Bringing Yourself Up to Speed with AAC, MP3, and Digital Audio - Understand Ripping, Encoding, and “Copying”
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Audio CDs store data in a format different to that of data CDs (for example, a CD containing software or your favorite spreadsheets). Most audio CDs use a format called Red Book and contain only audio data. Other CDs use a format called CD Extra that lets the creator include a data track as well as the audio tracks. This data track can contain any kind of data—for example, videos, pictures, or text.
Audio CDs store the data for their songs in a format that file-management programs on Windows (for example, Windows Explorer) and System 9 (for example, the Finder) can’t access directly. If you put an audio CD in your CD drive and open a Windows Explorer window or a System 9 Finder window, you’ll see only minuscule CDA (CD Audio) files rather than the huge uncompressed files that contain the songs. The CDA files are pointers to the song files. These pointers are called handles. You can use Windows Explorer or the Finder to copy the handles from the CD to your hard disk, but copying them won’t do you much good, because the audio will still be on the CD. By contrast, Mac OS X can access the data on an audio CD seamlessly.
To get the audio off the CD, you need to perform a process called ripping. Ripping sounds vigorous but simply means using a program to extract the audio from the CD (by using the handles to access the audio data). You can rip audio to uncompressed files—typically WAV files or AIFF files—or immediately encode it to a compressed file format such as AAC, MP3, or WMA.
TIP: Mac OS X lets you rip a song to an AIFF file by performing a Copy operation from the CD using the Finder. For example, drag the song from a Finder window to the desktop to rip it to an AIFF file there. However, in most cases, it makes more sense to use iTunes to rip songs and encode them to AAC files or MP3 files.
In iTunes, Apple uses the term “importing” to cover extracting the audio from CD, encoding it (if you’re using AAC or MP3), and saving it to disk. By contrast, in Windows Media Player, Microsoft uses the term “copying.” This is both accurate and inaccurate, clarifying and misleading, at the same time. It’s accurate because ripping and encoding a WMA file or MP3 file of a song on a CD does create a copy of it, with all the copyright implications involved. The term “importing” skates over the copyright implications of creating the compressed files.
Yet “copying” is inaccurate because, in the computer sense, a Copy operation almost always creates a perfect copy of the file involved, not a lower-quality version in a substantially different format. (For example, if you copy a Word document, you expect the copy to be a Word document with the same contents, not a WordPad or TextEdit document with a minimal amount of formatting and missing some of the less interesting parts of the text—as judged by the computer.) But for users who don’t understand how audio is stored on CDs and how compression works, the term “copying” implies creating a perfect copy of the CD audio on the computer’s hard disk. And that’s not the case.
Learn about CDDB and Other Sources of CD Information iTunes and many other ripping and encoding applications download CD information from the CD Database (CDDB; www.cddb.com). CDDB is a collaborative project that allows anyone who can connect to the Internet to access its data.
You can look up information manually by using the CDDB interface, but in most cases audio programs look up CD information automatically for you, either when you insert a CD or when you instruct the program to look up the current CD. If the CD you’re trying to look up doesn’t have an entry in CDDB, you can submit one.
 This is chapter three of How to Do Everything with Your iPod & iPod Mini, by Guy Hart-Davis (McGraw-Hill/Osborne, ISBN 0072254521, 2004). Check it out at your favorite bookstore today.
Buy this book now. |
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