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

Guillaume POIRIER poirierg
Thu Aug 16 23:11:51 CEST 2007


On 8/16/07, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Thu, Aug 16, 2007 at 04:41:21PM +0200, Guillaume POIRIER wrote:
> > Well, don't forget that according to Michael, FFmpeg's FFT sucks, so
> > writing a fixed-point version of a sucky implementation may not be so
> > wise :-(
> dont fear ill revert any cooley tukey fixed point FFTs which get commited

Hehe :)

> which brings us back to what i already said ... someone should implement
> a split radix fft (changing the current float fft to split radix would
> surely be nice as well...)

I have a question regarding the API of FFTs:

When I made my review of the state of the art, I noted that FFTW, IPP
and MKL seemed to offer only a pair of Real and Imaginary arrays to be
passed to their computation functions, whereas FFmpeg's API supports
only an array of pair of Real, Imaginary numbers.
So it looks like this:
fft_mkl(double *real_array, double *imaginary, int size)
fft_ffmpeg(struct_complex *pair, int size)

Michael, do you have any strong opinion about this?
This really isn't so much of an important thing, but since these major
libs use the same data layout, I have a hunch that this may be the
right way to go....

A soldier will fight long and hard for a bit of colored ribbon.
 -- Napoleon Bonaparte

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