Is it possible to add effects to iPhone/iPod app audio?

Question

Is it possible to capture audio coming from the iPod app in the iPhone OS 4+ and apply effects processing to it? For example, to add a reverb, or manipulate the built-in EQ from another app. It seems if you want to do this you would have to re-implement the entire media player.

Even then – is it possible to apply audio effects to the user's MP3 music library?

Answer 1

The iOS security sandbox prevents App store apps from capturing any raw audio coming from any other app, including the iPod player.

If you convert music from the user's mp3 library using AVAssetReader/AVAssetWriter into raw audio files, you could use some DSP processing to apply effects to those converted files as you play them using Audio Units.