id3_parser.ex

defmodule ID3Parser do

  def parse(file_name) do
    case File.read(file_name) do
      {:ok, binary} ->
        # ID3 tag information is located at the last 128 bytes.
        mp3_byte_size = (byte_size(binary) - 128)
        << _ :: [size(mp3_byte_size), binary], id3_tag :: binary >> = binary
        << "TAG", tags :: binary >> = id3_tag

        << title   :: [size(30), binary], 
           artist  :: [size(30), binary], 
           album   :: [size(30), binary], 
           year    :: [size(4),  binary], 
           comment :: [size(30), binary], 
           _rest   :: binary >> = tags

        IO.puts title   # I Was Made For Loving You
        IO.puts artist  # KISS
        IO.puts year    # 1979
        IO.puts album   # Dynasty
        IO.puts comment # Best wedding entrance song!

      _ -> 
        IO.puts "Couldn't open #{file_name}"
    end
  end
  
end

ID3Parser.parse("sample.mp3")