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WebVTT Ruby parser and segmenter

The WebVTT format is a standard captionning format used for HTML5 videos and HTTP Live Streaming (HLS).

Installation

Add this line to your application's Gemfile:

gem 'webvtt-ruby'

And then execute:

$ bundle

Or install it yourself as:

$ gem install webvtt-ruby

Usage

To parse a webvtt file:

require "webvtt"

webvtt = WebVTT.read("path/sub.vtt")
webvtt.cues.each do |cue|
  puts "identifier: #{cue.identifier}"
  puts "Start: #{cue.start}"
  puts "End: #{cue.end}"
  puts "Style: #{cue.style.inspect}"
  puts "Text: #{cue.text}"
  puts "--"
end

Converting from SRT

You can also convert an SRT file to a standard WebVTT file:

webvtt = WebVTT.convert_from_srt("path/sub.srt", "path/sub.vtt")
puts webvtt.to_webvtt

Segmenting for HTTP Live Streaming (HLS)

Segmenting is required to work with HLS videos.

WebVTT.segment("subtitles/en.vtt", :length => 10, :output => "subtitles/en-%05d.vtt", :playlist => "subtitles/en.m3u8")

It will also generate the playlist in m3u8:

#EXTM3U
#EXT-X-TARGETDURATION:17
#EXT-X-VERSION:3
#EXT-X-MEDIA-SEQUENCE:0
#EXT-X-PLAYLIST-TYPE:VOD
#EXTINF:13,
en-00000.vtt
#EXTINF:17,
en-00001.vtt
#EXTINF:12,
en-00002.vtt
#EXT-X-ENDLIST

To use the segmented webvtt files with your HLS playlist:

#EXTM3U

#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subs",NAME="English",DEFAULT=NO,AUTOSELECT=YES,FORCED=NO,LANGUAGE="en",URI="subtitles/en.m3u8"

#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=300000,SUBTITLES="subs"
demo-300000.m3u8

#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=600000,SUBTITLES="subs"
demo-600000.m3u8

CLI

You can also segment webvtt files using the command line webvtt-segmenter:

$ webvtt-segmenter -i subtitles/en.vtt -t 10 -m subtitles/en.m3u8 -o "subtitles/en-%05d.vtt"

$ webvtt-segmenter -h
Usage: bin/webvtt-segmenter [--arg]
    -i, --input [PATH]               WebVTT or SRT file
    -b, --base-url [URL]             Base URL
    -t, --target-duration [DUR]      Duration of each segments. Default: 10
    -o, --output [PATH]              Path where WebVTT segments will be saved. Default: fileSequence-%05d.vtt
    -m, --playlist [PATH]            Path where the playlist in m3u8 will be saved. Default: prog_index.m3u8

Note

webvtt-ruby was written in a few hours because there was no open source tool to segment webvtt files. It's not perfect at all but it does the job.

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request

Author

Bruno Celeste