title: Are there any Android Devices or any method can open front and back camera at the same time?
body: <p>For some reason, I need to open front and back cameras at the same time and I tried the new Camera2 API and get ERROR_MAX_CAMERAS_IN_USE error when I tried to open the second Camera on my Nexus 4. And  the document shows it may depend on the devices.</p>
  
  <p>So are there any devices can reach this by the public API? Or can any method like OpenCV can do it?</p>