The AppleTV Box in the second and third generation cannot easily play back its own media files. For the AppleTV 2 there is a jailbreak, after which software like XBMC can be installed, for the third generation of the small black box there is no jailbreak at all (and a Jailbreak for the AppleTV 3 is also not foreseeable). About a solution approach with the software PlexConnect reports now t3n.compermanent changes to the AppleTV 3 box are not necessary.
The trick: via its own DNS server, PlexConnect answers queries that were actually made to the iTunes servers with its own content. The content comes from a PlexServer, which has to run parallel on another computer in the network. Unfortunately there seems to be no Plex plugin for FreeNASas soon as there is something new it would be the ideal combination (an additional PC would not be necessary anymore). In any case, it's an exciting way to share media files away from iTunes with a AppleTV 3 ...to reproduce.
For all those who use PlexConnect as data supplier for their AppleTV 3 t3n has created an instructional video: