20mbps is raw DTV over the air, that is how much bandwidth my tuner detects while watching tv from my HDHomerun. When I encode using plex or something similar, my bandwidth can get as low as 500kbps but usually averages 1mbps. Below 500 and artifacts become noticeable. When I increase cpu for x264 encoding, I can get 384kbps comfortably (at the expense of superheating that box)