Content-based synchronization for multiple photos galleries

The large diffusion of photo cameras makes quite common that an event is acquired from different devices, conveying different subjects and perspectives of the same happening. Often, these photo collections are shared among different users through social networks and networked communities. Automatic tools are more and more used to support the users in organizing such archives, and it is largely accepted that time/space information is fundamental to this purpose. Unfortunately, both data are often unreliable, and in particular, timestamps may be affected by erroneous or imprecise setting of the camera clock, thus making the retrieval based on temporal tagging unreliable. In this paper, we propose to solve this well-known problem by introducing a synchronization algorithm that exploit the content of pictures to estimate the mutual delays among different cameras, thus achieving an a-posteriori synchronization of various photo collections referring to the same event. Experimental results show that, for sufficiently large archives, a notable accuracy can be achieved in the estimation of the synchronization information.