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CD and DVD Glossary
by Media Sciences

Interchangeable Media for Computer Mass Storage
• DVD and CD Optical Discs • Diskettes •
• Quality Testing • Training • Research • Product Certification •

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Browse alphabetically to find the meaning of more than 200 CD and DVD terms from 8-to-16 to Yellow Book.

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8-to-16
Eight-to-sixteen modulation used to convert eight data bits to sixteen channel bits prior to recording.
ADPCM
Adaptive Differential Pulse Code Modulation compression technique that encodes only the difference between sequential samples.
Angular Deviation
Angle between the incident and reflected laser beam caused by disc or lens tilt, resulting in different off-axis focal points for rays from different radii of the focussing lens and asymmetrical distortion of the focussed laser spot (coma).
ATime
Address information contained in a block identifying a unique block location for receiving systems in absolute elapsed time measured in minutes, seconds, and blocks referenced to the beginning of the program area.
ATIP
Absolute Time In Pregroove similar to ATime but used by a writer for unrecorded disc addressing.
Astigmatism
Distorted spot resulting from imperfect focus caused by a defect of an optical system.
Authoring
The process of designing, creating, capturing, editing, and integrating information for a CD or DVD. Or, creating a database for a CD or DVD using tagging and indexing that generates a search and retrieval document.
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Birefringence
Optical distortion caused by different indices of refraction for separate directions of polarization, often caused by stress in the optical medium. Produced during CD or DVD injection molding by shrinkage, flow lines, and inclusions in the substrate. Usually more severe near the outer diameter.
Bit
One binary information element having the value ZERO or ONE.
Bit Error Rate (BER)
Probability that a read bit does not match the written bit.
Block
Group of contiguous recorded characters treated as a unit and containing one or more logical records. A logical block contains 512x28 bytes, where n is an integer (0, 1, 2, ...) Normally used to characterize a DVD ECC block or a CD subcode block, or section, but can also refer to a CD frame.
Block Error Rate (BLER)
Number of blocks, each containing one or more erroneous bits, per unit of time (usually seconds).
Blu-ray Disc (BD)
120 mm optical disc achieving very high density through use of 405 nm blue-violet lasers, high numerical aperture optics, and, optionally, multiple information layers.
Blue Book
Proprietary Philips/Sony specification (blue cover) for Enhanced Music CD.
Bump
Exposed area on the master viewed from the entrance surface. Also used to designate indentations caused by foreign matter during molding.
Burst
Contiguous error groups usually caused by a large tangential physical defect. ISO burst limit for CD is less than seven successive frames, each containing two or more successive error bytes.
Burst Cutting Area (BCA)
Optional annular area on a DVD disc near lead-in containing low reflectance radial stripes of encoded content provider information.
Byte
Contiguous set of eight data bits, represented by an equal or greater number of channel or recorded bits.
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CAV
Constant Angular Velocity of the information track resulting in variable, radius-dependent bit rates.
CD-Bridge
Combined features of CD-ROM XA and CD-i, playable in CD-i player or CD-ROM XA drive.
C1 or C2
See CIRC
CD-DA
CD-Digital Audio using 16 bits of linear coding to represent each digital sample of an audio channel. First specified in the Red Book, later in IEC 908 (also see Digitize.)
CD Extra
See Enhanced Music CD.
CD-i
Compact Disc Interactive specified by Green Book, designed as a TV adjunct featuring simultaneous integration of various levels of sound, audio, animation, graphics, and limited video. Used for multimedia and interactive software.
CD-i Ready
CD-Audio disc with additional features such as graphics information that can be accessed in a CD-i player. CD-i information hidden in a long, 3 minute or more, track #1 index 0 pre-gap that is skipped by CD-DA players.
CD+G
Format adding graphics to CD-DA in reserved subcode bits R-W (6 bits per frame, 20 MB per disc). Primarily used for Karaoke.
