Channels mode in OggMachine

[The Belgain]

Could someone explain exactly what each of the channel modes is? I don't find the doom9's guide clear. I'm encoding from a 5.1 AC3.

What is the difference between surround and stereo (surround gives a 2 channel file as does stereo, how does the downmixing differ?)?

Is surround2 multichannel? Does downmixing to a 2 speaker system work? Does it require special players or will it work in WMP?

Does stereo just take the front-left and front-right channels and ignore the rest?

[Doom9]

stereo: downmix 5.1 -> 2.0 channel with no dolby pro logic coding (so you won't get any proper surround on any system). It's basically the same as selecting stereo in your software dvd player
surround: dolby pro logic downmix (same as selecting a pro logic downmix in your software dvd player)
dpl2: dolby pro logic II coding.. a dolby pro logic downmix with better channel separation.. it's the same as surround unless you have a dolby pro logic II capable receiver in which case you'll get better channel separation (most notably the rear channels will be separated whereas in surround mode it will be one channel only). this mode requires that you use an audio filter capable of that format (latest windvd and powerdvd can do it.. the rest can't).. or a special receiver. In the former case you'd have to connect your soundcard to your stereo using analogue 5.1 connection (as in 3 stereo cables) in the latter case you'd use the normal stereo plug and input to your a/v input at the receiver, then enable DPLII decoding on the receiver.