JVET-AM0075 AHG9: On packed regions information SEI message [T. Chujoh, Z. Fan, R. Ishimoto, T. Ikai (Sharp)]

VSEI version 4 has reached the DAM stage on the ISO/IEC standardization process. This contribution reports the following editorial and technical problems for the packed regions information SEI message, which has been revised to draft 6 of VSEI version 4 at the March/April online meeting and proposes their solutions.

1. Two variable names BtDepth_Y and BtDepth_C should be improved to BitDepth_Y and BitDepth_C.
2. The interface variables for the PRI SEI message are defined using the syntax elements pri_region_layer_id[ i ] and pri_num_regions_minus1 before their definition. They should be specified without the SEI syntax element.
3. The syntax element pri_use_max_dimensions_flag does not explain its semantics. It should be explained why these arrays are used in calculations for the region parameters.

For item 1, these changes would make the interface text awkward (by having something like "The variable X is set equal to X").

For item 2, the first sentence was awkward “using each layer identifier value, layer_Id, in AU, applied to this SEI message”. It would be possible to avoid the name of the specific syntax element. Item 2 is delegated to the editors.

It was noted that other locations in the spec refer to a syntax element before the syntax element is defined.

Agreed to item 3, which is editorial.

The editors are recommended to consider the naming of the bit depth interface variables.

JVET-AM0075 AHG9: On packed regions information SEI message