Using quantization groups in video coding

An example method of video processing includes applying, in a conversion between a video comprising multiple components and a bitstream representation of the video, a deblocking filter to video blocks of the multiple components. A deblocking filter strength for the deblocking filter of each of the multiple components is determined according to a rule that specifies to use a different manner for determining the deblocking filter strength for the video blocks of each of the multiple components.

TECHNICAL FIELD

This patent document relates to video coding techniques, devices and systems.

BACKGROUND

Currently, efforts are underway to improve the performance of current video codec technologies to provide better compression ratios or provide video coding and decoding schemes that allow for lower complexity or parallelized implementations. Industry experts have recently proposed several new video coding tools and tests are currently underway for determining their effectivity.

SUMMARY

Devices, systems and methods related to digital video coding, and specifically, to management of motion vectors are described. The described methods may be applied to existing video coding standards (e.g., High Efficiency Video Coding (HEVC) or Versatile Video Coding) and future video coding standards or video codecs.

In one representative aspect, the disclosed technology can be used to provide a method for video processing. The method includes applying, in a conversion between a video comprising multiple components and a bitstream representation of the video, a deblocking filter to video blocks of the multiple components. A deblocking filter strength for the deblocking filter of each of the multiple components is determined according to a rule that specifies to use a different manner for determining the deblocking filter strength for the video blocks of each of the multiple components.

In another representative aspect, the disclosed technology can be used to provide a method for video processing. The method includes performing a conversion between a first video unit of a video and a bitstream representation of the video. During the conversion, a deblocking filtering process is applied to the first video unit. A deblocking control offset of the first video unit is determined based on accumulating one or more deblocking control offset values at other video unit levels.

In another representative aspect, the disclosed technology can be used to provide a method for video processing. The method includes determining, for a conversion between a block of a video and a bitstream representation of the video, a quantization parameter used in a deblocking process based on usage of a transform skip (TS) mode or an adaptive color transform (ACT) mode for coding the block. The method also includes performing the conversion based on the determining.

In another representative aspect, the disclosed technology can be used to provide a method for video processing. The method includes performing a conversion between a block of a color component of a video and a bitstream representation of the video. The bitstream representation conforms to a rule specifying that a size of a quantization group of the chroma component is greater than a threshold K. The quantization group includes one or more coding units carrying a quantization parameter.

In one representative aspect, the disclosed technology may be used to provide a method for video processing. This method includes performing a conversion between a video unit and a coded representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that when a chroma quantization parameter (QP) table is used to derive parameters of the deblocking filter, processing by the chroma QP table is performed on individual chroma QP values.

In another representative aspect, the disclosed technology may be used to provide another method for video processing. This method includes performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that chroma QP offsets are used in the deblocking filter, wherein the chroma QP offsets are at picture/slice/tile/brick/subpicture level.

In another representative aspect, the disclosed technology may be used to provide another method for video processing. This method includes performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that chroma QP offsets are used in the deblocking filter, wherein information pertaining to a same luma coding unit is used in the deblocking filter and for deriving a chroma QP offset.

In another representative aspect, the disclosed technology may be used to provide another method for video processing. This method includes performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that chroma QP offsets are used in the deblocking filter, wherein an indication of enabling usage of the chroma QP offsets is signaled in the bitstream representation.

In another representative aspect, the disclosed technology may be used to provide another method for video processing. This method includes performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that chroma QP offsets are used in the deblocking filter, wherein the chroma QP offsets used in the deblocking filter are identical of whether JCCR coding method is applied on a boundary of the video unit or a method different from the JCCR coding method is applied on the boundary of the video unit.

In another representative aspect, the disclosed technology may be used to provide another method for video processing. This method includes performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that chroma QP offsets are used in the deblocking filter, wherein a boundary strength (BS) of the deblocking filter is calculated without comparing reference pictures and/or a number of motion vectors (MVs) associated with the video unit at a P side boundary with reference pictures of the video unit at a Q side boundary.

In another example aspect, another method of video processing is disclosed. The method includes determining, for a conversion between a video unit of a component of a video and a coded representation of the video, a size of a quantization group for the video unit, based on a constraint rule that specifies that the size must be larger than K, where K is a positive number and performing the conversion based on the determining.

Further, in a representative aspect, an apparatus in a video system comprising a processor and a non-transitory memory with instructions thereon is disclosed. The instructions upon execution by the processor, cause the processor to implement any one or more of the disclosed methods.

Additionally, in a representative aspect, a video decoding apparatus comprising a processor configured to implement any one or more of the disclosed methods.

In another representative aspect, a video encoding apparatus comprising a processor configured to implement any one or more of the disclosed methods.

Also, a computer program product stored on a non-transitory computer readable media, the computer program product including program code for carrying out any one or more of the disclosed methods is disclosed.

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

DETAILED DESCRIPTION

1. Video Coding in HEVC/H.265

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.

A deblocking filter process is performed for each CU in the same order as the decoding process. First, vertical edges are filtered (horizontal filtering), then horizontal edges are filtered (vertical filtering). Filtering is applied to 8×8 block boundaries which are determined to be filtered, for both luma and chroma components. 4×4 block boundaries are not processed in order to reduce the complexity.

FIG. 1 illustrates the overall processing flow of deblocking filter process. A boundary can have three filtering status: no filtering, weak filtering and strong filtering. Each filtering decision is based on boundary strength, Bs, and threshold values, β and tC.

