This is kind of a worn out question, but is an interesting discussion.
The simple answer is that one can not save a RTSP QuickTime Stream. The only way to download a QuickTime movie to your hard disk is via HTTP, FTP, AFP, or some other transport. There are capture utils that will save audio and/or video, but the quality will suffer.
Many of the videos offered on Apple's QuickTime Hot Picks section are also being served via HTTP if you know how to get the URLs out of the reference movies. Then you simply download the files using an HTTP downloader or wget from the Mac OS X command line.
If the movie is being offered exclusively via RTSP, you are out of luck.
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