4C Entity - The group of companies (IBM, Intel, MEI and Toshiba) that developed copy protection for DVD etc. (www.4centity.com)

AACS / Advanced Access Content System - A copy protection technology which offers flexible digital rights management suitable for HD DVD and Blu-ray discs. It was proposed in July 2004 by IBM, Intel, MEI, Toshiba, Disney, Sony and Time Warner.

ACMS / Advanced Content Management System - A 128-bit technology with revocable keys developed by the US National Institute of Standards and Technology (NIST) and likely to be used for copy protecting HD DVD and Blu-ray discs.

ACP - Macrovision’s Analogue Copy Protection system for DVD-Video developed and patented by Macrovision. It comprises two elements - Automatic Gain Control (AGC) and Colorstripe. ACP is supported by most DVD players, and causes VCRs to make distorted copies, with no entertainment value.

AES - Advanced Encryption Standard, a symmetric 128-bit data encryption technique, which was adopted by the US government in October 2000 to replace the DES encryption.

Alpha-Audio - A CD audio copy protection technology developed by the Korean company Settec. (www.settec.net).

Amaray Case - A plastic clamshell type case designed for DVD discs to differentiate them from CDs and to protect them. This has become the standard DVD style packaging type.

AOD - Advanced Optical Disc, a new format proposed by Toshiba and NEC as the next generation DVD. AOD discs would use a blue laser to read them and can hold 15 GB of data per side on a pre-recorded disc, but 20 GB on a re-writable version. The DVD Forum is studying AOD and has renamed it HD DVD.

Artwork Specifications - The exact dimensions which artwork must be prepared to in order to conform to the size of the object being printed. These will be supplied as necessary or available from our Print specifications section of the website.

Autoplay - A feature that for example allows a CD-ROM disc to play automatically when inserted.

BD - An abbreviation for Blu-ray Disc.

BD-RE - The re-writable Blu-ray discs with capacities of up to 27 GB (single layer) or 54 GB (dual layer). BD-RE media became available in 2003.

BD-R - The recordable Blu-ray discs with capacities of up to 27 GB (single layer) or 54 GB (dual layer). The BD-R specification version 0.5 is due to be released by about September 2004.

BD-ROM - The pre-recorded Blu-ray discs with a capacity of 25 GB (single layer) or 50 GB (dual layer). The BD-ROM specification version 0.5 is due to be released in May 2004.

BD-Video - Blu-ray Disc Video format for HD video and enhanced interaction.

Bit - A binary digit with values 0 or 1 used in binary computers.

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 measure of the integrity of the data retrieved from a CD. Most manufacturers set high standards working to an average BLER of under 40.

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 27GB per side/layer by employing a 405 nm blue-violet laser. (www.blu-raydisc-official.org).

Buffer Underrun – An interruption of the data transfer stream from a Hard Drive to a recording drive that can cause a burnt process to fail.

Byte - 8 Bits, normally used to represent a text character or an image pixel. Early microprocessors processed only a byte of data at a time. Current microprocessors (used in personal computers and game consoles) process 64 bits (8 bytes) or more at a time.

Caddy - Required to hold a CD or CD-R before it is loaded into some early CD-ROM drives or CD recorders. Caddies are also used for DVD-RAM discs and the first generation of Blu-ray re-writable discs (BD-RE).

CBR - Constant Bit Rate for MPEG-2 video encoding.

CCA - DVD Copy Control Association which administers the CSS copy protection for DVD-Video and distributes keys to licensees. (www.dvdcca.org).

CCCD - Copy-Control CD, used to identify copy protected CDs in Japan. A logo on the outer packaging of such CDs is used to identify them.

CCI - Copy Control Information, for example used by CPPM on a DVD-Audio disc and containing a number of parameters defining what if any copies can be made. These include Copy Permission, Sound Quality, Related Content and Transaction. The parameters define how many generations of copy at the specified quality and with the access constraints held elsewhere and pointed to by the Transaction Parameter.

