Study Of Speech Based On Prototype Waveform Interpolaton

This paper introduces a speech coding scheme and a tone modification method for Chinese speech synthesis based on prototype waveform interpolation (PWI) algorithm. PWI algorithm is proposed by Dr. W.B.Kleijn when he worked in AT&T Bell Laboratories. Based on the periodicity, voiced speech is interpreted as a concatenation of slowly evolving pitch-cycle waveforms. The waveform of a single pitch cycle, which will be referred to as the prototype waveform, is transmitted at regular intervals (of 20-30 ms) and then interpolated between theses update points.The principle and implementation method of the prototype waveform interpolation are analyzed and introduced in detail. On the base of the study of Regular Pulse Excitation-Long Term Prediction speech coding scheme (13kb/s) a voiced speech coding scheme used PWI method at 4.8kb/s is described, which greatly reduces the coding rate. The computer simulation results show that the synthesized speech quality of PWI scheme is close to that of the original one.In addition, this paper introduces a tone modification method for Chinese speech synthesis used PWI. Traditional algorithm, time-domain pitch–synchronous overlap-add (PSOLA) is capable of transforming prosodic features of the Chinese speech. But PSOLA algorithm shows some of shortcomings. When the pitch frequency is modified greatly, spectral envelope will distort, which means formant features produce inacceptable variation. This paper combines PWI and PSOLA algorithm, and improves the result of tone modification.