WO2021093801A1

WO2021093801A1 - Coding of low bit-depth visual media data

Info

Publication number: WO2021093801A1
Application number: PCT/CN2020/128301
Authority: WO
Inventors: Jizheng Xu; Li Zhang; Kai Zhang; Hongbin Liu
Original assignee: Beijing Bytedance Network Technology Co., Ltd.; Bytedance Inc.
Priority date: 2019-11-14
Filing date: 2020-11-12
Publication date: 2021-05-20
Also published as: CN115066897A

Abstract

Devices, systems and methods for video coding, which include low-bit-depth video and image coding, are described. An example method for video processing includes making a determination, for a conversion between a current block of a video and a bitstream representation of the video, about usage of an adaptive color transform coding tool based on an input bit-depth of a source sample in the current block. The method also includes performing the conversion based on the determination.

Description

CODING OF LOW BIT-DEPTH VISUAL MEDIA DATA

CROSS REFERENCE TO RELATED APPLICATIONS

Under the applicable patent law and/or rules pursuant to the Paris Convention, this application is made to timely claim the priority to and benefits of International Patent Application No. PCT/CN2019/118476, filed on November 14, 2019. For all purposes under the law, the entire disclosure of the aforementioned application is incorporated by reference as part of the disclosure of this application.

TECHNICAL FIELD

This document is related to video coding techniques, systems and devices.

BACKGROUND

Digital video accounts for the largest bandwidth use on the internet and other digital communication networks. As the number of connected user devices capable of receiving and displaying video increases, it is expected that the bandwidth demand for digital video usage will continue to grow.

SUMMARY

Devices, systems and methods related to digital video coding, which include low-bit-depth video and image coding, are described. The described methods may be applied to both the existing video coding standards (e.g., High Efficiency Video Coding (HEVC) and/or Versatile Video Coding (VVC) ) and future video coding standards or video codecs.

In one representative aspect, the disclosed technology may be used to provide a method for video processing. This method includes making a determination, for a conversion between a current block of a video and a bitstream representation of the video, about usage of an adaptive color transform coding tool based on an input bit-depth of a source sample in the current block. The method also includes performing the conversion based on the determination.

In another representative aspect, the disclosed technology may be used to provide a method for video processing. This method includes making a determination, for a conversion between a current block of a video and a bitstream representation of the video, that a reconstruction value or a prediction value of a sample of the current block is rounded according to an input bit-depth of a source value of the sample. The method also includes performing the conversion based on the determination.

In another representative aspect, the disclosed technology may be used to provide a method for video processing. This method includes making a determination, for a conversion between a current block of a video and a bitstream representation of the video, about usage of an in-loop filtering process based on an input bit-depth of a source sample in the current block. The method also includes performing the conversion based on the determination.

In another representative aspect, the disclosed technology may be used to provide a method for video processing. This method includes making a determination, for a conversion between a current block of a video and a bitstream representation of the video, about usage of a luma mapping with chroma scaling (LMCS) coding tool based on an input bit-depth of a source sample in the current block. The method also includes performing the conversion based on the determination.

In another representative aspect, the disclosed technology may be used to provide a method for video processing. This method includes making a determination, for a conversion between a block of a video and a bitstream representation of the video, about a pixel clipping range based on an input bit-depth of a source pixel. The method also includes performing the conversion based on the determination.

In another representative aspect, the disclosed technology may be used to provide a method for video processing. This method includes determining, during a conversion between a current block of video and a bitstream representation of the video, a given bit-depth based on a bit-depth used for representing the video, and performing the conversion using the given bit-depth as a computational bit-depth for at least one or more computations of the conversion.

In another representative aspect, the above-described method is embodied in the form of processor-executable code and stored in a computer-readable program medium.

In yet another representative aspect, a device that is configured or operable to perform the above-described method is disclosed. The device may include a processor that is programmed to implement this method.

In yet another representative aspect, a video decoder apparatus may implement a method as described herein.

The above and other aspects and features of the disclosed technology are described in greater detail in the drawings, the description and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of intra block copy.

FIG. 2 shows an example of a block coded in palette mode.

FIG. 3 shows an example of use of a palette predictor to signal palette entries.

FIG. 4 shows an example of horizontal and vertical traverse scans.

FIG. 5 shows an example of coding of palette indices.

FIG. 6 shows an example of 67 intra prediction modes.

FIG. 7 shows an example of the left and above neighbors of a current block.

FIG. 8A shows an example of adaptive loop filtering (ALF) filter shape.

FIG. 8B shows another example of adaptive loop filtering (ALF) filter shape.

FIG. 9A shows an example of subsampled Laplacian calculation.

FIG. 9B shows another example of subsampled Laplacian calculation.

FIG. 9C shows another example of subsampled Laplacian calculation.

FIG. 9D shows yet another example of subsampled Laplacian calculation.

FIG. 10 shows an example of modified block classification at virtual boundaries.

FIG. 11 shows an example of modified ALF filtering for a luma component at virtual boundaries.

FIG. 12 shows an example of four 1-D 3-pixel patterns for the pixel classification in an edge offset (EO) case of a sample adaptive offset (SAO) operation.

FIG. 13 shows an example of four bands that are grouped together, and represented by its starting band position.

FIG. 14 shows an example of top and left neighboring blocks used in combined inter and intra prediction (CIIP) weight derivation.

FIG. 15 shows an example of luma mapping with chroma scaling (LMCS) architecture.

FIG. 16 shows an example of an encoding flow with adaptive color transform (ACT) .

FIG. 17 shows an example of a decoding flow with ACT.

FIG. 18 is a flowchart for an example of a video processing method.

FIG. 19 is a block diagram of an example video processing system in which disclosed techniques may be implemented.

FIG. 20 is a block diagram that illustrates an example video coding system.

FIG. 21 is a block diagram that illustrates an encoder in accordance with some embodiments of the present disclosure.

FIG. 22 is a block diagram that illustrates a decoder in accordance with some embodiments of the present disclosure.

FIG. 23 is a flowchart representation of a method for video processing in accordance with the present technology.

FIG. 24 is a flowchart representation of another method for video processing in accordance with the present technology.

FIG. 25 is a flowchart representation of another method for video processing in accordance with the present technology.

FIG. 26 is a flowchart representation of another method for video processing in accordance with the present technology.

FIG. 27 is a flowchart representation of yet another method for video processing in accordance with the present technology.

DETAILED DESCRIPTION

The present document provides various techniques that can be used by a decoder of image or video bitstreams to improve the quality of decompressed or decoded digital video or images. For brevity, the term “video” is used herein to include both a sequence of pictures (traditionally called video) and individual images. Furthermore, a video encoder may also implement these techniques during the process of encoding in order to reconstruct decoded frames used for further encoding.

Section headings are used in the present document for ease of understanding and do not limit the embodiments and techniques to the corresponding sections. As such, embodiments from one section can be combined with embodiments from other sections.

1. Summary

This document is related to video coding technologies. Specifically, it is related to low bit-depth video and image coding. It may be applied to the existing video coding standard like HEVC, or the standard (Versatile Video Coding) to be finalized. It may be also applicable to future video coding standards or video codec.

2. Example embodiments for video coding

Video coding standards have evolved primarily through the development of the well-known ITU-T and ISO/IEC standards. The ITU-T produced H. 261 and H. 263, ISO/IEC produced MPEG-1 and MPEG-4 Visual, and the two organizations jointly produced the H. 262/MPEG-2 Video and H. 264/MPEG-4 Advanced Video Coding (AVC) and H. 265/HEVC standards. Since H. 262, the video coding standards are based on the hybrid video coding structure wherein temporal prediction plus transform coding are utilized. To explore the future video coding technologies beyond HEVC, Joint Video Exploration Team (JVET) was founded by VCEG and MPEG jointly in 2015. Since then, many new methods have been adopted by JVET and put into the reference software named Joint Exploration Model (JEM) . In April 2018, the Joint Video Expert Team (JVET) between VCEG (Q6/16) and ISO/IEC JTC1 SC29/WG11 (MPEG) was created to work on the VVC standard targeting at 50%bitrate reduction compared to HEVC.

2.1 Intra block copy

Intra block copy (IBC) , a. k. a. current picture referencing, has been adopted in HEVC Screen Content Coding extensions (HEVC-SCC) and the current VVC test model (VTM-4.0) . IBC extends the concept of motion compensation from inter-frame coding to intra-frame coding. As demonstrated in FIG. 1, the current block is predicted by a reference block in the same picture when IBC is applied. The samples in the reference block must have been already reconstructed before the current block is coded or decoded. Although IBC is not so efficient for most camera-captured sequences, it shows significant coding gains for screen content. The reason is that there are lots of repeating patterns, such as icons and text characters in a screen content picture. IBC can remove the redundancy between these repeating patterns effectively. In HEVC-SCC, an inter-coded coding unit (CU) can apply IBC if it chooses the current picture as its reference picture. The MV is renamed as block vector (BV) in this case, and a BV always has an integer-pixel precision. To be compatible with main profile HEVC, the current picture is marked as a “long-term” reference picture in the Decoded Picture Buffer (DPB) . It should be noted that similarly, in multiple view/3D video coding standards, the inter-view reference picture is also marked as a “long-term” reference picture.

