Mercurial > octave
view scripts/audio/lin2mu.m @ 29359:7854d5752dd2
maint: merge stable to default.
author | John W. Eaton <jwe@octave.org> |
---|---|
date | Wed, 10 Feb 2021 10:10:40 -0500 |
parents | 28de41192f3c 0a5b15007766 |
children | 796f54d4ddbf |
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######################################################################## ## ## Copyright (C) 1995-2021 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} =} lin2mu (@var{x}, @var{n}) ## Convert audio data from linear to mu-law. ## ## Mu-law values use 8-bit unsigned integers. Linear values use @var{n}-bit ## signed integers or floating point values in the range -1 @leq{} @var{x} ## @leq{} 1 if @var{n} is 0. ## ## If @var{n} is not specified it defaults to 0, 8, or 16 depending on ## the range of values in @var{x}. ## @seealso{mu2lin} ## @end deftypefn function y = lin2mu (x, n) if (nargin < 1) print_usage (); endif if (nargin == 1) range = max (abs (x (:))); if (range <= 1) n = 0; elseif (range <= 128) n = 8; warning ("lin2mu: no precision specified, so using %d", n); else n = 16; endif else if (n != 0 && n != 8 && n != 16) error ("lin2mu: N must be either 0, 8 or 16"); endif endif ## Transform real and n-bit format to 16-bit. if (n == 0) ## [-1,1] -> [-32768, 32768] x = 32768 * x; elseif (n != 16) x = 2^(16-n) .* x; endif ## Determine sign of x, set sign(0) = 1. sig = sign (x) + (x == 0); ## Take absolute value of x, but force it to be smaller than 32636; ## add bias. x = min (abs (x), 32635) + 132; ## Find exponent and fraction of bineary representation. [f, e] = log2 (x); y = 64 * sig - 16 * e - fix (32 * f) + 335; endfunction