JVET-AN0058 AHG9: On the NNPF SEI messages in VSEI version 4 [M. M. Hannuksela, F. Cricri (Nokia)]

Chaired by S. Deshpande on 04 October 2025 from 17:25-17:50.

The following changes are proposed to neural-network post-filter SEI messages in VSEI version 4:

1. It is proposed to make the presence of the u(v)-coded syntax element nnpfc_reserved_metadata_extension conditional so that its length is greater than 0.

It is asserted that u(0) is not defined.

Decision: Agreed

1. Temporally extrapolated pictures are handled similarly to temporally interpolated pictures in most places of the NNPF SEI message semantics. It is asserted that in two instances, the NNPFC SEI message semantics discusses only interpolated pictures, when the semantics should refer to both interpolated pictures and temporally extrapolated pictures. These two instances are proposed to be fixed to refer to both interpolated pictures and temporally extrapolated pictures.

Decision: Agreed

1. It is asserted that nnpfa_prompt_update_flag is allowed to be equal to 1 in an NNPFA SEI message even when text prompt auxiliary input is not enabled in the respective NNPFC SEI message. However, nnpfa_seed_update_flag is disallowed to be equal to 1 in an NNPFA SEI message when seed auxiliary input is not enabled in the respective NNPFC SEI message. It is proposed to require nnpfa_prompt_update_flag to be equal to 0, when text prompt auxiliary input is not in use.

Decision: Agreed

1. When an NNPFA SEI message is not included in a PON SEI message, it is proposed that nnpfa_num_input_pic_shift shall be equal to 0 rather than shall not be present. It is remarked that when nnpfa_num_input_pic_shift is not present, it is inferred to be equal to 0.

It was suggested to instead add a gating flag for nnpfa_num_input_pic_shift and code the syntax element with a minus1.

It was commented that nnpfa_num_pic_shift syntax element was added at the end for supporting the case where it may not be signalled. But the proposal changes that usage.

Decision: Agreed to add a gating flag before nnpfa_num_input_pic_shift and to code the syntax element as nnpfa_num_input_pic_shift_minus1.

1. There exists one instance of nnpfc_extrapolated_pics, which should be corrected to nnpfc_extrapolated_pics_minus1.

Delegated to the editors.

1. Editorial suggestions.

Delegated to the editors.

JVET-AN0058 AHG9: On the NNPF SEI messages in VSEI version 4