Menu

Expand
Rate this page:

Thanks for rating this page!

We are always striving to improve our documentation quality, and your feedback is valuable to us. How could this documentation serve you better?

Building a JS Video App: Recommendations and Best Practices

Overview

This guide provides recommendations and best practices for building a Video Application using twilio-video.js.

Contents

Helpful Links

Browser Support

This table shows the browsers and platforms that are supported by twilio-video.js. Please use the isSupported flag to find out if twilio-video.js supports the browser in which your application is running.

const { isSupported } = require('twilio-video');
if (isSupported) {
  // Set up your video app.
} else {
  console.error('This browser is not supported by twilio-video.js.');
}

Choosing Video Settings

Please take a look at this guide to choose the right ConnectOptions values for your use case.

Acquiring Local Media

Application Domain

twilio-video.js relies on getUserMedia to acquire local media. In order for this API to be available, please ensure that your application is running either on localhost or an https domain.

Autoplay Policy

The autoplay policy does not allow you to autoplay audio using <audio> or <video> elements unless the user has interacted with your application (clicking on a button, for example), especially if your application’s media engagement score is not high enough. So, we recommend that you use twilio-video.js only after the user has interacted with your application. Chrome 66+, Firefox 66+ and Safari 11+ all enforce the autoplay policy.

const { createLocalTracks, connect } = require('twilio-video');

// To work around the autoplay policy, use twilio-video.js only
// after a button click.
document.getElementById('join-room').onclick = async () => {
  const tracks = await createLocalTracks();
  const room = await connect('token', {
    name: 'my-cool-room',
    tracks
  });
};

Acquiring Camera in Mobile Browsers

In mobile browsers, the camera can be reserved by only one LocalVideoTrack at any given time. If you attempt to create a second LocalVideoTrack, video frames will no longer be supplied to the first LocalVideoTrack. So, we recommend that:

If you want to display your camera preview, pre-acquire media using createLocalTracks. You can then pass these LocalTracks to connect.

const { createLocalTracks, connect } = require('twilio-video');

const tracks = await createLocalTracks();

// Display camera preview.
const localVideoTrack = tracks.find(track => track.kind === 'video');
divContainer.appendChild(localVideoTrack.attach());

// Join the Room with the pre-acquired LocalTracks.
const room = await connect('token', {
  name: 'my-cool-room',
  tracks
});

If you want to switch between the front and back facing cameras, starting from SDK version 2.7.0, you can restart the existing LocalVideoTrack.

const { createLocalTracks, connect } = require('twilio-video');

const tracks = await createLocalTracks({
  audio: true,
  video: { facingMode: 'user' }
});

// Join the Room with the pre-acquired LocalTracks.
const room = await connect('token', {
  name: 'my-cool-room',
  tracks
});

const cameraTrack = tracks.find(track => track.kind === 'video');

// Switch to the back facing camera.
cameraTrack.restart({ facingMode: 'environment' });

In SDK versions 2.6.0 and below, you can stop and unpublish the existing LocalVideoTrack, use createLocalVideoTrack to create a new LocalVideoTrack and publish it to the Room.

const { createLocalTracks, createLocalVideoTrack, connect } = require('twilio-video');

const tracks = await createLocalTracks({
  audio: true,
  video: { facingMode: 'user' }
});

// Join the Room with the pre-acquired LocalTracks.
const room = await connect('token', {
  name: 'my-cool-room',
  tracks
});

// Capture the back facing camera.
const backFacingTrack = await createLocalVideoTrack({ facingMode: 'environment' });

// Switch to the back facing camera.
const frontFacingTrack = tracks.find(track => track.kind === 'video');
frontFacingTrack.stop();
room.localParticipant.unpublishTrack(frontFacingTrack);
room.localParticipant.publishTrack(backFacingTrack);

