pkg load signal
  close all
  clear all
  
  d=firls(128,[0 .2 .3 .4 .5 1],[0 0 1 1 0 0]);
  d=d/max(d);
  plot(d)
  N=6;
  k=find(abs(d)<2^(-N))
  hold on
  plot(k,0,'r.')
  line([1 128],[2^(-N) 2^(-N)])
  line([1 128],[-2^(-N) -2^(-N)])
  legend('filter coefficients',[num2str(N),' bit quantization'])
  kk=find(diff(k)>1);
  k(kk(1))
  k(kk(end))
  xlabel('cofficient num');ylabel('normalized coef. value')
  line([0 k(kk(1))],[0.1 0.1])
  line([k(kk(end)) 128],[0.1 0.1])
  text(10,0.15,'30 coefs at 0')
  text(110,0.15,'30 coefs at 0')