tencent cloud

TRTC supports screen sharing via the primary stream and substream on Windows:

• Substream sharing
  In TRTC, you can share the screen via a dedicated stream, which is called the substream. In substream sharing, an anchor publishes camera video and screen sharing images at the same time. This is the scheme used by VooV Meeting. You can enable substream sharing by setting the TRTCVideoStreamType parameter to TRTCVideoStreamTypeSub when calling the startScreenCapture API. To play substream video, call startRemoteSubStreamView.

• Primary stream sharing
  In TRTC, the channel via which camera images are published is the primary stream (bigstream). In primary stream sharing, an anchor publishes screen sharing images via the primary stream. As there is only one stream, an anchor cannot publish both camera video and screen sharing images. You can enable this mode by setting the TRTCVideoStreamType parameter to TRTCVideoStreamTypeBig when calling the startScreenCapture API.

Supported Platforms

APIs

Getting Sharable Sources

You can call getScreenCaptureSources to get a list of sharable sources, which is returned via the response parameter sourceInfoList.

Note：

On Windows, the desktop also counts as a window. When two monitors are used, each monitor corresponds to a desktop window. The list returned via getScreenCaptureSources includes desktop windows.

Each sourceInfo object in sourceInfoList represents a sharable source, which is described by the following parameters:

Based on the information, you can display a list of sharable sources on the UI for users to choose from.

Selecting Sharing Source

The TRTC SDK supports three screen sharing modes, which you can specify using selectScreenCaptureTarget.

• Share an entire screen:
  You can share an entire screen by selecting from sourceInfoList a source whose type is TRTCScreenCaptureSourceTypeScreen and setting captureRect to {0, 0, 0, 0}. This mode is supported when you split the screen onto multiple monitors.

• Share a portion of a screen:
  You can share a specific portion of a screen by selecting from sourceInfoList a source whose type is TRTCScreenCaptureSourceTypeScreen and setting captureRect to a non-null value, such as {100, 100, 300, 300}.

• Share a window:
  You can share a window by selecting from sourceInfoList a source whose type is TRTCScreenCaptureSourceTypeWindow and setting captureRect to {0, 0, 0, 0}.

Note：

Two additional parameters:

• captureMouse: specifies whether to capture the cursor.
• highlightWindow: specifies whether to highlight the window being shared and remind users to move the window when it is covered. The relevant UI design is implemented within the SDK.

Starting Screen Sharing

• After selecting a sharing source, you can call the startScreenCapture API to start screen sharing.
• During screen sharing, you can call selectScreenCaptureTarget to change the sharing source.
• The difference between pauseScreenCapture and stopScreenCapture is that the former pauses screen capturing and displays the image at the moment of pausing. Remote users see the last frame of video before pausing until screen capturing is resumed.

  /**
  * \brief 7.5 **Screen Sharing** Start screen sharing
  * \param: rendHwnd - HWND of the preview window
  */
  void startScreenCapture(HWND rendHwnd);
   /**
  * \brief 7.6 **Screen Sharing** Pause screen sharing
  */
  void pauseScreenCapture();
   /**
  * \brief 7.7 **Screen Sharing** Resume screen sharing
  */
  void resumeScreenCapture();
   /**
  * \brief 7.8 **Screen Sharing** Stop screen sharing
  */
  void stopScreenCapture();

Setting Video Quality

You can use the setSubStreamEncoderParam API to set the video quality of screen sharing, including resolution, bitrate, and frame rate. We recommend the following settings:

Watching Shared Screen

• Watch screens shared by macOS/Windows users
  When a macOS/Windows user in a room starts screen sharing, the screen will be shared through a substream, and other users in the room will be notified through onUserSubStreamAvailable in TRTCCloudDelegate.
  Users who want to watch the shared screen can start rendering the substream image of the remote user by calling the startRemoteSubStreamView API.

• Watch screens shared by Android/iOS users
  When an Android/iOS user starts screen sharing, the screen will be shared through the primary stream, and other users in the room will be notified through onUserVideoAvailable in TRTCCloudDelegate.
  Users who want to watch the shared screen can start rendering the primary stream of the remote user by calling the startRemoteView API.

//Sample code: watch the shared screen
void CTRTCCloudSDK::onUserSubStreamAvailable(const char * userId, bool available)
{
   LINFO(L"onUserSubStreamAvailable userId[%s] available[%d]\n", UTF82Wide(userId).c_str(), available);
  if (available)  {
        startRemoteSubStreamView(userId, hWnd);
  } else {
        stopRemoteSubStreamView(userId);
  }
}

FAQs

Can there be multiple channels of screen sharing streams in the same room at the same time?
Currently, a TRTC room can have only one screen sharing stream at a time.

When a specified window (SourceTypeWindow) is shared, if the window size changes, will the resolution of the video stream change accordingly?
By default, the SDK automatically adjusts encoding parameters according to the size of the shared window.
If you want a fixed resolution, call the setSubStreamEncoderParam API to set encoding parameters for screen sharing or specify the parameters when calling the startScreenCapture API.