Unable to get 400Hz IMU Data from ZED-X from ROS Topic Hz

Software ROS2
1

Hi, I am using ZED-X on Jetson Orin with Jetpack 6, ZED SDK 4.1.4, and a ZED Link Quad Capture Card. In the ZED tool’s Sensor Overview, I can see that all the data is being published at 400 Hz.

However, for the ROS wrapper, even though I set the frequency to 400 Hz, when I launch the camera and use ros2 topic hz to check the frequency, it only shows around 250 Hz.

Is anyone else facing a similar issue?

Another question: What is the best way to record data for images and IMU from multiple ZED cameras?

2

Hi @Alex-Beh
are you using the ROS or the ROS 2 Wrapper?

3

@Myzhar I am using ROS 2 Wrapper. The frequency output of camera is not stable at 30Hz also.

4

This is a “communication issue”.
First, ros2 topic hz is not the best way to benchmark a topic’s frequency. I recommend you use our benchmarking tool.
Second, you must check that you use a good QoS setup and middleware optimization.
Third, the IMU data retrieval/publishing run is done on a separate thread. If the Jetson device is overloaded the thread can run slower than required.

What DDS middleware are you using?

5

I am using cycloneDDS now. Do you have any recommendation for the middleware selection and configuration?

Currently we only launch two cameras on the Jetson Orin. so I believe it should have enough resource for the imu thread.

6

When using CycloneDDS I recommend following these guidelines to tune it for handling big-sized data:

I would also add this, which is not related to this problem, but still useful: Communicating across multiple computers with CycloneDDS - Autoware Documentation

7

We tried recording the data using the ZED Sensor Viewer. Although the UI shows 400Hz, when we calculate the frequency from the saved CSV file, it is only around 200Hz. May I know if it’s the same on your side?

8

I’m checking this behavior and I let you know.

9

Thanks. Let me know if you have any updates.

10

@Myzhar Hi, do you have any update on the experiment?

11

Hi @Alex-Beh
I apologize for the delay.
I’ve finally found the right moment to perform the test and I confirm the weird behavior.
I already reported it to the SDK team and it will be analyzed and eventually fixed.

1 Like
12

Hi @Alex-Beh
according to the team feedback, the behavior will be fixed with the ZED SDK v4.2 which will be hopefully released before the end of the week.

13

Tested the new ZED SDK v4.2 and it is fixed now. Thanks.

1 Like
14

@Alex-Beh thank you for the feedback