When I create an aggregate device with 2 hardware inputs and 1 output and I try to use it with AVAudioEngine, it fails to start. I get the error IsFormatSampleRateAndChannelCountValid(outputHWFormat)
If I use an aggregate device with only 1 input/output, it works.
The problem seems to stem from how aggregate devices handle channels. If I add a 2 channel device and a 1 channel device to the aggregate as inputs, I get an aggregate device with 3 channels.
However, if I try and get the format of the input node, it only reports the format of the first device in the aggregate. So instead of saying the device has 3 channels, it will say it has 1 or 2 depending on which device is the main device.
I've tried creating my own AVAudioFormat using channel layouts such as kAudioChannelLayoutTag_AAC_3_0, but this only works in very specific cases and is very unreliable.
Can anybody help with this? It is driving me crazy.
The main problem I am trying to solve is to combine/mix 2 hardware (or virtual hardware via HAL) audio devices in real-time for recording. An aggregate device alone doesn't work (see https://developer.apple.com/forums/thread/703258)
Thanks for any help, you would save my day/week.