Packet Size Variability in Real Time Transmission of Smoothed MPEG-4 Streams

It is desirable for the IP packet size variability of real time traffic classes to be small. This enables the adoption of schedulers such as weighted round robin, which are of low complexity and, under the assumption of approximately constant packet sizes, are suitable to real time traffic. Compressed video exhibits high variability in different time scales, so video smoothing techniques have been developed in order to reduce bit rate variability. This facilitates resource allocation to video streams. In particular, it may lead to schedulers that assume constant bit rate (CBR) on a per interval basis, as most smoothing techniques lead to a sequence of intervals of CBR. One such scheme is a version of weighted Round Robin scheduling. We carry out an experiment using traces of compressed video (MPEG-4) in order to establish how easily they can be packetised into fixed size packets.