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SpeechRecognitionEngine Class

Provides the means to access and manage an in-process speech recognition engine.

System.Object
  System.Speech.Recognition.SpeechRecognitionEngine

Namespace:  System.Speech.Recognition
Assembly:  System.Speech (in System.Speech.dll)

public class SpeechRecognitionEngine : IDisposable

The SpeechRecognitionEngine type exposes the following members.

  NameDescription
Public methodSpeechRecognitionEngine()Initializes a new instance of the SpeechRecognitionEngine class using the default speech recognizer for the system.
Public methodSpeechRecognitionEngine(CultureInfo)Initializes a new instance of the SpeechRecognitionEngine class using the default speech recognizer for a specified locale.
Public methodSpeechRecognitionEngine(RecognizerInfo)Initializes a new instance of the SpeechRecognitionEngine using the information in a RecognizerInfo object to specify the recognizer to use.
Public methodSpeechRecognitionEngine(String)Initializes a new instance of the SpeechRecognitionEngine class with a string parameter that specifies the name of the recognizer to use.
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  NameDescription
Public propertyAudioFormatGets the format of the audio being received by the SpeechRecognitionEngine.
Public propertyAudioLevelGets the level of the audio being received by the SpeechRecognitionEngine.
Public propertyAudioPositionGets the current location in the audio stream being generated by the device that is providing input to the SpeechRecognitionEngine.
Public propertyAudioStateGets the state of the audio being received by the SpeechRecognitionEngine.
Public propertyBabbleTimeoutGets or sets the time interval during which a SpeechRecognitionEngine accepts input containing only background noise, before finalizing recognition.
Public propertyEndSilenceTimeoutGets or sets the interval of silence that the SpeechRecognitionEngine will accept at the end of unambiguous input before finalizing a recognition operation.
Public propertyEndSilenceTimeoutAmbiguousGets or sets the interval of silence that the SpeechRecognitionEngine will accept at the end of ambiguous input before finalizing a recognition operation.
Public propertyGrammarsGets a collection of the Grammar objects that are loaded in this SpeechRecognitionEngine instance.
Public propertyInitialSilenceTimeoutGets or sets the time interval during which a SpeechRecognitionEngine accepts input containing only silence before finalizing recognition.
Public propertyMaxAlternatesGets or sets the maximum number of alternate recognition results that the SpeechRecognitionEngine returns for each recognition operation.
Public propertyRecognizerAudioPositionGets the current location of the SpeechRecognitionEngine in the audio input that it is processing.
Public propertyRecognizerInfoGets information about the current instance of SpeechRecognitionEngine.
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  NameDescription
Public methodDispose()Disposes the SpeechRecognitionEngine object.
Protected methodDispose(Boolean)Disposes the SpeechRecognitionEngine object and releases resources used during the session.
Public methodEmulateRecognize(String)Emulates input of a phrase to the speech recognizer, using text in place of audio for synchronous speech recognition.
Public methodEmulateRecognize(RecognizedWordUnit[], CompareOptions)Emulates input of specific words to the speech recognizer, using text in place of audio for synchronous speech recognition, and specifies how the recognizer handles Unicode comparison between the words and the loaded speech recognition grammars.
Public methodEmulateRecognize(String, CompareOptions)Emulates input of a phrase to the speech recognizer, using text in place of audio for synchronous speech recognition, and specifies how the recognizer handles Unicode comparison between the phrase and the loaded speech recognition grammars.
Public methodEmulateRecognizeAsync(String)Emulates input of a phrase to the speech recognizer, using text in place of audio for asynchronous speech recognition.
Public methodEmulateRecognizeAsync(RecognizedWordUnit[], CompareOptions)Emulates input of specific words to the speech recognizer, using an array of RecognizedWordUnit objects in place of audio for asynchronous speech recognition, and specifies how the recognizer handles Unicode comparison between the words and the loaded speech recognition grammars.
Public methodEmulateRecognizeAsync(String, CompareOptions)Emulates input of a phrase to the speech recognizer, using text in place of audio for asynchronous speech recognition, and specifies how the recognizer handles Unicode comparison between the phrase and the loaded speech recognition grammars.
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodStatic memberInstalledRecognizersReturns information for all of the installed speech recognizers on the current system.
Public methodLoadGrammarSynchronously loads a Grammar object.
Public methodLoadGrammarAsyncAsynchronously loads a speech recognition grammar.
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodQueryRecognizerSettingReturns the values of settings for the recognizer.
Public methodRecognize()Performs a synchronous speech recognition operation.
Public methodRecognize(TimeSpan)Performs a synchronous speech recognition operation with a specified initial silence timeout period.
Public methodRecognizeAsync()Performs a single, asynchronous speech recognition operation.
Public methodRecognizeAsync(RecognizeMode)Performs one or more asynchronous speech recognition operations.
Public methodRecognizeAsyncCancelTerminates asynchronous recognition without waiting for the current recognition operation to complete.
Public methodRecognizeAsyncStopStops asynchronous recognition after the current recognition operation completes.
Public methodRequestRecognizerUpdate()Requests that the recognizer pauses to update its state.
Public methodRequestRecognizerUpdate(Object)Requests that the recognizer pauses to update its state and provides a user token for the associated event.
Public methodRequestRecognizerUpdate(Object, TimeSpan)Requests that the recognizer pauses to update its state and provides an offset and a user token for the associated event.
Public methodSetInputToAudioStreamConfigures the SpeechRecognitionEngine object to receive input from an audio stream.
Public methodSetInputToDefaultAudioDeviceConfigures the SpeechRecognitionEngine object to receive input from the default audio device.
Public methodSetInputToNullDisables the input to the speech recognizer.
Public methodSetInputToWaveFileConfigures the SpeechRecognitionEngine object to receive input from a Waveform audio format (.wav) file.
Public methodSetInputToWaveStreamConfigures the SpeechRecognitionEngine object to receive input from a stream that contains Waveform audio format (.wav) data.
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodUnloadAllGrammarsUnloads all Grammar objects from the recognizer.
Public methodUnloadGrammarUnloads a specified Grammar object from the SpeechRecognitionEngine instance.
Public methodUpdateRecognizerSetting(String, Int32)Updates the specified setting for the SpeechRecognitionEngine with the specified integer value.
Public methodUpdateRecognizerSetting(String, String)Updates the specified speech recognition engine setting with the specified string value.
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  NameDescription
Public eventAudioLevelUpdatedRaised when the SpeechRecognitionEngine reports the level of its audio input.
Public eventAudioSignalProblemOccurredRaised when the SpeechRecognitionEngine detects a problem in the audio signal.
Public eventAudioStateChangedRaised when the state changes in the audio being received by the SpeechRecognitionEngine.
Public eventEmulateRecognizeCompletedRaised when the SpeechRecognitionEngine finalizes an asynchronous recognition operation of emulated input.
Public eventLoadGrammarCompletedRaised when the SpeechRecognitionEngine finishes the asynchronous loading of a Grammar object.
Public eventRecognizeCompletedRaised when the SpeechRecognitionEngine finalizes an asynchronous recognition operation.
Public eventRecognizerUpdateReachedRaised when a running SpeechRecognitionEngine pauses to accept modifications.
Public eventSpeechDetectedRaised when the SpeechRecognitionEngine detects input that it can identify as speech.
Public eventSpeechHypothesizedRaised when the SpeechRecognitionEngine has recognized a word or words that may be a component of multiple complete phrases in a grammar.
Public eventSpeechRecognitionRejectedRaised when the SpeechRecognitionEngine receives input that does not match any of its loaded and enabled Grammar objects.
Public eventSpeechRecognizedRaised when the SpeechRecognitionEngine receives input that matches any of its loaded and enabled Grammar objects.
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You can create an instance of this class for any of the installed speech recognizers. To get information about which recognizers are installed, use the static InstalledRecognizers method.

