Comparison of block-based and mesh-based motion estimation algorithms

In this paper, two mesh-based motion estimation algorithms are presented. Both algorithms compute the nodal motions in a hierarchical manner. Within each hierarchy level, the first algorithm (HMMA) minimizes the prediction error in the four elements surrounding each node, where the prediction is accomplished by a bilinear mapping. The optimal solution is obtained by a full search within a range defined by the topology of the mesh. The second algorithm (HBMA) minimizes the error in a block surrounding each node, assuming the motion in the block is constant. The two algorithms are compared with an exhaustive block matching algorithm (EBMA) by evaluating their performances in temporal prediction and in an H.263/TMN4 coder. In terms of the PSNR measure, the three algorithms achieve quite similar performances. However, HMMA and HBMA, avoid blocking artifacts introduced by EBMA. HMMA outperforms HBMA slightly for certain sequences at the expense of higher computational complexity.