Qv4l2 failed to open the video device

[Youke]

hi nvidia,
I used AGX orin device, jp6.0 for testing, inserted a USB camera, installed qv4l2 using apt, and executed qv4l2 -d /dev/video0 to open it but failed.
I can open the image using gst-launch-1.0, which means the USB camera is fine.
Please help me troubleshoot

[DaneLLL]

Hi,
Please try

Jetson AGX Orin FAQ
Q: Cannot run Cheese app to launch a USB camera

[Youke]

Hi,
After I delete the corresponding file according to error processing, qv4l2 still cannot be used, as shown in the following figure.

[DaneLLL]

Hi,
Please share how to install qv4l2 and the command. We will set up developer kit and check.

[Youke]

hi，
The installation command is as follows
sudo apt-get update
sudo apt-get install qv4l2

[DaneLLL]

Hi,
It looks like it fails in initializing display:

(gdb) run
Starting program: /usr/bin/qv4l2 -d /dev/video0
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/aarch64-linux-gnu/libthread_db.so.1".
[New Thread 0xfffff29df080 (LWP 65821)]
[New Thread 0xfffff201f080 (LWP 65822)]
[New Thread 0xffffe8e8f080 (LWP 65823)]
Opening in O_NONBLOCKING MODE
[Thread 0xffffe8e8f080 (LWP 65823) exited]

Thread 1 "qv4l2" received signal SIGSEGV, Segmentation fault.
0x0000fffff58c714c in glXGetCurrentContext () from /lib/aarch64-linux-gnu/libGLX.so.0

Does the binary have dependency to QT? By default Ubunutu OS is X11. Not sure if the binary can work in the environment.

[Youke]

hi，
Yes, you need to run qv4l2 on the Jetson desktop terminal.
We tested the default availability of JP5.1.2

[DaneLLL]

Hi,
Please run the command with -R:

$ DISPLAY=:0 qv4l2 -R -d /dev/video0

[Youke]

Hi，
I used the official backplane to test that DISPLAY=: 0 qv4l2- R - d/dev/video0 (video0 is a USB camera) can correctly display images;
Now use our customized backplane to test DISPLAY=: 0 qv4l2- R - d/dev/video8 (video8 is a USB camera). The error is reported as follows:

Test qv4l2- R - d/dev/video8, and it can be opened correctly to display the image;
Test qv4l2- R - d/dev/video0, and it can be opened correctly, but the image cannot be displayed (video0 is the camera we registered through serial deserialization, which can be opened through gst launch 1.0 to see the image);
Do you have any other suggestions? Can we/dev/video0 use qv4l2 to display images?

[DaneLLL]

Hi,
So video0 and video8 are both USB cameras but video0 cannot be launched in qv4l2?

[Youke]

hi，
Video0 is our registered camera device. It is connected to a gmal2 camera and can be opened through gst-launch-1.0
Video8 is a usb camera

[DaneLLL]

Hi,
Please also remove the lib for a try:

$ sudo rm /usr/lib/aarch64-linux-gnu/tegra/libv4l2_nvargus.so

[Youke]

hi,
After I deleted the library as required, the result remains unchanged.
Video 0 cannot open the image using qv4l2

[DaneLLL]

Hi,
OK. We don’t have further thoughts currently. Would see if other users can share experience. Probably you can check the source code of qv4l2.

And you may consider use v4l2src in gstreamer or refer to 12_camera_v4l2_cuda sample, to develop your use-case.

[Youke]

hi，
OK, thank you, I will test it again by myself,
We have asked nvidia to check again. Thank.

[DaneLLL]

Hi,
Jetpack 6.1 is released. Please upgrade and give it a try. The release has update in libv4l2_nvargus.so and it might be helpful for this.

[Youke]

hi，
Now we are still using jp6.0. Later, I will switch to jp6.1 for testing. If there is any problem, I will give feedback again. Thank you