This summer my organization put in what is probably the first G4/500 video editing station at my University; iMovie and Final Cut Pro. We needed to import and export to all major standards. That included Firewire, s-video and composite video/audio (RCA). Your only good, complete solution is to purchase a Sony DVMCA unit. It is a little box that has composite video/audio and s-video inputs and outputs with one firewire port. It allows for analog in and out and has worked flawlessley for us with both iMovie and Final Cut Pro. It was recommended to us by our Apple rep.
It will run you about $400, but is the best solution.
Also, Formac is making the same basic box with what appears to be the same basic connections for about the same price. The Formac device is already for sale in the most recent MacMall and Club Mac catalogs. The key here is that both the Sony device and the Formac device both have hardware CODEC. Meaning that it has digital/analog conversion through a processor in the box.
A good video editor should not be without this box.
[This message has been edited by jeromep (edited 01-11-2001).]