Subframe video synchronization by matching trajectories

We propose a novel approach to align unsynchronized video sequences of the same dynamic scene that can be subframe accurate and is applicable for different frame rate problem. The proposed approach relies on matching motion trajectories and it is assumed that the object moves on a planar surface. By exploring the invariants of planar trajectories under projective transformation, the cross ratio as an invariant feature is computed for each point along the trajectories and the similarity between invariant features of different trajectories is measured with a distance that takes into account the statistical properties of the cross ratio. Then the smooth high frame rate trajectory is synthesized for searching subframe temporal displacement under our alignment framework. The experimental results with synthetic and real-world sequences show that our approach achieves fairly accuracy and efficiency in subframe temporal alignment of the multiple unsynchronized video sequences.