www.pudn.com > voicebox2.zip > LPCRA2PF.M

function pf=lpcra2pf(ra,np) 
%LPCAR2PF Convert AR coefs to power spectrum PF=(RA,NP) 
% The routine is faster if NP+1 is a power of 2 
% For RA(:,p+1) the default value of np is p and the output is PF(:,p+2) 
 
 
%      Copyright (C) Mike Brookes 1997 
% 
%      Last modified Wed Dec 29 15:22:14 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(ra); 
if nargin<2 np=p1-1; end 
pp=2*np+2; 
if pp>=2*p1 
   pf=abs(rfft([ra zeros(nf,pp-2*p1+1) ra(:,p1:-1:2)].').').^(-1); 
else 
   pf=abs(rfft([ra(:,1:np+2) ra(:,np+1:-1:2)].').').^(-1); 
end