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1 ## Copyright (C) 1995, 1996, 1997 Andreas Weingessel |
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2 ## |
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3 ## This program is free software; you can redistribute it and/or modify |
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4 ## it under the terms of the GNU General Public License as published by |
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5 ## the Free Software Foundation; either version 2, or (at your option) |
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6 ## any later version. |
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7 ## |
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8 ## This program is distributed in the hope that it will be useful, but |
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9 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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10 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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11 ## General Public License for more details. |
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12 ## |
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13 ## You should have received a copy of the GNU General Public License |
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14 ## along with this file. If not, write to the Free Software Foundation, |
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15 ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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16 |
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17 ## -*- texinfo -*- |
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18 ## @deftypefn {Function File} {@var{x} =} synthesis (@var{y}, @var{c}) |
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19 ## Compute a signal from its short-time Fourier transform @var{y} and a |
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20 ## 3-element vector @var{c} specifying window size, increment, and |
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21 ## window type. |
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22 ## |
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23 ## The values @var{y} and @var{c} can be derived by |
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24 ## |
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25 ## @example |
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26 ## [@var{y}, @var{c}] = stft (@var{x} , @dots{}) |
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27 ## @end example |
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28 ## @end deftypefn |
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29 |
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30 ## Author: AW <Andreas.Weingessel@ci.tuwien.ac.at> |
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31 ## Description: Recover a signal from its short-term Fourier transform |
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32 |
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33 function X = synthesis (Y, c) |
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34 |
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35 if (nargin != 2) |
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36 usage ("X = synthesis (Y, c)"); |
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37 endif |
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38 |
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39 [nr, nc] = size (c); |
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40 if (nr * nc != 3) |
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41 error ("synthesis: c must contain exactly 3 elements"); |
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42 endif |
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43 |
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44 ## not necessary, enables better reading |
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45 win = c(1); |
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46 inc = c(2); |
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47 w_type = c(3); |
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48 |
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49 if (w_type == 1) |
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50 H = hanning (win); |
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51 elseif (w_type == 2) |
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52 H = hamming (win); |
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53 elseif (w_type == 3) |
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54 H = ones (win, 1); |
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55 else |
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56 error ("synthesis: window_type must be 1, 2, or 3"); |
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57 endif |
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58 |
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59 Z = real (ifft (Y)); |
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60 st = fix ((win-inc) / 2); |
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61 Z = Z(st:st+inc-1, :); |
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62 H = H(st:st+inc-1); |
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63 |
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64 nc = columns(Z); |
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65 for i = 1:nc |
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66 Z(:, i) = Z(:, i) ./ H; |
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67 endfor |
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68 |
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69 X = reshape(Z, inc * nc, 1); |
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70 |
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71 endfunction |
