Image Number 19 for United States Patent #5245662.
A speech coding system operated under a known code-excited linear prediction (CELP) coding method. The CELP coding is achieved by selecting an optimum pitch vector P from an adaptive codebook and the corresponding first gain and, at the same time, selecting an optimum code vector from a sparse-stochastic codebook and the corresponding second gain. Special code vectors are loaded in the sparse-stochastic codebook, which code vectors are hexagonal lattice code vectors each consisting of a zero vector with one sample set to +1 and another sample set to -1.
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