[FFmpeg-devel] [PATCH] make av_set_pts_info more robust

[Reimar Döffinger]

On Wed, Jul 01, 2009 at 10:23:24PM +0200, Michael Niedermayer wrote:
> On Wed, Jul 01, 2009 at 08:39:50PM +0200, Reimar D?ffinger wrote:
> > Hello,
> > I don't have a sample file for the issue, but the AVI demuxer and probably
> > more pass on user data unchecked to av_set_pts_info.
> > So I propose to change it in a way that will avoid a division by 0.
> > Not sure if that's the best idea, but it seemed like a good idea (I
> > originally thought this was the cause of a crash I am investigating).
> > Index: libavformat/utils.c
> > ===================================================================
> > --- libavformat/utils.c	(revision 19317)
> > +++ libavformat/utils.c	(working copy)
> > @@ -3308,8 +3308,10 @@
> >  {
> >      unsigned int gcd= av_gcd(pts_num, pts_den);
> >      s->pts_wrap_bits = pts_wrap_bits;
> > +    if (pts_num > 0 && pts_den > 0) {
> >      s->time_base.num = pts_num/gcd;
> >      s->time_base.den = pts_den/gcd;
> > +    }
> 
> rejected, this is definitly not reasonable

Agreed, I did not read the code right, and AVI at least does check the values
(no idea how I missed that).
There are demuxers like xa that don't do sufficient checking but it is probably
better to fix in the demuxers (I fear we have no volunteers?).