(57) Method and device for coding a signal segment of a sampled analog signal having a
repetitive nature according to the principle of long-term prediction (LTP). According
to the method, after determining the number of samples D between the beginning of
the segment to be coded and the beginning of the most similar segment determined according
to the LTP principle:
- the number of samples in the segment 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 is also increased by the
factor Ob,
- in the preceding segment, partial segments Cd are determined 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 segment to be coded and the initial time instant
of a partial segment Cd fulfils:
, in which d = 1, 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,
- in the segments Cd, sample values are determined by an interpolation technique at
predetermined positions, which predetermined positions are situated at a spacing Dd
from the original samples in the segment to be coded before its number of samples
was increased,
- a partial segment Cd is determined which is most similar to the segment to be coded,
- that segment Cd is chosen as the most similar segment which has a correlation value
Rd with the samples of the segment to be coded for which it is the case that Rd ≧
q * Rmax, where q < 1 and Rmax is the maximum correlation value which has been found in correlating the segments
Cd and the segment to be coded, and is that segment which yields the smallest associated
value of Dd.
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