how do I get the STFT inverse

I am using this this code to obtain the short time fourier transform:

 function y = STFT(x, sampling_rate, window, window_length, step_dist, padding)
%
%  y = STFT(x, sampling_rate, window, window_length, step_dist, padding)
%
%  STFT produces a TF image of "x".
%  The output is also stored in "y".
%
%  For "window", use one of the following inputs:
%  rectangular    = 1
%  Hamming        = 2
%  Hanning        = 3
%  Blackman-Tukey = 4
%
%  The time scale is associated with the center of the window,
%  if the window is of odd length.  Otherwise, the window_length/2
%  is used.  "Step_dist" determines the stepping distance between the number
%  of samples, and is arranged to maintain the proper time index
%  provided by "sampling_rate" in seconds.  "Padding" is the
%  total length of the windowed signal before the fft, which is
%  accomplished by zero padding.
%
%  Developed by Timothy D. Dorney
%               Rice University
%               April, 1999
%               [e-mail]
%
%  Coded using MATLAB 5.X.X.
%
%  REVISION HISTORY
%
%  VERSION 1.0.0    APR. 21, 1999  TIM DORNEY
%

if (nargin ~= 6) disp('STFT requires 6 input arguments!') return; end if ((window < 1) | (window > 4)) window = 1; disp('The argument "window" must be between 1-4, inclusively. Window set to 1!'); end if ((step_dist < 1) | (round(step_dist) ~= step_dist)) step_dist = 1; disp('The argument "step_dist" must be an integer greater than 0. Step_dist set to 1!'); end if (sampling_rate <= 0) disp('The argument "sampling_rate" must be greater than 0.'); break; end if (padding < window_length) padding = window_length; disp('The argument "padding" must be non-negative. Padding set to "window_length"!'); end

if (window == 1) WIN = ones(1,window_length); elseif (window == 2) WIN = hamming(window_length)'; elseif (window == 3) WIN = hanning(window_length)'; elseif (window == 4) WIN = blackman(window_length)'; end

[m,n] = size(x); if (m ~= 1) X = x'; else X = x; end [m,n] = size(X); if (m ~= 1) disp('X must be a vector, not a matrix!'); break; end

LENX = length(X); IMGX = ceil(LENX/step_dist); if (padding/2 == round(padding/2)) IMGY = (padding/2) + 1; else IMGY = ceil(padding/2); end

y = zeros(IMGX,IMGY);

if (window_length/2 == round(window_length/2)) CENTER = window_length/2; x_pad_st = window_length - CENTER - 1; x_pad_fi = window_length - CENTER; else CENTER = (window_length+1)/2; x_pad_st = window_length - CENTER; x_pad_fi = window_length - CENTER; end

X = [zeros(1,x_pad_st) X zeros(1,x_pad_fi)];

iter = 0; for kk = 1:step_dist:LENX iter = iter + 1; XX = X(kk:(kk + window_length - 1)); YY = XX .* WIN; ZZ = abs(fft(YY, padding)); y(iter,:) = ZZ(1:IMGY); end

freq = (1/sampling_rate)/2; imagesc([0:(step_dist*sampling_rate):(sampling_rate*(LENX-1))], ... [0:(freq/(IMGY-1)):freq],y'); xlabel('Time (seconds)'); ylabel('Frequency (Hz)'); axis('xy')

 How can I get the inverse stft to the one I am using?

Answer 1

[Bjorn Gustavsson]

Why not try the generic first step: LOOK AT THE FILE EXCHANGE?

I found:

http://www.mathworks.com/matlabcentral/fileexchange/33451-integrated-stft-istft-onset-detection

HTH

[Igor]

I dont understand this file, its very complex. I tried their exaple, but I use a signal, not a wav. file, so I dont know if it works. Anyhow, I would like to have the inverse to the stft code I use...

[Antoine Liutkus]

You can use this class with a vector instead of a wav file through mysigobject = Signal(data,samplingrate);

all the rest is the same

cheers