Nsync---a toolkit for building interactive multimedia presentations

Abstract

This chapter discusses a multimedia synchronization toolkit, called Nsync, to address the complicated issues inherent in designing flexible, interactive multimedia presentations. The toolkit consists of two primary components, a declarative synchronization definition language, and a run-time presentation management system. The synchronization definition language supports the specification of synchronous interaction, asynchronous interaction, fine-grained relationships, and combinations of each through the use of conjunctive and disjunctive operators. Precomputed playout schedules are too inflexible to deal with asynchronous interaction, and a more adaptive presentation management system is required. Nsync's run-time system uses a novel predictive logic to predict the future behavior of a presentation. As the viewer makes decisions, the presentation is updated and new predictions are made to maintain consistency with the viewer's wishes and the integrity of the presentation's message. The Nsync toolkit has been completely implemented in the Tcl/Tk scripting language. The total implementation effort was about 3,500 lines of Tel code extending over a 6 months period. Although, Nsync can model any granularity of skew relationship, it cannot currently enforce them. To address this issue, some parts of the system would need to be reimplemented in a lower-level programming language, such as C or C++.