This class is for running speech recognition engines in-process, and provides control over various aspects of speech recognition, as follows:

The SpeechRecognitionEngine object is for the sole use of the process that instantiated the object. By contrast, the SpeechRecognizer shares a single recognizer with any application that wants to use it.

NoteNote

Always call Dispose before you release your last reference to the speech recognizer. Otherwise, the resources it is using will not be freed until the garbage collector calls the recognizer object's Finalize method.

The following example shows part of a console application that demonstrates basic speech recognition. Because this example uses the Multiple mode of the RecognizeAsync method, it performs recognition until you close the console window or stop debugging.

using System;
using System.Speech.Recognition;

namespace SpeechRecognitionApp
{
  class Program
  {
    static void Main(string[] args)
    {

      // Create an in-process speech recognizer for the en-US locale.
      using (
      SpeechRecognitionEngine recognizer =
        new SpeechRecognitionEngine(
          new System.Globalization.CultureInfo("en-US")))
      {

        // Create and load a dictation grammar.
        recognizer.LoadGrammar(new DictationGrammar());

        // Add a handler for the speech recognized event.
        recognizer.SpeechRecognized += 
          new EventHandler<SpeechRecognizedEventArgs>(recognizer_SpeechRecognized);

        // Configure input to the speech recognizer.
        recognizer.SetInputToDefaultAudioDevice();

        // Start asynchronous, continuous speech recognition.
        recognizer.RecognizeAsync(RecognizeMode.Multiple);

        // Keep the console window open.
        while (true)
        {
          Console.ReadLine();
        }
      }
    }

    // Handle the SpeechRecognized event.
    static void recognizer_SpeechRecognized(object sender, SpeechRecognizedEventArgs e)
    {
      Console.WriteLine("Recognized text: " + e.Result.Text);
    }
  }
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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