Timestamps of ZED2i images using ZED2 ROS wrapper

Software ROS2
1

Hello,

I am using ZED 2i with Jetson orin nano devkit running ros2 humble and ubuntu 22.04. I collected static images with VGA resolution at 15 Hz.

I noticed that there is a constant frame drop that happens around ~46 to 50 s. Instead of 67 ms as interval for consecutive images, I see 133 ms. Is this an expected behavior? Is there a way to remove this frame drops or latency?
I attached the following plot. Thanks.

image
image563×432 12.3 KB

2

I synchronized the system time of Jetson Orin nano with 1 PPS using chrony.

3

Hi @ellarizza
Please provide more information regarding your setup.

How are you measuring the framerate?
Are you using the Jetson in MAXN power mode with jetson_clocks running?
Have you applied the recommended system settings?

4

Hi @Myzhar
To measure the frame rate, I get the absolute difference of timestamps from two consecutive images and get its reciprocal. For example: time_diff = 0.067 s; frame_rate = 1/0.067 = 14.92 ~ 15.

I am using Jetson in MAXN power mode, but I have not used jetson_clocks. But I have setup Chrony and use a 1 PPS source (ublox m8t) via GPIO.

I have not applied the recommended system settings.

I would appreciate your suggested next steps to correct my settings/setup.

Thank you.

5

Hi @ellarizza,

Can you share how you are retrieving the images? Are you recording the images additionally or doing some other type of processing?

6

Hi @mattrouss

I use ros2 bag record to retrieve the left and right image and imu topics in Jetson Orin Nano Dev Kit. Aside from time synchronization using chrony and 1 pps, there is no other related processing done.

7

Hi,

I strongly recommend you to set up your DDS communication with ROS2 following these recommendations.

Can you also let us know which SDK version you’re currently using ?

thanks !

Stereolabs Support