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Screen Sharing

Last updated: 2024-03-22 17:25:01

This tutorial mainly introduces how to implement screen sharing in TRTC Web SDK.
Usage
Start Screen Sharing
Call trtc.startScreenShare() to start screen sharing.
const trtcA = TRTC.create();
await trtcA.enterRoom({
  scene: 'rtc',
  sdkAppId: 140000000, // Fill in your sdkAppId
  userId: 'userA', // Fill in your userId
  userSig: 'userA_sig', // Fill in userSig corresponding to userId
  roomId: 6969
})
await trtcA.startScreenShare();
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// Setting a view if you need to preview local screen sharing.
await trtcA.startScreenShare({ view: 'local-screen-sharing-element-id' });
The SDK uses the 1080p parameter configuration by default to capture screen sharing, you can customize this parameter by referring to trtc.startScreenShare({ option: { profile: '720p' }})﻿
Play Remote Screen Sharing
const trtcB = TRTC.create();
trtcB.on(TRTC.EVENT.REMOTE_VIDEO_AVAILABLE, ({ userId, streamType }) => {
  // Main video stream
  if (streamType === TRTC.TYPE.STREAM_TYPE_MAIN) {
    trtcB.startRemoteVideo({ userId, streamType,  view: `${userId}_main` });
  } else {
    // Sub video stream, it's remote screen sharing.
    // 'view' is the element id of a div for video playback.
    trtcB.startRemoteVideo({ userId, streamType, view: `${userId}_screen` });
  }
});
﻿
await trtcB.enterRoom({
  scene: 'rtc',
  sdkAppId: 140000000, // Fill in your sdkAppId
  userId: 'userB', // Fill in your userId
  userSig: 'userB_sig', // Fill in userSig corresponding to userId
  roomId: 6969
})
What is the main/sub video stream?
1. TRTC has a main video stream (main stream) and an sub video stream (sub stream).
2. The camera is published through the main stream, and the screen sharing is published through the sub stream.
3. The main video stream includes: big stream and small stream. By default, TRTC.startRemoteVideo plays the big stream, and the small stream can be played through the small parameter. Refer to: Optimize Multi-Person Video Calls.
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Screen Sharing + System Audio
await trtcA.startScreenShare({ option: { systemAudio: true }});
Capturing system audio is only supported by Chromium based browser M74+, such as Chrome, Edge, Opera.
OS
System Audio
Tab Audio
Windows
Yes
Yes
MacOS
No
Yes
Linux
No
Yes
Non-Chromium based browser, such as Safari, Firefox
No
No
Check Share audio in the pop-up dialog box, and the system audio will be mixed with the local microphone and published. Other users in the room will receive the TRTC.EVENT.REMOTE_AUDIO_AVALIABLE event.
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Stop Screen Sharing
1. Call trtc.stopScreenShare() to start screen sharing. 
2. Other users in the room will receive the TRTC.EVENT.REMOTE_VIDEO_UNAVAILABLE event, and streamType is TRTC.TYPE.STREAM_TYPE_SUB.
 // Stop screen sharing
 await trtcA.stopScreenShare();
﻿
 trtcB.on(TRTC.EVENT.REMOTE_VIDEO_UNAVAILABLE, ({ userId, streamType }) => {
    // Remote user stopped the screen sharing.
    if (streamType === TRTC.TYPE.STREAM_TYPE_SUB) {}
 })
In addition, users may also stop screen sharing through the browser's own button, SDK will stop screen sharing when user click the Stop Button. You can listen for the TRTC.EVENT.SCREEN_SHARE_STOPPED event.
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// Listen for local screen sharing stop event
trtcA.on(TRTC.EVENT.SCREEN_SHARE_STOPPED, () => {
  console.log('screen sharing was stopped');
});
FAQ
1. Safari screen sharing error getDisplayMedia must be called from a user gesture handler
This is because Safari restricts the getDisplayMedia screen capture interface, which must be called within 1 second of the callback function of the user click event.
Refer to: webkit issue.
// good
async function onClick() {
  // It is recommended to execute the collection logic first when onClick is executed
  await trtcA.startScreenShare();
  await trtcA.enterRoom({ 
    roomId: 123123,
    sdkAppId: 140000000, // Fill in your sdkAppId
    userId: 'userA', // Fill in your userId
    userSig: 'userA_sig', // Fill in userSig corresponding to userId
  });
}
﻿
// bad
async function onClick() {
  await trtcA.enterRoom({ 
    roomId: 123123,
    sdkAppId: 140000000, // Fill in your sdkAppId
    userId: 'userA', // Fill in your userId
    userSig: 'userA_sig', // Fill in userSig corresponding to userId
  });
  // Entering the room may take more than 1s, and the collection may fail
  await trtcA.startScreenShare();
}
2. Mac Chrome screen sharing fails with the error message "NotAllowedError: Permission denied by system" or "NotReadableError: Could not start video source" when screen recording is already authorized.
It's a Chrome bug. Solution: 
2.1 Open Mac System Settings
2.2 Click Security & Privacy
2.3 Click Privacy
2.4 Click Screen Recording
2.5 Turn off Chrome screen recording authorization
2.6 Reopen Chrome screen recording authorization
2.7 Close Chrome browser
2.8 Reopen Chrome browser
3. ﻿WebRTC screen sharing known issues and workarounds﻿