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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} =} 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
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