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Speech Recognition with Keyword Spotting in C#

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Please review the content and code before using it in your application.

This sample demonstrates how to use the Azure Cognitive Services Speech SDK to recognize speech with keyword spotting in a C# console application.

Program.cs

How to generate this sample

Command

ai dev new speech-to-text-with-keyword --csharp

Output

AI - Azure AI CLI, Version 1.0.0
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This PUBLIC PREVIEW version may change at any time.
See: https://aka.ms/azure-ai-cli-public-preview

Generating 'speech-to-text-with-keyword' in 'speech-to-text-with-keyword-cs' (3 files)...

Program.cs

Generating 'speech-to-text-with-keyword' in 'speech-to-text-with-keyword-cs' (1 files)... DONE!

Program.cs

STEP 1: Read the connection and configuration details 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
var inputFileName = args.Length == 1 ? args[0] : null;
var keywordFileName = "keyword.table";

STEP 2: Check if the input file and keyword file exist:

Program.cs

if (inputFileName != null && !File.Exists(inputFileName))
{
    Console.WriteLine($"ERROR: Cannot find audio input file: {inputFileName}");
    return 1;
}

if (!File.Exists(keywordFileName))
{
    Console.WriteLine($"ERROR: Cannot find keyword file: {keywordFileName}");
    return 1;
}

STEP 3: 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 = inputFileName != null
    ? AudioConfig.FromWavFileInput(inputFileName)
    : AudioConfig.FromDefaultMicrophoneInput();

STEP 4: Create the speech recognizer and subscribe to events:

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);
    recognizer.Canceled += (s, e) => HandleCanceledEvent(e, sessionStoppedNoError);

    Task.Run(() =>
    {
        while (Console.ReadKey().Key != ConsoleKey.Enter) { }
        recognizer.StopContinuousRecognitionAsync();
    });

    var keywordModel = KeywordRecognitionModel.FromFile(keywordFileName);

    await recognizer.StartKeywordRecognitionAsync(keywordModel);
    Console.WriteLine("Listening for keyword; press ENTER to stop ...\n");

    return await sessionStoppedNoError.Task ? 0 : 1;
}

STEP 5: Define the event handlers:

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

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

private static void HandleSessionStoppedEvent(SessionEventArgs e)
{
    Console.WriteLine($"SESSION STOPPED: {e.SessionId}.");
}

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);
}