Performance comparison of split VQ and two-stage VQ-lattice VQ of LSP parameters in packet networks

In many speech coding systems, the LPC coefficients are transformed to the line spectrum pairs (LSP) parameters which are very effective representation for quantization of the LPC information. LSP representation consumes a large part of the total bit rate of the coder. Typically, the LSP are highly correlated from one frame to the next one, and a considerable reduction in bit rate can be achieved by exploiting this interframe correlation. However, interframe LSP coding can cause error propagation when frame erasures occur. In this paper, we compare the erasure performance of two intraframe quantization schemes namely a two-stage VQ-Lattice vector quantizer and a split vector quantizer based on the ITU G.723.1 standard coder. Our results show that a 24 bits/frame split vector quantizer improves the average of spectral distortion of the 24 bits/frame predictive split vector quantizer based on the ITU G.723.1 for different loss rates