Frequently Asked Questions
Q: What is CD EXTRA?A: 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 (Blue Book) is based on the multi-session 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 computers. 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:
The CD EXTRA format is supported by Microsoft, which worked with Philips and Sony on the specification, and Apple. Both companies have developed software tools to create CD EXTRA titles.
- Playable on a wide range of hardware including computers under Microsoft® 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 (that is, 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, that 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.