Improving temporal resolution by using LaGrange interpolation filter (LIF) [speech coding]

This paper introduces a new technique for improving speech quality of a low bit rate code-excited linear prediction (CELP) coder without introducing any increase in bit rate or complexity. The idea is to improve the resolution of the adaptive codebook contribution by using a LaGrange interpolation filter (LIF) in place of the Hamming sinc filter originally used. The designed filter is tested on a floating point C-simulation of the G.729 8 kb/s CS-ACELP coder (Salami et al, 1995). The results show that the designed filter has generally improved the temporal resolution by increasing the pitch prediction gain.