Macos/Swift Capture Audio with Avcapturesession

macOS/swift Capture Audio with AVCaptureSession

It's called for me. You don't show how you use it, but maybe your AudioCaptureSession is going out of scope and being deallocated.

How to record my Mac's internal sound, not the microphone!, using AVCaptureSession?

I have not found an easy way to do it but it turns out that it is possible to make the original code record the audio given that there is another software installed on my machine: Soundflower.

Soundflower is an open source kernel extension for MacOS, designed to create a virtual audio output device that can also act as an input.

Given that the Soundflower is installed, one can use configure the macOS using the Applications / Utilities / Audio MIDI Setup app to send the audio to both virtual and real audio devices. This way the code above captures the audio from the Soundflower but you can still hear it on your normal audio output device.

The setup of the Applications / Utilities / Audio MIDI Setup application is described here: How can I send my computer's audio to multiple outputs?.

Using AVCapture session to capture audio frames

It turns out (as @RhythmicFistman suggested) I was just missing setting weather or not I wanted the frame to be interleaved. So my settings look like this now:

    let audioSettings = [AVFormatIDKey : kAudioFormatLinearPCM,
                   AVSampleRateKey : 48000,
            AVLinearPCMBitDepthKey : 16,
             AVLinearPCMIsFloatKey : false,
       AVLinearPCMIsNonInterleaved : false] as [String : Any]

How to add multiple audio AVCaptureDevice to an AVCaptureSession

I thought multiple audio and video AVCaptureInputs were unsupported, yet I couldn't find any documentation on that either.

A while ago this person cleverly managed to create multiple video inputs and outputs by using addOutputWithNoConnections(), then manually creating the connections to the inputs (but why no addInputWithNoConnections()?):

https://stackoverflow.com/a/30191013/22147

That could be worth trying with audio! Please report back with your results if you try this!

However I like to wrap the input devices in an aggregate audio device and then configure the AVCaptureSession to use that. This gives you the convenience of working with a single "device" and you don't have to worry about multiple clocks and timestamps because both devices are synchronised.

You can create an aggregate audio device manually in Audio MIDI Setup.app: https://stackoverflow.com/a/65704755/22147

or programmatically, using AudioHardwareCreateAggregateDevice():
https://stackoverflow.com/a/56415699/22147
If you use the programmatic route you can hide the resulting aggregate device by setting kAudioAggregateDeviceIsPrivateKey to true. You might want to do this to stop users messing with it.

AVCaptureSession Record Video With Audio

You have not included the audio device:

AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
AVCaptureDeviceInput * audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:nil];
[session addInput:audioInput]

between beginConfiguration and commitConfiguration. It'll work!!!

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