How to Implement Speech-to-Text in Blazor

Are you tired of typing when you could be talking? What if I told you that with just a few lines of code, your Blazor app could understand your voice and convert it to text in real time? Whether you’re building a productivity tool, a chat interface, or a hands-free note-taking app, speech-to-text can revolutionize how users interact with your application. Let me walk you through a step-by-step guide to bring this voice power into your Blazor project.

Why Add Speech-to-Text in Blazor?

Speech input isn’t just a convenience; it’s a game-changer for accessibility, speed, and hands-free interactions. Blazor, with its capability to run in the browser (via WebAssembly), allows us to tap directly into the browser’s Web Speech API without plugins or third-party services.

Here’s what you’ll need:

• A Blazor WebAssembly app
• Basic understanding of JavaScript interop in Blazor
• A modern browser (Chrome, Edge, etc.)

Step 1: Prepare Your Blazor Project

Create a new Blazor WebAssembly project (or use an existing one):

dotnet new blazorwasm -o BlazorSpeechApp

Open the project in your favorite IDE and let’s move on.

Step 2: Create JavaScript Interop for Speech Recognition

Blazor doesn’t natively support the Web Speech API, so we’ll bridge the gap with a simple JavaScript file.

Create a speech.js file in wwwroot:

window.speechToText = {
    recognition: null,
    start: function (dotNetObjRef) {
        const SpeechRecognition = window.SpeechRecognition || window.webkitSpeechRecognition;
        if (!SpeechRecognition) {
            alert("Speech Recognition not supported");
            return;
        }

        this.recognition = new SpeechRecognition();
        this.recognition.continuous = true;
        this.recognition.interimResults = true;

        this.recognition.onresult = function (event) {
            let transcript = '';
            for (let i = event.resultIndex; i < event.results.length; ++i) {
                transcript += event.results[i][0].transcript;
            }
            dotNetObjRef.invokeMethodAsync('ReceiveTranscript', transcript);
        };

        this.recognition.start();
    },
    stop: function () {
        if (this.recognition) this.recognition.stop();
    }
};

Don’t forget to include this in your index.html:

<script src="speech.js"></script>

Step 3: Create a Razor Component for Speech Input

Now, create a new Razor component, e.g., SpeechInput.razor:

@inject IJSRuntime JSRuntime

<h3>Speech-to-Text</h3>
<p>@_transcript</p>

<button @onclick="StartRecognition">Start Listening</button>
<button @onclick="StopRecognition">Stop Listening</button>

@code {
    private string _transcript = "";
    private DotNetObjectReference<SpeechInput>? _objRef;

    protected override void OnInitialized()
    {
        _objRef = DotNetObjectReference.Create(this);
    }

    private async Task StartRecognition()
    {
        await JSRuntime.InvokeVoidAsync("speechToText.start", _objRef);
    }

    private async Task StopRecognition()
    {
        await JSRuntime.InvokeVoidAsync("speechToText.stop");
    }

    [JSInvokable]
    public void ReceiveTranscript(string transcript)
    {
        _transcript = transcript;
        StateHasChanged();
    }
}

Step 4: Test It Out

Run your app:

dotnet run

Navigate to the page with your SpeechInput component. Click “Start Listening”, speak, and see the text appear in real time!

Platform Limitations and Compatibility

Before you go all-in, it’s important to understand the limitations:

• Browser support: This implementation relies on the Web Speech API, which is supported only in Chromium-based browsers (Google Chrome, Microsoft Edge). Firefox, Safari, and some mobile browsers may not support it or have inconsistent behavior.
• Internet connection: Some browsers require an internet connection to process speech since they use online speech recognition services.
• Device permissions: The app requires microphone access. Users must grant permission in the browser for the feature to work.
• No built-in support in Blazor Server: This method is strictly for Blazor WebAssembly. Blazor Server apps would need a different approach for client-side speech processing.

Always test on your target browsers and devices to ensure compatibility.

FAQ: Speech-to-Text in Blazor Simplified

Conclusion: Give Your Blazor App a Voice!

With just a sprinkle of JavaScript and a clean Blazor component, you’ve enabled your application to understand human speech. This isn’t just a tech demo – it’s a productivity booster, accessibility enabler, and a seriously cool feature.

Why not integrate this into your next chat bot, task manager, or personal dashboard? Start simple, dream big, and let your app talk (well, listen)!