Patent ID: 7103104

Claim:
A method of embedding auxiliary data (XD) in an information signal (MP), comprising the step of modifying selected signal samples so as to represent respective symbols of said auxiliary data, characterized in that said signal samples are transform coefficients (c(i,j)) obtained by transform coding the information signal and encoded into variable-length code words, the method further comprising the steps of: decoding a variable-length code word indicative of a selected coefficient; modifying said selected coefficient so as to represent an auxiliary data symbol; encoding the modified coefficient into a new variable-length code word; and replacing the old code word by the new code word; wherein said step of replacing the old code word by a new code word is omitted if said replacing causes the length of a given sequence of code words to substantially exceed the original length of said sequence; said old code word being replaceable with a longer code word as long as the length of the given sequence is compensated with a shorter replaced code word so that the length of the given sequence does not substantially exceed the original length of said sequence.