解决jeston tx2板载相机open_cam_onboard()无法打开问题

nvidia官方论坛原解决问题地址：

https://devtalk.nvidia.com/default/topic/1043623/jetson-agx-xavier/on-board-cam

错误代码：

def open_cam_onboard(width, height):
    # On versions of L4T prior to 28.1, add 'flip-method=2' into gst_str
    gst_str = ('nvcamerasrc ! '
               'video/x-raw(memory:NVMM), '
               'width=(int)2592, height=(int)1458, '
               'format=(string)I420, framerate=(fraction)30/1 ! '
               'nvvidconv ! '
               'video/x-raw, width=(int){}, height=(int){}, '
               'format=(string)BGRx ! '
               'videoconvert ! appsink').format(width, height)
    return cv2.VideoCapture(gst_str, cv2.CAP_GSTREAMER)

修改为：

def open_cam_onboard(width, height):
    gst_str = ('nvarguscamerasrc ! '
               'video/x-raw(memory:NVMM), '
               'width=(int)2592, height=(int)1458, '
               'format=(string)NV12, framerate=(fraction)30/1 ! '
               'nvvidconv flip-method=2 ! '
               'video/x-raw, width=(int){}, height=(int){}, '
               'format=(string)BGRx ! '
               'videoconvert ! appsink').format(width, height)
    return cv2.VideoCapture(gst_str, cv2.CAP_GSTREAMER)