Glossary of terms
Please use the index in the left-hand collum to navigate through this extensive glossary.
A
A-characters
The character set used in the file naming convention
for ISO 9660 (Standard CD-ROM and CD-Digital Audio
format). It consists of capital A to Z, digits 0
to 9, and various symbols.
ANSI
American National Standards Institute. Publishes industry
standards for a wide range of technologies.
Asynchronous Data Transfer
A method of SCSI data transfer. This is the type of
transfer rate originally introduced with SCSI 1. With
this type of transfer method, transfer rates of 2 Mbytes/sec
are common. Asynchronous is faster on short cables,
while synchronous is faster on long cables.
Authoring
What you do to create an application that may eventually
be stored on CD. For example, if you wish to create
a multimedia game or CD presentation, you will
need CD-Rom Authoring software that allows you to combine
sound,
graphics,
and text, and provides some user interactivity. When
you have finished creating your application with authoring
software, you can use CD recording software such as
Easy CD Creator or Adaptec Toast to write it to CD.
Auto-Insert Notification
A feature of Windows 95 and Windows NT that causes
an audio CD to be played or an application disc to
launch an application (for some discs) as soon as the
disc is mounted in a CD drive. With earlier CD-R software
it was recommended that this feature be turned off,
but with Easy CD Creator and Direct CD it is preferable
to leave it on. This setting must be made for each
CD unit separately; in Windows 95 it can be made in
Control Panel - System - Device Manager - CD-ROM (your
CD-ROM drive) Settings.
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B
Barcode
A unique code for any manufactured unit. With recordable
CDs, this number is often printed in the clear inner
ring of the disc. Some CD recorders can also read
this information digitally.
Bit Depth
In color images, the number of colors used to represent
the image. Typical values are 8-, 16-, and 24-bit color,
allowing 256, 65,536 and 16,777,216 colors to be represented.
The latter is known as true color, because 16.8 million
different colors is about as many as the human eye
can distinguish.
BIOS
An acronym for Basic Input/Output System. This is usually
an EPROM (Erasable Programmable Read Only Memory) chip
with computer program instructions in it. A motherboard
BIOS (usually by companies such as Phoenix, Award and
AMI) controls the basic functions of the computer (such
as controlling the keyboard, monitor, on board controllers
etc.).
BOOK SPECIFICATIONS:
The Blue Book defines the Enhanced Music CD (also
known as CD EXTRA - the term CD Plus is not now recommended
to avoid confusion with similar formats) specification
for multisession pressed disc (ie not recordable) comprising
audio and data sessions. Enhanced Music CD discs are
intended to be played on any CD audio player, on PCs
and on future custom designed players. The current
version 1.0 was released in Jan 1996.
The Blue Book comprises of:
Disc specification and data format including the two
sessions (audio and data). The second, data session
must be a CD-ROM XA session. Directory structure (to
ISO 9660) including the directories for CD Plus information,
pictures and data. It also defines the format of the
CD Plus information files, picture file formats and
other codes and file formats. MPEG still picture data
format.
The Green Book, written originally in 1987, describes
the CD-interactive (CD-i) disc, player and operating
system and contains the following information:
- CD-I disc format (track layout, sector structure).
Data retrieval structure which is based on ISO
9660 with some additions. Audio data using ADPCM
levels A, B and C (cf CD-ROM XA) Real-time video
data which describes the disc coding of different
types of still images, the video decoder and visual
effects available.. Compact Disc Real Time Operating
System, which is the operating system used in every
CD-i player. The Green Book specifies the OS kernel,
file managers, drivers and all the system calls
available. Base case system which is a specification
of the minimum CD-i hardware configuration. Full
motion extension which defines the functions provided
by the MPEG cartridge and the software calls available
for MPEG decoding.
- The Green Book is the most comprehensive specification
of all the colored books, specifying in detail
not just the disc but the coding of data and the
architecture of the player hardware and software.
- Orange Book
The Orange Book defines CD-Recordable discs with multisession
capability. It is in three parts:
1. Part I defines
CD-MO (Magneto Optical) re-writable discs, last updated
in November 1990.
2. Part II defines CD-WO
(Write Once) discs, last updated in January 1994.
3. Part III defines
the CD-E (Erasable) disc format. The tentative version
0.8 was released in September 1995.
