I do care about portability and open source.

Everyone knows the best is .avi using Xvid/AC3 or MP3 codecs.

avi man here

.avi

Ogg Theora coupled with Ogg Vorbis video - or anything that DOESN'T support DRM.

I chose WMV, doesn't really make a difference to me, as long it that or AVI/MPEG.

I have all apple formats, and STUPID quicktime!

Of cource AVI

xvid with mp3/ac3 (depending on what it is)

i'd like to use x264 as i've seen and heard good things about it, but i've gotten lazy and use autogk all the time now

H.264 and other avc codecs! Especially if you video card supports hardware decoding

ATI Technologies' newest graphics processing unit (GPU), the Radeon X1000-series, features hardware acceleration of H.264 decoding starting in the Catalyst 5.13 drivers.

NVIDIA has released drivers for hardware H.264 decoding on its GeForce 7 Series and some GeForce 6 Series GPUs.

x264 for encoding:

x264 is a GPL-licensed H.264 encoder that is used in the free VideoLAN and MEncoder transcoding applications and, as of December 2005, remains the only reasonably complete open source and free software implementation of the standard, with support for Main Profile and High Profile. [5]A Video for Windows was available in previous revisions of x264, but it has been discontinued. x264 won an independent video codec comparison organized by Doom9.org in December 2005.[6] Program-pack called Gordian Knot uses x264 to encode ripped DVD video material.

CoreAVC is reportedly the fastest or most efficient software decoder:

CoreAVC by CoreCodec is a highly optimized commercial H.264 decoder. According to independent tests by people on the Doom9.org forums, it is the fastest software decoder as of June 2006. The standard version supports Baseline Profile, Main Profile and High profile, except interlaced video. The professional edition supports both PAFF and MBAFF interlaced video beginning from version 1.1. The professional edition also supports speedups on SMP capable systems.

http://en.wikipedia.org/wiki/H.264

http://forum.doom9.org/forumdisplay.php?f=77

I'm surprised to see people still answering this poll (but now I'm just as guilty of it I guess). Either ways, this has to be the most confused poll I've ever seen. Especially for the mpeg / avi category. It's far too encompassing (mpeg1, mpeg2 and mpeg4 all in one option?), is missing many very important or even crucial options (where's H.264 / MPEG4 AVC? no mkv container? how about an option for mpeg4 asp in general like DivX or XviD? ...) Instead, we have a bunch of options not really worth picking (VHS? Anything as long as it supports - a real WTF! or I Hate ALL sort of movie or video?)

Perhaps a better poll would have been like:

-MPEG1 (e.g. VCD)

-MPEG2 (e.g. DVD, SVCD, encoders like CCE and TMPEGEnc)

-MPEG 4 ASP (e.g. XviD, DivX, 3ivX)

-MPEG 4 AVC a.k.a. H.264 (e.g. x264, Ateme)

-WMV9 & VC1 (e.g. High Def DVDs like T2 Extreme, HD DVD, Blu-Ray, normal WMV files, streaming stuff...)

-RealVideo 10

-QuickTime (.mov, but then again, is that the old Sorenson codec or a crippled H.264 in a proprietary container?)

(if one really wants and there's enough options left, one can add entries for physical media perhaps: DVD, VHS, DV, BetaMax, Hi8, LaserDisc, whatever, but I don't think it really fits in a codec poll)

I wouldn't even bother to include Theora on that list. Basically nobody uses it, hardly anybody knows about it, much less care about it and for a reason: it's surprisingly low quality compared to any decent codec, it's based off VP3 and is hardly better than crappy old MPEG1 - it just sucks overall. I just can't think of anything worse - I'd take MPEG1, DivX 3 SBC or just about any old thing over it (all those have better software/hardware playback compatibility too).

Anyways. I'd like to vote for 2 things, even if it's technically not possible in regular polls:

Vote 1: MPEG4 AVC (x264, followed by Ateme). Best video quality of them all. Standard ISO MPEG4. Getting widely adopted by the industry as a whole. Decoding assisted by hardware (using certain video cards) which matters for HD contents. AAC for sound which is a very good codec (both for multichannel, and stereo, and at very good bitrates). The only reason why it's not my only vote is player support: it basically plays on none of the existing "divx players" people have. My XBOX (XBMC) just doesn't have enough power to handle the high quality stuff either (not when you enable the features that makes H.264 worthwhile).

Vote 2: MPEG4 ASP (XviD, followed by perhaps DivX). Not as good quality as H.264, but still good enough. Relatively easy to decode (lower CPU requirement than H.264). Basically everybody knows the stuff by now (typically in an avi container, sometimes mkv, with mp3 audio usually, otherwise AC3). Plays on basically everything (divx players, XBMC, pretty much any software like VLC, MPC, etc), easy to convert if one has to, etc. It's one of my choices basically for the same reason people still use mp3 for music, even though there are other codecs with (moderately) better audio quality: good enough, everybody uses it, supported by everything/playback on anything, etc.

I like MPEG

I like MPEG

That's about as specific as anwering "what's the best CPU?" by "x86". Could be MPEG1, MPEG2 at any profile/level and any type of chroma subsampling or whatever, MPEG4 ASP, MPEG4 AVC. Any type of resolution, framerate or anything. It really means nothing at all like that. Pretty much every single option on the poll is based on some type of MPEG: WMV9 and VC1? MPEG4. RealVideo 10? MPEG4. QuickTime? More MPEG4. So in reality it's more like having answered just "video" or such. It's almost a non-answer.

Nothing personal/not bashing or anything. Just saying... MPEG is just far too encompassing to be much of an answer.