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CD, CDR, CDRW, DVD and their Hybrid Standards

by Dennis Faas, infopackets editor
http://www.infopackets.com

A CD is an acronym for Compact Disc. It can refer to any media type which is based on CD technology. For example, a CD can be a computer disc, a music disc, or a video CD. Each CD standard is defined by ISSO-9660, a model used by the International Standards Organization. Because there are so many different CD formats, there are a number of books describing certain formats and specifications for each type.

For example, the ISSO-9660 Red Book defines standards that all devices which play music CDs must follow for 100% compatibility.

Here is a quick run-down about ISSO-9660 standards (adapted from http://www.pyramind.com/services/iso9660.html):

International Standards Organization ISO-9660

ORANGEBOOK
Write Once Standard (Any CD)

RED BOOK
CD-DA / Audio Only CD (44.1 Khz)

YELLOW BOOK
Data Storage - CD-ROM Format
Mode 1 - Error Correction - Data
Form 1 - ISO-9660=DOS / HFS=MAC
Form 2 - Hybrid-RockRidge/UNIX

Mode 2 - DATA + A/V (XA- SPEC)
Form 1
- CD-ROM/XA (Error Rate > Data Rate)
- Computer Data & Red Book
Form 2
- CD-ROM/XA (Data Rate > Error Rate)
- A/V Non-Red Book

Mixed & Bridge Mode CDs

BLUE BOOK
CD+G / CD-Plus / Enhanced CD

GREEN BOOK
Games CD-I / CD Interactive (ISO Mode 2 Form 1 or 2)

WHITE BOOK
Karaoke CD-V / Video CD (ISO Mode 2 Form 1 or 2)

BEIGE BOOK (Kodak Corp Formats)
Photo CD - CD-ROM/XA (ISO Mode 2 Form 1)
Portfolio CD - CD ROM/XA (ISO Mode 2 Form 2)

CDR / CDR-W

The acronym CD ROM stands for Compact Disc Read Only Memory. When CDs were first developed, they were read-only media and could not be written to -- only large corporations had access to this expensive technology. Since then, CD recordable technology has become affordable for the home computer user. CD recordables allow anyone to make their own CDs; the only problem with CD recordable (CD-R) media is that it does not allow the user to rewrite over a previously written section of the disc. A typical CD-R disc is able to hold anywhere from 650 megabytes of information (or 74 minutes of audio), to 700 megabytes (or 80 minutes of audio).

A CD-R disc is also referred to as WORM media (write once, read many) and is perfect for permanently archiving digital media. The CD is extremely durable and its shelf life outweighs records, cassette tapes, VHS, and the like. CD-R media can be read in virtually all devices, including computers, VCD players, DVD players, game machines, and more. Portability is one of the main reasons why CD-R media is such a great medium.

CD-R/W media was recently introduced as a way to overcome the inability to write more than once to the same area of a compact disc. CD re-writable media is generally much more expensive than CD-R media and is not as portable as a regular CD-R. For example, a CD-R/W disc cannot be played in most CD players, including some computer CD-ROM drives because it is still considered a recently new technology. However, the list of compatible devices is increasing.

VCD

A video CD (VCD) uses the White Book ISSO-9660 standard and looks exactly the same as a regular CD, and can only be played on a VCD compatible player. Some compatible players include: a VCD stand- alone player, a computer, and some DVD players. A VCD plays video using the mpeg-1 video codec compression format. Typically, a VCD movie fits on two discs.

SVCD

A SVCD stands for super-vcd, and is an extension of a VCD. Quality of a SVCD is usually better than a VCD because it uses mpeg-2 video compression, which means that it can store higher quality video and sound on the same size compact disc. A SVCD also has the ability to use menus and chapters like a DVD disc. Typically, a SVCD movie fits on two discs.

X(S)VCD

XVCD stands for extended VCD and is a hybrid of the VCD 2.0 standard. XSVCD stands for super extended VCD, and is a VCD 2.0 standard. However, both XVCD and XSVCD are not ISSO-9660 compatible, and many DVD players are unable to play these discs. However, the list of compatible DVD players able to read the X(S)VCD format is growing.

DVD / DVD-R / DVD-RW / DVD RAM

DVD is an acronym for Digital Versatile Disc; DVDR stands for DVD Recordable, and DVDRW refers to DVD rewriteable media. A DVD is an excellent medium because it can hold such a large amount of information: about 4.7 gigabytes on a single side of the disc, or about 7 times the amount of information of a regular CD.

Some DVDs come double-sided and can hold approximately 14 gigabytes of information. With the ability to hold such a large amount of information, a DVD is able to produce breathtaking video and sound quality, can hold multiple languages for the same video. Often, DVDs come with additional video footage which show scenes of a movie production.

DVD-R

DVD-R is primarily designed for DVD production used by large corporations. DVD-R is a non-rewriteable format and is compatible with many existing computer DVD-ROM drives and DVD video players.

DVD-RW

DVD-RW is a rewriteable format, and is primarily supported by Pioneer. DVD-RW media is compatible with many existing computer DVD-ROM drives and DVD video players.

DVD-RAM

DVD-RAM is an attempt to mimic the DVD standard, but is not compatible with most computer DVD-ROM drives and DVD video players. In essence, a DVD-RAM drive is simply a removable hard disk with medium that is much more expensive than a CD-R disc.

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Copyright 2002 | Dennis Faas, infopackets editor |
http://www.infopackets.com | Computer 411

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