pcm_a_encode.m

西交大刘树棠写的《数字信号处理》那本书的所有源代码

function [out]=pcm_a_encode(x)
%x encode to pcm alaw code
n=length(x);
%-4096<x<4096
for i=1:n
    if x(i)>0
        out(i,1)=1;
    else
        out(i,1)=0;
    end
    
    if abs(x(i))>=0&abs(x(i))<32
        out(i,2)=0;out(i,3)=0;out(i,4)=0;step=2;st=0;
    elseif 32<=abs(x(i))&abs(x(i))<64
        out(i,2)=0;out(i,3)=0;out(i,4)=1;step=2;st=32;
    elseif 64<=abs(x(i))&abs(x(i))<128
        out(i,2)=0;out(i,3)=1;out(i,4)=0;step=4;st=64;
    elseif 128<=abs(x(i))&abs(x(i))<256
        out(i,2)=0;out(i,3)=1;out(i,4)=1;step=8;st=128;
    elseif 256<=abs(x(i))&abs(x(i))<512
        out(i,2)=1;out(i,3)=0;out(i,4)=0;step=16;st=128;
    elseif 512<=abs(x(i))&abs(x(i))<1024
        out(i,2)=1;out(i,3)=0;out(i,4)=1;step=32;st=512;
    elseif 1024<=abs(x(i))&abs(x(i))<2048
        out(i,2)=1;out(i,3)=1;out(i,4)=0;step=64;st=1024;
    elseif 2048<=abs(x(i))&abs(x(i))<4096
        out(i,2)=1;out(i,3)=1;out(i,4)=1;step=128;st=2048;
    else out(i,2)=1;out(i,3)=1;out(i,4)=1;step=128;st=2048;
    end
    
    if (abs(x(i))>=4096)
        out(i,2:8)=[1 1 1 1 1 1 1];
    else
        tmp=floor((abs(x(i))-st)/step);
        t=dec2bin(tmp,4)-48;%函数dec2bin输出的是ASCII字符串，48对应0
        out(i,5:8)=t(1:4);
    end
end
%out=reshape(out',1,8*n)