gusucode.com > 语音信号处理工具箱 - Voicebox源码程序 > Voicebox\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. % % 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; 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