Fast and efficient block motion estimation in the wavelet space

Block matching algorithms (BMA) have been widely used as standard motion estimation (ME) techniques in video coding practice. In this paper, we present an iterative but analytical motion estimation algorithm with attractive computational efficiency. Our work can be viewed as generalization of the celebrated work of Lucas and Kanade (1981) on iterative image registration into the wavelet space. We demonstrate that block-based motion estimation can be performed efficiently in a coarse-to-fine fashion by propagating the estimate across the scale in the wavelet space. Our solution often takes a fraction of the computations required by the conventional BMA methods and reaches comparable MSE performance of prediction residues (fractional-pel motion accuracy is achieved due to the analytical nature of the proposed scheme). In spite of the iteration in the proposed scheme, it converges fast especially with a good initial estimate passed on from the low resolution. Our new ME scheme is particularly useful to the speed-up of implementing a new class of wavelet-based scalable video coders.