LSB in audio stegnography

% Embed message length in the first 16 samples 
% (I don't understand how.  Can any one explain?)
str = dec2bin(length(message),16);  
if length(message) < length(y)  
  for a = 1 : length(str)  
    y(a, nbits-1) = str(a);
  end
else 
  disp('error')
end

I don't understand how they are embedding here. Please help me.

[Walter Roberson]

Note: the proper term is "steganography" not "stegnography"

Answer 1

[Walter Roberson]

They are converting the message length to 16 text-coded binary locations, and are taking the resulting 16 bits and using them to replace the least significant bits of 16 successive text-coded binary representations.

Answer 2

[Muhammad fayyaz]

sir your answer is correct but i don't understand how this statement works, i need little bit more explanation here

y(a, nbits-1) = str(a);

[Walter Roberson]

Assume that the original signal has been converted into binary by using dec2bin(). dec2bin() returns an array of characters, each one being the character '0' or the character '1'. Then y(a,nbits-1) is a straight forward replacement of one element of the array with one element of the character vector "str".

Somewhere after this section of code, you will find a call to bin2dec(y) . That operation will take the character array y and convert the representation back into decimal numbers.

[Muhammad fayyaz]

THANK YOU SIR

Answer 3

[Muhammad fayyaz]

clc, clear all;

[x,fs,nbits]=wavread('camera.wav');

y=((2^(nbits-1)*x(:,1)));

for i=1:length(y)

if y(i)<0

      z(i)=1;
  else
      z(i)=0;
  end
  if y(i)<0
          y(i)=-1*y(i);
  end
  end
  y=dec2bin(y);

when i run this command the value of decimal is different from the value of binary i need help for example

value of y= 1011
11
.
.
.
.
.
100
101
1
11
1000

from 1 upto 311 column, i don't about these value from where it come after this 311 column the values of decimal is same with the value of binary

10  2
1101  13
111  7
1101  13
0  0
100  4
11  3
1001  9
10101  21
0  0
111  7
.
.
.
.

till the end

the values are same

i copy of all the value in xls file than i understand that after 311 column the values are matching

please help me sir.