When tracking fails¶
The hardest part of the whole analysis is following a small, fast, motion-blurred ball through a couple of hundred frames. When it goes wrong you will see it: a concern saying the hammer tracking is sparse, a path in the 3D viewer that jumps or kinks, a turn count that does not match what you did, or a release marked in the wrong place.
This is fixable, by you, in the browser, in a few minutes. You do not need to re-film and you do not need to understand any of the machinery.
Open the tagging tool¶
On the throw card, click Tag Video. (It is also available on the Annotate button inside the 3D viewer.) It opens on your video with four tabs across the top:
| Tab | What you correct there |
|---|---|
| Circle | Where the throwing circle is |
| Tags | Where the throw starts, where each turn ends, where release is, which foot is down |
| Implement | Where the hammer is, in frames where it was lost |
| Trim | Cutting the clip down to the throw |
Tag Video only appears on your own throws. If a run failed outright it is still there — a failed run is usually a run that failed because tracking was too sparse, which is exactly the case tagging exists for.
Fixing the hammer — the Implement tab¶
This is the one that matters most, and the one to do first.
- Look at the orange ◉ Ball Track overlay. After analysis it is on by default, with its button at the upper right of the video (click it to hide or show the overlay). It draws where the analysis thinks the hammer was, with a short fading trail:
- a filled dot — the tracker detected the ball on this frame;
- a hollow ring — an estimated position: the tracker lost the ball here and filled in a guess;
- no mark — there is no track on this frame.
Scrub through and tag the frames showing a ring or nothing, plus any where the dot has wandered off the ball, frozen, or jumped. 2. Go to a frame where it is wrong and the ball is clearly visible. 3. Click Mark. The button changes to Click the ball — it is now waiting for you. 4. Click the centre of the ball in the picture. 5. Repeat through the throw.
You are placing points, not drawing circles. One click on the middle of the ball is the whole interaction; there is no size to set.
How many, and where:
- Roughly every 20 frames through the throw is a good rhythm.
- Concentrate on the stretches that were wrong, not the ones that were already right.
- Include anchors at the start of the throw, at the low point of each orbit, and at release.
- 30 to 50 marks is usually plenty. More is not better; it is just slower.
Use Map to see the orbit laid out, and Important / Skip to walk the frames the analysis itself has flagged as the ones it most needs help with.
When you are done, click Save.
Do not save the Implement tab with nothing marked
Saving with zero ball marks in place erases any ball marks you saved earlier, and still reports that the save succeeded. If you open the tab, change nothing and want to leave, navigate away — do not press Save. This is a known defect; until it is fixed, treat an empty Save as destructive.
Fixing the circle — the Circle tab¶
If the reconstruction has you throwing from the wrong place, or the circle is drawn somewhere odd, set it by hand: click Place, then click five points around the rim of the circle in your video, and Save. Reset clears it and starts again.
You do not have to be accurate about the size. Only the position and the orientation are taken from what you click — the circle is always drawn and analysed at regulation size.
Fixing the phases — the Tags tab¶
Use this when the turn count is wrong, the throw is judged to start in the wrong place, or release is marked at the wrong frame.
Scrub to the right frame and click the tag it should carry:
| Button | Mark it at |
|---|---|
| T0 | The frame the throw proper begins — the end of the winds |
| Turn | Each turn boundary |
| Release | The frame the hammer leaves your hands |
| SS | Where you go onto one foot |
| DS | Where you come down onto two |
Show Auto overlays what the analysis worked out by itself, so you can see where it disagrees with you. Undo and Delete remove marks. Save stores them.
Then re-run it¶
Tagging does not change your results on its own. Go back to your throw card and press the
lightning bolt ⚡ — its tooltip now reads "Re-analyze to apply tags". The analysis runs
again from your video, this time using everything you marked.
Your marks are kept. If you trim the clip afterwards they are moved to match the new timing rather than thrown away.
Trimming — the Trim tab¶
If your clip has a lot of dead time before or after the throw, Set In and Set Out mark the piece you want and Save File writes it back. Undo Trim puts it back.
A trim never starts an analysis by itself. Your existing numbers stay on the card and are
flagged as being from the untrimmed version; press ⚡ when you are ready to run again.
When tagging is not the answer¶
Some footage cannot be rescued by marking it up. If you find yourself marking the ball in most frames because it genuinely cannot be seen, the problem is the video:
- Is the ball actually visible to you in the frames that failed?
- Was the camera moving?
- Is there something else round and dark in the background the tracker keeps grabbing?
- Was it filmed in slow motion, or in portrait?
What makes a good video covers what to change next time. If none of this matches what you are seeing, ask a person.