CD - Abbreviation for Compact disc. Generally any CD type disc, whether recordable or not, to differentiate it from a DVD, Hard Disk, Floppy Disk etc.

CD Business Card – Also referred to as ROM cards, IT cards, datacards and CD cards. For more information see our CD Business Card section of the website.

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

CD-EXTRA - Alternative name for Enhanced Music CDs, which are multisession CDs comprising a CD Audio session (with up to 98 tracks) followed by a single-track CD-ROM XA session, which contains the data. CD-EXTRA discs are compatible with all CD audio players (as the data session is not seen) and the data track can be played in a Windows 95 or 98 PC and/or a Macintosh depending on how the software was written.

CD-G / CD-Graphics - CD Graphics using the subcode channels R to W on an audio CD.

CD-i - Compact Disc interactive (CD-i), a multimedia standard introduced by Philips in 1987. The standard covers both disc and player. Approximately 1m CD-i players have been sold worldwide, but now only used for some education and training applications.

CD-i Bridge - A bridge standard allowing CD-ROM XA discs to play on CD-i players.

CD-i Ready - CDs that can be played on audio players (audio only) and CD-i players (CD-i data & audio).

CD-PROM - A recordable CD format developed by Kodak and combining recordable and read-only formats on a single disk. One application is for Picture CD, where the read-only section is used for software needed to display the photos, to avoid the need to write it to every CD-R containing photos.

CD-R / CD-Recordables - Recordable CD used where small quantities are required. 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.

CD-ROM - Compact Disc Read Only Memory, a compact disc that has been replicated (pressed) and used for storing computer data as opposed to audio, video, etc.

CD-ROM XA / CD-XA - Compact Disc Read Only Memory Extended Architecture, a version of CD-ROM disc where data is stored in sectors of 2048 bytes (with error correction) or 2324 bytes (without error correction). Sectors also include a subheader, which contains information to describe the contents of the sector. 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-RTOS - Compact Disc - Real Time Operating System for CD-i Players.

CD-RW - CD-ReWritable disc, which can be written to and re-written a large number of times.

CD TEXT - A recent addition to the CD audio specification allowing disc and track related information to be added to standard audio CDs for playback on suitably equipped CD audio players. The CD TEXT information, coded as characters for maximum efficiency, is contained in the R to W subcode channels in the lead-in and/or program area of a CD. CD TEXT is compatible with the ITTS (Interactive Text Transmission System) standard. CD TEXT equipped players can provide a range of display formats from one or two line, 20 character display to 21 lines of 40 colour alphanumeric or graphics characters. The specification also allows for the future addition of additional data such as JPEG coded images.

CD-Video / CD-V / Compact Disc-Video - CD audio with analogue video. This format was launched on the market in 1988 but has not been successful. CD-V discs should not be confused with Video CDs, which contain up to 74 minutes of digital video on a compact disc.

CDS - Cactus Data Shield - A CD audio copy protection technology originally developed by the Israeli company Midbar Tech, which was acquired by Macrovision in December 2002 and further developed since then. Three versions are available, CDS-100, CDS-200 and CDS-300, the last two including a second CD-ROM session containing compressed audio files, which play on a PC. CDS-300 also includes DRM features allowing limited copying of the audio tracks on a protected CD.

CEMA - Consumer Electronics Manufacturers Association, which is part of the Consumer Electronics Association (CEA). (www.ce.org).

CGMS - Copy Generation Management System, a method for controlling copying of DVD-Video discs. It allows only a first-generation copy to be made. The player embeds information such as "Copy free," "First generation only OK" or "Copy not possible" in the playback signal and outputs it together with the latter, and the recorder detects it.

Chapter - Subdivisions of a video title (e.g movie) on a DVD-Video disc, each chapter being a scene or other section as defined during authoring.

