87. The CPP of claim 81 , wherein: the determining CRPC means comprises CRPC means for causing the processor to determine whether at least a portion of the reconstructed codevector does not belong to the illegal space; and the outputting CRPC means comprises CRPC means for causing the processor to output a reconstructed portion of the speech or audio signal based on the reconstructed codevector when at least a portion thereof does not belong to the illegal space.
81. A computer program product (CPP) comprising a computer usable medium having computer readable program code (CRPC) means embodied in the medium for causing an application program to execute on a computer processor to perform inverse quantization of a vector representative of a portion of a speech or audio signal, the vector being quantized according to the steps of determining, among a set of candidate codevectors that include line spectral frequencies (LSFs), a best candidate codevector not belonging to an illegal space representative of illegal vectors, wherein the illegal space is defined by invalid spacing characteristics of LSF parameters, wherein the best candidate codevector corresponds to a quantization of the vector, and outputting a quantizer index identifying the best legal candidate codevector, the CRPC means comprising: producing CRPC means for causing the processor to produce a reconstructed codevector based on a received quantizer index; determining CRPC means for causing the processor to determine whether the reconstructed codevector does not belong to the illegal space; and outputting CRPC means for causing the processor to output a reconstructed portion of the speech or audio signal based on the reconstructed codevector when the reconstructed codevector does not belong to the illegal space.