Following a BV to find its reference block, the prediction can be generated by copying the reference block. The residual can be got by subtracting the reference pixels from the original signals. Then transform and quantization can be applied as in other coding modes.

However, when a reference block is outside of the picture, or overlaps with the current block, or outside of the reconstructed area, or outside of the valid area restricted by some constrains, part or all pixel values are not defined. Basically, there are two solutions to handle such a problem. One is to disallow such a situation, e.g. in bitstream conformance. The other is to apply padding for those undefined pixel values. The following sub-sessions describe the solutions in detail.

2.2 IBC in HEVC Screen Content Coding extensions

In the screen content coding extensions of HEVC, when a block uses current picture as reference, it should guarantee that the whole reference block is within the available reconstructed area, as indicated in the following spec text:

The variables offsetX and offsetY are derived as follows:

offsetX = (ChromaArrayType == 0) ? 0: (mvCLX [0] &0x7 ? 2: 0) (8-104)

offsetY = (ChromaArrayType == 0) ? 0: (mvCLX [1] &0x7 ? 2: 0) (8-105)

It is a requirement of bitstream conformance that when the reference picture is the current picture, the luma motion vector mvLX shall obey the following constraints:

- When the derivation process for z-scan order block availability as specified in clause 6.4.1 is invoked with (xCurr, yCurr) set equal to (xCb, yCb) and the neighbouring luma location (xNbY, yNbY) set equal to (xPb + (mvLX [0] >> 2) -offsetX, yPb + (mvLX [1] >> 2) -offsetY) as inputs, the output shall be equal to TRUE.

- When the derivation process for z-scan order block availability as specified in clause 6.4.1 is invoked with (xCurr, yCurr) set equal to (xCb, yCb) and the neighbouring luma location (xNbY, yNbY) set equal to (xPb + (mvLX [0] >> 2) + nPbW -1 +offsetX, yPb + (mvLX [1] >> 2) + nPbH -1 +offsetY) as inputs, the output shall be equal to TRUE.

- One or both of the following conditions shall be true:

- The value of (mvLX [0] >> 2) + nPbW + xB1 +offsetX is less than or equal to 0.

- The value of (mvLX [1] >> 2) + nPbH + yB1 +offsetY is less than or equal to 0.

- The following condition shall be true:

(xPb + (mvLX [0] >> 2) + nPbW -1 +offsetX) /CtbSizeY -xCb /CtbSizeY <= yCb /CtbSizeY - (yPb + (mvLX [1] >> 2) + nPbH -1 +offset) /CtbSizeY (8-106)

Thus, the case that the reference block overlaps with the current block or the reference block is outside of the picture will not happen. There is no need to pad the reference or prediction block.

2.3 IBC in VVC Test Model

In the current VVC test model, e.g. VTM-4.0 design, the whole reference block should be with the current coding tree unit (CTU) and does not overlap with the current block. Thus, there is no need to pad the reference or prediction block. The IBC flag is coded as a prediction mode of the current CU. Thus, there are totally three prediction modes, MODE_INTRA, MODE_INTER and MODE_IBC for each CU.

2.3.1 IBC Merge mode

In IBC merge mode, an index pointing to an entry in the IBC merge candidates list is parsed from the bitstream. The construction of the IBC merge list can be summarized according to the following sequence of steps:

Step 1: Derivation of spatial candidates

Step 2: Insertion of HMVP candidates

Step 3: Insertion of pairwise average candidates

In the derivation of spatial merge candidates, a maximum of four merge candidates are selected among candidates located in the positions depicted in the figures. The order of derivation is A1, B1, B0, A0 and B2. Position B2 is considered only when any PU of position A1, B1, B0, A0 is not available (e.g. because it belongs to another slice or tile) or is not coded with IBC mode. After candidate at position A1 is added, the insertion of the remaining candidates is subject to a redundancy check which ensures that candidates with same motion information are excluded from the list so that coding efficiency is improved. To reduce computational complexity, not all possible candidate pairs are considered in the mentioned redundancy check. Instead only the pairs linked with an arrow in depicted in the figures are considered and a candidate is only added to the list if the corresponding candidate used for redundancy check has not the same motion information.

After insertion of the spatial candidates, if the IBC merge list size is still smaller than the maximum IBC merge list size, IBC candidates from HMVP table may be inserted. Redundancy check are performed when inserting the HMVP candidates.

Finally, pairwise average candidates are inserted into the IBC merge list.

When a reference block identified by a merge candidate is outside of the picture, or overlaps with the current block, or outside of the reconstructed area, or outside of the valid area restricted by some constrains, the merge candidate is called invalid merge candidate.

It is noted that invalid merge candidates may be inserted into the IBC merge list.

2.3.2 IBC AMVP mode

In IBC AMVP mode, an AMVP index point to an entry in the IBC AMVP list is parsed from the bitstream. The construction of the IBC AMVP list can be summarized according to the following sequence of steps:

Step 1: Derivation of spatial candidates

Check A0, A1 until an available candidate is found.

Check B0, B1, B2 until an available candidate is found.

Step 2: Insertion of HMVP candidates

Step 3: Insertion of zero candidates

After insertion of the spatial candidates, if the IBC AMVP list size is still smaller than the maximum IBC AMVP list size, IBC candidates from HMVP table may be inserted.

Finally, zero candidates are inserted into the IBC AMVP list.

2.4 Palette Mode

The basic idea behind a palette mode is that the samples in the CU are represented by a small set of representative colour values. This set is referred to as the palette. It is also possible to indicate a sample that is outside the palette by signaling an escape symbol followed by (possibly quantized) component values. This is illustrated in FIG. 2.

2.5 Palette Mode in HEVC Screen Content Coding extensions (HEVC-SCC)

In the palette mode in HEVC-SCC, a predictive way is used to code the palette and index map.

2.5.1 Coding of the palette entries

For coding of the palette entries, a palette predictor is maintained. The maximum size of the palette as well as the palette predictor is signaled in the SPS. In HEVC-SCC, a palette_predictor_initializer_present_flag is introduced in the PPS. When this flag is 1, entries for initializing the palette predictor are signaled in the bitstream. The palette predictor is initialized at the beginning of each CTU row, each slice and each tile. Depending on the value of the palette_predictor_initializer_present_flag, the palette predictor is reset to 0 or initialized using the palette predictor intializer entries signaled in the PPS. In HEVC-SCC, a palette predictor initializer of size 0 was enabled to allow explicit disabling of the palette predictor initialization at the PPS level.

For each entry in the palette predictor, a reuse flag is signaled to indicate whether it is part of the current palette. This is illustrated in FIG. 3. The reuse flags are sent using run-length coding of zeros. After this, the number of new palette entries are signaled using exponential Golomb code of order 0. Finally, the component values for the new palette entries are signaled.

2.5.2 Coding of palette indices

The palette indices are coded using horizontal and vertical traverse scans as shown in FIG. 4. The scan order is explicitly signaled in the bitstream using the palette_transpose_flag. For the rest of the subsection it is assumed that the scan is horizontal.

The palette indices are coded using two main palette sample modes: 'INDEX' and 'COPY_ABOVE' . As explained previously, the escape symbol is also signaled as an 'INDEX' mode and assigned an index equal to the maximum palette size. The mode is signaled using a flag except for the top row or when the previous mode was 'COPY_ABOVE' . In the 'COPY_ABOVE' mode, the palette index of the sample in the row above is copied. In the 'INDEX' mode, the palette index is explicitly signaled. For both 'INDEX' and 'COPY_ABOVE' modes, a run value is signaled which specifies the number of subsequent samples that are also coded using the same mode. When escape symbol is part of the run in 'INDEX' or 'COPY_ABOVE' mode, the escape component values are signaled for each escape symbol. The coding of palette indices is illustrated in FIG. 5.

This syntax order is accomplished as follows. First the number of index values for the CU is signaled. This is followed by signaling of the actual index values for the entire CU using truncated binary coding. Both the number of indices as well as the the index values are coded in bypass mode. This groups the index-related bypass bins together. Then the palette sample mode (if necessary) and run are signaled in an interleaved manner. Finally, the component escape values corresponding to the escape samples for the entire CU are grouped together and coded in bypass mode.

An additional syntax element, last_run_type_flag, is signaled after signaling the index values. This syntax element, in conjunction with the number of indices, eliminates the need to signal the run value corresponding to the last run in the block.

In HEVC-SCC, the palette mode is also enabled for 4: 2: 2, 4: 2: 0, and monochrome chroma formats. The signaling of the palette entries and palette indices is almost identical for all the chroma formats. In case of non-monochrome formats, each palette entry consists of 3 components. For the monochrome format, each palette entry consists of a single component. For subsampled chroma directions, the chroma samples are associated with luma sample indices that are divisible by 2. After reconstructing the palette indices for the CU, if a sample has only a single component associated with it, only the first component of the palette entry is used. The only difference in signaling is for the escape component values. For each escape sample, the number of escape component values signaled may be different depending on the number of components associated with that sample.

2.6 Intra mode coding in VVC

To capture the arbitrary edge directions presented in natural video, the number of directional intra modes in VTM5 is extended from 33, as used in HEVC, to 65. The new directional modes not in HEVC are depicted as red dotted arrows in FIG. 6, and the planar and DC modes remain the same. These denser directional intra prediction modes apply for all block sizes and for both luma and chroma intra predictions.

