Calculate total video duration

Here is a little python shell script that uses the "ffmpeg" program to calculate the total duration for specified movies on the command line. This can be quite useful to calculate the required bitrate for encoding a bunch of to fit on a DVD as described in my earlier post. The calculated bitrate is adjusted by a parameter called "extra" to give you an extra buffer for the VBR of MPEG2 stream. So here it is:

#!/usr/bin/env python

"""calculates total movie length of all movies passed as parameters"""

import sys, re, os, subprocess, getopt

def main():
    sum = 0
    target_size = h2f("4.7G")
    audio_rate = h2f("224k")
    extra_rate = h2f("100k")

    try:
        opts, args = getopt.getopt(sys.argv[1:], "s:a:e:", ["size=", "audio-rate=", "extra"])
    except getopt.GetoptError, err:
        print str(err) # will print something like "option -a not recognized"
        usage()
        sys.exit(2)

    for opt, arg in opts:
        if opt in ("-s", "--size"):            
            target_size=h2f(arg)
        elif opt in ("-a", "--audio-rate"):
            audio_rate=h2f(arg)
        elif opt in ("-e", "--extra"):
            extra_rate=h2f(arg)

    for file in args:
        len = get_movie_length(file)
        print file, ":", len,"s"
        sum += len
          
                 
    print "total:", sum,"s"
    print "video bitrate:", calc_bitrate(seconds=sum,target_size=target_size,audio_br=audio_rate,extra=extra_rate), "kbps"
            

def h2f(size):
    d = {'k':1000, 'm':10**6,'g':10**9, 'K':8*1000, 'M':8*10**6, 'G':8*10**9}
    lc = size[-1]
    m = 1
    if lc in d.keys():
        m = d[lc]
    n = float(re.split(r"[" + ''.join(d.keys()) + "]", size)[0])
    return n*m
        

def get_movie_length(file):
    """returns the movie length in seconds"""

    len = 0
    p = subprocess.Popen("ffmpeg -i '" + file + "'", shell=True,
                     stdout=subprocess.PIPE, stderr=subprocess.PIPE)

    for line in p.stderr:
        if "Duration:" in line:
            h,m,s = (float(x) for x in re.findall("Duration: (\d+):(\d+):(\d+\.\d+)", line)[0])
            return h*3600+m*60+s
            break
    return 0


def calc_bitrate(seconds, target_size,audio_br,extra):
    """calculates the target bitrate in kbps for given target size and audio bitrate"""
    return (target_size/seconds - audio_br - extra)/1000


if __name__ == "__main__":
    main()