Optimal policies for playing buffered media streams

Abstract

This paper addresses a practical problem in our everyday use of streaming media on the Internet: as a user observes the buffering of a media stream with an uncertain transfer rate, when should that user initiate playback of the stream? The tension is that initiating playback prematurely will increase the likelihood of buffer starvation, while a delay in initiating playback is undesirable because it necessitates waiting. Three policies are studied: the optimal policy (exploiting full knowledge of the transfer process), the optimal static policy (the expected value of the optimal policy), and an online policy assuming only knowledge of the transfer rate observed thus far. Lower and upper bounds are derived on the optimal policy as well as the associated minimum cost; these bounds are expressed in terms of a (random) hitting time of the transfer process. Simulation results for a Markov modulated transfer rate process identify static and online policies as near-optimal depending on the time scale of the transfer rate process and the duration of the stream. © IFIP International Federation for Information Processing 2007.