How to record a rtsp video/audio stream.

Some days ago a friend asked me about the possibility of recording/save a
video that appear in a web and the header of the protocol was rtsp://

In that moment, to be sincerely, I didn't have idea of what it was...

I will take a look to it and I'll tell to you later what I guessed, I said.

Here is the answer:
- In Windows: There are many commercial programs to do that.

- In Linux: You can use the super-powerful video player "mplayer" to see that
stream and also save it on a file.

Example:
# mplayer -dumpstream -dumpfile stream.avi rtsp://the.web.with.the.video.rm

and then you can see with
# mplayer stream.avi