Today I had a large MP4 I wanted to break up into smaller chuncks because the disk was FAT32. Ends up you don’t need to re-encode. You can use ffmpeg and do something like this:
ffmpeg -ss 00:00:00 -t 01:30:00 -i input.mp4 -acodec copy -vcodec copy output1.mp4
That will copy the first 90 minutes to output1.mp4. Adjust the timecodes and output file to write another chunk to a different file. There may be a way to do it by filesize, but I didn’t figure out how. As always use a recent version of ffmpeg if you can.
That handy tip saves a ton of CPU time.