The Reduce Interlace Flicker effect reduces high vertical frequencies to make images more suitable for use in an interlaced medium (such as NTSC video). For example, images with thin horizontal lines can flicker when broadcast. Reduce Interlace Flicker applies a vertical directional blur to soften horizontal edges to reduce the flickering.
Up the amount to add softness, this effect is on
ly really practical if you are using NTSC Interlacing in your final product though.
If you are unsure what NTSC is, check out this: https://vimeo.com/142295708 and this: https://vimeo.com/118533139