I was asking whether you could use this camera to work out the speed of the diabolo, not just this video.
Of course you can? Why not. Just count rotations if you know slowing rate. As toby said.
Its quite easy to measure and calculate diabolo's moment of inertia - i write an article about it to finnish diabolo assosiation newsletter.
http://koti.kapsi.fi/~hel5am/sds/wp-content/uploads/2011/04/sdsnews7.pdf (page 2-4 its finnish, but you will understand at least results anyhow) When you know speed (angular velocity) of diabolo and moment of inertia, you can calculate rotational kinetic energy of diabolo.
I have nate sharpe's paper somewhere, but he only measured how big angular velocities you can get with different acceleration methods - i think it would be more interesting to study about energy conversion effiency with different acceleration methods and with different diabolo models!
There is lot of very elementary things that we dont know .. like "when you throw diabolo high and take it to string, how big part of diabolos highest state potential energy is possibly to convert to rotational kinetic energy" - wery interesting, dont you think?