How to interpret optical flow vector data

Gaming and Visualization Technologies Visualization Video Processing & Optical Flow
1

Please provide complete information as applicable to your setup.

• Hardware Platform (Jetson / GPU)
GPU
• DeepStream Version
6.1

I’m trying to come up with a good way of doing motion detection in video images. I’m succesful in capturing the optical flow meta from every buffer, but I’m having a hard time making sense of the values.

What I understand from the (very sparse?) docs is that every block of 4x4 (by default) pixels generates an x, y vector pair that’s telling something about the movement of THAT block of 4x4 pixels, right? So I would say that if the vector says (-15, 0) that this block has moved 15 pixels to the left. Or if it says (200, 10) that it has moved 200 pixels to the right and 10 pixels down. Assuming x0, y0 is top left corner.

But in reality I encounter (6400., 128.)? The video has a resolution of 1920x1080 so how would a pixel(block) move by 6000 pixels? Or do these values mean something else entirely?

3

Please refer to NVIDIA Optical Flow SDK | NVIDIA Developer. There is optical flow forum for your question.

4

Moving to optical flow board for better support, thanks.

6

With all the widespread use of optical flow technology, there must be some sort of documentation about this, right? Somewhere?

I’m amazed I can’t find anything. All documentation is about the technical side of things, which is fine. But what does the data MEAN exactly? What does a vector of (-6400, 128) actually say?