Optical disc recording technologies
Encyclopedia
Optical disc authoring
requires a number of different optical disc recorder
technologies working in tandem, from the optical disc
media to the firmware to the control electronics of the optical disc drive. This article discusses some of the more important technologies.
of the digital recording
medium in order to duplicate the effects of the pits and lands created when a commercial optical disc is pressed. Emerging technologies such as holographic data storage
and 3D optical data storage
aim to use entirely different data storage methods, but these products are in development and are not yet widely available.
The earliest form is magneto-optical, which uses a magnetic field in combination with a laser to write to the medium. Though not widely used in consumer equipment, the original NeXT
cube used MO media as its standard storage device, and consumer MO technology is available in the form of Sony
's MiniDisc
. This form of medium is rewriteable.
The most common form of recordable optical media is write-once organic dye technology, popularized in the form of the CD-R
and still used for higher-capacity media such as DVD-R
. This uses the laser alone to scorch a transparent organic dye (usually cyanine
, phthalocyanine
, or azo compound
-based) to create "pits" (i.e. dark spots) over a reflective spiral groove. Most such media are designated with an R (recordable) suffix. Such discs are often quite colorful, generally coming in shades of blue or pale yellow or green.
Rewritable, non-magnetic optical media are possible using phase change alloys, which are converted between crystalline and amorphous states (with different reflectivity) using the heat from the drive laser. Such media must be played in specially tuned drives, since the phase-change material has less of a contrast in reflectivity than dye-based media; while most modern drives support such media, many older CD drives cannot recognize the narrower threshold and cannot read such discs. Phase-change discs are designated with RW (ReWriteable) or RE (Recordable-Erasable). Phase-change discs often appear dark grey.
A new technology has emerged whereby physical changes to a long-lived media creates a new "write-once" option. A drive offered by Millenniata is supposed to record data on proprietary media with a data life-time said to be "forever".
modes. Each mode serves different purposes:
drives, optical disc recorder drives have generally used industry standard connection protocols. Early computer-based CD recorders were generally connected by way of SCSI
; however, as SCSI was abandoned by its most significant users (particularly Apple Computer
), it became an expensive option for most computer users. As a result, the market switched over to Parallel ATA
connections for most internal drives; external drives generally use PATA drive mechanisms connected to a bridge inside the case that connects to a high-speed serial bus such as FireWire or Hi-Speed USB 2.0
. A few, but becoming more and more common, very high-speed drives, mostly DVD recorder
s, use Serial ATA
.
Standalone recorders use standard A/V connections, including RCA connector
s, TOSlink
, and S/PDIF
for audio and RF
, composite video
, component video
, S-Video
, SCART
, and FireWire for video. High-bandwidth digital connections such as HDMI
are not yet commonplace.
Structures in the ATIP do not allow such sizes to be specified.
A buffer underrun
occurs during recording if the supply of data to the recorder is interrupted before the write is complete. Software typically moves the data to be recorded into a buffer
; underrun occurs if the recorder processes data in the buffer faster than the software reloads it. Historically, buffer underrun was often caused by writing data obtained from a slow device, or by slowness of the recording software, from a slow processor or a processor executing other tasks concurrently.
Various recorders minimize or cope with buffer underrun in the following ways:
Since the techniques for protecting against buffer underrun are proprietary and vendor-specific, technical details vary.
Buffer underrun is minimized by a strategy in which the recorder burns a packet rather than an entire session or an entire disc. When using rewritable media (CD-RW
, DVD-RW
, DVD-RAM
), the UDF
file system organizes the disc into packets that are written individually. The packets are referenced by a single, updated address table.
. Packet writing can be used both with once-writeable media and rewriteable media. Several competing and incompatible packet writing disk formats have been developed, including DirectCD and InCD
. The standardized formats for packet writing are the Universal Disk Format
in the plain, VAT, and spared builds.
.
. Features:
version 6.
) claims a life of 300 years on their archival gold CD
-R and 100 years for gold DVDs. Good alternatives would be to additionally backup one's media using other media technologies and/or investing in non-volatile memory
technologies.
