MultiLevel Recording
Encyclopedia
MultiLevel Recording (also known as M-ary) was a technology originally developed by Optex Corporation and promoted by Calimetrics
to increase the storage capacity of optical discs. It failed to establish itself on the market. Through a combination of proprietary media, recorder, reader and player modifications, Calimetrics
proposed that ML could increase the capacity of a CD-ROM
, CD-R
or CD-RW
to 2 GB, a single-layer DVD
, DVD-R
, DVD+R
, DVD-RW
, DVD+RW
or DVD-RAM
to 7.1 to 10 GB and a single-layer Blu-ray Disc
(BD) to as much as 60 GB. An optionally integrated Digital Rights Management
(DRM) system entitled MovieGuard was also suggested. An industry group called the ML Alliance was formed in 2000 to help commercialize ML technology. Members eventually included Calimetrics
, TDK, Sanyo Semiconductor, Plextor
, Matsushita Kotobuki Electronics, Mitsubishi Chemical Corporation
, Verbatim
, Teac
and Yamaha.
Several 2 GB ML CD-based recorders were developed for release in 2002 (TDK's MLCDRW1000 and Plextor's PX-ML3630), but never came to market. This was largely a business decision influenced by the rapid fall of CD-R/RW prices and the simultaneous rise in popularity of writable DVD technology. Calimetrics went on to work on more advanced DVD and Blu-ray Disc versions of their technology, including a proposal to build a next generation version of Enhanced Versatile Disc
(EVD). Calimetrics ceased operations in 2004.
. The codes used in most optical disc systems are binary, meaning that resulting surface has only two states: marks and non-marks. The following figure illustrates the EFM
code used in CDs and DVDs:
Because the edges are positioned on a grid that is finer than the minimum mark size, EFM
achieves about 1.5 bits per minimum-mark, even though it is a binary code.
MultiLevel recording refers to the use of multiple reflectivity values to encode data onto an optical disc. By using more than two levels, more information can be put into the minimum feature size. The following figure illustrates a MultiLevel code (note: colors are used only to represent differences in intensity):
The 8-level code used on the prototype systems is a convolutional code
, storing about 2.5 bits per data cell. By using this code in combination with a smaller mark size and a more efficient error-correction code, the capacity of CD media was tripled. When applied to dual-layer DVD, ML-recording can increase capacity by a factor of 1.9.
MultiLevel optical recording is an example of baseband
pulse-amplitude modulation
. While Non-binary, or M-ary, modulation is common in the telecom
industry, the technique was originally developed and patented for optical disc recording at Optex Corporation in the early 1990s (in conjunction with the University of Rochester) for use with their Electron Trapping Optical Media (ETOM). Although simple in principle, implementation of ML was challenging, in large part because data storage channels
are highly nonlinear
. The overall ML-system response is much more sensitive to variations in its individual components (operating temperature
, media uniformity, read-head fluctuation, etc.) than a conventional CD/DVD system. To compensate, the ML logical-format devotes a substantial portion of bits (as forward-error correction coding) to enhance robustness against media defects and signal noise. ML-drives used sophisticated power-optimization during writing and adaptive equalization during reading.
MultiLevel recording is sometimes confused with multi-layer storage, in which multiple data surfaces are combined into a single disc. Multi-layer and multiLevel technique can be combined (as in dual-layer ML-DVD ROM), where ML-modulation is applied to each individual layer of the disc.
Calimetrics
Calimetrics was founded in 1994 by Terrence Wong, Michael O'Neill, and Thomas Burke. Based on Dr. Wong and Dr. O'Neill's UC Berkeley research, the company received startup funding of $1.8M from an Advanced Technology Program grant to conduct research and development on pit depth modulated optical...
to increase the storage capacity of optical discs. It failed to establish itself on the market. Through a combination of proprietary media, recorder, reader and player modifications, Calimetrics
Calimetrics
Calimetrics was founded in 1994 by Terrence Wong, Michael O'Neill, and Thomas Burke. Based on Dr. Wong and Dr. O'Neill's UC Berkeley research, the company received startup funding of $1.8M from an Advanced Technology Program grant to conduct research and development on pit depth modulated optical...
proposed that ML could increase the capacity of a CD-ROM
CD-ROM
A CD-ROM is a pre-pressed compact disc that contains data accessible to, but not writable by, a computer for data storage and music playback. The 1985 “Yellow Book” standard developed by Sony and Philips adapted the format to hold any form of binary data....
