Audio watermarking of stereo signals based on echo-hiding method

In this paper, a novel non-blind audio watermarking scheme is proposed. The method makes use of both channels of stereo music signals. The signals are divided into segments and watermarks are embedded by hiding echoes into these segments. The embedded echoes represent the watermark bits. For single channel watermarking, echoes with two different delays are used. One is used to encode watermark bit ¿1¿ and the other one is used to encode watermark bit ¿0¿. In the proposed watermarking scheme, an echo is embedded only when the energy level of the intended segment exceeds a given threshold. Echoes with one value of delay are used to represent both binary bits. Echoes embedded in one channel are used to encode watermark bit ¿1¿ and echoes embedded in the other channel are used to encode watermark bit ¿0¿. The embedded echoes or watermark are extracted by detecting time delay of each embedded echo in cepstrum domain. Robustness and performance of this audio watermarking scheme under different types of attacks are investigated. It is found that the proposed watermarking scheme, compared with the single channel echo-hiding method, is significantly more robust against different types of attacks.