[FFmpeg-devel] [PATCH v4] H.264: reinitialize context on aspect ratio change as well

[Janusz Krzysztofik]

Tuesday 16 March 2010 03:38:45 Janusz Krzysztofik wrote:
> Tuesday 16 March 2010 03:10:58 Michael Niedermayer wrote:
> > On Tue, Mar 16, 2010 at 03:08:59AM +0100, Janusz Krzysztofik wrote:
> > > While using ffmpeg based vdr softdevice plugin for watching h.264
> > > encoded live tv, I found that after correct picture aspect ratio setup
> > > on a new stream (channel) startup, any following picture aspect ratio
> > > changes were not processed. The same can be seen while playing vdr
> > > caputured samples of this transmission with ffplay.
> > >
> > > This patch corrects the problem for me by reinitializing the decoder
> > > context on every valid aspect ratio change, not only size changes.
> > >
> > > Created against ffmpeg svn revision 22565.
> > > Tested with this revision ffplay.
> > >
> > > Signed-off-by: Janusz Krzysztofik <jkrzyszt at tis.icnet.pl>
> > > ---
> > > v4 changes:
> > > - use av_cmp_q() instead of comparing numerators and denominators
> > > separately (thanks to Michael Niedermayer for advising this).
> > >
> > > v3 changes:
> > > - check for non-zero values of both new numerator and denominator to
> > > avoid problems with some test samples (ie.
> > > cathedral-beta2-400extra-crop-avc.mp4).
> > >
> > > v2 changes: none (refresh only)
> > >
> > > --- trunk/libavcodec/h264.c.orig	2010-03-16 02:35:01.000000000 +0100
> > > +++ trunk/libavcodec/h264.c	2010-03-16 02:39:04.000000000 +0100
> > > @@ -1774,7 +1774,9 @@ static int decode_slice_header(H264Conte
> > >          s->height= 16*s->mb_height - 4*FFMIN(h->sps.crop_bottom, 3);
> > >
> > >      if (s->context_initialized
> > > -        && (   s->width != s->avctx->width || s->height !=
> > > s->avctx->height)) { +        && (   s->width != s->avctx->width ||
> > > s->height != s->avctx->height +            || (h->sps.sar.num &&
> > > h->sps.sar.den
> > > +                && av_cmp_q(h->sps.sar,
> > > s->avctx->sample_aspect_ratio)))) {
> >
> > do you need the explicit num den != 0 checks?
>
> Yes, both are required for correct playback of
> http://samples.ffmpeg.org/V-codecs/h264/cathedral-beta2-400extra-crop-avc.m
>p4.

Michael,
Sorry, I was wrong because of trying to play from the net directly.
Playing a local copy actually works correctly without those checks!

I'll revert v3 changes and resubmit tomorrow.

Thanks,
Janusz