If it helps...

Haven't done this, and am not really looking at it for the future, but anything web media is of interest so I tend to read anything I come across even remotely related. With that as a disclaimer, going from memory & trying to point out a few directions for research...

I *think* the Osprey cards are the most often used for real time capture and compression to streaming codec. Bruce Johnson I think had one or two reviews of equipment he tried out with a pbc station -> they appeared a *while* ago in DV (DV.com), and if I recall they were smallish boxes for handling multiple streams, allowing some editing, and real time capture/compression to streaming codecs.

I also recall seeing something about the operation behind the video broadcasts on Yahoo, where they did something similar, and might want to check out the company and their methods that does the video displays for individual seats I think in NYC and Hockey on the east coast - think they used some real-time automation stuff.

I think that the winmedia encoder 9 from MS has the capability to enter script &/or marker points during real time encoding, which might work to record edit points for later editing. And while not implemented in their free encoder, wmv9 allows editing without re-rendering/re-encoding if the file compression parameters remain constant. There might be some custom apps out there, or I imagine wouldn't be that difficult to have one written based on the winmedia sdk.

luck
mike