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

Reviewer : Seh Leng Lim

This paper studies 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 varying network delays.

The main contribution of the paper is its observation that an adaptive algorithm that explicitly adjusts to the sharp, spike-like increase in packet delay can achieve a lower rate of lost packets for both a given average playout delay and a given maximum buffer size. This contribution is important to the use of packetized audio over wide-area, packet-switched networks, which has seen a significant increase of interest in recent years.

The key main ideas expounded are :

(a) buffering audio packets for enough time so that majority of the packets have been received before their scheduled playout times

(b) either fixing or adaptively varying the additional artificial delay until playout

© packets which are not received before their scheduled playout time are considered lost

I think that the paper has a significant contribution (rating of 4) to the study of smooth streaming of audio over the Internet. Their approach of writing a simulator to simulate the behaviour of the four algorithms over the received packet trace file is a good and fair method for comparing the four algorithms.

Researchers and builders of interactive audio applications may have a better appreciation from this paper of the difficulties involved in delivering quality audio over the Internet.