This paper presents design, analysis, and implementation of a multiresource management system that enables criticality- and QoS-based resource negotiation and adaptation for mission-critical multimedia applications. With the goal of maximizing the number of high-criticality multimedia streams and the degree of their QoS, it introduces a dynamic scheduling approach using on-line QoS adjustment and multiresource preemption. An integrated multiresource management infrastructure and a set of scheduling algorithms for multiresource preemption and on-line QoS adjustment are presented. The optimality and execution efficiency of two preemption algorithms are analyzed. A primal-dual-algorithm-based approximation solution is shown (1) to be comparable to the linear-programming-based solution, which is near optimal; (2) to outperform a criticality-cognitive baseline algorithm; and (3) to be feasible for on-line scheduling. In addition, the dynamic QoS adjustment scheme is shown to greatly improve the quality of service for video streams. The multiresource management system is part of the Presto multimedia system environment prototyped at Honeywell for mission-critical applications.