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1 ## Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2002, 2005, 2006, |
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2 ## 2007 Andreas Weingessel |
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3 ## |
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4 ## This file is part of Octave. |
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5 ## |
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6 ## Octave is free software; you can redistribute it and/or modify it |
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7 ## under the terms of the GNU General Public License as published by |
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8 ## the Free Software Foundation; either version 3 of the License, or (at |
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9 ## your option) any later version. |
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10 ## |
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11 ## Octave is distributed in the hope that it will be useful, but |
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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14 ## General Public License for more details. |
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15 ## |
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16 ## You should have received a copy of the GNU General Public License |
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17 ## along with Octave; see the file COPYING. If not, see |
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18 ## <http://www.gnu.org/licenses/>. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} synthesis (@var{y}, @var{c}) |
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22 ## Compute a signal from its short-time Fourier transform @var{y} and a |
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23 ## 3-element vector @var{c} specifying window size, increment, and |
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24 ## window type. |
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25 ## |
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26 ## The values @var{y} and @var{c} can be derived by |
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27 ## |
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28 ## @example |
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29 ## [@var{y}, @var{c}] = stft (@var{x} , @dots{}) |
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30 ## @end example |
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31 ## @end deftypefn |
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32 |
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33 ## Author: AW <Andreas.Weingessel@ci.tuwien.ac.at> |
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34 ## Description: Recover a signal from its short-term Fourier transform |
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35 |
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36 function X = synthesis (Y, c) |
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37 |
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38 if (nargin != 2) |
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39 print_usage (); |
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40 endif |
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41 |
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42 [nr, nc] = size (c); |
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43 if (nr * nc != 3) |
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44 error ("synthesis: c must contain exactly 3 elements"); |
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45 endif |
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46 |
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47 ## not necessary, enables better reading |
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48 win = c(1); |
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49 inc = c(2); |
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50 w_type = c(3); |
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51 |
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52 if (w_type == 1) |
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53 H = hanning (win); |
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54 elseif (w_type == 2) |
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55 H = hamming (win); |
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56 elseif (w_type == 3) |
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57 H = ones (win, 1); |
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58 else |
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59 error ("synthesis: window_type must be 1, 2, or 3"); |
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60 endif |
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61 |
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62 Z = real (ifft (Y)); |
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63 st = fix ((win-inc) / 2); |
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64 Z = Z(st:st+inc-1, :); |
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65 H = H(st:st+inc-1); |
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66 |
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67 nc = columns(Z); |
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68 for i = 1:nc |
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69 Z(:, i) = Z(:, i) ./ H; |
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70 endfor |
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71 |
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72 X = reshape(Z, inc * nc, 1); |
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73 |
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74 endfunction |
