Adaptive Playout Scheduling with Audio Time - Scaling for the Nomadik Multimedia Processor

Some of the major challenges for interactive and streaming multimedia applications are the delay and delay jitter of today’s IP packet networks. In this paper, we present the implementation, on the STMicroelectronics NomadikTM multimedia processor family, of an advanced playout scheduling scheme that achieves high robustness against late packets while maintaining very low buffering delay at the receiver. We modified the porting on Nomadik of a common VoIP application in order to enable the adaptation of the playout time of each speech frame to the estimated network delay. Proper handling of time compression and expansion of speech frames is achieved using a time-scale modification technique that does not alter the frame frequency content. The same technique has also been adopted for the concealment of packet losses.