An Offline Bidirectional Tracking Scheme

A generic bi-directional scheme is proposed that robustifies the estimation of the maximum-a-posteriori (MAP) sequence of states of a visual object. It enables creative, non-technical users to obtain the path of interesting objects in offline available video material, which can then be used to create interactive movies. To robustify against tracker failure the proposed scheme merges the filtering distributions of a forward tracking particle filter and a backward tracking particle filter at some timesteps, using a reliability-based voting scheme such as in democratic integration. The MAP state sequence is obtained using the Viterbi algorithm on reduced state sets per timestep derived from the merged distributions and is interpolated linearly where tracking failure is suspected. The presented scheme is generic, simple and efficient and shows good results for a color-based particle filter.