Ygtjki

There is often a need in the open source or active developer community to publish large video segments online. (Meet-up videos, campouts, tech talks...) Being that I am a developer and not a videographer I have no desire to fork out the extra scratch on a premium Vimeo account. How then do I take a 12.5 GB (1:20:00) MPEG tech talk video and slice it into 00:10:00 segments for easy uploading to video sharing sites?

$ ffmpeg -i source-file.foo -ss 0 -t 600 first-10-min.m4v
$ ffmpeg -i source-file.foo -ss 600 -t 600 second-10-min.m4v
$ ffmpeg -i source-file.foo -ss 1200 -t 600 third-10-min.m4v
...

Wrapping this up into a script to do it in a loop wouldn't be hard.

Beware that if you try to calculate the number of iterations based on the duration output from an ffprobe call that this is estimated from the average bit rate at the start of the clip and the clip's file size unless you give the -count_frames argument, which slows its operation considerably.

Another thing to be aware of is that the position of the -ss option on the command line matters. Where I have it now is slow but accurate. The first version of this answer gave the fast but inaccurate alternative. The linked article also describes a mostly-fast-but-still-accurate alternative, which you pay for with a bit of complexity.

All that aside, I don't think you really want to be cutting at exactly 10 minutes for each clip. That will put cuts right in the middle of sentences, even words. I think you should be using a video editor or player to find natural cut points just shy of 10 minutes apart.

Assuming your file is in a format that YouTube can accept directly, you don't have to reencode to get segments. Just pass the natural cut point offsets to ffmpeg, telling it to pass the encoded A/V through untouched by using the "copy" codec:

$ ffmpeg -i source.m4v -ss 0 -t 593.3 -c copy part1.m4v
$ ffmpeg -i source.m4v -ss 593.3 -t 551.64 -c copy part2.m4v
$ ffmpeg -i source.m4v -ss 1144.94 -t 581.25 -c copy part3.m4v
...

The -c copy argument tells it to copy all input streams (audio, video, and potentially others, such as subtitles) into the output as-is. For simple A/V programs, it is equivalent to the more verbose flags -c:v copy -c:a copy or the old-style flags -vcodec copy -acodec copy. You would use the more verbose style when you want to copy only one of the streams, but re-encode the other. For example, many years ago there was a common practice with QuickTime files to compress the video with H.264 video but leave the audio as uncompressed PCM; if you ran across such a file today, you could modernize it with -c:v copy -c:a aac to reprocess just the audio stream, leaving the video untouched.

The start point for every command above after the first is the previous command's start point plus the previous command's duration.

Here is the one line solution:

ffmpeg -i input.mp4 -c copy -map 0 -segment_time 00:20:00 -f segment output%03d.mp4

Please note that this does not give you accurate splits, but should fit your needs. It will instead cut at the first frame after the time specified after segment_time, in the code above it would be after the 20 minute mark.

If you find that only the first chunk is playable, try adding -reset_timestamps 1 as mentioned in the comments.

ffmpeg -i input.mp4 -c copy -map 0 -segment_time 00:20:00 -f segment -reset_timestamps 1 output%03d.mp4

Faced the same problem earlier and put together a simple Python script to do just that (using FFMpeg). Available here: https://github.com/c0decracker/video-splitter, and pasted below:

#!/usr/bin/env python
import subprocess
import re
import math
from optparse import OptionParser
length_regexp = 'Duration: (d2):(d2):(d2).d+,'
re_length = re.compile(length_regexp)
def main():
 (filename, split_length) = parse_options()
 if split_length <= 0:
 print "Split length can't be 0"
 raise SystemExit
 output = subprocess.Popen("ffmpeg -i '"+filename+"' 2>&1 | grep 'Duration'",
 shell = True,
 stdout = subprocess.PIPE
 ).stdout.read()
 print output
 matches = re_length.search(output)
 if matches:
 video_length = int(matches.group(1)) * 3600 + 
 int(matches.group(2)) * 60 + 
 int(matches.group(3))
 print "Video length in seconds: "+str(video_length)
 else:
 print "Can't determine video length."
 raise SystemExit
 split_count = int(math.ceil(video_length/float(split_length)))
 if(split_count == 1):
 print "Video length is less then the target split length."
 raise SystemExit
 split_cmd = "ffmpeg -i '"+filename+"' -vcodec copy "
 for n in range(0, split_count):
 split_str = ""
 if n == 0:
 split_start = 0
 else:
 split_start = split_length * n
 split_str += " -ss "+str(split_start)+" -t "+str(split_length) + 
 " '"+filename[:-4] + "-" + str(n) + "." + filename[-3:] + 
 "'"
 print "About to run: "+split_cmd+split_str
 output = subprocess.Popen(split_cmd+split_str, shell = True, stdout =
 subprocess.PIPE).stdout.read()
def parse_options():
 parser = OptionParser()
 parser.add_option("-f", "--file",
 dest = "filename",
 help = "file to split, for example sample.avi",
 type = "string",
 action = "store"
 )
 parser.add_option("-s", "--split-size",
 dest = "split_size",
 help = "split or chunk size in seconds, for example 10",
 type = "int",
 action = "store"
 )
 (options, args) = parser.parse_args()
 if options.filename and options.split_size:
 return (options.filename, options.split_size)
 else:
 parser.print_help()
 raise SystemExit
if __name__ == '__main__':
 try:
 main()
 except Exception, e:
 print "Exception occured running main():"
 print str(e)

Note the exact punctuation of the alternative format is -ss mm:ss.xxx. I struggled for hours trying to use the intuitive-but-wrong mm:ss:xx to no avail.

$ man ffmpeg | grep -C1 position

-ss position

Seek to given time position in seconds. "hh:mm:ss[.xxx]" syntax is also supported.

References here and here.