Peerjs: How do I call without a MediaStream?

Created on 8 Jan 2016 · 5Comments · Source: peers/peerjs

I have a use-case where:

there are two people, Presenter and Viewer
Presenter opens the page and gets a peer ID
Presenter sends that peer ID to Viewer
Viewer uses that peer ID to call Presenter
Presenter sends his shared screen to the viewer

For this use-case I need, for the Viewer side:

var call = peer.call(presenterPeerID, null);
call.on('stream', function(theirWebcamStream) {
  showWebcamStream(theirWebcamStream);
});

This does not work, because peer.call(presenterPeerID, null) returns undefined.

How do I call without sending a MediaStream?

Source

jameshfisher

👍1

Most helpful comment

You can create empty stream with any track, or with both:

export const createEmptyAudioTrack = () => {
  const ctx = new AudioContext();
  const oscillator = ctx.createOscillator();
  const dst = oscillator.connect(ctx.createMediaStreamDestination());
  oscillator.start();
  const track = dst.stream.getAudioTracks()[0];
  return Object.assign(track, { enabled: false });
};

export const createEmptyVideoTrack = ({ width, height }) => {
  const canvas = Object.assign(document.createElement('canvas'), { width, height });
  canvas.getContext('2d').fillRect(0, 0, width, height);

  const stream = canvas.captureStream();
  const track = stream.getVideoTracks()[0];

  return Object.assign(track, { enabled: false });
};

...

const audioTrack = createEmptyAudioTrack();
const videoTrack = createEmptyVideoTrack({ width:640, height:480 });
const mediaStream = new MediaStream([audioTrack, videoTrack]);

peer.call('id', mediaStream);

afrokick on 27 Mar 2019

👍3

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Rastopyr on 15 Jan 2016

Have you tried initiating the call from the presenter to the viewer, providing the presenters mediastream in the call and answering the call with null as mediastream?

takacsv on 28 Jan 2016

I'm also hoping to do the same thing. See issue #158

doppio on 29 Jan 2016

mahmed0715 on 24 Oct 2016

You can create empty stream with any track, or with both:

export const createEmptyAudioTrack = () => {
  const ctx = new AudioContext();
  const oscillator = ctx.createOscillator();
  const dst = oscillator.connect(ctx.createMediaStreamDestination());
  oscillator.start();
  const track = dst.stream.getAudioTracks()[0];
  return Object.assign(track, { enabled: false });
};

export const createEmptyVideoTrack = ({ width, height }) => {
  const canvas = Object.assign(document.createElement('canvas'), { width, height });
  canvas.getContext('2d').fillRect(0, 0, width, height);

  const stream = canvas.captureStream();
  const track = stream.getVideoTracks()[0];

  return Object.assign(track, { enabled: false });
};

...

const audioTrack = createEmptyAudioTrack();
const videoTrack = createEmptyVideoTrack({ width:640, height:480 });
const mediaStream = new MediaStream([audioTrack, videoTrack]);

peer.call('id', mediaStream);

afrokick on 27 Mar 2019

👍3

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