Patent ID: 7808932

Claim:
An audio/video network, comprising: a packet-switched network over which data including audio and/or video data packets can be carried; a plurality of data sources connected to the packet-switched network and configured to assemble packetised data comprising audio/video data at a first resolution and at a second resolution greater than the first resolution, and configured to transmit data packets carrying one or more audio/video streams at the first resolution by multicast network transmission to a first multicast group, and to transmit data packets carrying one or more audio/video streams at the second resolution by multicast network transmission to a second multicast group different from the first multicast group; a client connected to the packet-switched network and configured to receive packetised audio/video data and to join the first multicast group to receive the one or more audio/video streams at the first resolution; means for selecting an audio/video stream and for issuing a unicast command to the client to cause the client to receive the one or more audio/video streams at the second resolution by joining the second multicast group in response to the unicast command from the means for selecting and issuing; a packet-based network switch; and a network control arrangement coupled to the network switch, the network control arrangement being arranged to provide virtual circuit-switched connections for transfer of packetised data from a source to the client via the network switch by: assigning multicast group identifier to sources, so that a source launches packetised data onto the packet-switched network as multicast data packets identified by a multicast group identifier, and instructing a client to issue a request to the network switch to join the multicast group of a source so as to receive data packets from that source, wherein the network control arrangement comprises the means for selecting and issuing.