Components of a complex multimedia application typically work reactively processing events such as notifications from other threads, signals, and network packets. To better support these applications we have built a message-based threading platform providing more flexibilty than event handling with one thread and easier synchronisation than conventional multithreading approaches. Reuse and reconfiguration are facilitated by using a uniform message interface for all types of events. Moreover, scheduling can be based on timing constraints attached to messages rather than to threads. The reimplementation of a multi-stream video player shows the benefits of this approach.