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 a predictive split vector quantizer to that of split vector quantizer based on the ITU G723.1 standard coder. Our results show that a 25 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.
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