flite | A small fast portable speech synthesis system

flite is a C library. flite has no bugs, it has no vulnerabilities and it has low support. However flite has a Non-SPDX License. You can download it from GitHub.

Flite is an open source small fast run-time text to speech engine. It is the latest addition to the suite of free software synthesis tools including University of Edinburgh's Festival Speech Synthesis System and Carnegie Mellon University's FestVox project, tools, scripts and documentation for building synthetic voices. However, flite itself does not require either of these systems to compile and run. The core Flite library was developed by Alan W Black awb@cs.cmu.edu (mostly in his so-called spare time) while employed in the Language Technologies Institute at Carnegie Mellon University. The name "flite", originally chosen to mean "festival-lite" is perhaps doubly appropriate as a substantial part of design and coding was done over 30,000ft while awb was travelling, and (usually) isn't in meetings. The voices, lexicon and language components of flite, both their compression techniques and their actual contents were developed by Kevin A. Lenzo lenzo@cs.cmu.edu and Alan W Black awb@cs.cmu.edu. Flite is the answer to the complaint that Festival is too big, too slow, and not portable enough. o Flite is designed for very small devices, such as PDAs, and also for large server machines which need to serve lots of ports. o Flite is not a replacement for Festival but an alternative run time engine for voices developed in the FestVox framework where size and speed is crucial. o Flite is all in ANSI C, it contains no C++ or Scheme, thus requires more care in programming, and is harder to customize at run time. o It is thread safe. o Voices, lexicons and language descriptions can be compiled (mostly automatically for voices and lexicons) into C representations from their FestVox formats. o All voices, lexicons and language model data are const and in the text segment (i.e. they may be put in ROM). As they are linked in at compile time, there is virtually no startup delay. o Although the synthesized output is not exactly the same as the same voice in Festival they are effectively equivalent. That is, flite doesn't sound better or worse than the equivalent voice in festival, just faster, smaller and scalable. o For standard diphone voices, maximum run time memory requirements are approximately less than twice the memory requirement for the waveform generated. For 32bit architectures this effectively means under 1M. o The flite program supports, synthesis of individual strings or files (utterance by utterance) to direct audio devices or to waveform files. o The flite library offers simple functions suitable for use in specific applications. Flite is distributed with a single 8K diphone voice (derived from the cmu_us_kal voice), a pruned lexicon (derived from cmulex) and a set of models for US English. Here are comparisons with Festival using basically the same 8KHz diphone voice. On a 500Mhz PIII, a timing test of the first two chapters of "Alice in Wonderland" (doc/alice) was done. This produces about 1300 seconds of speech. With flite it takes 19.128 seconds (about 70.6 times faster than real time) with Festival it takes 97 seconds (13.4 times faster than real time). On the ipaq (with the 16KHz diphones) flite synthesizes 9.79 time faster than real time.