1,720,961 research outputs found
OpenSatRelaying: a hybrid approach to real-time audio-video distribution over the Internet
No full textIn spite of massive research efforts devoted to the advance of the technologies for large-scale live distribution of audio-video IP streams, no totally satisfying solutions seem to have emerged so far. CDNs are still expensive and P2P-TV systems face substantial delay limitations. As the deployment of a global terrestrial IP multicast infrastructure still looks far, turning the attention to satellite-based multicast would seem a sensible choice. However, the cost of such technology has been a stumbling block until now. That is where the CHARMS architecture comes in. It is designed to take advantage of the formidable properties of the satellite without requiring a generic user to install any sort of satellite receiver or dish. Its cornerstone is the recursive terrestrial relaying of satellite streams a number of properly equipped hosts are able to receive. The present paper relates about the results of the OpenSatRelaying project, aimed at the implementation and testing of the CHARMS architecture
A Library for RTP Relaying and QoS Monitoring in Application Layer Multicast
No full textNative IP multicast would be the best solution to distribute live streaming contents among various destinations since the real-time nature of such applications usually imposes strict delay constraints. Application Layer Multicast (ALM) platforms are emerging as a solution to overcome the well- known lack of a globally supported native multicast. Since the development of ALM applications is slowed by complexity and portability issues, we designed an open source C library framework that takes care of RTP/RTCP technical details and fosters a modular and higher level design. Besides it frees ALM developers from spending time in porting operations from Unix to Windows operating systems
Large-Scale Terrestrial Relaying of Satellite Broadcasted Real-Time Multimedia Streams
No full textThe paper describes an architecture to relay on demand a real-time IP multicast audio-video stream broadcasted by a satellite on a terrestrial link. The stream is received by suitably equipped sites and then relayed to other sites that are not equipped with satellite receiving hardware but are nonetheless willing to receive the stream. By exploiting the properties of satellite transmission and adopting a hybrid satellite/terrestrial, multicast/unicast approach, the described architecture allows to overcome the restrictions suffered by multicast traffic in the global Internet, allowing it to scale easily across autonomous systems
CHARMS: Cooperative Hybrid Architecture for Relaying Multicast Satellite Streams to sites without a satellite receiver
No full textThe paper describes an architecture dedicated to the terrestrial relaying of a real-time IP multicast audio-video stream broadcasted by a satellite. Such relaying is performed by nodes equipped with both a satellite receiver and a terrestrial Internet link. The stream is requested and obtained by sites that are not equipped with satellite receiving hardware but are nonetheless willing to receive it. By exploiting the properties of satellite transmission and adopting an hybrid satellite/terrestrial, multicast/unicast approach the described architecture allows to overcome the restrictions suffered by multicast traffic in the global Internet, allowing it to scale easily across autonomous systems
Are P2P streaming systems ready for interactive e-learning?
No full textPeer-to-peer streaming is a well-known technology for the large-scale distribution of audio/video contents. Its widespread adoption derives from the possibility of having a good scalability without the need for the deployment of expensive infrastructures such as Content Delivery Networks (CDNs). We think real-time streaming of lessons could open new interesting opportunities in e-learning systems by encouraging interactivity between teachers and learners.
Delay requirements are very strict in interactive e-learning scenarios, where playback lag between the event in the real world and the received audio/video should not exceed a few seconds. Only a very short delay would allow students to ask questions during the lesson. At the same time, playback continuity is a key aspect too, since holes in the stream reproduction could seriously compromise the understanding of lectures. In this paper we compared some solutions that try to overcome the limitations of traditional mesh-based P2P systems, which are usually affected by long and unpredictable delays. We finally tried to outline which of the analyzed solutions appears the most suitable one to meet e-learning requirements
Towards a decentralized overlay for real-time live streaming: CHARMS meets the web
No full textIn recent years, the fifth revision of the HyperText Markup Language standard (HTML5) has promoted the porting of traditional desktop applications to the Web, thus allowing the rise of Rich Internet Applications (RIAs). Additionally, the progressive support to Web Real-Time Communication (WebRTC) standard in modern browsers for real-time communications is accelerating this process, enabling the migration of a number of complex network applications and services to Web, including peer-to-peer (P2P) overlays. At the same time, the increase of bandwidth in access networks enables end-users to become content producers too. Taking into consideration the aforementioned factors, this paper introduces a preliminary proposal of metrics and technologies to move towards a decentralized cooperative architecture for large scale, real-time live stream content delivery based on WebRTC, with no need of a Content Delivery Network (CDN) infrastructure. Such metrics and technologies are introduced to smooth the way for a transition in such direction of the already described and implemented CHARMS (Cooperative Hybrid Architecture for Relaying Multimedia Streams) architecture
Charms for e-learning: a case study
No full textIn this paper we describe the testing activities carried out to evaluate the benefits that the digital educational format implementation ILIADE (“Insegnare L’Informatica A Distanza Efficacemente”, Distance Teaching Computer Science Effectively) provides. The purpose of the ILIADE format is to enable the synchronous delivery of real-time lessons and multimedia contents - provided by one or more teachers - to a virtual classroom. The virtual classroom is the set consisting of both physical remote classrooms - hosting student groups – and individual stations (which are connected to individual students with their own computers). The setup of the virtual classroom allows the learning by doing approach to directly involve students: each student can intervene during the lesson, both dialoguing with the teacher and with his fellow students and share his/her experience with the rest of the class. The collaborative approach in the virtual classroom emphasizes the concepts expressed by the teacher, allowing the participants to improve the understanding and learning of the explained subjects. In ILIADE, multiple technologies are merged to enable real-time interaction between teacher and students, with the opportunity for participants to deal directly with the teacher, even in case of large-scale (large number of participants). This means that the virtual classroom is based on the distribution of audio-stream real-time video of the teacher station to learners, who can send questions to the same by means of a chat class (that is shared among all participants). In the ILIADE format, the subsystem CHARMS is responsible for the delivery of the A/V streamed lesson to all participants, organized into a cooperative overlay for the relaying purposes. This work is part of the project EDOC@ Work3.0
Study on Large-scale Terrestrial Relaying of Satellite Broadcasted Real-time Multimedia Streams
Full text linkThe chapter describes an architecture to relay on demand a real-time IP multicast audio-video stream broadcasted by a satellite on a terrestrial link. The stream is received by suitably equipped sites and then relayed to other sites that are not equipped with satellite receiving hardware but are nonetheless willing to receive the stream. By exploiting the properties of satellite transmission and adopting a hybrid satellite/terrestrial, multicast/unicast approach, the described architecture allows to overcome the restrictions suffered by multicast traffic in the global Internet, allowing it to scale easily across autonomous systems. All things considered, the proposed architecture outlines a large-scale interactive audio-video distribution system similar to those based on Content Distribution Networks (CDNs) and it compares favourably with them when performances, costs and scalability are examined
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