Patent ID: 7398205

Claim:
A code excited linear prediction speech decoder, comprising: an adaptive codebook configured to generate an adaptive code vector; a random codebook configured to generate a random code vector, the random codebook comprising: an input vector providing section configured to provide an input vector comprising at least one pulse, each pulse having a predetermined position and a respective polarity, a fixed waveform storage section configured to store at least one fixed waveform, a determination section configured to determine whether input speech is at least one of voiced and unvoiced, and to select the at least one fixed waveform when the input speech is determined to be unvoiced, while producing the input vector as the random code vector when the input speech is determined to be voiced, and a convolution section configured to convolute the at least one fixed waveform, which is selected when the input speech is determined to be unvoiced, with the input vector to thereby produce the random code vector; and a synthesis filter that receives a signal based on the adaptive code vector and the random code vector, and is configured to perfonn linear prediction coefficient synthesis on the signal to output synthesized speech.