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DVD-R and DVD+R
DVD-R offers write-once recording
with a capacity of 4.7GB per side (about 120 minutes of video).
Once files are burned onto the disc, they cannot be deleted or overwritten. The two
write-once formats include DVD-R, from the DVD Forum, and DVD+R, which is
not supported by the DVD Forum. DVD-R is the most compatible across player hardware platforms of all the recordable DVD media.
DVD-R
DVD-R discs make use of a similar technology to
CD-R but with a
different dye and smaller geometries. The first version of this
format had a capacity of 3.95GB but this has been increased to 4.7GB per
side.
There are two types of DVD-R disc ver 2.0 both with a capacity of
4.7GB.
- General purpose discs are intended for use by consumers but
do not allow any data to be written to the lead-in area. This means
that, for example, CSS copy protection cannot be used, but provision is
made for adding CPRM copy protection.
- Authoring use discs which are intended to be used by
authoring studios to test titles and also as media for glass mastering.
The two diferent types require two different recorders and media.
One recorder can only write one type of media.
| Parameter |
Ver 1.0 |
Authoring use |
General use |
| Capacity (GB) |
3.95 |
4.7 |
4.7 |
| Recording method |
Organic dye
layer |
| Laser wavelength |
635/650nm |
635nm |
650nm |
| Min pit length (microns) |
0.44 |
0.40 |
0.40 |
| Track pitch (microns) |
0.80 |
0.74 |
0.74 |
| Laser wavelength |
635/650nm |
635nm |
650nm |
| Pre-pit addressing |
increment |
increment |
decrement |
| Serialization for CPRM |
|
No |
Yes |
| Pre-recording |
|
No |
Yes |
| Track format |
Wobble
pre-groove |
| Modulation & error correction |
8 to 16 & RSPC |
All three common optical disc media (CD, DVD, and Blu-ray) use light from laser diodes,
for spectral purity and ability to be focused precisely. DVD uses light of 650 nm wavelength (red),
as opposed to 780 nm (far-red, commonly called infrared) for CD.
This shorter wavelength for DVD allows a smaller pit on the media surface compared to CDs (0.74 µm for DVD versus 1.6 µm for CD),
accounting in part for DVD's increased storage capacity.
DVD-R disc
After data is written on the DVD, you can see the area where the laser has burned information and where there is no data. The areas
look slightly different.
The recording material consists of organic dyes, most commonly AZO, Phthalocyanine, or Cyanine.
This is the light-sensitive "data layer". When the DVD burner's laser hits the dye, it causes localized heating
and a physical/chemical change (darkening the dye), which creates the 1s and 0s of digital data.
Unlike standard DVD-R discs (which use a heat-sensitive dye that is permanently burned once),
the phase-change alloy in a DVD-RW can be constantly melted and reshaped.
This allows the disc to be erased and rewritten approximately 1,000 times.
The metal alloy (typically silver, indium, antimony, and tellurium) used in DVD-RW (re-writable) can be written, read back or erased using
three distinct laser power settings.
DVD-R is compatible with DVD-ROM, DVD-Video and DVD-Audio so that
recorded DVD-R discs can be read on any suitable DVD hardware, depending
on the format of the data contained on the DVD-R. However discs
cannot use CSS copy protection. Also DVD-9 discs cannot be written
to DVD-R.
DVD-R discs comprise the following data areas:
- Power Calibration Area (PCA)
- Recording Management Area (RMA)
- Lead-in Area
- Data Recordable Area
- Lead-out Area
DVD-R discs allow incremental writing (cf CD-R multisession
writing). Two types of incremental writing are defined:
- Type 1 allows DVD-R discs to be read by an ISO 9660 system, and uses
the UDF Bridge file system.
- Type 2 is for drag and drop file transfer and uses UDF without ISO
9660.
For both types each section of data written to the disc is a Bordered
Area and is followed by the Border Out and Border In which precedes the
next Bordered Area (if any). Each Bordered Area begins with the UDF
file system and ends with the Virtual Allocation Table (VAT).
DVD+R
DVD+R discs should be called +R as they are not
recognized by the DVD
Forum. This format, which is essentially very similar to DVD-R, was
developed by Philips and Sony. It is an extension of the DVD+RW
format supported by the DVD+RW Alliance comprising HP, Philips, Ricoh,
Sony, Yamaha, Verbatim/Mitsubishi Chemical, Dell and Thomson.
This format is similar in functionality and compatibility to DVD-R
General media and is intended for widespread playback on DVD-ROM drives
and DVD-Video players. DVD+R drives write at up to 4X speed and provide a
reliable, low-cost storage solution for archiving video, audio, images and
other data.
DVD-ram
& DVD-rw
Columbia ISA Audio Video
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