iTunes and Metadata

Posted by Nick Loadholtes on April 22nd, 2006 filed in Apple, Blogging, Music, Probability, ipod

Its been almost a year since I started using iTunes, and in that time I’ve adapted to its way of looking at my music library. It took me a while to get used to its mangling of my music directory (I’m picky like that), but all in all things are pretty good now. I do have a few observations:

Metadata and the files

I like that when I play a song the album artwork is displayed. I think that’s neat. I was however really surprised to find out that the image of the album cover is stored in the mp3/m4p file, thus increasing its size. That struck me as really odd since if you have an album’s worth of songs, the same picture could be used for each song/file. It seems that over your entire music library that if there was only one copy of the image floating around, you’d have more file space, which is to say you could fit more songs onto your iPod.

Then I discovered the most interesting thing: The ratings that you assign for a song are not stored in the music file! They are kept in a separate file! I’m pretty sure that the MP3 file standard has a field for the user’s rating, it seems to me that setting the field (which is already there and wouldn’t add anything to size of the file) would be the way to do it, instead of storing that info in a file that if it gets corrupted will effect every rating in the library. Plus if you go an move the music file to another machine, you loose the rating info. I’ve been relying heavily on rating information lately.

Playlist fatigue

I’ve noticed lately that I’m getting really tired of my playlists, they seem to play the same songs over and over. Investigating further I found the problem is that the size of the playlists (which are mostly based off of the ratings of the song) is not as large as I thought they were. It turns out I have not rated a large portion of my music library. This means that the playlist is pulling selections from a rather limited pool. The smaller this pool, the more frequently you are going to hear a repeat.

Of course the way to get around this is to create an “unrated” playlist and force yourself to listen through it. As you listen to the songs, rate them. This will help enlarge the pool of possible songs the playlists can play from. Previous studies have shown the randomizer in iTunes does a pretty good job of picking songs randomly, so by increasing the playlist size you’ll find that you don’t have as many “I just heard that song!” moments.

Please note that the last item about the playlists applies to all music players, not just iTunes. I discovered this problem at work while using the Windows Media player. If you’ve got a small population of things to choose from, then there is a high probability that you are going to hear the same thing often.