Image Processing Reference
In-Depth Information
Tele-immersion enables groups of geographically isolated users to interact and
communicate in a realistic way, through real-time sharing of a virtual environment.
Users and objects are captured by 3D cameras, which digitize them into a cloud of
points or a 3D mesh. Moreover, virtual characters and objects can be generated and
animated with computer graphics techniques. Digitized and compressed real and
virtual users and objects are mixed into real reconstructed scenes or virtual worlds.
Despite advances in 3D media compression and mechanisms such as caches that
increase network efficiency [
1
], due to the large amount of exchanged data and the
significant requirements for interactivity, 3D immersive communications pose
severe challenges in networking infrastructure.
It is obvious that supporting real-time, network friendly 3D immersive commu-
nications requests for optimal, sometimes on demand, network overlay construction
to guarantee the efficient content delivery. The last few years, overlays construc-
tion, especially in the form of Application Layer Multicasting (ALM) overlays to
support stream multicasting, has been subject to many research projects and studies
[
2
,
3
]. However, these approaches are mainly based on network and geographic
only criteria for the node selection and the overlay construction and do not take into
account social interaction of the participants.
In this topic chapter, we focus on the social interaction aspects and the way that
social interaction of the participants could be taken into account for the construction
of the overlay network topology. More precisely, we analyse information that we
can mine from the social network structures and correlate it with the 3D immersive
communications network overlay optimization process. We extract information
from the interactivity between the participants, and their mobility behaviour to
select the overlay nodes that could potentially serve more than one users and thus
contribute toward the overall network optimization.
12.2 Network Overlay Categories
In typical immersive applications, the content exchanged may be grouped in two
categories: (a) the static, which is pre-created and includes collections of digital
objects (such as definitions of virtual worlds, background objects, 3D models, even
stored Audio or Video streams) and (b) the dynamic, which consists of the content
that is created and streamed “on-the fly”, during the execution of the service,
including control messages and 2D/3D video and audio in separate sessions. The
percentage of the content between these two categories is not predefined and
depends on the type of the application (e.g. interactive, social or serious games,
or educational activities). A common approach to deliver these types of data is to
create network overlays. Network overlays provide a higher level view on top of
current network infrastructure, in a broader sense similar to Virtual Private Net-
works (VPN), ready to be deployed for specialized services. Overlay functionality
typically focuses on QoS, fault tolerance, security, multicasting and content access,
as depicted in Fig.
12.1
.