Three kinds of boundaries may be involved in the filtering process: CU boundary, TU boundary and PU boundary. CU boundaries, which are outer edges of CU, are always involved in the filtering since CU boundaries are always also TU boundary or PU boundary. When PU shape is 2N×N (N>4) and RQT depth is equal to 1, TU boundary at 8×8 block grid and PU boundary between each PU inside CU are involved in the filtering. One exception is that when the PU boundary is inside the TU, the boundary is not filtered.

2.1.1. Boundary Strength Calculation

Generally speaking, boundary strength (Bs) reflects how strong filtering is needed for the boundary. If Bs is large, strong filtering should be considered.

Let P and Q be defined as blocks which are involved in the filtering, where P represents the block located in left (vertical edge case) or above (horizontal edge case) side of the boundary and Q represents the block located in right (vertical edge case) or above (horizontal edge case) side of the boundary. FIG. 2 illustrates how the Bs value is calculated based on the intra coding mode, existence of non-zero transform coefficients and motion information, reference picture, number of motion vectors and motion vector difference.

Bs is calculated on a 4×4 block basis, but it is re-mapped to an 8×8 grid. The maximum of the two values of Bs which correspond to 8 pixels consisting of a line in the 4×4 grid is selected as the Bs for boundaries in the 8×8 grid.

In order to reduce line buffer memory requirement, only for CTU boundary, information in every second block (4×4 grid) in left or above side is re-used as depicted in FIG. 3.

2.1.2. β and tC Decision

Threshold values β and tC which involving in filter on/off decision, strong and weak filter selection and weak filtering process are derived based on luma quantization parameter of P and Q blocks, QPP and QPQ, respectively. Q used to derive β and tC is calculated as follows.

A variable β is derived as shown in Table 1, based on Q. If Bs is greater than 1, the variable tC is specified as Table 1 with Clip3(0, 55, Q+2) as input. Otherwise (BS is equal or less than 1), the variable tC is specified as Table 1 with Q as input.

Derivation of threshold variables β and tC from input Q

2.1.3. Filter on/Off Decision for 4 Lines

Filter on/off decision is done for four lines as a unit. FIG. 4 illustrates the pixels involving in filter on/off decision. The 6 pixels in the two red boxes for the first four lines are used to determine filter on/off for 4 lines. The 6 pixels in two red boxes for the second 4 lines are used to determine filter on/off for the second four lines.

If dp0+dq0+dp3+dq3<β, filtering for the first four lines is turned on and strong/weak filter selection process is applied. Each variable is derived as follows.

If the condition is not met, no filtering is done for the first 4 lines. Additionally, if the condition is met, dE, dEp1 and dEp2 are derived for weak filtering process. The variable dE is set equal to 1. If dp0+dp3<(β+(β>>1))>>3, the variable dEp1 is set equal to 1. If dq0+dq3<(β+(β>>1))>>3, the variable dEq1 is set equal to 1.

For the second four lines, decision is made in a same fashion with above.

2.1.4. Strong/Weak Filter Selection for 4 Lines

After the first four lines are determined to filtering on in filter on/off decision, if following two conditions are met, strong filter is used for filtering of the first four lines. Otherwise, weak filter is used for filtering. Involving pixels are same with those used for filter on/off decision as depicted in FIG. 4.

As a same fashion, if following two conditions are met, strong filter is used for filtering of the second 4 lines. Otherwise, weak filter is used for filtering.

2.1.4.1. Strong Filtering

For strong filtering, filtered pixel values are obtained by following equations. Itis worth to note that three pixels are modified using four pixels as an input for each P and Q block, respectively.

When abs(Δ) is less than tC*10,

If dEp1 is equal to 1,

If dEq1 is equal to 1,

It is worth to note that maximum two pixels are modified using three pixels as an input for each P and Q block, respectively.

Bs of chroma filtering is inherited from luma. If Bs>1 or if coded chroma coefficient existing case, chroma filtering is performed. No other filtering decision is there. And only one filter is applied for chroma. No filter selection process for chroma is used. The filtered sample values p0′ and q0′ are derived as follows.

2.2 Deblocking Scheme in VVC

In the VTM6, deblocking filtering process is mostly the same to those in HEVC. However, the following modifications are added.

A) The filter strength of the deblocking filter dependent of the averaged luma level of the reconstructed samples.

B) Deblocking tC table extension and adaptation to 10-bit video.

G) Deblocking decision adapted to smaller difference in motion.

FIG. 5 depicts a flowchart of deblocking filters process in VVC for a coding unit.

2.2.1. Filter Strength Dependent on Reconstructed Average Luma

In HEVC, the filter strength of the deblocking filter is controlled by the variables β and tC which are derived from the averaged quantization parameters qPL. In the VTM6, deblocking filter controls the strength of the deblocking filter by adding offset to qPL according to the luma level of the reconstructed samples if the SPS flag of this method is true. The reconstructed luma level LL is derived as follow:

where, the sample values pi,k and qi,k with i=0 . . . 3 and k=0 and 3 can be derived. Then LL is used to decide the offset qpOffset based on the threshold signaled in SPS. After that, the qPL, which is derived as follows, is employed to derive the β and tC.

where QpQ and QpP denote the quantization parameters of the coding units containing the sample q0,0 and p0,0, respectively. In the current VVC, this method is only applied on the luma deblocking process.

