gusucode.com > 《MATLAB图像与视频处理实用案例详解》代码 > 《MATLAB图像与视频处理实用案例详解》代码/第 19 章 基于语音识别的信号灯图像模拟控制技术/voicebox/lpcrf2ar.m
function [ar,arp,aru,g]=lpcrf2ar(rf) %LPCRF2AR Convert reflection coefs to autoregressive coefs [AR,ARP,ARU,G]=(RF) % % Input: RF(:,p+1) gives reflection coefficients of one or more p-section lossless tubes % Ouputs: G is the gain of the all-pole AR filter % AR/G is the transfer function from U_in to the glottal input wave, U_g. % AR(:,1)=1 always. % ARP*K is the transfer function from U_in to the pressure just after the glottis % where K = rho*c/Alips: rho = air density 1.23 kg/m^3, c=sound speed 340 m/s, % Alips = effective area of free space beyond the lips. % ARU is the transfer function from U_in to the total volume velocity through the glottis % % where U_in=z^(p/2)*U_lips is the time-advanced volume velocity at the lips % % Energy into the vcal tract is equal to K*filter(ARP,1,Ulips).*filter(ARU,1,Ulips) % reverse glottal flows divided by 1-r0 where r0 is the glottal reflection coefficient. % The scale factor is included to avoid a zero answer when the glottis is closed giving r0=1. % % The transfer functions have ar(:,1)=art(:,1)=1 % They should both be multiplied by z^(p/2)/prod(1+rf) to correct the absolute % gain and to compensate for the delay of p/2 samples along the length of the tube. % % The energy into the vocal tract is given by ars(speech) * are(speech) % % Ref: D. M. Brookes and H. P. Loke. "Modelling energy flow in the vocal tract with % applications to glottal closure and opening detection." In Proc ICASSP'99, pages 213-216, Mar 1999. % Copyright (C) Mike Brookes 1997 % Version: $Id: lpcrf2ar.m,v 1.5 2007/05/04 07:01:39 dmb Exp $ % % VOICEBOX is a MATLAB toolbox for speech processing. % 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 % http://www.gnu.org/copyleft/gpl.html or by writing to % Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% [nf,p1]=size(rf); p2=p1+1; p=p1-1; pm=p-1; arf=[ones(nf,1) zeros(nf,p)]; arr=[zeros(nf,p) rf(:,p1)]; cr=zeros(nf,p); for k=1:p-1 rk=rf(:,(p1-k)*ones(1,k)); cr(:,1:k)=arr(:,p2-k:p1); arr(:,p1-k:p)=arr(:,p1-k:p)+rk.*arf(:,1:k); arf(:,2:k+1)=arf(:,2:k+1)+rk.*cr(:,1:k); end r1=rf(:,1); ar=arf+r1(:,ones(1,p1)).*arr; if nargout>1 kp=prod(1-rf(:,2:p1),2); arp=(arf-arr)./kp(:,ones(1,p1)); if nargout>2 g=prod(1+rf(:,2:p1),2); aru=(arf+arr)./g(:,ones(1,p1)); if nargout>3 g=g.*(1+rf(:,1)); end end end