WebRTC/getUserMedia: How to properly mute local video?

Question

I'm trying to implement the functionality for muting the local video MediaStreamTrack in my WebRTC application. Here's how I'm approaching this:

function muteVideo() {
  if (this._localStream && this._localStream.getVideoTracks().length > 0) {
    this._localStream.getVideoTracks()[0].enabled = false;
  }
}

In Firefox, the <video> element to which the local stream is attached correctly renders blackness on mute. In Chrome, blackness is not rendered but the picture freezes. However, in both browsers, the camera's green light stays on, which is clearly undesired behavior. (I want my users to see that the application actually disconnects from the camera on video mute.)

The camera's light goes off if I do this._localStream.stop(), but then the audio goes off, too.

The current draft of the Media Capture spec mentions the MediaStreamTrack.stop() method but it currently seems unimplemented in Chrome and Firefox.

So is there a way to mute local video while:

1. Making the camera's light go off
2. Not losing the audio track?

Answer 1

Today

track.stop() works just fine in Firefox. Chrome's behind. Spec way to end a track (https fiddle):

navigator.mediaDevices.getUserMedia({video: true, audio: true})
  .then(stream => video.srcObject = stream)
  .catch(e => log(e.name + ": "+ e.message));

let stop = k => video.srcObject.getTracks().map(t => t.kind == k && t.stop());

<video id="video" width="160" height="120" autoplay></video><br>
<button onclick="stop('video')">Stop Video</button>
<button onclick="stop('audio')">Stop Audio</button>

This gives you a way to turn off video while keeping audio, without permission re-prompt in Firefox. You still get prompted when turning video back on, so it's not perfect, but 50% better.

Until Chrome catches up, your other answer (drop and re-gUM each time) should work there, since they never re-prompt.

By browser-detecting and combining these answers, it should be possible to come up with something that works well in more than one browser, until browsers catch up.

Long term

The spec has recently addressed this by allowing browsers to turn off the camera light during temporal mute (e.g. track.enabled == false), provided a camera access indicator remains on:

"The User Agent is encouraged to provide ongoing indication of the current state of anyAccessible.

The User Agent is encouraged to provide ongoing indication of the current state of anyLive and to make any generic hardware device indicator light match."

Stronger language precedes these statements in the spec, making indicators a requirement.

Currently, browsers do not implement this correctly. Chrome is close, with a tiny camera access indicator inside the url bar on the right after recent access, but it fails to appear on page load to warn that persistent access was granted on a previous visit; the site can turn the camera on at any time.