US20210385439A1 - Context coding for transform skip mode - Google Patents

Context coding for transform skip mode Download PDF

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US20210385439A1
US20210385439A1 US17/399,904 US202117399904A US2021385439A1 US 20210385439 A1 US20210385439 A1 US 20210385439A1 US 202117399904 A US202117399904 A US 202117399904A US 2021385439 A1 US2021385439 A1 US 2021385439A1
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video block
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Weijia Zhu
Li Zhang
Jizheng Xu
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ByteDance Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/103—Selection of coding mode or of prediction mode
    • H04N19/105—Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/13—Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/18—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a set of transform coefficients
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/46—Embedding additional information in the video signal during the compression process
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
    • H04N19/61—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding in combination with predictive coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/70—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by syntax aspects related to video coding, e.g. related to compression standards
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/90—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals
    • H04N19/96—Tree coding, e.g. quad-tree coding

Definitions

  • This document is related to video and image coding and decoding technologies, systems, and devices.
  • 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.
  • Devices, systems and methods related to digital video coding, and specifically, to coefficient coding in transform skip mode for video coding are described.
  • the described methods may be applied to both the existing video coding standards (e.g., High Efficiency Video Coding (HEVC)) and future video coding standards (e.g., Versatile Video Coding (VVC)) or codecs.
  • HEVC High Efficiency Video Coding
  • VVC Versatile Video Coding
  • a method for visual media processing includes determining, for encoding one or more video blocks in a video region of a visual media data into a bitstream representation of the visual media data, a maximum allowed dimension up to which a current video block of the one or more video blocks is allowed to be encoded using a transform skip mode such that a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform; and including a syntax element indicative of the maximum allowed dimension in the bitstream representation.
  • a method for visual media processing includes parsing a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a maximum allowed dimension up to which the current video block of the one or more blocks of a video region is allowed to be coded using a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform; and generating a decoded video region from the bitstream representation by decoding the one or more video blocks according to the maximum allowed dimension.
  • a method for visual media processing includes determining that a current video block of visual media data is coded using a transform skip mode; and performing, based on the determining, a conversion between the current video block and a bitstream representation of the visual media data, wherein, during the conversion, the current video block is divided into a plurality of coefficient groups and signaling of a coded block flag for at least one of the plurality of coefficient groups is excluded in the bitstream representation, wherein, in the transform skip mode, a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transformation.
  • a method for visual media processing includes determining that a current video block of visual media data is coded using a transform skip mode; and performing, based on the determining, a conversion between the current video block and a bitstream representation of the visual media data, wherein, during the conversion, the current video block is divided into a plurality of coefficient groups, wherein, in the transform skip mode, a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transformation, and further wherein, during the conversion, a coefficient scanning order of the plurality of coefficient groups is determined based, at least in part, on an indication in the bitstream representation.
  • a method for visual media processing includes using, for encoding a current video block in a video region of a visual media data into a bitstream representation of the visual media data, a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform; and selecting a context of a sign flag of the current video block according to sign flags of one or more neighboring video blocks in a coefficient group associated with the current video block based upon division of the current video block into a plurality of coefficient groups.
  • a method for visual media processing includes parsing a bitstream representation of a visual media data comprising a video region comprising a current video block to identify a context of a sign flag used in a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform; and generating the decoded video region from the bitstream representation such that the context of the sign flag is according to sign flags of one or more neighboring video blocks in a coefficient group associated with the current video block based upon division of the current video block into a plurality of coefficient groups.
  • a method for visual media processing includes determining a position of a current coefficient associated with a current video block of visual media data when the current video block is divided into a plurality of coefficient positions; deriving, at least based on sign flags of one or more neighboring coefficients, a context of a sign flag for the current coefficient; and generating, based on the context, a sign flag for the current coefficient, wherein the sign flag of the current coefficient is used in a transform skip mode in which the current video block is coded without applying a transform.
  • a method for visual media processing includes determining, for encoding one or more video blocks in a video region of a visual media data into a bitstream representation of the visual media data, based on satisfying at least one rule that a chroma transform skip mode is applicable on a current video block, wherein, in the chroma transform skip mode a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation; and including a syntax element indicative of the chroma transform skip mode in the bitstream representation.
  • a method for visual media processing includes parsing a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks that at least one rule associated with application of a chroma transform skip mode is satisfied, wherein, in the chroma transform skip mode a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation; and generating a decoded video region from the bitstream representation by decoding the one or more video blocks.
  • a method for visual media processing includes making a decision, for encoding one or more video blocks in a video region of a visual media data into a bitstream representation of the visual media data, regarding a selective application of a transform skip mode to the current video block based on a condition; and including a syntax element indicative of the condition in the bitstream representation, wherein, in the transform skip mode, a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation.
  • a method for visual media processing includes parsing a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a condition relating to usage of a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform; and generating a decoded video region from the bitstream representation by decoding the one or more video blocks according to the condition.
  • a method for visual media processing includes making a decision, for encoding one or more video blocks in a video region of a visual media data into a bitstream representation of the visual media data, regarding a selective application of quantized residual block differential pulse-code modulation (QR-BDPCM) technique based on an indication of a transform skip mode in the bitstream representation, wherein, in the transform skip mode, a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation, wherein, in the QR-BDPCM technique, the residual of the prediction error in a horizontal direction and/or a vertical direction is quantized and entropy-coded; and including, in the bitstream representation, an indication of the selective application of the QR-BDPCM technique.
