FFmpeg live streaming webm video to multiple http clients over Nodejs

问题

I am trying to share a live stream of my screen over an ExpressJS server. I cannot save ffmpeg output to a file or start more than one ffmpeg instance for performance reason. My current solution is to pipe ffmpeg's stdout and stream it to each connected client.

index.js

const express = require('express');
const app = express();
const request = require('request');
const FFmpeg = require('./FFmpeg');

const APP_PORT = 3500;

app.get('/stream', function (req, res) {
  const recorder = FFmpeg.getInstance();

  res.writeHead(200, {
    "content-type": "video/webm",
  });
  recorder.stdout.on('data', res.write);
  req.on('close', FFmpeg.killInstance);
});

app.listen(APP_PORT, function () {
  console.log(`App is listening on port ${APP_PORT}!`)
});

FFmpeg.js

const spawn = require('child_process').spawn;
const ffmpegPath = 'ffmpeg';
const ffmpegOptions = [
  '-loglevel', 'panic',
  '-y',
  '-f',
  'alsa',
  '-ac',
  '2',
  '-i',
  'pulse',
  '-f',
  'x11grab',
  '-r',
  '25',
  '-i',
  ':0.0+0,0',
  '-acodec',
  'libvorbis',
  '-preset',
  'ultrafast',
  '-vf',
  'scale=320:-1',
  "-vcodec", "libvpx-vp9",
  '-f', 'webm',
  'pipe:1',
];

module.exports = {
  start,
  getInstance,
  killInstance,
};

let instance = null;
let connections = 0;

function killInstance() {
  connections -= 1;
  if (connections < 1) {
    instance.kill();
    instance = null;
  }
};

function getInstance() {
  connections += 1;
  if (!instance) instance = start();
  return instance;
};

function start() {
  return spawn(ffmpegPath, ffmpegOptions);
};

It is working well for one client, but I cannot manage to stream to several clients at the same time (might be related to missing keyframes).

来源：https://stackoverflow.com/questions/46683482/ffmpeg-live-streaming-webm-video-to-multiple-http-clients-over-nodejs

标签

node.js

express

ffmpeg

streaming

webm