another point that is important :
your video encoder software has to SUPPORT the features of your processor...
example:
a video takes 15 minutes to encode on a notebook with nvidia GeForce go7600
but only 4 minutes on another notebook with on-board Intel HD2000
both have around 128 mb dedicated video memory...
both are on dual core processor boards
one is Sandy bridge mainboard, the other one older (core2duo Centrino) both are 1.8Ghz with Intel speed step
google for encoding software that uses your system at its best.
if you have a newer, Cuda capable nvidia, there is special software...
if you have a second notebook with Intel Hd - it might be faster than older tower pcs with dedicated graphic cards