StackHorizontal

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

StackHorizontal(clip clip1, clip clip2 [, ...])
StackVertical(clip clip1, clip clip2 [, ...])

StackHorizontal takes two or more video clips and displays them together in left-to-right order. The heights of the images and their color formats must be the same. Most other information (sound track, frame rate, etc) is taken from the first clip - see here for the resulting clip properties.

StackVertical is similar, working top-to-bottom.

Examples:

# compare frames with and without noise reduction:
StackVertical(last, last.SpatialSoften(2, 3, 6))

# show clips in variables a,b,c,d in a box like this:
# a b
# c d
StackVertical(StackHorizontal(a, b), StackHorizontal(c, d))