This class represents the TTS engine, which has to be inherited to make the engine.
Enumeration for the audio types.
Enumeration for the error values that can occur.
Enumeration for the results.
Enumeration for the voice types.
An action with 2 input parameters returning an error.
An action with 2 out parameters returning an error.
Called when the TTS engine informs the engine service user about whole supported language and voice type list. This callback function is implemented by the engine service user, therefore, the engine developer does NOT have to implement this callback function.