Using 2 camera in a USB HUB

[crackwitz]

@Glordfaield

vid.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc(*'MJPG'))
vid.set(cv2.CAP_PROP_FRAME_WIDTH, 1280)
vid.set(cv2.CAP_PROP_FRAME_HEIGHT, 720)
vid.set(cv2.CAP_PROP_FPS, 120)

try putting the set(FOURCC) call last. maybe it didn’t correctly try to switch into MJPEG mode. I’ve seen people have issues with the order of these calls.

I think something isn’t USB 3 here, even though it should be. hubs are active devices. they must support USB 3, not just USB in general. a USB 2 hub will work for USB 3 devices, but they’ll run at USB 2 speeds then.

@Glordfaield

How can I correctly know in wich USB port the camera is ?

not with OpenCV. VideoCapture’s device number assignment is somewhat opaque and utterly unaware of a device’s identity or “where” a device was plugged in.

@Glordfaield

Because by default I use 0 and 1, but the camera can be in a different number ?

it will always assign IDs from 0 onwards. if you have another camera, even a virtual one, then it might be a good idea to test higher numbers. if not, then 0 and 1 are the only useful ones.