iOS: Sample code for simultaneous record and playback
I'm designing a simple proof of concept for multitrack recorder.
Obvious starting point is to play from file A.caf to headphones while simultaneously recording microphone input into file B.caf
This question -- Record and play audio Simultaneously -- points out that there are three levels at which I can work:
- AVFoundation API (AVAudioPlayer + AVAudioRecorder)
- Audio Queue API
- Audio Unit API (RemoteIO)
What is the best level to work at? Obviously the generic answer is to work at the highest level that gets the job done, which would be AVFoundation.
But I'm taking this job on from someone who gave up due to latency issues (he was getting a 0.3sec delay between the files), so maybe I need to work at a lower level to avoid these issues?
Furthermore, what source code is available to springboard from? I have been looking at SpeakHere sample ( http://developer.apple.com/library/ios/#samplecode/SpeakHere/Introduction/Intro.html ). if I can't find something simpler I will use this.
But can anyone suggest something simpler/else? I would rather not work with C++ code if I can avoid it.
Is anyone aware of some public code that uses AVFoundation to do this?
EDIT: AVFoundation example here: http://www.iphoneam.com/blog/index.php?title=using-the-iphone-to-record-audio-a-guide&more=1&c=1&tb=1&pb=1
EDIT(2): Much nicer looking one here: http://www.switchonthecode.com/tutorials/create-a-basic-iphone-audio-player-with-av-foundation-framework
EDIT(3): How do I record audio on iPhone with AVAudioRecorder?
Answer
To avoid latency issues, you will have to work at a lower level than AVFoundation alright. Check out this sample code from Apple - Auriotouch. It uses Remote I/O.