Firefox and Plugins/Mime type association

John Austin ja at
Mon Jun 25 09:53:33 UTC 2007


Firefox and F7

I really would like to know who or what decides how
the mime type to plugin/application mapping is determined.

The behaviour of FF seems to change depending upon which
plugins are installed.
If the vlc plugin is not there the mplayerplug-in is used
and the "Video Streaming VideoCam" fails on this site

mv /tmp
Select "Video Streaming VideoCam click here"
....Mplayerplug-in starts and fails 
mv /tmp/ .

Move it back and it uses vlc and works - How does it know that ?

In this example things start working with the additional plugin
What happens if things start failing ?

My /usr/lib/mozilla/plugins directory looks like this

lrwxrwxrwx 1 root root      39 2007-06-04 15:09 -> /usr/lib/flash-plugin/
lrwxrwxrwx 1 root root      58 2007-06-02 22:21 -> /usr/java/jre1.6.0_01/plugin/i386/ns7/
-rwxr-xr-x 1 root root 1077720 2007-06-18 18:35
-rwxr-xr-x 1 root root  276892 2007-03-25 06:58
-rwxr-xr-x 1 root root  276892 2007-03-25 06:58
-rwxr-xr-x 1 root root  276892 2007-03-25 06:58
-rwxr-xr-x 1 root root  278072 2007-03-25 06:58
-rwxr-xr-x 1 root root  276892 2007-03-25 06:58
-rw-r--r-- 1 root root    8260 2007-03-15 16:44 xine-logo.ogg
-rwxr-xr-x 1 root root   43404 2007-03-15 16:44

Part of my ~/.mozilla/firefox/pluginreg.dat file looks like this

naxos firefox 1006# cat pluginreg.dat | grep -i asx
16:application/x-mplayer2: mplayer2: asf,asx,asp:$
17:video/x-ms-asf-plugin: mms animation: asf,asx,asp:$
0:application/asx:Media Files:*:$
6:video/x-ms-asf:Media Files:asf,asx,*:$
14:application/x-drm-v2:Windows Media:asx,*:$
15:video/x-ms-asf-plugin:Windows Media Video:asf,asx:$
16:video/x-ms-asf:Windows Media Video:asf,asx:$
naxos firefox 1007#

I have renamed pluginreg.dat and it is regenerated when FF is started
diff between the original and the new shows them not to be the same

How does this get imported into FF as shown by 
Preferences/Content/File Types Management/Download Actions
(With "" set to false)

1. How does (if it does !) pluginreg.dat get interpreted by FF ?

2. If a mime type is supported by more than one plugin/application
   how is the download action table determined ?

3. Is there a secret way of changing the association as the
   FF Change Action GUI does not appear to give you this option ?


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