On the Accuracy of Estimated Synchronization Positions for Audio Digital Watermarks Using the Modified Patchwork Algorithm on Analog Channels

We investigated the accuracy of estimated synchronization positions for audio digital watermarking using the modified patchwork algorithm (MPA) on analog channels. We focused our efforts on synchronization since correct synchronization of DCT frames is crucial for watermark detection using this algorithm. We employed M-sequence synchronization patterns, and embedded this pattern as synchronization headers with the MPA watermark. The synchronization at the decoder was accomplished by detecting the maximum correlation between the detected sync pattern and the correct sync pattern. This synchronization was shown to be possible with embed frame length (EFL) of 32 samples and above with no perturbations. The accuracy degrades considerably with analog loop back. In addition, with modest levels of additive Gaussian noise and sample rate conversion in addition to analog loop back, robustness was shown for some samples, while for other samples, we were not able to detect synchronization for all trials tested.