multiresolution video

[grobelny]

Is it possible to divide a video stream into two streams: basic and extending? By "basic" I mean a video stream that has lower quality than the original (and so requires less bandwidth) and can be used on its own. By "extending" I mean a stream that provides more details to the "basic" stream, but can only be used with the "basic" stream. The idea is to send only "basic" stream when the network is congested and "basic+extending" streams when network conditions allow. If it's not possible as a end user functionality I would be interested if such a mpeg transport stream can be generated by VLC using any codec. Thanks in advance for any answers,