C# – good Speech recognition API


I am working on a college project in which I am using speech recognition. Currently I am developing it on Windows 7 and I'm using system.speech API package which comes along with .net and I am doing it on C#.

The problem I am facing is dictation recognition is not accurate enough. Then whenever I start my application the desktop speech recognition starts automatically. This is a big nuicance to me. As already the words I speak are not clear enough and conflicting recognition are interpreted as commands and actions like application switching minimize is being carried out.

This is a critical part of my app and i kindly request you to suggest any good speech API for me other than this Microsoft blunder. It will be good even if it can understand just simple dictation grammar.

Best Solution

I think desktop recognition is starting because you are using a shared desktop recognizer. You should use an inproc recognizer for your application only. you do this by instantiating a SpeechRecognitionEngine() in your application.

Since you are using the dictation grammar and the desktop windows recognizer, I believe it can be trained by the speaker to improve its accuracy. Go through the Windows 7 recognizer training and see if the accuracy improves.

To get started with .NET speech, there is a very good article that was published a few years ago at http://msdn.microsoft.com/en-us/magazine/cc163663.aspx. It is probably the best introductory article I’ve found so far. It is a little out of date, but very helfpul. (The AppendResultKeyValue method was dropped after the beta.)

Here is a quick sample that shows one of the simplest .NET windows forms app to use a dictation grammar that I could think of. This should work on Windows Vista or Windows 7. I created a form. Dropped a button on it and made the button big. Added a reference to System.Speech and the line:

using System.Speech.Recognition;

Then I added the following event handler to button1:

private void button1_Click(object sender, EventArgs e)
    SpeechRecognitionEngine recognizer = new SpeechRecognitionEngine();
    Grammar dictationGrammar = new DictationGrammar();
        button1.Text = "Speak Now";
        RecognitionResult result = recognizer.Recognize();
        button1.Text = result.Text;
    catch (InvalidOperationException exception)
        button1.Text = String.Format("Could not recognize input from default aduio device. Is a microphone or sound card available?\r\n{0} - {1}.", exception.Source, exception.Message);

A little more information comparing the various flavors of speech engines and APIs shipped by Microsoft can be found at What is the difference between System.Speech.Recognition and Microsoft.Speech.Recognition??

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