Adaptive multiresolution motion estimation techniques for wavelet-based video coding

Wavelet transform is an important tool for image and video coding applications. Several motion estimation techniques have been proposed in the wavelet domain. The coarse-to-fine motion estimation techniques generally have a lower complexity at the expense of inaccurate estimation. On the other hand, the fine-to-coarse motion estimation techniques provide a superior estimation, but at a higher complexity. In this paper, we propose an efficient video coder in the wavelet domain. First, we propose an adaptive resolution selection for motion estimation where a lowpass subband at an appropriate scale is employed for coarse motion estimation. The motion vectors of subbands from higher/lower resolutions are then predicted from the coarse motion vectors and are further refined using a small search window. Secondly, we propose an adaptive bit allocation technique where the bits are allocated optimally between the motion vectors and the displaced frame difference. This is performed by minimizing a cost function based on the Lagrange multiplier method. Simulation result shows that the proposed video coder provides a superior coding performance compared to other multi-resolution techniques proposed in the literature.