  • QR-BDPCM quantized residual block differential pulse-code modulation
  • a method for visual media processing includes parsing a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a selective application of quantized residual block differential pulse-code modulation (QR-BDPCM) technique based on an indication of a transform skip mode in the bitstream representation, wherein, in the transform skip mode, a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation, wherein, in the QR-BDPCM technique, the residual of the prediction error in a horizontal direction and/or a vertical direction is quantized and entropy-coded; and generating a decoded video region from the bitstream representation by decoding the one or more video blocks according to the maximum allowed dimension.
  • QR-BDPCM quantized residual block differential pulse-code modulation
  • a method for visual media processing includes making a decision, for encoding one or more video blocks in a video region of a visual media data into a bitstream representation of the visual media data, regarding a selective application of a separate or dual tree based on a condition; and including a syntax element indicative of the selective application of the separate or the dual tree in the bitstream representation.
  • a method for visual media processing includes parsing a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a selective application of a separate or dual tree based on or inferred from a condition; and generating a decoded video region from the bitstream representation by decoding the one or more video blocks according to the syntax element.
  • a video encoder or decoder apparatus comprising a processor configured to implement an above described method is disclosed.
  • a computer readable program medium stores code that embodies processor executable instructions for implementing one of the disclosed methods.
  • 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 multi-type tree splitting modes.
  • FIG. 7 shows an example of samples used to derive parameters in a cross-component linear model (CCLM) prediction mode.
  • CCLM cross-component linear model
  • FIG. 8 shows an exemplary architecture for luma mapping with chroma scaling.
  • FIGS. 9A-9E are flowcharts for examples of a video processing methods.
  • FIG. 10 is a block diagram of an example of a hardware platform for implementing a visual media decoding or a visual media encoding technique described in the present document.
  • FIG. 11 is a block diagram of an example video processing system in which disclosed techniques may be implemented.
  • FIG. 12 is a flowchart of an example method for visual media processing.
  • FIG. 13 is a flowchart of an example method for visual media processing.
  • FIG. 14 is a flowchart of an example method for visual media processing.
  • FIG. 15 is a flowchart of an example method for visual media processing.
  • FIG. 16 is a flowchart of an example method for visual media processing.
  • FIG. 17 is a flowchart of an example method for visual media processing.
  • FIG. 18 is a flowchart of an example method for visual media processing.
  • FIG. 19 is a flowchart of an example method for visual media processing.
  • FIG. 20 is a flowchart of an example method for visual media processing.
  • FIG. 21 is a flowchart of an example method for visual media processing.
  • FIG. 22 is a flowchart of an example method for visual media processing.
  • FIG. 23 is a flowchart of an example method for visual media processing.
  • FIG. 24 is a flowchart of an example method for visual media processing.
  • FIG. 25 is a flowchart of an example method for visual media processing.
  • FIG. 26 is a flowchart of an example method for visual media processing.
  • 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.
  • video is used herein to include both a sequence of pictures (traditionally called video) and individual images.
  • 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.
  • This document is related to video coding/decoding technologies. Specifically, it is related to coefficient coding in a transform skip mode in video 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.
  • 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 [1,2].
  • AVC H.264/MPEG-4 Advanced Video Coding
  • H.265/HEVC H.265/HEVC standards [1,2].
  • the video coding standards are based on the hybrid video coding structure wherein temporal prediction plus transform coding are utilized.
  • Joint Video Exploration Team JVET was founded by VCEG and MPEG jointly in 2015.
  • JVET Joint Exploration Model
  • VVC draft i.e., Versatile Video Coding (Draft 4)
  • Draft 4 Versatile Video Coding
  • VTM The latest reference software of VVC, named VTM, could be found at:
  • 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.
  • 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.
  • 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.
  • an inter-coded coding unit 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.
  • BV block vector
  • the current picture is marked as a “long-term” reference picture in the Decoded Picture Buffer (DPB).
  • DPB Decoded Picture Buffer
  • the prediction can be generated by copying the reference block.
  • the residual can be got by subtracting the reference pixels from the original signals.
  • transform and quantization can be applied as in other coding modes.
  • the luma motion vector mvLX shall obey the following constraints:
  • 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.
  • 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
  • a maximum of four merge candidates are selected among candidates located in the positions A1, B1, B0, A0 and B2.
  • 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.
  • 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.
  • IBC candidates from HMVP table may be inserted. Redundancy check are performed when inserting the HMVP candidates.
  • pairwise average candidates are inserted into the IBC merge list.
  • the merge candidate 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.
  • invalid merge candidates may be inserted into the IBC merge list.
  • 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
  • IBC candidates from HMVP table may be inserted.
  • AMVR Adaptive Motion Vector Resolution
  • MVDs motion vector differences
  • a CU-level adaptive motion vector resolution (AMVR) scheme is introduced. AMVR allows MVD of the CU to be coded in different precision.
  • the MVDs of the current CU can be adaptively selected as follows:
  • the CU-level MVD resolution indication is conditionally signalled if the current CU has at least one non-zero MVD component. If all MVD components (that is, both horizontal and vertical MVDs for reference list L0 and reference list L1) are zero, quarter-luma-sample MVD resolution is inferred.
