What is Divx?
DivX is the name of a revolutionary new video codec which is based on the new MPEG-4 compression standard for video. It produces high quality video using a low amount of bits (space).

The DivX codec makes it possible to compress/encode a full-length movie at near DVD-quality that's small enough to fit on a single CD (A DivX-compressed movie is about 8 to 12 times smaller than a DVD and ranges from 600 to 750 megabytes).

Over 30 million people across the world have downloaded and used DivX technology since its launch, DivX is quickly becoming the format of choice for digital video professionals and amateurs who want to distribute their videos with premium visual quality at small file sizes, earning DivX the popular moniker "The MP3 of Video."

DivX codec is free. You can download it from http://www.dvdapp.com/download.htm

After DivX installation, A1 DVD Ripper will load it automatically, You can check your selection as following:

Codec :
Short for compressor/decompressor. Codecs are various types of computer algorithms that are applied to audio, video, and image files to compress the size of the files

What is an ASPI driver?
An ASPI driver is required for digital audio extraction (DAE) or CD ripping. Windows 95 or 98 comes with the ASPI manager pre-installed, while NT does not.
To tell if you have an ASPI manager installed:

Windows 98 / ME :
windows\system\iosubsys\ apix.vxd
windows\system\ aspienum.vxd
windows\system\ winaspi.dll
windows\system\ wnaspi32.dll

Windows 2000 / NT:
winnt\system32\drivers\ aspi32.sys
winnt\system\ wowpost.exe
winnt\system\ winaspi.dll
winnt\system32\ wnaspi32.dll

Windows XP :
windows\system32\drivers\ aspi32.sys
windows\system\ wowpost.exe
windows\system\ winaspi.dll
windows\system32\ wnaspi32.dll

A1 DVD ripper comes with ASPI driver for win32 V4.7 .After installing A1 DVD ripper you can find it in the start menu group of A1 DVD Ripper.

For more information about ASPI driver,refer to http://www.adaptec.com

IFOs - InFOrmation
IFO Files give the player important navigational information, like where a chapter starts, where a certain audio or subtitle stream is located, etc. This is the reason why it's only possible to rip certain parts of a movie (like a chapter) with a ripper which can read this files.

BUPs - BackUP
BUP files are just backup files off the IFOs.

VOBs - Video OBjects
A VOB contains several streams multiplexed together: Video, Audio and Subtitles. Video is MPEG-2, audio can be AC-3, Linear PCM, Mpeg 2 multichannel or MPEG1 layer2 2 channel audio. A VOB can contain one main video stream and several multiangle streams, allowing you to switch (as an example) the perspective during the movie. This feature is mostly used to display storyboards or other extra features during playback. The maximum bitrate of the video stream is 9.8mbit/s. Together, video and audio stream must be below 10mbit/s at any given moment. It's possible to have up to 9 different audio streams and you can usually switch the audio stream during playback (this feature can be disabled during the authoring phase of a DVD). It's also possible to have up to 32 different subtitle streams. Subtitles are 4 color bitmaps which are overlayed over the video stream, they're usually not encoded into the video stream.
All DVD movies are stored in so-called VOB files. Vob files usually contain multiplexed Dolby Digital Audio and MPEG2 video. Vob Files are called as follows: vts_XX_y.vob where XX represents the title and Y the part of the title. There can be 99 titles and 10 parts, although VTS_XX_0.VOB does never contain any video, usually just menu or navigational information.

CSS
Content Scrambling System. Prioprietary scrambling system for video DVDs. Designed to stop people from making copies of DVDs, most commercial DVDs are encrypted using CSS. During playback, DVDs are then decrypted on the fly. Only parts of the DVD are encrypted (for instance all IFO and BUP files are not encrypted, and VIDEO_TS.VOB often isn't encrypted either) and the encryption scheme is rather weak and was quickly defeated. If you want to know what CSS does, insert a DVD video disc into your PC, start playing the disc using a software DVD player, then close the player. Now copy a 0.99GB VOB file from the disc to your harddisk and try to play back that VOB file in your software DVD player. You'll see a lot of funny colored blocks all over the picture making the movie unwatchable. But you'll also see parts of the movie (the parts that are not encrypted).