Multimedia synchronization with user interactions using interactive extended finite state machines (IEFSMS)

One of the main and required characteristics of multimedia systems is the user-interaction service. The user-interaction service is an essential requirement in some applications, e.g., Video-On-Demand (VOD) and News-On-Demand (NOD). The user-interaction service provides flexible multimedia presentations with user interactions. That is, users are allowed to have on-line adjustment of the presentation flow, e.g., skip some (boring) media units or reverse the presentation direction, to have some special features. In this paper, we propose an Interactive Extended Finite State Machine (IEFSM) model to specify synchronization issues in multimedia presentations with user interactions. By incorporating interrupt transitions and dynamic transitions in the IEFSM model, dynamic behaviors resulting from user interactions can be modeled using some IEFSMs. Using the IEFSM model, intra-medium synchronization is handled by an Actor, which is formally represented as an IEFSM; inter-media synchronization is handled by a Synchronizer, which is also formally represented as an IEFSM. The communication between IEFSMs is message-passing through some First-In-First-Out (FIFO) queues. In this way, the dynamic behaviors of user interactions, including reverse, skip, freeze-restart, and scale can be represented in IEFSM-based multimedia synchronization specifications.