Temporal alignment of video sequences for watermarking systems

Many watermarking applications may benefit from the availability of both the original and the watermarked media content to perform detection. However, one must take into account that the watermarked media might have undergone deformations such that direct correspondence between original and watermarked signal is not possible anymore. Extra processing is therefore needed to benefit from the availability of both signals. In video applications, besides the spatial deformations, one must also consider a possible temporal structure modification of the watermarked content. Such distortions include frame rate modifications, scene removal and temporal cropping. In this paper, we present how one can perform an automatic frames alignment of spatially and temporally deformed video sequences. Our approach consist in establishing a correspondence between automatically detected key-frames in the two sequences. The key-frame detection is inspired from existing methods dealing with scene cuts localization and semantics (MPEG7-like) scene classification. Different simulations show that the method can cope with common temporal deformations.