FreeCalypso > hg > gsm-codec-lib
annotate libtwamr/preemph.c @ 450:16bc3036cc84
LICENSE: acknowledge libtwamr origin from ETSI/3GPP
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Fri, 10 May 2024 01:48:20 +0000 |
parents | 3618b5cf25a6 |
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1 /* |
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2 ******************************************************************************** |
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3 * |
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4 * GSM AMR-NB speech codec R98 Version 7.6.0 December 12, 2001 |
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5 * R99 Version 3.3.0 |
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6 * REL-4 Version 4.1.0 |
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7 * |
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8 ******************************************************************************** |
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9 * |
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10 * File : preemph.c |
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11 * Purpose : Preemphasis filtering |
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12 * Description : Filtering through 1 - g z^-1 |
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13 * |
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14 ******************************************************************************** |
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15 */ |
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16 |
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17 /* |
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18 ******************************************************************************** |
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19 * MODULE INCLUDE FILE AND VERSION ID |
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20 ******************************************************************************** |
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21 */ |
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22 #include "namespace.h" |
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23 #include "preemph.h" |
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24 |
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25 /* |
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26 ******************************************************************************** |
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27 * INCLUDE FILES |
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28 ******************************************************************************** |
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29 */ |
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30 #include "typedef.h" |
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31 #include "basic_op.h" |
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32 #include "no_count.h" |
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33 |
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34 /* |
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35 ******************************************************************************** |
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36 * LOCAL VARIABLES AND TABLES |
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37 ******************************************************************************** |
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38 */ |
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39 |
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40 /* |
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41 ******************************************************************************** |
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42 * PUBLIC PROGRAM CODE |
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43 ******************************************************************************** |
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44 */ |
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45 |
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46 /************************************************************************* |
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47 * |
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48 * Function: preemphasis_reset |
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49 * Purpose: Initializes state memory to zero |
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50 * |
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51 ************************************************************************** |
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52 */ |
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53 void preemphasis_reset (preemphasisState *state) |
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54 { |
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55 state->mem_pre = 0; |
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56 } |
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57 |
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58 /* |
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59 ************************************************************************** |
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60 * Function: preemphasis |
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61 * Purpose: Filtering through 1 - g z^-1 |
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62 * |
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63 ************************************************************************** |
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64 */ |
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65 int preemphasis ( |
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66 preemphasisState *st, /* (i/o) : preemphasis filter state */ |
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67 Word16 *signal, /* (i/o) : input signal overwritten by the output */ |
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68 Word16 g, /* (i) : preemphasis coefficient */ |
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69 Word16 L /* (i) : size of filtering */ |
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70 ) |
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71 { |
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72 Word16 *p1, *p2, temp, i; |
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73 |
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74 p1 = signal + L - 1; move16 (); |
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75 p2 = p1 - 1; move16 (); |
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76 temp = *p1; move16 (); |
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77 |
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78 for (i = 0; i <= L - 2; i++) |
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79 { |
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80 *p1 = sub (*p1, mult (g, *p2--)); move16 (); |
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81 p1--; |
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82 } |
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83 |
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84 *p1 = sub (*p1, mult (g, st->mem_pre)); move16 (); |
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85 |
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86 st->mem_pre = temp; move16 (); |
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87 |
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88 return 0; |
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89 } |