A way to convert ros2 bags from one distribution to another

[chesterrc]

Description

A ros2 CLI tool to convert bag files to different distributions would be really helpful for collaborating with other users who have different ros2 distributions.

Related Issues

N/A

Completion Criteria

Argument in the CLI that would allow the conversion between different ROS2 distributions.

Implementation Notes / Suggestions

I would think that we want example metadata.yaml files of how different ROS2 distributions store their data as some sort of boilerplate.

[Jeffxzj]

Do you mean converting rosbag with different file formats? Like converting a SQLite3 formatted bag from older ROS2 distributions to an MCAP formatted bag using the ros2 bag cli ?

[lee-shun]

Do you mean converting rosbag with different file formats? Like converting a SQLite3 formatted bag from older ROS2 distributions to an MCAP formatted bag using the ros2 bag cli ?

Probably No. I think @chesterrc wants to ask if the bag recorded by Rolling can be played by Humble or vice versa. Because I got a similar request recently.

Do you have any suggestions?

[lee-shun]

Do you mean converting rosbag with different file formats? Like converting a SQLite3 formatted bag from older ROS2 distributions to an MCAP formatted bag using the ros2 bag cli ?

Probably No. I think @chesterrc wants to ask if the bag recorded by Rolling can be played by Humble or vice versa. Because I got a similar request recently.

Do you have any suggestions?

[MichaelOrlov]

Currently, the bag recorded by Humble can be replayed by all of its successor's distros up to the latest Rolling. We keep backward compatibility.
However, there is almost no way to make the bag recorded on Rolling to be replayed on Humble.
One workaround could be by deleting metadata.yaml file and run ros2 bag reindex path/to/robag2_folder on Humble.
The main difference is in the metadata serialized formats and internal data structures used when reading metadata.

One can see differences in a different version of metadata in unit tests https://github.com/ros2/rosbag2/blob/rolling/rosbag2_storage/test/rosbag2_storage/test_metadata_serialization.cpp
and in git history for the https://github.com/ros2/rosbag2/commits/rolling/rosbag2_storage/include/rosbag2_storage/bag_metadata.hpp

[lee-shun]

Oh，thank you for your quick reply！I will try this solution later！

Cheers 🍻