What can a dance app that gives feedback actually tell me?
Feedback apps work from pose estimation: a skeleton placed over each frame of your recording, compared with a skeleton from the reference. From that they can measure timing and joint angles; they cannot measure feel, musicality or how you look to a person, and they cannot see a limb the camera did not see. The useful question is not whether an app is "accurate" but whether it tells you one thing you can act on and admits when it could not see you.
Three kinds
- Live overlay: a skeleton on your camera feed while you dance, with cues in the moment. Immediate, and hard to attend to while moving.
- Upload and score: you send a video, the app returns a number and some notes. Simple, and the number is only as honest as the app’s idea of what a score means.
- Side-by-side comparison: your recording against a reference, frame by frame, with differences called out. The closest to what a coach does with a recording.
What a camera can measure
Joint positions in two dimensions, well; depth, roughly; timing against the reference, well if the two videos are aligned. Angles at the big joints — hips, knees, shoulders, elbows — are the reliable numbers. Fingers and feet are where estimation gets noisy.
What to ask
- Does it say when it could not see you, or does it guess?
- Does it give one correction, or a score that tells you nothing about what to change?
- Does the video leave your phone? An app that analyses on the device keeps your footage yours.
- Does it state its own margin of error? A number without a floor is a number to distrust.