March 20, 2008
MP3 ain’t all that
Other formats for getting your groove on
By John “jaQ” Andrews firstname.lastname@example.org
You may have noticed that I tend to not use the term “MP3 player.” While that would certainly be preferable to calling everything an “iPod” (much like all portable cassette players in the ‘80s were casually called “Walkmen”), it really doesn’t properly describe the things. Leaving aside the fact that most of them also play video, record sound, save calendar entries and do a zillion other things, the audio they play typically extends far beyond the MP3 format.
Even the venerable iPod itself, while perfectly capable of playing MP3 files, really wants to play Advanced Audio Coding (AAC) files, the default kind used in iTunes. The two formats work in essentially the same way, by stripping out mostly inaudible sounds to allow compression of file sizes; they just use different exact techniques to get there. The details are stupidly complicated and mathemagical, so suffice to say that AAC generally sounds better than MP3 the more compressed the files are. Compression ratios vary, but a typical song encoded at 128 kilobits per second is just under one megabyte per minute.
Compression is important because even though media players get more memory every day, that memory is still finite, and you want — nay, need — to have thousands of songs at your disposal. Otherwise you could just put your music in a lossless format. The most well-known is the WAV file, the most basic form of audio file on any Windows computer. Its equivalent on a Mac is AIFF. It uses what’s called pulse-code modulation (PCM) to sample an analog audio signal at regular intervals; the more frequently those samples occur, the more faithful a representation of the original analog signal is created. Compact discs use a sampling rate of 44,100 per second, so a WAV file ripped from a CD would have the same sampling rate and be about 10 megabytes per minute.
There are lossless formats that still provide some compression, but not much. The Free Lossless Audio Codec (FLAC) is popular for its open source nature and good performance; Windows Media Audio (WMA) also has a lossless version. They and other lossless formats provide about 2:1 compression compared to a WAV file, so while they’re not all that practical for portable media players, they’re often used by archivists or intense audiophiles.
Getting back to lossy formats, MP3 and AAC are hardly your only options. Music nerds will argue for hours about just which particular format is best, but as with most things, it really depends on your needs. MP3 is kind of the standard, but contrary to popular belief, it’s not really a free format. Every program that encodes or plays MP3 files needs to be licensed to do so. The same is true of lossy WMA.
Several music player manufacturers have introduced their own formats, chief among them being, of course, Sony. They cheekily called their format Adaptive Transform Audio Coding, or the homophonic ATRAC. (Say it out loud.) It never caught on much outside Sony’s inner circle, despite producing good sound at low bit rates.
In contrast, the weirdly-named Ogg Vorbis format is free and open, so has gained the loyalty of open source advocates. Its support among music players is scattered, however, and often isn’t even mentioned in product specs. Best Buy’s Insignia players do support it, as do most players from Cowon, iRiver, Meizu and Samsung’s Yepp line. The open source Rockbox replacement firmware also plays Vorbis files.
Oh, and did I mention video? I did. More on that next week.