diff extra codes/Lab4 stptpeaks.m @ 3:1c0f36c348d4

extra code for matlab

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/extra codes/Lab4 stptpeaks.m	Sat Apr 20 13:03:01 2013 +0100
@@ -0,0 +1,51 @@
+function y=stptpeaks(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
+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))); % peakss
+pmag = mX(ploc); % magnitude of peaks
+pphase = pX(ploc); % phase of peaks
+num_peak=length(ploc)/2; %Just positive peaks
+
+axis=linspace(0,pi,N2); %Axis for the whole frequency plot
+axis_peak=axis(ploc(1:num_peak));%Axis for just the peaks plot
+
+subplot(2,1,1); plot(axis,mX); hold on; %Magnitude plot
+plot(axis_peak,pmag(1:num_peak),'rx');%Magnitude peaks
+subplot(2,1,2); plot(axis,pX); hold on; %Phase plot
+plot(axis_peak,pphase(1:num_peak),'rx');%Phase peaks 
+
+pin = pin+H; % advance sound pointer
+end
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