1. Take the original flashvars string und URL decode it. Many ways to do it, but simplest.. Throw it here: http://meyerweb.com/eric/tools/dencoder/ and hit decode.

2. Ok, what have we here? playlistfile=http://www.rtvslo.si/media.php?id=173767487&mt=flv&mq=hi&wm=true&rm=false&file=playlist.xml

3. Play with the parameters, see how well you fare. Does not really seem to do anything useful other than provide the original playlist which uses rtmp. Seems to have some future framework for video tags, but its not working right now. So lets look at the original playlist:

We have a streamer entity: rtmp://stream.rtvslo.si/simplevideostreaming

And an asset location: 74/90/FredWilsonx201307291225x700000x351x413x.mp4

4. Load up VLC, File > Open Network Stream. For URL join the two parts we just got:

rtmp://stream.rtvslo.si/simplevideostreaming/74/90/FredWilsonx201307291225x700000x351x413x.mp4

Click Convert, choose a destination file name, and check Dump raw input (you can also click Settings and select Keep original video/audio track. I find VLC conversions to be a mixed bag.. Instead I used the next step after seeing the player was getting an FLV container.

5. ffmpeg -i FredWilsonx201307291225x700000x351x413x.mp4 -vcodec copy -acodec copy fred.mp4

You now have a pristine video file.

I'm sparing a bit of details, and in any such thing there is a bit of trial and error, and a bit of research. In this case I fired up Wireshark to see if there anything useful before looking at http://www.rtvslo.si/media.php, spent a few minutes on reading re jwplayer), and trusted the very capable VLC instead my inclination of going commando with rtmpdump.

This will obviously not work verbatim for other sites, but maybe give folks in this community some pointers next time they hit an unfriendly site.