is combined with other coding and decoding methods.

[0195] Item 72. The method according to Item 71, wherein the other coding and decoding methods include at least one of the following: conventional intra prediction mode, cross-component linear mode (CCLM), multi-mode learner mode (MMLM), convolutional cross-component model (CCCM), general linear mode (GLM), decoder-side intra mode derivation (DIMD), template-based intra mode derivation (TIMD), or intra TMP.

[0196] Item 73. The method according to Item 71, wherein the chrominance prediction using the one or more BV derivations is combined with at least one of the following: inter prediction mode, bi-directional prediction with coding unit-level weights (BCW), Merge mode with motion vector difference (MMVD), template matching (TM), IBC, affine, decoder-side motion vector refinement (DMVR), multi-pass DMVR, prediction refinement using optical flow (PROF), bi-directional optical flow (BDOF), sample-based BDOF, adaptive decoder-side motion vector refinement (ADMVR), overlapping block motion compensation (OBMC), TM-based OBMC, multi-hypothesis prediction (MHP), geometric segmentation mode (GPM), bilateral AMVP-Merge mode, or template matching AMVP-Merge mode.

[0197] Item 74. The method according to Item 71, wherein the chrominance prediction using the one or more BV derivations is combined with luminance prediction or luminance reconstruction.

[0198] Item 75. The method according to Item 71, wherein the weight for the combination is predefined, or the weight is indicated in the bitstream, or the weight is derived depending on coding and decoding information.

[0199] Item 76. The method according to Item 71, wherein whether to combine the chrominance prediction and / or the scheme for combining the chrominance prediction is indicated.

[0200] Item 77. The method according to Item 71, wherein whether to combine the chrominance prediction and / or the scheme for combining the chrominance prediction depends on coding and decoding information.

[0201] Item 78. The method according to Item 77, wherein whether to combine the chrominance prediction and / or the scheme for combining the chrominance prediction depends on whether the combination is used for the luma video unit of the same position.

[0202] Item 79. The method according to Item 77, wherein whether to combine the chrominance prediction and / or the scheme for combining the chrominance prediction depends on the sequence content.

[0203] Item 80. The method according to Item 71, wherein a high-level syntax (HLS) is signaled to indicate whether the combination is used.

[0204] Item 81. The method according to Item 71, wherein whether to combine the chrominance prediction and / or the scheme for combining the chrominance prediction is derived.

[0205] Item 82. The method according to Item 81, wherein a TM-based method is used to combine the chrominance prediction.

[0206] Item 83. The method according to any one of Items 1 to 82, wherein the chrominance BV of the video unit is used for subsequent video units.

[0207] Item 84. The method according to Item 83, wherein the chrominance BV of the video unit is stored.

[0208] Item 85. The method according to Item 83, wherein the chrominance BV of the current video unit is added to the HBVP table for chrominance.

[0209] Item 86. The method according to Item 83, wherein the chrominance BV of the video unit is used for the processing of the current block.

[0210] Item 87. The method according to Item 83, wherein the chrominance BV of the video unit is not used for the subsequent video units.

[0211] Item 88. The method according to any one of Items 1 to 87, wherein when IBC is used for the chrominance prediction, the target codec tool is allowed to be used.

[0212] Item 89. The method according to Item 88, wherein the target codec tool includes at least one of the following: IBC-TM, IBC with Merge mode having block vector difference (IBC-MBVD), reconstructed reordering IBC (RR-IBC), IBC-IBC, IBC-GPM, or IBC-intra-inter prediction jointly (IBC-CIIP).

[0213] Item 90. The method according to Item 89, wherein the syntax element is signaled in the bitstream to indicate whether the target codec tool is used for chrominance prediction.

[0214] Item 91. The method according to Item 88, wherein the flip type of the chrominance RR-IBC block is inherited from the flip type of the luma block.

[0215] Item 92. The method according to Item 91, wherein the luma block is at least one of the following: a co-located luma block, a spatially neighboring block of the co-located luma block, or a luma block having a different position from the co-located luma block.

[0216] Item 93. The method according to Item 88, wherein the flip type of the chrominance RR-IBC block is determined independently.