In VTM5, several conventional angular intra prediction modes are adaptively replaced with wide-angle intra prediction modes for the non-square blocks.

In HEVC, every intra-coded block has a square shape and the length of each of its side is a power of 2. Thus, no division operations are required to generate an intra-predictor using DC mode. In VTM5, blocks can have a rectangular shape that necessitates the use of a division operation per block in the general case. To avoid division operations for DC prediction, only the longer side is used to compute the average for non-square blocks.

To keep the complexity of the most probable mode (MPM) list generation low, an intra mode coding method with 6 MPMs is used by considering two available neighboring intra modes. The following three aspects are considered to construct the MPM list:

○ Default intra modes

○ Neighboring intra modes

○ Derived intra modes

A unified 6-MPM list is used for intra blocks irrespective of whether MRL and ISP coding tools are applied or not. The MPM list is constructed based on intra modes of the left and above neighboring block. Suppose the mode of the left block is denoted as Left and the mode of the above block is denoted as Above, the unified MPM list is constructed as follows (The left and above blocks are shown in FIG. 7) :

- When a neighboring block is not available, its intra mode is set to Planar by default.

- If both modes Left and Above are non-angular modes:

○ MPM list → {Planar, DC, V, H, V-4, V+4}

- If one of modes Left and Above is angular mode, and the other is non-angular:

○ Set a mode Max as the larger mode in Left and Above

○ MPM list → {Planar, Max, DC, Max -1, Max +1, Max -2}

- If Left and Above are both angular and they are different:

○ Set a mode Max as the larger mode in Left and Above

○ if the difference of mode Left and Above is in the range of 2 to 62, inclusive

■ MPM list → {Planar, Left, Above, DC, Max -1, Max +1}

○ Otherwise

■ MPM list → {Planar, Left, Above, DC, Max -2, Max +2}

- If Left and Above are both angular and they are the same:

○ MPM list → {Planar, Left, Left-1, Left +1, DC, Left -2}

Besides, the first bin of the mpm index codeword is CABAC context coded. In total three contexts are used, corresponding to whether the current intra block is MRL enabled, ISP enabled, or a normal intra block.

During 6 MPM list generation process, pruning is used to remove duplicated modes so that only unique modes can be included into the MPM list. For entropy coding of the 61 non-MPM modes, a Truncated Binary Code (TBC) is used.

For chroma intra mode coding, a total of 8 intra modes are allowed for chroma intra mode coding. Those modes include five traditional intra modes and three cross-component linear model modes (CCLM, LM_A, and LM_L) . Chroma mode signaling and derivation process are shown in Table 1 . Chroma mode coding directly depends on the intra prediction mode of the corresponding luma block. Since separate block partitioning structure for luma and chroma components is enabled in I slices, one chroma block may correspond to multiple luma blocks. Therefore, for Chroma DM mode, the intra prediction mode of the corresponding luma block covering the center position of the current chroma block is directly inherited.

Table 1: Derivation of chroma prediction mode from luma mode when cclm_is enabled

2.7 Block Differential Pulse-Code Modulation (BDPCM)

In some embodiments, a quantized residual block differential pulse-code modulation (QR-BDPCM) is proposed to code screen contents efficiently.

The prediction directions used in QR-BDPCM can be vertical and horizontal prediction modes. The intra prediction is done on the entire block by sample copying in prediction direction (horizontal or vertical prediction) similar to intra prediction. The residual is quantized and the delta between the quantized residual and its predictor (horizontal or vertical) quantized value is coded. This can be described by the following: For a block of size M (rows) × N (cols) , let r _i, j, 0≤i≤M-1, 0≤j≤N-1 be the prediction residual after performing intra prediction horizontally (copying left neighbor pixel value across the the predicted block line by line) or vertically (copying top neighbor line to each line in the predicted block) using unfiltered samples from above or left block boundary samples. Let Q (r _i, j) , 0≤i≤M-1, 0≤j≤N-1 denote the quantized version of the residual r _i, j, where residual is difference between original block and the predicted block values. Then the block DPCM is applied to the quantized residual samples, resulting in modified M × N array

with elements

When vertical BDPCM is signaled:

For horizontal prediction, similar rules apply, and the residual quantized samples are obtained by:

The residual quantized samples

are sent to the decoder.

On the decoder side, the above calculations are reversed to produce Q (r _i, j) , 0≤i≤M-1, 0≤j≤N-1. For vertical prediction case,

For horizontal case,

The inverse quantized residuals, Q ^-1 (Q (r _i, j) ) , are added to the intra block prediction values to produce the reconstructed sample values.

The main benefit of this scheme is that the inverse DPCM can be done on the fly during coefficient parsing simply adding the predictor as the coefficients are parsed or it can be performed after parsing.

2.8 Adaptive Loop Filter

In the VTM5, an Adaptive Loop Filter (ALF) with block-based filter adaption is applied. For the luma component, one among 25 filters is selected for each 4×4 block, based on the direction and activity of local gradients.

2.8.1.1 Filter shape

In the VTM5, two diamond filter shapes (as shown in FIG. 8) are used. The 7×7 diamond shape is applied for luma component and the 5×5 diamond shape is applied for chroma components.

2.8.1.2 Block classification

For luma component, each 4×4 block is categorized into one out of 25 classes. The classification index C is derived based on its directionality D and a quantized value of activity

as follows:

To calculate D and

gradients of the horizontal, vertical and two diagonal direction are first calculated using 1-D Laplacian:

Where indices i and j refer to the coordinates of the upper left sample within the 4×4 block and R (i, j) indicates a reconstructed sample at coordinate (i, j) .

To reduce the complexity of block classification, the subsampled 1-D Laplacian calculation is applied. As shown in FIGS. 9A-9D, the same subsampled positions are used for gradient calculation of all directions.

Then D maximum and minimum values of the gradients of horizontal and vertical directions are set as:

The maximum and minimum values of the gradient of two diagonal directions are set as:

To derive the value of the directionality D, these values are compared against each other and with two thresholds t ₁ and t ₂:

Step 1. If both

and

are true, D is set to 0.

Step 2. If

continue from Step 3; otherwise continue from Step 4.

Step 3. If

D is set to 2; otherwise D is set to 1.

Step 4. If

D is set to 4; otherwise D is set to 3.

The activity value A is calculated as:

A is further quantized to the range of 0 to 4, inclusively, and the quantized value is denoted as

For chroma components in a picture, no classification method is applied, e.g. a single set of ALF coefficients is applied for each chroma component.

2.8.1.3 Geometric transformations of filter coefficients and clipping values

Before filtering each 4×4 luma block, geometric transformations such as rotation or diagonal and vertical flipping are applied to the filter coefficients f (k, l) and to the corresponding filter clipping values c (k, l) depending on gradient values calculated for that block. This is equivalent to applying these transformations to the samples in the filter support region. The idea is to make different blocks to which ALF is applied more similar by aligning their directionality.

Three geometric transformations, including diagonal, vertical flip and rotation are introduced:

Diagonal: f _D (k, l) =f (l, k) , c _D (k, l) =c (l, k) ,

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

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

Herein, K is the size of the filter and 0≤k, l≤K-1 are coefficients coordinates, such that location (0, 0) is at the upper left corner and location (K-1, K-1) is at the lower right corner. The transformations are applied to the filter coefficients f (k, l) and to the clipping values c (k, l) depending on gradient values calculated for that block. The relationship between the transformation and the four gradients of the four directions are summarized in Table 2.

Table 2: Mapping of the gradient calculated for one block and the transformations

Gradient values	Transformation
g _d2 < g _d1 and g _h < g _v	No transformation
g _d2 < g _d1 and g _v < g _h	Diagonal
g _d1 < g _d2 and g _h < g _v	Vertical flip
g _d1 < g _d2 and g _v < g _h	Rotation

2.8.1.4 Filter parameters signaling

In the VTM5, ALF filter parameters are signaled in Adaptation Parameter Set (APS) . In one APS, up to 25 sets of luma filter coefficients and clipping value indexes, and up to one set of chroma filter coefficients nd clipping value indexes could be signaled. To reduce bits overhead, filter coefficients of different classification can be merged. In slice header, the indices of the APSs used for the current slice are signaled.

Clipping value indexes, which are decoded from the APS, allow determining clipping values using a Luma table of clipping values and a Chroma table of clipping values. These clipping values are dependent of the internal bit-depth. More precisely, the Luma table of clipping values and Chroma table of clipping values are obtained by the following formulas:

Herein, B equal to the internal bit-depth and N equal to 4 which is the number of allowed clipping values in VTM5.0.

The filtering process can be controlled at CTB level. A flag is always signaled to indicate whether ALF is applied to a luma CTB. A luma CTB can choose a filter set among 16 fixed filter sets and the filter sets from APSs. A filter set index is signaled for a luma CTB to indicate which filter set is applied. The 16 fixed filter sets are pre-defined and hard-coded in both the encoder and the decoder.

The filter coefficients are quantized with norm equal to 128. In order to restrict the multiplication complexity, a bitstream conformance is applied so that the coefficient value of the non-central position shall be in the range of -2 ⁷ to 2 ⁷-1, inclusive. The central position coefficient is not signaled in the bitstream and is considered as equal to 128.