CD-R
CD-Recordable, write once-read many disc specified by Orange Book Part II using a pre-stamped, wobbled groove to guide a write laser that irreversibly changes regions of a dye polymer layer to an optically absorbing state. A special drive is required for writing.
CD-ROM
CD-Read Only Memory, first specified in the Yellow Book, later in ISO/IEC 10149 (Second Edition 1995).
CD-ROM XA
CD-ROM eXtended Architecture standard of Philips/Sony that incorporates a subheader to support interleaving of audio, graphics, video and computer data using CD- ROM XA Mode 2/Form 1 and CD-ROM XA Mode 2/Form 2 sectors. CD-ROM XA EDC and ECC structures differ from those of CD-ROM Mode 2.
CD-RW
CD-ReWritable phase change media specified by Orange Book Part III that can be reversibly recorded, erased, or overwritten. Uses a pre-stamped groove to guide a write laser. Data is contained in an alloy layer that can be converted by a laser from a reflective crystalline state to a non-reflective amorphous state or erased back to the crystalline state, depending on laser power. A special drive is required for writing, but CD-RW recorded media can be read in modified CD-ROM drives capable of detecting the low light levels resulting from CD-RW reflectivity of 15-25%. (Formerly CD- Erasable or CD-E.)
Channel Bit
Binary elements by which ZERO and ONE data bits are represented by optical information on the disc after encoding and modulation. Multiple (usually 14 or 16) channel bits are commonly used to represent one eight bit data byte to achieve higher information density when combined with NRZ-I coding.
CIRC
Cross Interleave Reed-Solomon Code is a method of error detection and correction employing Reed-Solomon parity bytes together with different interleaving, or delay, patterns that assists in error correction by distributing concentrated read errors over multiple frames that then form the input to a CIRC decoder. After the first deinterleave, CD discs correct small read errors at the C1 level, followed by a second deinterleave and correction of large read errors at the C2 level.
Circular Polarization
Two linearly polarized, orthogonal (right angle) light beams that are 90 degrees out of phase. Produced from unpolarized light by a linear polarizer aligned 45 degrees from a major axis of a quarter wave plate.
Clamping Area
Region between the center hole and information area where the disc is physically connected to the drive spindle.
CLV
Constant Linear Velocity of the information track achieved by variable angular velocity using higher rotational drive speeds on the inner tracks and lower speeds on the outer tracks resulting in a constant scanning velocity and bit rate.
Closure
See finalization.
Coherent Light
Illumination in which phasor amplitudes at all object points vary in unison, such as light from a point source or a laser.
Color
Response of the eye to different wavelengths of light. Ultraviolet < 400 nm, violet 400-424 nm, blue 424-491 nm, green 491-575 nm, yellow 575-585 nm, orange 585-647 nm, red 647-700 nm, infrared > 700 nm. Maximum visibility occurs at 556 nm.
Compression
Decreasing the size of stored information by reducing the representation of the information without significantly diminishing the information itself, usually by removing redundancies. Requires decompression upon retrieval. Lossless compression allows the original data to be recreated exactly. Lossy compression sacrifices some accuracy to achieve greater compression. Fixed rate compression, such as MPEG-1, has been superceded by variable bit rate compression methods, such as MPEG-2, that dynamically adjust the compression ration between fixed upper and lower bounds depending on the complexity of the original information. Compression ratios can reach 175:1 depending on the specific coder/decoder (codec).
Control Byte
See subcode.
Conversion
Data transfer from one type of media to anotherş often using DLT or 8 mm tape or CD-R as input.
Crosstalk
Unwanted signal from adjacent tracks.
Cutting Master Format (CMF)
Specification for storing copyright protection and other information, such as Disc Description Protocol (DDP), that is required for full DVD mastering.
Cyclic Redundancy Check Code (CRCC or CRC)
Type of error detection code (see EDC).
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Data Area
Logical sectors in a volume containing descriptors, path tables, and files.
Data Bit
Information received from the host for storage or transmitted to the host after retrieval.
Data Field
A fixed length field containing the user information in a sector.
