Converting or Transcribing audio to text using C# and .NET System.Speech

Recently, I had a project where I needed to convert some audio to text. It took a bit more googling than I was used to in order to find the code, so I went ahead and whipped up a project that demonstrates its usage, so people can more easily find it.

This code uses the .NET System.Speech namespace and demonstrates how to transcribe audio using either a microphone or a previously created .wav file using C#.

The code can be divided into 2 main parts:

• configuring the SpeechRecognitionEngine object (and its required elements)
• handling the SpeechRecognized and SpeechHypothesized events.

Step 1: Configuring the SpeechRecognitionEngine

_speechRecognitionEngine = new SpeechRecognitionEngine();
_speechRecognitionEngine.SetInputToDefaultAudioDevice();
_dictationGrammar = new DictationGrammar();
_speechRecognitionEngine.LoadGrammar(_dictationGrammar);
_speechRecognitionEngine.RecognizeAsync(RecognizeMode.Multiple);

At this point, your object is ready to start transcribing audio from the microphone. You need to handle some events though, in order to actually get access to the results.

Step 2: Handling the SpeechRecognitionEngine Events

_speechRecognitionEngine.SpeechRecognized -= new EventHandler(SpeechRecognized);
_speechRecognitionEngine.SpeechHypothesized -= new EventHandler(SpeechHypothesizing);_speechRecognitionEngine.SpeechRecognized += new EventHandler(SpeechRecognized);
_speechRecognitionEngine.SpeechHypothesized += new EventHandler(SpeechHypothesizing);

private void SpeechHypothesizing(object sender, SpeechHypothesizedEventArgs e)
{
///real-time results from the engine
     string realTimeResults = e.Result.Text;
}

private void SpeechRecognized(object sender, SpeechRecognizedEventArgs e)
{
///final answer from the engine
     string finalAnswer = e.Result.Text;
}

That’s it. If you want to use a pre-recorded .wav file instead of a microphone, you would use _speechRecognitionEngine.SetInputToWaveFile(pathToTargetWavFile); instead of _speechRecognitionEngine.SetInputToDefaultAudioDevice();.

There are a bunch of different options in these classes and they are worth exploring in more detail. This covers the bare essentials for a prototype.