Use Ubuntu Tweak to change associations
There is a System Tool called "Ubuntu Tweak". I have used it under Gnome, but never tried it with KDE. Once installed, you can click on "System" (on the left side) and then click on "File Type Manager". You will see a list of categories. At the bottom, there is a check box, when checked, shows only those type which have an association (uncheck it to include those types without an association). Select the type (click on it) and you either click on the "Edit" button or double click (or more clicks) on the item selected. A box will pop up where you can see what is associated with the type (in some cases, more than one). By clicking on the "Add" button (one or more times), you will get a new list where you can select other apps that you may have installed to handle that type. There is also a "Use Custom Command" button, which will allow you to select (from the file system - usually in "usr/bin") an installed application that can handle that association - e.g., realplay for Real Player (I use it for MP3s).
BTW, this same action can also be achieved by "right-clicking" on the file and clicking on "Properties". Then click on "Open With" will bring up the same set of boxes as does "Ubuntu Tweak".
Unfortunately, Firefox seems to be worse. I did find an "Add-on" called "Force Content Type", which seems to work for those apps that don't show in the "Preferences -> Applications". I have found the new versions of Firefox to be a real pain in the tush - some MP3s aren't handled very well, some youtube videos won't play at all, etc. FireFox really needs to allow the user to add "new apps" For example, one version didn't have an entry for MP3 (missing in the mimetype.rdf file. I could not find a way to add it as Firefox kept replacing my changes (same with bookmarks I had from another bookmark file - I know, there is "sync" support, but it is also a PITA to use).
Last edited by bobc4012; 06-08-2010 at 02:38 AM.