Mismatch with VTM for inference rule of slice_height_in_tiles_minus1

[vdrugeon]

Currently, the inference rule for slice_height_in_tiles_minus1 is the following:
"When slice_height_in_tiles_minus1[ i ] is not present, the following applies:
– If NumTileRows is equal to 1, or tile_idx_delta_present_flag is equal to 0 and tileIdx % NumTileColumns is greater than 0), the value of slice_height_in_tiles_minus1[ i ] is inferred to be equal to 0.
– Otherwise (NumTileRows is not equal to 1, and tile_idx_delta_present_flag is equal to 1 or tileIdx % NumTileColumns is equal to 0), when tile_idx_delta_present_flag is equal to 1 or tileIdx % NumTileColumns is equal to 0, the value of slice_height_in_tiles_minus1[ i ] is inferred to be equal to slice_height_in_tiles_minus1[ i − 1 ]."

However, this is strange because when the condition under the "otherwise" (NumTileRows is not equal to 1, and tile_idx_delta_present_flag is equal to 1 or tileIdx % NumTileColumns is equal to 0) is fulfilled, then this syntax element is signalled. The only case where it would not be signalled is if there is no slice to signal at all, which would make this syntax element irrelevant anyway.

In addition, there is a mismatch with the software where if tile_idx_delta_present_flag is equal to 0 and tileIdx % NumTileColumns is greater than 0, the inference for this syntax element is not 0, but slice_height_in_tiles_minus1[ i − 1 ] (i.e what is currently decribed under the "otherwise").

So I believe that the text should probably be the following:
"When slice_height_in_tiles_minus1[ i ] is not present, the following applies:
– If NumTileRows is equal to 1, the value of slice_height_in_tiles_minus1[ i ] is inferred to be equal to 0.
– Otherwise (NumTileRows is not equal to 1), when tile_idx_delta_present_flag is equal to 0 and tileIdx % NumTileColumns is greater than 0, the value of slice_height_in_tiles_minus1[ i ] is inferred to be equal to slice_height_in_tiles_minus1[ i − 1 ]."

Could an expert in slice signalling please check?

[yk]

I believe you are right, and your suggestion is a good fix for this issue.

[eeehey]

It may be further simplified as following:

"When slice_height_in_tiles_minus1[ i ] is not present, the following applies:
– If NumTileRows is equal to 1, the value of slice_height_in_tiles_minus1[ i ] is inferred to be equal to 0.
– Otherwise (NumTileRows is not equal to 1), the value of slice_height_in_tiles_minus1[ i ] is inferred to be equal to slice_height_in_tiles_minus1[ i − 1 ]."

[yk]

Smart 👍

[yk]

Thanks! Will be fixed in Q2001-vD.