2.8.1.5 Filtering process

At decoder side, when ALF is enabled for a CTB, each sample R (i, j) within the CU is filtered, resulting in sample value R′ (i, j) as shown below,

where f (k, l) denotes the decoded filter coefficients, K (x, y) is the clipping function and c (k, l) denotes the decoded clipping parameters. The variable k and l varies between

and

where L denotes the filter length. The clipping function K (x, y) =min (y, max (-y, x) ) which corresponds to the function Clip3 (-y, y, x) .

2.8.1.6 Virtual boundary filtering process for line buffer reduction

In VTM5, to reduce the line buffer requirement of ALF, modified block classification and filtering are employed for the samples near horizontal CTU boundaries. For this purpose, a virtual boundary is defined as a line by shifting the horizontal CTU boundary with “N” samples as shown in FIG. 10, with N=4 for the Luma component and N=2 for the Chroma component.

Modified block classification is applied for the Luma component as depicted in FIG. 11. For the 1D Laplacian gradient calculation of the 4x4 block above the virtual boundary, only the samples above the virtual boundary are used. Similarly for the 1D Laplacian gradient calculation of the 4x4 block below the virtual boundary, only the samples below the virtual boundary are used. The quantization of activity value A is accordingly scaled by taking into account the reduced number of samples used in 1D Laplacian gradient calculation.

For filtering processing, symmetric padding operation at the virtual boundaries are used for both Luma and Chroma components. As shown in FIG. 11, when the sample being filtered is located below the virtual boundary, the neighboring samples that are located above the virtual boundary are padded. Meanwhile, the corresponding samples at the other sides are also padded, symmetrically.

2.9 Sample Adaptive Offset (SAO)

Sample adaptive offset (SAO) is applied to the reconstructed signal after the deblocking filter by using offsets specified for each CTB by the encoder. The HM encoder first makes the decision on whether or not the SAO process is to be applied for current slice. If SAO is applied for the slice, each CTB is classified as one of five SAO types as shown in Table 3. The concept of SAO is to classify pixels into categories and reduces the distortion by adding an offset to pixels of each category. SAO operation includes Edge Offset (EO) which uses edge properties for pixel classification in SAO type 1-4 and Band Offset (BO) which uses pixel intensity for pixel classification in SAO type 5. Each applicable CTB has SAO parameters including sao_merge_left_flag, sao_merge_up_flag, SAO type and four offsets. If sao_merge_left_flag is equal to 1, the current CTB will reuse the SAO type and offsets of the CTB to the left. If sao_merge_up_flag is equal to 1, the current CTB will reuse SAO type and offsets of the CTB above.

Table 3: Specification of SAO type

2.9.1 Operation of each SAO type

Edge offset uses four 1-D 3-pixel patterns for classification of the current pixel p by consideration of edge directional information, as shown in FIG. 12 . From left to right these are: 0-degree, 90-degree, 135-degree and 45-degree.

Each CTB is classified into one of five categories according to Table 4.

Table 4: Pixel classification rule for EO

Category	Condition	Meaning
0	None of the below	Largely monotonic
1	p< 2 neighbors	Local minimum
2	p< 1 neighbor &&p== 1 neighbor	Edge
3	p> 1 neighbor &&p== 1 neighbor	Edge
4	p> 2 neighbors	Local maximum

Band offset (BO) classifies all pixels in one CTB region into 32 uniform bands by using the five most significant bits of the pixel value as the band index. In other words, the pixel intensity range is divided into 32 equal segments from zero to the maximum intensity value (e.g. 255 for 8-bit pixels) . Four adjacent bands are grouped together and each group is indicated by its most left-hand position as shown in FIG. 13. The encoder searches all position to get the group with the maximum distortion reduction by compensating offset of each band.

2.10 Combined inter and intra prediction (CIIP)

In VTM5, when a CU is coded in merge mode, if the CU contains at least 64 luma samples (that is, CU width times CU height is equal to or larger than 64) , and if both CU width and CU height are less than 128 luma samples, an additional flag is signaled to indicate if the combined inter/intra prediction (CIIP) mode is applied to the current CU. As its name indicates, the CIIP prediction combines an inter prediction signal with an intra prediction signal. The inter prediction signal in the CIIP mode P _inter is derived using the same inter prediction process applied to regular merge mode; and the intra prediction signal P _intra is derived following the regular intra prediction process with the planar mode. Then, the intra and inter prediction signals are combined using weighted averaging, where the weight value is calculated depending on the coding modes of the top and left neighboring blocks (depicted in FIG. 14) as follows:

- If the top neighbor is available and intra coded, then set isIntraTop to 1, otherwise set isIntraTop to 0;

- If the left neighbor is available and intra coded, then set isIntraLeft to 1, otherwise set isIntraLeft to 0;

- If (isIntraLeft + isIntraLeft) is equal to 2, then wt is set to 3;

- Otherwise, if (isIntraLeft + isIntraLeft) is equal to 1, then wt is set to 2;

- Otherwise, set wt to 1.

The CIIP prediction is formed as follows:

P _CIIP= ( (4-wt) *P _inter+wt*P _intra+2) ＞＞2

2.11 Luma mapping with chroma scaling (LMCS)

In VTM5, a coding tool called the luma mapping with chroma scaling (LMCS) is added as a new processing block before the loop filters. LMCS has two main components: 1) in-loop mapping of the luma component based on adaptive piecewise linear models; 2) for the chroma components, luma-dependent chroma residual scaling is applied. FIG. 15 shows the LMCS architecture from decoder’s perspective. The light-blue shaded blocks in FIG. 15 indicate where the processing is applied in the mapped domain; and these include the inverse quantization, inverse transform, luma intra prediction and adding of the luma prediction together with the luma residual. The unshaded blocks in FIG. 15 indicate where the processing is applied in the original (e.g., non-mapped) domain; and these include loop filters such as deblocking, ALF, and SAO, motion compensated prediction, chroma intra prediction, adding of the chroma prediction together with the chroma residual, and storage of decoded pictures as reference pictures. The light-yellow shaded blocks in FIG. 15 are the new LMCS functional blocks, including forward and inverse mapping of the luma signal and a luma-dependent chroma scaling process. Like most other tools in VVC, LMCS can be enabled/disabled at the sequence level using an SPS flag.

2.12 Adaptive color transform (ACT)

2.12.1 ACT in HEVC Screen Content Coding Extensions

In the HEVC SCC Extensions, several tools have been proposed and employed to improve the SCC efficiency under the HEVC framework. For example, to exploit the repeated patterns in SC, an intra block copying (IBC) scheme was adopted. Similar to the motion compensation scheme used for inter pictures, the IBC mode searches for the repeated patterns in the already reconstructed region of the current picture. Another direction to improve SCC is to reduce the inter-color-component redundancy for the RGB/YCbCr sequences in the 4: 4: 4 chroma format.

The cross-component prediction (CCP) technology signals a weighting parameter index for each chroma color component of a transform unit. CCP provides good coding efficiency improvements with limited added complexity and thus, it was adopted to the HEVC Range Extensions and is part of HEVC Ver. 2 which specifies descriptions of Range Extensions, and other Extensions.

In order to further exploit inter-color-components correlation for SCC, an in-loop adaptive color-space transform (ACT) for HEVC SCC Extensions was employed. The basic idea of ACT is to adaptively convert the prediction residual into a color space with reduced redundancy among the three-color components. Before and after that, the signal follows the existing coding path in HEVC Range Extensions. To keep the complexity as low as possible, only one additional color-space (e.g., RGB to YCgCo-R inverse transform) is considered, which can be easily implemented with shift and add operations.

The encoding flow with ACT is shown in FIG. 16.

The decoding flow with ACT is shown in FIG. 17.

2.12.2 Transforms used in ACT

For lossy coding, the YCgCo transform is used while its reversible variant, e.g., YCgCo-R, is used for lossless coding.

The forward and inverse YCgCo transform process is listed as below: taking a pixel in (R, G, B) color format as an example:

Forward:

Inverse:

Different from YCgCo transform which could be implemented by a matrix multiplication, the reversible color-space transform, e.g., YCgCo-R, used in ACT can only be performed in lifting-based operation as follows:

Forward:

Inverse:

2.12.3 Usage of ACT

For each TU, a flag may be signaled to indicate the usage of color-space transform. In addition, for intra coded CUs, ACT is enabled only when the chroma and luma intra prediction modes are the same, e.g., the chroma block is coded with DM mode.

FIG. 16 shows the block diagram of the proposed method at the encoder with the residual signal derived from intra/inter prediction as the input. The proposed function blocks, including forward and reverse color-space transforms, are located in the coding loop and highlighted. As shown in FIG. 16, after the intra-or inter-prediction process (including the prediction process for IBC mode) , it is determined whether to perform the forward color-space transform. With the introduced color-space transform, the color space of the input signal may be converted to YCgCo with less correlation among the three-color components. After that, the original coding flow, such as CCP, integer transform (e.g., T in FIG. 16) , if applicable, quantization (e.g., Q in FIG. 16) and entropy coding processes, is further invoked in order. Meanwhile, during the reconstruction or decoding process as depicted in FIG. 17, after the conventional inverse quantization (e.g., IQ in FIG. 17) , inverse transform (e.g., IT in FIG. 17) and inverse CCP, if applicable, the inverse color transform is invoked to convert the coded residual back to the original color space. It should be noted that, the color-space conversion process is applied to the residual signal instead of the reconstruction signal. With such a method, the decoder only needs to perform the inverse color space transform process which could keep the complexity increase as low as possible. Furthermore, in ACT, fixed color space transforms, e.g., YCgCo and YCgCo-R, are utilized regardless of input color spaces.

