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T39 Audit — Instructions

Task 39 · 2103 frames · prod 2804–4906 · 248 flagged by algorithm · 301 flagged by Dan

Overview

T39 covers production frames 2804–4906. The audit flagged frames two ways: the algorithm identified 248 frames across four checks (missing detections, OOW-only, FP zone, isolated singles), and Dan manually reviewed the full dataset and set needs_review=true on specific boxes across 301 frames — shown as ⚑ in the report.

For each flagged frame: open it in CVAT, fix whatever is wrong, mark Done. Use comments for anything uncertain.

Zones

ZoneT39 framesProd framesOwner
Maya0–9592804–3763Maya
Andreea960–19023764–4706Andreea
FP zone1903–21024707–4906Shared — Dan's concentrated false positive area

Use the zone filter buttons to see only your frames. Filter by "Dan flagged" to isolate the 301 frames Dan explicitly marked.

Dan's Feedback

From labelling_feedback_batches2-4.pdf — four key corrections:

Check types

C1 Missing detections — box count drops sharply

This frame has fewer than 30% of its neighbors' median box count. People were likely missed.

What to do

  1. Open the frame in CVAT.
  2. Look for unboxed people — swimmers in water, adults on deck, instructors at pool edges.
  3. Box everyone visible and assign the correct label.
  4. If the frame is genuinely sparse (empty pool section, break in the session), check neighbors to confirm and mark Done with a comment: "confirmed sparse, no misses."
Dan found systematic misses of instructors and parents standing at pool deck edges. Check partial figures at the frame border.
C2 OOW-only frames — all boxes are out-of-water

Every box on this frame is out-of-water, but neighbors have in-water swimmers. Either swimmers were missed, or equipment was wrongly labeled as a person.

What to do

  1. Open the frame in CVAT.
  2. Check whether there are swimmers in the water. If yes, add boxes.
  3. Check the existing out-of-water boxes — are they people or equipment? Delete cones, lane markers, chairs.
  4. If the pool is genuinely empty at this moment, mark Done with a comment.
out-of-water is correct for people standing outside the pool. Cones, timing equipment, and lane dividers should not be boxed at all.
C3 FP zone — out-of-water shapes in last 200 frames

Dan flagged prod 4707–4906 (T39 frames 1903–2102) as a concentration of false positives — equipment boxed as people. Every out-of-water box here is suspect.

What to do

  1. Open the frame in CVAT.
  2. For each out-of-water box: swimmer on deck, coach, parent — keep. Cone, chair, inflatable, lane equipment — delete.
  3. If all boxes are valid people, mark Done.
  4. If you deleted boxes, mark Done with a comment noting what you removed.
This section was annotated during a break in the swim session when pool equipment was visible on deck. Equipment was systematically mislabeled. Priority zone.
C4 Isolated single-shape frames

This frame has exactly 1 box while neighbors average more than 3. People were likely missed.

What to do

  1. Open the frame in CVAT.
  2. Look for additional people not boxed — background swimmers, partial figures at edges.
  3. Add boxes for anyone visible.
  4. If only one person is genuinely on screen (others have left frame), mark Done with a comment.
Dan Dan's needs_review flags

Dan set needs_review=true on specific boxes across 301 frames. The flag shows as ⚑ label in the report — the label tells you which box Dan flagged on that frame. Filter to "Dan flagged" to work through these.

What to do

  1. Filter to "Dan flagged" in the report.
  2. Open the frame. Identify the box with the flagged label.
  3. For prob-above / prob-below flags: decide whether the swimmer is actually definitive. If you can clearly see the body position, switch to def-above / def-below. If it's genuinely ambiguous, keep prob.
  4. For def-below flags: is the swimmer fully visible underwater? If they're cut off at the edge, switch to out-of-frame or prob-below.
  5. Update the label if needed, then mark Done.
Decision guide (from Dan's feedback):
  • def-above / def-below — body position unambiguous, clearly visible
  • prob-above / prob-below — present but ambiguous: partially submerged, obscured, or uncertain
  • out-of-frame — cut off at frame edge, body extends beyond the border
  • out-of-water — person standing outside the pool
  • unknown — genuinely impossible to determine — use sparingly

Workflow

1
Select your name in the dropdown at the top of the report.
2
Filter to your zone (Maya or Andreea). To prioritize Dan's flags first, also enable the "Dan flagged" filter.
3
Work top to bottom. Click the prod frame number to open it directly in CVAT.
4
Fix annotations: add missing boxes, correct labels, delete false positives.
5
Click Done when the frame is corrected. Click Skip if you're unsure — add a comment explaining why.
6
Use the comment button for edge cases, questions, or anything that needs discussion before finalizing.
7
Check the progress bar at the top — clear your zone before the review deadline.

Label reference

LabelUse when
def-aboveClearly above waterline, body position unambiguous
prob-aboveProbably above water but ambiguous — partially submerged or obscured
unknownImpossible to determine position — use sparingly
prob-belowProbably underwater but not fully clear
def-belowClearly underwater, fully submerged, unambiguous
out-of-waterPerson standing outside the pool (deck, bleachers)
out-of-framePerson cut off at frame edge — body extends beyond the border