How does a DVD work?

★ wanayoo — archive 1999 http://howstuffworks.com/question61.htm

Nouvelle recherche | Portail wanayoo

Question of the Day

Q&A Archive

HSW keeps a complete archive of previously answered questions to help you find answers quickly. Please Click Here for a complete list of previously answered questions.

Asking Questions

If you would like to ask a question, you can click here.

Each weekday Marshall Brain answers questions submitted by the readers of How Stuff Works in the Question of the Day section of HSW. You can also view previously answered questions in the HSW Question Archive. Here is today's question!

Question

How does a DVD work?

Answer

In the HSW article entitled How Compact Disks Work, you learn about how patterns of bumps on a mirrored surface can be interpreted as bits. These bits can be assembled into bytes and then played back through an Analog-to-Digital converter to create music. A CD can hold about 650 megabytes of information or about 75 minutes of music.

A DVD works exactly the same way, but it can hold a lot more information - about 4.7 gigabytes of information (about 7 times as much as a CD). DVDs can hold more information than CDs because the bumps are smaller and the tracks are closer together. With all that space, a DVD can store a lot of information. Here's the typical contents of a movie stored on a DVD:

Up to 133 minutes of high-resolution video in letterbox or pan-and-scan format, 720 dots of horizontal resolution. The video compression ratio is typically 40:1 under MPEG-2.
Soundtrack presented in up to 8 languages using 5.1 channel Dolby digital surround sound
Subtitles in up to 32 languages

You can also use DVDs to store music. If you do, you can store almost 8 hours of music per side!

MPEG-2 compression is important to the whole scheme, because without a good compression algorithm there's no way a movie could fit on a DVD. See http://www.mpeg.org for more information on MPEG.

See How Compact Disks Work for more information on how both CDs and DVDs work!

See DVD EXPRESS for zillions of DVDs!

How Stuff Works Power Panel

	Table of Contents A complete list of all HSW articles		About Marshall Brain Information about the creator of HSW
	Search Search for any word or concept in HSW		Citing HSW Information about citing HSW in articles and papers
	Question of the Day Ask questions or browse hundreds in the archive		Books A variety of books for people interested in how stuff works
	HSW Newsletter Sign up to receive the monthly HSW newsletter		Contacting HSW Contact HSW directly with email
	What's New Review newsletters to chart HSW's development		Awards Check out HSW's awards and reviews!
	Disclaimer The disclaimer required by the lawyer		Author Information Learn how you can write for HSW
	HSW Fan Buttons Link to HSW with these snazzy fan buttons!		Suggestions Leave a suggestion in the suggestion box

How Stuff Works (http://www.howstuffworks.com) is a production of
BYG Publishing, Inc.
http://www.bygpub.com - questions@bygpub.com
P.O. Box 40492 - Raleigh, NC 27629

© 1998 BYG Publishing, Inc. All rights reserved.