Introduction

The LumenVox Speech Engine is a piece of core technology that will allow you to load audio and grammars (lists of words and phrases to be recognized by the Engine), and get back the decoded utterance. This task for returning decoded text from audio can be broken up into three general phases:

• Setup: Your application initializes a speech port, loads and activates grammars, and loads audio.
• Interacting with Audio: The Engine receives your audio and determines where speech begins and ends. It then decodes the audio and makes results available.
• Getting Results: Your application gets the results from the Engine. The Engine makes results available as a parse tree from a grammar or a semantic interpretation object. You can then close the speech port.

Overview of Application Design

The Engine accepts audio in one of two ways. The simplest way is in a batch (offline) mode, where you have audio files saved to disk and load them into the Engine. In this case, your application will need to follow a process like this:

1. Open a speech port.
2. Add audio from a file.
3. Add grammars.
4. Ask the Engine to decode the audio based on the loaded grammars.
5. Get results.

Most applications, however, will be more complex as they will require that a streaming (online) interface to load audio directly from a live source, such as a telephone caller. In this case, your application will have two separate threads.

The first thread will be a main processing thread, similar to the simple application process spelled out above:

1. Open the speech port.
2. Set up a streaming interface for the Engine to acquire audio.
3. Add grammars.
4. Start the streaming interface and wait for the Engine to return a decode.
5. Get results.

At the same time, you will have a streaming thread that loops:

1. Give audio data to the Engine.
2. The Engine will evaluate the audio data, looking for speech. If it detects speech, the Engine will announce it in the callback.
3. The Engine will continue to evaluate audio until it detects the end of speech.
4. At this point, the Engine will perform a decode if AutoDecode has been set; otherwise it will simply return that it is ready to decode.
5. The loop can then restart.

You will want to keep this overall design in mind as you get started learning about the Engine. This guide will walk you through the basic steps, providing example code along the way. To get started, continue on to Initializing a Speech Port.

If you are brand new to speech recognition, you may wish to browse through this core programming guide to get an idea of our API, and then immediately read our tutorial on writing SRGS grammars. Much of your application's success will depend on the quality of your grammars, so understanding how to write quality grammars is important.