How can I force Firefox to open webm files in a external application like mplayer?

Question

I want to open webm files from browsing sites (for example tagesschau.de) in mplayer through 'xterm -e' where I set a specific placement of the window and other parameters. Setting media.webm.enabled to false only disabled internal player, but does not open any option under Preferences -> File Types. Playing with advanced configuration I tried creating media.webm.handler{,default,application} according to other file type that are set to external applications. No luck. I have set mp4 files to use the same script (with execution permission) and it works exactly as I want.
Script:
<pre><nowiki>#!/bin/bash
FILENAME="`basename "$@"`"
xterm -fs 24 -bg black -fg white -title "$FILENAME" -geometry 96x8 -e "echo \"$FILENAME\"'\\nfrom\\n'\"$@\" && \
mplayer -geometry 100%:100% -vf dsize=400:-3 -volume 80 \"$@\" "</nowiki></pre>
The script itself works when I feed it a webm url (or any other media for that fact).
Linux 3.9.9-1-ARCH x86_64 GNU/Linux

Answer 1

I don't know about linux cos i'm win user. But you may start with disabling internal webm support. about:config -> media.webm and then I think you should install greasemonkey addon and custom script for playing content in 3rd partys players. (At least that is my configuration. I'm using VLC for youtube)