JVET-R0187 AHG12: On signalling for picture with one tile and multiple slices [Hendry, S. Paluri, J. Zhao, S. Kim (LGE)]
Discussed in AHG Session 1.10 Wednesday 8 April (chaired by GJS & YKW).
It is asserted that in the current picture partitioning signalling scheme when there is only one tile and the slices are rectangular slices, the syntax elements num_slices_in_pic_minus1 and tile_idx_delta_present_flag are not needed. In such situation, the number of slices in the picture can easily be known from the derived variable NumSlicesInTile[ 0 ] and the value of tile_idx_delta_present_flag is never be used.
Furthermore, it is asserted that by not signalling num_slices_in_pic_minus1 in the described scenario above, it would be possible to avoid having the encoder signal an incorrect value for num_slices_in_pic_minus1), i.e. a value that is different from the derived value (i.e., NumSlicesInTile[ 0 ]).
This contribution proposed to omit the signalling of num_slices_in_pic_minus1 and tile_idx_delta_present_flag when no_pic_partition_flag is equal to 0, NumTilesInPic is equal to 1, and rect_slice_flag is equal to 1.
It was commented that this might prevent having tiles that are split into a signalled number of slices.
No action was planned on this unless offline study determines otherwise.
Discussion stopped here for AHG Session 1.10 on Wednesday 8 April at 1715 UTC.