[FFmpeg-devel] [RFC] RGB32 / BGR32 ethernal bug

Stefano Sabatini stefano.sabatini-lala
Sun Jan 31 01:48:23 CET 2010


On date Tuesday 2010-01-26 09:17:12 +0100, Michael Niedermayer encoded:
> On Tue, Jan 26, 2010 at 01:06:18AM +0100, Stefano Sabatini wrote:
> > I, currently we have:
> > isRGB(RGB32   = LE:BGRA) == 1
> > isRGB(RGB32_1 = LE:ABGR) == 1
> > 
> > and similarly for isBGR(), this is the cause of an ethernal confusion
> > and frustration for who dares to takle the understanding of rgba
> > conversion code, my proposal is to change how the RGB stuff is dealt
> > and to use in the isRGB()/isBGRA() definitions something like:
> > 
> > #define isRGB(x)        (           \
> >            (x)==PIX_FMT_RGBA        \
> >         || (x)==PIX_FMT_ARGB        \
> >         ...
> > 
> > #define isBGR(x)        (           \
> >            (x)==PIX_FMT_BGRA        \
> >         || (x)==PIX_FMT_ABGR        \
> >         ...
> > 
> > which is also what the random sane person would expect, and to do the
> > necessary changes in the swscale code.
> 
> ive cleaned up the macros somewhat, which should also make their meaning
> clearer and ive added 2 so you can add your byte based shuffling code.
> 
> I think it goes without saying that adding new macros and using them
> is fine but giving a new and completely fliped meaning to existing macros
> is not fine. At least if people expect me to maintain this in the future.
> also your mail sounds only consistent because you skiped telling us what
> you do with the majority of rgb formats that arent byte based. like RGB15
> they dont fit in your sheme at all
> 
> 
> >  rgb2rgb.c |   25 +++++++++++++++++++++++++
> >  rgb2rgb.h |    7 +++++++
> >  swscale.c |   29 ++++++++++++++++++++++++++---
> >  3 files changed, 58 insertions(+), 3 deletions(-)
> > 71929befe054ce487ac7ca8be14acd67d7e496fb  fix-rgba-scaling.patch
> > Index: ffmpeg/libswscale/rgb2rgb.c
> > ===================================================================
> > --- ffmpeg.orig/libswscale/rgb2rgb.c	2010-01-20 23:06:57.000000000 +0100
> > +++ ffmpeg/libswscale/rgb2rgb.c	2010-01-20 23:07:01.000000000 +0100
> > @@ -442,3 +442,28 @@
> >          dst[i] = ((b<<1)&0x07) | ((g&0x07)<<3) | ((r&0x03)<<6);
> >      }
> >  }
> > +
> > +void rgb32torgb32_0123(const uint8_t *src, uint8_t *dst, long src_size)
> > +{
> > +    memcpy(dst, src, src_size);
> > +}
> > +
> > +#define RGB32_TO_RGB32_TRANSFORM_CONV(a, b, c, d)                       \
> > +void rgb32torgb32_##a##b##c##d(const uint8_t *src, uint8_t *dst, long src_size) \
> > +{                                                                       \
> > +    long i;                                                             \
> > +                                                                        \
> > +    for (i = 0; i < src_size; i+=4) {                                   \
> > +        dst[i + 0] = src[i + (a)];                                      \
> > +        dst[i + 1] = src[i + (b)];                                      \
> > +        dst[i + 2] = src[i + (c)];                                      \
> > +        dst[i + 3] = src[i + (d)];                                      \
> > +    }                                                                   \
> > +}
> > +
> > +RGB32_TO_RGB32_TRANSFORM_CONV(0, 3, 2, 1);
> > +RGB32_TO_RGB32_TRANSFORM_CONV(1, 2, 3, 0);
> > +RGB32_TO_RGB32_TRANSFORM_CONV(2, 1, 0, 3);
> > +RGB32_TO_RGB32_TRANSFORM_CONV(3, 0, 1, 2);
> > +RGB32_TO_RGB32_TRANSFORM_CONV(3, 2, 1, 0);
> 
> you write byte shuffling code, id suggest to call it accordingly
> theres nothing rgb specific on this, it could be usefull to do packed yuv
> shuffling as well.
> 
> like maybe:
> byte_shuffle_0123_to_0321
> but before you convert your code to this, what is the speed gain from
> a/b/c/d being constants instead of just passed into the function?
> there should be enough registers for this in theory
> also
> dst+=4; src+=4
> for(dst<dstend
> would reduce the register need

Patch+diff of the regression test attached, maybe rgb2rgb.{h,c} is not
the right place for the shuffle functions and you can suggest a better
place.

I have yet to try/benchmark with a generic shuffle_byte_4() function.

Regards.
-- 
FFmpeg = Freak & Freak Mystic Pitiless Ephemeral Geek
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