Your iPod does not have a prefered playlist


"Shuffle" really is random

Occasionally you'll see a blog post or just hear someone complaining that the "shuffle" setting on their iPod pulls up too many songs by the same artist or even the same album, or on the same subject. I 'splained some things to Brave Sir Robin last night, and I'm sure he won't mind if I borrow and clarify my rather long-winded explanation to make a post. He said:

Ok, I have 1023 songs on my iPod. 14 of them are by Bob Marley. That's 1.3%. Yet 4 come up in the first 12 songs I played?

First -- Fans of the TV show NUMB3RS have heard this explanation: What humans think of as a "random" pattern, especially visually, is really a set of evenly-spaced things mixed up with other sets of evenly-spaced things. Show enough evenly-spaced-out sets, and your brain will tell you that's "random." You want your songs by the same artist evenly-spaced-out in your playlist, but you're getting them randomly. Using the old coin-toss example: you're not going to get a "heads, tails, heads, tails" pattern when you toss a coin. You may get two, three, even four "heads" in a row before you ever see a "tail," or vice-versa. (Hmm, the same thing could be said of... nevermind.) But if you keep tossing long enough, the count for "heads" and "tails" will come out evenly, unless you've got a weighted coin. (/geek) Which leads us to...

Second -- That's too small a sample. If you look at the last 1050 tracks played, Mr. Marley and the Wailers will show up in about 1.3% of them. It's been a long time since I aced my Intro to Statistics final, so I can't remember the math to tell you how few a number of tracks you can listen to and have the percentage come out right in your particular instance, but I know it's a damnsight more than 1.17% (12 played outta 1 K available.) Tsk on me for forgetting my math, I know. I'm sure somebody with more, or more-recently-used, statistical skills will enlighten us promptly. (/mathmetician)

Third -- your iPod doesn't select songs. It selects files from a database via a program using a random number generating algorithm that's meant to mathematically imitate randomness as we know it in the analog world (and let's not bring quantum physics into the discussion, please.) Since this program considers ONLY the placement of each file in the database and not album name / artist, you may come up with several songs played close together that you consider to be "closely associated," but the program doesn't.

And no, I didn't write the program or the algorithm, so I can't tell you whether you can make the choices appear more varied by either spreading out or clumping songs by the same artist on your iPod, or even if the order of songs as you loaded them into your iPod is the order in which they're stored in the database and accessed by the program. Ask Apple. (/computer scientist) And remember from point one, the program is not selecting files that are evenly-spaced-out in the database. It's selecting random files.

As for your "shuffle" mode playing breaking-up songs whenever you've been dumped, I can't help you there. (Cue spooky Theremin music...)

And you thought I was a Mommy-blogger.

Posted: Fri - May 4, 2007 at 08:42 AM   Home         | | View Technorati reactions

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