If you really want to know all about CD-ROM in deep
detail, we suggest that you read the book, "Publish
Yourself" on CD-ROM, by Fabrizio Caffarelli & Deirdre'
Straughan. It explains all, and more than, you ever want
to know about CD-ROM in all its incarnations, and is
published by Random House Electronic Publishing, ISBN
Number 0-679-74297-2.
First - A Quick W98 CD-ROM Fixer Tip
Many people have reported a problem with their CD-ROM
drives after installing Windows 98. Many CD-ROMS are dual
channel IDE (Integrated Device Electronics) devices.
Windows has a special setting you need to set in order to
accommodate these devices. Try this fix if you experience
the problem:
Select Start, Settings, and Control Panel; then
double-click System
Select the Device Manager tab
Double-click the Hard Disk Controllers branch to expand
it, select your IDE controller, and then select Properties
Select the Settings tab
In the Dual IDE Channel Settings box, select Both IDE
Channels Enabled, and then click OK (2 times), and restart
your computer
CD Technology and CD Writer Introduction
Standards - Physical Structure -Logical Structure - CD/R Media
Theory of Operation - Introduction
The HP Colorado SureStore CD-Writer is a 5.25" half
height form factor drive designed to be integrated
internally into the computer and used under home or
office conditions. The CD-Writer allows the write once
recording of large quantities of data (up to 650 MB) in
each of the standard CD-formats: CDROM, CD-ROM(XA),
Photo CD, CD-I, and CD-DA. The CD-Writer operations
conform to the following Optical standards: Red Book,
Yellow Book, Green Book, and Orange Book, and therefore
the recorded discs can be read in any standard CDROM,
CD-ROM(XA), Photo CD, CD-I, or CD-DA player. Book
Standards will be discussed later in more detail.
The HP SureStore CD-Writer is a multi-speed device (
4x, 2x, and 1x read; 2x and 1x write where x=150KB per
sec) that creates universally readable discs. the disc
is read and written optically in fixed length sectors
by a movable head with a diode laser. Built in error
correction ensures high data integrity.
The HP SureStore CD-Writer is able to write to CR-R
media widely available today. CD-R media typically has
two physical sizes (120mm and 80mm) along with the 2
chemical formulations (Cyanine and Pthalocyanine). The
CD-R media is purchased blank, and is WORM (Write Once
Read Many) media that allows the user to create CDs.
During the write process the player writes to a
thermally sensitive media that is affected by the high
intensity laser of the CD-Writer. Blank media is
available from various suppliers and typically has a 5
-25 year (Cyanine) warranty, however HP Colorado will
be selling and promoting a chemically superior, higher
quality media with a warranty of up to 100 years
(Pthalocyanine).
Most CD-ROM is media produced using a stamping method
to create CDROM (Compact Disc Read Only Media) discs
for entertainment or mass distribution of information.
The CD-Writer is a direct access SCSI device that
requires a SCSI adapter to communicate with the host
computer. Included in the package with the CD- Writer
is a SCSI-2 Bus-Mastering DMA controller that ensures
smooth and continuous data transfer. The SCSI
controller incorporates RISC technology and improved
micro-code firmware to reduce PCA chip count which
increases reliability and improves performance.
Application software is included which allows the user
to either view Photo CDs, or read and write Audio CDs,
Data CDs, or Archive Data CDs. Further, this unit now
has the capability to write data as a single data
stream, called a session, or write multiple sessions on
one physical disc. A session includeds lead in
information, data, and lead out information.
Introduction to Standards:
The Compact Disc has become a widely used method for
distributing large amounts of data. In its most generic
form it is used to hold Audio data, formerly called
Compact Disc Digital Audio (CDDA), that is encoded onto
the disk using a two-layered Error-Detection/Correction
scheme (C1 And C2) together with data- scrambling and
interleaving according to Red Book specifications, the
world standard to which all CDDA and Data compact discs
must comply.
Data discs however require higher data reliability,
therefore a third Error- Detection/Correction is
implemented, called Third Layer Correction or C3.
Furthermore, ease of data-retrieval must be ensured
through standard data structures.
