[FFmpeg-devel] [PATCH v5] H.264: reinitialize context on aspect ratio change as well

[Michael Niedermayer]

On Tue, Mar 16, 2010 at 12:24:13PM +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>
> ---
> v5 changes:
> - drop non-zero checks introuduced in v3, those appeared not necessary for 
>   correct playback of cathedral-beta2-400extra-crop-avc.mp4 test sample 
>   (apparently num/den==0/0 case) after v4 changes.
> 
> 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 12:09:27.000000000 +0100
> +++ trunk/libavcodec/h264.c	2010-03-16 12:09:57.000000000 +0100
> @@ -1774,7 +1774,8 @@ 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
> +            || av_cmp_q(h->sps.sar, s->avctx->sample_aspect_ratio))) {
>          if(h != h0)
>              return -1;   // width / height changed during parallelized decoding
>          free_tables(h);

looks ok if it works

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

In fact, the RIAA has been known to suggest that students drop out
of college or go to community college in order to be able to afford
settlements. -- The RIAA
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