[python sound] 간단한 FIR 필터 만들기

간단한 FIR 필터 만들기

간단한 FIR 필터를 만듦. 예제로 moving average 필터를 사용함.
예전 예제에서 만든 wav file(".\WaveTest.wav")을 이용함

import wave import struct import numpy as np import matplotlib.pyplot as plt N = 20 #FIR filter length fname = ".\WaveTest.wav" wav_file = wave.open(fname, "r") framerate = float(wav_file.getframerate()) nframes = wav_file.getnframes() time = np.arange(0, nframes/framerate, 1/framerate) x = [] for i in range(nframes):     waveData = wav_file.readframes(1)     x.append(struct.unpack(" wav_file.close() b = [1.0/N]*N #FIR filter coefficient, moving averaging filter #Filtering mechanism #y[n] = b[0]*x[n] + b[1]*x[n-1] + b[2]*x[n-2] + ... + b[n-1]*x[1] + b[n]*x[0] ''' y = [0.0]*nframes for index in range(nframes):     for k in range(N):         if index-k >= 0:             y[index] = y[index] + b[k]*x[index-k] ''' y = np.convolve(b, x, "full")              plt.plot(time, x, time, y) plt.xlabel("times[s]") plt.ylabel("data") plt.xlim(0, 0.005) plt.show()

필터링 된 이미지

참고 :
위키백과 : http://en.wikipedia.org/wiki/Finite_impulse_response
scipy가 지원하는 fir filter : http://mpastell.com/2010/01/18/fir-with-scipy/