If you want to show interview clips in a presentation, publish a teaching video or make a recording easier to follow, you will need a subtitle file. Two widely used text formats are SRT and VTT. This guide explains what these formats are, when they are useful and how to get from a recording to a finished subtitle file.
What SRT and VTT are
Both formats are plain text files that contain the spoken text together with timing information. A video or audio player reads the file and displays each piece of text at the right moment. The subtitles are not burned into the video; they are stored in a separate file.
SRT (SubRip Subtitle format). According to the Library of Congress format description, an SRT file consists of numbered entries. Each entry contains a counter, a start and end time separated by the characters "-->", one or more lines of subtitle text and a blank line that marks the end of the entry. Times use the format hours:minutes:seconds,milliseconds, for example 00:00:00,000 (source).
An SRT entry looks like this:
1
00:00:01,200 --> 00:00:04,800
I think the hardest part was finding the time.VTT (WebVTT, Web Video Text Tracks). WebVTT is specified by the W3C. According to the specification, the format "is intended for marking up external text track resources in connection with the HTML <track> element" and provides captions or subtitles for video content (source). A WebVTT file must be encoded as UTF-8 and starts with the line "WEBVTT". In WebVTT timestamps, the seconds are separated from the thousandths of a second by a period, not a comma. The hours are optional and only required if they are not zero.
A short VTT file looks like this:
WEBVTT
00:01.200 --> 00:04.800
I think the hardest part was finding the time.In short, the formats are very similar. SRT is common in video editing and on many video platforms, while VTT is the format defined for subtitles on web pages.
When you need subtitle files
- Presentations and thesis defenses. If you play interview excerpts, subtitles help your audience follow, especially when the audio is unclear or the room is noisy.
- Teaching videos and lectures. Subtitles make recorded material easier to follow and to search.
- Accessibility. Subtitles and captions help people who are deaf or hard of hearing, as well as viewers who are not native speakers. Check whether your institution has specific accessibility requirements.
- Podcasts and video interviews. Many publishing platforms accept SRT or VTT files alongside the video.
If your recordings include research participants, make sure your consent forms allow you to show the clips, and anonymize names and other identifying details where necessary.
From recording to subtitle file: step by step
- Start with good audio. Clear audio leads to a better automatic draft and less correction work.
- Create a transcript with timestamps. Automatic transcription produces the text and the timing in one step.
- Check and correct the text. Automatic subtitles should always be checked. Listen to the recording, correct misheard words, names and technical terms and remove anything that should not be shown, such as identifying details.
- Check the timing. Play the recording with the subtitles and make sure each line appears while it is being spoken.
- Export in the right format. Choose SRT or VTT depending on where you will use the file. Name the file so that it is easy to match to the video.
- Test the file. Load the subtitle file in the player or platform you will use and watch the full clip once before presenting or publishing.
Common format errors
- Wrong decimal separator. SRT uses a comma before the milliseconds, while WebVTT uses a period. Converting a file by changing only the extension can cause this error.
- Missing "WEBVTT" header. A WebVTT file must start with the line "WEBVTT", as defined in the W3C specification.
- Wrong character encoding. WebVTT files must be UTF-8 encoded. Other encodings can turn accented characters and umlauts into unreadable symbols.
- Missing blank lines. In SRT, a blank line marks the end of each entry. If it is missing, entries can run together.
- Wrong arrow. The start and end times must be separated by "-->", with two hyphens and a right-pointing angle bracket.
How Stillscript can help
Stillscript creates an automatic transcript of your recording, which you then review and correct. You can export the result as SRT or VTT subtitles. Your recordings and transcripts stay on your device. As with any automatic transcript, check the text and timing before you use the subtitles.