# File lib/mp3info/id3v2.rb, line 145
  def to_bin
    #TODO handle of @tag2[TLEN"]
    #TODO add of crc
    #TODO add restrictions tag

    tag = ""
    @hash.each do |k, v|
      next unless v
      next if v.respond_to?("empty?") and v.empty?
      data = encode_tag(k, v.to_s)
      #data << "\x00"*2 #End of tag

      tag << k[0,4]   #4 characte max for a tag's key
      #tag << to_syncsafe(data.size) #+1 because of the language encoding byte
      tag << [data.size].pack("N") #+1 because of the language encoding byte
      tag << "\x00"*2 #flags
      tag << data
    end

    tag_str = ""
    #version_maj, version_min, unsync, ext_header, experimental, footer 
    tag_str << [ VERSION_MAJ, 0, "0000" ].pack("CCB4")
    tag_str << to_syncsafe(tag.size)
    tag_str << tag
    p tag_str if $DEBUG
    tag_str
  end