Testing the Microphone and Camera

In mobile browsers, getUserMedia is successful even when your microphone and/or camera are reserved by another tab or application. This can result in mobile Participants not being seen and/or heard by others in a Room. In order to work around this, we recommend that your application prompt users to test their microphone and camera before joining a Room. You can use createLocalAudioTrack to acquire the microphone, and use the Web Audio API to calculate its level. If the level is 0 even when the user is talking, then most likely the microphone is reserved by either another tab or application. You can then recommend that the user close all the other applications and reload your application, or worst case, restart the browser.

testmic.js

const { createLocalAudioTrack } = require('twilio-video');
const pollAudioLevel = require('./pollaudiolevel');

const audioTrack = await createLocalAudioTrack();

// Display the audio level.
pollAudioLevel(audioTrack, level => {
  /* Update audio level indicator. */
});

pollaudiolevel.js

const AudioContext = window.AudioContext || window.webkitAudioContext;
const audioContext = AudioContext ? new AudioContext() : null;

function rootMeanSquare(samples) {
  const sumSq = samples.reduce((sumSq, sample) => sumSq + sample * sample, 0);
  return Math.sqrt(sumSq / samples.length);
}

async function pollAudioLevel(track, onLevelChanged) {
  if (!audioContext) {
    return;
  }

  // Due to browsers' autoplay policy, the AudioContext is only active after
  // the user has interacted with your app, after which the Promise returned
  // here is resolved.
  await audioContext.resume();

  // Create an analyser to access the raw audio samples from the microphone.
  const analyser = audioContext.createAnalyser();
  analyser.fftSize = 1024;
  analyser.smoothingTimeConstant = 0.5;

  // Connect the LocalAudioTrack's media source to the analyser.
  const stream = new MediaStream([track.mediaStreamTrack]);
  const source = audioContext.createMediaStreamSource(stream);
  source.connect(analyser);

  const samples = new Uint8Array(analyser.frequencyBinCount);
  let level = null;

  // Periodically calculate the audio level from the captured samples,
  // and if changed, call the callback with the new audio level.
  requestAnimationFrame(function checkLevel() {
    analyser.getByteFrequencyData(samples);
    const rms = rootMeanSquare(samples);
    const log2Rms = rms && Math.log2(rms);

    // Audio level ranges from 0 (silence) to 10 (loudest).
    const newLevel = Math.ceil(10 * log2Rms / 8);
    if (level !== newLevel) {
      level = newLevel;
      onLevelChanged(level);
    }

    // Continue calculating the level only if the audio track is live.
    if (track.mediaStreamTrack.readyState === 'live') {
      requestAnimationFrame(checkLevel);
    } else {
      requestAnimationFrame(() => onLevelChanged(0));
    }
  });
}

module.exports = pollAudioLevel;

You can use createLocalVideoTrack to acquire the camera, and attach its corresponding <video> element to the DOM. If there are no video frames, then most likely the camera is reserved by either another tab or application. Your can then recommend that the user close all the other applications and reload your application, or worst case, restart the browser.

testcamera.js

const { createLocalVideoTrack } = require('twilio-video');

const videoTrack = await createLocalVideoTrack();

// Display the video preview.
const divContainer = document.getElementById('local-video');
const videoElement = videoTrack.attach();
divContainer.appendChild(videoElement);

NOTE: In iOS Safari, because of this WebKit bug, calling getUserMedia again will mute previously acquired LocalTracks. So, please make sure that the LocalTracks that you pass in ConnectOptions are neither muted nor stopped.

Application Backgrounding in Mobile Browsers

When an application that is running on a mobile browser is backgrounded, it will not have access to the video feed from the camera until it is foregrounded. So, we recommend that you stop and unpublish the camera's LocalVideoTrack, and publish a new LocalVideoTrack once your application is foregrounded. On the remote side, you can listen to the unsubscribed and subscribed events on the corresponding RemoteVideoTrackPublication in order to notify the user accordingly. You can use the Page Visibility API to detect backgrounding and foregrounding.

