Pitch detection for use in a predictive speech coder

DETAILED DESCRIPTION We claim: 1.
Method for detecting related data (M) in a representative signal split into blocks of samples including a rough M determination followed by a fine M determination, said method comprising the steps of: a.
for said rough M determination: 1.
setting a positive threshold (Th.
sup.
+) and a negative threshold (Th.
sup.
-) based on characteristics of the representative signal; 2.
locating and storing a plurality of samples representative of said blocks of samples, having magnitudes above and below said Th.
sup.
+ and Th.
sup.
- ; 3.
Identifying significant signal magnitude transitions within said blocks of samples; 4.
storing a set of values M' indicative of said samples between each of said significant signal magnitude transitions; and 5.
averaging said set of values M' to calculate said rough M determination; and b.
for said fine M determination: 1.
setting a plurality of autocorrelation zones about said plurality of samples; 2.
splitting said blocks of samples into consecutive sub-blocks of samples; 3.
autocorrelating, using the autocorrelation zones of a current sub-block of samples; and 4.
setting the fine M value equal to a maximum value for said current sub-block of samples in accordance with step 3 of said fine M determination.
2.
Method for detecting pitch related data (M) in a representative signal, as recited in claim 1, wherein said step of setting a plurality of autocorrelation zones about said plurality of samples includes the steps of: a.
locating a maximum value and a predetermined delta variation in each of said plurality of samples to define said autocorrelation zones; and b.
filtering said autocorrelation zones to remove any non significant values.
3.
Method for detecting pitch related data (M) in a representative signal, as recited in claim 1, further comprising the step of calculating a residual signal r(n) from said representative signal by a short-term filtering operation using a digital filter to be processed and subsequently quantized into an output signal