Copyright Michael Karbo, Denmark, Europe.


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    Chapter 26. About DVD and video discs

    The term video disk has not been particularly familiar in Europe before now. In Japan and the Far East films on video CDs have been distributed for many years. But with the DVD format things have really changed – we see many more films on DVD today.

    Lots of Danish homes have a DVD player now. But it can do other things than play DVD films. Let’s look closer at this advanced digital technology. At the end of the section, I will mention a number of DVD related products, which we will probably come to see more of in the coming years.

    What is DVD?

    During recent years, DVD players have become an enormous success. They are, in fact, globally the fastest growing technology ever. Their distribution has been explosive and much faster than, for example, transistor radios, VHS cassette recorders and CD players.

    Introduction to DVD

    DVD stands for Digital Versatile Disk, which means that the disk is a many-sided media and can be used for a lot of purposes. The disk itself is a so-called optical media – just like the familiar CDs. On the outside a DVD looks just like a CD. Inside there is a great deal of difference, as a DVD has a much larger capacity. Where there can be 700 MB data on a CD, there can be from 4,7 to 18,8 GB on a DVD disk.

    The DVD standard was developed in the middle of the 1990s by a large number of companies such as Philips and Sony. It was meant as an all-round disk for storing audio, video images and data. This would mean that a DVD could replace CD, the not very widespread laser disks plus the well-known VHS tape recorders.

    Figure 199. A DVD lexicon.

    DVD is best known as a media for ”videograms” (films for playing in the home), but there are, in fact, many different kinds of DVD machines:

  • DVD players for use in the home.

  • DVD Audio for hi-fi systems.

  • DVD players with a recording function and sometimes a built-in hard disk.

  • DVD drive fitted onto a computer, with both recording and playing functions.

  • Transportable DVD players for use in a car.

  • DVD recorders built into digital video cameras.

    There are probably more types than those named here, and there will certainly come more of them. Because DVD is obviously an incredibly flexible medium, which with time will be used for much more not only in cars but in all sorts of other places too.

    The disk – purely technically

    The DVD itself is a flat disk with a diameter of 12 cm. It is 1,2 mm thick. The data is stored on the disk by making small dots in a spiral shaped track, which covers the disk like on a CD. A DVD disk is read in a driver by a laser beam, which is more short-waved than that used with a CD. This gives smaller tracks and increased storage place.

    The data layer is, however, only half as thick as on a CD. This opens the possibility of writing data in two layers. The outside layer is semi-transparent to that the inside layer can also be read. The laser beam works with two different strengths. The most powerful reads the bottom layer.

    You can see here a normal drive for fitting onto a computer. It can read the discs, called DVD-ROM (Read Only Memory). They are disks, which have been factory- burnt, and which usually contain film or data. The drive can also read normal CDs.

    Figure 200. DVD drive on a computer. It looks exactly like a CD drive.

    DVD+RW

    A lot of computers are equipped with DVD burners, which can both read and write the disks – both CD and DVD, and both disks that can only be written once (R) and disks, which can be written over many times (RW).

    The problem has been that the drives are to be found in different versions each using different media. The most widespread standard is, I think, DVD+RW, but there are also DVD-RW and DVD RAM on the market. Some of the models can write for two types of media. There is also a detached DVD player for burning DVD disks. See Figure 207 on page 3.

    Various kinds of content

    There are DVDs with different types of content:

  • Pure data

  • DVD-Audio

  • DVD-Video

    When a DVD contains data, then it works just like an ordinary CD-ROM. But there is room for 6-7 times as much data on it. This sort of disk can, for example, be used for a lexicon as shown in Figure 199. The large data capacity can be used to store enormous amounts of information including audio and video files, which also take up a lot of room. These data disks are all in all very suitable for the distribution of multimedia contents. DVD burners are also fine for the backup of large amounts of data.

    DVD-Audio is the newest high quality format for the distribution of music, as mentioned earlier in the book.


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