No device connected(imshow example in wrappers)

[Rhymakers]

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Required Info
Camera Model	{ L515 }
Firmware Version	(1.5.8.1)
Operating System & Version	{ubuntu 22.04
Kernel Version (Linux Only)	(6.5.0-41-generic)
Platform	PC
SDK Version	{2.54.2}
Language	{C++, opnecv }
Segment	{Robot }

Issue Description

When I create a build directory to run the imshow example, run cmake .., make, and then run the ./imshow command, the following error appears.

1. It is captured well in realsense-viewer, but what is the reason?

2. Are there any examples that can be used when using multiple l515s?

3. At first, I couldn't get realsense, so I modified the cmakelist as shown below. Is this correct?

[MartyG-RealSense]

Hi @Rhymakers The RealSense OpenCV wrapper's example programs are built by building the RealSense SDK from source code with CMake and including the flag -DBUILD_CV_EXAMPLES=TRUE in the CMake build instruction.

Are you using the imshow code in a new project that you have created, please? If you are then doing so may result in necessary linkages to the librealsense library being absent from the CMakeLists.txt file.

A standalone C++ Getting Started project at the link below uses the same script as the rs-hello-realsense C++ example program but has a more complex CMakeLists.txt file than rs-hello-realsense. Reviewing the additional linkages in the Getting Started project's CMakeLists.txt may be helpful for you if you are attempting to get imshow's code working in a new project.

https://github.com/zivsha/librealsense/tree/getting_started_example/examples/getting-started

https://github.com/zivsha/librealsense/blob/getting_started_example/examples/getting-started/CMakeLists.txt

In regard to a multiple camera project, the RealSense SDK's rs-multicam C++ example should meet your needs. If you have built the SDK with example programs included then there should be a pre-built executable version of rs-multicam in your usr/local/bin Ubuntu folder.

https://github.com/IntelRealSense/librealsense/tree/master/examples/multicam

[Rhymakers]

Thank you for your response. When I run rs-multicam in usr/local/bin, it works, or before it works, my laptop fails. I'm connecting several things, and I'm using a powered usb hub. This is even true for realsens-veiwer. The computer doesn't work when I do the same version in Windows, but in Ubuntu my computer stops while running a viewr or multicam example. Why is that?

[MartyG-RealSense]

Does it make a difference if you launch Ubuntu programs in sudo admin permissions mode, such as sudo realsense-viewer and sudo rs-multicam

[Rhymakers]

Unfortunately, it's the same. My laptop is Lenovo Legion Slim 7i 16 Gen 8.

[MartyG-RealSense]

What other devices are connected to your laptop, please? Are any of them wireless USB devices such as a wireless mouse? If you do have wireless devices, does the computer behave better if they are unplugged?

[Rhymakers]

Unfortunately, it's the same. but It works well realsense-viewer in Windows.

[MartyG-RealSense]

Which OpenCV version are you using, please? The RealSense OpenCV wrapper's example programs such as imshow were designed for use with OpenCV 3.4.

[Rhymakers]

Well, first of all, it works by lowering the sdk version to 2.53.1! In the 2.54.2 version, the example l515 example processing code doesn't work. Thank you for your help.

[MartyG-RealSense]

You are very welcome. Thanks very much for the update. :)