SpeechSynthesizer Interface

At startup time, the SpeechSynthesizer component in the Engine opens an audio output channel of type TTS for the application to play Alexa speech responses to the user. SpeechSynthesizer has no messages of its own for the application to handle because it uses the standard audio output framework specified in the Core module. When Alexa responds to a user request with speech, the Engine publishes an AudioOutput.Prepare message with audioType TTS. The application uses the payload of the message to open the audio stream and buffer the audio data. The application plays the audio to the user when the Engine publishes an AudioOutput.Play message with matching token.