Decibel (dB)
Unit of measurement using a logarithmic scale to represent ratios of two values, A and B, calculated as log10(A/B).
Defect Management
Replacement of unusable regions of media with either a subsequent block or a block in a separate spare area. Normally used for rewritable discs.
Deflection
Vertical, or axial, displacement error of a disc measured from a flat reference plane.
Descriptor
Structure that contains information describing a volume or file.
Differential Phase
Use of phase, or time, differences instead of amplitude differences to provide a servo error signal.
Diffraction
Departure from perfect sharpness of the shadow edge of an illuminated object. Limits the minimum size of a focussed spot. See Huygens' principle.
Digital Sum Value (DSV)
Representation of the low frequency or DC component of a binary bit stream. The value +1 is assigned to a binary NRZ-I ONE and the value -1 is assigned to a binary NRZ-I ZERO. A cumulative sum of values is maintained for successive NRZ-I bits that may be used to select appropriate merging or channel bit patterns.
Digitize
Conversion of a sampled analog or continuous signal into a series of binary ones and zeros. Used for audio, graphic images, or physical measurements. Sampling frequency and number of binary elements affects accuracy of conversion back to analog form.
Directory
A file in a single extent belonging to only one directory hierarchy that contains contiguous records, each of which describe a file section or another directory.
Directory Hierarchy
One set of path tables and a multilevel set of directories defined by a volume descriptor and having a common character set and other properties.
Dropout
Significant loss of signal amplitude capable of affecting data and servo accuracy, usually related to a physical defect.
Duplication
Production of a copy using sequential, serial transfer of information elements from an original image to a duplicate. Low mastering and equipment costs and short preparation times are offset by low throughput, often limiting use to low volumes. Examples would be CD-R duplication from a digital master, or making copies of text using a line printer.
DVD
120 mm optical disc achieving higher data density through use of 650/635 nm lasers, high numerical aperture optics, and, optionally, multiple information surfaces and/or layers.
Dye Polymer
Organic chemical that changes reflectivity when exposed to intense light of a particular wavelength.
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Eccentricity
Variation in radius of an information track from the true axis of rotation of the disc. May be confused with runout.
ECC
Mathematically determined Error Correction Code specified in the standards that represents data and is recorded with that data to enable limited correction of read errors.
ECMA
European Computer Manufacturers Association, a regional member of ISO headquartered in Geneva, Switzerland that often initiates and issues standards that are precursors of subsequent ISO standards.
EDC
Mathematically determined Error Detection Code specified in the standards that represents data and is recorded with that data to support limited identification of read errors.
Effect Length
Electrical or optical length in the direction of an information track of a physical data feature such as a pit or land.
EFM
Eight-to-Fourteen Modulation used to convert eight data bits to fourteen channel bits prior to recording.
El Torito
Bootable CD specification named for the restaurant where it was initiated.
Enhanced Music CD
Multisession CD-DA and CD-ROM disc specified in Blue Book playable as an audio CD without data-generated static.
Entrance Surface (Readout Surface)
Substrate surface nearest to the optical pickup head where the laser beam enters and, after reflection, exits.
Equalizer
Electronic circuit that compensates for low read signal amplitudes from short pits (marks) and lands that result from optical bandwidth limits related to diffraction limited spot sizes and other effects.
Erasure Byte
Byte of known location containing one or more erroneous bits flagged by error detection for processing in a subsequent operation.
Error Byte
Byte of unknown location containing one or more erroneous bits.
Extent
Set of logical blocks having addressing numbers that form a continuous ascending sequence.
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F1-Frame
Group of 24 8-bit bytes after scrambling and before CIRC encoding during a write operation. Alternatively, after CIRC decoding and before de-scrambling during read.
F2-Frame
Group of 32 8-bit bytes after scrambling and after CIRC encoding during a write operation. Alternatively, before CIRC decoding and de-scrambling during read.
F3-frame
Group of 33 8-bit bytes consisting of the F2-frame plus 8 subcode bits.
