eSpeak NG Text-to-Speech

• Features
• Supported languages
• Documentation
• eSpeak Compatibility
• History
• License Information

The eSpeak NG is a compact open source software text-to-speech synthesizer for Linux, Windows, Android and other operating systems. It supports more than 100 languages and accents. It is based on the eSpeak engine created by Jonathan Duddington.

eSpeak NG uses a "formant synthesis" method. This allows many languages to be provided in a small size. The speech is clear, and can be used at high speeds, but is not as natural or smooth as larger synthesizers which are based on human speech recordings. It also supports Klatt formant synthesis, and the ability to use MBROLA as backend speech synthesizer.

eSpeak NG is available as:

• A command line program (Linux and Windows) to speak text from a file or from stdin.
• A shared library version for use by other programs. (On Windows this is a DLL).
• A SAPI5 version for Windows, so it can be used with screen-readers and other programs that support the Windows SAPI5 interface.
• eSpeak NG has been ported to other platforms, including Solaris and Mac OSX.

Features

• Includes different Voices, whose characteristics can be altered.
• Can produce speech output as a WAV file.
• SSML (Speech Synthesis Markup Language) is supported (not complete), and also HTML.
• Compact size. The program and its data, including many languages, totals about few Mbytes.
• Can be used as a front-end to MBROLA diphone voices. eSpeak NG converts text to phonemes with pitch and length information.
• Can translate text into phoneme codes, so it could be adapted as a front end for another speech synthesis engine.
• Potential for other languages. Several are included in varying stages of progress. Help from native speakers for these or other languages is welcome.
• Written in C.

See the ChangeLog for a description of the changes in the various releases and with the eSpeak NG project.

The following platforms are supported:

Platform	Minimum Version	Status
Linux
BSD
Android	4.0
Windows	Windows 8
Mac

Documentation

1. User guide explains how to set up and use eSpeak NG from command line or as a library.
2. Building guide provides info how to compile and build eSpeak NG from the source.
3. Index provides full list of more detailed information for contributors and developers.
4. Look at contribution guide to start your contribution.
5. Look at eSpeak NG roadmap to participate in development of eSpeak NG.

eSpeak Compatibility

The espeak-ng binaries use the same command-line options as espeak, with several additions to provide new functionality from espeak-ng such as specifying the output audio device name to use. The build creates symlinks of espeak to espeak-ng, and speak to speak-ng.

The espeak speak_lib.h include file is located in espeak-ng/speak_lib.h with an optional symlink in espeak/speak_lib.h. This file contains the espeak 1.48.15 API, with a change to the ESPEAK_API macro to fix building on Windows and some minor changes to the documentation comments. This C API is API and ABI compatible with espeak.

The espeak-data data has been moved to espeak-ng-data to avoid conflicts with espeak. There have been various changes to the voice, dictionary and phoneme files that make them incompatible with espeak.

The espeak-ng project does not include the espeakedit program. It has moved the logic to build the dictionary, phoneme and intonation binary files into the libespeak-ng.so file that is accessible from the espeak-ng command line and C API.

History

The program was originally known as speak and originally written for Acorn/RISC_OS computers starting in 1995 by Jonathan Duddington. This was enhanced and re-written in 2007 as eSpeak, including a relaxation of the original memory and processing power constraints, and with support for additional languages.

In 2010, Reece H. Dunn started maintaining a version of eSpeak on GitHub that was designed to make it easier to build eSpeak on POSIX systems, porting the build system to autotools in 2012. In late 2015, this project was officially forked to a new eSpeak NG project. The new eSpeak NG project is a significant departure from the eSpeak project, with the intention of cleaning up the existing codebase, adding new features, and adding to and improving the supported languages.

The historical branch contains the available older releases of the original eSpeak that are not contained in the subversion repository.

1.24.02 is the first version of eSpeak to appear in the subversion repository, but releases from 1.05 to 1.24 are available at http://sourceforge.net/projects/espeak/files/espeak/.

These early releases have been checked into the historical branch, with the 1.24.02 release as the last entry. This makes it possible to use the replace functionality of git to see the earlier history:

git replace 8d59235f 63c1c019

NOTE: The source releases contain the big_endian, espeak-edit, praat-mod, riskos, windows_dll and windows_sapi folders. These do not appear in the source repository until later releases, so have been excluded from the historical commits to align them better with the 1.24.02 source commit.

License Information

eSpeak NG Text-to-Speech is released under the GPL version 3 or later license.

The getopt.c compatibility implementation for getopt support on Windows is taken from the NetBSD getopt_long implementation, which is licensed under a 2-clause BSD license.

Android is a trademark of Google LLC.

Acknowledgements

The catalan extension was funded by [Departament de la Vicepresidència i de Polítiques Digitals i Territori de la Generalitat de Catalunya](https://politiquesdigitals.gencat.cat/ca/inici/index.html#googtrans(ca|en) within the framework of Projecte AINA.