update packages

[CreaPhase.git] / octave_packages / m / signal / stft.m

diff --git a/octave_packages/m/signal/stft.m b/octave_packages/m/signal/stft.m
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+## Copyright (C) 1995-2012 Andreas Weingessel
+##
+## This file is part of Octave.
+##
+## Octave 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 3 of the License, or (at
+## your option) any later version.
+##
+## Octave 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 Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {[@var{y}, @var{c}] =} stft (@var{x}, @var{win_size}, @var{inc}, @var{num_coef}, @var{win_type})
+## Compute the short-time Fourier transform of the vector @var{x} with
+## @var{num_coef} coefficients by applying a window of @var{win_size} data
+## points and an increment of @var{inc} points.
+##
+## Before computing the Fourier transform, one of the following windows
+## is applied:
+##
+## @table @asis
+## @item @nospell{hanning}
+## win_type = 1
+##
+## @item @nospell{hamming}
+## win_type = 2
+##
+## @item rectangle
+## win_type = 3
+## @end table
+##
+## The window names can be passed as strings or by the @var{win_type} number.
+##
+## If not all arguments are specified, the following defaults are used:
+## @var{win_size} = 80, @var{inc} = 24, @var{num_coef} = 64, and
+## @var{win_type} = 1.
+##
+## @code{@var{y} = stft (@var{x}, @dots{})} returns the absolute values
+## of the Fourier coefficients according to the @var{num_coef} positive
+## frequencies.
+##
+## @code{[@var{y}, @var{c}] = stft (@code{x}, @dots{})} returns the
+## entire STFT-matrix @var{y} and a 3-element vector @var{c} containing
+## the window size, increment, and window type, which is needed by the
+## synthesis function.
+## @end deftypefn
+
+## Author: AW <Andreas.Weingessel@ci.tuwien.ac.at>
+## Description: Short-Time Fourier Transform
+
+function [y, c] = stft(x, win_size, inc, num_coef, win_type)
+
+  ## Default values of unspecified arguments.
+  if (nargin < 5)
+    win_type = 1;
+    if (nargin < 4)
+      num_coef = 64;
+      if (nargin < 3)
+        inc = 24;
+        if (nargin < 2)
+          win_size = 80;
+        endif
+      endif
+    endif
+  elseif (nargin == 5)
+    if (ischar (win_type))
+      if (strcmp (win_type, "hanning"))
+        win_type = 1;
+      elseif (strcmp (win_type, "hamming"))
+        win_type = 2;
+      elseif (strcmp (win_type, "rectangle"))
+        win_type = 3;
+      else
+        error ("stft: unknown window type `%s'", win_type);
+      endif
+    endif
+  else
+    print_usage ();
+  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
+
+  ncoef = 2 * num_coef;
+  if (win_size > ncoef)
+    win_size = ncoef;
+    printf ("stft: window size adjusted to %f\n", win_size);
+  endif
+  num_win = fix ((nr - win_size) / inc);
+
+  ## compute the window coefficients
+  if (win_type == 3)
+    ## Rectangular window.
+    win_coef = ones (win_size, 1);
+  elseif (win_type == 2)
+    ## Hamming window.
+    win_coef = hamming (win_size);
+  else
+    ## Hanning window.
+    win_coef = hanning (win_size);
+  endif
+
+  ## Create a matrix Z whose columns contain the windowed time-slices.
+  z = zeros (ncoef, num_win + 1);
+  start = 1;
+  for i = 0:num_win
+    z(1:win_size, i+1) = x(start:start+win_size-1) .* win_coef;
+    start = start + inc;
+  endfor
+
+  y = fft (z);
+
+  if (nargout == 1)
+    y = abs (y(1:num_coef, :));
+  else
+    c = [win_size, inc, win_type];
+  endif
+
+endfunction