search

MPEGGroup / CMAF

Official MPEG repository to discuss public issues on CMAF (ISO/IEC 23000-19)
2 stars 0 forks source link

chroma_idc #33

Closed haudiobe closed 2 years ago

haudiobe commented 2 years ago

None of the media profiles set the chroma_idc to a specific value, but chroma_idc should be set to 1 for 4:2:0. Propose to fix this.

sdp198 commented 2 years ago

For HEVC it's already restricted to this by the requirement to use Main or Main 10 profiles. For AVC it's restricted to 0 or 1 (where 0 would be monochrome) by the limit of using High Profile which only allows those values. Other common profiles (Constrained Baseline, Main) don't allow it to be present (resulting in 1 as a default). Do you want to explicitly prevent monochrome video?

haudiobe commented 2 years ago

We propose to set chroma_idc to 1 for HEVC profiles. This is not yet addressed in any document as it requires some efforts.

sdp198 commented 2 years ago

I don't think that is necessary. The HEVC profiles currently in the spec only allow either Main profile or Main 10. In the HEVC specification for Main profile: Active SPSs for the base layer shall have chroma_format_idc equal to 1 only.

In the HEVC specification for Main 10 profile: – Active SPSs for the base layer shall have chroma_format_idc equal to 1 only.

It would be a duplication to add that separately into CMAF. Elsewhere in the spec notes or non normative language have been used when a restriction comes from elsewhere, if you feel it's really necessary to highlight in CMAF.