Data Disks are described in the following Standards
books, each of them specific to an area or type of data
application:
The Red Book:
World Standard for all Compact Discs (CD-DA).
The Yellow Book:
Covers CD-ROM and CD-ROM-XA Data Formats
The Green Book:
Covers CD-I Data Formats and Operating Systems
The Orange Book Part II:
Covers CD-WO (CD-Write Once) media.
These standards apply to media, hardware, and software.
A Compact disc is classified as Red book, Yellow book,
or Green book depending on the type of information
recorded on the disc. Different types of data are
written with different data and session structures
which will be explained later. The user specifies what
type of disc is created based upon the application used
to record to the media. The application then writes
data to the media in the perscribed standard.
The Physical Structure:
All Compact Discs have the same physical
characteristics. They are constructed of a
polycarbonate material with diameters of 12mm. Data is
recorded onto a layer that is protected between the
1.2mm thick polycarbonate bottom layer and the thin
protective label side. Directly below the label is the
reflective layer with the actual data held directly
beneath the reflective layer. Great care should be
taken not to damage the label side or the data beneath.
During the CD-R write process, data is written to the
disc in the following manner: A high intensity laser
heats the chemical dye media to the proper temperature.
At the proper temperature, the dye changes dye
characteristics, i.e..changing from an opaque dark spot
to a transluscent light spot.
During the read process, a laser reads the information
by focusing on the reflective layer and the amount of
light it reflects to the optical pickup sensor. When
the laser hits a light spot the reflected laser-light
value is larger than a dark spot to the optical pickup
sensor. The laser light is therefore modulated by the
changes in light reflection caused by the data spot.
This light modulation is transposed into an electrical
signal that represents a string of information that is
read from the disc.
The CD-Writer CD-R records data onto WORM media in a
string that is laid out in a continuous spiral string
that begins near the center hole and continues to the
outer edge of the disk. This spiral is actually a pre-
groove that is used to calibrate the rotational speed
of the compact disc.
The spiral form of the pre-groove exhibits a small
jitter, that when the disk is rotated at the correct
velocity, produces a frequency of 22.05 kHz. This
jitter or wobble, is used by the CD-R for constant
speed control and pre-groove tracking. The CD-R needs
more than just rotational speed information to know
where it is, so the 22.05KHz wobble is FM modulated
with time information called ATIP, (Absolute Time in
Pre-Groove). This time runs continuously from the
beginning to the end of the Pre-Groove spiral. This
explains why a disc has a pre-set capacity and allows
for space to be reserved which can be filled in later.
Logical Structure:
EFM Structure:
Data is encoded onto the disc in an EFM frame. EFM =
Eight to Fourteen Modulation. One EFM frame contains
588 bits including 24 Sync-bits, 33 data bytes(14 bits
per data-byte), 3 merging bits per data-byte, and 3
closing merging bits.
Sync bits indicate the beginning of the EFM frame.
Merging Bits are used to ensure the minimum length of a
pit is 3 bits and the maximum is 11 bits, and to
eliminate DC constant in the signal.
Not including the EFM Sync bits, merging bits, and
after demodulation, the frame contains 33 bytes
including 24 databytes, 4 Q parity bytes(for C2 Error
Corrections), 4 P parity bytes (for C1 Error
Correction), and 1 Control byte. The Control byte
carries the SubCode data.
The C1 Error Handling is used for recovery from random
errors such as noise. It restores missing databits,
using redundant information in the P parity bits. The
C2 layer is used for burst errors, like scratches and
dirt spots on the disc than can disrupt the whole
string of data. It depends on the data being scrambled
over many frames at recording time. As the data is read
and descrambled, the burst error is scattered. This
allows the data to be corrected frame by frame using
information in the Q parity bits. Together, C1 and C2
bytes provide a cross-interleaved ECC that cover every
data byte twice.
SubCode Structure:
SubCode information is contained in the Control Byte of
the EFM frame. Every bit of this byte represents one
bit in one of eight SubCode channels: P,Q,R,S,T,U,V,W.
The main SubCode channels are P and Q. The P channel
indicates a pause between audio or data tracks. It is a
relic, called the Pause-flag, from the time that CD
players were not fast enough for real-time decoding of
the SubCode. It was used for very simple search
algorithms.
