% EE 438 Digital Signal Processing with Applications 
%
%Matlab file used for class demo conducted during Session 12
%illustrating upsampling by a factor of 2.
%A word utterance is sampled at 12.5 KHz, a zero is
%inserted between each pair of samples and the result
%played back at 25 KHz
clear all;
clf
set(0,'defaultaxesfontsize',16);
h=remez(50,[0 .333 .665 1],[1 1 0 0]);
data=load('enf1s1t0');
Fs=8192;
clf

%plot(data)
%end1=input('end1?');
%end2=input('end2?');
%datar=data(end1:end2);
datar=data;
dl=length(datar);
input('Utterance played back at orignal sampling rate, Fs = 12.5 KHz'); 
soundsc(datar,Fs)

xlp=zeros(1,2*dl);
xlp(1:2:2*dl)=datar;
y=conv(h,xlp);
input('Utterance interpolated by a factor of 2 played back at 2*Fs = 25 KHz'); 
soundsc(y,2*Fs)

domega=2*pi/8192;
omega=-pi:domega:pi-domega;
yf1=abs(fftshift(fft(datar,8192)));
yf2=abs(fftshift(fft(y,8192)));
subplot(211)
plot(omega,yf1,'Linewidth',2)
axis([-pi pi 0 max(yf1)])
title('DTFT of original utterance');
xlabel('omega (radians/s)');
subplot(212)
plot(omega,yf2,'Linewidth',2)
axis([-pi pi 0 max(yf2)])
title('DTFT of utterance interpolated by a factor of 2');
xlabel('omega (radians/s)');

input('Original played back at twice orignal sampling rate, 2*Fs = 25 KHz'); 
soundsc(datar,2*Fs)
input('Interpolated data played back at orignal sampling rate, Fs = 12.5 KHz'); 
soundsc(y,Fs)
hf=abs(fftshift(fft(h,512)));

input('Plot of Frequency Response of LPF')
clf
domega=2*pi/512;
omega=-pi:domega:pi-domega;
plot(omega,hf,'Linewidth',4)
axis([-pi pi 0 max(hf)])
title('Frequency Response of LPF');
xlabel('omega (radians/s)');