eSpeak

eSpeak is a free and open-source, cross-platform, compact, software speech synthesizer. It uses a formant synthesis method, providing many languages in a relatively small file size. eSpeakNG (Next Generation) is a continuation of the original developer's project with more feedback from native speakers.

eSpeakNG
Original author(s)Jonathan Duddington
Developer(s)Alexander Epaneshnikov et al.
Initial releaseFebruary 2006 (2006-02)
Stable release
1.51 / 2 April 2022 (2022-04-02)
Repositorygithub.com/espeak-ng/espeak-ng/
Written inC
Operating systemLinux
Windows
macOS
FreeBSD
TypeSpeech synthesizer
LicenseGPLv3
Websitegithub.com/espeak-ng/espeak-ng/

Because of its small size and many languages, eSpeakNG is included in NVDA[1] open source screen reader for Windows, as well as Android,[2] Ubuntu[3] and other Linux distributions. Its predecessor eSpeak was recommended by Microsoft in 2016[4] and was used by Google Translate for 27 languages in 2010;[5] 17 of these were subsequently replaced by proprietary voices.[6]

The quality of the language voices varies greatly. In eSpeakNG's predecessor eSpeak, the initial versions of some languages were based on information found on Wikipedia.[7] Some languages have had more work or feedback from native speakers than others. Most of the people who have helped to improve the various languages are blind users of text-to-speech.

History

In 1995, Jonathan Duddington released the Speak speech synthesizer for RISC OS computers supporting British English.[8] On 17 February 2006, Speak 1.05 was released under the GPLv2 license, initially for Linux, with a Windows SAPI 5 version added in January 2007.[9] Development on Speak continued until version 1.14, when it was renamed to eSpeak.

Development of eSpeak continued from 1.16 (there was not a 1.15 release)[9] with the addition of an eSpeakEdit program for editing and building the eSpeak voice data. These were only available as separate source and binary downloads up to eSpeak 1.24. The 1.24.02 version of eSpeak was the first version of eSpeak to be version controlled using subversion,[10] with separate source and binary downloads made available on SourceForge.[9] From eSpeak 1.27, eSpeak was updated to use the GPLv3 license.[11] The last official eSpeak release was 1.48.04 for Windows and Linux, 1.47.06 for RISC OS and 1.45.04 for macOS.[12] The last development release of eSpeak was 1.48.15 on 16 April 2015.[13]

eSpeak uses the Usenet scheme to represent phonemes with ASCII characters.[14]

eSpeak NG

On 25 June 2010,[15] Reece Dunn started a fork of eSpeak on GitHub using the 1.43.46 release. This started off as an effort to make it easier to build eSpeak on Linux and other POSIX platforms.

On 4 October 2015 (6 months after the 1.48.15 release of eSpeak), this fork started diverging more significantly from the original eSpeak.[16][17]

On 8 December 2015, there were discussions on the eSpeak mailing list about the lack of activity from Jonathan Duddington over the previous 8 months from the last eSpeak development release. This evolved into discussions of continuing development of eSpeak in Jonathan's absence.[18][19] The result of this was the creation of the espeak-ng (Next Generation) fork, using the GitHub version of eSpeak as the basis for future development.

On 11 December 2015, the espeak-ng fork was started.[20] The first release of espeak-ng was 1.49.0 on 10 September 2016,[21] containing significant code cleanup, bug fixes, and language updates.

Features

eSpeakNG can be used as a command-line program, or as a shared library.

It supports Speech Synthesis Markup Language (SSML).

Language voices are identified by the language's ISO 639-1 code. They can be modified by "voice variants". These are text files which can change characteristics such as pitch range, add effects such as echo, whisper and croaky voice, or make systematic adjustments to formant frequencies to change the sound of the voice. For example, "af" is the Afrikaans voice. "af+f2" is the Afrikaans voice modified with the "f2" voice variant which changes the formants and the pitch range to give a female sound.

eSpeakNG uses an ASCII representation of phoneme names which is loosely based on the Usenet system.

Phonetic representations can be included within text input by including them within double square-brackets. For example: espeak-ng -v en "Hello [[w3:ld]]" will say Hello worldⓘ in English.

Synthesis method

eSpeakNG can be used as text-to-speech translator in different ways, depending on which text-to-speech translation step user want to use.

1. step — text to phoneme translation

There are many languages (notably English) which do not have straightforward one-to-one rules between writing and pronunciation; therefore, the first step in text-to-speech generation has to be text-to-phoneme translation.

