Tele-immersive systems development is always driven as well as restricted by the available immersive technology. Hence, existing such systems are described mainly from a technological point of view; their conceptual description is usually limited to the description of a scenario that is implementable with or circumvents the limitations of the chosen technology. This focus on technology makes it difficult to compare systems' concepts; moreover, it has led to different views on tele-immersion in different fields, such as remotely controlled robots, immersive video conferencing, and tele-collaboration. In this work, we give a general, structured principle to describe the conceptual part of any tele-immersion system. This principle naturally unifies the different views on tele-immersion. Our idea is based on the insight that, in order to be general, immersion must be described separately for each direction of communication. We characterize communication between locations using a graph; for each directed edge of this graph, we describe immersion as operations on volumes. Using this principle, we define a typology, which enables the comparison and enumeration of tele-immersion concepts. We apply this typology to survey the concepts of existing tele-immersion systems and thereby demonstrate how three well-known tele-immersive scenarios-Marvin Minsky's tele-operated robot, the Office of the Future, and the asymmetric Beaming scenario-integrate naturally. We show how the general principle can be utilized conveniently to grasp conceptual ideas in tele-immersion, such as direct interaction, locational presence, spatial consistency, symmetries, and self-inclusion.

Telepresence systems use 3D techniques to create a more natural human-centered communication over long distances. This work concentrates on the analysis of latency in telepresence systems where acquisition and rendering are distributed. Keeping latency low is important to immerse users in the virtual environment. To better understand latency problems and to identify the source of such latency, we focus on the decomposition of system latency into sub-latencies. We contribute a model of latency and show how it can be used to estimate latencies in a complex telepresence dataflow network. To compare the estimates with real latencies in our prototype, we modify two common latency measurement methods. This presented methodology enables the developer to optimize the design, find implementation issues and gain deeper knowledge about specific sources of latency.

Systems for immersive videoconferencing utilizing LHRDs face the problem of generating large amounts of data. A solution to reduce this data is essential to realize such systems. We present different possible approaches to do this and give an overview where these are applicable. This provides the reader with a first guide for design decisions when implementing such systems.