iCouldPlay horizontal VTT boxes: separate position, box size and text length

Horizontal VTT position and size settings both use percentages but answer different questions. A size of 50% does not mean half the sentence or half-size glyphs. Compare three original cues with identical wording and different position or size conditions. The task in iCouldPlay is selecting subtitles and inspecting playback, not finding an unverified percentage-entry panel.

1. Fix the horizontal viewing conditions

Prepare an owned clip lasting at least fourteen seconds with a clear background and confirm ordinary playback in iCouldPlay. Record its identity and source. Keep orientation and display mode fixed, without changing text size, aspect mode or player source. Create a UTF-8 subtitle in a plain-text editor and retain a plain fallback without positioning parameters. Use separate columns for source settings, wording, visible placement, wrapping and uncertainty. Describe placement as left, center or right; do not estimate exact pixels from screenshots in this round. A parameter with no discernible effect should remain a valid recorded outcome.

2. Construct three cues with identical wording

Copy this original subtitle. Between cues one and two, only position changes from 25% to 75%; size remains 40%. Between two and three, only size changes from 40% to 20%. center explicitly sets the position anchor’s alignment in this example. Read each source sentence aloud to verify identical wording, punctuation and case. Shortening cue three would confound box size with text length. The cues do not overlap, and no vertical setting is present. Do not transfer the horizontal percentages directly into conclusions about vertical-column movement.

WEBVTT

00:00:01.000 --> 00:00:04.000 position:25%,center size:40% align:center
Keep the small blue cup beside the notebook.

00:00:05.000 --> 00:00:08.000 position:75%,center size:40% align:center
Keep the small blue cup beside the notebook.

00:00:09.000 --> 00:00:12.000 position:75%,center size:20% align:center
Keep the small blue cup beside the notebook.

3. Sketch boxes rather than character quotas

Sketch a horizontal video rectangle and three boxes labeled with the source conditions. The W3C WebVTT layout description treats position and cue-box size together with alignment; box dimensions are not the ink width of the text. Your sketches express relative conditions, not device screenshots or pixel-exact promises for iCouldPlay. Neither 40% nor 75% is a character count or a number of pixels. Write the comparison goal in the expectation column and leave actual movement and wrapping for observation.

4. Compare the first two cues during continuous playback

Load the exercise subtitle and play from zero past eight seconds. Read each sentence fully before recording its relative position within the video. Keep player-control visibility comparable so a temporary layout change does not contaminate the comparison. If placement differs, record the direction; if not, state that no position difference was observed under these conditions. Do not infer that every VTT setting is unsupported. Replay to verify subtitle identity before editing. Changing device orientation or window size would create a different comparison.

5. Compare the second and third cues for width effects

Continue past twelve seconds. Confirm complete wording and record line count, clipping and any text outside the visible video. More lines do not establish smaller glyphs, so assess those separately. If both cues occupy one line, the wording, environment or rendering may not expose a difference. You need not force an outcome with a long sentence. To test longer wording, save a separate variant that changes both compared cues to the same longer sentence and restart the single-variable comparison. Keep conditions explicit instead of recording only a vague narrower-box impression.

6. Distinguish the video viewport, bars and whole screen

State the reference area: whole screen, visible video picture or playback area including bars. These can differ, and proximity to the screen edge does not establish how a source percentage was resolved. Record bars and cropping at the same picture time. If you change display mode, treat the result as a new round rather than merging it into the initial observation. No in-app viewport ruler or exact percentage measurement is assumed. Complete wording and consistent relative placement descriptions are sufficient for a reproducible reading record.

7. Troubleshoot syntax, track selection and appearance settings

If settings appear as visible words, check whether they were mistakenly placed in the cue text instead of after the end time on the timing line. For a missing cue, check blank lines, arrows, intervals and track identity. Record any real app appearance setting and compare one value at a time; do not invent an “ignore file layout” switch. If captions clip or obstruct reading, return to the plain fallback and retain the problem sample. Deleting the film or clearing the library is unnecessary. Change one identified issue at a time and record whether it resolved the symptom.

8. Finish with conditional conclusions

Keep the three source conditions, observed wording and placement, line counts for cues two and three, reference area and orientation. Check that box size never became a character quota or percentages became pixels. A missing visible difference is not evidence that the format lacks these concepts. Mark playback unperformed if you only edited files; otherwise limit conclusions to the tested sample and conditions. Save the exercise, fallback and dated notes together for later display changes. This supports traceable reading checks without representing external subtitle editing as a new app feature.

Related tutorials and sources

VTT vertical progression, VTT preparation basics.

Checked on November 11, 2026 against the official iCouldPlay App Store listing and Apple public lookup: version 1.1.1, requiring iOS / iPadOS 15.0 or later. The public 1.1.1 release notes list Kodi, OpenList / AList and S3-compatible storage, with improvements to source switching and captions after seeking. The tasks use this public scope and existing playback capabilities. Check controls in your installed version. Self-made samples, manual records and external file preparation are workflows, not newly promised automatic features. No physical-device or private-server test is claimed.