Patent ID: 6910008

Claim:
A code excited linear prediction speech decoder, comprising: an adaptive codebook capable of generating an adaptive code vector; a random codebook capable of generating a random code vector; a synthesis filter that receives a signal based on said adaptive code vector and said random code vector, and is capable of convoluting between an impulse response of the synthesis filter and said signal to generate a synthesized speech; said random codebook comprising: an input vector providing system capable of providing an input vector comprising at least one pulse, each pulse having a predetermined position and a respective polarity; a fixed waveform storage system capable of storing at least one fixed waveform; and an arranging system capable of arranging said at least one fixed waveform in accordance with the position and the polarity of said at least one pulse of said input vector to generate said random code vector comprising said arranged at least one fixed waveform; a determiner that determines whether input speech is at least one of voiced and unvoiced; and wherein when said input speech is voiced, said random code vector comprises a plurality of pulses, and when said input speech is unvoiced, said random code vector comprises said at least one fixed waveform as arranged by said arranging system.