Subtitle QA · browser-local pacing · 2026 · Solo — product framing, test-first caption logic, interaction design, accessibility, responsive verification, production deployment
Caption Cadence
A subtitle pacing bench that makes reading pressure visible before the edit ships.
The problem
Video editors and caption authors often make a final subtitle pass by reading an SRT as a text file or watching the whole cut in real time. That leaves reading pressure and line shape hard to compare across cues, especially when a short cue carries substantially more copy than its neighbors. Caption Cadence keeps the workflow bounded and inspectable: paste canonical SRT, map each cue into a duration-proportional temporal mark, select calm, tight, or overloaded moments, edit the caption, balance its line break near a natural word boundary, then copy or download the repaired SRT. The 20-characters-per-second and 42-characters-per-line references are editorial heuristics rather than accessibility guarantees; the tool does not retime footage, rewrite meaning, validate language, or replace a human accessibility review. Transcript text stays in the tab; there is no upload, account, persistence, paid API, tracking SDK, email, payment, advertising, or destructive operation. Production deployment dpl_3s3ewos1dpqG1AVhCrn7kZH1GEq7 reached READY before independent Foundry HTTPS deploy and seven-step behavior checks passed at the stable alias.
Architecture
Key decisions
Make time visible instead of summarizing it
The breath strip gives each cue horizontal room according to duration and vertical pressure according to character rate. It is the operating surface, not a decorative chart or arbitrary dashboard metric.
Keep repair under editorial control
Line balancing moves only a word boundary. Cadence never silently rewrites copy or changes timing, and it labels its reading limits as heuristics rather than compliance claims.
Use one warm editorial Operate bench
Paper, stone, Georgia display copy, monospace timing data, and sage/ochre/vermilion states produce source-to-strip-to-handoff causality without feature tiles, center stacking, blur, icon toppers, or generic tech color.
Turn gate failures into release evidence
An early server probe exposed analytics markers that existed only in the client bundle, and the initial browser lane lacked Chromium. Server-visible metadata and an isolated Playwright browser install repaired the real verification paths before deployment.