How to set iOS app to use usb audio for input and output to internal speakers
I think you can only achieve input via USB device and output through the speakers when the USB device has no audio output component.
I can't find any documentation that says exactly this, but my reasoning is as follows:
Mixing and matching audio devices is done via the generalised version of AVAudioSessionCategoryPlayAndRecord, the so called multi-route category (AVAudioSessionCategoryMultiRoute) and its documentation in AVAudioSession.h says that
- Input is limited to the last-in input port.
AVAudioSessionPortBuiltInSpeakeris only allowed to be used when there are no other eligible outputs connected
Point 1 is not a problem, but point 2 disallows your adapter 2 scenario.
NB This would allow adapter 1 & 2 to both work with USB input and line-out or headphones. Would that be of any use to you?
This is a bit of a long shot, but have you tried..
[session setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionDefaultToSpeaker error:nil]..instead of overrideOutputAudioPort:?