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MCAP

MCAP is a modular container format and logging library for pub/sub messages with arbitrary message serialization. It is primarily intended for use in robotics applications, and works well under various workloads, resource constraints, and durability requirements.

Documentation

• File format specification
  • Kaitai Struct definition
• Motivation
• Support Matrix

Developer quick start

MCAP libraries are provided in the following languages. For guidance on each language, see its corresponding README:

| Language | Readme | API docs | Package name | Version | | --------------------- | ---------------------- | --------------------------------------------------------------- | ------------ | ------------------------------------------------------------------------------------ | | C++ | readme | API docs | mcap | | | Go | readme | API docs | | see releases | | Python | readme | API docs | mcap | | | JavaScript/TypeScript | readme | API docs | @mcap/core | | | Swift | readme | API docs | | see releases | | Rust | readme | API docs | mcap | |

To run the conformance tests, you will need to use Git LFS, which is used to store the test logs under tests/conformance/data.

MCAP CLI

Inspect, merge, and split MCAP files from the command line using the MCAP CLI.

Install with brew install mcap or download the latest version directly from the releases page.

License

MIT License.

Release process

Release numbering follows a major.minor.patch format, abbreviated as "X.Y.Z" below.

CI will build the appropriate packages once tags are pushed, as described below.

Go library

1. Update the Version in go/mcap/version.go
2. Tag a release matching the version number go/mcap/vX.Y.Z.

CLI

Tag a release matching releases/mcap-cli/vX.Y.Z.

The version number is set at build time based on the tag.

C++

1. Update the version in all relevant files
   • cpp/bench/conanfile.py
   • cpp/build-docs.sh
   • cpp/build.sh
   • cpp/docs/conanfile.py
   • cpp/examples/conanfile.py
   • cpp/mcap/conanfile.py
   • cpp/mcap/include/mcap/types.hpp (MCAP_LIBRARY_VERSION)
   • cpp/test/conanfile.py
2. Tag a release matching the version number releases/cpp/vX.Y.Z

Python

There are several python packages; updating any follows a similar process.

1. Update the version in the appropriate __init__.py file
2. Tag a release matching releases/python/PACKAGE/vX.Y.Z
   • For example, releases/python/mcap/v1.2.3

TypeScript

There are several TS packages; updating any follows a similar process.

1. Update the version in the appropriate package.json
2. Tag a release matching releases/typescript/PACKAGE/vX.Y.Z
   • For example, releases/typescript/core/v1.2.3

Swift

Tag a release matching the version number releases/swift/vX.Y.Z

Rust

1. Update the version in rust/Cargo.toml
2. Tag a release matching the version number releases/rust/vX.Y.Z

Citations

If you use MCAP in your research, please cite it in your work. Our suggested citation format is:

@software{MCAP,
  title = {MCAP: serialization-agnostic log container file format},
  author = {{Foxglove Developers}},
  url = {https://mcap.dev},
  version = {your version},
  date = {your date of access},
  year = {2024},
  publisher = {{Foxglove Technologies}},
  note = {Available from https://github.com/foxglove/mcap}
}

Please replace the version and date fields with the version of the software you used, and the date you obtained it. Citing MCAP will help spread awareness of the project and strengthen the ecosystem.

Stay in touch

Join our Discord community to ask questions, share feedback, and stay up to date on what our team is working on.