Archives for February 2013

Unless you’ve been living under a rock on a very exclusive island for about a decade, you have at least heard and/or read the term “mp3.” But have you ever wondered what it is or what it really means? I was just going through the several hundred posts here on the Home Brew Audio website and discovered to my surprise that there were no articles or posts explaining what mp3s are. So I decided to write one.
Let’s just start out by saying that music, an inherently non-computer thing, had to be made computer-friendly in this, the computer age. In the old days, music was played by musicians and we listened at concerts, in living rooms, etc. Then we found a way to record that music – to capture it so it could be listened to when the musician was not actually playing it. Recordings were made by converting the actual sounds in the air into something (an “analog” of the music) that could be played back on either a record player or tape machine. We didn’t concern ourselves too much with whether the analog was made of magnetic particles (tape) or etched into wax or plastic by electric signals (records).
Once it became feasible to use computers to digitize music into ones and zeros, digital music had to made usable to people who wanted to listen to music. At first we end-users didn’t know much had changed except that we could now get our music on things called CDs and play them back on CD players. It was an adjustment, but most everyone made the leap.

File Format – Size Really Does Matter

Eventually we discovered that we could “rip” our CDs into our computers. Once we realized that we could move out music around like this, and that the music was no longer physical in any meaningful way (like when we had to transfer CDs and records to cassette tapes in order the share them with friends), we also realized that sharing (not to mention storing, cataloging, etc.) music was going to get a lot easier. The problem was that the de facto default file type (the wav file) was massive and could not easily be shared or transferred across networks and the internet. In the 1990s, for example, it might take an hour or two to transfer one song in wav format. Though speeds and capacity are much better these days, wav files are still considered too large to use as web audio. It seemed that any effort to reduce the file size also reduced music quality so much that it wasn’t worth sharing any more.

Time To Use Our Brains – Literally

It turned out the reason the audio quality of the music suffered so terribly when folks tried to reduce the file size of wavs was that important audio information was being removed, information that human brains are very sensitive too. It was like a wav file were a stack of wooden blocks (each with a design on one side) on a scale. The weight of the stack is like the file size. If we imagine in this metaphor that we desire to see a stack of blocks around 10-blocks high. It’s beautiful to us. We want to share this stack with friends and family, but we cant because they weigh too much to lift. Someone gets the bright idea to remove several of the heaviest blocks to make the stack lighter. Great, except for one problem. The stack isn’t pretty any more. In fact it’s downright ugly (just like wav files that folks attempted to make smaller by removing data that made it sound good to us). Fail.
Next, a really smart friend comes to us with a new proposal. He shaves off the back sides of the heaviest blocks, in some cases removing quite a bit of the wood. In the end, quite a lot of wood has been shaved off the backs of these blocks and the weight of the stack is reduced so much that we can now pick the stack up easily and move it around. Everyone that sees it says it is still beautiful because they only see it from the front, where all the pretty pictures are. Yes, if they inspect the stack closely they will find that some work was done in the back, but they don’t really care about that because it’s the front they want to see.

As a rough idea of how much smaller an mp3 is than it’s wav counterpart – a 30 MB song’s wav file (about a 3 minute song) can be converted into an mp3 version that is only about 3 MB. The mp3 ends up being about a tenth the size!

Mp3s are kind of like that (what? – stay with me). Some smart people (specifically several teams of engineers working with the Moving Picture Experts Group (MPEG) at Fraunhofer IIS, University of Hannover, AT&T-Bell Labs, Thomson-Brandt, CCETT, and others – reference: http://en.wikipedia.org/wiki/MP3) figured out a way to remove bits (no pun intended) of information from audio files that human brains didn’t really notice were missing unless we listened really closely. Heck, even then most humans still can’t tell. The result was an mp3, which technically stands for “MPEG, audio layer III.” These files are small enough, but still sound good enough, that it became a fantastic way to share music with e-mail, on the web, or with any computer-like device. As a rough idea of how much smaller an mp3 is than it’s wav counterpart – a 30 MB song’s wav file (about a 3 minute song) can be converted into an mp3 version that is only about 3 MB. The mp3 ends up being about a tenth the size!

The Upshot

Files like mp3s are sometimes called “lossy” because some musical information is “lost” in order to make a small file by compressing the data (removing information to reduce the size). That is also why mp3 is sometimes referred to as a data “compression” format. This is not to be confused with “audio compression” as an effect, by the way. There are lots of other types of lossy file formats out there now as well, such as AAC and Ogg Vorbis to name a few. AAC is the type used by Apple’s iPod. Interestingly, iPods are still frequently referred to generically as “mp3 players.”
So now you know. You will never have to wonder again what an mp3 is or even what it stands for.
Use the knowledge wisely my friends.
Cheers!