Say how long the read has left, and let it be stopped

[ibrahimweng]

Reading a video is the longest wait in the app. The button that starts it was also the button that showed the progress, and it greyed itself out for the duration — so there was no way to know how much longer and no way out. Loading the wrong file meant waiting it out or reloading the page.

The wait itself is not the fault

The obvious fix is to make it faster, so I measured that first. Sampling rate against moments found, on a dense thirty second clip with forty events in it:

samples per second	moments found
15 (current)	40 of 40
10	37
8	33
7	31
5	21

Going twice as fast halves the wait and loses nine of forty. The rate is paid once per clip and the miss is paid every time somebody looks for a moment that is not there, so the existing choice is the right one and it is left alone.

What changed

The button counts down. Reading · 10s left → 8s left → 5s left, worked out from the rate so far rather than guessed. A percentage answers a question nobody has; the one somebody does have is whether to wait or go and do something else. It says nothing until a twentieth of the way in, because before that the rate is mostly the cost of starting and the answer swings about by minutes. Rounded up to whole seconds, and to minutes past ninety.

It stays live, because it is the way to stop. Pressing it again calls the read off. The abort reaches the frame loop, not just the state — analyseMotion takes an AbortSignal and resolves rather than throws, since "I have changed my mind" and "this file cannot be read" are not the same thing to say to somebody.

Stopping keeps nothing. A pass over the first third of a clip would suggest sounds for the first third and say nothing about the rest, which reads as the app having found nothing there.

Checking

Four browser tests, each checked by putting its fault back:

• dropping the countdown fails one
• leaving the button disabled fails one
• removing the abort from the frame loop fails one — and this is the one worth naming. The first version of that test passed with the abort taken out, because the orphaned read finished after the assertions had run. Resetting what is on screen is not stopping: a read that was only forgotten about carries on and hands its results in half a minute later, so moments appear out of nowhere long after somebody pressed stop. The test now waits past the point the whole clip would have been read.

251 unit tests, 81 browser tests (was 77), build clean.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Ux1kydvUkLRoMbHp82ofDi

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Generated by Claude Code

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