CODEWITHSUNDEEP
swiftcameraavfoundationavcapturesessionavaudiosession
Dan Karbayev
Dan Karbayev

Reputation: 2920

How to add audio input to AVCaptureSession only when recording without interrupting video preview?

I'm struggling with an issue: I have AVCaptureSession with preview layer and I also want to provide haptic feedbacks when user taps on buttons. If I add audioInput to my AVCaptureSession then I'm not able to produce haptic feedback at all. I tried to to add audioInput right before starting record and to remove immediately after stopping but modifying capture session configuration (which I did in serial queue) leads to video preview hiccups (it's disrupted for a fraction of a second). And I still have no idea how Snapchat and Instagram do this trick. One of my guesses was that they somehow configure AVAudioSession but I couldn't figure it out.

My capture session initialization is pretty general so I won't paste it (notable here is that I have captureSession.automaticallyConfiguresApplicationAudioSession = false line and shared AVAudioSession is modified like so AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayAndRecord, mode: AVAudioSessionModeVideoRecording, options: [.mixWithOthers])), but I'll post my attempt to toggle audio input:

func addAudioInput() {
    self.sessionQueue.async { [unowned self] in
        self.captureSession.beginConfiguration()
        let microphone = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeAudio)
        if let audioInput = try? AVCaptureDeviceInput(device: microphone), self.captureSession.canAddInput(audioInput) {
            self.captureSession.addInput(audioInput)
        }
        self.captureSession.commitConfiguration()
    }
}

func removeAudioInput() {
    self.sessionQueue.async { [unowned self] in
        if let audioInput = self.captureSession.inputs.first(where: { ($0 as? AVCaptureDeviceInput)?.device.deviceType == .builtInMicrophone }) as? AVCaptureDeviceInput {
            self.captureSession.beginConfiguration()
            self.captureSession.removeInput(audioInput)
            self.captureSession.commitConfiguration()
        }
    }
}

Upvotes: 4

Views: 2699

Answers (1)

Dan Karbayev
Dan Karbayev

Reputation: 2920

I feel dumb enough for not figuring out the solution in short time. So, the solution was to create two AVCaptureSessions - one for video capture (session 1) and one for audio capture (session 2). Session 1 is always running, so that it provides us preview layer. Session 2 is started only when recording starts and stopped immediately after. Both sessions have corresponding AVCaptureOutputs and both of them outputs data buffers to the same delegate which, in turn, uses AVAssetWriter to write those buffers to a video file. That's all.

Upvotes: 5

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