DVD+RW
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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. From a business standpoint, the DVD+RW format was created largely in order to avoid paying royalties to the DVD Forum for the competing DVD-RW format.[1] Additionally, DVD+RW supports a method of writing called "lossless linking", which makes it suitable for random access and improves compatibility with DVD players.[1]
DVD+RW must be formatted before recording by a DVD recorder.
The rewritable DVD+RW standard was formalized earlier than the non-rewritable DVD+R (the opposite was true with the DVD- formats). Although credit for developing the standard is often attributed unilaterally to Philips, it was "finalized" in 1997 by the DVD+RW Alliance. It was then abandoned until 2001, when it was heavily revised (in particular, the capacity increased from 2.8 GB to 4.7GB).[citation needed]
Technical details
The recording layer in DVD+RW and DVD-RW discs is a phase change metal alloy (often GeSbTe) whose crystalline phase and amorphous phase have different reflectivity. The states can be switched depending on the power of the writing laser, so data can be written, read, erased and re-written. DVD-R and DVD+R discs use an organic dye.
The capacity of a single-layer disc is approximated as 4.7 × 109 bytes. In actuality, the disc is laid out with 2295104 sectors of 2048 bytes each which comes to 4,700,372,992 bytes, 4,590,208 kibibytes (KiB, binary kilobytes), 4482.625 mebibytes (MiB, binary megabytes), or 4.377563476 gibibytes (GiB, binary gigabytes).
Dual layer
A dual-layer DVD+RW specification was approved in March 2006 with a capacity of 8.5 GB.[2] However, manufacturing support for rewritable dual-layer discs did not materialize due to costs and expected competition from newer formats like Blu-ray and HD DVD, which boasted up to 25 GB on a single layer.
See also
References
- ^ a b http://www.tomshardware.com/reviews/dvd-burner-test,586-2.html
- ^ DVD+RW part 2: Dual Layer, volume 1; DVD+RW 8.5 Gbytes, Basic Format Specifications, version 1.0, March 2006
Further reading
- ISO/IEC 17341:2009, Data interchange on 120 mm and 80 mm optical disk using +RW format -- Capacity: 4,7 Gbytes and 1,46 Gbytes per side (recording speed up to 4X)
- ISO/IEC 26925:2009, Data interchange on 120 mm and 80 mm optical disk using +RW HS format -- Capacity: 4,7 Gbytes and 1,46 Gbytes per side (recording speed 8X)
- ISO/IEC 29642:2009, Data interchange on 120 mm and 80 mm optical disk using +RW DL format -- Capacity: 8,55 Gbytes and 2,66 Gbytes per side (recording speed 2,4X)