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

In the last years Peer-to-Peer (P2P) systems have gained ground for contentsharing between communities, determining a real revolution on the Internet.The characteristics of P2P systems make them a very good choice for multimediacontent distribution over IP networks. However, although P2P technology givesnew opportunities to define an efficient multimedia streaming application, atthe same time it involves a set of technical challenges and issues due to thebest-effort service offered by the Internet and its dynamic and heterogeneousnature. The most of existent protocols for video communications over P2Pmainly focus on tree topology maintenance, without paying any attention tothe encoding problem. The idea of this paper is to propose a multipoint video broadcast frameworkover a heterogeneous content distribution P2P network. In the proposed systemthe source generates the video flow by using an MPEG-4/FGS encoder, in sucha way that no losses occur at the Baselayer stream even in the presence ofshort-term bandwidth fluctuations. Although in the past the FGS was notemployed due to its encoding complexity, today, thanks to advances in hardwaretechnology, we were able to develop an MPEG-4/FGS encoder on low-cost PCswhich 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 theBase layer. To this aim, a protocol is defined in order to provide the sourcewith information related to the most stringent bottleneck link on the overlaynetwork. A technique to reorganize the content distribution tree is proposedand discussed. To evaluate the performance of the proposed framework a casestudy is introduced; improvements obtained with respect to several referencecases where FGS is not applied are also shown