Safety-net pyramid VQ of LSF parameters for wideband speech codecs

The authors propose a predictive pyramid VQ (PPVQ) that uses the safety-net concept to quantise the LSF parameters of wideband speech. A first-order a uto-regessive (AR) predictor is used to predict thr LSF parameters. To quan tise the prediction error signal effectively, a pyramid VQ (PVQ) is used wh ile a memoryless PVQ is used to encode low-correlation frames. By combining the PPVQ and the memoryless PVQ, denoted 'safety net pyramid VQ; the advan tages of both quantisation methods can br utilised. Thr average SD value of a safety-net pyramid VQ is 0.35 dB less than that of a predictive split VQ (PSVQ). The safety-net pyramid VQ also requires low complexity and does no t require any memory for the codebook storage.