All three parts contain the following sections:
Disc specification for the unrecorded disc and the
recorded disc. Pre-groove modulation which is necessary
for motor control information needed during writing.
Data organization including linking to allow writing
at different times. Multisession and hybrid discs
Recommendations for measurement of reflectivity, optimum
power control, environment, light fastness, push pull
magnitude, measurement of groove wobble amplitude,
wavelength dependency, jitter, use of pre-gap, serial
copy management and others.
The Red Book describes the physical properties of
the compact disc and the encoding of the digital audio
data. It comprises the following information:
Audio specification for 16-bit PCM Disc specification,
including physical parameters Optical stylus and parameters
including laser wavelength, numerical aperture, pit
sizes and track pitch. Deviations and block error rate.
Modulation system and error correction. Control and
display system (ie subcode channels)
A more recent addition to the Red Book describes the
CD graphics option using the subcode channels R to
W. This describes the various applications of these
subcode channels including graphics and MIDI, both
of which can be used for Karaoke applications.
The White Book defines the Video CD specification.
First published in 1993, there have been several versions:
- version 1.0: Karaoke CD specification, MPEG-1
data in tracks
- version 1.1: Video CD: as 1.0 but chapter marks
and multi-volume album facilities added
- version 2.0: Video CD: addition of stills, generic
menus, playlists, closed caption text.
- The White Book (version 2.0) comprises:
- Disc format including use of tracks, Video
CD information area, segment play item area,
audio/video tracks and CD-DA tracks. Data Retrieval
Structure, compatible with ISO 9660. MPEG audio/video
track encoding including image sizes allowed,
video/audio bit rate, sector interleaving and
examples of MPEG packets. Segment play item encoding
for video sequences, video stills and CD-DA tracks.
Play sequence descriptor to allow the playback
of preprogrammed sequences. User data fields
for scan data (enabling fast forward/reverse)
and closed captions. Examples of play sequences
and playback control.
- Yellow Book
The Yellow Book was written in 1984 to describe the
extension of CD to store computer data, ie CD-ROM.
This specification comprises the following content:
Disc specification which is a copy of part of the
Red Book. Optical stylus parameters (from Red Book)
Modulation and error correction (from Red Book) Control & display
system (from Red Book) Digital data structure, which
describes the sector structure and the ECC and EDC
for a CD-ROM disc.
As a separate extension to the Yellow Book, the CD-ROM
XA specification comprises the following:
- Disc format including Q channel and sector structure
using Mode 2 sectors. Data retrieval structure
based on ISO 9660 including file interleaving which
is not available for Mode 1 data. Audio encoding
using ADPCM levels B and C. Video image encoding
(ie stills)
Bootable
A CD (or floppy, hard disk, or other storage media)
from which a computer can be started up, because it
contains all the operating system software the computer
needs to run. A bootable CD contains a bootable image,
a file that is an exact representation of a floppy
or hard drive. Bootable CDs are usually made according
to the El Torito standard.
BUS
A pathway for data in a computer system. All PCs have
an expansion bus, which is designed to host add-on
(expansion) devices, such as modems, adapter boards
and video adapters. Expansion devices use the bus to
send data to and receive data from the PC's CPU or
memory. ISA (Industry Standard Architecture), EISA
(Enhanced ISA) and PCI (Peripheral Component Interconnect)
are the major bus standards used in PC's.
BUS Mastering
A high performance method of data transfer in which
the host adapter's on-board processor handles the transfer
of data directly to and from a computer's memory without
intervention from the computer's microprocessor. This
is the fastest method of data transfer available for
multitasking operating systems.
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C
Cache
A portion of RAM used for temporary storage of
data that must be accessed very quickly. In applications
that run from CD-ROMs, the cache is typically used
to store directory files.
Caching
This is a process by which data requested by the
operating system of a computer is retrieved from RAM
instead of from a hard disk (or some other mass storage
media). Caching algorithms will check if the requested
data is in its 'cache' (or RAM). RAM access is an order
of magnitude faster than today's mass storage devices,
so the more accesses to the cache, the faster overall
system performance will be. Cache can be on a host
adapter, on the motherboard (controlled by the operating
system), and on any number of devices.
Caddy
The plastic and metal carrier into which a CD must
be inserted before it is loaded into some CD-ROM drives
or CD recorders (others have trays that slide in and
out to receive the disc and do not need caddies).