  • a first flag is signalled to indicate whether quarter-luma-sample MVD precision is used for the CU. If the first flag is 0, no further signaling is needed and quarter-luma-sample MVD precision is used for the current CU. Otherwise, a second flag is signalled to indicate whether integer-luma-sample or four-luma-sample MVD precision is used for normal AMVP CU. The same second flag is used to indicate whether integer-luma-sample or 1/16 luma-sample MVD precision is used for affine AMVP CU.
  • the motion vector predictors for the CU will be rounded to the same precision as that of the MVD before being added together with the MVD.
  • the motion vector predictors are rounded toward zero (that is, a negative motion vector predictor is rounded toward positive infinity and a positive motion vector predictor is rounded toward negative infinity).
  • the encoder determines the motion vector resolution for the current CU using RD check.
  • the RD check of MVD precisions other than quarter-luma-sample is only invoked conditionally.
  • the RD cost of quarter-luma-sample MVD precision and integer-luma sample MV precision is computed first. Then, the RD cost of integer-luma-sample MVD precision is compared to that of quarter-luma-sample MVD precision to decide whether it is necessary to further check the RD cost of four-luma-sample MVD precision.
  • affine AMVP mode if affine inter mode is not selected after checking rate-distortion costs of affine merge/skip mode, merge/skip mode, quarter-luma sample1 MVD precision normal AMVP mode and quarter-luma sample MVD precision affine AMVP mode, then 1/16 luma-sample MV precision and 1-pel MV precision affine inter modes are not checked. Furthermore, affine parameters obtained in quarter-luma-sample MV precision affine inter mode is used as starting search point in 1/16 luma-sample and quarter-luma-sample MV precision affine inter modes.
  • palette mode The basic idea behind a palette mode is that the samples in the CU are represented by a small set of representative color 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 .
  • a palette predictor For coding of the palette entries, a palette predictor is maintained. The maximum size of the palette as well as the palette predictor is signalled in the SPS.
  • a palette_predictor_initializer_present_flag is introduced in the PPS. When this flag is 1, entries for initializing the palette predictor are signalled in the bitstream.
  • the palette predictor is initialized at the beginning of each CTU row, each slice and each tile.
  • the palette predictor is reset to 0 or initialized using the palette predictor initializer entries signalled in the PPS.
  • a palette predictor initializer of size 0 was enabled to allow explicit disabling of the palette predictor initialization at the PPS level.
  • 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.
  • the palette indices are coded using horizontal and vertical traverse scans as shown in FIG.
  • the palette indices are coded using two main palette sample modes: ‘INDEX’ and ‘COPY_ABOVE’.
  • 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’.
  • the palette index of the sample in the row above is copied.
  • the palette index is explicitly signalled.
  • a run value is signalled which specifies the number of subsequent samples that are also coded using the same mode.
  • escape component values are signalled 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 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.
  • last_run_type_flag 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.
  • each palette entry consists of 3 components.
  • 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.
  • JVET-M0464 and JVET-N0280 several modifications are proposed on the coefficients coding in transform skip (TS) mode in order to adapt the residual coding to the statistics and signal characteristics of the transform skip levels.
  • Subblock CBFs The absence of the last significant scanning position signalling requires the subblock CBF signalling with coded_sub_block_flag for TS to be modified as follows:
  • sig_coeff_flag context modelling The local template in sig_coeff_flag context modeling is modified to only include the neighbor to the left (NB 0 ) and the neighbor above (NB 1 ) the current scanning position.
  • the context model offset is just the number of significant neighboring positions sig_coeff_flag[NB 0 ]+sig_coeff_flag[NB 1 ]. Hence, the selection of different context sets depending on the diagonal d within the current transform block is removed. This results in three context models and a single context model set for coding the sig_coeff_flag flag.
  • abs_level_gt1_flag and par_level_flag context modelling a single context model is employed for abs_level_gt1_flag and par_level_flag.
  • abs_remainder coding Although the empirical distribution of the transform skip residual absolute levels typically still fits a Laplacian or a Geometrical distribution, there exist larger instationarities than for transform coefficient absolute levels. Particularly, the variance within a window of consecutive realization is higher for the residual absolute levels. This motivates the following modifications of the abs_remainder syntax binarization and context modelling:
  • coeff_sign_flag context modelling Due to the instationarities inside the sequence of signs and the fact that the prediction residual is often biased, the signs can be coded using context models, even when the global empirical distribution is almost uniformly distributed. A single dedicated context model is used for the coding of the signs and the sign is parsed after sig_coeff_flag to keep all context coded bins together.
  • QR-BDPCM Quantized Residual Block Differential Pulse-Code Modulation
  • JVET-M0413 a quantized residual block differential pulse-code modulation (QR-BDPCM) is proposed to code screen contents efficiently.
  • QR-BDPCM quantized residual block differential pulse-code modulation
  • 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 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.
  • the residual quantized samples ⁇ tilde over (r) ⁇ i,j are sent to the decoder.
  • 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.
  • bdpcm_flag[x0][y0] 1 specifies that a bdpcm_dir_flag is present in the coding unit including the luma coding block at the location (x0, y0) bdpcm_dir_flag[x0][y0] equal to 0 specifies that the prediction direction to be used in a bdpcm block is horizontal, otherwise it is vertical.
  • a CTU is split into CUs by using a quaternary-tree structure denoted as coding tree to adapt to various local characteristics.
  • the decision whether to code a picture area using inter-picture (temporal) or intra-picture (spatial) prediction is made at the leaf CU level.
