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annotate scripts/audio/lin2mu.m @ 11587:c792872f8942
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| author | John W. Eaton <jwe@octave.org> |
|---|---|
| date | Thu, 20 Jan 2011 17:35:29 -0500 |
| parents | fd0a3ac60b0e |
| children | 605ed5bbb643 |
| rev | line source |
|---|---|
| 11523 | 1 ## Copyright (C) 1995-2011 John W. Eaton |
| 2313 | 2 ## |
| 3 ## This file is part of Octave. | |
| 4 ## | |
| 5 ## Octave is free software; you can redistribute it and/or modify it | |
| 6 ## under the terms of the GNU General Public License as published by | |
| 7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
| 8 ## your option) any later version. | |
| 2313 | 9 ## |
| 10 ## Octave is distributed in the hope that it will be useful, but | |
| 11 ## WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 ## General Public License for more details. | |
| 14 ## | |
| 15 ## You should have received a copy of the GNU General Public License | |
| 7016 | 16 ## along with Octave; see the file COPYING. If not, see |
| 17 ## <http://www.gnu.org/licenses/>. | |
| 2303 | 18 |
| 3332 | 19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} lin2mu (@var{x}) |
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21 ## @deftypefnx {Function File} {} lin2mu (@var{x}, @var{n}) |
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22 ## Convert audio data from linear to mu-law. Mu-law values use 8-bit |
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23 ## unsigned integers. Linear values use @var{n}-bit signed integers or |
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24 ## floating point values in the range -1 @leq{} @var{x} @leq{} 1 if |
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25 ## @var{n} is 0. |
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c792872f8942
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26 ## If @var{n} is not specified it defaults to 0, 8, or 16 depending on |
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27 ## the range of values in @var{x}. |
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28 ## @seealso{mu2lin, loadaudio, saveaudio} |
| 3332 | 29 ## @end deftypefn |
| 5642 | 30 |
| 2311 | 31 |
| 3911 | 32 ## Author: Andreas Weingessel <Andreas.Weingessel@ci.tuwien.ac.at> |
| 2312 | 33 ## Created: 17 October 1994 |
| 34 ## Adapted-By: jwe | |
| 35 | |
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36 function y = lin2mu (x, n) |
| 2325 | 37 |
| 3911 | 38 if (nargin == 1) |
| 39 range = max (abs (x (:))); | |
| 40 if (range <= 1) | |
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41 n = 0; |
| 3911 | 42 elseif (range <= 128) |
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43 n = 8; |
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44 warning ("lin2mu: no precision specified, so using %d", n); |
| 3911 | 45 else |
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46 n = 16; |
| 3911 | 47 endif |
| 48 elseif (nargin == 2) | |
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49 if (n != 0 && n != 8 && n != 16) |
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50 error ("lin2mu: N must be either 0, 8 or 16"); |
| 3911 | 51 endif |
| 52 else | |
| 6046 | 53 print_usage (); |
| 1636 | 54 endif |
| 2325 | 55 |
| 3911 | 56 ## Transform real and n-bit format to 16-bit. |
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57 if (n == 0) |
| 3911 | 58 ## [-1,1] -> [-32768, 32768] |
| 59 x = 32768 * x; | |
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60 elseif (n != 16) |
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61 x = 2^(16-n) .* x; |
| 1636 | 62 endif |
| 63 | |
| 3911 | 64 ## Determine sign of x, set sign(0) = 1. |
| 1636 | 65 sig = sign(x) + (x == 0); |
| 66 | |
| 3911 | 67 ## Take absolute value of x, but force it to be smaller than 32636; |
| 68 ## add bias. | |
| 69 x = min (abs (x), 32635) + 132; | |
| 1636 | 70 |
| 3911 | 71 ## Find exponent and fraction of bineary representation. |
| 1636 | 72 [f, e] = log2 (x); |
| 73 | |
| 74 y = 64 * sig - 16 * e - fix (32 * f) + 335; | |
| 75 | |
| 76 endfunction |