Subtrajectory-Based Video Indexing and Retrieval

This paper proposes an approach for retrieving videos based on object trajectories and subtrajectories. First, trajectories are segmented into subtrajectories according to the characteristics of the movement. Efficient trajectory segmentation relies on a symbolic representation and uses selected control points along the trajectory. The selected control points with high curvature capture the trajectory various geometrical and syntactic features. This symbolic representation, beyond the initial numeric representation, does not suffer from scaling, translation or rotation. Then, in order to compare trajectories based on their subtrajectories, several matching strategies are possible, according to the retrieval goal from the user. Moreover, trajectories can be represented at the numeric, symbolic or the semantic level, with the possibility to go easily from one representation to another. This approach for indexing and retrieval has been tested with a database containing 2500 trajectories, with promising results.