IF you do not have the source file on your server?
For example, I have been to movie review websites and they have an embedded Flash video which plays something from the movie. I am not sure if the src files were sent to the web developers or if there is an actionscript code that allows instantaneous playback from your server to the server that houses the Flash video.
Because right now I have several Flash videos on my page and it opens up a new window to the actual Youtube page. I don’t really want that! :0