WO2021129805A1 - Signaling of parameters at sub-picture level in a video bitstream - Google Patents

Signaling of parameters at sub-picture level in a video bitstream Download PDF

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WO2021129805A1
WO2021129805A1 PCT/CN2020/139389 CN2020139389W WO2021129805A1 WO 2021129805 A1 WO2021129805 A1 WO 2021129805A1 CN 2020139389 W CN2020139389 W CN 2020139389W WO 2021129805 A1 WO2021129805 A1 WO 2021129805A1
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picture
sub
video
bitstream
equal
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PCT/CN2020/139389
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English (en)
French (fr)
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Kai Zhang
Zhipin DENG
Hongbin Liu
Li Zhang
Jizheng Xu
Ye-Kui Wang
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Beijing Bytedance Network Technology Co., Ltd.
Bytedance Inc.
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Priority to CN202080089302.4A priority Critical patent/CN115362677A/zh
Priority to KR1020227020327A priority patent/KR20220114555A/ko
Publication of WO2021129805A1 publication Critical patent/WO2021129805A1/en

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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
    • H04N19/70—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
    • H04N19/10—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
    • H04N19/187—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 scalable video layer
    • 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
    • H04N19/117—Filters, e.g. for pre-processing or post-processing
    • 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
    • H04N19/119—Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
    • 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
    • H04N19/124—Quantisation
    • 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
    • H04N19/132—Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
    • 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
    • H04N19/174—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 slice, e.g. a line of blocks or a group of blocks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
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    • 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
    • H04N19/184—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 bits, e.g. of the compressed video stream
    • 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
    • H04N19/186—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 colour or a chrominance component
    • 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
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    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/80—Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation
    • H04N19/82—Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation involving filtering within a prediction loop
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    • 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
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    • H04N21/234—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs
    • H04N21/2343—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs involving reformatting operations of video signals for distribution or compliance with end-user requests or end-user device requirements
    • H04N21/234363—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs involving reformatting operations of video signals for distribution or compliance with end-user requests or end-user device requirements by altering the spatial resolution, e.g. for clients with a lower screen resolution

Definitions

  • This document is related to video and image coding and decoding technologies.
  • 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.
  • Methods, systems and devices that signal parameters at a sub-picture level in a video bitstream are described.
  • the disclosed techniques may be used by video or image decoder or encoder embodiments for in which sub-picture based coding or decoding is performed.
  • a method of video processing includes performing a conversion between a video comprising a picture that comprises one or more sub-pictures and a bitstream of the video, wherein the bitstream conforms to a format rule, wherein the format rule specifies that the bitstream includes a set of parameters controlling a coding behavior of a sub-picture of the one or more sub-pictures associated with an identification (ID) of the sub-picture.
  • ID identification
  • a method of video processing includes performing a conversion between video comprising a picture that comprises one or more sub-pictures and a bitstream of the video, wherein a current set of parameters is configured to control a coding behavior of at least one sub-picture of the one or more sub-pictures, wherein the bitstream conforms to a format rule, wherein the format rule specifies that a default set of parameters corresponding to the current set of parameters is signaled in the bitstream before a difference between the current set of parameters and the default set of parameters is signaled in the bitstream.
  • a method of video processing includes performing a conversion between a video comprising a picture that comprises one or more sub-pictures and a bitstream of the video, wherein the bitstream conforms to a format rule, wherein the bitstream includes a set of parameters comprising a first control parameter and a second control parameter for controlling a coding property of a sub-picture; and wherein the format rule specifies whether or how the first control parameter is overwritten by the second control parameter for decoding.
  • a method of video processing includes performing a conversion between a video comprising a picture that comprises one or more sub-pictures and a bitstream of the video, wherein one or more first flags, corresponding to each of the one or more sub-pictures, are included in a sequence parameter set (SPS) , wherein each first flag of the one or more first flags indicates whether constraint information is signaled for a sub-picture corresponding to the each first flag, and wherein the constraint information indicates coding tools that are not applied to the corresponding sub-picture across a coded layer video sequence (CLVS) .
  • SPS sequence parameter set
  • the above-described method may be implemented by a video encoder apparatus that comprises a processor.
  • the above-described method may be implemented by a video decoder apparatus that comprises a processor.
  • these methods may be embodied in the form of processor-executable instructions and stored on a computer-readable program medium.
  • FIG. 1 shows an example of region constraint in temporal motion vector prediction (TMVP) and sub-block TMVP.
  • FIG. 2 shows an example of a hierarchical motion estimation scheme.
  • FIG. 3 shows an example of a picture with 18 by 12 luma CTUs that is partitioned into 12 tiles and 3 raster-scan slices.
  • FIG. 4 shows an example of picture with 18 by 12 luma CTUs that is partitioned into 24 tiles and 9 rectangular slices.
  • FIG. 5 shows an example of a picture that is partitioned into 4 tiles, 11 bricks, and 4 rectangular slices.
  • FIG. 6 is a block diagram showing an example video processing system in which various techniques disclosed herein may be implemented.
  • FIG. 7 is a block diagram of an example hardware platform used for video processing.
  • FIG. 8 is a block diagram that illustrates an example video coding system that can implement some embodiments of the present disclosure.
  • FIG. 9 is a block diagram that illustrates an example of an encoder that can implement some embodiments of the present disclosure.
  • FIG. 10 is a block diagram that illustrates an example of a decoder that can implement some embodiments of the present disclosure.
  • FIGS. 11-14 show flowcharts for example methods of video 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 technologies. Specifically, it is related to palette coding with employing base colors based representation 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 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:
  • FIG. 1 shows a region constraint in TMVP and sub-block TMVP
  • TMVP and sub-block TMVP it is constrained that a temporal MV can only be fetched from the collocated CTU plus a column of 4 ⁇ 4 blocks as shown in FIG. 1.
  • Whether in-loop filtering across sub-picture boundaries is disabled can be controlled by the bitstream for each sub-picture.
  • the DBF, SAO, and ALF processes are updated for controlling of in-loop filtering operations across sub-picture boundaries.
  • sub-picture width, height, horizontal offset, and vertical offset are signalled in units of luma samples in SPS.
  • Sub-picture boundaries are constrained to be slice boundaries.
  • Treating a sub-picture as a picture in the decoding process is specified by slightly updating the coding_tree_unit () syntax, and updates to the following decoding processes:
  • Sub-picture IDs are explicitly specified in the SPS and included in the tile group headers to enable extraction of sub-picture sequences without the need of changing VCL NAL units.
  • OSPS Output sub-picture sets
  • subpics_present_flag 1 indicates that subpicture parameters are present in the present in the SPS RBSP syntax.
  • subpics_present_flag 0 indicates that subpicture parameters are not present in the present in the SPS RBSP syntax.
  • max_subpics_minus1 plus 1 specifies the maximum number of subpictures that may be present in the CVS.
  • max_subpics_minus1 shall be in the range of 0 to 254. The value of 255 is reserved for future use by ITU-T
  • subpic_grid_col_width_minus1 plus 1 specifies the width of each element of the subpicture identifier grid in units of 4 samples.
  • the length of the syntax element is Ceil (Log2 (pic_width_max_in_luma_samples/4) ) bits.
  • NumSubPicGridCols (pic_width_max_in_luma_samples+subpic_grid_col_width_minus1*4+3) / (subpic_grid_col_width_minus1*4+4) (7-5)
  • subpic_grid_row_height_minus1 plus 1 specifies the height of each element of the subpicture identifier grid in units of 4 samples.
  • the length of the syntax element is Ceil (Log2 (pic_height_max_in_luma_samples/4) ) bits.
  • NumSubPicGridRows (pic_height_max_in_luma_samples+subpic_grid_row_height_minus1*4+3) / (subpic_grid_row_height_minus1*4+4) (7-6)
  • subpic_grid_idx [i] [j] specifies the subpicture index of the grid position (i, j) .
  • the length of the syntax element is Ceil (Log2 (max_subpics_minus1+1) ) bits.
  • SubPicTop [subpic_grid_idx [i] [j] ] SubPicLeft [subpic_grid_idx [i] [j] ]
  • SubPicWidth [subpic_grid_idx [i] [j] ] SubPicHeight [subpic_grid_idx [i] [j] ]
  • NumSubPics are derived as follows:
  • subpic_treated_as_pic_flag [i] 1 specifies that the i-th subpicture of each coded picture in the CVS is treated as a picture in the decoding process excluding in-loop filtering operations.
  • subpic_treated_as_pic_flag [i] 0 specifies that the i-th subpicture of each coded picture in the CVS is not treated as a picture in the decoding process excluding in-loop filtering operations.
  • the value of subpic_treated_as_pic_flag [i] is inferred to be equal to 0.
  • loop_filter_across_subpic_enabled_flag [i] 1 specifies that in-loop filtering operations may be performed across the boundaries of the i-th subpicture in each coded picture in the CVS.
  • loop_filter_across_subpic_enabled_flag [i] 0 specifies that in-loop filtering operations are not performed across the boundaries of the i-th subpicture in each coded picture in the CVS.
  • the value of loop_filter_across_subpic_enabled_pic_flag [i] is inferred to be equal to 1.
  • any coded NAL unit of subPicA shall succeed any coded NAL unit of subPicB in decoding order.
  • each subpicture when decoded, shall have its entire left boundary and entire top boundary consisting of picture boundaries or consisting of boundaries of previously decoded subpictures.
  • CtbToSubPicIdx [ctbAddrRs] for ctbAddrRs ranging from 0 to PicSizeInCtbsY-1, inclusive, specifying the conversion from a CTB address in picture raster scan to a subpicture index, is derived as follows:
  • num_bricks_in_slice_minus1 when present, specifies the number of bricks in the slice minus 1.
  • the value of num_bricks_in_slice_minus1 shall be in the range of 0 to NumBricksInPic-1, inclusive.
  • SubPicIdx SubPicLeftBoundaryPos
  • SubPicTopBoundaryPos SubPicRightBoundaryPos
  • SubPicBotBoundaryPos are derived as follows:
  • SubPicIdx CtbToSubPicIdx [CtbAddrBsToRs [FirstCtbAddrBs [SliceBrickIdx [0] ] ] ]
  • SubPicLeftBoundaryPos SubPicLeft [SubPicIdx] * (subpic_grid_col_width_minus1+1) *4
  • SubPicRightBoundaryPos (SubPicLeft [SubPicIdx] +SubPicWidth [SubPicIdx] ) * (subpic_grid_col_width_minus1+1) *4
  • SubPicTopBoundaryPos SubPicTop [SubPicIdx] * (subpic_grid_row_height_minus1+1) *4
  • SubPicBotBoundaryPos (SubPicTop [SubPicIdx] +SubPicHeight [SubPicIdx] ) * (subpic_grid_row_height_minus1+1) *4
  • variable cbWidth specifying the width of the current coding block in luma samples
  • variable cbHeight specifying the height of the current coding block in luma samples
  • variable currCb specifies the current luma coding block at luma location (xCb, yCb) .
