Verfahren zur schnellen Bestimmung der Grundfrequenz in Sprachcodierern mit langfristiger Prädiktion

A process for deriving voice pitch related delay values M to tune a Long-Term Prediction (LTP) filter to be used in an LTP based speech coder converting a speech derived digital signal r(n) into a lower bit rate signal, said filter being provided with a variable length delay line y(n) fed with a reconstructed signal r min (n). The process includes splitting r(n) into segments and each segment into sub-segments then cross-correlating the first current r(n) sub-segment with a previously reconstructed segment and sorting the cross-correlation values for peak location, whereby a first delay value M1 is derived and used to tune the filter. Then, said M1 is used to compute sample indexes n for a predefined number of samples located about M1/p, ..., M1, 2M1, pM1 and repeating cross-correlation and sorting operations to derive M2 and so on up to a full segment length (e.g. 160 samples). Then the process is started all over again.