  • Each leaf CU can be further split into one, two or four PUs according to the PU splitting type. Inside one PU, the same prediction process is applied and the relevant information is transmitted to the decoder on a PU basis.
  • a leaf CU can be partitioned into transform units (TUs) according to another quaternary-tree structure similar to the coding tree for the CU.
  • TUs transform units
  • a quadtree with nested multi-type tree using binary and ternary splits segmentation structure replaces the concepts of multiple partition unit types, i.e. it removes the separation of the CU, PU and TU concepts except as needed for CUs that have a size too large for the maximum transform length, and supports more flexibility for CU partition shapes.
  • a CU can have either a square or rectangular shape.
  • a coding tree unit (CTU) is first partitioned by a quaternary tree (a.k.a. quadtree) structure. Then the quaternary tree leaf nodes can be further partitioned by a multi-type tree structure. As shown in FIG.
  • the multi-type tree leaf nodes are called coding units (CUs), and unless the CU is too large for the maximum transform length, this segmentation is used for prediction and transform processing without any further partitioning. This means that, in most cases, the CU, PU and TU have the same block size in the quadtree with nested multi-type tree coding block structure. The exception occurs when maximum supported transform length is smaller than the width or height of the color component of the CU.
  • luma and chroma components have separate partition structures on I tiles.
  • CCLM cross-component linear model
  • Linear model parameter ⁇ and ⁇ are derived from the relation between luma values and chroma values from two samples, which are luma sample with minimum sample value and with maximum sample inside the set of downsampled neighboring luma samples, and their corresponding chroma samples.
  • the linear model parameters ⁇ and ⁇ are obtained according to the following equations.
  • FIG. 7 shows an example of the location of the left and above samples and the sample of the current block involved in the CCLM mode.
  • LMCS luma mapping with chroma scaling
  • FIG. 8 shows the LMCS architecture from decoder's perspective.
  • the shaded blocks in FIG. 8 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 light-yellow shaded blocks in FIG. 8 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.
  • Transform skip flag are applied on all prediction modes which increases the overhead cost and encoding complexity.
  • An exemplary method for video processing includes performing a conversion between a current video block and a bitstream representation of a video comprising the current video block, wherein the conversion selectively uses a transform skip mode for the conversion based on an indicator that is included in the bitstream representation, and wherein, using the transform skip mode, a residual of a prediction error of the current video block is represented in the bitstream representation without applying a transformation.
  • the indicator is a maximal allowed width and a maximal allowed height for the transform skip mode.
  • the maximal allowed width and height is signaled in a sequence parameter set (SPS), a video parameter set (VPS), a picture parameter set (PPS), a picture header, a slice header, a tile group header, a largest coding unit (LCU) row or a group of LCUs.
  • SPS sequence parameter set
  • VPS video parameter set
  • PPS picture parameter set
  • a picture header a slice header, a tile group header, a largest coding unit (LCU) row or a group of LCUs.
  • the maximal allowed width and height is signaled in different messages.
  • the maximal allowed width and height is signaled in a sequence parameter set (SPS) or a picture parameter set (PPS), and wherein an updated value of the maximal allowed width and height is signaled in a picture header, a slice header, a tile group header, a largest coding unit (LCU) row or a group of LCUs.
  • SPS sequence parameter set
  • PPS picture parameter set
  • an updated value of the maximal allowed width and height is signaled in a picture header, a slice header, a tile group header, a largest coding unit (LCU) row or a group of LCUs.
  • FIG. 9A shows a flowchart of another exemplary method for video processing.
  • the method 900 includes, at step 902 , determining that a current video block is coded using a transform skip mode.
  • the method 900 includes, at step 904 , performing, based on the determining, a conversion between the current video block and a bitstream representation of a video comprising the current video block.
  • the current video block is divided into a plurality of coefficient groups, and the bitstream representation omits signaling of a coded block flag for at least one of the plurality of coefficient groups.
  • the bitstream representation omits the signaling of the coded block flag for each of the plurality of coefficient groups.
  • the coded block flag omitted in the signaling in the bitstream representation is inferred based on one or more of the following: (1) a message signaled in a sequence parameter set (SPS), a video parameter set (VPS), a picture parameter set (PPS), a picture header, a slice header, a tile group header, a largest coding unit (LCU), an LCU row, a group of LCUs or a coding unit (CU), (2) a position of at least one of the plurality of coefficient groups, (3) a block dimension of the current video block or at least one neighboring block of the current video block, (4) a block shape of the current video block or the at least one neighboring block, (5) a most probable mode of the current video block or the at least one neighboring block, (6) a prediction mode of the at least one neighboring block, (7) an intra prediction mode of the at least one neighboring block, (8) one or more motion vectors of the at least one neighboring block, (9) an indication of a quantized residual
  • the current video block is divided into a plurality of coefficient groups, and the method 900 further includes the step of determining a coefficient scanning order for the plurality of coefficient groups.
  • the coefficient scanning order is based on a message signaled in a sequence parameter set (SPS), a video parameter set (VPS), a picture parameter set (PPS), a picture header, a slice header, a tile group header, a largest coding unit (LCU), an LCU row, a group of LCUs or a coding unit (CU).
  • the plurality of coefficient group or the coefficient scanning order is based on an intra prediction mode of the current video block.
  • the coefficient scanning order is vertical, and wherein the intra prediction mode is horizontally dominated.
  • the coefficient scanning order is horizontal, and wherein the intra prediction mode is horizontally dominated.
