JVET-R0248 AHG9: Supporting multiple slices within one tile for raster-scan slice mode [S.-T. Hsiang, L. Chen, C.-W. Hsu, Y.-W. Huang, S.-M. Lei (MediaTek)]
This contribution proposes three modifications related to signalling slice partitioning of the coded picture, summarized as follows:
- Support a slice that consists of one or more consecutive complete CTU rows within one tile in raster-scan slice mode. Two syntax elements, num_rows_in_slice_idc and tile_row_id, are designed for this.
- When slice_address is equal to ( NumTilesInPic − 1 ), the syntax element num_tiles_in_slice_minus1 is not coded and is inferred to be equal to 0.
- A new syntax element multiple_slices_in_tile_enabled_flag is signalled in the picture parameter set (PPS) to specify whether it is allowed to further partition a tile into more than one slice for pictures referring to the PPS.
It is asserted that a finer granularity of partitioning units is desirable when partitioing of each coded slice is adaptively determined during encoding and signalled in raster-scan slice mode. Software for this proposal is attached in the proposal package.
In version 2 of this contribution, a software bug is fixed, and partial simulation results are provided.
In version 3 of this contribution, the full simulation results are provided.
The motivation is to provide a finer granularity.
It was commented that this would basically proposes to back a functionality that was removed previously.
It was asked why such a functionality would be desired instead of the rectangular scan mode. The proponent indicated that the motivation is to avoid needing to signal the layout in the PPS.
The proposal to add such functionality was not considered desirable due to the late stage of work, so no action was taken on this.
Control of loop filtering across subpicture/tile/slice boundaries (7)
Discussion continued here for Track A on 22 April at 1440 UTC (chaired by GJS & YKW).