WebVTT (Web Video Text Tracks) is a file format that allows editing of external text tracks. Used in conjunction with HTML5’s <track> element allows information such as subtitles, closed captioning and descriptions for a media resource such as audio or video to be displayed synchronized with the media resource. The ability to add textual information in this way allows more options to the viewer and greater accessibility of media content to those who may be unable to listen to a video’s audio track due to auditory issues or language difficulties.
WebVTT files contain several types of information about the video including subtitles (transcription or translation of dialogue), captions (similar to subtitles but also including sound effects and other audio information), as well as descriptions, chapters and metadata, which provide information about the video and aid the viewer in navigation through the video.
WebVTT files are text files, encoded as UTF-8, with a .vtt file extension. It is an offshoot of the WebSRT (Web Subtitle Resource Tracks) file which is itself an adaptation of SubRip, both of which share an .srt file extension.
SubRip is a software program for Windows which (extracts) subtitles and their timings from video. It is free software, released under the GNU GPL (general public license). SubRip is also the name of the widely used and broadly compatible subtitle text file format created by this software.
Using optical character recognition, SubRip can extract from live video, video files and DVDs, then record the extracted subtitles and timings as a SubRip format text file. It can optionally save the recognized subtitles as bitmaps for later subtraction or erasure from the source video.
In practice, SubRip is configured with the correct codec for the video source, then trained by the user on the specific text area, fonts, styles, colors and video processing requirements to recognize subtitles. After trial and fine tuning, SubRip can automatically extract subtitles for the whole video source file during its playback. SubRip records the beginning and end times and text for each subtitle in the output text .srt file.
The SubRip .srt file format is supported by most software video players. For Windows software video players that do not support subtitle playback directly, the VSFilter Direct X filter displays SubRip and other subtitle formats. The SubRip format is supported directly by many subtitle creation and editing tools and some home media players. In 2008, YouTube added subtitle support to its Flash video player under the closed captioning option. Content producers can upload subtitles in SubRip format.