Arthur: Turning video into data

From SABR member Rob Arthur at Baseball Prospectus on March 27, 2020:

Last week I wrote about the next frontier in baseball data: biomechanics. Using an open-source software package called OpenPose, I used bog-standard broadcast clips to get the coordinates of Mike Trout’s limbs as he swung (first a golf club, then a baseball bat). The possibilities of biomechanics data are limitless, stretching from pitch tell-hunting to prospect analysis to injury detection, and well beyond.

But digitizing video clips is only half the problem. The camera (and thus the computer) sees images only in terms of pixels: the tiny dots of color which together compose the visual we see. We don’t want to do biomechanical analysis on pixels though–it doesn’t make sense to say that Trout’s rotational velocity is 5000 pixels/second. So we need to turn pixels into the common units we think about: feet and inches, specifically. With a little help from Statcast, we can go a long way towards that goal.

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Originally published: March 27, 2020. Last Updated: March 27, 2020.