test.m

PCM编码实例。包括均匀量化编码

a=randn(1,500);
%a=[20*randn(1,20),randn(1,480)];
n=16;
amax=max(abs(a));
a_quan=a/amax;%归一化
b_quan=a_quan;%赋初值
d=2/n;%量化间隔
q=d.*[0:n-1];
q=q-((n-1)/2)*d;%量化电平

for i=1:n
%定位第i个量化间隔码子
    a_quan(find((q(i)-d/2<=a_quan) & (a_quan<=q(i)+d/2)))=...
    q(i).*ones(1,length(find((q(i)-d/2<=a_quan)&(a_quan<=q(i)+d/2))));
    %赋值为相应的量化电平
    b_quan(find(a_quan==q(i))) =(i-1) .* ones(1,length(find(a_quan==q(i))));
end

a_quan=a_quan*amax;%恢复原值（量化后）
nu=ceil(log2(n));%编码
code=zeros(length(a),nu);
for i=1:length(a)
    for j=nu:-1:0
        if (fix(b_quan(i)/(2^j))==1)
            code(i,(nu-j))=1;
            b_quan(i)=b_quan(i)-2^j;
        end
    end
end
sqnr=20*log10(norm(a)/norm(a-a_quan))%求量化信噪比