Father
The first electroformed part made from a glass master and containing a reversed data image of the final disc.
File
Named collection of information stored in one or more extents.
File Section
Part of the file that is stored in any one extent and identified by a descriptor in a directory.
Finalization
Action in which lead-in and lead-out areas are recorded that must be performed at the end of a recording operation if the disc is to be readable in a conventional drive. Also referred to as closure.
Flag
Bits appended to information that are used to indicate the status of that information.
Form 1
CD-ROM XA Mode 2 sector containing three levels of error correction for reliable retrieval of error- sensitive data.
Form 2
CD-ROM XA Mode 2 sector containing two levels of error correction for information tolerant of uncorrectable errors.
Format
Structure used to organize data for information storage and retrieval.
Frame
Information group containing data bytes along with other information such as sync, address, and parity bytes for error correction and detection.
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Galois Field
Mathematical concept where the elements of the binary field GF(2m) are represented by 2m m-bit binary bytes, each expressible by an m-bit column vector. For example, GF(28) contains 256 eight-bit bytes. Named for the brilliant French mathematician Evariste Galois who developed the concept in the early 1830's. Killed in a duel at the age of 25, his work was unknown until Liouville published Galois' papers in 1846.
GB
Gigabyte, 1 GB equals 230 bytes or 1024 megabytes. Or, 1 GB may equal 109 bytes. Gb may denote gigabits.
Glass Master
Data image of the final CD or DVD disc generated by a Laser Beam Recorder (LBR), normally consisting of a thin photosensitive organic layer supported by a polished, optically flat glass substrate.
Green Book
Proprietary Philips/Sony specification (green cover) for CD-i.
Groove
Continuous, spiraled trench-like radial guidance track of a recordable or rewritable disc offset towards the entrance surface that defines track centerline for recording purposes and contains CLV clocking, addressing, and other information.
HD DVD
120 mm optical disc achieving very high bit density through of 405 nm blue-violet lasers, high numerical aperture optics, and, optionally, multiple information layers.
Header
Area appended to and preceding user data containing addressing, format, and other information.
HF
Analog signals containing High Frequency data information in contrast to low frequency servo information.
HFS
Hierarchical File Structure defining the native Apple MacIntosh format for mass storage.
High Sierra
Draft version of ISO 9660 (MS-DOS) standard for volume and file structure. Named for the Lake Tahoe, California hotel that hosted the conference resulting in the draft standard.
Holography
Recording of both amplitude and phase information of an object using interference between an object wave and a coherent reference wave, both incident on a photo sensitive medium. Coherent illumination of this medium, upon wavefront reconstruction, results in an image having both amplitude and phase characteristics of the original, resulting in three dimensional and other special properties.
Huygens' Principal
Qualitative explanation of diffraction stating that the propagation of a light wave can be predicted by assuming that each point of the wave front acts as the source of a secondary wave that spreads out in all directions. The envelope of all the secondary waves is the new wave front. Precisely defined by the Fresnel-Kirchhoff formula.
Hybrid
Disc containing both an ISO 9660 (MS-DOS) partition and an HFS partition. Or, a disc containing both ISO 9660 and UDF volume and file structures. Or, may indicate that the first session of a multi- session CD-R or CD-RW disc is a mastered session followed by recorded sessions.
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Image
Fully premastered data assembled in the exact format for recording.
Incremental
Recording method allowing subsequent append or overwrite operations without reformatting or loss of adjacent pre-recorded information.
Index
Searchable points within a CD track, up to 99 index points per track.
Indexing
Creation of a data index to speed up search and retrieval.
Indirection
Method whereby fixed virtual addresses are mapped into variable logical locations.
Information Area
One area of a physical track consisting of one lead-in (with TOC), one program area, and one lead- out.
Information Layer
Physical layer of a CD or DVD disc that contains optically recoverable data after replication or recording.
Injection Molding
Replication involving injection under pressure of molten plastic into the cavity of a mold followed by cooling and removal of the solidified part that retains a replica of the mold.
