Home > Geekboy > Archives > 2006 > January > 26
Thursday, January 26, 2006
Peeking behind the curtain of MP3
The Atlanta Journal-Constitution
MP3 players are as popular as free beer at Hooters.
The first question people have after getting an MP3 player, is “Where do I get MP3s?�
Over the next week or so we will discuss the legal and not-so legal ways of obtaining digital music.
While we see how my team of bosses react to the previous sentence, let’s try to get a handle on what an MP3 is.
In the early 1980s, the audio compact disc came into existence. They became popular because they were portable, durable and sounded great. The only problem with them was each song took up a lot of space, limiting each CD to about 20 songs max.
It took some high-powered geeks to fix this.
Geekboy’s History of the MP3
Once upon a time a team of smart Germans got together and, instead of invading France, decided to create a method of making large video and audio file sizes smaller.
Audio and video files needed to be smaller so they could be transmitted more easily over phone lines using modems, which, if anyone recalls, are as slow as molasses in a pre-global warming winter.
To prevent anyone from going to sleep, I will skip the technical details, but needless to say the scientists succeeded.
Their first release was called MPEG-1, and compressed audio and video, like that in a television broadcast. Not that you care, but MPEG stands for Motion Pictures Expert Group, the folks that set the standards for stuff like this.
Eventually, people migrated from slow modems to faster broadband connections and thus the vastly improved MPEG-2 came into being. Most DVDs are recorded in a slightly tweaked version of MPEG-2.
MP3 is a similar compression scheme without the video element. The scientists, who endlessly played Suzanne Vega’s “Tom’s Diner,� were trying to reduce the size of a music file, like those found on audio compact discs, without obvious loss of quality so you could fit more of them onto a hard drive, something every iPod owner appreciates.
How did they do it?
The simple answer is they threw out everything the human ear could not discern.
Digital music, like that on a CD, actually contains more information than the human ear can detect. MP3s basically eliminate all the extra information, making the file size much smaller.
How much smaller is an MP3 than the source music?
It depends.
The size of an MP3 file, and its audio quality, is determined by its “bit rate,� which is simply a measurement of how many packets of information are transmitted in a given period of time, usually per second.
The more bits per second, the better the song sounds, but the more space it will take on your hard drive. The songs on a CD are recorded at the bloated rate of 1400 kilobits per second.
Most listeners are quite happy with a bit rate of 128 kilobits per second, usually written as 128k.
A 128k MP3 is supposed to sound as good as FM radio, so that will likely suit most users. Other popular bit rates are 192k and 256k, which is supposed to sound as good as the CD itself.
A 128k MP3 is roughly a tenth as large as the original song, a 256k MP3 about a fifth as large.
I use 128k MP3s in portable devices, and so do most other people. Next week we will discuss how to acquire MP3s. Until then, let’s compare the various bit rates and see if you can tell a difference in quality.
The following links will fire up the opening few seconds of “Waters Partâ€? by Let’s Active, an old school band from North Carolina.
Can you tell the difference?
