Software for the Visually Handicapped
MBROLA: A speech synthesizer program.

  The multilingual applications developed at IIT Madras, use the MBROLA speech synthesizer program to produce speech output from the Indian language text dealt with by the application. The applications include

1. Multilingual editor
2. A text reading program to read Indian language text.
3. Sound enhanced web browser (based on Lynx)
4. An interface program to work with Jaws for Dos under Win95.

  All these applications cater to the multilingual requirements within the country. The choice of MBROLA as the speech engine was influenced by many factors. the development team at IIT Madras found this to be an excellent piece of software that relates well to the phonetic nature of Indian languages by allowing  phonemes to be synthesized elegantly. The syllable level representation of the text in Indian languages, a feature  unique to the IIT Madras software, makes it very easy for applications to support speech output.

  The Mbrola system is not an application that is ready for use. It is a building block in a system for producing speech and hence one must use it in a computer program which can identify the phonemes to be used for speaking out a text string. The MBROLA development team has been generous in making the software available as a library of functions which could be called from a computer application. They have this library available for a number of computer systems including Linux, Windows, Dos etc., and hence one can develop speech output applications on almost all the computer systems in use today.

  MBROLA derives its basic strength from the fact that it is a piece of software that produces speech output from a list of phonemes. Thus, its operation is not specific to a language and one can get true multilingual output using the speech engine by feeding appropriate phonemes to the engine and indicating the language used for generating the phonemes. Mbrola achieves this excellent capability through the concept of a speech data base which has the information required for producing the sound associated with the phoneme. The Mbrola team has been assisted by volunteers from many countries to produce speech databases in many languages of the world. Also, volunteers have contributed programs which could be used for mapping text strings in different languages to the associated phonemes thus making the job of text to speech conversion relatively easy.

  In respect of Indian languages, suitable data bases have not been developed yet and may take some time. However, it is possible to produce very satisfactory results for Indian languages, by using phonemes of languages for which a data base is already available. We have observed that Swedish has most of the phonemes required for the Indian languages and hence the development team at IIT Madras has used the same for its applications.

(Note: As of 2004, Mbrola voice data bases for Hindi and Telugu have been created. However, the support required for a full set of phonemes to cater to all the aksharas have not been included. A proper voice data base for Indian languages is yet to be fully realized.)

  The procedure for developing a speech data base for MBROLA, requires that a representative speech sample for each language be collected (the specs for this are available), a recording made and from this identification of diphones (the continuation of one phoneme into another in a smooth fashion) completed. For lack of time and recording resources, the IIT Madras development team has put this exercise off for the time being. Persons interested in contributing to MBROLA speech data bases for Indian languages may kindly get in touch with the IIT Madras development team via email (details in the contact IIT page).

  The data base used by the IITM team for speech output in English is known as EN1. The speech produced is very typical of what one might hear in England. For those in India, this is closer to their own understanding of spoken English compared to English spoken in the U.S.A.

  IIT Madras finds that MBROLA is very easy to work with on Windows as well as Linux platforms. Downloading and installing the software is also straightforward but help from a sighted friend may be needed to complete the installation on both systems.


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