[FFmpeg-devel] [RFC] Documenting metadata keys, informative (non-copied) metadata

[Tomas Härdin]

tor 2025-02-13 klockan 12:54 +0100 skrev Tomas Härdin:
> Hi
> 
> In the samples_md5 patch discussion Michael wanted the proposed key
> to
> be documented. But it turns out we don't have any documentation for
> metadata keys! So I'm starting this thread to talk about it. I reckon
> we create a new file called doc/metadata_keys.texi with a table
> listing
> keys and where they can appear (format, stream, frames), sorted by
> name, with a brief description of each one. Any keys that require
> more
> detailed documentation we could add sections for.
> 
> Another issue raised was that some metadata keys shouldn't be carried
> over automatically to muxers. In the samples_md5 thread it was
> pointed
> out by Andreas that we don't want to mux that in AIFF. It was also
> pointed out that it stops being valid if the audio is cut. This isn't
> the first time I've come across cases where we don't want metadata to
> be copied, so I'm taking the opportunity to propose informative
> output-
> only metadata could reside in their own namespace. I propose info:
> for
> that, so info:samples_md5 in this specific case, or maybe just
> info:md5. HEVC frames could similarly have such metadata applied.

Attached is a PoC for the latter part. Unlike the previous samples_md5
patch, this one only requires updating a FATE ref concerning a .flac
file.

I have to go, else I'd also post the documentation thing as well.

/Tomas
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