[FFmpeg-devel] Fwd: Fixpoint FFT optimization, with MDCT and IMDCT wrappers for audio optimization

Michael Niedermayer michaelni
Fri Aug 17 19:01:39 CEST 2007


On Fri, Aug 17, 2007 at 03:58:16PM +0200, Benjamin Larsson wrote:
> Michael Niedermayer wrote:
> > Hi
> > [...]
> >   
> > dont fear ill revert any cooley tukey fixed point FFTs which get commited
> >   
> Ok, then you can start by reverting revision 5. 
> http://svn.mplayerhq.hu/ffmpeg/trunk/libavcodec/ac3enc.c?view=markup&pathrev=5
> I don't see it as obvious that a split radix fft would be faster on 
> every fixed point platform out there. 

well on which is it not?

> Would it really hurt to have 
> several fft algos available in the source? 

depends on their speed, accuracy, ...
theres no sense in keeping things which are always inferrior
keeping them until they have been optimized and benchmarked is all fine
but we still are at step 0 (that is we dont have an implementation we rather
disscuss what we could do if we did had one which we dont ...)

> Without a radix-2 algo we 
> wouldn't have anything to compare against to back that claim anyway. I'm 
> not really doubting that a split radix fft would be faster in most cases 
> but I'd rather let the benchmark numbers prove the point.

who did suggest that we shouldnt benchmark the code?
iam just saying that id like to see a split radix fft in lavc, if someone
wants to write a radix2 one thats fine i wont stop him and ill surely look
at any benchmarks

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have often repented speaking, but never of holding my tongue.
-- Xenocrates
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