Found a bug I think, tried to play an mkv off network share, file will play on device but will not play if streamed via airplay, strangely Apple TV brings up the picture as about to play but stays paused and will not unpause. Other file types have played through airplay fine. Otherwise think its a great new feature.
Is your Apple TV connected to an AV receiver or just a TV?
If connected to just a TV, you may try disabling the Dolby Digital over AirPlay option which can be found in the audio playback settings menu.
Having the same issue on my iPhone 5 and iPad 3.
Dolby Digital over Airplay is disabled on both devices. Any clue?
This option is greyed out, Apple TV is connected via hdmi, track says its 5.1 Dolby digital, I tried a different mkv which plays fine however audio is standard. The problem was on the Apple TV, in audio settings Dolby digital was on auto, by switching to On the file played fine.
That’s the suggestion I was just about to make as well.
Thanks for following up.