What are important issues to solve when designing an MPEG system that enables a high Quality of Service. How to achieve a constant end-to-end delay, given the delays due to video coding, audio coding and packetization of video and audio. How buffers are required to multiplex video and audio into a single system stream. The delay caused by a multiplex and demultiplex operation and the video and audio data flow through the buffers. How to synchronize video and audio at players and how to model the decoding process, so that required buffer resources for players can be specified accurately. How can compliancy of streams and players to MPEG-2 Systems be specified unambiguously. What are important timing issues in the design of MPEG-2 systems. Use of a system clock at encoder and decoder and how to convey its value in a stream. Frequency and tolerance of the system clock in MPEG-1 and in MPEG-2 systems. Regeneration of the system clock in a player. How to ensure a high Quality of Service and the importance of transport layer independency.