Glossary

#pp (where # is a number, as in 4pp)
A printing term denoting the number of printed pages, i.e. 4pp means 4 printed pages

#X (where # is a number, as in 8X)
A speed identifier showing how fast a high speed diskette or optical drive can transfer data, compared to a standard drive. For example, the standard data transfer rate of an audio CD player is 150KB/s and this is considered 1X, therefore a 52X drive can transfer data at 7800KB/s (or 7.6MB/s) - 52 times as fast.

4mm
See DAT

4/1
Said '4 back 1', this is a printing term describing the number of colours printed on each side of a page, e.g. 4/1 is four colours (CMYK) on one side and one colour (black) on the other. Also used are 4/0 and 4/4.

8cm Disc
A compact disc measuring only 8cm across, as opposed to the usual 12cm. It has a capacity of 200MB (approximately 22 minutes of playtime), and is ideal for marketing and promotional use, due to its high novelty value.

AB-CD
A 12 cm disc where the inner 8cm is covered with a reflective aluminium layer, and the outer part of the disc remains clear. The full 12cm surface of the disc can be printed, allowing interesting print designs.

Absolute
A reference to the type of link between two files. An absolute link is where a file is referenced to the root of the drive on which it resides, for example,

C:\testarea\example.pdf

(See also Relative)

Amaray Case
A rectangular plastic clamshell type case designed to hold DVD discs and booklets, protecting and differentiating them from CDs.

Analogue
A device in which data is represented by continuously variable, measurable, physical quantities, such as length, width, voltage, or pressure. (See also Digital)

ASCII
American Standard Code for Information Interchange. It is a code for representing English characters as numbers, with each letter and number assigned a number from 0 to 127. Most computers use ASCII codes to represent characters. (See also EBCDIC)

Authoring System
Software that helps developers design interactive menu systems or presentations easily, without the need for complex computer programming.

Autorun
A feature of the Windows operating system allowing a CD-ROM disc to play automatically when placed in the drive.

Bit
Short for Binary Digit. The smallest unit of information able to hold only one of two values: 0 or 1. A collection of 8 consecutive bits is called a Byte.

Bitmap
Representation of characters or graphics by individual pixels arranged in row (horizontal) and column (vertical) order.

Bit Rate
The rate at which the compressed bitstream is delivered from the storage medium to the input of a decoder.

BLER
Block Error Rate. A quality measurement for CDs which, according to the Red Book, must be not more than 220 block errors per second.

Block
Unit describing the grouping of bytes on Tapes and CDs. Blocks on CD contain 2352 bytes of audio or computer data, and blocks on tape can contain any number of bytes, but typically 512, 1024 or 8192.

Blu-ray
A new optical disc format developed by nine of the original DVD Consortium (Hitachi, LG Electronics, MEI, Pioneer, Philips, Samsung, Sharp, Sony and Thomson Multimedia). The new format retains DVD's physical dimensions but achieves a capacity of up to 25GB per side/layer by employing a 405 nm blue-violet laser.

Blue Book
Specification that defines the Enhanced Music CD (also known as CD-EXTRA) for multisession pressed discs - not recordable - with audio and data sessions. (See also Green Book, Orange Book, Red Book, White Book and Yellow Book)

Bonding
The process of joining two substrates to make a DVD disc. The bonding process can be hot melt (for DVD-5 and DVD-10) or UV bonding (for DVD-9 where the bonding layer needs to be optically transparent). UV bonding is the more normal technology used for DVD discs.

Burning
Alternative term for Duplication, used to describe the low volume copying of CD and DVD recordables. (See also Replication)

Byte
One byte is composed of 8 Bits, which is enough to hold a text character. Large amounts of memory are indicated in terms of kilobytes (1024 bytes), megabytes (1048576 bytes) and gigabytes (1,073,741,824 bytes).

Catalogue number
When pressing your CDs, a unique identity code (which you may choose) must be present on all components (CD label and associated printed parts) to ensure proper handling of your order.

CAV
Constant Angular Velocity. A method for accessing data on optical discs. The disc rotates at a constant speed no matter where on the disc surface the data is located. This is a simpler and cheaper method to implement than CLV, because the drive motor speed does not have to change. (See also PCAV, CLV and ZCLV)

CD
Abbreviation for Compact Disc.

