To make digital watermarking accomplish several goals, a new method for simultaneously embedding multiple watermarks into the same audio signal is proposed. First, the original audio signal is segmented into frames of appointed lengths and all the element watermarks are encoded to achieve a mixed watermark. Then, the binary bits in the mixed watermark are embedded into the audio frames with the echo hiding technique. The watermark extraction can be performed without an original audio signal. Furthermore, in order to enhance the extraction accuracy and the robustness of the proposed algorithm against common signal manipulations, the autocorrelafion of the power cepstrum is utilized to estimate the echo delays in the watermarked audio frames to extract the mixed watermark and the corresponding decoding method is applied to achieve the element watermarks. Computer simulation results indicate that the proposed scheme has great robustness against common signal manipulations of Mp3 compressing, re-sampling, re-quantizing, low-pass filtering and white noise addition.