HEVC uses an 8×8 deblocking grid for both luma and chroma. In VTM6, deblocking on a 4×4 grid for luma boundaries was introduced to handle blocking artifacts from rectangular transform shapes. Parallel friendly luma deblocking on a 4×4 grid is achieved by restricting the number of samples to be deblocked to 1 sample on each side of a vertical luma boundary where one side has a width of 4 or less or to 1 sample on each side of a horizontal luma boundary where one side has a height of 4 or less.

2.2.3. Boundary Strength Derivation for Luma

The detailed boundary strength derivation could be found in Table 2. The conditions in Table 2 are checked sequentially.

Boundary strength derivation

Conditions
Y
U
V

P and Q are BDPCM
0
N/A
N/A

P or Q is intra
2
2
2

It is a transform block edge, and P or Q is CIIP
2
2
2

It is a transform block edge, and P or Q has non-zero transform coefficients
1
1
1

It is a transform block edge, and P or Q is JCCR
N/A
1
1

P and Q are in different coding modes
1
1
1

One or more of the following conditions are true:
1
N/A
N/A

1.
P and Q are both IBC, and the BV distance >= half-pel in x-

or y-di

2.
P and Q have different ref pictures*, or have different

number of MVs

3.
Both P and Q have only one mv, and the MV distance >=

half -pel in x- or y-dir

4.
P has two MVs pointing to two different ref pictures, and P

and Q have same ref pictures in the list 0, the MV pair in

the list 0 or list 1 has a distance >= half-pel in x- or y-dir

5.
P has two MVs pointing to two different ref pictures, and P

and Q have different ref pictures in the list 0, the MV of P

in the list 0 and the MV of Q in the list 1 have the

distance >= half-pel in x- or y-dir, or the MV of Pin the list

1 and the MV of Q in the list 0 have the distance >= half-pel

in x- or y-dir

6.
Both P and Q have two MVs pointing to the same ref

pictures, and both of the following two conditions are

The MV of P in the list 0 and the MV of Q in the list

0 has a distance >= half-pel in x- or y-dir or the MV

of P in the list 1 and the MV of Q in the list 1 has a

The MV of P in the list 0 and the MV of Q in the list

1 has a distance >= half-pel in x- or y-dir or the MV

of P in the list 1 and the MV of Q in the list 0 has a

*Note: The determination of whether the reference pictures used for the two

coding sublocks are the same or different is based only on which pictures are

referenced, without regard to whether a prediction is formed using an index

into reference picture list 0 or an index into reference picture list 1, and also

without regard to whether the index position within a reference picture list is

2.2.4. Stronger Deblocking Filter for Luma

The proposal uses a bilinear filter when samples at either one side of a boundary belong to a large block. A sample belonging to a large block is defined as when the width>=32 fora vertical edge, and when height>=32 for a horizontal edge.

The bilinear filter is listed below.

Block boundary samples pi for i=0 to Sp−1 and qi for j=0 to Sq−1 (pi and qi follow the definitions inHBEVC deblocking described above) are then replaced by linear interpolation as follows:

where tcPDi and tcPDj term is a position dependent clipping described in Section 2.2.5 and gj, fi, Middles,t, Ps and Qs are given below:

2.2.5. Deblocking Control for Luma

The deblocking decision process is described in this sub-section.

Wider-stronger luma filter is filters are used only if all of the Condition1, Condition2 and Condition 3 are TRUE.

The condition 1 is the “large block condition”. This condition detects whether the samples at P-side and Q-side belong to large blocks, which are represented by the variable bSidePisLargeBlk and bSideQisLargeBlk respectively. The bSidePisLargeBlk and bSideQisLargeBlk are defined as follows.

bSidePisLargeBlk=((edge type is vertical and p0 belongs to CU with width>=32)∥(edge type is horizontal and p0 belongs to CU with height>=32))?TRUE: FALSE

bSideQisLargeBlk=((edge type is vertical and q0 belongs to CU with width>=32)∥(edge type is horizontal and q0 belongs to CU with height>=32))?TRUE: FALSE

Based on bSidePisLargeBlk and bSideQisLargeBlk, the condition 1 is defined as follows.

Next, if Condition 1 is true, the condition 2 will be further checked. First, the following variables are derived:

dp0, dp3, dq0, dq3 are first derived as in HEVC

if (p side is greater than or equal to 32)

if (q side is greater than or equal to 32)

dpq0, dpq3, dp, dq, d are then derived as in HEVC.

Then the condition 2 is defined as follows.

Where d=dp0+dq0+dp3+dq3, as shown in section 2.1.4.

If Condition1 and Condition2 are valid itis checked if any of the blocks uses sub-blocks:

Finally, if both the Condition 1 and Condition 2 are valid, the proposed deblocking method will check the condition 3 (the large block Strongfilter condition), which is defined as follows. In the Condition3 StrongFilterCondition, the following variables are derived:

dpq is derived as in HEVC.

if (p side is greater than or equal to 32)

if (q side is greater than or equal to 32)

As in HEVC derive, StrongFilterCondition=(dpq is less than (β>>2), sp3+sq3 is less than (3*β>>5), and Abs(p0-q0) is less than (5*tC+1)>>1)? TRUE: FALSE

FIG. 6 depicts the flowchart of luma deblocking filter process.

