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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 ## usage: y = lin2mu (x) |
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21 ## |
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22 ## x is a vector of an 8- or 16-bit linearly encoded audio sample, |
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23 ## This is transformed into a mu-law encoded vector. |
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24 |
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25 function y = lin2mu (x) |
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26 |
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27 ## Written by AW (Andreas.Weingessel@ci.tuwien.ac.at) on Oct 17, 1994 |
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28 ## Copyright Department of Probability Theory and Statistics TU Wien |
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29 |
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30 if (nargin != 1) |
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31 usage ("y = lin2mu (x)"); |
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32 endif |
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33 |
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34 if (! is_vector (x)) |
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35 error ("lin2mu: x must be a vector"); |
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36 endif |
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37 |
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38 ## transform 8-bit format to 16-bit |
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39 if (max (abs (x)) <= 128) |
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40 x = 256 .* x; |
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41 endif |
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42 |
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43 ## determine sign of x, set sign(0) = 1. |
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44 sig = sign(x) + (x == 0); |
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45 |
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46 ## take absolute value of x, but force it to be smaller than 32636; |
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47 ## add bias |
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48 x = min (abs (x), 32635 * ones (size (x))) + 132; |
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49 |
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50 ## find exponent and fraction of bineary representation |
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51 [f, e] = log2 (x); |
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52 |
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53 y = 64 * sig - 16 * e - fix (32 * f) + 335; |
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54 |
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55 endfunction |
