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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 ## Author: AW <Andreas.Weingessel@ci.tuwien.ac.at> |
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26 ## Created: 17 October 1994 |
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27 ## Adapted-By: jwe |
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28 |
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29 function y = lin2mu (x) |
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30 |
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1636
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31 if (nargin != 1) |
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32 usage ("y = lin2mu (x)"); |
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33 endif |
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34 |
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35 if (! is_vector (x)) |
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36 error ("lin2mu: x must be a vector"); |
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37 endif |
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38 |
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39 ## transform 8-bit format to 16-bit |
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1636
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40 if (max (abs (x)) <= 128) |
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41 x = 256 .* x; |
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42 endif |
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43 |
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2303
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44 ## determine sign of x, set sign(0) = 1. |
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45 sig = sign(x) + (x == 0); |
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46 |
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2303
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47 ## take absolute value of x, but force it to be smaller than 32636; |
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48 ## add bias |
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49 x = min (abs (x), 32635 * ones (size (x))) + 132; |
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50 |
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2303
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51 ## find exponent and fraction of bineary representation |
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1636
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52 [f, e] = log2 (x); |
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53 |
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54 y = 64 * sig - 16 * e - fix (32 * f) + 335; |
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55 |
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56 endfunction |
