Compression
Marina applies several layers of compression when pushing datasets to registries. The defaults are chosen to maximise space savings while keeping pull times fast and data quality high.
PointCloud2 Compression
For ROS 2 sensor_msgs/PointCloud2 messages, Marina embeds the cloudini library, a specialised point cloud codec that achieves dramatically better compression ratios than general-purpose compressors.
Marina uses lossy compression with 1 mm accuracy by default. At this setting, individual point coordinates are rounded to the nearest millimetre before encoding. For virtually all outdoor LiDAR use cases (Velodyne, Ouster, Livox, etc.) this is imperceptible since 1 mm is well below sensor noise.
| Mode | Description |
|---|---|
off |
No PointCloud2 compression; messages are stored as-is |
lossy |
Coordinate rounding to pointcloud_accuracy (default: 1mm) |
lossless |
Lossless cloudini encoding; larger files than lossy |
MCAP Chunk Compression
MCAP files store messages in compressed chunks. Marina recompresses these chunks when packing a dataset.
Two contexts are configurable separately:
| Setting | Description |
|---|---|
packed_mcap_compression |
Compression applied to chunks inside the uploaded archive |
unpacked_mcap_compression |
Compression applied to chunks in the locally cached copy after pull |
Available codecs: none, lz4, zstd.
- LZ4: fast decompression, good for local cache where pull speed matters.
- Zstd: higher compression ratio, good for remote storage where bandwidth matters.
Archive Compression
The outer archive wrapping the MCAP files can be compressed as well for when folders contain much more than bags:
| Setting | Description |
|---|---|
packed_archive_compression |
Compression of the .tar archive uploaded to the registry |
Available modes: none, gzip.
Configuration File
Compression defaults live in ~/.config/marina/marina.rl under the compression block.
The format is ratslang — physical units are written directly (e.g. 1mm, 0.5mm).
compression {
pointcloud_mode = lossy
pointcloud_accuracy = 1mm # any length unit: mm, cm, m
packed_mcap_compression = zstd
packed_archive_compression = none
unpacked_mcap_compression = lz4
}
All fields are optional. Omitting a field uses the built-in default shown above.
Per-Command Overrides
Compression settings provided on the command line override the config for that invocation only. They do not modify the config file.
# Push with lossless point cloud compression
marina push outdoor-run:v2 ./bag/ --pointcloud-mode lossless
# Push with higher accuracy (0.1 mm)
marina push outdoor-run:v2 ./bag/ \
--pointcloud-mode lossy \
--pointcloud-accuracy-mm 0.1
# Push without any point cloud compression
marina push outdoor-run:v2 ./bag/ --pointcloud-mode off
# Change MCAP chunk compression
marina push outdoor-run:v2 ./bag/ \
--packed-mcap-compression lz4 \
--packed-archive-compression gzip
# Pull with no recompression of local cache
marina pull outdoor-run:v2 --unpacked-mcap-compression none
Plain Folder Support
For datasets that are not MCAP bagfiles (plain folders, non-ROS data), PointCloud2 compression is not applied. Archive and MCAP-level settings have no effect on non-MCAP content, and the data is stored as-is inside the archive.