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Glossary - CD, CDR, CDRW & DVD

Glossary - CD, CDR, CDRW & DVD

Authoring Software - Creation of a database for CD. The end product of authoring is usually a search and retrieval type document with the addition of a user interface. Specific authoring functions include tagging and indexing.

Buffer Underrun - A common error where the data stream being fed from the CD-Rs cache buffer falls behind the laser doing the writing.

CD - Compact Disc, a digital medium formed of a 12cm polycarbonate substrate, a reflective metalized layer, and a protective lacquer coating. The physical format of CDs is described by the ISO9660 industry standard. CD-Recordable discs also have an organic dye data layer between the substrate and the metal reflective layer.

CD-DA - Compact Disc Digital Audio. Commonly called a CD, this is an audio disc that contains up to 74 minutes of hi-fi stereo sound. A CD, 4 3/4" in diameter, is like a miniature phonograph record, except that only one side of the disc contains recorded material. A CD is a direct access device, and the individual selections can be played back in any sequence. Unlike phonograph records in which the disc platter contains "carved sound" the CD is recorded in digital form as a series of tiny pits that are covered with a clear, protective plastic layer. Instead of a needle vibrating in the grooves, a laser in the CD player shines light onto the pits and picks up the reflections as binary code. Sound is converted in digital code by sampling the sound waves 44.1KHz per second and converting each sample into a 16 bit number. It requires almost a million and a half bits of storage for each second of stereo hi-fi sound. The reason digital sound is so clear is that the numbers are turned into sound electronically. Other forms of CDs (CD ROM, CD ROM X/A, CD-I and DVI) all stem from the audio CD. The standard specification for CD is known as the Red Book.

CD-ROM - Compact Disc Read Only Memory. A compact disc format that is used to hold text, graphics and hi-fi stereo sound. The disc is almost the same as the music CD, but uses different tracks for data. The music CD player cannot play CD ROM discs, but most CD-ROM players are able to play CD discs. A CD-ROM player is cabled to and controlled by a card that is plugged into one of the computer's expansion slots. A CD ROM can hold 650 Mb of data, which is equivalent to about 250,000 pages of text or 20,000 medium-resolution images.

CD-ROM/XA - Compact Disc Read Only Memory Extended Architecture. The extended version of Mode 1 permits interleaving of compressed audio, video, and data, plus the encoding of PCM and ADPCM audio.

CD-R - Compact Disc-Recordable. This term is used to describe the technology of recordable CD as well as the equipment, software and media used to make recordable discs.

CD-I - Compact Disc-Interactive (Green Book) CDs are those that are done in the proprietary Philips format created for their CD-i players/game machines. This interactive multimedia system connects to a television and plays interactive games and movies. CD-I discs require a CD-I player and will not play a normal PC CD ROM player. Replaced by VideoCD or White Book, a cross between CD-i and standard ISO9660 CDs.

CD-W - Rewritable CDs. CD that cam be written and erased many times, unlike CDR (CD read only) disks that can only be written on once and not amended.

CODEC - The words compression and decompression combined.

DAT - Digital Audio Tape.

Data Layer - In CD-R, the organic dye sandwiched between the polycarbonate substrate and the metalized reflective layer of the media. CD-Recordable discs do not have any data on them until they are recorded. Instead the recording laser selectively melts "pits" into the dye layer -- but rather than burning holes in the dye, it simply melts it slightly, causing it to become non-translucent so the reading laser beam is refracted rather than reflected back to the reader's sensors. In pressed CDs, the data layer is part of the polycarbonate substrate, and is pressed into the top side of it by a "stamper" during the injection molding process.

Data Transfer Rate - The speed with which data can be read from a CD ROM drive. 150 kilobytes per second was the original standard rate; 2x = 300 kb/second; 4x = 600kb/s (etc.); 12x = 1.8 mb/s; 16x = 2.4 mb/s.

DDS Format - A format jointly developed by Sony and Hewlett Packard that is supported by all major hardware vendors as a format for data storage.

Digital Audio - The storage and processing of audio signals digitally. It usually requires at least 16 bits of linear coding to represent each digital sample and is normally referred to Red Book or 44.1 KHz audio in the computer industry.

Digital Data - Data in digital form. All data that are entered into the computer are then in digital form.

Digitize - To convert an analog or continuous signal into a series of ones and zeros, i.e., into a digital format. To convert an image or signal into digital code for input into the computer. It includes scanning an image, tracing a picture on a graphics tablet or converting camera images. 3-D objects can be digitized by a device which uses a mechanical arm that is moved on and around the object. Sound, temperature and movement are also said to be digitized when they are converted into digital code.

DVD - A new format jointly developed and agreed upon by Toshiba, Matsushita, Sony, Phillips, Time Warner, Pioneer, JVC, Hitachi, and Mitsubishi Electronics, which is now the universal format for high density compact discs. Strictly speaking, DVD stands for DVD, but it is commonly taken to be an acronym for Digital Versatile Disc or Digital Video Disc. For computer applications, the disc will be called DVD-ROM and for audio, DVD-Audio. The new format has the capacity of holding more information, and has a higher data transfer rate.

