Forcing iPhone Microphone as Audio Input

user_230896 0
Viewed 16076

I am developing an iOS application (targetted specifically for iPhone, at the moment) that requires the application to record audio only from iPhone internal microphone (even when headphone/headset is plugged in), and playback at headphone (let's assumed headphone is plugged in for now).

I am wondering if this is currently possible with the available APIs? If so, can anyone please shed some light on how do I go about doing this?

Thanks!

microphone core-audio ios
6 Answers

I believe the answer to this question to be 'no'. I used an iPhone 4 and the new-to-iOS 4 AVFoundation to experiment, focussing on the AVCaptureDevice class.

I added the following to an application:

NSLog(@"%@", [AVCaptureDevice devices]);

So that asks that all devices that can be used for capturing audio and/or video be listed. Without the headphones plugged in, I get:

(
    "Back Camera",
    "Front Camera",
    "iPhone Microphone" 
)

With the headphones plugged in I get:

(
    "Back Camera",
    "Front Camera",
    Headphones
)

So the iPhone microphone drops off the list of available AVCaptureDevices as soon as the headphones become available. To probe this further, I added a quick bit of code to grab the AVCaptureDevice instance for the available audio device and to print its unique ID. For both the device identifying itself as "iPhone Microphone" and the device identifying itself as "Headphones", I got:

com.apple.avfoundation.avcapturedevice.built-in_audio:0

It would seem to me to be obvious that two devices can't have the same unique ID, so clearly it's the same device changing its state. Although AVCaptureDevices have a lot of stuff for setting state, it's limited to visual things like focus, exposure, flash and white balance.

user_4273320

I am pretty confident this is possible via your application's Audio Session:

An audio session is an intermediary between your application and iOS. Each iPhone application has exactly one audio session. You configure it to express your application’s audio intentions. To start, you answer some questions about how you want your application to behave:

  • How do you want your application to respond to interruptions, such as a phone call?
  • Do you intend to mix your application’s sounds with those from other running applications, or do you intend to silence them?
  • How should your application respond to an audio route change, for example, when a user plugs in or unplugs a headset?

With answers in hand, you employ the audio session interface (declared in AudioToolbox/AudioServices.h) to configure your audio session and your application.

Dig on these docs:

And let me know how it goes!

user_1486640

I found that when using AirPod pro headphones and trying to record a voicemail greeting that the phone used the built in mic even though the headset was fully connected and in use.

user_65254030
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