From the command line
python ffmpeg_splitter --help
python ffmpeg_splitter.py source.mp4 1000000000 -t "out.mp4" # Will split `source.mp4` into files of 1GiB size (named out-x.mp4).
From Python
from ffmpeg_splitter import split_by_size
if __name__ == "__main__":
split_by_size("my_file.mp4", 1000000000, print_function=print) # Will also print output and useful information