MultiLevel Recording

Last updated

MultiLevel Recording (ML, also known as M-ary) was a technology originally developed by Optex Corporation [1] 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.

Contents

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.

Technology

To store information onto a physical surface, the data must be transformed into a series of marks, using a modulation code. 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:

Binary EFM code used in DVDs and CDs; example marks and corresponding signal EFM code.svg
Binary EFM code used in DVDs and CDs; example marks and corresponding signal

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):

8-level ML code; example marks and corresponding signal ML code.svg
8-level ML code; example marks and corresponding signal

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.

Related Research Articles

<span class="mw-page-title-main">CD-R</span> Recordable optical disc specification

CD-R is a digital optical disc storage format. A CD-R disc is a compact disc that can only be written once and read arbitrarily many times.

<span class="mw-page-title-main">Line code</span> Pattern used within a communications system to represent digital data

In telecommunication, a line code is a pattern of voltage, current, or photons used to represent digital data transmitted down a communication channel or written to a storage medium. This repertoire of signals is usually called a constrained code in data storage systems. Some signals are more prone to error than others as the physics of the communication channel or storage medium constrains the repertoire of signals that can be used reliably.

<span class="mw-page-title-main">Optical disc</span> Flat, usually circular disc that encodes binary data

An optical disc is a flat, usually disc-shaped object that stores information in the form of physical variations on its surface that can be read with the aid of a beam of light. Optical discs can be reflective, where the light source and detector are on the same side of the disc, or transmissive, where light shines through the disc to be detected on the other side.

Universal Disk Format (UDF) is an open, vendor-neutral file system for computer data storage for a broad range of media. In practice, it has been most widely used for DVDs and newer optical disc formats, supplanting ISO 9660. Due to its design, it is very well suited to incremental updates on both write-once and re-writable optical media. UDF was developed and maintained by the Optical Storage Technology Association (OSTA).

<span class="mw-page-title-main">Optical disc drive</span> Type of computer disk storage drive

In computing, an optical disc drive is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only read from certain discs, but recent drives can both read and record, also called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives.

<span class="mw-page-title-main">DVD-RAM</span> Variant of DVD designed with random access in mind

DVD-RAM is a DVD-based 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.

<span class="mw-page-title-main">DVD+R DL</span> DVD Recordable Dual Layer

DVD+R DL also called DVD+R9, is a derivative of the DVD+R format created by the DVD+RW Alliance. Its use was first demonstrated in October 2003. DVD+R DL discs employ two recordable dye layers, each capable of storing nearly the 4.7 GB capacity of a single-layer disc, almost doubling the total disc capacity to 8.5 GB. Discs can be read in many DVD devices and can only be created using DVD+R DL and Super Multi drives. DL drives started appearing on the market during mid-2004, at prices comparable to those of existing single-layer drives. As of March 2011 DL media is up to twice as expensive as single-layer media. The latest DL drives write double layer discs at a slower rate than current single-layer discs.

Eight-to-fourteen modulation (EFM) is a data encoding technique – formally, a line code – used by compact discs (CD), laserdiscs (LD) and pre-Hi-MD MiniDiscs. EFMPlus is a related code, used in DVDs and Super Audio CDs (SACDs).

<span class="mw-page-title-main">Kees Schouhamer Immink</span> Dutch engineer, inventor, and entrepreneur

Kornelis Antonie "Kees" Schouhamer Immink is a Dutch engineer, inventor, and entrepreneur, who pioneered and advanced the era of digital audio, video, and data recording, including popular digital media such as compact disc (CD), DVD and Blu-ray disc. He has been a prolific and influential engineer, who holds more than 1100 U.S. and international patents. A large portion of the commonly used audio and video playback and recording devices use technologies based on his work. His contributions to coding systems assisted the digital video and audio revolution, by enabling reliable data storage at information densities previously unattainable.

