NullifyNetwork

I was trying to get speech recognition to work as easily as text-to-speech synthesis and noticed that there's a gotcha in that you can't use it from an MTA STA thread, so you need to invoke it on another thread.  Calling BeginInvoke on an anonymous delegate instance of voidDelegate sorts this pretty easily and is a nice and brief method of avoiding the problem.

Here's the necessary code to make a blank form with two text boxes (called TextBox1 and TextBox2) do speech recognition continually.  To use this code you need a reference to System.Speech.DLL and a using clause pointing to System.Speech.Recognition.

Note that hypothesized text is also displayed, so you can see the speech recognition engine 'thinking' which is handy as it lets you tell if you need to do more training with the engine.

private void Form1_Load(object sender, EventArgs e)

{

       InitSpeechRecognition();

}

 

SpeechRecognitionEngine _recognitionEngine;

 

public void InitSpeechRecognition()

{

       voidDelegate d = new voidDelegate(initSpeechRecognition);

       d.BeginInvoke(null, null);

}

 

private delegate void voidDelegate();

 

private void initSpeechRecognition()

{

       _recognitionEngine = new System.Speech.Recognition.SpeechRecognitionEngine();

       _recognitionEngine.SetInputToDefaultAudioDevice();

       DictationGrammar d = new DictationGrammar();

       d.SpeechRecognized += new EventHandler<SpeechRecognizedEventArgs>(d_SpeechRecognized);

       _recognitionEngine.UnloadAllGrammars();

       _recognitionEngine.SpeechHypothesized += new EventHandler<SpeechHypothesizedEventArgs>(r_SpeechHypothesized);

       _recognitionEngine.RecognizeCompleted += new EventHandler<RecognizeCompletedEventArgs>(r_RecognizeCompleted);

       _recognitionEngine.LoadGrammar(d);

       _recognitionEngine.RecognizeAsync();

}

 

void r_RecognizeCompleted(object sender, RecognizeCompletedEventArgs e)

{

       BeginRecognition();

}

 

delegate void SpeechHypothesizedPassThroughDelegate(object sender, SpeechHypothesizedEventArgs e);

 

void r_SpeechHypothesized(object sender, SpeechHypothesizedEventArgs e)

{

       if (this.InvokeRequired)

       {

              this.Invoke(new SpeechHypothesizedPassThroughDelegate(r_SpeechHypothesized), sender, e);

       }

       else

       {

              textBox2.Text = e.Result.Text;

       }

}

 

delegate void SpeechPassThroughDelegate(object sender, SpeechRecognizedEventArgs e);

 

void d_SpeechRecognized(object sender, SpeechRecognizedEventArgs e)

{

       if (this.InvokeRequired)

       {

              this.Invoke(new SpeechPassThroughDelegate(d_SpeechRecognized), sender, e);

       }

       else

       {

              //display the recognised text, or process it here

              textBox1.Text += e.Result.Text + " ";

       }

}

 

private void BeginRecognition()

{

       new voidDelegate(delegate()

       {

              _recognitionEngine.RecognizeAsync();

       }).BeginInvoke(null, null);

}

 

private void StopRecognition()

{

       new voidDelegate(delegate()

       {

              _recognitionEngine.RecognizeAsyncStop();

       }).BeginInvoke(null, null);

}

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