1######################################################################## 2## 3## Copyright (C) 1995-2021 The Octave Project Developers 4## 5## See the file COPYRIGHT.md in the top-level directory of this 6## distribution or <https://octave.org/copyright/>. 7## 8## This file is part of Octave. 9## 10## Octave is free software: you can redistribute it and/or modify it 11## under the terms of the GNU General Public License as published by 12## the Free Software Foundation, either version 3 of the License, or 13## (at your option) any later version. 14## 15## Octave is distributed in the hope that it will be useful, but 16## WITHOUT ANY WARRANTY; without even the implied warranty of 17## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18## GNU General Public License for more details. 19## 20## You should have received a copy of the GNU General Public License 21## along with Octave; see the file COPYING. If not, see 22## <https://www.gnu.org/licenses/>. 23## 24######################################################################## 25 26## -*- texinfo -*- 27## @deftypefn {} {@var{y} =} mu2lin (@var{x}, @var{n}) 28## Convert audio data from mu-law to linear. 29## 30## Mu-law values are 8-bit unsigned integers. Linear values use @var{n}-bit 31## signed integers or floating point values in the range -1 @leq{} @var{y} 32## @leq{} 1 if @var{n} is 0. 33## 34## If @var{n} is not specified it defaults to 0. 35## @seealso{lin2mu} 36## @end deftypefn 37 38function y = mu2lin (x, n = 0) 39 40 if (nargin == 2) 41 if (n != 0 && n != 8 && n != 16) 42 error ("mu2lin: N must be either 0, 8, or 16"); 43 endif 44 elseif (nargin != 1) 45 print_usage (); 46 endif 47 48 ulaw = [32124, 31100, 30076, 29052, 28028, 27004, 25980, 24956, ... 49 23932, 22908, 21884, 20860, 19836, 18812, 17788, 16764, ... 50 15996, 15484, 14972, 14460, 13948, 13436, 12924, 12412, ... 51 11900, 11388, 10876, 10364, 9852, 9340, 8828, 8316, ... 52 7932, 7676, 7420, 7164, 6908, 6652, 6396, 6140, ... 53 5884, 5628, 5372, 5116, 4860, 4604, 4348, 4092, ... 54 3900, 3772, 3644, 3516, 3388, 3260, 3132, 3004, ... 55 2876, 2748, 2620, 2492, 2364, 2236, 2108, 1980, ... 56 1884, 1820, 1756, 1692, 1628, 1564, 1500, 1436, ... 57 1372, 1308, 1244, 1180, 1116, 1052, 988, 924, ... 58 876, 844, 812, 780, 748, 716, 684, 652, ... 59 620, 588, 556, 524, 492, 460, 428, 396, ... 60 372, 356, 340, 324, 308, 292, 276, 260, ... 61 244, 228, 212, 196, 180, 164, 148, 132, ... 62 120, 112, 104, 96, 88, 80, 72, 64, ... 63 56, 48, 40, 32, 24, 16, 8, 0 ]; 64 65 ulaw = [ -ulaw, ulaw ]; 66 67 ## Set the shape of y to that of x overwrites the contents of y with 68 ## ulaw of x. 69 y = x; 70 y(:) = ulaw(x + 1); 71 72 ## Convert to real or 8-bit. 73 if (n == 0) 74 ## [ -32768, 32767 ] -> [ -1, 1) 75 y /= 32768; 76 elseif (n == 8) 77 ld = max (abs (y (:))); 78 if (ld < 16384 && ld > 0) 79 sc = 64 / ld; 80 else 81 sc = 1 / 256; 82 endif 83 y = fix (y * sc); 84 endif 85 86endfunction 87