www.gusucode.com > 语音信号处理工具箱 - Voicebox源码程序 > Voicebox\lpcar2pp.m
function pp=lpcar2pp(ar) %LPCAR2PP LPC: Convert ar filter to power spectrum polynomial in cos(w) PP=(AR) % the pp is a polynomial such that |polyval(ar,e^jw)|^2 = polyval(pp,cos(w)) % Copyright (C) Mike Brookes 1998 % % Last modified Wed Jan 30 09:44:14 2002 % % 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. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% persistent tp; [nf,p1]=size(ar); ra=zeros(nf,p1); for i=1:p1 ra(:,i)=sum(ar(:,1:p1+1-i).*ar(:,i:p1),2); end % we check here if p is the same as before and reuse the tp matrix if size(tp,1)~=p1 p=p1-1; % chebyshev polynomials up to order p tp=zeros(p1,p1); tp(1,p1)=2; tp(2,p)=2; for i=3:p1 tp(i,p+2-i:p)=2*tp(i-1,p+3-i:p1)-tp(i-2,p+2-i:p); tp(i,p1)=-tp(i-2,p1); end tp(1,p1)=1; end pp=ra*tp;