Abstract: We present a possibility how to add proactive behaviour to Video-on-Demand systems. To do so we propose categorizing videos and using external information as well as observing the behaviour of our clients. We examined 23 predictor functions on artificial and real datasets using different similarity measures to compare them. Our model is quite simple; therefore some extensions are proposed at the end.

Abstract: Universal Multimedia Access (UMA) has become a driving concept behind a significant amount of research activities. One of MPEG’s (Moving Pictures Experts Group) responses to UMA is MPEG-21 Digital Item Adaptation (DIA). In this paper we present how tools as specified within DIA (i.e., normative XML-based description formats) are applied in streaming and constrained environments enabling piece-wise multimedia content adaptation including the adaptation decision-taking process and the actual resource adaptation in a coding format-independent way. Additionally, we demonstrate how the metadata overhead imposed by DIA tools can be reduced by means of appropriate metadata encoding tools.

Abstract: The diversity of end-terminal and access network capabilities as well as the dynamic nature of wireless connections pose significant challenges to providers of multimedia streaming services. In this paper, we present a system based on MPEG-21 Digital Item Adaptation (DIA) technologies that automatically adapts scalable multimedia resources, like upcoming MPEG-21 Scalable Video Coding (SVC) streams, in a generic and transparent way to the user and session context. This context includes terminal and network capabilities as well as user characteristics. A server side adaptation engine reacts to context changes by dynamic decision taking and accordingly modified bitstream adaptation. Furthermore, novel concepts are presented that facilitate multimedia adaptation in a distributed fashion along the delivery path.

Abstract: The precision of the predictors used in the ADMS[1] can be determined by similarity. There are already such measures[2] given, but we do not know exactly what efficiency they have and how well they show the difference between two lists. Kendall’s tau • Spearman’s footrule • Ulam’s distance We examined the characteristics of these similarity measures and developed some more measures that fit better our needs. One of the main goals is to consider the similarity more important at the begin of list, than at the end of list. Because the clients at the begin of the list probably will request more videos. During our work we defined 20 special ordered lists with 17 elements each. We tested the different measures on these lists. We also tested the Kemeny distance, which was defined in paper[3]. We modified the Spearman’s footrule and the Ulam’s distance according to the goal defined above (the top of the list considerate with higher weight (Weighted Spearman’s footrule, Weighted Ulam’s distance). Using the already known measures we developed a more complex, mixed measure, which uses more factors when defining the similarity. Finally we compared the 7 different measures using the artificially defined lists. With using the similarity measures we can tell how good the predictors[2] work in ADMS project. We could order the predictors by goodness, testing them on a real database (the World Cup ’98 Website’s access log).

Abstract: The seamless access to rich multimedia content on any device and over an network, usually known as Universal Multimedia Access, requires interoperable description tools and adaptation techniques to be developed. To address the latter issue, MPEG-21 Digital Item Adaptation (DIA) introduces the Bitstream Syntax Description (BSD) framework, which provides tools for adapting multimedia content in a generic (i.e., coding format independent) way. The basic idea is to use the eXtensible Markup Language (XML) to describe the high-level structure of a binary media bitstream, to transform its description (e.g., by means of eXtensible Stylesheet Language Transformations, XSLT), and to construct the adapted media bitstream from the transformed description. This paper presents how this basic BSD framework, initially developed for non-streamed content and suffering from inherent limitations and high memory consumption of XML-related technologies such as XSLT, can be advanced and efficiently implemented in a streaming environment and on resource-constrained devices. Two different attempts to solve the inherent problems are described. The first approach proposes an architecture based on the streamed processing of SAX (Simple Application Programming Interface for XML) events and adopts STX (Streaming Transformations for XML) as an alternative to XSLT, whereas the second approach breaks a BSD up into well-formed fragments called Process Units (PUs) that can be processed individually by a standard XSLT processor. The current status of our work as well as directions for future research are given.

Abstract: In multimedia applications, XML is being increasingly used to represent metadata; examples are MPEG-7 multimedia description schemes and MPEG-21 usage environment descriptions. As with the media data, the size of, or the overhead induced by, the XML metadata is important, particularly when used on constrained mobile devices. Therefore, compression (binary encoding) of the XML data becomes relevant to reduce this overhead. Within the MPEG-7 standardization effort, a Binary Format for Metadata (BiM) was developed, ´providing good compression efficiency and facilitating random access into, and manipulation of, the binary encoded bit stream. However, using binary encoded XML should not introduce interoperability issues with existing applications, nor add additional complexity to new applications. In this paper we investigate a solution for this issue by handling the binary encoded XML data by the XML parser. As such, applications do not need to be aware of the type of encoding of the XML data. In this paper, we introduce such an XML parser and evaluate its usability in different scenarios. We measure the memory requirements and compare the processing speed of parsing binary encoded XML to plain text XML.

Abstract: Proxy-cache deployment in the LANs has become a current practice aimed at increasing the availability of the data while also reducing client perceived latency, reduce the load on origin servers as well as the external network bandwidth consumption. As the load increases, due to an increase in client’s requests for both cached and non-cached data, it often happens that one single proxy-cache can not handle all the incoming requests. For those situations, when request dropping and cache replacement becomes necessary, we propose an alternative, namely proxy-cache splitting. Our solution is to dynamically deploy additional proxy-caches inside the LAN, and divert towards them some of the requests addressed to the original proxy-cache(s). By doing this we can achieve even better response time, load balancing, higher availability and robustness of the service than in the case in which a single proxy-cache is used.

Abstract: The importance of the historical and human aspects of the didactics of informatics is discussed. The threefold human aspects of teaching: by, for and about people is explored. Using the example of the notion of the procedure, the potential of the historical discussion is investigated. A strengthening of the historical and human view is required both in university research and in the curricula of the informatics education at both secondary and university levels.