Digital Audio Technology, 4th Edition

6 Codes for digital magnetic recording

The binary data representing an audio signal can be recorded on tape (or disc) in two ways: either directly, or after frequency modulation.

When frequency modulation is used, say, in helical-scan recorders, data can be modulated as they are, usually in a non-return-to-zero format (see below). If they are recorded directly, however, say, in stationary-head recorders and compact disc, they have to be transformed to some new code to obtain a recording signal which matches as well as possible the properties of the recording channel.

This code should have a format which allows the highest bit density permitted by the limiting characteristics of the recording channel (frequency response, dropout rate, etc.) to ...