[0217] Item 94. The method according to Item 8, wherein the target codec tool is used in a dual tree, or wherein the target codec tool is used in a single tree.

[0218] Item 95. The method according to any one of Items 1 to 87, wherein when IBC is used for the chrominance prediction, the target codec tool is not allowed to be used.

[0219] Item 96. The method according to any one of Items 1 to 95, wherein the video unit includes at least one of the following: a color component, a prediction block (PB), a transform block (TB), a codec block (CB), a prediction unit (PU), a transform unit (TU), a codec tree block (CTB), a codec unit (CU), a codec tree unit (CTU), a CTU row, a CTU group, a slice, a picture, a sub-picture, a block, a sub-region within a block, or a region containing more than one sample or pixel.

[0220] Item 97. The method according to any one of Items 1 to 95, wherein an indication of whether and / or how to utilize one or more BVs in the at least one BV candidate list for the chrominance prediction of the video unit is indicated at one of the following: sequence level, group of pictures level, picture level, slice level, or slice group level.

[0221] Item 98. The method according to any one of Items 1 to 95, wherein an indication of whether and / or how to utilize one or more BVs in the at least one BV candidate list for the chrominance prediction of the video unit is indicated in one of the following: sequence header, picture header, sequence parameter set (SPS), video parameter set (VPS), dependency parameter set (DPS), decoding capability information (DCI), picture parameter set (PPS), adaptive parameter set (APS), slice header, or slice group header.

[0222] Item 99. The method according to any one of Items 1 to 95, wherein an indication of whether and / or how to utilize one or more BVs in the at least one BV candidate list for chrominance prediction of the video unit is included in one of the following: a prediction block (PB), a transform block (TB), a codec block (CB), a prediction unit (PU), a transform unit (TU), a codec unit (CU), a virtual pipeline data unit (VPDU), a codec tree unit (CTU), a CTU row, a strip, a slice, a sub-picture; or a region containing more than one sample or pixel.

[0223] Item 100. The method according to any one of Items 1 to 95, further comprising: determining whether and / or how to utilize one or more BVs in the at least one BV candidate list for chrominance prediction of the video unit based on the coded information of the video unit, the coded information including at least one of the following: block size, color format, single-tree and / or dual-tree segmentation, color component, strip type, or picture type.

[0224] Item 101. The method according to any one of Items 1 to 100, wherein the conversion includes encoding the video unit into the bitstream.

[0225] Item 102. The method according to any one of Items 1 to 100, wherein the conversion includes decoding the video unit from the bitstream.

[0226] Item 103. 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 Items 1 to 102.

[0227] Item 104. A non-transitory computer-readable storage medium storing instructions that cause a processor to perform the method according to any one of Items 1 to 102.

[0228] Item 105. A non-transitory computer-readable recording medium storing a bitstream of a video generated by a method executed by an apparatus for video processing, wherein the method comprises: constructing at least one block vector (BV) candidate list for video units of the video; utilizing one or more BVs in the at least one BV candidate list for chrominance prediction of the video unit; and generating the bitstream based on the chrominance prediction of the video unit.

[0229] Item 106. A method for storing a bitstream of a video, comprising: constructing at least one block vector (BV) candidate list for video units of the video; utilizing one or more BVs in the at least one BV candidate list for chrominance prediction of the video unit; generating the bitstream based on the chrominance prediction of the video unit; and storing the bitstream in a non-transitory computer-readable medium. Example device

[0230] Figure 20 FIG. shows a block diagram of a computing device 2100 in which various embodiments of the present disclosure may be implemented. The computing device 2100 may be implemented as the source device 110 (or video encoder 114 or 200) or the destination device 120 (or video decoder 124 or 300), or may be included in the source device 110 (or video encoder 114 or 200) or the destination device 120 (or video decoder 124 or 300).

[0231] It should be understood that Figure 20 the computing device 2100 shown in is for illustrative purposes only and does not imply any limitation to the functions and scope of the embodiments of the present disclosure in any way.

