Playing movies via flashdrive question

What type of files does xbox support?

I tried playing a .mkv file, but nothing is coming up when I go on my flashdrive via my xbox.

Can anyone please help? Thank you

Whenever I play a movie from my USB drive it's either in the .AVI or .MP4 format. I know from experience .MKV is not supported, just find yourself a video file converter online and convert from .MKV to a supported format.