Freeswitch currently supports several TTS options.
- mod_unimrcp - TTS using MRCP protocol
- mod_cepstral - Commercial high-quality [Cepstral] voices & Text to Speech engine.
- mod_flite - An FOSS option, Flite / Festival Lite.
- The complete list of TTS modules is available on the modules list page.
Via mod_shout using online TTS
Using mod_shout allows you to stream audio from an URL, this allows you to utilize high quality online TTS services by writing out custom GET requests. Obviously since an Internet transfer occurs on each TTS transaction this approach might not me desired on a production environment.
Register for an API Key (appid): http://www.bing.com/developers/appids.aspx and replace the 'YOUR-KEY-HERE' in the GET url below. For more information see http://msdn.microsoft.com/en-us/library/ff512420.aspx.
You probably need to agree with Google API TOS, located at..? Please note google will fail to convert if the input text is to long so test url in browser first; Bing appears to be more lenient in this regard.