CD Bridge or CD-I Bridge
A set of specifications defining a way of recording
CD-I information on a CD-ROM XA disc. Used for Photo
CD and Video CD.
CD-Compatible
CD-R discs written that can be read in either a
CD-DA player or in a CD-ROM reader.
CD Extra or CD Plus
A multi-session disc containing a number of audio
tracks in the first session, and one CD-ROM XA data
track in the second session. Additional characteristics
are defined in the Blue Book standard. This is an alternative
to mixed-mode for combining standard CD-DA audio (which
can be played in a normal audio player), and a computer
application, on a single disc.
CD+G
(AKA karaoke) A special disc format in which simple
graphics and text are stored in the subchannels of
an audio disc, but you need a special player to read
and display this information. The data in the subchannels
cannot be copied with most current systems or software.
CD-DA
Compact Disc-Digital Audio. Jointly developed by
Philips and Sony and launched in the U.S. in October,
1982, CD-DA was the first incarnation of the compact
disc, used to digitally record and play back music
at unprecedented quality. The standard under which
CD-DA discs are recorded is known as the Red Book Standard.
CD-I
A compact disc format developed by Philips, designed
to allow interactive multimedia applications to be
played through a computer/disc player attached to a
television. Especially good for real-time animation,
video, and sound, the CD-I standard is called the Green
Book
CD-R
Compact disc-recordable. Same as CD-WO when referring
to recordable discs (media), often used to refer to
write-once discs, in contrast to CD-RW, or Compact
Disc Re-Writable.
CD-ROM
Compact Disc-Read Only Memory. A standard for compact
disc to be used as a digital memory medium for personal
computers. The specifications for CD-ROM were first
defined in the Yellow Book.
CD-ROM XA
"XA" stands for Extended Architecture.
CD-ROM XA is an extension of the Yellow Book standard,
generally consistent with the ISO 9660 logical format
but designed to add better audio and video capabilities
(taken from the CD-I standard) so that CD-ROM could
more easily be used for multimedia applications. CD-ROM
XA was abandoned as an independent multimedia format.
CD-ROM XA is also the physical format for Photo CD
discs.
CD-RW
CD recordable media that can be erased and re-recorded
up to 1000 times. CD-RW media can only be written in
a CD-RW recorder, not in a normal CD recorder, though
a CD-RW recorder can also record standard CD-R discs.
CD-Text
An audio CD format in which up to 5000 characters
of disc information (title, artist, song titles, etc.)
is written into the disc Table of Contents. This information
is displayed when the disc is played back on CD Text-enabled
audio players.
CIRC
Cross-Interleaved Reed-Solomon Code. The first
level of error correction used in every compact disc,
and the only one used for audio CDs.
Close Disc
To "close" a recordable disc so that
no further data can be written to it. This is done
when the last session's lead-in is written. The next
writeable address on the disc is not recorded
in that lead-in, so the CD recorder in subsequent attempts
to write has no way of knowing where to begin writing.
Note: It is NOT necessary to close a disc in order
to read it in a normal CD-ROM drive. Easy CD Audio
because it is single session, Red Book, it automatically
closes the disc, there is the option to close the session
and leave the disc open for adding more session. Note
only mutilsession CD Devices can read the add-on sessions.
Almost all standard audio players cannot.
Close Session
When a session is closed, information about its
contents is written into the disc's Table of Contents,
and a lead-in and lead-out are written to prepare the
disc for any subsequent sessions.
Compilation list
A list of audio files which are to be recorded
to a CD in Red Book format. This is the same as a cue
sheet.
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D
d-characters
The character set used in ISO 9660 Level 1 filenames,
if the standard is strictly adhered to (which is not
always necessary). Consists of capital A to Z, digits
0 to 9, and the underscore symbol ( _ ).
DAT
Digital Audio Tape.
Digital Audio Extraction
The process of copying CD-DA audio tracks digitally,
from your CD recorder or another CD-ROM drive, to hard
disk or to recordable CD. Not all CD-ROM drives
support this!
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.
Contrast with Track-at-Once. Not all CD recorders support
Disc-at-Once.
