Speech synthesis using a maximally decimated pseudo QMF bank for embedded devices

A fast speech waveform generation method using a maximally decimated pseudo quadrature mirror filter (QMF) bank is proposed. The method is based on subband coding with pseudo QMF banks, which is also used in MPEG Audio. In the method, subband code vectors for speech sounds are synthesized from magnitudes of spectral envelope and fundamental frequencies for periodic frames, and then waveforms are generated by decoding of the vectors. Since the synthesizing of the vectors is performed at the reduced sampling rate by the maximal decimation and the decoding is processed with fast discrete cosine transformation algorithms, faster speech waveform generation is achieved totally. Although preencoded vectors for noise components were used to reduce the computational costs in our former studies, in this study, all code vectors for noise components are made with a noise generator at run time for small footprint systems. In contrast, a subjective test for synthetic sounds by HMM-based speech synthesis using mel-cepstrum showed the proposed method was comparable to our former method and also the conventional method using a mel log spectrum approximation (MLSA) filter in quality of sounds.