gpx2srt

#!/usr/bin/env python2

# gpx
import gpxpy
import gpxpy.gpx

# srt
import pysrt

#misc
import argparse
import os
import sys

# parse argument
parser = argparse.ArgumentParser(description='Convert gpx info to srt')

parser.add_argument('-i', '--input',
        required=True,
        help='input gpx file')

parser.add_argument('-o', '--output',
        default='out.srt',
        help='output file, default to out.srt')

parser.add_argument('-f', '--force', action='store_true',
        help='force overwritting output file')

parser.add_argument('-s', '--start', type=int,
        help='start time offset in gpx, in seconds')

parser.add_argument('-e', '--end', type=int,
        help='end time from start of gpx, in seconds')

args = parser.parse_args()

# parse gpx
gpx_file = open(args.input, 'r')
gpx = gpxpy.parse(gpx_file)

# open srt
if not os.path.isfile(args.output):
    open(args.output, 'a').close()
else:
    if not args.force:
        print "Output file %s exists, use -f to force overwritting." % args.output
        sys.exit(1)
    else:
        open(args.output, 'w').close()
sub = pysrt.open(args.output)

prev = 0
index = 0
for track in gpx.tracks:
    for segment in track.segments:
        for point in segment.points:
            if prev == 0:
                prev = point
                start = point
                continue
            else:
                diff = point.time_difference(start)
                if diff < args.start or diff > args.end:
                    prev = point
                    continue
                speed = point.speed_between(prev)
                if speed != None:
                    start_time = pysrt.SubRipTime(seconds=point.time_difference(start) - args.start)
                    speed = point.speed_between(prev) * 3.6
                    item = pysrt.SubRipItem(start=start_time, text="speed: %f" %
                            speed, index=index)
                    index += 1
                    sub.append(item)
                    prev = point
sub.save()