According to ABBREVIATIONFINDER, DVD stands for Digital Versatile Disc or Digital Video Disc. It is a data storage medium that is also widely used for film distribution. In this text, you will learn about the main types of existing DVDs – DVD-RAM, DVD-ROM, DVD-R, DVD + R, DVD-RW and DVD + RW – and other characteristics of the technology, such as capabilities and geographic control.
What is DVD
DVD, as already mentioned, is a type of media for data storage or use in multimedia applications (movies, games and so on). The same size as a conventional CD (12 centimeters in diameter, although it can be found in other versions), the DVD differs from the latter in its much larger data storage capacity, made possible thanks to some techniques in the recording process.
All DVD development specifications and standards are executed and maintained by the DVD Forum, an entity formed by the main companies operating in the entertainment and electronic products segments.
At the beginning of the development of the technology, the intention of the manufacturers, in general, was to conquer the market for video applications, until then dominated by the traditional VHS tapes ( Video Home System ). With this goal in focus, DVD was successful quickly, though not easily: the first units of the most popular DVD standard – with 4.7 GB capacity and known as DVD-5 – were tested on models of equipment from different manufacturers and , in many cases, presented problems related to video quality – depending on the brand of the device, the disc was not even read.
Thanks to the initial problems, adjustments were being implemented and, finally, the industry became convinced that DVD would become a well-established standard for data storage and video applications, which it did.
DVD storage capabilities
The DVD Forum group created DVD media with varying data storage capacities. In addition to the aforementioned 4.7 GB DVD-5, there are DVD-9 (8.5 GB) and DVD-10 (9.4 GB), for example. In the latter, both sides of the disc are used. As each side has 4.7 GB, there is therefore 9.4 GB of storage capacity.
The big problem with the DVD-10 – which certainly made it unpopular – is that it is necessary to turn the disc over when the other side needs to be read, as with classic vinyl drives, for example.
In this respect, the DVD-9 standard presents itself as an interesting alternative: discs of the type have 8.5 GB of storage capacity on a single side. It is explained: the DVD-9 uses two layers ( Dual Layer ) to store the data. They are practically “fused” and can be distinguished only by the laser of the reader device. The problem is that the manufacture of this type of disc is expensive, which is why the DVD-9 also did not become very popular.
The table below lists the main types of DVD from a capacity perspective. It is possible to observe that the numbers in the denomination refer to the approximate amount of gigabytes that each variation can store.
|DVD-1||simple||an||8 cm||1.5 GB|
|DVD-2||simple||two||8 cm||2.7 GB|
|DVD-3||double||two||8 cm||2.9 GB|
|DVD-4||double||two + two||8 cm||5.3 GB|
|DVD-5||simple||an||12 cm||4.7 GB|
|DVD-9||simple||two||12 cm||8.5 GB|
|DVD-10||double||two||12 cm||9.4 GB|
|DVD-14||double||one + two||12 cm||13.2 GB|
|DVD-18||double||two + two||12 cm||17 GB|
Note that the DVD-4 and DVD-18 standards are quite peculiar: both can store data on both sides of the disc, each of which has two layers, hence the description “two + two” in the table. DVD-14 is similar, with the difference that one side has only one layer.
Why so much capacity
As you already know, the most popular DVD standard – the DVD-5 – has 4.7 GB of data storage capacity. A conventional CD, on the other hand, has only 650 MB of capacity, even with the same diameter, 12 centimeters. How does the DVD manage to be almost 7 times higher in this respect?
The “magic” begins with the DVD media manufacturing process, where the spacing between tracks (cavities that guide data recording) has been reduced from 1.6 microns (standard on CDs) to 0.74 microns. The smallest data size that can be recorded on the surface of the disc dropped from 0.83 (also standard on CDs) to 0.40 microns. Finally, the laser wavelength of the reader devices went from 780 nanometers (CDs) to approximately 650 nanometers, which is sufficient for reading.
DVDs don’t just vary in terms of storage capacity. It is also possible to find differences in the application: there are DVDs that can only be read, DVDs that can be written by the user only once and rewritable DVDs. Let’s look at the main types.
DVD-ROM is the most common type, as it is used, for example, to distribute films or recordings of musical shows. Just like a program or music CD, it comes with its factory-recorded content. It is not possible to erase or rewrite data on this type of DVD.
Little used, this is a type of recordable and rewritable DVD. Its main advantage over other standards is its useful life: by default, a DVD-RAM supports more than 100 thousand recordings, being very useful for periodic backups. In addition, this type of DVD can generally be used without a specific recording program, as if it were an HD.
The first DVDs of the type had 2.9 GB of capacity and were inside a protective cover, due to the media’s sensitivity to dirt and fingerprints. Subsequent versions appeared offering a recording capacity of 4.7 GB to 9.4 GB, no longer needing that cover.
This type is one of the most widely accepted in the most diverse devices. It is the best option for recording movies, as it is accepted by practically all DVD-players, except for some of the first models. DVD-R, like its predecessor CD-R, only accepts recording once, and after that, its data cannot be erased. Its standard storage capacity is 4.7 GB.
