Playback position in the video's own timeline.
Start of the rep's window, same timeline.
Length of the window; <= 0 disables bounding.
Whether the Loop control is engaged.
The action to apply to the media element.
A non-positive clipDurationSec means "no window" — the set carries no
usable time anchor, or there is no chart data to derive a span from — and
playback is then deliberately unbounded rather than clamped to an arbitrary
point. Callers must apply this on every advancing frame AND from a
timeupdate backstop: hanging it off the rAF loop alone lets a clip run past
its rep whenever that loop never arms (see ReplayPlayer).
Decides how playback should react to the current position of a replay whose playback is bounded to one rep's window.