<ROS> message_filters 对齐多种传感器数据的时间戳

#include <message_filters/subscriber.h>
#include <message_filters/synchronizer.h>
#include <message_filters/sync_policies/approximate_time.h>
#include <message_filters/sync_policies/exact_time.h>
#include <sensor_msgs/PointCloud2.h>
#include <sensor_msgs/Imu.h>
#include <ros/ros.h>
#include <iostream>

using namespace std;
using namespace sensor_msgs;
using namespace message_filters;

void callback(const PointCloud2ConstPtr& ori_pointcloud, const ImuConstPtr& ori_imu)
{
  // Solve all of perception here...
  syn_pointcloud = *ori_pointcloud;
  syn_imu = *ori_imu;
  cout << "syn velodyne points‘ timestamp : " << syn_pointcloud.header.stamp << endl;
  cout << "syn Imu‘s timestamp : " << syn_imu.header.stamp << endl;
  ROS_INFO("pointcloud stamp value is: %d", syn_pointcloud.header.stamp);
  ROS_INFO("imu stamp value is: %d", syn_imu.header.stamp);
}


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

  message_filters::Subscriber<Imu> imu_sub(nh, "/imu/data", 1);
  message_filters::Subscriber<PointCloud2> velodyne_sub(nh, "/velodyne_points", 1);
  typedef sync_policies::ApproximateTime<PointCloud2, Imu> MySyncPolicy;    
  Synchronizer<MySyncPolicy> sync(MySyncPolicy(10), velodyne_sub, imu_sub); //queue size=10
  sync.registerCallback(boost::bind(&callback, _1, _2));

  ros::spin();
  return 0;
}