Index »

Compact Disc & Optical Drive Terminology

#|A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z

Use CTRL-F To Search

A

• ATIP (Absolute Time In Pregroove) - A part of the disc that specifies characteristics of the disc, for example, number of blocks and manufacturer information.

B

• Blue Book - CD Extra Standard

C

• CD+G (aka karaoke) - A special disc format in which simple graphics and text are stored in the sub channels of an audio disc. You need a special player and application to read and display this information.

• CD-DA - CD-Digital Audio. Based on the Red Book standard (1981) that specified the physical structures for the track and sectors in the disc. CD-Digital Audio was implemented to hold about 60 minutes of audio data, in up to 99 tracks (songs) at a sampling rate of 44.1 KHz and a sample size of 16 bits, to produce high quality stereo sound. This is the format of all "stamped" or commercially made music discs, and is the basis for all CD recording.

• CD Extra -  A mixed mode CD Standard, 1st is Data, 2nd is CD-DA (CD Plus) - Examples: Game CD, PlayStation CD, and Enhanced CD.
• CD-ROM/XA - Extended Architecture Standard - MODE-1: Standard Yellow Book sectors; MODE-2: May be of form-1 or form-2; FORM-1: 2048 bytes of data, with error correction, for data; FORM-2: 2324 bytes of data, no error correction, for audio/video
• CD-Text - Philips' standard for encoding artist, album and track information on audio CDs
• CD-UDF - Industry-standard incremental packet-writing file system

• Closing a Disc - Closing a recordable disc means that no further data can be written to it. This is done when the last session's lead-in is written. The beginning address of the next available recording area is not recorded in that lead-in, so the CD recorder has no way of knowing where to begin writing for any succeeding sessions. Note: It is NOT necessary to close a disc in order to read it in a normal CD-ROM drive. See Finalizing a disc.

D

• DAE (Digital Audio Extraction) - Digial Audio Extraction, also known as DAE or 'ripping', is a method of taking the digital data stream, or Red Book track, directly off an audio CD and writing it to a hard disk or CD-R/RW disc.

• DAO (Disc-at-Once) - A method of writing CDs in which one or more tracks are written in a single operation and the disc is closed, without ever turning off the writing laser. See TAO (Track-at-Once).

E

• ECC (Error Correction Code) - A complicated algorithm is used to scramble and code the user data into a redundant form that is added to each sector. During playback, this redundant information is decoded and helps to detect and correct errors that may arise due to read errors, such as those caused by scratches, dust, or fingerprints on the media. A sector length is fixed by industry standards, but because errors in digital data are more critical than errors in audio data, the digital data formats use additional ECC code to insure a higher write accuracy, and contains less user data within each sector.

• EDC (Error Detection Code) - 32 bits in each sector that are used, in conjunction with the ECC, to detect errors in the sector data.

• EFM - Eight to Fourteen Modulation is used during encoding, because the 8-bit 'magnetic' Byte has to be modulated to a 14-bit 'optical' Byte. During the read process, the interface demodulates the 14- bit optical code to the 8-bit code used by the computer--and all modulation and processing remains transparent to the user.

• EIDE - An acronym for Extended Imbedded Drive Electronics. Also known as ATA (AT Attachment -From the days of the IBM AT) or ATAPI (AT Attachment Packet Interface), this is the standard interface in most computers. The first computers had proprietary controllers for hard disk control, and experienced interchangeability problems. The electronics are now imbedded on the peripheral for compatibility, and connect to a host adapter chip on the motherboard. Data transfer rates have reached 100 MB/sec with the introduction of the ATA-100 standard. Some limitations of the EIDE bus are cable length (maximum 18 inches) and the number of devices supported (maximum of two on each cable). A maximum of two buses (four devices) are supported.

F

• Finalizing a Disc - When a recording session is closed, and data will be added later, information about the session contents is written into the disc's Table of Contents, and a Lead-In, containing the address of the next available recording area, and Lead-Out are written to prepare the disc for a subsequent session.