  • slice_temporal_mvp_enabled_flag is equal to 0 or (cbWidth*cbHeight) is less than or equal to 32, both components of mvLXCol are set equal to 0 and availableFlagLXCol is set equal to 0.
  • the bottom right collocated motion vector and the bottom and right boundary sample locations are derived as follows:
  • SubPicRightBoundaryPos pic_width_in_luma_samples-1 (8-423)
  • botBoundaryPos subpic_treated_as_pic_flag [SubPicIdx] ?
  • yCb>>CtbLog2SizeY is equal to yColBr>>CtbLog2SizeY
  • yColBr is less than or equal to botBoundaryPos
  • xColBr is less than or equal to rightBoundaryPos
  • the variable colCb specifies the luma coding block covering the modified location given by ( (xColBr>>3) ⁇ 3, (yColBr>>3) ⁇ 3) inside the collocated picture specified by ColPic.
  • the luma location (xColCb, yColCb) is set equal to the top-left sample of the collocated luma coding block specified by colCb relative to the top-left luma sample of the collocated picture specified by ColPic.
  • both components of mvLXCol are set equal to 0 and availableFlagLXCol is set equal to 0.
  • Output of this process is a predicted luma sample value predSampleLX L
  • variable picW is set equal to pic_width_in_luma_samples and the variable picH is set equal to pic_height_in_luma_samples.
  • the luma interpolation filter coefficients fb L [p] for each 1/16 fractional sample position p equal to xFrac L or yFrac L are specified in Table 8-10.
  • subpic_treated_as_pic_flag [SubPicIdx] is equal to 1, the following applies:
  • xInt i Clip3 (SubPicLeftBoundaryPos, SubPicRightBoundaryPos, xInt L +i) (8-460)
  • yInt i Clip3 (SubPicTopBoundaryPos, SubPicBotBoundaryPos, yInt L +i) (8-461)
  • variable cbWidth specifying the width of the current coding block in luma samples
  • variable cbHeight specifying the height of the current coding block in luma samples.
  • the availability flag availableFlagSbCol is derived as follows.
  • availableFlagSbCol is set equal to 0.
  • slice_temporal_mvp_enabled_flag is equal to 0.
  • the location (xCtb, yCtb) of the top-left sample of the luma coding tree block that contains the current coding block and the location (xCtr, yCtr) of the below-right center sample of the current luma coding block are derived as follows:
  • xCtr xCb+ (cbWidth/2) (8-544)
  • the luma location (xColCtrCb, yColCtrCb) is set equal to the top-left sample of the collocated luma coding block covering the location given by (xCtr, yCtr) inside ColPic relative to the top-left luma sample of the collocated picture specified by ColPic.
  • the derivation process for subblock-based temporal merging base motion data as specified in clause 8.5.5.4 is invoked with the location (xCtb, yCtb) , the location (xColCtrCb, yColCtrCb) , the availability flag availableFlagA 1 , and the prediction list utilization flag predFlagLXA 1 , and the reference index refIdxLXA 1 , and the motion vector mvLXA 1 , with X being 0 and 1 as inputs and the motion vectors ctrMvLX, and the prediction list utilization flags ctrPredFlagLX of the collocated block, with X being 0 and 1, and the temporal motion vector tempMv as outputs.
  • variable availableFlagSbCol is derived as follows:
  • availableFlagSbCol is set equal to 1.
  • the luma location (xSb, ySb) specifying the top-left sample of the current coding subblock relative to the top-left luma sample of the current picture is derived as follows:
  • xSb xCb+xSbIdx*sbWidth+sbWidth/2 (8-551)
  • the location (xColSb, yColSb) of the collocated subblock inside ColPic is derived as follows.
  • subpic_treated_as_pic_flag [SubPicIdx] is equal to 1, the following applies:
  • variable tempMv is set as follows:
  • variable currPic specifies the current picture.
  • tempMv is set equal to mvL0A 1 :
  • tempMv is set equal to mvL1A 1 :
  • DiffPicOrderCnt (ColPic, RefPicList [1] [refIdxL1A 1 ] ) is equal to 0.
  • the location (xColCb, yColCb) of the collocated block inside ColPic is derived as follows.
  • subpic_treated_as_pic_flag [SubPicIdx] is equal to 1, the following applies:
  • xSbInt L , ySbInt L a luma location in full-sample units (xSbInt L , ySbInt L ) specifying the top-left sample of the bounding block for reference sample padding relative to the top-left luma sample of the reference picture
  • a luma location (xSb, ySb) specifying the top-left sample of the current subblock relative to the top-left luma sample of the current picture
  • Output of this process is a predicted luma sample value predSampleLX L
  • variable shift1 is set equal to Min (4, BitDepth Y -8)
  • variable shift2 is set equal to 6
  • variable shift3 is set equal to Max (2, 14-BitDepth Y ) .
  • variable picW is set equal to pic_width_in_luma_samples and the variable picH is set equal to pic_height_in_luma_samples.
  • the luma interpolation filter coefficients f L [p] for each 1/16 fractional sample position p equal to xFrac L or yFrac L are derived as follows:
  • the luma interpolation filter coefficients f L [p] are specified in Table 8-11 depending on hpelIfIdx.
  • subpic_treated_as_pic_flag [SubPicIdx] is equal to 1, the following applies:
  • xInt i Clip3 (SubPicLeftBoundaryPos, SubPicRightBoundaryPos, xInt L +i-3) (8-771)
  • yInt i Clip3 (SubPicTopBoundaryPos, SubPicBotBoundaryPos, yInt L +i-3) (8-772)
  • chroma location in full-sample units (xSbIntC, ySbIntC) specifying the top-left sample of the bounding block for reference sample padding relative to the top-left chroma sample of the reference picture
  • Output of this process is a predicted chroma sample value predSampleLX C
  • variable shift1 is set equal to Min (4, BitDepth C -8)
  • variable shift2 is set equal to 6
  • variable shift3 is set equal to Max (2, 14-BitDepth C ) .
  • the variable picW C is set equal to pic_width_in_luma_samples/SubWidthC and the variable picH C is set equal to pic_height_in_luma_samples/SubHeightC.
  • chroma interpolation filter coefficients f C [p] for each 1/32 fractional sample position p equal to xFrac C or yFrac C are specified in Table 8-13.
  • variable xOffset is set equal to (sps_ref_wraparound_offset_minus1+1) *MinCbSizeY) /SubWidthC.
  • subpic_treated_as_pic_flag [SubPicIdx] is equal to 1, the following applies:
  • xInt i Clip3 (SubPicLeftBoundaryPos/SubWidthC, SubPicRightBoundaryPos/SubWidthC, xInt L +i) (8-785)
  • yInt i Clip3 (SubPicTopBoundaryPos/SubHeightC, SubPicBotBoundaryPos/SubHeightC, yInt L +i) (8-786)
  • JCTVC-AI0023 proposes an encoder-only temporal filter.
  • the filtering is done at the encoder side as a pre-processing step.
  • Source pictures before and after the selected picture to encode are read and a block based motion compensation method relative to the selected picture is applied on those source pictures.
  • Samples in the selected picture are temporally filtered using sample values after motion compensation.
  • the overall filter strength is set depending on the temporal sub layer of the selected picture as well as the QP. Only pictures at temporal sub layers 0 and 1 are filtered and pictures of layer 0 are filter by a stronger filter than pictures of layer 1.
  • the per sample filter strength is adjusted depending on the difference between the sample value in the selected picture and the co-located samples in motion compensated pictures so that small differences between a motion compensated picture and the selected picture are filtered more strongly than larger differences.
  • a temporal filter is introduced directly after reading picture and before encoding. Below are the steps described in more detail.
  • Step 1 Pictures are read by the encoder
  • the overall filter strength, is set according to the equation below for RA.
  • n is the number of pictures read.
  • Step 3 Two pictures before and/or after the selected picture (referred to as original picture further down) are read. In the edge cases e.g. if is the first picture or close to the last picture, only the available pictures are read.
  • Step 4 Motion of the read pictures before and after, relative to the original picture is estimated per 8x8 picture block.
  • L0, L1 and L2 are illustrated in FIG. 2.
  • Subsampled pictures are generated by averaging each 2x2 block for all read pictures and the original picture, i.e. L1 in Figure 1.
  • L2 is derived from L1 using the same subsampling method.
  • FIG. 2 shows examples of different layers of the hierarchical motion estimation.
  • L0 is the original resolution.
  • L1 is a subsampled version of L0.
  • L2 is a subsampled version of L1.
  • motion estimation is done for each 16x16 block in L2.
  • the squared difference is calculated for each selected motion vector and the motion vector corresponding to the smallest difference is selected.
  • the selected motion vector is then used as initial value when estimating the motion in L1.
  • the same is done for estimating motion in L0.
  • subpixel motion is estimated for each 8x8 block by using an interpolation filter on L0.
  • VTM 6-tap interpolation filter was used:
  • Step 5 Motion compensation is applied on the pictures before and after the original picture according to the best matching motion for each block. I. e. so that the sample coordinates of the original picture in each block have the best matching coordinates in the referenced pictures.
  • Step 6 The samples of the processed one by one for the luma and chroma channels as described in the following steps.
  • Step 7 The new sample value, I n , is calculated using the following formula.
  • I o is the sample value of the original sample
  • I r (i) is the intensity of the corresponding sample of motion compensated picture i
  • w r (i, a) is the weight of motion compensated picture i when the number of available motion compensated pictures is a.
  • the weights, w r (i, a) is defined as follows:
  • weights, w r (i, a) is defined as follows:
  • Step 8 The filter is applied for the current sample.
  • the resulting sample value is stored separately.
  • Step 9 The filtered picture is encoded.
  • a picture is divided into one or more tile rows and one or more tile columns.
  • a tile is a sequence of CTUs that covers a rectangular region of a picture.
  • a tile is divided into one or more bricks, each of which consisting of a number of CTU rows within the tile.
  • a tile that is not partitioned into multiple bricks is also referred to as a brick.
  • a brick that is a true subset of a tile is not referred to as a tile.
  • a slice either contains a number of tiles of a picture or a number of bricks of a tile.
  • a subpicture contains one or more slices that collectively cover a rectangular region of a picture.
  • a slice contains a sequence of tiles in a tile raster scan of a picture.
  • a slice contains a number of bricks of a picture that collectively form a rectangular region of the picture. The bricks within a rectangular slice are in the order of brick raster scan of the slice.
  • FIG. 3 shows an example of raster-scan slice partitioning of a picture, where the picture is divided into 12 tiles and 3 raster-scan slices.
  • FIG. 4 shows an example of rectangular slice partitioning of a picture, where the picture is divided into 24 tiles (6 tile columns and 4 tile rows) and 9 rectangular slices.
