title: Audio session mixes with others even when its category is set to playback (Swift)?
body: <p>I am using <a href="http://audiokit.io/" rel="nofollow noreferrer">AudioKit</a> to manage the sound in my app. I am trying to show play/pause buttons on the lock screen, which requires the audio session to not be mixable with other audio sessions that may be running. To do this, I set my audio session to the category 'playback', which is not supposed to be mixable with others. Here is my method that sets this up:</p>
  
  <pre><code>private func configureAudio() {
      do {
          try AKSettings.setSession(category: .playback, with: [])
          try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback, with: [])
      } catch {
          print(error)
      }
      AKSettings.playbackWhileMuted = true;
  }
  </code></pre>
  
  <p>This works for making the audio play even when the app is not in focus, but the audio still mixes with other sessions even though it's supposedly set to 'playback'. What am I doing wrong?</p>