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qparcor[iJ: =parql[i,j]
END;
Note.- Vector pardll:] contains thefied decision levels for
each partial correlation coeficient and its contents are defined
in Table A7-I.*
4.5 Line codes for the partial
correlation coefficients
A line code corresponding to each quantized partial correlation
coefficient contained in qparcor[] shall be inserted into the
transmission frame. Each line code shall be generated by the
table look-up operation defined by:
a) for qparcor[l] use Table A7-2;
b) for qparcor[2] use Table A7-3;
c) for qparcorf31 use Table A7-4;
d) for qparcor[4] use TabIe A7-5;
e) for qparcor[5] use Table A7-6;
f) for qparcor[6] use Table A7-7;
g) for qparcor[7] use TabIe A7-8;
h) for qparcor/8] use TabIe A7-9;
i) for 'qparcor/9] use Table A7- 10; and
j) for qparcor! I01 use Table A7-I 1.
4.6 LPC filter tap step up
For each gparcor[], the vector qtaps[] shall be generated by
the operation defined by:
qtaps:=qparcor; {all 10 elements of vector qtclps set equal
to correspo~.lding ekmetits in qpa~or}
FOR i:=2 TO 10 DO
BEGIN
FOR j:=l TO pred(i) DO alpha[j]:=qtaps[j];
FOR j: = 1 TO pred(i) DO qtapslj']: =alpha/j]-
qtaps[i]*alpha[i-j]
Ern;
4.7 Long-term correlation
analysis
4.7.1 LPC INVERSE FILTERING
For each spch[], the vector residue[] shall. be generated by the
operation defined by:
FOR n:=O TO 159 DO
BEGIN
sum: =spch[n];
FOR i:= 1 TO 10 DO sum: =sum-qtaps[i]*spch[n.-i];
residuern]: =sum
END;
Note.- The values near the start ofeach spch[],for which
the index of spch[J is less thzrlz zero, refers to speech samples
at the end of the previous spch[]. For the first spch[]
processed by the encodel; these values shall be corzsidered to
be zero.
4.7.2 LONG-TERM
CORRELATION
For each residue[], the scalars gain and delay shall be
generated by the operation defined by:
mw:=O
FOR lag:=33 TO 96 DO
BEGIN
sum: =O;
FOR n:=O TO 159 DO sum:-
sum+residue[n] *residue[n-lag];
IF sum>max THEN
BEGIN
max:=sum;
delay:=lag
END
END;
sum: =O;
FOR n:=O TO 159 DO sum:=sum+sqr(residue[n-delay]);
IF sum=O THEN gazn:=O ELSE gain:=max/sum;
END;
~ ~- * All tables are located at the end of this chapter.
Part 1 Annex 10 - Aeronautical Telec~mmufiicuti~ns
Note 1.- The scalar delay is a 16-bit signed integer:
Note 2.- Negative values of the idices n-lag and n-delay
point to entries in rhe residue[] that were calculated for the
previous spch[] . For the jrsr spch[] processed, the referenced
entries in residue[] shall be considered to be zero.
4.7.3 QUANTIZATIAONND LINE ENCODING
OF THE SCALAR GAIN
For each gain, its contents shall be quantized and stored in
scalar qgain by the operation defined by:
IF gain>O. 75 THEN qgain:=0.9 ELSE
IF gain>0.45 THEN qgaia: =0.60 ELSE
IF gaio0.2 THEN qgain:=0.325 ELSE qgazn:=O. I
FOR i:= 1 TO 10 DO sum:=sum+qtaps[i]*
local-synrhspch[n-i];
local-synthspch[n]: =qgain *locaLs2[n-de/ay]+sum;
ermr[n]:=spch[nl-local-syntlzspch[n]
END;
Note.- This operation is perjonned for each of the jive
excitation frames cotztained within a rransmzsszon frame.
4.8.2 IMPULSE RESPONSE CALCULATION
For each qtups[], the vectors iresp[] and rpwr[] shall be
generated by the operation defined by the following:
iresp[O]:= 1;
ipwr[31]:= 1;
FOR n:=l TO 31 DO
A ?-bit line code corresponding to qgain shall be inserted into BEGIN
sum:=O;
the transmission frame. The line code shalI be generated by
the table look-up operation defined by Table A7-12.
FOR j:=l TO 10 DO IF n>=j THEN
sum:=sum+qtaps[j]*imsp[nj];
i resp[nl: = sum;
4.7.4 LINE ENCODING OF THE
ipwr[32-succ(n)]:=ipwr[32-n]+sqr(sum)
SCALAR DELAY
END;
Note.- Since the minimum possible value .for rhe delay
A line code corresponding to delay shall be generated by the parameter is 32, the long-rernz predictor has no influence on
table look-up operation defined by Table A7-13. the $rst 32 samples of the impulse response.
4.8.3 CROSS-CORRELATCIAOLNC ULATION
4.8 Excitation analysis
Note 1.- The transmission frame generated by this
encoding algorithm conrains five excitation frames. Each
group of jive excitation frames is associated with the same
speech frame (spch[]) "from which the partial correlation
coefficients of the current transmission frame were calculated.
Note 2.- Any operation that generates an output vurcable
that is a component of an excitarion frame must be pe$ormed
at the generation rate of the excitation frames (i-e. five
 
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