I just tried to play an MPEG4-video on my Archos 405 and I got the following (German) message:
"Quarter Pixel" und "GMC" wird nicht unterst├╝tzt.
In English, that means that "Quarter Pixel" and "GMC" are not supported. Does that change when I buy the "Cinema Plug-in"? Probably not, I guess, because that plug-in is only for MPEG2, not MPEG4, right?