2.2.6. Strong Deblocking Filter for Chroma

The following strong deblocking filter for chroma is defined:

The proposed chroma filter performs deblocking on a 4×4 chroma sample grid.

2.2.7. Deblocking Control for Chroma

The above chroma filter performs deblocking on a 8×8 chroma sample grid. The chroma strong filters are used on both sides of the block boundary. Here, the chroma filter is selected when both sides of the chroma edge are greater than or equal to 8 (in unit of chroma sample), and the following decision with three conditions are satisfied. The first one is for decision of boundary strength as well as large block. The second and third one are basically the same as for HEVC luma decision, which are on/off decision and strong filter decision, respectively.

FIG. 7 depicts the flowchart of chroma deblocking filter process.

2.2.8. Position Dependent Clipping

The proposal also introduces a position dependent clipping tcPD which is applied to the output samples of the luma filtering process involving strong and long filters that are modifying 7, 5 and 3 samples at the boundary. Assuming quantization error distribution, it is proposed to increase clipping value for samples which are expected to have higher quantization noise, thus expected to have higher deviation of the reconstructed sample value from the true sample value.

For each P or Q boundary filtered with proposed asymmetrical filter, depending on the result of decision making process described in Section 2.2, position dependent threshold table is selected from Tc7 and Tc3 tables that are provided to decoder as a side information:

For the P or Q boundaries being filtered with a short symmetrical filter, position dependent threshold of lower magnitude is applied:

Following defining the threshold, filtered p′i and q′i sample values are clipped according to tcP and tcQ clipping values:

where p′i and q′i are filtered sample values, p″i and q″j are output sample value after the clipping and tcPi tcPi are clipping thresholds that are derived from the VVC tc parameter and tcPD and tcQD. Term clip3 is a clipping function as it is specified in VVC.

To enable parallel friendly deblocking using both long filters and sub-block deblocking the long filters is restricted to modify at most 5 samples on a side that uses sub-block deblocking (AFFINE or ATMVP) as shown in the luma control for long filters. Additionally, the sub-block deblocking is adjusted such that that sub-block boundaries on an 8×8 grid that are close to a CU or an implicit TU boundary is restricted to modify at most two samples on each side.

Following applies to sub-block boundaries that not are aligned with the CU boundary.

Where edge equal to 0 corresponds to CU boundary, edge equal to 2 or equal to orthogonalLength-2 corresponds to sub-block boundary 8 samples from a CU boundary etc. Where implicit TU is true if implicit split of TU is used. FIG. 8 show the flowcharts of determination process for TU boundaries and sub-PU boundaries.

Filtering of horizontal boundary is limiting Sp=3 for luma, Sp=1 and Sq=1 for chroma, when the horizontal boundary is aligned with the CTU boundary.

2.2.10. Deblocking Decision Adapted to Smaller Difference in Motion

HEVC enables deblocking of a prediction unit boundary when the difference in at least one motion vector component between blocks on respective side of the boundary is equal to or larger than a threshold of 1 sample. In VTM6, a threshold of a half luma sample is introduced to also enable removal of blocking artifacts originating from boundaries between inter prediction units that have a small difference in motion vectors.

2.3. Combined Inter and Intra Prediction (CHIP)

In VTM6, 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 signalled 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 Pinter is derived using the same inter prediction process applied to regular merge mode; and the intra prediction signal Pintra 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 neighbouring blocks as follows:

The CIIP prediction is formed as follows:

2.4. Chroma QP Table Design in VTM-6.0

In some embodiments, a chroma QP table is used. In some embodiments, a signalling mechanism is used for chroma QP tables, which enables that it is flexible to provide encoders the opportunity to optimize the table for SDR and HDR content. It supports for signalling the tables separately for Cb and Cr components. The proposed mechanism signals the chroma QP table as a piece-wise linear function.

As in HEVC, the residual of a block can be coded with transform skip mode. To avoid the redundancy of syntax coding, the transform skip flag is not signalled when the CU level MTS_CU_flag is not equal to zero. The block size limitation for transform skip is the same to that for MTS in JEM4, which indicate that transform skip is applicable for a CU when both block width and height are equal to or less than 32. Note that implicit MTS transform is set to DCT2 when LFNST or MIP is activated for the current CU. Also the implicit MTS can be still enabled when MTS is enabled for inter coded blocks.

In addition, for transform skip block, minimum allowed Quantization Parameter (QP) is defined as 6*(internalBitDepth−inputBitDepth)+4.

