How to play audio in the background using AVFoundation

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Swift version: 5.10

Playing audio in the background allows your app to continue audio playback even when the user switches to another app or locks their device. This is essential for apps like music players, podcast apps, or meditation apps.

Prerequisites

To enable background audio playback, you need to:

1. Configure your Info.plist file.

2. Set up an AVAudioSession to support background playback.

3. Use AVPlayer or AVAudioPlayer for audio playback.

Step 1: Enable Background Audio in Info.plist

Open your Info.plist file and add the following key:

• UIBackgroundModes → audio

This tells iOS that your app intends to play audio in the background.

Step 2: Configure AVAudioSession for Background Playback

Before playing any audio, you must set up AVAudioSession to allow background playback.


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import AVFoundation

func setupAudioSession() {
    do {
        let audioSession = AVAudioSession.sharedInstance()
        try audioSession.setCategory(.playback, mode: .default, options: [])
        try audioSession.setActive(true)
        print("Audio session configured for background playback.")
    } catch {
        print("Failed to set up audio session: \(error.localizedDescription)")
    }
}

How it works:

• setCategory(.playback) allows audio playback in the background.

• setActive(true) activates the session.

Make sure to call setupAudioSession() in your AppDelegate or before playing audio.

Step 3: Play Audio in the Background

Now, you can play an audio file using AVPlayer or AVAudioPlayer.

Using AVPlayer for Streaming Audio


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import AVFoundation

var player: AVPlayer?

func playAudio() {
    guard let url = URL(string: "https://www.example.com/audio.mp3") else { return }
    
    player = AVPlayer(url: url)
    player?.play()
}

Using AVAudioPlayer for Local Files


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import AVFoundation

var audioPlayer: AVAudioPlayer?

func playLocalAudio() {
    guard let path = Bundle.main.path(forResource: "audio", ofType: "mp3") else { return }
    let url = URL(fileURLWithPath: path)
    
    do {
        audioPlayer = try AVAudioPlayer(contentsOf: url)
        audioPlayer?.prepareToPlay()
        audioPlayer?.play()
    } catch {
        print("Error playing audio: \(error.localizedDescription)")
    }
}

How it works:

• AVPlayer is great for streaming remote audio files.

• AVAudioPlayer is better for playing local files.

Step 4: Handle Audio Interruptions (Phone Calls, Siri, etc.)

To ensure smooth playback, handle interruptions like incoming phone calls.


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NotificationCenter.default.addObserver(self,
    selector: #selector(handleInterruption),
    name: AVAudioSession.interruptionNotification,
    object: nil)

@objc func handleInterruption(notification: Notification) {
    guard let userInfo = notification.userInfo,
          let typeValue = userInfo[AVAudioSessionInterruptionTypeKey] as? UInt,
          let type = AVAudioSession.InterruptionType(rawValue: typeValue) else { return }
    
    if type == .began {
        print("Audio interrupted")
        player?.pause()
    } else if type == .ended {
        print("Audio interruption ended")
        try? AVAudioSession.sharedInstance().setActive(true)
        player?.play()
    }
}

How it works:

• Pauses audio when interrupted (e.g., by a phone call).

• Resumes playback when the interruption ends.

Conclusion

By following these steps, your app can play audio in the background:

  • Enable background audio in Info.plist
  • Configure AVAudioSession for playback
  • Use AVPlayer for streaming or AVAudioPlayer for local files
  • Handle audio interruptions properly
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