What i need to do:
I am developing a (what I thought would be) simple app for a client where an iPad is connected to an Apogee Quartet. The Quartet will have several different speakers connected to discreet outputs. The interface has 6 buttons, each designed to map to a specific output on the apogee USB interface. I need to be able to route the default system audio to a specific USB output that is mapped to the button. It needs to change the system output because the app does not generate any audio of it's own; rather, the app simply routes the system audio to a specfic output so that you can hear audio from other apps—like Youtube or sound cloud—on diferent speakers.
What I have tried:
I have been through the lynda ios Audio tutorials, read the Core Audio Essentials Guide, Watched numerous WWDC videos,
But I cannot seem to find out how to change the system output to a specific channel of a USB audio interface. It seems like all of the online information and examples show you how to take input from a mic, a file or other audio units but never shows you how to simply change the default system output.
I can use either swift or objective-c to solve this. I just need to be pointed in the right direction as I have had the hardest time finding the correct information on this.