SpeechRecognitionEngine.RecognizeAsync Method

Definition

Namespace:

System.Speech.Recognition

Assembly:

System.Speech.dll

Package:

System.Speech v9.0.0

Starts an asynchronous speech recognition operation.

Overloads

RecognizeAsync()	Performs a single, asynchronous speech recognition operation.
RecognizeAsync(RecognizeMode)	Performs one or more asynchronous speech recognition operations.

Remarks

These methods perform single or multiple, asynchronous recognition operations. The recognizer performs each operation against its loaded and enabled speech recognition grammars.

During a call to this method, the recognizer can raise the following events:

• SpeechDetected. Raised when the recognizer detects input that it can identify as speech.

• SpeechHypothesized. Raised when input creates an ambiguous match with one of the active grammars.

• SpeechRecognitionRejected or SpeechRecognized. Raised when the recognizer finalizes a recognition operation.

• RecognizeCompleted. Raised when a RecognizeAsync operation finishes.

To retrieve the result of an asynchronous recognition operation, attach an event handler to the recognizer's SpeechRecognized event. The recognizer raises this event whenever it successfully completes a synchronous or asynchronous recognition operation. If recognition was not successful, the Result property on RecognizeCompletedEventArgs object, which you can access in the handler for the RecognizeCompleted event, will be null.

An asynchronous recognition operation can fail for the following reasons:

• Speech is not detected before the timeout intervals expire for the BabbleTimeout or InitialSilenceTimeout properties.

• The recognition engine detects speech but finds no matches in any of its loaded and enabled Grammar objects.

• The SpeechRecognitionEngine must have at least one Grammar object loaded before performing recognition. To load a speech recognition grammar, use the LoadGrammar or LoadGrammarAsync method.

• To modify how the recognizer handles the timing of speech or silence with respect to recognition, use the BabbleTimeout, InitialSilenceTimeout, EndSilenceTimeout, and EndSilenceTimeoutAmbiguous properties.

• To perform synchronous recognition, use one of the Recognize methods.

RecognizeAsync()

Source:

SpeechRecognitionEngine.cs

Performs a single, asynchronous speech recognition operation.

public:
 void RecognizeAsync();

public void RecognizeAsync ();

member this.RecognizeAsync : unit -> unit

Public Sub RecognizeAsync ()

Examples

The following example shows part of a console application that demonstrates basic asynchronous speech recognition. The example creates a DictationGrammar, loads it into an in-process speech recognizer, and performs one asynchronous recognition operation. Event handlers are included to demonstrate the events that the recognizer raises during the operation.

using System;  
using System.Globalization;  
using System.Speech.Recognition;  
using System.Threading;  

namespace AsynchronousRecognition  
{  
  class Program  
  {  
    // Indicate whether asynchronous recognition is complete.  
    static bool completed;  

    static void Main(string[] args)  
    {  
      // Create an in-process speech recognizer.  
      using (SpeechRecognitionEngine recognizer =  
        new SpeechRecognitionEngine(new CultureInfo("en-US")))  
      {  
        // Create a grammar for choosing cities for a flight.  
        Choices cities = new Choices(new string[]   
        { "Los Angeles", "New York", "Chicago", "San Francisco", "Miami", "Dallas" });  

        GrammarBuilder gb = new GrammarBuilder();  
        gb.Append("I want to fly from");  
        gb.Append(cities);  
        gb.Append("to");  
        gb.Append(cities);  

        // Construct a Grammar object and load it to the recognizer.  
        Grammar cityChooser = new Grammar(gb);  
        cityChooser.Name = ("City Chooser");  
        recognizer.LoadGrammarAsync(cityChooser);  

        // Attach event handlers.  
        recognizer.SpeechDetected +=  
          new EventHandler<SpeechDetectedEventArgs>(  
            SpeechDetectedHandler);  
        recognizer.SpeechHypothesized +=  
          new EventHandler<SpeechHypothesizedEventArgs>(  
            SpeechHypothesizedHandler);  
        recognizer.SpeechRecognitionRejected +=  
          new EventHandler<SpeechRecognitionRejectedEventArgs>(  
            SpeechRecognitionRejectedHandler);  
        recognizer.SpeechRecognized +=  
          new EventHandler<SpeechRecognizedEventArgs>(  
            SpeechRecognizedHandler);  
        recognizer.RecognizeCompleted +=  
          new EventHandler<RecognizeCompletedEventArgs>(  
            RecognizeCompletedHandler);  

        // Assign input to the recognizer and start an asynchronous  
        // recognition operation.  
        recognizer.SetInputToDefaultAudioDevice();  

        completed = false;  
        Console.WriteLine("Starting asynchronous recognition...");  
        recognizer.RecognizeAsync();  

