Syncfusion ASP.NET Core SpeechToText Control

Overview

The SpeechToText control enables users to convert spoken words into text using the Web Speech API in ASP.NET Core applications. This skill helps you implement, customize, and troubleshoot speech recognition using Razor Tag Helpers.

The main Razor Tag Helper that captures audio and converts speech to text in real-time using browser APIs.

Key Features:

• Real-time speech recognition via Web Speech API
• Multiple language support
• Customizable button and tooltip via tag helper attributes
• Event-driven architecture
• Programmatic control via JavaScript methods
• Accessibility support (ARIA labels, keyboard navigation)
• Localization support
• Error handling and recovery
• ASP.NET Core binding

Documentation

Getting Started

📄 Read: references/getting-started.md

• Installation via NuGet
• ASP.NET Core project setup
• Razor Tag Helper registration
• Basic control implementation
• CSS imports and theme selection
• First working example
• Script manager configuration

Speech Recognition Features

📄 Read: references/speech-recognition-features.md

• Retrieving transcripts in real-time
• Setting language for recognition
• Managing interim results
• Listening state management
• Handling speech-to-text conversion
• Real-time vs final results
• Multi-language support

Button and Tooltip Customization

📄 Read: references/button-and-tooltip-customization.md

• Button customization via tag helper attributes
• Icon customization using CSS classes
• Icon positioning
• Tooltip configuration
• Primary button styling
• CSS class styling (e-primary, e-success, etc.)
• Responsive design

Events and Methods

📄 Read: references/events-and-methods.md

• Event binding in Razor (onStart, onStop, onError, transcriptChanged)
• Event handling in script tag
• Error types and error handling
• startListening() and stopListening() methods
• Programmatic control via JavaScript
• Getting component instance with ej.base.getComponent()
• Event workflows and patterns

Globalization and Localization

📄 Read: references/globalization-and-localization.md

• Localization with L10n.load()
• Available locale strings
• Language-specific error messages
• RTL support via enableRtl attribute
• Accessibility labels and ARIA attributes
• Multi-language interface examples

Troubleshooting and Security

📄 Read: references/troubleshooting-and-security.md

• Common issues and solutions
• Browser compatibility matrix
• Microphone permission handling
• Security considerations for ASP.NET Core
• Privacy and data transmission
• Performance optimization
• Offline fallback strategies

Quick Start Example

@using Syncfusion.EJ2.Inputs

<div id='speechtotext-container'>
    <ejs-speechtotext id="speech-to-text" transcriptChanged="onTranscriptChanged"></ejs-speechtotext>
    <ejs-textarea id="output-textarea" rows="5" cols="50" value="" resizeMode="None" placeholder="Transcribed text will be shown here..."></ejs-textarea>
</div>

<script>
    function onTranscriptChanged(args) {
        var textareaObj = ej.base.getComponent(document.getElementById("output-textarea"), "textarea");
        textareaObj.value = args.transcript;
    }
</script>

<style>
    #speechtotext-container {
        gap: 20px;
        display: flex;
        flex-direction: column;
        align-items: center;
    }
</style>

Common Patterns

Pattern 1: Voice Form with Multiple Fields

@using Syncfusion.EJ2.Inputs

<div class="form-group">
    <label>Name (speak):</label>
    <ejs-speechtotext id="name-voice" transcriptChanged="onNameTranscript"></ejs-speechtotext>
    <ejs-textbox id="name-field"></ejs-textbox>
</div>

<div class="form-group">
    <label>Message (speak):</label>
    <ejs-speechtotext id="message-voice" transcriptChanged="onMessageTranscript"></ejs-speechtotext>
    <ejs-textarea id="message-field" rows="4"></ejs-textarea>
</div>

<script>
    function onNameTranscript(args) {
        var nameField = ej.base.getComponent(document.getElementById("name-field"), "textbox");
        nameField.value = args.transcript;
    }

    function onMessageTranscript(args) {
        var messageField = ej.base.getComponent(document.getElementById("message-field"), "textarea");
        messageField.value = args.transcript;
    }
</script>

