I don't even have to go read that, I can sum it up much more succinctly:
MPEG4 <-AVC>High Profile @ Level 4.1 for HD
MPEG4 High Profile @ Level 3.1 for SD
All lower levels accelerable as well.
and try and avoid useing "B-pyramids" in your Encodes as it causes smooth playback and decode problems on many hardware players.
its also wise to keep in mind today, the basic choices to keep HD Widescreen ratios when you get the choice to Encode your content are 848x480 (16:9) ,1280x720 (16:9) , 1360x768 (16:9) , and OC 1920x1080
stop typing "Mpeg4" were AVC or the long version "Mpeg4-part10" H.264 with it's lossless Encodeing/Decoding modes is ment, its confusing, (and just feeds into the worlds salesman/woman tactic to confuse and mislead your average person into buying old DivX HW) as they doesnt realise that "Mpeg4" was more in common with the old original Mpeg4-part2, divX, H.263 that was included in the spec first.
the main basic fact missing in these video assisted threads, seems to be that all these APIs are using their own special inbuilt seperate HW video decode ASIC, if your GFX card has the VDPAU ASIC inside , it will work at some point, if it doesnt have the ASIC ,it wont ever.
ATI and their UVD ASIC inside the X1xxx ?,HD2xxx,HD3xxx,and HD4xxx could be made to also work one day if AMD give out the currently closed UVD API for their UVD(2) ASIC sometime in the next few months if and when the UVD code review takes place over the next few Months as BM said they might, or NOT OK it.
any Intel HW assisted video ASIC seems to be far less talked about, do they infact have some HW assisted video ASIC inside their chips, if so ,what and which chips/SOC ?