        // Wait for the operation to complete.  
        while (!completed)  
        {  
          Thread.Sleep(333);  
        }  
        Console.WriteLine("Done.");  
      }  

      Console.WriteLine();  
      Console.WriteLine("Press any key to exit...");  
      Console.ReadKey();  
    }  

    // Handle the SpeechDetected event.  
    static void SpeechDetectedHandler(object sender, SpeechDetectedEventArgs e)  
    {  
      Console.WriteLine(" In SpeechDetectedHandler:");  
      Console.WriteLine(" - AudioPosition = {0}", e.AudioPosition);  
    }  

    // Handle the SpeechHypothesized event.  
    static void SpeechHypothesizedHandler(  
      object sender, SpeechHypothesizedEventArgs e)  
    {  
      Console.WriteLine(" In SpeechHypothesizedHandler:");  

      string grammarName = "<not available>";  
      string resultText = "<not available>";  
      if (e.Result != null)  
      {  
        if (e.Result.Grammar != null)  
        {  
          grammarName = e.Result.Grammar.Name;  
        }  
        resultText = e.Result.Text;  
      }  

      Console.WriteLine(" - Grammar Name = {0}; Result Text = {1}",  
        grammarName, resultText);  
    }  

    // Handle the SpeechRecognitionRejected event.  
    static void SpeechRecognitionRejectedHandler(  
      object sender, SpeechRecognitionRejectedEventArgs e)  
    {  
      Console.WriteLine(" In SpeechRecognitionRejectedHandler:");  

      string grammarName = "<not available>";  
      string resultText = "<not available>";  
      if (e.Result != null)  
      {  
        if (e.Result.Grammar != null)  
        {  
          grammarName = e.Result.Grammar.Name;  
        }  
        resultText = e.Result.Text;  
      }  

      Console.WriteLine(" - Grammar Name = {0}; Result Text = {1}",  
        grammarName, resultText);  
    }  

    // Handle the SpeechRecognized event.  
    static void SpeechRecognizedHandler(  
      object sender, SpeechRecognizedEventArgs e)  
    {  
      Console.WriteLine(" In SpeechRecognizedHandler.");  

      string grammarName = "<not available>";  
      string resultText = "<not available>";  
      if (e.Result != null)  
      {  
        if (e.Result.Grammar != null)  
        {  
          grammarName = e.Result.Grammar.Name;  
        }  
        resultText = e.Result.Text;  
      }  

      Console.WriteLine(" - Grammar Name = {0}; Result Text = {1}",  
        grammarName, resultText);  
    }  

    // Handle the RecognizeCompleted event.  
    static void RecognizeCompletedHandler(  
      object sender, RecognizeCompletedEventArgs e)  
    {  
      Console.WriteLine(" In RecognizeCompletedHandler.");  

      if (e.Error != null)  
      {  
        Console.WriteLine(  
          " - Error occurred during recognition: {0}", e.Error);  
        return;  
      }  
      if (e.InitialSilenceTimeout || e.BabbleTimeout)  
      {  
        Console.WriteLine(  
          " - BabbleTimeout = {0}; InitialSilenceTimeout = {1}",  
          e.BabbleTimeout, e.InitialSilenceTimeout);  
        return;  
      }  
      if (e.InputStreamEnded)  
      {  
        Console.WriteLine(  
          " - AudioPosition = {0}; InputStreamEnded = {1}",  
          e.AudioPosition, e.InputStreamEnded);  
      }  
      if (e.Result != null)  
      {  
        Console.WriteLine(  
          " - Grammar = {0}; Text = {1}; Confidence = {2}",  
          e.Result.Grammar.Name, e.Result.Text, e.Result.Confidence);  
        Console.WriteLine(" - AudioPosition = {0}", e.AudioPosition);  
      }  
      else  
      {  
        Console.WriteLine(" - No result.");  
      }  

      completed = true;  
    }  
  }  
}

Remarks

This method performs a single, asynchronous recognition operation. The recognizer performs the operation against its loaded and enabled speech recognition grammars.

During a call to this method, the recognizer can raise the following events:

• SpeechDetected. Raised when the recognizer detects input that it can identify as speech.

• SpeechHypothesized. Raised when input creates an ambiguous match with one of the active grammars.

• SpeechRecognitionRejected or SpeechRecognized. Raised when the recognizer finalizes a recognition operation.

• RecognizeCompleted. Raised when a RecognizeAsync operation finishes.

To retrieve the result of an asynchronous recognition operation, attach an event handler to the recognizer's SpeechRecognized event. The recognizer raises this event whenever it successfully completes a synchronous or asynchronous recognition operation. If recognition was not successful, the Result property on RecognizeCompletedEventArgs object, which you can access in the handler for the RecognizeCompleted event, will be null.

