[FFmpeg-devel] [PATCH] Fix crop filter for paletted formats != PAL8

[Stefano Sabatini]

On date Monday 2009-11-09 03:06:04 +0100, Michael Niedermayer encoded:
> On Mon, Nov 09, 2009 at 12:13:51AM +0100, Stefano Sabatini wrote:
> > Hi,
> > 
> > this is along the line of how paletted formats are treated in the
> > scale filter, note that with my tests I didn't noticed the issue as
> > data[1], when used with a paletted format different than pal8, only
> > contains a long sequence of zeros, and seems unused.
> > 
> > Anyway with the patch applied it looks more correct, also would be
> > useful some pointer towards a collection of paletted samples (I only
> > found few examples in the Mplayer archive).
> > 
> > Regards.
> > -- 
> > FFmpeg = Friendly Frenzy Mythic Patchable Empowered God
> 
> >  vf_crop.c |    8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 5f43c9d456054bd95b6e713d2f11745261839ae3  fix-crop-for-pal.patch
> > Index: libavfilter/vf_crop.c
> > ===================================================================
> > --- libavfilter/vf_crop.c	(revision 20479)
> > +++ libavfilter/vf_crop.c	(working copy)
> > @@ -33,6 +33,7 @@
> >  
> >      int bpp;            ///< bits per pixel
> >      int hsub, vsub;     ///< chroma subsampling
> > +    int input_is_pal;   ///< set a value different from 0 if the input format is paletted
> >  } CropContext;
> >  
> >  static int query_formats(AVFilterContext *ctx)
> > @@ -145,6 +146,11 @@
> >          return -1;
> >      }
> >  
> > +    crop->input_is_pal = link->format == PIX_FMT_PAL8      ||
> > +                         link->format == PIX_FMT_BGR4_BYTE ||
> > +                         link->format == PIX_FMT_RGB4_BYTE ||
> > +                         link->format == PIX_FMT_BGR8      ||
> > +                         link->format == PIX_FMT_RGB8;
> >      return 0;
> >  }
> >  
> > @@ -176,7 +182,7 @@
> >      ref2->data[0] += crop->y * ref2->linesize[0];
> >      ref2->data[0] += (crop->x * crop->bpp) >> 3;
> >  
> > -    if (link->format != PIX_FMT_PAL8) {
> > +    if (!crop->input_is_pal) {
> >          for (i = 1; i < 3; i ++) {
> >              if (ref2->data[i]) {
> >                  ref2->data[i] += (crop->y >> crop->vsub) * ref2->linesize[i];
> 
> why the temporary variable in the context ?

Oh well, I really don't care this or the other, I thought that it was
better to cache the value rather than recompute it each time in
start_frame(), I also find the first version of the patch slightly
more readable, also vf_scale.c is doing like in the first version.

Regards.
-- 
FFmpeg = Faboulous & Faboulous Mean Pacific Enlightening Guide
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