Video Synchronization Based on Displacements of Center of Motion
Abstract —Video synchronization is one of the ﬁrst steps inmost of the multi-camera systems. In this paper we introducea novel, computationally simple and reliable approach for videosynchronization that does not require any pre-computed camerageometries or tracking certain features. We deﬁne a featurecalled Center of Motion (COM) and obtain its trajectories alongthe temporal axis for both videos. Then the temporal shiftis estimated by correlating the trajectories. We follow a sub-sequence based approach to make our algorithm reliable andassign a conﬁdence measure to the estimated temporal shift.Whenever our algorithm fails to estimate the temporal shiftreliably it indicates its inability rather than giving a wrongoutput. Experimental results demonstrate promising capabilityof our approach. I. I NTRODUCTION A multi-camera system that captures the same scenefrom different viewpoints is commonly used for variousapplications such as surveillance, multiple view synthesisfor object recognition, dynamic scene reconstruction, etc.For such systems it is always important to represent allthe videos on a single time scale. If all the cameras areconnected to the same external clock signal then they will besynchronized automatically. But when cameras do not have acommon clock signal they have to be synchronized using thevisual information present in the videos. And for videos thathave been already captured synchronizing based on visualinformation is the only option.Video synchronization algorithms can be divided into twocategories: intensity based and feature based. Feature basedmethods use tracking and matching of speciﬁc features likepoints on moving objects, object trajectories, etc. whereasintensity based methods[1] use all the pixels and avoid featuretracking and matching. In [2] Caspi and Irani proposed amethod based on matching the trajectories of objects. But thismethod uses geometric correspondences for synchronizationand hence a sufﬁcient number of correspondences acrossimages are necessary, which may not be possible always. In[3] Wedge