The Q channel information depends on the part of the
disk the laser is reading. The physical disk has 3
parts: The Lead In area, the Program area which
contains user data, and the last part called the Lead
Out area. Within the Program Area of user data, the Q
channel carries information such as Control, Address,
Track No, Relative Time and Absolute Time, Univeral
Product Code, and International Standard Recording
Code. Within the Q channel Address block are 3 modes
which allow 3 types of data to be interleaved. The
remaining channels are available to be used by
applications such as MIDI and CD+G (on screen
graphics).
Sector Structure:
In Audio applications, it is necessary to have accurate
positioning only at the beginning of a song. This is
accomplished via Track positioning and Track jumping
which will be outlined in the next section.
For data applications, data has to be accessible in
much smaller blocks called Data-Sectors. Data-Sectors
are data-blocks that carry information such as sector
identification number and type, EDC (Error Detection
Code), and ECC (Error Correction Code).
The Sector Structure information is placed on top of
the SubCode Structure and corresponds to the SubCode
frame on a one to one basis. The information as a data
sector is handled as an audio sector, i.e.. it includes
EFM encoding, C1, C2, remapping and interleaving
information. One sector contains 2352 data bytes and no
error correction, the size of one Audio Sector.
The basic data-sector always contains the following information:
Sector Sync: 12 bytes (00 FF FF FF FF FF FF FF FF FF FF 00)
Header : 4 bytes
The Remaining 2336 bytes are sector type dependent.
Sector Types:
Type 1: Red Book Sector or Audio Sector:
2352 bytes user data (music)
Type 2: Yellow Book Data-Sector Mode 1:
12 bytes sync
4 bytes header
2048 bytes user data
4 bytes EDC
8 bytes blank
276 bytes ECC
Type 3: Yellow Book Data-Sector Mode 2:
12 bytes sync
4 bytes header
2336 bytes user data
Type 4: CDROM-XA and Green Book Data-Sector Mode 2 - Form 1:
12 bytes sync
4 bytes header
8 bytes subheader
2048 bytes user data
4 bytes EDC
276 bytes ECC
Type 5: CDROM-XA and Green Book Data-Sector Mode 2 - Form 2:
12 bytes sync
4 bytes header
8 bytes subheader
2324 bytes user data
4 bytes EDC
At this time only 5 different sector types exist
including the Audio sector. Type 1 is the Audio Sector,
and contains only Audio information. Type 2 - 5 are
Data Sectors. The 5 types of sectors are currently
divided into 2 families:
Computer Data Use
Compressed Audio/Video Data Use
Computer data needs extensive error-correction and
therefore Sector Types 2 and 4 are used.
Audio/Video data requires less error protection
therefore Sector Type 5 is commonly used (3 can be used
but is extremely rare).
Sector Type 4, the CDROM-XA (XA for Extended
Architecture) are used to introduce a Mixed Mode in one
track. Mixed Mode is necessary to make the interleaving
of Computer Data Sectors with Audio/Video sectors
possible. With appropriate interleaving, reproduction
of real-time Audio or Video is possible while
processing Computer Data.
Track Structure:
Tracks are units built from sectors that have the same
Mode. No Mode Mixing is allowed within a track on any
type of disk.
In CDDA, tracks contain one song. The access of songs
is done by track jumping. This is the basic data-unit
of CD-DA. Each track can start with an optional pre-gap
of 2 seconds of digital silence. (Note: current
software requires 2 sec pre-gap.)
Tracks also exist on Yellow and Green discs, but the
color of a track may not change within the track.
Intra-Track time is located in the Q channel and is
indicated by MIN, SEC, Frame and is known as Relative
Time. Inter-Track or disk time is also given in the Q
channel by AMIN, ASEC, AFRAME, and is also referred to
as Absolute Time and runs over track boundaries.
A Table of Contents is placed in the Q Channel during
creation of the Lead In. As a disc is read, the Table
of Contents is read into the memory of the CD-R unit,
subsequently the unit knows exactly where it is on the
disc by reading the SubCode information.
