Switched Lattice-Based Quantization of LSF Parameters

In this work, a switched lattice-based quantizer for the quantization of speech LSF parameters is presented. LSF di erence values are rst quantized using a scalar quantizer, as well as a two dimensional vector quantizer, and subsequently adjusted for a lower bit-rate using a lattice. A Euclidean distance measure is used as the distortion measure for the design, while a spectral distortion measure is used for the evaluation of the performance. LSF di erences are formed in a closed loop manner for which a rst-order prediction lter is used. The parameters for the prediction lter are calculated from a LSF database. Lattice-based double frame and single frame quantization is performed for each frame and the one which results in a lower distortion is chosen. Numerical results are presented showing an excellent performance with very low complexity. The results are compared to the split vector quantizer using common database for test and training showing substantial improvement. Finally, the issue of the robustness to channel errors is investigated. i