iOS 4.2.1: Video files not being played by MPMoviePlayerController on iPod Touch

I'm using the MPMoviePlayerController with my App. It works fine both with the XCode simulator and the device (iPod Touch with iOS 4.3.1), but when running the App in XCode's Debug Mode on an iPod Touch running 4.2.1, I get an error which says that the video format is not being supported.

The video is an mp4-开发者_如何学编程file and as far as I know the device should be able to play mp4 files.

Your help will be very much appreciated.

One possibility is that your video is H.264's Main Profile. This is supported by the iPod Touch 4th gen, but not the iPod touch gen 2 and gen 3 - these support only Low Complexity Baseline and Baseline profiles.