35. The method of claim 33 , wherein the illegal space is represented as an illegal criterion for LSF vectors, and the illegal criterion for LSF vectors includes first and second successive LSFs in a pair of LSFs being closer to each other than a minimum separation distance.
33. The method of claim 23 , wherein the vector is an input line spectral frequency (LSF) vector including line spectral frequencies (LSFs), and each candidate codevector is an LSF vector including LSFs.