title: AudioKit 4.6 no sound
body: <p>I've been developing an iOS app the last year with AudioKit-4.0.4.  Now that I have the app working I thought it was time to update my AudioKit library to a newer version.</p>
  
  <p>I have downloaded AudioKit-4.6 and merely swapped out the older "AudioKit For iOS.xcodeproj" in my XCode project with the new version.  Everything built just fine, except for AudioKit.start() now has to be wrapped with a "try".  No other changes were needed to get a successful build.</p>
  
  <p>But now my app does not produce any sound.</p>
  
  <p>Here is my code for starting AudioKit:</p>
  
  <pre><code>AKSettings.audioInputEnabled = true
  mix = AKMixer()
  
  AKSettings.playbackWhileMuted = true
  AudioKit.output = mix
  
  do {
      try AudioKit.start()
      print("----- AudioKit Started -----")
  } catch {
      print("Error AudioKit.start")
  }
  
  do {
      try AKSettings.setSession(category: AKSettings.SessionCategory.playback, with: AVAudioSession.CategoryOptions.mixWithOthers)
  } catch {
      print("Error setSession mixWithOthers")
  }
  </code></pre>
  
  <p>In addition to no audio, I am seeing these repeated messages in the console log:</p>
  
  <pre><code>----- AudioKit Started -----
  2019-04-08 15:03:45.709359-0700 HarmonicChimes[2708:2212995] [avas] AVAudioSessionPortImpl.mm:56:ValidateRequiredFields: Unknown selected data source for Port Speaker (type: Speaker)
  2019-04-08 15:03:45.711236-0700 HarmonicChimes[2708:2212995] [avas] AVAudioSessionPortImpl.mm:56:ValidateRequiredFields: Unknown selected data source for Port Speaker (type: Speaker)
  </code></pre>
  
  <p>These AV messages show on my iOS 12 device but not iOS 11 and older.  Some googling on the net indicates these AV messages are Apple's problem, not AudioKit, but I was not seeing them when running with AudioKit 4.0.4.</p>
  
  <p>The no sound problem is a show stopper! I have searched for "AudioKit no sound" but not found anything that makes sense.</p>
  
  <p>It would appear that 4.6 is not just a simple plug-in replacement for 4.0?  Is there a new AudioKit api to get the sound started?  My app's plist and capabilities are set to allow for background operation, could that have something to do with this?</p>
  
  <p><em>(I am using XCode 10.1, macOS 10.13.6, and iOS 12.)</em></p>