True once a sample at or after endTime has been seen.
Samples in [startTime, endTime], sorted by time.
triggerTime + postWindowSec, Unix ms.
Post-trigger window, seconds, fixed when the trigger fired.
Pre-trigger window, seconds, fixed when the trigger fired.
triggerTime - preWindowSec, Unix ms.
Time of the first sample past the threshold, Unix ms.
One trigger capture.