Question

Specifically, I just want to record something, reverse it, and play it back. I’ve looked through the apple docs and couldn’t find anything about editing audio. Is it possible?

Answer 1

Yes, it is definitely possible. Last I checked the Apple Core Audio docs were not very good, but it has been a few months since I’ve worked with it. Here are the steps that I would follow.

1. Record the audio sample.

2. Reverse the audio by looping through the first half of the array and swapping the value located there with one an equidistant from the end of the array.

3. Play the resulting audio clip.

Quite frankly, the first step is probably the hardest. Here is a decent article about doing audio on the iPhone including recording. Make sure you look at all of the different parts of the article. Here is another article about recording sound on the iPhone, but using a different framework. There are really several ways to go about recording on the iPhone though, last I checked, if you want to play audio while you are recording you have to use RemoteIO.

Edit:

If you would like to use RemoteIO(which I preferred), then this site is pretty helpful for getting started with it. Also, the aurioTouch sample program that Apple provides is immensely helpful (though more than you want).

If you don’t need RemoteIO (because it can be a major pain though it is more low-level and thus more flexible), then try the SpeakHere sample program. It is made just to record and play back. However, I just looked at it and it writes the recording to a file rather than a buffer which isn’t what you want. I would recommend going with RemoteIO for that reason (unless you can find a way to have it write to a buffer instead).