2.12.4 ACT in VVC

The ACT is based on CU instead of TU. The core transforms used for the color space conversions are kept the same as that used for the HEVC. Specifically, the following forward and inverse YCgCo color transform matrices, as described as follows, as applied.

Additionally, to compensate the dynamic range change of residuals signals before and after color transform, the QP adjustments of (-5, -5, -3) are applied to the transform residuals.

On the other hand, the forward and inverse color transforms need to access the residuals of all three components. Correspondingly, in the proposed implementation, the ACT is disabled in the following two scenarios where not all residuals of three components are available.

Separate-tree partition: when separate-tree is applied, luma and chroma samples inside one CTU are partitioned by different structures. This results in that the CUs in the luma-tree only contains luma component and the CUs in the chroma-tree only contains two chroma components.

Intra sub-partition prediction (ISP) : the ISP sub-partition is only applied to luma while chroma signals are coded without splitting. In the current ISP design, except the last ISP sub-partitions, the other sub-partitions only contain luma component.

2.13 Internal bit-depth increase (IBDI)

In HEVC and VVC coding, IBDI is used to increase the in-loop processing precision for better coding efficiency.

For example, for an image/video with 8-bit bit-depth, instead of directly encode the 8-bit signals, a 10-bit source is generated by left shift each pixel p by 2 bits, e.g. P << 2. Then for the encoder and decoder, they do not have the information that the original source is from 8-bit. Instead, it will be treated as a 10-bit video. At the decoding, if an 8-bit video needs to be reconstructed, a conversion from 10-bit to 8-bit with rounding will be applied. For example, let p denotes a 10-bit reconstructed pixel, an 8-bit reconstruction is then clip3 (0, 255, (P + 1) >> 2) ) .

However, being agnostic to the bit-depth of original source, e.g., input bit-depth, may hurt coding efficiency sometimes. For example, in transform skip coding, the lowest allowed QP should be aligned to the input bit-depth instead of internal bit-depth.

3. Examples of Problems Solved by Embodiments

(1) Currently quantization and dequantization in video coding only depend on internal bit-depth and do not consider input bit-depth.

(2) Currently in-loop filtering processes only depend on internal bit-depth and does not consider input bit-depth.

(3) Currently prediction processes only depend on internal bit-depth and does not consider input bit-depth.

(4) Currently LMCS processes only depend on internal bit-depth and does not consider input bit-depth.

(5) Currently reconstruction processes only depend on internal bit-depth and does not consider input bit-depth.

(6) Currently pixel clipping does not consider input bit-depth.

(7) Currently adaptive color transform does not consider input bit-depth.

4. Examples of Embodiments

The detailed inventions below should be considered as examples to explain general concepts. These inventions should not be interpreted in a narrow way. Furthermore, these inventions can be combined in any manner.

In the following, we denote internal bit-depth as IBD and input bit-depth as iBD.

1. Reconstruction value may be rounded according to input bit-depth.

a. In one example, for a value P in IBD bit-depth, the reconstruction may be clip3 (0, (1 << IBD) –1, (P + (1 << (IBD –iBD –1) ) ) >> (IBD –iBD) << (IBD –iBD) ) .

b. In one example, for a value P in IBD bit-depth, the reconstruction may be P >> (IBD –iBD) << (IBD –iBD) .

c. Alternatively, reconstruction value may be rounded according to the lowest allowed QP for transform skip blocks.

2. Prediction value may be rounded according to input bit-depth.

a. In one example, for a value P in IBD bit-depth, the prediction for later usage may be clip3 (0, (1 << IBD) –1 , (P + (1 << (IBD –iBD –1) ) ) >> (IBD –iBD) << (IBD –iBD) ) .

b. In one exmaple, for a value P in IBD bit-depth, the prediction for later usage may be P >> (IBD –iBD) << (IBD –iBD) .

c. Alternatively, prediction value may be rounded according to the lowest allowed QP for transform skip blocks.

3. In-loop filtering process may depend on input bit-depth.

a. In one example, the output of a in-loop filtering process may be rounded according to input bit-depth.

i. In one example, the output of deblocking process may be rounded according to input bit-depth.

ii. In one example, the output of ALF process may be rounded according to input bit-depth.

iii. In one example, the output of SAO process may be rounded according to input bit-depth.

iv. In one example, the output of CC-ALF process may be rounded according to input bit-depth.

b. Alternatively, in-loop filtering process may depend on the lowest allowed QP for transform skip blocks.

4. LMCS process may depend on input bit-depth.

a. In one example, the output of LMCS mapping may be rounded according to input bit-depth.

b. Alternatively, LMCS process may depend on the lowest allowed QP for transform skip blocks.

5. Pixel clipping range may depend on input bit-depth.

a. In one example, pixel clipping range may be [0, ( (1 << iBD) –1) << (IBD–iBD) ] .

b. In one example, pixel clipping range may be [0, 1020] when IBD is equal to 10 and iBD is equal to 8.

c. Alternatively, pixel clipping range may depend on the lowest allowed QP for transform skip blocks.

6. Adaptive color transform may depend on input bit-depth.

a. In one example, when iBD is equal to IBD, YCoCg-R color transform may be applied. The YCoCg color model, also known as the YCgCo color model, is the color space formed from a simple transformation of an associated RGB color space into a luma value (denoted as Y) and two chroma values called chrominance green (Cg) and chrominance orange (Co) . A scaled version of the transformation, sometimes called YCoCg-R (where the "-R" refers to RGB reversibility) , can be implemented efficiently with a reduced bit depth.

b. In one example, when IBD –iBD >= 2, YCoCg color transform may be applied.

c. Alternatively, adaptive color transform may depend on the lowest allowed QP for transform skip blocks.

7. In the above methods, input bit-depth may be indicated as a high-level syntax element.

a. In one example, input bit-depth may be indicated in DPS/VPS/SPS/Picture header/Slice header.

b. In one example, input bit-depth may be inferred from the lowest allowed QP for transform skip blocks.

8. Whether and/or how to apply the above methods may depend on the characteristics of the current block.

a. In one example, the above methods may be applied when QP for the current block is smaller than a given threshold.

b. In one example, the above methods may be applied when QP for the current block is larger than a given threshold.

c. In one example, the above methods may be applied when (QP %6) is equal to a certain value for the current block.

d. In one example, the above methods may be applied when the width and/or height and/or size of the current block is smaller than a give threshold.

e. In one example, the above methods may be applied when the width and/or height and/or size of the current block is larger than a give threshold.

f. In one example, the above methods may be applied only for luma blocks.

g. In one example, the above methods may be applied only for chroma blocks.

h. In one example, the above methods may be applied when the current block is coded with mode X.

i. In one example, X may refer to Intra mode.

ii. In one example, X may refer to Inter mode.

iii. In one example, X may refer to transform skip coding mode.

iv. In one example, X may refer to BDPCM mode.

v. In one example, X may refer to IBC mode.

vi. In one example, X may refer to Palette mode.

vii. In one example, X may refer to ISP mode.

viii. In one example, X may refer to MIP mode.

ix. In one example, X may refer to LMCS mode.

x. In one example, X may refer to CCLM mode.

xi. In one example, X may refer to DM mode.

xii. In one example, X may refer to DC mode.

xiii. In one example, X may refer to ACT mode.

The examples described above may be incorporated in the context of the method described below, e.g., method 1800, which may be implemented at a video decoder or a video encoder.

FIG. 18 shows a flowchart of an exemplary method 1800 for video processing. The method 1800 includes, at operation 1810, determining, during a conversion between a current block of video and a bitstream representation of the video, a given bit-depth (BD) based on a bit-depth used for representing the video.

The method 1800 includes, at operation 1820, performing the conversion using the given bit-depth as a computational bit-depth (cBD) for at least one or more computations of the conversion.

In some embodiments, the following technical solutions may be implemented:

A1. A method of video processing, comprising: determining, during a conversion between a current block of video and a bitstream representation of the video, a given bit-depth (BD) based on a bit-depth used for representing the video; and performing the conversion using the given bit-depth as a computational bit-depth (cBD) for at least one or more computations of the conversion.

A2. The method of solution A1, wherein the at least one or more computations comprises a rounding operation on a reconstruction value or a prediction value.

A3. The method of solution A2, wherein the rounding operation is defined as: Clip3 (0, (1 << cBD) –1, (P + (1 << (cBD –BD –1) ) ) >> (cBD –BD) << (cBD –BD) ) , wherein P is the reconstruction value or the prediction value with the computational bit-depth, and wherein Clip3 (x, min, max) is defined as:

A4. The method of solution A2, wherein the rounding operation is defined as: P >> (cBD –BD) << (cBD–BD) , wherein P is the reconstruction value or the prediction value with the computational bit-depth.

A5. The method of solution A2, wherein the rounding operation is based on a lowest allowed quantization parameter (QP) for transform skip blocks.

