Hierarchical motion compensation with spatial and luminance transformations

We present a new method for motion compensation, which combines transformations in the spatial and luminance domains. In most standardised video compression algorithms, motion information is assumed to be translation only, as used by the traditional block matching algorithm (BMA). Such an assumption is not always correct, as in most scenes, namely head and shoulders, object motions are rotations and zooms, among other effects, which cannot be represented as translations. In order to compensate these complex motion features more accurately, we applied geometric transformations (BMGT) for motion compensation. Nevertheless, spatial transformations alone are unable to compensate situations like uncovered background, masking between objects or changes in lighting conditions. In this sense, we introduced an additional transformation in the luminance domain (BMGTI), which has proven to be appropriate to overcome such problems. Experimental results have shown that BMGTI exceeds the performance of BMGT by about 2 dB, and achieves better results than the global brightness compensation (GBC) technique. This method is implemented using a spatial hierarchical block structure, which allows video encoding at low bit rates and reduction of the computational complexity