CD-DA
Compact Disc Digital Audio, defined in the Red Book.

CD-EXTRA
Alternative name for Enhanced Music CDs. A multisession compact disc that contains both audio and data tracks. The audio tracks can be accessed by CD players, and data tracks (typically containing multimedia content) can be accessed by a CD-ROM player in a computer. The CD-EXTRA specification is defined in the Blue Book.

CD-i
Compact Disc interactive (CD-i), a proprietary CD-ROM format developed by Philips that allows interactive multimedia applications to be run on a special player attached to a TV. The CD-i specification is defined in the Green Book.

CD-i Bridge
A CD-ROM XA disc with a CD-i application program able to be played on CD-i players.

CD-R
Compact Disc Recordable. CD-Rs allow data to be written either once only or in sessions for a multisession disc. This allows the data to be updated and/or added to until the disc is full. The data on a CD-R disc cannot be erased or re-written, hence their alternative name WORM (Write Once Read Many) disc. The CD-R specification is defined in the Orange Book.

CD-ROM
Compact Disc Read Only Memory. A compact disc used for storing computer data and for multimedia and games applications. The CD-ROM specification is defined in the Yellow Book.

CD-ROM XA (CD-XA)
Compact Disc Read Only Memory Extended Architecture, an extended version of the CD-ROM disc. CD-I, Video CD, Photo CD and CD EXTRA discs are based on the CD-ROM XA specification. The CD-ROM XA specification is contained in an extension to the Yellow Book.

CD-RW
CD-ReWritable disc. Using phase-change technology, they can be written to, erased and re-written a large number of times.

CD-TEXT
An superset of the CD-DA audio CD format that allows up to 5,000 characters of text information such as the artist, album name, and song names to be stored along with the song files. A CD player that recognises this information can read and display it for you.

CD-XA
See CD-ROM XA.

CLV
Constant Linear Velocity. A system used on older CD drives which alters the rotational speed of the disc depending upon where the data is located. The aim is to maintain a constant data transfer rate, and since less data can fit on the inside tracks of the disc than the outside, it has to rotate faster closer to the disc centre.
(See also CAV, PCAV and ZCLV)

CMYK
(C)yan-(M)agenta-(Y)ellow-(K)ey (which is black). A colour model for colour printing. Artwork submitted ready for printing on discs or paper parts must use the CMYK colour model (NOT RGB!), otherwise unknown results will occur. (See also RGB)

Codec
Coder/decoder. A device or software that encodes and decodes digital information, eg. video codecs allow different video formats to be played, manipulated and compressed.

Colour Disc/DVD
A standard CD or DVD, except the polycarbonate base of the disc is coloured, not clear, giving a very special appearance. They are available in a variety of different colours.

Compression
The conversion of data to a more compact form for storage or transmission. Compression can be lossy (used where there is redundant information in the original data) or lossless (where the original data can be recovered in its entirety).

Copy Protection
A technique used on CD and DVD discs to prevent the contents being copied and/or re-used. Technologies used include watermarking, signatures on disc and encryption.

CRC
Cyclic Redundancy Check used to check whether a data stream has suffered any corruption producing errors.

DAO
See Disc At Once

DAT
Digital Audio Tape. A 4mm wide tape used to record audio in digital form, usually by professional recording studios. Can be used to master compact discs from. A data version (DDS) is also available.

DDS
Digital Data Storage. A version of DAT used for storing computer data. Four types (DDS1, DDS2, DDS3 and DDS4) currently exist.

Decompression
To convert a compressed file or signal back into its original form before it was compressed.

Digital
A description of data which is stored or transmitted as a sequence of discrete symbols from a finite set, most commonly this means binary data represented using electronic or electromagnetic signals. (See also Analogue)

Disc
With a 'c' refers to CD, DVD, MiniDiscs and Laserdiscs.

Disc At Once (DAO)
Refers to the ability of certain CD-Recorders to record a CD-R or CD-RW disc in one continuous operation. This is the ideal mode in which to write CD masters being prepared for duplication/replication. (See also Track at Once).

Disk
With a 'k' refers to magnetic and magneto-optical disks (except MiniDisc).

