lpcar2cc

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.

0001 function cc=lpcar2cc(ar,np)
0002 %LPCAR2CC LPC: Convert ar filter to complex cepstrum CC=(AR,NP)
0003 % the "real" cepstrum is half the complex cepstrum
0004 % cc() does not include c0 whose value can be calculated
0005 % from the prediction residual energy, e, as ln(e)/2
0006 % for both real and complex cepstrum.
0007 
0008 
0009 
0010 %      Copyright (C) Mike Brookes 1998
0011 %      Version: $Id: lpcar2cc.m 713 2011-10-16 14:45:43Z dmb $
0012 %
0013 %   VOICEBOX is a MATLAB toolbox for speech processing.
0014 %   Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
0015 %
0016 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0017 %   This program is free software; you can redistribute it and/or modify
0018 %   it under the terms of the GNU General Public License as published by
0019 %   the Free Software Foundation; either version 2 of the License, or
0020 %   (at your option) any later version.
0021 %
0022 %   This program is distributed in the hope that it will be useful,
0023 %   but WITHOUT ANY WARRANTY; without even the implied warranty of
0024 %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0025 %   GNU General Public License for more details.
0026 %
0027 %   You can obtain a copy of the GNU General Public License from
0028 %   http://www.gnu.org/copyleft/gpl.html or by writing to
0029 %   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA.
0030 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0031 
0032 [nf,p1]=size(ar);
0033 p=p1-1;
0034 if (nargin<2) np=p; end
0035 cc=zeros(nf,np);
0036 cm=(1:np).^(-1);
0037 if np>p
0038   xm=-(1:p);
0039   nz=np-p;
0040   for k=1:nf
0041     cc(k,:)=filter(1,ar(k,:),[ar(k,2:p1).*xm zeros(1,nz)]).*cm;
0042   end
0043 else
0044   p1=np+1;
0045   xm=-(1:np);
0046   for k=1:nf
0047     cc(k,:)=filter(1,ar(k,:),ar(k,2:p1).*xm).*cm;
0048   end
0049 end