at least the current version seems to support 4096x2160, so 3840x2160 should also be possible.
I get the warning MFX_WRN_INCOMPATIBLE_VIDEO_PARAM if I select interlaced and the encoder switches to progressive, but the produced stream looks OK.
Do you set Width/Height CropH/CropW and the CodecLevel correct?
I'm using the DirectShow filter and i thought the resolution 1920x1080 is a limitation of the encoder. Perhaps it is a limitation of the DirectShow filter. I have installed version 3.0.014 GOLD now and i will try to install the newest one.
I need to clarify that last statement. While it is "supported", is not available "in hardware", as indicated by the "MFX_WRN_PARTIAL_ACCELERATION" result when the Medai SDK encoder is initialized.
Sorry for the confusion.