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- Types of DVD


- FAQs on the DVD

- Conclusions

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in 1998


Author:
Juan Herrerías Rey
 

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The DVD: a new standard?


 

Differences between the CD - ROM and the DVD

The initials DVD translate for themselves like Digital Video Device (device of digital video) or Digitalis Versatile Disc (versatile digital disc). There turns out to be curious this duplicity of interpretations, which makes us warn that while some consider it to be a simple storage for video, others prefer to emphasize that it has many other applications.

At first sight, a disc DVD is practically indistinguishable of a conventional CD; perhaps it has a more or less particular sheen, but leaving apart this we meet the classic round waffle of plastic material, 12 cm in diameter and the hole in the center. Then: what him differs from the classic CD - ROM or from the even more classic CD of music?

To see the difference we would need a microscope; in the DVD, as in the CD, the digital information is represented by means of microscopic marks like little holes in the surface of the CD (covered by a protective transparent resin). What happens is that in the DVD the above mentioned marks are smaller and are more together, therefore, on having fitted more, the capacity is major. Simple, truth?

Types of DVD

While of our old friend the CD only existed a type (apart from 8 cm Mini-CDs), in the DVD we have up to 4 varieties (and this and the grabables do not count): a face and a layer, a face and two layers, two faces and a layer and two faces and two layers. Face refers at two o'clock of the disc DVD: the same as forward and the same as behind (again a simple but effective solution); layer is something more complicated, it refers to layers of material (and therefore of information) superposed in the same face of the disc.

This way, the capacity of a DVD goes from the 4,7 GB of the variety of a face and one gelds even the 17 GB of that of two faces and two layers; or, equivalently, the capacity from 7 to 26 conventional CDs. Chilling, truth?

And why do you serve so much capacity, you will wonder? And I, the truth. To distribute programs not, undoubtedly, because: who is the gallant who has a hard disk of 17 GB? Is it imagined that the new version of Word will occupy more than 650 MB of a CD - ROM? No, the principal function is the storage of digital video, for which 17 GB is not a too exaggerated number.

Logotype of the consortium for the DVD-Vídeo

In the format MPEG-2, a format of compression of digital video (in which they express Satellite channel and Digital Route, for example), this 17 GB remain in less than 10 hours (of course, with sound Dolby Digital AC-3). And since the most common DVD variety is that of a face and a layer, they prove slightly more than 2 hours of video; sufficient for a movie with major quality than in VHS doubled in several languages and with subtitles in some more, to election of the user.

The DVD for computer information are named DVD-ROM, while those of video are named DVD-Vídeo or simply DVD. Also there exist norms that 8 cm DVDs defines, but probably little is used so like the CDs of this size.

FAQs on the DVD

Come to this point in which you already know what is the DVD (a species of tight CD that is used especially to keep video), we go to the practical thing, in the shape of FAQs (we go, of typical questions and answers):

  • Can I use a disc DVD in my unit of normal CD - ROM? No, for nothing; he needs a reading unit of DVDs, which cost like the double of one of CD - ROM of mark.
  • Can I use my CDs in a DVD unit? It depends. The CDs of audio and the CDs normal-ROMs, yes, without problems. The CDs grabables (like the habitual CDs copies), it depends on the unit but it is probable that yes. The CDs regrabables, probably not, but some readership of DVD is capable of doing it.
  • How are there of rapid these DVD units? They are fundamentally of speed "1x" and of "2x". Them 1x they are completely desfasadas, although they come like minimum to 1,2 MB/s (the equivalent to a CD of 8x). Those of 2x come like little up to 2,4 MB/s, the equivalent to a CD 16x, and sometimes 20x or even more if instead of a DVD we have introduced a CD - ROM.
  • Do I need anything more to see the video digital? Yes. He needs a card descompresora from video MPEG-2, which sometimes comes with the unit DVD and sometimes not, in whose case is usually more expensive. Also, it will have to have a powerful computer, says a Pentium 133 with 32 MB of RAM.
  • Do DVD grabables units exist? Yes, but not standard. At least two different and incompatible types exist, in addition to enough expensive, and it is not an insurance which will win... or if they will lose the two in favor of a third one.

Conclusions

Or what is the same: do I buy to myself the DVD or not? Since... for the time being, better not. The offer of qualifications of video in DVD is still very precarious, that of games nonexistent, and the ridiculous units "park"; does a DVD meet anybody with? And the fact is that to the DVD he lacks something to substitute the VHS: to record. If it was possible to record, it might substitute the CD - ROM, the video VHS and the CD and the cassette of the music center.

Nevertheless, for the distribution uses, there is enough the capacity of a CD or two; as unit for safety copies we need to record, skylight; the prices of the reading units are not very high, but they still have problems on having read CDs grabables and regrabables; and the units grabables are in the dangerous embryonic state. A panorama that he does not invite to the immediate buy, the truth.

I only would recommend it to the fans of the video and especially to the fanatics of the games, which it will be where it is used soon (although neither too much, he remembers that almost anybody has DVD but almost we all have CD - ROM); that in case they are going to buy a new computer, since the difference with a CD - ROM is not great if we do not include the card MPEG-2. For those who already have computer, it turns out to be better to wait a little to see what happens; meanwhile, the prices go down.

Certainly: the discs DVD are even more delicate opposite to the dust and the fingerprints that the CD - ROM. Why do not they invent a case instead of increasing the capacity? Or to do them of 8 cm, which would be more manageable and do the norms exist to make them? In a 8 cm DVD-ROM they would fit from 1,4 up to 4,95 GB; I was content, the truth.

 


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