--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/signal/stft.m	Fri Oct 23 05:44:01 1998 +0000
@@ -0,0 +1,114 @@
+## Copyright (C) 1995, 1996, 1997  Andreas Weingessel
+## 
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2, or (at your option)
+## any later version.
+## 
+## This program is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details. 
+## 
+## You should have received a copy of the GNU General Public License
+## along with this file.  If not, write to the Free Software Foundation,
+## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+## usage:  [Y, c] = stft (X [, win_size [, inc [, num_coef [, w_type]]]])
+##
+## Computes the short-term Fourier transform of the vector X with
+## "num_coef" coefficients by applying a window of "win_size" data
+## points and an increment of "inc" points.
+##
+## Before computing the Fourier transform, one of the following windows
+## is applied:  "hanning" (w_type = 1), "hamming" (w_type = 2),
+## "rectangle" (w_type = 3).  The window names can be passed as strings
+## or by the w_type number.
+##
+## If not all arguments are specified, the following defaults are used:
+## win_size = 80, inc = 24, num_coef = 64, w_type = 1.
+##
+## Y = stft (X [, ...]) returns the absolute values of the Fourier
+## coefficients according to the num_coef positive frequencies.
+## [Y, c] = stft (X [, ...]) returns the entire STFT-matrix Y and a
+## vector c = [win_size, inc, w_type] which is needed by the synthesis
+## function.
+
+## Author:  AW <Andreas.Weingessel@ci.tuwien.ac.at>
+## Description:  Short-term Fourier transform
+
+function [Y, c] = stft(X, win, inc, coef, w_type)
+  
+  ## default values of unspecified arguments
+  if (nargin < 5)
+    w_type = 1;
+    if (nargin < 4)
+      coef = 64;
+      if (nargin < 3)
+	inc = 24;
+	if (nargin < 2)
+	  win = 80;
+	endif
+      endif
+    endif
+  elseif (nargin == 5)  
+    if (isstr (w_type))
+      if (strcmp (w_type, "hanning"))
+	w_type = 1;
+      elseif (strcmp (w_type, "hamming"))
+	w_type = 2;
+      elseif (strcmp (w_type, "rectangle"))
+	w_type = 3;
+      else
+	error (["stft:  unknown window type `", w_type, "'"])
+      endif
+    endif
+  else
+    usage ("[Y [, c]] = ", ...
+	   "stft(X [, win_size [, inc [, num_coef [, w_type]]]])");
+  endif
+
+  ## check whether X is a vector
+  [nr, nc] = size (X);
+  if (nc != 1)
+    if (nr == 1)
+      X = X'; 
+      nr = nc;
+    else
+      error ("stft:  X must be a vector");
+    endif
+  endif
+
+  num_coef = 2 * coef;
+  if (win > num_coef)
+    win = num_coef;
+    printf ("stft:  window size adjusted to %f\n", win);
+  endif
+  num_win = fix ((nr - win) / inc);
+
+  ## compute the window coefficients
+  if (w_type == 3)		# rectangular window 
+    WIN_COEF = ones (win, 1);
+  elseif (w_type == 2)		# Hamming window
+    WIN_COEF = hamming (win);
+  else				# Hanning window
+    WIN_COEF = hanning (win);
+  endif
+  
+  ## create a matrix Z whose columns contain the windowed time-slices
+  Z = zeros (num_coef, num_win + 1);
+  start = 1;
+  for i = 0:num_win
+    Z(1:win, i+1) = X(start:start+win-1) .* WIN_COEF;
+    start = start + inc;
+  endfor
+
+  Y = fft (Z);
+
+  if (nargout == 1)
+    Y = abs (Y(1:coef, :));
+  else
+    c = [win, inc, w_type];
+  endif
+
+endfunction