80fps is impossible. For DVD's (and for all interlaced videos, so interlaced MKV's included) usually with 29.97fps, the most correct output frequency would be 59.94Hz, but on HiMedia 60Hz is the closest you can get. For pal 25fps DVD's it's 50Hz. You need to turn off 24 Hz (Auto frame rate) mode and manually switch to these freques before playback. Sticking with the half of the original interlaced frame rate results in half as fluid motion resolution.