I know that if I start an audio recording session in foreground, with Audio, Airplay, and Picture in Picture activated in Capabilities -> Background Modes; I am able to cont
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It turns out that Apple's SpeakHere sample code with some modifications will start recording audio in the background if you just add the audio multitasking flag to information. You might look https://github.com/benvium/SpeakHere for an updated version of SpeakHere since Apple hasn't updated it in awhile.
From Apple Documentation
An app that plays or records audio continuously (even while the app is running in the background) can register to perform those tasks in the background. You enable audio support from the Background modes section of the Capabilities tab in your Xcode project. (You can also enable this support by including the UIBackgroundModes key with the audio value in your app’s Info.plist file.) Apps that play audio content in the background must play audible content and not silence.
Typical examples of background audio apps include:
Music player apps Audio recording apps Apps that support audio or video playback over AirPlay VoIP apps
For tasks that require more execution time to implement, you must request specific permissions to run them in the background without their being suspended. In iOS, only specific app types are allowed to run in the background:
- Apps that record audio content while in the background
EDIT:
Also regarding your "Bluetooth device":
Check out the documentation for ExternalAccessory .
Be aware that you need to apply and get approved for a special developer program in order to be able to create external accessories.