Using xcorr in pitch detections

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Robert
Robert 2011-8-21
I'm currently switching from fft to this function and I found some questions. What I have known is that we should calculate the frequency through comparing the positons of adjacent local maxima, but I don't know how I should use my maxima. I'm testing things with a 120Hz sine wave:
t=(0:999)*(1/1000); x = sin(2*pi*120*t); R = xcorr(x); [pks,locs]=findpeaks( R );
the locs have differences of 8 or 9, which is still correct ( 1/(9/1000) < 120 < 1/(8/1000) )
But I don't know how to get 120 as my answer using effective codes.
How much maxima should I count into the average value, etc?
And I don't think my code works with mixed frequencies... Can someone give me a direction?

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Daniel Shub
Daniel Shub 2011-8-22
Pitch detection is a huge field with many different algorithms each with advantages and disadvantages. How close to 120 do you need to get. What i your answer is 121, 120.1, 120.01, ...
One easy way to get around the problem is to increase your sampling rate.
Fs = 1e6;
t=(0:(Fs-1))*(1/Fs);
x = sin(2*pi*120*t);
R = xcorr(x);
[pks,locs]=findpeaks(R);
[min(Fs./diff(locs)), mean(Fs./diff(locs)), max(Fs./diff(locs))]
ans =
119.9904 120.0000 120.0048
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Daniel Shub
Daniel Shub 2012-5-24
That is a lot of questions. Why don't you try and implement something with this code and see where you get stuck. Also if the answer is helpful, consider voting for it.

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