Audio data from CDs is read digitally for the purpose of saving audio tracks to hard disk and copying CDs.
Yes, you did read that correctly - digitally. All CD/DVD-ROM drives can play audio CDs in analogue format (i.e. through head sets or sound card) but not all can read audio data digitally and even then only a few of these drives produce good quality audio reading. So: the digital extraction of audio data is essentially different from simply playing an audio CD.
In practice the quality of the digitally read audio data is never going to be satisfactory. For example sometimes there are "jumps" in the audio data which are noticeable as unpleasant clicking noises when playing a saved audio file or listening to a copy CD. The amount of such defects in the audio data is heavily dependent on the type and make of the CD/DVD-ROM drive.
Before extracting audio data or copying CDs each owner of a CD ROM should be aware of how good the audio read quality of his own CD/DVD-ROM drive is. Armed with this knowledge unusable CD copies can be avoided by selecting better copy options. To diagnose your CD-ROM proceed as follows:
If there is a repetitive, regular zigzag line in the upper half over the entire area and a horizontal null line in the lower half, your CD/DVD-ROM drive has very good audio read qualities. If your drive can also read audio data quickly there is nothing to prevent you using your drive for fast copies of all kinds.
If the zigzag line appears exclusively in the upper row but sometimes has irregularities compared to previous or later runs, as if parts had been cut out and added again at some other point, your CD/DVD-ROM drive suffers from the "jitter effect" and is therefore only suitable to a limited extent for fast copies. If used for fast copies or to save audio tracks the burnt CD and/or the saved file may possibly contain unpleasantly audible clicks in the audio data. The CD/DVD-ROM drive can be used without any problems for fast copies of data CDs but only conditionally (i.e. allowing for loss of quality) for copying CDs with audio tracks.
If the zigzag line sometimes appears in the upper and sometimes in the lower row or if both displayed channels contain only "nonsense" (for example both channels have horizontal lines or quite different forms than the expected zigzag line on the left/upper channel) your CD/DVD-ROM drive does not have such good audio read quality. In this case we would seriously discourage you from using your CD/DVD-ROM drive for fast copies of CDs containing audio tracks or for saving audio tracks. The CD/DVD-ROM drive may, however, be used without any problem for fast copies of data CDs.
Nero CD Speed
You can also verify the audio read quality (DAE - Digital Audio Extraction) of the CD-/DVD drive using the benchmark program Nero CD Speed, a component of the Nero CD. You will find more details of this program in the chapter on Nero CD Speed.
See also: