Kids ask: What does DVD stand for?

DVD is an abbreviation for digital versatile disc or digital videodisc. The 4 1/4-inch disc contains codes that create images you can see and hear. When decoded with a laser, the information on a disc becomes the TV show or movie on your TV, DVD player or computer screen.

Terry Brown, chief technology officer of Mega Playground, a New York City-based TV and film production/post production company, said the codes etched in the DVD's plastic ridges are combinations of the same "0" and "1" codes that computer information is based on called binary codes. Magnify the plastic ridges that curl around a DVD disc thousands of times and the surface might look like an egg carton with troughs and peaks. Think of the trough where the egg sits as a "0" and the peak as a "1." Brown calls these trough-and-peak combinations pits and dimples.

"The tiny dimples on a DVD are 1s and no dimples (pits) are 0s. Each 1 or 0 is called a bit. Digital video and audio is made up of many bits - millions, even billions, of bits. A DVD typically has 8 million bits for every second of recorded material. The highest capacity DVD can have 128 billion bits on it. That's a lot of dimples."

Brown said that the process of recording on a DVD, CD and Blu-ray Disc works in the same way. "A laser heats up a soft plastic material inside the disc creating a very, very tiny dimple or pit, actually lots of dimples. DVDs are written on a track that starts in the middle of the disc and spirals outward. These tracks fit 128 billion dimples in a continuous line. Large capacity DVDs not only have recorded data on both sides, but there are multiple layers inside the disc as well. If someone could stretch out these spiral tracks on a double-layer, double-sided DVD into a straight line, it would be close to 30 miles long."

Two devices combine data to read the disc. A laser illuminates the dimples and pits. A light sensor reads the amount of light reflected back. The dimples do not reflect light; segments with no dimple reflect most of the light back.

Brown said, "Light or no light again corresponds to a 1 or a 0 so we have now recovered our original data. There can be 8 million bits or dimples per second being read off the DVD. The DVD player knows how to assemble these bits into the pixels and frames that make up the picture information and the samples of sound that make up the audio."

Mega Playground specializes in high-definition digital services, providing them for Comedy Central's "Michael and Michael Have Issues," Investigation Discovery Channel's "The Shift," and feature films including "New York I Love You" and the upcoming Barry Levinson-Al Pacino HBO film "You Don't Know Jack."

Check these outThe Cook Memorial Library in Libertyville suggests these titles on how DVDs work: bull; "Cool Stuff and How it Works," by Chris Woodford, Luke Collins, Clint Witchalls, Ben Morgan and James Flint bull; "Essential Atlas of Technology," by Nestor Navarrete bull; "Inventions," by Glenn Murphy