Crop and overlay videos using ffmpeg, to copy and paste in space rather than time

crop-and-overlay-videos.js

const exec = require('child_process').execSync;

// I got coordinates using the screenshot picker in quicktime player,
// but those are scaled to my screen, not the real video. Do some
// corrective fakery

const realDimensions = [ 1920, 1080 ];
const fakeWidth = 1680;
const fakeTom = [ 1400, 0, 280, 156 ];
const fakeVideo = [ 0, 100, 1470, 760 ];

const realTom = scale(fakeTom);
const realVideo = scale(fakeVideo);

console.log(realTom);
console.log(realVideo);

const name = 'whats-new-in-modern-javascript-20201205';

exec(`ffmpeg -i ${name}.mp4 -vf "crop=${realTom[2]}:${realTom[3]}:${realTom[0]}:${realTom[1]}" -c:v libx264 -c:a copy ${name}-tom.mp4 -y`);
exec(`ffmpeg -i ${name}.mp4 -vf "crop=${realVideo[2]}:${realVideo[3]}:${realVideo[0]}:${realVideo[1]}" -c:v libx264 -c:a copy ${name}-video.mp4 -y`);
exec(`ffmpeg -i ${name}-video.mp4 -vf "movie=${name}-tom.mp4[clip];[0][clip]overlay=main_w-overlay_w:0" ${name}-merged.mp4 -y`);

function scale(args) {
  return args.map(n => Math.floor(n * realDimensions[0] / fakeWidth));
}