libavdevice/v4l2.c:183: error: Uninitialized Value
  The value read from err was never initialized.

libavdevice/v4l2.c:183:9: 
181.         close(fd);
182. 
183.         return AVERROR(err);
             ^
184.     }
185.     if ((cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) == 0) {
