How to get syncronized image seqence number with oak-ffc-4p

Ffboris · Apr 1, 2023

I follow this instruction to do 4 camera sync https://docs.luxonis.com/projects/hardware/en/latest/pages/guides/sync_frames.html#oak-ffc-4p-fsin

I got sync camera frame successfully after few image frames coming. But as following log, the sequence number are not the name between 4 camera's image:

cam_a:0:00:01.574682 seq:5
cam_b:0:00:01.574662 seq:3
cam_c:0:00:01.574673 seq:4
cam_d:0:00:01.574705 seq:4

is it possible to get same sequence number with hardware synchronization? Also, Can I get synced frame at sequence=0? In this example, 4 camera synced after cam_d seq=4

cam_a:0:00:01.372946 seq:0 cam_a:0:00:01.406296 seq:1 cam_a:0:00:01.439647 seq:2 cam_c:0:00:01.444488 seq:0 cam_d:0:00:01.466839 seq:0 cam_a:0:00:01.473000 seq:3 cam_b:0:00:01.474608 seq:0 cam_c:0:00:01.477839 seq:1 cam_d:0:00:01.500190 seq:1 cam_b:0:00:01.507959 seq:1 cam_c:0:00:01.507972 seq:2 cam_d:0:00:01.507982 seq:2 cam_b:0:00:01.541311 seq:2 cam_c:0:00:01.541323 seq:3 cam_d:0:00:01.541347 seq:3 cam_a:0:00:01.574682 seq:5 cam_b:0:00:01.574662 seq:3 cam_c:0:00:01.574673 seq:4 cam_d:0:00:01.574705 seq:4 cam_a:0:00:01.608035 seq:6 cam_b:0:00:01.608014 seq:4 cam_c:0:00:01.608026 seq:5 cam_d:0:00:01.608044 seq:5 cam_a:0:00:01.641386 seq:7 cam_b:0:00:01.641366 seq:5 cam_c:0:00:01.641377 seq:6 cam_d:0:00:01.641395 seq:6

erik · Apr 5, 2023

Hi fboris ,

Sorry about the delay. For hardware syncing, I'd suggest checking our HW syncing documentation, and also OAK-FFC-4P syncing docs. That way, you should get all 4 frames of the same seq number at the same time. Let us know if this fixes your issue.

Thanks, Erik

Ffboris · Apr 7, 2023

The timestamp of 4 image are simliar(under millisecond). But sequence numbers are not.

I modify example from here and get following output:

rgb: 0:00:05.246721 seq: 108

left: 0:00:05.246732 seq: 107

right: 0:00:05.246741 seq: 107

camd: 0:00:05.246751 seq: 105

-------------------------------

rgb: 0:00:05.280073 seq: 109

left: 0:00:05.280087 seq: 108

right: 0:00:05.280096 seq: 108

camd: 0:00:05.280106 seq: 106

-------------------------------

It is obvious the sequence number are not the same even the timestamp are close between different camera image.
Any suggestion? Test 2.19, 2.20 and develop branch has similar issues.

here is code i wrote:

erik · Apr 10, 2023

Hi fboris , As a workaround, what about sync messages based on timestamp instead of sequence number?