  • FIG. 5 shows an example of a picture partitioned into tiles, bricks, and rectangular slices, where the picture is divided into 4 tiles (2 tile columns and 2 tile rows) , 11 bricks (the top-left tile contains 1 brick, the top-right tile contains 5 bricks, the bottom-left tile contains 2 bricks, and the bottom-right tile contain 3 bricks) , and 4 rectangular slices.
  • single_tile_in_pic_flag 1 specifies that there is only one tile in each picture referring to the PPS.
  • single_tile_in_pic_flag 0 specifies that there is more than one tile in each picture referring to the PPS.
  • uniform_tile_spacing_flag 1 specifies that tile column boundaries and likewise tile row boundaries are distributed uniformly across the picture and signalled using the syntax elements tile_cols_width_minus1 and tile_rows_height_minus1.
  • uniform_tile_spacing_flag 0 specifies that tile column boundaries and likewise tile row boundaries may or may not be distributed uniformly across the picture and signalled using the syntax elements num_tile_columns_minus1 and num_tile_rows_minus1 and a list of syntax element pairs tile_column_width_minus1 [i] and tile_row_height_minus1 [i] .
  • the value of uniform_tile_spacing_flag is inferred to be equal to 1.
  • tile_cols_width_minus1 plus 1 specifies the width of the tile columns excluding the right-most tile column of the picture in units of CTBs when uniform_tile_spacing_flag is equal to 1.
  • the value of tile_cols_width_minus1 shall be in the range of 0 to PicWidthInCtbsY-1, inclusive. When not present, the value of tile_cols_width_minus1 is inferred to be equal to PicWidthInCtbsY-1.
  • tile_rows_height_minus1 plus 1 specifies the height of the tile rows excluding the bottom tile row of the picture in units of CTBs when uniform_tile_spacing_flag is equal to 1.
  • the value of tile_rows_height_minus1 shall be in the range of 0 to PicHeightInCtbsY-1, inclusive. When not present, the value of tile_rows_height_minus1 is inferred to be equal to PicHeightInCtbsY-1.
  • num_tile_columns_minus1 plus 1 specifies the number of tile columns partitioning the picture when uniform_tile_spacing_flag is equal to 0.
  • the value of num_tile_columns_minus1 shall be in the range of 0 to PicWidthInCtbsY -1, inclusive. If single_tile_in_pic_flag is equal to 1, the value of num_tile_columns_minus1 is inferred to be equal to 0. Otherwise, when uniform_tile_spacing_flag is equal to 1, the value of num_tile_columns_minus1 is inferred as specified in clause 6.5.1.
  • num_tile_rows_minus1 plus 1 specifies the number of tile rows partitioning the picture when uniform_tile_spacing_flag is equal to 0.
  • the value of num_tile_rows_minus1 shall be in the range of 0 to PicHeightInCtbsY -1, inclusive. If single_tile_in_pic_flag is equal to 1, the value of num_tile_rows_minus1 is inferred to be equal to 0. Otherwise, when uniform_tile_spacing_flag is equal to 1, the value of num_tile_rows_minus1 is inferred as specified in clause 6.5.1.
  • the variable NumTilesInPic is set equal to (num_tile_columns_minus1+1) * (num_tile_rows_minus1+1) .
  • tile_column_width_minus1 [i] plus 1 specifies the width of the i-th tile column in units of CTBs.
  • tile_row_height_minus1 [i] plus 1 specifies the height of the i-th tile row in units of CTBs.
  • brick_splitting_present_flag 1 specifies that one or more tiles of pictures referring to the PPS may be divided into two or more bricks.
  • brick_splitting_present_flag 0 specifies that no tiles of pictures referring to the PPS are divided into two or more bricks.
  • num_tiles_in_pic_minus1 plus 1 specifies the number of tiles in each picture referring to the PPS.
  • the value of num_tiles_in_pic_minus1 shall be equal to NumTilesInPic–1.
  • the value of num_tiles_in_pic_minus1 is inferred to be equal to NumTilesInPic-1.
  • brick_split_flag [i] 1 specifies that the i-th tile is divided into two or more bricks.
  • brick_split_flag [i] 0 specifies that the i-th tile is not divided into two or more bricks.
  • the value of brick_split_flag [i] is inferred to be equal to 0.
  • uniform_brick_spacing_flag [i] 1 specifies that horizontal brick boundaries are distributed uniformly across the i-th tile and signalled using the syntax element brick_height_minus1 [i] .
  • uniform_brick_spacing_flag [i] 0 specifies that horizontal brick boundaries may or may not be distributed uniformly across i-th tile and signalled using the syntax element num_brick_rows_minus2 [i] and a list of syntax elements brick_row_height_minus1 [i] [j] .
  • the value of uniform_brick_spacing_flag [i] is inferred to be equal to 1.
  • brick_height_minus1 [i] plus 1 specifies the height of the brick rows excluding the bottom brick in the i-th tile in units of CTBs when uniform_brick_spacing_flag [i] is equal to 1.
  • the value of brick_height_minus1 shall be in the range of 0 to RowHeight [i] -2, inclusive.
  • the value of brick_height_minus1 [i] is inferred to be equal to RowHeight [i] -1.
  • num_brick_rows_minus2 [i] plus 2 specifies the number of bricks partitioning the i-th tile when uniform_brick_spacing_flag [i] is equal to 0.
  • the value of num_brick_rows_minus2 [i] shall be in the range of 0 to RowHeight [i] -2, inclusive. If brick_split_flag [i] is equal to 0, the value of num_brick_rows_minus2 [i] is inferred to be equal to -1. Otherwise, when uniform_brick_spacing_flag [i] is equal to 1, the value of num_brick_rows_minus2 [i] is inferred as specified in 6.5.1.
  • brick_row_height_minus1 [i] [j] plus 1 specifies the height of the j-th brick in the i-th tile in units of CTBs when uniform_tile_spacing_flag is equal to 0.
  • single_brick_per_slice_flag 1 specifies that each slice that refers to this PPS includes one brick.
  • single_brick_per_slice_flag 0 specifies that a slice that refers to this PPS may include more than one brick.
  • the value of single_brick_per_slice_flag is inferred to be equal to 1.
  • rect_slice_flag 0 specifies that bricks within each slice are in raster scan order and the slice information is not signalled in PPS.
  • rect_slice_flag 1 specifies that bricks within each slice cover a rectangular region of the picture and the slice information is signalled in the PPS.
  • brick_splitting_present_flag 1
  • the value of rect_slice_flag shall be equal to 1.
  • rect_slice_flag is inferred to be equal to 1.
  • num_slices_in_pic_minus1 plus 1 specifies the number of slices in each picture referring to the PPS.
  • the value of num_slices_in_pic_minus1 shall be in the range of 0 to NumBricksInPic-1, inclusive.
  • single_brick_per_slice_flag is equal to 1
  • the value of num_slices_in_pic_minus1 is inferred to be equal to NumBricksInPic-1.
  • bottom_right_brick_idx_length_minus1 plus 1 specifies the number of bits used to represent the syntax element bottom_right_brick_idx_delta [i] .
  • the value of bottom_right_brick_idx_length_minus1 shall be in the range of 0 to Ceil (Log2 (NumBricksInPic) ) -1, inclusive.
  • bottom_right_brick_idx_delta [i] when i is greater than 0 specifies the difference between the brick index of the brick located at the bottom-right corner of the i-th slice and and the brick index of the bottom-right corner of the (i–1) -th slice.
  • bottom_right_brick_idx_delta [0] specifies the brick index of the bottom right corner of the 0-th slice.
  • the value of the BottomRightBrickIdx [num_slices_in_pic_minus1] is inferred to be equal to NumBricksInPic–1.
  • the length of the bottom_right_brick_idx_delta [i] syntax element is bottom_right_brick_idx_length_minus1+1 bits.
  • brick_idx_delta_sign_flag [i] 1 indicates a positive sign for bottom_right_brick_idx_delta [i] .
  • sign_bottom_right_brick_idx_delta [i] 0 indicates a negative sign for bottom_right_brick_idx_delta [i] .
  • a slice shall include either a number of complete tiles or only a consecutive sequence of complete bricks of one tile.
  • the variable TopLeftBrickIdx [i] , BottomRightBrickIdx [i] , NumBricksInSlice [i] and BricksToSliceMap [j] which specify the brick index of the brick located at the top left corner of the i-th slice, the brick index of the brick located at the bottom right corner of the i-th slice, the number of bricks in the i-th slice and the mapping of bricks to slices, are derived as follows:
  • slice_pic_parameter_set_id the value of each of the slice header syntax elements slice_pic_parameter_set_id, non_reference_picture_flag, colour_plane_id, slice_pic_order_cnt_lsb, recovery_poc_cnt, no_output_of_prior_pics_flag, pic_output_flag, and slice_temporal_mvp_enabled_flag shall be the same in all slice headers of a coded picture.
  • the variable CuQpDeltaVal specifying the difference between a luma quantization parameter for the coding unit containing cu_qp_delta_abs and its prediction.
  • the variables CuQpOffset Cb , CuQpOffset Cr , and CuQpOffset CbCr specifying values to be used when determining the respective values of the Qp′ Cb , Qp′ Cr , and Qp′ CbCr quantization parameters for the coding unit containing cu_chroma_qp_offset_flag, are all set equal to 0.
  • slice_pic_parameter_set_id specifies the value of pps_pic_parameter_set_id for the PPS in use.
  • the value of slice_pic_parameter_set_id shall be in the range of 0 to 63, inclusive.
  • TemporalId of the current picture shall be greater than or equal to the value of TemporalId of the PPS that has pps_pic_parameter_set_id equal to slice_pic_parameter_set_id.
  • slice_address specifies the slice address of the slice. When not present, the value of slice_address is inferred to be equal to 0.
  • the slice address is the brick ID as specified by Equation (7-59) .
  • slice_address is Ceil (Log2 (NumBricksInPic) ) bits.
  • slice_address shall be in the range of 0 to NumBricksInPic-1, inclusive.
  • the slice address is the slice ID of the slice.
  • slice_address is signalled_slice_id_length_minus1+1 bits.
  • slice_address shall be in the range of 0 to num_slices_in_pic_minus1, inclusive. Otherwise, the value of slice_address shall be in the range of 0 to 2 (signalled_slice_id_length_minus1+1) -1, inclusive.
  • slice_address shall not be equal to the value of slice_address of any other coded slice NAL unit of the same coded picture.
  • the shapes of the slices of a picture shall be such that each brick, when decoded, shall have its entire left boundary and entire top boundary consisting of a picture boundary or consisting of boundaries of previously decoded brick (s) .
  • num_bricks_in_slice_minus1 when present, specifies the number of bricks in the slice minus 1.
  • the value of num_bricks_in_slice_minus1 shall be in the range of 0 to NumBricksInPic-1, inclusive.
  • SubPicIdx SubPicLeftBoundaryPos
  • SubPicTopBoundaryPos SubPicRightBoundaryPos
  • SubPicBotBoundaryPos are derived as follows:
  • subpics_present_flag 1 indicates that subpicture parameters are present in the present in the SPS RBSP syntax.
