DVD Disc Capacity Information

Perhaps now it is impossible to meet a person who would never hold a CD in his hands. Recently, these media have lost their positions seriously because of the active introduction of more sophisticated drives based on solid-state memory. Nevertheless, it is hardly expedient to completely abandon discs. The DVD capacity is sufficient to store most programs and multimedia files. Manufacturers indicate that the user is available 4.7 GB. In reality, for DVDs, the maximum information capacity is 4.38 GB, which is explained by the difference in the method of calculation. Today we will talk about the technology of Digital Versatile Disc and understand the nuances of calculating the volume of such media.

Problem with definitions

The term DVD, surprisingly, does not have an unambiguous interpretation. This technology was developed in order to replace conventional CDs of CD, whose capacities are increasingly becoming insufficient. Initially, the abbreviation DVD meant the Digital Video Disc (Digital Video Disc). However, later it became clear that you can record on it not only movies, but also other files. This was the reason that some began to put another meaning in the term, understanding the DVD Digital Versatile Disk. In general, both transcripts are correct.

By increasing the available volume

Earlier it was already mentioned that DVD-disks replaced CDs, whose capacities were not enough. In order to read digital data recorded on the surface, a thin laser beam must be used. In the device-drives for this is implemented a special unit, consisting of a radiating element and a focusing system. The main difference between the light beam used for reading and writing information is that it is coherent, that is, it is very narrowly focused. This makes it possible to virtually eliminate the effect of diffraction phenomena and interference of the light wave. In the development of the CD standard, the miniature semiconductor radiators available at that time were unable to create a sufficiently narrow beam, so the track width on the metal-based disc was about 1.6 μm. Subsequently, more advanced light-emitting diodes were developed, the beam of which was so thin that the width of the track was reduced by half. Thus, the information capacity of a DVD-disk became several times greater than a similar CD parameter. In addition to the width of the track, it was possible to change the distance between them, as well as the size of the pits.

"Pie" from the discs

The capacity of a DVD disc is determined not only by the above dimensions and the configuration of the laser beam. Such media were created , which, in fact, united several discs in one product at once while maintaining the standard dimensions. Such multi-layered compacts can be compared to a sandwich. In production, not one but two tracks are used, but located in such a way that the reading laser beam passes freely through the translucent upper surface. Their volume reached 8.54 GB. The maximum capacity of a DVD-disk, whose diameter is not 12, but 8 cm, is 5.32 GB. Structurally, the drive can have two radiators, each of which focuses on its depth (surface). There are models with one beam, which is controlled by electronics. Information capacity of DVD could be even greater when using so-called two-sided solutions. Outwardly, this is an ordinary compact, but recording / reading is possible from two sides, for which in most drives it was required to turn the medium over. The capacity of the DVD-ROM of this modification is from 9.4 GB (double-sided single-layer), to 17.08 (four layers, recording from both sides). Nevertheless, such "pies" were not widely used because of the higher cost of production and the need to treat them with extreme care, since the slightest scratch could lead to the impossibility of reading data from deep layers.

Keeping information

At the heart of RAM disks lies the technology of surface heating by a laser beam. Their feature is the ability to perform formatting in the familiar FAT-32 file system and selectively delete files. Structurally, these disks are located in special cartridges, which increases their reliability. Theoretically, if you remove the DVD-RAM from the enclosure, you can work with it on the drive labeled Multi. These are sufficiently reliable solutions. The information capacity of DVD of this type is from 1.46 GB (single-layer unilateral, 8 cm) to 9.4 GB (bilateral). The term RAM means that rewriting is physically possible. The abbreviation can be translated as "Memory with random access". In fact, this type of disk is designed to backup data and before the advent of alternative media was an excellent solution. Especially if we take into account the claimed duration of data storage (about 30 years) and the number of rewriting cycles (more than 100 thousand). The disadvantage is the relatively high cost and low distribution.

VideoCompacts

The following solutions are DVD-Video. These discs are designed to record a multimedia stream. Indicated as "DVD-1 ... 18". The first four are modifications with a reduced diameter (8 cm against the standard 12). Classics is DVD-5, from which it can be considered 4.7 GB (single-layer one-sided). Accordingly, the maximum capacity of DVD in this category is 17.08 GB (DVD-18, two sides, four layers). Since mass video players use the simplest focusing units, which makes it possible to reduce the cost of production, not all models are able to read large volumes of discs. The exception is single-layer two-sided, for work with which it is enough just to turn the disk in the drive. Their disadvantage is the lack of space for the label, so the name is indicated on the transparent part, next to the central hole.

Single write

The appearance of disk drives that can record digital data on disks at home has revolutionized the field of backup and the creation of the most real film libraries. DVD + -R is initially sold without recording. The owner of a special drive can store on this disk any information converted into digital form. The color is mirror-blue, with an outflow to the violet area of the spectrum. The DVD capacity of this type is from 4.7 GB (one layer on one side) to 17.08 GB. The volume depends, as usual, on the number of layers and sides. But still, because of the right price policy, the most common compacts are 4.7 GB. Earlier, the recording could be done only with the help of a computer disk drive, now this possibility is possessed by many video players capable of storing TV transmissions on disks. The compatibility problem "-" and "+" R has long been in the past and is not considered in the article.

Multiple writing

The drawback of the previous type of disks is obvious - they can not be re-recorded by deleting data. To solve this issue, fundamentally different disks, called DVD + -RW, were proposed. They can be used almost like a regular drive. The term RW stands for Rewritable, i.e. Rewritable. The capacity of DVDs of this class is exactly the same as that of "simple" R. However, two-layered ones are extremely rare due to the need to purchase a special drive capable of working with such disks. In addition, rewritable solutions, and so require careful handling, and the complication of their design means that with these disks actually have to blow off dust particles. A random scratch on the surface may not allow you to read information from the lower layers. Thus, the "classic" is a single-layer, one-sided disc. The color of the surface varies from gray to almost black. The number of rewriting cycles is officially about several thousand, but in practice such a disk can be written no more than 50-100 times. And that in due course reliability of data storage decreases. Thus, DVD-RW is suitable for short-term data storage and transfer. Recording can be done by the unit, as usual. At the same time, using the Windows mechanism, it is also possible to work with both a regular drive (reading / writing arbitrary files). However, due to the fact that the standard of rewritable discs does not allow to develop high speeds, one usually has to be satisfied with a fourfold equal to 5.5 MB.

Feature of recording

The standard capacity of the DVD can be slightly exceeded. This is achieved by using the lead-out zone. The Overburn function must be supported by the device itself. It can be activated in the popular Nero program by going to "Options - Expert Properties". We do not recommend using this feature unless absolutely necessary, since you can not read this disk on a drive that does not know how to work with Overburn.

How is the volume calculated

Many computer owners have noticed for a long time that it is impossible to write down to the CD the amount of information that is indicated by the manufacturer. In fact, there is no deception here. Just manufacturers of disks from marketing considerations consider that in 1 KB 1000 bytes, although in reality 1024 (we build a deuce in the tenth power). With increasing volume, this number grows in progression. Therefore, no more than "honest" 4.38 GB is placed on a standard DVD.