05/01/1998 09:00 AM
Computer Engineering
This paper addresses the clock recovery problem while transporting MPEG-2 Systems Layer streams over packet-switched networks. The packet delay variation (jitter) introduced by the network affects the stability and thus the quality of the recovered clock. A decoder design methodology is described in which a jitter estimator that performs restamping on all the incoming packets containing clock values is used in conjunction with a standard phase-locked loop (PLL). A simple implementation of this methodology is described, where a new heuristic has been added to the standard PLL to eliminate the effects of the jitter. The methodology is evaluated by both analysis and extensive simulation experiments in a multi-hop ATM network using constant bit-rate MPEG-2 Transport Streams produced by hardware encoders with varying levels of cross traffic. The results show that the restamping approach outperforms standard dejittering methods, especially under heavy load conditions.
