A Hybrid Coder Based On A New Phase Model For Synchronization

Abstract

This paper presents a hybrid coder with a new phase model to synchronize harmonic and waveform coded segments, with a target bit rate of 4 kbps. The coder also employs a new technique based on analysis by synthesis to distinguish between stationary and transitional segments. Harmonic excitation is synchronized with the LPC residual by transmitting the location of the pitch pulse closest to the frame boundary and a phase value that represents the shape of the corresponding pitch pulse. The performance of this phase model and the classification technique is evaluated using a hybrid coder. The coder has three modes: scaled white noise excitation colored by LPC for unvoiced, ACELP for transitions, and harmonic excitation for stationary segments. Subjective listening tests show that the coder produces good quality speech and the switching between the modes is transparent.