title: Access both back and front cameras simultaneously
body: <p>What I'm trying to achieve: access both front and back cameras at the same time.</p>
  
  <p>What I've researched: I know android camera API doesn't give support for using multiple instances of the Camera and you have to release a camera before using the other one. I've read tens of questions about this, I know on some devices it's possible (like Samsung S4, or other new devices from them). 
  I've also found out that it's possible to have access to both of them in Android KitKat on SOME devices.
  I also know that on api >= 21, using the camera2 API, it's possible to access both of them at the same time because it's thread safe.</p>
  
  <p>What I've got so far: implementation for accessing the cameras one at the time in order to provide a picture-in-picture.</p>
  
  <p>I know it's not possible to implement dual simultaneously camera on every device, I just want a way to make it available to some devices. </p>
  
  <p>How can I test to see if the device is capable of accessing both of them?</p>
  
  <p>I've also searched for a library that can allow me such thing, but I didn't find anything. Is there such a library?</p>
  
  <p>I would like to make this feature available for as many devices as possible, and for the others, I'll leave the current state (one by one) of the feature.</p>
  
  <p>Can anyone please help me, at least with some pieces of advice?</p>
  
  <p>Thanks
  !</p>