ATF: an Adaptive Three-layer Framework for inter-stream synchronization of SMIL multimedia presentations

In this paper, we propose an Adaptive Three-layer Framework (ATF) to guarantee the inter-stream synchronization, which is called as the APplication Quality of Service (APQoS) in this paper, of World Wide Web Consortium (W3C) Synchronized Multimedia Integration Language (SMIL) presentation. This ATF framework, which is composed of the Framework Control Layer (FCL), the Quality Guarantee Layer (QGL) and the Media Control Layer (MCL), functions as the middleware between underlying best-effort network protocol stacks and the SMIL client/server applications. The FCL at the SMIL client periodically monitors underlying network bandwidth and delay for the QGL to verify whether the total bandwidth requirements of all concurrent objects to meet the APQoS of the SMIL presentation can be satisfied with the available bandwidth, which is the sum of the monitored bandwidths of all concurrent objects. The QGL executes the novel Intra-SMIL Bandwidth Reallocation (ISBR) scheme to dynamically adjust bandwidth allocations among concurrent SMIL objects, according to their Media Importance (MI) values calculated by the MCL. If the available bandwidth is not enough, the ISBR scheme gracefully degrades the layer-encoded objects that have the smallest MI values and only allocate the necessary bandwidth for their base layer (BL) streams instead. Oppositely, it aggressively upgrades the degraded layer-encoded objects that have the largest MI values and allocate the necessary bandwidth for both the BL and enhancement layer (EL) streams. These bandwidths are then feedback to the remote media servers to modify the transmission rates accordingly. With the quantitative analysis for the SMIL presentation quality, this ATF framework achieves the APQoS with the best SMIL playback quality.