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Quickstart RTT within your application

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Important

Functionality described in this article is currently in public preview. This preview version is provided without a service-level agreement, and we don't recommend it for production workloads. Certain features might not be supported or might have constrained capabilities. For more information, see Supplemental Terms of Use for Microsoft Azure Previews.

Note

RTT is an accessibility compliance requirement for voice and video platforms in the EU starting June 30, 2025. You can find more information about this here: Directive 2019/882.

Learn how to integrate Real Time Text (RTT) into your calling applications to enhance accessibility and ensure that all participants can communicate effectively during meetings.

RTT allows users who have difficulty speaking to participate actively by typing their messages, which are then broadcast in near real-time to other meeting participants. This feature operates seamlessly alongside existing captions and ensures that typed messages are promptly delivered without disrupting the flow of conversation.

Real Time Text Feature Overview

Real Time Text (RTT) is designed to facilitate communication for users who may have difficulty speaking during calls. By allowing users to type their messages, RTT ensures that everyone in the meeting can stay engaged and informed. Messages are transmitted over Data Channels (ID 24) and are always active, appearing automatically when the first message is sent.

On supported platforms, RTT data can be displayed alongside captions derived from Speech to Text, providing a comprehensive view of all communications during a call.

Note

RTT Teams Interlop is not functional yet.

Naming Conventions

Different platforms may use varying terminology for RTT-related properties. Below is a summary of these differences:

Mobile (Android/iOS) Windows (C#)
Type Kind
Info Details

These aliases are functionally equivalent and are used to maintain consistency across different platforms.

RealTimeTextInfo/Details Class

The RealTimeTextInfo (or RealTimeTextDetails on Windows) class encapsulates information about each RTT message. Below are the key properties:

Property Description
SequenceId Unique identifier for the message sequence.
Text The content of the RTT message.
Sender Information about the sender of the message.
ResultType/
Kind		 Indicates whether the message is partial or final.
IsLocal Determines if the message was sent by the local user.
ReceivedTime Timestamp when the message was received.
UpdatedTime Timestamp when the message was last updated.

Models

Name Description
RealTimeTextInfo Represents a real-time text message entry, including sender information, message content, sequence ID, and status.

Get Real Time Text Feature

To access the Real Time Text feature, retrieve it from the Call object:

RealTimeTextCallFeature rttFeature = call.feature(Features.REAL_TIME_TEXT);

Feature Usage

Sending Real Time Text Messages

Bind a text input field to the send() method to transmit messages as the user types:

EditText messageEditText = findViewById(R.id.messageEditText);
messageEditText.addTextChangedListener(new TextWatcher() {
    @Override
    public void afterTextChanged(Editable s) {
        String text = s.toString();
        rttFeature.send(text);
    }
    // Other overridden methods...
});

Receiving Real Time Text Messages

Subscribe to the OnInfoReceived event to handle incoming messages:

rttFeature.addOnInfoReceivedListener((eventArgs) -> {
    RealTimeTextInfo info = eventArgs.getInfo();
    
    // Update your message list with the new info
    updateMessageList(info);
    
    // Clear the text input if the message is local and finalized
    if (info.isLocal() && info.getResultType() == RealTimeTextResultType.FINAL) {
        messageEditText.getText().clear();
    }
});

RealTimeTextInfo Class

The RealTimeTextInfo class provides detailed information about each real-time text message:

  • Sender: Information about who sent the message.
  • SequenceId: Unique identifier for the message.
  • Text: The content of the message.
  • ResultType: Indicates if the message is partial or finalized.
  • ReceivedTime: Timestamp when the message was received.
  • UpdatedTime: Timestamp when the message was last updated.
  • IsLocal: Indicates if the message was sent by the local user.

Models

Name Description
RealTimeTextInfo Represents a real-time text message entry, including sender information, message content, sequence ID, and status.

Get Real Time Text Feature

Access the Real Time Text feature from your Call object:

let rttFeature = call.feature(Features.realTimeText)

Feature Usage

Sending Real Time Text Messages

Bind a text input field to the send method to transmit messages as the user types:

@State var messageText: String = ""

TextField("Type your message", text: $messageText)
    .onChange(of: messageText) { newText in
        rttFeature?.send(newText)
    }

Receiving Real Time Text Messages

Subscribe to the OnInfoReceived event to handle incoming messages:

rttFeature?.addOnInfoReceivedListener { eventArgs in
    if let info = eventArgs.info {
        // Update your message list with the new info
        updateMessageList(info)
        
        // Clear the text input if the message is local and finalized
        if info.isLocal && info.resultType == .final {
            self.messageText = ""
        }
    }
}

RealTimeTextInfo Class

The RealTimeTextInfo class provides detailed information about each real-time text message:

  • Sender: Information about who sent the message.
  • SequenceId: Unique identifier for the message.
  • Text: The content of the message.
  • ResultType: Indicates if the message is partial or finalized.
  • ReceivedTime: Timestamp when the message was received.
  • UpdatedTime: Timestamp when the message was last updated.
  • IsLocal: Indicates if the message was sent by the local user.

Models

Name Description
RealTimeTextDetails Represents a real-time text message entry, including sender information, message content, sequence ID, and status.

Get Real Time Text Feature

Retrieve the Real Time Text feature from the Call object:

RealTimeTextCallFeature rttFeature = call.GetRealTimeTextCallFeature();

Feature Usage

Sending Real Time Text Messages

Connect a text input field to the Send method to transmit messages as the user types:

TextBox messageTextBox = new TextBox();
messageTextBox.TextChanged += (sender, args) => {
    string text = messageTextBox.Text;
    rttFeature.Send(text);
};

Receiving Real Time Text Messages

Subscribe to the DetailsReceived event to handle incoming messages:

rttFeature.DetailsReceived += (sender, e) => {
    RealTimeTextDetails details = e.Details;
    
    // Update your message list with the new details
    UpdateMessageList(details);
    
    // Clear the text input if the message is local and finalized
    if (details.IsLocal && details.Kind == RealTimeTextResultKind.Final) {
        messageTextBox.Text = string.Empty;
    }
};

RealTimeTextDetails Class

The RealTimeTextDetails class provides comprehensive information about each real-time text message:

  • Sender: Information about who sent the message.
  • SequenceId: Unique identifier for the message.
  • Text: The content of the message.
  • Kind: Indicates if the message is partial or finalized.
  • ReceivedTime: Timestamp when the message was received.
  • UpdatedTime: Timestamp when the message was last updated.
  • IsLocal: Indicates if the message was sent by the local user.

Next steps

For more information, see the following articles: