HTML Canvas - Record and stream to Twitch.tv | Used along with a server instance with ffmpeg https://github.com/karx/kaaroStream-bridge

kaaroStream-Twitch.js

let kaaro_stream_bridge_url = "boomboom.store:3012";
let stream_key = '<twitch_streaming_key>';

let mediaRecorder;
let mediaStream;
let ws_url = window.location.protocol.replace('http', 'ws') + '//' + // http: => ws:, https: -> wss:
  kaaro_stream_bridge_url +
  '/rtmp/' +
  encodeURIComponent(`rtmp://live-sin.twitch.tv/app/${stream_key}`);
console.log(ws_url);
const ws = new WebSocket(ws_url);
ws.addEventListener('open', (e) => {
  console.log('WebSocket Open', e);
  mediaStream = document.querySelector('canvas').captureStream(30); // 30 FPS
  mediaRecorder = new MediaRecorder(mediaStream, {
    mimeType: 'video/webm;codecs=h264',
    videoBitsPerSecond: 3000000
  });
  mediaRecorder.addEventListener('dataavailable', (e) => {
    ws.send(e.data);
  });
  mediaRecorder.addEventListener('stop', ws.close.bind(ws));
  mediaRecorder.start(1000); // Start recording, and dump data every second
});
ws.addEventListener('close', (e) => {
  console.log('WebSocket Close', e);
  mediaRecorder.stop();
});

Demo stream: https://www.twitch.tv/kaarostream/