Recording and playing back interactive media streams

Recording systems and media servers for networked audio and video streams have become an important part of today's Internet. In contrast to this, only a few recording and playback solutions currently exist for the data streams of interactive media applications (e.g., shared whiteboards and distributed virtual environments). So far these solutions are application-specific: individual algorithms and implementations are required for each application that is to be recorded. In this paper, we are proposing generic algorithms for the recording and playback of interactive media streams. These algorithms are based on a common model for the class of interactive media. They enable full random access to recordings by initializing the replaying applications with the required state information (e.g., the current slide in a recorded presentation). We have implemented these algorithms in the Interactive Media on Demand (IMoD) system. In order to interpret the semantics of an interactive media stream, the system requires that the Real-Time Application-Level Protocol for Distributed Interactive Media (RTP/I) protocol is used for the framing of the transmitted data. Any application using RTP/I can be recorded directly using the system without any modification. Interactive media streams not using RTP/I can be recorded using the generic recording algorithms. However, they require an adaptation of the system so that it is able to extract a minimal set of information from the application-level protocol of these streams. In addition to the generic recording algorithms, we present the architecture and major design considerations of the system and discuss the experiences gained from recording different interactive media applications.