[FFmpeg-devel] [PATCH] avformat/oggdec: Add page CRC verification

[Mattias Wadman]

On Tue, Apr 28, 2020 at 2:01 PM Lynne <dev at lynne.ee> wrote:
>
> Apr 27, 2020, 21:55 by michael at niedermayer.cc:
>
> > On Mon, Apr 27, 2020 at 05:19:49PM +0200, Mattias Wadman wrote:
> >
> >> Fixes seek issue with ogg files that have segment data that happens to be
> >> encoded as a "OggS" page syncword. Very unlikely but seems to happen.
> >>
> >> Have been observed to happen with ffmpeg+libvorbis and oggenc encoding
> >> to 441khz stereo at 160kbps.
> >> ---
> >>  libavformat/oggdec.c | 96 +++++++++++++++++++++++++++++++++-----------
> >>  1 file changed, 73 insertions(+), 23 deletions(-)
> >>
> >
> > breaks chained ogg
> >
> > ./ffmpeg -threads 1 -i ~/tickets/868/chained_streams.ogg -f null -
> >
> > frame=  954 fps=0.0 q=-0.0 Lsize=N/A time=00:00:31.79 bitrate=N/A speed= 105x
> > vs
> > frame=  120 fps=0.0 q=-0.0 Lsize=N/A time=00:00:03.99 bitrate=N/A speed= 289x
> >
> > stream should be here:
> > http://v2v.cc/~j/theora_testsuite/chained_streams.ogg
> >
> > thx
> >
>
> I've sent a patchset which amongst other things, implements this cleanly and does not break that file.
> Had this for a long time, wanted to finish Opus chaining, but seeing this made me send it to the list.

Aha thanks. I should have asked on the list before starting, but i
learned a lot.

I will review your patches and try with some files that have the
issue. Unfortunately i can't share them because of legal reasons.

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