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DVD Tutorial

What you need to know about DVD's physical and application formats


article last updated on 5.11.2003 | printer-friendly format click for printer-friendly format   

DVD, which is once stood for Digital Video Disc and later Digital Versatile Disc, is now just "DVD".  It is no longer an acronym that it once was.  DVD is today's premiere format for video, audio, and data storage.  In this tutorial, we'll explore the physical characteristics of the DVD format and its data capacity, and see what makes it different from the audio Compact Disc (CD) format with which we're all familiar.  Once we talk about physical format of DVD, we'll explore the various application formats of DVD: DVD-Video, DVD-Audio, and DVD-ROM.

The Disc

As a disc, DVD looks very much like the CD.  Both are shiny discs that are 4 3/4 inches (12.0 cm) in diameter.  Both are optical formats containing digital information.  This means a laser pickup is used to read the digital data encoded on the disc.  But that's where the similarities end.

DVD is actually a family of physical and application formats.  As far as the physical format, DVD  can hold anywhere from seven times to over 25 times the digital data on a CD, depending on the the disc's construction.  Additionally, the DVD may be used for video, audio, or data storage applications as a DVD-Video, DVD-Audio, or DVD-ROM application format, respectively. 

The Physical Format

There are three reasons for DVD's greater data capacity:
1. Smaller pit size
2. Tighter track spacing
3. Multiple layer capability

Smaller Pit Size. DVDs have smaller pit size than CDs.  Pits are the slight depressions or dimples on the surface of the disc that allow the laser pickup to distinguish between the digital 1's and 0's.

Tighter Track Spacing. DVDs also feature tighter track spacing (i.e., track pitch) between the spirals of pits.  In order for a DVD player to read the smaller pit size and tighter track spacing of the DVD format, a different type of laser with a smaller beam of light is required.  (This is one of the major reasons why CD players cannot read DVDs, while DVD players are capable of reading Audio CDs.)

CD vs. DVD pits and track spacing   

A comparison of a CD's pit size and track spacing vs. that of a DVD
(picture courtesy of Crutchfield.com)

Multiple Layer Capability. Finally, DVDs may have up to 4 layers of information, with two layers on each side.  To read information on the second layer (on the same side), the laser focuses deeper into the DVD and reads the pits on the second layer.  When the laser switches from one layer to another layer, it is referred to as the "layer switch" or the "RSDL (reverse spiral dual layer) switch".  To read information from the other side of the DVD, almost all DVD players require the user to manually flip the disc.

Based on DVD's dual-layer and double-sided options, there are four disc construction formats:
1. Single-sided, single-layered
3. Single-sided, dual-layered
2. Double-sided, single-layered
4. Double-sided, dual-layered

Single-Sided, Single-Layered. Also known as DVD-5, this simplest construction format holds 4.7 Gigabytes (GBytes) of digital data.  The "5" in "DVD-5" signifies the nearly 5 GBytes worth of data capacity.  Compared to 650 Megabytes (MB) of data on CD, the basic DVD-5 has over seven times the data capacity of that of a CD.  That's enough digital information for approximately two hours of digital video and audio for DVD-Video, or 74 minutes of high resolution music for DVD-Audio.

Single-Sided, Dual-Layered. The DVD-9 construction holds about 8.5 GBytes.  DVD-9s do not require manual flipping: the DVD player automatically switches to the second layer in a fraction of a second, by re-focusing the laser pickup on the deeper second layer.  This capability allows for uninterrupted playback of long movies up to four hours!  Frequently, DVD-9 is used to put a movie and its rich set of bonus materials on the same DVD-Video disc, or its optional DTS Surround Sound track.

Double-Sided, Single-Layered. Known as DVD-10, this construction features a capacity of 9.4 GBytes of data.  DVD-10s are commonly used to put a widescreen version of the movie on one side, and a full frame version of the same movie on the other side.  Almost all DVD players require you to manually flip the DVD, that's why the DVD-10 is called the "flipper" disc.  (There are a few DVD players that can perform the side flipping automatically.)