CMF - Cutting Master Format, which is a protocol, similar to DDP, that describes data that will be recorded onto an optical disc and allows the use of DVD-R for Authoring media instead of the more usual DLT. A single DVD-R disc can therefore serve as both a check disc for testing and for input to glass mastering. The CMF is written to the lead-in area. Titles that require CSS encryption, CGMS or region coding cannot currently be used with CMF.

CMYK - Cyan-Magenta-Yellow-Black. The standard four colour process used for printing. CMYK is an alternative expression for 4-Colour Process printing. When specified colours are required you must use spot colours instead (see PMS).

Codec - Coder/decoder, device or software that encodes and decodes digital information.

Colorstripe - Part of Macrovision’s Analogue Copy Protection (ACP) for DVD-Video, which makes recordings on VHS very distorted and unviewable.

Colour Palette - A table of colour values used to reduce the data per pixel for encoding graphics images. For example a palette of 256 colours can be programmed to any set of 256 colours from, say, a total of 16 million and therefore each pixel is represented by only 8 bits.

Component Video - A method for coding video signals as three separate components, normally YUV or RGB.

Composite Video - A video format that combines chrominance (colour), luminance (brightness) and blanking in one signal, rather than the component parts.

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.

Cover Layer - The transparent layer of an optical disc through which data encoded as pits or marks are read. For a CD the cover layer is the 1.2 mm thick polycarbonate substrate; for DVD and HD DVD discs it is a 0.6 mm substrate but for Blu-ray discs it is a much thinner 0.1 mm layer, which is either a thin film or spin coated lacquer.

CPPM - Content Copy Protection for Pre-recorded Media, developed by the 4C entity comprising IBM, Intel, Matsushita and Toshiba. CPPM is the digital copy protection system used for DVD-Audio discs and provides more protection than CSS does for DVD-Video. For example it allows a hacked playback device to be revoked through the use of a Media Key Block (MKB) containing a different key for every model of playback device instead of a single key.

CPRM - Content Copy Protection for Recordable Media, developed by the 4C consortium comprising IBM, Intel, Matsushita and Toshiba. CPRM was developed for recordable DVD discs and ensures that DVD discs cannot be copied unless it is permitted by the content owner. In particular a first generation copy cannot be further copied. It uses some of the methods used for CPPM, but each individual disc is uniquely identified.

CPSA - Content Protection System Architecture, which includes copy protection for DVD discs and Blu-ray in cooperation with the Copy Protection Technical Working Group (CPTWG).

CPTWG - The Copy Protection Technical Working Group, a voluntary working group formed in 1995 to study and evaluate content protection technologies for digital content in the home. Technologies studied include CSS, DTCP and HDCP. (www.cptwg.org).

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

CSS - Content Scrambling System, used for digital copy protection of DVD-Video discs. CSS involves scrambling the video and audio data using keys, which are stored in encrypted form on the disc. CSS scrambling is normally carried out during glass mastering.

DAO / Disc At Once - Disc At Once recording. Refers to the ability of certain CD-Recorders to record a CD-R or CD-RW disc in one continuous operation. This is necessary to avoid glitches when playing recordable audio discs.

DAT - Digital Audio Tape, used to record audio in digital form at sampling rates from 32kb/s to 48kb/s. Can be used to master compact discs from. A data version (DDS) is also available.

DataPlay - A new optical disc format comprising a 32 mm diameter disc in a caddy that can hold 250 MB of data per side. Music players and media have been available since 2002. (www.dataplay.com)

Data Fork - The part of a Macintosh HFS file containing the actual data.

DDCD - Double Density CD, a new version of the CD specification offering nearly twice the capacity of a standard CD by reducing the pit length and track pitch and making the modulation and error correction more efficient.