, CD-R
CD-R
A CD-R is a variation of the Compact Disc invented by Philips and Sony. CD-R is a Write Once Read Many optical medium, though the whole disk does not have to be entirely written in the same session....
or CD-RW
CD-RW
A CD-RW is a rewritable optical disc. It was introduced in 1997, and was known as "CD-Writable" during development. It was preceded by the CD-MO, which was never commercially released....
to 2 GB, a single-layer DVD
DVD
A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....
, DVD-R
DVD-R
DVD-R is a DVD recordable format. A DVD-R typically has a storage capacity of 4.71 GB. Pioneer has also developed an 8.5 GB dual layer version, DVD-R DL, which appeared on the market in 2005....
, DVD+R
DVD+R
DVD+R is part of optical disc recording technologies. It is a format for optical disc data storage that utilizes digital recording. It is similar to, but incompatible with, the older DVD-R standard...
, DVD-RW
DVD-RW
A DVD-RW disc is a rewritable optical disc with equal storage capacity to a DVD-R, typically 4.7 GB. The format was developed by Pioneer in November 1999 and has been approved by the DVD Forum. The smaller Mini DVD-RW holds 1.46 GB, with a diameter of 8 cm.The primary advantage of DVD-RW over...
, DVD+RW
DVD+RW
DVD+RW is a physical format for rewritable DVDs and can hold up to 4.7 GB. DVD+RW was created by the DVD+RW Alliance, an industry consortium of drive and disc manufacturers...
or DVD-RAM
DVD-RAM
DVD-RAM is a disc specification presented in 1996 by the DVD Forum, which specifies rewritable DVD-RAM media and the appropriate DVD writers. DVD-RAM media have been used in computers as well as camcorders and personal video recorders since 1998.-Design:DVD-RAM is one of three competing...
to 7.1 to 10 GB and a single-layer Blu-ray Disc
Blu-ray Disc
Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...
(BD) to as much as 60 GB. An optionally integrated Digital Rights Management
Digital rights management
Digital rights management is a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals with the intent to limit the use of digital content and devices after sale. DRM is any technology that inhibits uses of digital content that...
(DRM) system entitled MovieGuard was also suggested. An industry group called the ML Alliance was formed in 2000 to help commercialize ML technology. Members eventually included Calimetrics
Calimetrics
Calimetrics was founded in 1994 by Terrence Wong, Michael O'Neill, and Thomas Burke. Based on Dr. Wong and Dr. O'Neill's UC Berkeley research, the company received startup funding of $1.8M from an Advanced Technology Program grant to conduct research and development on pit depth modulated optical...
, TDK, Sanyo Semiconductor, Plextor
Plextor
is a brand best known for its optical disc recorders. The brand name is used for all products manufactured by the Electronic Equipment Division and Printing Equipment Division of Shinano Kenshi. The brand was formerly known as TEXEL by which name it introduced its first CD-ROM optical disk drive in...
, Matsushita Kotobuki Electronics, Mitsubishi Chemical Corporation
Mitsubishi Chemical Corporation
, or MCC, was a Japanese corporation. It merged with Mitsubishi Pharma Corporation to create Mitsubishi Chemical Holdings Corporation.-External links:...
, Verbatim
Verbatim Corporation
Verbatim Americas, LLC is a US company that markets storage media and flash memory products. It is a subsidiary of Mitsubishi Chemical Holdings Corporation of Japan and is based in Charlotte, North Carolina.-History:...
, Teac
Teac
TEAC Corporation is an electronics company based in Japan. TEAC was founded in 1953 as the Tokyo Electro Acoustic Company. TEAC has four divisions:*TASCAM - consumer to professional audio products, mostly recording...
and Yamaha.
