www.pudn.com > voicebox2.zip > LIN2PCMU.M

function p=lin2pcmu(x,s) 
%LIN2PCMU Convert linear to Mu-law PCM P=(X,S) 
%	pcmu = lin2pcmu(lin) where lin contains a vector 
%	or matrix of signal values within a range determined by 
%	the scale factor s (see table below). 
%	Values outside this range will be clipped. 
%	The input values will be converted to integer 
%	Mu-law pcm vlues in the range 0 to 255. 
%	 
%	Input values are multiplied by the scale factor s: 
% 
%		   s		Input Range 
% 
%		   1		+-8159 
%		4004.189931	+-2.03761563 (default) 
%		8159		+-1 
% 
%	The default input scaling factor 4004.189931 is equal to 
%	sqrt((2207^2 + 5215^2)/2) and follows ITU standard G.711. 
%	The sine wave with PCM-Mu values [158 139 139 158 30 11 11 30] 
%	has a mean square value of unity corresponding to 0 dBm0. 
 
 
 
%      Copyright (C) Mike Brookes 1998 
% 
%      Last modified Fri Apr  3 14:57:15 1998 
% 
%   VOICEBOX home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html 
% 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
%   This program 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 of the License, or 
%   (at your option) any later version. 
% 
%   This program 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 can obtain a copy of the GNU General Public License from 
%   ftp://prep.ai.mit.edu/pub/gnu/COPYING-2.0 or by writing to 
%   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 
if nargin < 2 s=4004.189931; end 
y=x*s; 
y=(abs(y+8031)-abs(y-8031))/2; 
q=floor((y+8032)/8032); 
[m,e]=log2(abs(y)+33); 
p=175+128*q-8*(e+abs(e-6))-floor(32*m-16);