Re: [FFmpeg-devel] [PATCH v4 3/6] Pass secondary ogg/opus chained streams metadata.

[Romain Beauxis <romain.beauxis@gmail.com>]

Le dim. 16 févr. 2025 à 15:02, Romain Beauxis <romain.beauxis@gmail.com> a
écrit :
>
> Hi again,
>
>
> Le ven. 14 févr. 2025 à 12:08, Romain Beauxis
> <romain.beauxis@gmail.com> a écrit :
> >
> > Le ven. 14 févr. 2025 à 11:55, Lynne <dev@lynne.ee> a écrit :
> > > Swallow the extra/metadata. Do not let OpusHead or their equivalents
in
> > > other codecs inside packets.
> > > Emit AV_PKT_DATA_NEW_EXTRADATA from the demuxer instead with the new
> > > data, which would contain the OpusHead unit (extradata).
> > > In the codec, if a packet contains AV_PKT_DATA_NEW_EXTRADATA, reinit
the
> > > decoder with it (we should do this in decode.c, but for now, doing it
in
> > > opusdec.c would be good enough).
> > >
> > > In the muxer, if a packet contains AV_PKT_DATA_NEW_EXTRADATA, write it
> > > to the bitstream.
> > >
> > > This also removes the need to cache metadata updates. If a packet
> > > contains metadata, simply pass that into the AVFrame->metadata once
the
> > > frame leaves the decoder in decode.c. The packet is not dereferenced
> > > yet, so you don't even need to cache it while the packet is being
decoded.
> >
> > This sounds like a plan, thanks I'll get to it.
>
> I'm looking into this again. Here are some notes:
>
> * Frames can potentially span several ogg packets so metadata should
> be cached in case a packet does not immediately return a decoded frame
> * The problem is extra header packets in the demuxed bitstream is
> orthogonal to the problem is passing new metadata
> * It seems more clear to use AV_PKT_DATA_METADATA_UPDATE to pass
> metadata updates and AV_PKT_DATA_NEW_EXTRADATA to pass new header
> packets
>
> Thus, I would like to divide up the work in the following order:
> 1. First a patcheset that adds a generic method to insert new metadata
> to decoded frames using AV_PKT_DATA_NEW_EXTRADATA. These changes
> wouldn't change the demuxing logic currently in place.

Sorry I meant AV_PKT_DATA_METADATA_UPDATE in the above.

> 2. Then a patchset to start adding ogg packet headers from secondary
> chained streams as AV_PKT_DATA_NEW_EXTRADATA and suppress them from
> the bitstream
>
> #2 might need some iterations, maybe one series that stash the header
> packets and hides them from the demuxer and another one that starts
> dumping them into the bitstream in the muxer. The reason being that,
> in order to be able to dump them in the muxer, we will also need to
> revise the PTS/DTS logic and that seems like a lot of work for one
> single patch series.
>
> How does the plan feel for you?
> -- Romain
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