Updated: November 2007

The Windows Desktop Speech Technology software offers a basic speech recognition infrastructure that digitizes acoustical signals, and recovers words and speech elements from audio input.

Applications use System.Speech.Recognition namespace to access and extend this basic speech recognition technology, by defining algorithms for identifying and acting on specific phrases or word patterns, and by managing the run time behavior of this speech infrastructure.

Applications manage and obtain use grammars -- sets of rules defining how specific combinations of words and phrases are to be understood --through the general purpose Grammar class, which hosts runtime, persisted, or dynamically constructed instances of SrgsDocument. SrgsDocument instances contain W3C Speech Recognition Grammar Specification (SRGS) compliant grammar documents.

A simplified means of specifying grammar documents is provided through the GrammarBuilder and Choices classes. Full support for generating SRGS compliant grammars is provided by the members of the System.Speech.Recognition.SrgsGrammar name space.

In addition, a special case grammar to support a conventional dictation model is available through DictationGrammar objects.

Instances of SpeechRecognizer and SpeechRecognitionEngine objects supplied with appropriate Grammar objects provide the primary access to the Windows Desktop Speech Technology recognition engines.

The SpeechRecognizer class is used to create client applications making use of a system's current recognition technology, which is configured through the Audio Input member of the Control Panel, and a computer's default audio input mechanism.

Building an application using SpeechRecognitionEngine allows for more control on the configuration and type of recognition engine, which runs in process. Using SpeechRecognitionEngine also provides for the dynamic selection of audio input, whether from devices or files.

 Classes

	Class	Description
	AudioLevelUpdatedEventArgs	Returns data from the AudioLevelUpdated event.
	AudioSignalProblemOccurredEventArgs	Returns data from the AudioSignalProblemOccurred event.
	AudioStateChangedEventArgs	Returns data from the AudioStateChanged event.
	Choices	Represents a list of alternative items to make up an element in a grammar.
	DictationGrammar	Represents a grammar used for free text dictation.
	EmulateRecognizeCompletedEventArgs	Returns data from the EmulateRecognizeCompleted event.
	Grammar	Provides run time support for obtaining and managing Speech grammar information.
	GrammarBuilder	Provides an easy-to-use mechanism for constructing complicated Grammar objects from simple inputs.
	LoadGrammarCompletedEventArgs	Returns data from the LoadGrammarCompleted event.
	RecognitionEventArgs	Base class for event arguments objects passed to handlers of the speech recognition events.
	RecognitionResult	Represents the result of recognition engine on audio input as detailed information about the best candidate phrases matching phrase, and a list of all candidate matching phrases.
	RecognizeCompletedEventArgs	Returns data from the RecognizeCompleted event.
	RecognizedAudio	Represents audio input a recognition engine used to generate candidate phrases result.
	RecognizedPhrase	Represents detailed information about a candidate phrase found by a recognition engine as matching audio input.
	RecognizedWordUnit	Provides the atomic unit of recognized speech.
	RecognizerInfo	Represents information about a SpeechRecognizer or SpeechRecognitionEngine.
	RecognizerUpdateReachedEventArgs	Returns data from the RecognizerUpdateReached event.
	ReplacementText	Contains originally recognized text replace using speech normalization by a recognition engine.
	SemanticResultKey	Attaches key string to SemanticResultValue values to define the SemanticValue objects created in Grammar using GrammarBuilder instances
	SemanticResultValue	Sets values to SemanticValue objects created in Grammar using GrammarBuilder instances.
	SemanticValue	Represents the semantic organization of a recognized phrase.
	SpeechDetectedEventArgs	Returns data from the SpeechDetected event.
	SpeechHypothesizedEventArgs	Infrastructure. Returns notification from the SpeechHypothesized event.
	SpeechRecognitionEngine	Provides access to run any properly installed speech recognition services found on a Windows Desktop system.
	SpeechRecognitionRejectedEventArgs	Returns notification from the SpeechRecognitionRejected event.
	SpeechRecognizedEventArgs	Returns notification from the SpeechRecognized event.
	SpeechRecognizer	Provides access to the default shared speech recognition service available on the Windows Desktop.
	SpeechUI	Provides text and status information to the operating system in speech user interface to display to the user.
	StateChangedEventArgs	Returns data from the StateChanged event.

 Enumerations

	Enumeration	Description
	AudioSignalProblem	Enumerates the types of audio signal problems.
	AudioState	Enumerates values of the recognizer's audio state.
	DisplayAttributes	Enumerates formats for the display of words in a recognized phrase.
	RecognizeMode	Enumerates values of the recognition mode.
	RecognizerState	Enumerates values of the recognizer's state.
	SubsetMatchingMode	Enumerates values of subset matching mode.