Hi- I've been using python now for about 2 months for plugin development within Maya (a commercial 3d application). I'm currently in the process of writing a sound analysis plugin for maya and have completed a good portion of it including the ability to retrieve the amplitude at certain intervals from a wav file. The next part of the project however consists of analysing the wav file and outputting the amplitude at certain frequencies. Due to the need of distributing this to many computers after it has been finished I'm reluctant to use an external python module for FFT'ing. Accuracy and speed aren't really issues as just a generalisation of the amplitude of low, medium and high frequencies is required. Do you either know of any generic FFT functions written in python that could just be inserted into my processing class (open source licensed). So far i've managed to put together a chunk of code but I'm not sure its returning the right values, any ideas? import wave import sys import array import struct from cmath import pi, exp def nextpow2(i): n = 2 while n < i: n = n * 2 return n def bitrev(x): N, x = len(x), x[:] if N != nextpow2(N): raise ValueError, 'N is not power of 2' for i in range(N): k, b, a = 0, N>>1, 1 while b >= a: if b & i: k = k | a if a & i: k = k | b b, a = b>>1, a<<1 if i < k: # important not to swap back x[i], x[k] = x[k], x[i] return x def fft(x, sign=-1): N, W = len(x), [] for i in range(N): # exp(-j...) is default W.append(exp(sign * 2j * pi * i / N)) x = bitrev(x) m = 2 while m <= N: for s in range(0, N, m): for i in range(m/2): n = i * N / m a, b = s + i, s + i + m/2 x[a], x[b] = x[a] + W[n % N] * x[b], x[a] - W[n % N] * x[b] m = m * 2 return x def ifft(X): N, x = len(X), fft(X, sign=1) # e^{j2\pi/N} for i in range(N): x[i] = x[i] / float(N) return x fp = wave.open("hankuncom.wav","rb") sample_rate = fp.getframerate() total_num_samps = fp.getnframes() fft_length = 4096 num_fft = (total_num_samps / fft_length ) - 2 temp = [] for i in range(num_fft): tempb = fp.readframes(fft_length) moo = struct.unpack("%uh"%(fft_length),tempb) temp.append(moo) listed = list(temp[0]) freq_pwr = fft(listed) print(freq_pwr) fp.close() Thanks!

# Python frequency analysis without numpy

Started by ●January 20, 2009

Reply by ●January 20, 20092009-01-20

debug <dom@reality-debug.co.uk> wrote:>Do you either know of any generic FFT functions written in python that >could just be inserted into my processing class (open source licensed).Have you thought about using boost.python? Steve

Reply by ●January 21, 20092009-01-21

> > So far i've managed to put together a chunk of code but I'm not sure its > returning the right values, any ideas? >Even though you don't want to use numpy in the distribution use it to verify you functions. You can create a unit test that will compare the results of your function to those of fftw. You can build in tolerated error into your unit test. Example of unit test here, http://www.myhdl.org/doku.php/users:cfelton:projects:recursivefft

Reply by ●January 22, 20092009-01-22

>debug <dom@reality-debug.co.uk> wrote: > >>Do you either know of any generic FFT functions written in python that >>could just be inserted into my processing class (open source licensed). > >Have you thought about using boost.python? > >Steve >The boost library contains FFT routines? If you don't want to use numpy you can allways right your own wrapper for kissfft, djbfft, or FFTW (or any other fft library you can find). If you want a pure python implementation (I wouldn't know why): http://www.uselesspython.com/download.php?script_id=178 Bjoern