Why the clip is the whole ballgame

Any video screening, from a free app to a professional markerless system, can only measure what the camera actually captured. Research on markerless systems shows they read side-on motion like stride length very well and rotational motion poorly.1 That is not a flaw you can fix after the fact. It is decided the moment you press record. So the few minutes you spend setting up the shot do more for accuracy than anything the software does later. If you want the background on how that software works, read [what AI pitching analysis actually is](/library/ai-pitching-analysis) first.

Note

The most common reason a screening comes back useless is not the pitcher or the software. It is the clip: filmed from the dugout at a slant, half the stride cut off, at normal speed. Set the shot up right once, then film it the same way every time.

The four things to get right

1. Angle: throwing-arm side, square and level

Stand on the same side as the pitcher's throwing arm, directly to the side of the mound, not in front of or behind it. Hold the camera level with the pitcher's chest, not angled up from the ground or down from a fence. A square, side-on view is the angle video measures best, because the delivery's biggest, most readable motions happen in that plane.1 An angled or tilted shot quietly distorts every measurement that follows.

2. Frame rate: slow motion, 120fps or higher

A pitch happens in a fraction of a second, and the fastest part of the arm is among the quickest motions in all of sports. Standard 30fps video smears it into a blur. Switch your phone to Slo-Mo, which records at 120 or 240 frames per second on most modern phones. More frames means more still images of the delivery, which is what lets any tool place the joints accurately through the throw.

3. Distance and framing: about 15 feet, full body in frame

Set up roughly 15 feet away, far enough that the entire delivery stays in the shot from first move to follow-through, with a little room above the head and below the feet. Film in landscape, not portrait. If the stride foot or the follow-through leaves the frame, the screening loses the lower-half information that drives much of safe velocity, and the clip is half a delivery.

4. Lighting and background: bright, even, uncluttered

Computer vision finds a pitcher by separating the body from the background, so help it. Film with light in front of the pitcher rather than behind, avoid shooting straight into the sun, and pick a plain backdrop without a crowd or a chain-link fence layered over the body. Good light and a clean background do more for tracking quality than most people expect.

Key idea

If you only remember one rule: throwing-arm side, level, full body, slow motion. Those four cover the vast majority of bad clips.

Why filming it the same way every time matters

A single pitch is a noisy sample, and a single clip is a snapshot. The value of screening comes from watching trends across a season, which only works if the conditions stay consistent. Quantitative video analysis of pitching has been shown to be reliable, meaning it gives repeatable readings, as long as the method stays the same.2 Change the angle or distance between sessions and you are no longer comparing the pitcher to himself. You are comparing two different setups.

Pick a routine and lock it in: same side, same distance, same height, same kind of light. Film two or three pitches so you have a clean one to choose from. Single-camera systems can capture a usable delivery when the shot is set up well, so your job is simply to give the tool its best chance every time.3

Common mistakes that wreck a clip

  • Filming from the front or behind. You lose the side-on view that video measures best.
  • Shooting in portrait. The follow-through and stride run out of the frame.
  • Normal speed instead of Slo-Mo. The fastest, most important part of the throw blurs.
  • Standing too close. Part of the delivery leaves the frame at the extremes.
  • Backlighting or a busy background. Tracking degrades when the body is hard to separate.
  • Changing the setup each time. You can no longer compare one session to the next.

None of this requires special gear. A recent phone, a steady hand or a cheap tripod, and a consistent routine are enough to produce a clip worth screening. Get the four basics right, repeat them, and the readings you get back will actually be about your pitcher rather than about your camera work. Once you have a clean clip, [screen it](/try) and read [how to tell if the mechanics are safe](/library/are-my-pitchers-mechanics-safe) to make sense of what comes back.

Education, not a medical diagnosis or treatment plan. If your pitcher has pain, consult a qualified sports-medicine professional.

Originally published on CritchPitch.