Convergence of the emerging IP Multimedia Subsystem (IMS) includes unlicensed, nondedicated and nondetemzinistic, hence uncontrollable computer access networks for IP multimedia services. It enables provision of resource demanding real-time sewices and multimedia communication raising new end-to-end Quality-of-Sewice (QoS) challenges, for which quality adaptation using resource management is proposed as a solution in this paper: This is an integrated solution taking both IMS and computer access networks into account as well as the two end-devices and the application sewers (AS) involved in communication. The best user experience is targeted under real-time variation of available network (e.g. bandwidth, buffer space) and end-device (e.g. battery, CPU, memory, storage) resources throughout a session. The multimedia content is dynamically adapted to$t the resource availability variations, achieving maximum system (i.e. network and end-devices) resource utilization and enhanced QoS. The resource availability update signalling is carried over Session Initiation Protocol (SIP) during the session. This is work in progress.