For Panasonic Videos.

mtime_from_moi.rb

# https://en.wikipedia.org/wiki/MOI_(file_format)
def get_date_from_moi(moi)
  File.open(moi, "rb") { |file|
    file.seek(6)
    bytes = file.read(10)
    y, mon, d, h, min, ms = bytes.unpack('nCCCCn')
    return Time.new(y, mon, d, h, min, ms/1000)
  }
end

def change_mtime_of_mpeg(mpeg_file)
  moi_file = mpeg_file.gsub(/mpg$/, 'moi')
  if File.exist?(moi_file)
    mtime = get_date_from_moi(moi_file)
    File.utime(mtime, mtime, mpeg_file)
  else
    puts "#{mpeg_file}: no #{moi_file}"
  end
end

ARGV.each {|mpeg_file|
  change_mtime_of_mpeg(mpeg_file)
}