Motion estimation techniques for a wavelet-based video coder

Wavelet transform has been proven to be a valuable tool for image and video coding applications. Recently, a multiresolution motion estimation (MRME) technique has been proposed for wavelet-based video compression. The MRME technique estimates the motion vector hierarchically from the low resolution to the high resolution wavelet subimages, thereby reducing the computational complexity. In this paper, we propose two techniques to enhance the coding performance of the baseline MRME technique. First, we propose to use an adaptive threshold to determine whether a motion vector should be sent to the receiver resulting in a reduced number of motion vectors and hence lower bit-rate. Secondly, we propose a bi-directional motion estimation technique in the wavelet transform domain. Here, we estimate the temporal flags (direction information) only for the blocks in the lowest resolution subimages and use the same information for the corresponding blocks in the higher resolution subimages. The proposed techniques provide a superior coding performance compared to MRME technique.