Patent Document ID: 5548680
Application ID: 08243295
Patent Flag: 1

Claim One:
1. A method of speech signal coding, comprising the steps of: (a) dividing a speech signal to be coded into digital sample frames each containing the same number of samples: (b) subjecting the samples of each frame to a predictive analysis for extracting from said signal parameters representative of long-term and short-term spectral characteristics and comprising at least a long-term analysis delay d, corresponding to a pitch period, and a long-term prediction coefficient b and gain G, and to a classification which indicates whether a respective frame corresponds to an active or inactive speech signal segment and for an active signal segment, whether the segment corresponds to a voiced or an unvoiced sound, a segment being considered as voiced if a respective prediction coefficient and gain are both greater than or equal to respective thresholds; (c) providing information on said parameters to coding units for insertion into a coded signal, together with signals indicative of the classification for selecting in said coding units different coding methods according to characteristics of respective speech segments; and (d) during said long-term analysis, estimating said delay is as a maximum of covariance function, weighted with a weighting function which reduces a probability that the period computed is a multiple of an actual period, inside a window with a length not less than a maximum value admitted for the delay, said thresholds for prediction coefficient and gain being thresholds which are adapted at each frame, in order to follow a background noise but not of the speech signal, adaptation of said thresholds being enabled only in active speech signal segments.