Multiresolution motion estimation techniques for video compression

The wavelet transform is a valuable tool in video processing because of its flexibility in representing nonstationary signals. Waveletbased compression has the advantages of efficient decorrelation of image frames and reduced-complexity multiresolution motion estimation (MRME). We propose three techniques to improve motion estimation in a wavelet-based coder. First, we propose to use an adaptive threshold for coding the motion vectors of the high-pass subimages. Secondly, we propose a bidirectional motion estimation (BMRME) technique in the wavelet transform domain. In BMRME, we estimate the temporal (i.e., direction information) flags only for the blocks in the lowest-resolution subimages and use the same information for the corresponding blocks in the higher-resolution subimages. Finally, we propose a fast multiresolution motion estimation technique where the directional subimages at each level of the wavelet pyramid are combined into a single subimage. Multiresolution motion estimation is then performed on the newly formed subimages. The proposed techniques improve the coding performance significantly over the baseline MRME technique In addition, they further reduce the computational complexity of the MRME technique.