H.264 stream replacement watermarking with CABAC encoding

This paper describes a watermarking method to directly embed information into a CABAC entropy coded H.264/AVC stream. In theory, modification of a part of an arithmetically coded stream will cause the rest of the stream to be misinterpreted and thus become undecodable. However, the method presented in this paper exploits a feature in the fixed-point integer implementation of the arithmetic coding to allow modifications without introducing such errors. Most of the hard work in this method goes into looking for watermarkable locations and building an embedding table during an analysis stage. This table identifies small segments of data in the encoded stream that can be replaced and identifies one or more replacement values. The embedding process is then very fast. It involves replacing each identified segment with one of the alternative values from the table. The choice of alternative is informed by the payload to be embedded. The resulting bitstream is guaranteed to be compliant with the H.264/AVC standard.