Pseudo-three-tap pitch prediction filters

Pitch filters play an important role in high-quality medium and low rate speech coders. The authors propose a pseudo-three-tap pitch filter with one degree of freedom or two degrees of freedom of the prediction coefficients, which gives a higher pitch prediction gain and also a more desirable frequency response than a one-tap pitch prediction filter. First, they describe an analysis model for the pseudo-three-tap pitch filter. Then, they apply the pseudo-three-tap concept together with a fractional pitch lag. The pitch prediction gain and frequency response of the pseudo-three-tap pitch filters are compared with one-tap and three-tap pitch predictors with an integer or a noninteger pitch lag. The pseudo-three-tap pitch filter with one degree of freedom outperforms a conventional one-tap pitch filter. Even better is a pseudo-three-tap filter which switches between two parameter values.<>