GMSL Cameras Synchronization Resolution

Hi,

We have 4 LI-AR0231-GMSL camera in group A on PX-2 and it works fine. We are digging deeper to see what’s the synchronization resolution btw cameras. Clearly it’s very small and we would love to know how small it is. Is it below 1ms between cameras? With GMSL protocol support, this looks like reasonable.

I did print out each frame’s timestamp which shows they are on the same ms when captured. But there is a note in document that Note due to technical limitations of the NVIDIA DRIVE PX 2 platform this is not the point in time where the image was actually taken.

Do you have some tested info?

cheers,

Steve

Dear scheng,

It depends on the configuration of DPX2. We’ve posted a guide to Time Sync on our FAQ like below
According to the above message, the test result is not a problem. Please let us know which part is the problem and we will check. Thanks.

https://devtalk.nvidia.com/default/topic/1031778/faq/drive-px2-time-sync-guide/
https://devtalk.nvidia.com/default/topic/1007100/faq/data-logging/

Hi SteveNV,

I guess they are the same timestamp in dwImageNvMedia->timestamp_us. I checked them last week. But it’s a timestamp at the time when image frame arrives at Aurix. Here I’m looking for the frame sync signal to GMSL cameras and these cameras will take a picture. There are some nice timing diagrams from MAXIM but unfortunately they don’t have any exact number.

Also my understanding is PTP is using for synchronization between multiple Aurixes. For 4 GMSL cameras on the same Aurix and MAXIM chip, PTP is not used there other than Aurix gets its time synchronization.

thanks,

Steve

Dear scheng,

If you check out: file:///usr/local/driveworks/doc/nvdwx_html/dwx_recording_library.html

There should be: The params must follow the params given to a Driveworks sensor at initialization. In order to record in other formats besides h264, add output-format=[raw,lraw,h264,raw+h264,lraw+h264] with one of the listed output formats to the params. In order to record camera frames at a lower rate than the default, use frame-skip-count in the params.
For example, a value of frame-skip-count=1 records at 15 FPS if the camera hardware runs at 30 FPS. Setting record-frame-count=2 with frame-skip-count=1 records two (2) frames and skips 1, and then repeats.

For certain kinds of camera, e.g., ar0231-rccb, the camera framerate can be controlled by the required-framerate option. Valid values for now are 20, 30, and 36.

Hi SteveNV,

Thanks for the link dwx_recording_library.html and I went through it. It didn’t answer my question of time difference between different GMSL cameras in the same group. It also didn’t cover whether PTP is used between multiple AURIX only.

thanks again for your help,

Steve