ROS Resources: Documentation | Support | Discussion Forum | Index | Service Status | ros @ Robotics Stack Exchange
Ask Your Question

Image_transport warning of unsyncronization

asked 2021-04-21 06:48:26 -0500

Alessandro Melino gravatar image


I am trying to use the package depthimage_to_laserscan. My launch file to do this is the following:

 <node pkg="depthimage_to_laserscan" type="depthimage_to_laserscan" name="depthimage_to_laserscan">
    <remap from="image" to="/camera/depth/image"/>
    <remap from="camera_info" to="/camera/depth/camera_info"/>

The problem comes when y launch it and am image_transport warn appears:

[ WARN] [1619004832.858784407]: [image_transport] Topics '/camera/depth/image' and '/camera/depth/camera_info' do not appear to be synchronized. In the last 10s:
    Image messages received:      75
    CameraInfo messages received: 75
    Synchronized pairs:           0

I have tried to use the ApproximateTimeSynchronizer to syncronize these topics, but with this, they still don't syncronize. this is my file to use the syncronizer:

#!/usr/bin/env python3

import rospy
import message_filters
from sensor_msgs.msg import Image
from sensor_msgs.msg import CameraInfo

rospy.loginfo("Sync started")

def callback(image_raw, image_info):

image_raw = message_filters.Subscriber('/camera/depth/image', Image)
image_info = message_filters.Subscriber('/camera/depth/camera_info', CameraInfo)
ts = message_filters.ApproximateTimeSynchronizer([image_raw, image_info], 10, 0.01, allow_headerless=True)

Checking the header of both topics, the stamp is almost equal (difference of 1-3 ms).

What is wrong?

Thanks in advance.

Best regards. Alessandro

edit retag flag offensive close merge delete


Your Image and CameraInfo topics are at 7.5hz. Is this intentional or is something bottlenecking?

When you run this node do you see "callback" printed? (If you are using roslaunch don't forget output:="screen" for the node)

OzzieTheHead gravatar image OzzieTheHead  ( 2021-05-06 10:04:17 -0500 )edit

1 Answer

Sort by ยป oldest newest most voted

answered 2021-10-14 03:36:14 -0500

Alessandro Melino gravatar image

The unsyncronization is due to the low processing power of the computer. With other computers or a GPU/TPU the framerate and the syncronization improve. Actually I am not using ApproximateTimeSynchronizer.

edit flag offensive delete link more

Question Tools



Asked: 2021-04-21 06:48:26 -0500

Seen: 164 times

Last updated: Oct 14 '21