[FFmpeg-devel] [PATCH] fftools/ffmpeg: Fallback to duration if sample rate is unavailable

[Michael Niedermayer]

On Wed, May 02, 2018 at 02:57:11AM +0200, wm4 wrote:
> On Tue,  1 May 2018 22:44:07 +0200
> Michael Niedermayer <michael at niedermayer.cc> wrote:
> 
> > Regression since: af1761f7
> > Fixes: Division by 0
> > Fixes: ffmpeg_crash_1
> > 
> > Found-by: Thuan Pham, Marcel Böhme, Andrew Santosa and Alexandru Razvan Caciulescu with AFLSmart
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  fftools/ffmpeg.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
> > index 5dc198f933..15fa54f24e 100644
> > --- a/fftools/ffmpeg.c
> > +++ b/fftools/ffmpeg.c
> > @@ -2706,8 +2706,12 @@ static int process_input_packet(InputStream *ist, const AVPacket *pkt, int no_eo
> >          ist->dts = ist->next_dts;
> >          switch (ist->dec_ctx->codec_type) {
> >          case AVMEDIA_TYPE_AUDIO:
> > -            ist->next_dts += ((int64_t)AV_TIME_BASE * ist->dec_ctx->frame_size) /
> > -                             ist->dec_ctx->sample_rate;
> > +            if (ist->dec_ctx->sample_rate) {
> > +                ist->next_dts += ((int64_t)AV_TIME_BASE * ist->dec_ctx->frame_size) /
> > +                                  ist->dec_ctx->sample_rate;
> > +            } else {
> > +                ist->next_dts += av_rescale_q(pkt->duration, ist->st->time_base, AV_TIME_BASE_Q);
> > +            }
> >              break;
> >          case AVMEDIA_TYPE_VIDEO:
> >              if (ist->framerate.num) {
> 
> Wouldn't it be better to error out here, instead of using yet another
> unreliable value and "hoping for the best"?
> 
> Also I'm not sure, but I think unknown durations are sometimes set to
> -1 instead of 0.

The same update this patch would add is also done in the AVMEDIA_TYPE_VIDEO
below the changed AVMEDIA_TYPE_AUDIO.

I can add a special case and error out but then audio and video differ more

about -1, ill add a assert, the existing code prior to the patch would
already misbehave (in some cases) if its -1. So i will have to fix this
even without the patch if it happens

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Why not whip the teacher when the pupil misbehaves? -- Diogenes of Sinope
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