Pitch Detection

autocorrolate.matlab

function out = autocorrolate(signal)
% AUTOCORROLATE  Multiply a signal by itself over a moving delay window.
% Max delay will be equal to the length of the signal
%   Y = AUTOCORROLATE(x) returns auto correlation of x
%
	N = length(signal);
	out = zeros(size(signal));
	for l = 1:N - 1
		for n = l+1:(N)
			out(l) = out(l) + (signal(n)*signal(n-l));
		end		
	end
	
end

pitchDetect.matlab

function out = pitchDetect(signal, Fs)
% PITCHDETECT Detect the F0 pitch in Hz of a signal with autocorrelation
%   Hz = PITCHDETECT(signal, Fs) return F0 of a signal with sample rate Fs
	y = autocorrolate(signal);
	local_max = find(islocalmax(y));
	last_value = 0;
	distances = [];
	for x = local_max
		distances = [distances,x - last_value];
		last_value = x;
	end
	out = Fs / mean(distances);
end