ZED X hardware sync with 3 cameras: timestamp differences not consistently within 15µs

Software
1

Hi, all!

I am working on synchronizing three ZED X cameras using hardware synchronization.
The required sync pinout wiring has already been completed.

I have tested both SVO playback mode and real-time grab() mode, and for the grab-based test I used the official multi-camera sample code from here:
https://github.com/stereolabs/zed-multi-camera/tree/master

According to the documentation, with hardware synchronization it should be possible to achieve synchronization accuracy on the order of ~15µs.
However, when comparing timestamps obtained via
getTimestamp(sl::TIME_REFERENCE::IMAGE) across the three cameras:

  • Occasionally the difference falls within ~15µs,

  • but in most cases the timestamp differences are larger than that.

  • This behavior is observed consistently in both SVO mode and live grab mode.

I would appreciate clarification on the following points:

  1. In a ZED X hardware-synchronized setup, is it expected that TIME_REFERENCE::IMAGE timestamps do not consistently stay within 15µs, even when the hardware sync wiring is correct?

  2. Does the TIME_REFERENCE::IMAGE timestamp strictly represent the sensor exposure time, or can internal buffering / pipeline effects introduce additional jitter that should be expected?

Any guidance on whether this behavior is normal or if there are additional checks or configurations recommended would be greatly appreciated.

Thank you for your support.

2

Hi @min
What you described is expected.
This support page explains the reason with details:
https://support.stereolabs.com/hc/en-us/articles/28554661445911-Why-frames-from-different-ZED-X-GMSL2-cameras-connected-to-the-same-capture-card-have-different-timestamps

If you are using a ZED Link Quad capture card, please also follow the instructions in this documentation page:

1 Like
3

Thanks for the explanation. I have a quick follow-up question.

From the documentation, the Master Mode – Trigger Out page mentions trigger and ground signals.
If I am using a single ZED Link Quad capture card to synchronize 3 ZED X cameras, do I need to explicitly connect the GND pin, and if so, where should it be connected in this setup?

Also, I previously followed the Jetson AGX Orin setup guide which mentions sync_mode = 1, but I sometimes get:

Unknown key name 'sync_mode' in section 'Service', ignoring

For a single Quad card with 3 ZED X cameras, which sync mode is currently recommended to ensure correct hardware synchronization?

Thank you.

4

Not on the same ZED Link Quad:

Are you using the latest version of the ZED X Driver?