Forward Error Correction for Multipath Media Streaming

We address the problem of joint optimal rate allocation and scheduling between media source rate and error protection rate in scalable streaming applications over lossy multipath networks. Starting from a distortion representation of the received media information at the client, we propose a novel optimization framework in which we analyze the performance of the most relevant forward error correction and scheduling techniques. We describe both optimal and heuristic algorithms that find solutions to the rate allocation and scheduling problem, and emphasize the main characteristics of the compared techniques. Our results show that efficient unequal error protection schemes improve the quality of the streaming process. At the same time we emphasize the importance of priority scheduling of the information over the best available network paths, which outperforms traditional first-in-first-out models or network flooding mechanisms

Interactivity And User-heterogeneity In On Demand Broadcast Video

Video-On-Demand (VOD) has appeared as an important technology for many multimedia applications such as news on demand, digital libraries, home entertainment, and distance learning. In its simplest form, delivery of a video stream requires a dedicated channel for each video session. This scheme is very expensive and non-scalable. To preserve server bandwidth, many users can share a channel using multicast. Two types of multicast have been considered. In a non-periodic multicast setting, users make video requests to the server; and it serves them according to some scheduling policy. In a periodic broadcast environment, the server does not wait for service requests. It broadcasts a video cyclically, e.g., a new stream of the same video is started every t seconds. Although, this type of approach does not guarantee true VOD, the worst service latency experienced by any client is less than t seconds. A distinct advantage of this approach is that it can serve a very large community of users using minimal server bandwidth. In VOD System it is desirable to provide the user with the video-cassette-recorder-like (VCR) capabilities such as fast-forwarding a video or jumping to a specific frame. This issue in the broadcast framework is addressed, where each video and its interactive version are broadcast repeatedly on the network. Existing techniques rely on data prefetching as the mechanism to provide this functionality. This approach provides limited usability since the prefetching rate cannot keep up with typical fast-forward speeds. In the same environment, end users might have access to different bandwidth capabilities at different times. Current periodic broadcast schemes, do not take advantage of high-bandwidth capabilities, nor do they adapt to the low-bandwidth limitation of the receivers. A heterogeneous technique is presented that can adapt to a range of receiving bandwidth capability. Given a server bandwidth and a range of different client bandwidths, users employing the proposed technique will choose either to use their full reception bandwidth capability and therefore accessing the video at a very short time, or using part or enough reception bandwidth at the expense of a longer access latency

Gesellschafts-Spiel Karte

Neben der fest verfassten und auf eine Tradition fundierter Erkenntnisse zurückblickenden wissenschaftlichen und der im Streben nach höchster Qualität diese normativen Resultate befolgenden angewandten Kartographie entsteht in den letzten Jahren eine weitere Gruppe kartographischer Akteure: Sowohl in der Wissenschaft als auch in der Praxis bearbeiten Menschen kartographische Themen, ohne sich in der Tradition einer Kartographie zu sehen, und oft ohne fundamentale kartographische Forschungsergebnisse zu berücksichtigen. Besonders die sehr stark technologie-getriebenen Web-Kartographien – sie zeichnen sich zusätzlich durch die hohe Zahl an beteiligten Akteuren aus – stehen im Zentrum eines handlungstheoretischen Zugangs, der untersucht, inwiefern die Diskurse in diesen »impliziten« Kartographien von denen einer traditionellen Kartenerstellung abweichen. Dies wird sowohl als Anstoß zur Diskussion über die Qualität solcher Kartierungen und allfällige weitere Forschung (auch des Autos selbst) betrachtet, als auch als Basis für eine Annäherung an diese neuen Kartographie mit ihren technologisch fortgeschrittenen Entwicklungen.Cartography has been an accepted branch of science as well as arts and a well-established profession for a number of decades. It builds upon funded results of elaborate research on a wide variety of aspects of maps. The applied cartography readily employs those findings in a permanent quest for a ever-higher quality of maps. In the last years there has developed another group of actors in the field of cartography: Both in academic and in applied fields, cartographic topics are being worked upon by people who don’t see themselves connected to Cartography, and who more often than not ignore fundamental findings of cartographic research. It is especially the technology-driven web-cartographies – also featuring a distinctly large number of participating actors – which are in the focus of this agency-centered approach to find the differences in the discourses of those “implicit” and traditional cartographies. The findings shall function as a discussion starting point on further studies on the characteristics of such cartographies, expect to read more from this author. Finally it can also be seen as a basis for bringing together the advantages of this new cartographies and their advanced technologies with the quality-assuring findings of a traditional Cartography