László Böszörményi

A survey of Web cache replacement strategies

Web caching is an important technique to scale the Internet. One important performance factor of Web caches is the replacement strategy. Due to specific characteristics of the World Wide Web, there exist a huge number of proposals for cache replacement. This article proposes a classification for these proposals that subsumes prior classifications. Using this classification, different proposals and their advantages and disadvantages are described. Furthermore, the article discusses the importance of cache replacement strategies in modern proxy caches and outlines potential future research topics.

The life cycle of multimedia metadata

During its lifetime, multimedia content undergoes different stages or cycles from production to consumption. Content is created, processed or modified in a postproduction stage, delivered to users, and finally, consumed. Metadata, or descriptive data about the multimedia content, pass through similar stages but with different time lines. Metadata may be produced, modified, and consumed by all actors involved in the content production-consumption chain. At each step of the chain, different kinds of metadata may be produced by highly different methods and of substantially different semantic value. Different metadata let us tie the different multimedia processes in a life cycle together. However, to employ these metadata, they must be appropriately generated. The CODAC Project, led by Harald Kosch, implements different multimedia processes and ties them together in the life cycle. CODAC uses distributed systems to implement multimedia processes. The projects core component is a multimedia database management system (MMDBMS) which stores content and MPEG-7-based metadata. It communicates with a streaming server for data delivery. The database is realized in the multimedia data cartridge (MDC) - which is an extension of the Oracle database management system - to handle multimedia content and MPEG-7 metadata.

VIDEX : an integrated generic video indexing approach

This paper presents an integrated generic technique for low-and high-level video indexing. The proposed approach tries to integrate the advantages of existing low- and high-level video indexing approaches by reducing their shortcomings. Furthermore, the model introduces concepts for a detailed structuring of video streams, and for correlations of low-and high-level video objects. The proposed model is called generic, as it only defines a framework of classes for an implementating a prototype of a distibuted multimedia information system supporting content-based video retrieval.

Metadata driven adaptation in the ADMITS project

Abstract The ADMITS project (Adaptation in Distributed Multimedia IT Systems) is building an experimental distributed multimedia system for investigations into adaptation, which we consider an increasingly important tool for multimedia systems. A number of possible adaptation entities (server, proxy, clients, routers) are being explored, different algorithms for media, component and application-level adaptations are being implemented and evaluated, and experimental data are being derived to gain insight into when, where and how to adapt, and how individual, distributed adaptation steps interoperate and interact with each other. In this paper the “adaptation-chain” of (MPEG-conforming) metadata based adaptation is described: from the creation stage at the server side, through its usage in the network (actually in a proxy), up to the consumption at the client. The metadata are used to steer the adaptation processes. MPEG-conformant metadata, the so-called variation descriptions, are introduced; an example of a complete MPEG-7 document describing temporal scaling of an MPEG-4 video is given. The meta-database designed to store the metadata is briefly discussed. We describe how the metadata can be extracted from MPEG-4 visual elementary streams and initial results from a temporal video scaling experiment are given. We further present how the metadata can be utilized by enhanced cache replacement algorithms in a proxy server in order to realize quality-based caching; experimental results using these algorithms are also given. Finally, an adaptive query and presentation interface to the meta- and media database is outlined.

Replacement strategies for quality based video caching

Video caching will be an important performance factor in future networked multimedia systems. A major component of caches is the replacement strategy. This paper presents replacement strategies for video caches that incorporate quality reduction and the use of metadata given by the content provider. The strategies are evaluated by simulation.

An evaluation of parallelization concepts for baseline-profile compliant H.264/AVC decoders

Due to the increasing performance requirements of decoding H.264/AVC in HDTV or larger resolutions, new approaches are necessary to enable real-time processing. According to the current trend to parallel computation in all performance classes, decoding of AVC must be mapped to these architectures even though this is complicated by the increased complexity and many data dependencies in the codec. We propose and evaluate different ways of using multithreading to speed-up our .NET implemented decoder. While slice based approaches scale best, this is not a flexible approach because of the reliance on specially encoded streams. Functional partitioning and macroblock pipelining prove to be a good alternative for almost all evaluated videos.

Why Java is notmy favorite first-course language

The choice of the first-course programming language for a university-level computer science curriculum has pedagogical ramifications in terms of comprehensibility and mastery of fundamental concepts. This paper compares the merits of Java and Modula-3 as a firstcourse language.

Content-Based Indexing and Retrieval Supported by Mobile Agent Technology

In this paper we present the MultiMedia Database Mobile agent technology (M3) which supports personalized content-retrieval and indexing in a distributed Oracle 8i DB. We implemented an agency on top of the Oracle 8i JServer and realized mobility with the embedded Visbroker Corba ORB. A performance comparison of our mobile agent technology with a client-server solution for a nearest-neighbor search in an image database shows the efficiency of the proposed solution.

Comprehensive treatment of adaptation in distributed multimedia systems in the ADMITS project

Adaptation is becoming an increasingly important tool for re-source and media management in distributed multimedia systems. Best-effort scheduling and worst-case reservation of resources are two extreme cases, none of them well suited to cope with large-scale, dynamic multimedia systems. The middle course can be met by a system which dynamically adapts its data, resource re-quirements, and processing components to achieve user satisfac-tion. Nevertheless, there is no agreement about the questions, where, when, what and who should adapt. A number of papers have been published in recent years, where adaptation is a central issue, however, in most different interpretations and generally in a somehow limited scope; e.g.,[1, 2, 8, 9, 10, 12]. A distributed multimedia system comprises several types of com-ponents, such as media servers, meta-databases, proxies, routers, clients. Also, a large number of adaptation possibilities exist, from simple frame dropping up to virtual server systems which dynamically allocate new resources on demand. The main ques-tion is, which kind of component can be best used for what kind of adaptation. In the

Teaching: people to people - about people a plea for the historic and human view

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.