firfilter.m

the implement of the encoder and the decoder of the CELP

function [ y, z ] = FIRfilter( coef, z, x, norder )

global szsubf olpc;

if nargin==4
    order=norder;
else
    order=olpc;
end
    
b=coef(2:order+1);                           % Cut off 1 in the coefficients

for t=1:szsubf
    y(t) = sum(z(1:order).*b(order:-1:1))+x(t);
    z(1:order)=[z(2:order),x(t)];
end