DL
Dual Layer. This refers to a DVD recordable disc with 2 recording layers, one on top of the other - essentially a recordable version of the DVD-9 pressed disc.

DLT
Digital Linear Tape. The tape format used to transfer pre-mastered DVD data for glass mastering. Also used as high capacity storage for server and network backups.

Dual Disc
See DVDPlus

Duplication
A general industry term used to describe the low volume burning of CD and DVD recordable discs. (See also Replication)

DVD
Digital Video Disc or Digital Versatile Disc depending upon who you listen to! It's a high capacity 'compact disc' that contains 7 times as much data as a standard CD on each of up to 4 layers.

DVD-5
A single-sided, single layer pre-recorded DVD disc format, with a capacity of 4.7 GB.

DVD-9
A single-sided, dual layer pre-recorded DVD disc format, with a capacity of 8.5 GB.

DVD-10
A double-sided pre-recorded DVD disc format, with a capacity of 9.4 GB.

DVD-18
A double-sided, dual layer pre-recorded DVD disc format, with a capacity of 17.1 GB. Very rare due to the difficult manufacturing processes involved.

DVD-Audio
A pre-recorded DVD format intended to carry high quality audio data plus optional images, text, video and menus. The format was defined in 1999 and players and discs appeared from late 2000.

DVD Authoring
The process of taking data assets such as video, audio, text, data and combining them into a DVD-Video or DVD-ROM compliant disc image. The inputs to this process might consist of compressed video files in MPEG2, compressed audio files in AC-3 and subtitles as bitmap images; the output or end result of the authoring process would typically be a DLT tape ready for DVD production.

DVD Books
The specifications for all DVD disc formats. The Books define the standards for DVD-Video, DVD-Audio, DVD-ROM, DVD-R, DVD-RW etc.

DVD-ROM
A pre-recorded DVD disc, which includes the DVD-Audio and DVD-Video formats. Also used to describe other DVD formats not defined in the DVD specifications including PC/Mac applications and DVD based games consoles etc.

DVD-R
A recordable write-once DVD format, with a capacity of 4.7GB per side.

DVD-R DL
See DL

DVD-RW
A rewritable DVD with a capacity of 4.7 GB per side.

DVD+R
A recordable write-once format, developed to combat incompatibility issues between DVD-R/RW discs and home DVD video players. Not recognised by the DVDForum.

DVD+RW
A rewritable 12 cm optical disc with a capacity of 4.7GB per side. It is claimed to offer almost total compatibility with existing players, but is not an official DVD format.

DVD+R DL
See DL

DVD-Video
A pre-recorded DVD format capable of carrying 133 minutes of high quality video (on a DVD-5) with multi-channel audio in up to 3 languages plus subtitles and menus to provide user interactivity. Other features include multiple camera angles, parental lock and random access.

DVDPlus
A double sided disc comprising a DVD substrate (with DVD-Video or DVD-Audio data) bonded to a CD substrate (containing CD audio). The CD substrate is usually about 0.9 mm thick so that the overall thickness is about 1.5 mm or less. An alternative name used by the major music companies is Dual Disc.

Dye
As a colour layer, the dye allows the recording of information onto a CD-R. During the process of recording the laser alters the organic features of the dye and creates the information structure. The resulting playback quality is similar to one of a pre-recorded CD or CD-ROM.

EBCDIC
Extended Binary-Coded Decimal Interchange Code. It is an IBM code for representing characters as numbers. Although it is widely used on large IBM computers, most other computers, including PCs and Macs, use ASCII codes. (See also ASCII)

Electroforming
A process for depositing nickel ions on a metal surface used to make stampers for CD and DVD manufacture.

Encryption
Data to be transmitted or stored is transformed to ensure that only the intended recipients can make use of the information.

Enhanced Music CD
See CD-EXTRA

Exabyte
A digital tape format based on 8mm videotape and used for transferring CD-ROM files for mastering and for backup purposes.

Father
A nickel disc that has been electroformed from the glass master. Fathers are used in the process of making stampers for manufacturing CDs and DVDs.

File Structure (or File System)
Additional data added to a CD-ROM or DVD disc that defines the directory and file structure on the disc plus other information about the contents of the disc. A file system is necessary for all data storage media to allow data files to be accessed. File systems in use include ISO 9660, HFS and UDF.