All Jumps and searches are done using the SubCode
information. This is true for all disc types, whether
Data-Disc or Audio-Disc. Data-Discs have a special
search algorithm added on top of the SubCode search
data.
Session Structure:
The Lead In specification is described in the Red Book
Standard. This piece of information located at a
specific fixed radius of the disc before the first
Track. It contains the Table of Contents plus other
information such as the disc label, disc ID number,
etc.. all stored in the SubCode information.
The Lead Out is used to indicate the end of an
information block and contains a Lead-out code in the
SubCode. Example: TNO=AA, (Track Number=AA.)
An information block with its Lead In, Table of
Contents and Lead Out information is called a Session.
Until 1990, a Session was the same as a disc, meaning a
disc could only contain one Session, which was
typically audio data. This was due to the mastering and
duplication process used in CD technology. Small
sessions wasted space on the disc, which was not
condusive to profitablitly and data distribution.
In 1992, Philips introduced the CD-R and its standard,
the Orange Book Part II, which makes it possible to
record audio and computer data on special discs that
are blank. They have none of the logical data and
structure elements described to this point. They have
no Tracks, SubCode, Lead In, Lead Out, or Sectors which
are written by the drive. The disk still has a physical
structure which includes the Pre-Groove.
The greatest benefit of the CD-R for those wishing to
create computer data disks is the multi-session
capability which is made possible through the
Transmutation process. During Transmutation, the user
has the option of selecting Fixate or Final Fixate.
Specified by the application, Fixate indicates to the
CD-R that the user wishes to record another session
after the one just completed. The Fixate command writes
the Lead In to the disc with a pointer to the start
position of the next Session (which does not actually
exist!), it also writes the Lead Out with a pointer to
its own Session start.
Final Fixate does not write the Lead In or Lead Out
with pointers to the next Session. This indicates to
the CD-R that no more Sessions may be written or added
to the disc. Fixation is required before the disc will
be readable in a player or ROM drive.
The HP Colorado SureStore CD-Writer is a Multi Session
device capable of detecting different Session types,
multiple Sessions, and Session structures.
Disc Types:
As described earlier, there are 5 different Sector
types from which different disc types can be generated.
A. The first is the CDDA or Audio CD disc which
contains Type 1 Audio sectors only and is described in
the Red Book. This sector type has 2352 total data
bytes, with 12 sector sync bytes and 4 header bytes.
B. The second is the CDROM disc. This disc is defined
in the Yellow Book and contains one of two subtypes,
CDROM Mode 1 or CDROM Mode 2.
C. A disc with a combination of CDDA and CDROM Tracks
is called a Mixed Mode disc which commonly has a CDROM
Track as the first Track and CDDA on the next Tracks.
D. CDROM(XA) Mode 2 allows multimedia applications to
read computer data while reproducing real time
audio/video data. This cannot be done in Mixed Mode due
to the amount of time required during Track Jumping.
CDROM(XA) Mode 2 also breaks into 2 types: Mode 2 Form
1 and Mode 2 Form 2. Form 1 is used for computer data
and Form 2 is used for compressed audio/video. These
two sector types can then be interleaved on the same
Track without breaking the rule that a Track can only
contain one Mode, however this does require special
interface electronics to separate the different Sector
types in Real-Time.
E. CD-I discs must comply with the Green Book Standard
which specifies both the disc and Operating System. CD-
I Tracks are identical to CDROM(XA) and are interleaved
to accomodate multimedia applications, however a CD-I
Track is not listed in the Table of Contents of the
disc. Logical Structure:
CDROM technology has become a De Facto interchange
standard between systems of unlike file structures such
as Unix, VMS, OS/2, and MS-DOS, meaning that the files
on a CDROM disc look like the files of the native
operating system.
This is accomplished by designing the file system used
on the CDROM according to the ISO 9660 standard,
commonly called the High Sierra File System. The ISO
9660 standard defines the following constraints:
ISO 9660 Interchange Levels:
Level 3
Subdirectories and filenames are alphabetically sorted.
Subdirectories have a max. depth of 8 levels.
Pathnames have a max. of 255 characters.
Supports interleaved files and multiple extents.
Level 2 : same as level 3 except:
No interleaving.
