import webvtt
filename = "emacsconf-2020-06--trivial-emacs-kits--corwin-brust.sbv"
if (filename.find('sbv')):
    vtt = webvtt.from_sbv(filename)
length = len(vtt)
for i in range(0, length - 1):
    vtt[i].end = vtt[i + 1].start
vtt.save()