@noiob sounds like integer scaling with lower N pixels of the square turned off.
E.g.: 320x240 interlaced signal upscaled 4x to 1280x960 and with zero-indexed lines line%4==3 (3, 7, 11, 15, 19, ..., 955, 959) being completely shut down, line%4==0 being updated every even (frame_no%2==0) frame and going black otherwise, line%4==1 being updated every frame, and line%4==2 being updated every odd frame (frame_no%2==1) and going black otherwise. This way you'd get really intense CRT feelings.