Interchange
Capability of media to function properly in various systems.
Interleaving
A physical process rendering data more immune to burst errors whereby bytes from one input group are assigned to multiple output groups upon recording using a precisely defined method. De-interleaving during reading reverses the interleaving process, assembling data while dispersing read errors (also see CIRC.)
Or, a logical process of recording multiple files whereby each file is divided into extents, each containing a fixed number of blocks, that are recorded in a predetermined pattern having a fixed spacing between extents, and are alternated with extents of other files. Padding extents may be utilized if files are not of the same size.
Intersymbol Interference
Unwanted signal from adjacent information on the same track.
ISO
International Organization for Standardization comprised of national and regional member bodies and headquartered in Geneva, Switzerland. This non-governmental organization was established in 1947, and selected ISO from the Greek isos meaning equal, as in isothermal.
ISO 9660
International standard defining logical volume and file structure requirements for CD-ROM.
ISO/IEC 10149
International standard defining data interchange requirements for CD-ROM.
ISO/IEC 16448
International standard defining data interchange requirements for DVD-ROM.
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Jitter
Variation in the time position of a read data event from the expected position.
kB
Kilobyte, 1 kB equals 210 or 1024 bytes. Or, 1 kB may equal 103 bytes. kb may be used to denote kilobits.
Label
Printed information on the surface opposite to the entrance surface. Note that the label side of a CD contains metallized pits and grooves, and usually employs a protective coating under the printed information.
Lacquer Splash
Dried protective coating material on the entrance surface or outer rim.
Land
Unrecorded optical surface area between pits, grooves, or marks, further away from the entrance surface than pits.
Laser
Light Amplification by Stimulated Emission of Radiation generates monochromatic, coherent light, usually from an excited gas or semiconductor.
Laser Beam Recorder (LBR)
Recording apparatus consisting of a gas laser that is intensity modulated by a data encoder and position controlled radially by an accurate lathe mechanism. The laser beam is incident upon a glass master rotated by a spindle motor having accurate speed control.
Lead-In
Area at the beginning of a disc or session containing the Table of Contents (TOC) and other important information. Lead-in is followed by the Program Area.
Lead-Out
Buffer area following the Program Area used in case the player reads past the track.
Length Deviation
Variation of effect length from a norm.
Linear Velocity
Linear speed at which a moving feature passes a fixed point (also see Scanning Velocity.)
Link Block
Identified or unidentified region containing errors at the boundary of two different incrementally recorded data regions.
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Mark
Low reflectance feature of a recording layer representing data that can be sensed by an optical system.
Master
Physical entity containing an image for duplication or replication (also see Glass Master.)
Mastering
The process of recording pre-mastered data on a master. The data source is sometimes referred to as a gold master.
MB
Megabyte, 1 MB equals 220 bytes or 1024 kB. Or, 1 MB may equal 106 bytes. Mb may denote megabits.
Micrometer (µm)
One millionth of one meter or 39.4 microinches.
Microsecond (µs)
One millionth of one second.
Millimeter (mm)
One thousandth of one meter or 0.0394 inches.
Millisecond (ms)
One thousandth of one second.
Miscorrect
Parity operation that incorrectly replaces valid data with erroneous data.
Misdetect
Parity operation that fails to detect erroneous data.
Mixed Mode
CD-ROM and CD-DA on the same disc, data on track 1, audio on tracks 2 up to 99.
Mode 1
CD-ROM format containing three levels of error correction for reliable retrieval of error-sensitive computer data.
Mode 2
CD-ROM format containing two levels of error correction for uncompressed audio, video, and other types of information tolerant of sporadic uncorrectable errors. Should not be confused with CD-ROM XA Mode 2 (see Form 1 and Form 2.)
Modulation
Conversion of data bits to channel bits that normally enhances storage capacity and minimizes low frequency components of recorded information that might interfere with servomechanism functions.
Monochromatic Light
Illumination containing a single wavelength.
Mother
The electroformed part made from a father and containing a data image of the final disc.
