fix_subtitles.rb

#!/usr/bin/env ruby
unless ARGV.size == 2
  puts
  puts "Usage: fix_subtitles.rb /path/to/file miliseconds_offset"
  puts "Example: If subtitles appear AFTER the sound, use -2000 to bring them back 2 seconds"
  puts
  puts "DISCLAMIER: I only tested them with srt files."
  puts
  exit()
end

file_in_name, offset, file_out_name = ARGV[0], ARGV[1], ARGV[0] + ".out"

output = ""
open(file_in_name).each_line do |line|
  output << line.gsub(/\d\d:\d\d:\d\d,\d\d\d/) do |s|
    timestamp  = s[0,2].to_i * 3_600_000
    timestamp += s[3,2].to_i * 60_000
    timestamp += s[6,2].to_i * 1000
    timestamp += s[9,3].to_i
    timestamp += offset.to_i
    hours = timestamp / 3_600_000
    timestamp -= hours * 3_600_000
    minutes = timestamp / 60_000
    timestamp -= minutes * 60_000
    seconds = timestamp / 1_000
    timestamp -= seconds * 1_000
    miliseconds = timestamp
    sprintf "%02d:%02d:%02d,%03d", hours, minutes, seconds, miliseconds
  end
end
open(file_out_name, 'w+') do |file_out|
  file_out.puts output
end