Abstract

Time synchronization of video sequences in a multi-camera system is necessary for successfully analyzing the acquired visual infor- mation. Even if synchronization is established, its quality may deterio- rate over time due to a variety of reasons, most notably frame dropping. Consequently, synchronization must be actively maintained. This paper presents a method for online synchronization that relies only on the video sequences. We introduce a novel definition of low level temporal signals computed from epipolar lines. The spatial matching of two such tem- poral signals is given by the fundamental matrix. Thus, no pixel corre- spondence is required, bypassing the problem of correspondence changes in the presence of motion. The synchronization is determined from reg- istration of the temporal signals. We consider general video data with substantial movement in the scene, for which high level information may be hard to extract from each individual camera (e.g., computing tra jec- tories in crowded scenes). Furthermore, a trivial correspondence between the sequences is not assumed to exist. The method is online and can be used to resynchronize video sequences every few seconds, with only a small delay. Experiments on indoor and outdoor sequences demonstrate the effectiveness of the method.