title: AVAudioSessionManager availableInputs "Unknown selected data source for port iPhone Microphone"
body: <p>I've noticed this error in my console log for a while. Though it does not affect the execution of my application, I find it really annoying. Thus, I started to trace where this error came from. It turns out when I call availableInputs</p>
  
  <pre><code>NSArray *inputs = [[AVAudioSession sharedInstance] availableInputs];
  </code></pre>
  
  <p>It will give me the log message:</p>
  
  <pre><code>ERROR:     [0x3d61318c] AVAudioSessionPortImpl.mm:50: ValidateRequiredFields: Unknown selected data source for Port iPhone Microphone (type: MicrophoneBuiltIn)
  </code></pre>
  
  <p>I tried to print out the inputs.. </p>
  
  <pre><code>Printing description of inputs:
  &lt;__NSArrayI 0x188c4610&gt;(
  &lt;AVAudioSessionPortDescription: 0x188c4580, type = MicrophoneBuiltIn; name = iPhone Microphone; UID = Built-In Microphone; selectedDataSource = (null)&gt;,
  &lt;AVAudioSessionPortDescription: 0x18835d90, type = BluetoothHFP; name = Valore-BTi22; UID = 00:23:01:10:38:77-tsco; selectedDataSource = (null)&gt;
  </code></pre>
  
  <p>So selectedDataSource is (null). I don't know what should I do to make it not null? iPhone Microphone is a built-in input... I suppose it's set by Apple already?</p>