A6. The method of solution A1, wherein the at least one or more computations comprises a rounding operation on an output value of an in-loop filtering process.

A7. The method of solution A6, wherein the in-loop filtering process comprises at least one of a deblocking process, an adaptive loop filtering (ALF) process, a sample adaptive offset (SAO) process or a cross-component ALF (CC-ALF) process.

A8. The method of solution A6, wherein the in-loop filtering process is based on a lowest allowed quantization parameter (QP) for transform skip blocks.

A9. The method of solution A1, wherein the at least one or more computations comprises a luma mapping with chroma scaling (LMCS) process.

A10. The method of solution A9, wherein the at least one or more computations comprises a rounding operation on an output of the LMCS process.

A11. The method of solution A9, wherein the LMCS process is based on a lowest allowed quantization parameter (QP) for transform skip blocks.

A12. The method of solution A1, wherein the at least one or more computations comprises a pixel clipping operation to an output pixel clipping range.

A13. The method of solution A12, wherein the output pixel clipping range is [0, ( (1 <<BD) –1) << (cBD –BD) ] .

A14. The method of solution A13, wherein cBD = 10 and BD = 8, and wherein the output pixel clipping range is [0, 1020] .

A15. The method of solution A12, wherein the output pixel clipping range is based on a lowest allowed quantization parameter (QP) for transform skip blocks.

A16. The method of solution A1, wherein the at least one or more computations comprises an adaptive color transform (ACT) .

A17. The method of solution A16, wherein the ACT comprises a YCoCg-R color transform upon a determination that BD is equal to cBD.

A18. The method of solution A16, wherein the ACT comprises a YCoCg color transform upon a determination that (cBD -BD) ≥2.

A19. The method of solution A16, wherein the ACT is based on a lowest allowed quantization parameter (QP) for transform skip blocks.

A20. The method of solution A1, wherein the given bit-depth is signaled in the bitstream representation as a high-level syntax element.

A21. The method of solution A20, wherein the given bit-depth is signaled in a decoder parameter set (DPS) , a video parameter set (VPS) , a sequence parameter set (SPS) , a picture header, or a slice header.

A22. The method of solution A20, wherein the given bit-depth is inferred from a lowest allowed quantization parameter (QP) for transform skip blocks.

A23. The method of any of solutions A1 to A22, wherein the at least one or more computations is further based on one or more characteristics of the current block.

A24. The method of solution A23, wherein the one or more characteristics comprises a quantization parameter (QP) for the current block being smaller than a predetermined threshold.

A25. The method of solution A23, wherein the one or more characteristics comprises a quantization parameter (QP) for the current block being larger than a predetermined threshold.

A26. The method of solution A23, wherein the one or more characteristics comprises (QP %6) being a predetermined value, wherein QP is a quantization parameter for the current block.

A27. The method of solution A23, wherein the one or more characteristics comprises a width, a height or a size of the current block being smaller than a predetermined threshold.

A28. The method of solution A23, wherein the one or more characteristics comprises a width, a height or a size of the current block being larger than a predetermined threshold.

A29. The method of solution A23, wherein the one or more characteristics comprises the current block being either a luma block or a chroma block.

A30. The method of solution A23, wherein the one or more characteristics comprises a coding mode of the current block being an Intra mode, an Inter mode, a transform skip coding mode, a block differential pulse-code modulation (BDPCM) mode, an intra block copy (IBC) mode, a palette mode, an intra sub-partition prediction (ISP) mode, a matrix-based intra prediction (MIP) mode, a luma mapping with chroma scaling (LMCS) mode, a cross-component linear model (CCLM) mode, a DM mode, a DC mode, or an adaptive color transform (ACT) mode.

A31. The method of any of solutions A1 to A30, wherein the conversion generates the current block from the bitstream representation.

A32. The method of any of solutions A1 to A30, wherein the conversion generates the bitstream representation from the current block.

A33. An apparatus in a video system comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to implement the method in any one of solutions A1 to A32.

A34. A computer program product stored on a non-transitory computer readable media, the computer program product including program code for carrying out the method in any one of solutions A1 to A32.

FIG. 19 is a block diagram showing an example video processing system 1900 in which various techniques disclosed herein may be implemented. Various implementations may include some or all of the components of the system 1900. The system 1900 may include input 1902 for receiving video content. The video content may be received in a raw or uncompressed format, e.g., 8 or 10 bit multi-component pixel values, or may be in a compressed or encoded format. The input 1902 may represent a network interface, a peripheral bus interface, or a storage interface. Examples of network interface include wired interfaces such as Ethernet, passive optical network (PON) , etc. and wireless interfaces such as Wi-Fi or cellular interfaces.

The system 1900 may include a coding component 1904 that may implement the various coding or encoding methods described in the present document. The coding component 1904 may reduce the average bitrate of video from the input 1902 to the output of the coding component 1904 to produce a coded representation of the video. The coding techniques are therefore sometimes called video compression or video transcoding techniques. The output of the coding component 1904 may be either stored, or transmitted via a communication connected, as represented by the component 1906. The stored or communicated bitstream (or coded) representation of the video received at the input 1902 may be used by the component 1908 for generating pixel values or displayable video that is sent to a display interface 1910. The process of generating user-viewable video from the bitstream representation is sometimes called video decompression. Furthermore, while certain video processing operations are referred to as “coding” operations or tools, it will be appreciated that the coding tools or operations are used at an encoder and corresponding decoding tools or operations that reverse the results of the coding will be performed by a decoder.

Examples of a peripheral bus interface or a display interface may include universal serial bus (USB) or high definition multimedia interface (HDMI) or Displayport, and so on. Examples of storage interfaces include SATA (serial advanced technology attachment) , PCI, IDE interface, and the like. The techniques described in the present document may be embodied in various electronic devices such as mobile phones, laptops, smartphones or other devices that are capable of performing digital data processing and/or video display.

FIG. 20 is a block diagram that illustrates an example video coding system 100 that may utilize the techniques of this disclosure.

As shown in FIG. 20, video coding system 100 may include a source device 110 and a destination device 120. Source device 110 generates encoded video data which may be referred to as a video encoding device. Destination device 120 may decode the encoded video data generated by source device 110 which may be referred to as a video decoding device.

Source device 110 may include a video source 112, a video encoder 114, and an input/output (I/O) interface 116.

Video source 112 may include a source such as a video capture device, an interface to receive video data from a video content provider, and/or a computer graphics system for generating video data, or a combination of such sources. The video data may comprise one or more pictures. Video encoder 114 encodes the video data from video source 112 to generate a bitstream. The bitstream may include a sequence of bits that form a coded representation of the video data. The bitstream may include coded pictures and associated data. The coded picture is a coded representation of a picture. The associated data may include sequence parameter sets, picture parameter sets, and other syntax structures. I/O interface 116 may include a modulator/demodulator (modem) and/or a transmitter. The encoded video data may be transmitted directly to destination device 120 via I/O interface 116 through network 130a. The encoded video data may also be stored onto a storage medium/server 130b for access by destination device 120.

Destination device 120 may include an I/O interface 126, a video decoder 124, and a display device 122.

I/O interface 126 may include a receiver and/or a modem. I/O interface 126 may acquire encoded video data from the source device 110 or the storage medium/server 130b. Video decoder 124 may decode the encoded video data. Display device 122 may display the decoded video data to a user. Display device 122 may be integrated with the destination device 120, or may be external to destination device 120 which be configured to interface with an external display device.

Video encoder 114 and video decoder 124 may operate according to a video compression standard, such as the High Efficiency Video Coding (HEVC) standard, Versatile Video Coding (VVC) standard and other current and/or further standards.

FIG. 21 is a block diagram illustrating an example of video encoder 200, which may be video encoder 114 in the system 100 illustrated in FIG. 20.

Video encoder 200 may be configured to perform any or all of the techniques of this disclosure. In the example of FIG. 21, video encoder 200 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of video encoder 200. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure.

The functional components of video encoder 200 may include a partition unit 201, a predication unit 202 which may include a mode select unit 203, a motion estimation unit 204, a motion compensation unit 205 and an intra prediction unit 206, a residual generation unit 207, a transform unit 208, a quantization unit 209, an inverse quantization unit 210, an inverse transform unit 211, a reconstruction unit 212, a buffer 213, and an entropy encoding unit 214.

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

Furthermore, some components, such as motion estimation unit 204 and motion compensation unit 205 may be highly integrated, but are represented in the example of FIG. 5 separately for purposes of explanation.

Partition unit 201 may partition a picture into one or more video blocks. Video encoder 200 and video decoder 300 may support various video block sizes.

Mode select unit 203 may select one of the coding modes, intra or inter, e.g., based on error results, and provide the resulting intra-or inter-coded block to a residual generation unit 207 to generate residual block data and to a reconstruction unit 212 to reconstruct the encoded block for use as a reference picture. In some example, Mode select unit 203 may select a combination of intra and inter predication (CIIP) mode in which the predication is based on an inter predication signal and an intra predication signal. Mode select unit 203 may also select a resolution for a motion vector (e.g., a sub-pixel or integer pixel precision) for the block in the case of inter-predication.

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

Motion estimation unit 204 and motion compensation unit 205 may perform different operations for a current video block, for example, depending on whether the current video block is in an I slice, a P slice, or a B slice.

