title: OpenCV VideoCapture can't run with 3 cameras
body: <p>I am running this class function in loop and plotting the return image at the same time. However, if I have more than 2 cameras this does not seem to work.
  I have this error (continuously):</p>
  <pre><code>CvCapture_MSMF::grabFrame videoio(MSMF): can't grab frame. Error: -2147483638
  </code></pre>
  <pre><code>def grab_frame(self):
      image = []
      timestamp = []
      for i in range(0, len(self.devs)):
          cap = self.cams[i]
          ret, frame = cap.read()
          if ret:
              timestamp.extend([time.time()-self.def_time])
              image.extend(frame)
      return timestamp, image
  </code></pre>