I'm trying to understand autocorrelation as related to some pitch detection
algorithms I've been looking at.
In example code for the autocorrelation, it is the summation of a sample at
indexes multiplied by a sample at indexes plus an offset.
eg
for (i=0;i<size;i++)
{
sum=0;
for (j=0;j<size;j++)
{
sum+=x[j]*x[j+i];
}
R[i]=sum;
}
When I graph this (R[i]) in a spreadsheet for various offsets, I do not get a
minima as expected when the samples match (I have tried with a couple of
generated periodic waves).
However, if I use the summation of the differences I do get the minima as
expected.
What am I missing?
Veronica
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