Reusing AudioUnit Graphics on iOS

Question

I use two AUGraphs in my iOS application, one for recording audio and one for playing audio. I use only one at a time. This works great if I create AUGraph instances every time I start using them.

I am trying to reuse these AUGraphs instead of creating and initializing a new instance each time every time I switch between recording and playback.

I am having problems with this because when I perform the following steps, I get an error message the next time I try to get microphone data from the I / O unit:

• schedule recording
• initialize recording schedule
• start recording schedule
• stop recording schedule
• schedule playback
• initialize the playback schedule
• start of playback schedule
• stop playback schedule
• start recording schedule

And then the call that causes the error, return code -50 (this statement works fine when you recreate the AUGraph every time):

OSStatus status = AudioUnitRender( remoteIoUnit, ioActionFlags, inTimeStamp, CB_remoteIoUnitInputElement, inNumberFrames, ioData ); 

Is reuse of AUGraphs even possible, and if so, how?

Answer 1

You can reuse the AU chart exactly as described in the question.

The problem, why this did not work for me, is that I had an error causing interference / overwriting between my two AUGraph instances. I found these errors only by accident. Since I fixed them, AUGraphs works as intended.

If the two AUGraph instances are completely separate, you can use and reuse as many AUGraph instances as you want. I have not tested whether they can be used at the same time.