The VTT timestamp shifter delays or advances a whole WebVTT track by a fractional number of seconds. A shift of +2.5 seconds moves the first cue from 00:00:02.000 to 00:00:04.500. It is useful when a web video has a caption track that appears too early or too late.
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Key facts
- Formula: new time = old time + shift, never below 00:00:00, applied to the numbers in the table below.
- Assumption: the offset may have fractions of a second and is added to every start and end time, and a time never drops below zero.
- Change the offset by a quarter of a second at a time and watch the first spoken word.
- The table is arithmetic, not a measurement of a recording or of a service.
Calculation and example
Formula: new time = old time + shift, never below 00:00:00
Before
WEBVTT 1 00:00:02.000 --> 00:00:04.500 Welcome to the webinar. 2 00:00:05.000 --> 00:00:08.000 Today we cover three topics.
After a +2.5 second shift
WEBVTT 1 00:00:04.500 --> 00:00:07.000 Welcome to the webinar. 2 00:00:07.500 --> 00:00:10.500 Today we cover three topics.
A shift of +2.5 seconds moves the first cue from 00:00:02.000 to 00:00:04.500.
| Topic | Answer |
|---|---|
| Other languages | No translation: the text stays in the language of the recording |
| Spoken languages | About 30 languages with good published results; a few more with warnings |
| Speakers and time | Speaker labels and timestamps can be switched on |
| Dictation | The separate desktop app of Potok dictates into any program; it recognises Russian speech |
| Accepted | Voice messages, audio and video |
From the table to your numbers
Read the formula first, then find the row of the table that is closest to your case. Replace its numbers with yours and apply the same rule. If the answer decides something important, round in the safe direction and keep a small reserve.
More
Terms used here are explained in the glossary. Handy helpers live in tools; apps are on the download page.
Common questions
How does the VTT timestamp shifter work?
It applies one rule: new time = old time + shift, never below 00:00:00. A shift of +2.5 seconds moves the first cue from 00:00:02.000 to 00:00:04.500.
What does the VTT timestamp shifter assume?
It assumes that the offset may have fractions of a second and is added to every start and end time, and a time never drops below zero. If your case differs, repeat the calculation by the same rule with your own numbers.
What does the table of the VTT timestamp shifter show?
It shows: Before, After a +2.5 second shift. Values: Before: WEBVTT / / 1 / 00:00:02.000 --> 00:00:04.500 / Welcome to the webinar. / / 2 / 00:00:05.000 --> 00:00:08.000 / Today we cover three topics.; After a +2.5 second shift: WEBVTT / / 1 / 00:00:04.500 --> 00:00:07.000 / Welcome to the webinar. / / 2 / 00:00:07.500 --> 00:00:10.500 / Today we cover three topics..
Where do the definitions behind the VTT timestamp shifter come from?
Units, formats and rules are described in the sources listed at the bottom of this page. The numbers in the table are calculated here by the formula above and are not copied from those sources.
How do I avoid a mistake with the VTT timestamp shifter?
Change the offset by a quarter of a second at a time and watch the first spoken word. Use it when a web video has a caption track that appears too early or too late.
Sources
Every source below was checked by hand on the date given. Sites change, so open the source if the exact wording matters.
- WebVTT: The Web Video Text Tracks Format (W3C), W3C · checked
- WebVTT (Wikipedia), Wikipedia · checked
Try it on your own recording
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