www.pudn.com > voicebox2.zip > LPCAR2CC.M

function cc=lpcar2cc(ar,np) 
%LPCAR2CC LPC: Convert ar filter to complex cepstrum CC=(AR,NP) 
% the "real" cepstrum is half the complex cepstrum 
% cc() does not include c0 whose value can be calculated 
% from the prediction residual energy, e, as ln(e)/2 
% for both real and complex cepstrum. 
 
 
 
%      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. 
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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 
%   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. 
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[nf,p1]=size(ar); 
p=p1-1; 
if (nargin<2) np=p; end 
cc=zeros(nf,np); 
cm=(1:np).^(-1); 
if np>p 
  xm=-(1:p); 
  nz=np-p; 
  for k=1:nf 
    cc(k,:)=filter(1,ar(k,:),[ar(k,2:p1).*xm zeros(1,nz)]).*cm; 
  end 
else 
  p1=np+1; 
  xm=-(1:np); 
  for k=1:nf 
    cc(k,:)=filter(1,ar(k,:),ar(k,2:p1).*xm).*cm; 
  end 
end