I have just downloaded this app so please bear with me if this has been asked 100's of times already.
I have a dlink 320L with a mix of movies, mkv, avi, mp4... Etc. they all play fine on my ipad4 using the app. When I try to send them to the atv the mkv files just send the audio and the video continues on the ipad, (I did a bit of reading) when I turn on mirror the sound continues through the tv, the screen goes blank/black and the video freezes on my ipad.
When I'm streaming something which uses the QuickTime player I believe... Everything works perfectly without the mirror on. Unfortunately most of my movies are in mkv format and the QuickTime won't play them.
Cheers
Z