rk3399pro无法opencv无法打开摄像头

1、rknn-toolkit的版本是1.2.1，opencv版本是3.4.1
2、代码：cap = cv2.VideoCapture(0)，之前在rknn-toolkit1.1.0的时候是可以正常使用的，但是现在出现报错：
OpenCV(3.4.1) Error: Unspecified error (GStreamer: unable to start pipeline
) in cvCaptureFromCAM_GStreamer, file /builddir/build/BUILD/opencv-3.4.1/modules/videoio/src/cap_gstreamer.cpp, line 890
VIDEOIO(cvCreateCapture_GStreamer(CV_CAP_GSTREAMER_V4L2, reinterpret_cast<char *>(index))): raised OpenCV exception:

OpenCV(3.4.1) /builddir/build/BUILD/opencv-3.4.1/modules/videoio/src/cap_gstreamer.cpp:890: error: (-2) GStreamer: unable to start pipeline
in function cvCaptureFromCAM_GStreamer

OpenCV(3.4.1) Error: Unspecified error (unicap: failed to get info for device
) in CvCapture_Unicap::initDevice, file /builddir/build/BUILD/opencv-3.4.1/modules/videoio/src/cap_unicap.cpp, line 139
VIDEOIO(cvCreateCameraCapture_Unicap(index)): raised OpenCV exception:

OpenCV(3.4.1) /builddir/build/BUILD/opencv-3.4.1/modules/videoio/src/cap_unicap.cpp:139: error: (-2) unicap: failed to get info for device
in function CvCapture_Unicap::initDevice

请问该如何解决这个问题，另外还有一个现象，就是升级了toolkit版本之后，发现每次init runtime都需要等很久，之前版本好像都挺快的