ACM SIGCOMM Computer Communication Review
Selected papers of the 4th joint conference on European networking conference
vic: a flexible framework for packet video
Proceedings of the third ACM international conference on Multimedia
Real-Time Scheduling Support in Ultrix-4.2 for Multimedia Communiation
Proceedings of the Third International Workshop on Network and Operating System Support for Digital Audio and Video
Successful multiparty audio communication over the Internet
Communications of the ACM
Towards a design methodology for adaptive applications
MobiCom '98 Proceedings of the 4th annual ACM/IEEE international conference on Mobile computing and networking
Real-time applications on the Internet
BT Technology Journal
Assessing the quality of voice communications over internet backbones
IEEE/ACM Transactions on Networking (TON)
Capturing OS expertise in an event type system: the Bossa experience
EW 10 Proceedings of the 10th workshop on ACM SIGOPS European workshop
An RTP/RTCP based approach for multimedia group and inter-stream synchronization
Multimedia Tools and Applications
HSI'03 Proceedings of the 2nd international conference on Human.society@internet
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The recent interest in multimedia conferencing is a result of the incorporation of cheap audio and video hard-ware in today's workstations, and also as a result of the development of a global infrastructure capable of supporting multimedia traffic - the Mbone. Audio quality is impaired by packet loss and variable delay in the network, and by lack of support for real-time applications in today's general purpose workstations. A considerable amount of research effort has focused on solving the network side of the problem by providing packet loss robustness techniques, and network conscious adaptive applications. Effort to solve the operating system induced problems has concentrated on kernel modifications. This paper presents an architecture for a real-time audio media agent that copes with the problems presented by the UNIX operating system at the application level. The mechanism produces a continuous audio signal, despite the variable allocation of processing time a real-time application is given under UNIX. Continuity of audio is ensured during scheduling hiccups by using the buffering capabilities of workstation audio devices drivers. Our solution also tries to restrict the amount of audio stored in the device buffers to a minimum, to reduce the perceived end-to-end delay of the audio signal. A comparison between the method presented here (adaptive cushion algorithm), and that used by all other audio tools shows substantial reductions in both the average end-to-end delay, and the audio sample loss caused by the operating system.