[FFmpeg-devel] [PATCHv2] flac: ignore IDv3 tags if vorbis tags exist

[Ben Boeckel]

On Tue, 03 Feb, 2015 at 04:13:49 GMT, Michael Niedermayer wrote:
> isnt the id3 + vorbis tag issue the same as if the user would seek
> back to the begin and read metadata afterwards ?

Metadata isn't in-stream for flac (AFAICT, it is only read with the
header; I certainly can't get the code to re-execute with just a simple
seek in mpv at least). I can try and set up an mpd flac stream, but I
imagine it's just going to use vorbis comments if anything (and I don't
see ffmpeg code to handle such updates). It is in-stream for vorbis, but
vorbis will junk the current metadata when an update packet comes in
anyways and ogg just doesn't support IDv3 at all (assuming there's some
actual reasoning behind this Wikipedia quote from the ID3 page):

    Other container-based formats use their own tagging formats. An
    example of this is Ogg, which uses Vorbis comments. Adding ID3 tags
    to these would break the container structure.

The only other place I see ff_vorbis_comment called is from Matroska,
but that reads it and looks for a specific tag then ignores the rest.

> your patch drops the encoder id metadata, which seems to
> also have contained the encoding parameters, is this intended ?

Currently, it ignores the whole IDv3 metadata block if vorbis tags are
found. I suppose it could be stored off then any field which is in IDv3,
but not in the vorbis one be added in (only if !compliant?). I'll try
that tomorrow (or Wednesday if I don't get time).

--Ben