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Python Smith Trigger for frequency analysis
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#ederwander | |
#date 10/02/2012 | |
from __future__ import division | |
import math | |
import wave | |
import numpy as np | |
freq = 0.; | |
trigfact = 0.6; | |
index1=100; | |
blockSize=4096; | |
spf = wave.open('440.wav','r'); | |
fs = spf.getframerate(); | |
signal = spf.readframes(-1); | |
signal = np.fromstring(signal, 'Int16'); | |
index2=index1+blockSize-1; | |
schmittBuffer=signal[index1:int(index2)+1] | |
A1 = 0; | |
A2 = 0; | |
for j in range(0,blockSize): | |
if (schmittBuffer[j]>0) and (A1<schmittBuffer[j]): | |
A1 = schmittBuffer[j]; | |
if (schmittBuffer[j]<0) and (A2<-schmittBuffer[j]): | |
A2 = -schmittBuffer[j]; | |
t1 = int( A1 * trigfact + 0.5); | |
t2 = - int( A2 * trigfact + 0.5); | |
startpoint=0; | |
j=1; | |
while((schmittBuffer[j]<=t1) and (j<blockSize-1)): | |
j=j+1; | |
#print j | |
while (~(schmittBuffer[j-1] >=t2 and schmittBuffer[j]< t2) and j<blockSize-2): | |
#print j | |
j=j+1; | |
startpoint=j; | |
schmittTriggered=0; | |
endpoint=startpoint+1; | |
tc=0; | |
for j in range(startpoint,blockSize-1): | |
if (~schmittTriggered): | |
schmittTriggered = (schmittBuffer[j] >= t1); | |
else: | |
if (schmittBuffer[j]>=t2 and schmittBuffer[j+1]<t2): | |
endpoint=j; | |
tc=tc+1; | |
schmittTriggered = 0; | |
if (endpoint > startpoint): | |
freq = float(fs)*float(tc/(endpoint-startpoint)); | |
print freq; |
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