Re: [FFmpeg-devel] [PATCH v4 5/6] ogg/vorbis: implement header packet skip in chained ogg bitstreams.

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

Le mer. 7 mai 2025 à 08:14, Michael Niedermayer
<michael@niedermayer.cc> a écrit :
>
> On Tue, May 06, 2025 at 09:19:31AM -0500, Romain Beauxis wrote:
> > ---
> >  libavformat/oggparsevorbis.c               | 11 +++++++++--
> >  tests/ref/fate/ogg-vorbis-chained-meta.txt |  3 ---
> >  2 files changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/libavformat/oggparsevorbis.c b/libavformat/oggparsevorbis.c
> > index 9f50ab9ffc..8b4ae872d2 100644
> > --- a/libavformat/oggparsevorbis.c
> > +++ b/libavformat/oggparsevorbis.c
> > @@ -418,6 +418,7 @@ static int vorbis_packet(AVFormatContext *s, int idx)
> >      struct ogg_stream *os = ogg->streams + idx;
> >      struct oggvorbis_private *priv = os->private;
> >      int duration, flags = 0;
> > +    int skip_packet = 0;
> >
> >      if (!priv->vp)
> >          return AVERROR_INVALIDDATA;
> > @@ -480,7 +481,13 @@ static int vorbis_packet(AVFormatContext *s, int idx)
> >          if (duration < 0) {
> >              os->pflags |= AV_PKT_FLAG_CORRUPT;
> >              return 0;
> > -        } else if (flags & VORBIS_FLAG_COMMENT) {
> > +        }
> > +
> > +        if (flags &
> > +            (VORBIS_FLAG_HEADER | VORBIS_FLAG_COMMENT | VORBIS_FLAG_SETUP))
> > +            skip_packet = 1;
>
> can the content of the header containing "global" tables for vorbis change?
> if so what does this patch do to such a stream ?
>
> (I mean is this breaking such streams? or do they not exist or did that never work?)

Thanks for pointing this out.

It was always working in my tests but, upon further inspection, the
vorbis decoding code was doing something with those headers packets.

I'm working on an updated patchset taking care of this by passing the
setup packet (last packet) as extradata and processing it in the
decoder to mimic what's currently done.

I'm also gonna take this opportunity to add some safeguard in the
vorbis and opus code to make sure we fail when a new stream starts
with different channels count or sample rate.

Generally speaking, I'm intending the changes to be on best effort
w.r.t. to what's already working/not working but I think those two
changes will add and are not too hard to put in.

I'm gonna take some time to clean and test and will re-submit.

Thanks,
-- romain

> thx
>
> [...]
> --
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>
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