DDP - Disc Description Protocol, a standard for files accompanying CD and DVD data for glass mastering, which identifies and describes collections of data that will be recorded onto a compact disc (CD) or digital versatile disc (DVD). DDP allows for automated transfer of data from data publishers to disc manufacturers. DDP is the de facto standard in the DVD industry for delivering disc image data to the replication plant for manufacturing. (www.dcainc.com).

DirectShow - Part of Microsoft's 32-bit API (DirectX) with provision for playing DVD-Video VOB files, ie containing MPEG-2 video, audio and navigation. DirectShow was called ActiveMovie and replaces MCI.

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 necessary to avoid glitches when playing recordable audio discs.

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

DL - Dual Layer, referring to DVD discs with a two layers per side as opposed to a single layer (SL).

DLT - Digital Linear Tape, the tape format used to transfer pre-mastered DVD data for glass mastering.

Dolby Digital - Formerly called Dolby AC-3, is the 5.1 channel surround sound audio compression format developed by Dolby and used on DVD-Video discs. (www.dolby.com/digital).

DTCP - Digital Transmission Copy Protection, a technology designed to protect content transferred from one device to another on a home network and developed by Intel, Hitachi, MEI, Sony and Toshiba.

DualDisc - A double sided disc comprising a DVD substrate (with 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 is DVDPlus.

DVD - A 'compact disc' that contains 7 times as much data as a CD on each of up to 4 layers. Originally Digital Video Disc then Digital Versatile Disc but officially is just DVD.

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

DVD-14 - A double-sided pre-recorded DVD disc format, with one dual layer side and one single layer side offering a capacity of 13.2 GB, yet to become available commercially.

DVD-18 - A double-sided, dual layer pre-recorded DVD disc format, with a capacity of 17.1 GB, currently used for a very small percentage of discs available.

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-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. (See DVD-Audio for more information).

DVD Books - The specifications for all DVD disc formats. There are currently 12 Books including DVD-Video, DVD-Audio, DVD-ROM, DVD-R, DVD-RW etc.

DVD CCA - DVD Copy Control Association (www.dvdcca.org), the organisation responsible for licensing CSS (Content Scramble System) to manufacturers of DVD hardware, discs and related products.

DVD Forum -The organisation that comprises the ten original DVD Consortium companies who developed the DVD formats plus other companies involved in DVD. There are now over 230 members. The original 10 member Steering Committee has been increased to 17. More information is available from their website, www.dvdforum.org.

DVD-R - A recordable write-once DVD format, with a capacity of 3.95 GB (first generation) or 4.7GB per side. There are two versions, Authoring version with no copy protection and General version (for consumer use) with copy protection (CPRM) and no CSS capability (which mean these discs cannot be used to copy CSS protected discs).

DVD-RAM - A re-writable DVD, with capacities of 2.6 GB (first generation) or 4.7 GB (second generation) per side.

DVD-ROM - The basic pre-recorded DVD disc, which supports 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-RW - A re-writable DVD with a capacity of 4.7 GB per side. The DVD-RW is an alternative to the DVD-RAM, which supports fewer re-write cycles than DVD-RAM but is claimed to be more compatible with DVD-ROM drives.

DVD+R - A recordable write-once format, developed by Philips and Sony but not recognised by the DVD Forum.

DVD+RW - A re-writable 12 cm optical disc with a capacity of 4.7GB per side developed by Philips and Pioneer as an alternative to DVD-RAM. It is claimed to offer almost total compatibility with existing players, but is not an official DVD format.

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. (See DVD-Video for more information).

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 DualDisc.
Easter Eggs - Extra video clips hidden on a DVD-Video disc but which can be played via a ‘hidden’ link on a menu, e.g where the user least expects to find it.

Encryption - Transformation of data to be transmitted or stored on optical or magnetic media to ensure that only the intended recipients can make use of the information.

Enhanced Music CD - An enhancement to the CD audio specification for audio and data contained in separate sessions, such that a CD audio player will only try to play the audio tracks and a PC will be able to access the CD-ROM track in the second session. The CD-ROM data can include video, images and software to access the Internet.

