srtscale

#!/usr/bin/env python
"""
   Script to scale the time in subtitle files in the .srt format. Script
   takes in the filename and the scale to expand or contract the subtitles.
   It then writes the new subtitles to the same file. Alternately you can
   specify the filename as '-' and then the script will read input from
   stdin and write output to stdout.

"""

__version__   = '1.0'
__author__    = 'Reid Ellis'
__date__      = 'Tue Aug 14, 2018'
__url__       = 'http://einaregilsson.com/2008/03/20/subtitle-fixer/' 

import sys, re, datetime

MILLISECOND = 1
SECOND = 1000 * MILLISECOND
MINUTE = 60 * SECOND
HOUR = 60 * MINUTE

def scale_time(time, scale):
    """ Takes in list with [hour, minute, second, millisecond] and returns
        it with scale applied
    """
    ms = sum(map(int.__mul__,  time, [HOUR, MINUTE, SECOND, MILLISECOND]))
    ms *= scale
    return [ms / HOUR, ms % HOUR / MINUTE, ms % MINUTE / SECOND, ms % SECOND]

def fix_subtitles(lines, scale, output):
    """ Takes in list (lines) with all the lines from the subtitle file, stretches
        by scale and writes the file to output.
    """
    for line in lines:
        pattern = r'(\d\d):(\d\d):(\d\d),(\d\d\d) --> (\d\d):(\d\d):(\d\d),(\d\d\d)'
        match = re.match(pattern, line)
        if match:
            nrs = [int(nr) for nr in match.groups(0)]
            start = scale_time(nrs[:4], scale)
            end = scale_time(nrs[4:8], scale)
            output.write('%02d:%02d:%02d,%03d' % tuple(start))
            output.write(' --> ')
            output.write('%02d:%02d:%02d,%03d\n' % tuple(end))
        else:
            output.write(line)

def print_header():
    print 'Subtitle Fixer v%s' % __version__
    print 'Author: %s' % __author__
    print __url__
    print ''
    
def str2scale(str):
    #if format matchs nn:nn/nn:nn, assume srtmin:srtsec/vidmin:videsec
    return float(str)

if __name__ == '__main__':
    if len(sys.argv) != 3:
        print_header()
        print 'Usage: srtscale <filename> <scale-from-0.0-to-whatever>'
        print 'Use - for filename to read from stdin and print to stdout'
        sys.exit(1)

    scale = str2scale(sys.argv[2])
    file = None
    if sys.argv[1] == '-': #Read from stdin and print to stdout
        fix_subtitles(sys.stdin.readlines(), scale, sys.stdout)
    else: #read from file and write to same file
        file = open(sys.argv[1], 'r')
        lines = file.readlines()
        file.close()
        file = open(sys.argv[1], 'w')
        fix_subtitles(lines, scale, file)
        file.close()
        print 'Finished scaling %s by a factor or %s' % (sys.argv[1], scale)