Nonsquare transform vector quantization

Several techniques for low-rate speech coding have emerged, requiring quantization of the spectral magnitudes. The set of spectral magnitudes may be considered as a variable-dimension vector with dimension dependent on the pitch period. The authors present a technique called nonsquare transform vector quantization (NSTVQ). This technique addresses the problem of variable-dimension vector quantization by combining a fixed-dimension vector quantizer with a variable-sized nonsquare transform. The experimental results presented show that NSTVQ outperforms existing harmonic magnitude quantization techniques.