In some examples, motion estimation unit 204 may perform uni-directional prediction for the current video block, and motion estimation unit 204 may search reference pictures of list 0 or list 1 for a reference video block for the current video block. Motion estimation unit 204 may then generate a reference index that indicates the reference picture in list 0 or list 1 that contains the reference video block and a motion vector that indicates a spatial displacement between the current video block and the reference video block. Motion estimation unit 204 may output the reference index, a prediction direction indicator, and the motion vector as the motion information of the current video block. Motion compensation unit 205 may generate the predicted video block of the current block based on the reference video block indicated by the motion information of the current video block.

In other examples, motion estimation unit 204 may perform bi-directional prediction for the current video block, motion estimation unit 204 may search the reference pictures in list 0 for a reference video block for the current video block and may also search the reference pictures in list 1 for another reference video block for the current video block. Motion estimation unit 204 may then generate reference indexes that indicate the reference pictures in list 0 and list 1 containing the reference video blocks and motion vectors that indicate spatial displacements between the reference video blocks and the current video block. Motion estimation unit 204 may output the reference indexes and the motion vectors of the current video block as the motion information of the current video block. Motion compensation unit 205 may generate the predicted video block of the current video block based on the reference video blocks indicated by the motion information of the current video block.

In some examples, motion estimation unit 204 may output a full set of motion information for decoding processing of a decoder.

In some examples, motion estimation unit 204 may do not output a full set of motion information for the current video. Rather, motion estimation unit 204 may signal the motion information of the current video block with reference to the motion information of another video block. For example, motion estimation unit 204 may determine that the motion information of the current video block is sufficiently similar to the motion information of a neighboring video block.

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

In another example, motion estimation unit 204 may identify, in a syntax structure associated with the current video block, another video block and a motion vector difference (MVD) . The motion vector difference indicates a 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.

As discussed above, video encoder 200 may predictively signal the motion vector. Two examples of predictive signaling techniques that may be implemented by video encoder 200 include advanced motion vector predication (AMVP) and merge mode signaling.

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

Residual generation unit 207 may generate residual data for the current video block by subtracting (e.g., indicated by the minus sign) the predicted video block (s) of the current video block from the current video block. The residual data of the current video block may include residual video blocks that correspond to different sample components of the samples in the current video block.

In other examples, there may be no residual data for the current video block for the current video block, for example in a skip mode, and residual generation unit 207 may not perform the subtracting operation.

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 a residual video block associated with the current video block.

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

Inverse quantization unit 210 and inverse transform unit 211 may apply inverse quantization and inverse transforms to the transform coefficient video block, respectively, to reconstruct a residual video block from the transform coefficient video block. Reconstruction unit 212 may add the reconstructed residual video block to corresponding samples from one or more predicted video blocks generated by the predication unit 202 to produce a reconstructed video block associated with the current block for storage in the buffer 213.

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

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

FIG. 22 is a block diagram illustrating an example of video decoder 300 which may be video decoder 114 in the system 100 illustrated in FIG. 20.

The video decoder 300 may be configured to perform any or all of the techniques of this disclosure. In the example of FIG. 22, the video decoder 300 includes a plurality of functional components. The techniques described in this 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 this disclosure.

In the example of FIG. 22, 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 transformation unit 305, and a reconstruction unit 306 and a buffer 307. Video decoder 300 may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to video encoder 200 (e.g., FIG. 21) .

Entropy decoding unit 301 may retrieve an encoded bitstream. The encoded bitstream may include entropy coded video data (e.g., encoded blocks of video data) . Entropy decoding unit 301 may decode the entropy coded video data, and from the entropy decoded video data, motion compensation unit 302 may determine motion information including motion vectors, motion vector precision, reference picture list indexes, and other motion information. Motion compensation unit 302 may, for example, determine such information by performing the AMVP and merge mode.

Motion compensation unit 302 may produce motion compensated blocks, possibly performing interpolation based on interpolation filters. Identifiers for interpolation filters to be used with sub-pixel precision may be included in the syntax elements.

Motion compensation unit 302 may use interpolation filters as used by video encoder 20 during encoding of the video block to calculate interpolated values for sub-integer pixels of a reference block. Motion compensation unit 302 may determine the interpolation filters used by video encoder 200 according to received syntax information and use the interpolation filters to produce predictive blocks.

Motion compensation unit 302 may uses some of the syntax information to determine sizes of blocks used to encode frame (s) and/or slice (s) of the encoded video sequence, partition information that describes how each macroblock of a picture of the encoded video sequence is partitioned, modes indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter-encoded block, and other information to decode the encoded video sequence.

Intra prediction unit 303 may use intra prediction modes for example received in the bitstream to form a prediction block from spatially adjacent blocks. Inverse quantization unit 303 inverse quantizes, e.g., de-quantizes, the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 301. Inverse transform unit 303 applies an inverse transform.

Reconstruction unit 306 may sum the residual blocks with the corresponding prediction blocks generated by motion compensation unit 202 or intra-prediction unit 303 to form decoded blocks. If desired, a deblocking filter may also be applied to filter the decoded blocks in order to remove blockiness artifacts. The decoded video blocks are then stored in buffer 307, which provides reference blocks for subsequent motion compensation/intra predication and also produces decoded video for presentation on a display device.

FIG. 23 is a flowchart representation of a method for video processing in accordance with the present technology. The method 2300 includes, at operation 2310, making a determination, for a conversion between a current block of a video and a bitstream representation of the video, about usage of an adaptive color transform coding tool based on an input bit-depth of a source sample in the current block. The method 2300 also includes, at operation 2320, performing the conversion based on the determination.

In some embodiments, during the conversion, a color transform from a Green-Blue-Red color space to a luma value Y and two chroma values including chrominance green (Cg) and chrominance orange (Co) with reversibility is applied in case the input bit-depth is same as an internal bit-depth of the adaptive color transform coding tool. In some embodiments, an internal bit-depth of the adaptive color transform coding tool is denoted as IBD and the input bit-depth is denoted as iBD. During the conversion, a color transform from a Green-Blue-Red color space to a luma value Y and two chroma values including chrominance green (Cg) and chrominance orange (Co) is applied in case IBD -iBD ≥2. In some embodiments, the adaptive color transform coding tool is applied based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.

FIG. 24 is a flowchart representation of a method for video processing in accordance with the present technology. The method 2400 includes, at operation 2410, making a determination, for a conversion between a current block of a video and a bitstream representation of the video, that a reconstruction value or a prediction value of a sample of the current block is rounded according to an input bit-depth of a source value of the sample. The method 2400 also includes, at operation 2420, performing the conversion based on the determination.

In some embodiments, the input bit-depth is denoted as iBD. A value P is represented in an internal bit-depth IBD. The reconstructed value or the prediction value corresponding to the value P is equal to clip3 (0, (1 << IBD) -1, (P + (1 << (IBD -iBD -1) ) ) >> (IBD -iBD) << (IBD -iBD) ) , where clip3 is defined as

In some embodiments, the input bit-depth is denoted as iBD. A value P is represented in an internal bit-depth IBD. The reconstructed value or the prediction value corresponding to the value P is equal to P >> (IBD -iBD) << (IBD -iBD) .

In some embodiments, the reconstructed value or the prediction value is determined based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.

FIG. 25 is a flowchart representation of a method for video processing in accordance with the present technology. The method 2500 includes, at operation 2510, making a determination, for a conversion between a current block of a video and a bitstream representation of the video, about usage of an in-loop filtering process based on an input bit-depth of a source sample in the current block. The method 2500 includes, at operation 2520, performing the conversion based on the determination.

In some embodiments, an output of the in-loop filtering process is rounded according to the input bit-depth. In some embodiments, the in-loop filtering process comprises at least one of: a deblocking process, an adaptive loop filtering process, a sample adaptive offset process, or a cross-component adaptive loop filtering process. In some embodiments, the usage of the in-loop filtering process is determined based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.

FIG. 26 is a flowchart representation of a method for video processing in accordance with the present technology. The method 2600 includes, at operation 2610, making a determination, for a conversion between a current block of a video and a bitstream representation of the video, about usage of a luma mapping with chroma scaling (LMCS) coding tool based on an input bit-depth of a source sample in the current block. The method 2600 also includes, at operation 2620, performing the conversion based on the determination.

In some embodiments, an output of the LMCS coding tool is rounded according to the input bit-depth. In some embodiments, the usage of the LMCS coding tool is determined based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.

FIG. 27 is a flowchart representation of a method for video processing in accordance with the present technology. The method 2700 includes, at operation 2710, making a determination, for a conversion between a block of a video and a bitstream representation of the video, about a pixel clipping range based on an input bit-depth of a source pixel. The method 2700 also includes, at operation 2720, performing the conversion based on the determination.

In some embodiments, an internal bit-depth of the conversion is denoted as IBD and the input bit-depth is denoted as iBD, and the pixel clipping range is equal to [0, ( (1 << iBD) -1) << (IBD -iBD) ] . In some embodiments, the pixel clipping range is [0, 1020] in case the internal bit-depth is 10 and the input bit-depth is 8. In some embodiments, the pixel clipping range is based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.

