52

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?

  • Special thanks to @StevenD for accommodating the new tags. – Gabriel Sep 6 '10 at 17:24
57
$ 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.

  • 1
    "cutting at exactly 10 minutes for each clip" is a good point. – Chris Sep 7 '10 at 11:42
  • maybe by using the -show_packets param you can make it more accurate. – rogerdpack Jun 13 '11 at 21:36
  • I said it in the answer: "using a video editor or player." Load the video file up in one, scrub to near the 10 minute mark, then look for a reasonable place to cut. Record the time showing on the timecode display. Move forward another 10-minutes-minus-a-skosh. Repeat until done. – Warren Young Sep 14 '12 at 21:47
  • how to put above in a loop? – kRazzy R Dec 6 '17 at 19:32
  • i Use this cmd ya it split into right but Now the video and audio are not on SYNC any help – Sunil Chaudhary Mar 16 '18 at 6:08
42

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
  • 2
    It actually gives you very accurate splits, if you value video quality. Rather than splitting based on a particular time, it splits on the nearest keyframe following the requested time, so each new segment always starts with a keyframe. – Malvineous Feb 25 '17 at 6:51
  • 3
    what are the units? 8s? 8min? 8h? – user1133275 Mar 20 '17 at 20:58
  • 1
    @user1133275 its second – Jon Mar 20 '17 at 21:11
  • 2
    On Mac, I found that this resulted in N output video chunks but only the 1st of them was a valid, viewable MP4. The other N-1 chunks were blank video (all black) with no audio. To make it work, I needed to add the reset_timestamps flag like so: ffmpeg -i input.mp4 -c copy -map 0 -segment_time 8 -f segment -reset_timestamps 1 output%03d.mp4. – jarmod Jun 5 '17 at 15:32
  • 2
    found that adding -reset_timestamps 1 fixes the issue for me – jlarsch Oct 30 '17 at 8:27
6

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: (\d{2}):(\d{2}):(\d{2})\.\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)
  • 1
    Next time do this please in a comment. Link-only answers aren't really liked here, and the same if you advert your site. If it is an opensource project with source code, maybe it is an exception, but I now risked my reviewing privileges by not voting for the removal of your answer. And yes, you can't post comments, but after you collected 5 upvotes (which seems very fast in your case) you will. – peterh Nov 21 '14 at 0:40
  • Hi and welcome to the site. Please don't post link only answers. While your script itself would probably make a great answer, a link to it is not an answer. It is a signpost pointing to an answer. More on that here. Since you kindly gave the link, I went ahead and included the script in the body of your answer. If you object to that, please delete the answer altogether. – terdon Nov 21 '14 at 1:54
2

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.

2

If you want to create really same Chunks must force ffmpeg to create i-frame on the every chunks' first frame so you can use this command for create 0.5 second chunk.

ffmpeg -hide_banner  -err_detect ignore_err -i input.mp4 -r 24 -codec:v libx264  -vsync 1  -codec:a aac  -ac 2  -ar 48k  -f segment   -preset fast  -segment_format mpegts  -segment_time 0.5 -force_key_frames  "expr: gte(t, n_forced * 0.5)" out%d.mkv
0

An Alternate more readable way would be

ffmpeg -i input.mp4 -ss 00:00:00 -to 00:10:00 -c copy output1.mp4
ffmpeg -i input.mp4 -ss 00:10:00 -to 00:20:00 -c copy output2.mp4

/**
* -i  input file
* -ss start time in seconds or in hh:mm:ss
* -to end time in seconds or in hh:mm:ss
* -c codec to use
*/

Here's the source and list of Commonly used FFmpeg commands.

0

Does anyone know why every segment is corruption after the first segment when using ffmpeg to generate segmented mp4's from stream input?

I am using this command:

ffmpeg -i stream_url -vcodec copy -f segment -segment_time 10 cam_out%04d.mp4

First segment is perfect, subsequent segments are the same size, but don't play using vlc or other media players.

0
#!/bin/bash

if [ "X$1" == "X" ]; then
    echo "No file name for split, exiting ..."
    exit 1
fi

if [ ! -f "$1" ]; then
    echo "The file '$1' doesn't exist. exiting ..."
    exit 1
fi

duration=$(ffmpeg -i "$1" 2>&1 | grep Duration | sed 's/^.*Duration: \(.*\)\..., start.*$/\1/' | awk -F: '{ print ($1 * 3600) + ($2 * 60) + $3 }')      #'
split_time=${split_time:-55}
time=0
part=1

filename=${file%%.*}
postfix=${file##*.}

while [ ${time} -le ${duration} ]; do

echo    ffmpeg -i "$1" -vcodec copy -ss ${time} -t ${split_time} "${filename}-${part}.${postfix}"
    (( part++ ))
    (( time = time + split_time ))

done
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-2

You shouldn't really be following any of the answers in this thread, instead just use what is built into ffmpeg to do exactly this.

ffmpeg -i invid.mp4 -threads 3 -vcodec copy -f segment -segment_time 2 cam_out_h264%04d.mp4

This will split it into roughly 2 second chucks, split at the relevant keyframes, and will output to the files cam_out_h2640001.mp4, cam_out_h2640002.mp4, etc.

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