my %all_mp3s = ();
opendir(MUSIC_DIR, $mp3_file_path) || die "$mp3_file_path coud not be opened: $!";
while( defined ( my $artist_dir = readdir MUSIC_DIR) ) {
  next if $artist_dir =~ /^\./;
  next if !(-d "$mp3_file_path/$artist_dir");
  print "scanning dir $mp3_file_path/$artist_dir\n";
  opendir(ARTIST_DIR, "$mp3_file_path/$artist_dir") || die "$mp3_file_path/$artist_dir coud not be opened: $!";
  while( defined ( my $album_dir = readdir ARTIST_DIR) ) {
    next if $album_dir =~ /^\.\.?$/;
    $all_mp3s{"$artist_dir/$album_dir"} = 0;
  }
}