MP3 and other music CDs

Secrets of MP3-CDs

MP3 is the audio track that's part of an MPEG (Moving Picture Experts Group) file. MPEGs are movie files. MP3 is derived from "MPEG Audio Layer 3", the formal name for the audio track in these files.

The reason for all the excitement about *.mp3 files is that they're small. They can be downloaded quickly from the Internet and take up less storage space. You can also create *.mp3 files by "ripping" tracks from regular (music) CDs. MP3 files are analogous to JPEG (Joint Photographic Experts Group) files. Both formats reduce the number of bits required by reducing fidelity or resolution.

The degree of MP3 compression depends on the bit rate used to create the *.mp3 file. If you select a high bit rate, less of the bits in the original audio file are thrown away. A lower bit rate requires the loss of more bits. Fewer bits means lower fidelity. This rate is not something you usually work with directly unless you're ripping tracks from CDs.

The amount of compression is determined by the sampling rate that's used. The size of MP3 files is approximately 1 MB [megabyte] per minute-of-music when sampled at 128 Kbps. Music has "near-CD-fidelity" at this rate. 1 MB per minute is much less than the 10 MB per minute used by CDs you buy at the music store. (10 MB x 70 minutes = 700 MB, which is approximately the capacity of a CD.)

Now for the fun part: The small size of *.mp3 files means it's feasible to carry a lot of personal music around with you when you go for your walk, ride the bus or whenever you want to multi-task your life. At first, storage for personal MP3 players was provided by the same kind memory you'd use in a laptop PC. MP3 players now use anything from flash memory, to miniature hard drives, to CDs for storage.

Don't be confused

An "Audio-CD" is not an MP3-CD. Most software for burning CDs can make both Audio-CDs and MP3-CDs from *.mp3 files. Audio-CDs are often called "Music-CDs", and they're really much like the standard music CDs you buy. MP3-CDs are more like Data-CDs.

The burning software must s-t-r-e-t-c-h *.mp3 files to match the original time in order to make CDs that will play on all sCD players. That's because CD players always spin at the same rate (1X). If you have 60 minutes of music the software must stretch the files to fill 600 MB (more or less). You'll only get about twenty 3-minute songs on an Audio-CD -- about what you get when you buy a CD.

On the other hand, the software does not need to stretch files to fill the time when you make an MP3-CD. That means you can get around 200 3-minute songs on an MP3-CD. You can arrange the files in folders, just as on any data disk. Most burning software also adds a "playlist" so that you can read what's playing on the MP3 player screen.
[Burn an Audio-CD] [Burn an MP3-CD]

The rub is, you'll need a special MP3 player that can play MP3-CDs to listen to them. These players load *.mp3 file into memory and then stretch the bits to fill the time. Most newer "stereo" CD players, including those in cars, can play MP3-CDs as well as Audio-CDs. There are many portable MP3-CD players out there to choose from. Most of them play audio as well MP3 formats.
[An MP3-CD player]
[MP3 Player "Supercenter"] [MP3 Personality Test]

You may want to listen to MP3 files on your PC. You'll need a software MP3 player to do that. There's a jillion to chose from. Here are just a few -- Windows Media Player comes with Windows, and it's hard to avoid the insistent offers for RealPlayer. They're both free. You may have other players on your computer already, like MusicMatch. These players are not limited to *.mp3 files. They play *.cda, *.wma, *.wav and *.ra files along with many other formats. (CDA -- Compact Disk Audio -- is the file format on audio CDs.)

More on the Web

Fred Langa has published an extensive but valuable compendium of information about "ripping" audio tracks, and burning MP3 files to CD. You'll probably want to click the "Print this article" link when you get there so that you can read the whole article (in your browser if you like) as one page.