Codecs for Dummies?

[Lee Christie]

Firstly, sorry if this is a bit of a slew of newbie questions. Hopefully you can tell I've done some research I just got confused about some things.

I just got a new iPod which can play video. I see from the specs it supports H.264 and MPEG-4. My question isn't directly about the iPod, but it got me looking in to codecs on Wikipedia and such, as well as fiddling around trying to get things to work...

I'm curious, of those of you who have backed up DVDs to a media library or whatever, what codec did you use? MPEG-2, WMV, WMV9, VC-1, MPEG-4, H.263, H.264, DivX, or XviD or what?

Also, have I got this correct? H.264 is part of MPEG-4? and VC-1 is based on WMV9? and DivX, and XviD are encoders for H.263.. or based on H.263 but better, but not as good as H.264?

So, if I wanted to play videos on say, Windows Media Centre, I should use WMV9, but if I wanted to play them on an iPod, I should use H.264 (and if I use a program DESIGNED for converting to iPod, will it be optimized for iPod playback only or will it be playable on any H.264 player such as PSP?) What if I wanted to have the freedom to play them on either device? Would encoding two copies be the only way forward?

And if H.264 is part of MPEG-4 (or am I misinformed), why to some video to iPod converters present two options, MPEG-4 for 320x240, and H.264 for 640x480, surely both use H.264?

I'm confused, I'm gunna go lie down.