Output optical flow

[Penghao1005]

Hello author, I tried to output the characteristics of optical flow and visualize them, but I ran into problems. I would like to ask which part of the code is the final optical flow that I want to output. Generally, optical flow has two horizontal and vertical components with dimensions of (2, H, W), and I see that the flow that can be output is a list with dimensions of (4, H, W). So which part is the final representation of the optical flow information?