Robustness and embedding capacity enhancement in time-spread echo-based audio watermarking

In echo-based audio watermarking methods, poor robustness and low embedding capacity are the main problems. In this paper, we propose a novel time-spread echo method for audio watermarking, aiming to improve the robustness and the embedding capacity. To improve the robustness, we design an efficient pseudonoise (PN) sequence and a corresponding decoding function. Compared to the conventional PN sequence used in time-spread echo hiding based method, more large peaks are produced during the autocorrelation of the proposed PN sequence. Our decoding function is designed to utilize these peaks to improve the robustness. To enhance the embedding capacity, multiple watermark bits are embedded into one audio segment. This is achieved by varying the delays of added echo signals. Moreover, the security of the proposed method is further improved by scrambling the watermarks at the embedding stage. Compared with the conventional time-spread echo-based method, the proposed method is more robust to conventional attacks and has higher embedding capacity. The effectiveness of our method is illustrated by simulation results.