Autocorrelation method for pitch determination: what is the input data form?
I have read a code for pitch determination using autocorrelation method. Can anybody please tell what would be the input data (passed as argument to DetectPitch()) function here:
double DetectPitch(short* data)
{
int sampleRate = 2048;
//Create sine wave
double *buffer = malloc(1024*sizeof(short));
double amplitude = 0.25 * 32768; //0.25 * max length of short
double frequency = 726.0;
for (int n = 0; n < 1024; n++)
{
buffer[开发者_C百科n] = (short)(amplitude * sin((2 * 3.14159265 * n * frequency) / sampleRate));
}
doHighPassFilter(data);
printf("Pitch from sine wave: %f\n",detectPitchCalculation(buffer, 50.0, 1000.0, 1, 1));
printf("Pitch from mic: %f\n",detectPitchCalculation(data, 50.0, 1000.0, 1, 1));
return 0;
}
It seems that "data" is used exactly the same way as the locally allocated "buffer", so I suppose it's something like
short data[1024]
, i.e. 1024 signal samples between -32768 and 32767 (the way "amplitude" is calculated makes suppose that the "short" type is 16 bit here).
By the way, as "max length of short" (as the comment says) I would expect 32767, not 32768 (there is a theoretical overflow with maximum positive values).
Regards
It looks like you need to at least change:
double *buffer = malloc(1024*sizeof(short));
to:
short *buffer = malloc(1024*sizeof(short));
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