Only one file extent.
Level 1: same as level 2 except:
Filenames limited to 8 dchars (uppercase only, A-Z, 0-
9, and underscore)
Ext. limited to 3 dchars
Directories limited to 8 dchars, no ext.
original MSCDEX.EXE.
Note: Most implementations, inlcuding MSCDEX, support
only level 1.
CD-R Media:
A typical CD-R Disc is created using a transparent
polycarbonate material as the substrate. This is the
same for conventional CD's. Onto this substrate an
opaque dye is applied. The substrate has already been
provided with a preformed track spiral into which the
data will be written during recording. On top of the
opaque layer are added a reflective gold layer and a
thin lable/protective layer.
There are two types of dye used to create CD-R discs
both of which are used in the industry today: Cyanine
and Phthalocyanine. These dyes were selected based upon
their properties of themal and optical properties,
i.e.. their ability to react to heat and light.
Test conducted with media created with both dyes
indicates that Phthalocyanine based discs are
significantly more stable when exposed to adverse
conditions such as heat and relative humidity.
The first test conducted was designed to test the dye
sensitivity to sunlight. A Carbon Arc Light was used to
simulate Sunlight. After 20 hours, the Cyanine disc
began to show signs of degradation which continued
though a 60 hour test.
The Phthalocyanine disc continued to show no signs of
dye degradation after 180 hours!
In addition, the Cyanine based disc exceeded the Orange
Book BLER (Block Error Rate) when exposed harsh
environmental conditions, 80 degrees Celsius and 85%
Relative Humidity.
When exposed to the same conditions, the Phthalocyanine
based disc remained stable with an insignificant BLER
for over 1000 hours while the Cyanine based disc
exceeded the BLER in approximately 40 hours! Using this
data to simulate accelerate aging conditions, the
Phthalocyanine based disc should achieve an extimated
life of about 100 years under nomal conditions, ie.. 25
degrees Celsius.
Based on this type of data, HP Colorado has chosen to
recommend discs that utilize Phtalocyanine and will
include 2 such discs in every CD-Writer package.
(Note: Typical Silver CD's, those which are mastered
using an aluminum stamping method have a life
expectancy of 5-7 years.)
A CD-R disc also differs from a conventional CD with
the inclusion of Additional CD-R Area that is required.
The Additional CD-R Area is divided into two areas:
1. The PMA, Program Memory Area which contains the
track numbers of the titles recorded with respective
start and stop points.
2. The PCA, Program Calibration Area which is disc
space required by the CD- Writer to calibrate the laser
energy needed for recording on the disc. Essentially a
trial recording area.
Note: Both the PMA and PCA areas of the CD-R disc are
unreadable by normal CD-DA players and ROM drives.
Their Optical sensors are incapable of positioning to
these areas.
Disk Capacities:
120mm Disc: 650 MB est; 74 Minutes Audio
80mm Disc: 184 MB est; 21 Minutes Audio
Estimated number of sessions written to disc based upon
varying data session sizes:
Disk Capacity
Data per Session
Maximum number
of Sessions
650 MB
1.4 MB
45
650 MB
12.5 MB
30
650 MB
149 MB
4
Theory of Operation:
The CD-Writer drive is responsible for encoding to the
media. This involves receiving a constant stream of
data to which it must add error correction codes and
interleave during the encoding process.
The CD-R utilizes C1, C2, and C3 error correction
schemes to protect user data. Interleave causes the
data to be written non-linearly or spread out across
the disc. This protects the disc from defects, such as
small spots in the disc, which then destroys small bits
of many blocks of data(which can be reconstructed with
ECC) as opposed to a large piece of a block which could
not be reconstructed.
The disadvantage of this type of write process is that
every block written depends on on the data in blocks
adjacent to it, because every block contains pieces of
the blocks around it. This causes a particular problem
if the data stream is interrupted during the write
process for any reason, i.e.. a data under- run.
The ISO 9660 Standard defines that there must be at
least 1 file system on a CD-ROM disk. As in hard disks,
a disk may have multiple partitions, but only 1 file
system per partition. For CD-ROM's, partitions are
created in ISO sets which use Sessions.
