Multiresolution displacement fields for motion compensated video coding

In motion compensated video coding, the rate-distortion efficiency of coding the motion information becomes increasingly critical as the overall bit rate of the coder drops. The efficiency can be improved by allocating bits to regions of the displacement field in accordance with the significance of each region. This forms the motivating factor to use multiresolution displacement fields, specifically nonuniformly sampled displacement fields. In this paper we examine two methods of constructing and coding multiresolution displacement fields. We propose a novel fast search scheme which combines the advantages of both methods, but with little sacrifice of performance. We compare these methods in terms of their rate-distortion performance, computational complexity, and motion compensation quality at very low bit rates.