Adaptive Playout Mechanisms for Packetized Audio Applications in Wide-Area Networks

Recent interest in supporting packet-audio applications over wide area networks has been fueled by the availability of low-cost, toll-quality workstation audio and the demonstration that limited amounts of interactive audio can be supported by today's Internet. In such applications, received audio packets are bu ered, and their playout delayed at the destination host in order to compensate for the variable network delays. In this paper we investigate the performance of four different algorithms for adaptively adjusting the playout delay of audio packets in an interactive packet-audio terminal application, in the face of such varying network delays. We evaluate the playout algorithms using experimentally-obtained delay measurements of audio tra c between several di erent Internet sites. Our results indicate that an adaptive algorithm which explicitly adjusts to the sharp, spike-like increases in packet delay which we observed in our traces can achieve a lower rate of lost packets for both a given average playout delay and a given maximum bu er size.