lpc_1a.m

这是一个用于语音信号处理的工具箱

function [cofa,rc1,energy,residue]= lpc_1a(sso,norder);
% Linear prediction (corvariance method),
% fixed order (=13).
% Input == Speech Signal
% Output == 
% 	cofa : AR cofficients
% 	rc1 : first reflection coefficient
% 	energy : energy of the underlying speech segment
% 	residue : the prediction error

sso=sso(:);
sso1=sso(norder+1:length(sso));
energy=sso1'*sso1;
rc1=sso1(1:length(sso1)-1)'*sso1(2:length(sso1))/energy;
%ssa=sso(:);	removed by john 4/15/93 with hu's ok

maxordera =norder;   
%N=length(ssa)-maxordera;
N=length(sso)-maxordera;

% allocate memory (john did this ...)
U = zeros(N,maxordera+1);
V = U;
B = zeros(maxordera+1,maxordera+1);

for k=1:maxordera+1
	%U(1:N,k) =ssa(k:N+k-1);
	U(1:N,k) =sso(k:N+k-1);
end;

V(:,1)=U(:,1);
rp(1)=V(:,1)'*V(:,1);
for k=1:maxordera+1
	V(:,k)=U(:,k);
	for i=1:k-1
		B(k,i)=(U(:,k)'*V(:,i))/(V(:,i)'*V(:,i));
		V(:,k)=V(:,k)-B(k,i)*V(:,i);
	end
		B(k,k)=1;
end;


ordera=norder+1;

residue=V(1:length(V), ordera).';
ordera=ordera-1;
bb= B(1:ordera,1:ordera);
invB=inv(bb);
pb=B(ordera+1,1:ordera);
cofb=pb*invB;
cofa=[1 -cofb(ordera:-1:1)];
cofa1=polystab(cofa);
if any(cofa-cofa1)
	cofa=cofa1;
	rr=filter(cofa1,1,sso);
	rr=rr(maxordera+1:length(rr));
	residue=rr(:)';
end;