mobileuser.js

const { connect, createLocalTracks, createLocalVideoTrack } = require('twilio-video');

const tracks = await createLocalTracks();

let videoTrack = tracks.find(track => track.kind === 'video');

const room = await connect('token1', {
  name: 'my-cool-room',
  tracks
});

if (/* isMobile */) {
  document.addEventListener('visibilitychange', async () => {
    if (document.visibilityState === 'hidden') {
      // The app has been backgrounded. So, stop and unpublish your LocalVideoTrack.
      videoTrack.stop();
      room.localParticipant.unpublishTrack(videoTrack);
    } else {
      // The app has been foregrounded, So, create and publish a new LocalVideoTrack.
      videoTrack = await createLocalVideoTrack();
      await room.localParticipant.publishTrack(videoTrack);
    }
  });
}

remoteuser.js

const { connect } = require('twilio-video');

function setupRemoteVideoNotifications(publication) {
  if (publication.isSubscribed) {
    // Indicate to the user that the mobile user has added video.
  }

  publication.on('subscribed', track => {
    // Indicate to the user that the mobile user has added video.
  });

  publication.on('unsubscribed', track => {
    // Indicate to the user that the mobile user has removed video.
  });
}

function setupRemoteVideoNotificationsForParticipant(participant) {
  // Set up remote video notifications for the VideoTracks that are
  // already published.
  participant.videoTracks.forEach(setupRemoteVideoNotifications);

  // Set up remote video notifications for the VideoTracks that will be
  // published later.
  participant.on('trackPublished', setupRemoteVideoNotifications);
}

const room = await connect('token2', { name: 'my-cool-room' });

// Set up remote video notifications for the VideoTracks of RemoteParticipants
// already in the Room.
room.participants.forEach(setupRemoteVideoNotificationsForParticipant);

// Set up remote video notifications for the VideoTracks of RemoteParticipants
// that will join the Room later.
room.on('participantConnected', setupRemoteVideoNotificationsForParticipant);

Handling Page Unload

When the user closes the tab/browser or navigates to another web page, we recommend that you disconnect from the Room so that other Participants are immediately notified.

const { createLocalTracks, connect } = require('twilio-video');

const tracks = await createLocalTracks();

const room = await connect('token', {
  name: 'my-cool-room',
  tracks
});

// Listen to the "beforeunload" event on window to leave the Room
// when the tab/browser is being closed.
window.addEventListener('beforeunload', () => room.disconnect());

// iOS Safari does not emit the "beforeunload" event on window.
// Use "pagehide" instead.
window.addEventListener('pagehide', () => room.disconnect());

Handling Errors

This section lists some of the important errors raised by twilio-video.js and provides recommendations on how best to handle them in order to provide the optimal user experience.

Media Errors

These errors are raised when twilio-video.js fails to acquire the user's local media (camera and/or microphone). Your app can catch these errors as shown below:

const { connect, createLocalAudioTrack, createLocalTracks, createLocalVideoTrack } = require('twilio-video');

function handleMediaError(error) {
  console.error('Failed to acquire media:', error.name, error.message);
}

// Handle media error raised by createLocalAudioTrack.
createLocalAudioTrack().catch(handleMediaError);

// Handle media error raised by createLocalVideoTrack.
createLocalVideoTrack().catch(handleMediaError);

// Handle media error raised by createLocalTracks.
createLocalTracks().catch(handleMediaError);

const mediaErrors = [
  'NotAllowedError',
  'NotFoundError',
  'NotReadableError',
  'OverconstrainedError',
  'TypeError'
];

// Since connect() will acquire media for the application if tracks are not provided in ConnectOptions,
// it can raise media errors.
connect(token, { name: 'my-cool-room' }).catch(error => {
  if (mediaErrors.includes(error.name)) {
    // Handle media error here.
    handleMediaError(error);
  }
});

The following table describes the possible media errors and proposes ways for the application to handle them:

Name Message Cause Solution
NotFoundError 1. Permission denied by system
2. The object cannot be found here
3. Requested device not found

