20 June 2003 Registration methods for nonblind watermark detection in digital cinema applications
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Abstract
Digital watermarking may be used to enforce copyright protection of digital cinema, by embedding in each projected movie an unique identifier (fingerprint). By identifying the source of illegal copies, watermarking will thus incite movie theatre managers to enforce copyright protection, in particular by preventing people from coming in with a handy cam. We propose here a non-blind watermark method to improve the watermark detection on very impaired sequences. We first present a study on the picture impairments caused by the projection on a screen, then acquisition with a handy cam. We show that images undergo geometric deformations, which are fully described by a projective geometry model. The sequence also undergoes spatial and temporal luminance variation. Based on this study and on the impairments models which follow, we propose a method to match the retrieved sequence to the original one. First, temporal registration is performed by comparing the average luminance variation on both sequences. To compensate for geometric transformations, we used paired points from both sequences, obtained by applying a feature points detector. The matching of the feature points then enables to retrieve the geometric transform parameters. Tests show that the watermark retrieval on rectified sequences is greatly improved.
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Philippe Nguyen, Philippe Nguyen, Raphaele Balter, Raphaele Balter, Nicolas Montfort, Nicolas Montfort, Severine Baudry, Severine Baudry, "Registration methods for nonblind watermark detection in digital cinema applications", Proc. SPIE 5020, Security and Watermarking of Multimedia Contents V, (20 June 2003); doi: 10.1117/12.479735; https://doi.org/10.1117/12.479735
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