S4.10 Multimode coding: Application to CELP
Shigeyuki, Robert M. Gray · 1989
We introduce a novel approach to narrow and medium band speech coding that can dynamically balance the transmission rate between the excitation and the spectral parameters. The coding algorithm, called multimode coding, operates several coding blocks each of which has a different bit assignment in parallel. and selects the optimum coding block frame by frame based on an evaluation of the reproduced speech quality. This coding algorithm is applied to 4.8 and 8.0 kbps CELP coders, and 2.0-2.4 dB of SNRseg improvement is achieved over conventional CELP coders. Furthermore, the spectral distortion measure is added as an evaluation function, and it successfully improves the subjective quality.