Changing a caption file's format is a transformation that deserves checking. The words may come from an approved track, but the destination can interpret timing, line breaks or special characters differently. Ask for a conversion check before treating the new file as interchangeable with the source.
The MDN WebVTT format documentation specifies a header, structured cues and UTF-8 text. A filename ending in the expected extension does not by itself demonstrate that the contents satisfy the destination's requirements. Leave the technical conversion to the responsible supplier and commission evidence of the result.
State what must be preserved
Identify the approved source track and the exact video it accompanies. Ask the converter to preserve the text, meaningful speaker information, intended time intervals and any supported presentation details. Where the target format cannot carry something, require an explicit explanation rather than allowing it to disappear without notice.
Separate formatting changes from editorial changes. Joining a line for a different display may be acceptable; removing a qualification is a content alteration. The person performing conversion should know which decisions they can make and which need the caption or project-content reviewer.
Keep the original track. It provides a reference for comparison and allows another conversion route if the first proves unsuitable. Avoid overwriting the only approved source with a destination-specific derivative whose transformation history is unclear.
Compare the result in two ways
First, compare the text and timing data for omissions, unexpected additions and shifted cues. Ask the supplier what checks it performed and what exceptions it found. A useful record identifies the affected cue or time range rather than saying only that the file opened successfully.
Second, play the converted track in the intended destination. This reveals display behaviour that a text comparison cannot. Check accented names, symbols, punctuation and intentional line breaks where they occur in the actual project film. A converter can preserve characters while a later import stage still renders them poorly.
Use a targeted exception list to guide detailed review, then confirm the whole track remains present. Spot-checking a correct opening is not evidence that the final section survived conversion. The scope of human review should be agreed with the responsible caption specialist, especially where the content carries important qualifications.
A hypothetical extension change
Imagine a builder's publisher requests a different caption format. Someone renames the supplied file because its contents look like ordinary text. The platform accepts the upload interface action but fails to display several later cues.
The buyer asks for a proper conversion, a source-to-result comparison and playback in the destination. That sequence distinguishes transfer success from usable text. It also avoids unnecessary retranscription of content that was already accurate in the approved source.
Put conversions in the delivery record
Record the source identity, target format, conversion owner and date checked. If the film or captions are later revised, create the derivative again from the current approved source rather than patching several loosely related files by hand.
Discuss caption formats and delivery destinations with Live Images. Confirm which transformations are included in production scope and which belong to the publishing team, with an agreed review route for any information the destination cannot preserve.
Prepared with AI assistance for Live Images. Planning guidance is general; suitability and production scope must be agreed for your project.