this should not be hard ... but it has flummoxed me.
I am trying to change which plugins in firefox (iceweasel) handle which mime-type. For example, I want to tell firefox to use the mplayer plugin for avi files rather than vlc plugin.
In theory, one should be able to go to edit-->preferences-->content-->manage file types.
But this just does not work for me. On some of the computers I have tried, the specific mime-type is not listed, and there is no means to add a new mime-type. In some cases, where the mime-type is listed, you can not change the plugin assigned to it (i.e. one plugin is listed, and this can not be changed or edited).
I have downloaded a mime-edit addon for firefox, but this does not help much either. It does allow me to add and edit mime-types, but not change which plugin handles them. For example, I can easily tell it to handle a pdf with the xpdf program rather than acroread, or vice versa, but I can't tell it to handle avi with the mplayer plugin and not vlc plugin (i.e. configuring external applications is fine, configuring plugins is not).
I am not alone is this difficulty. I have found these threads:
The second thread suggests manually editing the "do not edit" file called ~/.mozilla/firefox/pluginreg.dat
I am happy to do this. I haven't done it yet, but I am sure it will work. However, now I am really just curious about why this process is so difficult, and whether someone has found out something that I have missed.