  • subpics_present_flag 0 indicates that subpicture parameters are not present in the present in the SPS RBSP syntax.
  • sps_num_subpics_minus1 plus 1 specifies the number of subpictures. sps_num_subpics_minus1 shall be in the range of 0 to 254. When not present, the value of sps_num_subpics_minus1 is inferred to be equal to 0.
  • subpic_ctu_top_left_x [i] specifies horizontal position of top left CTU of i-th subpicture in unit of CtbSizeY.
  • the length of the syntax element is Ceil (Log2 (pic_width_max_in_luma_samples/CtbSizeY) ) bits.
  • the value of subpic_ctu_top_left_x [i] is inferred to be equal to 0.
  • subpic_ctu_top_left_y [i] specifies vertical position of top left CTU of i-th subpicture in unit of CtbSizeY.
  • the length of the syntax element is Ceil (Log2 (pic_height_max_in_luma_samples/CtbSizeY) ) bits.
  • the value of subpic_ctu_top_left_y [i] is inferred to be equal to 0.
  • subpic_width_minus1 [i] plus 1 specifies the width of the i-th subpicture in units of CtbSizeY.
  • the length of the syntax element is Ceil (Log2 (pic_width_max_in_luma_samples/CtbSizeY) ) bits.
  • the value of subpic_width_minus1 [i] is inferred to be equal to Ceil (pic_width_max_in_luma_samples/CtbSizeY) -1.
  • subpic_height_minus1 [i] plus 1 specifies the height of the i-th subpicture in units of CtbSizeY.
  • the length of the syntax element is Ceil (Log2 (pic_height_max_in_luma_samples/CtbSizeY) ) bits.
  • the value of subpic_height_minus1 [i] is inferred to be equal to Ceil (pic_height_max_in_luma_samples/CtbSizeY) -1.
  • subpic_treated_as_pic_flag [i] 1 specifies that the i-th subpicture of each coded picture in the CVS is treated as a picture in the decoding process excluding in-loop filtering operations.
  • subpic_treated_as_pic_flag [i] 0 specifies that the i-th subpicture of each coded picture in the CVS is not treated as a picture in the decoding process excluding in-loop filtering operations.
  • the value of subpic_treated_as_pic_flag [i] is inferred to be equal to 0.
  • loop_filter_across_subpic_enabled_flag [i] 1 specifies that in-loop filtering operations may be performed across the boundaries of the i-th subpicture in each coded picture in the CVS.
  • loop_filter_across_subpic_enabled_flag [i] 0 specifies that in-loop filtering operations are not performed across the boundaries of the i-th subpicture in each coded picture in the CVS.
  • the value of loop_filter_across_subpic_enabled_pic_flag [i] is inferred to be equal to 1. It is a requirement of bitstream conformance that the following constraints apply:
  • any coded NAL unit of subPicA shall succeed any coded NAL unit of subPicB in decoding order.
  • each subpicture when decoded, shall have its entire left boundary and entire top boundary consisting of picture boundaries or consisting of boundaries of previously decoded subpictures.
  • sps_subpic_id_present_flag 1 specifies that subpicture Id mapping is present in the SPS.
  • sps_subpic_id_present_flag 0 specifies that subpicture Id mapping is not present in the SPS.
  • sps_subpic_id_signalling_present_flag 1 specifies that subpicture Id mapping is signalled in the SPS.
  • sps_subpic_id_signalling_present_flag 0 specifies that subpicture Id mapping is not signalled in the SPS.
  • the value of sps_subpic_id_signalling_present_flag is inferred to be equal to 0.
  • sps_subpic_id_len_minus1 plus 1 specifies the number of bits used to represent the syntax element sps_subpic_id [i] .
  • the value of sps_subpic_id_len_minus1 shall be in the range of 0 to 15, inclusive.
  • sps_subpic_id [i] specifies that subpicture Id of the i-th subpicture.
  • the length of the sps_subpic_id [i] syntax element is sps_subpic_id_len_minus1+1 bits.
  • ph_pic_parameter_set_id specifies the value of pps_pic_parameter_set_id for the PPS in use.
  • the value of ph_pic_parameter_set_id shall be in the range of 0 to 63, inclusive.
  • TemporalId of the picture header shall be greater than or equal to the value of TemporalId of the PPS that has pps_pic_parameter_set_id equal to ph_pic_parameter_set_id.
  • ph_subpic_id_signalling_present_flag 1 specifies that subpicture Id mapping is signalled in the picture header.
  • ph_subpic_id_signalling_present_flag 0 specifies that subpicture Id mapping is not signalled in the picture header.
  • ph_subpic_id_len_minus1 plus 1 specifies the number of bits used to represent the syntax element ph_subpic_id [i] .
  • the value of pic_subpic_id_len_minus1 shall be in the range of 0 to 15, inclusive. It is a requirement of bitstream conformance that the value of ph_subpic_id_len_minus1 shall be the same for all picture headers that are referred to by coded pictures in a CVS.
  • ph_subpic_id [i] specifies that subpicture Id of the i-th subpicture.
  • the length of the ph_subpic_id [i] syntax element is ph_subpic_id_len_minus1+1 bits.
  • the list SubpicIdList [i] is derived as follows:
  • Inputs to this process are the reconstructed picture prior to deblocking, i.e., the array recPicture L and, when ChromaArrayType is not equal to 0, the arrays recPicture Cb and recPicture Cr .
  • Outputs of this process are the modified reconstructed picture after deblocking, i.e., the array recPicture L and, when ChromaArrayType is not equal to 0, the arrays recPicture Cb and recPicture Cr .
  • the vertical edges in a picture are filtered first. Then the horizontal edges in a picture are filtered with samples modified by the vertical edge filtering process as input.
  • the vertical and horizontal edges in the CTBs of each CTU are processed separately on a coding unit basis.
  • the vertical edges of the coding blocks in a coding unit are filtered starting with the edge on the left-hand side of the coding blocks proceeding through the edges towards the right-hand side of the coding blocks in their geometrical order.
  • the horizontal edges of the coding blocks in a coding unit are filtered starting with the edge on the top of the coding blocks proceeding through the edges towards the bottom of the coding blocks in their geometrical order.
  • the filtering process is specified on a picture basis in this Specification, the filtering process can be implemented on a coding unit basis with an equivalent result, provided the decoder properly accounts for the processing dependency order so as to produce the same output values.
  • the deblocking filter process is applied to all coding subblock edges and transform block edges of a picture, except the following types of edges:
  • variable treeType specifying whether the luma (DUAL_TREE_LUMA) or chroma components (DUAL_TREE_CHROMA) are currently processed
  • ChromaArrayType is not equal to 0 and treeType is equal to DUAL_TREE_CHROMA, the arrays recPicture Cb and recPicture Cr ,
  • variable edgeType specifying whether a vertical (EDGE_VER) or a horizontal (EDGE_HOR) edge is filtered.
  • Outputs of this process are the modified reconstructed picture after deblocking, i.e:
  • ChromaArrayType is not equal to 0 and treeType is equal to DUAL_TREE_CHROMA, the arrays recPicture Cb and recPicture Cr .
  • edges are filtered by the following ordered steps:
  • variable filterEdgeFlag is derived as follows:
  • edgeType is equal to EDGE_VER and one or more of the following conditions are true, filterEdgeFlag is set equal to 0:
  • the left boundary of the current coding block is the left boundary of the picture.
  • the left boundary of the current coding block is the left or right boundary of the subpicture and loop_filter_across_subpic_enabled_flag [SubPicIdx] is equal to 0.
  • the left boundary of the current coding block is the left boundary of the tile and loop_filter_across_tiles_enabled_flag is equal to 0.
  • the left boundary of the current coding block is the left boundary of the slice and loop_filter_across_slices_enabled_flag is equal to 0.
  • the left boundary of the current coding block is one of the vertical virtual boundaries of the picture and VirtualBoundariesDisabledFlag is equal to 1.
  • variable filterEdgeFlag is set equal to 0:
  • the top boundary of the current luma coding block is the top boundary of the picture.
  • the top boundary of the current coding block is the top or bottom boundary of the subpicture and loop_filter_across_subpic_enabled_flag [SubPicIdx] is equal to 0.
  • the top boundary of the current coding block is the top boundary of the tile and loop_filter_across_tiles_enabled_flag is equal to 0.
  • the top boundary of the current coding block is the top boundary of the slice and loop_filter_across_slices_enabled_flag is equal to 0.
  • the top boundary of the current coding block is one of the horizontal virtual boundaries of the picture and VirtualBoundariesDisabledFlag is equal to 1.
  • filterEdgeFlag is set equal to 1.
  • TPM triangular Prediction Mode
  • HMVP History-based Motion vector Prediction
  • VVC maintains a table of motion information to be used for motion vector prediction.
  • the table is updated after decoding a inter-coded block, but it is not updated if the inter-coded block is TPM-coded.
  • GEO as proposed in JVET-P0884 is an extension of TPM.
  • a block can be divided by a straight-line into two partitions, which may be or may not be triangles.
  • ALF Adaptive Loop-Filter
  • Virtual Boundary (VB) is adopted in VVC to make ALF friendly to hardware design.
  • VB Virtual Boundary
  • ALF is conducted in an ALF processing unit bounded by two ALF virtual boundaries.
  • CC-ALF as proposed in JVET-P1008, filters the chroma samples by referring to the information of luma samples.
  • the subpicture level information SEI message contains information about the level that subpictures in the bitstream conform to when testing conformance of extracted bitstreams containing the subpictures according to Annex A.
  • a subpicture level information SEI message When a subpicture level information SEI message is present for any picture of a CLVS, a subpicture level information SEI message shall be present for the first picture of the CLVS.
  • the subpicture level information SEI message persists for the current layer in decoding order from the current picture until the end of the CLVS. All subpicture level information SEI messages that apply to the same CLVS shall have the same content.
  • sli_seq_parameter_set_id indicates and shall be equal to the sps_seq_parameter_set_id for the SPS that is referred to by the coded picture associated with the subpicture level information SEI message.
  • the value of sli_seq_parameter_set_id shall be equal to the value of pps_seq_parameter_set_id in the PPS referenced by the ph_pic_parameter_set_id of the PH of the coded picture associated with the subpicture level information SEI message.
  • subpic_treated_as_pic_flag [i] shall be equal to 1 for each value of i in the range of 0 to sps_num_subpics_minus1, inclusive.
  • num_ref_levels_minus1 plus 1 specifies the number of reference levels signalled for each of the sps_num_subpics_minus1+1 subpictures.
  • explicit_fraction_present_flag 1 specifies that the syntax elements ref_level_fraction_minus1 [i] are present.
  • explicit_fraction_present_flag 0 specifies that the syntax elements ref_level_fraction_minus1 [i] are not present.
