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1 ## Copyright (C) 1995, 1996, 1997, 1999, 2000, 2002, 2004, 2005, 2006, |
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2 ## 2007 John W. Eaton |
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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} {} mu2lin (@var{x}, @var{bps}) |
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22 ## Converts audio data from linear to mu-law. Mu-law values are 8-bit |
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23 ## unsigned integers. Linear values use @var{n}-bit signed integers |
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24 ## or floating point values in the range -1<=y<=1 if @var{n} is 0. If |
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25 ## @var{n} is not specified it defaults to 8. |
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26 ## @seealso{lin2mu, loadaudio, saveaudio, playaudio, setaudio, record} |
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27 ## @end deftypefn |
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28 |
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29 ## Author: Andreas Weingessel <Andreas.Weingessel@ci.tuwien.ac.at> |
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30 ## Created: 18 October 1994 |
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31 ## Adapted-By: jwe |
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32 |
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33 function y = mu2lin (x, bit) |
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34 |
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35 if (nargin == 1) |
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36 ## COMPATIBILITY -- bps defaults to 8 for octave, 0 for Matlab |
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37 bit = 8; |
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38 elseif (nargin == 2) |
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39 if (bit != 0 && bit != 8 && bit != 16) |
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40 error ("mu2lin: bit must be either 0, 8 or 16"); |
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41 endif |
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42 else |
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43 print_usage (); |
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44 endif |
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45 |
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46 ulaw = [32124, 31100, 30076, 29052, 28028, 27004, 25980, 24956, \ |
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47 23932, 22908, 21884, 20860, 19836, 18812, 17788, 16764, \ |
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48 15996, 15484, 14972, 14460, 13948, 13436, 12924, 12412, \ |
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49 11900, 11388, 10876, 10364, 9852, 9340, 8828, 8316, \ |
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50 7932, 7676, 7420, 7164, 6908, 6652, 6396, 6140, \ |
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51 5884, 5628, 5372, 5116, 4860, 4604, 4348, 4092, \ |
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52 3900, 3772, 3644, 3516, 3388, 3260, 3132, 3004, \ |
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53 2876, 2748, 2620, 2492, 2364, 2236, 2108, 1980, \ |
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54 1884, 1820, 1756, 1692, 1628, 1564, 1500, 1436, \ |
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55 1372, 1308, 1244, 1180, 1116, 1052, 988, 924, \ |
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56 876, 844, 812, 780, 748, 716, 684, 652, \ |
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57 620, 588, 556, 524, 492, 460, 428, 396, \ |
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58 372, 356, 340, 324, 308, 292, 276, 260, \ |
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59 244, 228, 212, 196, 180, 164, 148, 132, \ |
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60 120, 112, 104, 96, 88, 80, 72, 64, \ |
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61 56, 48, 40, 32, 24, 16, 8, 0 ]; |
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62 |
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63 ulaw = [ -ulaw, ulaw ]; |
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64 |
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65 ## Set the shape of y to that of x overwrites the contents of y with |
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66 ## ulaw of x. |
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67 y = x; |
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68 y(:) = ulaw (x + 1); |
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69 |
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70 ## Convert to real or 8-bit. |
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71 if (bit == 0) |
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72 ## [ -32768, 32767 ] -> [ -1, 1) |
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73 y = y/32768; |
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74 elseif (bit == 8) |
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75 ld = max (abs (y (:))); |
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76 if (ld < 16384 && ld > 0) |
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77 sc = 64 / ld; |
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78 else |
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79 sc = 1 / 256; |
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80 endif |
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81 y = fix (y * sc); |
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82 endif |
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83 |
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84 endfunction |
