What Codecs and Why?

Well, I just wanted to see what everyone thought of codecs. I currently have DivX, Xvid, AC3 Filter, and FFDShow. Not knowing what AC3 and FFD do(Anyone explain?) I just got VLC and it looks really cool. What should every computer Video watcher have on their computer?

I like the DefilerPak.

I like to stay away from packages. Bloated with material you don't ever use/know/need.

Edit: Actually after looking at the link, its rather small. I may check it out. Thanks. Missing Xvid though?

1. Official free DIVX codec (now version 6) - I think only the Pro version has adware.
2. MPC Real/Quicktime Alternative.

I used the theorica codec pack for a while, it worked just fine for video playback, but some their codecs kind of messed with my video encoding programs like virtualdub so I just stick with the official divx codec. Media Player Classic has AC3 codecs included I think.

I'll give the defiler pack a try though.

AC3 is a sound codec which lets you experience surround sound through divx if I'm not mistaking. I just know whenever there's a movie with AC3, the sound is great. ffdshow has loads of features, I like the postprocessing features where you can get a blocky movie to look quite ok (takes cpu cycles though!). It's also used to customize subtitles for japanese movies for instance. Personally I am a big xvid fan cause it really gives you nice results.