This writing mode is especially useful for creating
a master disc that you will send off to a replicator
for mass production. In Disc-at-Once mode, the whole
disc - Lead-in, Data, and Lead-out areas are written
starting from the beginning of the disc to the end
of the disc without ever turning off the recording
laser. With Track-at-Once and Track Multi-session,
the data area is written first, then the Lead-out area,
then the Lead-in area; each time turning off the recording
laser to jump to the next area. Each time the recording
laser is turned off and on, link blocks are created
on the disc. These link blocks "link" tracks
with the Lead-in and Lead-out areas. However, these
link blocks are interpreted as "uncorrectable
errors" on most mastering systems at the replication
plant. Writing in Disc-at-Once mode eliminates the
link blocks because the recording laser never turns
off. Disc-at-Once requires the pre-mastering software
to send a "cue sheet" to the CD-R drive that
describes the disc layout. From there, the CD-R drive
accepts the data and begins writing the Lead-in with
the Table of Contents (TOC), the actual data, and the
Lead-out in that order, without interruption. Disc-at-Once
creates a single session disc only.
Disc Image
A single large file that is an exact representation
of the whole set of data and programs as it will appear
on a CD, in terms of both content and logical format.
This may be an ISO 9660 image (adhering strictly to
the ISO 9660 standard), or some proprietary format
such as the .cif format used by Easy CD Creator.
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E
ECC
Error Correction Code. A system of scrambling data
and recording redundant data onto disc as it is recorded.
During playback, this redundant information helps
to detect and correct errors that may arise during
data transmission.
EPS
A graphic file format specifically used to transfer
PostScript based data within compatible applications.
Usually created by drawing tools such as Adobe Illustrator,
an artist can transport curves, paths, spot colors
and graphics into PageMaker or QuarkXpress.
In Illustrator
you would use File > Save As > EPS.
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F
File System
A data structure that translates the physical (sector)
view of a disc into a logical (files, directories)
structure, which helps both computers and users locate
files. In other words, it records where files and
directories are located on the disc. Reference Logical
Format.
Frame
A single, complete picture in a video or film. A video
frame is made up of two interlaced fields of either
525 lines (NTSC) or 625 lines (PAL). Full-motion video
for NTSC runs at 30 frames per second (fps); for PAL,
25 fps. Film runs at 24 fps.
Free space
The amount of unused space available on a hard disk
or other device. It is important to have enough free
space when doing CD recording.
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G
Gap
The gap (more correctly called a pause) is a space
dividing tracks. In some situations a gap is required
by the standards (Red Book and other "color" books).
For example, if you have data and audio tracks within
the same session, they must be separated by a gap.
Also, there must be a gap of 2 to 3 seconds preceding
the first track on a disc.
The gap which "belongs" to a track is actually
the gap before it, not the one after it. This is why
on some audio CD players you will see a countdown (-02,
-01, etc.) before a track begins. It is counting down
to the next track, not counting up from the end of
the last one.
Green Book
The Philips/Sony specification for CD-I.
Gold Disc (CD-R Media not Gold ROM's)
The recordable disc used in recordable CD systems.
The blank disc is made of a bottom layer of polycarbonate,
with a preformed track spiral that the recording laser
follows when inscribing information onto the disc.
This type of disc is therefore also called pre-grooved.
A translucent layer of recordable material is laid
on top of the polycarbonate, then a reflective layer
of gold. On top, there are thin layers of lacquer and
label.
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H
HFS
The file system used by the Macintosh operating system
to organize data on hard and floppy disks. Can also
be used for CD-ROMs.
Hybrid
Under the Orange Book standard for recordable CD, hybrid
means a recordable disc on which one or more sessions
are already recorded, but the disc is not closed, leaving
space open for future recording. However, in popular
use the term "hybrid" often refers to a disc
containing both DOS/Windows and Macintosh software,
which on a DOS/Windows platform is seen as a normal
ISO 9660 disc, while on a Mac it appears as an HFS
disc.
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I
Image Pac
In Photo CD, a set of five versions of the same image,
at varying resolutions
Incremental (packet) Writing
This is also referred to a just "Incremental Writing".
This is a writing mode that is just a little ahead
of its time. The concept behind Incremental Writing
is simple: make the CD-R drive act like a hard disk
or other storage device; able to write as little as
a file at a time to the CD-R disc. While simple in
concept, implementation has been more difficult. ISO9660,
the current file system for CD-ROM, is not really appropriate
for a disc written incrementally, because the indexing
system (path tables) for ISO9660 depend on knowing
about all the files that are to be recorded on the
disc. Without this knowledge, the ISO9660 file system
will have a very difficult time retrieving a file.
