HIERARCHICAL MOTION ESTIMATION AND VIDEO SEGMENTATION IN PRESENCE OF MORE THAN ONE MOVING OBJECT IN A BLOCK

摘要

In hierarchical motion estimation motion vectors (dv₁, dv₂, ..., dv_N-1) are refined in successive levels of increasing search window pixel density and/or decreasing search window size. Within each hierarchical level, after finding an optimum vector at at least one pixel, based on the optimum vector, the absolute displaced frame difference or displaced frame difference for each pixel of the search window is determined (72, 75, 78). Within the search window, two or more groups of these pixels are determined (72, 75, 78), wherein each of these pixel groups is characterised by a different range of absolute displaced frame difference values or displaced frame difference values for the pixels. A segmentation of the search window into different moving object regions is carried out (72, 75, 78) by forming pixel areas according to the groups, which areas represent a segmentation mask (si₁, si₂, ..., si_N) for the search window. For at least one of the segmentation areas a corresponding motion vector (dv_N) is estimated (72, 75, 78).