Per camera two ‘video’ items added to /sys/class/video4linux directory

Issue Overview

Users are experiencing confusion regarding the appearance of multiple video device entries in the /sys/class/video4linux directory when connecting cameras to the Nvidia Jetson Orin Nano Dev board. Specifically, when one camera is connected, two entries (video0 and video1) are created, and when a second camera is added, additional entries (video2 and video3) appear.

This issue arises during the setup phase when users attempt to access these cameras through OpenCV. The primary symptom reported is uncertainty about which device identifiers to use for opening the cameras. Users are unsure whether they should use open(0) for the first camera and open(2) for the second, leading to potential misconfigurations in their applications.

The issue seems consistent across different setups, indicating a common behavior rather than an isolated defect. This can impact user experience by complicating camera access in software applications, especially for those new to using multiple cameras on this platform.

Possible Causes

• Hardware Configuration: The Nvidia Jetson Orin Nano Dev board may be designed to recognize multiple video streams from a single camera, resulting in multiple device entries.

• Driver Behavior: The drivers used for the cameras may inherently create multiple device nodes for each camera connected, which is a standard behavior rather than an error.

• User Misunderstanding: Users may not be aware that multiple video entries can be normal and expected behavior when connecting multiple cameras.

Troubleshooting Steps, Solutions & Fixes

1. Understanding Device Entries:

   • Check the /sys/class/video4linux directory after connecting each camera.
   • Verify that the number of video entries corresponds with the number of cameras connected.

2. Testing Camera Access:

   • Use OpenCV commands to test access to each video device:

     import cv2
     
     # Test first camera
     cap1 = cv2.VideoCapture(0)
     if not cap1.isOpened():
         print("Cannot open first camera")
     
     # Test second camera
     cap2 = cv2.VideoCapture(2)
     if not cap2.isOpened():
         print("Cannot open second camera")
     

3. Confirming Behavior:

   • If both cameras are accessible without errors, this confirms that the multiple entries are functioning as intended.
   • If issues persist in accessing either camera, consider checking connections or testing with different USB ports or cables.

4. Consulting Documentation:

   • Review Nvidia’s official documentation regarding camera support on the Jetson Orin Nano Dev board for any specific notes on multi-camera setups.

5. Best Practices:

   • Ensure that all drivers are up-to-date to avoid any compatibility issues.
   • Regularly check for firmware updates that may enhance device recognition or performance.

6. Further Investigation:

   • If users continue to experience issues or have questions about device management, consider engaging with community forums or Nvidia support for more tailored assistance.

By following these steps, users can better understand and manage multiple video devices on their Nvidia Jetson Orin Nano Dev board, ensuring smoother operation of their applications using OpenCV.