www.pudn.com > voicebox2.zip > LPCAR2RF.M

function rf=lpcar2rf(ar) 
%LPCAR2RF Convert autoregressive coefficients to reflection coefficients AR=(RF) 
% 
% Input:   ar(:,p+1)  Autoregressive coefficients 
% Output:  rf(:,p+1)  Reflection coefficients with rf(:,1)=1 
 
 
%      Copyright (C) Mike Brookes 1997 
% 
%      Last modified Fri Dec  3 15:21:40 1999 
% 
%   VOICEBOX is a MATLAB toolbox for speech processing. Home page is at 
%   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. 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 
[nf,p1] = size(ar); 
if any(ar(:,1)~=1) 
  ar=ar./ar(:,ones(1,p1)); 
end 
rf = ar; 
w=ones(nf,1); 
for j = p1-1:-1:2 
  k = rf(:,j+1); 
  d = (1-k.^2).^(-1); 
  wj=ones(1,j-1); 
  rf(:,2:j) = (rf(:,2:j)-k(:,wj).*rf(:,j:-1:2)).*d(:,wj); 
end