# BEFORE W1: narration

t=0 is the first video frame showing the overlay box (video time 0.04 s). Each mark changes the overlay colour; the t column is the first video frame showing that mark's colour (frame-accurate at 25 fps). Wall-clock prediction vs observed max error 0.027 s over 15 marks; frames at 15.46 s, 20.34 s, 27.66 s were extracted and checked.

Hold: /bounded held 3200 ms (HOLD_MS 2500 + measurement), framesDuringHold 72, loadingSeenDuringHold True.
The overlay reads `loading thread; /bounded held 2500 ms` (grey) from t=0 until the mount mark.

| t (s), first frame showing this mark | wall-clock prediction (s) | overlay text |
|---|---|---|
| 15.36 | 15.36 | thread mounted after the hold |
| 15.44 | 15.43 | wheel up 339 px |
| 16.08 | 16.08 | after wheel: gap 339 px (0.40 ch) gate ok |
| 16.16 | 16.13 | release t1-start |
| 17.16 | 17.14 | release t1-finish |
| 18.08 | 18.09 | release p1 |
| 19.24 | 19.26 | release t2-start |
| 20.24 | 20.26 | release t2-finish |
| 21.2 | 21.22 | release p2 |
| 22.32 | 22.34 | W4: no pill; wheel down 1696 px |
| 23.28 | 23.28 | release t3-start |
| 24.32 | 24.31 | release t3-finish |
| 25.28 | 25.28 | release p3 |
| 26.32 | 26.34 | release resumed |
| 27.56 | 27.54 | end of row |

## Samples

| label | scrollTop | scrollHeight | clientHeight | gap | anchor | anchorTop | pill | follow listeners (timeline/doc keydown) |
|---|---|---|---|---|---|---|---|---|
| S0 mounted | 5145 | 5993 | 848 | 0 | P090 | 61.3 | False | 0/0 |
| S_up | 4806 | 5993 | 848 | 339 | P084 | 64.9 | False | 0/0 |
| after t1-start | 5145 | 5993 | 848 | 0 | P090 | 61.3 | False | 0/0 |
| after t1-finish | 5145 | 5993 | 848 | 0 | P090 | 61.3 | False | 0/0 |
| after p1 | 5201 | 6049 | 848 | 0 | P091 | 61.2 | False | 0/0 |
| after t2-start | 5201 | 6049 | 848 | 0 | P091 | 61.2 | False | 0/0 |
| after t2-finish | 5201 | 6049 | 848 | 0 | P091 | 61.2 | False | 0/0 |
| after p2 | 5256 | 6104 | 848 | 0 | P092 | 62 | False | 0/0 |
| W4 resumed | 5256 | 6104 | 848 | 0 | P092 | 62 | False | 0/0 |
| after t3-start | 5256 | 6104 | 848 | 0 | P092 | 62 | False | 0/0 |
| after t3-finish | 5256 | 6104 | 848 | 0 | P092 | 62 | False | 0/0 |
| after p3 | 5312 | 6160 | 848 | 0 | P093 | 61.9 | False | 0/0 |
| after resumed | 5473 | 6321 | 848 | 0 | P095 | 59.7 | False | 0/0 |