StrobeSync Policy

Overview

This project provides a custom synchronization policy for ROS that takes into account the time shift between different topics. It's designed to help synchronize messages from multiple topics while considering potential delays or shifts in their timestamps.

You can find catkin package suitable version in 'ros-package' project branch

Features

• Header-only library for easy integration
• Compatible with ROS message filters
• Built with modern C++ (C++17)

Installation

Prerequisites

• ROS (ROS2 not tested)
• CMake (version 3.5 or higher)
• Boost
• C++17 compatible compiler

Building and Installing

1. Create a build directory and generate CMake instructions:

mkdir build && cd build
cmake ..

2. Install the library:

sudo make install

Dirrect copy

Another option is to directly copy and use the strobe_sync_policy.hpp file in your project.

#include "some/folder/strobe_sync_policy.hpp"

Testing

To build tests do a certain steps from the root folder:

mkdir build && cd build
cmake .. -DBUILD_TESTS=ON
sudo make install
cmake --build .

ctest --test-dir tests --verbose

Usage Example

#include <ros/ros.h>
#include <sensor_msgs/Image.h>
#include <message_filters/synchronizer.h>
#include <message_filters/subscriber.h>
#include <strobe_sync_policy/strobe_sync_policy.hpp>

void callback(const sensor_msgs::ImageConstPtr &, const sensor_msgs::ImageConstPtr &)
{
    ROS_INFO("Received synchronized messages");
}

int main(int argc, char **argv)
{
    ros::init(argc, argv, "strobe_sync_example");
    ros::NodeHandle nh;

    message_filters::Subscriber<sensor_msgs::Image> sub1(nh, "/topic1", 1);
    message_filters::Subscriber<sensor_msgs::Image> sub2(nh, "/topic2", 1);

    typedef message_filters::evo_sync_policies::StrobeSync<sensor_msgs::Image, sensor_msgs::Image> SyncPolicy;
    message_filters::Synchronizer<SyncPolicy> sync(SyncPolicy({0., 1.}, 2., .5), sub1, sub2);
    sync.registerCallback(boost::bind(&callback, _1, _2));

    ros::spin();

    return 0;
}

Examples

Here are some visual examples demonstrating the StrobeSync policy in action:

Example 1

f1 = 10hz, f2 = 10hz, f3 = 5hz, f4 = 5hz
s1 = 0, s2 = 0.07, s3 = 0, s4 = 0.05

Example 2

f1 = 5hz, f2 = 5hz
s1 = 0, s2 = 0.1 At 0.5 seconds, the third topic is interrupted

Example 3

f1 = 10hz, f2 = 10hz, f3 = 5hz, f4 = 5hz
s1 = 0.2, s2 = 0, s3 = 0.1, s4 = 0

Example 4

f1 = 10hz, f2 = 10hz, f3 = 10hz
s1 = 0, s2 = 1, s3 = 0

Example 5

f1 = 10hz, f2 = 10hz, f3 = 5hz, f4 = 5hz (it might seem that I really like these values)
s1 = 0, s2 = 0.07, s3 = 0, s4 = 0.05

In this experiment, we simulate point-wise message loss

Example 6

f1 = 10hz, f2 = 10hz, f3 = 10hz
s1 = 0, s2 = 1, s3 = 0

In this experiment, in addition to the known shift, messages themselves start publishing later