Speech synthesis

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This article is for collecting ideas and resources for using text-to-speech (TTS) speech synthesis on the XO.

Applications of Speech Synthesis wrt OLPC

Speech synthesis will not only be useful in improving the accessibility of the laptop but also for providing learning aides to the student.

Some simple educational activities that would benefit from the speech synthesis project include:

  • Pronounce - An activity teaching the child how to pronounce words correctly. It can be scaled up in the future to use speech recognition/ analysis of audio files to take audio input from the student. Based upon analysis and comparisons of the input audio file the activity can suggest appropriate corrections in the way the child speaks.
  • Story Book Reader - The Read activity can double up as an activity that would read stories that the child downloads on his/her XO. Children can be encouraged to read more and learn as much as they can. Learning through listening has its own advantages when compared to learning through reading and ad-hoc experimentation.
  • Listen and Spell - Students can listen to the XO speak a word. They must then spell the word and see if they did so correctly. This can be scaled up to a multiplayer game where students can challenge other students in their area. edit: Check out wiki.laptop.org/go/talkntype for beginning work in this area.
  • Talking Chatbots - Kids would love to shoot questions to an AI chatbot and hear it answer
  • Accessibility - Speech Synthesis tools are an integral component of software meant to improve accessibility. See http://live.gnome.org/Orca Orca] for more info.

Also see the following article which is a good read for the present context: Effective Adult Literacy Program

Existing software


Type text, and a funny face speaks what you typed. Pitch, speed, glasses, and mouth are adjustable.


There are FOSS Free Open Source Software Speech-Synthesis packages which run on devices comparable to the XO. We are much more concerned with localization than is typical. And dialects can be a political issue. But TTS would help with Accessibility. And could be very cool.

Speech synthesis has a set of complex tradoffs of synthesizer size versus fidelity versus effort to localize a new language. The Wikipedia speech synthesis article discusses software that is available, which includes festival, flite, and espeak.

Espeak is small enough for us to often bundle and covers quite a few languages: ~10 languages currently supported tuned by native speakers. Localization to ten more languages is underway.

Synthesis is essential for accessibility to content by people with vision problems, and will need to be integrated with the ATK library used, as well as literacy training, other uses as part of a GUI. Full localization therefore involves selection of a suitable synthesis system and integration into the ATK framework, along with localization of that system for the particular language involved.

Speech synthesis is usually not a good guide for pronunciation – but it may be better than a poor teacher who has never had the opportunity to learn from a native speaker of that language.


eSpeak is currently included on the xo. .. But does not work directly to the sound card since the XO uses ALSA instead of OSS as its main Sound System,and enabling OSS Emulation in ALSA is not yet the default. Manually configuring your XO to emulate OSS in ALSA will provide the system devices that you require and allow full espeak functionality - Dking

If you are lacking OSS Emulation on your XO's sound sytstem setup in ALSA, some text can be played by piping espeak's standard output to another file:

$ espeak --stdout "Ello world." | gst-launch fdsrc fd=0 ! wavparse ! alsasink
$ espeak --stdout -vpt "Bem-vindo ao wiki da OLPC" | gst-launch fdsrc fd=0 ! wavparse ! alsasink
$ espeak --stdout "Using aplay." | aplay -

However, for some initial sounds, espeak fails to output valid audio to standard out (Trac #4002) . This includes letters c, h, k, p, q, t, v, z and possibly others. For example, this still won't work in build 703 (aka Update.1, espeak v 1.28):

$ espeak --stdout "hello world." | aplay

A workaround is to first write the output to a file, then play back the file:

$ espeak -w temp.wav "hello world."; aplay temp.wav

Screen Reader is a DBus interface that allows the XO to use eSpeak via Python.


Flite is not currently included on the xo. Unless that changes, it would have to come out of your activity's space budget.

First, run /sbin/init 3 so yum doesn't run out of memory.  After yum, reboot.
$ yum install flite
$ flite -t 'Hello, world!'
Does it always sound this bad, or is just the default voice that works poorly? MitchellNCharity 16:42, 22 October 2007 (EDT)
The default voice isn't great. The arctic-hts voices are much better but also qite large (2-3MB each) and not lightweight on the CPU either. Mattdm 01:25, 4 October 2008 (UTC)

Festival is not currently included on the xo. Unless that changes, it would have to come out of your activity's space budget.

First, run /sbin/init 3 so yum doesn't run out of memory.  After yum, reboot.
$ yum install festival
$ echo 'Hello, world!' | festival --tts


The goal of FreeIconTospeech is to provide a low-cost assistive / augmentative communication tool for people with speech, motor, and/or developmental challenges. The immediate opportunity is to create open source software to allow a user to select concepts through a menu of icons, and synthesize speech from those selected concepts. See the FreeIconToSpeech page for more information.

The state of the art

Commercial Text-To-Speech programs are getting very good now. The examples at the Digital Future Software Company site are very clear. They use AT&T technology and provide examples of Male and Female speech in English, French and Spanish. The XO needs open-source software that can approach this quality in a wide range of languages.--Ricardo 04:07, 17 August 2007 (EDT)


See also