[MPlayer-dev-eng] [PATCH] vf_eq2 extensions

[Michael Niedermayer]

Hi

On Friday 31 January 2003 19:32, D Richard Felker III wrote:
> On Fri, Jan 31, 2003 at 06:17:20PM +0100, Michael Niedermayer wrote:
> > Hi
> >
> > On Friday 31 January 2003 17:20, D Richard Felker III wrote:
> > [...]
> >
> > > > I am reluctant to put this stuff in vf_eq.c because the main
> > > > function that I need (the main reason for vf_eq2 to exist) is
> > > > gamma correction and that's the one thing that can't be done
> > > > efficiently in vf_eq.c.
> > >
> > > Hmm, someone should add polynomial approx gamma correction to eq then
> > > so we can just make eq2 obsolete.
> >
> > i doubt that evaluating a polynom is faster than a single L1 cache read
> > from a 256 byte LUT
>
> Nope, it's not. But with MMX, evaluating 4 polynomials is just as fast
> as evaluating one. :) And loading a single byte from memory, then
> immediately using it as a 32bit offset into a lookup table, is VERY
> SLOW.
no

> x86 cpu's don't like mixing register sizes these days.
yes, thats why there are very fast instructions to load 8&16 bit stuff with 
zero or sign extension in a 32 bit register mov{z,s}{bl,wl}
IIRC i once saw some very suboptimal code from gcc 2.95 with mixed short & int 
code in the swscaler, just rewriting it in asm (no mmx) resulted in a 2x 
speedup

[...]

Michael