Filters with multiple input clips

There are some functions which combine two or more clips in different ways. How the video content is calculated is described for each function, but here is a summary which properties the result clip will have.

The input clips must always have the same color format and – with the exception of Layer and Overlay – the same dimensions.

Filter	Framerate	Framecount	Audio content	Audio sample rate
AlignedSplice, UnalignedSplice	must match	sum of all clips	see filter description	must match
Dissolve	first clip	sum of all clips minus the overlap(s)	follows video	must match
Merge, MergeLuma, MergeChroma, Merge(A)RGB	first clip	first clip: if the second clip is shorter, the last frame is repeated until the end	first clip	first clip
Layer, Overlay	first clip	first clip: if the second clip is shorter, the last frame is repeated until the end	first clip	first clip
Subtract	first clip	longer clip: the last frame of the shorter clip is repeated until the end	first clip	first clip
StackHorizontal, StackVertical	first clip	longest clip: the last frame(s) of the shorter clip(s) are repeated until the end	first clip	first clip
Interleave	n × (fps of first clip)	n × (framecount of longest clip): the last frame(s) of the shorter clip(s) are repeated until the end	first clip	first clip

As you can see the functions are not completely symmetric but take some attributes from the FIRST clip.