Entry

How does a DVD work?

Jan 21st, 2008 06:54
Khalid Saleh, Articles Way, How does a DVD work?

In the article How CDs 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 (about seven times as much as a 
CD). DVDs can hold more data than CDs because the bumps are smaller 
and the tracks are closer together, giving DVDs more storage space. 
Here are 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, at 720 dots of horizontal resolution (The video 
compression ratio is typically 40:1 under MPEG-2.) 
Soundtrack presented in up to eight 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 
eight 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. 

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