question: why in pairs segs=True?

[alexlib]

Hi @yosefm, just a question, why when we look at pairs in some frame, we request for trajectory to be active also in the next frame?

postptv/flowtracks/pairs.py

Line 57 in 81f27cd

segs=True)

[yosefm]

So that the last point will have a valid velocity. I guess we could relax this restriction when velocities are determined with SG smoothing or something, but when I started it, it was all forward differences.