What is DVD?



Pictured: Sony DVPNS325S DVD Player


The DVD-Video format has revolutionized the home entertainment industry by offering image and sound quality far superior to that of VHS videotape. This impressive digital format can generate pictures in amazing detail using nearly 500 lines of horizontal resolution! And, it's capable of delivering six discrete channels of exhilarating audio to create the ultimate surround sound experience. The DVD format also allows for an incredible amount of data to be stored on a single disc: up to 17 gigabytes worth!

Thanks to almost 500 lines of horizontal resolution, you'll immediately appreciate the startling brilliance and clarity of the picture quality delivered in the DVD-Video format nearly twice that of standard VHS tapes! And because DVD-Video uses a laser pick-up system, nothing touches the disc's playing surface. So it won't wear out. Of course, you don't rewind a disc, which makes it even more durable.

DVD-Video players are compatible with whatever aspect ratios are encoded on the DVD-Video disc you're watching. You can play movies recorded in a 4:3 format (conventional TV proportions), or in letterbox, which presents an image for panoramic viewing on a conventional TV. If you own one of the latest 16:9 widescreen TVs, you can select the widescreen format for maximum impact.

Much like a CD player, a DVD-Video player uses a laser to translate the microscopic pits that are in the disc, into music, video or information. But that's where the similarity ends. A DVD-Video disc holds much more information than a standard CD. Engineers increased its data-storage capacity by shrinking the microscopic pits and placing them closer together. However, the standard CD laser could not read this tightly packed information. A unique laser, with a thinner beam and shorter wavelength was developed.

Theoretically, the most efficient method to put more information onto a disc was to construct a disc with two layers of information. A dual-layer disc stores an astounding 8.5 gigabytes of information, while a dual-layer, double sided DVD-Video disc can store as much information as roughly 12,000 floppy discs, which would create a pile 120 feet high. That's 17 gigabytes worth of information!

DVD-Video players can also play CDs. In order to make this possible, a dual-focus hologram lens is used to split the beam of the already super-fine laser so that it can read two different depth levels, one for DVD-Video and one for CD or Video CD. Some players even have two lens.

DVD-Video has the same NTSC vs. PAL problem as videotape and laserdisc. The MPEG video on DVD is stored in digital format, but it's formatted for one of two mutually incompatible television systems.

Some players will only play NTSC discs, some players will only play PAL discs, and some will play both. All DVD players sold in PAL countries play both. These multi-standard players partially convert NTSC to a 60-Hz PAL (4.43 NTSC) signal.

DVD players also feature a system to protect motion picture studios that want to control the home release of movies in different countries. Therefore they have required that the DVD standard include codes that can be used to prevent playback of certain discs in certain geographical regions or zones. Each player is given a code for the region in which it's sold. The player will refuse to play discs that are not allowed in that zone. This means that discs bought in one country may not play on players bought in another country.

Regional codes are entirely optional for the maker of a disc. Discs without codes will play on any player in any country, but there aren't many of these out there. Some players (often called world zone players) will play all zones and other units can be modified to play all zones.

There is also a few forms of copy protection system incorporated on the discs, the most common is called macrovision. This system prevent a video recorder to lock on to the DVD picture rendering the copy unwatchable. If it was not for this system the piracy of movies would be enormous There are modifications for some units to turn macrovision off, so its often a good idea to do some research on the unit you are purchasing if you want a world zone unit or macrovision free unit.

For info on setting up a DVD player check out our DVD setup guide.

More of this Article

A Surround Sound Intro
Dolby Pro Logic Sound
Dolby Digital Sound
DTS Sound
Setup Your DVD player
What is Wide Screen TV

Feature History


Feature People

John Logie Baird

Feature Links

Top Selling Electronics
Amazon.com 100 Hot DVDs

Did You Know?

The Transistor invented in 1948 by J. Bardeen, W. Shockley and W. Brattain was invented by accident. They were experimenting with a diode when they discovered their creation.



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