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annotate libgsmefr/convolve.c @ 494:aaf4dec8bee0

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libgsmhr1: implement perfect SID detection
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 17 Jun 2024 23:14:19 +0000
parents 8de2f0f9bd78
children
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1 /*************************************************************************
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2 *
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3 * FUNCTION: Convolve
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4 *
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5 * PURPOSE:
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6 * Perform the convolution between two vectors x[] and h[] and
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7 * write the result in the vector y[]. All vectors are of length L
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8 * and only the first L samples of the convolution are computed.
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9 *
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10 * DESCRIPTION:
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11 * The convolution is given by
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12 *
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13 * y[n] = sum_{i=0}^{n} x[i] h[n-i], n=0,...,L-1
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14 *
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15 *************************************************************************/
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16
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17 #include "gsm_efr.h"
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18 #include "typedef.h"
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19 #include "namespace.h"
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20 #include "basic_op.h"
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21 #include "no_count.h"
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22 #include "sig_proc.h"
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24 void Convolve (
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25 Word16 x[], /* (i) : input vector */
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26 Word16 h[], /* (i) : impulse response */
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27 Word16 y[], /* (o) : output vector */
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28 Word16 L /* (i) : vector size */
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29 )
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30 {
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31 Word16 i, n;
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32 Word32 s;
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33
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34 for (n = 0; n < L; n++)
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35 {
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36 s = 0; move32 ();
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37 for (i = 0; i <= n; i++)
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38 {
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39 s = L_mac (s, x[i], h[n - i]);
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40 }
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41 s = L_shl (s, 3);
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42 y[n] = extract_h (s); move16 ();
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43 }
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44
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45 return;
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46 }