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Python script to adjust srt/subtitles files

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It's quite common to have synchronization problems with subtitles files. Indeed, very often the subtitle file is not adapted to our source video file. So we usually have a delay that goes from a few milliseconds to a few seconds which can be quite annoying when playing.

It's possible, with most players (vlc, mpv or mplayer); see here; to adjust the delay, but the configuration will be lost at the next playback. So it is more interesting to be able to adjust by directly modifying the subtitle file.

I already developed a script in bash to do just that, but I wanted to do it in Python so here it is.


  • Usage :
user@host:~$ ./ [srt file] [+/- time] user@host:~$ ./ -h usage: /movies/ -1.400 add/subtract delay on a srt file positional arguments: file srt file path delay delay in seconds with 0.000 format optional arguments: -h, --help show this help message and exit
  • Subtract 400 miliseconds to subtitles :
user@host:~$ ./ /home/std/ -0.400
  • Add 1.400 seconds to subtitles :
user@host:~$ ./ /home/std/ 1.400 Note : The new srt file will be wrote in the same folder than source srt file with "" suffix.

srt file format

  • This script has been built to work with this kind or srt files only :
[…] 1126 01:55:12,527 --> 01:55:14,461 I love you. 1127 01:55:20,735 --> 01:55:22,669 I really love you.


#! /usr/bin/python # Role : Add or subtract delay to a srt file # Author : # 1.0 first version import argparse import re, sys from datetime import datetime, timedelta import shutil from tempfile import mkstemp from os import path ###START PARSER : parser = argparse.ArgumentParser(description='add/subtract delay on a srt file',prog='', usage='%(prog)s /movies/ -1.400') parser.add_argument('file', help='srt file path') parser.add_argument('delay', help='delay in seconds with 0.000 format') args = parser.parse_args() ###END PARSER ###FUNCTION def timeop (hours, minutes, seconds, milliseconds, delay): "function which add or subtract delayed time then return result" time_src = datetime(year=1983, month=12, day=12, hour=int(hours), minute=int(minutes), second=int(seconds), microsecond=int(milliseconds)).timestamp() result = time_src + delay return result ###CHECK ARGUMENTS try: delay = float(args.delay) except: print("Error, float argument needed.") parser.print_help() sys.exit(1) if not path.exists(args.file): print("Error, file doesn't exist.") parser.print_help() sys.exit(1) fs = open(args.file, 'r') #open srt file, read mode fd, name = mkstemp() #returns a tuple containing an OS-level handle to an open file and the absolute pathname of that file, in that order. fout = open(name, 'w') #open temp file, write mode while 1: txt = fs.readline() if re.match(".*-->.*", txt): #if ".*-->.*" characters is in current line seq=txt.split(" --> ") hours_start, minutes_start, seconds_start = seq[0].split(":") hours_start = hours_start[-1:] seconds_start, milliseconds_start = seconds_start.split(",") milliseconds_start = int(milliseconds_start) * 1000 new_start = timeop(hours_start, minutes_start, seconds_start, milliseconds_start, delay) hours_end, minutes_end, seconds_end = seq[1].split(":") hours_end = hours_end[-1:] seconds_end, milliseconds_end = seconds_end.split(",") milliseconds_end = int(milliseconds_end) * 1000 new_end = timeop(hours_end, minutes_end, seconds_end, milliseconds_end, delay) txt = re.sub(seq[0], datetime.fromtimestamp(new_start).strftime('%H:%M:%S,%f')[:-3], txt) txt = re.sub(seq[1], datetime.fromtimestamp(new_end).strftime('%H:%M:%S,%f')[:-3], txt) + "\n" fout.write(txt) #write to tmp file else: fout.write(txt) #write to tmp file if txt == "": break fout.close() #close tmp file shutil.move(name, args.file.split(".srt")[0] + "") #copy tmp file to fs.close() #close srt file
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