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lmb-freiburg / flownet2

FlowNet 2.0: Evolution of Optical Flow Estimation with Deep Networks
https://lmb.informatik.uni-freiburg.de/Publications/2017/IMKDB17/
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what is the unit of value in .flo #66

Closed betterRunner closed 7 years ago

betterRunner commented 7 years ago

Dear flownet authors, I successfully run your project and the performance is outstanding! But I got little confused about the unit of the two value in .flo. I just know they stand for the optical flow value in axis x and axis y, but how they quantize to image pixes? Does it mean the number of pixels per second or something else? Thank you very much!

nikolausmayer commented 7 years ago

Hi,

the "optical flow" is defined as the per-pixel motion between the two input images, i.e. if you look up pixel (x,y) in the .flo and get the two values (u,v) there, you should find the pixel at position (x+u,y+v) in the second input image. It does not necessarily make sense to use a time unit here because optical flow can be applied to all sorts of inputs, not just temporally ordered images such as video frames.

TL;DR the unit is just "pixels".

betterRunner commented 7 years ago

Got it, your answer explains well. Thank your for your time!