[0232] As Figure 20 shown, the computing device 2100 includes a general-purpose computing device 2100. The computing device 2100 may include at least one or more processors or processing units 2110, a memory 2120, a storage unit 2130, one or more communication units 2140, one or more input devices 2150, and one or more output devices 2140.

[0233] In some embodiments, the computing device 2100 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 a mobile phone, a station, a unit, a device, a multimedia computer, a multimedia tablet computer, an Internet node, a communicator, a desktop computer, a laptop computer, a notebook computer, a netbook computer, a tablet computer, a personal communication system (PCS) device, a personal navigation device, a personal digital assistant (PDA), an audio / video player, a digital camera / video camera, a positioning device, a television receiver, a radio broadcast receiver, an e-book device, a gaming device, or any combination thereof, including accessories and peripherals of these devices or any combination thereof. It is contemplated that the computing device 2100 may support any type of interface to the user (such as a "wearable" circuitry, etc.).

[0234] The processing unit 2110 can be a physical processor or a virtual processor, and can implement various processes based on the programs stored in the memory 2120. In a multi-processor system, multiple processing units execute computer-executable instructions in parallel to improve the parallel processing ability of the computing device 2100. The processing unit 2110 can also be referred to as a central processing unit (CPU), a microprocessor, a controller, or a microcontroller.

[0235] The computing device 2100 generally includes various computer storage media. Such media can be any media accessible by the computing device 2100, including but not limited to volatile media and non-volatile media, or removable media and non-removable media. The memory 2120 can be a volatile memory (e.g., registers, caches, random access memory (RAM)), a non-volatile memory (such as read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), or flash memory), or any combination thereof. The storage unit 2130 can be any removable or non-removable media, and can include machine-readable media, such as a memory, a flash drive, a magnetic disk, or other media that can be used to store information and / or data and can be accessed in the computing device 2100.

[0236] The computing device 2100 can also include additional removable / non-removable storage media, volatile / non-volatile storage media. Although not shown in Figure 20 , a disk drive for reading from and / or writing to a removable non-volatile magnetic disk, and an optical disk drive for reading from and / or writing to a removable non-volatile optical disk can be provided. In this case, each drive can be connected to a bus (not shown) via one or more data media interfaces.

[0237] The communication unit 2140 communicates with another computing device via a communication medium. Additionally, the functions of the components in the computing device 2100 can be implemented by a single computing cluster or multiple computer machines, which can communicate via a communication connection. Therefore, the computing device 2100 can operate in a networked environment using a logical connection with one or more other servers, networked personal computers (PCs), or other general network nodes.

[0238] The input device 2150 can be one or more of various input devices, such as a mouse, a keyboard, a trackball, a voice input device, and so on. The output device 2160 can be one or more of various output devices, such as a display, a speaker, a printer, and so on. With the aid of the communication unit 2140, the computing device 2100 can also communicate with one or more external devices (not shown), such as a storage device and a display device, the computing device 2100 can also communicate with one or more devices that enable a user to interact with the computing device 2100, or if needed, the computing device 2100 can also communicate with any device (such as a network card, a modem, etc.) that enables the computing device 2100 to communicate with one or more other computing devices. Such communication can be carried out via an input / output (I / O) interface (not shown).

[0239] In some embodiments, some or all components of the computing device 2100 may 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 implement the functions described in the present disclosure. In some embodiments, cloud computing provides computing, software, data access, and storage services, which do 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, the 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 installed directly or otherwise on a client device.

[0240] In an embodiment of the present disclosure, the computing device 2100 can be used to implement video encoding / decoding. The memory 2120 may include one or more video codec modules 2125 having one or more program instructions. These modules are accessible and executable by the processing unit 2110 to perform the functions of various embodiments described herein.

[0241] In an example embodiment of performing video encoding, the input device 2150 may receive video data as input 2170 to be encoded. The video data may be processed, for example, by the video codec module 2125 to generate an encoded bitstream. The encoded bitstream may be provided as output 2180 via the output device 2160.

[0242] In an example embodiment of performing video decoding, the input device 2150 may receive the encoded bitstream as input 2170. The encoded bitstream may be processed, for example, by the video codec module 2125 to generate decoded video data. The decoded video data may be provided as output 2180 via the output device 2160.