2.6. Joint Coding of Chroma Residuals (JCCR)

In some embodiments, the chroma residuals are coded jointly. The usage (activation) of a joint chroma coding mode is indicated by a TU-level flag tu_joint_cbcr_residual_flag and the selected mode is implicitly indicated by the chroma CBFs. The flag tu_joint_cbcr_residual_flag is present if either or both chroma CBFs for a TU are equal to 1. In the PPS and slice header, chroma QP offset values are signalled for the joint chroma residual coding mode to differentiate from the usual chroma QP offset values signalled for regular chroma residual coding mode. These chroma QP offset values are used to derive the chroma QP values for those blocks coded using the joint chroma residual coding mode. When a corresponding joint chroma coding mode (modes 2 in Table 3) is active in a TU, this chroma QP offset is added to the applied luma-derived chroma QP during quantization and decoding of that TU. For the other modes (modes 1 and 3 in Table 3 Table 3 Reconstruction of chroma residuals. The value CSign is a sign value (+1 or −1), which is specified in the slice header; resJointC[ ][ ] is the transmitted residual.), the chroma QPs are derived in the same way as for conventional Cb or Cr blocks. The reconstruction process of the chroma residuals (resCb and resCr) from the transmitted transform blocks is depicted in Table 3. When this mode is activated, one single joint chroma residual block (resJointC[x][y] in Table 3) is signalled, and residual block for Cb (resCb) and residual block for Cr (resCr) are derived considering information such as tu_cbf_cb, tu_cbf_cr, and CSign, which is a sign value specified in the slice header.

At the encoder side, the joint chroma components are derived as explained in the following. Depending on the mode (listed in the tables above), resJointC{1,2} are generated by the encoder as follows:

Reconstruction of chroma residuals. The value CSign is

a sign value (+1 or −1), which is specified in the

tu_cbf_cb
tu_cbf_cr
reconstruction of Cb and Cr residuals
mode

Different QPs are utilized are the above three modes. For mode 2, the QP offset signaled in PPS for JCCR coded block is applied, while for other two modes, it is not applied, instead, the QP offset signaled in PPS for non-JCCR coded block is applied.

The corresponding specification is as follows:

8.7.1 Derivation Process for Quantization Parameters

The variable QpY is derived as follows:

The luma quantization parameter Qp′Y is derived as follows:

When ChromaArrayType is not equal to 0 and tree Type is equal to SINGLE_TREE or DUAL_TREE_CHROMA, the following applies:

FIG. 14A illustrates the placement of CC-ALF with respect to the other loop filters. CC-ALF operates by applying a linear, diamond shaped filter (FIG. 14B) to the luma channel for each chroma component, which is expressed as

where

Key features characteristics of the CC-ALF process include:

2.8 Derivation Process for Quantization Parameters

The QP is derived based on neighboring QPs and the decoded delta QP. The example texts related to QP derivation are given as follows.

Inputs to this process are:

FIG. 15 illustrates the decoding flowchart with the ACT be applied. As illustrated in FIG. 15, the color space conversion is carried out in residual domain. Specifically, one additional decoding module, namely inverse ACT, is introduced after inverse transform to convert the residuals from YCgCo domain back to the original domain.

In the VVC, unless the maximum transform size is smaller than the width or height of one coding unit (CU), one CU leaf node is also used as the unit of transform processing. Therefore, in the proposed implementation, the ACT flag is signaled for one CU to select the color space for coding its residuals. Additionally, following the HEVC ACT design, for inter and IBC CUs, the ACT is only enabled when there is at least one non-zero coefficient in the CU. For intra CUs, the ACT is only enabled when chroma components select the same intra prediction mode of luma component, e.g., DM mode.

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, as shown in (1), 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.

The control mechanism is shown in the following FIG. 16.

3. Drawbacks of Existing Implementations

DMVR and BIO do not involve the original signal during refining the motion vectors, which may result in coding blocks with inaccurate motion information. Also, DMVR and BIO sometimes employ the fractional motion vectors after the motion refinements while screen videos usually have integer motion vectors, which makes the current motion information more inaccurate and make the coding performance worse.

4. Example Techniques and Embodiments

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

The methods described below may be also applicable to other decoder motion information derivation technologies in addition to the DMVR and BIO mentioned below.

In the following examples, MVM[i].x and MVM[i].y denote the horizontal and vertical component of the motion vector in reference picture list i (i being 0 or 1) of the block at M (M being P or Q) side. Abs denotes the operation to get the absolute value of an input, and “&&” and “∥” denotes the logical operation AND and OR. Referring to FIG. 10, P may denote the samples at P side and Q may denote the samples at Q side. The blocks at P side and Q side may denote the block marked by the dash lines.

Regarding Chroma OP in Deblocking

The newly added texts are shown in underlined bold italicized font. The deleted texts are marked by [[ ]].

5.1. Embodiment #1 on Chroma QP in Deblocking

8.8.3.6 Edge Filtering Process for One Direction

The value of the variable β′ is determined as specified in Table 8-18 based on the quantization parameter Q derived as follows:

where slice_beta_offset_div2 is the value of the syntax element slice_beta_offset_div2 for the slice that contains sample q0,0.

The variable β is derived as follows:

The value of the variable tC′ is determined as specified in Table 8-18 based on the chroma quantization parameter Q derived as follows:

where slice_tc_offset_div2 is the value of the syntax element slice_tc_offset_div2 for the slice that contains sample q0,0. The variable tC is derived as follows:

5.2. Embodiment #2 on Boundary Strength Derivation

8.8.3.5 Derivation Process of Boundary Filtering Strength

Inputs to this process are:

5.3. Embodiment #3 on Boundary Strength Derivation

8.8.3.5 Derivation Process of Boundary Filtering Strength

Inputs to this process are:

8.8.3.6.1 Decision Process for Luma Block Edges

Inputs to this process are:

5.5. Embodiment #5 on Chroma Deblocking Filtering Process

8.8.3.6.3 Decision Process for Chroma Block Edges

This process is only invoked when ChromaArrayType is not equal to 0.

