PCPlus 302: How it works: MP3 compression

A fun one this article: talking about digital recordings and how they’re saved for later playback. Especially CDs and MP3s.

I chat a bit about audio quality, particularly with regard to the fact that MP3s are always lossy compressed data. But then again, so are CDs lossy to a certain extent: they are sampled, admittedly at 44.1KHz (it’s roughly double the limit of human hearing, plus a bit more to help encode very high frequency sounds without losing too much definition). Studies have shown that people listening to 256Kbps MP3s and CDs can’t tell the difference. 128Kbps MP3s are equivalent to good FM radio, and anything less you start to notice the muddiness of the audio.

Funny story about me and MP3s: back in the day (starting in 2002) I used to use a Sony Clié NX70V as my PDA. It was a great little device and I bought lots of little apps for it (this was waaaaay before Apple’s AppStore, mind you, so you had to go looking for them) like MathU Pro, Ultrasoft Money, Acid Solitaire and so on. It also has a good little MP3 player, and for flights to and from Las Vegas (where I was working at the time) it was ideal. The battery wasn’t brilliant and used to die after about two hours, but that was OK for the trips I was making (and besides which I bought an external battery pack that used AA batteries for those really long flights). The only problem with the MP3 player was that it could only reliably play 96Kbps MP3s, so at the time I ripped all my CDs to that particular bit rate, which as I said above is a bit less than FM quality. I still haven’t re-ripped all those MP3s so half my MP3 collection is at 96Kbps and the more modern half at 256Kbps. Sigh. And now of course everything is indexed by iTunes and replacing them will mean I lose my play information. (Hmm, I wonder if there’s a software solution for swapping them out. . .)

Anyway, the article is a good lightweight layman’s introduction to MP3s and how they work. It was ideal for the Christmas issue.

This article first appeared in issue 302, Christmas 2010.

You can read the PDF here.

(I write a monthly column for PCPlus, a computer news-views-n-reviews magazine in the UK (actually there are thirteen issues a year — there's an Xmas issue as well — so it's a bit more than monthly). The column is called Theory Workshop and appears in the Make It section of the magazine. When I signed up, my editor and the magazine were gracious enough to allow me to reprint the articles here after say a year or so.)

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