www.pudn.com > voicebox2.zip > LPCAR2LS.M

function ls=lpcar2ls(ar) 
%LPCAR2LS convert ar polynomial to line spectrum pair frequencies LS=(AR) 
% output vector elements will be in range 0 to 0.5 
% the returned vector will be of length p 
 
% This routine is nowhere near as efficient as it might be 
 
 
%      Copyright (C) Mike Brookes 1997 
% 
%      Last modified Tue May 12 13:57:15 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. 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 
[nf,p1]=size(ar); 
p = p1-1; 
p2 = fix(p/2); 
d=0.5/pi; 
 
if rem(p,2)		% odd order 
  for k=1:nf 
    aa=[ar(k,:) 0]; 
    r = aa + fliplr(aa); 
    q = aa - fliplr(aa); 
    fr = sort(angle(roots(r))); 
    fq = [sort(angle(roots(deconv(q,[1 0 -1])))); 0]; 
    f = [fr(p2+2:p+1).' ; fq(p2+1:p).']; 
    f(p+1) = []; 
    ls(k,:) = d*f(:).'; 
  end 
else 
  for k=1:nf 
    aa=[ar(k,:) 0]; 
    r = aa + fliplr(aa); 
    q = aa - fliplr(aa); 
    fr = sort(angle(roots(deconv(r,[1 1])))); 
    fq = sort(angle(roots(deconv(q,[1 -1])))); 
    f = [fr(p2+1:p).' ; fq(p2+1:p).']; 
    ls(k,:) = d*f(:).'; 
  end 
end