Setting compression mode when using rosbag2_py.SequentialCompressionWriter

Hi folks,

I'm writing a component for recording specific topics, and wanted to use the rosbag2_py library.
I'm having some difficulties finding out how I can set the compression mode? I see that you can set it in the bagmetadata, but I don't see how I can use that?
Anyone who has any examples of how I can do this?

Thanks in advance!

@bmdyrdal What storage backend and ROS 2 distro are you going to use?

If this is for Iron or Rolling - we have a special field in the StorageOptions

rosbag2/rosbag2_storage/include/rosbag2_storage/storage_options.hpp

Line 53 in b6f5b43

std::string storage_config_uri = "";

Please refer to the https://github.com/ros2/rosbag2#recording-with-a-storage-configuration and https://github.com/ros2/rosbag2/blob/rolling/rosbag2_storage_mcap/README.md#writer-configuration and https://github.com/ros2/rosbag2/blob/rolling/rosbag2_storage_sqlite3/README.md#storage-configuration-file
to see how to write config files for storage backend.

As far as I see the constructor of the Sequential Compression Writer has an argument of type rosbag2_compression::CompressionOptions

rosbag2/rosbag2_compression/include/rosbag2_compression/sequential_compression_writer.hpp

Lines 61 to 63 in d788e51

    
           explicit SequentialCompressionWriter( 
        
             const rosbag2_compression::CompressionOptions & compression_options = 
        
             rosbag2_compression::CompressionOptions());

However, this argument is not bound to Python accordingly in rosbag2_py

rosbag2/rosbag2_py/src/rosbag2_py/_writer.cpp

Lines 109 to 110 in d788e51

    
           pybind11::class_<PyCompressionWriter>(m, "SequentialCompressionWriter") 
        
           .def(pybind11::init())

Furthermore, the rosbag2_compression::CompressionOptions is not bound to Python.

So wouldn't it be correct to adapt the pybind11 code in rosbag2_py to adapt the API of the cpp version?

@MichaelOrlov Using Humble, store it using sqlite3 in our file system.
Works fine using it from the command line.

@simonsag96 Is spot on with his comment! 👍

While waiting for this I ended up writing a python node which starts the recording as a subprocess.

@bmdyrdal @simonsag96 Yes. The solution would be to provide pybind11 code in rosbag2_py package to map rosbag2_compression::CompressionOptions to Python and use it as the default parameter in the Python version of the SequentialCompressionWriter.

But unfortunately, I don't have time for this task. If some of you can provide a PR it would be great, otherwise, this task will go in the backlog.

Thanks for your answer @MichaelOrlov!

I could implement this over the course of next week!

@simonsag96 I needed this myself today, so I put together this PR: #1425

	explicit SequentialCompressionWriter(
	const rosbag2_compression::CompressionOptions & compression_options =
	rosbag2_compression::CompressionOptions());

	pybind11::class_<PyCompressionWriter>(m, "SequentialCompressionWriter")
	.def(pybind11::init())