Kappe
Kappe is an efficient data migration tool designed to seamlessly convert and split ROS2 MCAP files.
Install / Use
/learn @sensmore/KappeREADME
Kappe
Kappe is an efficient data migration tool designed to seamlessly convert and split MCAP files.
Table of content
- Kappe
Installation
pip install kappe
or
uv tool install kappe
or
uvx kappe
Usage
Create a yaml config file containing the migrations you want to perform.
Example:
config.yaml
topic:
mapping:
/points: /sensor/points
Run the converter:
kappe convert --config config.yaml ./input.mcap
Convert
kappe convert [-h] [--config CONFIG] [--overwrite] input output
For complete option details use kappe convert --help.
Converts a single file or a directory of files to the MCAP format.
Topic
Rename a topic
topic:
mapping:
/points: /sensor/points
Remove a topic
topic:
remove:
- /points
Frame ID Mapping
To change the frame_id for specific topics globally, you can use frame_id_mapping in your configuration:
frame_id_mapping:
"/imu/data": "imu_link_new"
"/lidar/points": "lidar_frame_new"
Drop Messages
To drop every nth message from a topic:
topic:
drop:
/high_frequency_topic: 2 # Keep every 2nd message
/camera/image: 10 # Keep every 10th message
Topic Times
The time_offset config manipulates the mcap message time and/or the ROS header timestamp.
When using default as topic name, the config will be applied to all messages.
Update the ROS header time
Adds 8 second and 300 nanosec to the ROS header.
time_offset:
/sensor/points:
sec: 8
nanosec: 300
Change ROS Timestamp to publish time
Change the time of the ROS Timestamp to the time the message was published.
time_offset:
/sensor/points:
pub_time: True
Change MCAP pub/log time from ROS header
Update the log/pub time from the ROS header.
If pub_time is set, pub time will be used as source.
If sec and/or nanosec is set, the offset is used.
time_offset:
/sensor/points:
update_publish_time: True
update_log_time: True
Add a time offset to ROS Timestamp
Add 15 seconds to the ROS Timestamp.
time_offset:
/sensor/points:
sec: 15
nanosec: 0
Pointcloud
Remove zero points from PointCloud2
point_cloud:
/sensor/points:
remove_zero: true
Rotate a pointcloud
point_cloud:
/sensor/points:
rotation:
euler_deg:
- 180
- 0
- 0
Remove ego bounding box points from the pointcloud
point_cloud:
/sensor/points:
ego_bounds:
x:
min: -1.0
max: 2.0
y:
min: -0.5
max: 0.5
z:
min: -0.2
max: 1.5
Rename PointCloud2 field name
Changes the field name of the PointCloud2 message, from AzimuthAngle to azimuth_angle.
point_cloud:
/sensor/points:
field_mapping:
AzimuthAngle: azimuth_angle
TF
To update a static transform you need to remove the old one and insert a new one.
Remove Transform
Removes transforms from /tf and /tf_static messages where the child_frame_id matches the specified values.
For /tf messages:
tf:
remove:
- test_data_frame
- other_frame
For /tf_static messages:
tf_static:
remove:
- test_data_frame
- other_frame
Or remove all transforms by using the string "all":
tf_static:
remove: all
Insert Static Transform
Rotation can be specified in
euler_degorquaternion
tf_static:
insert:
- frame_id: base
child_frame_id: also_base
- frame_id: base
child_frame_id: sensor
translation:
x: -0.1
y: 0
z: 0.1
rotation:
euler_deg:
- 0
- 90
- 0
Apply Transform Offsets
Apply translation and rotation offsets to existing transforms in both /tf and /tf_static messages. The offsets are added to the current transform values.
Rotation can be specified in
euler_degorquaternion
For /tf messages:
tf:
offset:
- child_frame_id: sensor_frame
translation:
x: 0.1
y: -0.05
z: 0.2
rotation:
euler_deg:
- 0
- 0
- 45
For /tf_static messages:
tf_static:
offset:
- child_frame_id: sensor_frame
translation:
x: 0.1
y: -0.05
z: 0.2
rotation:
euler_deg:
- 0
- 0
- 45
- child_frame_id: camera_frame
translation:
x: -0.1
y: 0.0
z: 0.0
rotation:
quaternion:
- 0.0
- 0.0
- 0.3827
- 0.9239
Schema Mapping
If the new schema is not already in the mcap, kappe will try to load it either from your ROS2 environment or from ./msgs.
msg_schema:
mapping:
std_msgs/Int32: std_msgs/Int64
Trim
Trim the mcap file to a specific time range.
time_start: 1676549454.0
time_end: 1676549554.0
Plugins
Kappe can be extended with plugins, for example to compress images or update camera calibration. Source code for plugins can be found in src/kappe/plugins/, additional plugins can be loaded from ./plugins.
Available built-in plugins:
image.CompressImage- Compress RGB images to JPEGimage.CropImage- Crop images to specified boundscamera_info.UpdateCameraInfo- Update camera calibration parameterscamera_info.InsertCameraInfo- Insert camera calibration from image topics
plugins:
- name: image.CompressImage
input_topic: /image
output_topic: /compressed/image
settings:
quality: 50
- name: camera_info.UpdateCameraInfo
input_topic: /camera/camera_info
output_topic: /camera/camera_info # Must remove /camera/camera_info topic (see above)
settings:
camera_info: # https://wiki.ros.org/camera_calibration_parsers#File_formats
image_height: 1080
image_width: 1920
camera_matrix:
rows: 3
cols: 3
data:
- 1070.0691945956082
- 0.0
- 783.0877059808756
- 0.0
- 1082.911613625781
- 544.1453400605368
- 0.0
- 0.0
- 1.0
distortion_model: plumb_bob
distortion_coefficients:
rows: 1
cols: 5
data:
- -0.317162192616218
- 0.09863188458267099
- 0.009339815359941763
- -0.000817443220874783
- 0.0
rectification_matrix:
rows: 3
cols: 3
data:
- 1.0
- 0.0
- 0.0
- 0.0
- 1.0
- 0.0
- 0.0
- 0.0
- 1.0
projection_matrix:
rows: 3
cols: 4
data:
- 1070.0691945956082
- 0.0
- 783.0877059808756
- 0.0
- 0.0
- 1082.911613625781
- 544.1453400605368
- 0.0
- 0.0
- 0.0
- 1.0
- 0.0
- name: camera_info.InsertCameraInfo
input_topic: /camera/image_raw
output_topic: /camera/camera_info
settings:
camera_info: # https://wiki.ros.org/camera_calibration_parsers#File_formats
image_height: 1080
image_width: 1920
camera_matrix:
rows: 3
cols: 3
data:
- 1070.0691945956082
- 0.0
- 783.0877059808756
- 0.0
- 1082.911613625781
- 544.1453400605368
- 0.0
- 0.0
- 1.0
distortion_model: plumb_bob
distortion_coefficients:
rows: 1
cols: 5
data:
- -0.317162192616218
- 0.09863188458267099
- 0.009339815359941763
- -0.000817443220874783
- 0.0
rectification_ma
