added page for converting ROS2 to ROS1 bag for the Kalibr

Author: Jakub Lenner

docs/120-miscellaneous/bagfile_convert_ros1_ros2.md

@@ -0,0 +1,32 @@
+# Converting from ROS2 bag file to ROS1 bag file
+
+Good tool for this is the `rosags-convert` utility.
+
+1. install rosbags package
+
+```bash
+pip install rosbags
+```
+
+2. Now you can convert the bag. Example:
+
+```bash
+rosbags-convert /rosbag2_2025_11_05-14_01_53/
+```
+
+This directory should contain `metadata,yaml` file. For this concrete example, the output should be in the file `rosbag2_2025_11_05-14_01_53.bag`.
+
+If you are getting error like this:
+
+```bash
+ERROR: Reading source bag: Rosbag2 version 9 not supported; please report issue.
+```
+
+simply open the `/rosbag2_<timestamp>/metadata.yaml` file and lower the version number at the beginning of the file.
+
+```yaml
+rosbag2_bagfile_information:
+  version: 9
+```
+
+In our case, just lowering it from `9` to `8` helped. This does not feel very correct, but if it works...

docs/90-software/kalibr.md

@@ -18,6 +18,9 @@ The Kalibr docker image is sourced from the `ctumrs` [dockerhub](https://hub.doc
 
 ## Howto
 
+0. If you have bag file from ROS2, you need to first [convert it to the ROS1 bag format](../120-miscellaneous/bagfile_convert_ros1_ros2.md)
+
+
 1. clone the [ctu-mrs/kalibr_docker](https://github.com/ctu-mrs/kalibr_docker) repository
 2. `cd compose_session`
 2. Pull the docker image by calling `docker compose pull`