MFDigital CD DVD Information Library
Thursday, July 08, 2004
Mixed Mode CD > Enhanced Music CD
Enhanced Music CD

Enhanced Music CDs are a type of mixed mode CD developed by Philips and Sony in conjunction with other companies such as Microsoft and Apple. Often referred to as CD EXTRA or CD Plus these discs contain two sessions. The first session contains up to 98 audio tracks; the second session contains the data track. When played on an audio player, it only sees the first session and so does not try to play the data session. The specification (the Blue Book) is based on the multisession pressed disc specification with some application specific additions for handling lyrics, titles and stills.

CD EXTRA discs, according to the Blue Book, are intended to be played on dedicated hardware as well as PCs. Therefore the data formats to be used are defined closely in a similar way to the White Book specification for Video CD. The main features of such discs are as follows.

Playable on a wide range of hardware including PCs under Windows 95, Macintosh computers, and dedicated CD Plus players (but not CD-i players which cannot play CD EXTRA discs).

Session one contains up to 98 tracks of audio data conforming to the Red Book specification.

Session two contains one track of CD-ROM XA (ie Mode 2) sectors and must include certain specified files and directories and use the ISO 9660 file system. For Macintosh compatibility, it is possible to make the data track include HFS as well as ISO9660. The following directories and files are required:

  • An AUTORUN.INF file in the root directory which meets the Windows 95 Autoplay specification.
  • A CDPLUS directory containing general information, lyrics and MIDI data.
  • A PICTURES directory containing pictures encoded in both MPEG and other formats.
  • An optional DATA directory containing additional data files depending on the application.

The CD EXTRA format is supported by Microsoft (who worked with Philips and Sony on the specification) and Apple. Both these companies have developed software tools to create CD EXTRA titles.