都安装了 还是如下 错误：
[toybrick@localhost LSF]$ python3 cv_test
Failed to query video capabilities: Inappropriate ioctl for device
libv4l2: error getting capabilities: Inappropriate ioctl for device
VIDEOIO ERROR: V4L: device /home/toybrick/LSF/input.mp4: Unable to query number of channels
mpi: mpp version: Without VCS info
mpp_rt: NOT found ion allocator
mpp_rt: found drm allocator
mpp: deprecated block control, use timeout control instead
warning: GStreamer: unable to query duration of stream (/builddir/build/BUILD/opencv-3.4.1/modules/videoio/src/cap_gstreamer.cpp:904)
warning: Cannot query video position: status=1 value=1 duration=-1
(/builddir/build/BUILD/opencv-3.4.1/modules/videoio/src/cap_gstreamer.cpp:952)