This paper proposes a framework for a virtual classroom application based on a Virtual Collaboration System (VCS), which is being developed under the VISNET II Network of Excellence (NoE) 1 , and discusses adaptation technologies that enable seamless access to classroom sessions while intellectual property and digital rights are managed. The proposed virtual classroom framework enables academic institutions to conduct their collaborative lecture series, to which registered students will be able to attend remotely and interactively over the Internet. Furthermore, the general public may also follow the classroom sessions under certain restrictions imposed by the participating institutions. In order to facilitate seamless access to a heterogeneous audience that is composed of users with various preferences and privileges accessing the classroom sessions over different network infrastructures and using terminal devices with diverse capabilities, context-aware content adaptation is required to meet constraints imposed by the usage context and enhance the quality of the user experience. Thus, this paper describes the concepts and functionalities of a context-aware content adaptation platform that suits the requirements of such multimedia application scenarios. This platform is able to consume low-level contextual information to infer higher-level contexts, and thus decide the need for and type of adaptation operations to be performed upon the content. In this way, it is aimed to meet usage constraints while also satisfying restrictions imposed by the Digital Rights Management (DRM) to govern the use of protected content.

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Abstract-Virtual collaboration concept allows remotely located partners to meet in a virtual environment using the state of the art communication and digital multimedia technologies. A virtual collaboration system is being developed under VISNET II Network of Excellence of the IST FP6 programme. This paper elaborates on a virtual collaboration scenario and proposes content adaptation technologies to fulfil needs of all participants. The proposed content adaptation techniques are based on scalable video coding. The content adaptation based on user preferences, profiles for usage, terminal and network capabilities are discussed. Initial experimental results have been proved to be effective and productive for a virtual office environment.

Applications such as transaction authentication may require speaker recognition systems to operate on compressed speech transmitted over mobile phone networks. However, speech compression degrades speech quality, and hence causes a reduction in recognition performance. It has been shown that the classic technique for extraction of Line Spectral Frequency (LSF) parameters in speech coders is prone to aliasing distortion. The use of a low-pass filtering on upsampled LSF vectors has been shown to alleviate this problem, therefore improving speech quality. In this paper, the effect of this Non-Aliased LSF (NA-LSF) extraction method on speaker recognition performance is observed using GSM-EFR coded speech. When the NA-LSFs are used in the coder the verification performance loss introduced by the GSM-EFR is reduced, producing similar performance to uncoded speech.