Description

This very simple program is designed to convert the rosbag2 jazzy "metadata.yaml" style into a format that humble understands.

jazzy and humble rosbag2 incompatibility issue

Any rosbags (sqlite3 or mcap - it doesn't matter) written to ROS2**jazzy are not readable in ROS2**humble. There is a backward compatibility.

Ready-made solutions to this problem were not found, the problem itself was encountered on the Internet 1-2 times, the solution is not specified. Converting to other formats using standard rosbag2 tools didn't help.

Error itself:

Exception on parsing info file: yaml-cpp: error at line ... bad conversion

The reason for the incompatibility of rosbags

By the method of research and comparison, it was determined that the reason for the unreadability of jazzy rosbags in humble lies in the fact that jazzy and humble "metadata.yaml" have different styles.

Differences in the "metadata.yaml" style

1. The line offered_qos_profiles:

• jazzy:

        offered_qos_profiles:
          - history: unknown
            depth: 10
            reliability: reliable
            durability: volatile
            deadline:
              sec: 9223372036
              nsec: 854775807
            lifespan:
              sec: 9223372036
              nsec: 854775807
            liveliness: automatic
            liveliness_lease_duration:
              sec: 9223372036
              nsec: 854775807
            avoid_ros_namespace_conventions: false

• humble:

        offered_qos_profiles: "- history: 3\n  depth: 0\n  reliability: 1\n  durability: 2\n  deadline:\n    sec: 9223372036\n    nsec: 854775807\n  lifespan:\n    sec: 9223372036\n    nsec: 854775807\n  liveliness: 1\n  liveliness_lease_duration:\n    sec: 9223372036\n    nsec: 854775807\n  avoid_ros_namespace_conventions: false"

2. The custom_data: and ros_distro: lines at the end of the humble file do not exist.

• jazzy:

  custom_data: ~
  ros_distro: jazzy

3. The type_description_hash: line exists in Jazzy metadata, but is absent in Humble metadata.

• jazzy:

    - topic_metadata:
        ...
        type_description_hash: RIHS01_e369d0f05a23ae52508854b66f6aa0437f3449d652e8cbf22d5abe85d020f087
      message_count: 12408

4. In some Jazzy metadata files, the expanded offered_qos_profiles block may be repeated for the same topic. The converter keeps one converted Humble-style QoS profile and skips the repeated expanded block.

• jazzy:

    - topic_metadata:
        name: /center
        type: sensor_msgs/msg/PointCloud
        serialization_format: cdr
        offered_qos_profiles:
          - history: unknown
            ...
            avoid_ros_namespace_conventions: false
          - history: unknown
            ...
            avoid_ros_namespace_conventions: false
        type_description_hash: RIHS01_614593df71d3c2b9bd4604a71b750fd218f0d65c045ea988b713719455a65b3b
      message_count: 15

Purpose of the program

The program rewrites jazzy "metadata.yaml" into humble "metadata.yaml", it simply refactors it.

It is based on a dictionary, written based on ROS2 QoS policies.

Program:

• changes the offered_qos_profiles: (in humble style)
• deletes the type_description_hash: (humble file doesn't have one)
• deletes the custom_data: (humble file doesn't have one)
• deletes ros_distro: (humble file doesn't have one)
• removes duplicate information of offered_qos_profiles: (humble file doesn't have it)

The program does not rewrite the source "metadata.yaml" file, but creates a new one based on it in the same directory.

Program launch

The program consists of a single file that needs to be run in the jazzy "metadata.yaml" directory.

cd <your_rosbag_metadata_dir>

g++ -o rosbag2_metadata_jazzy_to_humble.out rosbag2_metadata_jazzy_to_humble.cpp

./rosbag2_metadata_jazzy_to_humble.out

Program Parameters

Inside the code, you can specify the name of the output yaml file, by default it is "metadata_humble.yaml".

Program quality

The program was successfully tested on 15 rosbags, and everything was displayed properly in rviz. humble run .db3 and .mcap rosbags of jazzy.

However, rosbags converted by this program are not read by jazzy :)

If an error like this occurs when launching a converted rosbag:

requesting incompatible QoS. No messages will be sent to it. Last incompatible policy: RELIABILITY_QOS_POLICY

this means that the dictionary inside the program is formed incorrectly. Try changing the order of the numbers in the std::map dictionaries. It's possible that the keywords and meanings don't match correctly.

In an amicable way, it's needed to determine an unambiguous match in std::map based on some kind of ROS2 documentation, and not by experimenting. But for now, as it is.

I hope this information will be useful to someone. I will be glad to receive a feedback :)