Media filter doesn't work correctly for .mp3 or .rm files

Media filter doesn't work correctly for .mp3 or .rm files. Using a link like the following in an html page:
<a href="rtsp://server/path/file.rm"></a>
In Firefox no embedded player shows up. In IE the embedded player shows, but won't play even after clicking the play button. You must right-click the realmedia icon and pick play for it to work.
Links to .mpeg3 files bring up an external player instead of the internal player.