Informed detection of audio watermark for resolving playback speed modifications

Abstract

In this paper, we present a method for informed watermark detection in audio signals. In this context, informed detection refers to the mechanism in which the original media signal is used to improve robustness and/or complexity. Here, we focused on reducing complexity by addressing the geometrical distortion problem. In audio, geometrical distortion translates to time scaling. Generally, s speed changes of the audio signals necessitate a mechanism in the detector to retrieve the watermark. Usually this is done by some kind of (clever) exhaustive search algorithms. In this paper we show that the speed searching process can significantly be improved using fingerprinting technology. Particularly, an initial estimate of the speed is obtained by extracting the so-called local fingerprint time stamps. This initial estimate is then used as a starting point for the exhaustive speed search algorithm in the watermark detector. We also give analyses on the accuracies of the watermark detector and the fingerprint algorithm and the relations thereof. Moreover, we present the concept for integrating fingerprint algorithm in the watermark detector and discuss the influence of various parameters. We show that, apart from a significant complexity reduction, such integration can lead to an improvement in robustness as a byproduct.