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?