title: VPIO AUAudioUnit's 3A processing not stop at RemoteIO mode on iOS 14 device
body: <p>I found that in iOS 14+ device, after creating and running an AudioUnit in VPIO mode(with 3A processing), when I recreate my AudioUnit with RemoteIO mode, the 3A processing seems will remain working, which will make my ear loopback feature sounds discontinuous.</p>
  <p>And I found a tricky way to avoid this: before creating AudioUnit, set the PreferredInput to BuiltInMic for AudioSession at first......So weird.</p>
  <p>I uploaded my demo to Github: <a href="https://github.com/PandaraWen/AudioUnit_BugReport" rel="nofollow noreferrer">https://github.com/PandaraWen/AudioUnit_BugReport</a></p>
  <ol>
  <li>Build and run de demo in Xcode 12 on iOS 14 device, and plug in EarPods;</li>
  <li>Turn the &quot;Loopback&quot; switcher on;</li>
  <li>Click the &quot;AU-RemoteIO&quot; button, and say &quot;Ah~~~~~~~&quot;, you will hear your normal voice from EarPods;</li>
  <li>Click the &quot;AU-VPIO&quot; button, and say &quot;Ah~~~~~~~&quot;, you will hear your voice from EarPods discontinuously, that is because AEC I think;</li>
  <li>Click the &quot;AU-RemoteIO&quot; button again, and say &quot;Ah~~~~~~~&quot;, the bug occurs! You will hear your discontinuous and low voice! THAT IS ABSOLUTELY ABNORMAL!!!!!</li>
  <li>Turn the &quot;Should Set to build in mic&quot; switch on, and click the &quot;AU-RemoteIO&quot; button again, you will hear your normal voice from EarPods again.</li>
  </ol>
  <p>Finally, I found that the &quot;BuildInMic tricky way&quot; would cost some additional time, which would do hurt to user experience, so I hope that this problem can be fixed completely!!!!</p>