In this paper, we present a novel reliable MPEG-4 based packetisation scheme over UMTS (universal mobile telecommunications service) networks. Using this scheme, some lost crucial RTP packets can be delivered within a multiplex RTP packet. With the feedback of RTCP control packets, this paper presents a decision-making procedure by which we can calculate the number of the redundant packets in a multiplex packet during a RTCP interval, i.e., this procedure can precisely reflect current network congestion state dynamically. To support the proposed procedure, two conditions must be satisfied. The first one is the RTP packets loss constraint and the second one is the RTP packets delay limitation. Moreover, through investigating related RTP payload formats and FGS (fine granularity scalability) framework, we can deliver BL (MPEG-4 basic layer) data by the proposed scheme. EL (MPEG-4 enhancement layer) data will be delivered as the best-effort traffic. Finally, simulations over UMTS networks demonstrate the validity of this scheme. Further comparison between this scheme and the traditional schemes also is done. The results show that our scheme improves QoS of services significantly.