The Teranex 48fps format is interlaced, not progressive. It is derived from 24sf: segmented frame. When sent though a video DAC, the result is 48i, with both fields at the same time reference. The 24sf format was devised so that production equipment that can handle only interlaced video could be used. The Teranex can`t do 48fps progressive, or any other format that is not part of the ATSC spec.