DouKaku?

class TimeCode
  def initialize(h, m, s, f, frate)
    @hour, @minute, @second = h, m, s
    @frame, @frame_rate = f, frate
  end
  def treat
    form = proc{|*ary| ary.map{|s| format("%02d", s)}.join(':')}
    drop_frame
    "#{form.call(@hour, @minute, @second)}; #{@frame}."
  end
  attr_writer :frame_rate
  private
  def inspect() treat end
  def drop_frame
    check = @second.zero? && (@minute.modulo(10).nonzero? || @minute.zero?)
    @frame = [@frame%get_frate.ceil, check ? 0 : 2].max
  end
  def get_frate
    case @frame_rate.to_s
    when 'ntsc'  then 29.97
    when 'anime' then 24
    else
      raise RangeError if out_of_range?
      @frame_rate.to_i
    end
  end
  def out_of_range?() @frame_rate.to_i <= 0 end
end
p tc = TimeCode.new(22, 0, 0, 37, 'ntsc') #=> 22:00:00; 6.
tc.frame_rate = 5
p tc                                      #=> 22:00:00; 1.
p TimeCode.new(22,  0, 0, 0, 'anime')     #=> 22:00:00; 0.
p TimeCode.new(22, 10, 0, 0, 'anime')     #=> 22:10:00; 2.
p TimeCode.new(22, 10, 0, 0, -1)          #=> RangeError (RangeError)