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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 YouTube?

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

3 Answers 3

up vote 20 down vote accepted
$ 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. ffprobe doesn't scan the entire file for speed reasons, so it can be quite inaccurate.

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

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

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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
    
Using -ss after specifying the input file with -i is much slower but more accurate. Here for details. –  Francesco Turco Sep 14 '12 at 10:30
    
Thanks, @FrancescoTurco. I've updated the answer accordingly. –  Warren Young Sep 14 '12 at 10:40
    
How can I find these "natural cut point offsets"? –  JBernardo Sep 14 '12 at 19:58

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.

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Actually you can upload bigger files to youtue, if you verify your account with your mobile phone number http://support.google.com/youtube/bin/answer.py?hl=en&answer=71673

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