Starting from version 6.6, Elmedia Player automatically converts all streamed media to the format understandable by the Apple TV, so you are no longer limited in the format choice.
The only exception is online videos (opened through File → Open Online Video or otherwise), for which only the following formats are currently supported:
Video:
- H.264 video up to 1080p, 60 frames per second, High or Main Profile level 4.2 or lower;
- H.264 Baseline Profile level 3.0 or lower with AAC-LC audio up to 160 Kbps per channel, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats;
- MPEG-4 video up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Simple Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats.
Audio:
- HE-AAC (V1), AAC (16 to 320 Kbps), protected AAC (from iTunes Store), MP3 (16 to 320 Kbps), MP3 VBR, Audible (formats 2, 3, and 4), Apple Lossless, AIFF, and WAV; Dolby Digital 5.1 and Dolby Digital Plus 7.