Making DVDs : When a dvd is made. Is it true that they usually put it in this order : 1.L - 2.R - 3.C - 4.LFE - 5.Ls - 6.Rs - 7.Lt - 8.Rt - and when the dvd is read and a 5.1 audio system is detected it will play channels 1-6, and if a 5.1 audio system isn't detected it plays 7-8? (with dialnorm ensuring the volume is the same).
If the answer is "yes", then where exactly do AC3's fit in, and when are they most often used? Digital distribution like itunes and netflix? I like the idea that you can tailor the stereo mix, to make the film sound optimal in stereo, but you can't do that with an AC3 (since it folds down itself, according to how you encode it).