The number of different formats available in DVD drives can be confusing to anyone in the market for one. The list is much longer, but to address a few of the common formats, we have DVD-ROM, DVD-R, DVD-RW, DVD+R, DVD+RW, DVD-RAM ,DVD+R DL and DVD±RW. Wow! This list of common formats is long enough, no wonder it’s confusing!
The reason for various recordable DVD formats is that no one group owns the technology and different groups have chosen to support one technology over another. There is no industrial standard for manufacturers to reference, so for the time being consumers will have a few choices.
The first thing to address is DVD itself, which stands for Digital Versatile Disc. Some may argue that the V stands for Video, but with the capability to store video, audio, and data files, Versatile is definitely the keyword.
Start with the Basics
A DVD-ROM drive is the only one we will address that does not record. ROM stands for Read Only Memory, and refers to the typical drive that can merely read DVDs, as well as CDs (all DVD drives can read CDs). The Lite-On LTD-163-DO-R has attributes representative of your typical DVD-ROM drive, and features a maximum DVD read speed of 16x and a maximum CD read speed of 48x.
Before getting into the different recordable formats, let’s address the basics of what the R and RW stand for, regardless of whether there is a + or – in the middle. R stands for Recordable, which indicates that the disk may be recorded to only once. RW stands for ReWritable, which indicates that the disc may be recorded to more than once, and are generally rated for 1000 rewrites under good conditions.
The DVD+R/+RW format is a newer format, also based on CD-RW technology, and compatible with a large percentage of stand alone DVD players. The +R/+RW technology is not supported by the DVD Forum, and its main backing comes from a group called the DVD+RW Alliance. The Alliance “is a voluntary group of industry-leading personal computing manufacturers, optical storage and electronics manufacturers” with members such as Dell, Hewlett Packard, Sony, and Phillips Electronics.
The DVD-RAM format is based on PD-RW (Phase-Differential) drives, and actually uses a cartridge to hold the media (just like its PD-RW predecessor). Some DVD-RAM cartridges are double sided, making them ideal for companies to use as system backup, hence DVD-RAM is usually found only in commercial applications, and most end-users won’t ever need to use or see this type of drive. The DVD-RAM standard is also supported by the DVD Forum just like the DVD-R/RW format. However, because of its use of a cartridge (limiting it’s compatibility), and the scarcity and price of the media used, DVD-RAM is a distant third when compared to the DVD+R/+RW and DVD-R/–RW technology.
The +R/+RW and –R/-RW formats are similar, and the main difference DVD+R technology has is the ability to record to multiple layers (with its new DVD+R DL format), where DVD-R can only record to one layer (not all +R drives are capable of dual layer burning, but no -R drives are). The Plextor PX-504U is an example of an external DVD+R/+RW drive capable of recording single layer discs in the +R/+RW format, but also able to read discs recorded by a DVD-R drive.
DVD±RW is not actually a separate format, but the designation given to drives capable of both –R/–RW and +R/+RW operation. This type of drive is typically called a “Dual Drive” (not to be confused with a “Double Layer” drive) since it can write to both the +R/+RW and –R/–RW formats. The Samsung TS-H552 is a DVD±RW drive capable of reading and writing every format discussed so far, and then some. It takes advantage of DVD+R DL (Double Layer) technology available with the +R format, allowing the appropriate media to store virtually double the 4.37 GB capacity of a typical single layer disc.
The other main thing to consider with DVD burners is selecting the correct media. Media for DVD-R, DVD-RW, DVD+R and DVD+RW media may all look the same, but they are slightly different in order to match the specific recording formats. The price of media for either format is generally the same, with RW media costing a good deal more than R media of either format. Double Layer media is even more expensive, and is the only way for an owner of DVD+R DL drive to take advantage of the tremendous capacity increase. As the amount of Double Layer drives increase in the market, the price of the DVD+R DL media is expected to fall with increased production of the media. DVD Burners (as these drive are often referred to) can be picky about the media supported, so be sure to choose your media wisely.
DVD+R : Writes to DVD+R media (will also typically write to CD-R and CD-RW media)
DVD+RW : Writes to DVD+RW media (will also typically write to DVD+R, CD-R and CD-RW media)
DVD+R DL : Writes to DVD+R DL (Double Layer) media (will also typically write to DVD+R, DVD+RW, CD-R and CD-RW media; many Double Layer drives are ALSO dual drives – that is, able to write to BOTH +R/RW and –R/RW media)
DVD-RAM : Writes to DVD-RAM cartridges (not in wide use on consumer market – mainly a business format; can also read PD-RW discs. Will not usually be able to write to any other format including CD-R or CD-RW)
DVD-R : Writes to DVD-R media (will also typically write to CD-R and CD-RW media)
DVD-RW : Writes to DVD-RW media (will also typically write to DVD-R, CD-R and CD-RW media)
DVD±RW : Writes to DVD-RW and DVD+RW media (will also typically write to DVD-R, DVD+R, CD-R and CD-RW media; typically called “Dual Drives” since it can burn to two different DVD formats)
BD-ROM: Reads Blu-Ray discs
HD-DVD-ROM: Reads high-definition DVD discs.
The name Blu-ray Disc is derived from the blue-violet laser used to read and write this type of disc. Because of this shorter wavelength (405 nm), substantially more data can be stored on a Blu-ray Disc than on the common DVD format, which uses a red, 650 nm laser. In comparison to HD DVD, which also uses a blue laser, Blu-ray Disc has more information capacity per layer (currently 25 GB, but test media is up to 33 GB). Several manufacturers have released 50 GB recordable BDs and rewritable discs. All supporting studios have either already released or have announced release of movies on 50GB discs.
