Synthetic practice corpus · 1.0.0

Choose a case and predict the result

All twenty files are original synthetic text. Defaults: 20 characters/second and 42 characters/line. Structural findings require repair; editorial warnings require judgment; scope warnings identify checks this tool does not perform.

Open the existing subtitle checker, choose a downloaded case, then compare the findings below. Keep this page open as your reference.

Download versioned manifest and exact input strings

srt-clean · SRT clean control (SRT)

Establish a small readable numeric cue.

Download SRT case

Establish a small readable numeric cue.

Structural findings
None expected within this limited checker.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
1
00:00:01,000 --> 00:00:04,000
Map the room.
srt-unicode · SRT multilingual text (SRT)

Preserve original UTF-8 accents, CJK and emoji.

Download SRT case

Preserve original UTF-8 accents, CJK and emoji.

Structural findings
None expected within this limited checker.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
1
00:00:01,000 --> 00:00:06,000
Café — 東京 🌍
srt-dot · SRT decimal separator (SRT)

Reject periods under this corpus's comma-based SRT policy.

Download SRT case

Reject periods under this corpus's comma-based SRT policy.

Structural findings
  • Cue 1: Invalid SRT timestamp; check separators and minute/second ranges.
  • No readable timed cues found.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
1
00:00:01.000 --> 00:00:04.000
Map the room.
srt-range · SRT minute range (SRT)

Reject a minute component of 60.

Download SRT case

Reject a minute component of 60.

Structural findings
  • Cue 1: Invalid SRT timestamp; check separators and minute/second ranges.
  • No readable timed cues found.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
1
00:60:01,000 --> 00:60:04,000
Map the room.
srt-missing-end · SRT missing end timestamp (SRT)

Require a complete timing line.

Download SRT case

Require a complete timing line.

Structural findings
  • Cue 1: Missing or malformed timing line.
  • No readable timed cues found.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
1
00:00:01,000 -->
Map the room.
srt-reversed · SRT reversed duration (SRT)

Reject an ending before the start.

Download SRT case

Reject an ending before the start.

Structural findings
  • Cue 1: End time must be later than start time.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
1
00:00:04,000 --> 00:00:01,000
Map the room.
srt-empty · SRT empty caption (SRT)

Flag missing caption text under the local delivery policy.

Download SRT case

Flag missing caption text under the local delivery policy.

Structural findings
  • Cue 1: Cue text is empty.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
1
00:00:01,000 --> 00:00:04,000
srt-overlap · SRT intentional overlap (SRT)

Prompt editorial review of two simultaneous voices.

Download SRT case

Both intervals are well formed. Simultaneous captions can be intentional; inspect the intended player.

Structural findings
None expected within this limited checker.
Editorial warnings
  • Cue 2: Cue overlaps an earlier cue; confirm whether simultaneous captions are intentional.
Outside this check
None expected within this limited checker.
1
00:00:01,000 --> 00:00:05,000
Left.

2
00:00:02,000 --> 00:00:04,000
Right.
srt-missing-separator · SRT missing blank separator (SRT)

Detect a second timing line swallowed into caption text.

Download SRT case

Detect a second timing line swallowed into caption text.

Structural findings
  • Cue 1: Another timing line occurs inside cue text; check for a missing blank line between cues.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
1
00:00:01,000 --> 00:00:10,000
One.
2
00:00:05,000 --> 00:00:06,000
Two.
srt-zero-duration · SRT zero duration (SRT)

Require positive duration.

Download SRT case

Require positive duration.

Structural findings
  • Cue 1: End time must be later than start time.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
1
00:00:01,000 --> 00:00:01,000
Map the room.
vtt-clean · WebVTT clean control (VTT)

Accept short WebVTT timestamps.

Download VTT case

Accept short WebVTT timestamps.

Structural findings
None expected within this limited checker.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
WEBVTT

00:01.000 --> 00:04.000
Map the room.
vtt-settings · WebVTT valid positioning settings (VTT)

Keep valid line, position, size and alignment settings distinct from malformed timestamps.

Download VTT case

These settings use forms defined by the pinned draft. The checker leaves all settings unvalidated and asks for player inspection; this is a scope warning, not an editorial defect.

Structural findings
None expected within this limited checker.
Editorial warnings
None expected within this limited checker.
Outside this check
  • Cue 1: WebVTT cue settings are not validated; inspect positioning in the delivery player.
WEBVTT

00:01.000 --> 00:04.000 line:90% position:50% size:80% align:center
Map the room.
vtt-bom · WebVTT UTF-8 BOM (VTT)

Accept an optional initial byte-order mark with original UTF-8 text.

Download VTT case

Accept an optional initial byte-order mark with original UTF-8 text.