  1. input text is translated into pronunciation phonemes (e.g. input text xerox is translated into zi@r0ks for pronunciation).
  2. pronunciation phonemes are synthesized into sound e.g., zi@r0ks is voiced as zi@r0ks in monotone wayⓘ

To add intonation for speech i.e. prosody data are necessary (e.g. stress of syllable, falling or rising pitch of basic frequency, pause, etc.) and other information, which allows to synthesize more human, non-monotonous speech. E.g. in eSpeakNG format stressed syllable is added using apostrophe: z'i@r0ks which provides more natural speech: z'i@r0ks with intonationⓘ

For comparison two samples with and without prosody data:

  1. [[DIs Iz m0noUntoUn spi:tS]] is spelled in monotone wayⓘ
  2. [[DIs Iz 'Int@n,eItI2d sp'i:tS]] is spelled intonated wayⓘ

If eSpeakNG is used for generation of prosody data only, then prosody data can be used as input for MBROLA diphone voices.

2. step — sound synthesis from prosody data

The eSpeakNG provides two different types of formant speech synthesis using its two different approaches. With its own eSpeakNG synthesizer and a Klatt synthesizer:[22]

  1. The eSpeakNG synthesizer creates voiced speech sounds such as vowels and sonorant consonants by additive synthesis adding together sine waves to make the total sound. Unvoiced consonants e.g. /s/ are made by playing recorded sounds,[23] because they are rich in harmonics, which makes additive synthesis less effective. Voiced consonants such as /z/ are made by mixing a synthesized voiced sound with a recorded sample of unvoiced sound.
  2. The Klatt synthesizer mostly uses the same formant data as the eSpeakNG synthesizer. But, it also produces sounds by subtractive synthesis by starting with generated noise, which is rich in harmonics, and then applying digital filters and enveloping to filter out necessary frequency spectrum and sound envelope for particular consonant (s, t, k) or sonorant (l, m, n) sound.

For the MBROLA voices, eSpeakNG converts the text to phonemes and associated pitch contours. It passes this to the MBROLA program using the PHO file format, capturing the audio created in output by MBROLA. That audio is then handled by eSpeakNG.

Languages

eSpeakNG performs text-to-speech synthesis for the following languages:[24]

  1. Afrikaans[25]
  2. Albanian[26]
  3. Amharic
  4. Ancient Greek
  5. Arabic1
  6. Aragonese[27]
  7. Armenian (Eastern Armenian)
  8. Armenian (Western Armenian)
  9. Assamese
  10. Azerbaijani
  11. Bashkir
  12. Basque
  13. Belarusian
  14. Bengali
  15. Bishnupriya Manipuri
  16. Bosnian
  17. Bulgarian[27]
  18. Burmese
  19. Cantonese[27]
  20. Catalan[27]
  21. Cherokee
  22. Chinese (Mandarin)
  23. Croatian[27]
  24. Czech
  25. Chuvash
  26. Danish[27]
  27. Dutch[27]
  28. English (American)[27]
  29. English (British)
  30. English (Caribbean)
  31. English (Lancastrian)
  32. English (Received Pronunciation)
  33. English (Scottish)
  34. English (West Midlands)
  35. Esperanto[27]
  36. Estonian[27]
  37. Finnish[27]
  38. French (Belgian)[27]
  39. French (Canada)
  40. French (France)
  41. Georgian[27]
  42. German[27]
  43. Greek (Modern)[27]
  44. Greenlandic
  45. Guarani
  46. Gujarati
  47. Hakka Chinese3
  48. Haitian Creole
  49. Hawaiian
  50. Hebrew
  51. Hindi[27]
  52. Hungarian[27]
  53. Icelandic[27]
  54. Indonesian[27]
  55. Ido
  56. Interlingua
  57. Irish[27]
  58. Italian[27]
  59. Japanese4[28]
  60. Kannada[27]
  61. Kazakh
  62. Klingon
  63. Kʼicheʼ
  64. Konkani[29]
  65. Korean
  66. Kurdish[27]
  67. Kyrgyz
  68. Quechua
  69. Latin
  70. Latgalian
  71. Latvian[27]
  72. Lingua Franca Nova
  73. Lithuanian
  74. Lojban[27]
  75. Luxembourgish
  76. Macedonian
  77. Malay[27]
  78. Malayalam[27]
  79. Maltese
  80. Manipuri
  81. Māori
  82. Marathi[27]
  83. Nahuatl (Classical)
  84. Nepali[27]
  85. Norwegian (Bokmål)[27]
  86. Nogai
  87. Oromo
  88. Papiamento
  89. Persian[27]
  90. Persian (Latin alphabet)2
  91. Polish[27]
  92. Portuguese (Brazilian)[27]
  93. Portuguese (Portugal)
  94. Punjabi[30]
  95. Pyash (a constructed language)
  96. Quenya
  97. Romanian[27]
  98. Russian[27]
  99. Russian (Latvia)
  100. Scottish Gaelic
  101. Serbian[27]
  102. Setswana
  103. Shan (Tai Yai)
  104. Sindarin
  105. Sindhi
  106. Sinhala
  107. Slovak[27]
  108. Slovenian
  109. Spanish (Spain)[27]
  110. Spanish (Latin American)
  111. Swahili[25]
  112. Swedish[27]
  113. Tamil[27]
  114. Tatar
  115. Telugu
  116. Thai
  117. Turkmen
  118. Turkish[27]
  119. Uyghur
  120. Ukrainian
  121. Urarina
  122. Urdu
  123. Uzbek
  124. Vietnamese (Central Vietnamese)[27]
  125. Vietnamese (Northern Vietnamese)
  126. Vietnamese (Southern Vietnamese)
  127. Welsh
  1. Currently, only fully diacritized Arabic is supported.
  2. Persian written using English (Latin) characters.
  3. Currently, only Pha̍k-fa-sṳ is supported.
  4. Currently, only Hiragana and Katakana are supported.

