FreeCalypso > hg > gsm-codec-lib
annotate libgsmefr/preemph.c @ 95:f80a3202c8ff
libgsmefr: implement main decoder wrapper
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sat, 26 Nov 2022 18:58:56 +0000 |
parents | 9aef9e54b19d |
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rev | line source |
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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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parents:
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6 |
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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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15 |
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Mychaela Falconia <falcon@freecalypso.org>
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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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24 |
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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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28 |
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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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34 |
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35 *p1 = sub (*p1, mult (g, st->mem_pre)); |
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36 |
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37 st->mem_pre = temp; |
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Mychaela Falconia <falcon@freecalypso.org>
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38 |
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Mychaela Falconia <falcon@freecalypso.org>
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39 return; |
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40 } |