Structural findings
None expected within this limited checker.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
WEBVTT

00:01.000 --> 00:04.000
Café 🌍
vtt-note-identifier · WebVTT comment and identifier (VTT)

Skip an original NOTE block and accept a nonnumeric cue identifier.

Download VTT case

Skip an original NOTE block and accept a nonnumeric cue identifier.

Structural findings
None expected within this limited checker.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
WEBVTT

NOTE original practice note
No source recording exists.

room-label
00:01.000 --> 00:04.000
Map the room.
vtt-comma · WebVTT wrong separator (VTT)

Reject SRT-style commas in WebVTT.

Download VTT case

Reject SRT-style commas in WebVTT.

Structural findings
  • Cue 1: Invalid VTT timestamp; check separators and minute/second ranges.
  • No readable timed cues found.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
WEBVTT

00:01,000 --> 00:04,000
Map the room.
vtt-range · WebVTT second range (VTT)

Reject a seconds component of 60.

Download VTT case

Reject a seconds component of 60.

Structural findings
  • Cue 1: Invalid VTT timestamp; check separators and minute/second ranges.
  • No readable timed cues found.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
WEBVTT

00:60.000 --> 01:04.000
Map the room.
vtt-missing-end · WebVTT missing end timestamp (VTT)

Require an end timestamp.

Download VTT case

Require an end timestamp.

Structural findings
  • Cue 1: Missing or malformed timing line.
  • No readable timed cues found.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
WEBVTT

00:01.000 -->
Map the room.
vtt-start-order · WebVTT decreasing start times (VTT)

Classify decreasing start times as a structural violation of the pinned draft.

Download VTT case

The start times are out of order, but these two intervals do not intersect. Do not invent an overlap warning from the largest earlier end time.

Structural findings
  • Cue 2: Cue starts before the preceding cue.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
WEBVTT

00:05.000 --> 00:08.000
First.

00:01.000 --> 00:04.000
Second.
vtt-overlap · WebVTT intentional overlap (VTT)

Allow overlapping cues whose start times remain ordered.

Download VTT case

The pinned draft permits overlapping subtitle cues. Placement and simultaneous voices need editorial review; chapters are outside this corpus.

Structural findings
None expected within this limited checker.
Editorial warnings
  • Cue 2: Cue overlaps an earlier cue; confirm whether simultaneous captions are intentional.
Outside this check
None expected within this limited checker.
WEBVTT

00:01.000 --> 00:05.000
Left.

00:02.000 --> 00:04.000
Right.
vtt-header-separator · WebVTT missing header separator (VTT)

Require a blank line after the WEBVTT signature.

Download VTT case

Require a blank line after the WEBVTT signature.

Structural findings
  • Separate the WEBVTT header from the first cue with a blank line.
  • No readable timed cues found.
Editorial warnings
None expected within this limited checker.
Outside this check
None expected within this limited checker.
WEBVTT
00:01.000 --> 00:04.000
Map the room.

Practice a three-error repair with the walkthrough and reference. Playback and wording still need a separate review.

Cue A runs from one to four seconds and Cue B from three to five seconds. They overlap from three to four seconds despite positive durations and ordered starts.
Original Editorial Desk Media diagram, September 14, 2026. Reuse under CC BY 4.0 with credit and a link to this guide. Download the SVG. License terms.
These original text fixtures test a limited local checker. They are not real recordings, vendor exports, playback tests, or accessibility certification. Our editorial method

Choose a case, then test your reasoning

Download a case and read its expected findings. Open the existing subtitle checker, choose the downloaded file, and compare the report. Keep malformed timing separate from editorial decisions such as overlapping speakers.

Use the repair walkthrough for correction practice. Preserve the original; recheck the edited copy and inspect its synchronization and appearance in your intended delivery player. No synthetic clip is included because these cases exercise text structure, not audiovisual synchronization.

Method and boundaries

Version 1.0.0 uses twenty original UTF-8 text fixtures. Findings are specified independently of the checker and split into structural findings, editorial warnings, and checks outside its scope.

WebVTT cases use the May 20, 2026 W3C Candidate Recommendation Draft. SRT follows a separate documented local convention. This corpus does not claim complete validation of either format. A clean report does not establish correct words, synchronization, styling, or accessibility.

Take it with you

Download corpus manifest and expected outcomes

Download worksheet

Sources & verification

Product details and prices can change. Check the linked provider before buying.

  1. W3C WebVTT Candidate Recommendation Draft, May 20, 2026 (WebVTT only) Accessed 2026-09-14

Sources link directly to providers. Product buttons may use separately labeled affiliate links. Read our disclosure.

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Investigate for guest capture and an integrated recording-to-editing workflow.
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Checked 2026-09-13 · Pricing source

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Investigate for transcript-led editing and turning existing recordings into finished videos.
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Checked 2026-09-13 · Pricing source

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Related guides

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