zidaibianma.txt

设计了镜像滤波器opt_filter函数来实现子带分解与合成。取N=256

function[hopt,H,G]=opt_filter(N,nbands)
stopedge=1/nbands;
delta=0.001;
passedge=1/(4*nbands);
toll=0.000001;
step=0.1*passedge;
tcost=0;
mpc=1;
way=-1;
pcost=10;
flag=0;
s_time=cputime;
while flag==0
hopt=firpm(N,[0,passedge,stopedge,1],[1,1,0,0],[5,1]);
Hw=fft(hopt,4096);
HH=ovlp_ripple(Hw,nbands);
[tcost]=max(abs(HH-ones(max(size(HH)),1)));
if tcost>pcost
step=step/2;
way=-way;
end
if abs(pcost-tcost)<toll
flag=1;
end
pcost=tcost;passedge=passedge+way*step;
end
final_time=cputime-s_time;
flen=max(size(hopt));
t=sqrt(2)/2;
for k=1:nbands
a(2*k-1)=t+i*t;
a(2*k)=t-i*t;
end
for k=1:nbands
for l=1:flen
m1=cos(pi*(2*k-1)*(2*l-1)/(4*nbands));
m2=sin(pi*(2*k-1)*(2*l-1)/(4*nbands));
H(k,l)=2.0*(real(a(k))*m1-imag(a(k))*m2)*hopt(l);
end
for l=1:flen
m1=cos(pi*(2*k-1)*(2*l-1)/(4*nbands));
m2=sin(pi*(2*k-1)*(2*l-1)/(4*nbands));
G(k,l)=2.0*(real(a(k))*m1+imag(a(k))*m2)*hopt(l);
end
end
function HH=ovlp_ripple(Hin,Q)
N=max(size(Hin));
M=floor(2048/Q);HH=zeros(M,1);
for k=1:M
H(k)=abs(Hin(M-k+2))^2+abs(Hin(k))^2;
End