playing sound files on the iphone/ipod touch

What are the recommended formats to play sound files on the iphone/ipod touch devices. I am am developing an application that should be able to play long sound开发者_运维技巧 files on the device. Are there any limitations to the size of the sound file and which would be the best and most optimized file size to play on the iphone/ipod touch

Appendix D from the CoreAudio docs covers supported filetypes: http://developer.apple.com/iphone/library/documentation/MusicAudio/Conceptual/CoreAudioOverview/SupportedAudioFormatsMacOSX/SupportedAudioFormatsMacOSX.html

I think AAC is the preferred compressed audio format for the iPhone / iPod Touch. Plus it has the advantage of being better quality than MP3 at the same bit rate.