Adaptive Playout Mechanisms for Packetized Audio Applications in Wide-Area Networks
Reviewer: Robert Dugas
The problem addressed is that of variations in network delays affecting the reception
and playback of packetized audio.
Proposed and evaluated are 4 algorithms for coping with such problematic delays in audio transmission.
- Identifies delay as a major factor affecting audio performance
- Presents and evaluates 4 algorithms for estimating packet delay characteristics
- Describes relationship between packet delay and optimal playout buffer
This paper describes some useful techniques both in estimating delay, and in applying that knowledge
to optimizing voice playback. As IP telephony and other packetized audio applications gain popularity,
these techniques and others like them will become necessary for adapting from current circuit switched
Four algorithms are presented and evaluated based on performance of the NeVoT audio terminal application. Traces
are presented for loss percentages given experimentally obtained delay measurements of audio traffic between
several different sites. Although the specifics of that sampling are somewhat dubious, the results presented
seem to conform to expections of the effects of the different algorithms.
The techniques described in this paper will only apply well to voice audio packets. Since the author
takes advantage of the silence periods inherent in human voice to adjust the buffering status, such
techniques will not apply to other audio sources.
The data presented indicates that dynamic adjustment of delay measurements can enhance playback
performance when applied to receiver buffering.