ROS2 message filter approximate time policy callback doesn't run

asked 2020-08-16 12:10:31 -0600

80 ●15 ●22 ●24 https://www.linkedin.c...

updated 2020-08-20 11:09:01 -0600

I am trying to sync two message streams of 2 image topics. So I am using message filters. I was using a class to do all this, however, the callback doesnt seem to be running. I have echoed the rostopics in the terminal and they seem to be outputting the messages. What could be happening here?

What is allowed time delay in the approximate policy in receiving the two topic streams(I atleast have topics matching every second right now)?

I guess I may be doing something wrong there. (Things do work if i create two different subscribers with their own callbacks)

This is my code-

   class MultiSubscriber : public rclcpp::Node
    {
      public:
      message_filters::Subscriber<sensor_msgs::msg::Image> image_sub_;
          message_filters::Subscriber<sensor_msgs::msg::Image> disparity_sub_;              
        MultiSubscriber(const std::string& name)
        : Node(name)
        {
          image_sub_.subscribe(this, "/image_color");
          disparity_sub_.subscribe(this, "/image_disparity");
          typedef message_filters::sync_policies::ApproximateTime<sensor_msgs::msg::Image, sensor_msgs::msg::Image> approximate_policy;
          message_filters::Synchronizer<approximate_policy>syncApproximate(approximate_policy(10), image_sub_, disparity_sub_);
             syncApproximate.setMaxIntervalDuration(rclcpp::Duration(3,0)); // Added after a comment
          syncApproximate.registerCallback(&MultiSubscriber::disparityCb,this);

        }
        private:
        void disparityCb(const sensor_msgs::msg::Image::SharedPtr disparity_msg, const sensor_msgs::msg::Image::SharedPtr color_msg)
        {

            std::cout<<"Hello messages are being received";

        }};

Just to add to this. This is the output of -

ros2 node info /obstacle_detection

/obstacle_detection
  Subscribers:
    /image_disparity: sensor_msgs/msg/Image
    /image_color: sensor_msgs/msg/Image
    /parameter_events: rcl_interfaces/msg/ParameterEvent
  Publishers:
    /parameter_events: rcl_interfaces/msg/ParameterEvent
    /rosout: rcl_interfaces/msg/Log
  Service Servers:
    /obstacle_detection/describe_parameters: rcl_interfaces/srv/DescribeParameters
    /obstacle_detection/get_parameter_types: rcl_interfaces/srv/GetParameterTypes
    /obstacle_detection/get_parameters: rcl_interfaces/srv/GetParameters
    /obstacle_detection/list_parameters: rcl_interfaces/srv/ListParameters
    /obstacle_detection/set_parameters: rcl_interfaces/srv/SetParameters
    /obstacle_detection/set_parameters_atomically: rcl_interfaces/srv/SetParametersAtomically
  Service Clients:

  Action Servers:

  Action Clients:

Edit- Error Message on changing the registerCallback call to syncApproximate.registerCallback(std::bind (&MultiSubscriber::disparityCb, this,_1,_2)); image description

Edit 2- This github issue shows how the registercallback is to be called.

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I am assuming that the headers for each image message has been populated correctly. Try outputting the stamps msg->header.stamp.sec and msg->header.stamp.nsec from each message to debug if the times are syncing.

surfertas ( 2020-08-16 17:31:45 -0600 )edit

Also try using ros2 topic info <TOPIC> for each topic, and confirm that you observe expected values for Publisher count and Subscriber count.

surfertas ( 2020-08-16 17:38:21 -0600 )edit

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3 Answers

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answered 2020-08-17 00:22:39 -0600

surfertas

265 ●2 ●16 ●17 http://surfertas.github.io/

updated 2020-08-20 09:34:48 -0600

First, check if the signature of the callback is correct. (e.g. void callback(const std::shared_ptr<M const>&, const std::shared_ptr<M const>&) for 2 filters). If yes, proceed below.

Check if the Quality of Service (QoS) is compatible between the subscriber and publisher. You can specify a QoS by passing a rmw quality of service profile.
Use ros2 topic info <TOPIC> to confirm the expected number of publisher count and subscriber count.

If you are still having issues, you might be facing time stamps that doesn't meet the duration threshold.

Output the time stamps to visually compare.
Adjust the duration threshold by calling the method setMaxIntervalDuration() that takes as input a rclcpp::Duration() representation of time. (e.g. sync_policy.setMaxIntervalDuration(rclcpp::Duration(1,0)))

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Thanks for such an informative answer.

ros2 topic info results seem to be correct. (When I start the node, the topics' subscriber count does increase.)
Output time stamps visually I see both images coming in at least a second.
I used this function and set the duration to be 3 seconds (syncApproximate.setMaxIntervalDuration(rclcpp::Duration(3,0));)
I don't know how to check the compatibility between the publisher and subscriber . Btw I am using a bagfile (which publishes the messages, I am trying to subscribe to )

Harsh2308 ( 2020-08-20 02:01:18 -0600 )edit

Ok assuming everything compiles, seems like there might be QoS compatibility issue. Its recommended to use rmw_qos_profile_sensor_data with image topics, so it's possible that the creator of the bag file has used the sensor data profile.