  • ref_level_idc [i] indicates a level to which each subpicture conforms as specified in Annex A. Bitstreams shall not contain values of ref_level_idc other than those specified in Annex A. Other values of ref_level_idc [i] are reserved for future use by ITU-T
  • ref_level_fraction_minus1 [i] [j] plus 1 specifies the fraction of the level limits associated with ref_level_idc [i] that the j-th subpicture conforms to as specified in clause A. 4.1.
  • SubPicSizeY [j] is set equal to (subpic_width_minus1 [j] +1) * (subpic_height_minus1 [j] +1) .
  • ref_level_fraction_minus1 [i] [j] is inferred to be equal to Ceil (256*SubPicSizeY [j] ⁇ PicSizeInSamplesY*MaxLumaPs (general_level_idc) ⁇ MaxLumaPs (ref _level_idc [i] ) –1.
  • variable RefLevelFraction [i] [j] is set equal to ref_level_fraction_minus1 [i] [j] +1.
  • SubPicNumTileCols [j] and SubPicNumTileRows [j] are derived as follows:
  • SubPicCpbSizeVcl [i] [j] and SubPicCpbSizeNal [i] [j] are derived as follows:
  • SubPicCpbSizeVcl [i] [j] Floor (CpbVclFactor*MaxCPB*RefLevelFraction [i] [j] ⁇ 256) (D. 6)
  • SubPicCpbSizeNal [i] [j] Floor (CpbNalFactor*MaxCPB*RefLevelFraction [i] [j] ⁇ 256) (D. 7)
  • the resulting bitstream has a CpbSize (either indicated in the SPS or inferred) that is greater than or equal to SubPicCpbSizeVcl [i] [j] and SubPicCpbSizeNal [i] [j] .
  • bitstream conformance it is a requirement of bitstream conformance that the bitstreams resulting from extracting the j-th subpicture for j in the range of 0 to sps_num_subpics_minus1, inclusive, and conforming to a profile with general_tier_flag equal to 0 and level equal to ref_level_idc [i] for i in the range of 0 to num_ref_level_minus1, inclusive, shall obey the following constraints for each bitstream conformance test as specified in Annex C:
  • Ceil (256*SubPicSizeY [i] ⁇ RefLevelFraction [i] [j] ) shall be less than or equal to MaxLumaPs, where MaxLumaPs is specified in Table A. 1.
  • Ceil 256* (subpic_width_minus1 [i] +1) ⁇ RefLevelFraction [i] [j] ) shall be less than or equal to Sqrt (MaxLumaPs*8) .
  • Ceil 256* (subpic_height_minus1 [i] +1) ⁇ RefLevelFraction [i] [j] ) shall be less than or equal to Sqrt (MaxLumaPs*8) .
  • SubPicNumTileCols [j] shall be less than or equal to MaxTileCols and of SubPicNumTileRows [j] shall be less than or equal to MaxTileRows, where MaxTileCols and MaxTileRows are specified in Table A. 1.
  • the level information of the subpicture set is derived.
  • SubPicSetAccLevelFraction [i] for the total level fraction with respect to the reference level ref_level_idc [i] and the variables SubPicSetCpbSizeVcl [i] [j] and SubPicSetCpbSizeNal [i] [j] of the subpicture set, are derived as follows:
  • SubPicSetLevelIdc The value of the subpicture set sequence level indicator, SubPicSetLevelIdc, is derived as follows:
  • MaxTileCols and MaxTileRows are specified in Table A. 1 for ref_level_idc [i] .
  • SubPicSetLevelIdc shall obey the following constraints for each bitstream conformance test as specified in Annex C:
  • SubPicSetCpbSizeVcl [i] shall be less than or equal to CpbVclFactor *MaxCPB, where CpbVclFactor is specified in Table A. 3 and MaxCPB is specified in Table A. 1 in units of CpbVclFactor bits.
  • SubPicSetCpbSizeVcl [i] shall be less than or equal to CpbNalFactor *MaxCPB, where CpbNalFactor is specified in Table A. 3, and MaxCPB is specified in Table A. 1 in units of CpbNalFactor bits. MaxCPB
  • the resulting bitstream has a CpbSize (either indicated in the SPS or inferred) that is greater than or equal to SubPicCpbSizeVcl [i] [j] and SubPicSetCpbSizeNal [i] [j] .
  • a. TMVP in the affine constructed candidates may fetch a MV in the collocated picture out of the range of the current sub-picture.
  • the accessed reconstructed luma samples may be out of the range of the range of the current sub-picture.
  • the neighboring block may be out of the range of the current sub-picture, when deriving the luma intra prediction mode, reference samples for intra prediction, reference samples for CCLM, neighboring block availability for spatial neighboring candidates for merge/AMVP/CIIP/IBC/LMCS, quantization parameters, CABAC initialization process, ctxInc derivation using left and above syntax elements, and ctxIncfor the syntax element mtt_split_cu_vertical_flag.
  • the representation of subpicture may lead to subpicture with incomplete CTUs.
  • the CTU partitions and CU splitting process may need to consider incomplete CTUs.
  • the signaled syntax elements related to sub-picture may be arbitrarily large, which may cause an overflow problem.
  • sub-pictures may lead to non-rectangular sub-pictures.
  • the subpicture and subpicture grid is defined in units of 4 samples. And the length of syntax element is dependent on the picture height divided by 4. However, since the current pic_width_in_luma_samples and pic_height_in_luma_samples shall be an integer multiple of Max (8, MinCbSizeY) , the subpicture grid may need to be defined in units of 8 samples.
  • the SPS syntax, pic_width_max_in_luma_samples and pic_height_max_in_luma_samples may need to be restricted to be no smaller than 8.
  • the information could be inferred without signaling in some cases.
  • the IDs of two sub-pictures may be identical.
  • pic_width_max_in_luma_samples /CtbSizeY may be equal to 0, resulting in a meaningless Log2 () operation.
  • ID in PH is more preferable than in PPS, but less preferable than in SPS, which is inconsistent.
  • log2_transform_skip_max_size_minus2 in PPS is parsed depending on sps_transform_skip_enabled_flag in SPS, resulting in a parsing dependency.
  • loop_filter_across_subpic_enabled_flag for deblocking only consider the current sub-picture, without considering the neighbouring sub-picture.
  • sub-pictures are designed to provide a flexibility that regions at same positions in pictures of a sequences can be decoded or extracted independently.
  • the region may be under some special requirements. For example, it may be a Region of Interest (ROI) , which requires a high quality.
  • ROI Region of Interest
  • it may serve as a trace for fast skimming the video.
  • it may provide a low-resolution, low-complexity and low power-consuming bit-stream, which may be fed to a complexity-sensitive end user. All those applications may require that the region of a sub-picture should be encoded with a configuration different to other parts.
  • temporal filter is used to represent filters that require samples in other pictures (e.g., filters proposed in JCTVC-AI0023) .
  • Max (x, y) returns the larger one of x and y.
  • Min (x, y) returns the smaller one of x and y.
  • the position (named position RB) at which a temporal MV predictor is fetched in a picture to generate affine motion candidates must be in a required sub-picture, assuming the top-left corner coordinate of the required sub-picture is (xTL, yTL) and bottom-right coordinate of the required sub-picture is (xBR, yBR) .
  • the required sub-picture is the sub-picture covering the current block.
  • the temporal MV predictor is treated as unavailable.
  • position RB is out of the required sub-picture if x > xBR.
  • position RB is out of the required sub-picture if y > yBR.
  • position RB is out of the required sub-picture if x ⁇ xTL.
  • position RB is out of the required sub-picture if y ⁇ yTL.
  • position RB if outside of the required sub-picture, a replacement of RB is utilized.
  • the replacement position shall be in the required sub-picture.
  • position RB is clipped to be in the required sub-picture.
  • the position RB may be the bottom right position inside the corresponding block of current block in the collocated picture.
  • the proposed method may be utilized in other coding tools which require to access motion information from a picture different than the current picture.
  • whether the above methods are applied may depend on one or more syntax elements signaled in VPS/DPS/SPS/PPS/APS/slice header/tile group header.
  • the syntax element may be subpic_treated_as_pic_flag [SubPicIdx] , where SubPicIdx is the sub-picture index of sub-picture covering the current block.
  • the position (named position S) at which an integer sample is fetched in a reference not used in the interpolation process must be in a required sub-picture, assuming the top-left corner coordinate of the required sub-picture is (xTL, yTL) and the bottom-right coordinate of the required sub-picture is (xBR, yBR) .
  • the required sub-picture is the sub-picture covering the current block.
  • position S is out of the required sub-picture if x > xBR.
  • position S is out of the required sub-picture if y > yBR.
  • position S is out of the required sub-picture ifx ⁇ xTL.
  • position S is out of the required sub-picture if y ⁇ yTL.
  • position S is clipped to be in the required sub-picture.
  • whether position S must be in a required sub-picture may depend on one or more syntax elements signaled in VPS/DPS/SPS/PPS/APS/slice header/tile group header.
  • the syntax element may be subpic_treated_as_pic_flag [SubPicIdx] , where SubPicIdx is the sub-picture index of sub-picture covering the current block.
  • the fetched integer sample is used to generate gradients in BDOF and/or PORF.
  • the position (named position R) at which the reconstructed luma sample value is fetched may be in a required sub-picture, assuming the top-left corner coordinate of the required sub-picture is (xTL, yTL) and the bottom-right coordinate of the required sub-picture is (xBR, yBR) .
  • the required sub-picture is the sub-picture covering the current block.
  • position R is out of the required sub-picture if x > xBR.
  • position R is out of the required sub-picture if y > yBR.
  • position R is out of the required sub-picture if x ⁇ xTL.
  • position R is out of the required sub-picture if y ⁇ yTL.
  • position R is clipped to be in the required sub-picture.
  • whether position R must be in a required sub-picture may depend on one or more syntax elements signaled in VPS/DPS/SPS/PPS/APS/slice header/tile group header.
  • the syntax element may be subpic_treated_as_pic_flag [SubPicIdx] , where SubPicIdx is the sub-picture index of sub-picture covering the current block.
  • the fetched luma sample is used to derive the scaling factor for the chroma component (s) in LMCS.
  • the position (named position N) at which the picture boundary check for BT/TT/QT splitting, BT/TT/QT depth derivation, and/or the signaling of CU split flag must be in a required sub-picture, assuming the top-left corner coordinate of the required sub-picture is (xTL, yTL) and the bottom-right coordinate of the required sub-picture is (xBR, yBR) .
  • the required sub-picture is the sub-picture covering the current block.
  • position N is out of the required sub-picture if x > xBR.
  • position N is out of the required sub-picture if y > yBR.
  • position N is out of the required sub-picture if x ⁇ xTL.
  • position N is out of the required sub-picture if y ⁇ yTL.
  • position N is clipped to be in the required sub-picture.
  • whether position N must be in a required sub-picture (e.g. to do as claimed in 5.
  • a and/or 5.b) may depend on one or more syntax elements signaled in VPS/DPS/SPS/PPS/APS/slice header/tile group header.
