DVD

On July 1, 1997, in Opinion, by Brian Koponen

DVD is the wave of the future, replacing compact and laser discs. Some say DVD stands for Digital Versatile Disc or Digital Video Disc, it will in any case market well. Soon Apple and many clone makers will be including DVD drives in the computer instead of CD-ROM drives.

There is enough space on a single DVD movie disc so that movies can be played in up to three languages, which languages depend on the movie. About eight hours with 5.1 channel soundtrack can fit on one disc. From what I have seen, the colors are bright and clear. Some people have said it is too bright, but that can always be adjusted on a television set.

DVD discs are the same size as a CD, but they hold a lot more data. The music DVDs will be played in multiple channels, making it sound even better than CDs. The DVD-ROMs allow developers to do incredible things because they are not limited by space. Companies that put things on several CD-ROMs, such as national phone books, are the first to see the benefits because those CD-ROMs fit onto one DVD with room to spare.

DVD uses the MPEG-2 standard for video and Dolby AC-3 for audio. MPEG-2 is the quality of that used for satellite television transmissions. Dolby AC-3 is a 5 channel plus sub-woofer sound system that emulates that of a movie theater. There is left, right, center, rear-left, rear-right, and a universal sub-woofer.

Part of the reason that these two were chosen is that they compress data to very small amounts. This means that the data has to be decoded to be useful. As of yet, only hardware decoders are available to do this. Software replacements are planned, but are not yet available.

DVD can hold so much information because it uses a smaller laser than that used in CDs of today. The laser used in CDs is infrared and has a wavelength of 780 nanometers. The new laser is red and has wavelengths of 635 to 650 nanometers. It is variably focused, permitting multiple layers of information.

In a DVD disc, there are two sides. Each side can have two layers. One layer can hold 4.38 GB(gigabytes) of data. With this in mind, a double-sided, dual-layer disc could hold an astonishing 15.9 GB. None of this requires the disc to be flipped over like a laser disc, either. In the multi-layered discs, each one is semi-transparent so that the laser can be focused to the next layer. However, since almost no software company could possibly fill that much space for one program, most of the first DVD-ROMs will only have one layer to keep costs down. Even so, that is 4.38 gigabytes.

The first generation players will be able to read CDs and CD-ROMs. However, they will not be able to read CD-Rs (recordable CDs) or Photo CDs. They use a different method for writing to the CD. Instead of making a pit, it writes a color. Since the laser is smaller on the DVD, the colors will not be detectable. Second generations are planned to have another laser to read those.

The speed of DVD-ROMs will be about the same as a nine-speed CD-ROM drive. When reading a CD-ROM disc, however, the performance is decreased to that of about a six-speed drive. Still, as more and more software is put on DVD-ROMs, the performance will be quite high.

Movie companies have insisted that all DVD movies have a copy protection scheme. This is the Content Scrambling System, or CSS. Because of this, there has to be a hardware or software descrambler in your computer to play movie discs. There is also going to be regional codes on the disc and players that tells where it was made. If the disc’s code does not match the one in the player, it will not play. There are going to be six regions around the world, one being North America. Unless you plan on buying a player from each area, don’t plan on playing any imports.

DVD is a wonderful technology that is becoming a mainstream product. Video stores are renting them, while computer companies are incorporating them into their products. You can buy cards to add DVD to your current system, but remember that these players won’t be able to play any CD-R or Photo CD discs you may already have. I would suggest waiting until the second generation players arrive and then make a decision on whether to buy one or not.


Brian Koponen (briankop@mail.idt.net)

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