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

Father Disc - 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.

Field - One-half of an interlaced video frame, consisting of every other scan line.

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 and UDF.

Finalising- To completing a master disc any multisession or packet written discs need to be finalised. otherwise they can't be used for CD-R duplication or for glass mastering. They also won’t be readable in standard CD/DVD drives. Finalising involves adding the lead-in, lead-out and complete file-system data to the disc and is an option on all recording / burning software.

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

Frame - A unit of data on a CD comprising 24 audio samples, plus subcode and CIRC error correction. Also 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 - Specialist printing, packaging, secure warehousing and logistics services that complement CD and DVD manufacturing to meet the ever demanding needs of customers.

GB - Gigabyte, which can either be 1,000,000,000 or 1,024 x 1,024 x 1,024. The first meaning is used when giving the capacity of a DVD disc, eg 4.7 GB. The second meaning is more common for PC memory capacity, which is usually a power of 2.

GIF - Graphics Interchange Format used by CompuServe and the World Wide Web for 8-bit (256 colour) graphics images.

Glass Mastering / GM - The initial part of the CD and DVD disc manufacturing process. A Glass Master is a platter of precisely formed optically pure glass, with a light sensitive coating. Data is then etched into the coating of a photo-resist layer of a glass disc using a laser beam generated by an LBR. From this is 'grown' the metal Stamper which is placed in the CD or DVD Mould when the Discs are pressed.

Group - Every side of a DVD-Audio disc (also called an Album) can contain up to 9 Groups, each of which can be subdivided into up to 99 Tracks.

Hard-coat - A thin layer on the surface of a disc to protect the disc from scratches and other marks. A hard-coat is essential for Blu-ray discs to protect from both scratches and fingerprints, but is also used on DVD recordable and re-writable media.

HC-R - High capacity versions of CD-R discs having a capacity of 98 minutes, 29 seconds and 74 frames on a single session 12 cm disc. This extra capacity is achieved by reducing the track pitch to 1.28 microns and scanning velocity to 1.13 m/s.

HDCD - High Definition Compatible Digital, an enhanced version of PCM encoding that improves the quality of audio on a CD when using a HDCD player but does not impair the quality when playing on a normal CD player. HDCD uses the least significant bit of each sample to provide additional information to increase the number of bits per sample from 16 to 20. (www.hdcd.com).

HD DVD - The name given to a High Density DVD format, being studied by the DVD Forum to store HDTV content. Proposed by Toshiba and NEC it was originally called AOD (Advanced Optical Disc) and offers a capacity of 15 GB per layer, 20 GB for re-writable versions. HD DVD is one of two options being developed to meet the requirements of HDTV. The other is Blu-ray.

HD DVD-R - The recordable HD DVD format, offering a capacity of 15 GB per layer.

HD DVD-ROM - The pre-recorded HD DVD format, offering a capacity of 15 GB per layer and intended for distributing movies in HD video.

HD DVD-RW - The re-writable HD DVD format, offering a capacity of 20 GB per layer.

HD DVD-Video -Video format on HD DVD-ROM discs for HD video and enhanced interaction.

Header - The bytes in a CD-ROM sector that contain the time-code and mode.

HFS - Macintosh's Hierarchical Filing System, which is needed on Mac CD-ROMs instead of (or in addition to) ISO 9660.

Hotspots - Areas (usually rectangle) within a graphic or other image which when selected using a mouse or other user input device results in an action being performed. Hotspots are used in computers, multimedia applications, Video CDs and DVD-Videos for menus allowing interactivity.

Hybrid - Among other meanings this usually refers to the disc containing two file systems (usually ISO 9660 and HFS). The file system data, ie Volume Descriptors etc, occupy different areas on the disc. Hybrid discs are designed to be used on two different computer systems eg PC and Macintosh. The disc may contain common data, accessible by both file systems as well as data unique to only one system.