See also

References
  1. Switch to eSpeak NG in NVDA distribution #5651
  2. eSpeak TTS for Android
  3. espeak-ng package in Ubuntu
  4. "Download voices for Immersive Reader, Read Mode, and Read Aloud".
  5. Google blog, Giving a voice to more languages on Google Translate, May 2010
  6. Google blog, Listen to us now, December 2010.
  7. eSpeak Speech Synthesizer 3. LANGUAGES
  8. http://espeak.sourceforge.net/
  9. "ESpeak: Speech synthesis - Browse /Espeak at SourceForge.net".
  10. Subversion history (revision 1)
  11. Subversion history (revision 56)
  12. "Espeak: Downloads".
  13. http://espeak.sourceforge.net/test/latest.html
  14. van Leussen, Jan-Wilem; Tromp, Maarten (26 July 2007). "Latin to Speech". p. 6. CiteSeerX 10.1.1.396.7811.
  15. "Build: Allow portaudio 18 and 19 to be switched easily. · rhdunn/Espeak@63daaec". GitHub.
  16. "Espeakedit: Fix argument processing for unicode argv types · rhdunn/Espeak@61522a1". GitHub.
  17. "Switch to eSpeak NG in NVDA distribution · Issue #5651 · nvaccess/Nvda". GitHub.
  18. Taking ownership of the eSpeak project and its future
  19. Vote for new main eSpeak developer
  20. Rebrand the espeak program to espeak-ng.
  21. espeak-ng 1.49.0
  22. Klatt, Dennis H. (1979). "Software for a cascade/parallel formant synthesizer" (PDF). J. Acoustical Society of America, 67(3) March 1980.
  23. List of recorded fricatives in eSpeakNG
  24. "ESpeak NG Text-to-Speech". GitHub. 13 February 2022.
  25. Butgereit, L., & Botha, A. (2009, May). Hadeda: The noisy way to practice spelling vocabulary using a cell phone. In The IST-Africa 2009 Conference, Kampala, Uganda.
  26. Hamiti, M., & Kastrati, R. (2014). Adapting eSpeak for converting text into speech in Albanian. International Journal of Computer Science Issues (IJCSI), 11(4), 21.
  27. Kayte, S., & Gawali, D. B. (2015). Marathi Speech Synthesis: A review. International Journal on Recent and Innovation Trends in Computing and Communication, 3(6), 3708-3711.
  28. Pronk, R. (2013). Adding Japanese language synthesis support to the eSpeak system. University of Amsterdam.
  29. Mohanan, S., Salkar, S., Naik, G., Dessai, N. F., & Naik, S. (2012). Text Reader for Konkani Language. Automation and Autonomous System, 4(8), 409-414.
  30. Kaur, R., & Sharma, D. (2016). An Improved System for Converting Text into Speech for Punjabi Language using eSpeak. International Research Journal of Engineering and Technology, 3(4), 500-504.
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