That’s because normal capture device type is V4L2_BUF_TYPE_VIDEO_CAPTURE，but rockchip rkisp type is V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE, if you want to use fswebcam or other software, you may should add libv4l2 library, and use v4l2_ioctl/v4l2_open/v4l2_close instead of ioctl/open/close