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I got a mp4 video. I just want to split it in 4GB file parts using ffmpeg (to make it writeable on FAT32).

C:\ffmpeg\ffmpeg.exe -i "%NAME%.mp4" -n -t %LENGTH% -codec copy "%NAME%_1.mp4"
C:\ffmpeg\ffmpeg.exe -ss %LENGTH% -i "%NAME%.mp4" -n -codec copy "%NAME%_2.mp4"
  • The original file's overall bitrate is 9450 Kbps.
  • The first output's overall bitrate is 10.1 Mbps.
  • The second output's overall bitrate is 8727 Kbps.

I guess that the bitrate of the original video is variable and not equally distributed, is that right ?

How can I fix it (in a batch that would be great)? May I convert first the original video to constant bitrate?

Thanks for help guys !

  • Is the problem that the two parts don't land at less than 4GB every time? – Paul Jul 31 '14 at 1:30
  • Yes because I calculate the length of outputs based on bitrate. In the given example, the first output would be around 4,25GB. – kiwixz Jul 31 '14 at 1:33
  • Think about using the segmenter in ffmpeg. ffmpeg segmenter documentation Changing the bitrate will require a re-encode. Why not just undershoot to 3GB? – dstob Jul 31 '14 at 15:54
  • I'm actually not confident in re-encode (afraid of quality loss). So I'll undershoot, as you said. But I'm still looking for an answer if someone have one :) – kiwixz Jul 31 '14 at 18:51

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