iPhone recording audio

Question

I'm currently working on a project where it is necessary to record sound being played by the iPhone. By this, I mean recording sound being played in the background like a sound clip or whatever, NOT using the built-in microphone.

Can this be done? I am currently experimenting with the AVAudioRecorder but this only captures sound with the built-in microphone.

Any help would be appreciated!

Answer 1

This is possible only when using only the Audio Unit RemoteIO API or only the Audio Queue API with uncompressed raw audio, and with no background audio mixed in. Then you have full access to the audio samples, and can queue them up to be saved in a file.

It is not possible to record sound output of the device itself using any of the other public audio APIs.

Answer 2

Just to elaborate on hotpaw2's answer, if you are responsible for generating the sound then you can retrieve it. But if you are not, you cannot. You only have any control over sounds in your process. yes, you can choose to stifle sounds coming from different processes. but you can't actually get the data for these sounds or process them in any way.