With current multi-session writing, each time a session
is written, the whole file system (or Table of Contents)
must be re-written. A new file system has emerged called
ECMA 168. ECMA 168 builds on the ISO9660 file systems
and adds the flexibility to add data to a disc "a
file at a time", without having to re-write the
file system each time. The key drawback is that an
incremental disc cannot be read back on today's CD-ROM
drives without a special driver. Direct CD uses a variation
on this
Indexes
Indexes provide additional starting points within a
single audio track. Not all audio CD players support
indexes. Index markers are written into the Q subchannel
and are incremented by 1 sequentially during the track.
ISO 9660 Format
An international standard specifying the logical format
for files and directories on a CD-ROM or CD-ROM image.
format. Some other common logical formats such as Joliet
(for Windows) and Rock Ridge are extensions of ISO
9660.
ISO 9660 Interchange Levels
These are three methods of recording and naming files
on disc under the ISO 9660 standard. There are three
nested, downward-compatible Levels.
In Level 1 (the lowest common denominator, developed
with DOS file naming limitations in mind):
- Each file must be written on disc as a single,
continuous stream of bytes -- files may not be
fragmented or interleaved.
- A filename may not contain more than eight d-characters.
- A Filename Extension may not contain more than
three d-characters.
- A directory name may not contain more than eight
d-characters.
In Level 2, again, each file must be written on disc
as a single, continuous stream of bytes, but there
are no restrictions on filenames.
In Level 3 there are no restrictions. This allows for
writing files in multiple extents, so it is used for
packet writing (i.e.- using Direct CD to write the
disc).
ISRC
International Standard Recording Code. Some recorders
allow the ISRC to be recorded for each audio track
on a disc. The code is made up of: Country Code (2
ASCII characters), Owner Code (3 ASCII characters),
Year of Recording (2 digits), Serial Number (5 digits).
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J
Jewel Case
The hinged plastic case in which most CDs are often
stored.
Jewel Case Sleeve (commonly known as "booklet")
The pieces of paper which can be inserted into the
jewel case to help identify the contents of the CD
stored in the case. The sleeve on the front is called
the booklet, the sleeve in the back is the bottomcard
Joliet
Joliet is an extension of the ISO 9660 standard, developed
by Microsoft to allow CDs to be recorded using long
filenames, and using the Unicode international character
set. Joliet allows you to use filenames up to 64 characters
in length, including spaces.
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L
Lead-In
An area at the beginning of each session on a recordable
compact disc which is left blank for the session's
Table of Contents(track numbers and start points).
The lead-in is written when a session is closed,
and takes up 4500 sectors on disc (1 minute, or roughly
9 megabytes). The lead-in also contains the next
writeable address on the disc, (indicates whether
the disc is MultiSession) so that future sessions
can be added (unless the disc is closed).
Lead-Out
An area at the end of a session which indicates that
the end of the data has been reached, there is no actual
data written in the lead-out. 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).
Linked Multisession
A disc containing more than one session, in which all
(or selected) data from the various sessions can be
seen as if it had all been recorded in a single session.
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M
Mastering
Technically, refers to the process of creating a glass
master from which compact discs will be reproduced
in quantity. In desktop recordable CD systems, mastering
is done together with pre-mastering by the desktop
CD recorder, and the term is generally used to mean "recording."
Mixed-Mode Disc
A compact disc including both computer data and CD-DA
tracks. The data is all contained in Track 1, and the
audio in one or more following tracks.
MMC (Multi Media Command)
A standard command set used by some CD recorders. Many
newer recorders follow this standard, though many of
them also interpret it differently (so there are still
differences in how software must address these recorders,
despite the standard).
Mode
There are two recording modes for compact discs. In
Mode 1, used with CD-ROM applications, 288 bytes of
each sector are used for storing error correction code,
and the remaining 2048 bytes per sector are available
for user data. Mode 2, used in CD-I and CD-ROM XA,
has two forms: Form 1 is similar to Mode 1, as it is
also used to record data that requires error correction;
Form 2 is used for recording information such as sound
or images which do not require such extreme precision.
Since less error correction is needed, more bytes in
the sector can be freed for information storage, resulting
in a data area of 2336 bytes per sector.
Mode 1
A somewhat inaccurate way of referring to the CD-ROM
physical format.
