DVD recordable
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DVD recordable and DVD rewritable refer to DVD optical disc formats that can be recorded (written, "burned"), either 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 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. Dyes give the data side of a disc a distinct color. 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-R/DVD-RW (DVD "dash" (or DVD "minus" outside the US))
- 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.[citation needed]
- DVD+R/DVD+RW (DVD "plus")
- Developed by Philips and Sony with their DVD+RW Alliance. Introduced 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.
Multi-format drives can read (write) more than one format; e.g., DVD±RW (DVD plus-dash rewritable) is used to refer to drives that can write/rewrite both plus and dash formats, but not necessarily DVD-RAM.
DVD recordable media are sold in two standard sizes, a standard-sized 12cm size for home recording and computer usage, and a small 8cm size (sometimes known as a miniDVD) for use in compact camcorders and the like.
Contents |
[edit] DVD write-once formats
[edit] DVD rewritable formats
[edit] Speed
| Drive speed | Data rate | Disc write time | Equivalent CD rate | Reading speed | |
|---|---|---|---|---|---|
| 1× | 11.08 Mbit/s | 1.32 MB/s | 53 min | 9× | 8×–18× |
| 2× | 22.16 Mbit/s | 2.64 MB/s | 27 min | 18× | 20×–24× |
| 4× | 44.32 Mbit/s | 5.28 MB/s | 14 min | 36× | 24×–32× |
| 5× | 55.40 Mbit/s | 6.60 MB/s | 11 min | 45× | 24×–32× |
| 6× | 66.48 Mbit/s | 7.93 MB/s | 9 min | 54× | 24×–32× |
| 8× | 88.64 Mbit/s | 10.57 MB/s | 7 min | 72× | 32×–40× |
| 10× | 110.80 Mbit/s | 13.21 MB/s | 6 min | 90× | 32×–40× |
| 16× | 177.28 Mbit/s | 21.13 MB/s | 4 min | 144× | 32×–40× |
| 18× | 199.44 Mbit/s | 23.76 MB/s | 3 min | 162× | 32×–40× |
Notes:
- DVD 1× actual spin is 3 times that of CD 1×
- Disk write time in table does not include overhead, leadout, etc.
[edit] 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].[1]
Mini-DVDs sold for use with camcorders generally have a capacity of approximately 1.7GB.
DVD+R DL disc are advertised to hold 8.5 GB.
[edit] Longevity
According to a study published in 2008 by the Preservation Research and Testing Division of the U.S. Library of Congress, most recordable CD products have a higher probability of greater longevity compared to recordable DVD products.[2]
