Originally Posted by That_One_Guy
So I put about 20 movies on my HTC One and included in there was Avatar and Inglorious Basterds. They are both mp4's and work on my computer just fine. However, they won't play on the One. The movies show up as gray boxes with exclamation points in them. My first guess is that these movies are too long and the file is too large. Does anybody have a solution for this? They show up on my phone, they just won't actually play.
Had same issue with some of my converted blu-ray rips. Just download MX player, it plays mp4's fine and its free.