function la=lpcrf2la(rf)
%LPCRF2LA Convert reflection coefficients to log areas LA=(RF)
% areas are normalised to give la(p+2)=0, the log area of the free space beyond lips


%      Copyright (C) Mike Brookes 1997
%
%      Last modified Tue May 12 16:18:40 1998
%
%   VOICEBOX home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
%
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%   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.
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%   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
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r=max(min(rf,1-1E-6),1E-6-1);
lo=log((1-r)./(1+r));
la=fliplr([zeros(size(rf,1),1) cumsum(fliplr(log((1-r)./(1+r))).').']);