Optical disc authoring
Optical disc authoring, including DVD and Blu-ray Disc authoring , is the process of assembling source material—video, audio or other data—into the proper logical volume format to then be recorded onto an optical disc .-Process:To burn an optical disc, one usually first creates an...
requires a number of different optical disc recorder
Optical disc recorder
In computing, an optical disc drive is a disk drive that uses laser light or electromagnetic waves near the light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only read from discs, but recent drives are commonly both readers and recorders,...
technologies working in tandem, from the optical disc
Optical disc
In computing and optical disc recording technologies, an optical disc is a flat, usually circular disc which encodes binary data in the form of pits and lands on a special material on one of its flat surfaces...
media to the firmware to the control electronics of the optical disc drive. This article discusses some of the more important technologies.
Types of recordable optical disc
There are numerous formats of recordable optical direct to disk on the market, all of which are based on using a laser to change the reflectivityReflectivity
In optics and photometry, reflectivity is the fraction of incident radiation reflected by a surface. In general it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength...
of the digital recording
Digital recording
In digital recording, digital audio and digital video is directly recorded to a storage device as a stream of discrete numbers, representing the changes in air pressure for audio and chroma and luminance values for video through time, thus making an abstract template for the original sound or...
medium in order to duplicate the effects of the pits and lands created when a commercial optical disc is pressed. Emerging technologies such as holographic data storage
Holographic data storage
Holographic data storage is a potential technology in the area of high-capacity data storage currently dominated by magnetic and conventional optical data storage. Magnetic and optical data storage devices rely on individual bits being stored as distinct magnetic or optical changes on the surface...
and 3D optical data storage
3D optical data storage
3D optical data storage is the term given to any form of optical data storage in which information can be recorded and/or read with three dimensional resolution ....
aim to use entirely different data storage methods, but these products are in development and are not yet widely available.
The earliest form is magneto-optical, which uses a magnetic field in combination with a laser to write to the medium. Though not widely used in consumer equipment, the original NeXT
NeXT
Next, Inc. was an American computer company headquartered in Redwood City, California, that developed and manufactured a series of computer workstations intended for the higher education and business markets...
cube used MO media as its standard storage device, and consumer MO technology is available in the form of Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
's MiniDisc
MiniDisc
The disc is permanently housed in a cartridge with a sliding door, similar to the casing of a 3.5" floppy disk. This shutter is opened automatically by a mechanism upon insertion. The audio discs can either be recordable or premastered. Recordable MiniDiscs use a magneto-optical system to record...
. This form of medium is rewriteable.
The most common form of recordable optical media is write-once organic dye technology, popularized in the form of the 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....
and still used for higher-capacity media such as 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....
. This uses the laser alone to scorch a transparent organic dye (usually cyanine
Cyanine
Cyanine is a non-systematic name of a synthetic dye family belonging to polymethine group. Cyanines have many uses as fluorescent dyes, particularly in biomedical imaging...
, phthalocyanine
Phthalocyanine
Phthalocyanine is an intensely blue-green coloured macrocyclic compound that is widely used in dyeing. Phthalocyanines form coordination complexes with most elements of the periodic table...
, or azo compound
Azo compound
Azo compounds are compounds bearing the functional group R-N=N-R', in which R and R' can be either aryl or alkyl. IUPAC defines azo compounds as: "Derivatives of diazene , HN=NH, wherein both hydrogens are substituted by hydrocarbyl groups, e.g. PhN=NPh azobenzene or diphenyldiazene." The more...
-based) to create "pits" (i.e. dark spots) over a reflective spiral groove. Most such media are designated with an R (recordable) suffix. Such discs are often quite colorful, generally coming in shades of blue or pale yellow or green.
Rewritable, non-magnetic optical media are possible using phase change alloys, which are converted between crystalline and amorphous states (with different reflectivity) using the heat from the drive laser. Such media must be played in specially tuned drives, since the phase-change material has less of a contrast in reflectivity than dye-based media; while most modern drives support such media, many older CD drives cannot recognize the narrower threshold and cannot read such discs. Phase-change discs are designated with RW (ReWriteable) or RE (Recordable-Erasable). Phase-change discs often appear dark grey.
A new technology has emerged whereby physical changes to a long-lived media creates a new "write-once" option. A drive offered by Millenniata is supposed to record data on proprietary media with a data life-time said to be "forever".
