Efficient encoding of the MELP LSF parameters: Application of the switched split vector quantization

Speech coders operating at low bit rates necessitate efficient encoding of the linear predictive coding (LPC) coefficients. In this work, we developed an optimized switched split vector quantization (SSVQ) scheme applied for encoding the LPC coefficients represented by the line spectral frequencies (LSF) parameters. It will be shown that the SSVQ provides better performance in terms of bit-rate, spectral distortion and computational complexity than the traditional split vector quantizer. We further applied our SSVQ encoding system, called LSF-SSVQ encoder, to quantize the LSF parameters of the 2.4 Kbits/s normalised speech coder MELP operating over an ideal noiseless channel.