[FFmpeg-devel] Anybody has a Core 2? [PATCH] Small SSSE3 optimization

Zuxy Meng zuxy.meng
Sat May 12 21:20:18 CEST 2007


2007/5/13, Loren Merritt <lorenm at u.washington.edu>:
> On Sun, 13 May 2007, Zuxy Meng wrote:
> > 2007/5/9, Loren Merritt <lorenm at u.washington.edu>:
> >>
> >> You'd get even more speedup by also using SSE2/xmmregs. And both additions
> >> would be better written as macros, no need for code duplication.
> >
> > I saw your recent contribution in svn HEAD. And most interesting to me
> > is that in 'svn log' you gave exact cycles of different routines on
> > different CPUs. How did u get that? Are u using a simulator or you
> > simply measure using RDTSC?
> rdtsc, as per ffmpeg's START_TIMER/STOP_TIMER macros. And then subtract
> the time taken by the empty timer, which can be rather large on some
> cpus.
> For some functions the time is constant. For others (e.g. with random
> memory access) it can vary, but is still perfectly reproducible if I run
> the same encode twice.

Thanks Loren!

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