Are their any restriction imposed on encoder input/output resolution?
I was using DirectShow encoder filter that is included into Media SDK installer. Looks like hardware encoder doesn't work when picture height isn't a multiple of 32. This means that I can't encode 720x1280 video without rescaling. Input to encoder is in RGB32 format and comes from a screen capture filter.
I did run tests on Ivy bridge i5 PC with Quick Sync enabled.