[FFmpeg-devel] [BUG] Theora decoder displays green line

[Aurelien Jacobs]

On Sun, 6 May 2007 17:45:10 +0200
Michael Niedermayer <michaelni at gmx.at> wrote:

> On Sun, May 06, 2007 at 05:23:25PM +0200, Aurelien Jacobs wrote:
> > On Sun, 6 May 2007 17:12:21 +0200
> > Michael Niedermayer <michaelni at gmx.at> wrote:
> > 
> > > Hi
> > > 
> > > On Sun, May 06, 2007 at 02:26:36PM +0200, Diego Biurrun wrote:
> > > > Try the following sample:
> > > > 
> > > > http://mirrors.creativecommons.org/getcreative/Creative_Commons_-_Get_Creative.ogg
> > > > 
> > > > ffplay displays a green line at the bottom (as does MPlayer with lavc
> > > > decoder and lavf demuxer), while MPlayer with native demuxer and
> > > > libtheora decoder works fine.
> > > 
> > > ffmpeg -i output could be usefull
> > 
> > coded size is 400x304, display size should be 400x300.
> > Attached patch fixes this issue.
> > 
> > Aurel
> 
> > Index: libavcodec/vp3.c
> > ===================================================================
> > --- libavcodec/vp3.c	(revision 8918)
> > +++ libavcodec/vp3.c	(working copy)
> > @@ -1950,8 +1950,8 @@
> >          s->version = 1;
> >  
> >      s->avctx = avctx;
> > -    s->width = (avctx->width + 15) & 0xFFFFFFF0;
> > -    s->height = (avctx->height + 15) & 0xFFFFFFF0;
> > +    s->width = (avctx->coded_width + 15) & 0xFFFFFFF0;
> > +    s->height = (avctx->coded_height + 15) & 0xFFFFFFF0;
> >      avctx->pix_fmt = PIX_FMT_YUV420P;
> >      if(avctx->idct_algo==FF_IDCT_AUTO)
> >          avctx->idct_algo=FF_IDCT_VP3;
> > @@ -2385,6 +2385,8 @@
> >  
> >      s->width = get_bits(gb, 16) << 4;
> >      s->height = get_bits(gb, 16) << 4;
> > +    avctx->width = get_bits_long(gb, 24);
> > +    avctx->height = get_bits_long(gb, 24);
> 
> is there anything which ensures that the allocated buffer will
> be large enough for the picture which gets decoded?
> 
> also, avcodec_set_dimensions() should be used
> 
> 
> [...]
> > Index: libavformat/oggparsetheora.c
> > ===================================================================
> > --- libavformat/oggparsetheora.c	(revision 8918)
> > +++ libavformat/oggparsetheora.c	(working copy)
> > @@ -70,13 +70,15 @@
> >              return -1;
> >          }
> >  
> > -        st->codec->width = get_bits(&gb, 16) << 4;
> > -        st->codec->height = get_bits(&gb, 16) << 4;
> > +        st->codec->coded_width = get_bits(&gb, 16) << 4;
> > +        st->codec->coded_height = get_bits(&gb, 16) << 4;
> > +        st->codec->width = get_bits_long(&gb, 24);
> > +        st->codec->height = get_bits_long(&gb, 24);
> 
> coded_width=width unless lowres or other decoder side tricks
> are used
> 
> the allocated buffer always has its w/h rounded up to the next multiple
> of 16 with yv12
> that is coded_width is not the allocated width (see avcodec_align_dimensions)

Ok. It seems my usage of coded_width is wrong.
Now what should be used when the displayed picture is smaller than the
encoded picture ?
I could write a hack setting avctx->width and height to display size and
ensuring that the encoded width/height is equal to the display size rounded
to the next multiple of 16. This would solve current issue, but this don't
look very nice and isn't very versatile.

Aurel