Real-Time Operating Systems and Multimedia

Real-Time Operating Systems and Multimedia Support

Our work in real-time operating systems considers several types of problems: support for soft real-time scheduling of concurrent applications on commercial operating systems, the integration of hard real-time scheduling with scheduling audio and video streams, support of mutlimedia in real-time databases, and on developing smoothing algorithms for live video.

Multi-Level Soft Real-Time Scheduling with Guarantees

We have developed multi-level real-time scheduling that supports various types of real-time guarantees. This permits concurrent applications to run on a commercial operating system where each application can achieve a guaranteed performance. We also developed an integrated platform which is capable of meeting requirements of both traditional real-time processing and multimedia. This has enormous potential for accomodating various kinds of new applications. We have developed a multimedia server executing on a real-time multiprocessor operating system to provide different classes of guarantee to support both types of processing.

Selected Publications

J. Stankovic, Information Dominance via Global Virtual Databases, Workshop on Research Directions for the Next Generation Internet, March 1997.
H. Kaneko, J. Stankovic, S. Sen and K. Ramamritham, Integrated Scheduling of Multimedia and Hard Real-Time Tasks, Real-Time Systems Symposium, Dec. 1996.
J. Stankovic, S. Son and J. Liebeherr, BeeHive: Global Multimedia Database Support for Dependable, Real-Time Applications, chapter in Real-Time Database and Information Systems, Kluwer Academic Publishers, 1997, pp. 409-422.
J. Stankovic, Real-Time Global Virtual Machines, invited contribution, virtual roundtable discussion, IEEE Concurrency, Vol. 5, No. 3, Fall 1997.
O. Gonzalez, S. Sen, K. Ramamritham, and J. Stankovic, Incorporation of Multimedia Capabilities in Distributed Real-Time Applications, Workshop on Databases: Active and Real-Time, Nov. 1996.
J. Regehr and J. Stankovic, HLS: A Framework for Composing Soft Real-Time Schedulers, Proc. of the 22nd IEEE Real-Time Systems Symposium,, Dec. 2001.
J. Regehr and J. Stankovic, Augmented CPU Reservations: Towards Predictable Execution on General Purpose Operating Systems, Proc. of the Seventh IEEE Real-Time Technology and Applications Symposium,, June 2001.
J. Regehr, J. Stankovic, and M. Humphrey, The Case for Hierarchical Schedulers with Performance Guarantees,, Technical Report, CS-2000-07, March 2000.
J. Regehr, M. Jones, and J. Stankovic, Operating System Support for Multimedia: The Programming Model Matters, submitted for publication, Nov. 2002.

Smoothing Algorithms

Bandwidth smoothing techniques are effective at reducing the burstiness of a compressed, pre-recored video stream by prefetching frames into a client playback buffer in advance of each burst. In contrast to stored video, live applications have limited knowledge of frame sizes and often require bounds on the delay between the source and the client(s). We have developed solutions for smoothing live video transmissions.

Selected Publications

J. Rexford, S. Sen, J. Dey, W. Feng, J. Kurose, J. Stankovic, and D. Towsley, Online Smoothing of Live, Variable Bit Rate Video, NOSSDAV 97, 1997.
S. Sen, J. Dey, J. Kurose, J. Stankovic, and D. Towsley, CBR Transmission of VBR Stored Video, SPIE Int. Symp. and Education Program on Voice, Video, and Data Communications, Nov. 1997.