G

• Green Book - CD-I (Compact Disc Interactive) standard

H

• Hybrid CD - Mac and PC format written on the same disc, 1st is MAC, 2nd is PC.

I

• Interleaving - Interleaving is a recording method that reduces data errors during playback. Instead of the file being written in a contiguous data stream, the data sectors are intermixed along the recording track. If a disc should have a smudge or scratch, the entire data file is generally recoverable because a smaller amount of the file data is affected.

• ISO 9660 - Issued by the International Standards Organization, its formal title is ISO 9660: Information Processing--Volume and File Structure of CD-ROM for Information Exchange (1988). This multi-platform logical structure has been the key standard for the growth and worldwide acceptance of CD-ROM as a publishing and information distribution media and, since then, as the basic format structure for other implementations of CD-ROM in the computer arena.

J

• Jitter - Deviation from the original being copied.

L

• Lead-in Area - An area at the beginning of each session that is left blank for the TOC (Table Of Contents). The lead-in also contains space where future sessions can be added, unless the session has been closed.

• Lead out - An area at the end of a session that indicates that the end of the data has been reached. The first lead-out on a disc is 6750 sectors (1.5 minutes, about 13 megabytes) long; any subsequent lead-outs are 2250 sectors (.5 minute, about 4 megabytes). Writing the lead-out closes the session. CD-ROM drives and CD audio players cannot see the data/audio in a session until the session is closed.

• Link-Block - In TAO (Track-at-once) mode or in packet writing, a Link-Block is a sector written before a packet or track, to allow the recorder to synchronize with the data on the disc, and to finish up interleaved data. Four run-in blocks (sectors) and two run-out blocks (sectors) are written for each packet, in addition to a Link-Block.

M

• Merging bits - The 14-bit optical Byte is provided three additional channel bits, known as merging bits--to eliminate transition conflicts between consecutive optical Bytes.

• Mode 2 - Block formatting used by the majority of multimedia discs. Mode 2/Form 1 is similar to Mode 1, with a user block size of 2,048 Bytes and extra error-correction to ensure a high level of data integrity. Form 2 is used for audio and video, where small errors are usually not noticeable.

• MSF - The physical address on a CD, expressed as a sector count relative to either the beginning of the medium (absolute) or to the beginning of the current track (relative). As defined by the CD standards, each (F)rame is one sector; each (S)econd is 75 Frames; each (M)inute is 60 Seconds.

O

• OPC (Optimum Power Calibration) - OPC will write data to the PCA (Power Calibration Area) at the inside of the disc, using different laser power levels, and read this data back to determine the optimum recording power. The laser power is optimized to adjust for differences in recording conditions, such as sensitivity of the dye and minor variations in disc thickness.

• Orange Book - "The Recordable Compact Disc Standard" was published by Philips in 1990. The Orange Book defined two new 12cm CD products: the Magneto-Optical (Part 1) and the Write-Once (Part 2), more commonly known as CD-R. Part 2, Write-Once (CD-WO, or CD-R), defines tracks that can be written to, but not erased or rewritten. A Write-Once drive records appropriate 12cm CDs--which involve special recording layers, pre-grooved tracks and, generally, a gold reflective layer. Part 3 covers Re-Writable (CD-RW) products.

P

• Packet Writing - The format used for "drag and drop" recording, using an application such as Roxio's Direct CD or other packet writing software. The data is written in fixed or variable size packets, using Link, Run-In, and Run-Out blocks to separate the packets.

• PCA (Power Calibration Area) - Located before the Lead-In-Area, the PCA is where the OPC test is performed to find the optimum laser power setting for the writing laser and write strategy. "Running OPC" is another technique that we use in our CD Recorders to monitor and maintain write quality throughout the recording session.

• PMA (Program Memory Area) - An area that "temporarily" contains the TOC (Table of Contents) information when tracks are written in a session, which is not yet closed. When the session is closed, the TOC (Table of Contents) is written in the session lead-in-area.

