|Orange Book CD-r standard
The CD-R, originally named CD Write-Once (WO), specification was first
published in 1988 by Philips and Sony in the 'Orange Book'.
The Orange Book standard consists of several parts, furnishing details
of the CD-WO, CD-MO (Magneto-Optic), and CD-RW (ReWritable).
For Orange book
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The latest editions have abandoned the use of the term "CD-WO"
in favor of "CD-R", while "CD-MO" were practically
never used. Written CD-Rs and CD-RWs are fully compatible with the
Audio CD (Red Book) and CD-ROM (Yellow Book) standards. They use Eight-to-Fourteen
Modulation, CIRC error correction plus the third error correction
layer defined for CD-ROM.
The dye materials developed by Taiyo Yuden made it possible for
CD-R discs to be compatible with Audio CD and CD-ROM discs.
A standard CD-R is a 1.2 mm thick disc made of polycarbonate with
a 120 mm or 80 mm diameter.
CD-r has a storage capacity of 74 minutes of audio or 650 MiB of data.
CD-R/RWs are also available with capacities of 79 minutes, 59 seconds
and 74 frames (marketed as 80 minutes) /736,966,656 bytes (702 MiB),
which they achieve by burning at the maximum allowable tolerances
specified in the Orange Book CD-R/CD-RW standards.
Most CD-Rs on the market have an 80 minute capacity.
There are also 90 minute/790 MiB and 99 minute/870 MiB discs, although
they are rare.
Some drives use special techniques to write more data onto a given
disc, such as Plextor's GigaRec allowing as much as 1.2 GiB onto a
99 minute disc. Also, due to the limitations of the data structures
in the ATIP (see below), 90 and 99 minute blanks will identify as
80 minute ones and have to be burned using the "overburn"
options in the CD recording software.
The polycarbonate disc contains a spiral groove to guide the laser
beam upon writing and reading information.
The disc is coated on the side with the spiral groove with a very
thin layer of organic dye and subsequently with a thin, reflecting
layer of silver, a silver alloy or gold. Finally, a protective coating
of a photo-polymerizable lacquer is applied on top of the metal reflector
and cured with UV-light.
The blank disc has a pre-groove track onto which the data is written.
The pre-groove track, which also contains timing information, ensures
that the recorder follows the same spiral path as a conventional CD.
A CD recorder writes data to a CD-R disc by pulsing its laser to heat
areas of the organic dye layer.
The writing process does not produce indentations (pits); instead,
the heat permanently changes the optical properties of the dye, changing
the reflectivity of those areas.
Using a low laser power, so as not to further alter the dye, the disc
is read back in the same way as a CD-ROM. However, the reflected light
is modulated not by pits, but by the alternating regions of heated
and unaltered dye. The change of the intensity of the reflected laser
radiation is transformed into an electrical signal, from which the
digital information is recovered ("decoded").
Once a section of a CD-R is written, it cannot be erased or rewritten,
unlike a CD-RW. A CD-R can be recorded in multiple sessions. A CD
recorder can write to a CD-R using several methods including:
Disc At Once - the whole CD-R is written in one session with no gaps
and the disc is "closed" meaning no more data can be added and the
CD-R effectively becomes a standard read-only CD. With no gaps between
the tracks the Disc At Once format is useful for "live" audio recordings.
Track At Once - data is written to the CD-R one track at a time but
the CD is left "open" for further recording at a later stage.
It also allows data and audio to reside on the same CD-R.
Packet Writing - used to record data to a CD-R in packets allowing
extra information to be appended to a disc at a later time or information
on the disc can be made "invisible". In this way CD-R can
emulate CD-RW however each time information on the disc is altered
more data has to be written to the disc. There can be compatibility
issues with this format and some CD drives.
A rough estimation of the amount of data on a CD-R can be gained
by inspecting the playback side of the disc. A visible variation
in the surface can be observed. CD-Rs are written from the center
of the disc outwards.
Book Audio CD Standard
Book CD Standard
Book Enhanced CD, CD+G and CD-Plus
Book CD Standard CD-r CD-RW