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.

This paper presents a content prioritization technique for perceptually enhanced communication of 3D video data over wireless Local Area Network. The prioritisation is performed on the basis of a novel segmentation technique, which utilizes the depth information of 3D content for separating individual objects of the sequence. These objects are then encoded and transmitted separately under different protection levels depending on their perceived importance for perceptual visual quality. The algorithm performance is demonstrated for object based MPEG-4 video transmission over home network and is compared with a basic prioritisation scheme based on splitting a sequence into even and odd frames and encoding them separately with equivalent prioritization as in the proposed scheme. The results demonstrate significant improvement in subjective quality with the proposed scheme.

This paper presents a novel adaptation technique for optimisation of the source and error protection rates in response to varying channel conditions in wireless networks. The optimisation methodology is based on accurate modelling of video frame distortion at the encoder. An optimal value for the quantisation parameter is calculated for video frames based on these estimates, and then video packets are mapped to one of a number of different priority radio bearers, according to their expected distortion. The algorithm performance is demonstrated for object based MPEG-4 video transmission over a UMTS/FDD system. The results demonstrate that a significant performance gain is achieved with the proposed scheme, compared with the equal error protection scheme for video transmission over a fixed bandwidth channel.

Abstract-This paper introduces the virtual collaboration environment and discusses the problems encountered in wireless video transmissions of the participating users. Different schemes are proposed and evaluated to address various problems encountered in the wireless access links of the virtual collaboration system for enhancing the perceived visual quality. The schemes include radio network resource optimization, optimal joint source and channel rate allocation and error resilience enhancement using SVC-MDC. These schemes have been shown to offer a strong potential to be incorporated in a virtual collaboration system for quality enhancement.

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