Natural sounding speech coder operating at 2.4 kb/s and below
S. Yeldener, Ahmet M. KONDOZ, B.G. Evans · 2003
Accurate representation of periodic speech segments is essential for synthesizing high quality digital speech at very low bit rates. For bit rates at 4.8 kb/s and below, conventional code excited linear prediction (CELP) does not provide the appropriate degree of periodicity. It has been suggested that good quality low bit rate speech can be obtained from frequency domain techniques such as STC, NMR and MB-LPC vocoders. A MB-LPC vocoder operating at 2.4 kb/s and below is presented which exploits the advantages of both time- and frequency-domain speech coding to produce natural sounding, good quality speech. This also includes a new frequency domain post-filter which attenuates the noise in the formant nulls and enhances the synthesized speech.>