[FFmpeg-soc] vf_overlay with transparancy

[Zeger Knops]

On Wed, 2009-05-27 at 21:52 +0200, Vitor Sessak wrote:
> > +           //TODO rgb conversion if user is using rgb in alpha function
> > +            alpha->values[POV_cyuv] = (outrow_0[j]<<16) + (outrow_1[j_sub]<<8) + outrow_2[j_sub];
> > +            alpharow[j] = ff_parse_eval(alpha->value, alpha->values, alpha);
> 
> If you are using ff_parse_eval() here, this filter have no advantage 
> comparing to vf_applyfn. In the other hand, if you accept only YUVA420 
> as input and if you call ff_parse_eval() at most once per frame, this 
> filter can be _much_ faster (and no memcpy(), just modifying the buffer, 
> see vf_drawbox).

Compared to vf_applyfn this filter is faster since there is only a
single call to ff_parse_eval instead of 6, that could be an advantage.
Would this filter still be a nice addition to libavfilter if it is
fully replaceable by vf_applyfn?

Zeger Knops