01 What actually happens to your video
The phrase "AI swing analysis" covers several quite different things. Here is the specific pipeline TEKRISE uses, because "AI" on its own tells you nothing about accuracy.
- Pose tracking, on your phone. A pose model finds 12 body joints — shoulders, elbows, wrists, hips, knees, ankles — in every frame. This runs on the device itself: ML Kit on Android, Apple Vision on iOS. Nothing is uploaded for this step.
- Racquet and ball detection, also on your phone (Android). A separate object-detection model locates the racquet and ball. On iPhone this model is not shipped yet, so the analysis there runs on pose alone.
- Derived measurements. Raw joint coordinates are useless to a coach. They are converted into readable quantities: joint angles, hip–shoulder separation, torso lean, stance width relative to your own body, racquet-head speed, follow-through ratio.
- Coaching feedback. A short silent clip — at most 3 seconds, the swing you chose — is sent to our AI coaching engine, which returns the written coaching. Your full original recording stays on your phone.
02 How accurate is it, honestly
Accurate enough to spot technique patterns and track change over time. Not accurate enough to be treated as a laboratory measurement. That distinction is the whole answer, and it is worth being precise about why.
What it is genuinely good at
- Relative change. Comparing your shoulder turn this month against last month, filmed the same way, is reliable — systematic errors mostly cancel.
- Large, obvious deviations. An elbow at 130° when it should be near 165° is far outside the noise floor.
- Consistency. Whether you do the same thing every swing, which is often more diagnostic than any single value.
- Timing. When events happen relative to each other — coil peak versus contact — because that is measured within one clip.
What it is not good at
- Absolute precision. A single degree of difference between two swings is noise, not signal.
- Depth. One camera sees two dimensions. Anything happening towards or away from the lens is inferred, not measured.
- Anything off-axis. Widths and stances are projections and compress as the camera moves off-square. TEKRISE classifies your camera view and skips the checks that stop being trustworthy rather than reporting a confident wrong number.
- Grip, string tension, spin rate, ball speed. None of these are visible to a pose model.
- Whether the shot was the right choice. Technique and tactics are different questions.
The honest summary
Treat it as a very patient training partner with an excellent memory and a slow-motion replay — not as a measuring instrument, and not as a coach. It is a guide, not gospel.
03 What makes the analysis better or worse
| Factor | Effect | What to do |
|---|---|---|
| Camera angle | Largest single factor. Off-axis footage disables several measurements entirely. | Film square-on or side-on. Keep it consistent between sessions. |
| Whole body in frame | Cropped feet means no footwork, stance or weight-transfer data. | Frame head to feet, with room to move. |
| Lighting | Poor light degrades joint detection, which degrades everything downstream. | Daylight or a well-lit court. Avoid shooting into the sun. |
| Background | Other people in frame can confuse person detection. | Film when your half of the court is clear. |
| Frame rate | Contact lasts about 4 milliseconds. No phone camera catches it exactly. | Nothing — but it is why the contact frame is an estimate, not a certainty. |
| Camera stability | A moving camera adds apparent body movement that is not yours. | Prop the phone up. Do not hand-hold if you can avoid it. |
04 How this compares with a human coach
It is not a competition, and it is worth being clear about the size of the gap. Measuring a swing is perhaps a tenth of what a good coach does.
| AI swing analysis | A human coach | |
|---|---|---|
| Measures precise body angles | Yes, every swing | By eye, approximately |
| Perfect memory across months | Yes | Partially |
| Available at 7am on a Tuesday | Yes | No |
| Feeds you balls | No | Yes |
| Fixes your grip mid-rally | No | Yes |
| Reads your opponent, teaches tactics | No | Yes |
| Knows when you need encouragement | No | Yes |
| Cost per session | Free to start | Typically $50–100 |
The realistic use is the gap between lessons. A coach gives you an hour a week; the other six days you practise unsupervised and can quietly groove the very habit they just corrected. That is the problem this kind of tool actually solves.
05 What happens to your video
- Pose tracking — and racquet detection on Android — happens on your device. Your footage is not uploaded for those steps.
- Only a short silent clip is sent for coaching feedback — at most 3 seconds, the swing you selected, with no audio track. That clip is also stored with your analysis history so you can replay it later; you can have it deleted with your account.
- Your full original recording stays on your phone unless you choose to delete it.
- Full detail is in the privacy policy.
Frequently asked
How accurate is AI tennis swing analysis?
Accurate enough to identify technique patterns and track change over time; not accurate enough to be a laboratory measurement. It is reliable for large deviations, consistency between swings, and timing within a clip. It is unreliable for absolute precision, anything happening towards or away from the camera, and any measurement taken from badly off-axis footage.
Does AI swing analysis work from a normal phone camera?
Yes. Pose tracking runs on the phone itself using standard on-device models. Camera angle and framing matter far more than camera quality — a square-on or side-on shot with your whole body including your feet in frame beats a higher-resolution clip filmed from a bad angle.
Can AI replace a tennis coach?
No, and the gap is large. Measuring a swing is perhaps a tenth of what a coach does. Software cannot feed you balls, correct your grip mid-rally, teach tactics, read your opponent, or judge when you need pushing rather than encouragement. What it does well is cover the days between lessons, when most players practise unsupervised.
Does my tennis video get uploaded to the cloud?
Pose and racquet detection run entirely on your device. Only a short silent clip — at most 3 seconds, the swing you chose — is sent for the written coaching feedback. Your full original recording stays on your phone.
Why does the camera angle matter so much?
A single camera sees two dimensions, so any measurement involving width or depth is a projection that compresses as the camera moves off-square. Rather than report a confident wrong number, TEKRISE classifies your camera view and skips the measurements that stop being trustworthy at that angle.
Keep reading
See it on your own swing
TEKRISE measures every point on this page from a phone video of your swing, then tells you which one to work on first. Free to start — no credit card, no account needed.