Convert youtube timestamps to ffmpeg chapters

chapters.py

#!/usr/bin/env python3
from datetime import time
import fileinput
import re

time_re = re.compile(
    r'((?P<hour>\d+):)?(?P<minute>\d+):(?P<second>\d+)(.(?P<microsecond>\d+))?')

ini_start = '''\
;FFMETADATA1
encoder=Lavf58.65.100
'''

chap = '''\
[CHAPTER]
TIMEBASE=1/1000
START={start}
END={end}
title={title}\
'''


def main():
    with open('chapters.ini', 'w') as out:
        start_l = []
        title_l = []
        for line in fileinput.input():
            t, s = line.split(maxsplit=1)
            t = time(**{k:int(v) for k, v in time_re.match(t).groupdict().items() if v})
            t = ((t.hour * 60 + t.minute) * 60 + t.second) * 1000 + t.microsecond
            start_l.append(t)
            title_l.append(s)
        out.write(ini_start)
        # it need fake last chapter at the movie length to generate end in previous chapter
        for start, end, title in zip(start_l, start_l[1:], title_l):
            out.write(chap.format(start=start, end=end, title=title))
    print('OK\nRun: ffmpeg -i input_file -i chapters.ini -map_metadata 1 -codec copy output_file')


if __name__ == '__main__':
    main()