title: AVAudioEngine crash while connecting mic to mainMixerNode
body: <p>Сan't understand from documentation how to make it correctly and how to conform all input / output formats.</p>
  <pre><code>engine.connect(engine.inputNode, to: engine.mainMixerNode, format: engine.inputNode.inputFormat(forBus: 0))
  </code></pre>
  <pre><code>required condition is false: IsFormatSampleRateAndChannelCountValid(format)
  </code></pre>