Audio File Formats You Might Encounter When You Use iTunes

As you work with digital music and other audio files, you'll encounter a number of different file formats that you need to understand. This is important because each of these formats offers specific benefits and limitations that impact what you do with your music. For example, some file formats offer better music quality versus file size than others. You definitely don't need to have all the specifications for each of these formats committed to memory (nor will you find them in this book); instead, all you need to be able to do is to distinguish between them and to be able to choose the format that is the most appropriate for what you are trying to do.

Most audio file formats are encoded. What this means is that specific compression algorithms (because this is a computer book, I am required by contract to use that word at least once) are used to reduce the size of the audio file without, hopefully anyway, lowering the quality of the resulting sound very much. The higher the compression that is used, the lower the quality of the resulting music when it is played back. Note that the words higher and lower are relative. Often, it takes a musical expert to tell the difference between encoded and unencoded music, but even if it is imperceptible to us mere mortals, it does exist.

When it comes to digital audio files, one trade-off always has to be made. And that is file size versus sound quality. When you add thousands of songs to your iTunes Library, you can easily consume gigabytes of disk space. Although you might have a humungous hard drive in your computer, you might also have other files you want to store on it, such as photos, Word docs, and so on. Even I realize that computers can be used for more than just music.

To keep the amount of disk space required to store your music to a minimum, you will encode it. When you do, you choose the settings you want to use to encode that music. The more encoding you apply, the less space the music will consume, but the lower quality the playback will be. You will quickly find a happy medium between file size and how the music sounds to you.

You'll learn about this in more detail later in the book, but for now, you should read the following sections so you can become comfortable with the various audio file formats you will encounter.

CD Audio

The CD Audio format was the world's first widely used entry in the digital audio format life cycle. The creation of this format was the start of the CD revolution. Instead of vinyl albums, which were a pain to deal with and included lots of hisses, pops, and other distractions when played, listeners began enjoying digital music. In addition to being much easier to handle than LPs, CDs provided a much better listening experience and wereand aremuch more durable than records. They also sounded much better than cassettes and could be just as portable.

Caution

Some audio CDs use copyright-protection schemes that prevent you from listening to them on a computer (with the idea being that you won't be able to make copies of the songs for illegal purposes). Unfortunately, not only do these CDs not work in your computer, they can actually cause damage. Before playing a CD in your computer, check the CD's label carefully to make sure it doesn't contain any warnings about playing the CD in a computer or state that the CD is copy-protected. If it does have these warnings, don't try to use the CD in your computer.

Eventually, CD Audio made its way to computers, which now can provide all the music-listening enjoyment of a home stereo plus much more, thanks to applications such as iTunes.

Although you can use iTunes to listen to your audio CDs, typically you will just convert those CDs into one of the newer digital formats and store that content on your computer's hard disk so you don't have to use a CD when you want to listen to music. You will also make use of this format when you put your iTunes music on your own audio CD so that you can play your iTunes music when you are away from your computer.

MP3

Even if this book is your first foray into the wonderful world of digital music, you have no doubt heard of MP3. This audio file format started, literally, an explosion in music technology that is still reverberating and expanding today.

Note

Because encoded music files are relatively small, storing an entire music collection in a relatively small amount of disk space is possible, thus eliminating the need to bother with individual CDs. Using a digital music application such as iTunes, you can easily store, organize, and access an entire music collection on your desktop or laptop computer.

MP3 is the acronym for the audio compression scheme called Moving Picture Experts Group (MPEG) audio layer 3. The revolutionary aspect of the MP3 encoding scheme was that music data could be stored in files that are only about one-twelfth the size of unencoded digital music without a noticeable degradation in the quality of the music. A typical music CD consumes about 650MB of storage space, but the same music encoded in the MP3 format shrinks down to about 55MB. Put another way, a single 3.5-minute song shrinks from its 35MB on audio CD down to a paltry 3MB or so in MP3 format. The small size of MP3 files opened up a world of possibilities.

For example, MP3 enabled a new class of portable music devices. Because MP3 files can be stored in small amounts of memory, devices with no moving parts can store and play a fair amount of music; these were the early MP3 players, such as the Rio. Then came other devices containing small hard drivescan you say iPod?that can store huge amounts of music, enabling you to take your entire music collection with you wherever you go. These devices are extremely small and lightweight, and their contents can be easily managed.

You will encounter many MP3 files on the Internet, and with iTunes, you can convert your audio CDs into the MP3 format so that you can store them in iTunes and put them on an iPod.

AAC

The newest digital audio format is called Advanced Audio Coding or AAC. This format is part of the larger MPEG-4 specification. Its basic purpose is the same as the MP3 format: to deliver excellent sound quality while keeping file sizes small. However, the AAC format is a newer and better format in that it can be used to produce files that have better quality than MP3 at even smaller file sizes.

Also, as with MP3, you can easily convert audio CD files into the AAC format to store them on a computer and add them to an iPod. What's more, you can convert AAC files into the Audio CD or MP3 format when you want to put them on a CD to play on something other than your computer, such as a car stereo.

Note

Frankly, you aren't likely to notice any difference between AAC music files and MP3 files, except in one areasome portable digital music players (such as MP3 players) don't support AAC-formatted music. The iPod does, so if you use one (given that you are reading this book, I assume you do), you don't have to be concerned about this difference.

The AAC format also enables content producers to add some copy-protection schemes to their music. Typically, these schemes won't have any impact on you (unless of course, you are trying to do something you shouldn't).

One of the most important aspects of the AAC format is that all the music in the iTunes Music Store is stored in it; when you purchase music from the store, it is added to your computer in this format.

WAV

The Windows Waveform (WAV) audio format is a standard on Windows computers. It has been widely used for various kinds of audio, but because it does not offer the "quality versus file size" benefits of the MP3 or AAC formats, it is mostly used for sound effects or clips that people have recorded from various sources. Millions of WAV files are available on the Internet that you can play and download.

You can load WAV files into iTunes, and you can even use iTunes to convert files into the WAV format. However, because MP3 and AAC are much newer and better file formats, you aren't likely to want to do this very often. Occasionally, you might want to add WAV files to your iTunes music collection; this can be easily done, as you will learn later in this book.

Tip

If you ever want to find a sound byte from your favorite movie or TV show, you can probably do so at one of the many WAV Web sites on the Internet. One example is www.wavcentral.com. Interestingly enough, even the sound clips on these sites are being largely converted into MP3.

AIFF

The Audio Interchange File Format (AIFF) provides relatively high-quality sound, but its file sizes are larger than MP3 or AAC. As you can probably guess from its name, this format was originally used to exchange audio among various platforms.

As with the WAV format, because the MP3 and AAC formats provide better sound quality in smaller file sizes, you aren't likely to use the AIFF format very often. The most likely situation in which you might want to use it is when you want to move some music or sound from your iTunes collection into a different application that does not support the MP3 or AAC format.

Apple Lossless

This encoding format is also new; it is a compromise between the high-quality of WAV and AIFF formats and the small size of AAC files. Apple Lossless files are very high quality (equivalent to AIFF) but are only one-half the file size of those noncompressed formats. If you want the maximum quality of music playback (especially if you create audio CDs), this can be a useful encoder to use. About its only downside is that not all audio applications can play it (iTunes and the iPod can and those are all you really need anyway).