Third International Conference on Spoken Language Processing (ICSLP 94)
This paper describes modifications to a previously proposed 8 kb/s 4 ms-delay CELP speech coding algorithm with a view to improving the speech quality while maintaining the low delay and with only moderate increases in complexity. The modifications are based on improving the effectiveness of interframe pitch lag prediction as well as the level of sub-optimality of the coding of the excitation to the backward adapted synthesis filter by delayed decision and joint optimization techniques. Results of subjective listening tests using Japanese speech indicate that the coded speech quality is significantly superior to that of the 8 kb/s VSELP coder with 20 ms delay. A method that reduces the computational complexity of closed-loop 3-tap pitch prediction with no perceptible degradation in speech quality is proposed, based on representing the pitch-tap vector as the product of a scalar pitch gain and a normalized shape codevector.
Bibliographic reference. Rao, Preeti / Asakawa, Yoshiaki / Sekine, Hidetoshi (1994): "8 kb/s low-delay speech coding with 4 ms frame size", In ICSLP-1994, 2075-2078.