The media tracker only receives a media title from the YouTube and Vimeo player but not from other players such as HTML5.
Media Analytics plugin attemps to detect a media title from the tooltip and alternate text HTML attribute. If these are not set, the media title cannot be tracked and they will be reported as « Unknown ». The developer guide for enriching media data explains how to avoid unknown media titles and how to track a proper media title for all of your videos and audios.

Previous FAQ: I use a different media player that is not supported by the Media Analytics plugin, what can I do?