Motion Estimation Algorithms Using the Deformation of Planar Hierarchical Mesh Grid for Videoconferencing Applications at Low Bit-rate Transmission

摘要

This paper studies the issue of reducing the temporal redundancy between consecutive frames of a videoconferencing sequence at low bit-rate transmission. To overcome the drawbacks of the traditional block matching algorithm implemented in the most current video coding standards, we propose to better describe the motion of objects through the deformation of planar rectangular mesh grid adapted to the edges of the moving objects in the scene. The traditional inter coding modes are then replaced by two new classes of encoding algorithms. The first one concerns the 5-frames where the problem of motion estimation is solved by a bidirectional prediction algorithm which reconstructs the quadrilateral mesh grids without any coding cost. The second class of algorithm much more complex than the first one is specific to the P-frames based on the principle of merging two hierarchical grids of reference. This algorithm addresses not only the motion estimation problem based on the adaptive quadrilateral mesh grid but also the issue of the relevant information (e.g. the positions of the nodes, the connectivity of each quadrilateral mesh of the grid and the motion compensation) to efficiently encode. The implementation of these algorithms in a complete coding scheme offers good performance compared to the H.264/AVC video coder at low bit-rate transmission.