Predictive vector quantization of wideband LSF using narrowband LSF for bandwidth scalable coders

Abstract

For implementing a bandwidth-scalable coder, a wideband line spectral frequency (LSF) quantizer was developed. It works in combination with a narrowband LSF quantizer. A new predictive vector quantization was introduced to the wideband LSF quantizer. The predictive vector quantizer is based on the use of several predictive contributions, which include first-order auto regressive (AR) prediction and vector quantization (VQ) codebook mapping. One feature of the new predictive vector quantizer is exploitation of the correlation between wideband and narrowband LSFs quantized in the previous frame for estimating wideband LSF in the current frame. A 16-bit switched predictive three-stage vector quantizer was used to encode estimation residues. Results showed that introduction of the predictor brought about a performance improvement of 0.3 dB in spectral distortion. This paper describes procedures of designing the predictor and the three-stage codebook, as well as simulation results.