Measure Concurrent Caption Time Once, Not Once for Every Cue Pair — Free
Stacked captions can overlap in pairs without creating that much distinct overlapping time. Sweep the timeline, count each overloaded second once, and keep cue participation separate from the union.
The proof surface
Clock drift compares synchronization offsets; this sweeps start/end events to measure union time with more than a supplied number of simultaneous cues.
InputCue code | start seconds | end seconds; allowed simultaneous cues in this review model
Rare deviceClock drift compares synchronization offsets; this sweeps start/end events to measure union time with more than a supplied number of simultaneous cues.
Output artifactUnion duration exceeding the stated cue budget plus complete labeled working
Cost$0 local core · no account, card, paid key or subscription · filing proposal has no checkout
Sample, not your facts: Invented records: Cedar cue | 0 | 5; Willow cue | 3 | 7; Pine cue | 6 | 9. Allowed simultaneous cues in this review model = 1; expected Union duration exceeding the stated cue budget: 3 seconds over cue concurrency budget. These are not quotations, verified observations or personal evidence.
Before using the cue-concurrency strip
This is a timing review of supplied cue intervals, not a media player or accessibility certification. Multiple simultaneous cues may be intentional for speakers, positioning or a caption format. The budget is your review convention, not a WCAG threshold. Enter seconds on one consistent timeline, with starts included and ends excluded. Up to six decimals are converted to integer microseconds before comparison, avoiding floating-point phantom overlaps. No caption text, audio, screen position, subtitle file or speaker identity is collected. Review the actual content and playback with users and an accessibility specialist before interpreting a marked interval as a barrier.
Why the flat version breaks
Pairwise overlaps are added as distinct time
When three cues overlap, one second can appear in three pair intersections. Summing those intersections overstates how long the timeline exceeded a cue-count budget. This strip uses the overloaded time union for the headline and prints cue participation separately. The two measures intentionally differ rather than being forced to reconcile by hiding the triple overlap.
Same-time endpoints create a fake overlap
A sequential event processor can briefly count both an ending cue and a starting cue at one instant. That instant has no positive duration under [start,end). Grouping all changes before the next segment and using integer microseconds prevents the transient from becoming counted time. The convention is explicit so users can compare it with their actual caption format.
A concurrency number becomes an accessibility verdict
Whether concurrent cues are understandable depends on content, layout, speakers and playback. This tool has no evidence for those dimensions and no built-in compliance threshold. A marked span is a review location, not an automatic violation or proof that a captioner did poor work. Keep the review budget and boundary in shared results, and evaluate the actual experience with qualified help.
How to work the cue-concurrency strip
Put every cue on the same time origin
Use unique neutral cue codes and nonnegative start/end seconds. End must be strictly later than start; zero-duration markers are not caption intervals in this model. Times may run to 360,000 seconds and have at most six decimal places. Do not mix absolute clock times with elapsed media seconds or convert frame numbers without a known frame rate. The app has no media import and cannot detect an inconsistent origin from plausible numbers alone.
Choose the review concurrency budget
Enter a whole allowed-cue count from one to 200. One highlights any positive-duration stacking; two highlights only intervals with at least three simultaneous cues. The setting does not infer reading difficulty or standards compliance. Every supplied interval remains visible whether marked or not. A higher budget changes the question, not the underlying timing evidence, so retain the chosen number when copying or filing the reading.
Sweep grouped endpoint events over half-open segments
At each unique microsecond instant, apply all start/end changes together, then examine the open span to the next instant. Record spans where active count exceeds the budget and merge touching overloaded spans into one union interval. Sum their durations once. For each cue, compute its intersection with that union and show its own participation seconds. Also report maximum simultaneous count and union intervals. Grouping endpoint changes makes exact adjacency contribute no false duration.
Review the actual caption experience next
Use the union map to locate playback segments for inspection, not to declare failure from arithmetic alone. Read the captions with positioning, content and speaker context; test keyboard access and relevant assistive technology separately. If a media edit shifts timestamps, update the source intervals coherently. Ask an accessibility specialist or caption professional about actual barriers. The optional filing layer exports the displayed timing and boundary; it does not generate a compliant subtitle file.
What the cue-concurrency strip keeps distinct
Question
Before
Check this working
Pairwise overlaps are added as distinct time
When three cues overlap, one second can appear in three pair intersections. Summing those intersections overstates how long the timeline exceeded a cue-count budget. This strip uses the overloaded time union for the headline and prints cue participation separately. The two measures intentionally differ rather than being forced to reconcile by hiding the triple overlap.
Choose the review concurrency budget
Same-time endpoints create a fake overlap
A sequential event processor can briefly count both an ending cue and a starting cue at one instant. That instant has no positive duration under [start,end). Grouping all changes before the next segment and using integer microseconds prevents the transient from becoming counted time. The convention is explicit so users can compare it with their actual caption format.
Sweep grouped endpoint events over half-open segments
A concurrency number becomes an accessibility verdict
Whether concurrent cues are understandable depends on content, layout, speakers and playback. This tool has no evidence for those dimensions and no built-in compliance threshold. A marked span is a review location, not an automatic violation or proof that a captioner did poor work. Keep the review budget and boundary in shared results, and evaluate the actual experience with qualified help.
