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annotate libgsmefr/preemph.c @ 53:49dd1ac8e75b

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libgsmefr: import most *.c files from ETSI source
author Mychaela Falconia <falcon@freecalypso.org>
date Fri, 25 Nov 2022 16:18:21 +0000
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children 9aef9e54b19d
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49dd1ac8e75b libgsmefr: import most *.c files from ETSI source
Mychaela Falconia <falcon@freecalypso.org>
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1 /*---------------------------------------------------------------------*
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2 * routine preemphasis() *
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3 * ~~~~~~~~~~~~~~~~~~~~~ *
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4 * Preemphasis: filtering through 1 - g z^-1 *
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5 *---------------------------------------------------------------------*/
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6
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7 #include "typedef.h"
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8 #include "basic_op.h"
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9 #include "count.h"
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10
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11 Word16 mem_pre;
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12
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13 void preemphasis (
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14 Word16 *signal, /* (i/o) : input signal overwritten by the output */
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15 Word16 g, /* (i) : preemphasis coefficient */
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16 Word16 L /* (i) : size of filtering */
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17 )
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18 {
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19 Word16 *p1, *p2, temp, i;
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20
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21 p1 = signal + L - 1; move16 ();
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22 p2 = p1 - 1; move16 ();
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23 temp = *p1; move16 ();
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24
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25 for (i = 0; i <= L - 2; i++)
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26 {
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27 *p1 = sub (*p1, mult (g, *p2--)); move16 ();
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28 p1--;
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29 }
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31 *p1 = sub (*p1, mult (g, mem_pre)); move16 ();
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32
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33 mem_pre = temp; move16 ();
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34
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35 return;
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36 }