FPS
Frames Per Second. Film is 24 FPS, NTSC is 29.97 FPS and PAL/SECAM is 25 FPS.

Frame
A single, complete picture in video or film recording.

Frame rate
The number of frames displayed per second for film and video, ie FPS.

Fulfilment
Printing, packaging, warehousing and distribution services that complement media manufacturing.

Glass Mastering
Part of the CD and DVD disc manufacturing process that uses a laser (which is modulated by the data to be stored on the disc) to expose areas of a photo-resist layer on a glass disc, where the final pits are required. These areas are then developed and the photo resist layer metallised so that stampers can be grown by electroforming using this metal layer. The stampers are then used for moulding CD and DVD discs.

Green Book
Specification defining the CD-interactive (CD-i) standard. (See also Blue Book, Orange Book, Red Book, White Book and Yellow Book)

gsm
Grams per Square Metre. The standard system in Europe describing the weight of paper - how heavy 1 square metre of paper is in grams. The higher the number the 'thicker' the paper, e.g. company stationery may be printed on 90gsm paper, whereas CD wallets may be printed on 300gsm card.

HDCD
High Definition Compatible Digital. Is a patented process for delivering on CD the full richness and detail of the original microphone feed. When listening to HDCD recordings, you get the body, depth, and emotion of the original performance. HDCD-encoded CDs sound better because they are encoded with 20 bits of real musical information as compared with 16 bits for all other CDs. HDCD overcomes the limitation of the 16-bit CD format by using a sophisticated system to encode the additional 4 bits onto the CD while remaining completely compatible with the CD format

HDTV
High Definition Television. A digital television format, which combines high-resolution video and theater like sound to create a movie theater quality TV viewing experience.

HFS
Hierarchical Filing System. A file structure which is needed on Apple Mac CD-ROMs instead of (or in addition to - Hybrid) ISO 9660.

High Sierra Format
As the CD industry evolved it became obvious that a standard file system was necessary. A meeting was held at the High Sierra Hotel and Casino, in Lake Tahoe, Nevada in 1985 with representatives of various companies and a working paper was drafted which became known as the High Sierra Format. After a little revising, this format evolved into ISO 9660.

Hybrid
The use of two file structures on a single CD-ROM - usually ISO 9660 (PC) and HFS (Mac). The disc often has 'three areas', Mac only, PC only, and an area containing common data, accessible by both file systems - possibly movies, audio or high resolution images.

Image Resolution
The fineness or coarseness of an image measured in pixels per line, for display, or Dots Per Inch (DPI), for print applications.

Injection Moulding
In CD and DVD production, this is a process where polycarbonate is 'injected' into a mould under pressure. The plastic fills the cavity and, after cooling, the resulting disc (the base for a CD or DVD) is ready for the next stage of manufacture.

ISO 9660
A strict ISO standard for the CD-ROM file system, particularly for PC applications. Due to its limitations (i.e. no support for long filenames and not allowing deeply nested directories), extensions such as Joliet (PC Windows) and Rockridge (Unix) have been developed which allow features of their respective operating systems to be used on CD.

Jewel Case
A plastic case commonly used for CDs, containing the CD plus a booklet and inlay.

Jitter
On a CD or DVD disc, it defines the percentage change in pit length compared with its nominal value. If jitter is too high, pits can be incorrectly read leading to data errors.

Joliet
Microsoft's extension to the ISO 9660 file system, enabling the handling of long filenames and other features which were new to Windows 95.

Key2audio
A CD audio copy protection system developed by Sony DADC.

Lacquering
After metallising, all pressed CDs are protected with a lacquer by spin coating; and all our inkjet printed CDs are machine sprayed with a UV curable lacquer for extra protection before shipping.

LASER
Light Amplification by Stimulated Emission of Radiation. A device which produces an intense, coherent, directional beam of light which can be focused to a very small spot size - ideal for reading and writing compact discs.

Layer 0
The lower, semi-reflective layer of a dual layer (DVD-9) disc.

Layer 1
The upper, fully reflective layer of a dual layer (DVD-9) disc.

