Recently, some push-pull scheduling strategies have been proposed to replace the pull mechanism in mesh based P2P streaming systems. A push-pull mechanism is more efficient in terms of the overheads and leads to a much better playback delay performance since the pull part is mainly used either at startup or to recover lost content. In this work we combine the low scheduling delays of push scheduling with the resiliency and multi-parent ability of mesh overlays. We propose a pure push scheduling strategy, PurePush, where we replace the pull mechanism by a probabilistic push: Parents of a node push a packet with a relaying probability in order to reduce redundancy. Through simulations, we show that PurePush outperforms, with respect to playback delays, a typical push-pull strategy in the realistic situation where we consider packet loss.

Several recent P2P streaming systems have adopted mesh overlays to disseminate content to participating peers because this topology appears to be more resilient to churns. To cope with inferred problems, such as data redundancy, these systems opt for data-driven content retrieval mechanisms (pull mechanisms). Each node has a list of neighbors with whom it periodically exchanges buffer information and requests content fragments. One of the drawbacks of such a mechanism is that it does not offer intelligent selection of sending neighbors based on their characteristics. This is mainly because the most important criteria used to select nodes is the content availability. This can result in some performance degradation, for instance, due to peers that are sending very small or big parts of the needed data. Resiliency may then be weakened and overhead increased. In this paper we propose to study how the integration of some end nodes characteristics can improve the performance of a typical pull mechanism with random scheduling. We show that the improvement in performance is significant enough despite the fact that the room for improvement is bounded by the limitations of the pull mechanism. Hence we believe that the awareness of end characteristics is an important block upon which we can build more efficient content retrieval mechanisms. The gain in performance can also be amplified by proposing an alternative to the pull mechanism such as a combined pull-push approach.

Recently, some push-pull scheduling strategies have been proposed to replace the classical pull mechanism in mesh based P2P streaming systems. A push-pull mechanism is more efficient in terms of the overheads and leads to much better playback delay performance since the pull part is mainly used either at the beginning of the session or to recover lost content. Since a push-pull mechanism typically leads to low scheduling delays, the content delivery delay is impacted mostly by the overlay path length. New peering strategies are then needed to exploit such an advantage. In this paper, we propose two new peering strategies that we compare to a recent proposal of Ren et al. (2008). With resiliency in mind, the strategy variations being compared in this paper impose a fixed number of parents to each node. The two strategies that we propose lead to the lowest playback delays: They lead to overlays with short paths to the source.

Artists in new media arts explore the possibilities offered by digital technologies to create adaptive and interactive new media artworks integrating audio and video. In this paper, we are interested in adaptation mechanisms for such artworks and we focus on the design and implementation of adaptation scenarios. We formalize adaptation scenarios by using the event-condition-action paradigm and we introduce the concept of adaptation policy. We present the adaptation engine we have designed and prototyped to manage and execute adaptation scenarios

In this paper, we are interested in adaptation mechanisms for the design, creation and experimentation of adaptive and interactive new media artworks. Through a concrete case study, we propose an adaptation framework that combines semantic and physical adaptation and that can be specialized to the specific needs of various new media artists. This adaptation framework is supported by an adaptation engine, the kernel of the software architecture we are currently building. We have validated our adaptation framework through the implementation of a prototype of the adaptation engine. This prototype integrates the management of various types of metadata and allows a representation of adaptation scenarios as policies of the form event-condition-action. \nWe present how we used our adaptation engine to reconstruct and experiment the adaptation model of The Man of the Crowd, an existing adaptive new media installation, where the artist introduces a semantic adaptation of the video content displayed on four screens, according to the relative position of the viewer in the artistic installation.

In recent years, a lot of research effort has been dedicated to the management of quality of service (QoS), mainly in the fields of telecommunication networks and multimedia systems. Emerging applications such as electronic commerce, health-care applications, digital publishing or data mining also have requirements regarding the quality of service, the cost of service, the quality of data to be delivered, the accuracy and precision of the retrieved data. These examples show the need to consider the concept of QoS from a broader perspective, requiring the collaboration of all the distributed system components involved. In this paper, we propose an approach to integrate user-defined QoS requirements, together with the dynamic properties of the system components involved, into a distributed query processing environment. We then propose a query optimization strategy in which multiple goals may be considered with separate cost models. Furthermore, we discuss some experiment results confirming the effectiveness of our approach.

Most current approaches in designing and implementing distributed multimedia (MM) presentational applications have concentrated on the performance of the continuous media file servers in terms of seek-time overhead and real-time disk scheduling; particularly, the quality of service (QoS) negotiation mechanisms they provide are used in a rather static manner, i.e. these mechanisms are restricted to the evaluation of the capacity of certain system components. In contrast to those approaches, we propose a general QoS negotiation framework that supports the dynamic choice of a configuration of system components to support the QoS requirements of the user of a specific application: we consider different possible system configurations and select an optimal one to provide the appropriate QoS support. We document the design and implementation of a QoS negotiation procedure for distributed MM presentational applications, such as news-on-demand. The negotiation procedure described is an instantiation of the general framework for QoS negotiation. Our proposal differs in many respect with the negotiation functions provided by existing approaches: (1) the negotiation process uses an optimization approach to find a configuration of system components which supports the user requirements, (2) the negotiation process supports the negotiation of a MM document and not only a single monomedia object, (3) the QoS negotiation takes into account the cost to the user; (4) the negotiation process may be used to support automatic adaptation to react to QoS degradations, without intervention by the user/application.