Abstract
Newer social multimedia applications, such as Social TV or networked multi-player games,
enable independent groups (or clusters) of users to interact among themselves and share
services within the context of simultaneous media content consumption. In such scenarios,
concurrently synchronized playout points must be ensured so as not to degrade the user
experience on such interaction. We refer to this process as Inter-Destination Multimedia
Synchronization (IDMS). This paper presents the design, implementation and evaluation
of an evolved version of an RTCP-based IDMS approach, including an Adaptive Media Playout
(AMP) scheme that aims to dynamically and smoothly adjust the playout timing of
each one of the geographically distributed consumers in a specific cluster if an allowable
asynchrony threshold between their playout states is exceeded. For that purpose, we previously
had also to develop a full implementation of RTP/RTCP protocols for NS-2, in which
we included the IDMS approach as an optional functionality. Simulation results prove the
feasibility of such IDMS and AMP proposals, by adopting several dynamic master reference
selection policies, to maintain an overall synchronization status (within allowable limits)
in each cluster of participants, while minimizing the occurrence of long-term playout discontinuities
(such as skips/pauses) which are subjectively more annoying and less tolerable
to users than small variations in the media playout rate.