89. An encoder for quantizing a vector representative of a portion of a speech or audio signal, comprising: a codevector generator that generates a set of candidate codevectors that include line spectral frequencies (LSFs); a memory for storing an illegal space definition representing illegal vectors, wherein the illegal space definition defines invalid spacing characteristics of LSFs; a legal status tester that determines legal candidate codevectors among the set of candidate codevectors using the illegal space definition; a codevector selector that determines a best legal candidate codevector among the one or more legal candidate codevectors, whereby the best legal candidate codevector corresponds to a quantization of the vector; and a transmitter that transmits to a decoder a signal representative of the portion of the speech or audio signal based on the best legal candidate codevector.
89. An encoder for quantizing a vector representative of a portion of a speech or audio signal, comprising: a codevector generator that generates a set of candidate codevectors that include line spectral frequencies (LSFs); a memory for storing an illegal space definition representing illegal vectors, wherein the illegal space definition defines invalid spacing characteristics of LSFs; a legal status tester that determines legal candidate codevectors among the set of candidate codevectors using the illegal space definition; a codevector selector that determines a best legal candidate codevector among the one or more legal candidate codevectors, whereby the best legal candidate codevector corresponds to a quantization of the vector; and a transmitter that transmits to a decoder a signal representative of the portion of the speech or audio signal based on the best legal candidate codevector. 90. The encoder of claim 89 , further comprising: an error calculator that generates an error term corresponding to each legal candidate codevector, each error term being a function of the vector and the corresponding legal candidate codevector, wherein the codevector selector is configured to determine the best legal candidate codevector based on the error terms.