Lucky for us, Apple has provided one: http://tools.ietf.org/html/draft-pantos-http-live-streaming-...
All iOS apps must use HLS for videos longer than 10 minutes and Apple verifies compliance during the app store review process. As mentioned, with AirPlay all HLS media files are downloaded directly by the AppleTV, not piped through your device. I can tell you from experience it works very well.