MATLAB: How to read LSB of audio sample

audioaudio filelsbMATLABreadsamplessteganography

Hello everyone… I am working on audio steganography project.And i need to read and manipulate LSB of the audio sample.Please tell me a way to do this. Thanks in advance.

Best Answer

Here is an example of overwriting the least significant byte of a double with other bit patterns, in this case the string 'hidden':
% Arbitraty 6 element double vector
>> x = rand(1,6)
x =
   0.957166948242946   0.485375648722841   0.800280468888800   0.141886338627215   0.421761282626275   0.915735525189067
% Find the location of the least significant byte in the double for this machine
>> LSB = find(typecast(1,'uint8')~=typecast(1+eps,'uint8'))
LSB =
     1
% Re-interpret the bytes of the double vector as a uint8 vector

>> u = typecast(x,'uint8')
u =
  Columns 1 through 35
  153  127  112  148   28  161  238   63   82  133   98    6  101   16  223   63  124   40   48  201  229  155  233   63  216  151   19  224   84   41  194   63  202   83  230
  Columns 36 through 48
    8   35  254  218   63   32   30  143  150  180   77  237   63
% Our replacement data
>> s = 'hidden'
s =
hidden
% Construct the indexes for the replacement bytes
>> lower_bound = LSB
lower_bound =
     1
>> upper_bound = LSB + 8*(numel(s)-1)
upper_bound =
    41
% Replace the floating data with our new data
>> u(lower_bound:8:upper_bound) = s
u =
  Columns 1 through 35
  104  127  112  148   28  161  238   63  105  133   98    6  101   16  223   63  100   40   48  201  229  155  233   63  100  151   19  224   84   41  194   63  101   83  230
  Columns 36 through 48
    8   35  254  218   63  110   30  143  150  180   77  237   63
% Turn result back into double vector (note result is close to original x)
>> y = typecast(u,'double')
y =
   0.957166948242940   0.485375648722843   0.800280468888797   0.141886338627212   0.421761282626269   0.915735525189076
% Now do the reverse to recover our hidden data
% Re-interpret the bytes of the double vector as a uint8 vector
>> w = typecast(y,'uint8')
w =
  Columns 1 through 35
  104  127  112  148   28  161  238   63  105  133   98    6  101   16  223   63  100   40   48  201  229  155  233   63  100  151   19  224   84   41  194   63  101   83  230
  Columns 36 through 48
    8   35  254  218   63  110   30  143  150  180   77  237   63
% Pick off our hidden bytes and re-interpret as a string
>> char(w(lower_bound:8:upper_bound))
ans =
hidden
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