Digital Music Formats

by Bob Seidel

Before we begin, local resident Robert Zeid, working with the World Computer Exchange (WCE), is holding another used computer drive this year on January 22nd. See the ad here in the SPP for details. Unfortunately, there is no local pickup - only in Wilmington.

A reader sent me an email recently, asking a question about computer music formats, and which one would be best for her situation. Not being an in-depth expert on the various music formats, I can't directly answer the question. The simple answer is to try them - if your ear is not sensitive enough to discern the difference, don't worry about it! If you CAN detect the difference, then use the appropriate format.

But what I can do is to discuss music formats in general, and perhaps answer the questions of why there is more than one format, what is compression, and what is sampling.

In very coarse terms, analog music is continuous sound, a summation of lots of sine waves. Digital music is created by "sampling" the continuous analog sound at various intervals. The digital music players can then re-create the continuous analog music when you listen to it, from the samples. The frequency at which you sample, and how much data your record at each sample determine how big the digital file is going to be. CD quality music is sampled at 44.1 KHz. (kilohertz). A common recording rate is 128 Kbps (kilobits per second) but it can be smaller to conserve space or higher for better sound quality.

At these rates, your digital sound file can begin to get pretty big pretty quickly. An uncompressed digital music file (called a .WAV file) can easily be many megabytes in size. If your digital music player can only hold, for example, 16 megabytes of data, you won't hold too many songs. You can make the files smaller, but at a decrease in audio quality.

Coming to the rescue is "compression". This is a generic term, because there are many forms of compression, each to fit a different type of data, or to implement a different sound effect. The most popular form of photo compression is JPEG, and you will see most of the digital cameras today create .JPG files. JPEG compression gets its effectiveness from eliminating photo data that our eyes can't see - mostly in what is called the "luminance" range - the human eye is less sensitive to luminance than to hue or saturation. But that doesn't apply at all to sound.

The most common music compression format is MP3. This format was developed for motion picture compression - both video and sound. The sound part was not specifically intended for classical audio listening, but again more for booming action movies. MP3 audio compression tries to identify the background sounds that you can't hear and eliminates them.

But there are a number of other sound formats, using different compression techniques for different situations. Microsoft developed the WMA format for audio (not combined video/audio) use, and while not being better quality it can reduce the size of an equivalent music file by half over MP3. But there is a new format out now, called MP3Pro, which is equivalent to WMA in size. A newer version, MP4, is also starting to be used.

But there are other formats. Apple uses a different format for the iPod players (AAC), and there are others such as OGG and APE. Each of these represents an effort to find a compression format that is better for a given situation or a given type of listener.

Another issue in music file formats is DRM or Digital Rights Management. DRM prevents copying of copyrighted songs. Some audio formats support DRM, and some don't. If you have a player that requires DRM, you may not be able to play songs that are not in a DRM enabled format.

Well, that is the basics on file formats and compression. But if you stick to the standard MP3 and WMA, you should be OK most of the time.

Bob Seidel is a local computer consultant in the Southport - Oak Island area. You can visit his Website at www.bobseidel.com or e-mail questions or column ideas to him at bsc@bobseidel.com. For specific inquiries, please call Bob Seidel Consulting, LLC at 278-1007.