PERFORMANCE-MEASUREMENTS ON THE HEIDELBERG AUDIO VIDEO DISTRIBUTION-SYSTEM - METHODOLOGY AND RESULTS

The integration of continuous presentation media like audio and video into current workstation and networking environments imposes tight tim ing constraints on A/V data transfer. These constraints are summarized under the term Quality of Service (QoS), which comprise a number of p arameters. Among those, delay and delay jitter are the most important. In the study presented in this paper, measurement and modelling metho ds have been applied to analyse the delay and delay jitter incurred by audio/video streams. An experimental audio/video distribution system called HeiDi (Heidelberg A/V Distribution System) intended for the ful ly digital distribution of compressed, packetized audio and video over a token ring local area network served as testbed for the analysis. M easurements were conducted with the ZM4 (abbreviation for the German n ame Zahlmonitor 4) monitoring system developed at the University of Er langen-Nurnberg especially for performance analysis of distributed sys tems. For modelling, Monitoring Petri Nets are used, a class of Petri nets which lends itself well for the integration of measurement and mo delling. Results indicate that the audio/video subsystem and the commu nication subsystem must be closely integrated to yield a sufficient pe rformance.