Inputs to this process are:

5.6. Embodiment #6 on Chroma QP in Deblocking

8.8.3.6.3 Decision Process for Chroma Block Edges

This process is only invoked when ChromaArrayType is not equal to 0.

Inputs to this process are:

5.7. Embodiment #7 on Chroma QP in Deblocking

8.8.3.6.3 Decision Process for Chroma Block Edges

This process is only invoked when ChromaArrayType is not equal to 0.

Inputs to this process are:

5.8. Embodiment #8 on Chroma QP in Deblocking

When making filter decisions for the depicted three samples (with solid circles), the QPs of the luma CU that covers the center position of the chroma CU including the three samples is selected. Therefore, for the 1st, 2nd, and 3rd chroma sample (depicted in FIG. 11), only the QP of CUY3 is utilized, respectively.

In this way, how to select luma CU for chroma quantization/dequantization process is aligned with that for chroma filter decision process.

5.9. Embodiment #9 on QP Used for JCCR Coded Blocks

8.7.3 Scaling Process for Transform Coefficients

Inputs to this process are:

5.10 Embodiment #10 on QP Used for JCCR Coded Blocks

8.8.3.2 Deblocking Filter Process for One Direction

Inputs to this process are:

The variables first CompIdx and last CompIdx are derived as follows:

For each coding unit and each coding block per colour component of a coding unit indicated by the colour component index cIdx ranging from firstCompIdx to lastCompIdx, inclusive, with coding block width nCbW, coding block height nCbH and location of top-left sample of the coding block (xCb, yCb), when cIdx is equal to 0, or when cIdx is not equal to 0 and edge Type is equal to EDGE_VER and xCb % 8 is equal 0, or when cIdx is not equal to 0 and edge Type is equal to EDGE_HOR and yCb % 8 is equal to 0, the edges are filtered by the following ordered steps:

[[5. The picture sample array recPicture is derived as follows:

Depending on the value of edge Type, the following applies:

8.8.3.6.3 Decision Process for Chroma Block Edges

[[The variables QpQ and QpP are set equal to the QpY values of the coding units which include the coding blocks containing the sample q0,0 and p0,0, respectively.

The variable QpC is derived as follows:

8.8.3.6.3 Decision Process for Chroma Block Edges

[[The variables QpQ and QpP are set equal to the QpY values of the coding units which include the coding blocks containing the sample q0,0 and p0,0, respectively.

The variable QpC is derived as follows:

Decision Process for Chroma Block Edges

This process is only invoked when ChromaArrayType is not equal to 0.

Inputs to this process are:

Decision Process for Chroma Block Edges

This process is only invoked when ChromaArrayType is not equal to 0.

Inputs to this process are:

The example controlling logic is shown in FIG. 17.

7.3.7.1 General Slice Header Syntax

7.3.2.4 Picture Parameter Set RBSP Syntax

7.3.7.1 General Slice Header Syntax

7.4.3.4 Picture Parameter Set RBSP Semantics

7.4.3.6 Picture Header

8.8.3.6.3 Decision Process for Chroma Block Edges

The value of the variable β′ is determined as specified in Table 41 based on the quantization parameter Q derived as follows:

This embodiment is based on Embodiment #15.

7.3.2.4 Picture Parameter Set RBSP Syntax

7.3.7.1 General Slice Header Syntax

7.4.3.4 Picture Parameter Set RBSP Semantics

7.4.8.1 General Slice Header Semantics

8.8.3.6.3 Decision Process for Chroma Block Edges

The value of the variable β′ is determined as specified in Table 41 based on the quantization parameter Q derived as follows:

This embodiment is based on embodiment #17.

7.4.3.4 Picture Parameter Set RBSP Semantics

7.4.8.1 General Slice Header Semantics

8.8.3.6.1 Decision Process for Luma Block Edges

The value of the variable $3′ is determined as specified in Table 41 based on the quantization parameter Q derived as follows:

This embodiment is related to the ACT.

intra_bdpcm_chroma_flag equal to 1 specifies that BDPCM is applied to the current chroma coding blocks at the location (x0, y0), i.e. the transform is skipped, the intra chroma prediction mode is specified by intra_bdpcm_chroma_dir_flag. intra_bdpcm_chroma_flag equal to 0 specifies that BDPCM is not applied to the current chroma coding blocks at the location(x0, y0).

When intra_bdpcm_chroma_flag is not present [[it is inferred to be equal to 0.]].

intra_bdpcm_chroma_dir_flag equal to 0 specifies that the BDPCM prediction direction is horizontal. intra_bdpcm_chroma_dir_flag equal to 1 specifies that the BDPCM prediction direction is vertical.

This embodiment is related to the QP derivation for deblocking.

8.8.3.6.1 Decision Process for Luma Block Edges

Inputs to this process are:

6. Example Implementations of the Disclosed Technology

FIG. 12 is a block diagram of a video processing apparatus 1200. The apparatus 1200 may be used to implement one or more of the methods described herein. The apparatus 1200 may be embodied in a smartphone, tablet, computer, Internet of Things (IoT) receiver, and so on. The apparatus 1200 may include one or more processors 1202, one or more memories 1204 and video processing hardware 1206. The processor(s) 1202 may be configured to implement one or more methods described in the present document. The memory (memories) 1204 may be used for storing data and code used for implementing the methods and techniques described herein. The video processing hardware 1206 may be used to implement, in hardware circuitry, some techniques described in the present document, and may be partly or completely be a part of the processors 1202 (e.g., graphics processor core GPU or other signal processing circuitry).

