Concatenation Filter Analysis

[lexavtanke]

Checklist

• I've read the contribution guidelines.
• I've searched other issues and no duplicate issues were found.
• I've agreed with the maintainers that I can plan this task.

Description

There are some latency issues with point cloud concatenation in the concatenate_data filter of the pointcloud_preprocessor. We need to investigate and measure them.

We can use three types of time information for such purpose:

• Original unmodified point cloud header stamp
• Modified point cloud published_time stamp
• Rosbag stamp

We need to replace the rosbag stamp with the published_time stamp.

https://github.com/AIT-Assistive-Autonomous-Systems/ros2bag_tools this tool could be used for it.
By default, the restamp does: for all messages with headers, change the bag timestamp to their header stamp
But since the all modified point clouds share the same origin header, we need to somehow:
for published_time message types, use the published time stamps.
Then it should be perfectly visible in the rqt_bag timeline.
PublishedTime.msg

Purpose

Determine the actual timing patterns for the point cloud concatenation.

Possible approaches

Plan:

• Play the point cloud data (from AWSIM or sample-rosbag as both of them have at least 3 lidars to concat)
• Make sure localization works for distortion correction to work
• Put all lidars to the same point cloud container for the test
• Run the sensing and localization pipeline
• Publish published_time topics from the nodes in the pipeline
• Record them using rosbag (If possible, put rosbag under the point cloud container)
• Use rqt_bag to visualize the timing patterns from the bag file as on the image below
  

Definition of done

Measured timings of concatenate_data. Possible approach to speed up point cloud concatenation.

[xmfcx]

Related:

• Concatenate node algorithm didn't work the same as it described  #6832

[lexavtanke]

Concatenation has processing_time_ms debug output. It takes rougthly 50 ms to concatenate 3 point clouds according to my observations on Autoware sample_rosbag.
Here is the plot of the /sensing/lidar/concatenate_data_synchronizer/debug/processing_time_ms topic.

Y axis is processing time and X axis is a rosbag timeline.

 Now I'm working on integration published_time to concatenation node to get more clear data as previous node (ring_outlier_filter) already has it.

[xmfcx]

@tomas-pinto do you have any progress in this task?

[tomas-pinto]

@tomas-pinto do you have any progress in this task?

Unfortunately, I haven’t made much progress on the issue yet. However, I’m actively working on it and will provide an update by the end of this week.