Months ago it has not been a problem, streaming my own 1080p Videos from any iOS-Device to my ATV 3, but now it is horrible. It's buffering for minutes and still stucking after a few minutes of watching again.
Strange thing: all local apps like Trailers or YouTube work like a charm. Even streaming from my MacBook is working. What's the problem with my "new iPad" or "iPhone 5"?
Wifi-Check passed and on all devices I have no other network issues using a 5GHz WLAN over fritzbox.
Just wanted to throw my two cents in here as well.
I've recently been experiencing the exact same problem as all of you.
This is my setup.
15" Retina MacBook Pro running OS X 10.9.2
I stream personal content wirelessly using a dual-band router connected to my wireless-N network.
This streams from my MacBook Pro to an Apple TV 3 with the latest update using iTunes 11.1.5.
I have a 50+mbps connection so no issues there.
Netflix streams beautifully at its highest quality. YouTube videos load in seconds and play without a hiccup.
Apple Trailers are abysmal and I have given up on those a long time ago, but now, my personal videos won't stream at all unless they're limited to around 800mb or less. Anything over a gig will barely buffer, then choke and rebuffer until I swear and shut the whole thing down.
This "used" to work flawlessly, but sometime in the last month it's all gone down the toilet.