ZED Camera Tag not detect

[Harin99]

Dear maintainers @QQting,

Thank you for providing the QuickStart guide — I was able to successfully build the workspace by following your instructions.

However, when I run the command ros2 launch apriltag_ros tag_realsense.launch.py, the terminal outputs like below but does not proceed any further. I have already modified the image topic name directly within tag_realsense.launch.py.

ac@AC:~/apriltag_ros2_ws$ ros2 launch apriltag_ros tag_realsense.launch.py
[INFO] [launch]: All log files can be found below /home/ac/.ros/log/2025-05-07-09-13-06-159777-AC-450313
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [component_container-1]: process started with pid [450333]
[component_container-1] [INFO] [1746609186.617089197] [apriltag.tag_container]: Load Library: /home/ac/apriltag_ros2_ws/install/apriltag_ros/lib/libAprilTagNode.so
[component_container-1] [INFO] [1746609186.726054468] [apriltag.tag_container]: Found class: rclcpp_components::NodeFactoryTemplate
[component_container-1] [INFO] [1746609186.727206062] [apriltag.tag_container]: Instantiate class: rclcpp_components::NodeFactoryTemplate
[INFO] [launch_ros.actions.load_composable_nodes]: Loaded node '/apriltag' in container '/apriltag/tag_container'
[component_container-1] [WARN] [1746609191.764083270] [apriltag]: [image_transport] Topics '/zedx/zed_node/left/image_rect_color' and '/camera_info' do not appear to be synchronized. In the last 10s:
[component_container-1] Image messages received: 9
[component_container-1] CameraInfo messages received: 30
[component_container-1] Synchronized pairs: 9

Would you be able to provide any additional advice or suggestions?

My setup

• Ubuntu 20.04 + ROS2 foxy

[QQting]

Hi @Harin99 ,

I don't believe this is an apriltag_ros issue. The output log indicates that only 9 image frames are being received, which is the underlying problem that needs to be resolved.

Try debugging with ros2 topic echo /zedx/zed_node/left/image_rect_color.

Alternatively, consider using a different DDS middleware, such as CycloneDDS or FastRTPS.

[Harin99]

@QQting, Thank you for your reply!

I checked the image topic, and the images are being received correctly.
Currently, the image topic is published at 30Hz, while the camera_info topic is at 15Hz, which I believe initially caused a synchronization-related warning.
However, after rerunning the code, no sync warnings appear, but the process still gets stuck at the line below and does not proceed any further.

[INFO] [launch_ros.actions.load_composable_nodes]: Loaded node '/apriltag' in container '/apriltag/tag_container'

In addition, I have tried using a different DDS middleware such as CycloneDDS, but the process still gets stuck at the same line and does not proceed further.

I am currently using the 36h11 Apriltag family with ID 0.
Is there any other possible issue that I might be overlooking?

[QQting]

Hi @Harin99

I don't think you should use the left node.
Additionally, I'm not sure why the camera_info_sync_node is present.
In RealSense, there are no left, right, or sync nodes.