Hybrid DVD Audio - A version of the DVD-Audio format which comprises a CD layer (at the top of the disc) and a DVD-Audio layer, which is semi-reflective allowing a CD player to read the CD layer, which contains CD audio data. This has been studied by the DVD Forum and found not to be a viable format because of the way many DVD players read discs, ie they will tend to read the CD layer and ignore the DVD layer. An alternative is the DVDPlus or Dual Disc double sided disc.

Hybrid SA-CD - A version of the SA-CD format which comprises a CD layer (at the top of the disc) and a SA-CD high density audio layer, which is semi-reflective allowing a CD player to read the CD layer, which contains CD audio data.

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

Indexes -Sub-divisions of each track of a CD or DVD-Audio. Each track may, if necessary, be divided into up to 99 indexes to provide more than 99 'tracks' per disc.

Injection Moulding - A manufacturing process in which molten plastic (eg polycarbonate for CD and DVD discs) is 'injected' into a mould under pressure. The plastic fills the cavity and, after cooling, a perfect replica is created.

Interactive Video - The combination of video and computer technology offering user interaction for training and other applications.

Interlace - Scheme to display a video image by displaying alternate scan lines in two discrete fields.

Interpolation - The process of averaging pixel information when scaling an image.

ISO 9660 - ISO standard for CD-ROM file system, particularly for PC applications.

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

Jitter - On a CD or DVD disc 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 to handle long filenames that are part of the features of Windows 95.

JPEG - A popular image file format, which is often preferred and used for photographic images due to its compression format.

Key - A binary code that is assigned a unique value for encrypting data for security purposes. The key is usually also encrypted so that it can accompany the encrypted data but only allow the receiving device to decrypt it.

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

Lacquering - All CDs after metallising are protected with a lacquer by spin coating.

LASER - Light Amplification by Stimulated Emission of Radiation; a means of generating coherent light which can be focussed to a very small spot size and ideal for reading compact discs, in laser beam recording and for writing CD-R 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. Layer 1 can be Parallel Track Path (which starts at the ID) or Opposite Track Path (which starts above where the Layer 0 program area ends) to allow seamless playing from Layer 0 to Layer 1.

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.

Letter-box - A method for displaying wide screen video on a conventional TV by adding black bars to the top and bottom so that the full width of the image is seen.

Macrovision - Name of the company who developed analogue copy protection systems to prevent recording to VHS. A variant is used to prevent copying of DVD-Video discs. Macrovision also offer Safedisc copy protection for CD-ROM and SafeAudio for CD Audio. (www.macrovision.com).

MCPS - Mechanical Copyright Protection Society, which licenses the recording and use of music on behalf of its songwriter, composer and publisher members. (www.mcps.co.uk).

MD / MiniDisc - 6cm magneto-optical re-writable disc format developed by Sony for audio and data storage. MiniDiscs can store 74 minutes of compressed stereo audio.

Mini CD - A fully functioning small version of the CD format. It still conforms to all standard CD specifications but is only 80mm in diameter with a data capacity of 180MB or 23 minute of audio.

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. Various options are available to implement audio and data on the same disc, including CD-EXTRA.

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

MP3 - MPEG-1 layer 3 audio encoding, used to compress audio on CD-ROMs and for downloading via the Internet.

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. (www.mpegif.org).

MultiAudio - A specification adopted by OSTA to ensure that discs with compressed audio files, such as MP3 or WMA, are as easy to play as standard audio CDs. (www.osta.org/specs/multiaudio.htm).

MultiPlay - A specification adopted by OSTA that ensures that CD-R and CD-RW discs recorded on PCs can be played in consumer CD and DVD players. (See www.osta.org/specs/multiplay.htm).

MultiRead - A specification which defines the parameters necessary for PC optical drives to be capable of reading audio CD, CD-ROM, CD-R and CD-RW discs.

