FreeCalypso > hg > gsm-codec-lib

annotate libgsmefr/preemph.c @ 522:4d2cccaeb4a7

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libtest: implement TW-TS-005 reader function Spec reference: https://www.freecalypso.org/specs/tw-ts-005-v010002.txt
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 19 Sep 2024 03:08:47 +0000
parents 9aef9e54b19d
children
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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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7 #include "gsm_efr.h"
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8 #include "typedef.h"
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9 #include "namespace.h"
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10 #include "basic_op.h"
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11 #include "no_count.h"
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12 #include "sig_proc.h"
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13 #include "cnst.h"
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14 #include "dec_state.h"
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16 void preemphasis (
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17 struct EFR_decoder_state *st,
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18 Word16 *signal, /* (i/o) : input signal overwritten by the output */
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19 Word16 g, /* (i) : preemphasis coefficient */
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20 Word16 L /* (i) : size of filtering */
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21 )
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22 {
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23 Word16 *p1, *p2, temp, i;
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25 p1 = signal + L - 1;
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26 p2 = p1 - 1;
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27 temp = *p1;
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29 for (i = 0; i <= L - 2; i++)
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30 {
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31 *p1 = sub (*p1, mult (g, *p2--));
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32 p1--;
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33 }
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35 *p1 = sub (*p1, mult (g, st->mem_pre));
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37 st->mem_pre = temp;
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39 return;
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40 }