Google MeetでgetUserMediaをhookして好きな動画ファイルをカメラ替わりに流す

hook-getUserMedia.js

(()=>{
  const file = document.createElement('input');
  const video = document.createElement('video');
  video.loop = true;
  file.setAttribute('type', 'file');
  file.addEventListener('change', (evt) => {
    const url = window.URL.createObjectURL(file.files[0]);
    video.src = url;
    video.muted = true;
    video.playbackRate = 1.0; // 動画の再生速度を変更したいときはこのパラメータを変える。
    video.play();
  }, false);
  document.querySelector('div.jzP6rf').appendChild(file);
  if (navigator.mediaDevices._getUserMedia === undefined) 
    navigator.mediaDevices._getUserMedia = navigator.mediaDevices.getUserMedia;
  
  navigator.mediaDevices.getUserMedia = function (c) {
    return new Promise((resolve, reject) => {
      console.log('#', c);
      navigator.mediaDevices._getUserMedia(c)
      .then((stream) => {
        const newStream = video.captureStream(); 
        stream.removeTrack(stream.getVideoTracks()[0])
        stream.addTrack(newStream.getVideoTracks()[0]);
        resolve(stream);
      })
      .catch((err) => {
        reject(err);
      });
    });
  };
})();