Approximate time synchronizer, callback is not called

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Hi,

My approximate time synchronizer with two topics (Camera and Liar) works fine. But When I add one more topic to it, my callback function seems never get called..

I am attaching the codes below for help. First node is the time synchronizer and second node is additional topic that I want to synchronize with other two topics (camera and lidar).

Thank you in advance.

ros::Publisher image1_pub;
ros::Publisher image2_pub;
ros::Publisher image3_pub;

void callback(const sensor_msgs::Image::ConstPtr& image1, const sensor_msgs::PointCloud2::ConstPtr& image2, const sensor_msgs::PointCloud2::ConstPtr& image3)
{

ROS_INFO("Sync_Callback");

  image1_pub.publish(image1);

  image2_pub.publish(image2);

  image3_pub.publish(image3);

}

int main(int argc, char** argv)
{

 ros::init(argc, argv, "TimeSynchronizer");

  std::string zed1_img_topic = "/zed/right/image_rect_color";

  std::string zed2_img_topic = "/velodyne_points";

  std::string zed3_img_topic = "/chatter";

  ros::NodeHandle nh;

  message_filters::Subscriber<sensor_msgs::Image> image1_sub(nh, zed1_img_topic, 1);

  message_filters::Subscriber<sensor_msgs::PointCloud2> image2_sub(nh, zed2_img_topic, 1);

  message_filters::Subscriber<sensor_msgs::PointCloud2> image3_sub(nh, zed3_img_topic, 1);

  image1_pub = nh.advertise<sensor_msgs::Image>("/synchronized" + zed1_img_topic, 1000);

  image2_pub = nh.advertise<sensor_msgs::PointCloud2>("/synchronized" + zed2_img_topic, 1000);

  image3_pub = nh.advertise<sensor_msgs::PointCloud2>("/synchronized" + zed3_img_topic, 1000);

  typedef sync_policies::ApproximateTime<Image, PointCloud2, PointCloud2> MySyncPolicy;

  Synchronizer<MySyncPolicy> sync(MySyncPolicy(10), image1_sub, image2_sub, image3_sub);

  sync.registerCallback(boost::bind(&callback, _1, _2, _3));

  ros::spin();

  return 0;

}

Second node

#include "ros/ros.h" #include "std_msgs/String.h" #include <sstream> #include <sensor_msgs image.h=""> #include <sensor_msgs pointcloud2.h="">

int main (int argc, char **argv){

ros::init(argc, argv, "talker");

ros::NodeHandle n;

ros::Publisher chatter_pub = n.advertise<sensor_msgs::PointCloud2>("chatter", 1000);

    ros::Rate loop_rate(10); 

int speed = 100;

    while (ros::ok()){

            sensor_msgs::PointCloud2 msg;

    msg.height = speed;

            chatter_pub.publish(msg);

            loop_rate.sleep();

    }

return 0;

}