A high-quality, real-time text-to-speech synthesizer system (Fig. 1) handles an unlimited vocabulary with a minimum of hardware by using a microcomputer-software-compatible time domain methodology which requires a minimum of memory and computational power. The system first compares text words to an exception dictionary (Fig. 2). If the word is not found therein, the system applies standard pronunciation rules to the text word. In either instance, the text word is converted to a phoneme sequence. By the use of look-up tables addressed by pointers contained in a phoneme-and-transition matrix (Fig. 3), the synthesizer translates the sequence of phonemes and transitions therebetween into sequences of small speech segments capable of being expressed in terms of repetitions of variable-length portions of short digitally stored waveforms. In general, unvoiced transitions are produced by a sequence of segments which can be concatenated in forward or reverse order to generate different transitions out of the same segments; while voiced transitions are produced by interpolating adjacent phonemes for additioanl savings. Pitch can be varied for naturalness of sound, and/or for intonation changes derived from key words and/or punctuation in the text, by truncating or extending the waveforms of individual voice periods corresponding to voiced segments.
REAL-TIME TEXT-TO-SPEECH CONVERSION SYSTEM