Scalable speech coding at rates below 900 BPS

This paper introduces a novel scalable speech coding scheme based on embedded matrix quantization of LSF parameters in an LPC model. In the proposed quantizer, codewords are organized based on a tree structure through a cell-merging process, which leads to a fine-grain scalable coder at rates below 900 bps. Near natural sounding is achieved at very low rates by employing an efficient adaptive dual-band scheme to approximate the LPC excitation signals. Evaluation results, obtained from both overall quality measurement and intelligibility assessment, show that the proposed coder could be a reasonable choice for improving the bottom-line speech quality in low bit rates.