Text-to-Speech (TTS)

What Is Text-to-Speech, or TTS?

From Wikipedia, TTS (Text To Speech) is defined as follows:

"Speech synthesis (Text to speech) is the artificial production of human speech. A computer system used for this purpose is called a speech synthesizer, and can be implemented in software or hardware. A text-to-speech (TTS) system converts normal language text into speech; other systems render symbolic linguistic representations like phonetic transcriptions into speech."

Asterisk flite: Can replace Festival in Asterisk
asterisk-agi-audiotx: Asterisk AGI extension module that adds commands to allow the transfer of audio files to and from Asterisk via an AGI session
asterisk-espeak: Asterisk dialplan application providing speech synthesis using the eSpeak text-to-speech engine
Flite for asterisk 1.6 1.8 and 10
espeak for asterisk 1.6 1.8 and 10
Asterisk AGI script that uses Google's voice synthesis engine to render text to speech
Speech synthesis using Microsoft Translator API for Asterisk
Database Systems Corp. CTI technology with text to speech converter for IVR and voice broadcast applications.
Festival
asterisk-liambrola: Asterisk Dialplan application, which allows you to use Lia_Phon and Mbrola as a French speech synthesizer. Step by step instuctions on liambrola's installation under Asterisk (1.2, 1.4 and 1.6) can be found in this post: Speech synthesis in French under Asterisk.

Acapela Voices - including Arabic, Czech, Danish, Dutch (NL), Dutch (B), English (UK), English (US), Faroe, French, Finnish, German, Greek, Icelandic, Italian, Norwegian, Polish, Portuguese, Portuguese (Brazil), Russian, Spanish, Spanish (South America), Swedish and Turkish
TextSpeak Text to Speech - Human sounding TTS in over 20 world languages packaged in hardware modules and standalone enclosures
AT&T Labs voices - including German, French, Latin Am. Spanish
cepstral Medium quality, low-cost voices
ELAN SaySo - including German, French, Spanish and Italian voices/phonems
Loquendo TTS for Asterisk
Mbrola - a Freely Available Multilingual Speech Synthesizer for many languages
Nuance Realspeak - supports 24 languages and dialects and more than 30 voices
Sakrament TTS Engine - including Russian, with English coming soon

Verbose Text - can use any SAPI4 or SAPI5 voice
Verbio TTS - including Spanish, Portuguese, English, French, Catalonian, Euskera, Gallician, Brazilian and differents kinds of American Spanish for Asterisk