SpeechRecognitionEngine Class

Provides access to speech recognition services.

Namespace: Microsoft.Speech.Recognition
Assembly: Microsoft.Speech (in microsoft.speech.dll)

Syntax

'Declaration
Public Class SpeechRecognitionEngine
    Implements IDisposable

public class SpeechRecognitionEngine : IDisposable

public ref class SpeechRecognitionEngine : IDisposable

public class SpeechRecognitionEngine implements IDisposable

public class SpeechRecognitionEngine implements IDisposable

Remarks

Applications using SpeechRecognitionEngine select any of the recognition engines available on a given system, as well as choose a particular form of audio input -- including the standard audio input, streams, and files.

Therefore, SpeechRecognitionEngine based applications can be constructed as clients of a particular recognition engine, as standalone speech recognition applications using inprocess recognition engines, and as servers, providing access to a recognition engine to clients.

Applications using SpeechRecognitionEngine effectively do so by selecting the correct recognizer and culture when constructing an instance, connecting to the appropriate audio input, creating event handlers to receive audio recognition results, controlling the grammars used in recognition, and by starting and stopping recognition engines.

To support this, SpeechRecognitionEngine provides programmatic control over:

• Selection of audio inputs, recognition engines, language and culture (see SpeechRecognitionEngine, InstalledRecognizers, and SetInputToWaveFile, SetInputToAudioStream, SetInputToNull, SetInputToWaveStream, and SetInputToDefaultAudioDevice)

• The handling of both synchronous and asynchronous recognition operations (see Recognize, RecognizeAsync,.RecognizeAsyncStop, RecognizeAsyncCancel, and RecognizeCompleted).

• The grammars are used by the application (see LoadGrammar, UnloadGrammar, UnloadAllGrammars, and Grammars for more information).

• Define parameters for speech recognition operations (see RejectionThreshold, BabbleTimeout, InitialSilenceTimeout, EndSilenceTimeout, EndSilenceTimeoutAmbiguous, RejectionThreshold)

• How recognition engine events, such as recognition or rejection of a phrase, are handled (see SpeechDetected, SpeechHypothesized, SpeechRecognitionRejected, SpeechRecognized, and LoadGrammarCompleted for more information.

  These recognition events are the means used by instances of SpeechRecognitionEngine to return recognition results to applications.

• Control and monitor the recognition engine state (see QueryRecognitionEngineSetting, MaxAlternates, RecognzierInfo, RecognitionEngineUpdateReached, AudioStateChanged, AudioSignalProblemOccurred, and AudioLevelUpdated)

• Synchronizing and scheduling of configuration changes requested by a client application using members of used by an instance of SpeechRecognitionEngine.

  This is necessary because the engine can be shared between multiple applications and process and running a different processes. (See PauseRecognitionEngineOnRecognition, and RequestRecognitionEngineUpdate for more information.)

• Test an application’s use of the engine through emulation (see EmulateRecognize, EmulateRecognizeAsync, and EmulateRecognizeCompleted).

SpeechRecognitionEngine implements IDispose.

Inheritance Hierarchy

System.Object
  Microsoft.Speech.Recognition.SpeechRecognitionEngine

Example

The example below queries the system to find a recognition engine with the identification string and CultureID. Note, before this instance of SpeechRecognitionEngine can be used, it must have its input set, using SetInputToNull, SetInputToWaveStream, or SetInputToDefaultAudioDevice).

private SpeechRecognitionEngine SelectRecognitionEngine(CultureInfo requiredCulture, string requiredId) {
  // Select based on a specific recognitionEngine configuration:
  SpeechRecognitionEngine speechRecognitionEngine=null;
  foreach (RecognzierInfo config in SpeechRecognitionEngine.InstalledRecognizers()) {
    if (config.Culture.Equals(requiredCulture) && config.Id== requiredId) {
      speechRecognitionEngine = new SpeechRecognitionEngine(config);
      break;
    }
    
  }
  return speechRecognitionEngine;
}

Thread Safety

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

Platforms

Development Platforms

Windows XP Professional with Service Pack 2 (SP2), Windows Server 2003, Windows Vista Ultimate Edition, Windows Vista Business Edition, Windows Vista Enterprise Edition

Target Platforms

See Also

Reference

SpeechRecognitionEngine Members
Microsoft.Speech.Recognition Namespace