A G's profile - activity

I have a topic published with images from a camera and another topic with details of point cloud. When I plot these two topics, there is a time lag between the two plots. I am using approximate time sync to handle this time lag. But there is a drop in the frame rate as the approximate time sync algorithm is dropping some messages. Is there any method to handle this dropped messages?

Please help me to get a solution.

please check http://wiki.ros.org/rqt_bag as you may need rqt_bag_plugins as well.

I think you can use rqt. Please check http://wiki.ros.org/rqt

ok. Thanks mig!

@mig @Thomas D New issue-If I play rosbag with the loop option,the 1st loop will work,but during 2nd loop,callback function is not called.similar to the issue mentioned in the link http://answers.ros.org/question/10643... Please help me with your suggestions

Thanks @mig! Approximate time policy mentioned in your link worked. But I have to increment the timestamp of point cloud by 5sec using a subscriber node before passing it on to the TimeSynchronizer. Otherwise the callback function has never been called!

An addition to the above comment: When I tried with the TimeSynchronizer and ApproximateTimePolicy method , the behavior was like the callback function was never called.

Yes. I set use_sim_time to true and I am using --clock option while playing the rosbag.

Thanks, mig. I tried the above mentioned option. But it didn't work. Also i found a similar issue in the link mentioned below: http://answers.ros.org/question/14635... I even tried with approximate time policy mentioned in the above link.

Actual Issue: I have a topic published with images from a camera and another topic with details of point cloud. When I plot these two topics, there is a time lag between the two plots. Is there any method to synchronize this time lag by adjusting the time stamp of point cloud message?

I am using rosbag play for the above mentioned purpose.

Re-creating the Scenario I tried to simulate the above scenario using the below mentioned points: i. Created a subscriber node which subscribe to the topic(/point_cloud) with point cloud data. ii. Inside the callback function, I copied the message to a new pointer variable of the same type (sensor_msgs::PointCloud2) and incremented the timestamp by 3sec (The debug print shows that the timestamp has been successfully updated). iii. Then I published the modified point cloud data in a new topic(/point_cloud_new). iv. Created two instances of rviz which subscribes to the two topics, /point_cloud and /point_cloud_new respectively. v. Since the timestamp of /point_cloud_new was incremented by 3sec, I expected a 3sec delay between the two plots in the rviz. But it is not happening.

Since I am new to ROS, I am not sure whether it is the correct method to approach this issue. Please comment on the actual issue and the scenario re-created.

Please help me to sort out this issue.