Review the actual caption experience next
The cue-concurrency strip replaces this named manual reconciliation, not source verification or the responsible human's decision.
Run it on the samples, right here
FIRST-LOAD
HYPOTHESIS / PROTOTYPE — checkout unavailable. Calculation is local. A draft is saved automatically in this browser profile when storage is available; Reset to sample clears it. Optional Pro history stores only five summaries and has its own deletion control. State links encode your inputs and can remain in browser history, clipboard or recipients’ records; share only non-sensitive rows. Optional external AI formatting leaves this device. The required site analytics beacon reports page activity; shared URLs contain encoded inputs. Do not treat an encoded URL as private. The calculator has no input-collection endpoint.
Timing-union review only: no caption-content check, playback test or WCAG compliance verdict. Inspect actual media and cue layout with a qualified caption professional or accessibility specialist before treating a marked span as a barrier.
Data note: This cue-concurrency strip calculates in the tab from Cue code | start seconds | end seconds. No input-collection endpoint, AI request or file upload is built into it. Drafts may be saved locally; explicit input-state links and optional external formatting can disclose the records. Use non-sensitive codes and clear the draft when finished.
Go deeper: the companion app files the same reading as a paper ticker strip
The article demo above runs without limits. The companion app keeps a local history, exports the rows as CSV, prints the cue-concurrency strip reading, and holds your drafts on this device — one complete free app run; the proposed $4 one-time filing layer is not for sale.
Keep the complete cue-concurrency strip answer free; optional filing proposes its boundary-preserving print, row-and-summary CSV and five local reading summaries. The $4 one-time prototype is not for sale; another calculation remains free in the article demo.
Timing-union review only: no caption-content check, playback test or WCAG compliance verdict. Inspect actual media and cue layout with a qualified caption professional or accessibility specialist before treating a marked span as a barrier.
What this is built on
Declared local method: At each unique microsecond instant, apply all start/end changes together, then examine the open span to the next instant. Record spans where active count exceeds the budget and merge touching overloaded spans into one union interval. Sum their durations once. For each cue, compute its intersection with that union and show its own participation seconds. Also report maximum simultaneous count and union intervals. Grouping endpoint changes makes exact adjacency contribute no false duration.
Every sample code, measurement, date, price, fingerprint and scenario is invented. Artifact checks do not verify reader data, policies, actual files, tickets, votes or health/accessibility outcomes.
Google’s official Gemini pricing page, fetched 2026-10-01, lists AI Studio access in its Free section, limited model access and free input/output tokens. Free-tier content may be used to improve products. Optional external formatting may require an account; limits/access can change. Manual local entry needs none. Do not send sensitive records.
Before: pairwise overlaps inflated the apparent problem time. After: overloaded timeline union, peak count and per-cue participation are distinct, checkable quantities.
Three worked readings, with different inputs
Sample A — typical inputs
Cedar cue | 0 | 5
Willow cue | 3 | 7
Pine cue | 6 | 9
Setting: Allowed simultaneous cues in this review model = 1. Expected summary: 3 seconds over cue concurrency budget.
The concurrency budget of one is exceeded from second three to five and from six to seven: two seconds plus one second, totaling three. Willow participates in both intervals. The row-specific participation durations add to six because every overlapping second belongs to multiple cues; the headline is the time union and must not be reconstructed by summing those row durations.
Setting: Allowed simultaneous cues in this review model = 1. Expected summary: 6 seconds over cue concurrency budget.
More than one cue is active throughout seconds twelve to eighteen, a six-second union. Three are active from fourteen to sixteen, but that two-second interval is not counted again for each pair. Pairwise overlap lengths would total ten seconds and overstate the headline. The maximum concurrency metric separately reports three, so severity of stacking is not hidden by the union duration.
Sample C — boundary convention
East adjacent cue | 23.5 | 25.25
West adjacent cue | 25.25 | 28
Setting: Allowed simultaneous cues in this review model = 1. Expected summary: 0 seconds over cue concurrency budget.
One cue ends at exactly the instant the next starts. Under the stated half-open [start,end) convention they have no positive-duration overlap. Both endpoints remain exact to microseconds; no fuzzy tolerance turns adjacency into overlap. This temporal result is not a caption-quality pass: content, reading speed, positioning, speakers and player behavior have not been reviewed.
Optional AI formatting, never the calculation
Manual entry completes this cue-concurrency strip for free without signup. If available to you, the free AI Studio interface linked in the sources may format fictional or non-sensitive notes; external access may require an account. No API key or AI call is built into this tool. Free-tier content may be used to improve products. Review each cell and transcribe it to the labeled row schema; do not paste the JSON object into the row box.
Format only these fictional or non-sensitive notes for a cue-concurrency strip. Return strict JSON shaped as {"rows": [{"label": "string", "cells": ["string", "string"]}], "setting": "string"}. The columns are Cue code | start seconds | end seconds; the setting is Allowed simultaneous cues in this review model. Keep all supplied strings and quantities exactly; do not calculate, infer missing entries, invent dates or add advice. If any required value is missing, return an empty rows array and ask me for it separately. I will verify every cell against my source and manually transcribe rows using vertical bars before running the local calculator.
An AI response is not executed, fetched or trusted as a result. Missing values remain questions; the strict local parser checks the rows you actually enter.