Method and device for coding an analog signal having a repetitive nature utilizing over sampling to simplify coding

摘要

Speech signals coded according to the principle of high- resolution long-term prediction (HLTP) have a high accuracy due to the high- resolution which causes a high complexity. The ordinary LTP method is improved by use of oversampling and determining subsegments Cd lying in a preceding segment which precedes a subsegment to be coded, for which it is the case that the number of samples Dd, expressed in the numbers of samples after oversampling, between the initial time instant of the subsegment to be coded and the initial time instant of a subsegment Cd, fulfills the relation Dd=(D*Ob)/d, in which d=2,3,4 . . . n, where n is a positive integer and where Ob and n are chosen in a manner such that Dd is always an integer. Null sample values produced initially for oversampling are given significance by means of an interpolation technique, at predetermined positions which are situated at a spacing Dd from the original samples in the subsegment to be coded. In the oversampling the number of samples in the subsegment to be coded is increased by a predetermined factor Ob by always placing (Ob-1) samples having a value equal to 0 between two consecutive samples, and the number of samples in the preceding segment, which contains the selectable subsegments Cd, is also increased by the factor Ob.