DVD + R
This type is equivalent to DVD-R, including 4.7 GB of storage capacity. DVD + R can also be burned only once and does not allow you to delete your data. What is different about DVD-R from DVD + R, then? Little, the main difference being the fact that the data recorded on a DVD + R is accessed more quickly than on a DVD-R, a characteristic that comes from the manufacturing process of the latter, which is slightly different. In practical terms, however, this difference in access to data is barely noticeable.
DVD-RW is equivalent to CD-RW, as it allows recording and rewriting of data on the disc. The vast majority of DVD players are fully compliant with this standard, but require that the media be “closed” to play movies. “Open” media means that the user can enter data gradually, until the available space is fully used. However, if the person “closes it” (this is done through the recording software), the recording of new information is impossible, being necessary to format the DVD-RW to reuse it.
Like its “brother” DVD-R, the standard storage capacity of the DVD-RW is 4.7 GB.
DVD + RW
This format has almost the same characteristics as its “rival” DVD-RW, including storage capacity, whose standard is also 4.7 GB. On DVD + RW, it is also necessary to “close” the media for playing movies on DVD-players. In practice, its difference from DVD-RW lies in the slightly higher recording speed and the possibility of using technologies such as Lossless linking and Mount Rainier that allow, respectively, to interrupt a recording without causing errors and to change data from only one sector without need to format the disk.
Dual Layer and Double Layer
A DVD that has the already mentioned Dual Layer technology is capable of storing 8.5 GB, as you already know. This is possible thanks to the application of two layers of data on a single side of the media. For this, a layer is made of a material that causes a “semi-transparency” effect, allowing the laser beam of the device to be able to access the second layer “crossing” the first.
And the Double Layer technology , name can also be found when it comes to DVD? Some people think that discs of the type are those that allow recording on both sides. However, this is a mistake: media like this are called double side or double face .
Double Layer technology is actually equivalent to the Dual Layer standard. What happens is that the first type is the standard denomination of DVD-R that has such technology (also called DVD-R DL ). The second, in turn, is applied to DVD + R media. You will understand the reason for this duplication in the next topic.
DVD Forum versus DVD + RW Alliance
Now that you know the most important types of DVDs, you may be wondering why such a variety, since there are quite similar patterns. The answer, in short, is in the dispute between two entities: DVD Forum and DVD + RW Alliance .
The DVD Forum consortium is made up of giants like Time Warner, Pionner and Toshiba, and supports the specifications of the DVD-ROM, DVD-RAM, DVD-R and DVD-RW standards. In turn, the consortium DVD + RW Alliance (or DVD Alliance) was initially formed by companies such as Dell, HP and Sony to support similar DVD standards, whose differentiation is made by the positive sign in the names (DVD + R and DVD + RW) and the use of the term Double Layer in media with two layers.
The DVD Forum holds the rights to the logo (seen below) of DVD technology, which is why DVD + R and DVD + RW manufacturers do not insert this image on the packaging of such products. However, some of these companies display a logo with the words RW in the media, even those that are only recordable (DVD + R), which can cause confusion.
The two groups began to dispute the market, each defending their formats. This caused some manufacturers to make DVD recorders compatible only with DVD-R / RW and others to do so only for DVD + R / RW formats.
Who won this dispute? No one. All the standards offered ended up being well accepted. That is why there are so many formats. As companies were quick to realize this, it is quite common to find DVD recorders compatible with all standards, which meant that most of the companies involved finally supported the two consortia.
The film industry has benefited most from DVD: this type of media is cheaper, more durable and offers better image quality when compared to old VHS tapes. The problem is that this pattern also facilitates smuggling and piracy.
Because of this (at least that’s what companies claim), a geographic control was created: a DVD made in one region does not run on devices designed to work in others. This division is made into six regions, each comprising a group of countries:
- Region 1: United States, Bermuda and Canada;
- Region 2: Most countries in Europe and the Middle East, Japan, Egypt and South Africa;
- Region 3: Southeast and East Asia, including Hong Kong;
- Region 4: Latin America, the Caribbean, Australia, New Zealand and the Pacific Islands;
- Region 5: Russia, Ukraine, India, most of Africa, Central Asia, South Asia, North Korea and Mongolia;
- Region 6: China.
With this organization by region, a DVD made for Canada (region 1) will not work on a device made for the Japanese market (region 2), for example. To make this control possible, DVD players are given the code for the region for which it was produced. Thus, the device will only play movies whose discs have the same number.
It is worth mentioning that if the disc has no code, it can be played on any DVD drive. It is also worth noting that a disc can have more than one code, and can run in the corresponding regions.
Like the CD, the DVD also has a “substitute” technology: Blu-ray , which stands out for offering up to 25 GB in a single layer of the disc, equivalent to 6 hours of high-definition video.
This format was established in the market after competing for space with HD-DVD technology , which ended up not establishing itself. But, even though it was “winning”, Blu-ray did not manage to conquer as much market as DVD at its peak: both technologies are being used less and less because of the increase in the number of services that transmit films over the internet ( streaming ) and the use of more intuitive data storage devices, such as USB sticks and external hard drives.