Green Book Standard- The CD-I standard is known as the Green Book.

HFS - Hierarchial File System, used by Macinsosh platform. HFS formatted CD-ROM's have the same file structure as an Apple hard disk.

Hybrid Disc - A CD-ROM which can function on either the PC or the Macintosh platform. The disc contains separate ISO 9660 and HFS partitions.

Interactive - A software program in which the user has some control over how he or she interacts with the program.

ISO 9660 - A widely used file format for CD ROM. The ISO 9660 (formerly High Sierra) standard defines a directory structure which has been accepted by the International Standards Organization. This standard, supported by Microsoft in the MS/DOS Extensions, allows ISO 9660 formatted CD ROM discs to be read like a DOS write-protected hard disk.

ISO 9660 with Rockridge Extensions - A revision to the ISO specification to allow for UNIX specific exceptions to the ISO 9660 standard.

Indexing - Creation of a data index to speed up search and retrieval.

Jewel Box - The plastic box in which CDs are often shipped and sold.

Lacquer Spincoat - Acrylic lacquer is spincoated in a thin layer on top of the metal reflective layer of a CD to protect it from abrasion and corrosion. Usually a decorative label is also applied on top of the lacquer, but this is not a standard requirement.

Mastering - Mastering is the process of creating a stamper or set of stampers to be used in the injection molding stage of manufacturing compact discs. During this process a digital signal from a computer is used to guide a laser beam which etches a pattern of "pits and lands" (in the case of CDs) or a continuous groove (for CD-Rs) onto a highly polished glass disc coated with photoresist. This "glass master" is then cured (developed) with ultraviolet light and rinsed off, and a metal (nickel or silver) mold is electroformed on top of it. This mold is removed and then electroplated with a nickle alloy to create one or more stampers to be used in the injection molding machine to press the data into the polycarbonate substrate of CDs, or the guiding groove into the substrate of CD-Rs.

Media Conversion - The process of converting data from one type of media to another for premastering and mastering. Premastering software typically requires input data on hard disk. 8mm tape and compact disc are preffered as input media for the mastering process.

MIDI - Musical Instrument Digital Interface. CD ROM can be used to store music samples which can then be accessed via MIDI and used to compose/record musical programs.

Mixed Mode Disc - A CD-ROM that contains both a computer data track (#1) and audio tracks (#2-99)

Orange Book Standard- The standard for the recordable compact disc. The standard has two parts, one for M-O (rewritable) and one for W-O (write once).

Photo CD - A development from Kodak. Photographs and/or 35mm slides, can be scanned, digitized and recorded on the PHOTO CD and then played back through CD ROM X/A, PHOTO CD Player, CD-I players or Photo CD compatible drives and displayed on a TV set or computer monitor. Each disc can contain 100 photos. The photos can also be printed out on regular photographic print paper by a special Kodak machine for high resolution prints. In order to accommodate the different resolutions available for playback or printing, the format contains the picture in 5 different resolutions. It is also used in professional markets to store or archive photographs.

PQ Information - Information on a disc (or tape) that determines track start points, control bits, timming information, and etc.

Premastering/Mastering Software - The software layer that readies files for recording. This involves converting files structures to adhere to the ISO 9660 conventions, simulating the image on the hard disk as a CD-R, and sending the image to the CR-R drive.

Red Book Standard - See CD Audio. The CD standards for audio were originally published in a book with a red cover.

Reflective Layer - The metal layer on top of the dye that reflects the laser beam back to the reading assembly. This is usually 24K gold in CD-Recordable discs, but Mitsubishi has recently introduced a silver disc as well.

SMPTE Time Code - Society of Motion Picture and Television Engineers Time code. SMPTE is time code recorded on an audio pr cue channel of a tape and is used to label each block or frame of a tape with a unique identifying address. Commonly used when reffering to either DAT or U-Matic tape.

Substrate - The optical-quality, injection molded optical-quality clear polycarbonate plastic "bottom" of a CD or CD-R. For CD-Rs, this layer does not contain "pits and lands" but has a single spiral groove that guides the recorder's laser.

Transfer Rate - The amount of data which is transferred from the CD-ROM to the computer. The CD- ROM transfer rate is limited by the speed at which the disc rotates in the drive. The conventional CD-ROM transfer rate is approximately 150 kilobytes/sec, referred to as 1X. Therefore, a quadruple speed (4X) CD-ROM drive can transfer data at a rate of 600 KB/sec.

WORM - Write Once, Read Many; the current type of recordable CD.

Yellow Book Standard - International standard set by Philips and Sony which defines the physical properties of a CD-ROM disc.

  • JVC's Glossary of Terms
  • The CD Information Center's Compact Disc Terminology
  • The Sanyo Verbatim Glossary

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