[0243] 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: Constructing at least one block vector (BV) candidate list for a video unit for conversion between the video unit of a video and the bitstream of the video unit; Utilizing one or more BVs in the at least one BV candidate list for chrominance prediction of the video unit; And Performing the conversion based on the chrominance prediction of the video unit.

2. The method according to claim 1, wherein different chrominance components share the same BV in the at least one BV candidate list.

3. The method according to claim 2, wherein the different chrominance components include a Cb component and a Cr component.

4. The method according to claim 1, wherein one or more default BVs in the at least one BV candidate list are used for the chrominance prediction of the video unit.

5. The method according to claim 1, wherein one or more BVs in the at least one BV candidate list are derived from chrominance components.

6. The method according to claim 5, wherein one or more BVs of spatially adjacent video units of the video unit are used for the chrominance prediction of the video unit.

7. The method according to claim 5, wherein a historical block vector prediction (HBVP) table is constructed for chrominance components.

8. The method according to claim 7, wherein the scheme for generating the HBVP table for chrominance components is the same as the scheme for generating the HBVP table for luminance components, or wherein the scheme for generating the HBVP table for chrominance components is different from the scheme for generating the HBVP table for luminance components.

9. The method according to claim 7, wherein the scheme for using the HBVP table for chrominance components is the same as the scheme for using the HBVP table for luminance components, or wherein the scheme for using the HBVP table for chrominance components is different from the scheme for using the HBVP table for luminance components.

10. The method according to claim 7, wherein one or more BVs in the HBVP table for chrominance are used for the chrominance prediction.

11. The method according to claim 5, wherein when an adjacent video unit is encoded and decoded using a target mode, one or more BVs derived from the adjacent video unit are used for the chrominance prediction.

12. The method according to claim 11, wherein the target mode is one of the following: intra-template matching (intra-TMP) mode or intra-block copy (IBC) mode.

13. The method according to claim 1, wherein one or more BVs of the at least one BV candidate list for chrominance components are derived from luminance components.

14. The method according to claim 13, wherein the BV of a co-located luminance video unit is used.

15. The method according to claim 14, wherein the co-located luminance video is located by a luminance position (P L (x, y)), where the luminance position is obtained by a chrominance position (P C (x, y)) and downsampling rates for luminance and chrominance in different color formats.

16. The method according to claim 15, wherein P L (x, y) = P C (x * SubWidthC, y * SubHeightC).

17. The method according to claim 15, wherein the chromaticity position (P C (x, y)) is the center position of a chromaticity video unit.

18. The method according to claim 17, wherein (P C (x, y)) = (W / 2 - 1, H / 2 + 1), or where (P C (x, y)) = (W / 2 + 1, H / 2 - 1), or where (P C (x, y)) = (W / 2 - 1, H / 2 + 1), or where (P C (x, y)) = (W / 2 + 1, H / 2 + 1), and where W represents the width of the chrominance video unit, H represents the height of the chrominance video unit, x is in the range of 0 and W - 1, and y is in the range of 0 and H - 1.

19. The method according to claim 15, wherein the chromaticity position (P C (x, y)) is one of the following: The upper left position of the chrominance video unit, The upper right position of the chrominance video unit, the lower left position of the chrominance video unit, or the lower right position of the chrominance video unit.

20. The method according to claim 13, wherein one or more BVs of spatially adjacent video units of a co-located luma video unit are used for the chrominance prediction.

21. The method according to claim 13, wherein one or more BVs in the HBVP table for IBC of the luma component are used for the chrominance prediction.

22. The method according to claim 21, wherein BVs for previously transcoded blocks are inserted into the HBVP table.

23. The method according to claim 13, wherein when a neighboring video unit of a co-located luma video unit is coded / decoded using a target mode, one or more BVs derived from the neighboring video unit are used for the chrominance prediction.

24. The method according to claim 23, wherein the target mode is one of the following: intra TMP mode or IBC mode.

25. The method according to claim 13, wherein one or more BVs derived from the luma component are scaled before being used to construct the at least one BV candidate list.

