StrokeVision
Your AI tennis coach — record your swing, get clear feedback, fix your technique
Confidentiality Note
Code is private during active development. This case study covers architecture, system invariants, and engineering decisions — not implementation details. Happy to walk through architecture and modules live.
An AI-powered tennis coach that lives in your phone. Players record themselves practicing, the app studies the swing from feet to fingertips, and it tells them the one or two things to focus on this session and how to fix them. Built for the millions of recreational players who practice far more often than they can afford a coach.
Problem
Getting better at tennis is hard without regular coaching. Lessons cost $60–$150 each and most players only get one a week — but they practice three to five times more than that. The rest of the time, they're reinforcing whatever habits they already have. Filming yourself on your phone doesn't help much either: you watch the clip once, can't tell what's wrong, and shelve it.
Solution
StrokeVision turns any practice video into a coaching session. The player films one swing, the app studies it from feet to fingertips, and gives back specific, easy-to-act-on feedback — things like "your hips opened a fraction too early" or "your base was set well this time." Tips are written and reviewed by qualified tennis coaches before they reach the player. The app also lets players overlay their swing on a pro's so they can see exactly where their form differs.
Architecture
- Mobile app for recording and reviewing swings — iPhone first, Android next
- Cloud-based video analysis that processes each swing in the background while the player keeps using the app
- Computer vision tracks the player's body through every frame of the swing — feet, knees, hips, shoulders, arms, wrist
- Smart coaching layer picks the one or two most important things to work on this session, instead of overwhelming the player with a dozen tips
- Side-by-side and overlay comparison against pro reference clips so the player can see exactly where their form differs
- Built to grow with the player — starting with the forehand today and expanding to backhand, serve, volley, and overhead
Security & Reliability
- The app only coaches technique — never gives medical, injury, or rehab advice. That's a hard rule.
- Every coaching tip is written or reviewed by a qualified tennis coach before it ships. AI does the personalization; coaches own the content.
- If the camera angle or video quality means the app can't see something clearly, it says so. No fake confidence — same as a human coach watching a bad-angle clip.
- Player videos are uploaded directly to secure cloud storage and only the player can see them.
- Every tip has thumbs-up / thumbs-down buttons so players can flag anything that doesn't feel right — and that feedback loops back to improve the coaching.
Design Tradeoffs
- Ship one stroke really well, not five strokes poorly. Version 1 launches with the forehand fully coached. Backhand, serve, volley, and overhead are next — the foundations are already built for them.
- Honest first, magical second. The app tells the player when it can't see their swing clearly instead of guessing. Players trust feedback they know is real.
- Pro overlays are a reference, not a rulebook. The app shows how a player's swing compares to Federer or Sinner — without telling them "be Federer." Everyone's body is different, and good coaching reflects that.
Results
- Version 1 works end-to-end on the forehand — record, analyze, get tips, track progress over time
- Coaching content reviewed and approved by qualified tennis coaches before any of it reaches users
- App Store launch materials prepared; TestFlight beta submission in progress
- Foundation is built to add every other major stroke without re-doing the work