A high quality BI-CELP speech coder at 8 kbit/s and below

This paper describes “BI-CELP: baseline and implied CELP”, which is a high quality speech coding method based on a code excited linear prediction (CELP) model employing excitation vectors combined from two codebooks, one from the baseline codebook and the other from the implied codebook. In this method the index of the baseline codebook is coded and transmitted to the receiver while the index of the implied codebook is extracted from the synthesized speech. This method has been applied to a lower rate voice coder at 8 kbit/s to produce high quality voice comparable to that of the 16 kbit/s G.728 LD-CELP. The performance of the 8 kbit/s BI-CELP coder is measured in terms of SNRseg and MOS. The average SNRseg is 12.14 dB which is 0.6 dB higher than that of the 8 kbit/s G.729 CS-ACELP. The MOS for the quiet input is 3.8 which is 0.02 higher than that of G.729 CS-ACELP. BI-CELP algorithm is implemented in real-time on a single TMS320C31 with 27 MIPS of CPU