Mercurial > octave
annotate scripts/signal/stft.m @ 9072:bd8e388043c4
Cleanup documentation for signal.texi, image.texi, audio.texi
| author | Rik <rdrider0-list@yahoo.com> |
|---|---|
| date | Wed, 01 Apr 2009 17:06:45 -0700 |
| parents | eb63fbe60fab |
| children | 3140cb7a05a1 |
| rev | line source |
|---|---|
| 8920 | 1 ## Copyright (C) 1995, 1996, 1997, 1998, 2000, 2002, 2005, 2006, 2007, 2009 |
| 7017 | 2 ## Andreas Weingessel |
| 3426 | 3 ## |
| 3922 | 4 ## This file is part of Octave. |
| 5 ## | |
| 6 ## Octave is free software; you can redistribute it and/or modify it | |
| 7 ## under the terms of the GNU General Public License as published by | |
| 7016 | 8 ## the Free Software Foundation; either version 3 of the License, or (at |
| 9 ## your option) any later version. | |
| 3426 | 10 ## |
| 3922 | 11 ## Octave is distributed in the hope that it will be useful, but |
| 3191 | 12 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 3426 | 14 ## General Public License for more details. |
| 15 ## | |
| 3191 | 16 ## You should have received a copy of the GNU General Public License |
| 7016 | 17 ## along with Octave; see the file COPYING. If not, see |
| 18 ## <http://www.gnu.org/licenses/>. | |
| 3191 | 19 |
| 3449 | 20 ## -*- texinfo -*- |
| 6547 | 21 ## @deftypefn {Function File} {[@var{y}, @var{c}] =} stft (@var{x}, @var{win_size}, @var{inc}, @var{num_coef}, @var{w_type}) |
|
9072
bd8e388043c4
Cleanup documentation for signal.texi, image.texi, audio.texi
Rik <rdrider0-list@yahoo.com>
parents:
8920
diff
changeset
|
22 ## Compute the short-time Fourier transform of the vector @var{x} with |
| 3449 | 23 ## @var{num_coef} coefficients by applying a window of @var{win_size} data |
| 24 ## points and an increment of @var{inc} points. | |
| 3191 | 25 ## |
| 26 ## Before computing the Fourier transform, one of the following windows | |
| 3449 | 27 ## is applied: |
| 28 ## | |
| 29 ## @table @asis | |
| 30 ## @item hanning | |
| 31 ## w_type = 1 | |
| 32 ## @item hamming | |
| 33 ## w_type = 2 | |
| 34 ## @item rectangle | |
| 35 ## w_type = 3 | |
| 36 ## @end table | |
| 37 ## | |
| 38 ## The window names can be passed as strings or by the @var{w_type} number. | |
| 3191 | 39 ## |
| 40 ## If not all arguments are specified, the following defaults are used: | |
| 3449 | 41 ## @var{win_size} = 80, @var{inc} = 24, @var{num_coef} = 64, and |
| 42 ## @var{w_type} = 1. | |
| 3191 | 43 ## |
| 3449 | 44 ## @code{@var{y} = stft (@var{x}, @dots{})} returns the absolute values |
| 45 ## of the Fourier coefficients according to the @var{num_coef} positive | |
| 46 ## frequencies. | |
| 47 ## | |
| 48 ## @code{[@var{y}, @var{c}] = stft (@code{x}, @dots{})} returns the | |
| 49 ## entire STFT-matrix @var{y} and a 3-element vector @var{c} containing | |
| 50 ## the window size, increment, and window type, which is needed by the | |
| 51 ## synthesis function. | |
| 52 ## @end deftypefn | |
| 3191 | 53 |
| 3457 | 54 ## Author: AW <Andreas.Weingessel@ci.tuwien.ac.at> |
|
9072
bd8e388043c4
Cleanup documentation for signal.texi, image.texi, audio.texi
Rik <rdrider0-list@yahoo.com>
parents:
8920
diff
changeset
|
55 ## Description: Short-Time Fourier Transform |
| 3191 | 56 |
| 57 function [Y, c] = stft(X, win, inc, coef, w_type) | |
| 3426 | 58 |
| 8506 | 59 ## Default values of unspecified arguments. |
| 3191 | 60 if (nargin < 5) |
| 61 w_type = 1; | |
| 62 if (nargin < 4) | |
| 63 coef = 64; | |
| 64 if (nargin < 3) | |
| 3426 | 65 inc = 24; |
| 66 if (nargin < 2) | |
| 67 win = 80; | |
| 68 endif | |
| 3191 | 69 endif |
| 70 endif | |
| 3426 | 71 elseif (nargin == 5) |
| 5443 | 72 if (ischar (w_type)) |
| 3191 | 73 if (strcmp (w_type, "hanning")) |
| 3426 | 74 w_type = 1; |
| 3191 | 75 elseif (strcmp (w_type, "hamming")) |
| 3426 | 76 w_type = 2; |
| 3191 | 77 elseif (strcmp (w_type, "rectangle")) |
| 3426 | 78 w_type = 3; |
| 3191 | 79 else |
| 3457 | 80 error ("stft: unknown window type `%s'", w_type); |
| 3191 | 81 endif |
| 82 endif | |
| 83 else | |
| 6046 | 84 print_usage (); |
| 3191 | 85 endif |
| 86 | |
| 8506 | 87 ## Check whether X is a vector. |
| 3191 | 88 [nr, nc] = size (X); |
| 89 if (nc != 1) | |
| 90 if (nr == 1) | |
| 3426 | 91 X = X'; |
| 3191 | 92 nr = nc; |
| 93 else | |
| 3457 | 94 error ("stft: X must be a vector"); |
| 3191 | 95 endif |
| 96 endif | |
| 97 | |
| 98 num_coef = 2 * coef; | |
| 99 if (win > num_coef) | |
| 100 win = num_coef; | |
| 3457 | 101 printf ("stft: window size adjusted to %f\n", win); |
| 3191 | 102 endif |
| 103 num_win = fix ((nr - win) / inc); | |
| 104 | |
| 105 ## compute the window coefficients | |
| 8506 | 106 if (w_type == 3) |
| 107 ## Rectangular window. | |
| 3191 | 108 WIN_COEF = ones (win, 1); |
| 8506 | 109 elseif (w_type == 2) |
| 110 ## Hamming window. | |
| 3191 | 111 WIN_COEF = hamming (win); |
| 8506 | 112 else |
| 113 ## Hanning window. | |
| 3191 | 114 WIN_COEF = hanning (win); |
| 115 endif | |
| 3426 | 116 |
| 8506 | 117 ## Create a matrix Z whose columns contain the windowed time-slices. |
| 3191 | 118 Z = zeros (num_coef, num_win + 1); |
| 119 start = 1; | |
| 120 for i = 0:num_win | |
| 121 Z(1:win, i+1) = X(start:start+win-1) .* WIN_COEF; | |
| 122 start = start + inc; | |
| 123 endfor | |
| 124 | |
| 125 Y = fft (Z); | |
| 126 | |
| 127 if (nargout == 1) | |
| 128 Y = abs (Y(1:coef, :)); | |
| 129 else | |
| 130 c = [win, inc, w_type]; | |
| 131 endif | |
| 132 | |
| 133 endfunction |