1. User has disabled the input device for the browser in the system settings
2. User's machine does not have any such input device connected to it
1. User should enable the input device for the browser in the system settings
2. User should have at lease one input device connected
NotAllowedError 1. Permission denied
2. Permission dismissed
3. The request is not allowed by the user agent or the platform in the current context
4. The request is not allowed by the user agent or the platform in the current context, possibly because the user denied permission
1. User has denied permission for your app to access the input device, either by clicking the “deny” button on the permission dialog, or by going to the browser settings
2. User has denied permission for your app by dismissing the permission dialog
1. User should allow your app to access the input device in the browser settings and then reload
2. User should reload your app and grant permission to access the input device
TypeError 1. Cannot read property 'getUserMedia' of undefined
2. navigator.mediaDevices is undefined
Your app is being served from a non-localhost non-secure context Your app should be served from a secure context (localhost or https)
NotReadableError 1. Failed starting capture of a audio track
2. Failed starting capture of a video track
3. Could not start audio source
4. Could not start video source
5. The I/O read operation failed
The browser could not start media capture with the input device even after the user gave permission, probably because another app or tab has reserved the input device User should close all other apps and tabs that have reserved the input device and reload your app, or worst case, restart the browser
OverconstrainedError N/A The input device could not satisfy the requested media constraints If this exception was raised due to your app requesting a specific device ID, then most likely the input device is no longer connected to the machine, so your app should request the default input device

NOTE: Each error can log a different message depending on the browser and OS. This table lists all possible messages associated with each error.

Connection Errors

These errors are raised by twilio-video.js when it fails to join a Room. Your app can catch these errors as shown below:

const { connect } = require('twilio-video');

connect(token, { name: 'my-cool-room' }).catch(error => {
  if ('code' in error) {
    // Handle connection error here.
    console.error('Failed to join Room:', error.code, error.message);
  }
});

The following table describes the most common connection errors and proposes ways for the application to handle them:

Error Code Cause Solution
SignalingConnectionError 53000 The client could not establish a connection to Twilio's signaling server User should make sure to have a stable internet connection
SignalingServerBusyError 53006 Twilio's signaling server is too busy to accept new clients User should try joining the Room again after some time
RoomMaxParticipantsExceededError 53105 The Room cannot allow in any more Participants to join Your app should notify the user that the Room is full
RoomNotFoundError 53106 The client attempted to connect to a Room that does not exist If ad-hoc Room creation is disabled, then your app should make sure that the Room is created using the REST API before clients attempt to join
MediaConnectionError 53405 The client failed to establish a media connection with the Room 1. User should make sure to have a stable internet connection
2. If the user is behind a firewall, then it should allow media traffic to and from Twilio to go through

Disconnection Errors

These errors are raised by twilio-video.js when it is inadvertently disconnected from the Room. Your app can catch these errors as shown below:

const { connect } = require('twilio-video');

connect(token, { name: 'my-cool-room' }).then(room => {
  room.once('disconnected', (room, error) => {
    if (error) {
      console.log('You were disconnected from the Room:', error.code, error.message);
    }
  });
});

The following table describes the most common disconnection errors and proposes ways for the application to handle them:

Error Code Cause Solution
SignalingConnectionDisconnectedError 53001 The client failed to reconnect to Twilio's signaling server after a network disruption or handoff User should make sure to have a stable internet connection
SignalingConnectionTimeoutError 53002 The liveliness checks for the connection to Twilio's signaling server failed, or the current session expired User should rejoin the Room
ParticipantDuplicateIdentityError 53205 Another client joined the Room with the same identity Your app should make sure each client creates an AccessToken with a unique identity string
MediaConnectionError 53405 The client failed to re-establish its media connection with the Room after a network disruption or handoff 1. User should make sure to have a stable internet connection
2. If the user is behind a firewall, then it should allow media traffic to and from Twilio to go through
Rate this page:

Need some help?

We all do sometimes; code is hard. Get help now from our support team, or lean on the wisdom of the crowd browsing the Twilio tag on Stack Overflow.