I put the original 4k footage onto the timeline of Cyberlink Powerdirector 14 and did no further editing.

Then I clicked 'Produce' and selected the H.264 file format and MP4 in the drop down box underneath it.

Then Profile type: All
Then Profile name/Quality: MPEG-4 4K 3840x2160/30p (50Mbps)
Then Country/video format of disc: NTSC (this will preserve the 29.97 fps of the original footage...if you change it to PAL it will drop it to 25fps)

Then Fast video rendering technology: ticked
Then Hardware video encoder selected (These may or may not be selectable depending on your graphics card)

No other boxes ticked

Then click start.

This process took 6 mins 20 secs on my core i7, 32GB RAM,Radeon 6970 grahics card PC.

SEE THE COMMENT ON THE 'SVRT' UPLOAD IN THIS COLLECTION FOR THE REASON I THINK CYBERLINK POWERDIRECTOR 14 IS BETTER FOR RENDERING THAN HANDBRAKE/VEGAS...AND IT IS MUCH CHEAPER :)