Apple TV play media stored on Airport Extreme hard drive? The current gen Airport Extreme (802.11ac, you know... the tall white one) is capable of having a network accessible hard drive connected directly to it. Now that the new Apple TV can run apps, can I use the Airport's connected hard drive as a media server and have the new Apple TV access its content directly? Maybe by running the Plex app (or similar)?
VLC should do the trick. I confirmed I can access the drive inside my Time Capsule using VLC on my Apple TV.

I imagine it will also access the files on a USB-connected drive. Not tested the latter though.