Hierarchical motion estimator (HME) for block-based video coders

A hierarchical block-based motion estimation strategy for video sequence coding is proposed, which allows to reduce both the computational load and the number of transmitted motion vectors. The estimation is performed by first computing a coarse motion field at the lowest resolution of a Gaussian pyramid and then propagating and refining it till the maximum resolution. the main innovations concern the adaptive vector propagation and updating strategy, which allow an efficient recovery from wrong estimates while maintaining a low computational load. The advantages of the proposed method are manifold: first, it is able to decrease the computation of even two orders magnitude for an equivalent compensation; second, it generates a lower number of motion vectors, resulting in a lower information rate; third, it produces a more homogeneous motion field, thus easing a successive segmentation.