Mode 2
A not-quite-accurate but common way of referring to
the CD-ROM XA physical format.
Mount
To install a compact disc so that the computer recognizes
its presence and can read data from it.
MP3
MP3 is a scheme for compressing audio. MP3 files do
not maintain the quality of audio CD tracks, and cannot
be recorded directly to CD as standard audio tracks.
They can be recorded as data tracks and played back
via your computer using appropriate player software.
MPEG
Motion Picture Experts Group, whose name has been applied
to the standards (MPEG 1 and MPEG 2) promulgated by
the group for compression of full-motion video.
MSCDEX
Microsoft DOS extensions for CD-ROM. Allows the DOS
and Windows 3.x operating systems to recognize a CD-ROM
disc. Version 2.23 or higher is required.
MultiRead
An OSTA standard for CD-ROM and DVD-ROM drives. Drives
which follow the MultiRead standard can read commercial
CDs (audio and data), CD-R discs, and CD-RW discs.
They can also read discs written in fixed- or variable-length
packets. For more information, see MultiRead Specification
from OSTA. Note: Drives containing the MultiRead logo
that have been issued by Hewlett-Packard have been
tested for compliance with the MultiRead specification.
Drives labeled as "multi-read" (without the
logo) probably have not been tested for compliance
with the specification, and may not be able to read
CD-RW or packet-written discs.
Multisession
The Orange Book specification which allows more than
a single session to be recorded or read on a CD-ROM
or CD-ROM XA disc. A method of adding data incrementally
to a CD in more than one recording session. If data
is linked between sessions, all data on a multisession
disc, when read on a multisession CD-ROM drive, may
be seen as part of a single logical structure. Multisession
is very different from packet writing.
MultiTrack
The ability to record more than a single track on a
disc. Track numbers are from 1 to 99. They continue
to increment across session boundaries. For example,
if session 1 used tracks 1 to 4, session 2 would start
at track 5. Track numbers may start at any value, but
must be incremented sequentially on the disc.
Multivolume
A disc containing multiple sessions which are not linked
together, so that each "volume" on the disc
must be read as if it were a separate disc. You can
read different sessions on a disc using the Session
Selector in Easy CD Creator Deluxe.
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O
On the Fly
To write on the fly means to write directly from source
data to CD data without first writing a disc image
Same as Write Direct.
Optimum Power Calibration Area
(OPC Area) A special area near the center of the recordable
disc. Before writing a track on a disc, the CD recorder
must adjust the amount of power applied to the writing
laser to an optimum level for each individual disc.
The optimum calibration area is reserved for this purpose.
Orange Book
The Philips/Sony specification for Compact Disc Magneto-Optical
(CD-MO) and Write-Once (CD-WO) systems. It includes
the specification for the Hybrid Disc technology on
which Photo CD is based. In other words, the standard
by which recordable CDs are recorded.
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P
Packet Writing
A method of writing data on a CD in small increments
(contrast with Track-at-Once and Disc-at-Once). Packets
can be of fixed or variable length. Adaptec's Direct
CD software supports packet writing on CD recorders
which also support it -- not all CD recorders do;
check the manufacturer's specs and the Direct CD
recorders support list.
PCA
Power Calibration Area. A space reserved at the beginning
of the disc for calibrating the laser to record to
that disc. Reference OPC
Photo CD
A compact disc format based on the CD-ROM XA, Orange
Book and CD-I Bridge specification.
Physical Format
The physical format of a compact disc determines how
data is recorded in each sector. The various physical
formats are defined by the color book standards (Red
Book, Yellow Book, etc.)
PMA
(Program Memory Area) On a recordable disc, an area
which "temporarily" contains the Table of
Contents information when tracks are written in a session
which is not yet closed. When the session is closed,
this same information is written in the session lead-in.
Post-Gap
A space dividing tracks, recorded within the track
data area at its end. The post- gap is 150 sectors
(2 seconds) long and is required only where successive
tracks are of different types. However, because many
disc replicators expect a post-gap at the end of every
track and may erroneously strip out data sectors if
they do not find one, Adaptec software recording in
Track-at-Once mode (default) records a post-gap after
every track.
Pre-Gap
A space dividing tracks, recorded before the track
data area. The length of the pre-gap varies with the
CD recorder and the types of tracks. Where successive
tracks are both of data, one track is separated from
another by a track pre-gap of 150 sectors (2 seconds).