  • the syntax element may be subpic_treated_as_pic_flag [SubPicIdx] , where SubPicIdx is the sub-picture index of sub-picture covering the current block.
  • History -based Motion Vector Prediction (HMVP) table may be reset before decoding a new sub-picture in one picture.
  • the HMVP table used for IBC coding may be reset
  • the HMVP table used for inter coding may be reset
  • the HMVP table used for intra coding may be reset
  • the width of each element of the subpicture identifier grid in units of N samples.
  • the height of each element of the subpicture identifier grid in units of N samples.
  • N is set to the width and/or height of CTU.
  • the picture width may need to be restricted to be no smaller than 8.
  • the picture height may need to be restricted to be no smaller than 8.
  • a conformance bitstream shall satisfy that sub-picture coding and Adaptive resolution conversion (ARC) /Dynamic resolution conversion (DRC) /Reference picture resampling (RPR) are disallowed to be enabled for one video unit (e.g., sequence) .
  • ARC sub-picture coding and Adaptive resolution conversion
  • DRC Dynamic resolution conversion
  • RPR Reference picture resampling
  • signaling of enabling sub-picture coding may be under the conditions of disallowing ARC/DRC/RPR.
  • subpicture_present_flag 1
  • pic_width_in_luma_samples for all pictures for which this SPS is active is equal to max_width_in_luma_samples.
  • sub-picture coding and ARC/DRC/RPR may be both enabled for one video unit (e.g., sequence) .
  • a conformance bitstream shall satisfy that the donwsampled sub-picture due to ARC/DRC/RPR shall still be in the form of K CTUs in width and M CTUs in height wherein K and M are both integers.
  • a conformance bitstream shall satisfy that for sub-pictures not located at picture boundaries (e.g., right boundary and/or bottom boundary) , the donwsampled sub-picture due to ARC/DRC/RPR shall still be in the form of K CTUs in width and M CTUs in height wherein K and M are both integers.
  • CTU sizes may be adaptively changed based on the picture resolution.
  • a max CTU size may be signaled in SPS. For each picture with less resolution, the CTU size may be changed accordingly based on the reduced resolution.
  • CTU size may be signaled in SPS and PPS, and/or sub-picture level.
  • syntax element subpic_grid_col_width_minus1 and subpic_grid_row_height_minus1 may be constrained.
  • subpic_grid_col_width_minus1 must be no larger (or must be smaller) than T1.
  • subpic_grid_row_height_minus1 must be no larger (or must be smaller) than T2.
  • subpic_grid_col_width_minus1 and/or subpic_grid_row_height_minus1 must follow the constraint such as bullet 3.a or 3. b.
  • T1 in 3. a and/or T2 in 3. b may depend on profiles/levels/tiers of a video coding standard.
  • T1 in 3. a may depend on the picture width.
  • T1 is equal to pic_width_max_in_luma_samples/4 or pic_width_max_in_luma_samples/4+Off. Off may be 1, 2, -1, -2, etc.
  • T2 in 3. b may depend on the picture width.
  • T2 is equal to pic_height_max_in_luma_samples/4 or pic_height_max_in_luma_samples /4-1+Off. Off may be 1, 2, -1, -2, etc.
  • a CTU cannot be covered by more than one sub-picture.
  • the unit of subpic_grid_col_width_minus1 may be the CTU width (such as 32, 64, 128) , instead of 4 as in VVC.
  • the sub-picture grid width should be (subpic_grid_col_width_minus1+1) *CTU width.
  • the unit of subpic_grid_col_height_minus1 may be the CTU height (such as 32, 64, 128) , instead of 4 as in VVC.
  • the sub-picture grid height should be (subpic_grid_col_height_minus1+1) *CTU height.
  • the constraint in a conformance bit-stream, the constraint must be satisfied if the sub-picture approach is applied.
  • the constraint in a conformance bit-stream, the constraint must be satisfied if the sub-picture approach is applied.
  • Sub-picture may only contain rectangular slices. For example, in a conformance bit-stream, the constraint must be satisfied if the sub-picture approach is applied.
  • the constraint in a conformance bit-stream, the constraint must be satisfied if the sub-picture approach is applied.
  • two sub-pictures may be overlapped with each other.
  • the constraint in a conformance bit-stream, the constraint must be satisfied if the sub-picture approach is applied.
  • one sample may not belong to any sub-picture.
  • one sample may belong to more than one sub-pictures.
  • the width and height of a sub-picture defined in the SPS mapped to a resolution presented in the same sequence should be integer multiple times of N (such as 8, 16, 32) luma samples.
  • sub-pictures may be defined for certain layer and may be mapped to other layers.
  • sub-pictures may be defined for the layer with the highest resolution in the sequence.
  • sub-pictures may be defined for the layer with the lowest resolution in the sequence.
  • Which layer the sub-pictures are defined for may be signaled in SPS/VPS/PPS/slice header.
  • all resolutions may be integer multiple of a given resolution.
  • the width and/or height of a sub-picture defined in the SPS may be integer multiple times (e.g., M) of the CTU size.
  • sub-pictures and different resolutions in a sequence may not be allowed simultaneously.
  • Sub-pictures may only apply to a certain layer (s)
  • sub-pictures defined in a SPS may only apply to the layer with the highest resolution in a sequence.
  • sub-pictures defined in a SPS may only apply to the layer with the lowest temporal id in a sequence.
  • Which layer (s) that sub-pictures may be applied to may be indicated by one or multiple syntax elements in SPS/VPS/PPS.
  • Which layer (s) that sub-picture cannot be applied to may be indicated by one or multiple syntax elements in SPS/VPS/PPS.
  • the position and/or dimensions of a sub-picture may be signaled without using subpic_grid_idx.
  • the top-left position of a sub-picture may be signaled.
  • the bottom-right position of a sub-picture may be signaled.
  • the width of sub-picture may be signaled.
  • the height of a sub-picture may be signaled.
  • temporal filter when performing the temporal filtering of a sample, only samples within the same sub-picture that the current sample belongs to may be used. The required samples may be in the same picture that the current sample belongs to or in other pictures.
  • whether to and/or how to apply a partitioning method may depend on whether the current block (or partition) crosses one or multiple boundary of a sub-picture.
  • the picture boundary handling method for partitioning in VVC may also be applied when a picture boundary is replaced by a sub-picture boundary.
  • whether to parse a syntax element (e.g. a flag) which represents a partitioning method (such as QT, horizontal BT, vertical BT, horizontal TT, vertical TT, or not split, etc. ) may depend on whether the current block (or partition) crosses one or multiple boundary of a sub-picture.
  • a sample in the second set is not in any sub-pictures.
  • the second set may be encoded/decoded based on the information of the first set.
  • a default value may be utilized to mark whether a sample/MxK sub-region belonging to the second set.
  • the default value may be set equal to (max_subpics_minus1 + K) wherein K is an integer greater than 1.
  • the default value may be assigned to subpic_grid_idx [i] [j] to indicate that grid belongs to the second set.
  • subpic_grid_idx [i] [j] cannot be larger than max_subpics_minus1.
  • the codeword to code subpic_grid_idx [i] [j] cannot be larger than max_subpics_minus1.
  • any integer number from 0 to max_subpics_minus1 must be equal to at least one subpic_grid_idx [i] [j] .
  • IBC virtual buffer may be reset before decoding a new sub-picture in one picture.
  • all the samples in the IBC virtual buffer may be reset to -1.
  • Palette entry list may be reset before decoding a new sub-picture in one picture.
  • PredictorPaletteSize may be set equal to 0 before decoding a new sub-picture in one picture.
  • Whether to signal the information of slices may depend on the number of tiles and/or the number of bricks.
  • num_slices_in_pic_minus1 is not signaled and inferred to be 0.
  • the information of slices may not be signaled.
  • the number of slices may be inferred to be one. And the slice covers the whole picture. In one example, if the number of bricks in a picture is one, single_brick_per_slice_flag is not signaled and inferred to be one.
  • single_brick_per_slice_flag must be one.
  • Whether to signal slice_address may be decoupled from whether slices are signaled to be rectangles (e.g. whether rect_slice_flag is equal to 0 or 1) .
  • slice_address may depend on the number of slices when slices are signaled to be rectangles.
  • Whether to signal num_bricks_in_slice_minus1 may depend on the slice_address and/or the number of bricks in the picture.
  • loop_filter_across_bricks_enabled_flag may depend on the number of tiles and/or the number of bricks.
  • loop_filter_across_bricks_enabled_flag is not signaled if the number of bricks is less than 2.
  • a basic unit block (BUB) with dimensions CW ⁇ CH is a rectangle region.
  • a BUB may be a Coding Tree Block (CTB) .
  • the number of sub-pictures (denoted as N) may be signaled.
  • subpics_present_flag is equal to 1
  • N minus d i.e., N-d
  • d is an integer such as 0, 1, or 2.
  • N-d may be coded with fixed length coding e.g. u (x) .
  • x may be a fixed number such as 8.
  • x or x-dx may be signaled before N-d is signaled, where dx is an integer such as 0, 1 or 2.
  • the signaled x may not be larger than a maximum value in a conformance bitstream.
  • x may be derived on-the-fly.
  • x may be derived as a function of the total number (denoted as M) of BUBs in the picture.
  • M total number of BUBs in the picture.
  • x Ceil (log2 (M+d0) ) +d1, where d0 and d1 are two integers, such as -2, -1, 0, 1, 2, etc.
  • N-d may be coded with a unary code or a truncated unary code.
  • the allowed maximum value of N-d may be a fixed number.
  • N-d Ceil (log2 (M+d0) ) +d1, where d0 and d1 are two integers, such as -2, -1, 0, 1, 2, etc.
  • a sub-picture may be signaled by indications of one or multiple its selected positions (e.g., top-left/top-right/bottom-left/bottom-right position) and/or its width and/or its height.
  • the top-left position of a subpicture may be signaled in the granularity of a basic unit block (BUB) with dimensions CW ⁇ CH.
  • BBU basic unit block
  • the column index (denoted as Col) in terms of BUBs of the top-left BUB of the sub-picture may be signaled.
  • Col -d may be signaled, where d is an integer such as 0, 1, or 2.
  • d may be equal to Col of a sub-picture previously coded, added by d1, where d1 is an integer such as -1, 0, or 1.
  • the row index (denoted as Row) in term of BUBs of the top-left BUB of the sub-picture may be signaled.
  • Row -d may be signaled, where d is an integer such as 0, 1, or 2.
  • d may be equal to Row of a sub-picture previously coded, added by d1, where d1 is an integer such as -1, 0, or 1.
  • the row/column index (denoted as Row) mentioned above may be represented in the Coding Tree Block (CTB) unit, e.g., the x or y coordinate relative to the top-left position of a picture may be divided by CTB size and signaled.
  • CTB Coding Tree Block
  • whether to signal the position of a sub-picture may depend on the sub-picture index.
  • the top-left position may be not signaled.
