Speech-to-Text Continuous Recognition in C#

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This sample demonstrates how to perform continuous speech recognition using the Speech SDK in a C# console application. The application listens for speech from the default microphone and prints recognized text to the console in real-time.

Program.cs

How to generate this sample

Command

ai dev new speech-to-text-continuous-reco --csharp

Output

AI - Azure AI CLI, Version 1.0.0
Copyright (c) 2024 Microsoft Corporation. All Rights Reserved.

This PUBLIC PREVIEW version may change at any time.
See: https://aka.ms/azure-ai-cli-public-preview

Generating 'speech-to-text-continuous-reco' in 'speech-to-text-continuous-reco-cs' (2 files)...

SpeechToTextContinuousReco.csproj
Program.cs

Generating 'speech-to-text-continuous-reco' in 'speech-to-text-continuous-reco-cs' (2 files)... DONE!

Program.cs

STEP 1: Read the configuration settings from environment variables.

Program.cs

var speechKey = Environment.GetEnvironmentVariable("AZURE_AI_SPEECH_KEY") ?? "<insert your Speech Service API key here>";
var speechRegion = Environment.GetEnvironmentVariable("AZURE_AI_SPEECH_REGION") ?? "<insert your Speech Service region here>";
var speechLanguage = "en-US"; // BCP-47 language code

STEP 2: Create instances of a speech config, source language config, and audio config.

Program.cs

var config = SpeechConfig.FromSubscription(speechKey, speechRegion);
var sourceLanguageConfig = SourceLanguageConfig.FromLanguage(speechLanguage);
var audioConfig = AudioConfig.FromDefaultMicrophoneInput();

STEP 3: Create the speech recognizer from the above configuration information.

Program.cs

using (var recognizer = new SpeechRecognizer(config, sourceLanguageConfig, audioConfig))
{
    recognizer.Recognizing += (s, e) => HandleRecognizingEvent(e);
    recognizer.Recognized += (s, e) => HandleRecognizedEvent(e);
    var sessionStoppedNoError = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
    recognizer.SessionStarted += (s, e) => HandleSessionStartedEvent(e);
    recognizer.SessionStopped += (s, e) => HandleSessionStoppedEvent(e, sessionStoppedNoError);
    recognizer.Canceled += (s, e) => HandleCanceledEvent(e, sessionStoppedNoError);

STEP 4: Subscribe to recognizing and recognized events for handling intermediate and final recognition results.

Program.cs

    recognizer.Recognizing += (s, e) => HandleRecognizingEvent(e);
    recognizer.Recognized += (s, e) => HandleRecognizedEvent(e);

STEP 5: Subscribe to session started, stopped, and canceled events for handling session events and cancellations.

Program.cs

    recognizer.SessionStarted += (s, e) => HandleSessionStartedEvent(e);
    recognizer.SessionStopped += (s, e) => HandleSessionStoppedEvent(e, sessionStoppedNoError);
    recognizer.Canceled += (s, e) => HandleCanceledEvent(e, sessionStoppedNoError);

STEP 6: Start continuous recognition and wait for user input to stop.

Program.cs

    Task.Run(() =>
    {
        while (Console.ReadKey().Key != ConsoleKey.Enter) { }
        recognizer.StopContinuousRecognitionAsync();
    });
    await recognizer.StartContinuousRecognitionAsync();
    Console.WriteLine("Listening; press ENTER to stop ...\n");
    return await sessionStoppedNoError.Task ? 0 : 1;
}

STEP 7: Handle intermediate and final recognition results.

Program.cs

private static void HandleRecognizingEvent(SpeechRecognitionEventArgs e)
{
    Console.WriteLine($"RECOGNIZING: {e.Result.Text}");
}

private static void HandleRecognizedEvent(SpeechRecognitionEventArgs e)
{
    if (e.Result.Reason == ResultReason.RecognizedSpeech && !string.IsNullOrEmpty(e.Result.Text))
    {
        Console.WriteLine($"RECOGNIZED: {e.Result.Text}\n");
    }
    else if (e.Result.Reason == ResultReason.NoMatch)
    {
        Console.WriteLine($"NOMATCH: Speech could not be recognized.\n");
    }
}

STEP 8: Handle session start, stop, and cancellation events.

Program.cs

private static void HandleSessionStartedEvent(SessionEventArgs e)
{
    Console.WriteLine($"SESSION STARTED: {e.SessionId}.\n");
}

private static void HandleSessionStoppedEvent(SessionEventArgs e, TaskCompletionSource<bool> sessionStoppedNoError)
{
    Console.WriteLine($"SESSION STOPPED: {e.SessionId}.");
    sessionStoppedNoError.TrySetResult(true);
}

private static void HandleCanceledEvent(SpeechRecognitionCanceledEventArgs e, TaskCompletionSource<bool> sessionStoppedNoError)
{
    Console.WriteLine($"CANCELED: Reason={e.Reason}");
    if (e.Reason == CancellationReason.EndOfStream)
    {
        Console.WriteLine($"CANCELED: End of the audio stream was reached.");
    }
    else if (e.Reason == CancellationReason.Error)
    {
        Console.WriteLine($"CANCELED: ErrorCode={e.ErrorCode}");
        Console.WriteLine($"CANCELED: ErrorDetails={e.ErrorDetails}");
        Console.WriteLine($"CANCELED: Did you update the subscription info?");
    }
    sessionStoppedNoError.TrySetResult(e.Reason != CancellationReason.Error);
}