This library reads ROS bag files quickly without their message descriptions and without any dependencies.
Embag is available on PyPI and supports Linux and MacOS. To use it, simply install with pip:
pip install embag
See the python directory for details. The tests include more usage examples.
Embag is a native library and is available from Gemfury as a Debian package. You can also build it from source. To install the .deb package for the first time:
sudo sh -c "echo 'deb [trusted=yes] https://apt.fury.io/embark/ /' >> /etc/apt/sources.list.d/fury.list"
sudo apt update
sudo apt install embag
First, you'll need Bazel. It's often easiest to use Bazelisk, a convenient wrapper that installs it for you. To build, run:
# Embag echo demo binary
bazel build //embag_echo:embag_echo
# Run with
bazel-bin/embag_echo/embag_echo --bag /path/to/sweet.bag --topic /awesome/topic
# Shared object file
bazel build //lib:libembag.so
# Debian package
bazel build //lib:embag-debian
# Python Wheel (for example, you might use a specific installation of Python)
PYTHON_BIN_PATH=/usr/local/bin/python3.7.5 bazel build //python:wheel
To test, run:
# This will run both the C++ and Python tests against a small bag file
bazel test test:* --test_output=all
NOTE: If you're testing the python2 or python3 interface, you'll need to ensure that your system has numpy installed for each respective python version.
To use the C++ API:
Embag::View view{filename};
view.addBag("another.bag"); # Views support reading from multiple bags
for (const auto &message : view.getMessages({"/fun/topic", "/another/topic"})) {
std::cout << message->timestamp->to_sec() << " : " << message->topic << std::endl;
std::cout << message->data()["fun_array"][0]["fun_field"]->as<std::string>() << std::endl;
}See the tests for more usage examples.
These tests were performed on a 473M bag file compressed with lz4. The bag contains a number of complex topics and each library was asked to print the topic, timestamp, and deserialized message. Unfortunately, it's not possible to decode messages using the ROS C++ API without precompiled message definitions.
| Library | 6128 messages | 1000 messages |
|---|---|---|
| rospy | 57.898s | 1.815s |
| embag (Python API) | 3.655s | 1.093s |
| embag (C++ API) | 3.300s | 1.007s |
This library was heavily influenced by:
Copyright 2020 Embark Trucks
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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