a b s t r a c tRecent developments on Social TV point to an evolution from traditional IPTV services towards more social experiences. Newer applications and services have appeared wherein groups of people in different locations can watch multimedia content while synchronously communicating with each other. We name such applications as synchronous shared experiences. Realization of these shared experiences requires that users feel that they are coherently communicating with each other. This paper identifies and analyzes challenges that need to be tackled to achieve coherence: quality of service, mobility and distributed media synchronization. Furthermore, universal session handling is required to setup these sessions. We then present our solution to one of these challenges: distributed media synchronization. Our design uses the local lag mechanism over a distributed control or master-slave signaling architecture. We validate our implementation via experiments performed with one client located in Amsterdam and the other in Seoul. The experiments demonstrate a bound in play-out skew of 500 ms across these locations. Our results from user tests, presented elsewhere, show that this value is well within tolerance limits.

As Virtual Reality (VR) applications gain more momentum recently, the social and communication aspects of VR experiences become more relevant. In this paper, we present some initial results of understanding the type of applications and factors that users would find relevant for Social VR. We conducted a study involving 91 participants, and identified 4 key use cases for Social VR: video conferencing, education, gaming and watching movies. Further, we identified 2 important factors for such experiences: interacting within the experience, and enjoying the experience. Our results serve as an initial step before performing more detailed studies on the functional requirements for specific Social VR applications. We also discuss the necessary research to fill in current technological gaps in order to move Social VR experiences forward.

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In this paper, we describe a user study in which pairs of users watch a video trailer and interact with each other, using two social Virtual Reality (sVR) systems, as well as in a face-to-face condition. The sVR systems are: Facebook Spaces, based on puppet-like customized avatars, and a video-based sVR system using photo-realistic virtual user representations. We collect subjective and objective data to analyze users' Quality of Experience (QoE) and compare their interaction in VR to that observed during the real-life scenario. Our results show that the experience delivered by the video-based sVR system is comparable with real-life settings, while the puppet-based avatars limit the perceived quality of the interaction. Our protocol for QoE assessment is fully documented to allow replication in similar experiments.