Several 2 GB ML CD-based recorders were developed for release in 2002 (TDK's MLCDRW1000 and Plextor's PX-ML3630), but never came to market. This was largely a business decision influenced by the rapid fall of CD-R/RW prices and the simultaneous rise in popularity of writable DVD technology. Calimetrics went on to work on more advanced DVD and Blu-ray Disc versions of their technology, including a proposal to build a next generation version of Enhanced Versatile Disc
Enhanced Versatile Disc
The Enhanced Versatile Disc is an optical medium-based digital audio/video format, developed to provide a means for playing HDTV content using existing optical media. It was announced on November 18, 2003, by the People's Republic of China's Xinhua News Agency as a response to the popular...
(EVD). Calimetrics ceased operations in 2004.
Technology
To store information onto a physical surface, the data must be transformed into a series of marks, using a modulation codeModulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...
. The codes used in most optical disc systems are binary, meaning that resulting surface has only two states: marks and non-marks. The following figure illustrates the EFM
Eight-to-Fourteen Modulation
Eight-to-fourteen modulation is a data encoding technique – formally, a channel code – used by compact discs and pre-Hi-MD MiniDiscs. EFMPlus is a related code, used in DVDs and SACDs. EFM and EFMPlus were both invented by Kees A...
code used in CDs and DVDs:
Eight-to-Fourteen Modulation
Eight-to-fourteen modulation is a data encoding technique – formally, a channel code – used by compact discs and pre-Hi-MD MiniDiscs. EFMPlus is a related code, used in DVDs and SACDs. EFM and EFMPlus were both invented by Kees A...
achieves about 1.5 bits per minimum-mark, even though it is a binary code.
MultiLevel recording refers to the use of multiple reflectivity values to encode data onto an optical disc. By using more than two levels, more information can be put into the minimum feature size. The following figure illustrates a MultiLevel code (note: colors are used only to represent differences in intensity):
The 8-level code used on the prototype systems is a convolutional code
Convolutional code
In telecommunication, a convolutional code is a type of error-correcting code in which* each m-bit information symbol to be encoded is transformed into an n-bit symbol, where m/n is the code rate and...
, storing about 2.5 bits per data cell. By using this code in combination with a smaller mark size and a more efficient error-correction code, the capacity of CD media was tripled. When applied to dual-layer DVD, ML-recording can increase capacity by a factor of 1.9.
MultiLevel optical recording is an example of baseband
Baseband
In telecommunications and signal processing, baseband is an adjective that describes signals and systems whose range of frequencies is measured from close to 0 hertz to a cut-off frequency, a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies...
pulse-amplitude modulation
Pulse-amplitude modulation
Pulse-amplitude modulation, acronym PAM, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses....
. While Non-binary, or M-ary, modulation is common in the telecom
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
industry, the technique was originally developed and patented for optical disc recording at Optex Corporation in the early 1990s (in conjunction with the University of Rochester) for use with their Electron Trapping Optical Media (ETOM). Although simple in principle, implementation of ML was challenging, in large part because data storage channels
Channel (communications)
In telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel...
are highly nonlinear
Nonlinearity
In mathematics, a nonlinear system is one that does not satisfy the superposition principle, or one whose output is not directly proportional to its input; a linear system fulfills these conditions. In other words, a nonlinear system is any problem where the variable to be solved for cannot be...
. The overall ML-system response is much more sensitive to variations in its individual components (operating temperature
Operating temperature
An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...
, media uniformity, read-head fluctuation, etc.) than a conventional CD/DVD system. To compensate, the ML logical-format devotes a substantial portion of bits (as forward-error correction coding) to enhance robustness against media defects and signal noise. ML-drives used sophisticated power-optimization during writing and adaptive equalization during reading.
MultiLevel recording is sometimes confused with multi-layer storage, in which multiple data surfaces are combined into a single disc. Multi-layer and multiLevel technique can be combined (as in dual-layer ML-DVD ROM), where ML-modulation is applied to each individual layer of the disc.