In the present document, the term “video processing” may refer to video encoding, video decoding, video compression or video decompression. For example, video compression algorithms may be applied during conversion from pixel representation of a video to a corresponding bitstream representation or vice versa. The bitstream representation of a current video block may, for example, correspond to bits that are either co-located or spread in different places within the bitstream, as is defined by the syntax. For example, a macroblock may be encoded in terms of transformed and coded error residual values and also using bits in headers and other fields in the bitstream.

It will be appreciated that the disclosed methods and techniques will benefit video encoder and/or decoder embodiments incorporated within video processing devices such as smartphones, laptops, desktops, and similar devices by allowing the use of the techniques disclosed in the present document.

FIG. 13 is a flowchart for an example method 1300 of video processing. The method 1300 includes, at 1310, performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that when a chroma quantization parameter (QP) table is used to derive parameters of thedeblockingfilter, processingbythechromaQPtableisperformedonindividualchromaQPvalues.

Some embodiments may be described using the following clause-based format.

1. A method of video processing, comprising:

performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that when a chroma quantization parameter (QP) table is used to derive parameters of the deblocking filter, processing by the chroma QP table is performed on individual chroma QP values.

2. The method of clause 1, wherein chroma QP offsets are added to the individual chroma QP values subsequent to the processing by the chroma QP table.

3. The method of any of clauses 1-2, wherein the chroma QP offsets are added to values outputted by the chroma QP table.

4. The method of any of clauses 1-2, wherein the chroma QP offsets are not considered as input to the chroma QP table.

5. The method of clause 2, wherein the chroma QP offsets are at a picture-level or at a video unit-level.

6. A method of video processing, comprising:

performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that chroma QP offsets are used in the deblocking filter, wherein the chroma QP offsets are at picture/slice/tile/brick/subpicture level.

7. The method of clause 6, wherein the chroma QP offsets used in the deblocking filter are associated with a coding method applied on a boundary of the video unit.

8. The method of clause 7, wherein the coding method is a joint coding of chrominance residuals (JCCR) method.

9. A method of video processing, comprising:

performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that chroma QP offsets are used in the deblocking filter, wherein information pertaining to a same luma coding unit is used in the deblocking filter and for deriving a chroma QP offset.

10. The method of clause 9, wherein the same luma coding unit covers a corresponding luma sample of a center position of the video unit, wherein the video unit is a chroma coding unit.

11. The method of clause 9, wherein a scaling process is applied to the video unit, and wherein one or more parameters of the deblocking filter depend at least in part on quantization/dequantization parameters of the scaling process.

12. The method of clause 11, wherein the quantization/dequantization parameters of the scaling process include the chroma QP offset.

13. The method of any of clauses 9-12, wherein the luma sample in the video unit is in the P side or Q side.

14. The method of clause 13, wherein the information pertaining to the same luma coding unit depends on a relative position of the coding unit with respect to the same luma coding unit.

15. A method of video processing, comprising:

performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that chroma QP offsets are used in the deblocking filter, wherein an indication of enabling usage of the chroma QP offsets is signaled in the bitstream representation.

16. The method of clause 15, wherein the indication is signaled conditionally in response to detecting one or more flags.

17. The method of clause 16, wherein the one or more flags are related to a JCCR enabling flag or a chroma QP offset enabling flag.

18. The method of clause 15, wherein the indication is signaled based on a derivation.

19. A method of video processing, comprising:

performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that chroma QP offsets are used in the deblocking filter, wherein the chroma QP offsets used in the deblocking filter are identical of whether JCCR coding method is applied on a boundary of the video unit or a method different from the JCCR coding method is applied on the boundary of the video unit.

20. A method of video processing, comprising:

performing a conversion between a video unit and a bitstream representation of the video unit, wherein, during the conversion, a deblocking filter is used on boundaries of the video unit such that chroma QP offsets are used in the deblocking filter, wherein a boundary strength (BS) of the deblocking filter is calculated without comparing reference pictures and/or a number of motion vectors (MVs) associated with the video unit at a P side boundary with reference pictures and/or a number of motion vectors (MVs) associated with the video unit at a Q side.

21. The method of clause 20, wherein the deblocking filter is disabled under one or more conditions.

22. The method of clause 21, wherein the one or more conditions are associated with: a magnitude of the motion vectors (MVs) or a threshold value.

23. The method of clause 22, wherein the threshold value is associated with at least one of: i. contents of the video unit, ii. a message signaled in DPS/SPS/VPS/PPS/APS/picture header/slice header/tile group header/Largest coding unit (LCU)/Coding unit (CU)/LCU row/group of LCUs/TU/PU block/Video coding unit, iii. a position of CU/PU/TU/block/Video coding unit, iv. a coded mode of blocks with samples along the boundaries, v. a transform matrix applied to the video units with samples along the boundaries, vi. a shape or dimension of the video unit, vii. an indication of a color format, viii. a coding tree structure, ix.a slice/tile group type and/or picture type, x. a color component, xi. a temporal layer ID, or xii. a profile/level/tier of a standard.

