Fred,

To my knowledge, you can not explicitly do that with AVAudioSession. Even the 
setPreferredDataSource’s location setup can be misleading: Everything depends 
on the Polar Pattern you choose. So an Omni Polar Pattern on “Front” will 
result in using two microphones to achieve it. There is currently no way in 
accessing a specific source. 

Now on a different topic but related, at WWDC 2019 we saw a way of accessing 
two microphones and capturing them in two streams using AVCapture (link 1 
below). This is nice and it would be really nice to be able to bring this to 
AVAudioSession and CoreAudio Frameworks for Audio crowd to use.
I talked to some engineers at WWDC and submitted a Feedback Ticket for 
“Providing API Access in CoreAudio/AVAudioEngine for multi-microphone capture” 
(FB6131819) similar to AVCapture.

For me the worse is not being able to access Speaker Routing in iOS for devices 
that have four speakers! On those devices, if you have simultaneous use of 
microphone and speaker there’s no way to get rid of echo and to make things 
worse, the speakers are always next to a microphone! Using Echo Suppression 
algorithms doesn’t always help either! There’s also an old Feedback Ticket on 
this: FB6131819 (Provide API Access to individual speaker routing on Quad 
Stereo Devices).

If anyone knows workarounds, it’d be great to share! :) 


Arshia
www.antescofo.com <http://www.antescofo.com/> 


(1) WWDC 2019 - Introducing Multi-Camera Capture for iOS: 
https://developer.apple.com/videos/play/wwdc2019/249 
<https://developer.apple.com/videos/play/wwdc2019/249> 

> On 2 May 2020, at 23:37, Fred Melbow via Coreaudio-api 
> <[email protected]> wrote:
> 
> Hi everyone,
> 
> the latest iPhones (ever since the XS I believe) can record in stereo using 
> two of the built-in mics, at least using the native iOS Camera app.
> 
> I’m trying to achieve this in my app too. I know that a microphone 
> (front/back/bottom) can be selected using `setPreferredDataSource`, but this 
> method only allows selection of one mic (mono).
> 
> Is there any update on this - is recording on stereo possible using the 
> `AVAudioSession` API or otherwise?
> 
> Many thanks,
> Fred
> 
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