[vlc-devel] [PATCH] transcoding: avoid a divide by 0 when source video framerate is mistakenly set to 0 by a demuxer

[Emeric Grange]

2015-10-06 19:10 GMT+02:00 Ilkka Ollakka <ileoo at videolan.org>:
>
> On Tue, Oct 06, 2015 at 02:57:03PM +0200, Emeric Grange wrote:
>
> Hi,
>
> Patch looks ok, but I have feeling that most cases default framerate is wrong on cases where
> demuxer isn't able to give. Do you have some cases currently that
> demuxer fails to get framerate but that default is actually reasonable
> guess?
>
> > ---
> >  modules/stream_out/transcode/video.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
>
> > diff --git a/modules/stream_out/transcode/video.c b/modules/stream_out/transcode/video.c
> > index 2c2d4f3..8f85036 100644
> > --- a/modules/stream_out/transcode/video.c
> > +++ b/modules/stream_out/transcode/video.c
> > @@ -465,7 +465,7 @@ static void transcode_video_encoder_init( sout_stream_t *p_stream,
> >           i_dst_visible_width, i_dst_visible_height
> >       );
>
> > -    /* Handle frame rate conversion */
> > +    /* Handle frame rate conversion (encoder) */
> >      if( !id->p_encoder->fmt_out.video.i_frame_rate ||
> >          !id->p_encoder->fmt_out.video.i_frame_rate_base )
> >      {
> > @@ -485,6 +485,14 @@ static void transcode_video_encoder_init( sout_stream_t *p_stream,
> >          }
> >      }
>
> > +    /* Handle frame rate (decoder) */
> > +    if (!id->p_decoder->fmt_out.video.i_frame_rate ||
> > +        !id->p_decoder->fmt_out.video.i_frame_rate_base)
> > +    {
> > +        id->p_decoder->fmt_out.video.i_frame_rate = ENC_FRAMERATE;
> > +        id->p_decoder->fmt_out.video.i_frame_rate_base = ENC_FRAMERATE_BASE;
> > +    }
> > +
> >      id->p_encoder->fmt_in.video.orientation =
> >          id->p_encoder->fmt_out.video.orientation =
> >          id->p_decoder->fmt_in.video.orientation;
> --
> Ilkka Ollakka
> Each person has the right to take the subway.
>
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Hi,
Yes you are right the default will probably be wrong, the goal was
only to avoid VLC segfaulting. My use case was trancoding mp4 file
with "DASH style" tracks from youtube, and the problem was not an
exotic framerate but just the mp4 parser unable to get framerate. Most
files are 24fps so 25 is not that far of.
Maybe the proper way to handle that situation is just to fail with an
error trace then.

Emeric