Frequently Asked Questions About CD-R and CD-RW Discs

Please contact Media Sciences if your questions are not answered on these pages.

Recorded CD-R discs work fine in my CD-R drive but fail in some CD-ROM drives. Do I have format problems?

Although interchange failure is frequently related to out-of-spec parameters or errors, formats are often the culprit. It would be convenient if only one data format existed. However, market demands for multimedia, plus the popularity of CD-R recording, have created a complex web of formats, each defined by their own standard. Every drive may not comply with each format, creating a significant risk of interchange failure.

Digital Audio, or CD-DA, was the initial compact disc format. The Red Book standard of 1980 was followed in 1987 by IEC 908. Sound is recorded in frames, each containing 24 bytes of digitized audio. A continuous, spiral track consists of lead-in followed by pre-gap, then a single physical track of audio frames, then post-gap, and finally lead-out. Multiple songs are accessed by dividing the physical track into as many as 99 logical tracks, and by subdividing logical tracks using indexing. All compact disc drives must be capable of playing this CD-DA format.

Compact Disc Read Only Memory, or CD-ROM, was first specified in 1983 in the Yellow Book and later in ISO/IEC 10149. Data is organized into sectors, each containing 98 Red Book frames. Sector sync, headers, and error detection and correction are necessary for reliable data retrieval. CD-ROM use the CD-DA track structure of lead-in, pre-gap, data sections, post-gap, and lead-out. All CD-ROM drives must be capable of reading this format.

CD-ROM volume and file structure was defined in the High Sierra Standard of 1985 and later in ISO 9660. The Microsoft CD-ROM Extension, MSCDEX, is based on this Standard, and enables personal computers to access a CD-ROM drive as a large, read-only hard drive beginning with MS- DOS 3.1. Later enhancements to ISO 9660 included Joliet and Romeo extensions and the El Torito bootable CD specification. Operating system variations include HFS or Hierarchical File Structure, a native MacIntosh format, and Rock Ridge, a UNIX file system.

Multimedia first appeared in 1986 as CD-i, or Compact Disc Interactive. Detailed elements of this TV set-top box are defined in the Green Book. This novel system was the first real time multimedia application that simultaneously integrated sound, animation, data, text, graphics, and limited video. Many of its features were later integrated into other formats such as CD-ROM/XA, the 1991 CD-ROM Extended Architecture format that supports data and audio/video interleaving for smooth playback. CD-Bridge combined features of CD-I and CD-ROM/XA to create a format usable in either type of drive. CD-VIDEO added MPEG-1 video capability in the 1987 White Book. Photo CD was issued by Kodak in the Beige Book, and was the first multisession format. CD-ROM drives are not required to support these formats.

Compact Disc-Recordable was introduced in the 1988 Orange Book Part II. CD-R discs contain pre- stamped grooves that enable write once recording using affordable drives. Although CD-ROM compliant disc-at-once recording was initially used, other methods are allowed by the Orange Book. Track-at-once recording writes data first. Lead-in and lead-out are written last, resulting in link blocks. Multisession recording also generates link blocks between sessions, each consisting of lead-in, data, and lead-out. Packet recording adds further complications. CD-ROM drives are not required to read multiple sessions, and can be confused by link blocks.

CD-Enhanced multisession was introduced in the 1995 Blue Book. These discs combine Red Book, Yellow Book, and Orange Book methods, and require a multisession-capable drive. Rewritable discs were defined in the 1996 Orange Book Part III. These CD-RW discs, previously referred to as CD-E or erasable, reflect only 20% to 30% as much light as do CD-ROM discs, and require a CD-RW enabled drive. Current CD-ROM drives cannot read CD-RW discs.

The CD-DA, CD-ROM, CD-I, CD-ROM/XA, CD-Bridge, CD-VIDEO, Photo CD, CD-R, CD-RW alphabet soup confuses drives just as effectively as it baffles the reader. It is surprising that discs interchange at all. Technicolor standards such as Red, Yellow, Green, White, Beige, Blue, and Orange that were issued at various times make it impossible for all drives to be in conformance, since a drive may have been designed before a standard was issued.

Modern CD-ROM drives may satisfy multiple standards such as CD-DA, CD-ROM, CD-ROM/XA, CD-I, CD Bridge, and Photo CD. Carefully consult the manual to determine the capability of each target drive, then be certain that your recorded discs match those capabilities. To assure interchange in all drives, use only disc-at-once recording in accordance with ISO/IEC 10149. Avoid track-at-once, multisession, and packet recording if every disc is to work in every drive.