To perform synchronous recognition, use one of the Recognize methods.

This method stores in the task it returns all non-usage exceptions that the method's synchronous counterpart can throw. If an exception is stored into the returned task, that exception will be thrown when the task is awaited. Usage exceptions, such as ArgumentException, are still thrown synchronously. For the stored exceptions, see the exceptions thrown by Recognize().

See also

• BabbleTimeout
• InitialSilenceTimeout
• EndSilenceTimeout
• EndSilenceTimeoutAmbiguous
• SpeechDetected
• SpeechHypothesized
• SpeechRecognitionRejected
• SpeechRecognized
• RecognizeCompleted
• Recognize()
• EmulateRecognizeAsync(String)

RecognizeAsync(RecognizeMode)

Source:

SpeechRecognitionEngine.cs

Performs one or more asynchronous speech recognition operations.

public:
 void RecognizeAsync(System::Speech::Recognition::RecognizeMode mode);

public void RecognizeAsync (System.Speech.Recognition.RecognizeMode mode);

member this.RecognizeAsync : System.Speech.Recognition.RecognizeMode -> unit

Public Sub RecognizeAsync (mode As RecognizeMode)

Parameters

mode

RecognizeMode

Indicates whether to perform one or multiple recognition operations.

Examples

The following example shows part of a console application that demonstrates basic asynchronous speech recognition. The example creates a DictationGrammar, loads it into an in-process speech recognizer, and performs multiple asynchronous recognition operations. The asynchronous operations are cancelled after 30 seconds. Event handlers are included to demonstrate the events that the recognizer raises during the operation.

using System;  
using System.Globalization;  
using System.Speech.Recognition;  
using System.Threading;  

namespace AsynchronousRecognition  
{  
  class Program  
  {  
    // Indicate whether asynchronous recognition is complete.  
    static bool completed;  

    static void Main(string[] args)  
    {  
      // Create an in-process speech recognizer.  
      using (SpeechRecognitionEngine recognizer =  
        new SpeechRecognitionEngine(new CultureInfo("en-US")))  
      {  
        // Create a grammar for choosing cities for a flight.  
        Choices cities = new Choices(new string[] { "Los Angeles", "New York", "Chicago", "San Francisco", "Miami", "Dallas" });  

        GrammarBuilder gb = new GrammarBuilder();  
        gb.Append("I want to fly from");  
        gb.Append(cities);  
        gb.Append("to");  
        gb.Append(cities);  

        // Construct a Grammar object and load it to the recognizer.  
        Grammar cityChooser = new Grammar(gb);  
        cityChooser.Name = ("City Chooser");  
        recognizer.LoadGrammarAsync(cityChooser);  

        // Attach event handlers.  
        recognizer.SpeechDetected +=  
          new EventHandler<SpeechDetectedEventArgs>(  
            SpeechDetectedHandler);  
        recognizer.SpeechHypothesized +=  
          new EventHandler<SpeechHypothesizedEventArgs>(  
            SpeechHypothesizedHandler);  
        recognizer.SpeechRecognitionRejected +=  
          new EventHandler<SpeechRecognitionRejectedEventArgs>(  
            SpeechRecognitionRejectedHandler);  
        recognizer.SpeechRecognized +=  
          new EventHandler<SpeechRecognizedEventArgs>(  
            SpeechRecognizedHandler);  
        recognizer.RecognizeCompleted +=  
          new EventHandler<RecognizeCompletedEventArgs>(  
            RecognizeCompletedHandler);  

        // Assign input to the recognizer and start asynchronous  
        // recognition.  
        recognizer.SetInputToDefaultAudioDevice();  

        completed = false;  
        Console.WriteLine("Starting asynchronous recognition...");  
        recognizer.RecognizeAsync(RecognizeMode.Multiple);  

        // Wait 30 seconds, and then cancel asynchronous recognition.  
        Thread.Sleep(TimeSpan.FromSeconds(30));  
        recognizer.RecognizeAsyncCancel();  

        // Wait for the operation to complete.  
        while (!completed)  
        {  
          Thread.Sleep(333);  
        }  
        Console.WriteLine("Done.");  
      }  

      Console.WriteLine();  
      Console.WriteLine("Press any key to exit...");  
      Console.ReadKey();  
    }  

    // Handle the SpeechDetected event.  
    static void SpeechDetectedHandler(object sender, SpeechDetectedEventArgs e)  
    {  
      Console.WriteLine(" In SpeechDetectedHandler:");  
      Console.WriteLine(" - AudioPosition = {0}", e.AudioPosition);  
    }  

