> how does Sam440 play hd videos or 720p ones?

With H264 encoding in realtime not at all, AFAIK. They struggle to play DVDs on non-overclocked ones:

"we can read DVDs at nearly full speed on a Sam440 667 Mhz"
http://www.amigans.net/modules/newbb/viewtopic.php?post_id=53421#forumpost53421