LBR
Laser Beam Recorder. Used in glass mastering CD and DVD discs. A glass master disc, covered with a thin photo-resist coating is exposed by the laser in a laser beam recorder where pits will be formed in the final discs. The photo-resist is then developed and metallised with Nickel. Stampers used in the moulding of CDs and DVDs are then electroformed from the metallised glass master, which can then be recycled and re-used.

Lead-in
The starting area of a CD or DVD or of each session of a multisession CD. For a CD it contains the Table of Contents (TOC). For a DVD it contains information describing the contents of the disc and the type of disc.

Lead-out
The last area of a CD or session of a multisession disc or a DVD, immediately after the program area.

Locales
The name for regions of the world defined in the DVD-Video specification. Six regions are defined including 1: N America; 2: Europe and Japan...

Malware
Is short for (mal)icious soft(ware) and is used to describe software, such as viruses and trojan horses, which are designed to disrupt a users computer system.

Mastering
A general term used to describe the process of getting the customer data into a state ready for high/low volume copying - creating a Glass Master for replication, or creating a CD-R for duplication.

Magneto-Optical (MO) discs
A rewritable optical disc, which uses a laser together with a magnetic field to change the magnetic properties of the disc on a bit by bit basis. A laser is used to read the bits.

Mini CD
See 8cm Disc.

Mixed mode disc
A CD that comprises tracks of two or more different types, eg. one or more data tracks followed by one or more audio tracks. CD-EXTRA would be an example.

MO
See Magneto-Optical (MO) discs.

Mode 1
CD-ROM sectors containing 2048 bytes of data per sector plus error correction.

Mode 2
CD-ROM XA sectors, which can be either Form 1 (2048 bytes + error correction) or Form 2 (2324 bytes, no error correction).

Mother
A nickel 'disc' that has been electroformed from a nickel Father as part of the CD or DVD glass mastering process.

MPEG
ISO/CCITT Moving Pictures Expert Group JTC1/SC29/WG11. This group has defined MPEG-1, MPEG-2 and MPEG-4 video compression standards.

MPEG-1
ISO Moving Pictures Expert Group standard 11172, designed for CD-ROM applications.

MPEG-2
ISO Moving Pictures Expert Group standard ISO/IEC 13818, designed for broadcast TV applications and also used for DVD-Video.

MPEG-4
ISO Moving Pictures Expert Group standard originally intended for low bandwidth applications, but now offering SD and HD video, 2D and 3D graphics and animation, interactivity and scripting. It is one of the video codecs provisionally chosen for HD DVD.

Multisession
A CD with more than one session, where each session comprises of a Lead-in, Program area and Lead-out.

Multimedia
Refers to the delivery of information that combines different content formats including video, audio, photos, graphics, animation, text, etc.

NTSC
National Television Systems Committee of the Electronic Industries Association (EIA) that prepared the standard of specifications for the U.S., Canada, Japan, Central America, half of the Caribbean & half of South America.

Offset Printing
Print technology where an inked image is transferred from a metal plate onto a rubber blanket, mounted on a cylinder. The rubber blanket then transfers (or offsets) the image onto the disc as it passes through the press. Print resolutions of up to 200 lpi are possible.

Orange Book
Specification defining CD-Recordable discs. (See also Blue Book, Green Book, Red Book, White Book and Yellow Book)

Packet Writing
A method of writing data to a CD-R in smaller chunks than a session. Only useful if storing information for personal use, not for duplication or distribution because of its limitations.

PAL
Phase Alternation Line. Video format used in most of Western Europe, Australia and other countries.

Pantone Colours
Pantone, a company trademark, utilises a system to mix ink colour to create a library of new, standardised colours. Often used to ensure consistency of colours across different print mediums/substrates such as CD, paper and card.

PCA
Power Calibration Area. An area located at the beginning of a CD-R which is used for calibrating the laser power needed for writing.

PCAV
Partial Constant Angular Velocity. A method for reading data from a rotating CD or DVD disc. PCAV drives switch between CAV (Constant Angular Velocity) and CLV (Constant Linear Velocity) methods depending upon where the data is located.
(See also CAV, CLV and ZCLV)

PCM
Pulse Code Modulation. A method of transforming an analogue audio signal into a digital bit stream.