Double-Sided, Dual-Layered. The DVD-18 construction can hold approximately 17 GBytes (almost 26 times the data capacity of a CD), or about 8 hours of video and audio as a DVD-Video.  Think of DVD-18 as a double-sided DVD-9, where up to four hours of uninterrupted video and audio can be stored on one side.  To access the content on the other side of a DVD-18, you have to manually flip the DVD.  To date, few titles have been released using this construction.  Content providers (e.g., movie studios) usually choose to go with two DVD-9s than a single DVD-18 because DVD-18s cost far more to produce.

The Application Formats

Now that you understand the various physical aspects and data capacities of the DVD format, let's discuss the various application formats of DVD: DVD-Video, DVD-Audio, and DVD-ROM.  Each of these three application formats are based on the physical specifications we just discussed.  

DVD-Video. The DVD-Video format is by far the most widely known, as it is the first DVD application format to really take off.  As the name indicates, DVD-Video is principally a video and audio format used for movies, music concert videos, and other video-based programming.  This format first emerged in the spring of 1997 and is now considered mainstream, having pass the 10% milestone adoption rate in North America by late 2000.  Read more about the DVD-Video application format.

DVD-Audio. The DVD-Audio format features high-resolution 2-channel stereo and multi-channel (up to 6 discrete channels of) audio.  The format made its debut much later, in the summer of 2000, due to delay in squaring away the copy protection issue.  To date, DVD-Audio titles are still very few in number and have not reach mainstream status, even though DVD-Audio/Video players are numerous and widely available.  Read more about the DVD-Audio application format.

DVD-ROM. DVD-ROM is a data storage format just like CD-ROM.  DVD-ROMs can only be used in DVD-ROM drives in computer systems.  They allow for data archival and mass storage, as well as interactive and/or web-based content.

It should be noted that a DVD disc may contain any combination of DVD-Video, DVD-Audio, and/or DVD-ROM application content.  For example, some DVD movie titles contain DVD-ROM content portion on the same disc as the movie.  This DVD-ROM content provides additional interactive and web-based content that can be accessed when using a computer with a DVD-ROM drive.  As another example, some DVD-Audio titles are actually DVD-Audio/Video discs that actually have additional DVD-Video content that provide video-based bonus programming such as artist interviews, music videos, or a Dolby Digital and/or DTS surround soundtrack that can be played back by any DVD-Video player (in conjunction with a 5.1-channel surround sound home theater system).

Before we leave this general tutorial about the DVD format, let's briefly touch on the topic of recordable DVD formats.

What About Recordable DVD Formats?

As we mentioned before, DVD is actually a family of formats.  So far we have only discussed pre-recorded formats, those that have been manufactured with content already recorded (DVD-Video movies and DVD-Audio music recordings).  However, DVD also includes recordable formats.  In fact, there are three different recordable DVD formats:

  • DVD-R/RW format (with its write-once DVD-R variant and rewriteable DVD-RW variant)

  • DVD+R/RW format (with its write-once DVD+R variant and rewriteable DVD+RW variant)

  • DVD-RAM rewritable format

Each of these recordable DVD formats are slightly different.  Their differences are enough to create mutually incompatibility issues.  (That is, one recordable format can not be used interchangeably with the other two recordable formats.)  And not all recordable DVD discs are 100% backwards compatible with the tens of millions of existing DVD-Video players and computer DVD-ROM drives.  To learn more about the recordable DVD formats, read our Recordable DVD Tutorial.

Summary

In this tutorial, you learned about the physical aspects and data capacities of the DVD format.  We also briefly discussed the DVD-Video, DVD-Audio, and DVD-ROM application formats.  Now, you can read more about the DVD-Video and DVD-Audio application formats.

What do you want to do next?

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For more information on DVD technology:

Note: The Sony 301-disc DVD mega-changers, Sony DVP-CX860, Sony DVP-CX870D, and Sony DVP-CX875P, can mechanically flip the sides of a DVD-10 or DVD-18 without user intervention.

Did you find this DVD Tutorial helpful?  Let us know your thoughts, send an e-mail to us at Staff@TimeForDVD.com.

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In This Article

 

> The Disc

> The Physical Format

> The Application Formats

> What About Recordable DVD Formats?

> Summary

 

Also Read:

 

> DVD Overview

> DVD-Video Tutorial

> DVD-Audio Tutorial

 


DVD & Blu-ray Release Dates

 

> August 2010

> September 2010

> October 2010

> November 2010

> December 2010

> January 2011

more >>   

 




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