Patent ID: 7647223

Claim:
In a composite quantizer including first and second sub-quantizers, a method of sub-quantizing a residual vector representative of a portion of a signal using the first sub-quantizer, comprising: (a) receiving the residual vector that represents the difference between a Line Spectral Frequency (LSF) vector and a prediction of the LSF vector; (b) transforming each sub-codevector of a set of sub-codevectors into a corresponding candidate codevector by combining each sub-codevector with a transformation vector, thereby producing a set of candidate codevectors; (c) determining legal candidate codevectors among the set of candidate codevectors; (d) determining a best sub-codevector corresponding to a legal candidate codevector among the legal candidate codevectors, wherein the best sub-codevector corresponds to a quantization of the residual vector; and (e) outputting at least one of: the best sub-codevector, and an index identifying the best sub-codevector.