I have a 2012 MacBook Air, Apple TV (3rd generation), and AirPort Extreme (5th generation) and hooked them up to my HDTV to watch videos using AirPlay Mirroring. Standard Definition videos and iTunes HD content run perfectly well but 720p HD mkv files stutter/lag. The choppiness isn't so bad as to make them unwatchable but the videos don't run fluidly and once you notice it you can't ignore it! The problem is most apparent during long pans shots and fast action sequences. My laptop connects to the router at 300 Mbit/s and I wired the Apple TV to the router as that seems to be the commonly prescribed fix. However, this didn't help at all. Before I wired my Apple TV to the router it was connecting at 65 Mbit/s, which surprisingly seems to be the fastest speed at which the two can connect. I am very disappointed, especially as I have the latest hardware and don't see why AirPlay Mirroring isn't working as it's supposed to. I bought the Apple TV and the AirPort Extreme pretty much solely for mirroring stuff off my Mac. Any help would be much appreciated!