function [y,SNR]=ejer23senovar(x,a,Xmax,B);
ycod=dpcm_cod(x,a,Xmax,B);
y=dpcm_decod(ycod,a,Xmax,B);
figure(4);
plot(x);
hold on 
plot(y,'r');
% title('SNR');
% xlabel('Numero De Muestras');
% ylabel('Amplitud');
er=x-y;
hold on 
plot(er);