Method and apparatus for determination of an optimum fixed codebook vector

A digital signal processor for processing electrical signals to determine a codebook vector and a gain of said codebook vector comprising:

• means for pre-processing a sampled speech s{n} in a signal pre-processor so as to output at least a noise filtered speech output vector and a channel noise estimate,
• means for model parameter estimation of the noise filtered speech output vector so as to output a prediction residual and a long term prediction gain,
• means for encoding the residual so as to output an adaptive codebook vector including an index of impulse response functions of a filter and a fixed codebook vector gain,
• means for formatting encoded speech packets,
• wherein encoding is performed in the following order by:
• means for determination of the fixed codebook vector gain by choosing a start value close to a theoretical value, and
• means for vector optimisation by successive searching for an extremum of an estimate function based on a recursively corrected correlation vector.

An electronic apparatus comprising a digital signal processor for processing electrical signals to determine a codebook vector and a gain of said codebook vector, the digital signal processor comprising:

• means for pre-processing a sampled speech s{n} in a signal pre-processor so as to output at least a noise filtered speech output vector and a channel noise estimate,
• means for model parameter estimation of the noise filtered speech output vector so as to output a prediction residual and a long term prediction gain,
• means for encoding the residual so as to output an adaptive codebook vector including an index of impulse response functions of a filter and a fixed codebook vector gain,
• means for formatting encoded speech packets,
• wherein encoding is performed in the following order by:
• means for determination of the fixed codebook vector gain by choosing a start value close to a theoretical value, and
• means for vector optimisation by successive searching for an extremum of an estimate function based on a recursively corrected correlation vector.