26. The method according to claim 25, wherein whether and / or how to scale the one or more BVs depends on the color format.

27. The method according to claim 26, wherein bvCx = bvLx>>(SubWidthC - 1), or wherein bvCy = bvLy>>(SubHeightC - 1), and wherein bvLx and bvLy represent two components of the luma BV, and bvCx and bvCy represent two components of the scaled chrominance BV.

28. The method according to claim 1, wherein the one or more BVs are added to the at least one BV candidate list with different priorities.

29. The method according to claim 28, wherein BVs from a co-located luma video are added first.

30. The method according to claim 28, wherein BVs from a first candidate type are added before BVs from a second candidate type, and wherein the first candidate type is different from the second candidate type.

31. The method according to claim 30, wherein the first candidate type or the second candidate type is one of the following: adjacent spatially neighboring video units, non-adjacent spatially neighboring video units, HBVP, or video units coded / decoded by intra TMP.

32. The method according to claim 28, wherein a default BV is added to the last position of the at least one BV candidate list.

33. The method according to claim 1, wherein the at least one BV candidate list is re-ordered.

34. The method according to claim 33, wherein a template matching (TM) cost or a bilateral matching (BM) cost is used to re-order the at least one BV candidate list.

35. The method according to claim 33, wherein the at least one BV candidate list is divided into different subgroups, and the re-ordering of the at least one BV candidate list is applied within the subgroups.

36. The method according to claim 33, wherein the BV indices in the re-ordered BV candidate list are indicated in the bitstream.

37. The method according to claim 33, wherein the BV within the minimum TM cost or BM cost is implicitly used for the video unit without signaling.

38. The method according to claim 1, wherein the at least one BV candidate list is constructed in different ways for a single-tree structure and a dual-tree structure.

39. The method according to claim 38, wherein if the dual-tree structure is applied, different BV candidate lists are constructed for the luminance component and the chrominance component.

40. The method according to claim 38, wherein if the single-tree structure is applied, the at least one BV candidate list is shared by the luminance component and the chrominance component.

41. The method according to claim 1, wherein different chrominance components have different BVs.

42. The method according to claim 41, wherein the BVs for the two components are refined separately.

43. The method according to claim 41, wherein the refinement of the BV is template matching.

44. The method according to claim 1, wherein the BVs in the at least one BV candidate list are refined.

45. The method according to claim 44, wherein TM is used to refine the BV, or wherein BM is used to refine the BV.

46. The method according to claim 1, wherein an index is indicated in the bitstream to indicate which BV in the at least one BV candidate list is used for chrominance prediction.

47. The method according to claim 1, wherein an index is indicated in the bitstream to indicate which BV in the at least one BV candidate list is derived.

48. The method according to claim 1, wherein the first available BV in the at least one BV candidate list is used for the chrominance prediction.

49. The method according to claim 1, wherein the BV candidate is constructed by using at least one BV derived from the luminance component and at least one BV derived from the chrominance component.

50. The method according to claim 1, wherein the BV candidate is constructed by averaging one BV derived from the luminance component and one BV derived from the chrominance component.

51. The method according to any one of claims 1 to 50, wherein a BV offset is added to the one or more BVs used for the chrominance prediction.

52. The method according to claim 51, wherein the BV offset or the index indicating the BV offset in the offset set is indicated in the bitstream, or wherein the BV offset or the index indicating the BV offset in the offset set is derived.

53. The method according to claim 52, wherein the BV offset set is predefined, or wherein the BV offset is indicated in the bitstream.

54. The method according to claim 52, wherein the BV offset set is re-ordered.

55. The method according to claim 52, wherein the combination of the BV in the at least one BV candidate list and the BV offset in the offset set is reordered.

56. The method according to claim 52, wherein the offset set is defined as a distance table and a direction table.

57. The method according to claim 56, wherein the first index in the distance table and the second index in the direction table are separately encoded and decoded.

58. The method according to claim 52, wherein the offset set is defined as a single table.

59. The method according to claim 58, wherein the index indicating the BV offset in the offset set is encoded and decoded.

