openCV error in TX2, GStreamer: unable to start pipeline

Hi, i want to use webcam camera for my face recognition in TX2

when i run my face recognition script, i got these following error:

$ python3 face_rec_jetson.py 

Opening in O_NONBLOCKING MODE 
VIDEOIO ERROR: libv4l unable convert to requested pixfmt
Opening in BLOCKING MODE 
VIDEOIO ERROR: libv4l unable to ioctl VIDIOCSPICT

OpenCV Error: Unspecified error (GStreamer: unable to start pipeline
) in cvCaptureFromCAM_GStreamer, file /home/cognixy/src/opencv-3.4.0/modules/videoio/src/cap_gstreamer.cpp, line 890
VIDEOIO(cvCreateCapture_GStreamer(CV_CAP_GSTREAMER_V4L2, reinterpret_cast<char *>(index))): raised OpenCV exception:

/home/cognixy/src/opencv-3.4.0/modules/videoio/src/cap_gstreamer.cpp:890: error: (-2) GStreamer: unable to start pipeline
 in function cvCaptureFromCAM_GStreamer

how can i resolved this issue? any answer would be appreciated it. Thanks !

This looks like your camera is unable to be initiated by opencv due to format.
Please check what is pipeline that script "face_rec_jetson.py " tries to launch.