Delay Reduction Techniques for Playout Bu eringCormac

100 Delay Reduction Techniques for Playout Bu ering Cormac J. Sreenan, Jyh-Cheng Chen, Member, IEEE, Prathima Agrawal, Fellow, IEEE, and B. Narendran Abstract| Receiver synchronization of continuous media streams is required to deal with delay di erences and variations resulting from delivery over packet networks such as the Internet. This function is commonly provided using per-stream playout bu ers which introduce additional delay in order to produce a playout schedule which meets the synchronization requirements. Packets which arrive after their scheduled playout time are considered late and are discarded. In this paper, we present the Concord algorithm, which provides a delay-sensitive solution for playout bu ering. It records historical information and uses it to make short-term predictions about network delay with the aim of not reacting too quickly to short-lived delay variations. This allows an application-controlled tradeo of packet lateness against bu ering delay, suitable for applications which demand low delay but can tolerate or conceal a small amount of late packets. We present a selection of results from an extensive evaluation of Concord using Internet tra c traces. We explore the use of aging techniques to improve the effectiveness of the historical information and hence the delay predictions. The results show that Concord can produce signi cant reductions in bu ering delay and delay variations at the expense of packet lateness values of less than 1%. Keywords| multimedia stream synchronization, playout bu ering.