6.4 Overview of CD-RW and DVD
6.4.3 Digital audio extraction explained
The availability and relatively low cost of CD recorders and recordable media has put custom compilation audio CDs within the reach of many users. Since the inception of audio CDs, users have desired the ability to create their own custom CDs while keeping the quality of the music that digital recording provides. Digital audio extraction makes this possible.

Digital Audio Extraction (DAE) is the process of copying audio from a CD to another medium while keeping the audio in its original digital state. Also known as "ripping", most users use DAE techniques to pull tracks (songs) from an audio CD to a computer's hard drive and then to a recordable CD. Keeping the song in an all-digital format greatly reduces the chances of audio discrepancies.

When a CD player/drive plays a Red Book CD (CD audio format) the drive performs a digital-to-analog conversion in real-time so the audio can be played through speakers. Before digital audio extraction, this audio had to be re-recorded and re-digitized if a user decided to put the song on a recordable CD. This digital-to-analog-to-digital conversion was very time consuming and unwanted noise was usually introduced. Depending upon the quality of the CD-ROM drive, computer hardware, and software, digital audio extraction can make nearly flawless digital copies of songs at a fraction of the time.

Copying a song from a Red Book CD is much different than copying a file from a CD-ROM (the Red Book is discussed later in this chapter). Songs are stored in tracks on the CD and drives read these tracks as they spin under the laser assembly. Since the audio information is "streamed" to the drive, special digital audio extraction software must be used. This software reads the raw information of a track as it is streamed and collects the information into a .WAV file. This .WAV file can then be played on a computer or copied back to a recordable CD along with other songs to create a custom audio CD.

When DAE is used to create .WAV files on a computer, they are uncompressed and can be quite large in size. Other audio formats such as MP3 and Ogg Vorbis compress these raw files into much smaller files with minimal loss of song quality.