Mesh-based motion models for wavelet video coding

Discrete wavelet transforms, implemented using lifting along motion trajectories, are effective and efficient temporal decomposition tools that facilitate video compression competitive with the current standards. As recently shown, however, in order that a lifting-based motion-compensated wavelet transform be equivalent to its transversal (standard) implementation, motion transformation must be invertible and motion composition between frames must be well-defined. In this paper, we discuss various mesh-based motion models that satisfy requirements of invertibility and composition, and thus are suitable for use in motion-compensated lifting-based wavelet transforms. We propose a new mesh configuration that preserves regularity of the mesh structure but provides better motion compensation compared to previously-reported mesh topologies, particularly in the proximity of image boundaries. Our results show that an improvement in motion compensation and overall compression performance is possible with only a fractional increase in motion overhead bit-rate.