OpenCV Error on Nvidia Jetson Orin Nano When Using CTRL+Z

Issue Overview

Users have reported an issue when running OpenCV applications on the Nvidia Jetson Orin Nano Dev board, specifically when using the CTRL+Z command to stop their programs. The symptoms include:

• An error message indicating a failure to create a CaptureSession when attempting to re-run a script after it has been stopped with CTRL+Z.

• The error output includes:

  Error generated. /dvs/git/dirty/git-master_linux/multimedia/nvgstreamer/gst-nvarguscamera/gstnvarguscamerasrc.cpp, execute:762 Failed to create CaptureSession
  [ WARN:0] global ../modules/videoio/src/cap_gstreamer.cpp (935) open OpenCV | GStreamer warning: Cannot query video position: status=0, value=-1, duration=-1
  cv2.error: OpenCV(4.2.0) ../modules/highgui/src/window.cpp:376: error: (-215:Assertion failed) size.width>0 && size.height>0 in function 'imshow'
  

• The issue occurs consistently when the program is stopped using CTRL+Z but does not occur when using CTRL+C or manually closing the OpenCV window.

The context of this problem arises during the execution of a Python script that utilizes the Arducam IMX477 camera through OpenCV, specifically in the file CSI-Camera/simple_camera.py. Users have verified that their setup supports GStreamer and runs smoothly under normal circumstances.

Possible Causes

Several potential causes for this issue have been identified:

• Software Bugs or Conflicts: The behavior of CTRL+Z may be causing the application to enter a suspended state rather than terminating properly, leading to conflicts when trying to access camera resources again.

• Driver Issues: The nvargus-daemon service may not be handling suspended processes correctly, which can lead to resource locking or failure in reinitializing the camera session.

• Configuration Errors: There might be specific configurations in the GStreamer pipeline or OpenCV settings that are not compatible with how processes are suspended and resumed.

• User Errors: Using CTRL+Z may not be an appropriate method for stopping processes that rely on continuous resource access, such as camera feeds.

Troubleshooting Steps, Solutions & Fixes

To address the issue, users can follow these troubleshooting steps and potential solutions:

1. Restart the nvargus-daemon Service:

   • If you encounter the error after using CTRL+Z, restart the nvargus-daemon service:

     sudo systemctl restart nvargus-daemon.service
     

   • This has been reported as a temporary fix that allows users to run their scripts again.

2. Use CTRL+C Instead:

   • Instead of using CTRL+Z to stop your program, use CTRL+C. This method properly interrupts the process and allows for normal re-execution without encountering errors.

3. Close OpenCV Windows Manually:

   • If you need to stop your program, consider manually closing any OpenCV windows before terminating the script. This action helps ensure that resources are released properly.

4. Upgrade Jetpack Version:

   • Ensure you are using the latest version of Jetpack (5.1.3 or later). Some users have reported issues with earlier versions (5.1.1) that could affect camera detection and functionality.
   • To check your current Jetpack version, you can use:

     dpkg -l | grep jetpack
     

   • Follow Nvidia’s official documentation for upgrading Jetpack if necessary.

5. Check for Software Updates:

   • Regularly check for updates to OpenCV and GStreamer libraries as they may contain bug fixes relevant to this issue.

6. Review Resource Management Practices:

   • Familiarize yourself with best practices for managing camera resources in your applications to avoid conflicts caused by improper termination methods.

7. Documentation and Community Support:

   • Refer to Nvidia’s developer forums and documentation for additional insights and updates regarding known issues with specific versions of Jetpack and related libraries.

By following these steps, users should be able to mitigate or resolve issues encountered when stopping their OpenCV applications with CTRL+Z on the Nvidia Jetson Orin Nano Dev board. Further investigation may be required if problems persist after implementing these solutions.