  • an index of the intra prediction mode ranges from 2 to 33 or from 2 to 34.
  • the plurality of coefficient group or the coefficient scanning order is based on an intra prediction mode of the current video block.
  • the coefficient scanning order is vertical, and wherein the intra prediction mode is vertically dominated.
  • the coefficient scanning order is horizontal, and wherein the intra prediction mode is vertically dominated.
  • an index of the intra prediction mode ranges from 34 to 66 or from 35 to 66.
  • a context of a sign flag is based on neighboring information in a coefficient block associated with the current video block.
  • the context of the sign flag is further based on a position of a coefficient of the coefficient block.
  • the context of the sign flag is based on (x+y), min(x, y) or max(x, y), wherein x and y are a horizontal value and a vertical value of the position of the coefficient, respectively.
  • FIG. 9B shows a flowchart of yet another exemplary method for video processing.
  • the method 910 includes, at step 912 , determining, for a current video block, that a chroma transform skip mode is applicable.
  • the method 910 includes, at step 914 , performing, based on the determining, a conversion between the current video block and a bitstream representation of a video comprising the current video block.
  • the determining is based on a message signaled in a sequence parameter set (SPS), a video parameter set (VPS), a picture parameter set (PPS), a picture header, a slice header, a tile group header, a largest coding unit (LCU), an LCU row, a group of LCUs, a coding unit (CU) or a video data unit.
  • SPS sequence parameter set
  • VPS video parameter set
  • PPS picture parameter set
  • LCU largest coding unit
  • CU largest coding unit
  • CU coding unit
  • CU coding unit
  • the determining is based on decoded information from one or more representative video blocks that were decoded prior to the performing the conversion, and wherein a sample in each of the one or more representative video blocks and the current video block is based on a common color information.
  • the one or more representative video blocks comprises a luma block or a chroma block.
  • the one or more representative video blocks comprises a block within a collocated luma block.
  • FIG. 9C shows a flowchart of yet another exemplary method for video processing.
  • the method 920 includes, at step 922 , making a decision, during a conversion between a current video block and a bitstream representation of a video comprising the current video block, regarding a selective application of a transform skip mode to the current video block based on a condition.
  • the method 920 includes, at step 924 , performing, based on the decision, the conversion.
  • the condition is based on a message signaled in a sequence parameter set (SPS), a video parameter set (VPS), a picture parameter set (PPS), a picture header, a slice header, a tile group header, a largest coding unit (LCU), an LCU row, a group of LCUs, a coding unit (CU) or a video data unit.
  • SPS sequence parameter set
  • VPS video parameter set
  • PPS picture parameter set
  • LCU largest coding unit
  • CU largest coding unit
  • CU coding unit
  • CU coding unit
  • the condition is based on one or more of the following: (1) a block dimension of the current video block or at least one neighboring block of the current video block, (2) a block shape of the current video block or the at least one neighboring block, (3) a most probable mode of the current video block or the at least one neighboring block, (4) a prediction mode of the at least one neighboring block, (5) an intra prediction mode of the at least one neighboring block, (6) one or more motion vectors of the at least one neighboring block, (7) an indication of a quantized residual block differential pulse-code modulation (QR-BDPCM) mode of the at least one neighboring block, (8) a current quantization parameter (QP) of the current video block or the at least one neighboring block, (9) an indication of a color format of the current video block, (10) a separate or dual coding tree structure associated with the current video block, (11) a slice type, a tile group type or a picture type of the current video block, or (12) a temporal layer identification (ID
  • the application of the transform skip mode is performed, a prediction mode of the current video block is an inter block copy (IBC) mode, and a width or a height of the current video block is compared to a threshold.
  • IBC inter block copy
  • the threshold is signaled in the bitstream representation.
  • the threshold is 4, 8, 16 or 32.
  • the threshold is based on one or more of the following: (1) a message signaled in a sequence parameter set (SPS), a video parameter set (VPS), a picture parameter set (PPS), a picture header, a slice header, a tile group header, a largest coding unit (LCU), an LCU row, a group of LCUs or a coding unit (CU), (2) a temporal layer identification (ID), (3) a block dimension of the current video block or at least one neighboring block of the current video block, (4) a block shape of the current video block or the at least one neighboring block, (5) a most probable mode of the current video block or the at least one neighboring block, (6) a prediction mode of the at least one neighboring block, (7) an intra prediction mode of the at least one neighboring block, (8) one or more motion vectors of the at least one neighboring block, (9) an indication of a quantized residual block differential pulse-code modulation (QR-BDPCM) mode of the at least one neighboring block
  • FIG. 9D shows a flowchart of yet another exemplary method for video processing.
  • the method 930 includes, at step 932 , making a decision, during a conversion between a current video block and a bitstream representation of a video comprising the current video block, regarding a selective application of quantized residual block differential pulse-code modulation (QR-BDPCM) based on an indication of a transform skip mode in the bitstream representation.
  • QR-BDPCM quantized residual block differential pulse-code modulation
  • the method 930 includes, at step 934 , performing, based on the decision, the conversion.
  • the indication of the transform skip mode is signaled on a transform unit (TU) level.
  • TU transform unit
  • FIG. 9E shows a flowchart of yet another exemplary method for video processing.
  • the method 940 includes, at step 942 , making a decision, during a conversion between a current video block and a bitstream representation of a video comprising the current video block, regarding a selective application of a separate or dual tree based on a condition.
