1########################################################################
2##
3## Copyright (C) 1995-2021 The Octave Project Developers
4##
5## See the file COPYRIGHT.md in the top-level directory of this
6## distribution or <https://octave.org/copyright/>.
7##
8## This file is part of Octave.
9##
10## Octave is free software: you can redistribute it and/or modify it
11## under the terms of the GNU General Public License as published by
12## the Free Software Foundation, either version 3 of the License, or
13## (at your option) any later version.
14##
15## Octave is distributed in the hope that it will be useful, but
16## WITHOUT ANY WARRANTY; without even the implied warranty of
17## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18## GNU General Public License for more details.
19##
20## You should have received a copy of the GNU General Public License
21## along with Octave; see the file COPYING.  If not, see
22## <https://www.gnu.org/licenses/>.
23##
24########################################################################
25
26## -*- texinfo -*-
27## @deftypefn {} {@var{x} =} synthesis (@var{y}, @var{c})
28## Compute a signal from its short-time Fourier transform @var{y} and a
29## 3-element vector @var{c} specifying window size, increment, and window type.
30##
31## The values @var{y} and @var{c} can be derived by
32##
33## @example
34## [@var{y}, @var{c}] = stft (@var{x} , @dots{})
35## @end example
36## @seealso{stft}
37## @end deftypefn
38
39function x = synthesis (y, c)
40
41  if (nargin != 2)
42    print_usage ();
43  endif
44
45  if (numel (c) != 3)
46    error ("synthesis: C must contain exactly 3 elements");
47  endif
48
49  w_size = c(1);
50  inc    = c(2);
51  w_type = c(3);
52
53  if (w_type == 1)
54    w_coeff = hanning (w_size);
55  elseif (w_type == 2)
56    w_coeff = hamming (w_size);
57  elseif (w_type == 3)
58    w_coeff = ones (w_size, 1);
59  else
60    error ("synthesis: window_type must be 1, 2, or 3");
61  endif
62
63  z = real (ifft (y));
64  st = fix ((w_size-inc) / 2);
65  z = z(st+1:st+inc, :);
66  w_coeff = w_coeff(st+1:st+inc);
67
68  nc = columns (z);
69  for i = 1:nc
70    z(:, i) ./= w_coeff;
71  endfor
72
73  x = reshape (z, inc * nc, 1);
74
75endfunction
76