  • the top-left position may be inferred, e.g., to be (0, 0) .
  • the top-left position may be not signaled.
  • the top-left position may be inferred depending on information of sub-pictures previously signaled.
  • the width of a sub-picture may be signaled in the granularity of a BUB with dimensions CW ⁇ CH.
  • the number of columns of BUBs in the sub-picture (denoted as W) may be signaled.
  • W-d may be signaled, where d is an integer such as 0, 1, or 2.
  • d may be equal to W of a sub-picture previously coded, added by d1, where d1 is an integer such as -1, 0, or 1.
  • the height of a sub-picture may be signaled in the granularity of a BUB with dimensions CW ⁇ CH.
  • the number of rows of BUBs in the sub-picture (denoted as H) may be signaled.
  • H-d may be signaled, where d is an integer such as 0, 1, or 2.
  • d may be equal to H of a sub-picture previously coded, added by d1, where d1 is an integer such as -1, 0, or 1.
  • Col-d may be coded with fixed length coding e.g. u (x) .
  • x may be a fixed number such as 8.
  • x or x-dx may be signaled before Col-d is signaled, where dx is an integer such as 0, 1 or 2.
  • the signaled x may not be larger than a maximum value in a conformance bitstream.
  • x may be derived on-the-fly.
  • x may be derived as a function of the total number (denoted as M) of BUB columns in the picture.
  • x Ceil (log2 (M+d0) ) +d1, where d0 and d1 are two integers, such as -2, -1, 0, 1, 2, etc.
  • Row-d may be coded with fixed length coding e.g. u (x) .
  • x may be a fixed number such as 8.
  • x or x-dx may be signaled before Row-d is signaled, where dx is an integer such as 0, 1 or 2.
  • the signaled x may not be larger than a maximum value in a conformance bitstream.
  • x may be derived on-the-fly.
  • x may be derived as a function of the total number (denoted as M) of BUB rows in the picture.
  • x Ceil (log2 (M+d0) ) +d1, where d0 and d1 are two integers, such as -2, -1, 0, 1, 2, etc.
  • W-d may be coded with fixed length coding e.g. u (x) .
  • x may be a fixed number such as 8.
  • x or x-dx may be signaled before W-d is signaled, where dx is an integer such as 0, 1 or 2.
  • the signaled x may not be larger than a maximum value in a conformance bitstream.
  • x may be derived on-the-fly.
  • x may be derived as a function of the total number (denoted as M) of BUB columns in the picture.
  • x Ceil (log2 (M+d0) ) +d1, where d0 and d1 are two integers, such as -2, -1, 0, 1, 2, etc.
  • H-d may be coded with fixed length coding e.g. u (x) .
  • x may be a fixed number such as 8.
  • x or x-dx may be signaled before H-d is signaled, where dx is an integer such as 0, 1 or 2.
  • the signaled x may not be larger than a maximum value in a conformance bitstream.
  • x may be derived on-the-fly.
  • x may be derived as a function of the total number (denoted as M) of BUB rows in the picture.
  • x Ceil (log2 (M+d0) ) +d1, where d0 and d1 are two integers, such as -2, -1, 0, 1, 2, etc.
  • Col-d and/or Row-d may be signaled for all sub-pictures.
  • Col-d and/or Row-d may not be signaled for all sub-pictures.
  • Col-d and/or Row-d may not be signaled if the number of sub-pictures are less than 2. (equal to 1) .
  • Col-d and/or Row-d may not be signaled for the first sub-picture (e.g. with the sub-picture index (or subpicture ID) equal to 0) .
  • Col-d and/or Row-d may not be signaled for the last sub-picture (e.g. with the sub-picture index (or subpicture ID) equal to NumSubPics-1) .
  • W-d and/or H-d may be signaled for all sub-pictures.
  • W-d and/or H-d may not be signaled for all sub-pictures.
  • W-d and/or H-d may not be signaled if the number of sub-pictures are less than 2. (equal to 1) .
  • W-d and/or H-d may not be signaled for the last sub-picture (e.g. with the sub-picture index (or subpicture ID) equal to NumSubPics-1) .
  • a BUB may be a Coding Tree Block (CTB) .
  • CTB Coding Tree Block
  • the information of subpictures should be signaled after information of the CTB size (e.g. log2_ctu_size_minus5) has already been signaled.
  • subpic_treated_as_pic_flag [i] may not be signaled for each sub-pictures. Instead, one subpic_treated_as_pic_flag is signaled to control whether a sub-picture is treated as a picture for all sub-pictures.
  • loop_filter_across_subpic_enabled_flag [i] may not be signaled for each sub-pictures. Instead, one loop_filter_across_subpic_enabled_flag is signaled to control whether loop filters can be applied across sub-pictures for all sub-pictures.
  • subpic_treated_as_pic_flag [i] subpic_treated_as_pic_flag
  • loop_filter_across_subpic_enabled_flag [i] loop_filter_across_subpic_enabled_flag
  • subpic_treated_as_pic_flag [i] and/or loop_filter_across_subpic_enabled_flag [i] may not be signaled if the number of sub-pictures are less than 2. (equal to 1) .
  • RPR may be applied when sub-pictures are used.
  • the scaling ratio in RPR may be constrained to be a limited set when sub-pictures are used, such as ⁇ 1: 1, 1: 2 and/or 2: 1 ⁇ , or ⁇ 1: 1, 1: 2 and/or 2: 1, 1: 4 and/or 4: 1 ⁇ , ⁇ 1: 1, 1: 2 and/or 2: 1, 1: 4 and/or 4: 1, 1: 8 and/or 8: 1 ⁇ .
  • the CTB size of a picture A and the CTB size of a picture B may be different if the resolution of picture A and picture B are different.
  • SAW/SBW or SBW/SAW should be equal to Rw.
  • a subpiccutre index (or subpicture ID) may be signaled in the slice header, and the slice address is interrupted as the address in a sub-picture instead of the whole picture.
  • the subpicture ID of a first subpicture must be different to the subpicture ID of a second subpicture, if the first subpicture and the second subpicture are not the same sub-picture.
  • sps_subpic_id [i] it is a requirement in a conformance bitstream that sps_subpic_id [i] must be different from sps_subpic_id [j] , if i is not equal to j.
  • pps_subpic_id [i] it is a requirement in a conformance bitstream that pps_subpic_id [i] must be different from pps_subpic_id [j] , if i is not equal to j.
  • ph_subpic_id [i] it is a requirement in a conformance bitstream that ph_subpic_id [i] must be different from ph_subpic_id [j] , if i is not equal to j.
  • SubpicIdList [i] it is a requirement in a conformance bitstream that SubpicIdList [i] must be different from SubpicIdList [j] , if i is not equal to j.
  • a difference denoted as D [i] equal to X_subpic_id [i] -X_subpic_id [i -P] may be signaled.
  • X may be sps, pps or ph.
  • P is equal to 1.
  • iii For example, i > P.
  • D [i] must be larger than 0.
  • D [i] -1 may be signaled.
  • the length of a syntax element specifying the horizontal or vertical position of top left CTU may be derived to be Ceil (Log2 (SS) ) bits, wherein SS must be larger than 0.
  • SS (pic_width_max_in_luma_samples + RR) /CtbSizeY when the syntax element specifies the horizontal position of top left CTU (e.g. subpic_ctu_top_left_x) .
  • SS (pic_height_max_in_luma_samples + RR) /CtbSizeY when the syntax element specifies the vertical position of top left CTU (e.g. subpic_ctu_top_left_y) .
  • RR is a non-zero integer such as CtbSizeY-1.
  • the length of a syntax element specifying the horizontal or vertical position of top left CTU of a subpicture may be derived to be Ceil (Log2 (SS) ) bits, wherein SS must be larger than 0.
  • SS (pic_width_max_in_luma_samples + RR) /CtbSizeY when the syntax element specifies the horizontal position of top left CTU of a subpicture (e.g. subpic_ctu_top_left_x) .
  • SS (pic_height_max_in_luma_samples + RR) /CtbSizeY when the syntax element specifies the vertical position of top left CTU of a subpicture (e.g. subpic_ctu_top_left_y) .
  • RR is a non-zero integer such as CtbSizeY-1.
  • a syntax element (which may plus an offset P such as 1) specifying the width or height of a subpicture (e.g. subpic_width_minus1 or subpic_height_minus1) may be derived to be Ceil (Log2 (SS) ) -P, wherein SS must be larger than 0.
  • SS (pic_width_max_in_luma_samples + RR) /CtbSizeY when the syntax element specifies the default width (which may plus an offset P) of a subpicture (e.g. subpic_width_minus1) .
  • SS (pic_height_max_in_luma_samples + RR) /CtbSizeY when the syntax element specifies the default height (which may plus an offset P) of a subpicture (e.g. subpic_height_minus1) .
  • RR is a non-zero integer such as CtbSizeY-1.
  • the information of IDs of sub-pictures should be signaled at least in one of SPS, PPS, and the picture header if it is determined that the information should be signaled.
  • sps_subpic_id_signalling_present_flag pps_subpic_id_signalling_present_flag and ph_subpic_id_signalling_present_flag should be equal to 1 if sps_subpic_id_present_flag is equal to 1.
  • SubpicIdList [i] should be set equal to i+P, where P is an offset such as 0.
  • SubpicIdList [i] sps_subpic_id_present_flag? (sps_subpic_id_signalling_present_flag ? sps_subpic_id [i] : (ph_subpic_id_signalling_present_flag ? ph_subpic_id [i] : (pps_subpic_id_signalling_present_flag ? pps_subpic_id [i] : i) ) ) : i
  • the sub-picture IDs are set according to the information of sub-picture IDs signaled in SPS if they are signaled in SPS; Otherwise, the sub-picture IDs are set according to the information of sub-picture IDs signaled in PPS if they are signaled in PPS, Otherwise, the sub-picture IDs are set according to the information of sub-picture IDs signaled in the the picture header if they are signaled in the picture header.
  • An exemplary description is as below,
  • SubpicIdList [i] sps_subpic_id_present_flag? (sps_subpic_id_signalling_present_flag ? sps_subpic_id [i] : (pps_subpic_id_signalling_present_flag? pps_subpic_id [i] : (ph_subpic_id_signalling_present_flag? ph_subpic_id [i] : i) ) ) : i
  • the sub-picture IDs are set according to the information of sub-picture IDs signaled in the picture header if they are signaled in the picture header; Otherwise, the sub-picture IDs are set according to the information of sub-picture IDs signaled in PPS if they are signaled in PPS, Otherwise, the sub-picture IDs are set according to the information of sub-picture IDs signaled in the SPS if they are signaled in SPS.
  • An exemplary description is as below,
  • SubpicIdList [i] sps_subpic_id_present_flag? (ph_subpic_id_signalling_present_flag ? ph_subpic_id [i] : (pps_subpic_id_signalling_present_flag? pps_subpic_id [i] : (sps_subpic_id_signalling_present_flag? sps_subpic_id [i] : i) ) ) : i
  • the deblocking process on an edge E should depend on the determination of whether loop-filtering is allowed across the subpicture boundaries (e.g. determined by loop_filter_across_subpic_enabled_flag) on both sides (denoted as P-side and Q-side) of the edge.
