Access TX2 onboard camera from host: Cannot connect to X server

Robotics & Edge Computing Jetson & Embedded Systems Jetson TX2
1

Hello,

I’m trying to use NSight on a host machine running Ubuntu 16.04 to access the onboard camera of the Jetson TX2 developer module. I’m also using OpenCV 3.4 with GStreamer enabled. I have my host machine connected via ethernet to the TX2. I can successfully run the cross-compilation example at https://devblogs.nvidia.com/cuda-jetson-nvidia-nsight-eclipse-edition/.

Now I want to try and control the camera. From the host, I can ssh into the device and run the following command from the terminal fine.

gst-launch-1.0 nvcamerasrc ! nvvidconv ! xvimagesink

A video image appears on the host. So then I wrote the simple program below in NSight:

int main()
{
   std::cout << cv::getBuildInformation() << std::endl;
   cv::Mat img;

   std::string gst = "nvcamerasrc ! video/x-raw(memory:NVMM), width=(int)640, height=(int)480, format=(string)I420, framerate=(fraction)30/1 ! nvvidconv flip-method=0 ! video/x-raw, format=(string)I420 ! videoconvert ! video/x-raw, format(string)BGR ! appsink";

   cv::VideoCapture input(gst);

   for (;;)
   {
      if (!input.read(img))
         break;

      cv::imshow("img", img);
      char c = cv::waitKey(30);
      if (c == ' ')
         break;
   }

}

I can run this directly on the device itself and it works. When I try to compile it on the host and run it remotely, it seems like it starts to access the camera because I get the message

“NvCameraSrc: Trying to Set Default Camera Resolution. Selected sensorModeIndex = 1 WxH = 2592x1458 FrameRate = 30.000000 …”

But then I get a “cannot connect to X server” message immediately after. Looking around, it seems like it might have to do with X forwarding not being enabled when Nsight connects remotely to the device. But I’m not sure how to resolve this. Can anyone help me out? Thanks in advance.

2

You may try to check DISPLAY environment variable (you may use getenv/setenv in your app).
If you want to display on a local monitor attached to Jetson you may use DISPLAY=:0. If you want display on your host, you may use DISPLAY=$HOSTIP:0 where $HOSTIP is the IP of your host. You may have to allow external access to your host X server with command xhost.

3

Yes, that was it! I’m now able to display the video on a local monitor. Thank you!