24. The method of clause 20, wherein different QP offsets are used for TS coded video units and non-TS coded video units.

25. The method of clause 20, wherein a QP used in a luma filtering step is related to a QP used in a scaling process of a luma block.

26. A video decoding apparatus comprising a processor configured to implement a method recited in one or more of clauses 1 to 25.

27. A video encoding apparatus comprising a processor configured to implement a method recited in one or more of clauses 1 to 25.

28. A computer program product having computer code stored thereon, the code, when executed by a processor, causes the processor to implement a method recited in any of clauses 1 to 25.

29. A method, apparatus or system described in the present document.

FIG. 18 is a block diagram that illustrates an example video coding system 100 that may utilize the techniques of this disclosure.

As shown in FIG. 18, 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 (VVM) standard and other current and/or further standards.

FIG. 19 is a block diagram illustrating an example of video encoder 200, which may be video encoder 114 in the system 100 illustrated in FIG. 18.

Video encoder 200 may be configured to perform any or all of the techniques of this disclosure. In the example of FIG. 19, 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. 19 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 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.

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.

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. 20 is a block diagram illustrating an example of video decoder 300 which may be video decoder 114 in the system 100 illustrated in FIG. 18.

The video decoder 300 may be configured to perform any or all of the techniques of this disclosure. In the example of FIG. 20, 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. 20, 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 (FIG. 19).

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.

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, i.e., 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. 21 is a block diagram showing an example video processing system 2100 in which various techniques disclosed herein may be implemented. Various implementations may include some or all of the components of the system 2100. The system 2100 may include input 2102 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 2102 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 2100 may include a coding component 2104 that may implement the various coding or encoding methods described in the present document. The coding component 2104 may reduce the average bitrate of video from the input 2102 to the output of the coding component 2104 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 2104 may be either stored, or transmitted via a communication connected, as represented by the component 2106. The stored or communicated bitstream (or coded) representation of the video received at the input 2102 may be used by the component 2108 for generating pixel values or displayable video that is sent to a display interface 2110. 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. 22 is a flowchart representation of a method for video processing in accordance with the present technology. The method 2200 includes, at operation 2210, applying, in a conversion between a video comprising multiple components and a bitstream representation of the video, a deblocking filter to video blocks of the multiple components. A deblocking filter strength for the deblocking filter of each of the multiple components is determined according to a rule that specifies to use a different manner for determining the deblocking filter strength for the video blocks of each of the multiple components.

In some embodiments, the multiple color components comprise at least a Cb component and a Cr component. In some embodiments, each of the multiple color components is associated with deblocking parameter offsets beta and tc including a first syntax element beta_offset_div2 and a second syntax element tc_offset_div2 in a video unit. In some embodiments, the video unit comprises a part corresponding to picture parameter set. In some embodiments, the video unit comprises a part corresponding to picture header. In some embodiments, the video unit further comprises a part corresponding to slice header. In some embodiments, different syntax elements are applicable to a video block of a color components in case a joint coding of chroma residuals mode is applied to the video block.

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, performing a conversion between a first video unit of a video and a bitstream representation of the video. During the conversion, a deblocking filtering process is applied to the first video unit. A deblocking control offset of the first video unit is determined based on accumulating one or more deblocking control offset values at other video unit levels.

In some embodiments, the deblocking control offset comprises at least beta_offset_div2 or tc_offset_div2. In some embodiments, the first video unit comprises a slice, and the other video unit levels comprise at least a picture parameter set or a picture.

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, determining, for a conversion between a block of a video and a bitstream representation of the video, a quantization parameter used in a deblocking process based on usage of a transform skip (TS) mode or an adaptive color transform (ACT) mode for coding the block. The method 2400 also includes, at operation 2420, performing the conversion based on the determining.

In some embodiments, the quantization parameter is determined based on Max(QpPrimeTsMin, qP)−(cu_act_enabled_flag[xTbY][yTbY]? N. 0), N being a positive integer and qP being a real number. QpPrimeTsMin represents a minimal quantization parameter for blocks encoded in the TS mode, and cu_act_enabled_flag is a flag indicating usage of the ACT mode. In some embodiments, the quantization parameter is determined based on Max(QpPrimeTsMin, qP−(cu_act_enabled_flag[xTbY][yTbY]? N:0)), N being a positive integer and qP being a real number. QpPrimeTsMin represents a minimal quantization parameter for blocks encoded in the TS mode, and cu_act_enabled_flag is a flag indicating usage of the ACT mode. In some embodiments, qP is equal to a chroma quantization parameter for Cb or Cr component. In some embodiments, N is different for blocks of different color components. In some embodiments, N is equal to 5 in case the block is of Cb, B, G, or U component. In some embodiments, N is equal to 3 in case the block of Cr, R, B or V component.

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, performing a conversion between a block of a color component of a video and a bitstream representation of the video. The bitstream representation conforms to a rule specifying that a size of a quantization group of the chroma component is greater than a threshold K. The quantization group includes one or more coding units carrying a quantization parameter.

In some embodiments, wherein the size comprises a width of the quantization group. In some embodiments, the color component is a chroma component. In some embodiments, K is 4. In some embodiments, the color component is a luma component. In some embodiments, K is 8.

In some embodiments, the conversion includes encoding the video into the bitstream representation. In some embodiments, the conversion includes decoding the bitstream representation into the video.

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.