A low resolution pulse position coding method for improved excitation modeling of speech transition

We propose a new excitation model for transitional speech to re-duce the distortion due to the traditional two-excitation source, voiced and unvoiced, model. The proposed low resolution pulse position coding (LRPPC) algorithm detects the existence of pulses at frames of weak periodicity, which are determined as unvoiced, and transmits the approximate pulse positions. In the decoder, dis-persed pulses that have a flat magnitude spectrum are synthesized at the decoded positions to form the excitation signal. A subjec-tive quality test shows that the vocoder employing the LRPPC al-gorithm produces better quality of speech, and is very robust to mode decision errors. 1