High-payload spread spectrum watermarking based on informed code phase shift keying

Code phase shift keying (CPSK) is an efficient M-ary modulation that can be applied to spread spectrum (SS) based watermarking to improve the watermark payload. However, the host media acts as interference that degrades the watermark robustness, especially in high-payload applications. In this paper, an informed embedding method for CPSK-based watermarking is proposed. The host is utilized at the embedder to improve the decoding performance at the extractor. Theoretically, compared with the non-informed methods such as traditional CPSK and code division multiple access (CDMA), the proposed method can reduce the decoding error rate by several orders of magnitude under the same watermark strength and payload. Moreover, experiments are conducted in audio watermarking, and the informed CPSK method exhibits better robustness against signal processing and attacks.