Opened 12 years ago Closed 12 years ago #469 closed enhancement (fixed)chroma_format_idc has no need for a default value
Description
Section 7.4.2 says "When chroma_format_idc is not present, it is inferred to be equal to 1 (4:2:0 chroma format)." But chroma_format_idc is always present in the SPS. Change History (5)comment:1 Changed 12 years ago by DefaultCC Plugin
comment:2 Changed 12 years ago by pandrivoncomment:3 Changed 12 years ago by ksuehring
We decided to keep chroma_format_idc even in a 4:2:0 only main profile because this adds clarity and does not cost much. I think syntax element is unlikely to be removed in a potential later 4:2:2 or 4:4:4 profile. Thus I think the inference rule should be removed unless we have a profiled that omits the syntax element (as originally suggested). comment:4 Changed 12 years ago by bbross
comment:5 Changed 12 years ago by bbross
This will be fixed in JCVTC-K0030_v4. Note: See
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Indeed, it is inherited from AVC. For AVC, there is then a condition just above on profiles, certain profiles parse that syntax element whereas others use the equivalent inference you mention (like baseline profile and main profile). That semantic may be useful for HEVC for certain profiles (e.g. hypothetical 4:2:2 or 4:4:4 based profiles or non Main profile 4:2:0 based profiles). Should it be removed now to be then added in a further amendment?
I personally think that it does not disrupt the current draft and that it prepares for future professional profiles to happen.