[PD] fft beginner question

Mathieu Bouchard matju at artengine.ca
Thu Nov 22 00:34:02 CET 2007

On Thu, 22 Nov 2007, hard off wrote:

>>> cos^2+sin^2=1
> ah!
> so, actually the FFT doesn't HAVE to use imaginary numbers....but they
> are just used because "the complex-number system is
> two-dimensional and that signals to be analysed are presumed to be
> two-dimensional. They are decomposable into a sum of circular
> trajectories"

FFT can also be defined to only use real numbers, but the formulas are 
more complicated and the data layout is slightly irregular. Pd does not 
support those: it supports real-to-complex hybrids, just to avoid the 
irregularity (I mean: DC and Nyquist are special; and you'd have to put 
both cosines and sines in the same block in order to really have only 
one signal input). Because of the irregularity, you'd need to have 
FFT-specific signal objects that understand the FFT blocks and can handle 
their values correctly.

So, in the end, complex numbers may be complex, but real numbers are 

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