Optimum Power Calibration
Optimum Power Calibration (OPC) is a function that checks the proper laser power for writing a particular session in the media in use. More sophisticated is Active OPC, which calculates the optimum laser power and adjusts it in real-time.Recording modes
Optical discs can be recorded in Disc At Once, Track At Once, Session at Once (i.e. multiple burning sessions for one disc), or packet writingPacket writing
Packet writing or IPW , is an optical disc recording technology used to allow write-once and rewritable CD and DVD media to be used in a similar manner to a floppy disk from within the operating system, i.e., it allows users to create, modify, and delete files and directories on demand without the...
modes. Each mode serves different purposes:
- Disc At Once: writes the entire disc in one pass; preferred for duplication masters
- Track At Once: writes individual tracks with a gap between tracks; used for audio CDs
- Session At Once: writes and finalizes multiple sessions on one CD; usually not supported for CD Audio, and not universally supported by authoring software
- Packet writing: writes data to the medium on demand (see below)
Connection technologies
Unlike early CD-ROMCD-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....
drives, optical disc recorder drives have generally used industry standard connection protocols. Early computer-based CD recorders were generally connected by way of SCSI
SCSI
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
; however, as SCSI was abandoned by its most significant users (particularly Apple Computer
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
), it became an expensive option for most computer users. As a result, the market switched over to Parallel ATA
AT Attachment
Parallel ATA , originally ATA, is an interface standard for the connection of storage devices such as hard disks, solid-state drives, floppy drives, and optical disc drives in computers. The standard is maintained by X3/INCITS committee...
connections for most internal drives; external drives generally use PATA drive mechanisms connected to a bridge inside the case that connects to a high-speed serial bus such as FireWire or Hi-Speed USB 2.0
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
. A few, but becoming more and more common, very high-speed drives, mostly DVD recorder
DVD recorder
A DVD recorder , is an optical disc recorder that uses Optical disc recording technologies to digitally record analog signal or digital signals onto blank writable DVD media...
s, use Serial ATA
Serial ATA
Serial ATA is a computer bus interface for connecting host bus adapters to mass storage devices such as hard disk drives and optical drives...
.
Standalone recorders use standard A/V connections, including RCA connector
RCA connector
An RCA connector, sometimes called a phono connector or cinch connector, is a type of electrical connector commonly used to carry audio and video signals...
s, TOSlink
TOSLINK
TOSLINK is a standardized optical fiber connection system. Also known generically as an "optical audio cable," its most common use is in consumer audio equipment , where it carries a digital audio stream from components such as MiniDisc, CD and DVD players, DAT recorders, computers, and modern...
, and S/PDIF
S/PDIF
S/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
for audio and RF
RF modulator
An RF modulator is a device that takes a baseband input signal and outputs a radio frequency-modulated signal....
, composite video
Composite video
Composite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
, component video
Component video
Component video is a video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video information that is transmitted or stored as three separate signals...
, S-Video
S-Video
Separate Video, more commonly known as S-Video and Y/C, is often referred to by JVC as both an S-VHS connector and as Super Video. It is an analog video transmission scheme, in which video information is encoded on two channels: luma and chroma...
, SCART
SCART
SCART is a French-originated standard and associated 21-pin connector for connecting audio-visual equipment together...
, and FireWire for video. High-bandwidth digital connections such as HDMI
HDMI
HDMI is a compact audio/video interface for transmitting uncompressed digital data. It is a digital alternative to consumer analog standards, such as radio frequency coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA...
are not yet commonplace.
Overburning
Overburning is the process of recording data past the normal size limit.Structures in the ATIP do not allow such sizes to be specified.
Buffer underrun protection
Usually, the recorder must perform a complete write without pauses. Once the laser is on, stopping and restarting the recording process may introduce flaws.A buffer underrun
Buffer underrun
In computing, buffer underrun or buffer underflow is a state occurring when a buffer used to communicate between two devices or processes is fed with data at a lower speed than the data is being read from it. This requires the program or device reading from the buffer to pause its processing while...
occurs during recording if the supply of data to the recorder is interrupted before the write is complete. Software typically moves the data to be recorded into a buffer
Buffer (computer science)
In computer science, a buffer is a region of a physical memory storage used to temporarily hold data while it is being moved from one place to another. Typically, the data is stored in a buffer as it is retrieved from an input device or just before it is sent to an output device...
; underrun occurs if the recorder processes data in the buffer faster than the software reloads it. Historically, buffer underrun was often caused by writing data obtained from a slow device, or by slowness of the recording software, from a slow processor or a processor executing other tasks concurrently.
