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.
I'm not an expert on the DirectShow filters so others may be able to help more with getting this working. Just passing on the limited info I have in case it might help.
The Media SDK encoder itself requires width and height to be a multiple of 16 for progressive. For interlaced/field encoding width must be a multiple of 16 but height must be a multiple of 32. There may be additional simplifications/limitations for the directshow samples. As you' may have already seen, the directshow filters included with Media SDK are intended as samples to help you get started, not as production-ready components.