[music-dsp] fast convolution using the djbfft

Florian Walter flo at earshot.de
Thu Aug 21 02:33:00 EDT 2003

> This rings a bell, I dont think that djbfft returns the results in the
> normal order. I'd recommend using FFTW, which is easier to use and (as of
> version 3) just as fast.

The results of a single fft are out-of-order, but after an
fft-ifft-operation everything seems to be ok...

Convolution is very simple with the djbfft, because there is the
fftr4_mul256()-operation for the multiplication of the complex values.
Using the fftw I have to do this step by step in a loop.

In a first test a single circular convolution operation using the
djbfft is twice as fast as when using the fftw.

Best regards, Florian

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