title: OpenCV VideoCapture error: VIDIOC_REQBUFS: Inappropriate ioctl for device
body: <p>I have been trying to read videos from a file in Java using OpenCV. I am running OpenCV 4.0.0 on Ubuntu. Currently I have been trying to do so as follows: <br><br>
  <code>VideoCapture videoCapture = new VideoCapture("/home/gkammer/Downloads/test.mp4");</code> <br><br>
  However, this is giving me the error message <code>VIDIOC_REQBUFS: Inappropriate ioctl for device</code>.<br><br>
  I have already tried rebuilding OpenCV with FFMPEG like many similar questions recommend, but I still get the error. When I ran cmake this was the relevant output: <br><br>
  <code>Video I/O:
  DC1394:                      YES (ver 2.2.5)
  FFMPEG:                      YES
  avcodec:                   YES (ver 57.107.100)
  avformat:                  YES (ver 57.83.100)
  avutil:                    YES (ver 55.78.100)
  swscale:                   YES (ver 4.8.100)
  avresample:                YES (ver 3.7.0)
  GStreamer:                   NO
  v4l/v4l2:                    linux/videodev2.h</code> <br><br>
  Any suggestions for how to resolve this would be appreciated.</p>