More iTunes Math

markmcb writes "OmniNerd once again digs into the math behind iTunes. The 5-star ratings in iTunes are actually stored in a variable allowing values from 0 to 100, with 20 = 1-star, 40 = 2-star, etc. Known to few, if you set a rating to 30 (manually), it will show up as 1 1/2 stars in the program's GUI. Matt Schinckel provides interesting statistical evidence showing that not only do non-whole, non-half values (e.g., 47) not increase the amount a song will play, but neither do the half-star ratings (with the exception of .5 star)."

Comments

Re:Is it really surprising?

[TheSpoom]

Well, it's obviously a bug, but... Slashdot-worthy?

This just seems like something I'd quietly forward to their developers.

So it's basically fixed point math.

[voxel]

So, 32 of 100 is simply 1.6 stars.

Formula 32 / 20 = Number of stars.

Wow. I don't see why this article is on slashdot, what am I missing?

Re:So it's basically fixed point math.

[nathanh]

This story has everything to do with what this site stands for. It directly involves Apple, mathematics, software design, software analysis, software realiability, and so forth.

Indeed, this is a very interesting story that should appeal perfectly to the general Slashdot audience.

The hacker audience who is interested in such things has been dwindling both in numbers and as a percentage. Now the "general Slashdot audience" prefers to fawn over the latest consumer product from Apple, to complain about Microsoft, or to inexpertly argue their "Rights Online".

Articles about technology, impressive hacks, homebrew projects, science and mathematics would be extremely welcome. Unfortunately the editors are infatuated with content-free articles that are little more than advertisements for products like the PS3 and Xbox and iPod.

Future considerations, perhaps?

[CyricZ]

They could have just been leaving their options open for future expansion of the software. Indeed, it would be better for compatibility to already use the 0 to 100 range.

Suppose in the future they added support for giving a song a percentage ranking. It's quite easy to do with the system they're using now. Data from the new software could be used with the old, as the old software is already expecting and can cope with a value in the 0 to 100 range, even if it does so slightly differently than the future versions.

In a spirit of non-Disneyness...

[Expert Determination]

...I could announce that in the Palm ebook reader, eReader's PalmReader, you can uncover the markup used to format the text even though it isn't directly visible. You can do this by using the search facility to search for markup tokens from the "Peanut Markup Language" used. Curiously it skips the escape character ('\') and the first letter of each markup symbol, as if the original authors expected all markup symbols to be one character long. The markup also includes the filenames of included images which are stored in .png format. So you can search for images in an eReader ebook by searching for the string ".png". I discovered this by disassembling the executable - not by trial and error in the application. I think this was a much more interesting bit of sleuthing than this trivial iTunes one and wish it would get published on slashdot.

On the other hand, even I think this is too boring to tell other people.

Smart Shuffle might have something to do with it

[theurge14]

In the current Windows version of iTunes (6.0.2.23), in Preferences there is a tab for Playback. And in there is a section for Smart Shuffle.

The first control is a 3-setting slider for "more likely, random, less likely". The description below says "Smart shuffle allows you to control how likely you are to hear multiple songs in a row by the same artist or from the same album."

Below that are three radio boxes, labled Shuffle: ( ) Songs ( ) Albums ( ) Groupings.

Is it possible that this 100 scale rating system might be more fine grained to take these Smart Shuffle user settings into account? Perhaps that might be why it isn't simply the integers 0-5. /didnt rtfa

Re:I'm just saying this...

[Lisandro]

Why troll? He's damn right. Why how iTunes calculates ratings is considered a story? Why is it presented as "math", like it's advanced calculus? And why the hell is this on the science section?

Must only be interesting if

[Anonymous Coward]

introductory algebra is new to you. Sorry, it's not people who think this is boring that should be looking at Disney.com. It's people who think this is interesting that should be posting somewhere that's the Disney equivalent of Slashdot.

I don't use itunes, and while I realize many people do, this seems pretty mundane. It might be interesting to those who care - obviously there's some of you out there - but this hardly seems worthy of Slashdot. I'd expect something more hackerish along the lines of "NSA backdoor found in Windows". Math wise I'd expect something about a newer, better way to find prime numbers, or a new encryption algorithm. Not how cool it is that instead of 0-5, they use 0-100!!! And you can specify half a star. BAD ASS!

Just my useless, anonymous two cents.

Re:why linear?

[darkitecture]

Why is the rating system linear instead of exponential. I would like a song that has one more star than another to play TWICE more often.

Man, do you really want your favorite song to play 32 times for every 0-star rated song you have on your iPod? I don't care how much you love a song, after listening to it that often, you're bound to want to stab your iPod in the face. Or the closest fan of The Cure. Come to think of it, that'd be a win-win situation.