Using Audio Units to play several short audio files with overlap

Question

I have run through an audio units tutorial for a sine wave generator and done a bit of reading, and I understand basically how it is working. What I would actually like to do for my app, is play a short sound file in response to some external event. These sounds would be about 1-2 seconds in duration and occur at a rate of about about 1-2 per second.

Basically where I am at right now is trying to figure out how to play an actual audio file using my audio unit, rather than generating a sine wave. So basically my question is, how do I get an audio unit to play an audio file?

Do I simply read bytes from the audio file into the buffer in the render callback? (if so what class do I need to deal with to open / convert / decompress / read the audio file)

or is there some simpler method where I could maybe just hand off the entire buffer and tell it to play?

Any names of specific classes or APIs I will need to look at to accomplish this would be very helpful.

There should be a code sample on using the Channel Mixer unit on Apple's site. Don't have the link right now but I built my sound engine based on it and my games play several short, uncompressed effects concurrently. — Nicolas Miari, Jul 07 '12 at 03:42

Nicolas Miari · Accepted Answer · 2012-07-08T13:40:59.073

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OK, check this: http://developer.apple.com/library/ios/samplecode/MixerHost/Introduction/Intro.html

EDIT: That is a sample project. This page has detailed instructions with inline code to setup common configurations: http://developer.apple.com/library/ios/ipad/#DOCUMENTATION/MusicAudio/Conceptual/AudioUnitHostingGuide_iOS/ConstructingAudioUnitApps/ConstructingAudioUnitApps.html#//apple_ref/doc/uid/TP40009492-CH16-SW1

edited Jul 08 '12 at 13:40

answered Jul 07 '12 at 03:44

Nicolas Miari

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Thanks for the link. I am tracing through the program now. Its not much fun, haha. – wfbarksdale Jul 07 '12 at 19:25
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It's quite a bit of code just to set up the AUGraph, but please type it by hand, don't copy-paste. You will come out knowing something! – Nicolas Miari Jul 07 '12 at 19:58
And sorry for providing just a link; I'm on an iPhone! – Nicolas Miari Jul 07 '12 at 19:59

score 1 · Answer 2 · answered Jul 18 '12 at 02:04

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If you don't mind being tied to IOS 5+, you should look into AUFilePlayer. It is much easer then using the callbacks and you don't have to worry about setting up your own ring buffer (something that you would need to do if you want to avoid loading all of your audio data into memory on start-up)

answered Jul 18 '12 at 02:04

Beleg

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Never heard of that. Is it low-latency too? – Nicolas Miari Aug 18 '12 at 04:41

Using Audio Units to play several short audio files with overlap

2 Answers2