| 摘要 |
The invention relates to a method of coding a sampled speech signal vector by selecting an optimal excitation vector in an adaptive code book (100). This optimal excitation vector is obtained by maximizing the energy normalized square of the cross correlation between the convolution (102) of the excitation vectors with the impulse response (h w (n)) of a linear filter and the speech signal vector. Before the convolution the vectors of the code book (100) are block normalized (200) with respect to the vector component largest in magnitude. In a similar way the speech signal vector (s(n)) is block normalized (202) with respect to its component largest in magnitude. Calculated values for the squared cross correlation C I and the energy E I and corresponding values C N, E M for the best excitation vector so far are divided into a mantissa and a scaling factor with a limited number of scaling levels. The number of levels can be different for squared cross correlation and energy. During the calculation of the products C I .times. E M and E I .times. C M, which are used for determining the optimal excitation vector, the respective mantissas are multiplied and a separate scaling factor calculation is performed.
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