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I'm quite stumped on this issue. I have a large library of H.264 mp4 video files that I need to have play on iOS. Originally, I was targeting only iPad, but requirements have changed and now I need to include iPhone. But I've noticed that my iPod Touch, which has exactly the same OS version and build id as my iPad, won't play the same files that I've been successfully using on the iPad. I've confirmed this with a colleague who also has an iPhone and iPad with the same version & build. I've also seen the exact same behavior in the iPad simulator, but until now I figured it was a quirk of the simulator. Now I'm not so sure.