Peer-to-peer networks (P2Ps) are becoming more and more popular in video content delivery services, such as TV broadcast and Video on Demand (VoD), thanks to their scalability feature. Such characteristic allows for higher numbers of simultaneous users at a given server load and bandwidth with respect to alternative solutions. However, great efforts are still required to study and design reliable and QoS-guaranteed solutions. In this paper, within the scenario of P2P-based VoD services, we study the phenomenon of peer churns and propose four models of the peer behaviour to evaluate its impact on the system performance, which are based on the Gilbert-Elliot chain, the fluidic representation of the user behavior, and a queuing analysis of the system. The models are compared by computing the resources the system has to add on top of the P2P network to satisfy all the download requests. Simulations show important relationships between playback buffer length, peer request rate, peer average lifetime, and server upload rate.

Giovanni Branca

Thomas Schierl

Luigi Atzori

Theoretical Models for Video on Demand Services on Peer-to-Peer Networks

The subject of the future of the interactive Television medium has become a topic of great interest to the academic and industrial communities particularly since in the recent years there has been a dramatic increase in the pace of innovation of convergence of digital TV systems and services. The purpose of this paper is to provide a brief overview of what we know as digital TV converged services, to present and categorise the digital Television middleware technologies that contributed to it, and to present possible future trends and directions. A new Television era of converged wireless and mobile content delivery, user-authored content, multimodal interaction, intelligent personalisation, smart space awareness, and 3D content sensations is foreseen, creating ambient and immersive experiences.

Emmanuel Tsekleves

John Cosmas

Amar Aggoun

Jonathan Loo

Converged Digital TV Services: The Role of Middleware and Future Directions of Interactive Television

This paper introduces different standards implemented in existing Digital Terrestrial Television Broadcasting systems to allow the fruition of interactive services and applications through digital Set Top Boxes.  It focuses on the interoperability issue between the Brazilian and the European architectures. In fact, despite in Brazil the GEM specification has been designed to foster wide content compatibility across a range of interactive platforms, it has never come to a final implementation and deployment. As a result the interoperability issue has been deeply explored in the BEACON project and an innovative system architecture has been  developed to deploy t-learning services across Europe and Brazil, providing integration of those systems that were not able to interoperate until nowadays. This work is an important step in the direction of standards&#39; interoperability. As a result, MHP and Ginga NCL-Lua implementation appeared to be the very best choice to deliver interactive services in an interoperable mode between European and Brazilian digital television.

Jordi Amatller Claras&#243;

David Baldo

Giuliano Benelli

Giovanni Luca Daino

Riccardo Zambon

Interactive Digital Terrestrial Television: The Interoperability Challenge in Brazil

We propose an innovative scheme for multiple description coding (MDC) with regions of interest (ROI) support to be adopted in high-quality television. The scheme proposes to split the
stream into two separate descriptors and to preserve the quality of the region of interest, even in case
one descriptor is completely lost. The residual part of the frame (the background) is instead modeled
through a checkerboard pattern, alternating the strength of the quantization. The decoder is provided
with the necessary side-information to reconstruct the frame properly, namely, the ROI parameters and
location, via a suitable data hiding procedure. Using data hiding, reconstruction parameters are embedded
in the transform coefficients, thus allowing an improvement in PSNR of the single descriptions at the
cost of a negligible overhead. To demonstrate its effectiveness, the algorithm has been implemented in
two different scenarios, using the reference H.264/AVC codec and an MJPEG framework to evaluate the
performance in absence of motion-compensated frames on 720p video sequences.

M. Verza

N. Conci

G. Boato

F. G. B. De Natale

Multiple Description Coding Using Data Hiding and Regions of Interest for Broadcasting Applications

In the last years Peer-to-Peer (P2P) systems have gained ground for content
sharing between communities, determining a real revolution on the Internet.
The characteristics of P2P systems make them a very good choice for multimedia
content distribution over IP networks. However, although P2P technology gives
new opportunities to define an efficient multimedia streaming application, at
the same time it involves a set of technical challenges and issues due to the
best-effort service offered by the Internet and its dynamic and heterogeneous
nature. The most of existent protocols for video communications over P2P
mainly focus on tree topology maintenance, without paying any attention to
the encoding problem. The idea of this paper is to propose a multipoint video broadcast framework
over a heterogeneous content distribution P2P network. In the proposed system
the source generates the video flow by using an MPEG-4/FGS encoder, in such
a way that no losses occur at the Baselayer stream even in the presence of
short-term bandwidth fluctuations. Although in the past the FGS was not
employed due to its encoding complexity, today, thanks to advances in hardware
technology, we were able to develop an MPEG-4/FGS encoder on low-cost PCs
which turned out to be more feasible and appealing for its flexibility.
The FGS layer is sent together with the Base layer, but with a lower priority.
The source uses a rate controller to regulate the encoding rate of the
Base layer. To this aim, a protocol is defined in order to provide the source
with information related to the most stringent bottleneck link on the overlay
network. A technique to reorganize the content distribution tree is proposed
and discussed. To evaluate the performance of the proposed framework a case
study is introduced; improvements obtained with respect to several reference
cases where FGS is not applied are also shown.

Alfio Lombardo

Diego Reforgiato

Giovanni Schembra

P2P and MPEG FGS Encoding: A Good Recipe for Multipoint Video Transmission on the Internet

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International Journal of Digital Multimedia Broadcasting provides a forum for engineers and researchers whose interests are in digital multimedia broadcasting to share recent developments and challenges in order to design new and improved systems.

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