60. The method according to claim 52, wherein the index indicating the BV offset is contextually encoded and decoded.

61. The method according to claim 52, wherein the index indicating the BV offset in the reordered BV candidate list is encoded and decoded using a Rice parameter.

62. The method according to claim 52, wherein the offset set depends on the encoding and decoding information.

63. The method according to claim 52, wherein the BV offset is derived using a TM or BM based scheme.

64. The method according to claim 63, wherein the BV offset is shared by different color components, or wherein the BV offset is different for different color components.

65. The method according to claim 51, wherein whether to add the BV offset is indicated in the bitstream.

66. The method according to claim 65, wherein a syntax element is signaled to indicate whether the BV offset is used.

67. The method according to claim 65, wherein one or more syntax elements are signaled to indicate the BV offset.

68. The method according to claim 67, wherein the BV offset is equal to zero.

69. The method according to claim 67, wherein reordering is used to signal or derive the BV offset.

70. The method according to claim 51, wherein the BV offset of one component is predicted by the BV offset of another component.

71. The method according to any one of claims 1 to 70, wherein the chrominance prediction using the one or more BV derivations is combined with other encoding and decoding methods.

72. The method according to claim 71, wherein the other encoding and decoding methods include at least one of the following: conventional intra prediction mode, cross-component linear mode (CCLM), multi-mode learner mode (MMLM), convolutional cross-component model (CCCM), general linear mode (GLM), decoder-side intra mode derivation (DIMD), template-based intra mode derivation (TIMD), or intra TMP.

73. The method according to claim 71, wherein the chrominance prediction using the one or more BV derivations is combined with at least one of the following: inter prediction mode, bi-directional prediction with encoding and decoding unit-level weights (BCW), Merge mode with motion vector difference (MMVD), Template Matching (TM), IBC, Affine, Decoder - side Motion Vector Refinement (DMVR), Multi - pass DMVR, Prediction Refinement using Optical Flow (PROF), Bidirectional Optical Flow (BDOF), Sample - based BDOF, Adaptive Decoder - side Motion Vector Refinement (ADMVR), Overlapped Block Motion Compensation (OBMC), TM - based OBMC, Multiple Hypothesis Prediction (MHP), Geometric Partition Mode (GPM), Dual - side AMVP - Merge mode, or Template - matching AMVP - Merge mode.

74. The method according to claim 71, wherein the chrominance prediction derived using the one or more BVs is combined with the luminance prediction or luminance reconstruction.

75. The method according to claim 71, wherein the weight for the combination is predefined, or the weight is indicated in the bitstream, or the weight is derived depending on the coding - decoding information.

76. The method according to claim 71, wherein whether to combine the chrominance prediction and / or the scheme for combining the chrominance prediction is indicated.

77. The method according to claim 71, wherein whether to combine the chrominance prediction and / or the scheme for combining the chrominance prediction depends on the coding - decoding information.

78. The method according to claim 77, wherein whether to combine the chrominance prediction and / or the scheme for combining the chrominance prediction depends on whether the combination is used for the co - located luminance video unit.

79. The method according to claim 77, wherein whether to combine the chrominance prediction and / or the scheme for combining the chrominance prediction depends on the sequence content.

80. The method according to claim 71, wherein a High - level Syntax (HLS) is signaled to indicate whether the combination is used.

81. The method according to claim 71, wherein whether to combine the chrominance prediction and / or the scheme for combining the chrominance prediction is derived.

82. The method according to claim 81, wherein a TM - based method is used to combine the chrominance prediction.

83. The method according to any one of claims 1 to 82, wherein the chrominance BV of the video unit is used for subsequent video units.

84. The method according to claim 83, wherein the chrominance BV of the video unit is stored.

85. The method according to claim 83, wherein the chrominance BV of the current video unit is added to the HBVP table for chrominance.

86. The method according to claim 83, wherein the chrominance BV of the video unit is used for the processing of the current block.

87. The method according to claim 83, wherein the chrominance BV of the video unit is not used for the subsequent video units.

88. The method according to any one of claims 1 to 87, wherein when IBC is used for the chrominance prediction, the target coding - decoding tools are allowed to be used.

