Time-Spread Echo-Based Audio Watermarking With Optimized Imperceptibility and Robustness

We present a time-spread echo-based audio watermarking scheme with optimized imperceptibility and robustness. Specifically, convex optimization based finite-impulse-response (FIR) filter design is utilized to obtain the optimal echo filter coefficients. The desired power spectrum of the echo filter is shaped by the proposed maximum power spectral margin (MPSM) and the absolute threshold of hearing (ATH) of human auditory system (HAS) to ensure the optimal imperceptibility. Meanwhile, the auto-correlation function of the echo filter coefficients is specified as the constraint in the problem formulation, which controls the robustness in terms of watermark detection. In this way, a joint optimization of imperceptibility and robustness can be quantitatively performed. As a result, the proposed watermarking scheme is superior to existing solutions such as the ones based on pseudo noise (PN) sequence or modified pseudo noise (MPN) sequence. Note that the designed echo kernel is also highly secure in that only with the same filter coefficients can one successfully detect the watermark. Experimental results are provided to evaluate the imperceptibility and robustness of the proposed watermarking scheme.