  • the method 940 includes, at step 944 , performing, based on the decision, the conversion.
  • the condition is based on a message signaled in a sequence parameter set (SPS), a video parameter set (VPS), a picture parameter set (PPS), a picture header, a slice header, a tile group header, a largest coding unit (LCU), an LCU row, a group of LCUs, a coding unit (CU) or a video data unit.
  • SPS sequence parameter set
  • VPS video parameter set
  • PPS picture parameter set
  • LCU largest coding unit
  • CU largest coding unit
  • CU coding unit
  • CU coding unit
  • the condition is based on determining whether a slice, a tile, a largest coding unit (LCU), an LCU row, a group of LCUs or a video data unit comprising the current video block is screen content.
  • the determining is based on one or more of the following: (1) a message signaled in a sequence parameter set (SPS), a video parameter set (VPS), a picture parameter set (PPS), a picture header, a slice header, a tile group header, the LCU, the LCU row, the group of LCUs, the coding unit (CU) or the video data unit, (2) a block dimension of the current video block or at least one neighboring block of the current video block, (3) a block shape of the current video block or the at least one neighboring block, (4) a current quantization parameter (QP) of the current video block or the at least one neighboring block, (5) an indication of a color format of the current video block, (6) a separate or dual coding tree structure associated with the
  • FIG. 10 is a block diagram of a video processing apparatus 1000 .
  • the apparatus 1000 may be used to implement one or more of the methods described herein.
  • the apparatus 1000 may be embodied in a smartphone, tablet, computer, Internet of Things (IoT) receiver, and so on.
  • the apparatus 1000 may include one or more processors 1002 , one or more memories 1004 and video processing hardware 1006 .
  • the processor(s) 1002 may be configured to implement one or more methods (including, but not limited to, methods 900 , 910 , 920 , 930 and 940 ) described in the present document.
  • the memory (memories) 1004 may be used for storing data and code used for implementing the methods and techniques described herein.
  • the video processing hardware 1006 may be used to implement, in hardware circuitry, some techniques described in the present document.
  • the video coding methods may be implemented using an apparatus that is implemented on a hardware platform as described with respect to FIG. 10 .
  • a method of video processing includes making a determination about whether or not intra block copy mode is applicable for a conversion between a current video block of a video and a bitstream representation based on a type of coding tree structure corresponding to the current video block; and performing the conversion based on the determination.
  • the bitstream representation excludes an indication of the intra block copy mode. In other words, the bitstream does not carry an explicit signaling of the IBC mode.
  • the type of coding tree structure is a dual coding tree structure and the determination is that intra block copy mode is not applicable.
  • FIG. 11 is a block diagram showing an example video processing system 1100 in which various techniques disclosed herein may be implemented.
  • the system 1100 may include input 1102 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 1102 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 1100 may include a coding component 1104 that may implement the various coding or encoding methods described in the present document.
  • the coding component 1104 may reduce the average bitrate of video from the input 1102 to the output of the coding component 1104 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 1104 may be either stored, or transmitted via a communication connected, as represented by the component 1106 .
  • the stored or communicated bitstream (or coded) representation of the video received at the input 1102 may be used by the component 1108 for generating pixel values or displayable video that is sent to a display interface 1110 .
  • the process of generating user-viewable video from the bitstream representation is sometimes called video decompression.
  • 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.
  • peripheral bus interface or a display interface may include universal serial bus (USB) or high definition multimedia interface (HDMI) or Displayport, and so on.
  • storage interfaces include SATA (serial advanced technology attachment), PCI, IDE interface, and the like.
  • FIG. 12 is a flowchart of an example method for visual media encoding. Steps of this flowchart are discussed in connection with example embodiment 1 discussed in Section 4 of this document.
  • the process determines, for encoding one or more video blocks in a video region of a visual media data into a bitstream representation of the visual media data, a maximum allowed dimension up to which a current video block of the one or more video blocks is allowed to be encoded using a transform skip mode such that a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform.
  • the process includes a syntax element indicative of the maximum allowed dimension in the bitstream representation.
  • FIG. 13 is a flowchart of an example method for visual media decoding. Steps of this flowchart are discussed in connection with example embodiment 1 discussed in Section 4 of this document.
  • the process parses a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a maximum allowed dimension up to which the current video block of the one or more blocks of a video region is allowed to be coded using a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform.
  • the process generates a decoded video region from the bitstream representation by decoding the one or more video blocks according to the maximum allowed dimension.
  • FIG. 14 is a flowchart of an example method for visual media processing. Steps of this flowchart are discussed in connection with example embodiment 2 discussed in Section 4 of this document.
  • the process determines that a current video block of visual media data is coded using a transform skip mode.
  • the process performs, based on the determining, a conversion between the current video block and a bitstream representation of the visual media data, wherein, during the conversion, the current video block is divided into a plurality of coefficient groups and signaling of a coded block flag for at least one of the plurality of coefficient groups is excluded in the bitstream representation, wherein, in the transform skip mode, a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transformation.
  • FIG. 15 is a flowchart of an example method for visual media processing. Steps of this flowchart are discussed in connection with example embodiment 3 discussed in Section 4 of this document.
  • the process determines that a current video block of visual media data is coded using a transform skip mode.