Phase-Change
The technology used for CD-RW, DVD-RAM and DVD-RW discs, whereby the phase-change material can be in either of two phases: amorphous and crystalline. One phase represents a 0 at that point, the other a 1. A laser is used to change the phase of the active material where required.

Photo Resist
A light-sensitive coating (eg on a glass master). After exposing to light (eg using a laser) it can be developed so that the exposed areas are removed.

Picture Disc (pressed disc)
A CD or DVD which has been printed using 5 colours, a white base colour plus four colour separations: Cyan, Magenta, Yellow and Black (CMYK). A sixth 'spot' colour can be added for special effects.

Picture Disc (CD-R)
A CD recordable with no stacking ring area on top of the disc allowing an unbroken label to be printed from the outer edge to the inner hole of the disc.

PID
Postscribed ID. This is information which is added to the disc after it has been pressed, using a special laser. It can consist of serial numbers, registration codes or any other information (up to 240 Bytes). The PID is readable by CD drives and can be used in a variety of ways - disc authentication for example.

Pit Art
A method for adding labels to DVD discs by creating a hologram-like image in the blank substrate of a DVD-5 in place of pits that would be present on a DVD-9 or DVD-10 disc.

Pits
The hollows in a compact disc or DVD surface defining the data they contain. Pits measure less than 0.5 microns in width and are created by injection moulding using a nickel stamper.

Polycarbonate
A thermo-plastic material that is used to mould CD and DVD discs. It can be injection moulded and has the necessary mechanical and optical properties.

Pre-mastering
Process to convert the data representing audio or a CD-ROM application into the data to be stored on the CD. For PC CD-ROMs it will involve adding the ISO 9660 file structure data. Also refers to creating a disc image for a DVD-Video, DVD-Audio or DVD-ROM title, where the file system is Micro UDF.

Pressing
Alternative term for Replication, describing the high volume manufacture of CDs and DVDs. (See also Duplication)

Red Book
Specification defining the audio CD format and coding. (See also Blue Book, Green Book, Orange Book, White Book and Yellow Book)

Region Coding
In the DVD-Video specification, the world is divided into 6 regions or locales so discs can be made to play in only one or a limited number of regions.

Relative
A reference to the type of link between two files. A relative link is the location in the directory structure where the file to link to resides, in relation to the current file. For example,

..\testarea\example.pdf

would be a relative link. (See also Absolute)

Replication
A general industry term used to describe the high volume pressing of CDs and DVDs. (See also Duplication)

Resolution
The size of an image in number of lines, pixels per line or dots per inch.

RGB
(R)ed-(G)reen-(B)lue, the three primary colours used in the colour model to output video signals to a computer monitor. Print ready artwork should NOT contain any RGB images, otherwise unknown results will occur. (See also CMYK)

RID
Recorder ID, which is a 97-bit code recorded in the Q-channel of all CD-R and CD-RW discs when written to by CD-recorders. It comprises a brand name identifier, a type number and the drive serial number. The RID helps to prevent unauthorized copying by enabling the source of any recording to be identified.

Rockridge
Extensions to ISO 9660 for the Unix file system, allowing features such as long filenames and linked files.

Rootkit
A rootkit is a type of malicious software that is activated each time your system boots up. Rootkits are difficult to detect because they are activated before your computer's Operating System has completely booted up. Rootkits can allow such things as the installation of hidden files, processes, and hidden user accounts.

Run-In/Run-Out Blocks
These are written to a CD-R when recording in Track At Once mode. Two run-out blocks are written at the end of each track and five run-in blocks are written at the start of the next track.

SACD
See Super Audio CD

SAO
Session at once, where a complete session (Lead-in, Program and Lead-out areas) of a CD-R or CD-RW disc is written in one uninterrupted sequence.

Screen Printing
A process used for printing multi-colour labels on CD and DVD discs.

SCSI
Small Computer Systems Interface. Pronounced 'scuzzy', it is a common electronic drive interface (for tape/optical/hard disk) allowing multiple drive types to co-exist and communicate in the same computer system.

SDS
Simultaneous Double Sided. In reference to high speed floppy disk drives where both sides of the disk are written at the same time, unlike a standard drive which writes alternatively to side 0 and then side 1.

SECAM
"SEquential Couleur A Memoire" (sequential colour with memory). Video format used in France, Eastern Europe and other countries.

