Does anyone know how I could record some audio on the iphone then change the pitch of the audio?
Good answer for superuser.com, but not terribly helpful if he's looking to write his own pitch changer...
Matt Poush
2009-11-02 15:19:47
@Matt the "semicolon-dash-parens" sequence often signifies a joke. For example, ;-)
Rex M
2009-11-02 19:42:34
@Rexm actually ;-) is the endline character in the HappyEnding++ programming language
Chris Ballance
2009-11-02 19:51:31
I have not found the T-Pain app to be nearly autotuney enough. I wanted my money back instantly.
Nathan Bowers
2009-11-02 21:44:40
+2
A:
It looks like you'll want to start with the Core Audio Framework: http://developer.apple.com/IPhone/library/documentation/MusicAudio/Conceptual/CoreAudioOverview/
There doesn't seem to be a whole wealth of information on the AutoTune algorithm, but a good start would be to use a Fast Fourier Transform to analyze the pitch to determine what pitch your audio is actually at. It's a relatively simple to change the pitch from what it is to what it needs to be. For example, A is 440 Hz. Assuming the input is actually 466.164 (A#), and you want it to be A, you adjust the waveform by 0.94387383 (440 / 466.16400). An A# becomes an A.
If you want to achieve an auto tune effect, you'll want to subdivide the recording into tiny audio clips that you can re-pitch individually.
More info on pitch detection: http://en.wikipedia.org/wiki/Pitch%5Fdetection%5Falgorithm
Matt Poush
2009-11-02 15:33:24