Low data rate VFR coding of spectral information using contour quantization

This report describes two low data rate VFR coding schemes of spectral information based on contour quantization. The first is a basic coding scheme in which speech signal is first pre-segmented into phone-like sub-segments. The second one is an optimal coding scheme in which a joint optimization procedure for segmentation, quantization and codebook design is employed in the encoder to iteratively improve the coding efficiency to reach a lower bound of rate-distortion function. A complete vocoder to further consider the encoding of pitch and gain information is also discussed.