20. ROS2 Recording and Playback Tool

1. Introduction to Recording and Playback Tools

Bag2, a commonly used recording and playback tool in ROS2, is used to record topic data. We can use this command to store topic data as a file. Later, we can directly publish the topic data in the bag file without starting a node.

This tool is very useful when developing a real robot. For example, we can record topic data when the robot encounters a problem. After recording, we can publish it multiple times for testing and experimentation, or share the topic data with others to verify algorithms.

We will try using the bag tool to record topic data and replay it.

2. Usage Tutorial

2.1. Start the topic node to record

For example, the talker in the ros2 demo:

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ros2 run demo_nodes_py talker

2.2. Recording

/topic-name is the topic name

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# Record a single topic
ros2 bag record /topic-name
# Record multiple topics
ros2 bag record topic-name1 topic-name2
# Record all topics
ros2 bag record -a

Other Options

-o name Customize the output file name

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ros2 bag record -o file-name topic-name

-s Storage format

Currently only supports sqllite3; others are available with extensions.

2.3. Viewing Recorded Topic Information

Before playing a video, you can view relevant information about the video through the file information, such as the time, size, type, and number of topic records.

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# Assume the recorded file is rosbag2_2023_10_31-07_58_23
ros2 bag info rosbag2_2023_10_31-07_58_23

2.4. Play and View

2.4.1. Play

Next, we can replay the data using the following command.

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ros2 bag play rosbag2_2023_10_31-07_58_23

2.4.2. View

Use the ros2 topic command to view the data.

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ros2 topic echo /chatter

2.4.3. Playback Options

1. Play at Multiple Speeds -r

The -r option modifies the playback speed. For example, the -r value, for example, 10 means 10x speed, playing the topic ten times faster.

 ROS2 Launch startup file configuration
ROS2 URDF model