Reducing the complexity of MPEG-4 global motion estimation using pixel subsampling

MPEG-4 uses a perspective model for global motion estimation. The region of support for global motion representation consists of the entire image frame. Estimating global motion parameters is very expensive computationally, since all the pixels in the frames are involved in the computation. Therefore, computationally efficient global motion estimation techniques are sought-after. It is shown that real-time global motion estimation in an MPEG-4 video codec can be achieved by using a pixel subsampling method based on regular subsampling patterns. Simulation results demonstrated that the proposed method was capable of speeding up the conventional all- pixel GME approach by more than 11 times, with a subsampling ratio of 1/16, without significant loss in estimation accuracy and compression efficiency.