In some embodiments, the input bit-depth is indicated as a syntax element in the bitstream representation. In some embodiments, the syntax element is included in a decoder parameter set, a video parameter set, a sequence parameter set, a picture header, or a slice header in the bitstream representation. In some embodiments, the input bit-depth is determined based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.

In some embodiments, a manner of applying the determination in the above methods is based on a characteristic of the current block. In some embodiments, the determination is applied in case a quantization parameter of the current block is smaller than a threshold. In some embodiments, the determination is applied in case a quantization parameter of the current block is larger than a threshold. In some embodiments, a characteristic of the current block comprises a quantization parameter of the current block that is denoted as QP, and the determination is applied in case (QP %6) is equal to a predefined value. In some embodiments, the determination is applied in case a dimension of the current block is smaller than a threshold. In some embodiments, the determination is applied in case a dimension of the current block is greater than a threshold. In some embodiments, the determination is applied in case the current block is associated with a luma component of the video. In some embodiments, the determination is applied in case the current block is associated with a chroma component of the video. In some embodiments, the determination is applied in case the current block is coded in a specific coding mode. In some embodiments, the specific coding mode comprises at least a intra mode, an inter mode, a transform skip mode, a Block Differential Pulse-code Modulation (BDPCM) mode, an intra block copy mode, a palette mode, an intra sub-partition prediction mode, a matrix-based intra prediction mode, a luma mapping with chroma scaling mode, a cross-component linear model mode, a derived mode, a DC prediction mode, or an adaptive color transform mode.

In some embodiments, the conversion generates the current block from the bitstream representation. In some embodiments, the conversion generates the bitstream representation from the current block.

It will be appreciated that the disclosed techniques may be embodied in video encoders or decoders to improve compression efficiency using enhanced coding tree structures.

Some embodiments of the disclosed technology include making a decision or determination to enable a video processing tool or mode. In an example, when the video processing tool or mode is enabled, the encoder will use or implement the tool or mode in the processing of a block of video, but may not necessarily modify the resulting bitstream based on the usage of the tool or mode. That is, a conversion from the block of video to the bitstream representation of the video will use the video processing tool or mode when it is enabled based on the decision or determination. In another example, when the video processing tool or mode is enabled, the decoder will process the bitstream with the knowledge that the bitstream has been modified based on the video processing tool or mode. That is, a conversion from the bitstream representation of the video to the block of video will be performed using the video processing tool or mode that was enabled based on the decision or determination.

Some embodiments of the disclosed technology include making a decision or determination to disable a video processing tool or mode. In an example, when the video processing tool or mode is disabled, the encoder will not use the tool or mode in the conversion of the block of video to the bitstream representation of the video. In another example, when the video processing tool or mode is disabled, the decoder will process the bitstream with the knowledge that the bitstream has not been modified using the video processing tool or mode that was enabled based on the decision or determination.

The disclosed and other solutions, examples, embodiments, modules and the functional operations described in this document can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this document and their structural equivalents, or in combinations of one or more of them. The disclosed and other embodiments can be implemented as one or more computer program products, e.g., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more them. The term “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus.

A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document) , in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code) . A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

The processes and logic flows described in this document can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit) .

Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random-access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

While this patent document contains many specifics, these should not be construed as limitations on the scope of any subject matter or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular techniques. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.

Only a few implementations and examples are described and other implementations, enhancements and variations can be made based on what is described and illustrated in this patent document.

Claims

A method of video processing, comprising:

making a determination, for a conversion between a current block of a video and a bitstream representation of the video, about usage of an adaptive color transform coding tool based on an input bit-depth of a source sample in the current block; and

performing the conversion based on the determination.
The method of claim 1, wherein, during the conversion, acolor transform from a Green-Blue-Red color space to a luma value Y and two chroma values including chrominance green (Cg) and chrominance orange (Co) with reversibility is applied in case the input bit-depth is same as an internal bit-depth of the adaptive color transform coding tool.
The method of claim 1, wherein an internal bit-depth of the adaptive color transform coding tool is denoted as IBD and the input bit-depth is denoted as iBD, and wherein, during the conversion, acolor transform from a Green-Blue-Red color space to a luma value Y and two chroma values including chrominance green (Cg) and chrominance orange (Co) is applied in case IBD -iBD ≥ 2.
The method of any of claims 1 to 3, wherein the adaptive color transform coding tool is applied based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.
A method of video processing, comprising:

making a determination, for a conversion between a current block of a video and a bitstream representation of the video, that a reconstruction value or a prediction value of a sample of the current block is rounded according to an input bit-depth of a source value of the sample; and

performing the conversion based on the determination.
The method of claim 5, wherein the input bit-depth is denoted as iBD, wherein a value P is represented in an internal bit-depth IBD, and wherein the reconstructed value or the prediction value corresponding to the value P is equal to clip3 (0, (1 << IBD) -1, (P + (1 << (IBD -iBD -1) ) ) >> (IBD -iBD) << (IBD -iBD) ) , where clip3 is defined as
The method of claim 5, wherein the input bit-depth is denoted as iBD, wherein a value P is represented in an internal bit-depth IBD, and wherein the reconstructed value or the prediction value corresponding to the value P is equal to P >> (IBD -iBD) << (IBD -iBD) .
The method of any of claims 5 to 7, wherein the reconstructed value or the prediction value is determined based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.
A method of video processing, comprising:

making a determination, for a conversion between a current block of a video and a bitstream representation of the video, about usage of an in-loop filtering process based on an input bit-depth of a source sample in the current block; and

performing the conversion based on the determination.
The method of claim 9, wherein an output of the in-loop filtering process is rounded according to the input bit-depth.
The method of claim 10, wherein the in-loop filtering process comprises at least one of: a deblocking process, an adaptive loop filtering process, a sample adaptive offset process, or a cross-component adaptive loop filtering process.
The method of any of claims 9 to 11, wherein the usage of the in-loop filtering process is determined based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.
A method of video processing, comprising:

making a determination, for a conversion between a current block of a video and a bitstream representation of the video, about usage of a luma mapping with chroma scaling (LMCS) coding tool based on an input bit-depth of a source sample in the current block; and

performing the conversion based on the determination.
The method of claim 13, wherein an output of the LMCS coding tool is rounded according to the input bit-depth.
The method of claim 13 or 14, wherein the usage of the LMCS coding tool is determined based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.
A method of video processing, comprising:

making a determination, for a conversion between a block of a video and a bitstream representation of the video, about a pixel clipping range based on an input bit-depth of a source pixel; and

performing the conversion based on the determination.
The method of claim 16, wherein an internal bit-depth of the conversion is denoted as IBD and the input bit-depth is denoted as iBD, and wherein the pixel clipping range is equal to [0, ( (1 << iBD) -1) << (IBD -iBD) ] .
The method of claim 17, wherein the pixel clipping range is [0, 1020] in case the internal bit-depth is 10 and the input bit-depth is 8.
The method of any of claims 16 to 18, wherein the pixel clipping range is based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.
The method of any of claims 1 to 19, wherein the input bit-depth is indicated as a syntax element in the bitstream representation.
The method of claim 20, wherein the syntax element is included in a decoder parameter set, a video parameter set, a sequence parameter set, a picture header, or a slice header in the bitstream representation.
The method of claim 20 or 21, wherein the input bit-depth is determined based on a lowest allowed quantization parameter for one or more transform skip blocks associated with the current block.
The method of any of claims 1 to 22, wherein a manner of applying the determination is based on a characteristic of the current block.
The method of claim 23, wherein the determination is applied in case a quantization parameter of the current block is smaller than a threshold.
The method of claim 23, wherein the determination is applied in case a quantization parameter of the current block is larger than a threshold.
The method of claim 23, wherein a characteristic of the current block comprises a quantization parameter of the current block that is denoted as QP, and wherein the determination is applied in case (QP %6) is equal to a predefined value.
The method of claim 23, wherein the determination is applied in case a dimension of the current block is smaller than a threshold.
The method of claim 23, wherein the determination is applied in case a dimension of the current block is greater than a threshold.
The method of claim 23, wherein the determination is applied in case the current block is associated with a luma component of the video.
The method of claim 23, wherein the determination is applied in case the current block is associated with a chroma component of the video.
The method of claim 23, wherein the determination is applied in case the current block is coded in a specific coding mode.
The method of claim 31, wherein the specific coding mode comprises at least a intra mode, an inter mode, a transform skip mode, a Block Differential Pulse-code Modulation (BDPCM) mode, an intra block copy mode, a palette mode, an intra sub-partition prediction mode, a matrix-based intra prediction mode, a luma mapping with chroma scaling mode, a cross-component linear model mode, a derived mode, a DC prediction mode, or an adaptive color transform mode.
The method of any of claims 1 to 32, wherein the conversion generates the current block from the bitstream representation.
The method of any of claims 1 to 32, wherein the conversion generates the bitstream representation from the current block.
An apparatus in a video system comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to implement the method in any one of claims 1 to 32.
A computer program product stored on a non-transitory computer readable media, the computer program product including program code for carrying out the method in any one of claims 1 to 32.
A video processing apparatus comprising a processor configured to implement a method recited in any one or more of claims 1 to 32.
A computer-readable medium having a bitstream representation of a video stored thereupon, the bitstream representation being generated according to a method recited in any one or more of claims 1 to 32.