I don't use VideoToolbox or Mac, so won't test it. But looking at the script, it looks clean and nice Bash scripting. I like it. Nothing serious but one thing I would suggest is for just a little bit easier and cleaner look in the code, to use cat with EOF for the help, like in one of my scripts:

help_options() {
	cat %%EOF
options:
  -h                show help and exit
  -H                show all options, notes and exit
  -m HEIGHT         max height
  ... (and more)
EOF
}

Edit: I forgot that beehaw does not like the character for < and will destroy everything. So I changed them to %%, just replace it with the less than character, the opposite of >.

Another Edit: In your build sh script, I like you hardcode rm -rf ffmpeg_vt, and don't use a variable for. And also checking if its a directory and exit if it can't cd into cd ffmpeg_vt/ || exit 1 . Well done.