JVET-AJ0120 AHG9: Miscellaneous modifications for SEI messages in the VSEI draft [J. Nam, H. Tan, C. Kim, J. Lee, J. Lim, S. Kim (LGE)]

This contribution proposes miscellaneous modifications that are asserted to provide improvement to some aspects of SEI messages in VSEI v4 draft. The proposed modifications are as follows,

(Related to SPO/PON SEI messages)

1. Update conditions on repetition of SPO SEI message

2. Simplify constraints on presences of PON-nested SEI message

(Related to OMI SEI message)

3. Move position of byte-alignment for OMI SEI message

4. Add a constraint on free-form string of OMI SEI message

(Related to TDI SEI message)

5. Add a syntax to indicate importance level of TDI SEI message

6. Add a constraint on free-form string of TDI SEI message

Update conditions on repetition of SPO

Review of proposals 1, 2 moved to SPO section.

Proposal 3 already addressed in JVET-AJ0070.

For proposal 4, it was suggested that the label presence flag is global for all objects in a mask layer, so disallowing a null string might be inappropriate in cases where no label for a particular object is intended to be signalled.

Proposal 5 usefulness doesn’t seem clear.

Proposals 6 proposes to add a constraint that the string not be null for TDI SEIs.

It was commented that a restriction against null text strings applies to all purposes, including reserved values.

It as suggested that it may be useful to allow signalling a null string for TDI SEI when an encoder had considered to signal a text string but didn’t identify something to signal, and by signalling a null string is communicating that it had been considered. It was suggested that txt_num_strings_minus1 should not use minus1 if it is desired to not signal a text string.

Items 1 and 2 Chaired by S. Deshpande 19:25 PM local time 2 November 2024.

1. Update conditions on repetition of SPO SEI message

These are asserted editorial improvements to take into account newly added synaxt elements in PO from previous meeting.

One participant commented that some syntax elements are left out specifically in this part of the text and this was discussed at the last meeting.

Decision: Agreed to add the following syntax elements as proposed:

po_for_human_viewing_idc, po_for_machine_analysis_idc, po_breadth_first_flag: po_sei_importance_flag[ i ], po_sei_processing_degree_flag[ i ].

2. Simplify constraints on presences of PON-nested SEI message

Two participants commented that the goal of this proposal seems to be editorial simplification. As a history the current text was added during editing to clarify and add missing conditions exactly specifying which syntax elements to check for each SEI. And as proposed the conditions may not be clear (i.e. may be vauge) and so doing this change may not be the best option.

No action was taken on this.

JVET-AJ0120 AHG9: Miscellaneous modifications for SEI messages in the VSEI draft [J. Nam, H. Tan, C. Kim, J. Lee, J. Lim, S. Kim (LGE)]

Items 1 and 2.