## Copyright (C) 1996, 1997 John W. Eaton
##
## 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 2, 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, write to the Free
## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
## 02111-1307, USA.

## -*- texinfo -*-
## @deftypefn {Function File} {} mu2lin (@var{x}, @var{bps})
## If the matrix @var{x} represents audio data in mu-law encoding,
## @code{mu2lin} converts it to linear encoding.  The optional argument
## @var{bps} specifies whether the output data uses 8 bit samples (range
## -128 to 128), 16 bit samples (range -32768 to 32768) or 0 for
## real values (range -1 to 1).  The default is 8.
## @end deftypefn
## @seealso{lin2mu, loadaudio, saveaudio, playaudio, setaudio, and record}

## Author:  Andreas Weingessel <Andreas.Weingessel@ci.tuwien.ac.at>
## Created: 18 October 1994
## Adapted-By: jwe

## Paul Kienzle <pkienzle@users.sf.net>
##    handle [-1,1] input range
## 2001-10-23 Paul Kienzle <pkienzle@users.sf.net>
## * default to 8-bit as in octave
## 2001-12-11 Paul Kienzle <pkienzle@users.sf.net>
## * use asymmetric transformation [-32768,32767]->[-1,1] for real
## 2002-04-05 Paul Kienzle <pkienzle@users.sf.net>
## * restore symmetric behaviour for compatibility
## * slightly optimized transform

function y = mu2lin (x, bit)

  if (nargin == 1)
    ## XXX COMPATIBILITY XXX: bps defaults to 8 for octave, 0 for Matlab
    bit = 8;
  elseif (nargin == 2)
    if (bit != 0 && bit != 8 && bit != 16)
      error ("mu2lin: bit must be either 0, 8 or 16");
    endif
  else
    usage ("y = mu2lin (x, bit)");
  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 ];

  y = x;               # set the shape of y to that of x
  y(:) = ulaw (x + 1); # overwrite the contents of y with ulaw of x

  ## convert to real or 8-bit
  if (bit == 0)
    ## [ -32768, 32767 ] -> [ -1, 1) 
    y = y/32768;
  elseif (bit == 8)
    ld = max (abs (y (:)));
    if (ld < 16384 && ld > 0)
      sc = 64 / ld;
    else
      sc = 1 / 256;
    endif
    y = fix (y * sc);
  endif

endfunction
