JVET-AL0066 AHG9: Lossy compression with Object mask info SEI [J. Boyce, M. M. Hannuksela (Nokia)]

Chaired by S. Deshpande on 27 March 2025 at 16:00

The process described in the OMI SEI message to map sample positions to mask ID values compares the decoded auxiliary picture samples to signalled sample values. The process requires an exact match between the decoded sample value and the omi_aux_sample_value[ i ][ j ], which is not robust to lossy compression. It is proposed to modify the OMI SEI message to add robustness to lossy compression by adding syntax elements for an exact match flag and a tolerance value.

It was asked by a participant if encoder needs to give an indication to the decoder about exact match and separately to signal the tolerance range.

Proponent commented that it is also possible to consider an option where encoder signals exact match flag only and a note is added regarding how decoder could handle it in that case. It was commented that exact match flag by itself is not that helpful as it is just an indication. The proponent commented that the tolerance value can also be signalled unconditionally.

It was asked if decoder can figure out if it is lossy or lossless compression. One participant commented that the tolerance still can’t guarantee exact match. It was commented by proponent that exact match flag is just a recommendation and does not guarantee exact match. It was commented that tolerance value of 0 can indicate same information as exact match flag.

Decision: agreed (editors to consider renaming exact match flag to another name)