setting MTU at launchtime

[bmegli]

In:

• https://github.com/Extend-Robotics/camera_aravis/issues/21#issuecomment-1748827392

We identified that MTU has drastic effect in high bandwidth configurations for MotionCam3D.

We want to be able to set correct MTU at launch time or auto adapt to OS network interface MTU.

[bmegli]

In:

• https://github.com/Extend-Robotics/camera_aravis/issues/25#issuecomment-1755433428

We identified that there are:

• dynamic reconfigure mtu
• rosparam mtu

Setting rosparam mtu doesn't result in change on device

[bmegli]

The sequence of rosparam vs dynamic reconfigure server init is different in this fork and origin.

Origin

Reads rosparam

• https://github.com/FraunhoferIOSB/camera_aravis/blob/1423c11a364e2d5921f89ab7e5b436376e138335/src/camera_aravis_nodelet.cpp#L293
• after inital dynamic reconfigure server setup
• before pre-setting dynamic reconfigure values from actual config
  • https://github.com/FraunhoferIOSB/camera_aravis/blob/1423c11a364e2d5921f89ab7e5b436376e138335/src/camera_aravis_nodelet.cpp#L376
• before final dynamic reconfigure server setup
  • https://github.com/FraunhoferIOSB/camera_aravis/blob/1423c11a364e2d5921f89ab7e5b436376e138335 /src/camera_aravis_nodelet.cpp#L378

The first dynamic reconfigure callback is called when setting callback function.

As a result:

• this will setup value in dynamic reconfigure config
• but will not change the MTU on device
• because value is checked against current config which matches

This fork

• loads from MTU rosparam even before intial dynamic reconfigure setup
• and dynamic reconfigure value default will overwrite rosparam value

As a result:

• rosparam value is ignored
• this doesn't matter as value will not be set on device for same reason as in origin

Bottom Line

Neither works

[bmegli]

The main problem is:

• dynamic reconfigure initial callback checking value against same preset value
  • if anything it should be checking against value read from device
  • which is real current value

[bmegli]

The secondary problems are:

• sequence between rosparam vs dynamic reconfigure
• whether rosparam should exist at all if we have dynamic reocnfigure interface

[bmegli]

The problem in the original repository is assumption:

• that mtu is not GenICam feature

• it is GenICam feature which maps to:

  • GevSCPSPacketSize (deprecated)
  • DeviceStreamChannelPacketSize (not deprecated)

• https://github.com/FraunhoferIOSB/camera_aravis/blob/1423c11a364e2d5921f89ab7e5b436376e138335/src/camera_aravis_nodelet.cpp#L291-L293

[bmegli]

So one way of solving it is:

• set MTU with genicam from rosparam value or dynamic reconfigure default
• read the value with genicam
• set it as current/reference in dynamic reconfigure

[bmegli]

In 4232487 logic for setting MTU from rosparam was fixed.

Now there is question if this rosparam should be kept at all

[bmegli]

Dynamic reconfigure works by:

• loading defaults from .cfg
• overwriting them with values from parameter server
• running the reconfigure callback with above

What breaks this behavior is camera_aravis call

• https://github.com/FraunhoferIOSB/camera_aravis/blob/1423c11a364e2d5921f89ab7e5b436376e138335/src/camera_aravis_nodelet.cpp#L376

reconfigure_server_->updateConfig(config_);

• without that no explicit loading of rosparams should be necessary

But maybe there is a reason behind above call:

• for example the config is filled from values read from device
• and those should not be reset to dynamic reconfigure + rosparam defaults

[bmegli]

reconfigure_server_->updateConfig(config_);

But maybe there is a reason behind above call:

• this seems to be the commit when it was introduced
  • https://github.com/FraunhoferIOSB/camera_aravis/commit/2a1268bf9069957473b780bec331682f49c18756#diff-5fd7e4676854a17a9a5ca198ddb95d829321a50430db9781ecbe6f6375475ad0R217
• but this is major rewrite so not much can be said about this line

[bmegli]

Ok, let's leave the fixed MTU setup from rosparam for now.

The rest is separate and general issue.