Robust echo hiding scheme against pitch-scaling attacks

The pitch scaling conducts serious attacking on audio watermarked signals because it leads to a desynchronization problem. Based on the proposed analysis- by-synthesis echo watermarking scheme, this work develops a watermark extracting process to improve the robustness performance against pitch-scaling attacks. The positions of embedded echoes are altered in the cepstrum domain due to the pitch-scaling attacks that change the frequency content of audio signals. Hence, it is unable to determine the echo position a priori. In this work, the cepstrum values in a reasonable range of delay offsets affected by pitch-scaling attacks are addressed from auditory point of view. The moving average function is performed on several segments to eliminate the impact of host signals on cepstrum. In this extended range for searching delay offsets, the peak value of the cepstrum is adopted to determine the embedded watermark datum. Experimental results exhibit that the proposed robust echo watermarking scheme can be superior to the conventional audio watermarking schemes under pitch-scaling attacks and other attacks.