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- function y = stpt(x, w, N, H, fs, t)
- % Analysis/synthesis of a sound using the short-time Fourier transform
- % Authors: J. Bonada, X. Serra, X. Amatriain, A. Loscos
- % x: input sound, w: analysis window (odd size), N: FFT size, H: hop size
- % y: output sound
- %
- %--------------------------------------------------------------------------
- % This source code is provided without any warranties as published in
- % DAFX book 2nd edition, copyright Wiley & Sons 2011, available at
- % http://www.dafx.de. It may be used for educational purposes and not
- % for commercial applications without further permission.
- %--------------------------------------------------------------------------
- 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 in 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
- k = [0:1:N];
- freq = fs*k/N;
- %t = -80 ; % threshold
- while pin<pend
- %-----analysis-----%
- %clf;
- 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 window in fftbuffer
- fftbuffer(N-(M-1)/2+1:N) = xw(1:(M-1)/2);
- X = fft(fftbuffer); % compute FFT
- mX = 20*log10(abs(X(1:N2))); % magnitude spectrum of positive frequencies
- ploc = 1 + find((mX(2:N2-1)>t).*(mX(2:N2-1)>mX(3:N2)).*(mX(2:N2-1)>mX(1:N2-2)));
- pX = unwrap(angle(X(1:N2))); % unwrapped phase spect. of positive freq.
- pmag=mX(ploc);
- pphase=pX(ploc);
- %-----synthesis-----%
- Y = zeros(N,1); % initialize output spectrum
- Y(ploc) = 10.^(pmag/20).*exp(i.*pphase); % generate positive freq.
- Y(N-ploc) = 10.^(pmag/20).*exp(-i.*pphase);% generate negative frequency
- fftbuffer = real(ifft(Y)); % inverse FFT
- fftbuffer2 = fftbuffer.*hanning(N); % smoothing with a window
- yw(1:(M-1)/2) = fftbuffer(N-(M-1)/2+1:N); % undo zero-phase window
- yw((M+1)/2:M) = fftbuffer(1:(M+1)/2);
- y(pin-hM:pin+hM) = y(pin-hM:pin+hM) + H*yw(1:M); % overlap-add
- pin = pin+H; % advance sound pointer
- end
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