MPEG
Motion Pictures Expert Group compression methods for video, graphics, or audio information. MPEG-1 uses a fixed compression ratio while subsequent methods, such as MPEG-2 and MPEG-4, use variable bit rate compression.
MSCDEX
MicroSoft CD-ROM EXtension enabling computers using MS-DOS 3.1 or higher to access a CD-ROM as a large, read-only hard drive.
Multimedia
Integration of more than one form of information, such as text, graphics, audio, video, animation, and computer data.
Multisession
Multiple incremental recording events, or sessions, using non-incremental session-at-once or incremental track-at-once writing, each recording event resulting in a new lead-in (with TOC), program area, and lead-out. Multiple recording events at different times result in multiple sessions with a distinct TOC for each session.
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Nanometer (nm)
One thousandth of one micrometer or 0.0394 microinches. Equivalent to 10 Angstroms (Å).
Non-Return-to-Zero (NRZ)
Bi-level digital code in which one level represents a binary ONE and the other level represents a binary ZERO.
Non-Return-to-Zero-Inverted (NRZ-I)
Bi-level digital code in which the levels are changed by a binary NRZ ONE and remain unchanged by an NRZ ZERO.
NPR
Non-Photoresist Mastering method using a Laser Beam Recorder that employs an ablative process to write onto a dye layer supported by a polished, optically flat glass substrate.
NTSC
National Television Systems Committee organized by the Electronic Industries Association for the development of NTSC commercial television standards used in the United States and also Canada, Japan, and other countries. Black-and-white TV uses a scanning system of 525 lines at 60 fields per second. Color uses 525 lines at 59.94 fields per second with a 3.58 MHz color subcarrier.
Numerical Aperture (NA)
Resolution or "spot" size of a lens. A small spot is produced by a lens having a high numerical aperture achieved using a large physical aperture and/or a short focal length. NA is equal to one-half of the reciprocal of the f-stop.
Oil Stain
Organic residues under the metallic coating
One Off
A finalized CD-R. May also refer to a CD-R proof, or test, disc generated after premastering.
Orange Book
Proprietary multipart Philips/Sony specification (orange cover) for magneto-optical, CD-R, and CD- RW optical discs.
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Packet
Integral number of sectors forming a single unit of information that can be incrementally written or overwritten.
PAL
Phase Alternate Line video standard used in Europe and other parts of the world for composite color encoding, using 625 lines at 50 fields per second with a 4.438 MHz color subcarrier, although other scanning systems may be used.
Parity
Mathematical representation of data used for error detection or correction.
Partial Response Maximum Likelihood (PRML)
Electronic circuit that converts analog read signals to digital bits using soft-decision decoding of a bit sequence based on a two-step process that significantly reduces raw bit error rates. A Partial Response (PR) equalizer removes much of the intersymbol interference introduced by the write and read channels, after which a Maximum Likelihood (ML) detector compares the received data sequence to allowed sequences and selects the best match.
Partition
An extent of logical sectors within a volume; partitions may be allowed to overlap.
Path Table
A file in a single extent belonging to one directory hierarchy that contains contiguous records that fully describe the directory hierarchy.
PCA
Power Calibration Area of a recordable or rewritable disc that precedes lead-in and the PMA, where the optimum laser power level for writing can be determined by a recording drive.
Phase Change
State change of a recording layer caused by introduction of energy, resulting in information storage detectable by differences in optical properties of the physically different states.
Photo CD
Proprietary Eastman Kodak method of storing photographs on CD described in the Beige Book, using elements of Yellow Book, Orange Book, and CD-ROM XA.
PI or PO
See RS-PC.
Pit
Information area viewed as a depression from the label surface that can be sensed by an optical system.
Pitch
See Track Pitch.
PMA
Program Memory Area preceding lead-in of a recordable or rewritable disc containing a history of recorded track locations that are copied to the TOC upon finalization of the session or disc.
Polarization
Direction of the electric vector of an electromagnetic wave. Polarization is fixed for linear polarization or is rotating at right angles to the direction of propagation if circularly polarized.
