[Ffmpeg-devel] [PATCH] lowres chroma bug

[Michael Niedermayer]

Hi

On Fri, Feb 09, 2007 at 04:42:52PM +0900, Oleg Metelitsa wrote:
> Hello,
> 
> > 3)  We can add two extra pixels to image in lowres=2 mode:
> > image_stride =  image_width  +  2
> > chroma_stride = image_width/2 + 2
> > Then  the garbage will be written to those extra (dummy) pixels rather
> > than to the beginning of the next row.
> 
> Please,  find  the  patch  3)  attached.  It  may be not so interested
> comparing  to  the  patches  proposed earlier. But the advantage is it
> does not change non lowres H.264 operation.
> 
> Index: libavcodec/utils.c
> ===================================================================
> --- /libavcodec/utils.c (revision 7890)
> +++ /libavcodec/utils.c (working copy)
> @@ -279,7 +279,9 @@
>          if(!(s->flags&CODEC_FLAG_EMU_EDGE)){
>              w+= EDGE_WIDTH*2;
>              h+= EDGE_WIDTH*2;
> -        }
> +        } else if(s->lowres==2)
> +            w+= 4;
> +
>          avpicture_fill(&picture, NULL, s->pix_fmt, w, h);
>          pixel_size= picture.linesize[0]*8 / w;
> 
> The  idea  is  to  add 4 pixels before calling avpicture_fill() inside
> avcodec_default_get_buffer  function.  As  a  result  4 pixels will be
> added to linesize[0] and 2 pixels to linesize[1] and linesize[2].
> 
> All  sizes will be aligned inside avpicture_fill(). For example, if we
> have  coded_width=640  and  width=160 after applying lowres=2 mode, we
> will  have linesize[1]=176 and linesize[1]=88 as a result of alignment
> operation.

and it will fail if avocodec_default_get_buffer() isnt used aka for example
in mplayer

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

There will always be a question for which you do not know the correct awnser.
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