function?pitchwatch（xTs）
%?Plot?the?pitch?keys.
%?pitchwatch（x[Ts]）
%?
%?::?Syntax
%????The?array?x?is?the?input?signal?and?Ts?is?the?（optional）?sampling?period.
%????Example?on?use:?[xFs]?=?wavread（‘Hum.wav‘）;
%????????????????????pitchwatch（x1/Fs）;
%?
%?::?Information
%????Make?your?own?wav-files?with?the?Windows?Sound?Recorder.?Choose?the?attributes
%????PCM?8000Hz?16bit?Mono?when?saving?the?wav-file.?For?more?information?on?pitch
%????keys?go?to?http://www.bookrags.com/wiki/Piano_key_frequencies.

%?Set?parameters.
if?nargin?
%?Set?constants.
xlen?=?length（x）;
wlen?=?512;
wlag?=?128;

%?Zero-pad?signal.
xpad?=?wlag-rem（xlen-wlen-1wlag）-1;
x????=?[x（:）;?zeros（xpad1）];
L????=?（xlen+xpad-wlen）/wlag+1;
L????=?L-wlen/wlag/2;

%?Calculate?the?AMDF?and?AMDF-fractional?pitch?periods.
for?k1?=?1:L
???k2?=?（k1-1）*wlag;
???for?k3?=?1:wlen/2-1?c（k3）?=?sum（abs（x（k2+（1:wlen））-x（k2+k3+（1:wlen））））;?end
???
???n?=?findpeaks（