Sectors
Units of data on a CD-ROM of DVD-ROM disc containing 2048 bytes of data plus header information.

SecuROM
A CD-ROM copy protection technology developed by Sony for protecting games and other CD-ROM applications.

Session
An area of a multisession CD consisting of a Lead-In, Program area and a Lead-Out. On a CD-R, sessions can be written one at a time, and up to 99 sessions may be written to a single disc.

SHG Laser
Second Harmonic Generation laser, for creating a laser output with half the wavelength of the laser generating the light. This allows, for example, a red laser to be used to generate violet light. SHG is used for deep UV laser beam recorders that are needed for future formats such as Blu-ray.

SID Code
A unique set of codes on Compact Discs to identify where it was manufactured. The Mastering Code identifies the laser beam recorder used to master the title and the Mould Code identifies which moulding machine was used. SID Codes were introduced by the IFPI in conjunction with Philips Electronics.

SniffleDisc
Using the latest technology, SniffleDiscs have scents captured within the printed labels. The emotions and memories the customer associates with these smells make the discs stand out from the crowd and helps in selling them.

SniffleDVD
Like the SniffleDisc, the SniffleDVD has a scent captured within the printed label. As unique marketing tools the scents are associated with the products and should keep them fresh in mind.

Sputtering
A process for coating moulded CDs with aluminium whereby an aluminium target is bombarded with particles causing the aluminium to be deposited in a thin film on the CD surface. Sputtering is also used to deposit Gold or Silicon on the semi-reflective layer of dual layer DVD-9 discs.

Stamper
A nickel disc created by electroforming from the mother and used to mould CDs and DVDs.

Super Audio CD (SACD)
An alternative to the DVD-Audio format developed by Philips and Sony. It is designed to play on audio CD players and Super Audio CD players by comprising two layers: one with CD-Audio the other with high quality audio.

Super Video CD (SVCD)
An enhanced Video CD format which offers video quality and features closer to DVD-Video, although a full-length movie will require three discs.

SVCD
See Super Video CD

Table of Contents (TOC)
Table of Contents of a CD, listing the start time code of every track on the disc and contained in the subcode (Q-channel) in the Lead In area.

TAO
See Track at Once

Tilt
A measure of warping or dishing of an optical disc. Tilt is of particular importance for DVD discs and must be kept within strict limits.

TOC
See Table of Contents

Track At Once (TAO)
Refers to the way in which data can be written to CD-R or CD-RW discs, where a track is written in one action, but then waits before the next track is written. Each time the laser is stopped, it writes Run-Out blocks. When re-starting, it writes Run-In blocks (a total of 7 blocks), which can cause a glitch when playing audio CDs recorded in this way. (See also Disc at Once)

Trojan Horse
A destructive program that masquerades as a benign application.

UDF
Universal Disk Format, the file system used for DVD and CD-RW disks.

UV
Ultra violet light, used for curing the protective lacquer on CDs, the bonding resin for DVDs and the inks used for offset and screen printed labels on CD and DVD discs.

Varnish
Print surface finish for either label print or paper parts, e.g. gloss or matt.

Video CD
Up to 74 minutes of VHS quality MPEG-1 video on one CD. The Video CD standard is defined in the White Book.

Virus
A program or piece of code that is loaded onto your computer without your knowledge and runs without your consent. They are able to replicate and transmit themselves to other computers often damaging them in some way.

VOB
Video Object. A file on a DVD-Video disc containing MPEG video, audio and navigation data.

White Base (Full Base)
A white undercoat on the disc face to reduce the colour difference of the print on both aluminium and non-aluminium surfaces of the disc (outer and inner ring).

White Book
Specification defining the Video CD standard. (See also Blue Book, Green Book, Orange Book, Red Book, Yellow Book)

WORM
Write Once Read Many. CD-Recordable discs are sometimes referred to as WORM discs.

Yellow Book
Specification defining the physical format for data CDs (CD-ROM and CD-ROM XA). (See also Blue Book, Green Book, Orange Book, Red Book and White Book)

ZCLV
Zoned Constant Linear Velocity. A type of CLV which splits the disc surface into different speed zones and adjusts the rotational speed for each zone rather than across the whole disc. (See also CAV, CLV and PCAV)