  • P-side represents the side in the current block
  • Q-side represents the side in the neighbouring block, which may belong to a different sub-picture.
  • loop_filter_across_subpic_enabled_flag [P] 0/1 means that loop-filtering is disallowed/allowed across the subpicture boundaries of the subpicture containing P-side.
  • loop_filter_across_subpic_enabled_flag [Q] 0/1 means that loop-filtering is disallowed/allowed across the subpicture boundaries of the subpicture containing Q-side.
  • E is not filtered if loop_filter_across_subpic_enabled_flag [P] is equal to 0 or loop_filter_across_subpic_enabled_flag [Q] is equal to 0.
  • E is not filtered if loop_filter_across_subpic_enabled_flag [P] is equal to 0 and loop_filter_across_subpic_enabled_flag [Q] is equal to 0.
  • P-side of E is filtered if and only if loop_filter_across_subpic_enabled_flag [P] is equal 1.
  • Q-side of E is filtered if and only if loop_filter_across_subpic_enabled_flag [Q] is equal 1.
  • the signaling/parsing of a syntax element SE in PPS specifying the maximum block size used for transform skip should be decoupled from any syntax element in SPS (such as sps_transform_skip_enabled_flag) .
  • SE may be signaled in SPS, such as:
  • SE may be signaled in the picture header, such as:
  • Whether to and/or how to update the HMVP table (or named as list/storage/map etc. ) after decoding a first block may depend on whether the first block is coded with GEO.
  • the HMVP table may not be updated after decoding the first block if the first block is coded with GEO.
  • the HMVP table may be updated after decoding the first block if the first block is coded with GEO.
  • the HMVP table may be updated with the motion information of one partition divided by GEO.
  • the HMVP table may be updated with the motion information of multiple partitions divided by GEO
  • luma samples out of the current processing unit e.g., ALF processing unit bounded by two ALF virtual boundaries
  • ALF processing unit bounded by two ALF virtual boundaries e.g., ALF processing unit bounded by two ALF virtual boundaries
  • Padded luma samples out of the current processing unit may be used to filter the chroma samples in the corresponding processing unit.
  • Any padding method disclosed in this document may be used to pad the luma samples.
  • luma samples out of the current processing unit may be used to filter chroma samples in the corresponding processing unit.
  • a set of parameters controlling the coding behavior of a sub-picture may be signaled associated with the sub-picture. That is, for each sub-picture, a set of parameters may be signalled.
  • the set of parameters may comprise:
  • QP Quantization Parameter
  • delta QP for the luma component in the sub-picture for inter and/or intra slices/picture.
  • QP Quantization Parameter
  • delta QP for chroma components in the sub-picture for inter and/or intra slices/picture.
  • BT Maximum/Minimum Binary-Tree
  • BT Maximum/Minimum Binary-Tree
  • TT Maximum/Minimum Ternary-Tree
  • TT Ternary-Tree
  • Controls for coding tools, comprising: (The abbreviations can be found in JVET-P2001-v14) .
  • CCLM collocated chroma control
  • One flag may be firstly signaled to indicate whether all sub-pictures share the same parameters.
  • Predictive coding of parameters among different subpictures may be applied.
  • the differences of two values of the same syntax element for two subpictures may be coded.
  • a default set of parameters may be firstly signaled. Then the differences compared to the default values may be further signalled.
  • one flag may be firstly signaled to indicate whether the set of parameters of all subpictures are identical to those in the default set.
  • the set of parameters controlling the coding behavior of a sub-picture may be signaled in SPS or PPS or picture header.
  • the set of parameters controlling the coding behavior of a sub-picture may be signaled in a SEI message (such as the subpicture level information SEI message defined in JVET-P2001-v14) or a VUI message.
  • a SEI message such as the subpicture level information SEI message defined in JVET-P2001-v14
  • VUI message such as the subpicture level information SEI message defined in JVET-P2001-v14
  • the set of parameters controlling the coding behavior of a sub-picture may be signaled associated with the sub-picture ID.
  • a video unit (named SPPS, Sub-Picture Parameter Set) , different to VPS/SPS/PPS/picture header/slice header, comprising the set of parameters controlling the coding behavior of a sub-picture, may be signaled.
  • SPPS Sub-Picture Parameter Set
  • VPS/SPS/PPS/picture header/slice header comprising the set of parameters controlling the coding behavior of a sub-picture
  • a SPPS_index is signaled associated with a SPPS.
  • a SPPS_index is signaled for a sub-picture to indicate the SPPS associated with sub-picture.
  • a first control parameter in the set of parameters controlling a coding behavior of a sub-picture may overwrite or be overwritten by a second control parameter out of the set of parameters but controlling the same coding behavior.
  • the on/off control flag for a coding tool such as BDOF in the set of parameters of a sub-picture may overwrite or be overwritten by the on/off control flag for the coding tool out of the set of parameters.
  • the second control parameter out of the set of parameters may be in VPS/SPS/PPS/picture header/slice header.
  • the syntax elements associated with a slice/tile/brick/subpicture are dependent on the parameters associated with a subpicture containing the current slice, instead of being dependent on the parameters associated with a picture/sequence.
  • a first control parameter in the set of parameters controlling a coding behavior of a sub-picture must be the same to a second control parameter out of the set of parameters but controlling the same coding behavior.
  • a first flag is signalled in the SPS, one per each sub-picture, and the first flag specifies whether a general_constraint_info () syntax structure is signalled for the sub-picture associated with the first flag.
  • the general_constraint_info () syntax structure indicates tools that are not applied for the sub-picture across the CLVS.
  • a general_constraint_info () syntax structure is signalled for each sub-picture.
  • a second flag is signalled in the SPS, just once, and the second flag specifies whether the first flag is present or absent in the SPS for each sub-picture.
  • an SEI message or some VUI parameter are specified to indicate that certain coding tools are not applied or applied in a specific way for a set of one or more subpictures (i.e., for the coded slices of the set of subpictures) in the CLVS, such that when the set of subpictures are extracted and decoded, e.g., decoded by a mobile device, the decoding complexity is relatively low and consequently power consumption for the decoding is relatively low.
  • the same information is sginalled in the DPS, VPS, SPS, or a standalone NAL unit.
  • Embodiment 1 sub-picture constraint on affine constructed merge candidates (Solution 1)
  • JVET-O2001-v14 The working draft specified in JVET-O2001-v14 may be changed as below.
  • a luma location (xCb, yCb) specifying the top-left sample of the current luma coding block relative to the top-left luma sample of the current picture
  • the fourth (collocated bottom-right) control point motion vector cpMvLXCorner [3] , reference index refIdxLXCorner [3] , prediction list utilization flag predFlagLXCorner [3] and the availability flag availableFlagCorner [3] with X being 0 and 1 are derived as follows:
  • the reference indices for the temporal merging candidate, refIdxLXCorner [3] , with X being 0 or 1, are set equal to 0.
  • slice_temporal_mvp_enabled_flag is equal to 0
  • both components of mvLXCol are set equal to 0 and availableFlagLXCol is set equal to 0.
  • xColBr xCb+cbWidth (8-601)
  • SubPicRightBoundaryPos pic_width_in_luma_samples-1
  • botBoundaryPos subpic_treated_as_pic_flag [SubPicIdx] ?
  • yCb>>CtbLog2SizeY is equal to yColBr>>CtbLog2SizeY
  • yColBr is less than or equal to botBoundaryPos
  • xColBr is less than or equal to rightBoundaryPos
  • the variable colCb specifies the luma coding block covering the modified location given by ( (xColBr>>3) ⁇ 3, (yColBr>>3) ⁇ 3) inside the collocated picture specified by ColPic.
  • the luma location (xColCb, yColCb) is set equal to the top-left sample of the collocated luma coding block specified by colCb relative to the top-left luma sample of the collocated picture specified by ColPic.
  • both components of mvLXCol are set equal to 0 and availableFlagLXCol is set equal to 0.
  • Embodiment 2 sub-picture constraint on affine constructed merge candidates (Solution 2)
  • JVET-O2001-v14 The working draft specified in JVET-O2001-v14 may be changed as below.
  • a luma location (xCb, yCb) specifying the top-left sample of the current luma coding block relative to the top-left luma sample of the current picture
  • the fourth (collocated bottom-right) control point motion vector cpMvLXCorner [3] , reference index refIdxLXCorner [3] , prediction list utilization flag predFlagLXCorner [3] and the availability flag availableFlagCorner [3] with X being 0 and 1 are derived as follows:
  • the reference indices for the temporal merging candidate, refIdxLXCorner [3] , with X being 0 or 1, are set equal to 0.
  • slice_temporal_mvp_enabled_flag is equal to 0
  • both components of mvLXCol are set equal to 0 and availableFlagLXCol is set equal to 0.
  • xColBr xCb+cbWidth (8-601)
  • SubPicRightBoundaryPos pic_width_in_luma_samples-1
  • botBoundaryPos subpic_treated_as_pic_flag [SubPicIdx] ?
  • xColBr Min (rightBoundaryPos, xColBr)
  • yColBr Min (botBoundaryPos, yColBr)
  • the variable colCb specifies the luma coding block covering the modified location given by ( (xColBr>>3) ⁇ 3, (yColBr>>3) ⁇ 3) inside the collocated picture specified by ColPic.
  • the luma location (xColCb, yColCb) is set equal to the top-left sample of the collocated luma coding block specified by colCb relative to the top-left luma sample of the collocated picture specified by ColPic.
  • both components of mvLXCol are set equal to 0 and availableFlagLXCol is set equal to 0.
  • Embodiment 3 Fetching integer samples under the sub-picture constraint
  • Output of this process is a predicted luma sample value predSampleLX L
  • variable shift is set equal to Max (2, 14-BitDepth Y ) .
  • variable picW is set equal to pic_width_in_luma_samples and the variable picH is set equal to pic_height_in_luma_samples.
  • subpic_treated_as_pic_flag [SubPicIdx] is equal to 1, the following applies:
  • xInt Clip3 (SubPicLeftBoundaryPos, SubPicRightBoundaryPos, xInt)
  • yInt Clip3 (SubPicTopBoundaryPos, SubPicBotBoundaryPos, yInt)
  • the predicted luma sample value predSampleLX L is derived as follows:
  • predSampleLX L refPicLX L [xInt] [yInt] ⁇ shift3
  • Embodiment 4 deriving the variable invAvgLuma in chroma residual scaling of LMCS
  • JVET-O2001-v14 The working draft specified in JVET-O2001-v14 may be changed as below.
  • nCurrSw specifying the chroma transform block width
  • an (nCurrSw) x (nCurrSh) array predSamples specifying the chroma prediction samples of the current block

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