DVD recordable
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DVD recordable and DVD rewritable refer to DVD optical disc formats that can be recorded (written, "burned"), either [[wiktionary:write once|write once]] or rewritable (write multiple times) format written by laser, as compared to DVD-ROM, which is mass-produced by pressing. DVD recordable is a general term that refers to both write-once and rewritable formats, whereas DVD rewritable refers only to rewritable formats.
Like CD-Rs, DVD recordables also use dyes. Depending on the intensity of the laser, the reflective property of the dye on a particular spot will determine whether it is a peak or a valley representation from pressed DVD. Also because of the dyes, it gives the disc those distinct colors at the shiny side. Dyes are also the reason playback is not guaranteed. Their reflective properties are not as good as with stamped DVDs that commonly have aluminum as the reflective layer.
Recordable DVDs are divided into three incompatible camps:
- DVD "dash" (-)
- First DVD recordable format released in the market. Developed by Pioneer and backed by the DVD Forum. Has broader playback compatibility than the "+" especially with much older players. The dash format is based on an older CD-R/RW format for easy upgrade or migration for disc manufacturers.
- DVD "plus" (+)
- Developed by Philips and Sony with their DVD+RW Alliance. Came out after the "-" format.
- DVD-RAM
- As RAM stands for Random Access Memory, it works more or less like a hard-drive and was designed for corporate back-up use. Can only be read in drives that are DVD-RAM compatible. DVD Forum backs this format.
DVD write-once formats
DVD rewritable formats
Speed
| Drive speed | Data rate | Disc write time | Equivalent CD rate | Reading speed | |
|---|---|---|---|---|---|
| 1x | 11.08 Mbit/s | 1.32 MB/s | 53 min | 9x | 8x-18x |
| 2x | 22.16 Mbit/s | 2.64 MB/s | 27 min | 18x | 20x-24x |
| 4x | 44.32 Mbit/s | 5.28 MB/s | 14 min | 36x | 24x-32x |
| 5x | 55.40 Mbit/s | 6.60 MB/s | 11 min | 45x | 24x-32x |
| 6x | 66.48 Mbit/s | 7.93 MB/s | 9 min | 54x | 24x-32x |
| 8x | 88.64 Mbit/s | 10.57 MB/s | 7 min | 72x | 32x-40x |
| 10x | 110.80 Mbit/s | 13.21 MB/s | 6 min | 90x | 32x-40x |
| 16x | 177.28 Mbit/s | 21.13 MB/s | 4 min | 144x | 32x-40x |
- DVD 1x actual spin is 3 times that of CD 1x
- Disk write time in table does not include overhead, leadout etc
Capacities
A DVD advertised as 4.7 GB may seem to hold less than that because manufacturers quote the capacity of a writable DVD disc using decimal prefixes rather than the binary prefixes used by some software. This can be confusing. While a 4.7 GB DVD can store 4.7 billion bytes [4,700,000,000 bytes ÷ 1000 b/kB = 4,700,000 kB ÷ 1000 kB/MB = 4,700 MB ÷ 1000 MB/GB = 4.7 GB], using binary prefixes the same capacity is roughly 4.38 GiB [4,700,000,000 bytes ÷ 1024 b/KiB = 4,589,844 KiB ÷ 1024 KiB/MiB = 4,482.27 MiB ÷ 1024 MiB/GiB = 4.38 GiB]. [link]
External links
- [Understanding Recordable & Rewritable DVD] by Hugh Bennett
- [DVD Forum]
- [DVD+RW Alliance]
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