signal processing - kissfft scaling -

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i looking compute fast correlation using ffts , kissfft library, , scaling needs precise. scaling necessary (forward , backwards) , value use scale data?

the 3 common fft scaling factors are:

  • 1.0 forward fft, 1.0/n inverse fft

  • 1.0/n forward fft, 1.0 inverse fft

  • 1.0/sqrt(n) in both directions, fft & ifft

given possible ambiguity in documentation, , whatever scaling user expects "correct" purposes, best feed pure sine wave of known (1.0 float or 255 integer) amplitude , periodic in fft length fft (and/or ifft) in question, , see if scaling matches 1 of above, maybe different 1 of above 2x or sqrt(2), or desired scaling different.

e.g. write unit test kissfft in environment data types.


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