MediaStreamRecorder doesn't fire the ondataavailable event

Question

I am using an open source JavaScript library MediaStreamRecorder to record audio and video webRTC calls in Mozilla Firefox and Google Chrome.

The calls are recording successfully but I am facing the following issue.

If I use the time interval of 1 second (1000ms) in multiStreamRecorder.start() then multiStreamRecorder.ondataavailable event doesn't fire. And that's why No error or No log in console.

But, if I use the time interval of 1.5 seconds (1500ms) or greater, it fires the multiStreamRecorder.ondataavailable event and everything works perfectly fine. (Only in Video Case)

I want to keep the interval to 1 second (1000ms) only.

var ws;

function start() {

    ws = new WebSocket("wss://xyz/");

    ws.onopen = function () {
        console.log("WebSocket has been opened!");
    };

    ws.onmessage = function (message) {
        console.log("A messsage is received from WebSocket Server.", message);
    };

    ws.onclose = function (e) {
        console.log('WebSocket is closed. Reconnection will be attempted in 5 second.', e.reason);
        setTimeout(function () {
            start();
        }, 5000);
    };

    ws.onerror = function (err) {
        console.error('WebSocket encountered an error: ', err.message, 'Closing WebSocket');
        ws.close();
    };

}

start();


function startRecording(localStream, remoteStream) {

    if (localStream != null && remoteStream != null) {

        multiStreamRecorder = new MultiStreamRecorder([localStream, remoteStream], "video/webm");
        multiStreamRecorder.mimeType = "video/webm";

        multiStreamRecorder.ondataavailable = function (blob) {

            console.log("sending blob to websocket server", blob);
            ws.send(blob);

        };

        // It doesn't work with the 1000ms time interval
        multiStreamRecorder.start(1500);

    }
    else{
        console.error("One or more streams are null.");
    }

}

Answer 1

I suspect one second is not enough time for the camera stream to warm up. While you can attach a recorder to a stream instantly, it doesn't appear to be ready for play/recording in zero time.

Video elements have .onloadedmetadata to let you wait for data to be ready; recorders do not.

You can make one though (use https fiddle for Chrome):

var haveLoadedMetadata = stream => {
  let preview = document.createElement("video");
  preview.srcObject = stream;
  return new Promise(resolve => preview.onloadedmetadata = resolve); 
};

var start = ms => navigator.mediaDevices.getUserMedia({video: true})
  .then(stream => haveLoadedMetadata(stream)
    .then(() => record(stream, ms))
    .then(recording => {
      stop(stream);
      video.src = link.href = URL.createObjectURL(new Blob(recording));
      link.download = "recording.webm";
      link.innerHTML = "Download recording";
      log("Playing "+ recording[0].type +" recording:");
    }))
  .catch(log);

var record = (stream, ms) => {
  var rec = new MediaRecorder(stream), data = [];
  rec.ondataavailable = e => data.push(e.data);
  rec.start();
  log(rec.state + " for "+ (ms / 1000) +" seconds...");
  var stopped = new Promise((y, n) => (rec.onstop = y, rec.onerror = e => n(e.error || e.name)));
  return Promise.all([stopped, wait(ms).then(() => rec.stop())])
    .then(() => data);
};

var stop = stream => stream.getTracks().forEach(track => track.stop());
var wait = ms => new Promise(resolve => setTimeout(resolve, ms));
var log = msg => div.innerHTML += "<br>" + msg;

<button onclick="start(1000)">Record 1 second!</button>
<div id="div"></div><br>
<video id="video" height="120" width="160" autoplay></video>
<a id="link"></a>

(Both Chrome and Firefox implement MediaRecorder directly, so I've answered using that).

Answer 2

I had a similar problem. it didnt fired ondataavailable event unless i started recording and stopped several times. After 2 days found out that problem was my microphone drivers :). It probably keeps trying microphone so it takes few seconds till it figure out that it doesnt work. Once set audio to false all works perfectly. Just no sound lol.