Glossary of Terms
1630 Tape
Also known as a Sony PCM-1630 digital tape or U-matic tape. A tape format used frequently by audio mastering studios for master preparation. A properly prepared 1630 tape has been recorded with the data, error correction codes, and sub-codes, and has been converted to CD format.

A/D Conversion
It is the conversion of an analog signal to digital data.

A-Time
Absolute Time. It is the total length or running time of a disc, from the start of track 1 to the start of lead-out.

ASCII
American Standard Code for Interchange of Information. It is an 8 bit, 128-character set used to transfer data into binary values used internationally.

Birefringence
In optical discs, it is double refraction of light caused by improper cooling of the plastic from the injection molding process. High birefringence causes read errors and can only be detected with special equipment.

Bit
Binary digit. Defined by either a one or a zero. The smallest unit of information that a computer can utilize.

Block
also referred to as a sector or frame. It contains sync, header, user data, error detection and correction, and control information. For CD-ROM, a block is 1/75 of a second in length and contains 2352 bytes.

Blue Book
The CD-Extra - Enhanced CD protocol for recording data and audio in the same disc using CD-ROM XA sector structure for graphics and data.

Byte
A byte is eight bits grouped together.

CD-DA
Compact Disc Digital Audio. An audio-only format which is sampled at 44.1Khz and storing each sample as a 16-bit number. It could have a maximum of 99 tracks and 74min and 30 sec.

CD-R
Compact Disc Recordable. Defined by the Orange Book, it has a recordable dye layer as well as a reflective layer. Once written to, information can not be changed or altered. Also referred to as "one-off", or CD Write Once (CD-WO).

CD-ROM
Compact Disc Read Only Memory. Used to store computer data (text and graphics). It has additional error detection and correction per the Yellow Book.

CD-ROM XA
CD-ROM Extended Architecture. An extension to the Yellow Book, this format is used for computer data, compressed audio, graphics and video. It does not contain additional EDC (Error Detection Code) and ECC (Error Correction Code), therefore giving the user an additional 13% percent more data than the Yellow Book - Mode 1 format.

CIRC
Cross Interleaved Reed-Solomon Code. The error detection and correction code used within CD-Audio (at the frame level), and CD-ROM. CIRC has two levels of error correction known as C1 (meant to correct small errors), and C2 (which corrects larger errors and burst errors).

Data Transfer Rate
The speed at which data can be read from a CD-ROM drive. The first transfer rate was 150kilobytes per second. Manufacturers are now making drives that transfer data as high as 32x (32 times 150kbps).

Digital Audio
Red Book specifies CD-Digital Audio as being sampled at 44.1KHz, 44,100 samples per second. Analog audio signals are converted into digital samples, with each sample being assigned a value in a range of 65,536 possible values (16 bits).

DLT
Digital Linear Tape. Replicator's preferred source media for DVD projects, generally with a capacity between 10 and 40 gigabytes.

ECC
Error Correction Code. Contained in every CD-ROM sector, it is 276 bytes, used to correct data errors within a data block.

EDC
Error Detection Code. Contained in every CD-ROM sector, it is 4 bytes, which provides a method of determining errors that occur within a data block.

EFM
Eight to Fourteen Modulation. An encoding technique used to convert 8 bits of digital data to 14 bits. The CD player performs EFM demodulation.

Electroforming
The process of creating a metal master (called a father), by electroplating nickel onto a glass master until a sheet of nickel has been chemically grown to a usable thickness. After the "father" is made, the process is repeated to grow "mothers". Often, "sons" or "stampers" will be made to place in the injection molding machines for replication.

Father
The "father" or "metal master" is the first part created in the electroforming process when the nickel coating is removed from the glass master. The father is the opposite or inverted image of the glass master.

Frame
also referred to as a sector or block. It contains sync, header, user data, error detection and correction, and control information. For CD-ROM, a block is 1/75 of a second in length and contains 2352 bytes. In video, it is 1/30 of a second (NTSC Standard).

Glass Master
A glass disc which is cleaned and polished, and a layer of photoresist is applied. The photoresist is spin coated and baked onto the glass. A Laser Beam Recorder (LBR) is used to transfer data from the source material onto the glass master.

Green Book
The book that defines the specification for CD- I (Compact Disc Interactive).

HFS
Hierarchical File System. The directory structure used for the Macintosh computer.

Hub
The center hole of the disc also referred to as the clamping area and/or stacking ring.

Image File
In CD-ROM, it is a single file that has been pre-mastered and contains a bit for bit copy of the contents of a disc, usually in the ISO 9660 logical file format.

Index
Normally used in audio tracks, they are searchable points within a given track. A maximum of 99 indexes can be used within a track.

Injection Molding
In CD replication, it is the process where molten plastic (polycarbonate) is injected into the cavity of a mold under pressure, cooled and then removed as a solid clear plastic replicated disc.

ISO 9660
International Standards Organization. ISO 9660 is a standard, which describes the file structure for placing computer files on a compact disc. The original standard was named High Sierra.