  • the process performs, based on the determining, a conversion between the current video block and a bitstream representation of the visual media data, wherein, during the conversion, the current video block is divided into a plurality of coefficient groups, wherein, in the transform skip mode, a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transformation, and further wherein, during the conversion, a coefficient scanning order of the plurality of coefficient groups is determined based, at least in part, on an indication in the bitstream representation.
  • FIG. 16 is a flowchart of an example method for visual media encoding. Steps of this flowchart are discussed in connection with example embodiment 4 discussed in Section 4 of this document.
  • the process uses, for encoding a current video block in a video region of a visual media data into a bitstream representation of the visual media data, a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform.
  • the process selects a context of a sign flag of the current video block according to sign flags of one or more neighboring video blocks in a coefficient group associated with the current video block based upon division of the current video block into a plurality of coefficient groups.
  • FIG. 17 is a flowchart of an example method for visual media decoding. Steps of this flowchart are discussed in connection with example embodiment 4 discussed in Section 4 of this document.
  • the process parses a bitstream representation of a visual media data comprising a video region comprising a current video block to identify a context of a sign flag used in a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform.
  • the process generates the decoded video region from the bitstream representation such that the context of the sign flag is according to sign flags of one or more neighboring video blocks in a coefficient group associated with the current video block based upon division of the current video block into a plurality of coefficient groups.
  • FIG. 18 is a flowchart of an example method for visual media processing.
  • the process determines a position of a current coefficient associated with a current video block of visual media data when the current video block is divided into a plurality of coefficient positions.
  • the process derives, at least based on sign flags of one or more neighboring coefficients, a context of a sign flag for the current coefficient.
  • the process generates, based on the context, a sign flag for the current coefficient, wherein the sign flag of the current coefficient is used in a transform skip mode in which the current video block is coded without applying a transform.
  • FIG. 19 is a flowchart of an example method for visual media encoding. Steps of this flowchart are discussed in connection with example embodiment 5 discussed in Section 4 of this document.
  • the process determines, for encoding one or more video blocks in a video region of a visual media data into a bitstream representation of the visual media data, based on satisfying at least one rule that a chroma transform skip mode is applicable on a current video block, wherein, in the chroma transform skip mode a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation.
  • the process includes a syntax element indicative of the chroma transform skip mode in the bitstream representation.
  • FIG. 20 is a flowchart of an example method for visual media decoding. Steps of this flowchart are discussed in connection with example embodiment 5 discussed in Section 4 of this document.
  • the process parses a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks that at least one rule associated with application of a chroma transform skip mode is satisfied, wherein, in the chroma transform skip mode a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation.
  • the process generates a decoded video region from the bitstream representation by decoding the one or more video blocks.
  • FIG. 21 is a flowchart of an example method for visual media encoding. Steps of this flowchart are discussed in connection with example embodiment 6 discussed in Section 4 of this document.
  • the process makes a decision, for encoding one or more video blocks in a video region of a visual media data into a bitstream representation of the visual media data, regarding a selective application of a transform skip mode to the current video block based on a condition.
  • the process includes a syntax element indicative of the condition in the bitstream representation, wherein, in the transform skip mode, a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation.
  • FIG. 22 is a flowchart of an example method for visual media decoding. Steps of this flowchart are discussed in connection with example embodiment 6 discussed in Section 4 of this document.
  • the process parses a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a condition relating to usage of a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform.
  • the process generates a decoded video region from the bitstream representation by decoding the one or more video blocks according to the condition.
  • FIG. 23 is a flowchart of an example method for visual media encoding. Steps of this flowchart are discussed in connection with example embodiment 8 discussed in Section 4 of this document.
  • the process makes a decision, for encoding one or more video blocks in a video region of a visual media data into a bitstream representation of the visual media data, regarding a selective application of quantized residual block differential pulse-code modulation (QR-BDPCM) technique based on an indication of a transform skip mode in the bitstream representation, wherein, in the transform skip mode, a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation, wherein, in the QR-BDPCM technique, the residual of the prediction error in a horizontal direction and/or a vertical direction is quantized and entropy-coded.
  • the process includes, in the bitstream representation, an indication of the selective application of the QR-BDPCM technique.
  • FIG. 24 is a flowchart of an example method for visual media decoding. Steps of this flowchart are discussed in connection with example embodiment 8 discussed in Section 4 of this document.
  • the process parses a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a selective application of quantized residual block differential pulse-code modulation (QR-BDPCM) technique based on an indication of a transform skip mode in the bitstream representation, wherein, in the transform skip mode, a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation, wherein, in the QR-BDPCM technique, the residual of the prediction error in a horizontal direction and/or a vertical direction is quantized and entropy-coded.
  • the process generates a decoded video region from the bitstream representation by decoding the one or more video blocks according to the maximum allowed
  • FIG. 25 is a flowchart of an example method for visual media encoding. Steps of this flowchart are discussed in connection with example embodiment 9 discussed in Section 4 of this document.
  • the process makes a decision, for encoding one or more video blocks in a video region of a visual media data into a bitstream representation of the visual media data, regarding a selective application of a separate or dual tree based on a condition.
  • the process includes a syntax element indicative of the selective application of the separate or the dual tree in the bitstream representation.
  • FIG. 26 is a flowchart of an example method for visual media decoding. Steps of this flowchart are discussed in connection with example embodiment 9 discussed in Section 4 of this document.
  • the process parses a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a selective application of a separate or dual tree based on or inferred from a condition.
  • the process generates a decoded video region from the bitstream representation by decoding the one or more video blocks according to the syntax element.