Can you pass the QoS profile to the call to subscribe()?

.subscribe(this, "/some_topic", rmw_qos_profile_sensor_data);

surfertas ( 2020-08-20 07:32:38 -0600 )edit

Also as @KenYN has mentioned, my signature is consistent with his suggestion. Did you try that as well?

surfertas ( 2020-08-20 07:36:05 -0600 )edit

Modified to this but no change.

image_sub_.subscribe(this, "/image_color",rmw_qos_profile_sensor_data)disparity_sub_.subscribe(this, "/image_disparity", rmw_qos_profile_sensor_data);

2. syncApproximate.registerCallback(std::bind (&MultiSubscriber::disparityCb, this,_1,_2_)); is giving a compilation error. My callback signature is same as in the answer.

There is a huge error

Harsh2308 ( 2020-08-20 09:03:29 -0600 )edit

error: no matching function for call to ‘message_filters::Signal9<sensor_msgs::msg::image_<std::allocator<void> >, sensor_msgs::msg::Image_<std::allocator<void> >, message_filters::NullType, message_filters::NullType, message_filters::NullType, message_filters::NullType, message_filters::NullType, message_filters::NullType, message_filters::NullType>::addCallback<const m0constptr&,="" const="" m1constptr&,="" const="" m2constptr&,="" const="" m3constptr&,="" const="" m4constptr&,="" const="" m5constptr&,="" const="" m6constptr&,="" const="" m7constptr&,="" const="" m8constptr&>(std::_bind_helper<false,="" const="" std::_bind<void="" (multisensesubscriber::*(multisensesubscriber*,="" std::_placeholder<1="">, std::_Placeholder<2>))(std::shared_ptr<sensor_msgs::msg::image_<std::allocator<void> > >, std::shared_ptr<sensor_msgs::msg::image_<std::allocator<void> > >)>&, const std::_Placeholder<1>&, const std::_Placeholder<2>&, const std::_Placeholder<3>&, const std::_Placeholder<4>&, const std::_Placeholder<5>&, const std::_Placeholder<6>&, const std::_

Harsh2308 ( 2020-08-20 09:22:24 -0600 )edit

The callback needs to be of signature void callback(const std::shared_ptr<M const>&) as detailed here

Change this void disparityCb(const sensor_msgs::msg::Image::SharedPtr disparity_msg, const sensor_msgs::msg::Image::SharedPtr color_msg)

void disparityCb(const sensor_msgs::ImageConstPtr disparity_msg, const sensor_msgs::ImageConstPtr & color_msg)

surfertas ( 2020-08-20 09:26:27 -0600 )edit

I will leave this stack overflow discussion on differences for reference.

surfertas ( 2020-08-20 09:31:46 -0600 )edit

I have added the relevant part of the error message in the answer. I had to change the callback to -

void MultiSenseSubscriber::disparityCb(const boost::shared_ptr<sensor_msgs::msg::Image const>& disparity_msg, const boost::shared_ptr<sensor_msgs::msg::Image const> & color_msg)

Harsh2308 ( 2020-08-20 10:22:22 -0600 )edit

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answered 2020-08-17 01:13:02 -0600

KenYN

541 ●51 ●75 ●74

I think your registerCallback() looks odd; this is what I use on Foxy:

  syncApproximate.registerCallback(std::bind(&MultiSubscriber::disparityCb,
                                             this,
                                             std::placeholders::_1,
                                             std::placeholders::_2));

Also, my callback uses ConstSharedPtr, but the compiler should catch a mismatch.

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Could you share how your callback looks like?

Harsh2308 ( 2020-08-20 01:24:53 -0600 )edit

I looked at this issue for the way the registerCallback is to be called

Harsh2308 ( 2020-08-20 11:04:57 -0600 )edit

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answered 2023-02-22 04:10:08 -0600

tgulbudak
1 ●1

Hi,

I had the same issue as you and it is fixed when I define synchronizer as a static variable to keep it out of the constructor function.

If you still need it this is the change for you, I did similarly in my code.

static message_filters::Synchronizer<approximate_policy>syncApproximate(approximate_policy(10), image_sub_, disparity_sub_);

It works and it calls the callback function. However, I have the termination error because I define a variable as static in the function. I am looking solution for it.

I can use the time synchronizer and the application prints errors when I terminate it.

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