R

• Red Book - The Red Book Standard was developed to define specifications for producing audio CDs, and is the first of the book standards. The Red Book Standard contains specifications on size of the media, maximum recordable area, tracking information, etc. All subsequent books (Orange Book multisession specifications for CD-R/RW, Yellow Book for data, White book for CD-Interactive, etc.) are based on the physical specifications contained in the Red Book.

• Rock Ridge - Extensions allowing long filenames and UNIX-style symlinks

• Run-In Block - See Link Block

• Run-Out Block - See Link Block

S

• SCSI - An acronym for Small Computer System Interface. Pronounced "scuzzy", this interface was introduced as a method of connecting multiple peripherals to computers. Based on a parallel bus structure, with each device having a unique ID (or address), the SCSI bus will support up to seven devices plus the host adapter. Newer 'wide' interfaces, used almost exclusively for hard drives, can support up to 15 devices plus the host controller, and can transfer data at burst speeds of up to 320 MB/sec. Because of the multiple device support and extended cable length (up to 6 meters for SCSI-2), the higher transfer rate, and the ability to install multiple host adapters on the motherboard or in available connectors, the SCSI interface is used most often to connect external devices such as scanners, CD-ROMs, CD duplicators, and multi-drive storage enclosures, while at the same time connecting to SCSI devices internally, usually on the same adapter.

• Sector - The sector is the smallest addressable segment of a recording session. The Red Book Standard specifies the physical layout of the data in a sector. Excluding ECC and EDC, each sector is composed of 2352 bytes of data. The logical layout, or how those bytes are allocated for synchronization, data, additional error correction, etc., depends on the selected recording mode and is specified by the appropriate standard, or "book". The audio recording format, for example, uses all 2352 bytes for audio data. Mode 1 data recording, generally used for programs and data that cannot tolerate errors, uses only 2048 bytes for digital data. The remaining 304 bytes are used for sync and additional error correction.

• Session - A recorded segment of a compact disc, containing one or more data or audio tracks.

• Sub Channels (or Sub Codes) - Audio CDs have 8 sub channels of non-audio data interleaved with the audio data, called the P, Q, R, S, T, U, V, and W channels. You can think of them as small, separate streams of data running before and after the audio data sectors, and which can be read by a player at the same time as the audio, if the player is "smart" enough to interpret them. For example, CD+Graphics discs (karaoke) store rudimentary graphics and text in the sub channels, but you need a special player to read and display this information.
  
  The P and Q channels are used to tell an audio player how to play back an audio disc. The P channel indicates the start and end of each track. The Q channel contains the index markers or time codes that an audio player displays.

T

• TAO (Track-at-Once) - A method of writing CDs in which each time a track (data or audio) is completed, the recording laser is stopped, even if another track will be written immediately afterwards. Link and run in/out blocks are written when the laser is turned on and off.

• TOC (Table Of Contents) - Identifies the start position, and length of each track, on a recordable disc.

U

• UDF - The Universal Disc Format was promoted by the Optical Storage Technology Association (OSTA), as a single file system for interchange of information in the computer arena. OSTA's aim was to develop a UDF-based file format for CD-ROM, Write-Once and Re-Writable products.

W

• White Book - The White Book, produced by JVC and Philips, used the sector structure of CD-ROM-XA to produce a Video-CD ("bridge disc,' or a hybrid CD derived from the Karaoke-CD concept). Video-CDs can be played in CD-ROM-XA and CD-I drives as well. Video-CD uses interleaved full-motion MPEG video. Another implementation of the White Book is the Kodak Photo-CD.

Y

• Yellow Book - Published by Philips and Sony, the 'Yellow Book' used the Red Book as its basis for the physical specifications of sectors in a CD-ROM--designed for computer data. The Yellow Book specified two types of sector layout (Mode 1 and Mode 2), additional 'layered' error detection and correction to insure higher integrity of the contents, and much more. It also contains the standards for CD-ROM XA (extended architecture) providing higher quality for audio and video.