Adaptive video fingerprints for accurate temporal registration

Designing watermarks that can withstand geometric and temporal attacks is a notoriously difficult problem. The registration of a pirate content with the reference content, prior to the decoding of an embedded forensic mark, is therefore preferred. Semi-automatic registration systems, requiring the expert user to manually select and match control points through a suitable user interface, are not acceptable for content owners and do not usually provide very accurate results. A fully automated registration scheme is therefore chosen to synchronize pirate and master contents. By extracting robust and unique features, digital fingerprinting provides a relevant framework for automatic semi-blind content registration. In this paper we focus on temporal registration. In order to guarantee an accurate alignment while keeping the fingerprint size as small as possible, we propose a temporally adaptive approach. The registration scheme is designed around an adaptive motion description based on hierarchical encoding of the wavelet coefficients computed on the difference of successive frames.