Partition calculation based on subpicture level

An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:

• perform a conversion between a video comprising a video picture and a bitstream of the video,
• wherein the video picture comprises one or more tiles that form one or more tile rows and one or more tile columns,
• wherein the bitstream conforms to a format rule, and
• wherein the format rule specifies that a tile column index is derived for each coding tree block (CTB) column of a tile of the video picture,
• wherein the video picture also comprises one or more subpictures,
• wherein each subpicture comprises one or more slices that collectively form a rectangular subset of the video picture,
• wherein the format rule further specifies that a width of subpicture in units of tile columns is derived based on tile column indices of a left-most CTB and/or a right-most CTB included in the subpicture,
• wherein a width of an i-th subpicture in units of tiles columns, denoted as SubpicWidthTiles[i], is derived as follows:
• a loop is performed with i as a loop variable, wherein an initialization of the loop variable i is equal to 0, and a value of the loop variable i is incremented by one after each execution in the loop,
• when i is smaller than or equal to sps_num_subpics_minus1, for each i, an execution is performed to:
• set leftX equal to sps_subpic_ctu_top_left_x[i],
• set rightX equal to leftX+sps_subpic_width_minus1[i], and
• set SubpicWidthInTiles[i] equal to
• ctbToTileColIdx[rightX]+1−ctbToTileColIdx[leftX],
• wherein sps_num_subpics_minus1 plus 1 represents a number of subpictures in the video picture,
• wherein sps_subpic_ctu_top_left_x[i] represents a horizontal position of a top-left CTB of the i-th subpicture,
• wherein sps_subpic_width_minus1[i] plus 1 specifies the width of the i-th subpicture, and
• wherein ctbToTileColIdx[rightX] and ctbToTileColIdx[leftX] represent the tile column indices of the left-most CTB and the right-most CTB, respectively, included in the subpicture.

A non-transitory computer-readable storage medium storing instructions that cause a processor to:

• perform a conversion between a video comprising a video picture and a bitstream of the video,
• wherein the video picture comprises one or more tiles that form one or more tile rows and one or more tile columns,
• wherein the bitstream conforms to a format rule, and
• wherein the format rule specifies that a tile column index is derived for each coding tree block (CTB) column of a tile of the video picture,
• wherein the video picture also comprises one or more subpictures,
• wherein each subpicture comprises one or more slices that collectively form a rectangular subset of the video picture,
• wherein the format rule further specifies that a width of a subpicture in units of tile columns is derived based on tile column indices of a left-most CTB and/or a right-most CTB included in the subpicture,
• wherein a width of an i-th subpicture in units of tiles columns, denoted as SubpicWidthInTiles[i], is derived as follows:
• a loop is performed with i as a loop variable, wherein an initialization of the loop variable i is equal to 0, and a value of the loop variable i is incremented by one after each execution in the loop,
• when i is smaller than or equal to sps_num_subpics_minus1, for each i, an execution is performed to:
• set leftX equal to sps_subpic_ctu_top_left_x[i],
• set rightX equal to leftX+sps_subpic_width_minus1[i], and
• set SubpicWidthInTiles[i] equal to
• ctbToTileColIdx[rightX]+1−ctbToTileColIdx[leftX],
• wherein sps_num_subpics_minus1 plus 1 represents a number of subpictures in the video picture,
• wherein sps_subpic_ctu_top_left_x[i] represents a horizontal position of a top-left CTB of the i-th subpicture,
• wherein sps_subpic_width_minus1[i] plus 1 specifies the width of the i-th subpicture, and
• wherein ctbToTileColIdx[rightX] and ctbToTileColIdx[leftX] represent the tile column indices of the left-most CTB and the right-most CTB, respectively, included in the subpicture.

A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises:

• generating the bitstream of the video comprising a video picture according to a format rule,
• wherein the video picture comprises one or more tiles that form one or more tile rows and one or more tile columns,
• wherein the bitstream conforms to the format rule, and
• wherein the format rule specifies that a tile column index is derived for each coding tree block (CTB) column of a tile of the video picture,
• wherein the video picture also comprises one or more subpictures,
• wherein each subpicture comprises one or more slices that collectively form a rectangular subset of the video picture,
• wherein the format rule further specifies that a width of subpicture in units of tile columns is derived based on tile column indices of a left-most CTB and/or a right-most CTB included in the subpicture,
• wherein a width of an i-th subpicture in units of tiles columns, denoted as SubpicWidthTiles[i], is derived as follows:
• a loop is performed with i as a loop variable, wherein an initialization of the loop variable i is equal to 0, and a value of the loop variable i is incremented by one after each execution in the loop,
• when i is smaller than or equal to sps_num_subpics_minus1, for each i, an execution is performed to:
• set leftX equal to sps_subpic_ctu_top_left_x[i],
• set rightX equal to leftX+sps_subpic_width_minus1[i], and
• set SubpicWidthInTiles[i] equal to
• ctbToTileColIdx[rightX]+1−ctbToTileColIdx[leftX],
• wherein sps_num_subpics_minus1 plus 1 represents a number of subpictures in the video picture,
• wherein sps_subpic_ctu_top_left_x[i] represents a horizontal position of a top-left CTB of the i-th subpicture,
• wherein sps_subpic_width_minus1[i] plus 1 specifies the width of the i-th subpicture, and
• wherein ctbToTileColIdx[rightX] and ctbToTileColIdx[leftX] represent the tile column indices of the left-most CTB and the right-most CTB, respectively, included in the subpicture.