The double-density compact disc (DDCD) is an optical disc technology developed by Sony and Philips using the same 780 nm laser wavelength as a compact disc. The format was announced in July 2000 and is defined by the Purple Book standard document. Unlike the compact-disc technology it is based on, DDCD was designed exclusively for data, with no audio capabilities.

<span class="mw-page-title-main">Optical storage</span> Method to store and retrieve computer data using optics

Optical storage refers to a class of data storage systems that use light to read or write data to an underlying optical media. Although a number of optical formats have been used over time, the most common examples are optical disks like the compact disc (CD) and DVD. Reading and writing methods have also varied over time, but most modern systems as of 2023 use lasers as the light source and use it both for reading and writing to the discs. Britannica notes that it "uses low-power laser beams to record and retrieve digital (binary) data."

<span class="mw-page-title-main">DVD-R DL</span> DVD Recordable Dual Layer

DVD-R DL, also called DVD-R9, is a derivative of the DVD-R format standard. DVD-R DL discs hold 8.5 GB by utilizing two recordable dye layers, each capable of storing a little less than the 4.7 gigabyte (GB) of a single layer disc, almost doubling the total disc capacity. Discs can be read in many DVD devices and can only be written using DVD-R DL compatible recorders. It is part of optical disc recording technologies for digital recording to optical disc. DVD-R DL products started appearing on the market during mid-2004.

In computing, external storage refers to non-volatile (secondary) data storage outside a computer's own internal hardware, and thus can be readily disconnected and accessed elsewhere. Such storage devices may refer to removable media, compact flash drives, portable storage devices, or network-attached storage. Web-based cloud storage is the latest technology for external storage.

<span class="mw-page-title-main">DVD recordable</span> Recordable optical disk technology

DVD recordable and DVD rewritable are optical disc recording technologies. Both terms describe DVD optical discs that can be written to by a DVD recorder, whereas only 'rewritable' discs are able to erase and rewrite data. Data is written ('burned') to the disc by a laser, rather than the data being 'pressed' onto the disc during manufacture, like a DVD-ROM. Pressing is used in mass production, primarily for the distribution of home video.

<span class="mw-page-title-main">CD-RW</span> Optical disk technology

CD-RW is a digital optical disc storage format introduced in 1997. A CD-RW compact disc (CD-RWs) can be written, read, erased, and re-written.

Calimetrics was an American technology company 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 data storage systems. Over the years, Calimetrics raised approximately $50M from government, venture, angel, and corporate sources. Calimetrics was acquired in 2003 by LSI Logic and ceased operations in 2004.

<span class="mw-page-title-main">DVD</span> Optical disc format

The DVD is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind of digital data and has been widely used to store video programs, software and other computer files. DVDs offer significantly higher storage capacity than compact discs (CD) while having the same dimensions. A standard single-layer DVD can store up to 4.7 GB of data, a dual-layer DVD up to 8.5 GB. Variants can store up to a maximum of 17.08 GB.

<span class="mw-page-title-main">Blu-ray</span> Digital optical disc format

Blu-ray is a digital optical disc data storage format designed to supersede the DVD format. It was invented and developed in 2005 and released worldwide on June 20, 2006, capable of storing several hours of high-definition video. The main application of Blu-ray is as a medium for video material such as feature films and for the physical distribution of video games for the PlayStation 3, PlayStation 4, PlayStation 5, Xbox One, and Xbox Series X. The name refers to the blue laser used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs.

As of 2021, multiple consumer-oriented, optical-disk media formats are or were available:

<span class="mw-page-title-main">CD-ROM</span> Pre-pressed compact disc containing computer data

A CD-ROM is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both computer data and audio with the latter capable of being played on a CD player, while data is only usable on a computer.

References

  1. Earman, Allen, "Optical Data Storage With Electron Trapping Materials Using M-ary Data Channel Coding," Proceedings of the Optical Data Storage Conference, SPIE, Feb. 1992, San Jose, California. .