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annotate scripts/signal/synthesis.m @ 3238:041ea33fbbf4

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[project @ 1999-03-26 17:48:16 by jwe]
author jwe
date Fri, 26 Mar 1999 17:48:35 +0000
parents e4f4b2d26ee9
children f8dde1807dee
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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 ## usage: X = synthesis (Y, c)
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18 ##
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19 ## recovers a signal X from its short-time Fourier transform Y. c =
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20 ## [win_size, increment, window_type].
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21 ##
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22 ## Y and c can be derived by [Y, c] = stft (X [, ...]).
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23
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24 ## Author: AW <Andreas.Weingessel@ci.tuwien.ac.at>
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25 ## Description: Recover a signal from its short-term Fourier transform
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26
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27 function X = synthesis (Y, c)
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28
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29 if (nargin != 2)
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30 usage ("X = synthesis (Y, c)");
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31 endif
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32
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33 [nr, nc] = size (c);
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34 if (nr * nc != 3)
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35 error ("synthesis: c must contain exactly 3 elements");
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36 endif
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37
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38 ## not necessary, enables better reading
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39 win = c(1);
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40 inc = c(2);
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41 w_type = c(3);
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42
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43 if (w_type == 1)
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44 H = hanning (win);
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45 elseif (w_type == 2)
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46 H = hamming (win);
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47 elseif (w_type == 3)
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48 H = ones (win, 1);
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49 else
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50 error ("synthesis: window_type must be 1, 2, or 3");
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51 endif
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52
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53 Z = real (ifft (Y));
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54 st = fix ((win-inc) / 2);
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55 Z = Z(st:st+inc-1, :);
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56 H = H(st:st+inc-1);
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57
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58 nc = columns(Z);
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59 for i = 1:nc
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60 Z(:, i) = Z(:, i) ./ H;
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61 endfor
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62
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63 X = reshape(Z, inc * nc, 1);
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64
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65 endfunction