Extract subs from mkv and converts from vobsub to srt

extract_subs.rb

#!/usr/bin/env ruby
# Usage: extract_subs movie.mkv
ENGLISH_VARIATIONS = %w[eng en english].freeze

file = ARGV[0]
abort("Usage: #{$0} file.mkv") unless file && File.exist?(file)

# Run mkvinfo and capture output
mkvinfo_output = `mkvinfo "#{file}"`

subtitle_tracks = []
current_track_id = nil
current_language = nil
current_type = nil

mkvinfo_output.each_line do |line|
  stripped = line.strip

  if stripped =~ /\+ Track number: \d+ \(track ID for mkvmerge & mkvextract: (\d+)\)/
    current_track_id = Regexp.last_match(1)
    current_language = nil
    current_type = nil
  end

  if stripped =~ /\+ Track type: (\w+)/
    current_type = Regexp.last_match(1).downcase
  end

  if stripped =~ /\+ Language: (\w+)/
    current_language = Regexp.last_match(1).downcase
  end

  if stripped =~ /^\| \+ Track$/ || stripped =~ /^\+ Track$/ || stripped =~ /^\| \+ EBML void/
    if current_type == 'subtitles' && current_track_id && current_language
      subtitle_tracks << [current_track_id, current_language]
    end
    current_track_id = nil
    current_language = nil
    current_type = nil
  end
end

if current_type == 'subtitles' && current_track_id && current_language
  subtitle_tracks << [current_track_id, current_language]
end

subtitle_tracks.each do |track_id, lang|
  puts ">>> Extracting subtitles #{track_id}:#{lang}"
  system('mkvextract', 'tracks', file, "#{track_id}:#{lang}")
  puts ">>> Converting VobSub #{lang} to SRT"
  if ENGLISH_VARIATIONS.include?(lang)
    system('vobsub2srt', lang)
  else
    system('vobsub2srt', lang, '--lang', lang)
  end
end