Parameters in the cv2.calcOpticalFlowFarneback() function

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Hello,

I'm currently working on tracking objects and I've been reading tutorials like this: Optical flow. And in the section related to Dense Optical Flow in OpenCV, they do this:

flow = cv2.calcOpticalFlowFarneback(prvs,next, None, 0.5, 3, 15, 3, 5, 1.2, 0)

As I understood, prvs and next are corresponding frames, None means that there are no tracking points defined, but I still can't get what these numbers mean. I've read OpenCV documentation about this several times, but it didn't help me too much.

Thank you in advance.