A Session is:
A Leadin
A Program Area
A Leadout
When writing a Session to the disc an application may
use one of the following ISO Structures:
Disk at Once : All data to be written is available On-
line and the entire ISO structure is prepared by the
application prior to encoding. This requires larger
data buffers.
Session at Once : The data is available On-line and the
ISO structure for the Session is prepared by the
application prior to encoding.
Track at Once : The ISO structure is implicitly present
on the disk prior to any encoding process. Final ISO
stuctures are written during finalization and PVD is
written.
As is now evident, the original CD-Format, which was
designed for read only, makes user recording difficult.
All applications included with the CD-Writer utilize
the Track at Once method.
The CD -Writer drive is capable of writing through
minor dust or media defects by constantly monitoring
the reflected light during the write process. If the
amount of reflected light drops, the drives boosts
power to the Laser in an attempt to write throught
whatever defect is encountered. This is known as
Automatic Write Power Control. If power cannot be
boosted sufficiently to write through the defect, the
user is notified. No separate verify pass is needed.
CD-Recordable technology uses media similar to CD-ROM.
It utilizes media constructed of polycarbonate
substrate material through which data is read or
written. The polycarbonate substrate material material
acts as a plastic shield to protect the recording layer
which holds the actual data. Additionally, a reflective
layer and 2nd protective layer or label is added on top
of the disc.
After the disc has been loaded into the CD-Writer, a
high intensity laser is against the bottom side of the
disc. The laser light passes through the substrate to
the reflective layer and is reflected back to through
the substrate, through the drive's optics, and to the
light detector.
A normal CD-ROM has stamped or molded pits in the
recording area that cause the light to reflected with
less intensity back to the detector. The transitions
between the molded pits and the unaffected areas lands
are what encode the information. A standard CD-ROM uses
the data itself for tracking. CD-R uses a chemical dye
polymer as the recording medium within a shallow pre-
groove which is molded into the substrate. This
pregroove is invisible to normal CD-ROM players and is
used by the laser head to maintain track allignment and
allow the CD-R to maintain accurate disc speed or CLV,
Constant Linear Velocity.
The next layer is the dye polymer layer which is used
to record data. The dye is normally opaque, but when
exposed to the high intensity laser, it absorbs energy,
heats, and turns transparent. This exposes the next
layer, the reflective gold layer. Gold is used because
it is more reflective than the Aluminum used in normal
CD's. The dye, even when transparent still absorbs more
light than the polycarbonate substrate alone, and
requriers the extra reflectance of Gold.
CD-R media contains two areas invisible to CD-ROM
drives. The Power Calibration Area (PCA) and the
Program Memory Area (PMA). The PCA is used by CD-R
drives to calibrate the power of the Laser to the
particular piece of media being used. This area can
handle 100 such power calibrations. The PMA is a
scratchpad for recording the locations of written
tracks. This is necessary because the normal area of
recording track locations can be written to only once.
The recorder's normal mode of operation is to write
everything into the PMA, then transfer that information
into the Table of Contents (TOC) upon finalization,
thus recording the session. Preferences: CD Recording
Speed
The CD-Writer has the option available of recording at
1x or 2x speeds. Although writing faster is a time-
saver, it can cause problems in some situations. Data
is transferred from the computer's hard disk to the
buffer memory of the CD recorder, and thence to the
recording laser, which inscribes pits into the surface
of the CD at a steady speed which cannot be altered or
interrupted. The speed at which data must be
transferred depends on the physical format in which the
data is written and on the writing speed:
Format/Mode
(bits/ sector)
Required transfer rate at: 1x
2x
4x (Read Only)
CD-ROM Mode 1
(2048)
150 kb/sec
300 kb/sec
600 kb/sec
Audio
(2352)
172 kb/sec
344 kb/sec
688 kb/sec A number of users have been confused between
recording speed and playback speed: If a disc is
written at 2x, is it required to play it back on a 2x
CD-ROM drive? This can be explained as follows: CD
recording speed is simply a matter of how fast the bits
are inscribed by the laser on the disc surface, and has
nothing to do with how fast you read them back or how
much data you can fit on the disc.
-[30]-
