How to record video and play audio at the same time (swift tutorial)

Question

So you want to record a video and play music from the user's library at the same time? Look no further. Below is the answer.

Woodcut

Answer 1

For the audio playback you will use AVAudioPlayer. All you have to do is to declare the AVAudioPlayer as a global variable (I named it audioPlayer) and implement the code below.

Use this in after the user chose the song he/she wants to play:

func mediaPicker(mediaPicker: MPMediaPickerController, didPickMediaItems mediaItemCollection: MPMediaItemCollection) {
    let pickerItem: MPMediaItem = mediaItemCollection.items[0]
    let songURL = pickerItem.valueForProperty(MPMediaItemPropertyAssetURL)
    if let sURL = songURL as? NSURL
    {
        songTitle = pickerItem.title!
        do
        {
            audioPlayer = try AVAudioPlayer(contentsOfURL: sURL)
        }
        catch
        {
            print("Can't Create Audio Player: \(error)")
        }
    }
    dismissViewControllerAnimated(true, completion: { () -> Void in
        audioPlayer.play()
    })
}

You will also need to set up the audio session(in viewDidLoad). It's crucial if you want audio to play while recording:

 // Audio Session Setup
    do
    {
        try audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord)
    }
    catch
    {
        print("Can't Set Audio Session Category: \(error)")
    }
    AVAudioSessionCategoryOptions.MixWithOthers
    do
    {
        try audioSession.setMode(AVAudioSessionModeVideoRecording)
    }
    catch
    {
        print("Can't Set Audio Session Mode: \(error)")
    }
    // Start Session
    do
    {
        try audioSession.setActive(true)
    }
    catch
    {
        print("Can't Start Audio Session: \(error)")
    }

Now for the video recording. You will use AVCaptureSession. Declare the following as global variables:

let captureSession = AVCaptureSession()
var currentDevice: AVCaptureDevice?
var videoFileOutput: AVCaptureMovieFileOutput?
var cameraPreviewLayer: AVCaptureVideoPreviewLayer?

Then configure the session in viewDidLoad. Note: The video preview is in a container and the entire video related code is in a different view controller but just using a view instead of a container should work just as fine:

// Preset For 720p
captureSession.sessionPreset = AVCaptureSessionPreset1280x720

// Get Available Devices Capable Of Recording Video
let devices = AVCaptureDevice.devicesWithMediaType(AVMediaTypeVideo) as! [AVCaptureDevice]

// Get Back Camera
for device in devices
{
    if device.position == AVCaptureDevicePosition.Back
    {
        currentDevice = device
    }
}
let camera = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)

// Audio Input
let audioInputDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeAudio)

do
{
    let audioInput = try AVCaptureDeviceInput(device: audioInputDevice)

    // Add Audio Input
    if captureSession.canAddInput(audioInput)
    {
        captureSession.addInput(audioInput)
    }
    else
    {
        NSLog("Can't Add Audio Input")
    }
}
catch let error
{
    NSLog("Error Getting Input Device: \(error)")
}

// Video Input
let videoInput: AVCaptureDeviceInput
do
{
    videoInput = try AVCaptureDeviceInput(device: camera)

    // Add Video Input
    if captureSession.canAddInput(videoInput)
    {
        captureSession.addInput(videoInput)
    }
    else
    {
        NSLog("ERROR: Can't add video input")
    }
}
catch let error
{
    NSLog("ERROR: Getting input device: \(error)")
}

// Video Output
videoFileOutput = AVCaptureMovieFileOutput()
captureSession.addOutput(videoFileOutput)

// Show Camera Preview
cameraPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
view.layer.addSublayer(cameraPreviewLayer!)
cameraPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
let width = view.bounds.width
cameraPreviewLayer?.frame = CGRectMake(0, 0, width, width)

// Bring Record Button To Front & Start Session
view.bringSubviewToFront(recordButton)
captureSession.startRunning()
print(captureSession.inputs)

Then you create an @IBAction for handling when the user presses the record button (I just used a simple button which I made red and round):

@IBAction func capture(sender: AnyObject) {
    do
    {
        initialOutputURL = try NSFileManager.defaultManager().URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: true).URLByAppendingPathComponent("output").URLByAppendingPathExtension("mov")
    }
    catch
    {
        print(error)
    }
    if !isRecording
    {
        isRecording = true

        UIView.animateWithDuration(0.5, delay: 0.0, options: [.Repeat, .Autoreverse, .AllowUserInteraction], animations: { () -> Void in
            self.recordButton.transform = CGAffineTransformMakeScale(0.75, 0.75)
            }, completion: nil)

        videoFileOutput?.startRecordingToOutputFileURL(initialOutputURL, recordingDelegate: self)
    }
    else
    {
        isRecording = false

        UIView.animateWithDuration(0.5, delay: 0, options: [], animations: { () -> Void in
            self.recordButton.transform = CGAffineTransformMakeScale(1.0, 1.0)
            }, completion: nil)
        recordButton.layer.removeAllAnimations()
        videoFileOutput?.stopRecording()
    }
}

Then all there is left for you to do is to save the video to (presumably) the camera roll. But I won't include that. You must put in some effort yourselves. (hint: UISaveVideoAtPathToSavedPhotosAlbum)

So that's it folks. That's how you use AVFoundation to record a video and play music from the library at the same time.

Woodcut

Lawrence413, thanks so much, this was VERY helpful!! I have one question... is it possible to stop the microphone from recording. I just want the video with the audio from the file. This is done in various apps, including TikTok, Instagram and others. I have tried many things but cannot figure that out. Any help is appreciated!! – Periodical

I'm not sure but I think you can't. It's probably system audio and I don't think developers have access to that. I believe the way Instagram works is it merges the video with a song but you can't record. I don't know about TikTok. Even Apple's screen recording app doesn't record system audio so it should be a solid indicator that you can't do it. – Woodcut

actually it does record system audio! and it is possible! – Madrigal

@Periodical hi, was you able how to figure out or did you find any links that explain how to stop the mic but get the the audio and video together? – Phelips

@KevWats I'm trying to tap into the system audio output, just like Instagram does. How can I achieve that ? – Demarche

Answer 2

Once you set the AVAudioSession just like below, it'd work well.

try? AVAudioSession.sharedInstance().setCategory(AVAudioSession.Category.playAndRecord, mode: AVAudioSession.Mode.videoRecording, options: AVAudioSession.CategoryOptions.mixWithOthers)

Anelace

Any other hint. I got audio for some seconds of recording if I play two files one by one which is being recorded, the recording file ends up with no audio in it. Please help me – Miley