Time-spread echo method for digital audio watermarking using PN sequences

Conventional watermarking techniques based on echo hiding provide many benefits, but with several weak points, for example, a lenient decoding process, weakness against multiple encoding attack, etc. In this paper, to improve the weak points of conventional echo hiding, we propose a time-spread echo as an alternative to the conventional echo in the echo hiding. Spreading an echo is performed in the impulse response domain using PN sequences. We also evaluate the characteristics of the proposed method as a function of two parameters: gain and length of PN sequences used in spreading an echo. The proposed method is expected to provide more natural and colorless sounds as well as better imperceptibility of distortion as compared with conventional echo hiding.