[FFmpeg-devel] [PATCH] avfilter/fade: add color option.

[Clément Bœsch]

On Sat, Nov 09, 2013 at 01:30:40AM +0100, Clément Bœsch wrote:
[...]
> > This check is done a lot of times with the same result. Maybe move it
> > outside inner loop and implement loop twice: for 3 and 4 bytes per pixel
> > 
> 
> I tried this:
> 
> #define INTERP(layer, value) av_clip_uint8(((c[value]<<16) + ((int)p[layer] - (int)c[value]) * s->factor + (1<<15)) >> 16)
> #define FILTER_SLICE_RGB(do_alpha, step) do { \
>     for (i = slice_start; i < slice_end; i++) { \
>         uint8_t *p = frame->data[0] + i * frame->linesize[0]; \
>         for (j = 0; j < frame->width; j++) { \
>             p[r] = INTERP(r, 0); \
>             p[g] = INTERP(g, 1); \
>             p[b] = INTERP(b, 2); \
>             if (do_alpha) \
>                 p[a] = INTERP(a, 3); \
>             p += step; \
>         } \
>     } \
> } while (0)
> 
>     if (s->alpha) FILTER_SLICE_RGB(1, 4);
>     else          FILTER_SLICE_RGB(0, s->bpp);
> 
> Before:
>   24512648 decicycles in filter_slice_rgb, 32767 runs, 1 skips
> After:
>   22688265 decicycles in filter_slice_rgb, 32768 runs, 0 skips
> 
> (with no alpha)
> 
> Do you think it's worth the change? If so, consider the code changed locally.
> 
> > 
> > > +                p[a] = INTERP(a, 3);
> > > +            p += s->bpp;
> > >
> > 
> > I previous remark applied than can be constant +3/+4 maybe
> > 
> 
> Having alpha does not mean it will be +3/+4 (because alpha filtering can
> be disabled, or if later we add rgb0 and similar pix fmt). So in the case
> where there is no alpha (which is the common case), I can't skip this.
> 

Or maybe I can actually, which looks like this:

    if (s->alpha)         FILTER_SLICE_RGB(1, 4);
    else if (s->bpp == 3) FILTER_SLICE_RGB(0, 3);
    else if (s->bpp == 4) FILTER_SLICE_RGB(0, 4);
    else av_assert0(0);

Which leads to:
  19799915 decicycles in filter_slice_rgb, 32768 runs, 0 skips

-- 
Clément B.
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