Various recorders minimize or cope with buffer underrun in the following ways:
- Nearly all burners can slow the rotation of the disc and record at a slower rate. A burner may do so on sensing that it is drawing down the data in the buffer faster than software is reloading it.
- Recording software maintains larger buffers than when CD recorders were first introduced. Some recorders maintain their own buffer memory independently of the computer. This additional buffering ensures that momentary pauses in the supply of data do not cause buffer underrun.
- Some recorders are, in fact, able to stop writing in the middle of a session, and resume writing whenever the buffer is refilled. Recorders with such buffer underrun protection handle the interruption with an extremely small gap in the recorded track on the disc.
Since the techniques for protecting against buffer underrun are proprietary and vendor-specific, technical details vary.
Buffer underrun is minimized by a strategy in which the recorder burns a packet rather than an entire session or an entire disc. When using rewritable media (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....
, 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-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...
), the UDF
Universal Disk Format
Universal Disk Format is an implementation of the specification known as ISO/IEC 13346 and ECMA-167 and 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...
file system organizes the disc into packets that are written individually. The packets are referenced by a single, updated address table.
Packet writing
Packet writing is a technology that allows optical discs to be used in a similar manner to a floppy diskFloppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
. Packet writing can be used both with once-writeable media and rewriteable media. Several competing and incompatible packet writing disk formats have been developed, including DirectCD and InCD
InCD
InCD is a packet writing software developed by Nero AG for Microsoft Windows.InCD allows optical discs to be used in a similar manner to a floppy disk...
. The standardized formats for packet writing are the Universal Disk Format
Universal Disk Format
Universal Disk Format is an implementation of the specification known as ISO/IEC 13346 and ECMA-167 and 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...
in the plain, VAT, and spared builds.
BURN-Proof
BURN-Proof (Buffer Underrun-Proof) is a proprietary technology for buffer underrun protection developed by SanyoSanyo
is a major electronics company and member of the Fortune 500 whose headquarters is located in Moriguchi, Osaka prefecture, Japan. Sanyo targets the middle of the market and has over 230 Subsidiaries and Affiliates....
.
SafeBurn
SafeBurn is a proprietary technology for buffer underrun protection developed by Yamaha Corporation.Power Burn
Power Burn is a proprietary technology for buffer underrun protection, developed by SonySony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
. Features:
- Buffer underrun protection: When a buffer underrun occurs, the drive suspends writing. The drive memorizes the end writing point and timing, and immediately resumes writing from that exact point when sufficient data is filled in the buffer memory.
- Protection from write errors caused by shock and vibration: PowerBurn's Shock Proof technology pauses writing when the device is moved, and resumes after the drive becomes stable. This allows it to work in a mobile environment.
- Optimization of write conditions: The drive detects characteristics of each individual medium and optimizes all key writing conditions such as writing speed, laser power and write strategy.
JustSpeed
JustSpeed is a technology that automatically adapts the write speed to the medium inserted. It is supported by Nero Burning ROMNero Burning ROM
Nero Multimedia Suite is a popular software suite for Microsoft Windows by Nero AG . Version 10 of this product was released in April 2010.- Included products :The following applications are included in Nero 11 :Disc authoring...
version 6.
Longevity
Retail recordable/writable optical media contain dyes in/on the optical media to record data, whereas factory-manufactured optical media use physical "pits" created by plastic molds/casts. As a result, data storage on retail optical media does not have the life-span of factory-manufactured optical media. One must therefore be wary of storing family photos and videos (or any other miscellaneous important data) solely on dye-based optical media. MAM-A (MitsuiMitsui
is one of the largest corporate conglomerates in Japan and one of the largest publicly traded companies in the world.-History:Founded by Mitsui Takatoshi , who was the fourth son of a shopkeeper in Matsusaka, in what is now today's Mie prefecture...
) claims a life of 300 years on their archival gold CD
Gold CD
A gold CD is one in which gold is used in place of the super purity aluminiumcommonly used as the reflective coating on ordinary CDs or silver on ordinary CD-RsThe gold coats more evenly and reacts with oxygen more slowly, thus...
-R and 100 years for gold DVDs. Good alternatives would be to additionally backup one's media using other media technologies and/or investing in non-volatile memory
Non-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
technologies.
External links
- Understanding CD-R & CD-RW by Hugh Bennett
- Understanding Recordable & Rewritable DVD by Hugh Bennett
- Burning For The Long Haul
- CD and DVD Longevity: How Long Will They Last?