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Optical disc authoring requires a number of different optical discrecorder technologies working in tandem, from theoptical disc media to thefirmware to the control electronics of theoptical disc drive.
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There are numerous formats of recordable opticaldirect to disk on the market, all of which are based on using alaser to change thereflectivity of thedigital recording medium in order to duplicate the effects of the pits and lands created when a commercial optical disc is pressed. Emerging technologies such asholographic data storage and3D 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 ismagneto-optical, which uses a magnetic field in combination with a laser to write to the medium. Though not widely used in consumer equipment, the originalNeXT cube used MO media as its standard storage device, and consumer MO technology is available in the form ofSony'sMiniDisc. This form of medium is rewriteable.
The most common form of recordable optical media iswrite-onceorganic dye technology, popularized in the form of theCD-R and still used for higher-capacity media such asDVD-R. This uses the laser alone to scorch a transparent organic dye (usuallycyanine,phthalocyanine, orazo 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 usingphase change alloys, which are converted between crystalline and amorphous states (with different reflectivity) using the heat from the drivelaser. 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 olderCD 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.
Another technology creates pits in an inorganic carbon layer, a "write-once" option. Created by Millenniata,M-DISC, records data on special M-DISC with a data life-time of several hundred years.[1]
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 isActive OPC, which calculates the optimum laser power and adjusts it in real-time.
Optical discs can be recorded inDisc At Once,Track At Once,Session at Once (i.e. multiple burning sessions for one disc), orpacket writing modes. Each mode serves different purposes:
Unlike earlyCD-ROM drives, optical disc recorder drives have generally used industry standard connection protocols. Early computer-based CD recorders were generally connected by way ofSCSI; however, as SCSI was abandoned by its most significant users (particularlyApple Computer), it became an expensive option for most computer users. As a result, the market switched over toParallel 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 asFireWire or Hi-SpeedUSB 2.0. Nearly all modern drives, particularlyBlu-ray drives useSerial ATA.
Standalone recorders use standard A/V connections, includingRCA connectors,TOSlink, andS/PDIF for audio andRF,composite video,component video,S-Video,SCART, andFireWire for video. High-bandwidth digital connections such asHDMI are unlikely to feature as recorder devices are not permitted to decrypt theencrypted video content.
Overburning is the process of recording data past the normal, vendor-specified size limit of the recordable media. Structures in theATIP do not allow such sizes to be specified.
Overburning may be used to determine the actual capacity limit of a recordable disc, since the capacity rated by recordable disc vendors merely is theguaranteed capacity, beyond which the actual capacity is indefinite. Data located beyond the specified capacity is not guaranteed to be readable.[2]
Usually, the recorder must perform a complete write without pauses. Once the laser is on, stopping and restarting the recording process may introduce flaws.
Abuffer 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 abuffer; 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:
Buffer underrun is minimized by a strategy in which the recorder burns apacket rather than an entire session or an entire disc. When usingrewritable media (CD-RW,DVD-RW,DVD-RAM), theUDF file system organizes the disc into packets that are written individually. The packets are referenced by a single, updated address table.
BURN-Proof (BufferUnderrun-Proof) is a proprietary technology for buffer underrun protection developed bySanyo.[5]
FlextraLink is a proprietary technology forbuffer underrun protection developed byAsus.[6]
FlextraSpeed continuously monitors the recording media and sets the optimal writing speeds to ensure best recording quality, for discs that can’t withstand high-speed burning.[7]
Power Burn is a proprietary technology for buffer underrun protection, developed bySony. Features:
SafeBurn is a proprietary technology forbuffer underrun protection developed byYamaha Corporation.
Packet writing is a technology that allows optical discs to be used in a similar manner to afloppy disk. Packet writing can be used both with once-writeable media and rewriteable media. Several competing and incompatible packet writing disk formats have been developed, includingDirectCD andInCD. The standardized formats for packet writing are theUniversal Disk Format in the plain, VAT, and spared builds.
Using thesimulated writing orsimulated burning feature ofoptical disc authoring software, the writing process will be simulated, which means that the disc spins and the laser moves as if on an actual writing process, but without any data being recorded to the disc.
This feature allows for observing the writing speeds and patterns (e.g.constant angular velocity,constant linear velocity andP-CAV andZ-CLV variants) with different writing speed settings and testing the highest capacity of an individual disc that would be achievable usingoverburning.[8]
This feature is standardized onCD-R,CD-RW,DVD-R andDVD-RW, but not onDVD+R andDVD+RW, on which onlyPlextor optical drives support simulated writing so far.[9][10]
Retail recordable/writable optical media contain dyes in/on the optical media to record data, whereasfactory-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. The problem is exacerbated because as the writing laser of the recorder is used, its power output drops with age - typically after just a few years. Consequently, a disc written with a laser that is nearing the end of its useful life may not have a readable life that is as long as if a new laser had been used.
Dye based optical media should not be solely relied on to archive valuable data. MAM-A (Mitsui) claims a life of 300 years on their archivalgold 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 innon-volatile memory technologies.[11]
A series of follow-up studies conducted by theCanadian Conservation Institute in 2019 revealed thatCD-R withphthalocyanine-dye and a gold-metal layer had the greatest longevity at over 100 years when stored at ideal temperature and humidity-levels. The second longest wasDVD-R (gold-metal layer) with an average longevity of 50-100 years under ideal conditions.CD-R with phthalocyanine and a silver-metal-alloy layer also scored an average longevity of 50-100 years,however, the researchers noted that if the storage environment contains pollutants any CD-Rs that used a silver layer would likely degrade faster than discs with a gold layer. The researchers concluded the silver layer discs may not be a suitable solution for applications where longevity is important.[12] Both CD-R and DVD-R outperformed all forms ofBlu-ray disc in regards to longevity: the best performing Blu-ray disc, theBD-RE (rewritable Blu-ray) has an average longevity of 20-50 years, while non-rewritableBD-R discs have an average longevity of 10-20 years under ideal conditions.[12]
