On Thu, 22 Nov 2007, hard off wrote:
cos^2+sin^2=1ah! 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 complicated.
_ _ __ ___ _____ ________ _____________ _____________________ ... | Mathieu Bouchard - tél:+1.514.383.3801, Montréal QC Canada
_______________________________________________ PD-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
