function y = zhe13(x)
%本函數實現國際通用的PCM量化A律13折線特性近似
x = x/max(x); 
z = sign(x); 
x = abs(x); 
for i = 1:length(x);
    if((x(i) >= 0)&(x(i) < 1/64)) 
        y(i) = 16*x(i);
    else if((x(i) >= 1/64)&(x(i) < 1/32)) 
            y(i) = 8*x(i)+1/8;
         else if((x(i) >= 1/32)&(x(i) < 1/16)) 
            y(i) = 4*x(i)+2/8;
             else if((x(i) >= 1/16)&(x(i) < 1/8)) 
               y(i) = 2*x(i)+3/8;
                else if((x(i) >= 1/8)&(x(i) < 1/4))
                  y(i) = x(i)+4/8;
                   else if((x(i) >= 1/4)&(x(i) < 1/2)) 
                     y(i) = 1/2*x(i)+5/8;
                      else if((x(i) >= 1/2)&(x(i) <= 1)) 
                        y(i) = 1/4*x(i)+6/8;
 end;end;end;end;end;end;end;end;
y = z.*y;