Mercurial > octave
annotate scripts/signal/stft.m @ 17754:dffb1e9a6d3b
doc: Final spellcheck of documentation before 3.8 release.
* doc/interpreter/doccheck/aspell-octave.en.pws: Add new words to
Octave-specific dictionary.
* scripts/signal/stft.m: Final spellcheck of documentation before 3.8 release.
| author | Rik <rik@octave.org> |
|---|---|
| date | Thu, 24 Oct 2013 13:53:45 -0700 |
| parents | d63878346099 |
| children | 4197fc428c7d |
| rev | line source |
|---|---|
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1 ## Copyright (C) 1995-2013 Andreas Weingessel |
| 3426 | 2 ## |
| 3922 | 3 ## This file is part of Octave. |
| 4 ## | |
| 5 ## Octave is free software; you can redistribute it and/or modify it | |
| 6 ## under the terms of the GNU General Public License as published by | |
| 7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
| 8 ## your option) any later version. | |
| 3426 | 9 ## |
| 3922 | 10 ## Octave is distributed in the hope that it will be useful, but |
| 3191 | 11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 3426 | 13 ## General Public License for more details. |
| 14 ## | |
| 3191 | 15 ## You should have received a copy of the GNU General Public License |
| 7016 | 16 ## along with Octave; see the file COPYING. If not, see |
| 17 ## <http://www.gnu.org/licenses/>. | |
| 3191 | 18 |
| 3449 | 19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {@var{y} =} stft (@var{x}) |
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21 ## @deftypefnx {Function File} {@var{y} =} stft (@var{x}, @var{win_size}) |
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22 ## @deftypefnx {Function File} {@var{y} =} stft (@var{x}, @var{win_size}, @var{inc}) |
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23 ## @deftypefnx {Function File} {@var{y} =} stft (@var{x}, @var{win_size}, @var{inc}, @var{num_coef}) |
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24 ## @deftypefnx {Function File} {@var{y} =} stft (@var{x}, @var{win_size}, @var{inc}, @var{num_coef}, @var{win_type}) |
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25 ## @deftypefnx {Function File} {[@var{y}, @var{c}] =} stft (@dots{}) |
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26 ## Compute the short-time Fourier transform of the vector @var{x} with |
| 3449 | 27 ## @var{num_coef} coefficients by applying a window of @var{win_size} data |
| 28 ## points and an increment of @var{inc} points. | |
| 3191 | 29 ## |
| 30 ## Before computing the Fourier transform, one of the following windows | |
| 3449 | 31 ## is applied: |
| 32 ## | |
| 33 ## @table @asis | |
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34 ## @item @qcode{"hanning"} |
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35 ## win_type = 1 |
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36 ## |
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37 ## @item @qcode{"hamming"} |
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38 ## win_type = 2 |
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39 ## |
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40 ## @item @qcode{"rectangle"} |
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41 ## win_type = 3 |
| 3449 | 42 ## @end table |
| 43 ## | |
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44 ## The window names can be passed as strings or by the @var{win_type} number. |
| 3191 | 45 ## |
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46 ## The following defaults are used for unspecified arguments: |
| 3449 | 47 ## @var{win_size} = 80, @var{inc} = 24, @var{num_coef} = 64, and |
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48 ## @var{win_type} = 1. |
| 3191 | 49 ## |
| 3449 | 50 ## @code{@var{y} = stft (@var{x}, @dots{})} returns the absolute values |
| 51 ## of the Fourier coefficients according to the @var{num_coef} positive | |
| 52 ## frequencies. | |
| 53 ## | |
| 54 ## @code{[@var{y}, @var{c}] = stft (@code{x}, @dots{})} returns the | |
| 55 ## entire STFT-matrix @var{y} and a 3-element vector @var{c} containing | |
| 56 ## the window size, increment, and window type, which is needed by the | |
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57 ## @code{synthesis} function. |
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58 ## @seealso{synthesis} |
| 3449 | 59 ## @end deftypefn |
| 3191 | 60 |
| 3457 | 61 ## Author: AW <Andreas.Weingessel@ci.tuwien.ac.at> |
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62 ## Description: Short-Time Fourier Transform |
| 3191 | 63 |
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64 function [y, c] = stft (x, win_size = 80, inc = 24, num_coef = 64, win_type = 1) |
| 3426 | 65 |
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66 if (nargin < 1 || nargin > 5) |
| 6046 | 67 print_usage (); |
| 3191 | 68 endif |
| 69 | |
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70 if (ischar (win_type)) |
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71 switch (tolower (win_type)) |
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72 case "hanning" win_type = 1; |
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73 case "hamming" win_type = 2; |
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74 case "rectangle" win_type = 3; |
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75 otherwise |
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76 error ("stft: unknown window type '%s'", win_type); |
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77 endswitch |
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78 endif |
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79 |
| 8506 | 80 ## Check whether X is a vector. |
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81 if (! isvector (x)) |
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82 error ("stft: X must be a vector"); |
| 3191 | 83 endif |
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84 x = x(:); |
| 3191 | 85 |
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86 ncoef = 2 * num_coef; |
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87 if (win_size > ncoef) |
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88 win_size = ncoef; |
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89 printf ("stft: window size adjusted to %f\n", win_size); |
| 3191 | 90 endif |
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91 num_win = fix ((rows (x) - win_size) / inc); |
| 3191 | 92 |
| 93 ## compute the window coefficients | |
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94 switch (win_type) |
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95 case 1 win_coef = hanning (win_size); |
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96 case 2 win_coef = hamming (win_size); |
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97 case 3 win_coef = ones (win_size, 1); |
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98 endswitch |
| 3426 | 99 |
| 8506 | 100 ## Create a matrix Z whose columns contain the windowed time-slices. |
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101 z = zeros (ncoef, num_win + 1); |
| 3191 | 102 start = 1; |
| 103 for i = 0:num_win | |
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104 z(1:win_size, i+1) = x(start:start+win_size-1) .* win_coef; |
| 3191 | 105 start = start + inc; |
| 106 endfor | |
| 107 | |
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108 y = fft (z); |
| 3191 | 109 |
| 110 if (nargout == 1) | |
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111 y = abs (y(1:num_coef, :)); |
| 3191 | 112 else |
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113 c = [win_size, inc, win_type]; |
| 3191 | 114 endif |
| 115 | |
| 116 endfunction | |
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117 |