Hierarchical mesh-based global motion estimation, including occlusion areas detection

We present a method which is able to determine the occlusion areas appearing in a mesh-based motion estimation. The use of the motion estimation scheme based on a non-uniform hierarchical triangular mesh and the optimization of the nodal motion vectors by means of a multi-resolution differential method leads to efficient and fast motion estimation as well as motion field refinement. Although global motion estimation avoids the blocking artifacts due to the independence of the neighboring blocks of conventional block matching, it can only find the optimal motion parameters, which derive from the motion vectors at the node points that are shared by several patches of a continuous field. However real motion in a video sequence is discontinuous. Thus, our goal consists of modeling the artifacts, resulting from the occlusions by using a global mesh. Contrary to the segmented mesh associated with the video object when fast motion has to be estimated, surface mesh may contain overlapping triangles and the estimated image is thus deteriorated. In fact, these overlaps allow the detection of the occlusions. Thus, our method consists of taking into account this information to determine the optimal motion vectors in the continuous field and to generate the content of the uncovered area or to exclude the content of the covered area. To illustrate the new performances of the proposed method, results showing the capabilities of our mesh-based motion estimation to determine discontinuities lines are presented