title: Read H.265 and VP9 frame?
body: <p>I'm trying to compare 3 videos that are encoded by H.264, H.265, and VP9. 
  All of them are made by a same YUV video.</p>
  
  <p>I want to use OpenCV's function to read each frame of the video and do some comparison:</p>
  
  <pre><code>VideoCapture vCap1, vCap2, vCap3;
  vCap1.open("h264.mp4");
  vCap2.open("h265.mp4");
  vCap3.open("vp9.webm");
  Mat frame1, frame2, frame3;
  
  while (vCap1.read(frame1) &amp;&amp; vCap2.read(frame2) &amp;&amp; vCap3.read(frame3))
  {
      //do something
  }
  </code></pre>
  
  <p>The <code>vCap1</code> opened successfully, but <code>vCap2</code> and <code>vCap3</code> won't open.
  Did I miss something to include to make it work?</p>
  
  <p>Or OpenCV even not support the other 2 formats?</p>