Add power line parameter to avoid warning in launch file

[cychitivav]

[sysrsbuild-gh]

Can one of the admins verify this patch?

[Nir-Az]

@cychitivav thanks for the PR.
Any idea why the default value to be set is 3?
And why the new is 2?

regardless, please base your PE on ros2-development branch and target it, master is the stable release branch
Thanks!

[MartyG-RealSense]

Hi @Nir-Az I just wanted to comment that the power line parameter warning in the launch log has been present for years and occurs in many users' logs but has no negative effects. Users do occasionally ask about it though out of concern that it might be a problem.

Setting number 3 is Auto. I'm not certain how it decides what the appropriate value to use is though. The other settings are Disabled (0), 50 Hz (1) and 60 Hz (2). 50 Hz is common for European regions and 60 Hz is typically used in North American regions.

The most common reason for configuring this parameter manually is to reduce noise interference on the depth image when using the camera in a location with overhead fluorescent ceiling strip lights, which generate image noise due to flickering at rates difficult to see with the human eye. Matching the power line frequency setting of the camera as closely as possible to the electrical power Hz frequency used for lights in the country the camera is located in can reduce fluorescent light noise.

Support does not to get any reports of users with fluorescent lights these days though as LED ceiling lights have become much more common and they to not produce flicker noise.

I would recommend leaving the setting on 3 (Auto) and just removing the power line frequency warning.

[Nir-Az]

@MartyG-RealSense thanks for the info, we will evaluate this soon