title: Multiple VideoCapture on one camera
body: <p>I might have more than one VideoCapture for a Camera. Unfortunately sometimes the connection to the camera seems to get terminated. </p>
  
  <p>Example:</p>
  
  <pre><code>Mat img;
  VideoCapture v1(0);
  v1.read(img);      //img is a valid picture
  VideoCapture v2(0);
  v1.read(img);      //img is a valid picture
  v2.read(img);      //img is a valid picture
  v2 = v1;
  v2.read(img);      //img is not a valid picture. Connection seems to be closed
  </code></pre>
  
  <p>Is this correct behaviour, or is it a bug in OpenCV?</p>
  
  <p>Is there a way to check if a particular devicenumber is already open and get the responsible class?</p>
  
  <p>Pseudocode:</p>
  
  <pre><code>Mat img;
  VideoCapture v1(0);
  VideoCapture v2 = alreadyOpen(0);
  
  alreadyOpen(0){
      if(VideoCapture(0).isOpen()){ //how do i check that
          return "v1"               //how do i know where v1 is
      }else{
          return VideoCapture(0);
      }
  }
  </code></pre>