annotate extra/stftlab4.m @ 13:844d341cf643 tip

Back up before ISMIR

function y = stftlab4(x, w, N, H, t)
% Analysis/synthesis of a sound using the peaks
% of the short-time fourier transform
% x: input sound, w: analysis window (odd size), N: FFT size, H: hop size,
% t: threshold in negative dB, y: output sound
M = length(w); % analysis window size
N2 = N/2+1; % size of positive spectrum
soundlength = length(x); % length of input sound array
hM = (M-1)/2; % half analysis window size
pin = 1+hM; % initialize sound pointer at the middle of analysis window
pend = soundlength-hM; % last sample to start a frame
fftbuffer = zeros(N,1); % initialize buffer for FFT
yw = zeros(M,1); % initialize output sound frame
y = zeros(soundlength,1); % initialize output array
w = w/sum(w); % normalize analysis window
sw = hanning(M); % synthesis window
sw = sw./sum(sw);
while pin<pend
%-----analysis-----%
xw = x(pin-hM:pin+hM).*w(1:M)'; % window the input sound
fftbuffer(:) = 0; % reset buffer
fftbuffer(1:(M+1)/2) = xw((M+1)/2:M); % zero-phase fftbuffer
fftbuffer(N-(M-1)/2+1:N) = xw(1:(M-1)/2);
X = fft(fftbuffer); % compute the FFT
mX = 20*log10(abs(X(1:N2))); % magnitude spectrum of positive frequencies
pX = unwrap(angle(X(1:N2))); % unwrapped phase spectrum
ploc = 1+find((mX(2:N2-1)>t).*(mX(2:N2-1)>mX(3:N2)).*(mX(2:N2-1)>mX(1:N2-2))); % peaks
[nploc,npmag,npphase] = peakinterp(mX,pX,ploc); % refine peak values. i use new parameters
%so that i can plot the new values at the figures existed
pmag = mX(ploc); % finding the magnitude of the obtained locations (peaks)
pphase = pX(ploc); % finding the phase of the obtained locations (peaks)
 
% plotting the peak values on top of the magnitude and phase spectra at the
% magnitude and phase frame
  
subplot(211); 
plot(mX);
hold on
plot(ploc,pmag,'m*');   %m is for magenta color
plot(nploc,npmag,'c*'); %plot the new magnitude spectra
title('magnitude and peak values');
hold off
subplot(212);
plot(pX);
hold on
plot(ploc,pphase,'m*');
plot(nploc,npphase,'c*');
title('phase and peak values');
hold off
 
end