Automatic extraction of motion trajectories in compressed sports videos

This paper presents an algorithm for automatically extracting significant motion trajectories in sports videos. Our approach consists of four stages: global motion estimation, motion blob detection, trajectory evolution and trajectory refinement. Global motion is estimated from the motion vectors in the compressed video using an iterative algorithm with robust outlier rejection. A statistical hypothesis test is carried out within the Block Rejection Map(<i>BRM</i>), which is the by-product of the global motion estimation, for the detection of motion blobs. Trajectory evolution is the process in which the motion blobs are either appended to an existing trajectory or are considered to be the beginning of a new trajectory based on its distance to an adaptive trajectory description. Finally, the extracted motion trajectories are refined using a Kalman filter. Experimental results on both indoor and outdoor sports videos demonstrate the effectiveness and efficiency of the proposed method.