Multimedia plugins filter
From Carleton Moodle Docs
The Multimedia plugins filter finds a link in text that points to a multimedia resource and replaces the link with an appropriate multimedia player code which can play the resource. The actual player resides on each users' computer.
For example, a teacher may put a MP3 audio file as a resource in their course, or have a URL link to an external MP3 file. When the MP3 audio plugin has been turned on, the student will be able to play them in Moodle using a media player on their computer. See also Media embedding.
Required software on user's computer
Although Moodle prepares the media files to be played in the browser, the actual playback is handled by various types of browser plug-in software, primarily Adobe Flash, Quicktime, Windows Media Player and Real Player. If users do not have these installed they may be prompted to go and install them by their browser. These pieces of software are generally free, easily installed and widely used so this will only be an issue for small numbers of users.
Disabling this filter
If you do not want the filter to be applied you can disable at either for a specific activity or for the whole course. To disable for a specific activity, open the activity and then click on the Filters link in the Administration block under Activity Administration. To disable for the entire course page, start from the main course page and then click on Filters in the Administration block under Course Administration.
Using Moodle forum discussions: