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

function u=lpcifilt(s,ar,t,dc,fade) 
%LPCIFILT Apply inverse filter to speech signal U=(S,AR,T,DC,FADE) 
% 
% Inputs:	S             speech signal 
%				AR(nf,p+1)    array of ar coefficients; one row per frame 
%				T             column vector giving the index of the first sample in each frame 
%           DC(nf)        optional dc component will be subtracted from the signal 
%           FADE          AR coefficients will be linearly interpolated for FADE samples 
%                         either side offrame boundaries 
% 
 
%      Copyright (C) Mike Brookes 1997 
% 
%      Last modified Fri Sep  4 17:24:59 1998 
% 
%   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(ar); 
if nargin<4 | isempty(dc) 
   dc=zeros(nf,1); 
elseif length(dc)==1 
   dc=dc(ones(nf,1)); 
end 
if nf==1 
   u=filter(ar,1,s-dc); 
else 
   p=p1-1; 
   ns=length(s); 
   if nargin<5 | isempty(fade) 
      fade=0; 
      if nargin<3 | isempty(t) 
         t=p1+(0:nf-1)*(ns-p)/nf; 
      end 
   end 
   u=zeros(ns,1); 
   if fade<1 
      x0=(max(1,ceil(t(nf)-p)):ns)'; 
      u(x0)=filter(ar(nf,:),1,s(x0)-dc(nf)); 
      for i=nf-1:-1:2 
         x0=(max(1,ceil(t(i)-p)):ceil(t(i+1)-1))'; 
         u(x0)=filter(ar(i,:),1,s(x0)-dc(i)); 
      end 
      x0=(1:ceil(t(2)-1))'; 
      u(x0)=filter(ar(1,:),1,s(x0)-dc(1)); 
       
   else 
      tb=min(t(nf)+fade,(t(nf)+ns)/2); 
      ta=max(t(nf)-fade,(t(nf-1)+t(nf))/2); 
      t0=max(1,ceil(ta)-p); 
      x0=(t0:ns)'; 
      xb=x0-tb; 
      u(x0)=filter(ar(nf,:),1,s(x0)-dc(nf)).*max((1+(xb-abs(xb))/(2*(tb-ta))),0); 
      for i=nf-1:-1:2 
         td=tb; 
         tc=ta; 
         tb=min(t(i)+fade,ta); 
         ta=max(t(i)-fade,(t(i-1)+t(i))/2); 
         t1=floor(td); 
         t0=max(1,ceil(ta)-p); 
         x0=(t0:t1)'; 
         xb=x0-tb; 
         xc=x0-tc; 
         u(x0)=u(x0)+filter(ar(i,:),1,s(x0)-dc(i)).*max((1+(xb-abs(xb))/(2*(tb-ta))-(xc+abs(xc))/(2*(td-tc))),0); 
      end 
      t1=floor(tb); 
      x0=(1:t1)'; 
      xc=x0-ta; 
      u(x0)=u(x0)+filter(ar(1,:),1,s(x0)-dc(1)).*(1-(xc+abs(xc))/(2*(tb-ta))); 
       
   end 
end