Synchronized Multicast Media Streaming employing Server-Client Coordinated Adaptive Playout and Error Control

A new inter-client synchronization framework employing a server-client coordinated adaptive playout and error control toward one-to-many (i.e., multicast) media streaming is discussed in this paper. The proposed adaptive playout mechanism controls the playout speed of audio and video by adopting the time-scale modification of audio. Based on the overall synchronization status as well as the buffer occupancy level, the playout speed of each client is manipulated within a perceptually tolerable range. Additionally, the server implicitly helps increasing the time available for retransmission while the clients perform an interactive error recovery with the assistance of adaptive playout control. By coordinating the playout speed of each client, the inter-client synchronization with respect to the target presentation time is smoothly achieved. The cumulative feedback for retransmission assisted by both playout speed manipulation at clients and implicit help of a streaming server is also conducted to increase the reliability. Furthermore, RTCP-compatible signaling between the server and group-clients is performed, where the exchange of controlling message is restricted. The network-simulator based simulations show that the proposed framework can reduce the playout discontinuity without degrading the media quality, and thus mitigate the client heterogeneity.