Mercurial > jwe > octave
view scripts/audio/mu2lin.m @ 31047:13a7af4ca0da
Update lin2mu, mu2lin functions.
* lin2mu.m: Rewrite docstring. Use default argument for input 'n' to simply
input validation. Eliminate warning abut no precision certified. Add stricter
input validation 'n' input. Use inplace operators for better performnace.
Update BIST tests.
* mu2lin.m: Rewrite docstring. Use default argument for input 'n' to simply
input validation. Add BIST tests for function.
author | Rik <rik@octave.org> |
---|---|
date | Sat, 28 May 2022 23:21:53 -0700 |
parents | 796f54d4ddbf |
children |
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######################################################################## ## ## Copyright (C) 1995-2022 The Octave Project Developers ## ## See the file COPYRIGHT.md in the top-level directory of this ## distribution or <https://octave.org/copyright/>. ## ## This file is part of Octave. ## ## Octave is free software: you can redistribute it and/or modify it ## under the terms of the GNU General Public License as published by ## the Free Software Foundation, either version 3 of the License, or ## (at your option) any later version. ## ## Octave is distributed in the hope that it will be useful, but ## WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ## GNU General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with Octave; see the file COPYING. If not, see ## <https://www.gnu.org/licenses/>. ## ######################################################################## ## -*- texinfo -*- ## @deftypefn {} {@var{y} =} mu2lin (@var{x}) ## @deftypefnx {} {@var{y} =} mu2lin (@var{x}, @var{n}) ## Convert audio data from mu-law to linear. ## ## Mu-law values are 8-bit unsigned integers in the range 0 @leq{} @var{y} ## @leq{} 255. Linear values use floating point values in the range ## -@var{linmax} @leq{} @var{x} @var{linmax} (where ## @code{@var{linmax} = 32124/32768 =~ 0.98}) when @var{n} is zero (default). ## If @var{n} is 8 or 16 then @var{n}-bit signed integers are used instead. ## ## Programming Note: @code{mu2lin} maps maximum mu-law inputs to values ## slightly below the maximum ([-0.98, +0.98]) representable with a linear ## scale. Because of this, @code{mu2lin (lin2mu (@var{x}))} might not ## reproduce the original input. ## @seealso{lin2mu} ## @end deftypefn function y = mu2lin (x, n = 0) if (nargin < 1) print_usage (); endif if (nargin == 2) if (! isscalar (n) && ! isreal (n) || (n != 0 && n != 8 && n != 16)) error ("lin2mu: N must be either 0, 8, or 16"); elseif (isempty (n)) n = 0; endif endif ulaw = [32124, 31100, 30076, 29052, 28028, 27004, 25980, 24956, ... 23932, 22908, 21884, 20860, 19836, 18812, 17788, 16764, ... 15996, 15484, 14972, 14460, 13948, 13436, 12924, 12412, ... 11900, 11388, 10876, 10364, 9852, 9340, 8828, 8316, ... 7932, 7676, 7420, 7164, 6908, 6652, 6396, 6140, ... 5884, 5628, 5372, 5116, 4860, 4604, 4348, 4092, ... 3900, 3772, 3644, 3516, 3388, 3260, 3132, 3004, ... 2876, 2748, 2620, 2492, 2364, 2236, 2108, 1980, ... 1884, 1820, 1756, 1692, 1628, 1564, 1500, 1436, ... 1372, 1308, 1244, 1180, 1116, 1052, 988, 924, ... 876, 844, 812, 780, 748, 716, 684, 652, ... 620, 588, 556, 524, 492, 460, 428, 396, ... 372, 356, 340, 324, 308, 292, 276, 260, ... 244, 228, 212, 196, 180, 164, 148, 132, ... 120, 112, 104, 96, 88, 80, 72, 64, ... 56, 48, 40, 32, 24, 16, 8, 0 ]; ulaw = [ -ulaw, ulaw ]; ## Set the shape of y to that of x overwrites the contents of y with ## ulaw of x. y = x; y(:) = ulaw(x + 1); ## Convert to real or 8-bit. if (n == 0) ## [ -32768, 32767 ] -> [ -1, 1) y /= 32768; elseif (n == 8) ld = max (abs (y(:))); if (ld < 16384 && ld > 0) sc = 64 / ld; else sc = 1 / 256; endif y = fix (y * sc); endif endfunction ## Test functionality %!shared linmax %! linmax = 32124 / 32768; %!test %! x = [0, 128, 255]; %! y = x'; %! assert (mu2lin (x), (mu2lin (y))'); %! assert (mu2lin (x), [-linmax, +linmax, 0]); %!assert (mu2lin ([]), []) %!assert (mu2lin (255), 0) %!assert (mu2lin (255, 0), 0) %!assert (mu2lin (255, 8), 0) %!assert (mu2lin (255, 16), 0) %!assert (mu2lin (128, []), linmax) %!assert (mu2lin (128, 8), 125) %!assert (mu2lin (128, 16), 32124) %!assert (mu2lin (zeros (1, 1000), 0), repmat (-linmax, 1, 1000)) %!assert (mu2lin (255*ones (2, 2), 0), zeros (2, 2)) ## Test input validation %!error <Invalid call> mu2lin () %!error <N must be either 0, 8, or 16> mu2lin (1, 2) %!error <N must be either 0, 8, or 16> mu2lin (1, [1,2]) %!error <N must be either 0, 8, or 16> mu2lin (1, ones (1, 2)) %!error mu2lin ({2:5})