See Products   DVD Players & Recorders Find Out More   The Ultimate Movie Machine   Key Features Glossary   Frequently Asked Questions DVD Players Under The Surface Place a CD next to a DVD and the discs look nearly identical. And if you put a CD in a DVD player, it will play just fine (in fact, it'll sound great). But if you try to play a DVD in your CD player, it won't read it. It can't because a DVD disc has a different physical structure, data format, and error correction system than a CD. Where a CD is a single 1.2-millimeter-thick disc, all DVDs use a "sandwich" design — two 0.6-millimeter discs bonded together. This sandwich construction allows DVD discs to have information on both sides and on one or two layers per side. This design is also more stable and resistant to disc warping. The illustrations below show how hours of theater-quality pictures and sound can be squeezed onto a disc you can hold in your hand. Compared to CD, DVD uses smaller data pits and more closely-spaced pit rows of "tracks." This increased data density makes it possible for each layer on a DVD to hold more than six times the amount of data on a CD! DVD players use a red laser in place of the infrared laser found in CD players. The red laser's shorter wavelength, combined with a special lens design, result in a narrower, more tightly focused laser beam that can easily read the smaller pits. There's more than one way to put a movie on a DVD disc DVD is the first home entertainment medium that gives viewers so much control over how movies, concerts, documentaries and other programs are presented. The available options will vary from disc to disc (the disc producers make those decisions). Each DVD disc has an on-screen menu that makes it easy to select the type of presentation that best matches your A/V equipment and personal preferences: Screen shape or aspect ratio: Standard, Widescreen, or Letterbox. Soundtrack audio: Dolby Digital 5.1 surround, Pro Logic surround, or stereo. Soundtrack language: Often English and French for Zone #1 (USA and Canada), but other languages may be included as well. Subtitle languages: DVD discs can provide up to 32 subtitle tracks! The various video and audio options are typically listed on a DVD's packaging. It's a good idea to get in the habit of checking the packaging to see what's included, especially if you're interested in a specific version. Single-sided, single-layer: Even DVD discs with a single information layer can hold the complete audio and video for a movie up to 133 minutes long, including Dolby Digital 5.1 soundtracks in three different languages! Total capacity: 4.7 billion bytes (4.4 gigabytes). Double-sided, single-layer: Most discs of this type include a movie version formatted for a standard TV screen on one side, and a widescreen version on the other side. No current DVD players can change sides automatically. Total capacity: 9.4 billion bytes (8.75 gigabytes). Single-sided, dual-layer: This disc type has two information layers, providing nearly twice the data capacity of a single-layer DVD. The layer closer to the player's laser pickup has a semi-transparent coating. The laser is able to shine through this layer to read the deeper layer beneath it, then re-focus to read the semi-transparent layer. Total capacity: 8.5 billion bytes (8 gigabytes). Double-sided, dual-layer: This disc type provides the maximum amount of data capacity. It is basically two single-sided, dual-layer discs bonded together. As with all double-sided DVDs, you'll have to flip the disc over yourself. Total capacity: 17 billion bytes (15.9 gigabytes).