Improved time spread echo hiding method for robust and transparent audio watermarking

In this paper we propose an accurate and content-based algorithm for embedding and detecting watermarks within audio signals. The algorithm is based on a new time spread method with minimum signal distortion. At first a novel time spread method is introduced such that the detection process does not rely upon the presence of a peak at a special delay but instead it depends on a correlation quantity. Next we adoptively select the coefficients of embedding echoes in each segment based on a correlation quantity between the audio signal cepstral content and a pseudo random noise. In this method the effect of the original signal at the detector (prime source of error within non-attack environments), is removed, similar to the improved spread spectrum watermarking and is shifted to the encoder stage. This will make the system highly accurate and robust against signal processing attacks in comparison with conventional time spread methods. Good results were obtained for watermark inaudibility through Mean Opinion Test (MOS) test and SNR value comparisons.