Multisession - CD which comprises more than one session, each of which comprises Lead-in, Program area and Lead-out and (for a recordable CD) can be written at different times (ie sessions).

Multimedia - Refers to the delivery of information that combines different content formats (motion video, audio, still images, 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.

OTP / Opposite Track Path - Layer 1 of a DVD-9, where the data starts above the end of data on Layer 0 and ends at or near the ID of the disc. The Program Area on this type of layer is preceded by the Middle Area.

Packet Writing - A method of writing CD-ROM data to a CD-R in smaller increments than a session.

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

Pan & Scan - A method for displaying wide screen video on a conventional TV by showing only part of the full width. The part shown is normally adjusted during the video depending on where the most important action is.

Pantone - see PMS.

Paper Parts - Refers to the printed booklets, inlays and covercards which accompany CD and DVD cases and packaging.

Parallel Track Path - Layer 1 of a DVD-9, where the data starts at the ID of the disc and ends near the OD.

Parental Lock - A means to prevent certain scenes on a DVD-Video disc from being seen by children.

PCM - Pulse Code Modulation, the most common method of encoding an analogue audio signal into a digital bit stream.

Photo CD - CD format defined by Kodak and Philips for storing photographs for display and/or subsequent printing.

Picture CD - An alternative format to Photo CD for consumers, allowing digitised photos to be stored on CD-R or special CD-PROM discs. Picture CD does not include as many resolutions or options as Photo CD, but is used for storing photos which have been scanned from film following processing.

Picture 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.

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.

Pixels - An abbreviation for picture element. The minimum raster display element, represented as a point with a specified colour or intensity level.

PMS – Pantone Matching System - A popular colour matching system used by the printing industry to print spot colours. This works by specifying the required pantone colour or number from the PMS range. This assures that you get the right colour when printed, even though the colour may not look right when displayed on your monitor.

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.

Post-Gap - The area on a CD or CD-ROM comprising 150 sectors at the end of the track before one of a different type (ie at the end of a CD-ROM track followed by a CD-Audio track).

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.

Progressive scan - A method of scanning a TV display where all lines in a frame are displayed in sequence from top to bottom. This is the alternative to interlaced scan and also involves an increase in frame rate from 25 Hz to 50 Hz or 30 Hz to 60 Hz to avoid flicker.

Random access - The process of jumping to an arbitrary point on a CD or DVD in order to read and decode data there. Unlike tape CDs and DVDs offer fast random access to any part of the data on the disc.

Real-time - In computing, refers to an operating mode under which data is received and processed as fast as the data to be processed arrives. For example, decoding of an MPEG video stream requires real-time decoding for smooth continuous playback.

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.

Resolution - The size of an image in number of lines and pixels per line.

Resource Fork - The part of a Macintosh HFS file containing the Macintosh resources, such as information defining the file type.

RGB - Red-Green-Blue, the three primary colours used to output video signals eg from a PC to a monitor or DVD player to a TV display.

S-Video - Super-Video, a means for transferring video signals over a cable by dividing the video information into two separate signals - one for colour (chrominance), and the other for luminance. This is a higher quality alternative to composite video, which transfers both colour and luminance via a single wire. S-Video and Y/C Video have the same meaning.

SA-CD - Super Audio CD, 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. The audio encoding used is Direct Stream Digital (DSD).

SafeAudio - a copy protection system for CD Audio discs developed by Macrovision to prevent copying and piracy. This name has now been dropped following Macrovision's acquisition of Midbar Tech and its Cactus Data Shield technology.

SafeDisc - a copy protection system for CD-ROM titles originally developed originally by the UK company C-dilla (now owned by Macrovision) to prevent copying and piracy. It involves encrypting the data and placing a signature on the disc that cannot be copied but must be in place in order for the disc to be played. The latest version (version 4) also protects DVD-ROM titles.

