vtt to srt

vtt2srt.py

#!/usr/bin/env python
from datetime import datetime, timedelta

filename = 'input.vtt'
srt = []
delta = -10  # Subtitle timeline
count = 1
timeline = 0

def changetime(time, delta):
    '''
    delta is seconds
    '''
    if delta == 0:
        return time
    timelineformat = "%H:%M:%S.%f"
    t1 = datetime.strptime(time, timelineformat)
    t2 = t1 + timedelta(seconds=delta)
    return t2.strftime(timelineformat)[:-3]

with open(filename, 'r') as f:
    while True:
        l = f.readline()
        if l == '':
            break
        if timeline:
            try:
                t1,t2 = l.strip().split(' --> ')
            except Exception as e:
                print(l)
                raise e
            t1 = changetime(t1, delta)
            t2 = changetime(t2, delta)
            l = '{}\n'.format(' --> '.join([t1, t2]))
            timeline = 0
        if l == '\n':
            l = '\n{}\n'.format(count)
            count += 1
            timeline = 1
        srt.append(l)

with open('output.srt','w') as f:
    f.writelines(srt)