Jewel Case
this is the plastic storage or shipping case used to place CD's. There are many different types used in the advertising, marketing and promotion of CD-ROM products.

Jitter
is a time-based error in regards to the transition from pit to land on a CD. Jitter should be less than 35 nanoseconds for each individual pit and land, and is measured in relation to a known reference disc.

Lands
On a CD, it is the flat areas that separate "pits".

Laser
Light Amplification by Stimulated Emission of Radiation - Optical discs are read by lasers in the optical pickup of CD players.

Lead In
On a CD, it is the area preceding the track one, and contains the TOC (Table Of Contents). The Lead-In area precedes each program area on multi-session disc(s) as well.

Lead Out
On a CD, it is the area after the last track on the disc and can be used to store information to instruct the player to stop playing or go to the beginning of track one.

Mastering
The process which involves transferring data onto a glass master using a LBR (Laser Beam Recorder), and is the first step in the CD manufacturing process.

Micron
One thousandth of a millimeter or one millionth of a meter. On a CD, the track pitch is measured in microns (1.6 microns wide).

Mixed Mode
A CD that has a data track as track one, followed by 1 to 98 audio tracks.

Mother
The name given to the metal part electroformed (grown chemically) from the father in the electroforming process. Typically, multiple stampers are grown from the mother; to be placed in injection molding machines for replication.

NTSC
National Television Standards Committee. The committee that developed the color television standard for North America, Japan, Taiwan and others (30 frames a second).

Orange Book
The book that defines the standard for the recordable compact disc. It currently has three parts: Part 1, Magneto-Optical (CD-MO), Part 2, Write Once (CD-WO) and Part 3, Rewritable (CD-RW).

PCM
Pulse Code Modulation. A modulation code in which analog audio is sampled at 44.1KHz into a digital format.

Phase Change Technology
uses media that when it is changed from a crystalline state (which reflects light), to an amorphous or noncystalline state (which absorbs light) and vice versa, an optical laser can interpret the variances of reflectivity and encode data.

Photoresist
a substance which is applied and cured onto a glass substrate. When photoresist is exposed to a laser, its physical state changes, thus, creating a pattern of pits.

Pits
Pits are microscopic bumps that contain data, which are molded into the disc in a spiral track beginning at the inside of the disc.

Polycarbonate
The transparent plastic material used to form the substrate for compact discs.

Pre-Gap/Post-Gap
Pre-Gap is the area before the beginning of each track, postgap is the area after the end of each track, consisting of a stream of zeros for 2 seconds.

PQ Subcodes
The P subcode or channel designates the start of a track and the lead-in and lead-out areas of the disc. The Q subcode or channel contains control, address, Qdata, and an error detection code. PQ subcodes must be inserted into the source data.

Premastering
The process of preparing digital data to send to a manufacturer, such as Future Media Productions for mastering and replication. Specialized software and hardware are used to create an image file mirroring what the CD will contain, including the file structure (such as ISO 9660).

Program Area
Refers to the area where the user files are stored. The program area is between the lead-in and the lead-out, with each sector being numbered by time code.

Red Book
The CD-Audio protocol for recording audio onto compact discs is known as the Red Book.

Reflectivity
It is the variations of reflection from the reflective layer at different parts of a disc. Multi-read drives are being manufactured to be able to read different types of media because of variances in reflectivity in CD-RW, CD-R and the like.

Sector
also referred to as a frame or block. It contains sync, header, user data, error detection and correction, and control information. For CD-ROM, a block is 1/75 of a second in length and contains 2352 bytes.

SMPTE time log
A log showing the start, stop, and duration of each track based on the SMPTE time code included during the premastering phase. SMPTE stands for Society of Motion Picture and Television Engineers and is a time code widely used in the motion picture, television, and audio production industries. Full time code is in the format of hours: minutes: seconds: frames.

Stamper
A metal part electroformed from the mother. The stamper is then placed in a mold cavity for the replication of discs.

Substrate
The transparent polycarbonate layer of a CD. After being cooled (coming out of the injection molding machines) it is metalized, lacquer is dispensed across the disc, then labeled.

TOC
Table Of Contents. The table of contents provides critical information such as the number of tracks, their starting locations, and the total length of the data area of a disc.

Track
For audio, it is each recorded song. For data, there is only 1 track that starts in the center of the disc in a spiral rotation. A maximum of 99 tracks can be on a disc. The mixed-mode format contains 1 data track, and at least 1 audio track on the same disc.

UDF
Universal Disc Format. The file format promoted by the Optical Storage Technology Association. The format was developed for high-density read-only, recordable and rewritable discs and is cross-platform compatible. DVD will use this format similar to ISO9660 for compact discs.

Volume Descriptor
The area at the beginning of a CD reserved for the recording information about the origin, publisher, copyright etc.

White Book
The book that defines the specifications for Video CD.

Yellow Book
The book that defines the standard for Compact Disc Read Only Memory (CD-ROM).
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