Chalkline

Swing review for coaches who get ten minutes

The roster.

Film a few swings, get one thing to work on. Every player keeps a history, so next time the advice picks up where you left off.

Bats
How to film it thirty seconds of setup buys a much better read
  1. Stand on the open side — where you can see the hitter's chest and number, square to them, about 15 ft away.
  2. Phone at belt height, held still — lean it on a bucket or the fence. A moving camera reads as a moving hitter.
  3. Landscape, whole body in frame, head to feet, with room in front for the stride.
  4. Slo-mo if the phone has it. 60 fps or better sharpens every timing number. 30 fps still works.
  5. One swing per clip, a second or two on each end. Four to six swings makes a session worth trusting.

What this can and cannot see. It tracks the hitter's body — 33 joints, every frame — so it reads stride, balance, head movement, rotation and front-side mechanics well. It does not track the bat or the ball: on phone video the bat is a blur at contact, so anything claiming bat speed or exit velocity from a clip like this is guessing. Contact here is estimated from hand speed.

Where this lives

Everything stays on this device — no account, no upload. Checking how durable that is…