89. The method according to claim 88, wherein the target coding - decoding tools include at least one of the following: IBC - TM, IBC with Merge mode having block vector difference (IBC - MBVD), Reconstruction Reordering IBC (RR-IBC), IBC-IBC, IBC-GPM, or IBC-Combined Intra and Inter Prediction (IBC-CIIP).

90. The method according to claim 89, wherein a syntax element is signaled in the bitstream to indicate whether the target codec tool is used for chrominance prediction.

91. The method according to claim 88, wherein the flip type of a chrominance RR-IBC block is inherited from the flip type of a luma block.

92. The method according to claim 91, wherein the luma block is at least one of the following: A co-located luma block, A spatially neighboring block of the co-located luma block, or A luma block having a different position from the co-located luma block.

93. The method according to claim 88, wherein the flip type of a chrominance RR-IBC block is determined independently.

94. The method according to claim 8, wherein the target codec tool is used in a dual tree, or wherein the target codec tool is used in a single tree.

95. The method according to any one of claims 1 to 87, wherein when IBC is used for the chrominance prediction, the target codec tool is not allowed to be used.

96. The method according to any one of claims 1 to 95, wherein the video unit comprises at least one of the following: A color component, A prediction block (PB), A transform block (TB), A codec block (CB), A prediction unit (PU), A transform unit (TU), A codec tree block (CTB), A codec unit (CU), A codec tree unit (CTU), A CTU row, A CTU group, A slice, A picture, A sub-picture, A block, A sub-region within a block, or A region containing more than one sample or pixel.

97. The method according to any one of claims 1 to 95, wherein an indication of whether and / or how to utilize one or more BVs from the at least one BV candidate list for the chrominance prediction of the video unit is indicated at one of the following: Sequence level, Group of pictures level, Picture level, Slice level, or Slice group level.

98. The method according to any one of claims 1 to 95, wherein an indication of whether and / or how to utilize one or more BVs from the at least one BV candidate list for the chrominance prediction of the video unit is indicated in one of the following: Sequence header, Picture header, Sequence parameter set (SPS), Video parameter set (VPS), Dependency parameter set (DPS), Decoding capability information (DCI), Picture parameter set (PPS), Adaptive parameter set (APS), Slice header, or Slice group header.

99. The method according to any one of claims 1 to 95, wherein an indication of whether and / or how to utilize one or more BVs from the at least one BV candidate list for the chrominance prediction of the video unit is included in one of the following: Prediction block (PB), Transform block (TB), Codec block (CB), Prediction unit (PU), Transform unit (TU), Codec unit (CU), Virtual pipeline data unit (VPDU), Coding tree unit (CTU), CTU row, Slice, Picture, Sub-picture; or Region containing more than one sample or pixel.

100. The method according to any one of claims 1 to 95, further comprising: Based on the coded and decoded information of the video unit, determining whether and / or how to utilize one or more BVs in the at least one BV candidate list for chrominance prediction of the video unit, the coded and decoded information including at least one of the following: Block size, Color format, Single-tree and / or dual-tree segmentation, Color component, Slice type, or Picture type.

101. The method according to any one of claims 1 to 100, wherein the conversion includes encoding the video unit into the bitstream.

102. The method according to any one of claims 1 to 100, wherein the conversion includes decoding the video unit from the bitstream.

103. 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 102.

104. 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 102.

105. A non-transitory computer-readable recording medium storing a bitstream of a video generated by a method executed by an apparatus for video processing, wherein the method comprises: Constructing at least one block vector (BV) candidate list for video units of the video; Utilizing one or more BVs in the at least one BV candidate list for chrominance prediction of the video unit; And Generating the bitstream based on the chrominance prediction of the video unit.

106. A method for storing a bitstream of a video, comprising: Constructing at least one block vector (BV) candidate list for video units of the video; Utilizing one or more BVs in the at least one BV candidate list for chrominance prediction of the video unit; Generating the bitstream based on the chrominance prediction of the video unit; And Storing the bitstream in a non-transitory computer-readable medium.

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