On the hierarchical edge-based block motion estimation for video subband coding at low bit rates

In this paper, a new hierarchical edge-based block motion estimation scheme is proposed for the exact motion estimation in the passband structure. The basic idea is to estimate an initial motion at the top-most layer in order to increase the accuracy of the motion displacement at the next lower layers in the motion estimation pyramid. This is based on a blockmatching method by the block-edge pattern. In addition, we present a technique of classifying a block-edge pattern by use of only two parameters, which are obtained by calculating two highpass subband signals at the top-most layer in the motion estimation pyramid. Using this scheme, the coding performance is improved by the exact motion estimation. We also present a method to encode the residual errorframes in a passband structure. Simulation results show that the performance of the scheme with the edge-based initial motion estumation is better than without it, especially when the high degree of motion is existed.