How can I easily shrink over-large MP4s where high quality is not relevant?

Question

I have some smartphone video that is absurdly large for what is low-quality casual video: 100MB per minute. What is the easiest way to compress this (on Mac) using command-line or GUI, given that I don't want to optimize settings for this casual video -- just some sort of default?

I have found answers online (often quite outdated) to use ffmpeg -i in.mp4 -vf scale=1280:720 -preset slow -crf 18 out.mp4 or the like, but I am none too sure about what might be an acceptable default.

I also tried ffmpeg -i in.mp4 -fs 100M out.mp4, which gives decent results -- I am interested in any further good ideas.

Answer 1

I'd recommend a simple GUI app, such as Smart Converter [can't remember if it's free or paid, App Store won't tell you once you own it] or Handbrake (freeware) which is a lot like ffmpeg, but without all the typing.
In both you can set up, or choose from existing, presets.

Answer 2

This bash script may be useful. It simply uses ffmpeg to compress all large (>150MB) mp4 files in a directory to half the size.

#!/usr/bin/env bash
set -x
set -u
set -e

for fn in *.mp4 ; do
  filesize=$( ls  -l "$fn" | awk '{print $5}')
  if [ "$filesize" -gt "150000000" ]; then
    new_filesize=$(($filesize / 2 ))
    new_filesize_MB=$(($new_filesize / 1000000 ))
    fn_base="${fn%%.*}"
    fn_ext="${fn#*.}"
    ffmpeg -i "${fn}"  -fs $new_filesize "${fn_base}.${new_filesize_MB}M.${fn_ext}"
  fi
done