A method of demultiplexing an enhanced video stream conveying, in a plurality of packetised elementary streams of an MPEG-2 systems layer, base layer video VCL access units and enhancement layer Video Coding Layer and non-VCL access units, each access unit comprising a plurality of syntax structures, said method comprising: receiving a multiplexed transport stream in the MPEG-2 systems layer, the transport stream conveying, with different respective program identifiers, a base layer transport stream comprising both the syntax structures of the base layer VCL access units and the enhancement layer non-VCL units, and an enhancement layer transport stream containing the syntax structures of said enhancement layer VCL units, demultiplexing the transport stream using the respective program identifiers to separate the base layer transport stream from the enhancement layer transport stream, passing the syntax structures of the base layer transport stream to a base layer buffer, where the syntax structures include the non-VCL syntax structures of the enhancement layer, passing syntax structures of the enhancement layer transport stream to an enhancement layer buffer, where the syntax structures include all of the syntax structures of the VCL enhancement layer access units and none of the syntax structures of the non-VCL enhancement layer access units, outputting the syntax structures passed to the base layer buffer in a predetermined sequence, outputting the syntax structures passed to the enhancement layer buffer in a predetermined sequence, and recombining the sequences of syntax structures output by the base layer buffer and the enhancement layer buffer respectively to form a complete enhanced access unit, comprising base layer syntax structures of the MPEG-2 systems layer and enhancement layer syntax structures of the MPEG-2 systems layer in a predetermined sequence. receiving a multiplexed transport stream in the MPEG-2 systems layer, the transport stream conveying, with different respective program identifiers, a base layer transport stream comprising both the syntax structures of the base layer VCL access units and the enhancement layer non-VCL units, and an enhancement layer transport stream containing the syntax structures of said enhancement layer VCL units, demultiplexing the transport stream using the respective program identifiers to separate the base layer transport stream from the enhancement layer transport stream, passing the syntax structures of the base layer transport stream to a base layer buffer, where the syntax structures include the non-VCL syntax structures of the enhancement layer, passing syntax structures of the enhancement layer transport stream to an enhancement layer buffer, where the syntax structures include all of the syntax structures of the VCL enhancement layer access units and none of the syntax structures of the non-VCL enhancement layer access units, outputting the syntax structures passed to the base layer buffer in a predetermined sequence, outputting the syntax structures passed to the enhancement layer buffer in a predetermined sequence, and recombining the sequences of syntax structures output by the base layer buffer and the enhancement layer buffer respectively to form a complete enhanced access unit, comprising base layer syntax structures of the MPEG-2 systems layer and enhancement layer syntax structures of the MPEG-2 systems layer in a predetermined sequence.