ros2bagreader unable to parse "metadata.yaml"

Hello, I am trying to open a mcap ros2 bag and I receive the following error:

Error using ros2bagreader (line 478)

Unable to parse "metadata.yaml" file in the specified folder path. Ensure that the YAML file is correctly formatted.

I am using matlab 2024b version.

Any advice on how to solve this issue?

Thank you,

Annalisa

[Simone]

I have the same problem, probably the YAML file version in the rosbags is too recent for the ros2bagreader function. I tried with an old bag, and it works.

[Seigan]

I have the same issue. ros2bagreader can't read my .mcap file because there seems to be a problem inside the metadata.yaml file.

@Simone : could you please share your working metadata.yaml file? In order for us to compare the format/structure of this file.

[SACHIN KHANDELWAL]

Hi @Annalisa, @Simone, could you please share files to reproduce the issue ?

[Simone]

I can't share the entire metadata.yaml file, but I believe the issue can be identified by looking at just these few lines:

rosbag2_bagfile_information:

version: 9

storage_identifier: mcap

duration:

nanoseconds: 156929000527

starting_time:

nanoseconds_since_epoch: 1741604982945181385

message_count: 646482

topics_with_message_count:

- topic_metadata:

name: /mapping/global_slope

type: nav_msgs/msg/OccupancyGrid

serialization_format: cdr

offered_qos_profiles:

- history: unknown

depth: 0

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

type_description_hash: ..

message_count: 782

The 'offered_qos_profiles' entry was previously provided as a list, but now (version 9) each sub-entry appears on a new line, and the ros2bagreader function does not work

Answer 1

[Gayathri]

Hi @Annalisa @Simone,

The error you are experiencing may be due to MATLAB R2024b only supporting bag files created with the ROS 2 distribution "Humble Hawksbill." If your bag file was created using a different ROS 2 distribution, this could be causing the issue.

Starting with the MATLAB R2025a Prerelease, the function is compatible with the ROS 2 distribution "Jazzy Jalisco" and should work without any errors.

https://www.mathworks.com/help/releases/R2025a/ros/gs/ros-system-requirements.html

[Simone]

Alright, thank you for your support