What is DVD decoder?
A hardware or software component that allows a digital video disc (DVD) drive to display movies on your computer screen. In fact, DVD decrypter is part of it.
Three Main Features:
- Unlocks CSS copy protection applied to the video files on a DVD movie disc;
All DVD’s that are sold by the major movie studios include copy protection to make it difficult for you to easily make copies of the DVD’s data. The copy protection is called CSS and in order to view the file, a decoder is necessary to unlock the copy protection.
- Decodes MPEG-2 formatting applied to DVD video content;
DVD decoders decode the MPEG-2 format, recreating the data so that the original images can be viewed.
- Displays DVD Movie video through a viewer program installed in Windows like Windows Media Player;
The decoder makes it possible for these images to be played through a viewing program which is installed on your PC. Windows Media Player becomes a full-featured DVD player when combined with a DVD decoder (MPEG-2 decoder) with features such as full-screen video playback controls, DVD chapter listings, and integrated cover art.
Why we need DVD decoder?
DVDs are one of the most popular types of media sold today. They hold feature length motion pictures, videos, audio and countless other types of media such as software and data. DVD’s not only can be played in stand alone DVD players, but also most computers have a DVD drive. If a DVD includes media such as a feature length motion picture, this media has been encoded and sometimes compressed. In order for this type of DVD to be played on a computer’s DVD drive, the data on the DVD must first be decoded; this is done with computer software. It should be noted that there are many types of DVD formats, hence several types of encoder programs to make a DVD accessible to computer users.
How can I watch my personal protected DVD’s on computer or mobile devices like iPod, iPhone…
If you would like to play a standard DVD on a computer, you will not only need a DVD player commonly referred to as a DVD drive, but the decoding software. Decoding software is not free. Since the MPEG-2 is a licensed format, licensing and royalties must be paid to the patent holders in order to decode the DVD and view the data on it. If you already have a DVD drive, but require the software to decode the format, for example, play DVD Movie with Windows Media Player,
there are professional DVD Decoder plug-ins for Windows Media Player:
CinePlayer DVD Decoder for Windows XP cost $14.99
CinePlayer DVD Decoder for Windows Vista cost $14.99
Buy after you purchase these plug-ins, you can only play DVD with your media Player Player, you can’t convert your DVD to any video format, or enjoy it on your iPod, PSP, Zune…
this is the reason why there are no free alternatives. You can find a lot of products through Google, but I will not recommend it because we have better way to enjoy your DVDs on PC or any other mobile devices.
We would like to introduce you some really helping software:
These Product is called DVD Ripper: Software that is able to digitally extract data from a DVD disc and saves the data to the computer’s hard drive which can then be played by any media player or import to your iPod, iPhone, PSP, Zune etc.
DVD Ripper software For Windows OS Buy Now ($39)
DVD Ripper software For Mac OS Buy Now ($45)
Or you can called it DVD converter:A program that is able to switch or convert DVD to different video formats (DVD to VCD, DVD to CD, DVD to AVI,DVD to MP4 etc).
Benefits: With DVD Ripper or DVD Converter, You can rip video and audio off your protected 
DVDs (only for personal use), then just do what you want to do: drop part of them onto your CD, VCD, new DVD disc without protection. Play with Media Player, enjoy DVD video music on iPod, iPhone, Zune, PSP… it’s your own choices!
DVD Converter For Windows OS Buy Now ($59)
DVD Converter For Mac OS Buy Now ($49)
Backing Up Your DVDs – DVD Copy Software
If you own a DVD, specifically a feature length motion picture, you are legally allowed to make a copy or back up for your own private, personal use. However, since all feature length motion picture DVD’s distributed from the 
major motion picture studios include CSS copy protection, you will also need to undo the copy protection and then make a copy of the DVD. Thankfully there is software available that can accomplish this task. One software solution is Super clone DVD (Cost $59 ). It will unlock the copy protection and help you make a complete back up copy including menus, sub titles, audio tracks etc.
In many cases the retail DVD’s you buy in stores are dual layer DVD’s capable of storing over 8 GB’s of data. The vast majority of DVD recordable media sold in stores are single layer DVD’s storing about 4.38 GB’s. To make a back up of an 8 GB DVD to fit on a 4.38 GB DVD, you will first need to undo the copy protection and copy the DVD to your hard drive and then compress this large file into a smaller file that will fit on a 4.38 GB single layer DVD. Many software programs can handle this task including DVD Shrink (cost $39.95).
And you can read this article to know more about DVD Copy Software.
And if You are using Linux OS. Here you can find Top 10 best Linux DVD decoding, ripping and encoding software. And Thanks to Skittlz from StumbleUpon, I have added this top ten Linux DVD decoder for those who may need it.
Thoggen
It is an intuitive and simple GUI to rip your DVDs into the free codecs Ogg/Theora. The backend used is Gstreamer.
PRO: Nice and friendly GUI, cropping and resizing preview
CONTRO: It’s no possible to encode in other codecs
Kungfu DVD Ripper
An easy GUi based on Gstreamer framework
PRO: Chapter preview
CONTRO: early stage development
Bitterbpp
A Gtk/Perl GUI specifically done to encode in Matroska(mkv) container
PRO: various codec supported
CONTRO: no more active
Dvdrip
Full-featured dvd ripping suite since many years
PRO: many many features, distribuited computing
CONTRO: Nuclear Power Plant GUI
Lemonrip
Another mplayer frontend, with easy GUI
PRO: quality profiles, automatic cropping
CONTRO: sometimes crashes
xdvdshrink
A dvd shrink tool made with Gtk Toolkit
PRO: many options avalaible
CONTRO: The GUI could be more intuitive
gdvdshrink
A dvd shrink tool made with Gtk Toolkit
PRO: nice GUI
CONTRO: it’s no possible to cut the credits
Dvd95
Yet another dvd shrink tool made with Gtk Toolkit
PRO: Nice GUI and features
CONTRO: None
Winki the Ripper
Almost all features you are looking for
PRO: localization, community forum, many features
CONTRO: no mp4 container supported
Vive!
Another GUi with mp4 support
PRO: mp4 support
CONTRO: sometimes crashes
