Efficient and robust motion estimation in grid-based hybrid video coding schemes

In the past advanced motion compensation techniques have been introduced leading to improved temporal predictions in hybrid video coding schemes. The focus of this paper is on grid-based warping prediction. The advantage of this technique compared to the commonly used block translational motion compensation is its improved capability to handle non-translational motion. However, a disadvantage is its 2-dimensional interdependency of motion vectors. This can lead to poor predictions, if the dependencies are not considered during the motion estimation process. Therefore in this paper a new highly efficient motion estimation method for grid-based prediction is presented. Different means are developed to improve the prediction quality, to decrease the computational complexity and to enhance the robustness of the algorithm. By introducing a hierarchical iterative octagonal matching with spatial and temporal prediction of candidate vectors for the motion search into a wavelet-based hybrid video coder a coding gain of up to 1.5 dB compared to MPEG-4 can be achieved.