AVAudioPlayer initialization error 1685348671. How to check whether file is valid?

I am using AVAudioPlayer to play some ima4 files. The initialization of the player keeps failing with error code 1685348671 (dta) which according to the documentation means开发者_JS百科

The file is malformed, not a valid instance of an audio file of its type, or not recognized as an audio file. Available in iPhone OS 2.0 and later.

What I don't understand is how the files are invalid or malformed when I can play them with QuickTime? Can the file still be malformed? How can I check whether an ima4 file is valid or not?

Thanks.

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I'm having no probs playing ima4 files (in .aif) with AVAudioPlayer.

Maybe post some code.