Pattern 2: Programmatic Control

@using Syncfusion.EJ2.Inputs

<ejs-speechtotext id="speech-control"></ejs-speechtotext>

<div>
    <button onclick="startVoiceInput()">Start Recording</button>
    <button onclick="stopVoiceInput()">Stop Recording</button>
</div>

<script>
    function startVoiceInput() {
        var speechComponent = ej.base.getComponent(
            document.getElementById("speech-control"), 
            "speechtotext"
        );
        speechComponent.startListening();
    }

    function stopVoiceInput() {
        var speechComponent = ej.base.getComponent(
            document.getElementById("speech-control"), 
            "speechtotext"
        );
        speechComponent.stopListening();
    }
</script>

Pattern 3: Error Handling

@using Syncfusion.EJ2.Inputs

<ejs-speechtotext id="error-speech" 
    onError="handleError" 
    onStart="handleStart" 
    onStop="handleStop">
</ejs-speechtotext>

<div id="error-message" style="display:none; color: red; padding: 10px;"></div>

<script>
    function handleError(args) {
        var errorDiv = document.getElementById("error-message");
        errorDiv.style.display = "block";
        
        var errorMessages = {
            'no-speech': '🔇 No speech detected. Please try again.',
            'audio-capture': '🎙️ Microphone not found.',
            'not-allowed': '🔒 Microphone permission denied.',
            'network': '🌐 Network error occurred.'
        };
        
        errorDiv.textContent = errorMessages[args.error] || 'Error: ' + args.error;
        setTimeout(() => { errorDiv.style.display = "none"; }, 5000);
    }

    function handleStart() {
        console.log('🎤 Listening started');
    }

    function handleStop() {
        console.log('⏹️ Listening stopped');
    }
</script>

Key Properties

Property	Type	Description
lang	string	Language code (e.g., 'en-US', 'fr-FR')
transcript	string	Current transcribed text
allowInterimResults	boolean	Show real-time results (default: true)
listeningState	enum	Current state (Inactive, Listening, Stopped)
cssClass	string	CSS classes (e-primary, e-success, etc.)
enableRtl	boolean	Enable right-to-left layout
locale	string	Localization language code

Tag Helper Attributes

<ejs-speechtotext 
    id="speechId"
    lang="en-US"
    allowInterimResults="true"
    cssClass="e-primary"
    enableRtl="false"
    locale="en-US"
    transcriptChanged="onTranscriptChanged"
    onStart="onStartListening"
    onStop="onStopListening"
    onError="onError"
    created="onCreated">
    
    <e-speechtotext-buttonSettings 
        content="Start Listening" 
        stopContent="Stop Listening"
        iconCss="e-icons e-play"
        stopIconCss="e-icons e-pause"
        iconPosition="Right"
        isPrimary="true">
    </e-speechtotext-buttonSettings>
    
    <e-speechtotext-tooltipSettings 
        position="TopCenter"
        content="Click to start"
        stopContent="Click to stop">
    </e-speechtotext-tooltipSettings>
</ejs-speechtotext>

Event Handlers

Event	Args	Description
created	-	Fired when control is initialized
onStart	StartListeningEventArgs	Fired when listening begins
onStop	StopListeningEventArgs	Fired when listening ends
onError	ErrorEventArgs	Fired when error occurs
transcriptChanged	TranscriptChangedEventArgs	Fired when transcript updates

Methods

Method	Description
startListening()	Begin speech recognition
stopListening()	Stop speech recognition

Troubleshooting

Control not rendering

Solution: Check that <ejs-scripts></ejs-scripts> is in layout and CSS is imported

Events not firing

Solution: Verify event handlers are valid JavaScript functions in global scope

Microphone permission denied

Solution: Allow microphone access in browser settings

Speech not recognized

Solution: Check microphone volume, speak clearly, verify language setting