A Terminal-based Approach for Distributed Multimedia
Christian Blum, Refik Molva, Erich R?tsche
Institut Eur?com, Sophia-Antipolis, France
Broadband networks and ATM are the key technologies that promote distributed multimedia applications. With the emergence of affordable public broadband (ATM) networks the number of distributed multimedia applications and users will drastically increase. Current multimedia platforms [Chen 92, K?ppner 93, Dermler 92] use the paradigm of communicating peer systems. This paradigm is not suitable for multimedia services in telecommunication networks with a high number of users, where new applications and services must be introduced without changes to the end-systems. To solve this problem we propose an architecture that relies on lean multimedia terminals and on application pools that control and serve applications. Application pools control multimedia applications and terminals by means of a high level application interface. This interface facilitates the introduction of new applications and services. An application pool mediates communication applications, e.g., video conferences, by connecting terminals via media streams. Traditional applications based on alpha-numerical data are executed on the application pool.
Distributed multimedia requires broadband communication of high-speed data, still images at high resolution, and moving pictures (video, animated graphics). The aggregation of these data generates not only high-volume continuous data streams but also dynamic bursts of data. The processing of these data imposes a new type of load on the network, on the network adapter, and on the I/O subsystem of the workstation. Most current workstations are general purpose systems designed for computation and not for communication. Therefore they are not suited to handle multimedia communication and to guarantee quality of service (QoS) to a user. We propose a multimedia terminal that is optimized for the processing of multimedia data streams. It handles multimedia data streams between the users and the network with guaranteed QoS and provides functions to compress/decompress, to synchronize, and to render data streams. For wide usage a multimedia terminal must be as cheap and therefore as simple as possible. The resulting endsystem will look like a multimedia-enhanced X-station or a multimedia Minitel and it will provide optimal access to multimedia services in the network to the user.
In the following section we present the architecture of the distributed multimedia infrastructure. In Section 3, the architecture of the multimedia terminal is elaborated. The last section gives our conclusions.
2. An Architecture for Distributed Multimedia
We believe that the majority of today's distributed multimedia applications, among them all that are promising for commercial use, can be implemented on top of a common generic programming interface that provides a small but powerful set of abstractions. Most distributed multimedia applications treat the various available media as transparent streams rather than performing any processing on the media content itself. Implementing such commonly used