[FFmpeg-devel] [PATCH] split-radix FFT

[Diego Biurrun]

On Tue, Aug 05, 2008 at 11:28:04AM +0100, Robert Swain wrote:
> 2008/8/5 Siarhei Siamashka <siarhei.siamashka at gmail.com>:
> > On Mon, Aug 4, 2008 at 10:27 PM, matthieu castet
> > <castet.matthieu at free.fr> wrote:
> >> M?ns Rullg?rd wrote:
> >>> Loren Merritt <lorenm at u.washington.edu> writes:
> >>>
> >>>> $subject, vaguely based on djbfft.
> >>>> Changed from djb:
> >>>> * added simd.
> >>>> * removed the hand-scheduled pentium-pro code. gcc's output from
> >>>> simple C is better on all cpus I have access to.
> >>>> * removed the distinction between fft and ifft. they're just
> >>>> permutations of eachother, so the difference belongs in revtab[] and
> >>>> not in the code.
> >>>> * removed the distinction between pass() and pass_big(). C can always
> >>>> use the memory-efficient version, and simd never does because the
> >>>> shuffles are too costly.
> >>>> * made an entirely different pass_big(), to avoid store->load aliasing.
> >>>
> >>> Any progress on this?  IMDCT is taking 84% time decoding Vorbis on
> >>> ARM, and SIMD-optimising the FFT in svn seems silly.
> >>>
> >> Shouldn't fixed point stuff should help a lot on arm ?
> >
> > Yes, fixed point stuff should help on low end arm cores without fpu.
> > If you are interested in audio decoding on such cores, you are better
> > to use rockbox (http://www.rockbox.org/) and not FFmpeg at the moment.
> 
> What license is the RockBox stuff? Could it be ported to FFmpeg?

It is a patch for FFmpeg, but it needs cleanup.

Diego