% Command File
% Audio Steganography

global snd1;
global snd2;

[y, fs, nbits] = wavread(snd1);
[y2, fs2, nbits2] = wavread(snd2);

yleft=y(:,1);

y2left=y2(:,1);



figure(1)
specgram(yleft,256,fs);

figure(2)
specgram(y2left,256,fs);

[b1,a1]=butter(10,(5*fs/16)/(fs/2));
yfiltered=filter(b1,a1,yleft);

figure(3);
specgram(yfiltered,256,fs);

%[b2,a2]= butter(10,(fs/16)/(fs/2));

[b2a,a2a]=butter(10,((450)/(fs/2)),'high');
[b2b,a2b]=butter(10,((fs/16 + 450)/(fs/2)));

y2high=filter(b2a,a2a,y2left);
y2filtered=filter(b2b,a2b,y2high);

%y2filtered=filter(b2,a2,y2left);

figure(4);
specgram(y2filtered,256,fs2);


t=[0:size(y2left,1)-1]/fs;

%modulate=cos(2*pi*(7*fs/16)*t);
modulate=cos(2*pi*(7*fs/16-450)*t);

figure(5);
specgram(modulate,256,fs);

%y2mod = (1+y2filtered).*modulate';
y2mod = y2filtered.*modulate';

figure(6);
specgram(y2mod,256,fs);

size1=size(yfiltered,1);
size2=size(y2mod,1);

if (size2<size1)
   y2mod = [y2mod' zeros(1,size1-size2)]';
else
   yfiltered = [yfiltered' zeros(1, size2-size1)]';
end

yhidden=yfiltered+y2mod;

figure(7);
specgram(yhidden, 256, fs);


% steg2.m
% Receiver End


[b3, a3] = butter(10, (3*fs/8)/(fs/2), 'high');

[b4, a4] = butter(10, ((fs/2.05)/(fs/2)));

yrechigh = filter(b3,a3,yhidden);

figure(8);
specgram(yrechigh,256,fs);

yrecmod = filter(b4,a4,yrechigh);

figure(9);
specgram(yrecmod,256,fs);

size1=size(yrecmod,1);
size2=size(modulate,2);

if (size2<size1)
   modulate = [modulate zeros(1,size1-size2)];
else
   yrecmod = [yrecmod' zeros(1, size2-size1)]';
end

y2demod = yrecmod.*modulate';

figure(10);
specgram(y2demod, 256,fs);

[b5,a5]= butter(6,(fs/16)/(fs/2));

y2recovered=filter(b5,a5,y2demod);

figure(11);
specgram(y2recovered,256,fs);