function startLocalVideo(r1, g1, b1, r2, g2, b2) {
  const whiteNoise = (width, height, r, g, b) => {
    const canvas = Object.assign(document.createElement('canvas'), {width, height});
    const ctx = canvas.getContext('2d');
    ctx.fillRect(0, 0, width, height);
    const p = ctx.getImageData(0, 0, width, height);
    const draw = () => {
      for (let i = 0; i < p.data.length; i++) {
        const color = Math.random() * 255;
        p.data[i++] = color * r;
        p.data[i++] = color * g;
        p.data[i++] = color * b;
      }
      ctx.putImageData(p, 0, 0);
      requestAnimationFrame(draw);
    };
    requestAnimationFrame(draw);
    return canvas.captureStream();
  };
  const localVideo1 = document.getElementById('localVideo1');
  localVideo1.srcObject = whiteNoise(32, 32, r1, g1, b1);
  localVideo1.play();
  const localVideo2 = document.getElementById('localVideo2');
  localVideo2.srcObject = whiteNoise(32, 32, r2, g2, b2);
  localVideo2.play();
}
@param {number} r1 Video 1 Red channel level [0-1]
@param {number} g1 Video 1 Green channel level [0-1]
@param {number} b1 Video 1 Blue channel level [0-1]
@param {number} r2 Video 2 Red channel level [0-1]
@param {number} g2 Video 2 Green channel level [0-1]
@param {number} b2 Video 2 Blue channel level [0-1]