Optical flow techniques applied to video coding

Motion estimation is an important part of most video coding schemes because it enables us to exploit the high degree of temporal redundancy present. Though block matching algorithms (BMA) yield coarse and piecewise-constant elds, they are very popular due to their simplicity and low bit overhead. In this paper, we propose to use a more advanced gradient-based technique to overcome the disadvantages of BMA. A dense motion eld is estimated and compressed using a hierarchical nite element (HFE) representation, leading to an ef-cient, highly parallel, iterative, multiresolution optimization algorithm. The scheme also uses multireso-lution measurements and a coarse-tone strategy to estimate large displacements. At comparable bit rates, the motion elds are much smoother and more natural than those produced by BMA. Coding gains of about 0:6 dB were obtained on Claire. More importantly , substantial visual improvements were obtained, mainly due to improved performance near the edges.