The Blu-ray Disc is a similar PDD, another optical disc format developed by Sony (which has been available since 2004) but offering higher data transfer speeds. PDD was not intended for home video use and was aimed at business data archiving and backup, although currently it is gaining popularity as an HD video format medium. The UDO format is aimed at similar purposes. Blu-ray Disc is currently embroiled in a bitter format war against the HD DVD disc.
Initial versions of Sony’s Blu-ray Disc-authoring software only included support for MPEG-2 video, so the initial Blu-ray Discs were forced to use MPEG-2 rather than the newer codecs, VC-1 and H.264. An upgrade was subsequently released supporting the newer compression methods so the second wave of Blu-ray Disc titles were able to make use of this. The choice of codecs affects disc cost (due to related licensing/royalty payments) as well as program capacity. The two more advanced video codecs can typically achieve twice the video runtime of MPEG-2. When using MPEG-2, quality considerations would limit the publisher to around two hours of high-definition content on a single-layer (25 GB) BD-ROM.
For audio, BD-ROM players are required to support Dolby Digital AC-3, DTS, and linear PCM (up to 7.1 channels). Dolby Digital Plus, and lossless formats Dolby TrueHD and DTS HD are player optional. BD-ROM titles must use one of mandatory audiotracks for the primary soundtrack (linear PCM 5.1, Dolby Digital 5.1 or DTS 5.1.). A secondary audiotrack, if present, may use any of the mandatory or optional codecs.For uncompressed PCM and lossless audio in Dolby TrueHD or DTS-HD Master Audio formats, Blu-ray Discs support encoding in up to 24-bit/192 kHz for up to six channels, or up to eight channels of up to 24-bit/96 kHz encoding. For reference, even new big-budget Hollywood films are mastered in only 24-bit/48 kHz, with 16-bit/48 kHz being common for ordinary films.
For users recording digital television broadcasts, the Blu-ray Disc’s baseline datarate of 36 Mbit/s is more than adequate to record high-definition broadcasts. Support for new codecs will evolve as they are encapsulated by broadcasters into their MPEG-2 transport streams, and consumer set-top boxes capable of decoding them are rolled out. For Blu-ray Disc movies the maximum transfer rate is 54 Mbit/s (1.5x) for the combined audio and video payload, of which a maximum of 40 Mbit/s can be dedicated to video data. This compares favorably to the maximum of 36.55 Mbit/s in HD DVD movies for audio and video data.
Originally, Blu-ray Disc drives in production could only transfer approximately 4.5 MB/s or 36 Mbit/s (54 Mbit/s required for BD-ROM), but 2x speed drives with a 9 MB/s or 72 Mbit/s transfer rate are now available. Rates of 8x (288 Mbit/s) or more are planned for the future. First devices used AT Attachment but newest ones support Serial ATA.
HD DVD, High Density DVD, or High-Definition DVD is a high-density optical disc format designed for the storage of data and high-definition video.
The HD DVD disc is designed to be the successor to the DVD format and can store roughly 3-4 times the amount of data as its predecessor. Although it uses the same blue-violet 405 nm laser as Blu-ray Disc uses, technical differences make the two formats incompatible. The additional capacity of HD DVD means the discs are more suited to high-definition video than standard DVDs. In comparison to its main competitor, Blu-ray Disc, HD DVD has less information capacity per layer (15 gigabytes instead of Blu-ray Disc’s 25). HD DVD shares the same basic disc structure as a standard DVD: back-to-back bonding of two 0.6 mm thick, 120 mm diameter substrates.
The primary rival to Blu-ray Disc is HD DVD, championed by Toshiba, NEC Corporation, Microsoft, and Intel. HD DVD has a lower theoretical disc capacity per layer (15 GB vs 25 GB). The Blu-ray Disc version of the Adam Sandler movie Click was released on October 10, 2006 as the first ever dual-layer release. Sony’s goal is to use 50 GB dual-layer discs to store up to nine hours of HD video content. Alternatively, studios releasing movies on Blu-ray Disc can choose to use VC-1 or H.264/AVC instead of MPEG-2 as an alternative way to put four hours of high-definition content on a (single layer) BD.
Both HD DVD and Blu-ray Disc support the 24p (traditional movie) frame rate, but technical implementations of this mode are different among the two formats. Blu-ray Disc supports 24p with its native timing, while HD DVD uses 30i timing for 24p (replacing missing frames with “repeat field flags”). Decoders can ignore the “flags” to output 24p. There is no impact on picture resolution or storage space as a result of this, as the HD DVD format uses the exact same video information — it simply adds notational overhead.
On November 29, 2004 four Hollywood studios (New Line Cinema, Paramount Pictures, Universal Studios and Warner Bros.) announced non-exclusive agreements to support HD DVD. Since that time, Paramount and Warner have chosen to release titles in both Blu-ray Disc and HD DVD, while only Universal has since announced exclusive support for HD DVD. New Line has not released movies in either format yet but since it is owned by Warner it is expected to follow the parent company’s lead.
This article took a look at the more common formats of DVD drives in order to shed some light on all the choices available. The differences between them all may be subtle, but the compatibility issues can be quite frustrating. The simple answer to anyone considering a drive is to forget about + and – by themselves, and shoot for universal compatibility with a good DVD±RW with DVD+R DL support.
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||