Low-complexity global motion estimation from P-frame motion vectors for MPEG-7 applications

We present an algorithm for low-complexity global motion estimation, that works with block-coded video (e.g. MPEG-2). A superimposed global motion model is fitted to decoded P-frame motion vector fields, providing real-time performance. Therefore a robust M-estimator is applied since a lot of outliers have to be expected in the motion vector fields. The algorithm is compared to a state-of-the-art global motion estimator. The main characteristics of the global motion are captured accurately in most cases, although estimation may fail. We also report the integration of the estimator into a complete MPEG-7 system for search-and-retrieval of video based on motion characteristics.