MFDigital CD DVD Information Library
Thursday, June 10, 2004
Subcode Channels
In addition to the main data channel (which contains audio or other data) there are 8 subcode channels labelled P to W interleaved with the main channel on the disc and available for use by CD audio and CD-ROM players.

When the CD was first developed, the subcode was included as a means of placing control data on the disc. The main channel was intended entirely for audio not any other form of data. Since then the main channel has been used for other types of data and the new DVD specification omits the subcode channels used for CDs.