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 / Silkscreen Printing - A process used for printing multi-colour labels on CD and DVD discs. See our Printing section for more information.

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 area, Program area and a Lead-Out area. On a CD-R it allows the data to be written a session at a time. Up to 99 sessions may be written to a single disc.

Sputtering - A process for coating moulded CDs with aluminium whereby an aluminium target is bombarded with particles causing the aluminium to be deposited 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.
Subcode - A separate low speed data channel on every CD. The subcode comprises 8 channels. The P and Q channels are used to provide control information for CD discs. The R to W channels are used for CD Graphics.

Subheader - Subheader is one of the fields in a mode 2 sector and is used to describe the contents of the sector.

Subpicture - Overlay graphics image contained in a DVD-Video file for subtitles, menu highlighting and other purposes.

Substrate - The transparent plastic, usually polycarbonate, ‘disc’ that is bonded to a similar substrate to form a complete DVD or HD DVD disc. Each substrate is therefore 0.6 mm thick and 1.2 cm in diameter and contains the pits for that side or layer of the disc.

Super Audio CD - 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. The audio encoding used is Direct Stream Digital (DSD).

Surround sound - Multi-channel audio providing a two-dimensional sound resulting from the use of loudspeakers at the front and rear. A typical example is 5.1 channels (used in DVD-Video titles) comprising three front and two rear channels plus a low frequency effects channel.

SVCD / Super Video CD - An enhanced Video CD format, which uses variable bit rate MPEG-2 encoding at a higher data rate then Video CD version 2. It also includes an additional stereo audio channel or multi-channel audio and subpictures. SVCD offers video quality and features closer to DVD-Video, although a full-length movie will require three discs.

TAO - Track At Once - Refers to the way some CD-Recorders write CD-R or CD-RW discs, where a track (with post-gap) 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). This can cause a glitch when playing audio CDs recorded in this way, so other CD-Recorders use Disc at Once (DAO) recording.

Time Code - A frame-by-frame address code time reference recorded on the spare track of videotape or inserted in the vertical blanking interval. It is an eight-digit number encoding time in hours, minutes, seconds, and video frames (e.g.: 02:04:48:16).

TOC / Table of Contents - Table of Contents of a CD, listing the start time code of every track on the disc.
Tracks - Sub-divisions of the program area of a CD. Each disc may have up to 99 tracks each at least 4 seconds in length. Each track can contain data of only one type. Also refers to the sub-divisions of the audio on a DVD-Audio disc, which may comprise up to 9 Groups each consisting of up to 99 tracks.

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 printing labels on CD and DVD discs.

VBR / Variable Bit Rate - Bit rate varies with time during the decoding of a compressed bitstream. One example is MPEG-2 for DVD-Video where bit rate changes according to compression requirements to keep the average bit rate low. VBR encoding offers better quality than constant bit rate (CBR) at lower data rates.

Video CD - The White Book standard for up to 74 minutes of VHS quality MPEG-1 video on one CD.

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

Volume Descriptors - Data (at the start of the program area of a CD-ROM disc) containing file system information about the files and directories on the disc. ISO 9660 and other file systems use volume descriptors.

WAV - File extension for PCM Wave audio files.

Web CD - A CD which authored to automatically link to a Website. A Web DVD is the same concept operating from a DVD-ROM.

WMA - Microsoft’s Windows Media Audio, an audio compression format, offering higher quality than MP3 at the same bit rate, that is supported by Microsoft’s Windows Media Player (WMP).

WMP - Microsoft’s Windows Media Player - will play WMA, MP3 audio files as well as Red Book CD tracks and MPEG and WMV video files.

WMV - Microsoft Windows Media Video. WMV-9 includes a new codec called VC-9 and offers high quality at bit rates about 60% lower than MPEG-2.

WMV HD - Microsoft Windows Media Video High Definition, a new efficient video coding technology for HD video. It is one of the video codecs provisionally chosen for HD DVD.