Post-Gap
Two second area at the end of a CD program area or Mode change, encoded as null data or audio silence.
PQ Information
Subcode information determining track start points, control bits, timing, and other information.
Pre-Gap
Two second first part of a CD program area or track, normally encoded as null data or audio silence, but should contain track descriptor blocks if session-at-once or incremental track-at-once recording is used.
Pre-Groove
See Groove.
Premastering
Generating an image ready for mastering and replicating by formatting data into the exact sector, volume, and file structure required by the applicable standard.
Program Area
Region in the information area of the disc containing one or more logical tracks, each consisting of a pre-gap, followed by user data, and ending in a post-gap.
Protective Coating
Layer applied over the metal coating. Often a spin-coated UV-curable polymer.
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RAW
Real time Read-After-Write feature of certain mastering techniques. Or, a transparent, unmetallized disc.
Raw Bit Error Rate
Probability of a bit being erroneous without use of any error correction techniques.
Record
A sequence of bytes treated as a unit of information.
Recordable
Storage medium that can only be read, not modified, after information is initially written (also see WORM.)
Red Book
Proprietary Philips/Sony specification (red cover) for CD-Audio, subsequently published as IEC 908.
Reed-Solomon Code
Byte-structured parity format that cycles data multiple times through a mathematical transformation in order to increase its effectiveness, often used with optical and magnetic computer media for error detection and/or correction. The algebraic code belongs to the class of BCH (Bose-Chaudry-Hocquehen) multiple burst correcting cyclic codes. Method published in 1960 by Irving S. Reed and Gustave Solomon, staff members of MIT's Lincoln Laboratory.
Reference Plane
Plane normal to the axis of rotation of a disc defined by the perfectly flat annular surface of an ideal spindle onto which the CD or DVD clamping area is physically connected.
Reflectance (Reflectivity)
Proportion of incident light that is returned from a reflective surface.
Relative Time (PTime)
Elapsed time from the start of a logical track.
Replication
Production of a copy using simultaneous, parallel transfer of all information elements from an original image to a replica. High mastering and equipment costs and long preparation times are offset by high throughput, making the technique attractive for high volumes. Examples would be CD or DVD replication from a stamper using molding, stamping, or coining, or making copies of text by lithographic means (also see Injection Molding.)
Rewritable
Storage medium that can be overwritten multiple times, normally without pre-erasure.
Rock Ridge
IEEE standard for UNIX file structure, named for the mythical town in the movie Blazing Saddles.
RS-PC
Reed-Solomon Product Code is a method of error correction employing several (usually two) groups of Reed-Solomon parity bytes computed from rows, columns, or diagonals of a rectangular data array. DVD discs correct small read errors using inner parity, or PI, that operates on rows, and corrects large read errors using outer parity, or PO, that operates on columns of the data array.
Runout
Radial variation of a non-data physical dimension (also see Eccentricity.)
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s
One second of time.
Sample
Value of an analog or continuous signal at a single point of time (see Digitize.)
Scanning Velocity
Linear velocity at which optical data features pass a fixed point such as the pickup head of a drive.
Scarlet Book
Proprietary Philips/Sony specification (scarlet cover) for a Super Audio disc of one DVD layer and one CD layer.
Section
CD information group containing 98 consecutive frames of interleaved bytes from scrambled sectors, plus C1 and C2 CIRC, subcode, and frame sync. Also referred to as a subcode block.
Sector
Smallest addressable entity in the information area that can be addressed independently of other addressable parts.
Servomechanism
Electromechanical means of automatically maintaining a desired state by sensing variations from that state, and then correcting those variations by using very small amounts of power to control much larger amounts of power.
Session
Single recording event that creates a single information area (lead-in - program area - lead-out.)
Single Session
Single recording event resulting in one lead-in (with TOC), program area, and lead-out for the entire disc.
Slicer
Electronic circuit that converts analog read signals to channel bits using hard-decision decoding of individual bits.
