FreeCalypso > hg > gsm-codec-lib
annotate libgsmefr/dec_lag6.c @ 176:9fb22fa4d373
doc/RTP-analysis: document rtp-g711-extr
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Tue, 27 Dec 2022 01:29:14 +0000 |
parents | cb080ec1817e |
children | f387ee919f2c |
rev | line source |
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1 /************************************************************************* |
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2 * FUNCTION: Dec_lag6 |
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3 * |
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4 * PURPOSE: Decoding of fractional pitch lag with 1/6 resolution. |
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5 * Extract the integer and fraction parts of the pitch lag from |
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6 * the received adaptive codebook index. |
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7 * |
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8 * See "Enc_lag6.c" for more details about the encoding procedure. |
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9 * |
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10 * The fractional lag in 1st and 3rd subframes is encoded with 9 bits |
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11 * while that in 2nd and 4th subframes is relatively encoded with 6 bits. |
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12 * Note that in relative encoding only 61 values are used. If the |
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13 * decoder receives 61, 62, or 63 as the relative pitch index, it means |
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14 * that a transmission error occurred. In this case, the pitch lag from |
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15 * previous subframe is used. |
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16 * |
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17 *************************************************************************/ |
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18 |
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19 #include "gsm_efr.h" |
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20 #include "typedef.h" |
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21 #include "namespace.h" |
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22 #include "basic_op.h" |
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23 #include "no_count.h" |
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24 #include "codec.h" |
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25 #include "cnst.h" |
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26 #include "dec_state.h" |
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27 |
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28 Word16 Dec_lag6 ( /* output: return integer pitch lag */ |
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29 struct EFR_decoder_state *st, |
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30 Word16 index, /* input : received pitch index */ |
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31 Word16 pit_min, /* input : minimum pitch lag */ |
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32 Word16 pit_max, /* input : maximum pitch lag */ |
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33 Word16 i_subfr, /* input : subframe flag */ |
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34 Word16 L_frame_by2,/* input : speech frame size divided by 2 */ |
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35 Word16 *T0_frac, /* output: fractional part of pitch lag */ |
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36 Word16 bfi, /* input : bad frame indicator */ |
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37 Word16 *T0_min, |
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38 Word16 *T0_max |
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39 ) |
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40 { |
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41 Word16 pit_flag; |
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42 Word16 T0, i; |
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43 |
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44 pit_flag = i_subfr; move16 (); /* flag for 1st or 3rd subframe */ |
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45 test (); |
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46 if (sub (i_subfr, L_frame_by2) == 0) |
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47 { |
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48 pit_flag = 0; move16 (); |
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49 } |
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50 test (); |
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51 if (pit_flag == 0) /* if 1st or 3rd subframe */ |
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52 { |
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53 test (); |
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54 if (bfi == 0) |
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55 { /* if bfi == 0 decode pitch */ |
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56 test (); |
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57 if (sub (index, 463) < 0) |
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58 { |
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59 /* T0 = (index+5)/6 + 17 */ |
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60 T0 = add (mult (add (index, 5), 5462), 17); |
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61 i = add (add (T0, T0), T0); |
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62 /* *T0_frac = index - T0*6 + 105 */ |
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63 *T0_frac = add (sub (index, add (i, i)), 105); |
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64 move16 (); |
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65 } |
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66 else |
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67 { |
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68 T0 = sub (index, 368); |
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69 *T0_frac = 0; move16 (); |
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70 } |
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71 } |
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72 else |
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73 /* bfi == 1 */ |
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74 { |
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75 T0 = st->old_T0; |
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76 *T0_frac = 0; |
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77 } |
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78 |
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79 /* find T0_min and T0_max for 2nd (or 4th) subframe */ |
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80 |
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81 *T0_min = sub (T0, 5); |
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82 if (sub (*T0_min, pit_min) < 0) |
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83 { |
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84 *T0_min = pit_min; |
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85 } |
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86 *T0_max = add (*T0_min, 9); |
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87 if (sub (*T0_max, pit_max) > 0) |
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88 { |
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89 *T0_max = pit_max; |
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90 *T0_min = sub (*T0_max, 9); |
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91 } |
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92 } |
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93 else |
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94 /* second or fourth subframe */ |
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95 { |
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96 test (); test (); |
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97 /* if bfi == 0 decode pitch */ |
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98 if ((bfi == 0) && (sub (index, 61) < 0)) |
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99 { |
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100 /* i = (index+5)/6 - 1 */ |
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101 i = sub (mult (add (index, 5), 5462), 1); |
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102 T0 = add (i, *T0_min); |
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103 i = add (add (i, i), i); |
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104 *T0_frac = sub (sub (index, 3), add (i, i)); |
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105 } |
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106 else |
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107 /* bfi == 1 OR index >= 61 */ |
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108 { |
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109 T0 = st->old_T0; |
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110 *T0_frac = 0; |
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Mychaela Falconia <falcon@freecalypso.org>
parents:
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changeset
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111 } |
49dd1ac8e75b
libgsmefr: import most *.c files from ETSI source
Mychaela Falconia <falcon@freecalypso.org>
parents:
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changeset
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112 } |
49dd1ac8e75b
libgsmefr: import most *.c files from ETSI source
Mychaela Falconia <falcon@freecalypso.org>
parents:
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changeset
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113 |
65
cb080ec1817e
libgsmefr: dec_lag6.c compiles
Mychaela Falconia <falcon@freecalypso.org>
parents:
53
diff
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114 st->old_T0 = T0; |
53
49dd1ac8e75b
libgsmefr: import most *.c files from ETSI source
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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115 |
49dd1ac8e75b
libgsmefr: import most *.c files from ETSI source
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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116 return T0; |
49dd1ac8e75b
libgsmefr: import most *.c files from ETSI source
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
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117 } |