    // Handle the SpeechHypothesized event.  
    static void SpeechHypothesizedHandler(  
      object sender, SpeechHypothesizedEventArgs e)  
    {  
      Console.WriteLine(" In SpeechHypothesizedHandler:");  

      string grammarName = "<not available>";  
      string resultText = "<not available>";  
      if (e.Result != null)  
      {  
        if (e.Result.Grammar != null)  
        {  
          grammarName = e.Result.Grammar.Name;  
        }  
        resultText = e.Result.Text;  
      }  

      Console.WriteLine(" - Grammar Name = {0}; Result Text = {1}",  
        grammarName, resultText);  
    }  

    // Handle the SpeechRecognitionRejected event.  
    static void SpeechRecognitionRejectedHandler(  
      object sender, SpeechRecognitionRejectedEventArgs e)  
    {  
      Console.WriteLine(" In SpeechRecognitionRejectedHandler:");  

      string grammarName = "<not available>";  
      string resultText = "<not available>";  
      if (e.Result != null)  
      {  
        if (e.Result.Grammar != null)  
        {  
          grammarName = e.Result.Grammar.Name;  
        }  
        resultText = e.Result.Text;  
      }  

      Console.WriteLine(" - Grammar Name = {0}; Result Text = {1}",  
        grammarName, resultText);  
    }  

    // Handle the SpeechRecognized event.  
    static void SpeechRecognizedHandler(  
      object sender, SpeechRecognizedEventArgs e)  
    {  
      Console.WriteLine(" In SpeechRecognizedHandler.");  

      string grammarName = "<not available>";  
      string resultText = "<not available>";  
      if (e.Result != null)  
      {  
        if (e.Result.Grammar != null)  
        {  
          grammarName = e.Result.Grammar.Name;  
        }  
        resultText = e.Result.Text;  
      }  

      Console.WriteLine(" - Grammar Name = {0}; Result Text = {1}",  
        grammarName, resultText);  
    }  

    // Handle the RecognizeCompleted event.  
    static void RecognizeCompletedHandler(  
      object sender, RecognizeCompletedEventArgs e)  
    {  
      Console.WriteLine(" In RecognizeCompletedHandler.");  

      if (e.Error != null)  
      {  
        Console.WriteLine(  
          " - Error occurred during recognition: {0}", e.Error);  
        return;  
      }  
      if (e.InitialSilenceTimeout || e.BabbleTimeout)  
      {  
        Console.WriteLine(  
          " - BabbleTimeout = {0}; InitialSilenceTimeout = {1}",  
          e.BabbleTimeout, e.InitialSilenceTimeout);  
        return;  
      }  
      if (e.InputStreamEnded)  
      {  
        Console.WriteLine(  
          " - AudioPosition = {0}; InputStreamEnded = {1}",  
          e.AudioPosition, e.InputStreamEnded);  
      }  
      if (e.Result != null)  
      {  
        Console.WriteLine(  
          " - Grammar = {0}; Text = {1}; Confidence = {2}",  
          e.Result.Grammar.Name, e.Result.Text, e.Result.Confidence);  
        Console.WriteLine(" - AudioPosition = {0}", e.AudioPosition);  
      }  
      else  
      {  
        Console.WriteLine(" - No result.");  
      }  

      completed = true;  
    }  
  }  
}  

Remarks

If mode is Multiple, the recognizer continues performing asynchronous recognition operations until the RecognizeAsyncCancel or RecognizeAsyncStop method is called.

During a call to this method, the recognizer can raise the following events:

• SpeechDetected. Raised when the recognizer detects input that it can identify as speech.

• SpeechHypothesized. Raised when input creates an ambiguous match with one of the active grammars.

• SpeechRecognitionRejected or SpeechRecognized. Raised when the recognizer finalizes a recognition operation.

• RecognizeCompleted. Raised when a RecognizeAsync operation finishes.

To retrieve the result of an asynchronous recognition operation, attach an event handler to the recognizer's SpeechRecognized event. The recognizer raises this event whenever it successfully completes a synchronous or asynchronous recognition operation. If recognition was not successful, the Result property on RecognizeCompletedEventArgs object, which you can access in the handler for the RecognizeCompleted event, will be null.

An asynchronous recognition operation can fail for the following reasons:

• Speech is not detected before the timeout intervals expire for the BabbleTimeout or InitialSilenceTimeout properties.

• The recognition engine detects speech but finds no matches in any of its loaded and enabled Grammar objects.

To perform synchronous recognition, use one of the Recognize methods.

See also

• BabbleTimeout
• InitialSilenceTimeout
• EndSilenceTimeout
• EndSilenceTimeoutAmbiguous
• SpeechDetected
• SpeechHypothesized
• SpeechRecognitionRejected
• SpeechRecognized
• RecognizeCompleted
• Recognize()
• EmulateRecognizeAsync(String)