Pitch-congruent baseband speech coding

This paper examines a technique for reducing the effect of pitch-incongruence or harmonic offset in baseband speech coding of high pitched voices. The proposed method employs a variable-width baseband coding scheme. A nominal baseband width can be specified. Actual width of the baseband is determined in every frame to be a number closest to the nominal width that contains an integer number of multiples of fundamental pitch frequency. When baseband is copied up to higher bands, phase of the copied up bands must be frequency-adjusted to form a consistent overall phase function for that frame. This ensures more appropriate addition of harmonics to generate pitch pulses at desired positions in the regenerated residual signal. A method for making such adjustment to phase of the copied up bands is explored and its promises and limitations are discussed.