Where successive tracks are of different types, the
pre-gap is usually of 225 sectors (or three seconds).
If two successive tracks are audio, there may be no
pre-gap at all.
Pre-mastering
The technical process of preparing data to be recorded
(mastered) onto a compact disc. This includes dividing
the data into sectors (logical blocks) and recording
those sectors with the appropriate header (address)
and error correction information. In the case of recordable
CD systems, premastering and mastering are done in
one operation, resulting in a ready-to-read compact
disc.
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R
Random Erase
(Available with CD-RW discs and Direct CD 2.0). The
ability to erase a single file at a time from a CD-ReWritable
disc, freeing up disc space for immediate re-use,
just as you would do on a hard or floppy disk.
Recordable Disc
The media used in recordable CD systems. The blank
disc is made of a bottom layer of polycarbonate, with
a preformed track spiral which the recording laser
follows when inscribing information onto the disc.
A translucent layer of recordable material is laid
on top of the polycarbonate, then a reflective layer
(gold or silver colored). On top there is a thin layer
of lacquer and sometimes a printed label. The standard
recordable disc is "write-once" -- it cannot
be erased or re-used. For erasable discs, see CD-RW.
Red Book
The Philips/Sony specification for audio (CD-DA) compact
discs.
Replication
Making multiple copies of a compact
disc.
Resolution
Fineness of detail. In computer monitors it is measured
in pixels horizontal x vertical (usually) or in pixels
per inch.
Rock Ridge
An extension of the ISO 9660 file system designed to
support UNIX file system information (such as longer
filenames and deeper directory structures).
Run-In/Run-Out Blocks
Blocks of data written before and after a packet or
a track, to allow the recorder to synchronize with
the data on disc, and to finish up interleaved data.
Four run-in blocks and two run-out blocks are written
for each packet.
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S
SCSI
Small Computer System Interface. An interface that
allows up to seven peripheral devices to be linked
(daisy-chained) to a single controller. By contrast,
IDE allows two devices.
Sector
The smallest recordable unit on a CD. A disc can contain
[(75 sectors per second) x (60 seconds per minute)
x (number of minutes on disc)] sectors. The amount
of data contained in the sector depends on what physical
format it is recorded in; for "regular" CD-ROM
(Mode 1) data, you can fit 2048 bytes (2 kilobytes)
of data into a sector.
Sequential Erase
(Available with CD-RW discs.) Erasing the entire disc
so that it can be re-used.
Session
As defined in the Orange Book, a recorded segment of
a compact disc that may contain one or more tracks
of any type (data or audio). In data recording, there
is usually only one track per session. In audio recording,
all audio tracks are contained in a single session.
A lead-in and lead-out are recorded for every session
on a disc.
Session-at-Once
Session-at-Once is a subset of Disc-at-Once, used for
CD Extra. In Session-at-Once recording, a first session
containing multiple audio tracks is recorded in a single
pass, then the laser is turned off, but the disc is
not closed. Then a second (data) session is written
and closed.
SIF (Standard Input Format)
A format for compressed video specified by the MPEG
committee, with resolutions of 352 (horizontal) x 240
(vertical) x 29.97 (fps) for NTSC and 352 (horizontal)
x 288 (vertical) x 25.00 (fps) for PAL. SIF-resolution
video provides an image quality similar to VHS tape.
Silver Disc (Stamped)
A disc that is mastered by a stamping process. It is
read-only and cannot be modified.
Single Session
The smallest collection of information that can be
read by a CD-ROM compatible device. It contains the
ISO 9960 file structure and files. A single session
can contain a single track or multiple tracks. Contrast
MultiSession and MultiTrack.
Spindown
Many new CD-ROM drives save power by spinning down
(stopping the drive's spin) when the drive is not in
use. This may cause buffer underruns when recording
a CD by copying tracks or files from another CD-ROM
drive, if the drive "goes to sleep" and cannot
be woken up quickly enough to keep up with the CD recorder's
demand for a constant stream of data.
Subchannels (or subcodes)
Audio CDs have 8 subchannels 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 alongside the audio, 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 subchannels, 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 Q channel contains
the index markers. In the pause (gap) before a track
begins, the index marker is set to 0 (zero). When a
track begins, the index marker changes to 1. (If a
track contains subindexes, these are incremented by
1 sequentially during the track. In this case the Q
channel might contain 1, 2, 3, 4, etc.) When the track
ends, the Q channel index marker goes back to 0, then
re-starts at 1 when the next track begins.
