iPhone - How to convert aiff audio files into aac?

I'm developing an iphone app that records audio, right now it records aiff files, I need to convert these files to aac... any idea how to do th开发者_如何学Cis?

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Apple provides iOS sample code for the ExtAudioFile API that handles conversion: iPhoneExtAudioFileConvertTest

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There's also a open-source library for aac conversion based on Apple's sample code that's a bit easier to use (using Objective-C):

https://github.com/michaeltyson/TPAACAudioConverter

Here's a blog entry by the author describing the project, along with questions and answers:

http://atastypixel.com/blog/easy-aac-compressed-audio-conversion-on-ios/