An informed unipolar spread spectrum modulation for self-synchronized robust watermarking

This paper describes an informed unipolar spread spectrum (SS) modulation to improve the performance of SS-based watermark extraction with self-synchronization. Compared with bipolar SS, unipolar SS, realized by employing a pair of orthogonal codes to represent the watermark bits, is more robust against the distorted correlation between the received watermarked signal and the reference. The informed embedding utilizes the host interference to improve the performance of unipolar watermark synchronization and decoding. Experiments on audio signals show that the proposed scheme is robust against most of the attacks while preserving the media fidelity, and effective self-synchronization is achieved.