Paper Review: < RKTS94 >>
Adaptive Playout Mechanisms for Packetized Audio Applications in Wide-Area Networks

Reviewer: Oleg Elkhunovich


Audio needs to be played at a constant rate but packet delay in the network is varied. The solution is to buffer audio packets and delay their playout to compensate for the delay. The problem is to determine by how much should the playout be delayed.


This paper evaluates four different algorithms for adaptively adjusting the playout delay of audio packets in an interactive packet-audio terminal application.

Main Ideas

  • Principal challenge in supporting interactive audio over a wide-area network is the need to provide synchronous playout of audio packets in the face of stochastic end-to-end network delays.
  • There is a tradeoff between the delay that an audio application is willing to tolerate and the packet loss suffered as a result of the late arrival of packets.
  • There are frequent occurances of delay spikes in the audio packets transmitted. So, the best algorithm should adapt fast enough to such spikes - on their detection and when they are over.


    Significance: 4
    Paper addressed a very important problem in a relevant application. Author's assumtion that interest in transmitting audio over the internet is definately correct as today, seven years after this paper was written people all over the world can listed to to live feeds of audio over the Internet.
    Methodology of this paper in not extremely organized and clear. The experiements performed are not described in enough detail and more illustration of the results would be nice.
    Paper discusses a very limited problem and compares their algorithm to very simplistic alternatives.

    "What is good for one domain need not necessarily be good in another domain, even though the idea behind both (estimating delays) is the same" - same rules do not apply to audio packets as those to TCP packets.