iOS Bluetooth output + phone microphone input problem

MacOSX and iOS
1

Hi,

somehow I cannot get the Bluetooth output + phone mic input routing to work (tested with iPhone XR + iOS 13).

I’m pretty sure it has worked before, and it should still be possible. I downloaded a microphone app from App Store and it allows to route the audio output to a BT speaker while using the phone mic as the input. Works great.

According to docs I should use session category AVAudioSessionCategoryPlayAndRecord with option AVAudioSessionCategoryOptionAllowBluetoothA2DP. However, after I do this the Bluetooth device disappears after several route change events and the output is routed to speaker.

Any ideas?

Thanks,
-Pekka

2

I’d be very interested in this too. At the moment, when users switch to a (output only) Bluetooth device, they need to turn off the mic otherwise it doesn’t connect (iOS 17). It should be possible to keep the mic on the device.

3

Seems related to this: FR: Disable Bluetooth HFP by default

4

Thanks for the link. I think I had tried this solution (even commenting the 3 lines), but it didn’t make a difference.

In my case the problem is not a drop of quality, but simply the fact that sound will be output on the device when I specify any input channels, and return to the bluetooth speaker when I set the input channels to 0.

5

Bluetooth is a funny beast. I wonder if some kind of sample rate mismatch is occurring? I don’t think we have up/down sampling in our Device Combiner so if two devices don’t match they won’t work together, and bluetooth devices may change sample rate when different configurations are used (i.e if the number of channels changes).

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