COMPRESSION OF STORED WAVEFORMS FOR ARTIFICIAL SPEECH

In a digital text-to-speech conversion system of the type usually contained in all-software form on a floppy disk, memory requirements for the storage of digitized waveform samples are reduced while speech quality is improved, by providing compression techniques and anti-distortion techniques which interact to provide clear speech at widely varying speeds with a minimum of memory. These techniques include using Huffman coding of first- or second-order differences, encoding only differences between successive waveforms where feasible, using a demi-diphone organization of the speech to allow use of the same instruction lists for several sounds, selectively deleting or repeating waveforms in the concatenation to vary speed without affecting pitch, and encoding waveforms linearly or anti-logarithmically for storage while converting the stored linear or anti-logarithmic codes to logarithmic codes such as .mu.-law codes upon retrieval.