Songs formatted as m4p are not working in AVPlayer

Question

I am implementing a music related application. In my application I need to play the songs selected from iPod library using AVPlayer. I had a problem when playing songs from iPod library using AVPlayer. I am not able to play some songs that are downloaded form iTunes store.All the songs that play normally are formatted as .m4a. All the songs that won't play are formatted as .m4p. Can anyone help me how can I resolve this problem.

Thanks in Advance, Sekhar.