Jitter-free Audio Playout over Best Effort Packet Networks

The aim of this research is to explore important issues in playout of audio over best effort audio networks and the improvements that can be made at the upper layers without changing the underlying network. This paper starts with a review of existing methods, the experiments conducted based on them and comments on their performance. The point of departure is the modification to the autoregressive delay estimation based buffering algorithm to make it more sensitive to delay variations. This helps to minimize buffering delays without increasing losses. This is motivated by the dependence upon the weighting parameter in the autoregressive equation, of how closely the delays are tracked in the autoregressive delay estimation method used in existing algorithms. The second modification suggested is a generic procedure which can be incorporated into any playout algorithm to check the audio quality deterioration occurring due to delay adjustment in the buffering algorithm. All suggestions are supported by simulations on wide area network delay traces. Applications for these algorithms arise in audio services over packet networks, such as IP telephony and audio streaming. Keywords— adaptive playout, internet telephony, jitter control, packetized audio