  • a method for visual media encoding comprising:
  • a method for visual media decoding comprising:
  • syntax element parsing a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a maximum allowed dimension up to which the current video block of the one or more blocks of a video region is allowed to be coded using a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform;
  • a method for visual media processing comprising:
  • SPS sequence parameter set
  • VPS video parameter set
  • PPS picture parameter set
  • a picture header a slice header, a tile group header, a largest coding unit (LCU), an LCU row, a group of LCUs or a coding unit (CU)
  • (13) a slice type, a tile group type or a picture type of the current video block.
  • a method for visual media processing further comprising:
  • a method for visual media encoding comprising:
  • a method for visual media decoding comprising:
  • a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks that at least one rule associated with application of a chroma transform skip mode is satisfied, wherein, in the chroma transform skip mode a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation of the visual media data without applying a transformation;
  • a method for visual media encoding comprising:
  • a method for visual media decoding comprising:
  • syntax element parsing a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a condition relating to usage of a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform;
  • QR-BDPCM quantized residual block differential pulse-code modulation
  • SPS sequence parameter set
  • VPS video parameter set
  • PPS picture parameter set
  • a picture header a slice header, a tile group header, a largest coding unit (LCU), an LCU row, a group of LCUs or a coding unit (CU)
  • (13) a slice type, a tile group type or a picture type of the current video block.
  • a method for visual media encoding comprising:
  • QR-BDPCM quantized residual block differential pulse-code modulation
  • a method for visual media decoding comprising:
  • QR-BDPCM quantized residual block differential pulse-code modulation
  • a method for visual media encoding comprising:
  • a method for visual media decoding comprising:
  • syntax element parsing a syntax element from a bitstream representation of a visual media data comprising a video region comprising one or more video blocks, wherein the syntax element is indicative of a selective application of a separate or dual tree based on or inferred from a condition;
  • SPS sequence parameter set
  • VPS video parameter set
  • PPS picture parameter set
  • a picture header a slice header, a tile group header, the LCU, the LCU row, the group of LCUs, the coding unit (CU) or the video data unit
  • QP current quantization parameter
  • a video encoder apparatus comprising a processor configured to implement a method recited in any one or more of clauses A1-F5.
  • a video decoder apparatus comprising a processor configured to implement a method recited in any one or more of clauses A1-F5.
  • a method for visual media encoding comprising:
  • a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform
  • a method for visual media decoding comprising:
  • bitstream representation of a visual media data comprising a video region comprising a current video block to identify a context of a sign flag used in a transform skip mode in which a residual of a prediction error between the current video block and a reference video block is represented in the bitstream representation without applying a transform;
  • C (L+A), where C is a context id of the context of the sign flag of the current video block, L is a sign flag of a left neighbor of the current video block, and A is a sign flag of an above neighbor of the current video block.
  • C (L+A*2), where C is a context id of the context of the sign flag of the current video block, L is a sign flag of a left neighbor of the current video block, and A is a sign flag of an above neighbor of the current video block.
  • C (L*2+A), where C is a context id of the context of the sign flag of the current video block, L is a sign flag of a left neighbor of the current video block, and A is a sign flag of an above neighbor of the current video block.
  • the rule specifies selecting a first context of the sign flag.
  • a method for visual media processing comprising:
  • the rule specifies selecting a second context of the sign flag.
  • the rule specifies selecting a third context of the sign flag.
  • a video encoder apparatus comprising a processor configured to implement a method recited in any one or more of clauses B1-B16.
  • a video decoder apparatus comprising a processor configured to implement a method recited in any one or more of clauses B1-B16.
  • video processing or “visual media processing” may refer to video encoding, video decoding, video compression or video decompression.
  • 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.
  • 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.
  • Implementations of the subject matter and the functional operations described in this patent document can be implemented in various systems, digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Implementations of the subject matter described in this specification can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a tangible and non-transitory 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 of them.
  • data processing unit or “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 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 specification 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.
  • 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.
  • 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.
  • mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks.
  • a computer need not have such devices.
  • Computer readable media suitable for storing computer program instructions and data include all forms of nonvolatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices.
  • semiconductor memory devices e.g., EPROM, EEPROM, and flash memory devices.
  • the processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.
  • ⁇ sps_asdt_flag 1 specifies that the proposed method can be enabled on the current sequence. It equals to 0 specifies that the proposed method cannot be enabled on the current sequence. When sps_ASDT_flag is not present, it is inferred to be equal to 0.
  • slice_asdt_flag 1 specifies that the proposed method can be enabled on the current slice. It equals to 0 specifies that the proposed method cannot be enabled on the current slice. When slice_ASDT_flag is not present, it is inferred to be equal to 0.
  • slice_asdt_flag 1 specifies that the proposed method can be enabled on the current slice. It equals to 0 specifies that the proposed method cannot be enabled on the current slice. When slice_ASDT_flag is not present, it is inferred to be equal to 0.
  • Output of this process is a modified reconstructed picture before in-loop filtering.
  • the derivation process for quantization parameters as specified in clause 8.7.1 is invoked with the luma location (xCb, yCb), the width of the current coding block in luma samples cbWidth and the height of the current coding block in luma samples cbHeight, and the variable treeType as inputs.
  • the decoding process for coding units coded in ibc prediction mode consists of the following ordered steps:
  • NUMSBY ( CB HEIGHT>>2) (8-872)

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