Space
High reflectance feature of a recording layer representing data that can be sensed by an optical system.
Spherical Aberration
Optical distortion caused by non-optimum substrate thickness resulting in different on-axis focal points for rays from different radii of the focussing lens and a symmetrical increase in the size of the focussed laser beam.
Spindle
Mechanical means of coupling a disc to a rotating device.
Stamper
The electroformed part made from a mother and containing a reversed data image of the final disc. Becomes part of a mold for the injection molding replication process.
Standard for Recording
A document agreed upon by the originator and recipient of a volume specifying the recording and addressing methods for information, including;
a unique physical address for each recorded sector, and
the location of the data field within each sector, and
the length of the data field within each sector.
Subcode
Ninety-eight-bit codes used in the CD format. P and Q codes contain flag and control information. Codes R,S,T,U,V,W are available and may be used for CD+G or other specialized applications.
Subcode Block
Ninety-eight sequential CD frames. Also see Section.
Substrate
Transparent physical layer providing mechanical support through which the laser can access an information layer.
Sync
Unique bit pattern appended to and preceding information that establishes a reference point for decoding of that subsequent information.
System Area
The first sixteen logical sectors in a CD volume numbered 0 to 15.
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Table of Contents (TOC)
Lists number of CD tracks, their starting locations, total length of data on the disc, and identification of type of disc. The TOC is placed in Q-subcode in the lead-in area of a CD disc.
Tilt
See angular deviation.
Track
A physical track consists of one contiguous physical spiral area from inner diameter to outer diameter containing information (dual layer DVD discs have two physical tracks.) Or, the information contained within a single 360 ° rotation of the disc. Or, one contiguous logical element of information, such as a single CD audio track (a song) or computer data region (an information track.) One CD session contains from one up to 99 such logical tracks, each consisting of a pre-gap, user data, and a post-gap.
Track Pitch
Center-to-center distance between two radially adjacent information sequences.
Transition
Recorded information location at a pit-land juncture in CD and DVD. Normally a channel bit ONE.
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UDF
Universal Disc Format standard of the Optical Storage Technology Association designed to create a practical subset of the ISO/IEC 13346 random-access file system and volume structure format.
Variable Bit Rate (VBR)
Data compression technique that produces an output data stream varying between fixed minimum and maximum rates, with bandwidth decreasing or increasing depending on the complexity of the fixed rate incoming data.
Verification
Process of matching information on a copy to that on the original.
VIDEO CD
Special CD-Bridge implementation for MPEG-1 digital videoş specified in the White Book.
Viterbi Algorithm
Decoding method that greatly reduces the complexity of Maximum Likelihood decoding (see Partial Response Maximum Likelihood).
Volume
A dismountable CD-ROM disc. A mountable sector address space consisting of a single set of sector addresses, usually as a continuous sequence of sectors, and containing one or more directory hierarchies.
Volume Descriptor
One sector containing information describing the volume. If multiple volume descriptors are present, then the volume descriptor set must be recorded in consecutively numbered logical sectors.
Volume Set
A collection of one or more volumes with identical volume set identification, on which a set of files is recorded.
Volume Space
The set of all logical sectors on a volume encompassing the system and data areas.
White Book
Proprietary Philips/Sony specification (white cover) for VIDEO CD.
Wobble
Continuous, sinusoidal radial deviation of the prerecorded groove from track centerline. Usually includes CLV and other information, such as location, contained in phase or other forms of modulation.
Word
Contiguous set of data bytes. Four CD-DA bytes representing one stereo sample is often referred to as one word.
WORM
Write-Once-Read-Many recording on non-erasable blank media or media containing pre-stamped grooves to guide a write laser.
Write Strategy
Shaping recorder laser power as a function of time and/or adjusting the write time duration to be different than the desired time interval in order to achieve proper read characteristics.
Yellow Book
Proprietary Philips/Sony specification (yellow cover) for CD-ROM, subsequently published as ISO/IEC 10149 (Second Edition 1995.)
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