Synchronous Transfer
A method of SCSI data transfer. With this type of data
transfer, the SCSI host adapter and the SCSI device
agree to a transfer rate that both support (this is
known as synchronous negotiation). With this type of
data transfer method, transfer rates of 5 Mbytes/sec
or 10 Mbytes/sec (for FAST SCSI) are common.
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T
Termination
A physical requirement of the SCSI bus. The first and
last devices on the SCSI bus must have terminating
resistors installed, and the devices in the middle
of the bus must have terminating resistors removed.
The Single Ended electrical class depends on very tight
termination tolerances, but the passive 132-ohm termination
defined in 1986 is mismatched with the cable impedance
(typically below 100 ohms). Although not a problem
at low speeds when only a few devices are connected,
signal reflections can cause errors when transfer rates
increase and/or more devices are added. In SCSI-2,
an active terminator has been defined which lowers
termination to 110 ohms and is a major boost to system
integrity.
TOC (Table of Contents )
For a whole disc or any session within a disc, shows
the number of tracks, their starting locations, and
the total length of the data area. The TOC does NOT
show the length of each track, only it's starting point.
Track
Every time you write to CD, you will create at least
one track, which is preceded by a gap. Any session
may contain one or more tracks, and the tracks within
a session may be of the same or of different types
(for example, a mixed-mode disc contains data and audio
tracks). Using the Cue Sheet you can record more than
one track in a single writing. Packet Recording is
the only smaller unit recording.
Track-at-Once
A method of writing data to disc. 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 blocks are written when the
laser is turned on and off.
Track Multi-Session
This write mode is very similar to Track at Once. In
the Multi-session environment, each "session" must
contain at least one track. Again, the size of the
track must be at least 300 blocks. Track Multi-session,
as you have probably guessed, allows you to incrementally
add tracks to a disc. (Not to be confused with Incremental
Writing) Each session will take up about 13.5Mb of
disc space in overhead; what is called Lead-in and
Lead-out areas. So it does not make sense to record
small amounts of data (less than 50Mb), because each
time a write is performed, 13.5Mb of capacity on the
disc is lost. Since the disc can only be written to
99 times, this is important to factor).
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U
UDF
Universal Disc Format. A file system endorsed by OSTA
(the Optical Storage Technology Association) for
use with packet writing and other recordable optical
disc technologies, such as DVD.
UPC
Universal Product Code. With some CD recorders, you
may define a thirteen-digit UPC catalog number for
the entire disc, which will be written in the disc's
Table of Contents. Also known as EAN.
V
Video CD
A standard for displaying full motion pictures with
associated audio on CD. The video and sound are compressed
together using the MPEG 1 standard, and recorded
onto a CD Bridge disc. A Video CD disc contains one
data track recorded in CD-ROM XA Mode 2 Form 2. It
is always the first track on the disc (Track 1).
The ISO 9660 file structure and a CD-I application
program are recorded in this track, as well as the
Video CD Information Area which gives general information
about the Video CD disc. After the data track, video
is written in one or more subsequent tracks within
the same session. These tracks are also recorded
in Mode 2 Form 2. The session is closed after all
tracks have been written.
Virtual Image
A database of files to be written to CD, created by
dragging & dropping files into the main window.
Can be used to write directly to CD on the fly, or
to master a real ISO 9660 image to hard disk.
Volume
Under the ISO 9660 standard, "volume" refers
to a single CD-ROM disc. However, "volume" is
often used to mean a session on a multisession disc,
which is not linked to other sessions.
Volume Descriptors
For an ISO 9660 disc, the Volume Descriptors are a
set of optional information fields recorded at the
beginning of the data area on the disc. They were originally
designed for the needs of CD-ROM publishers. The full
set of Volume Descriptors is as follows:
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W
Write Direct
Also called on the fly. Files are written directly
to the CD disc, however the ISO 9660 structures are
temporarily written to the hard disk.
Write First to HD
Also called ISO image. Everything is written to the
hard disk first. Contrast it to Write Direct.
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Y
Yellow Book
The book that sets out the standard developed by Philips
and Sony for the physical format of compact discs
to be used for information storage (CD-ROM).
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