KenBurns
class KenBurns(val from: NormalizedRect, val to: NormalizedRect, val easing: Easing = Easing.EaseInOut) : EffectSpec(source)
Pan and zoom across the frame over the clip's span.
from and to are the regions filling the frame at the start of the clip and at its end, and every frame between them shows the region easing paces to. Both are fractions of the frame entering this effect, so a crop declared on the same clip has already chosen the framing this travels within.
The region is resampled to fill the frame it was measured against, so the frame keeps the size it arrived at and a rect whose shape differs from the frame's stretches to fill it.
Valid on a clip alone. Its result depends on where a frame sits in the clip's span, so it cannot be fanned onto a run of clips the way a track effect is, and a plan refuses it anywhere else.