[XviD-devel] [CVS commit] Linux amd64 preliminary support

[Edouard Gomez]

Selon Guillaume POIRIER <guillaume.poirier at etudiant.univ-rennes1.fr>:
> What a coincidence, I just happened to run a bench yesterday between the
> "original" AMD-64 SIMD port by Andre Werthmann against IA-34 SIMD
> version from you tla tree. I've been quite disappointed to see that the
> AMD-64 version was just as fast as IA-32 when libavcodec gives me (from
> the top of my head) a 50% bonus regarding encoding speed[1].

I doubt this can be true, technically using MMX/XMM/SSE2 should be equivalent
using the amd64 either as a 32bit CPU or a 64bit processor because the code is
exactly the same and is executed on the same simd units. The only way ffmpeg
could speedup by 50% is that it uses a "real" 64bit port using the extra
registers which could save some bandwidth in some parts of the code... but
really 50% is not realistic.

> So, Edouard, does your AMD-64 port features some more nice optimizations
> that allows a certain speed-up ?

No. Only the decoder is faster because i ported all the changes i made for the
ia32 1.1 tree to amd64.

> Anyway, thanks a lot for the work you've done, I'll test it and
> benchmark it tonight.

You're welcome.

--
Edouard Gomez