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1 ### Copyright (C) 1996 John W. Eaton |
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2 ### |
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3 ### This file is part of Octave. |
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4 ### |
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5 ### Octave is free software; you can redistribute it and/or modify it |
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6 ### under the terms of the GNU General Public License as published by |
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7 ### the Free Software Foundation; either version 2, or (at your option) |
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8 ### any later version. |
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9 ### |
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10 ### Octave is distributed in the hope that it will be useful, but |
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11 ### WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ### General Public License for more details. |
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14 ### |
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15 ### You should have received a copy of the GNU General Public License |
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16 ### along with Octave; see the file COPYING. If not, write to the Free |
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17 ### Software Foundation, 59 Temple Place - Suite 330, Boston, MA |
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18 ### 02111-1307, USA. |
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19 |
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20 function y = mu2lin (x, bit) |
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21 |
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22 ## usage: y = mu2lin (x [, bit]) |
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23 ## |
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24 ## If x is a vector of audio data with mu-law encoding, mu2lin (x) |
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25 ## holds the same data with linear encoding. |
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26 ## The optional argument bit specifies whether the input data is |
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27 ## 8 bit (default) or 16 bit. |
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28 |
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29 ## Written by AW (Andreas.Weingessel@ci.tuwien.ac.at) on Oct 18, 1994 |
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30 ## Updated by AW (Andreas.Weingessel@ci.tuwien.ac.at) on Oct 27, 1994 |
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31 ## Copyright Department of Probability Theory and Statistics TU Wien |
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32 |
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33 if (nargin == 1) |
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34 bit = 8; |
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35 elseif (nargin == 2) |
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36 if (bit != 8 && bit != 16) |
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37 error ("mu2lin: bit must be either 8 or 16"); |
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38 endif |
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39 else |
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40 usage ("y = mu2lin (x [, bit])"); |
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41 endif |
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42 |
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43 if (! is_vector (x)) |
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44 error ("mu2lin: x must be a vector"); |
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45 endif |
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46 |
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47 exp_lut = [0; 132; 396; 924; 1980; 4092; 8316; 16764]; |
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48 |
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49 ## invert x bitwise |
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50 x = 255 - x; |
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51 |
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52 ## determine sign of y |
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53 sig = (x > 127); |
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54 |
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55 ## determine exponent and fraction of y |
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56 e = fix (x / 16) - 8 .* sig + 1; |
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57 f = rem (x, 16); |
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58 |
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59 sig = 1 - 2 .* sig; |
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60 y = (pow2 (f, e + 2) + exp_lut (e)) .* sig; |
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61 |
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62 ## convert to 8-bit |
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63 if (bit == 8) |
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64 ld = max (abs (y)); |
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65 if (ld < 16384) |
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66 sc = 64 / ld; |
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67 else |
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68 sc = 1 / 256; |
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69 endif |
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70 y = fix (y * sc); |
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71 endif |
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72 |
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73 endfunction |
