A generic multilevel quality-of-service (QoS) model for distributed multimedia applications is presented. QoS mapping mechanisms are required to translate the QoS parameters among the hierarchical levels. One QoS mapping mechanism based on the spline functions is proposed, hence two splines are compared. One is natural splines and the other is B-splines. QoS measurement experiments were conducted, and it is found that the B-splines give more accurate mapping results than the natural splines once the knots for the splines are selected appropriately.

This paper proposes a media synchronization scheme with causality control for distributed multimedia applications in which the temporal and causal relationships exist among media streams such as computer data, voice, and video. In the scheme, the Δ-causality control is performed for causality, and the Virtual-Time Rendering (VTR) algorithm, which the authors previously proposed, is used for media synchronization. The paper deals with a networked shooting game as an example of such applications and demonstrates the effectiveness of the scheme by experiment.

For distributed multimedia applications, the development of adaptive QoS (quality of service) management mechanisms is needed to guarantee various and changeable end-to-end QoS requirements. In this paper, we propose an adaptive QoS management framework based on multi-agent systems. In this framework, QoS management mechanisms are divided into two phases, the flow establishment and renegotiation phase and the media-transfer phase. An adaptation to system resource changes and various user requirements is accomplished by direct or indirect collaborations of the agents in each phase. In the flow establishment and renegotiation phase, application agents determine optimal resource allocation with QoS negotiations to maximize the total users' utility. In the media-transfer phase, stream agents collaborate to adjust each stream QoS reactively. In addition, personal agents help a novice user to specify stream QoS without any a priori knowledge of QoS. To make the interworking of agents tractable, a QoS mapping mechanism is needed to translate the QoS parameters from level to level, since the expression of QoS differs from level to level. As an example of multimedia application based on the proposed framework, a one-way video system is designed. The experimental results of computer simulation show the validity of the proposed framework.

Distributed multimedia applications are often sensitive to the Quality of Service (QoS) provided by the communication network. They usually require guaranteed QoS service, so that real-time communication is possible. However, searching a route with multiple QoS constraints is known to be a NP-complete problem. In this paper, we propose a new simple and efficient distributed QoS routing algorithm, called "DQoSR," for supporting real-time communication in high-speed networks. It searches a route that could guarantee bandwidth, delay, and delay jitter requirements. Routing decision is based only on the modified cost, hop and delay vectors stored in the routing table at each node and its directly connected neighbors. Moreover, DQoSR is proved to construct loop-free routes. Its worst case message complexity is O(|V|2), where |V| is the number of nodes in the network. Thus DQoSR is fast and scales well to large networks. Finally, extensive simulations show that average rate of establishing successful connection of DQoSR is very near to optimum (the difference is less than 0.4%).