Flip

AviSynth+
Up-to-date documentation: https://avisynthplus.readthedocs.io

FlipHorizontal(clip clip)
FlipVertical(clip clip)

FlipHorizontal flips (or mirrors) the video left to right.

FlipVertical flips the video top to bottom.
It is useful for dealing with some video codecs which return an upside-down image.
It doesn't modify the interlaced parity flags.