FLV Actionscript playback from non-HTTP source

Question

I'm almost a total noob to Actionscript and FLV, but have been reading up on the documentation.

I'm under the impression that NetStream reads the data from the server, caches it locally, and then plays it while continuing to append to the local file as it reads more data from the network. Is that correct?

If so, is it possible to download the FLV file manually (say, from an FTP, rather than a URLObject/web server) but still hook the incoming data up to the NetStream and get the same behavior as progressive download from a web sever/HTTP?

Or would I basically need to write my own version of a NetStream-like object?